erratum erratum: carrier status for p.gly61glu and p.arg368his cyp1b1 mutations causing primary congenital glaucoma in iran ali heshmati, ms; peyman taghizadeh, ms; hamid ahmadieh, md; mehdi yaseri, phd; fatemeh suri, phd; mahsa alizadeh; marjan dadashzadeh; hajar khatami, msc; monireh moradkhah navi; parisa zamanparvar; hassan behboudi, md; elahe elahi, phd j ophthalmic vis res 2022; 17 (2): 311–311 the authors have informed the journal that tables 1 and 2 cited in the original article were missing in the full-text pdf and html of the article published in the journal of ophthalmic and vision research volume 16 issue 4. the online version of the article has therefore been updated on april 29, 2022 and can be accessed from https://doi.org/10.18502/jovr.v16i4.9747. table 1. screening of p.gly61glu in the city of talesh in guilan. no. individuals screened no. mutation carriers frequency of carriers* 95% confidence interval of mutation carriers total 1036 9 0.86% 0.45% 1.64% urban 584 5 0.85% 0.37% 1.99% rural 452 4 0.88% 0.34% 2.25% *the difference in frequency of carriers in urban and rural regions was not statistically significant. table 2. screening of p.arg368his in cities of the east of guilan province. no. individuals screened no. mutation carriers frequency of carriers* 95% confidence interval of mutation carriers all of east of total 3029 73 2.41% 1.91% 3.04% gilan urban 2160 51 2.36% 1.08% 3.09% rural 869 22 2.53% 1.68% 3.8% bandar anzali total 389 11 2.82% 1.57% 4.99% urban 336 8 2.38% 1.21% 4.63% rural 53 3 5.66% 1.94% 15.37% lahijan total 376 5 1.32% 0.58% 3.15% urban 226 4 1.77% 0.69% 4.46% rural 150 1 0.67% 0.12% 3.68% rasht total 2095 54 2.58% 1.98% 3.35% urban 1481 37 2.50% 1.82% 3.42% rural 614 17 2.77% 1.74% 4.39% astaneh ashrafieh total 169 3 1.78% 0.61% 5.09% urban 117 2 1.71% 0.47% 6.02% rural 52 1 1.92% 0.34% 10.12% *differences in frequencies among the cities and between the urban and rural regions of each of the cities were not statistically significant. © 2022 . this is an open access article distributed under the creative commons attribution license | published by knowledge e 311 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i2.10809&domain=pdf&date_stamp=2019-07-17 microsoft word jovr – ready.docx © this document is distributed under the creative commons attribution license (cc by). i issn: print – 2008-2010; online – 2008-322x https://knepublishing.com/index.php/jovr acknowledgement to reviewers 2022 the editorial team of the journal of ophthalmic and vision research would like to thank the following reviewers for their time and efforts in contributing to the reviews of the submissions received till the end of 2022. abolfazl karimiyan mansooreh jamshidian abouzar bagheri mantapond ittarat abrishami mojtaba maryam aletaha acieh es'haghi maryam yadgari afagh alavi masomeh kalantarion afshin lotfi-sedigh masood naseripour ahad sedaghat masoud mirghorbani ahmad kheirkhah masoumeh masoompour aidin meshksar mehdi khabbazkhoob aliakbar sabermoghaddam ranjbar mehdi moddareszadeh alireza esmaeili mehdi mazloumi alireza hedayatfar mehran zarei-ghanavati alireza khodabandeh mehrdad mohammadpour alireza peyman mehrnaz atighehchian alireza ramezani mehrnaz geranmayeh amir faramarzi mohadeseh feizi amir norouzpour mohammad soleimani amir azharlous mohammad banifatemi amirreza veisi mohammad hasan alemzadeh-ansari arash mirmohammadsadeghi mohammad hossein nowroozzadeh arezoo miraftabi mohammad reza niyousha arezoo miraftabi mohammad reza peyman asieh heirani-tabasi mohammad taher rajabi azadeh doozandeh mohammad-nasser hashemian bagher hoseini mohammad-reza sedaghat bahareh kheiri mohammadmehdi hatami bahman zeynali mohammadreza akbari-baghbani bahram eshraghi mohammadreza jafarinasab batoul mousavi mohsen azarmina behzad fallahi-motlagh mojdeh mohseni © this document is distributed under the creative commons attribution license (cc by). ii behzad khademi mojgan pakbin bita shalbafan mojtaba abrishami danial roshandel monireh mahjoob davoud gharebaghi morteza entezari dong hyun jo mozhgan rezaei kanavi ebrahim jafarzadehpour nader sheibani elham ashrafi narges fazili ensieh darbari narges hasanpour farhad fazel narsis daftarian farid karimian nasser karimi farideh sharifipour nasser shoeibi farzad pakdel naveed nilforushan farzaneh sabouni navid abolfathzadeh fatemeh alipour nazanin ebrahimiadib hamed esfandiari niloufar piri hamid riazi-esfahani pasha anvari hamid ahmadieh ramin nourinia hamid safi ramin beiranvand hamid sharifi reihaneh varshochian hamideh sabbaghi roshanak navahi hamideh sabbaghi saeed karimi hamidreza hasani saeed rahmani hassan khojaste-jafari sahba fekri hessam hashemian sara shafiei homayoun nikkhah sare safi hoshang faghihi seyed farzad mohammadi hossein darvish seyed javad hashemian hossein hasanpour seyed maryam hosseini hossein aghaei seyed-hossein abtahi hossein ashraf shiva samavat iman safari siamak moradian jalil jalili suzan rattan javad heravian shandiz tahmineh motevasseli kaveh abri aghdam vahid mansoury kaveh fadakar yasaman hadi khalil ghasemi falavarjani yousef alizadeh kiana hassanpour zahra soheili koorosh etemad zahra ghaemi kourosh shahraki zahra karjou leila ghiasian zahra khorami mansoor shahriari zakieh vahedian zhaleh rajavi letter torpedo retinopathy or chorioretinopathy? mahmoud dehghan1,2, md; ramin nourinia1,2, md; sahba fekri1,2, md; seyed-hossein abtahi1,2, md 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2department of ophthalmology, labbafinejad medical center, shahid beheshti university of medical sciences, tehran, iran orcid: mahmoud dehghan: https://orcid.org/0000-0001-5102-1109 seyed-hossein abtahi: https://orcid.org/0000-0002-1459-6752 j ophthalmic vis res 2022; 17 (4): 605–606 dear editor, we read with great interest the recent case series by venkatesh and colleagues about the spectrum and features of torpedo lesions described in nine subjects.[1] as far as we are aware, the journal of ophthalmic and vision research has recently published another report on the same topic,[2] and we have encountered such rare cases in our daily practice at labbafinejad medical center as one of the main tertiary centers for retinal diseases. herein, we would like to draw the kind attention of readers toward some pathophysiologic issues about the origin of torpedo lesions. in 1992, roseman and gass[3] described such lesions as solitary hypopigmented nevus of the retinal pigment epithelium (rpe) and defined them as rare congenital anomalies of the rpe that disrupt correspondence to: seyed-hossein abtahi, md. ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, boostan 9 st., paydarfard st., pasdaran ave., tehran, iran. email: shf.abathi@yahoo.com received: 06-04-2021 accepted: 19-02-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i4.12345 the outer retina. as well as the known term “torpedo maculopathy (tm)”, other nomenclatures, are sparsely used as paramacular albinotic spot syndrome, congenital hypomelanotic freckle, and atypical macular coloboma.[1–4] the embryonal origin of these congenital lesions is believed to be rooted in maldevelopment of rpe and disturbances of choroidal vasculature. furthermore, as discussed in a very recent systematic review, subtypes ii and iii of torpedo lesions have been suggested to be classified as choroidal cavitary disorders.[1, 2, 4–6] in oct angiography (octa) studies, the primary site of malformation was found to be in the rpe/choriocapillaris complex.[6] herein, we would like to underline the concluding statement of venkatesh and colleagues,[1] where they stated that torpedo lesions can occur away from the macula with the same appearance of tm. they proposed a change in the nomenclature for torpedo lesions in the retina from “torpedo maculopathy” to “torpedo retinopathy”. consistently, we endorse the notion this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: dehghan m, nourinia r, fekri s, abtahi sh. torpedo retinopathy or chorioretinopathy?. j ophthalmic vis res 2022;17:605–606. © 2022 dehghan et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 605 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i4.12345&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr letter; dehghan et al that such lesions are not exclusively limited to the posterior pole and they can be seen at nearperipheral retina. nevertheless, if we plan to revise the nomenclature, the choroidal origin of torpedo lesions should also be addressed. in conclusion, we believe that torpedo chorioretinopathy fits best as a comprehensive nomenclature covering both concerns about the pathophysiologic origin and the location of the torpedo lesions. financial support and sponsorship none. conflicts of interest none. references 1. venkatesh r, jain k, pereira a, thirumalesh, yadav nk. torpedo retinopathy. j ophthalmic vis res 2020;15:187– 194. 2. raval v, rao s, sudana p, das t. torpedo maculopathy. j ophthalmic vis res 2020;15:113–115. 3. roseman rl, gass jd. solitary hypopigmented nevus of the retinal pigment epithelium in the macula. arch ophthalmol 1992;110:1762. 4. zhao s, overbeek pa. regulation of choroid development by the retinal pigment epithelium. mol vis 2001;2:277– 282. 5. nassar s, tarbett ak, browning dj. choroidal cavitary disorders. clin ophthalmol 2020;14:2609–2623. 6. papastefanou vp, vázquez-alfageme c, keane pa, sagoo ms. multimodality imaging of torpedo maculopathy with swept-source, en face optical coherence tomography and optical coherence tomography angiography. retin cases brief rep 2018;12:153–157. 606 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 letter toxic intraocular syndrome alfredo amigó, md, phd; paula martinez-sorribes ms instituto oftalmológico amigó, santa cruz de tenerife, spain j ophthalmic vis res 2022; 17 (1): 155–156 over the last three decades, several noninfectious postoperative inflammatory syndromes have been described: toxic anterior segment syndrome (tass),[1] fibrin syndrome, sterile endophthalmitis, and toxic posterior segment syndrome (tpss).[2, 3] all have a common toxic origin but none describe all the clinical forms in which toxicity can occur and there are cases of toxicity that do not fit into any of these syndromes. this descriptive limitation can lead to confusion and delay a diagnosis that is essential in the prevention of new cases of ocular toxicity. the toxic intraocular syndrome (tios) that we describe encompasses all forms of toxicity described, referring to any postoperative intraocular inflammation, due to a noninfectious substance, which can occur after any type of intraocular surgery, resulting in toxic damage to any segment of the eye. postoperative intraocular toxicity is an underdiagnosed and underreported entity, with a reported frequency ranging from 0.2%[4] to 2.0%,[6] higher than that of infectious endophthalmitis. the most frequent clinical manifestation of tios consists of an early and painless postoperative decrease in vision. the operated segment is usually the most affected, however, there are mixed forms with involvement of both segments,[6, 7] as well as paradoxical forms with inflammatory involvement of the segment opposite to the intervened segment.[8–10] when the anterior segment (as) is affected, the predominant sign is limbus-to-limbus corneal edema to a variable degree, which may be accompanied by iritis, fibrin bands, hypopyon, and/or pupillary paresis. tass is a form of tios in which the signs and surgery are limited to the as. when the posterior segment (ps) is involved, the signs are more polymorphic, the vitreous may be clear or with the signs of vitritis, the retina may be intact or be associated with hemorrhages, vasculitis, pigment epithelium lesions, and macular edema. occasionally, early papillary pallor with optic atrophy may appear. tpss is a form of tios in which after ps surgery the findings are limited to this segment. every substance involved in the surgical process has been reported as a cause of operative toxicity. those related to the cleaning of microcannulated instruments, enzymatic soaps, endotoxins, intraocular dissolutions, denatured viscoelastic, perfluorocarbons, silicone, are among many others. the most important differential diagnosis is infectious endophthalmitis from which tios tends to be differentiated by presenting as a cold and early postoperative inflammation, with decreased vision and no other symptoms. the absence of initial pain, hyperemia, lid edema, or swelling may help to differentiate tios from infectious endophthalmitis. cultures, if taken, will always be negative. the prognosis of tios will depend on the type of toxin, its concentration, and time of exposure, ranging from complete spontaneous resolution to irreversible loss of vision or loss of the eyeball. there is no specific treatment for tios with prevention being the best current treatment. suspecting toxicity, as a possible origin of any postoperative inflammation, is essential in the prevention of new cases given the frequent presentation of tios in the form of an outbreak in the following surgical sessions. financial support and sponsorship nil. © 2022 amigó et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 155 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10184&domain=pdf&date_stamp=2019-07-17 letter; amigó et al conflicts of interest there are no conflicts of interest. references 1. monson mc, mamalis n, olson rj. toxic anterior segment inflammation following cataract surgery. j cataract refract surg 1992;18:184–189. 2. charles s. toxic posterior segment syndrome due to reuse of cannulated tools. similarities to tass should be considered. retina today 2009;july/august:26–27. 3. american society of cataract and refractive surgery. tpss registry [internet]. fairfax, va: american society of cataract and refractive surgery. available from: https:// ascrs.org/tpss-registry 4. park cy, lee jk, chuck rs. toxic anterior segment syndrome-an updated review. bmc ophthalmol 2018;18:276–284. 5. hernandez-bogantes e, navas a, naranjo a, amescua g, graue-hernandez e, flynn jr h, et al. toxic anterior segment syndrome: a review. surv ophthalmol 2019;64:463–476. 6. nelson m, tennant mts, sivalingam a, regillo c, belmont j, martidis a. infectious and presumed noninfectious endophthalmitis after intravitreal triamcinolone acetonide injection. retina 2003;23:686–691. 7. ness t, feltgen n, agostini h, böhringer d, lubrich b. toxic vitritis outbreak after intravitreal injection. retina 2010;30:332–338. 8. andonegui j, jimenez-lasanta l, aliseda d, lameiro f. outbreak of toxic anterior segment syndrome after vitreous surgery. arch soc esp oftalmol 2009;84:403– 405. 9. moisseiev e, barak a. toxic anterior segment syndrome outbreak after vitrectomy and silicone oil injection. eur j ophthalmol 2012;22:803–807. 10. ugurbas sc, akova ya. toxic anterior segment syndrome presenting as isolated cystoid macular edema after removal of entrapped ophthalmic ointment. cutan ocul toxicol 2010;29:221–223. correspondence to: alfredo amigó, phd. instituto oftalmológico amigó, c/ bravo murillo 16, santa cruz de tenerife 38003, islas canarias, spain. email: amigo@ioamigo.com received 15-04-2020; accepted 22-02-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10184 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: amigó a, martinez-sorribes p. toxic intraocular syndrome. j ophthalmic vis res 2022;17:155–156. 156 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 https://ascrs.org/tpss-registry https://ascrs.org/tpss-registry https://knepublishing.com/index.php/jovr letter epidemiology of dry eye and its determinants among university students seyed saber sahih alnasab1, ms; amir asharlous2, phd; asgar doostdar2, ms; payam nabovati2, phd, abbasali yekta3, phd, ms; mehdi khabazkhoob4, phd 1noor research center for ophthalmic epidemiology, noor eye hospital, tehran, iran 2rehabilitation research center, department of optometry, school of rehabilitation sciences, iran university of medical sciences, tehran, iran 3department of optometry, mashhad university of medical sciences, mashhad, iran 4department of basic sciences, school of nursing and midwifery, shahid beheshti university of medical sciences, tehran, iran orcid: seyed saber sahih alnasab: https://orcid.org/0000-0001-5068-7371 j ophthalmic vis res 2022; 17 (3): 447–448 dear editor, dry eye syndrome (des) is defined as a multifactorial disease of the tears and ocular surface which is associated with symptoms of discomfort and visual disturbance, with potential damage to the ocular surface.[1] dry eye may cause several ocular and visual symptoms (including stinging or burning, excessive tearing, gritty sensation, episodes of blurred vision, and redness) negatively impacting the quality of life due to its extensive ocular consequences.[1] about 60% of the patients complain about decreased quality of life in their daily and leisurely activities.[2] university students comprise a young population that spends a significant amount of time on reading and working with the computer. the aim of this letter is to evaluate the prevalence of des and its determinants in a population of iranian university students. for this purpose, we carried correspondence to: asgar doostdar, ms. department of optometry, school of rehabilitation sciences, iran university of medical sciences, tehran 158754391, iran email: asgar_doostdar@yahoo.com received: 16-02-2021 accepted: 19-02-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i3.11586 out a cross-sectional study on 850 university students (407 male subjects) with a mean age of 22.06 ± 4 years. first, the subjects who met the inclusion criteria completed the persian version of the standard ocular surface disease index (osdi) questionnaire, and their sleep hours and duration of working with the computer as well as outdoor activities were recorded as monthly average. next, the subjects underwent an ocular surface examination using a slit lamp to assess their ocular surface health. then, the tear meniscus height (tmh) was measured and the schirmer’s test (without anesthesia), tear break-up time (tbut), and fluorescein eye stain were done. a wash-out period was considered between tests. all subjects were examined in one room with similar conditions. the overall prevalence of des was 16.36%. abnormal schirmer’s test ≤5, tbut ≤10, and tmh ≤0.2 mm, osdi ≥23, and fluorescein eye stain results were observed as 21.45%, 65.12%, 39.66%, 32.25%, and 35.44%, respectively. at least one this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: sahih alnasab ss, asharlous a, doostdar a, nabovati p, yekta a, khabazkhoob m. epidemiology of dry eye and its determinants among university students. j ophthalmic vis res 2022;17:447–448. © 2022 sahih alnasab et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 447 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i3.11586&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr letter; sahih alnasab et al symptom according to osdi (sensitivity to light, gritty sensation, painful or sore eyes, blurred vision, poor vision) was always present in 15.25% of the cases. the prevalence of des was 22.40% in female and 12.78% in male (odds ratio = 1.09, p = 0.032) students. there was no correlation between the prevalence of des and age (p = 0.629). the prevalence of des in different ethnic groups was not statistically significant (p = 0.094) and increased significantly with an increase in working with computers (p = 0.013). the prevalence of des had no correlation with sleep hours (p = 0.155) and duration of outdoor activity (p = 0.593). the prevalence of des was higher in iranian students compared to other similar studies, which could be due to geographical, lifestyle, climatic, and even ethnic differences.[3] while some studies[4,5] reported a direct correlation between the prevalence of dry eye and age, this study found no significant relationship between des prevalence and age, which could be due to the limited age range of the subjects. in this study, like most previous studies,[4, 5] the prevalence of des was significantly higher in women than men, which is probably due to the hormonal changes, especially estrogen-related changes in women.[6] this study revealed a significant correlation between hours of working on digital monitors per day and des, which was consistent with previous studies.[7]the reason for this finding could be lower blinking during working with digital gadgets and the presence of the wide width of the palpebral fissure when working with computers.[7] in summary, the results showed a higher prevalence of des in young students as compared to the general population, which is in line with previous studies in literature. female gender and increased computer working time are risk factors of des in university students. ethics approval the ethics committee of iran university of medical sciences approved the study protocol, which was conducted in accord with the tenets of the helsinki declaration. all participants signed a written informed consent (iran university of medical sciences ethics approval: 965879). financial support and sponsorship this project was supported by iran university of medical sciences. conflicts of interest none. references 1. craig jp, nichols kk, akpek ek, caffery b, dua hs, joo ck, et al. tfos dews ii definition and classification report. ocul surf 2017;15:276–283. 2. li m, gong l, chapin wj, zhu m. assessment of visionrelated quality of life in dry eye patients. invest ophthalmol vis sci 2012;53:5722–5727. 3. lu p, chen x, liu x, yu l, kang y, xie q, et al. dry eye syndrome in elderly tibetans at high altitude: a population-based study in china. cornea 2008;27:545– 551. 4. moss se, klein r, klein be. prevalence of and risk factors for dry eye syndrome. arch ophthalmol 2000;118:1264– 1268. 5. albietz jm. prevalence of dry eye subtypes in clinical optometry practice. optom vis sci 2000;77:357–363. 6. chia em, mitchell p, rochtchina e, lee aj, maroun r, wang jj. prevalence and associations of dry eye syndrome in an older population: the blue mountains eye study. clin exp ophthalmol 2003;31:229–232. 7. sullivan da, rocha em, aragona p, clayton ja, ding j, golebiowski b, et al. tfos dews ii sex, gender, and hormones report. ocul surf 2017;15:284–333. 448 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 letter what is the real cost of intraoperative floppy iris syndrome in cataract surgery? argyrios tzamalis, md, phd; chrysanthos d. christou, md; efthymia prousali, md; asimina mataftsi, md, phd; nikolaos ziakas, md, phd 2nd department of ophthalmology, aristotle university of thessaloniki, papageorgiou general hospital, thessaloniki, greece orcid: argyrios tzamalis: https://orcid.org/0000-0002-3172-8542 j ophthalmic vis res 2023; 18 (1): 138–140 dear editor, since its original description by chang and campbell in 2005, intraoperative floppy iris syndrome (ifis) has been widely established as one of the most challenging conditions for cataract surgeons.[1] numerous studies have been published proving that the appearance of ifis significantly increases the risk of intraoperative complications.[2] however, there is no report so far in the literature dealing with the economic impact of ifis in cataract surgery. we conducted a retrospective analysis of the medical and financial records of all cases that underwent phacoemulsification surgery in a tertiary-care ophthalmology department during year 2019. data regarding patient demographics, phacoemulsification metrics, surgical time, complications, and postoperative follow-ups were retrieved from the electronic patient records and the cost of all consumables charged in every correspondence to: argyrios tzamalis, md, phd, ma, febo. 2nd department of ophthalmology, aristotle university of thessaloniki, papageorgiou general hospital, thessaloniki, 56429 greece. e-mail: argyriostzamalis@yahoo.com received: 05-12-2021 accepted: 29-09-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i1.12735 case was recorded from the individual billing form that was automatically produced for every surgery. the surgical duration was recorded by an independent theatre nurse in each case. the timer was started upon the first incision and the endpoint was defined as the removal of the surgical drape. the study was performed according to the tenets of the declaration of helsinki after approval of the institutional review board. in total, 1294 cases of 1178 cataract patients (mean age = 73.8 ± 8.9 years), with (n = 48) or without (n = 1246) a recorded ifis of any severity, were identified and enrolled in a multivariate analysis. as per our departmental policy, the presence of ifis was defined and further classified as the intraoperative occurrence of any of the following three signs according to the grading system proposed by chang and campbell: progressive miosis; billowing of the iris; iris prolapse through incisions.[3] patients with one of these three clinical signs were designated as having ifis. the average cost of surgical consumables charged among all cataract operations was 362.1 ± 90.9 €, while the mean this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: tzamalis a, christou cd, prousali e, mataftsi a, ziakas n. what is the real cost of intraoperative floppy iris syndrome in cataract surgery?. j ophthalmic vis res 2023;18:138–140. 138 © 2023 tzamalis et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i1.12735&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr letter; tzamalis et al table 1. average cost of surgical consumables and surgical duration in all cataract surgeries along with respective comparison between cases with and without ifis. ifis (n = 48) non-ifis (n = 1246) p-value∗ cost of surgical consumables (euros €) 420.2 ± 146.6 359.9 ± 87.5 <0.0001 surgical time (min) 30.9 ± 23.2 21.4 ± 14.8 <0.0001 extra cost from surgical consumables per case (euros €) 60.3 extra cost from prolonged surgical time per case (euros €) 41.04 total extra cost per case (euros €) 101.34 ∗assessed with student’s t-test. ifis, intraoperative floppy iris syndrome table 2. average cost of surgical consumables and surgical duration in uneventful cataract surgeries along with respective comparison between cases with or without ifis. ifis (n = 39) non-ifis (n = 1199) p-value cost of surgical consumables (euros €) 384.2 ± 48.3 352.8 ± 47.1 0.0003 surgical time (minutes) 23.2 ± 11.6 16.7 ± 8.4 <0.0001 extra cost from surgical consumables per case (euros €) 31.4 extra cost from prolonged surgical time per case (euros €) 28.08 total extra cost per case (euros €) 59.48 assessed with student’s t-test. ifis, intraoperative floppy iris syndrome duration of surgery was 21.75 ± 15.1 min (′). no statistically significant differences in cost or surgical time were noted regarding age, gender, medical history, medication intake, or other ophthalmic conditions such as pseudoexfoliation, glaucoma, and cataract grading (p > 0.05). cases that developed ifis demonstrated a significantly higher cost of surgical consumables (costifis = 420.2 ± 146.6 € vs costnon-ifis = 359.9 ± 87.5 €, p < 0.0001) as well as a longer duration of surgery (timeifis = 30.9 ± 23.2′ vs timenon-ifis = 21.4 ± 14.8′, p < 0.0001) [table 1]. this difference remained significant even when excluding all complicated cases (4.32% in total; 18.75% in ifis cases) such as posterior capsular rupture, zonular dehiscence, nucleus drop, and iris trauma [table 2]. notably, no pupillary expansion devices were used in any of the cases included in the analysis. the increased cost in cases of ifis was mainly due to the use of additional consumables such as extra ovds, dyes, single-use instruments, as well as anterior vitrectomy in complicated cases. moreover, we attempted to assess the additional cost that the aforementioned longer duration of surgery had imposed in cases with ifis. the cost of operating time in cataract surgery has already been evaluated in several cost-effectiveness analyses, ranging from 0.56 to 2.36 €/min (average = 1.21) in european countries[3] and from 8.3 to 11.24 us dollars ($)/min in the united states.[4, 5] the cost per minute of surgical time was evaluated by the departmental accounting officers and found to be 4.32 €/min. it was calculated by dividing the total minutes of all surgeries into their non-supply cost (sum of salaries and wages of all hospital personnel included in cataract surgery) for the single fiscal year of 2019, based on previous reports.[4, 5] subsequently, the appearance of ifis imposed an extra cost of 28.08 € per patient as an average in non-complicated surgeries and 41.04 € per patient when all cases were considered. summing up increased consumables and increased duration resulted in a total extra cost of 59.48 € in uneventful cases and 101.34 € when complicated cases were also included [tables 1 & 2]. it is of note that the average surgical duration of phacoemulsification in this study was found to be somewhat longer than in other similar studies. journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 139 letter; tzamalis et al this may be attributed to the fact that our analysis also included cases performed by trainees, who, as expected, required more time to complete the surgery. however, the occurrence of ifis and the respective intraoperative complications rate did not yield any statistically significant difference between senior surgeons and trainees (p = 0.43 and p = 0.17, respectively). further limitations of this study include its retrospective nature that may have had an impact on our results. although an electronic record is automatically produced for each surgery, it is possible that some cases of mild ifis may have been ignored or misidentified and consequently, not recorded. moreover, our study included cases performed by surgeons of various experience levels, and, thus, differences in phacoemulsification techniques and consumables used may have induced some bias. however, all surgeons that participated in the study initially utilized the same phaco technique (divide & conquer) and device (centurion vision system, alcon). in conclusion, the appearance of ifis seems to have a substantial economic impact in cataract surgery as it increases the cost of surgical consumables and the time needed to complete the procedure, even in uneventful cases. cataract surgeons should be aware of cases prone to develop ifis and they are justified from a financial point of view to use all appropriate measures to prevent and manage floppy iris avoiding extra costs and devastating ocular complications. financial support and sponsorship none. conflicts of interest none. references 1. chang df, campbell jr. intraoperative floppy iris syndrome associated with tamsulosin. j cataract refract surg 2005;31:664–673. 2. enright jm, karacal h, tsai lm. floppy iris syndrome and cataract surgery. curr opin ophthalmol 2017;28:29–34. 3. chang df, campbell jr, colin j, schweitzer c, study surgeon group. prospective masked comparison of intraoperative floppy iris syndrome severity with tamsulosin versus alfuzosin. ophthalmology 2014;121:829–834. 4. fattore g, torbica a. cost and reimbursement of cataract surgery in europe: a cross-country comparison. health econ 2008;17:s71–s82. 5. hosler mr, scott iu, kunselman ar, wolford kr, oltra ez, murray wb. impact of resident participation in cataract surgery on operative time and cost. ophthalmology 2012;119:95–98. 6. taravella mj, davidson r, erlanger m, guiton g, gregory d. time and cost of teaching cataract surgery. j cataract refract surg 2014;40:212–216. 140 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 editorial thiolated chitosan-carboxymethyl dextran nanoparticles: improving intravitreal drug bioavailability for retinoblastoma lauren a dalvin, md department of ophthalmology, mayo clinic, rochester, minnesota, usa orcid: lauren a dalvin: http://orcid.org/0000-0001-9710-4284 j ophthalmic vis res 2022; 17 (1): 1–3 in the current issue of journal of ophthalmic and vision research (jovr), delrish et al discuss the use of modified nanoparticles for intravitreal drug delivery in a rat model of retinoblastoma.[1] retinoblastoma is the most common intraocular malignancy of childhood, with an incidence of 11.8 cases per million children aged 0–4 years in the us and with recent increase in incidence reported in europe.[2, 3] while developing countries often face more advanced disease and worse survival prognosis, retinoblastoma is considered curable, and mortality is rare in well-developed nations.[4] although the primary goal of retinoblastoma treatment is to protect the child’s life, secondary and tertiary goals of globe salvage and visual acuity preservation have become more achievable with treatment advances, particularly the combination of intra-arterial and intravitreal chemotherapy. with current standard of care therapy, globe salvage can be achieved even for the most advanced group e eyes in about 50% of cases.[5] delrish et al describe what may be the next frontier in intravitreal chemotherapy delivery, with improved drug bioavailability using thiolated chitosan-carboxymethyl dextran nanoparticles (cmd-tcs-nps). although intravitreal injection offers direct drug access to the vitreous cavity and retina, it can take several hours for drug to diffuse across the entire vitreous cavity.[6, 7] moreover, in vitro experiments show that drug dispersion in the vitreous cavity is driven by advective mass transport rather than molecular diffusion, relying on natural saccadic movements to distribute the drug.[8, 9] drug distribution may be especially challenging in more formed pediatric vitreous, and speed of dispersion could be important to achieve tumor control in the setting of drugs such as melphalan, which have a short halflife.[10] thus, improved bioavailability of intravitreal chemotherapy agents could decrease injection burden and retinal toxicity, improve overall tumor control rates, and improve globe salvage for retinoblastoma with vitreous seeding. chitosan is a semi-synthetic cationic polysaccharide produced by partial or complete deacetylation of the naturally occurring polymer chitin, which can be harvested from crustacean shells or fungal cell walls.[11, 12] chitosan is highly biocompatible, nontoxic, and mucoadhesive; has favorable enzymatic biodegradability, low immunogenicity, and inherent antibacterial properties; and can disrupt epithelial tight junctions to enhance permeability.[13] given these favorable properties, combined with easy accessibility, chitosan has become a popular candidate for pharmaceutical development, and the us food and drug administration has already approved several chitosan-containing products.[13] mucoadhesive polymers like chitosan contain numerous charged molecular groups that can form non-covalent bonds with mucin, allowing bioadhesion to mucosal surfaces.[13] numerous factors can influence mucoadhesion, including ph, concentration, ionic strength, temperature, incubation time, surface charges, molecular weight, degree of deacetylation, and hydrophilicity, among others.[13] chitosan, in particular, has ph-dependent mucoadhesion, and certain modifications have been employed to improve the polymer’s mucoadhesive properties at physiologic ph relevant to ophthalmic drug delivery. trimethyl chitosan has been extensively studied and has © 2022 dalvin. this is an open access article distributed under the creative commons attribution license | published by knowledge e 1 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10163&domain=pdf&date_stamp=2019-07-17 editorial; dalvin strong mucoadhesive properties due to its high cationic charge. thiolated chitosan derivatives have also been studied, which have free thiol groups to form covalent bonds with cysteinerich subdomains of mucus glycoproteins.[13] compared to unmodified chitosan, thiolated chitosan has several advantages, including 6to 100-fold improved mucoadhesion, 1.6to 3fold enhanced permeability, and in situ gelling properties at physiologic ph.[14, 15] together, these properties improve drug residence time and increase bioavailability. thiolated derivatives require sulfhydryl groups to react, limiting use to cysteine-rich tissues,[13] but secreted protein acidic and rich in cysteine (sparc) has demonstrated localization to muller and ganglion cells in the retina, making the retina a reasonable target tissue.[16] in ophthalmology, initial interests aligned with the use of chitosan to improve bioavailability of topically administered medications, but there is a growing body of literature on possible intravitreal applications.[11] previous studies have demonstrated that nanoparticle surface properties are a key factor determining distribution in the retina and vitreous following intravitreal injection, and although glycosylated chitosan polymers maintained a positive charge and could reach the retina, these particles were not able to penetrate the internal limiting membrane.[17] thiolated derivatives, on the other hand, may have improved penetration due to their interaction with cysteine-rich sparc localized to muller cells. in this issue of jovr, delrish et al specifically compare the biodistribution of thiolated versus methylated chitosan-carboxymethyl dextran nanoparticles (cmd-tcs-nps vs cmd-tmcnps) following an intravitreal injection in a rat model of retinoblastoma.[1] the authors found improved uptake of cmd-tcs-nps in retinoblastoma cell culture, and in the rat model, 24 hr after injection; the cmd-tcs-nps demonstrated diffusion throughout the vitreous cavity and retinal penetration, while the cmdtmc-nps were immobilized in the vitreous.[1] the authors attributed these differences to improved bioadhesion of thiolated chitosan and prohibitive effects on vitreous diffusion of the greater positive charge of methylated chitosan (zeta potential +29mv) compared with the thiolated counterparts (+11mv).[1] although this was a small study with 10 rats, delrish et al concluded that surface charge is a key factor determining vitreous diffusion and retinal penetration for chitosan-derived intraocular drug-delivery mechanisms, and they propose future use of thiolated chitosan derivatives for intravitreal chemotherapy delivery aimed at retinoblastoma treatment.[1] of relevance to the article at hand, delrish et al recently reported improved efficacy and tumor control using thiolated chitosan nanoparticles containing topotecan compared to free topotecan in a rat model of retinoblastoma.[18] these early studies indicate feasibility and potential benefit of the application of thiolated chitosan derivatives in retinoblastoma treatment. although further study is required to investigate the safety and reproducibility prior to human trials, there are potential exciting applications of these biocompatible nanoparticles to improve treatment outcomes for retinoblastoma in the future, and this technology could also be applied to a wide variety of other retinal diseases which have traditionally been managed with intravitreal injections. financial support and sponsorship this publication was supported by grant no. p30 ca015083 from the national cancer institute. its contents are solely the responsibility of the authors and do not necessarily represent the official view of the national institutes of health. conflicts of interest there are no conflicts of interest. references 1. delrish e, ghasemi f, jabbarvand m, lashay a, atyabi f, soleimani m, et al. biodistribution of cy5-labeled thiolated and methylated chitosan-carboxymethyl dextran nanoparticles in an animal model of retinoblastoma. j opthalmic vis res 2022;17:58–68. 2. broaddus e, topham a, singh ad. incidence of retinoblastoma in the usa: 1975–2004. br j ophthalmol 2009;93:21–23. 3. stacey aw, bowman r, foster a, kivelä tt, munier fl, cassoux n, et al. incidence of retinoblastoma has increased: results from 40 european countries. ophthalmology 2021;128:1369–1371. 4. fabian id, abdallah e, abdullahi su, abdulqader ra, boubacar sa, ademola-popoola ds, et al. global retinoblastoma presentation and analysis by national income level. jama oncol 2020;6:685–695. 5. dalvin la, kumari m, essuman va, shipa ss, anconalezama d, lucio-alvarez ja, et al. primary intra-arterial chemotherapy for retinoblastoma in the intravitreal 2 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 editorial; dalvin chemotherapy era: five years of experience. ocul oncol pathol 2019;5:139–146. 6. agrahari v, mandal a, agrahari v, trinh hm, joseph m, ray a, et al. a comprehensive insight on ocular pharmacokinetics. drug deliv transl res 2016;6:735–754. 7. willekens k, reyns g, diricx m, vanhove m, noppen b, coudyzer w, et al. intravitreally injected fluid dispersion: importance of injection technique. invest ophthalmol vis sci 2017;58:1434–1441. 8. bonfiglio a, repetto r, siggers jh, stocchino a. investigation of the motion of a viscous fluid in the vitreous cavity induced by eye rotations and implications for drug delivery. phys med biol 2013;58:1969–1982. 9. modareszadeh a, abouali o, ghaffarieh a, ahmadi g. saccade movements effect on the intravitreal drug delivery in vitreous substitutes: a numerical study. biomech model mechanobiol 2013;12:281–290. 10. buitrago e, winter u, williams g, asprea m, chantada g, schaiquevich p. pharmacokinetics of melphalan after intravitreal injection in a rabbit model. j ocul pharmacol ther 2016;32:230–235. 11. ilochonwu bc, urtti a, hennink we, vermonden t. intravitreal hydrogels for sustained release of therapeutic proteins. j control release 2020;326:419–441. 12. mohammed ma, syeda jtm, wasan km, wasan ek. an overview of chitosan nanoparticles and its application in non-parenteral drug delivery. pharmaceutics 2017;9: 53. 13. zamboulis a, nanaki s, michailidou g, koumentakou i, lazaridou m, ainali nm, et al. chitosan and its derivatives for ocular delivery formulations: recent advances and developments. polymers 2020;12:1519. 14. liu d, li j, pan h, he f, liu z, wu q, et al. potential advantages of a novel chitosan-n-acetylcysteine surface modified nanostructured lipid carrier on the performance of ophthalmic delivery of curcumin. sci rep 2016;6: 28796. 15. bernkop-schnürch a, hornof m, guggi d. thiolated chitosans. eur j pharm biopharm 2004;57:9–17. 16. gilbert re, cox aj, kelly dj, wilkinson-berka jl, sage eh, jerums g, et al. localization of secreted protein acidic and rich in cysteine (sparc) expression in the rat eye. connect tissue res 1999;40:295–303. 17. koo h, moon h, han h, na jh, huh ms, park jh, et al. the movement of self-assembled amphiphilic polymeric nanoparticles in the vitreous and retina after intravitreal injection. biomaterials 2012;33:3485–3493. 18. delrish e, jabbarvand m, ghassemi f, amoli fa, atyabi f, lashay a, et al. efficacy of topotecan nanoparticles for intravitreal chemotherapy of retinoblastoma. exp eye res 2021;204:108423. correspondence to: lauren a dalvin, md. department of ophthalmology, mayo clinic, 200 1st st. sw, rochester, mn 55905, usa. email: dalvin.lauren@mayo.edu received: 28-08-2021 accepted: 12-11-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10163 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: dalvin la. thiolated chitosan-carboxymethyl dextran nanoparticles: improving intravitreal drug bioavailability for retinoblastoma. j ophthalmic vis res 2022;17:1–3. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 3 https://knepublishing.com/index.php/jovr editorial optical coherence tomography angiography: considerations regarding diagnostic parameters touka banaee, md department of ophthalmology and visual sciences, university of texas medical branch, galveston, texas, usa orcid: touka banaee: https://orcid.org/0000-0003-0312-487x j ophthalmic vis res 2022; 17 (3): 313–316 in this issue of journal of ophthalmic and vision research (jovr), two articles are published addressing changes in optical coherence tomography angiography (octa) parameters after acute changes in ocular perfusion pressure (opp). the first article by ashraf khorasani et al[1] is a study on changes in vascular density (vd) of the macula and optic nerve after an acute rise in intraocular pressure (iop), and the second paper is a case report by mirshahi et al[2] describing octa changes in acute systemic hypertension. studies on hemodynamics of the retina and optic nerve microvasculature is an old but still open area of research. with technologies evolving over time, a variety of diagnostic modalities have been used for detection and documentation of blood flow and vascular diameter, including fluorescein angiography, color doppler ultrasonography, doppler velocimetry, laser speckle flowgraphy, and doppler oct.[3–7] octa is a relatively new technology used for extraction of blood vessels on oct images by detecting movement of blood. this technology has been extensively used to evaluate circulation in different retinal vascular layers (superficial vascular plexus, svp and deep vascular plexus, dvp) and correspondence to: touka banaee , md. department of ophthalmology and visual sciences, university of texas medical branch, 300 university blvd., galveston, texas 77555-1106, usa. e-mail: tkbanaee@gmail.com received: 27-05-2022 accepted: 31-05-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i3.11567 choriocapillaris. evaluation of the peripapillary vascular network and optic disc vessels with octa has also become an active area of research in glaucoma. while the retina and optic nerve provide a unique target for in vivo evaluation of microvasculature, results of studies on this intricate system may not always corroborate with each other. this is due to the complex interplay between blood pressure, intraocular pressure, and retinal/optic nerve autoregulation, where subtle differences in study parameters can affect the response of blood vessels and impact the study results. the difference between ocular arterial pressure and intraocular pressure (iop) determines the ocular perfusion pressure (opp). as the ocular arterial pressure cannot be easily measured, brachial artery pressure has been used as its surrogate in most studies, although some corrections may be needed in the upright position.[8] autoregulation of blood flow is another factor that affects hemodynamics of ocular tissues, especially the retina and optic nerve, and needs to be considered in these types of studies. as autoregulation may need some time to fully take place, timing of measurements after a stimulus/event also seems to be important.[9] this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: banaee t. optical coherence tomography angiography: considerations regarding diagnostic parameters. j ophthalmic vis res 2022;17:313–316. © 2022 banaee . this is an open access article distributed under the creative commons attribution license | published by knowledge e 313 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i3.11567&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr editorial; banaee concerning the wide availability of octa machines, this modality has been extensively used to evaluate changes in retinal/optic nerve circulation under different conditions. there are two quantitative measures in octa that are mostly used to describe changes in retinal and optic nerve vasculature: flux and vd. flux is the intensity of flow signals while vd is the proportion of flow signals on the en-face octa image.[10] although not as accurate as methods that directly measure blood flow and vessel diameter such as laser speckle flowgraphy and doppler oct, vd in octa can be considered a useful clinical parameter to reflect changes in blood flow and vascular diameter.[11] when using this parameter to study ocular hemodynamics, some important points need to be kept in mind: octa detects blood flow above a certain threshold; above that threshold, the octa signal cannot reflect flow rate. hence, subtle changes in blood flow may not be detected by vd. at the same time, it is very sensitive to changes in small vessels diameter, even below its resolution.[11] vd also depends on the total length and diameter of vessels and will be affected by loss of small vessels in diseases such as diabetic retinopathy and retinal vein occlusions. vd is the sum of flow signals in an image and includes flow from all vessel diameters in the specified area, therefore the study area will define which vessel sizes are included. for example, vd in the parafoveal area will be a better representative of small vessels as compared to vd of a whole 3×3 or 6×6 octa picture. vd is affected by multiple parameters in addition to blood flow, including low signal strength. so, considering media quality (especially presence of cataracts) and excluding low signal strength images is crucial to ensure validity of data.[12] previous studies have used various methods to increase iop in human eyes, including dark room prone positioning in eyes prone to angle closure[13] and application of a suction cup.[6] there are also studies investigating changes in vasculature during iop rise after laser iridoplasty or intravitreal injections.[9, 14] the response of the vascular structure may be different with acute rises in iop such as when a suction cup is applied, or after intravitreal injections as compared to slower increases in iop as happens after laser iridoplasty or dark room prone positioning.[13] therefore, results of different studies may not be readily comparable. the article by ashraf khorasani et al is an interventional study, evaluating the effect of acute iop rise by application of a suction cup on vd in the dvp and svp, the peripapillary region and inside the disc in 12 healthy individuals and 12 patients with mild-moderate npdr. they achieved a mean iop elevation of 13.93 ± 3.41 mmhg and found that vd in both svp and dcp decreased in healthy individuals, while in diabetic patients there was a significant reduction of vd only in the dvp. in both groups, vd inside the disc was decreased significantly, while changes in the radial peripapillary capillaries was not significant. the two groups had different baseline octa parameters, which can be explained by the difference in age and the presence of diabetes with its associated effect on ocular vessels.[15, 16] as the dvp is considered to be mostly on the venous side of the retinal circulation,[17] it may be more affected by changes in intraocular pressure. on the other hand, older patients with diabetes may have stiffer arteries that are less affected by changes in perfusion pressure; hence the svp, which is closer to the arteries, may be less affected by a moderate amount of iop rise. in this study, changes in vd in response to iop rise was not different between the two groups. these results should be interpreted reservedly, as the study may have been underpowered to detect such a difference because of small sample size. another factor to consider is that stress during placement of the suction cup may cause blood pressure to rise and may partially mitigate the effect of iop rise by increasing ocular prefusion pressure. also, the degree of blood pressure rise may differ based on age and presence of diabetes. although blood pressure has been reported to be steady in healthy subjects during application of a suction cup in a prior study,[6] it would have been informative if blood pressure readings at the time of iop rise were available. the different response of the optic disc vessels, originating from choroidal arteries, and the peripapillary radial vessels which originate from the central retinal artery, to acute iop rise can be a confirmation of the previously known fact of different pressures within the retinal and choroidal systems.[18] prior studies have not reported a different response by radial peripapillary capillaries 314 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 editorial; banaee and vessels inside the disc after an acute rise in iop by intraocular injections.[9, 19] as stated before, the complex interplay of bp, iop, retinal/optic disc autoregulation and the timing of the measurements after iop rise affects the results of studies and makes standardization and comparisons difficult. although a small study with its limitations, this paper adds to the body of the evidence in this field and the authors should be congratulated for their work. the second article by mirshahi et al is a case report describing octa findings in acute hypertensive retinopathy. acute hypertensive retinopathy can cause various tissue reactions alongside the increase in ocular perfusion pressure: vascular contraction due to autoregulation, vascular leakage, and thrombosis.[20] although an increase in bp increases opp, autoregulation counteracts it and with vascular leakage and thrombosis happening in acute cases, there may be a decrease in blood flow and ischemia in octa contrary to what is expected from an increase in opp. ischemia is especially evident in the b scan octa images of this case as parafoveal acute middle maculopathy (hyper-reflectivity of the outer plexiform layer), coinciding with locations where capillary loss is visible in the svp and dvp. depth-enhanced visualization of blood vessels, a characteristic of octa, has enabled better visualization of retinal capillary loss. better visualization of ischemia in the choriocapillaris in comparison to fa can be attributed to the longer wavelength of infrared light used in octa that penetrates better through the rpe as compared to the blue light of fluorescein angiography (fa). these two articles remind us of the fact that in biological systems, the response to stimuli may not follow gross physical rules and need to be interpreted taking into account variability of intricate biological responses which may not always be simple to elucidate. references 1. ashraf khorasani m, garcia ga, anvari p, habibi a, ghasemizadeh s, ghasemi falavarjani k. optical coherence tomography angiography findings after acute intraocular pressure elevation in patients with diabetes mellitus versus healthy subjects. j ophthalmic vis res 2022;17: 360–367. 2. mirshahi a, roohipour r, karkhaneh r, rajabi mb, vahedian z, bazvand f. optical coherence tomography angiography findings in malignant hypertensive retinopathy. j ophthalmic vis res 2022;17:432–436. 3. nagel e, vilser w. autoregulative behavior of retinal arteries and veins during changes of perfusion pressure: a clinical study. graefes arch clin exp ophthalmol 2004;242:13–17. 4. joos km, kay md, pillunat le, harris a, gendron ek, feuer wj, et al. effect of acute intraocular pressure changes on short posterior ciliary artery haemodynamics. br j ophthalmol 1999;83:33–38. 5. schmetterer l, garhofer g. how can blood flow be measured? surv ophthalmol 2007;52:s134–s138. 6. puchner s, schmidl d, ginner l, augustin m, leitgeb r, szegedi s, et al. changes in retinal blood flow in response to an experimental increase in iop in healthy participants as assessed with doppler optical coherence tomography. invest ophthalmol vis sci 2020;61:33. 7. wei x, balne pk, meissner ke, barathi va, schmetterer l, agrawal r. assessment of flow dynamics in retinal and choroidal microcirculation. surv ophthalmol 2018;63:646–664. 8. caprioli j, coleman al, blood flow in glaucoma discussion. blood pressure, perfusion pressure, and glaucoma. am j ophthalmol 2010;149:704–712. 9. wen jc, chen cl, rezaei ka, chao jr, vemulakonda a, luttrell i, et al. optic nerve head perfusion before and after intravitreal antivascular growth factor injections using optical coherence tomography-based microangiography. j glaucoma 2019;28:188–193. 10. abdolahi f, zhou x, ashimatey bs, chu z, jiang x, wang rk, et al. optical coherence tomography angiographyderived flux as a measure of physiological changes in retinal capillary blood flow. transl vis sci technol 2021;10:5. 11. hormel tt, jia y, jian y, hwang ts, bailey st, pennesi me, et al. plexus-specific retinal vascular anatomy and pathologies as seen by projection-resolved optical coherence tomographic angiography. prog retin eye res 2021;80:100878. 12. brücher vc, storp jj, eter n, alnawaiseh m. optical coherence tomography angiography-derived flow density: a review of the influencing factors. graefes arch clin exp ophthalmol 2020;258:701–710. 13. zhang q, jonas jb, wang q, chan sy, xu l, wei wb, et al. optical coherence tomography angiography vessel density changes after acute intraocular pressure elevation. sci rep 2018;8:6024. 14. wang x, chen j, kong x, sun x. immediate changes in peripapillary retinal vasculature after intraocular pressure elevation – an optical coherence tomography angiography study. curr eye res 2020;45:749–756. 15. dimitrova g, chihara e, takahashi h, amano h, okazaki k. quantitative retinal optical coherence tomography angiography in patients with diabetes without diabetic retinopathy. invest ophthalmol vis sci 2017;58:190–196. 16. park ck, lee k, kim ew, kim s, lee sy, kim cy, et al. effect of systemic blood pressure on optical coherence tomography angiography in glaucoma patients. eye 2021;35:1967–1976. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 315 editorial; banaee 17. au a, sarraf d. vascular anatomy and its relationship to pathology in retinoschisis. eye 2019;33:693–694. 18. mäepea o. pressures in the anterior ciliary arteries, choroidal veins and choriocapillaris. exp eye res 1992;54:731–736. 19. barash a, chui typ, garcia p, rosen rb. acute macular and peripapillary angiographic changes with intravitreal injections. retina 2020;40:648–656. 20. cheung cy, biousse v, keane pa, schiffrin el, wong ty. hypertensive eye disease. nat rev dis primers 2022;8:14. 316 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 surgical technique trabeculectomy augmented with limited deep sclerectomy and cyclodialysis with use of scleral tissue as a spacer tanuj dada, md; jyoti shakrawal, md; priyanka ramesh, md; anin sethi, md glaucoma research facility & clinical services, dr. rajendra prasad centre for ophthalmic sciences, all india institute of medical sciences, new delhi, india orcid: tanuj dada: https://orcid.org/0000-0002-3111-396x abstract trabeculectomy remains the most commonly performed surgery for medically uncontrolled glaucoma. its success in primary open angle glaucoma is approximately 82% in the initial year after surgery and 64% at the end of five years. lower success rates have been found in secondary glaucomas like neovascular glucoma, uvietic glaucoma, post-traumatic glaucoma, and for repeat surgeries. to illustrate improvement of the efficacy of trabeculectomy, enhancement with cyclodialysis has been introduced. this involves the creation of a cyclodialysis cleft in a controlled manner to allow additional suprachoroidal drainage of the aqueous. cyclodialysis is the result of the separation of the longitudinal ciliary muscle fibers from the scleral spur, which creates an additional pathway for aqueous humor drainage. however, such a cleft often closes on its own due to associated inflammation caused by the filtration surgery. deep sclerectomy is a non-penetrating surgery that involves dissection of a scleral patch and excision of a block of scleral tissue, retaining a thin membrane for aqueous drainage. in this study, we introduce a novel surgical technique of combining trabeculectomy with a limited deep sclerectomy and a cyclodialysis in two pseudophakic patients who developed secondary glaucoma after vitreo-retinal surgery with silicone oil insertion. in this technique the excised scleral tissue obtained after deep sclerectomy was utilized as a spacer to maintain the patency of the cyclodialysis cleft. keywords: refractory glaucoma’s; cyclodialysis augmented trabeculectomy; deep sclerectomy. j ophthalmic vis res 2022; 17 (4): 596–600 correspondence to: tanuj dada, md. glaucoma research and clinical facility, dr. rajendra prasad centre for ophthalmic sciences, all india institute of medical sciences, ansari nagar, new delhi 110029, india. email: tanujdada@gmail.com received: 17-03-2021 accepted: 23-01-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i4.12342 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: dada t, shakrawal j, ramesh p. trabeculectomy augmented with limited deep sclerectomy and cyclodialysis with use of scleral tissue as a spacer. j ophthalmic vis res 2022;17:596–600. 596 © 2022 dada et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i4.12342&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr cyclodialysis augmented trabeculectomy ; dada et al introduction case 1 a 50-year-old female was referred with high intraocular pressure (iop) after vitreoretinal (vr) surgery. the patient had a rhegmatogenous retinal detachment in the left eye (le) for which she had undergone vitrectomy with silicone oil injection one year before and subsequently, after three months, underwent phacoemulsification with silicone oil removal. on examination, she had a visual acuity of 6/60 in the le and 6/6 in the right eye (re). le iop was 38 mmhg and 16 mmhg in re. he was started on oral acetazolamide and maximal topical medications, which further reduced the iop to 26 mmhg in le. the patient was pseudophakic with extensive peripheral anterior synechiae on gonioscopy. the le fundus showed a cup-discratio of 0.8 with attached retina and an epimacular membrane. case 2 a 38-year-old male presented with a history of le vr surgery with silicone oil insertion for retinal detachment eight months back. the patient developed raised iop after a few months. silicone oil removal was done five months after the vr surgery. on examination, visual acuity was 6/24 in the le and 6/6 in the re. iop in the le was 44 mmhg while using maximum topical medication and 14 mmhg in the re with no medications. on the slit-lamp examination, a few silicone oil droplets were present on the surface of the iris. gonioscopy revealed emulsified silicone oil in the superior angle. the posterior segment showed an optic disc with a cup-disc-ratio of 0.9 in the le. there was no significant cupping in examination of the re fundus. since the iop was not controlled by maximal medications and because of advanced glaucomatous optic neuropathy, we planned surgical management for both patients. considering the higher failure rate of conventional trabeculectomy with mitomycin-c (mmc) in post vr surgery glaucoma, presence of 360 encircling band, and non-affordability precluding the use of glaucoma drainage devices, we planned to augment the conventional trabeculectomy surgery with deep sclerectomy and cyclodialysis. surgical technique the surgical procedure was performed under peribulbar anesthesia, with aseptic precautions, after receiving written informed consent from the patient. 0.01 ml of 0.01% mmc was injected in the sub-conjunctival space superiorly. a fornixbased conjunctival flap was dissected, hemostasis was achieved using bipolar electric cautery and the surgical site was thoroughly washed with the balanced salt solution. a partial-thickness scleral flap measuring 4 × 4 mm, with its base at the limbus, was dissected using a 2.3 mm crescent blade (alcon, fort worth, usa). the remaining scleral bed was dissected further and a 3 × 3 mm block of scleral tissue was excised, thereby creating a deep sclerectomy [figures 1a & 1b]. the excised block of scleral tissue was carefully preserved in balanced salt solution. dissection of the deep scleral pocket was stopped at the scleral spur and no attempt was made to de-roof the canal of schlemm. a full-thickness incision measuring around 2 mm was made 2 mm behind the scleral spur to expose the ciliary body. using a cyclodialysis spatula, a controlled cyclodialysis was created [figure 1c]. the trabeculectomy ostium measuring 2× 1 mm was created at the base of the scleral flap and the silicone oil droplets from the anterior chamber were removed by using coaxial irrigation-aspiration. retained silicone oil droplets in the anterior chamber even after silicone oil removal can go up in the superior angle and block trabecular meshwork. therefore, this should be removed at the time of trabeculectomy, as retained droplets might block the trabeculectomy ostium. a peripheral iridectomy was made using vanna’s scissors. the preserved block of scleral tissue was rolled into a cylindrical configuration and inserted as a spacer in the cyclodialysis cleft [figure 1d] followed by suturing it to the overlying sclera with 10–0 nylon monofilament suture (aurolab nylon sutures, double arm, aurolab, india). the partialthickness scleral flap was closed using two fixed 10-0 nylon sutures. conjunctiva was closed with 8-0 vicryl sutures (ethicon; johnson & johnson, aurangabad, india) at the limbus [video 1]. postoperatively, the patient was started on topical antibiotics, topical steroids, and cycloplegics. patient was followed up on day one, week one, and at months one, two, and six, postoperatively. postoperative anterior segment journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 597 cyclodialysis augmented trabeculectomy ; dada et al ocular coherence tomography (asoct) and ultrasound biomicroscopy (ubm) were performed. results in case 1, on the first postoperative day, iop in the le was 10 mmhg with a diffuse, moderately elevated, and mildly vascular bleb with no leak (height2 extend2 vascularity2 seidel’s0),[4] with a formed anterior chamber. visual acuity was maintained at 6/60. six months after the surgery, iop was 12 mmhg with a well-functioning bleb [figure 2a]. asoct and ubm showed the patent cyclodialysis cleft with an elevated and microcystic bleb [figures 2b and 2c]. in the second case, iop dropped to 6 mmhg in the le on day one postoperatively. visual acuity improved to 6/18. there was a diffuse, moderately elevated, and moderately vascularized bleb with no leak (height2 extend2 vascularity3 seidel’s0)[4] [figure 2d]. iop was maintained at 10 mmhg, six months after the surgery. discussion trabeculectomy is a full-thickness filtering procedure performed widely for glaucomas with uncontrolled iop on maximum tolerable medical therapy. it has an efficacy of 75–100% in primary glaucomas.[1, 5] the main reasons for the failure of trabeculectomy include fibrosis in the sub-conjunctival space, scarring, and fibrosis of the tenon’s tissue, scleral fibrosis, and closure of the ostium.[6] trabeculectomy performed for secondary types of glaucoma such as neovascular glaucoma, post uveitic glaucoma, post penetrating keratoplasty glaucoma, aphakic glaucoma, and post silicone oil-induced glaucoma have a high risk of failure.[5] cyclodialysis combined with trabeculectomy was reported earlier to have achieved better outcomes. it involves the planned creation of a cyclodialysis cleft, creating an outflow tract to drain aqueous into the suprachoroidal space, along with the conventional outflow into the subconjunctival space and the schlemm’s canal.[7] sihota et al described ab-externo cyclodialysis along with trabeculectomy in post penetrating keratoplasty glaucoma with good outcomes.[7] they performed the procedure in 45 eyes out of which 30 eyes had prior failed trabeculectomy surgery.[8] skalicky et al reported good long-term outcomes with no major complications in 55 eyes over a follow-up of 11.2 years.[7] the cyclodialysis cleft created can undergo spontaneous closure with time, and to prevent this, many spacer materials such as healon (abbott medical optics, abbott laboratories inc., abbott park, il), high molecular weight hyaluronic acid, ologen collagen matrix, hydroxyethyl methacrylate capillary strip, and teflon tube implants have been used.[2] deep sclerectomy was described initially as a nonpenetrating glaucoma surgery. it involves dissecting the scleral tissue retaining a thin membrane for aqueous to drain. the aqueous collects in the scleral lake and there is drainage through the intrascleral route. when combined with trabeculectomy, it allows for drainage via the subconjunctival as well as the intrascleral route. this also takes care of the extend of the bleb, thereby limiting the complications like overhanging blebs, thereby limiting the complications associated with a large bleb.[3, 9] sharifipour et al also described a modified deep sclerectomy (mds) technique which included exposure of ciliary body after deep sclerectomy to promote suprachoroidal flow. they found similar iop reductions with mds as of with trabeculectomy.[10] in our technique, we have combined trabeculectomy with a limited deep sclerectomy and have used the excised scleral tissue block as a spacer to keep the cyclodialysis cleft open, preventing closure and fibrosis. the deep sclerectomy also creates a scleral lake to augment the drainage along with trabeculectomy and cyclodialysis. the use of patient’s scleral tissue eliminates the need for synthetic materials that are more expensive and less available. ologen implants have been previously used for this procedure,[11] however, the implant is expensive and degrades after a few months. our patients have shown promising results with no sight threatening complications during the short-term follow-up with the visualization of the cyclodialysis cleft as revealed on asoct and ubm. the utilization of deep sclerectomy tissue block as a stent to maintain the cyclodialysis cleft along with conventional trabeculectomy yields promising short-term results for iop reduction in post vitrectomy glaucoma patients. this technique allows aqueous drainage via multiple pathways, thus increasing the efficacy of trabeculectomy. this unique technique might be a possible substitute for 598 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 cyclodialysis augmented trabeculectomy ; dada et al figure 1. (a) intraoperative image showing the creation of deep crater after making partial thickness scleral flap. (b) dissection of the scleral block with vanna’s scissor (green arrow) and creating a deeper crater (yellow arrow), scleral block after dissection (white arrow). (c) full-thickness incision made for cyclodialysis and cleft is created by using cyclodialysis spatula. (d) scleral block is inserted in the cyclodialysis cleft (blue arrow). figure 2. (a) clinical photograph of case 1, six months postoperatively showing a diffuse, moderately elevated and mild vascular bleb. (b) asoct showing elevated cystic bleb with cyclodialysis cleft (yellow arrow). (c) ubm showing raised bleb with patent cyclodialysis cleft (red arrow). (d) six months postoperative clinical picture of case 2 showing a diffuse, moderately elevated, and vascular bleb. journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 599 cyclodialysis augmented trabeculectomy ; dada et al secondary glaucomas like neovascular glucoma, uvietic glaucoma, post-traumatic glaucoma, post vr surgery glaucoma, and for repeat surgeries. further studies with a longer follow-up are required to look for its long-term success rate. financial support and sponsorship the authors did not receive any financial support from any public or private sources. conflicts of interest the authors have no financial or proprietary interest in a product, method, or material described herein. no conflicting relationship exists for any author. references 1. lim sh, cha sc. long-term outcomes of mitomycin-c trabeculectomy in exfoliative glaucoma versus primary open-angle glaucoma. j glaucoma 2017;26:303–310. 2. dada t, sharma r, sinha g, angmo d, temkar s. cyclodialysis-enhanced trabeculectomy with triple ologen implantation. eur j ophthalmol 2016;26:95–97. 3. roy s, mermoud a. deep sclerectomy. dev ophthalmol 2017;59:36–42. 4. cantor lb, mantravadi a, wudunn d, swamynathan k, cortes a. morphologic classification of filtering blebs after glaucoma filtration surgery: the indiana bleb appearance grading scale. j glaucoma 2003;12:266–271. 5. agarwal hc, sharma tk, sihota r, gulati v. cumulative effect of risk factors on short-term surgical success of mitomycin augmented trabeculectomy. j postgrad med 2002;48:92–96. 6. mithal s, mathur ag, gupta a, kumar s. failure in glaucoma surgery and its management. indian j ophthalmol 1988;36:67–70. 7. skalicky se, lew hr. surgical outcomes of combined trabeculectomy-cyclodialysis for glaucoma. j glaucoma 2015;24:37–44. 8. sihota r, srinivasan g, gupta v. ab-externo cyclodialysis enhanced trabeculectomy for intractable post-penetrating keratoplasty glaucoma. eye 2010;24:976–979. 9. feusier m, roy s, mermoud a. deep sclerectomy combined with trabeculectomy in pediatric glaucoma. ophthalmology 2009;116:30–38. 10. sharifipour f, yazdani s, asadi m, saki a, nouri-mahdavi k. modified deep sclerectomy for surgical treatment of glaucoma. j ophthalmic vis res 2019;14:144–150. 11. senthil s, rao hl, babu jg, mandal ak, garudadri cs. comparison of outcomes of trabeculectomy with mitomycin c vs. ologen implant in primary glaucoma. indian j ophthalmol 2013;61:338–342. 600 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 case report tubercular osteomyelitis of the orbit presenting as periorbital cellulitis shruti bhattacharya, mbbs; usha k raina, md; shantanu k gupta, ms; manisha mishra, ms; varun saini, ms brajesh kumar, mbbs department of ophthalmology, guru nanak eye centre, maulana azad medical college, new delhi, india abstract purpose: osteomyelitis of the orbital bones presenting as an orbital cellulitis is a rare form of extrapulmonary tuberculosis (tb). we report a rare case of tubercular osteomyelitis of the orbital bones presenting as a periorbital cellulitis. case report: a seven-year-old female child presented to our tertiary eye care center with swelling involving the right eyelids and the right cheek for two months. she had been provisionally diagnosed elsewhere as pre-septal cellulitis and had been given oral antibiotics. we clinically diagnosed her as orbital cellulitis, but her non-responsiveness to intravenous antibiotics prompted us to get a contrast enhanced computed tomography (cect) of the orbit and paranasal sinuses, which was suggestive of tubercular etiology. however, the patient had no foci for tb elsewhere. we used a relatively new, but rapid test, called cartridge-based nucleic acid amplification test (cbnaat) on the pus aspirate which was positive for tb. thereafter, the patient was started on anti-tubercular treatment to which she responded wonderfully. conclusion: a high index of suspicion should be kept for tb infection in cases of orbital cellulitis with unusual clinical behavior in an endemic region such as india. keywords: orbital tuberculosis; periorbital cellulitis; tubercular osteomyelitis j ophthalmic vis res 2022; 17 (1): 146–149 introduction tuberculosis (tb) is a major cause of morbidity and mortality in developing nations. it is a multisystem infectious disease caused by mycobacterium tb. tb may be pulmonary or extrapulmonary correspondence to: manisha mishra, ms. guru nanak eye centre, maulana azad medical college campus, bahadur shah zafar marg, new delhi 110002, india. e-mail: manisha.mishra4266@gmail.com received 28-08-2019; accepted 22-05-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10181 depending on whether lungs are the primary site of infection or not. ocular tuberculosis (otb) is a manifestation of extrapulmonary tb. it is considered rare even in endemic areas. otb may be primary or secondary. when the eye is the initial portal of entry of the bacteria, it is considered a primary ocular tb. in secondary ocular tb, the involvement of the eye is due to spread from hematogenous route or this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: bhattacharya s, raina uk, gupta sk, mishra m, saini v, kumar b. tubercular osteomyelitis of the orbit presenting as periorbital cellulitis . j ophthalmic vis res 2022;17:146–149. 146 © 2022 bhattacharya et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10181&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr tubercular orbital osteomyelitis ; bhattacharya et al from adjacent structures.[1] ocular tb may have myriad presentations depending upon the site of infection as well as the severity. however, uveal involvement is more common because of its high blood supply.[2, 3] orbital tb is more commonly seen in children with a female predisposition. it is insidious in onset and is usually unilateral.[4] it may present as unilateral proptosis/draining sinus tract/orbital swelling/lid swelling/radiographic features of bony destruction. we present a rare case of tubercular osteomyelitis of the orbital bones masquerading as periorbital cellulitis. case report a seven-year-old female child presented to our tertiary eye care center with tender swelling involving the right eye and the right cheek for two months. this was not associated with decrease in vision, discharge, photophobia, or fever. on examination, the swelling involved the right upper and lower eyelid along with the right upper cheek; it was firm in consistency, tender and warm to touch, erythematous, with negative fluctuation tests, and no pus points or discharging sinuses (as shown in figures 1a & 1b). visual acuity was 6/6 in both eyes. anterior as well as posterior segment examination of the eye were unremarkable. despite the extensive edema, extraocular movements were full and free. direct and consensual light reflexes were normal. a note was made of the enlarged submandibular lymph nodes. these were 2 × 2 cm, non-tender, nonconglomerated, firm in consistency, not fixed to the overlying skin. the overlying skin was not red and non-tender. the child was otherwise afebrile and had no other systemic complaints. furthermore, the patient was being treated with oral antibiotics (no records brought) at a peripheral center for the past one month before presentation to our center, with a steady increase in the size of the swelling. history elicited from the attendants showed their noncompliance with the prescribed treatment. thereafter, the child was admitted for a course of intravenous antibiotics, with the provisional diagnosis being orbital cellulitis. however, poor response to intravenous antibiotics even after one week prompted us to investigate further. a contrast enhanced computerized tomography of the orbit and the paranasal sinuses (pns) was ordered which showed a peripherally enhancing collection in the anterolateral aspect of the right maxillary sinus and zygomatic arch, extending superiorly along the lateral aspect of right orbit, showing lytic erosive changes, along with periosteal thickening and bony sequestration in the zygoma (axial scan shown in figure 3a & 3b). these radiographic features were suggestive of tb. the child had no history of fever, night sweats, no previous history of tb, and no history of contact with tb. in addition, the swelling was not like a typical tubercular cold abscess and the lymph nodes were not matted nor fixed to the skin. but in view of high endemicity of tb in our country, it was still kept on top of our differentials. except for a raised erythrocyte sedimentation rate (esr), the complete blood count and liver function tests were unremarkable. the tuberculin sensitivity test (tst) showed 20 mm after 48 hr however this is nonspecific. fine needle aspiration cytology (fnac) was done from the swollen submandibular lymph nodes – it showed necrotic changes but no granuloma or acid fast bacilli (afb). sputum as well as gastric aspirate microscopy for afb showed no evidence of afb. antigravity aspirate of the swelling was done with a 26-gauge needle, under local anesthesia. around 1 ml of the watery yellowish aspirate was then sent for gram stain, bacterial and fungal cultures, and a relatively new test – the cartridgebased nucleic acid amplification test (cbnaat), also known as the genexpert test. cbnaat turned out to be positive, thus confirming the diagnosis of primary tubercular osteomyelitis of the right maxilla; the bacterial and gram stain reports were negative, thus ruling out secondary superinfection. the child was put on a fourdrug anti-tubercular treatment (isoniazid [10 mg/kg] rifampicin [15 mg/kg], ethambutol [20 mg/kg], and pyrazinamide [35 mg/kg]) and responded well to the treatment, by complete shrinkage of the swelling within six weeks [figures 2a & 2b]. discussion tuberculosis (tb) is a major health problem in developing countries. however, even in endemic areas, orbital tb is a rare entity. orbital tb can be diagnosed using the following criteria: (1) journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 147 tubercular orbital osteomyelitis ; bhattacharya et al clinical/radiological or histological evidence of tb from the orbital lesion associated with evidence of tb elsewhere, (2) demonstration of afb in the orbital lesion, (3) isolation of mycobacteria in culture from biopsied tissue, and (4) demonstration of mycobacterial infection by doing a pcr on the biopsied tissue.[5] orbital tb has been clinically classified into five categories: classical periostitis, orbital tuberculoma with no bony destruction, orbital tb with evidence of bony destruction (not classified as classical periostitis), orbital tb as a result of spread from paranasal sinuses and dacryoadenitis. patients with classical periostitis present with chronic ulceration or discharging sinus in the periorbital region. there may or may not be evidence of bony erosion or sclerosis radiographically. orbital tuberculoma presents with palpable mass, proptosis, or diplopia. when radiologic evidence of bony destruction, osteolytic changes, or erosion is seen, it is classified as orbital tb with bony destruction. maxillary sinus is the most commonly involved sinus from which tb can spread to orbit. such patients usually present with proptosis and dystopia of the globe. patients with tubercular dacryoadenitis present with a mass in the lacrimal region and regional lymphadenopathy.[5, 6] osteomyelitis of tubercular origin involving the orbital bones is rare. mandible is the most common craniofacial bone affected by tb.[7] this condition is usually secondary to a primary tubercular lesion elsewhere, such as the lungs and the abdomen. however, primary involvement of these bones have also been reported. our patient presented with swelling involving the right periorbital region extending up to the right cheek. she was given a course of antibiotics to which no response was seen and the patient was investigated for other etiologies including tb. our differentials at this time were local cellulitis, neoplasia, pseudotumor, easophillic granuloma, and tb, and she was investigated for all of these diagnoses. incision and drainage of the swelling was not done because an incision and drainage (i&d) would lead to a persistently discharging sinus in case it was tubercular in etiology. there was no histopathology evidence of tb but radiologically the lesion was suggestive of tb which was done a week later after no response to intravenous antibiotics. we waited for a week before imaging was done because the history of treatment given to her was very uncompliant and no intravenous antibiotics were given before the patient presented to us. we did keep in mind other conditions causing lytic changes in the orbit such as neoplastic, inflammatory, and rare causes like eosinophilic granulomas. our diagnosis of tb was confirmed by cbnaat test done on the sample from the orbital lesion. thereafter, the patient was started on antitubercular drugs. we should keep a high index of suspicion for orbital tb in cases like ours especially in endemic areas such as india. the patient should be investigated for the same. however, the diagnosis is often challenging in cases of extrapulmonary tb as the number of tb bacilli is often low in these sites.[8] although the demonstration of afb in culture is considered the gold standard for diagnosis, it may take up to six to eight weeks, thus delaying the treatment.[9] molecular diagnostics such as nucleic acid amplification test play an important role in cases of extrapulmonary tb. a new breakthrough has been the cbnaat, also known as the genexpert test. this test not only detects mycobacterium dna but also reveals whether it is sensitive to rifampicin or not, thereby identifying multidrug-resistant tb cases. the main advantage of cbnaat is the speed and accuracy with which it works. it has been shown to have comparable results with culture (which may take up to six to eight weeks). however, it has its own set of flaws such as high cost, need for a stable electricity supply, replenishment of the cartridges every 18 months, and a stable temperature ceiling.[10] interferon gamma release assays can also be used as an aid to diagnosis. these tests are based on the production of interferon gamma by t cells specific to antigens of tubercular bacilli. however, they are less sensitive for detection of latent tb infection.[1] radiological features of orbital tb include destruction of bone, most commonly the frontal and sphenoidal bones. there may or may not be associated bony sclerosis, inflammation, abscess formation which may extend to infratemporal fossa. lacrimal gland involvement may also be seen. involvement of lateral wall is usually suggestive of hematogenous route of infection while involvement 148 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 tubercular orbital osteomyelitis ; bhattacharya et al of medial wall is indicative of spread from adjoining paranasal sinuses. there may be associated preseptal thickening.[11] treatment of tubercular osteomyelitis is mainly done using anti-tubercular drugs. surgery is indicated in cases with extensive destruction, presence of secondary infection, and intracranial involvement. our patient was managed medically by anti-tubercular treatment. to conclude, although orbital tb is rare, it should still be kept in mind while seeing patients with orbital lesions in an endemic country, and new tests such as cbnaat should be used more frequently because of increased sensitivity and rapid diagnosis. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. shakrachi fi. ocular tuberculosis: current perspective. clin ophthalmol 2015;9:2223–2227. 2. helm cj, holland gn. ocular tuberculosis. surv ophthalmol 1993;38:229–256. 3. varma d, anand s, reddy ar, das a, watson jp, currie dc, et al. tuberculosis: an under-diagnosed aetiological agent in uveitis with an effective treatment. eye 2006;20:1068– 1073. 4. sen dk. tuberculosis of the orbit and lacrimal gland: a clinical study of 14 cases. j pediatr ophthalmol strabismus 1980;17:232–238. 5. mittala r, sharma s, rath s, barik mr, tripathy d. orbital tuberculosis: clinicopathological correlation and diagnosis using pcr in formalin-fixed tissues. orbit 2017;36:264– 272. 6. madge sn, prabhakaran vc, shome d, kim u, honavar s, selva d. orbital tuberculosis: a review of the literature. orbit 2008;27:267–277. 7. sethi a, sethi d, agarwal ak, nigam s, gupta a. tubercular and chronic pyogenic osteomyelitis of cranio-facial bones: a retrospective analysis. j laryngol otol 2008;122:799– 804. 8. lee jy. diagnosis and treatment of extra pulmonary tuberculosis. tuberc respir dis 2015;78:47–55. 9. singh kg, tandon s, nagdeote st, sharma k, kumar a. role of cb-naat in diagnosing mycobacterial tuberculosis and rifampicin resistance in tubercular peripheral lymphadenopathy. int j med res rev 2017;5:242–246. 10. sahana ks, prabhu as, saldanha prm. usage of cartridge based nucleic acid amplification test (cbnaat/genexpert) test as diagnostic modality for pediatric tuberculosis; case series from mangalore, south india. j clin tuberc other mycobact dis 2017;11:7–9. 11. khalil m, lindley s, matouk e. tuberculosis of the orbit. ophthalmology 1985;92:1624–1627. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 149 original article clinical evaluation of the 3nethra aberro handheld autorefractometer selvamani perumal1, ms; surya venkatramanan1, btech; venkatramanan rj1, mba; jayanthi t2, phd; jai adithya2, btech; anjaly abraham2, btech; henna cherian2, btech 1forus health pvt ltd, banashankari, bangalore, karnataka, india 2department of biomedical engineering, srm institute of science and technology, kattankulathur, chennai, tamil nadu, india orcid: selvamani perumal: https://orcid.org/0000-0002-4579-6693 venkatramanan rj: https://orcid.org/0000-0003-3674-8515 abstract purpose: to evaluate the 3nethra aberro auto refractometer device as an alternative tool for quick and reliable measurement of refractive errors and to compare it with the gold standard subjective refractive error measurement. methods: refractive errors were measured using both subjective refraction and the 3nethra aberro handheld autorefractometer. the refractive measurements were converted into equivalent vector notations of spherical equivalent and jackson cross-cylinder measurements j0 & j45. the resultant power vectors were compared with subjective measurements. results: this clinical study comprised 60 subjects (22 male and 38 female; with a mean age of 34 ± 16 years). data, when compared with the subjective refraction measurements, resulted in 90% of power vectors values in both left and right eyes being the same in the 3nethra aberro handheld autorefractometer and the subjective measurement. the refractive error measurements also had an agreement of 70% and 90% when the range of diopter was between ±0.25 and ±0.5d, respectively. when the bland-altman’s plot analysis was performed, about 98% of data lied within the ±2 standard deviation variation. an average correlation between the two methods of error measurement was 0.74, and the paired t-test showed p > 0.05 for all the power vectors except for the spherical equivalent in the right eye. conclusion: the 90% agreement between the error measurements done by two methods indicates that the 3nethra aberro handheld autorefractometer can function as an alternative for the time-consuming subjective refractive error measurement. keywords: aberro autorefractometer; non-mydriatic; pupil diameter; refractive index; subjective refractive error; vision; wavefront technology j ophthalmic vis res 2022; 17 (4): 536–542 536 © 2022 perumal et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i4.12314&domain=pdf&date_stamp=2019-07-17 3nethra aberro-autorefractometer ; perumal et al introduction visual impairment due to uncorrected refractive errors may lead to serious consequences. in a survey conducted in 2004, the world health organization (who) reported that globally 153 million people above the age of five years were visually impaired due to uncorrected refractive errors, of whom 8 million eventually experienced blindness.[1] this report emphasizes the importance of correcting refractive errors. the report also highlights that the reason for uncorrected refractive error is the lack of screening. the gold standard clinical method available for correcting refractive errors is subjective refraction (sr) measurement. the routine procedure of sr is time-consuming and also entirely dependent on the patient’s ability to read the snellen chart in conjunction with the skill level of the operator and hence cannot be applicable for mass screening. techniques involving the use of auto refractometers, which are portable and allow measurement under non-cycloplegia conditions, are considered to be an alternative for sr. however, the auto refractometer seems unreliable for higher-order aberrations.[2, 3] the auto refractometer measures the overall refractive index of the eye over a small region of the pupil. hence, autorefractometer measurements seems to have more deviation from the sr measurements.[4, 5] recently, the 3nethra aberro handheld autorefractometers (ahar), which work based on the shack-hartmann wavefront technology have been introduced. the aberration is reconstructed using the zernike polynomial of the reflected light pattern and is a preferred technique for measuring refractive errors in lasik surgery. it is observed that the vision will be almost back to normal after wavefront-guided lasik surgery due to the ability to precisely measure the refractive errors.[6, 7] the accuracy of the technique when measuring refractive errors correspondence to: venkatramanan rj, mba. forus health pvt ltd, banashankari 560070, bangalore, india. email: rjv.ramanan@forushealth.com received: 22-06-2021 accepted: 21-03-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i4.12314 in both highand low-order aberrations along with the quick results that are produced has familiarized the use of this option when performing visual examinations.[8, 9] as a consequence, the aim of the study is to propound the use of ahar measurement as a crucial tool for measuring refractive errors in mass screening. methods the device referred to as 3nethra ahar was used in the study. the 3nethra ahar is a device which works based on shack-hartmann wavefront sensing technology. some of the technical specifications of the device include the following: the spherical measurement range is from –14d to +14d and the cylindrical measurement range is from –7d to 0d both in increments of 0.25d; the axis measurement ranges from 0 to 180 degrees. in addition, the minimum pupil diameter that can be measured using the device is about 2.5 mm. it also has a fast measurement time of fewer than 5 sec per eye. the subjects for the study were selected randomly from the outpatient unit in the department of ophthalmology of a private hospital. informed consent was obtained from all the participants included in the study. our inclusion criteria were all subjects from age 5 to 60 years with refractive errors. the clinical exclusion for the study were people with acute cataract, severe eye infections, and those who underwent surgeries to extract cataracts or for any refractive correction. a total of 60 subjects were included in the study, 22 male and 38 female with a mean age of 34 ± 16 years. the patients were seated comfortably and asked to focus on the target at 6 m. the refractometry measurement was performed under non-cycloplegic conditions using the digital handheld 3nethra ahar. the sphere, cylinder, and cylindrical axis measurements were taken for each patient. all the measurements were carried out in the same room with uniform illumination for both the right and left eyes. the pupil diameter was also measured using the same device. this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: perumal s, venkatramanan s, rj v, t j, adithya j, abraham a. clinical evaluation of the 3nethra aberro handheld autorefractometer. j ophthalmic vis res 2022;17:536– 542. journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 537 https://knepublishing.com/index.php/jovr 3nethra aberro-autorefractometer ; perumal et al table 1. comparison of ahar and sr measurements. sl. no right eye left eye power vectors spe m j0 j45 spe m j0 j45 less than sr 11 1 1 12 2 0 equal to sr 46 59 58 47 57 60 greater than sr 3 0 1 1 1 0 ahar, aberro handheld autorefractometers; sr, subjective refraction; spe, spherical equivalent figure 1. the bland-altman plots for comparing the sr and ahar observations in the right and left eyes for spe. 95% limits of the agreement are indicated by the upper and lower dashed line, and the mean is indicated by a solid line. the customary clinical sr measurements were performed using a trained optometrist (who was also masked from the ahar measurements) with a usual set of lenses and the placement of the snellen visual acuity chart at 20 ft (6 m). based on their visual acuity, the prescription was made. results the evaluations were performed under noncycloplegic conditions for both the 3nethra ahar and sr readings. all the power measurements obtained using both methods, sr and 3nethra ahar, were converted into power vector notations spherical equivalent (spe m) and vertical and oblique cylindrical vectors (j0 and j45) using the method proposed by thibos et al.[10, 11] the power vector notations facilitate statistical analysis to perform an algebraic operation on the eye’s refractive index in an orthogonal 3-d base. the conversion was done for both sr and 3nethra ahar measurements as follows: spe m = sphere + cylinder/2 j0 = –(cylinder/2) × cos (2 x-axis) j45 = –(cylinder/2) × sin (2 x-axis), 538 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 3nethra aberro-autorefractometer ; perumal et al table 2. agreement of the ahar with sr power vector errors in both eyes. categories right eye agreement with sr left eye agreement with sr spe m (%) j0 (%) j45 (%) spe m (%) j0 (%) j45 (%) <0.25 42 83 85 53 80 90 <0.50 80 98 95 77 93 100 sr, subjective refraction; spe, spherical equivalent table 3. agreement of the ahar with sr errors in both eyes (compound representation). right eye agreement with sr left eye agreement with sr sphere (%) cylinder (%) axis (%) sphere (%) cylinder (%) axis (%) 73 (<0.25) 78 83 72 78 77 85 (<0.50) 88 87 88 87 80 ahar, aberro handheld autorefractometers; sr, subjective refraction where the sphere, cylinder, and axis measurements were obtained from the sr and ahar measurements. the descriptive statistical analysis was performed after the conversion. as indicated in table 1 in the right eye, 6% of eyes had an ahar reading less than the sr, 90.6% of the eyes had the same value in both ahar and sr, and 1.6% of the eyes had a greater value than sr. replicating the calculation in the left eye, 6.4% of the eyes had an ahar value less than the sr, 90.9% eyes had the same value in both ahar and sr, and about 0.5% of eyes resulted with greater values than the sr. table 2 illustrates the agreement between the two methods based on the diopter of error measured. table 3 indicates the same in compound numbers. as indicated, in the range of ±0.25d, there was about 70% agreement between the two methods in the right and 74% in the left eyes. correspondingly in the range of ±0.5d, the agreement between the ahar and sr measurements were 91% and 90% in the right and left eyes, respectively. the comparison of the mean and standard deviation of the measurements observed from the two methods was analyzed using blandaltman plots. figure 1 depicts the blandaltman plots for the three power vectors. it again shows the agreement between the sr and ahar measurements. visual analysis reveals that the majority of the readings were within the ±2 standard deviation range and consistently scattered around the mean value. correlation the ahar measurements are taken with ±0.25d accuracy while the sr measurement is made with a resolution of ±0.5d considering the eye accommodation. the correlation and paired t-test were performed on the measurements. figure 2 shows the regression plots for the three measurements (spe m, j0, and j45). the statistical analysis of the observations is indicated in table 4. the average correlation of 0.72 is achieved between the power vectors at 0.25d for both right and left eyes as indicated in table 2. the p-value being greater than 0.05 in the compared power vectors indicates that the errors are similar, not rejecting the null hypothesis. hence the power vectors are the same in both methods. the non-agreement of the errors in spe m in the left eye might be due to the ±0.25d margin for error by the device in 3nethra ahar, but it is not considered in sr. all statistical significance was set at 0.05, and the analysis was done using microsoft excel 2010. discussion numerous related studies have been done on the applicability of using autorefractometers versus sr journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 539 3nethra aberro-autorefractometer ; perumal et al figure 2. the correlation of the three power vectors in both the eyes. table 4. statistical analysis of the power vector errors in sr and 3nethra ahar. power vector device correlation between ahar & sr paired t-test p-value right eye left eye right eye left eye spe m sr 0.96 0.95 p > 0.05 p < 0.05 ahar j0 sr 0.85 0.95 p > 0.05 p > 0.05 ahar j45 sr 0.85 0.95 p > 0.05 p > 0.05 ahar ahar, aberro handheld autorefractometers; sr, subjective refraction; spe, spherical equivalent in assessing refractive errors, and the authors have agreed to the more reliable performance of ar measurements as compared to sr. in a study on 708 participants by nicholas et al, ar was mostly preferred by patients rather than by the visual acuity results. the authors also suggest that using ar is advantageous in rural health centers which can be used by minimally trained technicians.[12] samanth et al highlight the superior performance of autorefractometers in the study conducted using a nidek opd scan iii.[13] in the clinical evaluation of the l80 auto refractometer, einat et al conclude that an autorefractometer is a reliable tool for optometric practices.[14] as an advancement to the technology of the autorefractometers, the wavefront technology is efficient in creating the reconstruction of the zernike polynomial pattern in both highand low-order aberrations for individual patients.[15, 16] numerous related studies have been done on the applicability of using autorefractometers versus sr in assessing refractive errors, and the authors have agreed to the more reliable performance of ar measurements as compared to sr. in a study on 540 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 3nethra aberro-autorefractometer ; perumal et al 708 participants by nicholas et al, ar was mostly preferred by patients rather than by the visual acuity results. the authors also suggest that using ar is advantageous in rural health centers which can be used by minimally trained technicians.[12] samanth et al highlight the superior performance of autorefractometers in the study conducted using a nidek opd scan iii.[13] in the clinical evaluation of the l80 auto refractometer, einat et al conclude that an autorefractometer is a reliable tool for optometric practices.[14] the agreement of the 3nethra ahar measurement with the sr in 90% of the eyes validates the use of the device for direct prescription after assessment. the results suggest that the 3nethra ahar show good agreement with the sr error measurements. the 3nethra ahar refractive errors measured can be used for direct prescription ordering in cases where the sr may be time-consuming. the 3nethra ahar is also able to provide the measurement of pupil diameters along with the refractive errors. the functionality of this autorefractometer supports the diagnosis of pathologies related to pupillary muscles. with varying illumination, the functions of pupillary diameters’ relationship can be studied. the 3nethra ahar measurements allow for the ease of repeated measurements as compared to sr under non-cycloplegic conditions. the use of 3nethra ahar measurements is practical when assessing children who tend to be restless while being examined. the rapid assessment characteristics of the 3nethra ahar may enable the technology for use in mass screening and replacing the sr measurements for refractive errors. financial support and sponsorship none. conflicts of interest none declared. references 1. resnikoff s, pascolini d, mariotti sp, pokharel gp. global magnitude of visual impairment caused by uncorrected refractive errors in 2004. bull world health organ 2008;86:63–70. 2. bao j, le r, wu j, shen y, lu f, he jc. higherorder wavefront aberrations for populations of young emmetropes and myopes. j optom 2009;2:51–58. 3. bennett jr, stalboerger gm, hodge do, schornack mm. comparison of refractive assessment by wavefront aberrometry, autorefraction, and subjective refraction. j optom 2015;8:109–115. 4. lebow ka, campbell ce. a comparison of a traditional and wavefront autorefraction. optom vis sci 2014;91:1191–1198. 5. salmon to, van de pol c. evaluation of a clinical aberrometer for lower-order accuracy and repeatability, higher-order repeatability, and instrument myopia. optometry 2005;76:461–472. 6. khan ms, humayun s, fawad a, ishaq m, arzoo s, mashhadi f. effect of wavefront optimized lasik on higher order aberrations in myopic patients. pak j med sci 2015;31:1223–12236. 7. wei z, jianfeng l, funian l, zhile w. study on wave front fitting using zernike polynomials. ot 2005;31:675– 678. 8. liang j. wavefront technology for vision and ophthalmology. aberration-free refractive surgery. berlin, heidelberg: springer; 2004. p. 25–47. 9. bruce as, catania lj. clinical applications of wavefront refraction. optom vis sci 2014;91:1278–1286. 10. harris wf. the jackson cross-cylinder. part 1: properties. afr vision eye health 2007;66:41–55. 11. thibos ln, wheeler w, horner d. power vectors: an application of fourier analysis to the description and statistical analysis of refractive error. optom vis sci 1997;74:367–375. 12. durr nj, dave sr, lim d, joseph s, ravilla td, lage e. quality of eyeglass prescriptions from a low-cost wavefront autorefractor evaluated in rural india: results of a 708-participant field study. bmj open ophthalmol 2019;4:e000225. 13. mcginnigle s, naroo sa, eperjesi f. evaluation of the auto-refraction function of the nidek opd-scan iii. clin exp optom 2014;97:160–163. 14. shneor e, millodot m, avraham o, amar s, gordon-shaag a. clinical evaluation of the l80 autorefractometer. clin exp optom 2012;95:66–71. 15. mello gr, rocha km, santhiago mr, smadja d, krueger rr. applications of wavefront technology. j cataract refract surg 2012;38:1671–1683. journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 541 3nethra aberro-autorefractometer ; perumal et al 16. maeda n. wavefront technology in ophthalmology. curr opin ophthalmol 2001;12:294–299. 17. durr nj, dave sr, vera-diaz fa, lim d, dorronsoro c, marcos s, et al. design and clinical evaluation of a handheld wavefront autorefractor. optom vis sci 2015;92:1140–1147. 18. rubio m, hernández cs, seco e, perez-merino p, casares i, dave sr, et al. validation of an affordable handheld wavefront autorefractor. optom vis sci 2019;96:726–732. 542 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 original article effect of fasting on contrast sensitivity in healthy males zarife ekici gok, md; abuzer gunduz, md; cem cankaya, md inonu university school of medicine, department of ophthalmology, malatya, turkey orcid: zarife ekici gok: https://orcid.org/0000-0002-9250-9618 cem cankaya: https://orcid.org/0000-0002-7716-0438 abstract purpose: to evaluate the effect of fasting on contrast sensitivity (cs) in healthy male individuals during the month of ramadan. methods: this study included 45 healthy male individuals, aged between 20 and 40 years, working in the same environment. functional acuity contrast testing (f.a.c.t) was performed using the optec 6500 vision testing system. measurements taken during a state of satiety one week before ramadan were compared with those taken a minimum of 12 hours after the start of fasting in the first and fourth weeks of ramadan. results: contrast sensitivity (cs) was increased at the spatial frequency of three cycles per degree (cpd) at the end of the first week of ramadan in comparison to the cs measured before ramadan (𝑃 = 0.03). the mean cs values were increased at the spatial frequencies of 3 and 12 cpd at the end of the last week of ramadan in comparison to the mean values measured before ramadan (𝑃 = 0.01 for both). conclusion: although we found statistically significant increases in cs at certain frequencies, we can conclude that ramadan fasting has no negative effects on cs. keywords: contrast sensitivity; fasting; ramadan fasting j ophthalmic vis res 2019; 14 (3): 315–320 introduction ramadan is a holy month in the islamic calendar during which muslims avoid certain behaviors, such as eating and drinking, from sunrise to sunset due to their religious beliefs.[1, 2] correspondence to: cem cankaya, md. inonu university school of medicine, department of ophthalmology, turgut ozal medical center, battalgazi-malatya 44040, turkey. e-mail: cem_cankaya@yahoo.com received: 26-01-2018 accepted: 02-12-2018 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i3.4789 the contrast sensitivity (cs) test measures a patient’s ability to perceive large, medium-sized, and small symbols under various contrast conditions. the test examines the finer details of vision that cannot be measured with a visual acuity test and can also detect the visual losses that cannot be detected with the snellen test. typically, the test is used to investigate visual function and early signs of eye disorders.[3–5] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: gok ze, gunduz a, cankaya c. effect of fasting on contrast sensitivity in healthy males. j ophthalmic vis res 2019;14:315–320 @ 2019 j  o  v r | published by knowledge e 315 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i3.4789&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr fasting and contrast sensitivity; gok et al the majority of the studies investigating the effects of religious fasting on ocular parameters are related to anterior segment parameters, glaucoma, and tear film stability. theoretically, the restriction of fluid intake during the day may lead to the deterioration of tear film stability, and the shrinkage of the anterior chamber structures, including the lens and cornea. it is known that anterior chamber depth, refractive status of the eye, corneal curvature, as well as the tear film layer can be affected by dehydration.[6–10] to the best of our knowledge, there are no studies fully investigating the effect of ramadan fasting on cs in the literature, and therefore, in the current study, we aimed to address this gap in knowledge. methods this prospective study was performed at the department of ophthalmology in the inonu university medical faculty on 45 healthy, male volunteers aged between 20 and 40 years who were working in the same environment and fasting for ramadan between 27 june and 27 july in the summer of 2014. females were excluded from the study as the menstrual cycle leads to disruption in ramadan fasting. all participants gave informed and signed consent before the study, and the tenets of the declaration of helsinki were followed. ethics approval was obtained from the malatya ethics committee. a full ophthalmologic examination was conducted by the same ophthalmologist in all cases before ramadan. corrected and uncorrected visual acuity was evaluated with the snellen chart. all cases underwent biomicroscopic examinations, intraocular pressure (iop) measurements using the goldmann applanation tonometer, and fundus examinations. cases that had best corrected visual acuity (bcva) scores of 20/20 in both eyes and had no ocular or systemic pathology were included in the study. all cases were first informed about the cs test (grating test), which was then performed after a full ophthalmologic examination. this test, together with refraction and visual acuity tests, were performed right before ramadan and at the end of the first and fourth weeks of ramadan. baseline measurements were obtained in a state of satiety (between 3 and 5 pm) a week before ramadan. measurements taken after the start of ramadan fasting were obtained 12 to 14 hours after the cases began fasting. the mean duration of ramadan fasting was 16.5 hours during the year in which we were performing the study. contrast sensitivity measurement spatial contrast was evaluated with the fact (functional acuity contrast test, stereo optical co., chicago, il, usa) panel. this panel includes five spatial frequencies (1.5, 3, 6, 12, and 18 cycles per degree [cpd]) of nine sinusoidal grating patches. the contrast of the grating patch decreases logarithmically from left to right. test results were presented in log10 units of cs (logcs). statistical analyses for statistical analyses of the data, the spss software for windows, version 17.0 (statistical package for social sciences) was used. mean, standard deviation, minimum, and maximum values were calculated for each parameter and as the variables were not normally distributed, the non-parametric wilcoxon signed-rank test was used for comparison purposes. p-value < 0.05 was considered as statistically significant. results the mean age was 28.75 ± 8.42 years (range, 20 39 years) and the bcva was 20/20 in both eyes of all cases. biomicroscopic and fundus examinations were bilaterally normal and iop measurements were within normal limits in all cases. of the total 45 cases, 4.4% had emmetropia, 20% had hyperopia (range of +0.25 to +2.00 d), 68.8% had myopia (range of –3.00 to –0.25 d), and 6.6% had astigmatism (range of –2.00 to –0.25 d). the mean spherical equivalent was –0.22 ± 0.58 d. the bcva was 20/20 bilaterally when measured before ramadan and in the first and fourth weeks of ramadan. no statistically significant changes were observed in terms of refractive errors and visual acuity (p > 0.05). after measurements were taken at five spatial frequencies, the mean values equivalent to each grating, based on spatial frequencies, were recorded [table 1]. 316 j  o  v r volume 14, issue 3, july–september 2019 fasting and contrast sensitivity; gok et al table 1. the contrast values equivalent to each grating according to spatial frequency spatial frequency (cpd) 1st level 2nd level 3rd level 4th level 5th level 6th level 7th level 8th level 9th level a (1.5) 7 9 13 18 25 36 50 71 100 b (3) 10 15 20 29 40 57 80 114 160 c (6) 12 16 23 33 45 64 90 128 180 d (12) 8 11 15 22 30 43 60 85 120 e (18) 4 6 8 12 17 23 33 46 65 cpd, cycles per degree figure 1. comparison of the mean contrast sensitivity (cs) measurements. the cs was increased at the spatial frequency of three cpd at the end of the first week of ramadan in comparison to the value recorded before ramadan (p = 0.03). the mean cs values were increased at spatial frequencies of 3 and 12 cpd at the end of the last week of ramadan in comparison to before ramadan (p = 0.01 for both). no statistically significant differences were observed in cs values at other spatial frequencies [figure 1, tables 2 and 3]. although there was an increase in cs measurement values conducted at all spatial frequencies during the first and fourth weeks of ramadan, none of these were statistically significant (p > 0.05); [table 4]. discussion our findings show that cs was increased at the spatial frequency of three cpd at the end of the first week of ramadan in comparison to cs measured before ramadan. in addition, the mean cs values were increased at the spatial frequencies of 3 and 12 cpd at the end of the last week of ramadan compared to the values measured before ramadan. we found statistically significant alterations at certain spatial frequencies in the cs test during ramadan; however, in general, these alterations likely have no significant effect. the effect of fasting during ramadan on ocular parameters has been evaluated in many studies;[9, 10] however, cs has not yet been studied. j  o  v r volume 14, issue 3, july–september 2019 317 fasting and contrast sensitivity; gok et al table 2. the comparison of contrast sensitivity measurements conducted before the ramadan and in the first week spatial frequency (cpd) measurements before the ramadan (mean ± sd) ramadan first week measurements (mean ± sd) p-value a (1.5) 70.87 ± 22.52 71.78 ± 21.58 0.95 b (3) 118.45 ± 22.22 128.52 ± 24.25 0.03* c (6) 122.82±30.38 123.02 ± 31.40 0.75 d (12) 65.85 ± 25.55 71.89 ± 26.22 0.29 e (18) 23.57 ± 1.42 25.91 ± 14.43 0.28 cpd, cycles per degree; sd, standard deviation table 3. the comparison of contrast sensitivity measurements conducted before the ramadan and at the fourth week of ramadan spatial frequency (cpd) measurement before ramadan (mean ± sd) ramadan fourth week measurement (mean ± sd) p-value a (1.5) 70.87 ± 22.52 75.75 ± 21.88 0.17 b (3) 118.45 ± 22.22 128.84 ± 24.42 0.01* c (6) 122.82 ± 30.38 128.40 ± 26.18 0.49 d (12) 65.85 ± 25.55 76.35 ± 27.61 0.01* e (18) 23.57 ± 1.42 25.95 ± 13.20 0.13 cpd, cycles per degree; sd, standard deviation table 4. the comparison of contrast sensitivity measurements conducted in the ramadan 1st and 4th week spatial frequency (cpd) ramadan first week measurement (mean ± sd) ramadan fourth week measurement (mean ± sd) p-value a (1.5) 71.78 ± 21.58 75.75 ± 21.88 0.10 b (3) 128.52 ± 24.25 128.84 ± 24.42 0.91 c (6) 123.02 ± 31.40 128.40 ± 26.18 0.47 d (12) 71.89 ± 26.22 76.35 ± 27.61 0.83 e (18) 25.91 ± 14.43 25.95 ± 13.20 0.76 cpd, cycles per degree; sd, standard deviation when considering cs function in the human eye from very low spatial frequencies to very high spatial frequencies, in general, we observe a continuous decrease. cs in a normal eye increases from the lowest frequencies to approximately six cpd and then decreases with higher frequencies. this decrease in cs is due to the diffraction and aberration that makes visual details more difficult to perceive.[3–5] this pattern in cs function is due to the programming of the retinal-brain visual processing system.[11, 12] we found statistically insignificant increases at all frequencies and a statistically significant increase at three cpd in cs measurements in the first week of ramadan compared with the measurements made before ramadan. we also found statistically significant increases at 3 and 12 cpd and statistically insignificant increases at other frequencies in the measurements in the last week of the ramadan. 318 j  o  v r volume 14, issue 3, july–september 2019 fasting and contrast sensitivity; gok et al while the cs decreases gradually at frequencies higher than six cpd, our study showed a statistically significant increase at 12 cpd; however, statistically significant increases were not observed at all other frequencies. fasting leads to changes in physiological parameters and these changes affect the ocular system.[7] an increase in free fatty acid, norepinephrine, and cortisol concentrations occurs as a result of a decrease in insulin secretion and an increase in both glucagon levels and sympathetic activity.[8] retinal hyperperfusion and increased iop due to these hormones have been reported as the basic effects of ramadan fasting on ocular parameters.[9, 10] in a study conducted by koktekir et al, fasting was found to significantly decrease tear production and increase tear osmolarity but have no effect on corneal topographic parameters or produce ocular aberrations.[13] in another study conducted by selver et al, no significant differences were detected in any of the anterior segment parameters, visual acuity measurements, or iop measurements during ramadan fasting.[14] kerimoglu et al[15] demonstrated that fasting might lead to a decrease in iop; however, in the study conducted by kayikcioglu et al,[16] this correlation was not observed. refractive status, lens thickness, or corneal curvature changes may occur as a result of dehydration during the ramadan period. changes may occur in the refractive index of the dehydrated vitreous and this may affect the axial length, resulting in either a very small or no refractive change. although the anterior chamber depth is affected by fluctuations in the hydration status of the body, a long period of dehydration is required for changes in axial length to manifest.[17] according to the results of these studies, alterations in the anterior chamber parameters could also impair cs functions. in our study, we also evaluated refractive status and visual acuity of the subjects; however, no statistically significant change was observed in any of the measurements (p > 0.05). our cases demonstrated no visual acuity loss. one of the main limitations of our study was the number of participants. a larger cohort of participants may provide more supporting information on the effect of ramadan fasting on cs function. the other limitation of our study was the lack of a control group, as we compared cs measurements within the same patient population. our results may have been more valuable upon inclusion of a control group. in conclusion, we showed that ramadan fasting has no negative effects on visual acuity and cs. in fact, we found a statistically significant increase in cs at some frequencies using the cs test. we believe that additional studies need to be performed to obtain more supporting information on the effects of ramadan fasting on the eye and ocular cs function. we think that physicians working in countries with sizeable muslim populations should be aware of the physiological effects of ramadan fasting, particularly pertaining to various ocular problems and treatments. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. nowroozzadeh mh, mirhosseini a, meshkibaf mh, roshannejad j. effect of ramadan fasting in tropical summer months on ocular refractive and biometric characteristics. clin exp optom 2012;95:173–176. 2. nomani mz. diet during ramadan. int j ramadan fasting res 1999;3:1–6. 3. ginsburg ap. contrast sensitivity: determining the visual quality and function of cataract, intraocular lenses and refractive surgery. curr opin opht 2006;17:19–26. 4. loshin sd, white j. contrast sensitivity: the visual rehabilitation of the patient with macular degeneration. arch ophtalmol 1984;102:13030–13036. 5. olsen t, corydon l. contrast sensitivity as a function of focus in patients with the diffractive multifocal intraocular lens. j cataract ref surg 1990;16:703–706. 6. leiper jb, molla am, molla am. effects on health of fluid restriction during fasting in ramadan. eur j clin nutr 2003;57:30–38. 7. assadi m, akrami a, beikzadeh f, seyedabadi m, nabipour i, larijani b, et al. impact of ramadan fasting on intraocular pressure, visual acuity and refractive errors. singapore med j 2011;52:263–266. 8. cahill gf, jr. starvation in man. n engl j med 1970;282:668–675. 9. dadeya s, kamlesh, shibal f, khurana c, khanna a. effect of religious fasting on intra-ocular pressure. eye(lond) 2002;16:463–465. 10. javadi ma, assadi m, einollahi b. the effects of ramadan fasting on the health and function of the eye. j res med sci 2014;19:786–791. j  o  v r volume 14, issue 3, july–september 2019 319 fasting and contrast sensitivity; gok et al 11. holladay jt. outcomes of cataract surgery. in: yanoff m, duker j, editors. ophthalmology. 2nd ed. st louis (mo): mosby co; 2004: 391–394. 12. volkers acw, hagemans kh, wildt gj, schmitz pim. spatial contrast sensitivity and the diagnosis of amblyopia. br j ophthalmol 1987;71:58–65. 13. koktekir be, bozkurt b, gonul s, gedik s, okudan s. effect of religious fasting on tear osmolarity and ocular surface. eye contact lens 2014;40:239–242. 14. selver ob, palamar m, gerceker k, egrilmez s, yagci a. the effects of ramadan fasting on anterior segment parameters, visual acuity and intraocular pressures of the eye. open ophthalmology j 2017;11:152–155. 15. kerimoglu h, ozturk b, gunduz k, bozkurt b, kamis u, okka m. effect of altered eating habits and periods during ramadan fasting on intraocular pressure, tear secretion, corneal and anterior chamber parameters. eye (lond) 2010;24:97–100. 16. kayikçioglu o, güler c. religious fasting and intraocular pressure. j glaucoma 2000;9:413–414. 17. oltulu r, satirtav g, ersan i, soylu e, okka m, zengin n. the effect of dehydration and fasting on corneal biomechanical properties and intraocular pressure. eye contact lens 2016;42:392–394. 320 j  o  v r volume 14, issue 3, july–september 2019 review article orbital inflammation caused by aminobisphosphonates j gonzalez barlatay, md; c pagano boza, md; gv hernandez gauna, md; je premoli, md division of orbital and ophthalmic plastic surgery, hospital italiano de buenos aires, argentina orcid: j gonzalez barlatay: http://orcid.org/0000-0002-3412-359x abstract the aim of this review was to describe orbital inflammation secondary to aminobisphosphonates by analyzing demographic data, clinical presentation, and treatment of the disease. this is a narrative literature review. the search was performed using databases such as ovid/medline and cochrane. the searches were limited to papers in the english language. we found 43 cases of orbital inflammation due to aminobisphosphonates. zoledronate was the drug most associated with orbital side effects. clinical presentation was evident by unilateral involvement (89%), palpebral edema (88%), conjunctival congestion (81%), chemosis (79%), ocular pain (77%), ocular motility impairment (65%), proptosis (56%), and blurred vision (39%). it can affect both eyes (11%) and is accompanied by anterior uveitis (23%). orbital inflammation secondary to aminobisphosphonates is a severe side effect. clinically, it cannot be distinguished from idiopathic inflammation of the orbit. therefore, it is important to rule out previous drug exposure. timely treatment is vital to expect a favorable outcome, with systemic corticosteroids being the treatment of choice. keywords: alendronate; bisphosphonates; dacryoadenitis; myositis; pamidronate; zoledronate j ophthalmic vis res 2022; 17 (1): 118–122 introduction bisphosphonate group of drugs are widely used in diseases such as osteoporosis, paget’s disease, osteoclastic bone metastases, and multiple myeloma. these drugs have a high affinity for bone tissue, where they combine with hydroxyapatite crystals to inhibit bone resorption. as a result, correspondence to: j gonzalez barlatay, md. peron 4190, ciudad autónoma de buenos aires, argentina. email: joaquingonzalezbarlatay@gmail.com received 06-05-2020; accepted 01-08-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10176 untoward bone events decrease, and pain is relieved. among the well-known adverse effects, the possibility of triggering an acute systemic inflammatory phase response, characterized by fever, pain, nausea, and fatigue within the first 72 hr after administration occurs in approximately 40–50% of the patients.[1] symptoms are usually transient and resolve spontaneously. however, in several cases, they may be treated with analgesic and antipyretic drugs. the clinical presentation is accompanied by a decrease in the lymphocyte this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: barlatay jg, boza cp, gauna gvh, premoli je. orbital inflammation caused by aminobisphosphonates. j ophthalmic vis res 2022;17:118–122. 118 © 2022 barlatay et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10176&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr orbital inflammation and aminobisphosphonates; barlatay et al count and an increase in pro-inflammatory markers, such as il-6, ifn-γ, and tnf-α.[2–5] ocular adverse effects related to bisphosphonates have also been reported. the most frequent complications are conjunctivitis, anterior uveitis, episcleritis, and scleritis.[6] orbital inflammation indicates its clinical severity. it can range from minimal congestion to severe inflammation with visual impairment if not promptly diagnosed and treated in time. clinically, it cannot be differentiated from idiopathic orbital inflammation. the aim of this study was to perform a literature review on orbital inflammation secondary to bisphosphonates to increase the knowledge of rare adverse effects and determine the best management methods. methods the search was performed using databases such as ovid/medline and cochrane, using english language restriction in the electronic searches for papers. we searched electronic databases in august 2020. the keywords used for the search were: bisphosphonates, or orbital inflammation, or myositis, or ocular side effects, or ocular adverse effects, and or ocular inflammation. at the same time, the search was performed by changing the word bisphosphonate with aminobiphosphonates, zoledronate, ibandronate, alendronate, and pamidronate. selection criteria all the papers that described orbital inflammation due to aminobisphosphonates were included. patients with intraocular side effects that did not involve the orbit were excluded. a database with demographic data, type of drug, disease onset time, clinical characteristics, and treatment of choice was created. the study was approved by the institutional review board at the instituto universitario del hospital italiano de buenos aires and adhered to the tenets of the declaration of helsinki. results a total of 43 cases of orbital inflammation due to aminobisphosphonates were found in 26 articles published in ovid/medline and cochrane, including case reports and reviews.[7–33] the first article on this topic was published in 1999[7] and the last one in 2019.[33] demographic data of the patients are summarized in table 1. zoledronate was the drug most associated with orbital side effects. the clinical presentations are summarized in table 2. unilateral involvement occurred in 89% of the patients. symptoms and signs included palpebral edema (88%), conjunctival congestion (81%), chemosis (79%), ocular pain (77%), ocular motility impairment (65%), proptosis (56%), and blurred vision (39%). only two cases had complications, one had a severe reduction in visual acuity due to anterior ischemic optic neuritis (aion),[13] and other reported recurrent orbital inflammation without visual impairment.[30] a total of 27 patients stopped treatment with bisphosphonates due to orbital inflammation, three patients continued treatment despite orbital involvement, and no severe complications were reported. discussion orbital inflammation caused by bisphosphonates is a rare adverse drug reaction. to date, only 43 case reports have been published worldwide.[7–33] the route of administration seems to be associated with latency time for the onset of symptoms. the patients treated with oral alendronate started showing signs and symptoms between 15 and 21 days after treatment, while the patients treated with intravenous pamidronate and zoledronate presented them 3 days later. zoledronate is the bisphosphonate most frequently associated with this reaction when compared with others, and it can be related to it being the most frequently used for its effectiveness in the treatment of osteoporosis. the risk of suffering this acute response and its severity is higher after the first intravenous administration and occur less frequently with fewer symptoms in subsequent administrations. the horizon trial reported an incidence of orbital inflammation associated with the administration of 30% intravenous zoledronate with the first dose, 7% with the second, and 3% with the third dose.[34] unilateral orbital inflammation was most frequent (89%), but it may be bilateral (11%). clinical signs and symptoms included palpebral edema (88%), conjunctival congestion (81%), chemosis (79%), ocular pain (77%), ocular motility impairment (65%), proptosis (56%), and blurred vision (39%). journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 119 orbital inflammation and aminobisphosphonates; barlatay et al table 1. patients’ demographic data total patients 43 age (yr), mean ± sd 65.39 ± 9.1 sex female 60% (n = 26) male 40% (n = 17) reason for aminobisphosphonates use osteoporosis 56% (n = 24) metastasis 21% (n = 9) type of aminobisphosphonates zoledronate 67% (n = 29) alendronate 14% (n = 6) pamidronate 12% (n = 5) risedronate 7% (n = 3) sd, standard deviation table 2. clinical presentation and treatment clinical presentation unilateral 89% (n = 38) palpebral edema 88% (n = 38) conjunctival congestion 81% (n = 35) chemosis 79% (n = 34) ocular pain 77% (n = 33) motility impairment 65% (n = 28) proptosis 56% (n = 24) blurred vision 39% (n = 17) complications aion 2.32% (n = 1) type of treatment systemic corticoid 72% (n = 31) oral prednisolone alone 48.83% (n = 21) methylprednisolone ev + oral prednisolone 23.25% (n = 10) solve spontaneously 11.63% (n = 5) without data 9.30 (n = 4) nsaids 4.65 % (n = 2) topic prednisolone 2.23% (n = 1) aion, anterior ischemic optic neuritis; nsaids, nonsteroids anti-inflammatory drugs moreover, 23% of the cases were associated with anterior uveitis. on the contrary, this sign may not be associated with idiopathic orbital inflammation; for that reason, when anterior uveitis develops, physicians may exclude bisphosphonate administration. it is typically non-axial, due to the different structures that could be involved, such as lacrimal gland, extraocular muscles, or intraorbital fat, alone or together. the decrease in visual acuity can be multifactorial. among the causes, we found corneal keratitis, either because of proptosis or lagophthalmos, dacryoadenitis, due to a decrease in the production of tears; and anterior or posterior uveitis is associated with compressive or ischemic optic neuropathy. a 68-year-old male with metastatic prostate cancer was reported to experience severe complications. he consulted the physician two weeks after the onset of ocular pain and redness. he had visual acuity and visual field deficits because of an aion. ischemia may have been caused by orbital or ocular inflammation contiguously affecting the posterior ciliary arteries 120 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 orbital inflammation and aminobisphosphonates; barlatay et al that supply the optic disc, creating local smallvessel vasculitis. this highlights the importance of applying the timely treatment once symptoms have started.[13] the mechanism by which these drugs produce inflammation could be related to the presence of a nitrogenous group that rapidly activates monocytes and a subtype of t-cells called gamma-delta, in both in vitro[35–38] and in vivo conditions.[1, 39] this activation leads to the release of cytokines and inflammatory mediators that produce an acute inflammatory response. local inflammation is followed by an acute phase of systemic inflammatory response with the presence of symptoms such as fever, pain, nausea, and fatigue in 25% of the patients. it is worth mentioning that all patients who developed a bilateral orbital condition (11%) also had systemic symptoms. currently, oral systemic corticosteroids alone or following an intravenous corticosteroid cycle are the treatment of choice, with excellent results in 72% of the patients.[31] the response was effective in all cases; symptoms and ct scan or mri findings showed complete resolution when the treatment was started seasonally. delays in treatment are associated with an increased risk of complications.[13] only a few cases resolve spontaneously or with nonsteroidal antiinflammatory drugs (nsaids), limiting the current information to suggest this type of therapeutic decision. for this reason, these two options may only be considered in mild inflammation without the risk of visual impairment, or in patients with contraindications to corticosteroid treatment. it has not yet been proven that the treatment of orbital inflammation requires stopping the use of bisphosphonates. although most of the studies reported the suspension of the antiresorptive drug as treatment, the three cases published that continued with the bisphosphonate but associated with systemic steroids resolved the orbital inflammation without complications. thus, we recommend that in the event of mild symptoms of orbital compromise without risk of visual impairment, bisphosphonate treatment could be continued in conjunction with antiinflammatory treatment. however, in severe orbital inflammation with visual threat or optic neuropathy, bisphosphonates should be discontinued. summary orbital inflammation caused by aminobisphosphonates is rather infrequent; however, ophthalmologists must recognize this adverse effect secondary to the drug. this condition must be ruled out when orbital inflammation, with or without anterior uveitis is present. patients’ knowledge of the use of these drugs is key to diagnosis. the treatment of choice is the administration of systemic corticosteroids, which are effective in suppressing the inflammatory response with complete resolution when started appropriately. delayed treatment may be associated with a poor prognosis. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. olson k, van poznak c. significance and impact of bisphosphonate-induced acute phase responses. j oncol pharm pract 2007;13:223–229. 2. thiébaud d, sauty a, burckhardt p, leuenberger p, sitzler l, green jr, et al. an in vitro and in vivo study of cytokines in the acute-phase response associated with bisphosphonates. calcif tissue int 1997;61:386–392. 3. buckler hm, mercer sj, davison, hollis s, richardson p, anderson d. evaluation of adverse experiences related to pamidronate infusion in paget’s disease of bone. ann rheum dis 1998:57;572–572. 4. dicuonzo g, vincenzi b, santini d, avvisati g, rocci l, battistoni f, et al. fever after zoledronic acid administration is due to increase in tnf-α and il-6. j interferon cytokine res 2003;23:649–654. 5. reid ir, gamble gd, mesenbrink p, lakatos p, black dm. characterization of and risk factors for the acute-phase response after zoledronic acid. j clin endocrinol metab 2010;95:4380–4387. 6. macarol v, fraunfelder ft. pamidronate disodium and possible ocular adverse drug reactions. am j ophthalmol 1994;118:220–224. 7. mbekeani jn, slamovits tl, schwartz bh, sauer hl. ocular inflammation associated with alendronate therapy. arch ophthalmol 1999;117:837–838. 8. ryan pj, sampath r. idiopathic orbital inflammation following intravenous pamidronate. rheumatology 2001;40:956–957. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 121 orbital inflammation and aminobisphosphonates; barlatay et al 9. subramanian ps, kerrison jb, calvert pc, miller nr. orbital inflammatory disease after pamidronate treatment for metastatic prostate cancer. arch ophthalmol 2003;121:1335–1336. 10. benderson d, karakunnel j, kathuria s, badros a. scleritis complicating zoledronic acid infusion. clin lymphoma myeloma 2006;7:145–147. 11. phillips pm, newman sa. orbital inflammatory disease after intravenous infusion of zoledronate for treatment of metastatic renal cell carcinoma. arch ophthalmol 2008;126:137–139. 12. sharma ns, ooi j-l, masselos k, hooper mj, francis ic. zoledronic acid infusion and orbital inflammatory disease. n engl j med 2008;359:1410–1411. 13. seth a, anderson dp, albiani da, barton jjs. orbital inflammation and optic neuropathy with zoledronic acid for metastatic prostate cancer. can j ophthalmol 2009;44:467–468. 14. procianoy f, procianoy e. orbital inflammatory disease secondary to a single-dose administration of zoledronic acid for treatment of postmenopausal osteoporosis. osteoporos int 2010;21:1057–1058. 15. yang eb, birkholz es, lee ag. another case of bisphosphonate-induced orbital inflammation. j neuroophthalmol 2010:30:94–95. 16. missotten g, verheezen y. orbital inflammation after use of zoledronic acid for metastasized prostate carcinoma. bull soc belge ophtalmol 2010;315:23–24. 17. yeo j, jafer ak. zolendronate associated inflammatory orbital disease. nz med j 2010;1323:50–52. 18. kaur h, uy c, kelly j, moses am. orbital inflammatory disease in a patient treated with zoledronate. endocr pract 2011;17:e101–e103. 19. ortiz-perez s, fernandez e, molina jj, sanchez-dalmau b, navarro m, corretger x, et al. two cases of drug-induced orbital inflammatory disease. orbit 2011;30:37–39. 20. peterson jd, bedrossian eh. bisphosphonate-associated orbital inflammation—a case report and review. orbit 2012;31:119–123. 21. rahimy e, law sk. orbital inflammation after zoledronate infusion: an emerging complication. can j ophthalmol 2013;48;e11–e12. 22. schwab p, harmon d, bruno r, fraunfelder fw, kim dh. a 55-year-old woman with orbital inflammation. arthritis care res 2012;64:1776–1782. 23. böni c, kordic h, chaloupka k. bisphosphonateassociated orbital inflammatory disease and uveitis anterior a case report and review. klin monbl augenheilkd 2013;230:367–369. 24. lefebvre dr, mandeville jt, yonekawa y, arroyo jg, torun n, freitag sk. a case series and review of bisphosphonate-associated orbital inflammation. ocul immunol inflamm 2014;25:1–6. 25. vora mm, rodgers ir, uretsky s. nitrogen bisphosphonate-induced orbital inflammatory disease. ophthalmic plast reconstr surg 2014;30:e84–e85. 26. pirbhai a, rajak sn, goold la, cunneen ts, wilcsek g, martin p, et al. bisphosphonate-induced orbital inflammation: a case series and review. orbit 2015;34:331– 335. 27. gonzalez barlatay j, hernandez gauna g, premoli j, luis vr, jorge pe. orbital inflammation caused by bisphosphonates case report and literature review. ijoo 2016;2:148–151. 28. muruganandam m, sandhu h. orbital inflammation secondary to zoledronic acid, a rare presentation. j clin rheumatol 2016;22:384. 29. umunakwe oc, herren d, kim sj, kohanim s. diffuse ocular and orbital inflammation after zoledronate infusioncase report and review of the literature. digit j ophthalmol 2017;23:18–21. 30. tan m, kalin-hajdu e, narayan r, wong sw, martin tg. zoledronic acid-induced orbital inflammation in a patient with multiple myeloma. j oncol pharm pract 2019;25:1253–1257. 31. chehade lk, curragh d, selva d. bisphosphonateinduced orbital inflammation: more common than once thought? osteoporos int 2019;30:1117–1120. 32. herrera i, kam y, whittaker tj, champion m, ajlan rs. bisphosphonate-induced orbital inflammation in a patient on chronic immunosuppressive therapy. bmc ophthalmol 2019;19:51. 33. keren s, leibovitch i, ben cnaan r, neudorfer m, fogel o, greenman y, et al. aminobisphosphonate-associated orbital and ocular inflammatory disease. acta ophthalmol 2019;97:e792–e799. 34. black dm, delmas pd, eastell r, reid ir, boonen s, cauley ja, et al. once-yearly zoledronic acid for treatment of postmenopausal osteoporosis. n engl j med 2007;356:1809–1822. 35. kunzmann v, bauer e, feurle j, weissinger f, tony hp, wilhelm m. stimulation of γδ t cells by aminobisphosphonates and induction of antiplasma cell activity in multiple myeloma. blood 2000;96:384–392. 36. gober h-j, kistowska m, angman l, jenö p, mori l, de libero g. human t cell receptor γδ cells recognize endogenous mevalonate metabolites in tumor cells. j exp med 2003;197:163–168. 37. roelofs aj, jauhiainen m, mönkkönen h, rogers mj, mönkkönen j, thompson k. peripheral blood monocytes are responsible for γδ t cell activation induced by zoledronic acid through accumulation of ipp/dmapp. br j haematology 2009;144:245–250. 38. thompson k, keech f, mclernon dj, vinod k, may rj, simpson wg, et al. fluvastatin does not prevent the acutephase response to intravenous zoledronic acid in postmenopausal women. bone 2011;49:140–145. 39. kunzmann v, bauer e, wilhelm m. γ/δ t-cell stimulation by pamidronate. n engl j med 1999;340:737–738. 122 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 original article interocular axial length difference and treatment outcomes of anisometropic amblyopia monireh ghasempour1, ms; masoud khorrami-nejad2,3, phd; aidin safvati4, phd; babak masoomian3, md 1department of neuroscience, faculty of advanced technologies in medicine, iran university of medical sciences, tehran, iran 2optometry department, school of rehabilitation, tehran university of medical sciences, tehran, iran 3translational ophthalmology research center, farabi eye hospital, tehran university of medical sciences, tehran, iran 4school of optometry and vision science, university of new south wales, sydney, australia orcid: masoud khorrami-nejad: https://orcid.org/0000-0002-8270-9704 monireh ghasempour: https://orcid.org/0000-0002-3088-9758 abstract purpose: to evaluate the effect of interocular axial length (al) difference on outcomes of treatment for anisometropic amblyopia in comparison with normal participants. methods: in this historical cohort study, 83 patients with anisometropic amblyopia were divided into two age groups, 70 children (mean, 7.86 ± 1.56 and range, 5–15 years) and 13 adults (mean, 26.46 ± 10.87 and range, 16–45 years). the control group consisted of 43 non-amblyopic children and 17 non-amblyopic adults. treatment outcomes after a period of one year were defined as successful or unsuccessful when posttreatment amblyopic corrected distance visual acuity (cdva) was reported as ≤0.9 versus cdva ≤ 0.8, respectively. al was measured using a lenstar ls900 (haag-streit ag, switzerland). results: fifty-nine patients showed satisfactory treatment outcomes (55 children and 4 adults), while unsuccessful treatment outcomes were observed in 24 patients (15 children and 9 adults). the mean of amblyopia treatment duration was 1.24 ± 0.76 years. the mean of interocular al difference in all patients, control, successful and unsuccessful treatment outcome groups were 0.49 ± 0.70mm (range, 0.00–3.89 mm), 0.12 ± 0.07 mm (range, 0.02–0.41), 0.33 ± 0.23 mm (range, 0.00–0.99 mm), and 1.81 ± 0.80 mm (range, 1.14–3.89 mm), respectively. in both age groups, the mean of interocular al difference in patients with unsuccessful treatment outcomes was greater than those with successful treatment outcomes and that of the control group (p < 0.001). conclusion: the results of this study suggest that the outcome of anisometropic amblyopia treatment may depend on the interocular al difference. keywords: anisometropic amblyopia; axial length; refractive error j ophthalmic vis res 2022; 17 (2): 202–208 202 © 2022 ghasempour et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i2.10791&domain=pdf&date_stamp=2019-07-17 axial length and amblyopia treatment; ghasempour et al introduction anisometropic amblyopia is one of the most common types of amblyopia,[1–3] which is secondary to differences in refractive errors between the two eyes.[4, 5] amblyopia is a type of incomplete development of the visual system occurring in early childhood.[5, 6] it is one of the main causes of lifelong visual impairment[3] and is the most common cause of vision loss in childhood affecting 3.5% of children.[7] if amblyopia is not diagnosed or treated in due course, there will be a higher risk of vision impairment by conditions such as macular degeneration that may potentially occur in the non-amblyopic eye. based on a danish study, about 1.2% of patients with amblyopia will eventually suffer from severe visual impairment.[10] one of the main causes of amblyopia is uncorrected refractive error, which is hard to detect when compared to amblyopia caused by strabismus.[5, 7, 11] in fact, the initial factor causing anisometropic amblyopia (monocular blur) is the uncorrected refractive error. it leads to the inequality of image size between the two eyes. the blurriness of the image encumbers proper stimulation of the visual system and thus functions as an underlying cause of amblyopia.[4,5] although exceptions exist, various studies have reported that higher amounts of anisometropia may result in amblyopia with increased severity.[12, 13] despite the body of knowledge existing about the major risk factors such as the age of onset, the severity of anisometropia and the type of treatment, treatment of anisometropic amblyopia is reportedly unsuccessful in 65% to 94% of patients.[5] therefore, one could postulate that unknown risk factors may be involved, warranting further investigation into this area. correspondence to: masoud khorrami-nejad, phd. enghelab st., school of rehabilitation, tehran university of medical sciences, tehran, iran. email: dr.khorraminejad@gmail.com received: 26-06-2020 accepted: 23-07-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i2.10791 anisometropia is defined as a difference in refractive error of ≥1.00 diopter (d) between the two eyes.[6, 14] various studies have shown that with an increase in anisometropia, a higher difference in the axial length (al) between the two eyes may occur as well.[15–17] the severity of amblyopia is also one of the major risk factors for the failure of anisometropic amblyopia treatment.[7, 11, 18, 19] it seems a combination of these risk factors may influence the results of anisometropic amblyopia treatment, but it is not clear which factor is the most effective. the aim of this study was to evaluate the effect of the interocular al difference of each individual on the outcomes of anisometropic amblyopia treatment. methods this historical cohort study was conducted at najafzadeh eye clinic, karaj, iran from september 2016 to october 2018. in this study, data were collected observationally. the study was performed in accordance with the tenets of the declaration of helsinki and approved by the ethics committee of our clinic. eighty-three patients with anisometropic amblyopia with no congenital anomalies, organic lesions, fixation disorders, strabismus, or glaucoma, were included in this study. they were divided into two age groups, 5–15 years (n = 70) and 16–45 years (n = 13). we also included a control group consisting of 43 non-amblyopic children and 17 non-amblyopic adults. anisometropic amblyopia was defined as a difference of at least two lines in corrected distance visual acuity (cdva) between the two eyes with the cdva being equal to or worse than 20/30 due to uncorrected refractive error also with a difference of >1.50 d in spherical refractive error between the two eyes.[2, 17] with each age group we had two treatment outcomes: (1) a successful treatment outcome this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: ghasempour m, khorrami-nejad m, safvati a, masoomian b. the effect of interocular axial length difference on treatment outcomes of anisometropic amblyopia. j ophthalmic vis res 2022;17:202– 208. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 203 https://knepublishing.com/index.php/jovr axial length and amblyopia treatment; ghasempour et al (group a); whereby satisfactory cdva (≥0.90) was achieved following treatment of amblyopia using corrective glasses alone or with occlusion therapy and (2) an unsuccessful treatment outcome with residual amblyopia (group b), defined as cdva ≤ 0.8 after at least one year of treatment. control, non-amblyopic participants, were those who had cdva ≥ 1.00 and at least ±0.50 d anisometropia. routine ophthalmic examinations detailed below were performed for all participants. cdva was performed using an e-snellen chart at a distance of 6 m, and the findings were presented in decimals. alternate cover tests, versions and duction tests were performed to rule out strabismus and extraocular muscle movement limitations. a slit�lamp (sl-202®, shin-nippon, japan) was used to perform biomicroscopy and funduscopy for all amblyopic and normal participants. dry and cyclo refraction were measured by a nidek ark-710a auto keratorefractometer (nidek co. ltd, gamagori, japan) and confirmed by retinoscopy (heine optotechnic, hersching, germany). all participants underwent cyclorefraction by administering cyclopentolate 1% (two drops, 5 min apart, followed by refraction 30 min after the last drop). amblyopia treatment in all patients was started with at least three months of full-time wearing of corrective glasses. as described by the pediatric eye disease investigator group (pedig) studies, supplementary amblyopia therapies were provided at the end of three months.[20] in patients with unsuccessful treatment, the amblyopia treatment program was continued for at least one year. the mean duration of amblyopia treatment was also calculated. depending on the severity of amblyopia, treatment was continued until the resolution of the amblyopia. upon discontinuation of treatment, patients were followed-up for at least six months. in the last visit of patients, the al of both eyes was measured (lenstar ls900, haagstreit ag, switzerland), and the average of five measurements was recorded. statistical analysis was performed using spss v22 software for windows (ibm inc., armonk, new york, ny, usa). p-values < 0.05 were recorded as statistically significant. the shapiro–wilk test was used to evaluate the normal distribution of the interocular al difference, and the kruskal–wallis test was performed to compare the interocular al differences between the three groups (successful treatment outcome, unsuccessful treatment outcome, and control group). results eighty-three patients with anisometropic amblyopia were tested for this study (35 females and 48 males) with a mean age of 10.77 ± 8.10 years (range, 5–45). they were divided into two age groups, 5–15 years (group a, n = 70, mean 7.86 ± 1.56) and 16–45 years (group b, n = 13, mean 26.46 ± 10.87). additionally, 60 participants were selected as a control group consisting of nonamblyopic anisometropic participants (43 children aged 5–15 years with a mean age of 10.42 ± 2.95 years and 17 adults aged 16–45 years with a mean age of 22.47 ± 4.73 years). in the children’s group (group a), the time of diagnosis and first treatment was between the ages of 4 and 6 years, while in the adult group, it was at 15 years old and above. for all patients, the mean duration of amblyopia treatment was 1.24 ± 0.76 years, with a maximum of 2.50 years. this treatment period included at least three-months of full-time refractive correction (without any other active or passive modes of treatment for amblyopia). hours of patching for mild, moderate, and severe amblyopia were 2, 4, and 6 hr, respectively. all amblyopic patients had refractive anisometropic amblyopia. amblyopia was successfully treated in 59 (71.1%) patients (55 children and 4 adults), while 24 (28.9%) patients demonstrated an unsuccessful treatment outcome with residual amblyopia (15 children and 9 adults). the comparison of the pretreatment cdva (logmar) between children and adult groups, categorized based on amblyopia treatment outcomes in anisometropic amblyopic patients, are shown in table 1. the mean of pretreatment cdva in the children and the adult group was 0.51 ± 0.28 (range, 0.18–1.30) and 0.56 ± 0.31 (range, 0.18–1.30), respectively. after the treatment of amblyopia, the mean of cdva in the children and the adult group was 0.12 ± 0.29 (range, 0.00–1.30) and 0.30 ± 0.37 (range, 0.00–1.30), respectively. the mean of anisometropia in all anisometropic amblyopia patients, children and adult groups were 2.94 ± 1.94 d (range, 1.75–11.50), 2.77 ± 1.85 d (range, 1.75–11.50), and 3.88 ± 2.14 d (range, 1.75– 8.25), respectively. table 2 shows the comparison of the mean of anisometropia between the children and the adult groups, categorized by the treatment outcome. 204 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 axial length and amblyopia treatment; ghasempour et al table 1. the comparison of the pretreatment of corrected distance visual acuity (logmar) between children and adult groups, based on amblyopia treatment outcomes in anisometropic amblyopic patients. amblyopia treatment outcomes age group (yr) number minimum maximum mean ± sd mean standard error p-value good treatment outcome 5–15 55 0.18 1.00 0.43 ± 0.19 0.02 0.152 16–45 4 0.18 0.48 0.28 ± 0.14 0.07 failure of successfully treatment outcome 5–15 15 0.40 1.30 0.78 ± 0.35 0.09 0.499 16–45 9 0.40 1.30 0.68 ± 0.29 0.09 sd, standard deviation; yr, year table 2. comparison of the mean anisometropia (diopter) among children and adult groups based on amblyopia treatment outcomes. age group (yr) number minimum maximum mean ± sd mean standard error p-value control group 5–15 43 0.50 1.50 0.86 ± 0.25 0.04 0.279 16–45 17 0.50 1.75 0.92 ± 0.33 0.08 good treatment outcome 5–15 55 1.75 3.00 2.01 ± 0.33 0.05 0.536 16–45 4 1.75 3.25 2.25 ± 0.68 0.34 failure of successful treatment outcome 5–15 15 3.50 11.50 5.57 ± 2.43 0.63 0.329 16–45 9 2.25 8.25 4.61 ± 2.19 0.73 sd, standard deviation; yr, year the mean of the interocular al differences in all patients was 0.63 ± 0.78 mm. figures 1 and 2 show the box plot distribution of the interocular al differences and amount of anisometropia, categorized by treatment outcomes in the children and the adult groups. as shown in figure 1, the interocular al difference in the unsuccessful treatment outcome group was >1 mm (in both age groups). the mean of the interocular al difference was significantly larger in the anisometropic amblyopia group when compared to the control group (p < 0.001). also, there was a significant difference between the control group, the unsuccessful and successful treatment outcome groups (p < 0.001). in both age groups, the mean of the interocular al difference in the unsuccessful treatment outcome group was significantly greater than the successful treatment outcome group (p < 0.001). in the children group, when a successful treatment outcome was achieved, the mean al was larger than the control group (z = –5.539; p < 0.001; 2-tailed); however, in the adult group this difference was not statistically significant (t = –1.360; df = 3.323; p = 0.259). table 3 shows the comparison of the mean of the interocular al difference between children and adult groups as categorized by treatment outcome. discussion the findings of this study indicate that the interocular al difference in patients with unsuccessful treatment outcomes was significantly larger than patients with successful treatment outcomes and those of the control group. recent studies have indicated the existence of a significant correlation between anisometropia and the interocular al difference in anisometropic amblyopia patients.[13, 15, 17, 21, 22] studies suggest that amblyopia cannot be treated beyond a critical age because of the lack of adequate plasticity in the adult brain.[23] in this study, amblyopia was treated successfully in four adults. the findings of this study indicate that even in children, amblyopia may not be treated journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 205 axial length and amblyopia treatment; ghasempour et al table 3. comparison of the mean of the interocular axial length difference (mm) between the children and adult group based on amblyopia treatment outcomes. age group (yr) number minimum maximum mean ± sd mean standard error p-value control group 5–15 43 0.02 0.41 0.12 ± 0.08 0.01 p = 0.458 16–45 17 0.03 0.28 0.13 ± 0.06 0.02 good treatment outcome 5–15 55 0.00 0.99 0.34 ± 0.25 0.03 p = 0.407 16–45 4 0.05 0.38 0.22 ± 0.14 0.07 failure of successful treatment outcome 5–15 15 1.14 3.89 1.90 ± 0.91 0.24 p = 0.788 16–45 9 1.16 3.00 1.69 ± 0.61 0.20 sd, standard deviation; yr, year figure 1. the box plot distribution of the interocular axial length difference (mm), categorized based on amblyopia treatment outcomes in the children (a) and adults (b) groups. successfully in all patients. bonacorci et al reported that due to the flexibility of the visual system, the results of anisometropic amblyopic treatment could vary depending on the age of treatment.[23] meanwhile, lia et al have not mentioned age as a main factor in treatment outcomes.[24] we report that the mean of the interocular al difference was larger when treatment was unsuccessful (compared to the successful treatment group and the controls). this finding was consistent for both the children and the adult group. in both age groups, it seems that the interocular al difference may assist in predicting the outcomes of the amblyopia treatment. in our study, the interocular al difference was larger in the group with unsuccessful treatment outcomes when compared to the group with successful treatment and the controls. the higher interocular al difference in the group with unsuccessful treatment outcomes confirms that the hypermetropic amblyopic eye had an al that was shorter than the non-amblyopic eye. lempert et al in a study involving 927 anisohypermetropic amblyopic patients aimed at examining the al to the optic nerve disk area ratio 206 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 axial length and amblyopia treatment; ghasempour et al figure 2. the box plot distribution of the anisometropia (diopter), categorized based on amblyopia treatment outcomes in the children (a) and adult (b) groups. (al/da).[25] according to the report, the area of the optic nerve disc in the amblyopic eyes was significantly smaller than that of the non-amblyopic eyes. also, the size of the optic nerve disc and al in the more hypermetropic eye was smaller than the optic disc and al of the non-amblyopic eye. furthermore, in a study on monkeys, swadlow et al have reported that the diameter of axons with the highest transmission speed was 20 microns. in comparison, the axons with the slowest speed of transmission had a diameter of about 0.1 micron.[26] based on these two studies, it can be postulated that the speed of transmission of neural impulses may be linked to the diameter of axons. it can also be suggested that perhaps interocular al and optic disc size differences lead to some sort of interference in the speed of transmission of retinal images between the retina and the visual cortex, thus creating an abnormal development of the visual cortex of the amblyopic eyes. our results suggest that in anisometropic amblyopes who achieve better treatment outcomes as well as in controls, al shows smaller differences between the two eyes. interestingly, this finding was similar across the two tested age groups. based on the results of this study, the difference of al between the two eyes of each individual may assist with the prediction of treatment outcomes in anisometropic amblyopic patients. although our study has successfully determined the existing relationship between interocular al difference and treatment outcomes for anisometropic amblyopia, further studies using larger sample sizes are warranted to expand our knowledge on the topic. financial support and sponsorship nil. conflicts of interest none declared. references 1. aldebasi yh. prevalence of amblyopia in primary school children in qassim province, kingdom of saudi arabia. middle east afr j ophthalmol 2015;22:86–91. 2. khorrami-nejad m, akbari mr, khosravi b. the prevalence of strabismus types in strabismic iranian patients. clin optom 2018;10:19–24. 3. min fc, ophthal ms, thavaratnam lk, ophthal ms, shukor in, rahmat j, et al. visual impairment and amblyopia in malaysian pre-school children-the segpaeds study. med j malaysia 2018;73:25–30. 4. park sh. current management of childhood amblyopia. korean j ophthalmol 2019;33:557–568. 5. toor ss, horwood am, riddell pm. anisometropic amblyopia: factors influencing the success or failure of its treatment. br ir orthopt j 2015;2:9–16. 6. duman r, atilla h, çatak e. characteristics of anisometropic patients with and without strabismus. turk j ophthalmol 2018;48:23–26. 7. roberts cj, adams gg. contact lenses in the management of high anisometropic amblyopia. eye 2002;16:577–579. 8. van leeuwen r, eijkemans mj, vingerling jr, hofman a, de jong pt, simonsz hj. risk of bilateral visual impairment in individuals with amblyopia: the rotterdam study. br j ophthalmol 2007;91:1450–1451. 9. carlton j, karnon j, czoski-murray c, smith kj, marr j. the clinical effectiveness and cost-effectiveness of screening programmes for amblyopia and strabismus in children up to the age of 4–5 years: a systematic review and economic evaluation. health technol assess 2008;12:194. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 207 axial length and amblyopia treatment; ghasempour et al 10. tommila v, tarkkanen a. incidence of loss of vision in the healthy eye in amblyopia. br j ophthalmol 1981;65:575– 577. 11. lee ce, lee yc, lee sy. factors influencing the prevalence of amblyopia in children with anisometropia. korean j ophthalmol 2010;24:225–229. 12. weakley jr dr. the association between nonstrabismic anisometropia, amblyopia, and subnormal binocularity. ophthalmology 2001;108:163–171. 13. zaka-ur-rab s. evaluation of relationship of ocular parameters and depth of anisometropic amblyopia with the degree of anisometropia. indian j ophthalmol 2006;54:99–103. 14. donahue sp. the relationship between anisometropia, patient age, and the development of amblyopia. trans am ophthalmol soc 2005;103:313–316. 15. ghasempour m, khorrami-nejad m, akbari mr, amiri ma. the effect of different amblyopia treatment protocols on axial length of non-amblyopic eyes in anisohyperopic patients. j curr ophthalmol 2019;31:201–205. 16. burtolo c, ciurlo c, polizzi a, lantieri pb, calabria g. echobiometric study of ocular growth in patients with amblyopia. j pediatr ophthalmol strabismus 2002;39:209–214. 17. singh n, rohatgi j, kumar v. a prospective study of anterior segment ocular parameters in anisometropia. korean j ophthalmol 2017;31:165–171. 18. caputo r, frosini r, de libero c, campa l, del magro ef, secci j. factors influencing severity of and recovery from anisometropic amblyopia. strabismus 2007;15:209–214. 19. hussein ma, coats dk, muthialu a, cohen e, paysse ea. risk factors for treatment failure of anisometropic amblyopia. j aapos 2004;8:429–434. 20. cotter sa, pediatric eye disease investigator group. treatment of anisometropic amblyopia in children with refractive correction. ophthalmology 2006;113:895–903. 21. demircan s, gokce g, yuvaci i, atas m, baskan b, zararsiz g. the assessment of anterior and posterior ocular structures in hyperopic anisometropic amblyopia. med sci monit 2015;21:1181–1188. 22. hoshikawa r, ito m, yano t, tsutsui k, sato t, shimizu k. association between ocular dominance and anisometropic hyperopia. am orthopt j 2016;66:107–113. 23. bonaccorsi j, berardi n, sale a. treatment of amblyopia in the adult: insights from a new rodent model of visual perceptual learning. front neural circuit 2014;8:82. 24. lai xj, alexander j, he m, yang z, suttle c. visual functions and interocular interactions in anisometropic children with and without amblyopia. invest ophthalmol vis sci 2011;52:6849–6859. 25. lempert p. the axial length/disc area ratio in anisometropic hyperopic amblyopia: a hypothesis for decreased unilateral vision associated with hyperopic anisometropia. ophthalmology 2004;111:304–308. 26. swadlow ha, waxman sg. axonal conduction delays. scholarpedia 2012;7:1451. 208 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 original article how many fenestrations should i make when placing a baerveldt glaucoma implant? a laboratory study michael c yang1, md; christopher d yang1, bs; ken y lin1,2, md, phd 1gavin herbert eye institute, department of ophthalmology, university of california, irvine, california 2department of biomedical engineering, university of california, irvine, california orcid: michael c. yang: https://orcid.org/0000-0003-3292-8578 ken y. lin: https://orcid.org/0000-0002-6467-7219 abstract purpose: this study investigates the effect of one versus two fenestrations on both fluid egress and opening pressure from a non-valved glaucoma implant. methods: in this laboratory study, we used an in vitro closed system comprised of ligated silicone tubing connected to a fluid reservoir and manometer to simulate the tubing found in a baerveldt glaucoma drainage implant. fenestrations were created using an 8-0 vicryl tg140-8 suture needle. main outcome measures included volume of fluid egress and fenestration opening pressures, which were measured via micropipette and increasing pressure until fluid egress was observed. results: no significant difference was observed in fluid egress between tubing with one versus two fenestrations at pressures ≤40 mmhg. at 50 mmhg, a statistically significant difference was observed in fluid egress between tubing with one versus two fenestrations (p < 0.05). the first fenestration opened at 10.5 ± 3.77 mmhg and the second fenestration opened at 28.83 ± 5.09 mmhg (average ± standard deviation). conclusion: our in vitro findings suggest there may exist a critical pressure >40 mmhg at which the second fenestration starts to play a significant role in fluid drainage. there may be no difference in the amount of fluid egress and effect on intraocular pressure between one or two tube fenestrations when preoperative intraocular pressure is ≤40 mmhg. keywords: baerveldt; drainage implants; fenestration; glaucoma; opening pressure j ophthalmic vis res 2023; 18 (2): 157–163 correspondence to: ken y lin, md, phd. gavin herbert eye institute, irvine, ca 92697-4375, usa. email: linky@hs.uci.edu received: 08-11-2022 accepted: 12-01-2023 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i2.13181 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: yang mc, yang cd, lin ky. how many fenestrations should i make when placing a baerveldt glaucoma implant? a laboratory study. j ophthalmic vis res 2023;18:157– 163. © 2023 yang et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 157 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i2.13181&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr baerveldt implant fenestrations ; yang et al introduction in the recent years, glaucoma drainage implants (gdis) have become a mainstay in surgical glaucoma management becoming the preferred option over trabeculectomy in a growing number of glaucoma practices.[1] gdis share a common anatomy comprising of a silicone tube connected to an endplate. the silicone tube is surgically inserted into the eye to allow access to the aqueous humor, and the endplate is fixed to the sclera and covered with conjunctiva and tenon’s capsule. like trabeculectomy, gdis are considered penetrative glaucoma surgeries that create a de novo pathway for aqueous drainage. the two most common gdis on the market are the ahmed glaucoma drainage implant (agi; new world medical, rancho cucamonga, california) and the baerveldt glaucoma drainage implant (bgi; johnson & johnson, santa ana, california). when compared to the agi, the bgi results in a significantly lower mean intraocular pressure (iop) with lower rates of failure. however, the bgi carries a higher risk of postoperative hypotony, in part because it does not have a valve mechanism.[2, 3] valved implants generally have a pressure floor below which aqueous flow through the implants is disabled. the krupin implant utilizes a unidirectional valve that opens when iop is >11 mmhg.[4] the valve mechanism of the agi involves thin silicone membranes that open, via the venturi effect, when iop is >8–12 mmhg.[5] on the other hand, non-valved implants, like the bgi, allow for unrestricted flow of aqueous humor and rely on encapsulation around the endplate for flow resistance.[6] for this reason, flow through non-valved glaucoma implants must be restricted in the immediate postoperative period before encapsulation has occurred. one common restriction method is to ligate the silicone tube with dissolvable suture. it is common practice to fenestrate the ligated tubes to allow for some degree of aqueous humor drainage while the capsule is maturing.[6] little consensus exists regarding the number and manner with which fenestrations are created in non-valved gdis. similarly, no heuristics exist to guide how fenestrations should or should not be modified based on preoperative iop. such heuristics, even if theoretical or based on in vitro observations, are nevertheless important because they may help guide clinicians to achieve a more stable and predictable iop during the immediate postoperative period. moreover, only a few published experiments evaluating the number of fenestrations and their effects on outflow facility and iop in in vitro and ex vivo systems have been performed, with equivocal results.[7, 8] in an in vitro study of a ligated bgi with four fenestrations using a 7-0 vicryl tg140-8 needle, the volume of fluid egress was found to positively correlate with simulated iop.[8] in an ex vivo study of porcine eyes, three fenestrations with a 7-0 vicryl tg1408 needle led to a significantly lower final iop compared to a single fenestration after 15 min with an initial iop of 50 mmhg.[7] additional studies are needed to evaluate the wide spectrum of fenestration possibilities and their effects on fluid egress. in our study, we utilize an in vitro apparatus as a model for ligated bgi tubing to evaluate fluid efflux with one versus two fenestrations created with a vicryl tg140-8 needle at discrete intratubular pressures. in addition to quantifying the volume of fluid egress, we also identify an opening pressure at which fluid outflow begins from each fenestration. we hypothesized that the number of fenestrations in the tubing does not significantly affect the volume of fluid efflux until a critical intratubular pressure threshold is reached. methods glaucoma drainage implant experimental apparatus an in vitro experimental apparatus was created as a model for ligated bgi tubing [figure 1]. non-sterile silicone tubing (access technologies, 2 french silicone catheter, model bc-2s), with an internal diameter of 0.3 mm and outer diameter of 0.6 mm, was used to simulate the silicone tubing attached to the baerveldt glaucoma drainage implant (0.30 × 0.63 mm). the silicone tubing was connected to the system by a 27g cannula (eagle labs, 27ga × 1” cannula, model 113-27ns) attached to a three-way stopcock (medex, 3-way stopcock, model mx4311l). the open end of the silicone tube was clamped with a hemostat to create a closed system. the other two ends of the threeway stopcock were attached to intravenous tubing (baxter, continu-flo solution set, model 2c8537s) with a 50 ml syringe as a fluid reservoir (bd, 50 ml syringe luer-lok tip, model 309653) and to 158 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 baerveldt implant fenestrations ; yang et al a manometer (omega, absolute pressure meter, model hhc281). the fluid reservoir was filled with a balanced salt solution (alcon, bss sterile irrigating solution, model 9012632-1115). tube fenestration and fluid egress measurement at variable iop a simulated iop (or intra-tubular pressure) was held constant at a predetermined level by adjusting the height of the fluid reservoir (20, 30, 40, and 50 mmhg). tube fenestrations were created using a spatulated suture needle (ethicon, 7-0 vicryl, tg140-8 needle) by entering perpendicularly to the center of and passing through the front and far side of the tubing. the two fenestrations were approximately 1 mm apart. two horizontal slit openings (parallel to the walls of the tube, front and far sides of the tube) were created with a single fenestration [figure 2]. two fenestrations resulted in four horizontal slit openings. care was taken to enter and exit along the same needle path to avoid enlarging the fenestration. the total volume of egressed fluid was measured from both fenestrations after 5 min using betapette micropipettes to the nearest microliter. four trial measurements were obtained for each experimental replicate; each trial was conducted with new silicone tubing and newly created fenestrations [table 1]. a total of 32 trial measurements were obtained. opening pressure measurement simulated iop (or intra-tubular pressure) was initially held at atmospheric pressure. two fenestrations were then created in the manner as described in “measuring the volume of fluid egress at variable iop.” subsequently, the hydrostatic pressure was gradually increased by raising the reservoir height at an approximate rate of 1 mmhg per sec. the intra-tubular pressure was increased until both fenestrations were open. the opening pressure of the fenestration was defined as the pressure required to induce approximately 5 µl of fluid efflux, given that this volume of fluid would be visible underneath the microscope. five trial measurements were obtained for each of the six experimental replicates; each replicate was conducted with new silicone tubing and newly created fenestrations. statistical analysis data were recorded in an excel spreadsheet and statistical analysis was performed with an unpaired student’s t-test like other studies comparing similar outcomes.[7] p-values < 0.05 were considered statistically significant. imaging of the fenestrations were obtained with a digital camera (iphone 12 pro, apple, cupertino, united states) equipped with a microscope attachment (diple lux, smartmicrooptics, genoa, italy). results in the 20-mmhg trial, a single fenestration resulted in a mean fluid egress of 113.5 µl, two fenestrations 159 µl; not significantly different with a p-value of 0.16 [table 1]. in the 30-mmhg trial, a single fenestration resulted in a mean fluid egress of 188.25 µl, two fenestrations 263.5 µl; not significantly different with a p-value of 0.15. in the 40-mmhg trial, a single fenestration resulted in a mean fluid egress of 213.75 µl, two fenestrations 293.75 µl; not significantly different with a p-value of 0.08, but notably trending toward significance. in the 50-mmhg trial, a single fenestration resulted in a mean fluid egress of 247.75 µl, two fenestrations 548.75 µl; notably different with a significant pvalue of 0.02. although mean fluid egress trended toward increasing with an additional fenestration, it was only statistically significant in the 50-mmhg group [figure 3]. the first fenestration opened at 10.5 mmhg (range: 6–21 mmhg), while the second fenestration opened at 28.83 mmhg (range: 23–41 mmhg) with a p-value of < 0.001 [table 2]. notably, the first fenestration to open was not always the one closest to the fluid source. discussion the salient findings of our study are as follows: (1) at a simulated intraocular pressure of 50 mmhg, there is a statistically significant difference in total volume of egressed fluid from the silicone tube with one versus two fenestration(s); (2) there is no significant difference if simulated iop is 40 mmhg or less (the 40 mmhg group was very close to being statistically significant with a pvalue of 0.08); (3) in the opening pressure trials, journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 159 baerveldt implant fenestrations ; yang et al ۲ figure 1. diagram of in vitro experimental setup modeling a ligated silicone tube of a non-valved glaucoma drainage implant. two french silicone tubing connected to a 27-gauge cannula attached to a three-way stopcock. the open end of the silicone tube was clamped with a hemostat. the other two ends of the three-way stopcock were attached to intravenous tubing with a fluid reservoir and to a manometer. figure 2. microscopic images of fenestrations in silicone tubing. fenestrations were created with 7-0 vicryl on a tg140-8 spatulated needle. (a) uniplanar fenestration structure. (b) biplanar fenestration structure. (c) triplanar fenestration structure. the second fenestration opened at a pressure of 28.83 ± 5.09 mmhg. the last two observations suggest that a critical opening pressure exists between 40 and 50 mmhg beyond which the second fenestration significantly contributes to fluid drainage out of the silicone tube. it is possible that the critical pressure may actually exist at a pressure between 30 and 40 mmhg, given that the second fenestration opens at approximately 29 mmhg. these findings suggest that the creation of a second fenestration in the ligated baerveldt tube does not result in a significant decrease in iop if the preoperative iop is <40 mmhg. in other words, single fenestration should be sufficient when the preoperative iop is <40 mmhg. our in vitro experiment may provide some guidance to glaucoma surgeons when deciding the number of fenestrations to create intraoperatively. yet, given the inherent limitations of an in vitro study, the results reported here should be considered in the broader context of surgeons’ clinical and surgical expertise. olayanju et al characterized the outflow facility of a tube system with constant intraocular pressure and fenestrated with varying needles and blades.[8] they found that the outflow facility (ml/min/mmhg) was mainly dependent on intraocular pressure and did not significantly change by external weight on 160 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 baerveldt implant fenestrations ; yang et al table 1. fluid egress from silicone tube with one versus two fenestrations at varying simulated intraocular pressures after 5 min. fenestrations were created with 7-0 vicryl on a tg140-8 spatulated needle. simulated intraocular pressure (mmhg) number of fenestrations mean fluid egress at 5 min (µl) ± standard deviation minimum fluid egress at 5 min (µl) maximum fluid egress at 5 min (µl) p-value 20 mmhg 1 113.5 ± 23.3 82 130 0.156 2 159 ± 83.5 87 235 30 mmhg 1 188.25 ± 128.85 53 350 0.149 2 263.5 ± 10.01 235 283 40 mmhg 1 213.75 ± 87.18 135 295 0.083 2 293.75 ± 75.66 235 380 50 mmhg 1 247.75 ± 124.89 144 428 0.021 2 548.75 ± 174.81 505 620 *mmhg, millimeters of mercury; µl, microliters figure 3. fluid egress from silicone tube with one versus two fenestrations at varying simulated intraocular pressures after 5 min. blue bar indicates one fenestration. red bar indicates two fenestrations. fenestrations were created with 7-0 vicryl on a tg140-8 spatulated needle. *mmhg, millimeters of mercury; µl, microliters the tube (e.g., scleral patch graft). however, they made the observation that the microarchitecture of the fenestrations was widely variable; the same external forces (e.g., scleral patch graft) could either reinforce fenestration closure or hold the fenestrations open. the fenestrations created by the 7-0 vicryl tg140-8 needle appeared to exhibit the lowest outflow facility when compared to openings created by a 15 blade and 9-0 nylon cs140-6 needle with a suture stent. however, the authors did not investigate differences in volume outflow between varying numbers of vicryl needle fenestrations. honda et al utilized an ex vivo experimental set up with pig eyes and a syringe pump perfusing fluid into the system at the same rate as aqueous production (200 µl/hr).[7] various needles were used to create one or three fenestrations (70 vicryl, 7-0 pds, 5-0 pds, 3-0 pds). after fenestrations were created, iop was compared between needle types after 15 min of perfusion with a starting iop of 50 mmhg. only the 70 vicryl group had a significantly lower final iop between the one and three fenestration subsets. however, when comparing the iop curves between tubes with one versus three fenestrations, the slope of iop decline in the tube with three journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 161 baerveldt implant fenestrations ; yang et al table 2. opening pressure of first and second fenestration of silicone tube. fenestrations were created with 7-0 vicryl on a tg140-8 spatulated needle. mean opening pressure ± standard deviation (mmhg) minimum opening pressure (mmhg) maximum opening pressure (mmhg) p-value fenestration #1 10.5 ± 3.77 6 21 < 0.001 (1.76e-19) fenestration #2 28.83 ± 5.09 23 41 *mmhg, millimeters of mercury; e, 10𝑥 fenestrations was steeper between approximately 35–50 mmhg. interestingly, when iop was < 35 mmhg, both tubes (one and three fenestrations) appeared to exhibit similar slopes of iop decline. this suggests that honda et al also identified a critical opening pressure (approximately >35 mmhg) at which the second and third fenestrations begin to significantly contribute to fluid drainage out of the tube. this critical opening pressure phenomenon may be explained by the elasticity of the silicone tubing. in the absence or insufficiency of an internal fluid load, hydrodynamic pressure cannot overcome the elasticity of the silicone, and the tube will self-seal. like other reports evaluating glaucoma tube shunt fenestrations, our results varied widely between each trial.[7, 8] this may be due to microscopic variations in surgical technique resulting in a variety of differences in microarchitecture between fenestrations [figure 2]. we found that fenestrations with the 7-0 vicryl tg140-8 needle could take the form of a uniplanar, biplanar, or triplanar structure. certainly, other microarchitecture configurations are possible. it would be valuable to characterize the microstructure of each fenestration (e.g., uniplanar, biplanar, triplanar, etc.) and evaluate the differences in opening pressure and fluid egress of each microstructure type. although our results do not consistently demonstrate this, other authors have found that multiple fenestrations lead to a wider standard deviation of results compared to a single fenestration.[7] presumably, with an increased number of fenestrations, microarchitecture variability also increases. for example, the distance between each fenestration and the location of the fenestrations in relation to the scleral patch graft may affect opening pressure and/or fluid egress. honda et al also found that round needles (e.g., pds needles) allowed for more consistent fenestration construction and more predictable experimental outcomes,[7] further emphasizing the importance of fenestration microarchitecture. the limitations of our study were that we utilized an in vitro experimental apparatus instead of pig or human eyes. our model recapitulated a real eye but assumed no outflow via the traditional or uveoscleral pathways, and no peritubular flow. as with any in vitro model, our system does not perfectly mimic the normal physiology of aqueous drainage. to avoid variability in our measurements, we elected to hold the pressure at a constant level; however, in a human eye, iop would decrease as aqueous exits. in other words, the physiologic flow rate would be dynamic and decelerate as the pressure falls below the opening pressures of the fenestrations. additionally, we utilized balanced salt solution in place of aqueous humor. prior studies have indicated that aqueous humor, with its various proteins and blood products, can occlude fenestrations.[9] aqueous humor also has a different viscosity from balanced salt solution and, as such, the actual opening pressure of an implanted bgi may be slightly different; however, we posit that the relatively small contribution from the second fenestration in most of the iop ranges tested still holds clinically. it is important to keep in mind that the critical pressures reported in this study are likely lower than what would be seen in patients; the effect of episcleral fibrosis was not accounted for in this study. moreover, our model does not include a simulated scleral patch graft. in theory, the scleral patch graft may apply external pressure to the tubing, either facilitating flow or blocking the fenestrations.[8] however, prior studies (olayanju et al) simulated the presence of the patch graft with external weights and found no significant difference in outflow facility of the tubing. 162 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 baerveldt implant fenestrations ; yang et al the apparent difference between our observed critical pressure (>40 mmhg) and the opening pressure of the second fenestration (approximately 30 mmhg) may be explained by the design of our fluid egress experiments, in which simulated iop was increased in 10 mmhg intervals. these intervals do not precisely capture the pressure at which egress saturates. future experiments can be performed to expand on our study by conducting experiments between the 10 mmhg intervals, determining the effect of interfenestration distance on opening pressure, studying the effect of fenestration numbers greater than two, and quantifying the microarchitecture of manually created fenestrations. our study demonstrates no significant difference in fluid outflow from two french silicone tubing between one or two fenestrations created by a 7-0 vicryl tg140-8 needle at simulated iops ≤40 mmhg in an in vitro setting. the second fenestration has an opening pressure of approximately 29 mmhg but may not induce a significant effect on outflow until iop is >40 mmhg. our study is limited by several aforementioned factors which may restrict its translation to clinical practice in patients. however, assuming the egressed volume of fluid correlates with iop, our findings suggest that the creation of more than one fenestration in bgi tubing may not have a significant effect on postoperative iop unless preoperative iop is >40 mmhg. financial support and sponsorship kyl is a recipient of the clinician scientist award from the american glaucoma society. the gavin herbert eye institute is a recipient of an unrestricted grant from research to prevent blindness (rpb). conflicts of interest no conflicts exist for any author. references 1. vinod k, gedde sj, feuer wj, panarelli jf, chang tc, chen pp, et al. practice preferences for glaucoma surgery: a survey of the american glaucoma society. j glaucoma 2017;26:687–693. 2. budenz dl, barton k, gedde sj, feuer wj, schiffman j, costa vp, et al. five-year treatment outcomes in the ahmed baerveldt comparison study. ophthalmology 2015;122:308–316. 3. christakis pg, kalenak jw, tsai jc, zurakowski d, kammer ja, harasymowycz pj, et al. the ahmed versus baerveldt study: five-year treatment outcomes. ophthalmology 2016;123:2093–2102. 4. krupin t, podos sm, becker b, newkirk jb. valve implants in filtering surgery. am j ophthalmol 1976;81:232–235. 5. coleman al, hill r, wilson mr, choplin n, kotas-neumann r, tam m, et al. initial clinical experience with the ahmed glaucoma valve implant. am j ophthalmol 1995;120:23– 31. 6. poelman hj, wolfs rcw, ramdas wd. the baerveldt glaucoma drainage device: efficacy, safety, and place in therapy. clin ophthalmol 2020;14:2789–2797. 7. honda r, kasuga t, murakami a, matsuda a. effects of the numbers and the shapes of venting slits on intraocular pressure after baerveldt glaucoma drainage implant. curr eye res 2019;44:921–924. 8. olayanju j, borras t, qaqish b, fleischman d. outflow facility in tube shunt fenestration. j curr glaucoma pract 2018;12:113–118. 9. brooks se, dacey mp, lee mb, baerveldt g. modification of the glaucoma drainage implant to prevent early postoperative hypertension and hypotony: a laboratory study. ophthalmic surg 1994;25:311–331. journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 163 erratum erratum: side effects of brolucizumab j ophthalmic vis res 2022; 17 (1): 157–157 in the article titled “side effects of brolucizumab,” published on pages 670–675, issue 4, volume 16 of journal of ophthalmic and vision research,[1] the name of the second author is written incorrectly as “saeed mohammadi” instead of “s. saeed mohammadi.” references 1. motevasseli t, mohammadi s, abdi f, freeman wr. side effects of brolucizumab. j ophthalmic vis res 2021;16:670–675. © 2022 . this is an open access article distributed under the creative commons attribution license | published by knowledge e 157 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10185&domain=pdf&date_stamp=2019-07-17 authors’ reply ramesh venkatesh, ms; kushagra jain, ms; arpitha pereira, mrcsed, dnb; mb thirumalesh, md; naresh kumar yadav, do, frcs department of retina and vitreous, narayana nethralaya, bangalore, india orcid: ramesh venkatesh: https://orcid.org/0000-0002-4479-9390 j ophthalmic vis res 2022; 17 (4): 607–607 dear editor, we thank the author for showing interest in our article titled “torpedo retinopathy” and for providing important comments on it.[1] classically, torpedo maculopathy is considered as a retinal pigment epithelium (rpe) defect, typically in the temporal macula with a characteristic pointed, ”torpedo” shape, with one tip pointing toward the macula. several theories have been floating as to the etiology, including an hypopigmented rpe nevus, a developmental defect in the ”fetal temporal bulge”, or failure of the rpe to close overlying the region near the emissary canal of the long posterior ciliary artery and nerve.[2–4] our paper describes cases of torpedo lesions located at sites other than the macula in the fundus.[1] hence, we titled the paper as “torpedo retinopathy” and suggested a change in the routinely used nomenclature of “torpedo maculopathy”. with the use of advanced retinal imaging techniques such as optical coherence tomography (oct), oct-angiography, multicolor imaging, and adaptive optics imaging, it is increasingly becoming clear that the inner choroid, correspondence to: ramesh venkatesh, ms. department of retina and vitreous, narayana nethralaya, #121/c, chord road, 1st r block rajaji nagar, bangalore 560010, india. e-mail: vramesh80@yahoo.com received: 20-04-2022 accepted: 09-05-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i4.12346 mainly the choriocapillaris layer gets affected in the torpedo lesions.[5–7] hence, we do back the suggestion by the author that the revised nomenclature for the torpedo lesions in the fundus be termed as “torpedo chorioretinopathy” as it addresses the issues both related to its location and its involvement of the retina and choroid. references 1. venkatesh r, jain k, pereira a, thirumalesh mb, yadav nk. torpedo retinopathy. j ophthalmic vis res 2020;15:187– 194. 2. golchet pr, jampol lm, mathura jr jr, daily mj. torpedo maculopathy. br j ophthalmol 2010;94:302–306. 3. shields cl, guzman jm, shapiro mj, fogel le, shields ja. torpedo maculopathy at the site of the fetal “bulge”. arch ophthalmol 2010;128:499–501. 4. roseman rl, gass jd. solitary hypopigmented nevus of the retinal pigment epithelium in the macula. arch ophthalmol 1992;110:1358–1359. 5. raval v, rao s, sudana p, das t. torpedo maculopathy. j ophthalmic vis res 2020;15:113–115. 6. venkatesh r, bavaharan b, yadav nk. multicolor imaging findings in torpedo maculopathy. indian j ophthalmol 2019;67:295–297. 7. venkatesh r, yadav nk, sinha s, mehta r, akkali mc. structural-functional correlation using adaptive optics, visual fields, optical coherence tomography and multifocal electroretinogram in a case of torpedo maculopathy. indian j ophthalmol 2019;67:1502–1505. this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: venkatesh r, jain k, thirumalesh mb, yadav nk. authors’ reply. j ophthalmic vis res 2022;17:607–607. © 2022 venkatesh et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 607 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i4.12346&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr original article prevalence and causes of avoidable blindness in subjects over 50 years of age in honduras mariel eunice amador rosa1, md; alejandra lozano bustillo1, md; iván espinoza salvadó1, md; manuel sierra1, md; belinda rivera2, md 1department of ophthalmology, faculty of medical sciences, national autonomous university of honduras (unah) 2ophthalmology specialist in san felipe general hospital orcid: mariel eunice amador rosa: https://orcid.org/0000-0003-2354-4329 alejandra lozano bustillo: https://orcid.org/0000-0002-2131-3634 abstract purpose: to describe the prevalence and causes of avoidable blindness in people aged 50 and over in the areas of influence of doctors in social service during the years 2018–2019. methods: this observational, descriptive, cross-sectional study, with analysis of association of variables, was conducted on patients 50 years and older at the national level, selected under simple random sampling, where sociodemographic variables, background, and clinical characteristics were studied. an ophthalmological clinical examination was performed with prior informed consent, and the information was processed and analyzed using epi info 7.2 statistical package and spss version 25. results: overall, 7992 people were evaluated, with a mean age of 62 years; 60.8% (4861) were women and 39.2% (3131) were men. the prevalence of blindness for both eyes was 4.5% (356/7992, 95% ci: 4.1–5.1%, p < 0.001). the prevalence of severe and moderate visual impairment was 1.5% (118/127) and 12.9% (1029)/12.6% (1004) for the right and left eyes, respectively. the main causes of blindness were cataract, refractive error, and glaucoma. conclusion: the prevalence of avoidable blindness found in the study was higher than expected and the respective causes were consistent with previous studies. consequently, it is recommended to implement health policies aimed at the prevention and management of avoidable blindness. keywords: blindness; cataract; honduras; prevalence j ophthalmic vis res 2022; 17 (2): 225–232 © 2022 rosa et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 225 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i2.10794&domain=pdf&date_stamp=2019-07-17 avoidable blindness in honduras; rosa et al introduction in latin america and the caribbean, blindness and vision loss in adults continues to be a substantial public health problem. this challenge that occurs in the 50 years and older demographic is quite impactful on society.[1] according to the world health organization (who), there are 253 million people with visual impairment, 36 million with blindness, and 217 million with moderate to severe visual impairment.[2,3] the estimated number of blind people increased to 36.0 million in 2015. this change was attributable to three factors, namely an increase due to population growth (38.4%), increase in aging population (34.6%), and reduction in age-specific prevalence (36.7%).[4–6] in honduras, a single study of prevalence of blindness was carried out in 2013 by alvarado et al. based on the data from that study, an estimated prevalence of blindness of was 1.9%; the data obtained revealed the magnitude of this serious public health problem.[7] globally, the causes of both low vision and blindness were uncorrected refractive error, cataracts, age-related macular degeneration, glaucoma, and diabetic retinopathy.[3, 8, 9] among some regions of the world, causes of blindness and visual impairment in people over 50 years old varied markedly, with a high prevalence of age-related macular degeneration (>14% blindness) as the primary cause in high-income countries. however, the number of people with visual impairment due to diabetic retinopathy is increasing worldwide and represents an extensive proportion of all causes of blindness.[9–11] correspondence to: alejandra lozano bustillo, md. department of ophthalmology, faculty of medical sciences, national autonomous university of honduras (unah), tegucigalpa 11101, honduras. e-mail: alejandra301@gmail.com received: 24-01-2021 accepted: 06-02-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i2.10794 the prevalence of blindness and severe and moderate visual impairment are concentrated in the most socially disadvantaged sectors of the population.[12] consequentially in the midst of financial constraints, these communities require the development of eye care systems, including human resources and infrastructure elements to urgently determine the extent of diseases of the anterior and posterior segments of the eye as causes of visual impairment. in this study, we aim to establish the prevalence and causes of avoidable blindness in the 50 years and over segment of the population in the areas of influence which were attended by doctors who provided social services to the communities during the period of april 2018–april 2019. this study’s purpose is an attempt to generate interest for the creation of public policies geared toward early diagnosis and timely management of the main causes of blindness. methods this observational, descriptive, cross-sectional study was conducted for a period of one; the first stage consisted of training in basic ophthalmic examination of the social service doctors (last-year students) of the national autonomous university of honduras (unah) provided by ophthalmology residents and the scientific research unit; the second stage was the evaluation of patients over 50 years by these students; and the third and the final stage was the evaluation and treatment of patients in a specialized ophthalmological consultation in referral centers. for this evaluation, the ophthalmology residents were mobilized to referral centers in different cities of the country. this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: rosa mea, bustillo al, salvadó ie, sierra m, rivera b. prevalence and causes of avoidable blindness in subjects over 50 years of age in honduras. j ophthalmic vis res 2022;17:225–232. 226 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 https://knepublishing.com/index.php/jovr avoidable blindness in honduras; rosa et al the training of the last-year students consisted of 5-hr workshops with theoretical modules and supervised practices on visual acuity testing and basic ophthalmological evaluation. each student was given either a chart with an e optotype or the use of the application ”peek acuity” establishing 6 m as a distance for assessing visual acuity. the protocol was approved by the coordination of the ophthalmology postgraduate, ethics committee on biomedical research, and scientific research unit of the medical sciences faculty. in our study, we used the classification as: • mild: visual acuity worse than 0.3 to 0.5 of logmar chart or 20/25 to 20/60 in snellen chart (sc) • moderate: visual acuity worse than 0.5 to 1 or 20/60 to 20/200 in sc • severe: visual acuity worse than 1 to 2 or 20/200 to 20/400 in sc • blindness: visual acuity worse than 2 or 20/400 in sc the universe of the study was all nationwide adult patients over 50 years old who lived within the areas of influence by the last-year students who provided the social service. the sampling unit corresponded of a simple random selection of houses in these areas. prior to the selection, an updated sketch of all the areas of influence was prepared to select the geographic area where the surveys were applied also randomly. between november and december 2018, a simple random sample of patients aged 50 years or older from the areas of influence served by the last-year students were selected. a total of 7992 patients were evaluated. only the subjects that gave their informed consent and fulfilled the inclusion criteria (over 50 years of age and agreed to participate in the study) were considered. subject with mental disabilities that made impossible to measure visual acuity were excluded from the study. the students applied a survey that included sociodemographic variables, test of visual acuity (with and without glasses if the patient had it already and also with and without pinhole), personal pathology history, ophthalmological and surgical history, as well as ocular pathological family history and the existence of comorbidities (diabetes mellitus and high blood pressure).in diabetic patients, the onset of the disease and the current treatment were considered. every student practiced a basic ophthalmological examination and the visual acuity (with and without pinhole) through either printed snellen primers or the “peek acuity” application which has been used in multiple studies around the world.[13] all patients with visual acuity ≤20/200 were sent to reference centers nationwide (olancho, san pedro sula, la ceiba, santa rosa de copán, san lorenzo, comayagua, and tegucigalpa cities) according to their location where the ophthalmology resident was mobilized to assess them. the cause of blindness or severe visual impairment was then determined and the respective treatment started. data were entered into a database created with the statistical package epiinfo version 7.2 (cdc, atlanta usa). the analysis was made with the statistical program spss version 25 and consisted of simple frequency construction, univariate and bivariate analysis establishing statistical significance with chi-square tests for proportion comparison. ors were constructed with 95% confidence intervals. statistical significance was considered when ”p-value” was <0.05. results of the total of 7992 participants, 3131 (39.2%) were men and 4861 (60.8%) women. of them, 2042 (25.5%) participants were from the capital and 5950 (74.5%) from the rest of the country. all the study variables are presented in tables 1–5. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 227 avoidable blindness in honduras; rosa et al table 1. characterization of visual acuity per eye in patients aged 50 years and over, honduras 2018–2019 (n: 7992) category right eye left eye n % n % blindness 220 2.8 234 2.9 severe visual impairment 118 1.5 127 1.5 moderate visual impairment 1029 12.9 1004 12.6 normal/mild visual impairment 6625 82.9 6627 82.9 table 2. characterization of visual acuity for both eyes in patients aged 50 years and over, honduras 2018–2019 (n: 7992) category n % severe visual impairment 207 (2.5) moderate visual impairment 1482 (18.5) normal/mild visual impairment 7114 (89) ∗patients with at least one eye with any of the categories of visual acuity were taken into account table 3. comparison of sociodemographic data of adults aged 50 years and over, with and without blindness in both eyes in honduras, 2018–2019 (n: 7992) characteristic with blindness n: 356 without blindness n: 7636 age (yr) n (%) n (%) 50–59 70 (19.7) 3799 (49.8) 60–69 116 (32.6) 2179 (28.5) 70–79 93 (26.1) 1196 (15.7) 80–89 70 (19.7) 422 (5.5) 90–105 7 (2) 40 (0.5) sex female 213 (59.8) 4648 (60.8) male 143 (40.1) 2988 (39.1) scholarship illiterate 123 (34.6) 1519 (19.9) primary 191 (53.7) 3882 (50.8) high school 27 (7.6) 1597 (20.9) university 15 (4.2) 638 (8.4) table 4. main causes of blindness in patients aged 50 years or older evaluated in the reference centers, honduras, 2018–2019 (n: 67) cause of blindness right eye left eye both eyes n: 67 % n: 67 % n: 134 % cataract without treatment 25 37.3 31 46.3 56 41.7 refractive error 13 19.4 9 13.4 22 16.4 glaucoma 8 11.9 9 13.4 17 12.6 does not apply 2 3.0 0 0 2 1.4 no examination 6 9.0 7 10.4 13 9.7 another posterior segment 5 7.5 4 6.0 9 6.7 phthisis 1 1.5 1 0.7 diabetic retinopathy 6 9.0 4 6.0 10 7.4 surgical complications 0 0 1 1.5 1 0.7 other corneal opacities 1 1.5 2 1.5 3 2.2 ∗patients with blindness in at least one eye were considered 228 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 avoidable blindness in honduras; rosa et al table 5. reason why adult patients 50 years or older had not undergone surgery considering themselves blind from cataract, honduras, 2018–2019 (n: 210/206) reason right eye n: 210 left eye n: 206 n % n % no need 37 (17.6) 41 (19.9) fear of surgery or poor results 53 (25.2) 55 (26.6) can’t pay the price 84 (40.0) 87 (42.2) they refuse to provide the service 8 (3.8) 7 (3.3) i didn’t know there was a treatment 12 (5.7) 11 (5.3) cannot travel to care centers 30 (14.2) 27 (13.1) discussion according to global data, of the 7.33 billion people alive by 2015, 36.0 million were blind, 56% of these were women (20.1 million). most of the world population with blindness is situated in the asian region.[14] in latin america, the general prevalence of blindness in people over 50 years varies from region to region.[1] according to the results of our study, 4.5% of people over 50 years of age presented blindness in at least one eye, similar to that described by the who for worldwide estimates at 4.24%.[2] our study also coincides with data from other locations such as three developing world regions in sub-saharan west africa, east sub-saharan africa, and south asia with an estimated prevalence of 4%[14] and in countries such as panama where the prevalence is around 30.0%. it was higher than the result of the only previous study carried out in the country which was 1.9% and studies performed in other countries such as ecuador (1.7%) and urban areas in argentina (1.3%), brazil (1.6%), and chile (1.4%). the general prevalence of visual impairment (severe and moderate) varies from 8.0% in uruguay to 14.3% in el salvador.[1] in our study in honduras, this group had a percentage of 2.5% with severe visual impairment and 18.5% with moderate visual impairment. normal vision or mild visual impairment was present in 79%. all this similitude can be related and comparable among the latin-american region due to factors such as our race, customs and similar challenges as it pertains to access to public health. there was a higher prevalence of blindness in males but with no statistically significant difference. our results were different from a comparative study in 2015 on avoidable blindness and visual impairment completed in seven latin-american countries (argentina, el salvador, honduras, panama, paraguay, peru, uruguay) where the female population was shown to be predominant in all regions.[1] globally, the female population is the predominant sex to experience blindness in most of the studies.[14] another important consideration regarding our study is that most of the surveyed households were answered by the housewives since at that time of the survey, the partner was at work. functional presbyopia’s prevalence is increasing and is estimated to affect 666.7 million people 50 years of age and over worldwide[14] in the future. in our study, 18.9% patients reported having a history of presbyopia and 26% reported the use of near-vision lenses, which contrasts with global data where the percentage of presbyopia has reached 40%.[12, 14] uncorrected refractive errors in adults have been shown to lead to blindness in some regions.[15] presbyopia and myopia were the most frequent refractive errors found in our study with 18.9% and 18.3%, respectively. according to the current global data, of the 95 million people over 50 with visual impairment due to uncorrected journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 229 avoidable blindness in honduras; rosa et al refractive errors, the presbyopia was the main cause of visual impairment while 6.9 million are blind. education status is an important influential social factor in experiencing blindness. in our study, the illiterate patients and those who had attended only primary school accounted for 29% and 53%, respectively, and were the population with a higher index of blindness, similar to that reported by ko et al who reported that the factors associated with some degree of deterioration, nonrefractive visuals included aging, poverty, and a low educational level.[16] from 1990 to 2010, the number of people who were blinded due to cataracts decreased from 12.3 million to 10.8 million.[17] in this study, the personal history recorded of patients revealed that cataract and pterygium surgery were the most prevalent. in countries where the prevalence of cataract is very high, important underlying causes are cataract-induced myopia, uncorrected aphakia, and insufficient lens correction.[15] in this study, the age range of the patients with the highest prevalence of blindness in both eyes was 60–69 years, which differs from world statistics where the highest prevalence is found in a younger population group between the ages of 40 and 49 years.[17] globally, in 2010, it was determined that cataract causes blidness in a total of 32.4 million people and visual impairments in 191 million.[17] in a latinamerican study, cataract was the main cause of bilateral blindness ranging from 47% to 87%, followed by posterior segment disease, including glaucoma, diabetic retinopathy, and age-related macular degeneration, ranging from 7% to 44%. in our study, cataract was found to be the main cause of blindness at 41.7%, followed by refractive errors at 16.4% and glaucoma and retinopathy with equal percentages of 12.6% and 7.4%, respectively. this data differs from global estimates, where the main causes of visual impairment are reported as uncorrected refractive error and cataracts, 43% and 33%, respectively.[2,3] in countries like nepal, retinal disorders which account for 46.66% followed by cataract at 43.33% are the two main causes of blindness.[8] cataract was more common in rural poor areas while retinal disorders were prevalent among the urban population. of all blindness causes, 88% and 94% were curable and preventable.[18, 19] this data differs from global estimates, where the main causes of visual impairment are reported as uncorrected refractive error and cataracts, 43% and 33%, respectively.[2, 3] in bhaktapur district, a popular city of nepal, retinal disorders which account for 46.66% followed by cataract at 43.33% are the two main causes of blindness.[8] the reason most of the patients in the study experienced blindness due to cataract was as a result of their inability to pay for the surgery. in another study conducted in sub-saharan africa, similar causes were discovered that led to patients experiencing blindness because of a treatable illness. the additional barriers to treatment that were discovered included the surgical cost, the lack of family support, the lack of understanding of the need for surgery, and other social, infrastructural, and geographical factors, such as disparity in the distribution of ophthalmologists throughout the region.[21] the quality of cataract surgery also remains a concern, as poor results have reached up to 40% in some areas.[22] in conclusion, the prevalence of blindness in people over 50 years old at the national level in honduras has increased in the last five years (1.9% to 4.5%) and seems to be closely associated with data from national socioeconomic indicators. cataract continues to be the most important cause of blindness and it seems that this problem has not changed in the last five years years, despite being previously identified as the major cause of visual impairment and blindness. underestimating the impact of diabetic retinopathy, glaucoma, or other diseases is easy when there is insufficient 230 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 avoidable blindness in honduras; rosa et al data, but they are important causes of blindness that should always be considered. socioeconomic factors must be taken into account when implementing strategies to improve the prevention of blindness. cataract continues to be a challenge to address with the need to plan a comprehensive strategy related to the accessibility of eye care services. improving the outcome of cataract surgery in the low-income population should also be focused. these initiatives are already conditions outlined to achieve the basic global goal established by the who, which accounts for a 25% reduction in the prevalence of avoidable blindness and visual impairment by the year of 2020. the reduction of blindness and visual impairment may be achieved by establishing improvements in the quality of life and advocating for higher incomes for the patient, family, and society to increase accessibility to proper healthcare. acknowledgements the authors are thankful to all the patients who participated in the study. financial support and sponsorship none. conflicts of interest the authors declare no competing interests. references 1. silva, jc, mújica, oj, vega, e., barceló, a., lansingh, vc, mcleod j, et al. a comparative evaluation of avoidable blindness and visual impairment in seven latin american countries: prevalence, coverage and inequalities. rev panam public health 2015;37:13–20. 2. who. global data on visual impairments 2010. who; 2012. available from: https://www.who.int/blindness/ globaldatafinalforweb.pdf 3. pascolini d, mariotti sp. global estimates of visual impairment: 2010. br j ophthalmol 2012;96:614–618. 4. flaxman sr, bourne rr, resnikoff s, ackland p, braithwaite t, cicinelli mv, et al. global causes of blindness and distance vision impairment 1990–2020: a systematic review and meta-analysis. lancet glob health 2017;5:e1221–e1234. 5. foster a, resnikoff s. the impact of vision 2020 on global blindness. eye 2005;19:1133. 6. alvarado d, rivera b, lagos l, ochoa m, starkman i, castillo m, et al. national survey of avoidable blindness and visual impairment in honduras. rev panam salud publica 2014;36:300–305. 7. patil s, gogate p, vora s, ainapure s, hingane rn, kulkarni an, et al. prevalence, causes of blindness, visual impairment and cataract surgical services in sindhudurg district on the western coastal strip of india. indian j ophthalmol 2014;62:240. 8. thapa r, bajimaya s, paudyal g, khanal s, tan s, thapa ss, et al. prevalence and causes of low vision and blindness in an elderly population in nepal: the bhaktapur retina study. bmc ophthalmol 2018;18:42. 9. kocur i, resnikoff s. visual impairment and blindness in europe and their prevention. br j ophthalmol 2002;86:716–722. 10. rahi js, cable n, british childhood visual impairment study group. severe visual impairment and blindness in children in the uk. the lancet 2003;362:1359–1365. 11. naidoo ks, leasher j, bourne rr, flaxman sr, jonas jb, keeffe j, et al. global vision impairment and blindness due to uncorrected refractive error, 1990–2010. optom vis sci 2016;93:227–234. 12. chakravarthy u, biundo e, saka ro, fasser c, bourne r, little ja. the economic impact of blindness in europe. ophthalmic epidemiol 2017;24:239–247. 13. bastawrous a, rono hk, livingstone ia, weiss ha, jordan s, kuper h, et al. development and validation of a smartphone-based visual acuity test (peek acuity) for clinical practice and community-based fieldwork. jama ophthalmol 2015;133:930–937. 14. bourne rr, flaxman sr, braithwaite t, cicinelli mv, das a, jonas jb, et al. magnitude, temporal trends, and projections of the global prevalence of blindness and distance and near vision impairment: a systematic review and meta-analysis. lancet glob health 2017;5:e888– e897. 15. resnikoff s, pascolini d, mariotti sp, pokharel gp. global magnitude of visual impairment caused by uncorrected refractive errors in 2004. bull world health 2008;86:63– 70. 16. ko f, vitale s, chou cf, cotch mf, saaddine j, friedman ds. prevalence of nonrefractive visual impairment in us adults and associated risk factors, 1999-2002 and 20052008. jama 2012;308:2361–2368. 17. khairallah m, kahloun r, bourne r, limburg h, flaxman sr, jonas jb, et al. number of people blind or visually journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 231 https://www.who.int/blindness/globaldatafinalforweb.pdf https://www.who.int/blindness/globaldatafinalforweb.pdf avoidable blindness in honduras; rosa et al impaired by cataract worldwide and in world regions, 1990 to 2010. invest ophthalmol vis sci 2015;56:6762– 6769. 18. limburg h, von-bischhoffshausen fb, gomez p, silva jc, foster a. review of recent surveys on blindness and visual impairment in latin america. br j ophthalmol 2008;9 :315–319. 19. leasher jl, bourne rr, flaxman sr, jonas jb, keeffe j, naidoo k, et al. global estimates on the number of people blind or visually impaired by diabetic retinopathy: a meta-analysis from 1990 to 2010. diabetes care 2016;39:1643–1649. 20. duerksen r, limburg h, lansingh vc, silva, jc. review of blindness and visual impairment in paraguay: changes between 1999 and 2011. ophthalmic epidemiol 2013;20:301–307. 21. bastawrous a, dean wh, sherwin jc. blindness and visual impairment due to age-related cataract in subsaharan africa: a systematic review of recent populationbased studies. br j ophthalmol 2013;97:1237–1243 22. rao gn, khanna r, payal a. the global burden of cataract. curr opin ophthalmol 2011;22:4–9. 232 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 original article long-term visual and refractive outcomes of argon laser-treated retinopathy of prematurity majid farvardin1,2, md; zahra kalantari1,2, md; mohammadreza talebnejad1,2, md; marzieh alamolhoda2, phd; amir norouzpour3, md 1department of ophthalmology, school of medicine, shiraz university of medical sciences, shiraz, iran 2poostchi ophthalmology research center, shiraz university of medical sciences, shiraz, iran 3poostchi eye clinic, shiraz university of medical sciences, shiraz, iran orcid: majid farvardin: http://orcid.org/0000-0001-9047-0329 amir norouzpour: http://orcid.org/0000-0002-7175-1536 abstract purpose: in this case–control study, we measured visual acuity, objective refraction, ocular biometric parameters, and strabismus in premature cases classified according to the following categories: argon laser-treated retinopathy of prematurity (rop), untreated spontaneously regressed rop, no rop, and fullterm controls. methods: cases with a history of prematurity at six years of age were categorized into the following groups: patients with a history of treated type 1 rop using argon laser (group i), untreated spontaneously regressed rop (group ii), and no history of rop (group iii). group iv included age-matched healthy full-term controls. funduscopy was performed for all the cases and the control group. results: in total, 24 eyes of 12 laser-treated rop cases, 186 eyes of 93 spontaneously regressed rop patients, 74 eyes of 37 premature cases with no history of rop, and 286 eyes of 143 controls were included in the study. the mean spherical equivalent in the treated cases was not significantly different from that in the untreated cases and patients in group iii. however, the average cylindrical power was significantly different among the groups (p < 0.004). furthermore, anisometropia (≥1.5 diopters) was diagnosed with a higher rate in the treated cases (p = 0.03). the corneal curvature of the laser-treated eyes was significantly steeper and the axial length was significantly shorter than those in the other groups (p < 0.002 and p < 0.001, respectively, for multivariate analysis). strabismus was found in three treated patients (25%). additionally, there were three treated eyes (12.5%) diagnosed with macular dragging. conclusion: premature cases including those who had a history of argon lasertreated rop and those with untreated spontaneously regressed rop showed acceptable long-term visual and refractive outcomes along with a fairly low rate of ocular disorders. keywords: argon laser; ocular biometric parameters; refraction; retinopathy of prematurity j ophthalmic vis res 2022; 17 (3): 384–389 384 © 2022 farvardin et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i3.11576&domain=pdf&date_stamp=2019-07-17 visual outcomes in argon laser-treated rop; farvardin et al introduction retinopathy of prematurity (rop) is a leading cause of visual impairment worldwide.[1, 2] treatments including cryotherapy and diode laser therapy have been efficacious in preventing the progression of the disease as well as decreasing the incidence of severe ocular complications such as retinal detachment and eventual visual loss.[3–5] since about 1990, diode laser photocoagulation has been considered a therapeutic option with better visual outcomes than cryotherapy.[6] furthermore, argon laser therapy has also been used for patients with threshold rop for about two decades.[7] however, patients who have been treated with laser may experience a higher incidence of retinal disorders, myopia, and abnormalities in ocular biometric components when compared to other cases with spontaneously regressed rop and no-rop children.[8] in this study, we measured visual acuity, objective refraction, and ocular biometric components of six-years-old children, born prematurely, and compared the results with those from age-matched full-term controls. methods the study was approved by the institutional review board in shiraz university of medical sciences (ethical code: 3-2018-0050) and was conducted in accordance with the declaration of helsinki. informed consent was taken from the parents of each subject. participants all cases between six and seven years old who were born prematurely and were followed in our university referral center in shiraz poostchi ophthalmology clinic were selected from the medical records. premature cases were categorized as having either a birth weight (bw) correspondence to: amir norouzpour, md. poostchi eye clinic, shiraz university of medical sciences, shiraz 7134845794, iran. e-mail: anorouzpour@gmail.com received: 15-02-2021 accepted: 20-11-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i3.11576 equal or lower than 1500 gr or a gestational age (ga) equal or lower than 34 wk. all subjects either lived in shiraz or in the nearby towns. cases with corneal and media opacity that prevented fundus examination and optical measurements, those with central nervous system diseases that prevented their cooperation with the tests, ocular diseases other than rop, and those with a history of intravitreal anti-vascular endothelial growth factor injection, or vitrectomy were all excluded from the study. peripheral retinal argon laser ablation using binocular laser indirect ophthalmoscopy (ellex solitaire 532 green argon laser, ellex inc., adelaide, australia) was performed on eyes with type 1 rop including zone ii, stage ii or iii rop with plus disease.[9] after our selection process, we contacted the parents to invite their child to the study. subjects were classified into four groups: (i) children with a history of rop who had been treated using argon laser; (ii) children with spontaneously regressed rop who had not received any therapy; (iii) children who were born prematurely but with no history of rop; and (iv) full-term subjects as the control group. the controls (group iv) were age-matched healthy subjects who were born at full term (bw > 2500 gr and ga > 37 wk) and their records were included from our previous study.[10] all group i cases had been treated bilaterally. visual acuity, refraction, and ocular biometric parameters both eyes of each subject were examined. the corrected distance visual acuity (cdva) of the cases were measured by an experienced pediatric optometrist. snellen visual acuity was converted to the logarithm of the minimum angle of resolution (logmar) for statistical analysis. automated cycloplegic refraction by an automatic keratorefractometer (nidek ark 510a japan) was done this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: farvardin m, kalantari z, talebnejad m, alamolhoda m, norouzpour a. long-term visual and refractive outcomes of argon laser-treated retinopathy of prematurity. j ophthalmic vis res 2022;17:384–389. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 385 https://knepublishing.com/index.php/jovr visual outcomes in argon laser-treated rop; farvardin et al and refined manually by the same optometrist. complete eye examination including funduscopy and strabismus assessment was performed by an expert pediatric ophthalmologist for all of the children. ocular biometric parameters including mean keratometry (mean-k), anterior chamber depth, and axial length were measured using the iol master 500 (carl zeiss germany). statistical analysis numerical variables were presented as mean and standard deviation. the shapiro–wilk test was performed to test the normality of the numerical variables. if the data distribution was gaussian, analysis of variance (anova) was conducted to find differences in numerical variables among the four groups. for the non-gaussian data, kruskal–wallis test was done to compare the numerical variables among the groups. post hoc test was used for the significant results to find any difference for pairwise comparisons. chi-square or fisher’s exact test was used to assess associations between categorical variables among the four groups. spss software for windows, version 16.0 (spss inc., chicago, ill., usa) was used for the data analyses. a p-value < 0.05 was considered statistically significant. results one hundred and sixty-four cases met the study criteria and were invited to take part in the study. a total of 142 cases accepted to participate and completed the examinations. there were 12 cases in group i, 93 in group ii, and 37 in group iii. all participants in group i had a history of zone ii, stage ii, or iii rop with plus disease for which they had undergone laser therapy. one hundred and forty three subjects between the age of six and seven were recruited as group iv (controls) from a previous study.[10] demographic data of the subjects are presented in table 1. the mean bws and gas were significantly different among the four groups (p < 0.001 and p < 0.001, respectively). moreover, in pairwise comparisons, cases in groups i and ii had significantly lower bws than the patients in group iii (p = 0.04 and p = 0.04, respectively). furthermore, group i cases had significantly lower gas than those in group iii (p = 0.02). there was no significant difference in the mean ages of the subjects at the time of examination among the four groups (p = 0.88). the gender distributions were not significantly different among the groups (p = 0.92). the data for the visual, structural, and refractive outcomes of the four groups are presented in table 2. there was a significant difference in cdva among the groups in the right eyes (p = 0.04), but it was not significant in the left eyes (p = 0.14). there were 23 eyes (96%) in group i, 184 eyes (99%) in group ii, 74 eyes (100%) in group iii, and 273 eyes (100%) in group iv achieving 20/40 or better vision. macular abnormalities including dragging or scars were found in three eyes (12.5%) in group i, two eyes (1.1%) in group ii, zero eye in group iii, and two eyes (0.7%) in group iv. the two eyes in group iv had small macular scars likely due to either toxoplasma or ocular trauma in a case who had a history of trauma. the strabismus rate was significantly different among the groups (p = 0.04), where cases in group i had a higher strabismus rate than the subjects in the other three groups. strabismus was found in three patients (25%) in group i, six patients (6.5%) in group ii, one patient (2.7%) in group iii, and eight patients (5.6%) in group iv. for the refractive outcomes, the average cylindrical powers were significantly different among the four groups for both right and left eyes (p = 0.001 and p = 0.004, respectively). furthermore, in pairwise comparisons, the average cylindrical power magnitude of the right eyes of the patients in group i was significantly greater than that in group ii (p = 0.047), iii (p = 0.049), and iv (p = 0.001). likewise, the mean cylindrical power magnitudes for the left eyes of group i and ii cases were significantly greater than that in group iv (p = 0.04 and p = 0.002, respectively). there were 2 eyes (8.3%) in group i, 10 eyes (5.4%) in group ii, 8 eyes (10.8%) in group iii, and 26 eyes (9.1%) in group iv with high astigmatism (>1.5 diopters). the mean spherical equivalents were significantly different among the four groups for both eyes (p < 0.001). in pairwise comparisons, the average spherical equivalents of the cases in groups i, ii, and iii were significantly greater than that in groups iv for the right (p = 0.03; <0.001; <0.001, respectively) and the left eyes (p = 0.003; <0.001; <0.001, respectively). however, there was no significant difference between the mean spherical 386 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 visual outcomes in argon laser-treated rop; farvardin et al equivalents of the cases in group i through iii. clinically significant myopia (spherical equivalent ≥-1 diopter) was found in three eyes (12.5%) in group i, two eyes (1.1%) in group ii, zero eye in group iii, and twenty-five eyes (9.2%) in group iv. anisometropia (≥1.5 diopters) occurred in three cases (25%) in group i, two cases (2.2%) in group ii, one case (2.7%) in group iii, and six cases (4.4%) in group iv (p = 0.03). the data for the ocular biometric parameters of the subjects are presented in figure 1. the average corneal curvature was significantly different among the groups for both the right and left eyes (p = 0.001 and p = 0.002, respectively). in pairwise comparisons, the average corneal curvature of the right eyes of the cases in group i (45.99 ± 1.41 diopter) was significantly steeper than that in the other three groups (ii: 44.65 ± 1.80, p = 0.009; iii: 44.74 ± 1.51, p = 0.01; iv: 43.97 ± 1.48 diopter, p < 0.001). likewise, the average corneal curvature of the left eyes of group-i patients (46.05 ± 1.24 diopter) was significantly steeper than that in the other three groups (ii: 44.59 ± 2.01, p = 0.003; iii: 44.69 ± 1.51, p = 0.008; iv: 44.02 ± 1.46 diopter, p < 0.001). the average axial lengths of the patients gradually decreased from controls to group i cases with a significant difference in multivariate analysis for both the right and left eyes (p < 0.001). the average axial length of the right eyes of the patients in groups i (21.36 ± 0.69 mm) was significantly shorter than that in the other three groups (ii: 21.93 ± 2.13, p = 0.005; iii: 22.03 ± 0.72, p = 0.02; iv: 22.72 ± 0.70 mm, p < 0.001). similarly, the average axial length of the left eyes of the cases in group i (21.26 ± 0.51 mm) was significantly shorter than that in the other three groups (ii: 21.91 ± 2.13, p = 0.001; iii: 22.02 ± 0.74, p = 0.006; iv: 22.71 ± 0.73 mm, p <0.001). the mean anterior chamber depths of the participants’ eyes were significantly different among the four groups for the right eyes (i: 3.22 ± 0.19, ii: 3.26 ± 0.26, iii: 3.29 ± 0.21, iv: 3.39 ± 0.18 mm; p = 0.008), but not for the left eyes (i: 3.23 ± 0.19, ii: 3.30 ± 0.24, iii: 3.30 ± 0.22, iv: 3.36 ± 0.24 mm; p = 0.26). discussion patients with treated rop have a high risk of experiencing poor vision as a result of the advanced stages of the retinopathy, the therapeutic interventions, or a combination of both conditions. cryotherapy has been extensively used as treatment for eyes with threshold rop.[11] although the structural and functional outcomes of diode laser photocoagulation therapy for rop are better than those of cryotherapy,[6, 12] threshold rop cases treated with diode laser may have longterm poor vision with a high rate of myopia.[3, 8, 13, 14] in this case–control study, we found that type 1 rop patients treated with argon laser did not experience significantly lower vision than cases with spontaneously regressed rop and normal controls. the probable reasons why the visual outcome was not different among our premature cases are discussed in the following paragraphs. in our study, the treated rop cases had statistically the same mean spherical equivalent as the other premature cases [table 2]. although diode laser-treated eyes were diagnosed with a greater magnitude of myopia than untreated rop eyes in some studies,[8] there are reports showing that there was no significant difference in the spherical equivalent between diode laser-treated and untreated eyes.[15] however, we found a lower prevalence of myopia in our argon laser-treated cases. in our study, there were three myopic (spherical equivalent ≥–1 diopter) eyes (12.5%) in the treated rop cases in contrast to the 62% of the eyes reported with myopia in argon lasertreated rop patients[7] and the 64% myopia in diode laser-treated eyes.[16] the discrepancy might be due to different definitions for myopia as we considered the eyes with spherical equivalents of ≥–1 diopter as the myopic eyes whereas the other studies[7, 16] considered those with negative spherical equivalents (<0 diopter) as myopia.[7, 16] furthermore, since the goal of this study was to compare the outcomes of the argon lasertreated rop cases with those of untreated rop and healthy full-term subjects, more severe rop cases treated with other methods like vitrectomy or intravitreal anti-vegf injection were excluded from the study. the more severe cases might be associated with a higher incidence of myopia. therefore, development of myopia might probably be attributed to the severity of the disease rather than to argon laser therapy. we found three cases (25%) with anisometropia (≥1.5 diopters) in the argon laser-treated rop patients in contrast to the 46.7% rate in diode laser-treated cases reported in the literature.[3] the rate of anisometropia was significantly higher in our treated cases than in the other three groups (p = 0.03); however, the number of journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 387 visual outcomes in argon laser-treated rop; farvardin et al table 1. demographic data analysis of the four groups. variables laser-treated rop (group i) (n = 12) spontaneously regressed rop (group ii) (n = 93) no rop (group iii) (n = 37) control (group iv) (n = 143) p-value birth weight, gr (mean ± sd) 1358 ± 495 1454 ± 327 1680 ± 451 3517 ± 375 <0.001* gestational age, wks (mean ± sd) 29.42 ± 2.50 31.12 ± 1.63 31.54 ± 2.04 38.16 ± 1.14 <0.001* age, yrs (mean ± sd) 6.41 ± 0.18 6.44 ± 0.27 6.48 ± 0.26 6.43 ± 0.31 0.88* gender male, n (%) female, n (%) 7 (58%) 5 (42%) 51 (55%) 42 (45%) 19 (51%) 18 (49%) 73 (51%) 70(49%) 0.92∧ *kruskal–wallis; ∧chi-square; sd, standard deviation. anisometropic cases in our study was low making the type i error high. unilateral myopia resulted in anisometropia in treated cases in the current study. the possible causes of the refractive outcomes will be discussed. in addition, there was a greater magnitude of astigmatism in the right eyes of our treated cases than in the spontaneously regressed rop patients, cases with no history of rop, and controls. it was similar to the results reported for diode lasertreated rop patients.[17] moreover, in our study, other factors influencing vision such as strabismus and macular dragging or scars were not far from what was reported in the literature. strabismus was found in three treated patients (25%). it is close to the 30– 54% rate reported for the diode laser-treated patients,[3, 16] and the 28% rate for argon lasertreated cases.[7] in addition, there were three argon laser-treated eyes (12.5%) with macular dragging in our study, which is close to the reported 10.5% of diode laser-treated cases with macular dragging.[16] one eye with macular dragging was myopic (spherical equivalent of –4.38 diopters), and the child had anisometropia and strabismus. another case had bilateral macular dragging with no considerable anisometropia (<1.5 diopters) and no true strabismus but high positive angle kappa. overall, it seems that the fairly similar refractive status of premature cases partly contribute to somewhat similar vision status experienced among the premature groups in this study. the causes of the refractive outcomes in children with rop have remained obscure.[18] prematurity, rop, and laser treatment have been proposed to influence emmetropization.[13] in our study, the mean spherical equivalent was not significantly different among the premature cases with no rop, untreated spontaneously regressed rop, and laser-treated rop. therefore, our results did not support the assertion that rop or laser therapy would affect the mean spherical equivalents. however, the ocular biometric parameters in our cases may show why the refractive status was not different among the premature cases. the mean corneal curvatures of the treated rop cases were steeper than those of the cases with spontaneously regressed rop, premature subjects with no rop, and controls. it is similar to the results reported for diode laser-treated rop eyes which showed long-term steeper corneal curvature than full-term controls.[13] however, the treated eyes had shorter axial lengths than the other three groups [figure 1]. the axial length gradually decreased among the groups from the healthy controls to the treated rop cases. that might reduce the effects of increasing mean corneal curvature on refraction among the groups. absence of difference in the mean spherical equivalents among the three premature groups supports our thought. however, cellular and molecular studies are needed to explore the possible effects of prematurity, the severity of rop, as well as argon laser on emmetropization. despite our successful evaluation, our study was limited because of the small sample size of group i. further studies with a higher number of cases treated with argon laser are needed to confirm the results of our study. in summary, patients with type 1 rop treated with argon laser had significantly steeper corneal curvatures, shorter axial lengths, greater cylindrical 388 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 visual outcomes in argon laser-treated rop; farvardin et al powers, and a higher rate of anisometropia as compared to the other groups, but their spherical equivalents and visual acuities were not different compared to the other premature cases. our series with argon laser-treated rop had a low rate of ocular disorders with acceptable long-term visual and refractive outcomes. financial support and sponsorship this work was supported by shiraz university of medical sciences [no. 98014919597]. conflicts of interest none declared. references 1. ruan l, shan hd, liu xz, huang x. refractive status of chinese with laser-treated retinopathy of prematurity. optom vis sci 2015;92:s3–s9. 2. azami m, jaafari z, rahmati s, farahani ad, badfar g. prevalence and risk factors of retinopathy of prematurity in iran: a systematic review and meta-analysis. bmc ophthalmol 2018;18:83. 3. yang cs, wang ag, sung cs, hsu wm, lee fl, lee sm. long-term visual outcomes of laser-treated threshold retinopathy of prematurity: a study of refractive status at 7 years. eye 2010;24:14–20. 4. heidary f, gharebaghi r. outcomes of retinopathy of prematurity. med hypothesis discov innov ophthalmol 2016; 5:112–114. 5. kulkarni s, shah m, dole k, taras s, deshpande r, deshpande m. ocular outcomes and comorbidities in preterm infants enrolled for retinopathy of prematurity screening: a cohort study from western india. oman j ophthalmol 2019;12:10–14. 6. ng ey, connolly bp, mcnamara ja, regillo cd, vander jf, tasman w. a comparison of laser photocoagulation with cryotherapy for threshold retinopathy of prematurity at 10 years: part 1. visual function and structural outcome. ophthalmology 2002;109:928–934. 7. ospina lh, lyons cj, matsuba c, jan j, mccormick aq. argon laser photocoagulation for retinopathy of prematurity: long-term outcome. eye 2005;19:1213–1218. 8. wu wc, lin ri, shih cp, wang nk, chen yp, chao an, et al. visual acuity, optical components, and macular abnormalities in patients with a history of retinopathy of prematurity. ophthalmology 2012;119:1907–1916. 9. group etfropc. revised indications for the treatment of retinopathy of prematurity: results of the early treatment for retinopathy of prematurity randomized trial. arch ophthalmol 2003;121:1684. 10. talebnejad mr, nowroozzadeh mh, mahdaviazad h, khalili mr, masoumpour mb, keshtkar m, et al. the shiraz pediatric eye study; a population based survey of school age children: rationale, design and baseline characteristics. j ophthalmic vis res 2018;13:293–300. 11. multicenter trial of cryotherapy for retinopathy of prematurity: ophthalmological outcomes at 10 years. arch ophthalmol 2001;119:1110–1118. 12. connolly bp, ng ey, mcnamara ja, regillo cd, vander jf, tasman w. a comparison of laser photocoagulation with cryotherapy for threshold retinopathy of prematurity at 10 years: part 2. refractive outcome. ophthalmology 2002;109:936–941. 13. yang cs, wang ag, shih yf, hsu wm. long-term biometric optic components of diode laser-treated threshold retinopathy of prematurity at 9 years of age. acta ophthalmol 2013;91:e276–e82. 14. nguyen ph, catt c, nguyen tx, pham vt. refractive outcome of prethreshold retinopathy of prematurity treated by diode laser: follow-up at 5 years. clin ophthalmol 2015;9:1753–1758. 15. mcloone em, o’keefe m, mcloone sf, lanigan bm. longterm refractive and biometric outcomes following diode laser therapy for retinopathy of prematurity. j aapos 2006;10:454–459. 16. al-otaibi ag, aldrees ss, mousa aa. long term visual outcomes in laser treated threshold retinopathy of prematurity in central saudi arabia. saudi j ophthalmol 2012;26:299–303. 17. yang cs, wang ag, shih yf, hsu wm. astigmatism and biometric optic components of diode laser-treated threshold retinopathy of prematurity at 9 years of age. eye 2013;27:374–381. 18. kaur s, sukhija j, katoch d, sharma m, samanta r, dogra mr. refractive and ocular biometric profile of children with a history of laser treatment for retinopathy of prematurity. indian j ophthalmol 2017;65:835–840. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 389 original article p100 wave latency and amplitude in visual evoked potential records in different visual quadrants of normal individuals leila mirzaee saba1, ms; hassan hashemi2, md; ebrahim jafarzadehpour3, phd; ali mirzajani3, phd; abbasali yekta4, md; abolfazl jafarzadehpour1, ms; arghavan zarei2, ms; payam nabovati3, phd; mehdi khabazkhoob5, phd 1noor research center for ophthalmic epidemiology, noor eye hospital, tehran, iran 2noor ophthalmology research center, noor eye hospital, tehran, iran 3rehabilitation research center, department of optometry, school of rehabilitation sciences, iran university of medical sciences, tehran, iran 4refractive errors research center, mashhad university of medical sciences, mashhad, iran 5department of basic sciences, school of nursing and midwifery, shahid beheshti university of medical sciences, tehran, iran orcid: ebrahim jafarzadehpour: https://orcid.org/0000-0002-4451-800x leila mirzaee saba: https://orcid.org/0000-0001-6130-3126 abstract purpose: assessment of the pattern visual evoked potential (pvep) responses in different areas of visual fields in individuals with normal vision. methods: this study was conducted on 80 eyes of normal subjects aged 18–35 years. all participants underwent refraction and visual acuity examination. visual evoked potential (vep) responses were recorded in different areas of field. the repeated measure test was used to compare the p100 latency and amplitude of pvep among different areas. results: the repeated measures analysis of variance showed a statistically significant difference among different areas in terms of amplitude and latency of p100 (p = 0.002 and p < 0.001, respectively). according to the results, the highest and lowest amplitude of p100 was observed in inferior-nasal and superior areas, respectively. the highest and lowest latency of p100 was related to the temporal and inferior-nasal areas, respectively. conclusion: this study partially revealed the details of local pvep distribution in the visual field and there was a significant difference in the amplitude and latency of pvep wave in different areas of the visual field. keywords: amplitude; latency; normal vision; pattern reversal; visual evoked potential; visual field j ophthalmic vis res 2023; 18 (2): 175–181 correspondence to: ebrahim jafarzadehpour, phd. noor ophthalmology research center, noor eye hospital, tehran 19686, iran. email: jafarzadehpour.e@iums.ac.ir received: 06-01-2022 accepted: 05-12-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i2.13184 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: mirzaee saba l, hashemi h, jafarzadehpour e, mirzajani a, yekta a, jafarzadehpour a, zarei a, nabovati p, khabazkhoob m. p100 wave latency and amplitude in visual evoked potential records in different visual quadrants of normal individuals . j ophthalmic vis res 2023;18:175–181. © 2023 mirzaee saba et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 175 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i2.13184&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr quadrant-specific vep parameters ; mirzaee saba et al introduction visual field (vf) plays a significant role in clinical optometry and assessment of vf findings is important in the diagnosis and treatment of the diseases like glaucoma.[1,2] humphrey perimetry is the gold standard for detection of visual field defects; however, it has some limitations.[3] as it is a subjective test, it is largely patient dependent and the test duration may vary depending on the aptitude of the examinee. many individuals, especially older patients, are weak on subjective tests.[4–6] subjective perimetry is associated with a learning curve leading to complicating interpretation of the results in new patients. as a result, the test should be performed two to three times to obtain a valid result.[3,7] moreover, it is expected that a considerable loss of ganglion cells occurs before standard perimetry shows a visual field defect. therefore, more sensitive tests are required because about 25–50% of optic nerve fibers may be lost before a visual field defect is actually diagnosed.[4, 8] electroretinogram (erg)[7] and visual evoked potential (vep) are two objective methods used for the measurement of visual field sensitivity.[3, 8] studies show that multifocal visual evoked potential (mfvep) is one of the most advanced technology used in the measurement of visual field sensitivity.[9] stability of the mfvep system depends on a number of environmental factors. since the vep amplitude is measured within the range of microvolts, environmental factors such as noises that result from problems which occur with cortical electric changes in power supply such as voltage fluctuations may cause amplitude changes in one area of the field when presenting the stimulus. therefore, in order to decrease the noise effect, the calculation of more comparative averages is required for an overall more accurate averaging assessment. unfortunately, the technology used in the mfvep software does not produce many averages because the examination is time consuming.[3, 10] in addition, as the mfvep software is very complicated and costly, most centers are not equipped with the software. the present study aimed to assess the sensitivity of pattern visual evoked potential (pvep) in different areas of visual field while considering the need for objective perimetry with the unavailability of the mfvep software, and also considering the emphasis on clinical electrophysiology standards regarding multiple definitions of “normal” for age and race.[10] to decrease the effect of noise, the averaging of 100 measurements was considered in each area. for this purpose, a stimulus was presented at each of the eight areas to measure p100 amplitude and latency in pvep records of visually normal participants. methods this cross-sectional study was conducted to assess the p100 amplitude and latency of pvep in different visual field areas in visually normal individuals in the ophthalmic electrophysiology clinic of the school of rehabilitation, iran university of medical sciences. the participants were selected from eligible individuals attending the clinic who were willing to join the study and signed an informed consent form through convenient sampling. the inclusion criteria were as follows: (1) age 18–35 years, (2) corrected distance visual acuity of 20/20 or better in both eyes (best visual acuity 20/20 with or without correction), (3) myopia <–3 diopters (d) or astigmatism <2d,[11] and (4) lack of any systemic diseases that might affect pvep results. based on the values obtained from the articles, the mentioned standard deviation reported to be around 4.7.[12] taking into account the value of d equal to 2 and the confidence level of 95% and z equal to 1.96, based on the following equation the calculated number of samples would be 21; we however examined 40 people in this study. 𝑁 = 𝑍 2δ2 𝑑2 . the objective of the study was explained to the participants. first, visual acuity was tested with a snellen chart and then objective refraction was measured using a heine retinoscope (heine, germany) and the huvitz hrk-8000 autorefractometer (huvitz, south korea). subjective refraction responses were also evaluated. eyes were examined with slit lamp and ophthalmoscope for eye pathology determination. in the next stage, the p100 amplitude and latency of pvep were recorded in mesopic conditions. pvep the p100 amplitude and latency of pvep was assessed and recorded by metro vision (mon pack 176 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 quadrant-specific vep parameters ; mirzaee saba et al 3, perenchies, france) with a check size of 30 min of arc with a contrast of 85%. the test was performed monocularly under mesopic conditions (low-light conditions that are not completely dark) since it is more similar to everyday natural viewing conditions. in this study, the p100 latency and amplitude of the pvep were measured using passive, active, and ground electrodes. the placement of pvep electrodes was based on the international 10/20 system.[12] before the test was conducted, in an effort to achieve better signal transmission, the skin’s dead layers were removed with alcohol. the electrodes, which were filled with conductive gel, were then placed on appropriate places on the head and forehead using a special adhesive paste. the resistance of the electrode/skin junction was <5k ohms. after recording the patient’s name, the patient sat at a distance of 1 m from the stimulation display and the test was performed monocularly. first, a fullfield pvep was recorded for each patient; then, as the patient looked at the fixation point in the middle of the screen, a stimulus was randomly presented at different locations of the screen and the p100 amplitude and latency of pvep was recorded in the superior-nasal, inferior-nasal, superior-temporal, and inferior-temporal areas as well the superior, inferior, nasal, and temporal areas of the visual field. each of the visual field areas in the periphery were 30º away from the center. an example of a visual field area is shown in the figure 1. the spss version 20 was used for statistical analysis. mean and standard deviation were used to describe the data. according to the kolmogorov–smirnov test, all components had a normal distribution. since the data of different areas within the visual field in each eye was interdependent, repeated measures analysis of variance was used to compare them. a post hoc least significant difference (lsd) test was performed to show comparisons. in this study, a significance level of 0.05 was considered. considering that both eyes were analyzed, the correlation effect of fellow eyes was controlled in the analysis. ethical considerations the ethics committee of iran university of medical sciences approved the study protocol by the registration number of ir.iums. fmn.1395.02, which was conducted in accordance with the tenets of the helsinki declaration. all participants signed a written informed consent. results in this study, the mean p100 amplitude and latency were assessed in different visual field areas of 80 eyes of 40 patients with a mean age of 23.25 ± 3.44 years. of the 40 studied individuals, 20 were women. table 1 shows the mean and standard deviation of the p100 amplitude and latency in different areas of the visual field. there was no statistically significant difference in the average amplitude and latency of p100 in all areas between males and females (p > 0.05). the repeated measures analysis of variance showed a statistically significant difference among the different areas in terms of amplitude and latency of p100 (p = 0.002 and p < 0.001, respectively). according to the results, the highest and lowest amplitude of p100 was observed in the inferior-nasal and superior areas, respectively. the highest and lowest latency of p100 was related to the temporal and inferior-nasal areas, respectively. table 2 shows the comparison of the p100 amplitude and latency in the different areas of the visual field, and the effect size values are also presented. all comparisons were reported using bonferroni post-hoc test with bonferroni correction. discussion according to tables 1 and 2, there were variances in the recorded latency and amplitude values among different areas within the visual field, which were sometimes significant. therefore, it seems that within different areas of the retina with corresponding paths, and with the same neurons, the transmission speed of the messages was not the same, and did not have the same destination in the cortex. some studies also suggest that these differences exist.[12, 13] as silveira points out in her study, the conduction velocity of parvocellular (p) cells is slower than that of magnocellular (m) cells and about 80% of all ganglion cells are parvocellular cells.[14] according to clinical findings and electrophysiological standards, p100 is the journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 177 quadrant-specific vep parameters ; mirzaee saba et al table 1. the mean and standard deviation (sd) of p100 amplitude and latency in different areas of visual field. latency of p100 (ms) amplitude of p100 (microv) areas mean ± sd mean ± sd full 103.99 ± 6.63 7.95 ± 3.9 nasal 103.57 ± 12.37 3.89 ± 1.99 temporal 101.4 ± 7.28 5.19 ± 2.25 superior 100.22 ± 8.16 4.85 ± 2.82 inferior 102.48 ± 10.46 3.5 ± 1.76 superior nasal 100.17 ± 12.95 3.24 ± 1.89 inferior nasal 109.07 ± 14.52 2.76 ± 1.61 superior temporal 100.92 ± 8.39 3.9 ± 1.67 inferior temporal 98.85 ± 8.12 3.22 ± 1.51 sd, standard deviation; ms, millisecond, microv, microvolts figure 1. area pattern (a) and hemifield (b) patterns of visual evoked potential used in this study. most important and stable component of the pvep.[12, 14] table 1 presents an assessment of p100 latency and amplitude. considering the importance of p100 latency of pvep,[12] table 1 delineates the most important index for the assessment of recorded results. according to table 1, neurons in the inferior temporal area are the fastest and/or most superficial and/or the closest neurons to active pvep electrodes. according to studies by baseler et al, the central 178 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 quadrant-specific vep parameters ; mirzaee saba et al table 2. comparison of p100 amplitude and latency in different areas of visual field. amplitude of p100 (microv) latency of p100 (ms) quadrans effect size (95%ci) p-value* effect size (95%ci) p-value* full nasal 4.06 (2.91–5.22) <0.001 0.42 (-3.27–4.11) 1.000 temporal 2.76 (1.58–3.94) <0.001 2.59 (-0.06–5.25) 0.063 superior 3.10 (2.15–4.05) <0.001 3.77 (1.26–6.28) <0.001 inferior 4.45 (3.16–5.73) <0.001 1.51 (-1.73–4.74) 1.000 superior nasal 4.71 (3.39–6.03) <0.001 3.82 (-0.55–8.19) 0.177 inferior nasal 5.19 (3.68–6.69) <0.001 -5.08 (-10.9–0.75) 0.179 superior temporal 4.05 (2.82–5.28) <0.001 3.07 (0.02–6.12) 0.047 inferior temporal 4.73 (3.31–6.15) <0.001 5.14 (2.55–7.72) <0.001 nasal temporal -1.31 (-2.22–0.39) <0.001 2.17 (-2.35–6.7) 1.000 superior -0.97 (-1.82–0.11) 0.012 3.35 (-0.40–7.10) 0.145 inferior 0.38 (-0.48–1.25) 1.000 1.09 (-4.06–6.24) 1.000 superior nasal 0.64 (-0.06–1.35) 0.119 3.4 (-0.78–7.58) 0.306 inferior nasal 1.12 (0.22–2.02) 0.003 -5.5 (-12.23–1.23) 0.300 superior temporal -0.01 (-0.81–0.79) 1.000 2.65(-1.94 -7.24) 1.000 inferior temporal 0.67 (-0.14–1.47) 0.273 4.72 (0.58–8.86) 0.011 temporal superior 0.34 (-0.6–1.28) 1.000 1.18 (-1.96–4.31) 1.000 inferior 1.69 (0.82–2.56) <0.001 -1.08 (-4.56–2.39) 1.000 superior nasal 1.95 (0.94–2.95) <0.001 1.23 (-3.40–5.86) 1.000 inferior nasal 2.43 (1.41–3.44) <0.001 -7.67 (-14.14–1.2) 0.007 superior temporal 1.29 (0.59–2.00) <0.001 0.48 (-1.87–2.82) 1.000 inferior temporal 1.97 (1.08–2.86) <0.001 2.55 (-0.80–5.89) 0.491 superior inferior 1.35 (0.33–2.37) <0.001 -2.26 (-6.15–1.63) 1.000 superior nasal 1.61 (0.60–2.61) <0.001 0.05 (-3.72–3.82) 1.000 inferior nasal 2.09 (0.91–3.27) <0.001 -8.85 (-14.98–2.72) 0.000 superior temporal 0.95 (-0.04–1.94) 0.075 -0.7 (-4.31–2.91) 1.000 inferior temporal 1.63 (0.55–2.71) 0.000 1.37 (-2.04–4.78) 1.000 inferior superior nasal 0.26 (-0.60–1.12) 1.000 2.31 (-2.59–7.22) 1.000 inferior nasal 0.74 (-0.15–1.63) 0.250 -6.59 (-13.10–0.08) 0.044 superior temporal -0.4 (-1.18–0.39) 1.000 1.56 (-2.09–5.21) 1.000 inferior temporal 0.28 (-0.45–1.01) 1.000 3.63 (0.17–7.08) 0.029 superior nasal inferior nasal 0.48 (-0.37–1.33) 1.000 -8.9 (-16.05–1.75) 0.003 superior temporal -0.66 (-1.46–0.15) 0.307 -0.75 (-5.61–4.11) 1.000 inferior temporal 0.02 (-0.75–0.79) 1.000 1.32 (-3.26–5.89) 1.000 inferior nasal superior temporal -1.14 (-1.9–0.37) <0.001 8.15 (1.25–15.05) 0.007 inferior temporal -0.46 (-1.12–0.20) 0.892 10.22 (4.10–16.33) <0.001 superior temporal inferior temporal 0.68 (-0.03–1.39) 0.082 2.07 (-1.51–5.65) 1.000 *adjustment for multiple comparisons: bonferroni ci, confidence interval; ms, millisecond, microv, microvolts journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 179 quadrant-specific vep parameters ; mirzaee saba et al visual field which is mainly composed of p cells, sends stimuli to the inferior temporal area of the cortex, and the peripheral visual field, which is mainly caused by m cells, sends stimuli to the posterior area of the parietal cortex.[15, 16] according to horton’s findings, macular fibers are generally located in the posterior area of the occipital lobe close to the electrode site, while as we move toward the periphery, the fibers are present in the anterior area of the cortex.[16, 17] in addition, according to holliday and michael, producers of pvep responses in the cortex are located at different distances from the active electrode.[18] also, according to studies performed with functional magnetic resonance imaging (fmri), fovea is presented in the posterior occipital region and areas with increased eccentricity in the anterior area. the peripheral field is at the back of the parietal cortex and near the junction of the calcarine fissure. the horizontal meridians of the field are in the range of the calcarine fissure and the presentation of the upper part of the vertical meridians is below the calcarine fissure.[16] the findings of the recorded amplitude indicate the difference in neuronal density,[19] change distance recorded,[20] and inhibitory response.[21] according to table 1, the amplitude corresponding to the inferior temporal area findings was not among high recorded amplitudes. the reason could be that the density of p and m ganglion cells decreases toward the periphery.[22, 23] on the other hand, the recording interval is also effective in the responses. in humans, the visual cortex is projected along the superior and inferior regions of the calcarine fissure. the upper region of the calcarine fissure corresponds to the upper region of the retina where the lower visual field is represented and the upper visual field is represented above the calcarine fissure. according to a study by jeffroys et al, since the producers of the superior field are under the fissure and further away from the active electrode as compared to the producers of the inferior field, a lower amplitude is expected in the lower half of the retina,[11, 18] which is consistent with our findings. after the inferior temporal area, the fastest or the most superficial response was related to the superior nasal area, followed by the superior and superior temporal areas. the ganglion cells of the superior area of the retina are projected to the superior and medial regions of the lateral geniculate body. these superior fibers are then projected to the posterior region of the parietal lobe[20] and are therefore relatively closer to the active electrode. the amplitude corresponding to the superior and superior temporal areas was the highest amplitude recorded in the study. this finding may indicate a higher density of ganglion cells in the superior retina. on the other hand, these cells are located above the calcarine fissure and are closer to the active electrode as compared to the inferior area and therefore already possess better amplitude. the superior temporal area had higher amplitude than the superior nasal area. on average, above the horizontal meridian, the temporal retina had the larger response than the nasal retina.[11] the temporal retina had the highest response amplitude, indicating the greater density of nerve fibers in this region.[16] the inferior and nasal retina regions of the retina have a lower amplitude and higher latency. the ganglion cells of the inferior retina are projected to the temporal region of the lateral geniculate body. the ganglion cells of the nasal retina are projected to the contralateral lateral geniculate body in layers 1, 4, and 6; therefore, they are farther away from the ipsilateral active electrode and far from contralateral electrode.[20] on the other hand, in the retinal periphery, the density of ganglion cells is higher in the nasal area, producing a better amplitude than the inferior area.[22] the ganglion cells of the center are more superficial while the ganglion cells of the periphery are deeper.[24] the neurons become deeper and their latency increase as we move from the fovea toward the periphery. moreover, the inferior nasal had the lowest amplitude in the study. these fibers are projected to the contralateral geniculate body and are farther away from the active electrode.[20] similar to our study, min zhong’s study investigated the topographical changes of the visual field with vep, which, of course, examined the parameters of the vep wave in 37 areas of the visual field, with a matrix stimuli including a 61 hexagons pattern. in his study, latency is reduced in the temporal region.[11] based on the conducted studies, factors such as the position of the electrodes, neuronal density and pathway, and the size of the stimulus affect the electrophysiological responses. since the majority of the striate cortex responses is related to the 180 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 quadrant-specific vep parameters ; mirzaee saba et al central visual field which is presented at the tip of the occipital poles which is closer to the active electrode, a decrease in the responses was seen from the center to the periphery considering the cellular density, distribution of magnocellular and parvocellular neurons, and differences in the velocity of conducting messages to the cortex. the suggestion for further research is to perform these assessments in patients with glaucoma and other conditions associated with visual field defects and compare the findings with standard perimetry results to determine whether early diagnosis would be possible. a major limitation of this study is the lack of eye tracking during the pvep test, hence the possibility of fixation instability and unwanted fine eye movements during the test could affect the accuracy of the results. in summary, this study evaluated the details of local pvep distribution in different areas of the visual field. considering the significant difference in the amplitude and latency of the pvep in different areas, the inferior temporal (lowest latency) and temporal (highest amplitude) areas have the highest visual sensitivity. these findings are in line with the results of other studies. financial support and sponsorship none. conflicts of interest no conflicting relationship exists for any author. references 1. asakawa k, shoji n, ishikawa h, shimizu kjco. new approach for the glaucoma detection with pupil perimetry. clin ophthalmol 2010;4:617. 2. sample pa, bosworth cf, blumenthal ez, girkin c, weinreb rn. visual function-specific perimetry for indirect comparison of different ganglion cell populations in glaucoma. invest ophthalmol vis sci 2000;41:1783–1790. 3. jampel hd, singh k, lin sc, chen tc, francis ba, hodapp e, et al. assessment of visual function in glaucoma: a report by the american academy of ophthalmology. ophthalmology 2011;118:986–1002. 4. hood dc, greenstein vc, odel jg, zhang x, ritch r, liebmann jm, et al. visual field defects and multifocal visual evoked potentials: evidence of a linear relationship. arch ophthalmol 2002;120:1672–1681. 5. graham sl, klistorner a, grigg jr, billson fa. objective perimetry in glaucoma: recent advances with multifocal stimuli. surv ophthalmol 1999;43:s199–s209. 6. klistorner a, graham sl, martins a, grigg jr, arvind h, kumar rs, et al. multifocal blue-on-yellow visual evoked potentials in early glaucoma. ophthalmology 2007;114:1613–1621. 7. goldberg i, graham sl, klistorner ai. multifocal objective perimetry in the detection of glaucomatous field loss. am j ophthalmol 2002;133:29–39. 8. hood dc, greenstein vc. multifocal vep and ganglion cell damage: applications and limitations for the study of glaucoma. prog retin eye res 2003;22:201–251. 9. klistorner ai, graham sl, grigg j, balachandran c. objective perimetry using the multifocal visual evoked potential in central visual pathway lesions. br j ophthalmol 2005;89:739–744. 10. brigell m, bach m, barber c, kawasaki k, kooijman a. guidelines for calibration of stimulus and recording parameters used in clinical electrophysiology of vision. doc ophthalmol 1998;95:1–14. 11. yu mz, brown bjo, optics p. variation of topographic visually evoked potentials across the visual field. ophthalmic physiol opt 1997;17:25–31. 12. odom jv, bach m, brigell m, holder ge, mcculloch dl, mizota a, et al. iscev standard for clinical visual evoked potentials: (2016 update). doc ophthalmol 2016;133:1–9. 13. lam bl. electrophysiology of vision: clinical testing and applications. crc press; 2005. 14. silveira lc, perry vh. the topography of magnocellular projecting ganglion cells (m-ganglion cells) in the primate retina. neuroscience 1991;40:217–237. 15. baseler ha, sutter ee. m and p components of the vep and their visual field distribution. vision res 1997;37:675– 690. 16. deyoe ea, carman gj, bandettini p, glickman s, wieser j, cox r, et al. mapping striate and extrastriate visual areas in human cerebral cortex. proc natl acad sci u s a 1996;93:2382–2386. 17. horton jc, hoyt wf. the representation of the visual field in human striate cortex: a revision of the classic holmes map. arch ophthalmol 1991;109:816–824. 18. michael wf, halliday am. differences between the occipital distribution of upper and lower field patternevoked responses in man. brain res 1971;32:311–324. 19. snell rs. clinical neuroanatomy. lippincott williams & wilkins; 2010. 20. skrandies w. brain mapping of visual evoked activitytopographical and functional components. acta neurol taiwan 2005;14:164–178. 21. heckenlively jr, arden gb. principles and practice of clinical electrophysiology of vision. mit press; 2006. 22. curcio ca, allen ka. topography of ganglion cells in human retina. j comp neurol 1990;300:5–25. 23. croner lj, kaplan e. receptive fields of p and m ganglion cells across the primate retina. vision res 1995;35:7–24. 24. miller nr, walsh fb, hoyt wf. walsh and hoyt’s clinical neuro-ophthalmology. lippincott williams & wilkins; 2005. journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 181 original article cataract grading in pure senile cataracts: pentacam versus locs iii mohammad mirzaie1, md; erfan bahremani1, md; nazli taheri1, md; zhila khamnian2, md; banafshe kharrazi ghadim1, md 1nikoukari eye hospital, department of ophthalmology, school of medicine, tabriz university of medical sciences, tabriz, iran 2department of community medicine, tabriz university of medical sciences, tabriz, iran orcid: mohammad mirzaie: https://orcid.org/0000-0002-8672-8566 erfan bahremani: https://orcid.org/0000-0002-5104-8667 abstract purpose: to determine the diagnostic accuracy of pentacam cataract grading scale (pcgs) versus the lens opacities classification system (locs iii) in scaling pure age-related cataract. methods: between april 2016 and may 2017, eyes of 281 patients were evaluated for grading of lens opacity. we used locs iii and pcgs. patients with pure age-related cataract with no previous history of eye surgery, eye trauma, or chronic systemic disease between 50 and 95 years of age were included. the examination of the patients was done, using slit lamp and locs iii grading chart. the second examination was done a week later, using oculus pentacam. next, we graded them using a pns grading score. spearman’s rank correlation and a bland-altman plot were implemented for analysis using medcalc 14. 8.1. p < o.05 was considered as statistically significant. results: three hundred eyes were examined. of them, 189 patients were male, and patients between 70 to 80 years old were the most common group. the correlation between grades of two methods was 0.47 (p < 0.001). results of the bland-altman plot showed a moderate alignment between the two methods. conclusion: the association between locsiii and pcgs is not so favorable, however, it is an economical and effective method to assess lens opacities is locsiii. pcgs can be used in early diagnosis. for a definitive diagnosis and appropriate therapeutic intervention, an ophthalmological examination is needed. keywords: cataract; lens nucleus densitometry; lens opacities classification system iii; scheimpflug lens density; pentacam j ophthalmic vis res 2022; 17 (3): 337–343 © 2022 mirzaie et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 337 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i3.11570&domain=pdf&date_stamp=2019-07-17 age-related cataract grading ; mirzaie et al introduction pure senile cataract is the most common cause of reversible age-related blindness worldwide.[1, 2] as the lens ages, chemical modification and proteolytic cleavage of lens proteins results in the formation of high-molecular-mass protein aggregates, thereby reducing transparency and increasing opacity.[3, 4] cataract disease is a major public health issue around the world and poses a challenge especially to communities with rapidly ageing populations. early diagnosis and appropriate therapeutic interventions are necessary to control the burden of this disease.[5] although the gold standard of therapy is the surgical removal of the opacified lens, there are varieties of objective and subjective methods to diagnose and confirm cataracts.[6–8] one of the most commonly used subjective methods is the lens opacities classification system (locs) iii.[4, 9] this method is based on retro-illumination slit-lamp images and has been regarded as valid since 1993.[10] this well-known system is used in the diagnosis and treatment of cataract-related patients.[11, 12] the locs iii is a cost-effective valid method with high levels of reproducibility, but since it is subjective, it can be influenced by observerrelated factors such as the experience level of the ophthalmologist, inter-observer and intra-observer bias, slit-lamp settings, the illumination method and amount and the necessarily subjective assessment of lens density and opacity.[13] these limitations can lead to inconsistency in application over time and among different examiners,[14] indicating an emerging need for a more reliable and reproducible method.[15] correspondence to: erfan bahremani, md. nikoukari eye hospital, abbasi st., tabriz 5154645395, iran. e-mail: erfanbahremani@yahoo.com received: 11-01-2019 accepted: 07-01-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i3.11570 pentacam is an optical noncontact device of ophthalmologic examination that is programmed based on the principles of the scheimpflug rotating camera system to capture images.[16] scheimpflug is able to provide a focused and sectional representation of the lens, making it superior to conventional slit-lamp imaging.[17] it can also provide images. with a focus on a specific part of the lens, such as the nucleus.[18] the currently available pentacam rotating scheimpflug system (oculus, inc., wetzlar germany) gathers information from 25,000 points across the eye by capturing as many as 50 “slices” in a single 180º sweep across the central axis of the lens within 2 sec.[19] it provides a global evaluation of lens density and creates a precise single three-dimensional image of the anterior segment and lens.[20] the technology of the system leads to a reduced artifact effect and improved lens densitometry because of the uniform four plane of focus.[14] pentacam nucleus staging (pns) is a recently released software of pentacam rotating scheimpflug system that presents an accurate and precise measurement of lens density based on software capabilities such as generating a nuclear cataract grading score in five stages.[10] pns is a built-in lens densitometry software that provides an average and a maximal lens density with a cataract grading score from 0 to 5.[19] furthermore, pns can calculate the mean value and uses lens densitometry measurements by ”pentacam”.[21] pentacam lens densitometry is influenced by varying levels of corneal opacities, incorrect photographic illumination, and insufficient pupil dilation. film processing and analyzing are time consuming, and the use of the software is costly when compared to other alternatives.[10] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: mirzaie m, bahremani e, taheri n, khamnian z, ghadim bk. cataract grading in pure senile cataracts: pentacam versus locs iii . j ophthalmic vis res 2022;17:337–343. 338 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 https://knepublishing.com/index.php/jovr age-related cataract grading ; mirzaie et al accurate assessment of lens density and cataract grading is crucial for determining the optimal time for cataract surgery, choosing the appropriate surgical intervention, decreasing phaco time and phaco power, and minimizing periand post-operative complications. in the present study, we tried to determine the association between the pentacam scheimpflug method and locs iii for grading pure age-related cataracts and then find the correlation between two methods which are based on different imaging procedure. methods in this prospective cross-sectional observermasked study, 300 eyes of 281 age-related cataract patients were studied in a census manner. the study was conducted from april 2016 to may 2017 at nikoukari eye hospital in tabriz, iran. the study protocol was approved by the ethics committee, tabriz university of medical sciences and adhered to the guidelines of the helsinki declaration. an informed consent was obtained from all participants. patients referred to the hospital clinic during the study period and meeting the following inclusion criteria were recruited: age between 50 and 95 years, pure age-related nuclear cataract, and the desire to take part in the study. all patients with cortical or posterior subscapular cataracts, age-related cataract cornea or anterior segment pathologies, history of ocular trauma, prior history of ocular surgical intervention, or vitreoretinal disease were excluded. patients with chronic systemic disorders affecting vision such as hypertension, diabetes mellitus, or thyroid disease were also excluded. the sample size was calculated based on cochran’s sample size formula 5 with a confidence level of 95% (a = 0.05), a power of 80%, and age-related cataract prevalence, resulting in a total sample of 300 eyes. all participants underwent slit-lamp and fundus examination with a single experienced and trained ophthalmologist (mm) using a topcon japan sl-3c slit-lamp under full pupil dilation with tropicamide i% ophthalmic drop (two drops; mydrax®: sinadarou, tehran, iran). cataract grading was performed afterward by the same ophthalmologist according to locs iii standards.[4, 13] locs iii is measured with a slit-lamp examination composed of 16 pictures: six pictures for grading the color and opacity of lens nucleus, five retro-illumination pictures for cortical garnet, and five retro-illumination pictures for posterior sub capsular cataract.[22, 23] the six groups of patients that were divided according to the nuclear opalescence were: group 1, nuclear opalescence between 0.0 and 0.9; group 2, between 2.0 and 2.9; group 3, between 3.0 and 3.9; group 4, between 4.0 and 4.9; group 5, between 5.0 and 5.9; and group 6, between 6.0 and 6.9. after the slit-lamp examination, each eye was evaluated using a rotating scheimpflug camera imaging device; an oculus pentacam (oculus inc. germany) was used. each participant underwent pentacam examination after maximal pupil dilation by tropicamide 1% ophthalmic drop (two drops; mydrax sinadarou tehran, iran). the patient was seated in front of pentacam device like sitting in front of a slit lamp. the patient was asked to focus on a specific target and keep it fixed. the same device was used for all patients and was re-calibrated for each screening. subsequently, the operator set the device on automatic mode to minimize operator-dependent variables. in this mode, detection of required settings with the corneal apex is done automatically, followed by an automated scanning image capturing 50 images. these images were taken from anterior segment, in about 2 sec. using the three-dimensional plot of the anterior segment with each section running through the corneal vertex, we calculated the jens density by using pentacam software (pns). calculation was performed at 45º. the mean area was placed in the nucleus and measured 1.60 mm, 20% was the specified threshold value of the average nuclear density and nuclear cataract classification. cataract grading score that the pns software uses is 0 to 5.[19] all examinations, whether slit-lamp or pentacam were performed in the same room with minimal light sources to obtain reflex-free images and keep the environmental factor consistent for all patients. medcalc software version 14.8.1 was used for statistical analysis. descriptive data is presented as median or frequency (percentage). kolmogrov– smimov’s test was used for checking normality. spearman’s ranked correlation coefficient was calculated for determining the correlation between locs iii and pentacam cataract grading scale (pcgs – pns nuclear cataract grading score). a bland-altman plot was implemented for further journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 339 age-related cataract grading ; mirzaie et al studying the correlation between locs iii and pcgs. the level of significance was considered to be p < 0.05. results three hundred eyes of 281 patients were recruited in the study; 19 patients were examined in both eyes. ninety-two patients (32.7%) were female and 189 (67.3%) were male. the age range was 52 to 94 years, and the median age of participants was 75 years. kolmogrov–smirnov’s test showed that the age distribution was near normal. female patients were slightly older but the difference between two genders was not significant. based on the results of the ophthalmologist’s examinations, 11 eyes (3.7%) were grade 1, 165 (55%) grade 2, 109 (36.3%) grade 3, 14 (4.7%) grade 4, and just 1 was grade 5 in the cataract classification according to locs iii. no patient had a cataract grade above 5. the median grade was 2 and the mode was also 2. the pentacam oculus automated examination for cataract grading revealed that 8 eyes (2.7%) were grade 0, 129 (43%) grade 1, 127 (42.3%) grade 2, 34 (11.3%) grade 3, 1 grade 4, and one grade 5 according to the pns grading scale. our data demonstrated that 99% of the patients were grade 3 or lower based on the pentacam examination and 99% were grade 4 or lower in the locs iii grading system. table 1 shows the detailed results of pentacam grading scale with the locs iii results. the spearman ’s correlation coefficient was 0.47 between the ophthalmologist-graded cataract scaling using locs iii and the pns grading results via pentacam examination based on spearman’s ranked correlation (p < 0.001). this level of association shows a moderate correlation between the results of these two methods. because there were less than five eyes in some grades of pns and in one grade of locs iii, calculating the within-group coefficient was not possible based on statistical principles. in our study, 95% of the eyes were graded at 3 or less on the locs iii grading scale and 99% had a score of 4 or less on the pns grading score. a bland-altman plot for further assessing the association between measurements is shown below [figure l]. this illustrates the correlation between locs iii grading on the x-axis and the difference between the two methods on the yaxis, showing that most cases staging with pns have overlap with locs iii about one standard deviation. in moderate cataract cases, the results were convergent, although in milder or higher grades of senile cataract, the two methods may reveal divergent results. discussion as a multifactorial disease, senile cataract is the most common type of cataract and a major cause of reversible nontraumatic visual impairment in all communities.[5] surgical intervention is the choice of treatment b replacing the opacified lens by an intact artificial lens.[6] many factors may predispose individuals to cataracts, such as trauma, certain drugs, ocular disorders, and many systemic diseases,[24] however, most cataracts in senior citizens are caused by aging alone.[25] over 1.2 million surgeries are conducted for cure senile cataract in usa, annually.[7] definitive diagnosis and precise grading of senile cataracts are crucial in planning for treatment[6] and there are distinctive objective and subjective tools for this purpose. in this study, the association between the results of two methods, one subjective and one objective, was assessed. our study found a moderate correlation between the locs iii and the pns grading scales. magalhaes et al,[10] in a crosssectional study, evaluated 101 patients with clear cataracts for lens grading score. they have used locs iii in this evaluation. groups l to 5 could be noticed with pentacam lens densitometry program (pldp) and the pns mean value. however, there was a weak relationship between the pns grading and the locs iii classification. they further concluded that in a clinical setting, the mean value of nuclear density measured by pns may be more accurate than the pns score alone to evaluate the progress of nuclear opacification. they emphasized that the scores provided by pentacam should be studied more. pei et al[8] examined 180 eyes using both scheimpflug pentacam and locs iii in 138 patients. they reported their results following a variety of variables they studied and found a positive linear correlation between locs iii grading and the peak value of lens density measured using pentacam in pure nuclear cataract patients. they concluded that the locs iii criteria is a less expensive cataract grading system and provides data that are in concordance at a satisfactory 340 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 age-related cataract grading ; mirzaie et al table 1. pns grading score based on locs ill classification. locs iii pns grading frequency percentage (%) median (pns grading score) overall percentage 1 0 1 2 2 7 2 18.2 63.6 18.2 1 0.66 0.33 0.66 2 0 1 2 3 6 94 60 5 3.6 57.0 36.4 3.0 1 2.00 31.33 20.00 1.66 3 1 2 3 26 62 21 23.9 56.9 19.3 2 8.66 20.66 7.00 4 1 2 3 5 2 3 8 1 14.3 21.4 57.1 7.1 3 0.66 1.00 2.6 0.33 5 4 1 100.0 4 0.33 pns, pentacam nucleus staging 1 2 3 4 5 6 -1/5 -1/0 -0/5 0/0 0/5 1/0 1/5 2/0 2/5 3/0 locs iii l o c s i ii p c g s mean 0/78 -1.96 sd -0/60 +1.96 sd 2/17 figure 1. bland-altman plot for locs iii and pns grading score (pcgs). level with results obtained using more expensive instruments. therefore, locs iii can be considered a reliable and economical method in estimating the severity of age-related nuclear cataracts in societies with fewer medical resources. pan et al,[23] in a cross-sectional study in 2015, evaluated the correlation using locs iii against three other methods, including pentacam, in senile cataract and found that the lens opacity measured according to locs iii is strongly correlated with lens mean density, concluding that locs iii is a cost-effective tool in diagnosing early cortical cataract. however, as they did not focus on pure nuclear cataracts, comparing results directly is less effective. gupta et al,[13] during a longitudinal interventional research project, studied 100 eyes in 100 patients with pure age-related cataract for association between locs iii and scheimpflug maximum nuclear density grading scales with phacoemulsification parameters; all patients then underwent phacoemulsification and had permanent intraocular lenses implanted in their posterior chambers. they found positive linear correlation between the locs iii grading and scheimpflug maximum nuclear density. this correlation was stronger for the pentacam imaging system with these phacoemulsification parameters. finally, lim et al, based on a case–control design in 2015, evaluated pentacam images measuring the lens density to recommend the most reasonable phaco time for each individual patient. their investigation of 229 eyes with senile cataract revealed that the results of pentacam imaging were associated with locs iii classification, nucleus opacity (no) and nucleus color (nc).[19] magalhaes et al reported a mild correlation between the pns grading score and the locs iii, and lim et al found a stronger correlation. our results were more consistent with the results of magalhaes et al. however, as previous studies journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 341 age-related cataract grading ; mirzaie et al have analyzed the correlation based on pearson’s or spearmen’s correlation, our study implemented a bland-altman plot to further investigate the association. our results confirmed a mild-tomoderate correlation we had seen in spearman’s ranked correlation test. limitations the locs iii method for classifying pure nuclear cataracts is an observer-dependent subjective tool that may cause measurement biases or inter-observer heterogeneity of results. on the other hand, pentacam is an expensive method of examination because of the high cost of the pentacam device. conclusion considering all available data, we suggest that locs iii is the primary and remains the most useful and reliable grading tool for pure senile cataract diagnosis and treatment planning if done by an experienced, well-trained ophthalmologist. considering all aspects of subjective and objective methods, the oculus pentacam is a valuable and accurate device for early diagnosis and cataract grading, but relying solely on pentacam pns grading is not wise. pns needs to be considered together with other parameters that pentacam software can measure and calculate. pentacam and its related software for cataracts might also be useful in primary healthcare for screening and early detection of senile cataract, however, an ophthalmologist is still needed to visit patients and examine eyes for cataract, since many factors may influence pentacam cataract grading. our study was performed on 300 eyes for comparing the results between these two methods. we collected a greater sample size compared to previous studies but lacked other parameters of the pentacam examining tool. this study was aided by a single ophthalmologist for the locs iii classification. although the ophthalmologist was well-trained and highly experienced in cataract ophthalmologic examination, the use of a single doctor could cause observer bias. we would recommend that future studies should be designed based on a greater sample size and using two or more ophthalmologists for the locs iii method, calculating their agreement coefficient, and utilizing the pentacam system for further information. acknowledgements the present article was extracted from the dataset developed by erfan bahremani’s md thesis. authors would like to thank the deputy of research and technology, faculty of medicine, tabriz university of medical sciences; the manager and personnel of nikoukari eye hospital, and everyone else without whose help and support the present work would have been never conducted or published. warm thanks also go to all patients – without their patience and participation this study would never have been accomplished. ethical approval the study protocol was registered with the tabriz university of medical sciences and approved by the regional committee of ethics in medical research, and the protocol adhered to the guidelines of the helsinki declaration. an informed consent was obtained from all participants. financial support and sponsorship the authors declare no funding or support for the present study. conflicts of interest the authors declare that they have no conflict of interest. references 1. chang ma, congdon ng, baker sk, bloem mw, savage h, sommer a. the surgical management of cataract: barriers, best practices and outcomes. int ophthalmol 2008;28:247–260. 2. leske mc, wu sy, nemesure b, li x, hennis a, connell am. incidence and progression of lens opacities in the barbados eye studies. ophthalmology 2000;107:1267– 1273. 3. american academy of ophthalmology. basic and clinical science course, 2016–2017. san francisco (california): american academy of ophthalmology;2016. 34 p. 4. chylack lt jr, wolfe jk, singer dm, leske mc, bullimore ma, bailey il, et al. the longitudinal study of cataract study group. the lens opacities classification system iii. arch ophthalmol 1993;111:831–836. 342 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 age-related cataract grading ; mirzaie et al 5. yang y, lv h, wang y, jiang x, zhang m, li x. clinical outcomes following trifocal diffractive intraocular lens implantation for age-related cataract in china. clin ophthalmol 2018;12:1317–1324. 6. wong wl, li x, li j, cheng cy, lamoureux el, wang jj, et al. cataract conversion assessment using lens opacity classification system iii and wisconsin cataract grading system. invest ophthalmol vis sci 2013;54:280–287. 7. puk o, de angelis mh, graw j. lens density tracking in mice by scheimpflug imaging. mamm genome 2013;24:295–302. 8. pei x, bao y, chen y, li x. correlation of lens density measured using the pentacam scheimpflug system with the lens opacities classification system iii grading score and visual acuity in age-related nuclear cataract. br j ophthalmol 2008;92:1471–1475. 9. nixon dr. preoperative cataract grading by scheimpflug imaging and effect on operative fluidics and phacoemulsification energy. j cataract refract surg 2010;36:242–246. 10. magalhães fp, costa ef, cariello aj, rodrigues eb, hofling-lima al. comparative analysis of the nuclear lens opalescence by the lens opacities classification system iii with nuclear density values provided by oculus pentacam: a cross-section study using pentacam nucleus staging software. arq bras oftalmol 2011;74:110–113. 11. chylack lt jr, wolfe jk, friend j, tung w, singer dm, brown np, et al. validation of methods for the assessment of cataract progression in the roche european-american anticataract trial (react). ophthalmic epidemiol 1995;2:59–75. 12. davison ja, chylack lt jr. clinical application of the lens opacities classification system iii in the performance of phacoemulsification. j cataract refract surg 2003;29:138–145. 13. gupta m, ram j, jain a, sukhija j, chaudhary m. correlation of nuclear density using the lens opacity classification system iii versus scheimpflug imaging with phacoemulsification parameters. j cataract refract surg 2013;39:1818–1823. 14. grewal ds, brar gs, grewal sp. correlation of nuclear cataract lens density using scheimpflug images with lens opacities classification system iii and visual function. ophthalmology 2009;116:1436–1443. 15. lim sa, shin jy, chung sh. useful prediction of phacodynamics by scheimpflug lens densitometry in patients over age 70. semin ophthalmol 2017;32:482– 487. 16. al-mezaine hs, al-amro sa, kangave d, al-obeidan s, al-jubair km. comparison of central corneal thickness measurements using pentacam and ultrasonic pachymetry in post-lasik eyes for myopia. eur j ophthalmol 2010;20:852–857. 17. klein be, hubbard l, ferrier nj, klein r, klein dj, lee ke, et al. detecting progression of nuclear sclerosis by using human grading versus semiautomated computer grading. invest ophthalmol vis sci 2005;46:1155–1162. 18. ortiz d, alió jl, ruiz-colechá j, oser u. grading nuclear cataract opacity by densitometry and objective optical analysis. j cataract refract surg 2008;34:1345–1352. 19. lim dh, kim th, chung es, chung ty. measurement of lens density using scheimpflug imaging system as a screening test in the field of health examination for agerelated cataract. br j ophthalmol 2015;99:184–191. 20. baradaran-rafii a, amiri ma, mohaghegh s, zareighanavati m. lens densitometry after corneal cross-linking in patients with keratoconus using a scheimpflug camera. j ophthalmic vis res 2015;10:118–122. 21. kim js, chung sh, joo ck. clinical application of a scheimpflug system for lens density measurements in phacoemulsification. j cataract refract surg 2009;35:1204–1209. 22. karbassi m, khu pm, singer dm, chylack lt jr. evaluation of lens opacities classification system iii applied at the slitlamp. optom vis sci 1993;70:923–928. 23. pan ap, wang qm, huang f, huang jh, bao fj, yu ay. correlation among lens opacities classification system iii grading, visual function index-14, pentacam nucleus staging, and objective scatter index for cataract assessment. am j ophthalmol 2015;159:241–247.e2. 24. lin tj, peng ch, chiou sh, liu jh, lin-chung-woung, tsai cy, et al. severity of lens opacity, age, and correlation of the level of silent information regulator t1 expression in age-related cataract. j cataract refract surg 2011;37:1270–1274. 25. yu x, ping x, zhang x, cui y, yang h, tang x, et al. the impact of gja8 snps on susceptibility to age-related cataract. hum genet 2018;137:897–904. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 343 original article dermatological findings in glaucoma patients: comparison between pseudoexfoliative and primary open-angle glaucoma farnaz ahmadpour1, md; yalda nahidi1, md; ramin daneshvar2,3, md, ms 1department of dermatology, imam reza hospital, mashhad university of medical sciences, mashhad, iran 2eye research center, mashhad university of medical sciences, mashhad, iran 3department of ophthalmology, college of medicine, university of florida, gainesville, fl, usa orcid: farnaz ahmadpour: https://orcid.org/0000-0001-8853-1348 ramin daneshvar: https://orcid.org/0000-0002-0884-0907 abstract purpose: to compare the frequency of dermatological manifestations between patients with pseudoexfoliative glaucoma and those with primary open-angle glaucoma. methods: a cross-sectional study was done on all consecutive pseudoexfoliative glaucoma (pexg) and primary open-angle glaucoma (poag) patients evaluated in a tertiary eye hospital during the study period. eligible patients were referred to the dermatology department for complete skin, hair, nail, and mucosal examinations. results: twenty-one patients in the pexg group and 26 patients in the poag group were included in this study. the most common skin manifestations in the study were seborrheic dermatitis, dry skin, and cherry angioma. the frequency of lentigines was significantly higher in the pexg patients than in the poag group (p = 0.013). more than half of the study population had seborrheic dermatitis (57.1% and 61.5% in the pexg and poag groups, respectively); however, the difference between the groups was not statistically significant (p = 0.775). similarly, the frequencies of skin dryness, cherry angioma, nevus, psoriasis, contact dermatitis, itching, seborrheic keratoses, notalgia paresthetica, and vitiligo in the two groups were not statistically significantly different (p > 0.1 for all comparisons). there was no significant association between the frequency of the investigated skin manifestations and patients’ age, visual acuity, intraocular pressure, and cup-todisc ratio. conclusion: integumentary system disorders are pervasive in glaucoma patients, and dermatologic evaluation in glaucoma patients should be considered for diagnostic and therapeutic purposes. keywords: dermatitis; dermatologic finding; glaucoma; open-angle glaucoma; pseudoexfoliation j ophthalmic vis res 2022; 17 (4): 479–485 © 2022 ahmadpour et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 479 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i4.12298&domain=pdf&date_stamp=2019-07-17 dermatological manifestations in glaucoma patients; ahmadpour et al introduction pseudoexfoliation syndrome (pexs) is a systemic condition. many organ involvements, including lungs, heart, liver, gallbladder, kidneys, blood vessels, meninges, ear, optic nerves, eye, and eyelid skin have been reported in this syndrome.[1–5] histologic studies confirmed the presence of pseudoexfoliative materials in various tissues; nevertheless, the exact composition of these materials and their pathogenesis are still unknown. in ocular structures, these materials manifest as a group of proteins in the form of granular shells that resemble dandruff.[6, 7] build-up of these materials within the eye can result in pseudoexfoliative glaucoma (pexg), the most common secondary type of openangle glaucoma.[8] similar to the situation in the eye, there is evidence that pseudoexfoliative substances are also present in large areas of the skin and viscera.[3, 9, 10] however, there is still a lack of sufficient data about the characteristics of the manifestations of pexs in the skin. on the other hand, primary open-angle glaucoma (poag) is the most common type of glaucoma in general worldwide.[11] treatment with topical eye drops, which is usually the first line of management for glaucoma patients, can cause a wide range of systemic adverse effects, including disseminated skin eruptions.[12] interestingly, skin involvement is among the most common comorbidities in all forms of glaucoma.[13] however, dermatologic disease and adverse skin reactions caused by eye drops used in treating glaucoma have not been described sufficiently.[14] medical management of poag and pexg is usually the same, and one should expect similar drug-related skin manifestations in these two groups. as the pseudoexfoliative substance in ocular structures has also been found correspondence to: ramin daneshvar, md, ms. eye research center, khatam anbia eye hospital, ghareni blvd., mashhad 91959, iran. email: radaneshvar@gmail.com received: 06-01-2022 accepted: 28-04-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i4.12298 in skin, it seems reasonable to expect some additional clinical manifestations on dermatological evaluation of pexg patients. to the best of our knowledge, no study has been published specifically on the clinical dermatological manifestations of patients with pexs. the primary purpose of this cross-sectional study was to describe clinical findings in the dermatologic evaluation of patients with pexg and to compare them with those patients with poag. our working hypothesis was that the prevalence of specific dermatological manifestations that occur in the pexg group might differ from those that occur in the poag group. as the medical management is the same between pexg and poag, any variations discovered in dermatologic findings may highlight some probable associations with underlying pathology. furthermore, as pexg is highly prevalent in the elderly population in iran,[15] research on its multiple clinical manifestations seems relevant. we can better understand this syndrome and its various clinical presentations by identifying skin manifestations of pexs patients. this discovered correlation can also help with timely diagnosis and management of the associated glaucoma. methods this was a cross-sectional study in the ophthalmology and dermatology departments of mashhad university of medical sciences (mums), mashhad, iran, between april and september 2019. consecutive patients with a clinical diagnosis of pexg or poag were referred from the glaucoma clinic of khatam anbia eye hospital to the dermatology clinic of emam reza general hospital for a thorough dermatologic evaluation. the study adhered to the tenets of the declaration of helsinki, this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: ahmadpour f, nahidi y, daneshvar r. dermatological findings in glaucoma patients: comparison between pseudoexfoliative and primary open-angle glaucoma. j ophthalmic vis res 2022;17:479–485. 480 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 https://knepublishing.com/index.php/jovr dermatological manifestations in glaucoma patients; ahmadpour et al and all included subjects provided written informed consent before participation. the medical ethics committee at mums approved the study protocol (ir.mums.fm.rec.1394.646). all glaucoma diagnoses were made by a single glaucoma-fellowship-trained ophthalmologist (rd). the diagnosis of glaucoma was based on characteristic optic nerve damage and/or visual field defect in the presence of high intraocular pressure (iop) or a normal iop with a history of either iop-lowering medications, laser procedures, or surgeries. the pexg was diagnosed based on the presence of glaucoma with any of the following findings: pseudoexfoliative material at the edge of the pupil and/or anterior capsule of the lens after complete mydriasis, atrophy of the pupillary sphincter, zentmeyer line on the anterior lens capsule, or sampaolesi line in gonioscopy. in contrast, those with poag had a wide-open angle with normal angle pigmentation on non-indentation gonioscopy and without any finding of or underlying cause for secondary glaucoma. exclusion criteria comprised any possible secondary causes of glaucoma, including pseudoexfoliation, history of using steroid medications or cushing’s syndrome at any time, history of trauma to the eye, history of retinal vascular disease, history of radiotherapy, history of uveitis, and history of intraocular surgery. also, we excluded patients with skin conditions known as direct therapeutic side effects, such as allergic contact dermatitis, due to glaucoma drops. patients were referred to imam reza general hospital for a complete skin examination. at the dermatology clinic, all subjects underwent a thorough dermatologic evaluation, including a complete examination of the skin, hair, nails, and mucosa by one expert dermatologist (yn). if needed, a skin smear or biopsy was used to confirm the diagnosis of cutaneous disease. all findings were recorded with a particular focus on the frequency and types of exfoliative manifestations (such as psoriasis and seborrheic dermatitis) in skin, hair, nails, and mucosa. central tendency measures were used to summarize the quantitative variables. normal distribution of data was examined using the shapiro–wilk test and normality plots, and based on that, either the student t-test or mann– whitney u test was used to compare the two groups. qualitative data was presented by their frequencies and percentages and compared between the groups using the chi-square test. all statistical analyses were performed with spss software (version 18, ibm spss statistics, ibm corporation, chicago, il, usa). statistical significance was set at a p < 0.05 level, and the significance level was adjusted for multiple comparisons with bonferroni correction as appropriate. results in this study, a total of 47 subjects were enrolled, including 21 pexg and 26 poag cases. seven patients in the pexg group and 12 in the poag group were females (p = 0.551). patients with poag were younger than those with pexg (58.4 ± 15.2 vs 66.7 ± 8.3 years, p = 0.023). more poag patients were in the range of 30–50 years (8 vs 2 in pexg); however, the age distribution was almost similar for the 51–70 years and 71–90 years age groups. there was no significant difference in visual acuity (va), iop, and cup:disc ratio (cdr) between the two groups [table 1]. all pexg patients and 24 (92.3%) poag patients had at least one abnormal dermatological finding (p = 0.495). the most common dermatological manifestations in patients with pexg were seborrheic dermatitis, dry skin, and cherry angioma. other dermatologic manifestations of these patients included idiopathic guttate, hypomelanosis on the trunk and limbs, xeroderma pigmentosome and severe aging, lentigo maligna, and cafe au lait macules. in those with poag, the most common dermatological findings were seborrheic dermatitis, cherry angioma, and dry skin. other specific manifestations seen in these patients included androgenic alopecia, telogen effluvium due to acetazolamide, nail-biting, pityrosporum folliculitis, sebaceous hyperplasia, nail fungal infection, alopecia areata, photosensitivity, macular amyloidosis, lipoma, and venous lake. table 2 represents the frequency of different dermatologic manifestations in the study participants. moreover, 12 patients with pexg and 16 with poag had seborrheic dermatitis (p = 0.775). one patient in the pexg group and two in the poag group had seborrheic findings on both head and face. eleven patients in the pexg group and seven in the poag group had dry skin manifestations, journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 481 dermatological manifestations in glaucoma patients; ahmadpour et al table 1. baseline clinical characteristics of patients included in the study. pexg poag p-value* number of subjects 21 26 male: female 14:7 14:12 0.551 age, yr (mean ± sd) 66.7 ± 8.3 58.4 ± 15.2 0.023 age groups (yr) 30–50 2 8 0.150 51–70 9 11 0.970 71–90 10 7 0.146 va, logmar (mean ± sd) od 0.28 ± 0.29 0.21 ± 0.22 0.466 os 0.18 ± 0.23 0.22 ± 0.23 0.452 iop, mmhg (mean ± sd) od 15.7 ± 6.0 15.2 ± 4.1 0.838 os 16.0 ± 6.1 14.2 ± 2.3 0.488 cdr (mean ± sd) od 0.72 ± 0.19 0.66 ± 0.22 0.330 os 0.74 ± 0.22 0.67 ± 0.23 0.240 lp or nlp eyes 5 2 0.217 od, oculus dexter (right eye); os, oculus sinister (left eye); cdr, cup: disc ratio; iop, intraocular pressure; pexg, pseudoexfoliative glaucoma; poag, primary open-angle glaucoma; lp, light perception; nlp, no light perception; logmar, logarithm of minimum angle of resolution; sd, standard deviation ∗significant p-value with bonferroni adjustment is <0.004 table 2. frequency of dermatologic manifestations in the study groups. pexg (n = 21) poag (n = 26) p-value* seborrheic dermatitis 12 (57.1%) 16 (61.5%) 0.775 dry skin 11 (52.4%) 7 (26.9%) 0.130 cherry angioma 8 (38.1%) 9 (34.6%) 0.990 nevus 1 (4.8%) 3 (11.5%) 0.617 psoriasis 1 (4.8%) 1 (3.8%) 0.990 seborrheic keratosis 2 (9.5%) 1 (3.8%) 0.579 lentigo 5 (23.8) 0 (0%) 0.013 dermatitis 2 (9.5%) 1 (3.8%) 0.579 pruritis 3 (14.3%) 4 (15.4%) 0.990 vitiligo 0 (0%) 2 (7.7%) 0.495 notalgia paresthetica 1 (4.8%) 1 (3.8%) 0.990 pexg, pseudoexfoliative glaucoma; poag, primary open-angle glaucoma ∗significant p-value with bonferroni adjustment is <0.005 mainly in their extremities. although the frequency of dry skin was almost twice in those with pexg compared to the poag group, the difference failed to reach the level of statistical significance (p = 0.130). there was no significant difference in the frequency of nevus and angiomas between the two groups. however, lentigines were observed in five pexg patients, while none of the poag patients had this finding (p = 0.013). in the subgroup analysis, there was no association between gender or patients’ age and the frequency of dermatologic manifestations (p > 0.154 for all comparisons). moreover, the frequency of dermatologic findings was not 482 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 dermatological manifestations in glaucoma patients; ahmadpour et al correlated with va, iop, or cdr (p > 0.142 for all comparisons). discussion in this cross-sectional study, we reported the frequency of skin manifestations in patients with pexg and poag. interestingly, all included pexg patients and most (92.3%) poag subjects had at least one dermatologic finding. glaucoma is the most common cause of preventable, irreversible blindness in the world.[16] with a prevalence of 1–5%, it was estimated that almost 80 million people would be affected by glaucoma in 2020.[17] considering the prevalence of the disease and its significant health impact, investigation of the full range of clinical manifestations of the disease and its comorbidities, including skin manifestations, seems to be highly relevant.[18] while poag is the most common form of the disease, pexg is the most common secondary type of glaucoma.[19] pexs is a multi-organ systemic disease characterized by generalized microfibrillopathy.[20] a mutation in the lysyl oxidase-like-1 (loxl1) gene can be a culprit initial event;[21] however, different environmental factors, including biological stress and free radicals, infectious agents, and trauma, can initiate the disease process.[22–25] in addition to glaucoma, pexs has a wide range of systemic comorbidities, including but not limited to cardiovascular disease, cerebrovascular disease, alzheimer’s disease, and sensorineural hearing loss.[26–29] moreover, precipitation of pseudoexfoliative materials has been shown in different organ systems, including viscera, blood vessels, skin, and ocular tissues.[1, 30] pseudoexfoliative material is a highly crosslinked glycoprotein-proteoglycan complex, mainly composed of elastic microfibrillar components, such as fibrillin-1 and latent transforming growth factor binding proteins (ltbp), as well as chaperone molecules, such as clusterin, and cross-linking enzymes, such as loxl1 protein.[31] in some reports, these materials were shown to possess amyloid or amyloid-like features.[32] in 1993, schlötzer-schrehardt and colleagues examined eyelid skin biopsy specimens of 12 pexs patients. they found pseudoexfoliative material accumulations in the specimen of seven patients, which was confirmed by electron microscopy and immunological markers.[33] their findings are in line with other reports that found pseudoexfoliative materials in extraocular structures such as rectus and oblique muscles, vortex vein, optic nerve sheath, and the skin of the lateral canthus.[34]their findings provide first-hand data on dermatological involvement in pexs. despite these clinicopathological correlations, there is no published study on clinical dermatological findings in pexg patients. through the current research we are reporting a broad group of skin disorders in these patients; our findings can further support the possible association between pexs and skin disorders. we observed a high prevalence of skin manifestations in all glaucoma patients in the present study. the most common dermatological manifestations in both groups were seborrheic dermatitis, dry skin, and cherry angioma. erb et al reported skin diseases, including dry skin, as one of the most common comorbidities seen in all glaucoma patients.[13] their results are in line with our findings; however, they did not describe multiple types of skin lesions in their study. in addition, skin reactions were described in association with the use of anti-glaucoma eye drops.[14] there was no significant difference between our study groups in terms of glaucoma severity and management; however, we excluded patients with apparent allergic dermatitis from topical glaucoma medication, as investigating the possible role of topical medications was beyond the scope of this study with its cross-sectional design. seborrheic dermatitis was the most common dermatological finding in both pexg and poag patients. several studies reported a prevalence of 1–15% for seborrheic dermatitis in the general population,[35–37] which is much lower than the observed frequency (57.1–61.5%) in our patients. this difference in prevalence can be either due to an association between the seborrheic dermatitis and glaucoma or the presence of dermatological issues due to lower hygiene and skincare in glaucoma patients. there is evidence that patients with advanced glaucoma may have poorer socioeconomic conditions than those with mild glaucoma.[38] as a counterhypothesis, glaucoma may be secondary to primary dermatological disease. of note, glaucoma has also been reported following the use of topical corticosteroids to treat eyelid dermatitis, such as seborrheic journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 483 dermatological manifestations in glaucoma patients; ahmadpour et al and atopic dermatitis.[39] the eyelid’s chronic inflammatory processes like seborrheic dermatitis and meibomian gland dysfunction may also lead to glaucoma. it has been proposed that regular lid hygiene could prevent or treat glaucoma.[40] our study had several limitations. as this was a cross-sectional study, we could only report on possible associations, and no causal relationship could be speculated based on our findings. moreover, we had a limited sample size. indeed, the lack of statistical significance in many comparisons could be merely because of insufficient statistical power. for example, twice higher frequency of dry skin in pexg patients than in poag patients did not reach statistical significance; on the other hand, although pexg patients were almost a decade older than poag patients, we did not find any effect of age on the frequency of skin manifestations. one can acceptably argue that the higher frequency of dry skin in pexg was because they were older, and we ’failed’ to demonstrate the effect of age on this association. however, in the subgroup analysis, we had the same number of elderly subjects in both groups, which can decrease the effect of age on the observed difference in the frequency of dry skin. finally, we did not have a healthy control group with matched age, sex, and socioeconomic status, which was a major study limitation. presence of that group could further help to clarify the possible association of dermatological findings with glaucoma versus other confounding factors like age, job, and socioeconomic condition. despite these limitations, to the best of our knowledge, the current study is the first one that investigated the dermatologic manifestations in glaucoma patients. future studies with larger sample sizes, more diverse glaucoma patients, and a healthy control group can shed light on this less investigated aspect of glaucoma. in summary, we noticed a wide range of dermatologic findings in poag and pexg patients. we recommend ophthalmologists and dermatologists to collaborate by referring these types of patients to each other for more comprehensive evaluation and management of such possible comorbidies. this can help diagnose and treat glaucoma patients earlier and shift the focus from a merely ocular condition to a multi-system disorder. acknowledgments the authors would like to thank dr saeed shkoohi rad (associate professor of ophthalmology, mashhad university of medical sciences) for helping with recruiting eligible patients. financial support and sponsorship the study was supported by a research grant (no. 941297) from the vice-chancellor of research at mashhad university of medical sciences. conflicts of interest the authors declare no potential conflicts of interest for this article’s research, authorship, and publication. references 1. schlötzer-schrehardt um, koca mr, naumann go, volkholz h. pseudoexfoliation syndrome. ocular manifestation of a systemic disorder? arch ophthalmol 1992;110:1752–1756. 2. djordjevic-jocic j, jovanovic p, bozic m, tasic a, rancic z. prevalence and early detection of abdominal aortic aneurysm in pseudoexfoliation syndrome and pseudoexfoliation glaucoma. curr eye res 2012;37:617– 623. 3. sarenac-vulovic ts, petrovic ma, vulovic dd, pavlovic sm, simovic s, zdravkovic ns. systemic manifestations of pseudoexfoliation. serb j exp clin res 2014;15:29–32. 4. kaya e, öztürk f. evaluation of regional brain perfusion in patients with pseudoexfoliation syndrome. neuroophthalmology 2011;35:255–258. 5. cahill m, early a, stack s, blayney aw, eustace p. pseudoexfoliation and sensorineural hearing loss. eye 2002;16:261–266. 6. prince am, streeten bw, ritch r, dark aj, sperling m. preclinical diagnosis of pseudoexfoliation syndrome. arch ophthalmol 1987;105:1076–1082. 7. ritch r. exfoliation syndrome-the most common identifiable cause of open-angle glaucoma. j glaucoma 1994;3:176–177. 8. ritch r. exfoliation syndrome and occludable angles. trans am ophthalmol soc 1994;92:845–944. 9. ritch r, schlötzer-schrehardt u. exfoliation syndrome. surv ophthalmol 2001;45:265–315. 10. streeten bw, li zy, wallace rn, eagle rc jr, keshgegian aa. pseudoexfoliative fibrillopathy in visceral organs of a patient with pseudoexfoliation syndrome. arch ophthalmol 1992;110:1757–1762. 11. weinreb rn, khaw pt. primary open-angle glaucoma. lancet 2004;363:1711–1720. 484 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 dermatological manifestations in glaucoma patients; ahmadpour et al 12. santos v, castro r, lima c, moraes m, sugai tj. skin eruption and thrombocytopaenia in a woman with glaucoma. west indian med j 2010;59:102. 13. erb c, gast u, schremmer d. german register for glaucoma patients with dry eye. i. basic outcome with respect to dry eye. graefes arch clin exp ophthalmol 2008;246:1593–1601. 14. cantisani c, ambrifi m, frascani f, fazia g, paolino g, lisi r, et al. glaucoma eye drops adverse skin reactions. recent pat inflamm allergy drug discov 2014;8:192–195. 15. nouri-mahdavi k, nosrat n, sahebghalam r, jahanmard m. pseudoexfoliation syndrome in central iran: a population-based survey. acta ophthalmol scand 1999;77:581–584. 16. weinreb rn, aung t, medeiros fajj. the pathophysiology and treatment of glaucoma: a review. jama 2014;311:1901– 1911. 17. quigley ha, broman at. the number of people with glaucoma worldwide in 2010 and 2020. br j ophthalmol 2006;90:262–267. 18. ritch r. systemic associations of exfoliation syndrome. asia pac j ophthalmol 2016;5:45–50. 19. holló g, katsanos a, konstas ag. management of exfoliative glaucoma: challenges and solutions. clin ophthalmol 2015;9:907–919. 20. ritch r. ocular findings in exfoliation syndrome. j glaucoma 2018;27:s67–s71. 21. aragon-martin ja, ritch r, liebmann j, o’brien c, blaaow k, mercieca f, et al. evaluation of loxl1 gene polymorphisms in exfoliation syndrome and exfoliation glaucoma. mol vis 2008;14:533–541. 22. zenkel m, kruse fe, naumann go, schlötzer-schrehardt u. impaired cytoprotective mechanisms in eyes with pseudoexfoliation syndrome/glaucoma. invest ophthalmol vis sci 2007;48:5558–5566. 23. damji kf, bains hs, stefansson e, loftsdottir m, sverrisson t, thorgeirsson e, et al. is pseudoexfoliation syndrome inherited? a review of genetic and nongenetic factors and a new observation. ophthalmic genet 1998;19:175–185. 24. elhawy e, kamthan g, dong cq, danias j. pseudoexfoliation syndrome, a systemic disorder with ocular manifestations. hum genomics 2012;6:22. 25. amini h, daneshvar r, eslami y, moghimi s, amini n. earlyonset pseudoexfoliation syndrome following multiple intraocular procedures. j ophthalmic vis res 2012;7:190– 196. 26. aviv u, ben ner d, sharif n, gur z, achiron a. pseudoexfoliation: an ocular finding with possible systemic implications. isr med assoc j 2017;19:49–54. 27. gonen ka, gonen t, gumus b. renal artery stenosis and abdominal aorta aneurysm in patients with pseudoexfoliation syndrome. eye 2013;27:735–741. 28. singham nv, zahari m, peyman m. association between ocular pseudoexfoliation and sensorineural hearing loss. j ophthalmol 2014;2014:825936. 29. temporale h, karasinska-klodowska a, turno-krecicka a, morawska-kochman m, dorobisz k, dudek k, et al. evaluating the hearing of patients with pseudoexfoliation syndrome. adv clin exp med 2016;25:1215–1221. 30. schlötzer-schrehardt u, küchle m, naumann go. electronmicroscopic identification of pseudoexfoliation material in extrabulbar tissue. arch ophthalmol 1991;109:565–570. 31. zenkel m, lewczuk p, jünemann a, kruse fe, naumann go, schlötzer-schrehardt u. proinflammatory cytokines are involved in the initiation of the abnormal matrix process in pseudoexfoliation syndrome/glaucoma. am j pathol 2010;176:2868–2879. 32. yilmaz a, tamer l, ateş na, çamdeviren h, değirmenci u. effects of apolipoprotein e genotypes on the development of exfoliation syndrome. exp eye res 2005;80:871–875. 33. schlötzer-schredhardt u, küchle m, dörfler s, naumann go. pseudoexfoliative material in the eyelid skin of pseudoexfoliation-suspect patients: a clinicohistopathological correlation. ger j ophthalmol 1993;2:51–60. 34. sugino t. [exfoliative materials in the skin of patients with exfoliation syndrome]. nippon ganka gakkai zasshi 1990;94:856–869. 35. sanders mg, pardo lm, franco oh, ginger rs, nijsten t. prevalence and determinants of seborrhoeic dermatitis in a middle-aged and elderly population: the rotterdam study. br j dermatol 2018;178:148–153. 36. baş y, seçkin hy, kalkan g, takci z, çitil r, önder y, et al. prevalence and related factors of psoriasis and seborrheic dermatitis: a community-based study. turk j med sci 2016;46:303–309. 37. sampaio al, mameri âc, vargas tj, ramos-e-silva m, nunes ap, carneiro sc. seborrheic dermatitis. an bras dermatol 2011;86:1061–1071. 38. eslami y, amini h, zarei r, fakhraie g, moghimi s, mohammadi sf, et al. socioeconomic factors and disease severity at glaucoma presentation. j curr ophthalmol 2011;23:19–26. 39. daniel bs, orchard d. ocular side-effects of topical corticosteroids: what a dermatologist needs to know. australas j dermatol 2015;56:164–169. 40. rynerson jm, perry hd. debs a unification theory for dry eye and blepharitis [internet]. clin ophthalmol 2016;10:2455–2467. journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 485 letter authors’ reply navid manafi1, md; kaveh abri aghdam2, md, phd 1department of ophthalmology, david geffen school of medicine, university of california-los angeles, los angeles, ca, united states 2eye research center, eye department, the five senses health institute, school of medicine, iran university of medical sciences, tehran, iran orcid: navid manafi: https://orcid.org/0000-0002-4610-402x kaveh abri aghdam: https://orcid.org/0000-0001-7568-6455 j ophthalmic vis res 2022; 17 (2): 309–310 dear editor, we would like to thank dr siddharth madan and colleagues for their interest in our work.[1] we found that the majority of temporal artery biopsies (tabs) led to negative results and giant cell arteritis (gca) could be diagnosed based on clinical grounds rather than relying just on tab. the american college of rheumatology (acr) formulated its classification criteria for diagnosing gca in 1990.[2] these criteria were used for the classification of and not for early diagnosis of gca. the revised acr criteria were proposed as a diagnostic tool for earlier diagnosis of gca in 2016.[3] tab has been considered the gold standard test for the diagnosis of gca but it has suboptimal sensitivity and specificity. one of the main limitations of tab is the presence of “skip lesions”, which increases the false-negative rate. previous studies have revealed that an increase in tab lengths or cut sections of the specimen does not yield a higher true positive rate.[1, 3, 4] some imaging modalities have been suggested as surrogates for tab.[5–7] however, they are not currently included in the acr or other guidelines for diagnosing gca.[2, 8] currently, these modalities are compared with the tab as a gold standard test, which is an imperfect standard itself. color doppler ultrasound (cdus) and high-resolution magnetic resonance imaging (mri) with mr angiography (mra) have been studied regarding their role in diagnosing gca.[7, 9] the heterogeneous conclusions about the utility of cdus likely reflect the operator-dependent nature of the procedure and may also result from the variability of the clinical context, probe settings, technique, and equipment. standardization of these factors may lead to more widespread use of cdus for the diagnosis of gca. mra revealed to have a pooled sensitivity and specificity of 93% and 81%, respectively, when tab was used as the reference standard.[10] fluorescein angiography (fa) is an invasive test that shows delayed choroidal filling and/or retinal artery in 56% of patients with arteritic anterior ischemic optic neuropathy (aaion) and even in some cases of gca without visual symptoms but not in non-arteritic anterior ischemic optic neuropathy (naion).[11] optical coherence tomography angiography (octa) non-invasively images capillary perfusion at various levels of the retina and optic disc. it could show dilation and eventual attenuation of the superficial peripapillary capillaries in eyes with aaion, corresponding with visual field loss and might be used as an adjunctive imaging modality.[6, 12, 13] however, octa alone cannot differentiate naion from aaion. the increasing use of imaging modalities as diagnostic or adjunctive complements to © 2022 abri aghdam. this is an open access article distributed under the creative commons attribution license | published by knowledge e 309 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i2.10825&domain=pdf&date_stamp=2019-07-17 authors’ reply; abri aghdam tab is promising. the use of tab cannot be overlooked as it shows the actual pathology of the specimen and other modalities have not shown superior diagnostic values compared with tab. however, guidelines and criteria need to be updated and include modern imaging technologies. imaging modalities can also aid in the evaluation of other extracranial and intracranial arteries that might be affected by either gca or other vasculitides. references 1. aghdam ka, sanjari ms, manafi n, khorramdel s. temporal artery biopsy for diagnosing giant cell arteritis: a ten-year review. j ophthalmic vis res 2020;15:201–209. 2. hunder gg, bloch da, michel ba, stevens mb, arend wp, calabrese lh, et al. the american college of rheumatology 1990 criteria for the classification of giant cell arteritis. arthritis rheum 1990;33:1122–1128. 3. mahr a, saba m, kambouchner m, polivka m, baudrimont m, brocheriou i, et al. temporal artery biopsy for diagnosing giant cell arteritis: the longer, the better? ann rheum dis 2006;65:826–828. 4. navahi ra, chaibakhsh s, alemzadeh sa. the adequate number of histopathology cross-sections of temporal artery biopsy in establishing the diagnosis of giant cell arteritis. j ophthalmic vis res 2021;16:77–83. 5. dinkin m, johnson e. one giant step for giant cell arteritis: updates in diagnosis and treatment. curr treat options neurol 2021;23:6. 6. gaier ed, gilbert al, cestari dm, miller jb. optical coherence tomographic angiography identifies peripapillary microvascular dilation and focal nonperfusion in giant cell arteritis. br j ophthalmol 2018;102:1141–1146. 7. bley ta, wieben o, uhl m, thiel j, schmidt d, langer m. high-resolution mri in giant cell arteritis: imaging of the wall of the superficial temporal artery. am j roentgenol 2005;184:283–287. 8. mackie sl, dejaco c, appenzeller s, duftner c, gonzalezchiappe s, camellino d, et al. british society for rheumatology guideline on diagnosis and treatment of giant cell arteritis. rheumatology 2020;59:e1–e23 9. schmidt wa, kraft he, vorpahl k, völker l, gromnicaihle ej. color duplex ultrasonography in the diagnosis of temporal arteritis. n engl j med 1997;337:1336–1342. 10. klink t, geiger j, ness t, heinzelmann s, reinhard m, hollulrich k, et al. giant cell arteritis: diagnostic accuracy of mr imaging of superficial cranial arteries in initial diagnosis – results from a multicenter trial 1. radiology 2014;273:844– 852. 11. siatkowski rm, gass jdm, glaser js, smith jl, schatz nj, schiffman j. fluorescein angiography in the diagnosis of giant cell arteritis. am j ophthalmol 1993;115:57–63. 12. balducci n, morara m, veronese c, barboni p, casadei nl, savini g, et al. optical coherence tomography angiography in acute arteritic and non-arteritic anterior ischemic optic neuropathy. graefes arch clin exp ophthalmol 2017;255:2255–2261. 13. abri aghdam k, ashraf khorasani m, soltan sanjari m, habibi a, shenazandi h, kazemi p, et al. optical coherence tomography angiography features of optic nerve head drusen and nonarteritic anterior ischemic optic neuropathy. can j ophthalmol 2018;54:495–500. correspondence to: kaveh abri aghdam, md, phd. eye research center, eye department, the five senses health institute, school of medicine, iran university of medical sciences, tehran 1445613131, iran. email: kaveh.abri@gmail.com received: 09-06-2021 accepted: 06-11-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i2.10825 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: manafi n, abri aghdam k. authors’ reply. j ophthalmic vis res 2022;17:309–310. 310 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 https://knepublishing.com/index.php/jovr editorial application of artificial intelligence to improve imaging in ophthalmology mark christopher, phd hamilton glaucoma center, viterbi family department of ophthalmology and shiley eye institute, university of california san diego, california, usa j ophthalmic vis res 2023; 18 (1): 1–2 over the past decade, the literature has witnessed major advances in the field of artificial intelligence (ai). many of these developments have focused on applying specific ai approaches, including deep learning and convolutional neural networks (cnns), to image datasets which have greatly improved the accuracy of general image recognition and computer vision tasks.[1] there has also been great interest and progress in adapting these methods for use on medical imaging data to detect disease, assess prognosis, and improve patient care.[2] with respect to ophthalmic images specifically, ai models have been developed for diabetic retinopathy, macular degeneration, glaucoma, and even prediction of systemic health indicators.[3] the past few years have even seen regulatory approval of autonomous ai-based systems to detect diabetic retinopathy in the us.[4, 5] in the current issue of journal of ophthalmic and vision research, razaghi et al report the use of a deep learning approach to reduce errors in optical coherence tomography (oct) retinal nerve fiber layer (rnfl) segmentation.[6] it is known that using current standard device correspondence to: mark christopher, phd. hamilton glaucoma center, viterbi family department of ophthalmology and shiley eye institute, university of california san diego, 9415 campus point dr la jolla, california 92093, usa. e-mail: mac157@health.ucsd.edu received: 29-12-2022 accepted: 05-01-2023 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i1.12719 software, segmentation errors can be a common event.[7, 8] errors in the resulting structural and thickness measurements may provide incorrect information on which diagnostic and treatment decisions could be based. methods that provide accurate and robust segmentation methods are critical for ensuring that clinical decisions are based on correct information. a number of investigators have approached oct segmentation using deep learning techniques.[9–11] these reports have typically used manual segmentation by experts on oct data to train cnns designed specifically for image segmentation. based on their intended use, these algorithms can be trained to segment individual retinal layers, optic nerve head structures, or disease markers, or be programmed to perform simultaneous segmentation of all these parameters. these techniques exhibit variations in terms of modifications of the cnn architecture, training approaches, and pre-/post-processing procedures. razaghi et al focused on providing accurate and reliable rnfl segmentation. to achieve this, they adopted a commonly used fully convolutional cnn approach (u-net).[12] they then applied post-processing steps to help clean up the segmentation and provide accurate estimates of mean rnfl thickness. when applied to their test this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: christopher m. application of artificial intelligence to improve imaging in ophthalmology . j ophthalmic vis res 2023;18:1–2. © 2023 christopher . this is an open access article distributed under the creative commons attribution license | published by knowledge e 1 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i1.12719&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr editorial; christopher set, they have reported performances comparable to previous studies in terms of dice (a commonly used metric for image segmentation) and even exceeding prior results in terms of r2when comparing mean rnfl thickness to manual segmentation-based rnfl thickness values. in summary, ai is already demonstrating a massive impact on ophthalmology (and medicine is general) that will only continue to grow. ai-based tools have the potential to impact and hopefully improve all aspects of patient care. it is critical, however, that clinical integration of these tools be performed responsibly. this includes emphasis on thorough evaluation of ai models on diverse datasets and mindfulness of their limitations. financial support and sponsorship none. conflicts of interest there are no conflicts of interest. references 1. emmert-streib f, yang z, feng h, tripathi s, dehmer m. an introductory review of deep learning for prediction models with big data. front artif intell 2020;3:4. 2. aggarwal r, sounderajah v, martin g, ting dsw, karthikesalingam a, king d, et al. diagnostic accuracy of deep learning in medical imaging: a systematic review and meta-analysis. npj digit med 2021;4:65. 3. ting dsw, pasquale lr, peng l, campbell jp, lee ay, raman r,et al. artificial intelligence and deep learning in ophthalmology. br j ophthalmol 2019;103:167–175. 4. fda. fda permits marketing of artificial intelligencebased device to detect ceretain diabetes-related eye problems. accessed january 10, 2022. https: //www.fda.gov/news-events/press-announcements/fdapermits-marketing-artificial-intelligence-based-devicedetect-certain-diabetes-related-eye 5. lee kj. autonomous diabetic retinopathy screening system gains fda approval. accessed december 20, 2022. https://www.aao.org/headline/autonomousdiabetic-retinopathy-screening-system-g 6. razaghi g, aghsaei m, hejazi m. correction of retinal nerve fiber layer thickness determination on spectraldomain optical coherence tomographic images using unet architecture. j ophthalmic vis res 2023;18:1–11. 7. mansberger sl, menda sa, fortune ba, gardiner sk, demirel s. automated segmentation errors when using optical coherence tomography to measure retinal nerve fiber layer thickness in glaucoma. am j ophthalmol 2017;174:1–8. 8. miki a, kumoi m, usui s, endo t, kawashima r, morimoto t, et al. prevalence and associated factors of segmentation errors in the peripapillary retinal nerve fiber layer and macular ganglion cell complex in spectral-domain optical coherence tomography images. j glaucoma 2017;26:995–1000. 9. devalla sk, chin ks, mari jm, tun ta, strouthidis ng, aung t, et al. a deep learning approach to digitally stain optical coherence tomography images of the optic nerve head. invest ophthalmol vis sci 2018;59:63–74. 10. wilson m, chopra r, wilson mz, cooper c, macwilliams p, liu y, et al. validation and clinical applicability of wholevolume automated segmentation of optical coherence tomography in retinal disease using deep learning. jama ophthalmol 2021;139:964–973. 11. marques r, andrade de jesus d, barbosa-breda j, eijgen jv, stalmans i, walsum t, et al. automatic segmentation of the optic nerve head region in optical coherence tomography: a methodological review. comput methods programs biomed 2022;220:106801. 12. ronneberger o, fischer p, brox t. u-net: convolutional networks for biomedical image segmentation. 2015:arxiv:1505.04597. https://ui.adsabs.harvard.edu/ abs/2015arxiv150504597r 2 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 https://www.fda.gov/news-events/press-announcements/fda-permits-marketing-artificial-intelligence-based-device-detect-certain-diabetes-related-eye https://www.fda.gov/news-events/press-announcements/fda-permits-marketing-artificial-intelligence-based-device-detect-certain-diabetes-related-eye https://www.fda.gov/news-events/press-announcements/fda-permits-marketing-artificial-intelligence-based-device-detect-certain-diabetes-related-eye https://www.fda.gov/news-events/press-announcements/fda-permits-marketing-artificial-intelligence-based-device-detect-certain-diabetes-related-eye https://www.aao.org/headline/autonomous-diabetic-retinopathy-screening-system-g https://www.aao.org/headline/autonomous-diabetic-retinopathy-screening-system-g https://ui.adsabs.harvard.edu/abs/2015arxiv150504597r https://ui.adsabs.harvard.edu/abs/2015arxiv150504597r original article the influence of near vision tasks on intraocular pressure in normal subjects and glaucoma patients mohammad pakravan1, md; azadeh samaeili2, md; hamed esfandiari3, md; kiana hassanpour2, md; sadid hooshmandi2, md; shahin yazdani2, md; farideh sharifipour2, md; azadeh doozandeh2, md; bahram einollahi2, md; parastou pakravan4, ms; mohammad hasan shahriari5, ms; bahareh kheiri2, ms 1glaucoma and neuro-ophthalmologist, jones eye institute, university of arkansas for medical sciences, ar, usa 2ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 3department of ophthalmology, olmsted medical center, rochester, mn, usa 4miller school of miami, university of miami, miami, florida 5department of health information technology and management, school of science, shahid beheshti university of medical sciences, tehran, iran abstract purpose: to investigate the effect of static accommodative tasks on intraocular pressure (iop) of glaucomatous and normal eyes. methods: four groups of subjects categorized as primary open-angle glaucoma (poag), primary angle-closure suspects (pacs), normal age-matched controls, and normal young adults (nya; age <40 years) were enrolled. the baseline iops were measured after the subjects were looking at a distant target for 15 min. static accommodation was obtained by execution of near vision tasks (reading at 33 cm in daylight [300 lux] for 60 min). iops were measured at 15, 30, 45, and 60 min intervals while accommodating and then measured again after 15 min of relaxing accommodation while looking at a distant target. results: one-hundred and eighteen eyes of 98 subjects were recruited. the study groups consisted of the following categories: 25 poag (46 eyes), 24 pacs (47 eyes), 25 matched controls (50 eyes), and 24 nya (48 eyes). within all groups, the mean iop decreased throughout the accommodation period at all time points. maximum iop reduction after accommodation was detected at the 30-min time among the poag subjects, at the 45-min time in the pacs and matched control groups, and at 15 min after the relaxation of accommodation in the nya group. iop reduction levels showed no statistically significant difference among poag, pacs, and the normal matched groups in their response to accommodation. however, nya had significantly lower iop and greater iop reduction after the resting period (relaxation of accommodation). conclusion: static accommodative tasks can significantly reduce iop in normal, poag, and pacs individuals. encouraging glaucoma patients to practice periodical near vision tasks could be viewed as an adjunctive measure for glaucoma management. keywords: accommodation; accommodative tasks; intraocular pressure; primary openangle glaucoma j ophthalmic vis res 2022; 17 (4): 497–504 © 2022 pakravan et al . this is an open access article distributed under the creative commons attribution license | published by knowledge e 497 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i4.12350&domain=pdf&date_stamp=2019-07-17 near vision tasks and iop; pakravan et al introduction accommodation refers to the ability of the eye to change focus from a distant object to a near object. during accommodation, ciliary muscle contraction leads to zonular fiber relaxation which is then followed by a change in lens shape where it becomes more spherical. meanwhile, longitudinal fibers in the ciliary muscles that adhere to the scleral spur (ss) cause posterior movement of the ss during accommodation. as a result, the trabecular meshwork (tm) and adjacent schlemm’s canal expands and trabecular outflow of aqueous humor increases.[1] investigating the role of accommodation on intraocular pressure (iop) has presented contradictory results. static accommodation refers to focusing on a near target without changing to distance target for almost 3 min or more. while the patients look at near target and distance frequently for 3 s in repeated accommodation.[2] in some reports, both static and repeated accommodations have been shown to decrease iop in healthy individuals.[2, 3] the plausible mechanism could be the adjustment of elastic tissue structures of the chamber angle following numerous accommodation and ciliary muscle contractions. this modification could enhance trabecular aqueous humor drainage in a sinusoidal pattern.[4] however, further studies showed that repeated accommodation does not induce a significant reduction in iop as compared to static accommodation.[2] similarly, baser et al[5] reported that reading does not affect iop in healthy individuals. indeed, some studies have reported an increase in iops during accommodation. ha et al[6] investigated the effects of working with smartphones on the iop in normal patients and reported an increasing effect, especially in low-light conditions. similarly, correspondence to: azadeh samaeili, md. ophthalmology department of labbafinejad medical center, boostan 9 st. pasdaran ave., tehran 16666, iran. email: as100973@gmail.com received: 19-01-2021 accepted: 10-06-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i4.12350 vera et al[7] reported iop to increase while reading both in supine and sitting positions which was greater in the sitting position. considering the contradictory results on the effect of engaging in near vision work on iop and also the scarcity of studies about accommodation effects on the iop of glaucomatous eyes, we conducted the present study. this study aims to investigate the magnitude of iop changes induced by continuous or static accommodation during near vision work in glaucomatous and normal eyes. methods a total of 191 eyes of 98 patients were enrolled in the study. the institutional review board of shahid beheshti university of medical science approved the protocol of the study. our research adhered to the tenets of the declaration of helsinki. informed written consent was obtained from each subject. the study groups consisted of 25 poag subjects (46 eyes; group 1), 24 pacs subjects (47 eyes; group 2), 25 matched controls (50 eyes; group 3), and 24 normal young individuals (48 eyes; group 4). the first three groups were selected using the independent simple random sample selection technique. the fourth group were normal volunteers, young (not presbyopic and aged <40 years) residents of the center. it was assumed that residents experienced approximately equal amounts of weekly physical activities. diagnosis of poag was made by the detection of glaucomatous optic neuropathy in the presence of open angles on gonioscopy and also by the lack of any evidence of secondary causes of glaucoma after baseline examination. pacs was defined when the posterior tm was not visible at 180 or more degrees of the angle during gonioscopic examination.[8] exclusion criteria were the existence of peripheral anterior synechiae (pas), history of glaucoma surgery, ocular trauma, use of any topical or systemic medications that could affect this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: pakravan m, samaeili a, esfandiari h, hassanpour k, hooshmandi s, yazdani s, sharifipour f, doozandeh p, einollahi b, pakravan p, shahriari mh, kheiri b. the influence of near vision tasks on intraocular pressure in normal subjects and glaucoma patients. j ophthalmic vis res 2022;17:497–504. 498 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 https://knepublishing.com/index.php/jovr near vision tasks and iop; pakravan et al accommodation including pilocarpine, ocular pathologies that would compromise iop reading, high myopia (spherical equivalent refractive error >−6.00 d), and high hyperopia (defined as spherical equivalent hyperopia of more than 4.0 d). at baseline, the ophthalmologic examination included best-corrected visual acuity (bcva) measurement, slit-lamp examination (haag-streit, bern, switzerland), and iop measurement with rebound tonometry performed by a glaucoma specialist (icare finland oy, helsinki, finland). in addition, gonioscopy with a zeiss-style four-mirror lens (model opdsg, ocular instruments, inc., bellevue, wa), fundus examination, perimetry (humphrey visual field analyzer; model 750; carl zeiss meditec, dublin, california, usa), and central corneal pachymetry (quantel medical pocket, japan) were performed at baseline. using the shaffer gonioscopy classification, a trained ophthalmologist performed the gonioscopy at ×16 magnification in a darkroom setting. the same ophthalmologist measured the iop twice between 9 and 11 am. the ophthalmologist was masked about the patients’ group. an average of two readings were recorded as the patient’s iop. if two iops differed by more than 2 mmhg, the measurement was repeated, and the mean iop was recorded. to maintain a static accommodative state, patients were asked to continue their fixation on the object used for the near vision task examination with the opposite eye during iop measurements. after a complete explanation of the study protocol to the patients, they were seated in an upright position while the neck was in a neutral position. patients were then required to look at a distance target (6/12 snellen letters) for 15 min while wearing their corrective lenses. baseline iop was then measured. static accommodation was achieved by close monitoring of the volunteers while they focused on a near target (reading the same text from a 19 samsung monitor with brightness of 250 cd/m2 at 33 cm at daylight [300 lux]) for 1 hr while wearing their presbyopic glasses. icare iop measurements were then taken every 15 min during the 1 hr of the static accommodative task, and 15 min after focusing on a distant object in relaxed accommodative state. before the start of the study, all subjects’ iops were controlled either by topical medications or yttrium aluminum garnet (yag) laser peripheral iridotomy (pi) in the glaucoma cases, resulting in all iops becoming ≤ 23 mmhg. statistical analysis to present the data, we used mean and standard deviation analysis. to compare the results among the groups, and throughout the study whenever needed, we used gee (generalized estimating equations) to consider the possible correlation of the iop results in the eyes. the primary outcome measure was the change in iop 15 min after the start of accommodation. the iop values at other time intervals were considered as secondary outcome measures. to evaluate the changes within groups during the follow-up times we used paired t-test. in all the analyses, multiple comparison corrections were done using the bonferroni method. all statistical analyses were performed using the spss software (ibm corp. released 2017. ibm spss statistics for windows, version 25.0. armonk, ny: ibm corp.). a p-value <0.05 was considered statistically significant. results one hundred and ninety-one eyes of 98 consecutive participants were enrolled in the study. the mean age of participants in groups 1 to 4 were 55.44 ± 13.96, 56.32 ± 13.79, 51.64 ± 11.1, and 29.75 ± 3.65 years, respectively. there were no statistically significant differences among study groups 1, 2, and 3 in terms of age, refractive status, and central corneal thickness but there were statistically significant differences in group 4 [table 1]. none of the individuals were using either pilocarpine or other systemic agents that could constrict or dilate the pupil. eighty percent (37 eyes) of the poag patients were on glaucoma medications that presumably do not affect accommodation. baseline demographic and clinical characteristics of all groups are presented in table 1. for all groups, the iop was measured at baseline, and at every 15 min throughout the hour of the accommodation period. iop was measured again, 15 min after the release of accommodation where the patients focused on a distant target. journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 499 near vision tasks and iop; pakravan et al the mean iop decreased in all of the volunteers during the accommodating period. the mean baseline iop ± sd was 14.43 ± 3.96, 14.11 ± 3.99, 13.62 ± 4.57, and 14.27 ± 3.98 mmhg in groups 1 to 4, respectively (p = 0.807). table 2 shows the iop changes and differences from baseline within and among the groups. in group 1, iop significantly decreased from baseline with a mean change of 0.98 ± 2.2 mmhg (p = 0.004), –1.17 ± 2.24 mmhg (p = 0.001), and –0.8 ± 2.46 mmhg (p = 0.032) at 15, 30, and 45-min time points after static accommodation. in group 2, iop decreased significantly from baseline at all time points throughout the accommodation. the amount of iop decrease at each pre-determined 15 min time interval was –1.19 ± 2.09 (p < 0.001), –1.02 ± 2.93 (p = 0.021), –1.43 ± 2.89 (p = 0.002), and –1.17 ± 2.64 (p = 0.004), respectively. the iop reduction for group 2 was also significant after 15 min of relaxation of accommodation (–1.04 ± 2.41 mmhg; p = 0.005). in group 3, iop reduced throughout all examinations, however, it was significant only at the 30 and 45-min time points with a mean reduction of –1.06 ± 2.4 and –1.1± 2.4 mmhg, respectively (p = 0.003). in group 4, iop reduction was significant at all time points within and after accommodation (–1.29 ± 2.24, –1.54 ± 2.35, –2.08 ± 2.55, –1.75 ± 2.27, and –2.15 ± 2.67, respectively, p < 0.001; table 2). maximum iop reduction was observed 30 min after the near vision task in group 1 (– 1.17 ± 2.24 mmhg), 45 min after accommodation in groups 2 and 3 (–1.43 ± 2.89 and –1.1 ± 2.46 mmhg, respectively), and 15 min after the end of the release of accommodation in group 4 (–2.15 ± 2.67 mmhg). the mean iops and iop reductions showed no statistically significant difference among the study groups in time intervals of 15, 30, 45, and 60 min after the start of the accommodation [table 2, figure 1]. however, normal young adults showed significantly lower mean iop (12.13 ± 3.59, p = 0.04) and greater iop reduction (–2.15 ± 2.67, p < 0.001) after the release of the accommodation. utilizing multivariate analysis, only the factor of age was associated with greater iop reduction (p = 0.02). discussion this study found a consistent reduction in the mean iop during static accommodation in all groups. our results were in line with previous studies which showed that iop decreased during accommodation.[9, 10] iop is predominantly controlled by aqueous outflow through the tm, which is augmented by traction on the ss. increased traction on the ss enlarges the pores of the tm. there is histological, pharmacological, and electrophysiological evidence explaining the association between accommodation and iop; there is a connection between elastin fibers in the tendons of the longitudinal fibers of ciliary muscles and elastin fibers of the tm lamellae. ciliary muscle tendon density is highest in the juxtacanalicular tissue near the tm adjacent to the schlemm canal (sc).[11] therefore, the presence of pilocarpine or any factors that may trigger accommodation results in ciliary muscle contractions followed by a stretch of the tm and an increase in the area of the sc, and subsequent increase in aqueous outflow and iop reduction.[12, 13] however, human studies have not yet demonstrated the changes in sc and tm morphology on physiological accommodation. the mean iop reduction during accommodating occurs between the ranges of 1.8–4.5 mmhg as shown in the previous reports.[2, 14–16] the period of iop measurement was between 8 and 10 min immediately after accommodation in these studies which can justify a slightly higher iop reduction as compared to our results.[2, 14–16] we found that age was significantly associated with iop reduction in all groups. the magnitude of iop reduction was greater in older participants during accommodation. this observation may be explained by the pore sizes in tm. it is possible that changes in normal pore sizes have a limited effect on iop corresponding to a small age-related increase in iop seen between 20 and 60 years of age.[17] however, even a 0.25-micron change in the size of the small pore increasing with age can result in a 10 mmhg change in the iop.[18] we observed that the accommodation-induced reduction in the iop was seen in open-angle as well as angle-closure eyes. we argue that while accommodation pushes the iridolenticular diaphragm forward and shallows the angle, its beneficial effects on tm outweigh these changes and result in iop reduction. however, the lower iop reduction in poag individuals at the 60 min time point could be attributed to the stiffness of tm in this group of patients.[19] 500 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 near vision tasks and iop; pakravan et al table 1. the baseline demographic and clinical characteristics of the study participants. study groups total poag pacs control nya p-value sex m 48 (49.0%) 13 (52.0%) 12 (50.0%) 12 (48.0%) 11 (45.8%) 0.992* f 50 (51.0%) 12 (48.0%) 12 (50.0%) 13 (52.0%) 13 (54.2%) age ref 48.47 ± 15.62 55.44 ± 13.96 56.32 ± 13.79 51.64 ± 11.1 29.75 ± 3.65 <0.001* 0.34 ± 1.25 0.53 ± 1.36 0.66 ± 1.15 0.72 ± 1.12 -0.45 ± 0.99 <0.001* cct 536.56 ± 73.84 549.55 ± 36.35 547.49 ± 23.97 538.71 ± 44.62 522.8 ± 13.01 <0.001* baseline iop 14.1 ± 4.12 14.43 ± 3.96 14.11 ± 3.99 13.62 ± 4.57 14.27 ± 3.98 0.807** *based on fisher’s exact test; **based on generalized estimating equations; ref, refraction; cct, central corneal thickness; poag, primary open-angle glaucoma; pacs, primary angle-closure glaucoma; nya, normal young adults; iop, intraocular pressure table 2. changes in iop between and within study groups throughout the study. study groups p-value** overall effect size (cohen’s d) poag pacs control nya baseline iop 14.43 ± 3.96 14.11 ± 3.99 13.62 ± 4.57 14.27 ± 3.98 0.807 iop at 15min 13.46 ± 3.87 12.91 ± 3.73 13.32 ± 4.47 12.98 ± 3.93 0.884 iop change at 15 min –0.98 ± 2.2 –1.19 ± 2.09 –0.3 ± 1.93 –1.29 ± 2.24 0.06 0.11 p-within* 0.004 <0.001 0.277 <0.001 iop at 30 min 13.26 ± 3.62 13.09 ± 4.19 12.56 ± 4.2 12.73 ± 3.78 0.804 iop change from baseline at 30 min –1.17 ± 2.24 –1.02 ± 2.93 –1.06 ± 2.4 –1.54 ± 2.35 0.709 0.14 p-within* 0.001 0.021 0.003 <0.001 iop at 45 min 13.63 ± 3.3 12.68 ± 4.12 12.52 ± 4.07 12.19 ± 3.62 0.198 iop change from baseline at 45 min –0.8 ± 2.46 –1.43 ± 2.89 –1.1 ± 2.46 –2.08 ± 2.55 0.075 0.27 p-within* 0.032 0.002 0.003 <0.001 iop at 60 min 13.8 ± 3.51 12.94 ± 3.65 12.96 ± 4.03 12.52 ± 3.33 0.323 iop change from baseline at 60 min –0.63 ± 2.4 –1.17 ± 2.64 –0.66 ± 2.76 –1.75 ± 2.27 0.068 0.24 p-within* 0.081 0.004 0.097 <0.001 iop after 15 min rest 14.37 ± 4.28 13.06 ± 3.67 12.8 ± 4.25 12.13 ± 3.59 0.049 iop change from baseline after 15 min rest –0.07 ± 2.56 –1.04 ± 2.41 –0.82 ± 2.4 –2.15 ± 2.67 0.001 0.41 p-within* 0.864 0.005 0.019 <0.001 *p-within based on paired t-test; **based on generalized estimating equation (multiple comparison correction has been done with bonferroni method); nya, normal young adults; poag, primary open-angle glaucoma; pacs, primary angle-closure suspect; iop, intraocular pressure journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 501 near vision tasks and iop; pakravan et al figure 1. changes in iop between and within study groups throughout the study. maximum iop reduction was observed 30 min after a near task in poag, 45 min after accommodation in pacs and control groups, and 15 min after the end of accommodation in nya. poag, primary open-angle glaucoma; pacs, primary angle-closure suspect; nya, normal young adults. in contrast to our findings, some studies demonstrated that iop was elevated during accommodation while reading[7] or while using a smartphone[6] or in myopic eyes.[20, 21] however, this result is not consistently repeated in other studies.[22] the divergent reaction of iop to accommodation in myopic eyes could be the result of the differences in structure and function of the eyes between emmetropic and myopic subjects.[22] ahnul et al studied normal-tension glaucoma cases that were controlled by medication or filtering surgery. they found an elevation of iop after 25 min of working on a smartphone in low-light conditions.[23] however, their study varied in the type of glaucoma, the low-light conditions, the duration of the near vision task, and the use of smartphones versus computer screens as was done in the current study. another concern that may influence outcomes is that bending the head when reading on a smartphone may be comparable to prone positioning[24, 25] which is different from the upright position normally applied during computer work. although the iop reduction persisted throughout the accommodation and at least 15 min after accommodation in our study, it was hard to predict how long the hypotensive effect of accommodation would last especially when compared with alternative studies where iop was mainly measured during and immediately after accommodation.[20–22] of note, the effect sizes of iop estimated by cohen’s d demonstrated small to moderate differences among groups [table 2]. one limitation of the current study is that we did not include a control group with no accommodation. sitting upright could potentially have some hypotension effects, however, the literature review for this effect is inconclusive.[26–28] we also did not evaluate the biometric changes of the anterior chamber to determine the interaction between iop and changes in lens thickness and positioning, depth of the anterior chamber as well as angle parameters. in an anterior segment study, yan et al demonstrated that the anterior chamber became shallow, the lens thickened, and the angle narrowed during accommodation.[20] another limitation of the study is that only including pacs’ eyes makes it hard to estimate the reaction of eyes with complete angle-closure to accommodation. the effect of ciliary muscle contraction in the presence of pas could be opposite to that of the open-angle or pacs; it is shown that accommodation inhibits uveoscleral outflow resulting in paradoxical iop elevation in synechial angle closure.[4] further studies with a longer period of resting after accommodation along with analyses among different ethnicities are warranted to elucidate the duration of the effect of accommodation on iop as well as correlations as it pertains to other ethnicities. in summary, in this present study, iop was shown to be significantly reduced after static 502 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 near vision tasks and iop; pakravan et al accommodation for 1 hr in normal, poag, and pacs eyes. the hypotensive effect lasted at least 15 min after the relaxation of accommodation. encouraging glaucoma patients to perform periodic near vision tasks such as studying would not only improve knowledge on the topic but also be helpful as an adjunctive measure in glaucoma management. acknowledgment authors acknowledge the memory of our beloved coauthor dr. mohammad zare who passed away during his fight in frontline of covid-19. financial support and sponsorship none. conflicts of interest authors have no proprietary or commercial interest in any materials discussed in this article. references 1. lütjen-drecoll e. functional morphology of the trabecular meshwork in primate eyes. prog retin eye res 1999;18:91–119. 2. jenssen f, krohn j. effects of static accommodation versus repeated accommodation on intraocular pressure. j glaucoma 2012;21:45–48 3. priluck az, hoie ab, high rr, gulati v, ghate da. effect of near work on intraocular pressure in emmetropes. j ophthalmol 2020;2020. 4. johnstone ma. the aqueous outflow system as a mechanical pump: evidence from examination of tissue and aqueous movement in human and non-human primates. j glaucoma 2004;13:421–438. 5. baser g, karahan e, bilgin s, unsal u. evaluation of the effect of daily activities on intraocular pressure in healthy people: is the 20 mmhg border safe? int ophthalmol 2018;38:1963–1967. 6. ha a, kim yk, park yj, jeoung jw, park kh. intraocular pressure change during reading or writing on smartphone. plos one 2018;13. 7. vera j, redondo b, molina r, cárdenas d, jiménez r. acute intraocular pressure responses to reading: the influence of body position. j glaucoma 2020;29:581– 586. 8. weinreb rn, friedman ds. angle closure and angle closure glaucoma: reports and consensus statements of the 3rd global aigs consensus meeting on angle closure glaucoma. kugler publications; 2006. 9. mauger rr, likens cp, applebaum m. effects of accommodation and repeated applanation tonometry on intraocular pressure. am j optom physiol opt 1984;61:28–30. 10. read sa, collins mj, becker h, cutting j, ross d, savill ak, et al. changes in intraocular pressure and ocular pulse amplitude with accommodation. br j ophthalmol 2010;94:332–335. 11. park cy, lee jk, kahook my, schultz js, zhang c, chuck rs. revisiting ciliary muscle tendons and their connections with the trabecular meshwork by two photon excitation microscopic imaging. invest ophthalmol vis sci 2016;57:1096–1105. 12. barany e. the mode of action of miotics on outflow resistance. a study of pilocarpine in the vervet monkey cercopithecus ethiops. trans ophthalmol soc uk 1966;86:539–578. 13. chowdhury ur, hann cr, stamer wd, fautsch mp. aqueous humor outflow: dynamics and disease. invest ophthalmol vis sci 2015;56:2993–3003. 14. armaly mf, burian hm. changes in the tonogram during accommodation. ama arch ophthalmol 1958;60:60–69. 15. armaly mf, jepson nc. accommodation and the dynamics of the steady-state intraocular pressure. invest ophthalmol vis sci 1962;1:480–483. 16. cassidy l, delaney y, fitzpatrick p, blake j. effect of accommodation on intraocular pressure in glaucomatous eyes. irish j med sci 1998;167:17. 17. abu-hassan dw, acott ts, kelley mj. the trabecular meshwork: a basic review of form and function. j ocul biol 2014;2. 18. schachar ra. the mechanism of accommodation and presbyopia. int ophthalmol clin 2006;46:39–61. 19. wang k, li g, read at, navarro i, mitra ak, stamer wd, et al. the relationship between outflow resistance and trabecular meshwork stiffness in mice. sci rep 2018;8:1– 12. 20. yan l, huibin l, xuemin l. accommodation-induced intraocular pressure changes in progressing myopes and emmetropes. eye 2014;28:1334–1340. 21. young fa. the development and control of myopia in human and subhuman primates. 1975. 22. liu y, lv h, jiang x, hu x, zhang m, li x. intraocular pressure changes during accommodation in progressing myopes, stable myopes and emmetropes. plos one 2015;10. 23. ha a, kim yk, kim j-s, jeoung jw, park kh. changes in intraocular pressure during reading or writing on journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 503 near vision tasks and iop; pakravan et al smartphones in patients with normal-tension glaucoma. br j ophthalmol 2019. 24. cheng ma, todorov a, tempelhoff r, mchugh t, crowder cm, lauryssen c. the effect of prone positioning on intraocular pressure in anesthetized patients. anesthesiology 2001;95:1351–1355. 25. ozcan ms, praetel c, bhatti mt, gravenstein n, mahla me, seubert cn. the effect of body inclination during prone positioning on intraocular pressure in awake volunteers: a comparison of two operating tables. anesth analg 2004;99:1152–1158. 26. najmanová e, pluháček f, haklová m. intraocular pressure response affected by changing of sitting and supine positions. acta ophthalmol 2020;98:e368–372. 27. mayal𝚤 h, tekin b, kay𝚤kç𝚤oğlu ör, kurt e, i̇lker ss. evaluation of the effect of body position on intraocular pressure measured with rebound tonometer. turk j ophthalmol 2019;49:6. 28. uzlu d, akyol n, türk a, gürsoy n, somuncu am, oruç y. effect of body position on intraocular pressure measured by rebound tonometer in healthy children. turk j ophthalmol 2020;50:271–274. 504 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 review article prevalence of color blindness in iranian students: a meta-analysis leila rezaei1, md; ehsan hawasi1, medical student; nader salari2, phd; masoud mohammadi3, ms 1department of ophthalmology, faculty of medicine, kermanshah university of medical sciences, kermanshah, iran 2department of biostatistics, school of health, kermanshah university of medical sciences, kermanshah, iran 3cellular and molecular research center, gerash university of medical sciences, iran orcid: leila rezaei: https://orcid.org/0000-0001-6285-2629 masoud mohammadi: https://orcid.org/0000-0002-5722-8300 abstract color blindness (color vision deficiency) is a disorder that impairs the true perception of colors. using the information in this study, appropriate policy can be made to identify high-risk groups, as well as educational policies for families to perform more effective genetic diagnosis methods. this study aims to examine the prevalence of color blindness in iranian students through a meta-analysis. articles related to color blindness published between january 1990 and december 2020 were searched in scopus, cochrane library, web of science (wos), science direct, embase, sid, magiran, irandoc, medline, and google scholar databases. the keywords used were based on medical subject topics (mesh terms) and, after careful review, articles were selected according to varied sections of participants, exposure, comparison, and outcomes (peco). participants: students; exposure: students with color blindness were examined; comparison: students from multiple provinces and regions of iran were surveyed for color blindness; outcomes: the pooled prevalence of color blindness in iranian students reported from different provinces. the prevalence of color blindness in iranian students was 3.8% (95% ci: 2.7–5.4%). the pooled prevalence of color blindness in iranian male and female students was 4.7% (95% ci: 3.5–6.4%) and 0.7% (95% ci: 0.3–1.3%), respectively. the pooled prevalence of red–green color blindness (tritan) was 41.7% (95% ci: 18.9–68.8%). the pooled prevalence of red color blindness (protan) was 13.9% (95% ci: 7.8–23.8%), and the pooled prevalence of green color blindness (deutan) based on meta-analysis was 45.3% (95% ci: 29–62.7%). due to the high prevalence of color blindness in students, especially male students, it is necessary to be screened for through genetic tests in couples before having children. keywords: color blindness; color vision deficiency; iran; meta-analysis; prevalence; students j ophthalmic vis res 2022; 17 (3): 413–423 © 2022 rezaei et al . this is an open access article distributed under the creative commons attribution license | published by knowledge e 413 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i3.11580&domain=pdf&date_stamp=2019-07-17 color blindness in iranian students; rezaei et al introduction visual impairment is one of the most common disorders affecting the students’ academic performance that can directly affect their academic future.[1] some studies have addressed the psychological and social issues resulting from visual impairment problems in students.[2, 3] light receptors in the human retina called photoreceptors transmit messages to the brain and enable a person to perceive various colors.[10–12] color perception is a response to the physical motion of a narrow handle of an electromagnetic spectrum with a wavelength of 400–700 nm, absorbed by the photoreceptors of visual pigments.[13, 14] this visible spectrum is only a part of the electromagnetic waves, which includes a wide range of waves with different wavelengths.[12–15] color blindness or impaired color vision is the inability to perceive the differences between some colors.[12–15] it occurs when light-sensitive cells either do not perceive color signals or do not transmit them to the brain.[14, 15] in other words, color blindness is a condition in which the ability to distinguish some colors is considered to be less than normal.[15] many patients are unaware of the existence of their color blindness, and only during their studies or employment, based on their needs and tests, they discover that they have the color this disorder.[13–15] the color blindness disorder is divided into congenital and acquired categories.[4] congenital color blindness is often red–green and genderdependent, with a prevalence of 8% in men and about 0.4% in women and between 4% and 6.5% in men of chinese and japanese ethnicities.[5] the results of this study reported that the male-tofemale prevalence ratio is markedly different.[5] correspondence to: masoud mohammadi ms. cellular and molecular research center, gerash university of medical sciences, imam hossein blvd, daneshjoo blvd, gerash 74417-58666, iran e-mail: masoud.mohammadi1989@yahoo.com received: 04-01-2022 accepted: 16-04-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i3.11580 monochrome or complete color blindness is a rare type in which none of the cone cells are able to receive color. as a result, the person does not see any color,[4, 5] but if one of the three cone cells is damaged, the person does not see one of the colors. in fact, in one of the colors, the color becomes blind and the nose becomes dichromatic.[5] trichromat is one of the most common models of color blindness in which all three types of cone cells are active, but their irritability has changed.[5] dichromates usually have one of the defects of deuteranomaly, protanomaly, or tritanomaly.[6–9] deuteranomaly: in this disorder, due to the proximity of the green and red spectra, the person does not see the green color correctly.[9] protanomaly: in this disorder, the cells do not process red color properly, because the wavelengths of red and green are close, and so these people see red as close to green.[6–9] tritanomaly: in this disorder, a person’s sensitivity to the color blue decreases.[6–9] studies conducted in iran on the prevalence of color blindness in students have reported different prevalence from various parts of the country. in a study conducted on students located in the city of sari, the pooled prevalence was 2.41%, which was reported as 2.4% in male students and 0.06% in female students.[16] however, a study on students from the city of qazvin reported a pooled prevalence of 6.5%, which was 5.1% in male students and 1.4% in female students.[17] in another study conducted on students from the city of ahvaz, the pooled prevalence was 3.7%, which was 5.4% in male students and 2.1% in female students.[18] our study aims to determine the prevalence of color blindness in students through a meta-analysis. methods according to the preferred reporting items for systematic reviews and meta-analyses (prisma) this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: rezaei l, hawasi e, salari n, mohammadi m. prevalence of color blindness in iranian students: a metaanalysis. j ophthalmic vis res 2022;17:413–423. 414 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 https://knepublishing.com/index.php/jovr color blindness in iranian students; rezaei et al criteria, systematic search of databases was performed based on organizing documents for review, selection of studies, extraction and analysis. search strategy a systematic search for articles was performed in three iranian databases, irandoc, magiran, and sid using iranian keywords, and in the international databases of pubmed, cochrane library, science direct, scopus, web of science (wos), and embase using english keywords. the google scholar search engine using english keywords was also examined. the keywords used were based on medical subject topics (mesh terms) and, after careful review, were selected according to the varied sections of peco. peco: participants: students; exposure: students with color blindness were examined; comparison: students from multiple provinces and regions of iran were surveyed for color blindness; outcomes: the pooled prevalence of color blindness in iranian students reported from various provinces. the search process: “color blindness”, “visual disturbances”, “students”, “visual impairment”, “color vision impairment”, “visual impairment”, and their persian equivalent words and possible combinations. (and) and (or) operators were used for more comprehensive access to all articles. the search was conducted between january 1990 and december 2020. (and) and (or) operators: (color blindness or color vision defects or tritan defect or retinal diseases or deutan defect or achromatopsia or protan defect), (visual disturbances or vision disability or visual impairment), (color vision or color perception). the word and between keywords (color blindness and color vision and students and iran) was used in the mesh browser. processes for checking the entry and exit of articles cross-sectional studies that reported the prevalence of color blindness in students were eligible for inclusion. other observational studies as well as interventional studies and clinical trials were excluded from the study. selection of finalized studies the research in the mentioned databases was done independently and blindly by two researchers (eh and lr) and then the obtained articles were entered into endnote software for secondary review as well as removal of duplicate and unrelated articles. the two researchers reviewed the articles considering the inclusion criteria; if they could not reach an agreement and decide on an article, a third researcher (mm) reviewed the article and provided the final opinion on the study. quality assessment the quality of the studies confirmed by the strobe checklist was assessed.[15] this checklist uses 32 items to examine different aspects of the articles and rates the studies in the range of 0–32. in this review, scores >23 to 32 were classified as high quality and grades between 22 and 14 as moderate quality. data extraction after the search was completed, all articles with keywords such as “prevalence”, “color blindness”, and “iranian student” in their titles were included in the initial list. then a checklist including the author’s name, title, year and month of the publication, place of study, age, sample size, and the pooled prevalence by sex was made. all stages of data extraction were performed by two reviewers independently. statistical review cma software (version 2) and begg and mazumdar tests and funnel plots were used to analyze the information extracted in the studies to investigate the publication bias. to evaluate and detect the degree of heterogeneity in the studies, the i2 heterogeneity test was used, and a metaregression test based on population size and study time was used to investigate the effect of the heterogeneity factors. results literature search based on the prisma flowchart, the process of reviewing, extracting, and finalizing articles for journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 415 color blindness in iranian students; rezaei et al entering into the meta-analysis was reported; consequently, 11 studies were entered into the meta-analysis. fifteen studies were excluded from the study due to lack of relevance, and three studies due to the low quality [figure 1; table 1]. investigation bias in studies the result of the i2 test was 97.3%, and a randomeffects model was used to meta-analyze the results of the studies. the results of publication bias were measured using the begg test and were not statistically significant (p = 0.212). the pooled prevalence of color blindness in 26,660 people in the age range of 7–18 years, the pooled prevalence of color blindness in iranian students was 3.8% (95% ci: 2.7–5.4%) [figure 2]. the prevalence in male students the total number of samples included in the study was 11,982 people. based on the meta-analysis, the pooled prevalence of color blindness in iranian male students was 4.7% (95% ci: 3.5–6.4%) with the i2 test (92.4%). the highest prevalence of color blindness was reported in the city of yasuj with 9.5% (95% ci: 8.3–11%) in 2000,[20] and the lowest prevalence of color blindness was reported in the city of sari with 2.4% (95% ci: 1.8–3.4%) in 2001[16] [figure 3]. the prevalence in female students the pooled prevalence of color blindness reported was 0.7% (95% ci: 0.3–1.7%) with i2 test (95.04%). the highest color blindness was reported in the city of yasuj with 6.2% (95% ci: 5–7.8%) in 2000,[20] and the lowest rate of color blindness was in the city of sari with 0.06% (95% ci: 0.05–0.07%) in 2001[16] [figure 4]. color blindness by its types the prevalence of red–green color blindness (tritan) in iranian students was 41.7% (95% ci: 18.9– 68.8%) with the i2 test (93.8%) [figure 5]. the prevalence of red color blindness (protan) in iranian students was 13.9% (95% ci: 7.8–23.8%) with the i2 test (88.01%) [figure 6]. the prevalence of green color blindness (dutan) in iranian students was 45.3% (95% ci: 29–62.7%) with the i2 test (95.01%) [figure 7]. according to figure 8, color blindness in students decreases with an increasing sample size (p < 0.05). furthermore, according to figure 9, overall color blindness in students increases with the length of the research year but is not statistically significant (p = 0.765). the begg test measured the results of the publication bias in the studies and the mazumdar rank correlation test, according to the large sample size entered in the studies. the publication bias was not statistically significant (p = 0.275) [figure 10]. discussion understanding the epidemiology of a disease can help in addressing it on a macro level.[27] although color blindness is not a very common or dangerous disease, such a complication in students can have psychological effects on their educational status and future careers. therefore, this disorder presents a significant challenge when addressing the effects of medical disorders on the educational success in students. based on our analysis, the prevalence of color blindness in iranian students was reported as 3.8%, and the color blindness in iranian male and female students was reported as 4.7% and 0.7%, respectively. studies show that color blindness affects 1 in every 12 men and 1 in every 200 women.[28] one in six people carries the color blindness gene, which is passed on to their son causing color blindness.[28] due to the genetic nature of this disease, it was revealed that the greater the number of consanguineous marriages in the population, the higher the prevalence of color blindness.[28] the results of the prevalence of the current study was higher than the color blindness reported as 2.1% in nepal,[29] 2.6% in nigeria,[30] and 1% in bangladesh.[31] in studies conducted in europe and spain, the prevalence was 4.02% in boys and 0.46% in girls.[6–9, 33, 34] in a study by khataminia et al, it was reported that approximately 6% of men of european descent have color vision problems, compared with 4.9% of men and 0.64% of women in asian countries.[18] 416 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 color blindness in iranian students; rezaei et al records identified through database searching (n = 161) duplicates removed (n = 132) records screened (n = 29) articles assessed for eligibility (n =14) studies included in quantitative synthesis (meta-analysis) (n = 11) records excluded (n =15) articles excluded, with reasons (n = 3) figure 1. flow chart of the review process and selection and separation of studies based on prisma. this ratio is 3.1% in men and 0.7% in women of african countries, native american or mexican descent.[18, 28] in a study reported in africa and ethiopia, the prevalence was 4.2% in boys and 0.2% in girls.[35] in a united states study, a prevalence of 2.6% was reported in boys.[36] a study in australia reported that 8% of men and 0.4% of women have color blindness.[17] in the present study and in reviewing the metaregression results, it was reported that with an increasing sample size, the prevalence of color blindness in iranian students decreases, and the prevalence of color blindness in iranian students increases with increasing research years. methods used for determining the disorder and tools needed to investigate the disorder are not the same among different studies. multiple tests have been utilized to perform research including the use of ao-hr. r and pseudoisochromatic tests have been common[16, 37] since most studies have used the ishihara booklet.[16] however, different studies have mentioned the number of people surveyed and different age groups in justifying the significant differences in various studies.[16] the pooled prevalence of red–green color blindness (tritan) in iranian students was 41.7%, the pooled prevalence of red color blindness (protan) was 13.9%, and the pooled prevalence of journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 417 color blindness in iranian students; rezaei et al table 1. specifications of studies entered into the meta-analysis of the prevalence of color blindness in iranian students quality assessment prevalence (female) sample size (female) prevalence (male) sample size (male) pooled prevalence sample size participants’ age area publication year author row moderate 0.06 1450 2.4 1650 2.41 3000 – sari 2001 farokhfar et al[16] 1 high 1.4 900 5.1 900 6.5 1800 9.3 ± 1.5 qazvin 2016 mehrpour et al[17] 2 moderate 2.1 1250 5.4 1250 3.7 2500 13–18 ahwaz 2006 khataminia et al[18] 3 high 0.4 1000 3.6 1000 2 2000 – oromieh 2011 sharifi et al[19] 4 moderate 6.2 1166 9.5 1760 8.2 2926 11-14 yasouj 2000 nabavizadeh et al[20] 5 moderate – – – – 5.2 500 – tehran 2006 rezae et al[21] 6 high 0.4 1992 5.1 2408 3 4400 – mashhad 2011 ostadi et al[22] 7 moderate 0.2 1414 3.3 1414 1.7 2828 – kermanshah 2000 omidian et al[23] 8 moderate 0.35 – 7 – 4.4 706 – hamadan 1996 ramezani et al[24] 9 moderate – – – – 8.7 3000 – zanjan 2006 hossaini et al[25] 10 moderate 0.33 1500 4.2 1500 2.3 3000 – isfahan 2001 azarian et al[26] 11 figure 2. the prevalence of color blindness in iranian students. green color blindness (deutan) based on the metaanalysis was 45.3%. this is based on the opinion of the american ophthalmological society reports’ red–green vision deficiency in 8% of men and 0.5% of women.[18] a study conducted in croatia reported that 8.4% of the participants were color blinded, of which 1.2% were protan and 4.2% were deutan.[17,18] the deutan in ethiopia was 3.4%,[35] in turkey 2.2%,[38] in saudi arabia 1.9,[39] and in a spanish study 2.1%.[40] although color blindness is almost ineffective in most job activities, due to its high prevalence, especially among students, it can affect their 418 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 color blindness in iranian students; rezaei et al figure 3. the prevalence of color blindness in iranian male students. figure 4. the prevalence of color blindness in iranian female students. academic performance and limit their academic achievement, thus increasing public awareness through the mass media. and social media is essential to enhance genetic testing in couples before their children are born. parents of children should also be informed about color vision disorders in their child’s eyes so that with early diagnosis, specific treatment measures can be performed. also, since there is no effective treatment for color blindness, the psychological damage of this disorder can be reduced by reassuring individuals and students that color blindness does not affect their future careers, as well as providing their own education in schools. based on the information obtained, it is recommended that periodic screening of students for early detection of color blindness along with parental training to identify children who have color blindness symptoms should be performed. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 419 color blindness in iranian students; rezaei et al figure 5. the prevalence of red–green color blindness (tritan) in iranian students. figure 6. the prevalence of red color blindness (protan) in iranian students. strengths and limitations the most important strength of this research is that it is the first iranian meta-analysis and provides accurate population-based information. an important limitation of the study is the limited number of studies conducted in iran. conclusion due to the high prevalence of color blindness in students, especially male students, it is necessary to take appropriate measures through appropriate screening for genetic tests in couples and parents who have color-blind children, screening parents with color blindness, as well as genetic counseling for parents who have a color-blind child and planning to conceive again. this study also reports that the prevalence of different types of color blindness in students is high and requires continuous follow-up and screening. ethics approval the study protocol was approved by the vice chancellor for research and 420 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 color blindness in iranian students; rezaei et al figure 7. the prevalence of green color blindness (dutan) in iranian students. figure 8. heterogeneity check diagram of the color blindness by sample size. technology of kermanshah university of medical sciences with the following code: ir.kums.rec.1400.009. financial support and sponsorship this study was funded by the vice-chancellor for research and technology of kermanshah university of medical sciences. this fund had no effect on the process of conducting the present study. conflicts of interest the authors declare that they have no conflict of interest. references 1. sapkota yd, adhikari bn, pokharel gp, poudyal bk, ellwein lb. the prevalence of visual impairment in school children of upper-middle socioeconomic status in kathmandu. ophthalmic epidemiol 2008;15:17–23. 2. dandona r, dandona l, srinivas m, giridhar p, mccarty ca, rao gn. population-based assessment of refractive error journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 421 color blindness in iranian students; rezaei et al figure 9. heterogeneity check diagram of the color blindness by the year of research. figure 10. (funnel plot) the results of the prevalence of color blindness in iranian students. in india: the andhra pradesh eye disease study. clin exp ophthalmol 2002;30:84–93. 3. hall je, guyton ac. textbook of medical physiology. 11𝑡ℎ ed. vol. 2. philadelphia, usa: saunders co.; 2004. p. 176– 178. 4. asbury t, riordan-eva p. vaughan & ashbury’s general ophthalmology. 17𝑡ℎ ed. new york, usa: mcgraw hill; 2008. p. 302–312. 5. birch j. worldwide prevalence of red-green color deficiency. j opt soc am a opt image sci vis 2012;29:313–320. 6. ong cw, tan mc, lam m, koh vt. applications of extended reality in ophthalmology: systematic review. j med internet res 2021;23:e24152. 7. watane a, kalavar m, chen em, mruthyunjaya p, cavuoto km, sridhar j, et al. medical malpractice lawsuits involving ophthalmology trainees. ophthalmology 2021;128:938– 942. 8. chia a, gazzard g, tong l, zhang x, sim el, fong a, et al. red–green colour blindness in singaporean children. clin exp ophthalmol 2008;36:464–467. 9. rosenberg ea, sperazza lc. the visually impaired patient. am fam physician 2008;77:1431–1436. 10. quillen d. on ophthalmology rankings. ophthalmology 2019;126:1346–1349. 11. fleming fall l. color blindness. michigan, usa: gale encyclopedia of medicine; 2002. p. 293–297. 12. drover jr, kean pg, courage ml, adams rj. prevalence of amblyopia and other vision disorders in young newfoundland and labrador children. can j ophthalmol 2008;43:89–94. 422 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 color blindness in iranian students; rezaei et al 13. chen pl, chen jt, tai mc, fu jj, chang cc, lu dw. anisometropic amblyopia treated with spectacle correction alone: possible factors predicting success and time to start patching. am j ophthalmol 2007;143:54–60. 14. matsuo t, matsuo c, matsuoka h, kio k. detection of strabismus and amblyopia in 1.5and 3-year-old children by a preschool vision-screening program in japan. acta med okayama 2007;61:9–16. 15. kazeminia m, abdi a, shohaimi s, jalali r, vaisi-raygani a, salari n, et al. dental caries in primary and permanent teeth in children’s worldwide, 1995 to 2019: a systematic review and meta-analysis. head face med 2020;16:22. 16. farokhfar a. prevalence of color blindness in the primary school students in sari township 1999. j mazandaran univ med sci 2001;11:57–62. 17. mehrpour s, khalaj m, zeiaeiha m, mohammadi zaesi e. study of the prevalence of congenital color blindness in students aged 7 to 11 in qazvin in 1988-89. j edrak 2016;11:4–12. 18. khataminia gh, dejagah h, kazemi m. determining the prevalence of congenital color blindness in high school students in ahvaz. sci j med 2006;5:489–493. 19. samadi aydanlo sn. prevalence of blindness among high school students in urmia. sci j med syst org islamic repub iran 2011;29:157–161. 20. nabavizade sh, nejabat m. prevalence of blindness among middle school students in yasuj. yasuj j med sci 2000;5:18–24. 21. rezaei shekveh a, najafi ah. prevalence of color vision deficiency in male students in tehran. j islamic azad univ 2006;16:207–210. 22. ostadi moghaddam h, azimi a, heravian j, yekta a, sharifi f, khabazkhoob m, et al. the prevalence of congenital color blindness and its effect on contrast sensitivity and depth perception. mashhad j paramed sci rehabil 2011;1:47–52. 23. omidian j. prevalence of congenital hereditary color blindness in primary school students in kermanshah during 1998–1999. bina 2000;4;325–330. 24. ramezani a. a study of prevalence of congenital color blindness, among school students in hamadan city in 1995–1996. avicenna j clin med 2000;7:50–56. 25. hossaini m, ghadamaee m, bagherzadeh mr. prevalence of color blindness in middle school male students in zanjan 2002. iran j ophthalmol 2006;19:55–62. 26. azarian ghr, nasrollahi k, zandi ar. prevalence of color blindness in students: a study in schools in isfahan – 1999. res med sci 2001;6:109–110. 27. hashemi h, fotouhi a, mohammad k. the tehran eye study: research design and eye examination protocol. bmc ophthalmol 2003;3:8. 28. rosenberg ea, sperazza lc. the visually impaired patient. am fam physician 2008;77:1431–1436. 29. shrestha rk, joshi mr, shakya s, ghising r. color vision defects in school going children. jnma j nepal med assoc 2010;50:264–266. 30. tabansi pn, anochie ic, nkanginieme ke, pedro-egbe cn. screening for congenital color vision deficiency in primary children in port harcourt city; teachers’ knowledge and performance. niger j med 2008;17:428–432. 31. yasmin a, janan n, akhter r. assessment of color blindness and erythrocyte g6pd enzyme status among the school children of dhaka city. j bangladesh soc physiol 2009;4:64–70. 32. gordon n. colour blindness. pub health 1998;112:81–84. 33. kherumian r, baudry c, lacorne j, moullec j. the frequency of dyschromatopsias in france. presse med 1956;64:303–304. 34. lampert ej, andorra m, torres-torres r, ortiz-pérez s, llufriu s, sepúlveda m, et al. color vision impairment in multiple sclerosis points to retinal ganglion cell damage. j neurol 2015;262:2491–2497. 35. zein za. gene frequency and type of colour blindness in ethiopians. ethiop med j 1990;28:73–75. 36. choi tb, lee da, oelrich fo, amponash d, bateman jb, christensen re. a retrospective study of eye disease among first grade children in los angeles. j am optom assoc 1995;66:484–488. 37. kim hb, lee sy, choe jk, lee jh, ahn bh. the incidence of congenital color deficiency among koreans. j korean med sci 1989;4:117–120. 38. citirik m, acaroglu g, batman c, zilelioglu o. congenital color blindness in young turkish men. ophthalmic epidemiol 2005;12:133–137. 39. osuobeni ep. prevalence of congenital red-green color vision defects in arab boys from riyadh, saudi arabia. ophthalmic epidemiol 1996;3:167–170. 40. cabrero fj, ortiz ma, mesa ms, fuster v, moral p. redgreen colour blindness in the tormes-alberche valley (avila-central spain). anthropol anz 1997;55:295–301. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 423 original article a survey on orbital space-occupying lesions during a twelve-year period from a referral center in iran abbas bagheri1,2, md; parisa ashtar-nakhaie2, md; maryam aletaha1,2, md; bahareh kheiri2, ms; amirreza veisi2, md 1ocular tissue engineering research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran orcid: abbas bagheri: https://orcid.org/0000-0002-6736-7435 amirreza veisi: https://orcid.org/0000-0001-8304-3804 abstract purpose: in this study, we describe different orbital space-occupying lesions (sols) from a referral center in iran. methods: in this retrospective case series, all records of “orbital tumors” with a definite histopathologic diagnosis at a referral center in iran were reviewed from april 2008 to may 2020. results: a total of 375 orbital sols were included. the study population consisted of 212 (56.5%) female and 163 (43.5%) male subjects with overall mean age of 31.09 ± 21.80 years. the most common clinical presentation was proptosis and the superotemporal quadrant was the most frequent site of involvement. extraconal lesions (276 cases, 73.6%) outnumbered intraconal lesions (99 cases 26.4%). the great majority of sols (344, 91.7%) were primary, while 24 (6.4%) were secondary and 7 (1.9%) were metastatic. benign lesions (309, 82.4%) were much more common than malignant sols (66, 17.6%). overall, dermoid cysts and malignant lymphoma were the most prevalent benign and malignant orbital sols, respectively. the malignant to benign lesion ratio was 0.46 in children (≤18 years), 0.81 in middle-aged subjects (19–59 years), and 5.9 in older (≥60 years) cases. the most common type of malignancy was rhabdomyosarcoma in children, lymphoma in middle-aged subjects, and invasive basal cell carcinoma in older age group. conclusion: over the 12-year study period, benign, primary, extraconal orbital sols were more frequent than malignant, secondary, and intraconal lesions. the ratio of malignant lesions increased with age in this cohort of patients. keywords: benign tumor; extraconal tumor; intraconal tumor; malignant tumor; orbital tumor j ophthalmic vis res 2023; 18 (2): 202–211 correspondence to: amirreza veisi, md. labbafinejad medical center, shahid beheshti university of medical sciences, boostan 9 st., pasdaran ave., tehran 16666, iran. email: amirveisi3@gmail.com received: 21-05-2022 accepted: 04-01-2023 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i2.13187 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: bagheri a, ashtar-nakhaie p, aletaha m, kheiri b, veisi a. a survey on orbital space-occupying lesions during a twelve-year period from a referral center in iran . j ophthalmic vis res 2023;18:202–211. 202 © 2023 bagheri et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i2.13187&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr orbital tumors in iran ; bagheri et al introduction the orbit is a compact area which is comprised of different tissues including bone, fat, vascular, neural, and muscular components, each of which may be afflicted with various benign and malignant space-occupying lesions (sols). sols may originate from vestigial tissues or may be the result of invasion from periorbital spaces such as paranasal sinuses, nasal cavity, intracranial space, or even metastasis from distant areas.[1] orbital sols have different presentations ranging from trivial cosmetic issues to loss of sight or even life-threatening conditions.[2] the frequency of various orbital sols varies according to geographic area, ethnicity, age, and sex. this frequency also depends on the department where the study originates from; results from an oculoplastic department may differ from those of a neurosurgery or otolaryngology department.[2–6] diagnostic criteria are also critical and influence the results of studies; reports based on pathologically confirmed specimens are entirely different from studies that are limited to clinical or radiological diagnoses.[2–7] herein we provide data based on histopathologically confirmed orbital sols over a 12-year period from an oculoplastic referral hospital in iran. methods this retrospective study was based on data from records of patients registered with a general diagnostic code of “orbital tumor” from april 2008 to may 2020 at the oculoplastic service of the ophthalmology department at labbafinejad medical center. the study was approved by the ethics committees of the ophthalmic research center affiliated with shahid beheshti university of medical sciences; the approval number was ir.sbmu.orc.rec.1399.008. the study adhered to the declaration of helsinki and informed written consent was obtained from all patients or their guardians prior to surgery. in all included subjects, orbital sols had undergone either incisional or excisional biopsy, and a confirmed histopathologic diagnosis had been established. all cases with unconfirmed pathology were excluded from the study even if a clinical or radiological diagnosis was available. demographic data, including age, sex, and laterality of involvement, were determined. topographic involvement of the orbit was also documented according to results of imaging studies including ct scan and/or mri. as much as the results of the general physical examinations were documented in the files, these data were also recorded. based on definite histopathologic diagnosis, orbital sols were classified into seven principal groups including cystic lesions, vascular lesions, neurogenic lesions, inflammatory and lymphoproliferative lesions, mesenchymal lesions, epithelial lacrimal gland lesions, and secondary or metastatic lesions. notably, inflammatory lesions were included only if they had produced a mass lesion. lymphoproliferative and inflammatory lesions of the lacrimal gland were tabulated twice: first in the subgroup of inflammatory and lymphoproliferative lesions and a second time under lacrimal gland lesions; however, they were counted only once. we also classified each major group into subgroups, differentiated benign lesions from malignant lesions, and determined the relative frequencies of such lesions according to age. we used frequency (percentage), mean values, median, and range to describe the data. statistical analyses were performed using the spss software (version 25.0 released 2017, ibm spss statistics for windows, ibm corp. armonk, ny, usa). results the study population consisted of 375 patients, including 212 (56.5%) female and 163 (43.5%) male subjects with a mean age of 31.09 ± 21.80 (range: 1–94) years. the mean age was 29.0 ± 20.85 (range: 1–87) years in female patients and 33.9 ± 22.7 (range: 1–94) years in male subjects. we encountered no bilateral involvement in this study, and the right and left sides were almost equally involved. overall, out of the 375 sols, 309 lesions (82.4%) were benign and 66 (17.6%) were malignant; 276 lesions (73.6%) were extraconal while 99 (26.4%) were intraconal; 344 (91.7%) were primary lesions, 24 (6.4%) were secondary, and 7 (1.9%) were metastatic lesions [table 1]. the number and percentage of patients in major groups with mean age at presentation and gender ratios are summarized in table 2; corresponding journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 203 orbital tumors in iran ; bagheri et al table 1. demographic characteristics of patients and space-occupying lesions. specificity categories patients number (%) sex female 212 (56.5) male 163 (43.5) laterality left 190 (50.7) right 185 (49.3) position extraconal 276 (73.6) intraconal 99 (26.4) origination primary 344 (91.7) secondary 24(6.4) metastatic 7(1.9) pathology benign 309 (82.4) malignant 66 (17.6) age range (yr) children (≤18) 123 (32.8) middle aged (19–59) 209 (55.7) old aged (≥60) 43 (11.5) table 2. major subclassifications of orbital space-occupying lesions in order of their frequencies, together with their age and sex distribution. major pathologies number (%) mean age ± sd female/male cystic 138 (36.8) 15.89 ± 14.24 82/56 vascular 88 (23.5) 35.18 ± 16.79 53/35 inflammatory and lymphoproliferative 40 (10.7) 45.00 ± 19.38 22/18 secondary and metastatic 31 (8.2) 60.19 ± 18.79 16/15 neurogenic 29 (7.7) 36.65 ± 14.77 20/9 mesenchymal 28 (7.5) 26.29 ± 22.71 13/15 epithelial lesions of lacrimal gland 21 (5.6) 43.14 ± 20.25 6/15 total 375 (100) 31.09 ± 21.80 212/163 sd, standard deviation data for subgroups are presented in tables 3–9. the most prevalent orbital sols, irrespective of benign or malignant nature, are presented in table 10, and the most prevalent benign and malignant lesions stratified by age are shown in table 11. the most common category of lesions in this study was cystic lesions and the most common benign lesion was dermoid cyst. the leading malignant lesion was lymphoma, the most common secondary lesion was invasive eyelid basal cell carcinoma (bcc), and the most frequent metastatic lesion originated from breast carcinomas. we categorized predominant benign and malignant lesions of the orbit according to age at presentation in table 11. benign lesions were more prevalent in lower age groups and the frequency of malignant lesions increased with age. the ratio of malignant to benign lesions was 0.46 in children (≤18 years), 0.81 in middle-aged patients (19–59 years), and 5.9 in older individuals (≥60 years). the site of involvement is presented in table 12 and demonstrates that the most common site of involvement was the superotemporal quadrant of the orbit. the leading presenting symptoms and 204 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 orbital tumors in iran ; bagheri et al table 3. cystic orbital space-occupying lesions. cystic lesions number of patients (%) percentage of total dermoid cyst 113 (82.0) 30.1 ductul lacrimal gland cyst 7 (5.1) 1.8 epidermoid cyst 4 (2.9) 1.1 epithelial cyst (inclusion cyst) 4 (2.9) 1.1 mucocele 4 (2.9) 1.1 cystic teratoma 2 (1.4) <1 hydatid cyst 2 (1.4) <1 hematic cyst 1 (0.7) <1 fibroadipose vascular anomaly cyst 1 (0.7) <1 total 138 (100) 36.8 table 4. vascular orbital space-occupying lesions. vascular lesions number of patients (%) percentage of total cavernous hemangioma 66 (75.0) 17.6 lymphangioma 13(14.9) 3.4 hemangiopericytoma 4 (4.5) 1.1 capillary hemangioma 2 (2.3) <1 angiosarcoma 1 (1.1) <1 angioleiomyoma 1 (1.1) <1 arteriovenous malformation 1 (1.1) <1 total 88 (100) 23.5 signs are presented in table 13. proptosis was the most prevalent symptom in 42.4% of patients, while pain was only present in 3.2% of subjects in the current series. discussion this study evaluated all histopathologically confirmed orbital sols over a 12-year period from an oculoplastic referral center in iran. generally, there are two types of studies on the epidemiology of orbital sols in the medical literature. the first group categorizes the lesions according to the clinical and radiological findings; although such studies may be partly representative, the real findings are not definite. the second group of studies is based on a definite histopathologic diagnosis that suffers from omission of specific lesions which do not regularly undergo biopsy for a diagnosis, such as capillary hemangioma, optic nerve glioma, and meningioma. these second type of reports may also be representative of subjects who require surgical intervention because of functional or cosmetic issues.[6, 8] our study showed that the primary lesions were 11.1 times more common than secondary and metastatic lesions. these observations are in line with other large series.[2, 3, 6, 8–10] in our series, benign orbital lesions outnumbered malignant lesions by 4.7 times which is comparable to the report by kodsi et al,[11] however, in some of the other studies this predominance of benign lesions was less significant,[2, 6, 8, 12] which may be due to the younger age of our study population. dermoid cysts were the most common lesions comprising one-third of all lesions in our study, journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 205 orbital tumors in iran ; bagheri et al table 5. inflammatory and lymphoproliferative orbital space-occupying lesions. inflammatory & lymphoproliferative lesions number of patients (%) percentage of total pseudotumor 17 (42.5) 4.5 lymphoma 16 (40.0) 4.3 lymphoid hyperplasia of lacrimal gland 7 (17.5) 1.9 total 40 (100) 10.7 table 6. mesenchymal orbital space-occupying lesions. mesenchymal lesions number of patients (%) percentage of total rhabdomyosarcoma 8 (28.6) 2.1 dermolipoma 7 (25.0) 1.9 xanthogranuloma 5 (17.9) 1.3 fibroma 2 (7.1) <1 liposarcoma 2 (7.1) <1 osteoma 2 (7.1) <1 giant cell tumor of bone 1 (3.6) <1 chondrosarcoma 1 (3.6) <1 total 28 (100) 7.5 which is similar to other large series;[2, 3] however, in the study by ohtsuka et al, dermoid cysts were the fifth most common tumor.[9] cavernous hemangioma was the second most common tumor in our series, making up 17.6% of all lesions, which is comparable to some other comprehensive series.[2, 3, 6, 9, 13] lymphoma was the most common malignant tumor in our series, comprising 4.3% of all tumors, which is similar to findings by various alternate studies.[7, 14–16] it is notable that the incidence of lymphoma in some developed countries outweighs our rates by two to six times.[4, 5, 9, 17, 18] as an example, in two reports by shields et al;[3, 6] it was demonstrated that the rate of orbital lymphoma increased from 4% to 8% in the united states after 20 years which may reflect improvements in life expectancy, patient care, and diagnostic capabilities. moslehi et al[19] and sjo et al[20] have documented an increase in the incidence of non-hodgkin lymphoma in orbit and adnexa with increasing age. our study population was skewed toward younger subjects, and patients older than 60 years comprised only 11.5% of cases which may explain this relatively low rate. the most common secondary orbital sol in our report was invasive eyelid bcc which is compatible with the findings by bonavolonta et al.[2] kennedy reported orbital invasion by eyelid skin tumors as the second common cause of secondary orbital tumors following invasive tumors from paranasal sinuses.[8] shields et al, in a report in 1984,[3] noted orbital invasion by eyelid bcc and invasive choroidal melanoma as the most common secondary orbital tumors with an incidence of 3%. in another report by the same group of authors in 2004,[6] invasive bcc ranked fourth with an incidence of only 1% being outnumbered by invasive uveal melanoma and invasive paranasal sinus tumors. improved care and patient surveillance have probably decreased orbital invasion by eyelid skin malignancies, while more efficacious management for malignant uveal melanoma preserves the eye obviating the need for enucleation and possibly increasing the rate of orbital uveal melanoma. the incidence of orbital invasion by uveal melanoma in our series was only 0.5%. some older reports from developing areas have revealed that orbital invasion by retinoblastoma accounts for more than half of 206 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 orbital tumors in iran ; bagheri et al table 7. neurogenic orbital space-occupying lesions. neurogenic lesions number of patients (%) percentage of total meningioma 11 (37.9) 2.9 schwannoma 9 (31.0) 2.4 neurofibroma 8 (27.7) 2.1 glioma 1 (3.4) <1 total 29 (100) 7.7 table 8. secondary and metastatic orbital space-occupying lesions. secondary and metastatic number of patients (%) percentage of total bcc from eyelids 11 (35.5) 2.9 scc from eyelids 5 (16.1) 1.3 breast carcinoma 3 (9.7) <1 choroidal melanoma 2 (6.5) <1 sebaceous cell carcinoma 2 (6.5) <1 ewing sarcoma 2 (6.5) <1 scc from conjunctiva 1 (3.2) <1 leukemia 1 (3.2) <1 fibrosarcoma from paranasal sinuses 1 (3.2) <1 multiple myeloma 1 (3.2) <1 melanoma from skin 1 (3.2) <1 melanoma from conjunctiva 1 (3.2) <1 total 31 (100) 8.2 bcc, basal cell carcinoma; scc, squamous cell carcinoma all orbital sols in children.[21, 22] in the current series, although 32.8% of all subjects were <18 years of age, we observed no case of orbital invasion by retinoblastoma which may reflect timely diagnosis and treatment of retinoblastoma cases in our population. metastatic lesions comprised 1.9% of all orbital sols in our study, which is compatible with other studies.[6, 8] in the two studies by shields et al,[3, 6] the frequency of orbital metastasis increased from 2.5% to 4% over a 20-year period. similar to our research, some large series on orbital sols have revealed breast carcinoma as the most common source of orbital metastasis.[2–4, 6, 23, 24] the two other primary malignancies which may be among the common causes for orbital metastasis are lung and prostate cancers; however, they were not detected in our series.[2–6] it is notable that in various studies from japan, orbital metastasis from lung carcinoma outnumbered alternative sites of origin.[9, 25] we observed that the prevalent benign lesion in subjects under 18 years of age was dermoid cyst which accounted for 73 out of 123 cases (59.3%) in this age group, followed by lymphangioma, which involved 10 out of 123 patients (8.1%). this is compatible with multiple prior studies on orbital tumors in children; however, capillary hemangioma was shown to outnumber lymphangioma in these studies as the evaluation was based on clinical data instead of histopathology.[26–28] orbital malignancies are usually rare in the pediatric age group overall;[26, 27] the most common malignant lesion in this age group was rhabdomyosarcoma which accounted for 8 out of 123 cases (6.5%) and was comparable to previous studies.[2, 26, 28, 29] the ratio of extraconal to intraconal lesions in our study was 2.8, which is consistent with other journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 207 orbital tumors in iran ; bagheri et al table 9. lacrimal gland space-occupying lesions. lacrimal gland lesions number of patients (%) percentage of total epithelial lesions 21 (55.3) 5.6 pleomorphic adenoma 11 (28.9) 2.9 adenoid cystic carcinoma 8 (21.1) 2.1 malignant mixed tumor (pleomorphic adenocarcinoma) 2 (5.3) <1 lymphoproliferative lesions 10 (26.3) 2.6 benign lymphoid hyperplasia 7 (18.4) 1.9 lymphoma 3 (7.9) <1 ductal lacrimal gland cyst 7 (18.4) 1.9 total 38 (100) 10.1 table 10. the most prevalent orbital space-occupying lesions. orbital lesion number percentage of total dermoid cyst 113 30.1 cavernous hemangioma 66 17.6 pseudotumor 17 4.5 lymphoma 16 4.3 lymphangioma 13 3.4 pleomorphic adenoma 11 2.9 bcc from eyelid 11 2.9 schwannoma 9 2.4 rhabdomyosarcoma 8 2.1 total 264 70.2 comparable studies reporting ratios ranging from 2 to 7.[4, 9, 17] the most common topographic area of involvement in our series was the superotemporal quadrant of the orbit comprising about one-third of all cases. this finding is similar to an extensive study by bonavolonta et al[2] on 2480 patients with orbital tumors. in another study on a population older than 60 years, demirci et al[5] reported that the area of orbital involvement in 53% of cases was the superior orbit which is consistent with our study despite our younger population of subjects with a mean age of 30 years. our series included 38 cases of lacrimal gland lesions comprising 10.1% of all orbital tumors, which is line with previous reports.[2, 31] epithelial lesions were about twice more common than lymphoproliferative lesions, although these entities are often reported equally.[1] pleomorphic adenoma and adenoid cystic carcinoma were the most common benign and malignant epithelial tumors of the lacrimal gland which is consistent with previous studies on lacrimal gland tumors.[2, 8, 32] benign reactive lymphoid hyperplasia and lacrimal gland ductal cyst were the two most common non-epithelial lesions of the lacrimal gland in our study, which differs from many large studies reporting chronic dacryoadenitis as the leading pathology in this category.[3, 6, 8, 33] we observed two cases of malignant mixed tumors, both of which were primary tumors and not the recurrence of pleomorphic adenoma. in most studies, this tumor is reported to be less prevalent than adenoid cystic carcinoma.[2–4, 6] in a review article,[31] the rate of adenoid cystic carcinoma was 3.5 times that of pleomorphic adenocarcinoma. 208 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 orbital tumors in iran ; bagheri et al table 11. stratification of the most prevalent benign and malignant orbital space-occupying lesions according to age. orbital lesions ≤18 years 19–59 years ≥60 years benign (numbers) dermoid cyst (113) 73 39 1 cavernous hemangioma (66) 4 56 6 pseudotumor (17) 3 13 1 pleomorphic adenoma (11) 1 6 4 lymphangioma (13) 10 3 0 schwannoma (9) 2 7 0 others (80) 19 54 7 309 (82.4% of total) 112 (36.2% of benign) 178 (57.6% of benign) 19 (6.2% of benign) malignant (numbers) lymphoma (16) 0 10 6 bcc from eyelids (11) 0 1 10 rhabdomyosarcoma (8) 8 0 0 adenoid cystic carcinoma (8) 0 7 1 scc from eyelids (5) 0 2 3 breast carcinoma (3) 0 2 1 others (15) 3 9 3 66 (17.6% of total) 11 (16.7% of malignant) 31 (46.9% of malignant) 24 (36.4% of malignant) table 12. location of orbital space-occupying lesions. orbital location number of patients percentage of total superotemporal 123 32.8 intraconal 99 26.4 nasal 50 13.3 diffuse 48 12.8 superonasal 14 3.7 inferior 13 3.5 superior 13 3.5 temporal 6 1.6 inferonasal 6 1.6 inferotemporal 3 0.8 total 375 100 the most common clinical presentations in our series were proptosis and lump sensation in 42.4% and 31.7% of patients, respectively. this is consistent with a study that recorded clinical findings,[34] although in another study focusing on metastatic lesions, ocular motility problems was a more common symptom than mass effect.[24] some studies have reported bilaterality in 2–8% of their cases,[5, 17, 25] however we did not encounter any bilateral cases which may be due to the paucity of metastatic lesions in our series. this study suffers from referral bias and other drawbacks inherent to all retrospective studies. since only biopsy-proven cases were selected, a small number of familiar entities such as capillary journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 209 orbital tumors in iran ; bagheri et al table 13. signs and symptoms of patients. symptom or sign number of patients percentage of total proptosis 159 42.4 lump 119 31.7 ocular displacement 61 16.2 ptosis 34 9.1 lid shape deformity 25 6.7 conjunctival injection 13 3.5 pain 12 3.2 lid retraction 6 1.6 conjunctival chemosis 6 1.6 conjunctival mass 5 1.3 diplopia 5 1.3 hemangioma, optic nerve glioma, and meningioma were recorded. in summary, at our referral center, 91.7% of orbital sols were primary lesions, the most common orbital sols were cystic lesions, benign lesions were 4.7 times more common than malignant ones, and extraconal lesions were 2.8 times more common than intraconal lesions. acknowledgments the authors would like to thank dr. hossein salour who introduced and cared for some of the study patients. financial support and sponsorship none. conflicts of interest the authors have no financial interest in the subject of this article. references 1. dutton jj, sines dt, elner vm. orbital tumors. in: black eh, nesi fa, calvano cj, gladstone gj, levine mr, eds. smith and nesi’s ophthalmic plastic and reconstructive surgery. vol. 2. 3rd ed. new york, usa: springer; 2012:811–910. 2. bonavolonta g, strianese d, grassi p, comune c, tranfa f, uccello g, et al. an analysis of 2480 space-occupying lesions of the orbit from 1976 to 2011. ophthalmic plast reconstr surg 2013;29:79–86. 3. shields ja, bakewell s, augsburger j, flanagan jc. classification and incidence of space occupying lesions of the orbit. a survey of 645 biopsies. arch ophthalmol 1984;102:1606–1611. 4. shinder r, al-zubidi n, esmaeli b. survey of orbital tumors at a comprehensive cancer center in the united states. head neck 2011;33:610–614. 5. demirci h, shields cl, shields ja, honavar sg, mercado gj, tovilla jc. orbital tumors in the older adult population. ophthalmology 2002;109:243–248. 6. shields ja, shields cl, scartozzi r. survey of 1264 patients with orbital tumors and simulating lesions: the 2002 montgomery lecture, part 1. ophthalmology 2004;111:997–1008. 7. koopman jh, van dijk mr, bijlsma wr. incidence of primary malignant orbital tumors in the netherlands. eye 2011;25:461–465. 8. kennedy re. an evaluation of 820 orbital cases. trans am ophthalmol soc 1984;82:134–157. 9. ohtsuka k, hashimoto m, suzuki y. a review of 244 orbital tumors in japanese patients during a 21-year period: origins and locations. jpn j ophthalmol 2005;49:49–55. 10. lipowski p, raczynska k, murawska j, iwaszkiewiczbilikiewicz b. orbital tumors in the material of department of ophthalmology of medical university of gdansk in years 1991–2004. kin oczna 2004;106:460–462. 11. kodsi sr, shetlar dj, campbell rj, garrity ja, bartley gb. a review of 340 orbital tumors in children during a 60-year period. am j ophthalmol 1994;117:177–182. 12. seregard s, sahlin s. panorama of orbital space occupying lesions. the 24-year experience of a referral center. acta ophthalmol scand 1999;77:91–98. 13. bagheri a, jafari r, salour h, aletaha m, yazdani s, baghi s. a new surgical technique for excision of orbital cavernous hemangioma: a 15-year experience. orbit 2018;37:429–437. 14. hassan wm, bakry ms, hassan hm. incidence of orbital, conjunctival and lacrimal gland malignant tumors in usa from surveillance, epidemiology and end results. 1973– 2009. int j ophthalmol 2016;9:1808–1813. 210 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 orbital tumors in iran ; bagheri et al 15. shikishima k, kawai k, kitahara k. pathological evaluation of orbital tumors in japan: analysis of a large case series and 1379 cases reported in the japanese literature. clin exp ophthalmol 2006;34:239–244. 16. margo ce, mulla zd. malignant tumors of the orbit. analysis of the florida cancer registry. ophthalmology 1998;105:185–190. 17. ting dsj, perezlopez m, chew nj, clarke l, dickinson aj, neoh c. a 10 year review of orbital biopsy: the newcastle eye center study. eye 2015;29:1102–1106. 18. johanson s, heegaard s, bogeskov l, prause ju. orbital space-occupying lesions in denmark 1974–1997. acta ophthalmol scand 2000;78:547–552. 19. moslehi r, devesa ss, schairer c, fraumeni jr jf. rapidly increasing incidence of ocular non-hodgkin lymphoma. j natl cancer inst 2006;98:936–939. 20. sjo ld, ralfkiaer e, prause ju, madsen j, pedersen nt, heegaard s. increasing incidence of ophthalmic lymphoma in denmark from 1980 to 2005. invest ophthalmol vis sci 2008;49:3283–3288. 21. munirulhaq m. orbital tumors in children. orbit 1989;8:215–222. 22. abiose a, adido j, agarwal sc. childhood malignancies of the eye and orbit in northern nigeria. cancer 1985;55:2889–2893. 23. günalp i, gündüz k. metastatic orbital tumors. jpn j ophthalmol 1995;39:65–70. 24. shields ja, shields cl, brotman hk, carvalho c, perez n, eagle jr rc. cancer metastatic to the orbit. ophthalmic plast reconstr surg 2001;17:346–354. 25. amemiya t, hayashida h, dake y. metastatic orbital tumors in japan: a review of the literature. ophthalmic epidemiol 2002;9:35–47. 26. shields ja, bakewell r, augsburger jj, donoso la, bernardino v. space-occupying orbital masses in children, a review of 250 consecutive biopsies. ophthalmology 1986;93:379–384. 27. bullock jd, goldberg sh, rakes sm. orbital tumors in children. ophthalmic plast reconstr surg 1989;5:13–19. 28. gunalp i, gunduz k. pediatric orbital tumors in turkey. ophthalmic plast reconstr surg 1995;11:193–199. 29. bajaj ms, pushker n, chaturvedi a, betharia sm, kashyap s, balasubramanya r, et al. orbital spaceoccupying lesions in indian children. j pediatr ophthalmol strabismus 2007;44:106–111. 30. johonson te, senft sh, nasr am, bergqvist g, cavender jc. pediatric orbital tumors in saudi arabia. orbit 1990;9:205–215. 31. shields ja, shields cl, epstein ja, scartozzi r, eagle jr rc. review: primary epithelial malignancies of the lacrimal gland: the 2003 ramon l. font lecture. ophthalmic plast reconstr surg 2004;20:10–21. 32. weis e, rootman j, joly tj, berean kw, al-katan hm, pasternak s, et al. epithelial lacrimal gland tumors. pathologic classification and current understanding. arch ophthalmol 2009;127:1016–1028. 33. teo l, seah ll, choo ct, chee sp, chee e, looi a. a survey of the histopathology of lacrimal gland lesions in a tertiary referral center. orbit 2013;32:1–7. 34. ben simon gj, yoon mk, jane a, nakra t, mccann jd, goldberg ra. clinical manifestations of orbital mass lesions at the jules stein eye institute, 1999–2003. ophthalmic surg laser imaging 2006;37:25–32. journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 211 original article vision-related quality of life after bilateral implantation of monofocal and multifocal intraocular lenses shahram bamdad1, md; seyyed ahmad razavizadegan1, md; mohsen farvardin1, md; sahar mohaghegh2, ms 1poostchi ophthalmology research center, department of ophthalmology, school of medicine, shiraz university of medical sciences, shiraz, iran 2department of optometry, school of rehabilitation, shahid beheshti university of medical sciences, tehran, iran orcid: shahram bamdad: https://orcid.org/0000-0002-5609-016x sahar mohaghegh: https://orcid.org/0000-0002-5953-3085 abstract purpose: to evaluate vision-related quality of life in two sets of patients after routine cataract surgery implanting with traditional versus multifocal intraocular lens (iols). methods: in a cross-sectional prospective study, 58 and 33 candidates for cataract surgery were divided into traditional (acrysof sn60wf, alcon laboratories, inc) and multifocal iol (acrysof iq panoptix iol tfnt00, alcon laboratories, inc.) groups, respectively. the primary outcome was vfq-25 scores. the secondary outcomes were making comparisons between the two iol types in the near vision and the driving items. results: the mean patients’ age in traditional and multifocal iol groups was 60.85 ± 7.40 (55% female) and 59.85 ± 8.95 (36% female) years, respectively. the mean vfq-25 total scores in traditional and multifocal iol groups before and after surgery were 63.69 ± 4.95 and 72.15 ± 9.66, and 98.08 ± 0.70 and 95.70 ± 1.30, respectively (p = 0.001 & 0.001). the mean scores of night driving in traditional and multifocal iol groups were 38.79 ± 20.50 and 44.35 ± 21.12 (p = 0.1) before surgery which improved to 97.41 ± 7.68 and 56.45 ± 11.12 after surgery, respectively (p = 0.001). the mean scores of near vision in traditional and multifocal iol groups were 46.83 ± 10.56 and 50.53 ± 8.58 (p = 0.2) before surgery which improved to 89.94 ± 4.87 and 100.00 ± 0.00 after surgery, respectively (p = 0.001). conclusion: vision-related quality of life after cataract surgery with either type of traditional or multifocal (panoptix) iols improved to an excellent level. traditional iols provided more satisfaction in nighttime driving while multifocal iols provided increased satisfaction in near and intermediate vision. keywords: cataract surgery; multifocal iol; quality of life; presbyopia; vision-related quality of life j ophthalmic vis res 2022; 17 (1): 19–26 © 2022 bamdad et al . this is an open access article distributed under the creative commons attribution license | published by knowledge e 19 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10166&domain=pdf&date_stamp=2019-07-17 monofocal vs multifocal iols; bamdad et al introduction cataract is amongst the most prevalent causes of visual impairment in the world.[1] the prevalence of senile cataract increases with age during the years of presbyopia.[2] cataract surgery with an intraocular lens (iol) implantation is one of the most common and thought to be one of the most effective surgical procedures in any field of medicine.[1, 2] monofocal lens as the first generation and most common type of intraocular lenses brings far distance into clear focus.[2] however, the ideas of accommodative[3] and multifocal intraocular lenses[4] developed due to increasing demand for activities that require near sight adjustment in the modern life style. although the progress in the area of accommodative intraocular lenses did not advance as quickly as its counterparts,[3] the multifocal intraocular lenses progressed to a clinically satisfactory level and spectacle independency.[4–11] the trifocal intraocular lenses are the most recent type of multifocal intraocular lenses that provide clear vision not only for far and near distances but also for intermediate distances that facilitate vision for electronic devices and automobile dashboards.[10] trifocal intraocular lenses that are mostly pupil independent, designed to encompass the refractive–diffractive functionality in addition to extended depth of focus optics[8] which are mostly pupil independent, provide highly successful clinical outcomes,[5–11] increased visual satisfaction,[10–12] and improved quality of life as a result of enhanced vision.[11–15] the trifocal intraocular lens of panoptix (acrysof iq panoptix intraocular lens tfnt00, alcon laboratories, inc.) is a noble diffractive nonapodized pupil independent aspheric intraocular lens that provides clear vision in 40 cm, 60 cm, 120 cm, 4 m, and optical infinity distances.[10] some of the previous studies showed that panoptix correspondence to: sahar mohaghegh, ms. rehabilitation faculty, shahid beheshti university of medical sciences, damavand street, imam hossein square, tehran, iran. e-mail: saharmohaghegh79@gmail.com received 28-01-2019; accepted 14-09-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10166 provides increased satisfaction for near and intermediate vision patients as compared to other competing tri-focal intraocular lens brands.[8, 10, 11] photic phenomena which is defined as light scattering, halos and glare, presents itself when positioned in poor lighting environments. they are known to be the source of minor visual dissatisfaction that may occur after trifocal intraocular lens implantation.[14–16] photic phenomena occurs as a result of multiple diffraction of the light beam due to the optics of the intraocular lenses. while present in an environment of glare lighting, the optical bench evaluation revealed a decrease in the image quality of the multifocal when compared to the monofocal intraocular lens.[16] hence, it is of critical importance to evaluate the extent of the effect of these photic phenomena on the patient’s vision in order to present a more complete judgement about the patient’s state of vision after multifocal intraocular lens implantation. since patient-reported outcomes are of paramount importance when evaluating the success of treatments,[17] the first aim of the current study was to evaluate changes in vision as it related to the quality of life after bilateral traditional (monofocal) and multifocal (panoptix) intraocular lenses implantation in the iranian population. in this study, we used the persianversion of the visual function questionnaire-25 (vfq-25) which had been previously validated in the persian population.[18] this questionnaire has been widely utilized for evaluating the quality of life in cataractous patients.[14, 19, 20] quality of life measurements evaluates the level of improvement that a specific treatment may bring about in various life dimensions beyond the clinical evaluations. the second and third aims of the current study were to compare the near vision and driving items scores cumulated from the questionnaire between the two intraocular lens types. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: bamdad s, razavizadegan sa, farvardin m, mohaghegh s. vision-related quality of life after bilateral implantation of monofocal and multifocal intraocular lenses. j ophthalmic vis res 2022;17:19–26. 20 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 https://knepublishing.com/index.php/jovr monofocal vs multifocal iols; bamdad et al methods this cross-sectional prospective study was conducted at khalili eye hospital, shiraz, iran. the study protocol followed the tenets of the helsinki and was approved by the local ethics committee of shiraz university of medical sciences. informed consent was obtained from all patients. inclusion criteria were patients with bilateral cataract and corneal astigmatism <1.25 diopter power. in addition, patients who routinely drive were included. exclusion criteria were prior history of refractive surgery, and other ocular conditions that may affect the vision such as glaucoma, age-related macular degeneration, and diabetic retinopathy. prior to the surgery, optical coherence tomography was performed to exclude patients with any impairment in the macular area such as age-related macular degeneration disease, drusen, and diabetic exudate. corneal topography was also assessed for all patients to exclude patients with irregular or skewed astigmatism. the excluded patients were not good candidates for multifocal intraocular lens implantation. uncorrected distance visual acuity, best-corrected distance visual acuity, refraction, slit-lamp bio-microscopy and fundoscopy were performed at baseline and two months after surgery. the postsurgical examinations were performed for all patients in each follow-up session. keratometry and axial length measurements with intraocular lens master 500 (carl zeiss meditec, germany) was performed prior to the surgery for all patients. the intraocular lens dioptric power was selected to target emmetropia using the intraocular lens power that corresponded to the negative (myopic) predicted refractive outcome closest to zero. the appropriate formulas that corresponded to axial length were used for the intraocular lens power calculation. patients underwent the intracapsular cataract extraction for the first eye. two months after the first eye healed, the second eye surgery was performed. all surgical procedures were performed by the same surgeon (fm). according to the patients’ visual demand and desire expressed in the consultation session, either the monofocal intraocular lens with the double haptic aspheric design (acrysof sn60wf, alcon laboratories, inc.) or the multifocal intraocular lens (acrysof iq panoptix intraocular lens tfnt00, alcon laboratories, inc.) was chosen for implantation. it was impossible to randomize patients between these two groups because of the differences in the costs of the intraocular lens and the lifestyle of the patients. panoptix intraocular lens the multifocal intraocular lens of panoptix is an aspheric, hydrophobic intraocular lens with a blue filter and a 6.0-mm optical zone composed of a 4.5-mm large diffractive area with 15 diffractive zones and an outer refractive rim. it has three focal points from distance to intermediate and near ranges, dividing the incoming light to create intermediate and near add powers of 2.17 diopters (d) and 3.25 d, respectively. therefore, it provides optimal close reading distances at 60 cm and 42 cm. this novel diffractive structure provides high light utilization transmitting 88% of light at the simulated 3.0 mm pupil size to the retina. this light energy is distributed 25% each for near and intermediate and 50% for distance vision. the persian-version-vfq-25 we used the 25-item persian-version-vfq, shortform version of 51-item vfq. it was divided into 12 subscales including general health (two items), general vision (two items), ocular pain (two items), near vision (six items), distance vision (six items), vision-specific social functioning (three items), vision-specific mental health (five items), vision-specific role difficulties (four items), visionspecific dependency (four items), driving (three items), color vision (one item), and peripheral vision (one item). subscale responses were graded 0 to 100, higher vfq scores represent a better quality of life. the items were averaged to form subscales, and the sum of averages resulted in the total score. the persian-versionvfq-25 questionnaire, as determined in the iranian population, has been shown to be valid and reliable. through face-to-face interview by an ophthalmic technician the persian-versionvfq-25 results were obtained from all patients at baseline and two months after the cataract surgery of the second eye. for further comparison, we matched the groups of the monofocal and panoptix intraocular lenses according to the scores of the near vision and driving items at baseline. journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 21 monofocal vs multifocal iols; bamdad et al statistical analysis statistical analysis was performed using spss 18.0 for windows (spss inc., chicago, illinois, usa). we used descriptive statistics to illustrate the future of the data. the nonparametric test of wilcoxon and mann–whitney u-test were used to make a comparison between the before and after data within the two groups. p < 0.05 was considered as statistically significant. results fifty-eight patients (55% female [32 out of 58]) with the mean age 60.85 ± 7.40 years and 33 patients (36% female [12 out of 33]) with the mean age 59.85 ± 8.95 years were included in the monofocal and panoptix intraocular lenses groups, respectively. the mean binocular uncorrected distance visual acuity in the monofocal intraocular lens group was 1.24 ± 1.89 and 0.07 ± 0.04 before and after surgery, respectively, (p = 0.00) and in the panoptix group was 0.79 ± 1.08 and 0.00 ± 0.00 before and after surgery, respectively (p = 0.00). the mean scores of the persian-version-vfq-25 in the monofocal and panoptix intraocular lens groups before and after the cataract surgery are presented in tables 1 and 2. the mean scores of near vision and driving references in both groups are presented in graph 1. the driving reference is evaluated in the categories of day and nighttime driving and vision in driving in adverse conditions. two groups were matched in the mean scores of near vision driving references before surgery (p > 0.05). the differences in the references of near vision, nighttime driving, and vision in driving in adverse conditions were statistically significant between the two groups (p = 0.001). there were no intraor postoperative complications or adverse effects in the study population in the two groups. discussion nowadays, cataract surgery has the potential to provide excellent visual rehabilitation for all of the far, intermediate, and near distances by implanting multifocal intraocular lenses. however, monofocal intraocular lenses are still the most commonly used types of intraocular lenses across the world. multifocal intraocular lenses have the potential to provide spectacle independency for pandistances while they may increase the possibility of minor photic phenomena occurring due to their optical designs. previous clinical evaluations revealed that a high level of visual acuity and contrast sensitivity after multifocal intraocular lens implantation is obtainable. however, the mesopic contrast sensitivity in patients with multifocal intraocular lenses has been reported to be less than monofocal.[16] in the current study using the persian-version-vfq-25, we evaluated the state of improvement that cataract surgery by implanting monofocal and multifocal (panoptix) intraocular lenses may bring about in the patients’ quality of life. our data analysis shows that the visionrelated quality of life improved to an excellent level after cataract surgery with either type of monofocal or panoptix intraocular lenses. for both groups, the mean score values in all dimensions were approximately >90, except for the driving reference in the panoptix group (=75) that is discussed thoroughly in the paragraphs below. the prominent improvements observed in the dimensions of general and mental health, social function, dependency, and role limitation reveal that cataract surgery with either type of intraocular lenses improves both vision and sense of well-being. cataract surgery with either lenses reduces the patients’ stress level, and improves the patients’ social relationships and activities. our results are in agreement with the results of previous studies.[11, 13, 14, 21] akman et al[13]utilized the vf-14 quality-of-life questionnaire and evaluated the vision-related quality of life in 48 patients after panoptix implantation. similarly, they reported an overall high level of satisfaction and a high quality of life among these patients. in another study, carneros-llorente et al[11] compared the visual acuity, contrast sensitivity, and quality of life scores among three trifocal designs. they reported high satisfaction levels with all of the designs and a slightly improved intermediate vision with panoptix. hamidi et al[21] reported highly satisfactory results with the toric panoptix intraocular lens model in the eyes with longer or shorter axial length. the novelty of the panoptix intraocular lens is the provision of clear images at near and intermediate distances. since the panoptix group obtained the maximum score in the “near & 22 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 monofocal vs multifocal iols; bamdad et al table 1. vison-related quality of life in patients with monofocal intraocular lens mean ± std. deviation n = 58 mean ± std. deviation n = 58 p-value general health 47.84 ± 17.69 100.00 ± 0.00 0.001 general vision 54.31 ± 14.91 88.91 ± 12.47 0.001 peripheral vision 50.43 ± 12.81 100.00 ± 0.00 0.001 color vision 65.08 ± 12.33 100.00 ± 0.00 0.001 mental health 77.58 ± 7.68 100.00 ± 0.00 0.001 ocular pain 71.87 ± 15.23 88.36 ± 8.06 .001 near vision 46.83 ± 10.56 89.94 ± 4.87 0.001 distance vision 55.02 ± 7.47 100.00 ± 0.00 0.001 social function 70.47 ± 13.18 100.00 ± 0.00 0.001 role limitation 86.63 ± 8.71 100.00 ± 0.00 0.001 dependency 91.66 ± 6.24 100.00 ± 0.00 0.001 driving 47.27 ± 15.48 98.27 ± 4.05 0.001 total score 63.69 ± 4.95 98.08 ± 0.70 0.001 table 2. vison-related quality of life in patients with panoptix intraocular lens mean ± std. deviation (before) n = 33 mean ± std. deviation (after) n = 33 p-value general health 74.24 ± 14.63 96.96 ± 8.28 0.001 general vision 69.69 ± 14.99 93.18 ± 11.30 0.001 peripheral vision 64.39 ± 12.54 94.69 ± 10.37 0.001 color vision 100.00 ± 0.00 100.00 ± 0.00 >0.99 mental health 69.69 ± 14.58 89.77 ± 9.08 0.001 ocular pain 94.50 ± 6.00 100.00 ± 0.00 0.01 near vision 51.01 ± 9.02 100.00 ± 0.00 0.001 distance vision 77.02 ± 12.50 100.00 ± 0.00 0.001 social function 88.25 ± 10.33 96.59 ± 3.16 0.001 role limitation 68.56 ± 20.99 100.00 ± 0.00 0.001 dependency 69.69 ±17.77 100.00 ± 0.00 0.001 driving 44.08 ± 21.10 77.15 ± 3.70 0.001 total 72.15 ± 9.66 95.70 ± 1.30 0.001 intermediate fine works” category, it is evident that the panoptix design from the patients’ viewpoint was very successful in achieving its aim. although patients with a monofocal intraocular lens may take advantage of near glasses and obtain a good score the spectacle independency that panoptix provides has resulted in a prominently higher score in these patients. our results are in agreement with the results of previous studies.[22–24] chichester et al reported spectacle independence in 90% of patients with trifocal intraocular lenses, and all patients stated that they would be willing to repeat surgery with the same intraocular lens type.[22] akman et al[13]reported no difficulty journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 23 monofocal vs multifocal iols; bamdad et al figure 1. a comparison between monofocal and panoptix intraocular lenses. in near activities such as reading books and phone numbers, writing checks, performing computer tasks, wearing make-up, and cooking with panoptix. however, they reported a little difficulty in reading very small print sizes and sewing. rementería-capelo et al[15] reported high scores in near activities such as reading newspapers, viewing prices on goods, and doing handcrafts. our findings revealed that nighttime driving and driving in adverse conditions had a moderate improvement in the panoptix group. albeit the daytime driving reached the maximum level of improvement in this group. we relate that to the diffractive design of the panoptix lens and the light halos that appears in the field.[16, 25] trifocal panoptix intraocular lens provides three images simultaneously, so in poor lighting conditions, the multiple images’ shadows disturb the vision. it seems that the effect of shadows is significant in nighttime driving and is reflected in the patient’s reported outcome. moreover, the higher-order aberrations amount increases at nights due to the larger pupil size, that superimposes the previous problems of halos and glare with this design. although the results of our study were in agreement with previous studies,[12, 13] it has been reported that as a result of neural adaptation this problem described above decreases with time.[26] previous studies revealed that resolving the remaining uncorrected refractive errors with wavefront-guided lasers in situ keratomileuses can prominently enhance the satisfaction level of patients after multifocal lens implantation.[27] moreover, performing the incision after the corneal steep axis in surgery results in astigmatism 24 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 monofocal vs multifocal iols; bamdad et al reduction in the corneal, <1d power. consequently, this consideration with panoptix design improves the quality of vision and the satisfaction of the patients.[28] as expected, postoperative uncorrected visual acuity prominently improved after cataract surgery with both lens types and no adverse effects were observed in both groups. previous studies revealed that presurgical visual acuity should not be considered as the only indicator when performing cataract surgery. rather, vision-related quality of life measurements with validated questionnaires is recommended as a necessary additional tool for making decisions about surgery.[29] these tools are necessary because there might be high visual demands present in some patients’ lifestyles where even early stage cataract can profoundly degrade their quality of life and vision satisfaction. in choosing the intraocular lens design patients who are more demanding and are perfectionists may request multifocal lenses while the more easygoing patients may choose the traditional design. therefore, the personality of the patient itself may affect postoperative acceptance. in our study, we observed increased satisfaction from patients in near vision with panoptix. however, if the traditional group were served by panoptix, this resultant satisfaction may not be obtained, as panoptix intraocular lens requires making an adjustment for the near vison which easygoing patients may find inconvenient. the strength of our study was utilizing the persian-version vfq-25 as a validated questionnaire which is widely used in cataract evaluations[14, 19, 20] in global populations.[30–32] thus, it makes comparisons in future studies more convenient than using self-designed questionnaires. the study’s limitation was the short follow-up time. a longer follow-up period is recommended when considering the probability of neural adaptation in evaluating the state of nighttime driving after panoptix intraocular lens implantation. another limitation was not measuring and comparing the contrast sensitivity between the two groups. in addition, our study does not cover the high myopic and extremely hyperopic eyes. previous studies show satisfactory clinical outcomes in such cases, however less successful results when compared to patients with more normal refractive errors.[33, 34] therefore, in order to properly address these limitations that exist, more resources are required in determining the patients’ vision satisfaction and reported outcomes in such cases. in conclusion, we discovered that in all aspects of life both monofocal and panoptix intraocular lens provide patients with a substantial level of vision-related quality of life and visual satisfaction. the monofocal intraocular lenses enhanced the vision of the patient during nighttime driving as compared to that of the panoptix multifocal intraocular lens. in addition, the panoptix intraocular lens improved the quality of the vision of the patients in the near and intermediate categories as a result of its optical design. therefore, it is recommended in order to adequately assess choosing the suitable option it is mandatory to consider the patient’s visual demand prior to the cataract surgery and inform the patient about the probability of visual dissatisfaction occurring with nighttime driving if multifocal intraocular lenses are the chosen option. financial support and sponsorship nil. conflicts of interest none declared. references 1. thompson j, lakhani n. cataracts. prim care 2015;42:409–423. 2. asbell pa, dualan i, mindel j, brocks d, ahmad m, epstein s. age-related cataract. lancet 2005;365:599–609. 3. pepose js, burke j, qazi ma. benefits and barriers of accommodating intraocular lenses. curr opin ophthalmol 2017;28:3–8. 4. kohnen t. first implantation of a diffractive quadrafocal (trifocal) intraocular lens. j cataract refract surg 2015;41:2330–2332. 5. kohnen t, titke c, böhm m. trifocal intraocular lens implantation to treat visual demands in various distances following lens removal. am j ophthalmol 2016;161:71–77. e1. 6. alfonso jf, fernández-vega-cueto l, fernández-vega l, montés-micó r. visual function after implantation of a presbyopia-correcting trifocal intraocular lens. ophthalmic res 2020;63:152–164. 7. rodov l, reitblat o, levy a, assia ei, kleinmann g. visual outcomes and patient satisfaction for trifocal, extended depth of focus and monofocal intraocular lenses. j refract surg 2019;35:434–440. journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 25 monofocal vs multifocal iols; bamdad et al 8. yoon ch, shin i-s, kim mk. trifocal versus bifocal diffractive intraocular lens implantation after cataract surgery or refractive lens exchange: a meta-analysis. j korean med sci 2018;33:e275. 9. mencucci r, favuzza e, caporossi o, savastano a, rizzo s. comparative analysis of visual outcomes, reading skills, contrast sensitivity, and patient satisfaction with two models of trifocal diffractive intraocular lenses and an extended range of vision intraocular lens. graefes arch clin exp ophthalmol 2018;256:1913–1922. 10. ruiz-mesa r, abengózar-vela a, ruiz-santos m. a comparative study of the visual outcomes between a new trifocal and an extended depth of focus intraocular lens. eur j ophthalmol 2018;28:182–187. 11. de carneros-llorente am, de carneros am, de carnerosllorente pm, jiménez-alfaro i. comparison of visual quality and subjective outcomes among 3 trifocal intraocular lenses and 1 bifocal intraocular lens. j cataract refract surg 2019;45:587–594. 12. kohnen t, herzog m, hemkeppler e, schönbrunn s, de lorenzo n, petermann k, et al. visual performance of a quadrifocal (trifocal) intraocular lens following removal of the crystalline lens. am j ophthalmol 2017;184:52–62. 13. akman a, asena l, ozturk c, güngör sg. evaluation of quality of life after implantation of a new trifocal intraocular lens. j cataract refract surg 2019;45:130–134. 14. zhang f, sugar a, jacobsen g, collins m. visual function and spectacle independence after cataract surgery: bilateral diffractive multifocal intraocular lenses versus monovision pseudophakia. j cataract refract surg 2011;37:853–858. 15. rementería-capelo la, contreras i, garcía-pérez jl, blázquez v, ruiz-alcocer j. visual quality and patient satisfaction with a trifocal intraocular lens and its new toric version. j cataract refract surg 2019;45:1584–1590. 16. lee s, choi m, xu z, zhao z, alexander e, liu y. optical bench performance of a novel trifocal intraocular lens compared with a multifocal intraocular lens. clin ophthalmol 2016;10:1031–1038. 17. lamoureux e, pesudovs k. vision-specific quality-of-life research: a need to improve the quality. am j ophthalmol 2011;151:195–197. e2. 18. asgari s, hashemi h, nedjat s, shahnazi a, fotouhi a. persian version of the 25-item national eye institute visual functioning questionnaire (nei-vfq 39): a validation study. j curr ophthalmol 2011;23:5–14. 19. kirwan c, lanigan b, o’keefe m. vision-related quality of life assessment using the nei-vfq-25 in adolescents and young adults with a history of congenital cataract. j pediatr ophthalmol strabismus 2012;49:26–31. 20. zhu m, yu j, zhang j, yan q, liu y. evaluating visionrelated quality of life in preoperative age-related cataract patients and analyzing its influencing factors in china: a cross-sectional study. bmc ophthalmol 2015;15:160. 21. hamdi im. subjective perception of trifocal iol performance, including toric models. clin ophthalmol 2019;13:1955–1961. 22. cochener b, boutillier g, lamard m, auberger-zagnoli c. a comparative evaluation of a new generation of diffractive trifocal and extended depth of focus intraocular lenses. j refract surg 2018;34:507–514. 23. alió jl, plaza-puche ab, alió del barrio jl, amat-peral p, ortuño v, yébana p, et al. clinical outcomes with a diffractive trifocal intraocular lens. eur j ophthalmol 2018;28:419–424. 24. garcía-pérez jl, gros-otero j, sánchez-ramos c, blázquez v, contreras i. short term visual outcomes of a new trifocal intraocular lens. bmc ophthalmol 2017;17:72. 25. monaco g, gari m, di censo f, poscia a, ruggi g, scialdone a. visual performance after bilateral implantation of 2 new presbyopia-correcting intraocular lenses: trifocal versus extended range of vision. j cataract refract surg 2017;43:737–747. 26. rosa am, miranda âc, patrício m, mcalinden c, silva fl, murta jn, et al. functional magnetic resonance imaging to assess the neurobehavioral impact of dysphotopsia with multifocal intraocular lenses. ophthalmology 2017;124:1280–1289. 27. seiler tg, wegner a, senfft t, seiler t. dissatisfaction after trifocal iol implantation and its improvement by selective wavefront-guided lasik. j refract surg 2019;35:346–352. 28. xue s, zhao g, yin x, lin j, li c, hu l, et al. effect of incision on visual outcomes after implantation of a trifocal diffractive iol. bmc ophthalmol 2018;18:171. 29. date rc, al-mohtaseb zn. advances in preoperative testing for cataract surgery. int ophthalmol clin 2017;57:99–114. 30. suzukamo y, oshika t, yuzawa m, tokuda y, tomidokoro a, oki k, et al. psychometric properties of the 25-item national eye institute visual function questionnaire (nei vfq-25), japanese version. health qual life outcomes 2005;3:65. 31. broman at, munoz b, west sk, rodriguez j, sanchez r, snyder r, et al. psychometric properties of the 25-item nei-vfq in a hispanic population: proyecto ver. invest ophthalmol vis sci 2001;42:606–613. 32. labiris g, katsanos a, fanariotis m, tsirouki t, pefkianaki m, chatzoulis d, et al. psychometric properties of the greek version of the nei-vfq 25. bmc ophthalmol 2008;8:4. 33. steinwender g, schwarz l, böhm m, slavík-lencová a, hemkeppler e, shajari m, et al. visual results after implantation of a trifocal intraocular lens in high myopes. j cataract refract surg 2018;44:680–685. 34. alfonso jf, fernández-vega-cueto a, alfonso-bartolozzi b, rodríguez-uña i, montés-micó r. visual and refractive outcomes in hyperopic pseudophakic patients implanted with a trifocal intraocular lens. clin ophthalmol 2019;13:2261–2268. 35. garcía-pérez jl, gros-otero j, sánchez-ramos c, blázquez v, contreras i. short term visual outcomes of a new trifocal intraocular lens. bmc ophthalmol 2017;17:72. 26 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 original article clinico-microbiological profile of nontuberculous mycobacterial keratitis richa dhiman1, ms; meena lakshmipathy1, ms; dhanurekha lakshmipathy2, phd; therese k.lily2, phd 1cj shah cornea services, medical research foundation, sankara nethralaya, chennai, tamil nadu, india 2l & t microbiology research center, vision research foundation, sankara nethralaya, chennai, tamil nadu, india orcid: richa dhiman: https: orcid.org/0000-0002-9284-0829 meena lakshmipathy: https://orcid.org/0000-0001-5192-0083 abstract purpose: to assess the clinical and microbiological characteristics of nontuberculous mycobacterial (ntm) keratitis and to evaluate their response to medical therapy. methods: sixteen patients of ntm keratitis were retrospectively reviewed from may 2014 to may 2019. laboratory diagnosis were made using ziehl-nielsen acidfast staining, routine culture method of isolation of nontuberculous mycobacteria and further identification of species by pcr (polymerase chain reaction)-based dna sequencing targeting the heat shock protein-65 (hsp-65) gene. results: sixteen patients of microbiologically proven ntm keratitis were included. the average age at the time of presentation was 43.56 years (range, 24–73 years). the mean duration of symptoms was 2.23 months. the commonest risk factor was injury with organic material (43.7) followed by ocular surgery (25%). the majority of the nontuberculous mycobacteria were mycobacterium abscessus (87.6%) followed by m. fortuitum (6.2%) and m. chelonae (6.2%). the in vitro sensitivity showed maximum sensitivity to amikacin (amk; 100%) followed by azithromycin (azm; 85.7%), and clarithromycin (clr; 85.7%). out of a total of 16 patients, 12 (75%) had total success with medical therapy while 4 (25%) required surgical intervention. conclusion: this study is focused on rapid and reliable identification of ntm keratitis through pcr-based identification method to enable effective medical management. the antibiotic susceptibility testing of different subspecies of ntm further reduced the need for surgical intervention. the effective role of amk either alone or in combination with macrolide antibiotics is also highlighted in this study. keywords: atypical mycobacterial keratitis; m. abscessus; nontuberculous mycobacterial keratitis; polymerase chain reaction j ophthalmic vis res 2022; 17 (2): 160–169 160 © 2022 dhiman et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i2.10786&domain=pdf&date_stamp=2019-07-17 non-tuberculous mycobacterial keratitis; dhiman et al introduction nontuberculous mycobacteria (ntm) also known as atypical mycobacteria are free-living, aerobic, non-sporulating, and non-motile bacilli. although they are ubiquitous, for the past two decades, their frequency has increased in surgical instruments and surgical suites, especially after refractive procedures.[1–3] they have the ability to survive in artificial environments like daily water distribution systems, pools, and operating rooms on account of their significant pathogenic property of biofilm formation which shields the ntm from disinfectants.[4] in 1965, the first case of chronic keratitis was reported by turner et al which was caused by mycobacterium fortuitum, following the removal of a corneal foreign body.[5] out of the total cases of ntm keratitis, the m. fortuitum group and the m. chelonae (m. chelonae – m. abscessus) groups are responsible for 83.5% of the cases while the runyon groups i–iii, the slowly growing mycobacteria (sgm), accounts for other 16.5% of the cases.[6] several risk factors like history of ocular trauma, use of contact lenses, ocular implants, steroids, and multiple surgeries have been related with ntm ocular infections. these infections are a challenge to diagnose clinically and microbiologically leading to delay in the diagnosis and treatment. they have an indolent course that is prolonged if topical steroids are used. the ntm show varying degrees of susceptibility to the commonly used antibiotics including aminoglycosides, fluroquinolones, and erythromycin. the association of in vitro susceptibility and clinical response is not strong and surgical intervention is frequently required to eradicate the intractable infections caused by ntm. hence, ntm species identification by molecular techniques play a crucial role in the management of ntm keratitis. correspondence to: meena lakshmipathy, ms. cj shah cornea services, medical research foundation, sankara nethralaya, 18 college road, chennai 600006, tamil nadu, india. email: drmly@snmail.org received: 12-08-2020 accepted: 21-08-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i2.10786 this study was done to assess the clinical and microbiological characteristics of eyes with ntm keratitis and evaluate their response to medical therapy and their clinical outcome with special emphasis on early diagnosis by pcr-based dna sequencing targeting hsp65 gene for definite species recognition. methods we retrospectively reviewed 2759 cases of microbial keratitis from may 2014 to may 2019 after appropriate approval from the institutional review board adhering to the tenets of the declaration of helsinki. of these, 16 cases of ntm keratitis were identified. the study included a review of patients’ records for the mode of presentation, clinical details, and outcome. microbiological records of all the ocular specimens processed at the ocular microbiology laboratory were also reviewed. the corneal scrapings from all 16 patients were taken from the base and edge of the ulcer using a sterile 15 no. blade after instilling local anesthetic (0.5% proparacaine) under slit-lamp magnification and then they were smeared on the glass slides and inoculated on to the routine culture media directly. in most of the cases, the treatment was initiated based upon the direct smear report. later, the treatment was modified as per the culture, antibiogram report from the laboratory, or if the clinical response to the medication was inadequate. laboratory procedures direct smear and culture smears were made for 10% koh wet mount, gram’s stain and acid-fast stain. the microorganisms with morphological features indicative of mycobacteria on gram stain were then confirmed this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: dhiman r, lakshmipathy m, lakshmipathy d, k.lily t. clinico-microbiological profile of nontuberculous mycobacterial keratitis. j ophthalmic vis res 2022;17:160–169. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 161 https://knepublishing.com/index.php/jovr non-tuberculous mycobacterial keratitis; dhiman et al with ziehl–nielsen stain. the culture methods included in the study were as follows: blood agar, chocolate agar, mac conkey agar, sabouraud’s dextrose agar, and two liquid media – thioglycolate broth and brain heart infusion broth. based on clinical suspicion, non-nutrient agar with escherichia coli confluent overlay was included in the culture for isolation of acanthamoeba. ntm were identified by their typical colony morphology, rate of growth within 48–72 hr, and ability to grow on blood agar. if poorly staining gram-positive bacilli were seen on smears made from growth on blood agar, ziehl–nielsen stain was done to confirm the acid fastness of the bacterial growth. simultaneously, all isolates were also subjected to pcr-based dna sequencing method of species identification. extraction of dna and pcr targeting hsp65 gene dna extraction was performed by using a qiagen dna extraction mini kit (hilden, germany) as per the manufacturer’s instructions. for the pcr amplification, a 50 μl reaction was set with 5 μl of 10xpcr buffer (100 mm tris-hcl [ph 8.3], 500 mm kcl, 0.1% gelatin, 15 mm mgcl2), 8 μl of 200 μm of each dntps, 1 μl of 1 picomole of each primer[7] [forward primer tb 11: 5’ accaacgatggtgtgtccat 3’, reverse primer tb12: 5’ cttgtcgaaccgcataccct 3’], 0.75 μl of 2 units of taq polymerase, 5 𝜇l sterile glycerol, and 5 μl of extracted dna was used as the template and the final volume was reached up to 50 μl with sterile milli q water. the positive control used for the experiment was m. tuberculosis h37rv atcc dna. the pcr thermal profile consists of 40 cycles of denaturation at 94ºc for 1 min, annealing at 55ºc for 1 min and extension at 72ºc for 1 min and a final extension at 72ºc for 10 min. amplification of the 439-bp product of the hsp65 gene was identified by 2% agarose gel electrophoresis incorporated with 0.5 μg/ml ethidium bromide for visualization using a uv transilluminator. pcr-based dna sequencing targeting hsp65 gene the amplified products underwent dna sequencing by using an abi prism 3110 automated dna sequencer (applied biosystems, usa) followed by cycle sequencing of the amplified products in a 10-μl reaction volume, containing 1.5 μl of rr mix, 2.5 μl of sequencing buffer, 1 μl of forwarding primer/reverse primer, 4 μl milliq water, and 1 μl of pcr-amplified product. the perkin–elmer thermocycler was used for amplification using 25 cycles at 96ºc for 10 s, 50ºc for 5 s, and 60ºc for 4 min, and the initial denaturation was carried out at 96ºc for 1 min. these cycle-sequenced products were then subjected to purification and sequencing using the abi prism 3130 avant (applied biosystems, usa) genetic analyzer, which uses the principle of sanger’s dideoxy termination method for its working. the analysis of these sequences was done by sequence analysis software – bio edit sequence alignment software. further, to confirm the sequenced data with the standard strains and establish the percentage homology, blast analysis (www.ncbi.nlm.nih.gov/blast), using pubmed, was done. antibiotic susceptibility testing of ntm by disc diffusion method the isolated ntm were put up for amk, clr, azm, tobramycin (tob), ciprofloxacin (cip), gatifloxacin (gat), moxifloxacin (mox), ofloxacin (ofl), norfloxacin (nor), and imipenem (imp) obtained from hi-media laboratories, india for determination of sensitivity pattern of the isolated ntm using kirby bauer disc diffusion method as per standard clsi guidelines. categorization of patients patients were categorized into three groups based upon the success of medical therapy as (a) total success where complete corneal scarring occurred with no active corneal inflammation detected for at least one month post cessation of topical antibiotics; (b) partial success where additional procedures like glue and bandage contact lens was required; and (c) failure when worsening of the primary infiltrate/no response to topical antimicrobial therapy/perforation requiring therapeutic penetrating keratoplasty. results demographics and clinical details the age of the patients at the time of presentation ranged from 24 to 73 years (average, 43.56 162 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 non-tuberculous mycobacterial keratitis; dhiman et al table 1. clinical and microbiological details of 16 patients with ntm keratitis. no. age/sex risk factors visual acuity at presentation (log mar) depth of corneal infiltrate corneal scraping (afb stain) pcr (species) clinical outcome visual acuity at followup (log mar) duration of followup 1 38/m trauma 2 full positive m. abscessus failure 2.3 1 year 2 55/m nil 1.3 anterior 2/3 positive m. abscessus total success 0.47 2 months 3 30/m steroid use 2 ring positive* m. abscessus failure 2 1 year 4 66/m trauma 0.47 anterior 2/3 positive* m. abscessus total success 0.87 6 months 5 29/m foreign body 1.3 anterior 1/3 negative m. abscessus total success 0.3 4 months 6 47/f nil 0.3 anterior 2/3 negative m. abscessus total success 0.09 2 months 7 47/m nil 0.09 anterior 1/3 positive m. abscessus total success 0 2.5 months 8 27/m trauma 2 anterior 2/3 positive m. abscessus total success 0.47 3 months 9 29/f trauma 0 anterior 2/3 negative m. abscessus total success 0 2 months 10 67/m cataract surgery 2 anterior 2/3 positive* m. abscessus total success 2 3 months 11 32/m foreign body 0.6 anterior 2/3 positive m. abscessus total success 0.3 2 months 12 39/m cataract surgery 2.7 full negative m. chelonae failure 2.7 8 months 13 54/f cataract surgery 2 posterior 1/3 negative m. fortuitum total success 2.7 1 year 14 40/m foreign body 0.17 anterior 2/3 positive m. abscessus total success 0.09 2 months 15 24/m contact lens use 0.17 anterior 2/3 positive* m. abscessus total success 0 4 months 16 73/f cataract surgery 2 posterior 1/3 negative m. abscessus partial success 2.3 6 months *repeat scrapings done; afb, acid fast bacilli; pcr, polymerase chain reaction; logmar, logarithm minimum angle of resolution table 2. treatment of eyes infected with nontuberculous mycobacteria. treatment regimen % (number) of eyes (n = 12) topical amikacin alone 50 (6) topical amikacin + clarithromycin 16.6 (2) topical amikacin + azithromycin 8.3 (1) topical amikacin + tobramycin 8.3 (1) topical amikacin + ciprofloxacin 8.3 (1) topical amikacin + azithromycin + moxifloxacin 8.3 (1) journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 163 non-tuberculous mycobacterial keratitis; dhiman et al figure 1. nontubercular mycobacterial keratitis. (a) after trauma with vegetative matter showing infiltrate with vascularization. (b) dry-looking infiltrate mimicking fungal infection with hypopyon which was diagnosed as ntm on repeat scraping. (c) dense infiltrate after cataract surgery. (d) paracentral infiltrate with severe stromal edema. figure 2. slit-lamp image of case no. 4 which was treated as fungal corneal ulcer elsewhere came positive on corneal scraping (ziehl neelsen stain) after repeating twice (a) at presentation; (b) 15 days posttreatment with topical fortified amikacin (2.5%) and oral clarithromycin; and (c) after two months, scarred infiltrate with corneal vascularization. years). out of a total of 16 patients, 12 were male (70.6%) and 4 female (29.4%). the time from the onset of infection to the initial presentation ranged from three weeks to eight months (median, 2.23 months). eleven of the sixteen patients (65%) had a previous traumatic or surgical history [table 1]. seven out of eleven cases had trauma with vegetative or mineral matter. the four postsurgical corneal infections occurred within one year of elective cataract surgery. one patient each had 164 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 non-tuberculous mycobacterial keratitis; dhiman et al figure 3. (a) ziehl neelsen-stained corneal scrapings showing acid-fast bacilli against a blue background. (b) white colored, opaque, non-hemolytic colonies of ntm on blood agar. (c) amplification of a 439 bp-specific dna fragment of the hsp 65 region of mycobacterial dna. lane 1: negative control; lane 2–5: amplified mycobacterial dna (439 bp); lane 6: positive control; and lane 7: molecular weight marker (100 bp). figure 4. bar diagram showing the sensitivity and resistance pattern of in vitro antibiotic susceptibility pattern of ntm isolates (m. abscessus) included in the study (n = 14). journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 165 non-tuberculous mycobacterial keratitis; dhiman et al a history of contact lens use and steroid use alone, respectively. in three patients, no risk factor could be identified. out of the total infected eyes, 12 (75%) were already being treated before the presentation. of these, six (37.5%) were on antifungals and antibiotics, five (31.3%) on antibiotics, and one (6%) on antivirals. exposure to steroids – topical or systemic was found in 8/16 eyes (47%). the main presenting features in all patients were pain, redness, and diminution of vision. all patients presented with the stromal infiltrates at various depths associated with corneal epithelial defect [figures 1 and 2], of which three patients had hypopyon [table 1]. microbiology results of the 16 patients, 10 (58.8%) tested positive for direct smear with 1% afb stain, out of which 4 patients (40%) tested positive only on re-scraping. in all 16 patients, ntm grew on blood agar [figure 3]. no associated bacterial or fungal infections were seen in any of the cases. the average time for culture to grow ranged from two to five days. out of the16 isolates, 14 (87.6%) were identified as m. abscessus, one each (6.2%) as m. fortuitum, m. chelonae using pcr-based dna sequencing targeting the heat shock protein-65 gene. the sensitivity pattern of the 14 ntm isolates of m. abscessus is shown in figure 4. the in vitro sensitivity showed maximum sensitivity to amk in 14/14 eyes (100%) followed by azm in 12/14 (85.7%) and clr in 12/14 eyes (85.7%). the maximum resistance was to imp, nor (78.6%), and ofl (71.5%). the single isolate of m. chelonae showed sensitivity to amk, clr, azm, tob, and gat while m. fortuitum ntm isolate was sensitive to amk, cip, mox, gat, and imp. clinical course seventy-five percent (12/16) of eyes with cultureproven ntm infections were treated successfully with amk alone or in combination with other antibiotics [table 2]. fifty percent (6/12) of the eyes infected with ntm keratitis were treated with amk alone, 25% (3/12) with a macrolide antibiotic, 8.3% (1/12) with aminoglycoside antibiotic, and 8.3% (1/12) with fluoroquinolone antibiotic. the average time taken from diagnosis of ntm till its resolution was 3.2 months (ranged from two weeks to one year). the surgical intervention had to be done in 25% (4/16) of the infected eyes as they did not improve with the medical therapy [table 1]. among these, one patient had impending perforation, which was managed successfully with cyanoacrylate glue and bandage contact lens, while the remaining three underwent therapeutic penetrating keratoplasty (tpk). post tpk, the corneal button showed the same organism as identified by pcr. the follow-up of the patients varied from two months to one year. there was no recurrence in any case. the final best-corrected visual acuity after treatment (either medical or surgical) and eradication of infection ranged from the perception of light to 6/6 [table 1]. discussion nontuberculous mycobacteria was traditionally divided into groups i–iv by runyon based on colony characteristics, growth rate, and specific conventional biochemical reactions.[8] groups i, ii, and iii included the sgm with a growth rate of two to four weeks while the rapid growers with a growth rate of seven to ten days were included in group iv.[6, 9] mycobacterium chelonae, m. abscessus, and m. fortuitum are the rapid growers which have been reported as the commonest organisms isolated from the ocular infections.[10, 11] keratitis remains the most common ocular infection caused by the ntm.[2, 3, 5, 6] the prevalence of ntm infections is on the rise worldwide due to an increase in the number of refractive procedures like lasik and endothelial keratoplasties. as per literature, the commonest ntm-causing post-lasik keratitis was m. chelonae[12, 13] until the most recent studies by llovet et al[14] detected an increase in infectious keratitis caused by staphylococcus and mrsa after lasik. interestingly, none of our patients had a history of lasik surgery in the past, however, four patients had cataract surgery within the last one year. all 16 patients had a unilateral presentation with male preponderance with an increased incidence in middle-aged adults matching with the available reports in the literature.[6] the commonest risk factor for ntm keratitis in the present study was ocular trauma followed by surgery with delayed onset of indolent infection. thus, ntm should be suspected as the causative agent in the delayed onset of indolent corneal ulcers. 166 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 non-tuberculous mycobacterial keratitis; dhiman et al in the present series, 75% had already received treatment in the form of antibiotics, antifungals, antivirals, and/or steroids prior to their presentation to our institute which is in accordance with the study by girgis et al[10] and lalitha et al.[3] our patients presented with central or paracentral infiltrates at varying depths with no typical feature in contrast to a characteristic “cracked windshield” appearance described in ntm keratitis in the literature.[11] in our series, 12.5% of infected eyes had ring infiltrate similar to huang et al’s[2] study which may be confused with fungal or acanthamoeba keratitis. the antimicrobial susceptibility of ntm varies widely and hence the species identification of ntm is very crucial for the appropriate selection of antibiotic and better patient management. in our study, we were able to make an early diagnosis (within 24–48 hr) in 62% (10/16) as pcr-based dna sequencing was done in all cases as opposed to earlier reports. a similar method of rapid identification of mycobacterial species was used by telenti et al, in 1993 targeting the same hsp 65 region but with a different set of primers.[7] the pcr-based dna sequencing targeting hsp65 method is fast, cost-effective, highly specific, and efficient in comparison to the highperformance liquid chromatography (hplc) for species identification of ntm and hence can be easily adapted by clinical microbiology laboratories with molecular microbiology facilities.[15, 16] several studies have grouped the two species – m. chelonae and m. abscessus as “m. chelonae” because of the difficulty in separating them without molecular techniques. it is important to separate these two pathogens because they differ in their drug susceptibility. the commonest ntm identified in our study was m. abscessus (87.6%; 14/16) as opposed to earlier studies, where m. chelonae was the predominant isolate.[17, 18] this higher prevalence of m. chelonae in earlier studies is likely a reflection of inadequate methods for ntm identification or variation among the species of ntm geographically as indicated in a study by elliot et al.[19] it has been found that m. abscessus carries a chromosomal erythromycin methylase gene (erm41) which confers inducible macrolide resistance that is not found in m. chelonae.[20] this study showed 100% sensitivity to amk for all ntm isolates followed by 85.7% sensitivity to macrolides (azm and clr) which is comparable to the previous study by reddy et al.[21] since 87.5% were speciated to m. abscessus in our study, we infer that the most effective agents against m. abscessus are amk, clr, and azm which is in agreement to a study by elliot et al.[19] among fluoroquinolones, cip and gat were found to be resistant in 57.2% of m. abscessus isolates while mox was resistant in 64.3% of m. abscessus isolates. hence, fluoroquinolones (including the fourth generation) should not be considered among the first-line drugs for m. abscessus keratitis.[19] although we could not comment specifically on m. chelonae and m. fortuitum in vitro susceptibilities due to the low sample size (one patient in each group), we did find that m. chelonae had sensitivity for both aminoglycoside (tob) and fluoroquinolone (gat) while m. fortuitum showed sensitivity only to fluoroquinolones (cip, mox). this is in accordance with previous studies which indicate the role of fluoroquinolones in treating m. chelonae and m. fortuitum keratitis.[18, 22] however, studies done by cruz et al[23] and moshirfar et al[24] have shown resistance of fourth-generation fluoroquinolones to m. chelonae. hence, larger sample studies with time-kill studies and minimum bactericidal concentrations (mbc) assays are required to ascertain their role. in this study, a combination therapy was required for the clinical cure of 50% of the infected eyes. the treatment failure in some cases with the use of amk alone might be because of the poor penetration of amk into the intact epithelium while kuehne et al[25] reported adequate penetration of azm and clr into the intact corneal epithelium. on the other hand, ford et al[12] found that the topical clr is less tolerated because of ocular discomfort and toxic reaction. hence, based on our study sensitivity pattern, we suggest that topical amk (2.5%) can be used either alone or in combination with oral clr (500 mg) or azm (500 mg) for ntm keratitis specifically for m. abscessus. fluoroquinolones (including the fourth generation) remains the third line of drug for m. abscessus keratitis, although they have a slightly superior role for m. chelonae and m. fortuitum. limitations of our study include the small sample size of patients, retrospective analysis, and lack of mic (minimum inhibitory concentration) determination for in vitro susceptibility of ntm. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 167 non-tuberculous mycobacterial keratitis; dhiman et al to summarize, this study emphasizes that ntm must be kept as a differential diagnosis of infectious keratitis developing post-surgery or after injury by a foreign body injury, especially when an ulcer fails to respond adequately to the common antimicrobial drugs. it is interesting to note m. abscessus to be the commonest ntmcausing keratitis in contrast to the previous studies – maybe, the different geographic location plays an important role in species identification. we believe that pcr-based molecular method for definite identification of the species enables the clinicians to make an accurate and timely diagnosis. hence molecular diagnostic testing should be included in the battery of tests when faced with such indolent ulcers. further, therapy based on the antibiotic sensitivity pattern of ntm species helps to achieve the resolution of infection with medical therapy, thereby reducing the need for surgical intervention. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. covert tc, rodgers mr, reyes al, et al. occurrence of nontuberculous mycobacteria in environmental samples. appl environ microbiol 1999; 65: 2492–6. 2. huang scm, soong hk, chang js, et al. non tuberculosis mycobacterial keratitis: a study of 22 cases. br j ophthalmol 1996; 80: 962–8. 3. lalitha p, rathinam sr, srinivasan m. ocular infections due to non-tuberculous mycobacteria. indian j med microbiol 2004; 22: 231–7. 4. hall-stoodley l, lappin-scott h. biofilm formation by the rapidly growing mycobacterial species mycobacterium fortuitum. fems microbiology letters. 1998;168(1):77-84. 5. turner l, stinson i. mycobacterium fortuitum as a cause of corneal ulcer. am j ophthalmol 1965; 60:329-31. 6. moorthy rs, valluri s, rao na. nontuberculous mycobacterial ocular and adnexal infections. surv ophthalmol 2012; 57: 202–25. 7. telenti a, marchesi f, balz m, et al. rapid identification of mycobacteria to the species level by polymerase chain reaction and restriction analysis. j clin microbiol. 1993; 31:175–178. 8. runyon eh. anonymous mycobacteria in pulmonary disease. med clin north am 1959; 43: 273–90. 9. griffith de, aksamit t, brown-elliott ba, catanzaro a, daley c, gordin f, holland sm, horsburgh r, huitt g, iademarco mf, iseman m. an official ats/idsa statement: diagnosis, treatment, and prevention of nontuberculous mycobacterial diseases. american journal of respiratory and critical care medicine. 2007;175(4):367-416. 10. girgis do, karp cl, miller d. ocular infections caused by non-tuberculous mycobacteria: update on epidemiology and management. clinical & experimental ophthalmology. 2012;40(5):467-75. 11. kheir wj, sheheitli h, abdul fattah m, et al. nontuberculous mycobacterial ocular infections: a systematic review of the literature. biomed research international. 2015; 2015. 12. ford jg, huang aj, pflugfelder sc et al. nontuberculous mycobacterial keratitis in south florida. ophthalmology 1998; 105: 1652–8. 13. chang ma, jain s, azar dt. infections following laser in situ keratomileusis: an integration of the published literature. surv ophthalmol 2004; 49:269 – 80. 14. llovet f, de rojas v, interlandi e, et al. infectious keratitis in 204 586 lasik procedures. ophthalmology. 2010;117(2):232-8.e84 15. palani d, kulandai lt, naraharirao mh, et al. application of polymerase chain reaction-based restriction fragment length polymorphism in typing ocular rapidgrowing nontuberculous mycobacterial isolates from three patients with postoperative endophthalmitis. cornea. 2007;26(6):729-35. 16. chimara, e., ferrazoli, l., ueky, s.y.m. et al. reliable identification of mycobacterial species by pcr-restriction enzyme analysis (pra)-hsp65 in a reference laboratory and elaboration of a sequence-based extended algorithm of pra-hsp65patterns. bmc microbiol 8, 48 (2008). 17. srinivasan m, prajana l, prajana v. a cluster of cases of mycobacterium chelonae keratitis following penetrating keratoplasty. indian j ophthalmol. 2005; 53:67–68. 18. freitas d, alvarenga l, sampaio j et al. an outbreak of mycobacterium chelonae infection after lasik. ophthalmology 2003; 110: 276–85. 19. brown-elliott ba, mann lb, hail d, whitney c, wallace rj jr. antimicrobial susceptibility of nontuberculous mycobacteria from eye infections. cornea. 2012;31(8):900-906. 20. nash ka, brown-elliott ba, wallace rj jr. a novel gene, erm (41), confers inducible macrolide resistance to clinical isolates of mycobacterium abscessus but is absent from mycobacterium chelonae. antimicrob agents chemother. 2009; 53:1367–1376. 21. reddy ak, garg p, babu kh, et al. in vitro antibiotic susceptibility of rapidly growing nontuberculous 168 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 non-tuberculous mycobacterial keratitis; dhiman et al mycobacteria isolated from patients with microbial keratitis. curr eye res 2010; 35: 225–229. 22. hamam rn, nouredin b, salti hi et al. recalcitrant post-lasik mycobacterium chelonae keratitis eradicated after the use of fourth-generation fluoroquinolone. ophthalmology 2006; 113: 950–4. 23. de la cruz j, behlau i, pineda r. atypical mycobacteria keratitis after laser in situ keratomileusis unresponsive to fourth-generation fluoroquinolone therapy. j cataract refract surg 2007; 33: 1318–21. 24. moshirfar m, meyer jj, espandar l. fourthgeneration fluoroquinolone-resistant mycobacterial keratitis after laser in situ keratomileusis. j cataract refract surg 2007; 33: 1978–81. 25. kuehne j, yu alt, holland gn, et al. corneal pharmacokinetics of topically applied azithromycin and clarithromycin. am j ophthalmol 2004; 138:547– 553. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 169 original article adenosine receptors expression in human retina and choroid with age-related macular degeneration collin p. goebel1, md; yong-seok song1,2, ms; ismail s. zaitoun1,2, phd; shoujian wang1, md, phd; heather a. d. potter1, md; christine m. sorenson1,2, phd; nader sheibani1,2,3,4, phd 1department of ophthalmology and visual sciences, university of wisconsin school of medicine and public health, madison, wi, usa 2mcpherson eye research institute, university of wisconsin school of medicine and public health, madison, wi, usa 3department of cell and regenerative biology, university of wisconsin school of medicine and public health, madison, wi, usa 4department of biomedical engineering, university of wisconsin, madison, wi, usa orcid: nader sheibani: https://orcid.org/0000-0003-2723-9217 abstract purpose: adenosine signaling modulates ocular inflammatory processes, and its antagonism mitigates neovascularization in both newborns and preclinical models of ocular neovascularization including age-related macular degeneration (amd). the adenosine receptor expression patterns have not been well characterized in the human retina and choroid. methods: here we examined the expression of adenosine receptor subtypes within the retina and choroid of human donor eyes with and without amd. antibodies specifically targeting adenosine receptor subtypes a1, a2a, a2b, and a3 were used to assess their expression patterns. quantitative real-time pcr analysis was used to confirm gene expression of these receptors within the normal human retina and choroid. results: we found that all four receptor subtypes were expressed in several layers of the retina, and within the retinal pigment epithelium and choroid. the expression of a1 receptors was more prominent in the inner and outer plexiform layers, where microglia normally reside, and supported by rna expression in the retina. a2a and a2b showed similar expression patterns with prominent expression in the vasculature and retinal pigment epithelium. no dramatic differences in expression of these receptors were observed in eyes from patients with dry or wet amd compared to control, with the exception a3 receptors. eyes with dry amd lost expression of a3 in the photoreceptor outer segments compared with eyes from control or wet amd. conclusion: the ocular presence of adenosine receptors is consistent with their proposed role in modulation of inflammation in both the retina and choroid, and their potential targeting for amd treatment. keywords: caffeine; choroid; inflammation; neovascularization; neurodegeneration; retina j ophthalmic vis res 2023; 18 (1): 51–59 correspondence to: nader sheibani, phd. department of ophthalmology and visual sciences, university of wisconsin school of medicine and public health, 1111 highland ave., 9453 wimr, madison, wi 53705-2275, usa. e-mail: nsheibanikar@wisc.edu received: 09-06-2022 accepted: 08-09-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i1.12725 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: goebel pg, song y-s, zaitoun is, wang s, potter had, sorenson cm, sheibani n. adenosine receptors expression in human retina and choroid with age-related macular degeneration. j ophthalmic vis res 2023;18:51–59. © 2023 goebel et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 51 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i1.12725&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr adenosine receptors in donor eyes with armd; goebel et al introduction age-related macular degeneration (amd) is an inflammatory driven neurodegenerative disorder that develops in the elderly due to a combination of genetics, the environment, and other factors. it contributes to substantial irreversible central vision loss in the industrialized countries and was present in an estimated 6.5% of all american adults over the age of 40 as of 2011.[1] amd is characterized by the deposition of cellular debris, called drusen between the retina and choroid, and divided into the categories of wet and dry amd.[2] in patients with wet amd, subretinal neovascularization occurs, which may lead to edema and hemorrhage. in contrast, dry amd is characterized by drusen and retinal degeneration without neovascularization or hemorrhage. currently, treatment for amd, especially dry amd, is very limited. antibodies against vascular endothelial growth factor (vegf) improve visual outcomes in most patients with wet amd.[3, 4] in addition, antioxidant vitamins and minerals slow down the progression of moderate or severe dry amd but fail to prevent the development of moderate amd from mild amd.[5] thus, these therapeutics are best for preventing progression in patients who have already developed moderate or severe disease and are unable to halt or reverse the disease process. to develop better therapeutic targets for patients with amd, a more complete understanding of its pathophysiology is required. the dysfunction and death of retinal pigment epithelial (rpe) cells and degeneration of photoreceptors are observed in amd. however, the detailed cellular and molecular mechanisms driving this degeneration needs further investigation. several hypotheses have been proposed, including accumulation of toxins, dysfunction of mitochondria, and damage from reactive oxygen species in the rpe cells and choroidal vasculature.[5–8] recently, immune and inflammatory regulatory pathways have been proposed to be the central components in the pathophysiology of amd, and preclinical models have demonstrated complement and igg deposition in the rpe and choroid of mice with amd.[5, 8–10] recent investigations indicate the importance of adenosine receptors in modulation of ocular inflammatory processes. adenosine elicits its effects through its g-protein coupled receptors: a1, a2a, a2b, and a3.[11] adenosine receptor a1 activation inhibits calcium influx-induced release of neurotransmitters in the central nervous system (cns) under hypoxic conditions, creating a neuroprotective effect.[12] adenosine receptor a3 engagement has both proand anti-inflammatory properties throughout the body, including the lung, cardiac, and gastrointestinal systems.[10] blockade of the adenosine a2a receptor in microglial cells reduces inflammatory responses and photoreceptor cell loss in cultured human cells. furthermore, adenosine receptors a2a and a2b expression are upregulated by hypoxia-inducible factor during hypoxic conditions and inflammation in the eye,[13, 14] and their antagonism blocks ischemia-mediated retinal neovascularization.[15] thus, the process of inflammation and angiogenesis in dry and wet amd could be linked with adenosine receptor signaling. however, the function of these receptors in the rpe and choroid, and their potential activity in pathophysiology of amd, needs further evaluation. the importance of adenosine receptor signaling pathways in ocular inflammatory and neovascular diseases has been further supported by studies of caffeine, an adenosine receptor antagonist, in both preclinical models and humans.[16] maugeri and colleagues found evidence that caffeine decreases the permeability of the rpe layer and thus may inhibit the development of macular edema.[17] in addition, caffeine administered to infants born prematurely for apnea diminishes the severity of retinopathy of prematurity.[18] we recently showed that caffeine is efficacious in mitigating choroidal neovascularization in a preclinical model of wet amd.[19] however, the identity of adenosine receptor(s) involved in these activities remains unknown, and results have yet to be verified in humans. here we assessed the presence of specific adenosine receptors in the retina and choroid of human donor eye samples from control and patients with wet and dry amd. these studies, to the best of our knowledge, are the first to demonstrate the presence of specific adenosine receptors in the human retina and choroid and examine whether their expression pattern is altered under amd conditions. methods human donor eyes and other materials deidentified human ocular samples were from the lion gift of sight (st. paul, mn). the eyes were collected by written consent from donors or donors’ family for medical research as delineated by the declaration of helsinki. we were provided with a list of 28 potential donor samples with histological evaluations, of which 13 were control eyes and 15 were eyes with amd. eyes from two donors with wet amd, two donors with dry amd, and two donors with no amd were selected by the help of our 52 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 adenosine receptors in donor eyes with armd; goebel et al ocular pathologist from the available samples. each experimental group contained samples matched by age and gender, and all samples included the macula. presumptive diagnoses were confirmed histologically. anti-adora1 (55026-1-ap, proteintech, rosemont, il), anti-adora2a (pa1-042), anti-adora2b (pa5-72850), and anti-adora3 (pa5-36350) were obtained from thermo fisher scientific (carlsbad, ca). anti-collagen iv antibody was from southern biotech (1340-01; birmingham, al). cy5-labeled anti-goat (705-175-147) and cy2labelled anti-rabbit (305-225-045) were obtained from jackson immunoresearch laboratories (west grove, pa). antibody staining and microscopic analysis of eye sections four paraffin sections, taken from each donor eye, were placed on glass slides. sections were washed with xylene four times for five min. this was followed by two washes in 100% and 95% ethanol for 10 min, and the pure water for 5 min. slides were then heated in a citrate solution (h-3300, vector laboratories, burlingame, ca) for 11 min to retrieve epitopes. for each set of samples, slides were then stained overnight with 750 𝜇l adora1, adora2a, adora2b, and adora3 primary antibodies, diluted in blocking buffer (1:500; pbs with 1% bovine serum albumin, 0.2% skim milk powder, and 0.3% tritonx100). diluted anti-collagen iv antibody (1:500) was added to each sample to target vasculature in the samples, and dapi diluted 1:1000 was added to each sample to visualize the cellular nuclei of the retina and choroid. the slides were then rinsed with pbs buffer three times for 5 min, and 750 𝜇l of appropriate secondary antibodies (diluted 1:500 in pbs blocking buffer) were added to each sample. slides were incubated at room temperature for 4 h allowing the visualization of collagen in the vasculature and adenosine receptor expression. following staining with primary and secondary antibodies, the expression of the a1, 2a, 2b, and a3 receptors in donor eyes with wet amd, dry amd, or no amd were compared using fluorescence microscopy. light intensity and exposure time were standardized for each group of slides under the microscope. photographs were taken of fluorescence emission patterns for the adenosine receptor, collagen iv, and dapi located within the macula and underlying choroid. the fluorescence intensity in each sample was then compared to determine the predominant location of each adenosine receptor in the retina and choroid, as well as look for differences in adenosine receptor expression between wet and dry amd compared to control. rna isolation and quantitative pcr (qpcr) analysis the retina and rpe/choroid were dissected from at least three non-diseased human eyes of similar age (male and female) and cut into smaller pieces in cold pbs. the tissue samples were snap frozen in liquid nitrogen and stored at –80ºc for rna preparation. tissue samples (50–100 mg) were dissolved in 1 ml of trizol reagent (invitrogen, san diego, ca). total rna was extracted using rneasy mini kit as recommended (qiagen, valencia, ca). complementary dna was prepared using 1 μg of total rna and the rna to cdna ecodry premix (takara, mountain view, ca) and diluted 1:10. qpcr was conducted in triplicates using a mastercycler realplex (eppendorf, enfield, ct) and tb-green qpcr premix (takara). the cycles for amplification were 95ºc for 2 min; 40 cycles of amplification (95ºc for 15 s, 60ºc for 40 s); and dissociation curve step (95ºc for 15 s, 60ºc for 15 s, 95ºc for 15 s). the relative fluorescent units (rfus) at a threshold fluorescence value (ct) were used for linear regression line and assessment of nanograms of dna. the target gene expression levels were determined by comparing the rfu at the ct to the standard curve and normalized by the housekeeping gene ribosomal protein l13α (rpl13a). the primer sequences used in this study are listed in table 1. each sample was run in triplicates. statistical analysis differences between the expression level of adora in the retina and rpe/choroid were evaluated using t-tests and graphpad prism version 8 (graphpad software, la jolla, ca). p < 0.05 was considered significant. data are the mean ± standard deviation. results adenosine receptors expression in retina and choroid each eye section selected for fluorescent staining was from a patient between the ages of 76 and 100 years old at the time of death. one male and one female sample was chosen for each of the amd and control groups. each sample was preserved within 28 h of the patient’s death. all samples demonstrated journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 53 adenosine receptors in donor eyes with armd; goebel et al figure 1. expression of adora1 in retinal and choroidal cross sections. (a) adora1, (b) collagen iv, and (c) merged images and dapi staining of eye sections with no amd (control). (d) a higher magnification of c. (e) adora1, (f) collagen iv, and (g) merged images and dapi staining of eye sections with dry amd. (h) a higher magnification of g. (i) adora1, (j) collagen iv, and (k) merged images and dapi staining of eye sections with wet amd. (l) higher magnification of k. scale bar = 400 µm (a, b, c, e, f, g, i, j, and k) and 200 µm (d, h, and l). v, vitreous; c, choroid. figure 2. expression of adora2a in retinal and choroidal cross sections. (a) adora2a, (b) collagen iv, (c) merged images and dapi staining of eye sections with no amd (control). (d) a higher magnification of c. (e) adora2a, (f) collagen iv, and (g) merged images and dapi staining of eye sections with dry amd. (h) a higher magnification of g. (i) adora2a, (j) collagen iv, and (k) merged images and dapi staining of eye sections with wet amd. (l) a higher magnification of k. scale bar = 400 µm (a, b, c, e, f, g, i, j, and k) and 200 µm (d, h, and l). v, vitreous; c, choroid. 54 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 adenosine receptors in donor eyes with armd; goebel et al figure 3. expression of adora2b in retinal and choroidal cross sections. (a) adora2b, (b) collagen iv, and (c) merged images and dapi staining of eye sections with no amd (control). (d) a higher magnification of c. (e) adora2b, (f) collagen iv, (g) merged images and dapi staining of eye sections with dry amd. (h) a higher magnification of g. (i) adora2b, (j) collagen iv, and (k) merged images and dapi staining of eye sections with wet amd. (l) a higher magnification of k. scale bar = 400 µm (a, b, c, e, f, g, i, j, and k) and 200 µm (d, h, and l). v, vitreous; c, choroid. figure 4. expression of adora3 in retinal and choroidal cross sections. (a) adora3, (b) collagen iv, and (c) merged images and dapi staining of eye sections with no amd (control). (d) higher magnification of c. (e) adora3, (f) collagen iv, and (g) merged images and dapi staining of eye sections with dry amd. (h) higher magnification of f. (i) adora3, (j) collagen iv, and (k) merged images and dapi staining of eye sections with wet amd. (l) higher magnification of k. scale bar = 400 µm (a, b, c, e, f, g, i, j, and k) and 200 µm (d, h, and l). v, vitreous; c, choroid. journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 55 adenosine receptors in donor eyes with armd; goebel et al figure 5. quantitative pcr results demonstrating relative mrna expression of adenosine receptor subtypes in a human eye sample without amd. blue bars display mrna expression for each receptor in the retina, and orange bars display mrna expression for each receptor in the choroid. adora1 and adora2b showed significantly higher levels in the retina, while adora2a and adora3 showed significantly higher levels in the choroid. *p < 0.05, n = 3. table 1. list of primers. gene forward (5’ to 3’) reverse (5’ to 3’) adora1 gtccggtcctcatcctcac ccaccatcttgtaccggaga adora2a cacaccactctccctagactctc ttcctcacacttacatttttcctg adora2b cactgcttataatgctggtgatcta gggtggtcctcgagtggt adora3 cccaattatatctcccccact aagtcaggcctccaaaacact rpl13a aagcggatgaacaccaacc tgtggggcagcatacctc successful staining with each of the adenosine receptor antibodies. furthermore, vascular staining with collagen iv antibody and nuclear staining with dapi were performed for each of the samples. adenosine receptor a1 demonstrated expression throughout the retina. a1 expression was particularly prominent in the outer plexiform layer (opl), inner photoreceptor layer, and inner plexiform layer (ipl) of the retina. retinal pigment epithelium (rpe) was also positive. no noticeable differences in choroidal vascular or retinal expression of the a1 were appreciated between patients with amd compared to control patients regardless of sex. representative images of a1 receptor staining in the retina and choroid are shown in figure 1. receptor a2a primarily demonstrated expression within the retinal and choroidal vasculature, with a modest expression within the outer (onl) and inner nuclear layers (inls). the expression of the a2a was also detected in the rpe and was similar in patients with amd compared to control eyes. however, there did appear to be a modest decrease in a2a receptor expression in retinal and choroidal vasculature in samples from patients with wet and dry amd. there did not appear to be a dramatic difference in receptor a2a expression between patients with wet amd compared with dry amd [figure 2]. receptor a2b demonstrated expression throughout the retina in all samples, particularly the ganglion cell layer, onl, and inl, and rpe. receptor a2b was also strongly expressed in the retinal and choroidal vasculature in all samples. however, there was no dramatic difference in a2b receptor staining in the retina, retinal vasculature, or choroidal vasculature of patients with amd compared with control eyes. representative images of retinal and choroidal staining with antibodies to the a2b receptor are shown in figure 3. receptor a3 was expressed primarily within the ganglion cell layer, inl, and onl of the retina, and rpe. there was also some a3 receptor expression in the retinal and choroidal vasculature of each sample. a dramatic differences in a3 staining was observed in dry amd samples compared with control and wet amd samples. the dry amd samples lost the expression of a3 receptor in the photoreceptor outer segments, which was prominently present in control and wet amd samples. however, no additional differences in the intensity of staining were observed in retina or choroid in patients with amd compared 56 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 adenosine receptors in donor eyes with armd; goebel et al to those with no amd. representative images of a3 receptor staining are shown in figure 4. adenosine receptors mrna expression in retina and rpe/choroid tissues quantitative pcr of cdna prepared from the retinal and choroidal/rpe tissues from normal human eyes demonstrated notable expression of adenosine receptors within both the retina and choroid. adenosine receptor a1 displayed gene expression primarily within the retina, with little to no choroidal expression. this was consistent with predominant immunostaining of a1 receptor in ipl and opl, where microglia are normally residing. we previously showed predominant expression of a1 receptor in mouse microglia and retinal vascular cells.[19] receptors a2a, a2b, and a3 displayed gene expression within both the retina and choroid. although a1 receptor expression was significantly lower, the expression of a2a and a3 were significantly higher in the choroid/rpe compared with the retina, as we previously reported in human and mouse tissue samples.[19] the average relative expression of each adenosine receptor in both the retina and choroid/rpe is shown in figure 5. discussion the role of adenosine receptors in inflammatory pathways, as well as prior clinical and preclinical studies of their antagonism with caffeine suggest that these receptors may play important roles in the development of neurodegenerative diseases such as amd. however, previous literature has not sufficiently examined the distribution of the adenosine receptor subtypes in the human retina and choroid. furthermore, this is the first study to compare the expression patterns of adenosine receptors in the eyes of patients with and without amd. collectively, our qpcr and antibody staining experiments demonstrated that adenosine receptors are widely expressed throughout the human eye and are present within both the human retina and choroid. antibody staining suggested that receptors a1, a2a, a2b, and a3 are widely expressed in multiple layers of the human retina, providing further support for the importance of these receptors in the human ocular homeostasis and pathophysiology of amd. a recent study involving zebrafish studied the expression of all four adenosine receptor subtypes, reporting a2a and a2b receptors in both the inner and outer plexiform and nuclear layers, and the ganglion cell layer.[20] our results demonstrated similar distribution of the a2b receptors throughout the retina, but we primarily observed the a2a receptors expressed within the vasculature. much like our results, a3 receptors were primarily in the inner and onls and a1 receptors were primarily in the inner and opls.[20] therefore, our results indicate some overlap with the preclinical models mapping the expression of adenosine receptors in the retina, but we did find differences in human retinal expression compared to animal models. prior human studies have examined the location of adenosine a1 receptors in the retina of humans and other mammals. like our results, these studies demonstrated a1 expression in both the inner and outer retina, with expression in the inner plexiform, ganglion cell, inner nuclear, and photoreceptor layers.[21, 22] a separate study demonstrated the presence of a2 receptors within the human rpe but did not attempt to map the a2 receptors throughout the retina.[23] in addition to the human neuroretina, receptors a2a, a2b, and a3 were strongly expressed within the retinal and choroidal vasculature. studies have suggested that the loss of the inner choroidal vascular layer is associated with the development of amd and likely to occur due to inflammation within the choroid.[24] our observation of adenosine receptors within the choroidal vasculature and their involvement in inflammation suggests they may also have a role in hallmark amd changes within the choroid. we hypothesized that altered a2a expression in patients with wet and dry amd could contribute to pathophysiology of amd. prior studies have suggested that a2a receptor stimulation is proinflammatory, and antagonism of the a2a receptor can prevent neovascularization in the retina.[13–15] interestingly, our results suggest there may be a modest decrease in the expression of the a2a receptor in patients with amd disease process, which requires further verification in future studies. therefore, a change in the a2a receptor levels in the human retina and choroid may disrupt normal signaling in the eye potentially contributing to pathogenesis of amd. a previous study in our lab examined the effect of caffeine, an adenosine receptors antagonist, and istradefylline, a specific a2a receptor antagonist, on choroidal neovascularization after laser-induced rupture of bruch’s membrane. these studies demonstrated that antagonism of adenosine receptors, particularly a2a, was successful in journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 57 adenosine receptors in donor eyes with armd; goebel et al inhibiting choroidal neovascularization. we also demonstrated that caffeine inhibits the migration of retinal and choroidal endothelial cells.[19] thus, the results of the current study suggesting that the a2a receptor may have altered expression in human eyes with amd fits well with prior findings. together these results suggest a potential role for adenosine receptor antagonism in preventing changes associated with amd. in our previous study we noted variable and limited expression of a3 receptor in retina and choroid/rpe tissues from mouse eyes.[19] however, here we noted significant expression of a3 receptor in human eye sections with predominant expression in the choroid/rpe. the immune staining of the eye sections from dry amd patients lacked a3 staining in the photoreceptor outer segments, which was predominantly present in eye sections from control and wet amd patients. thus, downregulation of a3 receptor expression may specifically contribute to loss of photoreceptor cells in dry amd and awaits future studies of its significance in pathophysiology of dry amd. overall, this study suggests that adenosine receptors are present throughout the retina and choroidal vasculature and supports the potential role of adenosine as a key signaling molecule and inflammatory mediator in pathophysiology of amd. furthermore, there may be changes in the levels of adenosine receptor a2a and a3 expression in patients who have amd. however, the number of samples evaluated here were limited and awaits further confirmation of these results using additional samples in future studies as more suitable samples become available. we propose it is possible that the adenosine receptors contribute to the development of both wet and dry amd and are suitable candidates to be targeted in the ongoing search for amd therapeutics in future studies. ethical considerations the human eyes were obtained from lions gift of sight (formerly known as minnesota lions eye bank, saint paul, mn) with the written consent of the donor or the donor’s family for use in medical research in accordance with the declaration of helsinki. lions gift of sight is licensed by the eye bank association of america (accreditation #0015204) and accredited by the fda (fda established identifier 3000718528). donor tissue is considered pathological specimens and is therefore exempt from the process of institutional review board approval. acknowledgements the authors would like to thank the lion gift of sight (st. paul, mn) personnel for obtaining the eyes and preparing the tissues for immunostaining. they are also thankful to the donors and their families for their valuable contributions to the research. financial support and sponsorship this work and/or the investigator(s) were supported by an unrestricted award from research to prevent blindness to the department of ophthalmology and visual sciences, retina research foundation, rrf/daniel m. albert chair, and by national institutes of health grants p30 ey016665, r01 ey026078, ey030076, ey032543, and hl158073. cpg was recipient of a vitreoretinal surgery foundation research award, edina, mn. conflicts of interest the authors declare no conflict of interest. references 1. klein r, chou cf, klein be, zhang x, meuer sm, saaddine jb. prevalence of age-related macular degeneration in the us population. arch ophthalmol 2011;129:75–80. 2. bhutto i, lutty g. understanding age-related macular degeneration (amd): relationships between the photoreceptor/retinal pigment epithelium/bruch’s membrane/choriocapillaris complex. mol aspects med 2012;33:295–317. 3. hernandez-zimbron lf, zamora-alvarado r, ochoa-de la paz l, velez-montoya r, zenteno e, gulias-canizo r, et al. age-related macular degeneration: new paradigms for treatment and management of amd. oxid med cell longev 2018;2018:8374647. 4. martin df, maguire mg, ying gs, grunwald je, fine sl, jaffe gj. ranibizumab and bevacizumab for neovascular age-related macular degeneration. n engl j med 2011;364:1897–1908. 5. handa jt, bowes rickman c, dick ad, gorin mb, miller jw, toth ca, et al. a systems biology approach towards understanding and treating non-neovascular age-related macular degeneration. nat commun 2019;10:3347. 6. jabbehdari s, handa jt. oxidative stress as a therapeutic target for the prevention and treatment of early agerelated macular degeneration. surv ophthalmol 2020. 7. jager rd, mieler wf, miller jw. age-related macular degeneration. n engl j med 2008;358:2606–2617. 8. hollyfield jg, bonilha vl, rayborn me, yang x, shadrach kg, lu l, et al. oxidative damage-induced inflammation initiates age-related macular degeneration. nat med 2008;14:194–198. 58 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 adenosine receptors in donor eyes with armd; goebel et al 9. sakurai e, anand a, ambati bk, van rooijen n, ambati j. macrophage depletion inhibits experimental choroidal neovascularization. invest ophthalmol vis sci 2003;44:3578–3585. 10. nozaki m, raisler bj, sakurai e, sarma jv, barnum sr, lambris jd, et al. drusen complement components c3a and c5a promote choroidal neovascularization. proc natl acad sci u s a. 2006;103:2328–2333. 11. auchampach ja. adenosine receptors and angiogenesis. circ res 2007;101:1075–1077. 12. effendi wi, nagano t, kobayashi k, nishimura y. focusing on adenosine receptors as a potential targeted therapy in human diseases. cells 2020;9:785. 13. madeira mh, rashid k, ambrosio af, santiago ar, langmann t. blockade of microglial adenosine a2a receptor impacts inflammatory mechanisms, reduces arpe-19 cell dysfunction and prevents photoreceptor loss in vitro. scientific reports 2018;8:2272. 14. aherne cm, kewley em, eltzschig hk. the resurgence of a2b adenosine receptor signaling. biochim biophys acta 2011;1808:1329–1339. 15. merighi s, borea pa, stefanelli a, bencivenni s, castillo ca, varani k, et al. a2a and a2b adenosine receptors affect hif-1alpha signaling in activated primary microglial cells. glia 2015;63:1933–1952. 16. daly jw, shi d, nikodijevic o, jacobson ka. the role of adenosine receptors in the central action of caffeine. pharmacopsychoecologia 1994;7:201–213. 17. maugeri g, d’amico ag, rasà dm, la cognata v, saccone s, federico c, et al. caffeine prevents blood retinal barrier damage in a model, in vitro, of diabetic macular edema. j cell biochem 2017;118:2371–2379. 18. chen jf, zhang s, zhou r, lin z, cai x, lin j, et al. adenosine receptors and caffeine in retinopathy of prematurity. mol aspects med 2017;55:118–125. 19. sorenson cm, song y-s, zaitoun is, wang s, hanna ba, darjatmoko sr, et al. caffeine inhibits choroidal neovascularization through mitigation of inflammatory and angiogenesis activities. front cell dev biol 2021;9:737426. 20. grillo sl, mcdevitt ds, voas mg, khan as, grillo ma, stella sl, jr. adenosine receptor expression in the adult zebrafish retina. purinergic signal 2019;15:327–342. 21. blazynski c, perez mt. adenosine in vertebrate retina: localization, receptor characterization, and function. cell mol neurobiol 1991;11:463–484. 22. braas km, zarbin ma, snyder sh. endogenous adenosine and adenosine receptors localized to ganglion cells of the retina. proc natl acad sci u s a 1987;84:3906–3910. 23. friedman z, hackett sf, linden j, campochiaro pa. human retinal pigment epithelial cells in culture possess a2-adenosine receptors. brain res 1989;492:29–35. 24. farazdaghi mk, ebrahimi kb. role of the choroid in age-related macular degeneration: a current review. j ophthalmic vis res 2019;14:78–87. journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 59 original article optical coherence tomography angiography findings after acute intraocular pressure elevation in patients with diabetes mellitus versus healthy subjects maryam ashraf khorasani1, md; giancarlo a garcia2, md; pasha anvari1, md, mph; abbas habibi1, md; shahriar ghasemizadeh1, bs; khalil ghasemi falavarjani1,3, md 1eye research center, the five senses institute, iran university of medical sciences, tehran, iran 2byers eye institute at stanford university, palo alto, ca, usa 3stem cell and regenerative medicine research center, iran university of medical sciences, tehran, iran orcid: ashraf khorasani: https://orcid.org/0000-0003-2046-5633 khalil ghasemi falavarjani: https://orcid.org/0000-0001-5221-1844 abstract purpose: to assess the changes in optic nerve head and macular microvascular networks after acute intraocular pressure (iop) rise in healthy eyes versus the eyes of diabetic patients. methods: in this prospective, interventional, comparative study, 24 eyes of 24 adults including 12 eyes of healthy nondiabetic subjects and 12 eyes with mild or moderate non-proliferative diabetic retinopathy (npdr) were enrolled. iop elevation was induced by a suction cup attached to the conjunctiva. iop and optical coherence tomography angiographic (octa) images of the optic disc and macula were obtained before and immediately after the iop rise. results: baseline and post-suction iops were not significantly different between the two groups (all p > 0.05). the mean iop elevation was 13.93 ± 3.41 mmhg among all eyes and was statistically significant as compared to the baseline in both groups (both p < 0.05). after iop elevation, healthy eyes demonstrated a reduction in the vessel density in the whole image deep and superficial capillary plexuses and parafoveal deep capillary plexus (dcp) (all p < 0.05). in diabetic retinopathy, foveal vessel density at dcp decreased significantly following iop rise (p = 0.003). in both groups, inside disc vessel density decreased significantly after iop rise (both p < 0.05), however, no significant change was observed in peripapillary vessel density (both p > 0.05). conclusion: acute rise of iop may induce different levels of microvascular changes in healthy and diabetic eyes. optic disc microvasculature originating from the posterior ciliary artery may be more susceptible to iop elevation than that of retinal microvasculature. keywords: diabetic retinopathy; glaucoma; intraocular pressure; macula; ocular blood flow; ocular perfusion; optic nerve; optical coherence tomography angiography; retinal imaging; vessel density this paper was presented in part in 7𝑡ℎ oct and octa meeting, rome, december 2019. j ophthalmic vis res 2022; 17 (3): 360–367 360 © 2022 ashraf khorasani et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i3.11573&domain=pdf&date_stamp=2019-07-17 octa findings after acute iop elevation; ashraf khorasani et al introduction glaucoma is a major cause of irreversible vision loss and one of the leading causes of blindness worldwide.[1, 2] several studies have demonstrated that structural changes that occur in the retina and optic nerve in glaucoma are preceded by functional disorders.[3–10] the exact mechanism by which glaucoma leads to structural changes has not yet been well understood. both mechanical and vascular theories have been proposed to describe the pathogenesis of glaucoma-induced structural changes, though neither of these theories alone is sufficient to fully explain the disease mechanism. in both theories, however, increased intraocular pressure (iop) plays an important role.[11, 12] the mechanical theory proposes that increased iop compresses intraocular structures and attenuates axoplasmic flow leading to glaucomatous changes. in the vascular theory, it is believed that impaired blood supply leads to structural damages.[12–14] the latter theory is supported by findings that link systemic hypotension to increased risk of glaucomatous optic neuropathy. autoregulation is a mechanism that, despite the changes in ocular perfusion pressure (opp), maintains a relatively constant level of ocular blood flow (obf) and provides sufficient oxygen and nutrients for the cells.[15] opp is expressed as the difference between the arterial blood pressure and the iop. accordingly, a reduction in blood pressure or an increase in iop leads to a reduction of opp. in normal eyes, autoregulation compensates for these changes, and blood flow to the eye remains constant. if, however, autoregulation is impaired, or iop surpasses a threshold and the eye is unable to compensate, obf becomes unstable; in this correspondence to: khalil ghasemi falavarjani, md. eye research center, rassoul akram hospital, sattarkhan-niaiesh st., tehran 1449614535, iran. e-mail: drghasemi@yahoo.com received: 09-03-2021 accepted: 28-12-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i3.11573 context, small changes in iop lead to changes in obf that can induce glaucomatous changes.[16–19] dysfunctional ocular autoregulation that plays an important role in the development and progression of glaucoma occurs in diabetic patients as well.[18, 19] the pathophysiology of diabetes mellitus also involves dysfunctional vascular regulation, where the disease is believed to share an association with glaucoma, although a definitive link has not been established.[18, 19] various modalities have been utilized to asses obf changes after acute iop rise, including doppler sonography,[20, 21] laser interferometry,[20, 22] and laser doppler flowmetry.[21, 22] however, these methods are limited by their invasive nature and inability to record all retinal vascular layers simultaneously. optical coherence tomography angiography (octa), on the other hand, is a noninvasive technology that enables the visualization of blood vessels in different layers of the retina and choroid without dye injection.[23] this modality employs consecutive optical coherence tomography (oct) b-scans captured from the same location, comparing the decorrelation signal between scans to identify blood vessels and map blood flow.[24] previous studies have shown that octa is a reliable imaging modality for the diagnosis of different retinal, choroidal, and optic nerve diseases.[25–27] we herein utilized octa to assess changes in the optic nerve head, the macular vasculature, as well as retinal thickness following acute iop rise, and compared these changes in the eyes of healthy versus diabetic subjects. to the best of our knowledge, this is the first study assessing changes in the optic nerve head and macular vasculature as well as the retinal thickness around the optic disc and in the macular area following the acute rise of iop in normal versus diabetic subjects. this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: khorasani ma, garcia ga, anvari p, habibi a, ghasemizadeh s, falavarjani kg. optical coherence tomography angiography findings after acute intraocular pressure elevation in patients with diabetes mellitus versus healthy subjects. j ophthalmic vis res 2022;17:360–367. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 361 https://knepublishing.com/index.php/jovr octa findings after acute iop elevation; ashraf khorasani et al methods this prospective interventional comparative study was conducted at the ophthalmology clinic of the rassoul akram hospital, iran university of medical sciences. participants were enrolled between the periods of september and december 2018. the ethics committee of the iran university of medical sciences approved the study protocol (ir.iums.rec.1398.200). informed consent was obtained from the patients, and the study was conducted in accordance with the tenets of the helsinki declaration. in this study, nondiabetic healthy subjects with no ocular disorders and patients with mild or moderate non-proliferative diabetic retinopathy (npdr group) were included. all participants underwent a standard baseline comprehensive ophthalmic examination that included the snellen best-corrected visual acuity (bcva) measurements, iop measurements using a rebound tonometer (icare ic100, icare®, vantaa, finland), slit-lamp examination, and dilated fundus examination. all included eyes had to have an iop of <22mmhg and spherical equivalent refraction between –6 and +4 diopters. healthy eyes had a bcva of 20/20 or better with normal comprehensive ocular examinations. inclusion criteria for the npdr group were type 2 diabetics who were taking only oral antidiabetic medications, with clinical evidence of mild or moderate npdr in both eyes according to the early treatment of diabetic retinopathy study (etdrs) grading criteria.[28] exclusion criteria were any media opacity (e.g., cataract or vitreous hemorrhage) that might interfere with imaging, eyes with an oct scan quality of <7, and a history of any ocular surgery or ocular laser treatment. image acquisition and elevation of iop octa imaging was performed by a rtvue xr avanti device (version 2017.1.0.151, optovue, inc., fremont, ca, usa). baseline octa images included macular (3× 3) and optic disc (4.5 × 4.5) scans in the same session. iop was recorded using an icare device at baseline. the procedure for inducing iop elevation has been described elsewhere.[29] in brief, after achieving topical anesthesia using tetracaine 0.5% ophthalmic solution, the episcleral suction cup was attached to the temporal conjunctiva to apply negative pressure to the globe. immediately after the application of the suction cup, iop was recorded again while the suction cup was stable and the imaging was repeated with the same macular and optic disc protocols, with the suction cup in place. a drop of artificial tears was administered before post-suction measurements to avoid dry eye-induced image distortion. a minimum increase of 5 mmhg in iop was needed to proceed to postsuction image acquisition. if there was slippage of the suction cup, all measurements were postponed to another day. the parameters extracted included retinal vessel density at fovea and parafovea in the deep capillary plexus (dcp) and at the superficial capillary plexus (scp) layers. the scp en face image was automatically segmented with an inner boundary set at the internal limiting membrane (ilm) and an outer boundary set at 9 µm above the inner plexiform layer (ipl). the dcp en face image was segmented with an inner boundary set at 9 µm above the ipl and an outer boundary at 9 µm below the outer plexiform layer (opl). peripapillary and inside disc vessel density measurements were automatically recorded from the ilm to the lower border of the nerve fiber layer. from the angiodisc images, the peripapillary retinal nerve fiber layer (rnfl) thickness as well as the vessel density of the peripapillary and inside disc regions were recorded. “inside disc vessel density” was defined as the percentage of vessels inside the borders of the optic disc that was automatically determined by the octa software. peripapillary vessel density was calculated for the 750 µm wide ring-shaped area that is located circumferentially around the periphery of the optic disc margins. statistical analysis the spss software version 18.0 (spss, inc., chicago, il, usa) and medcalc software version 19 (medcalcsoftware, mariakerke, belgium) were utilized for statistical analysis. p-values < 0.05 were considered statistically significant. all continuous variables were expressed as mean ± standard deviation (sd). paired samples t-test was utilized to compare variables before and after the iop rise. the general linear model was used to adjust for differences in age and baseline vessel density measurements. 362 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 octa findings after acute iop elevation; ashraf khorasani et al table 1. baseline characteristics in the two groups. healthy eyes npdr eyes 𝑃-value number of eyes 12 12 age (years) 40.00 ± 11.38 56.17 ± 12.11 0.03 intraocular pressure (mmhg) 15.28 ± 2.95 17.34 ± 3.29 0.121 whole image scp vessel density (%) 47.47 ± 2.29 39.84 ± 5.38 <0.001 foveal scp vessel density (%) 18.22 ± 5.25 11.10 ± 5.09 0.003 parafoveal scp vessel density (%) 50.22 ± 2.50 41.97 ± 6.22 0.001 whole image dcp vessel density (%) 49.50 ± 2.72 45.06 ± 5.02 0.016 foveal dcp vessel density (%) 32.92 ± 6.53 25.21 ± 8.18 0.018 parafoveal dcp vessel density (%) 51.32 ± 2.64 47.23 ±5.16 0.026 whole image disc vessel density (%) 50.70± 1.22 48.46± 3.22 0.041 peripapillary vessel density (%) 53.64 ± 1.27 51.03 ± 4.09 0.055 inside disc vessel density (%) 49.97 ± 2.68 48.04 ± 3.48 0.142 peripapillary rnfl thickness (µm) 114.92 ± 12.39 105.08 ± 12.59 0.067 the data is presented as mean ± sd. scp, superficial capillary plexus; dcp, deep capillary plexus; rnfl, retinal nerve fiber layer; dm, diabetes mellitus; npdr, nonproliferative diabetic retinopathy table 2. baseline and post-suction values in healthy eyes. baseline post-suction p-value iop (mmhg) 15.28 ± 2.95 28.52 ± 3.33 <0.001 whole image scp vessel density (%) 47.47 ± 2.29 45.86 ± 2.54 0.015 foveal scp vessel density 18.22 ± 5.25 17.67 ± 5.29 0.336 parafoveal scp vessel density (%) 50.22 ± 2.50 48.75 ± 2.54 0.050 whole image dcp vessel density (%) 49.50 ± 2.72 47.22 ± 3.78 0.005 foveal dcp vessel density 32.92 ± 6.53 33.06 ± 6.49 0.745 parafoveal dcp vessel density (%) 51.32 ± 2.64 49.46 ± 3.70 0.010 whole image disc density (%) 50.70± 1.22 49.67 ± 2.43 0.081 peripapillary vessel density (%) 53.64 ± 1.27 53.12 ± 2.63 0.365 inside disc vessel density (%) 49.97 ± 2.68 47.46 ± 4.15 0.017 peripapillary rnfl thickness (µm) 114.92 ± 12.39 114.83 ± 11.91 0.862 iop, intraocular pressure; scp, superficial capillary plexus; dcp, deep capillary plexus; rnfl, retinal nerve fiber layer results in this study, 24 eyes (12 healthy eyes and 12 eyes with npdr) of 24 adult patients were included. baseline characteristics are shown in table 1. the mean age was 40.00 ± 11.38 and 56.17 ± 12.11 years in healthy and npdr eyes, respectively (p = 0.03). the baseline iop was 15.28 ± 2.95 mmhg and 17.34 ± 3.29 mmhg in healthy and npdr eyes, respectively (p = 0.121). at baseline, the retinal vessel density for whole image, foveal and parafoveal scp and dcp was significantly lower in the npdr group as compared to the healthy eyes (all p < 0.05). while vascular density of the whole optic nerve head was significantly lower in eyes with npdr as compared to the normal eyes (p = 0.041), journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 363 octa findings after acute iop elevation; ashraf khorasani et al table 3. baseline and post-suction measurements in eyes with nonproliferative diabetic retinopathy. baseline post-vacuum p-value iop (mmhg) 17.34 ± 3.29 31.96 ± 5.30 <0.001 whole image scp vessel density (%) 39.84 ± 5.38 38.64 ± 5.95 0.133 foveal scp vessel density 11.10 ± 5.09 10.52± 5.37 0.134 parafoveal scp vessel density (%) 41.97 ± 6.22 40.85 ± 6.79 0.179 whole image dcp vessel density (%) 45.06 ± 5.02 43.87 ± 3.62 0.226 foveal dcp vessel density 25.21 ± 8.18 24.25 ± 7.93 0.003 parafoveal dcp vessel density (%) 47.23 ±5.16 46.28 ± 3.64 0.313 whole image disc density (%) 48.46± 3.22 47.74 ± 2.66 0.233 peripapillary vessel density (%) 51.03 ± 4.09 51.12 ± 3.01 0.901 inside disc vessel density (%) 48.04 ± 3.48 44.35 ± 3.77 0.007 peripapillary rnfl thickness (µm) 105.08 ± 12.59 103.33 ± 12.31 0.005 iop, intraocular pressure; scp, superficial capillary plexus; dcp, deep capillary plexus; rnfl, retinal nerve fiber layer table 4. comparison of the measurement changes between healthy eyes and eyes with nonproliferative diabetic retinopathy after acute rise of intraocular pressure after adjustment for age. group 1 (healthy eyes) group 2 (npdr) p-value∗ iop (mmhg) 13.24 ± 3.97 14.62 ± 2.73 0.243 whole image scp vessel density (%) –1.62 ± 1.93 –1.20 ± 2.56 0.642 foveal scp vessel density –0.56 ± 1.92 –0.57 ± 1.23 0.774 parafoveal scp vessel density (%) –1.47 ± 2.31 –1.12 ± 2.71 0.767 whole image dcp vessel density (%) –2.27 ± 2.22 –1.20 ± 3.24 0.332 foveal dcp vessel density 0.14 ± 1.47 -0.96 ± 0.85 0.155 parafoveal dcp vessel density (%) –1.87 ± 2.08 –0.95± 3.11 0.966 whole image disc density (%) –1.03 ± 1.86 –0.72 ± 1.96 0.202 peripapillary vessel density (%) 0.52 ± 1.92 0.08 ± 2.27 0.143 inside disc vessel density (%) –2.51 ± 3.09 –3.69 ± 3.90 0.298 peripapillary rnfl thickness (µm) –0.08 ± 1.62 –1.75 ± 1.71 0.011 scp, superficial capillary plexus; dcp, deep capillary plexus; rnfl, retinal nerve fiber layer; dm, diabetes mellitus; npdr, nonproliferative diabetic retinopathy ∗p-value adjusted for age and baseline vessel density measurements using general linear model. there were no statistically significant differences in the peripapillary and inside disc vessel densitie between the two groups. the mean increase in iop after scleral suction was 13.24 mmhg in healthy eyes (range, 6.60– 19.40) and 14.62 mmhg in npdr eyes (range, 11.0– 19.90), corresponding to a mean of 13.93 ± 3.41 mmhg among all eyes. a post-suction increase of >9 mmhg was experienced by 90% of the healthy eyes, and in 100% of the npdr eyes. post-suction change in iop had no statistically significant differences between the two groups (p = 0.243). tables 2–3 display octa measurements after acute elevation in iop. after the iop rise in the healthy eyes, vessel density in the whole image of the scp and dcp, and parafoveal dcp was statistically significantly lower as compared to the baseline (all p < 0.05). in addition, the inside disc 364 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 octa findings after acute iop elevation; ashraf khorasani et al vessel density was significantly lower as compared to baseline measurements (p = 0.017). in the npdr group, foveal vessel density at dcp, inside disc vessel density, and peripapillary rnfl thickness decreased significantly after iop rise (p = 0.003, 0.007, and 0.005, respectively) [table 3]. comparison of the changes after acute iop rise between the two groups is presented in table 4. considering the differences between the mean ages between the two groups, the comparison was statistically adjusted for the age. none of the measurement changes showed statistically significant differences between the two groups after adjusting for baseline age, except for the peripapillary rnfl thickness (p = 0.011). discussion in this study, we evaluated the changes in macular and optic disc microvasculature after acute iop elevation and compared the differences in the eyes of patients without diabetes versus the eyes of diabetics with npdr. statistically significant changes in the scp, dcp, and the inside disc vascular density were observed after acute rise of iop in the healthy eyes. in the diabetic eyes, however, inside disc vessel density and foveal vessel density at dcp were the only octa parameters that changed significantly after iop elevation. peripapillary rnfl thickness also decreased significantly in patients with diabetic retinopathy following the iop rise. our findings suggest that the optic disc perfusion as shown by the inside disc vessel density is impaired after an acute iop elevation of approximately 13 mmhg in healthy and diabetic eyes. however, peripapillary vessel density did not change significantly after an iop rise. the microvascular perfusion inside the optic disc originates mainly from the posterior ciliary artery, while the central retinal artery supplies the nerve fiber layer.[27] this shows that the microvascular perfusion originating from choriocapillaris may be more susceptible to damage after acute iop elevation than the occurrence of retinal microvasculature. we observed a decrease in macular perfusion after an iop rise that was more prominent in the healthy eyes than in the eyes of diabetics. nagel and vilser reported a paradoxical response in the size of the veins and arteries after acute elevation of iop in the healthy eyes.[30] the arterial diameter increased by +1.9% and the venous vessel diameter decreased by –2.6%. therefore, the net consequence of these changes in the vascular caliber may explain the decrease in vessel density observed in our healthy eyes. the vascular wall in diabetic patients is stiffer, and thus less responsive to the acute rise of iop.[31] our study findings correlate with the discoveries of prior studies that suggest that dysfunctional obf autoregulation may be of importance in the development and progression of glaucoma which may also occur in diabetic individuals.[18, 19] our analyses were also notable for highlighting variations in octa indices in eyes with and without diabetic retinopathy before iop elevation. as expected, at baseline, eyes with npdr tended to demonstrate lower capillary density and flow in many octa indices as compared to eyes without retinopathy.[23, 32] several studies have evaluated the octa measurements of the optic disc and/or macula after iop elevation. zhang et al[33] did not observe any statistically significant change in optic disc or macular perfusion after moderate iop elevation (mean iop rise of 9.6 ± 4.2 mmhg) induced by the dark room prone provocative test (drppt) in 40 eyes who were suspected of acute primary angle closure, suggesting efficacy of retinal blood flow autoregulation in response to moderate iop rise. however, only individuals suspected of angle closure who experienced iop rise in response to drppt were enrolled in this study, thus their results may not be generalizable to other subjects. similarly, ma and colleagues[34] found no significant change in either the macular or papillary region perfusion following laser peripheral iridectomy (lpi) in subjects with a 10–20 mmhg iop rise. however, in people with iop elevation >20 mmhg, optic disc and macular perfusion decreased significantly, suggesting a threshold at which autoregulatory mechanisms fail to maintain retinal blood flow. their study was limited to a subgroup of subjects with occludable angles. in addition, lpi might have adversely affected the image quality and therefore subsequent vessel density measurements.[35] wen et al[36] investigated optic disc perfusion immediately after the administration of intravitreal anti-vegf injections and found a significant reduction in optic disc vessel density. similarly, in a study by barsash et al[37], both macular and papillary vessel densities decreased following the administration of intravitreal anti-vegf injections. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 365 octa findings after acute iop elevation; ashraf khorasani et al the superficial macular perfusion was affected more severely as compared to the other regions. in both of these studies, the occurrence of altered image quality[35] after intravitreal injections and including patients with different macular pathology (diabetic macular edema or age-related macular degeneration) were the major shortcomings. in contrast to previously mentioned studies, our study had the advantage of enrolling normal subjects as well as diabetic patients with npdr. this study has several limitations. the sample size was small, and icare rebound tonometry was used instead of applanation tonometry which is considered gold standard for iop measurements. however, this limitation may have been mitigated as the same standardized method was used to measure iop in all eyes both before and after iop elevation, as comparisons of iop between eyes were all drawn from measurements by the same device. in addition, iop elevation may not be the same after repetition of the suction procedure. higher levels of iop changes may affect the microvascular network differently. we also performed a single iop measurement after applying the suction and did not check the postsuction iop to determine probable iop changes. it is recommended that the clinical significance of the observed changes in microvasculature and retinal structure be explored further. future analyses with larger sample sizes are warranted. in summary, the results of our study show that retinal microvasculature in diabetics and healthy eyes respond differently to the acute elevation of iop. this study provides preliminary insight into changes in octa-measured indices after acute iop elevation, as well as into the potential disturbances in autoregulation that may occur in eyes with and without diabetic retinopathy. as glaucoma and diabetes are highly prevalent causes of vision loss worldwide and are commonly comorbid in patients, a fundamental understanding of potential pathophysiologic similarities is essential. whether these findings may be applicable to chronic elevation of iop, as is experienced in the majority of subtypes of glaucoma, remains to be determined. financial support and sponsorship none. conflicts of interest none declared. references 1. tham yc, li x, wong ty, quigley ha, aung t, cheng cy. global prevalence of glaucoma and projections of glaucoma burden through 2040: a systematic review and meta-analysis. ophthalmology 2014;121:2081–2090. 2. cook c, foster p. epidemiology of glaucoma: what’s new? can j ophthalmol 2012;47:223–226. 3. tatham aj, medeiros fa. detecting structural progression in glaucoma with optical coherence tomography. ophthalmology 2017;124:s57–s65. 4. zhang x, dastiridou a, francis ba, tan o, varma r, greenfield ds, et al. comparison of glaucoma progression detection by optical coherence tomography and visual field. am j ophthalmol 2017;184:63–74. 5. wollstein g, kagemann l, bilonick ra, ishikawa h, folio ls, gabriele ml, et al. retinal nerve fibre layer and visual function loss in glaucoma: the tipping point. br j ophthalmol 2012;96:47–52. 6. zhang x, dastiridou a, francis ba, tan o, varma r, greenfield ds, et al. baseline fourier-domain optical coherence tomography structural risk factors for visual field progression in the advanced imaging for glaucoma study. am j ophthalmol 2016;172:94–103. 7. sehi m, bhardwaj n, chung ys, greenfield ds; advanced imaging for glaucoma study group. evaluation of baseline structural factors for predicting glaucomatous visualfield progression using optical coherence tomography, scanning laser polarimetry and confocal scanning laser ophthalmoscopy. eye 2012;26:1527–1535. 8. el beltagi ta, bowd c, boden c, amini p, sample pa, zangwill lm, et al. retinal nerve fiber layer thickness measured with optical coherence tomography is related to visual function in glaucomatous eyes. ophthalmology 2003;110:2185–2191. 9. yalvac is, altunsoy m, cansever s, satana b, eksioglu u, duman s. the correlation between visual field defects and focal nerve fiber layer thickness measured with optical coherence tomography in the evaluation of glaucoma. j glaucoma 2009;18:53–61. 10. wollstein g, schuman js, price ll, aydin a, stark pc, hertzmark e, et al. optical coherence tomography longitudinal evaluation of retinal nerve fiber layer thickness in glaucoma. arch ophthalmol 2005;123:464– 470. 11. flammer j, orgül s, costa vp, orzalesi n, krieglstein gk, serra lm, et al. the impact of ocular blood flow in glaucoma. prog retin eye res 2002;21:359–393. 12. chan kk, tang f, tham cc, young al, cheung cy. retinal vasculature in glaucoma: a review. bmj open ophthalmol 2017;1:e000032. 13. wirostko b, ehrlich r, harris a. the vascular theory in glaucoma. glaucoma today [internet]. 2009 april. available from: https://glaucomatoday.com/articles/2009apr/gt0409_05-php 366 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 octa findings after acute iop elevation; ashraf khorasani et al 14. ahmad ss. controversies in the vascular theory of glaucomatous optic nerve degeneration. taiwan j ophthalmol 2016;6:182–186. 15. flammer j, mozaffarieh m. autoregulation, a balancing act between supply and demand. can j ophthalmol 2008;43:317–321. 16. hayreh ss. blood flow in the optic nerve head and factors that may influence it. prog retin eye res 2001;20:595– 624. 17. cherecheanu ap, garhofer g, schmidl d, werkmeister r, schmetterer l. ocular perfusion pressure and ocular blood flow in glaucoma. curr opin pharmacol 2013;13:36–42. 18. gerber al, harris a, siesky b, lee e, schaab tj, huck a, et al. vascular dysfunction in diabetes and glaucoma: a complex relationship reviewed. j glaucoma 2015;24:474– 479. 19. siesky ba, harris a, amireskandari a, tan o, sadda sr, srinivas s, et al. ocular blood flow autoregulation compromised in glaucoma patients with diabetes. invest ophthalmol vis sci 2014;55. 20. findl o, strenn k, wolzt m, menapace r, vass c, eichler hg, et al. effects of changes in intraocular pressure on human ocular haemodynamics. curr eye res 1997;16:1024–1029. 21. conway ml, wevill m, benavente-perez a, hosking sl. ocular blood-flow hemodynamics before and after application of a laser in situ keratomileusis ring. j cataract refract surg 2010;36:268–272. 22. weigert g, findl o, luksch a, rainer g, kiss b, vass c, et al. effects of moderate changes in intraocular pressure on ocular hemodynamics in patients with primary openangle glaucoma and healthy controls. ophthalmology 2005;112:1337–1342. 23. de carlo te, chin at, bonini filho ma, adhi m, branchini l, salz da, et al. detection of microvascular changes in eyes of patients with diabetes but not clinical diabetic retinopathy using optical coherence tomography angiography. retina 2015;35:2364–2370. 24. de carlo te, romano a, waheed nk, duker js. a review of optical coherence tomography angiography (octa). int j retina vitreous 2015;1:5. 25. falavarjani kg, sarraf d. optical coherence tomography angiography of the retina and choroid; current applications and future directions. j curr ophthalmol 2017;29:1–4. 26. khadamy j, abri aghdam k, falavarjani kg. an update on optical coherence tomography angiography in diabetic retinopathy. j ophthalmic vis res 2018;13:487–497. 27. akil h, falavarjani kg, sadda sr, sadun aa. optical coherence tomography angiography of the optic disc; an overview. j ophthalmic vis res 2017;12:98–105. 28. group et. grading diabetic retinopathy from stereoscopic color fundus photographs—an extension of the modified airlie house classification. ophthalmology 1991;98:786– 806. 29. harris a, joos k, kay m, evans d, shetty r, sponsel we, et al. acute iop elevation with scleral suction: effects on retrobulbar haemodynamics. br j ophthalmol 1996;80:1055–1059. 30. nagel e, vilser w. autoregulative behavior of retinal arteries and veins during changes of perfusion pressure: a clinical study. graefes arch clin exp ophthalmol 2004;242:13–17. 31. garhöfer g, zawinka c, resch h, kothy p, schmetterer l, dorner gt. reduced response of retinal vessel diameters to flicker stimulation in patients with diabetes. br j ophthalmol 2004;88:887–891. 32. thompson ia, durrani ak, patel s. optical coherence tomography angiography characteristics in diabetic patients without clinical diabetic retinopathy. eye 2019;33:648–652. 33. zhang q, jonas jb, wang q, chan sy, xu l, wei wb, et al. optical coherence tomography angiography vessel density changes after acute intraocular pressure elevation. sci rep 2018;8:6024. 34. ma zw, qiu wh, zhou dn, yang wh, pan xf, chen h. changes in vessel density of the patients with narrow antenior chamber after an acute intraocular pressure elevation observed by oct angiography. bmc ophthalmol 2019;19:132. 35. al-sheikh m, ghasemi falavarjani k, akil h, sadda sr. impact of image quality on oct angiography based quantitative measurements. int j retina vitreous 2017;3:13. 36. wen jc, chen cl, rezaei ka, chao jr, vemulakonda a, luttrell i, et al. optic nerve head perfusion before and after intravitreal antivascular growth factor injections using optical coherence tomography-based microangiography. j glaucoma 2019;28:188–193. 37. barash a, chui ty, garcia p, rosen rb. acute macular and peripapillary angiographic changes with intravitreal injections. retina 2019;40:648–656. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 367 original article structural and functional outcomes of surgery for lamellar macular holes with or without epimacular proliferations ramesh venkatesh, ms; arpitha pereira, do, dnb; kushagra jain, ms; naresh kumar yadav, do, fmrf department of retina-vitreous, narayana nethralaya eye hospital, rajaji nagar, benguluru, india orcid: ramesh venkatesh: https://orcid.org/0000-0002-4479-9390 abstract purpose: to compare the clinical, optical coherence tomography (oct) features, and surgical outcomes of lamellar macular hole (lmh) depending on the presence of epimacular membrane proliferation (empf). methods: this retrospective chart review included 112 eyes with lmh. the patients were divided into two groups depending on the presence of empf. group 1 had lmh without empf and group 2 had lmh with empf. the best-corrected visual acuity was recorded and oct scans were obtained. results: lamellar macular hole without and with empf was noted in 62 (55%) and 50 (45%) eyes, respectively. the presence of empf was associated with lower presenting visual acuity (p = 0.049), wider lmh size at the largest diameter on the horizontal scan (p = 0.001), thinner residual retinal tissue (p =<0.0001), and larger is-os defects (p =<0.0001) as compared to the non-empf group. of the 112 eyes, 18 eyes underwent surgery for lmh. seven eyes had empf and the remaining eleven did not have empf. the average follow-up time for patients post-surgery and under observation was 16.8 and 24.1 weeks, respectively. a significant improvement in visual acuity was noted in the operated eyes with no empf as compared to the eyes with empf (p = 0.008). worsening visual acuity (p = 0.021) was noted in eyes with lmh associated with empf which did not undergo surgery. eyes with lmh and no empf, which were not operated on showed a minimal negative change in visual acuity. conclusion: lmh with empf showed a higher association with accompanying ellipsoid zone disruption. better anatomical and functional outcomes were achieved in those eyes that underwent surgery for lmh with no presence of empf and ellipsoid zone defect. keywords: epimacular membrane proliferation; full-thickness macular hole; lamellar hole epithelial proliferation; lamellar macular hole; surgery j ophthalmic vis res 2022; 17 (1): 42–50 42 © 2022 venkatesh r. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10169&domain=pdf&date_stamp=2019-07-17 surgery for lamellar mh; venkatesh r introduction epimacular membrane proliferation (empf) was previously described as a “thick” epiretinal membrane (erm) by witkin et al in 2006, “dense non-tractional membrane” by parolini et al in 2011, and then more commonly as the lamellar hole epithelial proliferation (lhep) by pang and associates in 2014.[1–3] this different type of erm seen in cases of lamellar macular holes (lmh) on high-resolution optical coherence tomography (oct) was identified as a homogenous mass of medium reflectivity lying over the retinal surface.[3] in 2015, schumann et al renamed this phenomenon as “atypical epiretinal tissue”, because it occurred in conditions other than lmh, such as in a full-thickness macular hole (ftmh) condition.[4] the commonly accepted hypothesis for the formation of lmh is that it arises from the erm contraction, which then results in a tear in the inner retinal layers.[2, 5] during clinical examination, empf is identified as a yellow elastic jelly lying over the epiretinal surface and commonly associated with a thick non-contractile erm. its yellowish color is likely due to the xanthophyll pigment identified in histological analysis.[2, 6] despite the absence of a clear mechanism for empf formation, the most likely theory is that it results from the migration of the retinal muller glial cell.[3] the association of the empf with higher rates of ellipsoid disruption and positivity to pan-keratin created another theory of the retinal pigment epithelial origin of the disease.[4, 7–10] it has been reported that patients with empf tend to have lower baseline visual acuities, greater external mh diameters, thinner residual retinal tissue, and higher rates of inner segment-outer segment (is-os) band disruption when compared to non-empf eyes.[4, 7, 9] visual acuity in eyes with lmh varies from having baseline normal vision to correspondence to: ramesh venkatesh, ms. vitreo retina consultant, narayana nethralaya eye hospital, 121/c, chord road, 1st ’r’ block, rajaji nagar, benguluru 560010, india. email: vramesh80@yahoo.com received 05-12-2019; accepted 22-11-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10169 having lower visual acuities depending upon the integrity of the ellipsoid zone. a wide variety of anatomic and visual outcomes has been reported after the performance of vitrectomy for macular holes with and without empf presence. marques et al reported no differences in visual performance or closure rates between the empf group and non-empf group after surgery or in the subset of patients who did not undergo treatment.[11] one paper reported a significantly poor visual outcome for patients with lmh and empf after surgery,[6] while another study showed an increase in area of empf and a decline in the visual function in eyes who were managed conservatively.[12] the majority of retinal specialists in the indian subcontinent tend to manage the cases of lmh conservatively either because of underlying ellipsoid layer integrity, better presenting visual acuity, or associated poor visual prognosis. given the variable characteristics in the physical and structural properties of empf, there are no clear guidelines currently available regarding patient selection and timing of surgery in such eyes with lmhs. in addition, to the best of our knowledge, there is no reported literature from the indian subcontinent describing this clinical entity in these eyes or discussing the treatment outcomes either from surgery or through conservative management. in this report, we intend to analyze the morphological changes and visual outcomes of the lmh cases that presented with empf, and describe the surgical outcomes. by comparing the clinical and surgical data from the lmh cases with and without empf, we intend to appreciate and understand better the significance of this unique epimacular proliferation. the objective of this study is also to make the readers aware of this clinical entity in clinical/oct examinations and to encourage them to understand the relevance and impact it can have on the final outcome of the disease. methods this study was approved by narayana nethralaya institutional review board and ethics committee this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: venkatesh r, pereira a, jain k, yadav nk. structural and functional outcomes of surgery for lamellar macular holes with or without epimacular proliferations. j ophthalmic vis res 2022;17:42–50. journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 43 https://knepublishing.com/index.php/jovr surgery for lamellar mh; venkatesh r (c-2019/01/003). this retrospective study was conducted at the retina clinic of a tertiary eye hospital in southern india. in this study, a single observer (rv) reviewed the sd-oct images acquired by the spectralis, heidelberg machine, which were saved in the folders labelled as lamellar macular hole and epiretinal membrane between the january 2011 and december 2018. the diagnosis of lmh was based on the updated criteria proposed by the international vitreomacular traction study group.[13] according to the group, lmh is a non-full-thickness retinal defect seen at the macula. this defect is characterized by the presence of the following features on the sd-oct: (1) an irregular foveal contour; (2) inner foveal defect; (3) intraretinal splitting, typically between the outer plexiform and outer nuclear layers; and (4) presence of a photoreceptor layer at the base of the hole. the oct images were viewed to identify the presence or absence of empf in these eyes. empf was identified on the oct imaging as a homogenous material of medium reflectivity arising from the outer retinal layers, crawling along the walls of the macular hole and lying on the epiretinal surface. the eyes were categorized into two groups for further analysis: (1) lmh with no empf and (2) lmh with empf. demographic data records included age, gender, laterality, and snellen visual acuity (va) at presentation. features on oct which were recorded included presence of lmh, empf, is-os defect, and erm. the macular hole size in lmh was measured as the widest horizontal diameter at the level of the middle retinal layers at the foveal center. the length of the is-os defect and thickness of residual retinal tissue in lmh were manually measured at the fovea using the calipers provided with the software. the lmhs observed on the oct were further divided into tractional or degenerative types based on the classification proposed by govetto et al.[14] the tractional type was characterized by the schitic separation of neurosensory retina between outer plexiform and outer nuclear layers with an intact ellipsoid layer and was associated with tractional epiretinal membranes and/or vitreomacular traction at the fovea. the degenerative type was characterized by the presence of intraretinal cavitation, non-tractional epiretinal proliferation, a retinal ”bump” and with an early ellipsoidal zone defect. in addition, other documented data included treatment and outcome of surgery for the lmh, postoperative va, and anatomic status of the macular hole. the indications to operate in the lmh group were visual acuity < 6/12, patient who complained of metamorphopsia and had a presence of an epiretinal membrane. in the present study, we looked at patients with a minimum followup of eight weeks following surgery to analyze the outcomes. successful macular hole closure was defined as the collapse of the excavation between the outer nuclear and outer plexiform layers while achieving a normal foveal contour. surgical technique all the surgeries were performed by a single surgeon (nky). a three-port 23or 25-gauge pars plana vitrectomy was performed. after core vitrectomy, intravitreal triamcinolone acetonide was injected to stain the posterior cortical vitreous and the posterior vitreous detachment was then induced. in cases where epimacular membrane was present, removal was performed. care was taken to not forcibly peel the erm from the edge of the lmh. a vitrectomy cutter was used to trim and leave the adherent epiretinal tissue at the margin of the hole. an attempt was made to remove the empf that was lying over the internal limiting membrane (ilm). a 0.1–0.2 cc of brilliant blue green (bbg) dye was injected to stain the ilm to facilitate its removal from the macular area. if the erm was difficult to identify, bbg-assisted ilm peeling was done from outside the erm-covered area that was not stained. the erm was then removed along with the ilm. again, care was taken to not forcibly peel the erm/ilm from the edge of the hole. finally, air–fluid exchange was done and 15 % perfluoropropane (c3f8) or 20% sulphur hexafluoride (sf6) gas was used for an endotamponade procedure. a minimum of seven days of prone positioning was recommended. statistical analysis normal distribution of quantitative variables was checked using the kolmogorov–smirnov test. snellen’s vision data were converted to logarithm of minimum angle of resolution (logmar) vision for statistical analysis. categorical variables were labelled as numerical for easy analysis as in identification of the is-os defects, the erm, and 44 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 surgery for lamellar mh; venkatesh r the hole closures. value 1 indicated presence and value 0 absence of these findings. categorical variables between the two groups were compared using the chi-square test. the mann–whitney u-test was used to compare quantitative data between the two groups. correlations between the presence of empf and other variables were determined using the spearman correlation test. a correlation (r) value of 0 means no correlation between the two variables while values closer to –1 indicate strong negative correlation and values closer to +1 indicate strong positive correlation. for the analysis of surgical outcomes, the eyes were divided into two groups: (1) eyes with empf and (2) eyes without empf. wilcoxon signed-rank test was applied for the comparison of va changes in the two groups. all data were analyzed with graphpad prism software (version 8.1.1). p-values < 0.05 were considered statistically significant. results during the study period, a total of 112 eyes with lmhs were included. the number of eyes included in each group were: (1) group 1 – eyes with lmh and no empf (62, 55%); (2) group 2 – eyes with lmh and empf (50, 45%). the comparison of clinical and oct findings of patients with lamellar macular hole presenting with and without empf is described in table 1 and depicted in figure 1. tractional types of lmh were identified in 25 (22%) eyes, the degenerative types of lmh in 81 (72%) eyes, and mixed variety in 6 (6%) eyes. empf was most commonly seen with the degenerative type of lmh (45/50, 90%) followed by the mixed type (5/50, 10%). erm was absent in eight eyes with epmf and lmh. analysis of presence of empf with different oct features showed strong positive correlations with the presence (r = 0.742) and size (r = 0.743) of is-os defects while strong negative correlation was noted with thickness of the residual retinal tissue (r = –0.641) present within the mh [table 2]. moreover, 18 of the 112 (16%) cases with lmh were treated surgically using the pars plana vitrectomy procedure. the remainder of the cases were managed conservatively. of the 18 eyes which underwent surgery, 7 eyes had empf. table 3 compares the clinical and oct features of eyes with and without empf that were operated on. the width of the lmh (p = 0.027), size of the is-os defect (p = 0.002), and residual retinal tissue thickness (p = 0.000) showed statistically significant correlation between the two groups. the average follow-up period for patients post-surgery was 16.8 weeks. single surgery hole closure was achieved in 4 (57%) eyes and 11 (100%) eyes in cases with and without empf, respectively. of the remaining three eyes where surgical success was not achieved due to the development of a fullthickness macular hole, repeat surgery introducing a fluid-air exchange and silicone oil/intraocular gas tamponade was performed in all the eyes. in two eyes the hole closed while in one eye the hole remained open despite the second surgery. in the observation group, 43 of the 94 (46%) eyes, which were managed by observation, showed empf on the sd-oct scans. however, by the end of the final follow-up visit, an additional 16 eyes showed development of empf, thus increasing the number to 59 (63%) eyes for those who were managed conservatively. the average follow-up period for patients under observation was 24.1 weeks. the mean preoperative visual acuity in eyes with empf and without empf was 0.5 (20/63) and 0.592 (20/78) (p = 0.052), respectively. the eyes in the empf group showed a mean decrease of –0.312 logmar units (p = 0.797) in visual acuity following surgery while eyes in the non-empf group showed a mean of 0.272 logmar units’ improvement (p = 0.008) following surgery. by the end of the final follow-up visit, a significant decrease in visual acuity was noted in eyes with lmh and empf who were managed conservatively (p = 0.021). eyes with lmh and no empf who were managed conservatively showed a minimal worsening in visual acuity. changes in the visual acuity in the two groups before and after surgery is described in table 4. discussion the use of spectral domain oct has allowed us to visualize the presence of substantive material on the epiretinal surface in the lmh and the ftmh which we describe as empf or lhep as described by pang et al.[3] in this article, we studied the clinical and oct features and surgical outcomes of lmhs with and without empf. the findings in this study suggest that in lmhs, empf formation was accompanied by journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 45 surgery for lamellar mh; venkatesh r ellipsoid layer loss, a wider than normal macular hole diameter, deep retinal defects, and the presence of is-os defects in large-sized mhs. the erm was not present in all the cases of empf. the empf was yellowish in color and connected to the retinal tissue within the hole. taken together, these findings suggested that empf could be a secondary event following lmh formation and is usually accompanied with deep outer retina involvement. also, histological studies have shown absence of the inner retinal tissue within the epiretinal tissue.[2] many theories were proposed for the development of empf in lmh; however, none are conclusive.[3, 4, 10] the findings of this study reinforce an alternate theory for the empf formation. according to this theory, empf originates secondary to the defects in the ellipsoid zone which then allows the retinal pigment epithelial cells to migrate along the walls of the mh and then onto the retinal surface and finally leading to empf and erm formation. the prevalence of empf in lmh has ranged from 20.5% to 44% in previous studies.[3, 7, 8, 16] in our study, empf was noted in 44% of eyes with lmh. this is comparable to that observed with other studies. empf was seen more commonly with the degenerative variety of lmh (90%) as compared to the mixed or tractional variety. the presence of empf was associated with lower presenting visual acuity, larger mh size, thinner residual retinal tissue, and larger is-os defects before operation. as a result, the visual and anatomical outcomes following surgery in these eyes were significantly different from those with no empf. eyes with lmh with empf showed no visual acuity gain following surgery. also, successful anatomic closure of the mh was achieved in only four of the seven (57%) eyes following surgery compared to that of the non-empf group where the mh closed in all cases (100%). similar observations were also noted by choi et al and ko et al where the visual outcomes in lhep group was poorer as compared to the eyes with no lhep.[7, 16] however, lai et al reported no difference in the visual and anatomic outcomes between the lhep group and non-lhep group following surgery.[8] in their study, the largest mean diameter on the horizontal scan of the lmh in eyes with lhep (98.4 µ) was less than the eyes with no lhep (146.9 µ). while in our study, eyes with lmh with empf (1282 µ) had wider large mean diameters on the horizontal scan as compared to eyes with no empf (715 µ). also, the is-os defects were much larger in eyes with empf (808 µ) than in eyes with no empf (54.4 µ). this would explain the poor visual and anatomic outcomes following surgery in our study. the recommendations for the surgical repair of eyes with lmh remain controversial.[15, 16] while there have been reports with good surgical outcomes,[17, 18] there have also been reports that have advised caution with performing vitrectomy in these cases.[1, 2] in our series, only 18 of the 112 (16%) eyes with lmh underwent surgery. the rest of the eyes were managed conservatively through observation. in the observation group, 43 of the 94 (46%) eyes, which were managed by observation, showed empf on the sd-oct scans, this category further increased to 63% by the end of the final follow-up visit. thus, suggesting that solely observing such cases may lead to progression of the outer retinal defects and empf formation, ultimately leading to decrease in vision. consequently, we recommend surgery for eyes with lmh when visual acuity is 6/18 or less, there is the presence of epiretinal membrane causing retinal traction, presence of an intact ellipsoid zone, progression in the size of lmh on follow-up visits or progression to full-thickness within the macular hole. during surgery in cases that possess lmh with empf, it is recommended to peel the proliferative tissue while peeling the erm. the cellular composition of the empf may lead to the recurrence of the erm formation if not removed completely. however, aggressive peeling of the empf may lead to the conversion of the lmh to ftmh as seen in three cases in this study. care should be taken to not forcibly pull the erm from the edge of the hole. applying the least amount of traction as possible may theoretically reduce the possibility of retinal tissue damage or the formation of ftmh. in fact, a few studies have reported a high incidence of ftmh formation after the lhep was peeled in surgeries for lmh.[2, 3] shiraga et al recommended inversion of the pigment containing proliferative tissue into the lmh to facilitate normalization of the foveal contour;[21] however, we did not practice this technique in any of our cases. we did a conventional ilm peeling extending from arcade to arcade in all our cases with the intention of removing the cellular proliferative tissue where possible without much damage to the retina. in some cases, it is sometimes easier to start peeling 46 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 surgery for lamellar mh; venkatesh r figure 1. lamellar macular hole (lmh) with empf. (a) optical coherence tomography (oct) image of a patient with lmh in right eye showing the presence of epiretinal proliferative tissue at the margin of the hole (white arrow) with presence of ellipsoid zone defect (red star). (b) another oct scan passing through a different section acquired on the same day demonstrating the extension of the proliferative tissue (yellow arrow) from the ellipsoid zone defect (red star) and then crawling along the walls of the macular hole to lie over the retinal surface. table 1. clinical and optical coherence tomography findings of patients with and without empf in eyes with lmh variable lmh without empf (n = 62) lmh with empf (n = 50) p-value mean age (yr) 72.6 ± 8.25 69.9 ± 13.0 0.316# sex (m:f) 26:36 33:17 0.667# laterality (re:le) 35:27 31:19 0.667∗ mean presenting logmar va (snellen equivalent) 0.396 (20/50) 0.518 (20/66) 0.05# size of lmh (µm) 715 ± 305 986 ± 471 0.001# residual retinal thickness (µm) 144 ± 28.1 102 ± 33.7 <0.001# presence of is-os defect (n, %) 8 (13) 42 (84) >0.999∗ size of is-os defect (µm) 32.8 ± 101 401 ± 389 <0.001# presence of erm (n, %) 52 (84) 42 (84) 0.667∗ eyes undergoing surgery (n, %) 11 (18) 7 (14) 0.667∗ lmh, lamellar macular hole; empf, epimacular proliferative tissue; va, visual acuity; etdrs, early treatment diabetic retinopathy study; is–os, inner segment–outer segment; erm, epiretinal membrane #p-value calculated using the mann–whitney u-test; ∗p-value calculated using the chi-square test journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 47 surgery for lamellar mh; venkatesh r ta b le 2 .c or re la tio n of em pf w ith di ffe re nt cl in ic al an d o c t va ria bl es a g e s e x p re -o p lo g m a r v a t yp e o f lm h w id th o f lm h t h ic k n e ss o f re si d u a l re ti n a l ti ss u e is – o s d e fe ct s iz e o f th e is – o s d e fe ct e r m p o st o p lo g m a r v a lm h cl o su re em pf r va lu e –0 .14 5 –0 .2 43 –0 .2 57 0. 32 7 0. 23 3 –0 .6 41 0. 74 2 0. 74 3 –0 .0 82 –0 .6 41 –0 .6 65 p -v al ue # 0. 10 7 0. 0 07 0. 0 04 0. 0 0 0 0. 0 0 9 0. 0 0 0 0. 0 0 0 0. 0 0 0 0. 36 7 0. 0 0 1 0. 0 0 0 em pf ,e pi m ac ul ar pr ol ife ra tiv e tis su e; v a ,v is ua la cu ity ;l m h ,l am el la rm ac ul ar ho le ;i s– o s, in ne rs eg m en t– ou te rs eg m en t; er m ,e pi re tin al m em br an e # p -v al ue ca lc ul at ed us in g sp ea rm an ’c or re la tio n te st 48 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 surgery for lamellar mh; venkatesh r table 3. surgical outcomes in eyes with and without empf variable surgery in empf cases (n = 7) surgery without empf cases (n = 11) p-value pre-op mean logmar va (snellen equivalent) 0.5 (20/63) 0.592 (20/78) 0.052# mh width (µm) 1232 ± 528 795 ± 252 0.027# residual retinal thickness (µm) 82.1 ± 16.3 143 ± 30 0.0004# presence of is–os defect (n, %) 6(86) 2(18) 0.013∗ size of is–os defect (µm) 808 ± 757 54.4 ± 128 0.002# presence of erm (n, %) 6(86) 10(91) >0.999∗ hole closure achieved (n, %) 4(57) 11(100) 0.043∗ post op mean logmar va (snellen equivalent) 0.518 (20/130) 0.32 (20/42) 0.001# va, visual acuity; empf, epimacular proliferative tissue; mh, macular hole; is–os, inner segment–outer segment; erm, epiretinal membrane #p-value calculated using the mann–whitney u-test; ∗p-value calculated using the chi-square test table 4. visual acuity changes before and after surgery in eyes with and without empf mean pre-op logmar va (snellen equivalent) mean post-op logmar va (snellen equivalent) p-value# surgery in empf 0.5 (20/63) 0.812 (20/130) 0.797 surgery in no empf 0.592 (20/78) 0.32 (20/42) 0.008 empf, epimacular proliferative tissue; va, visual acuity; etdrs, early treatment diabetic retinopathy study; mh, macular hole #p-value calculated using the wilcoxon signed rank test by first engaging the ilm not occupied by the erm, and then removing the ilm along with the erm. our study has several clinical implications. our study suggests that surgery in eyes with lmh with empf have both poor anatomic and visual prognosis. intervention in eyes with lmh without empf/lhep and without ellipsoid zone disruption can have better visual and surgical prognosis. our study has the advantage of having an adequate number of eyes both with and without empf in lmhs for evaluation. the descriptive features of eyes with empf on oct confirms the outer retinal damage theory of empf origin. the study also describes the surgical outcomes of patients operated for lmh with empf. the most significant limitation of our study is its retrospective design in accessing pertinent data for evaluation. our study was further limited as there was only a single observer evaluating the oct scans, in addition, only a small number of eyes underwent surgery for management of lmh . extensive clinical and pathological studies may be required to complement our observations and to provide answers to the questions of the cellular origin of empf and the reason for its recurrence following surgery. from this study, we can conclude that empf in lmh has a poor visual prognosis when accompanied with ellipsoid zone disruption. better functional and anatomical outcomes can be achieved following surgery when lmh are not associated with empf and/or ellipsoid zone disruption. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. witkin aj, ko th, fujimoto jg, schuman js, baumal cr, rogers ah, et al. redefining lamellar holes and journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 49 surgery for lamellar mh; venkatesh r the vitreomacular interface: an ultrahigh-resolution optical coherence tomography study. ophthalmology 2006;113:388–397. 2. parolini b, schumann rg, cereda mg, haritoglou c, pertile g. lamellar macular hole: a clinicopathologic correlation of surgically excised epiretinal membranes. invest ophthalmol vis sci 2011;52:9074–9083. 3. pang ce, spaide rf, freund kb. epiretinal proliferation seen in association with lamellar macular holes: a distinct clinical entity. retina 2014;34:1513–1523. 4. schumann rg, compera d, schaumberger mm, wolf a, fazekas c, mayer wj, et al. epiretinal membrane characteristics correlate with photoreceptor layer defects in lamellar macular holes and macular pseudoholes. retina 2015;35:727–735. 5. gass jd. lamellar macular hole: a complication of cystoid macular edema after cataract extraction. arch ophthalmol 1976;94:793–800. 6. obana a, sasano h, okazaki s, otsuki y, seto t, gohto y. evidence of carotenoid in surgically removed lamellar hole-associated epiretinal proliferation. invest ophthalmol vis sci 2017;58:5157–5163. 7. choi ws, merlau dj, chang s. vitrectomy for macular disorders associated with lamellar macular hole epiretinal proliferation. retina 2018;38:664–669. 8. lai tt, chen sn, yang cm. epiretinal proliferation in lamellar macular holes and fullthickness macular holes: clinical and surgical findings. graefes arch clin exp ophthalmol 2016;254:629–638. 9. dell’omo r, virgili g, rizzo s, de turris s, coclite g, giorgio d, et al. role of lamellar hole-associated epiretinal proliferation in lamellar macular holes. am j ophthalmol 2017;175:16–29. 10. son g, lee js, lee s, sohn j. epiretinal proliferation associated with macular hole and intraoperative perifoveal crown phenomenon. korean j ophthalmol 2016;30:399– 409. 11. marques mf, rodrigues s, raimundo m, costa j, marques jp, alfaiate m, et al. epiretinal proliferations associated with lamellar macular holes: clinical and surgical implications. ophthalmologica 2018;240:8–13. 12. compera d, schumann rg, cereda mg, acquistapace a, lita v, priglinger sg, et al. progression of lamellar holeassociated epiretinal proliferation and retinal changes during long-term follow-up. br j ophthalmol 2018;102:84– 90. 13. duker js, kaiser pk, binder s, de smet md, gaudric a, reichel e, et al. the international vitreomacular traction study group classification of vitreomacular adhesion, traction, and macular hole. ophthalmology 2013;120:2611–2619. 14. govetto a, dacquay y, farajzadeh m, platner e, hirabayashi k, hosseini h, et al. lamellar macular hole: two distinct clinical entities? am j ophthalmol 2016;164:99–109. 15. ko j, kim ga, lee sc, lee j, koh hj, kim ss, et al. surgical outcomes of lamellar macular holes with and without lamellar hole-associated epiretinal proliferation. acta ophthalmol 2017;95:e221–e226. 16. kokame gt, tokuhara kg. surgical management of inner lamellar macular holes. ophthalmic surg lasers imaging 2010;41:418–424. 17. witkin aj, castro lc, reichel e, rogers ah, baumal cr, duker js, et al. anatomic and visual outcome of vitrectomy for lamellar macular holes. ophthalmic surg lasers imaging 2010;5:1–7. 18. garrettson br, pollack js, ruby aj, drenser ka, williams ga, sarrafizadeh r, et al. vitrectomy for a symptomatic lamellar macular hole. ophthalmology 2008;115:884–886. 19. sun jp, chen sn, chuang cc, lin cw, lin cj, huang jy, et al. surgical treatment of lamellar macular hole secondary to epiretinal membrane. graefes arch clin exp ophthalmol 2013;251:2681–2688. 20. ubukata y, imai h, otsuka k, nishizaki m, hara r, uenishi m, et al. the comparison of the surgical outcome for the full-thickness macular hole with/without lamellar hole-associated epiretinal proliferation. j ophthalmol 2017;2017:9640756. 21. shiraga f, takasu i, fukuda k, fujita t, yamashita a, hirooka k, et al. modified vitreous surgery for symptomatic lamellar macular hole with epiretinal membrane containing macular pigment. retina 2013;33:1263–1269. 50 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 editorial surgically managed orbital tumors: a case series from a referral center in iran arman mashayekhi, md ophthalmology department, mayo clinic, jacksonville, fl, usa orcid: arman mashyekhi: https://orcid.org/0000-0002-1739-1322 j ophthalmic vis res 2023; 18 (2): 141–142 the spectrum of orbital tumors is wide, including a variety of benign and malignant neoplasms. the reported incidence of different orbital tumors depends on several variables related to the geographic location of the study center and many other factors related to the type of study performed. the effect of geographic location is well illustrated by the reported incidence of orbital retinoblastoma. for example, in a study on pediatric orbital tumors from turkey, secondary orbital retinoblastoma accounted for 33% of cases, a rate much higher than that reported from more economically developed countries.[1] the selection criteria of the study affect the reported incidence of orbital tumors in many ways. whereas some studies include all clinically, radiographically, and pathologically diagnosed orbital space occupying tumors and pseudotumors,[2] others report only pathologically proven cases.[3] the age distribution of the included patients will have significant effects on the results of the study as the types of orbital tumors seen in children are drastically different from those reported in adults. in studies reported from the united states correspondence to: arman mashayekhi, md. ophthalmology department, mayo clinic, jacksonville, fl 32224, usa. email: mashayekhi.arman@mayo.edu received: 31-08-2022 accepted: 10-11-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i2.13178 on orbital tumors in children the most common tumors are benign cystic and vascular lesions but lymphoproliferative lesions are the most common tumors reported in older adults.[4–6] the characteristics of the reporting facility where the study was performed can also impact the results of the study. in a study from a large ocular oncology center, of the secondary orbital tumors, 29% were orbital extension of uveal melanoma and 13% were orbital extension of conjunctival melanoma.[2] majority of these patients were referred for treatment of the primary uveal or conjunctival melanoma and were found on further investigation to have orbital involvement. similarly, in another study from a comprehensive cancer center in the united states, the most common orbital tumors were found to be secondary tumors (26% of cases).[7] in this issue of the journal of ophthalmic and vision research, bagheri and coworkers report the results of a retrospective study on space-occupying lesions of the orbit from a referral ophthalmology center in tehran, iran.[8] their study includes orbital tumors that were managed over a 12-year period between 2008 and 2020 and had a definite histopathological diagnosis. this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: mashayekhi a. surgically managed orbital tumors: a case series from a referral center in iran. j ophthalmic vis res 2023;18:141–142. © 2023 mashayekhi . this is an open access article distributed under the creative commons attribution license | published by knowledge e 141 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i2.13178&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr editorial; mashayekhi the requirement for a histopathological diagnosis is both a strength and a limitation of this study. on the one hand, diagnosis of orbital space-occupying lesions based on histopathological evaluation is more accurate than that based on clinical and radiological studies alone. on the other hand, this requirement leads to exclusion of many orbital space-occupying lesions that do not undergo surgical resection. for instance, a small orbital tumor with radiological features consistent with a cavernous hemangioma incidentally discovered in an asymptomatic patient is more likely to be observed and therefore would not have been included in the study. in the study by shields and coworkers, only half of the presumed cavernous hemangiomas of the orbit underwent surgical removal.[2] the study by bagheri and coworkers includes patients of all ages, from 1 to 94 years, but is more skewed toward younger patients with a mean age of 31 years and with only 12% of the patients older than 60 years. it is therefore no surprise that dermoid cysts are the most common tumors in this study (one-third of all cases) and orbital lymphoma comprises only 4% of all the orbital tumors. in comparison, in the study by shields and coworkers, only 6% of the tumors were cystic and 10% were lymphoid or leukemic.[2] the geographic location of the medical center in which the patients were treated by dr bagheri and his coworkers, the capital city of tehran, could have affected the results of their study. although as a tertiary referral medical facility, the labbafinejad medical center provides medical care to patients from different parts of the country, it is quite likely that most of their patients were from tehran or surrounding areas where there is easier access to high-quality medical care. a noteworthy finding of the study by bagheri and coworkers is the absence of any cases of orbital invasion by retinoblastoma. although i am not aware of any older studies from iran, in an older study from turkey including patients seen between 1963 and 1993, about one-third of pediatric orbital tumors were secondary orbital invasion by retinoblastoma.[1] similarly, in a study that included patients managed in saudi arabia in the 1980s, 32% of pediatric orbital tumors proved to be orbital invasion of retinoblastoma.[9] a more recent study from a tertiary eye center in saudi arabia including pediatric patients managed between 2000 and 2013 does not show any cases of orbital retinoblastoma.[10] the absence of orbital invasion by retinoblastoma in the studies by bagheri and coworkers and by alkatan and coworkers most likely are due to improved medical care in the areas served by the respective treating medical facilities allowing timely diagnosis and treatment of retinoblastoma. the study by dr bagheri and his colleagues provides important information on the distribution of surgically resected orbital tumors in iran and the authors should be commended for their efforts. further studies on this subject from medical centers in other parts of the country are necessary to provide a more comprehensive view of the distribution of orbital tumors in the country. references 1. günalp i, gündüz k. pediatric orbital tumors in turkey. ophthalmic plast reconstr surg 1995;11:193–199. 2. shields ja, shields cl, scartozzi r. survey of 1264 patients with orbital tumors and simulating lesions: the 2002 montgomery lecture, part 1. ophthalmology 2004;111:997–1008. 3. montano n, lauretti l, d’alessandris qg, rigante m, pignotti f, olivi a, et al. orbital tumors: report of 70 surgically treated cases. world neurosurg 2018;119:e449– e458. 4. bullock jd, goldberg sh, rakes sm. orbital tumors in children. ophthalmic plast reconstr surg 1989;5:13–16. 5. castillo bv jr, kaufman l. pediatric tumors of the eye and orbit. pediatr clin north am 2003;50:149–172. 6. demirci h, shields cl, shields ja, honavar sg, mercado gj, tovilla jc. orbital tumors in the older adult population. ophthalmology 2002;109:243–248. 7. shinder r, al-zubidi n, esmaeli b. survey of orbital tumors at a comprehensive cancer center in the united states. head neck 2011;33:610–614. 8. bagheri a, ashtar-nakhaie p, aletaha m, kheiri b, veisi a. a survey on orbital space-occupying lesions during a twelveyear period from a referral center in iran. j ophthal vis res 2023;1. 9. johnson te, senft sh, nasr am, bergqvist g, cavender jc. pediatric orbital tumors in saudi arabia. orbit 1990;9:205– 215. 10. alkatan hm, al marek f, elkhamary s. demographics of pediatric orbital lesions: a tertiary eye center experience in saudi arabia. j epidemiol glob health 2019;9:3–10. 142 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 original article development of a spatio-temporal contrast sensitivity test for clinical use marcelo fernandes costa1,2, phd; leonardo dutra henriques1, phd; otávio côrrea pinho1, bpsy 1laboratório da visão, departamento de psicologia experimental, instituto de psicologia, universidade de são paulo, são paulo, brazil 2núcleo de neurociências aplicada, universidade de são paulo, são paulo, brazil orcid: marcelo fernandes costa: https://orcid.org/0000-0002-3944-8457 abstract purpose: we developed a contrast sensitivity test that considers an integrative approach of spatial and temporal frequencies to evaluate the psychophysical channels in processing two-dimensional stimulus for clinical use. our new procedure provides a more efficient isolation of the magnocellular and parvocellular visual pathways supporting spatiotemporal contrast sensitivity processing. methods: we evaluated 36 participants of both sexes aged 18–30 years with 20/20 or better best-corrected visual acuity. two spatial frequencies (0.5 cycles per degree [cpd] and 10 cpd), being in one of the three temporal frequencies (0.5 cycle per second [cps], 7.5 cps, and 15 cps), were presented in a highresolution gamma corrected monitor. a two-alternative forced-choice procedure was conducted, and the staircase method was used to calculate the contrast sensitivity. reliability was assessed using a retest procedure within a month (±5 days) under the same conditions. results: results showed statistical significance in 0.5 cpd and 10 cpd spatial frequencies for 0.5 cps (f = 77.36; p < 0.001), 7.5 cps (f = 778.37; p < 0.001), and 15 cps (f = 827.23; p < 0.001) with a very high (η2 = 0.89) effect size. no statistical differences were found between the first and second sessions for all spatial frequencies. for reliability, a significantly high correlation and high internal consistency were found in all spatiotemporal conditions. the limits were calculated for normality. conclusion: we developed an approach to investigate the spatiotemporal integration of contrast sensitivity designed for clinical purposes. the relative contribution of the low spatial frequencies/high temporal frequencies and the high spatial frequencies/low temporal frequencies of the psychophysical channels can also be evaluated separately. keywords: clinical psychophysics; drifting grating; dynamic contrast sensitivity; primary visual pathway; spatial vision j ophthalmic vis res 2022; 17 (1): 69–77 © 2022 costa et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 69 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10172&domain=pdf&date_stamp=2019-07-17 spatio-temporal contrast sensitivity test; costa et al introduction the evaluation of visual functions has improved in the last three decades with the development of visual tests for visual acuity (va),[1–6] contrast sensitivity (cs),[7–12] color vision (cv),[13–16] motion perception (mp),[17–20] and stereopsis (st),[21–26] among others. despite these developments and multiple studies showing that visual functions other than va provide diagnosis for subclinical and early impairments in visual function,[27–38] ophthalmology and visual sciences associated with optometry and orthoptic clinical practice have been preferentially using va as a measurement of visual function. the clear advantage of cs over va measurements is the more detailed description of spatial vision, since symptomatic changes can occur in cs with va within normal limits.[39, 40] further, the test for va is a measurement of the spatial separation function mediated by the parvocellular (pc) pathway, while cs measurements carry information mediated by the pc and magnocellular (mc) pathways.[41–45] since both pathways can be measured by a cs function, it is an obvious clinical test with more resources for diagnosis of visual impairments. clinical assessment of cs is mainly performed using charts such as pelli-robson and functional acuity contrast test (fact).[43, 46] both methodologies have significant limitations. the pelli-robson chart is based on a recognition va test; however, it has a fixed low spatial frequency in the overall chart, and the contrast steps are based on three letters, which could lead to a learning effect after only a few uses. another problem related to the pelli-robson chart is the need to read letters, which reduces testing potential for young children. the fact is composed of five correspondence to: marcelo fernandes costa, phd. departamento de psicologia experimental, instituto de psicologia, universidade de são paulo, av. prof. mello moraes, 1721 butantã, são paulo, sp 05508-030, brazil. e-mail: costamf@usp.br received 22-04-2020; accepted 11-03-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10172 spatial frequencies and nine contrast levels. one important problem is that almost all participants with normal vision can see the last contrast level for middle frequencies, inserting a roof effect to reduce the sensitivity of the test. they were unable to see more than half of the contrast levels for low and high spatial frequencies. furthermore, the suprathreshold contrast levels were also fixed, reducing the precision of sensitivity measurement. despite these problems, these methods have been successfully used to measure cs in clinical settings. some studies have proposed alternative methods to isolate the contribution of the pc and mc pathways for psychophysical measurements of cs with relative success.[47] however, they were designed to identify the psychophysical signature of the pc and mc pathways, and they took a long time to be completed (about one and a half hour), which made them unviable for clinical purposes. considering the above, we purposed a new cs test which intends to deal with chart measurement problems, and aimed to make the test user-friendly. the use of the same test for children and adults can make data comparable for development followups, including a dynamic variable that amplifies the differences between pc and mc pathways. the possibility of isolating visual pathways is mandatory because many ocular and cerebral diseases affect these pathways differently. our experience in the study of the traditional cs measurements in mercury,[30, 48–50] diabetes mellitus type 2,[51, 52] multiple sclerosis,[53] and leber’s ocular hereditary neuropathy[54–56] motivated us to develop a cs test with greater efficiency in isolating pc and mc pathways for clinical testing. methods participants we evaluated 36 participants (17 men and 19 women) with a best-corrected va of 20/20 or this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: costa mf, henriques ld, pinho oc. development of a spatio-temporal contrast sensitivity test for clinical use. j ophthalmic vis res 2022;17:69–77. 70 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 https://knepublishing.com/index.php/jovr spatio-temporal contrast sensitivity test; costa et al better, measured using the etdrs–tumbling e chart (xenônio rep. prod., são paulo, brazil). the exclusion criteria were absence of ophthalmologic complaints and/or diabetes mellitus, rheumatoid arthritis, systemic arterial hypertension, any other known systemic diseases, smokers, and the presence of dichromacy or anomalous trichromacy using the 38 plates version of the ishihara pseudoisochromatic plates (kanehara trade inc., tokyo, japan). the participants, aged between 18 and 30 years (m = 22.6; sd = 3.7) were undergraduate and graduate students of the institute of psychology of the university of são paulo. this study was approved by the local ethics committee via the approval number 66767317.5.0000.5561. all participants provided written consent for the inclusion of material about themselves and acknowledged that they could not be identified, as we ensured complete anonymity. the study followed the principles of the 1964 declaration of helsinki and its revised version. equipment and stimulus cs functions were also measured psychophysically with the software psycho for windows v2.36 (cambridge research) using a sony trinitron 19 in. (gfd-420). the monitor was driven by a cambridge research vsg 2/4 graphics board with a refresh rate of 100 hz non-interlaced and an 800 × 600 resolution. the stimuli used were horizontal sinusoidal gratings with an average luminance of 10 fl, that is, 34.4 cd/m², measured using an optical op200e photometer (cambridge research) and a visual angle of 4°. the luminance output of the screen was calibrated using a luminance meter (ls-110, konica minolta sensing, inc., osaka, japan). screen uniformity was checked at maximum output. the contrast of the sinusoidal grating is defined as a michelson contrast: 𝐶 = 𝐿max − 𝐿min 𝐿max + 𝐿min , where lmax is the maximum and lmin is the minimum luminance consisting of a dimensional value. gratings of 0.5 cycles per degree (cpd) and 10 cpd drifted rightward and leftward at temporal frequencies of 0.5, 7.5, and 15 cycles per second (cps). testing was conducted in a dark room with the participants positioned 1 m away from the video monitor. procedure participants were sat in a comfortable chair 1 m away from the monitor screen and were instructed to keep their eye fixed on a small black cross centered on the screen. head stabilization was not performed. ophthalmological patches (oftan, amp, são paulo, brazil) were used to cover one randomly chosen eye. at the beginning of the experiment, the participant was adapted to a gray mean luminance in the dark for 5 min. the stimulation consisted of a drifting grating with a randomly chosen spatial frequency presented by 1000 ms, followed by 3000 ms for the response in a two-alternative forced-choice (2-afc) procedure, pressing a specific keyboard key for the right (m) and left (z) based on their perception of the grating’s drifting side [figure 1]. a psychophysical staircase procedure with a dynamic step size was used to determine the threshold. the staircase began with a high contrast level (70 ± 10 randomly chosen), which changed the luminance to the mean luminance background. the change depended on the participant’s response: the grating contrast approached the background mean luminance every time there was a correct response and moved away from it when there was an incorrect response. the dynamic step consisted of a 50% reduction of the contrast level between the stimulus and background luminance. after the second reversal, the reduction changed to 12.5% between the stimulus level and background luminance. the contrast improvement always changed in increments of 25%. after seven staircase reversals, the program automatically calculated the contrast thresholds as the average luminance corresponding to the last five reversals. all testing procedures, including the adaptation time, lasted approximately 20 min. for all spatial frequencies, the contrast thresholds were converted to cs according to the following equation: 𝑆 = 1 𝐶𝑡 , where ct is the contrast threshold. to define the cs function, the cs for each spatial frequency was plotted. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 71 spatio-temporal contrast sensitivity test; costa et al 0.5hz/ 7.5hz/15hz 0.5hz/ 7.5hz/15hz 0.5hz/ 7.5hz/15hz 3,000ms 3,000ms motion direction rl figure 1. the illustrative timeline of the testing session. a spatial frequency randomly chosen was presented by 1 s, moving rightward or leftward in an also randomly chosen temporal frequency. the patient had up to 3 s to judge the movement of the grating in a two-afc procedure. test reliability was estimated by comparing cs measurements in a test–retest design. the retest of the cs measurements was performed in all participants with a mean interval of one month (±5 days) between the first and second measurements. the retests were also performed monocularly in the same eye and under the conditions of the first test. statistical analysis statistical analyses were performed using statistica v.6.0.4, (statsoft inc., tulsa, ok, usa, 2001). a complete descriptive analysis was performed. the normal distribution was checked by the shapiro– wilk and kolmogorov–smirnoff tests. a repeatedmeasures anova was used to evaluate the statistical differences between spatial frequencies, drift velocity, and test–retest conditions. the correlation was calculated using the pearson’s product moment correlation test. no significant differences (p < 0.05) were observed between the conditions. the effect size, which is a quantitative measure of the magnitude of the experiment effect, was assessed using cohen’s d classification, that is, d = 0.2 was considered a “small” effect size, d = 0.5 represented a “medium” effect size, d = 0.8 a “large” effect size, and d = 1.4 a “huge effect” size.[57] the interpretation of the effect size was that if the means of the two groups do not differ by 0.2 or more sd, the difference could be considered trivial, even if it is statistically significant. 72 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 spatio-temporal contrast sensitivity test; costa et al results all participants successfully completed both the first and second sessions. the cs measured in the first and second experimental sessions is described in detail in table 1. considering the spatial frequencies of the grating, statistically significant results were found between 0.5 cpd and 10 cpd for 0.5 cps (f = 77.36; p < 0.001), 7.5 cps (f = 778.37; p < 0.001), and 15 cps (f = 827.23; p < 0.001) in the first and second sessions. the calculated effect size was considered to be very high (η 2 = 0.89). no statistical difference was found between the first and second sessions for all spatial frequencies for 0.5 cps (f = 0.11; p = 0.73), 7.5 cps (f = 0.06; p = 0.93), and 15 cps (f = 0.24; p = 0.63). the results are shown in figure 2. reliability was assessed using pearson’s correlation, and the results are shown in figure 3. a significantly high correlation was found in 0.5 cpd for 0.5 cps (r = 0.988; p < 0.001), 7.5 cps (r = 0.919; p < 0.001), and 15 cps (r = 0.985; p < 0.001), and in 10 cpd for 0.5 cps (r = 0.989; p < 0.001), 7.5 cps (r = 0.972; p < 0.001), and 15 cps (r = 0.980; p < 0.001). internal consistency was assessed using cronbach’s alpha coefficient. a high internal consistency was obtained for 0.5 cpd (α = 0.8449) with high item-total correlation for 0.5 cps (r = 0.880), 7.5 cps (r = 0.836), and 15 cps (r = 0.894). similarly, a high item-total correlation was also observed for 10 cpd (α = 0.8963) to 0.5 cps (r = 0.997), 7.5 cps (r = 0.994), and 15 cps (r = 0.979). based on the tolerance limits, we calculated the boundaries of the cs normality range for clinical purposes. tolerance limits were calculated considering the mean value (x) and with a factor (k) multiplied by the standard deviation (sd).[58] the k factor can be chosen considering the percentage of the population covered (90%, 95%, or 99%) and the significance level of 0.90, 0.95, or 0.99, according to the number of participants. for our number of participants, we used the value 2.03, in which we covered 95% of the population with a pvalue of 0.95. the tolerance limits are presented in the rightmost columns of table 1. discussion clinical evaluation of cs has been improved in ophthalmological clinics[8, 9] and it is a good step forward in understanding the spatial vision of their patients, as va is a one-dimensional evaluation and cs is a two-dimensional test, since contrast is added to each spatial frequency measured. in our study, we included one more dimension by adding temporal modulation, which is a significant improvement, considering that objects in our visual environment are frequently moving. using this more complex approach to investigate spatial vision, we can potentially be able to help our patients more efficiently and conduct more informative studies about visual and ophthalmological diseases and about the visual impairment suffered. the robustness of our cs test was addressed by calculating the validity and reliability of the measurement. validity was assessed by measuring the pearson’s correlation coefficients of the first and second measurements. we had a high correlation coefficient for both low (0.5 cpd) and high (10 cpd) spatial frequencies, regardless of the temporal frequency used. since both the first and second measurements were highly correlated, this suggested that the influence of external variables had a low impact on the results obtained. further, the reliability was considered high, suggesting that the reliability of our test was strong. we also compared the mean contrast sensitivities of the first and second measurements. the absence of statistical significance in the same spatial frequencies compared to the first and second testing sessions and the statistical difference between the temporal frequencies within the first and the second testing sessions corroborate that our new cs test is robust. an additional advantage of our measurement is the possibility of isolating the mc and pc visual pathways that contribute to cs. using the amplitude of extracellular synaptic potential recordings for different michelson contrast levels, retinal cells that project to the mc layer of the lateral geniculate nucleus (lgn) showed a logarithmic curve, in which huge improvements in amplitude responses occurred with small contrast increments. for the retinal ganglion cells projecting to the pc layer of the lgn, a linear curve was modeled with a small increase in amplitude response with a moderate increase in contrast levels.[41] the psychophysical correlates of these visual pathways were obtained using a pedestal paradigm.[47] mcinferred responses were related to high temporal frequencies and pc-inferred responses related journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 73 spatio-temporal contrast sensitivity test; costa et al table 1. descriptive data from the first and second contrast sensitivity measurements spatial frequency first measurement second measurement 0.5 cps 7.5 cps 15 cps 0.5 cps 7.5 cps 15 cps 0.5 cpd 174.2 (32.5) 332.6 (78.6) 163.2 (37.4) 174.8 (32,2) 332.6 (56.9) 167.2 (33.4) 10 cpd 113.7 (43.7) 76.2 (25.4) 34.7 (7.8) 117.7 (41.3) 77.7 (25.9) 35.2 (6.9) cpd, cyle per degree; cps, cycle per second table 2. tolerance limits of contrast sensitivity for normality ranges spatial frequency tolerance limits 0.5 cps 7.5 cps 15 cps 0.5 cpd upper 240.3 492.2 239.1 lower 108.2 173 87.3 10 cpd upper 202.5 127.9 50.5 lower 24.8 24.6 18.8 cpd, cyle per degree; cps, cycle per second figure 2. the psychophysical cs signature for the low (0.5 cpd) and high (10 cpd) spatial frequency. (a) the mean and standard deviation of the spatiotemporal interaction. (b) the normality range to be used for clinical purposes. in both panels, it is evident that the middle and high temporal frequencies are more discriminable areas to isolate the mc and pc contribution in the cs. 74 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 spatio-temporal contrast sensitivity test; costa et al 100 150 200 250 300 350 400 450 500 100 150 200 250 300 350 400 450 500 100 150 200 250 300 350 400 450 500 100 150 200 250 300 350 400 450 500 100 150 200 250 300 350 400 450 500 100 150 200 250 300 350 400 450 500 20 40 60 80 100 120 140 160 180 200 20 40 60 80 100 120 140 160 180 200 20 40 60 80 100 120 140 160 180 200 20 40 60 80 100 120 140 160 180 200 20 40 60 80 100 120 140 160 180 200 20 40 60 80 100 120 140 160 180 200 1 st m e a su re m e n t (c s ) 2nd measurement (cs) 0.5cpd 10cpd 0.5cps 0.5cps 7.5cps 7.5cps 15cps 15cps figure 3. correlations between the first and second measurements for reliability purposes. a strong correlation is evident for both low and high spatial frequencies in all temporal frequencies. to low temporal frequencies. according to the spatial profile, low spatial frequencies were related to the mc-inferred pathway and the pc-inferred pathway related to high spatial frequencies.[45] the results obtained in our test are in line with earlier studies since the high spatial frequency with a low temporal modulation had better cs than the results for the middle or high temporal frequencies. on the other hand, better cs was obtained for the middle and high temporal modulations for low spatial frequencies. furthermore, we found a significantly different signature of cs spatiotemporal integration. for the low spatial frequency, there was a reduction in cs as the temporal frequency increased in an almost linear fashion. for the high spatial frequency, the curve had an inverted u-shape, in which there was an increase in cs as the temporal frequency increased from 0.5 to 7.5 hz and then, there was an inversion of the relation since the cs reduced as the temporal frequency increased from 7.5 to 15 hz. the different signatures of the mcand pc-cs measured psychophysically have two important implications. first, the test was successful in isolating the mc and pc contributions of the measured spatiotemporal cs. second, the difference in the cs shape has an important contribution for diagnostic purposes, adding resolution to the cs measurement. the isolation of mc and pc pathways has a huge clinical significance because many ophthalmological and neurological diseases affect these visual pathways differently. visual impairment related to reading problems in children with learning difficulties and dyslexia has been related to the reduction of cs at low spatial frequencies, suggesting an mc pathway failure.[32] mp, also an mc pathway function, is impaired in children with down’s syndrome[34] and strabismic amblyopia.[28, 59] we believe that our test improves the mcand pc-mediated cs measurements because it integrates spatial and temporal proprieties in one measurement. considering the significant clinical applications, we calculated the normality range for clinical purposes. of course, there are some restrictions on the use of normal ranges, as we calculated based on the age of our sample. for children and journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 75 spatio-temporal contrast sensitivity test; costa et al elderly patients, additional measurements should be performed in future studies. in summary, we developed a test to investigate the spatiotemporal integration of cs, designed for clinical purposes. the relative contribution of the low spatial frequencies/high temporal frequencies, and the high spatial frequencies/low temporal frequencies of the psychophysical channels can also be evaluated separately. the validation and replicability were highly successful, and tolerance limits were calculated to define the normality ranges. acknowledgments the authors would like to thank all the students at the psychology institute, university of são paulo, who voluntarily participated in the experiments. financial support and sponsorship this research was supported by grants from fapesp (projeto tematico # 2014/26818-2 to dora fix ventura and marcelo fernandes costa); cnpq #401153/2009-6 to m.f.c.; m.f.c. is cnpq research fellow. conflicts of interest the authors declare that they have no conflict of interest. references 1. ferris fl 3rd, kassoff a, bresnick gh, bailey i. new visual acuity charts for clinical research. am j ophthalmol 1982;94:91–96. 2. adoh to, woodhouse jm. the cardiff acuity test used for measuring visual acuity development in toddlers. vision res 1994;34:555–560. 3. bach m. the freiburg visual acuity test – variability unchanged by post-hoc re-analysis. graef arch clin exp 2007;245:965–971. 4. bastawrous a, rono hk, livingstone ia, weiss ha, jordan s, kuper h, et al. development and validation of a smartphone-based visual acuity test (peek acuity) for clinical practice and community-based fieldwork. jama ophthalmol 2015;133:930–937. 5. becker r, teichler g, graf m. comparison of visual acuity measured using landolt-c and etdrs charts in healthy subjects and patients with various eye diseases. klin monatsbl augenh 2011;228:864–867. 6. manny re, hussein m, gwiazda j, marsh-tootle w. repeatability of etdrs visual acuity in children. invest ophth vis sci 2003;44:3294–3300. 7. ginsburg ap. a new contrast sensitivity vision test chart. am j optom physiol opt 1984;61:403–407. 8. adams rj, mercer me, courage ml, vanhofvanduin j. a new technique to measure contrast sensitivity in human infants. optometry vision sci 1992;69:440–446. 9. alexander kr, mcanany jj. determinants of contrast sensitivity for the tumbling e and landolt c. optometry vision sci 2010;87:28–36. 10. alexander kr, xie w, derlacki dj. visual acuity and contrast sensitivity for individual sloan letters. vis res 1997;37:813–819. 11. choi aj, nivison-smith l, phu j, zangerl b, khuu sk, jones bw, et al. contrast sensitivity isocontours of the central visual field. sci rep 2019;9:11603. 12. dakin sc, turnbull pr. similar contrast sensitivity functions measured using psychophysics and optokinetic nystagmus. sci rep 2016;6:34514. 13. atchison da, bowman kj, vingrys aj. quantitative scoring methods for d15 panel tests in the diagnosis of congenital color-vision deficiencies. optometry vision sci 1991;68:41– 48. 14. bailey je, neitz m, tait dm, neitz j. evaluation of an updated hrr color vision test. visual neurosci 2004;21:431–436. 15. birch j. clinical use of the city university test (2nd edition). ophthalmic physiol opt 1997;17:466–472. 16. reffin jp, astell s, mollon jd. trials of a computercontrolled color-vision test that preserves the advantages of pseudoisochromatic plates. in: drum b, moreland jd, serra a, editors. colour vision deficiencies x. dordrecht: springer; 1991. 69–76 p. 17. armstrong v, maurer d, lewis tl. sensitivity to firstand second-order motion and form in children and adults. vis res 2009;49:2774–2781. 18. borghuis bg, tadin d, lankheet mjm, lappin js, van de grind wa. temporal limits of visual motion processing: psychophysics and neurophysiology. vision 2019;3:5. 19. hollants-gilhuijs ma, ruijter jm, spekreijse h. visual halffield development in children: detection of motion-defined forms. vis res 1998;38:651–657. 20. manny re, fern kd. motion coherence in infants. vis res 1990;30:1319–1329. 21. birch e, petrig b. fpl and vep measures of fusion, stereopsis and stereoacuity in normal infants. vis res 1996;36:1321–1327. 22. earle dc. perception of glass pattern structure with stereopsis. perception 1985;14:545–552. 23. langley k, fleet dj, hibbard pb. stereopsis from contrast envelopes. vis res 1999;39:2313–2324. 24. norman jf, norman hf, craft ae, walton cl, bartholomew an, burton cl, et al. stereopsis and aging. vis res 2008;48:2456–2465. 25. shea sl, fox r, aslin rn, dumais st. assessment of stereopsis in human infants. invest ophth vis sci 1980;19:1400–1404. 26. wilcox lm, harris jm, mckee sp. the role of binocular stereopsis in monoptic depth perception. vis res 2007;47:2367–2377. 27. costa m, oliveira a, santana c, ventura d, zatz m. redgreen color vision impairment in duchenne muscular dystrophy. neuromuscular disord 2007;17:815. 76 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 spatio-temporal contrast sensitivity test; costa et al 28. costa mf, cunha g, de oliveira marques jp, castelobranco m. strabismic amblyopia disrupts the hemispheric asymmetry for spatial stimuli in cortical visual processing. br j vis impair 2016;34:141–150. 29. costa mf, moreira sm, hamer rd, ventura df. effects of age and optical blur on real depth stereoacuity. ophthalmic physiol opt 2010;30:660–666. 30. costa mf, tomaz s, de souza jm, silveira lc, ventura df. electrophysiological evidence for impairment of contrast sensitivity in mercury vapor occupational intoxication. environ res 2008;107:132–138. 31. da costa mf, paranhos a, lottenberg cl, castro lc, ventura df. psychophysical measurements of luminance contrast sensitivity and color discrimination with transparent and blue-light filter intraocular lenses. ophthalmol ther 2017;6:301–312. 32. cormack fk, tovee m, ballard c. contrast sensitivity and visual acuity in patients with alzheimer’s disease. int j geriatr psychiatry 2000;15:614–620. 33. croningolomb a, sugiura r, corkin s, growdon jh. incomplete achromatopsia in alzheimers disease. neurobiol aging 1993;14:471–477. 34. del viva mm, tozzi a, bargagna s, cioni g. motion perception deficit in down syndrome. neuropsychologia 2015;75:214–220. 35. aaen-stockdale c, hess rf. the amblyopic deficit for global motion is spatial scale invariant. vis res 2008;48:1965–1971. 36. acheson jf, cassidy l, grunfeld ea, shallo-hoffman ja, bronstein am. elevated visual motion detection thresholds in adults with acquired ophthalmoplegia. br j ophthalmol 2001;85:1447–1449. 37. boets b, wouters j, van wieringen a, ghesquiere p. coherent motion detection in preschool children at family risk for dyslexia. vis res 2006;46:527–535. 38. ezzati a, khadjevand f, zandvakili a, abbassian a. higherlevel motion detection deficit in parkinson’s disease. brain res 2010;1320:143–151. 39. ginsburg ap. contrast sensitivity and functional vision. int ophthalmol clin 2003;43:5–15. 40. amesbury ec, schallhorn sc. contrast sensitivity and limits of vision. int ophthalmol clin 2003;43:31–42. 41. kaplan e, shapley rm. the primate retina contains two types of ganglion cells, with high and low contrast sensitivity. proc natl acad sci usa 1986;83:2755–2757. 42. keri s, benedek g. visual contrast sensitivity alterations in inferred magnocellular pathways and anomalous perceptual experiences in people at high-risk for psychosis. vis neurosci 2007;24:183–189. 43. pelli dg, bex p. measuring contrast sensitivity. vis res 2013;90:10–14. 44. alexander kr, barnes cs, fishman ga, pokorny j, smith vc. contrast sensitivity deficits in inferred magnocellular and parvocellular pathways in retinitis pigmentosa. invest ophthalmol vis sci 2004;45:4510–4519. 45. costa mf. clinical psychophysical assessment of the onand off-systems of the magnocellular and parvocellular visual pathways. neurosci med 2011;2:330–340. 46. onal s, yenice o, cakir s, temel a. fact contrast sensitivity as a diagnostic tool in glaucoma: fact contrast sensitivity in glaucoma. int ophthalmol 2008;28:407–412. 47. smith vc, sun vcw, pokorny j. pulse and steady-pedestal contrast discrimination: effect of spatial parameters. vis res 2001;41:2079–2088. 48. canto-pereira lhm, lago m, costa mf, rodrigues ar, saito ca, silveira lcl, et al. visual impairment on dentists related to occupational mercury exposure. environ toxicol pharmacol 2005;19:517–522. 49. feitosa-santana c, barboni mt, oiwa nn, paramei gv, simoes al, da costa mf, et al. irreversible color vision losses in patients with chronic mercury vapor intoxication. vis neurosci 2008;25:487–491. 50. ventura df, simoes al, tomaz s, costa mf, lago m, costa mtv, et al. colour vision and contrast sensitivity losses of mercury intoxicated industry workers in brazil. environ toxicol pharmacol 2005;19:523–529. 51. feitosa-santana c, oiwa nn, paramei gv, bimler d, costa mf, lago m, et al. color space distortions in patients with type 2 diabetes mellitus. vis neurosci 2006;23:663–668. 52. feitosa-santana c, paramei gv, nishi m, gualtieri m, costa mf, ventura df. color vision impairment in type 2 diabetes assessed by the d-15d test and the cambridge colour test. ophthalmic physiol opt 2010;30:717–723. 53. moura al, teixeira ra, oiwa nn, costa mf, feitosasantana c, callegaro d, et al. chromatic discrimination losses in multiple sclerosis patients with and without optic neuritis using the cambridge colour test. vis neurosci 2008;25:463–468. 54. gualtieri m, bandeira m, hamer rd, costa mf, oliveira ag, moura al, et al. psychophysical analysis of contrast processing segregated into magnocellular and parvocellular systems in asymptomatic carriers of 11778 leber’s hereditary optic neuropathy. vis neurosci 2008;25:469–474. 55. ventura df, gualtieri m, oliveira ag, costa mf, quiros p, sadun f, et al. male prevalence of acquired color vision defects in asymptomatic carriers of leber’s hereditary optic neuropathy. invest ophth vis sci 2007;48:2362– 2370. 56. ventura df, quiros p, carelli v, salomao sr, gualtieri m, oliveira ag, et al. chromatic and luminance contrast sensitivities in asymptomatic carriers from a large brazilian pedigree of 11778 leber hereditary optic neuropathy. invest ophth vis sci 2005;46:4809–4814. 57. cohen j. quantitative methods in psychology. psychol bull 1992;112:155–159. 58. dixon wj, massey fj. introduction to statistical analysis. 3rd ed. new york, ny: mcgraw-hill; 1969. 59. aaen-stockdale c, ledgeway t, hess rf. second-order optic flow deficits in amblyopia. invest ophth vis sci 2007;48:5532–5538. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 77 letter unvalidated cerebrospinal fluid pressure equations should not be used for research david fleischman1, md; hanspeter e. killer2, md 1department of ophthalmology, university of north carolina at chapel hill, chapel hill, north carolina, usa 2kantonsspital aarau, department of ophthalmology, aarau, switzerland orcid: david fleischman: https://orcid.org/0000-0002-1043-2021 j ophthalmic vis res 2022; 17 (4): 601–602 dear editor, we have found an unsettling trend of articles being published with the use of an unvalidated formula for estimating cerebrospinal fluid pressure. the study, “translaminar pressure difference and ocular perfusion pressure in glaucomatous eyes with different optic disc sizes’[1] by cruz and colleagues has a very intriguing hypothesis. however, the authors did not do their due diligence in confirming the origin of the estimation equation central to their investigation. they erroneously attributed the formula to xie et al’s study published in critical care, 2013.[2] biophysical parameters including, importantly, the anatomic marker of width of the orbital cerebrospinal fluid space, were used to devise their estimation equation. the equation utilized in cruz’s study, although found in other similarly flawed investigations, has not been validated. correspondence to: david fleischman, md, ms, facs. bioinformatics building #7040, department of ophthalmology, university of north carolina at chapel hill, chapel hill, north carolina 27599-7040, usa. e-mail: david8fleischman@gmail.com received: 11-08-2021 accepted: 01-02-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i4.12343 the use of estimation equations in general have been found to poorly represent csf pressure.[3] therefore, a parameter that is already exquisitely difficult to measure, perioptic subarachnoid space cerebrospinal fluid pressure, will be further confounded by using these faulty data. to substantiate the concept of the translaminar pressure gradient as a mechanism involved in the pathophysiology of glaucoma, we need robust data. flawed approximation of csf pressure is in no way helpful in advancing the science in glaucoma research. we obviously encourage further study into the relationship between cerebrospinal fluid and ophthalmic disease, but we must all be diligent to prevent further use of unvalidated methods infiltrating this field. financial support and sponsorship none. this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: fleischman d, killer he. unvalidated cerebrospinal fluid pressure equations should not be used for research. j ophthalmic vis res 2022;17:601–602. © 2022 fleischman & killer. this is an open access article distributed under the creative commons attribution license | published by knowledge e 601 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i4.12343&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr letter; fleischman & killer conflicts of interest there are no conflicts of interest. references 1. cruz nf, santos ks, matuoka ml, kasahara n. translaminar pressure difference and ocular perfusion pressure in glaucomatous eyes with different optic disc sizes. j ophthalmic vis res 2021;16:171–177. 2. xie x, zhang x, fu j, wang h, jonas jb, peng x, et al. noninvasive intracranial pressure estimation by orbital subarachnoid space measurement: the beijing intracranial and intraocular pressure (icop) study. crit care 2013;17:r162. 3. fleischman d, bicket ak, stinnett ss, berdahl jp, jonas jb, wang nl, et al. analysis of cerebrospinal fluid pressure estimation using formulae derived from clinical data. invest ophthalmol vis sci 2016;57:5625– 5630. 602 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 original article risk factors associated with keratoconus in an iranian population hossein mohammad-rabei1,2, md; shahrokh ramin3, md; sahar lotfi3, ms; hamideh sabbaghi3, 4, phd; farid karimian1, md; saeid abdi3, ms; mohammad hasan shahriari5, ms; bahareh kheiri1, ms; kourosh sheibani6, md; mohammad ali javadi1, md 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2department of ophthalmology, torfeh eye hospital, shahid beheshti university of medical sciences, tehran, iran 3department of optometry, school of rehabilitation, shahid beheshti university of medical sciences, tehran, iran 4ophthalmic epidemiology research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 5department of health information, technology and management, school of allied medical sciences, shahid beheshti university of medical sciences, tehran, iran 6basir eye health research center, tehran, iran orcid: hamideh sabbaghi: https://orcid.org/0000-0002-2627-7222 hossein mohammad-rabei: https://orcid.org/0000-0003-3653-6272 abstract purpose: to determine associated factors for keratoconus (kcn) in the iranian population. methods: in this retrospective case-control study, 100 kcn patients and 200 ageand sex-matched individuals, who were either candidates for photorefractive keratectomy or healthy referrals from the torfeh eye hospital, were included as the case and control groups, respectively. kcn patients were all registered at the iranian national registry of keratoconus (kcnreg®). demographic characteristics, patients’ symptoms and their habits, as well as systemic and ocular disorders were documented. clinical examinations included best corrected visual acuity (bcva) and refractive error measurements, biomicroscopic examination, and corneal imaging. results: in this case group, the frequency of mild, moderate, and severe kcn was 38%, 28%, and 34%, respectively. parental consanguinity (odds ratio [or] = 1.758, p = 0.029), positive familial history in patients’ first degree (or = 12.533, p < 0.001) and second degree (or = 7.52, p < 0.001) relatives, vernal keratoconjunctivitis (or = 7.510, p = 0.003), severe eye rubbing (or = 10.625, p < 0.001), and systemic diseases including migraine, hypertension, and thyroid disease (or = 6.828, p = 0.021) were found as associated factors for kcn. lesser frequency of kcn was observed in patients with fars ethnicity (or = 0.583, p = 0.042), with higher levels of wealth indices (or = 0.31, p < 0.001) and higher levels of education (or = 0.18, p = 0.024). conclusion: severe eye rubbing, vernal keratoconjunctivitis, parental consanguinity and positive familial history of kcn, low socioeconomic status, and low levels of education were significantly associated with kcn in our study population. keywords: associated factors; iran; keratoconus; population j ophthalmic vis res 2023; 18 (1): 15–23 © 2023 mohammad-rabei et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 15 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i1.12721&domain=pdf&date_stamp=2019-07-17 risk factors for keratoconus; mohammad-rabei et al introduction keratoconus (kcn) is a progressive noninflammatory corneal thinning disorder which commonly occurs bilaterally and asymmetrically. it appears in most patients between the second and fourth decades of their lives.[1–3] in previous literature, a prevalence of 50 to 2300 cases per 100,000 individuals has been reported for this disease in different geographical regions.[4–7] the annual incidence rate of kcn was reported within the range of 22.3 to 24.9 per 100,000 population in yazd, a province of iran with a hot and dry climate.[8] most patients complain of reduced vision due to induced myopia and irregular astigmatism secondary to the deformation of corneal tissue into a cone-shaped structure.[1–3] the reduction of visual acuity among patients decreases activity and quality of life.[1, 9] various environmental, socioeconomic, and familial factors including atopic diseases and eye rubbing,[10–12] exposure to sunlight and ultraviolet radiation,[1, 10] race,[10] older age,[10, 13] low socioeconomic status or low levels of education,[14] parental consanguinity,[15] and positive familial history[10] have all been reported as the probable risk factors for kcn. however, these risk factors are controversial.[3, 10, 16–19] considering different geographical regions, less prevalence of kcn has been found in northern europe,[10,20,21] north america,[10,22,23] and japan[10,24] as compared with india, china,[10, 25, 26] and eastern mediterranean countries.[10, 27, 28] due to the importance of kcn as a leading cause of visual impairment and the effectiveness of implementing preventive approaches in some higher risk individuals, we aimed to determine the possible associated factors for kcn among the iranian population. correspondence to: hamideh sabbaghi, phd. ophthalmic epidemiology research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, no. 23, paidarfard st., boostan 9 st., pasdaran ave., tehran, 16666, iran. e-mail: sabbaghi.opt@gmail.com received: 10-06-2021 accepted: 21-03-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i1.12721 methods patient enrolment in this case–control study, a total of 300 subjects in the age range of 16 to 61 years were studied as case (n = 100) and control (n = 200) groups between march 2016 and october 2017. kcn patients were all registered at the iranian national registry of keratoconus (kcnreg®). the study protocol adhered to the declaration of helsinki and was approved by the ethics committee of the ophthalmic research center, shahid beheshti university of medical sciences via the approval number ir.sbmu.orc.1397.12. the study details were explained to all participants and written consent was obtained prior to enrolling into the study.for the case group, we used the demographic and clinical records of 100 registered kcn patients from the kcnreg®. the control group comprised 200 ageand sex-matched individuals who were either candidates for photorefractive keratectomy or healthy referrals from the torfeh eye hospital. we excluded patients who were under suspicion of having a diagnosis of kcn or any other corneal pathological disorders from the control group. the questionnaire data collection was performed using a standard questionnaire based on the questionnaire used by owen and gamble,[29] which had been applied previously in other studies.[15, 28] in order for the questionnaire to be more comprehensive it was independently translated to the persian language by two bilingual translators (an ophthalmologist and an optometrist). the two translators mutually agreed about any differences. the document was also translated back into this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: mohammad-rabei h, ramin sh, lotfi s, sabbaghi h, karimian f, abdi s, shahriari mh, kheiri b, sheibani k, javadi ma. risk factors associated with keratoconus in an iranian population. j ophthalmic vis res 2023;18:15–23. 16 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 https://knepublishing.com/index.php/jovr risk factors for keratoconus; mohammad-rabei et al english by another translator and compared to the original questionnaire to check the consistency of the translation. it was then presented to an expert panel which included ophthalmologists, biostatisticians, and research methodologists to assess its format and content validity. finally, we asked 10 patients to read the questionnaire to determine whether there were any items that they could not understand. no shortcomings were detected by these individuals. in this questionnaire, demographic characteristics such as age, sex, occupation, birthplace, ethnicity, parental consanguinity, patients’ education and socioeconomic status were questioned. patients’ symptoms (blurred vision, diplopia, and dry eye) and their habits (smoking, eye rubbing, duration of sunlight exposure, and wearing of contact lens or sunglasses) were also documented. comorbidities of either general or systemic disorders (diabetes, atopic diseases, mitral valve prolapse, collagen diseases, renal dysfunction, and any other systemic disorders) and/or ocular diseases (vernal keratoconjunctivitis and glaucoma) among patients were also recorded in both groups. in addition, family history of kcn as well as any history of previous corneal surgery was recorded. for both the case and control groups, the questionnaires were filled either on paper, online, telephone, or via face-to-face interviews in order to increase the response rate. visual and ocular examinations clinical examinations included measurements of the best corrected visual acuity (bcva), refractive error, biomicroscopic examination, and corneal imaging using tomey topography (tms-4, tomey, nishi-ku, japan) and pentacam (wavelight allegro topolyzer vario, alcon, united states). funduscopy was also conducted by an indirect binocular ophthalmoscope through dilated pupil using a 78d lens. definitions kcn was diagnosed if any of the following signs were observed in any of the examination steps; presence of scissor reflex in retinoscopy, as well as vogt’s striae, fleischer ring, munson’s sign, stromal thinning, corneal scar, and hydrops in biomicroscopy. kcn diagnosis was also determined based on the corneal topography in cases with a sim k > 45.57d, corneal irregularity measurement (cim) between 0.69 and 100 µm, surface regularity index (sri) higher than 0.56, inferior–superior (i–s) asymmetry >1.8, and kcn severity index (ksi) >30%.[30] the severity of kcn was determined based on the rabinowitz classification[30] by an experienced cornea and anterior segment specialist (hmr). subjects were included in the control group if none of the kcn signs were observed in their examination. first-degree relatives were considered as the patients’ offspring, siblings, or their parents while the second-degree relatives included their uncles, aunts, nephews, nieces, grandparents, grandchildren, half-siblings, and double cousins. we asked the patients to determine the duration of eye rubbing during a day, where it was classified as high in cases with a duration of 10 to 180 s, low with eye rubbing of <10 s, and never in cases with no reports of eye rubbing during a day.[10] statistical analysis to present data, we used mean, standard deviation, median, range, frequency, and percentage. to evaluate the differences between the groups, we used the fisher’s exact test and the chi-square test. we also used generalized estimating equations when needed to consider the possible correlation of the results in the eyes. to assess the effect of the associated factor on the incidence of kcn, we first entered the associated factor in the model as univariate then each variable which had a p-value of <0.2 was entered into the model as multivariate. all statistical analyses were performed using the spss software version 25 (ibm corp. armonk, ny: ibm corp.). p-values < 0.05 were considered statistically significant. results in total 100 kcn patients and 200 controls with a mean age of 30.14 ± 7.93 years participated in the present case–control study. in the case group, the frequency of mild, moderate, and severe kcn was 38%, 28%, and 34%, respectively. table 1 represents the comparison of baseline characteristics between the case and the control groups. as shown, no significant difference was journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 17 risk factors for keratoconus; mohammad-rabei et al table 1. comparison of demographic characteristics between case and control groups. factors level total groups or 95% ci p-value* kcn (n = 100) control (n = 200) lower upper age (yr) mean ± sd 30.14 ± 7.93 29.54 ± 8.54 30.44 ± 7.61 0.985 1.017 0.955 0.356 median (range) 29 (16 to 61) 28 (16 to 61) 29 (16 to 55) sex male 150 (50.0%) 50 (50.0%) 100 (50.0%) 1 0.619 1.616 >0.999 female 150 (50.0%) 50 (50.0%) 100 (50.0%) 1 birthplace north 24 (8.0%) 7 (7.0%) 17 (8.5%) 0.961 0.378 2.443 0933 south 9 (3.0%) 4 (4.0%) 5 (2.5%) 1.867 0.483 7.207 0.365 west 66 (22.0%) 31 (31.0%) 35 (17.5%) 2.067 1.164 3.671 0.013 east 10 (3.3%) 1 (1.0%) 9 (4.5%) 0.259 0.032 2.094 0.205 center 191 (63.7%) 57 (57.0%) 134 (67.0%) 1 patient’s ethnicity fars 108 (36.0%) 28 (28.0%) 80 (40.0%) 0.583 0.347 0.981 0.042 others 192 (64.0%) 72 (72.0%) 120 (60.0%) 1 parental consanguinity yes 95 (31.7%) 40 (40.0%) 55 (27.5%) 1.758 1.059 2.916 0.029 no 205 (68.3%) 60 (60.0%) 145 (72.5%) 1 patient’s education (yr) 0–6 8 (2.7%) 5 (5.0%) 3 (1.5%) 1 6–12 162 (54.0%) 65 (65.0%) 97 (48.5%) 0.402 0.093 1.741 0.223 >12 130 (43.3%) 30 (30.0%) 100 (50.0%) 0.18 0.041 0.797 0.024 patient’s occupation indoor 200 (66.7%) 67 (67.0%) 133 (66.5%) 1 outdoor 100 (33.3%) 33 (33.0%) 67 (33.5%) 0.978 0.587 1.628 0.931 wealth index rich 102 (34.0%) 19 (19.0%) 83 (41.5%) 0.31 0.165 0.583 <0.001 normal 92 (30.7%) 36 (36.0%) 56 (28.0%) 0.871 0.493 1.539 0.635 poor 106 (35.3%) 45 (45.0%) 61 (30.5%) 1 sunlight exposure during a day (hr) 0–2 112 (37.3%) 37 (37.0%) 75 (37.5%) 1 3–4 88 (29.3%) 30 (30.0%) 58 (29.0%) 1.048 0.581 1.893 0.875 5–6 34 (11.3%) 11 (11.0%) 23 (11.5%) 0.969 0.427 2.2 0.941 >6 66 (22.0%) 22 (22.0%) 44 (22.0%) 1.014 0.531 1.933 0.968 wearing of sunglasses yes 128 (42.7%) 40 (40.0%) 88 (44.0%) 0.841 0.516 1.37 0.487 no 172 (57.3%) 60 (60.0%) 112 (56.0%) 1 kcn, keratoconus; or, odds ratio; ci, confidence interval; sd, standard deviation ∗based on binary logistic regression 18 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 risk factors for keratoconus; mohammad-rabei et al table 2. comparison of clinical characteristics between case and control groups to find the probable associated factors. factors level total groups or 95% ci p-value* kcn (n = 100) control (n = 200) lower upper kcn in family first-degree 35 (11.7%) 28 (28.0%) 7 (3.5%) 12.533 5.21 30.148 <0.001 seconddegree 17 (5.7%) 12 (12.0%) 5 (2.5%) 7.52 2.54 22.21 <0.001 no 248 (82.7%) 60 (60.0%) 188 (94.0%) 1 systemic diseases diabetes 3 (1%) 2 (2.0%) 1 (0.5%) 4.552 0.405 51.200 0.22 mvp 6 (2.0%) 2 (2.0%) 4 (2.0%) 1.138 0.203 6.388 0.883 renal 3 (1.0%) 2 (2.0%) 1 (0.5%) 4.552 0.405 51.200 0.220 asthma 7 (2.3%) 1 (1.0%) 6 (3.0%) 0.379 0.045 3.222 0.374 eczema 18 (6.0%) 8 (8.0%) 10 (5.0%) 1.821 0.684 4.849 0.231 allergy 65 (21.7%) 21 (21.0%) 44 (22.0%) 1.086 0.593 1.988 0.789 others 8 (2.7%) 6 (6.0%) 2 (1.0%) 6.828 1.338 34.841 0.021 no 190 (63.3%) 58 (58.0%) 132 (66.0%) 1 ocular diseases glaucoma 17 (5.7%) 7 (7.0%) 10 (5.0%) 1.577 0.58 4.286 0.372 vkc 13 (4.3%) 10(10.0%) 3 (1.5%) 7.510 2.015 27.997 0.003 no 270 (90.0%) 83 (83.0 %) 187 (93.5%) 1 eye rubbing never 110 (36.7%) 25 (25.0%) 85 (42.5%) 1 low 157 (52.3%) 50 (50.0%) 107 (53.5%) 1.589 0.909 2.776 0.104 high 33 (11.0%) 25 (25.0%) 8 (4.0%) 10.625 4.266 26.463 <0.001 dry eye never 177 (59.0%) 53 (53.0%) 124 (62.0%) 1 mild 90 (30.0%) 31 (31.0%) 59 (29.5%) 1.229 0.716 2.111 0.454 moderate 28 (9.3%) 13 (13.0%) 15 (7.5%) 2.028 0.903 4.555 0.087 severe 5 (1.7%) 3 (3.0%) 2 (1.0%) 3.509 0.570 21.614 0.176 smoking yes 35 (11.7%) 7 (7.0%) 28 (14.0%) 0.46 0.193 1.093 0.079 no 265 (88.3%) 93 (93.0%) 172 (86.0%) 1 kcn, keratoconus; or, odds ratio; ci, confidence interval; mvp, mitral valve prolapse; vkc, vernal keratoconjunctivitis; na, not available ∗based on binary logistic regression; ∗∗not available because of zero observation in one of the levels found between the two studied groups regarding age, sex, ethnicity, occupation, sunlight exposure, and wearing of sunglasses. however, it was found that patients living in the west regions of iran were at a higher risk of kcn as compared to the controls (odds ratio [or] = 2.067, p = 0.013). furthermore, parental consanguinity (or = 1.758, p = 0.029) was also found as another associated factor for kcn. journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 19 risk factors for keratoconus; mohammad-rabei et al table 3. comparison of topoand tomographic findings in case and control groups. factors kcn (n = 100) p-value* pairwise comparison control (n = 200) p-value** total severe (1) moderate (2) mild (3) kmin (d) 48.04 ± 4.53 50.46 ± 5.09 48.21 ± 3.23 44.63 ± 1.9 <0.001 (1,3) (2,3) 43.24 ± 1.62 <0.001 47.3 (39, 65.05) 49.7 (39, 65.05) 48.15 (42.6, 57.87) 45.35 (39.8, 46.95) 43.35 (38.4, 46.7) kmax (d) 51.57 ± 5.02 54.2 ± 5.71 51.93 ± 3.76 47.71 ± 1.42 <0.001 (1,3) (2,3) 44.26 ± 1.96 <0.001 50.8 (40.28, 64.14) 54.2 (40.28, 62.0) 51.1 (45.63, 64.14) 47.92 (45, 49.8) 44.3 (38.8, 55.7) kmeans (d) 49.81 ± 4.28 52.33 ± 4.42 50.07 ± 3.25 46.17 ± 1.54 <0.001 (1,3) (2,3) 43.74 ± 1.67 <0.001 49 (40.7, 61.0) 52.35 (40.7, 59.5) 49.3 (46.75, 61.0) 46.3 (42.85, 48.3) 43.75 (38.6, 50.7) cct (µm) 468.75 ± 47.89 429.26 ± 41.61 476 ± 34.79 499.56 ± 35.88 <0.001 (1,2) (1,3) 543.32 ± 32.5 <0.001 469 (352, 574) 430 (352, 551) 472 (401, 539) 499 (437, 574) 541.5 (405, 623) kcn, keratoconus; k, keratometry; d, diopter; cct, central corneal thickness; µm, micrometer ∗based on anova (bonferroni post hoc multiple comparison); ∗∗based on independent t-test however, less frequency of kcn was observed in patients with fars ethnicity (or = 0.583, p = 0.042), higher levels of wealth indices (or = 0.31, p < 0.001), and higher levels of education (or = 0.18, p = 0.024). table 2 shows the comparison of clinical characteristics between the case and the control groups. as presented, higher risk of kcn was observed in patients who had a positive familial history in their first(or = 12.533, p < 0.001) and second-degree (or = 7.52, p < 0.001) relatives, and in cases who had systemic diseases including migraine, hypertension, and thyroid disease (or = 6.828, p = 0.021). in addition, patients with vernal keratoconjunctivitis (or = 7.510, p = 0.003) and severe eye rubbing (or = 10.625, p < 0.001) were found to be at a higher risk of kcn as compared with the healthy controls. no significant differences were observed when comparing the other factors between the two groups. description of topographic findings at different stages of kcn and the control group is summarized in table 3. as shown, higher keratometric values (kmin, kmax, and k-means) and thinner central corneal thickness were observed in severe kcn patients as compared with the other stages of kcn and the normal controls (p < 0.001 for both). table 4 represents the effect of various factors on different stages of kcn. as shown, low wealth index was the only variable identified as associated factor among patients with severe kcn (p = 0.019). no statistically significant association was found when investigating other factors. discussion in the present study, parental consanguinity, positive familial history in patients’ firstand second-degree relatives, vernal keratoconjunctivitis, severe eye rubbing, and systemic diseases including migraine, hypertension, and thyroid disease were found as associated factors for kcn. on the other hand, lesser frequency of kcn was observed in patients with fars ethnicity, higher levels of wealth indices and education. we observed that kcn is more prevalent in cases who have positive familial history of kcn. it has been reported that 14% of patients with kcn have an affected family member which could be considered as evidence for the hereditary nature of kcn, which is in line with our observation.[31] hashemi et al identified this significant association between the incidence of kcn and positive familial history.[32] furthermore, we observed that kcn patients had higher percentages of parental consanguinity, which is in line with previous studies reporting a high prevalence of kcn among populations of pakistan, western mediterranean countries, and india who have a high percentage of consanguine marriages.[10, 15, 33, 34] due to the 20 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 risk factors for keratoconus; mohammad-rabei et al table 4. the stages of keratoconus and possible associated factors for severity. factors level total severity of kcn (n = 100) p-value* severe (n = 38) moderate (n = 28) mild (n = 34) birthplace north 7 (7.0%) 1 (2.6%) 4 (14.3%) 2 (5.9%) 0.476 south 4 (4.0%) 1 (2.6%) 2 (7.1%) 1 (2.9%) west 31 (31.0%) 13 (34.2%) 7 (25.0%) 11 (32.4%) east 1 (1.0%) 0 (0.0%) 1 (3.6%) 0 (0.0%) center 57 (57.0%) 23 (60.5%) 14 (50.0%) 20 (58.8%) patient’s ethnicity fars 28 (28.0%) 11 (28.9%) 7 (25.0%) 10 (29.4%) 0.916 others 72 (72.0%) 27 (71.1%) 21 (75.0%) 24 (70.6%) parental consanguinity yes 40 (40.0%) 18 (47.4%) 12 (42.9%) 10 (29.4%) 0.280 no 60 (60.0%) 20 (52.6%) 16 (57.1%) 24 (70.6%) patient’s education (yr) 0–6 5 (5.0%) 3 (7.9%) 2 (7.1%) 0 (0.0%) 0.559 6–12 65 (65.0%) 25 (65.8%) 17 (60.7%) 23 (67.6%) >12 30 (30.0%) 10 (26.3%) 9 (32.1%) 11 (32.4%) wealth index rich 19 (19.0%) 2 (5.3%) 5 (17.9%) 12 (35.3%) 0.019 normal 36 (36.0%) 14 (36.8%) 10 (35.7%) 12 (35.3%) poor 45 (45.0%) 22 (57.9%) 13 (46.4%) 10 (29.4%) kcn in family no 60 (60.0%) 24 (63.2%) 18 (64.3%) 18 (52.9%) 0.096 first-degree 28 (28.0%) 13 (34.2%) 7 (25.0%) 8 (23.5%) seconddegree 12 (12.0%) 1 (2.6%) 3 (10.7%) 8 (23.5%) ocular diseases glaucoma 7 (7.0%) 2 (5.3%) 4 (14.3%) 1 (2.9%) 0.826 vkc 10 (10.0%) 4 (10.5%) 2 (7.1%) 4 (11.8%) no 83 (83.0%) 32 (84.2%) 22 (78.6%) 29 (85.3%) eye rubbing never 25 (25.0%) 8 (21.1%) 6 (21.4%) 11 (32.4%) 0.373 low 50 (50.0%) 19 (50.0%) 13 (46.4%) 18 (52.9%) high 25 (25.0%) 11 (28.9%) 9 (32.1%) 5 (14.7%) kcn, keratoconus; vkc, vernal keratoconjunctivitis ∗based on chi-square test prevalence of consanguine marriages registering as high as 40% among the iranian population,[35] more comprehensive investigations of the iranian population might be necessary to better understand the role of inter family marriage on kcn. in the present study, we did not detect significant associations between allergy, asthma, eczema, and kcn, however atopic diseases have been reported as one of the probable risk factors for kcn.[10, 12, 32] this association was not detected in a study by bawazeer et al,[36] who believed that kcn is not directly related to atopic diseases. they believed, however, that it happens secondary to eye rubbing, which was also a factor significantly associated with kcn in our study. furthermore, eye rubbing was reported as a known risk factor of kcn in a meta-analysis and systematic review conducted by hashemi et al.[32] naderan et al[37] have reported that kcn patients with vernal keratoconjunctivitis or allergic conjunctivitis have significantly thinner and steeper corneas in comparison with non-allergic kcn patients. it was concluded that these patients journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 21 risk factors for keratoconus; mohammad-rabei et al experience more severe kcn and should be closely followed-up and intensively treated. regarding the geographical location, it was found that people living in the west regions of iran were at a higher risk of kcn. however, kelly et al[18] and millodot et al[38] showed higher prevalence of kcn among individuals living in tropical countries located around the equator, in comparison with european and north american countries. it can be considered as strong evidence of the significant association between kcn and exposure to sunlight and ultraviolet radiation. however, this significant relationship has not been found in other studies.[16, 17] regarding different iranian ethnicities, fars people were found to be at lesser risk of kcn, which is in line with the findings reported by hashemi et al,[39] showing a higher prevalence of kcn among arab, turk, kurd, and lur ethnicities as compared to the fars population. regardless of the sunlight exposure, some studies have reported less prevalence of kcn in several geographical regions like northern europe,[10, 20, 21] northern america,[10, 22, 23] and japan[10, 24] as compared to india, china,[10, 25, 26] and eastern mediterranean countries.[10, 27, 28] in addition, a strong relationship was found in children who live in families with low socioeconomic status or low levels of education,[14] as children living in poor families will be dealing with problems of contaminations found in the air, water, and waste.[40] we also noticed less frequency of kcn among people with higher levels of wealth indices and education. age is another probable associated factor with a positive relationship with the progression of kcn. due to the incomprehensible visual symptoms in the early stages of kcn, patients are usually diagnosed in older ages with more severe stages of the disease.[10, 13, 41] in the current study, a significant association was found between kcn and some systemic diseases including migraine, hypertension, and thyroid diseases. this finding was inconclusive due to the limited numbers of affected patients. one of the possible drawbacks of the present study is the selection bias regarding the participation of kcn patients with different levels of wealth status. in summary, based on our findings, severe eye rubbing, vernal keratoconjunctivitis, parental consanguinity and positive familial history of kcn, low socioeconomic status and low levels of education were significantly associated with kcn in the iranian population. acknowledgements this article is taken from the disease registry, titled ”the iranian national registry of keratoconus (kcnreg®)”, code number ir.sbmu.orc.rec.1397.12 from the ethics committee, which was supported by the deputy of research and technology at shahid beheshti university of medical sciences, tehran, iran (http://dregistry.sbmu.ac.ir). financial support and sponsorship none. conflicts of interest the authors have no conflict of interest with the subject matter of this manuscript. references 1. davidson ae, hayes s, hardcastle aj, tuft sj. the pathogenesis of keratoconus. eye 2014;28:189–195. 2. krachmer jh, feder rs, belin mw. keratoconus and related noninflammatory corneal thinning disorders. surv ophthalmol 1984;28:293–322. 3. rabinowitz ys. keratoconus. surv ophthalmol 1998;42:297–319. 4. kennedy rh, bourne wm, dyer ja. a 48-year clinical and epidemiologic study of keratoconus. am j ophthalmol 1986;101:267–273. 5. jonas jb, nangia v, matin a, kulkarni m, bhojwani k. prevalence and associations of keratoconus in rural maharashtra in central india: the central india eye and medical study. am j ophthalmol 2009;148:760–765. 6. gokhale ns. epidemiology of keratoconus. indian j ophthalmol 2013;61:382–383. 7. woodward ma, blachley ts, stein jd. the association between sociodemographic factors, common systemic diseases, and keratoconus: an analysis of a nationwide healthcare claims database. ophthalmology 2016;123:457–65.e2. 8. ziaei h, jafarinasab mr, javadi ma, karimian f, poorsalman h, mahdavi m, et al. epidemiology of keratoconus in an iranian population. cornea 2012;31:1044–1047. 9. aydin kurna s, altun a, gencaga t, akkaya s, sengor t. vision related quality of life in patients with keratoconus. j ophthalmol 2014;2014:694542. 22 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 risk factors for keratoconus; mohammad-rabei et al 10. gordon-shaag a, millodot m, shneor e, liu y. the genetic and environmental factors for keratoconus. biomed res int 2015;2015:795738. 11. carlson an. expanding our understanding of eye rubbing and keratoconus. cornea 2010;29:245. 12. kaya v, karakaya m, utine ca, albayrak s, oge of, yilmaz of. evaluation of the corneal topographic characteristics of keratoconus with orbscan ii in patientswith and without atopy. cornea 2007;26:945–948. 13. ihalainen a. clinical and epidemiological features of keratoconus genetic and external factors in the pathogenesis of the disease. acta ophthalmol suppl 1986;178:1–64. 14. naderan m, shoar s, rezagholizadeh f, zolfaghari m, naderan m. characteristics and associations of keratoconus patients. cont lens anterior eye 2015;38:199–205. 15. gordon-shaag a, millodot m, essa m, garth j, ghara m, shneor e. is consanguinity a risk factor for keratoconus? optom vis sci 2013;90:448–454. 16. georgiou t, funnell cl, cassels-brown a, o’conor r. influence of ethnic origin on the incidence of keratoconus and associated atopic disease in asians and white patients. eye 2004;18:379–383. 17. pearson ar, soneji b, sarvananthan n, sandford-smith jh. does ethnic origin influence the incidence or severity of keratoconus? eye 2000;14:625–628. 18. kelly tl, williams ka, coster dj, australian corneal graft registry. corneal transplantation for keratoconus: a registry study. arch ophthalmol 2011;129:691–697. 19. rabinowitz ys. the genetics of keratoconus. ophthalmol clin north am 2003;16:607–620. 20. gorskova en, sevost’ianov en. epidemiology of keratoconus in the urals. vestn oftalmol 1998;114:38–40. in russian 21. nielsen k, hjortdal j, pihlmann m, corydon tj. update on the keratoconus genetics. acta ophthalmol 2013;91:106– 113. 22. kennedy rh, bourne wm, dyer ja. a 48-year clinical and epidemiologic study of keratoconus. am j ophthalmol 1986;101:267–273. 23. hofstetter hw. a keratoscopic survey of 13,395 eyes. am j optom arch am acad optom 1959;36:3–11. 24. tanabe u, fujiki k, ogawa a, ueda s, kanai a. prevalence of keratoconus patients in japan. nihon ganka gakkai zasshi 1985;89:407–411. in japanese 25. jonas jb, nangia v, matin a, kulkarni m, bhojwani k. prevalence and associations of keratoconus in rural maharashtra in central india. american j ophthalmol 2009;148:760–765. 26. xu l, wang yx, guo y, you qs, jonas jb. prevalence and associations of steep cornea/keratoconus in greater beijing. plos one 2012;7:e39313. 27. mohd-ali b, abdu m, yaw cy, mohidin n. clinical characteristics of keratoconus patients in malaysia: a review from a cornea specialist centre. j optom 2012;5:38–42. 28. shneor e, millodot m, gordon-shaag a, essa m, anton m, barbara r, et al. prevalence of keratoconus amoung young arab students in israel. int j keratoconus ectatic corneal dis 2014;3:9–14. 29. owens h, gamble g. a profile of keratoconus in new zealand. cornea 2003;22:122–125. 30. alio j-l, vega-estrada a, sanz-garcia p, duran-garcia m-l, maldonado m. keratoconous management guidelines. int j keratoconous ectatic corneal dis 2015;4:1–39. 31. karimian f, aramesh s, rabei hm, javadi ma, rafati n. topographic evaluation of relatives of patients with keratoconus. cornea 2008;27:874–878. 32. hashemi h, heydarian s, hooshmand e, saatchi m, yekta a, aghamirsalim m, et al. the prevalence and risk factors for keratoconous: a systematic review and meta-analysis. cornea 2020;39:263–270. 33. al-gazali l, hamamy h. consanguinity and dysmorphology in arabs. hum hered 2014;77:93–107. 34. saadat m, ansari-lari m, farhud dd. consanguineous marriage in iran. ann hum biol 2004;31:263–269. 35. najmabadi h, hu h, garshasbi m, zemojtel t, abedini ss, chen w, et al. deep sequencing reveals 50 novel genes for recessive cognitive disorders. nature 2011;478:57–63. 36. bawazeer am, hodge wg, lorimer b. atopy and keratoconus: a multivariate analysis. br j ophthalmol 2000;84:834–836. 37. naderan m, rajabi mt, zarrinbakhsh p, bakhshi a. effect of allergic diseases on keratoconus severity. ocul immunol inflamm 2017;25:418–423. 38. millodot m, shneor e, albou s, atlani e, gordon-shaag a. prevalence and associated factors of keratoconus in jerusalem: a cross-sectional study. ophthalmic epidemiol 2011;18:91–97. 39. hashemi h, khabazkhoob m, fotouhi a. topographic keratoconus is not rare in an iranian population: the tehran eye study. ophthalmic epidemiol 2013;20:385– 391. 40. powell dl, stewart v. children. the unwitting target of environmental injustices. pediatr clin north am 2001;48:1291–1305. 41. weed kh, macewen cj, mcghee cn. the variable expression of keratoconus within monozygotic twins: dundee university scottish keratoconus study (dusks). cont lens anterior eye 2006;29:123–126. journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 23 photo essay iatrogenic pvd following dilated fundus examination: a new diagnosis or fluke? patrick w commiskey1, md; gagan kalra2, mbbs; jay chhablani1, md 1university of pittsburgh medical center, pittsburgh, pa, usa 2government medical college and hospital, chandigarh, india orcid: patrick w commiskey: https://orcid.org/0000-0002-3367-3047 jay chhablani: https://orcid.org/0000-0003-1772-3558 j ophthalmic vis res 2022; 17 (1): 150–151 presentation a 55-year-old woman with high myopia (spherical equivalent –8.25 right eye [od], –8.50 left eye [os]) and known history of sjogren syndrome presented for routine asymptomatic hydroxychloroquine screening. no other relevant past ocular, medical, or family history was noted. visual acuity was found to be 20/20 in both eyes (ou). dilated fundus examination (dfe) without indentation was performed using tropicamide and phenylephrine, and ancillary testing was performed. no signs of hydroxychloroquine toxicity, weiss ring, retinal tears, or peripheral retinal pathology were noted ou. incidentally, the screening spectral domain optical coherence tomography (sd-oct) revealed tenuous vitreous attachment to the optic disc os [figure 1a]. two hours after the screening outpatient examination, the patient experienced a new floater os for which she subsequently presented to the ophthalmology emergency. the on-call ophthalmologist noted a weiss ring os without correspondence to: jay chhablani, md. university of pittsburgh medical center, 203 lothrop st., pittsburgh, pa 15213, usa. e-mail: jay.chhablani@gmail.com received 11-06-2020; accepted 03-12-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10182 retinal tears or detachments ou. a subsequent sdoct scan in the left eye demonstrated a complete posterior vitreous detachment (pvd) [figure 1b]. the patient was reassured, counselled about the warning symptoms of retinal detachment, and scheduled for a repeat dfe in one week. discussion to the best of our knowledge, this is the first report of completion of an impending pvd following cycloplegic dfe. accommodation-induced ciliary body contraction, anterior displacement of the lens–iris diaphragm, and axial elongation of the vitreous cavity may be more pronounced in myopic patients.[1] there is a known anatomical relationship between ciliary body contraction and anterior movement of anterior vitreous body and zonules.[2, 3] anterior zonule movement results in adjacent anterior movement of the vitreous parallel to the sclera at the ora serrata.[4] while it is unclear if this force would translate to posterior vitreous movement, there is an interesting case report of vitreo-macular traction (vmt) following pilocarpine-induced miosis this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: commiskey pw, kalra g, chhablani j. iatrogenic pvd following dilated fundus examination: a new diagnosis or fluke? . j ophthalmic vis res 2022;17:150–151. 150 © 2022 commiskey et al . this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10182&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; commiskey et al figure 1. (a) two optical coherence tomography (oct) images at the initial visit for a dilated eye exam showed posterior vitreous still attached at the disc margin. (b)two oct images at the follow-up visit with new floaters due to posterior vitreous detachment (pvd) 2 hr following the initial exam. after mydriasis.[5] in a computer animation-based model of accommodation, it was found that during accommodation the vitreous base is pulled forward and the posterior vitreous is pushed backward.[6] axially, it is during the relaxation of accommodation that the posterior lens capsule moves anteriorly followed by subsequent anterior movement of posterior vitreous causing shearing at the retinal vitreous attachments.[6] although our report illustrates temporal association of completion of impending pvd following dfe, the precise changes in the posterior hyaloid in response to dfe are still unclear. further work could be done to elucidate the relationship between accommodative state and pvd. wide-field oct may expand our understanding of peripheral vitreoretinal physiology. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. culhae hm, winn b. dynamic accommodation and myopia. invest ophthalmol vis sci 1999;40:1968–1974. 2. araki m, tokoro t, matsuo c. movement of the ciliary body associated to accommodation. acta ophthalmol jpn 1964;68:1852–1857. 3. ljubimova f, eriksson a. numerical study of the effect of vitreous support on eye accommodation. acta bioeng biomech 2005;7:2. 4. croft ma, nork tm, mcdonald jp, katz a, lütjen-drecoll e, kaufman pl. accommodative movements of the vitreous membrane, choroid, and sclera in young and presbyopic human and nonhuman primate eyes. invest ophthalmol vis sci 2013;54:5049–5058. 5. walker jf, alvarez mm. vitreofoveal traction associated with the use of pilocarpine to reverse mydriasis. eye 2007;21:1430–1431. 6. goldberg db. computer-animated model of accommodation and presbyopia. j cataract refract surg 2015;41:437–445. journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 151 editorial connective tissue growth factor: a key factor among mediators of tissue fibrosis nader sheibani1,2,3,4, phd 1department of ophthalmology and visual sciences, university of wisconsin school of medicine and public health, madison, wi, usa 2department of cell and regenerative biology, university of wisconsin school of medicine and public health, madison, wi, usa 3mcpherson eye research institute, university of wisconsin school of medicine and public health, madison, wi, usa 4department of biomedical engineering, university of wisconsin, madison, wi, usa orcid: nader sheibani: https://orcid.org/0000-0003-2723-9217 j ophthalmic vis res 2022; 17 (4): 449–452 fibrosis is the increased accumulation of fibrous connective tissue in and around tissues with inflammation or damage, which initiates irreversible scar formation.[1] it is a main reason for the development of adverse events in many chronic inflammatory diseases. despite many efforts in the development of therapeutics for fibrosis, success has been very limited. however, recent advancements in single cell omics’ tools are helping to delineate the molecular and cellular mechanisms that contribute to fibrosis and provide the opportunity for more targeted new approaches for treatment of fibrosis.[2] fibrosis contributes to disorders in many tissues and organs including liver and heart dysfunction, rheumatoid arthritis, diabetic nephropathy and retinopathy, age-related macular degeneration, corneal wound healing, and glaucoma.[1, 3] however, correspondence to: nader sheibani, phd. department of ophthalmology and visual sciences, university of wisconsin, school of medicine and public health, madison, wi 53705, usa. email: nsheibanikar@wisc.edu received: 10-08-2022 accepted: 27-08-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i4.12294 the underlying cellular and molecular mechanisms may vary in different organs, and the commonality among these diverse fibrotic diseases is not fully delineated. connective tissue growth factor (ctgf) has been recognized as an important mediator of fibrosis and scar formation.[4–11] a recent study utilizing computational strategies identified ctgf as the common key molecule regulating fibrogenesis among eight different fibrotic diseases including ocular fibrosis.[12] thus, many efforts have focused on interfering with the expression and activity of ctgf, such as function blocking antibodies,[13–16] sirna,[17, 18] shrna,[19] microrna,[20, 21] yap/taz inhibitor,[22–24] and most recently crispercas9 system[25] to mitigate fibrosis in different cells, tissues, and organs including the eye. fibrosis is a complex and active process, which is impacted by various cell types, differentiation and signaling pathways, genes, and crosstalk.[1, 26] this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: sheibani n. connective tissue growth factor: a key factor among mediators of tissue fibrosis. j ophthalmic vis res 2022;17:449–452. © 2022 sheibani. this is an open access article distributed under the creative commons attribution license | published by knowledge e 449 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i4.12294&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr editorial; sheibani the deposition of excessive extracellular matrix proteins by myofibroblasts is common to many fibrotic conditions.[27–29] perivascular supporting cells, which are also tissue resident mesenchymal stem cells, are recently recognized as being the cells primarily involved in fibrotic responses in many organs and tissues.[30] we have noted that retinal and choroidal perivascular supporting cells express higher levels of ctgf compared to retinal or choroidal endothelial cells but lower than microglial and retinal pigment epithelial cells (our unpublished observations). the high levels of ctgf in microglial cells decreases while that of pericytes increases in response to high glucose conditions,[31] and may drive migration and/or loss of perivascular cells from retinal blood vessels during diabetes.[32] immune cells, such as macrophages, mediate inflammatory responses that are integrated with other profibrotic processes.[29, 31, 33–35] however, the details of these interactions remain poorly understood, but single-cell genomic, proteomic, and transcriptomic techniques are further unraveling the specific cell subtypes and their interactions in pathophysiology of fibrosis in various tissues. in terms of signaling pathways, tgf-β has been extensively recognized as key mediator of pro-fibrotic activity.[3] since the protein is made as an inactive precursor and deposited in the extracellular matrix (ecm), its mechanisms of activation by αvβ6 integrin, autotaxin, and galectin-3 have been targeted for potential therapeutics.[1, 3] unfortunately, targeting these mechanisms of tgf-β activation have been ineffective in treating and/or preventing fibrosis, especially in idiopathic pulmonary fibrosis.[26] these failures have been attributed, at least in part, to normal physiological functions of tgf-β, and its systemic inactivation could have many adverse effects. thus, not only the identification of pathways involved are important but determining their hierarchy is essential to their successful targeting for therapeutic intentions. ctgf is a downstream target of tgf-β in tissue remodeling and ecm synthesis. it is also proinflammatory and is recognized as a common key driver of fibrosis in various fibrotic disorders.[12] thus, focusing on the role of inflammatory cells and their mediators in modulation of innate immune cell responses in driving fibrosis could be beneficial.[26] revealing the identity, organization, and mechanical properties of the ecm environment in fibrosis could also provide additional unique clues to the mechanisms that drives inappropriate activation of target cells. trabeculectomy is a surgical treatment to lower intraocular pressure in glaucoma patients. however, excess scaring leads to failure of the filtering bleb and adversely affect the treatment outcome.[36, 37] it is well-established that ctgf expression is significantly upregulated during this fibrotic response and targeting ctgf using various modalities, as stated above, are shown to prevent fibrotic signaling including proliferation, ecm deposition, and proinflammatory activity in fibroblasts and retinal pigment epithelial cells, and in in vivo preclinical models. in a manuscript in this issue of jovr, hassanpour and colleagues[38] demonstrate subconjunctival delivery of antictgf is efficacious in prolonging the bleb life in a rabbit model of trabeculectomy. they did a careful analysis of the microstructural features of the bleb areas and provide histological proof on the inhibition or reduction of fibrosis in anti-ctgf treated trabeculectomy blebs. the changes in response to anti-ctgf were comparable with those noted in mitomycin c (mmc) treatment. they also showed mmc treatment was concomitant with decreased production of ctgf, likely as a result of the inhibition of cell proliferation by mmc. growth arrested cells, a limitation with use of mmc, are however metabolically active and could release other factors, which could exacerbate fibrosis. the recognition of ctgf as the common factor in driving fibrosis in various organs with fibrosis supports an import role for antagonism of ctgf for treatment of these diseases. the same group has previously shown that anti-ctgf is efficacious in mitigating fibrosis in preclinical models of neovascular age-related macular degeneration and proliferative vitreoretinopathy with minimal adverse effect on vision.[14, 16, 39] thus, a better understanding of the mechanisms of ctgf action and its cell autonomous activities may aid in development of new and complementary agents with effective antifibrotic activity. recent studies have also identified the hippo signaling pathway and its downstream effectors yap/taz as important modulator of ctgf production and activity.[22] the yap/taz inhibitor, verteporfin, suppresses ctgf production and mitigates fibrosis in the eye and heart.[23, 40, 41] we are beginning to know more about the expression and function of ctgf using transgenic mice including 450 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 editorial; sheibani ctgf reporter, and global and conditional ctgf null mice.[2, 42–44] we are learning about the role of ctgf in normal developmental and repair processes.[43] a recent study targeting the deletion of ctgf in endothelial cells demonstrated an import role for ctgf-yap axis for retinal angiogenesis and barrier formation.[2] in addition, deletion of ctgf in corneal epithelial cells interfere with proper corneal wound healing.[43] thus, a better understanding of how ctgf, and perhaps other mediators, aberrant expression and downstream signaling events are regulated during early and late stages of fibrotic diseases will help to identify the common and unique regulatory mechanisms involved. we recently identified bim expression, a proapoptotic member of bcl-2 family, as essential for clearance of macrophages and mitigation of fibrosis in a preclinical model of choroidal neovascularization and scar formation.[45] although there are some common pathways engaged by fibrosis in different organs, there are also unique pathways which we know little about. identification of these unique pathways and elucidation of their interactions will allow development of organ specific antifibrotic agents, which are tissue specific and more effective for treatment of fibrosis. financial support and sponsorship none. conflicts of interest there are no conflicts of interest. references 1. mallone f, costi r, marenco m, plateroti r, minni a, attanasio g, et al. understanding drivers of ocular fibrosis: current and future therapeutic perspectives. int j mol sci 2021;22:11748. https://doi.org/10.3390/ijms222111748 2. moon s, lee s, caesar ja, pruchenko s, leask a, knowles ja, et al. a ctgf-yap regulatory pathway is essential for angiogenesis and barriergenesis in the retina. iscience 2020;23:101184. 3. hachana s, larrivée b. tgf-β; superfamily signaling in the eye: implications for ocular pathologies. cells 2022;11:2336. 4. razzaque ms, foster cs, ahmed ar. role of connective tissue growth factor in the pathogenesis of conjunctival scarring in ocular cicatricial pemphigoid. invest ophthalmol vis sci 2003;44:1998–2003. 5. he s, jin ml, worpel v, hinton dr. a role for connective tissue growth factor in the pathogenesis of choroidal neovascularization. arch ophthalmol 2003;121:1283– 1288. 6. he s, chen y, khankan r, barron e, burton r, zhu d, et al. connective tissue growth factor as a mediator of intraocular fibrosis. invest ophthalmol vis sci 2008;49:4078–4088. 7. junglas b, kuespert s, seleem aa, struller t, ullmann s, bösl m, et al. connective tissue growth factor causes glaucoma by modifying the actin cytoskeleton of the trabecular meshwork. am j pathol 2012;180:2386–2403. 8. kuiper ej, de smet md, van meurs jc, tan hs, tanck mw, oliver n, et al. association of connective tissue growth factor with fibrosis in vitreoretinal disorders in the human eye. arch ophthalmol 2006;124:1457–1462. 9. esson dw, neelakantan a, iyer sa, blalock td, balasubramanian l, grotendorst gr, et al. expression of connective tissue growth factor after glaucoma filtration surgery in a rabbit model. invest ophthalmol vis sci 2004;45:485–491. 10. junglas b, yu ah, welge-lüssen u, tamm er, fuchshofer r. connective tissue growth factor induces extracellular matrix deposition in human trabecular meshwork cells. exp eye res 2009;88:1065–1075. 11. daniels jt, schultz gs, blalock td, garrett q, grotendorst gr, dean nm, et al. mediation of transforming growth factor-beta(1)-stimulated matrix contraction by fibroblasts: a role for connective tissue growth factor in contractile scarring. am j pathol 2003;163:2043–2052. 12. gu c, shi x, dang x, chen j, chen c, chen y, et al. identification of common genes and pathways in eight fibrosis diseases. front genet 2020;11:627396. 13. wang jm, hui n, fan yz, xiong l, sun nx. filtering bleb area and intraocular pressure following subconjunctival injection of ctgf antibody after glaucoma filtration surgery in rabbits. int j ophthalmol 2011;4:480–483. 14. daftarian n, rohani s, kanavi mr, suri f, mirrahimi m, hafezi-moghadam a, et al. effects of intravitreal connective tissue growth factor neutralizing antibody on choroidal neovascular membrane-associated subretinal fibrosis. exp eye res 2019;184:286–295. 15. bagheri a, soheili zs, ahmadieh h, samiei s, sheibani n, astaneh sd, et al. simultaneous application of bevacizumab and anti-ctgf antibody effectively suppresses proangiogenic and profibrotic factors in human rpe cells. mol vis 2015;21:378–390. 16. daftarian n, baigy o, suri f, kanavi mr, balagholi s, afsar aski s, et al. intravitreal connective tissue growth factor neutralizing antibody or bevacizumab alone or in combination for prevention of proliferative vitreoretinopathy in an experimental model. exp eye res 2021;208:108622. 17. lim dh, kim te, kee c. evaluation of adenovirusmediated down-regulation of connective tissue growth factor on postoperative wound healing after experimental glaucoma surgery. curr eye res 2016;41:951–956. 18. jing j, li p, li t, sun y, guan h. rna interference targeting connective tissue growth factor inhibits the transforming growth factorβ 2 induced proliferation in human tenon capsule fibroblasts. j ophthalmol 2013;2013:354798. journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 451 editorial; sheibani 19. lei d, dong c, wu wk, dong a, li t, chan mt, et al. lentiviral delivery of small hairpin rna targeting connective tissue growth factor blocks profibrotic signaling in tenon’s capsule fibroblasts. invest ophthalmol vis sci 2016;57:5171–5180. 20. wang wh, deng aj, he sg. a key role of microrna-26a in the scar formation after glaucoma filtration surgery. artif cells nanomed biotechnol 2018;46:831–837. 21. bao h, jiang k, meng k, liu w, liu p, du y, et al. tgfβ2 induces proliferation and inhibits apoptosis of human tenon capsule fibroblast by mir-26 and its targeting of ctgf. biomed pharmacother 2018;104:558–565. 22. futakuchi a, inoue t, wei fy, inoue-mochita m, fujimoto t, tomizawa k, et al. yap/taz are essential for tgf-β2mediated conjunctival fibrosis. invest ophthalmol vis sci 2018;59:3069–3078. 23. chen ws, cao z, krishnan c, panjwani n. verteporfin without light stimulation inhibits yap activation in trabecular meshwork cells: implications for glaucoma treatment. biochem biophys res commun 2015;466:221– 225. 24. liu z, li s, qian x, li l, zhang h, liu z. rhoa/rockyap/taz axis regulates the fibrotic activity in dexamethasone-treated human trabecular meshwork cells. front mol bioscis 2021;8:728932. 25. lee ej, han jc, park dy, cho j, kee c. effect of connective tissue growth factor gene editing using adeno-associated virus-mediated crispr-cas9 on rabbit glaucoma filtering surgery outcomes. gene ther 2021;28:277–286. 26. fang y, tian j, fan y, cao p. latest progress on the molecular mechanisms of idiopathic pulmonary fibrosis. mol biol rep 2020;47:9811–9820. 27. wilson se. fibrosis is a basement membrane-related disease in the cornea: injury and defective regeneration of basement membranes may underlie fibrosis in other organs. cells 2022;11. 28. wallace dm, murphy-ullrich je, downs jc, o’brien cj. the role of matricellular proteins in glaucoma. matrix biol 2014;37:174–182. 29. nikhalashree s, karthikkeyan g, george r, shantha b, vijaya l, ratra v, et al. lowered decorin with aberrant extracellular matrix remodeling in aqueous humor and tenon’s tissue from primary glaucoma patients. invest ophthalmol vis sci 2019;60:4661–4669. 30. kramann r, schneider rk, dirocco dp, machado f, fleig s, bondzie pa, et al. perivascular gli1+ progenitors are key contributors to injury-induced organ fibrosis. cell stem cell 2015;16:51–66. 31. kuiper ej, witmer an, klaassen i, oliver n, goldschmeding r, schlingemann ro. differential expression of connective tissue growth factor in microglia and pericytes in the human diabetic retina. br j ophthalmol 2004;88:1082–1087. 32. liu h, yang r, tinner b, choudhry a, schutze n, chaqour b. cysteine-rich protein 61 and connective tissue growth factor induce deadhesion and anoikis of retinal pericytes. endocrinology 2008;149:1666–1677. 33. seher a, nickel j, mueller td, kneitz s, gebhardt s, ter vehn tm, et al. gene expression profiling of connective tissue growth factor (ctgf) stimulated primary human tenon fibroblasts reveals an inflammatory and wound healing response in vitro. mol vis 2011;17:53–62. 34. suzuma k, naruse k, suzuma i, takahara n, ueki k, aiello lp, et al. vascular endothelial growth factor induces expression of connective tissue growth factor via kdr, flt1, and phosphatidylinositol 3-kinase-aktdependent pathways in retinal vascular cells. j biol chem 2000;275:40725–40731. 35. tanaka s, zheng s, kharel y, fritzemeier rg, huang t, foster d, et al. sphingosine 1-phosphate signaling in perivascular cells enhances inflammation and fibrosis in the kidney. sci transl med 2022;14:eabj2681. 36. rao a, cruz rd. trabeculectomy: does it have a future? cureus 2022;14:e27834. 37. koike kj, chang pt. trabeculectomy: a brief history and review of current trends. int ophthalmol clin 2018;58:117– 133. 38. hassanpour k, rezaei kanavi m, daftarian n, samaeili a, suri s, parkravan m, et al. the inhibitory effect of connective tissue growth factor antibody on postoperative fibrosis in a rabbit model of trabeculectomy. j ophthalmic vis res 2022;17;4:486–496. 39. motevasseli t, daftarian n, kanavi mr, ahmadieh h, bagheri a, hosseini sb, et al. ocular safety of intravitreal connective tissue growth factor neutralizing antibody. curr eye res 2017;42:1194–1201. 40. garoffolo g, casaburo m, amadeo f, salvi m, bernava g, piacentini l, et al. reduction of cardiac fibrosis by interference with yap-dependent transactivation. circ res 2022;131:239–257. 41. ho lty, skiba n, ullmer c, rao pv. lysophosphatidic acid induces ecm production via activation of the mechanosensitive yap/taz transcriptional pathway in trabecular meshwork cells. invest ophthalmol vis sci 2018;59:1969–1984. 42. dillinger ae, kuespert s, froemel f, tamm er, fuchshofer r. ccn2/ctgf promotor activity in the developing and adult mouse eye. cell tissue res 2021;384:625–641. 43. gibson dj, pi l, sriram s, mao c, petersen be, scott ew, et al. conditional knockout of ctgf affects corneal wound healing. invest ophthalmol vis sci 2014;55:2062–2070. 44. kuiper ej, roestenberg p, ehlken c, lambert v, van treslong-de groot hb, lyons km, et al. angiogenesis is not impaired in connective tissue growth factor (ctgf) knockout mice. j histochem cytochem 2007;55:1139–1147. 45. wang s, zaitoun is, darjatmoko sr, sheibani n, sorenson cm. bim expression promotes the clearance of mononuclear phagocytes during choroidal neovascularization, mitigating scar formation in mice. life 2022;12:208. 452 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 review article neuro-ophthalmic manifestations of coronavirus disease 2019 and its vaccination: a narrative review mohadeseh feizi1, md; danielle r. isen2, do; mehdi tavakoli2, md 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2university of alabama at birmingham heersink school of medicine, department of ophthalmology and visual sciences, birmingham, alabama, usa orcid: mohadeseh feizi: https://orcid.org/0000-0001-8558-8074 abstract coronavirus disease 2019 (covid-19) is a current pandemic caused by sars-cov-2 that has vastly affected the whole world. although respiratory disease is the most common manifestation of covid-19, the virus can affect multiple organs. neurotropic aspects of the virus are increasingly unfolding, in so far as some respiratory failures are attributed to brainstem involvement. the neuro-ophthalmic manifestations of covid-19 and the neuro-ophthalmic side effects of vaccination were reviewed. the major findings are that the sars-cov-2 infection commonly causes headaches and ocular pain. it can affect the afferent and efferent visual pathways by ischemic or inflammatory mechanisms. optic nerve may be the origin of transient or permanent visual loss from papillophlebitis, idiopathic intracranial hypertension, or optic neuritis. cerebrovascular strokes are not uncommon and may lead to cortical visual impairment or optic nerve infarction. sarscov-2 may affect the pupillomotor pathways, resulting in tonic pupil (adie’s syndrome) or horner’s syndrome. cranial neuropathies including third, fourth, sixth, and seventh nerve palsies have all been reported. rhino-orbital mucormycosis superinfections in covid-19 patients receiving steroids or other immunosuppressive therapies may result in unilateral or bilateral visual loss and ophthalmoplegia. autoimmune conditions such as guillainbarré, miller-fisher syndrome, and ocular myasthenia have been reported. keywords: corona virus; covid-19; neuro-ophthalmology; vaccination; vision loss j ophthalmic vis res 2023; 18 (1): 113–122 correspondence to: mohadeseh feizi, md. labbafinejad medical center, shahid beheshti university of medical sciences, boostan 9 st., pasdaran ave., tehran 16666, iran. e-mail: mohadeseh_feizi@yahoo.com received: 17-11-2021 accepted: 30-08-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i1.12731 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: feizi m, isen dr, tavakoli m. neuroophthalmic manifestations of coronavirus disease 2019 and its vaccination: a narrative review. j ophthalmic vis res 2023;18:113–122. © 2023 feizi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 113 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i1.12731&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr neuro-ophthalmic manifestations of covid; feizi et al introduction coronavirus disease-2019 (covid-19) is a novel β coronavirus of group 2b, first reported in december 2019 in wuhan city, that rapidly disseminated all over the world, resulting in an immense pandemic.[1] the disease presents in a widely variable range from asymptomatic carriers or mild infection to severe acute respiratory syndrome (sars), multi-organ failure, and death. besides respiratory distress syndrome, sarscov-2 may affect many other organs and cause cardiac or renal injury, dermatologic conditions, gastrointestinal symptoms, coagulopathy, severe inflammatory reaction, and central or peripheral nervous system involvement.[2] up to one-third of patients with covid-19 have neurological complications, and the incidence appears to be higher in patients with more severe infections.[3] the most common severe neurologic manifestations of covid-19 are acute cerebrovascular disease and altered level of consciousness.[4] a retrospective study in wuhan reported neurological symptoms in 36.4% of the hospitalized patients.[1] neurologic manifestations are mainly reported to be associated with severe cases of covid-19.[1, 5] moreover, covid-19related cases of ischemic stroke involving visual pathways have resulted in prolonged hospitalizations and fatality.[6, 7] findings have suggested that ischemic strokes in patients with covid-19 disease are more severe and disabling than strokes in the uninfected subjects.[8] in contrast, isolated cranial neuropathies involving the eye are typically associated with mild to moderate covid-19 disease that improves spontaneously or with local protocols.[9, 10] a recent review reported that over 4% of patients with covid-19 had ophthalmic findings requiring clinical attention.[11] based on an initial study in wuhan, visual impairment was described in 3 out of 214 (1.4%) hospitalized patients with covid-19.[1] various neuro-ophthalmologic manifestations have been reported in patients with covid19 infection. in this article, we reviewed and categorized sars-cov-2-related neuroophthalmic presentations. mechanisms of neurologic involvement in covid-19 several mechanisms have been postulated for neurologic involvement in covid-19 disease. direct viral invasion, hypoxia, hypercoagulable state, inflammatory reactions related to cytokine storm, delayed autoantibody formation, endothelial dysfunction, and retrograde axonal transport of the infection via cranial and peripheral nerves (most notably, the olfactory nerve) are the proposed underlying mechanisms for neuro-ophthalmic manifestations of covid-19.[2, 5] it is thought that direct viral invasion is mediated by viral fusion to the angiotensin-converting-enzyme 2 (ace-2) receptor, which is expressed on the surface of pulmonary type ii alveolar epithelial cells as well as neurons and glial cells.[12] the sars-cov-2 virus can affect nearly all neuro-ophthalmic pathways [table 1]. covid-19 can cause a wide range of pathologies within the afferent and efferent visual pathways. sars-cov-2 can cause central nervous system conditions such as seizures,[13] anosmia or ageusia,[14] altered level of consciousness, posterior reversible encephalopathy syndrome (pres),[15, 16] neuromyelitis optica (nmo) spectrum disorder,[4, 17] myelin oligodendrocyte glycoprotein (mog)-associated disease,[3, 18–22] acute disseminated encephalomyelitis (adem),[23] cerebral venous sinus thrombosis (cvst),[24, 25] and cerebrovascular strokes.[2, 6–8] it can also affect the peripheral nervous system, leading to conditions such as guillain-barré,[26] miller fisher syndrome,[27, 28] polyneuritis cranialis,[28] and myasthenia gravis.[29, 30] sars-cov-2 is associated with pathologies of the afferent visual pathways including optic neuritis (idiopathic[5, 14, 31–33] or immunemediated),[3, 4, 17–22] optic nerve infarction,[34] papillophlebitis,[35] and idiopathic intracranial hypertension.[36–38] the efferent visual pathways can be lesioned by covid-19-related isolated cranial neuropathies,[9, 27, 39–41] nystagmus,[42–46] tonic pupil,[47–51] horner’s syndrome,[12, 13, 52] and opsoclonus-myoclonus-ataxia syndrome (omas).[53–55] mucormycosis infections,[56] which are of exponentially increasing incidence in covid-19 patients, can occur as a superinfection and result in lesions of the afferent or efferent visual pathways or even both.[57, 58] 114 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 neuro-ophthalmic manifestations of covid; feizi et al interval between infection and neuroophthalmic manifestations neuro-ophthalmic manifestations of covid-19 may present either concurring with systemic and pulmonary symptoms or days to several weeks after their resolution. timeline latency between acute viral symptoms and neuro-ophthalmic manifestation, auto-antibody formation, and good response to steroid therapy favor an immunemediated mechanism.[49] guillain-barré, miller fisher syndrome, nmo, mog-associated disease, adem, tonic pupil, rhombencephalitis, bickerstaff encephalitis, myasthenia gravis (mg), and omas were all postulated to have delayed-immune mediated mechanisms related to covid-19. the delayed immune response may be from antibodies directed against sars-cov-2 proteins that cross-react with cellular proteins through a mechanism known as molecular mimicry. alternatively, covid-19 infection may impair immunologic self-tolerance.[29] headache/ocular pain ocular pain and headache are common and may be the initial manifestation of covid-19 infection.[1, 11, 59] headache was reported in 71% and ocular pain in 34% by healthcare workers in the netherlands in patients with a positive sars-cov2 polymerase chain reaction (pcr).[60] in another study, eye pain was amongst the most common of the ocular symptoms and seen in 16% of patients.[61] photophobia and itchy eyes were seen at a similar frequency (18% and 17%, respectively). headache characteristics in covid�19 patients were moderate to severe, pulsating or pressing, bilateral, and mostly in the temporoparietal, forehead, or periorbital regions. it has been postulated that an increase in proinflammatory cytokines, hypoxia, or activation of the trigeminal nerve endings from direct viral insult or vasculopathy explain the underlying pathophysiology of headache in covid-19 disease.[62] however, the exact mechanism is not clear, and viral encephalitis and meningitis should be considered. overall, it seems that headache and periocular pain are the most prevalent neuroophthalmic presentations of covid-19 but more comprehensive epidemiological studies are required to evaluate the prevalence of each neurological symptom. optic neuritis and other optic nerve disorders optic neuritis has been reported in association with covid-19 infections in multiple cases where no other etiologies have been determined.[5, 14, 31–33] covid-19 has also been the harbinger to optic neuritis in nmo spectrum disorder[4, 17] and mogrelated disease.[3, 18, 19, 21, 63, 64] optic neuritis in association with covid-19 infection has also been reported in the pediatric age group even in the context of demyelinating conditions.[65] covid-19related optic neuritis had a good response to intravenous (iv) corticosteroid therapy in all cases except four.[5, 14, 22, 32] optic neuritis was reported in conjunction with panuveitis in one case of covid-19, which resulted in optic atrophy despite corticosteroid treatment. however, the patient only received oral prednisone without high-dose iv corticosteroids. the authors postulated that ischemic insult due to the prothrombotic capacity of covid-19 or an inflammatory reaction resulted in optic atrophy in this case.[32] novi et al reported an adult patient with covid19 disease and bilateral retrobulbar optic neuritis with enhancing lesions in optic nerves, brain, and thoracic spine, consistent with adem.[23] cerebrovascular ischemia is a known complication of sars-cov-2 infection.[1] optic nerve infarction due to internal carotid artery occlusion was reported in a 50-year-old covidpositive male by tavakoli et al.[34] central retinal artery occlusion[66] or ophthalmic artery occlusion[67] due to internal carotid artery stroke have also been reported in covid-19 disease. there is one report of papillophlebitis in a 40-year-old male that occurred four weeks after the resolution of a typical covid-19 infection with elevated d-dimer and fibrinogen levels. the authors proposed that the covid-19 cytokine storm induced a hypercoagulable state and thrombotic microangiopathy, increasing the risk of papillophlebitis.[35] idiopathic intracranial hypertension can occur in adults with covid-19 disease, but it is rare, and most of the cases have been reported in children.[36–38] two of these cases were associated journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 115 neuro-ophthalmic manifestations of covid; feizi et al with increased intracranial pressure inducing sixth nerve palsies in idiopathic intracranial hypertension due to covid-19 multisystem inflammatory syndrome in children (mis-c).[36, 37] pupillary abnormalities tonic (adie’s) pupil refers to parasympathetic denervation of the pupil sphincter, which causes poor constriction of the pupil to the light but the reaction to the accommodation remains relatively spared. tonic pupil has been reported in association with covid-19, including unilateral[47] and bilateral[48] cases. one patient with covid-19related bilateral tonic pupil also had inflammatory multifocal choroiditis.[68] additionally, adie-holmes syndrome (with additional finding of loss of the deep tendon reflexes) has been described in a patient with covid-19 infection.[69] lastly, ordás et al reported a case of tonic pupil with contralateral trochlear palsy in association with covid-19 infection.[49] tonic pupil is often idiopathic, but it has been associated with other infections (e.g., syphilis, lyme’s disease, influenza or herpes viruses), autoimmune processes, trauma, choroidal and orbital tumors, and surgery.[47] in each of the above cases of tonic pupil,[47] there was a delay (ranging from two days to one month) between the onset of covid-related respiratory symptoms and development of tonic pupil. most of the authors hypothesized that tonic pupil in covid19 is secondary to a post-viral delayed immunemediated injury rather than direct viral entry into the central nervous system. moreover, a taper of prednisolone has been utilized for treatment with subsequent improvement in the tonic pupil.[50] horner’s syndrome has also been rarely described in covid-19 disease.[12, 13, 52] in each case, covid-19 pneumonia involving the upper part of the lungs was the suggested etiology of horner’s syndrome, and no other causes were discovered with subsequent imaging studies. central visual impairment and visual field defects covid-19 disease can induce hypercoagulable and inflammatory states, increasing the risk of cerebrovascular stroke.[6, 70] there are reports of ischemic stroke involving the visual pathways in association with sars-cov-2 infection, resulting in homonymous field defects[2] or even cortical blindness from bilateral occipital infarcts.[7] bondira et al reported a patient with covid-19 disease and bilateral occipital strokes, resulting in a partial right homonymous hemianopsia and difficulty with reading.[6] priftis et al presented a covid-positive patient with a left occipito-temporal ischemic stroke, resulting in alexia without agraphia syndrome and right homonymous hemianopsia.[8] covid-induced pres has been reported, resulting in transient cortical visual loss[15] or even hallucinatory palinopsia.[16] covid-associated cvst has also been described but is uncommon, and only a few cases have been associated with blurry vision and papilledema.[24, 25] the disproportionally low frequency of reported visual involvement in covid-associated cvst may be because of the severity of other symptoms or an altered level of consciousness. in addition, there are reports of visual loss due to pituitary apoplexy in the context of acute covid-19 infection.[71, 72] cranial nerve palsies and double vision damage to third, fourth, sixth, and seventh cranial nerves have all occurred in timeline relation to covid-19 infection. cranial nerve involvement may develop as a primary and isolated insult or in the context of a more generalized condition such as miller fisher syndrome, guillain-barré, myasthenia gravis, venous sinus thrombosis, and increased intracranial pressure. isolated oculomotor palsy with and without pupillary involvement has been reported in association with covid-19.[39, 40, 73] similarly, isolated abducens palsy has been described in covid-19.[9, 27] in these cases, there was no enhancement of the abducens nerve pathway on mri, and patients had underlying systemic hypertension. such findings raised the hypothesis that uncontrolled hypertension in the acute viral illness may cause abducens palsy. an alternative theory was that the abducens palsies occurred from the leptomeningeal invasion of sars-cov-2, given that two of these cases had optic nerve sheath enhancement on mri. as previously mentioned, there is one case of unilateral trochlear nerve palsy with contralateral tonic pupil[49] and another with bilateral trochlear nerve palsy in the setting of covid-related cerebral vasculitis.[74] 116 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 neuro-ophthalmic manifestations of covid; feizi et al table 1. a summary of reported neuro-ophthalmic manifestations of covid-19. clinical entity clinical characteristics references headache and ocular pain common and may be the initial manifestations. moderate to severe, pulsating/pressing, bilateral, temporo-parietal, forehead, or periorbital regions. mao l et al[1], 2020; chwalisz bk et al, 2020[11]; huang c et al[59], 2019 optic neuritis unilateral or bilateral, may be associated with neuromyelitis optica (nmo) spectrum disorders, myelin oligodendrocyte (mog)-related disease, panuveitis, acute disseminated encephalomyelitis (adem). caudill gb et al [31], 2020; benito-pascual b et al[32], 2019; marcos aet al[5], 2020; rodríguez-rodríguez ms et al[14], 2021; deane k et al[33], 2021; novi g et al[23], 2020 optic nerve infarction vision loss due to internal carotid artery occlusion, optic nerve ischemia revealed on dwi sequence. tavakoli et al[34], 2019 papillophlebitis decreased visual field sensitivity, dilated and tortuous retinal vessels, disc edema, and retinal hemorrhage; decreased vision due to macular edema. insausti-garcía a et al[35], 2020 idiopathic intracranial hypertension more reported in children than adults due to multisystem inflammatory syndrome (mis). verkuil ld et al[36], 2020; sofuoğlu ai et al[37], 2021; khalid mf et al[38], 2021 tonic adie’s pupil unilateral or bilateral, associated with multifocal choroiditis; trochlea palsy. gopal m et al[47], 2021; quijano-nieto ba et al[48], 2021; ortiz-seller a et al[68], 2020; kaya tutar n et al[69], 2021; ordás cm et al[49], 2020 horner syndrome associated with pneumonia involving the upper part of the lung. popiołek a et al[52], 2021; naor ms et al[12], 2021; portela-sánchez s et al[13], 2021 visual field defect and central visual impairment cerebrovascular stroke resulting in homonymous visual field defect, cortical visual blindness, reading difficulties. tisdale ak et al[70], 2020; bondira ip et al[6], 2021; cyr dg et al[7], 2020; priftis k et al[8], 2021 posterior reversible encephalopathy syndrome (pres) transient cortical visual loss and hallucinatory palinopsia. kaya y et al[15], 2020; ghosh r et al[16], 2020 cranial nerve palsy isolated or multiple cranial nerve involvement including third, fourth, sixth, and seventh. can occur in the context of miller fisher syndrome, guillain-barré, myasthenia gravis, venous sinus thrombosis, and increased intracranial pressure. ordás cm et al[49], 2020; douedi s et al[39], 2021; cicalese mp et al[73], 2022; john c et al[40], 2020; greer ce et al[9], 2020; dinkin m et al[27], 2020; de oliveira r de mc et al[74], 2020; gutiérrez-ortiz c et al[28], 2020; sansone p et al[26], 2021; restivo da et al[29], 2020; mas maresma l et al[30], 2020; lima ma et al[10], 2020; juliao caamaño ds et al[75], 2020 nystagmus and abnormal ocular movement acquired nystagmus due to acute labyrinthitis, benign paroxysmal positional vertigo, rhombencephalitis, bickerstaff encephalitis, opsoclonus-myoclonus-ataxia syndrome (omas). perret m et al[42], 2021; picciotti pm et al[43], 2021; wong p et al[44], 2022; llorente ayuso l et al[45], 2021; nelson jl et al[53], 2022; emamikhah m et al[54], 2021 rhino-orbital-cerebral mucormycosis (rocm) mostly occurs in patients receiving high-dose corticosteroid; presented with peri-ocular edema, vision loss, ptosis, and ophthalmo-paresis. sen m et al[57], 2021; pakdel f et al[58], 2022 different medications for covid-19-related cranial neuropathies such as hydroxychloroquine, azithromycin, corticosteroids, and iv immunoglobulin have been used. however, it is not known whether the neuro-ophthalmic benefit was conferred. cranial neuropathy in relation to covid-19 has also been seen in the context of miller fisher syndrome, guillain-barré, and polyneuritis cranialis. dinkin et al described a case of presumed miller fisher syndrome in a covid-positive patient with a partial left pupil involving oculomotor nerve palsy, journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 117 neuro-ophthalmic manifestations of covid; feizi et al bilateral abducens palsy, hyporeflexia, and gait ataxia.[27] the deficits partially improved following iv immunoglobulin infusions. gutiérrez-ortiz et al detailed a similar case of miller fisher syndrome in a patient with right fascicular oculomotor palsy, right internuclear ophthalmoparesis, ataxia, areflexia, albuminocytologic dissociation, anosmia, ageusia, and positive reverse transcriptase-pcr for sars-cov-2. most of the deficits were resolved following iv immunoglobulin infusions. these authors described a second covid-positive case with bilateral abducens palsy, areflexia, and albuminocytologic dissociation without ataxia or limb weakness secondary to polyneuritis cranialis.[28] in a systematic review published by sansone et al, of the 41 patients with sars-cov-2-related guillain-barré syndrome, 9 (22%) had diplopia, 7 (17%) had ocular palsy, and 13 (32%) had facial palsy. the average time between the onset of sarscov-2 symptoms and the first neurological signs of guillain-barré syndrome was 10 days.[26] covid-19 has also been the harbinger of new diagnoses of myasthenia gravis. restivo et al detailed three patients who developed diplopia, ptosis, or dysphagia and tested positive for elevated serum acetylcholine receptor antibodies following the sars-cov-2 infection.[29] fatigability and other myasthenic symptoms started four to seven days after the initial covid19 manifestations.[29, 30] similarity between sarscov-2 epitopes and neuromuscular junction components is postulated to induce molecular mimicry, resulting in auto-antibody formation and subsequently post-covid-19 myasthenia gravis.[29] isolated peripheral facial nerve palsy has also been reported either during or at the onset of the sars-cov-2 clinical course. in one of the eight peripheral facial nerve palsy cases reported by lima et al, ipsilateral abducens palsy was also present.[10] facial diplegia has also been reported as a parainfectious complication of covid-19 disease and was considered a rare variant of guillain-barré syndrome in the setting of concomitant albuminocytologic dissociation.[75] abnormal ocular movements and nystagmus acquired nystagmus has been seen in association with covid-19,[76] and may be due to various underlying etiologies including acute labyrinthitis,[42] benign paroxysmal positional vertigo,[43] rhombencephalitis,[44] and bickerstaff encephalitis.[45] several cases of omas have been described in covid-positive patients.[53–55] in all patients who were tested, work-up with a paraneoplastic panel was unrevealing for other causes of omas. a variety of infections besides sars-cov-2 including human immunodeficiency virus (hiv), west nile virus, epstein barr virus, and enterovirus have also been associated with omas.[53] treatments used for covid-associated omas include various combinations of the following: iv immunoglobulin, levetiracetam, sodium valproate, clonazepam, and corticosteroids. all cases were associated with a good therapeutic response and partial to complete recovery. emamikhah et al stated that the dramatic effect of immunotherapy on recovery suggests an immune-mediated parainfectious mechanism for covid-related omas.[54] neuro-ophthalmic presentation due to secondary mucormycosis there is strong evidence that infection with sars-cov-2 increases the risk of secondary fungal infections, notably rhino-orbital-cerebral mucormycosis (rocm). the incidence of rocm increased to epidemic proportions during the second wave of the covid-19 pandemic in india.[57] a retrospective, observational study was conducted in india involving 2826 patients with covid-associated rocm. the most common primary signs included periocular/facial edema (33%), loss of vision (21%), ptosis (12%), and proptosis (11%). ocular movement restriction and diplopia were infrequent signs (3%). most (87%) of the patients had received systemic corticosteroids prior to developing covid-associated rocm, and it was the most common risk factor for the condition followed by diabetes mellitus. neuro-ophthalmic complications of covid19 vaccines there are several reports of neuroophthalmic complications following covid-19 vaccination.[77–79] these complications occurred after all types of vaccines. they include acute ischemic stroke, intracranial hemorrhages, and cerebral venous sinus thrombosis.[78, 80] 118 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 neuro-ophthalmic manifestations of covid; feizi et al other reported neuro-ophthalmic complications include: bilateral arteritic anterior ischemic optic neuropathy (aaion),[81] post-vaccination cranial neuropathy, that is, third[73] and sixth[82–84] nerve palsies, facial palsy,[84–87] multiple cranial nerve palsies,[88] pupillary abnormalities such as horner’s syndrome, holmes-adie pupil, miosis and mydriasis,[78] eight nerve involvement and benign paroxysmal positional vertigo,[89] and post-vaccination optic neuritis.[90–92] in multiple sclerosis patients, bnt162b2 mrna vaccine was reported to be associated with a transient increase of ms symptoms in 3.8% but none of them needed treatment.[93] summary coronavirus disease 2019 and also all types of vaccines that have been made against it can affect the afferent and efferent visual pathways by ischemic or inflammatory mechanisms. the optic nerve may be the origin of transient or permanent visual loss from papillophlebitis, idiopathic intracranial hypertension, or optic neuritis. cerebrovascular strokes are not uncommon and may lead to cortical visual impairment. the pupillomotor pathways and cranial nerve including the third, fourth, sixth, and seventh nerve may also be involved. early detection of the neuroophthalmic features of covid-19 disease/vaccine will assist in preventing vision loss and oculomotor deficits. financial support and sponsorship this article is authors’ own work and has no sources of support. conflicts of interest the authors have no financial interest in the subject of this article. references 1. mao l, jin h, wang m, hu y, chen s, he q, et al. neurologic manifestations of hospitalized patients with coronavirus disease 2019 in wuhan, china. jama neurol 2020;77:683–690. 2. tisdale ak, dinkin m, chwalisz bk. afferent and efferent neuro-ophthalmic complications of coronavirus disease 19. j neuro-ophthalmol 2021;41:154–165. 3. rojas-correa dx, reche-sainz ja, insausti-garcía a, calleja-garcía c, ferro-osuna m. post covid-19 myelin oligodendrocyte glycoprotein antibody-associated optic neuritis. neuro-ophthalmology 2021;46:115–121. 4. shaw vc, chander g, puttanna a. neuromyelitis optica spectrum disorder secondary to covid-19. br j hosp med 2020;81:1–3. 5. da silva catharino am, neves mao, nunes nsm, do nascimento jsf, do nascimento jkf, castro rrt, et al. covid-19 related optic neuritis: case report. j clin neurol neurosci 2020;18:10. 6. bondira ip, lambert-cheatham na, sakuru rc, polingerhyman dj, pipitone bd, arnold ke. inability to read after prolonged covid-19 hospitalization: mri with clinical correlation. j neuro-ophthalmol 2021;41:e277–e278. 7. cyr dg, vicidomini cm, siu ny, elmann se. severe bilateral vision loss in 2 patients with coronavirus disease 2019. j neuro-ophthalmol 2020;40:403–405. 8. priftis k, prior m, meneghetti l, mercogliano t, bendini m. alexia without agraphia in a post covid-19 patient with left-hemisphere ischemic stroke. neurol sci 2021;42:2179–2181. 9. greer ce, bhatt jm, oliveira ca, dinkin mj. isolated cranial nerve 6 palsy in 6 patients with covid-19 infection. j neuroophthalmol 2020;40:520–522. 10. lima ma, silva mt, soares cn, coutinho r, oliveira hs, afonso l, et al. peripheral facial nerve palsy associated with covid-19. j neurovirol 2020;26:941–944. 11. chwalisz bk, dinkin mj. disease of the year: covid-19 and its neuro-ophthalmic complications. j neuro-ophthalmol 2020;40:283–284. 12. naor ms, mathew pg, sharon r. transient horner syndrome associated with covid-19: a case report. eneurologicalsci 2021;25:100349. 13. portela-sánchez s, sánchez-soblechero a, melgarejo otalora pj, rodríguez lópez á, velilla alonso g, palaciosmendoza ma, et al. neurological complications of covid19 in hospitalized patients: the registry of a neurology department in the first wave of the pandemic. eur j neurol 2021;28:3339–3347. 14. rodríguez-rodríguez ms, romero-castro rm, alvaradode la barrera c, gonzález-cannata mg, garcía-morales ak, ávila-ríos s. optic neuritis following sars-cov-2 infection. j neurovirol 2021;27:359–363. 15. kaya y, kara s, akinci c, kocaman as. transient cortical blindness in covid-19 pneumonia; a pres-like syndrome: case report. j neurol sci 2020;413:116858. 16. ghosh r, lahiri d, dubey s, ray bk, benito-león j. hallucinatory palinopsia in covid-19-induced posterior reversible encephalopathy syndrome. j neuroophthalmol 2020;40:523–526. 17. de ruijter ns, kramer g, gons ra, hengstman gj. neuromyelitis optica spectrum disorder after presumed coronavirus (covid-19) infection: a case report. mult scler relat disord 2020;46:102474. 18. zhou s, jones-lopez ec, soneji dj, azevedo cj, patel vr. myelin oligodendrocyte glycoprotein antibodyassociated optic neuritis and myelitis in covid-19. j neuro-ophthalmol 2020;40:398–402. 19. sawalha k, adeodokun s, kamoga gr. covid-19-induced acute bilateral optic neuritis. j investig med high impact case rep 2020;8:2324709620976018. journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 119 neuro-ophthalmic manifestations of covid; feizi et al 20. žorić l, rajović-mrkić i, čolak e, mirić d, kisić b. optic neuritis in a patient with seropositive myelin oligodendrocyte glycoprotein antibody during the postcovid-19 period. int med case rep j 2021;14:349–355. 21. kogure c, kikushima w, fukuda y, hasebe y, takahashi t, shibuya t, et al. myelin oligodendrocyte glycoprotein antibody-associated optic neuritis in a covid-19 patient: a case report. medicine 2021;100:e25865. 22. woodhall m, mitchell jw, gibbons e, healy s, waters p, huda s. case report: myelin oligodendrocyte glycoprotein antibody-associated relapse with covid-19. front neurol 2020;11:598531. 23. novi g, rossi t, pedemonte e, saitta l, rolla c, roccatagliata l, et al. acute disseminated encephalomyelitis after sars-cov-2 infection. neurol neuroimmunol neuroinflamm 2020;7:797. 24. dakay k, cooper j, bloomfield j, overby p, mayer sa, nuoman r, et al. cerebral venous sinus thrombosis in covid-19 infection: a case series and review of the literature. j stroke cerebrovasc dis 2021;30:105434. 25. klein de, libman r, kirsch c, arora r. cerebral venous thrombosis: a typical presentation of covid-19 in the young. j stroke cerebrovasc dis 2020;29:104989. 26. sansone p, giaccari lg, aurilio c, coppolino f, esposito v, fiore m, et al. post-infectious guillain-barré syndrome related to sars-cov-2 infection: a systematic review. life 2021;11:1–16. 27. dinkin m, gao v, kahan j, bobker s, simonetto m, wechsler p, et al. covid-19 presenting with ophthalmoparesis from cranial nerve palsy. neurology 2020;95:221–223. 28. gutiérrez-ortiz c, méndez-guerrero a, rodrigo-rey s, san pedro-murillo e, bermejo-guerrero l, gordo-mañas r, et al. miller fisher syndrome and polyneuritis cranialis in covid-19. neurology 2020;95:e601–e605. 29. restivo da, centonze d, alesina a, marchese-ragona r. myasthenia gravis associated with sars-cov-2 infection. ann intern med 2020;173:1027–1028. 30. mas maresma l, barrachina esteve o, navarro vilasaró m, moreno-ariño m. [myasthenia gravis associated with sars-cov-2 infection: a conjunction of several factors]. rev esp geriatr gerontol 2020;55:360–361. 31. caudill gb, wolin mj. myelin oligodendrocyte glycoprotein and neuromyelitis optica/aquaporin-4 antibody negative covid-19–associated optic neuritis. j neuro-ophthalmol 2022. 32. benito-pascual b, gegúndez ja, díaz-valle d, arriolavillalobos p, carreño e, culebras e, et al. panuveitis and optic neuritis as a possible initial presentation of the novel coronavirus disease 2019 (covid-19). ocul immunol inflamm 2020;28:922–925. 33. deane k, sarfraz a, sarfraz z, valentine d, idowu ar, sanchez v. unilateral optic neuritis associated with sarscov-2 infection: a rare complication. am j case rep 2021;22:e931665. 34. tavakoli m, sotoudeh m, rezaei a, saadatpour z, michael s, vaphides lb. optic nerve infarction in a patient with coronavirus disease 2019. j neuroophthalmol 2021;42e347–e348. 35. insausti-garcía a, reche-sainz ja, ruiz-arranz c, lópez vázquez á, ferro-osuna m. papillophlebitis in a covid19 patient: inflammation and hypercoagulable state. eur j ophthalmol 2020;32:np168–np172. 36. verkuil ld, liu gt, brahma vl, avery ra. pseudotumor cerebri syndrome associated with mis-c: a case report. lancet 2020;396:532. 37. sofuoğlu ai, akçay n, şevketoğlu e, bektaş g. pseudotumor cerebri syndrome as a neurologic involvement of multisystem inflammatory syndrome in children: a case report. j trop pediatr 2021;67:1–4. 38. khalid mf, micieli ja. idiopathic intracranial hypertension associated with sars-cov-2 b.1.1.7 variant of concern. can j neurol sci 2022;49:472–473. 39. douedi s, naser h, mazahir u, hamad ai, sedarous m. third cranial nerve palsy due to covid-19 infection. cureus 2021;13:e14280. 40. fitzpatrick jc, comstock jm, longmuir ra, donahue sp, fitzpatrick jm, bond jb. cranial nerve iii palsy in the setting of covid 19 infection. j neuro-ophthalmology 2020;41:e286–e287. 41. belghmaidi s, nassih h, boutgayout s, el fakiri k, el qadiry r, hajji i, et al. third cranial nerve palsy presenting with unilateral diplopia and strabismus in a 24-year-old woman with covid-19. am j case rep 2020;21:e925897. 42. perret m, bernard a, rahmani a, manckoundia p, putot a. acute labyrinthitis revealing covid-19. diagnostics 2021;11:482. 43. picciotti pm, passali gc, sergi b, de corso e. benign paroxysmal positional vertigo (bppv) in covid-19. audiology res 2021;11:418–422. 44. wong p, craik s, newman p, makan a, srinivasan k, crawford e, et al. lessons of the month 1: a case of rhombencephalitis as a rare complication of acute covid19 infection. clin med 2020;20:293–294. 45. llorente ayuso l, torres rubio p, beijinho do rosário rf, giganto arroyo ml, sierra-hidalgo f. bickerstaff encephalitis after covid-19. j neurol 2021;268:2035– 2037. 46. garcía-romo e, blanco r, nicholls c, hernández-tejero a, fernández-de-arévalo b. covid-19 presenting with nystagmus. arch soc esp oftalmol 2021;96:224–226. 47. gopal m, ambika s, padmalakshmi k. tonic pupil following covid-19. j neuro-ophthalmol 2021;41:e764–e766. 48. quijano-nieto ba, córdoba-ortega cm. [tonic pupil after covid-19 infection]. arch soc esp oftalmol 2021;96:353– 355. 49. ordás cm, villacieros-álvarez j, pastor-vivas ai, corralesbenítez á. concurrent tonic pupil and trochlear nerve palsy in covid-19. j neurovirol 2020;26:970–972. 50. kaya tutar n, kale n, tugcu b. adie-holmes syndrome associated with covid-19 infection: a case report. indian j ophthalmol 2021;69:773–774. 51. ortiz-seller a, martínez costa l, hernández-pons a, valls pascual e, solves alemany a, albert-fort m. ophthalmic and neuro-ophthalmic manifestations of coronavirus disease 2019 (covid-19). ocul immunol inflamm 2020;28:1285–1289. 52. popiołek a, chyrek-tomaszewska a, kłopocki j, dura m, pulkowski g. horner’s syndrome in the course of covid19: a case report. med res j 2021;6:274–275. 120 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 neuro-ophthalmic manifestations of covid; feizi et al 53. nelson jl, blume gm, bansal sk, kaufman jr, woods fr, zhang x, et al. postinfectious sars-cov-2 opsoclonusmyoclonus-ataxia syndrome. j neuro-ophthalmol 2022;42:251–255. 54. emamikhah m, babadi m, mehrabani m, jalili m, pouranian m, daraie p, et al. opsoclonus-myoclonus syndrome, a post-infectious neurologic complication of covid19: case series and review of literature. j neurovirol 2021;27:26–34. 55. shah pb, desai sd. opsoclonus myoclonus ataxia syndrome in the setting of covid-19 infection. neurology 2021;96:33. 56. veisi a, bagheri a, eshaghi m, rikhtehgar mh, rezaei kanavi m, farjad r. rhino-orbital mucormycosis during steroid therapy in covid-19 patients: a case report. eur j ophthalmol 2021;32:np11–np16. 57. sen m, honavar sg, bansal r, sengupta s, rao r, kim u, et al. epidemiology, clinical profile, management, and outcome of covid-19-associated rhino-orbital-cerebral mucormycosis in 2826 patients in india collaborative opai-ijo study on mucormycosis in covid-19 (cosmic), report 1. indian j ophthalmol 2021;69:1670–1692. 58. pakdel f, zand a, sharifi a, asadi m, abri aghdam k. challenges and pitfalls in the management of rhino-orbital mucormycosis in ophthalmology: a highlighted problem in the covid-19 era. j ophthalmic vis res 2022;17:424–431. 59. huang c, wang y, li x, ren l, zhao j, hu y, et al. clinical features of patients infected with 2019 novel coronavirus in wuhan, china. lancet 2020;395:497–506. 60. tostmann a, bradley j, bousema t, yiek wk, holwerda m, bleeker-rovers c, et al. strong associations and moderate predictive value of early symptoms for sars-cov-2 test positivity among healthcare workers, the netherlands, march 2020. euro surveill 2020;25:2000508. 61. pardhan s, vaughan m, zhang j, smith l, chichger h. sore eyes as the most significant ocular symptom experienced by people with covid-19: a comparison between pre-covid-19 and during covid-19 states. bmj open ophthalmol 2020;5:e000632. 62. bolay h, gül a, baykan b. covid-19 is a real headache! headache 2020;60:1415–1421. 63. colantonio ma, nwafor dc, jaiswal s, shrestha ak, elkhooly m, rollins s, et al. myelin oligodendrocyte glycoprotein antibody-associated optic neuritis and myelitis in covid-19: a case report and a review of the literature. egypt j neurol psychiat neurosurg 2022;58:62. 64. assavapongpaiboon b, apinyawasisuk s, jariyakosol s. myelin oligodendrocyte glycoprotein antibody-associated optic neuritis with covid-19 infection: a case report and literature review. am j ophthalmol case rep 2022;26:101491. 65. fernández alcalde c, granados fernández m, nieves moreno m, calvo rey c, falces romero i, noval martín s. covid-19 ocular findings in children: a case series. world j pediatr 2021;17:329–334. 66. murchison ap, sweid a, dharia r, theofanis tn, tjoumakaris si, jabbour pm, et al. monocular visual loss as the presenting symptom of covid-19 infection. clin neurol neurosurg 2021;201:106440. 67. deshpande g, giri p. acute monocular vision loss as presenting symptom of delayed stroke from internal carotid occlusion in covid-19. indian j ophthalmol 2021;69:1325–1327. 68. ortiz-seller a, martínez costa l, hernández-pons a, valls pascual e, solves alemany a, albert-fort m. ophthalmic and neuro-ophthalmic manifestations of coronavirus disease 2019 (covid-19). ocul immunol inflamm 2020;28:1285–1289. 69. kaya tutar n, kale n, tugcu b. adie-holmes syndrome associated with covid-19 infection: a case report. indian j ophthalmol 2021;69:773–774. 70. tisdale ak, chwalisz bk. neuro-ophthalmic manifestations of coronavirus disease 19. curr opin ophthalmol 2020;31:489–494. 71. katti v, ramamurthy lb, kanakpur s, shet sd, dhoot m. neuro-ophthalmic presentation of covid-19 disease: a case report. indian j ophthalmol 2021;69:992–994. 72. solorio-pineda s, almendárez-sánchez ca, tafurgrandett aa, ramos-martínez ga, huato-reyes r, ruiz-flores mi, et al. pituitary macroadenoma apoplexy in a severe acute respiratory syndrome-coronavirus2-positive testing: causal or casual? surg neurol int 2020;11:304. 73. cicalese mp, ferrua f, barzaghi f, cerri f, moro m, aiuti a, et al. third cranial nerve palsy in an 88-year-old man after sars-cov-2 mrna vaccination: change of injection site and type of vaccine resulted in an uneventful second dose with humoral immune response. bmj case rep 2022;15:e246485. 74. oliveira rm, santos dh, olivetti bc, takahashi jt. bilateral trochlear nerve palsy due to cerebral vasculitis related to covid-19 infection. arq neuropsiquiatr 2020;78:385– 386. 75. juliao caamaño ds, alonso beato r. facial diplegia, a possible atypical variant of guillain-barré syndrome as a rare neurological complication of sars-cov-2. j clin neurosci 2020;77:230–232. 76. garcía-romo e, blanco r, nicholls c, hernández-tejero a, fernández-de-arévalo b. covid-19 presenting with nystagmus. arch la soc española oftalmol 2021;96:224– 226. 77. ng xl, betzler bk, ng s, chee sp, rajamani l, singhal a, et al. the eye of the storm: covid-19 vaccination and the eye. ophthalmol ther 2022;11:81–100. 78. petzold a. neuro-ophthalmic implications of severe acute respiratory syndrome coronavirus 2 (sars-cov-2) related infection and vaccination. asia pac j ophthalmol 2022;11:196–207. 79. eleiwa tk, gaier ed, haseeb a, elsheikh rh, sallam ab, elhusseiny am. adverse ocular events following covid-19 vaccination. inflamm res 2021;70:1005–1009. 80. patone m, handunnetthi l, saatci d, pan j, katikireddi sv, razvi s, et al. neurological complications after first dose of covid-19 vaccines and sars-cov-2 infection. nat med 2021;27:2144–2153. 81. maleki a, look-why s, manhapra a, foster cs. covid19 recombinant mrna vaccines and serious ocular inflammatory side effects: real or coincidence? j ophthalmic vis res 2021;16:490–501. 82. pawar n, ravindran m, padmavathy s, chakrabarty s. acute abducens nerve palsy after covid-19 vaccination in a young adult. indian j ophthalmol 2021;69:3764–3766. journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 121 neuro-ophthalmic manifestations of covid; feizi et al 83. karam ez, ríos macias p, chahin g, kattah jc. inflammatory sixth nerve palsy post-covid-19 vaccination: magnetic resonance imaging findings. neuro-ophthalmol 2022;46:314–318. 84. veisi a, najafi m, hassanpour k, bagheri a. facial and abducens nerve palsies following covid-19 vaccination: report of two cases. neuro-ophthalmology 2022;46:203–206. 85. ish s, ish p. facial nerve palsy after covid-19 vaccination a rare association or a coincidence. indian j ophthalmol 2021;69:2550–2552. 86. shemer a, pras e, einan-lifshitz a, dubinsky-pertzov b, hecht i. association of covid-19 vaccination and facial nerve palsy: a case-control study. jama otolaryngol head neck surg 2021;147:739–743. 87. ozonoff a, nanishi e, levy o. bell’s palsy and sars-cov-2 vaccines. lancet infect dis 2021;21:450–452. 88. mungmunpuntipantip r, wiwanitkit v. multiple cranial nerve palsies and covid-19 vaccination. acta neurol scand 2022;145:375. 89. barreto rg, yacovino da, teixeira lj, freitas mm. teleconsultation and teletreatment protocol to diagnose and manage patients with benign paroxysmal positional vertigo (bppv) during the covid-19 pandemic. int arch otorhinolaryngol 2021;25:e141–e149. 90. roy m, chandra a, roy s, shrotriya c. optic neuritis following covid-19 vaccination: coincidence or sideeffect? a case series. indian j ophthalmol 2022;70:679– 683. 91. garcía-estrada c, gómez-figueroa e, alban l, ariascárdenas a. optic neuritis after covid-19 vaccine application. clin exp neuroimmunol 2022;13:72–74. 92. alvarez lm, ning neo y, davagnanam i, ashenhurst m, acheson j, abdel-hay a, et al. post vaccination optic neuritis: observations from the sars-cov-2 pandemic. ssrn electron j 2021. 93. dreyer-alster s, menascu s, mandel m, shirbint e, magalashvili d, dolev m, et al. covid-19 vaccination in patients with multiple sclerosis: safety and humoral efficacy of the third booster dose. j neurol sci 2022;434:120155. 122 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 original article implantation of a small aperture intraocular lens in eyes with irregular corneas and higher order aberrations fabrizio franco1, md; marco branchetti1, md; lidia vicchio1, md; federica serino1, md; marco piergentili1, md; vito spagnuolo1, md; francesca santoro1, bs; gianni virgili1, 2, md; fabrizio giansanti1, 2, md 1department of ophthalmology, careggi teaching hospital, florence, italy 2department of neurosciences, faculty of psychology, university of florence, pharmacology and children health, florence, italy orcid: fabrizio franco: https://orcid.org/0000-0002-3583-5898 marco branchetti: https://orcid.org/0000-0003-4242-4875 abstract purpose: corneal irregularities can lead to high order aberrations (hoas) and may influence the outcomes in terms of intraocular lens (iol) selection and visual acuity assessment. the aim of this study was to evaluate the visual acuity and satisfaction after ic-8 implants in patients characterized by corneal irregularities and hoas who could not undergo refractive surgery due to the poor residual thickness of the cornea or other conditions such as astigmatism secondary to previous radial keratotomy. methods: this descriptive, retrospective cohort study was conducted on nine eyes in six patients affected by corneal irregularities and hoas who had undergone ic-8 iol implantation. the primary endpoint was the best-corrected visual acuity (bcva), the subjective visual function, and the visual field. results: nine eyes of six patients (three bilateral implantation) were enrolled. for each patient, bcva, vision, and lifestyle quality were evaluated. in all patients, we noticed an improvement in all parameters without visual field defects. conclusion: our work encourages the use of the ic8 lens to improve visual acuity in patients with irregular corneas and hoas who cannot be treated with customized refractive surgery. patients experience a subjective improvement of their quality of vision and also more self-confidence in their daily life. ic-8 lenses do not interfere with the visualization of retinal fundus and there is no impairment of the visual field detected by patients. keywords: aberrations; cataract; ic-8; pinhole j ophthalmic vis res 2022; 17 (3): 317–323 correspondence to: marco branchetti md. largo piero palagi 1, 50139, florence, italy. e-mail: marco.branchetti89@gmail.com received: 27-12-2020 accepted: 23-01-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i3.11568 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: franco f, branchetti m, vicchio l, serino f, piergentili m, spagnuolo vito, santoro f, virgili g, giansanti f. implantation of a small aperture intraocular lens in eyes with irregular corneas and higher order aberrations. j ophthalmic vis res 2022;17:317–323. © 2022 franco et al . this is an open access article distributed under the creative commons attribution license | published by knowledge e 317 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i3.11568&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr ic-8 iol in irregular corneas; franco et al introduction cataract surgery is the most performed ophthalmic procedure worldwide. patients have higher expectations regarding postoperative refractive results and relative independence from spectacles, than in the past.[1] to determine the desired refractive results, a complete biometric measure should be performed to calculate the power of the intraocular lens (iol). central corneal power (k) is an important factor in the calculation formula to decide the power of the iol to be implanted.[2] nowadays, scheimpflug and oct-swept source ray tracing technology allow to study in a better way the anterior and posterior faces of the cornea with the aim of estimating its total power.[3] corneal irregularities could lead to high order aberrations (hoas) that can influence the outcomes in terms of iol selection and visual acuity.[4] recently, acufocus (irivne, ca) has made available ic-8: a one-piece, acrylic, hydrophobic, posterior chamber small-aperture iol that provides an increase in the range of vision from far to near, by extending the depth of focus.[5] it works by using the principle of the pinhole to improve visual acuity and minimize dysphotopsia symptoms by applying the same small-aperture principle optics as the kamra inlay: where peripheral rays are stopped while central light rays are allowed to pass with no interference and focus on the retina.[6] it is a biconvex lens with a total length of 12.50 mm and a diameter of 6 mm composed of polyvinylidene fluoride and nanoparticles of carbon incorporating a non-diffractive 3.23-mm diameter opaque mask with a 1.36-mm central aperture. the ic-8 could be implanted in conjunction with an aspheric monofocal iol implantation in the dominant eye, which will improve intermediate and near vision while preserving far vision in the eye with a monofocal optic iol.[7] the aim of this study was to evaluate the visual acuity and satisfaction after ic-8 implant in patients characterized by previous corneal irregularities and hoas who cannot undergo refractive surgery due to the poor residual thickness of the cornea or other conditions such as stigmata related to previous radial keratotomy. surgical method this was a descriptive, retrospective cohort study of nine eyes in six patients affected by corneal irregularities and hoas who had undergone ic8 iol implantation between october 2019 and january 2020 at careggi hospital in florence. all had monolateral implants except for three patients. patients with significative comorbidities affecting visual acuity such as glaucomatous neuropathy and maculopathy were excluded from the study. patients included in the study were subjected to a protocol that provided a baseline and three followup visits at day 1, month 1 and month 3, which included snellen best-corrected visual acuity (bcva), biomicroscopy, goldmann applanation tonometry, corneal topography and study of the corneal hoas (sirius cso florence), fundoscopy (volk lens) in miosis and after pharmacological dilation, as-oct (ms 30, cso florence). the aberrometry (osiris, cso florence) was performed, but the diameter of the opaque mask (1.36 mm central aperture) did not allow the machine’s rays to reach a good acquisition. all patients also underwent preoperatively and postoperatively a 30:2 humphrey visual field and esterman 120 points visual field. surgical technique all 9 ic-8 implants were performed by the same surgeon (ff) after phacoemulsification (clear lens extractions) under topical anesthesia. we used a dispersive viscoelastic device (ovd) into the anterior chamber and we made a 2.4 mm corneal incision. then, the surgeon performed a capsulorhexis, hydrodissection, hydrodelineation, and phacoemulsification. all small-aperture iols were placed in the capsular bag using the smallaperture iol injection system with haptic orientation at 12 o’clock and 6 o’clock. ic-8 iol was centered referring to the purkinje reflex. finally, the viscoelastic was removed with irrigation and aspiration and we hydrated the two paracenteses. in this study, no intraoperative or postoperative complications happened [figure 1]. outcomes primary outcomes were determined by the improvement of logmar bcva and the evaluation of the postoperative visual fields (humphrey 30:2 and esterman 120 points). secondary outcomes were reflected in the increase of visual quality and patients’ satisfaction, as revealed from performing the visual function questionnaire 25 (vfq-25). 318 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 ic-8 iol in irregular corneas; franco et al informed consent was obtained from all patients who underwent surgery. the study protocol was approved by the local ethics committee in compliance with the tenets of the declaration of helsinki. we used the vfq-25 questionnaire to assess self-reported vision-targeted health statuses. patients were contacted via telephone and answered the questionnaire; the answers were converted into numerical representative values. results the study sample included six patients, two males (33%) and four females (67%), with a mean age of 57 years old, three of which underwent surgery in both eyes. in total, nine eyes had been subjected to ic-8 implantation: four right eyes (44%) and five left eyes (56%). almost the entire sample (78%) presented corneal irregularity due to previous radial keratotomy, one (11%) had a previous decentralized refractive surgery with low residual corneal thickness and one (11%) had a previous pterygiectomy with residual irregularities on the anterior and posterior face of the cornea. in this case, we performed a photo-therapeutic keratectomy (ptk) on the anterior face with an unsuccessful result because of the irregular posterior face. we evaluated the high order corneal aberration (sirius cso florence): in six eyes (67%) the main hoa was coma (mean value 1.13 µm), in two patients (22%) four-leaf clover (mean value 1.41 µm), and in one patient (11%) clover (0.90 µm) [table 1]. bcva increased from a preoperative mean of logmar 0.32 (±0.17) to 0.26 (±0.30) on day 7, 0.22 (±0.20) at month 1, and 0.20 (±0.15) at month 3 [table 2]. the percentage reduction of mean logmar bcva at the end of the follow-up period (month 3) was 25%, compared to the one at the preoperative visit. our patients underwent a clear lens extraction and monofocal small aperture lenses were then implanted. this is very important because the prevalence of hoas is not influenced by cloudy lenses (all hoas come from corneal shape). the 1.36 mm central aperture and the non-diffractive 3.23 mm diameter opaque mask of the ic-8 recreate the pinhole principle. so, it is possible to “reflect” this effect onto the corneal surface: only the central 2 mm of the cornea becomes fundamental for vision. hoas are influenced by the central corneal diameter that we focused on: less corneal diameter means little hoas at topography study. aberrometric reviews confirmed the reduction of the major hoas of the patients in our study [table 3]. less hoas meant a better quality of eye vision. it is important to increase the number of selected patients with irregular cornea and ic-8 implants to ensure the validity of the data obtained. in fact, increasing the selection facilitates greater understanding of establishing the origins of the corneal irregularities and would also assist in determining which specific hoas would obtain the appropriate results with the implementations ic-8 iols. during this study, there were no instances of intraoperative or postoperative complications. discussion we focused our attention on the use of ic-8 iols in patients who suffered with cataract, severe corneal irregularities, and hoas. generally, when the corneal thickness allowed it, we preferred to correct the corneal irregularities with a customized laser ablation before the cataract surgery was performed. however, in this study, the corneas of patients could not be treated with refractive surgery due to the poor residual thickness of their cornea or presence of other conditions such as posterior corneal astigmatism. in our study, seven eyes (78%) had previous radial keratotomy (rk), one eye (11%) had a previous decentralized refractive surgery, and one (11%) had a previous pterygectomy with irregularity of the posterior face of the cornea. hoas cause difficult night vision, glare, halos, blurring, starburst patterns or double vision (diplopia), and cannot be corrected through conventional techniques (i.e., toric iols). furthermore, in these cases, the calculation of iol power is more challenging since the corneal power is hard to be assessed. in our study, the nine eyes in which the small-aperture ic-8 has been implanted experienced an increase of bcva, and a subjective vision quality improvement (objective and subjective visual outcomes). since the irregularities of the cornea cannot be corrected with customized refractive surgery because of the risk of low residual corneal thicknesses occurring or because of the resulting presence of many radial cuts, we decided to act according to the principles of a pinhole. a small pinhole, which reduce the effective pupil size, leads to a disruption of peripheral rays, while allowing central focused light to reach the retina, and increasing the depth of focus. ogle et al[8] found that there is an inverse relationship between the pupil size and the depth of focus. moreover, a relationship could be found journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 319 ic-8 iol in irregular corneas; franco et al figure 1. ic-8 iol placed in the capsular bag, cornea with previous radial keratotomy (left). small aperture iol specifications: optic and mask design (right). figure 2. predictive modifications of zernicke’s summary and visual summary from 5 to 2 mm of corneal diameter (sirius cso). between pupil size and hoas, where small pupils can attenuate the visual effect of corneal aberrations.[9, 10] the simulation of the visual quality of the sirius takes into account the corneal aberrations and demonstrates an aberration index point spread function (psf describes the shape of an image in an optical system) and the related strehl ratio change according to the size of the pupil. in all patients, the psf value was better at 2 mm (mean value 0.17569) than at 5 mm (mean value 0.06249). so, we decided to implant the ic-8 and take advantage of the small aperture iol principle to reduce visual aberrations and to improve the psf [figure 2]. the pinhole effect has been already exploited by the add-on xtrafocus lens (morcher), a total black iol for sulcus implantation, specifically designed for cases with corneal irregularities.[11–13] compared to the xtrafocus lens, which is an add-on lens without 320 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 ic-8 iol in irregular corneas; franco et al figure 3. visual field 30 – 2 (left) and 120 (right): no alterations related to ic8 lens. psf, point spread function; rms, root mean square; hoas, high order aberrations; ipf, irregularity’s posterior face of the cornea; rk, radial keratotomy; drs, decentralized refractive surgery figure 4. corneal topography study. logmar best-corrected visual acuity (bcva) during follow-up. figure 5. visual acuity study. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 321 ic-8 iol in irregular corneas; franco et al psf, point spread function; rms, root mean square; hoas, high order aberrations; ipf, irregularity’s posterior face of the cornea; rk, radial keratotomy; drs, decentralized refractive surgery figure 6. major hoas study. optical power, the ic-8 has optical power and can be placed directly in the capsular bag during the cataract surgery, with a 1.36 mm central aperture and a non-diffractive 3.23 mm diameter opaque mask that allows the possibility of studying the retina, and also performing retinal surgery. after the implantation of the ic-8 iol, we achieved a decrease of logmar bcva from a preoperative mean of 0.35 (±0.18) to 0.25 (±0.22) at month 3. subjective improvement of self-reported visiontargeted health status was observed as patients reported their satisfaction while answering the vfq25 questionnaire. especially, after receiving bilateral implants, patients reported that they felt more confident in daily life. the preoperative visual impairment that patients experienced was mainly related to the presence of hoas and on a smaller scale due to the presence of cataract. our findings confirm data reported in prior literature: shajari[3] reported in 17 eyes an improvement of corrected distance visual acuity (cdva) from the preoperative value of 0.37 to 0.19 logmar at month 3 after the ic-8 lens implantation in eyes with severe corneal irregularities. grabner et al[14] registered a similar result. schultz and dick reported the use of the ic-8 lens in a case of a patient with irregular cornea because of trauma: after surgery they experienced an improvement in visual acuity across all distances.[15] agarwal[16] implanted ic-8 iol in patients who had previous refractive surgery and hoas: she reported that the small-aperture iol reduced the effects of hoas on visual acuity and provides continuous depth of focus. examination of the posterior segment was always possible, although in non-mydriatic conditions, during the follow-up visits. the mask only extends to 3.23 mm in total, so that peripheral iol is clear and doesn’t preclude visualization of the peripheral retina with volk lens. these findings corroborate srinivasan’s[17] data from 15 patients: optical coherence tomography, posterior segment investigations including fundus photography, and perimetry could be safely performed in eyes with ic8 iols. moreover, srinivasan et al did not report any issues according to the intraoperative view and the surgeon could perform all vitrectomy procedures, without distortions and disc halos on the retina, as is common with diffractive and refractive multifocal lenses.[18] despite the presence of the opaque mask, measuring 3.23 mm, the field of vision was maintained. we performed a visual field (vf) humphrey 30:2 and a full-field 120-point screening test, where, even with the presence of the opaque mask, in the most extreme periphery of the visual field we did not detect any shrinkage or defect. we achieved the visual fields even in pharmacological mydriasis conditions to assess whether the visual impairment due to the mask would have been greater in a situation mimicking low light conditions. both conditions of the vf were performed at month 3 of follow-up to ensure that the patients were adapting to the presence of the ic-8 iol. in our study, we registered a good subjective adaptation, without any resultant shrinkage in visual field, in both bilateral (50% of the cases) and monolateral cases [figure 3]. no adverse events occurred during the followup. only one patient developed significant posterior capsule opacification (pco) that required yag laser capsulotomy only in the 1.36 mm central aperture. previous works have reported a small pco rate after ic-8 implantation (6.8% in ang’s work,[19] 7% in shajari’s study,[20] and 12% in hooshmand’s study,[21] which were treated with the yag laser without further complications. in summary, the result of our work encourages the use of the ic-8 lens to improve visual acuity in patients with irregular corneas and hoas that cannot be treated with customized refractive surgery. 322 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 ic-8 iol in irregular corneas; franco et al patients feel a subjective improvement in their quality of vision and more confident in daily life. the ic-8 lens does not interfere with visualization of fundus and no impairment of the visual field are detected by patients. financial support and sponsorship none. conflicts of interest there are no conflicts of interest. references 1. hawker mj, madge sn, baddeley pa, perry sr. refractive expectations of patients having cataract surgery. j cataract refract surg 2005;31:1970–1975. 2. barrett gd. an improved theoretical formula for intraocular lens power prediction. j cataract refract surg 1993;19:713–720. 3. shajari m, mackert m, langer j, kreutzer t, wolf a, kohnen t, et al. safety and efficacy of a small-aperture capsular bag-fixated intraocular lens in eyes with severe corneal irregularities j cataract refract surg 2020;46:188–192. 4. braga-mele r, chang d, dewey s, foster g, henderson ba, hill w, et al. multifocal intraocular lenses: relative indications and contraindications for implantation. j cataract refract surg 2014;40:313–322. 5. grabner g, ang re, vilupuru s. the small aperture ic-8 intraocular lens: a new concept for added depth of focus in cataract patient. am j ophthalmology 2015;160:1176– 1184.e1. 6. tucker j, charman wn. the depth-of-focus of the human eye for snellen letters. am j optom physiol opt 1975;52:3–21. 7. ang re. visual performance of a small-aperture intraocular lens: first comparison of results after contralateral and bilateral implantation. j refract surg 2020;36:12–19. 8. ogle kn, schwartz jt. depth of focus of the human eye. j opt soc am 1959;49:273–280. 9. yuan y, shao y, tao a, shen m, wang j, shi g, et al. ocular anterior segment biometry and high-order wavefront aberrations during accommodation. invest ophthalmol vis sci 2013;54:7028–7037. 10. munoz g, rohrweck s, sakla hf, altroudi w. pinhole irisfixated intraocular lens for dysphotopsia and photophobia. j cataract refract surg 2015;41:487–491. 11. trinidade blc, trindade fc, trindade clc, santhiago mr. phacoemulsification with intraocular pinhole implantation associated with descemet membrane endothelial keratoplasty to treat failed full-thickness graft with dense cataract. j cataract refract surg 2018;44:1280–1283. 12. trinidade cc, trindade bc, trindade fc, werner l, osher r, santhiago mr. new pinhole sulcus implant for the correction of irregular corneal astigmatism. j cataract refract surg 2017;43:1297–1306. 13. tsaousis kt, werner l, trindade clc, guan j, li j, reiter n. assessment of a novel pinhole supplementary implant for sulcus fixation in pseudophakic cadaver eyes. eye 2018;32:637–645. 14. grabner g, ang re, vilupuru s. the small aperture ic-8 intraocular lens: a new concept for added depth of focus in cataract patient. am j ophthalmology 2015;160:1176– 1184.e1. 15. schultz t, dick hb. small-aperture intraocular lens implantation in a patient with an irregular cornea. j refract surg 2016;32:706–708. 16. agarwal franzco s, thornell e. cataract surgery with a small-aperture intraocular lens after previous corneal refractive surgery: visual outcomes and spectacle independence. j cataract refract surg 2018;44:1150– 1154. 17. srinivasan s, khoo lw, koshy z. posterior segment visualization in eyes with small aperture intraocular lens. j refract surg 2019;35:538–542. 18. holladay jt, van dijk h, lang a, portney v, willis tr, sun r, et al. optical performance of multifocal intraocular lenses. j cataract refract surg 1990;16:413–422. 19. ang re. visual performance of a small-aperture intraocular lens: first comparison of results after contralateral and bilateral implantation. j refract surg 2020;36:12–19. 20. shajai m, mackert m, langer j, kreutzer t, wolf a, kohnen t, et al. safety and efficacy of a small-aperture capsular bag-fixated intraocular lens in eyes with severe corneal irregularities. j cataract refract surg 2020;46:188–192. 21. hooshmand j, allen p, huynh t, chan c, singh r, moshegov c, et al. small aperture ic-8 intraocular lens in cataract patients: achieving extended depth of focus through small aperture optics [epub ahead of print]. eye; 2019. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 323 original article conjunctival autograft versus combined amniotic membrane and mini-simple limbal epithelial transplant for primary pterygium excision ashok jha1, ms; abhay simba2, ms 1department of ophthalmology, military hospital gaya, gaya, india 2department of ophthalmology, anugrah narayan medical college, gaya, india orcid: ashok jha: https://orcid.org/0000-0001-7072-4168 abstract purpose: to compare outcomes of conjunctival autograft (cag) and combined amniotic membrane with mini-simple limbal epithelial transplant (mini-slet) after primary pterygium excision. methods: all consenting adults with primary pterygium were included in this study. after pterygium excision, patients were randomized to receive either cag or mini-slet and both grafts were held in place with fibrin glue. the patients were followed-up at days 1, 3, 7, 14, and 30 and subsequently at the third, sixth, and ninth months. the recurrence rate was considered as the primary outcome measure whereas the operating time, postoperative symptoms, and surgical complications were considered the secondary outcome measures. results: the study comprised of 264 eyes of 264 patients, of which 233 (88%) completed the nine months of follow-up. of these, 118 (51%) received cag and 115 (49%) received mini-slet. the groups were comparable at baseline. recurrence of pterygium was seen in two (1.6%) eyes in the cag group and three (2.6%) eyes in the mini-slet group (p = 0.68). operative time for mini-slet (20.33 ± 1.28 min) was significantly higher than that for cag (12.01 ± 1.26 min) (p < 0.001). graft displacement was observed in one case in group ii (p = 0.999). the lim bon siong (foreign body sensation, lacrimation, pain, and irritation) score in the cag group was statistically significant for all four symptoms at days 1 and 3; however, at day 7, foreign body sensation, pain, and irritation scores were significantly higher for the cag group. conclusion: in this study, the overall recurrence rate was very low and comparable between mini-slet and the established technique of cag after performing the primary pterygium excision. despite a longer surgical time, minislet appears to be a viable option for the management of primary pterygium. keywords: conjunctival autograft (cag); mini-simple limbal epithelial transplant (minislet); pterygium j ophthalmic vis res 2022; 17 (1): 4–11 4 © 2022 jha et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10164&domain=pdf&date_stamp=2019-07-17 two techniques for pterygium excision; jha et al introduction pterygium is a benign, fleshy triangular ocular lesion that can cross the limbus and encroach on the cornea, with subsequent visual impairment.[1] it most often involves nasal conjunctiva and may necessitate surgical removal if associated with visual impairment, astigmatic refractive errors, or cosmetic concerns. postoperative recurrence is not uncommon, hence surgical excision has been coupled with various adjunctive measures like beta irradiation[2] and anti-metabolites such as mitomycin c.[3, 4] although these methods are relatively safe, complications such as secondary bacterial infection, punctate keratitis, scleral melting, and raised intraocular pressure (iop) have been reported. to prevent these side effects and achieve superior results in terms of graft stability and potentially lower recurrence rates, human amniotic membrane grafting (amg)[5] and conjunctival autografting (cag)[6] were introduced to cover the bare sclera after pterygium excision. of these, ipsilateral cag is now the surgical procedure of choice, owing to the ease of the procedure and the difficulties in procuring amg. additionally, the efficacy and low recurrence rate of the cag method has been corroborated by many authors.[6–9] tissue adhesives like fibrin glue[10] which are used to secure the grafts in place after pterygium excision present many benefits such as lesser operating time, reduced discomfort during the postoperative period, and reduced complications associated with sutures.[11, 12] alternatively, the cag can be secured using autologous in situ blood coagulum.[13–15] more recently, hernández-bogantes et al have described a technique of using a combination of amg and small pieces of autologous limbal epithelial cells (mini-simple limbal epithelial transplant [slet])[16] to cover the bare sclera using tissue adhesive. authors reported excellent correspondence to: ashok jha, ms. department of ophthalmology, military hospital gaya, bihar 823005, india. e-mail: ashokjha1025@gmail.com received 04-05-2020; accepted 12-02-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10164 outcomes with this new technique, albeit in only 10 eyes. given these encouraging results, we believe that this may be an alternative technique to cag for surgical management of pterygium. at present there are very few head to head studies comparing outcomes of the well-established cag with the relatively new mini-slet after primary pterygium excision. hence, this study was performed to assess the efficacy and recurrence rate after the two aforementioned procedures. methods this prospective, randomized, interventional study was duly approved by the local institutional ethics committee (ethical clearance certificate no. 29/mh/2015 dated aug 11, 2015). this study was conducted in accordance with the tenets of the declaration of helsinki. patient enrollment occurred between august 2015 and january 2019. all consecutive adult patients visiting the outpatient department of our hospital with primary pterygium and requiring surgical excision for cosmesis, intense foreign body sensation, and reduced vision either due to induced astigmatism or encroachment on the visual axis were invited to participate in the study. patients who agreed to follow-up for nine months after surgery were recruited after their informed consent. patients with other ocular surface disorders, hypersensitivity to blood constituents, and seropositivity to hepatitis b, hepatitis c, and hiv were excluded from the study. sample size calculation was based on presumed differences in the recurrence rates of pterygium in the two groups. given 1:1 randomization, 90% power, and a precision error of 5% to detect a difference of 10% or more in proportion of patients experiencing recurrent pterygium, a required minimum sample size of 230 eyes (115 in each group) was obtained. to account for a 15% loss to follow-up, we recruited 264 patients for the study. using simple randomization, the patients were divided into two groups: one received this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: jha a, abhaysimba. conjunctival autograft versus combined amniotic membrane and mini-simple limbal epithelial transplant for primary pterygium excision. j ophthalmic vis res 2022;17:4–11. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 5 https://knepublishing.com/index.php/jovr two techniques for pterygium excision; jha et al the cag and the other received the mini-slet treatment. this simple randomization utilized serially generated computer codes along with allocation concealment. a parallel allocation strategy was used in a 1:1 allocation. the evaluating ophthalmologist (as) was masked to the type of graft used. the operating surgeon (aj) and patients were masked to the procedural details and the type of graft used. the sealed envelopes for the type of graft were opened just before the completion of the pterygium excision. the graft status was masked in all cases at every follow-up visit during the clinical testing. thorough medical and ocular history and demographic details such as age and gender of the participants were obtained. thereafter, a comprehensive examination of the eyes included best-corrected visual acuity assessment, slit-lamp evaluation of the pterygium, and the anterior and posterior segment evaluation using a +90d lens. pterygia were divided into three grades based on the classification proposed by tan and coworkers:[17] t1 = unobscured and distinguished episcleral vessels underneath the body of the pterygium; t2 = partially obscured or indistinct episcleral vessels; and t3 = completely obscured episcleral vessels by fibrovascular tissue. serial clinical photographs of patients were taken preoperatively, per-operatively, and postoperatively on days 1 and 30 in addition to the sixth and ninth months for both cohorts [figure 1]. peribulbar anesthesia (2% lidocaine hydrochloride) was used for all of the surgeries, which were performed by a single surgeon (aj). westcott scissors were used to draw horizontal incisions along the superior and inferior borders of the body of pterygium. subsequently, using moorefield’s conjunctival forceps, the pterygium was reflected toward the limbus making another peripheral incision parallel to the limbus. the remaining fibrovascular tissues underneath the bulbar conjunctiva were dissected and excised to the maximum possible extent. the bare sclera was then measured by a caliper. in the cag group, a near tenon-free cag, which was 1 mm larger in area than the bare sclera was harvested from the supero-temporal region. this thin graft was stuck to the exposed sclera using fibrin glue (baxter, tisseel) with correct orientation. the angled flat part of two iris spatulas was maneuvered horizontally and vertically utilized to expand the graft to its maximum possible size besides removing excess glue from the sclera bed. in the mini-slet cohort, after an initial one clock hour (10–11 o’clock for right eye and 1–2 o’clock for left eye) peritomy performed with westcott scissors, a limbal tissue 2 × 2 mm in size was excised with the help of a crescent blade. using vannas scissors, this strip was then sliced into six to eight pieces under increased magnification. these pieces were then affixed on the inlay amg closer to the limbus using fibrin glue. thereafter, an amg overlay was used to maintain graft pieces in the exact position. freeze-dried amg (amnio-care, biocover labs, india), available in 3 × 3 cm size was used for the study. a bandage contact lens was placed on the cornea at the end of the procedure. using a patented fibrinotherm device, the fibrin glue (tisseel vh, baxter ag) used in the above described procedures was prepared by reconstituting thrombin and freeze-dried protein concentrate in calcium chloride and fibrinolysis inhibitor solutions, respectively. both thrombin and fibrin were suctioned into separate syringes, which were mounted with a 27g canula. to use the glue, almost an equal number of drops of fibrin and thrombin were utilized for both the cohorts. total operating time was noted for both the groups. mitomycin c was not used in either group. in the first week of the postoperative period, patients received 1% prednisolone acetate and 0.5% moxifloxacin eye drops every 4 and 6 hr, respectively, followed by tapering dosages of topical steroid, which continued for one month. the patients were reviewed on postoperative days 1, 3, 7, 14, and subsequently at months 1, 3, 6, and 9. while early postoperative visits involved the assessment of graft positioning, later visits included reporting of the recurrence and disintegration of limbal pieces on the slit lamp by a masked investigator. recurrence was considered the primary outcome measure, which was defined as any fibrovascular growth that occurred at the surgical site at any time during the follow-up period. operating time and surgical complications were considered the secondary outcome measures. four symptoms (foreign body sensation, epiphora [watering], pain and irritation) were evaluated, based on a 5-point scale adapted from lim bon siong r et al. the patients were asked to complete a questionnaire in which 0 meant no pain, 1 meant presence of easily tolerable pain, 2 meant pain 6 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 two techniques for pterygium excision; jha et al causing some discomfort, 3 meant presence of pain partially interfering with sleep or usual activity, and 4 meant pain completely interfering with usual activity or sleep. statistical analysis the statistical analysis was performed using spss (statistical package for the social sciences) software version 20. a p-value < 0.05 was considered statistically significant. comparison of continuous variables such as age, preoperative bcva, operative time, and the dimensions of graft between the two groups was done using the parametric unpaired t-test. pearson’s chisquare test or the fisher’s exact test were used for comparative analysis of categorical variables like gender, laterality, grades of pterygium, and indication of surgery between the two groups. results a total of 264 consecutive eyes of 264 patients were enrolled in the study, of which 31 eyes (15 in cag and 16 in mini-slet groups) were ruled out due to inadequate follow-up. hence, data from 233 eyes (n = 118 cag and 115 in mini-slet) that finished nine months of followup was included in the final analysis. table 1 depicts the baseline characteristics of cag and mini-slet groups. baseline characteristics were statistically insignificant between the two groups. the comparative analysis of graft size and the operating time has been summarized in table 2. the mean operative time for mini-slet group (20.33 ± 1.28 min) was significantly higher (p < 0.001) than the cag group (12.01 ± 1.26 min). four postoperative symptoms have been compared in table 3 using the nonparametric mann–whitney utest. both groups exhibited foreign body sensation until day 7. a statistically significant difference in the median score of foreign body sensation was noted on day 1 (p < 0.001), day 3 (p < 0.001), and day 7 (p < 0.001) between the cag and minislet groups. this symptom improved significantly between days 1 and 7 in both group i (p < 0.001) and group ii (p < 0.001) as demonstrated by the wilcoxon signed-rank test. both groups showed persistence of epiphora (watering) till day 7. a statistically significant difference in the median score of epiphora (watering) was observed on day 1 (p < 0.001) and day 3 (p < 0.001) between the two groups. it was noted that this symptom, too, showed significant improvement at days 1 and 7 in both group i (p < 0.001) and group ii (p < 0.001). pain persisted until days 7 and 3 in groups i and ii, respectively. both the study and control groups exhibited significant difference in the median score of pain on day 1 (p < 0.001), day 3 (p <0.001), and day 7 (p = 0.008). despite a median score of 6 and 0, the significant difference at days 1 and day 7, respectively, is ascribed to the variance in the distribution of pain score between the two groups. a significant improvement in this symptom was observed between day 1 and day 7 in both the groups (p < 0.001). irritation in the operated eye persisted until day 7 in both the groups. the median score for irritation was noted to be statistically significant on day 1 (p < 0.001), day 3 (p < 0.001), and day 7 (p < 0.001) between the two groups. both the study and control groups showed significant improvement in this symptom between day 1 and day 7 (p < 0.001), and between day 1 and day 14, respectively. recurrence was observed at the first, third, sixth, and ninth months. two (1.6%) eyes in the cag group exhibited recurrence whereas three (2.6%) had recurrence in mini-slet group (p = 0.681). two patients in the cag group and one in the mini-slet group showed recurrence within three months. recurrence in the remaining two patients in the mini-slet group was observed between the third and sixth months. two cases in each group underwent revision surgery whereas one patient in the mini-slet group refused surgery. within the six months follow-up period, no recurrence was observed in any of the patients who underwent revision surgery. one eye (0.87%) in the mini-slet group exhibited amg displacement on the first postoperative day, which was repositioned on the very same day. none of the eyes in the study experienced any other adverse effects related to the grafts. discussion in this randomized study, we found a very low rate of recurrence in eyes that received cag versus mini-slet, with statistically insignificant difference in the recurrence rates between the two groups. the operating time was significantly higher in journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 7 two techniques for pterygium excision; jha et al table 1. comparison of baseline characteristics between the cag group and the mini-slet group characteristics cag group (n = 118) mini-slet group (n = 115) p-value age (yr) 53.81 ± 14.28 (range = 22–80) 52.38 ± 14.62 (range = 26–78) 0.446∗ sex f = 49.15% (n = 58) f = 44.35% (n = 51) 0.437† m = 50.85% (n = 60) m = 55.65% (n = 64) laterality right eye = 57.6% (n = 68) right eye = 53.9% (n = 62 ) 0.696† left eye = 42.4% (n = 50) left eye = 46.1% (n = 53) grade i 13.5% (n = 16) 12.2% (n = 14) 0.920† ii 61.9% (n = 73) 61.7% (n = 71) iii 24.6% (n = 29) 26.1% (n = 30) occupation outdoor = 61.1% (n = 72) outdoor = 67.8% (n = 78) 0.282† indoor = 38.9% (n = 46) indoor = 32.2% (n = 37) indications for surgery 0.895† cosmesis 40.7% (n = 48) 40% (n = 46) foreign body sensation 29.7% (n = 35) 26.1% (n = 30) reduced va due to astigmatism 16.1% (n = 19) 22.6% (n = 26) threatening visual axis 13.5% (n = 16) 11.3% (n = 13) preoperative bcva (logmar) 0.46 ± 0.38 (range = 0–1.46) 0.43 ± 0.26 (range = 0.16–1.18) 0.476∗ ∗unpaired t-test; †χ2test table 2. comparison of the size of the graft and operative time between the cag group and mini-slet group measures cag group (n = 118) mini-slet group (n = 115) p-value dimensions of the graft (mm) horizontal 5.10 ± 0.41 (range = 4.2–6.5) 5.14 ± 0.45 (range = 4.5–6.8) 0.448∗ vertical 6 ± 0.32 (range = 5.5–8.0) 6.09 ± 0.54 (range = 5.5–8.0) 0.097∗ operative time (min) 12.01 ± 1.26 (range = 10.1–14.0) 20.33 ± 1.28 (range = 18–22) <0.001∗ ∗unpaired t-test the mini-slet group, however, none of the eyes experienced intraor postoperative complications attributable to the surgery. pterygium is postulated to occur due to localized dysfunction of nasal limbal stem cells consequential to exposure to uvb light.[18] this theory forms the basis of the incorporation of limbal stem cells in the surgical treatment of pterygium. of all the techniques described in literature,[3–6] cag modality has been found to be associated with the lowest recurrence rate.[7, 8, 10] the cag can be attached to the bare sclera by sutures, fibrin glue, or autologous in situ blood coagulum. amongst the three techniques of fixing cag, fibrin glue definitely scores over others with the least operative time.[19] use of slet for the treatment of limbal stem cell deficiency was first advocated by sangwan et al.[20] subsequently, mini-slet[16] was innovatively used for treating 10 patients suffering with primary pterygium. the basis of using mini-slet for pterygium surgery was localized deficiency or dysfunction of limbal stem cells.[21, 22] the amg acts as a basement membrane and a substrate supporting the growth of epithelial progenitor cells.[23] amg is also endowed with antiinflammatory properties owing to the presence of protease inhibitors.[24] however, amg itself is 8 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 two techniques for pterygium excision; jha et al table 3. comparative outcome of the postoperative symptom score between the cag group and mini-slet group cag group (n = 118) mini-slet group (n = 115) p-value∗ min max median min max median foreign body sensation day 1 3 9 9 0 9 6 <0.001 day 3 0 9 6 0 6 3 <0.001 day 7 0 6 3 0 3 0 <0.001 day 14 0 6 0 0 0 0 0.255 day 30 0 0 0 0 0 0 0.999 epiphora (watering) day 1 0 9 6 0 9 6 <0.001 day 3 0 6 3 0 6 3 <0.001 day 7 0 6 0 0 6 0 0.511 day 14 0 0 0 0 0 0 0.999 day 30 0 0 0 0 0 0 0.999 pain day 1 0 9 6 0 6 3 <0.001 day 3 0 9 3 0 6 0 <0.001 day 7 0 6 0 0 6 0 0.008 day 14 0 6 0 0 0 0 0.089 day 30 0 0 0 0 0 0 0.999 irritation day 1 3 9 9 0 9 6 <0.001 day 3 0 9 6 0 6 3 <0.001 day 7 0 6 3 0 3 0 <0.001 day 14 0 6 0 0 6 0 0.183 day 30 0 0 0 0 0 0 0.999 statistically significant values are in boldface after ∗mann–whitney u-test figure 1. serial clinical photographs of two patients of primary pterygium: (patient 1 [a∼f]; patient 2 [g∼l]): preoperative, intraoperative, and postoperative. pterygium excision with cag with fibrin glue (a–f) and pterygium excision with mini-slet (g– l). (a) a case of primary nasal pterygium (left eye[le]) before pterygium excision with cag. (b) dissection of pterygium. (c) pod 1. (d) pod 30 graft well taken. (e & f) postoperative months 6 and 9, respectively: restoration of near normal anatomy without any recurrence. (g) a case of primary nasal pterygium (right eye [re]) before pterygium excision with mini-slet. (h) intraoperative photograph showing dissected pterygium with eight limbal pieces. (i) pod 1. (j) pod 30: well-settled graft. (k & l) postoperative months 6 and 9, respectively: restoration of near normal anatomy without any signs of recurrence. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 9 two techniques for pterygium excision; jha et al devoid of limbal stem cells, hence its solitary use to cover the bare sclera after pterygium excision, despite providing a mechanical barrier, does not address the underlying pathology of limbal stem cell deficiency. as a result, this may in turn lead to potentially more recurrences and tilt the balance toward cag in terms of beneficial outcomes. an extensive medline search did not reveal any similar study of this magnitude; hence we undertook a randomized trial to compare the aforementioned two techniques as mini-slet appeared to be a viable prospect for the treatment of pterygium.[16] in 2015, hernández-bogantes e et al,[16] elicited this interesting innovation in 10 patients with primary pterygium without any recurrence after eight months of follow-up. sati et al[25] reported a randomized control trial, comparing the outcomes between 42 cases of cag and 40 cases of mini-slet. the study reported a 9.5% recurrence in the cag group and 2.5% recurrence in the mini-slet group. although clinically meaningful, these differences were not found to be statistically significant. we experienced much lower rates of recurrence in the cag group and almost similar in the mini-slet group. minislet incorporates the use of amg and limbal stem cells, which could lower recurrence rates as is evident in our study. mini-slet is a miniaturized modification of the original slet technique first described by sangwan et al.[20] however, minislet technique scores over slet in terms of placing the limbal stem cells’ pieces over amniotic membrane in proximity to the limbus. in our opinion, mini-slet offers an alternative solution to patients with insufficient conjunctiva due to prior surgeries or those suspected of suffering with glaucoma. additionally, it is more likely to restore the normal anatomy of the limbus. there were a few limitations of the study such as the relatively low overall numbers of recurrences, which made it difficult to make robust conclusions while using statistical tools. follow-up of <12 months and the considerable number of excluded eyes (12%) also contributed toward limiting our evaluations. the strength of this study included its randomized and masked study design, the relatively large sample size, and the longer followup period, which exceeded that of other similar studies. in summary, the overall recurrence rate was very low in this study and comparable between mini-slet and the established technique of cag for primary pterygium excision. despite a longer surgical time, mini-slet appears to be a viable alternative to cag in the management of primary pterygium. the mini-slet may be considered as the procedure of choice for all cases of primary pterygium surgery, especially, if cost and availability are not an issue. also, mini-slet is more likely to replace the abnormal limbal stem cells compared to cag. in particular, this should be adopted as the procedure of choice as conjunctival-sparing surgery (especially in young patients, glaucoma, and cicatrizing conjunctivitis). acknowledgements the authors would like to thank dr. charima priya for excellent counselling and follow-up of patients. financial support and sponsorship the authors did not receive any financial support for the research, authorship, and/or publication of this article. conflicts of interest the authors report no conflict of interest. references 1. jaros pa, deluise vp. pingueculae and pterygia. surv ophthalmol 1988;33:41–49. 2. viani ga, fonseca ec, de fendi li, rocha em. conjunctival autograft alone or combined with adjuvant beta-radiation? a randomized clinical trial. int j radiat oncol bio phys 2012;82:507–511. 3. donnenfeld ed, perry hd, fromer s, doshi s, solomon r, biser s. subconjunctival mitomycin c as adjunctive therapy before pterygium excision. ophthalmology 2003;110:1012–1016. 4. rubinfeld rs, pfister rr, stein rm. serious complications of topical mitomycin-c after pterygium surgery. ophthalmology 1992;99:1647–1654. 5. yu cm, liang wl, huang yy, guan w. comparison of clinical efficacy of three surgical methods in the treatment of pterygium. eye sci 2011;26:193–196. 6. kenyon kr, wagoner md, hettinger me. conjunctival autograft transplantation for advanced and recurrent pterygium. ophthalmology 1995;92:1461–1470. 7. chen pp, ariyasu rg, kaza v. a randomized trial comparing mitomycin c and conjunctival autograft after excision of primary pterygium. am j ophthalmol 1995;120:151–160. 8. prabhasawat p, barton k, burkett g, tseng sc. comparison of conjunctival autografts, amniotic membrane grafts and primary closure for pterygium excision. ophthalmology 1997;104:974–985. 10 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 two techniques for pterygium excision; jha et al 9. al fayez mf. limbal versus conjunctival autograft transplantation for advanced and recurrent pterygium. ophthalmology 2002;109:1752–1755. 10. marticorena j, rodriguez-ares mt, tourino r. pterygium surgery; conjunctival autograft using fibrin adhesive. cornea 2006;25:34–36. 11. uy hs, reyes jmg, flores jdg. comparison of fibrin glue and sutures for attaching conjunctival autografts after pterygium excision. ophthalmology 2005;112:667–671. 12. bahar i, weinberger d, dan g. pterygium surgery: fibrin glue versus vicryl sutures for conjunctival closure. cornea 2006;25:1168–1172. 13. wit d, athanasiadis i, sharma a. sutureless and glue free conjunctival autograft in pterygium surgery: a case series. eye 2010;24:1474–1477. 14. malik kps, goel r, gupta a. efficacy of sutureless and glue free limbal conjunctival autograft for primary pterygium surgery. nepal j ophthalmol 2012;24:230–235. 15. singh pk, singh s, vyas c, singh m. conjunctival autografting without fibrin glue or sutures for pterygium surgery. cornea 2013;32:104–107. 16. hernández-bogantes e, amescua g, navas a. minor ipsilateral simple limbal epithelial transplantation (mini-slet) for pterygium treatment br j ophthalmol 2015;99:1598–1600. 17. tan dt, chee sp, dear kb, lim as. effect of pterygium morphology on pterygium recurrence in a controlled trial comparing conjunctival autografting with bare sclera excision. arch ophthalmol 1997;115:1235–1240. 18. aletras aj, trilivas i, christopulou me. uvb-mediated down regulation of proteasome in cultured human primary pterygium fibroblasts bmc ophthalmol 2018;18:328. 19. sati a, shankar s, jha a. comparison of efficacy of three surgical methods of conjunctival autograft fixation in treatment of pterygium. int ophthalmol 2014;34:1233– 1239. 20. sangwan vs, basu s, macneil s. simple limbal epithelial transplantation (slet): a novel surgical technique for the treatment of unilateral limbal stem cell deficiency. br j ophthalmol 2012;96:931–934. 21. cardenas-cantu e,zavala j,valenzuela j. molecular basis of pterygium development. semin ophthalmol 2014:1–17. 22. chui j, coroneo mt, tat lt. ophthalmic pterygium: a stem cell disorder with premalignant features. am j pathol 2011;178:817–827. 23. grueterich m, tseng sc. human limbal progenitor cells expanded on intact amniotic membrane ex-vivo. arch ophthalmol 2002;120:783–790. 24. shimmura s, shimazaki j, ohashi y, tsubota k. anti-inflammatory effects of amniotic membrane transplantation in ocular surface disorders. cornea 2001;20:408–413. 25. sati a, banerjee s, kumar p. mini-simple limbal epithelial transplantation versus conjunctival autograft fixation with fibrin glue after primary pterygium excision: a randomized controlled trial. cornea 2019;38;1345–1350. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 11 case report coats’-like response associated with linear scleroderma hassan behboudi1, md; habib zayeni2, md; asghar haji-abbasi2, md; zahra moravvej1, md ebrahim azaripour1, md; yousef alizadeh1, md; reza soltani-moghadam1, md 1eye research center, department of eye, amiralmomenin hospital, school of medicine, guilan university of medical sciences, rasht, iran 2rheumatology research center, razi hospital, school of medicine, guilan university of medical sciences, rasht, iran orcid: hassan behboudi: https://orcid.org/0000-0001-9149-9270 abstract purpose: to present a case of linear scleroderma known as “en coup de sabre” associated with coats’like response. case report: a 12-year-old boy presented with subacute painless vision loss in the ipsilateral side of the patient’s en coup de sabre lesion. ocular examination revealed vitreous hemorrhage with severe exudation of the posterior pole and telangiectatic vessels. fundus fluorescein angiography indicated multiple vascular beadings and fusiform aneurysms with leakage which was consistent with a coats’-like response. the patient was subsequently treated with intravitreal bevacizumab and targeted retinal photocoagulation. twelve months’ follow-up showed marked resolution of macular exudation with significant visual improvement. conclusion: physicians should be aware of the possible ophthalmic disorders accompanying en coup de sabre and careful ophthalmologic examinations should be performed in these patients. as presented in the current case, treatment with intravitreal anti-vegf agents and laser photocoagulation may be a beneficial option for patients with coats’-like response. keywords: bevcizumab; coat’s disease; craniofacial; en coup de sabre; scleroderma j ophthalmic vis res 2022; 17 (1): 135–139 introduction linear scleroderma known as “en coup de sabre” (ecds) is a form of localized scleroderma.[1] the correspondence to: hassan behboudi, md. eye research center, department of eye, amiralmomenin hospital, 17 shahrivar st., rasht, guilan 41396-37459, iran. e-mail: behboudi@gums.ac.ir received 04-06-2020; accepted 23-11-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10179 disorder presents with localized facial atrophy of the skin and the underlying tissue particularly in the frontoparietal area.[1] en coup de sabre has been associated with a number of periocular and ocular manifestations. periocular manifestations include enophthalmos and extraocular muscles and eyelids involvement. ocular findings such as this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: behboudi h, zayeni h, haji-abbasi a, moravvej z, azaripour e, alizadeh y, soltani-moghadam r. coats’-like response associated with linear scleroderma. j ophthalmic vis res 2022;17:135–139. © 2022 behboudi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 135 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10179&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr coats’-like response in scleroderma; behboudi et al corneal alterations, cataract, iritis, and iris atrophy have also been reported.[2, 3] we report a case of ecds presenting with decreased vision in the ipsilateral eye diagnosed as a coats’-like response. case report a 12-year-old boy noticed painless vision loss in his left eye several days before. there was no history of visual disturbances and no family history of significant ocular disorders. he did not report any previous trauma and prior use of any medication. on physical examination, linear depressed scarring of the cutaneous and subcutaneous tissue of the left frontoparietal area was noted. this atrophic band of skin extended from the left eyebrow to the frontoparietal scalp [figure 1]. his best-corrected visual acuity (bcva) was 20/20 in the right eye and 20/200 in the left eye. the size of pupils was normal and there was no afferent pupillary defect. ocular motility was within normal range. the intraocular pressure by applanation tonometry was 14 mmhg in both eyes. on slit lamp examination, the anterior segment was normal in both eyes. funduscopy of the left eye showed vitreous hemorrhage with severe exudation in the posterior pole and telangiectatic vessels and saccular aneurysms in the mid-peripheral and peripheral retina. the optic disc was normal. the right fundus examination was unremarkable. para-clinical evaluations with spectral-domain optical coherence tomography (sd-oct) and fundus fluorescein angiography (ffa) were performed. sd-oct of the left macula revealed intraretinal fluid and marked exudates [figure 2]. ffa demonstrated vascular tortuosity and multiple beading and fusiform aneurysms with distinct leakage in the mid-peripheral and peripheral regions. areas of capillary nonperfusion with no neovascularization were noted. the fundus findings were compatible with coats’like response. corresponding rheumatologic consultation diagnosed his atrophic skin lesion as “en coup de sabre” (ecds) a form of craniofacial linear scleroderma. further examinations did not show any neurological signs or systemic involvement of scleroderma. laboratory tests for antinuclear, anti-centromer, and scl70 antibodies, erythrocyte sedimentation rate, and blood composition were normal. the patient was scheduled for three monthly intravitreal injections of 1.25 mg/0.05 ml bevacizumab. on follow-up examinations, there was a significant decrease in macular exudation and vitreous hemorrhage. targeted laser photocoagulation was performed over the abnormal retinal vasculature. macular sd-oct demonstrated significant reduction of intraretinal fluid and exudates [figure 3]. at 12-month followup examination, bcva improved to 20/25 in the left eye. fundus examination and repeated ffa showed moderate resolution of vascular beading and tortuosity with no evidence of peripheral neovascularization [figure 4]. the patient was scheduled for ophthalmic visits every three months. after one year of follow-up, we noted a loss of visual acuity (bcva: 20/32) and moderate recurrence of macular edema and exudation. the patient was subsequently treated with one session of intravitreal injection of 1.25 mg/0.05 ml bevacizumab. he is currently under routine ophthalmic and rheumatologic observation. discussion craniofacial linear scleroderma known as “en coup de sabre” (ecds) presents with contraction and stiffness of the frontal or parieto-frontal area forming a depressed lesion in the skin and subcutaneous tissue.[1] various etiologies including trauma, radiotherapy, and autoimmunity have been proposed.[4] en coup de sabre usually affects children in the first decade and is predominantly seen in females.[5] ocular manifestations is not common in localized scleroderma, however, it has been reported to occur in 14% of the patients with ecds.[3] eyelid and adnexal involvement are the most common periocular abnormalities. also, anterior segment inflammation is reported as the most frequent ocular manifestation.[3] in the present case, a boy with ecds presented with ipsilateral vision loss. the specific clinical picture and ffa were in favor of a coats’-like response which refers to a fundus with the similar clinical appearance of coats’ disease in the setting of other ocular or systemic disorders. coats disease is defined as idiopathic retinal light bulb telangiectasias with intraretinal and/or subretinal exudation without appreciable retinal or vitreal traction.[6] the pathogenesis is believed to be related to the breakdown of blood–retinal barrier due to changes at the endothelial level and the presence of abnormal pericytes.[7] 136 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 coats’-like response in scleroderma; behboudi et al figure 1. photograph of the patient showing depressed left forehead skin lesion (en coup de sabre). to the best of our knowledge, there have been only five previous reports of this coats’-like response in patients with ecds.[8–12] one of them resulted in exudative retinal detachment and severe vision loss in early childhood.[8] unlike previous reports, our patient regained nearly normal vision following appropriate treatment. we believe that treatment with intravitreal antivegf agents and/or laser photocoagulation may be beneficial for patients with coats’ like response. this treatment may halt or at least delay progression of the retinal abnormalities. it is of value to mention progressive hemifacial atrophy (parry–romberg syndrome) which is a hemifacial atrophy mainly below the forehead with an unknown etiology.[13] overlapping features of ecds and ipsilateral hemifacial atrophy have been described in literature and it is thought that they may lie on the same spectrum.[13] coats’like response has been reported in a number of cases with progressive hemifacial atrophy.[14] the exact cause of this association remains undetermined; however, several theories have been suggested regarding the pathogenesis of scleroderma. the subclinical occlusive vasculitis can be caused by an inflammatory process with a probable autoimmune basis.[15] vascular abnormalities such as endothelial cells loss, increased vascular permeability, and defective angiogenesis have been recognized in linear journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 137 coats’-like response in scleroderma; behboudi et al figure 2. fundus fluorescein angiography. vascular tortuosity and fusiform aneurysms with leakage and non-perfusion areas in the mid-peripheral and peripheral regions. figure 3. macular optical coherence tomography at baseline, 3-month, 8-month, and 12-month visits (from left to right). scleroderma.[16] it is hypothesized that systemic endothelial cell injury leads to the production of ifnα and subsequent tissue hypoxia and expression of vegf.[15] intracranial vascular abnormalities have also been reported in patients with linear scleroderma. gunness et al described an ipsilateral brain cavernoma in a patient with localized scleroderma on the frontal side of scalp.[17] we presume that the vascular, inflammatory, and immunological processes involved may explain the vascular telangiectasia, dilatation, and leakage observed in coats’-like response. previous literature and the present case suggest that eyes as well as brain can be affected by linear scleroderma, which is commonly known as a limited skin disorder. accordingly, we advise routine ophthalmologic examination including dilated funduscopy every three to four months in the first three years of presentation in patients with ecds. also, those presenting with visual complaints should be examined promptly. pediatricians, dermatologists, and rheumatologists should be aware of the 138 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 coats’-like response in scleroderma; behboudi et al figure 4. fundus photograph at 12-month, showing reduced vascular tortuosity and beading. possible ophthalmic disorders associated with ecds. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. careta mf, romiti r. localized scleroderma: clinical spectrum and therapeutic update. an bras dermatol 2015;90:62–73. 2. segal p, jablonska s, mrzyglod s. ocular changes in linear scleroderma. am j ophthalmol 1961;51:807–813. 3. zannin me, martini g, athreya bh, russo r, higgins g, vittadello f, et al. ocular involvement in children with localised scleroderma: a multi-centre study. br j ophthalmol 2007;91:1311–1314. 4. peña-romero ag, garcía-romero mt. diagnosis and management of linear scleroderma in children. curr opin pediatr 2019;31:482–490. 5. orozco-covarrubias l, guzman-meza a, ridaura-sanz c, carrasco daza d, sosa-de-martinez c, ruiz-maldonado r. scleroderma ‘en coup de sabre’and progressive facial hemiatrophy. is it possible to differentiate them? j eur acad dermatol venereol 2002;16:361–366. 6. sen m, shields cl, honavar sg, shields ja. coats disease: an overview of classification, management and outcomes. indian j ophthalmol 2019;67:763. 7. recchia fm, capone a. coats’ disease. in: reynolds j, olitsky s, editors. pediatric retina. berlin, heidelberg: springer; c2011. 235–243 p. 8. fledelius hc, danielsen pl, ullman s. ophthalmic findings in linear scleroderma manifesting as facial en coup de sabre. eye 2018;32:1688. 9. george mk, bernardino cr, huang jj. coats-like response in linear en coup de sabre scleroderma. retin cases brief rep 2011;5:275–278. 10. holl-wieden a, klink t, klink j, warmuth-metz m, girschick h. linear scleroderma ‘en coup de sabre’associated with cerebral and ocular vasculitis. scand j rheumatol 2006;35:402–404. 11. lenassi e, vassallo g, kehdi e, chieng as, ashworth jl. craniofacial linear scleroderma associated with retinal telangiectasia and exudative retinal detachment. j aapos 2017;21:251–254. 12. neki a, sharma a. ipsilateral coat’s reaction in the eye of a child withen coup de sabre morphoea-a case report. indian j ophthalmol 1992;40:115. 13. el-kehdy j, abbas o, rubeiz n. a review of parry-romberg syndrome. j am acad dermatol 2012;67:769–784. 14. bucher f, fricke j, neugebauer a, cursiefen c, heindl lm. ophthalmological manifestations of parry-romberg syndrome. surv ophthalmol 2016;61:693–701. 15. fleming jn, nash ra, mahoney wm, schwartz sm. is scleroderma a vasculopathy? curr rheumatol rep 2009;11:103–110. 16. zulian f, vallongo c, woo p, russo r, ruperto n, harper j, et al. localized scleroderma in childhood is not just a skin disease. arthritis rheum 2005;52:2873–2881. 17. gunness vrn, munoz d, gonzález-lópez p, alshafai n, mikhalkova a, spears j. ipsilateral brain cavernoma under scleroderma plaque: a case report. pan afr med j 2019;32:13. journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 139 original article job satisfaction among ophthalmologists in iran hamideh sabbaghi1, 2, phd; masomeh kalantarion3, phd; mehdi yaseri4, 5, phd; bahareh kheiri4, ms; zhale rajavi1, 6, 7, md; sare safi1, phd 1ophthalmic epidemiology research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2department of optometry, school of rehabilitation, shahid beheshti university of medical sciences, tehran, iran 3department of medical education, virtual school of medical education and management, shahid beheshti university of medical sciences, tehran, iran 4ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 5department of epidemiology and biostatistics, school of public health, tehran university of medical sciences, tehran, iran 6negah specialty ophthalmic research center, shahid beheshti university of medical sciences, tehran, iran 7department of ophthalmology, school of medicine, shahid beheshti university of medical sciences, tehran, iran orcid: hamideh sabbaghi: https://orcid.org/0000-0002-2627-7222 masomeh kalantarion: https://orcid.org/0000-0003-4778-3973 abstract purpose: to estimate the level of job satisfaction among ophthalmologists in iran and determine the associated factors that may impact their overall job satisfaction. methods: in this cross-sectional study, 181 ophthalmologists (79.0% male) were interviewed by the warr-cook-wall questionnaire with 7-point-likert scale, which transformed responses from a 0 (most dissatisfied) to 100 (most satisfied). questionnaires were randomly distributed among registered ophthalmologists at the 29𝑡ℎ annual congress of the iranian society of ophthalmology in november 2019. satisfaction under each scale was considered as a score of >60% of the total score. results: a total of 181 ophthalmologists with a mean age of 47.8 ± 12.1 years and 16 ± 12 years of practice participated in the present study. they were mostly satisfied with their job as a whole (88.1%, mean score: 60.6 ± 20.7) and dissatisfied with their income (55.9%, mean score: 47.6 ± 20.3). high levels of job satisfaction was found among ophthalmologists with longer duration of practice (p < 0.001) while lower levels of satisfaction were identified among those who worked in academic centers (p = 0.004). conclusion: in this study, high levels of job satisfaction were found among ophthalmologists with longer duration of practice while low levels of satisfaction were identified among ophthalmologists who worked in academic centers. the factors of salary and working hours accounted for the least levels of job satisfaction. keywords: associated factors; iran; job satisfaction; ophthalmologists; warr-cook-wall questionnaire j ophthalmic vis res 2022; 17 (4): 543–550 © 2022 sabbaghi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 543 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i4.12315&domain=pdf&date_stamp=2019-07-17 job satisfaction in iranian ophthalmologists; sabbaghi et al introduction job satisfaction refers to the level of contentment that a person feels toward their job which is influenced by their expectations and how that feeling translates into their attitude and achievements.[1–3] job satisfaction is entirely obtainable in cases where successful achievements were matched with expectations, desires, and values in the profession.[2, 3] in general, job satisfaction which can be influential on different aspects of an occupation[4] is reported to have a positive relationship with creativity and productivity, the quality of work, the provision of higher work incentives, and lower absenteeism rates.[5]in addition, lack of attention to employees’ satisfaction can threaten the financial progression of each organization and may eventually lead to a gradual economic decline. job dissatisfaction may also cause anxiety, lower productivity, absenteeism, resignation, job abandonment, early retirement, as well as individual physical and mental discomforts.[6–9] job satisfaction of healthcare providers, especially physicians, is a substantial requirement in the healthcare system which can have a crucial role in improving physicians’ performance and, ultimately, the stability of the healthcare system,[10–12] while job dissatisfaction may lead to reduced patient care by physicians and increased healthcare system costs.[12, 13] a significant association between physicians’ job satisfaction and patients’ satisfaction was reported by some other studies.[14, 15] furthermore, job satisfaction is also an influential factor affecting the mental health of physicians and other health caregivers.[16] correspondence to: masomeh kalantarion, ms. department of medical education, virtual school of medical education and management, shahid beheshti university of medical sciences, tehran, iran. email: kalantarion65@gmail.com received: 26-01-2021 accepted: 26-01-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i4.12315 it is reported that organizational and environmental factors impact job satisfaction either directly or indirectly.[7] other factors that affect job satisfaction include salary and benefits, job security, justice, non-discrimination among employees, and access to work equipment.[17] a study conducted in norway showed that most psychiatrists and primary care physicians have higher levels of job satisfaction as compared to other medical groups.[18] furthermore, higher levels of job satisfaction were reported among norwegian physicians as compared to german physicians, which was due mainly to appropriate working hours, adequate salary, and good control over work affairs.[19] conversely, some other studies showed lower levels of job satisfaction among physicians who work in the united states and the united kingdom.[16, 20] as a consequence, identification of and addressing the known factors affecting job satisfaction is a fundamental step in improving productivity and quality of the job. although several studies exist investigating job satisfaction among other professions in iran,[3, 9] none was conducted among ophthalmologists. therefore, we aimed to estimate ophthalmologists’ job satisfaction levels in iran and determine the associated factors that may impact it. methods the present cross-sectional study investigated the job satisfaction levels among 181 iranian ophthalmologists (79.0% male) who participated in the 29𝑡ℎ annual congress of the iranian society of ophthalmology in november 2019. this study was approved by the ethics committee of the ophthalmic research center affiliated to shahid behshti university of medical sciences, tehran, iran via the approval code ir.sbmu.orc.rec.1394.04. the study details were explained to all participants and their information was kept confidential. this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: sabbaghi h, kalantarion m, yaseri m, kheiri b, rajavi z, safi s. job satisfaction among ophthalmologists in iran . j ophthalmic vis res 2022;17:543–550. 544 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 https://knepublishing.com/index.php/jovr job satisfaction in iranian ophthalmologists; sabbaghi et al 10-item warr-cook-wall questionnaire data collection was done using the 10-item warrcook-wall questionnaire which was customized and translated into the persian language by lavasani et al.[21, 22] this questionnaire was presented to an expert panel including five ophthalmologists (three academic and two nonacademic ophthalmologists) to revise it so that it would be aligned with the ophthalmology context. the revised questionnaire was then approved by other professors at the department of ophthalmology. all participants were interviewed by the10item warr-cook-wall questionnaire consisting of 10 questions scored based on a 7-point likert scale. this questionnaire recorded general information regarding the interviewees’ age, sex, location of practice, field and duration of practice, and their subspecialty. the job satisfaction of all participants was also recorded according to their responsibility, freedom to choose how to work, variety of work, relationship with colleagues, feelings toward the job, physical condition, opportunities, salary, acknowledgement of good performance, and working hours. for data analysis, the responses under each of the 10 items were transformed into a 0 (most dissatisfied) to 100 (most satisfied) scale. the questionnaire was filled out by the study participants at the time of registration for the congress in order to prevent duplication.[23, 24] in order to increase the response rate, participants were gifted a reduced snellen eye chart. statistical analysis to present data, we used mean, standard deviation, median, range, frequency, and percentage analyses. to identify the associated factors of job satisfaction, all items of the questionnaire were first entered into the univariate model. each variable with a p-value < 0.2 was statistically acceptable in order to enter the multivariate analysis. all statistical analyses were performed using the spss software version 25 (ibm corp. armonk, ny: ibm corp.). p-values < 0.05 were considered statistically significant. results a total of 181 ophthalmologists with the mean age of 47.8 ± 12.1 years participated in the present study. table 1 shows the demographic characteristics, academic degrees, duration and location of practice. the majority of them (63.5%) were general ophthalmologists and 56.9% had a duration of practice of >10 years. a total of 22.6% of participants were faculty members of whom 3.3% and 19.3% were in the fields of research and education, respectively. table 2 shows the mean score of the individuals’ job satisfaction in each item of the warr-cookwall questionnaire. a high level of satisfaction was observed in more than half of the study subjects (63.5%). highest job satisfaction levels were positively related to the following factors: freedom to choose how to work (98.3%); variety of work (93.2%); level of responsibility (88.1%); and feelings of satisfaction (88.1%). the lowest levels of job satisfaction were identified in the following categories: acknowledgement of good performance (66.1%); working hours (61.0%); and salary (55.9%). table 3 shows the level of job satisfaction in relation to the characteristics of the participants. we found that higher levels of job satisfaction were observed among older ophthalmologists (p = 0.001), who had longer duration of practice (p < 0.001) and worked in a private office (p = 0.004). the simultaneous analysis also showed that ophthalmologists with longer years of experience were more satisfied as compared to those having <10 years of experience (aor = 5.472, 95% ci: 2.202–13.599; p < 0.001). furthermore, ophthalmologists working in academic centers had lower levels of job satisfaction than those who worked in private offices (aor = 0.299, 95% ci: 0.131–0.679; p = 0.004). figure 1 shows the frequency of job satisfaction in different fields of ophthalmology. as seen, the highest (40.9%) and the lowest (6.1%) levels of satisfaction were observed among ophthalmologists working in the fields of anterior segment and glaucoma, respectively. discussion the main aim of the present study was to determine the job satisfaction levels among iranian ophthalmologists. in this regard, the persian version of the 10-item warr-cookwall questionnaire was filled by iranian ophthalmologists who participated in the 29𝑡ℎ journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 545 job satisfaction in iranian ophthalmologists; sabbaghi et al table 1. demographic characteristics of the study subjects. factors level value age (yrs) mean ± sd 47.8 ± 12.1 median (iqr) 47 (37 to 59) age category (yrs) ≤35 34 (18.8%) 36–50 76 (42.0%) 51–65 60 (33.1%) ≥66 11 (6.1%) sex (%) male 143 (79.0%) female 38 (21.0%) duration of practice (yrs) mean ± sd 16 ± 12 median (iqr) 14 (5 to 23) ≤10 78 (43.1%) 11–25 68 (37.6%) ≥26 35 (19.3%) last degree (%) general ophthalmologist 115 (63.5%) fellowship 66 (36.5%) field of fellowship (%) anterior segment 27 (40.9%) posterior segment 23 (34.8%) strabismus 12 (18.2%) glaucoma 4 (6.1%) faculty (%) research 6 (3.3%) educational 35 (19.3%) non-academic 140 (77.3%) status (%) private office 124 (68.5%) academic staff 57 (31.5%) iqr, inter quartile range; sd, standard deviation; yrs, years annual congress of the iranian society of ophthalmology. the present study demonstrated that more than half of the ophthalmologists had a high level of job satisfaction. however, the highest and lowest levels were related to the freedom to choose how to work and salary, respectively. the highest levels of job satisfaction were significantly observed among ophthalmologists who were older and those who had longer years of practice. additionally, lower levels of satisfaction were identified among ophthalmologists who worked in academic centers. our literature review shows that although most studies investigated job satisfaction among medical professionals, especially nurses,[25–27] few studies focused on ophthalmologists.[28, 29] in this regard, the discoveries of a study conducted by nair et al to investigate the job satisfaction among indian ophthalmologists can be used for comparison with the study on iranian ophthalmologists.[28] overall, the present study showed an acceptable level of job satisfaction (63.5%) among iranian ophthalmologists, which is consistent with the results reported among indian and nigerian ophthalmologists with job satisfaction levels of 54.21% and 78.5%, respectively.[28, 29] additionally, mean levels of satisfaction were reported among optometrists (145.9 ± 14.44) as compared to other medical specialists.[30] furthermore, high levels of job satisfaction were identified among 37.5% of the vision technicians studied by paudel et al.[31] 546 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 job satisfaction in iranian ophthalmologists; sabbaghi et al table 2. mean job satisfaction scores of study participants for every 10 questions of the questionnaire. items satisfaction score satisfied mean ± sd median (iqr) n (%) responsibility 58 ± 17.3 50 (50 to 66.7) 52(88.1%) freedom to choose how to work 61 ± 19.2 66.7 (50 to 66.7) 58 (98.3%) variety of work 61.2 ± 18.9 66.7 (50 to 66.7) 55 (93.2%) colleague 55.5 ± 18 50 (50 to 66.7) 47(79.7%) feeling of satisfaction 60.6 ± 20.7 66.7 (50 to 66.7) 52(88.1%) physical condition 57.6 ± 20.1 50 (50 to 66.7) 49(83.1%) opportunity 54.7 ± 16.9 50 (50 to 66.7) 39(67.2%) salary 47.6 ± 20.3 50 (33.3 to 50) 33(55.9%) acknowledgement of good performance 49.2 ± 21.2 50 (33.3 to 66.7) 39(66.1%) working hours 52 ± 19 50 (50 to 66.7) 36(61%) iqr, inter quartile range; sd, standard deviation figure 1. the frequency of job satisfaction in different fields of ophthalmology. of note, multiple style questionnaires were also used to assess ophthalmologists’ job satisfaction in related studies.[28, 29, 31] in this investigation, the 10-item warr-cook-wall questionnaire was used,[21] while in other studies, a questionnaire created by a researcher was used for data collection, whose responses were provided based on literature review and panel experts’ consensus.[28, 29, 31] a standard questionnaire (job satisfaction survey scale) designed by paul e spector for optometrists was applied in the study by chen et al.[30] this questionnaire also assesses job satisfaction from different dimensions including promotion, supervision, operating conditions, relationships with coworkers, work nature, and communication.[30] in the present study, the highest level of job satisfaction was related to the freedom to choose how to work (98.3%). this can be attributed to the fact that the majority of our study population who were general ophthalmologists (63.5%) and also worked in private office (68.5%) had the journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 547 job satisfaction in iranian ophthalmologists; sabbaghi et al table 3. job satisfaction of participants based on their characteristics. factors level satisfied p-value aor 95% ci p-value aor (backward) 95% ci p-value lower upper lower upper age (yrs) ≤35 4 (11.8%) 0.001 r 36–50 24 (32.0%) 2.501 0.7 8.931 0.158 51–65 23 (38.3%) 1.839 0.369 9.169 0.457 ≥66 8 (72.7%) 3.007 0.31 29.15 0.342 sex (%) male 52 (36.4%) 0.05 r r female 7 (18.9%) 0.421 0.16 1.109 0.08 0.425 0.164 1.103 0.079 duration of practice (yrs) ≤10 16 (20.5%) <0.001 r r 11–25 22 (32.8%) 1.347 0.509 3.565 0.549 1.602 0.737 3.483 0.234 ≥26 21 (60.0%) 4.634 1.075 19.974 0.04 5.472 2.202 13.599 <0.001 field of fellowship (%) anterior segment 10 (37.0%) 0.807 posterior segment 9 (39.1%) strabismus 6 (50.0%) glaucoma 1 (25.0%) status (%) private office 43 (36.8%) 0.004 r r academic staff 16 (25.4%) 0.322 0.139 0.746 0.008 0.299 0.131 0.679 0.004 faculty (%) research 1 (16.7%) 0.282 educational 15 (42.9%) nonacademic 43 (30.9%) xp-value for the comparison of the level to the reference level. *these variables remained statistically significant in the final model based on logistic regression. r, reference category. freedom to choose how to work. however, the study by paudel et al[31] reported acceptable levels of job satisfaction with the variety of work (70.8%) among vision technicians which is not in line with our findings. in some other studies, it was also reported that the highest levels of satisfaction were observed under the categories of patients’ treatment (94.9%) and the nature of the work.[29, 30] in the present study, the lowest level of job satisfaction was related to salary (55.9%), since the majority of our population had long practicing experience and they expected to earn higher levels of income. the highest level of job dissatisfaction (71.2%) among nigerian ophthalmologists was related to work facilities.[29] the results reported by other studies on ophthalmologists,[29] vision technicians,[31] doctors working at teaching hospitals,[32] and medical officers[33] indicated the lowest levels for salary satisfaction. however, the results of the study conducted on optometrists in malaysia demonstrated moderate salary satisfaction.[30] various studies reported a high level of satisfaction with colleagues, the rate of 78.7% was reported among nigerian ophthalmologists[29] and 66.7% among vision technicians.[31] 548 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 job satisfaction in iranian ophthalmologists; sabbaghi et al a low level of satisfaction with working hours (61.0%) was determined in the present study, which is consistent with the results reported on indian ophthalmologists.[28] in this study, there were higher levels of job satisfaction among ophthalmologists with older ages (p = 0.001) and long duration of practice (p < 0.001); however, paudel et al found no significant relationship between job satisfaction and age and duration of practice.[31] although the association between job satisfaction and all of the underlying factors was not examined in the study on the indian ophthalmologists, more challenges were reported among female ophthalmologists (p < 0.001).[28] meanwhile, jain et al found that female ophthalmologists complained about having fewer working hours and experiencing extra obstacles regarding job promotions and discrimination in the workplace. however, no evaluation of the job satisfaction was performed between genders in the current study.[34] multivariate analysis shows high levels of satisfaction among ophthalmologists with longer experience (<0.001) and lower levels of satisfaction among those working in academic centers (p = 0.004). it is noticeable that the lowest levels of job satisfaction recorded among the iranian ophthalmologists in this study were regarding their salary, acknowledgement of good performance, and working hours. it is necessary for these concerns to be investigated fully by the health policymakers and the iranian society of ophthalmology since high levels of job satisfaction can have a crucial impact when offering high-quality medical and educational services. extensive investigation using a combination of qualitative and quantitative research measures on a larger ophthalmologists’ population is recommended for future studies on job satisfaction. one advantage of the present study was the usage of the persian version of the warr-cook-wall questionnaire[22] which enhanced the efficiency and comprehensibility of this questionnaire. sample selection from the ophthalmology congress participants can be taken as a possible limitation of the present study, since it is expected that congress attendees are already more satisfied in their jobs and their responses may skew the results. additionally, the higher male respondent among our study participants could be considered as another limitation of the current study as it may not be accurately representative of the proportion of the male versus female ophthalmologists in iran. in summary, high levels of job satisfaction were found among ophthalmologists with longer duration of practice, while low levels of job satisfaction were identified among ophthalmologists who worked in academic centers. salary and working hours were determined to be the factors that were responsible for the lowest levels of job satisfaction assessed in this study. financial support and sponsorship none. acknowledgements the authors would like to express their gratitude to the ophthalmology research center, shahid beheshti university of medical sciences and all the loved ones who cooperated with this research project, especially ophthalmologists. conflicts of interest the authors declare that they have no conflict of interest. references 1. moorhead g. organizational behavior. alvani m, memarzade gh, translators. tehran, iran: morvarid; 1995. 2. mehrabian f, nasiripour aa, keshavarz mohammadian s. survey the level of job satisfaction among managers and supervisors in different units of guilan governmental hospitals in 1384. majallah-i danishgah-i ulum-i pizishki-i gilan 2007;16:65–73. 3. daneshmandi m, habibi h, sirati nayer m, zarei a, pishgouei ah. faculty members’ job satisfaction in selected military universities. indian j med educ 2012;12:458–466. 4. hooman ha. development and standardization of a job satisfaction scale. tehran, iran: presidential public management training center; 2002. 5. moosavi tabar sy, rahmani r, sirati nayyer m, abbas zadeh z. influence factors in job satisfaction of nurses in the selected military and civil hospital in tehran; 2013. journal of nurse and physician within war 2014;24:34–39. 6. fakhimi f. organization and management: theories, functions and responsibilities. 2nd ed. tehran, iran: hestan; 2013. journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 549 job satisfaction in iranian ophthalmologists; sabbaghi et al 7. muqeemi m. organization and management. tehran, iran: termeh; 2008. 8. robbins sp. organizational behavior: concepts, controversies, application. 9th ed. minnesota: prentice hall; 2001. 9. teymouri m, tootoonchi m, salehi m, hassanzadeh a. job satisfaction among faculty members of isfahan university of medical sciences. indian j med educ 2008;7:227–235. 10. ramirez aj, graham j, richards ma, cull a, gregory wm. mental health of hospital consultants: the effects of stress and satisfaction at work. lancet 1996;347:724–728. 11. aasland og, olff m, falkum e, schweder t, ursin h. health complaints and job stress in norwegian physicians: the use of an overlapping questionnaire design. soc sci med 1997;45:1615–1629. 12. lichtenstein rl. the job satisfaction and retention of physicians in organized settings: a literature review. med care rev 1984;41:139–179. 13. mick ss, sussman s, anderson-selling l, delnero c, glazer r, hirsch e, et al. physician turnover in eight new england prepaid group practices: an analysis. med care 1983;21:323–337. 14. linn ls, yager j, cope d, leake b. health status, job satisfaction, job stress, and life satisfaction among academic and clinical faculty. jama 1985;254:2775–2782. 15. mechanic d. the orginization of medical practice and practice orientations among physicians in prepaid and nonprepaid primary care settings. med care 1975;13:189– 204. 16. murray a, montgomery je, chang h, rogers wh, inui t, safran dg. doctor discontent. a comparison of physician satisfaction in different delivery system settings, 1986 and 1997. j gen intern med 2001;16:452–459. 17. siegel pa, post c, brockner j, fishman ay, garden c. the moderating influence of procedural fairness on the relationship between work-life conflict and organizational commitment. j appl psychol 2005;90:13–24. 18. nylenna m, gulbrandsen p, førde r, aasland og. unhappy doctors? a longitudinal study of life and job satisfaction among norwegian doctors 1994-2002. bmc health serv res 2005;5:4. 19. rosta j, nylenna m, aasland og. job satisfaction among hospital doctors in norway and germany. a comparative study on national samples. scand j public health 2009;37:503–508. 20. zuger a. dissatisfaction with medical practice. n engl j med 2004;350:69–75. 21. warr p, cook j, wall t. scales for the measurement of some work attitudes and aspects of psychological well-being. j occup psychol 1979;52:129–148. 22. gholamali lavassani m, keyvanzade m, arjmand n. spirituality, job stress, organizational commitment and job satisfaction among nurses in tehran. bjcp 2009;3:61–73. 23. rajavi z, kalantarion m, kheiri b, farzam p, akbarian s. patterns of amblyopia treatment employed by iranian ophthalmologists and optometrists in xxii annual congress of the iranian society of ophthalmology. bina j ophthalmol 2013;19:121–128. persian 24. katibeh m, ziaei h, eskandari a, moein h, mirzaei m, kalantarion m. prophylactic patterns for post-cataract surgery endophthalmitis in iran. bina j ophthalmol 2013;19:3–9. persian 25. assunção aá, pimenta am. job satisfaction of nursing staff in the public health network in a brazilian capital city. cien saude colet 2020;25:169–180. 26. yehya a, sankaranarayanan a, alkhal a, alnoimi h, almeer n, khan a, et al. job satisfaction and stress among healthcare workers in public hospitals in qatar. arch environ occup health 2020;75:10–17. 27. yasin ym, kerr ms, wong ca, bélanger ch. factors affecting nurses’ job satisfaction in rural and urban acute care settings: a prisma systematic review. j adv nurs 2020;76:963–979. 28. nair ag, jain p, agarwal a, jain v. work satisfaction, burnout and gender-based inequalities among ophthalmologists in india: a survey. work 2017;56:221– 228. 29. omolase c, seidu m, omolase b, agborubere d. job satisfaction amongst nigerian ophthalmologists: an exploratory study. libyan j med 2010;5:4629. 30. chen ah, jaafar sn, noor ar. comparison of job satisfaction among eight health care professions in private (non-government) settings. malays j med sci 2012;19:19– 26. 31. paudel p, cronjé s, o’connor pm, khadka j, rao gn, holden ba. development and validation of an instrument to assess job satisfaction in eye-care personnel. clin exp optom 2017;100:683–689. 32. shakir s, ghazali a, shah ia, zaidi sa, tahir mh. job satisfaction among doctors working at teaching hospital of bahawalpur, pakistan. j ayub med coll abbottabad. 2007;19:42–45. 33. chaudhury s, banerjee a. correlates of job satisfaction in medical officers. med j armed forces india 2004;60:329– 332. 34. jain ns, kersten hm, watson sl, danesh-meyer hv. gender differences in australasian ophthalmologists’ experiences of the workplace. clin exp ophthalmol 2019;47:706–712. 550 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 review article peripheral ulcerative keratitis: a review kiana hassanpour1, md, mph; reem h. elsheikh2, md; amir arabi1, md, mph; charles r. frank3, md; abdelrahman m. elhusseiny3,4, md; taher k. eleiwa5, md, phd; shiva arami6, md; ali r. djalilian3*, md; ahmad kheirkhah7, md 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2department of ophthalmology, faculty of medicine, cairo university, cairo, egypt 3department of ophthalmology and visual sciences, university of illinois at chicago, chicago, il, usa 4department of ophthalmology, harvey and bernice jones eye institute, university of arkansas for medical sciences, little rock, ar, usa 5department of ophthalmology, faculty of medicine, benha university, benha, egypt 6department of medicine, division of rheumatology, university of illinois at chicago, chicago, il, usa 7department of ophthalmology, long school of medicine, university of texas health at san antonio, san antonio, tx, usa orcid: kiana hassanpour: https://orcid.org/0000-0002-1788-7352 ali r. djalilian: https://orcid.org/0000-0002-1489-0724 ahmad kheirkhah: https://orcid.org/0000-0003-4217-3367 abstract peripheral ulcerative keratitis (puk) is a rare but serious ocular condition that is an important clinical entity due to its ophthalmological and systemic implications. it is characterized by progressive peripheral corneal stromal thinning with an associated epithelial defect and can be associated with an underlying local or systemic pro-inflammatory condition, or present in an idiopathic form (mooren ulcer). associated conditions include autoimmune diseases, systemic and ocular infections, dermatologic diseases, and ocular surgery. cell-mediated and autoantibody-mediated immune responses have been implicated in the pathogenesis of puk, destroying peripheral corneal tissue via matrix metalloproteinases. clinically, patients with puk present with painful vision loss, a peripheral corneal ulcer, and often adjacent scleritis, episcleritis, iritis, or conjunctivitis. diagnostic evaluation should be focused on identifying the underlying etiology and ruling out conditions that may mimic puk, including marginal keratitis and terrien marginal degeneration. treatment should be focused on reducing local disease burden with topical lubrication, while simultaneously addressing the underlying cause with antimicrobials or anti-inflammatory when appropriate. existing and emerging biologic immunomodulatory therapies have proven useful in puk due to autoimmune conditions. surgical treatment is generally reserved for cases of severe thinning or corneal perforation. keywords: autoimmune disease; immunomodulatory therapy; ulcerative keratitis j ophthalmic vis res 2022; 17 (2): 252–275 252 © 2022 hassanpour et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i2.10797&domain=pdf&date_stamp=2019-07-17 update on puk; hassanpour et al introduction peripheral ulcerative keratitis (puk) is an acute destructive peripheral keratitis, associated with epithelial defect and stromal thinning in all cases. puk is a sight-threatening condition that also carries a high risk of systemic morbidity and mortality when accompanied by an underlying collagen vascular disease, which occurs in almost half of noninfectious peripheral keratitis.[1] puk has an average incidence of 0.2–3 individuals per million population.[2] reviewing the current literature, the exact relationship of puk among other inflammatory lesions of the peripheral cornea is ill-defined. the current review discusses puk as an immune-mediated keratopathy associated with systemic immune alterations. these systemic immune disturbances may be caused by an autoimmune disease, a systemic infectious condition, or a systemic condition neither autoimmune nor infectious. we will review the etiology, clinical aspects, pathophysiology, and treatment options of puk, focusing on the updates of puk pathogenesis and therapeutic advances. features of the peripheral cornea compared to the central cornea, the corneal periphery differs in a few key ways. it contains characteristic features as a junction of cornea, conjunctiva, episcleral, and sclera.[3] histologically, the peripheral stroma has looser arrangements of collagen bundles, with the limbal vascular arcades and lymphatics extending about 0.5 mm into the clear cornea.[4] consequently, the corneal periphery has a higher density of langerhans correspondence to: ali r. djalilian, md, professor of ophthalmology, cornea service director, stem cell therapy and corneal tissue engineering laboratory, illinois eye and ear infirmary, 1855 w. taylor street, m/c 648, chicago, il 60612, usa. e-mail: adjalili@uic.edu ahmad kheirkhah, md. department of ophthalmology, long school of medicine, university of texas health, san antonio, san antonio, tx 78229, usa. email: kheirkhah@uthscsa.edu received: 30-07-2021 accepted: 10-02-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i2.10797 cells, immunoglobulin m, and c1 complement factor.[3, 5, 6] accordingly, any ocular or systemic condition that alters the dynamics of ocular surface immunity may be associated with an inflammatory response in the peripheral cornea. the peripheral corneal epithelium is more adherent to the underlying basement membrane with increased expression of cell surface-associated glycoprotein mucin-4 gene (muc4) that protects the corneal epithelium and controls the epithelial regeneration.[4, 7] in addition, the corneal periphery has proximity to the limbal epithelial stem cell niche and is the site with the maximum replicative activity of the corneal endothelium.[4, 8] lastly, the corneal periphery is less sensitive owing to less neural innervation compared to the central regions.[8] etiology of puk peripheral ulcerative keratitis (puk) can be caused by a variety of disorders including infectious and noninfectious conditions. noninfectious causes include autoimmune, dermatological, neurological, and postsurgical etiologies.[9] diagnosis of the underlying cause is crucial to reducing mortality and systemic and ocular morbidities.[10] figure 1 lays out a classification schema for the etiology of puk. autoimmune diseases represent almost half of the noninfectious causes of puk. rheumatoid arthritis (ra) has been reported to account for 34% of noninfectious puk with bilateral involvement in 50% of cases.[1] granulomatosis with polyangiitis (gpa) is a systemic vasculitis that is commonly associated with puk in later stages.[11] other autoimmune etiologies of puk include systemic lupus erythematosus (sle), polyarteritis nodosa (pan), progressive systemic sclerosis (pss), sjögren’s syndrome (ss), relapsing polychondritis (rp), and giant cell arteritis (gca).[12] dermatological causes include acne rosacea, which has been reported to have corneal involvement in 33% of patients.[13] this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: hassanpour k, elsheikh rh, arabi a, frank cr, elhusseiny am, eleiwa tk, arami a, djalilian ar, kheirkhah a. peripheral ulcerative keratitis: a review. j ophthalmic vis res 2022;17:252–275. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 253 https://knepublishing.com/index.php/jovr update on puk; hassanpour et al infections, which have been reported as the second most common cause of puk, are responsible for approximately 20% of all cases.[14] peripheral corneal infections must be associated with crescentic stromal thinning with ulceration and stromal inflammatory infiltrates to be defined as puk.[15] maintaining a high index of suspicion for infectious etiologies of puk is prudent, and they can be excluded by ordering relevant microbiological investigations based on the local prevalence of culprit organisms. sharma and colleagues reported that 19.7% of infectious puk was attributable to ocular sources, with bacteria representing 73.3% of cases.[14] systemic infections associated with puk include bacterial (tuberculosis, syphilis, lyme), viral (varicella-zoster), fungal, and parasitic etiologies.[12] sainz de la maza and colleagues reported puk in 7.4% of patients with scleritis.[15] also, they reported a high probability of puk occurrence in the presence of necrotizing scleritis. in their small case series, all cases of scleritis-associated puk had an underlying systemic vasculitis, which supports the hypothesis of coincidence of puk and scleritis secondary to an extension of vasculitis from the sclera to peripheral cornea.[15] fluorescein angiography studies of the anterior segment have shown that puk in scleritis is associated with vasoocclusive changes of conjunctival and episcleral vasculature, where the larger the area of vascular occlusion, the greater the degree of corneal stromal lysis.[16, 17] puk can present initial or be reactivated after ocular surgery. the site of disease is not necessarily close to the incision site. severe cases of postoperative puk have been reported in patients with associated sjogren syndrome.[18] interestingly, despite ra being one of the most common causes of puk, jones and maguire reported zero incidences of puk during the eightweek follow-up period after cataract surgery in a cohort of 70 patients with ra.[19] retrospectively, chanbour and colleagues reported late-onset puk three to six months after corneal crosslinking in 1.4% of 771 eyes.[20] as mentioned above, there is a broad range of potential causes of puk. a systematic workup based on current knowledge and clinical presentation is paramount to refining the probabilities and guides for ordering the appropriate investigations and mapping the therapeutic options. pathogenesis of puk fundamental knowledge of the unique anatomy and physiology of the peripheral cornea is pivotal to understanding the pathogenesis of puk. subconjunctival lymphatics accompany the limbal capillaries into the peripheral cornea allowing access to the afferent limb of the immune system.[21] an increase in inflammation via this vascular and lymphatic supply results in peripheral corneal ulceration due to the release of proteolytic enzymes from recruited cells.[21] the limbal vascular architecture, along with tight corneal collagen packing at the periphery, facilitate deposition of immune complexes and other large molecules such as igm and c1 at the corneal periphery.[22, 23] antigen-presenting cells— langerhan cells and limbal macrophages—present specifically at the limbus and peripheral cornea and act to propagate the immune-mediated corneal injury.[24] in addition, the presence of activated t-cells in the tears of patients with underlying immune conditions may develop or exacerbate the immune reactions in puk. finally, in the humoral-mediated immune arm, auto-antibodies against corneal stromal antigens have been postulated to be involved in the pathogenesis of corneal destruction in puk.[21, 25] although many uncertainties exist regarding the exact pathogenesis of puk, these common immune mechanisms have been implicated among the various types of puk. puk and t-cell immunity the polarization of the t-cell response and subsequent cytokine release plays an important role in protection against pathogens, as well as an important role in immunopathological conditions.[26] the role of t-cell subsets in autoimmune disease has been widely discussed in the literature. giscombe and colleagues concluded that the expansion of specific subsets of the t-cell population in correlation with disease activity suggests their role in the pathogenesis of that disease.[27] for example, the number of cd4 cells was found to be significantly greater in patients with ra.[28] furthermore, the relative stability of these cell populations correlates with the chronic nature of a disease, suggesting a prolonged inciting stimulus.[29, 30] t-cells can be pathogenic through directly causing tissue damage or through 254 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 update on puk; hassanpour et al unregulated auto-antibody and proinflammatory cytokine production.[26] there is overwhelming evidence that adaptive t-cell mediated immunity is involved in the autoimmune mechanism in puk. in a study conducted by mondino and colleagues, seven patients with the clinical diagnosis of mooren ulcer underwent macrophage migration inhibition factor testing to elucidate cellular immunity to corneal antigens. six of these patients showed positive results suggesting that cell-mediated immunity may play a role in the pathogenesis of mooren ulcer.[31] in another study by foster and colleagues on a patient with bilateral mooren ulcers, an immune panel was normal except for a positive blastogenic response of the patient’s t lymphocytes when exposed to the normal corneal stroma.[32] zhao and colleagues studied the immunological process involved in the development of mooren ulcer and found a regulatory imbalance in a subset of the t-cell population, with a decline in the number of suppressor cd8 t-cells compared to cd4 t helper cells, while also finding that the peripheral cornea and surrounding conjunctival lymphatics are directly implicated in the immunopathogenesis of the disease process.[33] th17 cells expressing il-17 along with other cytokines such as il-1, il-6, il-17, il-23 play a critical role in the pathogenesis of puk in patients with gpa.[34, 35] role of complement and innate immunity in puk the complement pathway can be activated via the classical pathway by antigen–antibody complexes, or via the alternative pathway by the direct binding of c3b.[23, 24] c1, which is the first component of the classical complement pathway, is activated by antigen–antibody complexes thus initiating the complement cascade. c1 is a large molecule, and its size hinders its uniform diffusion throughout the cornea, thus it resides mainly at the peripheral cornea and the limbus.[36] similarly, igm is a large molecule (almost 900,000 times the size of iga) causing it to be present in higher concentrations at the corneal periphery. upon initiation of complement activation, a series of events ensues including the formation of small polypeptides such as c3a and c5a, which possess chemotactic activity. in contrast to c5a, which has well established chemotactic effects on neutrophils and eosinophils, it was only recently established that c3a causes selective activation of eosinophils which subsequently stimulate neutrophils through il-8.[37, 38] finally the complement system converges on the formation of the c5,6,7,8,9 complex, which is responsible for causing stromal destruction and lysis of cell membranes. this process has been implicated in peripheral corneal damage from puk in ra as well as anca-associated vasculitis and has been considered a potential therapeutic target.[39] pathological examination of the corneas of patients with puk revealed numerous proinflammatory cells of the innate immune system including neutrophils, mast cells, and eosinophils.[9] it has been proposed that these cells are the source of destructive and collagenolytic enzymes that cause the subsequent tissue injury and corneal ulceration.[40] role of b cells and antibodies in puk igm is present with higher concentrations in the periphery of the cornea owing to its larger size and inability to diffuse centrally. patients with ra have a loss of normal b cell tolerance to their antigens and some have serum igm that is directed against their igg (rheumatoid factor). these immune complexes can deposit in the peripheral cornea result in subsequent complement activation leading to corneal inflammation and ulceration as detailed above.[21] furthermore, anti-citrullinated protein antibodies (anti-ccp antibodies), also found in patients with ra, have been associated with more severe ocular findings.[41] patients with sle have a disruption in the normally present b cell tolerance leading to the production of autoantibodies including antinuclear antibodies (ana). these antibodies form immunocomplexes that affect the clearing of apoptotic cells. this starts a vicious cycle as the uncleared apoptotic cells result in more nuclear antigens that bind to ana and cause more intense tissue damage. the damage extends also to areas devoid of immune complexes, as their presence in other areas and activation of complement results in the release of c3a and c5a, which perpetuate the inflammatory cycle and can lead to corneal melting.[42] a similar journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 255 update on puk; hassanpour et al process may occur in patients with gpa, where antineutrophil cytoplasmic antibodies (anca) bind to receptors on monocytesand neutrophil— forming complexes that release proinflammatory enzymes and destructive cytokines such as il-8.[35] antibodies directed toward corneal epithelium have been found in puk patients who had gpa and ra. john and colleagues studied antibodies directed toward the cornea in gpa and ra patients who had puk.[11] they reported two corneal antigens of interest, with sizes of 54 kda and 70 kda. they showed that antibodies to the 54 kda antigen, which is the main corneal specific antigen, appeared first after an attack of puk, thus linking them to the immunopathogenesis of the disease.[11] reynolds and colleagues also studied two 66kda corneal antigens, namely bcea-a and bcea-b, and the autoantibodies directed toward them. gpa and ra patients showed an increased level of bceaa where elevated levels of bcea-b were found in patients with egpa.[43] albers and colleagues reported the presence of circulating antibodies directed toward cornea in patients with rp.[44] mondino and colleagues reported that patients with mooren ulcers had a consistent finding of tissue-fixed and circulating antibodies to conjunctival epithelium [pmid: 3050690]. antibodies were found bound to the conjunctival basement membrane adjacent to the ulcerative lesion. patients with mooren ulcer also demonstrated an elevated level of iga.[45] in another study by gottsch and colleagues to study the level of antibodies toward cornea-associated antigen (co-ag) in patients with mooren ulcer, they reported a statistically significant difference in the level of antibodies in the serum of patients with mooren ulcer when compared to controls.[46] it should be noted that the presence of these antibodies in the puk patients does not prove causation, as the antibodies might be formed in response to the tissue damage incurred during the disease process.[11] in addition to the production of autoantibodies, b cells in patients with ra are a source of cytokines that cause the pathological t-cell response.[41] specifically, tnf and il-6 regulate downstream inflammatory cascades, and the latter is important in the regulation of the balance between t regulatory cells and th17.[47] in general, b cells are responsible for the regulation of the overall th1/th2 balance.[48] role of matrix metalloproteinases in puk the corneal stroma is formed of organized collagen lamellae embedded in a frame of glycosaminoglycans. in between the adjacent lamellae are macrophages, lymphocytes, polymorphonuclear leukocytes, and fibroblasts known as keratocytes.[49] mmps are a family of endopeptidases, proteolytic enzymes that result in the degradation and breakdown of specific extracellular matrix components.[50] the activity of mmps is generally governed by their respective tissue inhibitors (timp).[51, 52] imbalance and reduced expression of timp result in high collagenase activity and increased tissue destruction and ulceration. although different subsets of mmps exhibit substrate specificity, they have an overall similar mechanism of action and structure. mmps can be classified according to substrate specificity and structural organization into collagenases (mmp-1, -8, and -13), gelatinases (mmp-2, -9), stromelysins (mmp-3, -10), matrilysins (mmp-7, -26), membrane-type mmps (mt1emt6-mmps), and others (e.g., macrophage metalloelastase mmp-12 or enamelysin mmp20).[53] mmp-1, produced by macrophages and fibroblasts, and mmp-8, produced by neutrophils and invading inflammatory cells near the limbus, have an established pathogenic role in the etiology of puk.[54] they are the only known mammalian enzymes known to be able to initiate hydrolysis of fibrillar type 1 collagen, the main component of the corneal stroma.[54] the gelatinases (mmp-2, mmp9) can cleave basement membrane components (collagen types iv and vii, fibronectin, and laminin) and stromal collagen types iv, v, and vi, the core protein decorin and denatured collagens.[54, 55] smith and colleagues reported upregulation in the level of mmp-2 in keratocytes derived from corneas of patients with puk and accumulation of mmp-9 in tears of patients with active disease.[56] although most theories linked the collagenases, namely mmp-1, and/or the reduction of their timp to the pathogenesis of puk, smith and colleagues suggested that activated gelatinases are also linked to the progression of puk. they may cause corneal perforation by breaching the corneal basement membranes (epithelial cells and descemet membrane).[56] they could also impede the process of tissue repair leading to chronicity by 256 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 update on puk; hassanpour et al breaking down the newly formed non-crosslinked collagen. puk associated with systemic noninfectious diseases the most frequent systemic noninfectious diseases associated with puk are systemic collagen vascular diseases, accounting for nearly half of puk cases.[1] around one-third of puk cases is associated with ra.[57] following ra, ancavasculitis is an autoimmune disease commonly associated with puk. other associated diseases include sle, polyarteritis nodes (pan) and its variants, sjorgren’s syndrome, rp, and eosinophilic granulomatosis with polyangiitis (egpa) [table 1].[36, 58–60] puk can be the presenting sign of autoimmune systemic diseases, or it can be manifested in a patient with previously diagnosed disease. also, it can be the only ocular surface complication of the underlying systemic disease, or it may develop in association with necrotizing scleritis.[21] visual outcomes are poor in half of the puk cases associated with systemic immune diseases, despite topical and systemic therapy.[61] due to the diversity in the prevalence of different systemic autoimmune diseases, it is difficult to determine the exact epidemiology of puk in these patients. according to one report, puk was the second most common ocular complication of autoimmune diseases, following anterior uveitis.[62] from a clinical and pathophysiological perspective, it is impossible to distinguish between puk due to different systemic immune diseases, although some studies emphasize the function of cd4+ t-cells in puk secondary to ra and autoantibodies in puk associated with sle and gpa.[63] also, it has been postulated that puk is more common in long-standing ra, while in gpa and another vasculitis, it can occur earlier in the course of the disease.[63, 64] however, puk cases are mainly distinguished by differences in the clinical presentation, biomarkers, and other auxiliary examinations of the underlying systemic disease. although traditionally it is believed that puk occurs when the systemic disease is not controlled properly, in a recent series of puk patients with underlying ra and sjorgren’s syndrome, >80% of puk episodes arose before autoimmune disease diagnosis or with the systemic disease in remission by immunosuppressive treatments.[61] any patient with puk must have a detailed personal and family history elicited, and additional diagnostic tests should be considered in all cases with suspicious clinical signs or symptoms suggesting systemic collagen vascular diseases. raand anca-associated systemic vasculitic diseases are not the only associates of corneal ulcerations. puk is also an ocular complication of sarcoidosis and behcet’s disease. sarcoidosis is a granulomatous inflammation associated with systemic vasculitis.[27] with the involvement of the small vessels in the vasculitic course of sarcoidosis, it can be complicated by potential corneoscleral inflammation, even as the first manifestation of the systemic disease.[65, 66] similarly, puk can develop in patients with underlying behcet’s disease, although it is rare and poorly documented.[67] keratopathy is a rare manifestation of inflammatory bowel disease (e.g., crohn’s disease and ulcerative colitis), which is commonly associated with subepithelial infiltrates.[68] however, there are reports regarding the development of puk with corneal perforation in crohn’s disease.[69] among dermatologic immune diseases, puk has been reported in parallel to an exacerbation of psoriasis.[70] inflammatory ocular complications of psoriasis may occur in only 5% of patients, and corneal involvement is even less common. however, psoriasis-associated keratopathy can be equally severe as other ocular conditions, threatening patients’ vision.[70] puk has also been associated with severe hidradenitis suppurativa (hs).[71, 72] as a suppurative and cicatricial disease of the apocrine glands of the skin, hs is not generally considered as an autoimmune disease, and treatment is targeted to quiet the inflammatory stages of the disease, rather than treating a major underlying autoimmune process.[72] however, underlying immune dysregulation in hs patients may be associated with the risk of severe ocular surface diseases. although systemic autoimmune diseases are the primary etiology of noninfectious puk, systemic malignancies should also be considered as etiologic factors. there are reports of puk associated with both acute and chronic myelogenous leukemia, emphasizing the importance of a careful diagnostic approach, especially in cases with no underlying immune disease.[73–75] deposition of leukemic blast cells in the limbus and subsequent inflammatory reaction has been implicated in journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 257 update on puk; hassanpour et al table 1. some systemic noninfectious diseases associated with puk, and their key findings necessary for an ophthalmologist to know the systemic condition associated with puk key demographic features key systemic findings suggesting the diagnosis suggestive diagnostic evaluations non-anca associated small-vessel vasculitis rheumatoid arthritis between 35 and 50 years, more common in women symmetric polyarthritis, morning stiffness, hand joints involvement, rheumatoid sub-cutaneous nodules presence of rheumatoid factor, typical radiologic findings sle 90% of patients are women, between 15 and 45 years fatigue, fever, joint pain, stiffness and swelling, butterfly-shaped rash on the face that covers the cheeks and bridge of the nose skin lesions that appear or worsen with sun exposure ana positive, anti-ds dna positive, anti-sm positive sjogren’s syndrome between 40 and 60 years, more common in women dry eye and mouth anti-la and anti-ro positive anca-associated small-vessel vasculitis wegener’s granulomatosis between 55 and 70 years, more common in men nasal sinus inflammation, abnormal urine analysis, pulmonary signs and symptoms c-anca positive, granulomatous inflammation and necrotizing vasculitis on histopathology microscopic polyangiitis all ages, more common in men fever, loss of appetite and weight, rashes, muscle and/or joint pain, , pulmonary signs and symptoms neuropathic signs and symptoms, gastrointestinal signs and symptoms p-anca positive, patchy 3-layer inflammation of small arteries and vein on histopathology churg-strauss syndrome mean age of onset 40 years, more common in female asthma, peripheral neuropathic signs, and symptoms, transient pulmonary infiltration prominent eosinophilia, extravascular eosinophils on histopathology medium-sized vessel vasculitis pan between 40 and 50 years, more common in men fever, weight loss, palpable purpura, skin ulceration and infarction, recent-onset htn, testicular pain hbv serology, focal vascular stenosis, or microaneurysm on cta/mra large-sized vessel vasculitis giant cell arteritis over 50 years, more common in women headache and scalp tenderness, jaw claudication elevated esr and crp takayasu’s disease under 40 years, more common in men claudication of the extremities, the decreased pulse of brachial arteries, bruit over subclavian arteries arteriographic narrowing of the aorta other immune diseases behcet disease between 20 and 50 years, equally prevalent among men and women ocular or genital aphthous positive pathergy test, positive hla-b51 sarcoidosis between 20 and 60 years, more common in women pulmonary signs and symptoms, lymphadenopathy, skin lesions elevated ace and lysozyme ibd between 15 and 30 years, equally prevalent among men and women gastrointestinal signs and symptoms abnormal stool studies, characteristic colonoscopy findings progressive systemic sclerosis between 40 and 50 years, more common in women raynaud phenomenon, sclerodactyly, skin telangiectasia clinical diagnosis relapsing polychondritis between 40 and 60 years, equally prevalent among men and women or more common in women fever, painful erythematous plaques, inflammation of nasal and auricular inflammation clinical diagnosis 258 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 update on puk; hassanpour et al table 1. table (continued) the systemic condition associated with puk key demographic features key systemic findings suggesting the diagnosis suggestive diagnostic evaluations other immune diseases psoriasis between 20 and 50 years, more common in women red skin patches with silver scales clinical diagnosis pyoderma gangrenosum between 15 and 30 years painful skin lesions start with a small, red bump on the skin clinical diagnosis malignancies acute myelogenous leukemia over 50 years, more common in men fever, bone pain, lethargy and fatigue, pale skin abnormal wbc counts chronic myelogenous leukemia over 50 years, more common in men fever, bone pain, lethargy and fatigue, pale skin abnormal peripheral blood cell counts puk, peripheral ulcerative keratitis; ana, antinuclear antibodies; anca, antineutrophil cytoplasmic antibodies; sle, systemic lupus erythematosus; pan, polyarteritis nodosa figure 1. various etiologies associated with peripheral ulcerative keratitis (puk). the pathophysiology of leukemia-associated puk. this hypothesis was derived from the time of puk incidence in acute and chronic leukemia. in patients with chronic myelogenous leukemia, most puk cases have occurred in the blast crisis phase resembling acute leukemia. on the other hand, puk was detected in an untreated acute leukemia patient, when malignant cells were present in the journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 259 update on puk; hassanpour et al table 2. common immunosuppressive agents with their complications drug category drug name mechanism of action common complications alarming signs of complication occurrence monitoring of complications biologic agents etanercept tnf inhibitor opportunistic infections, lymphoma, injection site reactions, cutaneous vasculitis, multiple sclerosis, congestive heart failure mouth ulcers, fever, chills, bruising, pallor blood count and liver function test, 1–3 monthly dsdna – yearly infliximab tnf inhibitor opportunistic infections, lymphoma, injection site reactions, cutaneous vasculitis, multiple sclerosis, congestive heart failure mouth ulcers, fever, chills, bruising, pallor blood count and liver function tests before each infusion dsdna – yearly adalimumab tnf inhibitor opportunistic infections, lymphoma, drug-induced lupus, worsening or the initiation of congestive heart failure, cytopenias, worsening or the initiation of multiple sclerosis/neurological disease mouth ulcers, fever, chills, bruising, pallor blood count and liver function tests monthly for 3 months; then 3 monthly dsdna – yearly rituximab anti cd-20 cardiovascular and dermatological diseases, cytopenia, opportunistic infections, infusion reaction fatigue, pallor, dyspnea, fever, chills, abdominal pain, pruritus vital sign monitoring at each ophthalmic visit, blood count regularly daclizumab il-2 inhibitor granulomatous inflammation, opportunistic infections lymphadenopathy, rash, sore throat, pallor, fever, chills blood count regularly alkylating agents cyclophosphamide impaired cell proliferation due to dna damage cytopenia, mucositis, cystitis, pneumonia, opportunistic infections fever, bruising, pallor blood count, liver function test, and urine exam 10 days after the last dose and 2 days before next chlorambucil impaired cell proliferation due to dna damage cytopenia, mucositis, cystitis, pneumonia, opportunistic infections fever, bruising, pallor blood count, liver function test, and urine exam 10 days after the last dose and 2 days before next t cell inhibitors cyclosporine transcriptional suppression of t cells hypertension, cytopenia, nephrotoxicity peripheral edema, mouth ulcer, rash increased blood pressure blood count every 2 days for 6 weeks; then 1–2 monthly liver function tests monthly especially if concomitant nsaids lipids every 6 months tacrolimus transcriptional suppression of t cells hypertension, cytopenia, nephrotoxicity peripheral edema, mouth ulcer, rash increased blood pressure blood count every 2 days for 6 weeks; then 1–2 monthly liver function tests monthly especially if concomitant nsaids lipids every 6 months 260 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 update on puk; hassanpour et al table 2. table (continued) drug category drug name mechanism of action common complications alarming signs of complication occurrence monitoring of complications antimetabolites methotrexate impaired dna metabolism gastrointestinal signs and symptoms, cytopenia, increased liver enzymes fever, bruising, pallor, mouth ulcer, respiratory signs, and symptoms blood count and liver function test biweekly for 1 month; monthly for 6 months; then if stable, extend to 2–3 monthly azathioprine impaired dna metabolism gastrointestinal signs and symptoms, cytopenia, increased liver enzymes fever, bruising, pallor blood counts and liver function test monthly for 6–12 months; if stable extend to 6–8 weekly mycophenolate mofetil impaired dna metabolism gastrointestinal signs and symptoms, cytopenia, increased liver enzymes, respiratory symptoms, hematuria fever, bruising, pallor, mouth ulcer blood count weekly for 4 weeks; then monthly liver function test and esr and crp monthly circulating system.[75] similar pathogenesis may be responsible for puk in pyoderma gangrenosum, where an underlying immune dysregulation causes neutrophilic dermatoses characterized by the infiltration of neutrophils throughout the dermis.[59, 76–79] puk associated with systemic malignancies and pyoderma gangrenosum shares similarities with immune disease-associated puk. puk associated with systemic infectious diseases apart from noninfectious disorders, some systemic infectious conditions have also been associated with puk. systemic tb can predispose both pediatric and adult patients to puk.[80] immune reactions in tb patients can be manifested by unior bilateral corneal ulceration and interstitial keratitis, and it can occur in peripheral as well as central cornea.[81, 82] puk is a rare complication of syphilis, while stromal keratitis is the characteristic corneal involvement of these patients. puk associated with syphilis can be the presenting sign of acquired syphilis, and it can be complicated by corneal perforation. the pathogenesis most probably involves the immune reactions to spirochetal antigens.[83, 84] bilateral puk has also been reported following an episode of bartonella infection in conjunction with bilateral conjunctivitis.[85] the number of puk cases as the presenting sign of human immunodeficiency virus (hiv) infection is growing through the literature.[86–89] human hiv-associated vasculopathy can result in immune complex-mediated reactions, and the limbus can be the primary site of the inflammation. peripheral keratitis has also been reported following immune reconstruction associated with the initiation of hiv treatment.[90] both hepatitis b and c viruses have been associated with puk, where hepatitisassociated cryoglobulinemia has been implicated in the pathogenesis. cryoglobulinemia is more commonly observed with the hepatitis c virus and can cause vasculitis through deposition in small vessels. additionally, hepatitis b infection has been associated with inflammation of mediumsized vessels, an entity previously known as hbv-related pan. accordingly, limbal vasculitis, whether through cryoglobulinemia or direct vessel inflammation, can cause puk in hepatitis.[91–95] puk following ocular surgeries puk can occur after corneal surgeries, where corneal trauma induces immune reactions through altered corneal antigens. both puk and mooren’s ulcers have been reported to occur following ocular surgeries, including cataract surgery, laser in situ keratomileuses (lasik), and penetrating keratoplasty (pk).[96–100] it can happen weeks to months after uncomplicated cataract surgery journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 261 update on puk; hassanpour et al table 3. differential diagnoses for puk puk differential diagnoses distinguishing clinical features management marginal keratitis and catarrhal infiltrates dense white-gray stromal infiltration, the lucid interval between the infiltration and the limbus, more common in corneal sections in contact with the eyelid margins, associated with bacterial blepharitis detectable in the slit-lamp examination, mild to moderate ocular surface symptoms topical antibiotics with eyelid hygiene corneal involvement rapidly responds to topical corticosteroids any suspicion for bacterial keratitis should prompt immediate microbial smear and culture rosacea-associated peripheral keratitis circumferential superficial stromal infiltration with vascularization, prominent eyelid margin signs and mgd, facial pustular rashes may be present systemic treatment with antibiotics, especially tetracycline and doxycycline mgd-associated peripheral keratitis superficial corneal infiltration and neovascularization, conjunctival injection associated with meibomitis and eyelid margin telangiectasia eyelid hygiene with topical antibiotics and anti-inflammatory agents corneal phlyctenulosis subepithelial inflammatory nodule initially evident on the limbus, no lucid interval topical corticosteroids treatment of concomitant blepharitis consider tb in endemic regions and child patients peripheral infectious keratitis may be associated with hyper-acute conjunctivitis, history of corneal hsv infection, presence of underlying exposure keratitis, or history of contact lens wearing appropriate topical antibiotics or antiviral agents against neisseria gonorrhea, hemophilus influenza type 2, streptococcus, hsv, vzv, pseudomonas conservative measures for corneal repair consider systemic antibiotics in gonorrhea peripheral corneal degenerations terrien’s marginal degeneration progressive noninflammatory, peripheral corneal thinning, associated with corneal neovascularization, opacification, and lipid deposition new-onset against-the-rule astigmatism annular keratoplasty or lamellar graft in severe cases with prominent corneal thinning and progressive decreased vision furrow degeneration decreasing width of the peripheral cornea between the arcus senilis and limbus no therapy is required contact-lens induced peripheral infiltration sudden-onset, small, circular, focal anterior stromal infiltrate in the corneal periphery or mid periphery, associated with a significant overlying epithelial loss, resolving to corneal scars contact lens removal optional topical antibiotics any suspicion for bacterial keratitis should prompt immediate microbial smear and culture mooren’s ulcer peripheral corneal inflammation and thinning spreading circumferentially and centrally, lack of scleritis, lack of a systemic condition topical and systemic immunosuppressant corneal dellen peripheral corneal thinning due to stromal dehydration, associated with a paralimbal elevation that can induce a localized break in the precorneal oily layer of the tears lubrication and patching a bandage contact lens may be required exposure keratopathy incomplete eyelid closure, more common following eyelid surgeries or admitted patients, persistent epithelial defects in the inferior or central cornea with or without dense stromal infiltration intensive lubrication and eyelid taping consider transient or permanent tarsorrhaphy any suspicion for bacterial keratitis should prompt immediate microbial smear and culture through small corneal incisions.[99, 101] there is some controversy over whether postoperative puk is truly a unique entity or whether it is simply a sign of underlying systemic disease. the occurrence of postoperative necrotizing scleritis and keratitis in patients with previously diagnosed systemic vasculitis is documented in the literature.[100] for practical purposes, mild postsurgical keratitis in patients with no underlying disease may be considered to be isolated, but in severe cases, it is reasonable to perform a detailed systemic evaluation. 262 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 update on puk; hassanpour et al clinical presentation of puk the main symptoms of puk are photophobia, ocular redness, pain, and loss of vision secondary to either inflammation in the acute stage or scar-induced astigmatism in the chronic stage. on slit-lamp examination, the main signs include peripheral corneal crescentic stromal thinning, ulceration with overhanging edges, and mild to severe cellular infiltrates. corneal perforation is a rare serious complication in puk.[102, 103] varying degrees of corneal neovascularization surround the crescent-shaped peripheral corneal lesion. generally, puk involves a single corneal section and is unilateral, but bilateral asymmetric cases have been also reported.[57] puk may be associated with iritis, conjunctivitis, episcleritis, or scleritis. the presence of scleritis can influence the final prognosis since it can aggravate the course of puk and increase the rate of complication.[64, 104] the severity of corneal inflammation correlates with the concomitant scleritis severity, which is explained by the similar pathologic processes manifested by collagenolysis in both conditions.[105] differential diagnoses of puk any peripheral corneal disease associated with stromal infiltration or thinning can be considered in the differential diagnosis of puk [table 2]. immune-mediated peripheral infiltration and ulceration associated with ocular surface diseases marginal keratitis represents an immune reaction to staphylococcal antigens. it can occur in patients with symptomatic blepharoconjunctivitis, or it can be associated with asymptomatic staphylococcal colonization of the eyelids.[106] also known as catarrhal infiltrates, marginal keratitis can occur secondary to the eyelid infection by other microorganisms, such as hemophilus, moraxella, or streptococcus.[107, 108] distribution of bacterial antigens through tear film and their presence in the peripheral cornea induces a type-iii hypersensitivity reaction, where in-situ production and deposition of immune complexes trigger keratolysis and stromal infiltration.[24] the presence of a clear area between the ulcer and the adjacent limbus has traditionally been used to distinguish marginal keratitis from other conditions such as puk and phlyctenulosis. as another distinguishing feature, marginal keratitis responds rapidly to topical treatment, while puk almost always requires appropriate systemic medication. phlyctenular corneal disease is another immunemediated peripheral corneal lesion most commonly observed in association with longstanding staphylococcal blepharoconjunctivitis. phlyctenules are subepithelial nodules that first appear in the limbus and extend toward the cornea later in the course of the disease. rarely, corneal phlyctenules form a corneal ulcer. historically, there was a strong association between tuberculosis and phlyctenulosis, but more recent studies show that staphylococcal disease is the most frequent etiology.[24, 57] corneal involvement can occur in up to half of the patients with ocular rosacea, ranging from mild punctate epithelial keratitis to corneal ulceration and perforation. rosacea-associated keratitis is characterized by a spade-shaped triangular vascular lesion associated with subepithelial and stromal infiltration. occasionally, it can be complicated by significant peripheral corneal thinning, corneal melting, and perforation.[109] corneal infiltration and epithelial defects associated with meibomitis have been explained through the literature as meibomitis-related keratopathy or keratoconjunctivitis (mrkc).[110, 111] it is more common in young patients with severe meibomitis. mrkc may be manifested as a phlyctenule-like lesion with subepithelial infiltration, or it can be detected by superficial epithelial defects without stromal infiltration. the severity of mrkc has been correlated to the severity of mgd, the treatment of meibomitis is necessary for the remission of corneal complications.[112] post-infection peripheral keratitis herpetic simplex virus (hsv) keratitis should always be considered as an important differential diagnosis of central or peripheral keratitis. as opposed to marginal keratitis, hsv infection of the cornea starts with epithelial defect and evolves to ulcer through subsequent subepithelial infiltration. compared to other corneal ulcers, hsv-induced journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 263 update on puk; hassanpour et al keratitis is less symptomatic, which is explained in part by the presence of decreased sensation in the infected corneal neurons. puk-like lesions have also been reported in herpes zoster ophthalmicus associated with anterior uveitis.[113] neisseria gonorrhea is a virulent micro-organism that can penetrate the intact corneal epithelium. chemotic conjunctiva during the hyper-acute phase of gonorrheal conjunctivitis overlaps the peripheral cornea, exposing it to a recess of bacteria and enzyme-laden material. peripheral ulcers can evolve following primary stromal infiltration, and there is a prominent risk of corneal perforation.[108] similarly, hemophilus influenza type 2 and streptococcal hyper-acute conjunctivitis may be associated with a peripheral corneal ulcer, characterized by a mucopurulent base and an overhanging edge.[114] peripheral corneal ulcers due to moraxella occur following a defect in corneal epithelium, usually secondary to exposure keratitis in a debilitated patient, in the setting of a mild blepharoconjunctivitis (compared to the more severe conjunctivitis in gonorrhea or streptococcus infections).[115] peripheral keratitis secondary to pseudomonas is less common than central corneal involvement and commonly occurs in contact lens wearers and ill patients.[116] degenerative peripheral corneal diseases terrien’s marginal degeneration is a slowly progressive noninflammatory corneal thinning. it can be unior bilateral, and is commonly associated with peripheral corneal opacification, neovascularization, and lipid deposition. terrien’s degeneration can be diagnosed following newonset against-the-rule or oblique astigmatism. the peripheral thinning spreads circumferentially, starting from the superior limbus and rarely involving the inferior cornea. the corneal epithelium is usually intact over the thinning area, and the furrow may be crossed by superficial vessels. the condition can be complicated by corneal perforation following mild trauma, or it can develop acute corneal cysts due to descemet’s membrane ruptures.[117–119] another noninflammatory peripheral corneal thinning, furrow degeneration, is characterized by narrowing of the peripheral cornea between the arcus senilis and limbus. as a distinguishing feature, furrow degeneration lacks corneal vascularization, compared to terrien’s degeneration. also, it is rarely associated with visual disturbance, and the risk of corneal perforation is extremely rare.[120, 121] corneal dellen is caused by stromal dehydration and subsequent excavation of the peripheral cornea associated with a paralimbal elevation. the pathogenesis is related to a break in tear film overlying the peripheral cornea beyond the elevated conjunctiva. if untreated, corneal dellen can be complicated by perforation, but use of artificial tears and patching, in association with treating the elevated paralimbal tissue, helps the cornea to heal within a few weeks.[122–124] mooren ulcer mooren ulcer is the most similar entity to puk, and can essentially be thought of as an idiopathic form of puk. the pathophysiology of mooren ulcer is outlined in detail below; it is thought to be an autoimmune condition triggered by cornea-specific antigens that become exposed due to trauma or surgery.[125] it generally presents either as a chronic unilateral slowly progressive ulcer in older adults or bilateral rapidly progressing ulcers in younger adults. the pain is characteristically more severe and intolerable than puk, with associated redness and photophobia. by definition, there is no underlying causal systemic inflammatory condition (as opposed to puk), although mooren has been associated with helminthic infections,[126] exposure to viruses (hepatitis c), and the presence of hladr17 or dq2 antigens.[127] mooren ulcer starts at the limbus and proceeds to spread circumferentially and then centrally. it is most commonly found nasally or temporally adjacent to the interpalpebral limbus, without the clear area found in terrien’s (which is also typically painless).[18] there is no scleral involvement, as opposed to puk, which often has adjacent scleritis.[18] there is usually associated thinning, and the bed of the ulcer can become vascularized. eventually, it can progress to a complete circumferential defect, leaving only a central opaque and edematous intact cornea. in severe cases, the central cornea becomes consumed by a fibrovascular membrane as well, and perforation can occur.[51] the therapeutic regimens for mooren ulcer share many similarities with those for puk, 264 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 update on puk; hassanpour et al where the mainstay of the treatment is systemic immunosuppression.[128, 129] topical treatment with corticosteroids, acetylcysteine, cyclosporine, and interferon-α2𝑎 have been used with limited effect. surgical options include removal of the antigen source (lamellar keratoplasty), removal of the site of immunologic response (limbal/conjunctival resection), and tissue reinforcement to avoid perforation (patch grafts). there is no randomized control trial data to support any of the above treatment options, and no high-quality evidence supports the use of any one treatment.[130] management the first principle in approaching the treatment of puk is to address the underlying cause if one is present. this is fundamental for reducing the ocular morbidity and potential mortality associated with systemic inflammatory conditions.[9] beyond this, the current management paradigm consists of treatment during the acute phase with systemic immunosuppression, usually a corticosteroid and immunomodulatory agent. this is followed by gradual tapering of the corticosteroid and maintaining the immunomodulatory agent to avoid disease recurrence. throughout the disease course, aggressive topical immunosuppression and lubrication should be used to minimize stromal loss and optimize the ocular surface. if at any point there is concern for corneal perforation or worsening ulceration despite maximum medical therapy, early surgical intervention is indicated.[12] despite recent advances in immunosuppression therapeutic regimens, early diagnosis and optimal control of the accompanying systemic diseases remain the main prognostic factors in puk. topical treatment in cases of suspected infectious puk, empirical topical antimicrobial therapy should be started after collecting corneal scrapings for microbiological examination. knowing the local disease epidemiology, meticulous history taking, and systems review are key factors to reaching the causative organism. for instance, testing for tb in countries like india, china, pakistan, philippines, bangladesh, and south africa will have more likelihood of being positive because of the high prevalence of tb in these areas.[12] for suspected bacterial keratitis, empirical monotherapy with a fourth-generation fluoroquinolone is usually started till being replaced with specific therapy according to the results of the culture. to suppress the coexisting immune-mediated inflammatory puk, topical steroid therapy is usually started after 3 to 7 days of response to antibacterial treatment, or 14 days after starting the antifungal therapy in case of bacterial or fungal puk, respectively. for puk with suspected herpetic etiology, topical antiviral acyclovir or ganciclovir are prescribed. in noninfectious puk, local treatment is a cornerstone of symptom management and slowing the progression of corneal disease in puk. topical lubrication, which has the combined effect of improving the quality of the tear film and reducing discomfort, remains the mainstay treatment of puk. in addition, frequent use of preservative-free artificial tears will help washout the inflammatory mediators, decrease immunemediated keratolysis.[12] some of the available options include carboxymethylcellulose (0.25%, 0.5%, 1%), hydroxypropyl methylcellulose (0.3%), sodium hyaluronate (0.1%), polyethylene glycol (0.4%, 1%), and glycerine (1%). the frequency of instillation depends on the severity of keratoconjunctivitis sicca. nighttime application of lubricant ointment formulations will promote epithelial healing as well.[12] to more specifically target keratolysis, mmp inhibitors may be useful. mmps include two groups of zinc-related peptidases: collagenases and gelatinases, which play a role in the degradation of the corneal stroma, as discussed above.[131] n-acetylcysteine (nac) chelates mmp-associated calcium or zinc, causing irreversible inhibition of mmps, and has also been shown to reduce the release of various inflammatory cytokines in animal models.[132] despite the link between mmps and puk, and the clear in vitro inhibitory effects of nac on mmps, its clinical efficacy in the treatment of puk is not well established.[50] corticosteroids are an obvious potential therapeutic option for puk, given their potent antiinflammatory properties. selection of potency and frequency of instillation depends on the severity of the inflammation to be controlled. the potency of steroids may be low as in fluorometholone 0.1%, loteprednol etabonate 0.2% and 0.5%; moderate as in prednisolone sodium phosphate 0.5%, betamethasone 0.1%, dexamethasone 0.1%; or high as in prednisolone acetate 1%. dosing is journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 265 update on puk; hassanpour et al usually started four times a day, then adjusted as per response, and finally tapered down slowly.[12] however, cautious usage is advised, as they can inhibit collagen production and epithelial repair, leading to an increased risk of corneal perforation. for example, in puk associated with ra, topical steroids are not advised as they delay the wound healing process via suppressing fibroblast infiltration. also, avoiding adverse effects of long-term corticosteroid usage such as glaucoma and cataract is a critical consideration in puk, especially in cases associated with chronic underlying systemic disease, where a prolonged disease course is expected.[133, 134] in comparison with a topical corticosteroid, topical cyclosporine a 2% (csa) and tacrolimus 0.03% may be a safer and useful option to promote epithelial healing while avoiding nephrotoxicity associated with systemic administration. csa directly targets t lymphocytes, inhibiting calcineurin, thereby diminishing t cell function and signaling.[135] although the mechanism of action of csa makes it a less potent option for inhibiting innate immune effectors in puk, its safety and efficacy have been reported in severe corneal ulcers and recalcitrant cases of mooren’s ulcer.[136, 137] topical nonsteroidal anti-inflammatory drugs (nsaids) (e.g., ketorolac, diclofenac, bromfenac, nepafenac, flurbiprofen) are potential options to alleviate inflammation in puk; nevertheless, these agents may predispose to silent corneal melting, especially in elderly patients with concurrent ocular surface diseases and ra.[138] hence, a short course of low potency steroids (e.g., fluorometholone 0.1%, loteprednol etabonate 0.2%) twice or thrice a day may be prescribed over choosing nsaids for antiinflammatory effect in cases of puk with ra and a dry ocular surface, along with aggressive topical lubrication.[12] progestins have been cited as possible topical therapeutic agents for puk given their ability to downregulate ocular surface inflammation. medroxyprogesterone 1% binds to glucocorticoid receptors, through which it can exert antiinflammatory features. additionally, it can promote collagen synthesis in the cornea by inhibiting neutrophil-related collagenases. based on these characteristics, medroxyprogesterone has been used, in association with other collagenase inhibitors, to decrease the stromal degradation in instances of corneal thinning and keratolysis.[139, 140] however, there is no strong data to support its efficacy specifically in puk. furthermore, adjunct therapy with cycloplegics, along with pressure-lowering medications as required, may be of great help in reducing morbidity.[12] systemic treatment systemic therapy should be targeting both reducing the sight and life-threatening complications of the underlying systemic disease. the choice of drug(s) depends on the etiology, clinical presentation, severity of disease, and the suitability of the route of drug administration to the patient. systemic therapy to reduce ocular morbidity oral doxycycline 100 mg twice daily antagonizes local collagenolysis via irreversible inhibition of mmp through chelation of the catalytically and structurally active metal ions.[141] it may also help regeneration of a stable stratified epithelium by suppressing scar tissue formation through retarding the migratory keratocytes or fibroblasts.[141] in cases of peripheral corneal melting, oral ascorbic acid 1000 mg daily is added. therapeutic effects of ascorbic acid on promoting corneal epithelial healing and reducing postkeratitic scarring have been reported.[142, 143] in cases of associated scleritis, oral nsaids may be added to alleviate the pain and inflammation.[12] systemic therapy to reduce mortality from underlying systemic disease the presence of puk and necrotizing scleritis in autoimmune diseases highlight a fatal form of systemic vasculitis and requires aggressive systemic immunosuppressant therapy.[144, 145] immunosuppressenat therapy has been proved to reduce mortality in patients with puk and necrotizing scleritis.[146] foster and colleagues reported the mean time to death in subjects with puk and scleritis due to various underlying conditions (e.g., ra, gpa, sle) to be 24.7 years in patients on systemic immunosuppressant therapy versus 10.7 years in those without.[146, 147] since systemic immunosuppressant agents are often indicated for puk, it can be helpful 266 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 update on puk; hassanpour et al to coordinate care with a rheumatologist experienced in using these drugs and handling their adverse effects. detailed knowledge of different systemic immunosuppressive drugs used for autoimmune diseases may be out of the scope of an ophthalmologist’s practice. however, a basic understanding of these drugs, their mechanisms, and their adverse effects are helpful for any clinician involved in treating puk patients. table 4 summarizes important adverse effects and critical alarming signs of these drugs that an ophthalmologist recognizes during followup of puk [table 4]. moreover, in cases of pandemics due to viral agents, e.g., covid-19, immunosuppression may predispose to lethal opportunistic infections.[148] this risk must be discussed with the patient at the time of starting therapy. nonimmunomodulatory agents traditionally, systemic corticosteroid therapy has been the first-line therapy for acute puk. although many other immunosuppressive agents have been proposed for treating immune conditions, the availability of corticosteroids and their rapid therapeutic effect have solidified them as a mainstay in treating severe inflammatory diseases. corticosteroids, usually intravenous methylprednisolone or oral prednisone, are administered with a starting dosage of 1 mg/kg/day, followed by tapering based on clinical response. systemic corticosteroid therapy should never be delayed in cases with advanced corneal thinning and impending danger of permanent vision loss, and higher pulse doses (1 g/day iv methylprednisolone) may be used in severe cases.[1, 146, 149] long-term adverse effects of systemic steroids, in association with their documented failure of controlling systemic vasculitis in monotherapy regimens, often necessitates the concurrent use of systemic immunomodulatory agents. additionally, in patients with a worsening clinical course on corticosteroids or those who are unable to be tapered off of high-dose steroid therapy for longer than one month, an immunomodulatory agent should always be considered.[150] immunomodulatory agents immunosuppressive agents available for use in ocular inflammatory conditions include antimetabolites, t-cell inhibitors, biologic agents, and alkylating agents.[151] the choice of agent usually depends on the underlying systemic disease [table 3]. among antimetabolites, methotrexate, azathioprine, and mycophenolate mofetil have been widely used to treat puk.[150] in patients with ra-associated puk unresponsive to systemic corticosteroid therapy, methotrexate and azathioprine were found to be effective.[152] azathioprine is a purine nucleoside analog, which interferes with dna replication and rna transcription, primarily targeting b and t lymphocytes.[153] systemic azathioprine has been shown to control the ocular immune disease with a mean oral dose of 2 mg/kg/day.[78, 150] methotrexate is a folic acid analog inhibiting the production of thymidylate, an essential molecule necessary for dna replication. similar to azathioprine, methotrexate targets rapidly proliferating cells, such as peripheral lymphocytes. an oral regimen of methotrexate with a dosage of 7.5–25 mg/week has been reported to be effective in treating immune corneal ulcers.[145] mycophenolate mofetil, a selective inhibitor of guanosine nucleotide synthesis, appears to be safer and more effective for treating puk compared to methotrexate and azathioprine.[154, 155] particularly in cases where adverse effects of other drugs are not tolerable, mycophenolate mofetil is a viable option with an oral dosage of 1 g twice daily.[152] within the category of t-cell inhibitors, systemic cyclosporin a has been proposed as an effective initial immunosuppressant treatment for ocular immune conditions. however, it is generally not as useful for the treatment of severe systemic inflammatory conditions compared to antimetabolites and alkylating agents, so it is a more appropriate option in puk without underlying systemic vasculitis. it does carry a risk of nephrotoxicity, and so caution should be taken in patients with underlying renal dysfunction.[156] the alkylating agents, including cyclophosphamide and chlorambucil, are reserved for immune conditions unresponsive to antimetabolites and corticosteroids. these agents cause irreversible dna crosslinking, leading to apoptosis in rapidly dividing cells such journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 267 update on puk; hassanpour et al as t lymphocytes. they have been reported to be highly effective in persistent puk cases.[144] cyclophosphamide may be administered orally (1–2 m/kg/day) or intravenously (monthly pulses) for destructive ocular immune conditions. in a small case series, it was well-tolerated and effective and controlling both ocular disease and underlying systemic vasculitis.[157] one class of biologic agents that have been used to treat puk are anti-tnf drugs, including etanercept, infliximab, adalimumab, and golimumab. etanercept is a decoy receptor for tnf, while the other three agents are monoclonal anti-tnf antibodies. tnf-α is a proinflammatory cytokine released by macrophages and other immune cells that have been targeted by therapy in ra and other autoimmune conditions. anti-tnf drugs can inhibit both the activity of tnf-α and the production of mmps, halting the progression of immune keratolysis in puk.[158, 159] these agents have been successful in treating puk, uveitis, and scleritis associated with immune diseases.[160−−162] infliximab has shown success in halting corneal thinning, but there are reports of resistant disease, as well as severe cardiopulmonary side effects such as myocardial infarcation and pulmonary embolism.[163] etanercept is less efficacious than infliximab and has been associated with druginduced scleritis, which has limited its usage in ocular immune conditions.[160] accordingly, adalimumab has been proposed as an effective anti-tnf agent with acceptable safety and efficacy profile.[164] however, drug-induced corneal infiltrate has been reported in patients undergoing adalimumab therapy, which may limit its usage for ocular conditions in the future.[165] rituximab, another biologic immunomodulatory agent, is a monoclonal antibody against cd20, which is expressed on the surface of b lymphocytes. although the role of b cells and humoral immunity in the pathogenesis of puk is not well understood, anti-b cell therapy with rituximab has been described.[166] it has been used to treat uveitis, scleritis, and refractory puk associated with gpa, and the results have been promising.[167, 168] a recent small case series also reported success in the treatment of raassociated puk, with excellent control of ocular inflammation, and also improvement in the articular and vasculitic disease.[169] in addition to rituximab, tocilizumab, and belimumab are non-anti tnf antibodies to il-6r and baff, respectively, that have been used sparingly but successfully in the treatment of puk. in one case series of patients treated with rituximab, tocilizumab, or belimumab, these agents were found to be more effective than anti-tnf agents for treatment-resistant puk.[170] combination therapy with immunosuppressive agents is a common approach in treating systemic and ocular immune conditions. the main limitation in combination therapy is the cumulative risk of adverse effects. the most common combination regimens include an immunomodulatory agent with a systemic corticosteroid, to enhance therapeutic effect and facilitate steroid tapering.[150] the synergistic effect of combined therapy with antimetabolites and corticosteroids has been reported in treating ocular immune conditions.[171] the combination of antimetabolites and cyclosporine has been used widely as an anti-transplant rejection regimen and has been proposed for use in ocular conditions with an acceptable safety profile. although cyclophosphamide is frequently combined with corticosteroids for treating systemic vasculitis, the increased risk of opportunistic infections and malignancies has limited its use in conjunction with biologic or other immunomodulatory therapies.[150] recently, dominguez-casas and colleagues reported that 48% of patients who were initially started on an anti-tnf alpha agent had to be switched to another biological agent because of treatment failure or adverse effects.[170] biotherapy in most of their cohort achieved a rapid and maintained improvement in the efficacy outcome parameters after three months of starting therapy.[170] over the last 10 years, drugs known as janus kinase (jak) inhibitors have been reported in various autoimmune diseases, such as ra, psoriatic arthritis, ulcerative colitis, and others. in addition, jak inhibitors seem to be effective regimens for intractable noninfectious inflammatory eye disease, including uveitis and scleritis.[172] furthermore, novel therapeutic agents, e.g., cacicol® (a matrix regenerating agent) are being investigated.[173] sevik and colleagues reported complete epithelial healing in 86.9% of their case series with persistent epithelial defect refractory to conventional therapy after 2 to 20 days of treatment.[173] 268 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 update on puk; hassanpour et al surgical management along with systemic immunosuppression, surgical interventions are often required in puk with severe corneal thinning or corneal perforations for tectonic reconstruction.[151] systemic immunosuppression is mandatory to reduce graft melts, rejection rates, and puk recurrences.[12] early interventions with adequate immunosuppression have been reported to restore the integrity of the globe in 92% of cases.[144] in addition, the six-month graft survival rates after pk ranged from 20 to 40%.[144, 174] available options include tissue adhesives, bandage contact lens, penetrating or lamellar graft, and amniotic membrane transplantation (amt).[12] the choice of the intervention depends on the extent of the disease and the size of perforation. the use of tissue adhesives, followed by the application of a contact lens, is a straightforward and widely available option for the management of descemetocele or perforations smaller than 2–3 mm.[175, 176] cyanoacrylate tissue adhesives are tolerable and effective in managing immune corneal ulcers, such as puk associated with systemic diseases. the possibility of treatment failure, potential infectious complications, and patient discomfort following the application of tissue adhesives necessitate close followup.[177] reinforcement of corneal tissue with these adhesives often serves as a bridge to further surgical intervention. for perforations 3–5 mm, a tuck-in tenon patch graft may be a useful option.[178] the conjunctiva adjacent to the peripheral ulcer serves as a reservoir of immune cells, inflammatory cytokines, and proteolytic enzymes. accordingly, resection of the perilimbal conjunctiva has been proposed as a therapeutic intervention to promote the resolution of inflammation. however, this treatment is limited by a recurrence of the immune response as the conjunctiva grows back to the adjacent corneal ulcer. evidence on the efficacy of conjunctival resection is limited due to a small number of cases and short follow-up periods. therefore, the treatment is controversial. a recent report of three patients indicated that conjunctival resection could promote puk resolution and decrease the need for systemic immunosuppressive therapy, however, larger studies are needed to confirm the results of these clinical observations.[179] in conjunction with appropriate systemic treatment, corneal grafts can preserve the integrity of eyes with impending corneal perforation.[180] pk with large-diameter grafts (9–9.5 mm) may be needed to remove the inflamed peripheral cornea, but it is associated with a higher risk of graft rejection due to the presence of the adjacent limbal vasculature. large-diameter grafts are associated with a two-times higher risk of rejection compared to average-sized pk.[181, 182] this risk can even be higher in puk cases with active underlying inflammation, as maneo et al reported that keratoplasty performed for puk had the highest probability of rejection requiring regrafting compared to pk for other indications.[183] graft survival rates of <40% at six months have been reported in pk for puk.[184] to reduce the risk of graft rejection, small-diameter tectonic grafts ranging from 3 to 5.5 mm can be used, but they are associated with poorer visual outcomes.[182] as an alternative to pk, crescent-shaped, “match and patch” lamellar keratoplasty has become a commonly used technique in puk.[182] lamellar techniques provide some advantages over a penetrating graft in inflammatory corneal ulcers. first, the risk of graft rejection is lower for a lamellar graft. second, it avoids an intraocular procedure (if perforation has not yet occurred), reducing the risk of endophthalmitis, glaucoma, or cataract. finally, by adding to the thickness of the cornea, the risk of recurrent corneal perforation decreases in lamellar grafts, which can be a great advantage in cases of ongoing inflammation, such as in puk or mooren’s ulcers.[185] the crescentic lamellar keratoplasty technique consists of placing a ring-shaped lamellar graft on the peripheral cornea and suturing it to the host bed. the extent of the ulcer determines the size and shape of the graft.[182] as a modification to this technique in cases of perforation, doublelayer peripheral keratoplasty has been proposed for immune-mediated corneal thinning in mooren’s ulcers. a posterior corneal patch graft is placed under the crescent-shaped lamellar graft, reducing the rate of ulcer recurrence from 26% to 10% with successful visual outcomes.[186] in addition to crescentic lamellar grafts, a decentered largediameter superficial anterior lamellar keratoplasty (salk) has also been used in puk with a successful outcome.[187] amt can also be used in puk cases, having the dual effect of reducing inflammation of the journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 269 update on puk; hassanpour et al underlying cornea and providing mechanical support. expression of fas ligand and activation of suppressor t cells in amt was reported to be associated with anti-inflammatory properties.[188] amt has been also been shown to decrease the corneal inflammatory response via apoptosis of innate immune cells.[189] beyond its antiinflammatory effects, amt has been useful as a support for the physical corneal structure to reduce the risk of perforation in peripheral inflammatory and noninflammatory ulcers.[190, 191] although few studies have evaluated the role of amt in treating puk, this technique has been widely used for mooren’s ulcers. in two case series, amt reduced pain symptoms and stabilized vision in up to 50% of patients, although it occasionally required multiple applications.[192, 193] additionally, lamellar keratoplasty combined with amt is becoming a popular surgical option for perforations <4 mm.[194] lastly, the option of keratoprosthesis is also being explored for severe cases.[195] in conclusion, puk is a rare but serious ocular disease with important systemic implications. the underlying autoimmune pathogenesis is not fully understood but appears to involve both cell-mediated and auto-antibody-mediated components, resulting in the breakdown of peripheral corneal tissue. reducing ocular morbidity through topical and surgical methods, in addition to controlling systemic inflammation with immunomodulatory therapy, is paramount to successful treatment; emerging biologic therapies and surgical techniques have shown promise. financial support and sponsorship none. conflicts of interest none declared. references 1. tauber j, sainz de la maza m, hoang-xuan t, foster cs. an analysis of therapeutic decision making regarding immunosuppressive chemotherapy for peripheral ulcerative keratitis. cornea 1990;9:66–73. 2. mckibbin m, isaacs jd, morrell aj. incidence of corneal melting in association with systemic disease in the yorkshire region, 1995-7. br j ophthalmol 1999;83:941– 943. 3. robin jb, schanzlin dj, verity sm, barron ba, arffa rc, suarez e, et al. peripheral corneal disorders. surv ophthalmol 1986;31:1–36. 4. müller lj, pels e, schurmans lr, vrensen gf. a new threedimensional model of the organization of proteoglycans and collagen fibrils in the human corneal stroma. exp eye res 2004;78:493–501. 5. messmer em, foster cs. destructive corneal and scleral disease associated with rheumatoid arthritis. medical and surgical management. cornea 1995;14:408–417. 6. marsovszky l, resch md, németh j, toldi g, medgyesi e, kovács l, et al. in vivo confocal microscopic evaluation of corneal langerhans cell density, and distribution and evaluation of dry eye in rheumatoid arthritis. innate immun 2013;19:348–354. 7. gipson ik, hori y, argüeso p. character of ocular surface mucins and their alteration in dry eye disease. ocul surf 2004;2:131–148. 8. müller l, vrensen g, pels l, cardozo bn, willekens b. architecture of human corneal nerves. invest ophthalmol vis sci 1997;38:985–994. 9. gomes bf, santhiago mr. biology of peripheral ulcerative keratitis. exp eye res 2021;204:108458. 10. timlin hm, hall hn, foot b, koay p. corneal perforation from peripheral ulcerative keratopathy in patients with rheumatoid arthritis: epidemiological findings of the british ophthalmological surveillance unit. br j ophthalmol 2018;102:1298–1302. 11. john sl, morgan k, tullo ab, holt pj. corneal autoimmunity in patients with peripheral ulcerative keratitis (puk) in association with rheumatoid arthritis and wegener’s granulomatosis. eye 1992;6:630–636. 12. gupta y, kishore a, kumari p, balakrishnan n, lomi n, gupta n, et al. peripheral ulcerative keratitis. surv ophthalmol 2021;66:977–998. 13. tavassoli s, wong n, chan e. ocular manifestations of rosacea: a clinical review. clin exp ophthalmol 2021;49:104–117. 14. sharma n, sinha g, shekhar h, titiyal js, agarwal t, chawla b, et al. demographic profile, clinical features and outcome of peripheral ulcerative keratitis: a prospective study. br j ophthalmol 2015;99:1503–1508. 15. sainz de la maza m, foster cs, jabbur ns, baltatzis s. ocular characteristics and disease associations in scleritisassociated peripheral keratopathy. arch ophthalmol 2002;120:15–19. 16. watson pg, bovey e. anterior segment fluorescein angiography in the diagnosis of scleral inflammation. ophthalmology 1985;92:1–11. 17. watson pg. vascular changes in peripheral corneal destructive disease. eye 1990;4:65–73. 18. gomes baf, santhiago mr, jorge pa, et al. corneal involvement in systemic inflammatory diseases. eye contact lens 2015;41:141–144. 19. jones rr, maguire lj. corneal complications after cataract surgery in patients with rheumatoid arthritis. cornea 1992;11:148–150. 20. chanbour w, mokdad i, mouhajer a, jarade e. late-onset sterile peripheral ulcerative keratitis post-corneal collagen crosslinking. cornea 2019;38:338–343. 270 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 update on puk; hassanpour et al 21. messmer em, foster cs. vasculitic peripheral ulcerative keratitis. surv ophthalmol 1999;43:379–396. 22. allansmith mr, mcclellan bh. immunoglobulins in the human cornea. am j ophthalmol 1975;80:123–132. 23. mondino bj, brady kj. distribution of hemolytic complement in the normal cornea. arch ophthalmol 1981;99:1430–1433. 24. mondino bj. inflammatory diseases of the peripheral cornea. ophthalmology 1988;95:463–472. 25. dana mr, qian y, hamrah p. twenty-five-year panorama of corneal immunology: emerging concepts in the immunopathogenesis of microbial keratitis, peripheral ulcerative keratitis, and corneal transplant rejection. cornea 2000;19:625–643. 26. romagnani s, parronchi p, d’elios mm, romagnani p, annunziato f, piccinni mp, et al. an update on human th1 and th2 cells. int arch allergy immunol 1997;113:153–156. 27. rao da, gurish mf, marshall jl, slowikowski k, fonseka cy, liu y, et al. pathologically expanded peripheral t helper cell subset drives b cells in rheumatoid arthritis. nature 2017;542:110–114. 28. martinez valenzuela l, bordignon draibe j, fulladosa oliveras x, matamoros ob, garrit jmc, ambrós jt. tlymphocyte in anca-associated vasculitis: what do we know? a pathophysiological and therapeutic approach. clin kidney j 2019;12:503–511. 29. giscombe r, nityanand s, lewin n, grunewald j, lefvert ak. expanded t cell populations in patients with wegener’s granulomatosis: characteristics and correlates with disease activity. j clin immunol 1998;18:404–413. 30. mondino bj, brown si, rabin bs. cellular immunity in mooren’s ulcer. am j ophthalmol 1978;85:788–791. 31. foster cs, kenyon kr, greiner j, greineder dk, friedland b, allansmith mr. the immunopathology of mooren’s ulcer. am j ophthalmol 1979;88:149–159. 32. zhao jc, jin xy. immunological analysis and treatment of mooren’s ulcer with cyclosporin a applied topically. cornea 1993;12:481–488. 33. nogueira e, hamour s, sawant d, henderson s, mansfield n, chavele k-m, et al. serum il-17 and il-23 levels and autoantigen-specific th17 cells are elevated in patients with anca-associated vasculitis. nephrol dial transplant 2010;25:2209–2217. 34. tarzi rm, pusey cd. current and future prospects in the management of granulomatosis with polyangiitis (wegener’s granulomatosis). ther clin risk manag 2014;10:279–293. 35. shiuey y, foster cs. peripheral ulcerative keratitis and collagen vascular disease. int ophthalmol clin 1998;38:21–32. 36. nagata s, glovsky mm, kunkel sl. anaphylatoxininduced neutrophil chemotaxis and aggregation. limited aggregation and specific desensitization induced by human c3a and synthetic c3a octapeptides. int arch allergy appl immunol 1987;82:4–9. 37. metzemaekers m, gouwy m, proost p. neutrophil chemoattractant receptors in health and disease: doubleedged swords. cell mol immunol 2020;17:433–450. 38. quintana lf, kronbichler a, blasco m, zhao m-h, jayne d. anca associated vasculitis: the journey to complementtargeted therapies. mol immunol 2019;112:394–398. 39. albert dm, jakobiec fa. principles and practice of ophthalmology. vol 1. philadelphia: wb saunders; 2000. 74–82 p. 40. morgan-warren pj, dulku s, ravindran j, smith g. peripheral ulcerative keratitis as the presenting feature of systemic rheumatoid vasculitis without joint involvement. int ophthalmol 2014;34:933–935. 41. squatrito d, emmi g, silvestri e, ciucciarelli l, d’elios mm, prisco d, et al. pathogenesis and potential therapeutic targets in systemic lupus erythematosus: from bench to bedside. auto immun highlights 2014;5:33–45. 42. reynolds i, john sl, tullo ab, ayad s, morgan k, ballardie fw, et al. characterization of two corneal epithelium-derived antigens associated with vasculitis. invest ophthalmol vis sci 1998;39:2594–2601. 43. albers fw, majoor mh, van der gaag r. corneal autoimmunity in a patient with relapsing polychondritis. eur arch otorhinolaryngol 1992;249:296–299. 44. mondino bj, brown si, rabin bs. autoimmune phenomena of the external eye. ophthalmology 1978;85:801–817. 45. gottsch jd, liu sh, minkovitz jb, goodman df, srinivasan m, stark wj. autoimmunity to a cornea-associated stromal antigen in patients with mooren’s ulcer. invest ophthalmol vis sci 1995;36:1541–1547. 46. rodeghero r, cao y, olalekan sa, iwakua y, glant tt, finnegan a. location of cd4+ t cell priming regulates the differentiation of th1 and th17 cells and their contribution to arthritis. j immunol 2013;190:5423–5435. 47. bugatti s, vitolo b, caporali r, montecucco c, manzo a. b cells in rheumatoid arthritis: from pathogenic players to disease biomarkers. biomed res int 2014;2014:681678. 48. eghrari ao, riazuddin sa, gottsch jd. overview of the cornea: structure, function, and development. prog mol biol transl sci 2015;134:7–23. 49. jamerson ec, elhusseiny am, elsheikh rh, eleiwa tk, el sayed ym. role of matrix metalloproteinase 9 in ocular surface disorders. eye contact lens 2020;46:s57–s63. 50. watanabe r, ishii t, yoshida m, takada n, yokokura s, shirota y, et al. ulcerative keratitis in patients with rheumatoid arthritis in the modern biologic era: a series of eight cases and literature review. int j rheum dis 2017;20:225–230. 51. artifoni m, rothschild pr, brézin a, guillevin l, puéchal x. ocular inflammatory diseases associated with rheumatoid arthritis. nat rev rheumatol 2014;10:108–116. 52. visse r, nagase h. matrix metalloproteinases and tissue inhibitors of metalloproteinases: structure, function, and biochemistry. circ res 2003;92:827–839. 53. brejchova k, liskova p, cejkova j, jirsova k. role of matrix metalloproteinases in recurrent corneal melting. exp eye res 2010;90:583–590. 54. smith va, rishmawi h, hussein h, easty dl. tear film mmp accumulation and corneal disease. br j ophthalmol 2001;85:147–153. 55. smith va, hoh hb, easty dl. role of ocular matrix metalloproteinases in peripheral ulcerative keratitis. br j ophthalmol 1999;83:1376–1383. 56. yagci a. update on peripheral ulcerative keratitis. clin ophthalmol 2012;6:747–754. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 271 update on puk; hassanpour et al 57. gregory jk, foster cs. peripheral ulcerative keratitis in the collagen vascular diseases. int ophthalmol clin 1996;36:21–30. 58. bouchard cs, meyer ma, mcdonnell jf. bilateral peripheral ulcerative keratitis associated with pyoderma gangrenosum. cornea 1997;16:480–482. 59. garcía m, garrido g, ortiz a, et al. ab0370 peripheral ulcerative keratitis associated with autoimmune diseases: a typical ocurrence in the biologic era. ann rheum dis 2015;74:1017.1. 60. pelegrín l, hernández-rodríguez j, torras j, et al. ab0678 peripheral ulcerative keratitis associated to autoimmune systemic diseases: visual prognosis and occurrence while systemic disease in remission. vol. 772018; 1482.3-3. 61. levitt ae, mcmanus kt, mcclellan al, davis jl, goldhardt r, galor a. ocular inflammation in the setting of concomitant systemic autoimmune conditions in an older male population. cornea 2015;34:762–767. 62. cao y, zhang w, wu j, zhang h, zhou h. peripheral ulcerative keratitis associated with autoimmune disease: pathogenesis and treatment. j ophthalmol 2017;2017:7298026. 63. galor a, thorne je. scleritis and peripheral ulcerative keratitis. rheum dis clin north am 2007;33:835–854, vii. 64. fernandes sr, singsen bh, hoffman gs. sarcoidosis and systemic vasculitis. semin arthritis rheum 2000;30:33– 46. 65. siracuse-lee d, saffra n. peripheral ulcerative keratitis in sarcoidosis: a case report. cornea 2006;25:618–620. 66. harthan js, reeder re. peripheral ulcerative keratitis in association with sarcoidosis. cont lens anterior eye 2013;36:313–317. 67. ji ys, yoon kc. a rare case of peripheral ulcerative keratitis associated with behçet’s disease. int ophthalmol 2014;34:979–981. 68. mady r, grover w, butrus s. ocular complications of inflammatory bowel disease. the scientific world journal 2015;2015:438402-. 69. tan mh, chen sd, rubinstein a, bron aj. corneal perforation due to severe peripheral ulcerative keratitis in crohn disease. cornea 2006;25:628–630. 70. herbert vg, lögering b, von gruben v, filev f, klemm m, reich k. ulcerative keratitis in psoriasis: a rare variant of psoriatic ocular inflammatory disease. br j dermatol 2014;170:746–748. 71. mahmood ma, pillai s, limaye sr. peripheral ulcerative keratitis associated with hideradenitis suppurativa. cornea 1991;10:75–78. 72. meskin sw, carlson em. mooren’s-type ulceration associated with severe hidradenitis suppurativa: a case report and literature review. ocul immunol inflamm 2011;19:340–342. 73. sainz de la maza m, foster cs. peripheral ulcerative keratitis and malignancies. cornea 1994;13:364–367. 74. malecha ma, holland ej. peripheral keratitis associated with chronic myelomonocytic leukemia. cornea 2002;21:723–724. 75. morjaria r, barge t, mordant d, elston j. peripheral ulcerative keratitis as a complication of acute myeloid leukaemia. bmj case rep 2014;2014. 76. fournié p, malecaze f, coullet j, arné jl. pyoderma gangrenosum with necrotizing sclerokeratitis after cataract surgery. j cataract refract surg 2007;33:1987– 1990. 77. ayyala rs, armstrong s. corneal melting and scleromalacia perforans in a patient with pyoderma gangrenosum and acute myeloid leukemia. ophthalmic surg lasers 1998;29:328–331. 78. brown ba, parker ct, bower ks. effective steroid-sparing treatment for peripheral ulcerative keratitis and pyoderma gangrenosum. cornea 2001;20:117–118. 79. miserocchi e, modorati g, foster cs, brancato r. ocular and extracutaneous involvement in pyoderma gangrenosum. ophthalmology 2002;109:1941–1943. 80. arora t, sharma n, shashni a, titiyal js. peripheral ulcerative keratitis associated with chronic malabsorption syndrome and miliary tuberculosis in a child. oman j ophthalmol 2015;8:205–207. 81. rafiezadeh p, schmack i, shajari m, kohnen t. autoimmune keratitis in mycobacterium tuberculosis. j curr ophthalmol 2018;30:381–383. 82. kamal s, kumar r, kumar s, goel r. bilateral interstitial keratitis and granulomatous uveitis of tubercular origin. eye contact lens 2014;40:e13–e15. 83. ploysangam p, mattern rm. perforating peripheral ulcerative keratitis in syphilis. case rep ophthalmol 2019;10:267–273. 84. vignesh ap, srinivasan r, vijitha s. ocular syphilis masquerading as bilateral peripheral ulcerative keratitis. taiwan j ophthalmol 2016;6:204–205. 85. prasher p, di pascuale m, cavanagh hd. bilateral chronic peripheral ulcerative keratitis secondary to cat-scratch disease. eye contact lens 2008;34:191–193. 86. tavassoli s, gunn d, tole d, darcy k. peripheral ulcerative keratitis with corneal melt as the primary presentation in a case of human immunodeficiency virus. bmj case rep 2019;12:e226936. 87. soni nd, ingole ab, murade sm. an unusual case of peripheral ulcerative keratitis as a presenting feature in an otherwise healthy patient with undiagnosed human immunodeficiency virus infection and low cd4 counts. indian j ophthalmol 2013;61:138–139. 88. gharai s, venkatesh p, tandon r, garg s. peripheral ulcerative keratitis and central retinal vein occlusion as the initial manifestation of hiv infection. ocul immunol inflamm 2007;15:407–409. 89. chetty r. vasculitides associated with hiv infection. j clin pathol 2001;54:275–278. 90. du toit sh, smit dp. mooren’s ulcer of the cornea after immune reconstitution. aids 2014;28:139–140. 91. wei dw, pagnoux c, chan cc. peripheral ulcerative keratitis secondary to chronic hepatitis b infection. cornea 2017;36:515–517. 92. wilson se, lee wm, murakami c, weng j, moninger ga. mooren-type hepatitis c virus-associated corneal ulceration. ophthalmology 1994;101:736–745. 93. kedhar sr, belair ml, jun as, sulkowski m, thorne je. scleritis and peripheral ulcerative keratitis with hepatitis c virus-related cryoglobulinemia. arch ophthalmol 2007;125:852–853. 272 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 update on puk; hassanpour et al 94. enomoto m, nakanishi t, ishii m, tamori a, kawada n. entecavir to treat hepatitis b-associated cryoglobulinemic vasculitis. ann intern med 2008;149:912–913. 95. guillevin l, mahr a, callard p, godmer p, pagnoux c, leray e, et al. hepatitis b virus-associated polyarteritis nodosa: clinical characteristics, outcome, and impact of treatment in 115 patients. medicine 2005;84:313–322. 96. mondino bj, hofbauer jd, foos ry. mooren’s ulcer after penetrating keratoplasty. am j ophthalmol 1987;103:53– 56. 97. kiire ca, srinivasan s, inglis a. peripheral ulcerative keratitis after cataract surgery in a patient with ocular cicatricial pemphigoid. cornea 2011;30:1176–1178. 98. burkholder bm, kuo ic. peripheral ulcerative keratitis following laser in situ keratomileusis. case rep ophthalmol 2016;7:9–15. 99. díaz-valle d, benítez del castillo jm, castillo a, sayagués o, bañares a, garcía-sánchez j. immunologic and clinical evaluation of postsurgical necrotizing sclerocorneal ulceration. cornea 1998;17:371–375. 100. akpek ek, demetriades am, gottsch jd. peripheral ulcerative keratitis after clear corneal cataract extraction(1). j cataract refract surg 2000;26:1424–1427. 101. salamon sm, mondino bj, zaidman gw. peripheral corneal ulcers, conjunctival ulcers, and scleritis after cataract surgery. am j ophthalmol 1982;93:334–337. 102. ladas jg, mondino bj. systemic disorders associated with peripheral corneal ulceration. curr opin ophthalmol 2000;11:468–471. 103. keenan jd, mandel mr, margolis tp. peripheral ulcerative keratitis associated with vasculitis manifesting asymmetrically as fuchs superficial marginal keratitis and terrien marginal degeneration. cornea 2011;30:825–827. 104. odorcic s, keystone ec, ma jj. infliximab for the treatment of refractory progressive sterile peripheral ulcerative keratitis associated with late corneal perforation: 3-year follow-up. cornea 2009;28:89–92. 105. riley gp, harrall rl, watson pg, cawston te, hazleman bl. collagenase (mmp-1) and timp-1 in destructive corneal disease associated with rheumatoid arthritis. eye 1995;9:703–718. 106. mannis m, holland e. cornea. elsevier health sciences; 2016. 107. cohn h, mondino bj, brown si, hall gd. marginal corneal ulcers with acute beta streptococcal conjunctivitis and chronic dacryocystitis. am j ophthalmol 1979;87:541–543. 108. taylor pb, tabbara kf. peripheral corneal infections. int ophthalmol clin 1986;26:29–48. 109. awais m, anwar mi, iftikhar r, iqbal z, shehzad n, akbar b. rosacea – the ophthalmic perspective. cutan ocul toxicol 2015;34:161–166. 110. suzuki t, kinoshita s. meibomitis-related keratoconjunctivitis in childhood and adolescence. am j ophthalmol 2007;144:160–161; author reply 1. 111. suzuki t. meibomitis-related keratoconjunctivitis: implications and clinical significance of meibomian gland inflammation. cornea 2012;31:s41–s44. 112. suzuki t. inflamed obstructive meibomian gland dysfunction causes ocular surface inflammation. invest ophthalmol vis sci 2018;59:des94–des101. 113. mondino bj, brown si, mondzelewski jp. peripheral corneal ulcers with herpes zoster ophthalmicus. am j ophthalmol 1978;86:611–614. 114. kim hb, ostler hb. marginal corneal ulcer due to betastreptococcus. arch ophthalmol 1977;95:454–455. 115. baum j, fedukowicz hb, jordan a. a survey of moraxella corneal ulcers in a derelict population. am j ophthalmol 1980;90:476–480. 116. hutton wl, sexton rr. atypical pseudomonas corneal ulcers in semicomatose patients. am j ophthalmol 1972;73:37–39. 117. baijal v, palit mg, choudhary t, gurunadh vs, shanker s. terrien’s marginal degeneration: case report. med j armed forces india 1999;55:83. 118. wilson se, lin dt, klyce sd, insler ms. terrien’s marginal degeneration: corneal topography. refract corneal surg 1990;6:15–20. 119. ding y, murri ms, birdsong oc, ronquillo y, moshirfar m. terrien marginal degeneration. surv ophthalmol 2019;64:162–174. 120. rishi p, shields cl, eagle rc. conjunctival intraepithelial neoplasia with corneal furrow degeneration. indian j ophthalmol 2014;62:809–811. 121. rumelt s, rehany u. computerized corneal topography of furrow corneal degeneration. j cataract refract surg 1997;23:856–859. 122. accorinti m, gilardi m, giubilei m, de geronimo d, iannetti l. corneal and scleral dellen after an uneventful pterygium surgery and a febrile episode. case rep ophthalmol 2014;5:111–115. 123. fresina m, campos ec. corneal ’dellen’ as a complication of strabismus surgery. eye 2009;23:161–163. 124. sharma b, bajoria sk, patnaik a, barbhaya r. resolution of corneal dellen after an uneventful pterygium surgery with punctal cautery. cureus 2020;12:e8250-e. 125. kafkala c, choi j, zafirakis p, baltatzis s, livir-rallatos c, rojas b. mooren ulcer: an immunopathologic study. cornea 2006;25:667–673. 126. zelefsky jr, srinivasan m, kundu a, lietman t, whitcher jp, wang k, et al. hookworm infestation as a risk factor for mooren’s ulcer in south india. ophthalmology 2007;114:450–453. 127. zegans me, srinivasan m. mooren’s ulcer. int ophthalmol clin 1998;38:81–88. 128. srinivasan m, zegans me, zelefsky jr, kundu a, lietman t, whitcher jp, et al. clinical characteristics of mooren’s ulcer in south india. br j ophthalmol 2007;91:570–575. 129. watson pg. management of mooren’s ulceration. eye 1997;11:349–356. 130. alhassan mb, rabiu m, agbabiaka io. interventions for mooren’s ulcer. cochrane database syst rev 2014;6:cd006131. 131. thring tsa, hili p, naughton dp. anti-collagenase, antielastase and anti-oxidant activities of extracts from 21 plants. bmc complement altern med 2009;9:27. 132. ramaesh t, ramaesh k, riley sc, west jd, dhillon b. effects of n-acetylcysteine on matrix metalloproteinase-9 secretion and cell migration of human corneal epithelial cells. eye 2012;26:1138–1144. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 273 update on puk; hassanpour et al 133. perry hd, golub lm. systemic tetracyclines in the treatment of noninfected corneal ulcers: a case report and proposed new mechanism of action. ann ophthalmol 1985;17:742–744. 134. ralph ra. tetracyclines and the treatment of corneal stromal ulceration: a review. cornea 2000;19:274–277. 135. kaçmaz ro, kempen jh, newcomb c, daniel e, gangaputra s, nussenblatt rb, et al. cyclosporine for ocular inflammatory diseases. ophthalmology 2010;117:576–584. 136. tandon r, chawla b, verma k, sharma n, titiyal js. outcome of treatment of mooren ulcer with topical cyclosporine a 2%. cornea 2008;27:859–861. 137. zierhut m, thiel hj, weidle eg, waetjen r, pleyer u. topical treatment of severe corneal ulcers with cyclosporin a. graefes arch clin exp ophthalmol 1989;227:30–35. 138. goodman ls. goodman and gilman’s the pharmacological basis of therapeutics. vol. 1549. new york, ny: mcgraw-hill; 1996. 139. khan l, batavia e. medroxyprogesterone to treat corneal thinning postcurvularia keratitis. oman j ophthalmol 2019;12:194–196. 140. hicks cr, crawford gj. melting after keratoprosthesis implantation: the effects of medroxyprogesterone. cornea 2003;22:497–500. 141. smith v, cook s. doxycycline—a role in ocular surface repair. br j ophthalmol 2004;88:619–625. 142. chen j, lan j, liu d, backman lj, zhang w, zhou q, et al. ascorbic acid promotes the stemness of corneal epithelial stem/progenitor cells and accelerates epithelial wound healing in the cornea. stem cells transl med 2017;6:1356– 1365. 143. cho y-w, yoo w-s, kim s-j, chung i-y, seo s-w, yoo j-m. efficacy of systemic vitamin c supplementation in reducing corneal opacity resulting from infectious keratitis. medicine 2014;93:e125. 144. messmer em, foster cs. destructive corneal and scleral disease associated with rheumatoid arthritis. medical and surgical management. cornea 1995;14:408–417. 145. squirrell dm, winfield j, amos rs. peripheral ulcerative keratitis ’corneal melt’ and rheumatoid arthritis: a case series. rheumatology 1999;38:1245–1248. 146. foster cs, forstot sl, wilson la. mortality rate in rheumatoid arthritis patients developing necrotizing scleritis or peripheral ulcerative keratitis. effects of systemic immunosuppression. ophthalmology 1984;91:1253–1263. 147. ogra s, sims jl, mcghee cnj, niederer rl. ocular complications and mortality in peripheral ulcerative keratitis and necrotising scleritis: the role of systemic immunosuppression. clin exp ophthalmol 2020;48:434– 441. 148. monti s, balduzzi s, delvino p, bellis e, quadrelli vs, montecucco c. clinical course of covid-19 in a series of patients with chronic arthritis treated with immunosuppressive targeted therapies. ann rheum dis 2020;79:667–668. 149. araki-sasaki k, katsuta o, mano h, nagano t, nakamura m. the effects of oral and topical corticosteroid in rabbit corneas. bmc ophthalmol 2016;16:160. 150. jabs da, rosenbaum jt, foster cs, holland gn, jaffe gj, louie js, et al. guidelines for the use of immunosuppressive drugs in patients with ocular inflammatory disorders: recommendations of an expert panel. am j ophthalmol 2000;130:492–513. 151. tandon r, galor a, sangwan v, manotosh r. peripheral ulcerative keratitis. springer; 2017. 152. burska an, hunt l, boissinot m, strollo r, ryan bj, vital e, et al. autoantibodies to posttranslational modifications in rheumatoid arthritis. mediators inflamm 2014;2014:492873. 153. el-yazigi a, wahab fa. pharmacokinetics of azathioprine after repeated oral and single intravenous administration. j clin pharmacol 1993;33:522–526. 154. galor a, jabs da, leder ha, kedhar sr, dunn jp, peters 3𝑟𝑑 gb, et al. comparison of antimetabolite drugs as corticosteroid-sparing therapy for noninfectious ocular inflammation. ophthalmology 2008;115:1826–1832. 155. thorne je, jabs da, qazi fa, nguyen qd, kempen jh, dunn jp. mycophenolate mofetil therapy for inflammatory eye disease. ophthalmology 2005;112:1472–1477. 156. mccarthy jm, dubord pj, chalmers a, kassen bo, rangno kk. cyclosporine a for the treatment of necrotizing scleritis and corneal melting in patients with rheumatoid arthritis. j rheumatol 1992;19:1358–1361. 157. clewes ar, dawson jk, kaye s, bucknall rc. peripheral ulcerative keratitis in rheumatoid arthritis: successful use of intravenous cyclophosphamide and comparison of clinical and serological characteristics. ann rheum dis 2005;64:961–962. 158. hata m, nakamura t, sotozono c, kumagai k, kinoshita s, kurimoto y. atypical continuous keratitis in a case of rheumatoid arthritis accompanying severe scleritis. cornea 2012;31:1493–1496. 159. iliou c, anthis n, tsifetaki n, kitsos g, voulgari pv. clinical images: corneal melt in a woman with longstanding rheumatoid arthritis. arthritis rheum 2012;64:253. 160. gaujoux-viala c, giampietro c, gaujoux t, ea h-k, prati c, orcel p, et al. scleritis: a paradoxical effect of etanercept? etanercept-associated inflammatory eye disease. j rheumatol 2012;39:233–239. 161. oh jy, kim mk, wee wr. infliximab for progressive peripheral ulcerative keratitis in a patient with juvenile rheumatoid arthritis. jpn j ophthalmol 2011;55:70–71. 162. thomas jw, pflugfelder sc. therapy of progressive rheumatoid arthritis-associated corneal ulceration with infliximab. cornea 2005;24:742–744. 163. huerva v, ascaso fj, grzybowski a. infliximab for peripheral ulcerative keratitis treatment. medicine 2014;93:e176. 164. restrepo jp, medina lf, molina mdel p. [peripheral corneal melting syndrome in psoriatic arthritis treated with adalimumab]. rev bras reumatol 2015;55:387–389. 165. matet a, daruich a, beydoun t, cosnes j, bourges j-l. systemic adalimumab induces peripheral corneal infiltrates: a case report. bmc ophthalmol 2015;15:57. 166. tong l, thumboo j, tan yk, wong t-y, albani s. the eye: a window of opportunity in rheumatoid arthritis? nat rev rheumatol 2014;10:552–560. 167. freidlin j, wong ig, acharya n. rituximab treatment for peripheral ulcerative keratitis associated with wegener’s granulomatosis. br j ophthalmol 2007;91:1414. 274 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 update on puk; hassanpour et al 168. huerva v, sanchez mc, traveset a, jurjo c, ruiz a. rituximab for peripheral ulcerative keratitis with wegener granulomatosis. cornea 2010;29:708–710. 169. bonnet i, rousseau a, duraffour p, pouchot j, nguyen cd, gabison e, et al. efficacy and safety of rituximab in peripheral ulcerative keratitis associated with rheumatoid arthritis. rmd open 2021;7:e001472. 170. dominguez-casas lc, sánchez-bilbao l, calvo-río v, maíz o, blanco a, beltrán e, et al. biologic therapy in severe and refractory peripheral ulcerative keratitis (puk). multicenter study of 34 patients. semin arthritis rheum 2020;50:608–615. 171. pascalis l, pia g, aresu g, frongia t, barca l. combined cyclosporin a-steroid-mtx treatment in endogenous noninfectious uveitis. j autoimmun 1993;6:467–480. 172. paley ma, karacal h, rao pk, margolis tp, miner jj. tofacitinib for refractory uveitis and scleritis. am j ophthalmol case rep 2019;13:53–55. 173. sevik mo, turhan sa, toker e. topical treatment of persistent epithelial defects with a matrix regenerating agent. j ocul pharmacol ther 2018;34:621–627. 174. bernauer w, ficker la, watson pg, dart jk. the management of corneal perforations associated with rheumatoid arthritis. an analysis of 32 eyes. ophthalmology 1995;102:1325–1337. 175. fogle ja, kenyon kr, foster cs. tissue adhesive arrests stromal melting in the human cornea. am j ophthalmol 1980;89:795–802. 176. moorthy s, jhanji v, constantinou m, beltz j, grauehernandez eo, vajpayee rb. clinical experience with n-butyl cyanoacrylate tissue adhesive in corneal perforations secondary to herpetic keratitis. cornea 2010;29:971–975. 177. bodaghi b, lévy c, votan p, hoang-xuan t. [value of cyanoacrylate tissue adhesives in peripheral corneal ulcers of inflammatory origin]. j fr ophtalmol 1996;19:127– 132. 178. sharma n, singhal d, maharana pk, vajpayee rb. tuck-in tenon patch graft in corneal perforation. cornea 2019;38:951–954. 179. erikitola o-oc, jawaheer l, ramaesh k, anijeet d. conjunctival resection for peripheral ulcerative keratitis (puk). invest ophthalmol vis sci 2016;57:1261. 180. raizman mb, sainz de la maza m, foster cs. tectonic keratoplasty for peripheral ulcerative keratitis. cornea 1991;10:312–316. 181. speaker mg, arentsen jj, laibson pr. long-term survival of large diameter penetrating keratoplasties for keratoconus and pellucid marginal degeneration. acta ophthalmol suppl 1989;192:17–19. 182. lohchab m, prakash g, arora t, maharana p, jhanji v, sharma n, et al. surgical management of peripheral corneal thinning disorders. surv ophthalmol 2019;64:67– 78. 183. maeno a, naor j, lee hm, hunter ws, rootman ds. three decades of corneal transplantation: indications and patient characteristics. cornea 2000;19:7–11. 184. jhanji v, young al, mehta js, sharma n, agarwal t, vajpayee rb. management of corneal perforation. surv ophthalmol 2011;56:522–538. 185. bessant da, dart jk. lamellar keratoplasty in the management of inflammatory corneal ulceration and perforation. eye 1994;8:22–28. 186. liu j, shi w, li s, gao h, wang t. modified lamellar keratoplasty and immunosuppressive therapy guided by in vivo confocal microscopy for perforated mooren’s ulcer. br j ophthalmol 2015;99:778–783. 187. artaechevarria artieda j, estébanez-corrales n, sánchezpernaute o, alejandre-alba n. peripheral ulcerative keratitis in a patient with bilateral scleritis: medical and surgical management. case rep ophthalmol 2020;11:500–506. 188. wassmer c-h, berishvili e. immunomodulatory properties of amniotic membrane derivatives and their potential in regenerative medicine. curr diab rep 2020;20:31. 189. liu t, zhai h, xu y, dong y, sun y, zang x, et al. amniotic membrane traps and induces apoptosis of inflammatory cells in ocular surface chemical burn. mol vis 2012;18:2137–2146. 190. hanada k, shimazaki j, shimmura s, tsubota k. multilayered amniotic membrane transplantation for severe ulceration of the cornea and sclera. am j ophthalmol 2001;131:324–331. 191. solomon a, meller d, prabhasawat p, john t, espana em, steuhl k-p, et al. amniotic membrane grafts for nontraumatic corneal perforations, descemetoceles, and deep ulcers. ophthalmology 2002;109:694–703. 192. ngan nd, chau ht. amniotic membrane transplantation for mooren’s ulcer. clin exp ophthalmol 2011;39:386–392. 193. lambiase a, sacchetti m, sgrulletta r, coassin m, bonini s. amniotic membrane transplantation associated with conjunctival peritomy in the management of mooren’s ulcer: a case report. eur j ophthalmol 2005;15:274–276. 194. ke l, shen d, wang h, qiao c, zeng q. lamellar keratoplasty combined with amniotic membrane transplantation for the treatment of corneal perforations: a clinical and in vivo confocal microscopy study. biomed res int 2020;2020:7403842. 195. jerez-peña m, salvador-culla b, de la paz mf, barraquer ri. bilateral boston keratoprosthesis type 1 in a case of severe mooren’s ulcer. eur j ophthalmol 2021;31:np33– np8. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 275 erratum erratum: optical coherence tomography angiography findings in malignant hypertensive retinopathy ahmad mirshahi1, md; reza karkhaneh1, md; ramak roohipour2, md; mohammadbagher rajabi1, md; zakieh vahedian1, md; fatemeh bazvand1, md 1eye research center, farabi eye hospital, iran 2department of ophthalmology, morsani college of medicine, university of south florida, tampa, florida, united states j ophthalmic vis res 2022; 17 (4): 608–608 in the article titled “optical coherence tomography angiography findings in malignant hypertensive retinopathy” published on pages 432–436, volume 17, issue 3 of journal of ophthalmic and vision research,[1] the affiliation of the third author “ramak roohipour” is the second affiliation “department of ophthalmology, morsani college of medicine, university of south florida, tampa, florida, united states”. the online version of the article has therefore been updated on november 24, 2022 and can be accessed from https://knepublishing.com/index.php/jovr/article/view/11583/. references 1. mirshahi a, karkhaneh r, roohipour r, rajabi m, vahedian z, bazvand f. optical coherence tomography angiography findings in malignant hypertensive retinopathy. j ophthalmic vis res 2022;17:432–436. 608 © 2022 ahmad mirshahi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i4.12351&domain=pdf&date_stamp=2019-07-17 erratum erratum: biodistribution of cy5-labeled thiolated and methylated chitosan-carboxymethyl dextran nanoparticles in an animal model of retinoblastoma elham delrish, phd; fariba ghassemi, md; mahmoud jabbarvand, md; alireza lashay, md; fatemeh atyabi, phd; masoud soleimani, phd; rassoul dinarvand, phd j ophthalmic vis res 2022; 17 (2): 312–312 in the article titled “biodistribution of cy5-labeled thiolated and methylated chitosan-carboxymethyl dextran nanoparticles in an animal model of retinoblastoma” published on pages 58–68, volume 17, issue 1 of journal of ophthalmic and vision research,[1] the statement for ethical consideration was missing in the full-text pdf and html of the article. the online version of the article has therefore been updated on april 29, 2022 and can be accessed from https://doi.org/10.18502/jovr.v17i1.10171. ethical consideration the study protocol was approved by farabi eye hospital, tehran university of medical sciences ethics committee. the ethical code is “ir.tums.farabih.rec.1398.002”. the study has followed national ethical guidelines. all surveys conformed to the association for research in vision and ophthalmology (arvo) statement for the use of animals in research. references 1. delrish e, ghassemi f, jabbarvand m, lashay a, atyabi f, soleimani m, et al. biodistribution of cy5-labeled thiolated and methylated chitosan-carboxymethyl dextran nanoparticles in an animal model of retinoblastoma. j ophthalmic vis res 2022;17:58–68. 312 © 2022 . this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i2.10809&domain=pdf&date_stamp=2019-07-17 editorial an alternate technique for goniotomy kouros nouri-mahdavi, md, ms director, glaucoma advanced imaging laboratory, glaucoma division, stein eye institute, department of ophthalmology at david geffen school of medicine, los angeles ca orcid: kouros nouri-mahdavi: https://orcid.org/0000-0001-9403-8904 j ophthalmic vis res 2022; 17 (2): 158–159 trabeculotomy as a surgical option has a longstanding history in the field of glaucoma. performing trabeculotomy in adult eyes has taken a new life since the introduction of trabectome® followed by various other approaches for tearing or excising the trabecular meshwork. shute and colleagues report in this issue of the journal of ophthalmic and vision research the results of a novel low-cost approach for performing trabeculotomy and removal of trabecular meshwork with a 25g hypodermic needle, which they call bang (bent ab interno needle goniectomy).[1] the premise is that this simple and low-tech approach can remove the trabecular meshwork and reduce the iop as well as existing techniques such as goniotomy with kahook dual blade (kdb) or trabeculotomy with trabectome, which are costly due to the need for special instrumentation. this low-cost approach seems to be effective and promising based on the preliminary sixmonth results in 41 eyes. the authors do provide histopathological evidence that a strip of tm tissue can be removed with bang, however, it is not clear how easy and consistent bang is to remove the tm in every patient using this method. an average of 102º of trabeculotomy was performed in the patient cohort, likely a reflection of the efficacy and simplicity of this approach. the average (±sd) maximum intraocular pressure (iop) was 23.9 (±6.1) mmhg in the study cohort; it is not clear though if this represents untreated maximum iops. also, there are no data on washedout iops after surgery. the average preoperative iop was 17.4 (± 4.1) mmhg on 1.1 (± 1.4) topical glaucoma medications, which decreased to 13.3 (± 2.5 mmhg) at month six after the intervention; it must be noted that only 16 out of 22 eyes were receiving eye drops for iop reduction before surgery. the results seem to be consistent with prior publications on goniotomy with kdb or trabectome,[2–4] however, further experience is needed to confirm the utility of this approach. a similar procedure called trabeculotomy with microhook has been reported by japanese investigators with seemingly similar success rates as kdb goniotomy combined with phacoemulsification.[2, 3] various techniques are currently used for carrying out trabeculotomy with or without trabecular excision in glaucoma patients. overall, it appears that trabecular excision may not be necessary to achieve iop reduction although healing of the trabecular meshwork after trabeculotomy is not well studied and being able to actually remove the roof the schlemm’s canal might contribute to better long-term outcomes. before generalizing the conclusions, the characteristics of the study cohort need to be considered. this cohort of patients represents a group of eyes with early to moderate glaucoma with a low medication burden. despite or maybe due to these features, a 20% or higher iop reduction was achieved in 73% of patients and 73% of patients had a decrease in eyedrop burden by one or more medication. six months after surgery, 73% of patients did not need any medication for iop control. a six-month follow-up period is very short when considered within the lifespan of a glaucoma patient and longer follow-up is certainly required to establish the longevity of the iop reduction. i will be looking forward to reports on longer term results of this or larger cohorts utilizing bang to improve patient outcomes especially in 158 © 2022 nouri-mahdavi . this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i2.10785&domain=pdf&date_stamp=2019-07-17 editorial; nouri-mahdavi conjunction with cataract surgery. the authors are to be commended for attempting to make this type of surgery more accessible to clinicians and patients across the globe. financial support and sponsorship none. conflicts of interest none declared. references 1. shute t, green w, liu j, sheybani a. an alternate technique for goniotomy: description of procedure and preliminary results. j ophthalmic vis res 2022;17:1–7. 2. ibrahim lf, pereira afr, terenzi lao, vianello mp, dorairaj sk, prata ts, et al. phacoemulsification with kahook dual blade goniotomy in eyes with medically treated glaucoma: analysis of surgical outcomes and success predictors. arq bras oftalmol 2021:s0004–27492021005007230. 3. esfandiari h, shah p, torkian p, conner ip, schuman js, hassanpour k, et al. five-year clinical outcomes of combined phacoemulsification and trabectome surgery at a single glaucoma center. graefes arch clin exp ophthalmol 2019;257:357–362. 4. al habash a, albuainain a. long term outcome of combined phacoemulsification and excisional goniotomy with the kahook dual blade in different subtypes of glaucoma. sci rep 2021;11:10660. 5. aoki r, hirooka k, goda e, yuasa y, okumichi h, onoe h, et al. comparison of surgical outcomes between microhook ab interno trabeculotomy and goniotomy with the kahook dual blade in combination with phacoemulsification: a retrospective, comparative case series. adv ther 2021;38:329–336. 6. omoto t, fujishiro t, asano-shimizu k, sugimoto k, sakata r, murata h, et al. comparison of the short-term effectiveness and safety profile of ab interno combined trabeculotomy using 2 types of trabecular hooks. jpn j ophthalmol 2020;64:407–413. correspondence to: kouros nouri-mahdavi, md, ms. director, glaucoma advanced imaging laboratory, glaucoma division, stein eye institute, department of ophthalmology at david geffen school of medicine, los angeles 90095, ca. e-mail: nouri-mahdavi@jsei.ucla.edu received: 15-01-2022 accepted: 24-02-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i2.10785 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: nouri-mahdavi. an alternate technique for goniotomy. j ophthalmic vis res 2022;17:158–159. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 159 https://knepublishing.com/index.php/jovr authors’ reply natasha f s cruz1, md; katia s santos1, md; mateus l matuoka1, md; niro kasahara1,2, md 1department of ophthalmology, irmandade da santa casa de misericordia de sao paulo, sao paulo, brazil 2santa casa de sao paulo school of medical sciences, sao paulo, brazil. orcid: natasha cruz: https://orcid.org/0000-0002-5209-9204 niro kasahara: https://orcid.org/0000-0003-4101-0304 j ophthalmic vis res 2022; 17 (4): 603–604 dear editor, we appreciate d. fleischman’s comments on the recent article by cruz et al.[1] we deeply respect the colleague’s opinion on the subject. the first mention of an algorithm for the estimation of the cerebrospinal fluid pressure (csfp) appeared in the prospective observational comparative study by xie et al.[2] the authors included 72 neurology patients who underwent csfp measurement by lumbar puncture and 3.0-tesla orbital magnetic resonance imaging for different clinical reasons. after adjusting for body mass index (bmi) and mean arterial blood pressure (mabp), the authors developed three algorithms for the associations between csfp and orbital subarachnoid space width as follows: (a) csf-p = 9.31 × osasw (at 3 mm) + 0.48 × bmi + 0.14 × mabp – 19.94; (b) csf-p = 16.95 × osasw (at 9 mm) + 0.39 × bmi + 0.14 × mabp – 20.90; and (c) csf-p = 17.54 × osasw (at 15 mm) + 0.47 × bmi + 0.13 × mabp – 21.52. later, using the data obtained in xie et al´s study, jonas and colleagues from the same study group calculated a formula to estimate the csfp of a normal population. correspondence to: niro kasahara, md. department of ophthalmology, irmandade da santa casa de misericordia de sao paulo, sao paulo, brazil. e-mail: niro.kasahara@fcmsantacasasp.edu.br received: 23-08-2022 accepted: 07-09-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i4.12344 performing a multivariate analysis in the training group with the lumbar csfp measurements as dependent variable and age, bmi and blood pressure as independent variables revealed that estimated csfp was best described by the formula of estimated csfp [mmhg] = 0.44 × bmi × [kg/m ] + 0.16 × diastolic blood pressure [mmhg] – 0.18 × age [years] 1.91.[3, 4] in fact, xie was the coauthor of this second paper and since the data for the first study was used to estimate the csfp, we thought that paper should be cited and receive credit. this formula has been validated in the brazilian population. kasahara et al compared the real csfp and the estimated one by the algorithm in a small cohort of 39 patients scheduled for lumbar puncture for different medical reasons.[5]using the bland-altman plot of the differences between the two techniques against their averages, most data points were positioned between the two limits of agreement indicating concordance between the two methods. the authors highlighted that the use of the equation was not for clinical grounds; however, it might be a suitable surrogate method to predict csfp in clinical studies.[5] this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: cruz nfs, santos ks, matuoka ml, kasahara n. authors’ reply. j ophthalmic vis res 2022;17:603– 604. © 2022 cruz et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 603 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i4.12344&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr authors’ reply; cruz et al the following quote is attributed to sir issac newton: “if i have seen further it is by standing on the shoulders of giants.”[6] far from considering ourselves as giants, we believe that dr cruz’s paper is a small contribution to the emerging large body of evidence of the role of csfp in the pathogeny of primary open-angle glaucoma. this paper might inspire other researches to further elucidate the complexity of csfp and glaucoma. in science, researchers have to use whatever is available to develop their research and, in many instances, the methods are not ideal. in this study specifically, the measurement of csfp by lumbar puncture for study purposes only – with no clear medical reason – would definitely be unethical. other methods for noninvasive measurement of csfp have been developed and although some techniques may show great potential for specific applications, none of these methods can fully replace an invasive technique by lumbar puncture and none has yet been considered the gold standard for clinical science.[7] in the meantime, we believe that surrogate methods, particularly the proxy algorithm, are valid instruments to estimate csfp in clinical studies and no study using such methods should be disregarded. references 1. cruz nf, santos ks, matuoka ml, kasahara n. translaminar pressure difference and ocular perfusion pressure in glaucomatous eyes with different optic disc sizes. j ophthalmic vis res 2021;16:171–177. 2. xie xb, zhang xj, fu j, wang h, jonas jb, peng x, et al. intracranial pressure estimation by orbital subarachnoid space measurement. crit care 2013;17:r162. 3. jonas jb, wang n, wang yx, you qs, yang d, xie x, et al. subfoveal choroidal thickness and cerebrospinal fluid pressure: the beijing eye study 2011. invest ophthalmol vis sci 2014;55:1292–1298. 4. jonas jb, wang n, yang d, ritch r, panda-jonas s. facts and myths of cerebrospinal fluid pressure for the physiology of the eye. prog retin eye res 2015;46:67–83. 5. kasahara n, matuoka ml, santos ks, cruz nf, martins ar, nigro s. validation of an equation model to predict intracranial pressure in clinical studies. innov clin neurosci 2018;15:27–29. 6. hall ar, tilling l, editors. the correspondence of isaac newton. volume 5. cambridge: cup. p. 1709–1713. 7. price da, grzybowski a, eikenberry j, januleviciene i, verticchio vercellin ac, mathew s, et al. review of noninvasive intracranial pressure measurement techniques for ophthalmology applications. br j ophthalmol 2020;104:887–892. 604 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 editorial the impact of covid-19 on ophthalmology practice: changes and controversies in endophthalmitis risk mohammad riazi, md department of ophthalmology, gavin herbert eye institute, university of california irvine, irvine, california, usa j ophthalmic vis res 2023; 18 (3): 249–251 the covid-19 pandemic imposed major risks to both ophthalmologists and patients, resulting in significant changes to ophthalmology practices around the world. non-urgent ophthalmic services were temporarily halted, with a gradual reopening in a stepwise manner. in a 2020 survey conducted by the american society of retina specialists (asrs), about 40% of respondents indicated a reduction in staff. in some areas, ophthalmologists were redirected to serve in covid-related areas such as emergency wards or intensive care units. the pandemic has also accelerated the adoption of virtual visits and digital patient management. detection of viral rna particles in ocular secretions suggested the possibility of transmission through the eyes, resulting in recommendations for eye protection for ophthalmologists (such as slit lamp shields, goggles, or eye shields) and mandatory maskwearing and temperature screenings for both patients and staff. virtual visits were introduced in some areas to compensate for decreased patient numbers, and vaccination and testing protocols correspondence to: mohammad riazi, md; department of ophthalmology, gavin herbert eye institute, university of california irvine, irvine, california, usa. email: mriazies@hs.uci.edu received: 10-08-2022 accepted: 15-02-2023 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i3.13771 were established. mask-wearing might be thought to reduce the rate of endophthalmitis by reducing exposure to nasopharyngeal and oral flora, but it may also increase the flow of air and germs from the nose and oral cavity to the eyes. tight-fitting face masks used without adhesive tapes resulted in the highest amount of bacterial growth around the subject’s eye.[1] sakamoto et al reported an increased rate of post-vitrectomy endophthalmitis in the covid era, with more germs originating from the oral cavity.[2] several case reports have shown a link between covid-19 and ocular disorders, including conjunctivitis, keratitis, uveitis, and retinal vascular occlusions. the pathogenesis, in some cases, involves attachment of viral spike proteins to cell receptors such as angiotensin-converting enzyme 2 (ace-2) and cleavage by protein trans-membrane serine protease 2 (tmprss2) for cell entry in ocular tissues.[3] however, other mechanisms of viral infection such as alterations in coagulation cascades or immune function may also play a role. this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: riazi m. the impact of covid19 on ophthalmology practice: changes and controversies in endophthalmitis risk. j ophthalmic vis res 2023;18:249–251. © 2023 riazi. this is an open access article distributed under the creative commons attribution license | published by knowledge e 249 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i3.13771&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr editorial; riazi presentation of various ophthalmic disorders has been reported to change during the covid era. most of these differences may be attributed to limited access to providers, use of personal protective devices, and patient hesitancy/selfisolation, causing delayed presentation or referral. during the lockdown period, das and dave reported an increase in proliferative retinopathy or sight-threatening conditions among diabetic patients.[4] reports have also suggested an association between covid infection and fungal sepsis or fungal ophthalmic involvement.[5] in the current issue of journal of ophthalmic and vision research (jovr), two papers address changes in the rate of endophthalmitis among tertiary ophthalmic centers during the covid-19 pandemic. one paper by dr. karimi and colleagues[6] examines the risk of acute endophthalmitis after intravitreal injections associated with the widespread use of face masks. these authors compared 28,085 injections in the pre-covid era with 10,717 injections during the covid era and found no significant differences in the rate of endophthalmitis after injections (0.032% in pre-covid era vs 0.037% in covid era). although the use of masks helps limit the spread of the virus, it entails potential side effects, such as dry eye, infectious keratitis, or even endophthalmitis. in a study involving simulated intravitreal injections, patel et al showed that adhesive taping at the superior edge of the patients’ mask could decrease the rate of bacterial dispersion to the level of an n95 mask.[1] in karimi’s paper patients wore masks during the covid era, but held their masks under their nose during the injection, which avoids re-direction of air flow towards the eyes. another paper by dr. fortes and colleagues[7] is a multi-center retrospective case series that evaluates clinical characteristics and visual outcomes of patients with endophthalmitis before and during the covid-19 pandemic. the authors found similar etiology for endophthalmitis in both groups, as well as similar final visual outcomes at six months. however, the mean logmar visual acuity at presentation was worse during the pandemic as compared to the precovid period, which may be due to delayed presentation (18 days vs 7 days). despite reports of irreversible damage in neovascular amd, retinal vein occlusion, or retinal detachment due to delayed referral in the covid era,[8, 9] fortes[7] did not find a significant difference in the final outcome in patients with endophthalmitis. on the other hand, das and dave[4] reported an increase in the number of endogenous endophthalmitis and a decrease in post-traumatic forms during the covid era, which is in contrast to the report by fortes et al.[7] nevertheless, fortes did not find a significant difference in the rate of post-injection endophthalmitis during the pandemic, which is in agreement with karimi’s paper and the iris registry study.[10] in summary, the covid-19 era has resulted in significant changes in ophthalmology practices worldwide, including delayed patient referrals, universal mask-wearing by both patients and providers, and direct/indirect ocular involvement by the virus. although there are conflicting reports in the literature regarding the impact of these changes on the incidence of postoperative and post-injection endophthalmitis, the two studies included in this issue of jovr provide evidence that there have been no significant changes in the rate of endophthalmitis during the covid era. financial support and sponsorship none. conflicts of interest none. references 1. patel sn, mahmoudzadeh r, salabati m, soares rr, hinkle j, hsu j, et al. bacterial dispersion associated with various patient face mask designs during simulated intravitreal injections. am j ophthalmol 2021;223:178–183. 2. sakamoto t, terasaki h, yamashita t, shiihara h, funatsu r, uemura a, et al. increased incidence of endophthalmitis after vitrectomy relative to face mask wearing during covid-19 pandemic. br j ophthalmol. doi: 10.1136/bjophthalmol-2022-321357 3. maurin c, he z, mentek m, verhoeven p, pillet s, bourlet t, et al. exploration of the ocular surface infection by sarscov-2 and implications for corneal donation: an ex vivo study. plos med 2022;19:e1003922. 4. das av, dave vp. effect of lockdown and unlock following covid-19 on the presentation of patients with endophthalmitis at a tertiary eye center over one year. cureus 2021;13:e19469. 5. tsatsakis a, calina d, falzone l, petrakis d, mitrut r, siokas v, et al. sars-cov-2 pathophysiology and its clinical implications: an integrative overview of the 250 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 editorial; riazi pharmacotherapeutic management of covid-19. food chem toxicol 2020; 146:111769. 6. karimi s, nikkhah h, mohammadzadeh a, ramezani a, nouri h, abtahi s-h. intravitreal injections and face masks: endophthalmitis risk before and during the covid-19 pandemic. j ophthalmic vis res 2023;18:283–288. 7. fortes bh, tailor pd, xu tt, churchill ra, starr mr. clinical characteristics and outcomes of endophthalmitis pre-covid-19 pandemic versus during the covid-19 pandemic. j ophthalmic vis res 2023;18:289–296. 8. romano f, monteduro d, airaldi m, zicarelli f, parrulli s, cozzi m, et al. increased number of submacular hemorrhages as a consequence of coronavirus disease 2019 lockdown. ophthalmol retina 2020;4:1209–1210. 9. patel lg, peck t, starr mr, ammar mj, khan ma, yonekawa y, et al. clinical presentation of rhegmatogenous retinal detachment during the covid-19 pandemic: a historical cohort study. ophthalmology 2021;128:686–692. 10. lum f, li s, liu l, li c, parke dw, williams ga. the pandemic is not associated with endophthalmitis decrease after anti-vascular endothelial growth factor injections. ophthalmology 2022;129:719–721. journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 251 photo essay pigmentary retinopathy and chronic subretinal fluid associated with pseudoxanthoma elasticum and angioid streaks matthew r. starr, md; sophie j. bakri, md mayo clinic department of ophthalmology, rochester, mn, usa j ophthalmic vis res 2022; 17 (1): 152–155 presentation we present the ophthalmic findings of a 57-yearold female with pseudoxanthoma elasticum who was initially diagnosed in her 20s after a biopsy of abnormal neck lesions. she began to develop visual problems decades later, but currently has no other related medical problems, including any evidence of coronary artery disease. our patient complained of bilateral metamorphopsia but with preserved visual acuity of 20/25 in both eyes. in addition to the angioid streaks, the patient also had evidence of pigmentary changes at the posterior pole [figures 1a–1b]. optical coherence tomography imaging [figures 1c–1f] revealed the presence of bilateral subretinal fluid, shaggy photoreceptors, and intraretinal hyperreflective material concentrated within the outer retina that was stable for five years [figures 1 e & 1f]. discussion angioid streaks are breaks within a weakened bruch’s membrane. they are deep to the correspondence to: sophie j. bakri, md. mayo clinic, department of ophthalmology, 200 first st, southwest, rochester 55905, mn, usa. e-mail: bakri.sophie@mayo.edu received 23-07-2019; accepted 02-04-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10183 neurosensory retina and typically bilateral, irregular, and emanate from the optic disc. causes include ehler–danlos syndrome, paget’s disease, sickle cell, and other hemoglobinopathies, idiopathic, and pseudoxanthoma elasticum.[1] vision is typically not affected by angioid streaks unless patients develop choroidal neovascularization with resultant macular edema and retinal hemorrhages.[2] following our patient for 10 years (5 years with spectral domain oct), she has never had any evidence of a choroidal neovascular complex on fluorescein angiography and thus it was concluded that the subretinal fluid was the result of malfunctioning retinal pigment epithelium due to the pigmentary changes at the posterior pole, a rare finding first described by zweifel and colleagues in 2011, who concluded the fluid was due to a similar pathophysiology as pattern dystrophy.[3] clinicians should be aware of the ophthalmic manifestations of pseudoxanthoma elasticum which include angioid streaks which can lead to choroidal neovascularization and severe vision loss but also pigmentary changes at the posterior pole that can lead to chronic subretinal fluid and a milder effect on visual acuity. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: starr and bakri. pigmentary retinopathy and chronic subretinal fluid associated with pseudoxanthoma elasticum and angioid streaks . j ophthalmic vis res 2022;17:152–155. 152 © 2022 starr, bakri. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10183&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; starr, bakri figure 1. fundus images (a) with bilateral hyperpigmented lines emanating from the discs, consistent with angioid streaks (white arrows). on faf (b), the angioid streaks are easily appreciated (white arrows). also seen are punctate areas of hyperand hypofaf surrounding the disc and within the fovea (asterisks). the hyper-faf lesions are felt to be accumulations of photoreceptor lipofuscin while the hypo-faf lesions are thought to be related to subretinal drusenoid deposits. on oct (c-f), there is evidence of bilateral subretinal fluid (red arrows) consistent with chronic rpe damage that are stable over five years (c & d images taken five years before e & f images). journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 153 photo essay; starr, bakri financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. clarkson jg, altman rd. angioid streaks. surv ophthalmol 1982;26:235–246. 2. nakagawa s, yamashiro k, tsujikawa a, otani a, tamura h, ooto s, et al. the time course changes of choroidal neovascularization in angioid streaks. retina 2013;33:825–833. 3. zweifel sa, imamura y, freund kb, spaide rf. multimodal fundus imaging of pseudoxanthoma elasticum. retina 2011;31:482–491. 154 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 original article a modified formula for intraocular lens power calculation based on aphakic refraction in a pediatric population mohammad-reza jafarinasab1, md; behrooz khosravi2, md; hamed esfandiari2, md; sadid hooshmandi2, md; kiana hassanpour2, md, mph 1ophthalmic epidemiology research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 3department of ophthalmology, northwestern university feinberg school of medicine, chicago, il, usa orcid: mohammad-reza jafarinasab: https://orcid.org/0000-0001-7558-0351 kiana hassanpour: https://orcid.org/0000-0002-1788-7352 abstract purpose: to investigate and optimize the accuracy of aphakic refraction (ar) techniques for secondary intraocular lens (iol) power calculation in aphakic children. methods: thirty-three aphakic eyes of 18 patients who were candidates for secondary iol implantation were enrolled in the present study. axial length (al) measured by optical biometry was used in the biometric formula (srk-t, holladay ii, and hoffer-q). ar and spherical equivalent (se) were used in two ar-based formulas (ianchulev, leccissotti). true power was calculated based on postoperative se at three months’ follow-up. results: regarding the postoperative se, 13 (40%) eyes were within ±1.00 diopters (d) and 22 (66%) were within ±2.00 d. median absolute error (medae) was predicted to be 4.4 and 7.3 d with the use of ianchulev and leccissotti formulas, respectively. the corresponding value was 0.8 d with the biometric formula. all eyes were deemed to have myopic refraction when using the ar-based formulas except one eye with the ianchulev formula. the coefficient of our modified formula was 1.7 instead of 2.01 in the ianchulev formula. medae with the use of new formulae was 0.5 d and was comparable with the true iol power (p = 0.22). conclusion: both ianchulev and leccissotti formulas resulted in a significant myopic surprise in aphakic children aged between 4.5 and 14 years. the modified formula proved to determine a more accurate se that is comparable with biometric formulas. keywords: aphakic refraction; intraocular lens (iol); iol power calculation; pediatric cataract j ophthalmic vis res 2023; 18 (1): 34–40 correspondence to: kiana hassanpour, md, mph. ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, paidarfard st., boostan 9th st., pasdaran, ave., tehran 16666, iran. e-mail: kiana.hassanpour@gmail.com received: 02-03-2021 accepted: 14-09-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i1.12723 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: jafarinasab mr, khosravi b, esfandiari h, hooshmandi s, hassanpour k. a modified formula for intraocular lens power calculation based on aphakic refraction in a pediatric population. j ophthalmic vis res 2023;18:34–40. 34 © 2023 jafarinasab et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i1.12723&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr iol formula based on aphakic refraction; jafarinasab et al introduction intraocular lens (iol) power calculation remains a challenging issue in the pediatric population.[1] there are two methods of iol power calculation that are most commonly used in aphakic children including the use of either biometric formulas or refractive vergence formulas. anatomical measurements including axial length (al) and keratometry (k) are used in the biometric method formulas such as sanders–retzlaff–kraff (srk-t),[2] holladay ii,[3] or hoffer-q.[4] in aphakic refraction (ar)-based formulas, ar is applied to measure the power of the iol.[5] the data of al and k are not always available. ar could be used either preoperatively orintraand postoperatively, for both primary and secondary iol calculations in adults and children. when using this ar method of measurement intraoperatively for primary iol implantation, the anterior chamber should be formed after performing the lensectomy to refract the aphakic eye using either a portable auto refractometer or retinoscopy. the spherical equivalent (se) could then be placed in the formula without further need of the al and k measurements. currently, there are several available ar-based formulas including the hug,[6] khan,[7] ianchulev,[8] and leccissotti[9] formulas. in khan’s formula, al is calculated based on the ar, and k is assumed to be 44.[7] ianchulev et al[8] have introduced a formula that does not include al and k measurements compared favorably with the biometric iol power calculation. subsequently, leccissotti used aphakic se in a personal formula for high myopic patients as well as in the ianchulev formula for low myopic patients and reported a parabolic relationship between the se and iol power.[9] wong et al[10] investigated the accuracy of the iaunchulev and leccissotti formulas in 182 eyes of adult patients undergoing cataract surgery. the authors found that the ianchulev formula could be applied in all eyes except in those experiencing high myopia while the leccissotti formula worked particularly poorly in short eyes but performed better in eyes with myopia. in recent years, intraoperative wavefront aberrometry with optiwave refrctive analyzer (ora) system has shown comparable postoperative refractive outcomes when compared to conventional biometry (iol master) in adult patients who underwent routine cataract surgery. however, its use in the pediatric population is yet to be determined.[11] the application of refractive vergence formulas in the pediatric population remains a controversial issue. abdel-aziz et al[12] compared khan’s and hug’s formulas with the holladay i formula and found a 0.8 d reduction in the accuracy of the refractive vergence formula. similarly, nakhli et al reported better performance with the al vergence formula compared to the refractive vergence formula.[13] the current study is designed to investigate the accuracy of two refractive vergence formulas in secondary iol calculations in children as well as the clinical outcomes when modifying the ar formulas to determine more accurate predictive results. methods thirty-three aphakic eyes of 18 patients who were candidates of secondary iol implantation aged 4.5–14 years were all enrolled in this comparative case-series between october 2013 and september 2019. the exclusion criterion was a cornea that was too hazy for refraction. the study protocol was approved by the ethics committee of shahid beheshti university of medical sciences. the study adhered to the tenets of the declaration of helsinki and written informed consent was obtained from the legal guardians of the patients. biometric formulas all measurements before and after the operations were performed by an optometrist experienced in working with the pediatric population. al and keratometry were measured using optical biometry (lenstar ls 900, haag-streit ag, switzerland). to calculate secondary iol power, srkt[2] was used in eyes with al measuring >22 mm and hofferq[4] was the formula of choice in eyes with al measuring <22 mm. the patient’s age was used to determine the target refraction. target refraction was set for emmetropia in children older than six and 1 d of hyperopia in children younger than six years old. refractive vergence formulas an experienced pediatric ophthalmologist (bk) measured the ar with the use of an autorefractor journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 35 iol formula based on aphakic refraction; jafarinasab et al (nikon instruments inc., melville, new york, usa) or retinoscope (welch allyn suresight, welch allyn, skaneateles falls, new york). the mean of four se autorefraction measurements was used in the refractive vergence formulas of lanchulev and lescilloti. surgical technique all surgeries were performed by an experienced pediatric cataract surgeon (mrj). under general anesthesia, the main wound was created with a 2.8 mm keratome and intracameral diluted adrenaline (1/1000) was used for pupillary dilation. an ophthalmic viscoelastic device (ovd) was used to form the anterior chamber and release the synechiae. a three-piece foldable acrylic iol (acrysof ma60, alcon laboratories) was placed in the ciliary sulcus followed by irrigation and removal of the ovd. the wound was sutured with a 10-0 nylon (nylon, ethicon inc., somerville, nj) suture. subconjunctival betamethasone and cefazolin were injected upon the conclusion of the surgery. topical ciprofloxacin 0.3% (ciplex, sina daru, tehran, iran) was used four times per day for one week while betamethasone 0.1% (betasonate, sinadaru, tehran, iran) eye drops were used four times per day and tapered off over a month. patients were followed on day one, week one, month one, and month three postoperatively. the refraction was measured at the third-month followup visit. statistical analysis frequency and percentages were used to report the descriptive data. postoperative refraction was used to estimate the “actual” iol power; regarding postoperative se, the iol power that would cause emmetropia was calculated for each subject. this value was considered as “true” iol power. for each diopter of myopia, 1 d was reduced from the actual calculated iol power. similarly, for each diopter of hyperopia, 1.5 d were added to the actual calculated iol power. the mean (mean absolute error [mae]) and median (medae) of the difference between true iol power and calculated iol powers were then calculated for each formula. all statistical analyses were performed using spss (ibm). a p-value < 0.05 was considered significant. results thirty-three eyes of 18 patients were included in this study. median age of the patients was 8.7 ± 2.9 years ranging from 5 to 13.5 years. average al was 23.3 ± 1.8 mm ranging from 18.5 to 26.6 mm. al was >24 in 13 eyes (39.3.5 %), between 22 and 24 mm in 14 eyes (45.4%), and <22 mm in 6 eyes (18.8%) [table 1]. biometric formulas the mean preoperative se was +13.2 d (range, +8.0 to +20) that improved to –0.9 d (range, – 3.00 to +4.00) postoperatively. considering the multiple measurements of al, the mean se was –0.8, –0.98, and +0.62 d in als >24, between 22 and 24, and <22 mm, respectively. the medae and mae were –0.9 ± 2 and –1.1, respectively [table 2]. figure 1 demonstrates the postoperative se plotted against the preoperative se in each patient. refractive vergence formula theoretically, if the ianchulev formula was used to assess the refractive vergence, all eyes except one would reflect myopic refraction. the mean postoperative se would be –4.5 ± 2.6 d while one eye would have +1.50 d of hyperopic refraction. in eyes with al >24 mm, the mean se would have been –3.75 d (range, –1.0 to –6.0 d). the mean se would be –5.50 (range, –10.0 to +1.50) in al <24 mm. similarly, if the leccissotti formula was utilized, it would have resulted in an average se of –11.0 (range, –1.50 to –20.0) in al <24 and –4.85 (range, –4.85 to 8.50 d) in al >24 mm [tables 2 & 3]. with the use of the ianchulev formula, medae and mae would be 4.5 and 4.4 d, respectively. the corresponding values for the leccissotti formula were 8.7 and 7.3 d, respectively [figure 2]. modified formula with the step-by-step reduction of the coefficient of the ianchulev formula from 2.01 to 1.70, the mean se improved to –0.5 ± 2 (median –0.5, range from –4 to 5.4) d. twenty-two (66%) eyes would reflect myopic results, while 11 (34%) would reflect hyperopic refraction [table 2 & figures 1 & 2]. medae and mae were 0.5 and 0.5, respectively 36 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 iol formula based on aphakic refraction; jafarinasab et al table 1. baseline characteristics of study participants. parameter mean ± sd median (range) age (yr) 8.7 ± 2.9 8.0 (5.0 to 13.50) al 23.3 ± 1.8 23.5 (18.5 to 26.6) preoperative sphere 13.8 ± 3.2 13.3 (8.0 to 20.0) preoperative cylinder –1.0 ± 1.0 –1.0 (–3.3 to 0.8) preoperative se 13.2 ± 3.2 12.3 (8.0 to 20.0) postoperative sphere 0.1 ± 2.0 –0.3 (–3.0 to 6.0) postoperative cylinder –1.6 ± 1.0 –1.5 (–4.3 to 0.8) postoperative se –0.9 ± 2.0 –1.1 (–4.0 to 4.5) al, axial length; se, spherical equivalent; yr, years table 2. mean and median of calculated iol power with different formulas. parameter mean median (q1, q3) min max true power* 22.0 ± 5.4 19.4 (18.0, 26.3) 13.8 33.0 biometric formulas 22.8 ± 4.9 21.5 (19.5, 28.0) 15.0 32.0 postoperative se –0.9 ± 2.0 –1.1 (–1.9, –0.3) –4.0 4.5 leccissotti formula 30.7 ± 10.7 26.5 (23.0. 39.5) 15.9 54.6 error –8.7 ± 6.0 –7.3 (–11.7, –4.8) –21.6 –1.5 ianchulev formula 26.4 ± 6.7 24.1 (21.6, 32.3) 16.1 40.2 error –4.5 ± 2.6 –4.4 (–6.4, –3.1) –10.1 1.5 modified formula 22.5 ± 5.2 20.9 (19.3, 26.9) 14.1 33.3 error –0.5 ± 2.0 –0.5 (–1.8, 0.6) –4.0 5.4 iol, intraocular lens; q1, first quartile; q3, third quartile table 3. comparison between iol power calculated with different formulas subtracted from the true power. statistics used – true leccissotti – true ianchulev – true modified – true pearson correlation 0.931 0.931 0.931 0.932 icc 0.926 0.751 0.908 0.931 δ mean ± sd (diopter) –0.9 ± 2 –8.7 ± 6 –4.5 ± 2.6 –0.5 ± 2 95% ci –1.58 to –0.22 –10.73 to –6.67 –5.39 to –3.61 –1.17 to 0.17 p-value* <0.001 <0.001 <0.001 0.116 δ median (range) –1.1 (–4 to 4.5) –7.3 (–21.6 to 2.3) –4.4 (–10.1 to 2.2) –0.5 (–4 to 5.4) 95% loa –4.82 to 3.02 –20.46 to 3.06 –9.6 to 0.6 –4.42 to 3.42 *based on paired t-test true indicates the calculated power based on postoperative refraction correlation of eyes was considered in the calculation of sd, 95% ci, and loa iol, intraocular lens; icc, intra cluster correlation; δ, inter-formula difference; ci, confidence interval; loa, limits of agreement journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 37 iol formula based on aphakic refraction; jafarinasab et al figure 1. box and whisker plot demonstrating calculated iol powers (a) and the error using different formulas (b). error is based on the difference between true power (correct bar in a) and calculated powers using different formulas. figure 2. scatter plots demonstrating postoperative spherical equivalent (se) (a), the error of different formulas plotted against the calculated power based on the modified formula (b), ianchulev (c), and leccissotti (d). table 4 demonstrates the ranges of achieved refractions with the use of different formulas. discussion the refractive vergence formulas that use ar instead of al and keratometry could be used in assessing iol power calculations for aphakic children. iol power calculation in an eye that is still growing is a challenging process. recent advances in technologies resulted in more reliable al, and keratometry measurements improved the ability in predicting more accurate iol power and subsequent better visual outcome in pediatric cataract surgery. in this study, we have investigated the use of two refractive vergence 38 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 iol formula based on aphakic refraction; jafarinasab et al table 4. achieved refraction with the use of different formulae. achieved se (d) used formula ianchulev formula leccissotti formula modified formula within ± 0.5 6 (18.2 %) 0 (0%) 0 (0%) 7 (21.2 %) within ±1 13 (39.4 %) 2 (6.1%) 0 (0%) 19 (57.6 %) within ±2 22 (66.7 %) 4 (12.1%) 2 (6.1%) 27 (81.8 %) –2< se or se > +2 33 (100%) 33 (100 %) 33 (100%) 33 (100 %) se, spherical equivalent; d, diopter formulas in comparison to conventional formulas. in this series of 33 eyes, we demonstrated that refractive vergence formulas would result in reflecting significant myopic refraction, while the conventional formulas resulted in reflecting favorable refraction within ±0.5 d from the target refraction. furthermore, postoperative myopic refractive error was higher in eyes with shorter al. in high myopic patients, the leccissotti formula was slightly closer to target refraction than the ianchulev formula when calculated preoperatively. our findings are in line with previous studies on this subject, nakhli et al[13] compared the axial vergence formulas such as hoffer-q, srkt, and holladay with the refractive vergence formulas as presented by ianchulev, khan, and mackool in 31 pediatric cataract eyes. the authors reported more accurate results to target refraction with the preoperative axial vergence formulas when compared with the true iol calculations postoperatively. the amount of error was predicted to be –5.48 ± 3.55 diopters with the use of the ianchulev formula, which is comparable to the predictive error calculation of 4.5 ± 2.6 d observed in our study. our study differs from khan and al gaeed’s study in which al was estimated from the ar through the use of a complicated formula.[7] they used the estimated al as well as 44.0 as a constant keratometry value in the holladay formula. results of their comparison confirmed the comparable accuracy of the ar pre-calculation of al with the pre-calculated al using the holladay formula in 50 eyes where both formulas resulted in values that were close to the “true” iop power calculation postoperatively.[7] in nakhli et al’s study, khan’s method resulted in more accurate prediction as compared to the ianchulev formula (–1.66 ± 3.19 vs –5.48 ± 3.55 d).[13] due to the inability to retrieve accurate measurements for al and the limitation of using a constant to represent keratometry, we did not use this formula in our study. in another study comparing hug’s and khan’s refractive vergence formulas, the mean error was greater by 0.8 as compared to the standard biometric methods. the mean predicted error was 2.4 ± 2.0 with both khan’s and hug’s formulas as compared to –4.5 ± 2.6 d and –8.7 ± 6.0 in the ianchulev and leccissotti formulas, respectively.[12] notably, the betweenstudy comparison of predicted errors is biased due to differences in population, measurement, and surgical techniques. therefore, the results should be interpreted with caution. considering the significant myopic surprise with the ianchulev formula, we modified the current coefficient of the formula from 2.01 to 1.70. iol power calculation with the new coefficient proved to be comparable with the biometric formula. our modified coefficient is close to a coefficient proposed by mackool et al.[14] mackool et al suggested the following formula in determining the iol power in patients with post-lasik cataract extraction: iol power = 1.75 * ar (se). accurate biometry could be difficult in patients with a history of refractive surgery. the small difference between the mackool coefficient and ours could be attributed to the position of the iol. in our study, all the iols were placed into the sulcus in contrast to the bag implantation in mackool’s study. there are several limitations to our study including an assessment on a small population of patients which may affect the results and also precludes a valuable analysis of the hypothetical prediction of postoperative refractions with the use of refractive vergence formulas. in summary, the present study confirmed the superiority of the use of conventional biometric journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 39 iol formula based on aphakic refraction; jafarinasab et al formulas in the secondary iol power calculation in aphakic children. however, since the biometric measurements are not always available in aphakic children, the presence of a comparable refractive vergence formula is critical. we found that the use of aphakic se multiplied by our modified coefficient of 1.7 would result in favorable clinical outcomes in aphakic children aged between 4.5 and 14 years. to determine a more accurate prediction of error, the use of this formula in conjunction with testing on an expanded population in the real world is recommended. financial support and sponsorship none. conflicts of interest none. references 1. koch cr, kara-junior n, serra a, morales m. longterm results of secondary intraocular lens implantation in children under 30 months of age. eye 2018;32:1858–1863. 2. sanders dr, retzlaff ja, kraff mc, gimbel hv, raanan mg. comparison of the srk/t formula and other theoretical and regression formulas. j cataract refract surg 1990;16:341–346. 3. hoffer kj. clinical results using the holladay 2 intraocular lens power formula. j cataract refract surg 2000;26:1233–1237. 4. hoffer kj. the hoffer q formula: a comparison of theoretic and regression formulas. j cataract refract surg 1993;19:700–712. 5. sanders dr, retzlaff j, kraff mc. comparison of empirically derived and theoretical aphakic refraction formulas. arch ophthalmol 1983;101:965–967. 6. hug t. use of the aphakic refraction in intraocular lens (iol) power calculations for secondary iols in pediatric patients. am j ophthalmol 2005;139:585. 7. khan ao, algaeed a. paediatric secondary intraocular lens estimation from the aphakic refraction alone: comparison with a standard biometric technique. br j ophthalmol 2006;90:1458–1460. 8. ianchulev t, hoffer kj, yoo sh, chang df, breen m, padrick t, et al. intraoperative refractive biometry for predicting intraocular lens power calculation after prior myopic refractive surgery. ophthalmology 2014;121:56– 60. 9. leccisotti a. intraocular lens calculation by intraoperative autorefraction in myopic eyes. graefes arch clin exp ophthalmol 2008;246:729. 10. wong acm, mak st, tse rkk. clinical evaluation of the intraoperative refraction technique for intraocular lens power calculation. ophthalmology 2010;117:711–716. 11. zhang z, thomas lw, leu s-y, carter s, garg s. refractive outcomes of intraoperative wavefront aberrometry versus optical biometry alone for intraocular lens power calculation. indian j ophthalmol 2017;65:813. 12. abdel-hafez g, trivedi rh, wilson me, bandyopadhyay d. comparison of aphakic refraction formulas for secondary in-the-bag intraocular lens power estimation in children. j aapos 2011;15:432–434. 13. nakhli fr, emarah k, jeddawi l. accuracy of formulae for secondary intraocular lens power calculations in pediatric aphakia. j curr ophthalmol 2017;29:199–203. 14. mackool rj, ko w, mackool r. intraocular lens power calculation after laser in situ keratomileusis: aphakic refraction technique. j cataract refract surg 2006;32:435–437. 40 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 erratum erratum: long-term visual and refractive outcomes of argon laser-treated retinopathy of prematurity majid farvardin1,2, md; zahra kalantari1,2, md; mohammadreza talebnejad1,2, md; marzieh alamolhoda2, phd; amir norouzpour3, md j ophthalmic vis res 2022; 17 (4): 609–610 in the article titled “long-term visual and refractive outcomes of argonlaser-treated retinopathy of prematurity” published on pages 384–389, volume 17, issue 3 of journal of ophthalmic and vision research,[1] table 2 and figure 1 were missing in the full-text pdf and html of the article. the online version of the article has therefore been updated on november 24, 2022 and can be accessed from https://knepublishing.com/index.php/jovr/article/view/11576. table 2. visual, structural, and refractive outcomes of the four groups. variables laser-treated rop (group i) (n = 12) spontaneouslyregressed rop (group ii) (n = 93) no rop (group iii) (n = 37) control (group iv) (n = 143) p value corrected distance va, logmar (mean ± sd) od 0.09 ± 0.29 0.02 ± 0.14 0.00 ± 0.00 0.01 ± 0.05 0.04* os 0.00 ± 0.00 0.01 ± 0.06 0.00 ± 0.00 0.01 ± 0.05 0.14* macular dragging or scar od no, n (%) 10 (83.3) 92 (98.9) 37 (100) 142 (99.3) 0.01∧∧ yes, n (%) 2 (16.7) 1 (1.1) 0 (0) 1 (0.7) os no, n (%) 11 (91.7) 92 (98.9) 37 (100) 142 (99.3) 0.24∧∧ yes, n (%) 1 (8.3) 1 (1.1) 0 (0) 1 (0.7) strabismus, n (%) no (< 8 pd) 9 (75) 87 (93.5) 36 (97.3) 135 (94.4) 0.04∧ yes (≥ 8 pd) 3 (25) 6 (6.5) 1 (2.7) 8 (5.6) cylindrical power (d) (mean ± sd) od –1.06 ± 0.32 –0.77 ± 0.50 –0.80 ± 0.66 –0.70 ± 0.87 0.001* os –0.79 ± 0.44 –0.77 ± 0.56 –0.84 ± 0.77 –0.65 ± 0.79 0.004* spherical equivalent (d) (mean ± sd) od 0.24 ± 1.95 0.92 ± 1.04 1.04 ± 0.65 0.21 ± 1.64 <0.001* os 0.94 ± 1.07 0.86 ± 1.28 1.08 ± 0.77 0.27 ± 1.61 <0.001* od myopia (≤ -1 d), n (%) 2 (16.7) 1 (1.1) 0 (0) 15 (11) non-myopia (>-1 d), n (%) 10 (83.3) 92 (98.9) 37 (100) 121 (89)+ os myopia (≤ -1 d), n (%) 1 (8.3) 1 (1.1) 0 (0) 10 (7.4) non-myopia (>-1 d), n (%) 11 (91.7) 92 (98.9) 37 (100) 126 (92.6)+ © 2022 farvardin et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 609 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i4.12352&domain=pdf&date_stamp=2019-07-17 erratum; farvardin et al table 2. (continued). variables laser-treated rop (group i) (n = 12) spontaneouslyregressed rop (group ii) (n = 93) no rop (group iii) (n = 37) control (group iv) (n = 143) p value anisometropia, ≥ 1.5 d, n (%) 3 (25) 2 (2.2) 1 (2.7) 6 (4.4) 0.03∧∧ < 1.5 d, n (%) 9 (75) 91 (97.8) 36 (97.3) 130 (95.6)+ sd, standard deviation; logmar, the logarithm of the minimum angle of resolution; va, visual acuity; od, right eye; os, left eye; pd, prism diopter; d, diopter *kruskal–wallis; ∧chi-square; ∧∧fisher’s exact test; +missing data figure 1. ocular biometric parameters among the four groups for the right (od) and left (os) eyes. i–iv indicate groups 1 through 4. the first four plots (a–d) are boxplots analyzed using kruskal–wallis test, and the last two plots (e–f) were analyzed using anova. brackets with an asterisk (*) represent significant differences (p < 0.05). d, diopter; mm, millimeter; ac depth, anterior chamber depth; sem, standard error of mean. references 1. farvardin m, kalantari z, talebnejad m, alamolhoda m, norouzpour a. long-term visual and refractive outcomes of argon laser-treated retinopathy of prematurity. j ophthalmic vis res 2022;17:384–389. 610 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 original article ziv-aflibercept in diabetic macular edema: relation of subfoveal choroidal thickness with visual and anatomical outcomes siamak moradian1, md; masoud soheilian2, md; mahsan asadi3, md; abdolreza baghi3, md; hamid safi3, md seyed-hossein abtahi3, md 1ophthalmic epidemiology research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2ocular tissue engineering research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 3ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran orcid: siamak moradian: https://orcid.org/0000-0002-5328-7565 abstract purpose: to evaluate the effects of intravitreal ziv-aflibercept injections (ivz) on subfoveal choroidal thickness (sct) as well as on central macular thickness (cmt) and on best corrected visual acuity (bcva) changes in eyes with center-involved diabetic macular edema (ci-dme). methods: fifty-seven eyes of 36 patients with ci-dme were included in this prospective interventional case series. structural optical coherence tomography (oct) and enhanced depth imaging oct were performed at baseline followed by three monthly 1.25 mg ivz injections. changes of sct, cmt, and bcva at each follow-up session were assessed. the association between baseline sct and its monthly changes with final visual and anatomical outcomes were also assessed. results: cmt at baseline, and at the first, second, and third month follow-up sessions were 396 ± 119, 344 ± 115, 305 ± 89, and 296 ± 101 μm, respectively (p-value < 0.001). sct at baseline, and at months one, two, and three were 236 ± 47, 245 ± 56, 254 ± 54, and 241 ± 54 μm, respectively (pvalue > 0.99). corresponding figures for bcva were 0.58 ± 0.29, 0.47 ± 0.31, 0.4 ± 0.24, and 0.37 ± 0.23 logmar, respectively (p-value < 0.001). there was a statistically significant positive correlation between bcva and cmt changes following ivz injections (p-value < 0.001). however, there were no significant correlations between sct changes and visual acuity (va) and cmt changes following ivz injections. conclusion: ivz improved visual outcomes and macular thickness profiles in patients with ci-dme. however, ivz had no significant effect on sct. baseline sct and its monthly changes had no association with visual and anatomical outcomes. keywords: center-involved diabetic macular edema; central macular thickness; intravitreal; subfoveal choroidal thickness; ziv-aflibercept j ophthalmic vis res 2023; 18 (2): 164–169 correspondence to: siamak moradian, md. department of ophthalmology, labbafinejad medical center, shahid beheshti university of medical sciences, paidarfard st., boostan 9 st., pasdaran ave., tehran 16666, iran. email: moradian33195@yahoo.com received: 25-10-2021 accepted: 30-08-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i2.13182 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: moradian s, soheilian m, asadi m, baghi a, safi h, abtahi s-h. ziv-aflibercept in diabetic macular edema: relation of subfoveal choroidal thickness with visual and anatomical outcomes . j ophthalmic vis res 2023;18:164–169. 164 © 2023 moradian et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i2.13182&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr ziv-aflibercept for dme ; moradian et al introduction diabetic macular edema (dme) is the main cause of vision loss in diabetic patients.[1, 2]. the use of anti-vascular endothelial growth factors (antivegfs) is currently the main therapeutic choice for dme.[3] ziv-aflibercept (zaltrap, sanofi-aventis us, llc, bridgewater, new jersey, usa and regeneron pharmaceuticals, inc, tarrytown, new york, usa) is an fda-approved drug for treatment of colorectal and metastatic cancers. as an analogue of aflibercept, ziv-aflibercept is a monoclonal antibody that binds to vegf a and b of various isoforms and placental growth factor, which also possesses a good safety profile and is of lower cost.[4, 5] there is a growing body of evidence that intravitreal ziv-aflibercept (ivz) improves visual outcomes and macular thickness profiles in patients with dme.[6–11] however, the changes of choroidal thickness in eyes with dme treated with ivz and the effects of subfoveal choroidal thickness (sct) on visual and anatomical outcomes remain unknown. subfoveal choroidal thickness measurement performed by enhanced depth optical coherence tomography (edi-oct) in dme cases treated with anti-vegfs has been proposed as a predictor of therapeutic outcomes.[12] however, the correlation between baseline sct and treatment responses in patients with dme remains controversial.[3, 13, 14] thinning of sct might aggravate retinal hypoxia and accentuate vegf secretion resulting in increased breakdown of the blood retinal barrier (brb) and consequent dme deterioration.[15, 16] therefore, the association of sct with visual and anatomical outcomes should be elucidated. in this study, we investigated the effects of ivz on sct as well as on central macular thickness (cmt) and on best corrected visual acuity (bcva) changes in eyes with center-involved diabetic macular edema (ci-dme). a possible correlation between sct changes and visual and anatomical outcomes of dme cases treated with ivz is questioned. methods in this prospective interventional case series, cases of ci-dme were enrolled for intravitreal pharmacotherapy at labbafinejad medical center, tehran, iran between april 2019 and april 2020. the study protocol was reviewed and approved by the ethics committee, ophthalmic research center, shahid beheshti university of medical sciences, tehran, iran, and the approval number was ir.sbmu.orc.rec.1394.05. in addition, the protocol of the study complied with the guidelines for human studies and the tenets of declaration of helsinki. informed consent was obtained from all participants. based on the standard protocols, all patients underwent three monthly ivz injections (1.25 mg/0.05 ml).[17] complete ocular examinations, spectralis edi-oct (heidelberg engineering, heidelberg, germany), and sd oct were performed at baseline and repeated one month after each ivz injection. all visits and imaging procedures took place between 9 am and 12 am. bcva was evaluated using the snellen chart. cmt was assessed based on previously described oct software methodology (the 1mm early treatment diabetic retinopathy study (etdrs) circle centered on the fovea).[18] sct was measured manually as the distance between the rpe hyperreflective line and the chorio-scleral junction. only patients with cmts of >250 µm and bcva readings between 20/40 and 20/320 were included. patients with proliferative diabetic retinopathy (pdr), concomitant macular disease, a history of intravitreal injections of anti-vegfs or corticosteroids or retinal photocoagulation within three months of enrollment, a history of pars plana vitrectomy, refractive errors higher than ±5 diopters, a history of cardiovascular accidents, glaucoma, pregnancy, and uncontrolled systemic hypertension were excluded. statistical analysis data were presented using mean, standard deviation, median and range, frequency, and percentage. paired t-test was used to assess the improvement within the groups and t-test was used to evaluate the difference among the groups. minimal sample size needed for all variables was calculated as ≥45 individuals (g*power software [latest ver. 3.1.9.7; heinrich-heineuniversität düsseldorf, düsseldorf, germany]) to achieve a certain power (effect size dz = 0.5; α error probability = 0.05; power [1-β error probability] = 0.95). we also used generalized estimating equations (gee) to consider the possible journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 165 ziv-aflibercept for dme ; moradian et al correlation of the results in the eyes. correlation of variables was assessed using pearson’s correlation coefficient. all statistical analyses were performed using the spss (ibm corp. released 2017. ibm spss statistics for windows, version 25.0. armonk, ny: ibm corp.). p-value < 0.05 was considered statistically significant. results fifty-seven eyes of 36 patients with ci-dme were included in this prospective interventional case series. during the study period, no patient missed follow-up sessions or required further treatments (e.g., laser photocoagulation, vitrectomy) and no complications related to ivz were recorded in patients (signs of intraocular inflammation, change in the lens status, and systemic complications). past medical history and ocular examination findings were summarized in table 1. cmt decreased progressively through ivz monthly injections. a marginally significant decrease was recorded at the one month follow-up (p = 0.057); however, compared to the baseline a significant decrease was recorded after the second and third months. progressive bcva improvement was also observed after monthly ivz injections. significant changes were recorded after the second and third months as compared to the baseline. no significant changes in sct were observed after monthly ivz injections as compared to baseline [table 2]. at each follow-up interval, the level of improvement of bcva was correlated with the amount of cmt reduction. however, sct did not correlate with changes in bcva and cmt at follow-up visits [table 3]. discussion ziv-aflibercept (zaltrap) is a monoclonal antibody approved for the treatment of metastatic colorectal cancer. like its analogue, aflibercept, zivaflibercept blocks all isoforms of vegf a, b, and placental growth factor (plgf). while zivaflibercept (zaltrap) has higher osmolarity than aflibercept, studies showed no difference between the two drugs in the safety profile. malick et al compared the toxicity of aflibercept, zivaflibercept, bevacizumab, and ranibizumab on rpe cells in media culture. they observed mild mitochondrial toxicity following bevacizumab and ziv-aflibercept injections.[19] in an experimental study, 0.05 ml ivz had no deleterious effect on the osmolarity of the vitreous.[20] mansour et al showed the effect of ivz in patients with dme without any intraocular toxicity.[9] chhablani et al demonstrated the effect of ivz injection on patients with neovascular amd with no intraocular toxicity or retinal electrophysiological abnormalities.[21] additionally, no significant adverse effects related to ivz were detected, at least in a short-term follow-up. however, long-term adverse effects of ivz remains unknown. variable results have been reported regarding choroidal thickness changes in patients with dme.[14, 15, 22] there are reports of reduced choroidal thickness in these patients, which may be the consequence of choroidal vascular obstruction and development of non-perfusion areas similar to retinal vascular alterations.[15, 22] a histopathological study revealed thinning and attenuation of the choriocapillaris layer with subsequent reduction of choroidal thickness in diabetic retinopathy.[14] meanwhile, some studies showed increase of choroidal thickness in patients with dme. vegf overexpression causes dilation and congestion of choroidal vessels that result in thicker choroid in patients with dme. therefore, anti-vegfs for dme treatment could theoretically reduce the permeability and thickness of choroidal layers. however, no significant association was found between anti-vegf therapy and choroidal thickness changes in patients with ci-dme. the effect of anti-vegf treatment on choroidal thickness in dme has already been evaluated.[3, 12–14, 23–25] several studies reported reduction of choroidal thickness following intravitreal injection of bevacizumab (ivb).[3, 12, 23] rayess et al revealed that thicker baseline sct was associated with better anatomic and functional responses. they suggested baseline sct as a predictor of dme treatment response to ivb.[12] yiu et al reported no correlation between sct reduction and changes in visual acuity (va) and macular thickness.[3] in a clinical trial, no significant changes were observed in choroidal thickness following ivb injection in dme.[24] recently, it has been shown that intravitreal aflibercept had more effect on sct in dme as compared to intravitreal ranibizumab.[25] despite previous investigations using various forms of anti-vegfs, the effect of ivz on choroidal 166 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 ziv-aflibercept for dme ; moradian et al table 1. baseline characteristics and demographic features. n (%) eye od 30 (52.6%) os 27 (47.4%) lens status pseudophakic 20 (35.1%) phakic 37 (64.9%) history of mpc no 31 (54.4%) yes 26 (45.6%) history of injection no 28 (49.1%) yes 29 (50.9%) naïve no 36 (63.2%) yes 21 (36.8%) age mean ± sd 63.3 ± 5.93 number of injection mean ± sd 3.93 ± 1.03 duration of diabetes (yr) mean ± sd 12.37 ± 4.23 mpc, macular photocoagulation; od, right eye; os, left eye; sd, standard deviation table 2. best-corrected visual acuity, central macular thickness, subfoveal choroidal thickness before and at one, two, and three months after monthly injection of intravitreal ziv-aflibercept. baseline month 1 month 2 month 3 values values changes p-value values changes p-value values changes p-value bcva 0.58 ± 0.29 0.47 ± 0.31 –0.15 ± 0.22 0.202 0.4 ± 0.24 –0.19 ± 0.26 0.002 0.37 ± 0.23 –0.22 ± 0.27 <0.001 cmt 396 ± 119 344 ± 115 –52 ± 123 0.057 305 ± 89 –91 ± 132 <0.001 296 ± 101 –102 ± 144 <0.001 sfct 236 ± 47 245 ± 56 9 ± 55 >0.99 254 ± 54 18 ± 55 0.197 241 ± 54 7 ± 61 >0.99 p-value calculated using paired t-test bcva, best-corrected visual acuity; cmt, central macular thickness; sfct, subfoveal choroidal thickness table 3. correlation between central macular thickness changes, best corrected visual acuity changes, and subfoveal choroidal thickness changes at one, two, and three months after monthly injection of intravitreal ziv-aflibercept. time cmt and bcva sfct and cmt sfct and bcva month 1 pearson correlation 0.436** 0.186 –0.025 p-value 0.002 0.165 0.864 month 2 pearson correlation 0.446** 0.006 0.028 p-value 0.001 0.966 0.845 month 3 pearson correlation 0.456** 0.104 0.047 p-value 0.001 0.453 0.743 **correlation is significant at the 0.01 level (2-tailed) bcva, best-corrected visual acuity; cmt, central macular thickness; sfct, subfoveal choroidal thickness journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 167 ziv-aflibercept for dme ; moradian et al thickness in dme has not been evaluated so far. in our study, sct did not significantly change after ivz injection in patients with ci-dme. in addition, despite adequate sample size and statistical power of the analysis, we observed no correlation between sct and changes of cmt and bcva after ivz injections. it might be related to different receptor density and sensitivity of retinal and choroidal vasculature to vegf. it is believed that choroidal thickness reduction in dme may be related to factors other than vegf. hence, vegf may not be the sole contributor to choroidal thickness changes in dr.[26] there were few limitations in the current study. it lacked a contralateral eye comparison. the absence of correlation between ivz and changes in choroidal thickness might be related to the short follow-up time of the study. in addition, we did not compare the effect of ivz with other forms of anti-vegfs. sct changes might not represent the changes of the entire choroidal tissue. a more detailed assessment of the choroidal vascular index and stromal area could be a better way to assess the choroidal structure changes in response to intravitreal anti-vegf injections. in summary, ivz is a promising form of anti-vegf drug used to improve visual and anatomical outcomes in patients with ci-dme without significant short-term toxicity. the visual and anatomical effects of ivz on dme are not correlated with any changes in sct. financial support and sponsorship none. conflicts of interest none of the authors have any conflicts of interest to declare. references 1. moss se, klein r, klein be. the 14-year incidence of visual loss in a diabetic population. ophthalmology 1998;105:998–1003. 2. klein r, klein be, moss se, cruickshanks kj. the wisconsin epidemiologic study of diabetic retinopathy. xiv. ten-year incidence and progression of diabetic retinopathy. arch ophthalmol 1994;112:1217–1228. 3. yiu g, manjunath v, chiu sj, farsiu s, mahmoud th. effect of anti-vascular endothelial growth factor therapy on choroidal thickness in diabetic macular edema. am j ophthalmol 2014;158:745–751. 4. singh sr, stewart mw, chattannavar g, ashraf m, souka a, eldardeery m, et al. safety of 5914 intravitreal zivaflibercept injections. br j ophthalmol 2019;103:805–810. 5. mansour am, stewart mw, farah me, mansour ha, chhablani j. ziv-aflibercept: a cost-effective, off-label, highly potent antagonist of vascular endothelial growth factor. acta ophthalmol 2020;98:e540–e548. 6. hodjatjalali k, mehravaran s, faghihi h, hashemi h, kazemi p, rastad h. intravitreal injection of ziv-aflibercept in the treatment of choroidal and retinal vascular diseases. j curr ophthalmol 2017;29:228–231. 7. jabbarpoor bonyadi mh, baghi a, ramezani a, yaseri m, soheilian m. one-year results of a trial comparing 2 doses of intravitreal ziv-aflibercept versus bevacizumab for treatment of diabetic macular edema. ophthalmol retina 2018;2:428–440. 8. baghi a, jabbarpoor bonyadi mh, ramezani a, azarmina m, moradian s, dehghan mh, et al. two doses of intravitreal ziv-aflibercept versus bevacizumab in treatment of diabetic macular edema: a three-armed, double-blind randomized trial. ophthalmol retina 2017;1:103–110. 9. mansour am, dedhia c, chhablani j. three-month outcome of intravitreal ziv-aflibercept in eyes with diabetic macular oedema. br j ophthalmol 2017;101:166–169. 10. de andrade gc, de oliveira dias jr, maia a, farah me, meyer ch, rodrigues eb. intravitreal ziv-aflibercept for diabetic macular edema: 48-week outcomes. ophthalmic surg lasers imaging retina 2018;49:245–250. 11. ashraf m, kayal he, souka aar. safety and efficacy of ziv-aflibercept in the treatment of refractory diabetic macular edema. ophthalmic surg lasers imaging retina 2017;48:399–405. 12. rayess n, rahimy e, ying gs, bagheri n, ho ac, regillo cd, et al. baseline choroidal thickness as a predictor for response to anti-vascular endothelial growth factor therapy in diabetic macular edema. am j ophthalmol 2015;159:85-91.e1–e3. 13. bagheri n, rayess n, rahimy e, juhn a, hsu j. initial choroidal thickness and response to treatment in diabetic macular edema. invest ophthalmol vis sci 2014;55:1747. 14. cao j, mcleod ds, merges ca, lutty ga. choriocapillaris degeneration and related pathologic changes in human diabetic eyes. arch ophthalmol 1998;116:589–597. 15. querques g, lattanzio r, querques l, del turco c, forte r, pierro l, et al. enhanced depth imaging optical coherence tomography in type 2 diabetes. invest ophthalmol vis sci 2012;53:6017–6024. 16. adamis ap, miller jw, bernal mt, d’amico dj, folkman j, yeo tk, et al. increased vascular endothelial growth factor levels in the vitreous of eyes with proliferative diabetic retinopathy. am j ophthalmol 1994;118:445–450. 17. de oliveira dias jr, xavier co, maia a, de moraes ns, meyer c, farah me, et al. intravitreal injection of zivaflibercept in patient with refractory age-related macular degeneration. ophthalmic surg lasers imaging retina 2015;46:91–94. 18. grading diabetic retinopathy from stereoscopic color fundus photographs–an extension of the modified airlie house classification. etdrs report number 10. early treatment diabetic retinopathy study research group. ophthalmology 1991;98:786–806. 168 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 ziv-aflibercept for dme ; moradian et al 19. malik d, tarek m, caceres del carpio j, ramirez c, boyer d, kenney mc, et al. safety profiles of anti-vegf drugs: bevacizumab, ranibizumab, aflibercept and ziv-aflibercept on human retinal pigment epithelium cells in culture. br j ophthalmol 2014;98:i11–i16. 20. de oliveira dias jr, badaró e, novais ea, colicchio d, chiarantin gm, matioli mm, et al. preclinical investigations of intravitreal ziv-aflibercept. ophthalmic surg lasers imaging retina 2014;45:577–584. 21. chhablani j, narayanan r, mathai a, yogi r, stewart m. short-term safety profile of intravitreal ziv-aflibercept. retina 2016;36:1126–1131. 22. eliwa tf, hegazy os, mahmoud ss, almaamon t. choroidal thickness change in patients with diabetic macular edema. ophthalmic surg lasers imaging retina 2017;48:970–977. 23. lee sh, kim j, chung h, kim hc. changes of choroidal thickness after treatment for diabetic retinopathy. curr eye res 2014;39:736–744. 24. tatsumi t, oshitari t, baba t, takatsuna y, yamamoto s. effects of switching from anti-vegf treatment to triamcinolone acetonide in eyes with refractory macular edema associated with diabetic retinopathy or retinal vein occlusion. biomed res int 2020;2020:4529850. 25. sarda v, eymard p, hrarat l, fajnkuchen f, giocantiaurégan a. comparison of the effect of ranibizumab and aflibercept on changes in macular choroidal thickness in patients treated for diabetic macular edema. j ophthalmol 2020;5708354. 26. sohn hj, han dh, kim it, oh ik, kim kh, lee dy, et al. changes in aqueous concentrations of various cytokines after intravitreal triamcinolone versus bevacizumab for diabetic macular edema. am j ophthalmol 2011;152:686– 694. journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 169 original article incidence and risk factors for retinopathy of prematurity at a rural tertiary hospital in thailand mantapond ittarat1, md; supakorn chansaengpetch2, md; sunee chansangpetch3, md 1surin hospital and school of ophthalmology, suranaree university of technology, surin, thailand 2queen savang vadhana memorial hospital, chonburi, thailand 3center of excellence in glaucoma, faculty of medicine, chulalongkorn university and king chulalongkorn memorial hospital, thai red cross society, bangkok, thailand orcid: mantapond ittarat: https://orcid.org/0000-0001-8177-1234 sunee chansangpetch: https://orcid.org/0000-0002-8996-2868 abstract purpose: to estimate the incidence and identify the factors affecting retinopathy of prematurity (rop) in a rural tertiary hospital in thailand. methods: this retrospective chart review included all infants screened for rop. the study included all infants with gestational age (ga) ≤ 30 weeks or birth weight (bw) ≤ 1,500 gr or selected larger infants with an unstable clinical course. retinal findings were classified according to the revised international classification of rop. data were analyzed using univariate and multivariable logistic regression analyses. results: of the 113 screened infants, the incidences of any rop and rop requiring intervention were 17.7% and 8.8%, respectively. in univariate analysis, lower ga, lighter bw, total days of supplemental oxygen, days of continuous positive airway pressure (cpap), presence of apnea, and intraventricular hemorrhage (ivh) were associated with the development of any rop. in the stepwise multivariable logistic regression analysis, lighter bw, male gender, and bronchopulmonary dysplasia (bpd) were significant risk factors for the development of any rop. lower ga and being either a twin or triplet were significant risk factors for rop requiring intervention. however, no antenatal condition was identified as a risk factor for rop. conclusion: the incidence of rop in rural tertiary hospitals was relatively high as compared with previously published data from urban tertiary hospitals. lighter bw, male gender, and bpd were significantly associated with the development of rop in a local context. epidemiological studies are necessary to prevent ophthalmic morbidities. keywords: incidence; retinopathy of prematurity; risk-factors; thailand j ophthalmic vis res 2023; 18 (1): 81–87 correspondence to: mantapond ittarat, md. surin hospital and school of ophthalmology, suranaree university of technology, 68 lak muaeng road, muaeng, surin 32000, thailand. e-mail: mantapornittarat@gmail.com received: 04-08-2021 accepted: 01-08-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i1.12728 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: ittarat m, chansaengpetch s, chansangpetch s. incidence and risk factors for retinopathy of prematurity at a rural tertiary hospital in thailand . j ophthalmic vis res 2023;18:81–87. © 2023 ittarat et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 81 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i1.12728&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr rop in thailand; ittarat et al introduction retinopathy of prematurity (rop) is one of the leading causes of childhood preventable blindness worldwide. globally, it was estimated that 184,700 infants developed rop in 2010.[1] subsequently 20,000 became blind or suffered from severe visual impairment, which could have been avoided with timely screening and interventions for rop.[1, 2] many nations are now addressing rop as one of the major public health concerns.[3] various factors have demonstrated to be associated with the development of rop, some of which also influence its severity. gestational age (ga), birth weight (bw), and use of supplemental oxygen showed the strongest association with rop.[4, 5] other neonatal comorbidities such as respiratory distress syndrome (rds), bronchopulmonary dysplasia (bpd), intraventricular hemorrhage (ivh), and necrotizing enterocolitis are also well recognized as relevant risk factors for rop development.[5–7] recent advances in neonatal care have improved the survival rate of premature infants, leading to an increase in the incidence of rop.[3, 8, 9] however, the current situation in developing and asian countries, including thailand, is now considered an epidemic.[2, 3] the incidence of rop in any stage varies among different countries. even in the same country, the incidence and risk factors of rop differ from region to region, as there are differences in regional ethnicities and characteristics of antenatal and neonatal care between urban and rural areas. according to an urban tertiary hospital in bangkok, 40.7% of premature infants who underwent screening examinations during 2006–2009 developed rop.[10] worse, epidemiological data on rop in thailand are still lacking, particularly in rural areas; very few studies on rop have been published in the past decade. pinpointing our study to a regional context can provide key information for the further identification and investigation of more specific factors for rop. therefore, this study aimed to estimate the incidence of rop and identify potential risk factors for rop in a rural tertiary hospital in thailand. methods this study was a retrospective chart review conducted at surin hospital, northeastern thailand. surin hospitals are rural tertiary care hospitals that provide neonatal intensive care units with qualified neonatologists. this study was performed by reviewing the charts of consecutive patients who underwent screening examinations for rop between october 2019 and september 2020. ethical review approval was obtained from the institutional review board of surin hospital on march 2021 (irb no. 06/2564). this study was conducted in accordance with the principles of the declaration of helsinki. all charts were reviewed by the primary author and no personal data of the patients were disclosed. the study included all infants who met one of the following criteria: ga ≤ 30 weeks or bw ≤ 1,500 gr; ga > 30 weeks or bw > 1500 gr with an unstable clinical course and believed by their attending pediatrician or neonatologist to be at risk for rop. these inclusion criteria followed the recommendations of the american academy of pediatrics, american academy of ophthalmology, and american association for pediatric ophthalmology and strabismus.[11] patients lost to follow-up before the screening date were excluded. all examinations were performed by qualified ophthalmologists using binocular indirect ophthalmoscopy. infants underwent a screening examination at four weeks postnatal age or a corrected ga of 31 weeks, whichever occurred later. retinal findings and rop stages were recorded according to the revised international classification of retinopathy of prematurity.[12] the intervals of subsequent examinations were determined by the examining ophthalmologist in accordance with the severity of the findings. interventions were performed when rop reached type-1 pre-threshold disease or a diagnosis of aggressive posterior retinopathy of prematurity (aprop) was noted. the primary outcome was to estimate the incidence of any stage of rop (stages i–v) and rop requiring intervention. the identification of risk factors for the development of any rop and rop requiring intervention was the secondary outcome. the variables collected were as follows: (1) demographic information: sex, bw, and multiple gestations (twins or triplets). (2) antenatal factors: ga, maternal age, number of gestations, inadequate number of antenatal care (anc) visits (less than four visits), maternal diabetes mellitus, premature rupture of membranes, and severe preeclampsia. 82 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 rop in thailand; ittarat et al table 1. univariable analysis – risk factors for rop. no rop any rop p-value𝑎 rop requiring intervention p-value𝑏 n = 93 n = 20 n = 10 gender: male 45 (48.4) 14 (70.0) 0.079∗ 8 (80.0) 0.065* birth weight (gr) 1656.1 (500.9) 1294 (246.8) 0.002† 1287 (227.2) 0.037* twin/triplet 0.067∗ 0.001x twin 15 (16.1) 4 (20.0) 4 (40.0) 2 (20.0) triplet 1 (1.1) 2 (10.0) antenatal factors gestational age (wk) 32.2 (2.9) 30 (3.2) 0.002† 28.7 (1.3) 0.004 maternal age (yr) 25.4 (7.1) 27.5 (7.9) 0.103† 28.7 (8.7) 0.266† number of gestations 2 (1 to 3) 1 (1 to 2) 0.912‡ 1 (1 to 4) 0.780‡ inadequate number of anc visits 2 (2.3) 1 (5.9) 0.446x 1 (14.3) 0.192x maternal diabetes mellitus 4 (4.7) 1 (5.9) 1.000x 0 (0.0) 1.000x premature rupture of membranes 8 (9.3) 1 (5.9) 1.000x 0 (0.0) 1.000x severe preeclampsia 4 (4.7) 0 (0.0) 1.000x 0 (0.0) 1.000x neonatal factors 1-min apgar score 7.2 (2.4) 6.6 (3.0) 0.382† 7.1 (1.7) 0.953† 5-min apgar score 8.8 (2.0) 8.4 (2.8) 0.502† 9.4 (1.3) 0.277† 10-min apgar score 9.4 (1.5) 9.1 (1.9) 0.432† 9.8 (0.4) 0.292† apnea 11 (11.8) 7 (35.0) 0.012x 4 (40.0) 0.041x hypoglycemia 22 (23.7) 5 (25.0) 0.766∗ 2 (20.0) 1.000x sepsis 41 (44.1) 11 (55.0) 0.228∗ 7 (70.0) 0.085x hypothermia 8 (8.6) 2 (10.0) 0.672x 0 (0.0) 1.000x osteopenia of prematurity 4 (4.3) 2 (10.0) 0.261x 1 (10.0) 0.414x hypotension 5 (5.4) 1 (5.0) 1.000x 0 (0.0) 1.000x thrombocytopenia 3 (3.2) 1 (5.0) 0.523x 0 (0.0) 1.000x respiratory distress syndrome 38 (40.9) 10 (50.0) 0.299∗ 5 (50.0) 0.507* bronchopulmonary dysplasia 3 (3.2) 3 (15.0) 0.057∗ 1 (10.0) 0.414x necrotizing enterocolitis 18 (19.4) 2 (10.0) 0.516∗ 1 (10.0) 1.000x intraventricular hemorrhage 8 (8.6) 5 (25.0) 0.029x 2 (20.0) 0.214x heart disease (including pda) 23 (24.7) 5 (25.0) 0.844∗ 1 (10.0) 0.441x hematocrit level 40.5 (6.3) 38.2 (7.3) 0.164† 35.1 (4.2) 0.015† days of total oxygen (days) 6 (2 to 17) 14.5 (6 to 33.5) 0.045‡ 11.5 (8 to 23) 0.313‡ days of mechanical ventilation (days) 2 (0 to 7) 4 (5 to 8) 0.343‡ 3 (1 to 6) 0.930‡ days of cpap (days) 1 (0 to 3) 2 (1 to 5.5) 0.021‡ 2 (1 to 4) 0.207‡ use of surfactant 15 (16.1) 3 (15.0) 1.000x 2 (20.0) 0.789x rop, retinopathy of prematurity; pda, patent ducts arteriosus. 𝑎comparison between no rop and any rop; 𝑏comparison between rop requiring intervention and others (no intervention). ∗data shown as n (%); p-value was obtained from chi-squared test; †data shown as mean (sd); p-value was obtained from t-test; ‡data shown as median (iqr); p-value was obtained from mann–whitney u test; xdata shown as n (%); p-value was obtained from fisher’s exact test. journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 83 rop in thailand; ittarat et al figure 1. schematic diagram of study recruitment. rop, retinopathy of prematurity. table 2. stepwise multivariable logistic regression – risk factors for any rop. odds ratio 95% ci p-value birth weight 0.997 0.994–0.999 0.005* gender: male 4.907 1.079–22.325 0.040* bronchopulmonary dysplasia 17.047 1.453–199.946 0.024* rop, retinopathy of prematurity; ci, confidence interval ∗statistically significant. (3) neonatal factors: apgar scores at 1, 5, and 10 min, apnea of prematurity, hypoglycemia, neonatal sepsis (culture-positive or antibiotic administration for more than seven days), hypothermia, osteopenia of prematurity, hypotension, thrombocytopenia, rds, bpd, necrotizing enterocolitis, ivh, heart disease including patent ductus arteriosus, hematocrit level (on the date of discharge), use of surfactant, total days of oxygen therapy, days of mechanical ventilation, and days of continuous positive airway pressure (cpap). statistical analysis all analyses were performed using stata 13.0 (statacorp, college station, tx, usa). in the antenatal factor analysis, only one participant with multiple pregnancies was randomly selected to eliminate duplication of the data. univariable comparisons of risk factors between the groups were analyzed. for variables with univariable p-value < 0.2, forward stepwise multivariable logistic regression was then used to establish the association between risk factors and the development of any rop and rop requiring intervention. the significance level for adding a variable was set as 0.05. demographic, antenatal, and neonatal factors were explored using a stepwise model. regression analysis was performed to define associations. odds ratios (ors) and 95% confidence intervals (cis) were also calculated. continuous variables are shown as means with standard deviations (sd) or medians with interquartile ranges. categorical variables were presented as counts and percentages. 84 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 rop in thailand; ittarat et al table 3. stepwise multivariable logistic regression – risk factors for rop that required intervention. odds ratio 95% ci p-value ga 0.552 0.366–0.830 0.004* twin/triplet 10.530 1.629–68.058 0.013* rop, retinopathy of prematurity; ga, gestational age; ci, confidence interval. ∗statistically significant. continuous data were analyzed using the ttest or mann–whitney u test depending on the distribution of data. categorical data were analyzed using the chi-squared test or fisher’s exact test, as appropriate. for all tests, a p-value < 0.05 was considered statistically significant. results during the study period, 119 infants met the criteria for the rop examination. of the 119 infants, 40 (33.6%) had a ga of 30 weeks or below, and 53 (44.5%) had a bw of 1500 gr or below. thirtythree infants (27.7%) had a ga ≤ 30 weeks and bw ≤ 1500 gr. a total of 59 infants (49.6%) had a ga > 30 weeks and bw > 1500 gr. these infants underwent rop screening because of an unstable clinical course, including rds in 18 infants, pneumonia in 16 infants, and sepsis in 25 infants. of these, six patients were lost to follow-up before the date of screening; thus, they were excluded. subsequently, 113 participants underwent rop screening and were included in the present study [figure 1]. of the no rop-diagnosed infants, subsequent examinations were performed every 4 weeks until a postmenstrual age of at least 45 weeks, averaging 3.5 examinations. of the ropdiagnosed infants, subsequent examinations were performed every 2 weeks until a postmenstrual age of at least 54 weeks and were examined until total regression of rop was observed, which averaged approximately 12.3 examinations. the incidence rate of rop was 17.7% (20/113). of the rop-diagnosed patients, 40% (8/20), 10% (2/20), 15% (3/20), and 5% (1/20) developed stages 1, 2, 3, and 4 rop, respectively, and 30% (6/20) had aprop. none of them developed stage 5 rop. meanwhile, the incidence of rop requiring intervention was 8.8% (10/113) among all infants undergoing the examination and 50% (10/20) of known patients with rop. all patients with rop who required intervention achieved satisfactory anatomical outcomes after treatment. table 1 shows the results of the univariate analysis. infants with any stage of rop had significantly lower ga, lighter bw, higher incidence of ivh, higher incidence of apnea, longer duration of total supplemental oxygen, and longer duration of cpap than infants without rop. the mean ga and bw of infants with rop were 30 ± 3.2 weeks and 1294 ± 246.8 gr, respectively. while the mean ga and the mean bw of infants without rop were 32.2 ± 2.9 weeks and 1656.1 ± 500.9 gr, respectively. using stepwise multivariable logistic regression [table 2], the following were significant risk factors for rop development: lighter bw (or 0.997, 95% ci 0.994–0.999, p = 0.005), male gender (or 4.907, 95% ci 1.079–22.325, p = 0.040), and bpd (or 17.047, 95% ci 1.453–199.946, p = 0.024). lower ga (or 0.552, 95% ci 0.366– 0.830, p = 0.004) and being a twin/triplet (or 10.530, 95% ci 1.629–68.058, p = 0.013) were significant risk factors for the development of rop requiring intervention as shown in the multivariable logistic regression analysis [table 3]. no antenatal factor was identified as a predictor or risk factor of rop development. discussion the incidence of rop at any stage varies among countries, with reported figures ranging from 18.5% to 47%.[3, 8, 9] this was comparable to the result of hong kong’s study (any rop incidence of 18.5%).[9] in thailand, there are few published studies on the incidence of rop. a large study from an urban tertiary hospital in bangkok revealed that the incidence of rop during the last decade (2006–2009) was 40.7%; among these, 72% required intervention.[10] more recently, in 2020, a study conducted by another urban tertiary hospital showed that the incidence of rop and rop requiring intervention was 10% and 3%, journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 85 rop in thailand; ittarat et al respectively.[13] the current incidence of rop reported by rural tertiary hospitals ranges from 20.1 to 31.7%, and that of rop requiring intervention is 10.8%.[14, 15] it signifies that the incidence of rop varies considerably among local literature and this may be a reflection of the modification of rop screening criteria and the improvement of antenatal and neonatal cares over the past decade. additionally, evidence shows that the incidence of rop is higher in rural than in urban tertiary hospitals. the differences in specific risk factors, particularly the characteristics of neonatal care, could play a role in the disparity in the rop incidence between these two areas. to the best of our knowledge, lower ga and lighter bw are widely regarded as the major risk factors for rop development.[5] our univariable analysis showed that infants with any stage of rop had significantly lower ga and lighter bw than those without rop; however, only lighter bw was statistically significant in the multivariable logistic regression model. similarly, a recent korean nationwide population-based study demonstrated that the incidence of rop (317.14 per 1000 newborns) and the rate of visual impairment (4.5 per 100 person-years) were the highest among very low bw infants.[16] moreover, lower ga was the significant risk factor for both rop and rop requiring intervention, in stepwise analysis. this finding is consistent with the results of most studies.[4, 17–19] male gender was the other risk factor for any rop development in this study. yang et al also found a similar relationship in their analysis.[20] one possible explanation is male vulnerability. it has been described that morbidity and mortality are frequently reported to be higher in male gender than female gender in early life.[21] bpd was one of the important risk factors for any stage of rop in this study. our result was in line with two previous local studies.[13, 15] gebeşçe et al, holmström et al, and wu et al also found a similar relationship in multivariable analysis.[22–24] furthermore, singh and colleagues revealed the association between moderate-tosevere bpd and severe rop.[6] interestingly, it has been proposed that both bpd and rop may share common molecular mechanisms predisposing to dysregulation of angiogenesis.[25] being a twin or triplet was significantly correlated with the development of rop requiring intervention in our study; however, this condition was not associated with any rop development. likewise, port and colleagues identified multiple gestations as a risk factor for treatment requiring rop.[26] there is evidence that twins could exist in placental-sharing nutrition and blood supply situations, which may reduce bw discordance.[27] it is well-known that the proportion of infants with extremely low bw is greater in twins than in singletons.[28] the extreme low bw has been frequently identified as a major risk factor for rop requiring intervention.[8] the present study has some limitations that should be considered. this was a single-center retrospective study. further multicenter studies with larger sample sizes are still needed to provide generalizable epidemiological data on rop in thailand. in summary, the incidence of rop at any stage and rop requiring intervention was 17.7% and 8.8%, respectively, at a rural tertiary hospital in thailand. lighter bw, male gender, and bpd were significant risk factors for the development of any rop. lower ga and being a twin or triplet were other relevant conditions affecting rop requiring intervention. as the survival rates of preterm infants are increasing annually, investigation of the incidence of rop and its risk factors is critical for identifying potential hotspots for rop and establishing a screening protocol to prevent ophthalmic morbidities. guidelines must be updated in a local context, and further epidemiological studies are imperative. financial support and sponsorship the authors did not receive support from any organization for the submitted work. conflicts of interest the authors have no relevant financial or nonfinancial interests to disclose. references 1. blencowe h, lawn je, vazquez t, fielder a, gilbert c. preterm-associated visual impairment and estimates of retinopathy of prematurity at regional and global levels for 2010. pediatr res 2013;74:35–49. 2. adams ggw. rop in asia. eye 2020;34:607–608. 3. bowe t, nyamai l, ademola-popoola d, amphornphruet a, anzures r, cernichiaro-espinosa la, et al. the current 86 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 rop in thailand; ittarat et al state of retinopathy of prematurity in india, kenya, mexico, nigeria, philippines, romania, thailand, and venezuela. digit j ophthalmol 2019;25:49–58. 4. bas ay, demirel n, koc e, ulubas isik d, hirfanoglu i̇m, tunc t. incidence, risk factors and severity of retinopathy of prematurity in turkey (tr-rop study): a prospective, multicentre study in 69 neonatal intensive care units. br j ophthalmol 2018;102:1711–1716. 5. kim sj, port ad, swan r, campbell jp, chan rvp, chiang mf. retinopathy of prematurity: a review of risk factors and their clinical significance. surv ophthalmol 2018;63:618– 637. 6. singh jk, wymore em, wagner bd, thevarajah ts, jung jl, kinsella jp, et al. relationship between severe bronchopulmonary dysplasia and severe retinopathy of prematurity in premature newborns. j aapos 2019;23:209.e1–.e4. 7. watts p, adams gg, thomas rm, bunce c. intraventricular haemorrhage and stage 3 retinopathy of prematurity. br j ophthalmol 2000;84:596–599. 8. shah va, yeo cl, ling yl, ho ly. incidence, risk factors of retinopathy of prematurity among very low birth weight infants in singapore. ann acad med singap 2005;34:169– 178. 9. yau gs, lee jw, tam vt, liu cc, yip s, cheng e, et al. incidence and risk factors of retinopathy of prematurity from 2 neonatal intensive care units in a hong kong chinese population. asia pac j ophthalmol 2016;5:185– 191. 10. thitiratsanont u, supangkasen i, wutthiworavong b. screening for retinopathy of prematurity in queen sirikit nation institute of child health: bangkok, thailand. thai j ophthalmol 2011;25:9–16. 11. fierson wm; american academy of pediatrics section on ophthalmology; american academy of ophthalmology; american association for pediatric ophthalmology and strabismus; american association of certified orthoptists. screening examination of premature infants for retinopathy of prematurity. pediatrics 2018;142:e20183061. 12. the international classification of retinopathy of prematurity revisited. arch ophthalmol 2005;123:991– 999. 13. poovichayasumlit c. retinopathy of prematurity at thammasat university hospital. thammasat med j 2020;20:297–306. 14. paopongsawan p, jirapradittha j, kiatchoosakun p, wongwai p. retinopathy of prematurity in 5 neonatal units at the 7th health district of thailand. j med assoc thai 2018;101:1263–1267. 15. saleewan k. incidence and risk factors of retinopathy of prematurity (rop). med j srisaket surin buriram hosp 2016;31:99–110. 16. na kh, kim kh, kang tu, hann hj, ahn hs, kim hj. incidence, long-term visual outcomes, and mortality in retinopathy of prematurity in korea: a nationwide population-based study. invest ophthalmol vis sci 2020;61:14. 17. araz-ersan b n, kir, akarcay k, aydinoglu-candan o, sahinoglu-keskek n, demirel a, et al. epidemiological analysis of retinopathy of prematurity in a referral centre in turkey. br j ophthalmol 2013;97:15–17. 18. ying gs, bell ef, donohue p, tomlinson la, binenbaum g. perinatal risk factors for the retinopathy of prematurity in postnatal growth and rop study. ophthalmic epidemiol 2019;26:270–278. 19. freitas am, mörschbächer r, thorell mr, rhoden el. incidence and risk factors for retinopathy of prematurity: a retrospective cohort study. int j retina vitreous 2018;4:20. 20. yang mb, donovan ef, wagge jr. race, gender, and clinical risk index for babies (crib) score as predictors of severe retinopathy of prematurity. j aapos 2006;10:253– 261. 21. wells jc. natural selection and sex differences in morbidity and mortality in early life. j theor biol 2000;202(1):65–76. 22. gebeşçe a, uslu h, keleş e, yildirim a, gürler b, yazgan h, et al. retinopathy of prematurity: incidence, risk factors, and evaluation of screening criteria. turk j med sci 2016;46:315–320. 23. holmström g, broberger u, thomassen p. neonatal risk factors for retinopathy of prematurity–a population-based study. acta ophthalmol scand 1998;76:204–207. 24. wu t, zhang l, tong y, qu y, xia b, mu d. retinopathy of prematurity among very low-birth-weight infants in china: incidence and perinatal risk factors. invest ophthalmol vis sci 2018;59:757–763. 25. stark a, dammann c, nielsen hc, volpe mv. a pathogenic relationship of bronchopulmonary dysplasia and retinopathy of prematurity? a review of angiogenic mediators in both diseases. front pediatr 2018;6:125. 26. port ad, chan rv, ostmo s, choi d, chiang mf. risk factors for retinopathy of prematurity: insights from outlier infants. graefes arch clin exp ophthalmol 2014;252(10):1669–1677. 27. lewi l, cannie m, blickstein i, jani j, huber a, hecher k, et al. placental sharing, birthweight discordance, and vascular anastomoses in monochorionic diamniotic twin placentas. am j obstet gynecol 2007;197:587.e1-8. 28. blondel b, kogan md, alexander gr, dattani n, kramer ms, macfarlane a, et al. the impact of the increasing number of multiple births on the rates of preterm birth and low birthweight: an international study. am j public health 2002;92:1323–1330. journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 87 original article changes in intraocular pressure with use of periocular triamcinolone cream diana h. kim1,2, md; sana a. bautista1,2, md; elana meer2, ms; brendan mcgeehan3, ms; maureen g. maguire3, phd; césar a. briceño1,2, md 1department of ophthalmology, scheie eye institute, university of pennsylvania, philadelphia, pa, usa 2perelman school of medicine, university of pennsylvania, philadelphia, pa, usa 3center for preventative ophthalmology and biostatistics, university of pennsylvania, philadelphia, pa, usa orcid: diana h. kim: https://orcid.org/0000-0002-3232-8989 césar a. briceño: https://orcid.org/0000-0001-5301-0630 abstract purpose: to evaluate the effect of periocular topical triamcinolone cream on intraocular pressure. methods: a retrospective chart review identified 57 patients, 114 eyes using triamcinolone cream (0.1%, 0.025%) with subsequent intraocular pressure (iop) checks at three follow-up visits. descriptive, univariate, and multivariate analyses were performed to assess effects of age, therapy duration, consecutive weeks on steroid, prescription strength, time of day, and method of measurement on iop levels. generalized estimating equations were used in regression models to account for correlation of eyes within subjects and across visits. results: we identified 57 patients using triamcinolone cream for allergic or eczematous dermatitis of the eyelid. prescription strengths were 0.025% or 0.1% and patients were followed for a median of 4.9 months. measurements of iop at baseline did not change as compared to all iop measurements at follow-ups and did not change with steroid strength. the mean change in iop at all follow-up visits was 0.07 mm hg (95% confidence interval [ci]: –0.36, 0.50). after adjustment for the method of tonometer and the patient’s age, the mean change was 0.03 mm hg (95% ci: –0.68, 0.73, p = 0.93). prescription strength and consecutive weeks of therapy were not associated with iop. two patients experienced a significant elevation in iop of >10 mm hg, one through the concomitant consequences of systemic corticosteroids usage and the other through prolonged topical application. conclusion: in patients taking periocular triamcinolone cream, there was no clinically meaningful change in mean iop between baseline and follow-up visits, and iop measurements were not related to variances in prescription strength or duration of therapy. keywords: glaucoma; intraocular pressure; ocular hypertension; periocular dermatitis; steroids; triamcinolone j ophthalmic vis res 2022; 17 (3): 368–375 368 © 2022 kim et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i3.11574&domain=pdf&date_stamp=2019-07-17 triamcinolone cream usage and iop ; kim et al introduction atopic dermatitis (ad) is a common, chronic relapsing inflammatory skin condition with increasing incidence in the past decades, especially in industrialized nations.[1] it affects up to 20% of children and 3% of adults worldwide[2] and is most commonly treated with topical corticosteroids. it is expected that with increasing incidence of ad, including in the eyelid, the use of topical periocular corticosteroids will also increase over time. prolonged use of local (ocular surface, subconjunctival, sub-tenon’s, retrobulbar) and systemic corticosteroids is associated with a rise in intraocular pressure (iop) and resultant glaucoma.[3–6] several mechanisms are thought to be responsible for this effect, including corticosteroids leading to an accumulation of polymerized glycosaminoglycans in the trabecular meshwork and increases in the trabecular meshwork’s cell size and shape, leading to increased aqueous humor outflow resistance.[7] steroid potency is thought to be correlated to their ocular hypertensive effect,[8] while the duration of use has also been shown to increase ocular hypertension.[9] in the eyelid, increased use of topical corticosteroids may be particularly problematic given their close proximity to the eye. despite the growing body of literature that suggests that iop can be elevated both in response to systemic and local corticosteroids, the effect of periocular steroids in particular is still relatively unknown. while multiple case reports have described iop elevation or glaucoma as a direct result of periocular corticosteroid use,[10–15] larger studies remain inconclusive. in a retrospective case control of 9793 patients, garbe et al showed that nasal glucocorticoids were not associated with intraocular hypertension.[16] correspondence to: césar a. briceño, md. scheie eye institute, penn presbyterian medical center, 51 n. 39th st., philadelphia, pa 19104, usa. e-mail: cesar.briceno@pennmedicine.upenn.edu received: 18-01-2021 accepted: 23-01-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i3.11574 a retrospective study performed by tamagawamineoka et al on 65 patients demonstrated no association between topical periocular corticosteroid use and iop, whereas a study performed by maeng et al on 31 patients demonstrated a positive correlation only in patients with baseline iop > 14 mm hg.[17, 18] the latter two studies were limited by their sample sizes, the use of multiple brands of topical corticosteroids, and differing applications of prescription strength or usage patterns. recognizing the limited evidence on periocular corticosteroids and iop, the aim of this retrospective chart review was to evaluate the effect of periocular topical triamcinolone cream 0.1% and 0.025%, a commonly used topical corticosteroid in ad, on iop. our study seeks to identify associations with and risk factors for iop elevation, elucidating the effect of a single corticosteroid with a defined use on iop in real world practice. methods a chart review was performed of all patients at the university of pennsylvania with ad of the eyelids treated with topical periocular triamcinolone creams 0.1% and 0.025% twice daily from january 2010 to february 2020. patients were identified through billing codes for allergic dermatitis of the eyelid and eczematous dermatitis of the eyelid. patients with a diagnosis of glaucoma or ocular hypertension prior to the initiation of treatment were not included. patients who were included were required to have a baseline iop prior to the initiation of treatment and at least one iop measurement after the initiation of treatment. demographic data including age, sex, triamcinolone dose, iop measurements, method of measurements, and time of measurements were recorded for baseline (pretreatment) and at follow-up visits for those patients who remained this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: kim dh, bautista sa, meer e, mcgeehan b, maguire mg, briceño ca. changes in intraocular pressure with use of periocular triamcinolone cream . j ophthalmic vis res 2022;17:368–375. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 369 https://knepublishing.com/index.php/jovr triamcinolone cream usage and iop ; kim et al table 1. patients’ baseline characteristics. overall (n = 57) age mean (sd) 56.5 (18.3) median (q1, q3) 61.0 (46.0, 68.0) range 19.0–88.0 sex female 44 (77.2%) male 13 (22.8%) strength 0.025% 42 (73.7%) 0.10% 15 (26.3%) duration of follow-up (months) mean (sd) 10.9 (14.8) median (q1, q3) 4.9 (2.1, 14.6) range 0.5–78.6 sd, standard deviation table 2. description of iop at each visit. baseline (n = 114) visit 1 (n = 114) visit 2 (n = 68) visit 3 (n = 42) all follow-up visits (n = 224) iop, mmhg mean (sd) 14.8 (2.9) 14.9 (3.6) 15.1 (3.5) 13.5 (2.9) 14.7 (3.5) median (q1, q3) 15.0 (13.0, 16.0) 14.0 (13.0, 17.0) 15.0 (12.0, 17.3) 14.0 (12.0, 15.0) 14.0 (12.0, 17.0) range 7.0–23.0 5.0–28.0 9.0–23.0 7.0–21.0 5.0–28.0 change in iop from baseline, mmhg mean (sd) not applicable 0.1 (3.4) 0.5 (3.4) –0.7 (3.0) 0.07 (3.3) median (q1, q3) not applicable 0.0 (–2.0, 2.0) 0.0 (-2.0, 3.0) –1.0 (–2.8, 0.0) 0.0 (–2.0, 2.0) range not applicable –7.0 – 16.0 –6.0 – 9.0 –6.0 – 11.0 –7.0 – 16.0 iop, intraocular pressure; sd, standard deviation; n, number on the corticosteroid treatment. univariate and multivariable regressions were performed using the aforementioned covariates. in the multivariable settings, corticosteroid use and prescription strength were the covariates of interest in two separate models. additional covariates were utilized in a backward selection procedure based on a p-value cutoff of p ≤ 0.05 for model inclusion. generalized estimating equation regression (gee regression) was used to analyze changes between baseline iop and iop at follow-up visits to account for inter-eye correlation and repeated measures. all analyses were performed using r version 3.5.1. this study was determined to be exempt from review by the university of pennsylvania institutional review board. this study complies with the tenets of the declaration of helsinki and health insurance portability and accountability act regulations. results fifty-seven patients were identified as having had both a baseline visit and at least one subsequent follow-up visit at which they were still on triamcinolone. the mean age was 56.5 years (18.3%) and 44 (77.2%) were female (77.2%) [table 1]. triamcinolone cream prescription strengths were 370 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 triamcinolone cream usage and iop ; kim et al table 3. description of iop by corticosteroid use and by corticosteroid strength. baseline (n = 114) after corticosteroid use (n = 224) total (n = 338) p-value iop, mmhg 0.81 mean (sd) 14.8 (2.9) 14.7 (3.5) 14.7 (3.3) median (q1, q3) 15.0 (13.0, 16.0) 14.0 (12.0, 17.0) 14.5 (12.0, 17.0) range 7.0–23.0 5.0–28.0 5.0–28.0 baseline (n = 114) 0.025% (n = 162) 0.10% (n = 62) total (n = 338) p-value iop, mmhg 0.91 mean (sd) 14.8 (2.9) 14.6 (3.4) 14.9 (3.6) 14.7 (3.3) median (q1, q3) 15.0 (13.0, 16.0) 14.0 (12.0, 16.0) 15.0 (13.0, 17.0) 14.5 (12.0, 17.0) range 7.0–23.0 6.0–28.0 5.0–23.0 5.0–28.0 iop, intraocular pressure; sd, standard deviation; n, number table 4. univariate regression analysis of the association of features and iop for all iop measurements. feature lower 95% confidence limit upper 95% confidence limit p-value difference in iop per unit change, mmhg age (yrs) –0.04 –0.07 0.00 0.05 consecutive weeks of usage 0.00 –0.09 0.10 0.93 time of day (24-hr clock) –0.17 –0.37 0.04 0.11 model mean iop, mmhg sex female 14.68 13.84 15.52 male 14.78 13.78 15.78 0.88 strength none 14.76 14.05 15.47 0.025% 14.58 13.69 15.47 0.69 0.10% 14.92 13.34 16.50 0.84 corticosteroid usage no 14.76 14.05 15.47 yes 14.67 13.89 15.46 0.81 method of measurement applanation 14.21 13.36 15.06 other 15.14 14.24 16.04 0.11 iop, intraocular pressure journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 371 triamcinolone cream usage and iop ; kim et al table 5. results of regression analysis for iop with corticosteroid use as covariate of interest. term estimate lower 95% ci upper 95% ci 𝑃-value intercept 16.38 14.06 18.71 <0.001 corticosteroid-yes 0.03 –0.68 0.73 0.928 age –0.04 –0.07 0.00 0.025 non-applanation measurement method 1.07 0.00 2.13 0.049 ci, confidence interval table 6. results of regression analysis for iop with corticosteroid strength as covariate of interest. term estimate lower 95% ci upper 95% ci 𝑃-value intercept 16.43 14.11 18.75 <0.001 strength 0.025% 0.08 –0.82 0.98 0.859 strength 0.10% –0.09 –1.55 1.37 0.908 age –0.04 –0.07 0.00 0.025 non-applanation measurement method 1.07 0.00 2.14 0.050 0.025% in 42 patients (73.7%) and 0.10% in 15 patients (26.3%). overall mean duration between baseline and any follow-up visit was approximately 10.9 months, with a median of 4.9 months. baseline analysis of the 114 eyes of 57 patients revealed a mean iop of 14.8 ± 2.9 mm hg (n = 114). a total of 57 patients (n = 114) were available for an initial follow-up (visit 1), 34 patients (n = 68) were available for a second follow-up (visit 2), and 21 patients (n = 42) were available for a third followup (visit 3). mean iops for visit 1, visit 2, and visit 3 were 14.9 ± 3.6 mm hg, 15.1 ± 3.5 mm hg, and 13.5 ± 2.9 mm hg, respectively [table 2]. the average time from baseline to visit 1, visit 2, and visit 3 was approximately 4.3 months, 9.4 months, and 17.7 months, respectively [supplemental table 1]. measurements of iop at baseline (n = 114, 14.8 mm hg, 95% ci: 14.1–15.5) did not change as compared to all iops at follow-ups (n = 224, 14.7 mm hg, 95% ci: 13.9–15.5, p = 0.81). estimated mean change was –0.1 mm hg (95% ci: –0.8 to 0.6). further, the mean differences in iop from baseline to visit 1, visit 2, and visit 3 were 0.1 ± 3.4 mm hg, 0.5 ± 3.4 mm hg, and –0.7 ± 3.0 mm hg, respectively. measurements of iop at baseline (n = 114, 14.8 mm hg, 95% ci: 14.1–15.5) also did not change at follow-ups based on triamcinolone strengths of 0.025% (n = 162, 14.58 mm hg, 95% ci: 13.7–15.5, p = 0.69) or 0.1% (n = 62, 14.92 mm hg, 95% ci: 13.3–16.5, p = 0.84). estimated mean difference for 0.025% was –0.2 mm hg (95% ci: – 1.1 to 0.7) and for 0.1% was 0.1 mm hg (95% ci: –1.3 to 1.6) [table 3]. only two patients (3.5%) and three eyes (2.6%) had a clinically meaningful iop change by 10 mm hg or more at any time point. one of the two patients who experienced this iop change was on concomitant maintenance oral prednisone for immune thrombocytopenia and exhibited this iop increase after 1.3 months of topical triamcinolone use. the second patient experienced iop elevation at 19 months of continued triamcinolone use. he was unable to be located for follow-up and remained on triamcinolone longer than was recommended. the distribution of time and method of measurement (applanation, icare, tono-pen) was similar for baseline and follow-up visits [supplemental table 2]. concordance in the method of iop measurement between baseline and subsequent visits was also described. at any visit, at least 50% of eyes were measured with the same method of iop measurement that was used for the baseline visit. from baseline to all visits, 25 (43.9%) patients had iop measured by the same method of tonometer [supplemental table 3]. in univariate analysis, a –0.04 mm hg in iop (95% ci: –0.7 to 0.00; p = 0.05) was estimated for every year of age. other variables including 372 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 triamcinolone cream usage and iop ; kim et al consecutive weeks of usage, time of day, sex, triamcinolone usage, triamcinolone strength, and method of measurement were not significantly associated with iop [table 4]. after backward variable selection, only age and the non-applanation method of measurement were retained as statistically significant features associated with iop. when iop changes from baseline were estimated for corticosteroid use and adjusted for these two factors, the mean change was 0.03 mm hg (95% ci: –0.68 to 0.73; p = 0.928) [table 5 & 6]. when iop change from baseline was estimated for each of the two concentrations of triamcinolone cream and adjusted for age and nonapplanation method of measurement, the mean change was 0.08 mm hg (95% ci: –0.82 to 0.98; p = 0.86) for 0.025% concentration and –0.09 mm hg (95% ci: –1.55 to 1.37; p = 0.908) for 0.10% concentration [tables 5 & 6]. older patients had lower iop by –0.04 mm hg per year (95% ci: –0.7 to 0.00; p = 0.025) in both models. non-applanation measurement methods increased iop by 1.07 mm hg (95% ci: 0.00–2.14, p=0.050) in both models. discussion our retrospective dataset demonstrates that the mean iop change in eyes of patients after use of triamcinolone cream 0.1% or 0.025% is near zero in those who have subsequent iop measurements at follow-ups. neither dose nor consecutive weeks of therapy were associated with iop increases, suggesting that cumulative dosing does not have an effect. in our multivariate analysis, only age and method of measurement correlated with changes in iop at follow-up visits. given that our patients were on average 56 years of age, the decrease of 0.04 mm hg in iop per one year of age is consistent with previous reports that iop decreases with age beyond the sixth decade.[19, 20] our finding that non-applanation measurements with either tonopen or icare elevate iop is also consistent with the literature.[21, 22] topical periocular corticosteroids are currently the treatment of choice for periocular inflammatory conditions such as ad. there is currently no consensus on the risk of iop elevations from periocular corticosteroid use, which may create uncertainty in providers who wish to initiate therapy. our study is reassuring in that it suggests that triamcinolone cream 0.1% and 0.025% may be safe over several months of corticosteroid use without statistically significant elevations in iop. taken together, our study corroborates previous reports that topical triamcinolone or topical corticosteroids are not associated with changes in iop.[17, 23] our results may help guide management for medical providers who may be reluctant to use corticosteroids, preferring alternatives such as calcineurin inhibitors which are associated with increased risk of other adverse effects such as local skin irritation, burning, and higher costs.[24] despite the results of our study, we identified two patients (one of whom was already taking concomitant oral steroids and another was on triamcinolone longer than was intended) with iop elevations that may be connected to using topical triamcinolone cream. while a causal relationship cannot be established, it follows that elevation in iop after triamcinolone use is certainly possible and further studies need to address exactly which patient populations are at highest risk. given the limited number of patients with an increase in iop after triamcinolone use, no subgroup analysis could be performed. thus, providers should still recognize that the risk of iop elevation from periocular triamcinolone still exists in those with concomitant systemic steroid or excessive, prolonged use. our study appears to be the largest analyses to date in assessing associations between a single corticosteroid used for a single diagnosis and iop outcomes. moreover, we study a patient population who receive corticosteroids in a single practice, reflecting the heterogeneous adherence to steroid applications and their intervals of follow-up. our study is limited by its retrospective nature and relatively small cohort of patients. iop outcomes are inherently influenced by diurnal circulation, method of tonometry, and style of examiner. we nevertheless showed that the time of the day and the method of tonometry did not differ [supplemental table 2], and that patients consistently received the same type of repeated iop measurement in >50% of visits [supplemental table 3]. our study was also limited by the single iop measurement done only at each visit. further evaluation and analysis of these variables that influence the outcomes of iop measurements in addition to the execution of repeat measurements at follow-up visits may help control for such variances. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 373 triamcinolone cream usage and iop ; kim et al as is typical in real world practices, the followup times in our study varied and resulted in a wide range of times between visits throughout the sample. the duration of follow-up when including all three visits from baseline was approximately an average of 10 months, while the duration from baseline to the first visit was an average of 4 months. while some patients had shorter follow-ups, our follow-up duration captured the prolonged window of time in which iop elevations can develop after steroid use, which is typically about one month.[3, 7, 25] there is also evidence that iop elevation may occur immediately after initiation of therapy as there is evidence that iop elevation may occur early if at all after intravitreal triamcinolone injections.[26] however, patients with shorter follow-ups did not exhibit differences in iop as compared to those with longer ones. patients with previous iop elevations from known corticosteroid use or those suffering with glaucoma were also excluded from our analysis.[7, 17] unfortunately, family history was not recorded in our review so it is possible that patients with undiagnosed glaucoma were included in our study. two patients in our evaluation as described above had clinically significant iop elevations. patients whose initial measurement of iop was >20 mmhg in either eye did not have clinically significant elevations in iop in our study. case reports also suggest that iop elevations may be more dramatic in younger patients, which is also reflected in follow-up measurements over many years.[10, 13, 14] our study patient population is much older. finally, as all corticosteroids are unequal in their properties, it is possible that corticosteroids other than triamcinolone that were not studied may be associated with iop elevations. triamcinolone, like many other topical corticosteroids, are prescribed often as needed and used with inconsistency that may confound results. in our study, the vast majority of patients were prescribed triamcinolone twice daily or to be used as needed. in summary, in our retrospective analysis of 114 eyes, we demonstrated that iop measurements do not change after the initiation of periocular triamcinolone cream, but varied ages and methods of measurement influence iop. during our evaluation an anomaly was discovered where two patients experienced clinically significant iop elevation, one through the concomitant consequences of systemic steroid use and the other from the excessive prolonged topical usage for 19 months, suggesting that these may serve as risk factors for elevated iop. it is recommended that patients with either systemic steroid use or excessively prolonged topical usage be more closely monitored. in our study, however, our results serve to reassure providers that topical triamcinolone can be safely prescribed without a significant effect on iop. ethics approval this study was determined to be exempt from review by the university of pennsylvania institutional review board. this study complies with the tenets of the declaration of helsinki and health insurance portability and accountability act regulations. financial support and sponsorship nil. conflicts of interest the authors declare that they have no conflict of interest. references 1. nutten s. atopic dermatitis: global epidemiology and risk factors. ann nutr metab 2015;66:8–16. 2. kanwar aj. adult-onset atopic dermatitis. indian j dermatol 2016;61:662–663. 3. kersey jp, broadway dc. corticosteroid-induced glaucoma: a review of the literature. eye 2006;20:407– 416. 4. bernstein hn, mills dw, becker b. steroid-induced elevation of intraocular pressure. arch ophthalmol 1963;70:15–18. 5. françois j. corticosteroid glaucoma. ophthalmologica 1984;188:76–81. 6. herschler j. increased intraocular pressure induced by repository corticosteroids. am j ophthalmol 1976;82:90– 93. 7. phulke s, kaushik s, kaur s, pandav ss. steroid-induced glaucoma: an avoidable irreversible blindness. j curr glaucoma pract 2017;11:67–72. 8. cantrill hl, palmberg pf, zink ha, waltman sr, podos sm, becker b. comparison of in vitro potency of corticosteroids with ability to raise intraocular pressure. am j ophthalmol 1975;79:1012–1017. 9. bernstein hn, schwartz b. effects of long-term systemic steroids on ocular pressure and tonographic values. arch ophthalmol 1962;68:742–753. 374 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 triamcinolone cream usage and iop ; kim et al 10. cubey rb. glaucoma following the application of corticosteroid to the skin of the eyelids. br j dermatol 1976;95:207–208. 11. garrott hm, walland mj. glaucoma from topical corticosteroids to the eyelids. clin exp ophthalmol 2004;32:224–226. 12. vie r. glaucoma and amaurosis associated with long-term application of topical corticosteroids to the eyelids. acta derm venereol 1980;60:541–542. 13. zugerman c, saunders d, levit f. glaucoma from topically applied steroids. arch dermatol 1976;112:1326. 14. aggarwal rk, potamitis t, chong nh, guarro m, shah p, kheterpal s. extensive visual loss with topical facial steroids. eye 1993;7:664–666. 15. sahni d, darley cr, hawk jl. glaucoma induced by periorbital topical steroid use—a rare complication. clin exp dermatol 2004;29:617–619. 16. garbe e, lelorier j, boivin jf, suissa f. inhaled and nasal glucocorticoids and the risk of ocular hypertension or open-angle glaucoma. am j rhinol 1997;11:247. 17. maeng mm, de moraes cg, winn bj, glass lr. effect of topical periocular steroid use on intraocular pressure: a retrospective analysis. ophthal plast reconstr surg 2019;35:465–468. 18. tamagawa-mineoka r, yasuoka n, ueta m, katoh n. influence of topical steroids on intraocular pressure in patients with atopic dermatitis. allergol int 2018;67:388– 391. 19. han x, niu y, guo x, hu y, yan w, he m. age-related changes of intraocular pressure in elderly people in southern china: lingtou eye cohort study. plos one 2016;11:e0151766. 20. wong tt, wong ty, foster pj, crowston jg, fong cw, aung t, et al. the relationship of intraocular pressure with age, systolic blood pressure, and central corneal thickness in an asian population. invest ophthalmol vis sci 2009;50:4097–4102. 21. onochie c, okoye o, ogunro a, aribaba t, hassan k, onakoya a. comparisons of the tono-pen® and goldmann applanation tonometer in the measurement of intraocular pressure of primary open angle glaucoma patients in a hospital population in southwest nigeria. med princ pract 2016;25:566–571. 22. ting sl, lim lt, ooi cy, rahman mm. comparison of icare rebound tonometer and perkins applanation tonometer in community eye screening. asia pac j ophthalmol 2019;8:229–232. 23. haeck im, rouwen tj, timmer-de mik l, de bruin-weller ms, bruijnzeel-koomen ca. topical corticosteroids in atopic dermatitis and the risk of glaucoma and cataracts. j am acad dermatol 2011;64:275–281. 24. gutfreund k, bienias w, szewczyk a, kaszuba a. topical calcineurin inhibitors in dermatology. part i: properties, method and effectiveness of drug use. postepy dermatol alergol 2013;30:165–169. 25. feroze kb, khazaeni l. steroid induced glaucoma. statpearls publishing; 2020. 26. jonas jb, kreissig i, degenring r. intraocular pressure after intravitreal injection of triamcinolone acetonide. br j ophthalmol 2003;87:24–27. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 375 case report retrocorneal scleral patch supported glue: a technique for management of corneal perforation and corneoscleral melt following pterygium surgery ashok sharma1, ms; rajan sharma1, ms; verinder s. nirankari2, md ashok sharma, ms. cornea centre, sco 2463 2464, sector 22c, chandigarh 160022, india orcid: ashok sharma: https://orcid.org/0000-0003-0169-7033 abstract purpose: to describe a new method of treatment of corneal perforation with extensive corneoscleral melt. case report: a 42-year-old man presented with moderate-sized (3.5 mm) corneal perforation with extensive corneo-limbo-scleral ulceration following bare sclera excision of pterygium. no prior use of antimetabolites or postoperative beta radiation noted. we considered retrocorneal sclera patch supported cyanoacrylate application. the sclera was thinned to one-third thickness and a patch (4.5×4.5 mm) was punched. the sclera patch was placed on the iris, behind the corneal perforation, adequately covering it from inside. a minimal amount of adhesive was applied on the retrocorneal sclera patch and margin of corneal perforation. the ulcerating sclera was covered with double layered amniotic membrane. topical antibiotic, steroid, and cycloplegic drops were instilled thrice daily. corneal perforation healed and no recurrence occurred during the 18 months’ follow-up. conclusion: retrocorneal scleral patch supported cyanoacrylate is effective for corneal perforation with corneo-scleral melt. keywords: corneal perforation; cyanoacrylate tissue adhesive; pterygium surgery; scleral necrosis; scleral patch j ophthalmic vis res 2023; 18 (1): 123–129 correspondence to: ashok sharma, ms. cornea centre, sco 2463 2464, sector 22c, chandigarh 160022, india. e-mail: asharmapgius@yahoo.com received: 01-11-2021 accepted: 15-02-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i1.12732 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: sharma a, sharma r, nirankari vs. retrocorneal scleral patch supported glue: a technique for management of corneal perforation and corneoscleral melt following pterygium surgery . j ophthalmic vis res 2023;18:123– 129. © 2023 sharma et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 123 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i1.12732&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr retrocorneal scleral patch supported glue; sharma et al introduction pterygium excision with conjunctival autograft, pterygium excision with amniotic membrane graft, and pterygium excision with combined conjunctival autograft and amniotic membrane graft have been advocated for primary or recurrent pterygium.[1] the bare sclera technique, although technically simple and easy, is associated with a high incidence of recurrence (62%) and is no longer favored.[2] pterygium excision with conjunctival autograft is the preferred treatment modality for primary pterygium. scleral necrosis has been reported following the bare sclera excision technique and the use of beta radiation and antimetabolites (thiotepa and mitomycin c) in the postoperative period.[2, 3] cases of scleral necrosis following the bare sclera technique without the use of beta radiation and antimetabolites have also been reported.[3] corneal ulceration may be treated with amniotic membrane graft, deep anterior lamellar keratoplasty, or therapeutic penetrating keratoplasty.[4] scleral ulceration may be treated with amniotic membrane graft, conjunctival autograft, tenon’s capsule graft, and scleral graft.[5] moderate corneal perforation, extensive corneo-limbo-scleral melt is an extremely rare complication of pterygium surgery and poses a management challenge. in the presence of the extensive corneo-limbo-scleral ulceration, deep anterior lamellar keratoplasty or therapeutic penetrating keratoplasty could not be considered. application of cyanoacrylate tissue adhesive alone also was not feasible, as perforation was large. we report such a case successfully managed with retrocorneal sclera patch augmented cyanoacrylate tissue adhesive application. case report a 42-year-old man presented with persistent pain, redness, watering and diminution of vision in the right eye for three weeks. referring ophthalmologist performed pterygium surgery using bare sclera technique and patient was fine for four weeks and then developed symptoms. the referring ophthalmologist treated the patient with topical antibiotic and steroid for three weeks. observing no response, the patient was referred to. no antimetabolites or postoperative beta radiation were used in this case. the operating surgeon had used heat cautery on the sclera. patient did not reveal any history suggestive of systemic autoimmune disorder. at the time of presentation, his visual acuity was 4/60 in the right eye and 6/6 in the left eye. intraocular pressure in the left eye was 16 mmhg. slit-lamp biomicroscopy revealed large area of corneal perforation (3.5×3.5 mm) and extensive corneo-limbo-scleral necrosis [figure 1]. the left eye did not reveal any abnormality. the material obtained on corneal scrapings were subjected to the detailed microbiological tests. direct microscopy and cultures of the scraping material did not reveal any bacterial or fungal pathogen. hematological investigations including complete blood count, erythrocyte sedimentation rate, rheumatoid factor, anti-nuclear antibody, ant-dna antibodies, liver function tests, renal function tests, c-reactive protein and antineutrophil cytoplasmic antibodies were normal. serology markers of human immunodeficiency virus 1 and 2, varicella-zoster virus, hepatitis b surface antigen, hepatitis c and venereal disease research laboratory test were non-reactive. chest radiography and the montoux test were normal. surgical technique retrocorneal scleral patch augmented cyanoacrylate tissue adhesive application was done under peribulbar anesthesia, in the operating room using surgical microscope. the right eye was prepared and draped aseptically. the ocular surface was exposed using barraquer eye speculum. the area of corneo-limbo-scleral ulceration was cleaned and the debris was removed. the size of the corneal perforation was 124 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 retrocorneal scleral patch supported glue; sharma et al figure 1. corneal perforation (3.5 mm) with iris presenting at the site with extensive corneo-limbo-scleral melt. measured with castroviejo calipers. the corneal perforation measured 3.5×3.5 mm [figure 2a]. the donor sclera was obtained from eyes not suitable for optical pkp. donor sclera obtained from the local eye bank and stored in pure glycerin was taken out and placed in the normal saline for 15 min. the sclera was placed in the solution containing amikacin sulphate 2% (alfakim 500 mg/2 ml ranbaxy india) and vancomycin hydrochloride 5% (vanking 500 mg/vial neon laboratories india) for 5 min. the sclera was thinned to one-third of its thickness and a patch (4.5×4.5 mm) was punched out with skin biopsy punch [figure 2b]. the scleral patch was thinned to one-third of its thickness with crescent knife. the adhesions between the iris and the margin of corneal perforation were lysed. a small iridotomy was performed. the scleral patch was placed on the iris, beneath the corneal perforation [figure 2c]. the scleral patch and the surrounding cornea surface were dried with weck-cel ophthalmic sponge. isoamyl 2-cyanoacrylate (amcrylate; concord drugs ltd, hayathnagar, andhara pradesh, india) was drawn into a 2 ml disposable syringe with a 26 gauge needle. the minimal amount of cyanoacrylate tissue adhesive (amcrylate; concord drugs ltd, hayathnagar, andhara pradesh india) was applied on the retrocorneal sclera patch and margin of the corneal perforation [figure 2d]. the cyanoacrylate tissue adhesive was allowed to polymerize [figure 2e]. an air bubble was placed in the anterior chamber. the ulcerating limbus and the sclera were covered with double-layered amniotic membrane graft. amniotic membrane graft was sutured with vicryl 8 ‘0’ suture. a bandage contact lens was placed [figure 2f]. the patient was put on topical moxifloxacin 0.5% (vigamox; alcon laboratories, inc., fort worth, tx) four times a day, atropine sulfate 1% (atropine; jawa pvt. ltd., gurgaon, haryana, india) three times a day, and carboxymethylcellulose 1% (refresh liquigel; allergan, pithampur, madhya pradesh, india) four times a day. after 72 hr, topical prednisolone 1% (allergan ltd, west-port, co, mayo, ireland) four times a day was added. the patient was given intravenous methylprednisolone (1 gr) journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 125 retrocorneal scleral patch supported glue; sharma et al figure 2. diagramatic presentation of retrocorneal sclera patch supported cyanoacrylate tissue adhesive application: (a) corneal perforation (3.5×3.5 mm), corneal, limbal and sclera melt; (b) punching of sclera patch (4.5×4.5 mm) using a skin bopsy punch; (c) placing the thinned sclera patch behind the corneal perforation; (d) application of minimum quantity of cyanoacrylate tissue adhesive at the margin of perforation on the sclera patch; (e) injecting an air bubble in the anterior chamber; (f) at completion of surgical procedure, retrocorneal sclera patch (red arrow), cyanoacrlate tissue adhesive (blue arrow), and bandage contact lens (yellow arrow). daily for three days followed by oral prednisolone 60 mg daily for two weeks and tapered over six weeks. at 72 hr, the scleral patch, cyanoacrylate tissue adhesive plug, and double layered amniotic membrane graft were in place [figure 3a]. at two weeks, corneal perforation was sealed and scleral necrosis started healing [figure 3b]. at eight weeks’ follow-up, cyanoacrylate tissue adhesive plug became lose and the scleral patch developed vascularization. the cyanoacrylate tissue adhesive plug was carefully separated from the underlying sclera patch and removed. at 12 weeks, the corneal perforation healed and the patient developed 126 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 retrocorneal scleral patch supported glue; sharma et al figure 3. (a) sealed corneal perforation 72 hr after surgery (scleral patch, cta plug, and double layered amg in place). (b) corneal perforation sealed and corneo-limbo-scleral necrosis at healing stage at two-weeks’ follow-up. (c) healed corneal perforation (sclera patch in place) and pseudo-pterygium at 12 weeks’ follow-up. (d) healed corneal perforation (sclera patch in place) and pseudo-pterygium at 18 months’ follow-up. pseudo-pterygium. at 20 weeks, patient was diagnosed as suffering from intumescent cataract. cataract surgery was performed. he was advised excision of the pseudo-pterygium but was reluctant [figure 3c]. during the 18 months’ follow-up, patient did not develop any recurrence, the scleral patch remained in place and the patient had pseudopterygium [figure 3d]. discussion retrocorneal scleral patch supported cyanoacrylate tissue adhesive application healed the corneal perforation and the amniotic membrane graft healed the corneo-limbo-scleral melt following pterygium surgery. cyanoacrylate tissue adhesive is the gold standard treatment for corneal perforation.[6] cyanoacrylate tissue adhesive application used alone was not feasible because of the size (3.5 mm) of the perforation and also due to the risk of its inadvertent access into the anterior chamber.[7] due to extensive corneo-scleral ulceration around the corneal perforation, we did not consider scleral patch augmented cyanoacrylate tissue adhesive application technique.[8] in this technique, the partial thickness scleral patch is placed on the perforation anteriorly, and cyanoacrylate tissue adhesive is applied on the margin and surface of the scleral patch.[8] in another technique for moderate corneal perforations due to rheumatoid arthritis, a partial thickness scleral patch was placed in the intracorneal lamellar pocket and then cyanoacrylate tissue adhesive was applied.[9] since our patient had extensive corneal and sclera melt surrounding the corneal perforation, both these techniques could not be executed. the only option left to the authors was to place a sclera patch on the iris, behind the corneal perforation and then apply the cyanoacrylate tissue adhesive to seal the perforation. to the best of authors’ knowledge, this technique has not journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 127 retrocorneal scleral patch supported glue; sharma et al been reported in literature. amniotic membrane,[10] tenon’s capsule,[11] and cornea have also been used as tissue scaffolds to support cyanoacrylate tissue adhesive in treatment of moderate corneal perforations. bare-sclera technique of pterygium excision is not a favored treatment option.[2] most corneal surgeons prefer pterygium excision with conjunctival auto graft (cag for both primary and recurrent pterygium.[1] bare sclera technique has high recurrence rate (60– 80%).[2] bare sclera was previously combined with either post-op beta radiation or antimetabolites (thiotepa or mitomycin-c). however, the use of both postoperative beta radiation and thiotepa/mitomycin-c has been reported to cause scleral necrosis.[2] in most cases of scleral necrosis, mitomycin has been used several times more than the recommended concentration and dosage.[1] these agents are used to reduce the recurrence of pterygium excision. the underlying pathogenesis of sclera melt include obliterative endarteritis and inhibition of mitosis in capillary endothelium. therefore, the use of mitomycin with bare sclera technique is not advocated. low-dose mitomycin-c associated with pterygium excision and limbal conjunctival grafts have been found to be successful.[1] however, scleral necrosis and corneal melt have been reported following bare sclera technique in the absence of the use of postoperative beta radiation or anti-metabolite.[3] in our patient, the primary operating surgeon did not use any postoperative beta radiation or anti-metabolite. several ocular and systemic comorbidities can also predispose an inclination to sclera/cornea melt. our patient did not have any collagen vascular disorder including rheumatoid arthritis or wegner’s granulomatosis. to speculate the etiopathogenesis in our patient is difficult. underlying etiopathogenesis may be infection, ischemia, or inflammation. infective etiology was ruled out as all microbiological tests were negative. primary ischemic etiology was unlikely as the patient had not received intra/postoperative mitomycin c. light cautery application to bleeding vessels in the sclera bed could be held responsible for severe ischemia and scleral melt. it appears that bare sclera technique causing exposure of sclera was responsible for inducing inflammation that resulted in ischemia and ulceration. clinical presentation and signs in our case simulate surgery-induced necrosis of the sclera. in our patient, in addition to retrocorneal sclera patch augmented cyanoacrylate tissue adhesive application, double layered amniotic membrane graft was applied. amniotic membrane graft coupled with intravenous methylprednisolone and later oral prednisolone decreased inflammation, arrested corneal scleral ulceration, promoted healing and epithelization. patients not responding to corticosteroids or developing complications of oral steroids may need immunosuppressive agents. in summary, this case report demonstrates that retrocorneal sclera patch augmented cyanoacrylate tissue adhesive healed the moderate sized (3.5 mm) corneal perforation in association with extensive corneo-limbo-scleral melt following pterygium surgery. financial support and sponsorship none. conflicts of interest there are no conflicts of interest. references 1. sharma a, gupta a, ram j, gupta a. low-dose intraoperative mitomycin-c versus conjunctival autograft in primary pterygium surgery: long term follow-up. ophthalmic surg lasers 2000;31:301–307. 2. tan dt, chee sp, dear kb, lim as. effect of pterygium morphology on pterygium recurrence in a controlled trial comparing conjunctival autografting with bare sclera excision. arch ophthalmol 1997;115:1235–1240. 128 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 retrocorneal scleral patch supported glue; sharma et al 3. alsagoff z, tan dt, chee sp. necrotising scleritis after bare sclera excision of pterygium. br j ophthalmol 2000;84:1050–1052. 4. ti se, tan dt. tectonic corneal lamellar grafting for severe scleral melting after pterygium surgery. ophthalmology 2003;110:1126–1136. 5. siatiri h, mirzaee-rad n, aggarwal s, kheirkhah a. combined tenonplasty and scleral graft for refractory pseudomonas scleritis following pterygium removal with mitomycin c application. j ophthalmic vis res 2018;13:200–202. 6. saini js, sharma a, grewal sp. chronic corneal perforations. ophthalmic surg 1992;23:399–402. 7. sharma a, kaur r, kumar s, gupta p, pandav s, patnaik b, et al. fibrin glue versus n-butyl-2-cyanoacrylate in corneal perforations. ophthalmology 2003;110:291–298. 8. sharma a, mohan k, sharma r, nirankari vs. scleral patch graft augmented cyanoacrylate tissue adhesive for treatment of moderate-sized noninfectious corneal perforations (3.5–4.5 mm). cornea 2013;32:1326–1330. 9. sharma a, sharma r, nirankari vs. intracorneal scleral patch supported cyanoacrylate application for corneal perforations secondary to rheumatoid arthritis. indian j ophthalmol 2021;69:69–73. 10. kitagawa k, okabe m, yanagisawa s, zhang xy, nikaido t, hayashi a. use of a hyperdried cross-linked amniotic membrane as initial therapy for corneal perforations. jpn j ophthalmol 2011;55:16–21. 11. sharma n, singhal d, maharana pk, vajpayee rb. tuckin tenon patch graft in corneal perforation. cornea 2019;38:951–954. journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 129 original article effect of phacoemulsification on intraocular pressure in eyes with functioning tube shunts wesam shamseldin shalaby1,2, md; sonali patel3, bs; sophia s. lam3, bs; allen ganjei4, bs; aakriti garg shukla1, md; natasha kolomeyer1, md; daniel lee1, md; l. jay katz1, md; marlene r. moster1, md; jonathan myers1, md; reza razeghinejad1, md 1wills eye hospital, glaucoma research center, philadelphia, pa, usa 2tanta medical school, tanta university, tanta, gharbia, egypt 3sidney kimmel medical college, thomas jefferson university, philadelphia, pa, usa 4college of medicine, drexel university, philadelphia, pa, usa orcid: wesam shamseldin shalaby: https://orcid.org/0000-0003-2577-9412 reza razeghinejad: https://orcid.org/0000-0001-7961-8425 abstract purpose: to evaluate the effect of phacoemulsification on intraocular pressure (iop) in eyes with functioning tube shunts. methods: this was a retrospective chart review of primary open-angle glaucoma (poag) patients with a functioning tube who underwent phacoemulsification and had ≥24 months of follow-up. the primary end point was defined as surgical failure (iop > 21 mmhg) at month 24, progression to no light perception (nlp) vision, glaucoma reoperation, or implant removal. surgical failure defined as iop >18 and >15 mmhg, changes in visual acuity (va), iop, and number of medications were assessed. results: twenty-seven eyes of 27 patients with moderate or severe poag were included. the mean age of the patients was 64.2 ± 10.8 years. the interval between the tube shunt and phacoemulsification was 28.8 ± 25.0 months. at the end of the study, four (14.8%) eyes met the failure criteria; the average time to failure was 9.3 ± 3.8 months. the causes of failure were high iop in two (50.0%) and glaucoma reoperation in two (50.0%) eyes; however, no eyes progressed to nlp vision. surgical failure defined as iop >18 and >15 mmhg showed an increasing failure rate (18.5% and 48.5%, respectively). the mean iop and medications number remained stable at month 24 compared to baseline (p = 0.131 and p = 0.302, respectively). initially, va showed improvement, with the greatest improvement at 6 months (p = 0.001), but at 24 months the improvement was no longer significant (p = 0.430). conclusion: phacoemulsification in patients with functioning tubes did not change the mean iop in most of the patients (86.2%); the number of medications also did not increase. keywords: cataract extraction; glaucoma drainage implants; intraocular pressure; phacoemulsification j ophthalmic vis res 2023; 18 (2): 150–156 correspondence to: wesam shamseldin shalaby, md. glaucoma research center, wills eye hospital, 840 walnut st., suite 1140, philadelphia, pa 19107, usa email: wshalaby@willseye.org received: 25-10-2021 accepted: 30-08-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i2.13180 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: shalaby ws, patel p, lam ss, ganjei a, shukla ag, kolomeyer n, lee d, katz lj, moster mr, myers j, razeghinejad r. effect of phacoemulsification on intraocular pressure in eyes with functioning tube shunts . j ophthalmic vis res 2023;18:150–156. 150 © 2023 shalaby et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i2.13180&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr phacoemulsification after tube shunts; shalaby et al introduction cataract surgery in patients with preexisting glaucoma or glaucoma surgery is challenging considering the potential impairment of postoperative intraocular pressure (iop) control. the development of cataract after glaucoma surgery is not uncommon.[1] it has been suggested that intraocular inflammation during and after cataract surgery may result in scarring and fibrosis of the filtering trabeculectomy blebs.[2] similarly, the inflammatory cells and mediators may cause fibrosis around the shunt reservoir.[3] however, there is no definite evidence supporting this theory. several studies have investigated the effect of cataract surgery on trabeculectomy blebs. there have been mixed results on the bleb survival. while some studies showed increased failure of trabeculectomy and iop elevation,[4−−7] others reported no effect.[8−−10] the literature on the effect of cataract extraction in eyes with prior tube shunts is limited.[3, 11, 12] prior studies showed lack of change in iop and medications number in functioning tubes following phacoemulsification; however, they had a limited sample size, variable follow-up duration, and heterogenous type of glaucoma.[3, 11, 12] the study aimed to investigate the survival of tube shunts after phacoemulsification in patients with primary open-angle glaucoma (poag). methods this single-center retrospective case series was performed at a tertiary eye care center. the study protocol was reviewed and approved by the institutional review board of wills eye hospital, philadelphia, pa, united states; and the approval number was [19-857]. the study was conducted in accordance with the health insurance portability and accountability act regulations. the study protocol adhered to the tenets of the declaration of helsinki and the guidelines for human studies. as this was a retrospective study with de-identified data, informed consent was not required. the medical records of consecutive patients diagnosed with poag who were treated with tube shunts including the ahmed glaucoma valve (agv; new world medical inc., rancho cucamonga, ca, usa) or the baerveldt glaucoma implant (bgi; advanced medical optics, santa ana, ca, usa) followed by phacoemulsification between 2008 and 2018 were reviewed. patients aged 18 years or older who had undergone successful tube shunt surgery for poag with iop ≤ 21 mmhg, with or without medications, followed by phacoemulsification were included. exclusion criteria were angle closure, neovascular, or inflammatory glaucoma, cataract extraction by any technique other than phacoemulsification, phacoemulsification combined with any glaucoma surgery, or a followup of less than two years after phacoemulsification. in patients with both eyes meeting the inclusion criteria, only the first eye was included. visits at baseline, postoperative day 1, week 1, months 1, 3, 6, 12, 18, and 24 after the cataract surgery were reviewed. demographic data such as age and sex, and medical and surgical history were collected. preoperative clinical data included best-corrected visual acuity (bcva), iop, topical glaucoma medications, and cup/disc ratio (cdr) at three consecutive visits prior to phacoemulsification. postoperative data included bcva, iop, glaucoma medications, cdr, postoperative complications, and need for additional glaucoma surgery. the primary outcome measure was the cumulative rate of surgical failure at 24 months. surgical failure was defined as iop > 21 mmhg with medications at two consecutive visits, progression to no light perception (nlp) vision, and glaucoma reoperation including second tube shunts, cyclophotocoagulation, or removal of the existing tube shunt. changes in va, iop, glaucoma medications, and cdr at month 24 were compared to baseline. additionally, analyses of surgical failure defined as iop >15 and >18 mmhg were performed. statistical analysis statistical analyses were performed using the spss software version 27.0 (ibm analytics, chicago, il, usa). snellen va measurements were converted to logarithm of the minimum angle of resolution (logmar) equivalents for the purpose of data analysis. continuous variables were presented as mean ± standard deviation. proportions (%) were used to describe categorical variables. paired sample t-tests were used to compare continuous variables within the same group. p-values < journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 151 phacoemulsification after tube shunts; shalaby et al 0.05 were considered as significant. kaplan–meier survival analysis with log-rank tests were used to assess the survival. results twenty-seven eyes of 27 patients were included in this study (16 agv and 11 bgi). baseline patient characteristics are shown in table 1. the mean age was 64.2 ± 10.8 years, and 16 (59.3%) patients were females. all patients had moderate to severe glaucoma. six patients (22.2%) had prior trabeculectomy before the tube shunt surgery. the mean logmar va, iop, and number of glaucoma medications were 0.94 ± 0.92, 16.0 ± 4.7 mmhg, and 2.4 ± 1.5, respectively. the average interval between tube shunt surgery and phacoemulsification was 28.8 ± 25.0 months. at month 24, a total of four (14.8%) eyes met the failure criteria. failure occurred at 19.3 ± 3.8 months after cataract extraction. reasons for failure were high iop in two (50.0%) eyes and glaucoma reoperation in two (50.0%) others. no eye progressed to nlp vision. higher failure rate was observed with the surgical success defined as iop <18 and <15 mmhg (18.5% and 48.5%, respectively). the rate, reasons, and time to failure with the three failure criteria are shown in table 2. kaplan–meier survival analysis showing the cumulative rate of surgical failure at 24 months using the three failure criteria is displayed in figure 1. visual acuity improved after surgery and the difference with baseline was statistically significant at month six, with an improvement in logmar va of 0.41 ± 0.54 units (p = 0.001), but not at month 24 (0.11 ± 0.67-unit improvement, p = 0.430). no eyes progressed to nlp vision. baseline and follow-up iops are presented in figure 2. patients who met the failure criteria due to reoperation for glaucoma implant removal or progression to nlp vision were censored in statistical analysis of the follow-up visits. at postoperative day one visit, iop was higher compared to baseline (18.1 ± 6.2 mmhg vs 16.0 ± 4.7 mmhg, p = 0.053). then, a tendency for lower iop as compared to baseline was observed at all follow-up visits, but not statistically significant (p > 0.05), except in the third month at which iop was significantly lower compared to baseline (13.0 ± 3.7 mmhg vs 16.0 ± 4.7 mmhg, p = 0.011). at month 24, the iop was lower by 1.6 ± 5.1 mmhg compared to baseline (p = 0.131). figure 3 shows the number of glaucoma medications at baseline and follow-up. a decremental trend for the number of glaucoma medications was observed at all time points; however, it was statistically significant at postoperative months 6 and 12 compared to baseline (p = 0.02 and p = 0.016, respectively). at month 24, the mean number of medications was 0.3 ± 1.5 lower compared to the baseline (p = 0.302). hyphema (1 [3.7%]), iop spikes (iop elevation ≥ 10 mmhg from the baseline) (1 [3.7%]), and inflammatory reaction (>+1 cells in the anterior chamber) (14 [51.9%]) were the early postoperative complications; all resolved with conservative management. no eyes developed persistent corneal edema. during the follow-up period, one eye (3.7%) required tube revision and two (7.4%) eyes received second tube shunt. discussion our study shows that the mean iop and number of glaucoma medications remained stable for two years following cataract extraction in poag patients with a functional tube shunt. the rate of surgical failure was 14.8%, 18.5%, and 48.5% at iops of >21, <18, and <15 mmhg, respectively. while the effect of cataract surgery on the trabeculectomy function has been heavily studied,[4–10] there are limited studies on the tube shunts, and all have included various forms of open-angle glaucoma.[3, 11, 12] gujral et al[12] retrospectively investigated the outcomes of phacoemulsification in eyes with functioning agvs. the study included 23 eyes of 19 patients with an average follow-up of 1.6 ± 0.6 years after the cataract surgery. similar to our study, the mean iop and number of medications did not change after phacoemulsification (p > 0.05 for both). however, the follow-up in our study was longer. the pattern of postoperative iop change was similar to our study; increased from 14.5 ± 3 mmhg (preoperative) to 19.2 ± 6.3 mmhg on postoperative day one, declined at month one, and remained stable afterward. the surgical failure defined as iop >21 mmhg was observed in two (9%) eyes and one of them (4.0%) underwent second tube shunt. these 152 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 phacoemulsification after tube shunts; shalaby et al table 1. baseline characteristics of patients with phacoemulsification and prior tube shunt surgery. number of eyes 27 number of patients 27 age, yr 64.2 ± 10.8 sex, females: n (%) 16 (59.3) surgical eye, right: n (%) 16 (59.3) baseline visual acuity: logmar 0.94 ± 0.92 baseline intraocular pressure: mmhg 16.0 ± 4.7 baseline medications number 2.4 ± 1.5 baseline cup/disc ratio 0.7 ± 0.2 glaucoma severity: n (%) moderate 11 (40.7) severe 16 (59.3) glaucoma intervention prior to tube shunt surgery none 13 (48.1) selective laser trabeculoplasty 8 (29.6) trabeculectomy 6 (22.2) duration between tube shunt surgery and phacoemulsification: months 28.8 ± 25.0 table 2. month 24 failure in patients with phacoemulsification and prior tube shunt surgery. failure criteria 1: iop > 21 mmhg failure: n (%) 4 (14.8) reasons of failure: n (%) iop > 21 mmhg 2 (50.0) reoperation for glaucoma 2 (50.0) progression to nlp 0 (0.0) time to failure: months 19.3 ± 3.8 failure criteria 2: iop > 18 mmhg month 24 failure: n (%) 5 (18.5) reasons of failure: n (%) iop > 18 mmhg 3 (60.0) reoperation for glaucoma 2 (40.0) time to failure: months 17.8 ± 7.6 failure criteria 3: iop > 15 mmhg month 24 failure: n (%) 13 (48.1) reasons of failure: n (%) iop > 15 mmhg 11 (84.6) reoperation for glaucoma 2 (15.4) time to failure: months 12.6 ± 7.2 iop, intraocular pressure; nlp, no light perception journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 153 phacoemulsification after tube shunts; shalaby et al figure 1. kaplan–meier survival plot of cumulative probability of surgical failure in patients with phacoemulsification and prior tube shunt surgery. surgical failure was defined as intraocular pressure >21 mmhg (1a), >18 mmhg (1b), or >15 mmhg (1c). figure 2. intraocular pressure changes over time in patients with phacoemulsification and prior tube shunt surgery. intraocular pressure remained stable through two years following phacoemulsification. significant reduction was observed at month three (p = 0.011). figure 3. medication number changes over time in patients with phacoemulsification and prior tube shunt surgery. medication number remained stable through two years following phacoemulsification. significant reduction was observed at month six (p = 0.020) and month 12 (p = 0.016). 154 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 phacoemulsification after tube shunts; shalaby et al findings were comparable to our failure (14.8%) and reoperation (7.4%) rates. on the other hand, more eyes experienced iop spikes at day one postoperatively (17.0%) compared to ours (3.7%). erie et al[3] retrospectively studied the effects of phacoemulsification on nine eyes of eight patients with a functioning bgi with an average followup of 21.0 ± 3.0 months. the mean iop and number of medications did not change significantly at the last follow-up visit (p = 0.830 and p = 0.170, respectively). only one eye required second glaucoma surgery. in another retrospective study, 11 eyes of 11 patients with double plate molteno shunt (8), single plate molteno shubt (2), or bgi (1) were followed for 21.0 ± 27.0 months following cataract surgery.[11] phacoemulsification was performed in eight eyes and extracapsular cataract extraction was done in three eyes. no significant difference was observed between the mean iop and the number of medications before and after cataract extraction (p = 0.850 and p = 0.440, respectively). three eyes had iop >21 mmhg and only one of them required glaucoma surgery. although va improved in the first six months, the vision was not statistically different from baseline at month 24. this is consistent with prior studies, although in some studies it was attributed to corneal edema.[11, 12] corneal edema was not observed in our study. posterior capsule opacification could be a potential cause for the lack of change in vision after cataract extraction. the high iop at day one may be related to the postoperative period iop spikes following cataract surgery due to viscoelastic agents.[13, 14] the iop decline afterward could be because of the iop-lowering effect of phacoemulsification in glaucomatous eyes.[15, 16] the mechanism is not clear, but may be related to widening of the anterior chamber angle, decreased aqueous production by the ciliary body due to capsular bag contraction, or increased aqueous outflow due to trabecular meshwork stretching.[15–17] the results of our study are in line with other studies on iop profile following cataract extraction in patients with a functional tube, but the results on trabeculectomy are controversial. some studies showed that phacoemulsification increased the surgical failure of trabeculectomy,[4–7] and others found no effect on bleb survival.[8–10] the mechanisms of iop elevation following cataract surgery in those with a functional filtering surgery (trabeculectomy or tube shunts) seems to be similar. inflammatory cells and cytokines released following cataract surgery may cause scarring of the filtering bleb.[2, 11] the average duration between tube shunt surgery and phacoemulsification in this study was variable (28.8 ± 25.0 months). it is known that the time interval between the two surgeries may have prognostic ramifications. it is recommended to postpone the cataract surgery following filtering surgery as long as possible, without compromising patient’s quality of life. a six-month gap between filtering surgery and the subsequent cataract extraction increases the chances of bleb survival.[18] the patients in our study had phacoemulsification 28.8 months after shunt surgery and were followed for 24 months (about five years after shunt surgery). the failure rate in these patients was comparable with the rate reported in ahmed baerveldt comparison (abc) and ahmed versus baerveldt (avb) studies.[19, 20] these findings confirm that phacoemulsification, at least, had no negative impact on the survival of tube shunts. however, such comparisons cannot conclude that phacoemulsification may augment the iop-lowering effect of tube shunts, giving the different follow-up duration and the inclusion of secondary and refractory glaucoma types in the abc and avb studies.[19, 20] our study has several limitations. there were no preset criteria for the addition of medications or preforming another surgery and has been at the discretions of surgeons. this is the universal issue with all retrospective studies. additionally, the sample size was small as only poag patients with a complete two-year follow-up were included. the follow-up period in our study was longer than prior studies and contrary to them we included only one eye of each patient and only poag cases. compared to all prior studies we had the largest sample size (27 vs 9, 11, and 23 eyes), and all patients were followed-up for at least for 24 months.[3, 11, 12] furthermore, both valved (agv) and non-valved (bgi) tubes were included in this study which makes the results closer to the real-world practice.[19, 20] in summary, the current study showed that poag patients with functioning tube shunts can maintain iop control after phacoemulsification, suggesting that cataract surgery may not have a negative impact on the survival of tube shunts. journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 155 phacoemulsification after tube shunts; shalaby et al financial support and sponsorship none. conflicts of interest none. references 1. daugeliene l, yamamoto t, sawada a, kitazawa y. an image analysis study of cataract development after trabeculectomy with mitomycin c. ophthalmologica 1998;212:244–249. 2. chen pp, weaver yk, budenz dl, feuer wj, parrish rk, 2nd. trabeculectomy function after cataract extraction. ophthalmology 1998;105:1928–1935. 3. erie jc, baratz kh, mahr ma, johnson dh. phacoemulsification in patients with baerveldt tube shunts. j cataract refract surg 2006;32:1489–1491. 4. husain r, liang s, foster pj, gazzard g, bunce c, chew ptk, et al. cataract surgery after trabeculectomy: the effect on trabeculectomy function. arch ophthalmol 2012;130:165–170. 5. seah sk, jap a, prata ja jr, baerveldt g, lee pp, heueret dk, et al. cataract surgery after trabeculectomy. ophthalmic surg lasers 1996;27:587–594. 6. rebolleda g, munoz-negrete fj. phacoemulsification in eyes with functioning filtering blebs: a prospective study. ophthalmology 2002;109:2248–2255. 7. crichton ac, kirker aw. intraocular pressure and medication control after clear corneal phacoemulsification and acrysof posterior chamber intraocular lens implantation in patients with filtering blebs. j glaucoma 2001;10:38–46. 8. casson rj, riddell ce, rahman r, byles d, salmon jf. long-term effect of cataract surgery on intraocular pressure after trabeculectomy: extracapsular extraction versus phacoemulsification. j cataract refract surg 2002;28:2159–2164. 9. manoj b, chako d, khan my. effect of extracapsular cataract extraction and phacoemulsification performed after trabeculectomy on intraocular pressure. j cataract refract surg 2000;26:75–78. 10. park hj, kwon yh, weitzman m, caprioli j. temporal corneal phacoemulsification in patients with filtered glaucoma. arch ophthalmol 1997;115:1375–1380. 11. bhattacharyya ca, wudunn d, lakhani v, hoop j, cantor lb. cataract surgery after tube shunts. j glaucoma 2000;9:453–457. 12. gujral s, nouri-mahdavi k, caprioli j. outcomes of smallincision cataract surgery in eyes with preexisting ahmed glaucoma valves. am j ophthalmol 2005;140:911–913. 13. mcguigan lj, gottsch j, stark wj, maumenee ae, quigley ha. extracapsular cataract extraction and posterior chamber lens implantation in eyes with preexisting glaucoma. arch ophthalmol 1986;104:1301–1308. 14. yasutani h, hayashi k, hayashi h, hayashi f. intraocular pressure rise after phacoemulsification surgery in glaucoma patients. j cataract refract surg 2004;30:1219– 1224. 15. shingleton bj, gamell ls, o’donoghue mw, baylus sl, king r. long-term changes in intraocular pressure after clear corneal phacoemulsification: normal patients versus glaucoma suspect and glaucoma patients. j cataract refract surg 1999;25:885–890. 16. cinotti dj, fiore pm, maltzman ba, constad wh, cinotti aa. control of intraocular pressure in glaucomatous eyes after extracapsular cataract extraction with intraocular lens implantation. j cataract refract surg 1988;14:650–653. 17. steuhl kp, marahrens p, frohn c, frohn a. intraocular pressure and anterior chamber depth before and after extracapsular cataract extraction with posterior chamber lens implantation. ophthalmic surg 1992;23:233–237. 18. dada t, bhartiya s, begum baig n. cataract surgery in eyes with previous glaucoma surgery: pearls and pitfalls. j curr glaucoma pract 2013;7:99–105. 19. budenz dl, barton k, gedde sj, feuer wj, schiffman j, costa vp, et al. five-year treatment outcomes in the ahmed baerveldt comparison study. ophthalmology 2015;122:308–316. 20. christakis pg, kalenak jw, tsai jc, zurakowski d, kammer ja, harasymowycz pj, et al. the ahmed cersus baerveldt study: five-year treatment outcomes. ophthalmology 2016;123:2093–2102. 156 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 original article peak intraocular pressure time during water drinking test and its relationship with glaucoma severity carolina nicolela susanna1, md; bianca nicolela susanna1, md; fernanda nicolela susanna2, ms remo susanna jr2, md, phd; carlos gustavo de moraes3, md, phd 1department of ophthalmology, abc foundation school of medicine, santo andré, brazil 2department of ophthalmology, university of sao paulo school of medicine, sao paulo, brazil 3department of ophthalmology, columbia university irving medical center, new york, united states orcid: carolina nicolela susanna: https://orcid.org/0000-0003-1341-6112 remo susanna jr: https://orcid.org/0000-0001-9147-9528 abstract purpose: to investigate the association between the time of occurrence of intraocular pressure (iop) peaks during the water-drinking test (wdt) and visual field damage in a cohort of primary open-angle glaucoma (poag) patients. methods: in this retrospective, cross-sectional study, 98 eyes from 49 consecutive poag patients were followed in a referral clinical practice. the relationship between the time when iop peaks occurred during the wdt and the visual field mean deviation (md) assessed with 24-2 visual field was tested with mixed-effects models. results: md value was significantly associated with the time of iop peak occurrence (p = 0.020) when adjusting for the number of medications, but not with the iop peak values (p = 0.238). conclusion: the time of iop peaks occurrence during the wdt was associated with glaucoma severity among treated poag patients. keywords: glaucoma severity; iop peak time; primary open-angle glaucoma; water drinking test j ophthalmic vis res 2022; 17 (1): 27–32 introduction provocative tests have been widely employed in medicine to assess changes in physiological correspondence to: remo susanna jr. md, phd. department of ophthalmology, university of sao paulo school of medicine, av. dr. arnaldo, 455, sao paulo, 01246-903, brazil. e-mail: rsusannajr@gmail.com received 07-04-2021; accepted 01-08-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10167 systems when stressed under strenuous conditions. for instance, coronary ischemia, not usually noted in physiologic conditions, may become evident when the subject undergoes a treadmill provocative test or following intravenous pharmacological stimulation. depending on the magnitude of the change, treatment may be required to prevent long-term complications. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: susanna cn, susanna bn, susanna r, de moraes cg. peak intraocular pressure time during water drinking test and its relationship with glaucoma severity. j ophthalmic vis res 2022;17:27–32. © 2022 susanna et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 27 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10167&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr peak iop time in wdt; susanna et al similarly, the water-drinking test (wdt) is a stress test used to assess intraocular pressure (iop) behavior and indirectly evaluate the outflow facility of the eye.[1] glaucoma progression in patients whose iop is apparently well-controlled during clinic visits maintain a challenge. a satisfactory correlation between clinic-based iop measurements and mean circadian iop have been shown, even though not predictive of the peak iop.[2] in fact, more than 70% of iop peaks occur at night or in the early morning hours.[3–6] however, monitoring iop 24 hr is not practical in routine glaucoma practice. diurnal tension curves (dtc) misses iop peaks occurring overnight.[7] the wdt is a reliable and feasible means to estimate peak iop. while many glaucomatous eyes may have seemingly controlled iop during office hours or usual steady-state conditions, iop peaks triggered by this test may reveal pressure measurements inconsistent with controlled disease and which could yield to disease progression in the long run. in fact, the peak iop elicited during the wdt has been shown to correlate with the iop peak that occurs during the day[8–12] and is highly reproducible.[9, 13, 14] more importantly, it has been shown to be associated with the risk of visual field (vf) progression of glaucoma and disease severity.[15–18] recently, it has also been suggested that the wdt could be used to evaluate retinal ganglion cell function and hence have potential application for risk assessment.[18] in addition, the wdt is an indicator of treatment efficacy, assessing the effect of hypotensive drugs as well as surgeries.[9, 19–22] the mechanism of iop elevation remains unclear, but there are some postulates, such as limited outflow facility, increased episcleral venous pressure (evp), increased iop mediated by the autonomic nervous system, and choroidal expansion.[23–25] eyes with lower outflow facility should experience higher iop peaks after ingestion of water than eyes with normal outflow function, thus being a surrogate measure of the outflow system of the eye and its ability to respond to transient iop elevation.[26] the time interval in which peak iop occurs after the ingestion of water can also be related to the ability of the drainage system to maintain iop homeostasis. eyes with worse outflow facility may experience continued iop rise during the wdt, and as so, later iop peaks than eyes with better outflow facility. this study aims to investigate the association between severity of glaucomatous vf loss, the magnitude, and the time of iop peaks during the wdt in a group of treated primary open-angle glaucoma (poag) patients. methods this retrospective, cross-sectional study included 98 eyes from 49 consecutive poag patients followed in a referral glaucoma center. the study protocol adhered to the tenets of the declaration of helsinki[27] and was approved by the committee of ethics. informed consent for the research was obtained from all the patients. consecutive patients that met the inclusion and exclusion criteria were selected for the present study. a review of medical history, iop measurement with goldmann applanation tonometry, best-corrected visual acuity, and slit-lamp biomicroscopy was performed in these patients. patients were included if they had a glaucomatous appearing optic disc during disc photograph evaluation defined by a senior glaucoma specialist associated with glaucomatous vf loss on 242 standard automated perimetry. vf loss was defined according to the modified anderson’s criteria. these results were confirmed on at least two consecutive examinations. included eyes had a best-corrected visual acuity of at least 20/40, spherical refraction better than ±5.00 diopters, and cylinder correction within 3.00 diopters. we excluded participants with nonglaucomatous optic neuropathy, closed or narrow angle assessed by gonioscopic examination, retinal disease, secondary glaucoma, or any other abnormality that could interfere with vf testing. none of the patients had undergone trabeculectomy or laser trabeculoplasty and none had cataract surgery within the last six months before enrollment. the water-drinking test (wdt) consists of one baseline iop measurement, followed by ingestion of 800 ml of water in 5 min and three more iop measurements taken at 15-min intervals.[28] all participants were required to stop liquid ingestion 2 hr before the test. intraocular pressure measurements were performed with a goldmann applanation tonometer (haag-streit, gmbh, switzerland). the maximum value of the three measurements was considered as the iop 28 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 peak iop time in wdt; susanna et al table 1. baseline characteristics variables data number of eyes 98 age 60 ±12 (range: 33–95) race caucasian asian 88% 12% sex female male 54% 46% number of medications of 2 ± 1 (range: 0–5) latanoprost use 76 (77.5%) mean baseline md –8.23 ± 7.94 db (range: –31.19 to 2.38 db) mean baseline iop 14 ± 3 mmhg (range: 8 to 22 mmhg) mean peak iop 18 ± 4 mmhg (range: 10 to 30 mmhg) ∗presented mean ± standard deviation, calculated using summary statistics. md, mean deviation; iop, intraocular pressure table 2. distribution of number of eyes, mean md, and mean iop peak value of eyes according to the time of iop peak in the wdt time of iop peak number of eyes md value (db)† iop peak (mmhg)† 15 20 (20.4%) –4.36 ± 5.51 17 ± 4 30 42 (42.9%) –9.35 ± 7.98 19 ± 3 45 36 (36.7%) –9.13 ± 8.56 19 ± 5 †presented as mean ± standard deviation, calculated using summary statistics. md, mean deviation; iop, intraocular pressure; wdt, water-drinking test. peak during the wdt.[9] the time of the peak was defined as the time when the maximum iop was measured. to minimize the effect of the iop circadian rhythm, all wdt were performed between 4:00 pm and 5:00 pm. standard achromatic perimetry was performed with the humphrey vf analyzer (24-2 sitastandard; carl zeiss meditec inc., dublin, ca). all patients underwent vf testing and reliable exams (<20% fixation losses, <33% false-positive and false-negative rates) were analyzed. visual field tests and wdt were performed up to four months apart. statistical analyses statistical comparisons were performed between patients with mixed-effects models, which considers the correlation between both eyes of the same patient. statistical analysis was performed using stata version 14 (statacorp lp, college station, tx). statistical significance was reached at p < 5%. results ninety-eight eyes from 49 poag patients were analyzed. the mean age of patients was 60 ± 12 years (range, 33–95) and 54% were women. patients were on a mean of 2 ± 1 (range, 0–5) iop lowering medications. the mean of mean deviation values (md) was –8.23 ± 7.94 db (range, –31.19 to 2.38 db). baseline characteristics are described in table 1. table 2 depicts the distribution of the number of eyes, mean md values (db), and mean iop peak according to the time point of the wdt in which the iop peak occurred. the mean iop peak and the mean md values (17 ± 4 mmhg and 4.36 ± 5.51 db, respectively) were lower at 15 min compared to 30 min (19 ± 3 mmhg and –9.35 ± 7.98 db) and 45 min (19 ± 5 mmhg and –9.13 ± 8.56 db) in the wdt. the box plot of the distribution of md value in each time iop peak occurrence (figure 1) shows lower md values in the later time points (30 and 45 min) compared to 15 min. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 29 peak iop time in wdt; susanna et al table 3. results of the mixed model evaluating the association between the md and time of iop peak, iop peak value, and number of medications. parameter coefficient 95% ci p-value time of iop peak –0.155 –0.284 to –0.025 0.020 peak value – 0.237 –0.630 to 0.156 0.238 number of medications –1.137 –2.899 to 0.625 0.206 constant 3.859 –4.691 to 12.411 0.376 †calculated using mixed effect model. ci, confidence interval figure 1. distribution of mean deviation value at each time point of the wdt. †boxplot depicting the md distribution. md, mean deviation; iop, intraocular pressure; wdt, water-drinking test; min, minutes. separate multivariable models showed a statistically significant relationship between the time of iop peak and md values (p = 0.010) adjusting for number of medications. however, peak value was not associated with md values when adjusting for number of medications (p = 0.117). the results of the mixed-effect model relating md values to the time of iop peak, iop peak value, and number of medications together are presented in table 3. eyes with more damage in vfs had later iop peaks during wdt (p = 0.020). neither number of medications nor iop peak value were significantly related to md values (p = 0.238 and p = 0.206, respectively). discussion intraocular pressure peak is a key risk factor for glaucoma progression.[29–31] to better investigate other parameters obtained from the wdt, we tested whether the iop peak time was related to the level of glaucomatous functional damage, which might reflect the eye’s outflow system status of a given eye. therefore, it is expected that in eyes with worse outflow facility, iop elevation may remain rising for longer time, leading to later iop peaks during the wdt. razeghinejad et al[32] investigated the effect of wdt after tube shunt surgery and trabeculectomy and showed that 30 min after the wdt, iop in the trabeculectomy group initiated to decline, whereas for the tube shunt group it remained increasing 30 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 peak iop time in wdt; susanna et al up to 60 min, which might have implications on tubes’ efficacy in advanced glaucoma patients. additionally, waisbourd et al[22] investigated the effect of the wdt on the iop of patients with angle-closure glaucoma and demonstrated that after peripheral iridotomy was performed, patients had a more pronounced iop recovery, probably due to an increased trabecular meshwork area exposure following treatment. this corroborates the reasoning that eyes with impaired outflow have different time responses during the wdt. we found that the time during wdt of iop peaks’ occurrence was associated with glaucoma severity in a population with treated poag. specifically, eyes with more severe disease had a later iop peak than eyes with less severe disease (p = 0.020). in other words, eyes with later iop peaks experienced continued iop rise during the wdt until the maximum iop was reached (iop peak) and as so, a longer period of iop elevation than eyes with earlier iop peaks, possibly reflecting a better ability of these eyes to handle transient iop elevation. accordantly, de moraes et al[33] showed that the number of long peaks assessed with contact lens sensor (cls) was the best predictors of faster progression in treated glaucoma patients.[33] in contrast with results found by other authors,[15–17] there was no association between peak iop value and md (p = 0.238) in our study. probably because patients were under treatment based on physician’s discretion, which was adjusted to reduce iop peaks elicited by the wdt. therefore, patients showing more advanced glaucoma were likely prone to receive aggressive therapy in both eyes to achieve lower target iop peaks. one limitation is that this was a retrospective study. in order to reduce selection bias, we consecutively selected patients from a cohort in which all patients had routinely been submitted to the wdt. further prospective studies evaluating these wdt parameters, preferably with patients free of topical treatment, should be done to better understand the relationship between the peak time and vf defect. in conclusion, this study demonstrated that the time of occurrence of iop peak measured with the wdt was associated with glaucoma severity and might be an additional tool to evaluate glaucomatous patients. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. kronfeld c. water drinking and outflow facility. invest ophthalmol 1975;14:49–52. 2. nakakura s, nomura y, ataka s, shiraki k. relation between office intraocular pressure and 24-hour intraocular pressure in patients with primary openangle glaucoma treated with a combination of topical antiglaucoma eye drops. j glaucoma 2007;16:201–204. 3. barkana y, anis s, liebmann j, tello c, ritch r. clinical utility of intraocular pressure monitoring outside of normal office hours in patients with glaucoma. arch ophthalmol 2006;124:793–797. 4. liu jhk, zhang x, kripke df, weinreb rn. twentyfour-hour intraocular pressure pattern associated with early glaucomatous changes. invest opthalmol vis sci 2003;44:1586. 5. liu jhk, kripke df, hoffman re, twa md, loving rt, rex km, et al. nocturnal elevation of intraocular pressure in young adults. invest ophthalmol vis sci 1998;39:2707– 2712. 6. liu jhk, kripke df, twa md, hoffman re, mansberger sl, rex km, et al. twenty-four-hour pattern of intraocular pressure in the aging population. invest ophthalmol vis sci 1999;40:2912–2917. 7. goldberg i, clement ci. the water drinking test. am j ophthalmol 2010;150:447–449. 8. kumar rs, de guzman mhp, ong py, goldberg i. does peak intraocular pressure measured by water drinking test reflect peak circadian levels? a pilot study. clin exp ophthalmol 2008;36:312–315. 9. susanna r, clement c, goldberg i, hatanaka m. applications of the water drinking test in glaucoma management. clin exp ophthalmol 2017;45:625–631. 10. olatunji o, olawoye o, ajayi bgk. correlation and agreement between water drinking test and modified diurnal tension curve in untreated glaucoma patients in nigeria. j glaucoma 2020;29:498–503. 11. v de moraes cg, furlanetto rl, reis asc, vegini f, cavalcanti nf, susanna r jr. agreement between stress intraocular pressure and long-term intraocular pressure measurements in primary open-angle glaucoma. clin exp ophthalmol 2009;37:270–274. 12. vasconcelos-moraes cg, susanna r. correlation between the water drinking test and modified diurnal tension curve in untreated glaucomatous eyes. clinics 2008;63:433– 436. 13. hatanaka m, alencar lm, de moraes cg, susanna r. reproducibility of intraocular pressure peak and fluctuation of the water-drinking test. clin exp ophthalmol 2013;41:355–359. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 31 peak iop time in wdt; susanna et al 14. babic m, de moraes cg, hatanaka m, ju g, susanna r. reproducibility of the water drinking test in treated glaucomatous patients. clin exp ophthalmol 2015;43:228–233. 15. susanna r, hatanaka m, vessani rm, pinheiro a, morita c. correlation of asymmetric glaucomatous visual field damage and water-drinking test response. invest ophthalmol vis sci 2006;47:641–644. 16. de moraes cg, susanna r, sakata lm, hatanaka m. predictive value of the water drinking test and the risk of glaucomatous visual field progression. j glaucoma 2017;26:767–773. 17. susanna r, vessani rm, sakata l, zacarias lc, hatanaka m. the relation between intraocular pressure peak in the water drinking test and visual field progression in glaucoma. br j ophthalmol 2005;89:1298–1301. 18. gameiro g, monsalve p, golubev i, ventura l, porciatti v. neurovascular changes associated with the water drinking test. j glaucoma 2018;27:429–432. 19. kerr nm, lew hr, skalicky se. selective laser trabeculoplasty reduces intraocular pressure peak in response to the water drinking test. j glaucoma 2016;25:727–731. 20. martinez p, trubnik v, leiby be, hegarty se, razeghinejad r, savant s, et al. a comparative study of the water drinking test in eyes with open-angle glaucoma and prior trabeculectomy or tube shunt. j glaucoma 2017;26:119– 125. 21. germano ras, susanna r, de moraes cg, susanna bn, susanna cn, chibana mn. effect of switching from latanoprost to bimatoprost in primary open-angle glaucoma patients who experienced intraocular pressure elevation during treatment. j glaucoma 2016;25:e359– e366. 22. waisbourd m, savant sv, sun y, martinez p, myers js. water-drinking test in primary angle-closure suspect before and after laser peripheral iridotomy. clin exp ophthalmol 2016;44:89–94. 23. spaeth gl, vacharat n. provocative tests and chronic simple glaucoma. i. effect of atropine on the waterdrinking test: intimations of central regulatory control. ii. fluorescein angiography provocative test: a new approach to separation of the normal from the pathological. br j ophthalmol 1972;56:205–216. 24. diestelhorst m, krieglstein gk. the effect of the water-drinking test on aqueous humor dynamics in healthy volunteers. graefes arch clin exp ophthalmol 1994;232:145–147. 25. de moraes cgv, reis asc, cavalcante af de s, sano me, susanna r. choroidal expansion during the water drinking test. graefes arch clin exp ophthalmol 2009;247:385– 389. 26. bhartiya s, ichhpujani p. water drinking test: the second innings scorecard. clin exp vis eye res 2020;3:1–3. 27. world medical association. world medical association declaration of helsinki: ethical principles for medical research involving human subjects. jama 2013;310:2191– 2194. 28. susanna cn, susanna r, hatanaka m, susanna bn, susanna fn, de moraes cg. comparison of intraocular pressure changes during the water drinking test between different fluid volumes in patients with primary open-angle glaucoma. j glaucoma 2018;27:950–956. 29. konstas agp, quaranta l, mikropoulos dg, nasr mb, russo a, jaffee ha, et al. peak intraocular pressure and glaucomatous progression in primary open-angle glaucoma. j ocul pharmacol ther 2012;28:26–32. 30. de moraes cg, liebmann jm, greenfield ds, gardiner sk, ritch r, krupin t. risk factors for visual field progression in the low-pressure glaucoma treatment study. am j ophthalmol 2012;154:702–711. 31. v de moraes cg, juthani vj, liebmann jm, teng cc, tello c, susanna r jr, et al. risk factors for visual field progression in treated glaucoma. arch ophthalmol 2011;129:562–568. 32. razeghinejad m, tajbakhsh z, nowroozzadeh m, masoumpour m. water drinking test: intraocular pressure changes after tube surgery and trabeculectomy. j ophthalmic vis res 2017;12:390. 33. de moraes cg, jasien jv, simon-zoula s, liebmann jm, ritch r. visual field change and 24-hour iop-related profile with a contact lens sensor in treated glaucoma patients. ophthalmology 2016;123:744–753. 32 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 original article ray tracing versus thin-lens formulas for iol power calculation using swept-source optical coherence tomography biometry reza ghaffari1,2, md; parisa abdi1, md; alireza moghaddasi1, md; somayeh heidarzadeh1, ms; hossein ghahvhechian3, md; maryam kasiri1, ms 1eye research center, department of cornea, farabi eye hospital, tehran university of medical sciences, tehran, iran 2stein eye institute and department of ophthalmology, david geffen school of medicine at the university of california, los angeles (ucla), los angeles, california, usa 3eye research center, the five senses health institute, rassoul akram hospital, iran university of medical sciences, tehran, iran abstract purpose: to evaluate the ray tracing method’s accuracy employing okulix ray tracing software and thin-lens formulas to calculate intraocular lens (iol) power using a swept-source optical coherence tomography (ss-oct) biometer (oa2000). methods: a total of 188 eyes from 180 patients were included in this study. an oa-2000 optical biometer was used to collect biometric data. the predicted postoperative refraction based on thin-lens formulas including srk/t, hoffer q, holladay 1, and haigis formulas and the ray tracing method utilizing the okulix software was determined for each patient. to compare the accuracy of approaches, the prediction error and the absolute prediction error were determined. results: the mean axial length (al) was 23.66 mm (range: 19–35). in subgroup analysis based on al, in all ranges of als the ray tracing method had the lowest mean absolute error (0.56), the lowest standard deviation (sd; 0.55), and the greatest proportion of patients within 1 diopter of predicted refraction (87.43%) and the lowest absolute prediction error compared to the other formulas (except to srk/t) in the al range between 22 and 24 mm (all p < 0.05). in addition, the okulix and haigis formulas had the least variance (variability) in the prediction error in different ranges of al. conclusion: the ray tracing method had the lowest mean absolute error, the lowest standard deviation, and the greatest proportion of patients within 1 diopter of predicted refraction. so, the okulix software in combination with ssoct biometry (oa2000) performed on par with the third-generation and haigis formulas, notwithstanding the potential for increased accuracy in the normal range and more consistent results in different ranges of al. keywords: biometry; intraocular; lenses; optical phenomena; phacoemulsification j ophthalmic vis res 2022; 17 (2): 176–185 176 © 2022 ghaffari et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i2.10788&domain=pdf&date_stamp=2019-07-17 oct biometry; ghaffari et al introduction accurate intraocular lenses (iol) power calculation and precision refractive outcomes following cataract surgery are now seen as a critical component in determining the success of refractive surgery. in recent years, there have been advancements in this field with the introduction of newer devices for ocular biometry and iol power calculation formulas. however, choosing the best method for iol power calculation is still a challenging issue.[1, 2] since 1999, with the introduction of iol master, optical biometry has established itself as the standard for axial length (al) measurement. since 2009, newer devices such as the al-scan (nidek co, aichi, japan), lenstar (haag-streit, switzerland), aladdin (topcon eu, tokyo, japan), and iol master 700 (carl zeiss meditec ag, jena, germany) have been launched and made accessible. each of these biometers are made up of four closely related technologies: optical low-coherence interferometry (olci), optical lowcoherence reflectometry (olcr), partial coherence interferometry (pci), and swept-source optical coherence tomography (ss-oct).[3–6] the oa-2000 (tomey, nagoya, japan) has lately superseded the oa-1000 model. the oa2000, which was just released, employs ss-oct with a laser wavelength of 1060 nm. the al, anterior chamber depth (acd), crystalline lens thickness (lt), central corneal thickness (cct), corneal diameter (cd), pupil size, and keratometry (k) could all be examined with this equipment.[7,8] a firm agreement has also been reported between the oa-2000 and the reference iol master 500 biometer for almost all biometry measurements.[9] concerning the iol power calculation formulas most commonly used in clinical practice, the thin-lens formulas, including the third-generation *correspondence to: hossein ghahvehchian, md. rassoul akram hospital, sattarkhan niayesh st., tehran 1455364, iran. email: hosein_gh1370@yahoo.com received: 10-08-2019 accepted: 25-12-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i2.10788 theoretical and fourth-generation formulas like haigis, are currently widely used by cataract surgeons. the gullstrand eye model is the main structure of these formulas. in this mode, it is assumed that the cornea is a thin optical lens with a refractive index of 1.3375 (or 1.3315 in the haigis formula) and a constant ratio of the anterior/posterior curvature, along with gaussian optics assumptions which only apply to paraxial rays, are the basis of all of these formulas.[2] as an alternative approach, ray-tracing technology has been applied for iol power calculation with promising results in both nonoperated eyes, especially in high myopic and hyperopic patients, and post-refractive surgery eyes.[10,11] the ray-tracing method offers the potential to increase iol power calculation accuracy by considering the geometric and optical properties of different interfaces like the cornea and the iol, taking into account the effect of aberrations like spherical aberrations, and performing analyses of single rays limited only by the pupillary zone.[12,13] as a result, in order to design lenses and optical systems, the ray tracing method has now become the standard technique.[14] in this investigation, the okulix ray-tracing program was used to assess the accuracy of iol power calculation, which combines corneal topography data for iol power calculation, in comparison with the secondand third-generation formulas and the fourth-generation haigis formula using an ss-oct biometer (oa2000). methods this prospective study was conducted between may 2015 and may 2016. the institutional review board of our hospital approved the study protocol, and the study was conducted by the tenets of the declaration of helsinki. written informed consent was obtained from all participants. this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: ghaffari r, abdi p, moghaddasi a, heidarzadeh s, ghahvhechian h, kasiri m. ray tracing versus thin-lens formulas for iol power calculation using swept-source optical coherence tomography biometry. j ophthalmic vis res 2022;17:176–185. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 177 https://knepublishing.com/index.php/jovr oct biometry; ghaffari et al study population this study included 188 eyes of 180 patients who had visually significant cataracts. patients with a history of previous intraocular or refractive surgery, corneal grafts, corneal scars, keratoconus, edema, pseudoexfoliation syndrome, glaucoma, and posterior segment disease (e.g., macular hole, neovascular age-dependent maculopathy, macular edema, or geographic atrophy) were excluded from the study. patients with intraoperative complications like decentered capsulorhexis, tear in the anterior or posterior capsule, vitreous loss, or those with a postoperative best-corrected visual acuity (bcva) < 20/40 were excluded as well. preoperative measurements complete ophthalmic examinations, including visual acuity testing, tonometry, and fundus examination, were performed before surgery. biometric data including al, acd, cct, and lt were collected using the oa 2000 optical biometer (nagoya, japan, software v.1.0r) in the immersion mode. a swept-source laser with a wavelength of 1060 was used to measure the optical distance between ocular surfaces. the device can analyze corneal curvature in nine rings, each with 256 points in a 5.5 mm zone using placido-based topography of the anterior corneal surface. to experience the best correlation with the iol master, keratometry values in the 2.5 mm optical zone were utilized for the iol power calculation for the thin-lens formulae. the iol power for each patient was chosen in accordance with the intended refraction of 0.00 d. the iol power and the predicted postoperative refraction based on thin-lens formulas, thirdgeneration formulas (srk/t, hoffer q, and holladay 1), and the fourth-generation haigis formula were determined by the device software for each patient. the optimized iol constants for each iol and formula provided by the user group for laser interference biometry (available at http: //www.augenklinik.uniwuerzburg.de/ulib/c1.htm, accessed april 12, 2017) were used for calculations. ray-tracing method okulix ray-tracing program (tedics peric & jöher gbr, dortmund, germany) was used to assess the iol power and also to forecast postoperative refraction while relying upon the implanted iol type used for the ray-tracing method. okulix is a software that calculates the iol power using corneal topography and has been used extensively in prior cases.[2] the program is capable of modeling the monochromatic optical capacities of the pseudophakic human eye. unlike gaussian optics-based formulas, which are only applicable for paraxial rays, okulix performs an analysis of single rays limited only by the pupillary zone, taking into account the effect of spherical aberration. ray tracing covers the region between the fovea and the cornea. the software also considers the effect of oblique incidence of light rays (stiles-crawford effect). light rays undergo refractions on different interfaces (vitreous, lens, aqueous humor, cornea), and the refractive index changes at each interface. the okulix database contains labeled iol data, such as anterior and posterior vertex radii, central thickness, refractive index, and asphericity of both surfaces for aspheric iols. the pupil size in the ray-tracing software was set at 2.5 mm at iris plane. all calculations of the okulix were set for the optimal focus, that was described by the international organization for standardization (iso 11979-2) as the ray that contacts the pupil plane at a determined distance (𝑑 = 0.5 × √2 × 𝑝𝑢𝑝𝑖𝑙 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟) for each meridian. the position of the postoperative iol was determined using an algorithm based on acd and crystalline lt.[13] surgical technique all patients underwent phacoemulsification performing a 2.8 mm temporal approach with astigmatically neutral or near-neutral posterior limbal incisions.[16] aiming at a 5-mm capsulorhexis size, the standard phacoemulsification technique was used to remove the cataract. the following spherical monofocal iols, c-flex 570c (rayner intraocular lenses ltd, east sussex, uk), rayner superflex 620h, and acry-sof sa60at (alcon alcon laboratories inc, ft worth, texas), and an aspheric iol, rayner superflex aspheric 920h (rayner) were selected, assigned, and implanted in the capsular bag of the respective patients. iol power selection was based on the al. the srk-t was used in al > 26, holladay 1 for al between 22 178 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 http://www.augenklinik.uniwuerzburg.de/ulib/c1.htm http://www.augenklinik.uniwuerzburg.de/ulib/c1.htm oct biometry; ghaffari et al and 26, and the hoffer-q in al < 22. all operations were performed by the same experienced surgeon (rg). outcome measures the prediction error (pe) and absolute pe were used to assess accuracy (ae). the difference between the spherical equivalent (se) of the refraction predicted by the formula for the implanted iol and the actual postoperative refraction was designated as the pe. subjective refraction using a 6-m acuity chart was employed to detect manifest refraction one month postoperatively. statistical analysis the mean, median, and standard deviation (sd) of pe and absolute pe were calculated to show the distribution of the data. the formulas were compared using linear mixed models and pairwise comparisons with bonferroni correction after accounting for inter-eye correlation. the heterogeneity of the variances was analyzed by the leven’s test. subgroup analysis based on the al and iol type was also done by pairwise comparisons with bonferroni correction. the percentage of eyes within the predicted refractions of 0.25, 0.5, and 1 d for each formula was calculated, and the significance of their differences was analyzed by the generalized estimating equation (gee) analysis. results the study included 188 eyes of 180 patients (100 women; mean age, 62.4 ± 10.4 years). the mean al was 23.66 ± 2 mm (range: 19–35). table 1 shows the distribution of the al in our patients. the implanted iol models included the rayner c-flex 570c (59 eyes), rayner superflex 620h (22 eyes), rayner superflex aspheric 920h (70 eyes), and acry-sof sa60at (37 eyes). the mean power of the implanted iols was 18.87 ± 6.12 d (range: –9 to 39) and the mean postoperative manifest refraction was 0.1 ± 0.78 d (range: –4.62 to +2.75). in four patients, the postoperative absolute refractive se error was more than 2 d. the mean and sd of the pe and ae of all seven formulas, and the percentage of the patients within the predicted refractions of 0.25, 0.5, and 1 d for each formula have been shown in table 2. comparison of the pe between different formulas showed the significant superiority of the okulix formula in terms of the lowest mean ae (mae), the lowest sd, and the narrowest range of pe. the heterogeneity of variances was significantly based on leven’s test (p < 0.001). as shown in table 3 and figure 1, pairwise comparisons of the formulas with bonferroni correction revealed statistically significant lower values in the mae of the okulix as compared to other formulas (all p < 0.05). there were no significant differences between the srk/t, hoffer q, holladay 1, haigis standard, and haigis optimized formulas. comparison of the pe of the formulas in subgroup analysis based on the al using pairwise comparisons with the bonferroni correction showed that the okulix had the lowest mae as compared to other formulas (except srk/t) in the al range of 22–24 mm (table 4). there were no statistically significant differences between formulas in the subgroup analysis based on the al [figure 2]. regarding the percentage of eyes within the predicted refractions of 0.25, 0.5, and 1 d, although the okulix had the highest proportion of the eyes in each group [table 2 and figure 3], based on the gee analysis for the percentage of eyes within the 0.25 and 0.5 d, the difference was not significant. however, there was a significant difference in the percentages of eyes within 1 d of predicted refraction between the okulix and all the other formulas (p < 0.05). the distribution of the pe and ae error for each formula based on the al has been shown in figures 4 and 5, respectively. as shown in these figures, the okulix and haigis formulas had the least variability (minimum variance) of change in the pe in different ranges of al. in subgroup analysis based on the implanted iol type using the linear mixed model and ad-hoc bonferroni’s test, thirdgeneration formulas did not seem to favor one iol model over others. there was significant precision calculated for c-flex 570c among other iols for the okulix (p < 0.05), however, no statistical difference was found between the okulix and other formulas in subgroup analysis for other iols. the detailed journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 179 oct biometry; ghaffari et al table 1. the axial length measurements of patients and the frequency of axial length ranges mean median sd range frequency (%) <22 mm 22-24 mm 24-26 mm 26-30 mm >30 mm total 23.66 mm 23.29 mm ±2.07 19 to 35 mm 22(11.7) 112(59.6) 37(19.7) 13(6.9) 4(2.1) 188(100) sd, standard deviation table 2. prediction and absolute prediction error and percentage of patients within the predicted refraction for each formula formula pe ae % within predicted refraction mean sd median range mean sd median range ±0.25d ±0.50 d ±1.00 d srk/t 0.18 1.07 0.18 -4.14 to 4.09 0.75 0.79 0.50 0.01 to 4.14 25.00 50.53 78.19 hoffer q 0.13 1.06 0.11 -5.11 to 3.97 0.74 0.77 0.48 0.02 to 5.11 20.21 53.19 76.60 holladay 1 0.16 1.02 0.12 -4.72 to 4.03 0.71 0.75 0.48 0.01 to 4.72 24.47 53.72 80.32 haigis 0.24 1.06 0.20 -5.53 to 4.31 0.71 0.82 0.49 0.00 to 5.53 25.00 52.66 80.85 okulix 0.09 0.79 0.01 -1.89 to 1.49 0.56 0.55 0.47 0.01 to 1.89 29.94 55.69 87.43 pe, prediction error; ae, absolute prediction error; sd, standard deviation results based on the iol type have been shown as supplemental data [table 1]. discussion our study results showed that the ray tracing method using the okulix software together with the oa2000 swept-source optical biometer performed comparable other third-generation and haigis formulas. the mean al of our study population was 23.66 mm, which is within the range of the mean al reported in the normal population. incidentally, our study included a vast range of als (19–35 mm) and patients with short (11.7 % with al < 22 mm) and long eyes (9% with al > 26 mm). in this study, based on a pairwise comparison of the formulas, the okulix had the lowest absolute error when the analysis included all als. however, in subgroup analysis based on al, the difference in absolute error was statistically significant in the al 22–24 mm (except to srk/t). there were no significant differences between the other thirdgeneration and haigis formulas when the al was not considered. the good results of the ray-tracing method may be due to the fact that the ray tracing uses the exact snell’s law as compared to the conventional thin-lens formulas which rely on gaussian optics assumptions which apply only to the paraxial rays in the optical system. therefore, it can model the human eye optics more precisely.[11,17] the raytracing also incorporates corneal topography data, which means it may be more accurate in calculating corneal power since more wide surface data is entered into the ray-tracing program.[17] incorporation of the crystalline lens position and thickness as biometric parameters in addition to factors like the al for prediction of the postoperative pseudophakic acd could be another reason for improved results of the ray-tracing method in our study. hoffman et al reported improved results (9% reduction in the mae) by taking into account the effect of the crystalline lens position and thickness in the algorithm used to predict the postoperative iol position as compared to the algorithm only using the al [appendix1].[13] some other modern formulas like the holladay 2 and olsen also employ the crystalline lt as an important biometric measurement in their calculations for predicting the effective lens position (elp). this finding is consistent with previous reports about pe of the third-generation formulas.[18,19] regarding the relationship between the pe and al changes, the okulix and haigis formulas had the least variance in different ranges of the al. as shown in figure 2, in normal and short als, 180 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 oct biometry; ghaffari et al table 3. pairwise comparison of absolute prediction error between okulix and other formulas formula(j) mean difference(i-j) se p value 95% confidence interval for difference srk/t -0.180 0.037 < 0.001 -0.293 to -0.066 okulix(i) hoffer q -0.168 0.036 < 0.001 -0.279 to -0.057 holladay 1 -0.140 0.035 0.002 -0.247 to -0.033 haigis -0.144 0.038 0.003 -0.260 to -0.029 se, standard error figure 1. the absolute prediction error of each formula. comparison of the prediction error of the formulas in subgroup analysis based on the al using pairwise comparisons with the bonferroni correction showed that the okulix had the lowest mae compared to other formulas (all p < 0.05). and especially in the al 22–24 mm, there was the least discrepancy between the formulas. as the al increased, remarkable differences could be observed in each formula’s absolute error, so that both the mean absolute error of each formula and also the discrepancy between different formulas increased in als > 26 mm. however, the okulix had the lowest changes in the absolute error based on the al. these findings are in agreement with the results of the study by hoffman.[20] in this study, the holladay 1 formula in als < 24 mm and the haigis formula in als > 24 mm had the lowest error after the okulix. the methods used for prediction of the iol position in each formula could be a factor explaining differences observed in multiple als. third-generation formulas use different iol constants, als, and keratometry readings for elp prediction. using keratometry readings to calculate the corneal height as a basis for this formula is implicated as a source of error in elp estimation in different combinations of the al and keratometry, resulting in non-physiologic irregularities in the prediction of the iol power as described in the srk/t formula.[21,22] on the other hand, the use of parameters like the ac depth in the haigis formula [which uses three different constants a0, a1, a2 related to the iol, ac depth, and al, respectively] and the ac depth and lt in the okulix formula instead of indirect assumptions based on keratometry readings is associated with a higher degree of overall accuracy in the prediction of the iol position in different ranges of the al. similar to the results reported by hoffman et al comparing the accuracy of the okulix and journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 181 oct biometry; ghaffari et al figure 2. the absolute prediction error of the formulas based on the axial length. there were no statistically significant differences between the other formulas in subgroup analysis based on the axial length. figure 3. percentage of eyes within the predicted refraction in each formula. regarding the percentage of eyes within the predicted refractions of 0.25, 0.5, and 1 d, although the okulix had the highest proportion of the eyes in each group, the difference was not significant based on the generalized estimating equation analysis for the percentage of eyes within the 0.25 and 0.5 d. however, there was a significant difference in the percentages of eyes within 1 d of predicted refraction between the okulix and all the other formulas (p < 0.05). the third-generation formulas, we observed results that were on par among (and even more accurate results in the al 22–24 mm) these formulas. however, unlike their results, we did not find any significant superiority of the okulix formula in the high myopic and hyperopic eyes, which may be related to the small sample size of these patients in this study population. according to figure 3, the number of cases with refractive surprise was also lower in the okulix than other formulas. the predicted error was 1 d and lower in 87.5% of the patients based on the 182 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 oct biometry; ghaffari et al figure 4. distribution of absolute prediction errors based on axial length for each formula. the okulix and haigis formulas had the lowest magnitude of change in the absolute prediction error in different ranges of axial length. most cases of refractive surprise were myopic eyes with als > 26 mm. figure 5. distribution of absolute prediction errors based on axial length for each formula. the okulix and haigis formulas had the lowest magnitude of change in the prediction error in different ranges of axial length. okulix, while 80.7% of the patients based on the haigis and 78.2% based on the srk/t formula were within the pe of 1 d. according to figure 4, most cases of refractive surprise were myopic eyes with als > 26 mm. hoffman et al compared the accuracy of the ray tracing between aspheric aberration-correcting and spherical iols and reported the particular benefits of the ray tracing method for iol power calculation for aspheric iols.[20] in this study, we journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 183 oct biometry; ghaffari et al did not find any significant differences between aspheric and spherical iol types, which may be related to the smaller sample size of our study. the relatively small sample size is the first limitation of this study. we did not use optimization for other third-generation and haigis formulas for comparisons which may be necessary for the final achievable accuracy with these formulas since the current software for the okulix on the oa-2000 device does not allow for optimization. however, because the optimized iol constants are not usually available to the surgeon, the results of this study are still valid in helping ophthalmologists to choose the appropriate iol power formula in the clinical setting. in addition, we did not compare our results with some other modern formulas like the holladay 2, olsen, and barret’s formulas. another limitation is the limited follow-up of our patients. iol position changes due to fibrosis of capsule that could happen in the first three months after surgery may cause refractive changes. however, there are also papers[20,23−−26] using refraction at one month as the outcome. it should also be mentioned that using different iol types could lead to variation in refractive outcomes. however, due to limitations in the power of lenses available, different types of iol were used in the study. in summary, the results of this study demonstrated that the ray tracing method using the okulix software and the biometric data provided by the new swept-source biometer yielded comparable results with the third-generation and haigis formulas. where all patients were included, the okulix formula had the lowest mean absolute error and a more constant pattern of performance in different ranges of the al when compared to other formulas. based on our results, the raytracing method may be an accurate and robust method for calculation of the iol power in virgin corneas. financial support and sponsorship none. conflicts of interest the authors declare that there are no conflicts of interest. appendix 1 the assumed postoperative iol position is calculated two formulas:[13] 1) a𝑎= c𝑚× ( 𝑎 𝑎𝑚) 0.7+ a𝑚– c𝑚– 0.5 × (d – d𝑚) a𝑎= anterior chamber depth with the iol in the eye of interest cm = distance between the posteriorcornea and center of a 21.00-d iol in a mean-sized eye (4.6 mm) a, am = axial length of the eye of interest and a mean-sized eye (23.6 mm) am = anterior chamber depth with the iol model of interest in a mean-sized eye d, dm = thickness of the iol of interest and 21.00d iol of the same model. 2) a𝐿 = a𝐿 + 0.574 × t𝐿 – 0.632 – (0.5 × d) a𝐿 = anterior chamber depth with the iol in the eye of interest ap = preoperative anterior chamber depth t𝐿 = thickness of the crystalline lens d = thickness of the iol references 1. rozema jj, wouters k, mathysen dg, tassignon mj. overview of the repeatability, reproducibility, and agreement of the biometry values provided by various ophthalmic devices. am j ophthalmol 2014;158:1111–20.e1. 2. preussner pr, wahl j, lahdo h, dick b, findl o. ray tracing for intraocular lens calculation. j cataract refract surg 2002;28:1412–1419. 3. akman a, asena l, gungor sg. evaluation and comparison of the new swept source oct-based iolmaster 700 with the iolmaster 500. br j ophthalmol 2016;100:1201–1205. 4. huang j, savini g, li j, lu w, wu f, wang j, et al. evaluation of a new optical biometry device for measurements of ocular components and its comparison with iolmaster. br j ophthalmol 2014;98:1277–1281. 5. hoffer kj, shammas hj, savini g. comparison of 2 laser instruments for measuring axial length. j cataract refract surg 2010;36:644–648. 6. mandal p, berrow ej, naroo sa, wolffsohn js, uthoff d, holland d, et al. validity and repeatability of the aladdin ocular biometer. br j ophthalmol 2014;98:256–258. 7. santodomingo-rubido j, mallen eah, gilmartin b, wolffsohn js. a new non-contact optical device for ocular biometry. br j ophthalmol 2002;86:458. 184 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 oct biometry; ghaffari et al 8. wang q, savini g, hoffer kj, xu z, feng y, wen d, et al. a comprehensive assessment of the precision and agreement of anterior corneal power measurements obtained using 8 different devices. plos one 2012;7:e45607. 9. kongsap p. comparison of a new optical biometer and a standard biometer in cataract patients. eye and vis 2016;3:27. 10. nabil k. accuracy of intraocular lens power calculation using partial coherence interferometry and okulix ray tracing software in high myopic cataract patients. delta j ophthalmol 2017;18:77–80. 11. saiki m, negishi k, kato n, torii h, dogru m, tsubota k. ray tracing software for intraocular lens power calculation after corneal excimer laser surgery. jpn j ophthalmol 2014;58:276–281. 12. olsen t, funding m. ray-tracing analysis of intraocular lens power in situ. j cataract refract surg 2012;38:641–647. 13. hoffmann p, wahl j, preussner pr. accuracy of intraocular lens calculation with ray tracing. j refract surg 2012;28:650–655. 14. jin h, rabsilber t, ehmer a, borkenstein af, limberger ij, guo h, et al. comparison of ray-tracing method and thin-lens formula in intraocular lens power calculations. j cataract refract surg 2009;35:650–662. 15. international organization for standardization. iso 11979-2:2014. ophthalmic implants – intraocular lenses – part 2: optical properties and test methods 2014 [internet]. iso; 2014. available from: https://www.iso.org/standard/55682.html 16. hoffmann pc, auel s, hutz ww. results of higher power toric intraocular lens implantation. j cataract refract surg 2011;37:1411–1418. 17. preussner pr, hoffmann p, petermeier k. [comparison between ray-tracing and iol calculation formulae of the 3rd generation]. klin monbl augenheilkd 2009;226:83– 89. 18. hoffer kj. the hoffer q formula: a comparison of theoretic and regression formulas. j cataract refract surg 1993;19:700–712. 19. brandser r, haaskjold e, drolsum l. accuracy of iol calculation in cataract surgery. acta ophthalmol scand 1997;75:162–165. 20. hoffmann pc, lindemann cr. intraocular lens calculation for aspheric intraocular lenses. j cataract refract surg 2013;39:867–872. 21. cooke dl, cooke tl. prediction accuracy of preinstalled formulas on 2 optical biometers. j cataract refract surg 2016;42:358–362. 22. haigis w. occurrence of erroneous anterior chamber depth in the srk/t formula. j cataract refract surg 1993;19:442–446. 23. lyle wa, jin gjc. prospective evaluation of early visual and refractive effects with small clear corneal incision for cataract surgery. j cataract refract surg 1996;22:1456– 1460. 24. masket s, tennen dg. astigmatic stabilization of 3.0 mm temporal clear corneal cataract incisions. j cataract refract surg 1996;22:1451–1455. 25. cooke dl, cooke tl. comparison of 9 intraocular lens power calculation formulas. j cataract refract surg 2016;42:1157–1164. 26. hoffer kj, hoffmann pc, savini g. comparison of a new optical biometer using swept-source optical coherence tomography and a biometer using optical low-coherence reflectometry. j cataract refract surg 2016;42:1165–1172. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 185 original article subthreshold micropulse laser for long-lasting submacular fluid after rhegmatogeous retinal detachment surgery giulia esposti1, md; pier luigi esposti1, md, francesco costantino2, md; dario zappalà2, md; antonio pinna3, md; mario fruschelli4, md 1studio oculistico esposti, siena, italy 2graduate school of ophthalmology, university of siena, siena, italy 3department of medical, surgical, and experimental sciences, ophthalmology unit, university of sassari, sassari, italy 4dipartimento di scienze mediche chirurgiche e neuroscienze, university of siena, siena, italy orcid: giulia esposti: https://orcid.org/0000-0001-5486-8647 mario fruschelli: https://orcid.org/0000-0002-3869-8593 abstract purpose: to assess the safety and efficacy of subthreshold micropulse laser (sml) photo-stimulation in the management of persistent subfoveal fluid (psf) after surgery for rhegmatogenous retinal detachment (rrd). methods: in this pilot study, 11 eyes of 11 patients (8 men, 3 women) with longlasting (12–18 months) psf after surgery for rrd were evaluated before and after photostimulation with subthreshold micropulse yellow laser. ophthalmic examination included best-corrected visual acuity (bcva), amsler grid test, ophthalmoscopy, autofluorescence (af), and optical coherence tomography (oct) with measurement of central point foveal thickness (cpft). primary outcome was subfoveal fluid resolution and secondary outcome was bcva improvement. results: the mean cpft and bcva were, respectively, 436.8 ± 28.8 μm and 0.25 ± 0.1 µm decimal equivalent (de) before photostimulation and 278 ± 54.4 μm and 0.57 ± 0.2 µm de after photostimulation, a statistically significant difference (p < 0.001). nine (81.8%) eyes showed improved bcva, disappearance of macular detachment on ophthalmoscopy, reduced retinal pigment epithelium distress on af, and restored macular profile with no neuroretinal alterations on oct scans. conclusion: although psf after rrd surgery is often a self-limiting disease, our results suggest that sml photostimulation may be effective and safe in patients with clinically significant long-lasting psf. larger case–control studies are necessary to confirm these results. keywords: optical coherence tomography; retinal pigment epithelium; rhegmatogenous retinal detachment; subretinal fluid; subthreshold micropulse laser j ophthalmic vis res 2022; 17 (3): 390–396 390 © 2022 esposti et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i3.11577&domain=pdf&date_stamp=2019-07-17 micropulse laser for subretinal fluid ; esposti et al introduction retinal detachment occurs when the neuroepithelium separates from the underlying retinal pigment epithelium (rpe) and fluid accumulates in the subretinal space.[1] nontraumatic rhegmatogenous retinal detachment (rrd) in phakic eyes has an incidence of about 1:10.000/year. surgery is the gold standard treatment for rrd. there are three main types of rrd surgery: episcleral, intrascleral, and vitreoretinal. regardless of the surgical technique chosen, the surgical goals are to identify and close all the breaks and reduce vitreoretinal traction. closure of the breaks occurs when the edges of the retinal break are brought into contact with the underlying rpe. persistence of subretinal fluid (srf) after closure of the retinal breaks is much higher after scleral buckle surgery than after vitrectomy (55% vs 15%).[2, 3] persistence of srf may impair visual recovery and be responsible for poor central vision, metamorphopsia, and loss of depth perception. srf is usually selflimiting,[4] but may occasionally become chronic and damage photoreceptors with permanent vision loss.[5] several authors have suggested possible explanations for srf formation after rrd surgery, but without conclusive evidence.[6] rpe plays a crucial role in subretinal fluid resorption.[1, 7] however, if rpe function is insufficient to restore the normal retinal anatomy and the fluid accumulates in the macular area, persistent subfoveal fluid (psf) with metamorphopsia and visual loss may occur.[4, 5] the presence of psf after episcleral or vitreoretinal surgery for rrd is a relatively uncommon, self-limiting complication.[2, 3] the management of psf following repair of rrd has typically been observation, because this condition often resolves spontaneously. in refractory correspondence to: mario fruschelli, md. viale m. bracci 16, siena 53100, italy. e-mail: mario.fruschelli@unisi.it received: 02-08-2021 accepted: 29-01-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i3.11577 cases, vitrectomy with gas tamponade may be considered.[5] recently, koinzer et al have suggested a noninvasive approach by selective retina therapy, a new laser technology using a train of µs-laser pulses to selectively damage rpe cells.[8] the aim of this pilot study was to investigate the efficacy and safety of subthreshold micropulse laser (sml) photostimulation[9] in 11 eyes of 11 patients with symptomatic, long-lasting psf after successful rrd surgery. methods this study was conducted in compliance with the tenets of the declaration of helsinki for research involving human subjects. institutional ethics review board approval was obtained. each participant received detailed information and provided written consent. a total of 11 patients (8 men, 3 women; mean age 54.3 ± 5.5 years), who had undergone rrd surgery at our ophthalmology unit between september 2012 and october 2016, were recruited in this pilot study. eight patients had episcleral surgery only, whereas three had episcleral + vitreoretinal surgery. all patients complained of long-lasting (range: 12–18 months, mean: 14.72 months) distorted vision and difficulty in reading after surgery. common diagnosis was macular detachment due to psf after rrd surgery. all subjects underwent a full ophthalmic examination, including measurement of best-corrected visual acuity (bcva), funduscopic evaluation under pharmacological mydriasis (volk 90d no contact slit-lamp lens, volk opticals, mentor on the lake, oh, usa), amsler grid test, central point foveal thickness (cpft) determined by structural optical coherence tomography (oct) (rtvue100®, optovue inc. fremont, ca, usa), and autofluorescence (af) with ultra-widefield imaging (daytona𝑇𝑀, optos, marlboruogh ma, usa). this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: esposti g, esposti pl, costantino f, zappalà d, pinna a, fruschelli m. subthreshold micropulse laser for long-lasting submacular fluid after rhegmatogeous retinal detachment surgery . j ophthalmic vis res 2022;17:390–396. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 391 https://knepublishing.com/index.php/jovr micropulse laser for subretinal fluid ; esposti et al figure 1. cases 1 and 2: oct before sml treatment showed an optically empty macular space between rpe and neuroepithelium with granular deposits adhering to the outer photoreceptor segments (a & c) . after photostimulation, psf was undetectable by oct and granular deposits were unchanged (b & d). figure 2. case 5. oct in a myopic patient with evidence of multiple areas of serous detachment of the neuroepithelium (a). six months after sml photostimulation there are no detectable areas of detachment (b). a single session of sml photostimulation with yellow diode laser (iq 577𝑇𝑀, iridex corporation, mountain view, ca, usa) was performed. the following protocol was used: mydriasis with topical 1% tropicamide, anesthesia with 4% benoxinate eye-drops, application of an area centralis® contact lens (field of view 70/84º, image magnification 1.06x, laser spot 0.94%, volk opticals, mentor on the lake, oh, usa), and sml photostimulation. laser parameters were set as follows: confluent spots at 70% of the minimum power necessary to obtain retinal whitening in micropulse mode, 100 µm diameter (100 µm x 0.94 laser factor = 94 µm), 200 ms duration, 5% operating duty cycle. the power used was 440 to 530 mw (mean: 466.3 mw). laser spots were performed on the entire edematous area; then, tobramycin-dexamethasone eyedrops were administered twice a day for 15 days. patients were re-examined after one, two, and three months and then every three months for 12–36 months. each follow-up evaluation included bcva, ophthalmoscopy, amsler grid test, af and oct. the raw data were reported in an excel sheet and then transferred to the statistical package for the social sciences, version 21 (ibm corporation, armonk, ny, usa) for analysis. preand posttreatment bcva and cft were analyzed using paired student’s ttest. 392 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 micropulse laser for subretinal fluid ; esposti et al ta b le 1. d et ai ls of pa tie nt s w ho un de rw en t su bt hr es ho ld m ic ro pu ls e la se r (s m l) ph ot os tim ul at io n fo r pe rs is te nt su bf ov ea l flu id (p sf ) af te r rh eg m at og en ou s re tin al de ta ch m en ts ur ge ry . s e x/ a g e e p is cl e ra ls u rg e ry (e ) o r vi tr e ct o m y (v ) t im e b e tw e e n su rg e ry a n d p h o to st im u la ti o n (m o n th s) c e n tr a lp o in t fo ve a lt h ic k n e ss p re p h o to st im u la ti o n v is u a la cu it y p re p h o to st im u la ti o n p o w e r, m w n u m b e r o f sp o ts c e n tr a lp o in t fo ve a lt h ic k n e ss p o st p h o to st im u la ti o n v is u a la cu it y p o st p h o to st im u la ti o n f o llo w -u p (m o n th s) t im e b e tw e e n p h o to st im u la ti o n a n d re so lu ti o n o f p s f (m o n th s) (d e ci m a l e q u iv a le n t) (d e ci m a l e q u iv a le n t) m /5 0 e 18 50 3 0. 02 5 50 0 40 0 21 9 0. 3 24 3 m /5 5 e 18 40 2 0. 3 48 0 40 0 24 5 1 21 3 f/4 5 e 16 44 3 0. 2 53 0 76 6 24 6 0. 7 33 2 m /6 0 e+ v 12 42 3 0. 2 44 0 68 0 27 1 0. 7 12 6 m /5 2 e 16 43 8 0. 1 49 0 45 0 27 0 0. 6 36 6 m /6 3 e 14 44 0 0. 2 42 0 45 0 26 5 0. 4 12 2 f/5 5 e+ v 12 42 0 0. 3 49 0 43 0 36 5 0. 3 15 n r * f/5 7 e 12 46 6 0. 3 45 0 52 0 27 0 0. 6 15 1 m /5 1 e 14 42 1 0. 4 44 0 46 0 25 6 0. 7 18 6 m /4 9 e 12 44 4 0. 3 45 0 53 0 40 0 0. 4 21 n r * m /6 0 e+ v 18 40 5 0. 4 44 0 49 0 25 1 0. 6 15 1 m ea n ± sd 54 .3 ± 5 .5 yr s 14 .7 3 ± 2 .5 7 43 6. 82 ± 28 .7 7 0. 25 ± 0. 11 46 6 ± 34 50 6 ± 11 6 27 8 ± 54 .4 0. 57 ± 0. 21 20 ± 8 3. 3 ± 2 .12 *n o re so lu tio n of ps f journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 393 micropulse laser for subretinal fluid ; esposti et al results the mean cpft before and after photostimulation were 436.8 ± 28.8 and 278 ± 54.4𝜇m, respectively, a statistically significant difference (p < 0.00001). the mean bcva before and after photostimulation were 0.25 ± 0.1 and 0.57 ± 0.2 decimal equivalent (de), respectively, again a statistically significant difference (p < 0.0001). there was bcva improvement in 10 (90.9%) eyes, whereas vision remained unchanged in patient 7, who had undergone episcleral + vitreoretinal surgery. there was a mean decrease in cpft of 149.8 μm (34.2%). in all cases, subfoveal fluid was ophthalmoscopically undetectable, amsler grid test was negative, and oct scans showed a marked reduction of the optically empty space between rpe and neuroepithelium. time between photostimulation and psf resolution was one to six months (mean: 3.3 ± 2.1 months), but in two cases (case 7, who had undergone episcleral + vitreoretinal surgery, and case 10, who had undergone episcleral surgery) the treatment was ineffective [table 1]. no rpe changes were detected on oct and af during the followup period. all patients underwent only one session of sml photostimulation. in cases 1 and 2, granular deposits adherent to the outer photoreceptor segments remained unchanged after photostimulation [figure 1]. case 5 had diffuse myopic degeneration, positive amsler grid test, af evidence of apparently normal posterior pole, but oct evidence of multiple areas of serous detachment of the neuroepithelium. six months after photostimulation, amsler grid test was negative and oct confirmed disappearance of the neuroepithelial detachment, whereas ophthalmoscopy and af pictures remained unchanged [figure 2]. in the remaining cases, no remarkable photostimulation-induced alterations were found. no adverse effects related to sml photo-stimulation were recorded. discussion in this pilot study investigating the efficacy and safety of sml photostimulation in eyes with symptomatic, long-lasting psf after successful rrd surgery, we found that the mean cpft and bcva improved significantly after sml treatment. overall, 9 (81,8%) eyes out of 11 showed improved bcva, disappearance of macular detachment on ophthalmoscopy, reduced retinal pigment epithelium distress on af, and restored macular profile with no neuroretinal alterations on oct scans. to maintain adhesion to rpe, the neuroepithelium relies on a variety of active and passive mechanisms (hydrostatic and choroid oncotic pressure).[1] rpe, an active pump, is responsible for the main mechanism, draining fluid toward the choroid at a rate of 0.1–0.3 ml/h/mm2and accounting for 70% of transepithelial fluid movement. this polarized monocellular layer maintains ionic gradients by means of the na+/k+ pump and aquaporin-1 channels at the apex of the plasma membrane.[10] other adhesion factors between the retina and choroid include apical interdigitations of the rpe and a mucopolysaccharide matrix, known as interphotoreceptor matrix, in the subretinal space.[11, 12] rpe activity is therefore essential for adhesion of the neuroepithelium and resorption of residual subretinal fluid after rrd surgery. we used sml photostimulation with the aim to reactivate rpe and favor resorption of residual subfoveal fluid. micropulse diode laser has the appropriate characteristics for this purpose.[13, 14] a continuous laser emits a constant flow of energy, albeit with very short exposure times, whereas in micropulse mode the emission is fractionated into a train of brief impulses, the duration (on) and interval (off) of which can be varied by the operator. brief duration limits the time during which laser-induced heat diffuses into adjacent tissues (neuroepithelium); a longer interval allows more time for tissue cooling.[15] this type of laser emission is therefore devoid of endpoint retinal “whitening”.[7, 9] no laser trace is left on the retina, undetectable by ophthalmoscopy during and after treatment, or by af or oct scans after treatment.[16, 17] the choice of wavelength 577 nm is justified by the interaction of the laser with the tissue and conversion of laser energy into heat. the three main chromophores that absorb light are melanin (the most efficient, located in the rpe and choroid, where energy is converted into heat), hemoglobin (the highest absorption coefficient of 577-nm radiation is found in oxyhemoglobin of the choriocapillaris), and xanthophyll (found in the inner and outer plexiform layers of the macula, where light of this wavelength is only minimally absorbed). all this favors laser selectivity for rpe, sparing the internal 394 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 micropulse laser for subretinal fluid ; esposti et al layers of the neuroretina. certain wavelengths can penetrate deeper layers, regardless of the uneven distribution of melanin. the different distribution of the three chromophores ensures a uniform effect of the laser in eyes with little or irregular fundus pigmentation.[18] subthreshold micropulsed laser has beneficial intracellular biological effects without any visible damage during or after treatment. photostimulation reactivates rpe cellular activity,[19, 20] with upand downregulation of various rpe factors stimulating fluid resorption,[21, 22] such as overexpression of stromal cell-derived factor 1 (sdf1), which attracts stem cells and restores the normal function of rpe by renewing dead epithelial and endothelial cells.[23, 24] photothermal stimulation induces the expression of heat shock protein (hsp), which normalizes the levels of cytokines and reduces chronic inflammation.[19] psf after retinal surgery for rrd is a relatively uncommon and self-limiting condition, which can occasionally cause major visual loss. the management of psf following repair of rrd has typically been observation. in refractory cases, vitrectomy with gas tamponade may be considered. in our small case series, sml photostimulation with yellow diode laser yielded a statistically significant improvement in cpft (p < 0.00001) and bcva (p < 0.0001). our results are consistent with the observation reported by landa.[25] overall, these findings suggest that sml photostimulation may be an effective, noninvasive, and safe approach for psf management. as this was a pilot study, the number of patients was small and sample size planning to ensure an adequate power was unnecessary. the main limitation of our investigation is that it was not a randomized prospective case–control study. as there is no definitive proof of efficacy of steroids or oral diuretics in this condition,[26] multicentric randomized studies comparing sml photostimulation with simple observation are warranted to establish whether, or not, sml can be considered as a potential, noninvasive alternative for the treatment of psf after rrd surgery. ethical approval this article does not contain any study with animals performed by any of the authors. all procedures performed in this study involving human participants were done in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 helsinki declaration and its later amendments or comparable ethical standards. informed consent was obtained from all individual participants included in the study. financial support and sponsorship this research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. conflicts of interest the authors report no conflicts of interest. the authors alone are responsible for the content and writing of the paper. references 1. marmor mf. ryan’s retina. in: schachat r, editor. mechanisms of normal retinal adhesion. volume iii. st. louis: mosby; 2006. p. 1891–908. 2. gharbiya m, malagola r, mariotti c, parisi f, de vico u, ganino c, et al. spectral-domain optical coherence tomography analysis of persistent subretinal fluid after scleral buckling surgery for macula-off retinal detachment. eye 2015;29:1186–1193. 3. benson se, schlottmann pg, bunce c, xing w, charteris dg. optical coherence tomography analysis of the macula after vitrectomy surgery for retinal detachment. ophthalmology 2006;113:1179–1183. 4. ricker lj, noordzij lj, goezinne f, cals d, berendschot t, liem a, et al. persistent subfoveal fluid and increased preoperative foveal thickness impair visual outcome after macula-off retinal detachment repair. retina 2011;31:1505– 1512. 5. reichstein da, larsen bp, kim je. management of persistent subretinal fluid following retinal detachment repair. jama ophthalmol 2013;131:1240–1244. 6. veckeneer m, derycke l, lindstedt ew, van meurs j, cornelissen m, bracke m, et al. persistent subretinal fluid after surgery for rhegmatogenous retinal detachment: hypothesis and review. graefes arch clin exp ophthalmol 2012;250:795–802. 7. lanzetta p, dorin g, piracchio a, bandello f. theoretical bases of non-ophthalmoscopically visible endpoint photocoagulation. semin ophthalmol 2001;16:8–11. 8. koinzer s, elsner h, klatt c, porksen e, brinkmann r, birngruber r, et al. selective retina therapy (srt) of chronic subfoveal fluid after surgery of rhegmatogenous retinal detachment: three case reports. graefes arch clin exp ophthalmol 2008;246:1373–1378. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 395 micropulse laser for subretinal fluid ; esposti et al 9. ohkoshi k, tsuiki e, kitaoka t, yamaguchi t. visualization of subthreshold micropulsed diode laser photocoagulation by scanning laser ophthalmoscopy in the retro mode. am j ophthalmol 2010;150:856–862. 10. stamer wd, bok d, hu j, jaffe gj, mckay bs. aquaporin1 channels in human retinal pigment epithelium: role in transepithelial water movement. invest ophthalmol vis sci 2003;44:2803–2808. 11. berman er. mucopolysaccharides (glycosaminoglicans) of the retina: identification, distribution and possible biological role. bibl ophthalmol 1969;79:5–31. 12. edelman gm. cell adhesion molecules. science 1983;219:450–457. 13. dorin g. subthreshold and micropulse diode laser photocoagulation. semin ophthalmol 2003;18:147–153. 14. lanzetta p, polito a, verritti d. subthreshold laser. ophthalmology 2008;115:216–216.e1. 15. berger jw. thermal modeling of micropulsed diode laser retinal photocoagulation. lasers surg med 1997;20:409– 415. 16. desmettre tj, mordon sr, buzawa d, mainster ma. micropulsed and continuous-wave diode retinal photocoagulation: visible and subvisible laser parameters. br j ophthalmol 2006;90:709–712. 17. dorin g. evolution of retinal laser therapy: minimum intensity photocoagulation (mip). can the laser heal the retina without harming it? semin ophthalmol 2004;19:62– 68. 18. yu ak, merrill kd, truong sn, forward km, morse ls, telander dg. the comparative histologic effects of subthreshold 530-and 810-nm diode micropulse laser on the retina. invest ophthalmol vis sci 2013;54:2216–2224. 19. inagaki k, shuo t, katakura k, ebihara n, murakami a, ohkoshi k. sublethal photothermal stimulation with a micropulse laser induces heat shock protein expression in arpe-19 cells. j ophthalmol 2015;2015:729–792. 20. ricci fu, mazzarelli p, zonetti mj, missiroli f, cesareo m, pucci s. 810 nm micropulse laser irradiation selectively regulates vegf 165 isoforms expression acting on rna binding splice factor activation in indocyanine green loaded arpe19 and caco2 cultured cells. invest ophthalmol vis sci 2010;51:409–415. 21. wilson as, hobbs bg, shen wy, speed tp, schmidt u, begley cg, et al. argon laser photocoagulation-induced modification of gene expression in the retina. invest ophthalmol vis sci 2003;44:1426–1434. 22. flaxel c, bradle j, acott t, samples jr. retinal pigment epithelium produces matrix metalloproteinases after laser treatment. retina 2007;27:629–634. 23. harris jr, brown ga, jorgensen m, kaushal s, ellis ea, grant mb, et al. bone marrow-derived cells home to and regenerate retinal pigment epithelium after injury. invest ophthalmol vis sci 2006;47:2108–2113. 24. caballero s, kent dl, sengupta n, li calzi s, shaw l, beli e, et al. bone marrow-derived cell recruitment to the neurosensory retina and retinal pigment epithelial cell layer following subthreshold retinal phototherapy. invest ophthalmol vis sci 2017;58:5164–5176. 25. landa g. micropulse laser for persistent sub-retinal fluid in a patient previously treated for rhegmatogenous retinal detachment. med hypothesis discov innov ophthalmol 2018;7:190–194. 26. arezu h, jiun d, hossein a. eplerenone as a novel treatment for persistent subretinal fluid following retinal detachment surgery. am j ophthalmol case rep 2018;10:261–263. 396 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 case report peripapillary capillary network in methanol induced optic neuropathy kiana hassanpour1,2, md, mph; negin mohammadi1, md; hamideh sabbaghi3,4, phd; alireza amirabadi1, md mohammad pakravan1, md 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2department of ophthalmology, imam hossein hospital, shahid beheshti university of medical sciences, tehran, iran 3ophthalmic epidemiology research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 4department of optometry, school of rehabilitation, shahid beheshti university of medical sciences, tehran, iran orcid: mohammad pakravan: https://orcid.org/0000-0002-5421-0359 kiana hassanpour: https://orcid.org/0000-0002-1788-7352 abstract purpose: to present the optical coherence tomography angiography (octa) findings of the radial peripapillary capillary (rpc) network in an individual with severe bilateral methanol-induced toxic optic neuropathy (mton) in comparison to a normal subject and a patient with retinitis pigmentosa. case report: a 35-year-old man with severe bilateral mton was referred to the neuro-ophthalmology clinic at the labbafinejad medical center. the angio vue oct 3d set of 4.5 × 4.5 mm was used to measure the disc and peripapillary vessel density. two subjects were examined with the same protocol as controls to determine the effect on the rpc vessel density in multiple scenarios. one of the controls was a healthy individual with the prerequisite matches of age and sex while the second one was a known retinitis pigmentosa (rp) patient. rpc density was measured as 37.7 in the patient with mton, 46.9 in the rp patient, and 54.7 in the healthy control. conclusion: the reduction in the rpc vessel density in a patient with mton compared to that of a healthy individual and also a patient with rp may be due to the loss of capillaries secondary to the loss of nerve fibers and ganglion cells. moreover, mton can be considered an optic neuropathy with direct mitochondrial damage to the endothelial cells of the capillaries. keywords: methanol-induced toxic optic neuropathy; optical coherence tomography angiography; radial peripapillary capillary network j ophthalmic vis res 2022; 17 (1): 140–145 140 © 2022 hassanpour et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10180&domain=pdf&date_stamp=2019-07-17 peripapillary circulation in methanol toxicity ; hassanpour et al introduction methanol poisoning could be caused by drinking homemade alcoholic beverages.[1] patients who survive this life-threatening condition may also suffer other morbidities including methanolinduced toxic optic neuropathy (mton).[2] formic acid, a metabolite of methanol can result in acute retinal ganglion cells injury and edema of the optic nerve. the presence of the intraretinal fluid revealed in the optical coherence tomography (oct) reports could present an argument for the role of vessel injury as one of the plausible culprits in the pathophysiology of the disease, mton. nurieva et al showed a progressive and chronic loss of those axons that survived after methanol poisoning which supports the aforementioned hypothesis.[3] due to the rarity of these cases, studies are scarce and the exact mechanism behind the progressive axonal loss remains unknown. to examine retinal vascularity in mton, fluorescein angiography (fa) is not always feasible because of the concurrent poor general status and high prevalence of renal insufficiency in these patients. optical coherence tomography angiography (oct-a) as a noninvasive novel technique for visualization of vascular flow is viable and provides high-resolution images of both retinal and radial peripapillary capillaries.[4] in this report, we present the oct-a findings of the radial peripapillary capillary (rpc) network in an individual with severe bilateral mton. case report a 35-year-old man with the chief complaint of bilateral decreased visual acuity following the ingestion of a homemade alcoholic beverage two weeks prior was referred to us. he had been in a coma for two days and had undergone correspondence to: mohammad pakravan, md. department of ophthalmology, labbafinejad medical center, paidarfard st., boostan 9 st., pasdaran, tehran 16666iran. e-mail: mohpakravan@gmail.com received 21-01-2020; accepted 22-09-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10180 hemodialysis twice during the acute phase. he had previously received the protocol suggested by the author (mp) that included erythropoietin and intravenous steroid.[2, 6] visual loss was detected after the improvement of consciousness. when we first saw him, visual acuity was counting fingers at 30 cm in the right eye and no light perception (nlp) in the left eye. trace afferent pupillary defect was detected in the left eye. the anterior segment slitlamp biomicroscopy and goldmann applanation tonometry results were normal. in the funduscopy, the optic nerves were mildly swollen. macula and retinal periphery tests were normal bilaterally. the perimetry test was not possible to execute. the oct-a was performed using xr avanti angio vue octa (optovue inc., fermont, ca, usa). the angio vue oct 3d set of 4.5× 4.5 mm was used to measure disc and peripapillary vessel density. for vessel analysis, a slab between the outer limit of the retinal nerve fiber layer (rnfl) and the internal limiting membrane was made. two regions of interest (roi) were defined for measuring vessel density within the area occupied by the vessels. two elliptical contour lines were used first for defining the disc area which was determined manually and second for corresponding to a peripapillary area with a width of 0.75 mm from the first elliptical line. two subjects were examined with the same protocol as controls. one of the controls was a healthy individual with the matching prerequisites of age and sex while the second one was a known patient with a history of retinitis pigmentosa (rp), which started from early adulthood and visual acuity of counting fingers at 4 m in both eyes. in examination of the rp patient, it was revealed that he had optic pallor in both eyes as well as arterial narrowing, diffuse retinal degeneration, and peripheral bone spicules. capillary peripapillary vessel density was 37.7% in the mton patient, 46.9% in the rp patient, and 54.7% in the healthy control. figure 1 shows the oct-a images of all three cases. in the mton case, measurements of the oct-a angio vue vessel analysis were all lower, as compared to that of the this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: hassanpour k, mohammadi n, sabbaghi h, amirabadi a, pakravan m. peripapillary capillary network in methanol induced optic neuropathy . j ophthalmic vis res 2022;17:140–145. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 141 https://knepublishing.com/index.php/jovr peripapillary circulation in methanol toxicity ; hassanpour et al table 1. peripapillary oct-a parameter in mton, rp, and healthy control variables mton vessel density (%) rp vessel density (%) healthy control vessel density (%) capillaries all capillaries all capillaries all whole image od 38.4 45.5 45.7 49.5 50.1 56.5 os 37.1 43.6 44.7 48 49.9 56.6 inside disc od 39.4 51 39.7 50 45.2 54.7 os 34.6 44.5 44.4 53.2 47.0 57.8 peripapillary od 37.7 44.9 46.9 50.2 54.7 60.6 os 36 43.3 42.3 45.1 54.1 60.5 superior hemifield od 36.5 44.2 46.9 50.2 54.8 60.9 os 39.1 46 39.7 41.9 53.5 61.2 inferior hemifield od 39 45.5 47 50.1 54.5 60.2 os 32.7 41.3 45.1 48.5 54.8 59.7 nasal od 34 47 52 os 32 47 63 temporal od 51 52 54 os 27 41 47 mton, methanol-induced toxic optic neuropathy; rp, retinitis pigmentosa controls [table 1]. peripapillary oct in the patient with mton revealed an average rnfl thickness of 148 microns in the right eye and 140 microns in the left eye. discussion in this case report, we described the findings of the peripapillary oct-a in a case of mton. we discovered the reduction in the rpc vessel density two weeks after the mton situation was compared to a healthy individual and also to a patient with optic pallor secondary to rp. the possible mechanism explaining the reduced vascular density may be the loss of capillaries secondary to the loss of nerve fibers and ganglion cells.[5] loss of rnfl and the ganglion cell layer (gcl) happens as a result of two separate mechanisms. formic acid which is a toxic metabolite produced after methanol ingestion directly enters the ganglion cells and causes severe structural and functional damage. ganglion cell damage then results in nerve fiber loss. moreover, the edema subsequent to rnfl damage may cause a compartment syndrome.[6] various studies investigating oct-a in different optic neuropathies reported a reduction of peripapillary vessel density, for example, in non-arteritic anterior ischemic optic neuropathy (naion),[7] optic neuritis,[8] optic atrophy secondary to retinal dystrophies,[9] thyroid eye disease,[10] vitamin deficiency,[11] or leber hereditary optic neuropathy (lhon).[12] two possible mechanisms may explain peripapillary vessel density reduction in different optic neuropathies. first, any diseases causing axonal loss leads to reduced metabolic need in the rnfl layer and consequently reduces capillaries through autoregulatory mechanisms.[5] the next mechanism is the direct injury of the capillaries by the acquired disease. while the former is thought to be more prominent in vessel dropouts, the latter can also be highlighted in optic neuropathies with mitochondrial damages such as with lhon which can also have a direct adverse impact on vascular endothelial and vascular smooth muscle cells viability.[13] examining both eyes of the patient, the eye with more severe visual loss showed lower vessel density in all four quadrants. rnfl thickness cannot be a reliable measure in the acute phase, 142 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 peripapillary circulation in methanol toxicity ; hassanpour et al figure 1. peripapillary oct-a images in mton compared to rp and a healthy individual. from left to right, slo images, en-face oct-a (ilm-nfl), corresponding b-scan, vessel density map in mton, rp patient, and a healthy control. vessel density analysis has been done between two slabs shown in b-scans. however, the thickness was slightly higher in the right eye (148 and 140 in the right and left eyes, respectively). previous reports confirmed the accordance of peripapillary vessel dropout and rnfl loss in different acute and chronic optic neuropathies including glaucoma and non-arteritic ischemic optic neuropathy (naion),[8, 14] so lower temporal vessel density can indicate higher axonal damage in this important area. in mton, formate toxicity inhibits the mitochondrial function through inhibition of the cytochrome oxidase system. production of journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 143 peripapillary circulation in methanol toxicity ; hassanpour et al reactive oxygen species and toxic aldehydes exacerbate mitochondrial damage.[15] therefore, mton can be considered an optic neuropathy with both direct mitochondrial damage of endothelial cells of capillaries and secondary autoregulatory reduction of peripapillary vessels. another striking finding in our patient was the lower vessel density in the temporal quadrant of the nlp eye; this finding could strengthen the hypothesis of direct mitochondrial damage of the vessels in the event of methanol poisoning. rnfls of the papillomacular bundle which is directly responsible for central visual acuity contain more vulnerable and smaller fibers. previous studies confirmed the order of rnfl involvement in leber hereditary optic neuropathy (lhon), a disease of mitochondrial involvement, first affects the temporal quadrant and lastly the nasal quadrant.[16] in rp, vascular damage is the early event and optic neuropathy can be considered as a secondary event resulting from peripapillary vessel attenuation and photoreceptor degeneration.[9] in our rp patient, optic pallor was obvious, yet the vessel density was higher in all quadrants as compared to the mton patient. although the lower rp vessel density compares to the mton in only one case which might not be conclusive, it could imply that both mechanisms are connected in mton. in other words, rnfl, gcl, and vascular endothelial cell destruction together accentuate the damage of vessels and these could explain why rpc vessel dropout is more severe in mton. oct-a is a safe and fast method to evaluate retinal vessels in survivors of methanol poisoning in whom fa may be contradicted. spaide et al comparing fa and oct-a in 12 patients with different optic neuropathies concluded oct-a outperforms fa in the visualization of the precapillary network.[17] moreover, the quantitative measurement of onh vessels is possible with oct-a rather than fa. nevertheless, many patients with nlp cannot be evaluated by oct-a as a result of poor fixation. in conclusion, mton as a rare and devastating optic neuropathy can be further evaluated by octa. our report demonstrated a reduction in rpc vessel density for the first time. future studies are needed to confirm our findings in a series of patients. acknowledgment this article is taken from the disease registry, titled “the iranian national registry of inherited retinal dystrophy (irdreg®)” and code number of ir.sbmu.orc.rec.1396.15 from the ethic committee, that was supported by the deputy of research and technology in shahid beheshti university of medical sciences (http://dregistry.sbmu.ac.ir). financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. massoumi g, saberi k, eizadi-mood n, shamsi m, alavi m, morteza a. methanol poisoning in iran, from 2000 to 2009. drug chem toxicol 2012;35:330–333. 2. pakravan m, sanjari n. erythropoietin treatment for methanol optic neuropathy. j neuroophthalmol 2012;32:325–328. 3. nurieva o, diblik p, kuthan p, sklenka p, meliska m, bydzovsky j, et al. progressive chronic retinal axonal loss following acute methanol-induced optic neuropathy: four-year prospective cohort study. am j ophthalmol 2018;191:100–115. 4. akil h, falavarjani kg, sadda sr, sadun aa. optical coherence tomography angiography of the optic disc; an overview. j ophthal vis res 2017;12:98. 5. falavarjani kg, tian jj, akil h, garcia ga, sadda sr, sadun aa. swept-source optical coherence tomography angiography of the optic disk in optic neuropathy. retina 2016;36:s168–s77. 6. pakravan m, esfandiari h, sanjari n, ghahari e. erythropoietin as an adjunctive treatment for methanolinduced toxic optic neuropathy. am j drug alcohol abuse 2016;42:633–639. 7. sharma s, ang m, najjar rp, sng c, cheung cy, rukmini av, et al. optical coherence tomography angiography in acute non-arteritic anterior ischaemic optic neuropathy. br j ophthalmol 2017;101:1045–1051. 8. chen jj, abouchehade je, iezzi jr r, leavitt ja, kardon rh. optical coherence angiographic demonstration of retinal changes from chronic optic neuropathies. neuroophthalmology 2017;41:76–83. 9. mastropasqua r, borrelli e, agnifili l, toto l, di antonio l, senatore a, et al. radial peripapillary capillary network in patients with retinitis pigmentosa: an optical coherence tomography angiography study. front neurol 2017;8:572. 144 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 peripapillary circulation in methanol toxicity ; hassanpour et al 10. zhang t, xiao w, ye h, chen r, mao y, yang h. peripapillary and macular vessel density in dysthyroid optic neuropathy: an optical coherence tomography angiography study. invest ophthalmol vis sci 2019;60:1863–1869. 11. pellegrini f, prosdocimo g, papayannis a, cirone d. optical coherence tomography angiography findings in deficiency optic neuropathy. neuroophthalmology 2019;43:401–406. 12. takayama k, ito y, kaneko h, kataoka k, ra e, terasaki h. optical coherence tomography angiography in leber hereditary optic neuropathy. acta ophthalmol 2017;95:e344–e345. 13. chiong m, cartes-saavedra b, norambuena-soto i, mondaca-ruff d, morales pe, garcía-miguel m, et al. mitochondrial metabolism and the control of vascular smooth muscle cell proliferation. front cell dev biol 2014;2:72. 14. jia y, wei e, wang x, zhang x, morrison jc, parikh m, et al. optical coherence tomography angiography of optic disc perfusion in glaucoma. ophthalmology 2014;121:1322– 1332. 15. liesivuori j, savolainen h. methanol and formic acid toxicity: biochemical mechanisms. pharmacol toxicol 1991;69:157–163. 16. pan bx, ross-cisneros fn, carelli v, rue ks, salomao sr, moraes-filho mn, et al. mathematically modeling the involvement of axons in leber’s hereditary optic neuropathy. invest ophthalmol vis sci 2012;53:7608– 7617. 17. spaide rf, klancnik jm, cooney mj. retinal vascular layers imaged by fluorescein angiography and optical coherence tomography angiography. jama ophthalmol 2015;133:45–50. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 145 original article binocular function in different gaze positions amir asharlous1, phd; asgar doostdar1, phd; vahid ghaemi2, ms; mina farzi1, ms; abbasali yekta3, phd; abolghasem mortazavi4, md; hadi ostadimoghaddam5, phd; mehdi khabazkhoob6, phd 1rehabilitation research center, department of optometry, school of rehabilitation sciences, iran university of medical sciences, tehran, iran 2noor research center for ophthalmic epidemiology, noor eye hospital, tehran, iran 3department of optometry, school of paramedical sciences, mashhad university of medical sciences, mashhad, iran 4sina hospital, department of neurosurgery, tehran university of medical sciences, tehran, iran 5refractive errors research center, mashhad university of medical sciences, mashhad, iran 6department of basic sciences, school of nursing and midwifery, shahid beheshti university of medical sciences, tehran, iran orcid: amir asharlous: https://orcid.org/0000-0003-4631-215x abbasali yekta: https://orcid.org/0000-0003-4356-9064 abstract purpose: to evaluate varied aspects of binocular function in multiple gaze positions. methods: in 2018, this cross-sectional study was conducted on 21 participants (male = 11) with an age range of 19–25 years. having emmetropia and 10/10 visual acuity in both eyes were conditions of the inclusion criteria for the crosssectional study. the following aspects of binocular function including amplitude of accommodation (aa), near point of convergence, near phoria, and monocular accommodative facility were evaluated in five gazes (primary, upward, downward, left, and right) for all subjects. results: near point of convergence values showed significant differences in all gaze positions (p < 0.001). the lowest near point of convergence value was seen in the primary gaze (2.69 cm) and the downward gaze (3.47 cm) and the highest near point of convergence value was seen in the left gaze (7.5 cm). there was also a significant difference in the amplitude of accommodation among the upward, downward, and the primary gaze (p < 0.001) positions but no difference was observed among the temporal, nasal, and the primary gaze positions. there was a significant difference in near phoria between the upward gaze and the primary gaze (p = 0.008) while no significant differences were observed among the other gazes. there was no significant variance in the monocular accommodative facility among the different gaze positions (p = 0.175). conclusion: the results of this study indicated variations that exist in the convergence and accommodation reflex functions in multiple gaze positions, which proved to be more prominent in the convergence system. although the accommodative sufficiency evaluation was inconsistent among the multiple gaze positions, the accommodative facility evaluation was consistent in all gazes. keywords: accommodation; binocular vision; convergence; facility; gaze; phoria j ophthalmic vis res 2022; 17 (2): 209–216 © 2022 asharlous et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 209 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i2.10792&domain=pdf&date_stamp=2019-07-17 binocular function in different gazes; asharlous et al introduction binocular vision incorporates several reflexes including accommodation and convergence. accommodation is a conditional reflex that provides a clear retinal image at different distances through regulating the crystalline lens curvature.[1] convergence is another conditional reflex of the visual system that is stimulated by disparity on the retina. it occurs following diplopia resulting from stimulation of non-corresponding points in the fellow eyes and preventing diplopia through the disconjugate movement of the eyes.[2] therefore, convergence is an anti-diplopia reflex while accommodation is an anti-blur mechanism. these two reflexes cooperate in forming a single and clear image at different distances. suppression or stimulation of the accommodative reflex cause changes in the vergence reflex and vice versa. therefore, these reflexes have important codependent interactions where disorders in either one can disturb the function of the other.[3] as a result of the multiple gaze positions, especially in upward and downward gazes, vertical rectus, horizontal rectus, and oblique muscles are involved in abduction and adduction processes, so the amount of convergence may vary at different directions.[4] the presence of deviations with a, v, x, and y patterns indicates that within these deviations, varied amounts of convergence in upward and downward gazes results in diverse amounts of esotropia and exotropia in multiple directions.[5–7] since the accommodative system has a neural link with the vergence system and there is interaction between them, it is expected that the accommodative function will vary in multiple gaze positions, especially in the vertical direction. a few studies have investigated accommodation and convergence variances in correspondence to: abbasali yekta, phd. department of optometry, school of paramedical sciences, mashhad university of medical sciences, mashhad 9177948964, iran. email: yektaa@mums.ac.ir received: 10-04-2021 accepted: 07-09-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i2.10792 multiple gaze positions in the past.[8–11] ripple et al reported marked differences in aa in varied gaze positions,[8] while atchison et al found no significant variances in this regard.[9] as for convergence, a study by sheni et al on nine subjects found multiple values for convergence in varied gaze positions.[10] the results of an interesting study by nguyen et al in 2008 showed changes in the accommodative convergence/accommodation results when tested in different gaze positions.[12] as mentioned previously, there were discrepancies in the results of previous studies which suffered from serious shortcomings and flaws. one of the main flaws of these studies was that they only assessed the accommodative or convergence system exclusively and did not evaluate both of them and their codependent effects. in addition, the sample size was very small in some studies like the one conducted by nguyen et al. another shortcoming was that they only addressed the amplitude of accommodation and did not study other functional aspects like facility. therefore, it is recommended that comprehensive studies be conducted to assess the accommodative system from both aspects of amplitude and facility in multiple gaze positions while also comparing the convergence amplitude in the same gaze directions. in addition, besides these two reflexes, the amount of phoria should also be investigated in multiple gaze positions. considering the strong interaction among these parameters, such studies help to understand their impact on the mechanism of binocular vision in varied gaze positions. this study was conducted to evaluate the binocular function aspects of accommodative and convergence systems as well as phoria in multiple gaze positions. methods this cross-sectional study was conducted on a group of volunteers aged 19–25 years who this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: asharlous a, doostdar a, ghaemi v, farzi m, yekta a, mortazavi a, ostadimoghaddam h, khabazkhoob m. binocular function in different gaze positions. j ophthalmic vis res 2022;17:209–216. 210 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 https://knepublishing.com/index.php/jovr binocular function in different gazes; asharlous et al met the inclusion criteria in 2019. the inclusion criteria were the following: a corrected visual acuity of 10/10 in both eyes; hyperopia, myopia, and astigmatism of maximum 0.5 diopter; complete ocular health; lack of strabismus; and no history of strabismus surgery. the tenets of the declaration of helsinki were observed in this study and its protocol was approved by the ethics committee of shahid beheshti university of medical sciences. the participants were assured of data anonymity and confidentiality and informed consent was obtained from all of them. primary examinations demographic data of the participants were recorded and history of ocular and visual problems was taken. all examinations were conducted by an expert optometrist. auto refraction was done for both eyes to evaluate the inclusion criteria (topcon, kr-8900, japan) and the visual acuity of the fellow eyes was measured using a snellen chart. ocular health was then evaluated using a slit lamp (topcon sl-6e, japan). the patients were admitted into the study if they met the inclusion criteria. binocular examinations all subjects who met the inclusion criteria and joined the study underwent complete binocular examinations including the measurement of accommodative amplitude, near point of convergence, monocular accommodative facility, and near-cover test to measure near phoria in the primary gaze as well as the upward, downward, left, and right gazes. positioning for the test target was determined relative to the primary gaze where the visual target was presented at an angle of 40º in each of the various gaze positions. a protractor and ruler were used to fix the angle at the different gaze positions. using a protractor and placing the zero degree on the primary position (facing the patient’s pupil), 40º to the relevant gaze was determined and then a 33-cm long ruler was placed from the center of the protractor and at a 40º angle position in the direction of the respective gaze. the target was then placed at the end of the ruler, in the direction of the center of the cornea, and the angle and distance for each test were checked again. all these measurements were done very carefully. in all of the studied gazes, great emphasis was placed on the correct determination of the 40º angle. how to control the angle and distance is illustrated in figure 1. the order of the tests was randomized within the various subjects and also within the multiple gaze positions. a 5-min washout time was applied between each test and measurements in the varied gaze positions. the optotypes on the 20/30 line of a near snellen chart were used as the fixation target. one eye was occluded and the patient was asked to fixate on the target during the test and try to keep it single and clear. negative lenses were then added at 0.25 diopter steps. when the target became clear, stronger lenses were introduced. this process continued until the patient reported a sustained blur and could not see the target clearly using the last applied lens. in this condition, the immediate previous lens’ power was recorded as the final lens power. the final lens power was then added to 2.5 diopter and the result was recorded as the amplitude of accommodation. this process was done in all of the five gaze positions. the optotypes on the 20/30 line of a near snellen chart were also used as the fixation target for the near point of convergence measurement. with both eyes open, the target was moved towards the patient’s eyes along the nasal bridge at a speed of 1 cm/s and the patient was asked to keep the target single and clear. the nearest distance between the target and the nasal bridge at which the patient reported a sustained double vision (subjective) or the examiner noticed an ocular deviation or a fusion break (objective) was considered the near point of convergence and its value was recorded in cm. in addition to the primary gaze position, this measurement was repeated in the other four gaze positions at an angle of 40º. the monocular accommodative facility was measured using ±2.00 diopter flippers. the 20/30 optotypes were presented to the patient at 40 cm and the patient was asked to fixate on the target during the test and try to keep it single and clear with one eye closed. positive and negative lenses were alternately presented to the patient and the patient was asked to report the moment the target became clear. a stopwatch was used to measure the time in seconds from the moment the first lens was applied. each instance of clearing both plus journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 211 binocular function in different gazes; asharlous et al and minus lenses was counted as one cycle, and the number of cycles per 1 min was recorded as the monocular accommodative facility. an alternate cover test was applied to measure near phoria. ocular recovery movements were evaluated upon alternate occlusion and the direction of deviation was determined using the recovery direction. a prism bar was then used to measure the amount of deviation using the prism alternate cover test. corrective prism was added until no recovery movements were noticed on the alternate cover test. exophoria and esophoria were recorded as minus and plus values, respectively. statistical analysis the spss software was used for statistical analysis. mean and standard deviation were used to describe the data. for statistical comparison, data normality was checked using the kolmogorov–smirnov test. to compare the five gazes, the mean values of the gazes were used. to evaluate the difference in variables between males and females, t-test was used if the data had a normal distribution and mann–whitney was applied if the data had a nonnormal distribution. for analytical analysis, because the data were dependent variables, repeated measured analysis of variance was applied for comparison between the different gaze positions. p-values <0.05 were considered significant. results in this study, the data of 21 subjects, including 11 men (mean age = 21.90 ± 1.78 years) were analyzed. the mean and standard deviation of the parameters in five gaze positions are presented in table 1 and table 2 according to sex and all cases, respectively. none of the studied parameters were significantly different between male and female [table 1]. there was a significant variance in the amplitude of accommodation among the different gaze positions (p < 0.001). the results indicated a significant difference in the amplitude of accommodation among the upward and downward gaze positions and the primary gaze position (p = 0.002), while there was no significant difference among the left (p = 0.261) and right (p = 0.149) gaze positions and the primary gaze position. there was a significant variance in near point of convergence among the different gaze positions (p < 0.001). pairwise comparison between each type of gaze and the primary gaze position indicated significant variances in all gazes (p < 0.018). the smallest and largest near point of convergence value was seen in the primary and left gaze position, respectively. repeated measured analysis of variance (anova) showed a significant variance in the amount of near phoria among the five gaze positions (p = 0.026), and post-hoc revealed that the difference between the primary gaze and the up-gaze position (p = 0.008) showed the highest amount of exophoria. there was no significant difference in the monocular accommodative facility among the different gaze positions (p = 0.175). discussion this study compared multiple functions of binocular vision among different gaze positions. as mentioned earlier, there was a significant variance in the near point of convergence among the varied gaze positions. these findings were exactly similar to the results of a study by sheni et al[10] that reported the minimal vergence amplitude in 40º left and right gaze positions and the maximal vergence range between 10º and 20º below the primary horizontal plane. according to their study, the vergence range increased from the straightahead gaze position to 20º below the primary horizontal plane and then decreased from 20º to 40º in the same direction such that the vergence value was smaller in 40º below the horizontal plane as compared to the primary gaze.[10] in addition, near point of convergence findings showed convergence conditions in multiple degrees of gaze as compared to the primary position of gaze in the horizontal plane, while it was not true for vertical gaze positions. therefore, it can be stated that in the various horizontal gaze positions, the function of the horizontal rectus muscles, including medial rectus and lateral rectus, decrease symmetrically in the left and right gaze positions. it seems that the muscle force of lateral rectus and medial rectus is similar to the degrees of the right and left gaze position. however, this functional symmetry is not seen 212 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 binocular function in different gazes; asharlous et al table 1. the mean and standard deviation (sd) of indices in different gazes according to sex gaze male female p-value* p-value** mean ± sd mean ± sd phoria (pd) primary –4.00 ± 3.69 –2.4.0 ± 2.8 0.118 0.28 up –4.91 ± 3.81 –4.00 ± 3.16 0.2 0.561 down –3.18 ± 5.47 –1.00 ± 2.00 <0.001 0.426∗∗∗ left –4.36 ± 3.44 –2.8 ± 3.26 0.015 0.197∗∗∗ right –3.73 ± 2.83 –2.60 ± 3.13 0.006 0.426∗∗∗ aa (d) primary 9.45 ± 1.46 9.40 ± 1.54 0.056 0.934 up 9.09 ± 1.58 9.30 ± 1.44 0.016 0.918∗∗∗ down 9.91 ± 1.56 9.75 ± 1.57 0.152 0.819 left 9.73 ± 1.46 9.35 ± 1.36 0.2 0.547 right 9.32 ± 1.35 9.20 ± 1.49 0.2 0.851 npc (cm) primary 22.73 ± 17.94 31.50 ± 16.17 0.044 0.152∗∗∗ up 73.18 ± 31.01 60.50 ± 31.57 0.2 0.365 down 26.82 ± 20.03 43.50 ± 18.86 0.123 0.065 left 67.73 ± 33.86 83.00 ± 27.71 0.2 0.275 right 74.09 ± 50.59 66.00 ± 29.42 0.2 0.664 maf (cpm) primary 13.18 ± 8.32 7.10 ± 5.63 0.2 0.067 up 10.82 ± 7.19 8.00 ± 7.13 0.2 0.379 down 12.00 ± 6.93 7.80 ± 7.05 0.189 0.185 left 12.09 ± 7.20 7.90 ± 6.64 0.161 0.183 right 12.64 ± 7.42 8.80 ± 7.58 0.159 0.256 aa, accommodation amplitude; npc, near point of convergence; maf, monocular accommodative facility; cm, centimeter; cpm, cycle per minutes; pd, prism diopters ∗p-value was calculated by kolmogorov–smirnov for normality; ∗∗p-value was calculated by independent sampl t-test; ∗∗∗p-value was calculated by mann–whitney u-test in the vertical plane. convergence decreased in the upward and downward gaze positions as compared to the primary position of the gaze, which was more noticeable in the up-gaze position. the reason for this finding may be that horizontal rectus muscles do not apply a similar muscle force in varied degrees of the vertical gaze, which was reported in previous studies as well. previous studies also found that the muscle force of lr and mr decreased in the extreme up and down gaze positions as compared to the primary gaze.[13,14] another reason for decreased convergence power in upand down-gaze positions may be the interaction of superior and inferior oblique muscles in these positions. since these muscles are both abductor muscles, this abduction decreases convergence in the up-gaze position due to the function of the inferior oblique muscle and in the down-gaze position due to the function of the superior oblique muscle.[15] the question is why is convergence stronger in the downward gaze as compared to the upward gaze position? the first reason may be the conditional nature of the vergence reflex.[16] convergence is a conditional reflex, that is, it is capable of learning and improving over time.[16,17] it can be concluded that more ocular work in the down-gaze position during life due to normal activities like reading and other near-work activities, which are usually done in this gaze position, strengthen the vergence reflex in the down-gaze position as compared to the up-gaze position. this is also consistent with the results of a study by sheni that reported the maximal vergence range between 10º and 20º below horizontal plane, which is the gaze position used journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 213 binocular function in different gazes; asharlous et al table 2. the mean and standard deviation (sd) of indices in different gazes left right down up primary p-value∗ p-value∗∗ mean ± sd mean ± sd mean ± sd mean ± sd mean ± sd aa (d) 9.54 ± 1.38 9.26 ± 1.38 9.83 ± 1.52 9.19 ± 1.47 9.42 ± 1.46 0.2 0.001 npc (cm) 7.50 ± 3.13 7.02 ± 4.10 3.47 ± 2.08 6.71 ± 3.11 2.69 ± 1.79 0.2 0.001 maf (cpm) 10.10 ± 7.09 10.81 ± 7.56 10.00 ± 7.14 9.48 ± 7.13 10.29 ± 7.64 0.099 0.175 phoria (pd) –3.62 ± 3.36 –3.19 ± 2.96 –2.14 ± 4.29 –4.48 ± 3.45 –3.24 ± 3.21 0.2 0.026 aa, accommodation amplitude; npc, near point of convergence; maf: monocular accommodative facility; cm, centimeter; cpm, cycle per minutes; pd, prism diopters ∗p-value was calculated by kolmogorov–smirnov for normality in mean of five gazes; ∗∗p-value was calculated by repeated measured anova figure 1. how to adjust angles and distances for measurements at different gaze positions. cm; centimeter. for reading and other near-work activities,[18,19] as compared to the primary position of the gaze.[10] the second reason may be related to the neural link of the vergence and accommodative systems, that is, the ratio of accommodative convergence to accommodation.[20] since the results of this study and some previous studies showed a stronger accommodative reflex in the down-gaze versus the up-gaze position,[8,9] it can be expected that the same may be true for convergence as well. in fact, because there is more accommodation in the down-gaze position, accommodative convergence is also stronger, resulting in higher amplitude of convergence. the accommodative findings of the present study revealed the largest accommodative power in the down-gaze and the smallest in the upgaze position. some previous studies found similar results. ripple et al found that the largest amplitude of accommodation was for the down-gaze position followed by the nasal gaze.[8] however, the dioptric amount of difference was much larger in their study as compared to the present study such that the amplitude difference was 3 diopters between the extremes of the vertical plane and 1.5 diopter between the extremes of the horizontal plane. atchison et al found a higher amplitude of accommodation at the down-gaze position as compared to other directions and reported that this difference, although clinically unimportant, was statistically significant.[9] their findings are consistent with our results. in general, as for amplitude of accommodation changes in different gaze positions, it can be stated that accommodation usually has slightly larger amplitude in the primary and down-gaze positions and is weaker in the up-gaze position. a relatively stronger accommodation in the down-gaze position may be due to the conditional nature of the accommodative reflex. accommodation is also a conditional reflex and repeated usage of conditional reflexes during life strengthens 214 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 binocular function in different gazes; asharlous et al them.[16] it may seem logical that because routine near-work activities are done in the down-gaze position, this reflex is strengthened in this position and because the use of accommodation is very limited in the up gaze, its amplitude is not as large. regarding phoria, only the difference in near phoria between the up-gaze and primary gaze positions was significant, and this gaze had the largest amount of exophoria. the highest and lowest amount of exophoria was seen in the upand down-gaze positions, respectively, while there was no significant difference in the amount of exophoria between leftand right-gaze positions and the primary position of gaze. these findings were consistent with the results of near point of convergence. a larger range of vergence in the down-gaze and a smaller range in the upgaze position contribute to more exophoria in the up-gaze position. on the other hand, there was no difference in near point of convergence between the leftand right-gaze positions and the primary position of the gaze, which was similar to exophoria. an even more interesting finding was that near point of convergence was slightly larger in the left gaze versus the right gaze (which was not statistically significant), indicating a stronger convergence in the right gaze. this finding was consistent with the results of phoria in the resent study, indicating lower exophoria in the right-gaze position. although there were significant differences in amplitude of accommodation and vergence range between different gaze positions, no significant difference was found in accommodative facility. therefore, it can be concluded that amplitude of accommodation has no marked relationship with facility from a functional point of view and they have separate functions, which emphasizes that different aspects of the accommodative function should be evaluated separately and their findings should be analyzed independently in the clinical setting. based on the results of the present study, it can be concluded that amplitude of accommodation and convergence are inconsistent in multiple gaze positions. this difference is more apparent in the vertical plane in the accommodative system and in both the vertical and horizontal planes in the vergence system. convergence decreases symmetrically from the primary position of gaze toward leftand right-gaze positions (horizontal plane) while its changes are completely asymmetrical in the vertical plane with a larger decrease in the up-gaze position. although amplitude of accommodation varies in different gaze positions, there is no variance in accommodative facility among the different gaze directions. phoria changes were similar to and consistent with convergence changes in various gaze positions: the highest and lowest amount of exophoria was seen in the upward and downward gaze positions respectively, while there was no significant difference in the amount of exophoria between the horizontal gaze positions and the primary position of gaze. financial support and sponsorship this project was supported by iran university of medical sciences. conflicts of interest no conflicting relationship exists for any author. references 1. schachar ra. the mechanism of accommodation and presbyopia. int ophthalmol clin 2006;46:39–61. 2. mcgregor ml. convergence insufficiency and vision therapy. pediatr clin north am 2014;61:621–630. 3. murray c, newsham d. the normal accommodative convergence/accommodation (ac/a) ratio. j binocul vis ocul motil 2018;68:140–147. 4. demer jl, clark ra. functional anatomy of extraocular muscles during human vergence compensation of horizontal heterophoria. j neurophysiol 2019;122:105–117. 5. azonobi ir, olatunji fo, addo j. prevalence and pattern of strabismus in ilorin. west afr j med 2009;28:253–256. 6. nizza a, dufeck dr. the ’a’ and ’v’ pattern syndromes. j am optom assoc 1985;56:133–140. 7. taylor jn, richardson b. the pattern of ”a” and ”v” syndromes. aust j ophthalmol 1974;2:24–26. 8. ripple ph. variation of accommodation in vertical directions of gaze. am j ophthalmol 1952;35:1630–1634. 9. atchison da, claydon ca, irwin se. amplitude of accommodation for different head positions and different directions of eye gaze. optom vis sci 1994;71:339–345. 10. atchison da, claydon ca, irwin se. amplitude of accommodation for different head positions and different directions of eye gaze. optom vis sci 1994;71:339–345. 11. takeda t, neveu c, stark l. accommodation on downward gaze. optom vis sci 1992;69:556–561. 12. nguyen d, vedamurthy i, schor c. cross-coupling between accommodation and convergence is optimized for a broad range of directions and distances of gaze. vision res 2008;48:893–903. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 215 binocular function in different gazes; asharlous et al 13. collins cc, carlson mr, scott ab, jampolsky a. extraocular muscle forces in normal human subjects. invest ophthalmol vis sci 1981;20:652–664. 14. miller jm, robins d. extraocular muscle forces in alert monkey. vision res 1992;32:1099–1113. 15. porter jd, baker rs, ragusa rj, brueckner jk. extraocular muscles: basic and clinical aspects of structure and function. surv ophthalmol 1995;39:451–484. 16. pavlov pi. conditioned reflexes: an investigation of the physiological activity of the cerebral cortex. ann neurosci 2010;17:136–141. 17. coakes rl, clothier c, wilson a. binocular reflexes in the first 6 months of life: preliminary results of a study of normal infants. child care health dev 1979;5:405–408. 18. pärssinen o, kauppinen m. associations of reading posture, gaze angle and reading distance with myopia and myopic progression. acta ophthalmol 2016;94:775–779. 19. buehren t, collins mj, carney lg. near work induced wavefront aberrations in myopia. vision res 2005;45:1297–1312. 20. mutti do, jones la, moeschberger ml, zadnik k. ac/a ratio, age, and refractive error in children. invest ophthalmol vis sci 2000;41:2469–2478. 216 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 original article mutation screening of six exons of abca4 in iranian stargardt disease patients ensieh darbari1, phd; hamid ahmadieh2,3, md; narsis daftarian2,3, md; mozhgan rezaei kanavi2,3, phd; fatemeh suri2, phd; hamideh sabbaghi4,5, phd; elahe elahi1*, phd 1school of biology, college of science, university of tehran, tehran, iran 2opthalmic research center, research institute for ophthalmology and vision science, shahid university of medical sciences, tehran, iran 3ocular tissue engineering research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 4ophthalmic epidemiology research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 5department of optometry, school of rehabilitation, shahid beheshti university of medical sciences, tehran, iran orcid: ensieh darbari: https://orcid.org/0000-0003-1050-6999 elahe elahi: https://orcid.org/0000-0002-6897-2223 abstract purpose: stargardt disease type 1 (stgd1) is a recessively inherited retinal disorder that can cause severe visual impairment. abca4 mutations are the usual cause of stgd1. abca4 codes a transporter protein exclusively expressed in retinal photoreceptor cells. the gene contains 50 exons. mutations are most frequent in exons 3, 6, 12, and 13, and exons 10 and 42 each contain two common variations. we aimed to screen these exons for mutations in iranian stgd1 patients. methods: eighteen stgd1 patients were recruited for genetic analysis. diagnosis by retina specialists was based on standard criteria, including accumulation of lipofuscin. the six abca4 exons were pcr amplified and sequenced by the sanger method. results: one or more abca4-mutated alleles were identified in 5 of the 18 patients (27.8%). five different mutations including two splice site (c.1356+1g>a and c.5836-2a>g) and three missense mutations (p.gly1961glu, p.gly1961arg, and p.gly550arg) were found. the p.gly1961glu mutation was the only mutation observed in two patients. conclusion: as abca4 mutations in exons 6, 12, 10, and 42 were identified in approximately 25% of the patients studied, these may be appropriate exons for screening projects. as in other populations, stdg1 causative abca4 mutations are heterogeneous among iranian patients, and p.gly1961glu may be relatively frequent. keywords: abca4; mutation screening; retinal dystrophy; stargardt disease; stgd1 j ophthalmic vis res 2022; 17 (1): 51–58 introduction stargardt disease type 1 (stgd1: omim no. 248200) is a relatively common form of macular correspondence to: elahe elahi, phd. college of science, university of tehran, tehran, iran. email: elaheelahi@ut.ac.ir, elahe.elahi@gmail.com received 19-11-2020; accepted 21-05-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10170 dystrophy with a prevalence of 1 in 8000 to 1 in 10,000.[1, 2] it is a genetic disease with an autosomal recessive pattern of inheritance. stargardt disease begins in childhood or young adulthood, and causes progressive bilateral loss of central vision, this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: darbari e, ahmadieh h, daftarian n, kanavi mr, suri f, sabbaghi h, elahi e. mutation screening of six exons of abca4 in iranian stargardt disease patients. j ophthalmic vis res 2022;17:51–58. © 2022 darbari et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 51 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10170&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr abca4 mutations in stargardt disease; darbari et al impairment of color vision, and degeneration of retinal pigment epithelium (rpe) cells.[2, 3] accumulation of orange–yellow flecks in the macula is often observed during ophthalmoscopic examination. atp-binding cassette sub-family a member 4 (abca4, omim: 601691; also known as abcr) is the most important stargardt diseasecausing gene.[4–10] this gene is positioned on chromosome 1p21-p22, contains 50 exons, and encodes a 2273 amino acid protein that belongs to abc transporter protein family. abc transporter proteins have four essential domains, including two transmembrane domains (tmds) and two cytoplasmic nucleotide-binding domains (nbds). tmds are responsible for translocation of substrates, and nbds bind to atp and hydrolyze atp to adp to produce energy for the translocation. abca4 expression is specific to the retina and its protein product is responsible for the transport of vitamin a derivatives in the outer segment disc membranes of photoreceptors.[11, 12] mutations in the gene result in accumulation of toxic bisretinoid adducts in rpe cells, eventually leading to rpe cell death and macular degeneration.[13] in addition to stgd1, mutations in abca4 can cause several other types of retinal degenerative diseases.[14–16] this suggests a complex genotype/phenotype relationship between mutations in the gene and the consequent phenotypes. additionally, the number of sequence variations and disease-associated variations in abca4 is astounding. variability in frequencies of the variations in different populations is also notable. the human genome mutation database (hgmd, http://www.hgmd.cf.ac.uk) reports 1467 mutations in the abca4 gene as cause of various retinal degenerative diseases; 629 of the mutations are associated with stgd1. the genome aggregation database (gnomad v2.1.1; https://gnomad.broadinstitute.org) reports 3979 sequence variations for abca4, including exonic, intronic, utr, splicing, and indel variations; the frequency of 3930 of these is <0.01. the iranome database (http://www.iranome.ir) which comprises exome sequence data on 800 healthy iranians reports 389 abca4 sequence variations, and the frequency of 301 of these is <0.01. clearly, common sequence variations are unlikely to contribute to disease status, but rare variations may have deleterious effects. here, we report the results of mutation screening of six exons of the abca4 gene in 18 unrelated iranian stargardt disease patients. to the best of our knowledge, mutation screening of this gene in iranians has not been previously reported. among the 50 exons of abca4, exons that were more likely to contain mutations were screened. based on the hgmd database, more mutations have been reported in exons 3, 6, 12, and 13 than in other exons. these exons of abca4 have, respectively, 33, 33, 39, and 45 reported mutations. in addition to these, exons 10 and 42 were also screened. a common nucleotide sequence variation that causes p.his432arg is positioned in exon 10. although now considered a polymorphism, this variation was earlier thought to contribute to disease status. exon 42 was screened because the most frequent disease-associated variation in various populations is positioned within this exon. this variation causes p.gly1961glu. methods this research was performed in accordance with the declaration of helsinki, with informed consent of participants or responsible guardians, and with the approval of the ethics board of the university of tehran. eighteen unrelated stargardt patients were sequentially recruited from the retina clinic of labbafinejad medical center affiliated to shahid beheshti university of medical sciences, tehran, iran. ophthalmic examinations included visual acuity assessment, fundus photographs (color, infrared, and autofluorescence) and fluorescein angiography (fa) for accumulation of lipofuscin in the retina, measurement of macular thickness by optical coherence tomography (oct), visual field (vf) testing, and electroretinography (erg). a combination of clinical presentations and progression, decreased visual acuity, fundus photographs, fa, vf, oct, and erg results were considered for the diagnosis of stargardt disease.[17] for genetic analysis, genomic dna was isolated from the white blood cells of the peripheral blood of the patients. exons 3, 6, 10, 12, 13, 42, and flanking intronic regions of abca4 were amplified by the polymerase chain reaction (pcr). primer sequences are available upon request. the amplified pcr products were sequenced using the sanger sequencing protocol. sequences were analyzed using the sequencher software (gene codes corporation, ann arbor, mi). variations were assessed by comparison with abca4 reference 52 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 http://www.hgmd.cf.ac.uk http://www.iranome.ir abca4 mutations in stargardt disease; darbari et al figure 1. fundus photographs (color, infrared, and autofluorescence), fluorescein angiography (fa), visual field (vf), optical coherence tomography (oct), and electroretinography (erg) findings in a representative patient (stg-5). (a–d) and (f–i) represent color (a & f), infrared (b & g), autofluorescence (c & h), and fluorescein angiographic (d & i) fundus photographs of the patient’s right and left eyes, respectively, and demonstrate the lipofuscin accumulation in the macula. vf defects are evident in the right (e) and left eyes (j). reduced central macular thicknesses were illustrated in the oct images of the right (k) and left (l) eyes. note the abnormal photopic erg graphs and values for both eyes in (m). sequence available at ncbi (nc_000001.10, nm_000350.3, np_000341.2). results the average age of patients at the disease onset was 17 years (range 6–41 years). of the 18 included patients, 11 (61%) were male. the average age at the examination was 26 years (range 8–45 years). all investigated patients demonstrated decreased best-corrected visual acuity and evidence of lipofuscin accumulation in the macula, decreased central macular thickness, constricted visual fields, and variable degrees of erg abnormalities [figure 1]. of the 18 patients screened, three (stg-2, stg-6, and stg-18) had two definitive diseasecausing mutated abca4 alleles [table 1]. of these, two patients had homozygous mutations (p.gly1961arg and p.gly550arg), consistent with them having been born to consanguineous parents. the third patient had compound heterozygous mutations; one was the very common p.gly1961glu-causing mutation in exon 42 that was noted above, and the other was a donor splice site mutation in intron 10 (c.1356+1g>a). patient stg-1 harbored a splice site mutation (c.5836-2a>g) in intron 41 and a variation in exon 6 that causes p.arg212his [table 1]. the intronic mutation is a known stgd1-causing mutation. as the p.arg212his-causing variation was observed in the homozygous state, the allele with the c.58362a>g intronic mutation must be in cis with a c.635g>a variation that causes p.arg212his. although the p.arg212his-causing variation has sometimes been considered a polymorphism because of its relatively high allele frequency (0.052720), it was reported to contribute to stgd1 status in a turkish patient.[4, 7, 18, 19] it is possible that in an individual with a clearly disease-causing mutation such as the splice site mutation of patient stg-1, the presence of p.arg212his will result in disease presentation. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 53 abca4 mutations in stargardt disease; darbari et al figure 2. sequence chromatograms of five mutations observed among the stargardt disease-affected patients studied. (a) c.5836-2a>g in patient stg-1; (b) c.5881g>a mutation in patient stg-2; (c) c.5882g>a mutation in patient stg-5 and stg6; (d) mutation c.1356+1g>a in patient stg-6; and (e) mutation c.1648g>a in patient stg-18. alternatively, the second mutated abca4 allele in patient stg-1 may be positioned in one of the many exons not screened in this study. patient stg-5 also harbored two variations in abcd4, a variation that causes p.gly1961glu and the intronic variation c.1356+11t>g. although the intronic mutation is rare (0.0001), bioinformatics tools including human splice finder (http://umd.be/redirect.html) and nnsplice (https://www.fruitfly.org/seq_tools/splice.html) predict that it would not affect splicing. therefore, the second mutated abca4 allele in patient stg-5 is likely positioned in one of the exons not screened. the presence of a shared haplotype between the two mutated alleles that cause p.gly1961glu cannot be ascertained because of phase issues in the two heterozygous carriers, stg-5 and stg-6. sequence chromatographs of the reported stgd1-associated mutations are shown in figure 2. discussion all diseases associated with abca4 are progressive retinopathies accompanied by degeneration of photoreceptor cells that can lead to blindness. there is a significant association between the severity of phenotype and the nature of the abca4 mutations. stargardt disease is generally considered to be less severe than cone-rod dystrophy (crd) or retinitis pigmentosa (rp).[20, 21] deletions, nonsense mutations, and indels are usually associated with severe phenotypes.[5] missense mutations are more commonly found in less severely affected patients. it is interesting that the pathogenicity of some missense mutations, such as p.his432arg and p.arg212his discussed above, and even of p.gly1961glu that is described below, remains controversial. 54 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 http://umd.be/redirect.html https://www.fruitfly.org/seq_tools/splice.html abca4 mutations in stargardt disease; darbari et al ta b le 1. d at a on pa tie nt s w ith at le as to ne ca nd id at e st ar ga rd td is ea se -c au si ng m ut at io n in a b c a 4 p a ti e n t id s e x c o n sa n g u in o e u s p a re n ts a o s a a e v is u a la cu it y c a n d id a te d is e a se -c a u si n g va ri a ti o n s n o n -d is e a se a ss o ci a te d va ri a ti o n s o d o s v a ri a ti o n h o m o / h e t e xo n / in tr o n e ff e ct m a f g n o m a d a c m g a n n n o ta ti o n v a ri a ti o n id v a ri a ti o n h o m o / h e t m a f g n o m a d a c m g a n n n o ta ti o n v a ri a ti o n id st g -2 f + 6 8 20 /2 0 0 20 /2 0 0 c. 58 81 g >a h om o ex on 42 p. g ly 19 61 a rg 0. 0 0 0 1 li ke ly pa th og en ic rs 14 22 53 67 0 st g -6 f – 29 31 1/1 0 1/1 0 c. 13 56 +1 g >a h et in tro n 10 sp lic in g n o da ta n ov el c. 30 2+ 26 a > g h et 0. 49 53 7 n o da ta rs 22 97 63 4 c. 58 82 g >a h et ex on 42 p. g ly 19 61 g lu 0. 0 0 35 li ke ly pa th og en ic rs 18 0 0 55 3 c. 58 36 -1 1g >a h et 0. 20 35 n o da ta rs 18 0 07 39 c. 58 44 a >g h om o 0. 19 78 b en ig n rs 22 75 02 9 st g -1 8 m + 6 37 20 /15 0 20 /2 0 0 c. 16 48 g >a h om o ex on 12 p. g ly 55 0 a rg 0. 0 0 0 0 04 u nc er ta in si gn ifi ca nc e rs 61 74 85 58 st g -1 f – 12 20 20 /16 0 20 /16 0 c. 63 5g >a * h om o ex on 6 p. a rg 21 2h is * 0. 0 52 72 b en ig n rs 66 57 23 9 c. 58 36 -2 a > g h et in tro n 41 sp lic in g n o da ta c s1 61 78 4 st g -5 f – 16 17 c f at 50 0 cm c f at 40 0 cm c. 58 82 g >a h et ex on 42 p. g ly 19 61 g lu 0. 0 0 35 li ke ly pa th og en ic rs 18 0 0 55 3 c. 13 56 +1 1t >g h et 0. 0 0 0 13 7 n o da ta rs 11 30 55 35 0 *c on si de re d to po ss ib ly co nt rib ut e to di se as e st at us as de sc rib re d in th e te xt f, fe m al e; m ,m al e; a o s, ag e at on se t; a a e, ag e at ex am in at io n; o d ,r ig ht ey e; o s, le ft ey e; c f, co un tin g fin ge r; h om o, ho m oz yg ou s; h et ,h et er oz yg ou s; m a f, m in or al le le fre qu en cy journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 55 abca4 mutations in stargardt disease; darbari et al one or more abca4-mutated alleles were identified in 5 of the 18 iranian stgd1 patients (27.8%) in whom only six of the gene’s 50 exons were screened. no variant nucleotide was found in exons 3 and 13, and the single variation found by screening exon 10 was in fact in intron 10. without considering p.arg212his as a mutation that affects disease status, five different mutations were observed. three of the mutations were missense mutations. p.gly1961glu and p.gly1961arg affect an amino acid that is localized in the second nbd domain. although p.gly1961glu has been reported as one of the most frequent mutations in stargardt patients of various populations, its pathogenicity has been questioned largely because of the relatively high frequency of its coding allele in some populations.[22] for example, its frequencies in the somalian, ashkenazi, qatar, and iranian populations are reported to be 0.10,[22] 0.024 (gnomad), 0.023,[23] and 0.026 (iranome), respectively. the consensus appears to be that p.gly1961glu is a moderate mutation.[5, 24] in the homozygous state, it presents a mild form of stgd1; in the compound heterozygous state with a more deleterious mutation, it can contribute to a severe form of stargardt disease.[5] as in other populations, p.gly1961glu may be relatively common among iranian stgd1 patients, as it was observed in two patients of the relatively small cohort studied here. p.gly1961arg is found less frequently than p.gly1961glu in retinal dystrophy patients. the frequency of the allele that causes p.gly1961arg among iranians is 0.0025, and the frequency is <0.01 in most other populations as well (iranome, gnomead). p.gly550arg, that has been reported as a stargardt disease-causative mutation, was the third missense mutation found in the iranian cohort.[25] p.gly550 is localized in the extracytosolic domain 1 (ecd1) of the protein encoded by abca4. the molecular consequences of two observed splice site mutations were not critically investigated. c.5836-2a> g that abolishes the acceptor splice site in intron 41 was previously reported in a crd patient of a chinese cohort.[6] c.1356+1g>a is being reported for the first time in a stargardt disease-affected patient, although c.1356+1g>t was previously reported in agerelated macular degeneration patients.[26] this signifies potential variability of phenotypic features associated with any abca4 mutation. to the best of our knowledge, this is the first report of the abca4 mutation screening of the iranian patients affected by stargardt disease. of course, more patients need to be screened in order to achieve a representative profile of abca4 mutation in this population. this knowledge will be needed for various purposes, including possible initiatives for gene therapy. acknowledgments some of patients in the current article are provided by the disease registry, titled ”the iranian national registry of inherited retinal dystrophy (irdreg®)” and code number of ir.sbmu.orc.rec.1396.15 from the ethic committee, that was supported by the deputy of research and technology in shahid beheshti university of medical sciences. (http://dregistry.sbmu.ac.ir). financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. blacharski pa. fundus flavimaculatus. in: newsome da, editor. retinal dystrophies and degenerations. new york, ny: raven press; 1988. 135–159p. 2. tombran-tink j, barnstable cj. retinal degenerations: biology, diagnostics, and therapeutics. totowa, nj: humana press; 2007. 3. north v, gelman r, tsang sh. juvenile-onset macular degeneration and allied disorders. dev ophthalmol 2014;53:44–52. 4. rivera a, white k, stöhr h, steiner k, hemmrich n, grimm t, et al. a comprehensive survey of sequence variation in the abca4 (abcr) gene in stargardt disease and age-related macular degeneration. am j hum genet 2000;67:800–813. 5. simonelli f, testa f, zernant j, nesti a, rossi s, allikmets r, et al. genotype-phenotype correlation in italian families with stargardt disease. ophthalmic res 2005;37:159–167. 6. jiang f, pan z, xu k, tian l, xie y, zhang x, et al. screening of abca4 gene in a chinese cohort with stargardt disease or cone-rod dystrophy with a report on 85 novel mutations. invest ophthalmol vis sci 2016;57:145–152. 7. riveiro-alvarez r, aguirre-lamban j, lopez-martinez ma, trujillo-tiebas mj, cantalapiedra d, vallespin e, et al. frequency of abca4 mutations in 278 spanish controls: an insight into the prevalence of autosomal recessive stargardt disease. br j ophthalmol 2009;93:1359–1364. 56 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 abca4 mutations in stargardt disease; darbari et al 8. garces f, jiang k, molday ll, stöhr h, weber bh, lyons cj, et al. correlating the expression and functional activity of abca4 disease variants with the phenotype of patients with stargardt disease. invest ophthalmol vis sci 2018;59:2305–2315. 9. nassisi m, mohand-saïd s, dhaenens cm, boyard f, démontant v, andrieu c, et al. expanding the mutation spectrum in abca4: sixty novel disease causing variants and their associated phenotype in a large french stargardt cohort. int j mol sci 2018;19:2196. 10. salles mv, motta fl, martin r, filippelli-silva r, dias da silva e, varela p, et al. variants in the abca4 gene in a brazilian population with stargardt disease. mol vis 2018;24:546–559. 11. illing m, molday ll, molday rs. the 220-kda rim protein of retinal rod outer segments is a member of the abc transporter superfamily. j biol chem 1997;272:10303– 10310. 12. sun h, nathans j. stargardt’s abcr is localized to the disc membrane of retinal rod outer segments. nat genet 1997;17:15–16. 13. quazi f, molday rs. atp-binding cassette transporter abca4 and chemical isomerization protect photoreceptor cells from the toxic accumulation of excess 11-cis-retinal. proc natl acad sci usa 2014;111:5024–5029. 14. klevering bj, deutman af, maugeri a, cremers fp, hoyng cb. the spectrum of retinal phenotypes caused by mutations in the abca4 gene. graefes arch clin exp ophthalmol 2005;243:90–100. 15. rong wn, wang xg, sheng xl. [abca4 mutations and phenotype of different hereditary retinopathies in 3 pedigrees]. zhonghua yan ke za zhi [chinese j ophthalmol] 2018;54:775–781. 16. allikmets r, shroyer nf, singh n, seddon jm, lewis ra, bernstein ps, et al. mutation of the stargardt disease gene (abcr) in age-related macular degeneration. science 1997;277:1805–1807. 17. tanna p, strauss rw, fujinami k, michaelides m. stargardt disease: clinical features, molecular genetics, animal models and therapeutic options. br j ophthalmol 2017;101:25–30. 18. briggs ce, rucinski d, rosenfeld pj, hirose t, berson el, dryja tp. mutations in abcr (abca4) in patients with stargardt macular degeneration or cone-rod degeneration. invest ophthalmol vis sci 2001;42:2229– 2236. 19. ozgül rk, durukan h, turan a, oner c, ogüs a, farber db. molecular analysis of the abca4 gene in turkish patients with stargardt disease and retinitis pigmentosa. hum mutat 2004;23:523. 20. cideciyan av, swider m, aleman ts, tsybovsky y, schwartz sb, windsor ea, et al. abca4 disease progression and a proposed strategy for gene therapy. hum mol genet 2009;18:931–941. 21. gerth c, andrassi-darida m, bock m, preising mn, weber bh, lorenz b. phenotypes of 16 stargardt macular dystrophy/fundus flavimaculatus patients with known abca4 mutations and evaluation of genotypephenotype correlation. graefes arch clin exp ophthalmol 2002;240:628–638. 22. guymer rh, héon e, lotery aj, munier fl, schorderet df, baird pn, et al. variation of codons 1961 and 2177 of the stargardt disease gene is not associated with age-related macular degeneration. arch ophthalmol 2001;119:745– 751. 23. rodriguez-flores jl, fakhro k, agosto-perez f, ramstetter md, arbiza l, vincent tl, et al. indigenous arabs are descendants of the earliest split from ancient eurasian populations. genome res 2016;26:151–162. 24. fakin a, robson ag, fujinami k, moore at, michaelides m, pei-wen chiang j, et al. phenotype and progression of retinal degeneration associated with nullizigosity of abca4. invest ophthalmol vis sci 2016;57:4668–4678. 25. shroyer nf, lewis ra, yatsenko an, wensel tg, lupski jr. cosegregation and functional analysis of mutant abcr (abca4) alleles in families that manifest both stargardt disease and age-related macular degeneration. hum mol genet 2001;10:2671–2678. 26. fritsche lg, fleckenstein m, fiebig bs, schmitzvalckenberg s, bindewald-wittich a, keilhauer cn, et al. a subgroup of age-related macular degeneration is associated with mono-allelic sequence variants in the abca4 gene. invest ophthalmol vis sci 2012;53:2112– 2118. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 57 original article biometry and intraocular lens power calculation by combined scheimpflug-placido disc versus optical interferometry devices mehlan juliane1, md; lehman anne-isabel1, md; cichocki myriam1, md; druchkiv vasyl1, ms, katz toam1,3, md; stephan j linke1,2, md 1department of ophthalmology, university medical center hamburg-eppendorf (uke), hamburg, germany 2zentrumsehstärke, hamburg, germany 3carevision hamburg, germany orcid: mehlan juliane: https://orcid.org/0000-0003-0677-6937 abstract purpose: to compare the results of the current gold standard, laser interferometry, and keratometry by the iol-master, with a newly developed galilei g6 using raytracing software okulix for intraocular lens (iol) power calculations. methods: for comparison of the iol-power calculation of both devices, we analyzed the difference between the actual one-month postoperative subjective refraction and the theoretically calculated target refraction before cataract surgery. the iol was selected according to the iol master recommendation aiming for emmetropia after surgery. we analyzed the differences of the measurements of the basic biometric data in 205 healthy eyes by each device. results: our study included 205 healthy, unoperated eyes from 117 patients (61 women, 56 men) aged 20 to 75 years. twenty-two eyes of cataract patients were also included in this retrospective study design. the mean difference between the prediction of the postoperative refraction and the refraction actually achieved was 0.03 d for the iol master and –0.23 d for the galilei g6. the difference was not statistically significant (p = 0.059). the difference between the iol power calculation of the iol master and the calculation of the g6 was not statistically significant (p = 0.064). the difference between the predicted refraction of the g6 and the refraction achieved after one month was also not statistically significant (p = 0.12) and neither was the difference between the predicted refraction of the iol master and the achieved refraction (p = 0.39). the mean axial length was calculated as 24.21 ± 0.80 mm using the iol master and 24.27 ± 0.82 mm using the galilei g6 device. the mean value regarding anterior chamber depth (acd) of the iol master was 3.46 ± 0.23 mm and for the galilei was g6 3.51 ± 0.25 mm. when comparing the white to white (wtw) values of the iol master, it showed mean values of 12.32 ± 0.31 and galilei showed mean values of g6 12.21 ± 0.28. all of these differences (between galileo and iol master measurements) were statistically significant (p < 0.001). conclusion: both the laser interferometry/keratometry performed by the iol master and the interferometry/raytracing biometry strategy performed by the galilei g6 demonstrated equal results when executing the iol power calculation before cataract surgery in eyes with no prior ocular surgery. keywords: cataract surgery; iol calculation; ray tracing j ophthalmic vis res 2022; 17 (4): 453–461 © 2022 mehlan et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 453 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i4.12349&domain=pdf&date_stamp=2019-07-17 galilei g6 vs iolmaster biometry ; mehlan et al introduction cataract surgery is the most often performed operation worldwide with an estimated number of 32 million procedures in 2020 according to the world health organization. precise measurement of the dimensions of the eye and the consecutive calculations are especially essential to guarantee a reliable determination of the intraocular lens (iol) power. to further increase the precision of the measurement, new devices incorporating tomography (anterior and posterior corneal surfaces) have been developed. a widespread device for iol power calculation is iol master 500 (zeiss, germany) which uses partial coherence interferometry for the axial length and lens thickness and placido and scheimpflug technology for the k values and calculates the iol-power using the established formulas such as haigis, srk/t, etc. ziemer galilei g6 (ziemer ophthalmic systems ag, port, switzerland) is an ocular biometry device combining scheimpflug and placido analyses for detailed corneal analyses and a-scan optical interferometry (880 nm wavelength) for optical measurement of all parts of the eye from the anterior corneal surface to the retina which corresponds with the axial length. in addition to the standard iol-calculation formulas, galilei g6 has the option to use an additional (external) iol-power calculation software called okulix® which uses ray-tracing measurements and calculations for a potentially more precise iol power calculation. three different ray-traced iol power calculation approaches are used: the first calculation named “parax” focuses on the calculation of paraxial light rays. this calculation model is focused on the almost unrefracted light rays entering the eye near the optical axis. correspondence to: mehlan juliane, md. universitätsaugenklinik hamburgeppendorf martinistr. 52, 20246 hamburg, germany. email: j.mehlan@uke.de received: 22-07-2021 accepted: 21-03-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i4.12349 the second calculation which is called “best focus” takes into account light rays over a pupil diameter of 2.5 mm to determine the iol power. the third calculation approach is referred to as the total refraction calculation which provides the sphero-cylindrical iol power which takes into account the corneal anterior and posterior surfaces. this study was designed to compare the combined scheimpflug/placido and optical ascan interferometer biometer (galileo g6, [ziemer ophthalmic systems ag, port, switzerland]) with the previous gold standard, a partial coherence interferometer biometer (iol master 500, zeiss, germany). methods our study included 205 healthy, unoperated eyes from 117 participants (61 women, 56 men) aged 20 to 75 years. only subjects without ocular pathology or prior ocular surgery were included in this study. part i for our first analysis, the power of the implanted iol for the 22 cataract patients (trilisa 1st q or alcon sa60at) was determined according to the iol master recommendation using the haigis formula while aiming for post-surgical emmetropia. the prediction for the postoperative spherical equivalent (se) of the iol master 500 (partial coherence interferometry + distance-independent telecentric keratometry) using the haigis formula was compared to the prediction of the galilei g6 systems using the okulix ray tracing formula for the same iol. we decided to evaluate the data after one month because of uncomplicated cataract surgery and the refraction could be expected to stabilize after one month.[9] this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: juliane m, anne-isabel l, vasyl d, toam k, linke sj. biometry and intraocular lens power calculation by combined scheimpflug-placido disc versus optical interferometry devices . j ophthalmic vis res 2022;17:453–461. 454 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 https://knepublishing.com/index.php/jovr galilei g6 vs iolmaster biometry ; mehlan et al to compare the accuracy of the iol-power calculation of both devices, first, we analyzed the difference between the actual one-month postoperative subjective refraction and the preoperative theoretically calculated target refraction. preand postoperative measurement of the uncorrected and corrected distance visual acuity (udva & cdva) was also performed. postoperative examinations were performed one month after the operation. part ii in addition to the iol power and target refraction measurements, we compared the following parameters that were also calculated by each device: axial length (al), white-to-white (wtw), and anterior chamber depth (acd). measurements of the keratometry were not compared directly with each other because the devices use different procedures and measuring zones. the iol master uses a distanceindependent telecentric keratometer for the keratometry and the keratometry is measured at 32 points in two concentric rings (diameter 1.65 and 2.3 mm) while the galilei g6 uses simulated keratometry data that is measured using placidobased corneal topography. iol master 500 was at the moment of this retrospective study the gold standard for calculating the appropriate power of the intraocular lenses for successful cataract surgery. its axial length measurement is based on the application of partial coherence interferometry. diagnostic limitations of this device include mature cataract, central scarring of the cornea and epiretinal membranes. anterior chamber depth is measured from the anterior corneal surface to the anterior lens surface using the scheimpflug principle. this is only possible with phakic eyes, otherwise the rear border is missing. a measurement of the anterior depth chamber is only possible if the corneal radii have been calculated before executing the scheimpflug method. wtw measures the horizontal diameter of the iris and the deviation of the visual axis from the center of the iris. the range of the measurement is usually from 8 to 16 mm. for measuring the axial length, a range between 14 and 39 mm is specified. the measuring range of the keratometer is 5 to 10 mm. measurement of the anterior chamber depth is possible in the range of 1.5 to 6.5 mm. scaling for all three measured variables takes place in 0.01 mm increments. galilei g6 combines the technologies of placido topography, dual-scheimpflug tomography, and optical biometry. for measuring the axial length, a range between 14 and 40 mm is specified. the measuring range of the keratometer is 4.5 to 13.5 mm. measurement of the anterior chamber depth is possible in the range of 1.5 to 6.5 mm. galilei g6 enables the measurement of the anterior and posterior surfaces of the cornea, as well as the thickness of the cornea and the thickness of the lens. the ocular ray tracing allows for a calculation of the refraction based on snell’s law. snell’s law describes the change in the direction of propagation of a plane wave when it transitions into another medium. the reason for the change in direction is the change in the material-dependent phase velocity, which is defined and represented as the refractive index. rays can be calculated for any distance from the optical axis and for other parameter variations. there are three different evaluation modes for the galilei g6 – parax, best-focus, and total refraction calculation. these modes will only be briefly explained here in order not to go beyond the scope of this manuscript. the rating mode ”parax” means the paraxial iol power. this is the calculation that best focuses the light rays on the retina. the best focus calculation also considers light rays above a pupil diameter of 2.5 mm to calculate the iol. the total refraction calculation means the spherocylindrical iol power, which takes into account the anterior and posterior corneal surfaces. only the best focus analysis was used for this evaluation. statistical analysis distribution of differences between the refraction achieved and predicted by galilei and the iol master was illustrated using the bland–altman plots. differences were determined by the “limits of agreement” and their confidence intervals summarized. the 95% limits of agreement show where 95% of the differences can be expected. one can contrast the theoretical values against the confidence intervals of these limit values and thus assess the level of repeatability. the journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 455 galilei g6 vs iolmaster biometry ; mehlan et al mean and its confidence interval are also on the graph to show the possible orientation of the differences between the achieved and the predicted measurements. other visualization methods were also used. on the one hand, we illustrated the achieved and predicted refraction in the predefined intervals using a bar chart and showed the results ungrouped using the box plots. the differences in distribution between the achieved and predicted refraction were checked using the non-parametric wilcoxon sign test. bland–altman graphics were used again for the repeatability of the measurements for al, wtw, and acd calculated. the influence of the escaping cases was prevented by utilizing the yuen test for trimmed differences used. the two tests dealt with in the conclusion are the mentioned non-parametric wilcoxon sign test and the yuen test. results part i twenty-two eyes (eight male and seven female patients) were operated by the same experienced surgeon using phacoemulsification. the mean difference between the prediction of the postoperative refraction and the refraction actually achieved was 0.03 d for the iol master [figure 1]. in contrast, the difference was –0.23 d for the galilei g6 [figure 2]. the difference between the prediction of refraction and actual achieved refraction for iol master and galilei was not statistically significant (p = 0.059). even if one looks at the standard deviation (iol master: 0.371 d; g6: 0.504 d), the difference was not statistically significant. the pitman–morgan test was not significant for both variances (p = 0.189). figure 3 shows the predicted postoperative refraction values for iol master and galilei g6, as well as the actual postoperative values. calculation with the iol master predicted that 92% of the cases would be in the emmetropic range. calculation with the galilei g6 system using ray tracing, after matching the iol strength and the iol model, predicted 50% in the emmetropic range. the range from –1.0 d to +1 d was predicted with a 92% probability by the iol master and 91% by the galilei g6 system. half of the postoperative results, using the iol power calculation based on the iol master biometry, ranged from –0.25 d to 0.25 d, 68% of the postoperative results were in the range of – 0.50 d to +0.50 d (emmetropia) and 91% of the results ranged from –1 d to +1 d. figure 4 shows the results of the comparison of the predicted refraction of the iol master and the galilei g6 and the results of the refraction actually achieved one month after the operation. difference between the calculations of the iol master and the calculations of the g6 were not statistically significant (p = 0.064). difference between the predicted refraction of the g6 and the refraction achieved after one month was also not statistically significant (p = 0.12) and neither was the difference between the predicted refraction of the iol master and the achieved refraction (p = 0.39). the box plot shows a tendency toward a wider spread of the values measured with the galilei g6. however, there is a tendency toward a myopic refractive shift when calculating with the okulix ray tracing software. part ii – comparison of the biometric data we compared the calculations for the axial length, anterior chamber depth and white-to-white measured with the galilei g6 and the iol master of all 205 eyes. due to different procedures and measuring zones in each device we did not compare the measurements of the keratometry directly with each other (see above). evaluation of the biometric standard data in table 1 shows a mean axial length of 24.21 ± 0.80 with the iol master and 24.27 ± 0.82 with the galilei g6. the difference was statistically significant (p < 0.001). there was also a significant difference in the acd (p < 0.001). the mean value for the iol master was 3.46 ± 0.23 and for the galilei g6 was 3.51 ± 0.25. when comparing the wtw values of the iol master which showed mean values of 12.32 ± 0.31 with that of the galilei g6 which revealed mean values of 12.21 ± 0.28, these differences were again statistically significant (p < 0.001). in general, there was a statistically significant longer axial length, deeper anterior chamber, and a steeper cornea in the measurements of the galilei g6 as compared to the iol master. 456 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 galilei g6 vs iolmaster biometry ; mehlan et al figure 1. bland–altman plot to visualize the difference of the iolm to post op se. figure 2. bland–altman plot to visualize the difference of the g6 theoretical calculation post op se if lens calculated with g6. journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 457 galilei g6 vs iolmaster biometry ; mehlan et al figure 3. comparison of achieved and predicted spherical equivalent. figure 4. the quotient of the predicted and achieved refraction is shown. discussion in the first part of this study, the prediction for the postoperative se of the iol master 500 using the haigis formula was compared to the prediction of the galilei g6 systems using the okulix ray tracing formula for the same iol. the mean difference between the iol masters’ predicted values in comparison to the actually achieved postoperative se is 0.032 d. the galilei g6 using ray tracing demonstrated a mean difference pre-surgical calculation to post-surgical subjective refraction se of –0.234 d. the calculations using the okulix ray tracing software seem to have a slight tendency toward a myopic shift. before treatment, the iol-master calculation (haigis formula) predicted that 92% of the cases would be in the emmetropic range. however, only 68% of the operated eyes reached the emmetropic range postoperatively (–0.5 dpt to +0.5 dpt). calculation with the galilei g6 system using ray tracing predicted 50% in the emmetropic region after matching the iol power and the iol model. if you look at the range from –1.0 d to +1 d, then 92% of the calculations with the iol master and 91% of the calculations with the galileo reach the range. 458 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 galilei g6 vs iolmaster biometry ; mehlan et al table 1. biometric standard data. factors range (min / max) mean ± sd* al galilei 29.95 / 31.69 24.27 ± 0.82 iol – master 20.94 / 31.64 24.21 ± 0.80 difference -1.56 / 0.45 -0.05 ± 0.03 pwert < 0.001 acd galilei 2.31 / 5.49 3.51 ± 0.25 iol – master 2.31 / 4.68 3.46 ± 0.23 difference -0.81 / 1.26 -0.05 ± 0.05 pwert < 0.001 wtw galilei 11.23 / 13.02 12.21 ± 0.28 iol – master 11.50 / 13.40 12.32 ± 0.31 difference -0.77 / 1.01 0.12 ± 0.06 pwert < 0.001 al, axial length; iol, intracocular lens; acd, anterior chamber depth; wtw, white-towhite; sd, standard deviation *trimmed means with winzorized standard deviations an exact iol calculation is essential for a reliable and precise outcome when performing cataract surgery and phacoemulsification. the main hurdle in terms of reaching target refraction at the moment is the difference between the estimated and effective lens/iol position (li et al; 2019). in an effort to have a more accurate calculation for the iol to be selected, many parameters of the optical system should be included in the calculation formula of the iol. currently the lens calculation using the iol master is the gold standard for preoperative lens calculations. however, new devices that are capable of retrieving additional parameters are emerging, which include galilei g6, and other systems such as iol master or cassini, which include galilei g6 and other systems such as cassini. in our study, the iol power was calculated using the iol master 500. regarding figure 4, the box plot shows a tendency toward a wider spread of the values measured with the galilei g6. however, there is a tendency toward myopic shift when calculating with the okulix ray tracing software. you should keep this in mind when choosing lenses and pay attention accordingly. despite the noticeable differences between the predictive values of the two measurement devices versus the actually achieved postoperative refraction calculated for the same iol, there was no statistically significant difference between the two devices (p = 0.059). preoperative correction planning had a positive impact on the discrepancies between the actually achieved postoperative se and the predicted target refractions from both the iol master and galilei g6. it can cause the actual refraction values to be closer to the predicted values. with regard to astigmatism, it is important to mention that a postoperative astigmatism value reduced to –1.0 dpt was consciously tolerated. should it be more, the implantation of a toric iol was discussed with the patient. a postoperative reading for astigmatism reduced down to –1.0 d was deliberately tolerated. if it occurred beyond that, the implantation of a toric iol was discussed with the patient. if the patient prefers not to wear varifocal glasses after the operation, there is also the option of performing an additional lasik procedure postoperatively or performing limbal relaxing journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 459 galilei g6 vs iolmaster biometry ; mehlan et al incisions during the initial operation to reduce the postoperative astigmatism. preoperative correction planning is now part of everyday clinical practice and has been modified so that a postoperative astigmatism of >–0.5 d would be avoided. ghoreishi et al reported similar results in 2018.[2] they compared the iol okulix ray tracing software with the srkt and hoffer q formula on 104 patients with cataract. in this instance , the iol was also selected using the iol master 500. they could not find a statistically significant difference when comparing the okulix ray tracing software with the other two formulas (p = 0.25). ventura et al also showed that there were no significant differences in their calculations between the iol masters 500 and the galilei g6 system.[8] the recommended lens power was calculated for each patient using the haigis formula for the acrysof sn60wf iol. in the iol calculation for postoperative emmetropia there was no statistically significant difference (p = 0.49) between the predictive calculation and the actual postoperative calculation. if we look at the differences in the calculation between the iol master and the galilei g6 in terms of the se achieved after one month, there are varying results. the difference between calculation of the iol master and calculation of the g6 is not statistically significant (p = 0.064). the difference between the predicted refraction of the g6 and the refraction achieved after one month is also not statistically significant (p = 0.12) and neither is the difference between the predicted refraction of the iol master and the achieved refraction (p = 0.39). in the second part of the current study, we compared the measurements of al, acd, and wtw from the iol master 500 and the galilei g6 system. as there exists multiple measurement methods including different areas/zones regarding the k values, we have not compared them directly to each other. there are statistically significant differences between each of the measurements of al, acd, and wtw (p each <0.001). these results partially contradict other studies. ventura et al[8] measured 88 eyes with the iol master 500 and the galilei g6 and could not find statistically significant differences regarding al (p = 0.456), acd (p = 0.468) or the k-values (average p = 0.432). lee et al[4] did not find a significant difference between iol master 500 and galilei g6 system when measuring the al (p = 0.321). however, the measurements of acd and k-values were statistically significantly different between the two devices (p <0.001 and p = 0.028, respectively). the statistically significant difference regarding the k-values could again be due to different measurement methods. in summary they stated that the absolute prediction error for the iol master 500 and galilei g6 regarding postoperative refraction is not significantly different (p = 423):[4] in the study of jung et al,[3] the iol master 700 and galilei g6 were compared. both devices showed reliable repeatability, but the iol master 700 was slightly superior to the galilei g6. there were no significant differences in axial length, anterior chamber depth, steepest k, white-to-white corneal diameter or lens thickness. however, the flat k-value and the central corneal thickness differed (p < 0.05). the iol master 700, like the iol master 500, utilizes a distance-independent telecentric keratometer for keratometry measurements and the keratometry values are measured at 32 points that are arranged in two concentric rings with a diameter of 1.65 and 2.30 mm. the galilei g6 system uses simulated keratometry data measured using placido-based corneal topography.[3] the iol master 700 utilizes swept source technology in contrast to the iol master 500. shajari m et al performed a study on 79 patients to analyze possible differences in the parameters used for lens calculation (axial length, corneal curvature, and anterior chamber depth). the pentacam axl (scheimpflug technology with partial coherence interferometry), the iol master 700 (swept-source optical coherence tomography), and the iol master 500 (optical biometer) were all compared. in conclusion, they could state that there were no statistically significant differences regarding those parameters.[9] dalto et al described the differences between the srkt and haigis formulas in terms of preoperative factors and refractive outcomes.[1] all eyes were implanted with the alcon-sn60wf iol and preoperative measurements were made with lenstar from haag-streit (optical biometry). their research revealed that there were differences in lens recommendations for the two formulas. eyes that had myopia and 460 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 galilei g6 vs iolmaster biometry ; mehlan et al recorded lower k-values preoperatively had the possibility of a slight myopic shift with the haigis formula. on the other hand, these eyes were predisposed to have a hyperopic shift with the srkt formula.[1] furthermore, zhu et al performed a comparison between the haigis, srkt, and the holladay formulas with patients diagnosed with high myopic eyes. their conclusion was that for these patients, the haigis or srkt formulas can reduce the errors in the iol calculation where the haigis formula is always preferable when k ≤ 43 d and the axis length is over 30 mm.[8] it should be noted, however, that while it is mathematically possible for the target refraction to be ±0.1 d, the art lenses are so far available only in 0.5 d increments and even with the same iol from the same manufacturer, there can be subtle differences in refractive strength. thus, the mathematical accuracy can still be difficult to implement in practice. it should also be considered that patients’ compliance has an impact on the results. comorbidities, such as spinal or neck problems, ptosis and dermatochalasis or sicca also play a major role in determining the choice of iol calculation. in summary, there is no significant difference between the results of the ray tracing method of the galilei g6 and the measurements derived from the iol master. regarding the prediction of the postoperative se for the respective iol, we could not determine any inferiority of the galilei g6 system as compared to the current gold standard of the iol master 500. the relevance for clinical use and also the possible benefits in eyes with previous operations or after refractive surgery should be evaluated in further studies. financial support and sponsorship none. conflicts of interest none. references 1. dalto rf, ferreira ma, queiroz w, coelho rp, paula js, messias a. haigis and srkt formulae accuracy for intentional myopic overcorrection. int ophthalmol 2018;38:1459–1463. 2. ghoreyshi m, khalilian a, peyman m, mohammadinia m, peyman a. comparison of okulix ray-tracing software with srk-t and hoffer-q formula in intraocular lens power calculation. j curr ophthalmol 2018;30:63–67. 3. jung s, chin hs, kim nr, lee kw, jung jw. comparison of repeatability and agreement between swept-source optical biometry and dual-scheimpflug topography. j ophthalmol 2017;2017:1516395. 4. lee jw, park sh, seong mc, cho hy, kang mh. comparison of ocular biometry and postoperative refraction in cataract patients between galilei-g6® and iol master®. j korean ophthalmol soc 2015;56:515. 5. micieli ja, arshinoff sa. cataract surgery. cmaj 2011;183:1621. 6. ventura bv, ventura mc, wang l, koch dd, weikert mp. comparison of biometry and intraocular lens power calculation performed by a new optical biometry device and a reference biometer. j cataract refract surg 2017;43:74–79. 7. shajari m, cremonese c, petermann k, singh p, müller m, kohnen t. comparison of axial length, corneal curvature, and anterior chamber depth measurements of 2 recently introduced devices to a known biometer. am j ophthalmol 2017;178:58–64. 8. zhu xj, he ww, du y, qian dj, dai jh, lu y. [intraocular lens power calculation for high myopic eyes with cataract: comparison of three formulas]. zhonghua yan ke za zhi 2017;53:260–265. 9. liu yc, wilkins m, kim t, malyugin b, mehta js. cataracts. lancet 2017;390:600–612. journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 461 photo essay subconjunctival and orbital (twin) cysticercosis in a child kasturi bhattacharjee1, ms, dnb, frcs (ed.); manpreet singh2, ms, dnb, faico; dipankar das1, ms harsha bhattacharjee1, ms, frcp, frcs 1department of orbit, ophthalmic plastic and reconstructive surgery, sri sankaradeva nethralaya, beltola, guwahati, assam, india 2department of ophthalmology, advanced eye centre, post graduate institute of medical education and research, chandigarh, india orcid: kasturi bhattacharjee: https://orcid.org/0000-0001-5769-2915 j ophthalmic vis res 2019; 14 (3): 387–389 presentation a seven-year-old indian boy presented with a reddish mass over the outer part of right eye; the mass had been present for two months. it was associated with pain, discharge, and intermittent double vision. there was no history of ocular trauma, surgery, or any similar complaints. the patient was afebrile with no swelling over any other parts of the body. the ophthalmic examination revealed stretched right upper and lower eyelids, temporal displacement of the lateral canthus, and matting of the eyelashes. a well-defined, reddish yellow, oval mass measuring 15 × 12 mm was noted in the temporal quadrant of the right orbit. the overlying conjunctiva was stretched with prominent blood vessels and a distinctively yellow inferior correspondence to: kasturi bhattacharjee, ms, dnb, frcs (ed.). department of orbit, ophthalmic plastic and reconstructive surgery, sri sankaradeva nethralaya, beltola, guwahati, assam 781 028, india. e-mail: kasturibhattacharjee44@hotmail.com received: 11-01-2018 accepted: 16-04-2018 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.jovr_109_16 segment [figure1(a), arrow]. conjunctival congestion was more prominent on the temporal surface of the mass [figure 1(b)]. a mild restriction of abduction was observed. the rest of the right and left eye examination revealed all findings within normal limits. the b-scan ultrasonography of the right orbit revealed a highly echogenic structure within a hypoechoic cystic lesion inside the lateral rectus muscle belly [figure 2(a)]. the axial scans of computed tomography (ct) showed a hyperdense spec inside a hypodense lesion over the anterolateral part of the right globe [figure 2(b)] and a bulky lateral rectus belly containing another heterogenous lesion [figure 2(c)]. the brain ct showed a healed granuloma in the left parietal lobe [figure 2(d)]. the history, clinical features, and radiological features were suggestive of right twin-orbital myocysticercosis with healed neurocysticercosis. on retrospective history, there was a contributory history of frequent consumption of smoked pork. there was no history of headache, this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: bhattacharjee k, singh m, das d, bhattacharjee h. subconjunctival and orbital (twin) cysticercosis in a child. j ophthalmic vis res 2019;14:387–389 @ 2019 j  o  v r | published by knowledge e 387 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.jovr_109_16&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; bhattacharjee et al figure 1. (a) an oval, reddish-yellow cystic mass measuring 15 × 12 mm, protruding from the lateral orbital quadrant and causing the stretching of both tarsal plates and the vertical palpebral fissure. the overlying conjunctiva shows prominent blood vessels. (b) in levodepression, the dilated prominent conjunctival vessels are clearly appreciable on the lateral surface of the cyst. figure 2. (a) b-scan ultrasound shows a hypoechoic lesion with high internal echogenicity suggestive of scolex in the right lateral rectus muscle. (b) computed tomography axial scans show a cystic lesion abutting the right globe anteriorly. the heterogenous lesion has a hypodense cavity with a hyperdense internal spec suggestive of a scolex. (c) the superior axial section shows another heterogenous, posterior lesion in the belly of the lateral rectus muscle. (d) the left parietal lobe shows a hypodense lesion with a spec of internal hyper density, even though the classic ring-enhancement is absent. figure 3. (a) intraoperatively, the lateral rectus was isolated with the muscle hook for a better and minimally damaging dissection. (b) the in-to excised cystic mass with distinct anterior yellowish portion. (c) the gross specimen revealing the bilobed cystic mass with overlying blood vessels. the anterior brownish and posterior yellowish portions are clearly discernible. (d) an intact cyst with turbid contents showing a yellowish-white scolex (arrow). the surrounding region shows inflammatory fibrosis. 388 j  o  v r volume 14, issue 3, july–september 2019 photo essay; bhattacharjee et al vomiting, or seizure, and neurology clearance was obtained before prescribing oral albendazole (15 mg/kg/day in two divided doses) and oral steroids (1 mg/kg/day). the enzyme-linked immune sorbent assay (elisa) for cysticercosis and stool examination was negative. to prevent the spontaneous rupture and extrusion of the large, anterior, subconjunctival cyst, an “in-toto” surgical excision of the cyst was performed under general anesthesia. intraoperatively, the lateral rectus muscle was hooked, and a gentle and blunt dissection was performed to remove the cyst in-toto [figure 3(a)]. a reddishyellow cystic mass (18 × 15 mm) was excised with an anteroinferior yellowish region suggestive of cysticercosis cyst [figure 3(b)]. the formalin-fixed gross pathological specimen classically demonstrated a bilobed cystic mass with a smooth (orbital) surface and an intact pseudo capsule [figure 3(c)]. the anterior part of superior calotte revealed an intact cyst with clear contents and pearly-white scolex [figure 3(d)]. the posterior region showed collapsed cyst with surrounding inflammatory fibrosis. oral albendazole was continued for six weeks with weekly tapering of oral steroids. at a 12 months follow-up, the child recovered completely without any recurrence or sequelae. discussion the infiltration of cysticerci (larvae of taenia solium) into ophthalmic tissues is called ocular or adnexal cysticercosis. the larvae spread to ophthalmic tissues via the hematogenous route, and the involvement of extraocular muscles is known as orbital myocysticercosis.[1] in adults, the orbital myocysticercosis may have an acute presentation akin to idiopathic orbital inflammatory disease (ioid), while in the younger age, it may present as an anteriorly prolapsed subconjunctival cyst.[1–3] in the latter scenario, there can be another “twin-cyst” or a continuation of posterior cyst in the associated rectus belly.[4] orbital imaging (ultrasonography, ct, or mri) may reveal the internal contents, extent, and association of cystic lesion inside the extraocular muscles or orbit. the extraocular muscles have a rich vascular supply favoring the lodgment of cysticercosis larvae.[1–4] traditionally, medical management is the first line of treatment for orbital myocysticercosis, but an anterior subconjunctival cyst, amenable to surgical excision, can be removed, preventing spontaneous inflammatory rupture of the cyst. acute painful orbital conditions should be included in the differential diagnosis of the orbital myocysticercosis. our case depicts a classical presentation of orbital myocysticercosis with a radiologically detected posterior “twin-cyst” and its successful surgical management. the authors also want to emphasize on the therapeutic medical management of orbital myocysticercosis in case of posteriorly placed orbital cysts. financial support and sponsorship sri kanchi sankara health & educational foundation, india. conflicts of interest there are no conflicts of interest. references 1. murthy r, samant m. extraocular muscle cysticercosis: clinical features and management outcome. strabismus 2008;16:97–106. 2. bhatia k, sengupta s, sharma s. spontaneous extrusion of subconjunctival cysticercosis cyst. jama ophthalmol 2016;134:e155025. 3. obedulla h, pujari a, gupta y, basheer s. spontaneous extrusion of subconjunctival cysticercosis cyst. bmj case rep 2017; 2017: bcr-2017-221470. 4. mukherjee pk, agrawal s. sub-conjunctival twin cysticercosis. indian j ophthalmol 1975;23:28–29. j  o  v r volume 14, issue 3, july–september 2019 389 original article inferior spear-like lens opacity as a sign of keratoconus ramin salouti1,2, md; amir khosravi1, md; majid fardaei3, phd; mohammad zamani2, md mahmoud nejabat1, md; maryam ghoreyshi2,4, md; mahboobeh yazdanpanah3, ms; kia salouti5, bd; m. hossein nowroozzadeh, md1 1department of ophthalmology, school of medicine, shiraz university of medical sciences, shiraz, iran 2salouti cornea research center, salouti eye clinic, shiraz, iran 3department of medical genetics, shiraz university of medical sciences, shiraz, iran 4health policy research center, shiraz university of medical sciences, shiraz, iran 5science department, the university of british columbia, vancouver, canada orcid: ramin salouti: https://orcid.org/0000-0002-5853-4799 m. hossein nowroozzadeh: https://orcid.org/0000-0002-7412-1900 abstract purpose: to report 21 cases of typical inferior feather-shape lens opacity associated with keratoconus. methods: in this cross-sectional study, we evaluated the association of keratoconus with inferior feather-shape lens opacity in refractive surgery candidates. visual acuity, demographic, refractive, and topographic characteristics of 26 eyes of 21 patients with inferior feather-shape lens opacity were evaluated in detail. pedigree analysis was also performed to assess possible inheritance. results: overall, 2122 out of 33,368 cases (6.4%) without lens opacity had keratoconus, while 20 out of 21 patients (95.2%) with peculiar lens opacity had definite keratoconus (p < 0.001). lens opacity was bilateral in 5 cases (24%), and keratoconus was bilateral in all 20 patients with lens opacity. nine eyes out of thirty-six with a complete data record (25%) had a severe keratoconus and underwent deep lamellar keratoplasty, while 11 (31%) had forme fruste keratoconus. pedigrees were drawn for eight patients, most families of whom suggested an x-linked recessive inheritance. conclusion: the present study was the first to investigate patients with a peculiar inferior feather-shape lens opacity accompanied by bilateral keratoconus, which was observed in 95% of the patients. this finding should raise awareness as to the possibility of diagnosing keratoconus in the eyes of the patients with these characteristics. keywords: cataract; feather-shape; keratoconus; lens opacity; sectoral j ophthalmic vis res 2022; 17 (1): 12–18 12 © 2022 salouti et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10165&domain=pdf&date_stamp=2019-07-17 lens opacity in kcn; salouti et al introduction keratoconus is a noninflammatory, often bilateral, and asymmetric corneal disorder[1] in which the progressive central or paracentral corneal thinning leads to the bulging of the thinned cornea.[2] keratoconus often occurs as an isolated disorder.[3, 4] despite the extensive studies carried out over the recent decades on the etiology and pathogenesis of keratoconus, the exact pathophysiology and biochemical mechanisms of keratoconus is yet to be fully understood. however, several environmental (such as eye rubbing, atopy, sun exposure, and geography), genetic (i.e., familial inheritance, association with other known genetic disorders, and predisposing mutations), and biomechanical mechanisms have been proposed to contribute to this ectatic disorder.[5] investigating the possible association of keratoconus with other diseases requires understanding of the pathogenesis and biochemical mechanisms of this condition. since keratoconus is a progressive disorder, an early diagnosis to save uncorrected visual performance is of utmost importance. unfortunately, certain detection of early keratoconus in refractive surgery candidates is impossible, even with the help of the latest corneal imaging technologies. extra-corneal clues such as genetic susceptibility might help to spot early keratoconus in uncertain situations. in our current study, we report 21 patients with an inferior feather-shape lens opacity accompanied by bilateral keratoconus at different stages in almost all of the cases. methods from january 2010 to july 2017, all refractive surgery candidates who were referred to salouti eye clinic were evaluated for inferior feather-shape correspondence to: m. hossein nowroozzadeh, md. poostchi ophthalmology research center, poostchi clinic, zand street, shiraz 7134997446, iran. e-mail: nowroozzadeh@hotmail.com received 30-05-2020; accepted 11-03-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10165 lens opacity by using slit-lamp examinations with dilated pupils. pentacam hr (oculus optikgeräte gmbh) was also obtained for all of these patients, where any grade of keratoconus could be detected. we also collected and analyzed all relevant data from these 21 patients who were diagnosed with typical feather-shape lens opacity. they underwent a complete ophthalmic examination including visual acuity, refraction, slit-lamp biomicroscopy, and fundus examination. the recorded data comprised of the corrected distance visual acuity, spherical equivalent refraction, pentacam keratometric, pachymetric and keratoconus indices (topographic keratoconus classification [tkc]). the pentacam keratoconus indices consisted of the index of surface variance (isv), index of vertical asymmetry (iva), keratoconus index (ki), center keratoconus index (cki), index of height asymmetry (iha), index of height decentration (ihd), and minimum sagittal curvature (rmin). clinical evaluations were followed by a detailed interview, which included questions about demographics, the assessment of the presence or absence of other diseases, drug intake, etc. pedigrees were drawn up to three generations in order to evaluate the keratoconus mode of inheritance. informed consent was obtained from the 21 participants who had cataract. the study protocol was approved by the ethics committee at shiraz university of medical sciences and adhered to the principles of the declaration of helsinki. all statistical analyses were performed using spss for windows (version 22 spss inc., chicago, il, usa). numerical variables were described as median (minimum to maximum). results we assessed the medical charts of 33,389 refractive surgery candidates, of whom 21 patients had the typical feather-shape lens opacity. overall, 2122 out of 33,368 cases (6.4%) without lens opacity had keratoconus, while 20 out of 21 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: salouti r, khosravi a, fardaei m, zamani m, nejabat m, ghoreyshi m, yazdanpanah m, salouti s, nowroozzadeh mh. inferior spear-like lens opacity as a sign of keratoconus. j ophthalmic vis res 2022;17:12–18. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 13 https://knepublishing.com/index.php/jovr lens opacity in kcn; salouti et al patients (95.2%) with lens opacity had definite keratoconus (p < 0.001). all lens opacities were inferior sectoral and triangular in shape, with bases toward the equator. although the width of the opacities varied among the patients, most had a width of about one clock hour or less. densities of the opacities were also different among the patients, some of whom had a central dense line. the borders of the cataracts were fluffy, and most of them resembled a feather [figure 1]. the opacities were bilateral in 5 cases (24%), and keratoconus was bilateral in all 20 cases who had the ectatic disorder. no patients had down syndrome, atopic disease, or history of corticosteroid use. nine out of thirty-six eyes with complete data (25%) recorded had a severe keratoconus and underwent deep lamellar keratoplasty, and 11 (31%) had forme fruste keratoconus (grade 1 in pentacam). all diagnoses of combined lens-opacity/keratoconus were made before any intervention for treating keratoconus. only one female patient with this characteristic form of lens opacity had no corneal finding in favor of keratoconus in her prior frequent examinations. however, her first-degree relatives had a positive history of keratoc. the other three patients did not agree to be interviewed/re-examined, so their detailed data are unavailable. as a result, a total of 18 patients, 14 males and 4 females, were evaluated in detail. the median age was 27.5 years, ranging from 13 to 52 years. the median of the visual acuities of the patients with combined keratoconus/lens-opacity was 20/50 ranging from 20/20 to 20/200. the median of patient’s spherical equivalent refraction was –4.00 d (range, –13.25 to –0.50). the medians (ranges) of the keratometric and pachymetric indices were as follows: mean keratometry, 48.8 d (44.1 to 55.1); maximum keratometry, 54.6 d (45.3 to 63.9); astigmatic keratometry, 3.3 d (1.0 to 7.6); and thinnest point, 475 µm (362 to 558). tables 1 and 2 summarize the patients’ demographic, refractive, and topographic information. of the nine eyes with more advanced keratoconus that had undergone the graft procedure, eight belonged to men (28.6% of male’s eyes) and only one to a woman (12.5% of female’s eyes), suggesting a more severe phenotype in males. this is further corroborated by the lower median of tkc in females as compared to males (1.5 vs 2.0). however, due to the limited number of patients, we were not able to perform a complete statistical analysis on the patients. none of the 18 patients interviewed declared any family relationship with one another. according to the information accessed, eight patients reported to have at least one other person with keratoconus among their family members [table 1]. we were able to draw the pedigrees of all these patients, which were more suggestive of an x-linked recessive inheritance in most cases [figure 2]. as an ongoing project, we will try to elucidate the genetic basis of combined keratoconus/feather-shape lens opacity in future studies. discussion in this study, we introduced a novel association between inferior feather-shape lens opacities and keratoconus. this type of lens opacity is more easily visualized when the pupils are dilated; however, they could still be detected in most eyes with undilated pupils. keratoconus is a multifactorial disorder, originating from complex interaction between many genetic and environmental factors. in this regard, previous studies have reported that 0.5 to 15.0% of individuals with down syndrome are also affected by keratoconus. this association is 10–300 times higher as compared with a normal population.[6–8] it has been suggested that the primary cause of this association is eye rubbing due to the increased rate of blepharitis observed in about 46% of patients with down syndrome.[8] other studies have reported a higher incidence or a more severe form of keratoconus in subjects with vernal keratoconjunctivitis.[9, 10] about 40% of patients with leber’s congenital amaurosis are affected by keratoconus;[11, 12] genetic factors and eye rubbing have been suggested as possible mechanisms.[12] there are also possible associations reported between keratoconus and advanced mitral valve prolapse,[13, 14] and certain connective tissue disorders such as osteogenesis imperfecta[15] and ehlers-danlos syndrome subtype vi.[16] a few studies have found this association between keratoconus and lens opacities. a family affected with keratoconus and anterior polar cataract was reported back in 1931.[17] the same phenotype with a supposed genetic association was reported in a large northern irish family.[18–20] co-incidence of cataract and 14 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 lens opacity in kcn; salouti et al table 1. demographic, refractive, and keratometric characteristics of cases case age sex keratoconus in family eye se cdva kmean kmax kastig pmin (yr) (d) (d) (d) (d) (µm) 1 24 m cousin od –6.25 20/25 49.7 54.5 3.1 452 os –6.5 20/30 49.7 55.9 3.6 422 2 16 m cousin od –3.75 20/200 48 53.9 4.2 459 os –9.75 20/60 44.9 51.2 2.8 572 3 25 m sister; cousin; two first cousins once removed od –2.25 20/40 46.8 49.5 2.1 516 os –5.75 20/200 51.1 55.3 2.8 498 4 52 m – od –9 20/100 45.3 53.9 4.2 558 os –0.5 20/50 45.5 53.9 4 545 5 13 m – od –1.5 20/20 47.7 54.6 2 517 os –1 20/25 47.9 53.2 1.9 451 6 26 m – od –3 20/20 46.8 57.6 7.6 478 os –0.5 20/200 54.2 59.5 6.6 475 7 33 m two uncles od –3.75 20/50 42.9 50.7 4.2 687 os –1.25 20/50 49.3 52.1 1.3 410 8 24 m – od –2.5 20/30 51.2 55.2 3.2 391 os –1.5 20/30 52 55.9 3 362 9 32 m sister od –3.75 20/40 42.6 50.1 8.2 541 os –10 20/60 48.8 58.5 5.7 495 10 29 f – od –5.25 20/60 49.4 63.9 3.9 548 os –4 20/40 44.3 52 4.5 492 11 27 f sister od –4 20/30 44.1 45.3 1.4 530 os –3 20/30 43.5 45.5 2 543 12 29 m cousin od –1.5 20/20 44.1 45.3 1.4 530 os –0.5 20/20 47.3 56.1 3.6 523 13 43 m – od –3.25 20/40 47.4 48.4 0.9 530 os –2.75 20/30 47.8 48.6 1 522 14 26 m cousin od –3.25 20/40 45.3 50 1.7 519 os –2.75 20/30 45.2 48.3 0.7 516 15 35 f mother and brother od –3.25 20/40 45.7 48.5 3.3 486 os –6.75 20/50 47.6 48.5 4.2 480 16 37 m – od –9.25 20/50 47.8 54 3.5 455 os –9.75 20/50 47.9 54 4.8 449 17 27 f – od –11.25 20/50 52 54.6 4.1 397 os –11.25 20/40 51.9 54.6 3.3 408 18 28 m – od –13.25 20/80 53.4 55.2 3.7 445 os –13 20/80 55.1 55.2 2.9 421 cdva, corrected distance visual acuity; d, diopter; f, female; kastig, astigmatic keratometry; kmean, mean keratometry; kmax, maximum keratometry; m, male; od, right eye; os, left eye; pmin, minimum pachymetry; y, year. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 15 lens opacity in kcn; salouti et al table 2. pentacam keratoconus indices and feather-shape lens opacity in reported cases case eye lens opacity tkc* isv† iva† ki† cki† iha† ihd† rmin † 1 od + 1 50 0.38 1.08 1.02 33.8 0.048 6.2 os 1 60 0.56 1.02 1.03 40.1 0.066 6.03 2 od + 2–3 98 1.15 1.3 1.04 27.2 0.089 6.27 os post-graft 50 0.45 0.92 0.97 5.2 0.047 6.59 3 od 1 44 0.46 1.1 1.03 15.3 0.028 6.82 os + 2 83 0.82 1.16 1.07 15.6 0.06 6.11 4 od + post-graft 57 0.42 0.88 0.96 12.1 0.054 6.26 os post-graft 57 0.42 0.88 0.96 12.1 0.054 6.26 5 od post-graft 48 0.43 1.08 0.97 26 0.038 6.19 os + 2–3 94 1.12 1.24 1.05 4.6 0.103 6.34 6 od + 2 76 0.64 1.09 0.97 37.6 0.069 5.86 os + post-graft 80 0.8 0.88 1.01 20.1 0.125 5.67 7 od post-graft 47 0.31 0.96 0.96 9.9 0.024 6.65 os + 2 74 0.74 1.23 1.04 5.9 0.05 6.47 8 od + 2 76 0.77 1.24 1.05 1 0.076 6.12 os + 2 83 0.81 1.24 1.05 2.6 0.078 6.03 9 od 1 52 0.24 0.94 0.99 16.4 0.017 6.73 os + 1 63 0.55 1.09 0.97 7.3 0.047 5.76 10 od + post-graft 18 0.1 1.08 0.97 26 0.038 6.2 os 1 44 0.5 1.1 1.03 15.1 0.028 6.82 11‡ od + 0 14 0.03 1.01 1.01 0.2 0.001 7.45 os 0 18 0.07 1.02 1.01 5.1 0.005 7.42 12 od post-graft 14 0.03 1.01 1.01 0.2 0.001 7.45 os + post-graft 51 0.25 0.97 0.97 23.5 0.024 6.02 13 od 1 23 0.12 1.04 1.01 5.5 0.01 6.97 os + 1 24 0.13 1.09 1.01 5.6 0.01 6.95 14 od + 1–2 44 0.5 1.1 1.03 15.1 0.028 6.82 os 1 45 0.52 1.3 1.03 16.3 0.032 6.7 15 od + 1 42 0.47 1.1 1.01 25.6 0.035 6.78 os + 2 60 0.66 1.15 1.04 21 0.05 6.48 16 od 1 42 0.31 1.03 1.02 26.8 0.05 6.57 os + 1–2 51 0.45 1.09 1.02 20 0.055 6.49 17 od + 2 77 0.61 1.25 1.06 34 0.053 5.99 os + 2–3 87 0.76 1.3 1.06 21 0.058 6.08 18 od + 3 115 1.1 1.31 1.12 61.1 0.124 5.56 os + 3 98 0.76 1.24 1.1 35 0.081 5.6 *the cases that are marked as “post-graft” are those that had undergone lamellar keratoplasty for advanced keratoconus †the typographical coding of pentacam keratoconus indices are based on the pentacam definition, in which plain text refers to normal index, underlined letters to abnormal, and italic letters to suspicious values ‡this case had typical cataract but no sign of keratoconus cki, center keratoconus index; iha, index of height asymmetry; ihd, index of height decentration; isv, index of surface variance; iva, index of vertical asymmetry; ki, keratoconus index; rmin, minimum sagittal curvature; tkc, topographic keratoconus classification 16 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 lens opacity in kcn; salouti et al figure 1. the typical inferior feather-shape lens opacity in 10 eyes of 10 cases from the cohort. figure 2. the pedigree drawings of eight cases with combined inferior feather-shape lens opacity and keratoconus. the number assigned to each case corresponds to the patients’ numbers provided in tables 1 and 2. keratoconus has also been reported in patients with atopic dermatitis.[21, 22] this is the first study to report a combination of keratoconus with a peculiar feather-shape lens opacity in a series of patients. we are not sure about the pattern of inheritance; however, the absence of male-to-male transmission, the lower number of affected females, and the milder phenotype in females are mostly suggestive of an x-linked inheritance in most pedigrees. in addition, the penetrance of the lens opacity was varied in the keratoconus cases of the index patients’ families. intuitively, the inferior location of both the lens opacity and the keratoconus cone might suggest a developmental error in the early fetal development of the eye, where the lens and cornea must be precisely separated from each other. since some cases with bilateral keratoconus (which is usually asymmetric) have unilateral feather-shape lens opacity, the proposed developmental error might present in different severities with resultant phenotypes of various origins. it is logical to suppose that the keratoconus and the related lens opacity have the same genetic basis but with different degrees of penetrance and expressivity. in other words, the background lens abnormality probably involves both eyes; however, the visible lens opacity may be present in one or both eyes. whether or not there exists a single gene basis for such an association is the subject of our future investigation. among the limitations of our study, mention can be made of the retrospective nature in the primary collection of data for all of the cases. however, all patients who were willing to participate were re-examined and interviewed prospectively, and the nature of the findings was not subject to classic biases posed by retrospective design (such as inadequate recording, misclassification, etc.). in addition, although we amassed detailed information on our patients, there was an inability to exact genetic evidence for the observed association, which would be the subject of future investigation for this cohort of patients. in summary, our study revealed that the typical inferior feather-shape lens opacity is suggestive of an associated keratoconus, particularly in cases who might not show the clinical signs journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 17 lens opacity in kcn; salouti et al of keratoconus. therefore, we recommend an appropriate workup to diagnose keratoconus in patients with such type of cataract. financial support and sponsorship none. conflicts of interest none declared. references 1. zadnik k, steger-may k, fink ba, joslin ce, nichols jj, rosenstiel ce, et al. between-eye asymmetry in keratoconus. cornea 2002;21:671–679. 2. auffarth gu, wang l, volcker he. keratoconus evaluation using the orbscan topography system. j cataract refract surg 2000;26:222–228. 3. rabinowitz ys. keratoconus. surv ophthalmol 1998;42:297–319. 4. li x, rabinowitz ys, rasheed k, yang h. longitudinal study of the normal eyes in unilateral keratoconus patients. ophthalmology 2004;111:440–446. 5. gordon-shaag a, millodot m, shneor e, liu y. the genetic and environmental factors for keratoconus. biomed res int 2015;2015:795738. 6. cullen jf, butler hg. mongolism (down’s syndrome) and keratoconus. br j ophthalmol 1963;47:321–330. 7. krachmer jh, feder rs, belin mw. keratoconus and related noninflammatory corneal thinning disorders. surv ophthalmol 1984;28:293–322. 8. shapiro mb, france td. the ocular features of down’s syndrome. am j ophthalmol 1985;99:659–663. 9. totan y, hepsen if, cekic o, gunduz a, aydin e. incidence of keratoconus in subjects with vernal keratoconjunctivitis: a videokeratographic study. ophthalmology 2001;108:824–827. 10. cingu ak, cinar y, turkcu fm, sahin a, ari s, yuksel h, et al. effects of vernal and allergic conjunctivitis on severity of keratoconus. int j ophthalmol 2013;6:370–374. 11. damji kf, sohocki mm, khan r, gupta sk, rahim m, loyer m, et al. leber’s congenital amaurosis with anterior keratoconus in pakistani families is caused by the trp278x mutation in the aipl1 gene on 17p. can j ophthalmol 2001;36:252–259. 12. elder mj. leber congenital amaurosis and its association with keratoconus and keratoglobus. j pediatr ophthalmol strabismus 1994;31:38–40. 13. lichter h, loya n, sagie a, cohen n, muzmacher l, yassur y, et al. keratoconus and mitral valve prolapse. am j ophthalmol 2000;129:667–668. 14. sharif kw, casey ta, coltart j. prevalence of mitral valve prolapse in keratoconus patients. j r soc med 1992;85:446–448. 15. beckh u, schonherr u, naumann go. [autosomal dominant keratoconus as the chief ocular symptom in lobstein osteogenesis imperfecta tarda]. klin monbl augenheilkd 1995;206:268–272. 16. robertson i. keratoconus and the ehlers-danlos syndrome: a new aspect of keratoconus. med j aust 1975;1:571–573. 17. sander p. a family affected with keratoconus and anterior polar cataract. br j ophthalmol 1931;15:23–25. 18. hughes ae, dash dp, jackson aj, frazer dg, silvestri g. familial keratoconus with cataract: linkage to the long arm of chromosome 15 and exclusion of candidate genes. invest ophthalmol vis sci 2003;44:5063–5066. 19. dash dp, silvestri g, hughes ae. fine mapping of the keratoconus with cataract locus on chromosome 15q and candidate gene analysis. mol vis 2006;12:499–505. 20. hughes ae, bradley dt, campbell m, lechner j, dash dp, simpson da, et al. mutation altering the mir-184 seed region causes familial keratoconus with cataract. am j hum genet 2011;89:628–633. 21. longmore l. atopic dermatitis cataract and keratoconus. australas j dermatol 1970;11:139–141. 22. brunsting la, reed wb, bair hl. occurrence of cataracts and keratoconus with atopic dermatitis. ama arch derm 1955;72:237–241. 18 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 perspective retinal pigment epithelium transplantation: past, present, and future ayyad zartasht khan1, md, phd; tor paaske utheim2, 3, 4, 5, 6, md, phd; jon roger eidet6, md, phd 1department of medical biochemistry, oslo university hospital, kirkeveien 166, nydalen, oslo, norway 2department of oral biology, faculty of dentistry, university of oslo, sognsvannsveien 10, oslo, norway 3department of plastic and reconstructive surgery, oslo university hospital, kirkeveien 166, nydalen, oslo, norway 4department of ophthalmology, sørlandet hospital arendal, lundsiden, kristiansand, norway 5department of ophthalmology, stavanger university hospital, stavanger, norway 6department of ophthalmology, oslo university hospital, kirkeveien 166, nydalen, oslo, norway orcid: ayyad zartasht khan: https://orcid.org/0000-0002-2048-225x abstract retinal pigment epithelium (rpe) is a monolayer of cells situated between photoreceptors and the underlying choroid. it is essential for normal retinal function. damaged rpe is associated with diseases such as age-related macular degeneration, stargardt’s macular dystrophy, and retinitis pigmentosa. rpe cells can easily be visualized in vivo, sustainable in vitro, and differentiated from stem cells with a relatively straightforward protocol. due to these properties and the clinical significance of this epithelium in various retinal diseases, rpe transplantation as a treatment modality has gained considerable interest in the last decade. this paper presents the main techniques for rpe transplantation and discusses recent clinically relevant publications. keywords: retinal pigment epithelium; retinal pigment epithelium transplantation; regenerative medicine; vitreoretinal surgery; tissue engineering. j ophthalmic vis res 2022; 17 (4): 574–580 introduction retinal pigment epithelium (rpe) is a cell layer sandwiched between photoreceptors apically and bruch’s membrane basally. rpe cells are cuboidal with apical microvilli gaping photoreceptor outer segments.[1] their cytoplasms contain correspondence to: ayyad zartasht khan, md, phd. department of medical biochemistry, oslo university hospital, kirkeveien 166, p.o. box 4956, nydalen, 0424 oslo, norway. email: aakhan@studmed.uio.no received: 05-02-2022 accepted: 12-05-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i4.12325 melanin pigments, lipofuscin granules, melanolipofuscins, and phagosomes.[1] these cells adhere to each other via zonula occludentes, creating a mosaic-patterned layer of tightly adjoined hexagonally shaped cells. rpe performs several functions essential for vision, such as adsorption of excessive light, transport of nutrients to and from the neuroretina, protection against photooxidation, regeneration of 11 cis-retinal this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: khan az, utheim tp, eidet jr. retinal pigment epithelium transplantation: past, present, and future. j ophthalmic vis res 2022;17:574–580. 574 © 2022 khan et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i4.12325&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr rpe transplantation; khan et al for the visual cycle, and phagocytosis of shed photoreceptor outer segments.[1, 2] it also constitutes the outer part of the blood–retinal barrier.[1] rpe dysfunction is seen in several retinal disorders, such as age-related macular degeneration (amd),[3] proliferative vitreoretinopathy (pvr), and retinitis pigmentosa (rp). regarding amd, it is still unclear whether drusen formation is a consequence or a cause of rpe dysfunction.[4] however, both are strongly associated with each other.[5] in pvr, rpe cells contribute to the folding of the retina by detaching and translocating from the underlying basement membrane.[6–8] similarly, rpe disintegration and migration are responsible for the bone-spicule pigmentation that is pathognomonic for rp.[9] thus, when rpe fails to function correctly, the retina suffers. replacing rpe cells is an idea that arose shortly after the characterization of these cells about 40 years ago.[10] their anatomical accessibility, in vitro resilience, and clinical importance made them attractive for transplantation scientists. the first proof-of-concept study of rpe transplantation was performed in 1984 by gouras et al in monkeys.[11] four years later, li and turner published a report demonstrating that subretinal injection of rpe cells prevented photoreceptor degeneration in rats.[12] the field has subsequently matured at a rapid pace with not only animal studies,[13–15] but also human trials, using rpe of fetal,[16, 17] post-mortem adult,[18–20] autologous,[21–23] induced pluripotent stem cell (ipsc)-derived[24] and embryonic stem cell (esc)-derived origin.[25–27] the introduction of ipscand esc-derived rpe have been critical for the advancement of clinical rpe research during the recent years, and has, to a large extent, solved the issue of sourcing rpe donor tissue. while ipscs offer an unlimited supply of autologous cells and (to some degree) do not require the use of immunosuppressants, they may carry patients’ own genetic vulnerabilities contributing to disease processes.[28] this can be avoided by using escs. however, escs raise ethical concerns[29–31] and are, in contrast to ipscs, neither autologous nor unlimited in supply. the methods for generating rpe cells from ipscs[32, 33] and escs[34, 35] have been described in detail. as the succeeding paragraphs will demonstrate, ongoing clinical trials employ these two stem cell sources to generate mature, transplantation-ready rpe. transplantation techniques there are currently three techniques for subretinal rpe transplantation: (1) surgical placement of rpe as an intact cell sheet (with or without scaffold), (2) injection of rpe as a cell suspension, and (3) macular translocation. transplantation of rpe as an intact cell sheet was first described in 1991 by peyman et al, who treated one patient with an autologous pedicle flap and another with an allogeneic graft consisting of rpe with an underlying choroid.[19] similar procedures have later been performed by others.[24, 26, 36, 37] delivering rpe as a patch increases the likelihood of correct anatomical placement and the structural integrity of the graft. major complications associated with this technique are subretinal hemorrhage and proliferative vitreoretinopathy. delivery by injection is technically easier and probably less traumatizing to the adjacent tissue. however, cell clumping, poor attachment, and disorganization of rpe upon injection[38] are important drawbacks. the third approach, macular translocation, involves rotating the retina away from a subretinal pathology to an area of healthy rpe. this technique is surgically less straightforward and complicated by cataract, retinal detachment, and diplopia.[39] current state of the rpe transplantation to give the reader an idea of the current state of rpe transplantation, selected recent studies are briefly discussed below. in a phase 1/2 clinical trial, schwartz and associates injected human esc-derived rpe subretinally via a small 38-gauge retinotomy in 18 patients; nine with amd and nine with stargardt’s macular dystrophy (smd).[27] visual acuity improved in the majority of patients. no ocular or systemic safety issues were registered, apart from surgery-associated complications, such as vitreous inflammation, cataract, and endophthalmitis. this study suggested that escderived rpe is a potential and safe source of cells for the treatment of retinal disorders. while schwartz et al delivered the cells via injection, kashani and colleagues described a journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 575 rpe transplantation; khan et al table 1. rpe transplantation trials listed on clinicaltrials.gov. no. study title status publications conditions sponsor/ collaborators phase study type estimated study start estimated study completion study location (country) nct number related projects (nct numbers) 1 safety and tolerability of rpesc-derived rpe transplantation in patients with damd not yet recruiting no publications available damd luxa biotechnology, llc; nih; nei; regenerative research foundation phase 1/2 interventional february 2022 september 2025 usa nct04627428 2 treatment of rp and lca by primary rpe transplantation unknown status no publications available lca; rp eyecure therapeutics inc.; beijing tongren hospital phase 1 interventional august 2018 march 2020 china nct03566147 3 autologous transplantation of induced pluripotent stem cell-derived rpe for geographic atrophy associated with amd recruiting no publications available amd nih; nei phase 1/2 interventional september 2020 may 2029 u.s.a. nct04339764 4 subretinal transplantation of rpe in treatment of amd unknown status no publications available damd chinese academy of sciences; beijing tongren hospital phase 1/2 interventional january 2018 december 2020 china nct02755428 nct03944239 5 treatment of damd with rpe derived from human embryonic stem cells unknown status no publications available damd chinese academy of sciences; the first affiliated hospital of zhengzhou university phase 1/2 interventional september 2017 december 2020 china nct03046407 6 clinical study of subretinal transplantation of human embryo stem cell derived rpe in treatment of macular degeneration diseases unknown status no publications available amd; smd southwest hospital, china phase 1/2 interventional may 2015 december 2019 china nct02749734 7 transplantation of autologous rpe versus translocation of autologous rpe and choroid in amd completed [42] amd the ludwig boltzmann institute of retinology and biomicroscopic laser surgery not applicable interventional february 2004 september 2008 austria nct00401713 576 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 rpe transplantation; khan et al table 1. (continued). no. study title status publications conditions sponsor/ collaborators phase study type estimated study start estimated study completion study location (country) nct number related projects (nct numbers) 8 safety and tolerability of sub-retinal transplantation of human embryonic stem cell derived rpe in patients with smd completed [27, 43] smd astellas institute for regenerative medicine phase 1/2 interventional december 13, 2011 september 30, 2015 u.k. nct01469832 nct02941991; nct01345006; nct01344993; nct02445612; nct02463344; nct02563782; nct02122159; nct03167203 9 study of subretinal implantation of human embryonic stem cell-derived rpe cells in advanced damd active, not recruiting [40, 41] damd regenerative patch technologies, llc phase 1/2 interventional february 2016 june 2023 u.s.a. 10 rpe safety study for patients in b4711001 active, not recruiting [26] amd moorfields eye hospital nhs foundation trust phase 1/2 interventional september 2016 october 2020 u.k. nct03102138 11 a phase i/iia, open-label, single-center, prospective study to determine the safety and tolerability of sub-retinal transplantation of human embryonic stem cell derived rpe (ma09-hrpe) in patients with advanced damd unknown status no publications available damd chabiotech co., ltd phase 1/2 interventional september 2012 june 2020 republic of korea nct01674829 nct01625559; nct03305029 12 safety and efficacy study of opregen for treatment of advanced dry-form age-related macular degeneration active, not recruiting no publications available amd lineage cell therapeutics, inc.; cellcure neurosciences ltd. phase 1/2 interventional april 2015 december 2024 u.s.a.; israel nct02286089 nct, national clinical trial; rpesc, retinal pigment epithelial stem cell; damd, dry age-related macular degeneration; nih, national institutes of health; nei, national eye institute; rp, retinitis pigmentosa; lca, leber congenital amaurosis; rpe, retinal pigment epithelium; amd, age-related macular degeneration; smd, stargardt’s macular dystrophy; mmd, myopic macular degeneration. patch of esc-derived rpe monolayer attached to a synthetic parylene substrate.[40] the initiative is called california project to cure blindness. they implanted this engineered patch in 16 patients with advanced non-neovascular amd with a median age of 78 years in a singlearm, open-label, prospective, non-randomized, phase 1/2 study.[41] critical inclusion criteria were advanced non-neovascular amd, pseudophakia, and severe vision loss. mild to moderate subretinal hemorrhages and macular holes were reported as adverse events. one patient developed ischemic colitis, possibly related to immunosuppression. employing a similar approach, an initiative called “the london project to cure blindness” published data on a phase 1 trial encompassing journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 577 rpe transplantation; khan et al two patients with severe wet amd.[26] their patch was also made of differentiated esc-derived rpe, but the scaffold was made of polyester membrane coated with human vitronectin. using purposebuilt microsurgical tools, the rpe patches were delivered subretinally to one eye in each of the two patients with severe exudative amd. they reported successful delivery and survival of the rpe patch and a visual acuity gain of 29 and 21 letters in the two patients, respectively, over 12 months. importantly, preclinical safety studies did not reveal tumorigenicity or notable proliferative capacity of the esc-derived rpe cells. undifferentiated escs were not detected in the final differentiated rpe product. furthermore, investigation of systemic biodistribution 26 weeks after implantation of the rpe grafts in pigs did not provide any evidence of migration of cells distant to the administration site. although the number of patients included in the study is too low to conclude on the clinical efficiency of the rpe patch, the report provides valuable information about the surgical technique, stability of the transplant, and the safety of the escderived cells. conclusion as the aforementioned reports indicate, human rpe transplantation is still in its early days. significant challenges related to graft composition, graft vehicle, and surgical technique need to be addressed. however, it is encouraging that, despite these challenges, the mentioned studies report positive outcomes following transplantation. future clinical trials are therefore eagerly awaited. as of this writing, 12 rpe transplantation projects are listed on the clinical trials database clinicaltrials.gov [table 1], all being phase 1/2 trials assessing safety, side effects, and dosing. the most frequently occurring indication remains amd. however, smd, rp, and leber congenital amaurosis are other diseases listed as indications for some ongoing trials. the majority of the projects seem to employ rpe cells derived from esc. based on this and the aforementioned recent studies, it is the authors’ impression that the current front-line of rpe transplantation is based on cell delivery as a patch using esc-derived rpe. financial support and sponsorship none. conflicts of interest there are no conflicts of interest. tpu and jre hold a patent on the culture of retinal pigment epithelial cells: https://patents. google.com/patent/us20180119097a1/en. references 1. klettner ak, dithmar s. retinal pigment epithelium in health and disease. springer international publishing; 2020. 2. strauss o. the retinal pigment epithelium in visual function. physiol rev 2005;85:845–881. 3. khandhadia s, cherry j, lotery aj. age-related macular degeneration. in: ahmad si, editor. neurodegenerative diseases [internet]. new york, ny: springer; 2012. p. 15– 36. https://doi.org/10.1007/978-1-4614-0653-2_2. 4. spraul cw, lang ge, grossniklaus he, lang gk. histologic and morphometric analysis of the choroid, bruch’s membrane, and retinal pigment epithelium in postmortem eyes with age-related macular degeneration and histologic examination of surgically excised choroidal neovascular membranes. surv ophthalmol 1999;44:s10– 32. 5. al-hussaini h, schneiders m, lundh p, jeffery g. drusen are associated with local and distant disruptions to human retinal pigment epithelium cells. exp eye res 2009;88:610–612. 6. li zy, possin de, milam ah. histopathology of bone spicule pigmentation in retinitis pigmentosa. ophthalmology 1995;102:805–816. 7. snead dr, james s, snead mp. pathological changes in the vitreoretinal junction 1: epiretinal membrane formation. eye 2008;22:1310–1317. 8. machemer r, laqua h. pigment epithelium proliferation in retinal detachment (massive periretinal proliferation). am j ophthalmol 1975;80:1–23. 9. fahl e, jaissle gb, may ca. pavert svd, wenzel a, claes e, et al. bone spicule formation in retinitis pigmentosa: insights from a mouse model. invest ophthalmol vis sci 2008;49:2199–2199. 10. flood mt, gouras p, kjeldbye h. growth characteristics and ultrastructure of human retinal pigment epithelium in vitro. invest ophthalmol vis sci 1980;19:1309–1320. 11. gouras p, flood mt, kjeldbye h. transplantation of cultured human retinal cells to monkey retina. an acad bras cienc 1984;56:431–443. 12. li lx, turner je. inherited retinal dystrophy in the rcs rat: prevention of photoreceptor degeneration by pigment epithelial cell transplantation. exp eye res 1988;47:911– 917. 578 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 https://patents.google.com/patent/us20180119097a1/en https://patents.google.com/patent/us20180119097a1/en rpe transplantation; khan et al 13. lopez r, gouras p, brittis m, kjeldbye h. transplantation of cultured rabbit retinal epithelium to rabbit retina using a closed-eye method. invest ophthalmol vis sci 1987;28:1131–1137. 14. lopez r, gouras p, kjeldbye h, sullivan b, reppucci v, brittis m, et al. transplanted retinal pigment epithelium modifies the retinal degeneration in the rcs rat. invest ophthalmol vis sci 1989;30:586–588. 15. sheedlo hj, li l, turner je. photoreceptor cell rescue in the rcs rat by rpe transplantation: a therapeutic approach in a model of inherited retinal dystrophy. prog clin biol res 1989;314:645–658. 16. algvere pv, berglin l, gouras p, sheng y, kopp ed. transplantation of rpe in age-related macular degeneration: observations in disciform lesions and dry rpe atrophy. graefes arch clin exp ophthalmol 1997;235:149–158. 17. algvere pv, berglin l, gouras p, sheng y. transplantation of fetal retinal pigment epithelium in age-related macular degeneration with subfoveal neovascularization. graefes arch clin exp ophthalmol 1994;232:707–716. 18. del priore lv, kaplan hj, tezel th, hayashi n, berger as, green wr. retinal pigment epithelial cell transplantation after subfoveal membranectomy in age-related macular degeneration: clinicopathologic correlation. am j ophthalmol 2001;131:472–480. 19. peyman ga, blinder kj, paris cl, alturki w, nelson nc jr, desai u. a technique for retinal pigment epithelium transplantation for age-related macular degeneration secondary to extensive subfoveal scarring. ophthalmic surg 1991;22:102–108. 20. tezel th, del priore lv, berger as, kaplan hj. adult retinal pigment epithelial transplantation in exudative age-related macular degeneration. am j ophthalmol 2007;143:584– 595. 21. binder s, krebs i, hilgers rd, abri a, stolba u, assadoulina a, et al. outcome of transplantation of autologous retinal pigment epithelium in age-related macular degeneration: a prospective trial. invest ophthalmol vis sci 2004;45:4151–4160. 22. binder s, stolba u, krebs i, kellner l, jahn c, feichtinger h, et al. transplantation of autologous retinal pigment epithelium in eyes with foveal neovascularization resulting from age-related macular degeneration: a pilot study. am j ophthalmol 2002;133:215–225. 23. treumer f, bunse a, klatt c, roider j. autologous retinal pigment epithelium-choroid sheet transplantation in age related macular degeneration: morphological and functional results. br j ophthalmol 2007;91:349–353. 24. mandai m, watanabe a, kurimoto y, hirami y, morinaga c, daimon t, et al. autologous induced stem-cell-derived retinal cells for macular degeneration. n engl j med 2017;376:1038–1046. 25. song wk, park km, kim hj, lee jh, choi j, chong sy, et al. treatment of macular degeneration using embryonic stem cell-derived retinal pigment epithelium: preliminary results in asian patients. stem cell reports 2015;4:860– 872. 26. da cruz l, fynes k, georgiadis o, kerby j, luo yh, ahmado a, et al. phase 1 clinical study of an embryonic stem cell-derived retinal pigment epithelium patch in age-related macular degeneration. nat biotechnol 2018;36:328–337. 27. schwartz sd, regillo cd, lam bl, eliott d, rosenfeld pj, gregori nz, et al. human embryonic stem cell-derived retinal pigment epithelium in patients with age-related macular degeneration and stargardt’s macular dystrophy: follow-up of two open-label phase 1/2 studies. lancet 2015;385:509–516. 28. panopoulos ad, ruiz s, izpisua belmonte jc. ipscs: induced back to controversy. cell stem cell 2011;8:347– 348. 29. almond b. using and misusing embryos: the ethical debates. in: king-tak ip, editor. the bioethics of regenerative medicine. springer dordrecht: springer; 2009. p. 77–92. 30. blackford r. stem cell research on other worlds, or why embryos do not have a right to life. j med ethics 2006;32:177–180. 31. mcgee g. trading lives or changing human nature: the strange dilemma of embryo-based regenerative medicine. in: king-tak ip, editor. the bioethics of regenerative medicine. springer dordrecht: springer; 2009. p. 93–106. 32. buchholz de, hikita st, rowland tj, friedrich am, hinman cr, johnson lv, et al. derivation of functional retinal pigmented epithelium from induced pluripotent stem cells. stem cells 2009;27:2427–2434. 33. hirami y, osakada f, takahashi k, okita k, yamanaka s, ikeda h, et al. generation of retinal cells from mouse and human induced pluripotent stem cells. neurosci lett 2009;458:126–131. 34. kawasaki h, suemori h, mizuseki k, watanabe k, urano f, ichinose h, et al. generation of dopaminergic neurons and pigmented epithelia from primate es cells by stromal cell-derived inducing activity. proc natl acad sci usa 2002;99:1580–1585. 35. osakada f, ikeda h, mandai m, wataya t, watanabe k, yoshimura n, et al. toward the generation of rod and cone photoreceptors from mouse, monkey and human embryonic stem cells. nat biotechnol 2008;26:215–224. 36. van zeeburg ej, maaijwee kj, missotten to, heimann h, van meurs jc. a free retinal pigment epithelium–choroid graft in patients with exudative age-related macular degeneration: results up to 7 years. am j ophthalmol 2012;153:120–127.e122. https://doi.org/10.1016/j.ajo.2011.06.007 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 579 rpe transplantation; khan et al 37. van meurs jc, van den biesen pr. autologous retinal pigment epithelium and choroid translocation in patients with exudative age-related macular degeneration: shortterm follow-up. am j ophthalmol 2003;136:688–695. 38. john s, natarajan s, parikumar p, shanmugam p m, senthilkumar r, green dw, et al. choice of cell source in cell-based therapies for retinal damage due to agerelated macular degeneration: a review. j ophthalmol 2013;2013:465169. 39. stanga pe, kychenthal a, fitzke fw, halfyard as, chan r, bird ac, et al. retinal pigment epithelium translocation after choroidal neovascular membrane removal in age-related macular degeneration. ophthalmology 2002;109:1492–1498. 40. kashani ah, lebkowski js, rahhal fm, avery rl, salehi-had h, dang w, et al. a bioengineered retinal pigment epithelial monolayer for advanced, dry age-related macular degeneration. sci transl med 2018;10(435):eaao4097. https://doi.org/10.1126/scitranslmed.aao4097 41. kashani ah, uang j, mert m, rahhal f, chan c, avery rl, et al. surgical method for implantation of a biosynthetic retinal pigment epithelium monolayer for geographic atrophy: experience from a phase 1/2a study. ophthalmol retina 2020;4:264–273. 42. falkner-radler ci, krebs i, glittenberg c, povazay b, drexler w, graf a, et al. human retinal pigment epithelium (rpe) transplantation: outcome after autologous rpechoroid sheet and rpe cell-suspension in a randomised clinical study. br j ophthalmol 2011;95:370–375. 43. schwartz sd, hubschman jp, heilwell g, francocardenas v, pan ck, ostrick rm, et al. embryonic stem cell trials for macular degeneration: a preliminary report. lancet 2012;379:713–720. 580 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 original article psychological impact of covid-19 on ophthalmologists in iran masomeh kalantarion1,2*, ms; zhale rajavi3,4*, md; hamideh sabbaghi2, 5, phd; bahareh kheiri6, ms; mohammad hasan shahriari7, ms; farinaz fatahi mozafar8, ms 1department of medical education, virtual school of medical education and management, shahid beheshti university of medical sciences, tehran, iran 2ophthalmic epidemiology research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 3negah aref ophthalmic research center, shahid beheshti university of medical sciences, tehran, iran 4department of ophthalmology, school of medicine, shahid beheshti university of medical sciences, tehran, iran 5department of optometry, school of rehabilitation, shahid beheshti university of medical sciences, tehran, iran 6ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 7department of electrical engineering, faculty of computer engineering, university of isfahan, isfahan, iran 8department of psychology, kish international branch, islamic azad university, kish island, iran *these two authors equally contributed to this work. orcid: masomeh kalantarion: https://orcid.org/0000-0003-4778-3973 zhale rajavi: https://orcid.org/0000-0002-4078-3017 hamideh sabbaghi: https://orcid.org/0000-0002-2627-7222 abstract purpose: to identify the psychological impact of coronavirus disease on ophthalmologists practicing in iran between august and december 2020. methods: in this cross-sectional online survey, a standard patient health questionnaire9 (phq9) was completed by 228 ophthalmologists who were practicing in iran. the phq9 questionnaire was revised by adding two additional questions specifically applicable for the assessment of the psychological impact of coronavirus disease on the iranian ophthalmologists. an organized classification regarding the assessment of different depression severities identified as no (0–4), mild (5–9), moderate (10–14), or severe (15–21) was then considered for data analysis. results: the mean age of our participants was 49.0 ± 15.61 years and the majority of them (67.1%) were male. depression was discovered in 73.68% (n = 168) with different severities ranging from mild (n = 61, 26.75%), moderate (n = 63, 27.63%), and severe (n = 44, 19.3%). it was found that participants with depression were older as compared to those without depression (p = 0.038). higher percentages of severe depression were noticed in the high-risk regions contaminated with corona virus as compared to the other low-risk regions (p = 0.003). based on multivariable models, we determined that ophthalmologists who were somewhat concerned about their training/ profession (or: 0.240; 95% ci: 0.086–0.672; p = 0.007) and those with no concerns about their income had lower association with depression (or: 0.065; 95% ci: 0.005–0.91; p = 0.042). conclusion: high prevalence of depression was observed among older aged iranian ophthalmologists living in high-risk contaminated regions who possessed serious concerns with respect to their training/profession and income. it is recommended that the health policymakers of iran pay more attention to the ophthalmologists who experience the aforementioned factors. keywords: coronavirus disease; iran; ophthalmologists; psychological impact j ophthalmic vis res 2022; 17 (2): 233–241 © 2022 kalantarion et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 233 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i2.10795&domain=pdf&date_stamp=2019-07-17 psychological impact of covid19 on ophthalmologists; kalantarion et al introduction coronaviruses (covs) are the known types of viruses affecting both birds and mammals, which developed into a pandemic following the outbreak of the covid-19.[1] this was first identified in wuhan, china at the end of 2019 and was later announced as the public health emergency of international concern by the world health organization (who) on january 30, 2020.[2–5] in terms of gender incidence, the disease was more prevalent in males with an estimation of 54.3% and a median age of 56 years in wuhan, china.[3] both physical and psychological complications have been reported in patients with covid-19 virus.[6–9] in terms of psychological concerns, the medical staff and healthcare workers showed acute stress reactions during the covid-19 pandemic through emotional, cognitive, physical, and social reactions.[8] corona-phobia is a public concern which is mostly observed in the majority of healthcare professionals who are in direct contact with quarantined patients in hospitals.[7] medical workers such as doctors, nurses, and paramedical staff are currently in a stressful working environment due to the lack of suitable protection which makes them at high risk for infection, caring for patients while experiencing negative emotions, working for long hours, and isolation from family and loved ones.[7] numerous mental disorders attributed to the covid-19 pandemic have been reported among the healthcare workers. these include increased depression/depressive symptoms, anxiety, psychological distress, and poor sleep quality.[7] these psychological problems such as stress, depressive symptoms, insomnia, denial, anger, fear would result to decreasing the quality correspondence to: hamideh sabbaghi, phd. ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, 23 paidar fard, bostan 9, pasdaran ave., tehran 16666, iran. email: sabbaghi.opt@gmail.com received: 09-02-2021 accepted: 28-12-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i2.10795 of life. these findings were also reported among chinese medical workers and italian general practitioners.[10, 11] in the current pandemic, due to the ocular manifestations, ophthalmologists have also encountered a high referral rate of patients with covid-19 virus.[12] they have a potentially high risk of contracting coronavirus infections via transmission of the virus through droplets due to the close proximity needed for examination and the direct contact with patients’ lids and ocular surfaces.[13–15] these possibilities illustrate that they are working in a highly stressful conditions. noticeable transient mental health problems including depression, anxiety, and stress were reported among the training and practicing ophthalmologists as well as the ophthalmic surgeons in india.[14] the current pandemic also had an adverse effect on the mental health of the highest record of ophthalmology residents (70.5%) in saudi arabia.[16] due to the prevalence of the covid-19 epidemic in iran as well as the increased referral rate of patients to the eye centers, we decided to identify the psychological impact of covid-19 on ophthalmologists practicing in iran. methods in this cross-sectional online survey, a standard patient health questionnaire-9 (phq-9) was distributed to our target population of ophthalmologists who were practicing throughout iran. the current study was conducted between august and december 2020. this study was approved by the ethics committee of the ophthalmic research center, shahid beheshti university of medical sciences (approval no.: ir.sbmu.orc.rec.1399.016). a brief explanation regarding our study objectives and the instructions about how to complete the questionnaire were distributed to our target this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: kalantarion m, rajavi z, sabbaghi h, kheiri b, shahriari mh, mozafar ff. psychological impact of covid-19 on ophthalmologists in iran. j ophthalmic vis res 2022;17:233–241. 234 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 https://knepublishing.com/index.php/jovr psychological impact of covid19 on ophthalmologists; kalantarion et al population – all registered ophthalmologists in the society of ophthalmology – either by email or via various social media platforms. to ensure adequate and timely feedback from participants they were also sent three reminders. we assured our participants that their information was kept anonymous and confidential. patient health questionnaire-9 (phq-9) data were collected using a standard questionnaire as previously applied in the study by khanna et al.[13] a persian version of this questionnaire with the sensitivity of 73.8% and specificity of 76.2% was applied in the present study.[17] in addition to the nine specific questions regarding the assessment of depression, sociodemographic characteristics such as gender, age, marital status, duration of practice, last degree, and type of services offered were also recorded on the questionnaire. the phq9 questionnaire was revised to include three additional questions that were specific to the purpose of this study. two questions focused on the ophthalmologists’ concerns about their training/profession and their income and another question was introduced to clarify the association of the current situation with depression. afterward, this was presented to an expert panel including ophthalmologists, psychologists, biostatisticians, and research methodologists to assess its content validity. the questionnaire was accessible by all participants through the link address: https://docs.google.com/forms/d/e/ 1faipqlsfpclv5xi7dzekrgx_wawjth_mdyvotd5 rxff3x3m6c7gsfka/viewform?usp=sf_link. an organized classification representing different depression severities of no (0–4), mild (5– 9), moderate (10–14), or severe (15–21) were then considered for data analysis.[18, 19] the prevalence of depression was also reported based on the severity of the covid-19 contamination in different regions of iran which were reported by the iranian national headquarter for the control of covid-19 epidemic in december 2020.[20] statistical analysis to analyze the data, we used frequency (%), mean ± sd, median and range. to evaluate the difference between the two groups of the ophthalmologists who had depression and those without it, we used t-test, mann–whitney, chi-square, and fisher’s exact test. we used binary logistic regression to calculate the or and effect of each associated factor. the correlation of all considered factors with depression was analyzed based on both univariate and multivariable models, in which all assumptions were considered. a p-value < 0.05 was considered as statistically significant. all statistical analyses were performed by spss software (ibm corp. released 2017. ibm spss statistics for windows, version 25.0. armonk, ny: ibm corp.). results in this cross-sectional online survey, a phq9 questionnaire was completed by 228 ophthalmologists (response rate: 16.9%) with a mean age of 49.0 ± 15.61 years (median, 40.0; range, 31–85) where the majority of the study participants (67.1%) were male. depression was assessed in 73.68% (n = 168) of the participants with severities ranging from mild (n = 61, 26.75%), moderate (n = 63, 27.63%), and severe (n = 44, 19.3%) among our studied subjects. it was revealed that depressed ophthalmologists were older as compared to those without depression (p = 0.038). additionally, an increased prevalence of depression was identified among ophthalmologists who had either a previous psychological problem (p = 0.047) or considerable concerns regarding their training, profession (p < 0.001), and their income (p = 0.002). regarding the other sociodemographic factors presented in table 1, no statistically significant difference was observed between the ophthalmologists with depression versus those without depression. figure 1 illustrates the frequency of varied severities of depression in different residential regions of iran classified based on the level of contamination with the covid-19 virus. as shown, 42.11% of ophthalmologists practicing in the lowor moderate-risk regions had mild depression, while the higher percentage of the severe depression was found in the high-risk regions as compared to the other regions (p = 0.003). the univariate model shows that ophthalmologists in vitreoretinal fellowship had lower frequency of depression as compared to general ophthalmologists (or: 0.415; 95% journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 235 https://docs.google.com/forms/d/e/1faipqlsfpclv5xi7dzekrgx_wawjth_mdyvotd5rxff3x3m6c7gsfka/viewform?usp=sf_link. https://docs.google.com/forms/d/e/1faipqlsfpclv5xi7dzekrgx_wawjth_mdyvotd5rxff3x3m6c7gsfka/viewform?usp=sf_link. https://docs.google.com/forms/d/e/1faipqlsfpclv5xi7dzekrgx_wawjth_mdyvotd5rxff3x3m6c7gsfka/viewform?usp=sf_link. psychological impact of covid19 on ophthalmologists; kalantarion et al table 1. sociodemographic characteristics of the study population regarding depression factors level total depression p-value no (n = 60) yes (n = 168) gender (%) male 153 (67.1%) 41 (68.3%) 112 (66.7%) 0.874 female 75 (32.9%) 19 (31.7%) 56 (33.3%) age (yr) mean ± sd 49 ± 15.61 51.7 ± 10.68 66.25 ± 10.11 0.038 median (range) 40 (31 to 85) 51.5 (31 to 70) 60 (50 to 85) marital status (%) married 196 (85.97%) 54 (90.0%) 142 (84.5%) 0.388 single 32 (14.03%) 6 (10.0%) 26 (15.5%) duration of practice (yr) mean ± sd 17.26 ± 10.86 19.1 ± 10.46 16.6 ± 10.95 0.127 median (range) 18 (0–50) 20 (1–43) 16.5 (0–50) last degree (%) general ophthalmologist 98 (42.99%) 20 (33.3%) 78 (46.4%) 0.151 fellowship cornea & anterior segment 46 (20.17%) 10 (16.7%) 36 (21.4%) vitreoretinal 55 (24.12%) 21 (35.0%) 34 (20.2%) strabismus 8 (3.50%) 3 (5.0%) 5 (3.0%) glaucoma 8 (3.50%) 1 (1.7%) 7 (4.2%) oculoplastic 12 (5.29%) 4 (6.6%) 8 (4.8%) pathology 1 (0.43%) 1 (1.7%) 0 (0.0%) type of services (%) governmental 115 (50.43%) 31 (51.7%) 84 (50.0%) 0.609 in training 12 (5.26%) 4 (6.7%) 8 (4.8%) private 97 (42.56%) 23 (38.3%) 74 (44.0%) ngo 4 (1.75%) 2 (3.3%) 2 (1.2%) concerns about training or profession (%) not at all 4 (1.7%) 4 (6.7%) 0 (0.0%) <0.001 somewhat 64 (28.1%) 29 (48.3%) 35 (20.8%) considerable 96 (42.1%) 17 (28.3%) 79 (47.0%) seriously 64 (28.1%) 10 (16.7%) 54 (32.1%) concerns about income (%) not at all 5 (2.19%) 4 (6.7%) 1 (0.6%) 0.002 somewhat 58 (25.43%) 22 (36.7%) 36 (21.4%) considerable 88 (38.59%) 20 (33.3%) 68 (40.5%) seriously 77 (33.77%) 14 (23.3%) 63 (37.5%) probable associated factors with depression (%) coronavirus no 118 (51.75%) 33 (55.0%) 85 (50.6%) 0.652 yes 110 (48.24%) 27 (45.0%) 83 (49.4%) communication problem no 94 (41.22%) 20 (33.3%) 74 (44.0%) 0.17 yes 134 (58.77%) 40 (66.7%) 94 (56.0%) previous psychological problem no 205 (89.91%) 58 (96.7%) 147 (87.5%) 0.047 yes 23 (10.08%) 2 (3.3%) 21 (12.5%) financial problem no 158 (69.29%) 48 (80.0%) 110 (65.5%) 0.05 yes 70 (30.70%) 12 (20.0%) 58 (34.5%) distress due to losing relatives no 219 (96.05%) 58 (96.7%) 161 (95.8%) >0.999 yes 9 (3.94%) 2 (3.3%) 7 (4.2%) isolation no 208 (91.22%) 57 (95.0%) 151 (89.9%) 0.296 yes 20 (8.77%) 3 (5.0%) 17 (10.1%) others no 228 (100%) 60 (100.0%) 168 (100.0%) – yes 0 (0.0%) 0 (0.0%) 0 (0.0%) ngo, nongovernmental organization; sd, standard deviation; yrs, years 236 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 psychological impact of covid19 on ophthalmologists; kalantarion et al figure 1. the prevalence of various severities of depression among ophthalmologists working in different regions of iran in 2020. ci: 0.199–0.864, p = 0.019). furthermore, ophthalmologists who were somewhat concerned about their training/profession had a lower association with depression as compared to those having serious concerns (or: 0.223; 95% ci: 0.097–0.515, p < 0.001). this finding was correspondent among ophthalmologists who were somewhat concerned (or: 0.364; 95% ci: 0.166–0.797, p = 0.012) or who had no (or: 0.056; 95% ci: 0.006–0.536, p = 0.012) concerns about their income. based on multivariable models, we determined that ophthalmologists who were somewhat concerned about their training/profession (or: 0.240; 95% ci: 0.086– 0.672; p = 0.007) and those with no concerns about their income possessed lower association with depression (or: 0.065; 95% ci: 0.005–0.91; p = 0.042) [table 2]. discussion the current study was purposed to investigate the prevalence of depression among the registered ophthalmologists who were practicing in iran. depression was found in 73.68% (n = 168) of our studied subjects with severities ranging from mild (26.75%), moderate (27.63%), and severe (19.3%). the study by grover et al, which was conducted in 2020 with a response rate of 24.8%, reported depression in 53% of the indian ophthalmic surgeons.[14] depression was also discovered in 32.6% of all studied ophthalmologists practicing or training in india in 2020 and varied severities of mild, moderate, and severe depression were identified at 21.4%, 6.9%, and 4.3%, respectively.[13] additionally, 64.7% of all turkish physicians who participated in 2020[21] and 50.4% of chinese physicians with the response rate of 68.7% in the study year of 2020[22] had symptoms of depression during the covid-19 pandemic. the higher percentage of depression in our study as compared with other reports could be attributed to the longer working hours of iranian ophthalmologists as well as the high incidence and mortality rates of coronavirus disease in our country. it should also be considered that the various levels of severity of depression were all discovered in our study, as compared to the indian study where most of the subjects had only mild depression.[13] depression and gender in our study, no statistically significant difference was observed in the prevalence of depression between different genders which was in line with the study by chambers et al.[25] however, higher incidence of depression was identified among female doctors as revealed in the annual report by the world health organization (who), the annual global prevalence, reported by cyranowski et al ford et al, and the study conducted on the indian surgeon ophthalmologists and saudi arabian ophthalmologists.[13, 24–27] it was also discovered in a study investigated by elbay et journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 237 psychological impact of covid19 on ophthalmologists; kalantarion et al table 2. univariate and multivariable analyses of the probable associated factors with depression among ophthalmologists factors level univariate analysis multivariable analysis or 95% ci p-value or 95% ci p-value lower upper lower upper gender male 0.927 0.493 1.743 0.814 – – – – female r – – – – – – – residential region high risk r – – – – – – – low risk – – – – – – – – moderate risk 2.363 0.87 6.42 0.092 0.379 0.014 10.064 0.562 marital status married 0.607 0.237 1.556 0.298 single r – – – – – – – last degree general ophthalmologist r – – – – – – – cornea & anterior segment 0.923 0.392 2.172 0.855 2.653 0.631 11.161 0.183 glaucoma 0.427 0.094 1.941 0.271 1.855 0.421 8.174 0.414 strabismus 1.795 0.209 15.441 0.594 1.085 0.139 8.458 0.938 vitreoretinal 0.415 0.199 0.864 0.019 2.976 0.244 36.367 0.393 pathology _ _ _ _ _ _ _ _ oculoplastic 0.513 0.14 1.876 0.313 0.99 0.241 4.068 0.989 type of services government 2.71 0.366 20.078 0.329 – – – in training 2 0.201 19.914 0.554 – – – – private 3.217 0.429 24.134 0.256 – – – – ngo r – – – – – – – concerns about training or profession not at all – – – – – – – – somewhat 0.223 0.097 0.515 <0.001 0.24 0.086 0.672 0.007 considerable 0.861 0.366 2.022 0.73 0.827 0.0.333 2.411 0.827 seriously r concerns about income not at all 0.056 0.006 0.536 0.012 0.065 0.005 0.91 0.042 somewhat 0.364 0.166 0.797 0.012 1.107 0.441 2.776 0.829 considerable 0.756 0.352 1.622 0.472 0.913 0.388 2.471 0.858 seriously r – – – – – – – ngo, nongovernmental organization; ci, confidence interval; or, odds ratio; r, reference al that the incidence of depression was reported higher among female physicians in his sample.[21] depression and age in this study, it was revealed that a higher percentage of older ophthalmologists suffered from depression. our findings were in contrast with the study by khanna et al on indian ophthalmologists that reported the decreasing odds of 3% for depression with increasing age.[13] this difference in comparison may be attributed to longer practice and training program hours conducted among the older ophthalmologists which may lead to increased prevalence of physical and psychological pressures. depression and marriage although in our study there was no difference between married and single ophthalmologists regarding depression, elbay et al discovered that being married was associated with less incidence of depression and other psychological problems such as anxiety and stress.[21] studies on physicians and indian ophthalmologists also showed that being single was considered an influential factor 238 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 psychological impact of covid19 on ophthalmologists; kalantarion et al in increasing the depressive symptoms during the covid-19 outbreak.[13, 21] depression and duration of practice the mean duration of practice among our study participants was 17.26 ± 10.86 years, which was not significantly associated with depression. however, elbay et al found that higher levels of depression and other mental disorders were observed among physicians who, as a result of having less working experience, executed excessive working hours in rotating shifts with minimal rest periods.[21] depression and last degree we found a lower percentage of depression among ophthalmologists in vitreoretinal fellowship as compared to the general ophthalmologists. this lower percentage might be attributed to the fact that as most of the retinal diseases need urgent management, patients with different types of retinal pathologies were referred to the vitreoretinal fellowship ophthalmologists during the covid19 pandemic as was done in the past. another reason for lower percentages of depression among vitreoretinal fellowship participants may be as a subspecialty group they have adapted to operating under these challenging conditions while managing most of these complicated retinal diseases. on the contrary, almater et al reported that depressive symptoms were significantly higher in fellows as compared to residents and consultants among the saudi arabian ophthalmologists.[27] this discrepancy can be related to the different facilities which have been provided for different grades of ophthalmologists in different countries. depression and types of services no statistically significant association was observed between depression and different services presented by the ophthalmologists. however, a higher level of depression was reported among intraining indian ophthalmologists because of their concern regarding their training or profession challenges and getting their living .13] almater et al did not find any difference between ophthalmologists who were working in the specialized eye centers and those who were practicing in general hospitals in terms of the depression incidence.[27] depression and concerns about training/profession and income the substantial record of depressed ophthalmologists is those that had serious concerns about their training/profession and income in this pandemic period, which proved to be an additional influence in maximizing depression. this finding was also reported in united kingdom, saudi arabia, and india illustrating the significant impact of coronavirus disease on the ophthalmology-training program.[13, 16, 28] the reduction of training courses for patient examination and surgeries at the educational hospitals due to the decreased number of referral patients and communication restrictions as a result of healthcare protocols contributed toward the negative impact on the ophthalmology training program. a higher level of depression was also reported among in-training indian ophthalmologists because of their concern regarding their training or profession challenges and earning to sustain their living costs.[13] association of different factors with depression in assessing the prevalence of depression during the covid-19 pandemic as it relates to multiple factors, it was determined that no inherent factors of coronavirus, communication problems, financial challenges, distress due to losing relatives or isolation were found to be influential. higher percentages of depression was found even among patients with no prior history of psychological problems, so the direct impact of coronavirus on depression was able to be isolated. our analysis shows that depression was discovered in ophthalmologists who were somewhat concerned as compared to those having serious concerns about their training/profession (or = 0.024, 95%ci: 0.086–0.672; p = 0.007) while those with no concerns about their income had lower association with depression (or: 0.065; 95% ci: 0.005–0.91; p = 0.042). depression in regions with different levels of risk of coronavirus disease all ophthalmologists located in the low-risk regions had moderate depression and most of the journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 239 psychological impact of covid19 on ophthalmologists; kalantarion et al participants (47.1%) located in the moderate-risk region had mild depression. however, we noticed higher percentages of severe depression in ophthalmologists located in the high-risk regions. it has been reported that ophthalmologists are considered as one of the frontline physicians with the high risk of contracting coronavirus disease, due to their close proximity toward patients during vision testing, slit lamp, and fundus examinations.[27] consequently, the application of personal protective equipment is necessary during patients’ examination. in addition, supportive proceedings by the government, health administrations, and the iranian society of ophthalmology should also be considered, particularly in the high-risk regions. the usage of the standard phq-9 questionnaire as our study tool can be a strength while the cross-sectional study design can be considered as our study limitation. low response rate can also be taken into account as another limitation of the present study in spite of the sending several reminders, which can be attributed to the common taboo among our study population regarding the mental health problems. in conclusion, high prevalence of depression was observed among older aged iranian ophthalmologists living in high-risk contaminated regions who possessed serious concerns with respect to their training/profession and income. it is recommended that the health policymakers of iran pay more attention to ophthalmologists who experience the aforementioned factors. availability of data and materials the datasets used and analyzed during this study can be made available from the corresponding authors upon reasonable request. acknowledgments the authors would like to express their gratitude to the negah specialty ophthalmic research center, shahid beheshti university of medical sciences and all the loved ones who cooperated with this research project, especially ophthalmologists. financial support and sponsorship there were no sources of funding for the research. conflicts of interest the authors report no conflict of interest. references 1. tavakoli a, vahdat k, keshavarz m. novel coronavirus disease 2019 (covid-19): an emerging infectious disease in the 21st century. iran south med j 2020;22:432–450. 2. peyronnet v, sibiude j, deruelle p, huissoud c, lescure x, lucet j-c, et al. infection par le sars-cov-2 chez les femmes enceintes. état desconnaissances et proposition de prise en charge. cngof, gynécologie obstétrique fertilité & sénologie; 2020. available from: https://doi.org/10.1016/j. gofs.2020.03.014. 3. sohrabi c, alsafi z, o’neill n, khan m, kerwan a, aljabir a, et al. world health organization declares global emergency: a review of the 2019 novel coronavirus (covid-19). int j surg 2020;76:71–76. 4. farnoosh g, alishiri g, hosseini zijoud sr, dorostkar r, jalali farahani a. understanding the 2019-novel coronavirus (2019-ncov) and coronavirus disease (covid19) based on available evidence – a narrative review. j mil med 2020;22:1–11. 5. rajavi z, safi s, mohammadzadeh m. guidance for ophthalmologists and ophthalmology centers during the covid-19 pandemic. j ophthalmic vis res 2020;15:438– 441. 6. wang d, hu b, chang hu c, fangfang zhu f, xing liu x, jing zhang j, et al. clinical characteristics of 138 hospitalized patients with 2019 novel coronavirus-infected pneumonia in wuhan, china. jama 2020;323:1061–1069. 7. vindegaard n, benros me. covid-19 pandemic and mental health consequences: systematic review of the current evidence. brain behav immun 2020;89:531–542. 8. walton m, murray e, christian md. mental health care for medical staff and affiliated healthcare workers during the covid-19 pandemic. eur heart j acute cardiovasc care 2020;9:241–247. 9. qiu j, shen b, zhao m, wang z, xie b, xu y. a nationwide survey of psychological distress among chinese people in the covid-19 epidemic: implications and policy recommendations. gen psychiatr 2020;33:e100213. 10. kang l, li y, hu s, chen m, yang c, yang bx, et al. the mental health of medical workers in wuhan, china dealing with the 2019 novel coronavirus. lancet psychiat 2020;7:e14.5 11. amerio a, bianchi d, santi f, costantini l, odone a, signorelli c, et al. covid-19 pandemic impact on mental health: a web-based cross-sectional survey on a sample of italian general practitioners. acta biomed 2020;91:83– 88. 12. seah i, agrawal r. can the coronavirus disease 2019 (covid-19) affect the eyes? a review of coronaviruses and ocular implications in humans and animals. ocul immunol inflamm 2020;28:391–395. 13. khanna rc, honavar sg, metla al, bhattacharya a, maulik pk. psychological impact of covid19 on ophthalmologists-in-training and practising ophthalmologists in india. indian j ophthalmol 2020;68:994–998. 240 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 psychological impact of covid19 on ophthalmologists; kalantarion et al 14. grover r, dua p, juneja s, chauhan l, agarwal p, khurana a. depression, anxiety and stress in a cohort of registered practicing ophthalmic surgeons, post lockdown during covid-19 pandemic in india. ophthalmic epidemiol 2020;13:1–8. 15. zhang y, ma zf. impact of the covid-19 pandemic on mental health and quality of life among local residents in liaoning province, china: a cross-sectional study. int j environ res public health 2020;17:2381. 3. 16. alahmadi as, alhatlan hm, bin helayel h, khandekar r, al habash a, al-shahwan s. residents’ perceived impact of covid-19 on saudi ophthalmology training programs – a survey. clin ophthalmol 2020;14:3755–3761. 17. khamseh me, baradaran hr, javanbakht a, mirghorbani m, yadollahi z, malek m. comparison of the ces-d and phq-9 depression scales in people with type 2 diabetes in tehran, iran. bmc psychiatry 2011;11:61. 18. spitzer r, kroken k, williams jb. validation and utility of a self-report version of prime-md: the phq primary care study. primary care evaluation of mental disorders. patient health questionnaire. jama 1999;282:1737. 19. kocalevent rd, hinz a, brahler e. standardization of the depression screener patient health questionnaire (phq-9) in the general population. gen hosp psychiatry 2013;35:551–555. 20. https://coronomy.ir/20/11/2020. 21. elbay ry, kurtulmus a, arpac𝚤oglu s, karadere e. depression, anxiety, stress levels of physicians and associated factors in covid-19 pandemics. psychiatry res 2020;290:113130. 22. lai j, ma s, wang y, cai z, hu j, wei n, et al. factors associated with mental health outcomes among health care workers exposed to coronavirus disease 2019. jama network open 2020;3:e203976. 23. chambers r, campbell ii. anxiety and depression in general practitioners: associations with type of practice, fundholding, gender and other personal characteristics. fam pract 1996;13:170–173. 24. who. depression and other common mental disorders: global health estimates. geneva: who; 2017 [cited 2020 jun 15]. available from: https:// apps.who.int/iris/bitstream/handle/10665/254610/whomsd-mer-2017.2 eng.pdf?sequence=1 25. cyranowski jm, frank e, young e, shear mk. adolescent onset of the gender difference in lifetime rates of major depression: a theoretical model. arch gen psychiatry 2000;57:21–27. 26. ford de, erlinger tp. depression and c-reactive protein in us adults: data from the third national health and nutrition examination survey. arch intern med 2004;164:1010–1014. 27. almater ai, tobaigy mf, younis as, alaqeel mk, abouammoh ma. effect of 2019 coronavirus pandemic on ophthalmologists practicing in saudi arabia: a psychological health assessment. middle east afr j ophthalmol 2020;27:79–85. 28. hussain r, singh b, shah n, jain s. impact of covid-19 on ophthalmic specialist training in the united kingdomthe trainees’ perspective. eye 2020;34:2157–2160. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 241 case report corneal toxicity due to datura inoxia rajesh subhash joshi, dnb, ms (ophth) department of ophthalmology, shri vasantrao naik government medical college, yavatmal, india orcid: rajesh subhash joshi: https://orcid.org/0000-0001-5646 abstract purpose: to report corneal toxicity following intentional inoculation of the juice of crushed leaves of datura (datura inoxia). case report: a 70-year-old male presented with diminished vision, redness, watering, and photophobia in his right eye one day before his presentation. the patient had instilled the juice of datura leaves in his right eye to treat his ocular problems. slit lamp examination revealed mild conjunctival and circumcorneal congestion, corneal edema, and folds in descemet’s membrane. the left eye was pseudophakic with an otherwise unremarkable examination. the patient was treated with dexamethasone, cycloplegics, and lubricants. the cornea did not sufficiently recover after one month of treatment leaving him with permanent corneal decompensation that required a referral for keratoplasty. the patient was followed up for six months. we hypothesize damage to the corneal endothelial na+/k+-atpase pump by tropane alkaloids as a cause for corneal decompensation. conclusion: awareness about toxicity of this commonly grown plant in the tropics and subtropics is essential in order to avoid blindness due to accidental or deliberate use. keywords: datura; datura inoxia; toxic keratitis j ophthalmic vis res 2019; 14 (3): 366–369 introduction datura belongs to a group of plants from the solanaceae variety. they are commonly known as daturas or the devil’s trumpets or moonflower.[1] it is a popular ornamental plant in western europe.[2] they are short-lived and can reach up to 2 meters in height. the leaves are alternately placed with correspondence to: rajesh subhash joshi, dnb, ms (ophth). 77, panchtara housing society, manish nagar, somalwada, nagpur 440015, maharashtra, india. e-mail: jrajesh5@rediffmail.com received: 15-02-2018 accepted: 16-07-2018 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i3.4792 a lobed or toothed margin. the flowers are erect or spreading trumpet-shaped. the color of the flower varies from white to yellow, pink, and pale purple. the fruit is a spiny capsule that releases numerous seeds when split open [figure 1]. for centuries, datura has been used as a herbal medicine to relieve symptoms of asthma and as an analgesic during surgery. other medicinal uses include relief from sore throat, relief from toothaches, antispasmodic medicine, antimalarial drug, treatment for patchy baldness, and antiparasitic medication. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: joshi rs. corneal toxicity due to datura inoxia. j ophthalmic vis res 2019;14:366–369 366 @ 2019 j  o  v r | p  published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i3.4792&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr corneal toxicity with datura inoxia; joshi datura is found in the tropical and warmtemperate zones of wide areas of asia, africa, the middle east, north america, central america, and south america.[3] in india, the datura flowers and leaves are used to worship lord shiva and ganesh. thus, it is not uncommon to get ocular injuries caused by accidental contact with the latex of leaves, flowers, or seeds of datura in rural or urban population. however, to the best of our knowledge, there are no reports of datura corneal toxicity. in this study, we report corneal toxicity caused by intentional ocular exposure to the leaves of the datura plant. case report a 70-year-old man presented with a history of diminished vision, pain, redness, watering, and photophobia after instillation of juice of datura in his right eye. based on his friend’s advice, the patient had used the juice of datura leaves in his right eye to treat his ocular problems, one day before his presentation. the patient had foreign body sensation for the past two days in his right eye before the instillation of datura juice. he had undergone cataract surgery with implantation of intraocular lens three years earlier in his right eye and two years before in the left eye. the review of previous records revealed that his postoperative follow-up was uneventful. visual acuity of the right eye was light perception. slit lamp examination was not possible until the instillation of 0.5% proparacaine hydrochloride drops that allowed the patient to open his eye. the patient had a narrow palpebral aperture with conjunctival and circumcorneal congestion. epithelial and stromal corneal edema was present. there were folds in descemet’s membrane [figure 2(a)]. the pupil was dilated and did not react to direct light. no reaction was noted in the anterior chamber. the posterior chamber intraocular lens was in place. corneal staining with fluorescein was negative. on ophthalmoscopy, a faint glow was visible, but nothing more specific could be noted. optic disc and retinal vessels were not evaluable. the visual acuity in the left eye was 20/20 with a normal cornea and 3-mm pupil reacting to light. his systemic examination revealed tachycardia (pulse rate 100/minute). the rest of the systemic examination was normal. figure 1. the leaves, flower and fruit of datura inoxia. a b figure 2. (a) slit lamp photograph of a patient after exposure to the juice of datura leaves showing corneal edema and folds in the descemet’s membrane. (b) slit lamp photograph showing persistent folds in descemet’s membrane at six months of follow up. the patient was medicated with 0.5% moxifloxacin eye drops four times a day, topical lubricants (carboxymethylcellulose 0.5%, refresh tear eye drop, allergan india pvt. ltd.) four times a day, cycloplegics (homatropine 2%, homide, indico remedies limited, india) three times a day, and dexamethasone 0.1% eye drops (decolite, intas pharmaceuticals pvt. ltd. india) six times a day. systemic non-steroidal anti-inflammatory and analgesic agents (ibuprofen 400 mg and paracetamol 325 mg, combiflam, sanofi india, pvt. ltd.)) were given for pain relief. on day 3, the patient experienced symptom relief. visual acuity improved to 20/200. however, slit lamp examination still showed stromal edema and folds in descemet’s membrane. intraocular pressure by applanation tonometry was 10 mm hg in both eyes. pulse rate was 80 beats/minute. the patient was followed up for six months. no improvement in the visual acuity was noted. corneal epithelial and stromal edema was still present. however, the epithelium was intact [figure 2(b)]. right eye fundus at six months was faintly j  o  v r volume 14, issue 3, july–september 2019 367 corneal toxicity with datura inoxia; joshi visible with a normal appearing disc and retinal vessels. foveal reflex could not be seen due to corneal edema. due to the non-availability of specular microscopy, endothelial cell count could not be performed. intraocular pressure was 10 mm hg at six months of follow-up. the patient was referred for penetrating keratoplasty. the corneal graft was clear and there were no signs of recurrence at five months of follow-up. discussion datura plants contain tropane alkaloids such as scopolamine, hyoscyamine, and atropine. these alkaloids have both medicinal and hallucinogenic properties. tropane alkaloids are known to be absorbed through the corneal layers.[4] tropane has an action on the circular pupillary sphincter muscle, causing cycloplegia and mydriasis. there are reports of dilated fixed pupil after contact with the datura leaf.[5, 6] self-limited mydriasis has been reported after simple exposure to the flowers of devil trumpet.[7] however, corneal endothelial toxicity due to exposure to the leaf of datura has not been reported. the patient was pseudophakic and previously had good vision in his right eye, which was documented on his previous records. the left eye was also pseudophakic and normal in all aspects. he had complained of foreign body sensation in the right eye for which he was told to instill the juice of crushed datura leaves by his close friend. he did not instill datura juice in his left eye. the patient’s presentation was similar to a corneal ulcer with the exception of no epithelial defect being present. thus, dexamethasone eye drops were administered to reduce ocular inflammation. a study has demonstrated that steroids result in an increase in na+/k+-atpase pump activity in cultured corneal endothelial cells.[8] local application of steroids may increase pump activity in the remaining healthy endothelial cells leading to the recovery of cornea. however, in the present case, cornea did not recover and visual acuity did not return to the baseline. this could be due to the frequent instillation of datura juice in the present case. basak et al presented a case series on ocular toxicity by latex of calotropis procera and showed that the majority of eyes (17/24 eyes) had corneal endothelial loss in a followup period of three months in comparison to the fellow eyes.[9] the epithelium remained intact. in our case, the epithelium was also found to be intact, but there were folds in descemet’s membrane and persistent corneal edema. this suggests that toxins liberated from the datura leaf are toxic to the endothelium without having any effect on the epithelium. this may be dependent on the dose of the juice instilled and the exposure to the cornea. due to the non-availability of specular microscope, endothelial cell density could not be measured. further studies are needed to determine the exact mechanism by which the toxins damage the endothelium while sparing epithelium. however, we hypothesize tropane alkaloids have their effect on na+/k+-atpase pump, leading to persistent corneal edema and folds in descemet’s membrane. corneal endothelial na+/k+-atpase pump dysfunction affects the endothelial ion transport.[10] this further causes loss of transparency and corneal edema and impairs vision. the specific concentration and duration of exposure of alkaloids that leads to the damage to the corneal endothelium is unknown and merits further research. toxic keratitis generally responds well to topical steroids, although some endothelial cell loss is natural in toxic endotheliitis. in this case, the corneal edema failed to resolve even at six months. this is a somewhat atypical sequelae of toxic keratitis/endotheliitis. thus, it can be concluded that the juice of datura possibly causes corneal blindness. datura has some historical and medicinal uses; therefore, people might use its extract to treat common ocular diseases. therefore, public education is important to prevent accidental or intentional exposure to this widely distributed plant in asian and western countries to prevent its serious consequences on the cornea. simple health tips like the use of gloves, washing hands, and avoiding the rubbing of eyes while plucking flowers, leaves, or seeds of datura may prevent such type of corneal blindness. financial support and sponsorship nil. conflicts of interest there are no conflict of interests. 368 j  o  v r volume 14, issue 3, july–september 2019 corneal toxicity with datura inoxia; joshi references 1. djibo a, bouzou sb. acute intoxication with “sobilobi”(datura). four cases in niger. bulletin de la societe de pathologie exotique (1990) 2000;93:294–297. 2. roemer hc, von both h, foellmann w, golka k. angel’s trumpet and the eye. j r soc med 2000;93:319. 3. kintz p, villain m, bargul y, charlot jy, cirimele v. testing for atropine and scopolamine in hair by lc-ms-ms after datura inoxia abuse. j anal toxicol 2006 1;30:454–457. 4. eraslan m. anisocoria due to the datura plant. marmara med j 2012;25:93–95. 5. firestone d, sloane c. not your everyday anisocoria: angel’s trumpet ocular toxicity. j emerg med 2007;33:21– 24. 6. andreola b, piovan a, da dalt l, filippini r, cappelletti e. unilateral mydriasis due to angel’s trumpet. clin toxicol (phila) 2008;46:329–331. 7. havelius u, asman p. accidental mydriasis from exposure to angel’s trumpet (datura suaveolens). acta ophthalmol scand 2002;80:332–335. 8. hatou s, yamada m, mochizuki h, shiraishi a, joko t, nishida t. the effects of dexamethasone on the na, katpase activity and pump function of corneal endothelial cells. curr eye res 2009;34:347–354. 9. basak sk, bhaumik a, mohanta a, singhal p. ocular toxicity by latex of calotropis procera (sodom apple). indian j ophthalmol 2009;57:232–234. 10. bonanno ja. molecular mechanisms underlying the corneal endothelial pump. exp eye res 2012;95:2–7. j  o  v r volume 14, issue 3, july–september 2019 369 perspective challenges and pitfalls in the management of rhino-orbital mucormycosis in ophthalmology: a highlighted problem in the covid-19 era farzad pakdel1, md; amin zand2, md; ali sharifi2, md; masih asadi3, md; kaveh abri aghdam3, md, phd 1department of oculo-facial plastic surgery, department of ophthalmology, farabi hospital, tehran university of medical sciences, tehran, iran 2department of ophthalmology, shafa hospital, kerman university of medical sciences, kerman, iran 3eye research center, eye department, the five senses health institute, school of medicine, iran university of medical sciences, tehran, iran orcid: farzad pakdel: https://orcid.org/0000-0001-7392-6056 kaveh abri aghdam: https://orcid.org/0000-0001-7568-6455 abstract secondary infections in hospitalized and ill patients with coronavirus disease 2019 (covid-19) are common. one of these life-threatening infectious diseases is rhino-orbital mucormycosis, which made an outbreak recently. this outbreak was mainly caused by the administration of high-dose corticosteroids in patients with covid-19, especially those with diabetes mellitus. the increased incidence of rhino-orbital mucormycosis in the covid-19 era presents different challenges for healthcare providers including ophthalmologists who are directly involved in disease management. we summarized the main challenges and recommendations for ophthalmologists on the management of rhino-orbital mucormycosis. j ophthalmic vis res 2022; 17 (3): 424–431 introduction the coronavirus disease 2019 (covid-19) pandemic has created different challenges for healthcare systems including the occurrence of secondary infections in affected patients. in correspondence to: kaveh abri aghdam, md, phd. eye research center, eye department, the five senses health institute, rassoul akram hospital, sattarkhan-niaiesh st. 1449614535, tehran, iran. e-mail: kaveh.abri@gmail.com received: 15-03-2022 accepted: 16-04-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i3.11582 hospitalized and severely ill patients suffering with covid-19, secondary infections are more common. studies have shown that the incidence of fungal infections including candidiasis, aspergillosis, and mucormycosis is cumulatively 10-times more in these patients.[1–3] recently, rhino-orbital mucormycosis impacted a substantial population in several countries. some studies estimated this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: pakdel f, zand a, sharifi a, asadi m, abri aghdam k. challenges and pitfalls in the management of rhinoorbital mucormycosis in ophthalmology: a highlighted problem in the covid-19 era. j ophthalmic vis res 2022;17:424–431. 424 © 2022 pakdel et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i3.11582&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr challenges of mucormycosis in ophthalmology; pakdel et al the pooled prevalence of covid-19-associated mucormycosis much higher than the highest recorded background of mucormycosis (7/1000 vs 0.14/1000 cases). most of the cases were diagnosed several days to a few weeks after admission for covid-19.[1–4] mucormycosis is a form of zygomycosis caused by the mucorales species of the phylum zygomycota.[5] it is much more common in immunocompromised humans, especially in patients with diabetes mellitus (dm), leukemia, or lymphoma.[6] the main contributing factors for this deadly disease in the covid-19 era are the presence of pre-existing immunodeficiency conditions, mainly dm, hematologic, and solid malignancies, the consumption of immunosuppressive and immunomodulatory agents, and the administration of intravenous corticosteroids. systemic corticosteroids including methylprednisolone and dexamethasone are commonly administered to covid-19 patients to reduce lung injury and respiratory failure. following a rapid rise in the incidence of the covid-19 delta variant in 2021 on an overwhelmed healthcare system, it was observed that a remarkable number of patients received unattended prescriptions of drugs including systemic corticosteroids at home. in addition, unnecessary treatment as well as overtreatment using these agents was seen even in those under professional care.[1–4] we overviewed different aspects of the challenges and pitfalls in the management of rhino-orbital mucormycosis from the ophthalmology perspective. which ophthalmic findings are important and helpful for making the diagnosis and evaluating the treatment response in follow-up visits? there are no definite criteria for the diagnosis and management of mucormycosis. based on reported clinical and paraclinical features of covid-19associated mucormycosis and the available guidelines for mucormycosis, the following clinical features should alert the physician for justified intensive interventions:[2, 6–8] sudden decrease of vision in any patient with a recent covid-19 diagnosis; recent peri-orbital swelling in any patient with a recent covid-19 diagnosis; orbital or facial pain or headache in any patient with a recent covid-19 diagnosis; blood mixed with nasal discharge; drooping of the eyelid, proptosis of the globe, or ophthalmoplegia; multiple and unrelated palsies of the cranial nerves; black, necrotic tissues in nasal turbinates that are easily mistaken for crusted blood. in all patients with mucormycosis, whether the orbit is involved or not in the imaging studies, initial and serial comprehensive ophthalmic evaluations include checking the following: visual acuity: relative afferent pupillary defect (rapd); extraocular motilities; eyelid exam for any subtle changes (e.g., swelling, erythema, or ptosis); globe malpositioning such as proptosis; any ocular surface disorders (e.g., corneal epithelial defects or conjunctival chemosis); eye globe firmness and intraocular pressure (iop); and a funduscopy exam (for evaluation of optic nerve head, retinal vessels, and retinal status), which are all necessary to be performed by ophthalmologists. we have seen patients with mucormycosis and active proliferative diabetic retinopathy or glaucoma where these sight-threatening ophthalmic situations were missed, because either none or inadequate ophthalmology examinations were done during the disease management. other symptoms and signs that must be checked are periorbital, cheek, alveolar, or dental pain which may radiate to the ear, neck, and head. hypoesthesia/anesthesia over the cheek is a relatively uncommon sign in patients with rhino-orbital mucormycosis and represents the involvement of the infraorbital nerve. investigation of the hard and soft palate and gingiva mucosa for any necrotic tissue is also helpful for diagnosis. patients must be visited frequently during the treatment period to assess their response to the treatments and make immediate decisions for further interventions. what are the imaging findings of rhinoorbital mucormycosis? there are no specific signs of rhino-orbital mucormycosis in the computed tomography (ct) scans and magnetic resonance imaging (mri) of the paranasal sinuses (pns) and orbit. mucosal thickening with mild and heterogeneous enhancement in post-contrast pns ct scans could be seen. another feature that may be revealed journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 425 challenges of mucormycosis in ophthalmology; pakdel et al by the imaging is the orbital abscess and its soft tissue thickening. orbital bony destruction is not common. isodense lesions relative to muscle/brain and isointense lesions relative to the brain in t1weighted images are seen on the ct scan and mr images of most patients, respectively, however, the signal intensity in t2-weighted images is variable.[9] the combination of ct scans and mris helps the physician to make a more accurate diagnosis and evaluation of the extension of involvement. in patients with signs of intracranial or skull base involvement in imaging (e.g., involvement of pterygopalatine fossa or cavernous sinus), immediate interventions including administration of high doses of an antifungal drug, salvage combination therapy, and surgical debridement should be considered.[2] be aware of masquerading diseases! abscess formation, tumors (benign or malignant), and other infectious diseases like bacterial or other fungal sinusitis may mimic symptoms and signs of rhino-orbital mucormycosis. therefore, complete investigation including ct scans and mris of the pns, orbital cavities, and brain, as well as performing a nasal endoscopy are imperative in patients suspicious of having rhino-orbital mucormycosis. some reports have also shown concomitant mucormycosis with other fungal species including aspergillosis and candidiasis, especially in immunocompromised patients.[10, 11] these situations need combined anti-fungal drugs administration to treat the diseases. is empirical therapy recommended? although all suspected cases of rhino-orbital mucormycosis need to be confirmed by positive culture and histopathological changes, any delay in the disease management may be associated with irreparable morbidities. on the other hand, medical treatment with antifungal drugs may have serious and even fatal side effects in some patients with certain underlying diseases. in addition, administration of empirical antifungal treatments for suspected patients may have considerable cost to them, especially in lowincome countries.[12, 13] therefore, the decision for empirical therapy remains an important challenge for clinicians; multidisciplinary team working for proper diagnosis of disease in suspected cases is also recommended, emphatically. logically, in suspected cases with disseminated and lifethreatening diseases (including cases with signs of intracranial involvement), treatment must be initiated as soon as possible along with the control of other underlying diseases. how to initiate treatment? treatment of rhino-orbital mucormycosis is a combination of surgical debridement of the involved tissues and medical therapy with antifungal drugs. in addition, risk assessment is an important issue in the control of the disease.[8] consultation with an internist is necessary to control serum glucose levels and diabetic ketoacidosis (dka). blood glucose monitoring is a logical step during the treatment. the drug of choice for initiation of treatment is intravenous amphotericin b. it is a polyene antifungal drug that binds with ergosterol on the fungal cell membranes, forming pores in them and leading to cell death. the drug has two main forms, deoxycholate (conventional) and liposomal. the liposomal form of the drug is superior to the deoxycholate form, because its toxic effects on organs (including the kidney) are fewer, and its efficacy and penetration into the blood–brain barrier and distribution throughout the central nervous system is also more than that of the deoxycholate form.[14] this drug has frequent and significantly adverse effects that need careful monitoring by multiple disciplines including infectious diseases specialists, internists, nephrologists, hematologists, and clinical pharmacologists. amphotericin b can cause urinary potassium wasting and hypokalemia. so, the drug must be administered slowly with vital signs and cardiac monitoring. other renal complications of the drug are urinary magnesium wasting and hypomagnesemia, metabolic acidosis, and polyuria due to nephrogenic diabetes insipidus.[14] due to these adverse effects, serial visits by internists and regular checking of blood pressure, serum potassium (k) and magnesium (mg), atrial blood gas (abg), regular renal function laboratory tests including blood urea nitrogen (bun) and serum creatinine (cr) are recommended. 426 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 challenges of mucormycosis in ophthalmology; pakdel et al the correct dosage preparation of the drug is important in preventing lethal consequences of a drug overdose. the recommended dosage of liposomal amphotericin b for the treatment of rhino-orbital mucormycosis is varied – between 3.0 and 5.0 mg/kg/day. this dose can be increased to 10 mg/kg/day for patients with intracranial involvement. the recommended dosage for the deoxycholate (conventional) form is 0.5–1.0 mg/kg/day.[14] so, the dosage of the deoxycholate form is about one-fifth of the liposomal form. this significant difference is very important and needs to be taken into account during the preparation of the deoxycholate form to prevent the lethal consequences of ingesting an inaccurate dosage. some reports of cardiac arrest and mortality following amphotericin b overdoses have been reported.[15] cardiac toxicity is a rare but potentially lethal adverse effect of amphotericin b administration. ventricular arrhythmias and bradycardia have been reported not only in acute overdose but even with correct dosage with slow rates of drug infusion.[16, 17] previous studies showed the drug itself could be cardiotoxic and these complications were reported even in patients with a normal concentration of potassium and magnesium.[18] the drug could be embryotoxic if administered during pregnancy. the drug is classified as a pregnancy category b by the united states food and drug administration (fda).[19] an experimental study showed that 0.5 mg/kg of amphotericin b and 2 mg/kg of its methyl derivative can be embryotoxic in rats.[20] so, in pregnant and lactating women with rhino-orbital involvement, treatment initiation with amphotericin b must be done with excessive caution using as low as possible doses. therefore, planning for the administration of alternative antifungal drugs that have fewer adverse effects must be considered in particular cases. when are combined antifungal treatments suggested? few studies have shown that combination therapy with triazoles and polyenes in patients with disseminated mucormycosis (e.g., intracranial involvement), especially in neutropenic or dka patients can be beneficial.[21] the suggested drugs to be added to amphotericin b therapy are: caspofungin: combination therapy with caspofungin was associated with significantly improved survival for patients with dka and rhinoorbito-cerebral mucormycosis.[22] the evidence for use in humans is still weak. micafungin: combination therapy with micafungin improved survival in neutropenic and dka mice with disseminated mucormycosis.[23] the evidence for use in humans is still weak. posaconazole: combination therapy with oral posaconazole in febrile neutropenic patients with disseminated infection can significantly improve the survival rate.[24] isavuconazole: it has shown activity against mucormycosis with efficacy similar to amphotericin b. isavuconazole can be used in combination with amphotericin b for the treatment of rhino-orbital mucormycosis.[25] in addition, posaconazole or isavuconazole can be administrated as salvage therapy for patients who do not respond to or cannot tolerate amphotericin b.[8] how long is the duration of treatment? after the achievement of acceptable clinical responses to the administration of intravenous liposomal amphotericin b, which usually takes more than three to six weeks, patients can be switched to oral posaconazole or isavuconazole as step-down therapy.[6] treatment must be continued until the resolution of the clinical and radiographic signs of the active disease. it is important to control the underlying causes of the immunosuppression conditions, before treatment cessation. when is surgical debridement necessary? necrotic and infected areas in the nasal cavity and pns should be extensively debrided. necrotic areas in the orbit and brain may also be debrided limitedly when appropriate. ophthalmology and otolaryngology consultations are necessary in all suspicious cases of rhino-orbital mucormycosis. early surgical interventions in pns (e.g., functional endoscopic sinus surgery: fess) is one of the essential steps in establishing the diagnosis (by finding necrotic tissues and making specimens for the potassium hydroxide [koh] wet mount and mycology staining and cultures) and also limiting the disease progression by debridement journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 427 challenges of mucormycosis in ophthalmology; pakdel et al of necrotic tissues from pns cavities in early phases. repetition of pns mucosa debridement is necessary in progressive and severe cases.[26] is regular irrigation of the nasal cavity and pns with amphotericin b recommended? some studies showed that nasal irrigation with 100 or 200 μg/ml of amphotericin b did not create a greater benefit than using normal saline solution after pns debridement surgery.[27, 28] according to the results of an in vitro study, irrigation of growth media plates embedded with 10 species of fungi commonly found in the nasal cavity, with 20 ml of amphotericin b at concentrations of 200 or 300 μg/ml (twice per day for six weeks), prevented fungal growth successfully.[29] therefore, the possible benefits of this route of amphotericin b administration are limited and adjuvant regular irrigation of the nasal cavity and pns with the drug is controversial. when are topical medications for the ocular surface problems necessary? in patients with orbital mucormycosis, ocular surface complications including dry eye, corneal epithelial erosions and defects, and conjunctival chemosis must be managed carefully with topical lubricants, emollients, and antibiotics. when is the retrobulbar injection of amphotericin b indicated? retrobulbar injection of amphotericin b may facilitate improvement of orbital mucormycosis, in combination with systemic antifungal drugs, and reduce the rate of aggressive interventions including orbital tissues debridement or exenteration. retrobulbar injections of amphotericin b are recommended in patients with signs of optic nerve compression including progressive decrease in visual acuity and positive rapd. in addition, this route of drug administration is recommended when other symptoms and signs of orbital involvement including pain, proptosis, globe firmness, limitation of extraocular motility or conjunctival chemosis, and ocular surface exposure have progressed despite complete systemic medical and surgical interventions.[30] this route of drug delivery is reported to be effective in the improvement of cerebritis in patients with intracranial involvement.[31] retrobulbar injection of the drug is a suitable treatment option for cases in which orbital surgical intervention is not possible, especially for patients admitted to an intensive care unit (icu). in the covid-19 era, a high portion of cases were icuadmitted and were not candidates for surgical intervention (including fess and orbital surgery). therefore, this route of administration is a good and superior choice for that group of patients. reports showed that well-timed decisions for this type of drug administration is important to achieve acceptable results. the recommended dosage for the retrobulbar injection is 3.3–3.5 mg/1 ml of liposomal (preferred) amphotericin b. there is no protocol for the frequency of the drug injections, but some reports recommended injections at least three times during the course of three days, continuously.[32] however, this route of drug administration has some limitations. first, retrobulbar injections are a risky intervention that may cause globe perforation by the syringe needle, retrobulbar hemorrhage, and even inadvertent drug administration to the brain stem. second, amphotericin b is neurotoxic, and this toxicity is much higher in the conventional form of the drug as compared to the liposomal form.[32, 33] therefore, even with the administration of a correct dosage of liposomal amphotericin b, the possibility of the occurrence of toxic optic neuropathy should be considered. third, in some reports, the retrobulbar injection of the drug caused orbital compartment syndrome.[34] fourth, local injection of amphotericin b (especially the deoxycholate form) may induce inflammation by causing soft-tissues edema, especially after the first injection.[14] however, this side effect is usually transient and self-limited. fifth, amphotericin b has a high molecular weight and drug distribution in orbital connective and fatty tissues is slow and limited.[32] as a consequence, multiple injections are necessary and logical. the previously mentioned adverse effects limit the frequencies of the drug administration to the orbital cavity via the retrobulbar route. the senior author (fp) has gained experience with the administration of a higher frequency of injections at different levels of dosages. it should be mentioned that the retrobulbar injection of amphotericin b is rapidly becoming a standard practice. 428 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 challenges of mucormycosis in ophthalmology; pakdel et al what is the role of conservative orbital debridement and adjuvant local amphotericin b irrigation? in a retrospective study by seiff et al, on seven immunocompromised patients with rhino-orbital mucormycosis and good visual acuity, surgical debridement of necrotic tissue of the involved pns and orbits were done. then, a catheter was inserted and placed into the orbital cavities for regular irrigation of them with amphotericin b solution (with volume of 3–4 ml, and concentration of 0.25–1.00 mg/ml, four times per day, for 5–14 days). they claimed this technique improved the therapeutic outcomes. joos et al reported successful management of a patient with rhinoorbital mucormycosis with the similar technique (surgical debridement of necrotic tissues, and then regular irrigation of the involved orbital cavity with 5 ml [1 mg/ml] non-liposomal amphotericin b, once a day for seven days).[35, 36] nowadays, this technique is not popular among oculoplastic surgeons, because the benefits of this technique in comparison to its potential risks are low. some of these potential risks are including uneventful and iatrogenic harms to the orbital components (e.g., nerves and extraocular muscles), creating a route for the entrance of other pathogens, and possible ocular toxicity by the drug. moreover, the sufficiency of the whole necrotic tissue debridement process and the adequate distribution of the drug into the orbital cavity is under question. when is orbital exenteration indicated? one of the most challenging decisions in the management of orbital mucormycosis is planning for exenteration in those cases where the nature of the disease is life-threatening. here, the main questions are whether exenteration can reduce the mortality rate and whether the benefits of exenteration are satisfactory enough against its lifetime disabling effects. there is no standard protocol for choosing to perform orbital exenteration in patients with rhino-orbital mucormycosis; it is mainly dependent on the judgment of the physician. the most important deciding factors for performing exenteration in patients with orbital mucormycosis are the presence of ophthalmoplegia and cranial nerves palsy, proptosis, ocular tissues involvement, progressive visual impairment or vision loss, general necrosis of the orbital cavity and its adnexa, major immunosuppressive conditions including underlying diseases and neutropenia, cerebral extension, prolonged disease despite adequate medical and surgical interventions, and unsatisfactory response to the initial treatments.[37, 38] generally, in cases resistant to all medical and surgical interventions with progressive signs and symptoms of the disease, especially the probability of intracranial involvement and fulminant infection, some physicians recommended orbital exenteration to decrease the mortality risk. however, a review on indications of orbital exenteration in patients with mucormycosis revealed there are no standard guidelines for making decision of exenteration in these patients. they showed that just exenterated patients with fever were more likely to survive compared with non-exenterated febrile cases.[38] which care measures are necessary after orbital exenteration? after orbital exenteration, patients need frequent socket examinations for the occurrence of any infections including the recurrence of the fungal infection. the socket should be inspected and cleaned with diluted betadine solution for the first three weeks until the surface is adequately epithelialized. in some patients with superficial recurrence of mucormycosis, regular irrigation with an amphotericin b solution is recommended. sometimes, debridement of remnant necrotic tissues of the orbital cavity is necessary.[39] many patients will be dissatisfied with the cosmetic outcomes of the surgery. this condition creates significant psycho-social challenges for the patients. therefore, a counseling plan for the patients is necessary to rehabilitate their cosmesis. prosthetic reconstruction of orbital defects with facial plastic surgeries is suggested.[40] which variables are more important in patients’ survival? in a review by hargrove et al,[38] the investigators revealed that patients aged >46 years with frontal sinus involvement and fever had less survival rates in comparison to those without these conditions, journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 429 challenges of mucormycosis in ophthalmology; pakdel et al regardless of performing orbital exenteration in patients with rhino-orbital mucormycosis. in addition, they showed patients treated with amphotericin b and those with diabetes were more likely to survive compared with those without these conditions. what has been the impact of the covid19 pandemic on the prevalence of mucormycosis? according to a meta-analysis by hussain et al,[41] the pooled prevalence of rhino-orbito-cerebral mucormycosis among hospitalized covid-19 patients was 7 cases per 1000 patients. this rate was much higher in comparison to the prevalence of the disease among comorbid populations before the covid-19 pandemic (0.14/1000).[42, 43] in addition, the estimated global incidence rate of mucormycosis varies between 0.005 and 1.7 per million population.[44] therefore, a very significant surge in the disease’s prevalence occurred during the covid-19 era, and lead to an additional burnout and workload among healthcare providers. in conclusion, management of patients with rhinoorbital mucormycosis is challenging. the first step is making the accurate diagnosis of the disease, and differentiate it from other possible debilitating ocular comorbidities. after making the diagnosis, well-timed management of the disease is life-saving, and needs a multidisciplinary teamwork including infectious diseases specialists, otolaryngologists, ophthalmologists, and internists. due to unpredictable and mysterious progression of the disease, patients should receive regular follow-up visits to assess and timely revise the treatment plan. by considering the important adverse effects of amphotericin b on serum electrolytes, heart, and kidney, regular monitoring (by monitoring the vital signs, laboratory testing, and electrocardiography) is necessary for these patients. the current management protocols of the disease needs review to make them safer with more cost-effectiveness outcomes (e.g., focusing on combined systemic antifungal regimens and locally targeted administration of the drug in addition to systemic medications). also, introducing guidelines for controlling the load of intravenous steroids (including dexamethasone, or methylprednisolone) administration in covid-19 patients seems to be necessary. financial support and sponsorship none. conflicts of interest none. references 1. singh ak, singh r, joshi sr, misra a. mucormycosis in covid-19: a systematic review of cases reported worldwide and in india. diabetes metab syndr 2021;15:102146. 2. pakdel f, ahmadikia k, salehi m, tabari a, jafari r, mehrparvar g, et al. mucormycosis in patients with covid19: a cross-sectional descriptive multicentre study from iran. mycoses 2021;64:1238–1252. 3. raiesi o, hashemi sj, mohammadi ardehali m, ahmadikia k, getso mi, pakdel f, et al. molecular identification and clinical features of fungal rhinosinusitis: a 3year experience with 108 patients. microb pathog 2021;158:105018. 4. hoenigl m, seidel d, carvalho a, rudramurthy sm, arastehfar a, gangneux jp, et al. the emergence of covid-19 associated mucormycosis: analysis of cases from 18 countries [internet]. ssrn electron j [preprint]. 2021. available from: https://doi.org/10.2139/ssrn.3844587. 5. pak j, tucci vt, vincent al, sandin rl, greene jn. mucormycosis in immunochallenged patients. j emerg trauma shock 2008;1:106–113. 6. cornely oa, arikan-akdagli s, dannaoui e, groll ah, lagrou k, chakrabarti a, et al. escmid and ecmm joint clinical guidelines for the diagnosis and management of mucormycosis 2013. clin microbiol infect 2014;20:5–26. 7. smith hw, kirchner ja. cerebral mucormycosis; a report of three cases. ama arch otolaryngol 1958;68:715–726. 8. skiada a, lass-floerl c, klimko n, ibrahim a, roilides e, petrikkos g. challenges in the diagnosis and treatment of mucormycosis. med mycol 2018;56:93–101. 9. herrera da, dublin ab, ormsby el, aminpour s, howell lp. imaging findings of rhinocerebral mucormycosis. skull base 2009;19:117–125. 10. singh a, mohanty a, jha s, gupta p, kaistha n. concomitant mucormycosis with aspergillosis in patients with uncontrolled diabetes mellitus: a case series. j clin diagnostic res 2021;15:dr01–dr03. 11. nambiar m, varma sr, jaber m, sreelatha sv, thomas b, nair as. mycotic infections mucormycosis and oral candidiasis associated with covid-19: a significant and challenging association. j oral microbiol 2021;13:1967699. 12. hoenigl m, seidel d, carvalho a, rudramurthy sm, arastehfar a, gangneux jp, et al. the emergence of covid-19 associated mucormycosis: a review of cases from 18 countries. lancet microbe 2022. available from: https://doi.org/10.1016/s2666-5247(21)00237-8 13. darwish rm, almasri m, al-masri mm. mucormycosis: the hidden and forgotten disease. j appl microbiol 2022;132:4042–4057. 430 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 challenges of mucormycosis in ophthalmology; pakdel et al 14. hamill rj, amphotericin b. amphotericin b formulations: a comparative review of efficacy and toxicity. drugs 2013;73:919–934. 15. burke d, lal r, finkel kw, samuels j, foringer jr. acute amphotericin b overdose. ann pharmacother 2006;40:2254–2259. 16. soler ja, ibañez l, zuazu j, julià a. bradycardia after rapid intravenous infusin of amphotericin b. lancet 1993;341:372–373. 17. aguado jm, hidalgo m, moya i, alcazar jm, jimenez mj, noriega ar. ventricular arrhythmias with conventional and liposomal amphotericin. lancet 1993;342:1239. 18. laniado-laborín r, cabrales-vargas mn. amphotericin b: aide effects and toxicity. rev iberoam micol 2009;26:223– 227. 19. pilmis b, jullien v, sobel j, lecuit m, lortholary o, charlier c. antifungal drugs during pregnancy: an updated review. j antimicrob chemother 2015;70:14–22. 20. moguchenok ea. [study of embryotoxic and teratogenic effects of amphotericin b and a methyl derivative of amphotericin b in rats after their intravenous and intraamniotic administration]. antibiot khimioter 1992;37:25– 28. 21. spellberg b, ibrahim a, roilides e, lewis re, lortholary o, petrikkos g, et al. combination therapy for mucormycosis: why, what, and how? clin infect dis 2012;54:s73–s78. 22. spellberg b, fu y, edwards je jr, ibrahim as. combination therapy with amphotericin b lipid complex and caspofungin acetate of disseminated zygomycosis in diabetic ketoacidotic mice. antimicrob agents chemother 2005;49:830–832. 23. ibrahim as, gebremariam t, fu y, edwards je jr, spellberg b. combination echinocandin-polyene treatment of murine mucormycosis. antimicrob agents chemother 2008;52:1556–1558. 24. ullmann aj, cornely oa, burchardt a, hachem r, kontoyiannis dp, töpelt k, et al. pharmacokinetics, safety, and efficacy of posaconazole in patients with persistent febrile neutropenia or refractory invasive fungal infection. antimicrob agents chemother 2006;50:658–666. 25. marty fm, ostrosky-zeichner l, cornely oa, mullane km, perfect jr, thompson gr 3rd, et al. isavuconazole treatment for mucormycosis: a single-arm open-label trial and case–control analysis. lancet infect dis 2016;16:828– 837. 26. selarka l, sharma s, saini d, sharma s, batra a, waghmare vt, et al. mucormycosis and covid-19: an epidemic within a pandemic in india. mycoses 2021;64:1253–1260. 27. jiang rs, hsu sh, liang kl, amphotericin b. amphotericin b nasal irrigation as an adjuvant therapy after functional endoscopic sinus surgery. am j rhinol allergy 2015;29:435–440. 28. jiang rs, twu cw, liang kl. efficacy of nasal irrigation with 200 μg/ml amphotericin b after functional endoscopic sinus surgery: a randomized, placebocontrolled, double-blind study. int forum allergy rhinol 2018;8:41–48. 29. shirazi ma, stankiewicz ja, kammeyer p. activity of nasal amphotericin b irrigation against fungal organisms in vitro. am j rhinol 2007;21:145–148. 30. colon-acevedo b, kumar j, richard mj, woodward ja. the role of adjunctive therapies in the management of invasive sino-orbital infection. ophthal plast reconstr surg 2015;31:401–405. 31. safi m, ang mj, patel p, silkiss rz. rhino-orbitalcerebral mucormycosis (rocm) and associated cerebritis treated with adjuvant retrobulbar amphotericin b. am j ophthalmol case rep 2020;19:100771. 32. hirabayashi ke, kalin-hajdu e, brodie fl, kersten rc, russell ms, vagefi mr. retrobulbar injection of amphotericin b for orbital mucormycosis. ophthal plast reconstr surg 2017;33:e94–e97. 33. harmsen s, mclaren ac, pauken c, mclemore r, amphotericin b. amphotericin b is cytotoxic at locally delivered concentrations. clin orthop relat res 2011;469:3016–3021. 34. brodie fl, kalin-hajdu e, kuo ds, hirabayashi ke, vagefi r, kersten rc. orbital compartment syndrome following retrobulbar injection of amphotericin b for invasive fungal disease. am j ophthalmol case rep 2016;1:8–10. 35. seiff sr, choo ph, carter sr. role of local amphotericin b therapy for sino-orbital fungal infections. ophthal plast reconstr surg 1999;15:28–31. 36. joos zp, patel bc. intraorbital irrigation of amphotericin b in the treatment of rhino-orbital mucormycosis. ophthal plast reconstr surg 2017;33:e13–e16. 37. songu m, unlu hh, gunhan k, ilker ss, nese n. orbital exenteration: a dilemma in mucormycosis presented with orbital apex syndrome. am j rhinol 2008;22:98–103. 38. hargrove rn, wesley re, klippenstein ka, fleming jc, haik bg. indications for orbital exenteration in mucormycosis. ophthal plast reconstr surg 2006;22:286–2891. 39. karadeniz uğurlu ş, selim s, kopar a, songu m. rhinoorbital mucormycosis: clinical findings and treatment outcomes of four cases. turk j ophthalmol 2015;45:169– 174. 40. jain s, jain p. rehabilitation of orbital cavity after orbital exenteration using polymethyl methacrylate orbital prosthesis. j indian prosthodont soc 2016;16:100–104. 41. hussain s, riad a, singh a, klugarová j, antony b, banna h, et al. global prevalence of covid-19-associated mucormycosis (cam): living systematic review and metaanalysis. j fungi 2021;7:985. 42. chander j, kaur m, singla n, punia rp, singhal sk, attri ak, et al. mucormycosis: battle with the deadly enemy over a five-year period in india. j fungi 2018;4:46. 43. petrikkos g, skiada a, lortholary o, roilides e, walsh tj, kontoyiannis dp. epidemiology and clinical manifestations of mucormycosis. clin infect dis 2012;54:s23–s34. 44. prakash h, chakrabarti a. global epidemiology of mucormycosis. j fungi 2019;5:26. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 431 original article rapid assessment of avoidable visual impairment in two coastal districts of eastern india for determining effective coverage: a cross-sectional study amit bhardwaj1, msw; praveen vashist1, md; suraj singh senjam1, md; vivek gupta1, md; noopur gupta2, md souvik manna1, md 1community ophthalmology, dr. rajendra prasad centre for ophthalmic sciences, all india institute of medical sciences, new delhi, india 2department of ophthalmology, dr. rajendra prasad centre for ophthalmic sciences, all india institute of medical sciences, new delhi, india orcid: amit bhardwaj: https://orcid.org/0000-0002-7689-072x souvik manna: https://orcid.org/0000-0002-8870-8542 abstract purpose: to measure the prevalence and causes of visual impairment (vi) among the 40+ age population in two coastal districts of india and to determine the levels of effective cataract surgical coverage (ecsc) and effective refractive error coverage (erec) in the study population. methods: a cross-sectional study was done on 4200 people chosen using cluster sampling in two coastal districts of odisha, an eastern state in india. a team consisting of trained optometrists and social workers conducted the ocular examination which included unaided, pinhole, and aided visual acuity assessments followed by examination of the anterior segment and lens. results: overall, 3745 (89.2%) participants were examined from 60 study clusters, 30 in each district. among those examined, 1677 (44.8%) were men, 2554 (68.2%) were educated and number? (17.8%) used distance spectacles during the survey. the prevalence of vi adjusted for age and gender was 12.77% (95% ci 11.85–13.69%). multiple logistic regression showed that older age (or 3.1; 95% ci 2.0–4.7) and urban residence (or 1.2; 95% ci 1.0–1.6) were associated with vi. being educated (or 0.4; 95% ci 0.3–0.6) and using glasses (or 0.3; 95% ci 0.5–0.2) were found to provide protection; therefore, resulting in lower instances of vi. cataract (62.7%) and uncorrected refractive errors (27.1%) were the two main causes of vi. the ecsc was 35.1%, the erec for distance was 40.0%, and the erec for near was 35.7%. conclusion: vi remains a challenge in odisha, as the prevalence is high and the surgical coverage is poor. nearly 90% of vi is avoidable indicating that targeted interventions are required to address this problem. keywords: blindness; cataract; refractive error j ophthalmic vis res 2023; 18 (2): 182–191 correspondence to: souvik manna, md. community ophthalmology, dr. rajendra prasad centre for ophthalmic sciences, aiims, new delhi 110029, india. email: souvikmanna311@yahoo.com received: 06-01-2022 accepted: 06-11-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i2.13185 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: bhardwaj a, vashist p, senjam ss, gupta v, gupta n, manna s. rapid assessment of avoidable visual impairment in two coastal districts of eastern india for determining effective coverage: a cross-sectional study. j ophthalmic vis res 2023;18:182–191. 182 © 2023 bhardwaj et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i2.13185&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr raab in india; bhardwaj et al introduction vision impairment (vi), including blindness, is an alarming global public health issue with a disproportionately larger prevalence in lowand middle-income countries (lmics). as per the recent who estimates, globally, approximately 2.2 billion people have near and distance vi of which almost 50% need either prevention or treatment measures.[1] in october 2019, who launched the first world report on vision to draw attention to the increasing need for eye care.[2] india has the second largest population in the world with nearly 4.8 million of the population suffering from blindness and 74 million experiencing vi.[3] cataract and uncorrected refractive errors (ure) are the two commonest reasons for vi in india.[3] in a country like india, where the population is diverse and heterogeneous, it is imperative to have regionally representative, valid, and robust public health data so that appropriate public health strategies can be planned at the local level. rapid assessment of vi (ravi) surveys are less expensive and less time-consuming as compared to detailed and resource-intensive epidemiological studies. for tracking progress at country and regional levels, ravi surveys are needed at periodic intervals to assess baseline status and progress toward targets. effective refractive error coverage (erec) and effective cataract surgical coverage (ecsc) are also tracer indicators that gauge the eye care scenario in a country.[4] the global targets include a 30% increase in ecsc and a 40% increase in erec, by 2030.[4, 5] ravi surveys have been completed in many areas of southern, western, central, and northern india; however, relevant data on the magnitude of the vi burden, especially in the remote underprivileged population from eastern india is missing. a ravi study was conducted in the population aged 40+ in two coastal districts of odisha with the purpose of assessing the magnitude and causes of vi in the two districts and to determine the levels of ecsc and erec in the study population. methods two coastal districts were selected in the state of odisha: ganjam which is predominantly rural and khordha which is predominantly urban.[6, 7] the sample size of 2100 per district was selected using a prevalence of 15% vi in the 40+ age group, a relative precision of 15%, confidence interval (ci) of 95%, 1.75 design effect (cluster size 70), and a nonresponse rate of 20%.[8] the study protocol was reviewed and approved by institute ethics committee of all india institute of medical sciences, new delhi, india under the approval number iec562/02.12.2016,rp/8/2016, op-10/06.03.2020. in addition, the protocol of the study complied with the guidelines for human studies and the world medical association declaration of helsinki. sampling was done in multiple stages using cluster random techniques. in urban regions of india, the district is divided into municipal wards, whereas in the rural areas the administrative divisions are villages. a list of all the municipal wards and villages in the district was obtained from the census office, india. in the first stage of sampling, all the subdivisions were selected, and within each subdivision, a list of 30 psus (primary sampling units) comprising of urban wards and villages was chosen based on the probability proportionate to size (pps) techniques. the psus had a maximum population size of 2000. if a village or ward had a population greater than 2000, it was divided into smaller psus of size 2000, each of which was independently entered into the sampling frame. within each psu, the selection of households involved a compact segment sampling technique in which the selected psu was divided into multiple segments of 300– 500 people and one such segment was chosen randomly by a draw of chits. in the selected segment, the survey proceeded from one corner and all contiguous houses were visited until 70 people were enumerated. by covering a total of 30 such segments, the target sample of 2100 in each district was achieved. the sample population comprised of all those who were aged 40+ and were habitual residents of the selected districts (living in the area for at least six months). two teams were dispatched to visit 30 clusters in each district. before the commencement of the study, a two-day training was given to the team regarding standard study protocols, method of cluster selection and coding, enumeration methods, clinical examination, and barrier information. inter-observer variations among the optometrists for clinical diagnosis, journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 183 raab in india; bhardwaj et al distant and near vision examinations were checked in the clinic and community. the inter-observer agreement was good (kappa > 0.8) for all survey procedures among optometrists as each team consisted of members from local areas who were helpful in overcoming any language or cultural barriers. the survey was conducted using the standard ravi questionnaire. it captured data on the avoidable reasons for blindness and vi in people aged 40+. this questionnaire was modified from the standard raab (rapid assessment of avoidable blindness), and had extra sections for near vision, use of glasses, and unaided visual acuity. presenting binocular near vision was measured using a simplified “e” chart having n60 and n6 optotypes with five letters in one line. the procedure was performed at a distance of 40 cm, which was ensured by using a headband attached to a rope 40 cm in length. near vision was calculated first using the n60 optotype and then using the n6 optotype. the criterion for determining the category of vision at a certain level was selection of four correct letters out of five from the simplified “e” chart. distance visual acuity (va) was tested utilizing tumbling “e” charts both with and without spectacles. va was examined with “e” snellen optotypes of different sizes for va of 6/12, 6/18, and 6/60 at 6 m. the criterion for measuring vision at any of the levels was the selection of four correct answers consecutively, or four correct out of five tumbles. if the person wore spectacles for distance vision, the pinhole was placed in front of the spectacles. the lens assessment was done in an undilated pupil with a pen torch [figure 1]. the primary outcome measure was vi, which was defined as presenting visual acuity (pva) < 6/12 according to the international classification of diseases (icd-10 as revised by who)).[9] the main cause of pva < 6/12 was separately ascertained for each eye, and the more avoidable cause was taken as the diagnosis for each person. in cases with multiple causes for vi, the disease that was more preventable/amenable to treatment to achieve va ≥ 6/12 was considered as the principal cause. the data entry was done in specially designed epi-data 3.1-based database with all checks in place for validation and data consistency. double data entry was done to minimize errors and data cleaning was done to remove all inconsistent findings and outliers. data analysis was done using the stata 15.1 software package (stata corp., college station, texas, usa). age and gender disaggregated prevalence of vi along with 95% ci were calculated. univariate and multivariate analyses were done to find factors associated with vi. the sample prevalence (unstandardized) was directly standardized using the age-sex distribution of the combined population of the two districts, using stata software. association of vi with age, gender, education, and locality was checked by using multiple logistic regression analysis. results overall, 4200 individuals aged 40+ were enumerated, of whom 3745 (89.2%) were examined. the number of males was 1677 (44.8%) and that of females was 2068 (55.2%). the response rate was better among females (91.6%) than males (86.4%), as far as clinical examination was concerned. out of the 455 not examined, 441 were either not available or were unable to communicate and 14 refused to undergo examination. there was no significant difference between the socio-demographic profile of the sample and target population (odisha state) (p = 0.57) [table 1]. the age and sex standardized prevalence of vi including blindness was 12.77% (95% c.i. 11.85–13.69). although the prevalence of vi (including blindness) was higher in males (16.33%, 95% ci: 14.56–18.11) than females (14.74%, 95% ci:13.21–16.27), the difference was not statistically significant (p = 0.181). the standardized prevalence of moderate vi (mvi: presenting visual acuity <6/18 to 6/60 in the better eye) and severe vi (svi: presenting visual acuity <6/60 to 3/60 in the better eye) in study subjects was 4.84% and 1.13%, respectively. the blindness prevalence in the study population was 1.14% (95% c.i. 0.84–1.45) [table 2]. the prevalence of vi and ure exhibited a rising trend with age. maximum vi (including blindness) was seen in females above the age of 80 years (68.3%) [figure 2 & table 3]. out of the 3745 study participants, 343 (9.2%) had ure. another 155 (4.1%) had corrected refractive errors (re) giving a total of 498 individuals with any form of re (13.3%). 184 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 raab in india; bhardwaj et al table 1. socio-demographic profile of 40+ sample population in khordha and ganjam districts compared with odisha state. variable sample odisha male (%) female (%) total (%) male (%) female (%) total (%) age groups (yr) 40–49 449 (26.7) 705 (34.1) 1154 (30.8) 26,00,286 (41.3) 24,25,218 (40.1) 50,25,504 (40.7) 50–59 438 (26.1) 550 (26.6) 988 (26.4) 17,01,815 (27.0) 16,29,717 (26.9) 33,31,532 (26.9) 60–69 440 (26.2) 510 (24.7) 950 (25.4) 12,25,484 (19.5) 12,28,102 (20.3) 24,53,586 (19.9) 70–79 260 (15.5) 240 (11.6) 500 (13.4) 5,63,929 (8.9) 5,68,941 (9.4) 11,32,870 (9.2) ≥80 90 (5.4) 63 (3.0) 153 (4.1) 2,04,857 (3.3) 1,93,135 (3.2) 3,97,992 (3.2) total 1677 2068 3745 62,96,371 60,45,113 1,23,41,484 education illiterate 274 (16.3) 917 (44.3) 1191 (31.8) 18,76,376 (29.8) 36,96,032 (61.2) 55,72,408 (45.2) up to 4𝑡ℎ 380 (22.7) 548 (26.5) 928 (24.8) 12,06,268 (19.2) 8,34,639 (13.8) 20,40,907 (16.6) 5𝑡ℎ–9𝑡ℎ pass 419 (24.9) 351 (16.9) 770 (20.6) 18,98,155 (30.2) 10,83,901 (17.9) 29,82,056 (24.2) >10𝑡ℎ pass 604 (36.0) 252 (12.2) 856 (22.9) 13,06,345 (20.8) 4,24,874 (7.0) 17,31,219 (14.0) total 1677 2068 3745 62,87,144 60,39,446 1,23,26,590 table 2. prevalence of visual impairment and blindness among 40+ population in khordha and ganjam districts of odisha. combined % (95% ci) unstandardized prevalence (%) standardized prevalence (%) definition male (n = 1677) female (n = 2068) total blind pva < 3/60 in be* 27 1.61 (1.00–2.21) 27 1.30 (0.81–1.79) 54 1.44 (1.06–1.95) 1.14 (0.84–1.45) svi pva < 6/60 – 3/60 in be* 23 1.37 (0.81–1.93) 30 1.45 (0.93–1.96) 53 1.41 (1.15–1.73) 1.13 (0.83–1.43) mvi pva < 6/18 – 6/60 in be* 107 6.38 (5.20–7.55) 113 5.46 (4.48–6.44) 220 5.87 (5.10–6.75) 4.84 (4.22–5.46) mild vi pva < 6/12 – 6/18 in be* 117 6.97 (5.75–8.19) 135 6.52 (5.46–7.59) 252 6.72 (5.74–7.86) 5.64 (4.96–6.33) vi pva< 6/12 in be* 274 16.33 (14.56–18.11) 305 14.74 (13.21–16.27) 579 15.46 (14.06–16.96) 12.77 (11.85–13.69) *pva, presenting visual acuity; be, better eye with available correction or with best correction or pinhole (bcva or pinva); svi, severe visual impairment; mvi, moderate visual impairment; vi, visual impairment; ci, confidence interval. table 3. age-wise prevalence of visual impairment and uncorrected refractive error among 40+ population in khordha and ganjam districts of odisha. age group (yr) prevalence of vi (pva < 6/12 in better eye) (%) prevalence of uncorrected refractive error (%) with 95% ci male prev (%) female prev (%) total prev (%) odds ratio p-value 40–49 11 2.4 20 2.8 31 2.7 1 0.000 3.1 (2.19–4.29) 50–59 44 10.0 37 6.7 81 8.2 3.28 (2.15–5.00) 0.000 7.7 (6.11–9.53) 60–69 83 18.9 106 20.8 189 19.9 9.06 (6.13–13.38) 0.000 14.4 (12.25–16.82) 70–79 82 31.5 99 41.2 181 36.2 20.38 (13.65–30.42) 0.000 14.2 (11.26–17.57) 80+ 54 60.0 43 68.3 97 63.4 62.75 (38.62–101.95) 0.000 15.0 (9.77–21.70) total 274 16.3 305 14.7 579 15.5 9.2 (8.25–10.13) *prev, prevalence; vi, visual impairment; ci, confidence interval; pva, presenting visual acuity journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 185 raab in india; bhardwaj et al figure 1. examination protocol of the raavi study in khordha and ganjam districts of odisha. figure 2. age-wise prevalence of visual impairment among 40+ population in khordha and ganjam districts of odisha. 186 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 raab in india; bhardwaj et al table 4. cataract surgical coverage and effective coverage among 40+ population in khordha and ganjam districts of odisha. csc (persons) male (%) female (%) total (%) pinva < 3/60 88.29 88.11 88.19 pinva < 6/60 84.30 79.88 81.72 pinva < 6/18 66.67 59.83 62.74 pinva < 6/12 49.08 46.04 47.40 ecsc 33.70 36.09 35.02 erec for distance 38.10 41.91 40.08 erec for near 40.01 32.83 35.65 *csc, cataract surgical coverage; pinva, pinhole visual acuity; ecsc, effective cataract surgical coverage; eerc, effective refractive error coverage table 5. multiple logistic regression analysis for finding determinants of visual impairment in khordha and ganjam districts of odisha. variable odds ratio 95% confidence interval z-value p-value age groups (yr) 40–49 1 50–59 3.07 2.00–4.69 5.16 <0.001 60–69 7.71 5.16–11.51 9.97 <0.001 70–79 16.48 10.86–25.03 13.15 <0.001 ≥80 51.19 30.61–85.60 15.00 <0.001 gender male 1 female 0.79 0.64–0.99 –1.98 0.048 locality rural 1 urban 1.26 1.02–1.57 2.18 0.03 education illiterate 1 up to 4𝑡ℎ 0.62 0.48–0.81 –3.53 <0.001 5𝑡ℎ–9𝑡ℎ pass 0.62 0.45–0.84 –3.09 0.002 >10𝑡ℎ pass 0.39 0.27–0.56 –5.04 <0.001 use of distance glasses no 1 yes 0.31 0.46–0.21 –5.84 <0.001 *raavi, rapid assessment of avoidable visual impairment; va, visual acuity; vi, visual impairment; co, corneal opacity. prevalence of ure among males was 9.5% (95% ci: 8.12–10.99) and among females was 8.9% (95% ci: 7.71–10.21); the difference was not significant (p = 0.538) [table 3]. the prevalence of vi in rural participants was 16%, which was higher than that of urban participants (14.6%). cataract was the single most important cause of blindness (72.2%) and vi (62.7%) in this region [figure 3]. a total of 536 cataract surgeries were reported among people from the study population. more journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 187 raab in india; bhardwaj et al figure 3. causes of blindness and visual impairment (pva < 6/12 in better eye) among 40+ population in khordha and ganjam districts of odisha. females reported surgery (288) as compared to males (248). the proportion of surgeries with an intraocular lens (iol) implant was 94.0%. out of the 377 persons (536 eyes) who underwent cataract surgery, 159 were bilaterally operated while 218 had undergone unilateral cataract surgery. it was observed that the majority of unilateral and bilateral cataract surgeries were performed in people aged 60 years and above. when visual outcomes were assessed in the operated eye, it was seen that 355 eyes (66.2%) had very good outcomes (≥6/12), 54 (10.1%) had good outcomes (<6/12 to 6/18), 57 (10.6%) had borderline outcomes (<6/18 to 6/60), and 70 (13.1%) had poor outcomes (<6/60). poor outcomes were caused by operative complications in 50 (71.4%) eyes, ocular comorbidity in 18 (25.7%), and re in 2 (2.9%) eyes. nearly half of the surgeries, that is, 253 (47.2%) were performed in the last five years. the visual outcomes were better among surgeries reported in the last five years as compared to surgeries performed before that, and the difference was statistically significant (p = 0.014). the csc (cataract surgical coverage) in two districts of odisha for 40+ population was 47.4% by 6/12 cutoff and 88.19% for pinhole vision <3/60. the ecsc was 35.1%, erec for distance was 40.0%, and erec for near was 35.7% for the same population [table 4]. out of the 536 cataract surgeries, 300 (55.9%) took place in non-governmental organizations (ngo)/private sector as compared to 236 (44.0%) in the public sector, and 287 (53.5%) of the surgeries were paid irrespective of the place of surgery. the usage of distance glasses was reported by only 518 (13.8%) study participants (males 265 [15.8%] and females 253 [12.2%]). similarly, near glasses were being used by only 666 (17.8%) participants (males 364 [21.7%] and females 302 [14.6%]). out of a total of 735 participants who received refraction services, 505 (68.7%) had their last refraction more than two years back. most refractions, that is, 557 (75.8%) took place in the ngo/private sector (males 74.7% and females 77.3%). the majority (89.7%) of participants reported having to pay for their glasses irrespective of place of refraction. barriers to not wearing glasses among those who were identified as having ure/presbyopia or uncorrected aphakia were assessed. the most common barriers were need not felt (57.5%), financial constraints (13.8%), uncomfortable glasses (8.2%), various local reasons like no one to accompany them, and other personal preoccupations (11.0%) in addition to lack of awareness (5.0%). multiple logistic regression was done to find determinants of vi in the study population. the odds of vi increased significantly in higher ages and were greater among the urban population (or 1.2; 95% ci 1.0–1.6). being educated (or 0.4; 95% ci 0.3–0.6) and use of glasses (or 0.3; 95% ci 0.5– 0.2) were protective. all these risk factors are wellestablished as associated with vi [table 5]. discussion the current study utilized the novel ravi methodology to determine the prevalence and causes of vi in two districts of odisha, india. according to the national blindness survey (nbs), the prevalence of blindness in the 50+ age population in india was 1.99% and cataract (66.2%) was the most important cause of blindness followed by corneal opacity (8.2%).[10] 188 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 raab in india; bhardwaj et al in the current study, the age-sex-adjusted prevalence of blindness was 1.14%; mvi was 4.84%, and vi was 12.77% among the 40+ age population in odisha. the nbs was conducted among the 50+ age population in one district of odisha (nayagarh) and the prevalence of blindness and mvi reported were 1.77% and 13.4%, respectively.[3, 10] although the prevalence figures in the current study are lower as compared to nbs, it might be due to the lower age group (40+) and other differences among the survey participants. despite this, the vi due to cataract and re needs to be managed promptly as the study clearly highlights poor coverage for cataract and re services in odisha. the study demonstrated that the risk of vi increased significantly with age, which is being corroborated by numerous studies done in both south and north india.[8, 11, 12] a previous study on blindness had reported that females were at 1.41 times higher risk of blindness in urban areas and 1.51 times in rural areas, compared to their male counterparts.[13] however, no significant difference was observed by gender in the current study. cataract is a major cause of vi and blindness in the current study. these findings are similar to the findings from south india.[14] cataract and res combined contributed to >90% of vi both of which are amenable to treatment as compared to the other causes. cataract surgery has been identified as surgical intervention that costs <$200 per disability-adjusted life years averted.[15] the csc of odisha for the 40+ age population was determined as 47.4%. in the nbs, a csc (persons) of 50.0% at a va cut-off of 6/18 was reported in nayagarh, odisha.[3] another raab study by sightsavers in the kalahandi district of odisha reported a csc of 45.5%.[16] in both studies, males had higher csc than females, similar to the findings of the current study. a study from rural northern india reported higher csc in females than males, with csc of 43.2% at 6/60 cut-off.[17] lower csc and thereby higher prevalence of cataract and vi was observed in rural areas in many countries.[18, 19] the ecsc determined in the current study was 35.02% and it was higher in females as compared to males. very few studies have reported ecsc from the indian subcontinent. a preliminary analysis (unpublished) of 47 population-based surveys from 11 countries revealed a significant range in ecsc between countries, from 2.8% to 88.5%.[4] data from repeated population-based surveys within four lmics revealed an average annual percentage point increase in ecsc of 1.1% (range = 0.8% 1.4%). in addition, gender inequities in ecsc have been reported: it is estimated that globally, women were 1.21 times more susceptible to having cataract vi as compared to men, and the mean level of inequality amongst women in ecsc is 4.6%.[20, 21] in order to know the exact number of people with vi due to re, uncorrected visual acuity needs to be measured, that is, without spectacles or contact lenses.[4] the current study employed this methodology, and the prevalence found was 9.2%. in the current study, the erec for distance was 40.1%, while for the near vision it was 35.6%. rates of erec for near is lower than 20% in sub-saharan africa, while the same figures in north america are reported to be higher than 90%.[22] the impact of res is manifold and includes loss of livelihood, schooling, and financial resources.[23] estimates of global economic burden of distant vi due to ure is huge (us$ 202 billion).[24] globally, nearly 800 million people suffer from distance vi (i.e., myopia and hypermetropia) or near vi (i.e., presbyopia) who need just a pair of spectacles, while another 100 million persons have moderate-to-severe distance vi or blindness that is amenable by cataract surgery.[25] the sustainability of programs for treatment of cataract and re need huge expenditure in terms of equipment, manpower, and spectacles. hence, sale of customized spectacles can also be explored as an alternative source of revenue by hospitals that want to scale-up their cataract surgical and refractive services, as envisioned by the vision 2020 right to sight initiative. the government of india launched the national program for control of blindness and visual impairment (npcb&vi) in 1976 and it currently has the provision of free services for cataract and other subspecialties; however, with the increase in the number of re, there is a need to introduce a provision of subsidized/free spectacles also into the program to alleviate some of the additional costs ensued.[26] generation of demand for services and addressing various barriers for accessing those services is necessary to scale-up the provision of cataract surgical and refractive error services to the population. the who has given targets for achieving universal eye health coverage (uhc) by 2030, that is, a 30% point increase in ecsc and 40% increase in erec from baseline.[4] this means that odisha journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 189 raab in india; bhardwaj et al needs to achieve an ecsc and erec of 65.0% and 80.1%, respectively, by 2030, from the baseline figures reported in the current study. this can be possible only if the management of vi is prioritized in odisha in a systematic way. shortage of trained human resources and resource constraints are always bottlenecks for such ambitious targets. the national program for control of blindness and visual impairment (npcbvi) can provide effective re and cataract surgical services free of cost or at subsidized rates, which can be incorporated in the health insurance packages available to the people. the current raavi study has a few limitations. first, it is not adequately powered to determine the prevalence of blindness. the sample size was deduced based on the prevalence of vi in previous studies and would only provide accurate estimation of the prevalence of vi. second, the findings of the study cannot be extrapolated to other districts of odisha, and separate surveys need to be conducted in each of the districts to accurately gauge the magnitude of the problem in the entire state. the burden of vi needs prompt attention in odisha, majority of which is caused by cataract and re. the findings suggest that the absolute number of people susceptible to avoidable blindness is enormous, and free or subsidized cataract and re services is the need of the hour. it is hoped that this baseline study from odisha will be instrumental in planning eye care services in the state in the future. some of the major recommendations from the current study include, graded scaling up of cataract and re services over the next decade to achieve uhc targets by 2030, reducing cost of services by incorporating services in insurance packages and prioritizing vulnerable individuals like the elderly, illiterate, and urban poor. raavi studies need to be conducted in all the districts of odisha, and districtspecific interventions need to be planned. ethical considerations the study protocol was reviewed and approved by institute ethics committee of all india institute of medical sciences, new delhi, india under the approval number iec-562/02.12.2016,rp/8/2016, op-10/06.03.2020. in addition, the protocol of the study complied with the guidelines for human studies and the world medical association declaration of helsinki. a participant information sheet (pis) in local language odia was given to each participant. in case of illiterate or visually impaired participants, the pis was read out to the participant. written consent was obtained from each participant before they were included in the study. in case of illiterate persons, left thumb impression was obtained. participants who were identified with treatable or curable conditions were provided referral services to the nearest secondary/tertiary eye hospital. acknowledgements dr. sabyasachi pattanayak from dhs odisha and lt. dr. mihir bal from ecos eye hospital, brahmapur. financial support and sponsorship financial support for this study was provided by cbm, india. consent for publication was taken according to the icmje recommendations for protection of research participants. conflicts of interest none. references 1. who. world report on vision. 2019. p. 180. 2. who. integrated people-centred eye care, including preventable vision impairment and blindness. who; 2020. p. 1–4. 3. vashist p, senjam s, gupta v, gupta n, rajshekhar v, shamanna br. national blindness & visual impairment survey india 2015–19. a summary report [internet]. new delhi; 2019. 4. who. proposed global targets for 2030 on integrated people-centred eye care. who; 2020. p. 1–19. 5. keel s, müller a, block s, bourne r, burton mj, chatterji s, et al. keeping an eye on eye care: monitoring progress towards effective coverage. lancet glob heal 2021;9:e1460–1464. 6. census. district census handbook khordha village and townwise primary census abstract. 2011. p. 1–381. 7. census. district census handbook ganjam village and town-wise primary census abstract. 2011. p. 1–615. 8. marmamula s, khanna rc, kunkunu e, rao gn. population-based assessment of prevalence and causes of visual impairment in the state of telangana, india: a cross-sectional study using the rapid assessment of visual impairment (ravi) methodology. bmj open 2016;6:1–7. 9. who. change the definition of blindness. who. 10. vashist p, senjam ss, gupta v, gupta n, shamanna br, wadhwani m, et al. blindness and visual impairment and their causes in india: results of a nationally representative survey. plos one 2022;17:e0271736. 190 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 raab in india; bhardwaj et al 11. marmamula s, madala sr, rao gn. rapid assessment of visual impairment (ravi) in marine fishing communities in south india–study protocol and main findings. bmc ophthalmol 2011;11:26. 12. gupta n, vashist p, malhotra s, senjam ss, amit bhardwaj vm. rapid assessment of visual impairment in urban population of delhi, india. plos one 2015;10:1–11. 13. murthy gvs. trends in gender and blindness in india. community eye heal j 2016;29:4–5. 14. marmamula s, narsaiah s, shekhar k, khanna rc, rao gn. visual impairment in the south indian state of andhra pradesh: andhra pradesh rapid assessment of visual impairment (ap-ravi) project. plos one 2013;8. 15. horton s, gelband h, jamison d, levin c, nugent r, watkins d. ranking 93 health interventions for lowand middle-income countries by cost-effectiveness. plos one 2017;12:1–12. 16. jolley e, buttan s, engels t, gillani m, jadoon mz, kabona g, et al. prevalence of visual impairment and coverage of cataract surgical services: associations with sex, disability, and economic status in five diverse sites. ophthalmic epidemiol 2020;27:429–437. 17. sobti s, sahni b, bala k. surgical coverage of cataract in a rural area of north india: a cross�sectional study. j fam med prim care 2020;9:4112–4117. 18. khanna r, murthy gv. inequities in cataract surgical coverage in south asia. community eye heal j 2016;29:6–9. 19. vijaya l, george r, rashima a, raju p, arvind h, baskaran m, et al. outcomes of cataract surgery in a rural and urban south indian population. indian j ophthalmol 2010;58:223–228. 20. bourne rra, steinmetz jd, saylan m, mersha am, weldemariam ah, wondmeneh tg, et al. causes of blindness and vision impairment in 2020 and trends over 30 years, and prevalence of avoidable blindness in relation to vision 2020: the right to sight: an analysis for the global burden of disease study. lancet glob heal 2021;9:e144–e160. 21. ramke j, gilbert ce, lee ac, ackland p, limburg h, foster a. effective cataract surgical coverage: an indicator for measuring quality-of-care in the context of universal health coverage. plos one 2017;12:1–13. 22. fricke tr, tahhan n, resnikoff s, papas e, burnett a, ho sm, et al. global prevalence of presbyopia and vision impairment from uncorrected presbyopia: systematic review, meta-analysis, and modelling. ophthalmology 2018;125:1492–1499. 23. wu m. rapid assessment of avoidable blindness in kunming, china. commun eye heal 2007;20:10. 24. fricke tr, holden ba, wilson da, schlenther g, naidoo ks, resnikoff s, et al. global cost of correcting vision impairment from uncorrected refractive error. bull world health organ 2012;90:728–738. 25. bourne rra, flaxman sr, braithwaite t, cicinelli mv, das a, jonas jb, et al. magnitude, temporal trends, and projections of the global prevalence of blindness and distance and near vision impairment: a systematic review and meta-analysis. lancet glob heal 2017;5:e888–e897. 26. mohfw. national programme for control of blindness | national health portal of india. available from: https://www.nhp.gov.in/national-programme-for-control-ofblindness_pg. journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 191 original article accuracy of iol power calculation formulas for acrysof sn60wf versus tecnis zcb00 intraocular lenses cynthia c jiang, md; noah m hodson, md; daniel a johnson, md, mba; ahmad kheirkhah, md department of ophthalmology, university of texas health san antonio, san antonio, texas, usa orcid: cynthia c jiang: https://orcid.org/0000-0002-9371-0006 ahmad kheirkhah: https://orcid.org/0000-0003-4217-3367 abstract purpose: to compare the accuracy of various intraocular lens power formulas for two monofocal hydrophobic foldable lenses, the acrysof sn60wf and the tecnis zcb00. methods: this retrospective study included 409 eyes from 409 patients who underwent uncomplicated cataract surgery (299 eyes with sn60wf and 110 eyes with zcb00). biometry was performed for all eyes with an iolmaster 700. predicted refraction from five different iol power formulas (barrett universal ii, haigis, hoffer-q, holladay 2, and srk/t) was compared to postoperative refraction at one to three months for the following axial length strata: short eyes (<22.5 mm), medium eyes (22.5–25.5 mm), and long eyes (>25.5 mm). results: in patients with medium eyes, there were no significant differences in the mean absolute error (mae) and the percentage of eyes within ±0.5 d (%±0.5 d) between both iols. in short eyes, although mae was similar between both lenses, %±0.5 d was significantly higher for barrett universal ii in zcb00 than in sn60wf (p = 0.01) while hoffer-q and holladay 2 performed equally for both lenses. in long eyes, zcb00 had a higher mae than sn60wf for barrett universal ii, haigis, and hoffer-q. additionally, in long eyes, the percentage of eyes within %±0.5 d was significantly higher for sn60wf than zcb00 for all formulas (p < 0.001). conclusion: although there were no significant differences in the formula accuracy between these two lenses in medium eyes for all formulas and in short eyes for most formulas, the accuracy decreased significantly in long eyes for zcb00 compared to sn60wf. the effect of iol model on the postoperative outcomes should be further investigated. keywords: formula accuracy; intraocular lens; sn60wf; zcb00 j ophthalmic vis res 2022; 17 (3): 344–352 correspondence to: ahmad kheirkhah, md. medical arts and research center, 8300 floyd curl dr., san antonio, tx 78229, usa. e-mail: kheirkhah@uthscsa.edu received: 29-01-2021 accepted: 17-01-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i3.11571 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: jiang cc, hodson nm, johnson da, kheirkhah a. accuracy of iol power calculation formulas for acrysof sn60wf versus tecnis zcb00 intraocular lenses. j ophthalmic vis res 2022;17:344–352. 344 © 2022 jiang et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i3.11571&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr iol formula accuracy for sn60wf vs zcb00; jiang et al introduction cataract surgery is now considered a form of refractive surgery. there is an increasing demand by patients to have optimal uncorrected distance visual acuity postoperatively. in fact, it has been shown that such vision is an important determinant of patient’s satisfaction after cataract surgery.[1] to achieve this goal, it is critical to have a postoperative refraction which is as close as possible to the target refraction. this is largely dependent on choosing an intraocular lens (iol) with the most accurate power.[2, 3] to obtain such iol power, precise biometry as well as an accurate formula for iol power calculation are required. however, there still remains the question of which formula provides the most consistent and accurate refractive outcome for each individual eye. many formulas have been developed to calculate the iol power.[4–7]each of these formulas takes into consideration certain variables of the eye, such as corneal power, axial length, anterior chamber depth, or effective lens position, in order to predict the power of the lens.[8, 9] the parameters utilized in these equations vary by each formula which is why accuracy of these formulas varies widely.[10–13] furthermore, it has been shown that physical and biometric characteristics of the eye can affect the accuracy of different iol power formulas to different degrees.[14, 15] for example, there have been several studies that have investigated the effects of abnormal values of different parameters, such as long and short eyes, on the accuracy of iol power calculations.[16−−20] although many studies have evaluated the effects of ocular characteristics on the accuracy of iol power, the possible effects of the type of iol on this accuracy remains unknown. this is critical as different iols have different physical characteristics.[21, 22] multiple previous studies relied on a single type of iol,[19, 23–25] or grouped multiple iols into a single dataset.[14, 18, 26, 27] in addition, it remains unclear whether some formulas play better for some lenses than for others. to evaluate the possible effects of the iol type on the accuracy of iol power formulas, in this study we compared this accuracy for two different models of iol. for this, we used two aspheric monofocal hydrophobic acrylic lenses, the acrysof sn60wf (alcon laboratories, inc., fort worth, tx, usa), and the tecnis zcb00 (johnson & johnson vision, santa ana, ca, usa), both of which are commonly used in cataract surgery. methods this retrospective study included 409 eyes from 409 patients who had cataract surgery with implantation of either acrysof sn60wf or tecnis zcb00. the study was performed at ut health san antonio, san antonio, texas, usa. the study protocol was approved by the institutional review board, and the study was compliant with tenets of the health insurance portability and accountability act (hipaa) of 1996. inclusion criteria consisted of adult patients who had undergone uncomplicated cataract surgery. in patients with bilateral cataract surgery, only data from the eye with the earliest surgery were used. we included only eyes with available data on electronic medical records regarding the preoperative iol power calculation for all formulas studied and postoperative manifest refraction at one to three months after surgery. we excluded eyes with corneal or anterior segment disease or trauma. we also excluded patients with previous corneaor lens-based refractive surgery. for each patient, demographics, ocular biometric values, the power of the iol used in surgery, and the one-to-three-month postoperative manifest refraction were collected from electronic medical records. all patients had biometry performed with an iolmaster 700 (carl zeiss meditec ag). the following biometric values were collected: axial length, lens thickness, anterior chamber depth, white-to-white diameter, and keratometry. furthermore, we gathered the iol power measured by five different iol power formulas. the formulas and optimized iol constants for sn60wf and zcb00, respectively, assessed in this study were barrett universal ii (lens factor = 1.88 and 2.09), haigis (a0 = –0.769 and –1.302; a1 = +0.234 and +0.210; a2 = +0.217 and +0.251), hoffer-q (pacd = 5.64 and 5.80), holladay 2 (acd constant = 5.601 and 5.786), and srk/t (a = 119.00 and 119.30). to evaluate the accuracy of each formula, we calculated the mean numerical error (mne) and the mean absolute error (mae). the mne was defined as the average of actual postoperative refraction minus the predicted refraction by the iol power formula used for the eye (actual journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 345 iol formula accuracy for sn60wf vs zcb00; jiang et al refraction – predicted refraction).[28] the mae was defined as the average of the absolute values of actual postoperative refraction minus the predicted refraction for each formula. moreover, we also determined the percentage of eyes within 0.25 d (%±0.25 d), 0.5 d (%±0.5 d), 1.0 d (%±1.0 d), and 2.0 d (%±2.0 d) of the predicted refraction for each formula. we further stratified the eyes into subgroups based on the axial length. these subgroup strata were as follows: short eyes (<22.5 mm), medium eyes (22.5-25.5 mm), and long eyes (>25.5 mm). then, the aforementioned accuracy parameters were evaluated in each subgroup of axial length. no adjustment was performed for eyes with long axial length. statistical analysis statistical analysis was performed using spss (ibm, version 25). shapiro–wilk test was first conducted to evaluate the normality of data distribution. different qualitative and quantitative parameters were compared between sn60wf and zcb00 groups using chi-square and mann–whitney tests, respectively. friedman test followed by post hoc bonferroni test was performed to compare the mne and the mae among different formulas for each lens. percentage of eyes within a specific dioptric range postoperatively was compared between the two lenses using chi-square and among different formulas for each lens using cochran’s q test. results this study included 409 eyes from 409 patients (253 women and 156 men) with a mean age of 70.6 ± 8.6 years (range, 41–91 years). there were 299 eyes with sn60wf and 110 eyes with zcb00. there were no significant differences between the two groups regarding demographics or ocular biometric values [table 1]. however, postoperative refraction was significantly different between the two lenses (–0.17 ± 0.55 d for sn60wf vs –0.01 ± 0.51 d for zcb00, p = 0.02). table 2 demonstrates the mae and the mne for each formula for both sn60wf and zcb00 lenses. for the mae, there were no significant differences between both iols for any formula. although there were no significant differences in the mae among various formulas for sn60wf, such difference reached statistical significance for zcb00, with srk/t having the highest mae and barrett universal ii and holladay 2 showing the lowest mae (p < 0.01). for the mne, there were no significant differences between both iols for all formulas except for hoffer-q in which the mne was significantly lower for sn60wf compared to zcb00 (p = 0.04). for sn60wf, there were significant differences in mne among various formulas with barrett universal ii and holladay 2 having the highest and lowest mne, respectively (p < 0.01). for zcb00, the difference in the mne among various formulas was statistically significant and the highest and lowest mne was seen in srk/t and holladay 2 formulas, respectively (p < 0.01). table 3 shows the percentage of eyes within ±0.25 d, ±0.5 d, ±1.0 d, and ±2.0 d of the predicted refraction for various formulas for both lenses. there were no statistically significant differences between the sn60wf and zcb00 lenses for percentage of eyes within ±0.25 d, ±0.5 d, ±1.0 d, or ±2.0 d of the predicted refraction (all p-values > 0.05). for both sn60wf and zcb00, there were statistically significant differences in the percentage of eyes within ±0.25 d, ±0.5 d, and ±1.0 d, but not ±2.0 d, among various formulas. for %±0.5 d, the highest percentage was seen by barrett universal ii for sn60wf (p < 0.001) and by barrett universal ii and holladay 2 for zcb00 (p = 0.02). effects of the axial length on the formula accuracy the mae and percentage of eyes within ±0.5 d for each formula across different axial lengths for both iols have been shown in tables 4 and 5, respectively. sn60wf lenses in short and medium eyes, the mae was similar among various formulas. in long eyes, however, the mae was significantly different among various formulas (p < 0.001), with barrett universal ii having the lowest and hoffer-q having the highest values. regarding %±0.5 d, there were significant differences among formulas across all axial lengths. the highest percentage of eyes ±0.5 d from the predicted refraction was seen with hoffer-q in short eyes and by barrett universal ii in medium and long eyes. on the other hand, 346 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 iol formula accuracy for sn60wf vs zcb00; jiang et al table 1. patient demographics and ocular biometric values for eyes with sn60wf and zcb00 lenses. sn60wf (n = 299) zcb00 (n = 110) p-value age (yr) 70.71 ± 8.60 70.41 ± 8.63 0.57 sex (f/m) 178/121 75/35 0.14 iol power used in surgery (d) 20.31 ± 3.21 20.59 ± 3.32 0.46 axial length (mm) 23.85 ± 1.11 23.90 ± 1.07 0.74 lens thickness (mm) 4.61 ± 0.41 4.57 ± 0.41 0.38 anterior chamber depth (acd) 3.12 ± 0.39 3.17 ± 0.34 0.25 white-to-white diameter (mm) 11.97 ± 0.44 12.00 ± 0.51 0.35 mean keratometry (d) 43.88 ± 1.58 43.76 ± 1.69 0.48 postoperative refraction (d) –0.17 ± 0.55 –0.01 ± 0.51 0.02 table 2. mean absolute error (mae) and mean numerical error (mne) for each formula for both sn60wf and zcb00 lenses. formula mean absolute error (mae) mean numerical error (mne) sn60wf zcb00 p-value sn60wf zcb00 p-value barrett universal ii 0.41 ± 0.37 0.42 ± 0.37 0.94 0.21 ± 0.52 0.28 ± 0.48 0.21 haigis 0.42 ± 0.38 0.46 ± 0.38 0.24 0.14 ± 0.55 0.20 ± 0.56 0.30 hoffer-q 0.44 ± 0.38 0.48 ± 0.39 0.43 0.15 ± 0.56 0.29 ± 0.55 0.04 holladay 2 0.42 ± 0.36 0.41 ± 0.36 0.69 0.09 ± 0.54 0.18 ± 0.51 0.23 srk/t 0.49 ± 0.36 0.49 ± 0.66 0.66 0.15 ± 0.54 0.31 ± 0.76 0.07 ∗p-value 0.27 0.002 <0.001 <0.001 ∗this p-value is for comparison of different formulas in each lens. the lowest %±0.5 d value was seen by barrett universal ii and haigis in short eyes, by hoffer-q in medium eyes, and by hoffer-q and holladay 2 in long eyes. zcb00 lenses in short eyes, the mae was similar among various formulas. in medium and long eyes, however, the mae was significantly different among various formulas (p < 0.05). the lowest and highest values of mae were obtained by holladay 2 and srk/t, respectively, in medium eyes, and by barrett universal ii and hoffer-q, respectively, in long eyes. although there were no significant differences in the percentage of eyes within ±0.5 d in short and long eyes, this value was significantly lower in long eyes compared with short and medium eyes for all formulas (all p-values < 0.05). in medium eyes, there were significant differences in %±0.5 d among various formulas, with holladay 2 having the highest and haigis having the lowest values. for all formulas, the %±0.5 d was significantly different among short–medium–long eyes (all p < 0.05). sn60wf versus zcb00 lenses in short and medium eyes, the mae was similar between sn60wf and zcb00. however, in long eyes, the mae was significantly higher in zcb00 compared with sn60wf for barrett universal ii (p = 0.04), haigis (p = 0.03), and hoffer-q (p = 0.04). in medium eyes, the %±0.5 d for zcb00 and sn60wf was similar. however, in short eyes, although there were no statistically significant differences in %±0.5 d between both lenses for haigis, hoffer-q, and holliday 2, zcb00 had a journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 347 iol formula accuracy for sn60wf vs zcb00; jiang et al table 3. percentage of eyes within ±0.25 d, ±0.5 d, ±1.0 d, and ±2.0 d of the predicted refraction for both sn60wf and zcb00 lenses. formula sn60wf zcb00 ±0.25 d ±0.5 d ±1.0 d ±2.0 d ±0.25 d ±0.5 d ±1.0 d ±2.0 d barrett universal ii 40.8% 70.6% 93.0% 99.7% 40.9% 68.2% 91.8% 100.0% haigis 41.5% 66.9% 91.6% 99.3% 39.1% 64.6% 89.1% 100.0% hoffer-q 35.8% 65.9% 93.0% 99.7% 33.6% 66.4% 86.4% 99.1% holladay 2 40.5% 66.6% 92.6% 99.7% 43.6% 68.2% 92.7% 100.0% srk/t 38.5% 67.6% 93.0% 99.7% 37.3% 66.4% 90.9% 98.2% ∗p-value <0.001 <0.001 0.01 0.41 <0.001 0.02 0.001 0.17 *this p-value is for comparison of different formulas in each group. table 4. mean absolute error (mae) for sn60wf and zcb00 lenses in short, medium, and long eyes. formula short eyes (al: <22.5 mm) medium eyes (al: 22.5–25.5 mm) long eyes (al: >25.5 mm) sn60wf zcb00 p-value sn60wf zcb00 p-value sn60wf zcb00 p-value barrett universal ii 0.37 ± 0.26 0.34 ± 0.36 0.78 0.43 ± 0.38 0.40 ± 0.35 0.62 0.35 ± 0.34 0.69 ± 0.50 0.04 haigis 0.36 ± 0.28 0.53 ± 0.41 0.11 0.44 ± 0.40 0.43 ± 0.35 0.93 0.36 ± 0.37 0.78 ± 0.57 0.03 hoffer-q 0.30 ± 0.24 0.33 ± 0.34 0.75 0.45 ± 0.38 0.45 ± 0.36 0.87 0.53 ± 0.40 0.95 ± 0.64 0.04 holladay 2 0.30 ± 0.23 0.37 ± 0.38 0.67 0.43 ± 0.38 0.38 ± 0.33 0.31 0.45 ± 0.34 0.77 ± 0.58 0.08 srk/t 0.36 ± 0.28 0.55 ± 0.51 0.36 0.44 ± 0.37 0.48 ± 0.68 0.48 0.41 ± 0.31 0.70 ± 0.52 0.21 p-value* 0.48 0.13 0.3 0.005 <0.001 0.04 ∗this p-value is for comparison of different formulas in each axial length group. higher %±0.5 d for barrett universal ii (p = 0.01) while sn60wf had a higher %±0.5 d for srk/t (p = 0.01). in long eyes, sn60wf had a higher %±0.5 d than zcb00 for all formulas (p < 0.001 for all formulas). discussion in this study, we evaluated the accuracy of five iol power formulas for two aspheric monofocal hydrophobic acrylic foldable iols, the acrysof sn60wf, and tecnis zcb00. we found that the accuracy of the iol power formulas for these two lenses varied based on the eye’s axial length. although there were no significant differences in the accuracy between these two lenses in medium eyes, the accuracy decreased in short and especially long eyes where postoperative refractive predictability was different for the sn60wf and the zcb00. furthermore, relative accuracy of each formula compared to others was also dependent on the axial length and iol type. although the accuracy of iol power calculation formulas and the role of ocular parameters in such accuracy have been well studied, there are limited data on the effects of iol model on the accuracy. melles et al[28] compared two lenses from the same manufacturer, acrysof sn60wf to sa60at (alcon), and found similar rankings of seven iol formulas (barrett universal ii, haigis, holladay 1, holladay 2, hoffer-q, olsen, and srk/t, and hoffer-q) between these two lenses. in our study, however, we compared the iol power formula accuracy between two aspheric monofocal acrylic hydrophobic lenses from two different manufacturers as it has been shown that they have different physical characteristics and visual performance.[29, 34–36] for evaluation of the accuracy of iol power formulas in this study we used the mae, the 348 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 iol formula accuracy for sn60wf vs zcb00; jiang et al table 5. percentage of eyes within ±0.5 d of the predicted refraction for sn60wf and zcb00 lenses for short, medium, and long eyes. formula short eyes (al: <22.5 mm) medium eyes (al: 22.5–25.5 mm) long eyes (al: >25.5 mm) sn60wf zcb00 p-value sn60wf zcb00 p-value sn60wf zcb00 p-value barrett universal ii 70.0% 85.7% 0.001 69.6% 68.8% 0.87 81.8% 42.9% <0.001 haigis 70.0% 57.1% 0.05 65.6% 66.7% 0.88 77.3% 42.9% <0.001 hoffer-q 83.3% 85.7% 0.55 64.4% 67.7% 0.55 59.1% 28.6% <0.001 holladay 2 76.7% 71.4% 0.33 66.0% 70.8% 0.44 59.1% 28.6% <0.001 srk/t 73.3% 57.1% 0.01 66.4% 68.8% 0.65 72.7% 42.9% <0.001 p-value* 0.02 0.16 <0.001 0.04 0.004 0.41 ∗this p-value is for comparison of different formulas for each lens in each al group. mne, and the percentage of eye within ±0.5 d of the predicted refraction, as reported before.[37] gale et al[30] established the benchmark standards for refractive outcomes as percentage of eyes within ±1.0 d of the predicted refraction >85% and percentage of eyes within ±0.5 d of the predicted refraction >55%. our data indicates this benchmark was met for all formulas for all ranges of axial length in sn60wf lenses. for zcb00 lenses, however, this benchmark was met for all formulas only for short and medium eyes, but not for any formula in long eyes, showing the effects of iol model on the accuracy of iol power formulas. although the difference in the accuracy of iol power formulas between the two lenses was less evident when all axial lengths were taken together, the difference was more prominent when evaluating eyes with different axial lengths separately. in medium eyes with an axial length of 22.5–25.5 mm, the mae and the percentage of eyes within ±0.5 d were similar between sn60wf and zcb00 for any formula. in short eyes (<22.5 mm), however, although there was no significant difference between the lenses in the mae, the percentage of eyes within ±0.5 d was different between the two lenses for some formulas such as barrett universal ii in which this formula performed better for zcb00 than for the sn60wf. the difference between the two iols was most remarkable in long eyes with an axial length >25.5 mm. in these eyes, the mae was significantly higher for zcb00 compared with sn60wf for most of the formulas evaluated showing a potential error in iol power calculation in this iol model. in addition, the percentage of eyes within ±0.5 d was significantly higher for sn60wf compared with zcb00 for all formulas. although the reasons for such performance of iol power formulas for zcb00 lenses in long eyes remain to be determined, adjustment of iol power formulas may be considered for such situations. it is well known that iol power formulas have different accuracies for eyes with different axial lengths.[14,27] for all axial lengths combined, some studies have indicated that barrett universal ii has a significantly lower mae and highest percentage within ±0.25 d, ±0.5 d, or ±1.0 d of the target refraction than haigis, hoffer-q, holladay 1, holladay 2, srk/t, and t2 for sn60wf,[24] and a lower mae and highest percentage within ±0.25 d, ±0.75 d, or ±1.0 d of the target refraction than holladay 2, hoffer-q, and srk/t for zcb00.[32] however, our findings showed that formula performance is also dependent on the iol type. in fact, such accuracy can affect our choice of iol implant for each individual eye. in medium eyes in our study, for sn60wf there was no significant difference in the mae between formulas, but barrett universal ii had the highest percentage (69.6%) of eyes within ±0.5 d of the predicted refraction. for zcb00 lenses, in contrast, holladay 2 formula was associated with the lowest mae and the highest percentage (70.8%) of eyes within ±0.5 d. aristodemou et al[31] found similar accuracy for eyes implanted with either li61ao sofport or akreos fit (bausch & lomb, rochester, ny) with axial length between 22.50 and <25.00 mm when comparing the mae between hoffer-q, holladay 1, and srk/t. narváez et al[33] similarly did not find a difference between formulas (hoffer-q, journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 349 iol formula accuracy for sn60wf vs zcb00; jiang et al holladay 1, holladay 2, and srk/t) in average (22.0 to <24.5 mm) and medium-long (24.5 to <26.0 mm) eyes implanted with either cc4204bf collamer plate-haptic iol or aa4203vf silicone plate-haptic iol (staar surgical, monrovia, ca). notably, neither of those studies included barrett universal ii or compared sn60wf and zcb00 lenses. tang et al[40] found no significant difference in accuracy for short (<22.0 mm), medium (22.0–25.0 mm), or long (>25.0 mm) eyes implanted with sn60wf between holladay 2, barrett universal ii, and hillrbf formulas. kane et al[24] found statistically significant differences in the mae among seven different formulas for their established ranges of medium (22.0 to <24.5 mm) and medium-long (24.5 to <26.0 mm) eyes implanted with sn60wf. for both groups, barrett universal ii had the lowest mae, and srk/t performed better than both haigis and hoffer-q formulas for medium eyes but not medium-long eyes.[24] barrett universal ii additionally had a significantly higher percentage within ±0.25 d, ±0.5 d, ±1.0 d, or ±2.0 d for medium eyes.[24] as previous studies have used only one iol model or considered all iol models together, no comparison can be made with our findings. for short eyes with axial length of <22.5 mm, we did not find any significant difference in the mae and the percentage within ±0.5 d between the five formulas for zcb00 lenses. for sn60wf lenses, although there was no significant difference in the mae for different formulas, the percentage within ±0.5 d was significantly higher in hoffer-q (83.3%). previously, it has been shown that neither hoffer-q, holladay 2, nor srk/t consistently outperformed one another in eyes implanted with acrysof sn60wf or sa60at (alcon laboratories, inc., fort worth, tx) or li61ao sofport or akreos fit (bausch & lomb, rochester, ny) with an axial length <22.0 mm.[28, 31] in comparing the accuracy of barrett universal ii, haigis, hoffer-q, holladay 1, holladay 2, srk/t, and t2 formulas, kane et al[24] did not find any significant difference in formulas with an axial length <22.0 mm in eyes implanted with sn60wf. a 2017 meta-analysis investigating the accuracy of six iol power formulas (haigis, hofferq, holladay 1, holladay 2, srk/t and srk ii) in short eyes (axial length <22.0 mm) demonstrated that although holladay 2 offered the smallest mae (not statistically significant), haigis may be superior to hoffer-q (p = 0.003), srk/t (p = 0.009), and srk/t ii (p = 0.01) for short eyes.[38] the iols used in this meta-analysis included sa60at, ma60 (alcon laboratories, inc., fort worth, tx), li61a0 sofport/akreos fit, amo sensar ar40e and tecnis za9003 (johnson & johnson vision, santa ana, ca), acr6d (laboratoires cornéal, paris, france), hoya py-60ad (hoya corporation, japan), and sn60wf.[38] for long eyes with an axial length of >25.5 mm, we noted that barrett universal ii formula had the lowest mae compared with other four formulas for both zcb00 and sn60wf lenses. barrett formula also had the highest percentage (81.8%) of eyes within ±0.5 d of the predicted refraction for sn60wf lenses. although there were no significant differences between the percentage of eyes within ±0.5 d among the five formulas for zcb00 lenses in long eye, the values were significantly less compared with short and medium eyes. a 2018 systematic review and meta-analysis investigating the accuracy of six iol power formulas (barrett universal ii, haigis, hoffer-q, holladay 1, holladay 2, and srk/t) for long eyes with an axial length of >24.5 mm found that barrett universal ii not only had a significantly lower mae than holladay 1, holladay 2, hofferq, and srk/t (all p < 0.001), but had significantly higher percentage of eyes within ±0.5 d of the predicted refraction than all formula.[39] iols used in this study included li61a0 sofport/akreos fit, sn60wf, sa60at, py-60ad, ar40e, and sn60at and ma60ac/bm/ma.[39] kane et al[24] also found barrett universal ii to be the most accurate for eyes with an axial length ≥26.00 mm for sn60wf. kane et al[24] found long eyes implanted with sn60wf to have formulas with much lower percentage of eyes within target refraction compared to medium or medium-long axial lengths; however, from our study this was only true for zcb00. in our study, postoperative refractive predictability was significantly better for the sn60wf than the zcb00 in long eyes with a higher percentage within ±0.5 d for all formulas: for example, 81.8% versus 42.9%, respectively, for barrett universal ii formula. although sn60wf and zcb00 lenses are commonly used during cataract surgery, a potential limitation to our study is that we did not evaluate other models of iols, including those with other materials such as hydrophilic acrylic or silicone iols. furthermore, eyes with previous surgeries, including keratorefractive surgery, were excluded from our study. the differential effects of these surgeries on the accuracy of iol power formulas 350 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 iol formula accuracy for sn60wf vs zcb00; jiang et al for various lenses remain to be determined. newer iol power formulas, such as kane, olson, and hillradial basis function (rbf), may also have different accuracies compared to the formulas evaluated in our study for different iol models. moreover, although many different methods of adjustments have been suggested for the long eyes, such as axial length adjustment,[41] we did not apply any of these adjustments in this study as it is unknown whether such adjustments are dependent on the iol model. in summary, our study showed that the accuracy of iol power formula can be different for acrysof sn60wf or tecnis zcb00. as such, difference may be true for other iol models, studies on the iol formula accuracy should report the results for each iol model separately and should avoid combining different iol models into one group. different adjustments may be required for various iol types in different axial lengths. although significant differences in lens performance were not seen in medium eyes, cataract surgery in short or particularly long eyes should prompt deliberation in choice of iol. financial support and sponsorship none. conflicts of interest none declared. references 1. davis g. the evolution of cataract surgery. mo med 2016;113:58–62. 2. hahn u, krummenauer f, kölbl b, neuhann t, schayanaraghi k, schmickler s, et al. determination of valid benchmarks for outcome indicators in cataract surgery: a multicenter, prospective cohort trial. ophthalmology 2011;118:2105–2112. 3. lee es, lee sy, jeong sy, moon ys, chin hs, cho sj, et al. effect of postoperative refractive error on visual acuity and patient satisfaction after implantation of the array multifocal intraocular lens. j cataract refract surg 2005;31:1960–1965. 4. hoffer kj. the hoffer q formula: a comparison of theoretic and regression formulas. j cataract refract surg 1993;19:700–712. 5. retzlaff ja, sanders dr, kraff mc. development of the srk/t intraocular lens implant power calculation formula. j cataract refract surg 1990;16:333–340. 6. haigis w, lege b, miller n, schneider b. comparison of immersion ultrasound biometry and partial coherence interferometry for intraocular lens calculation according to haigis. graefes arch clin exp ophthalmol 2000;238:765– 773. 7. barrett gd. an improved universal theoretical formula for intraocular lens power prediction. j cataract refract surg 1993;19:713–720. 8. hoffer kj. clinical results using the holladay 2 intraocular lens power formula. j cataract refract surg 2000;26:1233–1237. 9. miraftab m, hashemi h, fotouhi a, khabazkhoob m, rezvan f, asgari s. effect of anterior chamber depth on the choice of intraocular lens calculation formula in patients with normal axial length. middle eastern afr j ophthalmol 2014;21:307–311. 10. lee ac, qazi ma, pepose js. biometry and intraocular lens power calculation. curr opin ophthalmol 2008;19:13–17. 11. olsen t. prediction of the effective postoperative (intraocular lens) anterior chamber depth. j cataract refract surg 2006;32:419–424. 12. maclaren re, natkunarajah m, riaz y, bourne rra, restori m, allan bds. biometry and formula accuracy with intraocular lenses used for cataract surgery in extreme hyperopia. am j ophthalmol 2007;143:920–931. 13. zhou d, sun z, deng g. accuracy of the refractive prediction determined by intraocular lens power calculation formulas in high myopia. indian j ophthalmol 2019;67:484–489. 14. zhang y, liang xy, liu s, lee jw, bhaskar s, lam ds. accuracy of intraocular lens power calculation formulas for highly myopic eyes. j ophthalmol 2016;2016:1917268. 15. liao x, peng y, liu b, tan qq, lan cj. agreement of ocular biometric measurements in young healthy eyes between iolmaster 700 and oa-2000. sci rep 2020;10:3134. 16. hoffer kj, savini g. iol power calculation in short and long eyes. asia pac j ophthalmol 2017;6:330–331. 17. moschos mm, chatziralli ip, koutsandrea c. intraocular lens power calculation in eyes with short axial length. indian j ophthalmol 2014;62:692–694. 18. abulafia a, barrett gd, rotenberg m, kleinmann g, levy a, reitblat o, et al. intraocular lens power calculation for eyes with an axial length greater than 26.0 mm: comparison of formulas and methods. j cataract refract surg 2015;41:548–556. 19. kane jx, van heerden a, atik a, petsoglou c. accuracy of 3 new methods for intraocular lens power selection. j cataract refract surg 2017;43:333–339. 20. olsen t, thim k, corydon l. accuracy of the newer generation intraocular lens power calculation formulas in long and short eyes. j cataract refract surg 1991;17:187– 193. 21. lee bs, chang df. comparison of the rotational stability of two toric intraocular lenses in 1273 consecutive eyes. ophthalmology 2018;125:1325–1331. 22. sakai h, shimizu k. physical characteristics of various intraocular lenses. j cataract refract surg 1987;13:151– 156. 23. roberts tv, hodge c, sutton g, lawless m, contributors to the vision eye institute iol outcomes registry. comparison of hill-radial basis function, barrett universal and current journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 351 iol formula accuracy for sn60wf vs zcb00; jiang et al third generation formulas for the calculation of intraocular lens power during cataract surgery. clin exp ophthalmol 2018;46:240–246. 24. kane jx, van heerden a, atik a, petsoglou c. intraocular lens power formula accuracy: comparison of 7 formulas. j cataract refract surg 2016;42:1490–1500. 25. cooke dl, cooke tl. comparison of 9 intraocular lens power calculation formulas. j cataract refract surg 2016;42:1157–1164. 26. reitblat o, levy a, kleinmann g, kleinmann g, lerman tt, assia ei. intraocular lens power calculation for eyes with high and low average keratometry readings: comparison between various formulas. j cataract refract surg 2017;43:1149–1156. 27. gökce se, zeiter jh, weikert mp, koch dd, hill w, wang l. intraocular lens power calculations in short eyes using 7 formulas. j cataract refract surg 2017;43:892–897. 28. melles rb, holladay jt, chang wj. accuracy of intraocular lens calculation formulas. ophthalmology 2018;125:169– 178. 29. salvatore s, lupo s, nebbioso m, huang yh, vingolo em. new insight into visual function with aspherical intraocular lenses (iols): tecnis zcb00 and acrysof sn60wf. int ophthalmol 2011;31:417–419. 30. gale rp, saldana m, johnston rl, zuberbuhler b, mckibbin m. benchmark standards for refractive outcomes after nhs cataract surgery. eye 2009;23:149–152. 31. aristodemou p, knox cartwright ne, sparrow jm, johnston rl. formula choice: hoffer q, holladay 1, or srk/t and refractive outcomes in 8108 eyes after cataract surgery with biometry by partial coherence interferometry. j cataract refract surg 2011;37:63–71. 32. kim sy, lee sh, kim nr, chin hs, jung jw. accuracy of intraocular lens power calculation formulas using a sweptsource optical biometer. plos one 2020;15(1):e0227638. 33. narváez j, zimmerman g, stulting rd, chang dh. accuracy of intraocular lens power prediction using the hoffer q, holladay 1, holladay 2, and srk/t formulas. j cataract refract surg 2006;32:2050–2053. 34. beiko gh. a pilot study to determine if intraocular lens choice at the time of cataract surgery has an impact on patient-reported driving habits. clin ophthalmol. 2015;9:1573–1579. 35. johnson & johnson vision. technis monofocal 1-piece iol. johnson & johnson vision; 2021. available from: https://www.jnjvisionpro.com/products/tecnis®-1-piece-iol 36. acrysof iq. product information. alcon laboratories, inc.; 2015. available from:https://www.accessdata.fda.gov/ cdrh_docs/pdf4/p040020s050d.pdf 37. wang l, koch dd, hill w, abulafia a. pursuing perfection in intraocular lens calculations: iii. criteria for analyzing outcomes. j cataract refract surg 2017;43:999–1002. 38. wang q, jiang w, lin t, wu x, lin h, chen w. meta-analysis of accuracy of intraocular lens power calculation formulas in short eyes. clin exp ophthalmol 2018;46:356–363. 39. wang q, jiang w, lin t, zhu y, chen c, lin h, et al. accuracy of intraocular lens power calculation formulas in long eyes: a systematic review and meta-analysis. clin exp ophthalmol 2018;46:738–749. 40. tang ks, tran em, chen aj, rivera dr, rivera jj, greenberg pb. accuracy of biometric formulae for intraocular lens power calculation in a teaching hospital. int j ophthalmol 2020;13:61–65. 41. wang l, shirayama m, ma xj, kohnen t, koch dd. optimizing intraocular lens power calculations in eyes with axial lengths above 25.0 mm. j cataract refract surg 2011;37:2018–2027. 352 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 https://www.accessdata.fda.gov/cdrh_docs/pdf4/p040020s050d.pdf https://www.accessdata.fda.gov/cdrh_docs/pdf4/p040020s050d.pdf original article prevalence and burden of refractive errors at national and sub-national levels in iran seyed farzad mohammadi1, mdfico; farshad farzadfar2, md; parinaz mehdi pour2, ms elham ashrafi1, phd; alireza lashay1, md; bahram mohajer2, md; mohsen asadi lari3, md 1translational ophthalmology research center, farabi eye hospital, tehran university of medical sciences, tehran, iran 2non-communicable diseases research center, endocrinology and metabolism research institute, tehran university of medical sciences, tehran, iran 3department of epidemiology, school of public health, iran university of medical sciences, tehran, iran orcid: seyed-farzad mohammadi:0000-0002-9209-3034 elham ashrafi:0000-0001-8640-0168 abstract purpose: to estimate the prevalence, burden of refractive errors and their associated trend from 1990 to 2018 and geographic inequalities in iran. methods: data regarding the epidemiology of refractive errors was extracted from three different sources: systematic review of published literature, data from visual school screening programs, and data from iran’s national health survey (nhs). the pool of all available data on refractive errors as well as demographic, location, and socioeconomic status covariates were fitted in spatio-temporal and gaussian process regression models to predict the prevalence of refractive errors from the years 1990 to 2018 in 31 provinces grouped by age and sex in order to calculate years lived with disability (ylds). results: in 2018, the age-adjusted prevalence of refractive errors was 16.32% (95% uncertainty interval [ui]: 12.44–21.48%) in both sexes, 17.98% (95% ui: 13.74– 23.61%) in women, and 14.66% (95% ui: 11.14–19.36%) in men. the prevalence of refractive errors reveals that it increases with age. refractive errors contributed to 441.41 and 348.38 ylds in men and women, respectively. the age-standardized prevalence growth was 31.30% in females and 24.32% in males from the years 1990 to 2018. significant geographical heterogeneity was observed. the agestandardized ylds rates of refractive errors represent an increasing trend of 28.9% increase from 1990 to 2018. conclusion: over 28 years, the prevalence of refractive errors increased significantly. women tend to have higher rates of prevalence. the prevalence increased in older ages. border provinces had the lowest prevalence. agestandardized ylds rates of refractive errors increased by about 30%. keywords: burden; disability-adjusted life years; iran; prevalence; refractive errors j ophthalmic vis res 2022; 17 (1): 78–88 78 © 2022 mohammadi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10173&domain=pdf&date_stamp=2019-07-17 refractive errors in iran; mohammadi et al introduction refractive errors are recognized as approximately half of the causes of visual impairment (vi) and the second leading cause of functional blindness.[1] it impinges on patients’ quality of life through functional, psychosomatic, and cosmetic issues while also causing economic burden.[2] refractive errors are listed among one of the four non-fatal disorders classified in the 20 top causes of disability-adjusted life years (dalys).[3] since refractive disorders mostly initiate early in life, remarkable morbidity assessed by years of living with disability (ylds) is associated more with this eye disorder as compared to other ocular diseases.[3] compared to other causes of vi, refractive errors in most cases is easily treatable by prescribing glasses which is one of the most cost-effective interventions in eye care. if left uncorrected, refractive errors can affect performance, reduce employability, and productivity, and compromise the entire life of patients.[2–5] uncorrected refractive disorders relative to the total dalys increased by 42% globally when compared to 1990,[6] and refractive disorders were responsible for the loss of healthy life of approximately 44.8 years per 100,000 population globally with an increasing trend and with an advance in age from 40 years onward.[7, 8] the eastern mediterranean region has the second-highest daly recorded from refractive errors among world regions. this is the consequence of a higher prevalence (188.7; 95% uncertainty interval [ui]: 125.3–276.9%) of refractive error in addition to the suboptimal implementation of prevention/treatment options. therefore, cost-effective prevention programs are recommended to address this epidemiological correspondence to: elham ashrafi, phd. translational ophthalmology research center, farabi eye hospital, tehran university of medical sciences, qazvin square, tehran 1336616351, iran. e-mail: eashrafi@sina.tums.ac.ir received 29-05-2021; accepted 21-09-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10173 priority.[6] refraction/accommodation (functional) disorders in iran accounted for 0.42% daly in 1990 and 0.47% in 2010, where the associated costs and issues were greater than that of other causes of vi, namely cataract, glaucoma, and macular degeneration.[9] providing reliable evidence and situational analysis is required for promoting good health practices. global burden of disease (gbd) 2017 has presented estimates for the economic and social burden of refractive errors; which, however, lack subnational estimates and comprehensive inclusion of the present national surveys data in iran. this study aims to estimate the incidence, prevalence, burden, and trend of refractive errors during the period of 1990 to 2018 at the national and sub-national levels in iran. methods data sources this research represents secondary data analysis on three data sources; the systematic review of published literature, data from the ministry of health and medical education (mohme) screening programs, and iran’s national health survey (nhs) data [figure 1]. a detailed explanation of the search strategy and cleaning process of all data sources is presented in a supplementary document.[10] systematic review published literature between january 1980 and december 2018 present in medline (pubmed), isi web of science, scopus, iranian digital databases of sid (http://www.sid.ir), barakat knowledge network system (http://health.barakatkns.com), and in the national ophthalmic literature database by noor ophthalmology research center (http://iraneyedoc.com) were all searched. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: mohammadi sf, farzadfar f, pour pm, ashrafi e, lashay a, mohajer b, lari ma. prevalence and burden of refractive errors at national and sub-national levels in iran. j ophthalmic vis res 2022;17:78– 88. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 79 https://knepublishing.com/index.php/jovr http://www.sid.ir http://health.barakatkns.com http://iraneyedoc.com refractive errors in iran; mohammadi et al additionally, the abstract books of the iranian ophthalmology annual congresses from the years 2008 through 2010 were screened and included only if the inclusion criteria was satisfied. a detailed explanation of the study selection criteria and critical appraisal is described in the protocol paper.[10] a crosswalk method was applied in extracting the pertinent data where cases related to myopia/hyperopia/astigmatism were combined to those of refractive error and modified the rural/urban scope. a total of 146 data points from 10 provinces were extracted from the systematic review and included in the analysis [table 1]. refractive error screening programs unpublished official data for the prevalence of refractive errors occurring in the years 2007, 2010, and 2012 were gathered from screening programs performed in the elementary schools of all the provinces. a total of 1156 data points were extracted [table 1]. national health survey the national health survey (nhs) includes two self-reporting questions about spectacles use (“do you use glasses?”) and spectacles need (“do you need glasses to see clearly?”) in all age groups and provinces in the years 1990 and 2000. after an adjustment of the nhs data by mohme/systematic review data while using a crosswalk method and adjusting for missing data, a total of 1488 data points were generated [table 1]. statistical analysis a total number of 2790 data points were included from the above data sources. we aimed to estimate the prevalence of refractive errors for different age groups, between the two sexes, at national level, and in 31 provinces, from the years 1990 to 2018. generalized linear mixed model (glmm) was applied to impute missing values of these age-sex-location-time combinations. in this model, we predicted the prevalence of refractive errors with fixed covariates, including years of schooling, wealth indices, urbanization ratios, as well as the random effects of the location of the provinces. urbanization ratios and population data were retrieved from the national censuses, which were conducted by the statistical center of iran (sci). to calculate other covariates in the statistical models, we used household expenditure and income surveys from the years 1990 to 2018, which were also conducted by the sci. the second step after applying the glmm was the application of an age-spatio-temporal (ast) model capturing all variations for time, location (province), and age groups of residuals from the first model. in the ast model, we assumed that there were unmeasured variations in residuals that were derived from glmm. to estimate these variations, we weighted adjacent years, provinces, and ages by three matrices and used neighboring elements of the matrix that had more correlation with each other where this measure decreased by increasing their distances. the weighted residuals were then added back to glmm predictions and final estimates of prevalence were produced. in order to have robust estimates with certainty, using estimated rates, we employed gaussian process regression (gpr) which is a bayesian technique. it defines a flexible model with hierarchical priors for its parameters and it also has a mean and covariance function. in this study, these functions were defined in the ast model and the matérn function, respectively. gaussian process regression (gpr) samples were drawn from the posterior distribution by using the markov chain monte carlo method and we calculated the median for the final estimates of prevalence and 2.5 and 97.5 percentiles for its uncertainty.[10] the data collected from the 2018 record of the national population in iran was used as the standard population in a direct age-standardized analysis to facilitate the statistical comparisons between provinces. since refractive errors do not have fatal consequences, dalys were considered equal to ylds, which were estimated by multiplying the prevalence by the reported disability weight for refractive errors in the gbd study, and the duration of symptoms. results prevalence of refractive errors at national level, in the year 2018, the age-adjusted prevalence of refractive errors was estimated at 80 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 refractive errors in iran; mohammadi et al table 1. data source specifications. source sex age (yr) province year coverage number of data point systematic review male/female all ages 10 1999–2014 sub-national 146 (5.23%) ministry of health male/female 7–15 31 2007, 2010, 2012 national/subnational 1156 (37.6%) national health survey male/female all ages 31 1990, 2000 national 1049 (41.43%) table 2. prevalence of refractive errors by sex and age group in year 2018. age group (yr) sex prevalence lower limit upper limit 0–6 female 1.25 1.1 1.41 0–6 male 1.01 0.9 1.13 7–11 female 4.26 3.04 5.97 7–11 male 3.33 2.34 4.75 12–14 female 7.6 5.56 10.39 12–14 male 6.1 4.42 8.42 15–17 female 7.31 5.22 10.27 15–17 male 5.58 3.91 7.95 18–24 female 12.32 9.62 15.75 18–24 male 9.48 7.17 12.54 25–34 female 11.42 8.69 14.98 25–34 male 8.53 6.57 11.05 35–44 female 16.35 12.96 20.66 35–44 male 13.1 10.12 17.02 45–54 female 27.16 21.51 34.23 45–54 male 25.62 19.56 33.56 55–64 female 30.71 24.55 38.45 55–64 male 23.12 18.1 29.6 65–74 female 32 24.99 40.95 65–74 male 26.43 21.05 33.17 75–84 female 36.22 26.91 48.93 75–84 male 27.94 20.57 38.14 85 female 29.22 20.72 41.31 85 male 25.75 19 34.95 16.32% (95% ui: 12.44%, 21.48%). it is 17.98% (95% ui: 13.74–23.61%) in women and 14.66% (95% ui: 11.14–19.36%) in men. the age-standardized prevalence increased by 31.30% in females and 24.32% in males during the years 1990 to 2018. the prevalence of refractive errors showed an increasing trend with age in both sexes, with the highest prevalence among women older than 85 years with a prevalence of 29.22% (95% ui: 20.72– 41.31%) in 2018. the highest rise is seen in ages 35 to 44 years [table 2; figures 2 & 3]. geographic distribution of refractive errors the age-standardized prevalence of refractive errors in different provinces is reported in figure 4. provinces heterogeneity was observed journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 81 refractive errors in iran; mohammadi et al table 3. age-standardized dalys per 100,000 in different years and sex. year male female 1990 144.95 177.86 1995 172.69 213.64 2000 205.87 257.28 2005 255.14 319.81 2010 302.38 381.64 2018 348.38 441.41 figure 1. analysis process for ylds calculation. daly, disability-adjusted life years; yld, years lived with disability. consistently during the study period. the highest age-standardized prevalence recorded in 2018 was 20.4% in north khorasan while the lowest was discovered in tehran with a prevalence of 13.8%. country provinces located at the borders tend to have lower levels of refractive errors while central provinces showed higher levels, particularly in recent years. the data also show a negative association with the wealth index (r: 0.6; p: 0.032). the burden of refractive errors (per 100,000) refractive errors contributed to 441.41 and 348.38 ylds in men and women, respectively. the ylds in 2018 in age and gender groups are summarized in table 3. the highest number of years of life lost was seen in women over 85 years with 499.55 ylds. nationally, the age-standardized ylds rates of refractive errors reveal an increasing trend of 28.9% during this period [figure 5]. discussion this study represented a national first effort to collect data from multiple sources at the individual level to estimate the prevalence of refractive errors over an extended period in iran. it revealed that a total of 13 million iranian citizens are affected by refractive errors. similar to the global patterns, advancing age, female gender, and lower socioeconomic status were identified as risk factors.[6, 11] refractive error prevalence carries an inherent “age-related” feature; where it was determined through the study that the possibility of developing some kind of refractive error increases with age. while in viewing the data of the decade one age category a prevalence of under 10% refractive error was noticed in 2018 throughout the country, it increased to approximately 17% in the ninth decade age category. several phenomena may explain this, juvenile myopia generally commences before 6 years of age and continues to occur and increase in severity up to 16 years or more. in later years, keratoconus incidence in the second and third decades contributes modestly to increased refractive error. in later years especially where people approach their 40s, presbyopia and latent hyperopia may develop and manifest in patients. the incidence of the presbyopia 82 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 refractive errors in iran; mohammadi et al figure 2. refractive errors prevalence at national level by sex and age group from 1990 to 2018. and hyperopia conditions fluctuates to a higher level during the middle aged category of the population which is clearly reflected in the study diagrams. decoupling of lenticular astigmatism (from corneal astigmatism) and emergence of nuclear sclerosis may also contribute to the agerelated changes. the latter should explain the trend in the >70 years (index myopia) category. diabetes mellitus is another source for incidental refractive error in the middle to older ages as it may induce refractive index shifts in the crystalline lens. the increasing trend in the prevalence of refractive errors is consistent with other reports in journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 83 refractive errors in iran; mohammadi et al figure 3. trend of refractive errors prevalence at national level by sex and age groups from 1990 to 2018. the world and region.[6, 11] however, our prevalence estimates in iran are lower as compared with corresponding figures in the region. in addition, relative to global estimates, refractive errors prevalence estimated in iran reflects a more positive outcome.[11] it is known that the world is experiencing a pandemic of refractive errors.[12] in 2010, about 28% of the world’s population was affected by shortsightedness. this is predicted to rise to 34% by 2020 and then to approximately 50% by 2050.[13] the aging population has many more people with refractive errors (demographic transition). presbyopia and manifest hyperopia are the two major contributors in older ages. the myopia epidemic, on the other hand, may be caused by epidemiologic transition factors; daily habits that encompass the use of digital, sight-intensive, and night and near vision-oriented activities may affect the state of vision in molecularly vulnerable people where they may become more prone to myopia. many ecological studies suggested a correlation between indoor and nightlife activities with the prevalence of myopia and its related severity.[14–16] in addition, lifestyle changes involving the execution of more intense visual tasks such as using a computer or a smartphone led to glasses being prescribed even for patients diagnosed with minimal myopia. an increase in the prevalence of refractive errors in iran may be attributed to lifestyle changes due to technological advancements and behavioral factors relating to specific age groups. the initial and progressive pace of juvenile myopia in recent years were both attributed to near-work activities and digital life. cohort studies have proven the axial growth in the eyes in the global population.[17] the covid-19 pandemic due to the lifestyle restrictions has exacerbated the use of digital apparatus and the need for indoor entertainment where now there are frequent studies revealing more myopia incidence and progression.[18] however, it should also be mentioned that based on particular studies this phenomenon seems to not be consistent 84 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 refractive errors in iran; mohammadi et al figure 4. geographic distribution of age-standardized prevalence in different years (a: females, b: males). journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 85 refractive errors in iran; mohammadi et al figure 5. age-adjusted dalys (ylds) per 100,000 at national level by sex from 1990 to 2018. among all races, asians being the most sensitive while africans seem unsusceptible.[11] the agestandardized prevalence estimates of refractive error in our study from the years 1990 to 2018 translate into >100% rise which mostly follows the trend of juvenile myopia.[13, 19] the authors of the current study would like to indicate the challenge experienced in the conducting the assignment of the disability index for vi to refractive errors. refractive errors are highly heterogeneous and their severity is divergent. although some refractive errors are essentially a variation of normality, others are so disabling that without correction they constitute clear handicap and “functional” blindness. as a result of our analysis, we recommend that the approach to addressing the global burden of this disease needs major improvement in this regard including cost estimation and social attribution of the disability. dalys attributed to refractive disorders increased 52% worldwide as compared to 1990 and increased by 82% in iran.[9] our study showed a higher prevalence and daly as compared to institute for health metrics and evaluation (ihme). this might be due to the nature of ihme estimation and imputation of missing data by neighboring data because of security and insufficient evidences from iran in prior years. imputation from neighboring countries’ evidence may constitute another source of disparity. in our study, it was revealed that the prevalence of refractive errors in central provinces which generally possess better socioeconomic status (better education and more indoor occupations) is higher than those of the marginal provinces. prior studies on the prevalence of refractive errors have already confirmed higher myopia prevalence in environments that possess more advanced levels of education, income, and professional occupations.[20] modern careers tend to be 86 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 refractive errors in iran; mohammadi et al associated with sight-intensive work. in several epidemiological studies[21–26] as a consequence of the mentioned trends, increased attention is now directed to addressing unmet refractive error correction and control of myopia conditions. in summary, the challenging data extraction process in our current study proved useful in determining the prevalence of the refractive errors phenomena in iran. this study has provided the required evidence in determining the associated burden (economic and social) of these conditions and the basis for the recommendation to the respective health authorities about the necessity to address these issues. over a span of 28 years, the prevalence of refractive errors has increased significantly in iran by 16.32% (the age-standardized prevalence growth was 31.30% in females and 24.32% in males from the years 1990 to 2018). prevalence in females was 3.5% higher than that of males. the prevalence rates increased in older ages. significant geographical heterogeneity was observed where border provinces possessed a lower prevalence of refractive errors. the age-standardized ylds rates of refractive errors showed an increasing trend of 28.9% during the period. lifestyle changes and behavioral adaptions due to technological advancements and other social restrictions continues to perpetuate the onslaught of myopia and other vi issues globally, which further emphasizes the need to manage diagnoses, their prevention and treatment of these related issues. financial support and sponsorship this work was partially supported by the tehran university of medical sciences under grant number 24423. conflicts of interest there are no conflicts of interest. references 1. naidoo ks, leasher j, bourne rr, flaxman sr, jonas jb, keeffe j, et al. global vision impairment and blindness due to uncorrected refractive error, 1990–2010. optom vis sci 2016;93:227–234. 2. kandel h, khadka j, goggin m, pesudovs k. impact refractive error on quality of life: a qualitative study. clin exp ophthalmol 2017;45:677–688. 3. who. the global burden of disease: 2004 update [internet]. geneva: world health organization; 2008 [cited 2015 september 1]. available from: http://www.who.int/healthinfo/global_burden_disease/ gbd_report_2004update_full.pdf.accessed june 25, 2019. 4. holden ba. blindness and poverty: a tragic combination. clin exp optom 2007;90:401–403. 5. tahhan n, papas e, fricke tr, frick kd, holden ba. utility and uncorrected refractive error. ophthalmology 2013;120:1736–1744. 6. lou l, yao c, jin y, perez v, ye j. global patterns in health burden of uncorrected refractive error. invest ophthalmol vis sci 2016;57:6271–6277. 7. murray cj, barber rm, foreman kj, ozgoren aa, abdallah f, abera sf, et al. global, regional, and national disability-adjusted life years (dalys) for 306 diseases and injuries and healthy life expectancy (hale) for 188 countries, 1990-2013: quantifying the epidemiological transition. lancet 2015;386:2145–2191. 8. pascolini d, mariotti sp. global estimates of visual impairment: 2010. br j ophthalmol 2012;96:614–618. 9. hatef e, mohammadi sf, alinia c, ashrafi e, mohammadi sm, lashay a, et al. national burden of eye diseases in iran, 1990-2010; findings from the global burden of diseases study 2010. middle east afr j ophthalmol 2016;23:89–95. 10. ashrafi e, mohammadi sf, fotouhi a, lashay a, asadi-lari m, mahdavi a, et al. national and sub-national burden of visual impairment in iran 1990-2013; study protocol. arch iran med 2014;17:810–815. 11. hashemi h, fotouhi a, yekta a, pakzad r, ostadimoghaddam h, khabazkhoob m. global and regional estimates of prevalence of refractive errors: systematic review and meta-analysis. j curr ophthalmol 2017;30:3−22. 12. dolgin e. the myopia boom. nature 2015;519:276–278. 13. holden ba, fricke tr, wilson da, jong m, naidoo ks, sankaridurg p, et al. global prevalence of myopia and high myopia and temporal trends from 2000 through 2050. ophthalmology 2016;123:1036–1042. 14. ono k, hiratsuka y, murakami a. global inequality in eye health: country-level analysis from the global burden of disease study. am j public health 2010;100:1784–1788. 15. rahi js, cumberland pm, peckham cs. myopia over the life course: prevalence and early life influences in the 1958 british birth cohort. ophthalmology 2011;118:797–804. 16. huang hw, teh chang ds, chang wu p. the association between near work activities and myopia in children— a systematic review and meta-analysis. plos one 2015;10:e0140419. 17. french an, morgan ig, mitchell p, rose ka. risk factors for incident myopia in australian schoolchildren: the sydney adolescent vascular and eye study. ophthalmology 2013;120:2100–2108. 18. zhang x, cheung ssl, chan hn, zhang y, wang ym, yip bh, et al. myopia incidence and lifestyle changes among school children during the covid-19 pandemic: a population-based prospective study. br j ophthalmol 2021;bjophthalmol-2021-319307. 19. the impact of myopia and high myopia. report of the joint world health organization–brien holden vision journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 87 http://www.who.int/healthinfo/global_burden_disease/gbd_report_2004update_full.pdf.accessed http://www.who.int/healthinfo/global_burden_disease/gbd_report_2004update_full.pdf.accessed refractive errors in iran; mohammadi et al institute global scientific meeting on myopia. university of new south wales, sydney, australia, march 16–18, 2015. geneva: world health organization; 2017 [cited 2019 june 25]. available from: https://www.who.int/blindness/ causes/myopiareportforweb.pdf. 20. foster pj, jiang y. epidemiology of myopia. eye 2014;28:202–208. 21. wu pc, tsai cl, hu ch, yang yh. effects of outdoor activities on myopia among rural school children in taiwan. ophthalmic epidemiol 2010;17:338–342. 22. deng l, gwiazda j, thorn f. children’s refractions and visual activities in the school year and summer. optom vis sci 2010;87:406–413. 23. dirani m, tong l, gazzard g. outdoor activity and myopia in singapore teenage children. br j ophthalmol 2009;93:997–1000. 24. rose ka, morgan ig ip j. outdoor activity reduces the prevalence of myopia in children. ophthalmology 2008;115:1279–1285. 25. jones las, sinnott lt, mutti do, mitchell gl, moeschberger ml, zadnik k. parental history of myopia, sports and outdoor activities, and future myopia. invest ophthalmol vis sci 2007;48:3524–3532. 26. onal s, toker e, akingol z. refractive errors of medical students in turkey: one year follow-up of refraction and biometry. optom vis sci 2007;84:175–180. 88 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 https://www.who.int/blindness/causes/myopiareportforweb.pdf https://www.who.int/blindness/causes/myopiareportforweb.pdf original article individual and combined effects of diabetes and glaucoma on total macular thickness and ganglion cell complex thickness: a cross-sectional analysis dhruven shah, dnb, do; rita dhamankar, ms, do; vijay shetty, ms, dnb, frcs, faico; suhas s haldipurkar, doms, faico; prakash chipade, ms; shabnam tanwar, dnb; prachi sankhe, dnb; devendra venkatramani, dnb, fico, frcs, mrcs; paresh mhatre, m optom; maninder singh setia, md, phd, mph laxmi eye institute, maharashtra, india orcid: dhruven shah: https://orcid.org/0000-0001-6683-4161 maninder singh setia: https://orcid.org/0000-0003-1291-9033 abstract purpose: presence of diabetes in glaucoma patients may influence findings while documenting the progression of glaucoma. we conducted the study to compare individual and combined effects of diabetes and glaucoma on macular thickness and ganglion cell complex thickness. methods: the present study is a cross-sectional analysis of 172 eyes of 114 individuals. the groups were categorized according to the following conditions: glaucoma, diabetes mellitus, both glaucoma and diabetes (‘both’ group), and none of these conditions (‘none’ group). patients with diabetes did not have diabetic retinopathy (dr). we compared retinal nerve fiber layer (rnfl) thickness, ganglion cell complex (gcc) thickness, foveal loss of volume (flv), and global loss of volume (glv) among the groups. we used random effects multivariate analysis to adjust for potential confounders. results: the mean (sd) age of these individuals was 60.7 (10.1) years. the total average rnfl and gcc were significantly lower in the glaucoma group (rnfl: -36.27, 95% confidence intervals [ci]: -42.79 to -29.74; p <0.05, and gcc: -26.24, 95% ci: -31.49 to -20.98; p<0.05) and the ‘both’ group (rnfl: -24.74, 95% ci: -32.84 to -16.63; p<0.05, and gcc: -17.92, 95% ci: -24.58 to -11.26; p<0.05) as compared with the ‘none’ group. there were no significant differences in the average rnfl values and total average gcc between the diabetes group and the ‘none’ group. the values of flv and glv were significantly higher in the ‘glaucoma’ group and the ‘both’ group as compared with the ‘none’ group. the foveal values were not significantly different across these four groups. among the glaucoma cases, 25% were mild, 30% were moderate, and 45% were severe; there was no significant difference in the proportion of severity of glaucoma between the ‘glaucoma only’ and ‘both’ groups (p=0.32). after adjusting for severity and type of glaucoma, there were no statistically significant differences in the values of average rnfl (6.6, 95% ci: -1.9 to 15.2; p=0.13), total average gcc (3.6, -95% ci: -2.4 to 9.6; p=0.24), and glv (-3.9, 95% ci: -9.5 to 1.6; p=0.16) in the ‘both group’ as compared with the glaucoma only group. conclusion: we found that diabetes with no dr did not significantly affect the retinal parameters in patients with glaucoma. thus, it is less likely that thickness of these parameters will be overestimated in patients with glaucoma who have concurrent diabetes without retinopathy. keywords: glaucoma; diabetes; combined effects; macular thickness; ganglion cell complex thickness j ophthalmic vis res 2022; 17 (3): 505–514 © 2022 shah et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 505 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i4.12303&domain=pdf&date_stamp=2019-07-17 macular oct parameters in dm and glaucoma; shah et al introduction glaucoma is characterized by progressive optic neuropathy caused by high intraocular pressure (iop) leading to gradual death of retinal ganglion cells (rgc). the most common type of glaucoma is primary open angle glaucoma (poag).[1, 2] the inner retinal layers also known as the ganglion cell complex (gcc) are composed of macular nerve fibre layer (nlf), ganglion cell layer (gcl), and inner plexiform layer (ipl), which are specifically involved in glaucomatous damage.[3] accuracy of gcc measurement in detecting glaucoma is comparable to the detection of glaucoma by measuring peripapillary retinal nerve fibre layer (rnfl) thickness. gcc measurements can potentially be used to monitor glaucoma progression.[? ] zeimer and colleagues suggested that analyzing macular parameters may be used as an alternative or additional parameter to peripapillary rnfl thickness in diagnosing glaucoma.[7] it has been shown that macular thickness is correlated with optic disc cupping and rnfl thickness in diagnosing glaucoma.[8, 9] furthermore, macular thickness also correlates with rgc counts and perimetry parameters in both glaucomatous and normal eyes when diagnosing glaucoma and analyzing its progression.[8–11] the estimated global prevalence of diabetes was 9.3% in 2019.[12] diabetic retinopathy (dr) is the most common microvascular complication of diabetes mellitus. studies in experimental animal models have indicated that neuroglial tissue loss may occur at early stages of diabetic retinopathy and even precede vascular changes.[13–15] in diabetic patients, adenosine monophosphate�activated protein kinase activation and metabolic stress probably occur as a result of hyperglycemia, hypoglycemia, and hypoxia; thus, the intraretinal neural tissue may not adapt to the metabolic stress of diabetes.[16, 17] correspondence to: maninder singh setia, md, phd, mph. laxmi eye institute, panvel, maharashtra 410206, india. e-mail: maninder.setia@karanamconsultancy.in received: 27-04-2021 accepted: 10-06-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i4.12303 this may partially explain the pathogenesis of neurodegeneration as an additional component to microvascular pathomechanism of diabetic retinopathy. araszkiewicz et al suggested that intraretinal neural tissue loss associated with type 1 diabetes directly affects neurodegeneration.[18] other authors reported that inner retinal layers including rnfl, gcl, ipl in the macula had lesser thickness in patients with type 2 diabetes and early diabetic retinopathy as compared to controls.[19] furthermore, they also found a linear correlation between gcl thickness and duration of diabetes.[19] other authors have also found a relationship between reduction and the duration of diabetes, where the reduction in rnfl thickness was associated with longer duration of diabetes and this loss was evident in diabetics with and without diabetic retinopathy.[20, 21] although studies have reported that diabetes is an additional risk factor for poag, the association is controversial.[22, 24, 25] macular thickness measurement (using asymmetry analysis) can help for detection and progression of glaucoma, and is useful in determining the role of diabetes in neurodegeneration.[26] it is quite likely that presence of diabetes in glaucoma patients may influence the findings while documenting the progression of glaucoma. previous studies have compared the retinal nerve fibre layer in patients with glaucoma and diabetes versus those without diabetes. some have found no difference in rnfl thickness in diabetic versus non-diabetic poag patients; whereas other authors have suggested that diabetes may over-estimate the progression of glaucomatous optic neuropathy.[27, 28] thus, we conducted the present study to compare the individual and combined effects of diabetes and glaucoma on macular thickness and ganglion cell complex thickness. this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: shah d, dhamankar r, shetty v, haldipurkar ss, chipade p, tanwar s, sankhe p, venkatramani d, mhatre p, setia ms. individual and combined effects of diabetes and glaucoma on total macular thickness and ganglion cell complex thickness: a cross-sectional analysis . j ophthalmic vis res 2022;17:505–514. 506 journal of ophthalmic and vision research volume 17, issue 3, october-december 2022 https://knepublishing.com/index.php/jovr macular oct parameters in dm and glaucoma; shah et al methods this cross-sectional analysis was performed on 172 eyes of 114 individuals. the study was conducted at laxmi eye institute, panvel, india. we recruited the following four types of individuals: those with glaucoma, diabetes mellitus, both glaucoma and diabetes (‘both’ group), and those without any of these conditions (none group). patients with glaucoma (primary open angle or angle closure glaucoma) diagnosed by anderson’s criteria (three non-edge points on the pattern deviation map, pattern standard deviation (psd), and glaucoma hemifield test) were included in the glaucoma group. individuals who were diagnosed with diabetes (based on fasting blood sugar of ≥ 126 mg/dl, two hour post prandial blood sugar of ≥ 200 mg/dl, or glycated hemoglobin of ≥ 6.5 %)s) were included in the diabetes group and individuals with both diabetes and glaucoma were included in the ‘both group’. consenting individuals in the age group of 40-80 years were included for the present study. the exclusion criteria were: presence of any intraocular or neurological diseases affecting rnfl, optic disc, visual field and macular thickness (due to any reason other than diabetes and glaucoma), diabetic patients with dr, past history of any treatment for diabetic retinopathy; past history of any vitreoretinal surgery, prior history of uveitis/retinal disease, significant media opacity (such as corneal scarring, any opacity affecting visual axis, advanced cataract or vitreous opacities which could affect retinal and perimetry scans); hyperopia > +3d; and high myopia >-6d. all patients underwent complete ophthalmological examination. these were: 1) best corrected visual acuity (bcva) for distance and near (using snellen’s chart and logmar) and axial length; 2) measurement of iop using goldmann applanation tonometer; 3) four mirror gonioscopy (indirect gonioscopy using zeiss gonio lens); 4) slit lamp examination ; 5) dilated fundus examination with slit-lamp biomicroscopy and indirect ophthalmoscopy); 6) visual field testing using humphrey field analyser (carl zeiss, germany, usa); 7) optical coherence tomography with rtvue (optovue, usa); 8) rnfl thickness (superior rnfl, inferior rnfl, average rnfl); 9) gcc thickness -total gcc, superior gcc, inferior gcc; 10) focal loss volume (flv) and global loss volume (glv); 11) full retinal thickness maps. a glycated hemoglobin (hba1c) test was also performed in these individuals. we classified the glaucoma into three categories based on the mean deviation (md) values (early defect, moderate defect, and severe defect).[29] we used spectral domain optical coherence tomography (sd-oct) rtvue-100 (optovue inc., fremont, california, usa) to evaluate the study parameters. the instrument uses an 840±10 nm wavelength illumination source capable of 26000 a-scans/s with a depth resolution of 5 μ. the peripapillary rnfl thickness map was generated from multiple circular scans in an area of 3.45 mm diameter circle with the optic disc as its center. the distance between the internal limiting membrane and the outer edge of the rnfl was estimated to be the rnfl thickness. the gcc complex thickness maps were taken by multiple horizontal and vertical line scans in a region 1mm temporal to the fovea. the gcc thickness for the present study was the combined thickness of the rnfl, ganglion cell layer, and inner plexiform layer. we also assessed the pattern-based parameters: focal loss volume (flv) and global loss volume (glv). the flv was the percentage of the total sum of statistically significant gcc volume loss divided by the gcc map area. the glv was the percentage of the sum of negative fractional deviation in the entire measurement area.[30] we assessed the retinal macular thickness by using the retina map scan which consisted of multiple horizontal and vertical line scans all centered at the fovea. we only analysed scans with a signal strength of > 65. statistical analysis we estimated the mean and standard deviation (sd), and median and interquartile range (iqr) for continuous variables and the proportions for categorical variables. the means across the groups were compared using analysis of variance (anova) with a pair-wise post-hoc comparison with tukey’s correction. the medians were compared using the kruskal-wallis test with dunn’s correction. the proportions were compared using the chi square test or fisher’s exact test for low expected cell counts. we used pearson’s correlation co-efficient (r) as measure of correlation between two linear variables. we used random effects linear models for multivariate analysis. the advantages of these models are that they account for both withinindividual and between-individual variance. since journal of ophthalmic and vision research volume 17, issue 3, october-december 2022 507 macular oct parameters in dm and glaucoma; shah et al in some instances we used both eyes from the same individual, these models were useful.[31] while building these multivariate models, we did not consider each eye as a separate entity but accounted for the fact that two eyes might belong to the same individual. data was entered in ms excel (© microsoft, usa) and analysed using stata version 15.1 (© statacorp, college station, texas, usa). a p value of < 0.05 was considered statistically significant. the study was approved by the institutional ethics committee of laxmi eye institute and charitable hospital. results the mean ± sd age of participants was 60.7 ± 10.1 years; it was significantly lower in the group without any condition (53.7 ± 7.0) as compared with all the other three groups (table 1). we included 72 (63%) males and 42 (37%) females in the present study; there was no significant difference in the distribution of gender across these groups (p=0.43). the hba1c mean ± sd was 5.60 ± 0.67; it was significantly lower in the ‘none’ group (5.07 ± 0.31) as compared with the diabetes group (6.10 ± 0.52) (p<0.001) and ‘both group’ (6.01 ± 0.66) (p<0.001). however, there were no significant differences in the hba1c values between the none group and the glaucoma group (p=0.93) or between the diabetes group and ‘both group’ (p=0.91). the median (iqr, bcva) in our population was 0.18 (0 to 0.18); it was not significantly different across all four groups. the mean iop in our population was 16.7 ± 3.9 mm hg; it was maintained and not significantly different across these groups (p=0.61). we have provided additional details of each parameter in table 1. the median (iqr, bcva) duration of diabetes mellitus in our study population was 7 (range, 5 to 12) years. in our glaucoma cases, 25% were mild, 30% were moderate, and 45% were severe; there was no significant difference in the proportion of severity of glaucoma in the ‘glaucoma only’ and ‘both’ groups (p=0.32). the mean ± sd rnfl thickness was maximum in the ‘none’ (104.9 ± 7.2) group and minimum in the glaucoma group (67.5 ± 13.3). all measurements of rnfl followed this pattern. in general, we found that there was no significant difference in rnfl thickness between the ‘none’ group and diabetes group; however, mean rnfl in the glaucoma and ‘both’ group was significantly lower as compared with the ‘none’ group and diabetes group (table 2). the mean ± sd total average gcc was also significantly higher in the ‘none’ group as compared with the glaucoma and ‘both’ groups (figure 1). the median (iqr) flv in the ‘none’ group (0.51 [0.09 to 1.60]) was significantly lower as compared with the glaucoma (7.84 [3.68 to 10.15]) (p<0.001) and ‘both’ groups (6.75 [2/31 to 9.29]) (p<0.001); however, it was not significantly different from the diabetes group (0.70 [0.30 to 1.39]) (p>0.99). there was no significant difference in the median (iqr) flv between the glaucoma group and the ‘both’ group (p=0.84) (figure 2). similarly, the median (iqr) glv in the ‘none’ group (1.18 [0.20 to 2.73]) was significantly lower as compared with the glaucoma (20.44 [15.45 to 32.68]) (p<0.001) or ‘both’ groups (18.49 [10.57 to 24.21]) (p<0.001); however, it was not significantly different from the diabetes group (2.39 [1.12 to 6.27]) (p=0.33). as with the glv values, there was no significant difference between the glaucoma group and ‘both’ group (p=0.39) (figure 2). in general, total foveal value was only significantly different between the diabetes group and glaucoma group. however, individual foveal values were lower in the glaucoma group and ‘both’ group as compared with the ‘none’ group and diabetes group except for superior and nasal parafoveal values which were higher in the glaucoma group when compared to the “both” and “none” groups. the values of these two parameters, i.e. the glv and fv values were only significantly lower in the glaucoma group as compared with the ‘none’ and diabetes only groups. we have presented all the data in table 3. among diabetics, the correlation between hba1c and average rnfl was weak and not statistically significant (r = 0.02; p=0.79); a similar weak correlation was found with individual rnfl values. similarly, the correlation between hba1c and total average gcc was weak and not statistically significant (r = -0.06; p=0.56); this similar weak correlation was observed in individual gcc values. the mean ± sd axial length (available for analysis) was 23.15 ± 0.99 mm. after adjusting for demographics and type of eye, we found that even though the average rnfl reduced with each mm increase in axial length, it was not statistically significant (estimate: -5.01, 95% ci: 11.64 to 1.63; p=0.13). similarly, after adjusting for 508 journal of ophthalmic and vision research volume 17, issue 3, october-december 2022 macular oct parameters in dm and glaucoma; shah et al total avg gcc: none vs glaucoma <0.001, glaucoma vs diabetes <0.001, none vs both < 0.001, diabetes vs both < 0.001 sup avg gcc: none vs glaucoma <0.001, glaucoma vs diabetes <0.001, none vs both < 0.001, diabetes vs both < 0.001, glaucoma vs both p,0.05 inf avg gcc: none vs glaucoma <0.001, glaucoma vs diabetes <0.001, none vs both < 0.001, diabetes vs both < 0.001 0.0 20.0 40.0 60.0 80.0 100.0 120.0 normal glaucoma diabetes both total avg gcc sup avg gcc inf avg gcc figure 1. the mean values for ganglion cell complex (gcc) thickness in patients with glaucoma, diabetes, both (diabetes and glaucoma), and none (172 eyes). flv: none vs glaucoma <0.001, glaucoma vs diabetes <0.001, none vs both < 0.001, diabetes vs both < 0.001 glv: none vs glaucoma <0.001, glaucoma vs diabetes <0.001, none vs both < 0.001, diabetes vs both < 0.001 0 1 0 2 0 3 0 4 0 5 0 normal glaucoma diabetes both flv glv figure 2. box plot showing the focal loss of volume (flv) and global loss of volume (glv) parameters in patients with glaucoma, diabetes, both (diabetes and glaucoma), and none (172 eyes). journal of ophthalmic and vision research volume 17, issue 3, october-december 2022 509 macular oct parameters in dm and glaucoma; shah et al table 1. table showing the demographic and clinical characteristics of 172 eyes, india. none (a) diabetes (b) glaucoma (c) both (d) p-value total eyes 43 43 43 43 total individuals 26 28 29 31 age: mean ± sd 53.7 ± 7 61.5 ± 8.9 61.1 ± 10.1 65.4 ± 8.9 <0.001 gender male 16 (62) 19 (68) 15 (52) 22 (71) 0.43 female 10 (38) 9 (32) 14 (48) 9 (29) bcdva (logmar) median (iqr) 0 (0 to 0.18) 0 (0 to 0.18) 0.18 (0 to 0.18) 0.18 (0 to 0.18) 0.31 hba1c: mean ± sd 5.07 ± 0.31 6.10 ± 0.52 5.15 ± 0.34 6.01 ± 0.66 <0.001 intraocular pressure (iop); mean ± sd 16.91 ± 3.13 16.62 ± 3.65 16.07 ± 4.21 17.16 ± 4.62 0.61 bcdva, best corrected distance visual acuity both indicates patients with both diabetes and glaucoma hba1c is glycated hemoglobin table 2. table showing the retinal nerve fibre layer (rnfl) values in patients with diabetes, glaucoma, both, and none (43 eyes each). none (a) diabetes (b) glaucoma (c) both (d) p-value average rnfl 104.1 ± 7.2 99.3 ± 10.2 67.5 ± 13.3 78.5 ± 14.5 b,c,d,e,f average superior rnfl 104.2 ± 16.5 101.6 ± 11.5 69.2 ± 15.9 82.1 ± 16.6 b,c,d,e,f average inferior rnfl 101.7 ± 7.7 97.0 ± 10.5 65.9 ± 13.0 74.9 ± 13.7 b,c,d,e,f superior rnfl 127.3 ± 11.7 121.4 ± 16.3 80.0 ± 20.7 95.5 ± 23.1 b,c,d,e,f temporal rnfl 78.1 ± 8.9 74.9 ± 10.9 58.9 ± 15.6 64.6 ± 11.3 b,c,d,e inferior rnfl 128.5 ± 11.3 120.5 ± 15.0 76.3 ± 16.3 87.2 ± 20.3 b,c,d,e,f nasal rnfl 83.2 ± 8.8 80.8 ± 11.9 54.7 ± 12.1 66.7 ± 13.8 b,c,d,e,f 𝑎 a vs b <0.05, 𝑏 a vs c <0.05, 𝑐a vs d < 0.05, 𝑑 b vs c < 0.05, 𝑒 b vs d < 0.05, 𝑓 c vs d < 0.05 in average superior rnfl the scan shows the rnfl thickness of entire superior hemisphere (180 degrees) so only 2 values presentaverage superior and average inferior. on the other hand, in a superior rnl thickness, only superior 90 degrees thickness is calculated. foveal thickness is central most thickness of diameter 1mm around the fovea both indicates patients with both diabetes and glaucoma these parameters, the change in total average gcc was -3.29 units (95% ci: -8,53 to 1.95; p=0.21). after adjusting for age, gender, hba1c values, and iop, we found that the average rnfl and total average gcc were significantly lower in the glaucoma group and ‘both’ group as compared with the ‘none’ group. furthermore, rnfl and gcc values in the glaucoma group were significantly lower as compared with the ‘both’ group. there was no significant difference in the average rnfl values and total average gcc between the diabetes group and ‘none’ group. the values of flv and glv were significantly higher in the ‘glaucoma’ group and ‘both’ group as compared with the ‘none’ group. only, the glv was significantly different between the glaucoma group and the ‘both’ group. as with the earlier two parameters (rnfl and gcc), there was no significant difference in the flv and glv values between the diabetes group and ‘none’ group. the foveal value was not significantly different across these four groups. in general, age, hba1c values, and iop were not 510 journal of ophthalmic and vision research volume 17, issue 3, october-december 2022 macular oct parameters in dm and glaucoma; shah et al table 3. table showing the foveal parameters in patients with diabetes, glaucoma, both (diabetes and glaucoma), and none (43 eyes each). none (a) diabetes (b) glaucoma (c) both (d) p-value foveal 244.60 ± 31.61 251.11 ± 20.49 236.00 ± 26.68 244.40 ± 19.03 d superior hemisphere parafoveal 307.69 ± 20.52 306.41 ± 18.48 287.09 ± 20.30 297 ± 21.69 b,d inferior hemisphere parafoveal 307.51 ± 20.78 304.51 ± 19.49 282.09 ± 21.84 290.09 ± 22.75 b,c,d,e temporal parafoveal 297.60 ± 22.45 298.00 ± 19.73 273.67 ± 20.42 283.84 ± 21.77 b,c,d,e superior parafoveal 311.95 ± 19.67 308.67 ± 18.19 289.18 ± 20.26 298.56 ± 22.19 b,d nasal parafoveal 310.81 ± 22.85 309.83 ± 20.54 293.41 ± 22.51 302.48 ± 23.13 b,d inferior parafoveal 310.32 ± 20.04 305.30 ± 19.93 281.16 ± 23.05 289.35 ± 23.70 b,c,d,e superior hemisphere perifoveal 287.65 ± 19.07 280.02 ± 16.94 261.20 ± 19.32 267.00 ± 17.37 b,c,d,e inferior hemisphere perifoveal 279.88 ± 13.22 272.67 ± 17.96 250.37 ± 18.88 254.63 ± 18.39 b,c,d,e temporal perifoveal 274.76 ± 14.23 267.79 ± 17.46 247.79 ± 18.37 252.04 ± 17.91 b,c,d,e superior perifoveal 285.04 ± 18.93 276.27 ± 17.48 257.83 ± 20.16 263.18 ± 17.46 b,c,d,e nasal perifoveal 302.81 ± 20.38 295.95 ± 17.74 274.18 ± 20.42 282.16 ± 19.31 b,c,d,e inferior perifoveal 272.79 ± 12.99 265.25 ± 18.56 242.58 ± 19.60 245.79 ± 18.96 b,c,d,e 𝑎 a vs b <0.05, 𝑏 a vs c <0.05, 𝑐a vs d < 0.05, 𝑑 b vs c < 0.05, 𝑒 b vs d < 0.05, 𝑓 c vs d < 0.05 table 4. table showing the estimates and 95% confidence intervals (ci) multivariate analysis for retinal nerve fibre layer (rnfl), ganglion cell complex (gcc), focal loss of volume (flv), global loss of volume (glv), and foveal in 172 eyes. average rnfl total average gcc focal loss of volume global loss of volume foveal estimate (95% ci) estimate (95% ci) estimate (95% ci) estimate (95% ci) estimate (95% ci) none reference reference reference reference reference diabetes -3.4 (-11.4 to 4.7) -0.8 (-7.3 to 5.8) -0.03 (-2.05 to 1.99) 1.55 (-3.70 to 6.80) 9.43 (-6.36 to 25.23) glaucoma -36.3 (-42.8 to -29.7)* -26.2 (-31.5 to -20.9)* 6.50 (4.88 to 8.13)* 20.98 (16.76 to 25.21)* -3.27 (-16.02 to 9.48) both -24.7 (-32.8 to -16.6) *,𝑎 -17.9 (-24.6 to -11.3)*,𝑎 4.72 (2.66 to 6.77)* 14.84 (9.56 to 20.12)*,𝑎 1.63 (-14.19 to 17.45) age 0.1 (-0.2 to 0.3) 0.1 (-0.1 to 0.3) -0.01 (-0.07 to 0.05) -0.08 (-0.24 to 0.08) 0.25 (-0.23 to 0.73) gender female reference reference reference reference reference male -4.1 (-8.8 to 0.6) -4.4 (-8.3 to -0.6)* 0.79 (-0.40 to 1.97) 3.07 (0 to 6.13)* 12.70 (3.49 to 21.89) hba1c -0.6 (-5.2 to 3.9) -1.8 (-5.6 to 1.9) 0.24 (-0.91 to 1.39) 0.60 (-2.37 to 3.57) -2.25 (-11.16 to 6.4) iop 0.2 (-0.3 to 0.7) -0.3 (-0.8 to 0.1) 0.001 (-0.13 to 0.13) 0.15 (-0.18 to 0.48) 0.11 (-0.81 to 1.03) constant 101.4 (73.3 to 129.4)* 111.6 (88.7 to 134.5)* 0.20 (-6.86 to 7.27) -0.47 (-18.75 to 17.81) 229.96 (175.15 to 284.76) rho 0.76 0.41 0.43 0.65 0.79 * p < 0.05; 𝑎 the values in glaucoma patients are significantly lower compared with both group both indicates patients with both diabetes and glaucoma iop = intraocular pressure journal of ophthalmic and vision research volume 17, issue 3, october-december 2022 511 macular oct parameters in dm and glaucoma; shah et al significantly associated with any of the parameters. gender, however, was associated with some of these parameters; males had significantly lower total average gcc values and higher glv values as compared with females. we have presented all the estimates in table 4. in the subgroup analysis (only on patients in the glaucoma or ‘both’ groups), we found that after adjusting for severity (mild, moderate, severe) and type of glaucoma (open angle/close angle) in addition to the above factors, there were no statistically significant differences in the values of average rnfl (6.6, 95% ci: -1.9 to 15.2; p=0.13), total average gcc (3.6, -95% ci: -2.4 to 9.6; p=0.24), and glv (-3.9, 95% ci: -9.5 to 1.6; p=0.16) in the ‘both group’ when compared with the glaucoma group. the severe glaucoma group however, showed significantly low values of all these parameters. in another subgroup analysis (only patients in the diabetes only or ‘both’ groups), we found that average rnfl (-19.1, 95% ci: -26.1 to -12.1; p<0.001) and total average gcc (-15.9, 95% ci: -21.6 to 10.3; p<0.001) were significantly lower in the ‘both’ group as compared with the diabetes only group. whereas, flv (4.2, 95% ci: 2.7 to 5.7; p<0.001) and glv (11.9, 95% ci: 7.9 to 15.9; p<0.001) were significantly higher in the ‘both’ group as compared with the diabetes only group. duration of diabetes was not significantly associated with any of these parameters. discussion the study found that average rnfl, average gcc, flv, and glv were significantly lower in individuals with glaucoma and those with both glaucoma and diabetes versus the controls or patients with diabetes only. after adjusting for the severity of glaucoma, we did not find any significant differences in the retinal parameters in glaucoma patients with or without diabetes. furthermore, there were no significant differences in average rnfl, average gcc, flv, and glv between controls and diabetes only groups. thus, we found that the presence of diabetes without retinopathy did not have any significant effect on the retinal parameters either in patients who had glaucoma or those who did not have glaucoma. it has been hypothesized that degeneration of retinal neurons and glial cells may play a role in the pathogenesis of diabetic retinopathy and may even occur before the development of aneurysms.[32–34] leakage of serum proteins and lipids in the intraretinal space because of increased retinal vascular permeability in diabetic patients may result in higher values of retinal parameters observed in diabetic patients. araszkiewicz et al found that mean rnfl, and superior and inferior ganglion cell layer (gcl) were significantly thicker in diabetic patients as compared with controls, and were significantly thinner in diabetic patients with retinopathy.[18] a similar finding was also reported by garcia-martin and colleagues;[35] who reported that the gcl thickness was significantly less in patients with diabetes as compared with healthy controls. however, in their study, they found that the rnfl was significantly thinner only in the outer inferior quadrant. another study found that although serum hb1ac levels had a significant negative correlation with the whole rnfl thickness, it was not significantly correlated with other parameters such as average macular gcl and average macular thickness.[36] some authors have suggested that thinning of the inner retina may be seen in patients with diabetes even before changes suggestive of diabetic retinopathy.[37] however, other studies did not find any significant difference in the mean rnfl values between poag patients with and without diabetes, or correlation between rnfl, and diabetic and ocular parameters.[27, 38] as seen in our study, diabetes was not significantly associated with any of these parameters. there were no significant differences between controls and diabetic patients, or between patients who had glaucoma with or without diabetes. furthermore, neither hba1c levels nor the duration of diabetes was significantly associated with any of these parameters. spaide compared the retinal neurovascular parameters in three groups – controls, diabetic patients, and glaucoma patients.[39] the author found that rnfl thickness and gcl volume were significantly lower in the glaucoma group as compared with the healthy controls. however, only gcl volume was significantly lower in diabetics as compared with healthy controls. another study reported there was a linear trend of reduction in the rnfl thickness based on the visual field defects in patients with glaucoma.[40] both of these studies have not used multivariate analysis to estimate the mean differences. in our study, after adjusting for potential confounders (such as 512 journal of ophthalmic and vision research volume 17, issue 3, october-december 2022 macular oct parameters in dm and glaucoma; shah et al age, duration of diabetes, hb1ac levels, iop) we found that there was a significant difference in the retinal parameters between healthy individuals and those with glaucoma, and those with glaucoma and diabetes. however, there were no significant differences between the glaucoma group and those with glaucoma and diabetes. furthermore, we also found that even though there was a significant reduction in the retinal parameters in individuals with severe vf defects, there was no association with iop, duration of diabetes, or hba1c levels. thus, even though similar pathways of neuroretinal inflammation has been proposed in the retinal changes occurring from both glaucoma and diabetes,[41, 42] we did not find the parameters to be significantly altered due to diabetes in individuals with and without glaucoma. we only assessed data at one point in time– a cross-sectional analysis, so as a consequence a longitudinal follow-up study is recommended to identify the trajectory of the changes to the retinal parameters and its association with progression in glaucoma and diabetes. nonetheless, as we have used random effects multivariate models to study the association between retinal parameters and the presence of diabetes, glaucoma, or both, this study is an addition to the existing literature. as discussed in the methods section, these models account for both between-individual and withinindividual variances.[31] the effect of systemic conditions (such as diabetes) on both eyes in the same individual may be correlated; this needs to be considered while modelling for multivariate analysis. we have used models which account for this correlation. a group of diabetic patients with dr and glaucoma together could potentially show that retinal thickening might hide glaucomatous rnfl and gcc thinning; as a result, we did not include these patients in the study. in summary, we found that diabetes without retinopathy did not significantly affect the retinal parameters in patients with glaucoma. furthermore, the values of retinal parameters were not significantly lower in patients with diabetes when compared with healthy controls. we did not find any significant effect of diabetes on rnfl, gcc, and macular thickness parameters. thus, it is less likely that we may overestimate the thickness of these parameters in patients with glaucoma who have concurrent diabetes without retinopathy. references 1. peters d, bengtsson b, heijl a. lifetime risk of blindness in open-angle glaucoma. am j ophthalmol 2013;156:724– 730. 2. quaranta l, riva i, gerardi c, oddone f, floriani i, konstas ag. quality of life in glaucoma: a review of the literature. adv ther 2016;33:959–981. 3. scuderi g, fragiotta s, scuderi l, iodice cm, perdicchi a. ganglion cell complex analysis in glaucoma patients: what can it tell us? eye brain 2020;12:33–44. 4. lee kh, kang mg, lim h, kim cy, kim nr. a formula to predict spectral domain optical coherence tomography (oct) retinal nerve fiber layer measurements based on time domain oct measurements. korean j ophthalmol 2012;26:369–377. 5. gonzalez-garcia ao, vizzeri g, bowd c, medeiros fa, zangwill lm, weinreb rn. reproducibility of rtvue retinal nerve fiber layer thickness and optic disc measurements and agreement with stratus optical coherence tomography measurements. am j ophthalmol 2009;147:1067–1074, 1074.e1. 6. wojtkowski m, srinivasan v, fujimoto jg, ko t, schuman js, kowalczyk a, et al. three-dimensional retinal imaging with high-speed ultrahigh-resolution optical coherence tomography. ophthalmology 2005;112:1734–1746. 7. zeimer r, asrani s, zou s, quigley h, jampel h. quantitative detection of glaucomatous damage at the posterior pole by retinal thickness mapping. a pilot study. ophthalmology 1998;105:224–231. 8. oli a, joshi d. can ganglion cell complex assessment on cirrus hd oct aid in detection of early glaucoma? saudi j ophthalmol 2015;29:201–204. 9. asrani s, challa p, herndon l, lee p, stinnett s, allingham rr. correlation among retinal thickness, optic disc, and visual field in glaucoma patients and suspects: a pilot study. j glaucoma 2003;12:119–128. 10. araie m, saito h, tomidokoro a, murata h, iwase a. relationship between macular inner retinal layer thickness and corresponding retinal sensitivity in normal eyes. invest ophthalmol vis sci 2014;55:7199–7205. 11. mathers k, rosdahl ja, asrani s. correlation of macular thickness with visual fields in glaucoma patients and suspects. j glaucoma 2014;23:e98–104. 12. saeedi p, petersohn i, salpea p, malanda b, karuranga s, unwin n, et al. global and regional diabetes prevalence estimates for 2019 and projections for 2030 and 2045: results from the international diabetes federation diabetes atlas, 9𝑡ℎ edition. diabetes res clin pract 2019;157:107843. 13. martin pm, roon p, van ells tk, ganapathy v, smith sb. death of retinal neurons in streptozotocin-induced diabetic mice. invest ophthalmol vis sci 2004;45:3330– 3336. 14. barber aj. a new view of diabetic retinopathy: a neurodegenerative disease of the eye. prog neuropsychopharmacol biol psychiatry 2003;27:283– 290. 15. cabrera debuc d, somfai gm. early detection of retinal thickness changes in diabetes using optical coherence tomography. med sci monit 2010;16:mt15–21. journal of ophthalmic and vision research volume 17, issue 3, october-december 2022 513 macular oct parameters in dm and glaucoma; shah et al 16. antonetti da, barber aj, bronson sk, freeman wm, gardner tw, jefferson ls, et al. diabetic retinopathy: seeing beyond glucose-induced microvascular disease. diabetes 2006;55:2401–2411. 17. hardie dg, hawley sa, scott jw. amp-activated protein kinase—development of the energy sensor concept. j physiol 2006;574:7–15. 18. araszkiewicz a, zozulińska-ziółkiewicz d, meller m, bernardczyk-meller j, piłaciński s, rogowicz-frontczak a, et al. neurodegeneration of the retina in type 1 diabetic patients. pol arch med wewn 2012;122:464–470. 19. van dijk hw, verbraak fd, kok ph, stehouwer m, garvin mk, sonka m, et al. early neurodegeneration in the retina of type 2 diabetic patients. invest ophthalmol vis sci 2012;53:2715–2719. 20. lee mw, lim hb, kim ms, park gs, nam ky, lee yh, et al. effects of prolonged type 2 diabetes on changes in peripapillary retinal nerve fiber layer thickness in diabetic eyes without clinical diabetic retinopathy. sci rep 2021;11:6813. 21. lim hb, shin yi, lee mw, park gs, kim jy. longitudinal changes in the peripapillary retinal nerve fiber layer thickness of patients with type 2 diabetes. jama ophthalmol 2019;137:1125–1132. 22. de voogd s, ikram mk, wolfs rc, jansonius nm, witteman jc, hofman a, et al. is diabetes mellitus a risk factor for open-angle glaucoma? the rotterdam study. ophthalmology 2006;113:1827–1831. 23. pasquale lr, kang jh, manson je, willett wc, rosner ba, hankinson se. prospective study of type 2 diabetes mellitus and risk of primary open-angle glaucoma in women. ophthalmology 2006;113:1081–1086. 24. chopra v, varma r, francis ba, wu j, torres m, azen sp, et al. type 2 diabetes mellitus and the risk of open-angle glaucoma the los angeles latino eye study. ophthalmology 2008;115:227–232.e1. 25. leske mc, wu sy, hennis a, honkanen r, nemesure b, group be, et al. risk factors for incident open-angle glaucoma: the barbados eye studies. ophthalmology 2008;115:85–93. 26. van dijk hw, verbraak fd, kok ph, garvin mk, sonka m, lee k, et al. decreased retinal ganglion cell layer thickness in patients with type 1 diabetes. invest ophthalmol vis sci 2010;51:3660–3665. 27. akkaya s, can e, öztürk f. comparison of the corneal biomechanical properties, optic nerve head topographic parameters, and retinal nerve fiber layer thickness measurements in diabetic and non-diabetic primary openangle glaucoma. int ophthalmol 2016;36:727–736. 28. takahashi h, goto t, shoji t, tanito m, park m, chihara e. diabetes-associated retinal nerve fiber damage evaluated with scanning laser polarimetry. am j ophthalmol 2006;142:88–94. 29. susanna r jr, vessani rm. staging glaucoma patient: why and how? open ophthalmol j 2009;3:59–64. 30. arintawati p, sone t, akita t, tanaka j, kiuchi y. the applicability of ganglion cell complex parameters determined from sd-oct images to detect glaucomatous eyes. j glaucoma 2013;22:713–718. 31. snijders ta, bosker rj. multilevel analysis: an introduction to basic and advanced multilevel modeling. sage publication; 2004. p. 1–266. 32. gardner tw, antonetti da, barber aj, lanoue kf, levison sw. diabetic retinopathy: more than meets the eye. surv ophthalmol 2002;47:s253–s262. 33. park sh, park jw, park sj, kim ky, chung jw, chun mh, et al. apoptotic death of photoreceptors in the streptozotocin-induced diabetic rat retina. diabetologia 2003;46:1260–1268. 34. peng ph, lin hs, lin s. nerve fibre layer thinning in patients with preclinical retinopathy. can j ophthalmol 2009;44:417–422. 35. garcia-martin e, cipres m, melchor i, gil-arribas l, vilades e, polo v, et al. neurodegeneration in patients with type 2 diabetes mellitus without diabetic retinopathy. j ophthalmol 2019;2019:1825819. 36. gundogan fc, akay f, uzun s, yolcu u, çağ�ltay e, toyran s. early neurodegeneration of the inner retinal layers in type 1 diabetes mellitus. ophthalmologica 2016;235:125– 132. 37. chhablani j, sharma a, goud a, peguda hk, rao hl, begum vu, et al. neurodegeneration in type 2 diabetes: evidence from spectral-domain optical coherence tomography. invest ophthalmol vis sci 2015;56:6333– 6338. 38. takis a, alonistiotis d, panagiotidis d, ioannou n, papaconstantinou d, theodossiadis p. comparison of the nerve fiber layer of type 2 diabetic patients without glaucoma with normal subjects of the same age and sex. clin ophthalmol 2014;8:455–463. 39. spaide rf. measurable aspects of the retinal neurovascular unit in diabetes, glaucoma, and controls. am j ophthalmol 2019;207:395–409. 40. geng w, wang d, han j. trends in the retinal nerve fiber layer thickness changes with different degrees of visual field defects. j ophthalmol 2020;2020:4874876. 41. rubsam a, parikh s, fort pe. role of inflammation in diabetic retinopathy. int j mol sci 2018;19. 42. vohra r, tsai jc, kolko m. the role of inflammation in the pathogenesis of glaucoma. surv ophthalmol 2013;58:311– 320. 514 journal of ophthalmic and vision research volume 17, issue 3, october-december 2022 original article influence of donor thickness on visual acuity in descemet’s stripping automated endothelial keratoplasty tomislav kuzman, md, phd; ana meter, md, phd; miro kalauz, md, phd; sanja masnec, md, phd; ivan škegro, md, phd; ivana jonjić, md department of ophthalmology, university hospital center zagreb, zagreb, croatia orcid: tomislav kuzman: https://orcid.org/0000-0002-7137-5059 ivana jonjic: https://orcid.org/0000-0003-1740-9198 abstract purpose: conventional descemet’s stripping automated endothelial keratoplasty (dsaek) is a corneal transplantation procedure where the patient’s inner dysfunctional layer is replaced with donor lamella. the data currently present in the literature about the correlation between lamellar thickness and visual acuity is sometimes contradictory and lacks clarity. methods: study included 55 eyes that underwent the conventional dsaek procedure. patients had no other comorbidities that could affect visual acuity. data about lamellar thickness and visual acuity were measured six months after surgery with anterior segment optical coherent tomography (a5-oct). results: the results show that visual acuity before surgery improved from 0.82 to 0.25 logmar after surgery. better visual acuity of 0.20 logmar was achieved with postoperative lamellas thinner than 124 μm, while statistically significantly lower visual acuity of 0.29 logmar was gained with postoperative lamellas thicker than 124 μm. conclusion: our results suggest that the goal after conventional dsaek is to have postoperative lamellas thinner than 124 μm in the eye, as this will result in better postoperative visual acuity. this value represents the optimal thickness for conventional dsaek surgery that could minimize tissue loss for eye banks and surgeons may experience fewer problems during surgery, while obtaining good final visual acuity. keywords: cornea; corneal transplantation; descemet stripping endothelial keratoplasty; fuchs’s endothelial dystrophy j ophthalmic vis res 2022; 17 (4): 462–469 462 © 2022 kuzman et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i4.12296&domain=pdf&date_stamp=2019-07-17 donor thickness and va in dsaek ; kuzman et al introduction the first contact with the outside world through light transition begins in the cornea which also acts as the first barrier against infection. thus, millions of people around the world who suffer from corneal scarring may experience total or partial vision loss if remain untreated.[1] cornea is a multilayered organ composed of the epithelium, stroma, and endothelium. the corneal epithelium is the most anterior nonkeratinized, five to six cells thick layer.[1] the stroma is resilient, collagenous tissue arranged in sheets of fibrils called lamellae. the corneal endothelium is the last but not the least barrier comprising one layer of the cells incapable to regenerate after damage. the most common diseases causing endothelial damage are fuchs’s endothelial dystrophy and pseudophakic bullous keratopathy. fuchs’s endothelial dystrophy is a slowly progressive disease that usually affects both eyes; more common in women in later life. the key pathophysiological moment is the decay of the endothelial cells that causes increased accumulation of fluid and subsequently edematous stroma leading to cloudy cornea. the pathophysiological mechanism responsible for bullous keratopathy is the inability of the corneal endothelium to maintain a normally dehydrated cornea. the corneal endothelium trauma can occur after cataract surgery, excessive flow of fluid during surgery, high dissipated ultrasound energy during emulsification of hard cataracts or after applying intracameral agents.[2–4] the term pseudophakic bullous keratopathy is used in the occurrence of bullous keratopathy in patients who have had intraocular lens insertion after phacoemulsification (phaco) surgery. the innovative improvements in corneal transplant surgery has made it possible today to replace the diseased layers of the recipient cornea. correspondence to: ivana jonjić, md. department of ophthalmology, university hospital center zagreb, kišpatićeva st., 12, 10000, zagreb, croatia. email: ivanajonjic91@gmail.com received: 04-03-2021 accepted: 21-03-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i4.12296 lamellar endothelial keratoplasty has replaced penetrating keratoplasty (pk) as the standard for treating endothelial corneal diseases. the most common surgical technique is descemet stripping automated endothelial keratoplasty (dseak) which has rapidly become the preferred alternative to pk because of its smaller incision size, faster rehabilitation, and minimal induction of astigmatism and refractive shift.[5–7] dsaek employs mechanical stripping of the host endothelium and replaces it with a healthy homograft of posterior corneal lenticule harvested using an automated microkeratome.[6] advantage of dsaek over pk includes preservation of biomechanical corneal properties because there is no need for corneal stitches.[8] further development in dsaek graft preparation encouraged toward more delicate and thinner lamellas, so surgeons could use nano-thin (< 50 μm), ultra-thin (< 100 μm), or conventional (> 100 μm) grafts.[9] surgeons’ special requests to eye banks for thin and ultra-thin graft thickness have led to real implications including: increased risks of tissue loss during graft processing, and during the logistics of tissue distribution with increased associated costs and pricing for special tissue processing.[10] over time, there has been a change in the definition of subtypes of the dsaek method depending on the thickness of the lamella. as confirmed by a recent study, the conventional and ultra-thin dsaek methods’ definitions have been confirmed by 56% of experienced surgeons who defined donor lamellar thickness <100 μm as ultrathin dsaek and lamellar thickness >100 μm as the conventional dsaek method. conventional dsaek is the most used keratoplasty procedure in the united states.[11] the data currently present in the literature about the correlation between lamellar thickness and the visual acuity is sometimes contradictory and lacks clarity [table 1]. many authors found that this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: kuzman t, meter a, kalauz m, masnec s, škegro i. influence of donor thickness on visual acuity in descemet’s stripping automated endothelial keratoplasty . j ophthalmic vis res 2022;17:462–469. journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 463 https://knepublishing.com/index.php/jovr donor thickness and va in dsaek ; kuzman et al there is correlation between final visual acuity and thickness of donor lamella, concluding that transplanting thinner donor lamellas result in better visual acuity.[6, 8, 10, 12–14] on the other hand, there are also many authors whose results found no correlation between postoperative lamellar thickness and visual acuity after dseak surgery, suggesting that donor graft thickness did not influence final visual acuity.[15–20] some authors, for example, tourabaly et al in recent papers suggest that there were no significant differences in final visual acuity between all investigated groups with varied postoperative lamellar thickness which includes lamellas from nano-thin grafts (15–49 μm) all through to very thick group of grafts (150–250 μm).[20] such significant inconsistencies inspired this research. this research would encourage more accurate and explicit definitions of prospective criteria when selecting the conventional dseak method. in addition, when performing dseak operations, more consideration would be paid toward frame design and focusing on establishing clearer lamellae thickness criteria which would encourage improved tissue safety, technical concerns, and result in better surgical outcomes such as enhanced visual acuity improvement. however, preparation and handling of thinner grafts would not be without challenges;[8] such as determining whether the surgeons in an effort to easily perform surgical procedures while achieving optimal visual outcomes for their patients should insist on creating thinner graft tissue, or determining how thin the donor lamellas should be in order to avoid tissue loss during preparation. methods the study was approved by the ethics committee of university hospital centre zagreb (approved 19.09.2017.; reference number: 02/21 ag). all patients signed the informed consent form to take part in the study. the study was performed according to the icmje recommendations for protection of research participants and adhering to the newest revision of the helsinki declaration. subjects this prospective case series study enrolled 55 eyes of patients. criteria for eligibility were fuchs endothelial dystrophy (26 patients) and pseudophakic bullous keratopathy (29 patients), that underwent dsaek. the average patient age was 70.9 +/– 9.4 years. the study excluded patients with other illnesses that might have affected visual acuity, such as macular degeneration, macular edema, diabetic retinopathy, visual nerve damage, postoperative complications and glaucoma. eyes with preoperative lamellar thickness of <100 μm were also not considered for the study because tissue processing for ultra-thin or nano-thin dsaek is not performed in our eye bank as it requires a more intricate procedure which is different from what is utilized in conventional standard dsaek procedure. patient follow-up was six months with the 100% enrollment all through the study. informed consents were obtained from all patients enrolled in the study. each patient underwent a complete ophthalmology examination preoperatively and at six months post treatment which included: bestcorrected visual acuity (bcva; early treatment diabetic retinopathy study [etdrs] chart – logmar table), goldmann aplanation tonometry, slit-lamp examination and fundus evaluation. information about the thickness of cornea and lamella were examined by anterior segment oct visante (carl zeiss meditec, jena, germany). the corneas were stored in the university hospital centre zagreb eye bank in either hypothermic storage or tissue culture media. corneas in a hypothermic storage medium were stored at a temperature of 4ºc for a maximum of seven days, and were then prepared for lamellar keratoplasty immediately before planned operation. the other corneas were kept in a tissue culture media at a temperature of 31ºc for a maximum of 28 days. during storage in tissue culture, the media was microbiologically controlled. at the end of storage, the endothelial cell viability and morphology were determined. corneas during storage in tissue culture becomes much thicker.[21] to return to the physiological thickness, it must be stored in a transport media containing dextran, for at least for 24 hr before the preparation for lamellar keratoplasty. due to the short corneal validity in the transport media (depending on the manufacturer, alchemy five days, eurobio four days), the cornea were placed in the transport medium only when assigned to patient. the transport medium was kept until the third microbiological control that was taken in the incubator at 31ºc. after taking 464 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 donor thickness and va in dsaek ; kuzman et al table 1. influence of lamella thickness on visual acuity with data regarding to the author, number of patients, method of measurement, and lamellar thickness. author n method avg lamella preop (µm) avg lamella postop (µm) influence of lamella thickness on visual acuity pogorelov et al[6] 15 postop slit-lamp, as oct 191 100 yes maier et al[10] 65 as oct 169 153 yes neff et al[12] 33 as oct / 131 yes dickmann et al[8] 79 as oct / 97 yes busin et al[13] 279 as oct intraop / 78 yes roberts et al[14] 130 preop us post as oct 95 90 yes cleyenenbreugel et al[19] 37 preop us 175 / no woodward et al[16] 64 post as oct 199 165 no terry et al[15] 418 preop us post as oct 162 / no phillips et al[17] 144 preop us post as oct 145 / no ivarsen et al[18] 125 post as oct / 149 (n = 11) 183 (n = 19) no tourabaly et al[20] 150 post as oct / 74 no n, number of patients; us, ultrasound pachymetry; as oct, anterior segment optical coherence tomography; avg lamella preop, average lamellar thickness preoperative; avg lamella postop, average lamellar thickness postoperative table 2. arithmetic mean and associated standard deviation, median and total range of at least to the highest value for variables of best-corrected visual acuity (bcva) before and after surgery (six months follow-up) *p < 0.05. surgery m (sd) c tr (min–max) bcva before 0.15 (0.107) (0.82 logmar) 0.10* 0.50 (0.10–0.60) after six months follow-up 0.57 (0.202) (0.25 logmar) 0.60* 0.75 (0.10–0.60) bcva, best-corrected visual acuity; m, arithmetic mean; sd, standard deviation; c, central value; tr, total range; *p < 0.05 the last microbiological control, it was kept in the thermostat at 22ºc until release. the procedure for preparing corneas for lamellar keratoplasty was performed by specially trained employees using the automatic microkeratome (gebauer slc original, neuhausen, germany). each cornea was placed on the artificial eye chamber filled with corneal storage media to preserve the endothelial cell viability. the epithelium of each cornea was removed to make the cut as precise as possible. the permissible variation of the knife, which was 30 μm, should be considered. the cornea was carefully removed from the artificial eye chamber and stored in a transport media for delivery to transplantation center. all patients underwent dsaek and were operated in university hospital centre zagreb, croatia. the dsaek was performed by one surgeon using a standardized operative technique. all surgeries were performed under general anesthesia. the patients with fuchs dystrophy and cataract underwent combined phacoemulsification and dsaek surgery. descemet stripping was performed under air bubble or with use of viscoelastic during combined procedures. implantation of lamella was performed with use of busin glider to minimize tissue trauma. the lamella was attached with air bubble. journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 465 donor thickness and va in dsaek ; kuzman et al table 3. t-test for differentiated lamellar thickness between preoperative and postoperative determined according to the lamellar thickness. lamellar thickness (µm) n m (sd) t-test bcva ≤124 28 (50.9%) 0.63 (0.162) (0.2 logmar) >124 27 (49.1%) 0.51 (0.221) (0.29 logmar) 2.390* *p < 0.01 t-test, test for paired samples; m, arithmetic mean; sd, standard deviation; bcva, best-corrected visual acuity statistics microsoft spss statistical package for windows was used. results were expressed as mean value and standard deviation (sd). differences between the groups were tested by student’s ttest. a p-value of<0.05 was considered statistically significant. results the current study included a total of 55 eyes of 55 patients (34 female, 61.8%) aged 48 to 73 years. the average age was 70.9 years. table 2 shows the data of descriptive statistics (arithmetic mean and associated standard deviation, median and total range of at least to the highest value) for variables of visual acuity before and six months after surgery. the preoperative bcva ranged from a minimum of 1.00 logmar to a maximum of 0.22 logmar and postoperatively from 1.00 logmar to 0.07 logmar. the average bcva before surgery was 0.82 logmar while after surgery improved to 0.25 logmar which was statistically significant (p < 0.05 t-test for pair samples). subjects were divided in two groups: above or under the donor lamella thickness median after surgery (c = 124 μm) in order to determine whether the visual acuity was statistically significant to the lamellar thickness. we observe them as a group of 50% of the subjects below and the group of 50% of the subjects above the central value (c = 124 μm). table 3 shows 28 subjects (50.9%) had a lamella thickness of 124 μm or less, while for the remaining 27 subjects the lamella was above 124 μm. there was a statistically significant difference in the mean values of these two groups (t = 2.390 p < 0.01). better visual acuity of 0.20 logmar was achieved with lamellas thinner than 124 μm, while statistically significant lower visual acuity was 0.29 logmar for lamellas thicker than 124 μm. discussion the results of our study show that in conventional dsaek, donor lamella thickness correlates with the bcva, suggesting that thinner lamellae may result in better visual acuity. all factors related to visual acuity improvement are being intensively investigated as endothelial keratoplasty has become more widely used today than full corneal pk when treating corneal endothelial disease.[22, 23] dsaek, unlike pk, provides faster recovery, less postoperative eye irritation, less postoperative refractive error, better visual acuity, and less invasive eye surgery.[24] the method of transplanting only the descemet membrane called dmek (descemet membrane endothelial keratoplasty) was introduced as an improvement to the technique of endothelial keratoplasty. in dmek, only descemet’s endothelial membrane without adjacent stroma is transplanted. dmek gives superior results of postoperative visual acuity compared to dsaek or pk.[25, 26] through experience, it became clear that the thin part of the stroma transplanted in dsaek affects the poorer visual acuity compared to dmek. unlike dsaek, dmek although a better method in terms of final visual acuity is not still the most popular due to the long learning curve and the complexity of the operative technique.[25, 27, 28] as dsaek became the method of choice for the treatment of endothelial diseases of majority of surgeons, they tried to reduce the thickness of the lamella to catch up with the visual acuity results achieved with dmek. although many methods have been developed to prepare extremely thin lamellas in a nonstandard way, they have not yet entered into wider application. further developments in the preparation of lamellas for dsaek successfully created thinner lamellas, resulting in lamellas characterized as nano-thin lamellae thinner than ≤50 μm, then ultra-thin lamellae thinner than ≤100 466 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 donor thickness and va in dsaek ; kuzman et al μm, and conventional lamellae thicker than ≥100 μm.[9] in addition to the special techniques required in preparing ultra-thin lamellae, there are increased risks of tissue loss in tissue processing, logistics, and distribution with increased tissue processing costs.[10] our research dealt with the lamellae that define the conventional dsaek method, which is implemented by most eye banks in the world. however, even conventionally prepared lamellas can vary in their thickness from 100 to 250 μm. although it is much safer for eye bank staff to cut a thicker lamella because the possibility of damage to the transplant is less and although it is easier for the surgeon to manipulate the thicker lamella during surgery, it is still debatable as to whether transplanting thicker donor lamellas results in the same visual acuity as the thin ones. studying the literature, we came across several researchers who tried to determine whether there was any correlation between postoperative visual acuity and the thickness of the lamellae used to perform the keratoplasty procedures [table 1]. after processing our results, we concluded that with conventional dsaek, surgeons should strive toward selecting lamellae thinner than 124 μm because better visual acuity is achieved, potential tissue loss during eye bank preparation is not influenced, and is sufficient for safe manipulation during surgery. in our study the improvement of visual acuity was from an average of 0.82 logmar before surgery to 0.25 logmar after surgery [table 2]. however, patients with thinner lamellae below 124 µm achieved better visual acuity of 0.20 logmar than those with lamellae thicker than 124 µm with an acuity of 0.29 logmar [table 3]. the average postoperative visual acuity after dsaek in similar studies generally ranged from 0.45 to 0.15 logmar and corroborates with our results confirming the success of the procedure itself.[29] our results have been deemed comparable with other studies that support the thesis that thinner lamellae selected for dsaek procedures are better for achieving improved visual acuity. our conclusions were similar with pogorelov’s research which included 15 respondents with deturgescence of donor lamellas from 191 to 100 μm six months after surgery.[6] deturgescence of donor lamella begins after implantation in the eye and continues for several months. postoperative thickness of lamella stabilizes six months after surgery, which is why we performed final measurements at that time. although the study of maier et al was retrospective, almost identical results were obtained when compared with our study. their study was conducted on 65 eyes and showed that lamellar thickness of <120 μm correlated with better visual acuity.[10] neff et al also obtained similar results in their retrospective study on 33 eyes, and concluded that donor lamellas below 131 μm resulted in better visual acuity.[12] dekaris et al conducted a similar study and concluded in a 20 subjects that lamellae thinner than 180 μm facilitates better and faster visual recovery than thicker grafts, although measurements were made on the first postoperative day and postoperative deturgescence was not taken into account.[30] there are various studies that suggest that where thinner donor lamellas, in most cases ultra-thin lamellas, were utilized in performing keratoplasty procedures the resultant visual acuity was better as compared to those that utilized thicker lamellas. although comparative research studies focused on using ultra-thin lamellas, it still supports our thesis even though alternative operative techniques were used. busin conducted research in 108 eyes and concluded that visual acuity after ut-dsaek was comparable to dmek but better than conventional dsaek.[13] this research is interesting because it showed that visual acuity was better after the application of thin lamellae. however, this research is related to ultra-thin lamellae prepared by a special technique of double-lamella cutting, which is currently not performed in every eye bank. a similar study was conducted by roberts et al who developed a special technique for preparing ultra-thin lamellae by using the donor tissue dehydration method. this prospective study of ultra-thin lamellae on a group of 130 eyes concluded that thinner donor lamellae transplantation achieve better visual acuity that is close to the results of dmek transplantation.[14] cleynenbreugel et al measured lamella thickness in 37 eyes by ultrasound pachymetry intraoperatively and concluded that lamella thickness had no direct effect on visual acuity or endothelial cell count.[19] this study does not take into account postoperative lamella deturgescence.[31] woodward et al performed a retrospective review on 64 eyes and concluded that there was a poor correlation of bcva at the final visit with preoperative or postoperative lamella thickness.[16] possible reasons for this conclusion can be found in the large postoperative journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 467 donor thickness and va in dsaek ; kuzman et al range of lamellae from 88 to 335 μm, and various postoperative thickness measurement time. terry et al conducted a retrospective study on 418 eyes and obtained similar results to our study for a group of lamellae with a range of 80 to 124 μm that had better visual acuity, but eventually concluded that in a large group of lamellae between 100 and 200 μm donor lamella thickness has a weak association with postoperative visual acuity.[15] the mentioned research was limited as preoperative thickness was measured without taking deturgescence into account. a study conducted by phillips et al on 144 eyes found no correlation between lamella thickness and visual acuity, but the authors compared preoperative thickness of the lamella with postoperative visual acuity.[17] tourabaly et al in recent papers suggest that there were no significant differences in final visual acuity regardless of lamellar thickness from 15 to 250 μm.[20] it can be concluded that there are studies that confirm our research, while those that reflect the opposite are usually comparing preoperative lamella thickness with postoperative visual acuity. these studies that don’t support our research also do not take into account postoperative deturgescence which may contribute toward thinning of the lamella in the eye which stabilizes from four to six months after surgery.[6, 32] some researchers are also focusing on alternative factors that could affect visual acuity in dsaek. ivarsen et al investigated the influence of light scattering and total corneal thickness of the recipient on the visual outcome after dsaek. this study conducted on 125 eyes focused more on corneal densitometry after transplantation, and the authors believe that changes in corneal structure and potential unwanted light scattering at the donor graft and cornea recipient interface are more important for final vision quality than lamella thickness alone.[18] khakshour et al concluded in a group of 16 eyes that there was a significant correlation between lamellae and corneal interface reflection and visual acuity, emphasizing that higher order corneal aberrations have negative influence on visual acuity.[33] graffi et al evaluated the relationship between graft thickness, regularity, and visual acuity in 89 eyes and concluded that dsaek grafts thinner than 100 μm are also more regular than thicker ones, and that in fuchs endothelial dystrophy thinner grafts result in better visual acuity.[34] further research is recommended in determining which qualities of the lamellae, that is, either the thickness of the lamellae and their respective architecture or the interface with the recipient’s cornea are responsible for better visual acuity postoperatively. our results suggest that the goal after conventional dsaek is to have postoperative lamellas thinner than 124 μm in the eye, as this will result in better postoperative visual acuity. this value can be the optimal thickness for conventional dsaek surgery that could minimize tissue loss for eye banks and the surgeons could have fewer problems during surgery, while obtaining good final visual acuity. ethical considerations this study was approved by the ethics committee of university hospital centre zagreb (approved 19.09.2017.; reference number: 02/21 ag). all patients signed the informed consent form to participate in the study. financial support and sponsorship none. conflicts of interest there are no conflicts of interest. references 1. hertsenberg aj, funderburgh jl. stem cells in the cornea. prog mol biol transl sci 2015;134:25–41. 2. hyndiuk ra, schultz ro. overview of the corneal toxicity of surgical solutions and drugs: and clinical concepts in corneal edema. lens eye toxic res 1992;9:331–350. 3. mcdermott ml, edelhauser hf, hack hm, langston rh. ophthalmic irrigants: a current review and update. ophthalmic surg 1988;19:724–733. 4. schultz ro, glasser db, matsuda m, yee rw, edelhauser hf. response of the corneal endothelium to cataract surgery. arch ophthalmol 1986;104:1164–1169. 5. hood ct, woodward ma, bullard ml, shtein rm. influence of preoperative donor tissue characteristics on graft dislocation rate after descemet stripping automated endothelial keratoplasty. cornea 2013;32:1527–1530. 6. pogorelov p, cursiefen c, bachmann bo, kruse fe. changes in donor corneal lenticule thickness after descemet’s stripping automated endothelial keratoplasty (dsaek) with organ-cultured corneas. br j ophthalmol 2009;93:825–829. 468 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 donor thickness and va in dsaek ; kuzman et al 7. melles gr. posterior lamellar keratoplasty: dlek to dsek to dmek. cornea 2006;25:879–881. 8. dickman mm, cheng yy, berendschot tt, van den biggelaar fj, nuijts rm. effects of graft thickness and asymmetry on visual gain and aberrations after descemet stripping automated endothelial keratoplasty. jama ophthalmol 2013;131:737–744. 9. cheung ay, hou jh, bedard p, grimes v, buckman n, eslani m, et al. technique for preparing ultrathin and nanothin descemet stripping automated endothelial keratoplasty tissue. cornea 2018;37:661–666. 10. maier ak, gundlach e, klamann mk, gonnermann j, bertelmann e, joussen am, et al. einfluss der spenderlamellendicke auf die sehschärfe nach “descemet’s stripping automated endothelial keratoplasty” (dsaek). ophthalmologe 2014;111:128– 134. 11. sharma n, maharana pk, singhi s, aron n, patil m. descemet stripping automated endothelial keratoplasty. indian j ophthalmol 2017;65:198–209. 12. neff kd, biber jm, holland ej. comparison of central corneal graft thickness to visual acuity outcomes in endothelial keratoplasty. cornea 2011;30:388–391. 13. busin m, madi s, santorum p, scorcia v, beltz j. ultrathin descemet’s stripping automated endothelial keratoplasty with the microkeratome double-pass technique: two-year outcomes. ophthalmology 2013;120:1186–1194. 14. roberts hw, mukherjee a, aichner h, rajan ms. visual outcomes and graft thickness in microthin dsaek—oneyear results. cornea 2015;34:1345–1350. 15. terry ma, straiko md, goshe jm, li jy, davis-boozer d. descemet’s stripping automated endothelial keratoplasty: the tenuous relationship between donor thickness and postoperative vision. ophthalmology 2012;119:1988– 1996. 16. woodward ma, raoof-daneshvar d, mian s, shtein rm. relationship of visual acuity and lamellar thickness in descemet stripping automated endothelial keratoplasty. cornea 2013;32:e69–e73. 17. phillips pm, phillips lj, maloney cm. preoperative graft thickness measurements do not influence final bscva or speed of vision recovery after descemet stripping automated endothelial keratoplasty. cornea 2013;32:1423–1427. 18. ivarsen a, hjortdal j. recipient corneal thickness and visual outcome after descemet’s stripping automated endothelial keratoplasty. br j ophthalmol 2014;98:30–34. 19. van cleynenbreugel h, remeijer l, hillenaar t. descemet stripping automated endothelial keratoplasty: effect of intraoperative lenticule thickness on visual outcome and endothelial cell density. cornea 2011;30:1195–1200. 20. tourabaly m, chetrit y, provost j, georgeon c, kallel s, temstet c, et al. influence of graft thickness and regularity on vision recovery after endothelial keratoplasty. br j ophthalmol 2020;104:1317–1323. 21. pels e, schuchard y. organ-culture preservation of human corneas. doc ophthalmol 1983;56:147–153. 22. park cy, lee jk, gore pk, lim cy, chuck rs. keratoplasty in the united states: a 10-year review from 2005 through 2014. ophthalmology 2015;122:2432–2442. 23. dickman mm, peeters jm, van den biggelaar fj, ambergen ta, van dongen mc, kruit pj, et al. changing practice patterns and long-term outcomes of endothelial versus penetrating keratoplasty: a prospective dutch registry study. am j ophthalmol 2016;170:133–142. 24. kim se, lim sa, byun ys, joo ck. comparison of longterm clinical outcomes between descemet’s stripping automated endothelial keratoplasty and penetrating keratoplasty in patients with bullous keratopathy. korean j ophthalmol 2016;30:443–450. 25. woo jh, ang m, htoon hm, tan d. descemet membrane endothelial keratoplasty versus descemet stripping automated endothelial keratoplasty and penetrating keratoplasty. am j ophthalmol 2019;207:288–303. 26. heinzelmann s, böhringer d, eberwein p, reinhard t, maier p. outcomes of descemet membrane endothelial keratoplasty, descemet stripping automated endothelial keratoplasty and penetrating keratoplasty from a single centre study. graefes arch clin exp ophthalmol 2016;254:515–522. 27. pereira nc, gomes já, moriyama as, chaves lf, forseto ad. descemet membrane endothelial keratoplasty outcomes during the initial learning curve of cornea fellows. cornea 2019;38:806–811. 28. singh sk, sitaula s. visual outcome of descemet membrane endothelial keratoplasty during the learning curve in initial fifty cases. j ophthalmol 2019;2019:5921846. 29. singh a, zarei-ghanavati m, avadhanam v, liu c. systematic review and meta-analysis of clinical outcomes of descemet membrane endothelial keratoplasty versus descemet stripping endothelial keratoplasty/descemet stripping automated endothelial keratoplasty. cornea 2017;36:1437–1443. 30. dekaris i, pauk m, draca n. pasalic. descemet stripping automated endothelial keratoplasty – is a thinner donor lamella the better choice? j transpl technol res 2012;2:1– 5. 31. romano v, steger b, myneni j, batterbury m, willoughby ce, kaye sb. preparation of ultrathin grafts for descemet-stripping endothelial keratoplasty with a single microkeratome pass. j cataract refract surg 2017;43:12–15. 32. shinton aj, tsatsos m, konstantopoulos a, goverdhan s, elsahn af, anderson df, et al. impact of graft thickness on visual acuity after descemet’s stripping endothelial keratoplasty. br j ophthalmol 2012;96:246–249. 33. khakshour h, nikandish m, salehi m, ghooshkhanehei h, vejdani a. evaluation of interface reflectivity and corneal aberrations following descemet’s stripping automated endothelial keratoplasty. oman j ophthalmol 2019;12:108–113. 34. graffi s, leon p, mimouni m, nahum y, spena r, mattioli l, et al. anterior segment optical coherence tomography of post-descemet stripping automated endothelial keratoplasty eyes to evaluate graft morphology and its association with visual outcome. cornea 2018;37:1087– 1092. journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 469 original article safety and precision of two different flap-morphologies created during low energy femtosecond laser-assisted lasik johannes steinberg1,2,3, md; juliane mehlan1, md; bulat mudarisov1, md; toam katz1,3, md; andreas frings4,5, md; vasyl druchkiv1,2, ms; stephan j linke1,2,3, md 1department of ophthalmology, university hospital hamburg-eppendorf, hamburg, germany 2hamburg vision clinic, hamburg, germany 3carevision gmbh, hamburg, germany 4univ.-augenklinik düsseldorf, düsseldorf, germany 5augenarztpraxis pd dr. frings, nürnberg, germany orcid: johannes steinberg: https://orcid.org/0000-0002-3091-9347 abstract purpose: currently, two major principles exist to create lasik flaps: firstly, a strictly horizontal (2d) cut similar to the microkeratome-cut and secondly an angled cut with a “step-like” edge (3d). the strictly horizontal (2d) cut method can be performed using apparatus such as the low-energy femto ldv z8 laser and its predecessors which are specific to this type. alternatively, the low-energy femto ldv z8 laser’s 3d flap design creates an interlocking flap-interface surface which potentially contributes toward flap stability. in addition, the femto ldv z8 offers flap-position adjustments after docking (before flap-creation). the current study analyzed precision, safety, efficacy, as well as patient self-reported pain and comfort levels after applying two different types of lasik flap morphologies which were created with a low-energy, high-frequency femtosecond (fs) laser device. methods: a prospective, interventional, randomized, contralateral eye, single-center comparison study was conducted from november 2019 to march 2020 at the hamburg vision clinic/ zentrumsehstärke, hamburg, germany. eleven patients and 22 eyes received low-energy fs lasik treatment for myopia or myopic astigmatism in both eyes. before the treatment, the eyes were randomized (one eye was treated with the 2d, the other eye with the 3d method). results: the mean central flap thickness one month after surgery was 110.7 ± 1.6 μm (2d) and 111.2 ± 1.7 μm (3d); p = 0.365 (2d vs 3d). flap thickness measured at 13 different points resulted in no statistically significant differences between any of the measurement points within/between both groups; demonstrating good planarity of the flap was achieved using both methods. despite not being statistically significant, the surgeons recognized an increase in the presence of an opaque bubble layer in the 3d flap eyes during surgery and some patients reported higher, yet not statistically significant, pain scores in the 3d flap eyes during the first hours after the treatment. overall, safetyand efficacy indices were 1.03 and 1.03, respectively. conclusion: in this prospective, randomized, contralateral eye study, the low-energy fs laser yielded predictable lamellar flap thicknesses and geometry at one-month followup. based on these results, efficacy and safety of the corresponding laser application, that is, 2d vs 3d, are equivalent. keywords: cornea; femtosecond laser; flap morphology; lasik; refractive surgery j ophthalmic vis res 2023; 18 (1): 3–14 © 2023 steinberg et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 3 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i1.12720&domain=pdf&date_stamp=2019-07-17 two different femto-lasik flaps; steinberg et al introduction more than 30 years ago, laser in situ keratomileusis, better known as lasik, started its journey to become the most frequently performed treatment to correct ametropia in otherwise healthy eyes. over the past decades, several modifications were made to further improve its safety, efficacy, and predictability, as well as the comfort levels for both patients and surgeons.[1, 2] one of the improvements was to create a highly precise lasik flap with a femtosecond (fs) laser to reduce variations in terms of flap thickness (ft) and flap-related complications when compared to microkeratome-created flaps.[3, 4] in addition, the fs laser enables different flap-morphology designs to potentially further improve the safety of the surgery. currently, two methods exist to create lasik flaps: firstly, a strictly horizontal two-dimensional (2d) flapcutting geometry, comparable to that of the microkeratome and secondly, a three-dimensional (3d) flap-cutting geometry which is in essence a combination of the horizontal cut and an angled side-cut, leading to a “step-like” edge. the first option is only possible with the use of the lowenergy femto ldv z8 laser (ziemer ophthalmic systems ag, switzerland) and its predecessors. whilst the 3d method creates a perfectly fitting angled flap, the interface morphology is believed to contribute toward flap stability and might also lead to a decreased number of flap striae and/or epithelial ingrowth.[5–7] however, due to the entrapped air emerging during the fs-laser “cutting” process of the horizontal flap-interface, the occurrence of opaque bubble layers (obl) increases and potential tissue bridges might also occur in the 3d-flaps.[8] therefore, the ldv z8 fs laser creates additional “venting tunnels” during the 3d flap preparation, which lead correspondence to: johannes steinberg, md. department of ophthalmology, university hospital hamburg-eppendorf, martinistr. 52, hamburg 20251, germany. e-mail: steinberg@zentrumsehstaerke.de received: 01-09-2021 accepted: 21-03-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i1.12720 the gas formed during the flap-cutting process into the direction of the flap bed downward and outward, to allow the gas to dissipate out of the stroma. several ft predictability (intended versus achieved) comparisons were made in the past, where multiple fs lasers were used and were responsible for creating the flaps.[9–11] however, the current study was done to analyze the predictability, precision, safety, efficacy, as well as the patients’ pain and comfort levels when comparing the application of two different flap morphologies which were both created using the same low-energy, high-frequency fs laser. methods this single-center (hamburg vision clinic, hamburg, germany), prospective, interventional, randomized, contralateral eye study was conducted from november 2019 to march 2020. the study was registered in clinicaltrials.gov (nct04426175) after hamburg ethics committee approval and performed in accordance with the tenets of the declaration of helsinki. all patients signed an informed consent form after being advised in detail about the study rationale. all patients received fs lasik treatment for myopia or myopic astigmatism on both eyes from one of the two trained surgeons (sl/js). the inclusion and exclusion criteria were similar to the criteria defined by the national committee defining the inclusion and exclusion criteria recommendations for refractive surgery in germany (krc). hence, the inclusion criteria were: myopia up to 8 diopters, astigmatism up to 5 diopters, minimal corneal thickness of 480 μm, and a minimum of two weeks of no contact lens wearing. patients with predicted residual stromal thickness (rst) under the flap after ablation of <250 μm, former ocular surgery, ocular diseases (including, but not limited to, signs of keratoconus), this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: steinberg j, mehlan j, mudarisov b, katz t, frings a, druchkiv v, linke sj . safety and precision of two different flap-morphologies created during low energy femtosecond laser-assisted lasik. j ophthalmic vis res 2023;18:3–14. 4 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 https://knepublishing.com/index.php/jovr two different femto-lasik flaps; steinberg et al aged younger than 18 years, and concurrent participation in another ophthalmological clinical study were excluded. just before the treatment commenced, every patient was assigned according to our randomization list, those with a 2d flap created in one eye and those with a 3d-flap creation in the other eye. schematic drawings of the morphology and geometry of both flap designs are displayed in figures 1 (2d) and 2 (3d). in our study, the option of two venting tunnels (3d flap) was chosen [figure 2]. in all eyes, the flap was created with the femto ldv z8 (ziemer ophthalmic systems ag, port) with a target thickness of 110 μm along with a superior hinge configuration. the subsequent excimer laser ablation was performed with the wavelight® ex500 excimer laser (alcon fort worth, usa). an optical coherence tomography (oct) image for flap visualization can be displayed, at the surgeon’s discretion, on the screen before and/or after the flap resection. before flap creation, flap visualization may serve as an optional safety measure confirming the flap’s positioning with respect to the bowman’s layer and the stroma, or, post flap-creation, where the presence of gas bubbles can be assessed as an additional safety measure before flap lifting [figure 3]. in addition, the intraoperative oct feature can be useful for the visualization of the applanation area. antibiotic eyedrops were instilled for one week, while steroids and lubricants were reduced gradually over the course of one month. the primary objective of this study was to compare central ft predictability in 110 µm lasik flaps between 2d and 3d flap geometry groups with spectral domain anterior segments (as)oct (maestro 1, topcon medical systems tokyo, japan) performed one month postoperatively. after measuring the cornea with the oct using a scan protocol consisting of 12 b-scans in a radial pattern, the anterior surface was automatically marked in the image by the device. three centrally located manual thickness measurements from the anterior surface to the interface were done and the average value was noted. secondary objectives of the study were to assess the following parameters: postoperative flap planarity with as-oct (maestro 1, topcon, japan) at one month follow-up. after measuring the cornea with the oct using a scan protocol consisting of 12 b-scans in a radial pattern, the anterior surface was automatically marked in the image by the device. then, three manual thickness measurements from the anterior surface to the interface were done in 12 different measurement points as displayed in figure 4. for every measurement point, three consecutive measurements were done and the average was noted. subjective intraoperative flap morphology assessment included: stromal bed quality, ease of flap lifting, and presence of obl. the grading was given by the surgeon directly after the completion of the treatment and was based on their assessment during/after the flap lift. self-reported pain perception and visual experience with 2d and 3d flap geometries during the early postoperative period. during the one-day follow-up examination, patients were asked to respond to three different questions. safety and efficacy index (ei) defined as the best-corrected visual acuity (bcva) after treatment divided by corrected distance visual acuity (cdva) before treatment (bcva post/bcva pre), and uncorrected visual acuity (ucva) after treatment divided by bcva before treatment (uncorrected distance acuity (udva) post/bcva pre), respectively, were calculated. statistical analysis statistical analyses were performed using the sas® software version 9.4 and r software (https://www.r-project.org). a two-sided t-test was used to test the primary hypothesis. further two-sided t-tests were used to test the difference between the 2d and 3d flap geometries for continuous parameters, while fisher’s exact test was used to test categorical parameters. in the case of multiple comparisons (for instance, between the regions or distances) the p-values were adjusted with holm’s method. the sample size was estimated using nquery® v4.0. results eleven patients (22 eyes) were included in our study. seven (63.6%) patients were female, while four (36.4%) were male. the mean age journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 5 two different femto-lasik flaps; steinberg et al at the time of surgery was 37.27 ± 10.32 years (range: 21 to 54). preoperative refraction and corneal thickness data are displayed in table 1. none of the analyzed demographic, refractive or tomography parameters, displayed statistically significant differences between the 2d and 3d group (for all p > 0.05). primary objective postoperative central ft for the 2d and 3d cutting geometries were measured at the one-month follow-up visit. target ft was 110 µm. the results are displayed in table 2. figure 4 displays the differences from the target ft (110 µm). based on the equivalence test and the null-hypothesis test combined, we can conclude that the observed effect is statistically not different from zero nor statistically equivalent to zero for 2d and 3d cutting geometries. at the one-month follow-up visit, the mean central ft ± sd measured for 2d geometry flaps was 110.67 ±1.60 μm, and for the 3d geometry flaps was 111.21 ±1.65 μm. the mean difference ± sd between the target and achieved ft for each individual cutting geometry group was 0.67 ± 1.60 µm (2d) and 1.21 ± 1.65 µm (3d). although the 2d cutting geometry group showed a lower mean difference in terms of ft predictability, the difference was not statistically significant (p = 0.440). secondary objectives the results of the secondary objectives are displayed in tables 3–5. concerning postoperative flap planarity at the one-month follow-up visit measured with as-oct; for both 2d and 3d flap cut geometry groups, a series of three consecutive thickness measurements were taken at four distinct measurement points (±1, ±2, and ±3 mm from the center) along four different meridians (further called subgroups), namely: superior, inferior, nasal, and temporal [figure 5]. the mean values were taken for each point and then the averages of the means were compared in terms of subgroups. data of the respective means and overall averages were analyzed [table 3]. for our analyses, we allocated the measurement points to four subgroups: superior, inferior, nasal, and temporal. when comparing these subgroups, we couldn’t demonstrate any statistical relevant differences among the four subgroups for either 3d or 2d flaps, neither when comparing the totals of the four subgroups of 3d with the totals of the four subgroups of 2d (all p > 0.05). we also combined all horizontal and all vertical measurement points to analyze potential differences between the 2d and 3d flaps. again, no statistically significant differences could be demonstrated (all p > 0.05). furthermore, no statistically significant changes from the central to the periphery of the cornea (i.e., potentially increasing or decreasing flap thickness) could be demonstrated either for 2d or 3d flaps. regarding our secondary objective of analyzing subjective intraoperative flap morphology, we used a predefined grading and surgeon’s assessment during and after the procedure where the flaps were lifted [table 4]. eight eyes (72.7%) in the 2d group which were compared to five eyes (45.5%) in the 3d group presented with a flat stromal bed (p = 0.387). despite not being statistically significant, both surgeons found corneal stromal striae in two eyes (18.2%) (p = 0.476) and “rastered” interface in one eye (9.1%) (p = 1.000) in the 3d geometry group as compared to none in the 2d flap-cutting geometry group. surgeons were able to easily lift nine flaps (81.8%) from the 2d and six flaps (54.5%) from the 3d group (p = 0.361). no obl was found in nine eyes that received 2d flaps (81.8%) or six eyes that received 3d flaps (54.5%), respectively (p = 0.453). regarding the secondary objective of this study, analyzing postoperative subjective pain and visual perception, a questionnaire was completed during the first day follow-up visit where patients assessed their own visual quality and perceived pain levels during the first hours after the treatment. whereas more than half of the eyes treated with either a 2d or 3d flap morphology experienced none to moderate pain, reported during the first hours after surgery, higher pain scores were reported for some of the eyes treated with a 3d flap. in summary, pain perception was slightly better in the 2d group, however, it was not statistically significant. regarding the visual assessment right after the treatment and at the beginning of the first day after surgery, no statistically or clinically 6 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 two different femto-lasik flaps; steinberg et al significant differences could be demonstrated. detailed results are displayed in table 5. the patients were also asked to give an assessment of their visual quality and pain level at the one-week follow-up visit. none of the patients reported any noticeable differences when comparing their 3d and 2d-flap eyes. table 6 provides a better representation of the functional parameters. preoperative and postoperative ucva data for the respective followup examinations are presented, and converted from snellen notation to the logarithm of the minimum angle of resolution (logmar). the mean ucva (n = 22) improved significantly (p < 0.0001) between the preoperative visit 0.97 ± 0.36 logmar and the one-month follow-up visit 0.00 ± 0.02 logmar. safety and efficacy for all eyes combined, the overall mean ucva (n = 22) measured at one month after treatment was 0.00 ± 0.02 logmar. the safety index (si) was 1.03, and the ei was 1.03 with no statistically significant differences between the 2d and 3d flap groups (all p > 0.05). discussion published literature comparing microkeratome and fs laser created flaps is not a novelty anymore.[3, 4, 13] correspondingly, various publications exist comparing the predictability of ft measurements among fs lasers.[9, 11, 14] to the best of our knowledge, this is the first study that compared the predictability of two flap-cutting geometries (2d vs 3d) created by the same low-energy high-spot density fs laser. in this prospective, randomized, contralateral, single-center study, we were able to demonstrate central ft predictability and discuss the objective and subjective intraand postoperative flap morphology, as well as patients’ visual and pain experience between the two groups. furthermore, it was verified that both geometry groups displayed comparable overall linear and planar fts from the center to the periphery of the cornea. concerning ft predictability in other studies, a retrospective series published in 2013 by cummings et al where 120 µm intended thickness flaps were created by the fs200 fs laser (alcon, wavelight, fort worth, usa) in 162 eyes and measured by the as-oct (3d oct-2000, topcon medical systems tokyo, japan) postoperatively, showed a mean ft of 121.94 ± 10.52 µm.[9] in another prospective study, 87 consecutive eyes received either 110 or 120 µm intended flaps created by the 200 khz visumax fs laser (carl zeiss meditec, jena, germany). results showed a mean achieved ft of 112.3 ± 3.84 μm (range, 109.6 to 115.1) and 122.2 ± 3.93 μm (range, 115.8 to 129.0 μm) at one-month follow-up visit for the respective intended flaps created.[15] in a study where 110 µm intended flaps were measured with fd-oct one week postoperatively, results showed a mean central ft of 105.4 ± 3.4 µm for fs200 and 110.8 ± 3.9 µm for visumaxcreated flaps which was found to be statistically significant; p < 0.01.[16] in the current study, although the mean central ft measured for 2d geometry flaps (110.67 ± 1.60 μm) was closer to the 110 µm target ft as compared to the 3d geometry flaps (111.21 ± 1.65 μm) at one-month follow-up, no statistically significant difference was found between the two groups; p = 0.440. therefore, our results suggest that excellent predictability was achieved regardless of the flap geometry utilized, that is, 2d versus 3d. one of the secondary objectives of our study was to analyze postoperative ft in both groups along 13 different data points across the horizontal and vertical meridians, starting from the center of the cornea to ±1.0, ±2.0, and ±3.0 mm. our results seem to be in line with the literature discussed below: jagow et al demonstrated in their prospective comparative study, where fts were created either by a 60 khz fs laser (intralase, advanced medical optics) or a mechanical microkeratome (zyoptix xp, bausch & lomb) and assessed with an as-oct for 20 points measured from the corneal vertex across each flap, for an intended 100 µm ft. the mean ft achieved ranged between 108 and 124 µm, with up to 16 µm of sd.[17] zheng et al compared flap morphology with the fd-oct (uniformity, accuracy, predictability) of 110 µm intended flaps created by the fs200 (alcon, wavelight, fort worth, usa) (n = 200 eyes) and the visumax fs laser (carl zeiss meditec, jena, germany) (n = 200 eyes), one week postoperatively. nine thickness measurements were obtained across the length of the flaps at the meridians of 0º, 45º, 90º, and 135º with the cursor manually placed at ±4, ±3, ±2, and ±1 mm journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 7 two different femto-lasik flaps; steinberg et al table 1. descriptive summary (preoperative refraction and pachymetry) of the 2d and 3d groups. 2d (n = 11) 3d (n = 11) parameter (unit) median (q1/q2) mean ± sd min/max median (q1/q2) mean ± sd min/max sphere (d) –2.00 (–3.25; –1.75) –2.45 ± 1.36 –5.50/–1.0 –2.25 (–4.25; –1.50) –2.61 ± 1.69 –6.25/–0.25 cylinder (d) –0.75 (–1.50; –0.50) –0.93 ± 0.77 –2.75/0.00 –0.50 –1.00; –0.50) –0.79 ± 0.69 –2.50/0.00 se (d) –2.38 (–4.00; –1.88) –2.92 ± 1.43 –6.00/–1.50 –2.62 (–4.63; –1.75) –3.01 ± 1.62 –6.25/–1.00 cct (µm) 566 (531; 591) 564 ± 37 514/642 565 (533; 588) 564 ± 34 516/632 se, spherical equivalent; cct, central corneal thickness p-values from a two-sided t-test = all >0.05 table 2. postoperative central flap thickness measured with as-oct at one-month follow-up visit. 2d 3d p-value∗ characteristics (unit) median (q1/q3) mean ± sd min/max median (q1/q3) mean ±sd min/max flap thickness achieved (µm) 110.3 (109.3/111.7) 110.67 ± 1.60 108.3/114.3 110.7 (110.3/111.3) 111.21 ± 1.65 109.3/114.3 0.440 achieved thickness minus target (µm)* 0.33 (–0.67/1.67) 0.67 ± 1.60 –1.7/4.3 0.67 (0.33/1.33) 1.21 ±1.65 –0.7/4.3 0.440 ∗p-value from a two-sided t-test table 3. mean flap thickness for 2d vs 3d flaps measured with as-oct from central along the superior, inferior, nasal, and temporal meridians at respective points: ±1, ±2, and ±3 mm at one-month follow-up visit. 2d (n = 11) central (µm) mean ± sd ±1 mm (µm) mean ± sd ±2 mm (µm) mean ± sd ±3 mm (µm) mean ± sd superior 110.67 ± 1.60 111.33 ± 1.56 111.85 ± 2.34 111.58 ± 2.80 inferior 110.67 ± 1.60 111.61 ± 2.27 112.18 ± 1.82 111.76 ± 2.18 nasal 110.67 ± 1.60 111.21 ± 2.30 110.91 ± 2.10 111.18 ± 2.72 temporal 110.67 ± 1.60 111.12 ± 2.58 111.30 ± 1.64 110.70 ± 2.35 overall average 110.67 ± 1.60 111.32 ± 1.92 111.56 ± 1.69 111.30 ± 2.17 3d (n = 11) central (µm) mean ± sd ±1 mm (µm) mean ± sd ±2 mm (µm) mean ± sd ±3 mm (µm) mean ± sd superior 111.21 ± 1.65 111.70 ± 1.74 111.85 ± 1.77) 111.58 ± 2.53 inferior 111.21 ± 1.65 112.85 ± 1.98 111.73 ± 2.11 111.91 ± 2.23 nasal 111.21 ± 1.65 111.33 ± 2.08 111.06 ± 2.63 112.52 ± 2.83 temporal 111.21 ± 1.65 112.76 ± 3.30 111.33 ± 2.86 111.55 ± 2.37 overall average 111.21 ± 1.65 112.16 ± 1.85 111.49 ± 2.03 111.93 ± 2.24 8 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 two different femto-lasik flaps; steinberg et al table 4. summary of intraoperative assessments: stromal bed quality, ease of flap lift, and presence of opaque bubble layer (obl). characteristics category 2d 3d p-value* stromal bed quality, n (%) smooth 8 (72.7) 5 (45.5) 0.387 tissue bridges 3 (27.3) 3 (27.3) 0.659 lines 0 2 (18.2) 0.476 rastered 0 1 (9.1) 1.000 ease of flap lift, n (%) easily 9 (81.8) 6 (54.5) 0.361 sticky 2 (18.2) 5 (45.5) presence of obl, n (%) no obl 9 (81.8) 6 (54.5) 0.453 <30% of flap surface 1 (9.1) 2 (18.2) 30–40% of flap surface 1 (9.1) 3 (27.3) *p-value from a fisher’s exact test for stromal bed quality: because one eye could display more than one variable, p-values were given for each variable comparing 2d and 3d. in all other analyzes, the overall p-value for the fisher’s exact test was given. table 5. summary of postoperative self-reported pain perception and visual experience stratified between 2d and 3d flap geometry groups on day-one follow-up visit. category 2d(n = 11) 3d(n = 11) overall(n = 22) p-value* “rate your pain in the right eye/left eye during the hours after the treatment.” no pain 4 (36.4) 3 (27.3) 7 (31.8) 0.821 mild pain 2 (18.2) 1 (9.1) 3 (13.6) moderate pain 3 (27.3) 2 (18.2) 5 (22.7) severe pain 2 (18.2) 4 (36.4) 6 (27.3) intense pain 0 1 (9.1) 1 (4.5) rate your first visual experience immediately after treatment: right eye/left eye. as good as with glasses before treatment 2 (18.2) 2 (18.2) 4 (18.2) 1.000 almost as good as with glasses before treatment 2 (18.2) 3 (27.3) 5 (22.7) a little blurred 4 (36.4) 3 (27.3) 7 (31.8) blurry like seeing through foggy glasses 3 (27.3) 3 (27.3) 6 (27.3) “rate your visual acuity a few minutes after awakening this morning for the right and the left eye.” as good as with glasses before treatment 5 (45.5) 5 (45.5) 10 (45.5) 1.000 almost as good as with glasses before treatment 2 (18.2) 3 (27.3) 5 (22.7) a little blurred 4 (36.4) 3 (27.3) 7 (31.8) ∗p-value from a fisher’s exact test journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 9 two different femto-lasik flaps; steinberg et al figure 1. flap morphology in planar (2d) flaps. side view on the 2d lasik flap. the flap is generated after applanation in a strictly horizontal plane leading to a minimum-angled flap edge after the applanation (a & b). planar rim cut at approximately 30º (c). source: femto ldv z8; surgical procedure manual cornea; ziemer ophthalmology. figure 2. flap morphology in planar (3d) flaps. side (upper row) and top (lower row) views on the 3d lasik flap. the flap is generated after applanation combining a strictly horizontal plane with a 90º side cut (a & b). additional venting tunnels (optionally 2–5 tunnels, see lower row) have to be created to release the otherwise enclosed air. source: femto ldv z8; surgical procedure manual cornea; ziemer ophthalmology. from the center of the flap. in total, 36 thickness measurements were analyzed for each flap. the mean ft achieved with the fs200 was 105.7 ± 2.6 µm, which was significantly less (p < 0.01) than for the visumax (111.2 ± 2.3 µm).[17] although both lasers used the 3d cutting geometry, the visumax results were found to be closer when corresponding to our 3d group. in our study, seeing that no statistically significant differences were found between the central and overall ft (13 points) results for both cutting geometry groups, we can conclude that both 2d and 3d flap-cutting geometries demonstrated high precision in terms of fts. regarding our subjective intraoperative flap morphology findings, despite no statistically significant differences between both groups, both surgeons (sl, js) noted from a clinical perspective a tendency toward a more homogeneous interface with a less adhesive flap and less obl in the 2d flap geometry. regarding postoperative selfreported pain perception and visual experience stratified between 2d and 3d flap geometry groups, the patients were unaware of which eye received 2d or 3d flap morphology (i.e., blinded study design). for seven eyes (31.8%) “no pain” was reported. four of them belonged to the 2d group. however, despite not being statistically significant in our 22 eyes-analyses, higher pain scores were reported for some of the eyes treated with the “3d-flap”. regarding the subjective visual quality assessment, no differences could be identified. minutes after waking up the first morning post operation, for 10 eyes (equally distributed between 10 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 two different femto-lasik flaps; steinberg et al figure 3. intraoperative oct before flap lifting. the yellow line defines the cut position. figure 4. the mean differences of flap thickness from 110 µm. squares: mean differences from 110 µm. dashed lines equivalence bounds (–4.58; 4.58). thick line around differences is tost (two one-sided tests) confidence interval. 2d 90% ci (–0.207; 1.54); 3d 90% ci (0.311; 2.113). thin line nhst (null hypothesis significance test) 95% confidence interval. 2d 95% ci (–0.407; 1.741); 3d 95% ci (0.105; 2.32). 2d and 3d eyes), patients rated their visual acuity to be “as good as with glasses before treatment”. no statistically significant differences between intraoperative flap quality and patient’s perception could be demonstrated during the first hours after the treatment. however, differences between both flap geometry groups regarding a tendency toward more adhesive and more obl-prone flaps, potentially leading to the perceived (patient) discomfort in 3d flaps as compared to 2d flap geometry group, were clinically noticed. furthermore, it is important to keep in mind that the analyses of the intra-op flap-/interface morphology and the patients’ postoperative assessments were secondary objectives of the study. since the power analysis was based on the primary objective, that is, comparing the central ft predictability in both flap geometries and by taking the contralateral character of the study into account, we had to limit the number of eyes included in the study. in case clinically relevant differences regarding subjective pain perception and morphology are to be assessed, bigger sample sizes would be necessary for future investigations. however, due to the low number of eyes included, the fisher’s exact test was used in these analyses. our pvalues > 0.05 indicate no correlation between the different categories and the 2d and 3d flap morphologies. technically, each flap-cutting geometry has its own special advantages. as mentioned, the 2d flap-cutting geometry only exists in the low-energy journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 11 two different femto-lasik flaps; steinberg et al figure 5. schematic illustration to display the four measurement points in each meridian. high-spot density femto ldv z8 laser and its predecessors. due to the nature of the 2d flap configuration, one would expect it to be relatively easy when lifting such a flap. with the femto ldv z8, not only are round flaps (as with the 2d) are a possibility but oval-shaped flaps can also be created with the 3d flap-cutting geometry tool. according to the patient requirements, 3d flap geometries can be resized or repositioned on the patient’s eye, and side cut angles can be programmed from 30º to 150º around the globe. the biggest advantage of the low-energy femto ldv z8 is the additional software option that exists called optima which allows the surgeon to start with a 2d flap approach and switch intraoperatively to a 3d flap-mode after docking. as 2d flaps are generated without an angled site-cut, these flaps have to be created in the center of the applanated corneal surface. adjusting the flap position after applanation would lead to a potentially irregular flap shape and/or a much too small or long hinge-configuration. therefore, no such option for the surgeon exists other than in 3d flap-creation. with the 3d, angled side-cut geometry, even after applanation of the cornea, the surgeon can change settings including the flap position as well as the hinge position based on a live image. as mentioned before, the angled side cut in 3d geometry flaps creates a perfectly fitting angled flap and interface morphology believed to contribute toward flap stability which might lead to a decreased number of flap striae and/or epithelial ingrowth.[5–7] considering the aforementioned advantages and disadvantages of 2d versus 3d flap geometries as well as the flexibility to intraoperatively switch after docking in case the surgeon wants to shift the centration before flap-cutting commences, the low-energy femto ldv z8 seems to be the preferred choice in performing lasik surgeries. one of the limitations of our study was the lack of comparison of the induced corneal higher order aberrations (hoa) due to flap striaes which would be another important parameter when comparing the two flap-cutting techniques. as a result, it is recommended that we research this aspect for follow-up studies. another limitation occurred with our small sample size as we had to limit the number of eyes included in our study to properly achieve our primary objective. in summary, this study compared two different flap morphologies created during lasik, whilst using the same low-energy, high-frequency octequipped fs laser. both the 2d and 3d flap-cutting geometries demonstrated comparable precision and predictability in terms of fts combined with a high safety and efficacy performance. 12 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 two different femto-lasik flaps; steinberg et al table 6. summary of preand postoperative uncorrected visual acuity( logmar). characteristics category 2d(n = 11) 3d(n = 11) overall(n = 22) p-value** preop ucva n (missing) 11 (0) 11 (0) 22 (0) mean (sd) 0.91 (0.32) 1.03 (0.39) 0.97 (0.36) 0.4224 95% ci 0.69; 1.12 0.77; 1.30 0.81; 1.13 median 1.00 1.00 1.00 q1; q3 0.70; 1.10 0.88; 1.10 0.80; 1.10 min; max 0.2; 1.3 0.4; 2.0 0.2; 2.0 one day post-op ucva n (missing) 11 (0) 11 (0) 22 (0) mean (sd) 0.11 (0.08) 0.10 (0.04) 0.11 (0.06) 0.5668 95% ci 0.06; 0.17 0.07; 0.13 0.08; 0.14 median 0.10 0.10 0.10 q1; q3 0.10; 0.18 0.10; 0.10 0.10; 0.10 min; max 0.0; 0.3 0.0; 0.2 0.0; 0.3 one week post-op ucva n (missing) 11 (0) 11 (0) 22 (0) mean (sd) 0.06 (0.08) 0.06 (0.11) 0.06 (0.09) 1.0000 95% ci 0.01; 0.11 0.00; 0.14 0.02; 0.10 median 0.00 0.00 0.00 q1; q3 0.00; 0.10 0.00; 0.18 0.00; 0.10 min; max 0.0; 0.2 0.0; 0.3 0.0; 0.3 one month post-op ucva n (missing) 11 (0) 11 (0) 22 (0) mean (sd) 0.01 (0.03) 0.00 (0.00) 0.00 (0.02) 0.3293 95% ci 0.00; 0.03 0.00; 0.00 0.00; 0.01 median 0.00 0.00 0.00 q1; q3 0.00; 0.00 0.00; 0.00 0.00; 0.00 min; max 0.0; 0.1 0.0; 0.0 0.0; 0.1 p-value* <0.0001 financial support and sponsorship none. conflicts of interest none. references 1. kim ti, alió del barrio jl, wilkins m, cochener b, ang m. refractive surgery. lancet 2019;393:2085–2098. 2. moshirfar m, bennett p, ronquillo y. laser in situ keratomileusis. treasure island, fl: statpearls; 2021. 3. pajic b, vastardis i, pajic-eggspuehler b, gatzioufas z, hafezi f. femtosecond laser versus mechanical microkeratome-assisted flap creation for lasik: a prospective, randomized, paired-eye study. clin ophthalmol 2014;8:1883–1889. 4. pietilä j, huhtala a, mäkinen p, salmenhaara k, uusitalo h. laser-assisted in situ keratomileusis flap creation with the three-dimensional, transportable ziemer femto ldv model z6 i femtosecond laser. acta ophthalmol 2014;92:650–655. 5. dos santos am, torricelli aa, marino gk, garcia r, netto mv, bechara sj, et al. femtosecond laser-assisted lasik flap complications. j refract surg 2016;32:52–59. 6. güell jl, elies d, gris o, manero f, morral m. femtosecond laser-assisted enhancements after laser in situ keratomileusis. j cataract refract surg 2011;37:1928– 1931. 7. letko e, price mo, price fw jr. influence of original flap creation method on incidence of epithelial ingrowth after journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 13 two different femto-lasik flaps; steinberg et al lasik retreatment. j refract surg 2009;25:1039–1041. 8. mastropasqua l, calienno r, lanzini m, salgari n, de vecchi s, mastropasqua r, et al. opaque bubble layer incidence in femtosecond laser-assisted lasik: comparison among different flap design parameters. int ophthalmol 2017;37:635–641. 9. cummings ab, cummings bk, kelly ge. predictability of corneal flap thickness in laser in situ keratomileusis using a 200 khz femtosecond laser. j cataract refract surg 2013;39:378–385. 10. prakash g, agarwal a, yadav a, jacob s, kumar da, agarwal a, et al. a prospective randomized comparison of four femtosecond lasik flap thicknesses. j refract surg 2010;26:392–402. 11. zheng y, zhou y, zhang j, liu q, zhai c, wang y. comparison of laser in situ keratomileusis flaps created by 2 femtosecond lasers. cornea 2015;34:328–333. 12. eldaly zh, abdelsalam ma, hussein ms, nassr ma. comparison of laser in situ keratomileusis flap morphology and predictability by wavelight fs200 femtosecond laser and moria microkeratome: an anterior segment optical coherence tomography study. korean j ophthalmol 2019;33:113–121. 13. reinstein dz, sutton hf, srivannaboon s, silverman rh, archer tj, coleman dj. evaluating microkeratome efficacy by 3d corneal lamellar flap thickness accuracy and reproducibility using artemis vhf digital ultrasound arc-scanning. j refract surg 2006;22:431–440. 14. ahn h, kim jk, kim ck, han gh, seo ky, kim ek, et al. comparison of laser in situ keratomileusis flaps created by 3 femtosecond lasers and a microkeratome. j cataract refract surg 2011;37:349–357. 15. ju wk, lee jh, chung ty, chung es. reproducibility of lasik flap thickness using the zeiss femtosecond laser measured postoperatively by optical coherence tomography. j refract surg 2011;27:106–110. 16. zheng y, zhou y, zhang j, liu q, zhai c, wang y. comparison of laser in situ keratomileusis flaps created by 2 femtosecond lasers. cornea 2015;34:328–333. 17. von jagow b, kohnen t. corneal architecture of femtosecond laser and microkeratome flaps imaged by anterior segment optical coherence tomography. j cataract refract surg 2009;35:35–41. 14 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 original article relationship between ocular surface alterations and concentrations of aerial particulate matter maría a gutiérrez1,2, phd, fiacle; daniela giuliani2, bs; atilio a porta2, phd; darío andrinolo1, phd 1university extension environmental programme (paeu), faculty of exact sciences, national university of la plata, buenos aires, argentina 2center for environmental research (cim), unlp conicet, buenos aires, argentina orcid: maría a. gutiérrez: https://orcid.org/0000-0002-3491-6151 abstract purpose: to evaluate ocular surface alterations in two populations at different exposure levels to particulate matter (pm) in their living and work environments. methods: a cross-sectional study was conducted, including 78 volunteers from argentina who lived and worked under different pollution levels in an urban (u; n = 44) or industrial zone (i; n = 34). mean exposure level to pm was evaluated. responses to the ocular symptom disease index and mcmonnies questionnaire were obtained from all subjects. subsequently, an assessment through the schirmer i test (st), slit lamp microscopy, vital staining, and tear breakup time was conducted. statistical analyses with chi-square and bartlett’s tests, as well as student’s t-tests and principal component analysis (pca), were performed. results: particles of size < 2.5 μm (pm2.5) level was significantly higher in the i group than the u group (p = 0.04). ocular surface parameters including bulbar redness, eyelid redness, and the degree of vital staining with fluorescein (sf) and lissamine green (slg) exhibited difference between the groups. with regards to the tear film, statistically significant differences in the st value and meibomian gland dysfunction between the groups were detected (p = 0.003 and p = 0.02, respectively). conjunctival sf and slg, and st values were identified as factors which could distinguish groups exposed to different pm levels. conclusion: subjects exposed to higher levels of pm in the outdoor air presented greater ocular surface alterations. thus, st, sf, and slg values could be used as convenient indicators of adverse health effects due to exposure to air pollution. keywords: environmental; ocular surface; particulate matter; schirmer i test; vital staining j ophthalmic vis res 2019; 14 (4): 419–427 correspondence to: maría a. gutiérrez, phd, fiacle. university extension environmental programme (paeu), faculty of exact sciences, national university of la plata, 47 and 115 st., buenos aires 1900, argentina. e-mail: mgutierrez@biol.unlp.edu.ar received: 08-11-2018 accepted: 11-06-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i4.5441 introduction the ocular surface comprises various structures in contact with the environment, namely the palpebral and bulbar conjunctival epithelium, corneoscleral limbus, corneal epithelium, and tear film, which provide anatomical, physiological, and immunological this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: gutiérrez ma, giuliani d, porta aa, andrinolo d. ocular surface changes due to air particles. j ophthalmic vis res 2019;14:419–427. © 2019 journal of ophthalmic and vision research | published by knowledge e 419 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5441&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr ocular surface sensitivity to particulate matter; gutiérrez et al protection. the adnexal structures, including the anterior lamellae of the eyelids, eyelashes, meibomian glands, and lacrimal system, are essential for appropriate protection and function of the ocular surface.[1] the ocular surface functions in generating good visual quality, nourishing and lubricating tissues, and protecting the eye against cellular debris and foreign particles.[2] it can be affected by trauma, infections, or environmental factors, which may compromise the structural integrity of its components. this can lead to various forms of corneal and conjunctival dysfunction such as increasing order of severity, pain and itching,[3] mild corneal abrasion to severe loss of stem cells, decreased vision,[4] and blindness.[5] ocular surface disorders occur in patients with various conditions including limbal stem-cell deficiency and ocular surface disease (osd) due to systemic diseases.[1] dry eye is an ocular surface disorder which has a prevalence rate of 5 to 50% worldwide. dry eye is considered a multifactorial osd characterized by a loss of homeostasis of the tear film, ocular symptoms of instability and hyperosmolarity of the tear film, and inflammation. ocular surface damage and sensorineural anomalies may have etiological roles in this disease.[6] clinically, dry eye is characterized by a loss of tear volume, rapid breakup of the tear film, and increased evaporation of tears from the ocular surface.[7] recent studies have demonstrated subclinical alterations of the ocular surface that can be attributed to air pollution. these include changes in the tear break-up time (tbut) and schirmer i test (st) value, [8–12] the incidence of palpebral affectations such as blepharitis,[13] and effects on the ocular mucosa that indicate a significant positive association between exposure to the air pollutant nitrogen dioxide and goblet cell hyperplasia in the human conjunctiva.[14] additionally, reports have indicated that the presence of high concentrations of air pollutants such as nitric oxide, nitrogen dioxide, or sulfur dioxide makes the tear film increasingly acidic. collectively, these findings suggest that symptoms of ocular discomfort and alterations in the tbut could be used as bioindicators of the adverse health effects of air pollution due to vehicular traffic.[10] the mechanisms by which air pollutants interact with the tear film, cornea, and conjunctiva remain unclear, although increases in muc5ac mrna level upon chronic exposure to particulate matter (pm) and nitrogen dioxide have been implicated.[12] further studies focused on the compensatory mechanisms of the ocular surface to changes induced by chronic exposure to air pollution and patient susceptibility are required to enable early treatment that prevents chronic disorders and promotes eye health. this study aimed to evaluate ocular surface alterations in two populations at different exposure levels to pm in their living and work environments. methods study population a total of 78 volunteers between 18 and 62 years old, who lived and worked in la plata (n = 44) and ensenada (n = 34), two regions in argentina with different pollution levels, were included in this study. la plata is the capital of the province of buenos aires, which has a high vehicle-to-person ratio and was considered the urban zone (u) in this study. ensenada is a city with high levels of air pollution, mainly due to industrial activity, and was considered the industrial zone (i) [figure 1]. both study areas have similar meteorology due to geographical proximity (6 km), with north and north-east winds at an average speed of 15.9 km/h, a humidity of 68.9%, and a temperature of 18.2ºc. the sex distribution of both populations was 45% female and 55% male, and the ages of the subjects from ensenada and la plata (mean ± sd) were 34 ± 13 and 29 ± 6 years, respectively. an affidavit of residency and working place was obtained from all volunteers to ensure a minimum of 14 h daily exposure to the study area. tests were performed simultaneously in both groups in the laboratory of the university extension environmental programme (paeu, programa ambiental de extensión universitaria) at the faculty of exact sciences (facultad de ciencias exactas), the national university of la plata (unlp, universidad nacional de la plata). the study was conducted according to the declaration of helsinki of 1975, as revised in 2000. the research protocol was approved by the central advisory committee on bioethics (comité consultivo central de bioética) of the unlp, and informed consent was obtained from all subjects before they were registered in the study. 420 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 ocular surface sensitivity to particulate matter; gutiérrez et al figure 1. map of the cities of la plata, berisso, and ensenada, depicting both study areas –industrial zone (dark gray box) and urban zone (light gray box) – and monitoring points (black circles), obtained from google my maps. the exclusion criteria were as follows: pregnancy, usage of oral/topical antibiotics or prescribed eye medications, or usage of contact lenses. in all participants, medical treatment with drugs of any kind was withheld during the study period. previous reports have indicated an expected value of maximal percentage variation expressed as coefficient of variation (cv%) of approximately 60%.[9, 10] based on the results obtained through statistical calculations corresponding to this dispersion value,[8] a total of 30 volunteers per treatment group (zone) were considered adequate to allow statistical conclusions with 80% power (beta, type ii error) and a significance level of 0.01 (alpha, type i error). assessment of exposure pm was utilized as an indicator of air pollution exposure, and samples were collected using a lowvolume sampler (pm-2.5 minivol𝑇𝑀 tas; airmetrics co., springfield, oregon, usa). this draws air at a rate of 5 l/min through an impactor, separating it according to particle size, and a filter, thereby capturing pm.[15] a polytetrafluoroethylene (ptfe) membrane with a 46.2-mm diameter and 2-μm pore-size was used as the filter. particles of size < 2.5 μm (pm2.5) and aerodynamic diameter ≤ 10 μm (pm10) were both detected. gravimetric analysis was used to determine the particle content of each sample. data of pm level in both working areas were obtained through discrete monitoring. analysis of the ocular surface all analyses were performed in the morning by the same examiner, at the same setting, under the same conditions of temperature and humidity. questionnaires the ocular surface disease index (osdi) and mcmonnies (mm) questionnaires in validated spanish-translated form[16–18] were given to all subjects before examination and clinical tests. ocular surface structure the evaluation of the ocular surface was performed using slit-lamp biomicroscopy with an adapted imaging system (canon eos rebel t3i digital single-lens reflex camera) 30 min after the st. aspects of the eyelids, cornea, conjunctiva, and tear film were evaluated and entered into the patient’s medical record, according to the cornea and contact lens research unit (cclru) guidelines and efron grading scales.[19, 20] journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 421 ocular surface sensitivity to particulate matter; gutiérrez et al evaluation of the tear film schirmer i test: study participants were subjected to the st (hub pharmaceuticals, ca, usa) without the use of topical anesthesia. an obtained value ≤ 10 mm was considered abnormal.[21] tear-meniscus height: a slit lamp was used to establish the central height of the tear meniscus in relation to the free edge of the lower eyelid. a tear meniscus height < 0.35 mm was considered to indicate low tear volume and suspected dry eye.[22] tear break-up time: tbut was measured with fluorescein (sf) strips (hub pharmaceuticals, ca, usa) moistened with saline solution, which were gently applied to the inferior fornix. a value ≤ 10 sec was considered abnormal.[23] meibomian gland dysfunction: meibomian gland dysfunction (mgd) was observed using digital slitlamp biomicroscopy[24] and graded using the efron scale.[20] lipid patterns: interferometric images can be acquired using specular reflection techniques. in our study, such images were acquired using a highintensity slit lamp at a magnification of 25×.[25] the observed patterns were classified according to the system of guillon.[26] corneal and conjunctival vital staining in this study, vital staining with sf and lissamine green (slg) was conducted using dye-impregnated strips (hub pharmaceuticals, ca, usa) moistened with saline solution that were gently applied to the inferior fornix. the respective pattern of corneal and conjunctival staining was graded,[19, 27] and the presence of the lid parallel conjunctival folds (lipcof) was taken into account.[28] statistical analysis the data acquired were tested for normality and heterogeneity of variance using chi-square analysis and bartlett’s test, respectively. student’s ttests were performed for normally distributed data to determine statistically significant differences between two means. a p-value < 0.05 was considered to indicate statistical significance. principal component analysis (pca) was used for dimension reduction of the data; consequently, the number of variables was decreased to a few principal components (pcs) that accounted for most of the variation. all calculations were performed using infostat software (universidad nacional de córdoba, córdoba, argentina). results exposure to air pollution to confirm the previously reported differences in air quality of the two selected areas,[29, 30] pm levels at both locations were monitored throughout the study period with the help of local volunteers. mean values obtained through these discrete measurements throughout the study period are shown in table 1. the level of pm2.5was significantly higher in zone i than in zone u (p < 0.024, student’s t-test), which confirmed the presence of differences in air pollution between the two studied areas. moreover, an increase was also detected in the pm10 level in zone i in comparison with zone u. however, the difference was not statistically significant. analysis of the ocular outer surface results obtained for the different variables and accompanying parametric comparisons (student’s t-test) are shown in table 2. with regards to the results shown in table 2, higher levels of bulbar redness (br) and lid redness (lr), increased sf and slg staining values, and an increased mgd grade were noted in the i group compared to the u group. this suggested that the former population were more susceptible to developing higher levels of epithelial damage and mgd than the latter population. in addition, statistically lower mean st values were obtained in the i group, which indicated abnormalities in the tear film. no significant differences were present between the groups with respect to the osdi and mm questionnaires. consequently, six variables that showed significant differences between the two groups were included in the pca utilized as a multivariate dimensionality-reduction tool. data (volunteers in 422 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 ocular surface sensitivity to particulate matter; gutiérrez et al table 1. pm levels in both studied areas are expressed as the annual average. the results are expressed as mean ± sd. the asterisk denotes significant differences (p < 0.04) in pm 2.5 levels between populations i and u. n i n u p pm2.5[µg/m 3] 13 17.1 ± 8.4* 7 10.5 ± 3.6* 0.024 pm10[µg/m 3] 5 41.4 ± 16.4 5 28.2 ± 9.5 0.127 pm, particulate matter; i, industrial; u, urban; sd, standard deviation; n, number table 2. outer segment characteristics. the values of the number of the sample (n) are detailed; the mean (μ); the median (m); and the standard deviation (sd) for each study area are provided. the p-value is also reported according to the student’s t-test. the variables that presented significant differences between populations (*) are indicated in bold font. variables industrial zone urban zone µ m sd µ m sd p questionnaires osdi score 8.88 4.16 11.8 7.19 4.16 8.68 0.3046 mcmonnies score 7.56 6.50 5.71 7.20 6.00 4.81 0.6749 ocular surface without vital staining bulbar redness (grade)* 2.79 3.00 0.56 2.39 2.00 0.60 0.0001 lid redness (grade)* 2.47 2.50 0,48 2.15 2.00 0.62 0.0009 limbal redness (grade) 2.29 2.00 0.78 2.42 2.5 0.71 0.289 blepharitis (grade) 0.58 0.00 0.97 0.36 0.00 0.84 0.145 with vital staining fluorescein type of cornea (grade) 0.26 0.00 0.65 0.35 0.00 0.62 0.426 depth of cornea (grade) 0.18 0.00 0.33 0.27 0.00 0.44 0.220 extent of cornea (grade) 0.18 0.00 0.33 0.25 0.00 0.37 0.316 conjunctival (grade)* 3.23 3.00 0.73 2.48 3.00 0.64 – lipcof (grade) 2.24 2.50 0.93 2.42 3.00 0.89 0.231 lissamine green lissamine green (grade)* 2.17 2.00 1.14 1.25 1.00 0.87 – tear film volume schirmer i test (mm)* 24.73 29.50 11.20 31.33 35.00 5.39 – tear meniscus height (mm) 0.25 0.25 0.09 0.29 0.30 0.1 0.041 stability tbut (s) 5.65 5.20 3.12 6.40 5.35 3.46 0.245 lipid layer mgd (grade)* 0.45 0.00 0.63 0.17 0.00 0.36 0.001 osdi, ocular surface disease index; liocof, lid parallel conjunctival folds six-dimensional space) were presented as a twodimensional graph defined by the first two directions of maximal variability of the data points [axis or pc], as shown in figure 2. based on pca, 54% of the total data variability was attributed to the main plane (pc 1 and 2). the variables of conjunctival staining with sf and slg were increased to the left on the horizontal axis, indicating a strong positive correlation with pc 1. conversely, that of st was increased to the right on the same axis, indicating negative correlation; the two variables had a strong inverse relationship. in contrast, the variables of br, lr, and mgd were considered to have positive correlations with pc 2. as shown in figure 2, the areas of provenance of the sample are journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 423 ocular surface sensitivity to particulate matter; gutiérrez et al figure 2. principal component analysis graph. each point represents a volunteer: the open circle and black triangle correspond to zones u and i, respectively. the vectors represent the projection of variables: br, bulbar redness; lr, lid redness; sf, vital staining with fluorescein; slg, vital staining with lissamine green; st, schirmer i test; and mgd, meibomian gland dysfunction. analysis was carried out using the infostat software. clearly separated in the horizontal direction of the plot. discussion existing reports in the literature on the effects of air pollution on ocular health are limited to physiological symptoms or signs and/or alterations at a morphological level.[4] as such, reports on the impact of atmospheric pollution on ocular health at a clinical level, which could ultimately progress professional practice, are lacking. in order to characterize ocular health in individuals exposed to different levels of air pollutants, as well as to identify the associations between effectors and symptoms, reports have indicated the use of various tests and/or questionnaires.[8, 9, 11, 12] the osdi evaluates ocular alterations based on the symptomatology declared by patients independent of their environmental conditions. in our study, the osdi was not effective in distinguishing populations exposed to different concentrations of pm [table 2]. here, normal values were noted in both populations, in agreement with those reported by schiffman et al and miller et al.[16, 31] both the united states national eye institute (nei) and the tear film and ocular surface society (tfos) recommend the use of the osdi for all optometric/ophthalmological consultations. nevertheless, objective tests to evaluate the ocular surface should also be performed, since the association between clinical tests and questionnaires used for diagnosis is not adequate.[32, 33] objective clinical tests are essential to identify patients with early alterations who may not present any symptoms. in our study, significant differences in ocular surface alterations which correlated with increased pm2.5 in the i group were identified [table 2]. this is consistent with the results of other studies including populations exposed to high air pollution,[9] pollutants related to traffic,[10] and individuals who travel to highly contaminated areas.[8] pca involving the statistically different variables was performed. as a result, st value and conjunctival sf and slg staining grades were identified as three variables that could discriminate between individuals from the two zones with different levels of air pollution, indicating their potential use as bioindicators of the health status of the ocular surface. from a clinical point of view, these variables enable classification of the population into eight groups, represented in figure 3 by eight 3d cubes. from a clinical point of view, these variables enable classification of the population into eight groups, represented in figure 3 by eight 3d cubes. in this analysis, cut-off values for each variable (sf, 3; slg, 3; st, 10 mm) were employed to analyze the effects on the population according 424 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 ocular surface sensitivity to particulate matter; gutiérrez et al figure 3. projection of variables that separate populations with different levels of particulate matter (pm). sf, vital staining with fluorescein; slg, vital staining with lissamine green; and st, schirmer test i. the black cube represents the population that exhibits alteration of all three variables, while the white cube represents the population that does not present any alteration of these variables. the cut-off values of each variable were sf: 3; slg: 3; and st: 10 mm. to the combination of significant variables against environmental factors. regarding the st axis, the cubes below the cutoff value of 10 mm represent individuals with tear (aqueous) hyposecretion, corresponding to groups with aqueous-deficient dry eye (adde);[4, 25] the cubes above the cut-off (st values of > 10 mm) correspond to individuals with clinically normal eyes in terms of basal and reflex tear secretion. despite noting st values < 10 mm in some individuals, the mean st value of both populations was above the cut-off level (i, 24.73 ± 11.2; u, 31.33 ± 0.0033 mm), which indicated that both populations comprised individuals with clinically normal st values. the results of our investigation agree with those of gupta et al who demonstrated a decrease in the mean st value (22.75 ± 8.91 vs 30.30 ± 7.92 mm) in individuals exposed to high levels of pollutants, and of saxena who demonstrated lower mean st values in individuals traveling in heavily polluted areas of new delhi compared to controls (13.42 ± 6.67 vs 15.95 ± 6.14 mm). the unique finding of our study was that ocular surface cellular alterations, such as an increase in the level of vital staining with both sf and slg, were correlated with air pollution. the follow-up of individuals with normal st values and a trend toward high sf and slg values is important since tear hyperosmolarity may damage the superficial epithelium by activating inflammatory pathways at the ocular surface, as proposed by baudouin. moreover, this cellular damage may cause a loss of goblet cells and dysregulation of the expression of mucins, which leads to instability of the tear film and exacerbation of hyperosmolarity at the ocular surface, thereby reinitiating the dry eye cycle.[34] consequently, evidence of such ocular surface damage could indicate a high risk of developing recurrent or chronic inflammation in these individuals. therefore, early detection would enable prompt therapeutic intervention aimed at preventing the development of dry eye disease. moreover, recent studies have demonstrated pm2.5induced human corneal epithelial cell damage in vitro.[35] considering the collective findings of previous studies and those of our study, a study to develop a clinical index of ocular alterations including the aforementioned three variables is therefore required. based on our results, the relationship among these variables (formula) is expressed as the sum of the loads of each variable multiplied by the standardized variable as follows: formula = 0.7748 × (𝑆𝐹 − 𝜇sf/sdsf) +0.7453 × (slg − 𝜇slg/sdslg) −0.5944 × (st − 𝜇st/sdst) journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 425 ocular surface sensitivity to particulate matter; gutiérrez et al where st, sf, and sgl are considered as coefficients. st, schirmer i test; sf, vital staining with fluorescein; sgl, vital staining with lissamine green; μ, mean; sd, standard deviation. further studies to validate the relationship between air pollution and effects at the ocular level are required to develop tools to facilitate the diagnosis of patients and enable the differentiation of individuals with ocular surface alterations sensitive to different levels of air pollution. moreover, given the increased prevalence of dry eye worldwide,[30, 36–39, 41] the early detection of incipient and asymptomatic alterations is important, since it is a key aspect for improving patients’ quality of life.[42] in conclusion, subjects exposed to higher levels of pm in outdoor air presented greater ocular surface alterations. our study highlights that st, sf, and slg values have potential uses as convenient indicators of adverse health effects due to exposure to air pollution. financial support and sponsorship the authors would also like to thank the universidad nacional de la plata (unlp), the consejo nacional de investigaciones científicas y técnicas (conicet) and the centro de investigaciones científicas (cic) for their financial support to the present study. conflicts of interest there is no conflict of interest. references 1. lee wb, mannis mj, holland ej, editors. historical concepts of ocular surface disease. in: ocular surface disease: cornea, conjunctiva and tear film. elsevier; 2013:3–10. 2. rieger g. the importance of the precorneal tear film for the quality of optical imaging. brit j ophthalmol 1992;76:157– 158. 3. mcmonnies cw, ho a. responses to a dry eye questionnaire from a normal population. j am optom assoc 1987;58:588–591. 4. ma lemp. report of the national eye institute/industry workshop on clinical trials in dry eyes. clao j 1995:21:221–232. 5. dews. the definition and classification of dry eye disease : report of the definition and classification subcommittee of the international dews. ocul surf 2007;5:75–92. 6. craig jp, nichols kk, akpek ek, caffery b, dua hs, joo ck, et al. tfos dews ii definition and classification report. ocul surf 2017;15:276–283. 7. willcox mdp, argüeso p, georgiev ga, holopainen jm, laurie gw, millar tj, et al. tfos dews ii tear film report. ocul surf 2017;15:366–403. 8. saxena r, srivastava s, trivedi d, anand e, joshi s, gupta sk. impact of environmental pollution on the eye. acta ophthalmol scan 2003;81;491–494. 9. gupta sk, gupta sc, agarwal r, sushma s, agrawal ss, saxena r. a multicentric case-control study on the impact of air pollution on eyes in a metropolitan city of india. indian j occup environ med 2007;11:37–40. 10. novaes p, saldiva ph, matsuda m, macchione m, rangel mp, kara-josé n, et al. the effects of chronic exposure to traffic derived air pollution on the ocular surface. environ res 2010;110:372–374. 11. moen be, norbäck d, wieslander g, bakke jv, magerøy n, granslo jt, et al. can air pollution affect tear film stability? a cross-sectional study in the aftermath of an explosion accident. bmc pub health 2011;11:235. 12. torricelli aam, matsuda m, novaes p, braga alf, saldiva phn, alves mr, et al. effects of ambient levels of trafficderived air pollution on the ocular surface: analysis of symptoms, conjunctival goblet cell count and mucin 5ac gene expression. environ res 2014;131:59–63. 13. malerbi fk, martins lc, saldiva phn, braga alf. ambient levels of air pollution induce clinical worsening of blepharitis. environ res 2012;112:199–203. 14. novaes p, do n saldiva ph, kara-josé n, macchione m, matsuda m, racca l, et al. ambient levels of air pollution induce goblet-cell hyperplasia in human conjunctival epithelium. environ health persp 2007;115:1753–1756. 15. baldauf rw, lane dd, marotz ga, wiener rw. performance evaluation of the portable minivol particulate matter sampler. atmos environ 2001;35:6087–6091. 16. schiffman rm, christianson md, jacobsen g, hirsch jd, reis bl. reliability and validity of the ocular surface disease index. arch ophthalmol 2000;118:615–621. 17. beltran f, ramos betancourt n, martinez j, santacruz valdes c, babayan a, ramírez-assad c, et al. transcultural validation of ocular surface disease index (osdi) questionnaire for mexican population. invest ophth vis sci 2013;54:6050. 18. babayan a, ramos betancourt n, beltran f, martinez j, santacruz valdes c, ramírez-assad c, et al. transcultural validation of mcmonnies questionnaire for mexican population. invest ophthalmol vis sci 2013;54:6049. 19. terry rl, schnider cm, holden ba, cornish r, grant t, sweeney d, et al. cclru standards for success of daily and extended wear contact lenses. optometry vision sci 1993;70:234–243. 20. efron n. efron grading scales for contact lens complications in contact lens practice. elsevier. 2000;453–455. 21. dews. dews diagnostic methodology. methodologies to diagnose and monitor dry eye disease: report of the diagnostic methodology subcommittee of the international dry eye workshop. ocul surf 2007;5:108–152. 22. mainstone jc, bruce as, golding tr. tear meniscus measurement in the diagnosis of dry eye. curr eye res 1996;15:653–661. 426 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 ocular surface sensitivity to particulate matter; gutiérrez et al 23. vitali c, moutsopoulos hm, bombardieri s. the european community study group on diagnostic criteria for sjogren’s syndrome. sensitivity and specificity of tests for ocular and oral involvement in sjogren’s syndrome. ann rheum dis 1994;53:637–647. 24. bron aj, benjamin l, snibson gr. meibomian gland disease. classification and grading of lid changes. eye 1991;5:395–411. 25. yokoi n, takehisa y, kinoshita s. correlation of tear lipid layer interference patterns with the diagnosis and severity of dry eye. am j ophthalmol 1996;122:818–824. 26. jp guillon. non-invasive tearscope plus routine for contact lens fitting. cont lens anterio 1998;21:s31–s40. 27. norn ms. lissamine green. vital staining of cornea and conjunctiva. acta ophthalmol 1973;51:483–491. 28. höh h, schirra f, kienecker c, ruprecht kw. lid-parallel conjunctival folds are a sure diagnostic sign of dry eye. der ophthalmol 1995;92:802–808. 29. rehwagen m, müller a, massolo l, herbarth o, ronco a. polycyclic aromatic hydrocarbons associated with particles in ambient air from urban and industrial areas. sci total environ 2005;348:199–210. 30. cianni n, aguilar m, massolo l, colman e, müller a, matamoros n, et al. calidad del aire en zonas urbana e industrial y patología respiratoria en niños. mesa redonda en i congreso internacional de toxicología de la infancia y la adolescencia. xvi congreso argentino de toxicología. 24 al 27 de junio de 2009, puerto madryn. patagonia, argentina; 2009. 31. miller kl, walt jg, mink dr, satram-hoang s, wilson se, perry hd, et al. minimal clinically important difference for the ocular surface disease index. arch ophthalmol 2010;128:94–101. 32. nichols kk, mitchell gl, zadnik k. the repeatability of clinical measurements of dry eye. cornea 2004;23:272– 285. 33. vehof j, sillevis smitt-kamminga n, nibourg sa, hammond cj. predictors of discordance between symptoms and signs in dry eye disease. ophthalmology 2017;124:280–286. 34. baudouin c. the vicious circle in dry eye syndrome: a mechanistic approach | un nouveau schéma pour mieux comprendre les maladies de la surface oculaire. j fr ophtalmol 2007;30: 239–246. 35. fu q, lyu d, zhang l, qin z, tang q, yin h, et al. airborne particulate matter (pm2.5) triggers autophagy in human corneal epithelial cell line. environ pollut 2017;227:314– 322. 36. mccarty ca, stanislausky yl, bansal ak, livingston pm, taylor hr. the epidemiology of dry eye in melbourne, australia. ophthalmology 1997;105:1114–1119. 37. schein od, hochberg mc, muñoz b, e al. dry eye and dry mouth in the elderly: a population-based assessment. arch int med 1999;159:1359–1363. 38. schein od, muñoz b, tielsch jm, bandeen-roche k, west s. prevalence of dry eye among the elderly. am j ophthalmol 1997;124:723–728. 39. moss se, klein r, klein be. prevalence of and risk factors for dry eye syndrome. am j ophthalmol 2000;18:1264– 1268. 40. lin p-y, tsai s-y, cheng c-y, liu j-h, chou p, hsu w-m. prevalence of dry eye among an elderly chinese population in taiwan: the shihpai eye study. ophthalmology 2003;110:1096–1101. 41. schaumberg da, sullivan da, buring je, dana mr. prevalence of dry eye syndrome among us women. am j ophthalmol 2003;136:318–326. 42. johnson me, murphy pj, boulton m. carbomer and sodium hyaluronate eyedrops for moderate dry eye treatment. optometry vis sci 2008;85:750–757. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 427 original article eye bank records on pediatric keratoplasty seyed mohamadmehdi moshtaghion1*, md; mohammad abolhosseini1*, md; bahareh kheiri2, ms; mohammad ali javadi2,3, md; leila ziaee ardakani4, md; mozhgan rezaei kanavi1,3, md 1ocular tissue engineering research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 3central eye bank of iran, tehran, iran 4school of medicine, shahid beheshti university of medical sciences, tehran, iran orcid: mozhgan rezaei kanavi: http://orcid.org/0000-0002-1497-2260 seyed mohamadmehdi moshtaghion: https://orcid.org/0000-0002-6039-4246 mohammad abolhosseini: https://orcid.org/0000-0002-1914-4309 *seyed mohamadmehdi moshtaghion and mohammad abolhosseini have equally contributed to this work. abstract purpose: to report eye bank records for pediatric keratoplasty in iran between 2006 and 2019. methods: in a retrospective study, all electronic records of the central eye bank of iran for pediatric keratoplasty between april 2006 and march 2019 were analyzed in terms of indications for keratoplasty, surgical techniques, their corresponding trends, and post-transplantation graft clarity. results: our database included 2178 eyes from 2050 pediatric cases. the leading indications for keratoplasty included acquired nontraumatic diseases (75.8%), congenital abnormalities (12.7%), corneal regraft (8.3%), and acquired traumatic diseases (3.2%). keratoconus was the most common acquired nontraumatic cause (58%) and more common in the age group >12 years than those ≤12 years (p < 0.001). congenital corneal abnormalities and regrafts were more common in the age group ≤12 years (both p < 0.001). the most common surgical technique was penetrating keratoplasty (pkp, 90.9%) followed by deep anterior lamellar keratoplasty (dalk, 7.3%), descemet stripping automated endothelial keratoplasty (dsaek, 1.1%), anterior lamellar keratoplasty (0.5%), and keratolimbal allograft transplantation (0.2%). dsaek was more common in the age group ≤12 years (p = 0.002), which, unlike pkp and dalk, showed a significant ascending trend over the 14-year period (p = 0.018). posttransplantation graft clarity was 96.8%. conclusion: keratoconus was the leading indication for pediatric keratoplasty in iran. although pkp was the predominant keratoplasty procedure for the treatment of pediatric corneal disorders, it showed a significant descending trend over the 14 years. keywords: deep anterior lamellar keratoplasty; descemet membrane stripping automated endothelial keratoplasty; keratoconus; pediatric keratoplasty; penetrating keratoplasty j ophthalmic vis res 2022; 17 (3): 324–337 324 © 2022 moshtaghion et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i3.11569&domain=pdf&date_stamp=2019-07-17 pediatric keratoplasty eye bank records; moshtaghion et al introduction one of the major pediatric health problems especially in developing countries is corneal blindness.[1] the etiology of corneal blindness varies depending on the differences in the race, region, hygienic conditions, and economical status. for instance, unlike developed countries in which corneal congenital disorders are the leading indication for pediatric keratoplasty,[2–6] infectious keratitis and corneal traumatic injuries have been the major indications in the developing countries.[7–9] corneal transplantation is the ultimate treatment of corneal blindness in children.[10] given that it is a challenging procedure, due to its preoperative, intraoperative, and postoperative considerations,[1] it is not performed very routinely.[11] however, with the adoption of partial thickness microsurgical techniques, the numbers as well as the success rates of pediatric keratoplasty have increased over the last decade;[2, 4] the surgical techniques in cases with congenital hereditary endothelial dystrophy (ched) and anterior stromal disorders have transitioned from full thickness to lamellar keratoplasty techniques.[6, 9] nevertheless, penetrating keratoplasty (pkp) still accounts for 90% of all pediatric keratoplasties performed in 95 countries.[10] currently, pediatric keratoplasty is predominantly performed in the university-based ophthalmic centers in iran. tissue requirements for corneal transplantation are mainly provided by the central eye bank of iran located in the capital, tehran. in this study, we intend to investigate the records of the central eye bank of iran in terms of indications for keratoplasty and their corresponding trends, surgical techniques and their corresponding evolving trends, as well as postoperative graft clarity between 2006 and 2019. correspondence to: mozhgan rezaei kanavi, md. ocular tissue engineering research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, no.23, paidarfard st., boostan 9 st., pasdaran ave., tehran 1666673111, iran. e-mail: rezaeikanavi@sbmu.ac.ir received: 19-09-2021 accepted: 28-12-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i3.11569 methods study design the current study was approved by the ethics committee of the research institute for ophthalmology and vision science affiliated to shahid beheshti university of medical sciences, tehran, iran (ir.sbmu.orc.rec.1384.8). population and measurements all eye bank records of pediatric keratoplasty cases (≤18 years old) performed between april 2006 and march 2019 throughout the country were compiled from the central eye bank of iran. the patients’ data were reviewed in terms of demographic data, indications for keratoplasty and their corresponding trends, surgical techniques and their corresponding trends, as well as posttransplantation graft clarity reported to the central eye bank of iran. all variables were also analyzed in two subgroups of ≤12 and >12 years of age. indications for keratoplasty indications for keratoplasty, according to the previous studies, were categorized into four groups:[12, 13] congenital corneal abnormalities (corneal dystrophies, congenital corneal opacities), acquired nontraumatic diseases (keratoconus, corneal degenerations, aphakic/pseudophakic bullous keratopathies, corneal infections, and nonspecified corneal opacities), acquired traumatic diseases (mechanical injuries, chemical or thermal injuries), and regraft. the regraft group was also investigated for the cause of graft failure and the original indications for keratoplasty. surgical techniques pkp, descemet stripping automated endothelial keratoplasty (dsaek), deep anterior lamellar this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: moshtaghion sm, abolhosseini m, kheiri b, javadi ma, ardakani lz, kanavi mr. eye bank records on pediatric keratoplasty. j ophthalmic vis res 2022;17:324–337. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 325 https://knepublishing.com/index.php/jovr pediatric keratoplasty eye bank records; moshtaghion et al keratoplasty (dalk), anterior lamellar keratoplasty (alk), and keratolimbal allograft transplantation (klal) were surgical techniques implemented for pediatric keratoplasty in our survey. statistical analyses statistical analyses were performed using the spss software (version 25; spss inc., chicago, il, usa). data were presented as mean ± standard deviation. linear regression analyses were applied to analyze the trend of indications and surgical techniques over time. considering statistical values such as goodness of fit and r-square, the spss chose the best model to determine the regression process. p-values < 0.05 were considered statistically significant. results patients our database included 2178 eye bank records from 2050 pediatric cases that had undergone pediatric keratoplasty between 2006 and 2019. the patients’ age ranged from 1 month to 18 years with the mean age of 11.2 ± 4.5 years at the time of surgery, where 61% were male. the 128 eye bank records corresponded to the patients in whom either the fellow eyes were transplanted (70 eyes from 70 patients) or the transplanted eyes underwent regraft (58 eyes from 56 patients). the annual rates of pediatric keratoplasty revealed a significant decline of trend over the 14-year period (p < 0.001). out of the 2178 eye bank records, 1061 (48.7%) cases were≤12 years old and the remaining 1117 (51.3%) were >12 years of age. indications for corneal transplantation the leading indications for pediatric keratoplasty, in order of descending frequency, were acquired nontraumatic diseases (1651 eyes, 75.8%), congenital corneal abnormalities (277 eyes, 12.7%), regraft (181 eyes, 8.3%), and acquired traumatic diseases (69, 3.2%) [table 1]. acquired nontraumatic diseases the acquired nontraumatic diseases indicated a significant downward trend (p < 0.001) over the 14 years [figure 1a] and were more frequent in the older (>12 years) than the younger age (≤12 years) group (p < 0.001) [table 1]. the most common acquired nontraumatic disease was keratoconus (956, 58%) followed by aphakic/pseudophakic bullous keratopathies (258, 15.6%), non-specified corneal opacities (244, 14.8%), corneal infections (179, 10.8%), and corneal degenerations (12, 0.7%) [table 1]. active corneal infections accounted for 84.4% (151 eyes) of the eyes that were categorized as corneal infection. as illustrated in figure 2a–2e, a significant descending trend was noted in the keratoconus (p < 0.001), aphakic/pseudophakic bullous keratopathies (p = 0.002), and corneal infections (p = 0.043) over the 14-year period. unlike keratoconus which was more common in the elder age group (p < 0.001), aphakic/pseudophakic bullous keratopathies, non-specified corneal opacities, and corneal infections were more common in the younger age group (all p < 0.001). in the age group ≤12 years, the rate of keratoconus (235 eyes, 22.1%) was even higher than the rate of congenital corneal abnormalities (196 eyes, 18.5%) (p = 0.035). congenital corneal abnormalities congenital corneal abnormalities showed a significant diminishing trend (p = 0.014) over the 14-year period [figure 1b] and were higher in the younger than the older age group (p < 0.001) [table 1]. the most common congenital corneal abnormality was corneal dystrophy (188, 67.9%), followed by congenital corneal opacities (89, 32.1%). both corneal dystrophies and congenital corneal opacities were more common in the younger age group (p < 0.001) [table 1]. unlike the meaningful descending trend of corneal dystrophies (p = 0.036), the declining trend of congenital corneal opacities over the 14 years was not statistically significant (p = 0.073) [figure 2f–2g]. out of the 188 eyes that underwent corneal transplantation for corneal dystrophies, ched was present in 77.7% (146), followed by macular corneal dystrophy (n = 24, 12.7%), granular corneal dystrophy (n = 13, 6.9%), lattice corneal dystrophy (n = 3, 1.6%), and reis-buckler corneal dystrophy (n = 2, 1.1%) [table 1]. congenital corneal opacities (89 eyes) in our survey included limbal dermoids 326 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 pediatric keratoplasty eye bank records; moshtaghion et al (41, 46.1%), peter’s anomaly (25, 28.1%), posterior keratoconus (10, 11.2%), sclerocornea (9, 10.1%), and congenital glaucoma (4, 4.5%). regraft regraft did not indicate any significant change of trend (p = 0.69) over the 14-year period [figure 1d] and was more frequently observed in the younger than the older age group (p < 0.001) [table 1]. the causes of graft failure in 181 regraft cases were chronic endothelial graft rejection/dysfunction of the allograft in 158 (87.3%) and primary graft failure in 23 (12.7%) eyes. according to the database of the central eye bank of iran, the original diagnoses were specified only in 58 eyes of 56 pediatric cases, where the five leading diagnoses were congenital corneal abnormalities (18 eyes, 31%), keratoconus (13 eyes, 22.4%), non-specified corneal opacities (13 eyes, 22.4%), aphakic/pseudophakic bullous keratopathies (6 eyes, 8.6%), and corneal infections (4 eyes, 6.9%). the leading indications in the category of primary graft failure (23 eyes) were keratoconus in six, congenital corneal abnormalities in five, and corneal infections in four eyes. acquired traumatic diseases acquired traumatic diseases revealed a significant downward trend (p = 0.021) over the 14 years [figure 1c] and were more common in the younger age group (p = 0.012) [table 1]. the most common acquired traumatic disease was mechanical injuries (40, 58%), followed by chemical injuries (29, 42%). unlike mechanical injuries which were more common in the younger age group (p < 0.001) [table 1], chemical injuries were not different between the two age groups (p = 0.746). unlike the borderline change of trend in the mechanical injuries (p = 0.07), chemical injuries indicated a significant falling trend (p = 0.036) over the 14-year period [figure 2h & 2i]. surgical techniques used for pediatric corneal transplantation the most common surgical technique used for pediatric keratoplasty was pkp (1981, 90.9%) followed by dalk (159, 7.3%), dsaek (24, 1.1%), alk (10, 0.5%), and klal (4, 0.2%) [table 2]. although pkp remained the main type of keratoplasty performed over the 14 years, it showed a significant diminishing trend (p < 0.001) during the specified time period. similarly, dalk showed a meaningful downward trend (p = 0.018) over the 14 years. unlike the significant ascending trend in the rate of dsaek (p = 0.018), the change of trend for alk was borderline (p = 0.068), while for klal it was not significant (p = 0.278) [figure 3]. in contrast to pkp, alk, and klal which did not differ between the two age groups (p = 0.634, 0.082, and 0.178, respectively), dalk and dsaek were more common in the older (p < 0.001) and younger (p = 0.002) age groups, respectively [table 2]. the leading three indications for pkp were keratoconus (41.3%), aphakic/pseudophakic bullous keratopathies (12.6%), and non-specified corneal opacities (12.1%). the major leading indications for dalk, dsaek, alk, and klal were keratoconus (87.4%), ched (54.2%), non-ched corneal dystrophies (70%), and chemical burns (100%), correspondingly [figure 4]. postoperative reports based on the postoperative data reported to the central eye bank of iran, except 69 (3.2%) eyes, the others (96.8%) reported graft clarity up to one month after corneal transplantation. in the category of short-term reports on postoperative unclear corneas, 50.7% were male, 53.6% aged >12 years, and only three cases required regraft. the four primary indications for keratoplasty in this category were keratoconus (44, 63.8%), followed by nonspecified corneal opacities (8, 11.6%), active corneal infections (6, 8.7%), and aphakic/pseudophakic bullous keratopathies (6, 8.7%). pkp (49, 71%) was the most common surgical procedure in this group, followed by dalk (19, 27.5%) and alk (1, 1.4%). discussion the field of pediatric keratoplasty is relatively young and studies on surgical trends as well as indications for pediatric keratoplasty are limited. to the best of our knowledge, after the report of 2620 pediatric cases from the eye bank association of america,[14] the current survey is the largest case series reported for pediatric keratoplasty so far. the results of this cross-sectional study on journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 327 pediatric keratoplasty eye bank records; moshtaghion et al table 1. indications for pediatric keratoplasty in iran between 2006 and 2019 and the corresponding distribution in two age groups of ≤12 and >12 years. distribution of the indications for pediatric keratoplasty of each age group preoperative diagnosis total age group (yr) p-value ≤ 12 12 < mean age 11.2 ± 4.5 7.5 ± 3.8 14.5 ± 1.6 <0.001 acquired non-traumatic 1651 (75.8%) 703 (66.3%) 948 (84.9%) <0.001 keratoconus 958 (58.0%) 235 (33.4%) 723 (76.3%) <0.001 aphakic/pseudophakic bullous keratopathy 258 (15.6%) 171 (24.3%) 87 (9.2%) <0.001 non-specified corneal opacities 244 (14.8%) 161 (22.9%) 83 (8.8%) <0.001 corneal infections 179 (10.8%) 128 (18.2%) 51 (5.4%) <0.001 viral 27 (15.1%) 15 (11.7%) 12 (23.5%) 0.057 bacterial 61 (34.1%) 42 (32.8%) 19 (37.3%) 0.573 fungal 13 (7.3%) 9 (7%) 4 (7.8%) 0.831 amebic 0 (0%) 0 (0%) 0 (0%) n/a unknown 78 (43.6%) 62 (48.4%) 16 (31.4%) 0.038 corneal degenerations 12 (0.7%) 8 (1.1%) 4 (0.4%) 0.223 congenital corneal abnormalities 277 (12.7%) 196 (18.5%) 81 (7.3%) <0.001 corneal dystrophies 188 (67.9%) 129 (65.8%) 59 (72.8%) <0.001 ched 146 (77.7%) 117 (90.7%) 29 (49.2%) <0.001 mcd 24 (12.7%) 5 (3.9%) 19 (32.2%) <0.001 gcd 13 (6.9%) 3 (2.3%) 10 (16.9%) <0.001 lcd 3 (1.6%) 3 (2.3%) 0 (0%) 0.320 reis-buckler corneal dystrophy 2 (1.1%) 1 (0.8%) 1 (1.7%) 0.627 congenital corneal opacity 89 (32.1%) 67 (34.2%) 22 (27.2%) <0.001 limbal dermoids 41 (46.1%) 35 (52.2%) 6 (27.3%) 0.023 peter’s anomaly 25 (28.1%) 14 (20.9%) 11 (50%) 0.005 posterior keratoconus 10 (11.2%) 6 (9%) 4 (18.2%) 0.121 sclerocornea 9 (10.1%) 9 (13.4%) 0 (0%) 0.128 congenital glaucoma 4 (4.5%) 3 (4.5%) 1 (4.5%) 0.494 acquired traumatic 69 (3.2%) 44 (4.1%) 25 (2.2%) 0.012 mechanical injuries 40 (58.0%) 29 (65.9%) 11 (44.0%) 0.003 chemical injuries 29(42.0%) 15 (34.1%) 14 (56.0%) 0.746 regraft 181 (8.3%) 118 (11.1%) 63 (5.6%) <0.001 total 2178 (100.0%) 1061 (100.0%) 1117 (100.0%) 0.09 ched, congenital hereditary endothelial dystrophy; mcd, macular corneal dystrophy; gcd, granular corneal dystrophy; lcd, lattice corneal dystrophy the 14-year data for 2178 transplanted pediatric eyes, obtained from the central eye bank of iran, demonstrated that acquired nontraumatic corneal disorders, with keratoconus on the top of this category, were the major leading causes of pediatric keratoplasty and observed more commonly in the age group >12 years. even in the age group ≤12 years, keratoconus exceeded 328 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 pediatric keratoplasty eye bank records; moshtaghion et al table 2. number of surgical techniques used for pediatric keratoplasty between 2006 and 2019, and the corresponding distribution in two age groups of ≤12 and >12 years. surgical techniques total age group (yr) p-value ≤12 >12 pkp 1981 (90.9%) 998 (94.1%) 983 (88.0%) 0.634 dalk 159 (7.3%) 38 (3.6%) 121 (10.8%) <0.001 dsaek 24 (1.1%) 19 (1.8%) 5 (0.4%) 0.002 alk 10 (0.5%) 3 (0.3%) 7 (0.6%) 0.082 klal 4 (0.2%) 3 (0.3%) 1 (0.1%) 0.178 sum 2178 (100%) 1061 (48.7%) 1117 (51.3%) 0.777 pkp, penetrating keratoplasty; dalk, deep anterior lamellar keratoplasty; dsaek, descemet stripping automated endothelial keratoplasty; alk, anterior lamellar keratoplasty; klal, keratolimbal allograft figure 1. trends of indications for pediatric keratoplasty between 2006 and 2019. note the significant falling trend for acquired non-traumatic diseases (a; p < 0.001); congenital abnormalities (b; p = 0.014), and acquired traumatic diseases (c; p = 0.021). no significant change of trend is observed for the regraft over the 14-year period (d; p = 0.69). the congenital corneal abnormalities. pkp, in our survey, was the most common surgical technique for pediatric keratoplasty, similar to the other reports in which pkp was the only or the predominant surgical procedure for pediatric corneal transplantation.[5, 7, 12, 14–20] the indications for pediatric keratoplasty differ worldwide depending on the geographic region. for instance, in developed countries, congenital corneal disorders and nontraumatic acquired keratectasias are the leading indications for pediatric keratoplasty, while acquired corneal scars and ulcers of traumatic or infectious etiologies are on the top in developing countries.[21] table 3 summarizes published data on indications for pediatric keratoplasty in both developed and developing countries with the present study included.[5, 7, 8, 12, 14–20, 22–29] keratoconus in our study, similar to the reports from pediatric keratoplasty in countries such as new zealand, italy, and australia, was the most common indication for keratoplasty.[14–16] this was in contrast to the reports from the united states, singapore, saudi arabia, eastern china, journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 329 pediatric keratoplasty eye bank records; moshtaghion et al ta b le 3 .p ub lic at io ns on pe di at ric ke ra to pl as ty si nc e 19 68 ,i n th e de ve lo pe d an d de ve lo pi ng co un tr ie s in cl ud in g th e pr es en ts tu dy . c o u n tr y/ ye a r n u m b e r o f e ye s/ p a ti e n ts a cq u ir e d n o n tr a u m a ti c k e ra to co n u s a p h a k ic / p se u d o p h a k ic b u llo u s ke ra to p a th y n o n sp e ci fi e d co rn e a l o p a ci ti e s c o rn e a l in fe ct io n s c o rn e a l d e g e n e ra ti o n s c o n g e n it a l co rn e a l a b n o rm a lit ie s c o rn e a l d ys tr o p h ie s/ c h e d / n o n -c h e d c o n g e n it a l co rn e a lo p a ci ty a cq u ir e d tr a u m a ti c r e g ra ft to ta l k e ra to p la st ie s d ev el op in g c ou nt rie s ira n/ 20 0 620 19 21 78 /2 0 50 16 51 (7 5 .8 % ) 95 8 (4 4% ) 25 8 (11 .9 % ) 24 4 (11 .2 % ) 17 9 (8 .2 % ) 12 (0 .6 % ) 27 7 (12 .7 % ) 18 8/ 14 6/ 42 (8 .6 % / 6. 7% /1. 9% ) 0 69 (3 .2 % ) 18 1( 8. 3% ) 21 78 (10 0 % ) b ra zi l/2 0 19 51 /4 3 9 (17 .7 % ) n /s n /s n /s 9 (17 .7 % ) n /s 37 (7 2 .6 % ) 8/ 8/ n /s (15 .7 % /8 % ) 29 (5 6. 9% ) 5 (9 .8 % ) n /s 51 (10 0 % ) ea st er n c hi na /2 0 0 820 17 10 59 /10 26 17 5 (16 .5 % ) 11 8 (11 .1% ) 5 (0 .5 % ) 24 (2 .3 % ) 26 (2 .5 % ) 2 (0 .2 % ) 79 0 (7 4. 6% ) 8/ n /s /n /s (0 .8 % ) 78 2 (7 3. 8% ) 38 (3 .6 % ) 56 (5 .3 % ) 10 59 (10 0 % ) m al ay si a/ 20 0 820 17 16 /14 10 (6 2 .5 % ) n /s n /s 1( 6. 3% ) 9 (5 6. 3% ) n /s 3 (18 .8 % ) n /s 3 (18 .8 % ) 2 (12 .5 % ) 1( 6. 3% ) 16 (10 0 % ) m ex ic o/ 19 95 -2 0 11 57 4/ (n /s ) 46 1( 80 .3 % ) 31 9 (5 5 .6 % ) 35 (6 .1% ) 19 (3 .3 % ) 88 (15 .3 % ) n /s 70 (12 .2 % ) n /s 70 (12 .2 % ) 43 (7 .5 % ) n /s 57 4 (10 0 % ) in di a/ 20 07 -2 0 11 66 /6 6 33 (5 0 % ) n /s n /s n /s 22 (3 3. 3% ) 11 (16 .7 % ) 24 (3 6. 4% ) 18 /6 /12 (2 7. 3% /9 .1% /18 .2 % ) 6 (9 .1% ) 5 (7 .6 % ) 4 (6 .1% ) 66 (10 0 % ) tu ni si a/ 20 0 320 0 8 16 /15 8 (5 0 % ) 5 (3 1.3 % ) n /s n /s 3 (18 .8 % ) n /s 2 (12 .5 % ) 1/ n /s /n /s (6 .3 % ) 1( 6. 3% ) 6 (3 7. 5% ) n /s 16 (10 0 % ) c hi na (s ha ng ha i)/ 20 0 320 07 15 6/ 14 9 71 (4 5 .5 % ) 17 (10 .9 % ) n /s 8 (5 .1% ) 46 (2 9. 5% ) n /s 37 (2 3. 7% ) 7/ 7/ n /s (4 .5 % /4 .5 % ) 30 (19 .2 % ) 48 (3 0. 8% ) n /s 15 6 (10 0 % ) n or th c hi na /19 94 -2 0 0 5 41 0/ 37 1 14 8 (3 6. 1% ) 37 (9 % ) n /s 11 (2 .7 % ) 93 (2 2 .7 % ) 7 (1. 7% ) 11 2 (2 7. 3% ) 29 /n /s /n /s (7 .1% ) 83 (2 0. 2% ) 15 0 (3 6. 6% ) n /s 41 0 (10 0 % ) sa ud i a ra bi a/ 19 90 20 0 3 16 5 /13 4 18 (10 .9 % ) n /s n /s n /s 18 (10 .9 % ) n /s 13 0 (7 8. 8% ) 35 /3 5 /n /s (2 1.2 % ) 95 (5 7. 6% ) 17 (10 .3 % ) n /s 16 5 (10 0 % ) in di a/ 19 98 -2 0 04 16 8/ 15 4 89 (5 3% ) n /s 2 (1. 2% ) n /s 73 (4 3. 5% ) 14 (8 .3 % ) 57 (3 3. 9% ) 14 /n /s /n /s (8 .3 % ) 43 (2 5 .6 % ) 22 (13 .1% ) n /s 16 8 (10 0 % ) in di a/ 19 88 -1 99 5 16 2 /14 0 85 (5 2 .5 % ) n /s n /s 31 (19 .1% ) 54 (3 3. 3% ) n /s 47 (2 9% ) 20 /2 0/ n /s (12 .4 % /12 .4 % ) 27 (16 .7 % ) 22 (13 .6 % ) 8 (4 .9 % ) 16 2 (10 0 % ) d ev el op ed c ou nt rie s u sa /2 0 0 520 17 26 20 /(n /s ) 19 31 (7 3. 7% ) 88 3 (3 3. 7% ) 11 8 (4 .5 % ) 83 6 (3 1.9 % ) 94 (3 .6 % ) n /s 41 9 (16 % ) 26 2 /5 8/ 20 4 (10 % /2 .2 % /7 .8 % ) 15 7 (% 6) 79 (3 % ) 19 1( 7. 3% ) 26 20 (10 0 % ) fi nl an d/ 19 68 -2 0 11 39 /(n /s ) 16 (4 1% ) 7 (18 % ) n /s 7 (18 % ) 1( 2 .6 % ) 1( 2 .6 % ) 12 (3 0. 8% ) 4/ n /s /n /s (10 .3 % ) 8 (2 0. 5% ) 11 (2 8. 2% ) n /s 39 (10 0 % ) 330 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 pediatric keratoplasty eye bank records; moshtaghion et al ta b le 3 .( c on tin ue d ). c o u n tr y/ ye a r n u m b e r o f e ye s/ p a ti e n ts a cq u ir e d n o n tr a u m a ti c k e ra to co n u s a p h a k ic / p se u d o p h a k ic b u llo u s ke ra to p a th y n o n sp e ci fi e d co rn e a l o p a ci ti e s c o rn e a l in fe ct io n s c o rn e a l d e g e n e ra ti o n s c o n g e n it a l co rn e a l a b n o rm a lit ie s c o rn e a l d ys tr o p h ie s/ c h e d / n o n -c h e d c o n g e n it a l co rn e a lo p a ci ty a cq u ir e d tr a u m a ti c r e g ra ft to ta l k e ra to p la st ie s ita ly /2 0 10 -2 0 13 54 /4 3 30 (5 5 .6 % ) 20 (3 7% ) 2 (3 .7 % ) 6 (11 .1% ) 2 (3 .7 % ) n /s 13 (2 4. 1% ) n /s 13 (2 4. 1% ) 6 (11 .1% ) 5 (9 .3 % ) 54 (10 0 % ) si ng ap or e/ 19 91 20 11 10 5 /10 5 58 (4 5 .7 % ) 15 (11 .8 % ) 5 (3 .9 % ) 26 (2 0. 5% ) 12 (9 .5 % ) n /s 45 (3 5 .4 % ) 2 /1/ 1 (1. 6% /0 .8 % /0 .8 % ) 43 (3 3. 9% ) 2 (1. 6% ) 22 (17 .3 % ) 12 7 (10 0 % ) d en m ar k/ 19 68 20 0 8 63 /6 0 38 (5 2 .1% ) 12 (16 .4 % ) n /s 5 (6 .8 % ) 21 (2 8. 8% ) n /s 13 (17 .8 % ) n /s 13 (17 .8 % ) 9 (12 .3 % ) 13 (17 .8 % ) 73 (10 0 % ) u sa (c al ifo rn ia )/1 99 120 0 6 60 /4 7 13 (12 .3 % ) 2 (1. 9% ) n /s n /s 11 (10 .4 % ) n /s 37 (3 4. 9% ) 7/ 7/ n /s (6 .6 % /6 .6 % ) 30 (2 8. 3% ) 10 (9 .4 % ) 46 (4 3. 4% ) 10 6 (10 0 % ) n ew ze al an d/ 19 91 20 0 3 58 /5 2 43 (7 4. 1% ) 39 (6 7. 2% ) n /s n /s 4 (6 .9 % ) n /s 9 (15 .5 % ) 7/ 2 /5 (12 .1% /3 .5 % /8 .6 % ) 2 (3 .5 % ) 6 (10 .3 % ) n /s 58 (10 0 % ) a us tr al ia /19 84 20 02 19 /16 0 (0 % ) n /s n /s n /s n /s n /s 8 (4 2 .1% ) 2 /1/ 1 (10 .5 % /5 .3 % /5 .3 % ) 6 (3 1.6 % ) 11 (5 7. 9% ) n /s 19 (10 0 % ) c h ed ,c on ge ni ta lh er ed ita ry en do th el ia ld ys tro ph y journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 331 pediatric keratoplasty eye bank records; moshtaghion et al figure 2. trends of the indications for pediatric keratoplasty in each main category in iran between 2006 and 2019. note the significant declining trend for keratoconus (a; p < 0.001); bullous keratopathies (b; p = 0.002); corneal infections (d; p = 0.043); corneal dystrophies (f; p = 0.036); and chemical injuries (i; p = 0.036). no significant change of trend is noted for non-specified corneal opacities (c; p = 0.173), corneal degenerations (e; p = 0.341), congenital corneal opacities (g; p = 0.073), and mechanical injuries (h; p = 0.07) over the 14-year period. malaysia, and india in which congenital corneal abnormalities and corneal infections were the top causes of keratoplasty in the pediatric age group.[7, 12, 17–20] congenital corneal abnormalities in our series ranked the second following acquired nontraumatic diseases; however, they were reported as the top indication for pediatric corneal transplantation in the united states (61.60%), singapore (40.90%), saudi arabia (78.79%), and eastern china (74.6%).[12, 18–20] the high prevalence of keratoconus in our keratoplasty series can be due to the common occurrence of vernal keratoconjunctivitis in iran as well as challenges in wearing contact lens in the keratoconus pediatric patients, which had made keratoplasty the best option for this series of the patients.[30] nevertheless, the rate of keratoconus in our survey showed a descending trend over the 14-year period which can be due to the recent adoption of corneal cross-linking in such cases.[30] keratoconus in our series was also more prevalent in the elder age group, which may be explained by the surgeons’ preference for performing keratoplasty in more advanced ages to achieve favorable surgical results.[11, 25, 26] ched, similar to the report from saudi arabia, was the most common corneal dystrophy in the pediatric age group in iran.[20] zhu et al also reported congenital corneal abnormalities as one of the primary indications for corneal transplant in the youngest age group.[27] while corneal dystrophies were the most common congenital corneal abnormalities in our series, they were not a common indication for pediatric keratoplasty in the other reports.[8, 24, 27] as reported in table 3, the rate of bullous keratopathies in our series (11.8%) was higher than the rate reported from italy (6.1%), eye bank association of america (2.3%), and new zealand (1.7%).[14, 16, 27] this may be explained by the increased adoption of cataract surgery for pediatric age group in iran and the occurrence of corneal endothelial decompensation due to post-surgical complications. however, the number of pediatric keratoplasties due to aphakic/pseudopkakic bullous keratopathies did not show a change of trend over the 14-year period. non-specified corneal opacities ranked the third in the group of acquired nontraumatic diseases, and showed no significant change of trend during the 14 years. they were more common in the younger age group. as outlined in table 3, the rate of corneal opacities of unknown etiologies was higher in the reports from developed countries such as usa (31.9%) and singapore (20.5%) and from developing countries like india (19.1%) than 332 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 pediatric keratoplasty eye bank records; moshtaghion et al figure 3. trends of surgical techniques for pediatric keratoplasty in iran between 2006 and 2019. note the significant downward trend for pkp (a; p < 0.001) and dalk (b; p = 0.018); the remarkable ascending trend for dsaek (c; p = 0.018); the borderline change of trend for the alk (d; p = 0.068), and the lack of change of trend for klal (e; p = 0.278). pkp, penetrating keratoplasty; dalk, deep anterior lamellar keratoplasty; dsaek, descemet stripping automated endothelial keratoplasty; alk, anterior lamellar keratoplasty; klal, keratolimbal allograft. the value reported in our survey (11.2%).[19, 26, 27] we assume that some of the non-specified corneal opacity cases in our series might have had infectious or traumatic etiologies which were missed by the corresponding surgeons when preparing the patients’ data for the eye bank. the rate of regraft in our survey (8.3%) was similar to the rates reported from developing and developed countries [table 3]. there is only one report from the california, usa, in which regraft was the major leading indication for pediatric keratoplasty (43.4%).[18] the regraft cases in our series, similar to the report by zhao et al, was more common in the younger age group.[12] chronic endothelial graft rejection/dysfunction of the allograft was the predominant cause of graft failure in our series. a more active immune system has long been suggested as the main reason for the increased rate of corneal graft rejections observed in the younger recipients.[31] corneal infections were reported as the most common indication for pediatric keratoplasty not only in the developing countries such as india and malaysia but also in a developed country such as denmark (table 3).[7, 17, 29] however, in our survey, it ranked the fourth in the category of acquired nontraumatic diseases and revealed a descending trend during the 14 years. this may be attributed to the public awareness on eye health and the presence of accessible eye care facilities for the treatment of ocular infections throughout the nation. although corneal infections were accounted as the main cause of pediatric corneal graft failure in developing countries, only 5.3% (8 out of 151) of the active keratitis cases in our series were reported as graft failure following corneal transplantation.[7] acquired traumatic diseases in the literature accounted for 1.6% to 57.9% of pediatric keratoplasties [table 3], [5, 7, 8, 14–20, 22–29] and were journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 333 pediatric keratoplasty eye bank records; moshtaghion et al figure 4. the proportion of indications for each surgical procedure. keratoconus was the leading indication for pkp (41.3%) and dalk (87.4%), while corneal dystrophies were the main cause for dsaek (54.2%) and alk (70%). klal technique was exclusively used for chemical injuries (100%). pkp, penetrating keratoplasty; dalk, deep anterior lamellar keratoplasty; dsaek, descemet stripping automated endothelial keratoplasty; alk, anterior lamellar keratoplasty; klal, keratolimbal allograft. reported as the leading indication for pediatric corneal transplantation in both developed and developing countries.[8, 15, 24, 28] however, they were not common in the current study and accounted only for 3.2% of the transplanted eyes. mechanical injuries were the most common cause in this category and were observed more frequently in the younger age group. with the growing activity of the central eye bank of iran, there has been a growing trend in the annual rate of keratoplasty in iran over the last decades; however, the annual rate of pediatric keratoplasty showed a significant diminishing trend over the 14-year period. this may be partially explained by the surgeons’ preference for performing keratoplasty when the patients are over 18 years of age, especially in the keratoconus cases. pkp was the most common surgical procedure for pediatric keratoplasty in our survey. in a study by javadi et al,[32] post-pkp graft quality in patients with ched was relatively high up to three years after surgery. however, in the last decade, this technique of surgery has been replaced with the partial thickness procedures such as alk in cases with anterior stromal involvements, dalk in keratoconus patients, and dsaek in ched, bullous keratopathies, and regraft. given that pkp has a high risk of postoperative complications and graft failure, implementation of partial thickness procedures can be superior to the full thickness surgical techniques in certain pediatric corneal disorders.[33–35] nevertheless, the partial thickness procedures may have limitations such as the need for a committed pediatric cornea service, steep learning curve for the pediatric cornea surgeons, and unforeseeable visual outcomes.[27, 33] it was estimated that only about one-third of the currently practicing cornea surgeons are performing partial thickness procedures in pediatric cases.[36] in our survey, the proportion of dsaek showed a significant growth over the 14-year period and ched was the main indication in half of the cases. this technique can be advantageous over pkp in pediatric cases with ched due to the small corneal incision, use of a “closed system” condition, few sutures, and early suture removal causing rapid visual rehabilitation and improved visual outcomes.[37] dalk is another partial thickness surgical procedure which was mainly performed for keratoconus eyes in our series. although dalk has been reported with the same visual outcomes as pkp, while causing fewer complications and offering higher safety than the pkp, it had a significant descending trend over the 14 years in iran.[38, 39] this may be mainly attributed to 334 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 pediatric keratoplasty eye bank records; moshtaghion et al the downward trend of keratoconus as well as underreporting of some dalk cases to the eye bank by the corresponding surgeons.[40] with the recent development in ocular surface reconstruction in iran, keratolimbal techniques have been currently used for the patients with limbal stem cell deficiency.[41, 42] in our survey, klal was the main procedure for the management of chemical burn-induced ocular surface disorders in four pediatric cases. implementation of this surgical procedure was not certainly specified in prior studies on pediatric keratoplasty. the optical graft clarity was reported in the majority of the transplanted pediatric eyes (about 97%) in our series. most of the eyes in the category of postoperative unclear corneas underwent pkp and the main indication was keratoconus. the current study had limitations in terms of the retrospective nature of the survey and unavailable long-term follow-up data such as postoperative complications and final visual outcomes. in summary, our survey was one of the largest case series reported on pediatric keratoplasty in terms of indications, surgical techniques, and postoperative optical clarity outcomes. in this survey, acquired non-traumatic corneal disorders were the most common indication for pediatric corneal transplantation in iran, among which keratoconus was on the top. pkp was the most common surgical procedure, which, parallel to the decreasing rate of keratoconus, revealed a significant downward trend over the 14 years. nevertheless, a part of the decline in the trend of pkp may be attributed to the shift from pkp to partial thickness procedures such as dsaek for ched and dalk for keratoconus. financial support and sponsorship none. conflicts of interest the authors declare that they have no conflict of interest. references 1. trief d, marquezan mc, rapuano cj, prescott cr. pediatric corneal transplants. curr opin ophthalmol 2017;28:477–484. 2. park cy, lee jk, gore pk, lim cy, chuck rs. keratoplasty in the united states: a 10-year review from 2005 through 2014. ophthalmology 2015;122:2432–2442. 3. droutsas k, bagikos g, miltsakakis d, georgalas i, lazaridis a, chatzistefanou k, et al. trends in indications and techniques of corneal transplantation from 1999 through 2015 at a tertiary referral center in athens, greece. j ophthalmol 2018;2018:9132083. 4. bozkurt tk, acar b, kilavuzoglu ae, akdemir mo, hamilton dr, cosar yurteri cb, et al. an 11-year review of keratoplasty in a tertiary referral center in turkey: changing surgical techniques for similar indications. eye contact lens 2017;43:364–370. 5. gulias-cañizo r, gonzalez-salinas r, hernandez-zimbron lf, hernandez-quintela e, sanchez-huerta v. indications and outcomes of pediatric keratoplasty in a tertiary eye care center: a retrospective review. medicine 2017;96:e8587. 6. ting ds, sau cy, srinivasan s, ramaesh k, mantry s, roberts f. changing trends in keratoplasty in the west of scotland: a 10-year review. br j ophthalmol 2012;96:405– 408. 7. sharma n, prakash g, titiyal js, tandon r, vajpayee rb. pediatric keratoplasty in india: indications and outcomes. cornea 2007;26:810–813. 8. shi w, jin h, li s, liu m, xie l. indications of paediatric keratoplasty in north china. clin exp ophthalmol 2007;35:724–727. 9. dong pn, han tn, aldave aj, chau ht. indications for and techniques of keratoplasty at vietnam national institute of ophthalmology. int j ophthalmol 2016;9:379–383. 10. mathews pm, lindsley k, aldave aj, akpek ek. etiology of global corneal blindness and current practices of corneal transplantation: a focused review. cornea 2018;37:1198– 1203. 11. lowe mt, keane mc, coster dj, williams ka. the outcome of corneal transplantation in infants, children, and adolescents. ophthalmology 2011;118:492–497. 12. zhao s, le q, yao w, xu j. indications and techniques of pediatric keratoplasty in eastern china from 2008 to 2017. cornea 2019;38:1370–1376. 13. stulting rd, sumers kd, cavanagh hd, waring go 3rd, gammon ja. penetrating keratoplasty in children. ophthalmology 1984;91:1222–1230. 14. patel hy, ormonde s, brookes nh, moffatt ls, mcghee cn. the indications and outcome of paediatric corneal transplantation in new zealand: 1991–2003. br j ophthalmol 2005;89:404–408. 15. mcclellan k, lai t, grigg j, billson f. penetrating keratoplasty in children: visual and graft outcome. br j ophthalmol 2003;87:1212–1214. 16. buzzonetti l, ardia r, petroni s, petrocelli g, valente p, parrilla r, et al. four years of corneal keratoplasty in italian paediatric patients: indications and clinical outcomes. graefes arch clin exp ophthalmol 2016;254:2239–2245. 17. mun-wei l, md said h, punitan r, ibrahim m, shatriah i. indications, clinical outcomes, and survival rate of pediatric penetrating keratoplasty in suburban malaysia: a 10-year experience. cureus 2018;10:e3744. 18. huang c, o’hara m, mannis mj. primary pediatric keratoplasty: indications and outcomes. cornea 2009;28:1003–1008. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 335 pediatric keratoplasty eye bank records; moshtaghion et al 19. low jr, anshu a, tan ac, htoon hm, tan dt. the outcomes of primary pediatric keratoplasty in singapore. am j ophthalmol 2014;158:496–502. 20. al-ghamdi a, al-rajhi a, wagoner md. primary pediatric keratoplasty: indications, graft survival, and visual outcome. j aapos 2007;11:41–47. 21. di zazzo a, bonini s, crugliano s, fortunato m. the challenging management of pediatric corneal transplantation: an overview of surgical and clinical experiences. jpn j ophthalmol 2017;61:207–217. 22. xavier dos santos araújo me, santos nc, souza lb, sato eh, de freitas d. primary pediatric keratoplasty: etiology, graft survival, and visual outcome. am j ophthalmol 2020;212:162–168. 23. kusumesh r, vanathi m. graft rejection in pediatric penetrating keratoplasty: clinical features and outcomes. oman j ophthalmol 2015;8:33–37. 24. limaiem r, chebil a, baba a, ben youssef n, mghaieth f, el matri l. pediatric penetrating keratoplasty: indications and outcomes. transplant proc 2011;43:649–651. 25. hong j. xu j, sheng m, liu y, zhu l. pediatric penetrating keratoplasty in shanghai: a retrospective multiple centre study from 2003 to 2007. chin med j 2008;121:1911–1914. 26. aasuri mk, garg p, gokhle n, gupta s. penetrating keratoplasty in children. cornea 2000;19:140–144. 27. zhu ay, prescott cr. recent surgical trends in pediatric corneal transplantation: a 13-year review. cornea 2019;38:546–552. 28. majander a, kivelä tt, krootila k. indications and outcomes of keratoplasties in children during a 40-year period. acta ophthalmol 2016;94:618–624. 29. hovlykke m, hjortdal j, ehlers n, nielsen k. clinical results of 40 years of paediatric keratoplasty in a single university eye clinic. acta ophthalmol 2014;92:370–377. 30. kanavi mr, javadi ma, sanagoo m. indications for penetrating keratoplasty in iran. cornea 2007;26:561– 563. 31. alldredge oc, krachmer jh. clinical types of corneal transplant rejection. their manifestations, frequency, preoperative correlates, and treatment. arch ophthalmol 1981;99:599–604. 32. javadi ma, baradaran-rafii ar, zamani m, karimian f, zare m, einollahi b, et al. penetrating keratoplasty in young children with congenital hereditary endothelial dystrophy. cornea 2003;22:420–423. 33. sharma n, agarwal r, jhanji v, bhaskar s, kamalakkannan p, nischal kk. lamellar keratoplasty in children. surv ophthalmol 2020;65:675–690. 34. madi s, santorum p, busin m. descemet stripping automated endothelial keratoplasty in pediatric age group. saudi j ophthalmol 2012;26:309–313. 35. foroutan ar, gheibi gh, joshaghani m, ahadian a, foroutan p. traumatic wound dehiscence and lens extrusion after penetrating keratoplasty. cornea 2009;28:1097–1099. 36. zhu ay, marquezan mc, kraus cl, prescott cr. pediatric corneal transplants: review of current practice patterns. cornea 2018;37:973–980. 37. yang f, hong j, xiao g, feng y, peng r, wang m, et al. descemet stripping endothelial keratoplasty in pediatric patients with congenital hereditary endothelial dystrophy. am j ophthalmol 2020;209:132–140. 38. keane m, coster d, ziaei m, williams k. deep anterior lamellar keratoplasty versus penetrating keratoplasty for treating keratoconus. cochrane database syst rev 2014;2014:cd009700. 39. henein c, nanavaty ma. systematic review comparing penetrating keratoplasty and deep anterior lamellar keratoplasty for management of keratoconus. cont lens anterior eye 2017;40:3–14. 40. ali javadi m, kanavi mr, safi s. a 27-year report from the central eye bank of iran. j ophthalmic vis res 2020;15:149–159. 41. baradaran-rafii a, eslani m, djalillian ar. complications of keratolimbal allograft surgery. cornea 2013;32:561–566. 42. baradaran-rafii a, ebrahimi m, kanavi mr, taghi-abadi e, aghdami n, eslani m, et al. midterm outcomes of autologous cultivated limbal stem cell transplantation with or without penetrating keratoplasty. cornea 2010;29:502– 509. 336 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 review article prevalence, incidence and ecological determinants of diabetic retinopathy in iran: systematic review and meta-analysis golnoush sadat mahmoudi nezhad1,2,3, md; reza razeghinejad4, md; mohsen janghorbani5,6, phd; alireza mohamadian2,7, md; mohammad hassan jalalpour2, md; somaye bazdar1,2, md; alireza salehi1, md; hossein molavi vardanjani1, phd 1mph department, shiraz university of medical sciences, shiraz, iran 2poostchi ophthalmology research center, department of ophthalmology, shiraz university of medical sciences, shiraz, iran 3glaucoma division, stein eye institute, david geffen school of medicine, university of california at los angeles, los angeles, ca, usa 4glaucoma service, wills eye hospital, philadelphia, pa, usa 5department of epidemiology and biostatistics, school of public health, isfahan university of medical sciences, isfahan, iran 6isfahan endocrine and metabolism research center, isfahan university of medical sciences, isfahan, iran 7student research committee, shiraz university of medical sciences, shiraz, iran orcid: golnoush sadat mahmoudi nezhad: https://orcid.org/0000-0002-9233-9882 hossein molavi vardanjani: https://orcid.org/0000-0001-7024-8894 abstract purpose: to estimate the pooled prevalence and incidence of diabetic retinopathy (dr) in iran and to investigate their correlations with the human development index (hdi), healthcare access (i.e., density of specialists and sub-specialists), and methodological issues. methods: electronic databases such as pubmed, embase, scopus, web of science, google scholar, and local databases were searched for cohort and cross-sectional studies published prior to january 2018. prevalence and incidence rates of dr were extracted from january 2000 to december 2017 and random effects models were used to estimate pooled effect sizes. the joanna briggs institute critical appraisal tool was applied for quality assessment of eligible studies. results: a total of 55,445 participants across 33 studies were included. the pooled prevalence (95% ci) of dr in diabetic clinics (22 studies), eye clinics (4 studies), and general population (7 studies) was 31.8% (24.5 to 39.2), 57.8% (50.2 to 65.3), and 29.6% (22.6 to 36.5), respectively. it was 7.4% (3.9 to 10.8) for proliferative dr and 7.1% (4.9 to 9.4) for clinically significant macular edema. the heterogeneity of individual estimates of prevalence was highly significant. hdi (𝑃 < 0.001), density of specialists (𝑃 = 0.004), subspecialists (𝑃 < 0.001), and sampling site (𝑃 = 0.041) were associated with heterogeneity after the adjustment for type of dr, duration of diabetes, study year, and proportion of diabetics with controlled hba1c. conclusion: human development and healthcare access were correlated with the prevalence of dr. data were scarce on the prevalence of dr in less developed provinces. participant recruitment in eye clinics might overestimate the prevalence of dr. keywords: access to health care; diabetic retinopathy; epidemiology; human development; iran j ophthalmic vis res 2019; 14 (3): 321–335 correspondence to: hossein molavi vardanjani, phd. department of mph, medical school, shiraz university of medical sciences, zand st., shiraz 71348, iran. e-mail: h.molavivardanjani@gmail.com received: 22-12-2018 accepted: 06-04-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i3.4790 @ 2019 j  o  v r | published by knowledge e 321 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i3.4790&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr diabetic retinopathy and its correlates in iran; mahmoudi nezhad et al this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: mahmoudi nezhad gs, razeghinejad r, janghorbani m, mohamadian a, jalalpour mh, bazdar s, et al. prevalence, incidence and ecological determinants of diabetic retinopathy in iran: systematic review and meta-analysis. j ophthalmic vis res 2019;14:321–335. introduction diabetic retinopathy (dr) is the leading cause of vision loss in adults aged 20-74 years, and remains one of the foremost causes of blindness and visual impairment worldwide.[1–4] despite significant development in the prevention and control of dr, the proportion of dr increased by 7.7% among all declining causes of blindness between 1990 and 2015.[5] the prevalence of dr strongly correlates with both the duration of diabetes and the level of glycemic control.[6] therefore, timely management of dr stemming from screening programs, appropriate referral for treatment, and improving healthcare accessibility are important in preserving vision in diabetics.[7] although the treatment of dr can decrease the risk of visual loss by 60%, it imposes a heavy cost to the healthcare system.[8] despite some improvements in diagnostic assessment and treatment options,[6] the lack of qualified healthcare services along with a westernized lifestyle have caused the burden of dr to be high and on the rise in developing countries.[7, 8] dr is a pressing public health matter, probably due to suboptimal access to diabetes care services such as eye care professionals and eye care services, especially in lowto middle-income countries.[8] low human development might be another correlate of the increasing burden of dr. to the best of our knowledge, no study has investigated the correlation between human development and dr. the only study on this subject assessed the association between the human development index (hdi) and the number of studies published on dr.[9] hdi is abstracted from income, education, and life expectancy markers and ranks areas into different levels of human development.[10] despite the high prevalence of diabetes, there are few reliable national studies on the incidence, prevalence, and correlates of dr in developing countries.[11] of note, iran is a country in transition, having a high variety of healthcare access options and human development as well as a huge variation in the prevalence and incidence of dr across its geographic regions.[12–14] therefore, besides assessing the prevalence and incidence of dr, their adjusted correlations with hdi and healthcare access were investigated in the current observational study. methods protocol and registration the meta-analysis of observational studies in epidemiology (moose) guidelines were followed.[15] the study protocol was approved by the shiraz university of medical sciences (ethical approval code: ir.sums.med.rec.1397.256). eligibility criteria observational studies (prospective or retrospective cohort and cross-sectional) were included if they provided sufficient information about the incidence and prevalence of dr and clinically significant macular edema (csme). no restriction was applied on the year of publication or type of diabetes, and all studies published in persian or english language were included. these two languages covered all studies published about the iranian population and we did not find studies in other languages. search strategy we performed a systematic search for the prevalence and incidence of dr, summarized in figure 1. pubmed, scopus, web of science, google scholar, embase, and the local databases of sid and iran doc were searched for articles published between january 2000 and december 2017. our search was limited to studies related to iran. the search terms included: “diabetes” or “diabetic” combined with ”complication” or “retina” or “vision” or “visual” or “retinopathy” or “blindness” or “clinically significant macular edema” and “iran” and “epidemiology” or “incidence” or “prevalence” or “proportion”. review articles and their references were checked for additional studies. the gray literature evaluation was performed using international and regional 322 j  o  v r volume 14, issue 3, july–september 2019 diabetic retinopathy and its correlates in iran; mahmoudi nezhad et al congresses that were held during the study period around the world and specifically in iran, and we selected and hand searched the abstract books that were obtainable as much as possible. we also searched university websites for thesis and reports that were related to the subject during the study period. references of all included studies were also searched for potentially eligible studies. in cases where the full text of an article was unavailable, the corresponding author was contacted. documents were catalogued using endnote x4. study selection in case of repeated publications from one study, the newest publication was included. titles, abstracts, and the full texts of retrieved articles were reviewed independently by two experts in the field and eligible articles were selected. studies on children, pregnant women, or noniranian populations were excluded as well as experimental studies, secondary studies, letters, case-reports, case-series, commentaries, and editorials. clinical trials were also excluded. studies with a non-representative sample or irrelevant comorbidities were also excluded. also, in the case of disagreement regarding exclusion or inclusion of a study, a consensus was reached through discussion between the authors. data extraction and risk of bias assessment we performed a comprehensive literature review and designed a conceptual framework. an excel (ms office) data sheet based on clinical principles was prepared for data extraction using our framework. the following variables were included in the data extraction form: first author, publication year, study year, study location (i.e., province/district), urbanization ratio (number of participants from the urban area/number of participants from the rural area; based on the data presented in each individual study), sampling site (diabetes clinic, eye clinic, or general population), sampling design (random, multistage, convenient, unknown), study design (cross-sectional, cohort), sample size (overall and for subgroups), age range (or mean age), duration of study, gender (or female/male ratio), diagnostic methods of dr,[16] proportion of diabetics (in population-based studies), type of diabetes (or type i/type ii ratio), type of dr (i.e., non-proliferative diabetic retinopathy [npdr]) and its stage (mild, moderate, or severe), proliferative diabetic retinopathy (pdr), csme, mean hba1c (overall, among dr patients, and among non-dr patients), number of dr patients (or estimated prevalence and its standard error), number of incident cases of dr (or cumulative incidence rate; only for cohort studies), number of person-years of follow-up (in cohort studies), duration of dm (overall, among dr patients, and among non-dr patients), mean age at the onset of dm, mean duration of dr, and proportion of patients with newly diagnosed dm. the aforementioned data were extracted (if available) and 25% of the extracted data were randomly cross-checked by another author. also, in the case of disagreement regarding data extraction, a consensus was reached through discussion between the authors. since several studies had not reported exact values for some variables, more than 30 disagreements on the most appropriate estimates for these missing values were discussed in the team. the joanna briggs institute (jbi)’s critical appraisal tool[17] was applied for quality assessment of eligible studies. quality assessments and critical appraisals were performed by two different authors independently. in the case of disagreement regarding the quality score, a consensus was reached through discussion between the authors (4 studies out of the included 33 studies). data on human development and healthcare access the density of specialists and subspecialists (numbers of specialists and subspecialists in the healthcare system of each province to the total population in that province) was retrieved from a recent reliable report by haghdoost et al[18] as indices of healthcare access. density ratios were categorized into quantiles. haghdoost et al gathered the number of physicians based on the questionnaires filled out by medical universities all around iran. their study was a part of a project to define the national treatment map of iran in 2025 (naghsh-e rahe darman-e iran). in order to control the precision of completing the questionnaire, their data was crosschecked with the medical registry information system and different medical insurance companies.[18] j  o  v r volume 14, issue 3, july–september 2019 323 diabetic retinopathy and its correlates in iran; mahmoudi nezhad et al figure 1. flow diagram summarizing the systematic search and review process for identifying evidence regarding the prevalence and diabetic retinopathy. inclusion and exclusion criteria are provided in the text. hdi indices (less developed, moderately developed, and developed) were retrieved for each province according to the study performed by safaeipour et al[12] and used as an independent variable in meta-regression modeling. data preparation and statistical analysis point estimates of prevalence were extracted or calculated as the number of patients with dr divided by the number of patients with dm. additionally, prevalence estimates of dr in the population, regardless of diabetic status, were estimated as the number of participants with dr divided by the number of total participants in populationbased studies. a 95% confidence interval (ci) for all individual point estimates of prevalence was estimated where it was not mentioned.[19] cumulative incidence proportions (per 100 person-years) were calculated as the number of new dr cases divided by the number of at-risk person-years (i.e., number of study subjects multiplied by number of follow-up years). to ensure the independence of point estimates in primary studies as well as to prevent repeated counting of participants in primary studies, only one of the overall or subgroup point estimates of each primary study was included in the meta-analysis and meta-regression models. the heterogeneity of individual estimates of prevalence was assessed according to the i-square statistic above 50%.[20] in cases of high heterogeneity, correlates were 324 j  o  v r volume 14, issue 3, july–september 2019 diabetic retinopathy and its correlates in iran; mahmoudi nezhad et al conceptualized. then, the significance and magnitude of their correlation were investigated using the random-effects meta-regression technique. subgroup analyses were performed according to the most important correlates of heterogeneity if applicable (i.e., sampling site, geographical location, hdi and healthcare access). due to persistent heterogeneity (even after subgroup analysis), individual estimates of prevalence and incidence were pooled using the dersimonian and laird randomeffects modeling method. publication bias was investigated using begg’s and egger’s tests. data analysis and calculations were performed using stata software, version 11.2 (stata corporation, college station, tx, usa). a two-sided 𝑃 < 0.05 was considered as statistically significant. we also provided appropriate tables and graphs for showing our results (i.e., included studies, shortage in studies, methods applied for the diagnosis of dr by primary studies, study flowchart, and study forest plot by hdi categories). the study protocol was registered in the international prospective register of systematic reviews (prospero), under the registration number crd42018104626. results the initial search resulted in 2,153 records. of these, 426 records were included in the fulltext review process, and finally, 33 studies were included in the meta-analysis. overview of included studies thirty cross-sectional and three cohort studies were included in the analysis, representing an overall number of 55,445 diabetic patients including 17,155 patients with dr [table 1]. among cross-sectional studies, seven had a populationbased sampling design representing 24,623 participants including 5,657 diabetic patients and 2,049 patients with dr. included cohort studies represented 1,174 diabetic patients (equivalent to 5,400 person-years) and 613 incident cases of dr. assessment of heterogeneity in individual estimates for prevalence of diabetic retinopathy in cross-sectional studies conducted in diabetes clinics, individual estimates for the prevalence of dr were significantly heterogeneous for overall diabetics (i-square, 99.5; 𝑃 < 0.001; the heterogeneity was similar between genders [i-square, 99.4; 𝑃 < 0.001]). also, individual estimates for the prevalence of dr were highly heterogeneous in studies conducted in eye clinics (i-square, 98.0; 𝑃 < 0.001) and population-based studies (i-square, 95.7; 𝑃 < 0.001). additionally, in three cohort studies, the estimates of individual cumulative incidence of dr were statistically heterogeneous with a highly significant i-square of 97.9 (𝑃 < 0.001). determinants of dr prevalence (correlates of heterogeneity of individual estimates) according to the random-effects meta-regression model, hdi (as an ordinal variable of tertile of hdi; adjusted or: 0.12, 95% ci: 0.05 to 0.34, 𝑃 < 0.001), density of specialists (as an ordinal variable including quintile of density ratio; adjusted or: 1.13, 95% ci: 1.04 to 1.23, 𝑃 = 0.004), density of subspecialists (as an ordinal variable including quintile of density ratio; adjusted or: 0.85, 95% ci: 0.78 to 0.91, 𝑃 < 0.001), type of dr (reference is pdr; adjusted or: 1.30, 95% ci: 1.10 to 1.42, 𝑃 < 0.001), duration of diabetes (adjusted or: 1.05, 95% ci: 1.04 to 1.07, 𝑃 < 0.001), site of study sampling (reference is population-based sampling; adjusted or: 1.09, 95% ci: 1.02 to 1.17, 𝑃 = 0.041), study year (adjusted or: 0.97, 95% ci: 0.96 to 0.98, 𝑃 < 0.001), and proportion of diabetics with controlled hba1c (adjusted or: 0.92, 95% ci: 0.87 to 0.97, 𝑃 = 0.005) were significantly associated with the heterogeneity of individual estimates of dr prevalence. risk of bias was not associated with heterogeneity (𝑃 = 0.683). type of diabetes was not a significant determinant of heterogeneity for individual estimates of dr prevalence (𝑃 = 0.10). due to the lack of enough data to achieve individual estimates of cumulative incidence, metaregression modeling for cumulative incidence was not applicable. j  o  v r volume 14, issue 3, july–september 2019 325 diabetic retinopathy and its correlates in iran; mahmoudi nezhad et al ta b le 1. c ha ra ct er is tic s of st ud ie s in cl ud ed in th e m et aan al ys is s o u rc e s tu d y d e si g n s a m p le si ze t yp e o f d m n o o f d m s it e o f sa m p lin g p ro vi n ce h d i d m d u ra ti o n (y e a r) h b a 1c (m e a n ) p o r io f d r (9 5 % c i) js ja ng ho rb an ie ta l[2 1] 20 0 3 c oh 54 9 ii 54 9 d m c lin ic is fa ha n 0. 72 4 5 .8 10 .6 8. 9 (7 .9 ,10 .1) * l m an av ia te ta l[2 2] 20 04 c -s 59 0 ii 59 0 d m c lin ic ya zd 0. 72 89 10 .2 – 39 .3 (4 3. 2 ,3 5 .4 ) m a bd ol la hi et al [2 3] 20 0 6 c -s 18 1 i& ii 18 1 d m c lin ic te hr an 0. 75 96 9. 9 – 37 .6 (4 4. 7, 30 .5 ) m a bd ol la hi et al [2 4] 20 0 6 c -s 15 2 ii 15 2 d m c lin ic te hr an 0. 75 96 1.2 7.1 13 .8 (19 .3 ,8 .3 ) m a m in ie ta l[2 5] 20 07 c oh 50 5 ii 50 5 d m c lin ic is fa ha n 0. 72 4 10 .2 7. 5 14 .4 (12 .9 ,1 5 .9 )* m m an av ia te ta l[2 6] 20 0 8 c oh 12 0 ii 12 0 d m c lin ic ya zd 0. 72 89 11 .6 – 11 .4 (8 .6 ,1 4. 2) * h a m in ie ta l[1 4] 20 0 8 c -s 71 0 ii 71 0 d m c lin ic is fa ha n 0. 72 4 0. 5 9. 5 9 (11 .1, 6. 9) m g ha ra ag aj ie ta l[2 7] 20 0 8 c -s 59 1 i 59 1 ey e c lin ic te hr an 0. 75 96 9. 7 – 37 .9 (4 1.8 ,3 4. 0) l g ol ba ha re ta l[2 8] 20 0 8 c -s 25 4 ii 25 4 ey e c lin ic fa rs 0. 68 44 9 8. 1 48 .8 (5 4. 9, 42 .7 ) m h at ef et al [13 ] 20 0 8 c -s 43 54 i& ii 19 3 po pu la tio n te hr an 0. 75 96 – – 17 .0 (2 2 .3 ,1 1.7 ) l h os se in ie ta l[2 9] 20 0 9 c -s 37 34 ii 37 34 po pu la tio n is fa ha n 0. 72 4 7 8. 9 54 .0 (5 5 .6 ,5 2 .4 ) l ja va di et al [3 0 ] 20 0 9 c -s 79 89 i& ii 63 4 po pu la tio n te hr an 0. 75 96 8. 9 6. 9 37 .8 (4 1.6 ,3 4. 0) l so le ym an ie ta l[3 1] 20 12 c -s 14 0 ii 14 0 ey e c lin ic m az an dr an 0. 70 57 8. 9 – 36 .4 (4 4. 4, 28 .4 ) m ja va nb ak ht et al [3 2] 20 12 c -s 34 72 ii 34 72 po pu la tio n ira n 0. 7 8. 1 – 40 .4 (4 2 .0 ,3 8. 8) l n aj afi et al [3 3] 20 13 c -s 24 3 ii 24 3 d m c lin ic te hr an 0. 75 96 9. 1 7. 6 22 .8 (2 8. 1, 17 .5 ) l sh ag ha gh ie ta l[3 4] 20 14 c -s 23 4 ii 23 4 d m c lin ic w es t a ze rb ai ja n 0. 64 36 12 – 33 .3 (3 9. 3, 27 .3 ) m ya gh oo bi et al [3 5] 20 14 c -s 18 0 ii 18 0 d m c lin ic te hr an 0. 75 96 – 8. 9 48 .9 (5 6. 2 ,4 1.6 ) m h os se in ie ta l[3 6] 20 14 c -s 30 5 ii 30 5 d m c lin ic te hr an 0. 75 96 8. 2 – 35 .7 (4 1.1 ,3 0. 3) l m ag hb oo li et al [3 7] 20 14 c -s 12 28 ii 12 28 d m c lin ic te hr an 0. 75 96 11 .3 7. 5 26 .6 (2 9. 1, 24 .1) m ta zh ib ie ta l[3 8] 20 14 c -s 35 35 ii 35 35 d m c lin ic is fa ha n 0. 72 4 7.1 – 53 .4 (5 5 .0 51 .8 ) m 326 j  o  v r volume 14, issue 3, july–september 2019 diabetic retinopathy and its correlates in iran; mahmoudi nezhad et al ta b le 1. c on tin ue d. s o u rc e s tu d y d e si g n s a m p le si ze t yp e o f d m n o o f d m s it e o f sa m p lin g p ro vi n ce h d i d m d u ra ti o n (y e a r) h b a 1c (m e a n ) p o r io f d r (9 5 % c i) js g ho ds ie ta l[3 9] 20 14 c -s 97 8 ii 97 8 d m c lin ic fa rs 0. 68 44 10 .3 9. 3 10 .4 (12 .3 ,8 .5 ) m d eh gh an et al [4 0 ] 20 14 c -s 20 90 i& ii 53 9 po pu la tio n ya zd 0. 72 89 – 8. 8 29 .5 (3 3. 4, 25 .6 ) l a zi zi -s ol ei m an et al [4 1] 20 15 c -s 17 82 ii 17 82 d m c lin ic is fa ha n 0. 72 4 5 .8 9. 1 61 .7 (6 4. 0, 59 .4 ) l sh am sh irg ar an et al [4 2] 20 15 c -s 30 0 ii 30 0 d m c lin ic a rd ab il 0. 65 97 7. 7 8. 4 20 .7 (2 5 .3 ,1 6. 1) l r as ou lin ej ad et al [4 3] 20 15 c -s 15 62 i& ii 15 62 ey e c lin ic m az an dr an 0. 70 57 10 .5 8. 9 64 .1 (6 6. 5 ,6 1.7 ) h m eh ra va re ta l[4 4] 20 16 c -s 56 2 ii 56 2 d m c lin ic te hr an 0. 75 96 15 .6 7. 9 28 .1 (3 1.8 ,2 4. 4) l v al iz ad eh et al [4 5] 20 16 c -s 20 6 ii 20 6 d m c lin ic ke rm an 0. 68 91 13 – 45 .1 (5 1.9 ,3 8. 3) l sa m ad ia id en lo o et al [4 6] 20 16 c -s 30 10 i& ii 18 1 po pu la tio n w es t a ze rb ai ja n 0. 64 36 7. 3 5 .6 32 .6 (3 9. 4, 25 .8 ) l h as he m ie ta l[4 7] 20 16 c -s 93 7 i& ii 10 3 po pu la tio n m az an dr an 0. 70 57 – – 24 .3 (3 2 .6 ,1 6) l d eh gh an e et al [4 8] 20 17 c -s 25 1 ii 25 1 d m c lin ic g ol es ta n 0. 67 36 8. 7 8. 4 51 .4 (5 7. 6, 45 .2 ) l sh am sh irg ar an et al [4 9] 20 17 c -s 69 4 ii 69 4 d m c lin ic a rd ab il & ea st a ze rb ai ja n 0. 67 5 6. 6 8. 4 16 .0 (18 .7 ,1 3. 3) l es te gh am at ie ta l[1 1] 20 17 c -s 30 20 2 i& ii 30 20 2 d m c lin ic ira n 0. 7 8 8. 0 21 .9 (2 2 .4 ,2 1.4 ) l ka tib eh et al [5 0 ] 20 17 c -s 25 0 1 i& ii 53 5 po pu la tio n g ila n 0. 68 86 – – 24 .5 (2 8. 1, 20 .9 ) l cs, cr os s se ct io na l; co h, co ho rt ;d m ,d ia be te s m el lit us ;d r ,d ia be tic re tin op at hy ;h ,h ig h; i, in ci de nc e; p, pr ev al en ce ;j b i, th e jo an na b rig gs in st itu te cr iti ca la pp ra is al ; js ,j b is co re ;l ,l ow ;m ,m od er at e; n o of d m ,n um be ro fd ia be tic s *in ci de nc e j  o  v r volume 14, issue 3, july–september 2019 327 diabetic retinopathy and its correlates in iran; mahmoudi nezhad et al prevalence of dr among diabetic patients due to high heterogeneity, pooled prevalence estimates might have some extent of bias from an epidemiological point of view. the range for overall prevalence of dr among diabetics was 9.063.4%. (the pooled estimate of prevalence using randomeffect model was 33.6% [95% ci: 27.9, 39.2], 40.6% [95% ci: 28.9, 52.3], and 35.7% [95% ci: 26.0, 39.4] overall in males and females, respectively [figure 2]). the pooled prevalence of npdr, mild npdr, moderate npdr, and severe npdr among diabetic patients were 24.8% (95% ci: 18.7, 30.9), 14.1% (95% ci: 9.1, 19.2), 8.9% (95% ci: 4.7, 13.0), and 3.3% (95% ci: 2.0, 4.6), respectively. the pooled prevalence of pdr and csme were 7.4% (95% ci: 3.9, 10.8) and 7.1% (95% ci: 4.9, 9.4), respectively. due to significant heterogeneity among studies, the analysis was performed through subgroup analysis based on the most important correlates of heterogeneity. prevalence of dr among patients referred to diabetic clinics the overall pooled prevalence rate of dr among diabetic patients was 31.8% (95% ci: 24.5, 39.2) and 39.1% (95% ci: 23.5, 54.6) among male subjects and 34.6% (95% ci: 23.2, 45.9) among female subjects. the pooled prevalence rates of npdr, mild npdr, moderate npdr, and severe npdr among diabetic patients were 21.0% (95% ci: 12.7, 29.3), 11.1% (95% ci: 3.3, 18.9), 5.6% (95% ci: 0.7, 11.9), and 2.2% (95% ci: 1.2, 3.3), respectively. the pooled prevalence rates of pdr and csme among diabetic patients were 2.9% (95% ci: 1.3, 4.5) and 7.4% (95% ci: 6.1, 8.6). the pooled estimate of prevalence of dr based on studies including only type ii diabetics was 33.3% (95% ci: 24.4, 42.2), whereas, it was 22.6% (95% ci: 12.8, 32.3) in those with both types of diabetes. the pooled prevalence rates of dr in the central, northeast, northwest, southeast, and southwest geographic regions of iran were 42.9% (95% ci: 30.4, 55.3), 51.4% (95% ci: 45.2, 57.5), 26.6% (95% ci: 18.6, 34.6), 45.1% (95% ci: 40.3, 49.9), and 10.4% (95% ci: 8.7, 12.5), respectively, and 30.8% (95% ci: 26.6, 35.0) for tehran (the capital city of iran). prevalence of dr among patients referred to eye clinics the overall pooled prevalence of dr among diabetic patients was 57.8% (95% ci: 50.2, 65.3) and 63.0% (95% ci: 60.4, 65.6) among males and 61.3% (95% ci: 57.0, 65.7) among females. the pooled prevalence rates of npdr and pdr were 29.0% (95% ci: 23.4, 34.5) and 19.4% (95 % ci: 14.6, 24.3), respectively. the pooled estimate of dr prevalence was 48.8% (95% ci: 42.7, 55.0) in studies including only type ii diabetics and 64.6% (95% ci: 62.2, 67.0) in studies including both types of diabetes. the pooled prevalence rates of dr in the north and southwest geographical regions of iran were 58.4% (95% ci: 51.3, 65.5) and 48.8% (95% ci: 44.5, 53.2), respectively, and 39.1% (95% ci: 27.2, 51.0) in tehran. prevalence of dr among patients in population-based studies the overall pooled prevalence of dr was 29.6% (95% ci: 22.6, 36.5) and 36.8% (95% ci: 30.5, 43.2) among male subjects and 29.0% (95% ci: 24.6, 33.6) among female subjects. the pooled prevalence rates of dr in the central, north, and northwest geographical regions of iran were 29.9% (95% ci: 26.4, 33.4), 24.4% (95% ci: 21.3, 27.5), and 32.5% (95% ci: 27.7, 37.4), respectively, and 32.8% (95% ci: 22.3, 43.3) in tehran. prevalence of dr in the general population the overall pooled prevalence of dr (according to the population-based studies) was 3.6% (95% ci: 2.4, 5.0) and 3.5% (95% ci: 1.5, 6.4) among male subjects and 3.6% (95% ci: 2.1, 5.6) among female subjects. cumulative incidence rate of dr in diabetics the overall pooled cumulative incidence rate (per 100 person-years) of dr was 11.7% (95% ci: 8.0, 15.9) and 9.6% (95% ci: 7.8, 11.8) among male subjects and 8.7% (95% ci: 7.5, 10.0) among female 328 j  o  v r volume 14, issue 3, july–september 2019 diabetic retinopathy and its correlates in iran; mahmoudi nezhad et al figure 2. forest plot of diabetic retinopathy prevalence by human development index categories and source of data (clinic vs population-based studies). ci, confidence interval; es, estimation of diabetic retinopathy prevalence (%); hdi, human development index. subjects [figure 3]. the pooled cumulative incidence rates (per 100 person-years) for npdr and pdr were 11.7% (95% ci: 9.1, 14.9) and 0.2% (95 % ci: 0.0, 1.1), respectively. more details on the association of hdi and the prevalence of dr the estimation of linear correlation coefficient between hdi and the prevalence of dr among diabetics was -0.18 with a 𝑃 of 0.029 (a relatively low but significant linear correlation) [figure 4]. reporting and methodological shortcomings one study used the survey data analysis technique to consider multistage sampling design.[50] two studies reported age-adjusted estimates.[30, 40] only 33.3% (n = 11) of the studies reported their dr results by gender [table 2]. assessment of dr according to the current results, 54.54% (n = 18) of studies performed indirect ophthalmoscopy with pupillary dilatation for the evaluation of dr. others probably used the same method; however, this matter was not clearly stated [table 3]. publication bias there was no significant publication bias (begg’s test 𝑃 = 0.824; egger’s test 𝑃 = 0.075) in the current study. discussion in the current study, the pooled prevalence and incidence of dr including pdr and npdr among iranian diabetic subjects referred to diabetes clinics and eye clinics and the pooled prevalence of dr among diabetics retrieved form populationbased studies were determined based on the english language studies only. persian articles were excluded due to poor quality score in our j  o  v r volume 14, issue 3, july–september 2019 329 diabetic retinopathy and its correlates in iran; mahmoudi nezhad et al figure 3. forest plot of cumulative incidence rate of diabetic retinopathy. ci, confidence interval; es, estimation of diabetic retinopathy incidence (%) figure 4. scatter plot of the linear correlation of prevalence and the human development index. dr, diabetic retinopathy assessment. we found no publication bias among the included studies. the human development, access to subspecialists and specialists, and site of study sampling had a correlation with the prevalence of dr among diabetics. studies from other parts of the world reflect significant differences in the prevalence of dr depending on the factors such as ethnicity, demography, and access to healthcare systems.[51, 52] according to the current results, an increase in hdi was independently correlated with lower dr prevalence. in order to avoid the bias of ecological inference fallacy, this finding could only be interpreted from an ecological point of view. therefore, we cannot directly relate the dr prevalence in individuals to the hdi in each province. however, hdi may potentially be a good index of quality of diabetes care in developing countries such as iran at a national level. this finding is consistent with previous evidence from low-income regions of developed countries.[53] the prevalence of dr and pdr/npdr ratio were higher in eye clinics in 330 j  o  v r volume 14, issue 3, july–september 2019 diabetic retinopathy and its correlates in iran; mahmoudi nezhad et al table 2. number (%) of studies reporting important criteria required in epidemiological studies on diabetic retinopathy reportable variables studies on subjects with dm n (%) studies on subjects with dr n (%) study year 26 (78.7) 26 (78.7) source of recruitment 33 (100) 33 (100) sample size 33 (100) 30 (90) gender 33 (100) 11 (33.3) age (mean ± sd) 22 (66.6) 16 (48.4) dividing sample of study by age groups 1 (3.0) 1 (3.0) type of dm 27 (81.8) 27 (81.8) proportion of dm types (n = 11)* 2(18.2) 0 duration of dm 14 (42.4) 11 (33.3) proportion of patients with controlled dm 1(3.0) 0 type of retinopathy 14 (42.4) 14 (42.4) mean age at diagnosis of diabetes 3.0 (9.0) 3.0 (9.0) hba1c (mean ± sd) 20 (60.6) 15 (45) age-gender adjusted prevalence of retinopathy 2 (6) 2 (6) *only 11 studies included both types of dm. the others reported one type of the dm in their sample size. proportion of the dm types in these 11 studies is considered to be an important factor for both diabetics and patients with dr. dm, diabetes mellitus; dr, diabetic retinopathy; hba1c, hemoglobin a1c; n, number; sd, standard deviation table 3. findings about diagnostic methods for diabetic retinopathy diagnostic method number of studies percent indirect ophthalmoscopy 11 33.33 indirect ophthalmoscopy and fluorescein angiography 3 9.09 indirect ophthalmoscopy and fundus photography 4 12.12 questionnaires/records 7 21.21 fundoscopic and angiographic findings 1 3.03 slit-lamp biomicroscopy of the posterior pole using contact lens 1 3.03 eye examination and fundus photography 1 3.03 ophthalmic examination (not mentioned exactly) 5 15.15 total number of studies 33 100 comparison to the dm clinics. it might be due to the higher detection rate of dr, especially pdr in eye clinics.[54–56] in other words, more advanced patients are usually referred to the eye clinics. the density of subspecialists was negatively correlated with the prevalence of dr. this could be due to health literacy, greater access to healthcare services in regions where subspecialists work, leading to more effective diabetes control. this finding is in accordance with previous reports.[51, 52, 57] of note, many confounding factors such as social factors could be associated with the density of subspecialists and prevalence of dr. it might also be due to the interest of subspecialists to be in areas with higher socioeconomic status in which inhabitants may also have a better access to j  o  v r volume 14, issue 3, july–september 2019 331 diabetic retinopathy and its correlates in iran; mahmoudi nezhad et al healthy food, causing more controlled dm and less prevalence of dr. the pooled population-based prevalence of dr among diabetics was close to the maximum estimates of dr prevalence reported in developing countries such as pakistan (29% vs 2529%), while it was lower than the prevalence reported in developed countries.[58–62] population aging and westernized lifestyle could have been among the factors increasing the prevalence of diabetes and dr in iran and other developing countries.[11, 58, 63] in addition, the higher prevalence of dr among male subjects could be attributed to lifestyle habits such as cigarette smoking, which is consistent with studies conducted in india and nepal.[58, 59] the pooled prevalence of dr among diabetics referred to eye clinics was significantly higher than that in diabetes clinics. routine screening by an ophthalmologist is not a common practice in developing countries.[64] thus, this higher prevalence may be due to higher rates of referral for patients presenting with visual symptoms. there is a need for improving screening programs in primary healthcare services and communication between primary healthcare providers and ophthalmologists to ensure diabetics receive timely ophthalmic examinations. based on the results of the current study, the estimation of dr prevalence among diabetics in eye clinics may not be a good indicator of dr prevalence among diabetics; however, a comparison of dr prevalence in diabetic and eye clinics could help determine the sensitivity and specificity of referrals to eye clinics by clinicians and over/underutilization of eye care in developing countries. although, overall and gender-specific pooled prevalence rates of dr among diabetics referred to diabetes clinics were relatively higher than those in population-based studies, these differences were not meaningful. in addition, the female/male ratio of estimated dr prevalence in dm clinics studies was almost equal to the population-based studies (88% vs 80%). therefore, considering the difficulties in conducting robust population-based studies, it is reasonable to estimate the prevalence of dr in diabetes clinics, especially in developing counties such as iran. the pooled estimate of dr incidence among diabetics in iran was less than recent reports from developed countries such as canada, the uk, and spain.[61, 65, 66] moreover, the estimated incidence was relatively higher than india, south korea, and denmark.[67–69] according to the current study, the available data on the incidence of dr in iran is inadequate; further studies are needed to determine the incidence of dr in iran. among the eligible studies included in the current meta-analysis, only one study reported the prevalence of dr among type i diabetics.[27] accordingly, the pooled estimates provided in the current study are mostly representative of the prevalence of dr among type ii diabetics. more studies on the incidence and prevalence of dr among type i diabetics are needed. the results of this study showed that there is a lack of research on the prevalence of dr in less developed provinces, such as sistan and balochistan, bushehr, hormozgan, khorasan, khozestan, kermanshah, kordistan, kohkiloieye, chaharmahal and bakhtiyari, and lorestan. missing data from these provinces could have affected the results of the current study. in addition to the paucity of data in some provinces, there is a significant heterogeneity among studies, which means that making an accurate single prevalence estimate of dr is not possible. the pooled prevalence of dr was 29%. however, the prevalence rate varied from 9% to 64.1%. thus, it might not be completely representative of the actual dr prevalence. in addition to the aforementioned factors, the method used for detecting dr is a major factor that can influence prevalence estimates. it is crucial to know which specific diagnostic method (i.e., dilated fundus examination, direct or indirect ophthalmoscopy, digital imaging, etc.) was used in each study.[70] the ophthalmic examination methods were not adequately explained in at least 12 included studies. in the course of dr, patients might develop maculopathy with no significant change in vision and may not seek medical care. optical coherence tomography (oct) is an important test in the evaluation and management of diabetic macular edema and can detect subclinical macular edema. missing oct evaluation could lead to many diabetics remaining undiagnosed in the early stage of dr.[71] the current study has some limitations. the pooling of data from different sources introduced potential sources of heterogeneity that could impact accuracy. various studies could have different inclusion criteria, sample selection, or study 332 j  o  v r volume 14, issue 3, july–september 2019 diabetic retinopathy and its correlates in iran; mahmoudi nezhad et al protocols. for example, the sample from a diabetes clinic differs from an eye clinic or population-based studies. the pooled estimate of dr prevalence by gender in the current study was sometimes not compatible with the total prevalence in the subgroups, which was due to the lack of reporting dr by gender in some studies. studies in which the diagnosis of dm was based on patient selfreport, without lab test confirmation, could have led to an overestimation of dr prevalence due to the exclusion of undiagnosed diabetes from the study sample. although it is desirable to have the hdi and density of specialists and subspecialists at the time of each study to calculate the correlations and perform the analyses, only two up-to-date and available studies were used for estimating the value of both mentioned variables. also, the absence of studies from the eastern, western, and southern regions of iran could have also affected the validity and generalizability of the current findings. although our findings on the prevalence and incidence of dr may not be generalizable to all countries, it could be useful for developing countries, especially regions with similar socioeconomic, demographic, cultural, and geographic conditions. summary despite the scarcity of research in less developed regions, a reasonable estimate for the prevalence of dr among iranian diabetic subjects is around 30% (29% among female and 37% among male subjects). hdi, density of specialists and subspecialists, and sampling site were independently correlated with the prevalence of dr in iran. the most reliable evidence on dr prevalence is likely to be retrieved from diabetes clinics in developing countries. furthermore, providing a list of essential items for reporting the descriptive epidemiology of dr and performing studies in less developed regions could generate stronger evidence for health policy programs. acknowledgments this study was supported by the shiraz university of medical sciences and approved under code 97-01-01-16865. the study was extracted from the thesis written by golnoush sadat mahmoudi nezhad for md-mph degree. financial support and sponsorship nil. conflicts of interest there is no conflict of interest. references 1. buch h, vinding t, la cour m, appleyard m, jensen gb, nielsen nv. prevalence and causes of visual impairment and blindness among 9980 scandinavian adults: the copenhagen city eye study. ophthalmology 2004;111:5361. 2. brazionis l, jenkins a, keech a, ryan c, brown a, boffa j, et al. diabetic retinopathy in a remote indigenous primary healthcare population: a central australian diabetic retinopathy screening study in the telehealth eye and associated medical services network project. diabet med 2018;35:630-639. 3. tan gs, gan a, sabanayagam c, tham yc, neelam k, mitchell p, et al. ethnic differences in the prevalence and risk factors of diabetic retinopathy: the singapore epidemiology of eye diseases study. ophthalmology 2018;125:529-536. 4. cheung n, mitchell p, wong ty. diabetic retinopathy. lancet 2010. 10;376:124-136. 5. flaxman sr, bourne rr, resnikoff s, ackland p, braithwaite t, cicinelli mv, et al. global causes of blindness and distance vision impairment 1990-2020: a systematic review and meta-analysis. the lancet glob health 2017;5:e1221-e1234. 6. solomon sd, chew e, duh ej, sobrin l, sun jk, vanderbeek bl, et al. diabetic retinopathy: a position statement by the american diabetes association. diabetes care 2017;40:412-418. 7. ding j, wong ty. current epidemiology of diabetic retinopathy and diabetic macular edema. curr diab rep 2012;12:346-354. 8. ting dsw, cheung gcm, wong ty. diabetic retinopathy: global prevalence, major risk factors, screening practices and public health challenges: a review. clin exp ophthalmol 2016;44:260-277. 9. caglar c, demir e, kucukler fk, durmus m. a bibliometric analysis of academic publication on diabetic retinopathy disease trends during 1980-2014: a global and medical view. int j ophthalmol 2016;9:1663. 10. publications un, programme und. human development report 2016: human development for everyone: united nations publications; 2017. 11. esteghamati a, larijani b, aghajani mh, ghaemi f, kermanchi j, shahrami a, et al. diabetes in iran: prospective analysis from first nationwide diabetes report of national program for prevention and control of diabetes (nppcd2016). sci rep 2017;7:13461. 12. safaeipour m, maveddat e. assessment of areas with an emphasis on social indicators-economic and human development indicators in combination with the use of j  o  v r volume 14, issue 3, july–september 2019 333 diabetic retinopathy and its correlates in iran; mahmoudi nezhad et al gis techniques and topsis. studies on urban planning 2013;1:11-27 [in persian]. 13. hatef e, fotouhi a, hashemi h, mohammad k, jalali kh. prevalence of retinal diseases and their pattern in tehran: the tehran eye study. retina 2008;28:755-762. 14. amini m, aminorroaya a, safaei h, behrooz z, teimori a. prevalence of diabetic retinopathy in newly diagnosed type 2 diabetic patients in isfahan, iran. acta endocrinologica 2008;4:415-423. 15. stroup df, berlin ja, morton sc, olkin i, williamson gd, rennie d, et al. meta-analysis of observational studies in epidemiology: a proposal for reporting. jama 2000;283:2008-2012. 16. salz da, witkin aj. imaging in diabetic retinopathy. middle east afr j ophthalmol 2015;22:145. 17. joanna briggs institute. critical appraisal tools. australia: the university of adelaide; 2018 [cited 2018 jun 01]. available from: http://joannabriggs.org/research/criticalappraisal-tools.html 18. haghdoost a, hashemi h, haji aghajani m, janbabaee g, maher a, noori hekmat s, et al. specialized and geographic distribution of specialists in iran in 2016 and its estimates in 2026. iran j epidemiol 2018;13:122-132. 19. brown ld, cai tt, dasgupta a. interval estimation for a binomial proportion. stat sci 2001;16:101-133. 20. huedo-medina tb, sánchez-meca j, marín-martínez f, botella j. assessing heterogeneity in meta-analysis: q statistic or i index? psychol methods 2006;11:193. 21. janghorbani m, amini m, ghanbari h, safaiee h. incidence of and risk factors for diabetic retinopathy in isfahan, iran. ophthalmic epidemiol 2003;10:81-95. 22. manaviat mr, afkhami m, shoja mr. retinopathy and microalbuminuria in type ii diabetic patients. bmc ophthalmol 2004;4:9. 23. abdollahi a, daneshpazhooh m, amirchaghmaghi e, sheikhi s, eshrati b, bastanhagh m-h. dermopathy and retinopathy in diabetes: is there an association? dermatology 2007;214:133-136. 24. abdollahi a, malekmadani m, mansoori m, bostak a, mirshahi maa. prevalence of diabetic retinopathy in patients with newly diagnosed type ii diabetes mellitus. acta med iran 2006;44:415-419. 25. amini m, safaei h, aminorroaya a. the incidence of microalbuminuria and its associated risk factors in type 2 diabetic patients in isfahan, iran. rev diabet stud 2007;4:242. 26. manaviat m, rashidi m, afkhami-ardekani m. four years incidence of diabetic retinopathy and effective factors on its progression in type ii diabetes. eur j ophthalmol 2008;18:572-577. 27. gharaagaji r, fagihzadeh s, meshkani m, rohipor r. the prevalence of diabetic retinopathy and related risk factors in diabetic type i, in tehran, iran. res j bio sci 2008;3:596600. 28. golbahar j, rahimi m, tabei mb, aminzadeh ma. clinical risk factors and association of hyperhomocysteinemia with diabetic retinopathy in iranian type 2 diabetes patients: a cross-sectional study from shiraz, southern iran. diabetes metab syndr 2008;2:192-201. 29. hosseini sm, maracy mr, amini m, baradaran hr. a risk score development for diabetic retinopathy screening in isfahan-iran. j res med sci 2009;14:105. 30. javadi ma, katibeh m, rafati n, dehghan mh, zayeri f, yaseri m, et al. prevalence of diabetic retinopathy in tehran province: a population-based study. bmc ophthalmol 2009;9:12. 31. soleymani a, moazzezi z, gorjizadeh a. frequency of ophthalmic complications on 140 cases of type ii diabetes mellitus, babol-iran. world app sci j 2012;18:550-553. 32. javanbakht m, abolhasani f, mashayekhi a, baradaran hr. health related quality of life in patients with type 2 diabetes mellitus in iran: a national survey. plos one 2012;7:e44526. 33. najafi l, malek m, valojerdi ae, aghili r, khamseh me, fallah ae, et al. dry eye and its correlation to diabetes microvascular complications in people with type 2 diabetes mellitus. j diabetes complicat 2013;27:459-462. 34. shaghaghi a, ahmadi a, matlabi h. iranian patients require more pertinent care to prevent type 2 diabetes complications. adv prev med 2014;2014:409391. 35. gholamhossein y, behrouz h, asghar z. diabetic retinopathy risk factors: plasma erythropoietin as a risk factor for proliferative diabetic retinopathy. korean j ophthalmol 2014;28:373-378. 36. hosseini ms, rostami z, saadat a, saadatmand sm, naeimi e. anemia and microvascular complications in patients with type 2 diabetes mellitus. nephrourol mon 2014;6:e19976. 37. maghbooli z, pasalar p, keshtkar a, farzadfar f, larijani b. predictive factors of diabetic complications: a possible link between family history of diabetes and diabetic retinopathy. j diabetes metab disord 2014;13:55. 38. tazhibi m, sarrafzade s, amini m. retinopathy risk factors in type ii diabetic patients using factor analysis and discriminant analysis. j educ health promot 2014;3:85. 39. ghodsi r, hamayelimeharbani h, avand a-q, bordbar a, ahmadzadeh s. a study on the prevalence of diabetic complications in fasa diabetes clinic. asian j med pharm res 2014;4:68-72. 40. dehghan mh, katibeh m, ahmadieh h, nourinia r, yaseri m. prevalence and risk factors for diabetic retinopathy in the 40 to 80 year-old population in yazd, iran: the yazd eye study. j diabetes 2015;7:139-141. 41. azizi-soleiman f, heidari-beni m, ambler g, omar r, amini m, hosseini s-m. iranian risk model as a predictive tool for retinopathy in patients with type 2 diabetes. can j diabetes 2015;39:358-363. 42. shamshirgaran sm, ataei j, alamdari mi, safaeian a, aminisani n. predictors of health-related quality of life among people with type ii diabetes mellitus in ardabil, northwest of iran, 2014. prim care diabetes 2016;10:244250. 43. rasoulinejad sa, hajian-tilaki k, mehdipour e. associated factors of diabetic retinopathy in patients that referred to teaching hospitals in babol. caspian j intern med 2015;6:224. 44. mehravar f, mansournia ma, holakouie-naieni k, nasliesfahani e, mansournia n, almasi-hashiani a. associations between diabetes self-management and microvascular complications in patients with type 2 diabetes. epidemiol health 2016;38:e2016004. 45. valizadeh r, moosazadeh m, bahaadini k, vali l, lashkari t, amiresmaili m. determining the prevalence of retinopathy and its related factors among patients with type 334 j  o  v r volume 14, issue 3, july–september 2019 diabetic retinopathy and its correlates in iran; mahmoudi nezhad et al 2 diabetes in kerman, iran. osong public health res perspect 2016;7:296-300. 46. aidenloo ns, mehdizadeh a, valizadeh n, abbaszadeh m, qarequran s, khalkhali h. optimal glycemic and hemoglobin a1c thresholds for diagnosing diabetes based on prevalence of retinopathy in an iranian population. iran red crescent med j 2016;18:31254. 47. hashemi h, khabazkhoob m, nabovati p, ostadimoghaddam h, shafaee s, doostdar a, et al. the prevalence of age-related eye disease in an elderly population. ophthalmic epidemiol 2017;24:222-228. 48. dehghan h, charkazi a, kouchaki gm, zadeh bp, dehghan ba, matlabi m, et al. general self-efficacy and diabetes management self-efficacy of diabetic patients referred to diabetes clinic of aq qala, north of iran. j diabetes metab disord 2017;16:8. 49. shamshirgaran s, mamaghanian a, aliasgarzadeh a, aiminisani n, iranparvar-alamdari m, ataie j. age differences in diabetes-related complications and glycemic control. bmc endocr disord 2017;17:25. 50. katibeh m, behboudi h, moradian s, alizadeh y, beiranvand r, sabbaghi h, et al. rapid assessment of avoidable blindness and diabetic retinopathy in gilan province, iran. ophthalmic epidemiol 2017;24:381-387. 51. williams r, airey m, baxter h, forrester j, kennedymartin t, girach a. epidemiology of diabetic retinopathy and macular oedema: a systematic review. eye (lond) 2004;18:963. 52. sivaprasad s, gupta b, crosby-nwaobi r, evans j. prevalence of diabetic retinopathy in various ethnic groups: a worldwide perspective. surv ophthalmol 2012;57:347370. 53. french dd, behrens jj, jackson kl, kho an, walunas tl, evans ct, et al. payment reform needed to address health disparities of undiagnosed diabetic retinopathy in the city of chicago. ophthalmol ther 2017;6:123-131. 54. gibson dm. eye care availability and access among individuals with diabetes, diabetic retinopathy, or age-related macular degeneration. jama ophthalmol 2014;132:471477. 55. maclennan pa, mcgwin g, heckemeyer c, lolley vr, hullett s, saaddine j, et al. eye care use among a highrisk diabetic population seen in a public hospital’s clinics. jama ophthalmol 2014;132:162-167. 56. tajunisah i, wong p, tan l, rokiah p, reddy s. awareness of eye complications and prevalence of retinopathy in the first visit to eye clinic among type 2 diabetic patients. int j ophthalmol 2011;4:519. 57. gibson dm. the local availability of eye care providers and the vision health of adults in the united states. ophthalmic epidemiol 2016;23:223-231. 58. thapa r, twyana sn, paudyal g, khanal s, van nispen r, tan s, et al. prevalence and risk factors of diabetic retinopathy among an elderly population with diabetes in nepal: the bhaktapur retina study. clin ophthalmol 2018;12:561. 59. pradeepa r, anitha b, mohan v, ganesan a, rema m. risk factors for diabetic retinopathy in a south indian type 2 diabetic population-the chennai urban rural epidemiology study (cures) eye study 4. diabet med 2008;25:536542. 60. mumtaz sn, fahim mf, arslan m, shaikh sa, kazi u, memon ms. prevalence of diabetic retinopathy in pakistan: a systematic review. pak j med sci 2018;34:493. 61. kanjee r, dookeran ri, mathen mk, stockl fa, leicht r. six-year prevalence and incidence of diabetic retinopathy and cost-effectiveness of tele-ophthalmology in manitoba. can j ophthalmol 2016;51:467-470. 62. vila l, viguera j, aleman r. diabetic retinopathy and blindness in spain: epidemiology and prevention. endocrinol nutr 2008;55:459-475. 63. bourne rr, stevens ga, white ra, smith jl, flaxman sr, price h, et al. causes of vision loss worldwide, 1990-2010: a systematic analysis. lancet glob health 2013;1:e339e349. 64. zheng y, he m, congdon n. the worldwide epidemic of diabetic retinopathy. indian j ophthalmol 2012;60:428. 65. romero-aroca p, navarro-gil r, valls-mateu a, sagarraalamo r, moreno-ribas a, soler n. differences in incidence of diabetic retinopathy between type 1 and 2 diabetes mellitus: a nine-year follow-up study. br j ophthalmol 2017;101:1346-1351. 66. romero-aroca p, fernàndez-alart j, baget-bernaldiz m, méndez-marín i, salvat-serra m. diabetic retinopathy epidemiology in type ii diabetic patients. effect of the changes in the diagnostic criteria and stricter control of the diabetes between 1993 and 2005 on the incidence of diabetic retinopathy. arch soc esp oftalmol 2007;82:209-218. 67. raman r, ganesan s, pal ss, gella l, kulothungan v, sharma t. incidence and progression of diabetic retinopathy in urban india: sankara nethralaya-diabetic retinopathy epidemiology and molecular genetics study (sndreams ii), report 1. ophthalmic epidemiol 2017;24:294302. 68. song sj, han k, choi ks, ko sh, rhee ej, park cy, et al. trends in diabetic retinopathy and related medical practices among type 2 diabetes patients: results from the national insurance service survey 2006-2013. j diabetes investig 2018;9:173-178. 69. bek t, lund-andersen h, hansen ab, johnsen kb, sandbæk a, lauritzen t. the prevalence of diabetic retinopathy in patients with screen-detected type 2 diabetes in denmark: the addition study. acta ophthalmol 2009;87:270-274. 70. ruta l, magliano d, lemesurier r, taylor h, zimmet p, shaw j. prevalence of diabetic retinopathy in type 2 diabetes in developing and developed countries. diabet med 2013;30:387-398. 71. sikorski bl, malukiewicz g, stafiej j, lesiewska-junk h, raczynska d. the diagnostic function of oct in diabetic maculopathy. mediators inflamm 2013;2013;434560. j  o  v r volume 14, issue 3, july–september 2019 335 review article a review of systemic biologics and local immunosuppressive medications in uveitis neesurg s. mehta, md; parisa emami-naeini, md, mph department of ophthalmology and vision science, university of california, davis, sacramento, ca, usa orcid: parisa emami-naeini: https://orcid.org/0000-0002-4494-7517 neesurg mehta: https://orcid.org/0000-0002-7988-9601 abstract uveitis is one of the most common causes of vision loss and blindness worldwide. local and/or systemic immunosuppression is often required to treat ocular inflammation in noninfectious uveitis. an understanding of safety and efficacy of these medications is required to individualize treatment to each patient to ensure compliance and achieve the best outcome. in this article, we reviewed the effectiveness of systemic biologic response modifiers and local treatments commonly used in the management of patients with noninfectious uveitis. keywords: corticosteroids; immunosuppression; uveitis j ophthalmic vis res 2022; 17 (2): 276–289 introduction uveitis, defined as inflammation in the uveal tract, is a major cause of vision loss and disability especially in the young working-age population.[1] based on the etiology of inflammation, it can be categorized into infectious or noninfectious uveitis (niu). the mainstay of treatment in niu is systemic and/or local immunosuppression. systemic therapy with corticosteroids or corticosteroid-sparing immunomodulatory therapy (imts) is used for long-term control of uveitis. correspondence to: parisa emami-naeini, md, mph. 4860 y street, suite 2400, sacramento, ca 95817, usa. email: parisaemami@gmail.com received: 13-12-2021 accepted: 28-12-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i2.10804 these medications achieve sustained control of inflammation while avoiding the risk of perior intraocular corticosteroid injections. however, they are associated with an increased risk of systemic infections, malignancies, and other side effects.[1–4]local treatment, on the other hand, yields faster control of inflammation without causing systemic immunosuppression. these medications, however, are associated with a higher risk of ocular side effects including infection, increased intraocular pressure (iop), and cataract formation. often times, a combination of systemic and local treatment is required in order this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: mehta ns, emami-naeini p. a review of systemic biologics and local immunosuppressive medications in uveitis. j ophthalmic vis res 2022;17:276–289. 276 © 2022 mehta and emami-naeini . this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i2.10804&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr systemic and local immunosuppressive; mehta and emami-naeini to achieve appropriate control of inflammation. in thisarticle, we reviewed biologic response modifiers (or biologics) and local treatments used in the management of niu. systemic biologics immunomodulatory therapy (imts) modifies the immune response and controls inflammation. these medications are divided into conventional imts and biologics. conventional imts, including antimetabolites (methotrexate, azathioprine, mycophenolate mofetil) are usually the firstline treatment.[1] other imts include calcineurin inhibitors (cyclosporine, sirolimus, tacrolimus) and alkylating agents (cyclophosphamide, chlorambucil).[1] biologics are used when niu is recalcitrant to conventional imts and as first-line treatment in select cases. tumor necrosis factor-a inhibitors these agents constitute a group of biologics that suppress tnf-a, which is an integral cytokine in the inflammatory cascade.[1]currently, five tnf-a inhibitors are approved by the united states food and drug administration (fda) for the treatment of rheumatologic conditions, which include infliximab, adalimumab, golimumab, and certolizumab, all of which are monoclonal tnf-a antibodies, in addition to etanercept, which is a fusion protein that functions as a decoy receptor that binds to tnfa.[5] common side effects of this group of medications include headache, nausea, abdominal pain, diarrhea, constipation, with more severe complications including cytopenia, hepatotoxicity, heart failure, malignancy, and reactivation of infections.[6] higher risk of demyelinating disorders has been linked to these medications. hence, they should not be used in patients with history of multiple sclerosis and used with caution if a family history of demyelinating disease is present.[7, 8] anti-tnf-a induced lupus is another complication that is most commonly seen with infliximab use, followed by etanercept and adalimumab.[9] the mechanism is proposed to be autoantibody production secondary to a “cytokine shift” due to anti-tnf-a suppression of t helper 1 response, and hence increasing t helper 2-mediated cytokine and autoantibody production.[9] treatments involve discontinuation of the anti-tnf-a agents, and sometimes addition of immunosuppressants.[9] infliximab infliximab (remicade®) is an igg1 chimeric monoclonal antibody against membrane-bound and soluble tnf-a and is administered as an intravenous infusion most commonly at weeks 0, 2, and 6 (induction), and then every eight weeks (maintenance).[10] in uveitis patients, infliximab may be given at a low (<10 mg/kg), moderate (≥10–15 mg/kg), or a high (≥15–20 mg/kg) dose.[11] efficacy of infliximab has been widely studied in treatment of uveitis associated with behcet’s disease (bd),[12–17] juvenile idiopathic arthritis (jia),[18–22] sarcoidosis,[23] and other nius. these studies have shown an overall clinical efficacy and remission rate of 80–90% for infliximab.[24–26] in a prospective observational study looking at patients with refractory posterior uveitis receiving infliximab, a complete response was noted in 68% of patients.[27] another study noted a complete remission in 40% of patients after only three infusions.[28] a retrospective study looking at longterm (>2 years) use of infliximab in patients with refractory jia-associated uveitis showed clinical remission (defined as no flares for >6 months) in ∼20% of patients,[22] while another study looking at pediatric patients with refractory niu noted uveitis control in 89% of patients.[20] in a metaanalysis evaluating efficacy of anti-tnf-a therapy in childhood uveitis, infliximab was found to be effective in 72% of patients.[21] response to infliximab (and less commonly, other anti-tnf-a agents) can be adversely affected by the presence of anti-tnf-a antibodies. these antibodies are reportedly seen in ∼20% of patients and can cause treatment failure and reaction to infliximab infusions.[29] concurrent use of immunosuppressant including methotrexate or azathioprine can decrease the risk of autoantibody formation by 50%.[29] autoantibodies are less commonly seen in adalimumab, which is due to journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 277 systemic and local immunosuppressive; mehta and emami-naeini the fact that adalimumab is a fully humanized molecule.[9] adalimumab adalimumab (humira®) is a fully humanized antitnf-a monoclonal antibody and is the only imt approved by the fda for use in patients with intermediate, posterior, or panuveitis.[30] it is administered subcutaneously 40 mg (or 20 mg if patient’s weight is <30 kg) every other week, often after an initial loading dose of 80 mg.[30] it has been commonly used to treat uveitis associated with jia,[18, 21, 22, 31, 32] sarcoidosis,[33] ankylosing spondylitis (as),[34] and bd,[35] in addition to other nius.[36–41] in a double-blind, randomized, placebocontrolled trial, the sycamore study group looked at patients on a stable dose of methotrexate with active jia-associated uveitis and found that the addition of adalimumab resulted in lower rates of treatment failure (27% in the treatment group vs 60% in the control group, p < 0.0001).[31] the visual i trial, a phase-3 randomized clinical trial, showed that use of adalimumab was associated with a lower rate of uveitis flare and treatment failure in patients with active niu.[37] the visual ii trial was conducted to assess efficacy of adalimumab in inactive niu and found that treatment failure occurred in 39% of patients treated with adalimumab compared to 55% in the control group, and time to treatment failure was longer in the adalimumab group.[40] the visual iii trial was a phase-3 open-label extension study involving patients who met treatment failure criteria or those who completed the visual i and ii trials and were followed to 78 weeks.[41] this study found that 60% of patients with active uveitis and 74% of patients with inactive uveitis achieved quiescence on adalimumab.[41] although there are no randomized clinical trials comparing the efficacy of infliximab and adalimumab in uveitis, there are many retrospective and observational studies juxtaposing the two anti-tnf-a agents. while several studies have reported similar efficacy between the two drugs in treatment of niu,[42–44] some studies evaluating jia-associated uveitis have noted better efficacy of adalimumab compared to infliximab.[18, 21, 22] drug retention rates were similar between the two groups and concomitant use of disease-modifying antirheumatic drugs or treatment history did not affect the retention rates.[45] it has also been reported that in the case of loss of initial response of uveitis to one of these two agents, switching to the other one may result in better control of inflammation.[46] golimumab golimumab (simponi®), a fully human anti-tnfa monoclonal antibody, is administered monthly (50 mg) as a subcutaneous injection[47] and has been studied in uveitis associated with spondyloarthropathies,[48, 49] bd,[50, 51] and other nius.[52, 53] the go-easy study looked at patients treated with golimumab for as-related uveitis and noted a reduction in acute anterior uveitis rate.[49] certolizumab pegol certolizumab (cimzia®) is pegylated fab fragment of humanized monoclonal antibody against tnfa.[56] it is administered subcutaneously every other week for three injections (400 mg/dose) initially, and then 200 mg every other week.[54] it has been studied most commonly in uveitis associated with spondyloarthropathy, in addition to other refractory nius.[55–58] in an ongoing 96-week open-label phase-4 study, the 48 weeks results revealed an 87% reduction in the incidence of anterior uveitis flare in patients with spondyloarthropathy associated anterior uveitis.[59] similarly, the rapidaxspa trial showed a decrease in the frequency of uveitis flares over 96 weeks.[54] etanercept etanercept (enbrel®) functions as a decoy receptor for tnf-a.[60] although effective in treating rheumatologic conditions, it is not commonly used for uveitis as it is not as efficacious in comparison to other anti-tnf-a agents,[60] and there is risk for drug-induced uveitis and sarcoidosis.[61, 62] 278 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 systemic and local immunosuppressive; mehta and emami-naeini anti-interleukin-1 anakinra and canakinumab anakinra (kineret®) is a humanized il-1 receptor antagonist and canakinumab (ilaris®) is an anti-il1b monoclonal antibody.[63, 64] they have shown effectiveness in uveitis associated with bd and ms.[57, 65, 68] adverse reactions to this group of medications include injection site reactions, anaphylaxis, and infections such as pneumonia.[69] gevokizumab gevokizumab (xoma 052) is a humanized antiil-1β monoclonal antibody and is administered intravenously or subcutaneously.[70–72] it has been studied in uveitis associated with bd and noninfectious scleritis.[62–64, 73] although rapid control of bd-related uveitis was noted in the pilot and phase-2 studies,[70, 71] the phase-3 eyeguard-b trial failed to meet its primary endpoint and the medicine did not significantly alter the risk of flares.[72] anti-interleukin-2 daclizumab daclizumab (zinbryta®) is a humanized monoclonal antibody that inactivates t lymphocytes by binding to the cd25 portion of the il-2 receptor and is administered subcutaneously.[74] nussenblatt et al. reported that patients with niu treated with daclizumab needed less concomitant immunosuppression while maintaining baseline vision at 26 weeks.[75] however, the medicine was withdrawn from the market in 2018 following cases of hepatic injury and meningoencephalitis.[76] anti-il-interleukin-6 tocilizumab tocilizumab (actemra®) is a recombinant humanized monoclonal antibody against the il-6 receptors and is most commonly administered subcutaneously (162 mg every two weeks).[79] an intravenous form is also available. efficacy of this medicine has been studied in uveitis associated with jia,[77, 78] bd,[79] uveitic macular edema,[80–83]and other nius. calvo-rio et al[78] found that tocilizumab was effective in treating refractory jia-associated uveitis, however, the phase-2 aptitude trial noted efficacy of only 34% which did not meet the primary endpoint of control of inflammation at week 12.[77] in the stop-uveitis study, 37 patients received monthly intravenous infusions of 4 mg/kg or 8 mg/kg of tocilizumab over six months and found that 43% of patients had two-step decrease in vitreous haze and 30% gained two lines or more vision, although there was no statistically significant difference in vision and central macular thickness (cmt) between two doses.[84] common side effects include injection site reactions, arthralgia, and headaches.[77] sarilumab sarilumab (kevzara®) is a human monoclonal antibody blocking the il-6 receptor and is commonly administered subcutaneously.[85] the phase-2 saturn study evaluated the efficacy and safety of sarilumab over 16 weeks in patients with intermediate, posterior, or panuveitis.[85] this study found that in comparison to the placebo group, patients taking sarilumab achieved a statistically significant reduction in use of corticosteroids or at least two-step reduction in vitreous haze when assessed by investigators (64.0% vs 35.0%, p = 0.03), but not when assessed based on fundus photography and by central reading center (46.1 vs 30.0%, p = 0.2).[85] the most common adverse reactions include injection site reaction, respiratory tract infection, urinary infections, nasopharyngitis, transaminitis, while more severe adverse reactions include neutropenia and infections.[86] anti-interleukin-17 secukinumab (cosentyx®) is a fully human monoclonal antibody against il-17a and is administered subcutaneously.[87] three phaseiii trials examined the efficacy of secukinumab in patients with bd-associated uveitis, active niu, and quiescent niu.[87] none of these studies showed a statistically significant difference in uveitis recurrence between secukinumab and placebo. the most common adverse reactions include journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 279 systemic and local immunosuppressive; mehta and emami-naeini headache, diarrhea, upper respiratory infections, neutropenia, inflammatory bowel disease, and malignancy.[88] anti-interleukin-23 ustekinumab (stelara®) is a humanized monoclonal antibody against il-12 and il-23 and is administered most commonly subcutaneously.[89] studies have reported successful control of uveitis associated with psoriatic arthritis, plaque psoriasis,[90] and crohn’s disease.[91] adverse reactions include headache, fatigue, injection site reaction, upper respiratory infections, urinary tract infections, malignancy, and cardiovascular events.[89] anti-cd20 ritixumab (rituxan®) is a humanized monoclonal antibody against cd20 and is administered intravenously.[92–96] it has been studied in uveitis associated with bd,[96, 97] jia,[93, 98] noninfectious scleritis,[99–101] granulomatosis with polyangiitis,[102–106] vogt-koyanagi-harada disease (vkh),[107] susac syndrome,[108] in addition to other nius.[92, 109, 110] lasave et al reported on 21 eyes with refractory noninfectious posterior uveitis of which 82% achieved control of inflammation on fluorescein angiography at two years.[92] cao et al examined patients with refractory noninfectious scleritis and found that 86.6% of cases achieved scleritis activity score of zero at month six.[99] common adverse reactions include infusion reaction (fever, rigor, and chills), while more severe side effects include infections, progressive multifocal leukoencephalopathy, and hepatitis b reactivation.[110] selective costimulation modulator abatacept (orencia®) is a recombinant fusion protein made up of the extracellular domain of human cytotoxic t-lymphocyte antigen 4 (ctla-4) and fragment of fc domain of human igg.[111] this molecule competitively inhibits antigen-presenting cells (apcs) from binding to cd80 and cd86 on t cells, hence, preventing apcs from delivering a co-stimulatory response and activating t cells.[111] studies have shown that abatacept can be effective in controlling jia-associated uveitis.[112–115] common side effects include headache, upper respiratory tract infection, and nausea while serious adverse reactions include infection.[116, 117] interferons interferons have been studied widely in the treatment of niu,[118] especially in bd-associated uveitis.[119–125] studies have found that ifn-alpha is effective in 84–92% of patients with bd-associated posterior or panuveitis[121, 123] as well as uveitic macular edema[126, 127] and macular edema related to presumed ocular tuberculosis.[128, 129] ifn-beta has shown effectiveness in reducing macular edema and improving vision in intermediate uveitisassociated macular edema.[130] common adverse effects include nausea, fatigue, flu-like symptoms, psychiatric sequelae, elevated transaminases, and hematologic toxicity.[118, 131] janus kinase inhibitors tofacitinib (xeljanz®) is a small molecule that reversibly inhibits janus-associated kinases (jaks).[132] jaks mediate cytokine receptor signaling, initiating a downstream pathway which eventually leads to transcription of inflammatory genes.[132] in a case of jia-associated uveitis only responsive to intravitreal dexamethasone implants, tofacitinib successfully controlled the uveitis and arthritis, and the patient no longer required corticosteroid implants.[133] similarly, misrocchi et al.[134] reported on four cases of refractory jia-associated uveitis and noted a good uveitis response, though a less favorable arthritis response when treated with jak inhibitors. paley et al[132] reported one case of refractory anterior and intermediate uveitis and another case of refractory scleritis treated successfully with jak inhibitors. common adverse effects include upper respiratory infection, diarrhea, headache, and malignancy.[135] local treatments perior intraocular administration of immunosuppressives can provide a high dose 280 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 systemic and local immunosuppressive; mehta and emami-naeini of medication to the posterior segment of the eye while avoiding systemic side effects. these medications are more commonly used in unilateral uveitis. periocular or intraocular corticosteroid injections local corticosteroids have been widely studied in the treatment of uveitis. these medications are effective at local control of inflammation. side effects include ocular infection, cataract formation and increase in iop.[136] triamcinolone acetonide triamcinolone acetonide (ta) can be administered adjacent but outside the globe in the posterior sub-tenon space through the orbital septum (kenalog® 40 mg/ml, bristol-myers squibb company, princeton, nj) or in the vitreous cavity (triesence® 40 mg/ml, alcon pharmaceuticals, fort worth, tx). triesence® is preservative-free and more expensive than the preserved formulation (kenalog®). sub-tenon’s ta typically lasts two to three months, although this can be variable due to variable crystal sizes. intravitreal ta crystals are more uniformly sized, hence, triesence® has a more predictable duration of action of four to six weeks (less in vitrectomized eyes).[136] effectiveness of these steroids has been studied extensively.[137] it has been demonstrated that both injections are effective in patients with niu, however, intravitreal corticosteroids were more effective in improving vision and macular edema, although a significantly higher risk of iop elevation was associated with intravitreal corticosteroids compared to periocular injection.[137] dexamethasone intravitreal implant the dexamethasone implant (ozurdex®) is a bioerodible, sustained release injectable implant that gradually releases dexamethasone into the posterior chamber and usually lasts three to four months.[138] it is fda approved for use in patients with posterior segment inflammation. in a prospective, randomized, controlled clinical trial, the huron study group looked at patients with noninfectious intermediate or posterior uveitis who were randomized to receive dexamethasone implant (0.7 mg or 0.35 mg) or sham.[138] at week eight (primary endpoint), patients in the dexamethasone implant group experienced significant reduction in vitreous haze and cmt compared to the control group. the percentage of eyes gaining >15 letters was twoto sixfolds higher in the implant groups as compared to the sham group. less than 5% of the eyes developed iop of >35 mmhg across all groups. other side effects included cataract formation (as high as 29% after 12 months) and migration of implant to the anterior chamber, which caused corneal decompensation.[139] fluocinolone acetonide intravitreal implant (injectable) the fluocinolone acetonide intravitreal implant (yutiq®) (fai) is a non-bioerodible injectable intravitreal implant containing 0.18 mg fluocinolone acetonide. it is designed to release the steroid over 36 months and is fda approved for noninfectious posterior uveitis.[140] in a large prospective, randomized, sham-controlled trial, jaffe et al[140] evaluated 129 patients with chronic noninfectious posterior uveitis over three years who received either the fai or sham. at 36 months, the recurrence rate was 5.7% in fai group versus 28.6% in sham group (p < 0.001) and the median time to first recurrence was significantly lower in the fai group (657 days vs 70.5 days, respectively).[141] about 11.9% of the patients in the fai group required glaucoma surgery (compared to 5.7% in the sham group) and as expected most patients (73.8%) in the fai group required cataract surgery (compared to 23.8% in the sham group).[141] fluocinolone acetonide implant (surgical) the retisert ®implant contains 0.59 mg fluocinolone acetonide (releasing approximately 2 µg/day for three years) and is implanted through the pars plana in the vitreous cavity during surgery.[142] the multicenter uveitis steroid treatment (must) trial compared this implant journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 281 systemic and local immunosuppressive; mehta and emami-naeini to systemic immunosuppression and found that although the implant group showed improved visual acuity and uveitis control at two years,[142] the opposite was true at seven years.[143] this should be interpreted with caution as majority of patients who received the implant did not receive an additional implant and a significant number of patients were lost to follow-up or received cross-over treatment. suprachoroidal corticosteroids administration of drugs in the suprachoroidal space (between choroid and sclera) has been investigated as an alternate technique for targeted delivery of molecules to the posterior chorioretinal structures.[144] an investigational corticosteroid formulation (preservative-free ta, cls-ta, clearside biomedical, alpharetta, georgia, usa) injected into the suprachoroidal space has been studied in patients with uveitic macular edema. safety and efficacy of this formulation was studied in an open label safety trial (azalea trial) and phase-3 randomized trial (peachtree trial).[145, 146] these studies showed a statistically significant reduction in macular edema and improvement in visual acuity in the treatment arm compared to the control group, without a significant increase in the rate of cataract formation or iop.[146] this special formulation (xipere𝑇𝑀, ta injectable suspension 40 mg/ml, bauch + lomb and clearside biomedical) injected via the proprietary microinjector® recently received fda approval for use in the treatment of uveitis macular edema. non-steroidal injections methotrexate methotrexate was the first systemic non-steroidal imt that received fda approval for use in autoimmune disease.[147] efficacy of intravitreally administered methotrexate in patients with noninfectious uveitis has been reported in retrospective studies.[148, 149] safety and efficacy of this drug in patients with macular edema is currently under investigation in the macular edema ranibizumab versus intravitreal anti-inflammatory therapy (merit) multicenter, randomized controlled.[150]intravitreal methotrexate is also used in patients with vitreoretinal lymphoma.[151] side effects include risk of infection and corneal epitheliopathy.[151] sirolimus sirolimus is an inhibitor of the mammalian target of rapamycin and downstream production of proinflammatory cytokines.[152, 153] the one-year results from the save1 study showed that although intravitreal formulation was better tolerated, there was no difference in efficacy between subconjunctival and intravitreal administration of sirolumus in treatment of noninfectious intermediate, posterior or panuveitis.[153, 154] the save2 trial illustrated that monthly injections of 440 µg intravitreal sirolimus was better at reducing vitreous haze, cmt, and improving vision when compared to the 880 µg bimonthly dose.[155] in a combined analysis of 592 patients in phase-3 trials, sakura1 and -2, merrill et al[152] showed that a significantly higher proportion of patients treated with intravitreal sirolimus 440 µg compared with 44 µg achieved vitreous haze of 0 at five months, though there were similar percentages of patients with >5 letter improvement in vision and those tapered off corticosteroids in both dose groups. anti-tnf agents efficacy and safety of intravitreal infliximab was studied in animal models and human studies.[156–159] human studies reported variable efficacy of intravitreal infliximab in controlling inflammation but raised safety concerns, including development of intraocular inflammatory response,[156] decreased electroretinogram amplitudes, and visual field measurements.[157] intravitreal adalimumab has shown effectiveness in controlling inflammation and macular edema in small retrospective studies.[160, 161] more studies are required to evaluate long-term safety and efficacy of intravitreally administered medicine. 282 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 systemic and local immunosuppressive; mehta and emami-naeini rituximab intravitreally administered rituximab (alone or together with methotrexate) is widely used and proven effective in patients with vitreoretinal lymphoma.[162]side effects include transient iop elevation and iridocyclitis.[163] novel technologies: electroporation the biotechnology company eyevensys (paris, france) has created the first gene expression technology that uses plasmids to induce production of cytokines.[164] using a small needle, the device inserts plasmids into the ciliary muscle and a series of short electrical pulses induce uptake of these plasmids into the cells.[164] eys606 is a treatment being investigated in an ongoing phase-i/ii trial (nct03308045) in the european union for treatment of niu by introducing a plasmid encoding for tnf-a inhibitors. preliminary study included nine patients receiving escalating doses of the eye606 treatment.[165] one patient noted a ≥10 letter gain in vision after two weeks and two patients noted a ≥20% reduction in macular edema and ≥12 letter gain in vision after six to eight months (186).[165] the ongoing part two of the study will assess safety and efficacy of the highest and maximally tolerated eys606 dose over 48 weeks. the electro study ((nct03308045) is an ongoing phase-2 trial in the us assessing safety and efficacy of two doses of eys606.[166] common practice and future horizons systemic and/or local immunosuppression are mainstay of treatment in niu and usually a combination of these modalities is needed to control inflammation and achieve quiescence. in systemic management of uveitis, a “stepladder” approach is recommended. this approach starts with local and/or systemic corticosteroids followed by imts (as needed) with the goal of reducing the dose of systemic corticosteroids to <5–10 mg of prednisone per day.[167, 168]patients with chronic uveitis need to be counselled on the need for longterm treatment, the different options available to them, and the side effects of systemic and local therapeutics, all in an effort to tailor treatment to each patient and increase long-term compliance. the advent of novel local and systemic treatment options has decreased the risk of breakthrough inflammation and long-term vision loss in patients with niu. financial support and sponsorship nil. conflicts of interest the authors declare that they have no conflict of interest. references 1. you c, sahawneh hf, ma l, kubaisi b, schmidt a, foster cs. a review and update on orphan drugs for the treatment of noninfectious uveitis. clin ophthalmol 2017;11:257–265. 2. durnian jm, stewart rm, tatham r, batterbury m, kaye sb. cyclosporin-a associated malignancy. clin ophthalmol 2007;1:421–430. 3. o’neill jo, edwards lb, taylor do. mycophenolate mofetil and risk of developing malignancy after orthotopic heart transplantation: analysis of the transplant registry of the international society for heart and lung transplantation. j heart lung transplant 2006;25:1186–1191. 4. kempen jh, daniel e, dunn jp, foster cs, gangaputra s, hanish a, et al. overall and cancer related mortality among patients with ocular inflammation treated with immunosuppressive drugs: retrospective cohort study. bmj 2009;339:b2480. 5. leal i, rodrigues fb, sousa dc, duarte gs, romão vc, marques-neves c, et al. anti-tnf drugs for chronic uveitis in adults—a systematic review and meta-analysis of randomized controlled trials. front med 2019;6:104. 6. aziz m, fatima r. infliximab [internet]. treasure island, fl: statpearls publishing; 2022 [updated 2021 jul 25]. available from: https://www.ncbi.nlm.nih.gov/books/nbk500021/ 7. van oosten bw, barkhof f, truyen l, boringa jb, bertelsmann fw, von blomberg bm, et al. increased mri activity and immune activation in two multiple sclerosis patients treated with the monoclonal anti-tumor necrosis factor antibody ca2. neurology 1996;47:1531–1534. 8. tnf neutralization in ms: results of a randomized, placebo-controlled multicenter study. the lenercept multiple sclerosis study group and the university of british columbia ms/mri analysis group. neurology 1999;53:457–465. 9. almoallim h, al-ghamdi y, almaghrabi h, alyasi o. anti-tumor necrosis factor-α induced systemic lupus erythematosus. open rheumatol j 2012;6:315–319. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 283 systemic and local immunosuppressive; mehta and emami-naeini 10. kruh jn, yang p, suelves am, foster cs. infliximab for the treatment of refractory noninfectious uveitis: a study of 88 patients with long-term follow-up. ophthalmology 2014;121:358–364. 11. sukumaran s, marzan k, shaham b, reiff a. high dose infliximab in the treatment of refractory uveitis: does dose matter? isrn rheumatol 2012;2012:765380. 12. cantini f, niccoli l, nannini c, kaloudi o, cassarà e, susini m, et al. efficacy of infliximab in refractory behçet’s disease-associated and idiopathic posterior segment uveitis: a prospective, follow-up study of 50 patients. biologics 2012;6:5–12. 13. el garf ak, shahin aa, shawky sa, azim ma, effat da, abdelrahman sk. efficacy of infliximab in refractory posterior uveitis in behcet’s disease patients. the egyptian rheumatologist 2018;40:93–97. 14. keino h, okada a, watanabe t, taki w. long-term efficacy of infliximab on background vascular leakage in patients with behçet’s disease. eye 2014;28:1100–1106. 15. fabiani c, sota j, vitale a, emmi g, vannozzi l, bacherini d, et al. ten-year retention rate of infliximab in patients with behçet’s disease-related uveitis. ocul immunol inflamm 2019;27:34–39. 16. giardina a, ferrante a, ciccia f, vadalà m, giardina e, triolo g. one year study of efficacy and safety of infliximab in the treatment of patients with ocular and neurological behçet’s disease refractory to standard immunosuppressive drugs. rheumatol int 2011;31:33–37. 17. okada aa, goto h, ohno s, mochizuki m, ocular behçet’s disease research group of japan. multicenter study of infliximab for refractory uveoretinitis in behçet disease. arch ophthalmol 2012;130:592–598. 18. constantin t, foeldvari i, anton j, de boer j, czitromguillaume s, edelsten c, et al. consensus-based recommendations for the management of uveitis associated with juvenile idiopathic arthritis: the share initiative. ann rheum dis 2018;77:1107–1117. 19. richards jc, tay-kearney ml, murray k, manners p. infliximab for juvenile idiopathic arthritis-associated uveitis. clin exp ophthalmol 2005;33:461–468. 20. miraldi utz v, bulas s, lopper s, fenchel m, sa t, mehta m, et al. effectiveness of long-term infliximab use and impact of treatment adherence on disease control in refractory, non-infectious pediatric uveitis. pediatr rheumatol online j 2019;17:79. 21. simonini g, druce k, cimaz r, macfarlane gj, jones gt. current evidence of anti–tumor necrosis factor α treatment efficacy in childhood chronic uveitis: a systematic review and meta-analysis approach of individual drugs. arthritis care res 2014;66:1073–1084. 22. cecchin v, zannin me, ferrari d, pontikaki i, miserocchi e, paroli mp, et al. long-term safety and efficacy of adalimumab and infliximab for uveitis associated with juvenile idiopathic arthritis. j rheumatol 2018;45:1167– 1172. 23. baughman rp, bradley da, lower ee. infliximab in chronic ocular inflammation. int j clin pharmacol ther 2005;43:7– 11. 24. naganuma m, sakuraba a, hisamatsu t, ochiai h, hasegawa h, ogata h, et al. efficacy of infliximab for induction and maintenance of remission in intestinal behçet’s disease. inflamm bowel dis 2008;14:1259–1264. 25. sharma pk, markov gt, bajwa a, foster cs. longterm efficacy of systemic infliximab in recalcitrant retinal vasculitis. retina 2015;35:2641–2446. 26. maleki a, sahawneh hf, ma l, meese h, he y, foster cs. infliximab therapy in patients with noninfectious intermediate uveitis resistant to conventional immunomodulatory therapy. retina 2017;37:836–843. 27. cantini f, niccoli l, nannini c, kaloudi o, cassarà e, susini m, et al. efficacy of infliximab in refractory behçet’s disease-associated and idiopathic posterior segment uveitis: a prospective, follow-up study of 50 patients. biologics 2012;6:5–12. 28. el garf ak, shahin aa, shawky sa, azim ma, effat da, abdelrahman sk. efficacy of infliximab in refractory posterior uveitis in behcet’s disease patients. the egyptian rheumatologist 2018;40:93–97. 29. lee ly, sanderson jd, irving pm. anti-infliximab antibodies in inflammatory bowel disease: prevalence, infusion reactions, immunosuppression and response, a meta-analysis. eur j gastroenterol hepatol 2012;24:1078– 1085. 30. lamattina kc, goldstein da. adalimumab for the treatment of uveitis. expert rev clin immunol 2017;13:181–188. 31. ramanan av, dick ad, jones ap, hughes da, mckay a, rosala-hallas a, et al. adalimumab in combination with methotrexate for refractory uveitis associated with juvenile idiopathic arthritis: a rct. health technol assess 2019;23:1–140. 32. horton s, jones ap, guly cm, hardwick b, beresford mw, lee rw, et al. adalimumab in juvenile idiopathic arthritis-associated uveitis: 5-year follow-up of the bristol participants of the sycamore trial. am j ophthalmol 2019;207:170–174. 33. erckens rj, mostard rl, wijnen pa, schouten js, drent m. adalimumab successful in sarcoidosis patients with refractory chronic non-infectious uveitis. graefes arch clin exp ophthalmol 2012;250:713–720. 34. rudwaleit m, rødevand e, holck p, vanhoof j, kron m, kary s, et al. adalimumab effectively reduces the rate of anterior uveitis flares in patients with active ankylosing spondylitis: results of a prospective open-label study. ann rheum dis 2009;68:696–701. 35. fabiani c, vitale a, emmi g, vannozzi l, lopalco g, guerriero s, et al. efficacy and safety of adalimumab in behçet’s disease-related uveitis: a multicenter retrospective observational study. clin rheumatol 2017;36:183–189. 36. suhler eb, lowder cy, goldstein da, giles t, lauer ak, kurz pa, et al. adalimumab therapy for refractory uveitis: results of a multicentre, open-label, prospective trial. br j ophthalmol 2013;97:481–486. 37. jaffe gj, dick ad, brézin ap, nguyen qd, thorne je, kestelyn p, et al. adalimumab in patients with active noninfectious uveitis. n engl j med 2016;375:932–943. 38. díaz-llopis m, salom d, garcia-de-vicuña c, corderocoma m, ortega g, ortego n, et al. treatment of refractory uveitis with adalimumab: a prospective multicenter study of 131 patients. ophthalmology 2012;119:1575–1581. 39. dobner bc, max r, becker md, heinz c, veltrup i, heiligenhaus a, et al. a three-centre experience with adalimumab for the treatment of non-infectious uveitis. br j ophthalmol 2013;97:134–138. 284 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 systemic and local immunosuppressive; mehta and emami-naeini 40. nguyen qd, merrill pt, jaffe gj, dick ad, kurup sk, sheppard j, et al. adalimumab for prevention of uveitic flare in patients with inactive non-infectious uveitis controlled by corticosteroids (visual ii): a multicentre, double-masked, randomised, placebo-controlled phase 3 trial. lancet 2016;388:1183–1192. 41. suhler eb, adán a, brézin ap, fortin e, goto h, jaffe gj, et al. safety and efficacy of adalimumab in patients with noninfectious uveitis in an ongoing open-label study: visual iii. ophthalmology 2018;125:1075–1087. 42. lejoyeux r, diwo e, vallet h, saadoun d, tezenas du montcel s, bodaghi b, et al. infliximab and adalimumab in uveitic macular edema. ocul immunol inflamm 2018;26:991–996. 43. vallet h, seve p, biard l, baptiste fraison j, bielefeld p, perard l, et al. infliximab versus adalimumab in the treatment of refractory inflammatory uveitis: a multicenter study from the french uveitis network. arthritis rheumatol 2016;68:1522–1530. 44. martel jn, esterberg e, nagpal a, acharya nr. infliximab and adalimumab for uveitis. ocul immunol inflamm 2012;20:18–26. 45. fabiani c, vitale a, emmi g, bitossi a, lopalco g, sota j, et al. long-term retention rates of adalimumab and infliximab in non-infectious intermediate, posterior, and panuveitis. clin rheumatol 2019;38:63–70. 46. dhingra n, morgan j, dick ad. switching biologic agents for uveitis. eye 2009;23:1868–1870. 47. boyce eg, halilovic j, stan-ugbene o. golimumab: review of the efficacy and tolerability of a recently approved tumor necrosis factor-α inhibitor. clin ther 2010;32:1681–1703. 48. calvo-río v, blanco r, santos-gómez m, rubio-romero e, cordero-coma m, gallego-flores a, et al. golimumab in refractory uveitis related to spondyloarthritis. multicenter study of 15 patients. semin arthritis rheum 2016;46:95– 101. 49. van bentum re, heslinga sc, nurmohamed mt, gerards ah, griep en, koehorst cbjm, et al. reduced occurrence rate of acute anterior uveitis in ankylosing spondylitis treated with golimumab the go-easy study. j rheumatol 2019;46:153–159. 50. fabiani c, sota j, rigante d, vitale a, emmi g, vannozzi l, et al. rapid and sustained efficacy of golimumab in the treatment of multirefractory uveitis associated with behçet’s disease. ocul immunol inflamm 2019;27:58–63. 51. vitale a, emmi g, lopalco g, fabiani c, gentileschi s, silvestri e, et al. long-term efficacy and safety of golimumab in the treatment of multirefractory behçet’s disease. clin rheumatol 2017;36:2063–2069. 52. cordero-coma m, calvo-río v, adán a, blanco r, álvarezcastro c, mesquida m, et al. golimumab as rescue therapy for refractory immune-mediated uveitis: a three-center experience. mediators inflamm 2014;2014:717598. 53. miserocchi e, modorati g, pontikaki i, meroni pl, gerloni v. long-term treatment with golimumab for severe uveitis. ocul immunol inflamm 2014;22:90–95. 54. rudwaleit m, rosenbaum jt, landewé r, marzo-ortega h, sieper j, van der heijde d, et al. observed incidence of uveitis following certolizumab pegol treatment in patients with axial spondyloarthritis. arthritis care res 2016;68:838–844. 55. gómez-santos m, llorenz v, mesquida m, blanco r, calvorio v, maiz o, et al. efficacy of certolizumab in patient with refractory uveitis to other biologic therapy. study of 7 cases [1251]. abstract presented at: 2014 acr/arhp annual meeting; 2014 nov 14–19; boston, ma. 56. sharon y, chu ds. certolizumab pegol tumor necrosis factor inhibitor for refractory uveitis. am j ophthalmol case rep 2020;18:100633. 57. llorenç v, mesquida m, sainz de la maza m, blanco r, calvo v, maíz o, et al. certolizumab pegol, a new anti-tnfα in the armamentarium against ocular inflammation. ocul immunol inflamm 2016;24:167–172. 58. tosi gm, sota j, vitale a, rigante d, emmi g, lopalco g, et al. efficacy and safety of certolizumab pegol and golimumab in the treatment of non-infectious uveitis. clin exp rheumatol 2019;37:680–683. 59. van der horst-bruinsma i, van bentum r, verbraak fd, rath t, rosenbaum jt, misterska-skora m, et al. the impact of certolizumab pegol treatment on the incidence of anterior uveitis flares in patients with axial spondyloarthritis: 48-week interim results from c-view. rmd open 2020;6:e001161. 60. foster cs, tufail f, waheed nk, chu d, miserocchi e, baltatzis s, et al. efficacy of etanercept in preventing relapse of uveitis controlled by methotrexate. arch ophthalmol 2003;121:437–440. 61. lim ll, fraunfelder fw, rosenbaum jt. do tumor necrosis factor inhibitors cause uveitis? a registry-based study. arthritis rheum 2007;56:3248–3252. 62. iqbal km, hay mw, emami-naeini p. medication-induced uveitis: an update. j ophthalmic vis res 2021;16:84–92. 63. sota j, vitale a, insalaco a, sfriso p, lopalco g, emmi g, et al. safety profile of the interleukin-1 inhibitors anakinra and canakinumab in real-life clinical practice: a nationwide multicenter retrospective observational study. clin rheumatol 2018;37:2233–2240. 64. dinarello ca, simon a, van der meer jw. treating inflammation by blocking interleukin-1 in a broad spectrum of diseases. nat rev drug discov 2012;11:633–652. 65. fabiani c, vitale a, emmi g., lopalco g, vannozzi l, guerriero s, et al. interleukin (il)-1 inhibition with anakinra and canakinumab in behçet’s disease-related uveitis: a multicenter retrospective observational study. clin rheumatol 2017;36:191–197. 66. fabiani c, vitale a, rigante d, emmi g, lopalco g, di scala g, et al. the presence of uveitis is associated with a sustained response to the interleukin (il)-1 inhibitors anakinra and canakinumab in behçet’s disease. ocul immunol inflamm 2020;28:298–304. 67. ugurlu s, ucar d, seyahi e, hatemi g, yurdakul s. canakinumab in a patient with juvenile behcet’s syndrome with refractory eye disease. ann rheum dis 2012;71:1589– 1591. 68. lopalco g, schiraldi s, venerito v, guerriero s, iannone f. effectiveness and safety profile of anakinra in a hla-b27 positive patient with multiple sclerosis-associated uveitis. mult scler relat disord 2020;42:102152. 69. sota j, vitale a, insalaco a, sfriso p, lopalco g, emmi g, et al. safety profile of the interleukin-1 inhibitors anakinra and canakinumab in real-life clinical practice: a nationwide multicenter retrospective observational study. clin rheumatol 2018;37:2233–2240. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 285 systemic and local immunosuppressive; mehta and emami-naeini 70. gül a, tugal-tutkun i, dinarello ca, reznikov l, esen ba, mirza a, et al. interleukin-1β-regulating antibody xoma 052 (gevokizumab) in the treatment of acute exacerbations of resistant uveitis of behcet’s disease: an open-label pilot study. ann rheum dis 2012;71:563–566. 71. tugal-tutkun i, kadayifcilar s, khairallah m, lee sc, ozdal p, özyazgan y, song jh, et al. safety and efficacy of gevokizumab in patients with behçet’s disease uveitis: results of an exploratory phase 2 study. ocul immunol inflamm 2017;25:62–70. 72. tugal-tutkun i, pavesio c, de cordoue a, bernardpoenaru o, gül a. use of gevokizumab in patients with behçet’s disease uveitis: an international, randomized, double-masked, placebo-controlled study and open-label extension study. ocul immunol inflamm 2018;26:1023– 1033. 73. knickelbein je, tucker wr, bhatt n, armbrust k, valent d, obiyor d, et al. gevokizumab in the treatment of autoimmune non-necrotizing anterior scleritis: results of a phase i/ii clinical trial. am j ophthalmol 2016;172:104–110. 74. wroblewski k, sen hn, yeh s, faia l, li z, sran p, et al. long-term daclizumab therapy for the treatment of noninfectious ocular inflammatory disease. can j ophthalmol 2011;46:322–328. 75. nussenblatt rb, peterson js, foster cs, rao na, see rf, letko e, et al. initial evaluation of subcutaneous daclizumab treatments for noninfectious uveitis: a multicenter noncomparative interventional case series. ophthalmology 2005;112:764–770. 76. brooks m. ms drug daclizumab (zinbryta) pulled from the market [internet]. medscape; 2018. available from: https://www.medscape.com/viewarticle/893352 77. ramanan av, dick ad, guly c, mckay a, jones ap, hardwick b, et al. tocilizumab in patients with anti-tnf refractory juvenile idiopathic arthritis-associated uveitis (aptitude): a multicentre, single-arm, phase 2 trial. lancet rheumatol 2020;2:e135–e141. 78. calvo-río v, santos-gómez m, calvo i, gonzálezfernández mi, lópez-montesinos b, mesquida m, et al. anti-interleukin-6 receptor tocilizumab for severe juvenile idiopathic arthritis-associated uveitis refractory to anti-tumor necrosis factor therapy: a multicenter study of twenty-five patients. arthritis rheumatol 2017;69:668– 675. 79. atienza-mateo b, calvo-río v, beltrán e, martínezcosta l, valls-pascual e, hernández-garfella m, et al. anti-interleukin 6 receptor tocilizumab in refractory uveitis associated with behçet’s disease: multicentre retrospective study. rheumatology 2018;57:856–864. 80. adán a, mesquida m, llorenç v, espinosa g, molins b, hernández mv, et al. tocilizumab treatment for refractory uveitis-related cystoid macular edema. graefes arch clin exp ophthalmol 2013;251:2627–2632. 81. deuter cme, zierhut m, igney-oertel a, xenitidis t, feidt a, sobolewska b, et al. tocilizumab in uveitic macular edema refractory to previous immunomodulatory treatment. ocul immunol inflamm 2017;25:215–220. 82. mesquida m, molins b, llorenç v, hernández mv, espinosa g, sainz de la maza m, et al. twenty-four month follow-up of tocilizumab therapy for refractory uveitisrelated macular edema. retina 2018;38:1361–1370. 83. vegas-revenga n, calvo-río v, mesquida m, adán a, hernández mv, beltrán e, et al. anti-il6-receptor tocilizumab in refractory and noninfectious uveitic cystoid macular edema: multicenter study of 25 patients. am j ophthalmol 2019;200:85–94. 84. sepah yj, sadiq ma, chu ds, dacey m, gallemore r, dayani p, et al. primary (month-6) outcomes of the stop-uveitis study: evaluating the safety, tolerability, and efficacy of tocilizumab in patients with noninfectious uveitis. am j ophthalmol 2017;183:71–80. 85. heissigerová j, callanan d, de smet md, srivastava sk, karkanová m, garcia-garcia o, et al. efficacy and safety of sarilumab for the treatment of posterior segment noninfectious uveitis (saril-niu): the phase 2 saturn study. ophthalmology 2019;126:428–437. 86. fleischmann r, genovese mc, lin y, st john g, van der heijde d, wang s, et al. long-term safety of sarilumab in rheumatoid arthritis: an integrated analysis with up to 7 years’ follow-up. rheumatology 2020;59:292–302. 87. dick ad, tugal-tutkun i, foster s, zierhut m, melissa liew sh, bezlyak v, et al. secukinumab in the treatment of noninfectious uveitis: results of three randomized, controlled clinical trials. ophthalmology 2013;120:777– 787. 88. deodhar a, mease pj, mcinnes ib, baraliakos x, reich k, blauvelt a, et al. long-term safety of secukinumab in patients with moderate-to-severe plaque psoriasis, psoriatic arthritis, and ankylosing spondylitis: integrated pooled clinical trial and post-marketing surveillance data. arthritis res ther 2019;21:111. 89. langley rg, lebwohl m, krueger gg, szapary po, wasfi y, chan d, et al. long-term efficacy and safety of ustekinumab, with and without dosing adjustment, in patients with moderate-to-severe psoriasis: results from the phoenix 2 study through 5 years of follow-up. br j dermatol 2015;172:1371–1383. 90. mugheddu c, atzori l, del piano m, lappi a, pau m, murgia s, et al. successful ustekinumab treatment of noninfectious uveitis and concomitant severe psoriatic arthritis and plaque psoriasis. dermatol ther 2017;30. 91. chateau t, angioi k, peyrin-biroulet l. two cases of successful ustekinumab treatment for non-infectious uveitis associated with crohn’s disease. j crohns colitis 2020;14:571. 92. lasave af, you c, ma l, abusamra k, lamba n, valdes navarro m, et al. long-term outcomes of rituximab therapy in patients with noninfectious posterior uveitis refractory to conventional immunosuppressive therapy. retina 2018;38:395–402. 93. miserocchi e, modorati g, berchicci l, pontikaki i, meroni p, gerloni v. long-term treatment with rituximab in severe juvenile idiopathic arthritis-associated uveitis. br j ophthalmol 2016;100:782–786. 94. ahmed a, foster cs. cyclophosphamide or rituximab treatment of scleritis and uveitis for patients with granulomatosis with polyangiitis. ophthalmic res 2019;61:44–50. 95. umran rmr, shukur zyh. rituximab for sight-threatening refractory pediatric vogt-koyanagi-harada disease. mod rheumatol 2018;28:197–199. 96. davatchi f, shams h, rezaipoor m, sadeghi-abdollahi b, shahram f, nadji a, et al. rituximab in intractable ocular 286 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 systemic and local immunosuppressive; mehta and emami-naeini lesions of behcet’s disease; randomized single-blind control study (pilot study). int j rheum dis 2010;13:246– 252. 97. sadreddini s, noshad h, molaeefard m, noshad r. treatment of retinal vasculitis in behçet’s disease with rituximab. mod rheumatol 2008;18:306–308. 98. heiligenhaus a, miserocchi e, heinz c, gerloni v, kotaniemi k. treatment of severe uveitis associated with juvenile idiopathic arthritis with anti-cd20 monoclonal antibody (rituximab). rheumatology 2011;50:1390–1394. 99. cao jh, oray m, cocho l, foster cs. rituximab in the treatment of refractory noninfectious scleritis. am j ophthalmol 2016;164:22–28. 100. iaccheri b, androudi s, bocci eb, gerli r, cagini c, fiore t. rituximab treatment for persistent scleritis associated with rheumatoid arthritis. ocul immunol inflamm 2010;18:223– 225. 101. ahmadi-simab k, lamprecht p, nölle b, ai m, gross wl. successful treatment of refractory anterior scleritis in primary sjogren’s syndrome with rituximab. ann rheum dis 2005;64:1087–1088. 102. ahmed a, foster cs. cyclophosphamide or rituximab treatment of scleritis and uveitis for patients with granulomatosis with polyangiitis. ophthalmic res 2019;61:44–50. 103. taylor sr, salama ad, joshi l, pusey cd, lightman sl. rituximab is effective in the treatment of refractory ophthalmic wegener’s granulomatosis. arthritis rheum 2009;60:1540–1547. 104. joshi l, lightman sl, salama ad, shirodkar al, pusey cd, taylor sr. rituximab in refractory ophthalmic wegener’s granulomatosis: pr3 titers may predict relapse, but repeat treatment can be effective. ophthalmology 2011;118:2498–2503. 105. cheung cm, murray pi, savage co. successful treatment of wegener’s granulomatosis associated scleritis with rituximab. br j ophthalmol 2005;89:1542. 106. onal s, kazokoglu h, koc a, yavuz s. rituximab for remission induction in a patient with relapsing necrotizing scleritis associated with limited wegener’s granulomatosis. ocul immunol inflamm 2008;16:230– 232. 107. umran rmr, shukur zyh. rituximab for sight-threatening refractory pediatric vogt-koyanagi-harada disease. mod rheumatol 2018;28:197–199. 108. monferrer-adsuara c, remolí-sargues l, hernández-bel l, gracia-garcía a, hernández-garfella ml, cervera-taulet e. rituximab in the treatment of susac’s syndrome: report of a case. eur j ophthalmol 2021;31:np48–np52. 109. miserocchi e, modorati g. rituximab for noninfectious uveitis. dev ophthalmol 2012;51:98–109. 110. tomkins-netzer o, taylor sr, lightman s. can rituximab induce long-term disease remission in patients with intraocular non-infectious inflammation? ophthalmologica 2013;230:109–115. 111. kremer jm, dougados m, emery p, durez p, sibilia j, shergy w, et al. treatment of rheumatoid arthritis with the selective costimulation modulator abatacept: twelvemonth results of a phase iib, double-blind, randomized, placebo-controlled trial. arthritis rheum 2005;52:2263– 2271. 112. tappeiner c, miserocchi e, bodaghi b, kotaniemi k, mackensen f, gerloni v, et al. abatacept in the treatment of severe, longstanding, and refractory uveitis associated with juvenile idiopathic arthritis. j rheumatol 2015;42:706–711. 113. galstian l, zholobova e. sat0510 abatacept in the treatment of juvenile idiopathic arthritis associated with uveitis. ann rheum dis 2015;74:845. 114. zulian f, balzarin m, falcini f, martini g, alessio m, cimaz r, et al. abatacept for severe anti-tumor necrosis factor alpha refractory juvenile idiopathic arthritis-related uveitis. arthritis care res 2010;62:821–825. 115. birolo c, zannin me, arsenyeva s, cimaz r, miserocchi e, dubko m, et al. comparable efficacy of abatacept used as first-line or second-line biological agent for severe juvenile idiopathic arthritis-related uveitis. j rheumatol 2016;43:2068–2073. 116. curtis jr, yang s, patkar nm, chen l, singh ja, cannon gw, et al. risk of hospitalized bacterial infections associated with biologic treatment among us veterans with rheumatoid arthritis. arthritis care res 2014;66:990– 997. 117. blair ha, deeks ed. abatacept: a review in rheumatoid arthritis. drugs 2017;77:1221–1233. 118. plskova j, greiner k, forrester jv. interferon-alpha as an effective treatment for noninfectious posterior uveitis and panuveitis. am j ophthalmol 2007;144:55–61. 119. eser-ozturk h, sullu y. the results of interferon-alpha treatment in behçet uveitis. ocul immunol inflamm 2020;28:498–504. 120. lee jh, lee cs, lee sc. interferon alpha-2a treatment for refractory behcet uveitis in korean patients. bmc ophthalmol 2018;18:52. 121. kötter i, zierhut m, eckstein ak, vonthein r, ness t, günaydin i, et al. human recombinant interferon alfa-2a for the treatment of behçet’s disease with sight threatening posterior or panuveitis. br j ophthalmol 2003;87:423–431. 122. guillaume-czitrom s, berger c, pajot c, bodaghi b, wechsler b, kone-paut i. efficacy and safety of interferon-α in the treatment of corticodependent uveitis of paediatric behçet’s disease. rheumatology 2007;46:1570–1573. 123. sobaci g, erdem u, durukan ah, erdurman c, bayer a, köksal s, et al. safety and effectiveness of interferon alpha-2a in treatment of patients with behçet’s uveitis refractory to conventional treatments. ophthalmology 2010;117:1430–1435. 124. bodaghi b, gendron g, wechsler b, terrada c, cassoux n, thi huong dl, et al. efficacy of interferon alpha in the treatment of refractory and sight threatening uveitis: a retrospective monocentric study of 45 patients. br j ophthalmol 2007;91:335–339. 125. deuter cm, zierhut m, möhle a, vonthein r, stöbiger n, kötter i. long-term remission after cessation of interferonα treatment in patients with severe uveitis due to behçet’s disease. arthritis rheum 2010;62:2796–2805. 126. de simone l, sangiovanni a, aldigeri r, mastrofilippo v, bolletta e, invernizzi a, et al. interferon alpha-2a treatment for post-uveitic refractory macular edema. ocul immunol inflamm 2020;28:322–328. 127. deuter cm, doycheva d, koetter i, zierhut m. longterm results of treatment with interferon alpha for chronic journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 287 systemic and local immunosuppressive; mehta and emami-naeini uveitic cystoid macular edema. invest ophthalmol vis sci 2012;53:4262. 128. oray m, onal s, uludag g, akbay ak, tugal-tutkun i. interferon alpha for the treatment of cystoid macular edema associated with presumed ocular tuberculosis. j ocul pharmacol ther 2017;33:304–312. 129. invernizzi a, iannaccone f, marchi s, mastrofilippo v, coassin m, fontana l, et al. interferon alpha-2a for the treatment of post-infectious uveitis secondary to presumed intraocular tuberculosis. ocul immunol inflamm 2019;27:643–650. 130. mackensen f, jakob e, springer c, dobner bc, wiehler u, weimer p, et al. interferon versus methotrexate in intermediate uveitis with macular edema: results of a randomized controlled clinical trial. am j ophthalmol 201;156:478–486.e1. 131. sleijfer s, bannink m, van gool ar, kruit wh, stoter g. side effects of interferon-alpha therapy. pharm world sci 2005;27:423–431. 132. paley ma, karacal h, rao pk, margolis tp, miner jj. tofacitinib for refractory uveitis and scleritis. am j ophthalmol case rep 2018;13:53–55. 133. bauermann p, heiligenhaus a, heinz c. effect of janus kinase inhibitor treatment on anterior uveitis and associated macular edema in an adult patient with juvenile idiopathic arthritis. ocul immunol inflamm 2019;27:1232– 1234. 134. miserocchi e, giuffrè c, cornalba m, pontikaki i, cimaz r. jak inhibitors in refractory juvenile idiopathic arthritisassociated uveitis. clin rheumatol 2020;39:847–851. 135. wollenhaupt j, lee eb, curtis jr, silverfield j, terry k, soma k, et al. safety and efficacy of tofacitinib for up to 9.5 years in the treatment of rheumatoid arthritis: final results of a global, open-label, long-term extension study. arthritis res ther 2019;21:89. 136. yamanuha j, albini t. current and new steroid therapy in noninfectious uveitis. retina specialist [internet]. 2019. available from: https://www.retinaspecialist.com/article/current-and-new-steroid-therapy-innoninfectious-uveitis/ 137. thorne je, sugar ea, holbrook jt, et al. periocular triamcinolone vs. intravitreal triamcinolone vs. intravitreal dexamethasone implant for the treatment of uveitic macular edema: the periocular vs. intravitreal corticosteroids for uveitic macular edema (point) trial. ophthalmology 2019;126:283–295. 138. lowder c, belfort r, lightman s, foster cs, robinson mr, schiffman rm, et al. dexamethasone intravitreal implant for noninfectious intermediate or posterior uveitis. arch ophthalmol 2011;129:545–553. 139. moisseiev e, goldstein m, waisbourd m, barak a, loewenstein a. long-term evaluation of patients treated with dexamethasone intravitreal implant for macular edema due to retinal vein occlusion. eye 2013;27:65–71. 140. jaffe gj, foster cs, pavesio ce, paggiarino da, riedel ge. effect of an injectable fluocinolone acetonide insert on recurrence rates in chronic noninfectious uveitis affecting the posterior segment: twelve-month results. ophthalmology 2019;126:601–610. 141. jaffe gj, pavesio ce, study investigators. effect of a fluocinolone acetonide insert on recurrence rates in noninfectious intermediate, posterior, or panuveitis: threeyear results. ophthalmology 2020;127:1395–1404. 142. multicenter uveitis steroid treatment trial research group, kempen jh, altaweel mm, holbrook jt, jabs da, sugar ea. the multicenter uveitis steroid treatment trial: rationale, design, and baseline characteristics. am j ophthalmol 2010;149:550–561.e10. 143. writing committee for the multicenter uveitis steroid treatment (must) trial and follow-up study research group. association between long-lasting intravitreous fluocinolone acetonide implant vs systemic antiinflammatory therapy and visual acuity at 7 years among patients with intermediate, posterior, or panuveitis. jama 2017;317:1993–2005. 144. emami-naeini p, yiu g. medical and surgical applications for the suprachoroidal space. int ophthalmol clin 2019;59:195–207. 145. henry cr, shah m, barakat mr, dayani p, wang rc, khurana rn, et al. suprachoroidal cls-ta for noninfectious uveitis: an open-label, safety trial (azalea). br j ophthalmol 2021;bjophthalmol-2020-318019. 146. yeh s, khurana rn, shah m, henry cr, wang rc, kissner jm, et al. efficacy and safety of suprachoroidal cls-ta for macular edema secondary to noninfectious uveitis: phase 3 randomized trial. ophthalmology 2020;127:948–955. 147. conrady cd, yeh s. a review of ocular drug delivery platforms and drugs for infectious and noninfectious uveitis: the past, present, and future. pharmaceutics 2021;13:1224. 148. taylor sr, banker a, schlaen a, couto c, matthe e, joshi l, et al. intraocular methotrexate can induce extended remission in some patients in noninfectious uveitis. retina 2013;33:2149–2154. 149. taylor sr, habot-wilner z, pacheco p, lightman sl. intraocular methotrexate in the treatment of uveitis and uveitic cystoid macular edema. ophthalmology 2009;116:797–801. 150. macular edema ranibizumab v. intravitreal antiinflammatory therapy trial (merit) (2017). clinicaltrial.gov identifier: nct02623426. available from: https: //clinicaltrials.gov/ct2/show/nct02623426?cond= macular+oedema+ranibizumab+v.+intravitreal+antiinflammatory+therapy+trial&draw=2&rank=1 151. frenkel s, hendler k, siegal t, shalom e, pe’er j. intravitreal methotrexate for treating vitreoretinal lymphoma: 10 years of experience. br j ophthalmol 2008;92:383–388. 152. merrill pt, clark wl, banker as, fardeau c, franco p, lehoang p, et al. efficacy and safety of intravitreal sirolimus for noninfectious uveitis of the posterior segment: results from the sirolimus study assessing double-masked uveitis treatment (sakura) program. ophthalmology 2020;127:1405–1415. 153. vigil em, sepah yj, watters al, sadiq ma, ansari m, bittencourt mg, et al. assessment of changes in quality of life among patients in the save study – sirolimus as therapeutic approach to uveitis: a randomized study to assess the safety and bioactivity of intravitreal and subconjunctival injections of sirolimus in patients with noninfectious uveitis. j ophthalmic inflamm infect 2015;5:13. 154. ibrahim ma, sepah yj, watters a, bittencourt m, vigil em, do dv, et al. one-year outcomes of the save study: 288 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 https://clinicaltrials.gov/ct2/show/nct02623426?cond=macular+oedema+ranibizumab+v.+intravitreal+anti-inflammatory+therapy+trial&draw=2&rank=1 https://clinicaltrials.gov/ct2/show/nct02623426?cond=macular+oedema+ranibizumab+v.+intravitreal+anti-inflammatory+therapy+trial&draw=2&rank=1 https://clinicaltrials.gov/ct2/show/nct02623426?cond=macular+oedema+ranibizumab+v.+intravitreal+anti-inflammatory+therapy+trial&draw=2&rank=1 https://clinicaltrials.gov/ct2/show/nct02623426?cond=macular+oedema+ranibizumab+v.+intravitreal+anti-inflammatory+therapy+trial&draw=2&rank=1 systemic and local immunosuppressive; mehta and emami-naeini sirolimus as a therapeutic approach for uveitis. transl vis sci technol 2015;4:4. 155. nguyen qd, sadiq ma, soliman mk, agarwal a, do dv, sepah yj. the effect of different dosing schedules of intravitreal sirolimus, a mammalian target of rapamycin (mtor) inhibitor, in the treatment of non-infectious uveitis (an american ophthalmological society thesis). trans am ophthalmol soc 2016;114:t3. 156. hamza mm, macky ta, sidky mk, ragab g, soliman mm. intravitreal infliximab in refractory uveitis in behcet’s disease: a safety and efficacy clinical study. retina 2016;36:2399–2408. 157. giganti m, beer pm, lemanski n, hartman c, schartman j, falk n. adverse events after intravitreal infliximab (remicade). retina 2010;30:71–80. 158. giansanti f, ramazzotti m, vannozzi l, rapizzi e, fiore t, iaccheri b, et al. a pilot study on ocular safety of intravitreal infliximab in a rabbit model. invest ophthalmol vis sci 2008;49:1151–1156. 159. theodossiadis pg, liarakos vs, sfikakis pp, charonis a, agrogiannis g, kavantzas n, et al. intravitreal administration of the anti-tnf monoclonal antibody infliximab in the rabbit. graefes arch clin exp ophthalmol 2009;247:273–281. 160. kheir wj, mehanna cj, abdul fattah m, al ghadban s, el sabban m, mansour am, et al. intravitreal adalimumab for the control of breakthrough intraocular inflammation. ocul immunol inflamm 2018;26:1206–1211. 161. hamam rn, barikian aw, antonios rs, abdulaal mr, alameddine rm, el mollayess g, et al. intravitreal adalimumab in active noninfectious uveitis: a pilot study. ocul immunol inflamm 2016;24:319–326. 162. sobolewska b, chee sp, zaguia f, goldstein da, smith jr, fend f, et al. vitreoretinal lymphoma. cancers 2021;13:3921. 163. hashida n, ohguro n, nishida k. efficacy and complications of intravitreal rituximab injection for treating primary vitreoretinal lymphoma. transl vis sci technol 2012;1:1. 164. eyevensys. plasmid-based uveitis therapy proceeding to phase i trial [internet]. san francisco, ca: american academy of ophthalmology; 2017. available from: https://www.aao.org/headline/plasmid-based-uveitistherapy-proceeding-to-phase165. buggage r, behar-cohen ff. eys606 for the treatment of chronic non-infectious uveitis (niu): results from part 1 of a first-in-human (eys606-ct1) study. invest ophthalmol vis sci 2020;61:3170. 166. businesswire. eyevensys presents initial data from phase i/ii trial of innovative, non-viral gene therapy for ocular diseases at 11th annual ophthalmology innovation summit [internet]. businesswire; 2019. available from: https://www.businesswire.com/news/ home/20191011005298/en/eyevensys-presents-initialdata-from-phase-iii-trial-of-innovative-non-viralgene-therapy-for-ocular-diseases-at-11th-annualophthalmology-innovation-summit 167. jabs da, nussenblatt rb, rosenbaum jt, standardization of uveitis nomenclature (sun) working group. standardization of uveitis nomenclature for reporting clinical data. results of the first international workshop. am j ophthalmol 2005;140:509–516. 168. jabs da. immunosuppression for the uveitides. ophthalmology 2018;125:193–202. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 289 https://www.businesswire.com/news/home/20191011005298/en/eyevensys-presents-initial-data-from-phase-iii-trial-of-innovative-non-viral-gene-therapy-for-ocular-diseases-at-11th-annual-ophthalmology-innovation-summit https://www.businesswire.com/news/home/20191011005298/en/eyevensys-presents-initial-data-from-phase-iii-trial-of-innovative-non-viral-gene-therapy-for-ocular-diseases-at-11th-annual-ophthalmology-innovation-summit https://www.businesswire.com/news/home/20191011005298/en/eyevensys-presents-initial-data-from-phase-iii-trial-of-innovative-non-viral-gene-therapy-for-ocular-diseases-at-11th-annual-ophthalmology-innovation-summit https://www.businesswire.com/news/home/20191011005298/en/eyevensys-presents-initial-data-from-phase-iii-trial-of-innovative-non-viral-gene-therapy-for-ocular-diseases-at-11th-annual-ophthalmology-innovation-summit https://www.businesswire.com/news/home/20191011005298/en/eyevensys-presents-initial-data-from-phase-iii-trial-of-innovative-non-viral-gene-therapy-for-ocular-diseases-at-11th-annual-ophthalmology-innovation-summit letter primary atypical lipomatous tumor of the orbit mahmood dhahir al-mendalawi, mb, ch.b, dch, ficms department of paediatrics, al-kindy college of medicine, university of baghdad, baghdad, iraq orcid: mahmood dhahir al-mendalawi: https://orcid.org/0000-0003-2872-453x j ophthalmic vis res 2019; 14 (4): 536–536 sir, i read with interest the case report by dworak et al on orbital atypical lipomatous tumor (alt), a rare variety of liposarcoma, in an american patient.[1] it is obvious that in addition to opportunistic infections, patients infected with human immunodeficiency virus (hiv) are also more susceptible to various types of tumors. the origin of these tumors is thought to be multifactorial, including immunosuppression, co-infection with oncogenic viruses, and life prolongation secondary to the use of antiretroviral therapy.[2] among these tumors, liposarcomas have been reported in hiv-positive patients.[3, 4] to my knowledge, hiv infection is a distressing health threat in the united states of america (usa). according to the available data, an estimated 1.1 million people aged ≥ 13 years were living with hiv infection in the usa at the end of 2015, including an estimated 162,500 (15%) persons with undiagnosed infections.[5] i presume that hiv infection ought to be considered in the patient studied in the aforementioned case. hence, testing of hiv status using the diagnostic panel of cd4 count and viral overload measurements was solicited in the studied patient. if that diagnostic panel was conducted and disclosed hiv infection, the case in question could surely be considered novel as hiv-associated orbital alt has never been reported in the literature so far. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. dworak dp, patel sa, chennuri r, falco d. primary atypical lipomatous tumor of the orbit: a case report. j ophthalmic vis res 2018;13:78–80. 2. valencia ortega me. malignancies and infection due to the human immunodeficiency virus. are these emerging diseases? rev clin esp 2018; 218:149–155. 3. grieger ta, carl m, liebert hp, cotelingam jd, wagner kf. mediastinal liposarcoma in a patient infected with the human immunodeficiency virus. am j med 1988;84:366. 4. leonetti g, forte a, covotta a, manfredelli s, campo s, bezzi m, et al. cervico-thoracic liposarcoma in an hiv patient. g chir 2008;29:427–428. 5. dailey af, hoots be, hall hi, song r, hayes d, fulton p, et al. vital signs: human immunodeficiency virus testing and diagnosis delays united states. mmwr 2017;66:1300– 1306. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. correspondence to: mahmood dhahir al-mendalawi, mb, ch.b, dch, ficms. baghdad post office, baghdad 55302, iraq. email: mdalmendalawi@yahoo.com received: 01-12-2018 accepted: 10-02-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i4.5479 how to cite this article: al-mendalawi md. atypical lipomatous tumor of the orbit. j ophthalmic vis res 2019;14:536–536. 536 © 2019 j  o  v r | p  knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5479&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay tantalum surgical clip presenting as an intraorbital foreign body george p. kung1, bs; jeremy d. clark2, md; austin gerber2, md; niloofar piri1, md 1department of ophthalmology, saint louis university school of medicine, st. louis, missouri 2department of ophthalmology and visual sciences, kentucky lions eye center, university of louisville, louisville, kentucky orcid: niloofar piri: https://orcid.org/0000-0002-0685-028x george kung: https://orcid.org/0000-0001-8554-5613 j ophthalmic vis res 2023; 18 (1): 135–137 presentation an 87-year-old female presented to the emergency room after she was partially run over by a truck and sustained multiple injuries including skull and facial trauma. facial bones ct scan was significant for a large, metallic intraorbital foreign body on the left side [figure 1]. per radiology, an intraocular foreign body (iofb) could not be ruled out. ophthalmology department was consulted to evaluate. she had a history of scleral buckling in the left eye for rhegmatogenous retinal detachment in the 1990s, with chronic mild low vision at baseline. her near corrected visual acuity was 20/20 od and 20/60 os; intraocular pressures were 14 od, 11 mmhg os. a relative afferent pupillary defect was present on the left. examination revealed left upper lid hematoma, lower lid ecchymosis, deep laceration above eyebrow, superior subconjunctival hemorrhage, and pseudophakia. fundus exam on the left revealed no vitreous hemorrhage, 360 high buckle effect, temporal cryopexy scars, and small hemorrhage on the buckle. no intraocular penetration site was seen, and foreign body appeared to be intraorbital only. correspondence to: niloofar piri, md. department of ophthalmology, saint louis university school of medicine, 1008 south spring ave, st. louis, mo 63110, usa. e-mail: niloofar.piri@health.slu.edu received: 05-02-2022 accepted: 01-06-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i1.12734 laceration was the suspected entry site. clinical exam was not concerning for iofb, but given the large, and irregular shape of the foreign body in addition to embedding on the globe with air track, the decision was made to proceed with exploratory orbitotomy and foreign body removal. superior orbitotomy through upper lid crease was performed with opening of the septum. exploration and irrigation failed to retrieve any foreign body. intraoperative skull x-ray was performed, which revealed the presence of a small metallic foreign body in the superonasal orbit in a regular shape similar to a surgical clip [figures 2a & 2b]. surgical plan was changed, and superior 120º peritomy was performed with isolation of the superior rectus muscle. metallic foreign body was revealed to be a tantalum surgical clip. upon contact with the retina surgeon’s office, it was confirmed to be a non-magnetic tantalum clip used to secure the scleral buckle. discussion while ophthalmologists have moved onto the usage of sutures or silicone sleeves to secure this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: kung gp, clark jd, gerber a, piri n. tantalum surgical clips presenting as an intraorbital foreign body. j ophthalmic vis res 2023;18:135–137. © 2023 kung et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 135 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i1.12734&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr tantalum clips presenting as foreign body; kung et al figure 1. orbital ct scan. axial sections with suspected intraocular hyperdense metallic foreign body (left panel). large metallic foreign body with irregular borders complicated by streak artifact and air track superonasally embedding into the sclera (right panel). ct, computed tomography. figure 2. (a) intraoperative x-ray demonstrating metallic foreign body in left orbit to be symmetric surgical clip. (b) metallic surgical clip used to secure buckle located superonasally. scleral buckles in the past two decades, tantalum clips were a common option in historical scleral buckle surgery.[1] the properties of tantalum posed a unique diagnostic challenge in this case. while radiopaque on x-rays, tantalum has the disadvantage of producing streak artifacts on ct.[1–3] the irregular margins of the foreign body produced by the artifact on ct made it difficult to not only see the shape of the clip but also localize its location. plain radiographs are not a typical part of foreign body workup due to their underestimation of common radiolucent foreign bodies such as wood or plastic.[4, 5] had an x-ray been considered in the context of the patient’s surgical history and artifact on ct, the surgical clip likely would have been identified earlier and surgery been avoided. in summary, foreign bodies can present a complex problem when initial diagnostic imaging is uncertain. in patients with a historical scleral buckle procedure, consider the presence of tantalum clips as a possibility. financial support and sponsorship none. conflicts of interest none. 136 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 tantalum clips presenting as foreign body; kung et al references 1. wilkinson cp, michels rg, rice ta. michels retinal detachment. mosby; 1997. p. 1163. 2. gross sc, kowalski jb, lee sh, terry b, honickman sj. surgical ligation clip artifacts on ct scans. radiology 1985;156:831–832. 3. schepens cl, hartnett me, hirose t. schepens’ retinal detachment and allied diseases. butterworth-heinemann; 2000. p. 792. 4. pinto a, brunese l, daniele s, faggian a, guarnieri g, muto m, et al. role of computed tomography in the assessment of intraorbital foreign bodies. semin ultrasound ct mri 2012;33:392–395. 5. bryden fm, pyott aa, bailey m, mcghee cnj. real time ultrasound in the assessment of intraocular foreign bodies. eye 1990;4:727–731. journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 137 photo essay a unique case of bilateral valsalva retinopathy v g madanagopalan, ms mrcs; girish velis, dnb vitreo-retinal services, aravind eye hospital, thavalakuppam, pondicherry, india orcid: v g madanagopalan: https://orcid.org/0000-0002-9970-466x j ophthalmic vis res 2019; 14 (4): 528–529 correspondence to: v g madanagopalan, ms mrcs. vitreo-retinal services, aravind eye hospital, thavalakuppam, pondicherry 605007, india. e-mail: drmadanagopalan@gmail.com received: 2017-10-20 accepted: 2018-06-17 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i4.5471 presentation a 45-year-old man presented to the eye clinic with complaints of diminished bilateral central vision for four days. he had constipation and bleeding during defecation over the past five months. he experienced severe straining accompanied by a particularly heavy episode of bleeding that occurred five days ago. thereafter, a surgeon diagnosed an anal fissure that was treated with 2% topical glyceryl trinitrate ointment. visual acuity in both eyes was 20/200, and the examination of the anterior segment was normal. retinal examination with an indirect ophthalmoscope revealed multiple hemorrhages in all quadrants of the retina (figures 1(a), right eye; 1(b), left eye). the fovea in both eyes was obscured by hemorrhages that was responsible for the mechanical obstruction of the central vision (arrows). hemorrhages were noted at the center of the macula as well (arrows). these hemorrhages beneath the internal limiting membrane (ilm) were confirmed with optical coherence tomography (oct), obliterating the foveal dip (arrowheads). a diagnosis of valsalva retinopathy was made. hematological investigations showed a hemoglobin level of 7 g/dl (normal range: 13.5 to 17.5 g/dl) and a platelet count of 140,000 (normal range: 150,000 to 450,000). the patient was asked to continue the treatment with his surgeon and was reviewed regularly at the eye clinic. the treatment for the anal fissure was successful, and he was relieved of constipation in one month. three months later, visual acuity in both eyes improved to 20/20. retinal examination showed a complete resolution of hemorrhages. hematological evaluation revealed that the hemoglobin level was 13.8 g/dl and the platelet count was 270,000. discussion valsalva retinopathy was described by duane in 1972.[1] in contrast to both retinal arterial and venous systems being affected in purtscher’s retinopathy, the preretinal hemorrhages noticed in valsalva retinopathy are attributed to the changes in the venous system alone. an abrupt increase in intra-thoracic or intra-abdominal pressure– particularly against a closed glottis as may occur with coughing, vomiting, lifting weights, or straining – causes visual loss due to premacular hemorrhages.[2] in valsalva retinopathy, the premacular hemorrhage can be a subhyaloid hemorrhage or a sub-ilm hemorrhage.[3] in our patient, fissure in ano was the cause of constipation. consequently, straining during stools this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: madanagopalan vg, velis g. bilateral valsalva retinopathy. j ophthalmic vis res 2019;14:528–529. 528 © 2019 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5471&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; madanagopalan and velis figure 1. a montage of images of the retina and macular optical coherence tomography (oct) in the right eye (panel a), and left eye (panel b). multiple superficial retinal hemorrhages are seen in all quadrants. the hemorrhages at the fovea (arrows) are responsible for defective central vision. the presence of hemorrhages obliterating the foveal photoreceptors is confirmed on oct (arrowheads). was responsible for valsalva retinopathy. with the hematological profile presented, the possible role of anemia could also be considered in this patient. anemic retinopathy presents with extravasation of blood into the retina due to retinal vasodilation as a response to relative retinal ischemia in the setting of acute blood loss.[4] as the sub-ilm hemorrhage at the fovea in both eyes was small in size, the patient was not subjected to ocular treatment. while encountering larger premacular hemorrhages, clinicians may utilize laser hyaloidotomy or vitrectomy to evacuate the hemorrhage.[3, 5] the images presented demonstrated the retinal changes responsible for visual loss in both eyes, encountered by a patient who developed valsalva retinopathy secondary to anal fissure. financial support and sponsorship nil. conflicts of interest there is no conflict of interest. references 1. duane td. valsalva hemorrhagic retinopathy. trans am ophthalmol soc 1972;70:298–313. 2. garcía fernández m, navarro jc, castaño cg. long-term evolution of valsalva retinopathy: a case series. j med case rep 2012;6:346. 3. de maeyer k, van ginderdeuren r, postelmans l, stalmans p, van calster j. sub-inner limiting membrane haemorrhage: causes and treatment with vitrectomy. br j ophthalmol 2007;91:869–872. 4. turco cd, la spina c, mantovani e, gagliardi m, lattanzio r, pierro l. natural history of premacular hemorrhage due to severe acute anemia: clinical and anatomical features in two untreated patients. ophthalmic surg las im 2014;45:e5–e7. 5. khan mt, saeed mu, shehzad ms, qazi za. nd:yag laser treatment for valsalva premacular hemorrhages: 6 month follow up: alternative management options for preretinal premacular hemorrhages in valsalva retinopathy. int ophthalmol 2008;28:325–327. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 529 letter safety of the excimer laser in lasik and prk for patients with implantable cardiac devices: our clinical experience in the past two decades tirth j. shah1,2, md; majid moshirfar3,4,5, md, facs; phillip c. hoopes, sr3,4, md 1college of medicine, university of arizona, phoenix, arizona, usa 2department of ophthalmology and visual sciences, university of iowa hospitals and clinics, iowa city, iowa 3john a. moran eye center, department of ophthalmology and visual sciences, university of utah school of medicine, salt lake city, ut, usa 4hdr research center, hoopes vision, draper, ut, usa 5utah lions eye bank, murray, ut, usa orcid: tirth j. shah: https://orcid.org/0000-0001-7924-8444 j ophthalmic vis res 2019; 14 (4): 530–531 sir, continued high prevalence in cardiac morbidity in the us has led to more refractive surgical candidates with cardiac implantable electronic devices (cied), although the food and drug administration (fda) studies have consistently excluded such populations during laser-assisted in situ keratomileusis (lasik) or photorefractive keratectomy (prk) evaluations. major manufacturers have discouraged laser eye surgery in patients with cieds until recently when medtronic and st. jude, the two largest manufacturers of such devices, approved lasik surgery with recommendations to shielding the cied with a magnet and closely monitoring the heart rate during the surgery.[1] we aim to share our insights and experiences over the years, hopefully mitigating some of the concerns in clinical practice. the excimer laser can electromagnetically interfere with the cieds and cause changes in a surgical setting[2] with potential adverse effects including cardiac stimulation inducing ventricular tachycardia or ventricular fibrillation, unexpected movement of the body, and interference with the ability of the cieds to adequately monitor for potential arrhythmias.[3] the factors affecting electromagnetic interference depend on the frequency of the emitting device, the distance between the devices, and the amount of shielding of the affected device.[2] particularly, with excimer use, l’esperance et al[4] demonstrated that nearly all of the 193 nm energy is absorbed by the cornea indicating that the frequency of light emitted by the ablation process may not cause significant interference with the cieds. furthermore, a recent study by sher et al[5] demonstrated that in-vitro operation with the three most commonly used ophthalmic lasers (visx star s4 excimer laser, lumenis selecta ii glaucoma laser, and laserex ultra q photodisruptor) did not lead to oversensing, inappropriate therapy, or change in the programming of the atlas ii+ implantable cardioverter defibrillators (icds) or the st. jude medical victory pacemaker. we retrospectively analyzed data from 1997 to 2014, and found at least 13 patients documented with a cied, although we expect more patients with such a device who did not disclose this information to us, necessitating the surgeon to ask this important question to all refractive surgery candidates. the average age of patients undergoing lasik/prk correction in our center was approximately 35 years (range: 23–60), and in this cohort was 52 years (range: 27–77) with a male predominance (69%) – a consistent finding in individuals with arrhythmia or heart disease. the indications of cied were primarily for atrial fibrillation (46%), although one male patient aged 27 years had the device for wolf-parkinson-white syndrome. the other small subset of patients had the device for either ventricular tachycardia, atrioventricular block of unknown degree, or an unspecified arrhythmia. out of 13 patients, one patient developed ventricular tachycardia two 530 © 2019 j  o  v r | p  knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5473&domain=pdf&date_stamp=2019-07-17 letter; shah et al weeks postoperatively. however, the consulting cardiologist felt the etiology was due to her uncontrolled underlying condition, rather than any electromagnetic interference from the femtosecond and excimer laser that may have offset the device settings. from our records, none of the other patients experienced any cied-related complications during the surgery. there was no clinically detectable change in the heart rate or rhythm, and postoperatively, the programmed parameters of the pacemakers and/or icds remained unchanged. due to the older age, lasik enhancement was usually used to achieve emmetropia following the cataract surgery. thus, we believe this information may be particularly helpful to those clinicians who tend to perform lasik on the elderly population in their practice. each laser and cied has a unique design and may interfere with one another differently. the current body of evidence and our concomitant experiences illustrate a low risk of complications in patients with cied during refractive surgery. we believe it is safest to inactivate any anti-tachycardia functions if electrocautery is used during surgery[3] and to follow manufacturer recommendations at all times. with the recent paradigm shift in the advancements to leadless pacemakers, some of these newer devices are immune to electromagnetic interference up to a very high threshold.[5] these remarkable technological advancements will only make ophthalmic lasers safer for patients with cieds in the future. financial support and sponsorship this study was funded by an unrestricted grant from the research to prevent blindness (rpb), 360 lexington avenue, 22nd floor new york, ny 10017. no support was received for the publication of this article. conflicts of interest there is no conflict of interest. references 1. medtronic. medical and dental procedures [cited 2018 jun 6]. available from: http://www.medtronic.com/us-en/ patients/electromagnetic-guide/medical-dental.html 2. l’esperance fa jr, labuda ef, johnson am. photocoagulation delivery systems for continuous-wave lasers. br j ophthalmol 1969;53:310–322. 3. lakshmanadoss u, chinnachamy p, daubert pj. electromagnetic interference of pacemakers. in: das mm, editor. modern pacemakers-present and future. norderstedt, germany: bod – books on demand.-15916820831591682083. 4. sher an, golben mp, kresge k, selznick l, adabag s. an in vitro evaluation of electromagnetic interference between implantable cardiac devices and ophthalmic laser systems. europace 2011;13:583–588. 5. audoubert m, ostiguy g, nguyen d, plante m, dubuc m, guerra p, et al. resistance of the medtronic micra leadless pacemaker to 60 hz electric fields. can j cardiol 2017;33:s155. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. correspondence to: majid moshirfar, md, facs. hdr research center ¨c hoopes vision 11820 s. state st., suite #200 draper, ut 84020. email: cornea2020@me.com received: 07-01-2019 accepted: 29-04-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i4.5473 how to cite this article: shah tj, moshirfar m, hoopes pc. safety of excimer lasers with cardiac devices. j ophthalmic vis res 2019;14:530–531. j  o  v r volume 14, issue 4, october-december 2019 531 http://www.medtronic.com/us-en/patients/electromagnetic-guide/medical-dental.html http://www.medtronic.com/us-en/patients/electromagnetic-guide/medical-dental.html https://knepublishing.com/index.php/jovr letter author’s reply neha goel, ms, dnb, frcs (glasg) icare eye hospital and postgraduate institute, noida, uttar pradesh, india orcid: neha goel: https://orcid.org/xxx j ophthalmic vis res 2020; 15 (1): 122–122 i thank dr. mahmood dhahir al-mendalawi for his interest in our article and his comments. the patient described in this report was hiv negative. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i1.5967 how to cite this article: goel n. author’s reply. j ophthalmic vis res 2020;15:122–122. 122 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i1.5967&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr editorial topical calcineurin inhibitors: expanding indications for corneal and ocular surface inflammation hamed ghasemi1, md; ali djalilian2, md 1eye research center, farabi eye hospital, tehran university of medical sciences, tehran, iran 2university of illinois at chicago, usa orcid: hamed ghasemi: https://orcid.org/0000-0003-0694-1840 j ophthalmic vis res 2019; 14 (4): 398–399 the immune system protects the host against environmental and pathogenic insults while maintaining tolerance to self-antigens and commensal microbial flora. inflammation and hyperactivity of the immune system play a central role in the pathophysiology of many ocular diseases such as vernal keratoconjunctivitis (vkc), dry eye disease, stromal keratitis, etc. inflammation is the key target in the treatment of most cornea and ocular surface diseases. despite many advances in the last several decades, corticosteroids still remain the mainstay of therapy for anterior segment inflammation and are the most widely used topical anti-inflammatory drugs. however, unwanted ocular side effects such as glaucoma and cataract often preclude their use on a chronic basis. calcineurin inhibitors such as cyclosporine a and tacrolimus are now commonly used as “steroid sparing” topical agents to prevent and treat diseases with t-cell-mediated pathophysiology. they specifically inhibit calcineurin which plays a central role in t-cell activation. successful treatment of multiple refractory anterior segment inflammatory diseases has been reported with these agents. these conditions include prophylaxis and treatment of corneal graft rejection, chronic allergic keratoconjunctivitis, and ocular graft-versus-host disease.[1–5] both cyclosporin and tacrolimus are insoluble in water which creates a challenge for making a topical eye drop. earlier studies often reported dissolving them in oil-based vehicles which were poorly tolerated by the patients. emulsions and liposomal preparations appear to be better tolerated. as far as the choice between tacrolimus and cyclosporin a, we tend to favor tacrolimus given that it is more hydrophilic with a higher transcorneal diffusion rate than cyclosporine. the potency of tacrolimus is also 10–100 times higher than cyclosporine. these characteristics make tacrolimus theoretically more effective for the treatment of deeper corneal inflammation. while topical cyclosporin is available as a commercial preparation, a commercial preparation of topical tacrolimus eye drop is only available in a few countries (japan, brazil, etc.), and therefore it often needs to be compounded. we recommend a concentration of 0.03 to 0.05% for compounded tacrolimus. as most practitioner know, there is also a skin ointment preparation of tacrolimus (0.03% and 0.1%) that has been used in the eye. in patients who are unable to get compounded medication, we have prescribed the skin ointment off label and have them apply it to the lid margin. finally, it is worth noting that there is a theoretical risk that topical application of tacrolimus could increase the risk of developing local cancers such as lymphoma, however, this has not been found to be the case on the eye. in this issue of the journal of ophthalmic and vision research, akbari et al have reported that addition of 0.05% topical tacrolimus to conventional treatment enhances visual acuity and reduces corneal inflammation, neovascularization, and scarring in eyes with herpetic stromal keratitis.[6] this study highlights the utility of tacrolimus for deeper corneal inflammation. likewise, the study by chatterjee et al concluded that topical cyclosporine a 0.05% is effective and safe in indian children with moderate to severe vkc with good steroid-sparing effect.[7] this confirms previous observations that topical calcineurin inhibitors are highly effective for chronic allergic diseases which is well-known 398 © 2019 journal of ophthalmic and vision research | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5435&domain=pdf&date_stamp=2019-07-17 editorial; ghasemi and djalilian to be medicated by type 2 t helper (th2) cells. as mentioned earlier, one of the main limitations of both topical cyclosporin and topical tacrolimus is their tolerability which appears to be concentration dependent. patients with significant ocular surface disease and dry eye appear to have the most trouble tolerating these medications. strategies to improve the tolerance of calcineurin inhibitors include refrigerating the drops and using shortterm topical steroids to control the inflammation prior to starting therapy. future formulations are expected to improve the tolerance and bioavailability of these medications; thus, they will likely remain one of the important steroid-sparing agents for patients with inflammatory corneal and ocular surface diseases. references 1. lee yj, kim sw, seo ky. application for tacrolimus ointment in treating refractory inflammatory ocular surface diseases. am j ophthalmol 2013;155:804–813. 2. miyazaki d, tominaga t, kakimaru-hasegawa a, nagata y, hasegawa j, inoue y, et al. therapeutic effects of tacrolimus ointment for refractory ocular surface inflammatory diseases. ophthalmology 2008;115:988–992. 3. ghaffari r, ghassemi h, zarei-ghanavati m, latifi g, dehghani s, haq z, et al. tacrolimus eye drops as adjunct therapy in severe corneal endothelial rejection refractory to corticosteroids. cornea 2017;36:1195–1199. 4. hashemian mn, latifi g, ghaffari r, ghassemi h, zareighanavati m, mohammadi sf, et al. topical tacrolimus as adjuvant therapy to corticosteroids in acute endothelial graft rejection after penetrating keratoplasty: a randomized controlled trial. cornea 2018;37:307–312. 5. kheirkhah a, zavareh m, farzbod f, mahbod m, behrouz mj. topical 0.005% tacrolimus eye drop for refractory vernal keratoconjunctivitis. eye (lond) 2011;25:872–880. 6. akbari a, soltani moghadam r, elmi r, nosrati a, taghiabadi e, aghdami, n. topical tacrolimus as an adjunct to conventional therapy for stromal herpetic keratitis: a randomized clinical trial. j ophthalmic vis res 2019;3– 14. 7. chatterjee a, bandyopadhyay s, bandyopadhyay sk. efficacy, safety and steroid-sparing effect of topical cyclosporine a 0.05% for vernal keratoconjunctivitis in indian children. j ophthalmic vis res 2019;15–21. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i4.5435 how to cite this article: ghasemi h, djalilian a. topical calcineurin inhibitors. j ophthalmic vis res 2019;14:398–399. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 399 https://knepublishing.com/index.php/jovr letter to editor multiple pit defects in a foldable hydrophobic intraocular lens arjun srirampur, ms, frcs; pasyanthi balijepalli, ms anand eye institute, hyderabad, india orcid: arjun srirampur: https://orcid.org/0000-0002-3016-8336 j ophthalmic vis res 2020; 15 (1): 118–119 correspondence to: arjun srirampur, ms, frcs. cornea, cataract and refractive surgery anand eye institute, habsiguda, hyderabad 500007, india. e-mail:sarjuneye@gmail.com received: 09-02-2019 accepted: 29-05-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i1.5963 dear editor, we are writing to share our observations regarding the article “multiple pit defects of unknown etiology in a foldable hydrophobic intraocular lens” by thabit et al.[1] we would like to congratulate the authors for documenting this interesting phenomenon. the authors mentioned no obvious reason for the formation of pit-like deposits on the anterior surface of the intraocular lens (iol). we want to disagree with this statement in that iol pit formation is a well-established phenomenon where opacification of hydrophilic acrylic iols occurs after corneal transplantations such as penetrating keratoplasty and descemet’s stripping endothelial keratoplasty (dsek).[2] factors such as ocular inflammation and systemic comorbidities that affect ocular metabolism may contribute to the opacification of iols.[3] surgical interventions with the injection of different materials into the anterior chamber such as air or gas seem to increase the risk of iol opacification, particularly in hydrophilic iols. the pits are limited to a more or less circular area of the anterior optical surface of the iol corresponding to the zone of contact with the instilled air or gas. prolonged breakdown of the blood-aqueous barrier has been suggested as a contributory factor in iol pit formation. the air in the anterior chamber causes dehydration of the anterior surface of the hydrophilic iols, and postoperative inflammation induces a metabolic change in the anterior chamber leading to an increase in aqueous proteins and calcium content that causes subsequent crystallization of the lens.[4] it is our observation that opacification of hydrophilic iols develop in eyes that undergo dsek and receive an air tamponade intraoperatively [figures 1 and 2]. figure 1. slit lamp image on diffuse illumination showing the pits confined to the central undilated pupillary area of the intraocular lens. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: srirampur a, balijepalli p. multiple pit defects in a foldable hydrophobic intraocular lens. j ophthalmic vis res 2020;15:118– 119. 118 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i1.5963&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr letter; srirampur and balijepalli figure 2. polychromatic opacification of the pits on the anterior surface of the intraocular lens on retroillumination. references 1. thabit a, gatzioufas z, mclintock c, elalfy m, hamada s. multiple pit defects of unknown etiology in a foldable hydrophobic intraocular lens. j ophthalmic vis res 2018;13:514–551. 2. fellman ma, werner l, liu et, stallings s. calcification of a hydrophilic acrylic intraocular lens after descemetstripping endothelial keratoplasty: case report and laboratory analyses. j cataract refract surg 2013;39:799–803. 3. werner l, wilbanks g, ollerton a, michelson j. localized calcification of hydrophilic acrylic intraocular lenses in association with intracameral injection of gas. j cataract refract surg 2012;38:720–721. 4. dhittal a, spalton dj, goyal s, werner l. calcification in hydrophilic intraocular lenses associated with injection of intraocular gas. am j ophthalmol 2012;153:1154–1160. journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 119 photo essay bilateral anterior ischemic optic neuropathy accompanied with unilateral central retinal artery occlusion in a biopsy-proven case of giant cell arteritis kaveh abri aghdam1, md, phd; ali aghajani1,2, md; mehdi khakpour1, md; mostafa soltan sanjari1, md 1eye research center, eye department, the five senses health institute, school of medicine, iran university of medical sciences, tehran, iran 2isfahan eye research center, department of ophthalmology, isfahan university of medical sciences, isfahan, iran orcid: kaveh abri aghdam: https://orcid.org/0000-0001-7568-6455 ali aghajani: https://orcid.org/0000-0002-7790-6033 j ophthalmic vis res 2022; 17 (3): 443–446 presentation an 80-year-old male patient was referred to the neuro-ophthalmology clinic with a history of sudden vision loss in the right eye one week earlier and vision loss in the left eye four days after that. the vision assessment was no light perception in both eyes at the time of the initial examination. both eyes were pseudophakic and anterior segment examination was unremarkable. funduscopic examination revealed a swollen optic disc in the right eye and a diffuse retinal whitening with a cherry-red spot, arterial attenuation, and a chalky-white blurredmargin optic disc in the left eye (figures 1a & 1b). fluorescein angiography (fa) disclosed a diffuse choroidal filling delay with leakage from the optic correspondence to: ali aghajani, md. department of ophthalmology, eye research center, the five senses institute, rassoul akram hospital, niayesh avenue, sattarkhan st., tehran 1445613131, iran. e-mail: aliaghajani_y@yahoo.com received: 13-06-2021 accepted: 22-09-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i3.11585 nerve head in the venous phase in the right eye and nasal choroidal filling delay and diffuse delay in the retinal arterial filling in the left eye [figure 2]. the erythrocyte sedimentation rate was 98 mm/hr, and the level of c-reactive protein was 76 mg/l. the patient was admitted and pulse corticosteroid therapy was commenced with the diagnosis of giant cell arteritis (gca). the diagnosis was later confirmed with a histopathologic evaluation of the left side temporal artery biopsy specimen [figure 1c]. unfortunately, even though treatment was started immediately, it failed to improve the patient’s vision. discussion giant cell arteritis (gca) is a granulomatous vasculitis that involves largeand medium-sized vessels. anterior ischemic optic neuropathy (aion), this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: abri aghdam k, aghajani a, khakpour m, sanjari ms. bilateral anterior ischemic optic neuropathy accompanied with unilateral central retinal artery occlusion in a biopsy-proven case of giant cell arteritis. j ophthalmic vis res 2022;17:443–446. © 2022 abri aghdam et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 443 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i3.11585&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; abri aghdam et al figure 1. color fundus photograph of the right eye showing a blurred-margin optic disc; note the paleness of the swollen optic disc (a). color fundus photograph of the left eye showing diffuse opaque retina, severe arterial attenuation, box-carring, and chalky white blurred-margin optic disc with multiple superficial hemorrhages (b). photomicrograph of the biopsy specimen from the left temporal artery reveals fibrinoid necrosis (arrowheads), endothelial destruction, and transmural infiltration of lymphocytes, polymorphonuclear neutrophils (black asterix), histiocytes, and giant cells (black arrow). organized thrombi in the lumen are seen (white asterix). the overall findings are compatible with the diagnosis of giant cell arteritis (hematoxylin and eosin staining, 40x magnification) (c). central retinal artery occlusion (crao), and posterior ischemic optic neuropathy (pion) are the most reported ophthalmic presentations of gca.[1] the main goal of corticosteroid therapy in gca is to prevent the occurrence or progression of visual loss. bilateral ocular involvement is another concern in these patients. hayreh et al[2] reported that in all gca patients with bilateral vision impairment, older changes could be found in one eye, suggesting that the patients were unaware of vision loss in one eye until the second eye was affected giving the erroneous interpretation of simultaneous bilateral ocular involvement. thus, the estimations of the prevalence of simultaneous bilateral gca ocular involvement suffer from the inaccuracy in the timing of the examination and perhaps were mostly imprecise and possibly preventable. crao is a rare but well-known disaster that has been reported in 4% of gca patients.[3] 444 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 photo essay; abri aghdam et al figure 2. fluorescein angiography in the early arteriovenous phase (30 sec) reveals a diffuse choroidal filling delay in the right eye (a), and a choroidal filling defect in the nasal retina as well as arterial filling delay in the left eye (b). fluorescein angiography in the venous phase (1 min), patchy choroidal filling defects accompanied with optic disc leakage in the right eye (c), and a sectoral choroidal filling defect in the nasal fundus as well as arterial filling delay in the left eye (d). fluorescein angiography in the late phase (5 min) shows patchy choroidal filling defect and optic nerve head leakage in the right eye (e), and patchy choroidal filling defect and arterial filling delay in the left eye (f). journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 445 photo essay; abri aghdam et al crao in these patients is almost invariably associated with aion, and posterior ciliary artery occlusion (revealed by fa study in patients with crao) is highly suggestive of the arteritic nature of the occlusion.[4] there has been only one report of a similar presentation of gca in literature.[5] although we cannot confirm the similarity of the extent of bilateral involvement between these two cases due to the lack of sufficient angiographic data, both reports have one thing in common, which is neither of these patients has enjoyed vision improvement after pulse corticosteroid therapy. overall, this report presents an extreme manifestation of gca with detailed illustrations to emphasize the importance of timely diagnosis and urgent treatment in these patients. consent to participate informed consent including publication of photographs in medical journals was obtained from the participant of this study. financial support and sponsorship the authors did not receive any financial support or funding for this work. conflicts of interest the authors have no conflicts of interest to declare. references 1. fein as, ko mw. neuro-ophthalmologic complications of giant cell arteritis: diagnosis and treatment. semin neurol 2019;39:673–681. 2. hayreh ss. giant cell arteritis: its ophthalmic manifestations. indian j ophthalmol 2021;69:227–235. 3. singh ag, kermani ta, crowson cs, weyand cm, matteson el, warrington kj. visual manifestations in giant cell arteritis: trend over 5 decades in a population-based cohort. j rheumatol 2015;42:309–315. 4. hayreh ss, zimmerman mb. central retinal artery occlusion: visual outcome. am j ophthalmol 2005;140:376.e1–376.e. 5. joseph add, pradeepan ja, kumanan t, malaravan m. combined left central retinal artery occlusion and bilateral anterior ischemic optic neuritis: a rare presentation of giant cell arteritis. case rep rheumatol 2019;2019:3236821. 446 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 original article renal function following fluorescein angiography in diabetic patients with chronic kidney disease nazanin ebrahimiadib1, md; shaghayegh hadavand mirzaei1, md; hamid riazi-esfahani1, md; manouchehr amini2, md 1eye research center, farabi eye hospital, department of ophthalmology, tehran university of medical sciences, tehran, iran 2department of nephrology, tehran university of medical sciences, tehran, iran orcid: nazanin ebrahimiadib: https://orcid.org/0000-0002-2058-9225 manouchehr amini: https://orcid.org/0000-0002-4618-0866 abstract purpose: to evaluate the effect of fluorescein dye usage on renal function in patients with diabetic retinopathy (dr) and chronic kidney disease (ckd). methods: diabetic patients with retinopathy who were candidate for fundus fluorescein angiography (fa) were evaluated for serum creatinine and urea levels within five days prior to performing the fa. serum creatinine levels of 1.5 mg/dl or more in males and 1.4 mg/dl or more in females were both identified as ckd and were included in the study. an increase of 0.5 mg/dl or 25% in creatinine after fa was considered as contrast-induced acute kidney injury (aki). estimated glomerular filtration rate (egfr) was also calculated for all patients using a ckd-epi formula. ckd grading was determined based on egfr values. results: forty-two patients agreed to participate, of which 23 (54.8%) were male. seventeen patients were identified with grade 3a or lower ckd, 12 with grade 3b, 11 with grade 4, and two with grade 5 ckd. considering all grades of ckd, the mean blood urea before and after angiography was 58.48 ± 26.7 and 57 ± 27.81 mg/dl, respectively (p = 0.475). the mean serum creatinine before and after the test was 1.89 ± 1.04 and 1.87±0.99 mg/dl, respectively (p = 0.993). the mean egfr before and after the test was 44.024 ± 23.5447 and 43.850 ± 21.8581 ml/min/1.73 m2 (p = 0.875). conclusion: according to the findings of this study, fa does not seem to further deteriorate kidney function in patients with diabetic associated ckd. keywords: acute kidney injury; chronic kidney disease; diabetic retinopathy; fluorescein angiography; nephropathy; serum creatinine j ophthalmic vis res 2023; 18 (2): 170–174 correspondence to: manouchehr amini, md. nephrology research center, shariati hospital, tehran university of medical sciences, tehran 14166, iran. email: aminimd@tums.ac.ir received: 19-02-2022 accepted: 10-12-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i2.13183 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: ebrahimiadib n, mirzaei sh, riazi-esfahani h, amini m. renal function following fluorescein angiography in diabetic patients with chronic kidney disease . j ophthalmic vis res 2023;18:170–174. 170 © 2023 ebrahimiadib et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i2.13183&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr fa in diabetic patients with ckd ; ebrahimiadib et al introduction fundus fluorescein angiography (fa) is a valuable method to evaluate microvascular complications in patients with diabetic retinopathy (dr). this procedure involves injection of fluorescein dye, which is a non-ionizing contrast, intravenously. fluorescein dye is metabolized by the kidneys and excreted in the urine during the first 48–72 hr after injection.[1] during this time, contrast-induced nephropathy usually manifests.[2] considering that concomitant diabetic nephropathy is possible in patients with dr, there is a concern as to whether fluorescein usage can deteriorate the kidney function further.[1–4] chronic kidney disease (ckd) is defined as a gradual decline in renal function which is initially subclinical. contrast-induced acute kidney injury (aki) is defined by an increase in serum creatinine of ≥0.5 mg/dl or 25% from the baseline that occurs around 48 hr after contrast administration.[1] although renal side effects have been attributed to fluorescein usage in previous studies, there is still no consensus in this regard.[5, 6]some angiography centers require a nephrology consult, in addition to blood and urine workup, before preceding to fa in patients with ckd. apart from the burden of cost and time on patients and healthcare system, referral of these patients for additional testing may cause a delay in diagnosis and treatment of the eye condition. in this study, we are going to determine whether the fluorescein can cause contrast-induced aki in diabetic patients with ckd who are candidates for fundus fa. methods this prospective study was performed in the retinal imaging section of farabi eye hospital from january 2019 until january 2020. the study protocol was reviewed and approved by the ethics committee of tehran university of medical sciences under approval number 96014334034. prior to recruitment, all patients were informed of the details of the study through verbal and written communication. according to the helsinki declaration, a written consent was also obtained from patients. patients with dr who were referred to the imaging section for performing fa to confirm the stage of retinopathy were routinely asked for a history of renal dysfunction. those with a positive history were sent for blood test to determine urea and creatinine levels. if creatinine levels were ≥1.5 mg/dl in men and ≥1.4 mg/dl in women, they were included in the study.[7]the glomerular filtration rate (gfr) (ml/min/1.73 m2) was calculated for all patients based on the chronic kidney disease epidemiology collaboration (ckdepi) equation.[8]the ckd grading was determined based on the egfr levels. according to the kidney disease outcomes quality initiative guidelines, egfr of ≥90 ml/min per 1.73m2is considered stage 1 ckd, 60–89 stage 2, 30–59 stage 3 (45–59 stage 3a and 30–44 stage 3b), 15–29 stage 4, and <15 would be considered stage 5 ckd.[8] the process of fa involved an injection of 2.5 ml of 10% fluorescein sodium solution (1g/5cc) [sterop, belgica] into the antecubital vein access in 5 s. for at least 10 min after the dye injection, fundus images were captured by heidelberg retina angiography with confocal slo (heidelberg engineering, heidelberg, germany). patients were then monitored for about 15 more minutes for any complications. blood urea and creatinine levels were retested 48–72 hr after the fluorescein injection. serum creatinine levels, before and after contrast administration, were compared and if increased by ≥0.5 mg/dl or 25% from the baseline were considered as aki.[2] moreover, patients who had received contrast material for imaging during the prior two months or those with kidney failure due to another cause, final stage of renal dysfunction requiring dialysis, chronic heart failure, pregnancy and breastfeeding, history of sensitivity to the contrast agent, consumption of nonsteroidal anti-inflammatory drug, angiotensin receptor blocker, angiotensin converting enzyme inhibitor, or intravenous diuretic were all excluded from the study. data analysis was performed using the spss software version 18 (spss, inc., chicago, il, usa). alterations of the variables with normal distribution was analyzed using paired sample t-test, and wilcoxon singed-rank test was used to compare nonparametric variables. p < 0.05 was considered as significant. results we included 42 patients, with the mean age of 58.1 years. of them, 23 (54.8%) were male. regarding journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 171 fa in diabetic patients with ckd ; ebrahimiadib et al the ckd grading, 17 patients were identified with grade 3a or lower ckd, 12 with grade 3b, 11 with grade 4, and two with grade 5. overall mean urea in patients before and after angiography was 58.48 ± 26.7 and 57 ± 27.81 mg/dl, respectively (p = 0.475). the mean serum creatinine levels were 1.89 ± 1.04 and 1.87± 0.99 mg/dl as the preand postangiography values (p = 0.993). the mean egfr before and after the test was 44.024 ± 23.5447 and 43.850 ± 21.8581 ml/min/1.73 m2 (p = 0.875) [table 1]. differential changes in egfr before and after fa in all stages of ckd was not significant [table 2]. discussion findings in our study showed that fa does not exacerbate kidney dysfunction (aki) in diabetic patients with an already reduced gfr (ckd). therefore, for patients with diabetic nephropathy in this instance who are candidates for fa, nephrology consult or additional tests before and after fluorescein injection are not required. in a retrospective study by kameda et al, patients’ serum creatinine level within one month before and after fa were investigated to calculate the estimated glomerular filtration rate (egfr). they categorized patients with egfr of <60 ml/min/m2 into three grades of severity from grade 3 to 5 ckd. none of these subgroups showed a significant alteration in egfr following fluorescein injection.[3] in another study by chung et al, patients were divided into three categories based on serum creatinine levels before angiography; including low (<1.5 mg / dl), moderate (1.5–2 mg/dl), and high (>2 mg/dl).[9]then, the effect of fa on renal function was evaluated in these patients. however, the actual timing that they tested the serum creatinine levels before and after fa was indeterminate, especially as there were some delayed measurements after fa, which might have influenced the omission of cases with aki. aki definitions are based on changes up to a maximum of seven days following the presumed insult.[10]they also included patients with other causes of renal dysfunction other than diabetes. they reported a significant change in serum creatinine levels in the high-risk group and suggested caution be applied for these patients.[9] in another study by alemzadeh et al on 44 diabetic patients, serum creatinine levels showed a significant increase 72 hr after fa in 20% of patients. in contrast to studies by kameda and chung, alemzadeh study showed that an increase in serum creatinine and aki can happen secondary to fa. however, their patients were not categorized in terms of kidney damage.[11] in our study, although the mean creatinine level was higher as compared to the alemzadeh’s study both before and after fa, the dose of injected fluorescein was 250 mg which was half of the dose used in their study. kidney damage and increase in serum creatinine following the use of contrasts in susceptible patients has been attributed to vasoconstriction, which reduces blood flow to the medulla. of note, renal blood flow auto regulation is defective in patients with ckd. identifying high-risk patients and preventing the occurrence of aki is critical,[12]especially as diabetes mellitus is the leading cause of propensity toward renal dysfunction. it is noteworthy that most kidney damage related to contrast agents has been due to iodinated contrast agents, while fluorescein is a non-iodinated one.[13–16] however, in a recently published article with a retrospective design, fluorescein was found to play a role in the progression of nephropathy. nevertheless, the authors were not sure of the clinical significance of their result due to two reasons. firstly, under normal circumstances fluctuations of up to 15% are possible each time the serum creatinine level is tested. the second reason is related to the criteria used; in a patient with aki, creatinine-based formulas are prone to overestimating the egfr. therefore, due to uncertainty about creatinine levels, their conclusion about the effect of the fluorescein on nephropathy is dubious.[17] our study was a prospective study on patients with dr and ckd. we found no significant effect on renal function shortly after performing fa. we used half of the recommended dosage of fluorescein and could still obtain good-quality images of fundus angiography. nephrology consults and further evaluation for these group of patients seem to be unnecessary. there are two major limitations for our study. firstly, the relatively small number of cases. secondly, we did not categorize our patients according to the multiple types of medications 172 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 fa in diabetic patients with ckd ; ebrahimiadib et al table 1. values of blood urea and creatinine levels and estimated gfr, before and after fluorescein angiography in patients with chronic kidney disease. grades of ckd egfr (ml/min/1.73 m2) p-value pre post g1 98.50 ± 3.50 89.70 ± 11.05 0.309 g2 67.13 ± 7.98 64.20 ± 7.86 0.430 g3a 50.62 ± 5.12 51.25 ± 10.38 0.822 g3b 37.65 ± 5.44 40.54 ± 8.03 0.133 g4 21.74 ± 4.52 22.18 ± 4.23 0.640 g5 10.95 ± 5.02 10.50 ± 4.10 0.614 ckd, chronic kidney disease; egfr, estimated glomerular filtration rate table 2. alteration of egfr following fluorescein angiography. mean ± sd (range) median (range) 95% ci p-value lower upper urea (mg/dl) pre 58.48 ± 26.7 (0.7–6) 55 (23 to 134) post 57 ± 27.81 46 (21 to 126) change –1.48 ± 13.27 1.5 (–35 to 25) –5.61 2.66 0.475 creatinine (mg/dl) pre 1.89 ± 1.04 (0.7–6) 1.65 (0.7 to 6) post 1.87 ± 0.99 (0.7–5.9) 1.55 (0.7 to 5.9) change –0.02 ± 0.25 0 (–1.1 to 0.4) –0.1 0.06 0.993 egfr by ckd-epi (ml/min/1.73 m2) pre 44.024 ± 23.54 (7.4–102) 55 (7 to 98) post 43.850 ± 21.86 (7.6–97.1) 46 (7 to 95) change –0.174 ± 22.69 0.17 (–40 to 67) –2.039 2.38 0.875 sd, standard deviation; ci, confidence interval; ckd-epi, chronic kidney disease epidemiology collaboration equation; ckd, chronic kidney disease; egfr, estimated glomerular filtration rate used by each patient; such as oral hypoglycemic agents, diuretics, or statins. however, as overall we did not observe fluorescein injection causing any aki, lack of such data might not be affecting the results. financial support and sponsorship none. conflicts of interest none. references 1. almalk wh, abdalla an, elkeraie af, abdelhadi am, elrggal m, elrggal me. effect of fluorescein angiography on renal functions in type 2 diabetes patients: a pilot study. saudi j kidney dis transpl 2017;28:491–498. 2. mehran r, aymong ed, nikolsky e, lasic z, lakovou l, fahy m, et al. a simple risk score for prediction of contrast-induced nephropathy after percutaneous coronary intervention: development and initial validation. j am coll cardiol 2004;44:1393–1399. 3. kameda y, babazone t, haruyama k. renal function following fluorescein angiography in diabetic patients with chronic kidney disease. diabetes care 2009;32:e31–e3.1. 4. klein r, klein be, moss se, davis md, demets dl. the wisconsin epidemiologic study of diabetic retinopathy. v. proteinuria and retinopathy in a population of diabetic persons diagnosed prior to 30 years of age. in: friedman journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 173 fa in diabetic patients with ckd ; ebrahimiadib et al ea, l’esperance fa, editors. diabetic renal-retinal syndrome. vol. 3. grune & stratton; 1986, p. 245–264. 5. stein mr, parker cw. reactions following intravenous fluorescein. am j ophthalmol 1971;72:861–868. 6. yun d, kim dk, lee jp, kim ys, oh s, lim cs. can sodium fluorescein cause contrast-induced nephropathy? nephrol dial transplant 2021;36:819–825. 7. amini m, salarifar m, amirbaigloo a, masoudkabir f, esfahani f. n-acetylcysteine does not prevent contrastinduced nephropathy after cardiac catheterization in patients with diabetes mellitus and chronic kidney disease: a randomized clinical trial. trials 2009;10:45. 8. van den brand ja, van boekel ga, willems hl, kiemeney la, den heijer m, wetzels jf. introduction of the ckd-epi equation to estimate glomerular filtration rate in a caucasian population. nephrol dial transplant 2011;26:3176–3181. 9. chung b, lee cs. renal function following fluorescein angiography. iovs meeting 2014;55:258. 10. thomas me, blaine c, dawnay a, devonald ma, ftouh s, laing c, et al. the definition of acute kidney injury and its use in practice. kidney int 2015;87:62–73. 11. alemzadeh-ansari mj, beladi-mousavi ss, feghhei m. effect of fluorescein on renal function among diabetic patients. nefrologica 2011;31:612–613. 12. kwiterovich ka, maguire mg, murphy rp, schachat ap, bressler nm, bressler sb, et al. frequency of adverse results and systemic reactions after fluorescein angiography. a prospective study. ophthalmology 1991;98:1139–1142. 13. yannuzzi la, rohrer kt, tindel lj, sobel rs, costanza ma, shields w, et al. fluorescein angiography complication survey. ophthalmology 1986;93:611–617. 14. imai e, horio m, nitta k, yamagata k, iseki k, hara s, et al. estimation of glomerular filtration rate by the mdrd study equation modified for japanese patients with chronic kidney disease. clin exp nephrol 2007;11:41–50. 15. brown jr, devries jt, piper wd, robb jf, hearne mj, northern new england cardiovascular disease study group, et al. serious renal dysfunction after percutaneous coronary interventions can be predicted. am heart j 2008;155:260–266. 16. solomon r, dauerman hl. contrast induced acute kidney injury. circulation 2010;122:2451–2455. 17. yun d, kim dk, lee jp, kim ys, oh s, lim cs. can sodium fluorescein cause contrast-induced nephropathy? nephrol dial transplant 2021;36:819–825. 174 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 case report glaucoma in ectropion uveae syndrome: a case report and literature review mohammadmehdi hatami, md; azadeh doozandeh, md; mohadeseh feizi, md ophthalmic research center, shahid beheshti university of medical sciences, tehran, iran orcid: mohammadmehdi hatami: https://orcid.org/0000-0003-2733-7802 abstract purpose: to report a case of advanced childhood glaucoma secondary to congenital ectropion uveae (ceu). case report: the patient was a seven-year-old boy with unilateral glaucoma secondary to ceu and facial asymmetry, mild unilateral ptosis, and proptosis in the left eye. the intraocular pressure (iop) was 28 mmhg and cup-to-disc ratio was 0.8 in the left eye. after starting glaucoma medication, iop decreased to 21 mmhg. in view of the uncontrolled iop with medication and high cup-to-disc ratio and increased axial length of the left eye, mitomycin-c (mmc)-augmented trabeculectomy was planned. despite sub-tenon mmc injection and bleb needling, the bleb failed after six months, and we had to perform a shunt procedure to control the iop. conclusion: although ceu is rare, ophthalmologists should be familiar with this syndrome because of the high frequency of glaucoma and its challenging management during childhood. keywords: congenital ectropion uveae; facial hemihypertrophy; intraocular pressure; mitomycin-c; ptosis; secondary glaucoma j ophthalmic vis res 2019; 14 (3): 370–375 introduction ectropion uveae (eu) is defined as the presence of iris pigment epithelium on the anterior surface of the iris. although eu is usually acquired, it may occur as an isolated congenital anomaly or in association with systemic diseases such as neurofibromatosis. correspondence to: mohammadmehdi hatami, md. department of ophthalmology, labbafinejad medical center, boostan 9 st., pasdaran ave., tehran 16666, iran. e-mail: drmehdihatami@gmail.com received: 08-05-2018 accepted: 23-08-2018 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i3.4793 the most important complication of eu is glaucoma, and its diagnosis and treatment are challenging during childhood because the intraocular pressure (iop) cannot be easily measured in a crying toddler under routine settings, and significant damage may have already occurred by the time of presentation. hence, early detection, close monitoring, and prompt treatment are mandatory to safeguard lifelong vision of the child. we report a case of glaucoma secondary to eu and its management, along with a literature review. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: hatami m, doozandeh a, arumugam j, feizi m. glaucoma in ectropion uveae syndrome: a case report and literature review. j ophthalmic vis res 2019;14:370–375 370 @ 2019 j  o  v r | p  published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i3.4793&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr ectropion uveae syndrome; hatami et al figure 1. general appearance of the patient. mild ptosis and facial hemihypertrophy is seen. case report a seven-year-old boy was referred to glaucoma service for mild ptosis and gradual decrease in the left eye vision. he had facial asymmetry, with left hemifacial hypertrophy and moderate ptosis and proptosis of the left eye [figure 1]. there was no history of any medical or surgical intervention; family history was unremarkable. best-corrected visual acuity were 20/20 and 20/30 in right and left eyes, respectively. full cycloplegic refraction was +1.75 diopters in the right eye and −3.5 diopters in the left eye. relative afferent pupillary defect was +1 in the left eye. there was 2 mm ptosis in the left eye with normal levator palpebrae function. hertel exophthalmometry measurements were 14 and 21 mm with bar reading of 107 mm. the axial length was 22.21 and 24.51 mm in the right and left eyes, respectively. extraocular muscle movement was normal. on slit lamp examination, the cornea was clear and the anterior chamber (ac) depth was normal. the iris was cryptless and there was a band of hyperpigmentation at the margin of the pupil consistent with eu [figure 2]. gonioscopy showed anterior iris insertion and angle dysgenesis. since eu may be associated with systemic disorders, the figure 2. slit lamp view shows ectropion uvea in left eye. right eye is normal. whole body was examined carefully to detect any remarkable signs of probable associated diseases. skin examination was normal, and there was no café-au-lait spot or any other sign of neurofibromatosis. dental examination was also normal. his height and weight measurements were within normal limits for his age. his mental and intellectual abilities were age-appropriate. iop was 13 and 28 mmhg without medication in the right and left eyes, respectively. after starting three glaucoma medications for the left eye, iop decreased to 21 mmhg. cup-to-disc ratio was 0.2 and 0.8 in the right and left eyes, respectively, with significant rim loss in the left eye [figure 3]. horizontal corneal diameter was 12 and 12.5 mm, and central corneal thickness was 578 and 589 𝜇m in the right and left eye, respectively. peripapillary nerve fiber layer optical coherence tomography (oct) and perimetry were normal in the right eye, but in the left eye there was severe nerve fiber layer loss in all quadrants in peripapillary oct and a double arcuate scotoma in perimetry [figure 4]. axial and coronal orbital computerized tomography (ct) scan showed left proptosis and axial elongation of the left globe [figure 5]. due to asymmetric corneal diameter and antimetropia, the clinical impression was that the glaucoma in this patient was of early onset and has been missed; hence, prompt intervention was crucial. the patient was planned for mitomycin-c (mmc)-augmented trabeculectomy, which was performed without complications. at the onemonth postoperative examination, iop was 17 j  o  v r volume 14, issue 3, july–september 2019 371 ectropion uveae syndrome; hatami et al figure 3. fundus photograph shows advanced cupping of left optic disc. mmhg without medication, and the bleb was moderately vascularized and shallow [figure 6]. although subtenon mmc was injected in the superior fornix, the bleb failed after six months, and iop increased to 20 mmhg. bleb needling and mmc injection were not successful, and we had to perform a shunt procedure to control the iop. six months after the shunt procedure, iop was controlled with the timolol-dorzolamide fixed combination. discussion ectropion uveae is characterized by the presence of iris pigmented epithelium on the anterior surface of the iris. it can be acquired, associated with systemic diseases, or can manifest itself as an isolated congenital syndrome. acquired eu may be associated with any inflammatory, ischemic, or neoplastic process involving the iris such as neovascular glaucoma or iridocorneal endothelial (ice) syndrome. this type of ectropion is commonly progressive. eu can be associated with systemic diseases, such as: neurofibromatosis type 1 (nf1), prader-willi syndrome, and rieger syndrome. ritch et al reported eight patients with ceu and glaucoma, of which three had nf1.[1] morales et al found glaucoma in 13 of 56 patients with nf1 with orbital involvement, and eight of these thirteen cases had eu.[2] in another study, all five patients with orbitofacial nf1 and glaucoma demonstrated histopathological eu.[3] so, the presence of eu in a neonate necessitates a workup for nf.[4] isolated ceu syndrome is usually unilateral and tends to be non-progressive. it is characterized by iris pigment hyperplasia onto the anterior surface of the iris around the pupillary margin. in contrast to acquired eu, the iris sphincter muscle and stroma are not affected in ceu and are not everted on histopathologic examination.[5] the iris-pigmented epithelium hyperplasia is thought to be induced by an embryological remnant that fails to fully regress in the ac.[6] this anomaly may be caused by a late developmental arrest of neural crest tissue in utero.[5] typical clinical findings include a smooth and cryptless iris surface, proliferation of iris pigment epithelium onto the anterior surface of the iris, and glaucoma. gonioscopy typically reveals anterior iris insertion, angle dysgenesis, and incomplete formation of trabecular meshwork and schlemm’s canal,[1, 5, 6] which is the primary mechanism of glaucoma in ceu. glaucoma is a frequent complication of ceu. in one report, glaucoma occurred in seven of eight cases,[1] and in another study, in nine of ten ceu cases.[5] so, all patients with ceu should be evaluated periodically to detect and treat glaucoma.[1, 5] the affected eye may exhibit mild ptosis with good levator function. this finding is most likely related to the neural crest origin of mueller’s muscle. in the aforementioned study , ptosis was reported in one of eight cases[1] and in six of ten cases with ceu.[5] our patient also had antimetropia in cycloplegic refraction because of greater axial length in the left eye. there was combined pseudo and true proptosis, because the amount of proptosis of the left eye on hertel exophthalmometry was greater than the axial length difference, and hemifacial hypertrophy seemed to play a role in proptosis. this finding also presented in case 1 of a study by bansal et al,[7] who reported 6 mm proptosis and 2.2 mm difference in axial length. although they did 372 j  o  v r volume 14, issue 3, july–september 2019 ectropion uveae syndrome; hatami et al figure 4. perimetry shows double arcuate scotoma in left eye. j  o  v r volume 14, issue 3, july–september 2019 373 ectropion uveae syndrome; hatami et al figure 5. axial computerized tomography (ct) scan shows left proptosis and different globe size. figure 6. slit lamp photograph one month after trabeculectomy. the bleb is shallow and moderately vascularized. not mention combined mechanism proptosis, the report was similar to the present study. in the approach to a patient with ceu and glaucoma, we should consider diseases that commonly mimic it, such as axenfeld-rieger syndrome (ars), iridocorneal endothelial (ice) syndrome, and nf1. in ars, the findings include a high iris insertion, angle dysgenesis, eu, and glaucoma. however, the syndrome can be distinguished from ceu using other clinical findings such as posterior embryotoxon, corectopia, or polycoria, and facial abnormalities such as maxillary hypoplasia and dental defects.[8] ice syndrome is an acquired condition with glaucoma and eu. ice syndrome predominantly affects middle-aged women, and its occurrence in children is rare.[9] the treatment of glaucoma in patients with ceu usually requires surgery, although medical management should be attempted initially. effective surgical interventions for ceu-associated glaucoma differ from the techniques used in primary congenital glaucoma, and the success rate is much lower, presumably due to severe angle dysgenesis in this disorder. glaucoma filtration surgery or a shunt procedure may be necessary.[8, 10] in one study, a total of six goniotomies in three patients with glaucoma associated with ceu did not control iop, and they finally required trabeculectomy.[5] early failure of trabeculectomy in our patient might suggest prompt consideration of a shunt procedure in ceu-associated patients, when iop is not controlled with medical treatment. in conclusion, although ceu is a rare syndrome, it is associated with systemic diseases and high frequency of glaucoma and its management in children is challenging. hence, ophthalmologists should be familiar with this rare syndrome to prevent irreversible vision loss. declaration of patient consent the authors certify that they have obtained all appropriate patient consent form. in the form, the patient has given his consent for his images and other clinical information to be reported in the journal. the patient understands that his name and initials will not be published and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. ritch r, forbes m, hetherington j, jr, harrison r, podos sm. congenital ectropion uveae with glaucoma. ophthalmology 1984;91:326–331. 374 j  o  v r volume 14, issue 3, july–september 2019 ectropion uveae syndrome; hatami et al 2. morales j, chaudhry ia, bosley tm. glaucoma and globe enlargement associated with neurofibromatosis type 1. ophthalmology 2009;116:1725–1730. 3. edward dp, morales j, bouhenni ra, patil j, edward pr, cummings tj, et al. congenital ectropion uvea and mechanisms of glaucoma in neurofibromatosis type 1: new insights. ophthalmology 2012;119:1485–1194. 4. skuta gl, cantor lb, cioffi ga. childhood glaucoma. in: glaucoma 2013-2014. section 10. san francisco, ca: american academy of ophthalmology (aao); 2004: 148. 5. dowling jl, jr, albert dm, nelson lb, walton ds. primary glaucoma associated with iridotrabecular dysgenesis and ectropion uveae. ophthalmology 1985;92:912–921. 6. wilson me. congenital iris ectropion and a new classification for anterior segment dysgenesis. j pediatr ophthalmol strabismus 1990;27:48–55. 7. bansal a, luck j. primary iris pigment epithelial hyperplasia and glaucoma. brit j ophthalmol 2002;86:352–353. 8. beck ad. diagnosis and management of pediatric glaucoma. ophthalmol clin north am 2001;14:501–512. 9. salim s, shields mb. iridocorneal endothelial syndrome and glaucoma. eyenet magazine 2011;15:47–49. 10. salim s, walton ds. goniotomy and trabeculotomy. in: yanoff m, duker js. ophthalmology. 3rd ed. new york: elsevier; 2008: 1241–1245. j  o  v r volume 14, issue 3, july–september 2019 375 original article clinical and autofluorescence findings in eyes with pinguecula and pterygium amir-hooshang beheshtnejad1, md; hamed ghassemi2, md; hossein abdolkhalegh2, md; mehrnaz atighehchian2, md 1department of ophthalmology, farabi eye hospital, tehran university of medical sciences, tehran, iran 2eye research center, farabi eye hospital, tehran university of medical sciences, tehran, iran orcid: amir-hooshang beheshtnejad: http://orcid.org/0000-0003-2633-268x mehrnaz atighehchian: http://orcid.org/0000-0002-6357-1033c abstract purpose: to assess the autofluorescence size and properties of pterygium and pinguecula by anterior segment autofluorescence (as-af) imaging and demonstrate the difference of autofluorescence size presented in as-af imaging compared to the extend size of the conjunctival lesion measured by anterior segment slit-lamp photography (as-sle). methods: twenty-five patients with primary pterygium and twenty-five with pinguecula were included in the study. in addition, 25 normal subjects were also enrolled as the control group. the as-af characteristics of pterygium and pinguecula lesions were analyzed. the size of lesions displayed in the as-sle photography versus the as-af images were also compared. as-af images were obtained using a heidelberg retina angiograph which focused on the anterior segment. as-sle photography was acquired using a digital imaging system (bx900 haagstreit). results: there were 44 (58.7%) male and 31 (41.3%) female patients; 19 (76%) and 20 (80%) patients had bilateral pterygium and pinguecula, respectively. all pinguecula lesions reflected hyperautofluorescence pattern in the as-af imaging. in 24 (96%) patients, the hyperautofluoresecence pattern was larger than the size of the clinical lesions displayed with the as-sle photography. twenty-one (84%) patients with pterygium reflected a hyperautofluorescence pattern in as-af images; in one (4%) patient, the hyperautofluorescence pattern was larger than the clinical lesion size and four (16%) patients had no autofluorescence patterns in the as-af images. in the control group, in 14 (56%) subjects, a hypoautofluorescent pattern was revealed in the conjunctiva in as-af images. however, in 11 (44%) patients, hyperautofluorescence patterns were detected. conclusion: as-af is a useful modality to monitor vascularization in conjunctival lesions. pingueculae and pterygium show hyperautofluorescence in as-af imaging. the real size of the pinguecula lesions may be estimated with as-af characteristics, mostly presenting larger than the area size in as-sle photography. the autofluorescence size of the pterygium is smaller than the extent of visible pterygium in slit-lamp photography. keywords: autofluorescence; pinguecula; pterygium j ophthalmic vis res 2023; 18 (3): 260–266 260 © 2023 beheshtnejad et al . this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i3.13773&domain=pdf&date_stamp=2019-07-17 autofluorescence of pingueculae and pterygia; beheshtnejad et al introduction a pterygium is an inflammatory ocular surface disease and triangular fibrovascular growth that emanates from the bulbar conjunctiva and crosses the cornea at the interpalpebral fissure on the nasal or temporal sides of the eye; mostly affecting the nasal rather than the temporal side.[1–4] a pinguecula is a benign yellowish protruding lesion adjacent to the limbus that does not cross the cornea and may be visible on both sides of the cornea but is more often seen on the nasal side.[5] the pathogenesis of these conjunctival lesions remains indistinctive. these degenerative conditions are affected by several intrinsic and extrinsic factors such as age, wind, solar, and ultraviolet radiation exposure.[5, 6] fluorescence is the ability of specific molecules to radiate light energy of a longer wavelength when stimulated by a shorter wavelength light without injecting dye.[7] recently, fundus autofluorescence (af) has been a beneficial imaging modality for the diagnosis of different retinal disorders. retinal autofluorescence imaging is based on the stimulated emission of light from lipofuscin and is a noninvasive retinal pigment epithelium examination technique.[7–10] the size of pinguecula can be evaluated by af features, and often has a larger autofluorescence area size in the af imaging than the visible lesion size in clinical examination by slit-lamp biomicroscopy.[5, 7] to the best of our knowledge, there have been a few reports on anterior segment autofluorescence (as-af) imaging for evaluating anterior segment disorders. the previous studies did not compare autofluorescence patterns between pterygium and pinguecula;[7] therefore, in this study, we aimed correspondence to: hamed ghassemi, md. eye research center, farabi eye hospital, tehran university of medical sciences, tehran 13366, iran. email: h_ghassemi@tums.ac.ir mehrnaz atighehchian, md. eye research center, farabi eye hospital, tehran university of medical sciences, tehran 13366, iran. email: mehrnaz.atighehchian@gmail.com received: 20-05-2022 accepted: 04-01-2023 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i3.13773 to assess the discrepancy of as-af properties on these two wide-spread conjunctival diseases, and compare the as-af results to actual lesions’ size displayed by slit-lamp photography. methods patients the patients included in this study were those who visited the ocular surface eye clinic, farabi eye hospital, tehran university of medical sciences. patients with pinguecula or primary pterygium with no other ocular surface disease were included in this study. seventy-five patients (31 women, 44 men) between the ages of 21 and 73 years were enrolled, of whom 25 patients were diagnosed with pterygium and 25 were diagnosed with pingueculae. in addition, 25 healthy subjects with neither pterygium nor pinguecula were considered as a control group. each patient underwent general ophthalmic examination including visual acuity assessment, slit-lamp biomicroscopy, intraocular pressure measurement with goldmann applanation tonometry, and posterior segments examination with indirect ophthalmoscopy. inclusion criteria were confirmation of either having primary pterygium or pinguecula through slit-lamp biomicroscopy, and patients being older than 21 years. in bilateral cases, only one eye with primary pterygium with less inflammatory features and more advance stage was considered. pterygium were classified into three stages according to the following method suggested by yang et al – stage i, the head of the pterygium does not reach the midline between the limbus and pupillary margin; stage ii, the head of the pterygium passes the midline but does not reach the pupil; and stage iii, the head of the pterygium passes the pupillary margin.[1] the inflammation was clinically graded according to hyperemia in this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: beheshtnejad ah, ghassemi h, abdolkhalegh h, atighehchian m. clinical and autofluorescence findings in eyes with pinguecula and pterygium. j ophthalmic vis res 2023;18:260–266. journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 261 https://knepublishing.com/index.php/jovr autofluorescence of pingueculae and pterygia; beheshtnejad et al a b figure 1. (a) normal conjunctiva in slit-lamp photography. (b) hypoautofluorescence pattern at the temporal area in as-af imaging. a b figure 2. (a) pinguecula at the temporal side in slit-lamp photography. (b) hyperautofluoresecence pattern at the temporal side in as-af. the size of the autofluorescence area is larger than the size of the visible pinguecula in slit-lamp photography. a b figure 3. pterygium at the nasal side of the left eye in slit-lamp photography. (b) faint punctuate hyperautofluoresecence pattern is seen at the nasal side in as-af imaging. the size of the autofluorescence area of pterygium is smaller than the visible pterygium size in slit-lamp photography. 262 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 autofluorescence of pingueculae and pterygia; beheshtnejad et al a b figure 4. (a) pterygium. (b) complete hypoautofluorescence pattern in as-af imaging. table 1. the comparison of lesions size between slit-lamp photography and as-af imaging. subjects mean slit-lamp photography area (mm2) mean as-af imaging1area (mm2) std. d2 slit-lamp photography area (mm2) std. d as-af imaging area (mm2) difference 95% confidence interval of the difference p-value pinguecula 10.128 19.320 4.149 7.795 –9.192 –11.446 to –6.937 <0.001 pterygium 50.924 7.194 21.286 5.461 43.730 33.570 to 53.889 <0.001 normal 0 0.388 0 0.526 –0.388 –0.605 to –0.170 0.001 as-af imaging, anterior segment autofluorescence imaging; mm2, square millimeter; std, standard deviation p-value < 0.05 the site of pterygium excision zone as follows: 0 = none, 1 = mild, 2 = moderate, and 3 = severe.[4] exclusion criteria were a history of topical medication usage other than artificial tears one month before the study, recurrent pterygium, keratitis, atopic keratoconjunctivitis, inflammatory conjunctival disorders, previous ocular surface surgery, severe dry eye disease, abnormal eyelid function, conjunctival scarring, and symblepharon. this study adhered to the tenets of the declaration of helsinki and the protocol of the study was approved by the ethics committee of tehran university of medical sciences, tehran, iran; the approval number was ir.tums.vcr.rec.1396.4797. informed consent was obtained from all patients and demographic characteristics of the patients including age, sex, family history, and, outdoor period time were considered. slit-lamp photography and as-af image techniques and analysis anterior segment slit-lamp photography was obtained using a digital imaging system (bx900 haag-streit). a confocal scanning laser ophthalmoscope (heidelberg retina angiography hra2, heidelberg) was used for the evaluation of anterior segment af images. as-af imaging can be used for determining the size of conjunctival lesions such as pterygium and pinguecula. this device uses argon blue laser stimulating light with a 488 nm wavelength and a barrier filter that allows the passage of stimulating lights >500 nm wavelength. the focus on the conjunctiva is obtained with the infrared mode of this device and af images are saved in fluorescein angiogram mode without using fluorescein dye.[7] in the present study, the pinguecula and pterygium lesions’ size at the temporal or nasal of the cornea in slit-lamp photography was compared journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 263 autofluorescence of pingueculae and pterygia; beheshtnejad et al with the autofluorescence size of the lesions displayed in as-af. the autofluorescence region size in as-af was analyzed and measured in mm2 with image j software. statistical analysis this study is a cross-sectional study. statistical analysis was performed using spss software version 17. the correlation between the lesion size in as-af and slit-lamp photography was evaluated using a pearson correlation test. chisquare test was used for the study of the qualitative results and independent t-test was used for evaluating the quantitative findings. a p-value < 0.05 was considered as statistically significant. discriminated analysis was used to evaluate the role of confounding factors. results a total of 75 patients were included in the study. of these, 25 patients had primary pterygium and 25 had pinguecula. the remaining 25 patients neither had pterygium nor pinguecula and were considered as the control group. on slit-lamp biomicroscopy, 24 (96%) patients had nasal pterygium and only 1 (4%) patient had temporal pterygium. pinguecula was detected on the nasal and temporal sides in 13 (52%) and 12 (48%) patients, respectively. moreover, 19 (76%) patients with pterygium and 20 (80%) patients with pinguecula had bilateral lesions. the mean age of patients was 46.89 ± 1.37 years (range: 21–73 years). overall, 44 (58.7%) patients were males and 31 (41.3%) were females. there were 16 men and 9 women who had both pinguecula and pterygium. while the prevalence of both lesions was slightly more in men than in women, there was no statically significant correlation between sex and presentation of these lesions (p = 0.41). comparison of lesions’ size between slit-lamp photography and as-af imaging a statistically significant correlation was observed between the lesions’ size displayed in slit-lamp photography and the autofluorescence area size displayed in as-af imaging for pterygium and pinguecula. in 25 patients with pinguecula, the mean size of pinguecula lesions in slit-lamp photography was 10.128 mm2 and the mean size of the autofluorescence area displayed through the asaf imaging was 19.32 mm2. the difference was –9.19 mm2 (95% ci: –11.44 to –6.94, p < 0.001). so, the mean size of the autofluorescence area displayed in asaf imaging was 9.19 mm2 larger than the mean size of the pinguecula displayed in slit-lamp photography (p = 0.001). in 25 patients with pterygium, the mean size of the pterygium lesions displayed in slit-lamp photography versus the autofluorescence area displayed in as-af imaging was 50.92 mm2 and 7.19 mm2, respectively. the difference was 43.73 mm2 (95% ci: 33.57 to 53.88, p < 0.001). so, the mean size of the autofluorescence area displayed in the as-af imaging was 43.73 mm2 smaller than the mean size of the pterygium displayed in slitlamp photography (p = 0.001). in addition, in 14 (56%) participants with healthy conjunctiva and intact vessels who did not have either pinguecula or pterygium, their conjunctiva revealed a hypoautofluorescence pattern in the as-af images [figure 1]. however, in 11 (44%) subjects, a hyperautofluorescence pattern was detected. the mean size of the autofluorescence area of the healthy conjunctiva was 0.388 mm2. the difference was 0.388 mm2 (95% ci: –0.60 to –0.17, p < 0.001). so, the mean size of the healthy conjunctiva reflected in the autofluorescence area in normal subjects in the as-af imaging was 0.388 mm2 larger than the normal conjunctiva images reflected in slit-lamp photography (p = 0.001). table 1 shows the comparison of lesion sizes displayed between slit-lamp photography and asaf imaging. comparative images between slit-lamp photography and as-af imaging the pinguecula lesions were revealed as hyperautofluorescence pattern in the asaf images in all patients. this well-defined autofluorescence area in 24 (96%) patients displayed a greater size than the visible part extension of pinguecula lesions displayed on slit-lamp photography [figure 2]. the pterygium lesions were revealed as hyperautofluorescence patterns in the as-af images of 21 (84%) patients. this autofluorescence area displayed a greater size than the pterygium size displayed in slit-lamp photography in one (4%) patient [figure 3]. on the other hand, four (16%) patients with pterygium did not demonstrate an autofluorescence pattern and were reflected 264 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 autofluorescence of pingueculae and pterygia; beheshtnejad et al completely as hypoautofluorescence pattern in the as-af images [figure 4]. discussion pinguecula is a common conjunctival disease and pterygium is another benign conjunctival disorder that usually grows from the bulbar conjunctiva and invades the corneal surface. these degenerative disorders typically affect the interpalpebral conjunctiva, mostly the nasal side.[1–4, 11] sun (ultraviolet light) exposure and exposure to environmental factors such as wind and dust increase the risk of these ocular surface diseases.[12–16] huseyin dundar et al investigated the effects of using soft contact lenses on pinguecula prevalence.[6] recently, af was introduced as a noninvasive imaging modality for the diagnosis and follow-up of several retinal disorders.[9−−10,17−−19] the af is obtained by the 488 nm stimulating wavelength light argon blue laser and with a barrier filter at 500 nm wavelength, which suppresses the excitation light. this barrier filter allows the passage of wavelengths of >500 nm. shortwavelength excited signals are mainly derived from the rpe lipofuscin.[7, 9, 10] it is possible to capture anterior segment images with the infrared process of this modality, where as-af images are then registered in fluorescein angiography mode, without using fluorescein dye.[7–9] to the best of our knowledge, few studies have discussed the use of as-af imaging for determining pinguecula or pterygium size. moreover, limited studies showed pinguecula had larger diffuse or punctuate autofluorescence patterns than the clinical lesions size.[5, 7] our study is based on the evaluation of the autofluorescence size and pattern of pinguecula and pterygium by as-af imaging. it also shows the comparison of visible conjunctival lesion sizes displayed in slit-lamp photography. as the present study showed, in most patients with pinguecula, the af pattern was punctate hyperautofluorescence which showed greater size than the clinical features as revealed through slit-lamp photography. on the other hand, in most patients with pterygium, the af pattern was hyperautofluorescence which had a smaller size than the visible lesion size reflected in slit-lamp photography. it is noted that the pinguecula lesions were characterized by hyperautofluorescence patterns with greater size than the clinical features of the actual lesion while pterygium lesions were displayed as hyperautofluorescence patterns with a smaller size than the clinical features of the actual lesions. moreover, the as-af imaging of 16% of patients with pterygium did not display autofluorescence patterns, whereas the as-af imaging of 44% of patients with normal conjunctiva displayed a small-size hyperautofluorescence pattern. hence, this study shows that although early inflammatory damages of pinguecula and pterygium may not be detected in clinical examinations, as-af via autofluorescence changes can show early signs of inflammatory damage before clinical presentation. af imaging can reveal any changes in various retinal diseases based on rpe lipofuscin deposits.[10] these lipofuscin granules contain specified fluorophores that are responsible for creating faf imaging.[5, 7] the lipofuscin accumulation may be associated with conjunctival degenerative disorders and some evidence showed oxidative damage plays an important role in lipofuscin genesis.[20] therefore, the hyper-af pattern in pinguecula may originate from lipofuscin granules. however, in pterygium lesions, the reduction or absence of autofluorescence reflectivity may depend on the decreased level of lipofuscin granules or some fibrovascular blockage. hence, further studies with histopathological and molecular complimentary evaluations are needed to confirm this hypothesis. in summary, normal conjunctiva with healthy epithelial surface and intact vascular pattern reveals a hypoautofluorescence pattern in as-af imaging; however, a hyperautofluorescence pattern may suggest the early stage of a conjunctival disorder. therefore, this imaging modality can be beneficial for detecting the pathological changes in the early stages of the conjunctival diseases including pinguecula and pterygium. financial support and sponsorship none. journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 265 autofluorescence of pingueculae and pterygia; beheshtnejad et al conflicts of interest none. references 1. kim yj, yoo sh, chung jk. reconstruction of the limbal vasculature after limbal-conjunctival autograft transplantation in pterygium surgery: an angiography study. invest ophthalmol vis sci 2014;55:7925–7933. 2. gulkilik g, kocabora s, taskapili m, ozsutcu m. a new technique for pterygium excision: air-assisted dissection. ophthalmologica 2006;220:307–310. 3. akbari m, soltani-moghadam r, elmi r, kazemnejad e. comparison of free conjunctival autograft versus amniotic membrane transplantation for pterygium surgery. j curr ophthalmol 2017;29:282–286. 4. ghoz n, elalfy m, said d, dua h. healing of autologous conjunctival grafts in pterygium surgery. acta ophthalmol 2018;96:e979–e988. 5. kim th, chun ys, kim jc. the pathologic characteristics of pingueculae on autofluorescence images. korean j ophthalmol 2013;27:416–420. 6. dundar h, kocasarac c. relationship between contact lens and pinguecula. eye contact lens 2019;45:390–393. 7. utine ca, tatlipinar s, altunsoy m, oral d, basar d, alimgil lm. autofluorescence imaging of pingueculae. br j ophthalmol 2009;93:396–399. 8. spaide rf. fundus autofluorescence and age-related macular degeneration. ophthalmology 2003;110:392– 399. 9. boon cj, jeroen klevering b, keunen je, hoyng cb, theelen t. fundus autofluorescence imaging of retinal dystrophies. vision res 2008;48:2569–2577. 10. sepah yj, akhtar a, sadiq ma, hafeez y, nasir h, perez b, et al. fundus autofluorescence imaging: fundamentals and clinical relevance. saudi j ophthalmol 2014;28:111– 116. 11. zhao f, cai s, huang z, ding p, du c. optical coherence tomography angiography in pinguecula and pterygium. cornea 2020;39:99–103. 12. yazar s, cuellar-partida g, mcknight cm, quachthanissorn p, mountain ja, coroneo mt, et al. genetic and environmental factors in conjunctival uv autofluorescence. jama ophthalmol 2015;133:406–412. 13. wolffsohn js, drew t, sulley a. conjunctival uv autofluorescence–prevalence and risk factors. cont lens anterior eye 2014;37:427–430. 14. elhamaky tr, elbarky am. outcomes of vertical split conjunctival autograft using fibrin glue in treatment of primary double-headed pterygia. j ophthalmol 2018;2018:9341846. 15. jiang j, gong j, li w, hong c. comparison of intraoperative 0.02% mitomycin c and sutureless limbal conjunctival autograft fixation in pterygium surgery: fiveyear follow-up. acta ophthalmol 2015;93:e568–e572. 16. hueber a, grisanti s, diestelhorst m. photodynamic therapy for wound-healing modulation in pterygium surgery. a clinical pilot study. graefes arch clin exp ophthalmol 2005;243:942–946. 17. mcbain va, townend j, lois n. fundus autofluorescence in exudative age-related macular degeneration. br j ophthalmol 2007;91:491–496. 18. schmitz-valckenberg s, pfau m, fleckenstein m, staurenghi g, sparrow jr, bindewald-wittich a, et al. fundus autofluorescence imaging. prog retin eye res 2021;81:100893. 19. holz fg, steinberg js, göbel a, fleckenstein m, schmitzvalckenberg s. fundus autofluorescence imaging in dry amd: 2014 jules gonin lecture of the retina research foundation. graefes arch clin exp ophthalmol 2015;253:7–16. 20. davies s, elliott mh, floor e, truscott tg, zareba m, sarna t, et al. photocytotoxicity of lipofuscin in human retinal pigment epithelial cells. free radic biol med 2001;31:256– 65 266 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 original article effect of uncomplicated cataract surgery on central macular thickness in diabetic and non-diabetic subjects brahm prakash guliani, ms ophthal1; isha agarwal, mbbs1; mayuresh p. naik, mbbs, ms, dnb2 1department of ophthalmology, vardhaman mahavir medical college & safdarjung hospital, new delhi, india 2department of ophthalmology, hamdard institute of medical sciences & research, hakeem abdul hameed centenary hospital, new delhi, india orcid: mayuresh naik: https://orcid.org/0000-0002-7167-557x abstract purpose: to assess the quantitative changes of macula in diabetic and non-diabetic eyes after uncomplicated cataract surgery. methods: in this prospective interventional study being performed in a tertiary healthcare hospital, a total of 660 eyes were divided into two groups. group 1 included 330 eyes from healthy subjects and group 2 included 330 eyes from well-controlled diabetic subjects with no diabetic retinopathy planned for phacoemulsification with foldable iol implantation by the same surgeon under similar settings. optical coherence tomography (heidelberg spectralis sd-oct) was used to assess preoperative and postoperative central macular thickness (cmt) at weeks 1 and 6. results: the mean cmt in group 1 preoperatively, at postoperative week 1, and at post-operative week 6 was 257.03 ± 20.904, 262.82 ± 17.010, and 265.15 ± 20.078 µm, respectively. the corresponding values in group 2 were 255.36 ± 17.852, 259.15 ± 16.644, and 266.09 ± 18.844 µm, respectively. there was no significant difference in the mean cmt values between the two groups on any of the three occasions when the cmt was measured (p = 0.374 and p = 0.313 at weeks 1 and 6, respectively). conclusion: there was no statistically significant difference in cmt between normal subjects and diabetic subjects without diabetic retinopathy preoperatively and in early postoperative period after uncomplicated phacoemulsification surgery. keywords: central macular thickness; diabetic macular edema; uncomplicated phacoemulsification j ophthalmic vis res 2019; 14 (4): 442–447 correspondence to: mayuresh p. naik, mbbs, ms, dnb. room no. 3 of eye opd, first floor of opd building, department of ophthalmology, h.i.m.s.r & h.a.h.c hospital, near gk2, alaknanda, new delhi 110062, india. e-mail: mayureshpnaik@gmail.com received: 17-02-2018 accepted: 24-03-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i4.5447 introduction cataract extraction is one of the most commonly performed ophthalmic surgeries. recent innovations in instrumentation, lens design, and surgical technique have improved the outcome of cataract surgery.[1] currently, the preferred technique is this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: guliani bp, agarwal i, naik mp. changes in cmt after cataract surgery. j ophthalmic vis res 2019;14:442–447. 442 © 2019 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5447&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr cataract surgery and cmt; guliani et al phacoemulsification using small incisions and implantation of a foldable intraocular lens (iol).[2] this is an efficient procedure, and uneventful surgery is generally associated with good visual results.[3] however, the development of cystoid macular edema (cme) can lead to suboptimal postoperative vision.[4] this can occur in patients with ocular diseases, such as uveitis or diabetic retinopathy (dr), even after uncomplicated cataract surgery.[5] cme following cataract surgery was initially reported by irvine in 1953 and demonstrated angiographically by gass and norton in 1966 and has come to be known as the irvine gass syndrome.[6] it is not uncommon to encounter cme in otherwise healthy eyes after uneventful phacoemulsification surgery.[7] the incidence after phacoemulsification is reported to be 0.1–2% in healthy populations.[7] although the exact pathophysiology is not known, the role of surgical trauma with the release of prostaglandins and blood–retinal barrier disruption is suspected.[8] light toxicity and vitreomacular traction might also have a role.[9] the incidence of pseudophakic cme depends on the methodology used in its detection. it has been suggested that prophylactic use of nonsteroidal anti-inflammatory drugs preoperatively, and steroids and anti-inflammatory drugs in the postoperative period, reduces the incidence of postoperative pseudophakic cme.[10] diabetes mellitus increases the probability of developing cataract and the risk of decreased visual outcomes after cataract surgery.[7] it has been suggested that in diabetics macular edema after cataract surgery occurs predominantly in those with concurrent pre-existing diabetic macular edema (dme) involving the center of the macula.[11] while others have reported that the development of postoperative macular edema does not need pre-existing dme,[11] these were published before the availability of optical coherence tomography (oct) technology. the dynamics of macular edema and cataract surgery in those with dr can be explored using the qualitative and quantitative oct-based data. here we evaluate the retinal thickness changes in the early postoperative course of six weeks in non-diabetic and diabetic subjects after uncomplicated phacoemulsification with intracapsular iol implantation. methods ethical clearance was obtained from the ethics committee, the institutional review board at vardhaman mahavir medical college (v.m.m.c), and the safdarjung hospital, new delhi. this tertiary health center-based observational study was conducted on adult patients posted for cataract surgery at the department of ophthalmology, vmmc and safdarjung hospital, new delhi. assuming the effect size to be 0.8 (ratio of difference of two means/standard error), power to be 85%, and the level of significance to be 5%, a sample size of 330 eyes per group, including the 10% loss to follow-up, was required for the study, using software g power 3.1. the patients were divided into two groups based on the inclusion and exclusion criteria as follows: group 1, 330 healthy subjects planned for phacoemulsification with foldable iol implantation by the same surgeon under similar settings; group 2, 330 well-controlled diabetic subjects with no dr posted for phacoemulsification with foldable iol implantation by the same surgeon under similar settings. the inclusion criteria for group 1 (healthy subjects) included age > 40 years and senile cataract undergoing uncomplicated cataract surgery. patients with complicated cataract surgery, intraocular pressure > 21 mmhg, dense white cataract in whom oct could not be performed, and any ocular diseases that might influence central macular thickness (cmt), such as glaucoma, uveitis, and age-related macular degeneration, were excluded from the study. patients with a history of previous eye surgery or a history of macular edema in the fellow eye were also excluded. group 2 (well-controlled diabetic subjects) had similar inclusion criteria along with a diagnosis of diabetes mellitus of any duration, controlled on oral hypoglycemic agents or insulin, blood sugar < 200 mg% (all-india-ophthalmological-society (aios) guidelines to prevent intraocular infection, 2009) and hba1c < 7% (american diabetes association ada a1c goals, standards of medical care in diabetes-2015), and an absence of any evidence of dr as assessed by indirect ophthalmoscopy and oct.[12] besides similar exclusion criteria as for group 1, group 2 patients were also excluded based on the presence of anemia [men (> 15 yr), < journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 443 cataract surgery and cmt; guliani et al 13 g/dl; women (> 15 yr), < 12 g/dl],[13] pregnancy, or diabetic nephropathy (abnormal kidney function test including serum electrolytes, microalbuminuria, serum creatinine, and serum urea). oct (heidelberg spectralis sd-oct) was used to assess preand postoperative (at weeks 1 and 6) cmt (central subfield thickness equating to mean thickness in the central 1000-μm diameter area). repeated measure analysis and multiple comparison correction with the bonferroni method were applied to the data. p < 0.05 was considered statistically significant. results the majority of the patients (47%) were in the age group of 51–60 years [table 1]. more than half of the patients in group 1 (54.5%) and 39.4% of patients in group 2 were between 51 and 60 years old (no significant difference when comparing groups, p = 1.71). the mean age in group 1 was 58.30 ± 7.66 years, while the mean age in group 2 was 63.24 ± 9.74 years (p = 2.89). overall, the study comprised of 390 (59%) males and 270 (41%) females [table 1]. group 1 comprised of 51.5% males and 48.5% females and group 2 of 66.7% males and 33.3% females (p = 2.12). the mean cmt values in group 1 preoperatively and at postoperative weeks 1 and 6 were 257.03 ± 20.90, 262.82 ± 17.01, and 265.15 ± 20.07 µm, respectively [table 2]. the mean cmt changes in group 1 preoperatively versus postoperative week 1 versus postoperative week 6 were statistically significant (both p-values < 0.001). the mean cmt changes at postoperative weeks 1 and 6 were also significantly different (p-value < 0.001). the mean cmt values in group 2 preoperatively, at postoperative week 1, and at postoperative week 6 were 255.36 ± 17.85, 259.15 ± 16.64, and 266.09 ± 18.84 µm, respectively [table 2]. the mean cmt changes in group 2 preoperatively versus postoperative week 1 versus postoperative week 6 were both statistically significant (p-value < 0.001). the mean cmt changes at postoperative weeks 1 and 6 were also significantly different (p-value < 0.001). no significant difference was noted in the mean cmt values between the two groups on any of the three occasions when cmt was measured [table 2]. there was no significant change in the variation of mean cmt at weeks 1 and 6 postoperatively from baseline when groups 1 and 2 were compared [table 2]. in our study, none of the patients developed clinical macular edema or cme on oct. discussion this prospective comparative study was undertaken to assess the effect of uncomplicated phacoemulsification procedure with iol implantation on cmt in diabetic and nondiabetic subjects in the early postoperative period (up to six weeks). the cmt used for comparison among the study subjects in our study corresponded to the mean thickness of all points in the central subfield of 1mm diameter of the etdrs macular subfields. the cmt was assessed with oct preoperatively, and at weeks 1 and 6 postoperatively, and comparisons were made between the measurements of the two study groups. the macula in healthy controls as well as in controlled diabetics without dr was increased significantly at the end of the first and sixth weeks postoperatively compared to the preoperative results. in both groups, this thickening persisted until six weeks postoperatively in all subjects and did not regress to preoperative levels till the last follow-up at six weeks. this study demonstrated that the influence of uncomplicated cataract surgery on cmt in well-controlled diabetic patients without dr did not significantly differ from healthy non-diabetic subjects after uncomplicated cataract surgery. in other words, well-controlled diabetics without dr and nondiabetic patients showed similar intragroup thickening of the central macular subfield at weeks 1 and 6 after uncomplicated phacoemulsification, and the intergroup comparison was not statistically significant. the rate of development of macular edema following cataract surgery at different time intervals in people with diabetes (with or without dr) varies from 31% to 81%.[14] certain minimal changes in the retina like subclinical cme and retinal leakage can occur even after uneventful cataract surgery. these subclinical changes in macular thickness after cataract surgery can be easily diagnosed on oct and fluorescein angiography (fa).[15] it has been reported by some studies that macular edema after cataract surgery, in people with diabetes, may occur predominantly in patients 444 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 cataract surgery and cmt; guliani et al table 1. ageand sex-wise distribution of study subjects among the two study groups age groups (years) group 1 group 2 male female male female 41–50 30 (9.09%) 20 (6.06%) 20 (6.06%) 10 (3.03%) 51–60 100 (30.30%) 80 (24.24%) 70 (21.21%) 60 (18.18%) 61–70 40 (12.12%) 40 (12.12%) 50 (15.15%) 40 (12.12%) > 70 15 (4.54%) 5 (1.51%) 40 (12.12%) 40 (12.12%) total 170 (51.5%) 160 (48.5%) 220 (66.7%) 110 (33.3%) total 330 (100%) 330 (100%) table 2. groups 1 and 2: repeated measure analysis and multiple comparison correction with bonferroni method depicting change in mean central macular thickness from baseline to postoperative week 1 and week 6 group 1 group 2 pre-op cmt 257.03 ± 20.904 255.36 ± 17.852 week 1 post-op cmt 262.82 ± 17.010 259.15 ± 16.644 week 6 post-op cmt 265.15 ± 20.078 266.09 ± 18.844 change in mean cmt at week 1 post-op as compared to pre-op baseline 5.788 ± 11.324 (p-value 0.006 for intragroup comparison) 3.788 ± 6.066 (p-value 0.001 for intragroup comparison) p-value 0.374 for intergroup comparison change in mean cmt at week 6 post-op as compared to pre-op baseline 8.121 ± 11.056 (p-value < 0.001 for intragroup comparison) 10.727 ± 9.722 (p-value < 0.001 for intragroup comparison) p-value 0.313 for intergroup comparison change in mean cmt at week 6 post-op as compared to week 1 post-op 2.333 ± 9.504 (p-value 0.172 for intragroup comparison) 6.939 ± 7.208 (p-value < 0.001 for intragroup comparison) p-value 0.336 for intergroup comparison cmt, central macular thickness, pre-op, preoperative; post-op, postoperative with concurrent pre-existing dme involving the center of the macula. on the other hand, some researchers have reported that for postoperative macular edema to develop, pre-existing dme is not required.[11] however, these studies were completed prior to the availability of oct technology. for detecting cme, the sensitivity and specificity of oct is 96% and 100%, respectively, compared with fa.[16] oct can detect not only macular thickening before any angiographic evidence of macular edema but also produces reproducible and consistent quantitative results that are ideal for follow-up and assessment of the treatment response.[16, 17] for these reasons, we chose oct as the investigative modality in our observational study. there is some disagreement in the observations of various studies reporting an increase in cmt or development of macular edema after cataract surgery in patients with diabetes without dr. in a case-control study conducted on around 4,500 diabetics without preoperative macular edema, the incidence of postoperative macular edema was 4%, which was higher than that in the population journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 445 cataract surgery and cmt; guliani et al without diabetes (p < 0.001).[17] these authors also reported a higher risk for the development of macular edema (rr 1.80) in diabetic subjects without dr compared to patients without diabetes (rr 1.17).[17] on the other hand, katsimpris et al found increased macular thickness after uncomplicated cataract surgery in diabetics without dr compared to preoperative values or to a control group of patients at all follow-ups up to 12 months after cataract surgery.[18] the eyes of diabetic patients without dr presented higher cmt and a higher incidence of cme after cataract surgery compared to the eyes of healthy controls, thus explaining the unsatisfactory visual acuity following cataract surgery in these patients.[18] however, a recently conducted meta-analysis among diabetic patients without dr observed no statistically significant increase in cmt values after cataract surgery at one, three, and six months after cataract extraction.[19] many studies have postulated an association between progression of dr and cataract surgery,[20] whereas other studies did not observe any significant association and consider any diabetic retinal changes as part of the natural course of the disease.[21] in our study, the preoperative cmt measured by oct is the same between the two groups. this is in accordance with a study conducted by massin et al, who also found no differences in macular thickness comparing healthy subjects and diabetics without cme.[22] there are, unfortunately, three limitations in our study. first, there are certain variables affecting the quality of oct, despite it being a fast, noninvasive, non-contact, reproducible, and reliable invivo imaging technique.[23] when media opacities, such as cataract, are present (especially in the form of cortical and subcapsular types), reliable scans might not be obtained preoperatively.[23] to avoid this difficulty, we excluded patients with dense media opacities. second, though our study showed no significant statistical difference between the two groups, few other studies have shown a significant rise in the cmt postoperatively in well-controlled diabetics with no dr. therefore, large-scale studies with a longer followup period are likely required to accurately elucidate the role of diabetes control and dr status on the postoperative visual prognosis of patients undergoing uncomplicated phacoemulsification. last, the current study is limited by the duration of follow-up of patients that precludes any firm clinical conclusions based on the results of the study. in conclusion, cmt is increased after uncomplicated phacoemulsification both at weeks 1 and 6 postoperatively in both healthy nondiabetic subjects and in well-controlled diabetic patients without dr; the difference between the two groups is not statistically significant. it is postulated that good diabetes control is needed to prevent an increase in cmt and postoperative macular edema after uncomplicated uneventful phacoemulsification procedure. however, long term follow-up studies may be required so that management algorithms can be formulated in order to dictate our surgical paradigms. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. decroos fc, afshari na. perioperative antibiotics and anti-inflammatory agents in cataract surgery. curr opin ophthalmol 2008;19:22–26. 2. panchapakesan j, rochtchina e, mitchell p. five-year change in visual acuity following cataract surgery in an older community: the blue mountains eye study. eye 2004;18:278–282. 3. linebarger ej, hardten dr, shah gk, lindstrom rl. phacoemulsification and modern cataract surgery. surv ophthalmol 1999;44:123–147. 4. o’brien tp. emerging guidelines for use of nsaid therapy to optimize cataract surgery patient care. curr med res opin 2005;21:1131–1137. review erratum in: curr med res opin 2005;21:1431–1432. 5. nelson ml, martidis a. managing cystoid macular edema after cataract surgery. curr opin ophthalmol 2003;14:39– 43. 6. nelson ml, martidis a. managing cystoid macular edema after cataract surgery. curr opin ophthalmol 2003;14:39– 43. 7. gass jd, norton ew. cystoid macular edema and papilledema following cataract extraction. a fluorescein fundoscopic and angiographic study. arch ophthalmol 1966;76:646–661. 446 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 cataract surgery and cmt; guliani et al 8. ursell pg, spalton dj, whitcup sm, nussenblatt rb. cystoids macular edema after phacoemulsification: relationship to blood-aqueous barrier damage and visual acuity. j catarct refract surg 1999;25:1492–1497. 9. flach aj. the incidence, pathogenesis and treatment of cystoids macular edema following cataract surgery. trans am ophthalmol soc 1998;96:557–634. 10. rho ds. treatment of acute pseudophakic cystoid macular edema: diclofenac versus ketorolac. j cataract refract surg 2003;29:2378–2384. 11. kim sj, equi r, bressler nm. analysis of macular edema after cataract surgery in patients with diabetes using optical coherence tomography. ophthalmology 2007;114:881– 889. 12. aios guidelines to prevent intraocular infection. 2009. available from http://www.aios.org/guidelines endoph .pdf 13. fao; who. world declaration and plan of action for nutrition. in: international conference on nutrition. rome: food and agriculture organization of the united nations; december 1992. 14. dowler jg, sehmi ks, hykin pg, hamilton am. the natural history of macular edema after cataract surgery in diabetes. ophthalmology 1999;106:663–668. 15. lara sa, cakiner et. diabetes and cataract surgery: preoperative risk factors and positive nursing interventions. insight 2014;39:18–20. 16. biro z, balla z, kovacs b. change of foveal and perifoveal thickness measured by oct after phacoemulsification and iol implantation. eye 2008;22:8–12. 17. sahin m, cingu ak, gozum n. evaluation of cystoid macular edema using optical coherence tomography and fundus autofluorescence after uncomplicated phacoemulsification surgery. j ophthalmol 2013;2013:376013. 18. katsimpris jm. , petropoulos ik. , zoukas g. , patokos t. , brinkmann c.k. , theoulakis p.e. central foveal thickness before and after cataract surgery in normal and in diabetic patients without retinopathy. klin monbl augenheilkd 2012; 229:331-337. 19. akcay bi, bozkurt tk, güney e, unlü c, erdogan g, akcali g, et al. quantitative analysis of macular thickness following uneventful and complicated cataract surgery. clin ophthalmol 2012;6:1507–1511. 20. chu cj, johnston rl, buscombe c, sallam ab, mohamed q, yang yc. risk factors and incidence of macular edema after cataract surgery a database study of 81984 eyes. ophthalmology 2016;123:316–323. 21. liu j, jones re, zhao j, zhang j, zhang f. influence of uncomplicated phacoemulsification on central macular thickness in diabetic patients: a meta-analysis. plos one 2015;10:e0126343. 22. massin p, bandello f, garweg jg, hansen ll, harding sp, larsen m, et al. safety and efficacy of ranibizumab in diabetic macular edema (resolve study): a 12-month, randomized, controlled, double-masked, multicenter phase ii study. diabetes care 2010;33:2399-405. 23. henricsson m, heijl a, janzon l. diabetic retinopathy before and after cataract surgery. br j ophthalmol 1996;80:789–793. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 447 http://www.aios.org/guidelines original article in vivo intraocular lens thickness measurement and power estimation using optical coherence tomography ehsan barzanouni1,2, md; diba idani3, medical student; farideh sharifipour1,2, md 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2department of ophthalmology, school of medicine, shahid beheshti university of medical sciences, tehran, iran 3school of medicine, shahid beheshti university of medical sciences, tehran. orcid: ehsan barzanouni: https://orcid.org/0000-0001-8672-4496 farideh sharifipour: https://orcid.org/0000-0002-1511-9608 abstract purpose: to estimate the power of an implanted intraocular lens (iol) by measuring iol thickness using anterior segment optical coherence tomography (as-oct) and to assess the repeatability of measurements. methods: ninety-seven eyes were studied one month after uneventful phacoemulsification within the bag acrysof sa60at iol implantation (range +11 to +35). all eyes had postoperative refraction of ±0.5 d of target refraction. as-oct was used to measure the central thickness of the iol. correlation between labelled iol power and central iol thickness as well as the measure of repeatability, for example, intraclass correlation coefficient (icc), were evaluated. iol thicknesses were also calculated using a formula and compared with as-oct derived measurements. results: iol thickness correlated significantly with labelled iol power (r2 = 0.985, p < 0.001). the regression equation (iol power = [0.04 × iol thickness in micron] – 7.56) indicates 25 microns of central iol thickness change per 1d power change. over the studied range, iol power could be estimated with a precision of 0.85 ± 0.02 d (95% confidence interval: 0.83–0.94d). icc for repeated measurements was 0.999. there was a significant correlation between calculated and measured (as-oct) iol thickness (r2 = 0.984, p < 0.001). conclusion: central iol thickness measurements with the as-oct are highly repeatable and closely correlated with the labelled iol power, which can predict the iol power with ±0.85 d from the actual power. this method can be helpful in cases of postoperative iol surprise. keywords: anterior segment optical coherence tomography; as-oct; intraocular lens; iol; iol thickness j ophthalmic vis res 2022; 17 (3): 353–359 © 2022 barzanouni et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 353 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i3.11572&domain=pdf&date_stamp=2019-07-17 in-vivo iol power estimation by oct ; barzanouni et al introduction cataract removal with intraocular lens (iol) implantation is one of the most frequently performed ophthalmic surgeries. microsurgical techniques, improved iol material and designs, sophisticated biometry methods, and advanced iol power calculation formulas have altered the role of cataract surgery even as a refractive surgery, where in addition to removing opaque crystalline lens also corrects any preexisting ametropia. the accuracy of the ocular measurements and iol calculation, as well as selection of the appropriate biometric formula, are the main factors in achieving the desired postoperative refractive results.[1] however, despite all these measures, refractive surprise might happen as a result of transcription errors, wrong patient biometry, wrong iol selection, changes in planned procedure, incorrect iol brought into the theatre, left/right eye selection errors, communication errors, and positive/negative iol power errors.[2] in rare cases, incorrect iol labelling might be the cause.[3–5] however, in 25–38% of the cases, the cause of refractive surprises remains unknown.[2] although there is a need to calculate the power of an implanted iol, currently there is no established method, and knowledge of implanted iol power is only restricted to the medical records of the patients. the introduction and evolution of imaging techniques especially optical coherence tomography (oct) has made it possible to image the ocular structures with micron-level precision. oct measurements have been shown to highly correlate with real values, making it an ideal method for evaluating anterior segment structures.[6, 7] scheimpflug imaging has been used for central iol thickness measurement and in vivo calculation of iol power.[8] this study correspondence to: farideh sharifipour, md, department of ophthalmology, labbafinejad medical center, 9th boostan st., pasdaran ave., tehran 1666663111, iran. e-mail: sharifipourf@yahoo.com received: 11-06-2021 accepted: 15-12-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i3.11572 was conducted to assess the correlation of iol thickness measured by anterior segment oct (asoct) with the actual power of implanted iol to calculate the power of an unknown iol. methods this prospective study was performed at a private clinic. the study protocol adhered to the tenets of the declaration of helsinki. informed consent was obtained from all patients and the test was performed free of charge. the study included consecutive patients who underwent uneventful phacoemulsification within the bag acrysof sa60at iol (alcon) implantation. at postoperative month one, patients with uncorrected visual acuity of 20/25 or better who manifested refraction within ±0.5 d spherical equivalent of target refraction were enrolled in the study. patients with corneal opacity precluding high-quality images, history of trauma or anterior segment diseases causing pupil abnormality, iol decentration, iridodonesis, pseudophacodonesis, and iol tilt were excluded. acrysof sa60at iol is a monofocal foldable, single-piece posterior chamber acrylic lens with an asymmetric biconvex 6 mm optic, overall length of 13 mm, and a refractive index of 1.55. available powers range from 6.0 to 30.0 d in 0.5 d increments and from 30 to 40 in 1d increments. optical coherence tomography measurements oct scans were performed using anterior segment module, (topcon 3d oct-1000 topcon corporation, tokyo, japan) after pupillary dilation. the scan line was centered on the iol along the horizontal line and three images were captured. the presence of a reflex saturation beam indicated the perpendicularity of the iol to the scanning beam [figure 1]. lens thickness was measured this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: barzanouni e, idani d, sharifipour f. in vivo intraocular lens thickness measurement and power estimation using optical coherence tomography. j ophthalmic vis res 2022;17:353–359. 354 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 https://knepublishing.com/index.php/jovr in-vivo iol power estimation by oct ; barzanouni et al figure 1. representative image of iol thickness measurement method using anterior segment oct. figure 2. plot of iol thickness (microns) against labelled iol power (d). using a built-in caliper from the anterior to the posterior surface of iol at the point of greatest convexity. on each scan, measurements were done by two observers (fs, di) masked to the iol power. the average of the three closest measurements was used for the analyses. scans with a lens tilt, motion artefact, and adhesion of posterior capsule to the iol were discarded. statistical analysis statistical analysis was performed using the spss software version 18.0 (spss inc., chicago, usa). the intraand interobserver repeatability of iol thickness measurements were assessed using intraclass correlation coefficient (icc). correlation between iol thickness and labelled iol power was evaluated by pearson’s correlation and linear regression analysis; 95% confidence intervals (ci) were calculated for every iol prediction based on thickness measurements. in addition, we calculated central iol thickness using the formula proposed by naeser et al[9] for each iol power and compared them with oct-derived thickness measurements. 𝑇 = 𝐸 + 2 × (|(𝑛2−1.336)× 1000 1/2×𝑃 | −√((𝑛2 − 1.336)× 1000 1/2 × 𝑃 ) 2 − 1 4𝐷2 ) (1) the formula calculates the central thickness of an iol from variables normally supplied by manufacturers where t is the central thickness of journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 355 in-vivo iol power estimation by oct ; barzanouni et al figure 3. plot of labelled iol power against iol power calculated by the measured regression equation showing significant correlation. figure 4. plot of difference of labeled and calculated iol powers against actual iol power. the majority of labelled iol powers lie within mean ± sd of difference of labeled and calculated iol powers. iol optic (mm); e is edge thickness of the iol optic (mm); n2 is the refractive index of the iol; p is iol power (diopter); and d is iol optic diameter (mm). for the type of iol, we used e = 0.21 mm, n2 = 1.55, and d = 6 mm. p-values < 0.05 were considered statistically significant. results a total of 88 participants (115 eyes) fulfilled the inclusion criteria, among them 14 patients (18 eyes) were excluded due to low-quality scans, artifacts, decentration, and adhesion of posterior capsule to the iol. data from 97 eyes (74 patients) were used for the analyses. the patients included 30 men and 356 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 in-vivo iol power estimation by oct ; barzanouni et al figure 5. plot of iol thickness against confidence interval (ci) width showing that 95% ci is the narrowest for iol thicknesses between 600 and 900 microns and becomes wider outside this range. 44 women with a mean age of 61.57 ± 8.08 years (range, 45–86 years). known iol power ranged from +11 to +35 d. icc (95% ci) for intraand inter-observer repeatability was 0.999 (0.995–0.998) and 0.997 (0.996–0.998), respectively. iol thickness correlated significantly with the labelled iol power (r2 = 0.985, p < 0.001) [figure 2]. the regression equation is as follows: iol power (d) = (0.04 × iol thickness in micron) – 7.56. for instance, an iol with a central thickness of 700 microns predicts an iol power of 20.43d. figure 3 shows a plot of labelled iol power against iol power calculated by the measured regression equation for our patients indicating a significant correlation (r2 = 0.970, p < 0.001). the majority of labelled iol powers were within mean ± sd of difference of iol power and calculated iol power [figure 4]. for each prediction, 95% ci width was generated (ci width =√0.695+ (𝐼𝑂𝐿 𝑡ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠(µ)−792.31)2 627755 ), yielding an average of 0.84 ± 0.02 (range, 0.83–0.91). for iol thicknesses between 600 and 900 microns, 95% confidence interval did not exceed 0.86 d, however, farther from the mean, the ci was wider indicating that the accuracy of prediction is highest within this range and decreases with iol thicknesses outside this range [figure 5]. central iol thickness was also calculated theoretically using the naeser et al formula.[9] the calculated iol thicknesses and the asoct-measured central iol thicknesses were significantly correlated (r2 = 0.984, p < 0.001). discussion in this study, we demonstrated that measuring the central thickness of sa60at iol by as-oct was highly repeatable and closely correlated with labelled iol power, which could predict the iol power within ±0.85d of actual power. we also determined the correlation of as-oct-measured iol thickness with the theoretically calculated iol thickness and observed a significant correlation between the two thicknesses. therefore, measuring iol thickness using as-oct can provide an almost precise estimation of unknown iol power using the naeser et al formula as well.[9] although our results are most likely applicable to the specific iol type and power range used in this study, many iols share the same characteristics in terms of size, optic diameter, and refractive index, so it is possible that the formula would apply to many iol trademarks. the use of accurate biometry techniques and appropriate iol calculation formulas has greatly improved the refractive outcomes of cataract surgery. however, in cases with refractive surprise after cataract surgery, possible sources of error include decentered iol, undiagnosed keratoconus, inaccurate biometry, upside down iol implantation, incorrect iol brought into the journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 357 in-vivo iol power estimation by oct ; barzanouni et al theatre, mixed-up documentation of patients, and mislabeled iols.[3–5] in the past, some surgeons used to evaluate lens resolution and measure the iol power before inserting the lens into the eye to make sure that the manufacturing iol is truly the correct power.[10] in a study by turner et al using scheimpflug imaging, the central thickness of ma60ac iol (alcon) was correlated with known iol power and a similar formula was obtained. as compared to our study, they had a limited range of iol power (11 to 26.5d).[8] the iol thickness measurements using scheimpflug imaging was different from our as-oct-derived measurements, for example, a 600 micron thickness in their study represented iol power of 20.451 d, while in our study 700 microns represent 20.43 d iol power. the difference in measurements obtained by different imaging techniques and even among different oct machines has been well-documented which indicates that the measurements cannot be used interchangeably.[11–13] we observed that for iol thicknesses between 600 and 900 microns, 95% confidence interval did not exceed 0.86 d, however, farther from the mean, ci was wider indicating that the accuracy of prediction is highest within this range and decreases with iol thicknesses outside this range [figure 5]. additionally, iol surprise most commonly happens in the extreme iol powers with less accuracy in the prediction of the iol power. our study had the advantage of including a wide range of iol powers and comparing our measurements to the theoretic formula for calculating iol thickness. however, using a single type of iol precludes extrapolation of our results to other iol brands with different designs or refractive index and powers outside the range used in this study. since oct imaging uses backscattered infrared light, for accurate iol thickness measurements by oct, media anterior to the iol should be clear. therefore, dense corneal opacities can interfere with image acquisition and accurate measurements, as are titling or decentration of the iol, which preclude the presence and adjustment of reflex saturation beam as the indicator of perpendicularity of the iol to the scanning beam. these limitations of iol thickness measurement by oct were considered as the exclusion criteria in our study. attachment of posterior capsule to the iol may result in falsely greater thickness. however, posterior capsule opacification (pco) per se is not a limitation to iol thickness measurements provided that the posterior capsule could be visualized separately behind the iol. in summary, our study was successful in determining that central iol thickness measurements by as-oct shows a strong correlation with iol power with high accuracy and repeatability and can be used with the regression equation obtained for this iol type in cases of iol surprise. further studies with other types of iols are warranted to evaluate the applicability of our results. future studies are needed to evaluate applicability of oct to measure iol tilt and the resulting induced cylinder. it is also recommended that the manufacturers provide iol thickness on the iol boxes along with other iol characteristics, which could be compared with oct-derived thicknesses in case of iol surprise. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest.references references 1. olsen t. calculation of intraocular lens power: a review. acta ophthalmol scand 2007;85:472–485. 2. steeples lr, hingorani m, flanagan d, kelly sp. wrong intraocular lens events-what lessons have we learned? a review of incidents reported to the national reporting and learning system: 2010–2014 versus 2003–2010. eye 2016;30:1049–1055. 3. kohnen s. postoperative refractive error resulting from incorrectly labeled intraocular lens power. j cataract refract surg 2000;26:777–778. 4. antičić m, ardjomand n, sarny s, schweighofer j, elshabrawi y. numbers sometimes lierefractive surprise following iol mislabeling by the manufacturer. eye 2019;33:868–870. 5. ravi k, senthil s, pesala v. refractive surprise following implantation of correct powered intraocular lens—a real surprise! int ophthalmol 2012;32:603–605. 6. ang m, baskaran m, werkmeister rm, chua j, schmidl d, aranha dos santos v, et al. anterior segment optical coherence tomography. prog retin eye res 2018;66:132– 156. 7. tan gs, he m, zhao w, sakata lm, li j, nongpiur me, et al. determinants of lens vault and association with narrow angles in patients from singapore. am j ophthalmol 2012;154:39–46. 358 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 in-vivo iol power estimation by oct ; barzanouni et al 8. turner sj, lee ej, hu v, hollick ej. scheimpflug imaging to determine intraocular lens power in vivo. j cataract refract surg 2007;33:1041–1044. 9. naeser k, naeser ev. calculation of the thickness of an intraocular lens. j cataract refract surg 1993;19:40–42. 10. mcreynolds wu, snider nl. the quick, simple measurement of intraocular lens power and lens resolution at surgery. j am intraocul implant soc 1978;4:15–17. 11. barkana y, gerber y, elbaz u, schwartz s, ken-dror g, avni i, et al. central corneal thickness measurement with the pentacam scheimpflug system, optical low-coherence reflectometry pachymeter, and ultrasound pachymetry. j cataract refract surg 2005;31:1729–1735. 12. kanellopoulos aj, asimellis g. comparison of highresolution scheimpflug and high-frequency ultrasound biomicroscopy to anterior-segment oct corneal thickness measurements. clin ophthalmol 2013;7:2239–2247. 13. leung ck, li h, weinreb rn, liu j, cheung cy, lai ry, et al. anterior chamber angle measurement with anterior segment optical coherence tomography: a comparison between slit lamp oct and visante oct. invest ophthalmol vis sci 2008;49:3469–3474. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 359 original article diagnostic performance of the palmscan vf2000 virtual reality visual field analyzer for identification and classification of glaucoma vijay shetty, ms, dnb, frcs, faico; prachi sankhe, dnb; suhas s haldipurkar, doms, faico tanvi haldipurkar, ms; rita dhamankar, doms, ms; priyanka kashelkar, dnb; dhruven shah, do, dnb paresh mhatre, moptom; maninder singh setia, md, phd laxmi eye institute, panvel, maharashtra, india orcid: vijay shetty: http://orcid.org/0000-0003-0544-0200 maninder singh setia: http://orcid.org/0000-0003-1291-9033 abstract purpose: to evaluate the diagnostic test properties of the palm scan vf2000® virtual reality visual field analyzer for diagnosis and classification of the severity of glaucoma. methods: this study was a prospective cross-sectional analysis of 166 eyes from 97 participants. all of them were examined by the humphrey® field analyzer (used as the gold standard) and the palm scan vf 2000® virtual reality visual field analyzer on the same day by the same examiner. we estimated the kappa statistic (including 95% confidence interval [ci]) as a measure of agreement between these two methods. the diagnostic test properties were assessed using sensitivity, specificity, positive predictive value (ppv), and negative predictive value (npv). results: the sensitivity, specificity, ppv, and npv for the virtual reality visual field analyzer for the classification of individuals as glaucoma/non-glaucoma was 100%. the general agreement for the classification of glaucoma between these two instruments was 0.63 (95% ci: 0.56-0.78). the agreement for mild glaucoma was 0.76 (95% ci: 0.61-0.92), for moderate glaucoma was 0.37 (0.140.60), and for severe glaucoma was 0.70 (95% ci: 0.55-0.85). about 28% of moderate glaucoma cases were misclassified as mild and 17% were misclassified as severe by the virtual reality visual field analyzer. furthermore, 20% of severe cases were misclassified as moderate by this instrument. conclusion: the instrument is 100% sensitive and specific in detection of glaucoma. however, among patients with glaucoma, there is a relatively high proportion of misclassification of severity of glaucoma. thus, although useful for screening of glaucoma, it cannot replace the humphrey® field analyzer for the clinical management in its current form. keywords: glaucoma; sensitivity; specificity; test properties; virtual reality perimetry j ophthalmic vis res 2022; 17 (1): 33–41 © 2022 shetty et al . this is an open access article distributed under the creative commons attribution license | published by knowledge e 33 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10168&domain=pdf&date_stamp=2019-07-17 virtual reality vf analyzer ; shetty et al introduction glaucoma, the second most common cause of vision loss in the world, is an important cause of blindness in india.[1–3] about 6.48 million people were estimated to have primary openangle glaucoma in india.[3] it may be rightly termed as “the silent disease”, as it causes bilateral, painless, and progressive vision loss.[4] one of the instruments used for the diagnosis and management of glaucoma, the humphrey® field analyzer (zeiss/usa) (hfa), is an automated perimeter and is well-known to ophthalmologists and optometrists. it is considered to be accurate, reliable, and a trusted method to detect the visual field defects of patients.[5] however, like other devices, hfa also has certain disadvantages and limitations. it is big and bulky, non-portable, demands a dark room, time-consuming, and may be difficult for patients with neck problems, old age, children, or those with any disability where it is difficult to keep their heads in a fixed slot to maintain good fixation.[6] the palm scan vf2000® (mmd/usa) is a virtual reality (vr)-based visual field analyzer developed to measure the patient’s visual field defect. it is a battery-operated portable device. the vf2000 consists of a system with three main sections connected to each other by a wireless mechanism. these three major components are: (1) the vr goggles worn by the patients; (2) the controller device operated by the healthcare staff who sets the testing strategy, technical parameters, and monitors the entire test; and (3) the clicker, which will be clicked by the patient when visualizing the stimulus.[6] there is a classic perimeter bowl in hfa whereas the palm scan vf 2000® vr visual field analyzer has vr goggles. however, the vr perimetry has algorithms in place to make the stimuli appear on the retina as if they have been projected from the classic perimeter bowl.[7] the correspondence to: maninder singh setia, md, phd. laxmi eye institute, panvel, maharashtra 410206, india. e-mail: maninder.setia@karanamconsultancy.in received 24-04-2020; accepted 11-11-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10168 entire vr perimetry system fits in a small portable unit and it does not require a dedicated dark room or the fellow eye to be occluded. furthermore, the vf2000 perimeter may be a more practical device for examining the visual fields in children, as well as in patients who are unable to perform hfa testing such as those with disabilities, those in nursing homes, and those who are hospitalized.[7] although, there are apparent advantages of the vf2000, it is also important to evaluate its accuracy in diagnosis and classification of glaucoma. previous studies have shown that there is a correlation between the tablet-based visual field assessment and hfa; however, they have not discussed the performance of these instruments in the classification of the severity of glaucoma.[7, 8] with this background, we designed the present study to evaluate the diagnostic test properties of the palm scan vf2000® vr visual field analyzer for the diagnosis of glaucoma and the classification of the severity of glaucoma. we compared the agreement for diagnosis and classification of glaucoma between vr perimetry and hfa. methods the present study was a prospective crosssectional analysis of 166 eyes from 97 participants. study site the study was conducted at the laxmi eye hospital, a tertiary eye care center situated at a distance of about 50 km from mumbai, india. the study was approved by the ethics committee at lei for primary data analysis. study population we recruited 97 consenting patients who presented to the center. of these, 57 individuals (86 eyes) had glaucoma and 40 (80 eyes) did not. the inclusion criteria for the glaucoma group this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: shetty v, sankhe p, haldipurkar ss, haldipurkar t, dhamankar r, kashelkar p, shah d, mhatre p, setia s. diagnostic performance of the palmscan vf2000 virtual reality visual field analyzer for identification and classification of glaucoma. j ophthalmic vis res 2022;17:33–41. 34 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 https://knepublishing.com/index.php/jovr virtual reality vf analyzer ; shetty et al were: (1) aged between 20 and 65 years; (2) those classified as glaucoma based on the anderson criteria[9] – three non-edge points on the pattern deviation map, pattern standard deviation (psd), and glaucoma hemifield test along with an intraocular pressure (iop) of ≥20; and (3) those consenting for the study. the inclusion criteria for the non-glaucoma group were: (1) aged between 20 and 65 years; (2) those who were negative for all three parameters in the aforementioned criteria with an iop of <20; and (3) those consenting for the study. the exclusion criteria were: (1) those with visual acuity <6/60 and (2) any other coexisting ocular comorbidities that are likely to affect the test like corneal or macular pathology (such as any corneal opacity or any macular scar). we used the following reliability indices for glaucoma cases: fixation losses (0.2); the fraction was converted to a decimal number form; <20% for false-positive and false-negative errors. study procedures all the study participants were examined with the hfa (zeiss/usa) and the vf 2000® vr visual field analyzer (mmd/usa) on the same day by the same examiner. we had performed perimetry on all these patients previously at least twice using the hfa; the criteria for fixation losses, false positive, and false negative were based on the acceptable and standard cut-off values. hfa (zeiss/usa): the participant sat in a comfortable (rested forehead and chin) position in front of the hfa (zeiss/usa) bowl in a semi-dark room. the patient was told to look at the central fixation target and click the buzzer whenever the light stimulus was visualized. the lens power and type were provided by the hfa (zeiss/usa) analyzer in patients with refractive errors. in these cases, wire-rimmed full aperture lenses were used. we tested one eye at a time and the eye which was not being tested was occluded with a patch. we used the swedish interactive thresholding algorithm (sita) standard 24-2 for these cases. palm scan vf2000® virtual reality (vr) visual field analyzer (mmd/usa): participants wore the vr glasses; these glasses are fitted with a strap and adjusted to avoid any tilt. the participant was told to look at the central fixation target and click the buzzer whenever the light stimulus was visualized. the examiner adjusted the focus using two rotating knobs present on the instrument; this was to correct the refractive errors. the palm scan vf 2000® vr visual field analyzer (mmd/usa) has an occluder within the system. thus, even though the eyes were tested alternatively, no external occlusion patch is required [figure 1a]. all participants underwent the hfa test followed by the palm scan vf2000® vr visual field analyzer. they were given a rest of 1 hr at least between the tests on these two machines. we used the central 24-2 threshold test with a stimulus size of three and a presentation time of 200 ms for both these perimeters. the background illumination was 31.5 apostilb for hfa (zeiss/usa) and 36 decibels for palm scan vf 2000® vr visual field analyzer (mmd/usa). the software measured fixation losses by the heijl–krakau blind spot method. the false positives were events in which the participant responded only to audible stimulus (not visual stimulus) and false negatives were events in which participant failed to respond to supra threshold stimuli.[10] for each test type, we extracted the following data; mean deviation (md), pattern standard deviation (psd), and visual field index (vfi). those with an md of <6 were classified as mild, with 2– 12 as moderate, and with values >12 as severe glaucoma; this categorization was done according to the hoddap classification.[11] statistical analysis data were entered in ms excel (©microsoft, usa) and analyzed using stata version 15.1 (©statacorp, college station, texas, usa). we estimated the means and standard deviation (sd) or median and interquartile range (iqr) for continuous variables, and proportions for categorical variables. the means were compared using t-tests and the medians were compared using the mann–whitney test. the proportions were compared using the chisquare test or fisher’s exact test for low expected cell counts. we estimated the kappa statistic and its 95% confidence interval (ci) as a measure of agreement between the two methods. the diagnostic test properties of palm scan vf 2000® vr visual field analyzer (mmd/usa) was assessed using sensitivity, specificity, positive predictive value (ppv), and negative predictive value (npv); hfa (zeiss/usa) was considered as the gold standard journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 35 virtual reality vf analyzer ; shetty et al figure 1. figure showing the use of the instrument in a participant. for this analysis. the following analyses were done: (1) comparison of glaucomatous versus nonglaucomatous eyes and (2) severity of glaucoma (mild/moderate/severe) in eyes that were classified as glaucomatous. we used intraclass correlation coefficient (icc) as a measure of reliability for continuous variables (md, psd, and vfi). these paired values were also visualized using the bland altman plot. a p-value of < 0.05 was considered statistically significant. all procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 helsinki declaration and its later amendments or comparable ethical standards. results the mean age (sd) of individuals was 51.3 (14.9) years. about 62% of participants in the study were males and 38% were females. of the 86 glaucomatous eyes, 22 (26%) had mild, 18 (21%) had moderate, and 46 (53%) had severe glaucoma (based on the gold standard – hfa [zeiss/usa]). comparison of glaucomatous and nonglaucomatous eyes in these analyses, the agreement between palm scan vf 2000® vr visual field analyzer and hfa for diagnosis of glaucoma was 1.00 (95% ci: 1.001.00). according to palm scan vf 2000® vr visual field analyzer, the proportion for true positives and true negatives was 100% respectively. thus, the sensitivity and specificity for palm scan vf 2000® vr visual field analyzer for classifying individuals as glaucoma/non-glaucoma was 100%. the ppv and npv were both 100%. glaucomatous eyes we initially classified these individuals into mild vs moderate/severe glaucoma. the true positive proportion for moderate/severe glaucoma was 92% and the true negative proportion was 86%. thus, sensitivity and specificity of palm scan vf 2000® vr visual field analyzer for the detection of moderate/severe glaucoma was 92.2% and 86.4%, respectively. the ppv was 95.2% and the npv was 79.2%. detailed estimates and their 95% ci are presented in table 1. we also classified the eyes mild/moderate vs severe glaucoma. the true positive proportion 36 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 virtual reality vf analyzer ; shetty et al a) b) c) figure 2. a) bland altman plot of the mean deviation values from both the instruments, b) bland altman plot of the pattern standard deviation values from both the instruments, c) bland altman plot of visual field index values from both the instruments. for mild/moderate glaucoma was 90% and the true negative proportion for severe was 80%. the sensitivity of palm scan vf 2000® vr visual field analyzer for identification of mild/moderate glaucoma was 90.0%, and the specificity was 80.4%. the ppv was 80% and the npv was 90.2%. we have presented all the diagnostic test properties (estimates and 95% ci) in table 1. we also tested the kappa agreement between these two instruments for severity of glaucoma. the overall agreement for severity of glaucoma between these two instruments was 0.63 (95% ci: 0.56-0.78). we have presented kappa values and their 95% ci in table 2. for classification of glaucoma as moderate or severe, the kappa value was 0.43 (95% ci: 0.22-0.65). the agreement was journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 37 virtual reality vf analyzer ; shetty et al table 1. table showing the diagnostic test properties (including the area under the curve) of the palm scan vf2000® virtual reality visual field analyzer in 166 eyes. estimate 95% confidence intervals glaucoma vs non-glaucoma sensitivity 100% 95.7%-100% specificity 100% 95.5%-100% positive predictive value 100% 95.7%-100% negative predictive value 100% 95.5%-100% roc area under the curve 1.00 1.00-1.00 type of glaucoma mild/moderate vs severe sensitivity 80.4% 66.1%-90.6% specificity 90.0% 76.3%-97.2% positive predictive value 90.2% 76.9%-97.3% negative predictive value 80.0% 65.4%-90.4% roc area under the curve 0.85 0.78-0.93 mild vs moderate/severe sensitivity 92.2% 82.7%-97.4% specificity 86.4% 65.1%-97.1% positive predictive value 95.2% 86.5%-99.0% negative predictive value 79.2% 57.8%-92.9% roc area under the curve 0.89 0.81-0.97 table 2. table showing the kappa agreement and 95% confidence intervals between palm scan vf2000® virtual reality visual field analyzer and humphrey field analyzer kappa estimate 95% confidence intervals glaucoma vs non-glaucoma 1.00 1.00-1.00 classification of glaucoma mild glaucoma 0.76 0.61-0.92 moderate glaucoma 0.37 0.14-0.60 severe glaucoma 0.70 0.55-0.85 group of glaucoma included mild or moderate 0.49 0.20-0.78 moderate or severe 0.43 0.22-0.65 mild or severe 0.67 0.39-0.95 best for classification of glaucoma as mild or severe (kappa: 0.67-95% ci: 0.39-0.94) [table 2]. we found that the highest proportion of misclassification was in the moderate group; they were classified as mild (28%) or severe (17%). furthermore, about 20% of severe cases were misclassified as moderate by the vr visual field analyzer [table 3]. other parameters the icc for md was 0.96 (95% ci: 0.94-0.97), for psd was 0.93 (95% ci: 0.92-0.95), and for vfi was 0.92 (95% ci: 0.90-0.95). the bland altman plots for these three parameters are presented in figures 2a–2c. the median (iqr) fixation loss in 38 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 virtual reality vf analyzer ; shetty et al table 3. table showing the classification of severity of glaucoma according to palm scan vf2000® virtual reality visual field analyzer and humphrey field analyzer in 86 glaucomatous eyes. humphrey vr perimetry total mild moderate severe mild 1986.36 % 29.09 % 14.55 % 22100 % moderate 527.78 % 1055.56 % 316.67 % 18100 % severe 00 % 919.57 % 3780.43 % 46100 % total 2427.91 % 2124.42 % 4147.67 % 86100 % χ2 = 72.053; df = 4; cramer’s v = 0.647; fisher’s p < 0.001 the hfa group was 0.45 (0-13.3) and in the palm scan vf 2000® vr visual field analyzer group was 0 (0-18.2); the difference was not statistically significant (p = 0.89). similarly, the median (iqr) difference for false negative responses was not significantly different in both these methods (hfa (zeiss/usa): 0 [0, 6] vs palm scan vf 2000® vr visual field analyzer (mmd/usa): 0 [0, 18]; p = 0.07). however, we found the median (iqr) false positives were significantly higher in the hfa (0 [0, 2]) compared with that of the palm scan vf 2000® vr visual field analyzer (0 [0, 0]); the difference was statistically significant (p = 0.0003). discussion this study showed that palm scan vf2000® vr visual field analyzer had a perfect agreement with hfa for the detection of glaucoma. the sensitivity and ppv for identifying glaucoma were 100%; however, the sensitivity, specificity, ppv, and npv was lower for the severity of glaucoma. the agreement was best for the classification of glaucoma as mild or severe; however, the agreement was not good for classification cut-off at mild or moderate, and moderate or severe. glaucoma may go unnoticed in the early stages as it starts with loss of peripheral vision. the patient may not realize the loss and hence may not seek any medical advice.[12] hence, it is important to have screening tools for this disease so that patients in initial stages can be identified because in glaucoma, optic nerve damage is irreversible and it may progress in most cases without appropriate treatment.[13] as seen in our study, the vr visual field analyzer had perfect agreement[14] with the hfa for classification of eyes as glaucomatous or non-glaucomatous; the diagnostic test properties were also good. in fact, the sensitivity and specificity observed in our study was better compared with that of the optical coherence tomography (oct) for classification of eyes as glaucomatous or non-glaucomatous.[15] tpaskis and colleagues, and mees and coworkers found an excellent correlation between these two methods in detecting glaucoma.[7, 16] the main advantage of the hfa is the current gold standard. however, the disadvantages are that it cannot be used in community screenings due to the difficulty in transportation of the instrument or for patients who are unable to sit or are immobile (due to any reason such as post-surgery). the main advantage of the vr perimetry is that it can be used for communityand clinic-based screenings. it can also be used with patients with back pain who have difficulty to sit for perimetry or those who are immobile or confined to the bed.[6, 7] however, it cannot be used to identify the severity of glaucoma and hence is not very useful in the management of the condition in the present form. it has been suggested that due to the subjectivity in visual filed testing, the variability in examination recorded is likely to be higher when the damage is greater.[7, 17, 18] in general, portable and/or tablet based, or online perimeters have shown to be reliable and assess the visual fields fairly accurately,[8, 19–22] however , a recently published report found that a vr head-mounted device did not identify the deficits reliably.[16] as seen in our study, the agreement between these two instruments was best when the glaucoma was classified as either mild or severe. furthermore, we did find that a large proportion of moderate glaucoma cases were misclassified as mild. thus, the present algorithm is not able to classify the glaucoma appropriately. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 39 virtual reality vf analyzer ; shetty et al the study was conducted in a clinic-based setting; this is a more controlled setting with better co-operation by patients. hence, we may have overestimated some of the diagnostic test properties. for example, patients who came to the clinic were more likely to be aware of glaucoma and its importance for vision. thus, they are more likely to adhere to all the instructions during these tests. this may influence the test results. it will be appropriate to test the properties of this instrument in community settings as well. although, we would like to suggest the use of this instrument as a screening tool for glaucoma, a community-based study will provide additional evidence to this effect. this study is an important contribution to the literature. we went beyond the glaucoma/nonglaucoma differentiation and evaluated the instrument for classification of glaucoma. we did find that the instrument in its current form is able to differentiate between glaucomatous and non-glaucomatous eyes. however, among patients with glaucoma, the instrument is not able to correctly classify the stage of glaucoma. particularly, moderate glaucoma is more likely to be misclassified as mild or severe. hence, it cannot replace the hfa in clinical settings in its current form for the management of glaucoma. the algorithm needs to be refined to account for this discrepancy. the instrument may be used in screening of individuals for the presence/absence of glaucoma in community settings, health camps, and clinical practices. it is also useful for those patients who are unable to come to the examination room or sit in the examination chair due to back problems/surgeries, old age, neck problems, and disabilities. however, based on the evidence generated from this study, in the current form, the instrument may only be used as a screening tool for identification of glaucoma. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. cook c, foster p. epidemiology of glaucoma: what’s new? can j ophthalmol 2012;47:223–226. 2. world health organization. blindness and vision impairment [internet]. who; 2019 [cited 2020 february 27]. available from: https://www.who.int/news-room/factsheets/detail/blindness-and-visual-impairment. 3. george r, ve rs, vijaya l. glaucoma in india: estimated burden of disease. j glaucoma 2010;19:391–397. 4. kulkarni u. early detection of primary open angle glaucoma: is it happening? j clin diagn res 2012;6:667– 670. 5. alencar lm, medeiros fa. the role of standard automated perimetry and newer functional methods for glaucoma diagnosis and follow-up. indian j ophthalmol 2011;59:s53–s58. 6. wroblewski d, francis ba, sadun a, vakili g, chopra v. testing of visual field with virtual reality goggles in manual and visual grasp modes. biomed res int 2014;2014:206082. 7. tsapakis s, papaconstantinou d, diagourtas a, droutsas k, andreanos k, moschos mm, et al. visual field examination method using virtual reality glasses compared with the humphrey perimeter. clin ophthalmol 2017;11:1431–1443. 8. kong yx, he m, crowston jg, vingrys aj. a comparison of perimetric results from a tablet perimeter and humphrey field analyzer in glaucoma patients. transl vis sci technol 2016;5:2. 9. anderson dr, drance sm, schulzer m, collaborative normal-tension glaucoma study group. natural history of normal-tension glaucoma. ophthalmology 2001;108:247– 253. 10. nayak b, dharwadkar s. interpretation of autoperimetry. j clin ophthalmol res 2014;2:31–59. 11. hodapp e, parrish ri, anderson d. clinical decisions in glaucoma. st. louis, mo: mosby; 1993. 12. cioffi g. glaucoma. basic and clinical science course (book 10). usa: american academy of ophthalmology; 2011. 13. mcmanus jr, netland pa. screening for glaucoma: rationale and strategies. curr opin ophthalmol 2013;24:144–149. 14. mchugh ml. interrater reliability: the kappa statistic. biochem med 2012;22:276–282. 15. brusini p. oct glaucoma staging system: a new method for retinal nerve fiber layer damage classification using spectral-domain oct. eye 2018;32:113–119. 16. mees l, upadhyaya s, kumar p, kotawala s, haran s, s rajasekar, et al. validation of a head mounted virtual reality visual field screening device. j glaucoma 2020;29:86–91. 17. wall m, wild j. perimetry update 1998/1999: repeatability of abnormality and progression in glaucomatous standard and swap visual fields. proceedings of the xiiith international perimetric society meeting; 1998. gardone riveira (bs), italy: kugler publications. 18. wall m, woodward kr, doyle ck, artes ph. repeatability of automated perimetry: a comparison between standard automated perimetry with stimulus size iii and v, matrix, and motion perimetry. invest ophthalmol vis sci 2009;50: 974–979. 40 journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 virtual reality vf analyzer ; shetty et al 19. 19. prea sm, kong yxg, mehta a, he m, crowston jg, gupta v. six-month longitudinal comparison of a portable tablet perimeter with the humphrey field analyzer. am j ophthalmol 2018;190:9–16. 20. schulz am, graham ec, you y-y, klistorner a, graham sl. performance of ipad-based threshold perimetry in glaucoma and controls. clin exp ophthalmol 2018;46:346–355. 21. ianchulev t, pham p, makarov v, francis b, minckler d. peristat: a computer-based perimetry self-test for costeffective population screening of glaucoma. curr eye res 2005;30:1–6. 22. lowry ea, hou j, hennein l, chang rt, lin s, j keenan, et al. comparison of peristat online perimetry with the humphrey perimetry in a clinic-based setting. transl vis sci technol 2016;5:4. journal of ophthalmic and vision research volume 17, issue 1, january-march 2021 41 original article impact of color and polarity on visual resolution with varying contrast ratios and different text backgrounds ai-hong chen, phd; nurulain muhamad, b optom optometry, faculty of health sciences, universiti teknologi mara, cawangan selangor, kampus puncak alam, malaysia orcid: ai-hong chen: https://orcid.org/0000-0003-4568-0495 abstract purpose: to assess the impact of color and polarity in predicting the changes of visual resolution for different text backgrounds with increasing contrast ratios. methods: text-background designs of eight contrast ratios (0.15, 0.30, 0.47, 0.52, 0.57, 0.60, 0.70, and 0.78) and two text polarities (positive; black text and negative; white text) were compared with and without the presence of background color (blue, green, orange, and red). the visual resolution was measured in logmar using landolt c. the rate of changes in visual resolution measurements was analyzed using linear regression as contrast ratios increased with and without background color. results: visual resolution varied significantly with and without the background color element under both polarity investigations (p < 0.05). contrast ratio accounts for 77.4% of the variation within the visual resolution measurement with a color background [f(1,6) = 20.76, p < 0.01]. contrast ratio accounts for 97.16% of the variation in visual resolution measurements without a color background [f(1,6) = 205.63, p < 0.01]. conclusion: as contrast decreases, color plays a more significant role than the non-color factor in the resolution of fine details in both polarities as it influences the visual resolution outcome which is reflected in the measurements in logmar units. keywords: color; contrast; polarity; text-background; visual resolution j ophthalmic vis res 2022; 17 (2): 217–224 correspondence to: ai-hong chen, phd. optometry, faculty of health sciences, universiti teknologi mara, cawangan selangor, kampus puncak alam, 42300 bandar puncak alam, selangor darul ehsan 42300, malaysia. e-mail: aihong0707@yahoo.com received: 21-05-2020 accepted: 02-01-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i2.10793 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: chen ah, muhamad n. impact of color and polarity on visual resolution with varying contrast ratios and different text backgrounds. j ophthalmic vis res 2022;17:217–224. © 2022 chen and muhamad . this is an open access article distributed under the creative commons attribution license | published by knowledge e 217 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i2.10793&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr color, contrast and polarity; chen and muhamad introduction in any environment, contrast is the element that influences the visibility of an object. contrast is the manifestation of differences in attributes such as luminance and color of a visual object seen simultaneously.[1, 3] the changes in luminance due to the difference between two areas (e.g., between an object and its immediate background) is known as the contrast ratio, which calculates the ratio between the two specified areas.[4, 5] contrast aids vision by providing good legibility of the objects seen.[6] without a sufficient amount of contrast, the stimulus for vision is affected. colored objects viewed on a colored background present a color contrast as well as a luminance contrast.[7, 8] high contrast is the primary determinant factor for maintaining compelling reading.[9, 10] luminance contrast alone is sufficient to maintain visual performance but color alone is not enough.[7] however, low contrast and mid-range wavelength (yellow) color reduce visual acuity.[11] text-background color seems to improve contrast perception.[11, 12] the effect of text-background color on visual functions, such as reading speed,[7, 8] visual search,[10] viewing distance,[13] legibility,[14, 15] and polarity[16–18] has been studied extensively. however, the influence of color and polarity on readability remains debatable. some researchers reported better legibility of lighter letters on a darker background than the traditional darker letter on a lighter background in non-color and colored backgrounds.[16, 18] contradictorily, others found the darker target on the lighter background provided better visual performance by enhancing the legibility of the target as compared to a lighter target on a darker background.[19–21] the positive and negative polarity of the achromatic stimulus have a negligible effect on legibility in high-contrast ratio conditions.[11, 22] since color impacts visual acuity and is contrast-dependent, this may indicate that the color at multiple contrast ratio levels may affect legibility in varied ways.[11, 12] in the present study, we investigated the impact of color and polarity in predicting the changes of visual resolution with different contrast ratio. methods experimental design text-background design of eight contrast ratios (0.15, 0.30, 0.47, 0.52, 0.57, 0.60, 0.70, and 0.78) and two text polarities (positive; black text and negative; white text) were compared with and without the presence of background color (blue, green, orange, and red) [figure 1]. the dependent variable was visual resolution. the rate of changes in visual resolution measurements with increasing contrast ratios with and without background color was analyzed using linear regression. a repeated measures design was used for this study, whereby the same subjects were tested at all testing conditions. trials from each condition were randomly interleaved, and the task was always the same. visual stimuli and apparatus the visual resolution was measured through spatial threshold determination by using four-orientation landolt c. it was recorded as logmar (logarithm minimum angle of resolution) using the detection of the gap in a four-orientation landolt c. a four-orientation design of landolt c chart was produced on a photo matte surface material and presented to the subjects.[2, 3] the chart was internally illuminated with a light-emitting diodes lamp that provided enhanced color properties with reduced flicker.[2, 5, 24] the matte surface minimized specular reflections to produce an even, diffused, dark-grey background. the experiments were divided into two parts corresponding to the different text designs (black text and white text). the comparison was between backgrounds with and without color in each text-background design. the luminance of the landolt c was measured using a calibrated konica minolta luminance meter ls110. the contrast ratio between the text and the background was calculated using the luminance contrast definition of michelson.[2, 6] the formula was constructed using the maximum and minimum luminance of the text and the background [table 1]. 218 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 color, contrast and polarity; chen and muhamad (a) with background color (b) without background color figure 1. the view of the test scenario at 16 trials, photographed with the subjects’ eye level at 4 m working distance: (a) with background color and (b) without background color. table 1. summary of luminance information used in the four-position landolt-c chart designs landolt-c chart designs (text/background) luminance, l (cd/m2) text background black/blue 6.76 9.13 black/red 6.76 12.20 black/green 6.76 24.55 black/orange 6.76 18.67 white/blue 71.47 9.13 white/red 71.47 12.20 white/green 71.47 24.55 white/orange 71.47 18.67 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 219 color, contrast and polarity; chen and muhamad y = -0.3423x + 0.4351 r² = 0.7742 y = -0.1349x + 0.2691 r² = 0.8073 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 v is u a l re so lu ! o n ( lo g m a r ) contrast ra!o with colour without colour linear (with colour) linear (without colour) b/g b/b w/b b/o b/r w/r w/o w/g figure 2. mean visual resolution measurement (logmar) as a function of contrast ratio for with and without color of textbackground design. b/b, black-on-blue; b/r, black-on-red; b/o, black-on-orange; b/g, black-on-green; w/o, white-on-orange; w/g, white-on-green; w/r, white-on-red; w/b, white-on-blue. room setup and experimental procedure our experiment room was well controlled, and detailed with systematic procedures to minimize technical error and learning bias. wellcontrolled settings were essential in reducing inter-variation. unwanted reflectance might cause color interference and veiling luminance that may lead to glare sensation. the wall, floor, and ceiling of the experiment room were covered with black cloth to reduce light reflection and stray light. the calculated reflectance of the room wall and floor were 0.16 and 0.10, respectively. the room illuminance was controlled at 100 lux. the chart was internally illuminated and placed at 4 m from the subject. the midpoint of the chart panel was positioned at eye level (approximately 1.3 m above the floor). the subjects verified the threshold of the legible letter cs using four orientation approach of the landolt c charts. five-minute dark adaptation was allowed at the beginning of each measurement. instructions regarding the procedure were explained. the landolt c charts were presented to the subject in random order. the subject was required to give their response by indicating the orientation of the landolt c gap. the performance was scored and measured as the minimum angle of resolution. participants this study adhered to the tenets of the declaration of helsinki and was approved by the university’s research ethics committee. all power calculations were conducted using the gpower analysis program.[28] given a total sample size of n = 31 and assuming α = 0.05, population effects of size f = 0.80 (large effects[28]) could be detected for the independent variables with a probability of 1 – β = 0.95. thirty-one subjects were young adults (mean age of 22.46 ± 1.85 years) with no known ocular pathology. all participants were screened with a d-15 color vision test to rule out any known color deficiencies. the inclusion criteria were as follows: (i) logmar 0.20 or better habitual distance visual acuity; (ii) logcs 1.65 or better contrast sensitivity; and (iii) a pass with a circular result diagram of d15 color vision test. in our contrast-color-polarity investigation, a single individual went through a similar process 16 times (representing each chart). the best acuity was obtained for each chart. subjects were tested with their habitual visual acuity and natural pupil. simple randomization was used to reduce the learning effect due to repetitive measurements.[29] the technique maintained complete randomness of the assignment of a stimulus presented. the random numbers were 220 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 color, contrast and polarity; chen and muhamad generated using the randbetween function in excel. statistical analysis the current investigation utilized a within-subject study design, where repeated measures of the same subjects were performed. the data collected from all 31 subjects were analyzed using the spss statistic software version 20. the visual resolution measurements were analyzed using friedman’s two-way analysis of variance test and linear regression analysis. results in the positive polarity investigation (contrast range, 0.15–0.80), the visual resolution of white text was found to vary significantly with background color wavelength [friedman’s twoway analysis of variance test: 𝜒2 = 35.46, p < 0.05]. moreover, the effect of positive polarity on the visual resolution remained significant without color element [friedman’s two-way analysis of variance test: 𝜒2 = 21.00, p < 0.05]. in negative polarity investigation, the visual resolution of white text was found to vary significantly with background color wavelength [friedman’s two-way analysis of variance test: 𝜒2 = 16.64, p < 0.05]. similarly, the impact of negative polarity on the visual resolution stayed significant without color element [friedman’s two-way analysis of variance test: 𝜒2 = 13.43, p < 0.05]. linear regression was run to understand how the contrast ratio predicts the polarity and color element in visual resolution measurements. a mean and standard deviation of contrast ratio against visual resolution measurements (logmar) with superimposed regression line was plotted with and without a color background in figure 2. visual inspection of these two plots indicated a linear relationship between the variables. the prediction equation was: with background color: 𝑦 = −0.3423𝑥 + 0.4351, 𝑅2 = 0.7742 (1) without background color: y = −0.1349x + 0.2691, r2 = 0.8073 (2) contrast ratio accounts for 77.4% of the variation in visual resolution measurement with color background [f(1,6) = 20.76, p < 0.01]. contrast ratio accounts for 97.16% of the variation in visual resolution measurements without color background [f(1,6) = 205.63, p < 0.01]. discussion this study investigated how contrast ratio affects the polarity and color elements in visual resolution measurements. our findings show that adding color to the background enhances resolution thresholds that hold only for contrast levels of 0.3 and higher. in comparison to earlier findings, the enhancement in the resolution threshold was found at much higher contrast levels of 0.5 and higher.[30] in the case of positive polarity (black text), the present experiment reveals that the visual resolution measurements (as indicated by the logmar scores obtained) worsen as the contrast decreases in both conditions with and without color factors. the comparison between these two conditions (with and without color factors) shows that visual resolution reduces at the lower contrast level of 0.15 as compared to the higher contrast level of 0.3. the visual resolution readings exhibit approximately two lines of reduction at 0.15 contrast level with background color (0.43 logmar) in comparison to the background without color (0.29 logmar). the chart used is similar to the smith-kettlewell institute low luminance (skill) card test: both are designed with similar chart progression and multiple levels of background luminance.[31] however, the skill card test was intended for a viewing distance of 40 cm, whereas the current study tested for a distance of 4 m. nevertheless, both studies seem to agree that in visually normal persons, darker chart (reduced luminance at 15% contrast for the current study and 14% contrast for skill’s study) acuity is responsible for high variance in the logmar score. in comparison, high-contrast acuity contributes to lesser variance journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 221 color, contrast and polarity; chen and muhamad (better logmar). the average recommended background luminance for standard va charts is 85 cd/m2 to 300 cd/m2.[32, 33] however, the background luminance was unable to be set at the recommended value in current study due to color element. therefore, incorporating color elements in any road signs should be done with caution. the reduced light level used in the current study can be likened to what is experienced by motorists driving at twilight. presentation of dark letters (indicated by lower luminance) on a light background (marked by higher luminance) is usually referred to as positive polarity, as opposed to negative polarity with light letters or symbols on a dark background.[19] positive polarity is the preferred choice of the print construct, as evidenced by its abundant use in books, journals, newspapers, and printed office documents. a significant reduction in resolution was observed when shorter color wavelengths were applied at much lower contrast (0.15) as the chart’s background color. however, the reduction is only significant in the black text but not in the white text in our study. our findings further suggest that black text used against shorter wavelengths (blue) is harder to resolve by human eyes than is white text. these results are consistent with those of an earlier study that found when the color blue was applied as a background color, it reduced visual performance.[21] this assessment further suggests that larger-scale mechanisms are needed for color-based information processing rather than for luminance-based processing. our study only examined four colors. the color characteristics could be examined from different perspective like hues, correlated color temperature, color rendering index, and spectral power distribution variation. our data without color factor are consistent with a previous study that reported that the luminance factor that contributes to the contrast ratio on its own was sufficient for reading rate and shape detection.[7, 34] visual resolution is controlled by the resultant luminance fluctuation between text and background, influencing the contrast ratio. our combine findings with and without color factors further support the earlier study that discovered visual acuity for achromatic conditions was better than that for color conditions.[35] this was evidently due to the lack of neural high-pass filtering in the color system as compared to the luminance system.[36] previous studies found that contrast sensitivity was about two times better for luminance-modulated gratings than chromatic gratings at all spatial frequencies. current findings also accord with earlier studies in that we discovered that acuity with a grayscale background is more accurate as it yields better logmar than a colored background.[5] the impact of the color element was further investigated and comparisons were made between the two text polarities within our study. we found that black text displays more accurate visual resolution than the white text under luminance influence. a study on contrast polarity and myopia development revealed that the choroid became about 16 µm thinner in only 1 hr when subjects read black text on a white background.[37] in comparison, the choroid became about 10 µm thicker when subjects read white text on a black background.[37] they further suggested that reading white text on a black screen or tablet might be a way to inhibit myopia, while conventional black text on a white background might stimulate myopia.[37] in summary, our study reveals that as contrast decreases, color plays a more significant role than the non-color factor in both polarities in the resolution of fine detail as it influences the visual resolution outcome, which is reflected by the results of the poorer logmar. although our study was successful in determining the impact of color and polarity on visual resolution, there were two limitations to our study. our subjects were tested with their habitual visual acuity and natural pupil. we were unable to control the chromatic aberration because we test our subjects at their habitual visual acuity and natural pupils. future research is recommended to study the impact of chromatic aberrations on color visual resolution. our sample only evaluated young adults. hence, application of these results in assessing alternate age demographics may be incongruous. additional research is required to consider the impact of agerelated variations on the visual resolution in color and polarity. 222 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 color, contrast and polarity; chen and muhamad acknowledgements authors would like to thank amirul ad-din majid for technical support. financial support and sponsorship this work was supported by [600-irmi 5/3/gip (079/2019)]. conflicts of interest authors declare that there are no conflicts of interest references 1. millodot m. dictionary of optometry and visual science. oxford, uk: butterworth heinemann; 2009. 2. north rv. work and the eye. oxford, uk: butterworth heinemann; 2001. visual performance; p. 1–17. 3. boyce p. human factors in lighting. boca raton, florida, united states: crc press taylor & francis group; 2014. 4. nadler mp, miller d, nadler d. glare and contrast sensitivity for clinicians. new york, ny: springer publishing company; 1990. 5. legge ge, rubin gs, luebker a. psychophysics of reading: v. the role of contrast in normal vision. vision res 1987;27:1165–1177. 6. hung gk, ciuffreda kj. models of the visual system. dordrecht, netherlands: kluwer academic; 2002. neural models of motion perception; p. 487–519. 7. knoblauch k, arditi a, szlyk j. effects of chromatic and luminance contrast on reading. j opt soc am a 1991;8:428. 8. legge ge, parish dh, luebker a, wurm leeh. psychophysics of reading?: xi. comparing color contrast and luminance contrast. j opt soc am a 1990;7:2002– 2010. 9. tinker ma, paterson dg. studies of typographical factors influencing speed of reading vii. variations in color of print and background. am j appl psychol 1931;15:471–479. 10. ling j, van schaik p. the effect of text and background color on visual search of web pages. displays 2002;23:223–230. 11. chen a, muhamad n. contrast ratios, color elements, and polarities in visual acuity measurements. int j eng technol 2018;7:89–93. 12. tanaka y, yokoyama s, horai r, kojima t, hiroyuki s, kato y, et al. effect of background luminance level on the assessment of color visual acuity using colored landolt rings in young healthy subjects. curr eye res 2018;43:428–434. 13. shieh k, lin c. effects of screen type, ambient illumination, and color combination on vdt visual performance and subjective preference. int j ind ergon 2000;26:527–536. 14. humar i, gradisar m, turk t, erjavec j. the impact of color combinations on the legibility of text presented on lcds. appl ergon 2014;45:1510–1517. 15. humar i, gradisar m, turk t. the impact of color combinations on the legibility of a web page text presented on crt displays. appl ergon 2008;38:885– 899. 16. chen a, muhamad n. greater effect of contrast polarities on visual acuity measurements using chart with shorter wavelength background. malaysian j fundam appl sci 2018;14:515–519. 17. westheimer g. visual acuity with reversed-contrast charts: i. theoretical and psychological investigations. optom vis sci 2003;80:745–748. 18. westheimer g, chu p, huang w, tran t, dister r. visual acuity with reversed-contrast charts: ii. clinical investigation. optom vis sci 2003;80:749–752. 19. piepenbrock c, mayr s, buchner, a. smaller pupil size and better proofreading performance with positive than with negative polarity displays. ergonomics 2014;57:1670–1677. 20. piepenbrock c, mayr s, mund i, buchner a. positive display polarity is advantageous for both younger and older adults. ergonomics 2013;56:1116–24. 21. buchner a, baumgartner n. text – background polarity affects performance irrespective of ambient illumination and color contrast. ergonomics 2007;50:1036–1063. 22. bernal-molina p, esteve-taboada jj, ferrer-blasco t, montés-micó r. influence of contrast polarity on the accommodative. j optom 2019;12:38–43. 23. schrauf m, stern c. the visual resolution of landolt-c optotypes in human subjects depends on their orientation: the ’gap-down’ effect. neurosci lett 2001;299:185–188. 24. fang p, liu yf. energy channeling led driver technology to achieve flicker-free operation with true single stage power factor correction. ieee trans power electron 2017;32:3892–3907. 25. santos rl dos, rufino dm, morais mbm, sa em. a charge-pump led driver with pfc and low-frequencyflicker reduction. 2017 brazilian power electron conf 2017:1–7. 26. schwartz sh. visual perception: a clinical orientation. new york, ny: mcgraw-hill; 2010. 27. sawilowsky ss. new effect size rules of thumb. j mod appl stat methods 2009;8:597–599. 28. erdfelder e, faul f, buchner a. gpower: a general power analysis program. behav res methods, instruments, comput 1996;28:1–11. 29. suresh k. an overview of randomization techniques: an unbiased assessment of outcome in clinical research. j hum reprod sci 2011;4:8–11. 30. greenlee mw, heitger f. the functional role of contrast adaptation. vision res 1998;28:791–797. 31. portnoy gh, brabyn j, schneck me, jampolsky a. the skill card: an acuity test of reduced luminance and contrast. investig opthalmology vis sci 1997;38:207–218. 32. bailey i. borish’s clinical refraction. oxford, uk: butterworth heinemann. 2006. visual acuity. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 223 color, contrast and polarity; chen and muhamad 33. international council of ophthalmology. visual acuity measurement standard. ital j ophthalmol 1998;2:1–15. 34. stephane c, bloj m, harris jm. interactions between luminance and color signals: effects on shape. j vis 2013;13:1–23. 35. mullen kt. the contrast sensitivity of human color vision to red-green and blue-yellow chromatic gratings. j physiol 1985;359:381–400. 36. rovamo jm, kankaanpaa mi, kukkonen h. modelling spatial contrast sensitivity functions for chromatic and luminance-modulated gratings. vision res 1999;39:2387– 2398. 37. aleman ac, wang m, schaeffel f. reading and myopia: contrast polarity matters. sci rep 2018;8:1–8. 224 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 original article post-saccadic eye movement indices under cognitive load: a path analysis to determine visual performance marzieh salehi fadardi1, moptom, phd; javad salehi fadardi2,3,4, phd; monireh mahjoob5, phd; hassan doosti6, phd 1department of optometry & vision sciences, university of melbourne, melbourne, australia 2department of psychology, ferdowsi university, mashhad, iran 3claremont graduate university, california, usa 4school of psychology, bangor university, bangor, uk 5health promotion research center, department of optometry, rehabilitation faculty, zahedan university of medical sciences, zahedan, iran 6department of statistics, macquarie university, sydney, australia orcid: marzieh salehi fadardi: https://orcid.org/0000-0002-5422-7695 monireh mahjoob: https://orcid.org/0000-0001-9455-0721 abstract purpose: the evidence on the linear relationship between cognitive load, saccade, fixation, and task performance was uncertain. we tested pathway models for degraded task performance resulting from changes in saccadic and post-saccadic fixation under cognitive load. methods: participants’ (n = 38) eye movements were recorded using a post-saccadic discrimination task with and without arithmetic operations to impose cognitive load, validated through recording heart rate variability and subjective measurement. results: results showed that cognitive load led to longer latencies of saccade and fixation; more inaccurate responses and fewer secondary saccades (p < 0.001). longer saccade latencies influenced task performance indirectly via increases in fixation latency, therefore, longer reaction times and higher response errors were observed due to limited fixation duration on desired target. conclusion: we suggest that latency and duration of fixation indicate efficiency of information processing and can predict the speed and accuracy of task performance under cognitive load. keywords: eye movement; saccades; task performance j ophthalmic vis res 2022; 17 (3): 397–404 correspondence to: monireh mahjoob, phd. department of optometry, rehabilitation sciences faculty, zahedan university of medical sciences, zahedan 9816743463, iran. e-mail: mahjoob_opt@yahoo.com received: 28-07-2021 accepted: 19-02-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i3.11578 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: fadardi ms, fadardi js, mahjoob m, doosti h. post-saccadic eye movement indices under cognitive load: a path analysis to determine visual performance. j ophthalmic vis res 2022;17:397–404. © 2022 fadardi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 397 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i3.11578&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr visual performance under cognitive load; fadardi et al introduction saccadic eye movements are rapid and conjugate eye movements that voluntarily move the eyes from one target to another. several parts of the cerebral cortex, such as the frontal eye field and the parietal eye field, play an important role in performing a saccade.[1] an individual’s performance of visual tasks can be degraded due to task conditions such as cognitive load and mental stress.[2–8] cognitive load refers to the amount of information that working memory deals with at a time. visual tasks under high cognitive load conditions can limit the application of top–down processes and result in poor task performance.[2–8] distracted minds can also lead to the degradation of an individual’s performance during daily activities where both accuracy and speed are required to deal with visual targets under high load situations such as driving. in order to see a target, individuals require both to get the eyes on the desired target (fixation) that is to “collect” the sensory visual inputs-, and then to “process” the consequent visual information. however, this is not always the case, even for normally sighted individuals. in some instances, it has been reported that individuals have looked at but failed to see a visual target or saw it very late while driving and doing another task at the same time.[9] previous investigations in normally sighted individuals have reported that cognitive demands of concurrent tasks can affect saccade eye movements and individuals’ visual task performance.[2–7] fadardi and abel found that both latencies of saccade and fixation on the desired target increased and task performance decreased when participants were required to perform a post-saccadic task concurrently with an arithmetic task.[8] they suggested that such changes in saccades may give rise to late eye fixation which itself may further limit fixation duration and efficiency of information processing under time-restricted situations.[8] however, the cause–effect relationship between the changes in saccades and post-saccadic task performance is not yet clear. path analysis is an extension of multiple regression statistical analysis that is used to evaluate causal models by examining the relationships between several dependent variables and independent variables. this method as a methodological tool can estimate the magnitude and strength of effects in causal connections between variables. in addition, path analysis is useful for comparing different causal models to examine the best fit with the data.[10] here, we aim to investigate the cause– effect relationship between changes in saccade characteristics, fixation duration, accuracy, and speed of task performance within subjects. we have hypothesized that task-induced changes in saccades give rise to the degradation of an individuals’ performance of post-saccadic tasks indirectly by imposing changes in eye fixation on the desired target. the results of this study have agreed with this theory and has also suggested that the timing aspects of fixation (latency and duration) which may give rise to poor visual task performance may also be utilized in its prediction. methods participants thirty-two graduate students from the university of melbourne (24 females and 8 males) with a mean age of 30.81 ± 12.5 years participated in the experiment. all participants had normal general health condition and a visual acuity ≥6/9 in each eye. participants were requested to avoid sedatives and alcohol consumption the night before the tasks. apparatus and procedures all procedures contributing to the current study conformed to the declaration of helsinki and were approved by the institutional review board of the university of melbourne. all participants volunteered for the experiment, and the signed written informed consent was obtained from them. the tasks were presented using the sr research experiment builder 1.6.2 (sr research, mississagua, ontario) and a 1024×728 nec-wt610 projector with a screen placed at a distance of 160 cm from participants. participants were required to look at a fixation point presented at the central gaze position until it disappeared within a random time between 1500—3000 ms. the fixation point was followed by a tumbling e target presented randomly across ±25º horizontally away from center in 5º steps. participants were required to 398 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 visual performance under cognitive load; fadardi et al look at and promptly discriminate the direction of the e target (right or left) using a game player console. participants were highly encouraged to do the tasks with the highest accuracy and speed as much as possible. the submission of manual responses was followed by the fixation target re-appearing and participants were required to look back to the center and wait for another e target to be presented. the size of the tumbling e and fixation targets were the same; that is, 0.3 log mar. each eccentric gaze position was tested every five times. the task was repeated with a concurrent arithmetic task to impose a high level of mental load within participants. for the arithmetic task, the participants were required to continuously subtract 7 from a number between 100 and 200 and verbalize the arithmetic responses in 0.5 s. participants’ performance on the arithmetic task was recorded and was qualitatively monitored after the experiment was terminated. task performance was measured using participants’ reaction time to the e targets and the percent rate of accurate responses was manually submitted. the time-related variables including participants’ reaction time and latency of eye movements were measured using the onset time of each target on the screen; that was determined by installing a photocell in a corner of the screen which recorded luminance changes. eye movements were recorded during the tasks using an eyelink ii high-speed head mounted video eye tracker (sr research, mississagua, ontario) at a sampling rate of 500 hz in pupil tracking mode with an accuracy of 0.5º or better. head movements were minimized during the tasks using an adjustable supportive headrest. participants’ head movements were also qualitatively evaluated offline by plotting the positions of the head markers of the eyelink ii. concurrent heart rate recordings and a retrospective subjective rating score using a computer version of nasa tlx (task load index) were used to confirm within-subjects’ variation in level of cognitive load across the task conditions. eye movements analysis using the analogue output from the eyelink ii (resampled at 1000 hz) allowed us to synchronize the time of the eye movements with the target timing. the digital output from eyelink ii was used for the analysis of eye position in matlab r2012a after being digitally low-pass filtered with a cut-off at 70hz. a bidirectional filter (using the matlab filtfilt command) was applied to the data to avoid time delays. the filter used a mean squares algorithm to produce the least error signal; that is, the difference between the desired and the actual signal. velocity data were derived from the position data and smoothed using a second-order differentiator with a cut-off frequency of 62.5 hz. saccades were selected using a custom written matlab program that presented potential saccades for manual review and selection. the program used the criteria of 10º/s and 8000º/s[2] for saccade onset and offset after the target step. trials associated with blinks, predictive saccades, or saccades with directional error or gain of <0.5 or >1.5 were not included in the analysis.[11] asymptotic peak velocity, saccade latency, and gain were measured under each task condition. occurrence of any secondary saccade was also marked for each trial. latency of initial eye fixation, also termed target acquisition time,[8] was determined as the time between the target onset on the screen and the initial placement of the eye gaze within 0.5º of the target of interest which was typically located at the end of the saccadic eye movements. trials with fixation losses due to saccades larger than 1º were not included in the analysis. fixation duration was measured as the time of duration of fixating on the target before a manual response to the target of either right or left, was submitted. data analysis task conditions were compared within participants to determine whether any significant effects on task performance exist, and to monitor saccade eye movements; that is, latency, gain, and velocity of pre-saccades, the probability of the occurrence of secondary saccades, and the latency and duration of eye fixation on the desired target. correlation and regression tests investigated potential relations among participants’ changes in multiple variables including task performance, cognitive load, and eye movement variables. the chi-square and its corresponding p-value of 0.05 were used as the criteria to exclude a variable from the model. values >0.05 were excluded from journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 399 visual performance under cognitive load; fadardi et al the analysis. exclusion or replacing the unaffected variables did not show to have any significant effect on the pathway models. during the next step, path analysis (standardized regression coefficients and correlation between variables) was used to develop a model to assess how the changes in load indicators affected visual task performance through possible alterations in saccades and/or fixation eye movements. an acceptable model was determined using the criteria of 0.90–1.00 for comparative fit index (cfi) and 0.00–0.06 for root mean square error of approximation (rmsea). the models with the largest cfi and the smallest rmsea were determined as the final path models selected to analyze the effects of cognitive load on participants’ reaction time and response errors submitted for the discrimination task. the ibm spss with amos graphics versions 24 (ibm corporation, somers, ny) was used to analyze data. results both rating scores of mental load and heart rate significantly increased among participants during the task with mental arithmetic when compared to the task without arithmetic (mean difference (se); for the load score: 15.77 (1.17), p < 0.001; for the heart rate: 10.25 (1.17) bpm, p < 0.001). it was confirmed that the level of cognitive load significantly increased during the task with arithmetic. figure 1 shows the changes in heart rate, saccade variables, and task performance from the low to high load within participants. latencies of saccade and fixation increased significantly during the high load when compared to the low load (for saccade latency: 37.37(32.14) ms, p < 0.001; for fixation: 40.86(8.85) ms, p < 0.001). the saccade gain was just significantly greater for the high load when compared to the low load (0.029(0.011), p = 0.042). the probability of the occurrence of the secondary saccades was less under the high load than under the low load (0.123(0.024), p < 0.001). inaccurate responses submitted on the discrimination task significantly increased under the high load when compared to the low load (10.8% vs 0.97%; wilcoxon signed ranks test: p < 0.001). fixation duration tended to decrease with the high load, however, the changes in fixation duration and participants’ reaction time to the targets were not significant with cognitive load (fixation duration under low load: 391.33(40.36) ms; and under high load: 348.29(11.95) ms; participants’ reaction time under low load: 766.49(10.92) ms; and under high load: 785.04 (35.89)). an inverse correlation was found between changes in fixation duration and response errors from the low to high load (r = –0.54, p = 0.004). a significant correlation was found between participants’ reaction time to the e targets and latency of fixation on the desired target (r = 0.313, p = 0.015). the increase in the response errors submitted for the discrimination task was significantly associated with less probability of the occurrence of secondary saccades (r = –0.401, p = 0.001). the correlation between the changes in task performance metrics, that is, reaction time and accuracy of manual responses, from the low to the high load just failed to be significant (r = –0.503, p = 0.05). path analyses were employed to investigate potential relationships among the task-induced changes in heart rate, mte score, task performance, and eye movement variables, that is, latency, gain and velocity of saccades, latency and duration of fixation, occurrence of secondary saccades. figure 2 illustrates the best path models for the effects of task condition on performance metrics including participants’ reaction time (chisquare: 0.098, df = 2, p = 0.952, rmsea: 0.000, nfi = 0.031), and response errors (chi-square: 6.334, df = 10, p = 0.786; rmsea: 0.000, nfi = 0.737). for both models (the model of reaction time and model of response errors), changes in the task condition was best represented by heart rate and negative effects shown on an individuals’ task performance via changes in saccade latency. changes in heart rate, used as the metric of cognitive load, showed an increasing effect on saccade latency (standardized regression weight [β= 0.07]). there was an inverse relationship between saccade latency and the probability of the occurrence of secondary saccades (β = –0.18). the increase in saccade latency was found to delay fixation on the desired target (β = 0.18) which showed an increasing effect on participants’ reaction time (β = 0.08). the delay in fixation was found to limit fixation duration (β = –0.32). shorter duration of fixation was found to contribute in the probability of the submission of inaccurate responses increased on discrimination tasks (β = –0.59). 400 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 visual performance under cognitive load; fadardi et al figure 1. heart rate (a), saccade latency (b), saccade gain (c), latency of target acquisition; i.e., fixation on target of interest (d), participants’ reaction time (e), and response errors (f) in post-saccadic discrimination task under low and high cognitive loads. black lines represent changes from low to high cognitive load for each participant. red circles with vertical lines express the mean ± sd under the low and high loads; except for response errors that the red circles express median values. red diagonal lines represent changes in the means for (a–e) and changes in the medians for (f) from low to high cognitive load. discussion results obtained by the current study showed cognitive load can indirectly affect an individuals’ task performance at the post-saccadic position via changes in eye movements. increase in saccade latency with high cognitive load can degrade visual task performance indirectly by an increase in the fixation latency and a decrement in the duration of fixation on the desired target. consistent with previous studies, our findings showed that cognitive demands affect saccade latency.[1, 5–12, 15–17] post saccadic visual tasks, such as discrimination, have been found to increase the probability of secondary saccades occurring.[13] however, the probability of secondary saccades developing decreased under the high load possibly because attention allocated to the discrimination task was reduced by the concurrent arithmetic task. although the nature of secondary saccades is reflexive,[14] the controlled execution of saccades can suppress reflexive saccades under high load conditions.[5, 15] in addition, the programming of secondary saccades is done prior to their execution and during the latency of the initial saccades.[16] like initial saccades, secondary saccades contribute toward the target acquisition time and final eye position.[17] under cognitive conditions, cost-effective programing of the saccades (trade of between timing and accuracy of saccadic task) might encourage the saccade system to fixate on the desired target more by using a single saccade rather than saccade sequences. despite changes in the occurrence of secondary saccades with the high load, we did not find any effect of secondary saccades on visual task performance. longer saccade latency resulted in the decrease in task performance brought about mainly by an increase in the latency of fixation on the desired target. according to figure 2, a delay in eye fixation on the target can follow a delay in an journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 401 visual performance under cognitive load; fadardi et al figure 2. illustration of final path models for the indirect effects of the changes in the cognitive load indicated by heart rate, from low to high load on subjects’ reaction time and submission of inaccurate responses. individual’s reaction time to the target; that is, being slow in reacting to visual stimulus. our results are consistent with the findings of wang et al who examined eye movements in a group of patients with involuntary continuous ocular oscillations, whose complaints of delayed visual capture were common (infantile nystagmus).[18] delayed visual capture can also occur among normally sighted individuals, for example, when drivers report that they looked at a target but either did not see an object or saw it late.[9] “being slow to see” has been identified clinically as prolonged visual recognition time is predicted as the result of an increase in the latency of fixation; which has been demonstrated by our results that expressed changes in the timing of eye movements and the participant’s reaction time during high compared low cognitive loads [figure 2]. investigations of eye movements and reaction times in both of these types of patients, those with involuntary continuous ocular oscillations versus normally sighted individuals, concluded that longer times taken to respond to a visual target at post-saccadic positions is mainly as a result of the increased time taken to fixate on a desired target rather than longer saccade latency or the duration of fixation on the target.[8, 19] thus, an increase in recognition time is predicted to follow an increase in the latency of fixation; which has been demonstrated by our results that expressed changes in the timing of eye movements and the participant’s reaction time during low to high cognitive loads [figure 2]. despite associations between changes in task performance and latency of eye movements, our results did not show any significant differences in the task conditions as it relates to participants’ reaction times and fixation durations. previous investigations have suggested two behavioral profiles for the discrimination tasks with mental arithmetic; those include focusing on either the accuracy or speed of responses at the expense of the other.[20] one possible reason for no significant change in our participants’ reaction time can be the perceived task urgency which might result in the participants becoming more concerned about the speed of their performance rather than the accuracy of their responses. task urgency and accuracy also affect saccade latency albeit via different mechanisms;[3, 21, 22]that is, perceptual urgency – the extent to which the participant feels the time is restricted – can lower the threshold of saccade execution while the other one (accuracy) can affect saccade latency via the information processing system of the brain.[23] it seems that the level of the task urgency perceived by our participants was not large enough to avoid increasing the latency of saccades with mental arithmetic. according to previous investigations, prolonged visual recognition time is unlikely due to the slow speed of information processing.[8, 19] using a simulated driving task concurrently with phone conversing, recarte and nunes measured longer latency of fixation, and more individuals’ response errors with no significant change in the participants’ reaction time.[25] consistently, fadardi and abel have suggested that efficiency of information processing, despite no significant change in its 402 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 visual performance under cognitive load; fadardi et al duration, gives rise to resolving target details including both visual inputs and processing of the information during fixation.[8] previous results have suggested that performance was not degraded due to the time restriction to perform a visual task but resulted from poor information processing.[8, 25] according to our results, a decrement in fixation duration predicted more response errors in an individual’s task performance [figure 2]. in other words, a subject who showed longer fixation duration is expected to submit a correct response to a post-saccadic visual task. our results are consistent with previous findings by tsai et al who used auditory arithmetic evaluations concurrently with a simulated driving task.[26] their results showed that although fixation duration did not change across cognitive levels, they could predict upcoming errors when it decreased just before an error was made in the arithmetic task.[26] the results obtained through the scene viewing studies have shown that information extracted during fixation affects the onset timing of the subsequent saccade essentially terminating that fixation.[27] another study showed that increased cognitive level of a scene viewing task resulted in longer duration of fixation.[27]the task design and the comparisons within subjects that were used in the current study make it unlikely for the target features to affect our results obtained for fixation duration. the efficiency of the information processing can be reflected in the participants’ task performance in terms of both the speed and accuracy of the responses.[24] according to our results, it seems that providing a correct response to the visual target requires longer time in the presence of a limited capacity of information processing or the quality of processing being degraded despite the presence of healthy oculomotor systems. the current study showed that varied levels of cognitive load changed individuals’ response errors and reaction times indirectly through changes in saccade latency. increased saccade latency predicts longer time requiring for getting the eyes on the desired target. if the allocated time duration between the onset of visual onset and providing response to the target is restricted, a delay in eye fixation on the target can further limit fixation duration before the subject submits the response to the visual target. our data showed that saccade latency can be used as an indicator of cognitive load, but also flags degraded efficiency of information processing which can demand longer fixation duration to protect accuracy of the subject’s response to the visual target. therefore, latencies of saccade and fixation can be used to monitor forecasted performance especially when both time and accuracy matter, for example, when driving. ethical approval all procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 helsinki declaration and its later amendments or comparable ethical standards. acknowledgements same data of the eye movement recorded for some participants attended in this study were used in another study by fadardi and abel (2018)[8] as the control data collected for task performance and eye movement reaction time including saccadic latency. financial support and sponsorship this work was supported by the university of melbourne. conflicts of interest no conflicting relationship exists for any author. references 1. simon o, mangin jf, cohen l, le bihan d, dehaene s. topographical layout of hand, eye, calculation, and language-related areas in the human parietal lobe. neuron 2002;33:475–487. 2. drewes j, vanrullen r . ongoing eeg oscillations and saccadic latency. j vis 2010;10:508–508. 3. drewes j, vanrullen r . this is the rhythm of your eyes: the phase of ongoing electroencephalogram oscillations modulates saccadic reaction time. j neurosci 2011;31: 4698–4708. 4. fadardi ms, abel la. the effect of cognitive load on saccadic charactristics. invest ophthalmol vis sci 2012;53:4865–4865. 5. roberts rj, hager ld, heron c. prefrontal cognitive processes: working memory and inhibition in the antisaccade task. j exp psychol gen 1994;123:374. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 403 visual performance under cognitive load; fadardi et al 6. stuyven e, van der goten k, vandierendonck a, claeys k, crevits l . the effect of cognitive load on saccadic eye movements. acta psychol 2000;104:69–85. 7. mahjoob m, anderson aj . contrast discrimination under task-induced mental load. vis res 2019;1:84–89. 8. fadardi ms, abel la. saccades under mental load in infantile nystagmus syndrome and controls. optom vis sci 2018;95:373–383. 9. simons dj. attentional capture and inattentional blindness. trends cogn sci 2000;4:147–155. 10. lleras c. path analysis. enc soc meas 2005;3:25–30. 11. bieg hj, bresciani jp, bülthoff hh, chuang ll. looking for discriminating is different from looking for looking’s sake. plos one 2012;7:e45445. 12. anderson aj, smyrnis n, noorani i, carpenter rh. modelling prosaccade latencies across multiple decisionmaking tasks. neuroscience 2021;452:345–353. 13. kapoula z, robinson d. saccadic undershoot is not inevitable: saccades can be accurate. vis res 1986;26:735–743. 14. walker r, mcsorley e. the parallel programming of voluntary and reflexive saccades. vis res 2006;46:2082– 2093. 15. halliday j, carpenter rh. the effect of cognitive distraction on saccadic latency. perception 2010;39:41– 50. 16. zhai x, enderle jd. visually guided horizontal saccades under the double-step paradigm. j biomed eng med devices 2016;10:1–7. 17. toyomura a, omori t. saccadic undershoot can be explained as a trade-off between accuracy and flight-time. proc isscie int symp stoch syst theory appl 2004;130– 134. 18. wang z, dell’osso l. being “slow to see” is a dynamic visual function consequence of infantile nystagmus syndrome: model predictions and patient data identify stimulus timing as its cause. vis res 2007;47:1550–1560. 19. dunn mj, margrain th, woodhouse jm, erichsen jt. visual processing in infantile nystagmus is not slow. invest ophthalmol vis sci 2015;56: 5094–5101. 20. salvia e, guillot a, collet c. the effects of mental arithmetic strain on behavioral and physiological responses. j psychophysiol 2013;27:173–184. 21. reddi b, asrress kn, carpenter rh. accuracy, information, and response time in a saccadic decision task. j. neurophysiol 2003;90:3538–3546. 22. reddi b, carpenter rh. the influence of urgency on decision time. nat neurosci 2000;3:827. 23. guyader n, malsert j, marendaz c. having to identify a target reduces latencies in prosaccades but not in antisaccades. psychol res prpf 2010;74:12–20. 24. van stockum s, macaskill mr, myall d, anderson tj. a perceptual discrimination task abnormally facilitates reflexive saccades in parkinson’s disease. eur j neurosci 2011;33: 2091–2100. 25. recarte ma, nunes lm. mental workload while driving: effects on visual search, discrimination, and decision making. j exp psychol appl 2003;9:119. 26. tsai yf, viirre e, strychacz c, chase b, jung t.p. task performance and eye activity: predicting behavior relating to cognitive workload. aviat space environ med 2007:78:b176–b185. 27. nuthmann a. fixation durations in scene viewing: modeling the effects of local image features, oculomotor parameters, and task. psychon bull rev 2017;24:370–392. 404 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 authors’ reply zisis gatzioufas, md, phd; mohamed elalfy, md; samer hamada, md department of ophthalmology, corneo-plastic unit, queen victoria hospital nhs trust, east grinstead, uk orcid: zisis gatzioufas: https://orcid.org/xxx j ophthalmic vis res 2020; 15 (1): 120–120 dear editor, we thank srirampur and balijepalli[1] for their interest in our case report. we completely agree with their important comment on the mechanism of hydrophilic intraocular lens opacification after keratoplasty, particularly following endothelial keratoplasty in which air or gas tamponade is performed. however, we reported a case of hydrophobic intraocular lens opacification after penetrating keratoplasty, and to the best of our knowledge, this was the first time that this type of intraocular lens opacification occurred. anterior segment surgeons should be aware of this rare complication, as advised by srirampur and balijepalli. references 1. srirampur a, balijepalli p. multiple pit defects in a foldable hydrophobic intraocular lens. ophthalmic vis res 2020;15:118–119. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. correspondence to: zisis gatzioufas md, phd. corneo-plastic unit, queen victoria hospital, holtye rd, east grinstead rh19 3dz, united kingdom. e-mail: zisisg@hotmail.com access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i1.5964 how to cite this article: gatzioufas z, elalfy m, hamada s. authors’ reply. j ophthalmic vis res 2020;15:120–120. 120 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i1.5964&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr letter to editor prevalence of visual impairment in school children reza gharebaghi1, md, mph, faao; fatemeh heidary1, 2, md, mph, phd, faao, fico 1international virtual ophthalmic research center (ivorc), tehran, iran 2department of ophthalmology, faculty of medicine, infectious ophthalmic research center, ahvaz jundishapur university of medical sciences, ahvaz, iran orcid: reza gharebaghi: https://orcid.org/0000-0002-4906-8597 fatemeh heidary: https://orcid.org/0000-0002-6558-6132 j ophthalmic vis res 2020; 15 (1): 123–124 correspondence to: fatemeh heidary, md, mph, phd, faao, fico. department of ophthalmology, faculty of medicine, infectious ophthalmic research center, ahvaz jundishapur university of medical sciences, ahvaz 61357, iran. e-mail: drfatemehheidari@yahoo.com received: 25-11-2018 accepted: 22-01-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i1.5968 dear editor, the recent published article by talebnejad et al sheds light on the prevalence of visual impairments and their associated determinants in school children in shiraz, south of iran.[1] we hope this imperative report spurs community action regarding the importance of population-based studies and provides basic information about the targeted prevention programs for children. of course, the results should be compared with the outcomes of the iranian state welfare organization (iswo) visual screening programs for children. we previously published two major studies in this field that derived from the same sample size of the current study but unfortunately were not cited in the recent publication. firstly, we included 262 eyes of iranian primary school children in shiraz between 6 and 13 years of age and found that intraocular pressure (iop) and central corneal thickness (cct) in healthy school children were positively correlated.[2] secondly, in another published study, we analyzed the relationship between different parameters of ocular response analyzer (ora) and corvis st (cst) in school-aged children in shiraz, and the relationship between parameters of these two instruments versus the iop measured by goldmann applanation tonometer (gat) was evaluated. we found the highest iop overestimation by cst and the lowest by cornealcompensated iop (iop-cc) compared with gat. overall, either low positive correlation or negligible correlation was found among the iop measurements by three instruments.[3] furthermore, there are several studies discussing the effect of race on the biometric data of ocular structures. this is an essential issue since recently in a metaanalysis, the authors showed that corneal thickness is thinner in children originating from mixed malayindian race than in most other locations.[4] lastly, a few publications have revealed that age may affect the ocular biometrics.[5] therefore, we would this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: gharebaghi r, heidary f. prevalence of visual impairment in school children. j ophthalmic vis res 2020;15:123–124. © 2020 journal of ophthalmic and vision research | published by knowledge e 123 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i1.5968&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr letter; gharebaghi and heidary suggest that the authors reiterate all measurements as a cohort analysis since almost five years have passed since the initiation of the study in 2015. references 1. talebnejad mr, nowroozzadeh mh, mahdaviazad h, khalili mr, masoumpour mb, keshtkar m, et al. the shiraz pediatric eye study; a population based survey of school age children: rationale, design and baseline characteristics. j ophthalmic vis res 2018;13:293– 300. 2. nejabat m, heidary f, talebnejad mr, salouti r, nowroozzadeh mh, masoumpour m, et al. correlation between intraocular pressure and central corneal thickness in persian children. ophthalmol ther 2016;5:235– 243. 3. salouti r, alishiri aa, gharebaghi r, naderi m, jadidi k, shojaei-baghini a, et al. comparison among ocular response analyzer, corvis st and goldmann applanation tonometry in healthy children. int j ophthalmol 2018;11:1330–1336. 4. farvardin m, heidary f, sayehmiri k, gharebaghi r, jabbarvand behrooz m. a comprehensive meta-analysis on intra ocular pressure and central corneal thickness in healthy children. iran j public health 2017;46:724– 732. 5. doughty mj, zaman ml. human corneal thickness and its impact on intraocular pressure measures: a review and meta-analysis approach. surv ophthalmol 2000; 44:367– 408. 124 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 letter idiopathic intracranial hypertension with normal cerebrospinal fluid pressure masoud aghsaei fard, md, fico department of ophthalmology, farabi eye hospital, tehran university of medical sciences, tehran, iran orcid: masoud aghsaei fard: https://orcid.org/0000-0003-4005-2967 j ophthalmic vis res 2019; 14 (4): 532–533 sir, i have read with enthusiasm the article published recently,[1] based on which i would like to raise several concerns: 1. it is unclear how the diagnosis of idiopathic intracranial hypertension was made. in idiopathic intracranial hypertension, the opening pressure should be high. based on this study, every patient with pale optic disc and normal lumbar puncture should be diagnosed as having idiopathic intracranial hypertension. the opening pressure of 18 cm h2o measured in this case report is not considered high. additionally, the position (supine or lateral decubitus) during the lumbar puncture was not disclosed in the published article. in a large study conducted to find the reference range for cerebrospinal fluid pressure in 472 children,[2] a threshold value of 28 cm h2o in the lateral recumbent position was set for high intracranial pressure. authors recommended that for children an opening pressure above 28 cm h2o should be considered as elevated intracranial pressure. another study also considered cerebrospinal fluid measures ≤ 28 cm h2o as ”normal” for most children.[3] the two case reports that the authors cited with normal cerebrospinal fluid pressure had other features of idiopathic intracranial hypertension such as papilledema, headache, and pulsatile tinnitus.[4] 2. the pale optic nerve thickness in this study was transformed confirming papilledema, which seems strange. in other words, the patient’s retinal nerve fiber layer optical coherence tomography (rnfl oct) values were 66 µm (in figure 3(b), 41 µm) and 54 µm in the text; based on the authors’ previous study, these were transformed to 400 and 560 µm thickness consistent with papilledema. no similar methods exist in the literature, except the authors’ previous article in the journal of contemporary medicine science.[5] if we accept this transformation in rnfl thickness, all optic atrophies with double hump appearance on rnfl oct such as glaucoma and ischemic optic neuropathies would have papilledema. 3. figure 1(c) had a very poor quality. the ganglion cell layer had artifacts and comparisons with figures 3(b) and 3(c) (posttreatment) are not reasonable and do not support their claim that gc atrophy has improved. 4. authors stated that asymptomatic mitochondrial mutation for leber’s hereditary optic neuropathy (lhon) could be present in general population, however, the patient in question had signs of optic neuropathy (i.e., optic atrophy). 5. spontaneous visual recovery is possible in lhon with 14,484 mutation, and therefore visual improvement in this patient could also be explained with the natural course of lhon. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. sajjadi h, poorsalman h. previously diagnosed leber’s hereditary optic neuropathy with clinical signs of idiopathic intracranial hypertension responsive to acetazolamide therapy. j ophthalmic vis res 2019;14:109–113. 532 © 2019 journal of ophthalmic and vision research | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5475&domain=pdf&date_stamp=2019-07-17 letter; fard 2. avery ra, shah ss, licht dj, seiden ja, huh jw, boswinkel j, et al. reference range for cerebrospinal fluid opening pressure in children. n engl j med 2010;363:891– 893. 3. avery ra. interpretation of lumbar puncture opening pressure measurements in children. j neuroophthalmol 2014;34:284–287. 4. suh sy, kim sj. iih with normal csf pressures? indian j ophthalmol 2013;61:681–682. 5. sajjadi f, mh khoshnevisan, jf doane, sajjadi h. new predictive value of optical coherence tomography analysis in the diagnosis of idiopathic intracranial hypertension. journal of contemporary medical sciences 2017, [s.l.],3, (10), date accessed: 08 oct. 2019. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. correspondence to: masoud aghsaei fard, md, fico. farabi eye hospital, tehran university of medical sciences, tehran 13366, iran. email: masood219@gmail.com received: 06-02-2019 accepted: 01-04-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i4.5475 how to cite this article: fard ma. idiopathic intracranial hypertension with normal csf pressure. j ophthalmic vis res 2019;14:532–533. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 533 https://knepublishing.com/index.php/jovr original article high prevalence of asthenopia among a population of university students hassan hashemi1,2, md; mohammad saatchi1, ms; abbasali yekta3, phd; babak ali3, ms hadi ostadimoghaddam4, phd; payam nabovati5, phd; mohamadreza aghamirsalim6, md; mehdi khabazkhoob7, phd 1noor research center for ophthalmic epidemiology, noor eye hospital, tehran, iran 2noor ophthalmology research center, noor eye hospital, tehran, iran 3department of optometry, school of paramedical sciences, mashhad university of medical sciences, mashhad, iran 4refractive errors research center, mashhad university of medical sciences, mashhad, iran 5rehabilitation research center, department of optometry, school of rehabilitation sciences, iran university of medical sciences, tehran, iran 6eye research center, tehran university of medical sciences, tehran, iran 7department of psychiatric nursing and management, school of nursing and midwifery, shahid beheshti university of medical sciences, tehran, iran orcid: abbasali yekta: https://orcid.org/0000-0003-4356-9064 hassan hashemi: https://orcid.org/0000-0002-2109-0856 abstract purpose: to determine the prevalence of asthenopia and its associated factors in a sample of university students in iran. methods: in this cross-sectional study, participants were selected using multistage cluster sampling. presence of at least one of the 10 symptoms—foreign body sensation, diplopia, blurred vision, eye swelling, dry eye, eye pain, difficulty in sustaining visual operations, decreased visual acuity, tearing, and photophobia—was considered as asthenopia. ocular examinations, including uncorrected/corrected visual acuity measurement, objective/subjective refraction, cover test, amplitude of accommodation (aa), and near point of convergence (npc) were performed. results: of the 1,462 students (mean age: 22.8 ± 3.1 years), 73% were women. the ageand genderstandardized prevalence was 70.9% (95% confidence interval [ci]: 68.3–73.5), 39.8% (95% ci: 36.4–43.1), and 19.7% (95% ci: 16.0–23.3) based on the presence of at least one, two, and three symptoms, respectively. the prevalence was significantly higher in females (p = 0.048), hyperopic students (p <0.001), and astigmatic participants (p < 0.001). the mean aa and npc were 9.7 ± 2.6 d and 10.2 ± 4.2 d (p = 0.008) and 7.0 ± 2.1 cm and 7.7 ± 3.9 cm (p < 0.001) in participants with and without asthenopia, respectively. multiple regression model revealed age (28–29 years), astigmatism, and npc as independent associated factors (odds ratios: 3.51, 1.61, and 0.91, respectively). conclusion: this study shows relatively high prevalence of asthenopia in university students. demographic factors and visual system disorders are important risk factors and timely correction of conditions may lead to decreased asthenopia. keywords: asthenopia; astigmatism; photophobia; prevalence j ophthalmic vis res 2019; 14 (4): 474–482 correspondence to: abbasali yekta, phd. department of optometry, school of paramedical sciences, mashhad university of medical sciences, mashhad 91838, iran. email: yektaa@mums.ac.ir received: 30-12-2017 accepted: 24-04-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i4.5455 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: hashemi h, saatchi m, yekta a, ostadimoghaddam h, nabovati p, aghamirsalim m, khabazkhoob m. asthenopia in university students. j ophthalmic vis res 2019;14:474–482. 474 © 2019 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5455&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr asthenopia among university students; hashemi et al introduction asthenopia is a general term used to define a group of somatic or perceptive symptoms that usually occur following computer work, reading, or other near visual activities.[1] headache, sore and/or itching eyes, blurred vision, epiphora, dry eye, double vision, photophobia, and foreign body sensation are the most common complaints, with several studies considering the presence of at least one of these symptoms as asthenopia.[2, 3] few studies have addressed the prevalence of asthenopia as compared with studies on other ocular conditions and diseases. however, there are reports of a prevalence of 12.4–32.2% in children below 18 years[4] to 57% in students below 30 years.[5] despite contradictory reports on the causes of asthenopia, epidemiological studies have identified three major groups of risk factors: visual disorders, such as refractive errors and accommodative dysfunctions;[6, 7] psychological factors such as daily stress and poor mental state;[8] and environmental factors such as low ambient lighting, nonstandard monitor brightness;[9] and long study periods. social networking with the resulting near work and increased duration of eye exposure to smartphones, laptop screen, and tablets and educational tasks and long studying hours at the graduate level have made students vulnerable to asthenopic symptoms. considering the importance of ocular health in the educational success and the interference of asthenopia with visual activities resulting in learning disorders and decreased quality of life, and because no study has already evaluated the prevalence of asthenopia in iranian university students, the present study was conducted to determine the prevalence of asthenopia and its associated risk factors in a sample of iranian university students. methods the present university-based, cross-sectional study was conducted in kazerun, south of iran, in 2017. multi-stage sampling was used to select the participants. there are four universities in kazerun and each university was considered a stratum. next, a list of all academic majors in each university was prepared, and each academic major was considered a cluster. in each university, a number of majors were randomly selected using a random number table in proportion to their share in the total number of majors of four universities. finally, a total of 27 majors were selected. after coordinating with the deputy of educational affairs of each university, the list of all students in each major was obtained and each student was assigned a unique code in a continuous manner. subsequently, proportional to the size of students in each major, some numbers were randomly selected from a table of random numbers. in the next step, students whose unique code matched the last two (or three) digits of the random numbers were selected. telephone numbers of the selected subjects were obtained from their universities; these students were contacted to invite them to participate in the study after explaining its objectives. refractive error was considered as the main outcome of the study. the prevalence of myopia was selected to reach a maximum sample size. based on similar studies[10, 11] and considering a prevalence of 41%, type i error of 0.05, precision of 0.04, and a sample size of 580 were estimated. with regard to the sampling method, a design effect of 2.5 was considered. after an addition of 10% non-response rate to the calculated sample size, the final sample size was 1,595 participants. examinations first, uncorrected visual acuity (ucva) was measured using snellen eye chart at 6 meters(m). following this, objective refraction was calculated using the auto-refractometer (topcon rm-8800; topcon corp., tokyo, japan), and the results were refined using the heine beta 200 retinoscope (heine optotechnik; herrsching, germany). next, subjective refraction was used to determine the best optical correction, and the best corrected distance and near visual acuities (bcvas) were recorded. in the next stage, binocular and accommodative examinations were performed according to the best optical correction. first, unilateral and alternate cover tests were conducted at 6 m and 40 cm, following which the magnitude of near and distance phoria was measured using the alternate cover test and prism bar. an accommodative target was used for the cover test, including one line above the bcva on the near and distance snellen charts. in the next stage, dander’s push-up method journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 475 asthenopia among university students; hashemi et al was used to monocularly measure the near point of accommodation (npa) using the royal air force rule (raf), with a line equivalent to the visual acuity of 20/25 as the accommodative target. the npa was subsequently converted to accommodative amplitude (aa) in diopters (d) by dividing 100 by npa. near point of convergence (npc) in cm was then measured by slowly moving the accommodative target (a character one line above the bcva) toward the participant’s eyes along the midline until the participant reported diplopia or the examiner observed fusion break. after completion of optometric examinations, cyclo-refraction was performed by instilling two drops of 1% cyclopentolate, separated by 5 min and repeating retinoscopy 30 min after the last drop. definition of asthenopia to be consistent with other studies, the presence of at least one of the ten symptoms—foreign body sensation, diplopia, blurred vision, eye swelling, dry eye, eye pain, difficulty in sustaining visual operations, decreased visual acuity, tearing, and photophobia—occurring during near visual activities was considered as asthenopia. moreover, the prevalence of asthenopia was determined based on the presence of two or three symptoms. the exclusion criteria included age > 40 years; unwillingness to participate in the study; history of intraocular surgery and ocular trauma; systemic conditions or diseases affecting accommodation and binocular vision including hormonal or metabolic diseases and conditions such as pregnancy, diabetes, and thyroid dysfunctions, and neurologic diseases such as myasthenia gravis and multiple sclerosis; the use of ocular or systemic medications affecting accommodation and binocular vision including cycloplegic drops, central nervous system stimulants, and phenothiazine derivates; strabismus, amblyopia; and bcva < 20/40 in either eye. statistical analysis the stata software version 11 (statacorp; college station, tx, usa) was used for data analysis. the prevalence of asthenopia was reported as percentage and 95% confidence interval (ci). to determine the associated risk factors of asthenopia, multiple logistic regression was used in a backward manner by running the survey analysis command of stata according to the presence of at least one symptom from the aforementioned asthenopic symptoms. the ageand gender-standardized prevalence of asthenopia was calculated based on the age and gender distribution of students in 2015 using direct standardization. variables evaluated in this study included age, gender, body mass index (bmi), years of study, anisometropia, astigmatism, spherical equivalent (se) of refraction, near phoria, aa, and npc. to determine the years of study and its effect on asthenopia, students were divided into two groups: < 2 years (four academic terms) and > 2 years. according to the world health organization (who) guidelines,[12] bmi was categorized as underweight (< 18.5), normal (18.5–24.5), and overweight (< 24.5). based on cycloplegic refraction, myopia and hyperopia were defined as ≤ 0.50 and > 0.50 d of se, respectively. anisometropia was defined as se difference ≥ 1.00 d between the eyes. due to the significant correlation of both eyes in aa (pearson’s correlation coefficient = 0.97), only the aa of the right eye was considered for statistical analysis. p < 0.05 was considered statistically significant. ethical considerations the ethics committee of the mashhad university of medical sciences approved the protocol of the study according to the declaration of helsinki. informed consent was obtained from all participants. the students were assured that their data would remain anonymous and confidential. results of the 1,595 invited individuals, 1,462 participated in the study. of these selected students with a mean age of 22.8 ± 3.1 years (range: 18–40 years), 73% were women. based on the presence of at least one, two, and three symptoms, the prevalence of asthenopia calculated to be 71.2% (95% ci: 68.4– 74.0), 40.6% (95% ci: 37.7–43.4), and 19.7% (95% ci: 16.3%–23.2%), respectively. table 1 presents the prevalence of asthenopia based on one, two, and three symptoms according to gender, age, se, astigmatism, bmi, academic term, near phoria, and anisometropia. as shown in table 1, the prevalence of asthenopia was significantly higher in females (p = 0.048), hyperopic students (p < 0.001), and 476 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 asthenopia among university students; hashemi et al participants with astigmatism (p < 0.001). the mean aa was 9.7 ± 2.6 d and 10.2 ± 4.2 d in participants with and without asthenopia, respectively (p = 0.008). the mean npc was 7.0 ± 2.1 cm and 7.7 ± 3.9 cm in asthenopic and non-asthenopic students, respectively (p < 0.001). figure 1 shows the prevalence of asthenopic symptoms: photophobia was the most common symptom (48.7%). table 2 presents the prevalence of asthenopic symptoms by gender. according to table 2, the prevalence of most of the asthenopic symptoms was higher in females than in the male students. table 3 presents the results of logistic regression model for associated risk factors of asthenopia. as seen in multiple regression model, age group of 28 to 29 years, astigmatism, and npc were independent associated risk factors of asthenopia with odds ratios of 3.51, 1.61, and 0.91, respectively. discussion the present study is the first of its kind to demonstrate the prevalence of asthenopia and its associated risk factors in students above 18 years of age in kazerun, south of iran. according to our findings and based on the presence of at least one symptom, the prevalence of asthenopia was calculated to be 71%, which is much higher than the results of a similar study (57%) conducted by han et al in chinese students with a mean age of 21 years.[5] moreover, another study showed a prevalence of 46% for asthenopia in indian computer operators with a mean age of 25 years.[1] aakre et al[10] and ostrovsky et al[11] evaluated the prevalence of asthenopia in regular computer users. the limited number of population-based studies, especially studies on students aged 18 to 30 years, makes it difficult to compare our results with similar studies. in other words, lack of studies on similar age groups; use of different criteria and outcomes, including eye strain and fatigue,[13] and evaluation of some occupations with more exposure to computers and monitors hinder the comparison of the results of the present study with other similar studies. our findings showed that based on at least two or three symptoms, the prevalence of asthenopia was much higher than that in the younger age groups in other studies (adolescents under 18 years). in a study by hashemi et al,[14] the prevalence of asthenopia based on at least two symptoms was 24% in adolescents aged 12 to 18 years, whereas our findings revealed a prevalence of 40% in the university students. considering the importance of students in individual and social achievements, timely diagnosis and treatment of this condition are essential. according to the conducted studies, adequate sleep, regular intake of vegetables, and a good mental frame play a crucial role in preventing asthenopia.[5, 15] therefore, considering the lifestyle of iranian students, their life in dormitories and lack of proper nutrition, a high prevalence of asthenopia is not unexpected in this group. another point related to the high prevalence of asthenopia is that given the various symptoms considered for its diagnosis, each symptom may be associated with another disease or condition; for example, headache is one of the most common symptoms in several diseases.[16] according to our findings, photophobia was the most common symptom in more than 48% of the cases, which is not consistent with the results of some studies that reported headache or tearing as the most common symptom of asthenopia.[4, 17] there exist several reasons for the sensitivity of eye to light; however, an underlying disease can also cause photophobia. moreover, ocular surface diseases may result in photophobia.[18] the high prevalence of photophobia in our study population is an alarm sign and warrants further investigation into its underlying reasons. based on these findings, the prevalence of asthenopia in women was around 8% and more than in men. there are contradictory results on the effect of gender; moreover, some studies have failed to find a significant effect of gender on asthenopia.[5, 19] contrary to our results, han et al[5] and agrawal et al[10] found no significant difference in the prevalence of asthenopia between men and women, whereas shima et al[20] and bahanderi et al[1] reported a higher prevalence of asthenopia symptoms in women. furthermore, except for foreign body sensation, dry eye, and decreased visual acuity, the prevalence of other symptoms was higher in women. different physiological structure and pain threshold as well as different lifestyles of boys and girls may significantly affect the odds of developing asthenopia and asthenopic complaints. our findings showed that the prevalence and odds of asthenopia increased significantly from 20 to 29 years but decreased thereafter. moreover, bahanderi et al[1] and maccoi et al[8] have reported aging journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 477 asthenopia among university students; hashemi et al table 1. the prevalence of asthenopia among 1,462 participants number of symptoms total number of subjects one or more p-value two or more three or more percent (95% ci) percent (95% ci) percent (95% ci) age sex standardized 70.9 (68.3–73.5) 39.8 (36.4–43.1) 19.7 (16.0–23.3) sex male 65.5 (60.8–70.2) 0.048 31.6 (26.7–36.5) 12.8 (9.8–15.8) 389 female 73.3 (70.5–76.1) 43.8 (41.1–46.6) 22.2 (18.6–25.9) 1,073 age group (year) 18–19 72.2 (66.9–77.9) 0.219 38.9 (30.5–47.3) 23.3 (17.6–29.1) 90 20–21 70.2 (65.5–75.0) 37.2 (32.3–42.1) 19.3 (13.5–25.0) 441 22–23 71.6 (67.4–75.8) 42.3 (38.2–46.4) 18.5 (13.8–23.2) 546 24–25 72.6 (66.8–79.4) 42.4 (35.7–49.2) 22.4 (16.4–28.5) 205 26–27 75.3 (64.8–84.8) 48.1 (31.6–64.5) 23.4 (11.5-35.3) 77 28–29 81.5 (66.2–96.9) 55.3 (41.2–69.3) 23.7 (14.9–32.5) 38 ≥ 30 58.4 (45.0–71.8) 29.2 (16.5–41.9) 13.8 (4.5–23.2) 65 refractive errors emmetropia 70.2 (62.9–71.0) <0.001 34.3 (29.5–32.9) 15.5 (10.5–20.5) 803 hyperopia 79.6 (73.9–78.7) 47.5 (44.8–50.1) 24.6 (20.3–28.9) 625 myopia 79.4 (53.7–99.9) 61.7 (35.4–88.0) 29.4 (8.2–50.5) 34 astigmatism no 68.5 (65.9–71.1) <0.001 36.7 (33.8–39.7) 16.9 (12.8–21.0) 1,030 yes 77.7 (73.0–82.4) 49.7 (45.0–54.4) 26.3 (23.2–29.5) 432 bmi underweight 72.7 (64.2–81.3) 0.774 40.8 (28.5–53.1) 21.0 (9.4–32.7) 147 normal 70.6 (66.9–74.4) 40.3 (38.2–42.4) 19.1 (16.2–22.0) 986 overweight 72.3 (68.2–76.4) 41.6 (34.9–48.4) 20.9 (16.3–25.5) 329 semester 1–4 (≤ 2 year) 72.4 (68.3–76.5) 0.374 39.3 (35.5–43.1) 20.0 (15.3–24.7) 709 > 4 (> 2 year) 70.3 (66.7–73.8) 41.8 (38.2–45.4) 19.5 (14.4–24.5) 753 near phoria no 70.5 (66.4–74.7) 0.141 40.4 (37.5–43.3) 19.2 (15.9–22.5) 974 exo 71.7 (68.3–75.2) 39.8 (36.7–43.0) 19.2 (13.8–24-7) 467 eso 86.8 (74.2–99.5) 60.5 (43.7–77.3) 34.9 (27.7–51.1) 38 hyper 57.1 (18.5–95.8) 14.3(8.2–46.8) 14.2 (8.2–46.7) 7 anisometropia no 70.9 (68.1–73.7) 0.283 40.0 (37.3–42.8) 19.3 (16.2–22.5) 1,409 yes 79.2 (63.3–95.1) 54.7 (34.7–74.4) 30.1 (16.2–44.1) 53 the presence of at least one of the 10 symptoms of foreign body sensation, diplopia, blurred vision, eye swelling, dry eye, eye pain, difficulty in sustaining visual operations, decreased visual acuity, tearing, and photophobia was considered as asthenopia. bmi, body mass index; ci, confidence interval; eso, esophoria; exo, exophoria as a determinant of asthenopia. several studies have confirmed age as one of the most important determinants of different ocular disorders. however, it is reported that in addition to age,[21, 22] the duration of computer use greatly affects the development of asthenopia. the bachelor’s level study is usually finished by 22 years of age, following which students start post-graduate courses. long years of academic studies and increased exposure to computers could explain the increased prevalence of asthenopia in subjects below 30 years. furthermore, the study population has an important role in explaining the relationship between age and the prevalence of asthenopia. for example, in a population-based study by schelini et al,[23] the highest prevalence of asthenopia was seen in the first two decades of life and its prevalence decreased significantly after the age of 40 years. 478 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 asthenopia among university students; hashemi et al table 2. prevalence of symptoms by gender symptom female (95% ci) male (95% ci) p-value eye pain 15.4 (12.4–18.5) 10.5 (7.8–13.2) 0.017 dry eye 7.5 (5.3–9.7) 5.6 (3.7–7.5) 0.211 eye swelling 6.4 (4.2–8.5) 2.5 (0.9–4.1) 0.004 blurred vision 23.6 (19.0–28.2) 17.4 (14.2–20.7) 0.012 diplopia 8.39 (6.0–10.7) 4.6 (2.9–6.3) 0.015 foreign body sensation 11.4 (8.7–14.2) 11.0 (7.9–14.2) 0.827 photophobia 51.8 (48.3–55.3) 40.3 (32.3–48.3) < 0.001 tearing 30.0 (25.2–34.7) 22.6 (16.5–28.7) 0.005 decreased visual acuity 2.1 (0.8–3.4) 2.5 (1.4–3.7) 0.627 ci, confidence interval figure 1. the prevalence of asthenopic symptoms in 1,465 students above 18 years in the city of kazerun. therefore, taking into consideration the repeated computer work and reading, a higher prevalence of asthenopia is expected in university students and those in academia. based on the available reports, the refractive status, especially astigmatism, is a crucial factor in developing asthenopia.[6, 19, 24] our findings showed that odds of asthenopia were 1.61 times higher in astigmatic subjects as compared with that in students without astigmatism. moreover, a population-based study in brazil showed that astigmatism was the most important risk factor associated with asthenopia.[23] similarly, kotegava et al[25] reported that proper and adequate correction of refractive errors decreased the prevalence of asthenopia and improved accommodative dynamics in the study population. similar results were reported by abdi et al.[26] our findings revealed no significant association between asthenopia and phoria. kaufmann et al[27] reported that it was difficult to draw a causal relationship between phoria and asthenopia for three journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 479 asthenopia among university students; hashemi et al table 3. simple and multi-variable logistic regression for the associated risk factors of asthenopia or unadjusted 95% ci p-value or adjusted 95% ci p-value sex female 1.44 1.01–2.05 0.041 male reference age group (year) 18–19 1.85 0.85–4.02 0.111 1.66 0.73–3.77 0.203 20–21 1.68 0.89–3.18 0.101 1.68 0.78–3.65 0.167 22–23 1.79 1.03–3.13 0.042 1.69 0.87–3.29 0.108 24–25 1.89 0.90–3.96 0.085 1.89 0.83–4.31 0.116 26–27 2.17 0.90–5.20 0.077 2.06 0.93–4.55 0.071 28–29 3.15 1.40–7.07 0.01 3.51 1.26–9.89 0.021 ≥ 30 reference reference refractive error emmetropia reference myopia 1.58 1.27–1.98 0.001 hyperopia 1.89 0.38–9.35 0.394 astigmatism no reference reference yes 1.6 1.24–2.06 0.002 1.61 1.22–2.13 0.003 bmi normal reference underweight 1.1 0.71–1.72 0.617 overweight 1.08 079–1.48 0.584 semester 1–4(≤ 2 year) reference > 4(> 2 year) 0.9 0.69–1.17 0.418 anisometropia no reference yes 1.58 0.584.14 0.337 near phoria no reference eso 1.06 0.79–1.42 0.671 exo 2.76 0.98–7.75 0.054 hyper 0.56 0.12–2.66 0.427 aa (diopter) 0.95 0.92–0.98 0.007 npc (cm) 0.91 0.87–0.96 < 0.002  0.91  0.86–0.97  0.008 aa, accommodative amplitude; bmi, body mass index; npc, near point of convergence; or, odds ratio 480 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 asthenopia among university students; hashemi et al reasons: lack of objective criteria for detecting asthenopia, non-recognition of the pathogenetic mechanism of the effect of phoria on asthenopia, and the presence of other conditions with similar symptoms such as dry eye, accommodative anomalies, and aniseikonia. results obtained from most studies suggest that prolonged computer work is an important risk factor in the development of asthenopia. for instance, han et al[5] reported that the odds of asthenopia were 21% higher in students who worked on computer every day as compared with those without daily use of computer. moreover, it has been reported that computer work for 6 h a day or 30 h a week has a strong association with asthenopia. one of the limitations of this study was that we did not evaluate near work duration, which we plan to consider in future studies. moreover, the possible organic causes of asthenopia were not assessed. although exophoria is a well-known determinant of asthenopia, its effect was not significant in our study, probably owing to the low number of participants suffering from this type of phoria. in conclusion, the present study demonstrated for the first time a high prevalence of asthenopia in iranian university students above 18 years as compared with the results of other similar studies, including those on subjects below 18 years. financial support and sponsorship this project was supported by mashhad university of medical sciences. conflicts of interest there is no conflict of interest. references 1. bhanderi dj, choudhary s, doshi vg. a communitybased study of asthenopia in computer operators. indian j ophthalmol 2008;56:51–55. 2. garcia-munoz a, carbonell-bonete s, cacho-martinez p. symptomatology associated with accommodative and binocular vision anomalies. j optom 2014;7:178–192. 3. ayanniyi aa, folorunso fn, adepoju fg. refractive ocular conditions and reasons for spectacles renewal in a resource-limited economy. bmc ophthalmol 2010;10:12. 4. vilela ma, pellanda lc, fassa ag, castagno vd. prevalence of asthenopia in children: a systematic review with meta-analysis. j pediatr (rio j) 2015;91:320–325. 5. han cc, liu r, liu rr, zhu zh, yu rb, ma l. prevalence of asthenopia and its risk factors in chinese college students. int j ophthalmol 2013;6:718–722. 6. wajuihian so. frequency of asthenopia and its association with refractive errors. afr vis eye health 2015;74:74–80. 7. wiggins np, daum km. visual discomfort and astigmatic refractive errors in vdt use. j am optom assoc 1991;62:680–684. 8. mocci f, serra a, corrias ga. psychological factors and visual fatigue in working with video display terminals. occup environ med 2001;58:267–271. 9. sanchez-roman fr, perez-lucio c, juarez-ruiz c, velezzamora nm, jimenez-villarruel m. [risk factors for asthenopia among computer terminal operators]. salud publica mex 1996;38:189–196. 10. agarwal s, goel d, sharma a. evaluation of the factors which contribute to the ocular complaints in computer users. j clin diagn res 2013;7:331–335. 11. ostrovsky a, ribak j, pereg a, gaton d. effects of jobrelated stress and burnout on asthenopia among high-tech workers. ergonomics 2012;55:854-862. 12. who expert consultation. appropriate body mass index for asian populations and its implications for policy and intervention strategies. lancet 2004;363:157–163. 13. vertinsky t, forster b. prevalence of eye strain among radiologists: influence of viewing variables on symptoms. ajr am j roentgenol 2005;184:681–686. 14. hashemi h, khabazkhoob m, forouzesh s, nabovati p, yekta aa, ostadimoghaddam h. the prevalence of asthenopia and its determinants among schoolchildren. j compr pediatrics 2017;8:e43208. 15. rocha le, debert-ribeiro m. working conditions, visual fatigue, and mental health among systems analysts in sao paulo, brazil. occup environ med 2004;61:24–32. 16. ahmed f. headache disorders: differentiating and managing the common subtypes. br j pain 2012;6:124–132. 17. mvitu mm, kaimbo wk. [manifestations of asthenopia in black subjects]. bull soc belge ophtalmol 2003;289:45– 49. 18. digre kb, brennan kc. shedding light on photophobia. j neuroophthalmol 2012;32:68–81. 19. abdi s, lennerstrand g, pansell t, rydberg a. orthoptic findings and asthenopia in a population of swedish schoolchildren aged 6 to 16 years. strabismus 2008;16:47–55. 20. shima m, nitta y, iwasaki a, adachi m. [investigation of subjective symptoms among visual display terminal users and their affecting factors–analysis using log-linear models]. nihon eiseigaku zasshi 1993;47:1032–1040. 21. stevens ga, white ra, flaxman sr, price h. global prevalence of vision impairment and blindness: magnitude and temporal trends, 1990–2010. ophthalmology 2013;120:2377–2384. 22. hashemi h, khabazkhoob m, yazdani n, ostadimoghaddam h, derakhshan a, soroush s, et al. the prevalence of refractive errors among iranian university students. iran j ophthalmol 2014;26:129–135. 23. schellini s, ferraz f, opromolla p, oliveira l, padovani c. main visual symptoms associated to refractive errors and journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 481 asthenopia among university students; hashemi et al spectacle need in a brazilian population. int j ophthalmol 2016;9:1657–1662. 24. daum km, good g, tijerina l. symptoms in video display terminal operators and the presence of small refractive errors. j am optom assoc 1988;59:691–697. 25. kotegawa y, hara n, ono k, arimoto a, mukuno k. [influence of accommodative response and visual symptoms on visual display terminal adult operators with asthenopia through adequately corrected refractive errors]. nippon ganka gakkai zasshi 2008;112:376–381. 26. abdi s, rydberg a. asthenopia in schoolchildren, orthoptic and ophthalmological findings and treatment. doc ophthalmol 2005;111:65–72. 27. kaufmann h, h. s. heterophorie und asthenopie. in: ru¨ssmann wgk, editors. strabismus: thieme;2012:119– 221. 482 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 original article oral vitamin d supplementation and clinical outcomes of intravitreal bevacizumab injection for macular edema secondary to retinal vein occlusions saeed karimi1,2, md; farhad parvizi2, md; amir arabi2, md; toktam shahraki2, md; sare safi3, phd 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2department of ophthalmology, torfeh medical center, shahid beheshti university of medical sciences, tehran, iran 3ophthalmic epidemiology research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran orcid: saeed karimi: https://orcid.org/0000-0002-3231-8414 abstract purpose: to evaluate the therapeutic response of retinal vein occlusion (rvo) to intravitreal bevacizumab (ivb) with and without concomitant vitamin d supplementation. method: seventy eyes of 68 patients with macular edema associated with branch retinal vein occlusion (brvo) and central retinal vein occlusion (crvo) received three monthly ivb injections. patients with serum 25-hydroxyvitamin d (25(oh) d) higher than 30 ng/ml were considered as the sufficient group. cases with serum 25(oh) d levels below 30 ng/ml were randomized into the treatment and control groups. the control group received 50,000 iu of oral vitamin d, weekly for two months. one month after the last ivb injection, best-corrected visual acuity (bcva) and central macular thickness (cmt) were measured and compared with the preinjection values. results: while 43 eyes (61.4%) of 42 patients had brvo, 27 eyes (38.6%) of 26 patients had crvo. in brvo patients, changes of cmt and bcva were not significantly different between the sufficient, control, and treatment groups (p = 0.58 and 0.64, respectively). in the crvo group, cmt reduction in the control group was significantly less than the sufficient and treatment groups (p = 0.048). in addition, improvement of bcva in the control group was significantly less (p = 0.036) than the sufficient and treatment groups. conclusion: oral vitamin d supplement therapy may improve anatomical and functional outcomes in patients with crvo and vitamin d deficiency. keywords: 25-hydroxyvitamin d; bevacizumab; insufficiency; intravitreal; macular edema, retinal vein occlusion j ophthalmic vis res 2022; 17 (3): 376–383 376 © 2022 karimi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i3.11575&domain=pdf&date_stamp=2019-07-17 vitamin d supplement and response to ivb in rvo ; karimi et al introduction retinal vein occlusion (rvo) is a major cause of vision loss worldwide. based on the location of vascular occlusion, rvo can be manifested as branch retinal vein occlusion (brvo), central retinal vein occlusion (crvo), or hemi-crvo.[1] in crvo, the blockage occurs in the main retinal vein, whereas a brvo is begun by an occlusion in smaller veins, mainly at arteriovenous crossovers through the retinal circulation. macular edema and macular ischemia are the main causes of visual impairment in rvo, which are more frequent and less responsive to treatment in crvo.[1] vitamin d is a nutritional supplement which plays an important role in various pathways in the body through the presence of its receptor in several tissues, including the bones, vascular myocytes, cardiac cells, hepatocytes, and immune cells. recently, the role of this vitamin in vascular system health has been established through various studies.[2] both animal models and human studies have shown a positive correlation between vitamin d insufficiency and hypertension, vascular events, and mortality.[3, 4] a few studies have evaluated the relationship between different kinds of rvo and vitamin d insufficiency.[1, 5, 6] the results of these studies suggest the role of vitamin d in preventing ocular vascular diseases. in the present study, in addition to the prevalence of vitamin d insufficiency in rvo cases, we assessed the effects of supplementing oral vitamin d on the efficacy of intravitreal bevacizumab (ivb) injections in rvo. correspondence to: saeed karimi, md. ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, no. 23, boostan 9 st., paidarfard st., pasdaran ave., tehran 16666, iran. email: dr.saeedkarimi@gmail.com received: 05-02-2021 accepted: 25-04-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i3.11575 methods the current prospective, interventional, singlecenter, randomized comparative study was carried out at a tertiary care center in tehran between march 2018 and february 2019. the study was approved by the research ethics committees of school of medicine, shahid beheshti university of medical sciences, tehran, iran. the study followed the tenets of the declaration of helsinki. written consent was obtained from all of the patients. patients with center-involving macular edema secondary to perfused brvo or non-ischemic crvo with an onset of less than three months prior were enrolled in the study. the diagnoses of rvo were made clinically by a single ophthalmologist (sk). a diagnosis of center-involving macular edema was made if the retinal thickness within central 1-mm of macula was >300 μm as shown on the optical coherence tomography (oct) image (spectralis oct, heidelberg engineering). the eyes received treatment if the bcva was between 20/40 and 20/320 using the snellen. the exclusion criteria were the following: age less than 18 years; patients on vitamin d supplementation or therapeutic diets; history of intravitreal anti-vegf injections for the studied eye in the last three months of enrolment; history of intraocular surgery on the studied eye other than uncomplicated surgery for senile cataract; eyes with proliferative diabetic retinopathy or diabetic macular edema; and patients with renal, hepatic, and skin disease or chronic alcoholism. all patients received ivb (avastin®) three times monthly. all injections were performed at the torfeh eye hospital. during the administration of the injections, ophthalmologists were masked to the details of the study groups. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: karimi s, parvizi f, arabi a, shahraki t, safi s. oral vitamin d supplementation and clinical outcomes of intravitreal bevacizumab injection for macular edema secondary to retinal vein occlusions . j ophthalmic vis res 2022;17:376–383. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 377 https://knepublishing.com/index.php/jovr vitamin d supplement and response to ivb in rvo ; karimi et al demographic data and clinical parameters including bcva and central macular edema (cmt) were measured for each subject. visual acuity measurements were obtained through the snellen chart examination by a trained optometrist who was masked to the study groups. before the first injection, 25(oh) d was measured in venous blood samples. patients whose measurements of 25hydroxyvitamin d revealed to be >30 ng/ml were considered as the vitamin d-sufficient group, while those with <30 ng/ml were randomly assigned to the control and the treatment groups through simple consecutive randomization. there were three groups: group 1 (serum vitamin d ≥ 30 ng/ml), group 2 (vitamin d-insufficient group treated with vitamin d), and group 3 (control group). the treatment group received 50,000 iu of vitamin d3 weekly for eight weeks. for patients with bilateral rvo and macular edema (two patients), both eyes were enrolled in the same study group. follow-up examination and oct imaging were performed one month after the completion of the ivb injection protocol. the mean changes in visual acuity and macular thickness were considered as primary and secondary outcomes, respectively. oral vitamin d supplementation was prescribed for the control group at the end of the study protocol. statistical analysis to present data, mean and standard deviation were used. chi-square and fisher exact tests were used to compare between qualitative data. t-test and anova (bonferroni for pairwise comparison) were used for comparing quantitative parameters among the three study groups. to measure the role of treatment on bcva and cmt, we used paired t-test analysis. the differences were considered as significant if p-value was <0.05. all statistical analyses were performed by spss (ibm corp. released 2017. ibm spss statistics for windows, version 24.0. armonk, ny: ibm corp.). results seventy eyes of 68 patients (55.7% male and 44.3% female) were enrolled in this study. the mean age of the patients was 62 ± 8 years. while 43 eyes (61.4%) of 42 patients were diagnosed with brvo, 27 eyes (38.6%) of 26 patients had crvo [figure 1]. the difference between the mean age of patients in the sufficient, control, and treatment groups was not statistically significant (mean difference = 2.11, p = 0.571, and 95% ci [0.65–5.28] for crvo, mean difference = 1.98, p = 0.305, and 95% ci [0.31–7.1] for brvo). the difference between the gender of patients and laterality of the affected eyes was also not statistically significant between these groups (p > 0.05). the mean age of brvo and crvo patients was 63.40 ± 7.49 and 58.85 ± 7.73 years, respectively, and the difference was statistically significant (mean difference = 5.81, p = 0.017, and 95% ci [3.69–9.37]) [table 1]. while 28 patients had a sufficient level of 25(oh) d before the initiation of treatment, 40 patients had vitamin d deficiency. the prevalence of vitamin d deficiency in our study was 58.8%. compared to the prevalence of vitamin d deficiency in iranian population (55%),[7] the prevalence of vitamin d deficiency in our rvo patients was not significantly different (p > 0.05). twenty-six eyes (60.4%) from the brvo group and fifteen (27.2%) eyes from the crvo group had insufficient levels of vitamin d. for both the groups, the prevalence of vitamin d deficiency was not significantly different from the reported prevalence among the iranian population. additionally, the levels of serum vitamin d were not significantly different between brvo and crvo patients (mean difference = 0.65, p = 0.25 and 95% ci [0.15–0.82]). there was no significant correlation between serum vitamin d levels and bcva or cmt at baseline [table 2]. the changes of cmt following three monthly ivb injections were statistically significant in all brvo subgroups. there were no significant differences in cmt changes among the “sufficient”, “control”, and “treatment” groups [table 3]. table 4 shows the changes of bcva following three ivb injections in brvo patients. the improvement of bcva in the “sufficient” and “treatment” groups were statistically significant, but for the “control” group, this improvement was not statistically significant (p = 0.179). changes of bcva were not significantly different among 378 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 vitamin d supplement and response to ivb in rvo ; karimi et al figure 1. flowchart of patient’s enrollment. ivb, intravitreal bevacizumab. table 1. characteristics of studied patients. parameter crvo p-value brvo p-value p-rvo sufficient control treatment sufficient control treatment age 60.5 ± 7.81 56.57 ± 5.06 58.38 ± 9.69 0.571*** 63.41 ± 6.94 65.5 ± 5.49 60.92 ± 9.81 0.305*** 0.017** 25(oh)d level 40.31 ± 12.74 18.3 ± 7.83 19.49 ± 6.32 <0.001*** 40.68 ± 15.76 23.65 ± 4.72 18.07 ± 8.49 <0.001*** 0.913** gender male 8 (66.7%) 6 (85.7%) 6 (85%) 0.461* 7 (44%) 5 (35.7%) 6 (50.0%) 0.761* female 4 (33.3%) 1 (14.3%) 1 (15%) 9 (56%) 9 (64.3%) 6 (50.0%) eye od 7 (58.3%) 2 (28.6%) 3 (37.5%) 0.405* 7 (41.2%) 8 (57.1%) 4 (33.3%) 0.452* os 5 (41.7%) 5 (71.4%) 5 (62.5%) 10 (58.8%) 6 (42.9%) 8 (66.7%) * according to chi-square test and fisher exact test; **according to t-test; ***according to anova (bonferroni for pairwise comparison); crvo, central retinal vein occlusion; brvo, branch retinal vein occlusion. the “sufficient”, “control”, and “treatment” groups (mean difference = 0.06, p = 0.64, and 95% ci [0.01–0.13]). three monthly ivb injections significantly decreased cmt in all crvo subgroups (p < 0.05). however, the decrement of cmt in the control group was less than the “sufficient” and “treatment” groups, and the difference among cmt changes in the crvo subgroups was statistically significant (p = 0.047) [table 5]. in crvo patients, improvement of bcva following three ivb injections was statistically significant in the “sufficient” and “treatment” subgroups (p < 0.05); however, in the “control” journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 379 vitamin d supplement and response to ivb in rvo ; karimi et al table 2. the correlation between vitamin d levels, bcva and cmt. baseline bcva in brvo eyes baseline bcva in crvo eyes baseline cmt in brvo eyes baseline cmt in crvo eyes vitamin d serum level pearson’s correlation –0.042 0.083 0.101 –0.022 p-value 0.715 0.685 0.541 0.741 bcva, best-corrected visual acuity; cmt, central retinal thickness; crvo, central retinal vein occlusion; brvo, branch retinal vein occlusion. table 3. changes of cmt following ivb in brvo subgroups. cmt brvo group p-value* sufficient treatment control baseline cmt 469.82 ± 139.2 520 ± 182.03 491.33 ± 165.93 0.578cmt at 3-month visit 355.88 ± 113.06 339.14 ± 101.87 366.83 ± 90.02 change of cmt –126.44 ± 128.17 –180.86 ± 178.25 –124.5 ± 175.9 p-value** <0.001 <0.001 0.007 *according to anova analysis; **according to paired t-test; cmt, central retinal thickness; brvo, branch retinal vein occlusion. table 4. the changes of bcva following three ivb injections in brvo subgroups. bcva (log mar) brvo group p-value** sufficient treatment control baseline bcva 0.6 ± 0.33 0.55 ± 0.45 0.57 ± 0.48 0.64bcva at 3-month visit 0.47 ± 0.34 0.29 ± 0.19 0.39 ± 0.28 change of bcva –0.14 ± 0.16 –0.26 ± 0.26 –0.17 ± 0.38 p-value* 0.03 0.0179 0.179 *according to paired t-test; **according to anova; bcva, best-corrected visual acuity; brvo, branch retinal vein occlusion. table 5. changes of cmt following three ivb injections in crvo subgroups groups. cmt crvo group p-value* sufficient treatment control baseline cmt 592.42 ± 272.63 575.14 ± 198.41 596.5 ± 248.69 0.047cmt at 3-month visit 413.58 ± 190.3 403.29 ± 190.92 455.75 ± 97.26 change of cmt –178.83 ± 216.64 –171.86 ± 112.69 –141.75 ± 290.98 p-value** 0.0012 0.0039 0.016 *according to anova analysis; **according to paired t-test; cmt, central retinal thickness; crvo, central retinal vein occlusion. 380 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 vitamin d supplement and response to ivb in rvo ; karimi et al table 6. improvement of bcva following three ivb injections in crvo subgroups. bcva (log mar) crvo group p-value* sufficient treatment control baseline bcva 0.94 ± 0.6 1.11 ± 0.69 1.1 ± 0.43 0.035bcva at 3-month visit 0.64 ± 0.4 0.69 ± 0.42 1.01 ± 0.31 change of bcva –0.3 ± 0.26 –0.42 ± 0.57 –0.09 ± 0.72 p-value** 0.042 0.0236 0.844 *according to paired t-test; **according to anova; bcva, best corrected visual acuity; crvo, central retinal vein occlusion. group, change of bcva was not statistically significant (p = 0.84). improvement of bcva in the “control” group was significantly less than the “sufficient” and “treatment” groups (p = 0.035) [table 6]. discussion in the present study, although the prevalence of vitamin d deficiency in patients with brvo and crvo was higher than the overall prevalence of vitamin d deficiency in the iranian population,[7] the difference was not statistically significant. we did not find significant correlations between serum vitamin d levels and their effect on the baseline bcva and cmt measurements in brvo and crvo patients. in the brvo subgroups, vitamin d supplement therapy did not have significant influence on anatomical and functional outcomes of the ivb injections. in crvo subgroups, however, vitamin d supplement therapy had significant beneficial effects on both anatomical and functional outcomes of the ivb injections. the changes of bcva and cmt following three ivb injections were lower in patients with crvo and vitamin d insufficiency who were not treated with oral vitamin d supplement therapy. vitamin d, whether as a nutritional supplement or as a hormone, has numerous roles to play.[8] it participates in the synthesis of many factors which are involved in various metabolic mechanisms other than calcium homeostasis. vitamin d insufficiency can be caused by limited uv exposure, limitations of dietary intake, and by numerous chronic skin and internal diseases. through its dependence on sunlight exposure and dietary habits, serum levels of vitamin d may be affected by some cultural and geographic issues.[9] recently, a positive correlation has been postulated between vitamin d insufficiency and the incidence of different vascular diseases. this correlation has been established for cardiac and cerebrovascular diseases, as well as hypertension.[10] both epidemiologic and observational studies have reported higher mortality due to vascular events in vitamin ddeficient patients, which may happen during winter and in regions with less uv-b exposure.[11] low serum vitamin d levels may be a risk factor for vascular diseases.[12] it is notable that systemic vascular diseases and retinal vascular occlusions have some risk factors in common. a non-classical function of vitamin d, an improvement in the vascular endothelial function, has been reported following vitamin d supplement therapy.[13] a meta-analysis reported that patients with type 2 diabetes mellitus and vitamin d deficiency have a higher risk of diabetic retinopathy.[14] additionally, it is believed that vitamin d plays a critical role in the modulation of the immune system. it has been suggested that 25(oh) d dampens the activation of cytokines and reduces the proliferation of inflammatory cells.[15] vitamin d has received attention for its role in reducing vascular events, regulating the reninangiotensin system and endothelial hemostasis, controlling coagulation, and promoting antiinflammatory properties.[16] the role of 25(oh) d deficiency in systemic vascular risks, endothelial homeostasis, and inflammatory conditions could possibly relate to the pathogenesis of rvo. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 381 vitamin d supplement and response to ivb in rvo ; karimi et al after diabetic retinopathy, rvo is considered as the most frequent retinal vascular disease.[17] macular edema secondary to venous occlusion is the most common cause of visual loss in rvo patients.[18] it can happen via inflammatory mechanisms, vascular endothelial growth factor production, or mechanical effects of increased intraluminal pressure. atherosclerotic and vascular risk factors, including hypertension and hyperlipidemia, have been established to be involved in rvos.[18] similarly, the role of inflammation in progression and complications of retinal diseases, such as rvo, has been recognized.[19] the potential role of thrombophilia in rvo has also drawn attention during recent years.[20] according to a recent study by epstein et al, vitamin d is deficient in 50% of crvo patients.[5] vitamin d deficiency had been previously reported in a case of crvo.[6] the results of a recent study on a subset of indian patients pointed toward the role of vitamin d in ocular vascular mechanisms and retinal vascular occlusion.[1] these studies have also suggested a seasonal variation for rvo. in addition, recently, a probable positive role has been postulated for short-term vitamin d supplementation in reducing inflammatory and oxidative damage of the vascular system.[21] to the best of our knowledge, this is the first study evaluating the role of vitamin d supplement therapy in anatomical and functional outcomes of ivb injections in rvo patients. for each rvo subgroup (brvo and crvo), the patients were categorized as vitamin d-sufficient versus -deficient. the anatomical effects of the ivb injections were statistically significant in all study groups. the improvement of bcva following three ivb injections were not statistically significant in patients with brvo or crvo along with vitamin d insufficiency who were not treated with oral vitamin d supplement therapy. additionally, in crvo subgroups, a positive correlation was observed between 25(oh) d supplementation and better anatomical and functional outcome of ivb injections. a small sample size is the main limitation of the present study. another limitation existed where serum vitamin d levels were not re-measured throughout the study to confirm the efficacy of supplementation therapy. finally, there may be some confounding factors such as different dietary intake of vitamin d among our patients along with seasonal variations during the study. future randomized clinical trials with larger sample sizes are needed to reveal the exact role of vitamin d in rvo patients. in summary, we observed that oral vitamin d supplement therapy significantly improved both the functional and anatomical outcomes of ivb injections in crvo patients with vitamin d insufficiency. patients receiving oral supplementation experienced more decrease in cmt and better improvement in bcva following ivb therapy, compared to the control group. oral vitamin d supplement therapy did not change the outcomes of ivb injections in the brvo cases. ethical approval all procedures performed in the study were in accordance with the 1964 helsinki declaration. this study was approved by the ethics committee of the ophthalmic research center at shahid beheshti university of medical sciences, tehran, iran. financial support and sponsorship none. conflicts of interest none. references 1. oli a, joshi d. serum vitamin d levels in indian patients with retinal venous occlusions. saudi j ophthalmol 2017;31:76–79. 2. deluca hf. overview of general physiologic features and functions of vitamin d. am j clin nutr 2004;80:1689s– 1696s. 3. weishaar re, simpson ru. vitamin d3 and cardiovascular function in rats. j clin invest 1987;79:1706–1712. 4. akin f, ayça b, köse n, duran m, sari m, uysal ok, et al. serum vitamin d levels are independently associated with severity of coronary artery disease. j investig med 2012;60:869–873. 382 journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 vitamin d supplement and response to ivb in rvo ; karimi et al 5. epstein d, kvanta a, lindqvist pg, vitamin d. vitamin d deficiency in patients with central retinal vein occlusion: a case control study. curr eye res 2017;42:448–451. 6. talcott ke, eliott d. central retinal vein occlusion associated with severe vitamin d deficiency. ophthalmic surg lasers imaging retina 2016;47:372–375. 7. vatandost s, jahani m, afshari a, amiri mr, heidarimoghadam r, mohammadi y. prevalence of vitamin d deficiency in iran: a systematic review and meta-analysis. nutr health 2018;24:269–278. 8. zittermann a, schleithoff ss, götting c, dronow o, fuchs u, kuhn j, et al. poor outcome in end-stage heart failure patients with low circulating calcitriol levels. eur j heart fail 2008;10:321–327. 9. li yc. vitamin d regulation of the renin-angiotensin system. j cell biochem 2003;88:327–331. 10. snijder mb, lips p, seidell jc, visser m, deeg dj, dekker jm, et al. vitamin d status and parathyroid hormone levels in relation to blood pressure: a population-based study in older men and women. j intern med 2007;261:558–565. 11. giovannucci e, liu y, hollis bw, rimm eb. 25hydroxyvitamin d and risk of myocardial infarction in men: a prospective study. arch intern med 2008;168:1174–1180. 12. targher g, bertolini l, padovani r, zenari l, scala l, cigolini m, et al. serum 25-hydroxyvitamin d3 concentrations and carotid artery intima-media thickness among type 2 diabetic patients. clin endocrinol 2006;65:593–597. 13. sugden ja, davies ji, witham md, morris ad, struthers ad. vitamin d improves endothelial function in patients with type 2 diabetes mellitus and low vitamin d levels. diabet med 2008;25:320–325. 14. luo ba, gao f, qin ll. the association between vitamin d deficiency and diabetic retinopathy in type 2 diabetes: a meta-analysis of observational studies. nutrients 2017;9:307. 15. yin k, agrawal dk. vitamin d and inflammatory diseases. j inflamm res 2014;7:69–87. 16. danik js, manson je. vitamin d and cardiovascular disease. curr treat options gastroenterol 2012;14:414– 424. 17. cugati s, wang jj, rochtchina e, mitchell p. ten-year incidence of retinal vein occlusion in an older population: the blue mountains eye study. arch ophthalmol 2006;124:726–732. 18. karia n. retinal vein occlusion: pathophysiology and treatment options. clin ophthalmol 2010;4:809–816. 19. yoshimura t, sonoda kh, sugahara m, mochizuki y, enaida h, oshima y, et al. comprehensive analysis of inflammatory immune mediators in vitreoretinal diseases. plos one 2009;4:e8158. 20. vieira mj, campos a, do carmo a, arruda h, martins j, sousa jp. thrombophilic risk factors for retinal vein occlusion. sci rep 2019;9:18972. 21. martins d, meng yx, tareen n, artaza j, lee je, farodolu c, et al. the effect of short term vitamin d supplementation on the inflammatory and oxidative mediators of arterial stiffness. health 2014;6:1503–1511. journal of ophthalmic and vision research volume 17, issue 3, july-september 2022 383 original article correction of retinal nerve fiber layer thickness measurement on spectral-domain optical coherence tomographic images using u-net architecture ghazale razaghi1, ms; masoud aghsaei fard2, md; marjaneh hejazi1,3, phd 1medical physics and biomedical engineering department, school of medicine, tehran university of medical sciences, tehran, iran 2department of ophthalmology, farabi eye hospital, tehran university of medical sciences, tehran, iran 3research center for molecular and cellular imaging, bio-optical imaging group, tehran university of medical sciences, tehran, iran orcid: ghazale razaghi: http://orcid.org/0000-0003-3121-4602 marjaneh hejazi: http://orcid.org/0000-0002-1823-2876 abstract purpose: in this study, an algorithm based on deep learning was presented to reduce the retinal nerve fiber layer (rnfl) segmentation errors in spectral domain optical coherence tomography (sd-oct) scans using ophthalmologists’ manual segmentation as a reference standard. methods: in this study, we developed an image segmentation network based on deep learning to automatically identify the rnfl thickness from b-scans obtained with sd-oct. the scans were collected from farabi eye hospital (500 b-scans were used for training, while 50 were used for testing). to remove the speckle noise from the images, preprocessing was applied before training, and postprocessing was performed to fill any discontinuities that might exist. afterward, output masks were analyzed for their average thickness. finally, the calculation of mean absolute error between predicted and ground truth rnfl thickness was performed. results: based on the testing database, sd-oct segmentation had an average dice similarity coefficient of 0.91, and thickness estimation had a mean absolute error of 2.23 ± 2.1 μm. as compared to conventional oct software algorithms, deep learning predictions were better correlated with the best available estimate during the test period (r2 = 0.99 vs r2 = 0.88, respectively; p < 0.001). conclusion: our experimental results demonstrate effective and precise segmentation of the rnfl layer with the coefficient of 0.91 and reliable thickness prediction with mae 2.23 ± 2.1 μm in sd-oct b-scans. performance is comparable with human annotation of the rnfl layer and other algorithms according to the correlation coefficient of 0.99 and 0.88, respectively, while artifacts and errors are evident. keywords: deep learning; optical coherence tomography; retinal nerve fiber layer j ophthalmic vis res 2023; 18 (1): 41–50 correspondence to: marjaneh hejazi, phd. medical physics and biomedical engineering department, university of medical sciences, tehran 1417613151, iran. e-mail: mhejazi@sina.tums.ac.ir received: 26-12-2021 accepted: 10-11-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i1.12724 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: razaghi g, aghsaei m, hejazi m. correction of retinal nerve fiber layer thickness measurement on spectral-domain optical coherence tomographic images using u-net architecture. j ophthalmic vis res 2023;18:41–50. © 2023 razaghi et al . this is an open access article distributed under the creative commons attribution license | published by knowledge e 41 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i1.12724&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr correction of rnfl measurement by ai; razaghi et al introduction treatment of retinal diseases can be greatly improved by early diagnosis and monitoring of optic neuropathies. glaucoma and other optic neuropathies can be diagnosed based on assessing the thickness of the retinal nerve fiber layer (rnfl).[1−−3]rnfl thickness can now be measured quantitatively with optical coherence tomography (oct) software which is a convoluted imaging technology. rfnl thickness is currently measured automatically by spectral domain oct (sdoct) using segmentation algorithms. however, despite improvements in sd-oct hardware and software, rnfl segmentation errors are still rather common. according to the literature, artifacts or segmentation errors can be found anywhere from 19.9% to 46.3% of sd-oct scans of the rnfl.[4, 5]there are several factors associated with these segmentation errors in oct images, which include image decentration, epiretinal membranes, long axial lengths, and poor visual acuity.[5] although manually correcting the segmentation errors is possible, accomplishing this in a busy clinical practice could be infeasible due to the lengthy time commitment.[6] sd-oct has been applied in the diagnosis and segmentation of rnfl throughout several recent studies that used deep learning (dl) models.[7]devalla et al developed a dl technique that allowed for more precise optic nerve head tissue segmentation than the manual method.[8] a higher level of accuracy (acc) was achieved by the algorithm as compared to manual segmentation performed by two graders. accordingly, this algorithm yielded 8.85 ± 3.40% and 9.01 ± 4.20% errors for rnfl thicknesses calculations, while between the two graders, 5.94 ± 2.30% errors were observed. thompson et al in their article demonstrated that glaucomatous eyes could be distinguished from healthy eyes by training a dl algorithm on raw sdoct b-scans.[9] with an area under the receiver operating characteristic (roc) curve of 0.96, the proposed algorithm is superior to the conventional rnfl thickness parameters used in the instrument’s printout (p < 0.001). in another study by ma et al,[10] u-net with residual block for rnfl thickness estimation was used in raw oct images. they achieved an acceptable correlation, and the dice similarity index was 0.92 for test samples. in order to quantify the thickness of the retinal nerve fiber layer on oct images for three test set groups, mariottoni et al[11] provided a dl segmentationfree method based on resnet34 that had been pre-trained on the imagenet dataset. the 2doct scan has been used without a training mask and any previous biomarker definition as input in segmentation-free approaches. also, medeiros et al[12] and an et al[13] obtained the average thickness directly without segmentation according to their network design on thickness maps and fundus images. the clinical relevance of examining trends in retinal layer thickness changes and retinal structure deformation is due to the fact that for some diseases, changes in rnfl thickness for a specific period are less than the axial resolution of oct. this thickness change cannot be determined by oct software, but dl is able to do so. therefore, dl-based methods let clinicians explore the disease progression in the early stages. accordingly, some studies have concentrated on segmenting more than one layer. fang et al used a hybrid convolutional neural network (cnn) model for segmenting nine retinal layer boundaries in age-related macular degeneration (amd) patients,[14] and pekala et al designed cnn in densenet architecture for retinal oct segmentation.[15] to reduce the segmentation error, we used a dl algorithm based on convolution to determine the average rnfl thickness in this study. our proposed method can be considered as a more robust method of rfnl thickness estimation than the conventional segmentation algorithms as dl segmentation according to our hypothesis, would provide more accurate measurements of rnfl thickness for images which have segmentation errors. to develop and evaluate a system that is reliable at measuring rnfl layer thickness, this study aims at developing and evaluating a dl system. with enough database of sd-oct images to prevent overfitting, dl models were trained on oct images to illustrate the algorithm’s acc and reliability in analyzing and quantifying the thickness of the rnfl. methods this study used dl to develop an algorithm for measuring rnfl thickness. figure 1 summarizes 42 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 correction of rnfl measurement by ai; razaghi et al our proposed workflow. the first step involved reducing speckle noise using a preprocessing method. cnns were then used to delineate rnfl contours. a morphological method was applied to remove any inappropriate patterns in segmentation results. finally, rnfl thickness was determined according to our dl rules. data collection from 90 left eyes and 62 right eyes of participants (age range of 20–80 years), sd-oct images of healthy and unhealthy (glaucomatous optic neuropathy) patients were collected. the heidelberg oct machine at the farabi eye hospital captured all of the data, which was anonymized to fulfill the human ethics criteria of the tehran university of medical sciences. all 500 images in the dataset were randomly divided into training (80%, 400 oct images) and validation (20%, 100 oct images) groups, and 50 oct images were used in the test group. pre-processing to prepare oct images for segmentation, we applied a preprocessing step after extracting each image. preprocessing was primarily focused on reducing the speckle noise. to minimize these image artifacts, morphological opening filters (square and kernel size 3×3) in opencv (version 4.5.1, https://opencv.org, gary bradsky 1999) were used. the image signal-to-noise ratio factor improved from 25 to 40 db as a result of this method. images must match the input size of a network in order to train it and make predictions on test data. therefore, images were resized to 256×256 pixels with zero padding. preprocessing becomes more crucial if the dataset contained a limited amount of data. in our study, reducing speckle noise allowed the network to learn useful information like rnfl boundaries efficiently. retinal nerve fiber layer segmentation after preprocessing the image, it is first necessary to segment rnfl accurately to measure the thickness of the fiber layer. an established image segmentation network, u-net, is used to segment rnfl accurately in this study. the u-net created by ronneberger et al[16] (https://lmb.informatik.unifreiburg.de/people/ronneber/u-net) has robust performance in the absence of adequate training data. the u-net has advantages in performing segmentation tasks. first, this model allows for simultaneously using global location and context. second, it performs better for segmentation tasks even with a few training images. another advantage is that u-net uses a loss function for each image pixel, which helps quickly identify individual cells within the segmentation map. u-net’s detailed network architecture is shown in figure 2. as input, x is passed to the network, and at the last convolution layer, a binary mask is emitted by the network that includes the rnfl region. the u-net architecture has skip connections to connect encoders and decoders. x’s resolution is downsized by a factor of two in the encoder module using max-pooling for the purpose of capturing contextual details at different resolution steps, and then by up-sampling using up-convolution, the resolution is restored in the decoder module, enabling precise localization. moreover, the architecture shows that the input images are passed through the model and then followed by a series of convolutional layers with the relu activation function. in the encoder architecture, we also have multiple convolutional layers with an increasing number of filters (16, 32, 64, 128, 256). we notice that, as we progress toward the decoder, the number of filters in the convolutional layers decreases along with a gradual upsampling of the following layers toward the top. the neural network was carried out with python programming language (python 3.5 software foundation, https://www.python.org/). in our u-net network, we used adam with a default learning rate as an optimizer and binary cross entropy as a loss function. the batch size was equal to 16 with 100 epochs, and we saved the network weights from the “best” epoch by checkpoint and earlystop function. the training images were manually segmented under the supervision of an expert ophthalmologist using labelme (http://labelme.csail.mit.edu) to create ground truth masks. with the rnfl oct images and their respective ground truth masks which were prepared by labelme, at the last step, the u-net model was trained and validated. we used our trained and validated model to predict the output of the rnfl images in the test set without the corresponding label. predictions were journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 43 correction of rnfl measurement by ai; razaghi et al figure 1. flowchart for steps in material and methods. compared with ground truth masks for analyzing and determining model operation on the test set. postprocessing the generated binary masks may contain gaps and speckles as a consequence of implementing the segmentation algorithm. morphological algorithms were applied as post-processing methods to fill the gaps. after applying edge detection filters such as the binary threshold or canny on binary masks to detect white objects from a black background, the ”findcountours” function in opencv can be used to find continuous contours. it looks for borders and pixels with similar intensities to identify contours. average thickness estimation following the post-processing phase, the average thickness of the rnfl was determined using the python environment and the euclidean distance transform (edt)[17, 18] approach. a binary digital image was subjected to the edt to determine the distance between each nonfeature (non-zero pixels) and each feature (zero pixels, i.e., rnfl contour). a numerical value is assigned to each binary image pixel by the edt method indicating how far the black pixel is from the nearest white pixel of the image. for the 2d cases with 256×256 pixels, the edt metric is fast enough to create a distance map for output binary masks. to find the centerline of the rnfl, we implemented the skeleton algorithm on edt outputs. skeleton is a thinning operation that reduces an object region in edt output to a matrix of one row. this matrix preserves the significant pixel information (maximum pixel value in edt results) of the rnfl region. as stated in the formulas below, the average thickness of rnfl is calculated according to eq. 2 and as it indicates the mean of maximum values are determined based on eq. 1. if a1, a2,...a𝑛 is the maximal distance values that were extracted by the skeleton algorithm from the edt result, to get the thickness diameter, the mean distance value calculated in eq. 1 was multiplied by two in eq. 2. in eq. 1 “n” is the total number of maximum values (“n” is equal to the number of columns in output mask). in eq. 2, f is the factor that depends on the 44 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 correction of rnfl measurement by ai; razaghi et al figure 2. summary of the u-net architecture. the network receives input x and generates a prediction mask. resolution of the oct system. in our study, the axial resolution was 2.8 μm. 𝑚𝑒𝑎𝑛 𝑜𝑓 𝑚𝑎𝑥𝑖𝑚𝑢𝑚 𝑣𝑎𝑙𝑢𝑒𝑠 = 𝑎1 + 𝑎2 + ⋯ + 𝑎𝑛 𝑛 (1) 𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑡ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 = 𝑚𝑒𝑎𝑛 × 2 × 𝐹 (2) performance metrics we used a variety of metrics to measure the oct segmentation model’s performance, including acc, sensitivity (sen), specificity (spe), and dice similarity coefficient (dsc). in the resulting binary mask, sen, and spe correspond to the percentages of correctly classified pixels. according to eq. 3 and eq. 4, sen and spe depend on pixels classification by the number of true positive (tp), false negative (fn), true negative (tn), and false positive (fp) pixels. the significant alert here is that >50% of the pixels in our output masks are black and are in the background class, so if the u-net model only predicted background correctly, the acc, spe, and sen are more than 0.5, and it can lead to a huge mistake. since dsc is a combination of sen and spe, it stands out more from the other metrics for measuring this task. 𝑆𝐸𝑁 = 𝑇𝑃 𝑇𝑃 + 𝐹𝑁 (3) 𝑆𝑃𝐸 = 𝑇𝑁 𝑇𝑁 + 𝐹𝑃 (4) the dsc is another established metric for comparing binary masks resulting from image segmentation with their ground truth counterparts. the equations of the dsc metric are written as: 𝐷𝑆𝐶 = 2 × 𝑆𝐸𝑁 × 𝑆𝑃𝐸 𝑆𝐸𝑁 + 𝑆𝑃𝐸 (5) figure 3 shows the dsc metric by an example. as shown in figure 3, the dsc index was calculated by multiplying the overlap (between the prediction and the ground truth) and dividing it by both areas (of the prediction and the ground truth). results to predict the average thickness of the rnfl, we developed a dl algorithm based on u-net and trained using sdoct b-scans. to compare algorithm results with the best estimate of rnfl average thickness determined by the ophthalmologist, dice coefficients and mean absolute errors (mae) were calculated. we have two steps for effective examination, the first step being the dl model evaluation, and the second being consideration of the thickness measurement algorithm performance. figure 4 shows some examples generated by the proposed methodology on the dataset validation, where it was observed that our u-net model was able to extract the boundary of rnfl at different thicknesses. to prove the validity of the proposed, the test set was used, and figure 5 shows the segmentation results for two samples in the test set. to evaluate quantitatively the u-net performance on the validation and the test sets, journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 45 correction of rnfl measurement by ai; razaghi et al figure 3. dice coefficient calculation formula. sen, spe, and dsc were utilized as evaluation metrics. table 1 lists the evaluation results obtained by using the proposed framework on validation and test sets. testing and validating images with the u-net model demonstrated a high level of performance. as shown in table 1, the dsc index between segmentation results and manual segmentation by an expert was 0.93, and for the test images, the dsc index was 0.91. in the second step, the average rnfl thickness resulting from the model and thickness determined by the conventional algorithm were compared with the reference rnfl thickness measured by the expert on the test images. a strong correlation was found between the dl segmentation estimates of rnfl thickness and the best measurement of rnfl thickness (pearson’s r = 0.996; p < 0.001), with an mae of 2.23 ± 2.1 µm. figure 6 shows the fluctuation of absolute error for the test images. in addition, the algorithm was not affected by other factors, such as gender or race. figure 7 presents a scatter plot between the u-net prediction thickness values and measured thickness values by an expert from 50 sd-oct bscans. based on the test data, a linear regression model is fitted with an r-squared value of 0.9919. as a result, the predicted values are highly linearly related to the measured values, showing that despite the small variance, the predicted thickness values are reliable. to demonstrate oct software function, average thicknesses resulting from conventional software were compared with the thicknesses which were estimated by an expert. figure 8 illustrates the relation between oct software thickness prediction and the best thickness value recognized by an ophthalmologist. a linear regression model fitted to the data yields an r-square of 0.8811 and mae was 9.12 ± 6.9 μm which has a significant error according to rnfl thickness in normal and abnormal oct images. discussion in the present study, we developed a segmentation dl algorithm capable of predicting rnfl average thickness from b-scans in this study. there was a strong correlation between algorithm estimates of rnfl average thickness and expert measurements of rnfl thickness. on normal images without artifacts, conventional software performed well, but dl-based segmentation estimated rnfl average thickness that is significantly closer to the ground truth values for rnfl thickness than conventional segmentation software. on the test set, the dice coefficient is 0.91, and the mae is 2.23 ± 2.1 μm in this study. several u-net-based models have recently been proposed with promising results for retinal layer segmentation. devalla et al developed drunet for retinal segmentation.[8] the resulting rnfl thickness provided by this algorithm had an error of 8.85 ± 3.40% and at 9.01± 4.20% when compared to each grader, while the graders had an error of 5.94 ± 2.30% between each other. thompson et al found an area under the roc curve of 0.96 vs 0.87 for the global peripapillary rnfl thickness (p < 0.001). ben-cohen et al detected four retinal boundaries using a combination of u-net’s fully convolutional network, sobel’s edge detection, and graph search.[19] the dice index in this study for rnfl was 0.95, and the mean difference for thickness was 1.12 pixels. also, the mean difference for oct explorer was 3.65 46 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 correction of rnfl measurement by ai; razaghi et al figure 4. u-net output on validation data. original image, manually segmented image, and output image, in that order. figure 5. u-net prediction for two samples of the test set. original image and u-net prediction. pixels. lf-unet,[20] u-net++,[21] and resu-net[22] are other models for segmentation of more than one layer in retinal images; dice scores were 0.83, 0.88, and 0.92, respectively, in comparison to our dice index that is equal to 0.91. ma et al proposed u-net with residual blocks and received 0.92 for dice when adding transfer learning to the model and r2 was 0.98 in this study, but we found 0.99 for dsc.[10] whereas prior sd-oct segmentation methods based on journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 47 correction of rnfl measurement by ai; razaghi et al table 1. dsc, spe, and sen value for u-net model on validation and test images. metric sen spe dice validation 0.94 0.93 0.93 test 0.93 0.90 0.91 sen, sensitivity; spe, specificity; dsc, dice similarity coefficient figure 6. thickness absolute error between prediction results and best measurement by the expert for each sample in the test set. mae for 50 samples is equal to 2.23 ± 2.1(μm).. figure 7. scatterplot illustrating the relationship between the prediction thickness value and best estimation thickness measurement by the expert for the test set. 48 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 correction of rnfl measurement by ai; razaghi et al figure 8. scatterplot illustrating the relationship between the conventional oct software and the best estimation thickness measurement by an expert for the test set. dl mostly focused on enhancing segmentation performance, our research demonstrates that efficient thickness estimate algorithms are also crucial. other studies that work with oct images received reliable results but u-net model is easier for clinical application because u-net does not have complexity and does not need much space in memory and gpu systems. the response of u-net is fast enough and results are accurate in comparison to conventional software. as you can see in figure 5, at least 15–20% of images have an unavoidable error in thickness estimation via conventional software. our findings imply that segmentation based on dl technique can offer reliable rnfl thickness estimations in both images with and without segmentation error by using u-net network and thickness measurement algorithm. we achieved mae 2.23 ± 2.1 μm that is less than axial resolution 2.8 μm for oct conventional algorithms. according to our hypothesis, the proposed method segmented rnfl similarly to ophthalmologists by a dsc score of 0.91. such a method could prove useful in clinical practice to determine rnfl thickness without the need to refine segmentation, thus avoiding the time-consuming process of segmentation. ethical considerations all procedures implemented in studies involving human participants were done in accordance with the ethical standards of the research ethics committees of school of medicine, tehran university of medical sciences under “ir.tums.medicine.rec.1398.827”. financial support and sponsorship none. conflicts of interest none. all authors read and approved the final manuscript. references 1. pierro l, gagliardi m, iuliano l, ambrosi a, bandello f. retinal nerve fiber layer thickness reproducibility using seven different oct instruments. invest ophthalmol vis sci 2012;53:5912–5920. 2. asrani s, essaid l, alder bd, santiago-turla c. artifacts in spectral-domain optical coherence tomography measurements in glaucoma. jama ophthalmol 2014;132:396–402. 3. liu y, simavli h, que cj, rizzo jl, tsikata e, maurer r, et al. patient characteristics associated with artifacts in spectralis optical coherence tomography imaging of the journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 49 correction of rnfl measurement by ai; razaghi et al retinal nerve fiber layer in glaucoma. am j ophthalmol 2015;159:565–576. 4. jammal aa, thompson ac, ogata ng, mariottoni eb, urata cn, costa vp, et al. detecting retinal nerve fibre layer segmentation errors on spectral domain-optical coherence tomography with a deep learning algorithm. sci rep 2019;9:1–9. 5. mansberger sl, menda sa, fortune ba, gardiner sk, demirel s. automated segmentation errors when using optical coherence tomography to measure retinal nerve fiber layer thickness in glaucoma. am j ophthalmol 2017;174:1–8. 6. shen d, wu g, suk hi. deep learning in medical image analysis. annu rev biomed eng 2017;19:221–248. 7. christopher m, bowd c, belghith a, goldbaum mh, weinreb rn, fazio ma, et al. deep learning approaches predict glaucomatous visual field damage from oct optic nerve head en face images and retinal nerve fiber layer thickness maps. ophthalmology 2020;127:346–356. 8. devalla sk, renukanand pk, sreedhar bk, subramanian g, zhang l, perera s, et al. drunet: a dilated-residual unet deep learning network to segment optic nerve head tissues in optical coherence tomography images. biomed opt express 2018;9:3244–3265. 9. thompson ac, jammal aa, berchuck si, mariottoni eb, medeiros fa. assessment of a segmentation-free deep learning algorithm for diagnosing glaucoma from optical coherence tomography scans. jama ophthalmol 2020;138:333–339. 10. ma r, liu y, tao y, alawa ka, shyu m-l, lee rk. deep learning–based retinal nerve fiber layer thickness measurement of murine eyes. transl vis sci technol 2021;10:21. 11. mariottoni eb, jammal aa, urata cn, berchuck si, thompson ac, estrela t, et al. quantification of retinal nerve fibre layer thickness on optical coherence tomography with a deep learning segmentation-free approach. sci rep 2020;10:1–9. 12. medeiros fa, jammal aa, thompson ac. from machine to machine: an oct-trained deep learning algorithm for objective quantification of glaucomatous damage in fundus photographs. ophthalmology 2019;126:513–521. 13. an g, omodaka k, hashimoto k, tsuda s, shiga y, takada n, et al. glaucoma diagnosis with machine learning based on optical coherence tomography and color fundus images. j healthc eng 2019;2019:1–9. 14. fang l, cunefare d, wang c, guymer rh, li s, farsiu s. automatic segmentation of nine retinal layer boundaries in oct images of non-exudative amd patients using deep learning and graph search. biomed opt express 2017;8:2732–2744. 15. pekala m, joshi n, liu tya, bressler nm, debuc dc, burlina p. deep learning based retinal oct segmentation. comput biol med 2019;114:103445. 16. ronneberger o, fischer p, brox t. u-net: convolutional networks for biomedical image segmentation. med image comput assist interv 2015;234–241. 17. kipli k, enamul hoque m, thai lim l, afendi zulcaffle tm, kudnie sahari s, hamdi mahmood m. retinal image blood vessel extraction and quantification with euclidean distance transform approach. iet image process 2020;14:3718–3724. 18. tang x, zheng r, wang y. distance and edge transform for skeleton extraction. ieee/cvf iccvw 2021;2136–2141. 19. ben-cohen a, mark d, kovler i, zur d, barak a, iglicki m, et al. retinal layers segmentation using fully convolutional network in oct images. rsip vision 2017;1–8. 20. lu d, heisler m, ma d, dabiri s, lee s, ding gw, et al. cascaded deep neural networks for retinal layer segmentation of optical coherence tomography with fluid presence. arxiv preprint arxiv:1912.03418. 21. zhou z, siddiquee mmr, tajbakhsh n, liang j. unet++: a nested u-net architecture for medical image segmentation. deep learn med image anal multimodal learn clin decis support 2018;11045:3–11. 22. matovinovic iz, loncaric s, lo j, heisler m, sarunic m. transfer learning with u-net type model for automatic segmentation of three retinal layers in optical coherence tomography images. 11th international symposium on image and signal processing and analysis (ispa) 2019;49–53. 50 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 editorial genetic basis of primary angle closure glaucoma: the role of collagens and extracellular matrix elahe elahi, phd department of biotechnology, college of science, university of tehran, tehran, iran orcid: elahe elahi: https://orcid.org/0000-0002-6897-2223 j ophthalmic vis res 2020; 15 (1): 1–3 glaucoma is a heterogeneous group of optic neuropathies characterized by a specific pattern of optic nerve degeneration and visual field loss that is usually accompanied by increased intraocular pressure (iop).[1] it is a major cause of irreversible blindness worldwide.[2] primary glaucoma is classified into three major forms based on the anatomy of the anterior chamber drainage angle of the eye and the age of onset: primary congenital glaucoma (pcg), primary open angle glaucoma (poag), and primary angle closure glaucoma (pacg).[1] in glaucoma patients with increased iop, the increase is thought to be mainly due to impaired drainage of aqueous humor from the anterior chamber.[3] the etiology of all forms of glaucoma includes a genetic component as evidenced by variable prevalence in different ethnic groups, observations on familial clustering, and results of pedigree and sib-pair studies. for pcg, which is usually a monogenetic mendelian disease, three causative genes have been identified.[4–7] poag and pacg are generally considered complex multifactorial disorders.[8] several poag-causing genes have been identified, but mutations in these account for disease in less than 10% of patients.[9–13] compared to the other forms of glaucoma, there is much less definitive genetic data pertaining to pacg. this likely reflects the contribution of multiple genetic and perhaps environmental factors that affect various anatomical and functional features associated with pacg. pacg is an important public health entity. it is estimated that 15.7 million individuals in the world are affected with pacg. it is projected that 21 million will be affected by 2020, and that pacg by that time will cause bilateral blindness in 5.3 million people.[14–16] most pacg patients are from asia, particularly china, mongolia, singapore, and india. ultimately, the defining feature of pacg in individuals with glaucomatous optic nerve damage is iridocorneal angle closure. recently, col18a1 which encodes collagen type xviii was identified as a gene that affects angle closure in patients of three unrelated families.[17] the inheritance pattern of angle closure causing mutations in col18a1 was autosomal dominant. it appears that mutations in this gene may cause angle closure in the fourth decade of life or later. furthermore, col18a1 mutations are not expected to be a common cause of angle closure-related phenotypes. the significance of having identified col18a1 as a potential pacg-causing gene lies in emphasis on the importance of collagens and the extracellular matrix in glaucoma pathology. in pursuit of identifying genes that contribute to pacg disease, association studies and candidate gene studies have been performed and the results of these have implicated possible roles for several genes.[18–25] however, these findings are not generally considered definitive, and putative roles of genes suggested by some studies were not confirmed in independent studies. factors known to be associated with pacg include hyperoptic refractive error, shallow anterior chamber, thick crystalline lens, short axial length, small corneal diameter, and narrow iridocorneal angle.[26–28] clearly, some of these also associate with each other. in an article published in this issue of the journal of ophthalmic and vision research, the authors relied on transcriptome data pertaining to eye anterior segment tissues to select five single nucleotide polymorphisms (snps) whose genotypes may be associated with pacg among patients of northeast iran.[29–31] interestingly, one of the snps for which an association with pacg was reported is positioned in a gene (fermt2) that © 2020 journal of ophthalmic and vision research | published by knowledge e 1 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i1.5930&domain=pdf&date_stamp=2019-07-17 editorial; elahi encodes a component of the ecm. results of an association study that included tens of thousands of patients and controls had also implicated the same gene with respect to pacg.[20] there exists accumulating evidence that implicates various collagens specifically and the extracellular matrix more generally in the pathogenesis of glaucoma.[7, 32–36] eight loci were identified in one or both of two recent large genome-wide association (gwa) studies on pacg patients, and col11a1 that encodes one of the alpha chains of type xi collagen was one of the genes identified in both of the studies.[18, 20] an snp in col1a1 was associated with increased risk of myopia in japanese and chinese individuals.[37, 38] a gwa study of pacg in a dog breed identified col1a2 as a susceptibility locus.[39] and of course, col18a1 was identified as a gene that affects iridocorneal angle closure in humans.[17] in addition to collagens, genes with roles in the extracellular matrix and also associated with glaucoma include mmp-9, mthfr, ltbp2, cyp1b1, and sparc. it has been suggested that inter-individual differences in tolerance to iop as reflected in glaucoma diagnosis with normal tension in some and ocular hypertension without glaucoma in others reflect variations in biomechanical properties of the extracellular matrix of relevant ocular tissues.[32] references 1. ray k, mukhopadhyay a, acharya m. recent advances in molecular genetics of glaucoma. mol cell biochem 2003;253:223–231. 2. thylefors b, negrel ad, pararajasegaram r, dadzie ky. global data on blindness. b world health organ 1995;73:115–121. 3. tamm er, braunger bm, fuchshofer r. intraocular pressure and the mechanisms involved in resistance of the aqueous humor flow in the trabecular meshwork outflow pathways. prog mol biol transl 2015;134:301–314. 4. souma t, tompson sw, thomson br, siggs om, kizhatil k, yamaguchi s, et al. angiopoietin receptor tek mutations underlie primary congenital glaucoma with variable expressivity. j clin invest 2016;126:2575–2587. 5. stoilov i, akarsu an, sarfarazi m. identification of three different truncating mutations in cytochrome p4501b1 (cyp1b1) as the principal cause of primary congenital glaucoma (buphthalmos) in families linked to the glc3a locus on chromosome 2p21. hum mol genet 1997;6:641– 647. 6. ali m, mckibbin m, booth a, parry da, jain p, riazuddin sa, et al. null mutations in ltbp2 cause primary congenital glaucoma. am j hum genet 2009;84:664–671. 7. narooie-nejad m, paylakhi sh, shojaee s, fazlali z, rezaei kanavi m, nilforushan n, et al. loss of function mutations in the gene encoding latent transforming growth factor beta binding protein 2, ltbp2, cause primary congenital glaucoma. hum mol genet 2009;18:3969–3977. 8. sakurada y, mabuchi f. advances in glaucoma genetics. prog brain res 2015;220:107–126. 9. stone em, fingert jh, alward wl, nguyen td, polansky jr, sunden sl, et al. identification of a gene that causes primary open angle glaucoma. science 1997;275:668– 670. 10. monemi s, spaeth g, dasilva a, popinchalk s, ilitchev e, liebmann j, et al. identification of a novel adult-onset primary open-angle glaucoma (poag) gene on 5q22.1. hum mol genet 2005;14:725–733. 11. rezaie t, child a, hitchings r, brice g, miller l, coca-prados m, et al. adult-onset primary open-angle glaucoma caused by mutations in optineurin. science 2002;295:1077–1079. 12. pasutto f, matsumoto t, mardin cy, sticht h, brandstatter jh, michels-rautenstrauss k, et al. heterozygous ntf4 mutations impairing neurotrophin-4 signaling in patients with primary open-angle glaucoma. am j hum genet 2009;85:447–456. 13. fingert jh, robin al, stone jl, roos br, davis lk, scheetz te, et al. copy number variations on chromosome 12q14 in patients with normal tension glaucoma. hum mol genet 2011;20:2482–2494. 14. bonomi l. epidemiology of angle-closure glaucoma. acta ophthalmol scand 2002;236:11–13. 15. quigley ha, broman at. the number of people with glaucoma worldwide in 2010 and 2020. brit j ophthalmol 2006;90:262–267. 16. cedrone c, mancino r, cerulli a, cesareo m, nucci c. epidemiology of primary glaucoma: prevalence, incidence, and blinding effects. prog brain res 2008;173:3–14. 17. suri f, yazdani s, chapi m, safari i, rasooli p, daftarian n, et. al. col18a1 is a candidate eye iridocorneal angleclosure gene in humans. hum mol genet 2018;27:3772– 3786. 18. vithana en, khor cc, qiao c, nongpiur me, george r, chen lj, et al. genome-wide association analyses identify three new susceptibility loci for primary angle closure glaucoma. nat genet 2012;44:1142–1146. 19. nongpiur me, khor cc, jia h, cornes bk, chen lj, qiao c, et al. abcc5, a gene that influences the anterior chamber depth, is associated with primary angle closure glaucoma. plos genet 2014;10:e1004089. 20. khor cc, do t, jia h, nakano m, george r, abu-amero k, et al. genome-wide association study identifies five new susceptibility loci for primary angle closure glaucoma. nat genet 2016;48:556–562. 21. wang ij, chiang th, shih yf, lu sc, lin ll, shieh jw, et al. the association of single nucleotide polymorphisms in the mmp-9 genes with susceptibility to acute primary angle closure glaucoma in taiwanese patients. mol vis 2006;12:1223–1232. 22. awadalla ms, thapa ss, burdon kp, hewitt aw, craig je. the association of hepatocyte growth factor (hgf) gene with primary angle closure glaucoma in the nepalese population. mol vis 2011;17:2248–2254. 23. awadalla ms, thapa ss, hewitt aw, craig je, burdon kp. association of enos polymorphisms with primary angle-closure glaucoma. invest ophthalmol vis sci 2013;54:2108–2114. 2 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 editorial; elahi 24. ayub h, khan mi, micheal s, akhtar f, ajmal m, shafique s, et al. association of enos and hsp70 gene polymorphisms with glaucoma in pakistani cohorts. mol vis 2010;16:18–25. 25. shi h, zhang j, zhu r, hu n, lu h, yang m, et al. primary angle closure and sequence variants within microrna binding sites of genes involved in eye development. plos one 2016;11:e0166055. 26. congdon ng, youlin q, quigley h, hung pt, wang th, ho tc, et al. biometry and primary angle-closure glaucoma among chinese, white, and black populations. ophthalmology 1997;104:1489–1495. 27. foster pj, alsbirk ph, baasanhu j, munkhbayar d, uranchimeg d, johnson gj. anterior chamber depth in mongolians: variation with age, sex, and method of measurement. am j ophthalmol 1997;124:53–60. 28. salmon jf. predisposing factors for chronic angle-closure glaucoma. prog retin eye res 1999;18:121–132. 29. yousefian a, shokoohi-rad s, abbaszadegan mr, morshedi rad d, zargari s, milanzadeh s, et al. primary angle closure glaucoma-associated genetic polymorphisms in northeast iran. j ophthalmic vis res 2019;15:45–52. 30. westra hj, peters mj, esko t, yaghootkar h, schurmann c, kettunen j, et al. systematic identification of trans eqtls as putative drivers of known disease associations. nat genet 2013;45:1238–1243. 31. consortium g. the genotype-tissue expression (gtex) pilot analysis: multitissue gene regulation in humans. science 2015;348:648–660. 32. huang w, fan q, wang w, zhou m, laties am, zhang x. collagen: a potential factor involved in the pathogenesis of glaucoma. med sci monitor basic res 2013;19:237–240. 33. vithana en, aung t, khor cc, cornes bk, tay wt, sim x, et al. collagen-related genes influence the glaucoma risk factor, central corneal thickness. hum mol genet 2011;20:649–658. 34. aihara m, lindsey jd, weinreb rn. ocular hypertension in mice with a targeted type i collagen mutation. invest ophthalmol vis sci 2003;44:1581–1585. 35. sawaguchi s, yue by, fukuchi t, abe h, suda k, kaiya t, et al. collagen fibrillar network in the optic nerve head of normal monkey eyes and monkey eyes with laser-induced glaucoma–a scanning electron microscopic study. curr eye res 1999;18:143–149. 36. suri f, yazdani s, elahi e. glaucoma in iran and contributions of studies in iran to the understanding of the etiology of glaucoma. j ophthal vis res 2015;10:68–76. 37. inamori y, ota m, inoko h, okada e, nishizaki r, shiota t, et al. the col1a1 gene and high myopia susceptibility in japanese. hum genet 2007;122:151–157. 38. zhang d, shi y, gong b, he f, lu f, lin h, et al. an association study of the col1a1 gene and high myopia in a han chinese population. mol vis 2011;17:3379–3383. 39. ahram df, cook ac, kecova h, grozdanic sd, kuehn mh. identification of genetic loci associated with primary angle-closure glaucoma in the basset hound. mol vis 2014;20:497–510. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i1.5930 how to cite this article: elahi e. genetic basis of primary angle closure glaucoma: the role of collagens and extracellular matrix. j ophthalmic vis res 2020;15:1–3. journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 3 https://knepublishing.com/index.php/jovr perspective eye: the hard-hit victim of covid-19 pandemic aman gaur1, mbbs, ms; prathama sarkar2, mbbs, ms, dnb 1vardhman mahavir medical college & safdarjung hospital, new delhi 2deen dayal upadhyay hospital, new delhi orcid: aman gaur: http://orcid.org/0000-0002-7980-6300 prathama sarkar: http://orcid.org/0000-0002-1152-7858 abstract the covid-19 pandemic has brought the entire world to a standstill. wearing of mask and time-to-time sanitization have become a customary daily practice. additionally, as the outdoor activities and movements have been curtailed, concept of work from home is being widely adopted. hence, the screen exposure time has considerably increased. all these conditions have directly or indirectly impacted the health of eye. this article emphasizes on the repercussions of this pandemic on eye health. it also focuses on the precautions that may be taken to prevent them as well as some solutions to manage them. keywords: kwd j ophthalmic vis res 2022; 17 (2): 290–295 introduction the covid-19 pandemic since the end of year 2019 has not only forced the entire world into lockdown but it has also tremendously changed the way we live and work. this has given rise to various health concerns. eye problems amidst this crisis is no more a mere possibility. but rather it has now become a reality. in this covid era, apart from sars-cov-2 viral conjunctivitis, other eye-related problems are also correspondence to: aman gaur, mbbs, ms. cghs specialist wing & department of ophthalmology, vardhman mahavir medical college & safdarjung hospital, ansari nagar west 110029, new delhi. e-mail: gaur.aman@gmail.com received: 05-06-2021 accepted: 28-12-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i2.10805 on a rise due to sudden changes in ergonomics. as nonessential outdoor activities are being avoided, most institutes and office spaces have been abandoned and work from home has become a common practice. conference meetings and teaching sessions have been replaced by web conferencing. with increased dependency on digital platforms, our screen exposure time has also increased. this has resulted in sudden upsurge in patients complaining of dry eyes and eyestrain. incessant use of sanitizers and disinfectants is giving rise to yet another problem of sanitizer aerosol-driven ocular surface disease (sadosd).[1] also, reckless use of steroids in the management of covid may predispose these patients to this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: gaur a, sarkar p. eye: the hard-hit victim of covid19 pandemic. j ophthalmic vis res 2022;17:290–295. 290 © 2022 gaur and sarkar . this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i2.10805&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr repercussions of covid-19 pandemic on eye health; gaur and sarkar opportunistic infections,[2–5] including rhino–orbital mucormycosis[6–10] which is a serious ophthalmic concern. since most patients are opting for telemedicine, conducting direct eye examination and other investigations now have a limited role to play. hence, it has become imperative to know about the changing pattern of eye diseases in the population to deliver the best possible care under these limitations. in this article, the authors have attempted to provide the most up-to-date information regarding the new emerging pattern of eye diseases during the covid-19 pandemic which may be helpful to ophthalmologists while providing eye consultations. few common eye problems which may arise as a result of this pandemic are discussed below. viral conjunctivitis conjunctivitis may either be the first presentation in patients infected with novel covid-19[11, 12] coronavirus or it may be associated with respiratory illness.[13–16] in the “report of the who–china joint mission on coronavirus disease 2019 (covid�19),” conjunctival congestion was reported in 0.8% of 55,924 laboratory-confirmed covid-19-positive patients as per data collected in the period between february 16 and 20, 2020.[17] similarly, a meta-analysis of three studies from china including 1167 patients reported an overall rate of conjunctivitis as 1.1%. the rate of conjunctivitis was higher in severe (3%) as compared to non-severe (0.7%) covid-19 patients with an odds ratio of 3.4.[18] however, a systematic review which included 11 published articles analyzing 252 sars-cov2 patients infected globally reported a variable prevalence of conjunctivitis ranging between 0 and 32%, although no meta-analysis was performed. altogether, 17 patients had conjunctivitis of which three were tested positive for tear pcr and 14 had negative-tear pcr.[19] “pink eye” due to covid-19 may present like any viral conjunctivitis. in a study conducted at a tertiary care hospital in wuhan, out of 121 patients with confirmed covid-19, 8 patients (6.6%) showed ocular symptoms which included itching (62.5%), redness (37.5%), tearing (37.5%), discharge (25%), and foreign body sensation (25%).[13] there was no statistical correlation of ocular findings with duration of illness.[13] a study from hubei province in china reported ocular symptoms in 12 out of 38 covid-19-positive patients with signs including hyperemia, chemosis, and epiphora. about one-third cases with ocular signs were observed to have severe covid-19 manifestations. patients with ocular manifestations had a higher white blood cell and neutrophil count along with higher levels of procalcitonin, c-reactive protein, and lactate dehydrogenase as compared to patients without ocular complaints.[14] a case study from shenzhen, china reported a patient who presented with bilateral conjunctivitis on day 13 of illness having complaints of redness, foreign body sensation, and tearing in both eyes without any blurring of vision.[15] on slit-lamp examination, moderate conjunctival injection was noticed with watery discharge and inferior palpebral follicles. bilateral preauricular lymph nodes were tender and palpable. patient showed improvement in ocular signs and symptoms from day 15 of illness on ribavirin eye drops with complete resolution of symptoms by day 19. conjunctival swabs collected on day 13, 14, and 17 of illness were positive for sars-cov-2 on rt-pcr which became negative on day 19. this suggests a potential of disease transmission during the course of conjunctivitis. the ct (cycle threshold) value for detection of sars-cov-2 in tear rt-pcr however showed a rising trend with progression in duration of illness, indicating a decrease in tear viral load.[15] the first case of hemorrhagic conjunctivitis with pseudo membrane in covid-19 patient was reported from france, where ocular manifestations like conjunctival congestion and watery discharge were first noted at day 17 of systemic illness.[16] direct microscopy/culture of conjunctival swabs and scrapings were done which ruled out any bacterial, chlamydial, and other viral etiology (like herpes and adenovirus). ocular condition worsened by day 19, with occurrence of petechiae, follicles, tarsal hemorrhages, chemosis, and formation of a yellowish white pseudo membrane in the lower lids. examination under fluorescein staining revealed superficial punctate keratitis. rtpcr of conjunctival swab and scrapings on day 20 was negative for sars-cov-2. daily debridement of membrane was done while patient was started on azithromycin and low-dose dexamethasone, journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 291 repercussions of covid-19 pandemic on eye health; gaur and sarkar resulting in improvement of signs and symptoms from day 21 to day 26.[16] furthermore, conjunctivitis can either be the first or only manifestation of covid-19. this has been highlighted in a case series from italy where four middle-aged patients (three male and one female) who had recent history of travel to a region with high number of covid-19 cases presented with acute conjunctivitis.[11] having a high index of suspicion based on their travel history, nasopharyngeal swabs were taken and sent for rt-pcr which confirmed sars-cov-2. they were advised self-quarantine and prescribed topical antibiotics with symptomatic treatment. on follow-up none of them complained of any fever, malaise, or respiratory illness. in another case report, a 27-year-old male from argentina who had redness and foreign body sensation in one eye took telephonic consultation from an ophthalmologist. he had lid edema in the same eye with moderate conjunctival hyperemia. there were no systemic complaints at the time of presentation but 12 hr later he developed fever, headache, cough, and severe dyspnea. he was tested positive for sars cov-2 on rt-pcr of nasopharyngeal swabs.[12] thus, there are no hallmark clinical features of covid-19 conjunctivitis. watering, itching, dry eyes, and blurring of vision are common presenting symptoms, while major clinical signs include photophobia, conjunctival congestion, chemosis, follicles and preauricular lymphadenopathy.[20] definitive diagnosis can be established by detection of virus in conjunctival swab samples via rt-pcr.[21] however, reported positivity rate for sars cov-2 in conjunctival swab is as low as 5%.[15] few studies have also reported a positivity rate of 2.5%.[13, 22] hence, diagnosis remains mostly presumptive, in patients with confirmed covid-19 infection on rt-pcr of nasopharyngeal swabs. close examination should be avoided as much as possible in such patients and follow-up should preferably be done through telemedicine. while examining these patients, all standard precautions and safety guidelines as recommended by american academy of ophthalmology[23] should be followed. slit lamps should be equipped with breath shields or slitlamp barriers and talking to the patient during examination should be better avoided or kept minimal.[23] since viral shedding may persist for a prolonged period (longest duration reported in one study is 37 days[24]), aao recommends that a repeat rtpcr test should be done prior to nonemergency procedures if conducted within six weeks of diagnosing covid-19 infection.[23] in emergency cases, if patient is covid-19positive or status is unknown, use of n95 masks, gowns, face shields, and goggles should be considered. similarly, patients should wear surgical mask during the procedure.[23] sanitizer aerosol-driven ocular surface disease (sadosd) apart from infection, another common possible cause of conjunctivitis in the covid era can be the frequent use of sanitizers and hand rubs. this has been discussed in a case report where 26year-old female complained of recurrent episodes of redness, irritation, and burning sensation in her eyes over past few weeks. on enquiring about any recent change in cosmetics or toiletries she admitted to hourly use of hand sanitizer spray. the authors also reported that 60% of their teleconsultations had been for eye redness, of which only about one-fourth was infective, rest being nonspecific. about 40% were related to healthcare workers.[1] abhr (alcohol-based hand rub)-induced conjunctivitis may be attributable to associated ocular allergy or desiccation stress induced on ocular surface due to the dehydrating property of alcohol.[1] also, aerosolized chemicals from sanitizers and disinfectants can adversely affect ocular surface and precorneal tear film.[25] some preventive measures which can be taken to protect eyes from harmful effects of aerosolized chemicals include judicious use of sanitizers and other disinfectants and ensuring proper ventilation through doors/windows. while spraying, the airconditioning should be turned off, the bottle nozzle of sanitizer should be below eye level, and eyes to be closed. hyaluronate-based lubricants should preferably be used for problems related to ocular discomfort and tear film.[1] mask and dry eye wearing a face mask is becoming the current standard. masks may, however, also cause 292 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 repercussions of covid-19 pandemic on eye health; gaur and sarkar problems such as intermittent dry eyes,[26] where patient may complain of burning and stinging in eyes after prolonged wearing of face mask. with an increase in the use of oxygen concentrators and approval of cpap machines in covid-19 patients with respiratory difficulty, there is also a concern regarding rise in the incidence of dry eyes.[26] continuous flow of exhaled air due to leakage through the top of the face/cpap/oxygen masks is directed straight to our eyes, which can accelerate the evaporation of natural tears. this may cause eye irritation and increased desiccation stress, resulting in inflammation. hence, promoting normal tear film development and control of inflammation may become vital to prevent dry eyes. patients experiencing dry eye symptoms from extended mask wear should take breaks every few hours whenever feasible to take off the mask and reapply lubricant eye drops. gel-based lubricants can provide long-term symptomatic relief, mitigating the need for frequent instillation of eye drops. hyaluronic acid-based lubricants can also be used as they not only increase tear retention time but also suppress inflammation.[27] preference should be given to the masks with a pliable nose-wire, with proper fitting of the shape of the wire to prevent air being directed toward the eyes.[26] masks may be taped at the top to stop the upward airflow, while taking care that the lower lid movement is not affected.[26] digital eyestrain/computer vision syndrome implementation of lockdown worldwide has compelled people to work from home, even teach and study from home. as outdoor recreational activities are forbidden, people are resorting to digital entertainment. this has resulted in an increased screen exposure time. eye strain, dry or itchy eyes, headache, blurred vision, physical and mental fatigue are common problems today, even for those who never had them, which is also referred to as computer vision syndrome.[28] to combat these problems, the following steps are advised. increasing the blink rate the normal spontaneous blinking rate of a person varies from 12 to 15/min.[29] however, under relaxed conditions, it has been found up to 22 blinks/min.[21] blink rate may decrease significantly while reading a book or seeing an electronic device.[30] less blinking leads to evaporation of tears leading to make the eyes lose moisture and become dry. thus, the strain on eyes tend to increase. hence, the patient should be advised to blink more during the period of screen work. artificial tears can also be prescribed to reduce the complaint of dryness. frequent breaks the 20-20-20 rule should be followed when spending a lot of time looking at a screen. look 20 feet away for 20 s every 20 min when engaged in screen-related work.[31] proper lighting of surroundings an equally balanced lighting in the working area not only provides visual comfort but also serves to minimize eyestrain.[28] excessive sunlight can be filtered with window blinds and tinting.[28, 31] several workplaces have a set of very intense fluorescent lights overhead; in other situations, some of them may be shut off or substituted with lamps fullspectrum or replaced with daylight. lamps with incandescent bulbs which contain mostly red light (“warmer color”) can also be helpful in preventing eyestrain.[28] minimizing glare use of screen filters on computer helps to reduce the reflection, improve contrast, thereby relieving eyestrain.[28, 31] wearing the right glasses uncorrected hypermetropia, astigmatism, and presbyopia can further contribute to development of eyestrain while using a digital display device.[31] hence, a proper refractive workup and correction is required which should include cycloplegic refraction. contact lenses may further aggravate the symptoms of ocular discomfort caused due to dry eye.[28] it is advised that people wearing contact lenses may switch to glasses when working in front journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 293 repercussions of covid-19 pandemic on eye health; gaur and sarkar of the computer screen to prevent the irritation and dry eye caused by prolonged use of lenses. progressive lenses may be preferred in presbyopes who do jobs related to prolonged computer work. use of base in and base up prisms can also relieve digital eyestrain by decreasing the effort required in elevation and convergence.[28] adjusting the display settings on the screens you use this includes display devices like television, computer, and mobile devices. increasing the type size on computer prevents from leaning over and squinting into the screen. according to a study by kochurova et al, text size on computer/laptop screen should be at least twice the visual acuity of user for comfortable reading.[32] screen should be kept clean from dust and fingerprints.[31] computer display settings like brightness and contrast can be adjusted. correct ergonomics it is especially important to maintain sufficient distance from the monitor to prevent the sideeffect of prolonged exposure. one should view the smartphone at an angle below the eyebrows and hold the device at a comfortable distance with larger font and brighter screen. computer users should maintain 20 to 28 inches distance from the monitor with eye level 4 to 5 inches above the center of the screen.[31] covid-associated mucormycosis covid patients are at a higher risk of developing opportunistic infections,[2−−5] including rhino– orbital mucormycosis[6−−10] which is a serious concern for an ophthalmologist as it is a potentially sight-threatening condition. this higher vulnerability to secondary infections can be attributed to the interplay of various factors like steroid use, systemic comorbidities (like uncontrolled diabetes, malignancy, transplantation), and use of immunomodulatory drugs like tocilizumab and immune dysregulation caused by coronavirus.[10] however, history of steroid use and uncontrolled diabetes were the two most frequently reported risk factors in covid-associated mucormycosis.[6−−10] rhino–orbito cerebral mucormycosis is an invasive fungal infection involving the nasal cavity, paranasal sinuses, orbit and brain causing high morbidity and mortality. overall survival rate is reported to be 59.5% with treatment and 21% without treatment.[33] it can also cause serious ophthalmic complications like central retinal artery occlusion resulting in vision loss. therefore, timely diagnosis and early intervention is of utmost importance. however, absence of reliable diagnostic markers and poor yield on tissue culture make it a diagnostic challenge. hence, one must have a high index of suspicion especially when patient is not responding to intensive antibiotic therapy and repeated cultures are negative. early clinical features are facial pain, periorbital swelling and black eschar over skin overlying the orbit, nasal cavity, and palate. later orbital involvement may result in ophthalmoplegia, proptosis, ptosis, superior orbital fissure/orbital apex syndrome.[34] radiological investigations include ct scan and mri; however, diagnosis is confirmed only on histopathology and culture. in case of repeated cultures, tissue biopsy is gold standard.[34] management involves control of causative risk factors, systemic antifungal treatment and surgical debridement. exenteration may be required in case of extensive orbital spread.[34] summary this covid-19 pandemic is long to stay. the only method to survive this period is to take all possible precautions. eye health although often neglected is also getting affected in the current corona crisis. therefore, following proper hygiene, exercises of the eye, and maintaining the eye health is also important. financial support and sponsorship: none. conflicts of interest none. references 1. shetty r, jayadev c, chabra a, maheshwari s, d’souza s, khamar p, et al. sanitizer aerosol-driven ocular surface 294 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 repercussions of covid-19 pandemic on eye health; gaur and sarkar disease (sadosd)—a covid-19 repercussion? indian j ophthalmol 2020;68:981–983. 2. salehi m, ahmadikia k, badali h, khodavaisy s. opportunistic fungal infections in the epidemic area of covid-19: a clinical and diagnostic perspective from iran. mycopathologia 2020;185:607–611. 3. song g, liang g, liu w. fungal co-infections associated with global covid-19 pandemic: a clinical and diagnostic perspective from china. mycopathologia 2020;185:599– 606. 4. garcia-vidal c, sanjuan g, moreno-garcía e, puertaalcalde p, garcia-pouton n, chumbita m, et al. incidence of co-infections and superinfections in hospitalized patients with covid-19: a retrospective cohort study. clin microbiol infect 2021;27:83–88. 5. segrelles-calvo g, de s araújo gr, frases s. systemic mycoses: a potential alert for complications in covid-19 patients. future microbiol 2020;15:1405–1413. 6. mehta s, pandey a. rhino-orbital mucormycosis associated with covid-19. cureus 2020;12:e10726. 7. mekonnen zk, ashraf dc, jankowski t, grob sr, vagefi mr, kersten rc, et al. acute invasive rhino-orbital mucormycosis in a patient with covid-19-associated acute respiratory distress syndrome. ophthalmic plast reconstr surg 2021;37:e40–e80. 8. sen m, lahane s, lahane tp, parekh r, honavar sg. mucor in a viral land: a tale of two pathogens. indian j ophthalmol 2021;69:244–252. 9. sarkar s, gokhale t, choudhury ss, deb ak. covid19 and orbital mucormycosis. indian j ophthalmol 2021;69:1002–1004. 10. garg d, muthu v, sehgal is, ramachandran r, kaur h, bhalla a, et al. coronavirus disease (covid-19) associated mucormycosis (cam): case report and systematic review of literature. mycopathologia 2021;186:289–298. 11. scalinci sz, trovato battagliola e. conjunctivitis can be the only presenting sign and symptom of covid-19. idcases 2020;20:e00774. 12. daruich a, martin d, bremond-gignac d. ocular manifestation as first sign of coronavirus disease 2019 (covid-19): interest of telemedicine during the pandemic context. j fr ophtalmol 2020;43:389–391. 13. zhou y, duan c, zeng y, tong y, nie y, yang y, et al. ocular findings and proportion with conjunctival sars-cov-2 in covid-19 patients. ophthalmology 2020;127:982–983. 14. wu p, duan f, luo c, liu q, qu x, liang l, et al. characteristics of ocular findings of patients with coronavirus disease 2019 (covid-19) in hubei province, china. jama ophthalmol 2020;138:575–578. 15. chen l, liu m, zhang z, qiao k, huang t, chen m, et al. ocular manifestations of a hospitalised patient with confirmed 2019 novel coronavirus disease. br j ophthalmol 2020 06;104:748–751. 16. navel v, chiambaretta f, dutheil f. haemorrhagic conjunctivitis with pseudomembranous related to sarscov-2. am j ophthalmol case rep 2020;19:100735. 17. world health organisation. report of the who–china joint mission on coronavirus disease 2019 (covid-19) [internet]. who; 2020. available from: https://www.who.int/docs/defaultsource/coronaviruse/who-china-joint-mission-on-covid-19final-report.pdf 18. loffredo l, pacella f, pacella e, tiscione g, oliva a, violi f. conjunctivitis and covid-19: a meta-analysis. j med virol 2020;10.1002/jmv.25938. 19. aiello f, gallo afflitto g, mancino r, li jo, cesareo m, giannini c, et al. coronavirus disease 2019 (sars-cov2) and colonization of ocular tissues and secretions: a systematic review. eye 2020;34:1206–1211. 20. gupta pc, kumar m p, ram j. covid-19 pandemic from an ophthalmology point of view. indian j med res 2020;151:411–418. 21. xia j, tong j, liu m, shen y, guo d. evaluation of coronavirus in tears and conjunctival secretions of patients with sars-cov-2 infection. j med virol 2020;92:589– 594. 22. kumar k, prakash aa, gangasagara sb, rathod sb, ravi k, rangaiah a, et al. presence of viral rna of sars-cov-2 in conjunctival swab specimens of covid-19 patients. indian j ophthalmol 2020;68:1015–1017. 23. chodosh j, holland gn, yeh s. important coronavirus updates for ophthalmologists [internet]. american san francisco, ca: academy of ophthalmology; 2020 [cited 2020 july 23]. available from: https://www.aao.org/headline/alert-important-coronaviruscontext 24. cevik m, tate m, lloyd o, maraolo a, schafers j, ho a. sars-cov-2, sars-cov, and mers-cov viral load dynamics, duration of viral shedding, and infectiousness: a systematic review and meta-analysis. lancet microbe 2021;2:e13–e22. 25. wolkoff p. ocular discomfort by environmental and personal risk factors altering the precorneal tear film. toxicol lett 2010;199:203–212. 26. moshirfar m, west w, marx d. face mask-associated ocular irritation and dryness. ophthalmol ther 2020;9:397–400. 27. aragona p, simmons pa, wang h, wang t. physicochemical properties of hyaluronic acid-based lubricant eye drops. transl vis sci technol 2019;8:2. 28. blehm c, vishnu s, khattak a, mitra s, yee rw. computer vision syndrome: a review. surv ophthalmol 2005;50:253–262. 29. hart wm. adler’s physiology of the eye. 9th ed. st. louis: mosby; 1992. the eyelids. 30. abusharha aa. changes in blink rate and ocular symptoms during different reading tasks. clin optom 2017;9:133–138. 31. american optometric association. computer vision syndrome [internet]. st. louis, mo: american optometric association [cited 2021 may 16]. available from: https://www.aoa.org/healthy-eyes/eye-and-visionconditions/computer-vision-syndrome 32. kochurova o, portello j, rosenfield m. is the 3× reading rule appropriate for computer users? displays 2015;38:38–43. 33. vaughan c, bartolo a, vallabh n, leong sc. a metaanalysis of survival factors in rhino-orbital-cerebral mucormycosis-has anything changed in the past 20 years? clin otolaryngol 2018;43:1454–1464. 34. wali u, balkhair a, al-mujaini a. cerebro-rhino orbital mucormycosis: an update. j infect public health 2012;5:116–126. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 295 original article corneal parameters in healthy subjects assessed by corvis st ramin salouti1, 2, md; mansoureh bagheri1, md; anis shamsi1, md; mohammad zamani2, md maryam ghoreyshi3, md; m. hossein nowroozzadeh1, md 1poostchi ophthalmology research center, department of ophthalmology, school of medicine, shiraz university of medical sciences, shiraz, iran 2salouti cornea research center, salouti eye clinic, shiraz, iran 3health policy research center, shiraz university of medical sciences, shiraz, iran orcid: ramin salouti: https://orcid.org/0000-0002-5853-4799 m. hossein nowroozzadeh: https://orcid.org/0000-0002-7412-1900 abstract purpose: to evaluate corneal biomechanics using corvis st in healthy eyes from iranian keratorefractive surgery candidates. methods: in this prospective consecutive observational case series, the intraocular pressure (iop), central corneal thickness (cct), and biomechanical properties of 1,304 eyes from 652 patients were evaluated using corvis st. keratometric readings and manifest refraction were also recorded. results: the mean (±sd) age of participants was 28 ± 5 years, and 31.7% were male. the mean spherical equivalent refraction was –3.50 ± 1.57 diopters (d), the mean iop was 16.8 ± 2.9 mmhg, and the mean cct was 531 ± 31 𝜇m for the right eye. the respective means (±sd) corneal biomechanical parameters of the right eye were as follows: first applanation time: 7.36 ± 0.39 milliseconds (ms); first applanation length: 1.82 ± 0.22 mm; velocity in: 0.12 ± 0.04 m/s; second applanation time: 20.13 ± 0.48 ms; second applanation length: 1.34 ± 0.55 mm; velocity out: –0.67 ± 0.17 m/s; total time: 16.84 ± 0.64 ms; deformation amplitude: 1.05 ± 0.10 mm; peak distance: 4.60 ± 1.01 mm; and concave radius of curvature: 7.35 ± 1.39 mm. in the linear regression analysis, iop exhibited a statistically significant association with the first and second applanation times, total time, velocity in, peak distance, deformation amplitude, and concave radius of curvature. conclusion: our study results can be used as a reference for the interpretation of corvis st parameters in healthy refractive surgery candidates in the iranian population. our results confirmed that iop is a major determinant of corvis parameters. keywords: central corneal thickness; corneal biomechanics; corvis st; intraocular pressure j ophthalmic vis res 2020; 15 (1): 24–31 correspondence to: m. hossein nowroozzadeh, md. poostchi ophthalmology research center, poostchi clinic, zand st., shiraz 71349, iran. e-mail: nowroozzadeh@hotmail.com received: 01-10-2018 accepted: 28-02-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i1.5936 introduction the cornea has a complex biomechanical structure that determines its response under this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: salouti r, bagheri m, shamsi a, zamani m, ghoreyshi m, nowroozzadeh mh. corneal parameters in healthy subjects assessed by corvis st. j ophthalmic vis res 2020;15:24–31. 24 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i1.5936&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr corvis parameters in healthy eyes; salouti et al stress conditions.[1] currently, ophthalmologists are deeply interested in characterizing the corneal biomechanical properties in pathological conditions and after refractive surgery.[2] furthermore, corneal biomechanics affect intraocular pressure (iop) measurement and may also be an important risk factor for the development of glaucomatous optic neuropathy.[3] to date, only two devices have been designed to evaluate corneal biomechanical properties in vivo: the ocular response analyzer (ora; reichert ophthalmics, depew, ny), a dynamic bidirectional applanation device and the corvis st (oculus optikgeräte gmbh, wetzlar, germany), a dynamic non-contact scheimpflug analyser device.[2] both devices use an air pulse to impress the cornea.[4] in contrast to the ora, which cannot display the dynamics of the corneal deformation process in real time, the corvis st uses the realtime corneal deformation data to analyze corneal biomechanics. to accomplish this, corvis st captures a series of horizontal scheimpflug images using a high-speed camera that gathers 4,300 frames per sec within a 100 milliseconds (ms) period.[1, 5] currently, there are few reports regarding the normal distribution of corvis st parameters from different populations.[1, 6–10] because ethnicity is a known determinant of corneal biomechanical properties,[11] the normative database from various populations are very useful and can guide us in spotting abnormal cases. the aim of this study was to evaluate the corneal biomechanical properties using the corvis st in healthy eyes from iranian patients who have been evaluated for keratorefractive surgery. methods study population in this prospective case series, which was conducted from january 2012 to december 2013, corneal biomechanical parameters from corvis st were recorded for 1,304 eyes from 652 consecutive healthy keratorefractive surgery candidates with no eye disorders except myopia. a complete eye examination, including visual acuity measurement, slit-lamp biomicroscopy, and fundus exam using a 90-diopter noncontact lens was performed on each eye. cases with positive history (or objective signs) of ocular disorders (e.g., glaucoma, uveitis, corneal ectatic disorders, fuchs’s corneal dystrophy, and diabetic retinopathy), chronic use of topical medications, previous ocular surgery, corneal scars or opacities, irregular astigmatism, systemic diseases, or inability to cooperate with any measurement device were excluded. the research protocol adhered to the tenets of the declaration of helsinki and detailed informed consent was signed by all individuals. the study protocol was approved by the ethics committee at the shiraz university of medical sciences. measurements refraction was measured using an autorefractometer (canon r-50; canon inc., tokyo, japan), and keratometric measurements were recorded from pentacam hr (oculus optikgeräte gmbh, wetzlar, germany) scan reports. ocular biomechanical parameters, iop, and central corneal thickness (cct) were obtained using corvis st. corvis st measures the biomechanical response of the cornea at the moment of the first and second applanations, and highest concavity events. iop is calculated based on the timing of the first applanation event.[11] corvis st measures and records the time to reach applanation (t1, t2), the length of the flattened segment in a scheimpflug image (l1, l2), and corneal movement velocity during applanation (v1, v2) at the moment of both first and second applanations, respectively. it also measures the total time (t), deformation amplitude (da), distance between bending points of the cornea (pd), and the concave radius of curvature (r) at the point of highest concavity. all of the described corvis st parameters were recorded for analysis. each instrument was calibrated at the outset of the study, and then at regular intervals (as per manufacturer recommendations). all measurements from each device were performed by the same qualified operator using the criteria provided by the devices manufacturer. statistical analysis data were analyzed using ibm spss statistics software version 21 (spss inc., chicago, il) and journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 25 corvis parameters in healthy eyes; salouti et al medcalc version 12.2.1 (medcalc software, mariakerke, belgium). descriptive statistical results were reported as mean ± standard deviation (sd). corvis st data were presented as mean and normal range (mean ± 1.96 sd). only data from the right eyes of participants were used for regression analysis. factors with p < 0.05 in simple linear regression analysis were entered into a multiple stepwise linear regression analysis. p < 0.05 was considered to be statistically significant. results the mean (± sd) age of patients was 28 ± 5 years (range: 20 to 47 years), and 31.7% were male. the majority of the enrolled cases were persian. the baseline characteristics of both eyes are presented in table 1. the mean and normal range of corvis st parameters along with the evaluation of absolute and relative variations between right and left eyes are shown in table 2. linear regression analysis was used to evaluate the possible association between different demographic and ocular factors with each corvis st parameter [tables 3–5, and figures 1–3]. the most important and clinically relevant associations [with standardized coefficient (sc) > 0.3] were as follows: iop (sc: 0.964) and cct (sc: 0.403) for t1; iop (sc: –0.328) for v1; iop (sc: –0.568) for t2; and iop (sc: –0.651) for da. table 6 presents the normal values of corvis st parameters, stratified based on the corresponding iop. considering gender, only v1 and t have independently been influenced by the gender. the mean v1 and t was 0.110 ± 0.033 vs 0.117 ± 0.037 m/s (p = 0.021) and 16.7 ± 0.6 vs 16.9 ± 0.6 ms (p = 0.001) for the males vs females, respectively. discussion corvis st biomechanical parameters are some geometrical factors that are generated during inward and then outward movements of the cornea after a single puff of air and are essentially determined as a product of three different factors: the air puff pressure, the iop, and the corneal biomechanical properties. air puff pressure is constant in all cases, and the incident apparent iop could be provided for each patient. however, corneal biomechanical properties including viscosity, elasticity, and viscoelasticity are much more difficult to be determined in vivo. these factors may be changed during the process of certain ocular disorders such as keratoconus and glaucoma,[1] and are claimed to be detectable before their clinical or topographic counterparts in conditions such as forme fruste keratoconus.[6] therefore, an accurate method to evaluate corneal biomechanics in vivo is crucial for predicting corneal surgical outcomes and for optimum surgical planning.[2] corvis st corneal parameters may be considered a proxy for actual corneal biomechanical factors; however, because of substantial influences from other determinants such as cct, keratometry, and particularly iop,[4] these factors should be interpreted with caution. t1, the time to first applanation, is the factor that has been essentially used for estimating iop,[11] and hence showed a perfect direct association with iop [figure 1]. t1 also showed a weaker direct association with cct, which reminds the confounding effect of cct on iop measurement. because this factor is closely related to iop, it is not suitable for use as a proxy for corneal biomechanical properties. v1, t2, t, da, pd, and r were also more or less affected by iop. for these parameters (t2 and da, in particular), an iop-corrected value (based on the regression analysis) or iop-stratified charts (such as the one that is shown in table 6 or those that were provided by huseynova et al[1]) should be used; otherwise, significant mistakes may occur. for example, based on the normative data displayed in table 2, a da of 1.24 mm should be considered normal, whereas it is outside normal range for eyes with iop ≥ 16 mmhg [table 6]. the present study has provided a reference for normal range of corvis st parameters [tables 2 and 6] in iranian population. data from individuals who satisfy the enrolment criteria of this study may cautiously be compared with the provided normal values. in addition to normal range of parameters, we have also provided the normal range of the interocular differences. because the two fellow eyes are almost symmetric in most topographic and biomechanical properties, an out of range value may prompt further investigations for possible implicit disorders. the interocular ranges are provided as both absolute (95% range of real difference) and relative (absolute variation divided by the mean of the fellow 26 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 corvis parameters in healthy eyes; salouti et al table 1. baseline characteristics of the study cohort right eyes𝑎 left eyes𝑎 se, d –3.50 ± 1.57 –3.47 ± 1.59 km, d 43.7 ± 1.3 43.7 ± 1.3 ka, d 1.2 ± 0.8 1.2 ± 0.8 cct, 𝜇m 531 ± 31 531 ± 31 iop, mmhg 16.8 ± 2.9 16.6 ± 2.7 𝑎data are presented as the mean ± standard deviation. cct, central corneal thickness; d, diopter; iop, intraocular pressure; ka, astigmatic keratometry; km, mean keratometry; se, spherical equivalent refraction table 2. mean and normal range of corvis parameters among participants right eyes𝑎 left eyes𝑎 absolute variation𝑏 (95% range) relative variation𝑐 (95% range) t1, milliseconds 7.36 (6.60 to 8.12) 7.34 (6.61 to 8.07) ± 0.66 ± 9.0% l1, mm 1.82 (1.37 to 2.23) 1.83 (1.38 to 2.28) ± 0.095 ± 5.2% v1, m/s 0.12 (0.04 to 0.20) 0.12 (0.04 to 0.20) ± 0.65 ± 565% t2, milliseconds 20.13 (19.19 to 21.07) 20.15 (19.23 to 21.07) ± 0.58 ± 2.9% l2, mm 1.34 (0.26 to 2.42) 1.38 (0.26 to 2.50) ± 0.40 ± 29.4% v2, m/s –0.67 (–1.00 to –0.34) –0.67 (–1.06 to –0.28) ± 1.45 ± 216% t, milliseconds 16.84 (15.59 to 18.09) 16.88 (15.70 to 18.06) ± 1.29 ± 7.7% da, mm 1.05 (0.85 to 1.25) 1.06 (0.86 to 1.26) ± 0.19 ± 12.3% pd, mm 4.60 (2.62 to 6.58) 4.63 (2.66 to 6.58) ± 2.56 ± 55.5% r, mm 7.35 (4.63 to 10.07) 7.35 (4.34 to 10.37) ± 3.29 ± 44.8% 𝑎data are presented as the mean (95% range) 𝑏calculated as: ± 1.96 sd of the mean difference (right–left) 𝑐calculated as: ± [(1.96 sd of the mean difference)/(mean value of both eyes)] * 100 da, deformation amplitude; l1, length of applanation 1; l2, length of applanation 2; pd, peak distance; r, radius; t, time of highest concavity; t1, time of applanation 1; t2, time of applanation 2; v1, velocity of applanation 1; v2, velocity of applanation 2 table 3. linear regression analysis demonstrating association between selected demographic and ocular factors to each corvis st parameters at the first applanation moment t1 l1 v1 sc p-value𝑎 sc p-value𝑎 sc p-value𝑎 age sex (male to female) –0.091 0.021𝑏 se km ka cct 0.403 < 0.001𝑏 iop 0.964 < 0.001𝑏 –0.328 < 0.001𝑏 𝑎only factors with p-value < 0.05 in simple linear regression analysis are shown here 𝑏denotes factors that remained significant after multiple stepwise linear regression analysis cct, central corneal thickness; iop, intraocular pressure; ka, astigmatic keratometry; km, mean keratometry; l1, length of applanation 1; sc, standardized coefficient; se, spherical equivalent refraction; t1, time of applanation 1; v1, velocity of applanation 1 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 27 corvis parameters in healthy eyes; salouti et al table 4. linear regression analysis demonstrating association between selected demographic and ocular factors to each corvis st parameters at the second applanation moment t2 l2 v2 sc p-value𝑎 sc p-value𝑎 sc p-value𝑎 age sex (male to female) se km –0.092 0.021𝑏 ka –0.117 0.003𝑏 cct 0.134 0.001𝑏 0.107 0.007𝑏 iop –0.568 < 0.001𝑏 𝑎only factors with p-value < 0.05 in simple linear regression analysis are shown here 𝑏denotes factors that remained significant after multiple stepwise linear regression analysis cct, central corneal thickness; iop, intraocular pressure; ka, astigmatic keratometry; km, mean keratometry; l2, length of applanation 2; sc, standardized coefficient; se, spherical equivalent refraction; t2, time of applanation 2; v2, velocity of applanation 2 table 5. linear regression analysis demonstrating an association between selected demographic and ocular factors to each corvis st parameters at the highest concavity moment t da pd r sc p-value𝑎 sc p-value𝑎 sc p-value𝑎 sc p-value𝑎 age sex (male to female) 0.125 0.001𝑏 se 0.086 0.028𝑏 km ka cct –0.218 < 0.001 0.211 < 0.001𝑏 iop 0.135 0.001𝑏 –0.651 < 0.001𝑏 –0.241 < 0.001𝑏 0.189 < 0.001𝑏 𝑎only factors with p < 0.05 in simple linear regression analysis are shown here 𝑏denotes factors that remained significant after multiple stepwise linear regression analysis cct, central corneal thickness; da, deformation amplitude; iop, intraocular pressure; ka, astigmatic keratometry; km, mean keratometry; pd, peak distance; r, radius; sc, standardized coefficient; se, spherical equivalent refraction; t, time of highest concavity table 6. mean and normal range of corvis parameters categorized based on the intraocular pressure intraocular pressure, mm hg𝑎 10.00–12.99 (n = 30) 13.00–15.99 (n = 230) 16.00–18.99 (n = 252) 19.00–22.00 (n = 104) t1, milliseconds𝑏 6.78 (6.54 to 7.01) 7.06 (6.76 to 7.37) 7.39 (7.10 to 7.68) 7.80 (7.46 to 8.14) v1, m/s𝑏 0.114 (0.042 to 0.186) 0.130 (0.074 to 0.185) 0.117 (0.050 to 0.184) 0.080 (0.020 to 0.140) t2, milliseconds𝑏 21.21 (20.75 to 21.68) 20.32 (19.43 to 21.20) 20.01 (19.34 to 20.69) 19.87 (19.27 to 20.48) t, milliseconds𝑏 16.16 (15.47 to 16.86) 16.80 (15.48 to 18.11) 16.93 (15.74 to 18.12) 16.86 (15.82 to 17.91) da, mm𝑏 1.15 (1.04 to 1.26) 1.11 (0.942 to 1.28) 1.04 (0.908 to 1.17) 0.989 (0.764 to 1.21) pd, mm𝑏 5.46 (5.11 to 5.81) 4.77 (2.81 to 6.73) 4.49 (2.50 to 6.49) 4.36 (2.41 to 6.30) r, mm𝑏 7.42 (3.53 to 11.31) 7.13(4.29 to 9.97) 7.35 (4.75 to 9.95) 7.47 (6.09 to 8.86) 𝑎data are presented as the mean (95% range); only analyses of right eyes are shown here 𝑏only parameters that have shown significant association with iop are presented here da, deformation amplitude; pd, peak distance; r, radius; t, time of highest concavity; t1, time of applanation 1; t2, time of applanation 2; v1, velocity of applanation 1 28 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 corvis parameters in healthy eyes; salouti et al male female mean difference: 0.007 figure 1. significant determinants of the selected corvis st parameters at the first applanation moment. cct, central corneal thickness; iop, intraocular pressure. r square: 0.322 r square: 0.009 r square: 0.014 r square: 0.018 r square: 0.011 figure 2. significant determinants of the selected corvis st parameters at the second applanation moment. cct, central corneal thickness; iop, intraocular pressure; km, mean keratometry; ka, astigmatic keratometry. journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 29 corvis parameters in healthy eyes; salouti et al male female r square: 0.007 r square: 0.048 r square: 0.044 r square: 0.018 r square: 0.036 r square: 0.423 r square: 0.058 mean difference: 0.17 figure 3. significant determinants of the selected corvis st parameters at the highest concavity moment. cct, central corneal thickness; iop, intraocular pressure; se, spherical equivalent refraction. eyes) variations. for relative variation values < 10%, this parameter may be more informative because it incorporates the mean value as well; but for the relative variation > 10% (typically for those with small mean value), the relative variation measurements are exaggerated and useless. absolute variation values may be more clinically useful for this class of corvis st parameters. several previous studies have evaluated corvis st parameters in normal and abnormal eyes. hong et al reported that corvis st demonstrated excellent consistency in iop measurement perhaps because it might be less affected by corneal properties.[5] reznicek et al reported good repeatability and good accuracy of corvis st compared to standardized ultrasound pachymetry or goldmann applanation tonometry for measuring cct and iop in healthy subjects, and in patients with ocular hypertension and glaucoma.[7] the results of our regression analysis of the factors associated with corvis st parameters closely parallels the findings of huseynova et al.[1] in both studies, t 1 and r were significantly associated with cct, and t1, t2, and da were correlated to iop.[1] in both studies, t1 and r were significantly associated with cct. also, t1, t2, and da were correlated with iop. in a recent study on healthy brazilian patients, valbon and colleagues[11] reported a normal range of corvis st parameters. compared to our study, they enrolled fewer patients (n = 90), but with broader enrolment criteria (age range: 21 to 79 30 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 corvis parameters in healthy eyes; salouti et al years). the mean values of corvis st parameters that were reported by valbon et al were quite different compared to ours: t1 (8.32 vs 7.36 ms); t (18.38 vs 16.84 ms); t2 (23.80 vs 20.13 ms); l1 (2.07 vs 1.82 mm); l2 (2.37 vs 1.34 mm); da (1.05 vs 1.05 mm); r (11.09 vs 7.35 mm); v1 (0.21 vs 0.12 m/s); and v2 (–0.33 vs –0.67 m/s), respectively.[7] however, these differences were not unexpected, because their study population enrolled older patients from a different ethnicity. previous studies have established the role of ethnicity on cct and iop,[12, 13] the two fundamental determinants of corvis st parameters.[1] the differences in corvis st values between the two studies further underscores the importance of using customized charts, based on underling ocular and demographic factors, to improve accuracy of detecting abnormal cases in each particular population. the present study has the advantage of including a large number of cases leading to more precise normative ranges, but it is limited due to its relatively strict enrolment criteria, which reduces the generalizability of the findings. in addition, we did not document the ethnicity. however, our sample was relatively homogenous with the majority of our patients consisting of those with persian ethnicity. our results should only be used for the population of refractive surgery candidates with similar age range, ethnicity, and refractive error. in conclusion, this study has provided a reference normative database for corvis st parameters in iranian refractive surgery candidates, which can be used with caution in selected patients who satisfy the enrolment criteria. several demographic and ocular factors, and iop in particular, essentially affected the corvis st parameters, and this issue should be considered when interpreting the results. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. huseynova t, waring go, roberts c, krueger rr, tomita m. corneal biomechanics as a function of intraocular pressure and pachymetry by dynamic infrared signal and scheimpflug imaging analysis in normal eyes. am j ophthalmol 2014;157:885–893. 2. pinero dp, alcon n. in vivo characterization of corneal biomechanics. j cataract refract surg 2014;40:870– 887. 3. ambrósio r, ramos i, luz a, faria fc, steinmueller a, krug m, et al. dynamic ultra high speed scheimpflug imaging for assessing corneal biomechanical properties. rev bras oftalmol 2013;72:99–102. 4. hassan z, modis l, jr, szalai e, berta a, nemeth g. examination of ocular biomechanics with a new scheimpflug technology after corneal refractive surgery. cont lens anterior eye 2014;37:337–341. 5. hong j, xu j, wei a, deng sx, cui x, yu x, et al. a new tonometer–the corvis st tonometer: clinical comparison with noncontact and goldmann applanation tonometers. invest ophthalmol vis sci 2013;54:659–665. 6. tian l, huang yf, wang lq, bai h, wang q, jiang jj, et al. corneal biomechanical assessment using corneal visualization scheimpflug technology in keratoconic and normal eyes. j ophthalmol 2014;2014:147516. 7. reznicek l, muth d, kampik a, neubauer as, hirneiss c. evaluation of a novel scheimpflug-based noncontact tonometer in healthy subjects and patients with ocular hypertension and glaucoma. br j ophthalmol 2013;97:1410–1414. 8. vellara hr, ali nq, gokul a, turuwhenua j, patel dv, mcghee cn. quantitative analysis of corneal energy dissipation and corneal and orbital deformation in response to an air-pulse in healthy eyes. invest ophthalmol vis sci 2015;56:6941–6947. 9. wang w, he m, he h, zhang c, jin h, zhong x. corneal biomechanical metrics of healthy chinese adults using corvis st. cont lens anterior eye 2017;40:97–103. 10. lee h, kang dsy, ha bj, choi jy, kim ek, seo ky, et al. biomechanical properties of the cornea using a dynamic scheimpflug analyzer in healthy eyes. yonsei med j 2018;59:1115–1122. 11. valbon bf, ambrosio r, jr, fontes bm, luz a, roberts cj, alves mr. ocular biomechanical metrics by corvis st in healthy brazilian patients. j refract surg 2014;30:468– 473. 12. chua j, tham yc, liao j, zheng y, aung t, wong ty, et al. ethnic differences of intraocular pressure and central corneal thickness: the singapore epidemiology of eye diseases study. ophthalmology 2014;121:2013– 2022. 13. fern kd, manny re, gwiazda j, hyman l, weise k, marshtootle w. intraocular pressure and central corneal thickness in the comet cohort. optom vis sci 2012;89:1225– 1234. journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 31 original article primary angle closure glaucoma-associated genetic polymorphisms in northeast iran ali yousefian1, md; saeed shokoohi-rad1, md; mohammad reza abbaszadegan2, phd dorsa morshedi rad3, ms; selma zargari2, ms; saman milanizadeh2, ms negar morovatdar4, md; ramin daneshvar1, md, ms 1eye research center, mashhad university of medical sciences, mashhad, iran 2medical genetics research center, mashhad university of medical sciences, mashhad, iran 3immunology research center, avicenna research institute, mashhad university of medical sciences, mashhad, iran 4clinical research unit, faculty of medicine, mashhad university of medical sciences, mashhad, iran orcid: ali yousefian: https://orcid.org/0000-0002-9139-4601 ramin daneshvar: https://orcid.org/0000-0002-0884-0907 abstract purpose: to evaluate the association of five different polymorphisms from a genomewide-associated study with susceptibility to glaucoma in the northeast iranian population. methods: hundred and thirty patients with primary angle closure glaucoma (pacg) and 130 healthy controls were genotyped for the polymorphic regions with the aid of tetraamplification refractory mutation system-polymerase chain reaction. the association of these variants with the disease susceptibility was measured statistically with the logistic regression method. results: hundred and thirty patients with pacg (53 males, 77 females) with a mean age of 64.5 ± 6.2 years and 130 healthy control subjects (51 males, 79 females) with a mean age of 64.0 ± 5.7 years were selected for evaluation. there was a significant association between rs3816415 (p = 0.005), rs736893 (p < 0.001), rs7494379 (p < 0.001), and rs1258267 (p = 0.02) with pacg susceptibility. this association could not be shown for rs3739821. conclusion: it was revealed that studied variants in glis3, epdr1, fermt2, and chat genes can contribute to the incidence of pacg. additional studies in other populations are needed to evaluate dpm2-fam102a. keywords: polymorphism; primary angle closure glaucoma; rs3816415; rs736893; rs7494379; rs1258267 j ophthalmic vis res 2020; 15 (1): 45–52 correspondence to: ramin daneshvar, md, ms. khatam-al-anbia eye hospital, abutaleb cross, mashhad 91959, iran. e-mail: daneshvarr@mums.ac.ir received: 21-02-2019 accepted: 11-08-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i1.5942 introduction glaucoma is one of the leading causes of blindness worldwide. approximately 70 million people this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: yousefian a, shokoohi-rad s, abbaszadegan mr, morshedi rad d, zargari s, milanizadeh s, morovatdar n, daneshvar r. primary angle closure glaucoma-associated genetic polymorphisms in northeast iran. j ophthalmic vis res 2020;15:45–52. © 2020 journal of ophthalmic and vision research | published by knowledge e 45 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i1.5942&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr pacg genetic polymorphisms; yousefian et al are affected and it is predicted that by 2020, this number will rise to around 79.6 million globally.[1] the incidence of glaucoma varies in different populations and geographic regions. while primary open-angle glaucoma (poag) is the most common type, primary angle closure glaucoma (pacg) is associated with a more severe presentation and bilateral blindness.[2–4] the visual function in pacg could be saved if early and proper treatments are adopted.[5] pacg is characterized by apposition between the peripheral iris and trabecular meshwork, which can ultimately lead to compromised outflow and high intraocular pressure (iop).[6] stress induced by iop on optic disc results in compression, deformation, and remodeling of the lamina cribrosa with subsequent mechanical axonal damage and disruption of axonal transport or ischemic damage to the neural tissue.[7] pacg is a complex disease influenced by a combination of environmental and genetic risk factors. recently, col18a1, which encodes collagen type xviii, has been identified as a gene that affects angle closure in humans and can lead to pacg.[8] an unusually higher incidence among firstdegree relatives of affected patients compared with the general population suggests that genetic risk factors may play an important role in the development of pacg.[9, 10] another factor indicating a genetic influence in pacg development is the heritability for narrow-angle and a shallow anterior chamber (two important causes of disease) that are approximately 49% and 93%, respectively.[9, 11] although several genome-wide association studies (gwass) for pacg revealed multiple genetic variants correlated with disease susceptibility, these results demonstrate that the exact mechanisms by which the culprit gene could cause pacg is not completely understood and the association of different single nucleotide polymorphisms (snps) with glaucoma are still controversial.[12, 13] among different reported variants, expression quantitative trait locus (eqtl) mapping databases indicate that rs7494379 on chromosome 14 position 53,411,391, gene locus fermt2, rs736893 on chromosome 9 position 4,217,028, gene locus glis3, rs1258267 on chromosome 10 position 50,895,770, gene locus chat, rs3816415 on chromosome 7 position 37,988,311, gene locus epdr1, and rs3739821 on chromosome 9 position 130,702,477, gene locus dpm2-fam102a are significantly expressed in ocular anterior segment tissues such as iris, ciliary body, and trabecular meshwork,[14, 15] which mark them as potential variants for pacg incidence. the current study aimed to evaluate the association of these five snps evaluated in gwas with pacg susceptibility in the northeast of iran. methods population study this case-control study was conducted on subjects that were following up for pacg at khatam eye hospital, a referral eye center in mashhad, northeast of iran, between 2017 and 2018. the case group included 130 patients with pacg that were diagnosed and followed by a glaucomatrained ophthalmologist according to optic nerve exam, gonioscopy, iop, and visual field changes and completed the interview of competency (53 males and 77 females). individuals with primary angle closure and primary angle closure suspect (with only obstructed angle and/or increased iop with no obvious optic nerve cupping or visual field defect) were not selected for the study and only patients with established optic nerve, head damage, or glaucomatous perimetric changes due to pacg were considered for evaluation. control subjects were 130 healthy individuals (51 males and 79 females)[16] without any glaucoma findings or signs of angle closure in gonioscopy. clinical information including age and sex was gathered. the ethics committee of the mashhad university of medical sciences approved the study. snp selection criteria the analyzed polymorphisms were selected on the basis of recent gwas analysis and the databases prepared on the national center for biotechnology information snp database (https://www.ncbi.nlm. nih.gov/snp/) (access date: dec 20, 2018) and literature searches. we selected five validated snps with a minor allele frequency >1%.[17, 18] genotyping dna was extracted from the whole blood using the standard salting-out method 46 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 https://www.ncbi.nlm.nih.gov/snp/ https://www.ncbi.nlm.nih.gov/snp/ pacg genetic polymorphisms; yousefian et al which was previously described by miller et al.[19] genotyping was carried out by tetraamplification refractory mutation systempolymerase chain reaction (tetra-arms pcr). for amplification of the sequences containing polymorphic site, compatible and specified primers were designed using generunner v3.01 (http://generunner.net/) and ncbi blast was used (https://www.ncbi.nlm.nih.gov/tools/primer-blast/) for ensuring the specificity. properties of designed primers are listed in table 1. pcr reaction was performed in a final volume of 15 𝜇l consisting 100 ng genomic dna, 8 𝜇l of pcr master mix (ampliqon a/s, stenhuggervej 22, dk-5230 odense m, denmark), 0.5 𝜇m of inner primers, and 0.25 𝜇m of outer primers. amplified products were visualized by 2% agarose gel electrophoresis. to confirm the results, 10% of samples were randomly re-genotyped by direct sequencing on abi3130xl genetic analyzer (thermo fisher scientific, usa) and the results were reproducible, with no discrepancy. statistical analysis chi-square test was used for determining the statistical significance of non-association between different variables. logistic regression analysis was performed to estimate the association between polymorphism variants and the risk of pacg in different genders. the odds ratios (or) and 95% confidence intervals (ci) were adjusted. reported p-values were two-sided and the significance level was considered < 0.05. the spss, version 23.0 program (spss, inc., chicago, il) was used for statistical analysis. results this study included 130 patients with pacg (mean age: 64.5 ± 6.2 years) and 130 healthy control subjects (mean age: 64.0 ± 5.7 years). age and sex of the participants were comparable between the two groups (p > 0.05). detailed properties of the study subjects are demonstrated in table 2. the tetra-arms pcr method was successfully applied to genotype five different snps. the association of genotypes and allelic frequencies of five polymorphisms with pacg was determined. genotype frequencies of all tested polymorphisms were in hardy–weinberg equilibrium. genotype frequencies of analyzed snps are demonstrated in table 3. as evident in table 3, a highly significant association and perhaps predisposing effect was found for g/a genotype of rs736893 in the glis3 gene and t/t genotype of rs7494379 in the fermt2 gene (p < 0.001). statistically meaningful association of rs1258267 in the chat gene and rs3816415 in the epdr1 gene with pacg was also confirmed, but rs3739821 in the dpm2-fam102a genes did not have any significant association with pacg frequency in our study population. the correlation of rs736893, rs1258267, and rs7494379 with the disease was stronger in males than in females, and rs3816415 had more association with the disease in females [table 4]. overall, a highly significant (p < 0.001) predisposing effect for the c/t genotype of rs3816415 in the epdr1 gene and g/a genotype of rs736893 in the glis3 was observed [table 3]. genotype frequency analysis revealed that heterozygote genotype in rs736893, a/a genotype in rs1258267, c/c genotype in rs3816415, and heterozygote genotype in rs3739821 were more frequent. however, genotype distribution in rs7494379 was not consistent and c/c genotype and c/t genotype were more frequent in cases and controls, respectively. discussion the results of the present study reveal significant differences in the frequencies of genotypes of epdr1, glis3, chat, and fermt2 polymorphisms between pacg patients and controls. the significantly higher frequencies of genotype g/a of glis3 and c/t of epdr1 in patients with pacg than those in the controls indicated that these genotypes may be associated with a susceptibility to this disease. previous studies showed controversial results on the association of pacg with genetic variants investigated in the current study. zhuang et al found that only snps rs3753841 in col11a1, rs1258267 in chat, and rs736893 in glis3 are associated with pacg in northern chinese people; however, other studies demonstrated epdr1, glis3, chat, fermt2, and dpm2fam102a polymorphisms contribution to the disease susceptibility.[12, 18, 20] fermt2 encodes a protein called pleckstrinhomology-domain-containing family c member journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 47 http://generunner.net/ https://www.ncbi.nlm.nih.gov/tools/primer-blast/ pacg genetic polymorphisms; yousefian et al table 1. tetra-arms primer details. snp sequence product length (nucleotide) tm (degree centigrade) rs736893 forward 5’tgctaccaggacttgtggttgtg3’ 240 57reverse 5’ctatgttcttcccagcacacattc3’ forward 5’acaatagcctaagagcacagagg3’ 130 reverse 5’ggaaccatgactcttggatttaaa3’ rs1258267 forward 5’gaggaaggctcattgcgatgg3’ 327 61reverse 5’tcctgactcaaatctcctgccttc3’ forward 5’tgagattctgatgagcaagtgcatg3’ 130 reverse 5’ccaggttgcctgcacctgct3’ rs3816415 forward 5’tggtggcttggtcaatctg3’ 216 57reverse 5’tcatgtgcctagtgtttataaaca3’ forward 5’attactagctaggcaatcactttac3’ 96 reverse 5’atgctcggtctgacctgtg3’ rs3739821 forward 5’agaagatcgttacctgccagcc3’ 215 61reverse 5’gggaacacactcacacctcgtg3’ forward 5’cgagtgtgcagcctgaccagt3’ 145 reverse 5’agtgacttgcctgtcccagagag3’ rs7494379 forward 5’gcaccattccaccaaataagcac3’ 286 60reverse 5’cttaacgtgatcattaagtatggtattca3’ forward 5’tccacttctgtgagatgcaatgtac3’ 155 reverse 5’catttatgttggagttgcatgttagg3’ snp, single nucleotide polymorphism table 2. characteristics of the study groups study groups pacg patients control group p-value number of subjects 130 130 gender 0.450 male, n (%) 53(40.8) 51(39.2) female, n (%) 77(59.2) 79(60.8) age (years) mean (sd) 64.5(6.2) 64.0(5.7) 0.657 n, number; pacg, primary angle closure glaucoma; sd, standard deviation 1 (plekhc1), a component of the extracellular matrix, and could thus have a role in cell adhesion; cell–cell adhesion has been proposed as an important process in the pathogenesis of pacg.[21] glis3 is a member of the gli-similar subfamily of krüppel-like zinc-finger proteins.[22] earlier studies have shown that mutations in glis3 cause neonatal diabetes and congenital hypothyroidism.[23] snp markers mapping close to glis3 have been observed to be significantly associated with type 1 diabetes in europeans (rs7020673),[24] type 2 diabetes in east asians (rs7041847),[25] and fasting plasma glucose levels in a large meta-analysis of european collections (rs7034200);[26] however, metabolic pathways through which zinc-finger activation could 48 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 pacg genetic polymorphisms; yousefian et al table 3. genotype frequencies genotypes snps pacg patients n (%) controls n (%) or (95%ci) p-value rs736893 < 0.001 g/g 10(7.6) 46(35.3) reference reference g/a 120(92.4) 84(64.7) 6.77(3.2–14.2) < 0.001 a/a 0 0 – – rs1258267 0.02 a/a 97(74.6) 113(86.9) reference reference a/g 30(23) 17(13.1) 2(1–3.9) 0.033 g/g 3(2.4) 0 1.5(1.3–1.7) 0.078 rs3816415 0.005 c/c 120(92.3) 129(99.2) reference reference c/t 10(7.7) 1(0.8) 10.75(1.3-85.4) 0.025 t/t 0 0 – – rs3739821 0.42 t/t 28(21.5) 23(17.6) reference reference t/c 79(60.7) 76(58.4) 1.69(0.7–3.7) 0.18 c/c 23(17.8) 31(24) 1.46(0.7–2.7) 0.23 rs7494379 < 0.001 c/c 48(36.9) 80(61.5) reference reference c/t 50(38.4) 37(28.4) 2.28(1.3-3.9) 0.004 t/t 32(24.7) 13(10.1) 4.08(1.9-8.5) < 0.001 contribute to pathogenesis of pacg is not well understood.[12] chat on chromosome 10 encodes choline acetyltransferase, an enzyme responsible for the synthesis of the neurotransmitter acetylcholine, which has a role in pupillary constriction. anticholinergic medications can precipitate acute pacg through pupillary dilatation mechanisms and subsequent pupillary block. therefore, it is plausible that natural genetic variation in a gene influencing acetylcholine metabolism could alter the risk for pacg.[27] epdr1 encodes a glycosylated type ii transmembrane protein known as ependymin-related 1. it potentially has a role in cell adhesion, and it has some similarity to protocadherins and ependymins.[26] as mentioned earlier, disturbance in cell–cell adhesion could have some roles in the pathogenesis of pacg.[12] snp rs3739821 is located in an intergenic region between dpm2 and fam102a, a gene yet to be fully characterized. mutations in dpm2 have been linked to congenital defects in glycosylation,[28] leading to severe pathological neurological phenotypes. although not much is known about fam102a, except that its expression is sensitive to the addition of 𝛽-estradiol, the nearby pip5kl1 gene has been reported to be involved in cell proliferation[29] and potentially in tumorigenesis. expression analysis revealed that all three genes (fam102a, dpm2, and pip5kl1) were expressed in all eye tissues tested, thus providing biological support for their potential role in pacg development.[12] the expression of all these genes in the cornea, lens, retina, choroid, and optic nerve head confirms the function of these genes in these tissues.[12] the activity of these genes products in the ocular system can explain how different variations in these genes may contribute to the pacg. in conclusion, characterizations of these variations suggest that they can contribute to pacg susceptibility; however, the penetrance of the alleles may be low. being able to divide the population journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 49 pacg genetic polymorphisms; yousefian et al table 4. genotype frequencies in male and female groups genotypes gender pacg patients n (%) controls n (%) or (95%ci) p-value rs736893 <0.001 g/g male 5(9) 19(37) reference reference g/a 48(91) 32(63) 5(1.5–16.5) 0.007 a/a 0(0) 0(0) – – g/g female 5(7) 27(34) reference reference g/a 72(93) 52(66) 7(2.5–22.2) 0.01 a/a 0(0) 0(0) – – rs1258267 0.02 a/a male 39(74) 43(84) reference reference a/g 12(22) 8(16) 2.7(0.8–9.2) 0.1 g/g 2(4) 0(0) 10(0.1–11.1) 0.98 a/a female 58(75) 70(89) reference reference a/g 18(23) 9(11) 1.5(0.6–4) 0.3 g/g 1(2) 0(0) 11(0.6–27.4) 0.8 rs3816415 0.005 c/c male 47(89) 51(11) reference reference c/t 6(11) 0(0) 18(0.2–23.4) 0.98 t/t 0(0) 0(0) – – c/c female 73(95) 78(99) reference reference c/t 4(5) 1(1) 3.6(0.3–25.4) 0.2 t/t 0(0) 0(0) – – rs3739821 0.42 t/t male 12(23) 5(10) reference reference t/c 28(53) 31(61) 0.4(0.1–1.5) 0.19 c/c 13(24) 15(29) 0.3(0.1–1.3) 0.11 t/t female 16(21) 18(23) reference reference t/c 15(66) 45(57) 1(0.4–2.6) 0.83 c/c 10(13) 16(20) 0.7(0.2–2.4) 0.66 rs7494379 < 0.001 c/c male 16(31) 32(63) reference reference c/t 22(41) 14(27) 2.6(0.9–7.4) 0.063 t/t 15(75) 5(10) 8.4(2.2–32.1) 0.002 c/c female 32(42) 48(61) reference reference c/t 28(36) 23(29) 1.6(0.7–3.5) 0.2 t/t 17(22) 7(10) 3(1–8.8) 0.04 50 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 pacg genetic polymorphisms; yousefian et al into risk categories would allow tailored screening, prognosis, and treatment programs according to the risk of each individual. additional studies in other populations with more participants should be considered to evaluate the association of dpm2fam102a with the disease. financial support and sponsorship the authors would like to thank the vice chancellor of research, mashhad university of medical sciences, mashahd, iran (grant # 950495). conflicts of interest there are no conflicts of interest. references 1. quigley ha, broman at. the number of people with glaucoma worldwide in 2010 and 2020. br j ophthalmol 2006;90:262–267. 2. shastry bs. genetic susceptibility to primary angle closure glaucoma (pacg). discov med 2013;15:17–22. 3. cheng j-w, zong y, zeng y-y, wei r-l. the prevalence of primary angle closure glaucoma in adult asians: a systematic review and meta-analysis. plos one 2014;9:e103222. 4. tham y-c, li x, wong ty, quigley ha, aung t, cheng cy. global prevalence of glaucoma and projections of glaucoma burden through 2040: a systematic review and meta-analysis. ophthalmology 2014;121:2081–2090. 5. chen m-s, chang c-c, lin c-p, wang p-c, lin l-r, hou pk, et al. role of vascular endothelial growth factor in the breakdown of the blood-aqueous barrier after retinal laser photocoagulation in pigmented rabbits. j ocul pharmacol th 2012;28:83–88. 6. quigley ha, addicks em, green wr, maumenee ae. optic nerve damage in human glaucoma: ii. the site of injury and susceptibility to damage. arch ophthalmol 1981;99:635–649. 7. burgoyne cf, downs jc, bellezza aj, suh jk, hart rt. the optic nerve head as a biomechanical structure: a new paradigm for understanding the role of iop-related stress and strain in the pathophysiology of glaucomatous optic nerve head damage. prog retin eye res 2005;24:39–73. 8. suri f, yazdani s, chapi m, safari i, rasooli p, daftarian n, et al. col18a1 is a candidate eye iridocorneal angleclosure gene in humans. hum mol genet 2018;27:3772– 3786. 9. amerasinghe n, zhang j, thalamuthu a, he m, vithana en, viswanathan a, et al. the heritability and sibling risk of angle closure in asians. ophthalmology 2011;118:480– 485. 10. sihota r, ghate d, mohan s, gupta v, pandey rm, dada t. study of biometric parameters in family members of primary angle closure glaucoma patients. eye 2008;22:521– 527. 11. yazdani s, akbarian s, pakravan m, afrouzifar m. prevalence of angle closure in siblings of patients with primary angle-closure glaucoma. j glaucoma 2015;24:149–153. 12. khor cc, do t, jia h, nakano m, george r, abu-amero k, et al. genome-wide association study identifies five new susceptibility loci for primary angle closure glaucoma. nat genet 2016;48:556–562. 13. lee y, song g. tnf-𝛼-308 a/g and-238 a/g polymorphisms and susceptibility to glaucoma: a meta-analysis. genet mol res 2015;14:4966–4977. 14. westra h-j, peters mj, esko t, yaghootkar h, schurmann c, kettunen j, et al. systematic identification of trans eqtls as putative drivers of known disease associations. nat genet 2013;45:1238–1243. 15. consortium g. the genotype-tissue expression (gtex) pilot analysis: multitissue gene regulation in humans. science 2015;348:648–660. 16. li z, khor cc. current development in genome wide association studies of glaucoma. curr ophthalmol rep 2018;6:79–85. 17. rong ss, tang fy, chu wk, ma l, yam jc, tang sm, et al. genetic associations of primary angle-closure disease: a systematic review and meta-analysis. ophthalmology 2016;123:1211–1221. 18. nongpiur me, cheng cy, duvesh r, vijayan s, baskaran m, khor cc, et al. evaluation of primary angle-closure glaucoma susceptibility loci in patients with early stages of angle-closure disease. ophthalmology 2018;125:664– 670. 19. miller s, dykes d, polesky h. a simple salting out procedure for extracting dna from human nucleated cells. nucleic acids res 1988;16:1215. 20. zhuang w, wang s, hao j, xu m, chi h, piao s, et al. genotype-ocular biometry correlation analysis of eight primary angle closure glaucoma susceptibility loci in a cohort from northern china. plos one 2018;13:e0206935. 21. shen z, ye y, kauttu t, seppänen h, vainionpää s, wang s, et al., novel focal adhesion protein kindlin-2 promotes the invasion of gastric cancer cells through phosphorylation of integrin 𝛽1 and 𝛽3. j surg oncol 2013;108:106–112. 22. kim ys, nakanishi g, lewandoski m, jetten am. glis3, a novel member of the glis subfamily of krüppel-like zinc finger proteins with repressor and activation functions. nucleic acids res 2003;31:5513–5525. 23. senée v, chelala c, duchatelet s, feng d, blanc h, cossec jc, et al. mutations in glis3 are responsible for a rare syndrome with neonatal diabetes mellitus and congenital hypothyroidism. nat genet 2006;38:682–687. 24. barrett jc, clayton dg, concannon p, akolkar b, cooper jd, erlich ha, et al. genome-wide association study and meta-analysis find that over 40 loci affect risk of type 1 diabetes. nat genet 2009;41:703–707. 25. cho ys, chen ch, hu c, long j, ong rt, sim x, et al. metaanalysis of genome-wide association studies identifies eight new loci for type 2 diabetes in east asians. nat journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 51 pacg genetic polymorphisms; yousefian et al genet 2012;44:67. 26. dupuis j, langenberg c, prokopenko i, saxena r, soranzo n, jackson au, et al. new genetic loci implicated in fasting glucose homeostasis and their impact on type 2 diabetes risk. nat genet 2010;42:105–116. 27. wan y, li s, gao y, tang l, cao w, sun x. col11a1 polymorphisms are associated with primary angle-closure glaucoma severity. j ophthalmol 2019;2019:2604386. 28. barone r, aiello c, race v, morava e, foulquier f, riemersma m, et al. dpm2-cdg: a muscular dystrophy– dystroglycanopathy syndrome with severe epilepsy. ann neurol 2012;72:550–558. 29. shi l, zhao m, luo q, ma ym, zhong jl, yuan xh, et al. overexpression of pip5kl1 suppresses cell proliferation and migration in human gastric cancer cells. mol biol rep 2010;37:2189–2198. 52 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 original article abnormal visual function: an under-recognized risk factor of road traffic injuries hassan hashemi1, md; payam nabovati2, phd; abbasali yekta3, phd; ali borojerdi4, ms; hamidreza fallahkohan4, ms; farhad rezvan5, md; mehdi khabazkhoob6, phd 1noor research center for ophthalmic epidemiology, noor eye hospital, tehran, iran 2rehabilitation research center, department of optometry, school of rehabilitation sciences, iran university of medical sciences, tehran, iran 3department of optometry, mashhad university of medical sciences, mashhad, iran 4budget and planning office of road maintenance and transportation organization, tehran, iran 5noor ophthalmology research center, noor eye hospital, tehran, iran 6department of medical surgical nursing, school of nursing and midwifery, shahid beheshti university of medical sciences, tehran, iran orcid: hassan hashemi: https://orcid.org/0000-0002-6086-1537 abstract purpose: to determine the relationship between road accidents with visual acuity, refractive errors, visual field, and contrast sensitivity. methods: this population-based case–control study was conducted on roads leading to tehran province, iran. the case group comprised drivers who had met with accidents and were at fault for the accident. the cases were selected in an ongoing manner (incidence cases). the controls were drivers who were the opposing victims in the same. after an initial interview, optometric and ophthalmic examinations including the measurement of visual acuity, refraction, visual field assessment, contrast sensitivity measurement, and slit lamp biomicroscopy were performed for all study participants. results: in this study, 281 and 204 individuals were selected for the case and control groups. the mean uncorrected visual acuity was 0.05 ± 0.12 and 0.037 ± 0.10 logmar in the case and control groups, respectively (p = 0.095). of the participants in the case and control groups, 32.8% and 23% had a visual field defect in at least one eye, respectively (adjusted odds ratios [aor] = 1.63, 95% confidence interval [ci]: 1.08–2.48; p = 0.021). moreover, 16.2% of the cases and 8.3% of the controls had visual field defects in both eyes (aor = 2.13, 95% ci: 1.17–3.86; p = 0.012). contrast sensitivity was worse in the case group in all spatial frequencies under non-glare conditions. however, under glare conditions, the contrast sensitivity was significantly worse in the case group only in the spatial frequency of 12 cycles per degree (cpd). conclusion: reduced contrast sensitivity, especially under non-glare conditions, and visual field defects are risk factors that influence the prevalence of road accidents. it is strongly advised that special attention be paid to these visual functions in legal assessments to apply the necessary interventions in individuals with these types of disorders. keywords: case–control study; contrast sensitivity; road traffic injury; visual field j ophthalmic vis res 2022; 17 (4): 529–535 © 2022 hashemi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 529 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i4.12306&domain=pdf&date_stamp=2019-07-17 vision and road traffic injuries; hashemi et al introduction in 2018, the world health organization (who) reported an increase in the number of road accident fatalities to 1.35 million victims per year with 20–50 million people suffering from non-fatal injuries.[1] globally, road accidents are the eighth cause of death in all ages and the leading cause of death in children and adolescents aged 5– 29 years.[2] according to available reports, road traffic injuries are the second leading cause of mortality in iran.[3, 4] therefore, it is very important to identify the risk factors associated with road accidents to reduce mortality through necessary measures.[5] driving is a complex task which is affected by different sensory, mental, motor, and compensatory capabilities of human body, among which the visual system provides >90% of the input information required for driving.[6, 7]therefore, the process of driving is considered a visually demanding task.[8] due to the importance of the visual system, multiple studies have evaluated the relationship between the visual system function and the driving process and safety.[8] several studies have pointed out the importance of including evaluations of varied aspects of the visual system function such as visual acuity,[9–11] contrast sensitivity,[12–14] color vision,[15, 16] and visual field[17, 18] in primary and periodic driving qualification examinations. it should be mentioned that most of the studies in this regard were descriptive studies that have merely assessed the visual system status or the prevalence of visual disorders or ocular pathologies in a group of drivers. therefore, due to the lack of a control group, correspondence to: hassan hashemi, md. noor research center for ophthalmic epidemiology, noor eye hospital, tehran 1968653111, iran. email: hhashemi@noorvision.com received: 17-10-2021 accepted: 08-03-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i4.12306 it is not possible to judge on the relationship between these visual parameters and the increased chance of accidents with certainty. moreover, many of these studies investigated the relationship between a limited number of visual indices and the drivers’ safety and performance without controlling the effects of confounding factors. it should be noted that different parameters of the visual system affect each other.[19] to comment on the association of each of these parameters with the drivers’ safety and performance, it is necessary to evaluate them simultaneously and control their confounding effects on other parameters. few studies included a control group; however, they reported inconsistent and even contradictory results regarding the association between different visual indices and car accidents, indicating the need for further research in this regard. in addition, the extent of the effect of each visual parameter on the drivers’ performance may be different depending on the geographical conditions (weather, road lighting) of each country. the present study aimed to determine the visual risk factors associated with the occurrence of road car accidents. identifying these visual risk factors can help reduce road accidents and their fatalities through appropriate periodic visual qualification examinations as well as necessary ophthalmic therapeutic measures and environmental modifications. methods this population-based case–control study was conducted on roads leading to tehran province from september 2018 to march 2019. the study population comprised drivers that drove on the roads leading to tehran province during the study period. the subjects were selected using convenience sampling. this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: hashemi h, nabovati p, yekta a, borojerdi a, fallahkohan h, rezvan f, khabazkhoob m. abnormal visual function: an under-recognized risk factor of road traffic injuries . j ophthalmic vis res 2022;17:529–535. 530 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 https://knepublishing.com/index.php/jovr vision and road traffic injuries; hashemi et al in this study, exposure and outcome were defined as visual system disorders and being at fault for the accident, respectively. the drivers that were involved in accidents during the study period according to police reports and were recognized at fault for the accident were considered as the cases and selected in an ongoing or incidence case manner. the control group included drivers who were the opposing victims in same accidents and were not at fault. so, the controls were matched with cases in terms of confounding factors such as the road on which the accident occurred and the accident time. since the road’s physical status and driving time can significantly affect the odds of traffic accidents, it seemed necessary to select the controls among the drivers who matched with the cases in terms of these two factors. sampling was continued until the required sample size was achieved in each group. the subjects that were involved in accidents in the aforementioned roads were included in the study if the accident did not affect their level of consciousness. exclusion criteria were a history of using drugs, alcohol, and psychedelics, an unwillingness to participate in the study, and any physical condition hampering the interview. the official police report of the accident was also used to collect the required data. finally, all of the subjects were invited to participate in further interviews and examinations. informed consent was obtained from all participants before entering the study. interviews were performed to collect demographic data, education level, history of driving, ocular diseases, type of driver’s license, type of vehicle, type of accident, and extent of injury. in addition, a brief history of previous accidents, time of driver’s license renewal, and examinations were also obtained. subjects were referred for examination after the interview. the interviewer was unaware of the study objectives and was masked to the case and control groups. all study participants underwent optometric examinations by two experienced optometrists who were unaware of the study objectives and were masked to the case and control groups. the agreement between the two examiners was >85% for the measurement of uncorrected visual acuity and refraction. first, uncorrected distance visual acuity (ucva) was measured at 6 m using a snellen e chart. then, objective refraction was performed using the topcon ar-8800 autorefractometer (topcon corp, tokyo, japan) and the results were refined using the heine beta 200 retinoscope (heine optotechnic, germany). next, optimal distance optical correction was determined using subjective refraction and the best-corrected distance visual acuity (bcva) was measured. contrast sensitivity was measured at spatial frequencies of 3, 6, 12, and 18 cycles per degree (cpd) using the cvs-1000 test (vectorvision, greenville, sc, usa). contrast sensitivity was measured with the best optical correction for subjects with a ucva of <20/20. all participants underwent contrast sensitivity measurements (in log units) under non-glare and glare conditions at 2.5 m from the measuring apparatus. after contrast sensitivity testing, static perimetry was performed by an experienced optometrist using the sita-standard 24-2 protocol with a white target using the humphrey visual field analyzer (carl zeiss, dublin, ca, usa). finally, all study participants underwent slit-lamp biomicroscopy by an ophthalmologist. in this study, hyperopia and myopia were defined as a spherical equivalent (se) of subjective refraction worse than –0.5 d and +0.5 d, respectively. a visual field defect was defined as any result outside the normal limits on the final printout. the area under the contrast sensitivity curve (auc) was calculated based on the following formula: auc = 0.477 × mean (3 cpd, 6 cpd) + 0.7782 × mean (6cpd, 12cpd) + 0.7782 × mean (12 cpd, 18 cpd) statistical analysis considering visual impairment as the main outcome, its prevalence varies in individuals with car accidents versus normal population groups according to different studies.[20] by considering 12% (p1) and 7% (p2) prevalence of visual impairment in the accident and non-accident groups (normal population),[21, 22] respectively, according to previous studies, a type 1 error (α) of journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 531 vision and road traffic injuries; hashemi et al 0.05, and power (β) of 0.80, 270 subjects were required in each group based on the following formula: 𝑛 = (𝑧1− α2 + 𝑧1−β) 2𝑝𝑞 (𝑝1 − 𝑝2) 2 = 270. data were presented as frequency and percentage along with mean and standard deviation (sd). binary logistic regression was applied to evaluate the association between visual parameters and accidents in the case and control groups. finally, a multivariable logistic regression model was used to control the effects of the confounding factors, and the results of the final model, which was run in a backward-stepwise manner, were reported as crude odds ratios (cor) or adjusted odds ratios (aor). ethical considerations the tenets of the declaration of helsinki were considered in all stages of the study. informed consent was obtained from all participants. results two hundred and thirty-six subjects were selected for the control group and 281 for the case group, of whom 204 individuals in the control group (86.4%) and 259 individuals in the case group (92.2%) participated in the study. the mean age of the participants was 40.66 ± 10.30 and 39.57 ± 9.78 years in the case and control groups, respectively (p = 0.258). the mean ucva was 0.05 ± 0.12 logmar in the case group and 0.037 ± 0.10 logmar in the control group (p = 0.095). an ucva of equal to or worse than 20/40 in the better eye was found in 7.8% of the cases versus 3.9% of the controls (cor = 2.05, 95% ci: 0.88–4.75); however, there was no statistically significant difference in terms of bcva between the two groups (p = 0.854). the mean se was –0.68 ± 1.20 diopters (d) in the case group and –0.037 ± 1.04 d in the control group (p = 0.774). the prevalence of myopia was 27.3% and 24% and the prevalence of hyperopia was 25% and 29% in the case and control groups, respectively (p = 0.419 and p = 0.339). the results of myopia and hyperopia did not change after an adjustment for age. astigmatism was found in 55.6% of the subjects in the case group and 57.4% of the individuals in the control group (p = 0.695). the results showed that 32.8% and 23% of the participants in the case and control groups had a visual field defect in at least one eye, respectively (cor = 1.63, 95% ci: 1.08–2.48; p = 0.021); this relationship was still significant after adjusting for the effects of age and visual acuity in logmar (aor = 1.58, 95% ci: 1.03–2.42; p = 0.035). moreover, 16.2% of the cases and 8.3% of the controls had visual field defects in both eyes (cor = 2.13, 95% ci: 1.17–3.86; p =. 0.012); this significant relationship was still observed after adjusting for the effects of age and visual acuity (aor = 1.90, 95% ci: 1.04– 3.49; p = 0.037). table 1 presents the mean contrast sensitivity values in log units in different spatial frequencies under glare and non-glare conditions in the case and control groups. the case group had worse contrast sensitivity in all spatial frequencies under non-glare conditions (p < 0.001); however, under the glare conditions, the contrast sensitivity was significantly worse in the case group only in the spatial frequency of 12 cpd. in addition, according to table 1, the auc of contrast sensitivity was significantly worse in the case group than in the control group in both glare and non-glare conditions. the relationship between contrast sensitivity in different spatial frequencies and being at fault for the accident was evaluated after adjusting for the effects of age and visual acuity. under glare conditions, no significant relationship was found between contrast sensitivity in different spatial frequencies and being at fault in the accident; however, the auc of contrast sensitivity was worse in the case group in a marginally significant manner (p = 0.089). contrast sensitivity values at different spatial frequencies were highly correlated with each other. therefore, the relationship between contrast sensitivity in each spatial frequency with the case and control groups was evaluated separately in a backward multivariable logistic regression model by controlling the effects of age and visual acuity. 532 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 vision and road traffic injuries; hashemi et al table 1. contrast sensitivity values in log units in the case and control groups. spatial frequency case control glare 3 cpd 1.65 ± 0.17 1.68 ± 0.16 6 cpd 1.79 ± 0.19 1.82 ± 0.17 12 cpd 1.38 ± 0.25 1.43 ± 0.24 18 cpd 0.91 ± 0.25 0.95 ± 0.23 auc 2.94 ± 0.40 3.02 ± 0.36 non-glare 3 cpd 1.72 ± 0.18 1.76 ± 0.12 6 cpd 1.86 ± 0.18 1.92 ± 0.16 12 cpd 1.51 ± 0.23 1.57 ± 0.20 18 cpd 1.02 ± 0.23 1.07 ± 0.20 auc 3.15 ± 0.38 3.25 ± 0.29 cpd, cycles per degree; auc, area under the curve table 2. the association between contrast sensitivity in different spatial frequencies under glare and non-glare conditions and being at fault for the accident after adjusting for the effect of age and visual acuity in a multivariable logistic regression model. contrast sensitivity age uncorrected visual acuity spatial frequency aor (95%ci); p-value aor (95%ci); p-value aor (95%ci); p-value glare 3 cpd 0.44 (0.13–1.50); 0.190 1.01 (0.99–1.03); 0.525 0.95 (0.86–1.05); 0.342 6 cpd 0.56 (0.19–1.61); 0.279 1.01 (0.99–1.03); 0.472 0.95 (0.86–1.05); 0.343 12 cpd 0.48 (0.21–1.09); 0.079 1.01 (0.99–1.03); 0.526 0.96 (0.87–1.07); 0.466 18 cpd 0.58 (0.26–1.31); 0.191 1.01 (0.99–1.03); 0.451 0.96 (0.87–1.06); 0.384 auc 0.63 (0.37–1.07); 0.090 1.01 (0.99–1.03); 0.542 0.96 (0.87–1.07); 0.470 non-glare 3 cpd 0.24 (0.06–0.93); 0.039 1.01 (0.99–1.03); 0.566 0.95 (0.86–1.05); 0.323 6 cpd 0.20 (0.06–0.69); 0.011 1.00 (0.98–1.02); 0.695 0.96 (0.87–1.07); 0.473 12 cpd 0.34 (0.13–0.85); 0.021 1.00 (0.99–1.02); 0.625 0.97 (0.88–1.07); 0.545 18 cpd 0.46 (0.19–1.15); 0.096 1.01 (0.99–1.03); 0.540 0.96 (0.87–1.06); 0.418 auc 0.44 (0.24–0.82); 0.009 1.00 (0.98–1.02); 0.735 0.97 (0.88–1.08); 0.591 aor, adjusted odds ratio; cpd, cycles per degree; auc, area under the curve the results of the backward multivariable logistic regression for each spatial frequency and the auc are shown separately in table 2. as seen, after controlling for the effects of age and visual acuity, the contrast sensitivity under non-glare conditions at spatial frequencies of 3, 6, and 12 and the auc were significantly worse in the case group. discussion the current study showed no significant association between corrected visual acuity and the risk of road traffic injuries, which is consistent with most previous studies. a review of the relationship between visual acuity and risk of vehicle accidents in 1999 found that the relative risk values reported in previous studies were often <2 with a few exceptions; therefore, the authors concluded that there was a weak association between reduced visual acuity and risk of road accidents.[23] keefe et al studied 2594 subjects and found no significant difference in the risk of car crashes between individuals with a visual acuity of <6/12 compared to those with a better visual acuity.[9] several other studies have also indicated no significant association between journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 533 vision and road traffic injuries; hashemi et al visual acuity and the risk of car accidents.[11, 13, 24, 25] several factors may explain this lack of significant relationship. the first may be low variation in the visual acuity of the participants, because most of the studies compared intermediate visual acuities with relatively normal or slightly lower visual acuities. another factor may be that decreased visual acuity has an overt nature and any individual is usually aware of this problem. therefore, drivers with compromised visual acuity may deliberately adopt a series of compensatory reactions like limiting driving, avoiding driving at night and in risky conditions, and avoiding high-risk behaviors while driving,[26, 27] resulting in decreased risk of car accidents. the results of this study showed a significant relationship between reduced contrast sensitivity and increased risk of road accidents. several previous studies revealed a relationship between contrast sensitivity disorders and increased risk of car accidents. marottoli et al reported a twofold increase in the risk of car accidents in individuals with impaired contrast sensitivity compared to those with normal contrast sensitivity.[12] cross et al also studied 363 car crashes and concluded that a high percentage of these accidents were due to impairment in the contrast sensitivity of the drivers.[13] in 2001, owsley et al found that cataract and resulting decreased contrast sensitivity played significant roles in car crashes leading to disabling or death. according to the results of the present and previous studies, it can be concluded that the risk of car crashes is markedly higher in people with compromised contrast sensitivity, which indicates a direct correlation between contrast sensitivity disorders and risk of car crashes.[14] visual field was another risk factor for assessing the impact on the incidence of car accidents in the present study. the results showed that the prevalence of bilateral visual field defects was significantly higher in the case group as compared to the control group. there are contradictory reports of the relationship between visual field defects and the drivers’ safety and performance in the literature. primary studies did not show such a relationship while later studies proved this association. danielson did not find a significant relationship between the horizontal visual field and risk of car crashes.[28] similarly, adekoya et al also found no significant association between visual field defects and road traffic accidents.[18] however, johnson and keltner studied 10,000 subjects and found that bilateral visual field defects significantly increased the risk of car accidents.[29] on the other hand, haymes et al showed a six-time increased risk of car accidents in subjects with glaucoma and visual field defects as compared to other drivers.[30] in 2015, huisingh et al concluded that severe bilateral visual field defects increased the risk of road traffic accidents by 40%. moreover, they reported that the risk was higher if the defect was in the inferior or left visual field.[31] a limitation of the present study is that there are various environmental, psychological, and mental factors that may affect the relationship between visual functions and road accidents. it seems impossible to control all these factors. therefore, these potential confounders must also be considered when interpreting the study findings. in summary, according to the findings of the present study, decreased contrast sensitivity and visual field defect were risk factors that influenced the prevalence of road accidents. since these two parameters are not routinely assessed in the driver’s physical qualification examination in iran, it is strongly advised that special attention be paid to these visual functions in legal assessments to apply the necessary interventions in subjects with these disorders. moreover, it is recommended that a series of environmental modifications be applied to reduce the effects of visual disorders on the performance of drivers. financial support and sponsorship this project was financially supported by noor research center for ophthalmic epidemiology. conflicts of interest: no conflicting relationship exists for any author. 534 journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 vision and road traffic injuries; hashemi et al references 1. world health organization (who). global status report on road safety 2018: summary. world health organization; 2018. 2. urie y, velaga nr, maji a. cross-sectional study of road accidents and related law enforcement efficiency for 10 countries: a gap coherence analysis. traffic inj prev 2016;17:686–691. 3. saadat s, yousefifard m, asady h, moghadas jafari a, fayaz m, hosseini m. the most important causes of death in iranian population; a retrospective cohort study. emergency 2015;3:16–21. 4. shahbazi f, soori h, khodakarim s, ghadirzadeh, m, hashemi-nazari ss, et al. analysis of mortality rate of road traffic accidents and its trend in 11 years in iran. arch trauma res 2019;8:11–16. 5. bahadorimonfared a, soori h, mehrabi y, delpisheh a, esmaili a, salehi m, et al. trends of fatal road traffic injuries in iran (2004-2011). plos one 2013;8:e65198. 6. oladehinde mk, adeoye ao, adegbehingbe bo, onakoya ao. visual functions of commercial drivers in relation to road accidents in nigeria. indian j occup environ med 2007;11:71–75. 7. wood jm. aging, driving and vision. clin exp optom 2002;85:214–220. 8. owsley c, mcgwin g jr. vision and driving. vision res 2010;50:2348–2361. 9. keeffe je, jin cf, weih lm, mccarty ca, taylor hr. vision impairment and older drivers: who’s driving? br j ophthalmol 2002;86:1118–1121. 10. gresset ja, meyer fm. risk of accidents among elderly car drivers with visual acuity equal to 6/12 or 6/15 and lack of binocular vision. ophthalmic physiol opt 1994;14:33–37. 11. rubin gs, ng es, bandeen-roche k, keyl pm, freeman ee, west sk. a prospective, population-based study of the role of visual impairment in motor vehicle crashes among older drivers: the see study. invest ophthalmol vis sci 2007;48:1483–1491. 12. marottoli ra, richardson ed, stowe mh, miller eg, brass lm, cooney lm jr, et al. development of a test battery to identify older drivers at risk for self-reported adverse driving events. j am geriatr soc 1998;46:562–568. 13. cross jm, mcgwin g jr, rubin gs, ball kk, west sk, roenker dl, et al. visual and medical risk factors for motor vehicle collision involvement among older drivers. br j ophthalmol 2009;93:400–404. 14. owsley c, stalvey bt, wells j, sloane me, mcgwin g jr. visual risk factors for crash involvement in older drivers with cataract. arch ophthalmol 2001;119:881–887. 15. mäntyjärvi m, juntunen v, tuppurainen k. visual functions of drivers involved in traffic accidents. accid anal prev 1999;31:121–124. 16. cole bl. protan colour vision deficiency and road accidents. clin exp optom 2002;85:246–253. 17. racette l, casson ej. the impact of visual field loss on driving performance: evidence from on-road driving assessments. optom vis sci 2005;82:668–674. 18. adekoya bj, owoeye jf, adepoju fg, ajaiyeoba ai. visual function survey of commercial intercity vehicle drivers in ilorin, nigeria. can j ophthalmol 2009;44:261–264. 19. usrey wm, reid rc. synchronous activity in the visual system. annu rev physiol 1999;61:435–456. 20. onabolu oo, bodunde ot, otulana to, ajibode ha, awodein og, onadipe oj, et al. visual acuity of commercial motor drivers in ogun state of nigeria. niger postgrad med j 2012;19:225–229. 21. hashemi h, yekta a, jafarzadehpur e, doostdar a, ostadimoghaddam h, khabazkhoob m. the prevalence of visual impairment and blindness in underserved rural areas: a crucial issue for future. eye 2017;31:1221–1228. 22. shahriari ha, izadi s, rouhani mr, ghasemzadeh f, maleki ar. prevalence and causes of visual impairment and blindness in sistan-va-baluchestan province, iran: zahedan eye study. br j ophthalmol 2007;91:579–584. 23. owsley c, mcgwin g jr. vision impairment and driving. surv ophthalmol 1999;43:535–550. 24. decina le, staplin l. retrospective evaluation of alternative vision screening criteria for older and younger drivers. accid anal prev 1993;25:267–275. 25. mccloskey lw, koepsell td, wolf me, buchner dm. motor vehicle collision injuries and sensory impairments of older drivers. age ageing 1994;23:267–273. 26. freeman ee, muñoz b, turano ka, west sk. measures of visual function and their association with driving modification in older adults. invest ophthalmol vis sci 2006;47:514–520. 27. lyman jm, mcgwin g jr, sims rv. factors related to driving difficulty and habits in older drivers. accid anal prev 2001;33:413–421. 28. danielson rw. the relationship of fields of vision to safety in driving; with a report of 680 drivers examined by various screening methods. am j ophthalmol 1957;44:657–680. 29. johnson ca, keltner jl. incidence of visual field loss in 20,000 eyes and its relationship to driving performance. arch ophthalmol 1983;101:371–375. 30. haymes sa, leblanc rp, nicolela mt, chiasson la, chauhan bc. risk of falls and motor vehicle collisions in glaucoma. invest ophthalmol vis sci 2007;48:1149–1155. 31. huisingh c, mcgwin g jr, wood j, owsley c. the driving visual field and a history of motor vehicle collision involvement in older drivers: a population-based examination. invest ophthalmol vis sci 2014;56:132–138. journal of ophthalmic and vision research volume 17, issue 4, october-december 2022 535 original article changes in corneal asphericity after myoring implantation in moderate and severe keratoconus masoud khorrami-nejad1, ms; ozra aghili1, ms; hesam hashemian2, md; mohamad aghazadeh-amiri1, od farshid karimi1, ms 1department of optometry, school of rehabilitation, shahid beheshti university of medical sciences, tehran, iran 2eye research center, farabi eye hospital, tehran university of medical sciences, tehran, iran orcid: masoud khorrami-nejad: https://orcid.org/0000-0002-8270-9704 hasan hashemian: https://orcid.org/0000-0003-0836-8937 abstract purpose: to evaluate the effect of myoring implantation on corneal asphericity in moderate and severe keratoconus (kcn). methods: this cross-sectional observational study comprised 32 eyes of 28 patients with kcn, who had femtosecond-assisted myoring corneal implantation. the primary outcome measures were preoperative and six-month postoperative corneal asphericity in 6-, 7-, 8-, 9-, and 10-mm optical zones in the superior, inferior, nasal, temporal, and central areas. the secondary outcome measures included uncorrected distance visual acuity (udva), corrected distance visual acuity (cdva), manifest refraction, thinnest location value, and keratometry readings. results: a significant improvement in the udva and cdva was observed six months after the surgery (p < 0.001) with a significant reduction in the spherical (4.67 diopters (d)) and cylindrical (2.19 d) refractive errors. a significant reduction in the corneal asphericity in all the optical zones and in the superior, inferior, nasal, temporal, and central areas was noted (p < 0.001). the mean thickness at the thinnest location of the cornea decreased from 437.15 ± 30.69 to 422.81 ± 36.91 μm. a significant corneal flattening was seen. the k1, k2, and km changes were 5.32 d, 7 d, and 6.17 d, respectively (p < 0.001). conclusion: myoring implantation is effective for improving corneal asphericity in patients with kcn. it allows successful corneal remodeling and provides a significant improvement in udva, cdva, and refractive errors. keywords: cornea; corneal topography; keratoconus j ophthalmic vis res 2019; 14 (4): 428–435 correspondence to: hesam hashemian, md. eye research center, farabi eye hospital, tehran university of medical sciences, tehran 16169, iran. e-mail: hashemian_md706@yahoo.com received: 01-09-2018 accepted: 06-02-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i4.5443 introduction keratoconus (kcn) is the most prevalent primary corneal ectasia which commonly causes bilateral this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: khorrami-nejad m, aghili o, hashemian h, aghazadeh-amiri m, karimi f. corneal asphericity after myoring implantation. j ophthalmic vis res 2019;14:428–435. 428 © 2019 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5443&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr corneal asphericity and myoring implantation; khorrami-nejad et al asymmetrical thinning of the paracentral cornea.[1] thinning of the cornea usually occurs in the central and the inferior temporal region,[2] although thinning in the upper area has also been reported.[3, 4] thinning of the cornea leads to myopia and irregular astigmatism, which affects visual quality. in most studies, the reported prevalence of kcn in the general population was between 50 and 230 per 100,000.[5–7] recent studies have shown that kcn starts from the posterior corneal surface and the posterior curvature is affected to a greater extent than the anterior curvature in the early stage of kcn.[8, 9] therefore, devices based on direct evaluation of the two surfaces of the cornea (scheimpflug principle) have been specifically addressed in recent studies.[10, 11] corneal topography, the most accurate method for detecting and confirming kcn, is also based on placido disc and scheimpflug imaging, which are sensitive methods for assessing the shape of the cornea.[12, 13] since the cornea accounts for the largest amount of the dioptric power of the eye, a small change in the shape of the cornea is sufficient to produce a significant dioptric change.[14] aspheric cornea affects the lower and the higher order aberrations, particularly compensates for the spherical aberrations, and ultimately improves the retinal image quality. therefore, corneal asphericity has a potentially significant effect on visual quality.[15, 16] myoring is a 360° continuous full-ring implanted into a corneal pocket using a pocketmaker microkeratome or a femtosecond laser. the myoring has a diameter of 5–8 mm, a thickness of 200–400 μm, and a body width of 0.5 mm. myoring implantation has proven to be safe and effective for the treatment of myopia, ectasia, and kcn.[17–19] the use of an intrastromal corneal ring in the periphery of the cornea causes frontal displacement of the cornea. it also causes central corneal flattening (the arcshortening effect).[20] very few studies have evaluated the corneal asphericity before and after myoring implantation. due to the effect of corneal asphericity on the quality of vision, we aimed to study the changes in these parameters in our study. the prediction of the effect of myoring on corneal asphericity may determine whether the patient is a good candidate for myoring implantation. the selection of suitable candidates for this surgery may increase the quality of vision and, ultimately, the quality of life. methods this cross-sectional observational study included 32 eyes of 28 patients with a mean age of 26.75 ± 6.46 years (ranging 18 to 42 years). the statistical population of this study consisted of stage 2 and stage 3 kcn patients referred to the farabi eye hospital between 2014 and 2016 who underwent femtosecond-assisted myoring implantation. thirty-two eyes of 28 patients were included in the study and all of these 28 patients were evaluated. this study was performed in accordance with the tenets of the declaration of helsinki, and the ethics committee of the shahid beheshti university of medical sciences approved the study. the records were de-identified and anonymous. the exclusion criteria for this study consisted of any defect in documentation, presence of corneal scar, previous corneal surgery of any type, use of contact lenses three weeks before surgery, presence of other ocular or systemic diseases (retinal abnormalities, diabetic retinopathy, cataract, glaucoma, etc.), the inability of acquiring reliable imaging, and failure to complete postoperative examinations six months after the procedure. the records of the patients included in the study were examined by the observation method. in all cases, the pocket for myoring implantation was created using the 150 khz femtosecond technology (intralase, advanced medical optics inc., santa ana, ca, usa). after the creation of the pocket, a space was gently formed by passing a spatula through the temporal incision between the closed flap and the bed. data extracted from the patients’ records included the axes and amount of total, anterior, and posterior corneal astigmatism measured by the pentacam (oculus optikger te gmbh, wetzlar, germany), as well as the spherical and cylindrical refractive errors. corneal asphericity in different zones of the cornea was measured using a refractive map of the pentacam. all patients fulfilling the inclusion criteria during the study period were included in the study. all surgeries were performed by a single surgeon. in the present study, myorings with diameters of 5 mm and 6 mm and thicknesses of 240 μm and 280 μm were used according to the size of the pupil in mesopic conditions and the severity of kcn. uncorrected distance visual acuity (udva), corrected distance visual acuity (cdva), journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 429 corneal asphericity and myoring implantation; khorrami-nejad et al manifest refraction, corneal asphericity at 6, 7, 8, 9, and 10 mm optical zones in the superior, inferior, nasal, temporal, and central areas, minimum corneal thickness, and keratometry readings were the outcome measures of the study. they were measured preoperatively and six months after myoring implantation. kcn patients were divided into four categories according to the amsler krumeich kcn classification.[21] the stage was determined if one characteristic each from the following was present: grade 1: induced myopia and/or astigmatism less than 5 d, keratometric reading ≤ 48.00 d, vogt’s striae, and/or eccentric steepening; grade 2: induced myopia and/or astigmatism of 5–8 d, keratometric reading less than 53 d, lack of scar, and/or minimum corneal thickness greater than 400 μm; grade 3: induced myopia and/or astigmatism of 8–10 d, mean keratometric reading greater than 53 d, no scar, and/or minimum corneal thickness of 200–400 μm; and grade 4: refraction not measurable, the keratometric reading greater than 55 d, central scar, and/or the corneal thickness less than 200 μm. in the next step, patients with grade 2 and grade 3 kcn who underwent the myoring implantation and fulfilled the inclusion criteria for the study were selected as the statistical population. data were gathered using pentacam hr (oculus optikger te gmbh, wetzlar, germany), topcon auto-kerato refractometer kr 8800 (topcon corporation, tokyo, japan), heine beta 200 retinoscope (heine optotechnik gmbh & co., herrsching, germany), and an etdrs chart (at a distance of 4 m). visual acuity was recorded using the logmar system. statistical analysis was performed using the spss software for windows (version 22, ibm inc., armonk, new york, usa). data were analyzed using statistical indices, including the mean and standard deviation. all data were checked for normality using the shapiro–wilk test, followed by a comparison of the data before surgery with those after six months of surgery using the paired ttest. to compare the normal variables in multiple groups, one-way or two-way analysis of variance was used. p < 0.05 was considered statistically significant. results in the present study, 32 eyes of 28 patients [13 (40.6%) males and 19 (59.4%) females] with stage 2 and stage 3 of kcn were examined. the mean age was 26.75 years, with a range of 18 to 42 years. six-month postoperative follow-up was carried out for all patients. eighteen right eyes (25.56%) and fourteen left eyes (75.43%) were included in the study. according to the amsler krumeich kcn classification, 24 eyes (75%) had grade 2 kcn and 8 eyes (25%) had grade 3 kcn. the mean spherical and cylindrical refractive errors and the mean logmar cdva and udva before and after the myoring implantation are presented in table 1. the mean spherical and cylindrical refractive errors significantly decreased (p < 0.001) and the mean udva and cdva improved significantly after the surgery (p < 0.001). means and standard deviations of minimum, average, and maximum keratometry before the surgery were 48.86 ± 3.14, 51.19 ± 3.6, and 53.63 ± 54.3 d, respectively. the mean and standard deviation of minimum, average, and maximum keratometry six months after the myoring implantation were 43.34 ± 3.36, 45.01 ± 36.36, and 46.59 ± 3.67 d, respectively, whereas those for the thickness at the thinnest point of the cornea were 437.15 ± 30.69 μm before the surgery and 422.181 ± 36.91 μm after the myoring implantation [table 2]. the thinnest point of the cornea after the surgery was 14.34 ± 16.53 μm thinner than the preoperative value (p < 0.001). the means and the standard deviations of the asphericity based on the position of the cornea (nasal, temporal, upper, and lower) in the 6-, 7, 8-, 9-, and 10-mm optical zones are presented in table 3. the mean and standard deviation of the asphericity in the entire cornea were also determined for these optical zones [table 3]. the mean corneal asphericity before the surgery was the highest in the 6-mm zone and the lowest in the 10-mm zone. however, after the myoring implantation, the greatest and the least changes in the corneal asphericity values were observed in the 6-mm and 10-mm zones, respectively. the change in the mean corneal asphericity was significant in all optical zones after the myoring implantation (p < 0.001). the changes in the mean temporal, nasal, upper, and lower asphericity in all 430 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 corneal asphericity and myoring implantation; khorrami-nejad et al table 1. descriptive statistics for refractive errors, the corrected distance visual acuity, and the uncorrected distance visual acuity variables unit mean maximum minimum standard deviation p-value sphere pre-operation diopter –4.95 0 –11.00 3.03 < 0.001 post-operation –2.08 +4.00 –4.00 1.60 cylinder pre-operation diopter –4.28 –1.00 –8.00 1.85 < 0.001 post-operation –2.08 0 –6.00 1.32 cdva pre-operation logmar 0.32 0.1 0.5 0.17 < 0.001 post-operation 0.22 0 0.5 0.15 udva pre-operation logmar 1.12 0.4 2.2 0.45 < 0.001 post-operation 0.44 0.1 1.6 0.31 cdv, corrected distance visual acuity; logmar, logarithm of the minimum angle of resolution; udva, uncorrected distance visual acuity table 2. descriptive statistics of the keratometry and the thinnest point of the cornea variables unit mean minimum maximum standard deviation p-value thinnest point pre-operation μm 437.15 380 486 30.69 < 0.001 post-operation 422.81 343 491 36.91 k-min pre-operation diopter 48.86 43.3 54.1 3.14 < 0.001 post-operation 43.54 36.8 50.3 3.36 k-max pre-operation diopter 53.69 45.3 60.3 3.54 < 0.001 post-operation 46.59 38.2 54.8 3.67 k-mean pre-operation diopter 51.19 44.3 56.7 3.06 < 0.001 post-operation 45.01 38 51.4 3.36 k-max, maximum keratometry values; k-mean, mean keratometry values; k-min, minimum keratometry values optical zones of the cornea after the surgery were also found to be significant (p < 0.001). discussion the radius of curvature of a cornea with kcn changes after the myoring implantation, making it flatter. due to this change in shape, the cornea with kcn may become similar to a normal physiological cornea after the surgery. however, creating a flattening effect in the center of the cornea without following a specific asphericity pattern leads to a positive asphericity (rather than improvement in the negative diopter value) of the cornea and the cornea may become completely oblate after surgery. to achieve excellent results using intrastromal rings, it is necessary to control the flattening pattern induced by them. in the present study, significant decreases in myopia and the cylindrical refractive errors were observed, with a greater reduction in myopia than in astigmatism at six months postoperatively. the mean reductions in the spherical and cylindrical refractive errors were 4.67 and 2.19 d, respectively. these findings are consistent with those of previous studies. in the study by daxer et al, the mean variations in the spherical and cylindrical refractive errors were 5.23 and 2.23 d, respectively, which journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 431 corneal asphericity and myoring implantation; khorrami-nejad et al table 3. descriptive statistics of the asphericity variables based on the corneal zones asphericity zone preoperation postoperation mean standard deviation mean standard deviation nasal 6 mm –2.14 1.3 0.6 1.23 7 mm –1.72 0.88 0.26 0.92 8 mm –1.51 0.63 –0.07 0.73 9 mm –1.38 0.49 –0.38 0.62 10 mm –1.21 0.44 –0.55 0.55 temporal 6 mm –0.97 0.72 1.11 1.29 7 mm –0.93 0.57 0.7 0.99 8 mm –0.92 0.42 0.33 0.78 9 mm –0.90 0.32 0.01 0.61 10 mm –0.87 0.34 –0.25 0.46 superior 6 mm –1.86 1.2 0.28 1.58 7 mm –1.69 0.83 0.39 1.2 8 mm –1.47 0.61 0.29 0.89 9 mm –1.26 0.48 0.05 0.69 10 mm –1.09 0.4 –0.21 0.51 inferior 6 mm –0.10 0.94 1.51 1.9 7 mm –0.43 0.73 0.92 1.48 8 mm –0.66 0.64 0.44 1.18 9 mm –0.85 0.56 0.06 0.96 10 mm –0.97 0.49 –0.27 0.78 entire cornea 6 mm –1.27 0.64 0.88 1.19 7 mm –1.20 0.51 0.57 0.94 8 mm –1.14 0.4 0.25 0.73 9 mm –1.07 0.34 –0.06 0.57 10 mm –0.97 0.45 –0.29 0.46 are comparable with our results.[22] in another study by jabbarvand et al, the average postoperative changes in the spherical and cylindrical refractive errors were 5.74 and 3.23 d, respectively.[23] the follow-up evaluations were performed 1, 6, and 12 months after the surgery, with similar results at each evaluation. the amount of myopia and astigmatism correction achieved in our study was greater than that in the studies using intracorneal ring segment (icrs) implantation for the treatment of kcn.[24, 25] therefore, myoring may have more potential for the correction of myopia and astigmatism than icrs in patients with kcn. this is probably due to the arc-shortening effect of complete rings. in the present study, the reduction in the spherical and cylindrical refractive errors after myoring implantation was consistent with a significant improvement in visual acuity, as expected. the mean increase in the udva after the surgery was 0.68 ± 0.44 logmar, a finding similar to those from the studies by jabarvand et al[23] and alio et al.[19] improvement in the udva by 0.62 and 0.75 logmar, respectively, has been reported in both the studies. in the present study, the mean improvement in the cdva was 0.1 logmar, which is similar to the findings in the study by alio et al.[19] in other studies by mahmood et al[26] and jabarvand et al,[23] the mean improvement in the cdva was 432 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 corneal asphericity and myoring implantation; khorrami-nejad et al 0.17 logmar and 0.26 logmar, respectively. in a study conducted by saeed et al, no significant change was observed in the thickness of the thinnest point of the cornea after the myoring implantation.[27] however, in the present study, a statistically significant decrease of 14.34 μm in the thickness of the thinnest point of the cornea was observed. in the present study, a significant central flattening of the corneal topography was observed six months after the surgery, which was consistent with the refractive changes. based on the results obtained in this study, the mean keratometry was reduced by 6.17 d, which is similar to the result of an average keratometric reduction by 5.76 diopters in the study by daxer et al.[22] in the studies by alio et al[19] and mahmood et al,[26] this decrease was approximately 8 d, which is slightly higher than that found in our study. in the study by alio et al, the pupil size was not considered in the mesopic conditions, and only the myorings with a diameter of 5 mm and a thickness of 280 μm were implanted in all patients. in the present study, based on the size of the pupil of the patients under the mesopic conditions and on preoperative keratometry, myorings with diameters of 5 and 6 mm and thicknesses of 240 and 280 μm were implanted. the smaller diameter and higher thickness of the myoring increase the effect of corneal flattening by the ring (the arc-shortening effect).[23] the reason for the difference in the keratometric reduction between the two studies may be the difference in the size and thickness of the myoring. in the study by mahmood et al, the size of the pupil in patients under mesopic conditions was ignored as the sample size was small (six eyes). two patients had a cross-linking history. moreover, the study did not take into account the specific inclusion and exclusion criteria. jabbarvand et al reported a 9.78 d reduction in the mean keratometry reading,[23] which is significantly different from that in the present study and in other studies. the authors used an orbscan to evaluate the anterior corneal surface, while in the present study, we used the pentacam hr for corneal imaging. according to some studies, the reproducibility of pentacam is higher than that of orbscan.[28] in the study by jabbarvand et al, 70% of the patients were male, and the minimum age of the subjects was 19 years with no maximum age limit. in the present study, approximately 60% of the patients were female and the age range was 18–42 years. we observed a significant change in the corneal asphericity after the myoring implantation. after the surgery, the corneal prolate shape was reduced and the cornea became oblate. the result was predictable because a considerable flattening was achieved in the center of the cornea with the myoring implantation. an interesting finding was that the mean decrease in the asphericity at the 6– 10-mm zones followed the similar slope. in this study, the nasal position of the cornea had the highest asphericity changes, and the inferior of the cornea had the lowest amount of asphericity compare to other regions (in the 6-mm optical zone). it is our belief that the present study was the first study that evaluated the changes in corneal asphericity in the 6–10-mm optical zones according to the nasal, temporal, upper, and lower corneal regions after myoring implantation. alio et al studied the changes in the mean corneal asphericity in the 8-mm zone.[19] they reported a decrease of 1.72 in the mean asphericity six months after the surgery, which is almost consistent with the present study (1.39 ± 0.56). a slight difference between the two studies may be due to a greater corneal flattening in the study by alio et al due to the use of myorings with a smaller diameter and a greater thickness. in their study, asphericity changes were evaluated one and two months postoperatively. this follow-up period is shorter than the follow-up of six months in the present study. in another study by hosny et al, the corneal asphericity was evaluated only in a myoring with a diameter of 6 mm.[29] the mean change in the corneal asphericity was 0.43 ± 2.6 after the myoring implantation. the less favorable outcome of this study compared to the present study could be due to the difference in the duration of followup after the surgery. in the study by hosny et al, the results were evaluated one month after the surgery. torquetti et al evaluated the changes in the corneal asphericity after implantation with icrss in kcn.[16] they reported a mean decrease of 0.53 in the corneal asphericity. the mean asphericity before the surgery in their study was –0.85. they suggested that the change in the thicker and the paired segments was more than in the journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 433 corneal asphericity and myoring implantation; khorrami-nejad et al single segments. the myoring has a stronger arc-shortening effect than the icrss due to its 360° design. the reason for the low amount of variation in the asphericity in the study by torquetti et al may be the use of icrss instead of the myoring. in conclusion, we found that myoring implantation significantly reduced the cylindrical and spherical refractive errors due to central corneal flattening. this technique appears to be effective for decreasing myopia and corneal steepness, and effectively affects the corneal shape. a more detailed examination of the corneal parameters such as asphericity in patients with kcn can result in better understanding of the changes associated with kcn. positive spherical aberration worsens contrast sensitivity and may compromise the visual outcomes after myoring implantation. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. sugar j, macsai ms. what causes keratoconus? cornea 2012;31:716–719. 2. auffarth gu, wang l, völcker he. keratoconus evaluation using the orbscan topography system. j cataract refr surg 2000;26:222–228. 3. prisant o, legeais j-m, renard g. superior keratoconus. cornea 1997;16:693–694. 4. weed k, mcghee c, macewen c. atypical unilateral superior keratoconus in young males. contact lens anterio 2005;28:177–179. 5. wheeler j, hauser ma, afshari na, allingham rr, liu y. the genetics of keratoconus: a review. microscopy 2012;6;(suppl 6). pii: 001. 6. piñero dp, alió jl, alesón a, vergara me, miranda m. corneal volume, pachymetry, and correlation of anterior and posterior corneal shape in subclinical and different stages of clinical keratoconus. j cataract refr surg 2010;36:814–825. 7. alió jl, piñero dp, alesón a, teus ma, barraquer ri, murta j, et al. keratoconus-integrated characterization considering anterior corneal aberrations, internal astigmatism, and corneal biomechanics. j cataract refr surg 2011;37:552– 568. 8. miháltz k, kovács i, takács á, nagy zz. evaluation of keratometric, pachymetric, and elevation parameters of keratoconic corneas with pentacam. cornea 2009;28:976– 980. 9. aslani f, khorrami-nejad m, amiri ma, hashemian h, askarizadeh f, khosravi b. characteristics of posterior corneal astigmatism in different stages of keratoconus. j ophthalmic vision res 2018;13:3. 10. savini g, barboni p, carbonelli m, hoffer kj. repeatability of automatic measurements by a new scheimpflug camera combined with placido topography. j cataract refr surg 2011;37:1809–1816. 11. khosravi b, khorrrami-nejad m, rajabi s, amiri m, hashemian h, khodaparast m. characteristics of astigmatism after myoring implantation. med hypothesis dis innov ophthalmol j 2017;6:130-135. 12. swartz t, marten l, wang m. measuring the cornea: the latest developments in corneal topography. curr opin ophthalmol 2007;18:325–333. 13. auffarth gu, borkensein afm, ehmer a, mannsfeld a, rabsilber tm, holzer mp. scheimpflug and topography systems in ophthalmologic diagnostics. der ophthalmologe 2008;105:810–817. 14. mathur a, atchison da. effect of orthokeratology on peripheral aberrations of the eye. optometry vision sci 2009;86:e476–e484. 15. calossi a. corneal asphericity and spherical aberration. j refract surg 2007;23:505. 16. torquetti l, ferrara p. corneal asphericity changes after implantation of intrastromal corneal ring segments in keratoconus. j emmetropia 2010;1:178–181. 17. daxer a, ettl a, hörantner r. long-term results of myoring treatment of keratoconus. j optometry 2017;10:123–129. 18. daxer a. myoring treatment of myopia. j optometry 2017;10:194–198. 19. alio jl, piñero dp, daxer a. clinical outcomes after complete ring implantation in corneal ectasia using the femtosecond technology: a pilot study. ophthalmology 2011;118:1282–1290. 20. jabbarvand m, salamatrad a, hashemian h, mazloumi m, khodaparast m. continuous intracorneal ring implantation for keratoconus using a femtosecond laser. j cataract refract surg 2013;39:1081–1087. 21. weed k, macewen c, cox a, mcghee c. quantitative analysis of corneal microstructure in keratoconus utilising in vivo confocal microscopy. eye 2007;21:614–623. 22. daxer a, mahmoud h, venkateswaran rs. intracorneal continuous ring implantation for keratoconus: one-year follow-up. j cataract refract surg 2010;36:1296–1302. 23. jabbarvand m, salamatrad a, hashemian h, khodaparast m. continuous corneal intrastromal ring implantation for treatment of keratoconus in an iranian population. am j ophthalmol 2013;155:837–842.e2. 24. shabayek mh, alió jl. intrastromal corneal ring segment implantation by femtosecond laser for keratoconus correction. ophthalmology 2007;114:1643–1652. 25. piñero dp, alio jl, kady be, coskunseven e, morbelli h, uceda-montanes a, et al. refractive and aberrometric outcomes of intracorneal ring segments for 434 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 corneal asphericity and myoring implantation; khorrami-nejad et al keratoconus: mechanical versus femtosecond-assisted procedures. ophthalmology 2009;116:1675–1687. 26. mahmood h, venkateswaran r, daxer a. implantation of a complete corneal ring in an intrastromal pocket for keratoconus. j refract surg 2011;27:63–68. 27. saeed a. corneal intrastromal myoring implantation in keratoconus treatment. j egypt ophthalmol soc 2014;107:106. 28. lackner b, schmidinger g, pieh s, funovics ma, skorpik c. repeatability and reproducibility of central corneal thickness measurement with pentacam, orbscan, and ultrasound. optometry vision sci 2005;82:892–899. 29. hosny m, el–mayah e, sidky mk, anis m. femtosecond laser-assisted implantation of complete versus incomplete rings for keratoconus treatment. clin ophthalmol 2015;9:121. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 435 original article pattern and visual prognostic factors of behcet’s uveitis in northwest iran leila alizadeh ghavidel1, md; masood bagheri2*, md, ms; farideh mousavi3, md; leila rezaei2, md; somayyeh hazeri4, ms; hesam-sadat hashemi5, md 1cornea & external eye diseases, department of ophthalmology, royal victoria hospital, mcgill university, montreal, canada 2vitreoretina surgery, department of ophthalmology, imam khomeini eye center, kermanshah university of medical sciences, kermanshah, iran 3vitreoretina surgery, department of ophthalmology, nikookari eye center, tabriz university of medical sciences, tabriz, iran 4biologist, department of biology, concordia university, montreal, canada 5department of ophthalmology, nikookari eye center, tabriz university of medical sciences, tabriz, iran orcid: leila alizadeh ghavidel: https://orcid.org/0000-0002-1343-2887 masood bagheri: https://orcid.org/0000-0002-9288-7475 abstract purpose: to investigate the pattern of ocular involvement in behcet’s disease (bd) with predictors of patients’ final state of vision. methods: this historical cohort encompassed the clinical records of 200 patients diagnosed according to the international criteria for bd (icbd), over a period of 17 years between 2004 and 2021. results: the prevalence of behcet’s uveitis (bu) was more common in females and patients in the fourth decade of life. ninety-five patients (47.5%) had evidence of ocular involvement in the initial ophthalmologic evaluation, and 171 patients (85.5%) manifested evidence of bu during the follow-up visits of which bilateral non-granulomatous panuveitis was the most common anatomical pattern of involvement (32.9%) followed by posterior (27.6%), anterior (26.5%), and intermediate (13.8%) uveitis. the prevalent accompanying signs were oral aphthous (67%), skin lesions (29%), and genital ulcers (19.5%). cystoid macular edema (cme) was the most frequent ocular complication (62%), followed by cataract (57.5%) and epiretinal membranes (erm) (36.5%). univariate analysis showed the following determinants: male gender, younger age at onset, panuveitis, posterior uveitis, retinal vasculitis, and longer duration of uveitis as poorer visual prognostic factors of the disease. multivariate analysis demonstrated a higher chance of poor visual prognosis of bd in patients with panuveitis, posterior uveitis, retinal vasculitis, and longer duration of uveitis. conclusion: this cohort study demonstrated an overview on epidemiological patterns of bu along with the visual prognostic factors in iranian patients. keywords: behcet’s disease; behcet’s syndrome; behcet’s uveitis; iran; prognosis; uveitis j ophthalmic vis res 2022; 17 (2): 242–251 242 © 2022 ghavidel et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i2.10796&domain=pdf&date_stamp=2019-07-17 behcet’s uveitis in iran ; ghavidel et al introduction behçet’s disease (bd) is a chronic, multisystem autoimmune vasculitis of unknown etiology with a wide range of clinical presentations, distinctive geographic distribution, and remarkable genetic background.[1] diagnosis is made clinically, characterized by relapsing oral–genital aphthous lesions, uveitis, and skin lesions. in addition, bd may involve multiple systems including pulmonary, musculoskeletal, gastrointestinal tract, and nervous systems.[2] behçet’s disease is prevalent in the mediterranean, middle east, and far east regions, an area encompassing countries along the ancient silk road (iran, turkey, china, japan, saudi arabia, and greece) with the highest human leukocyte antigen-b51 (hla-b51) prevalence.[3] it commonly involves the younger population often in the third and fourth decades of life with a male/female ratio of more than one.[3] although etiopathogenesis of bd has not yet been clarified, both immunogenetic susceptibility along with environmental predisposing factors have been implicated in its evaluation.[2] hla-b51 is the most well-known immunogenetic association link with bd and some studies have reported that ocular involvement is prevalent in hlab51-positive patients.[4, 5] ocular involvement in the form of recurrent severe uveitis has poor prognosis, potentially culminating in irreversible visual loss despite recent dramatic advances in diagnostic–therapeutic measures. behcet’s uveitis (bu) is characterized by bilateral recurrent non-granulomatous panuveitis and occlusive retinal vasculitis, however, anterior, intermediate, or posterior uveitis can also occur.[2] posterior segment involvement has been reported in 50–93% of cases and relapsing uveitic attacks in the posterior segment may cause blindness due correspondence to: masood bagheri. department of ophthalmology, imam khomeini eye center, kermanshah university of medical sciences, kermanshah 6714776584, iran. e-mail: bagheri.m1368@gmail.com received: 22-05-2021 accepted: 29-01-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i2.10796 to irreversible retinal damage leading to atrophic maculopathy, optic atrophy, macular scarring,[2] and even blindness. although the treatment of many cases of noninfectious uveitis is similar, regarding bd, its distinction from other causes has therapeutic and prognostic implications, for example, the need for aggressive treatment with immunomodulator therapy in the earlier stages.[6] it is difficult to define the visual outcome of a bd case because of its ophthalmic clinical variability, and the unavailability of a validated and widely accepted tool for prognostication. as it is one of the most prevalent etiologies of noninfectious uveitis and one of the most common sight-threatening systemic diseases,[7, 8] determining pattern of involvement along with predictors of the patients’ final state of vision is critical for epidemiological planning, appropriate treatment, patient follow-up, and estimation of visual prognosis. this study evaluated the epidemiological pattern of bu with the respective visual prognostic factors over a 17-year follow-up period at a referral center in northwestern iran. methods in this historical cohort, the clinical records of patients with bd who were referred to the uveitis clinic of a tertiary ophthalmology hospital over the last 17 years were reviewed. according to the existing protocol defined in clinics at tabriz university of medical sciences, all patients with a diagnosis of bd, based on the international criteria for bd (icbd),[9] were referred to our ophthalmology center, nikookari eye care hospital, for evaluation and regular follow-up at the uveitis clinic. these patients formed the statistical population in this cohort study. we included all referred patients to this interdisciplinary uveitis clinic between 2004 and 2018 in addition to a follow-up period of less than three years or irregular this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: ghavidel la, bagheri m, mousavi f, rezaei l, hazeri s, hashemi h-s. pattern and visual prognostic factors of behcet’s uveitis in northwest iran . j ophthalmic vis res 2022;17:242–251. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 243 https://knepublishing.com/index.php/jovr behcet’s uveitis in iran ; ghavidel et al follow-up periods, incomplete file information, or ages <16 years were excluded from the study. general clinical variables extracted included age at diagnosis of bd and bu, the first ophthalmic consultation, the first ocular involvement, gender, accompanying symptoms, and the type of topical, local, or systemic treatments (steroids, anti-metabolites, or cytotoxic agents). evaluation of accompanying symptoms at the first ophthalmologic visit included searching for systemic involvement (oral aphthous, genital ulcer, skin lesions, pulmonary, musculoskeletal, gastrointestinal tract, and nervous systems manifestations) and positivity for hla-b5 and b51. ophthalmologic variables extracted consisted of best-corrected visual acuity (bcva), intraocular pressure (iop), type of uveitis, clinical course of disease (acute, recurrent, or chronic), number of uveitic attacks per year, paraclinical imaging results, and ocular complications (cataract, glaucoma, retinal detachment, macular edema, optic atrophy, atrophic maculopathy, band keratopathy, and ocular hypotony). in all patients with the diagnosis of uveitis, fluorescein angiography (fag) was performed to evaluate the presence of retinal vasculitis. in this study, we defined moderate visual loss (mvl) and severe visual loss (svl) as bcva ≤ 20/40 and ≤20/200, respectively. anatomical location of involvement was classified based on the standardization of uveitis nomenclature (sun) working group,[10] which is widely accepted today and is now the standard required for publication of uveitis studies in the peer-reviewed journals. all factors affecting vision in terms of predictive and prognostic factors were extracted from patients’ records including general clinical variables, ophthalmologic variables, and accompanying findings. finally, the data were analyzed using spss software version 20 (ibm corp., armonk, ny, usa). the data are presented using descriptive statistical methods (i.e., mean, standard deviation, frequency, and percentage). normality of data was tested using the kolmogorov–smirnov test. to compare the data, anova and chi-square tests were used for all ratio and nominal variables, respectively. cox regression analysis was used for multivariate evaluation of risk factors. a p-value < 0.05 was considered as statistically significant. the current study was approved by the ethical committee of the tabriz university of medical sciences (code ir.tbzmed.rec.1397.239). results in this study, we reviewed clinical records of 200 patients with bd who were referred to the uveitis clinic during the last 15 years from 2004 to 2018. the mean time interval between the diagnosis of bd and referral to the uveitis clinic was 28 days (range, 2–70 days). of the 200 patients, 72 were male and 128 female with a male/female ratio of 0.56. the mean age of the patients at the time of diagnosis of bu was 33.09 ± 8.06 years for the cohort, 31.31 ± 7.21 years for males, and 36.01 ± 10.12 years for females; the youngest and oldest patients were 16 and 52, respectively. ninety-five patients (47.5%) had evidence of ocular involvement at the initial ophthalmic evaluation. most patients with bd and bu were in the age group of 31 to 40 years (53.5% and 62.1%, respectively). thus, the prevalence of bu was more common in the fourth decade of life and in the female gender (29 were male and 66 were female) with a male/female ratio of 0.44. figure 1 shows the age distribution of patients with bd and bu. of the 400 eyes of 200 cases, one eye (0.25%) had no light perception (nlp), one (0.25%) had light perception (lp) and 127 eyes (31.75%) had 20/20 bcva at presentation. frequencies of ≤20/40 and ≤20/200 bcva at the first ophthalmic visit were 37.75% and 16.5%, respectively. the mean iop was 13.7 ± 2.90 and 12.3 ± 2.30 in the right and left eyes, respectively (range, 10–25 mmhg). out of the 95 patients with bu, 80 (85.1%) were bilateral and panuveitis was the most common type of anatomical pattern of involvement with a prevalence of 32.9%, followed by posterior (27.6%), anterior (26.5%), and intermediate (13.8%). figure 2 shows the frequency of different types of uveitis at the initial ophthalmologic visit. in patients with ocular involvement, 60 (63.8%) had cystoid macular edema (cme), 60 (63%) had retinal vasculitis (macular, peripheral, or optic disc), and 14 (14.8%) had hypopyon. retinal vasculitis was most commonly seen in panuveitis (29 cases, 39.72%), followed by posterior (18 cases, 38.29%), intermediate (9 cases, 31.03%), and anterior (4 cases, 14.28%) bu. the prevalence of uveitic ocular manifestations at the first ophthalmic visit is shown in figure 3. 244 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 behcet’s uveitis in iran ; ghavidel et al 0 10 20 30 40 50 60 70 80 16-20 21-25 26-30 31-35 36-40 41-45 46-50 51-55 bd bu figure 1. frequency of bd (blue color) and bu (red color) in different age groups at first ophthalmologic visit. as shown, most patients with bu were in the age group of 31–40 years (62.1%). bd, behcet’s disease; bu, behcet’s uveitis. table 1. mean bcva at the initial and last visits and the change in bcva for different groups with the p-values of comparisons. initial bcva bcva in last follow-up change in bcva p-value overall 0.39 ± 0.03 0.82 ± 0.05 0.43 ± 0.04 0.02 male/female 0.42 ± 0.03/0.33 ± 0.03 0.87 ± 0.06/0.72 ± 0.06 0.45 ± 0.05/0.39 ± 0.04 0.02 ant. uveitis 0.45 ± 0.04 0.37 ± 0.03 -0.08 ± 0.03 0.61 middle uveitis 0.43 ± 0.04 0.48 ± 0.04 0.05 ± 0.04 0.73 post. uveitis 0.27 ± 0.02 1.03 ± 0.09 0.76 ± 0.07 0.00 panuveitis 0.35 ± 0.03 0.97 ± 0.08 0.62 ± 0.05 0.01 retinal vasculitis 0.40 ± 0.03 1.02 ± 0.07 0.62 ± 0.04 0.01 macular inflammatory exudate 0.57 ± 0.03 0.97 ± 0.07 0.40 ± 0.05 0.02 macular hemorrhage 0.60 ± 0.03 1.03 ± 0.10 0.43 ± 0.06 0.02 hypopyon 1.05 ± 0.08 0.73 ± 0.05 -0.32 ± 0.06 0.02 kp 0.57 ± 0.05 0.43 ± 0.04 -0.14 ± 0.05 0.06 cme 0.87 ± 0.07 0.57 ± 0.04 -0.30 ± 0.05 0.03 papillitis 0.92 ± 0.08 0.72 ± 0.06 -0.20 ± 0.07 0.04 bcva, best corrected visual acuity; ant. uveitis, anterior uveitis; mid. uveitis, middle uveitis; post. uveitis, posterior uveitis; kp: keratic precipitate; cme, cystoids macular edema the prevalent accompanying symptoms were oral aphthous with a frequency of 67%, followed by skin lesions (29%) and genital ulcer (19.5%); hlab5 or b51 was positive in 115 cases (57.5%). based on dermatology consults, the most common skin lesions included the following: papulopustular lesions (37 cases 18.5%); followed by reactivity of the skin to needle prick or injection (pathergy reaction) (35 cases, 17.5%); erythema nodosum-like lesions (31 cases, 15.5%); superficial thrombophlebitis (14 cases, 7%); furuncles (7 cases, 3.5%); extragenital ulceration (6 cases, journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 245 behcet’s uveitis in iran ; ghavidel et al 0 5 10 15 20 25 30 35 ant. uveitis mid. uvei�s post. uvei�s pan-uvei�s 0 10 20 30 40 50 60 70 80 ant. uveitis mid. uvei�s post. uvei�s pan-uvei�s figure 2. frequency of uveitis type in study patients at first (left chart) and last (right chart) ophthalmic visits. as shown, panuveitis was the most common anatomical pattern of ocular involvement, followed by posterior uveitis. ant. uveitis, anterior uveitis; int. uveitis, intermediate uveitis; post. uveitis, posterior uveitis. 3%); pyoderma gangrenosum-like (4 cases, 2%); erythema multiforme-like lesion (3 cases, 1.5%); hemorrhagic bullae (2 cases, 1%); and abscesses (one case, 0.5%). figure 3 illustrates the most common systemic presentations in this cohort of patients. at the time of referral, only 2 (1%) cases were on no systemic therapy, 188 (94%) were on systemic corticosteroid therapy, and 173 (86.5%) were receiving immunomodulatory treatment, which included antimetabolites, cytotoxic agents, or biologic response modifiers in 131 (65.5%), 18 (9%), and 24 (12%) cases, respectively. thirty-five (17.5%) patients were on monotherapy (25 with steroids and 10 with immunomodulatory), and the majority of patients (147, 73.5%) were on dual therapy with prednisone and immunomodulatory agents. 246 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 behcet’s uveitis in iran ; ghavidel et al 0% 10% 20% 30% 40% 50% 60% 70% hypopyon kps cme re nal vasculi s papili s re nal exudate re nal hx 0% 10% 20% 30% 40% 50% 60% 70% 80% figure 3. frequency of ocular uveitic signs (left) and accompanying systemic symptoms and findings (right) at the first ophthalmologic visit in patients with bu. hla, human leukocyte antigen. 0 10 20 30 40 50 60 70 80 od os figure 4. frequency of the bcva separately in the right (blue color) and left (red color) eyes at final ophthalmologic visit. the ophthalmologic examination of 400 eyes of 200 cases at the final visit showed that 9 eyes (2.25%) were no light perception (nlp), 9 (2.25%) had light perception (lp), and 123 (30.75%) had a 20/20 best corrected visual acuity (bcva). generally, frequencies of ≤20/40 and ≤20/200 bcva at last follow-up were 53.75% and 35.75%, respectively. nlp, no light perception; lp, light perception; hm, hand motion; f.c, fingers counting. sixteen (8%) patients were receiving triple therapy with prednisone, azathioprine, and cyclosporine. eyes with macular involvement (including inflammatory exudates in 6 eyes, hemorrhage in 6 eyes, and cme in 60 eyes) or anterior uveitis accompanied with hypopyon (14 eyes) at presentation had the worst baseline bcva compared to eyes without macular involvement (p = 0.01) or hypopyon (p < 0.001) which had the best bcva at presentation. patients were followed for 7.3 years and the minimum and maximum follow-up periods were 3 and 17 years, respectively. during the followup period, all patients with bu underwent topical or local treatment to control active disease, and with the interdisciplinary cooperation, systemic medication doses were adjusted or changed by rheumatologists. during the follow-up ophthalmic visits, 171 patients (85.5%) subsequently manifested evidence of ocular involvement. of the 400 eyes at the final visit, 9 (2.25%) had nlp, 9 (2.25%) had lp, and 123 (30.75%) had a 20/20 bcva [figure 4]. the frequencies of mvl and svl at the last follow-up were 17.75% and 35.75%, respectively. in journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 247 behcet’s uveitis in iran ; ghavidel et al 0% 10% 20% 30% 40% 50% 60% 70% figure 5. frequency of ocular complications in patients with bu in the follow-up. as shown cme (62%) was the most common complication, followed by cataract (57.5%) and erm (36.5%). (cme: cystoids macular edema, erm: epiretinal membrane, rd: retinal detachment). addition, 42 (29.16%) and 63 (43.75%) eyes of males and 29 (11.32%) and 80 (31.25%) eyes of females were affected by mvl and svl, respectively, both being significantly higher in males (p = 0.01 and 0.02, respectively). the mean iop of patients was 15.82 ± 3.60 and 15.3 ± 4.35 mmhg in the right and left eyes, respectively (range, 0– 31 mmhg). similar to the occurrence at the initial visit, bilateral non-granulomatous panuveitis was the most common pattern of manifestation during the follow-up, followed by posterior, anterior, and intermediate uveitis in order of prevalence [figure 2]. all cases had bilateral and non-granulomatous manifestations but no unilateral or granulomatous involvement was seen. males were more likely to experience pan or posterior uveitis in addition to both mvl and svl over time. in total, 142 patients (250 eyes) developed 630 complications during the follow-up period. cme was the most frequent (62%), followed by cataract (57.5%) and epiretinal membranes (erm) (36.5%). detailed information about ocular complications in bu during follow-up is illustrated in figure 5. the mean difference in bcva between presentation and the follow-up visits was greatest for eyes with retinal vasculitis, macular inflammatory exudates, and hemorrhage. eyes with retinal vasculitis, retinal exudates, or hemorrhage presented as the first uveitic signs, experienced worse bcva in follow-up compared to those with hypopyon, keratic precipitate (kp), cme, and papillitis [table 1]. in addition, eyes with no uveitis at the first ophthalmologic visit had the best visual outcome in general (data not shown). visual prognosis in univariate analysis reflected worse in male, younger age at onset, presence of retinal vasculitis, panuveitis, posterior uveitis, and longer duration of uveitis; however, the male gender and younger age were not significantly associated with a higher risk of svl in multivariate analysis. regression analysis demonstrated a higher chance of poor visual prognosis in patients with panuveitis (or: 3.468 (1.338–8.989), p = 0.01), posterior uveitis (or: 5.008 (1.625–15.432), p = 0.005), retinal vasculitis (or: 3.825 (1.414–10.343), p = 0.008), and longer duration of uveitis (or: 1.002 (1.001–1.003), p = 0.002). if we exclude the eyes with glaucoma and cataract, posterior and panuveitis have a significant correlation with the evolution of structural complications (data not shown). several variables including patients’ age (p = 0.7), the presence of systemic manifestation of bd at baseline visit (p = 0.7), and hla-b51 (p = 0.3) were not associated with either a significant higher rate of svl or poor visual prognosis. among ocular uveitic complications [figure 5], atrophic maculopathy, optic atrophy, and hypotony had statistically significant association with svl (p = 0.005, p= 0.005, and p< 0.001, respectively). subgroup survival analysis of the risk of svl 248 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 behcet’s uveitis in iran ; ghavidel et al for the patients over five-years follow-up was significantly different between patients diagnosed before 2010 and those diagnosed after 2014 with a lower rate of svl (p = 0.043) in the latter group, however, there is no difference in visual outcomes of patients treated with conventional immunomodulatory therapy (imt) versus biologic agents in this cohort (p = 0.058). discussion bd is a visually threatening inflammation with serious implications for the patient as its ocular complications may be irreversibly detrimental, particularly when ischemic complications occur.[11] we performed this study to map the epidemiological pattern of ocular involvement of bd in northwestern iran and determine causes of vision loss and significant impact on eyesight over time. we further aimed to elucidate the influence of each of the ocular complications on the final visual outcome in 400 eyes of 200 confirmed patients who were referred for ophthalmic counseling and were regularly followed-up afterward. the prevalence of ocular involvement in bd was 85.5% in this series, which is significantly higher than the 70% previously reported in other studies.[12, 13] in this historical cohort study, bu occurred predominantly in the fourth decade of life with a male/female ratio of about 0.44. the most common anatomical pattern of involvement was bilateral non-granulomatous panuveitis and the prevalent uveitic ocular manifestations at the first ophthalmic visit were cme and retinal vasculitis. overall, 35.75% of the eyes had svl at presentation which correlated with the presence of macular inflammatory exudates or hemorrhage, cme, and the presence of hypopyon. the most common causes of irreversible svl were atrophic maculopathy, optic atrophy, and hypotony. visual prognosis evaluated through univariate analysis was worse under the following variables: male, younger age at onset, presence of retinal vasculitis, panuveitis, posterior uveitis, and longer duration of uveitis; however, multivariate analysis demonstrated that male gender and younger age variables were not significantly associated with a higher risk of svl. this was due to the higher prevalence of posterior or panuveitis in men than in women and the longer duration of uveitis in the latter. in this study, the prevalence of bu was evaluated higher in females than males, although contrary to the results of the majority of comparative reports,[14] it was in line with alternate reports carried out in the us and western europe.[11, 15, 16] in addition, an epidemiologic study conducted over a period of 44 years from 1968 to 2011 by accorinti et al demonstrated that the incidence of ocular bd is increasing in females.[17] despite the corroborating evidence to suggest the increase of ocular bd in females, there is a consensus regarding the poorer visual prognosis in males as is demonstrated in our report.[11] the multivariate analysis of the current cohort explained the poor prognosis in men and the higher prevalence of posterior or panuveitis in this subgroup. taylor et al demonstrated male gender, unilateral uveitis, left-sided bu, non-white race, and the non-usage of biologic agents as predisposing factors for svl at shortand long-term follow-ups, but ocular ischemic manifestation, age at diagnosis of bu, and duration of bd were not associated with svl.[11] a monocentric italian study by sota and colleagues found that the duration of bu for >15 years, panuveitis, and positive hla-b51 were predictors of long-term structural complications.[18] cataract was determined as the prevalent complication, followed by erm and cme. another study by celiker et al reported patients’ age as the only visual prognostic variable in bu while receiving interferon alpha-2a.[19] in their study, the male gender was found to be a poor prognostic factor in univariate analyses, but it was not statistically significant when evaluated through multivariate analysis. in a cohort study by amer et al, posterior and panuveitis were also deemed potentially sight-threatening presentations of bu which needed aggressive immunosuppressive therapy.[14] subgroup survival analysis of our cohort demonstrated reduced risk of svl in patients diagnosed after 2014 as compared to patients diagnosed before 2010 over five-years of follow-up, which may indicate better control of disease with newly emerged immunomodulatory treatments in recent years. many studies also reported that early and aggressive immunomodulatory treatment and the use of biologic agents are crucial for preventing recurrences and improving visual prognosis.[2, 11] more recently, in a cohort study by taylor and colleagues, the risk of severe visual loss after journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 249 behcet’s uveitis in iran ; ghavidel et al 10-year follow-up was estimated to be 13%.[11] bcva of patients in the current study measured at both initial and follow-up visits was often worse when compared to other studies. possible causes may be the delay in referral or diagnosis, and ophthalmic consultation immediately after diagnosis (before appearance of the treatment effects). on the other hand, our study was historical, so it encompasses elements of selection bias, given that the center is a tertiary referral center, most probably referred patients already had more severe disease with higher probability of ophthalmic involvement. nevertheless, this study provides important findings regarding the epidemiological pattern of bd and highlights some visual prognostic factors of the disease. in conclusion, in this cohort, the prevalence of ocular involvement in bd was 47.5% and 85.5% in the first and follow-up ophthalmic exams, respectively. it was also discovered that bilateral non-granulomatous panuveitis was the prevalent pattern of bu. retinal vasculitis, posterior and panuveitis were revealed to be risk factors for svl, and complications such as atrophic maculopathy, optic atrophy, and hypotony correlated with svl. although bu was more prevalent in women, males were more likely to have pan or posterior uveitis with poorer visual prognosis over time. finally, our patients reported worse bcva at initial and followup visits as compared to alternate studies which may be due to delays in diagnosis or later referral of patients. so, the need for earlier diagnosis along with more aggressive treatment are an important point in improving the visual prognosis of patient. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. yazici h, seyahi e, hatemi g, yazici y. behçet syndrome: a contemporary view. nat rev rheumatol 2018;14:107. 2. çakar özdal p. behçet’s uveitis: current diagnostic and therapeutic approach. turk j ophthalmol 2020;50:169– 182. 3. khairallah m, accorinti m, muccioli c, kahloun r, kempen jh. epidemiology of behçet disease. ocul immunol inflamm 2012;20:324–335. 4. horie y, meguro a, ohta t, lee eb, namba k, mizuuchi k, et al. hla-b51 carriers are susceptible to ocular symptoms of behçet disease and the association between the two becomes stronger towards the east along the silk road: a literature survey. ocul immunol inflamm 2017;25:37–40. 5. meguro a, inoko h, ota m, katsuyama y, oka a, okada e, et al. genetics of behçet disease inside and outside the mhc. ann rheum dis 2010;69:747–754. 6. tugal-tutkun i, onal s, stanford m, akman m, twisk jwr, boers m, et al. an algorithm for the diagnosis of behçet disease uveitis in adults. ocul immunol inflamm 2020;10:1–10. 7. bagheri m, ahoor mh, jafari a, hashemi hs, mohammadkhani m. pattern of uveitis in iran: a systematic review. j ophthalmic vis res 2021;16:93–102. 8. ghavidel la, mousavi f, bagheri m, asghari s. clinical course of uveitis in children in a tertiary ophthalmology center in northwest iran. crescent j med biol sci 2017;4:200–204. 9. davatchi f, assaad-khalil s, calamia k, crook j, sadeghiabdollahi b, schirmer m, et al. international team for the revision of the international criteria for behçet’s disease (itr-icbd). the international criteria for behçet’s disease (icbd): a collaborative study of 27 countries on the sensitivity and specificity of the new criteria. j eur acad dermatol venereol 2014;28:338–347. 10. standardization of uveitis nomenclature working group. standardization of uveitis nomenclature for reporting clinical data. results of the first international workshop. am j ophthalmol 2005;140:509–516. 11. taylor sr, singh j, menezo v, wakefield d, mccluskey p, lightman s. behçet disease: visual prognosis and factors influencing the development of visual loss. am j ophthalmol 2011;152:1059–1066. 12. al akrash ls, al semari ma, al harithy r. ocular manifestations of dermatological diseases part i: infectious and inflammatory disorders. int j dermatol 2021;60:5–11. 13. hatemi g, seyahi e, fresko i, talarico r, hamuryudan v. one year in review 2018: behçet’s syndrome. clin exp rheumatol 2018;36:13–27. 14. amer r, alsughayyar w, almeida d. pattern and causes of visual loss in behçet’s uveitis: short-term and longterm outcomes. graefes arch clin exp ophthalmol 2017;255:1423–1432. 15. sáenz-francés f, elías-de-tejada m, martinez-de-lacasa j, calvo-gonzález c, fernández-vidal a, méndezhernández c, et al. ocular inflammatory signs observed in a cohort of spanish patients with behçet disease and ocular inflammation. eur j ophthalmol 2008;18:563–566. 16. evereklioglu c. current concepts in the etiology and treatment of behçet disease. surv ophthalmol 2005;50:297–350. 250 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 behcet’s uveitis in iran ; ghavidel et al 17. accorinti m, pesci fr, pirraglia mp, abicca i, pivettipezzi p. ocular behçet’s disease: changing patterns over time, complications and long-term visual prognosis. ocul immunol inflamm 2017;25:29–36. 18. sota j, cantarini l, vitale a, sgheri a, gentileschi s, caggiano v, et al. long-term outcomes of behçet’s syndrome-related uveitis: a monocentric italian experience. mediators inflamm 2020;15:6872402. 19. celiker h, kazokoglu h, direskeneli h. factors affecting relapse and remission in behçet’s uveitis treated with interferon alpha2a. j ocul pharmacol ther 2019;35:58– 65. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 251 original article epidemiological and clinical features of pediatric open globe injuries: a report from southern iran ali azimi1, md; fardad abdollahi1, md; elham sadeghi1, md; amir reza farsiani2, md; shadi moshksar1, md; maryam nadi1, md 1poostchi ophthalmology research center, department of ophthalmology, school of medicine, shiraz university of medical sciences, shiraz, iran 2department of ophthalmology, zanjan university of medical sciences, zanjan, iran orcid: ali azimi: https://orcid.org/0000-0001-7744-5858 elham sadeghi: https://orcid.org/0000-0003-3802-3219 abstract purpose: to evaluate the epidemiological features of open globe injury (ogi) in a tertiary ophthalmic center in the south of iran. methods: the medical files of pediatric patients diagnosed with ogi between march 2014 and march 2019 were reviewed retrospectively. demographic data, laterality, time of injury, cause of trauma, location and mechanisms, complications, and the involved tissues, visual acuity, type of operation, and antibiotic therapy were all analyzed. data were processed using the spss. results: in total, 110 eyes of 108 patients were included. ages <7 years comprised 49.1%, 7–12 years 26.4%, and 13–18 years 24.5% of cases. of the 108 patients, 76 (70.3%) were males. no significant difference between right versus left eyes was seen. the incidence of ogi was lowest in winter and highest in spring, and it had more prevalence on the weekends. sharp objects were the most common cause of ogi in ages <7 years, while blunt objects, accidents and falls, and guns and fireworks were more prevalent in older children. home was the most common place of injury overall. the most common type of injury was penetrating trauma. upon arrival, most of the children had a visual acuity <0.1 decimal. primary wound closure was the most prevalent type of surgery done predominantly within 24 hr from admission time. conclusion: ages <7 years and male gender were the most common age and sex of pediatric ogi, respectively, and sharp objects were the predominant etiology. early management and primary repair are essential for prevention of complications such as endophthalmitis and amblyopia. keywords: eye injury; ocular trauma; pediatric; open globe injury; epidemiology j ophthalmic vis res 2023; 18 (1): 88–96 correspondence to: elham sadeghi, md. poostchi clinic, zand st., shiraz 71349, iran. e-mail: elham.sadeghi@rocketmail.com received: 12-09-2021 accepted: 30-08-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i1.12729 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: azimi a, abdollahi f, sadeghi e, farsiani ar, moshksar s, nadi m. epidemiological and clinical features of pediatric open globe injuries: a report from southern iran . j ophthalmic vis res 2023;18:88–96. 88 © 2023 azimi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i1.12729&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr pediatric open globe injuries; azimi et al introduction twenty to fifty percent of all ocular injuries occur in the pediatric age group. due to a lack of cooperation and poor compliance for assessment and therapy, this group’s management is complicated.[1] pediatric ocular trauma is the most leading cause of acquired unilateral vision loss in childhood, especially in developing countries.[2] despite all that has been done to reduce the risk of trauma in children, it remains common worldwide.[3] ocular injuries are divided into two main groups: closed globe injuries and open globe injuries (ogis). an ogi is a severe form of trauma leading to a full-thickness defect in the cornea, sclera, or both, exposing the intraocular compartments to the external environment. ogis are classified into four groups: penetrating injury (only an entrance wound or same entrance/exit wound), perforating injury (separate entrance and exit wounds), rupture (resulting from blunt trauma causing a full-thickness defect at the weakest point of the eyewall), and intraocular foreign body (iofb). the lack of treatment in childhood trauma may lead to various complications such as cataract, retinal detachment, vitreous hemorrhage, corneal opacity, amblyopia, iofb and toxicity due to chronic foreign bodies, endophthalmitis, and sympathetic ophthalmia.[4] knowledge of the epidemiological characteristics of the ogi can assist in the prevention of catastrophic damage to children’s physiological and psychological health. world health organization (who) has recognized childhood blindness as one of the leading causes of preventable blindness. determination of epidemiologic risk factors and prognosis of ogis are essential in achieving a healthier outcome and also reducing its prevalence.[5] therefore, we carried out a retrospective study to evaluate the clinical course and outcomes in all patients younger than 18 years old who were admitted to this tertiary referral university-affiliated ophthalmology center in the south of iran due to ogi. methods in this retrospective study, the medical charts of pediatric patients suffering from ogis were reviewed. the medical records of 110 eyes of 108 children (age ≤18 years) admitted to this hospital due to ocular trauma and diagnosed by slit-lamp examination or examination under anesthesia from march 2014 to march 2019 were evaluated. patients who had a full-thickness ocular injury repaired at other centers were excluded. in the medical charts, the initial ophthalmology examination sheets, hospital records, details of the operation notes, and outpatient follow-up were all reviewed. demographic data were collected on age, sex, injured eye, ocular status before the trauma, laterality, place of trauma, month and year of injury, and mechanism of trauma. the initial best corrected distance visual acuity (bcdva), evaluated by snellen chart, was recorded. no light perception (nlp) visual acuity (va) was confirmed using an indirect ophthalmoscope with a bright and highest intensity light source. clinical data such as intraocular pressure (iop) with goldman tonometer, location of injury (home, school, and street), type of injury, uvea and pupil status, hyphema, lens status, vitreous, retina and choroidal conditions, involvement of orbit, presence of uveitis or endophthalmitis, and types of required surgeries were all recorded. based on the birmingham eye trauma terminology (bett), cases were classified into penetrating, perforating, or iofb injury. the study protocol was approved by the ethics committee of the university hospital. it adhered to the tenants of the declaration of helsinki. continuous parameters were reported as mean ± sd. chi-square and fisher’s exact tests were used to compare the categorical data, and independent t-test and anova tests were used to compare the continuous data. statistical analysis was performed using the spss for windows (spss inc, chicago, il). data analysis was interpreted using a significance level of p < 0.05. results a total of 110 eyes of 108 pediatric patients initially diagnosed as ogi was included in this five-year study period (from march 2014 to march 2019). patients’ mean age was 7.8 ± 5.2 years (range, 6 months to 18 years) with a median of 7 years and a mode of 2 years. the mean age was 8.7 ± 5.4 years for boys, while the girls’ mean age was 5.8 ± 4.1 years (p = 0.006). patients’ eyes were divided into three different age groups: <7 years (49.1% n = 54), 7–12 years journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 89 pediatric open globe injuries; azimi et al (26.4% n = 29), and 13–18 years (24.5% n = 27). the majority of our cases were in the preschool age (<7years) group (p < 0.001). in our study, 69.1% of eyes were related to the male gender (n = 76) and 30.9% were related to females (n = 34). boys were statistically more susceptible to experience ogi than girls (ratio 2.2:1; p < 0.001). this predominance rose sharply from preschool children to older children 13–18 years old (1.57:1 to 8:1) (p < 0.001). as shown in figure 1, there is a negative correlation between age and incidence of ogi in girls. the rate of right eye involvement was 53.6% (n = 59), and the left eye was 46.3% (n = 51) with no statistically significant difference. there were two cases with bilateral eye involvement caused by motor vehicle accident and mine explosion. as shown in table 1, the incidence of ogi was lowest in winter and highest in spring with no statistically significant difference by season (p = 0.76). incidences were more on the weekends, but there were no significant differences regarding the day of the week (weekdays vs weekends; p = 0.37) [table 2]. most of the injuries were caused by sharp objects (37.3% n = 41), followed by blunt objects (35.3% n = 39), accidents and falls (17.3% n = 19), and guns and fireworks (10% n = 11). a statistically significant difference was identified between causative objects of the injuries and different age groups (p = 0.027). sharp objects comprised a greater number of ogi in the preschool age group (<7 years), while blunt objects, accidents and falls, and guns and fireworks accounted for more injuries in older children (7–18 years). knives and wooden sticks were the most common tools among the sharp and blunt objects that provoked ogi in all children [table 3]. home was the most predominant place of injury (54% n = 60), followed by outdoor environment (street 25.5% n = 28, farm 7.3% n = 8, industrial places 0.9% n = 1) and school (11.8% n = 13). home was the top place that injuries occurred amid the preschool age group (<7), while the outdoor environment was more frequent in older ages (all ps < 0.001) [table 4]. most of the injuries (68% n = 75) occurred while playing. in decreasing order of frequency, accidents (17.3% n = 19), assaults (10% n = 11), and occupation-related factors (4.5% n = 5) were the other activities that led to injuries (p < 0.001). the majority of the injuries in both boys and girls happened during playing, but assaults and occupation-related factors encompassed a higher percentage of injuries in boys (boys to girls’ ratio for assaults is 7.3:2.7, and for occupational is 3.6:0.9) (p < 0.001). the most common types of injury, according to bett, were penetrating injuries (60.9% n = 67), followed by rupture (7.3% n = 8), iofb (6.4% n = 7) and perforating injury (0.9% n = 1). of the 110 traumatized eyes, 25 (22.7%) had multiple eye involvement and could not be categorized based on the bett system. two (1.8%) cases only had a partial-thickness laceration of the eye. penetrating traumas were the primary type of injuries in all age groups and genders, however, rupture injuries were observed mainly in boys and children over seven years of age (87%, seven out of eight rupture cases). we had only one case of perforating injury; a 16-year-old boy hit by a shotgun while playing on the farm. laceration layers in penetrating injuries were mostly corneoscleral (47.7% n = 32), followed by corneal (29.8% n = 20) and scleral (22.3% n = 15) layers. corneoscleral involvement rose sharply in boys as compared to girls (25:10 cases). there were no significant statistical differences in penetrating injuries between different genders (p = 0.38) and age (p = 0.16) according to the laceration layers. the mean size of lacerations in corneal penetrating injuries was 5.7 ± 3.1 mm with a median of 5 mm, while it was 3.47 ± 2.3 mm in scleral penetrating injuries with a median of 3 mm. in 57 cases of corneal penetrating injuries, the main site of laceration was nasal (35% n = 20), followed by temporal (28% n = 16), central (15.8% n = 9), superior (12.3% n = 7), and inferior (8.8% n = 5). in 52 cases of scleral penetrating injuries, the most common site of laceration was nasal (36% n = 19), followed by temporal (28% n = 15), inferior (17% n = 9), superior (15% n = 8), and central (1.9% n = 1) [table 5]. upon arrival, va could not be evaluated in 36.4% (n = 40) of the cases because they were uncooperative. in four cases, va was recorded using the csm method (central, steady, and maintained eye position), which all of them presented c+s+m+va. bcdva upon arrival was categorized into three groups: 0.5–1, 0.1–0.49, and under 0.1 decimal. in 90 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 pediatric open globe injuries; azimi et al figure 1. distribution of trauma according to sex and age groups. figure 2. vision categories by sex and age groups. table 1. number of ogi by season. season number percentage spring 34 30.9 p = 0.76 summer 28 25.5 fall 25 22.7 winter 23 20.9 ogi, open globe injury table 2. distribution of trauma by days of the week. days of the week n percentage saturday 14 12.7 p = 0.37 sunday 18 16.4 monday 15 13.6 tuesday 12 10.9 wednesday 11 10.0 thursday 19 17.3 friday 21 19.1 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 91 pediatric open globe injuries; azimi et al table 3. causative objects of open globe injuries in children. objects n (%) objects n (%) knife 23 (20.9%) belt 3 (2.7%) accidents 16 (14.5%) eye glass 3 (2.7%) wood 12 (10.9%) fall 3 (2.7%) metal, wire, nails 8 (7.2%) fist 3 (2.7%) stone 7 (6.4%) animal horn 2 (1.8%) gun 5 (4.5%) pen 2 (1.8%) fireworks 5 (4.5%) explosion 1 (0.9%) needle 4 (3.6%) others 13 (11.8%) table 4. place of injury according to age groups. age groups (yr) place of injury home school outdoor p-value n (%) <7 43 (39.1) 1 (0.9) 10 (9.1) <0.001 7–18 17 (15.5) 12 (10.9) 27 (24.5) <0.001 66 eyes, which had registered va upon arrival, most of the eyes had va under 0.1 (62.1% n = 41), followed by 0.5–1 (25.7% n = 17) and 0.1–0.49 (12.1% n = 8). in under 0.1 categories, va was counting fingers in 13 cases, hand-motion in 6 cases, light perception in 9 cases, and nlp in 13 cases. as shown in figure 2, in the male group, the va under 0.1 was clearly higher than the female group. additionally, the cases between 7 and 18 years old, compared to patients <7 years old, significantly presented the va under 0.1 upon arrival. operation was performed on 93.6% of the cases (n = 103) with an initial diagnosis of ogi. ninety-five percent of the operations (n = 98) were performed within 24 hr from the admission time. five children only had an examination under sedation (eus). three children were discharged voluntarily despite the physicians’ recommendation for surgery. out of the 98 patients who underwent surgery, 47.3% were operated on once; 33.6% (n = 37) had two surgeries; and 12.7% (n = 14) had more than two surgeries. primary repair of lacerations was the most common type of the initial operation (75.7% n = 78). peritomy comprised 24.2 % (n = 25) of the initial operations. table 6 shows operations that were done after the initial surgeries. of the 110 eyes with ogi, injuries finally led to the enucleation of the eyes in 7.2% of the cases (n = 8). about 88% of the patients received antibiotics during admission to the hospital. children in preschool-age received more intravitreal antibiotics or a combination of both intravitreal and intravenous antibiotics, while antibiotic therapy in older aged children was mainly via the intravenous route (p = 0.008) [table 7]. about 84% of the patients (n = 93) received intravenous antibiotics. the mean days of receiving antibiotics were 3.4 ± 1.2 days, with a median of three days. a combination of ceftazidime and vancomycin were the most common antibiotics used intravenously (75% n = 70), followed by cefazolin and gentamicin (22% n = 21) and ceftriaxone and vancomycin (2.1% n = 2). from 20 cases who received intravitreal antibiotics during operation, cefazoline was the main choice (18 out of 20), and two other cases received intravitreal gentamycin and imipenem. discussion pediatric ogi can cause lifelong complications and unilateral blindness.[6] since prevention is better than cure, solutions must be found to reduce it. our study revealed an increase in ogi in preschoolaged children (<7 years). this is similar to the 92 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 pediatric open globe injuries; azimi et al table 5. complications and eye layers involvement. complication n (%) complication n (%) corneal laceration 59 (53) retina: hemorrhage 5 (4.5) scleral laceration 55 (50) retina: edema 3 (2.7) uvea in wound 5 (4.5) retina: tear 2 (1.8) hyphema 76 (69) retina: dialysis/detachment 3 (2.7) iris injury 28 (25) external muscles 2 (1.8) hypotony 108 (98.18) lid 19 (17.2) optic nerve injury 26 (23) lacrimal system 2 (1.8) lens: cataract 40 (36) orbit: fracture 5 (4.5) lens: subluxated/dislocated 3 (2.7) orbit: foreign body 1 (0.9) vitreous: hemorrhage 17 (15.4) orbit: hemorrhage 4 (3.6) vitreous: prolapse 2 (1.8) inflammation: uveitis 9 (8.1) choroid: hemorrhage 2 (1.8) inflammation: endophthalmitis 5 (4.5) choroid: rupture 1 (0.9) table 6. operations after the initial surgeries. operation n (%) operation n (%) lensectomy 21 (19) pupiloplasty 4 (3.6) deep viterectomy 21 (19) phaco 2 (1.8) anterior viterectomy 2 (1.8) tarsoplasty 2 (1.8) suture removal 9 (8.1) iris cystectomy 2 (1.8) enucleation 8 (7.2) lateral canaloplasty 1 (0.9) iofb removal 6( 5.4) dacryocystorhinostomy 1 (0.9) iol implantation 5 (4.5) erms removal 1 (0.9) pciol implantation 3 (2.7) posterior capsulectomy 1 (0.9) lid reconstruction 4 (3.6) orbital wall repair 1 (0.9) study by el-sebaity et al,[7] but some reports have found increasing ogi risk in the 7–12 years old age group.[8–10] different studies showed different ratios of female ogl, but all agree that males’ injury is statistically higher than females’ injury, which is related to the propensity of the male gender to higher risk activities with less parental supervision as part of their natural growth.[4, 11–15] besides, the differences between the sexes among the older age groups (12–18 years) increased significantly, and there was a negative correlation between age and incidence of ogi in females. it suggests that girls’ dangerous and risky activities may reduce with aging. there was no significant difference between the right and the left eyes. this is similar to the results of the study by tan et al,[16] however, some reports have revealed that in adult cases, the right eye is more susceptible to injuries because, in adults, most injuries occur in the workplace.[17, 18] it must also be kept in mind that severe traumatic accidents, explosions, or intentional assault injuries may induce bilateral ocular involvement. we have reported the ogi trend during vacation, as mentioned in other studies.[19, 20] a higher incidence of ogi on fridays shows that children have more dangerous activities on the weekend. the risk increase in spring is a result of norouz holidays in iranian culture. at this time, the weather becomes warmer, and children tend journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 93 pediatric open globe injuries; azimi et al table 7. route of antibiotic injection by age groups. age groups (yr) route of antibiotic p-value intravitreal intravenous both 0.008 n (%) <7 11 (11.3) 27 (27.8) 12 (12.4) 7–18 3 (3.1) 39 (40.2) 5 (5.2) to play outdoor group games without parental supervision. it may be avoided with parental supervision, keeping dangerous devices out of children’s reach, and educating children about proper safety considerations. the prevailing etiological agent causing ogi in the preschool age group is sharp material such as knives, which correlates with previous studies.[6, 21, 22] ocular trauma with knives usually happens accidentally. it is crucial to either decrease access to sharp objects or replace them with round blunt-tipped knives.[1] older children are injured more by blunt objects, accidental falls, guns, and fireworks, predominantly in males related to practicing more aggressive behavior. these injuries can be prevented with proper training and using protective eyewear. ocular trauma during car and motor accidents were the cause of 14.5% of ogi, and it is usually due to glass particles or blunt trauma. using seatbelts and helmets may reduce the risk of experiencing ocular trauma during a road accident. prior studies have revealed that ocular injuries most frequently occur at home.[4, 12, 23] in this study, home was the main place for the incidence of ocular injuries occurring in preschool-aged children. as this age group spends most of their time at home, the use of toys with blunt edges and increased parental supervision may reduce the ocular trauma risk. covering the sharp edges of household items with protective equipment may also be useful. further awareness of parents and babysitters is recommended to prevent preschoolage ogi.[24] some reports have shown that outdoor spaces are the most common place for ogi occurrences in pediatrics.[25, 26] in our study, the outdoor environment is the primary place for older children, especially in the male group, due to accidents, assaults, and occupation-related factors. educating children to follow safety principles and practice anger management can be useful in reducing the occurrence of accidents, assaults, and occupational hazards that may lead to ogi. analysis of ogi in this report revealed that penetrating injuries were the most common type of ocular trauma (60.9%), which was consistent with data published by puodžiuvienė et al.[8] the rate of globe ruptures was 7.3%, which was lower than the data reported by court et al.[27] ogi with iofb is more often experienced in adults. however, it is not rare in children.[28] the rate of iofb injuries in our study was 6.4%. compared to other types of ogi in pediatrics, perforating injury is not common in this group[29] as this type of injury is most often caused by shotgun usage which is not normally used in this age group. in our study, one patient was 16 years old with perforating ogi caused by firing a shotgun while playing on the farm. the majority of wounds involve both cornea and sclera (47.3%), and hypotony is the most common presentation (98.18%). two patients did not have hypotony because the laceration was partial thickness. hyphema was the second most common sign (69%). one study had shown that hyphema was significantly related to closed globe injuries.[30] the other prevalent signs in ogi are traumatic cataract, iris injury, optic nerve injury, lid laceration, and vitreous hemorrhage. in this study, 37.3% of cases had <0.1 va upon arrival where 78% were males. this measurement is justified as more severe injuries occur in males due to their inherently more aggressive behavior. primary repair of the wound and repositioning of the prolapsed tissue is the most common surgery performed initially, usually within 24 hr from admission.[4] endophthalmitis is one of the most serious and poor prognosis complications after ogi, which is preventable by primary wound closure.[31] about one-third (33.6%) of cases underwent surgeries twice, and 12.7% of them underwent surgeries three times. lensectomy and deep vitrectomy were the most common types of surgery performed after the initial operation. in 94 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 pediatric open globe injuries; azimi et al an effort to prevent sympathetic ophthalmia, 7.2% of cases underwent enucleation and conformer placement surgery due to devastating injury and nlp va. antibiotics administration plays a role in prophylaxis and treatment of endophthalmitis.[32] traumatic endophthalmitis is usually seen in delayed wound closure, iofb, posterior capsule rupture, delayed initiation of prophylactic antibiotic therapy after 24 hr from ocular trauma, and wound contamination with organic material.[33, 34] the antibiotic selected for treatment should have a broad spectrum acting against a larger group of microorganisms.[35] the visual prognosis in pediatric ogi is not good. statistics show that patients with ocular trauma in one eye are susceptible to trauma in the fellow eye.[36] assessing ocular trauma is more important in the pediatric group due to longer lifespans and the more incidence of ocular complications in this group including cataract, retinal detachment, vitreous hemorrhage, corneal opacity, amblyopia, iofb and toxicity due to chronic foreign bodies, endophthalmitis, and sympathetic ophthalmia; hence emphasizing that prevention is better than treatment. education of parents, babysitters, and school teachers about children’s supervision and choosing suitable toys according to child’s age is needed. keeping dangerous objects with sharp edges out of the reach of children is essential. using protective eye glasses may play a useful role in preventing ocular trauma, while playing or working with sharp objects. to prevent eye injuries during an accident, using safety measures like suitable child seats, seat belts, and helmets are effective. older children should be educated to avoid using guns, fireworks, and explosive devices. this report is a retrospective and nonrandomized study with some limitations because it was limited to medical files during hospitalization. further studies may be needed to determine the overall burden of disease, post-discharge follow-up data, final va, and delayed complications. the second limitation is that as ocular trauma patients were referred to multiple centers, the actual number of patients with ogi recorded in this report is incomplete. in summary, the results suggest the importance of prevention in reducing the frequency of ocular trauma in children due to longer lifespan. also, it has recommended early primary wound closure to reduce or prevent devastating ocular complications. additionally, it has counsel that extended follow-up is necessary to reduce and manage further complications such as amblyopia. more studies are recommended to accurately evaluate the prognosis of ogi in the long-term. acknowledgements this work was supported by shiraz university of medical sciences and poostchi ophthalmology research center. financial support and sponsorship none. conflicts of interest the authors declare that they have no conflict of interest. references 1. hosseini h, masoumpour m, keshavarz-fazl f, razeghinejad mr, salouti r, nowroozzadeh mh. clinical and epidemiologic characteristics of severe childhood ocular injuries in southern iran. middle east afr j ophthalmol 2011;18:136–140. 2. ilhan hd, bilgin ab, cetinkaya a, unal m, yucel i. epidemiological and clinical features of paediatric open globe injuries in southwestern turkey. int j ophthalmol 2013;6:855–860. 3. batur m, seven e, akaltun mn, tekin s, yasar t. epidemiology of open globe injury in children. j craniofac surg 2017;28:1976–1981. 4. li x, zarbin ma, bhagat n. pediatric open globe injury: a review of the literature. j emerg trauma shock 2015;8:216–223. 5. ojabo co, malu kn, adeniyi os. open globe injuries in nigerian children: epidemiological characteristics, etiological factors, and visual outcome. middle east afr j ophthalmol 2015;22:69–73. 6. aldahash f, mousa a, gikandi pw, abu el-asrar am. pediatric open-globe injury in a university-based tertiary hospital. eur j ophthalmol 2020;30:269–274. 7. el-sebaity dm, soliman w, soliman am, fathalla am. pediatric eye injuries in upper egypt. clin ophthalmol 2011;5:1417–1423. 8. puodžiuvienė e, jokūbauskienė g, vieversytė m, asselineau k. a five-year retrospective study of the epidemiological characteristics and visual outcomes of pediatric ocular trauma. bmc ophthalmol 2018;18:10. 9. shoja m, mir aa. pediatric ocular trauma. 2006. journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 95 pediatric open globe injuries; azimi et al 10. sofi ra, wani js, keng mq, sofi ra. profile of children with ocular trauma. jk-practitioner 2012;17:44–50. 11. baiyeroju-agbeja am, olurin-aina oi. penetrating eye injuries in children in ibadan. afr j med med sci 1998;27:13–15. 12. ahmadabadi mn, alipour f, tabataei sa, karkhane r, rezaei h, ahmadabadi en. sharp-object-induced openglobe injuries in iranian children admitted to a major tertiary center: a prospective review of 125 cases. ophthalmic res 2011;45:149–154. 13. liu x, liu z, liu y, zhao l, xu s, su g, et al. determination of visual prognosis in children with open globe injuries. eye 2014;28:852–856. 14. saxena r, sinha r, purohit a, dada t, vajpayee rb, azad rv. pattern of pediatric ocular trauma in india. indian j pediatr 2002;69:863–867. 15. choovuthayakorn j, patikulsila p, patikulsila d, watanachai n, pimolrat w. characteristics and outcomes of pediatric open globe injury. int ophthalmol 2014;34:839–844. 16. tan a, mallika p, asokumaran t, mohamad aziz s, intan g. paediatric ocular trauma in kuching, sarawak, malaysia. malays fam physician 2011;6:68–71. 17. unterlauft jd, rehak m, wiedemann p, meier p. firework-related eye trauma in germany. curr eye res 2018;43:1522–1528. 18. unterlauft jd, wiedemann p, meier p. [firework-related eye trauma from 2005 to 2013]. klin monbl augenheilkd 2014;231:915–920. 19. madan ah, joshi rs, wadekar pd. ocular trauma in pediatric age group at a tertiary eye care center in central maharashtra, india. clin ophthalmol 2020;14:1003–1009. 20. maurya rp, srivastav t, singh vp, mishra cp, al-mujaini a. the epidemiology of ocular trauma in northern india: a teaching hospital study. oman j ophthalmol 2019;12:78– 83. 21. lee ch, lee l, kao ly, lin kk, yang ml. prognostic indicators of open globe injuries in children. am j emerg med 2009;27:530–535. 22. xu yn, huang ys, xie lx. pediatric traumatic cataract and surgery outcomes in eastern china: a hospital-based study. int j ophthalmol 2013;6:160–164. 23. dulal s, ale jb, sapkota yd. profile of pediatric ocular trauma in mid western hilly region of nepal. nepal j ophthalmol 2012;4:134–137. 24. gunes a, kalayc m, genc o, ozerturk y. characteristics of open globe injuries in preschool children. pediatr emerg care 2015;31:701–703. 25. skiker h, laghmari m, boutimzine n, ibrahimy w, benharbit m, ouazani b, et al. [open globe injuries in children: retrospective study of 62 cases]. bull soc belge ophtalmol 2007:57–61. 26. tok o, tok l, ozkaya d, eraslan e, ornek f, bardak y. epidemiological characteristics and visual outcome after open globe injuries in children. j aapos 2011;15:556–561. 27. court jh, lu lm, wang n, mcghee cnj. visual and ocular morbidity in severe open-globe injuries presenting to a regional eye centre in new zealand. clin exp ophthalmol 2019;47:469–477. 28. zhang t, zhuang h, wang k, xu g. clinical features and surgical outcomes of posterior segment intraocular foreign bodies in children in east china. j ophthalmol 2018;2018:5861043. 29. jandeck c, kellner u, bornfeld n, foerster mh. open globe injuries in children. graefes arch clin exp ophthalmol 2000;238:420–426. 30. el-sebaity dm, soliman w, soliman am, fathalla am. pediatric eye injuries in upper egypt. clin ophthalmol 2011;5:1417–1423. 31. zheng l, tan j, liu r, yang x, he h, xiao h, et al. the impact of primary treatment on post-traumatic endophthalmitis in children with open globe injuries: a study in china. int j environ res public health 2019;16. 32. abouammoh ma, al-mousa a, gogandi m, al-mezaine h, osman e, alsharidah am, et al. prophylactic intravitreal antibiotics reduce the risk of post-traumatic endophthalmitis after repair of open globe injuries. acta ophthalmol 2018;96:e361–e365. 33. schmidseder e, de kaspar hm, kampik a, klauß v. posttraumatic endophthalmitis after penetrating eye injury. risk factors, microbiological diagnosis and functional outcome. ophthalmologe 1998;95:153–157. 34. dehghani ar, rezaei l, salam h, mohammadi z, mahboubi m. post traumatic endophthalmitis: incidence and risk factors. glob j health sci 2014;6:68–72. 35. ahmed y, schimel a, pathengay a, colyer m, flynn hw. endophthalmitis following open-globe injuries. eye 2012;26:212–217. 36. ozturk t, cetin dora g, ayhan z, kaya m, arikan g, yaman a. etiology and visual prognosis in open globe injuries: results of a tertiary referral center in turkey. sci rep 2019;9:17977. 96 journal of ophthalmic and vision research volume 18, issue 1, january-march 2023 editorial time to call into question the fundus-based evaluation of diabetic retinopathy after intravitreal injections ramin tadayoni, md, phd université de paris, ophthalmology department, ap-hp, hôpital lariboisière, f-75010, paris, france orcid: ramin tadayoni: https://orcid.org/0000-0001-5616-3579 j ophthalmic vis res 2020; 15 (1): 4–6 diabetic retinopathy (dr) scores have two fundamental objectives: (1) detecting dr complications and their severity and (2) predicting the risk of progression to dr complications when they are not yet present. detecting complications is the easiest part as it only requires to properly evaluate the existing situation such as finding new vessels or an edema. on the contrary, predicting the risk of progression is the most challenging part as it involves predicting the future. over the last century, the airlie house classification group and later the early treatment diabetic retinopathy study research (etdrs) group have done an outstanding work, even with the current standard, to create and improve a scoring to be used to predict the risk of dr progression before the occurrence of complications.[1] not all diseases and complications can be predicted with the exploration tools available. for example, the occurrence of diabetic macular edema cannot yet be appropriately predicted. conversely, proliferative dr might be predicted based on the signs seen on fundus examination or, even better, on fundus photos.[1] the etdrs group has done a very precise stepby-step work, evaluating not only the value of the signs but also the reproducibility of their evaluation, to identify the most suitable signs. their choices were also based on pragmatism. they did not have all the currently available imaging modalities, so they have mainly used 7-field fundus photos covering for that time a satisfactory wide surface of the fundus. eventually, fluorescein angiography has been found to be slightly more powerful than standard photos. however, as it is an invasive technique, the extra power supplied has not been considered justified given the treatments available at that time.[2] the diabetic retinopathy severity scale (drss) and its simplified versions have finally become the gold standard for evaluating dr in clinical studies and for treating patients. dr pathophysiology is better known today and it is obvious that, before the occurrence of proliferation, fundus signs act as surrogates for diabetesrelated changes: deep hemorrhages are signs of capillary non-perfusion that leads to ischemia and vascular endothelial growth factor (vegf) secretion, while venous beading is a feature of vessel impregnation with vegf for example. some hemorrhages may eventually disappear over time despite persistent non-perfusion but if the nonperfusion area expands, new hemorrhages appear. therefore, the higher the extand of hemorrhages is, the more new non-perfusion areas occur, and the higher the risk of progression to proliferation is. it should be noted that these signs do not correspond to the disease itself (i.e. retinal héamorrahges per se are not the problem), but are used to estimate the risk of dr progression to its complicated forms. the drss and its variants have been used for so long that over time many clinicians have ended up merging these surrogate signs with their meaning and the disease itself. thus, a reduction in hemorrhages has become the equivalent of dr improvement. this might have been acceptable as far as there was no mean to dissociate disease progression and its surrogate signs. intravitreal injections, in particular anti-vegf agents, have since been developed and used for the treatment of diabetic macular edema. as expected from an effective anti-angiogenic agent, anti-vegf drugs have been shown to be able to 4 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i1.5971&domain=pdf&date_stamp=2019-07-17 editorial; tadayoni control new vessels in dr eyes. more interestingly, it has also been shown that the drss score based on color fundus photos could improve after antivegf intravitreal injections.[3, 4] for these reasons, they have immediately been labeled as agents improving dr. in case of regression of a complication of dr, including new vessels or edema, it may be legitimate to call it dr improvement. however, in case of reduction in signs of non-complicated dr, this can only be acceptable if the risk of progression is proportionally reduced. in other words, if, after anti-vegf injection, the etdrs-drss fundus photo score decreases from 53, that is, severe non-proliferative diabetic retinopathy (npdr), to 35, that is, mild npdr, the risk of progression to proliferative dr during the year should decrease from > 50% to < 10%, and it should evolve at least as any mild npdr that is likely to progress to severe npdr usually several years thereafter. data on dr evolution after anti-vegf treatment are limited but the reported series tend to suggest that anti-vegf intravitreal injections clear the fundus from hemorrhages and signs of vessel impregnation with vegf without eliminating the risks of neovascularization shortly after treatment discontinuation.[5] this may indicate that despite a drss score improvement, ischemia persists. to explore this assumption, we have conducted two successive studies evaluating retinal perfusion after three anti-vegf injections. in the first study based on fluorescein angiography, no vessel reperfusion was found despite an improved drss score on color photos. indeed, even after this short treatment, new vessels, when present, regressed partly or totally. fundus signs also improved in others. then, the drss score improved by at least one stage in 61% of eyes. meanwhile, in our study based on ultrawide-field fluorescein angiography, no significant reperfusion of arterioles or venules was observed in or around the non-perfusion areas.[6] in the second study, using a similar method but based on wide-field oct angiography, we found that despite a rapid drss score improvement after anti-vegf treatment, no reperfusion occurred, including at the capillary level.[7] thus, our two studies have shown that the drss score can improve in the absence of reperfusion. it is now the time to question the fundus-based evaluation of dr after intravitreal injections. when after intravitreal injection a severe npdr (score 53 etdrs-drss) changes its appearance to the one of a mild npdr (score 35) on fundus photography but continue to have the non-perfusion of a score 53, will it evolve as a mild npdr or as a severe npdr? if one considers that the non-perfusion is the cause of ischemia and vegf production leading to proliferation, unless other mechanisms are involved, the evolution should be closer to the evolution of a severe npdr. this substantial doubt on the value of fundus-based etdrs-drss scores invalidates relying only on color fundus for grading npdr after intravitreal injections. waiting more data or a new method for assessing the risk of progression available, what may be the practical effects of such an uncertainty on the post-injection value of the etdrs-drss scores? in clinical practice, if the injections are continued with short enough intervals, they may prevent any complications, but if they are discontinued, to be on the safe side, regardless of the fundus appearance, the risk should be considered the highest measured during the medical history of the eye and the follow-up should be decided accordingly. in some cases, oct angiography or fluorescein angiography may also help to reevaluate the status of retinal perfusion. in upcoming clinical trials on this topic, it would be safe to include as much as possible multimodal imaging to compile data and also to be able to provide information required by the updated standards when they will end. we can indeed hope that in the forthcoming years, we will better understand with which modality and how we should evaluate dr for eyes treated by intravitreal injections. more generally, regardless of injections, isn’t it time to try to switch from the historical classification of dr to new modalities using the best available modern images and all available data? references 1. fundus photographic risk factors for progression of diabetic retinopathy. etdrs report number 12. early treatment diabetic retinopathy study research group. ophthalmology 1991;98:823–833. 2. fluorescein angiographic risk factors for progression of diabetic retinopathy. etdrs report number 13. early treatment diabetic retinopathy study research group. ophthalmology 1991;98:834–840. 3. ip ms, domalpally a, sun jk, ehrlich js. long-term journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 5 editorial; tadayoni effects of therapy with ranibizumab on diabetic retinopathy severity and baseline risk factors for worsening retinopathy. ophthalmology 2015;122:367–374. 4. writing committee for the diabetic retinopathy clinical research network, gross jg, glassman ar, jampol lm, inusah s, aiello lp, et al. panretinal photocoagulation vs intravitreous ranibizumab for proliferative diabetic retinopathy: a randomized clinical trial. jama 2015;314:2137–2146. 5. wubben tj, johnson mw; anti-vegf treatment interruption study group. anti-vegf therapy for diabetic retinopathy: consequences of inadvertent treatment interruptions. am j ophthalmol 2019;204:13–18. 6. bonnin s, dupas b, lavia c, erginay a, dhundass m, couturier a, et al. anti-vascular endothelial growth factor therapy can improve diabetic retinopathy score without change in retinal perfusion. retina 2019;39:426– 434. 7. couturier a, rey pa, erginay a, lavia c, bonnin s, dupas b, et al. swept-source wide-field oct-angiography versus ultra-wide-field fluorescein angiography assessments of retinal non-perfusion in diabetic retinopathy and edema treated with anti-vegf. ophthalmology 2019;126:1685– 1694. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i1.5971 how to cite this article: tadayoni r. time to call into question the fundusbased evaluation of diabetic retinopathy after intravitreal injections. j ophthalmic vis res 2020;15:4–6. 6 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 https://knepublishing.com/index.php/jovr original article association between nsaid and statin therapy and the incidence of intravitreal anti-vascular endothelial growth factor injections and nd:yag laser treatment after cataract surgery in finland sirpa loukovaara1, md, phd; jjari haukka2,3, phd 1unit of vitreoretinal surgery, department of ophthalmology, helsinki university hospital, and individualized drug therapy research program, university of helsinki, helsinki, finland 2department of public health, university of helsinki, helsinki, finland 3faculty of medicine and health technology, tampere university, finland orcid: sirpa loukovaara: https://orcid.org/0000-0002-2506-3900 abstract purpose: to examine the association between the use of topical non-steroidal antiinflammatory (nsaid) medication, systemic statin therapy, and the incidence rate of two of the most common postsurgical procedures in adult patients undergoing cataract surgery in finland between january 1, 2010 and december 31, 2016. methods: this retrospective, nationwide cohort study considered 176,052 cataract operations coded with the international classification of disease coding: early adult (h25.0), normal (h25.1), other senile (h25.8), pre-senile (h26.02), or other (related to trauma, other eye disease, or medication). operations were linked to purchased and reimbursed medications using anatomical therapeutic chemical codes. the incidence rate of intravitreal anti-vascular endothelial growth factor (vegf) injections, and neodymium-doped yttrium aluminum (nd:yag) laser treatments of posterior capsular opacification were evaluated using the poisson regression model. results: in our registry cohort, patients with a prescription of topical nsaid (ketorolac) at the time of cataract surgery were less likely treated with intravitreal anti-vegf injections after surgery (adjusted poisson regression model irr 0.3; 95% ci: 0.15–0.60, p = 0.0007), and also had reduced incidence of nd:yag laser (0.59, ci: 0.43–0.81, p = 0.0011) treatments. unlike topical nsaid, the use of systemic statin therapy was not associated with these two most common surgical procedures (rr 1.04, 95% ci: 0.96–1.12, p = 0.33). conclusion: the use of topical nsaids is associated with reduced rates of intravitreal anti-vegf injections and nd:yag laser treatments after cataract surgery. more observational and experimental studies are warranted to confirm possible benefits of topical nsaid administration after cataract surgery. keywords: anti-inflammatory; capsulotomy; cataract surgery; cystic macular edema; epidemiology; intravitreal injection; ketorolac; nationwide cohort study; nsaid; secondary cataract; statin therapy j ophthalmic vis res 2022; 17 (2): 186–196 186 © 2022 loukovaara and haukka. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i2.10789&domain=pdf&date_stamp=2019-07-17 nsaid and statin use and post cataract surgery interventions ; loukovaara and haukka introduction cataract surgery is the most commonly performed surgical procedure in the world.[1] posterior capsular opacification (pco) can occur a few months to many years after uncomplicated clear corneal phacoemulsification with intraocular lens implantation, demanding further treatment with neodymium-doped yttrium aluminum (nd:yag)laser capsulotomy.[2] in some operated eyes, removal of cataract can also cause postoperative cystoid macular edema (cme), leading to the need for intravitreal anti-vascular endothelial growth factor (vegf) treatment.[3, 4] to treat postoperative inflammation after cataract surgery, both topical steroidal and nonsteroidal anti-inflammatory (nsaid) drops are widely used. lately, immunomodulatory systemic statin therapy has also been shown to be beneficial in ophthalmology.[5–7] the use of systemic statins are known to decrease inflammatory responses, reduce fibrosis formation, as well as lower the risk of ophthalmic surgical interventions.[6, 8–12] recently, a systematic review and meta-analysis of a sample of approximately 310,000 patients showed that the use of statins could moderately increase the risk of future cataracts (relative risk, 1.13; 95% ci: 1.01–1.25).[13] however, more information is needed to analyze the potential association of systemic statin use, and the rate of intravitreal anti-vegf injection treatment or nd:yag-laser treatment after cataract surgery. the purpose of this study was to examine the incidence rate of intravitreal anti-vegf injections and nd:yag laser procedures after cataract surgery in adult patients in a large finnish cohort correspondence to: sirpa loukovaara, md, phd. associate professor, unit of vitreoretinal surgery, department of ophthalmology, university of helsinki and helsinki university hospital, haartmaninkatu 4 c, 00290 helsinki, finland, europe. email: sirpa.loukovaara@hus.fi received: 28-10-2020 accepted: 11-03-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i2.10789 in addition to establishing whether the rate of administering these two most common procedures correlates with the use of topical nsaid drops and/or systemic statin therapy at the time of surgery? methods this was a population-based epidemiologic study of adult patients who underwent cataract surgery from july 1, 2010 to december 31, 2016 in finland. in brief, we obtained information of cataract operations (phacoemulsification with implantation of artificial lens in posterior chamber; coded as cje20) based on the nordic medico-statistical committee (nomesco) codes, and data were retrieved from the database of the national institute for health and welfare (thl) (permission ref. thl/2038/5.05.00/2017). the adult cataract eyes were coded with international classification of disease (icd)-codes as follows: h25.0 (early adult cataract), h25.1 (normal cataract), h25.8 (other senile cataract), h26.02 (presenile cataract), or other (i.e., related to trauma, other eye disease, or medication). the data consisted of the patient-related variables (date, type of operation/procedure code, laterality of the eye, age, sex, systemic comorbidities). after cataract surgery, the two major ophthalmic surgical procedure codes defined by nomesco were included: intravitreal injection of anti-vegf medication (ckd05) and treatment of pco with neodymium-doped yttrium aluminum (nd:yag) laser (cjb10). all purchased and reimbursed medications were recorded in the finnish prescription register with anatomical therapeutic chemical (atc) code (whocc atc/ddd index. 2012). for each drug, reimbursement-related factors, including the dispensing date (date of purchase), atc code, and the quantity dispensed (amount in defined daily doses) were recorded. this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: loukovaara s, haukka j. association between nsaid and statin therapy and the incidence of intravitreal anti-vascular endothelial growth factor injections and nd:yag laser treatment after cataract surgery in finland. j ophthalmic vis res 2022;17:186–196. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 187 https://knepublishing.com/index.php/jovr nsaid and statin use and post cataract surgery interventions ; loukovaara and haukka we included the following drugs (purchased during the prior six months) as time-dependent variables: statins (atc code c10aa; simvastatin, atorvastatin, rosuvastatin, other), insulins (a10a), and other diabetes drugs (odd) (a10b). patients were classed as statin users if they had purchased the prescription for any statins in the six months prior to the cataract surgery. patients were prescribed different statin doses, once or twice daily, but this could not be taken into account in the analysis. we analyzed the data of ophthalmic drugs with atc codes starting with code s (covering steroids, nsaids, antibiotic, glaucoma, antiallergic, immunomodulatory, and lubricating drops). these drugs were prescribed one month before or one week after the cataract operation [suppl table 1]. medications-related data were obtained from the social insurance institution of finland (kela permission ref. 93/522/2017). the frequency of topically administered nsaids could not be taken into account in the final analysis. finnish registry for reimbursed medication includes reimbursement rights and diagnosis, and special reimbursement rights. we used the following reimbursement rights (no/yes) as covariates: diabetes, hypothyreosis, psychiatric and other mental illnesses, glaucoma, breast cancer, prostate cancer, transplantation, other cancer, kidney disease with dialysis, chronic heart disease, connective tissue disease, rheumatic diseases and other related conditions, chronic hypertension, coronary heart disease and hypercholesterolemia, chronic arrhythmia, colitis ulcerosa, and crohn´s disease. the dates and cause of death (icd-10) were obtained from statistics finland (tk-52-1785-18). all data from four registers were linked by means of the unique personal identification number assigned to all people living in finland. the follow-up started at first procedure of any type of cataract operation type and ended on death or december 31, 2016. the two most common secondary procedures, that is, anti-vegf injection or nd:yag laser treatment between the first operation and the end of follow-up (death or december 31, 2016) were recorded. the ethics approval was obtained from the institutional committees of the hjelt institute, university of helsinki, and the hospital district of helsinki and uusimaa, helsinki, finland. the study was register-based and without patient contact. statistical analysis intravitreal anti-vegf injection and nd:yag-laser treatments were the main endpoints, and the completion of the follow-up process or death were treated as censoring events. the main exposures were topical nsaid (ketorolac) and systemic immunomodulatory statin treatment defined by having prescriptions both before and after operations in half-year time windows. current diabetes medication (insulin, other diabetes drugs [oad]) were defined in a similar way. we modelled incidence of secondary operation, that is, need for the anti-vegf and nd:yaglaser treatment using poisson regression models. incidence rate ratios (irr) which were calculated along with the cumulated follow-up time were taken into account. confounding was controlled using background variables (sex, age, baseline usage of insulin, and other diabetes drugs [oad], chronic diseases, calendar year of cataract surgery, and time since start of follow-up at the time of cataract surgery). we used natural splines with knots in 0.5, 1.5, 2.5, 3.5, 4.5, and 5.5 years for modelling time from the start of the followup period. we calculated predicted incidence as a function of time from the start of the followup period using the lowest category for each covariate. all calculations were carried out using r language.[14] results altogether 269,929 cataract operations took place in finland between july 1, 2010 and december 31, 2016. in 135,305 (50.1%) of the operations, the laterality of the cataract surgery was not known, so these operations were excluded. finally, our study population consisted of 89,201 individuals who underwent cataract surgery, with 89,201 right eyes and 86,851 left eyes in our cohort (n = 176,052 operations). the baseline characteristics of the study’s patients are shown in table 1. the cataract operations were performed in 11 hospital districts representing both highand low-volume clinics around finland whose population is 5.5 million. in our study, the majority of the eyes (93.7%) were operated due to normal age-related cataract (coded as h25.0, h25.1, h25.8), 2.1% of operated eyes had pre-senile cataract, and 4.2% were operated due to trauma or other eye disease. 188 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 nsaid and statin use and post cataract surgery interventions ; loukovaara and haukka figure 1. kaplan-meier cumulative events curves with 95% confidence intervals. figure 2. predicted incidence with 95% confidence interval for intravitreal anti-vegf injection and nd:yag-laser capsulotomy based on poisson regression model. of the operated patients, 62.7% were female. the median age of the patients was 75.6 years (range 68.9–81.1). of note, of all operated patients, 35.2% used statin therapy (simvastatin 21%, atorvastatin 8.7%, rosuvastatin 2.8%, other statin 2.7%). the proportion of statin users differed among specific cataract subgroups, the lowest being among patients who were operated on due to pre-senile cataract (coded as h26.02; 17.9%). as regards to the systemic comorbidities, 14.3% had diabetes, 12.4% systemic hypertension, 10% chronic heart disease, 2.7% rheumatoid arthritis, 1.9% hypothyrosis, 1.8 % prostate cancer, and 1.6% had breast cancer. according to our analysis, these comorbidities did not reveal any associations with main event rates. altogether, 8.9% of all cataract operations were performed on glaucoma patients. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 189 nsaid and statin use and post cataract surgery interventions ; loukovaara and haukka table 1. basic characteristics of finnish study cohort (n = 176 052). icd-10 code type of cataract h25.0 h25.1 h25.8 h26.02 other overall early adult normal adult other senile pre-senile n 6432 138765 19738 3640 7473 176052 sex, female (%) 4048 (62.9) 87685 (63.2) 12345 (62.5) 1949 (53.5) 4307 (57.6) 110334 (62.7) age (median [iqr]) 75.97 [69.18, 81.37] 75.91 [69.68, 81.19] 76.73 [70.20, 81.95] 55.38 [49.90, 59.46] 69.88 [59.56, 77.59] 75.58 [68.91, 81.05] age (%; yr) 45 12 (0.2) 598 (0.4) 32 (0.2) 372 (10.2) 567 (7.6) 1581 (0.9) 45–65 912 (14.2) 16336 (11.8) 2105 (10.7) 3124 (85.8) 2137 (28.6) 24614 (14.0) >65 5508 (85.6) 121831 (87.8) 17601 (89.2) 144 (4.0) 4769 (63.8) 149853 (85.1) insulin (%) 388 (6.0) 9884 (7.1) 1741 (8.8) 307 (8.4) 768 (10.3) 13088 (7.4) oral antidiabetic medication (%) 980 (15.2) 22845 (16.5) 3450 (17.5) 394 (10.8) 1048 (14.0) 28717 (16.3) simvastatin (%) 1439 (22.4) 29770 (21.5) 4186 (21.2) 389 (10.7) 1229 (16.4) 37013 (21.0) atorvastatin (%) 469 (7.3) 12264 (8.8) 1797 (9.1) 169 (4.6) 541 (7.2) 15240 (8.7) rosuvastatin (%) 153 (2.4) 4005 (2.9) 554 (2.8) 69 (1.9) 160 (2.1) 4941 (2.8) other statin (%) 157 (2.4) 3776 (2.7) 596 (3.0) 26 (0.7) 162 (2.2) 4717 (2.7) any statin (%) 2216 (34.5) 49783 (35.9) 7129 (36.1) 651 (17.9) 2088 (27.9) 61867 (35.1) ketorolac (%) 44 (0.7) 1985 (1.4) 1080 (5.5) 90 (2.5) 261 (3.5) 3460 (2.0) comorbidities glaucoma (%) 546 (8.5) 12112 (8.7) 1303 (6.6) 151 (4.1) 1523 (20.4) 15635 (8.9) diabetes (%) 799 (12.4) 19930 (14.4) 3100 (15.7) 381 (10.5) 964 (12.9) 25174 (14.3) connective tissue diseases, rheumatoid arthritis, and comparable diseases (%) 199 (3.1) 3684 (2.7) 556 (2.8) 94 (2.6) 255 (3.4) 4788 (2.7) chronic coronary heart disease (%) 558 (8.7) 14107 (10.2) 2255 (11.4) 133 (3.7) 561 (7.5) 17614 (10.0) the eyes with cataract were coded with international classification of disease (icd)-codes as follows: h25.0 (early adult cataract), h25.1 (normal cataract), h25.8 (other senile cataract), h26.02 (presenile cataract), or other (i.e., related trauma, other eye disease, or medication). oad, oral antidiabetic drug; iqr, interquartile range. after cataract surgery, the intravitreal anti-vegf injection was administered to 1180 (0.7%) operated eyes, of which 191 eyes were diagnosed with diabetic macular edema (dme) and 989 eyes with cme. nd:yag-laser capsulotomy was performed due to the development of pco on 2268 (1.3%) eyes. combinatory topical antibiotic-cortisone eye drops were used in the majority of the operated study eyes. topical nsaid (ketorolac) was used in 3460 (2.0%) of the operated eyes, the majority of the nsaid (ketorolac) users being in the h25.8 group (5.5%). the incidence rates of secondary surgery overall incidence rates (any event per 100 personyears) showed that out of all the cataract-operated patients, according to the univariate model, those with insulin treatment had an 83% higher risk for secondary operations (intravitreal anti-vegf injection or nd:yag-laser) (irr1.21, 95% confidence interval, ci: 1.10–1.34), however, only 13% of diabetic patients with oad had a higher risk for secondary operations (intravitreal anti-vegf injection or nd:yag-laser). of note, female patients had a 20% higher risk for both intravitreal injection 190 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 nsaid and statin use and post cataract surgery interventions ; loukovaara and haukka table 2. incidence rates (per 100 person-years) for nd:yag laser capsulotomy and intravitreal anti-vegf injection with 95% confidence interval. incidence rate ratio (irr) from univariate poisson model with 95% confidence interval. group person-years (1/100) n rate (1/100) irr n rate (1/100) irr yag-laser treatment injection sex male 1771 593 0.33 (0.31–0.36) (reference) 504 0.28 (0.26–0.31) (reference) female 3172 1675 0.53 (0.50–0.55) 1.58 (1.44–1.73) 676 0.21 (0.20–0.23) 0.75 (0.67–0.84) age (yr) <45 48 67 1.39 (1.08–1.76) (reference) 31 0.64 (0.44–0.91) (reference) 45–65 759 467 0.62 (0.56–0.67) 0.44 (0.34–0.57) 164 0.22 (0.18–0.25) 0.34 (0.23–0.49) >65 4136 1734 0.42 (0.40–0.44) 0.30 (0.24–0.39) 985 0.24 (0.22–0.25) 0.37 (0.26–0.53) insulin no 4605 2109 0.46 (0.44–0.48) (reference) 933 0.20 (0.19–0.22) (reference) yes 338 159 0.47 (0.40–0.55) 1.03 (0.87–1.21) 247 0.73 (0.64–0.83) 3.60 (3.13–4.15) oral antidiabetic medication no 4170 1929 0.46 (0.44–0.48) (reference) 925 0.22 (0.21–0.24) (reference) yes 773 339 0.44 (0.39–0.49) 0.95 (0.84–1.06) 255 0.33 (0.29–0.37) 1.49 (1.29–1.71) simvastatin no 3853 1826 0.47 (0.45–0.50) (reference) 889 0.23 (0.22–0.25) (reference) yes 1090 442 0.41 (0.37–0.44) 0.86 (0.77–0.95) 291 0.27 (0.24–0.30) 1.16 (1.01–1.32) atorvastatin no 4563 2086 0.46 (0.44–0.48) (reference) 1061 0.23 (0.22–0.25) (reference) yes 380 182 0.48 (0.41–0.55) 1.05 (0.90–1.22) 119 0.31 (0.26–0.37) 1.35 (1.11–1.63) rosuvastatin no 4825 2204 0.46 (0.44–0.48) (reference) 1142 0.24 (0.22–0.25) (reference) yes 118 64 0.54 (0.42–0.69) 1.19 (0.92–1.52) 38 0.32 (0.23–0.44) 1.36 (0.98–1.88) ketorolac no 4795 2228 0.46 (0.45–0.48) (reference) 1172 0.24 (0.23–0.26) (reference) yes 148 40 0.27 (0.19–0.37) 0.58 (0.42–0.79) 8 0.05 (0.02–0.11) 0.22 (0.11–0.44) glaucoma no 4508 2072 0.46 (0.44–0.48) (reference) 1079 0.24 (0.23–0.25) (reference) yes 436 196 0.45 (0.39–0.52) 0.98 (0.85–1.13) 101 0.23 (0.19–0.28) 0.97 (0.79–1.19) connective tissue diseases no 4818 2222 0.46 (0.44–0.48) (reference) 1144 0.24 (0.22–0.25) (reference) yes 125 46 0.37 (0.27–0.49) 0.80 (0.60–1.07) 36 0.29 (0.20–0.40) 1.21 (0.87–1.69) chronic coronary heart disease no 4481 2105 0.47 (0.45–0.49) (reference) 1066 0.24 (0.22–0.25) (reference) yes 463 163 0.35 (0.30–0.41) 0.75 (0.64–0.88) 114 0.25 (0.20–0.30) 1.04 (0.85–1.26) or nd:yag-laser operations (irr 1.20, 95% 1.12– 1.29) [supplemental table 1]. when intravitreal anti-vegf injections and nd:yag-laser were studied separately, significant differences were observed [table 2]. in males, the incidence of nd:yag-laser was higher than in females, but the association was the opposite for intravitreal anti-vegf injections. the journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 191 nsaid and statin use and post cataract surgery interventions ; loukovaara and haukka table 3. incidence rate ratios (with 95% confidence intervals) based on poisson regression model. adjusted for calendar year and time since start of follow-up. nd:yag-laser treatment anti-vegf injection sex (male vs female) 1.61 (1.47–1.77) 0.84 (0.75–0.94) age (yr) <45 (reference) (reference) 45–65 0.44 (0.33–0.57) 0.46 (0.31–0.69) >65 0.30 (0.23–0.38) 0.55 (0.38–0.81) insulin (yes vs no) 1.09 (0.92–1.29) 3.34 (2.86–3.90) oral antidiabetic medication (yes vs no) 1.03 (0.91–1.16) 0.99 (0.85–1.16) simvastatin (yes vs no) 0.93 (0.83–1.04) 1.10 (0.95–1.27) atorvastatin (yes vs no) 1.15 (0.98–1.34) 1.11 (0.91–1.36) rosuvastatin (yes vs no) 1.29 (1.00–1.66) 1.15 (0.82–1.60) other statin (yes vs no) 1.03 (0.80–1.33) 0.69 (0.45–1.05) ketorolac (yes vs no) 0.59 (0.43–0.81) 0.30 (0.15–0.60) diagnosis h25.1 (reference) (reference) h25.0 0.09 (0.05–0.16) 0.23 (0.13–0.42) h25.8 0.23 (0.18–0.30) 0.35 (0.26–0.47) h26.02 0.52 (0.38–0.72) 0.48 (0.27–0.84) other 1.03 (0.85–1.25) 2.04 (1.66–2.51) glaucoma (yes vs no) 0.97 (0.84–1.12) 0.91 (0.74–1.12) connective tissue diseases (yes vs no) 0.75 (0.56–1.00) 1.13 (0.81–1.58) chronic coronary heart disease (yes vs no) 0.85 (0.72–1.00) 0.86 (0.70–1.05) anti-vegf, anti-vascular endothelial growth factor; nd:yag, neodymium-doped yttrium aluminum laser incidence for intravitreal anti-vegf injections was higher in insulin users (irr 3.60, 3.13–4.15). cumulative events curves showed that during the first two postoperative years, the probability of administering intravitreal anti-vegf injections was more common than the probability of using nd:yaglaser, however, after two years the situation was reversed [figure 1]. poisson regression analysis according to our analysis, after adjusting for age and chronic diseases, we detected that insulin usage among cataract-operated patients was associated with a higher risk for intravitreal anti-vegf injection (irr 3.5, 95% ci: 2.9–4.1; p < 0.0001) treatment, but the use of oad was not (irr 1.1, 95% 0.92–1.33, p = 0.30). the unadjusted incidence rates showed that systemic use of simvastatin (irr 1.16, 95% ci: 1.0–1.32), atorvastatin (irr 1.35, 95% ci: 1.1–1.6), and rosuvastatin (irr 1.36, 95% ci: 0.98–1.9) were associated with an increased rate of intravitreal injections after cataract surgery [table 2]. however, after an adjustment for baseline confounders with the poisson model, no differences were found. we found no association between the usage of rosuvastatin (p = 0.05), simvastatin (p = 0.21), or atorvastatin (p = 0.09) and the incidence rate for nd:yag-laser treatment in our cohort. of note, the use of topical nsaid (ketorolac) was associated with reduced intravitreal injection rates (irr 0.3; 95% ci: 0.15–0.60, p = 0.0007) as well as reduced incidence of nd:yag-laser (irr 0.59; 95% ci: 0.43–0.81, p = 0.0011) treatments after cataract operations. accordingly, the female gender was associated with a decreased rate of intravitreal injections (irr 0.84; 95% ci: 0.74–0.94, p = 0.0026) administration, but with a significantly increased 192 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 nsaid and statin use and post cataract surgery interventions ; loukovaara and haukka rate of nd:yag-laser treatments (irr 1.67; 95% ci: 1.47–1.78, p < 0.0001). predicted incidence curves of intravitreal injections and nd:yag laser procedures after cataract surgery predicted incidence plots showed that the incidence of nd:yag-laser capsulotomy peaked about four-and-a-half years after cataract operation [figure 2]. conversely, intravitreal injections were given typically during the first few months after surgery or later after about four-and-a-half years after surgery. discussion in our study, based on 176,052 cataract operations performed during the years 2010 to 2016 in finland, the use of topical nsaid (ketorolac) was associated with a 70% (40–85%) reduced incidence rate of intravitreal anti-vegf injection to treat postoperative me and a 41% (19–57%) reduced incidence rate of nd:yag-laser to treat pco or fibrosis after cataract surgery. unlike ketorolac, systemic statin use was not associated with the rate of nd:yag-laser capsulotomy after cataract surgery. although there was a trend toward a statistically significant association between systemic rosuvastatin use and an increased need for nd:yag-laser capsulotomy, this finding could still be a statistical coincidence, as no association was found between simvastatin or atorvastatin usage and the incidence rate of nd:yag laser treatment. despite all technological advancements, cataract surgery always induces an inflammatory response, leading to side effects, cme and pco.[4,15,16] today, nsaids are used to treat the postoperative anterior chamber inflammation after cataract surgery either combined with steroids or alone.[17,18] however, topical medication protocols vary worldwide, being specific to each surgical unit. of note, in our register-based study, the operated eyes were routinely treated with combined antibiotic-steroid eye drops, and only minority (2%) of eyes received topical nsaid (ketorolac), confirming our recent findings that revealed that the least common combination after cataract operation was the triple treatment (steroids, antibiotic, and topical nsaid).[19] out of other topical commercially available nsaids (nepafenac, bromfenac, diclofenac), only diclofenac was used in our study, but could not be analyzed due to the limited number of eyes treated. historically, the treatment protocol with topical nsaids after cataract surgery began in the 1970s.[20,21] in the first double-blind, randomized, single-center study of 59 adults undergoing cataract surgery, topical ketorolac tromethamine 0.5% was shown to be as effective and welltolerated as prednisolone acetate 1% solution in controlling postoperative inflammation and pain.[22] the addition of topical bromfenac to steroids was shown to reduce inflammation better than the use of steroids alone after cataract surgery.[23] pretreatment, by nsaids or steroids, has been shown to reduce postoperative inflammation and risk of cme.[24]recently, topical nsaids offered efficacy comparable to steroids in reducing postoperative inflammation, however, nsaids were also superior in reducing the risk of cme after cataract surgery.[3] of note, in our study, the use of systemic statin was neither beneficial nor detrimental after cataract surgery. the pathogenesis of pco is known to include a fibrotic reaction of lens epithelial cells caused by transforming growth factors, and statins are known to prevent fibrosis.[8, 25] in finland we have official guidelines to treat secondary cataract once the visual acuity has dropped to <0.6 on snellen, meaning that we do not treat the secondary cataract patients with va better than 0.6 in the tertiary clinics. however, in the private sector there are no such strict guidelines. despite many reports suggesting that statins could reduce fibrosis in various ophthalmic conditions,[7, 10, 26]no association was found in the incidence rate of nd:yag capsulotomies in statin-treated cataract patients as compared with non-statin treated. we do acknowledge the following limitations. our study was based on administrative register data, and there are some inaccuracies in procedure coding such as missing data. we considered only baseline medications (at the time when the cataract operation took place). therefore, it is probable that, for example, statin usage was changed during the six-year follow-up period. it is also worth mentioning that the prevalence of postoperative macular edema (me) is known to vary from study to study depending on how me is defined. previous studies have shown that there journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 193 nsaid and statin use and post cataract surgery interventions ; loukovaara and haukka is a low incidence of 0.1% to 2.4% of clinically significant postoperative me in patients with no risk factors. in our study, altogether, 0.7% of study eyes received anti-vegf injections for postoperative me after cataract surgery. in finland, in cases with postoperative me (either cme or dme), there is a recommendation to use topical nsaid for two months postoperatively. if there is no response to topical nsaid, the patient will then be referred to a medical retina unit for consultation including optical coherence tomography measurements, initiation of anti-vegf treatment, and in very rare cases for insertion of a dexamethasone implant. in addition to diabetes, many ophthalmic factors are also related to the increased risk of me. these include the duration of phaco surgery, the need for additional instrumentation due to small pupils or exfoliation syndrome (including iris hooks or malyugin ring), intraoperative complications, and the severity profile of the operated eyes (dense cataract). unfortunately, these important factors could not be taken into account in this observational register-based study. cataract causes 25% of global blindness, especially in the developing world.[28] compared with a recent paper, cataract patients in our study were older and the proportion of patients with comorbidities such as diabetes and hypertension was smaller.[29] in finland with a care guarantee, cataract surgery is available for everybody in need, despite household income status, education, or occupation. in finland, the cataract surgery rate is 7000 per 1 million people, which is proportionate to the range of 4000 to 10,000 per million performed in developed countries.[30] in conclusion, our study is the first populationbased study of cataract-operated eyes providing an estimate of anti-vegf and nd:yag laser procedures in finland post cataract surgery. based on our register study, we recommend use of topical non-steroidal anti-inflammatory prophylaxis after cataract surgery, unless the patient has systemic contraindications such as asthma, because topical nsaid (ketorolac) was associated with a remarkably lower incidence rate of nd:yag-laser and intravitreal anti-vegf injection after cataract surgery. however, although systemic statin use did not seem to have beneficial effects after cataract surgery as regards the development of pco or cme, it was good to observe that neither did it seem to increase the burden of ophthalmic interventions after cataract surgery. financial support and sponsorship this study was supported by y1014silm1 grant (sl) and funded by university of helsinki, finland (jh). conflicts of interest there are no proprietary interests or conflicts of interest related to this submission. references 1. eurostat. surgical operations and procedures statistics – statistics explained [internet]. eurostat; 2020 [cited 2017 nov 30]. available from: http://ec. europa.eu/eurostat/statistics-explained/index.php?title= surgical_operations_and_procedures_statistics&oldid= 27060. 2. ursell pg, dhariwal m, majirska k, ender f, kalson-ray s, venerus a, et al. three-year incidence of nd:yag capsulotomy and posterior capsule opacification and its relationship to monofocal acrylic iol biomaterial: a uk real world evidence study. eye 2018;32:1579–1589. 3. kessel l, tendal b, jørgensen kj, erngaard d, flesner p, lundgaard andresen j, et al. post-cataract prevention of inflammation and macular edema by steroid and nonsteroidal anti-inflammatory eye drops: a systematic review. ophthalmology 2014;121:1915–1924. 4. grzybowski a, sikorski bl, ascaso fj, huerva v. pseudophakic cystoid macular edema: update 2016. clin interv aging 2016;11:1221–1229. 5. park jh, yoo c, kim yy. e?ect of lovastatin on woundhealing modulation after glaucoma filtration surgery in a rabbit model. invest ophthalmol vis sci 2016:57:1871– 1877. 6. loukovaara s, sahanne s, takala a, haukka j. statin use and vitreoretinal surgery: findings from a finnish population-based cohort study. acta ophthalmol 2018:96:442–451. 7. ooi kg, khoo p, vaclavik v, watson sl. statins in ophthalmology. surv ophthalmol 2019:64:401–432. 8. kawahara s, hata y, kita t, arita r, miura m, nakao s, et al. potent inhibition of cicatricial contraction in proliferative vitreoretinal diseases by statins. diabetes 2008;57:2784– 2793. 9. tuuminen r, sahanne s, loukovaara s. low intravitreal angiopoietin-2 and vegf levels in vitrectomized diabetic patients with simvastatin treatment. acta ophthalmol 2014;92:675–681. 10. tuuminen r, haukka j, loukovaara s. statins in rhegmatogenous retinal detachment are associated with low intravitreal angiopoietin-2, vegf and mmp-2 levels, and improved visual acuity gain in vitrectomized patients. graefe’s arch clin exp ophthalmol 2015;253:1685–1693 11. vail d, callaway nf, ludwig ca, saroj n, moshfeghi dm. lipid-lowering medications are associated with lower risk of retinopathy and ophthalmic interventions among u.s. patients with diabetes. am j ophthalmol 2019;207:378– 384. 194 journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 http://ec.europa.eu/eurostat/statistics-explained/index.php?title=surgical_operations_and_procedures_statistics&oldid=27060. http://ec.europa.eu/eurostat/statistics-explained/index.php?title=surgical_operations_and_procedures_statistics&oldid=27060. http://ec.europa.eu/eurostat/statistics-explained/index.php?title=surgical_operations_and_procedures_statistics&oldid=27060. http://ec.europa.eu/eurostat/statistics-explained/index.php?title=surgical_operations_and_procedures_statistics&oldid=27060. nsaid and statin use and post cataract surgery interventions ; loukovaara and haukka 12. kang e y, chen th, garg sj, sun c-c, kang j-h, wu wc, et al. association of statin therapy with prevention of vision-threatening diabetic retinopathy. jama ophthalmol 2019:137:363–371. 13. yu s, chu y, li g, ren l, zhang q, wu l. statin use and the risk of cataracts: a systematic review and meta-analysis. j am heart assoc 2017;6:e004180. 14. r core team. r: a language and environment for statistical computing. r foundation for statistical computing; 2019. available from: https://www.r-project.org/ 15. stein jd, grossman ds, mundy km, sugar a, sloan fa. severe adverse events after cataract surgery among medicare beneficiaries. ophthalmology 2011;118:1716– 1723. 16. stein jd. serious adverse events after cataract surgery. curr opin ophthalmol 2012;23:219–225. 17. duan p, liu y, li j. the comparative efficacy and safety of topical non-steroidal anti-inflammatory drugs for the treatment of anterior chamber inflammation after cataract surgery: a systematic review and network meta-analysis. graefes arch clin exp ophthalmol 2017;255:639–649. 18. anisimova ns, arbisser lb, petrovski g, petrichuk sv, sobolev np, petrovski b, et al. effect of nsaids on pupil diameter and expression of aqueous humor cytokines in flacs versus conventional phacoemulsification. j refract surg 2018;34:646–652. 19. loukovaara s, lehtinen v, nieminen r, moilanen j. topical levofloxacin, nepafenac and prednisolone acetate medication after cataract surgery in the biggest tertiary eye hospital in finland during 2015-2018. acta ophthalmol 2019;97:e943–e945. 20. podos sm. prostaglandins, nonsteroidal anti-inflammatory agents and eye disease. trans am ophthalmol soc 1976;74:637–660. 21. miyake k. prevention of cystoid macular edema after lens extraction by topical indomethacin (i). a preliminary report. albrecht von graefes arch klin exp ophthalmol 1977;203:81–88. 22. simone jn, pendelton ra, jenkins je. comparison of the efficacy and safety of ketorolac tromethamine 0.5% and prednisolone acetate 1% after cataract surgery. j cataract refract surg 1999;25:699–704. 23. coassin m, iovieno a, soldani a, cavuto s, cimino l, sartori a, et al. bromfenac ophthalmic solution 0.09% as an adjunctive therapy to topical steroids after cataract surgery in pseudoexfoliation syndrome. j cataract refract surg 2016;42:1119–1125. 24. relhan n, forster rk, flynn hw jr. endophthalmitis: then and now. am j ophthalmol 2018;187:xx–xxvii. 25. shu dy, lovicu fj. myofibroblast transdifferentiation: the dark force in ocular wound healing and fibrosis. prog retin eye res 2017;60:44–65. 26. tuuminen r, loukovaara s. statin medication in patients with epiretinal membrane is associated with low intravitreal epo, tgf-beta-1, and vegf levels. clin ophthalmol 2016;23:921–928. 27. al-janabi a, lightman s, tomkins-netzer o. statins in retinal disease. eye 2018;32:981–991. 28. lee cm, afshari na. the global state of cataract blindness. curr opin ophthalmol 2018;28:98–103. 29. salowi ma, goh pp, lee my, adnan th, ismail m. the malaysian cataract surgery registry: profile of patients presenting for cataract surgery. asia pac j ophthalmol 2015;4:191–196. 30. wang w, yan w, fotis k, prasad nm, lansingh vc, taylor hr, et al. cataract surgical rate and socioeconomics: a global study. invest ophthalmol vis sci 2016;57:5872– 5881. journal of ophthalmic and vision research volume 17, issue 2, april-june 2022 195 original article biodistribution of cy5-labeled thiolated and methylated chitosan-carboxymethyl dextran nanoparticles in an animal model of retinoblastoma elham delrish1, phd; fariba ghassemi1,2, md; mahmoud jabbarvand1, md; alireza lashay1, md fatemeh atyabi3,4, phd; masoud soleimani5, phd; rassoul dinarvand3,4, phd 1translational ophthalmology research centre, farabi eye hospital, tehran university of medical sciences, tehran, iran 2retina & vitreous service, farabi eye hospital, tehran university of medical sciences, tehran, iran 3nanotechnology research centre, faculty of pharmacy, tehran university of medical sciences, tehran, iran 4department of pharmaceutics, faculty of pharmacy, tehran university of medical sciences, tehran, iran 5department of hematology, school of medical sciences, tarbiat modares university, tehran, iran orcid: elham delrish: https://orcid.org/0000-0003-4993-7593 abstract purpose: the use of more potent medicine for local chemotherapy of retinoblastoma in order to minimize local and systemic adverse effects is essential. the main goal of this investigation was to assess the biodistribution of thiolated and methylated chitosancarboxymethyl dextran nanoparticles (cmd-tcs-nps and cmd-tmc-nps) following intravitreal (ivt) injection into rat eyes with retinoblastoma. methods: an ionic gelation method was used to fabricate cy5-labelled cmd-tcs-nps and cmd-tmc-nps. the nps were characterized. cellular internalization of cy5-labelled nps was investigated using confocal microscopy and the absorption of labeled nps was quantified by flow cytometry in human retinoblastoma (y79) cells. in addition, the cy5-labeled distribution of nanoparticles in the posterior segment of the eye was histologically imaged by confocal microscopy after ivt injection of nps into the eyes of rats with retinoblastoma. results: cmd-tcs-nps and cmd-tmc-nps showed a mean diameter of 34 ± 3.78 nm and 42 ± 4.23 nm and zeta potential of +11 ± 2.27 mv and +29 ± 4.31mv, respectively. the in vivo study of intraocular biodistribution of cy5-labeled cmd-tcs-nps and cmd-tmcnps revealed that there is more affinity of cmd-tcs-nps to the retina and retinoblastoma tumor after ivt administration while methylated chitosan nanoparticles are immobilized in the vitreous and are not able to reach the retina even after 24 hr. conclusion: the ionic gelation technique was efficient in synthesizing a biocompatible polymeric nanosystem for drug delivery into the posterior segment of the eye. the current study demonstrated increased ocular bioavailability of cmd-tcs-nps relative to cmd-tmc-nps in retinoblastoma induced rat eyes. keywords: biodistribution; carboxymethyl dextran; chitosan; cy5-labeled; nanoparticles; retinoblastoma j ophthalmic vis res 2022; 17 (1): 58–68 58 © 2022 delrish et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10171&domain=pdf&date_stamp=2019-07-17 biodistribution of nanoparticles; delrish et al introduction the blood–retinal barrier prevents large molecules from passing into the retina from the blood and choriocapillaris.[1] the presence of efflux transporters and the pigmented structure of the choroid are the major limiting factors affecting therapeutic molecule penetration from the choroid to the retina and subsequently into the vitreous.[2, 3] sclera mainly limits the delivery of lipophilic drugs. the effect of the molecular radius however is greater than that of lipophilicity, which affects the scleral permeability of the drug.[1] vitreous, which consists mostly of 99% water, also contains only a few solid components, such as collagen and glycosaminoglycans.[4] the vitreous poses a substantial barrier to injectable therapeutic molecules, especially to the diffusion of suspended solids or combinations of high molecular weight.[5] intravitreal (ivt) injection is the most popular method for delivering drugs into the posterior portion of the eye. it delivers the needed therapeutic concentration of the drug to the posterior segment with minimal but considerable hazards.[6–8] with recent developments in nanocarriers, polymeric carriers are being employed in facilitating drug delivery to the eye to improve the drug’s bioavailability.[9–12] natural polysaccharides are attractive for the formulation of ocular medications because they are nontoxic, economical, available, generally biodegradable and biocompatible, and usually amenable to chemical modification to fabricate new derivatives.[13–18] chemical modifications have been recently used to fabricate derivatives with improved properties in terms of mucoadhesion, increased ocular bioavailability, and drug solubilization.[19–23] the bioavailability of nps in the retina can be enhanced using this technique. it is proven that peg-coated polystyrene nps with neutral surface correspondence to: mahmoud jabbarvand, md. translational ophthalmology research centre, farabi eye hospital, tehran university of medical sciences, tehran 1336616351, iran. email: ma.jabarvand@gmail.com received 21-12-2020; accepted 11-08-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10171 charge up to the size of 750 nm could freely diffuse through bovine vitreous to reach the retina. diffusion coefficients in nanoparticles were found to be greater at 100–500 nm rather than at 750 nm. carboxylic groups coating was used to fabricate negatively charged beads, which were able to readily diffuse through the vitreous. negatively charged nanoparticles, on the other hand, are more impacted by size than neutrally charged nps, as a negative-500nm-particle was unable to efficiently disperse through vitreous fluid.[26] when nanoparticles made of human serum albumin (hsa), hyaluronic acid, or a combination of the two are injected intravitreally, they can reach the retina. polyethylene imine nanoparticles with positive surface charge cannot spread through the vitreous when intravitreally injected and are therefore not beneficial for ivt route. nanoparticles fabricated from glycosylated chitosan (200–500 nm) can reach the retina when intravitreally injected but are not able to penetrate inner limiting membrane.[27] to the best of our knowledge, no study has been performed to investigate the bioavailability of cy5 fluorescent dye oligonucleotide labeled thiolated and methylated chitosan nanoparticles following ivt injection in the eyes of rats with retinoblastoma. therefore, in this investigation, we characterized the effects of the surface charge of thiolated and methylated chitosan nps on the diffusion and tissue distribution after a single ivt injection into the retinoblastoma bearing rat eyes. methods materials medium-molecular-weight chitosan (cs) with a degree of deacetylation of about 89% was purchased from primex (karmoy, norway). n-ethylcarbodiimide hydrochloride (edc), nhydroxysuccinimide (nhs), carboxymethyl dextran (cmd) sodium salt (10–20 kd, 1.1–1.5 mmol carboxyl/g), ellman’s reagent, rpmi-1640 tissue this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: delrish e, ghassemi f, jabbarvand m, lashay a, atyabi f, soleimani m, dinarvand r. biodistribution of cy5-labeled thiolated and methylated chitosan-carboxymethyl dextran nanoparticles in an animal model of retinoblastoma . j ophthalmic vis res 2022;17:58– 68. journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 59 https://knepublishing.com/index.php/jovr biodistribution of nanoparticles; delrish et al culture medium, fetal bovine serum (fbs), and dialysis tubing (molecular weight cut-off 2, and 12 kda)‘1 were purchased from sigma-aldrich (missouri, usa). n-methyl-2-pyrrolidone (nmp), sodium chloride, hydrochloric acid, and sodium hydroxide (naoh) were all purchased from merck (darmstadt, germany). the human retinoblastoma cell line (y79). all chemicals were of analytical grade. synthesis and characterization of tmc tmc was synthesized according to the method reported by sieval et al.[28] the degree of quaternization (% dq) was distinguished using 1h nmr spectrum of tmc which was prepared by a 600 mhz spectrometer (bruker-biospin, germany). the %dq was estimated by the following formula: dq = [[(ch3)3 / [h] × 1/9] × 100, where dq is the level of quaternization; [(ch3)3] is the integral of chemical shift of the hydrogens of n+(ch3)3 groups at 3.4 ppm; and [h] is the integral of h-1 peaks between 4.7 and 5.7 ppm.[29] synthesis and characterization of tmccysteine conjugates: the method of synthesis was according to margit et al.[30] in the first step, 100 milligrams (mgr) of synthesized tmc was dissolved in 5 ml of distilled water (di) and then 200 mgr of cysteine was added and then mixed until dissolved. in the second stage, edc and nhs were added. the mixture was then incubated for 3 hr in the dark under continuous stirring at room temperature and the ph was balanced to 5. afterward, the solution was dialyzed (membrane dialysis mw cut-off = 2 kda) using 1 mm hcl for three days at 4ºc. eventually, the solution was lyophilized to obtain a powdery substance (tmc-cys) and stored at 4ºc. the amount of free thiol groups attached on the tmc backbone was determined by photometry with ellman’s reagent. the thioglycolic acid standards curve was used to determine the quantitative amount of thiol groups.[31] ft-ir spectra of tcs were prepared with an ftir spectrophotometer (vectore 22, germany). preparation of cmd-tcs nanoparticles the nanoparticles were fabricated by a simple coacervation technique.[32] carboxymethyl dextran (cmd) was used as the cross-linking agent. nanoparticles were prepared by adding cmd solutions to tcs or tmc solutions. then, an instant vortex stirring was executed and samples were incubated at room temperature for 2 hr. nanoparticles characteristics the particle size of the nanoparticles was distinguished by applying dynamic light scattering on a malvern zetasizer nano-zs (worcestershire, united kingdom). a zetasizer nano series (malvern instruments) was performed to determine the surface charge of the nps. field emission scanning electron microscopy (fesem; zeiss) and transmission electron microscopy (tem, zeiss, em 900) were used to study the morphology of nanoparticles. in vitro cellular uptake of nanoparticles qualitative cellular uptake of cy5-loaded nps was investigated with a confocal laser scanning microscope (nikon, eclipse).[33] for this purpose, the y79 cells were cultured in 6-wells at the density of 2 × 105 cells per well. when the cells reached confluence, the cells were then incubated with cy5-labeled tmc-cmd-nps and tmc-cys-cmd-nps suspension to track their uptake in y79 cells. as a result of this procedure, the nanoparticles were well-dispersed in the culture medium at concentrations of 100 μg/ml. nanoparticle dispersions were incubated at 37ºc in a 5% co2 atmosphere for 2 hr. after aspiration of the medium, the cells were rinsed with 10 ml of cold phosphate buffered saline (pbs) (ph7.4) to eliminate any traces of nanoparticles remaining in the medium. then, the cells were fixed with 2% paraformaldehyde for 10 min at room temperature and stained with dapi (4’,6diamidino-2-phenylindole dihydrochloride). the fluorescence of the cy5-labeled nanoparticles was monitored applying a confocal microscope (excitation 640.8 nm/emission 662–737 nm). 60 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 biodistribution of nanoparticles; delrish et al quantifying level of nps cellular uptake by flow cytometry the cellular internalization of cy5-labeled cmdtmc-nps and cmd-tcs-nps were reconfirmed and compared by flow cytometric analysis in the y79 cells. to execute, the cells were cultured in a 6well plate at a density of 250 × 104 cells/well. after 24 hr of incubation, the cells were treated with cy5-labeled nps at 37ºc for 2 hr. after the incubation, cells were washed with pbs and analyzed for intracellular fluorescence of cy5labeled nps using bd facs calibur flow cytometer (bd biosciences, san jose, ca, usa).[34] rat xenograft model of retinoblastoma for this study, 10 wistar albino rats (male, two months old, purchased from pasteur institute, karaj, iran) were used. all rats were treated in accordance with the arvo (association for vision and ophthalmology research) declaration on the procedure of animals in ophthalmic and vision research, approved by the university of medical sciences of tehran. surgeries were performed by the same surgeon (fg). the rats were immunosuppressed with daily injections of cyclosporin a (csa) (sandimmun®; novartis). approximately 1 × 106 y79 cells were intravitreally injected to the rat eyes.[35] after retinoblastoma tumor formation, cy5-labeled tmc-cmd-nps and tmc-cys-cmd-nps (100 µg/ml) was intravitreally injected. the control eyes received ivt normal saline as same concentration. all the animals were euthanized 24 hr after the ivt injection of cy5-labeled nanoparticles and enucleation was performed on them. afterward, tissues were cut into 5-µm thick layers using a microtome for investigation of qualitative ocular uptake and biodistribution of cy5-labeled nps, which was done with a confocal laser scanning microscope (nikon, eclipse). results nanoparticles characteristics the 1h nmr spectrum of tmc is shown in figure 1. in the 1h nmr spectrum of tmc, the signals at 3.3 to 3.8 ppm were attributed to the methyl group at the n,n,n-trimethylated site ([h3]–[h6]).[36] ftir spectroscopy is an efficient tool for the investigation of the physicochemical attributes of polysaccharide. in this study, the syntheses of tmc and tcs were corroborated by the ftir spectra illustrated in figure 2. the tmc-cys conjugate was synthesized by the development of amide bonds between the amino group of methylated chitosan and carboxylic acid group of cysteine. meanwhile, for tmc the peak at 1470 cm−1 corresponded to the characteristic absorption of n–ch3. the peak at around 1250 cm−1 in the spectra of compound was accredited to the c–sh stretching band. also, the spectra of thiolated-chitosan displayed two powerful characteristic absorptions at 1641 cm−1 and 2500 cm−1 which were attributed to the c = o double bonds of the amido group and stretching vibration of –sh, respectively [figure 2].[37, 38] furthermore, the degree of substitution of thiols using ellman’s protocol was determined as 11%. in addition, cmd-tcs-nps and cmd-tcs-nps had diameters of 34 ± 3.78 and 42 ± 4.23and zeta potentials of 11 ± 2.27 and 29 ± 4.31 (mv), respectively. the polydispersity index (pi) is a parameter used to investigate the homogeneity in the particle size distribution of synthesized nps, pi values <0.3 guarantees the stability of colloidal dispersion.[39] the size distributions of the cmdtcs-nps and cmd-tcs-nps were 0.27 ± 0.05 and 0.21 ± 0.05, respectively. as demonstrated by the sem images [figures 3a & 3b], cmd-tmc-nps and cmd-tcs-nps were spherical in shape. uptake of cy5-labeled nanoparticles by y79 cells the cellular uptake of cy5-labeled cmd-tcs-nps and cmd-tmc-nps by y79 cells was visualized using a confocal microscope after 2 hr of exposure [figure 4]. meanwhile, the nuclei of the y79 cells were stained by dapi (blue fluorescence) in order to ascertain the location of internalized nps. a direct indicator of uptake enhancement by the y79 cells could be increasing the number of uptakes of nps, which was documented by the increase in the intensity of the red color as seen in figure 4. in the cy5-labeled nps groups, the red signal that appeared, was mostly located in cytoplasm. contrastingly, a stronger red signal was discovered to be distributed inside the cells treated with cmd-tcs-nps. compared with cmdtmc-nps, more bioadhesive cmd-tcs-nps were better adsorbed by cell membrane, resulting in journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 61 biodistribution of nanoparticles; delrish et al improved endocytosis of y79 cells and efficacious cellular uptake [figure 4]. uptake with flow cytometry a rapid method for the determination of the absorption of nanoparticles in y79 cells using flow cytometry has been used in this research. the cellular uptake of cy5-labeled cmd-tcsnps and cmd-tmc-nps by y79 cells was further investigated by flow cytometry analysis. the fluorescence intensity of cell emission determined by flow cytometry can be a good marker of the amount of nps internalized by y79 cells. as shown in figure 5, the peak of the fluorescence intensity shifted to a higher level when the cmd-tcs-nps were used, suggesting the promoted cy5-labeled cmd-tcs-nps internalization by y79. animal model diffusion study within the first 24 hr after the ivt injection, the eyes were enucleated and severed into 5 μm thick sections. the nps distribution was investigated by taking confocal images after the ivt injection of the cy5-labeled nps [figure 6]. the two chitosan compositions showed various diffusion rates in the vitreous. after the injection, only cy5-labeled cmdtcs-nps freely disseminated all over the vitreous cavity; 24 hr after the ivt injection, confocal microscopy demonstrated that the cy5-labeled cmd-tcs-nps had accumulated throughout the different retinal layers [figure 6]. also, it showed that cationic cmd-tcs-nps with zeta potentials +11 ± 2.27 mv were able to penetrate efficiently into the rat retina, while cmd-tmc-nps with zeta potential value of +29 mv were trapped in the vitreous. the distinguished diffusion rate between the groups receiving cmd-tmc-nps versus cmdtcs-nps might be due to the difference in surface charges of nps. discussion chemotherapy by nanoparticles has been an effective approach in ophthalmic research in overcoming poor intraocular bioavailability of drugs due to the presence of anatomical barriers and it has also contributed toward improving therapeutic efficiency. the main purpose in the engineering of nano-carriers in this investigation was to develop a promising vehicle via biopolymers to transport drugs to the posterior part of the eye. chitosan is a polymer that has been discovered by researchers for the application of ophthalmic drug delivery systems. mucoadhesive chitosan formulations were also considered as an effective strategy in overcoming the rapid elimination of topical ophthalmic drugs.[40, 41] due to its solubility in acidic solutions (ph = 6), the efficacy of chitosan can be reduced at the site of action. hence, a chemical alteration of chitosan was employed to fabricate a watersoluble derivative of cs. in this study, the nps were fabricated using hydrophilic biopolymers such as tmc, tmc-cys (tcs) and cmd to design efficient and safe drug delivery systems for the posterior segment of the eye.[42] the solubility of tmcnps may also be decreased as a consequence of a high degree of methylation (dq%), which results in a high level of o-methylation. the beneficial approach of combining tmc and cys to fabricate tmc-cys conjugate in preparing desirable derivatives was used in this study to improve the solubility of fabricated nps and minimize the formation of agglomerates.[43, 44] conjugation of polymers with the thiol group is the most common method used in the manufacture of mucoadhesive delivery systems.[45] endocytosis is the dominant mechanism in the adsorption of nanoparticles with a size of <100 nm. the rate of spherical np internalization is affected by size, shape, surface charge, composition, and surface hydrophilicity. non-phagocytic cells absorb the highest number of spherical nanoparticles with sizes between 20 and 50 nm.[46] by labeling nps with cy5, a qualitative assessment of their number can be obtained by evaluating the intensity of the staining seen through the confocal microscope to compare the cell uptake of the nps. an increase in the red color intensity in the staining in the nps-treated group, as compared to the control, could be due to better cellular uptake of nps by y79 cells. therefore, the intensity of the red color that occurs after the labelling can be considered as a direct criterion for assessing the cellular uptake of nps. as shown in figure 4, to prove the presence of nps in the cytoplasm, the cell nucleus was stained with dapi. flow cytometry was also utilized in order to provide a qualitative evaluation of the difference in cellular uptake between the two formulations of nps. as can be seen in figure 5, the cellular uptake of thiolated chitosan nps by y79 cells was better, 62 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 biodistribution of nanoparticles; delrish et al figure 1. ft-ir spectra of cs, tmc, and tcs. figure 2. 1h-nmr spectrum of tmc in d2o. journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 63 biodistribution of nanoparticles; delrish et al figure 3. sem images of cmd-tmc-nps (a) and cmd-tcs-nps (b). figure 4. intracellular localization of cmd-tmc-nps (a–c) and cmd-tcs-nps (d–f) in y79 cells by cy5-labeled nps. labeled nps appear in red in the confocal microscopy fluorescence images. which could be due to greater bioadhesion of tcs (tmc-cys) nanoparticles owing to the tmc combination with the thiol group. in this research, tcs adhesion properties were founded by electrostatic interactions with cysteine. when the nps are intravitreally injected, they must be able to cross the vitreous barrier to reach their destination. the vitreous body is a polyanionic gellike mass which is made up of collagen fibers and glycosaminoglycan.[47] pitkänen et al showed that the major obstacle to nonviral gene delivery systems is the vitreous.[48] peeters et al.[49] also stated that only pegylated particles <500 nm are able to have unrestricted movement through the vitreous. later, it was declared that cationic liposomes with zeta potentials below +20 mv were allowed to defuse efficiently into the murine retina, while liposomes with zeta potential value above +20 mv were completely trapped in the vitreous humor.[50, 51] the drug bioavailability is dependent on the route of drug administration into the eye. 64 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 biodistribution of nanoparticles; delrish et al a: (fl4-h) cy5: mean : 90.8 b: (fl4-h) cy5: mean : 127 figure 5. flow cytometry analysis of cellular uptake of cy5-labeled (a) cmd-tmc-nps and (b) cmd-tcs-nps in y79 cells after 2 hr incubation time. figure 6. confocal microscopy of the retinoblastoma and retina at 24 hr after intravitreal injection of cy5-labeled nps into the vitreous cavity of rat with retinoblastoma. (a–e) control group; untreated retinoblastoma (a) and untreated retina (c). (e–h) eyes injected with cy5-labeled cmd-tcs-nps. the cy5-labeled cmd-tcs-nps diffused to the tumor mass (f) and through the retinal layers (h). (i–l) eyes injected with cy5-labeled cmd-tmc-nps. cy5-labeled cmd-tmc-nps are entirely trapped in the vitreous and are not able to reach the retina even after 24 hr. journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 65 biodistribution of nanoparticles; delrish et al effectiveness of systematically administrated drug vehicles for ocular posterior segment drug delivery is limited by different factors including the wide drug distribution to the offtarget sites and the presence of the blood–retinal barrier.[52] therefore, in this study, in order to achieve maximum bioavailability, ivt injection of nanoparticles has been used. cmd-tmc and cmd-tcs nanoparticles with identical sizes and diverse surface charges were employed to examine the connection between their diffusion rates and their composition. confocal imaging was used to track real-time diffusion in the vitreous cavity of the injected cy5-labelled nanoparticles. by comparing the images of the cmd-tmc-nps, cmd-tcs-nps, and the control groups, the cy5 signal of labeled nps was determined, and the variations of fluorescence intensity in the confocal images illustrated the distribution of cy5-labelled nps [figure 6]. two biocopolymers (tmc and tcs) could self-assemble into nps with identical sizes and various surface charges. tcs could self-assemble into 34 nm nps and with +11mv surface charges, while tmc nps assembled into 42 nm nps with a +29 mv zeta potential. the difference in the surface charges between tmc and tcs nps may result in different diffusion rates of nps after the ivt injection. in the two polymer confocal images of figure 6, tcs with the 11 ± 2.27 mv surface charges displayed the most noticeable alterations in fluorescence signals (red color). the results of this study indicated that the surface charge of nanoparticles might perform a negative or positive role in influencing the retinal penetration of intravitreally injected nps. this investigation also proved that vitreous with anionic properties is a weak barrier for the movement of nps with zeta potentials +11 ± 2.27mv, but vitreous can remarkably limit tmcdiffusion with zeta potentials of +29 ± 4.31mv in vivo [figure 6]. tmc-nps with zeta potentials of +29 ± 4.31 mv are completely immobilized in the vitreous via electrostatic interactions with negatively charged hyaluronic acid and collagen fibers. as shown in figure 6, methylated chitosan nanoparticles are completely trapped in the vitreous and are unable to reach the retina even after 24 hr. thus, a powerfully positive charge (+29 ± 4.31 mv) on the particle surface has a remarkable negative impact on diffusion after ivt injection. through comparing the fluorescence changes in the eye injected with tcs or tmc, the results illustrated in figure 6 indicate that the appropriate surface charges on the particle surface (i.e., +11 ± 2.27 mv) improved the diffusion efficacy of the particles after ivt injection. accordingly, surface improving of the nps with the thiol group in cmdtcs-nps boosts the transfection efficacy of the nps through the development of intra-chain disulphide bonds within the complex. after the success of this elementary step, we plan to use nanoparticlebased cmd-tcs as a controlled drug delivery system for anticancer drugs for retinoblastoma treatment. in conclusion, an effort to facilitate the application of more potent medicine for the local chemotherapy of retinoblastoma to ensure minimization of local and systemic adverse effects, we embarked on the current study. one challenge that is evident in delivering the relevant medicine to the posterior of the eye is the ability of the medicine to break through the vitreous cavity. nanoparticles have been determined to be a viable alternative in targeting specific areas for medication due to their ability to adsorb and diffuse medication in specific areas locally. our study has revealed that appropriate surface charges (preferably +11 ± 2.27 mv) on the surface of nanoparticles nps that were manufactured with different chitosan derivatives may boost their diffusion after ivt injection. a positive charge adversely affects the rate of vitreous diffusion of nps. this research showed that when nps were intravitreally injected, the surface, charge of nps is the most significant limiting factor in their penetration through the vitreous. the cationic bio-polymer with appropriate surface charges is able to reach the retina and diffuse through the retinal layers. the ionic gelation technique was efficient in synthesizing a biocompatible polymeric nanosystem for drug delivery into the posterior segment of the eye. the current study demonstrated increased ocular bioavailability of cmd-tcs-nps relative to cmd-tmc-nps in retinoblastoma containing rat eyes. financial support and sponsorship this research was funded by tehran university of medical sciences, tehran, iran. 66 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 biodistribution of nanoparticles; delrish et al conflicts of interest the authors report no conflicts of interest in this work. references 1. lawrence ms, miller jw. ocular tissue permeabilities. int ophthalmol clin 2004;44:53–61. 2. cheruvu np, amrite ac, kompella ub. effect of eye pigmentation on transscleral drug delivery. invest ophthalmol vis sci 2008;49:333–341. 3. kennedy bg, mangini nj. p-glycoprotein expression in human retinal pigment epithelium. mol vis 2002;8:422– 430. 4. le goff mm, bishop pn. adult vitreous structure and postnatal changes. eye 2008;22:1214–1222. 5. mains j, wilson cg. the vitreous humor as a barrier to nanoparticle distribution. j ocul pharmacol ther 2013;29:143–150. 6. pershing s, bakri sj, moshfeghi dm. ocular hypertension and intraocular pressure asymmetry after intravitreal injection of anti-vascular endothelial growth factor agents. ophthalmic surg lasers imaging retina 2013;44:460– 464. 7. ghasemi falavarjani k, nguyen qd. adverse events and complications associated with intravitreal injection of antivegf agents: a review of literature. eye 2013;27:787–794. 8. kumar a, sehra sv, thirumalesh mb, gogia v. secondary rhegmatogenous retinal detachment following intravitreal bevacizumab in patients with vitreous hemorrhage or tractional retinal detachment secondary to eales’ disease. graefes arch clin exp ophthalmol 2012;250:685–690. 9. al-halafi am. nanocarriers of nanotechnology in retinal diseases. saudi j ophthalmol 2014;28:304–309. 10. yasin mn, svirskis d, seyfoddin a, rupenthal id. implants for drug delivery to the posterior segment of the eye: a focus on stimuli-responsive and tunable release systems. j control release 2014;196:208–221. 11. rawas-qalaji m, williams ca. advances in ocular drug delivery. curr eye res 2012;37:345–356. 12. rowe-rendleman cl, durazo sa, kompella ub, rittenhouse kd, di polo a, weiner al, et al. drug and gene delivery to the back of the eye: from bench to bedside. invest ophthalmol vis sci 2014;55:2714. 13. kritchenkov as, andranovits s, skorik ya. chitosan and its derivatives: vectors in gene therapy. russ chem rev 2017;86:231–239. 14. tiwari s, bahadur p. modified hyaluronic acid based materials for biomedical applications. int j biol macromol 2019;121:556–571. 15. poshina dn, raik sv, poshin an, skorik ya. accessibility of chitin and chitosan in enzymatic hydrolysis: a review. polym degrad stab 2018;156:269–278. 16. berezin as, lomkova ea, skorik ya. chitosan conjugates with biologically active compounds: design strategies, properties, and targeted drug delivery. russ chem bull 2012;61:781–795. 17. pettignano a, charlot a, fleury e. carboxyl-functionalized derivatives of carboxymethyl cellulose: towards advanced biomedical applications. polym rev 2019;59:510–560. 18. fernando ips, kim d, nah jw, jeon yj. advances in functionalizing fucoidans and alginates (bio) polymers by structural modifications: a review. chem eng j 2019;355:33–48. 19. siafaka pi, titopoulou a, koukaras en, kostoglou m, koutris e, karavas e, bikiaris dn. chitosan derivatives as effective nanocarriers for ocular release of timolol drug. int j pharm 2015;495:249–264. 20. rassu g, gavini e, jonassen h, zambito y, fogli s, breschi mc, giunchedi p. new chitosan derivatives for the preparation of rokitamycin loaded microspheres designed for ocular or nasal administration. j pharm sci 2009;98:4852–4865. 21. bongiovì f, di prima g, palumbo fs, licciardi m, pitarresi g, giammona g. hyaluronic acid-based micelles as ocular platform to modulate the loading, release, and corneal permeation of corticosteroids. macromol biosci 2017;17:1700261. 22. zambito y, di colo g. thiolated quaternary ammoniumchitosan conjugates for enhanced precorneal retention, transcorneal permeation and intraocular absorption of dexamethasone. eur j pharm biopharm 2010;75:194–199. 23. hume lr, lee hk, benedetti l, sanzgiri yd, topp em, stella vj. ocular sustained delivery of prednisolone using hyaluronic acid benzyl ester films. int j pharm 1994;111:295–298. 24. xu q, boylan nj, suk js, wang y-y, nance ea, yang j-c, et al. nanoparticle diffusion in, and microrheology of, the bovine vitreous ex vivo. j control release 2013;167:76–84. 25. koo h, moon h, han h, na jh, huh ms, park jh, et al. the movement of self-assembled amphiphilic polymeric nanoparticles in the vitreous and retina after intravitreal injection. biomaterials 2012;33:3485–3493. 26. xu q, boylan nj, suk js, wang yy, nance ea, yang jc, et al. nanoparticle diffusion in, and microrheology of, the bovine vitreous ex vivo. j control release 2013;167:76–84. 27. koo h, moon h, han h, na jh, huh ms, park jh, et al. the movement of self-assembled amphiphilic polymeric nanoparticles in the vitreous and retina after intravitreal injection. biomaterials 2012;33:3485–3493. 28. sieval ab, thanou m, kotze´ af, verhoef jc, brussee j, junginger he. nmr preparation characterization of highly substituted n-trimethyl chitosan chloride. carbohydr polym 1998;36:157–165. 29. snyman d, hamman jh, kotze js, rolling je, kotze af. the relationship between the absulote molecular weight and the degree of quaternization of n-trimethy chitosan chloride. carbohydr polym 2002;50:145–150. 30. margit dh, constantia ek, bernkop-schnürch a. in vitro evaluation of the viscoelastic properties of chitosan– thioglycolic acid conjugates. eur j pharm biopharm 2003;55:185–190. 31. roldo m, hornof m, caliceti p, danbernkop-schnurch a. mucoadhesive thiolated chitosans as platforms for oral controlled drug delivery: synthesis an in vitro evaluation. eur j pharm biopharm 2004;57:115–121. 32. tekie fsm, kiani m, zakerian a, pilevarian f, assali a, soleimani m, et al. nano polyelectrolyte complexes journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 67 biodistribution of nanoparticles; delrish et al of carboxymethyl dextran and chitosan to improve chitosan-mediated delivery of mir-145, carbohydr polym 2017;159:66–75. 33. lanlan l, jiawei g, yuquan w, xiaoxing x, hui t, jin l, et al. a broad-spectrum ros-eliminating material for prevention of inflammation and drug-induced organ toxicity. adv sci 2018;5:1800781. 34. zhigang x, shiying l, yuejun k, mingfeng w. glutathioneand ph-responsive nonporous silica prodrug nanoparticles for controlled release and cancer therapy. nanoscale 2015;7:5859–5868. 35. chevez-barrios p, hurwitz my, louie k, marcus kt, holcombe vn, schafer p, et al. metastatic and nonmetastatic models of retinoblastoma. am j pathol 2000;4:1405–1412. 36. de britto d, celi goy r, campanafilho sp, assis obg. quaternary salts of chitosan: history, antimicrobial features, and prospects. int j carbohydr chem 2011;2011:312539. 37. fang l, lijiew, jingjing z, wenqiang t, yuan ch, fang d, et al. preparation and characterization of quaternized chitosan derivatives and assessment of their antioxidant activity. molecules 2018;23:516. 38. zhu x, su m, tang s, wang l, liang x, meng f, et al. synthesis of thiolated chitosan and preparation nanoparticles with sodium alginate for ocular drug delivery. mol vis 2012;18:1973–1982. 39. maciel mvob, almeida ar, machado mh, de meloa pz, da rosa cg, de freitas dz, et al. syzygium aromaticum l. (clove) essential oil as a reducing agent for the green synthesis of silver nanoparticles. open j appl sci 2019;9:45–54. 40. irimia t, ghica m, popa l, anuta v, arsene al, dinu-pîrvu ce. strategies for improving ocular drug bioavailability and corneal wound healing with chitosan-based delivery systems. polymers 2018;10:1221. 41. felt o, furrer p, mayer j, plazonnet b, buri p, gurny r. topical use of chitosan in ophthalmology: tolerance assessment and evaluation of precorneal retention. int j pharm 1999;180:185–193. 42. bernkop-schnurch a, hornof m, zoidl t. thiolatedpolymers-thiomers: synthesis and in vitro evaluation of chitosan-2-iminothiolane conjugates. int j pharm 2003;260:229–237. 43. bernkop-schnürch a. thiomers: a new generation of mucoadhesive polymers. adv drug deliv rev 2005;57:1569–1582. 44. shin jm, song sh, vijayakameswara rao n, lee es, ko h, park jh. a carboxymethyl dextran-based polymeric conjugate as the antigen carrier for cancer immunotherapy. biomater res 2018;22:21. 45. vasic k, knez ž, konstantinova ea, kokorin ai, gyergyek s, leitgeb m. structural and magnetic characteristics of carboxymethyl dextran coated magnetic nanoparticles: from characterization to immobilization application. react funct polym 2020;148:104481. 46. kulkarni ad, patel hm, surana sj, vanjari yh, belgamwar vs, pardeshi cv. n,n,n-trimethyl chitosan: an advanced polymer with myriad of opportunities in nanomedicine. carbohydr polym 2017;157:875–902. 47. foroozandeh p, abdul aziz a. insight into cellular uptake and intracellular trafficking of nanoparticles. nanoscale 2018;13:339. 48. käsdorf bt, arends f, lieleg o. diffusion regulation in the vitreous humor. biophys j 2015;109:2171–2181. 49. pitkänen l, ruponen m, nieminen j, urtti a. vitreous is a barrier in nonviral gene transfer by cationic lipids and polymers. pharm res 2003;20:576–583. 50. peeters l, sanders nn, braeckmans k, boussery k, de voorde jv, smedt scd, et al. vitreous: a barrier to nonviral ocular gene therapy. invest ophthalmol vis sci 2005;46:3553–3561. 51. lee j, goh u, lee hj, kim j, jeong m. effective retinal penetration of lipophilic and lipid-conjugated hydrophilic agents delivered by engineered liposomes. mol pharm 2017;14:423–430. 52. ravar f, saadat e, gholami m, dehghankelishadi p, mahdavi m, azami s. hyaluronic acid-coated liposomes for targeted delivery of paclitaxel, in-vitro characterization and in-vivo evaluation. j control release 2016;10:10–22. 53. kompella ub, amrite ac, pacha ravi r, durazo sa. nanomedicines for back of the eye drug delivery, gene delivery, and imaging. prog retin eye res 2013;36:172– 198. 68 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 original article eye care in young children: a parents’ perspective of access and barriers ali m alsaqr, phd department of optometry, college of applied medical sciences, king saud university, saudi arabia orcid: ali m alsaqr: https://orcid.org/0000-0002-2900-2662 abstract purpose: to evaluate parental perspectives of accessing eye care for children aged under seven years. methods: the survey was conducted during september 2020 to march 2021 using online applications and distributed to parents whose children were between the ages of three and seven years. the survey included parents’ background, their knowledge of the provision of eyecare services, and the possible barriers that existed to access eye-care services. the relationship between parents’ knowledge, barrier scores, level of parental education, and demographic or socioeconomic status was assessed using nonparametric tests. results: in total, 1037 questionnaires were completed. the respondents were from 50 cities across saudi regions. the participants’ age was 39 ± 7.5 years, and 54% of them had at least one child under the age of seven (n = 564). further, 47% had not taken their children for vision screening at reception/year one (n = 467). in addition, 65% of them were not aware of the mandatory screening program at reception/year 1; whereas, only 20% (n = 207) knew how to access eye-care services; and only 39% of the children had undergone any kind of eye or vision test. the pathways to eye care and the cost of eye services/glasses were the main limitations. the parents’ responses were significantly influenced by their demographic and socioeconomic characteristics (kruskal wallis, p < 0.05). conclusion: there was a need for enhancing parent information on how to access eye care for young children and the currently available vision screening programs. finally, a national protocol to cover the cost of the eye exam as well as spectacle prescription shall be proposed as a mean of incentive. keywords: amblyopia; refractive errors; saudi arabia; strabismus; vision disorders; vision screening j ophthalmic vis res 2023; 18 (2): 192–201 correspondence to: ali m. alsaqr, phd. department of optometry, college of applied medical sciences, king saud university, po box 10219, riyadh 11433, saudi arabia. email: aalsaqr@ksu.edu.sa received: 04-04-2021 accepted: 10-11-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i2.13186 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: alsaqr am. eye care in young children: a parents’ perspective of access and barriers . j ophthalmic vis res 2023;18:192–201. 192 © 2023 alsaqr . this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i2.13186&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr parents’ perspective of eye care; alsaqr introduction a great number of population-based studies have indicated that the main visual disorders in children are refractive errors, amblyopia, and strabismus.[1–12] early proactive interventions for reduced vision are predominantly important during this critical period of visual development in children and should be started as early as possible.[7, 13] reduced visual acuity has marked implications on education, health, social outcomes, and quality of life of affected children.[14–20] if untreated or not detected early, these disorders would eventually lead to amblyopia and visual impairment.[21, 22] furthermore, in 2007, it was estimated that uncorrected refractive errors have a global economic burden of approximately $269 billion per annum because of productivity losses.[23] specifically, several studies have stated the importance of vision screening in children under seven years old.[10, 20, 24] these children are at risk of functionally low vision.[25, 26] in the agenda of vision 2020 (the right to sight), the world health organization set the management of childhood visual disability as a priority.[27] the american academy of pediatrics, the american association for pediatric ophthalmology and strabismus, and the american academy of ophthalmology have also set a joint policy statement on child vision screening.[27] preschool vision screening policies vary due to differences in the policies that exist in countries.[13, 16, 17, 26] in saudi arabia (sa), according to government laws, the ministry of education requires an obligatory medical examination, which includes an assessment of visual acuity for all school entrants.[28] however, it is observed that examination facilities may be inadequate.[11] interested individuals involved in preschool vision screenings include parents, school teachers, and health professionals (optometrists, ophthalmologists, etc.). the perception, awareness, and level of accepted responsibilities of these individuals could play a crucial role in the efficacy of child vision screening programs and the development of policies for school and preschool-age children.[24, 29–31] a study conducted in england reported that approximately 30% of children did not attend follow-up visits after failing screening tests at schools’ entry year.[9] several studies have emphasized the importance of parents’ awareness in combating children’s visual problems.[29–32] the parents’ knowledge of the potential visual disorders at younger age and receiving the screening outcome of children who failed visual screening could be essential for seeking health counseling.[18, 29, 32] specifically, parents as caregivers play the fundamental role in seeking eye-care services for their children to avoid experiencing visual disorders that may go untreated.[33] parents’ socioeconomic status could also pose as an important factor when accessing eye-care services.[8, 34, 35] to date, very few studies have been done on accessibility and barriers to eye care for children in sa, and generally in the middle east region. the problems outlined through this research is of critical importance toward understanding the extent and complexity of the challenges facing policy makers and eye-care professionals. this knowledge gap provided an opportunity to establish a point of reference as compared to other studies conducted in other worldwide countries.[7, 31, 32, 36–38] therefore, this study evaluated parents’ knowledge of how to access eye care and what barriers might disable them from accessing eye care for their children. methods the study protocol was reviewed and approved by the irb ethical committee of king saud university, saudi arabia, and the approval number is e22-7412. in addition, the protocol of the study complied with the guidelines for human studies and the world medical association declaration of helsinki, and parental consent was electronically obtained before filling out the questionnaires. in order to ensure transparency and to receive honest responses from participants, information and aims of the survey were absolutely and clearly described to the parents at the beginning of the survey. this study is cross-sectional in design and targeted toward the parents of children under seven years of age in different regions of sa. the survey used in this study was adapted from a previously published study.[32] the survey involved parents’ demographic data, general medical and ocular history, and their knowledge and barriers regarding accessing eye-care services. to compute the required sample size, we used epi info, version 7 (centers for disease control, atlanta, ga, usa; http://wwwn.cdc.gov/epiinfo/7/), journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 193 parents’ perspective of eye care; alsaqr and the number of children under seven years in sa were approximately 6 million.[39] furthermore, in the calculation, 95% confidence intervals, an expected frequency of 50%, a design effect of 2, and the number of clusters of five regions (central, northern, western, eastern, and southern regions) were included. the overall sample size was estimated to be 760 parents. the sample was expected to be unequal in each cluster but proportionate to the number of inhabitants in each region as they differed to a large extent (e.g., central region has approximately 8 million inhabitants and there are approximately 2 million inhabitants in the northern region). the survey was promoted for about six months (from september 2020 to march 2021) in order to recruit sufficient participants representing the saudi population. the survey used an online questionnaire, which was accessible without any restrictions. emails were sent to the members of the saudi optometry society to promote the survey in their areas using all accessible legal means, and the survey was distributed using all available social media applications (e.g., twitter, whatsapp, and telegram). to avoid duplicate responses, at the beginning of the survey, a note was placed stating that responding to the survey more than once is prohibited. lastly, the raw responses were properly reviewed and checked for duplication and to detect the parents who did not have children under seven years old, and eventually, 125 responses out of the 1162 initial ones were excluded. data were explored for normality using the kolmogorov–smirnov test, which indicated that the data was not normally distributed. therefore, the nonparametric kruskal–wallis test was performed to consider any possible relationship among the factors of parents’ knowledge, barrier scores, level of parental education, and demographic or socioeconomic status. data were collected in excel (microsoft corporation, redmond, wa, usa) and analyzed using the statistical package for the social sciences (ibm corp., armonk, ny, usa). results the number of participants was 1037, with 83% (n = 861) being mothers. most participants were married (96%, n = 995), and the rest were either divorced or widowed (2% for each category). the participants were recruited from across five regions, involving 50 cities. parents’ background characteristics the participants’ mean age was 39 ± 7.5 years and their educational level ranged from dropout (people who left school at the age of 16 years without formal degree) to doctor of philosophy (phd) degree [figure 1]. the participants’ occupations were diverse – unemployed, civil employees, teachers, health professionals, security forces, entrepreneurs, and assistant executive officers. in terms of their monthly incomes, the responses ranged from under $1400 to >$8000 [figure 2]. none of them had more than four children (one child: 564 [54%], two children: 407 [39%], three children: 75 [6%], four children: 15 [1%], respectively). additionally, 18% (n = 187) had a general medical history (e.g., systemic hypertension, diabetes, asthma, thyroid gland dysfunction, and back pain). lastly, approximately 33% of the participants reported some form of ocular disorder (e.g., refractive error, dry eye, cataract, keratoconus, amblyopia, and diabetic retinopathy). parents’ eye care-seeking behavior interestingly, about half of the parents (467, 45%) responded that they had not taken their children to a vision screening at the entry of reception/year one. when asked if they were aware of the mandatory vision exam at the entry of reception/year one, 65% of the parents’ responded with “no” and another 13% with “maybe”. the parents’ responses to questions directed toward the current visual status are summarized in table 1. regarding children who refused an eye test, only seven parents reported that they were given a reason for not being provided the service [table 1]. reasons included poor cooperation, young age, cost of service, waiting time, and presence of autism in a child. the survey also checked to understand the reasons why parents would consider seeking eye care for their children. their responses varied across different reasons as listed in table 2. some participants reported other reasons for intentionally seeking eye care, including excessive use of electronic devices, dry eyes, juvenile 194 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 parents’ perspective of eye care; alsaqr (42) (114) (695) (135) (32) 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 leaving school at 16 high school bachelor’s degree master degree phd % of respondents (n) e d u c a ti o n figure 1. respondents’ education profiles, saudi arabia in year 2021. (130) (373) (280) (130) (72) (42) 0 5 10 15 20 25 30 35 40 under $1400 $1,335 to $2,650 $2,655 to $4,000 $4,001 to $5,350 $5,355 to $8,000 > $8,000 % of respondents (n) m o n th ly i n c o m e figure 2. respondents’ monthly income profiles, saudi arabia in year 2021. table 1. parental responses to the questions on the current visual status of their children, saudi arabia in year 2021. query yes (n, %) no (n, %) not sure (n, %) routine vision screening in child’s school 99, 9.5% 793, 76.5% 145, 14% concerns about child’s eyes or vision 436, 42% 441, 42.5% 160, 15.5% know how to access an eye test appropriate for your child’s age 207, 20% 778, 75% 52, 5% child’s close family members who wear glasses and have a lazy eye or an eye turn 736, 71% 259, 25% 42, 4% has child ever had any kind of eye or vision test? 405, 39% 601, 58% 31, 3% has child ever been refused an eye test? 36, 3.5% 990, 95.5% 11, 1% from previous question, what reason was given if an eye test was refused? 7 of 36, 19.5% 21 of 36, 58% 8 of 36, 22% journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 195 parents’ perspective of eye care; alsaqr table 2. parental responses to the question stating, ”for what reasons would you consider seeking an eye examination for your child?” the parents were allowed to choose more than one choice, saudi arabia in year 2021. inquiry response (n,%) advised by healthcare provider or teacher 347, 33.5% concerns about poor vision 550, 53% concerns about eyes not being straight/having an eye turn 249, 24% headaches 239, 23% poor concentration/short attention span 300, 29% poor school achievement and/or difficulties with literacy 224, 22.50% complaints of double vision 166, 16% routine checkup 353, 34% family history 322, 31% others 36, 3.50% table 3. parental responses toward questions directed to existing knowledge about child vision and vision screening, saudi arabia in year 2021. query agree (n, %) disagree (n, %) not sure (n, %) children can only have an eye test when they know the names of the letters 207, 20% 498, 48% 332, 32% wearing glasses if you need them when under age of seven years will make your eyes and vision stronger 492, 47.5% 166, 16% 379, 36.5% it is normal for a child aged one to seven years to occasionally have an eye turn 264, 25.5% 332, 32% 441, 42.5% school vision screening tests for all eye problems 254, 24.5% 410, 39.5% 373, 36% diabetes, eye redness, itching, and excessive blinking. in addition, the parents were surveyed based on their preexisting knowledge related to child vision and vision screening [table 3]. barriers to eye care-seeking behavior the parents were asked about the barriers that might prevent them from taking their children for an eye test [table 4]. some parents mentioned additional barriers including their beliefs that the vision of their children was normal, the child being uncooperative, and personally not seeing a reason for an eye test and challenges with time management. parents’ background related to their knowledge and barriers an investigation was conducted to determine whether the responses were influenced by the parents’ background or other related factors that included gender, marital status, age, income, working status, level of education, and family history of eye problems. after the investigation, it was ascertained that those characteristics influenced some of the parents’ responses listed in table 5. discussion this study showed that half of the parents had not taken their children for vision screening at 196 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 parents’ perspective of eye care; alsaqr table 4. parental responses to the question stating the possible reasons that may prevent the parents from taking their children for an eye test. the parents were allowed to choose more than one choice, saudi arabia in year 2021. inquiry response (n,%) i do not know how and/or where to arrange an appointment for an eye test 342, 33% i am worried about the cost of an eye test 135, 13% i am worried about the cost of glasses 82, 8% i think my child is too young to have an eye test 270, 26% i am worried my child does ’not know all the letters yet 124, 12% i have been told that my child is too young for an eye test 52, 5% i do not want my child to wear glasses 114, 11% i am worried my child may be given glasses he/she does not need 218, 21% i am worried if my child is given glasses that it will make his/her eyes weaker 156, 15% others 73, 7% reception/year one. the majority of them were not even aware of the mandatory screening program. further, only one-fifth of them knew of the pathways to access eye-care services. about 60% of the children had not undergone any kind of eye or vision test. barriers and misconceptions related to eye-care services, which needed intensive and in-depth strategies to deal with, were detected. participants’ backgrounds and socioeconomic characteristics also played a major role in some of the parents’ responses. accessibility to vision screening is important for the well-being of children.[10, 40] understanding the barriers to and knowledge of accessing eye-care services for children from a parental perspective is fundamental in determining strategies and programs that enrich the parents’ awareness and provide methods to direct them for the best possible access to checking the vision of their children.[32] parental knowledge of risk factors related to not checking children’s vision could contribute to early detection and management of various visual disorders, such as amblyopia and strabismus.[34, 35, 41] this would also require the cooperation of eye-care professionals.[7] in 2019, cassetti et al suggested that it is imperative to consider parents’ lack of eye health education as well as the importance of enhancing specialists’ experience when treating children, and how to tackle parents’ negative attitudes toward diagnosis and treatment.[7] in this study, the percentage of parents whose children had received any kind of eye or vision test was closely similar to a report of a study in english children (45% vs 51%, respectively).[32] in comparison to another study, our findings were better than those found in swaziland children, where 60% of their participants had never taken their children for an eye test.[38] furthermore, concerns were raised about the efficacy of mandatory assessments at school reception/year one in light of poor awareness of the screening program, supported by the findings of donaldson et al who reported that only 15% of the parents whose children go to a school with a screening program knew of its existence.[32] moreover, only a few participants had been given a reason for not being provided the service, and not allowing a child to undergo vision screening could cause major consequences on the child’s well-being and quality of life.[29, 42] the reasons given by healthcare workers for not providing vision screening were mainly due to a lack of cooperation by the underaged subjects, a lack of financial resources by the parents, or the patients’ ailments that would require more intricate testing and evaluation. providing more professional training, giving out vouchers for eye examinations in schools, and easing the access to eye-care services provided by governmental hospitals may be very helpful in alleviating the lack of eye care for young children.[7, 32] in agreement with previous research, parents may also need journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 197 parents’ perspective of eye care; alsaqr table 5. influence of the participants’ background characteristics on some of the parents’ responses, saudi arabia in year 2021. factors findings kruskal–wallis test gender the number of children who have been tested at reception/year one in mothers’ response was greater than that in males. h (2) = 5.22; p = 0.02 the mothers was higher than that of males who had been refused eye-care services for their children. h (2) = 5.73; p = 0.02 marital status married couples were more informed about the mandatory eye exam at reception/year one. h (2) = 6.26; p = 0.04 age older parents were more likely to test their children at reception/year one. h (4) = 17, p = 0.001 older parents were more informed about the mandatory eye exam at reception/year one. h (4) = 9.6, p = 0.02 older parents were more informed about eye tests conducted at schools. h (4) = 7.9, p = 0.048 older parents were more likely to take their young children to eye-care service. h (4) = 18.6, p < 0.0001 older parents were more likely to have a medical eye history. h (4) = 22.3, p < 0.0001 parents’ education the higher the parents’ education, the more they know about the mandatory eye examination at reception/year one. h (4) = 12.5, p = 0.01 the higher the parents’ education, the more they know about pathways on how to access eye-care service. h (4) = 15.4, p = 0.004 the higher the parents’ education, the more they positively believe that using glasses, if needed, under the age of seven years will make their children’s vision stronger. h (4) = 13.7, p = 0.01 parents’ working status teachers were the most informed about the mandatory eye examination at reception/year one. h (6) = 13.8, p = 0.01 teachers had more knowledge about the routine eye examinations performed at schools. h (6) = 11.66, p = 0.02 teachers had more concerns about their children’s vision. h (6) = 12.7, p = 0.01 housewives accounted for the greatest number of those who believe that wearing glasses, if needed, will make their children’s eyes and vision stronger. h (6) = 10.6, p = 0.03 housewives had the most number among those not knowing how to access eye-care services. h (6) = 11.69, p = 0.02 parents’ income children of parents who had a lesser income were the least of being tested at reception/year one. h (5) = 11.5, p = 0.04 parents with lesser income were more likely to be refused to provide eye-care services. h (5) = 15.2, p = 0.01 parents with lesser income were more likely to believe that it is normal for a child under the age of seven years to occasionally have an eye turn. h (5) = 18.2, p = 0.003 presence of ocular history parents with an ocular history tend to not test their children at reception/year one. h (2) = 6.9; p = 0.01 parents with an ocular history have the highest response of ”yes” among those who have been provided with reasons for refusing eye-care services. h (2) = 5.5; p = 0.02 more health education and more effective and accessible eye-care services.[38, 43, 44] parental misconceptions about eye examinations for children and their vision were the main barriers to taking children for a vision test. similar to previous research, not knowing how and where to access eye-care services and not being able to afford the cost of service/glasses were other observed barriers.[37, 45, 46] effective efforts to correct those misconceptions, explaining the methods for accessing eye-care services and making these services free of charge 198 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 parents’ perspective of eye care; alsaqr are expected to increase the number of children taken to an eye test, exceeding the current 45% observed in this study. potential strategies for enhancing parents’ knowledge include distributing leaflets, providing online links to vision screening information, and giving out references to pathways for accessing eye-care services.[32] in addition, it is important to advise parents that vision screening is not a comprehensive examination and it is only the first step as certain other conditions may be missed if complete examinations are not performed.[32] the demographic and socioeconomic factors of the parents significantly influenced their responses, and this has also been supported in previous research.[36] based on the results reported in this study, educating new parents, easing accessibility to vision screening, making them free of charge, and increasing parental awareness across all working fields, including unemployed parents could increase the number of children being evaluated for vision.[7, 32] although based on our findings, teachers could be important mediums to refer children for vision screening. nevertheless, less educated parents and those with or without medical/ocular history should be properly educated about the importance of vision screening for children; education should focus more on providing fathers with more information about the vision of children and informing parents generally about patients’ right to avoid/handle potential test refusal.[18, 37, 38, 47] currently, no efficient national guidelines were applied to suggest pathways for vision screening, although the ministry of health and education has recently agreed on a newer pathway for vision screening at school reception/year one and another at grade 4. however, the method in which the program would handle the referral for comprehensive eye examinations for children who fail the initial eye test is unclear, which may vary depending on local arrangements in different regions of sa as it was previously suggested in other countries.[32] moreover, studies have suggested that the most common reason for not undergoing comprehensive eye care after the child fails the initial vision screening was the parents’ lack of knowledge about the outcome of the primary screening and/or what it means.[18, 47] finally, hartmann et al proposed developing a national integrated data system that would include child-level vision screening data, referral records, and follow-up diagnosis and treatment; following such a route can be very efficient.[48] this study enrolled 1037 parents, most of whom were mothers (83%). the unbalanced gender recruitment could be a limitation of this study, although mothers may be more attached and closer to children than fathers. the recruited parents were diverse in terms of where they lived, their age, income, education, and the number of children. furthermore, approximately one-third of the participants did experience some ocular disorders, indicating that they were aware of the importance of vision screening in children. this diversity in response could provide the representation required to reflect the assessment of the targeted population in different regions of the country. the recruitment method used in this study was not typical or similar to other studies that have distributed the questionnaires in hard copies in schools;[32, 33, 45] however, the method in this study avoided possible bias that existed in other studies due to sample selection from a clinically based population.[33] this could be because younger children may not have visited the eye clinic; alternatively, researchers might not have been able to distribute the questionnaires nationwide to have a sample representing the targeted population. that being said, the online survey may have some biases, like including the responses of parents who do not have any children under the age of seven, or parents who may ask for someone’s help in responding to these inquiries, so it does not reflect their own thoughts and feelings about the topic. although, we implanted a question in the survey to verify whether the respondents had children under seven years and excluded some of the collected data as stated in the method section, the responses of some parents who had no children under seven years of age might still have been included. unfortunately, the second possible bias could not be verified, we were only able to trust the respondents’ integrity and voluntary participation stated in their consent. in summary, this study showed that the majority of parents lack the knowledge about the importance of vision screening and the existing pathways to accessing eye care for young children. it is recommended that parents’ awareness of eye-care services be enhanced, and improved communication is needed to educate parents about the importance of vision screening for children, how to access eye-care journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 199 parents’ perspective of eye care; alsaqr services, and share knowledge of the existence of any national/mandatory screening programs. a second recommendation would be developing well-structured protocols to inform parents about their children’s vision screening results and provide referral pathways to avoid any dropouts after failing school vision screening. and finally, a national protocol to cover the cost of eye services/glasses may be needed to address those parents who are unable to pay for the cost of eye services. acknowledgments the author extends his appreciation to the college of applied medical sciences research center and the deanship of scientific research at king saud university for funding this research. furthermore, the author thanks the rssu at king saud university for their technical support. financial support and sponsorship none. conflicts of interest the author has no conflicts of interest to declare. references 1. ranganathan p, pramesh cs, buyse m. common pitfalls in statistical analysis: clinical versus statistical significance. perspect clin res 2015;6:169–170. 2. lefort sm. the statistical versus clinical significance debate. image j nurs sch 1993;25:57–62. 3. schober p, bossers sm, schwarte la. statistical significance versus clinical importance of observed effect sizes: what do p values and confidence intervals really represent? anesth analg 2018;126. 4. mariani aw, pêgo-fernandes pm. statistical significance and clinical significance. sao paulo med j 2014;132:71–72. 5. page p. beyond statistical significance: clinical interpretation of rehabilitation research literature. int j sports phys ther 2014;9:726–736. 6. houle tt, stump da. statistical significance versus clinical significance. semin cardiothorac vasc anesth 2008;12:5– 6. 7. cassetti v, sanders t, bruce a. challenges of eye health care in children and strategies to improve treatment uptake: a qualitative study from the perspective of eye care professionals in the uk. br ir orthopt j 2019;15:96– 104. 8. williams c, northstone k, howard m, harvey i, harrad ra, sparrow jm. prevalence and risk factors for common vision problems in children: data from the alspac study. br j ophthalmol 2008;92:959–964. 9. bruce a, outhwaite l. uptake, referral and attendance: results from an inner city school based vision screening programme. br ir orthopt j 2012;10:41–45. 10. alsaqr am, ibrahim g, sharha aa, fagehi r. investigating the visual status of preschool children in riyadh, saudi arabia. middle east afr j ophthalmol 2017;24:190–194. 11. al-rowaily ma. prevalence of refractive errors among preschool children at king abdulaziz medical city, riyadh, saudi arabia. saudi j ophthalmol 2010;24:45–48. 12. jonas de, amick hr, wallace if, feltner c, vander schaaf eb, brown cl, et al. vision screening in children aged 6 months to 5 years: evidence report and systematic review for the us preventive services task force. jama 2017;318:845–858. 13. hopkins s, sampson gp, hendicott p, wood jm. review of guidelines for children’s vision screenings. clin exp optom 2013;96:443–449. 14. bruce a, sanders t, sheldon ta. qualitative study investigating the perceptions of parents of children who failed vision screening at the age of 4–5 years. bmj paediatr open 2018;2:e000307. 15. williams km, bertelsen g, cumberland p, wolfram c, verhoeven vj, anastasopoulos e, et al. increasing prevalence of myopia in europe and the impact of education. ophthalmology 2015;122:1489–1497. 16. kvarnström g, jakobsson p, lennerstrand g. visual screening of swedish children: an ophthalmological evaluation. acta ophthalmol scand 2001;79:240–244. 17. rasesemola rm, matshoge gp, ramukumba ts. compliance to the integrated school health policy: intersectoral and multisectoral collaboration. curationis 2019;42:e1–e8. 18. su z, marvin ek, wang bq, van zyl t, elia md, garza en, et al. identifying barriers to follow-up eye care for children after failed vision screening in a primary care setting. j aapos 2013;17:385–390. 19. bruce a, fairley l, chambers b, wright j, sheldon ta. impact of visual acuity on developing literacy at age 4– 5 years: a cohort-nested cross-sectional study. bmj open 2016;6:e010434. 20. webber al. the functional impact of amblyopia. clin exp optom 2018;101:443–450. 21. ciner e, schmidt p, orel-bixler d, dobson v, maguire m, cyert l, et al. vision screening of preschool children: evaluating the past, looking toward the future. optom vis sci 1998;75:571–584. 22. resnikoff s, pascolinia d, mariott sp, pokharel gp. global magnitude of visual impairment caused by uncorrected refractive errors in 2004. bull world health organ 2008;86:63–70. 23. smith tst, frick kd, holden ba, fricke tr, naidoo ks. potential lost productivity resulting from the global burden of uncorrected refractive error. bull world health organ 2009;87:431–437. 24. cotter sa, cyert la, miller jm, quinn ge, national expert panel to the national center for children’s vision and eye health. vision screening for children 36 to <72 months: recommended practices. optom vis sci 2015;92:6–16. 25. gilbert c, ellwein l, group resics. prevalence and causes of functional low vision in school-age children: results from standardized population surveys in asia, africa, and 200 journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 parents’ perspective of eye care; alsaqr latin america. invest ophthalmol vis sci 2008;49:877– 881. 26. mema sc, mcintyre l, musto r. childhood vision screening in canada: public health evidence and practice. can j public health 2012;103:40–45. 27. committee on practice and ambulatory medicine, section on ophthalmology, american association of certified orthoptists, american association for pediatric ophthalmology and strabismus, and american academy of ophthalmology. eye examination in infants, children, and young adults by pediatricians. pediatrics 2003;111:902–907. 28. bardisi wm, bin sadiq bm vision screening of preschool children in jeddah, saudi arabia. saudi med j 2002;23:445–449. 29. mathers m, keyes m, wright m. a review of the evidence on the effectiveness of children’s vision screening. child care health dev 2010;36:756–780. 30. ross el, stein jd. enhancing the value of preschool vision screenings. jama ophthalmol 2016;134:664–665. 31. akuffo ko, abdul-kabir m, agyei-manu e, tsiquaye jh, darko ck, addo ek, assessment of availability, awareness and perception of stakeholders regarding preschool vision screening in kumasi, ghana: an exploratory study. plos one 2020;15:e0230117. 32. donaldson l, subramanian a, conway ml. eye care in young children: a parent survey exploring access and barriers. clin exp optom 2018;101:521–526. 33. ebeigbe ja, emedike cm. parents’ awareness and perception of children’s eye diseases in nigeria. j optom 2017;10:104–110. 34. alsaqr am, masmali am. the awareness of amblyopia among parents in saudi arabia. ther adv ophthalmol 2019;11:1–7. 35. dirani m, chan yh, gazzard g, hornbeak dm, leo sw, selvaraj p, et al. prevalence of refractive error in singaporean chinese children: the strabismus, amblyopia, and refractive error in young singaporean children (stars) study. invest ophthalmol vis sci 2010;51:1348–1355. 36. balasubramaniam sm, kumar ds, kumaran se, ramani kk. factors affecting eye care-seeking behavior of parents for their children. optom vis sci 2013;90:1138–1142. 37. ebeigbe ja. factors influencing eye-care seeking behaviour of parents for their children in nigeria. clin exp optom 2018;101:560–564. 38. sukati vn, moodley vr, mashige kp. knowledge and practices of parents about child eye health care in the public sector in swaziland. afr j prim health care fam med 2018;10:e1–e13. 39. saudi authority of statistics. https://www.stats.gov.sa/en. february 2021 [cited february 2021 february 2021]; available from: https://www.stats.gov.sa/en. 40. canadian paediatric society. vision screening in infants, children and youth. paediatr child health 2009;14:246– 251. 41. multi-ethnic pediatric eye disease study group. prevalence of myopia and hyperopia in 6to 72month-old african american and hispanic children: the multi-ethnic pediatric eye disease study. ophthalmology 2010;117:140–147.e143. 42. tadić v, cumberland pm, lewando-hundt g, rahi js. do visually impaired children and their parents agree on the child’s vision-related quality of life and functional vision? br j ophthalmol 2017;101:244–250. 43. sharma a, congdon n, patel m, gilbert c. school-based approaches to the correction of refractive error in children. surv ophthalmol 2012;57:272–283. 44. senthilkumar d, balasubramaniam sm, kumaran se, ramani kk. parents’ awareness and perception of children’s eye diseases in chennai, india. optom vis sci 2013;90:1462–1466. 45. vongsachang h, friedman ds, inns a, kretz am, mukherjee mr, callan j, et al. parent and teacher perspectives on factors decreasing participation in school-based vision programs. ophthalmic epidemiol 2020;27:226–236. 46. burnett a, paudel p, massie j, kong n, kunthea e, thomas v, et al. parents’ willingness to pay for children’s spectacles in cambodia. bmj open ophthalmol 2021;6:2020– 000654. 47. kimel ls. lack of follow-up exams after failed school vision screenings: an investigation of contributing factors. j sch nurs 2006;22:156–162. 48. hartmann ee, block ss, wallace dk. vision and eye health in children 36 to <72 months: proposed data system. optom vis sci 2015;92:24–30. journal of ophthalmic and vision research volume 18, issue 2, january-march 2023 201 original article levodopa plus occlusion therapy versus occlusion therapy alone for children with anisometropic amblyopia majid farvardin1, md; mohammad reza khalili1, md; mehdi behnia2, md 1poostchi ophthalmology research center, shiraz university of medical sciences, shiraz, iran 2noor ophthalmology research center, noor eye hospital, tehran, iran orcid: majid farvardin: https://orcid.org/0000-0001-9047-0329 abstract purpose: this study aimed to compare the effects of short-term administration of levodopa plus occlusion therapy versus occlusion therapy alone in preschool children with hyperopic anisometropic amblyopia. methods: this comparative interventional study included 40 eligible preschool children aged 6 to 7 years with hyperopic anisometropic amblyopia. the primary outcome measure was the logarithm of the minimum angle of resolution (logmar) best-corrected visual acuity recorded at baseline, 3 weeks after the treatment initiation and 12 weeks after the treatment termination. the results were compared between the two groups. results: no statistically significant intergroup difference was observed in baseline logmar visual acuities (p = 0.92). the mean logmar visual acuities of the amblyopic eyes were significantly better in both groups three weeks after the treatment initiation than the baseline (p < 0.01 in both groups). at 12 weeks after treatment termination, the logmar visual acuities of the amblyopic eyes were significantly better than the baseline values (p < 0.001 in the placebo group and p = 0.09 in the levodopa group). intergroup comparisons revealed no statistically significant difference in visual acuities 3 weeks after the treatment initiation (p = 0.11) and 12 weeks after the treatment termination (p=0.10). twelve weeks after the treatment termination, visual acuities regressed 0.037 logmar in the placebo group and 0.042 logmar in the levodopa group. these regression rates were not significantly different (p = 0.89). conclusion: the results of this study provide evidence that adding short-term administration of levodopa to occlusion therapy in hyperopic anisometropic amblyopia offers no additional benefit in visual outcomes and provides no advantage in terms of the regression rate. keywords: amblyopia; anisometropic; levodopa; occlusion therapy j ophthalmic vis res 2019; 14 (4): 457–464 correspondence to: majid farvardin, md. poostchi ophthalmology research center, shiraz university of medical sciences, shiraz 71349, iran. e-mail: majidfarvardinjahromi@gmail.com received: 17-10-2018 accepted: 09-04-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i4.5451 introduction for more than 200 years, the standard treatment for amblyopia has been occlusion of the dominant eye.[1] however, noncompliance is common this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: farvardin m, khalili mr, behnia m. levodopa for children with anisometropic amblyopia. j ophthalmic vis res 2019;14:457– 464. © 2019 j  o  v r | published by knowledge e 457 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5451&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr levodopa for anisometropic amblyopia; farvardin et al because of cosmetic dissatisfaction and interference of occlusion with daily activities.[2, 3] therefore, developing a treatment modality for amblyopia with improved efficacy, shorter duration, and better compliance has been a research goal. in the past years, several studies have evaluated the effects of levodopa on visual function in children with amblyopia.[4–12] levodopa is a precursor of dopamine, a neurotransmitter in the brain and retina. the effects of dopamine in the management of amblyopia are explained by its neuromodulator and neurotransmitter roles in the retina and central visual pathway. studies have suggested that increased dopamine levels lead to a reduction in the size of the receptive field in the retina, thereby improving visual function.[8, 9, 13] in addition, studies have hypothesized that increased dopamine levels reduce the size of the suppression scotoma. measurement via functional magnetic resonance imaging has shown that dopamine changes the volume of cortical activation even after a singledose administration.[14, 15] peripheral decarboxylase inhibitors, such as carbidopa or benserazide, prevent the breakdown of levodopa at peripheral sites and allow more levodopa to cross the blood–brain barrier, where it can have central effects.[16, 17] several studies on the influence of levodopa on visual function in amblyopia have used levodopa without occlusion of the dominant eye,[4, 7, 8] whereas some studies have combined levodopa with occlusion of the dominant eye.[5, 6, 10–12] the results of studies comparing the effects of levodopa plus occlusion therapy and occlusion therapy alone in amblyopia are controversial, and a debate persists whether augmenting occlusion therapy with a pharmacologic agent such as levodopa could affect the management of patients with amblyopia. in a singledose study, and in another three-week longitudinal study, leguire et al demonstrated that levodopa combined with occlusion improved the visual acuity in children with amblyopia to a greater extent than did placebo combined with occlusion.[5, 6] however, in children with anisometropic and strabismic amblyopia, bhartiya et al showed that levodopa supplementation has no additional benefit over occlusion therapy alone.[12] therefore, the present study aimed to assess the effectiveness of short-term administration of levodopa combined with standard occlusion treatment on the visual acuities of preschool children with hyperopic anisometropic amblyopia, and to compare it to that of occlusion therapy alone. methods study design and participants in this comparative interventional study, we included 40 eligible patients with hyperopic anisometropic amblyopia. the patients were preschool children aged 6 to 7 years with amblyopia caused by hyperopic anisometropia [table 1 and figure 1]. all patients were selected among the preschool children referred from the national amblyopia screening program to our strabismus and pediatric ophthalmology clinic affiliated to the shiraz university of medical sciences because of decreased visual acuity. the inclusion criteria were as follows: patients with hyperopic anisometropia (with more than 1.5 diopters of difference between the two eyes) and the logarithm of the minimum angle of resolution (logmar) best-corrected visual acuity (bcva) worse than 0.2 log-unit in the amblyopic eye or at least a 2-line difference in bcva between the two eyes. the eye with worse bcva was included in the study. at an alpha level of 0.05, 18 patients were required in each group to find a difference of 0.1 logmar visual acuity between the treatment and placebo groups. considering a 10% possibility of non-adherence, 40 patients were included. patients with strabismic amblyopia, other types of anisometropic amblyopia and deprivation amblyopia, and patients with a history of previous amblyopia therapy were excluded from the study. we also excluded patients with neurologic and cognitive disorders, including cerebral palsy, autism spectrum disorders, and attention deficit hyperactive disorder, as well as those with any systemic disorders such as diabetes, thyroid disease, and rheumatologic disease. eyes with a history or objective sign of trauma, previous intraocular surgery, uveitis, corneal opacity, or any ocular disorder other than amblyopia and hyperopic anisometropia were also excluded. all eligible patients underwent a complete ocular examination, including visual acuity measurement, slit-lamp examination, dilated fundus examination, ocular motility test, and appropriate strabismus tests (including prism-cover test and modified krimsky test). we used the snellen e-chart, and snellen 458 j  o  v r volume 14, issue 4, october-december 2019 levodopa for anisometropic amblyopia; farvardin et al table 1. absolute refractive errors of both groups and differences in refractive errors (mean and standard deviation of the spherical equivalent of anisometropia in both groups) placebo levodopa p-value normal eye 1.99 ± 0.69 1.69 ± 0.77 0.28 amblyopic eye 4.49 ± 0.59 4.29 ± 0.58 0.94 difference 2.49 ± 0.82 2.61 ± 0.96 0.49 figure 1. flow diagram outlining the enrollment of the amblyopic children into the study. visual acuity was measured under standardized lighting conditions in the same room with the same projector unit and at a viewing distance of 6 m. refraction was measured under cycloplegia with 1% cyclopentolate eye drops (cycloplegic refraction). we assessed the best subjective refraction, measured visual acuity by using optical correction, and registered the bcva. all interventions were conducted according to the tenets of the declaration of helsinki, and the study was approved by the ethics committee of our institution. signed informed consent was obtained from at least one parent, and assent was obtained from each child at the beginning of the study. eligible preschool children were divided into two groups of 20 patients each. in the first group, part-time occlusion therapy was administered 3 h/day combined with an oral placebo, and in the second group, part-time occlusion therapy was administered 3 h/day with levodopa. the dosage of levodopa was based on each patient’s body weight; each patient received 6 mg/kg as a loading dose. thereafter, each patient received 2 mg/kg/day levodopa in three divided j  o  v r volume 14, issue 4, october-december 2019 459 levodopa for anisometropic amblyopia; farvardin et al doses administered for three weeks. the pharmacy department of the shiraz university of medical sciences prepared the levodopa-benserazide and placebo capsules. the placebo was made using the same capsules used for levodopa, but they were filled with lactose instead of the active drug. patients were instructed to take one capsule three times/day at approximately 8-h intervals after a meal. visual acuities were measured and recorded by an expert optometrist. neither patients nor examiners were aware of the difference. the patients were followed up and examined at weeks 1 and 3 during the treatment regimen and 12 weeks after the termination of all treatments. all patients were informed about the potential side effects of the drug such as nausea, vomiting, headache, dizziness, dry mouth, fatigue, nightmares, and mood changes. parents were instructed to record the date(s) of any side effects. at each follow-up, the patients were asked whether they experienced any subjective changes or side effects. systolic and diastolic blood pressure and pulse rate were also measured at each examination session. laboratory tests, including complete blood count and differential, liver function tests, blood urea nitrogen (bun), and plasma creatinine level measurements were performed at baseline, one week and three weeks after the initiation of treatment, and at three months (12 weeks) after the termination of all treatments. if a patient’s laboratory test results were not within the normal limits, the patient was excluded from the study. study outcome measures a change in snellen bcva was regarded as the primary outcome measure. the amblyopic eye was always tested first, and one varying line was presented each time to prevent memorization within a test session. the line in which the patient could read more than half of the letters was considered as the line of visual acuity. if the new glasses resulted in better bcva, the glasses were changed, and the patient was given time to adapt to the new prescription before starting the assigned treatment. the bcva values were converted to logmar visual acuities for statistical purposes. the regression rate and side effects were secondary outcome measures. statistical analysis all statistical analyses were performed using spss statistics for windows/macintosh, version 17.0 (spss inc., chicago, il). a paired two-tailed t-test was used to compare the logmar visual acuities in consecutive test sessions in each group. the independent samples t-test was used to compare the logmar visual acuities between the two groups. a p < 0.05 was considered statistically significant. results the mean (±standard deviation) age of the patients was 6.4 years (±0.416) in the levodopa group and 6.4 years (±0.447) in the placebo group. both groups included 10 male and 10 female patients. the absolute refractive errors of both groups and the difference in refractive errors (mean and standard deviation of the spherical equivalent of anisometropia in both groups) are shown in table 1. no statistically significant difference was observed between the groups in the spherical equivalent of anisometropia (p = 0.49). the mean and standard deviation of logmar visual acuities of the patients in both groups at each examination are represented in table 2. no statistically significant difference was observed between the groups in the baseline visual acuities of the amblyopic eyes (p = 0.92). visual acuities were significantly better at three weeks after the initiation of treatment than at the baseline in both groups (p = 0.002 in the placebo group and p = 0.007 in the levodopa group). the improvement in visual acuities in the amblyopic eyes was not significantly different between the levodopa and placebo treatment groups (p = 0.11). to assess the stability of the treatment effects, we repeated the examinations 12 weeks after the termination of all treatments. visual acuities at this examination were still significantly better than the baseline visual acuities (p < 0.001 in the placebo group and p = 0.09 in the levodopa group). no statistically significant difference was observed between the visual acuities of the levodopa and placebo treatment groups (p = 0.10). visual acuities regressed 0.037 logmar in the placebo group and 0.042 logmar in the levodopa group 12 weeks after 460 j  o  v r volume 14, issue 4, october-december 2019 levodopa for anisometropic amblyopia; farvardin et al the termination of all treatments. a comparison of the regression rates between the groups showed no statistically significant difference (p = 0.89). compliance all patients completed all test sessions. according to previous reports, capsule consumption compliance was determined using the number of remaining capsules at the end of the treatment period.[10] regimen capsule compliance in both groups was good, and no capsule remained at the end of the treatment. tolerance patients were asked, during each follow-up, whether they experienced any side effects. in the first week, four patients in the placebo group (20%) had an episode of mild nausea lasting for few hours, but it did not continue during the course of the study and did not necessitate discontinuation of the treatment. no patient reported headache, dizziness, fatigue, nightmares, and dry mouth. no patients reported side effects in the levodopa group. no significant changes were observed in systolic or diastolic blood pressures or pulse rate over the 15-week study period. moreover, no occlusion amblyopia occurred in the fellow eyes in the control and treatment groups. laboratory tests a comparison of the baseline and 15-week study results revealed no changes in various laboratory tests. the complete blood count and differential results remained unchanged. no specific changes were observed in the serum bun and creatinine levels. moreover, no change was noted in the liver function test results. discussion the results of this placebo-controlled interventional study suggest that adding short-term administration of levodopa to the standard part-time occlusion therapy in preschool children with hyperopic anisometropic amblyopia does not yield better visual outcomes. for this study, we selected patients with hyperopic anisometropic amblyopia, which is the most common type of anisometropic amblyopia. other types of amblyopia, such as strabismic amblyopia and stimulus deprivation amblyopia are usually diagnosed by parents at an earlier age and, hence, treatment begins earlier. however, patients with anisometropia have normal general appearance and usually present at a later age; they are frequently diagnosed during preschool amblyopia screening programs. thus, the problem of neglected amblyopia is of major importance in anisometropic amblyopia, and anisometropia is the most common cause of amblyopia in adults.[3] several studies on the treatment of amblyopia have shown the beneficial effects of levodopa.[4–11] the beneficial effects of levodopa and benserazide in decreasing the fixation scotoma size and improving contrast sensitivity in amblyopia have already been demonstrated.[7] like carbidopa, benserazide is a peripheral decarboxylase inhibitor. levodopa is a precursor to the neurotransmitter dopamine and is administered to increase the dopamine level in the central nervous system. however, most levodopa is decarboxylated to dopamine before it reaches the brain, and since dopamine is unable to cross the blood–brain barrier, this leads to little therapeutic effect in the brain with strong peripheral side effects. by inhibiting the aforementioned decarboxylation, benserazide allows dopamine access to the brain. in addition, the adverse effects caused by peripheral dopamine, such as vasoconstriction, nausea, and arrhythmia are minimized. in a study on adults with amblyopia, gottlob et al showed an improvement in visual acuity after one-week levodopa therapy.[8] in a single pilot study, leguire et al demonstrated the effects of levodopa/carbidopa on visual function.[4] based on these initial findings, other studies were designed to evaluate the effects of levodopa in human amblyopia.[5, 6, 9–12] some studies compared the effects of levodopa therapy alone and levodopa plus occlusion therapy on the visual function of amblyopic eyes.[9, 10] other studies compared the effects of levodopa plus occlusion therapy and occlusion therapy alone in amblyopia. the results of these studies appeared to be contradictory; some studies suggested beneficial effects,[5, 6, 18] whereas others demonstrated that this treatment was ineffective.[12, 19] leguire et al, in a placebocontrolled, single-dose study and in another j  o  v r volume 14, issue 4, october-december 2019 461 levodopa for anisometropic amblyopia; farvardin et al table 2. visual acuities of patients in the placebo and levodopa groups at each examination group baseline mean ± sd logmar va three-week mean ± sd logmar va fifteen-week mean ± sd logmar va placebo group 0.425 ± 0.231 0.234 ± 0.096 0.271 ± 0.087 levodopa group 0.432 ± 0.242 0.187 ± 0.085 0.229 ± 0.071 p-value 0.92 0.11 0.10 logmar, logarithm of the minimum angle of resolution; sd, standard deviation; va, visual acuity three-week longitudinal study on children with amblyopia, showed that levodopa combined with occlusion resulted in more improved visual acuity than did placebo combined with occlusion.[5, 6] dadeya et al also compared the effects of combined levodopa and occlusion therapy to those of occlusion therapy alone in the management of patients with strabismic amblyopia; more patients in the levodopa group gained more than two lines of visual acuity.[18] contrary to these studies, in a randomized, placebo-controlled study on children with amblyopia, bhartiya et al reported that levodopa supplementation did not have any advantage over occlusion therapy alone.[12] rashad et al also observed that in children and adults with different types of amblyopia, the mean logmar was similar in the occlusion and levodopa enhancement groups.[19] in their study, a higher percentage of strabismic amblyopia was observed in the levodopa group and a higher percentage of mixed-etiology amblyopia was noticed in the occlusion group. unlike the abovementioned studies, we exclusively included patients with hyperopic anisometropic amblyopia in both groups and, therefore, compared similar groups. the similar age (preschool children) in both groups in the present study also allowed for a more reliable comparison. despite several differences among the studies, the present study findings are in agreement with the studies of bhartiya et al and rashad et al who showed that supplementation of occlusion therapy with levodopa offers no additional benefits in patients with amblyopia compared with occlusion therapy alone. moreover, a randomized trial of levodopa as a treatment for residual amblyopia in older children demonstrated that oral levodopa administration while continuing patch therapy 2 h/day does not produce a clinically or statistically significant improvement in comparison with placebo administration or patching alone.[20] the aim of amblyopia therapy is to improve the visual acuity of the amblyopic eye and to prevent the regression of visual acuity. many patients with successfully treated amblyopia are known to exhibit a regression of visual acuity once standard occlusion therapy is terminated.[2] long-term follow-up of levodopa treatment in children with amblyopia has shown that the regression of visual acuity in patients receiving levodopa therapy alone was more (2.1 lines) than that in those receiving levodopa plus occlusion (1.4 lines).[11] pandey et al also showed that visual acuity regressed significantly when levodopa was not combined with occlusion therapy.[21] mohan et al demonstrated that the addition of full-time occlusion to levodopa helped maintain improved visual acuity for a longer duration than did levodopa alone.[22] according to our results, visual acuities regressed 0.037 logmar in the placebo plus occlusion treatment group and 0.042 logmar in the levodopa plus occlusion treatment group 12 weeks after the termination of all treatments. although the mean value of regression was less in the placebo group, a comparison of the regression rates between the groups showed no statistically significant difference. following the termination of treatments in both groups, and when the regression of visual acuity occurred, the patients still had better visual acuities than their baseline visual acuities. both groups completed all test sessions and tolerated treatment well without significant side effects. before enrollment, the parents or other caregivers were informed about the possible adverse effects of medications, such as hypotension, arrhythmias, disorientation, confusion, and extreme emotional states, particularly anxiety, insomnia, visual hallucinations, somnolence, narcolepsy, depression, and psychosis. however, 462 j  o  v r volume 14, issue 4, october-december 2019 levodopa for anisometropic amblyopia; farvardin et al these side effects are very uncommon given the short duration of study. moreover, no significant side effect was reported by the patients in the present study. abnormalities in laboratory tests may occur in patients receiving levodopa.[23–25] these include elevations in liver and kidney function test parameters, such as alkaline phosphatase, serum glutamic-oxaloacetic transaminase/aspartate aminotransferase, serum glutamic-pyruvic transaminase/alanine aminotransferase, and bilirubin levels, and abnormalities in bun and creatinine levels.[23] thrombocytopenia has also been reported. nevertheless, in our study, no abnormality in laboratory data was detected.[24, 25] one limitation of our study was the small sample size. however, according to calculations, 18 patients were required in each group to find a difference of 0.1 logmar visual acuity between the treatment and placebo groups, and considering a 10% possibility of non-adherence, we included 40 patients. in addition, the present study was performed on children with hyperopic anisometropia aged 6 to 7 years old; hence, the results cannot be generalized to other amblyopia types and to patients in other age groups. in conclusion, the results of the present study indicated that in preschool children with hyperopic anisometropic amblyopia, short-term administration of levodopa combined with conventional occlusion therapy offered no additional benefits in visual outcomes than did occlusion therapy alone. moreover, the combined treatment offered no advantage over the placebo treatment in terms of the regression rate. this clearly indicates the need for more studies to clarify the role of levodopa in the management of amblyopia. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. von noorden gk. binocular vision and ocular motility: theory and practice of management of strabismus. 5th ed. lous mosby-year book: usa, st. louis, missouri 63146; 1996:216–254,512–520. 2. keech rv. practical management of amblyopia. in: focal points: clinical modules for ophthalmologist. san francisco, ca: american academy of ophthalmology; 2000:18. 3. arruga a. effect of occlusion of amblyopic eye on amblyopia and eccentric fixation. trans oph soc uk 1962;82:45–49. 4. leguire le, rogers gl, bremer dl, walson p, hadjieonstantinou-neff m. levodopa and childhood amblyopia. j pediatr ophthalmol strabismus 1992;29:290–298. 5. leguire le, roger gl, bremer dl, walson pd, mcgregor ml. levodopa/carbidopa for childhood amblyopia. invest ophthalmol vis sci 1993;34:3090–3095. 6. leguire le, walson pd, rogers gl, bremer dl, mcgregor ml. longitudinal study of levodopa/carbidopa for childhood amblyopia. j pediatr ophthalmol strabismus 1993;30:354–360. 7. gottlob i, stangler-zuschrott e. effect of levodopa on contrast sensitivity and scotomas in human amblyopia. invest ophthalmol vis sci 1990;31:776–780. 8. gottlob i, charlier j, reincoke rd. visual acuities and scotomas after one week levodopa administration in human amblyopia. invest ophthalmol vis sci 1992;33:2722– 2728. 9. leguire le, walson pd, rogers gl, bremer dl, mcgregor ml. levodopa/carbidopa treatment for amblyopia in older children. j pediatr ophthalmol strabismus 1995;32:143– 151. 10. leguire le, rogers gl, walson pd, bremer dl, mcgregor ml. occlusion and levodopa-carbidopa treatment for childhood amblyopia. j aapos 1998;2:257–264. 11. leguire le, komaromy kl, nairus tm, rogers gl. longterm follow-up of l-dopa treatment in children with amblyopia. j pediatr ophthalmol strabismus 2002;39:326– 330;quiz 345–346. 12. bhartiya p, sharma p, biswas nr, tandon r, khokhar sk. levodopa-carbidopa with occlusion in older children with amblyopia. j aapos 2002;6:368–372. 13. nguyen-lergos j, durand j, simon a. catecholamine cell types in the human retina. clin vis sci 1992;7:435– 447. 14. algaze a, leguire le, roberts c, ibinson jw, lewis jr, rogers g. the effects of ldopa on the functional magnetic resonance imaging response of patients with amblyopia: a pilot study. j aapos 2005;9:216–223. 15. yang ci, yang ml, huang jc, wan yl, jui-fang tsai r, wai yy, et al. functional mri of amblyopia before and after levodopa. neurosci lett 2003;339:49–52. 16. yeh kc, august tf, bush df, lasseter kc, musson dg, schwartz s, et al. pharmacokinetics and bioavailability of sinemet cr: a summary of human studies. neurology 1989;39:25–38. 17. bartholine g, pletscher a. cerebral accumulation and metabolism of 14c-dopa after selective inhibition of peripheral decarboxylase. j pharmacol exp ther 1968;161:14–20. 18. dadeya s, vats p, malik kp. levodopa/carbidopa in the treatment of amblyopia. j pediatr ophthalmol strabismus 2009;46:87–90;quiz 91–92. j  o  v r volume 14, issue 4, october-december 2019 463 levodopa for anisometropic amblyopia; farvardin et al 19. rashad ma. pharmacological enhancement of treatment for amblyopia. clin ophthalmol 2012;6:409–416. 20. repka mx, kraker rt, dean tw, beck rw, siatkowski rm, holmes jm, et al. a randomized trial of levodopa as treatment for residual amblyopia in older children. ophthalmology 2015;122:874–881. 21. pandey pk, chaudhuri z, kumar m, satyabala k, sharma p. effect of levodopa and carbidopa in human amblyopia. j pediatr ophthalmol strabismus 2002;39:81–89. 22. mohan k, dhankar v, sharma a. visual acuities after levodopa administration in amblyopia. j pediatr ophthalmol strabismus 2001;38:62–67;quiz 96–97. 23. dhall r, kreitzman dl. advances in levodopa therapy for parkinson disease: review of rytary (carbidopa and levodopa) clinical efficacy and safety. neurology 2016;86:s13–s24. 24. lee ke, kang hs, yu hj, roh sy. thrombocytopenia associated with levodopa treatment. j mov disord 2013;6:21– 22. 25. giner v, rueda d, salvador a, hernández jc, esteban mj, redón j. thrombocytopenia associated with levodopa treatment. arch intern med 2003;163:735–736. 464 j  o  v r volume 14, issue 4, october-december 2019 original article efficacy, safety and steroid-sparing effect of topical cyclosporine a 0.05% for vernal keratoconjunctivitis in indian children arkendu chatterjee1, ms; sabyasachi bandyopadhyay2, ms; samir kumar bandyopadhyay1, ms 1nrs medical college & hospital, kolkata, india 2r.g.kar medical college & hospital, kolkata, india orcid: arkendu chatterjee: https://orcid.org/0000-0001-7884-6928 sabyasachi bandyopadhyay: https://orcid.org/0000-0003-4617-7832 abstract purpose: to evaluate the efficacy, safety, and steroid-sparing effect of topical cyclosporine a (cs a) 0.05% in patients with moderate to severe steroid dependent vernal keratoconjunctivitis (vkc). methods: a prospective, comparative, placebo controlled study was carried out on 68 vkc patients, with 34 patients treated with topical cs a 0.05% and the remaining 34 with topical carboxymethyl cellulose 0.5% (placebo). both groups also received topical loteprednol etabonate 0.5%. symptom (itching, photophobia, tearing, and discharge) score, sign (tarsal and limbal papillae, corneal involvement, and conjunctival hyperemia) score, and drug score (steroid drop usage/day/eye) were recorded at baseline and each followup visit. the intraocular pressure (iop) measurement and evaluation of any ocular side effects were carried out. results: significant reduction in symptom score and sign score was seen in both groups. cs a group significantly showed more reduction in symptom (p < 0.0001 in all follow-up visits) and sign (p < 0.0001 in all follow-up visits) scores compared to the placebo group. at day 7, mean steroid usage reduced from 4 to 3.44 ± 0.5 and 3.79 ± 0.4 in cs a and placebo groups, respectively (p < 0.0001). steroid drops completely stopped in 21 patients at day 60 in the cs a group compared to none in the placebo group. no significant rise in iop or any side effects were noted in either group. conclusion: topical cs a 0.05% is effective and safe in patients with moderate to severe vkc with good steroid-sparing effect. keywords: allergic conjunctivitis; intraocular pressure; topical cyclosporine a; topical loteprednol etabonate; vernal keratoconjunctivitis j ophthalmic vis res 2019; 14 (4): 412–418 correspondence to: sabyasachi bandyopadhyay, ms. 11/11, ghosal para road, dakshin para, barasat. kolkata 700124, india. e-mail: sabyasachi.bandyopadhyay@yahoo.com received: 25-11-2018 accepted: 30-06-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i4.5439 introduction vernal keratoconjunctivitis (vkc) is a seasonal bilateral chronic allergic inflammatory disease of the ocular surfaces, mainly occurring in this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: chatterjee a, bandyopadhyay s, bandyopadhyay sk. topical cyclosporine a for pediatric vkc. j ophthalmic vis res 2019;14:412–418. 412 © 2019 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5439&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr topical cyclosporine a for vkc; chatterjee et al children and adolescents living in dry and temperate regions.[1, 2] itching, photophobia, tearing, and mucoid discharge may occur in patients with vkc.[3] superior tarsal and limbal papillae, conjunctival hyperemia, and corneal involvement in the form of punctate epithelial keratitis, epithelial macroerosions, shield ulcers, plaque formation, and corneal neovascularization are also observed.[4] vkc can be described as ige and tcell mediated ocular allergic reaction with varied etiological factors comprising environmental allergens, climate, and genetic predisposition.[5] mast cells, eosinophils, and their mediators play a major role in the clinical manifestation of the disease.[5] topical mast cell stabilizers and antihistaminic drugs (sodium cromoglycate 2% and olapatadine 0.1%) are the first line of drugs used in mild cases, but in moderate to severe cases, additional topical steroids such as prednisolone and dexamethasone or other immunomodulators such as cyclosporine a (cs a) and tacrolimus may be needed.[6, 7] however, topical prednisolone and dexamethasone are associated with ocular adverse reactions, including increase in intraocular pressure (iop);[8] therefore, 0.5% topical loteprednol etabonate (le), with a relatively milder effect on iop, has been used in the treatment of vkc with good efficacy and less side effects.[9, 10] le is a novel corticosteroid manufactured via retrometabolic design, which is rapidly metabolized by tissue esterases to d1 cortienic acid etabonate and eventually to d1 cortienic acid, thereby reducing any potential side effects. despite its relatively safer applications, le should still be used with caution, since a significant rise in iop due to le administration has been reported in allergic conjunctivitis as compared to that with placebo or olopatadine.[11] cs a is an immunosuppressive molecule, which reduces ocular inflammation by inhibiting th2 lymphocyte proliferation, interleukin-2 production, and histamine release from mast cells and basophils.[12, 13] several studies have been performed with topical cs a 0.05% in moderate to severe steroid dependent (le, fluorometholone acetate, or prednisolone acetate) vkc patients with good efficacy of treatment and reduction in doses of topical steroids.[4, 14, 15] in the present study, we aimed to evaluate the safety, efficacy, and possible steroid-sparing effect of topical cs a 0.05% in an aqueous solution compared to placebo in indian children with vkc concurrently treated with topical le 0.5%. methods the present study is a prospective comparative, placebo-controlled study of 68 patients (aged 5–15 years) with moderate to severe vkc, who visited a tertiary care hospital in eastern india from january 1, 2017 to june 30, 2017. patients were randomly allocated either into cs a group (34 patients treated with topical cs a 0.05% plus topical le 0.5%) or placebo group (34 patients treated with carboxymethyl cellulose 0.5% and topical le 0.5%) according to a computer generated predetermined randomization list. vkc was diagnosed based on the presence of itching, tearing, mucoid discharge, photophobia, tarsal and limbal papillae, corneal involvement, and conjunctival hyperemia. patients using systemic steroids or any immunosuppressive drugs or non-steroidal anti-inflammatory medications, or having associated corneal diseases, uveitis, glaucoma, and optic atrophy were excluded from the study. all the participating patients were diagnosed with active disease at the time of enrolment. any prior topical medication for vkc was stopped for three days and only physical measures were advised during that period. thereafter, topical eye drops were instituted according to the protocol. both eyes of each patient were examined. the study was carried out in accordance with the ethical principles outlined in the declaration of helsinki and informed parental consent was obtained. the protocol was approved by the institutional ethics committee. patients in the cs a group were treated with aqueous ophthalmic solution of topical cs a 0.05% (hydroeyes 0.05% w/v®; lupin ltd., mumbai, india) in either eye with one drop four times/day, and those in the placebo group were treated with topical carboxymethyl cellulose 0.5% (refresh tears®; allergan inc., irvine, ca, usa) in either eye with one drop four times/day. both groups received one drop of topical le (0.5%) (lotepred®; sun pharma (avesta), mumbai, india) four times daily initially, and the dose then tapered off from the first followup at day 7 according to the clinical response. steroid dosage reduction was approved if both the sign and symptom scores were ≤ 4 and steroid was discontinued if both the sign and symptom scores were ≤ 1. follow-up check-ups were carried out on days 7, 14, 30, 60, and 90. at baseline (day 0), detailed demographic information, clinical history, and specific symptoms journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 413 topical cyclosporine a for vkc; chatterjee et al of the patients were obtained. a complete ophthalmological examination including visual acuity determination by snellen chart, anterior segment evaluation by slit lamp biomicroscopy, iop measurement by goldmann applanation tonometer, and indirect ophthalmoscopy were performed. the same examination procedures were repeated in each follow-up visit. scores ranging 0 to 3 (according to severity) were assigned to each symptom (itching, tearing, photophobia, and discharge) and sign (tarsal papillae, corneal involvement, limbal papillae, and conjunctival hyperemia), and total symptom and sign scores were calculated at each visit, similar to that of ozlem et al [table 1].[4] statistical calculations were based on these evaluated scores. statistical analysis the collected data were incorporated into microsoft excel 2007 (microsoft corporation, redmond, wa, usa) worksheet and analyzed using spss version 15.0 (spss inc., chicago, il, usa). simple correlations and linear regressions were performed between both eyes for validation of data obtained from either eye. to compare the differences between and within the groups, friedman test, anova with bonferroni’s posthoc test, wilcoxon and kruskal–wallis test for categorical variables, and repeated measurement anova for continuous variables were performed. a p-value < 0.05 was considered statistically significant. results the patients in cs a group comprised 20 males and 14 females with mean age of 10.23 ± 2.7 years. the placebo group had 21 males and 13 females with mean age of 10.35 ± 3.26 years. at day 0 (baseline), there were no significant differences between the mean symptom scores (6.94 ± 1.9 and 7.2 ± 1.77 in cs a and placebo groups, respectively; p = 0.4037) and mean sign scores (7.14 ± 2.13 and 6.88 ± 1.8 in cs a and placebo groups, respectively; p = 0.4363) in either group. mean symptom score in cs a group at day 7 reduced to 2.7 ± 0.96 with further reduction observed upon subsequent visits (p < 0.0001 in all cases) [figure 1]. mean symptom score in placebo group also showed reduction at day 7 (3.73 ± 0.89), which further decreased in follow-up visits (p < 0.0001 in all cases). a comparison between the two groups indicated that cs a group showed higher symptom score reduction over the placebo group in all follow-up assessments (p < 0.0001 in all cases). mean sign score in cs a group decreased to 3.58 ± 1.19 at day 7 with continued reduction observed upon subsequent visits (p < 0.0001 in all cases) [figure 2]. similarly, in the placebo group, mean sign score showed reduction at day 7 (4.00 ± 1.11), which further decreased in follow-up visits (p < 0.0001 in all cases). cs a group showed more reduction in sign score over placebo group from day 7 (p = 0.04), which was more evident from day 14 (p < 0.0001 in all cases). initial steroid drop usage score was four drops per eye per day in both groups. in follow-up visits, there was a higher reduction in steroid drop usage in cs a group (3.44 ± 0.5) at day 7 than in the placebo group (3.79 ± 0.4; p < 0.0001) [figure 3]. this trend persisted in all the subsequent visits with complete termination of steroid drop use in 21 patients in the cs a group as compared to none in the placebo group at day 60. mean iop at baseline in cs a group was 16.7 ± 2.3 mm hg in the right eye and 16.58 ± 2.28 mm hg in the left eye, which did not show any significant increase at day 30 (16.23 ± 2.24 mm hg in the right eye, p = 0.1988 and 16.52 ± 1.86 mm of hg in the left eye, p = 0.8723). in the placebo group, the mean iop at baseline was 17.11 ± 2.51 mm hg in the right eye and 16.82 ± 2.61 mm hg in the left eye, which also did not show any significant increase at day 30 (17.52 ± 1.97 mm hg in the right eye, p = 0.2558 and 17 ± 1.98 mm of hg in the left eye, p = 0.6809). no side effects were reported in either group during the follow-up visits. discussion the treatment of vkc is aimed at controlling the symptoms and prevention of complications. in mild cases, topical mast cell stabilizers and antihistaminics may be sufficient, but moderate to severe cases require topical steroids for adequate control.[6, 7] however, long-term topical steroid use, particularly that of dexamethasone phosphate and prednisolone acetate, is restricted due to the known side effects, such as increased iop usually after the second week of therapy.[8] newer synthetic corticosteroids, such as le (0.5%), which 414 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 topical cyclosporine a for vkc; chatterjee et al figure 1. mean symptom scores at baseline and during follow-up visits. figure 2. mean sign scores at baseline and during follow-up visits. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 415 topical cyclosporine a for vkc; chatterjee et al table 1. the scoring method of symptoms and signs of vernal keratoconjunctivitis variable score 0 1 2 3 symptom itching none occasional frequent constant tearing normal mild moderate severe photophobia none mild moderate severe discharge none small moderate profuse sign conjunctival hyperemia none mild moderate severe tarsal papillae none < 1 mm 1–3 mm > 3 mm limbal papillae none < 2 mm or < 90° 2–4 mm or 90°–180° > 4 mm or > 180° corneal involvement normal cornea fine spek* coarse spek/macro erosion shield ulcer/pannus *spek, superficial punctate epithelial keratitis figure 3. mean steroid drop usage per day per eye (drug score) at baseline and during follow-up visits. show relatively lower propensity for increase in iop and are more effective in vkc, also show some side effects.[9, 11] in this context, reduction in dosage of topical le is essential after one week of therapy in steroid-dependent and steroid-resistant vkc cases. topical cs a has been found to be a suitable alternative, either upon single use or as an adjunct to steroid therapy aimed at reducing the dosage of steroids.[4, 16] earlier studies with high concentrations of up to 2% cs a have shown effectiveness with vkc, although they were less tolerated due to stinging and burning sensations probably attributed to the use of maize or olive oils as vehicles.[17–19] newer aqueous formulations 416 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 topical cyclosporine a for vkc; chatterjee et al of cs a in lower concentrations (0.1% and 0.05%) were found to be safe, effective, and well tolerated in vkc patients.[4, 16] these formulations have been observed to be good steroid sparing agents in steroid responsive vkc patients, but their optimal effect in reducing the signs and symptoms was achieved only after two weeks of therapy.[4, 16–19] hence, we used the combination of 0.5% le with 0.05% cs a for a prompt initial response and also to attempt to lower the frequency of steroid drop usage along with cs a after the first week of therapy depending upon the clinical response. we observed a significant improvement in symptoms and signs of vkc in both groups; however, the cs a group showed more pronounced improvement as compared to the placebo group, which was similar to the observations made by baiza-duran et al and ozlem et al.[4, 16] both groups showed no serious side effects, including no increase in iop, which was corroborative with daniell et al, baizaduran et al, and ozlem et al.[4, 14, 16] in this study, we observed that the aqueous formulation of cs a 0.05% is more effective in reducing steroid drops in vkc as compared to placebo since the first week of therapy and complete termination of steroid therapy was noted in 21 out of 34 patients in the cs a group as compared to no patients discontinuing steroid dosage in the placebo group at day 60. in a recent study with 30 vkc patients, ozlem et al observed that cs a 0.05% can help in reducing corticosteroid usage and is a safe and effective alternative for the treatment of resistant vkc.[4] baiza-duran et al compared 0.1% and 0.05% aqueous formulation of cs a in 112 mexican children with vkc and found that both concentrations were safe, effective, and equally well-tolerated.[16] keklikci et al studied the efficacy of topical cs a 0.05% in patients with severe vkc and noted significant clinical improvement as well as decreased density of inflammatory cells in conjunctival impression cytology specimens.[20] akpek et al performed a randomized trial with topical cs a 0.05% in topical steroid resistant atopic keratoconjunctivitis. they found that topical cs a 0.05% was safe and effective in alleviating signs and symptoms of severe akc that was refractory to topical steroid treatment.[21] in another study, de smedt et al examined patients with vkc in rwanda, central africa and found no significant differences in terms of efficiency between 2% topical cs a and 0.1% dexamethasone in the management of acute vkc.[22] however, cs a drops caused more stinging in patients than the oil placebo and dexamethasone. in a retrospective review on the use of 0.05% topical cs a for pediatric allergic conjunctivitis in chinese patients in hong kong, wu mm et al found it to be significantly effective and safe in reducing ocular symptom and sign scores three months after use.[23] keklikci et al in their placebo-controlled, randomized prospective study of 62 patients with vkc observed that 0.05% topical cs a eye drops were safe and effective in the treatment of patients with vkc.[24] however, daniell et al observed that 0.05% topical cs a had no benefit over placebo as a steroid sparing agent in 18 akc and 22 vkc patients.[14] they opined that the dosage of cs a might have been insufficient or use of steroid might have masked the benefits of cs a. the limitation of our study is that we did not analyze recurring cases after cessation of therapy. in our study period, we did not come across any recurrence during treatment. however, the study would have been strengthened had we included the evaluation of any recurrences, which is definitely an important aspect to be considered for a future continuation study. in conclusion, topical application of 0.05% cs a in an aqueous preparation as one drop four times a day along with topical le 0.5% is an effective and safe treatment module for patients with moderate to severe vkc, with good steroid sparing effect. further completely randomized, doubleblind, placebo-controlled studies with larger samples and longer follow-up periods are required to determine the optimal duration of treatment and likelihood of recurrence after cessation of therapy with cs a. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 417 topical cyclosporine a for vkc; chatterjee et al references 1. leonardi a. vernal keratoconjunctivitis: pathogenesis and treatment. prog retin eye res 2002;21:319–339. 2. leonardi a, secchi ag. vernal keratoconjunctivitis. int ophthalmol clin 2003;43:41–58. 3. vichyanond p, pacharn p, pleyer u, leonardi a. vernal keratoconjunctivitis: a severe allergic eye disease with remodeling changes. pediatr allergy immunol 2014;25:314–322. 4. ozlem ey, nihal du. efficacy and safety of topical cyclosporine a 0.05% in vernal keratoconjunctivitis. singapore med j 2016;57:507–510. 5. leonardi a. management of vernal keratoconjunctivitis. ophthalmol ther 2013;2:73–88. 6. allansmith mr, ross rn. ocular allergy and mast cell stabilizers. surv ophthalmol 1986;30:229–244. 7. gokhale ns. systematic approach to managing vernal keratoconjunctivitis in clinical practice: severity grading system and a treatment algorithm. indian j ophthalmol 2016;64:145–148. 8. mcghee cn, dean s, danesh-meyer h. locally administered ocular corticosteroids: benefits and risks. drug saf 2002;25:33–55. 9. oner v, turkeu fm, tas m, iscan y. topical loteprednol etabonate 0.5% for treatment of vernal keratoconjunctivitis: efficacy and safety. jpn j ophthalmol 2012;56:312– 318. 10. eliaç𝚤k m, erdoğan f, bayramlar h, karaman s, gülk𝚤l𝚤k g. comparison of efficacy and safety of loteprednol etabonate 0.5% versus fluorometholone acetate 0.1% for the treatment of vernal keratoconjunctivitis in pediatric subjects. nobel med 2014;11:76–82. 11. wu lq, chen x, lu h, cheng jw, wei rl. loteprednol etabonate in the treatment of allergic conjunctivitis: a meta-analysis. curr med res opin 2015;31:1509–1518. 12. fukushima a, yamaguchi t, ishida w, fukata k, liu ft, ueno h. cyclosporin a inhibits eosinophilic infiltration into the conjunctiva mediated by type iv allergic reactions. clin exp ophthalmol 2006;34:347–353. 13. kari o, saari km. updates in the treatment of ocular allergies. j asthma allergy 2010;3:149–158. 14. daniell m, constantinou m, vu ht, taylor hr. randomised controlled trial of topical ciclosporin a in steroid dependent allergic conjunctivitis. br j ophthalmol 2006;90:461– 464. 15. tatlipinar s, akpek ek. topical cyclosporin in the treatment of ocular surface disorders. br j ophthalmol 2005;89:1363–1367. 16. baiza-duran lm, gonzález-villegas ac, contreras-rubio y, juarez-echenique jc, vizzuett-lopez iv, suarezsanchez r, et al. safety and efficacy of topical 0.1% and 0.05% cyclosporine a in an aqueous solution in steroiddependent vernal keratoconjunctivitis in a population of mexican children. j clin exp ophthalmol 2010;1:115. doi: 10.4172/2155-9570.1000115 17. hingorani m, moodaley l, calder vl, buckley rj, lightman s. a randomized placebo-controlled trial of topical cyclosporine a in steroid-dependent atopic keratoconjunctivitis. ophthalmology 1998;105:1715–1720. 18. pucci n, novembre e, cianferoni a, lombardi e, bernardini r, caputo r, et al. efficacy and safety of cyclosporine eyedrops in vernal keratoconjunctivitis. ann allergy asthma immunol 2002;89:298–303. 19. spadavecchia l, fanelli p, tesse r, brunetti l, cardinale f, bellizzi m, et al. efficacy of 1.25% and 1% topical cyclosporine in the treatment of severe vernal keratoconjunctivitis in childhood. pediatr allergy immunol 2006;17:527–532. 20. keklikci u, soker si, sakalar yb, unlu k, ozekinci s, tunik s. efficacy of topical cyclosporine a 0.05% in conjunctival impression cytology specimens and clinical findings of severe vernal keratoconjunctivitis in children. jpn j ophthalmol 2008;52:357–362. 21. akpek ek, dart jk, watson s, christen w, dursun d, yoo s, et al. a randomized trial of topical cyclosporine 0.05% in topical steroid-resistant atopic keratoconjunctivitis. ophthalmology 2004;111:476–482. 22. de smedt s, nkurikiye j, fonteyne y, tuft s, de bacquer d, gilbert c, et al. topical ciclosporin in the treatment of vernal keratoconjunctivitis in rwanda, central africa: a prospective, randomised, double-masked, controlled clinical trial. br j ophthalmol 2012;96:323–328. 23. wu mm, yau gs, lee jw, wong al, tam vt, yuen cy. retrospective review on the use of topical cyclosporin a 0.05% for pediatric allergic conjunctivitis in hong kong chinese. scient world j 2014;2014:396987. doi: 10.1155/2014/396987 24. keklikci u, dursun b, cingu ak. topical cyclosporin a 0.05 % eye drops in the treatment of vernal keratoconjunctivitis. randomized placebo-controlled trial. adv clin exp med 2014;23:455–461. 418 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 case report pigmented corneal ulcer sonam yangzes, ms; parul chawla gupta, ms; vivek jha, ms; jagat ram, ms, fams department of ophthalmology, post graduate institute of medical education and research, chandigarh, india orcid: sonam yangzes: https://orcid.org/0000-0002-1862-0254 jagat ram: https://orcid.org/0000-00016251-2800 abstract purpose: to report the clinical characteristics, laboratory findings, and treatment of a rare case of keratitis caused by pigmented fungi bipolaris hawaiiensis. case report: a 55-year-old man presented with a history of trauma with vegetative matter in his left eye. slit lamp biomicroscopic examination revealed the presence of a brownish-black pigmented plaque with surrounding infiltrates. corneal scrapings revealed multiple septate hyphae. culture revealed growth of the bipolaris species. the patient was treated with topical natamycin 5%, topical voriconazole 1%, and oral itraconazole followed by intracameral amphotericin b (5 μg/ml). the patient responded well to the treatment. conclusion: brown pigmented infiltrates are an important clinical feature of dematiaceous fungi. b. hawaiiensis is a rare cause of corneal phaeohyphomycosis. our patient responded well to intracameral amphotericin b, which obviated the need for penetrating keratoplasty. keywords: corneal ulcer; keratitis; pigmented j ophthalmic vis res 2019; 14 (4): 506–508 correspondence to: jagat ram, ms, fams. department of ophthalmology, post graduate institute of medical education and research, chandigarh 160012, india. e-mail: drjagatram@gmail.com received: 15-05-2018 accepted: 09-09-2018 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i4.5461 introduction fungal keratitis is one of the most common causes of keratitis in tropical countries.[1, 2] dematiaceous fungi are the third most common cause of keratomycosis, with curvularia and bipolaris being the most common infecting species.[3, 4] bipolaris hawaiiensis is a darkly pigmented fungus, widely distributed in nature, that causes cutaneous and soft tissue diseases known as phaeohyphomycosis;[5] it is an extremely uncommon cause of keratitis. oral itraconazole and topical natamycin have been used for this condition, while a few case reports have described additional use of topical amphotericin b in refractory cases. we report a case of keratomycosis, caused by b. hawaiiensis, that was treated with intracameral amphotericin b and showed a good response. case report a 55-year-old male farmer with a history of trauma to the left eye with vegetative matter presented at the ophthalmology clinic with complaints of diminution of vision, redness, photophobia, and black discoloration of his left eye. the visual acuity this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: yangzes s, gupta pc, jha v, ram j. pigmented corneal ulcer. j ophthalmic vis res 2019;14:506–508. 506 © 2019 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5461&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr fungal corneal ulcer; yangzes et al figure 1. (a) a corneal ulcer measuring 6.5 × 5.5 mm, with a central pigmented plaque 4 × 4 mm with hypopyon. (b) slit view showing area of corneal thinning. figure 2. lactophenol cotton blue staining showing acute angled septate hyphae with boat-shaped conidia. figure 3. healed ulcer with central scarring and peripheral vascularization. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 507 fungal corneal ulcer; yangzes et al in the right eye was 6/6, while vision in the affected eye was restricted to the perception of light. slit lamp biomicroscopy revealed conjunctival congestion, a central pigmented corneal ulcer, and hypopyon. there were no other predisposing factors such as diabetes or other immunocompromised states. the central ulcer measured 6.5 x 5.5 mm, and showed a pigmented, elevated brownish-black plaque measuring 4 x 4 mm, with surrounding infiltrates. the ulcer appeared dry, with the presence of immobile hypopyon [figures 1(a) and (b)]. the right eye presented with a clear cornea, early cataract, and a normal fundus. the plaque was scraped off and used to inoculate culture media. due to the typical appearance of the ulcer (dry, pigmented plaque), we initiated hourly topical antifungal natamycin 5% treatment along with two-hourly topical moxifloxacin 0.5%, and cycloplegic and lubricating eyedrops. the culture revealed growth of the bipolaris species. lactophenol cotton blue staining showed acuteangled septate hyphae with boat-shaped conidia [figure 2]. the hypopyon remained refractory to treatment after which amphotericin b (5 μg/ml) was injected intracamerally. the infiltrates became organized and the hypopyon disappeared. the lesion healed completely with central scarring and vascularization [figure 3]. the final visual acuity was finger counting close to the face with accurate projection of light. discussion the bipolaris species is classified as a dematiaceous or darkly pigmented fungus that causes phaeohyphomycosis, rarely infecting humans. the most frequently reported species are b. spicifera, b. australiensis, and b. hawaiiensis.[6] anadi et al have reported corneal ulcers due to bipolaris spp. infection in a leprosy patient,[7] while bashir et al have reported keratomycosis with endophthalmitis in an immunocompetent individual.[8] b. hawaiiensis is widely distributed in plants or soil and is commonly found in tropical regions. dematiaceous fungal keratitis presents typically as recalcitrantpigmented plaques that prevent the penetration of drugs, making superficial keratectomy essential in many cases.[9] culture shows dark septate hyphae with numerous conidia of the bipolaris species. although, the use of topical natamycin has been reported to be successful in treating most cases of dematiaceous fungal keratitis,[3] our case responded well to intracameral amphotericin b injection, which obviated the need for long-term use of oral antifungal drugs as well as therapeutic penetrating keratoplasty. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. chowdhary a, singh k. spectrum of fungal keratitis in north india. cornea 2005;24:8–15. 2. tanure ma, cohen ej, sudesh s, rupuano cj, laibson pr. spectrum of fungal keratitis at wills eye hospital, philadelphia, pennsylvania. cornea 2000;19:307–312. 3. garg p, gopinathan u, chaudhary k, rao gn. keratomycosis: clinical and microbiologic experience with dematiaceous fungi. ophthalmology 2000;107:574–580. 4. gopinathan u, garg p, fernandes m, sharma s, athmanathan s, rao gn. the epidemiological and laboratory results of fungal keratitis: a 10 year review at referral eye care center in south india. cornea 2002;21:555–559. 5. ajello l, georg lk, steigbigel rt, wang cj. a case of phaeohyphomycosis caused by a new species of phialophora. mycologia 1974;66:490–498. 6. cunha kc, sutton da, fothergill aw, cano j, gené j, madrid h, et al. diversity of bipolaris species in clinical samples in the united states and their antifungal susceptibility profiles. j clin microbiol 2012;50:4061–4066. 7. anandi v, suryawanshi nb, koshi g, padhye aa, ajello l. corneal ulcer caused by bipolaris hawaiiensis. j med vet mycol 1988;26:301–306. 8. bashir g, hussain w, rizvi a. bipolaris hawaiiensis keratomycosis and endophthalmitis. mycopathologia 2009;167:51–53. 9. garg p, vemuganti gk, chatarjee s, gopinathan u, rao gn. pigmented plaque presentation of dematiaceous fungal keratitis: a clinicopathologic correlation. cornea 2004;23:57–576. 508 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 review article update on management of non-proliferative diabetic retinopathy without diabetic macular edema; is there a paradigm shift? amir arabi1,2, md, mph; ramin tadayoni3, md, phd; hamid ahmadieh1,4, md; toktam shahraki1,5, md homayoun nikkhah1,2, md 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2department of ophthalmology, torfeh medical center, shahid beheshti university of medical sciences, tehran, iran 3université de paris, ophthalmology department, ap-hp, lariboisière, saint louis and fondation adolphe de rothschild hospitals, paris, france 4department of ophthalmology, labbafinejad medical center, shahid beheshti university of medical sciences, tehran, iran 5department of ophthalmology, imam hossein medical center, shahid beheshti university of medical sciences, tehran, iran orcid: amir arabi: https://orcid.org/0000-0002-6523-7533 homayoun nikkhah: https://orcid.org/0000-0002-2414-4661 abstract diabetic retinopathy (dr) is the major cause of visual impairment and blindness in the working-age population. conventional management for nonproliferative diabetic retinopathy (npdr) without diabetic macular edema (dme) is derived from the findings of the early treatment diabetic retinopathy study (etdrs). although the etdrs protocol basically includes observation, selected cases of severe npdr may undergo scatter laser photocoagulation. post-hoc analysis of recent trials has shown that patients with npdr receiving intravitreal anti-vascular endothelial growth factor (anti-vegf) for dme would experience improvement in the dr severity scale (drss). in addition, recent randomized trials (panorama and protocol w) have revealed that early intervention with intravitreal aflibercept in eyes with moderately severe to severe npdr is associated with significant improvement in drss and reduced vision-threatening complications of dr. based on recent studies, it seems that the therapeutic approach to npdr may undergo a substantial change and a paradigm shift toward considering early intervention with the administration of intravitreal anti-vegf injections. however, the long-term results and the duration of adherence to anti-vegf therapy for eyes with npdr are not yet defined. it is also not apparent whether improvement in drss is a true disease modification. studies showed that drss improvement is not associated with retinal reperfusion. in addition, drcr.net protocol w showed no visual acuity benefit with the early intravitreal aflibercept injection in moderate to severe npdr as compared with performing observation plus intravitreal aflibercept applied only after progression to proliferative dr or vision-impairing dme. the cost–benefit ratio is also a challenge. herein, we look at different aspects of early anti-vegf application and discuss its pros and cons in the process of treating npdr. keywords: diabetic macular edema; management; nonproliferative diabetic retinopathy; paradigm shift j ophthalmic vis res 2022; 17 (1): 108–117 108 © 2022 arabi et al . this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v17i1.10175&domain=pdf&date_stamp=2019-07-17 npdr without dme; arabi et al introduction according to the recent report of the international diabetes federation (idf), about 400 million people live with diabetes mellitus (dm) worldwide; this prevalence is estimated to approach 600 million individuals by 2035.[1] one of the most common microvascular complications of dm is diabetic retinopathy (dr), which is reported to be the leading cause of visual impairment in the working-age population.[2, 3] diabetic retinopathy is classically categorized into two types: nonproliferative diabetic retinopathy (npdr) and proliferative diabetic retinopathy (pdr). diabetic macular edema (dme) is another important manifestation of dr, which may be experienced across all dr severity stages. while approaches to the patients with pdr or dme is straightforward, the therapeutic approach to npdr patients with no dme has not been well established. conventional management for npdr without dme, which is derived from the findings of the early treatment diabetic retinopathy study (etdrs)[4] includes observation for mild and moderate npdr. most cases of severe npdr are also followed closely; however, selected cases may undergo scatter laser photocoagulation. post-hoc analysis of recent trials has shown that patients with npdr receiving intravitreal anti-vascular endothelial growth factor (anti-vegf) drugs for dme would experience amelioration in the dr severity scale (drss).[5, 6] in addition, more recent randomized controlled trials (panorama study and drcr.net protocol w) have revealed that early intervention with intravitreal injection of aflibercept in eyes with moderately severe to severe npdr may be associated with significant improvement in drss and reduced vision-threatening complications although the effect on visual acuity has not been correspondence to: homayoun nikkhah, md. ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, no. 23, paidarfdard st., boostan 9 st., pasadaran ave., tehran 16666, iran. e-mail: h.nikkhah52@gmail.com received 13-08-2021; accepted 11-11-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v17i1.10175 significantly different compared to proper follow-up with timely treatment of complications.[7, 8] based on recent studies, the therapeutic approach toward treating npdr may undergo a significant change and paradigm shift to early intervention with intravitreal anti-vegf injections that may substitute the conventional approach. however, the longterm results of anti-vegf therapy for eyes with npdr are not yet determined, and it is not clear how durable this approach will be and whether it is connected with enhanced visual functions and improved quality of life (qol). the cost– benefit ratio is also a challenge that needs to be addressed. herein, we review the different aspects of npdr management and the early application of anti-vegf therapy. management of npdr without dme management of npdr patients without dme involves all interventions that prevent occurrence of vision-threatening complications including pdr and dme. this goal can be achieved by both systemic and ocular interventions. systemic management glycemic control control of hyperglycemia remains the basis of care in diabetic patients. intensive glycemic control evaluated in two landmark trials, the diabetes control and complications trial (dcct) and the uk prospective diabetes study (ukpds), assisted in reducing the risk of developing retinopathy and slowing the dr progression in both type 1 and type 2 dm[9, 10] these results have been supported in other studies.[11, 13] as an observation in the dcct and ukpds, the people in the early intensive glycemic control group had a significantly lower risk for long-term retinopathy progression and microvascular disorders regardless of the glycemic condition in the later course of the diabetes.[14, 15] the american diabetes association (ada) this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: arabi a, tadayoni r, ahmadieh h, shahraki t, nikkhah h. update on management of non-proliferative diabetic retinopathy without diabetic macular edema; is there a paradigm shift? . j ophthalmic vis res 2022;17:108–117. journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 109 https://knepublishing.com/index.php/jovr npdr without dme; arabi et al recommends a hemoglobin a1c (hba1c) of <7%, with the recommendation of adjustment on an individual basis to avoid probable complications, such as hypoglycemia.[16] blood pressure control several studies have investigated the role of blood pressure regulation in the incidence and progression of dr. some of these studies have demonstrated a positive effect from the intensive control of blood pressure, whereas no beneficial effect on the incidence and progression of dr has been observed in others.[17–20] generally, blood pressure control has been recommended as a principal part of the standard care in diabetic patients, primarily because of its known beneficial effect on macro-vascular complications of dm rather than for its effect on dr.[21] however, blood pressure control may also reduce the damage to endothelial cells, through which slowing of dr progression may be achieved.[22] the available evidence does not support the idea that blood pressure control alone can inhibit or slow the progression of dr.[23] control of hyperlipidemia the effects of dyslipidemia on dr incidence and progression have been controversial. in a new meta-analysis, no significant difference in lipid profile was observed between patients with and without dr.[24] however, sankara nethralaya diabetic retinopathy epidemiology and molecular genetic study (sn-dreams ii) reported a threefold increase in the risk of dr progression to pdr stage in patients with higher triglycerides levels.[25] the accord eye study has confirmed that fenofibrate benefits patients with dr.[26] furthermore, the field study confirmed that fenofibrate could prevent the progression of dr independent of serum lipids’ levels.[27] it is postulated that the role of fenofibrate is more effective via iron chelation rather than hyperlipidemia treatment. given the role of iron in retinal damages via oxidative pathways, iron chelation with fenofibrate may play a protective role in reducing retinal damage in dr.[28] in the collaborative atorvastatin diabetes study and the heart protection study, the progression of dr did not differ between patients treated with statins and those who received placebo.[29, 30] miscellaneous systemic risk factors anemia is considered a risk factor of the microvascular complications of diabetic patients.[31, 32] some studies have suggested that lower hemoglobin levels may be linked to progression of dr.[33, 34] dietary modification, regular monitoring of anemia, and treatment with supplements may stop the progression of dr.[35] a meta-analysis has revealed an association between vitamin d deficiency and increased risk of dr in type 2 dm.[36] recently, it has been postulated that vitamin d3 exerts protective effects against retinal cell apoptosis and vascular damage in dr patients via an anti-inflammatory mechanism.[37] a new meta-analysis discovered that the risk of dr was greater in smokers with type 1 diabetes; while in those patients who suffered with type 2 diabetes, the risk of pdr significantly decreased in smokers in comparison with nonsmokers.[38] in the wisconsin epidemiologic study of diabetic retinopathy (wesdr), smoking was not significantly associated with the progression of dr in a 4-year and 10-year follow-up period.[39] although the relationship between smoking and progression of dr remains inconclusive, there is evidence that suggests that smoking encourages macro-vascular complications associated with dm. as a result, it is recommended that patients who suffer with dm be strongly advised to cease smoking. ophthalmic management laser photocoagulation for npdr as dr reaches proliferative stage, retinal photocoagulation is applied to preserve the vision. this indication was derived from the presentation of two landmark studies, diabetic retinopathy study (drs) and etdrs, where the findings convinced ophthalmologists to reach consensus on laser photocoagulation as a gold standard procedure for high-risk pdr (hrpdr).[40] nevertheless, the question remains: can retinal photocoagulation for patients with nonproliferative stages of dr decrease the risk of visual impairment by preventing the progression to pdr stage? patients with either pdr in at least one eye or severe npdr in both eyes were included 110 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 npdr without dme; arabi et al in the drs.[41] one eye of each patient was randomly assigned to laser photocoagulation and the second eye was considered as the control group. the two-year risk of severe visual loss in eyes with severe npdr was 3.2% and 2.8% in the control and laser photocoagulation groups, respectively. the four-year rates were 12.8% and 4.3%, respectively. although the researchers found that 50% of the eyes with severe npdr who were in the control group developed new vessels in one year, after considering the small risk of severe visual loss in the control group and the possible side effects of laser photocoagulation they did not recommend laser photocoagulation for all npdr patients. nevertheless, the drs offered laser photocoagulation in npdr eyes in some instances: one eye of a patient with severe npdr in both eyes, presence of severe retinal ischemia, when the patient was pregnant or there was coexisting disorders such as renal failure that might accelerate the course of dr.[40] the etdrs remains the only study addressing the question of the suitable time for starting laser photocoagulation.[4] patients with moderate to severe npdr or early pdr were included. early photocoagulation was randomly performed in one eye of each patient and the other eye was assigned to deferred photocoagulation. in the latter, patients underwent laser therapy when high-risk pdr was detected. in the deferred photocoagulation group who had severe npdr, the rate of pdr development was 51%, 71%, and 79% in the first-, third-, and fifth-year visits, respectively.[4] compared to deferred photocoagulation, early photocoagulation decreased progression to highrisk pdr by 25% and 50% with full scatter and mild scatter photocoagulation, respectively.[4] however, the rate at the five-year visit determined that severe visual loss was low and comparable among the study groups (2.6% and 3.7% in early and deferral photocoagulation groups, respectively).[4] a recent survey built a markov model to explore whether it would be cost-effective either to apply panretinal photocoagulation (prp) at the npdr stage or to wait until hrpdr developed.[43] they found that earlier prp at the severe npdr stage was less costly and more effective than administering prp to patients with high-risk pdr. it meant that fewer patients in the earlier prp group progressed to more advanced stages of dr. the most common complications of prp are decreased visual field and exacerbation of macular edema.[44, 45] fong et al have reported that visual field defects may occur in almost half of the treated patients, and the incidence is correlated with the intensity of the laser therapy.[46] a recent study based on optical coherence tomography angiography (oct-a) has reported that in lasertreated severe npdr eyes, ocular blood flow is significantly reduced, which may be associated with decreased visual acuity in these patients.[47] anti-vegf for npdr intravitreal anti-vegf therapy for npdr is an evolving concept. clinical data show that vegf contributes to the pathogenesis of both npdr and pdr.[48, 49] according to the results of retrospective studies, anti-vegf treatment can improve the drss and reduce the rate of pdr development.[50] utilization of anti-vegf in npdr with dme rise and ride were two phase-iii, doubleblind randomized clinical trials of intravitreal ranibizumab versus sham in patients with dme. in an exploratory analysis of rise and ride trials, among the eyes with baseline etdrs severity level of 53 (severe npdr) or less, monthly intravitreal ranibizumab injection administered for 24 months was associated with a ≥2-step improvement in drss in 47% of eyes, as compared to 6.8% in the sham group (p < 0.001).[5] furthermore, it has been noted that the cumulative probability of dr progression was 34% in the sham-treated patients and 11.2–11.5% in the ranibizumab-treated patients by month 24.[5] in addition, it has been reported that intravitreal ranibizumab in patients of rise and ride trials slowed the progression of retinal non-perfused areas.[51] similarly, in the vivid-dme and vista-dme trials, a significantly greater proportion of patients treated with aflibercept (week 100: 34.9%) compared with those treated with laser (13%) achieved a ≥2 step drss improvement (p < 0.0001).[52] in addition, the proportion of patients who developed pdr was significantly less in those who received intravitreal aflibercept as compared with the sham-treated group (week 100: 2.2% vs 9.1%, p < 0.0001).[52] drcr.net protocol t compared the efficacy of intravitreal aflibercept, ranibizumab, and bevacizumab in the treatment of dme. based on a post hoc analysis of the protocol t, journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 111 npdr without dme; arabi et al 25%, 22% and 31% of npdr eyes receiving aflibercept, bevacizumab, and ranibizumab for dme demonstrated improvement in drss at two-year follow-up, respectively.[53] there were no statistically significant differences among the three commercially available anti-vegfs in terms of inducing the regression of dr. utilization of anti-vegf in npdr without dme the panorama study was the first randomized clinical trial evaluating the role of intravitreal aflibercept on drss and incidence of visionthreatening complications (pdr and/or anterior segment neovascularization) and center-involved (ci) dme in patients with moderately severe to severe npdr without dme. in this phase-3 clinical trial, 402 patients were randomly assigned to sham versus aflibercept administered every 8 weeks after 5 monthly loading doses versus aflibercept administered every 16 weeks after 3 monthly loading doses. at two-year followup, the proportion of eyes with 2-step or more improvement in drss was 12.8%, 62.2%, and 50% in the sham group, every 16 weeks aflibercept group and every 8 weeks (converted to pro re nata [prn] in the second year) aflibercept group, respectively (p < 0.001 for both).[7] furthermore, the proportion of eyes that developed visionthreatening complications and/or ci-dme were 50.4%, 16.3%, and 18.7% in the sham group, every 16 weeks and every 8 weeks aflibercept groups, respectively (p < 0.001 for both comparisons). drcr.net protocol w is a phase-3 randomized clinical trial evaluating the role of intravitreal aflibercept (injected at baseline, months 1, 2, and 4; and after that every four months through to two years) versus sham in reducing vision-threatening complications in eyes with moderate to severe npdr.[8] while the primary endpoint was recently reported at two years, the patients will be followedup to four years. the two-year risk of developing ci-dme with decreased visual acuity or pdr was 16.3% and 43.5% in the aflibercept and sham groups, respectively (adjusted hazard ratio, 0.32 [97.5% confidence interval {ci}, 0.21–0.5; p < 0.001]). drss improved ≥2-steps from baseline to year 2 in 44.8% and 13.7% of eyes receiving aflibercept and sham, respectively (adjusted odds ratio, 5.91 [97.5% ci, 3.19–10.95; p < 0.001]). monte carlo simulation of a real-world cohort of treatment-naive patients with npdr from the ibm® explorys® database suggested that severe npdr treatment with anti-vegf would significantly decrease the probability of progression to pdr by 51.7% at the five-year follow-up period. furthermore, the incidences of sustained blindness in severe npdr patients were reduced with antivegf therapy by 57.7% over a 10-year follow-up period.[54] the phase-2 boulevard trial compared the efficacy of faricimab, a bispecific antibody, inhibiting both vegf-a and angiopoietin-2, with ranibizumab in the treatment of patients with dme.[55] at the six-month follow-up period, among the patients who were treatment-naïve, 2-steps or greater improvement in the drss was achieved in 12.2%, 27.7%, and 38.6% of eyes in the 0.3 mg ranibizumab, 1.5 mg faricimab, and 6 mg faricimab groups, respectively.[55] discussion conventional management of npdr without dme included observation along with controlling the systemic condition. the etdrs showed that in one year, 26% of eyes with moderately severe npdr and 52% of eyes with severe npdr in the deferred photocoagulation group would progress to pdr, a vision-threatening complication of dr. the rate of progression to pdr reached 66% and 75–81% at the five-year follow-up period.[42] recently, there has been increasing evidence that anti-vegf treatments would improve drss and decrease the risk of vision-threatening complications such as pdr and dme,[7, 8] raising an important question: is it recommended to target the dr at the nonproliferative stage by administering intravitreal anti-vegf injections to prevent the disease progression and reduce the risk of vision threatening complications? there are pros and cons for this evolving approach. pros of using anti-vegf in npdr without dme there is increasing evidence in favor of administering intravitreal anti-vegf injection in nonproliferative stages of dr without dme. the panorama study showed that intravitreal aflibercept reduces the risk of vision-threatening complications by 77% and 83% in every 16 weeks and every 8 weeks (prn in the second year) 112 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 npdr without dme; arabi et al groups, respectively, as compared with the sham group at 100 weeks.[7] at the end of the second year, data were also emphasized in the drcr.net w protocol, where the risk of vision-threatening complications was 16.3% and 43.5% for the aflibercept and the sham groups, respectively.[8] extension of non-perfusion areas is the major pathology in dr. diabetic retinopathy leads to upregulation of vegf and contributes to further progression of non-perfusion areas as a vicious cycle. it was demonstrated that anti-vegf therapy slows the development and progression of retinal non-perfusion in patients with dme.[51] however, a small interventional cohort with short term follow-up showed that anti-vegf induced improvement of drss could occur without any retinal reperfusion.[56] epidemiological studies have shown that dr has an adverse effect on the quality of life (qol). a recent longitudinal and observational study showed that qol significantly decreases with aggravation of dr severity from mild npdr to pdr.[57] furthermore, a cross-sectional study showed that vision-related functional burden is significantly greater in patients with severe npdr or pdr versus those with no retinopathy.[58] longitudinal population-based studies have shown that more advanced dr at diagnosis is associated with higher risk of developing sustained blindness.[59] kaplan-meier’s analysis of a recent epidemiological study has shown that eyes with moderate npdr, severe npdr, and pdr were 2.6, 3.6, and 4 times, respectively, more likely to develop sustained blindness, as compared to eyes with mild npdr, after two years of follow-up.[59] cons of using anti-vegf in npdr without dme at the end of two-year follow-up in the panorama study, 49.6% of eyes in the sham group did not develop vision-threatening complications and/or ci-dme.[7] this shows that nearly half of the patients who have npdr will not progress to pdr or develop dme despite not receiving any intraocular injection. some complications have been reported regarding the use of intravitreal anti-vegf injections. common complications are the incidence of floaters and the rise of iop.[60, 61] the most devastating complication is infectious endophthalmitis. the prevalence of endophthalmitis following intravitreal injections is estimated to be 0.01–0.26%.[62] it is not clear whether intravitreal anti-vegf for severe npdr can be associated with enhanced visual function and improved qol. drcr.net protocol w, during a two-year period, showed no visual benefit of the preventive intravitreal aflibercept treatment in eyes with moderate to severe npdr as compared with those eyes that underwent observation plus aflibercept which was administered only after progression to pdr or vision-impairing ci-dme. the mean change of visual acuity was –0.9 and –2.0 etdrs letters in aflibercept and sham groups, respectively (p = 0.47).[8] the long-term real-world benefits of anti-vegf therapy for eyes with npdr are not yet determined. it is not clear how durable the treatment is and how long the patients should receive antivegf treatment. in the second year of the panorama study, those patients who initially received aflibercept every eight weeks transitioned to prn. concomitantly the rate of 2-steps or more improvement in drss reduced from 79.9% to 50%.[7] furthermore, in the rise/ride open label extension (ole) study, nearly 40% of eyes that did not receive any more ranibizumab injections during the ole experienced 2-steps or more worsening in the drss.[63] it is not apparent whether improvement in the drss following intravitreal injections of antivegfs is a true disease modification. in a case series by couturier et al, no reflow of vessels or reperfusion of capillary bed was found in non-perfusion areas using ultra-widefield (uwf) fluorescein angiography (fa) and swept-source widefield (ss-wf) oct-a in eyes with dr after 3 anti-vegf injections.[64] in addition, bonnin et al showed that after administering anti-vegf injections in dr eyes, the improvement in the drss score based on color fundus photograph could occur without retinal reperfusion on uwf fa.[65] in an ole of rise/ride study, it was shown that patients with anti-vegf injection induced moderate npdr were more prone to dr progression compared to patients with moderate npdr at enrollment who were randomized to the sham group.[63] journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 113 npdr without dme; arabi et al the cost–benefit ratio is also a challenge that needs to be addressed. answering this question requires more time and further studies. possible effects of vegf-independent drugs on npdr course inhibition of the vegf independent pathways may also affect the course of dr. there is some evidence that angiopoietin/tie2 and rhoassociated kinase (rock) play an influential role in retinal perfusion. inhibition of angiopoietin 2 may enhance the effects of vegf inhibition in improving the drss.[55] expression of rho-associated kinase (rock) is increased in diabetic eyes and activation of rock-1 induces focal retinal vasoconstriction and subsequent retinal ischemia.[66, 67] an in vivo study showed that fasudil (a specific rock inhibitor) decreased vasoconstriction, improved retinal flow, and could potentially reduce the retinal ischemia.[67] intravitreal ripasudil also decreased the retinal non-perfusion areas and improved retinal blood flow in a murine model of retinal vein occlusion.[68] ahmadieh et al reported that a combination of intravitreal bevacizumab and fasudil in eyes with persistent dme and macular ischemia was associated with significantly more visual improvement as compared with solely administering intravitreal bevacizumab. this significant visual improvement could be due to improved perfusion induced by the rock inhibitor.[69] further research is needed to determine the role of rock inhibitors in ameliorating diabetes-induced retinal microvascular damage and improving drss. summary the concept of slowing the progressive course of dr and preventing the vision-threatening complications of this potentially blinding disease may represent the initial sign of a paradigm shift from the observation, which has been the standard care for patients with npdr to a new strategy comprising intravitreal anti-vegf injections. however, there is not enough evidence supporting this paradigm shift at present. a new classification may help improving the management of npdr based on recent progress in understanding of the pathophysiology and advances in treatment of dr and addresses the need to possible paradigm shift in the future. financial support and sponsorship the authors declare that they did not receive any fund for the current manuscript or any research relevant to the present study. conflicts of interest the authors have no conflicts of interest to declare. references 1. gao hx, regier ee, close kl. international diabetes federation world diabetes congress 2015. j diabetes 2016;8:300–302. 2. shaw je, sicree ra, zimmet pz. global estimates of the prevalence of diabetes for 2010 and 2030. diabetes res clin pract 2010;87:4–14. 3. klein r, lee ke, knudtson md, gangnon re, klein be. changes in visual impairment prevalence by period of diagnosis of diabetes: the wisconsin epidemiologic study of diabetic retinopathy. ophthalmology 2009;116:1937– 1942. 4. early treatment diabetic retinopathy study research group. early photocoagulation for diabetic retinopathy. etdrs report number 9. ophthalmology 1991;98:766– 785. 5. ip ms, domalpally a, hopkins jj, wong p, ehrlich js. long-term effects of ranibizumab on diabetic retinopathy severity and progression. arch ophthalmol 2012;130:1145–1152. 6. mitchell p, mcallister i, larsen m, staurenghi g, korobelnik jf, boyer ds, et al. evaluating the impact of intravitreal aflibercept on diabetic retinopathy progression in the vivid-dme and vista-dme studies. ophthalmol retina 2018;2:988–996. 7. brown dm, wykoff cc, boyer d, heier js, clark wl, emanuelli a, et al. evaluation of intravitreal aflibercept for the treatment of severe nonproliferative diabetic retinopathy: results from the panorama randomized clinical trial. jama ophthalmol 2021;139:1–10. 8. maturi rk, glassman ar, josic k, antoszyk an, blodi ba, jampol lm, et al. effect of intravitreous antivascular endothelial growth factor vs sham treatment for prevention of vision-threatening complications of diabetic retinopathy: the protocol w randomized clinical trial. jama ophthalmol 2021;139:701–712. 9. diabetes control and complications trial research group. effect of intensive diabetes treatment on the development and progression of long-term complications in adolescents with insulin-dependent diabetes mellitus: diabetes control and complications trial. j pediatr 1994;125:177–188. 10. stratton im, kohner em, aldington sj, turner rc, holman rr, manley se, et al. ukpds 50: risk factors for incidence and progression of retinopathy in type ii diabetes over 6 years from diagnosis. diabetologia 2001;44:156–163. 114 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 npdr without dme; arabi et al 11. shichiri m, kishikawa h, ohkubo y, wake n. long-term results of the kumamoto study on optimal diabetes control in type 2 diabetic patients. diabetes care 2000;23:b21– b29. 12. wang ph, lau j, chalmers tc. meta-analysis of effects of intensive blood-glucose control on late complications of type i diabetes. lancet 1993;341:1306–1309. 13. ohkubo y, kishikawa h, araki e, miyata t, isami s, motoyoshi s, et al. intensive insulin therapy prevents the progression of diabetic microvascular complications in japanese patients with non-insulin-dependent diabetes mellitus: a randomized prospective 6-year study. diabetes res clin pract 1995;28:103–117. 14. drzewoski j, kasznicki j, trojanowski z. the role of ”metabolic memory” in the natural history of diabetes mellitus. pol arch med wewn 2009;119:493–500. 15. holman rr, paul sk, bethel ma, matthews dr, neil ha. 10-year follow-up of intensive glucose control in type 2 diabetes. n engl j med 2008;359:1577–1589. 16. american diabetes association. standards of medical care in diabetes-2014. diabetes care 2014;37:s14–s80. 17. uk prospective diabetes study group. tight blood pressure control and risk of macrovascular and microvascular complications in type 2 diabetes: ukpds 38. bmj 1998;317:703–713. 18. schrier rw, estacio ro, jeffers b. appropriate blood pressure control in niddm (abcd) trial. diabetologia 1996;39:1646–1654. 19. klein r, klein be, moss se, cruickshanks kj. the wisconsin epidemiologic study of diabetic retinopathy: xvii. the 14-year incidence and progression of diabetic retinopathy and associated risk factors in type 1 diabetes. ophthalmology 1998;105:1801–1815. 20. estacio ro, jeffers bw, gifford n, schrier rw. effect of blood pressure control on diabetic microvascular complications in patients with hypertension and type 2 diabetes. diabetes care 2000;23:b54–b64. 21. hansson l, zanchetti a, carruthers sg, dahlof b, elmfeldt d, julius s, et al. effects of intensive bloodpressure lowering and low-dose aspirin in patients with hypertension: principal results of the hypertension optimal treatment (hot) randomised trial. hot study group. lancet 1998;351:1755–1762. 22. raum p, lamparter j, ponto ka, peto t, hoehn r, schulz a, et al. prevalence and cardiovascular associations of diabetic retinopathy and maculopathy: results from the gutenberg health study. plos one 2015;10:e0127188. 23. do dv, wang x, vedula ss, marrone m, sleilati g, hawkins bs, et al. blood pressure control for diabetic retinopathy. cochrane database syst rev 2015;1:cd006127. 24. zhou y, wang c, shi k, yin x. relationship between dyslipidemia and diabetic retinopathy: a systematic review and meta-analysis. medicine 2018;97:e12283. 25. srinivasan s, raman r, kulothungan v, swaminathan g, sharma t. influence of serum lipids on the incidence and progression of diabetic retinopathy and macular oedema: sankara nethralaya diabetic retinopathy epidemiology and molecular genetics study-ii. clin exp ophthalmol 2017;45:894–900. 26. chew ey, davis md, danis rp, lovato jf, perdue lh, greven c, et al. the effects of medical management on the progression of diabetic retinopathy in persons with type 2 diabetes: the action to control cardiovascular risk in diabetes (accord) eye study. ophthalmology 2014;121:2443–2451. 27. keech ac, mitchell p, summanen pa, o’day j, davis tm, moffitt ms, et al. effect of fenofibrate on the need for laser treatment for diabetic retinopathy (field study): a randomised controlled trial. lancet 2007;370:1687–1697. 28. mandala a, armstrong a, girresch b, zhu j, chilakala a, chavalmane s, et al. fenofibrate prevents iron induced activation of canonical wnt/ß-catenin and oxidative stress signaling in the retina. npj aging mech dis 2020;6:12. 29. colhoun hm, betteridge dj, durrington pn, hitman ga, neil ha, livingstone sj, et al. primary prevention of cardiovascular disease with atorvastatin in type 2 diabetes in the collaborative atorvastatin diabetes study (cards): multicentre randomised placebo-controlled trial. lancet 2004;364:685–696. 30. collins r, armitage j, parish s, sleigh p, peto r. mrc/bhf heart protection study of cholesterol-lowering with simvastatin in 5963 people with diabetes: a randomised placebo-controlled trial. lancet 2003;361:2005–2016. 31. hosseini ms, rostami z, saadat a, saadatmand sm, naeimi e. anemia and microvascular complications in patients with type 2 diabetes mellitus. nephrourol mon 2014;6:e19976. 32. thomas m, tsalamandris c, macisaac r, jerums g. anaemia in diabetes: an emerging complication of microvascular disease. curr diabetes rev 2005;1:107–126. 33. traveset a, rubinat e, ortega e, alcubierre n, vazquez b, hernandez m, et al. lower hemoglobin concentration is associated with retinal ischemia and the severity of diabetic retinopathy in type 2 diabetes. j diabetes res 2016;2016:3674946. 34. ranil pk, raman r, rachepalli sr, pal ss, kulothungan v, lakshmipathy p, et al. anemia and diabetic retinopathy in type 2 diabetes mellitus. j assoc physicians india 2010;58:91–94. 35. idiculla j, nithyanandam s, joseph m, christeena j. anemia as a risk factor for diabetic retinopathy (dr) with special reference to nutritional etiology. diabetes 2018;67:591. 36. luo ba, gao f, qin ll. the association between vitamin d deficiency and diabetic retinopathy in type 2 diabetes: a meta-analysis of observational studies. nutrients 2017;9:307. 37. lu l, lu q, chen w, li j, li c, zheng z. vitamin d3 protects against diabetic retinopathy by inhibiting high-glucose-induced activation of the ros/txnip/nlrp3 inflammasome pathway. j diabetes res 2018;2018:8193523. 38. cai x, chen y, yang w, gao x, han x, ji l. the association of smoking and risk of diabetic retinopathy in patients with type 1 and type 2 diabetes: a meta-analysis. endocrine 2018;62:299–306. 39. moss se, klein r, klein be. cigarette smoking and tenyear progression of diabetic retinopathy. ophthalmology 1996;103:1438–1442. 40. moutray t, evans jr, lois n, armstrong dj, peto t, azuara-blanco a. different lasers and techniques for proliferative diabetic retinopathy. cochrane database syst rev 2018;3:cd012314. journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 115 npdr without dme; arabi et al 41. the diabetic retinopathy study research group. indications for photocoagulation treatment of diabetic retinopathy: diabetic retinopathy study report no. 14. int ophthalmol clin 1987;27:239–253. 42. early treatment diabetic retinopathy study research group. fundus photographic risk factors for progression of diabetic retinopathy. etdrs report number 12. ophthalmology 1991;98:823–833. 43. mistry h, auguste p, lois n, waugh n. diabetic retinopathy and the use of laser photocoagulation: is it cost-effective to treat early? bmj open ophthalmol 2017;2:e000021. 44. royle p, mistry h, auguste p, shyangdan d, freeman k, lois n, et al. pan-retinal photocoagulation and other forms of laser treatment and drug therapies for nonproliferative diabetic retinopathy: systematic review and economic evaluation. health technol assess 2015;19:v– xxviii, 1–247. 45. el rami h, barham r, sun jk, silva ps. evidence-based treatment of diabetic retinopathy. semin ophthalmol 2017;32:67–74. 46. fong ds, girach a, boney a. visual side effects of successful scatter laser photocoagulation surgery for proliferative diabetic retinopathy: a literature review. retina 2007;27:816–824. 47. iwase t, kobayashi m, yamamoto k, ra e, terasaki h. effects of photocoagulation on ocular blood flow in patients with severe non-proliferative diabetic retinopathy. plos one 2017;12:e0174427. 48. aiello lp, avery rl, arrigg pg, keyt ba, jampel hd, shah st, et al. vascular endothelial growth factor in ocular fluid of patients with diabetic retinopathy and other retinal disorders. n engl j med 1994;331:1480–1487. 49. adamis ap, miller jw, bernal mt, d’amico dj, folkman j, yeo tk, et al. increased vascular endothelial growth factor levels in the vitreous of eyes with proliferative diabetic retinopathy. am j ophthalmol 1994;118:445–450. 50. zhao y, singh rp. the role of anti-vascular endothelial growth factor (anti-vegf) in the management of proliferative diabetic retinopathy. drugs context 2018;7:212532. 51. campochiaro pa, wykoff cc, shapiro h, rubio rg, ehrlich js. neutralization of vascular endothelial growth factor slows progression of retinal nonperfusion in patients with diabetic macular edema. ophthalmology 2014;121:1783– 1789. 52. mitchell p, mcallister i, larsen m, staurenghi g, korobelnik jf, boyer ds, et al. evaluating the impact of intravitreal aflibercept on diabetic retinopathy progression in the vivid-dme and vista-dme studies. ophthalmol retina 2018;2:988–996. 53. bressler sb, liu d, glassman ar, blodi ba, castellarin aa, jampol lm, et al. change in diabetic retinopathy through 2 years: secondary analysis of a randomized clinical trial comparing aflibercept, bevacizumab, and ranibizumab. jama ophthalmol 2017;135:558–568. 54. lim ji. long-term clinical impact of intravitreal antivegf therapy for severe non-proliferative diabetic retinopathy (npdr): analyses through a discrete event simulation model. association for research in vision and ophthalmology annual meeting; may 6, 2021; virtual meeting. 55. sahni j, patel ss, dugel pu, khanani am, jhaveri cd, wykoff cc, et al. simultaneous inhibition of angiopoietin-2 and vascular endothelial growth factor-a with faricimab in diabetic macular edema: boulevard phase 2 randomized trial. ophthalmology 2019;126:1155–1170. 56. bonnin s, dupas b, lavia c, erginay a, dhundass m, couturier a, et al. anti-vascular endothelial growth factor therapy can improve diabetic retinopathy score without change in retinal perfusion. retina 2019;39:426–434. 57. yadav p, singh sv, nada m, dahiya m. impact of severity of diabetic retinopathy on quality of life in type 2 indian diabetic patients. int j community med public health 2021;8:207–211. 58. willis jr, doan qv, gleeson m, haskova z, ramulu p, morse l, et al. vision-related functional burden of diabetic retinopathy across severity levels in the united states. jama ophthalmol 2017;135:926–932. 59. wykoff cc, khurana rn, nguyen qd, kelly sp, lum f, hall r, et al. risk of blindness among patients with diabetes and newly diagnosed diabetic retinopathy. diabetes care 2021;44:748–756. 60. wu l, martinez-castellanos ma, quiroz-mercado h, arevalo jf, berrocal mh, farah me, et al. twelve-month safety of intravitreal injections of bevacizumab (avastin): results of the pan-american collaborative retina study group (pacores). graefes arch clin exp ophthalmol 2008;246:81–87. 61. shikari h, silva ps, sun jk. complications of intravitreal injections in patients with diabetes. semin ophthalmol 2014;29:276–289. 62. menchini f, toneatto g, miele a, donati s, lanzetta p, virgili g. antibiotic prophylaxis for preventing endophthalmitis after intravitreal injection: a systematic review. eye 2018;32:1423–1431. 63. goldberg ra. what happens to diabetic retinopathy severity scores with less aggressive treatment? a post hoc analysis of the rise and ride open label extension study. paper presented at: the american society of retina specialists annual meeting; july 29, 2019; chicago, il. 64. couturier a, rey pa, erginay a, lavia c, bonnin s, dupas b, et al. widefield oct-angiography and fluorescein angiography assessments of nonperfusion in diabetic retinopathy and edema treated with anti-vascular endothelial growth factor. ophthalmology 2019;126:1685– 1694. 65. bonnin s, dupas b, lavia c, erginay a, dhundass m, couturier a, et al. anti-vascular endothelial growth factor therapy can improve diabetic retinopathy score without change in retinal perfusion. retina 2019;39:426–434. 66. arita r, hata y, nakao s, kita t, miura m, kawahara s, et al. rho kinase inhibition by fasudil ameliorates diabetesinduced microvascular damage. diabetes 2009;58:215– 226. 67. rothschild pr, salah s, berdugo m, gélizé e, delaunay k, naud mc, et al. rock-1 mediates diabetes-induced retinal pigment epithelial and endothelial cell blebbing: contribution to diabetic retinopathy. sci rep 2017;7:8834. 68. hida y, nakamura s, nishinaka a, inoue y, shimazawa m, hara h. effects of ripasudil, a rock inhibitor, on retinal edema and nonperfusion area in a retinal vein occlusion murine model. j pharmacol sci 2018;137:129–136. 116 journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 npdr without dme; arabi et al 69. ahmadieh h, nourinia r, hafezi-moghadam a, sabbaghi h, nakao s, zandi s, et al. intravitreal injection of a rho-kinase inhibitor (fasudil) combined with bevacizumab versus bevacizumab monotherapy for diabetic macular oedema: a pilot randomized clinical trial. br j ophthalmol 2019;103:922–927. journal of ophthalmic and vision research volume 17, issue 1, january-march 2022 117 letter author’s reply mohammad reza talebnejad1, md; m. hossein nowroozzadeh1, md; hamideh mahdaviazad1,2, md 1poostchi ophthalmology research center, shiraz university of medical sciences, shiraz, iran 2department of family medicine, school of medicine, shiraz university of medical sciences, shiraz, iran orcid: mohammad reza talebnejad: https://orcid.org/0000-0001-8667-7490 hamideh mahdavihazad: https://orcid.org/0000-0002-8998-1209 j ophthalmic vis res 2020; 15 (1): 125–125 we appreciate suggestions presented by gharebaghi and heidary regarding our article titled “the shiraz pediatric eye study – a populationbased survey of school – age children: rationale, design, and baseline characteristics”.[1] in that study, we aimed to provide a valid source of data via a standard protocol and effective quality assurance strategies. our article had just described the design, methods, eye examination techniques, and baseline characteristics of the participants. although the two mentioned studies[2, 3] were conducted on a small fraction of the same population, we did not find any scientific justifications to cite them in this publication. they might be cited in future articles from the shiraz pediatric eye study, if it was deemed necessary. their suggestions regarding the prevalence of visual impairments, associations of the race and age with the ocular structures, and the continuing cohort of biometric data are useful. considering the specific goals of our study (last paragraph of introduction),[1] we have planned to apply the mentioned suggestions and much more in future publications of the shiraz pediatric eye study. conflicts of interest there are no conflicts of interest. references 1. talebnejad mr, nowroozzadeh mh, mahdaviazad h, khalili mr, masoumpour mb, keshtkar m, et al. the shiraz pediatric eye study; a population based survey of school age children: rationale, design and baseline characteristics. j ophthalmic vis res 2018;13:293–300. 2. nejabat m, heidary f, talebnejad mr, salouti r, nowroozzadeh mh, masoumpour m, et al. correlation between intraocular pressure and central corneal thickness in persian children. ophthalmol ther 2016;5:235–243. 3. salouti r, alishiri aa, gharebaghi r, naderi m, jadidi k, shojaei-baghini a, et al. comparison among ocular response analyzer, corvis st and goldmann applanation tonometry in healthy children. int j ophthalmol 2018;11:1330–1336. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. correspondence to: hamideh mahdaviazad, md. poostchi ophthalmology research center, shiraz university of medical sciences, shiraz 71936, iran. e-mail: mahdavih@sums.ac.ir access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i1.5970 how to cite this article: talebnejad mr, nowroozzadeh mh, mahdaviazad h. author’s reply. j ophthalmic vis res 2020;15:125–125. © 2020 journal of ophthalmic and vision research | published by knowledge e 125 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i1.5970&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr letter optic nerve cysticercosis at the orbital apex mahmood dhahir al-mendalawi, mb, ch.b, dch, ficms department of paediatrics, al-kindy college of medicine, university of baghdad, baghdad, iraq orcid: mahmood dhahir al-mendalawi: https://orcid.org/0000-0003-2872-453x j ophthalmic vis res 2020; 15 (1): 121–121 dear editor, i read with interest the case report by goel[1] published in the october–december 2018 issue of the journal of ophthalmic and vision research. the author described nicely a case of optic nerve cysticercosis at the orbital apex presenting as optic neuritis in an indian patient.[1] it is wellknown that due to compromised immune system, individuals infected with human immunodeficiency virus (hiv) are more susceptible to various types of viral, bacterial, fungal, and parasitic infections compared to the individuals with healthy immune system. among parasitic infections, cysticercosis has been reported among hiv-positive patients.[2] to my knowledge, hiv infection is a distressing health issue in india. the available data pointed out to 0.26% hiv seroprevalence compared with a global average of 0.2%,[3] and the overall seropositivity for cysticercosis was reported to be 5% among hiv-positive patients in india.[4] i assume that the underlying hiv infection ought to be taken into consideration in the studied patient. accordingly, planning for the diagnostic battery of blood cd4 count and viral overload measurements for hiv infection was envisaged. if that battery was contemplated and it disclosed hiv reactivity, the case in question could be obviously regarded the second novel case report of hiv-associated orbital cysticercosis in india. the first report was of subretinal cysticercosis in an indian patient with aids reported nearly two decades ago.[5] financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. goel n. optic nerve cysticercosis at the orbital apex presenting as optic neuritis. j ophthalmic vis res 2018;13:508–510. 2. chianura l, sberna m, moioli c, villa mr, orcese c, causarano r. neurocysticercosis and human immunodeficiency virus infection: a case report. j travel med 2006;13:376–380. 3. paranjape rs, challacombe sj. hiv/aids in india: an overview of the indian epidemic. oral dis 2016;22:10–14. 4. parija sc, gireesh ar. a serological study of cysticercosis in patients with hiv. rev inst med trop sao paulo 2009;51:185–189. 5. george ae, biswas j, agarwal r, kumarasamy n, solomon s. subretinal cysticercosis in a patient with aids: treatment with xenon arc photocoagulation. retina 1999;19:467– 468. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. correspondence to: mahmood dhahir al-mendalawi, mb, ch.b, dch, ficms. baghdad 55302, iraq. e-mail: mdalmendalawi@yahoo.com received: 25-11-2018 accepted: 25-01-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i1.5965 how to cite this article: al-mendalawi md. optic nerve cysticercosis at the orbital apex. j ophthalmic vis res 2020;15:121–121. © 2020 journal of ophthalmic and vision research | published by knowledge e 121 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i1.5965&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr letter author’s reply hamid sajjadi1,2, md, facs; hossein poorsalman3, md 1san jose eye and laser medical center, cupertino, california, usa 2department of ophthalmology, acacia medical center. dubai, uae 3department of ophthalmology, red crescent hospital, dubai, uae orcid: hamid sajjadi: https://orcid.org/0000-0002-7897-2091 j ophthalmic vis res 2019; 14 (4): 534–535 sir, thank you for your interest in our article.[1] you raised some questions about our case report; below please notice our answers: 1. as we mentioned in our article the mitochondrial mutation for leber hereditary optic neuropathy (lhon) was not present in this case and the patient had been labeled as lhon by previous clinicians. therefore, the diagnosis of lhon was completely presumptive. the icp that was measured in our case was 18 cmh2o in lateral decubitus position which used to be high before 2016; however, it has been challenged in recent articles that in children it can be up to 26 cmh2o. however, these articles also state that in children you have to interpret the icp measurement in the context of clinical signs and symptoms, there in effect an lumbar puncture (lp) is not reliable in children. our patient had some mri signs of pseudotumor cerebri (ptc) including extensive fluid around the optic nerve and hygroma. hygromas are normal in older than 60 years olds but not in a child. there are also ample reports of low tension ptcs in the literature.[2, 3] normal iop does not exclude ptc and what makes our report unique is the dramatic response of vision and stereopsis to the icp lowering treatment. 2. as optic atrophy is an ultimate sign of every optic neuropathy, finding a way in elucidating the definite cause of it is really important. there are lots of cases of optic atrophy with unknown cause and there should be a way to explain their origin. our previous article was an effort to open this discussion and was based on many neuroophthalmology cases that we have seen in these years. our diagnosis was not merely based on the optic nerve head (onh) feature of our patient, but was also dependent on the mri findings and the dramatic response to acetazolamide therapy. as explained, we have reported 164 cases of lp proven ptc without visible papilledema.[3] many of these cases presented with optic atrophy and no papilledema but did have high icp on lp. 3. we think our pictures have the best possible quality with topcon oct device and no other machine would produce a better ganglion cell layer (gcl) analysis. the first picture was taken by a topcon 2000 machine and the later ones were done at different center by the most recent software; therefore, they look different. however, the presence of central scotoma is obvious in the original gcl analysis which opened up as the patient’s central vision improved. in his last visit (4 months ago), his bcva was 20/20 in each eye. 4. it is mentioned in our article that the mitochondrial mutation for lhon was not present in this patient. there were neither 14484 nor any other mutations in our case. therefore, the theory of visual recovery secondary to this mutation cannot be correct. 5. although spontaneous stopping of damage has been reported in lhon, an improvement from 20/200 to 20/20 has never been reported. references 1. sajjadi h, poorsalman h. previously diagnosed leber’s hereditary optic neuropathy with clinical signs of idiopathic intracranial hypertension responsive to acetazolamide therapy. j ophthalmic vis res 2019;14:109-113. 2. suh sy, kim sj. iih with normal csf pressures. indian j ophthalmol 2013;61:681–682. 3. abdelfatah ma. normal pressure pseudotumor cerebri: a series of six patients. turk neurosurg 2017;27:208-211. 534 © 2019 journal of ophthalmic and vision research | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5477&domain=pdf&date_stamp=2019-07-17 letter; sajjadi and poorsalman 4. sajjadi f, khoshnevisan mh, doane jf, sajjadi h. new predictive value of optical coherence tomography analysis in the diagnosis of idiopathic intracranial hypertension. j contemp med sci 2017;3:197–207. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i4.5477 how to cite this article: sajjadi h, poorsalman h. author’s reply. j ophthalmic vis res 2019;14:534–535. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 535 https://knepublishing.com/index.php/jovr case report tapioca melanoma of the iris: a case report saeed karimi1,2, md; pouyan pahlevani1,2, md 1ophthalmic research center, shahid beheshti university of medical sciences, tehran, iran 2department of ophthalmology, torfeh medical center, shahid beheshti university of medical sciences, tehran, iran orcid: saeed karimi: https://orcid.org/0000-0002-3231-8414 pouyan pahlevani: https://orcid.org/0000-0003-3931-0973 abstract purpose: to report an extremely rare case of tapioca melanoma of the iris in an iranian patient. case report: a 50-year-old male patient presented with ocular pain and redness in the right eye for two weeks. the visual acuity was 7/10 and the intraocular pressure (iop) was 30 mmhg. a lobulated amelanotic vascularized and nodular (tapioca-like) iris mass with a 180o extent was seen in the right eye. incisional biopsy of the mass revealed atypical mixed type (epithelioid and spindle cell) melanoma. brachytherapy with the ruthenium-106 plaque resulted in complete regression of the tumor. conclusion: tapioca melanoma of the iris should be considered in the differential diagnosis of patients presenting with nodular vascularized amelanotic iris mass and elevated iop. brachytherapy with ruthenium106 seems to be an effective treatment for tapioca melanoma of the iris. keywords: brachytherapy; iris melanoma; tapioca melanoma j ophthalmic vis res 2019; 14 (3): 376–381 introduction tapioca melanoma of the iris is a rare form of diffuse iris melanoma,[1, 2] typically presenting with heterochromia and elevated intraocular pressure (iop), mainly because of aqueous outflow blockade. this tumor could also manifest as a diffuse, circumferential, and lightly pigmented or amelanotic lesion.[3, 4] almost 3–5% of patients develop correspondence to: pouyan pahlevani, md. ophthalmic research center, shahid beheshti university of medical sciences, boostan 9 ave., paidarfard ave., pasdaran st., tehran 16666, iran. e-mail: pouyan.pahlevani@gmail.com received: 12-03-2018 accepted: 20-08-2018 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i3.4794 distant metastasis of tumor.[5] histopathologically, tapioca melanoma is similar to other types of iris melanomas, but can be distinguished by their specific clinical presentations.[6] tapioca melanoma is characterized by weakly pigmented spindle or epithelioid malignant cells with a spreading pattern.[3, 4] compared to the other types of iris melanomas, tapioca melanoma is an uncommon type characterized by seeding and high iop in younger patients.[5] a collection of epithelioid cells in the anterior chamber angle may cause glaucoma.[4] the s-100 is a strong marker for diagnosis of cutaneous melanoma, but iris melanomas this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: karimi s, pahlevani p. tapioca melanoma of the iris: a case report. j ophthalmic vis res 2019;14:376–381 376 @ 2019 j  o  v r | p  published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i3.4794&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr tapioca melanoma of the iris; karimi and pahlevani figure 1. primary presentation: conjunctiva and ciliary injection of the right eye. figure 2. amelanotic, nodular, and vascularized iris mass with prominent feeder vessels. figure 3. high resolution ultrasound biomicroscope shows diffuse thickening and infiltration of iris with the tumor. have diverse morphologies and different abilities to take up this stain. therefore, diagnosis of atypical iris melanomas may be difficult and challenging.[2, 7] early diagnosis and treatment of atypical iris melanomas are essential for preventing the progression of the disease and saving the patients’ eyesight and life.[8, 9] case report a 50-year-old male patient presented with ocular pain and redness in the right eye for two weeks. the best-corrected visual acuity was 7/10 and 9/10 in the right and left eyes, respectively, figure 4. enlarged vascularized iris mass, two weeks after first visit. figure 5. ru-106 plaque (cia design) to treat the iris tapioca melanoma. without afferent pupillary defect. extraocular movements were within normal limits in both eyes. except for controlled diabetes mellitus, the past medical and surgical history were unremarkable. slit lamp examination revealed “1+” cells in the anterior chamber and fine keratic precipitates on the corneal endothelium. there was a lobulated, nodular, amelanotic, and highly vascularized mass measuring about four clock hours of the iris nasally, disrupting the normal iris structure [figures 1 and 2]. the iop was 16 and 15 mmhg in the right and left eyes, respectively. dilated fundus examination and optical coherence tomography images revealed moderate non-proliferative diabetic retinopathy without diabetic macular edema in both eyes. ultrasound biomicroscopy (ubm) determined diffuse iris thickening (2.02 mm) and tumoral involvement of the iris with minimal spread j  o  v r volume 14, issue 3, july–september 2019 377 tapioca melanoma of the iris; karimi and pahlevani figure 6. histopathologic images (a) epithelioid and spindle-shaped neoplastic cells with apoptotic bodies and mild scattered melanin pigments [hematoxylin and eosin stain (h&e) ×400]; (b,c)-dysplastic tumor cells mainly of epithelioid type with large nuclei, prominent nucleoli, and apoptosis, h&e ×1000, higher magnification; patchy immune-reactivity to hmb45 (d), strong immunereactivity to s100 (e) and ki67 (f), magnification ×400; (g) patchy immune-reactivity to melan-a, magnification ×400. 378 j  o  v r volume 14, issue 3, july–september 2019 tapioca melanoma of the iris; karimi and pahlevani figure 7. high resolution ultrasound biomicroscopy (ubm) of the iris, five months after brachytherapy with ru-106 plaque reveals complete tumor regression and iris atrophy. figure 8. photo-slit image of the right eye five months after treatment: complete tumor regression, iris atrophy, localized posterior synechia, and mild cataract noted. to the ciliary body [figure 3]. systemic workup tested negative for metastasis, granulomatous diseases, or any extraocular primary tumor. two weeks later, ocular pain and redness increased, the iop peaked at 30 mmhg, and the mass grew and involved the six o’clock region of the iris [figure 4]. with the provisional diagnosis of iris tapioca melanoma, incisional biopsy of the iris and brachytherapy with ruthenium-106 cia radioactive plaque (eckert & ziegler bebig gmbh, 100 gy, berlin, germany) were performed simultaneously [figure 5]. microscopic examination of the biopsied tissue demonstrated atypical epithelioid and spindle cells with large nuclei and prominent nucleoli with melanin pigments [figure 6]. there was a strong immunoreactivity to s-100 and ki-67 and patchy immunoreactivity to hmb45 and melan-a. all examinations revealed a rare subtype of iris malignant melanoma called tapioca melanoma. no metastasis was found in the systemic work-up. one week after treatment, the tumor regressed, and iop decreased to 14 mmhg. five months after brachytherapy, there was no sign of tumor recurrence or metastasis. slit lamp examination and ubm demonstrated complete tumor regression with iris atrophy and mild lens opacity [figures 7 and 8]. discussion tapioca melanoma, a rare form of diffuse iris melanoma presenting as a hyperchromic iris heterochromia with unilateral elevation of iop due to the aqueous outflow obstruction.[4] it seems that agglomeration of epithelioid cells in the anterior chamber angle is the cause of iop elevation.[3] tapioca is derived from a native brazilian word denoting the pale granular starch material obtained from manioc tubers.[6] algernon reese used the term “tapioca melanoma” for the first time in 1972, owing to the resemblance of these pale tumor nodules to tapioca pudding.[2, 3, 10] earlier in 1959, lorenz e zimmerman diagnosed this lesion and described it as an atypical iris melanoma.[3] compared to the other types of iris melanoma, tapioca melanoma mostly occurs in younger patients.[1] the youngest reported case was that of a seven-year-old patient.[3] there could be a connection between the inception of hormonal changes at puberty and the commencement of uveal melanoma.[11] the mean age of surgery in tapioca melanoma patients was 30 years, whereas in other types of iris melanoma it was 46.[3] our patient was 50 years old, but remarkably, this rare type of melanoma is very uncommon in adults. different presentations of tapioca iris melanoma in different populations may be related to the varying genomic types of the disease.[12] there are several predisposing factors of uveal melanoma, including ocular melanocytosis, neurofibromatosis type 1, dysplastic nevus syndrome, and familial uveal melanoma.[11] however, there was no remarkable family history for uveal melanoma in this case. this tumor usually presents as a vascularized mass with nodular surface.[6] diseases such as fuch’s heterochromic iridocyclitis, neurofibromatosis, and cogan-reese may present with iris nodules and elevated iop.[1] in neurofibromatosis, there are yellow-brown dome-shaped papules on the iris j  o  v r volume 14, issue 3, july–september 2019 379 tapioca melanoma of the iris; karimi and pahlevani called lisch nodules, while cogan-reese presents irregular corneal endothelium with pedunculated and pigmented nodules. in sarcoidosis, patients have systemic signs and symptoms along with papillitis, papilledema, and granulomas in any part of the eye.[13] juvenile xantogranuloma, lisch and koeppe nodules, infectious granulomas, vascular tumors, leiomyoma, metastases, and iris nevus syndrome are some of the relevant differential diagnosis.[8, 12] due to the rarity of tapioca iris melanoma, there are no well-defined criteria for the identification of this type of tumor, and hence its diagnosis can be challenging. although the iris tumor in our case may not have had the exact appearance of a typical tapioca-like iris melanoma, it could be classified as a tapioca iris melanoma considering its characteristic iris nodules, anterior uveitis, rapid growth, high iop, and high rate of vascularization. immunohistochemical staining is often used to confirm the diagnosis. s-100 marker is usually used to stain melanoma and neural tissues, while ki-67 and hmb-45 are used to mark proliferating cells.[1, 8] in the present case, immunostaining was positive for s-100, hmb-45, ki67, and melan-a that confirmed the diagnosis of iris melanoma. there is no agreement on the specific size of iris tumor for surgical treatment. some authors believe in tumor excision for lesions > 3 mm in diameter or 1 mm in thickness.[13] sectoral iridectomy is advocated in patients with localized tumors that are limited to the iris without satellite lesions, while en bloc excision is recommended when the anterior chamber angle is involved.[9] leiden used ruthenium-106 plaque brachytherapy to treat the iris and anterior ciliary body melanomas for the first time in 1997.[14] only two recurrences were observed among 36 patients with anterior uveal melanoma during the six and a half years of follow-up. ruthenium-106 plaques are 𝛽-emitter sources. therefore, the optic disc and macula are exposed to lower doses of radiation as compared to the 𝛽-emitter sources like i-125 plaques. [15] ruthenium-106 plaque treatment for iris melanoma has a significant effect on the control of tumor without any recurrence.[16] our patient was treated with ruthenium-106 cia plaque, and there was complete regression of the tumor without any recurrence after 18 months of followup. in conclusion, tapioca iris melanoma should be considered in differential diagnosis of any iris tumor presenting as a nodular vascularized iris mass and elevated iop.[1] brachytherapy with ruthenium-106 plaque would be a useful treatment for tapioca iris melanoma. financial support and sponsorship nil. conflict of interest there are no conflicts of interest. references 1. pick zs, wilson ga. tapioca melanoma of the iris. clin exp optom 2009;922:154–156. 2. iwamoto t, reese ab, mund ml. tapioca melanoma of the iris. 2. electron microscopy of the melanoma cells compared with normal iris melanocytes. am j ophthalmol 1972;745:851–861. 3. reese ab, mund ml, iwamoto t. tapioca melanoma of the iris. 1. clinical and light microscopy studies. am j ophthalmol 1972;745:840–850. 4. demirci h, shields cl, shields ja, eagle rc, jr, honavar sg. diffuse iris melanoma: a report of 25 cases. ophthalmology 2002;1098:1553–1560. 5. de keizer rj, oosterhuis ja, houtman wa, de wolffrouendaal d. tapioca melanoma of the iris. ann ophthalmol 1993;255:195–198. 6. viestenz a, conway rm, kuchle m. tapioca melanoma of the iris mimicking a vascular tumour: a clinicopathological correlation. clin exp ophthalmol 2004;323:327–330. 7. heegaard s, jensen oa, prause ju. immunohistochemical diagnosis of malignant melanoma of the conjunctiva and uvea: comparison of the novel antibody against melan-a with s100 protein and hmb-45. melanoma res 2000;104:350–354. 8. hassenstein a, bialasiewicz aa, von domarus d, schafer h, richard g. tapioca melanomas of the iris: immunohistology and report on two cases. graefes arch clin exp ophthalmol 1999;2375:424–428. 9. naumann g, volcker he. [block-excision of intraocular processes. ii. epithelial ingrowth into the anterior segment of the eye (author’s transl)]. klin monbl augenheilkd 1975;1664:448–457. 10. zakka ka, foos ry, sulit h. metastatic tapioca iris melanoma. br j ophthalmol 1979;6311:744–749. 11. singh ad, shields cl, shields ja, sato t. uveal melanoma in young patients. arch ophthalmol 2000;1187:918–923. 12. viestenz a, berger t, kuchle m. cutaneous melanoma metastasizing to the iris and choroid: a case report. graefes arch clin exp ophthalmol 2002;24012:1036– 1038 380 j  o  v r volume 14, issue 3, july–september 2019 tapioca melanoma of the iris; karimi and pahlevani 13. bach a, mcgowan s, gold as, villegas vm, wildner ac, ehlies fj, et al. tapioca melanoma of the iris without iris heterochromia. optom vis sci 2014;914:s20–s24 14. razzaq l, keunen je, schalij-delfos ne, creutzberg cl, ketelaars m, de keizer rj. ruthenium plaque radiation therapy for iris and iridociliary melanomas. acta ophthalmol 2012;903:291–296. 15. wilkinson da, kolar m, fleming pa, singh ad. dosimetric comparison of 106ru and 125i plaques for treatment of shallow (<or=5 mm) choroidal melanoma lesions. br j radiol 2008;81970:784–789. 16. agraval u, sobti m, russell hc, lockington d, ritchie d, cauchi p, et al. use of ruthenium-106 brachytherapy for iris melanoma: the scottish experience. br j ophthalmol 2018;1021:74–78. j  o  v r volume 14, issue 3, july–september 2019 381 original article serum levels of vitamin d in diabetic patients with and without retinopathy mehrdad afarid1, md; naghme ghattavi2, md; mohammadkarim johari1, md 1poostchi ophthalmology research center, department of ophthalmology, school of medicine, shiraz university of medical sciences, shiraz, iran 2student research committee, shiraz university of medical sciences, shiraz, iran orcid: mehrdad afarid: https://orcid.org/0000-0003-2348-9163 mohammadkarim johari: https://orcid.org/0000-0002-5442-0073 abstract purpose: to evaluate the levels of vitamin d in the serum of diabetic patients with and without diabetic retinopathy (dr). methods: thirty patients with dr and thirty diabetic patients without retinopathy were included in this cross-sectional study. based on ophthalmic examination, patients with dr were categorized into having non-proliferative retinopathy (npdr) and proliferative retinopathy (pdr). patients were tested for fasting blood sugar (fbs), hemoglobin a1c (hba1c), 25-hydroxy vitamin d (25 (oh) d), and creatinine levels in the serum, and for urine protein. vitamin d deficiency was defined as a serum 25 (oh) d level < 20 ng/ml. results: we found that all diabetic patients had mild vitamin d deficiency (serum 25 (oh) d level = 10–20 ng/ml). the mean serum 25 (oh) d concentration in patients with dr was lower than in those without dr (12.10 ± 14.62 ng/ml vs 15.61 ± 9.40 ng/ml, respectively, p = 0.012). trace or more proteinuria was frequently present in patients with dr than in those without dr (56% in dr vs 30% in non-dr; p = 0.037). there were no significant differences in the fbs, hba1c, and serum creatinine levels between patients with or without retinopathy. conclusion: the present study demonstrated that patients with dr had lower levels of serum vitamin d compared with those without retinopathy. keywords: diabetes mellitus; diabetic retinopathy; 25-hydroxy vitamin d j ophthalmic vis res 2020; 15 (2): 172–177 introduction the prevalence of diabetes mellitus, a metabolic syndrome with several complications, has correspondence to: mohammadkarim johari, md. poostchi ophthalmology research center, department of ophthalmology, school of medicine, shiraz university of medical sciences, poostchi st., shiraz 714737, iran. e-mail: mkjoharii@gmail.com received: 21-10-2018 accepted: 23-10-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i2.6734 increased worldwide in the recent decades.[1] based on the latest global burden of disease estimates in 2011 (surfncd-2011), the prevalence of type 2 diabetes in the iranian population is 11%.[2] diabetic retinopathy (dr) is a major complication of diabetes mellitus that can result in retinal vascular abnormalities and severe visual this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: afarid m, ghattavi n, johari m. serum levels of vitamin d in diabetic patients with and without retinopathy. j ophthalmic vis res 2020;15:172–177. 172 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i2.6734&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr vit d levels in diabetes; afarid et al impairment. dr is defined as a vascular disease resulting from hyperglycemia, and is characterized by altered structure of retinal endothelial vessels and disrupted blood–retinal barrier. the retinal vasculature is gradually damaged resulting in ischemic changes that lead to the formation of new vessels and its consequences.[3] different studies have reported abnormalities in the metabolism of calcium, phosphate, and vitamin d in diabetic patients. bayani et al showed that vitamin d concentration was significantly lower in diabetic patients compared with that in healthy individuals.[4] moreover, animal and human studies have demonstrated a correlation between vitamin d deficiency and impaired insulin production and secretion as well as insulin sensitivity.[5–7] another study reported that reduced serum insulin levels could be related to the lower level of 1,25(oh)2 d. [8] vitamin d has an inhibitory effect on vascular angiogenesis.[9] it is believed that vitamin d deficiency, which is described as a serum 25 (oh) d concentration < 20 ng/ml, affects the pathogenesis and progression of dr.[10] vitamin d deficiency is a common public health concern. a study reports that the prevalence of vitamin d deficiency varies across different populations.[11] the prevalence of vitamin d deficiency in the united states was reported to be 41.6% in 2005.[12] additionally, individuals who had no college education and had low serum levels of high-density lipoprotein cholesterol, high body mass index (bmi), hypertension or were on low calcium diet had low serum vitamin d levels.[12] a study in tehran, iran reported the prevalence of vitamin d deficiency to be 43.3% among adolescents, with higher rates in females compared to males.[13] the most likely crucial role of vitamin d related to diabetic pathogenicity and its main complications such as dr is its involvement in several body mechanisms such as adjustment of blood glucose or body vascular consistency. therefore, we decided to investigate the serum levels of vitamin d in our diabetic patients with and without dr in fars province, iran. methods this cross-sectional study was conducted on patients with type 2 diabetes who were referred to the ophthalmology clinics of the shiraz university of medical sciences. the study was approved by the shiraz university of medical sciences ethics committee. thirty patients with dr and thirty patients without retinopathy were included. patients with a history of smoking, chronic kidney disease, active infection, liver disease, primary or secondary hyperparathyroidism, serum creatinine levels > 2 mg/dl, and those receiving vitamin d, calcium supplements, or any other medication that could change vitamin d metabolism, such as rifampin or phenytoin, were excluded from the study. patients who had a history of bone fracture or orthopedic surgeries during the past year were also excluded. age, sex, and duration of diabetes were recorded for all subjects. patients were categorized into two groups based on the duration of diabetes (< 10 years and > 10 years). all patients underwent complete ophthalmic examination by a vitreoretinal surgeon for diagnosing dr; this examination consisted of funduscopy with a slit-lamp and 90 d lenses and an indirect ophthalmoscopy. dr was diagnosed in the presence of one or more of the following signs: microaneurysms, cotton-wool spots, intraretinal hemorrhages, or macular edema. dr was categorized into mild to severe non-proliferative diabetic retinopathy (npdr) based on the absence of any neovascularization and proliferative diabetic retinopathy (pdr). mild npdr was defined as having only microaneurysms, whereas severe npdr was defined as having any one of the following features: severe intraretinal hemorrhages in four quadrants, venous beading in two or more quadrants and intraretinal microvascular anomalies (irmas) in one or more quadrants; moderate npdr was between the above two categories. in cases of asymmetrical retinopathy, the patient was assigned to the group corresponding to the eye with the more severe retinopathy scale. blood samples were drawn in the morning after a 12-h fast. fasting blood sugar (fbs) and glycated hemoglobin a1c (hba1c) and serum calcium, phosphorus, and creatinine levels were measured. the presence of protein in the urine was checked with dipstick method. serum vitamin d level was assessed measuring the level of serum 25-oh vitamin d. the 25 (oh) d levels were measured from serum samples using solid phase enzyme-linked immunosorbent assay (drg 25 (oh) d total elisa kit; drg instruments gmbh, germany). the serum concentration journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 173 vit d levels in diabetes; afarid et al > 30 ng/ml was considered as sufficient. cutoffs for serum vitamin d concentration status are described in table 1. statistical analysis spss 17.0 software for windows (spss inc., chicago, il, usa) was used for data analysis. the variables with a normal distribution are shown as mean ± standard deviation, and nominal variables are expressed as number and percentage. the normality assumption in continuous variables was evaluated using the kolmogorov–smirnov test. distributions higher than p > 0.05 were accepted as normally distributed variables. the differences between normally distributed and continuous independent variables were assessed by the independent samples t-test. those without a normal distribution were compared using the mann–whitney u test between the groups. categorical variables were compared using the chi-squared test. for all comparisons, p < 0.05 was considered significant. results the study included 15 female subjects with mean age (± standard deviation) of 60.13 ± 6.02 years and 15 males with mean age of 57.60 ± 5.43 years in the group with dr and 16 females with mean age of 59.05 ± 6.25 years and 14 males with mean age of 57.30 ± 8.50 years in the group without dr. there was no statistically significant difference between the groups regarding their age (p = 0.73) and sex (p = 0.75). the demographic and clinical characteristics of the patients in the study are shown in table 2. among patients with dr, 21 patients had npdr (13 mild to moderate and 8 severe) and 9 patients had pdr. all patients had mild vitamin d deficiency. the mean serum vitamin d concentration in patients with dr (12.10 ± 14.62 ng/ml; npdr and pdr) was lower than in those without dr (15.61 ± 9.40 ng/ml) (p = 0.012). regression analysis with independent variables (fbs, duration of diabetes and insulin use) showed similar results (p = 0.031). the mean 25 (oh) d concentration between the dr subgroups (severe npdr and pdr vs mild to moderate npdr) was 10.51 ± 10.45 ng/ml and 13.45 ± 8.4 ng/ml, respectively (p = 0.681). serum 25 (oh) d concentration in all patients was compared among the age groups. the mean ± sd in patients with age ranging from 41 to 50 years, 51 to 60 years, and ≥ 60 years were 10.11 ± 9.50, 14.15 ± 16.06, 14.99 ± 6.94, respectively (p = 0.128). regarding the treatment, 46% of patients without dr and 86.6% of patients with dr were taking insulin. univariate analysis between the two groups showed that the use of insulin in patients with dr was significantly higher than in those without dr (p = 0.014). the duration of diabetes was different between the groups. nine (30%) patients with no diabetic retinopathy (ndr) had diabetes for more than 10 years and 16 (53%) patients with dr had diabetes for more than 10 years. however, the difference was not statistically significant (p = 0.081). binomial variable multiple logistic regression analysis with independent variables revealed that fbs, hba1c, bun, serum creatinine, and serum vitamin d levels did not show the duration of diabetes as an independent risk factor for dr (p = 0.067). however, this value was significant in terms of the type of treatment (insulin use or not) (p = 0.005). patients with dr had a higher positive dipstick test rate for proteinuria than those without dr (56% of the patients with dr had traces of or more proteinuria vs 30% in no dr; p = 0.037). fbs, serum bun, and creatinine levels were not different between the patients with or without retinopathy. although vitamin d may influence the levels of serum calcium, our data showed no significant difference in serum calcium or phosphorus between the two groups (p = 0.511 and p = 0.416, respectively). discussion in the current study, we evaluated the serum levels of vitamin d in diabetic patients with and without dr. furthermore, we investigated other possible factors that could influence the progression of dr. similar to previous studies, all included patients had 25 (oh) d deficiency.[15–17] the current study showed that the mean serum 25 (oh) d concentration in patients with dr was lower than in those without dr, especially those with severe npdr and pdr. these results were comparable to other studies. for example, payne et al found that diabetic patients, especially those with pdr, had lower 25 (oh) d levels than those without diabetes.[19] similarly, luo et al in their meta-analysis that included 174 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 vit d levels in diabetes; afarid et al table 1. serum 25(oh) d concentration[14] 25(oh) d concentration 25(oh) d status ≤ 10 ng/ml severe deficiency 10–20 ng/ml mild deficiency 20–30 ng/ml insufficient 30 ≤ ng/ml adequate 100 ≤ ng/ml potential toxicity table 2. demographic and clinical characteristics of patients patients with no dr patients with dr p-value gender (female/male), n 16/14 15/15 0.73 age (years), mean ± sd 58.30 ± 7.23 58.57 ± 5.78 0.75 fbs (mg/dl), mean ± sd 146.43 ± 58.91 164.37 ± 88.98 0.54 hba1c (%), mean ± sd 7.18 ± 1.58 7.90 ± 2.25 0.45 hb (g/dl), mean ± sd 14.20 ± 1.22 13.48 ± 2.04 0.78 bun (mg/dl), mean ± sd 13.66 ± 3.98 17.03 ± 7.40 0.41 cr (mg/dl), mean ± sd 1.02 ± 0.25 1.21 ± 0.72 0.33 calcium (mg/dl), mean ± sd 9.26 ± 0.45 8.92 ± 0.48 0.511 phosphorus (mg/dl), mean ± sd 3.75 ± 0.42 3.66 ± 0.50 0.416 25-oh d (ng/ml) mean ± sd 15.61 ± 9.40 12.10 ± 14.62 0.012 bun, blood urea nitrogen; cr, creatinine; dr, diabetic retinopathy; fbs, fasting blood sugar; hba1c, hemoglobin a1c; hb, hemoglobin; sd, standard deviation. eight studies involving 13,435 participants showed vitamin d deficiency (serum 25 (oh) d levels < 20 ng/ml) increased the risk of dr (or = 2.03, 95% ci: 1.07–3.86)[20] on the contrary, some studies found no differences in serum vitamin d levels between diabetic patients with and without retinopathy.[16, 18] evidence shows that vitamin d may affect the pathogenesis of dr via its effects on angiogenesis by changing the presence of hypoxiainducible products, such as vascular endothelial growth factor (vegf).[9] ben-shoshan et al found that 1, 25 (oh)2d3 decreases the protein expression of both regulated hypoxia-inducible factor (hif)-1α subunit and the vegf in human cancer cells.[21] vitamin d reduces inflammatory products by decreasing the lymphocyte proliferation and cytokine production.[22] moreover, vitamin d deficiency influences the activity of tissue matrix metalloproteinase (mmps) and c-reactive protein (crp) that are involved in microangiopathies.[23] we demonstrated that dr occurred more frequently in patients who were on insulin therapy than in those who used oral hypoglycemic agents to control their blood sugar (p = 0.005). this could be attributed to low vitamin d concentration in these patients that could disturb the regulation of internal insulin secretion and increase the need for external insulin to control the blood sugar.[7, 8] in the present study, there were no statistically significant differences between groups regarding their hba1c, fbs, and the duration of diabetes. furthermore, patients with dr had higher proteinuria than those without, which could demonstrate a correlation between dr and nephropathy. multiple studies reported that the presence of dr in type 2 diabetic patients was associated with longer duration of diabetes and higher levels of hba1c. [24–26] however, in the present study, such correlation was not found; this disagreement could be explained by the small sample size of the current study that was not sufficient to detect these associations. the cross-sectional design and the small sample size are the limitations of our study. furthermore, journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 175 vit d levels in diabetes; afarid et al outdoor activity time, patients’ daily diet, and the mean blood pressure of patients, which are known to affect vitamin d levels,[27] were not considered in the study. although there are several published studies on this topic with different results, to the best of our knowledge, no study on this subject is available from fars province, iran. to improve our understanding of vitamin d deficiency and dr, a larger population-based study is required. in conclusion, the current study showed that patients with type 2 diabetes and dr had lower serum vitamin d levels than those without dr. financial support and sponsorship shiraz university of medical sciences. conflicts of interest there are no conflicts of interest. acknowledgement the authors are grateful to dr. kazem kamran, retinal specialist, and dr. roustsa statistician, and all staff members of the poostchi ophthalmology research center involved in the study that contributed to the recruitment of participants and supported our activities. references 1. geiss ls, wang j, cheng yj, thompson tj, barker l, li y, et al. prevalence and incidence trends for diagnosed diabetes among adults aged 20 to 79 years, united states, 1980–2012. jama 2014;312:1218–1226. 2. ncd risk factor collaboration (ncd-risc). worldwide trends in diabetes since 1980: a pooled analysis of 751 population-based studies with 4.4 million participants. lancet 2016;387:1513–1530. 3. wan tt, li xf, sun ym, li yb, su y. recent advances in understanding the biochemical and molecular mechanism of diabetic retinopathy. biomed pharmacother 2015;74:145–147. 4. bayani ma, akbari r, banasaz b, saeedi f. status of vitamin-d in diabetic patients. caspian j intern med 2014;5:40–42. 5. cangoz s, chang yy, chempakaseril sj, guduru rc, huynh lm, john js, et al. vitamin d and type 2 diabetes mellitus. j clin pharm ther 2013;38:81–84. 6. mathieu c, gysemans c, giulietti a, bouillon r. vitamin d and diabetes. diabetologia 2005;48:1247–1257. 7. wimalawansa sj. associations of vitamin d with insulin resistance, obesity, type 2 diabetes, and metabolic syndrome. j steroid biochem mol biol 2018;175:177–189. 8. michaud se, renier g. direct regulatory effect of fatty acids on macrophage lipoprotein lipase: potential role of ppars. diabetes 2001;50:660–666. 9. albert dm, scheef ea, wang s, mehraein f, darjatmoko sr, sorenson cm, et al. calcitriol is a potent inhibitor of retinal neovascularization. invest ophthalmol vis sci 2007;48:2327–2334. 10. zhang j, upala s, sanguankeo a. relationship between vitamin d deficiency and diabetic retinopathy: a metaanalysis. can j ophthalmol 2017;52:219–224. 11. langlois k, greene-finestone l, little j, hidiroglou n, whiting s. vitamin d status of canadians as measured in the 2007 to 2009 canadian health measures survey. health rep 2010;21:47–55. 12. forrest ky, stuhldreher wl. prevalence and correlates of vitamin d deficiency in us adults. nutr res 2011;31:48–54. 13. larijani b, hossein-nezhad a, feizabad e, maghbooli z, adibi h, ramezani m, et al. vitamin d deficiency, bone turnover markers and causative factors among adolescents: a cross-sectional study. j diabetes metab disord 2016;15:46. 14. holick mf. vitamin d deficiency. n engl j med 2007;357:266–281. 15. rhee sy, hwang yc, chung hy, woo jt. vitamin d and diabetes in koreans: analyses based on the fourth korea national health and nutrition examination survey (knhanes), 2008–2009. diabet med 2012;29:1003– 1010. 16. bonakdaran s, shoeibi n. is there any correlation between vitamin d insufficiency and diabetic retinopathy? int j ophthalmol 2015;8:326–331. 17. isaia g, giorgino r, adami s. high prevalence of hypovitaminosis d in female type 2 diabetic population. diabetes care 2001;24:1496. 18. alam u, amjad y, chan aw, asghar o, petropoulos in, malik ra. vitamin d deficiency is not associated with diabetic retinopathy or maculopathy. j diabetes res 2016;2016:6156217. 19. payne jf, ray r, watson dg, delille c, rimler e, cleveland j, et al. vitamin d insufficiency in diabetic retinopathy. endocr pract 2012;18:185–193. 20. luo ba, gao f, qin ll. the association between vitamin d deficiency and diabetic retinopathy in type 2 diabetes: a meta-analysis of observational studies. nutrients 2017;9:3. 21. ben-shoshan m, amir s, dang dt, dang lh, weisman y, mabjeesh nj. 1alpha,25-dihydroxyvitamin d3 (calcitriol) inhibits hypoxia-inducible factor-1/vascular endothelial growth factor pathway in human cancer cells. mol cancer ther 2007;6:1433–1439. 22. wu-wong jr, nakane m, ma j, ruan x, kroeger pe. effects of vitamin d analogs on gene expression profiling in human coronary artery smooth muscle cells. atherosclerosis 2006;186:20–28. 23. timms pm, mannan n, hitman ga, noonan k, mills pg, syndercombe-court d, et al. circulating mmp9, vitamin d and variation in the timp-1 response with vdr genotype: mechanisms for inflammatory damage in chronic disorders? qjm 2002;95:787–796. 24. pan cw, wang s, qian dj, xu c, song e. prevalence, 176 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 vit d levels in diabetes; afarid et al awareness, and risk factors of diabetic retinopathy among adults with known type 2 diabetes mellitus in an urban community in china. ophthalmic epidemiol 2017;24:188– 194. 25. bansal p, gupta r, kotecha m. frequency of diabetic retinopathy in patients with diabetes mellitus and its correlation with duration of diabetes mellitus. med j dr dy patil univ 2013;6:366–369. 26. jenchitr w, samaiporn s, lertmeemongkolchai p, chongwiriyanurak t, anujaree p, chayaboon d, et al. prevalence of diabetic retinopathy in relation to duration of diabetes mellitus in community hospitals of lampang. j med assoc thai 2004;87:1321–1326. 27. vashi pg, lammersfeld ca, braun dp, gupta d. serum 25hydroxyvitamin d is inversely associated with body mass index in cancer. nutr j 2011;10:51. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 177 original article a 27-year report from the central eye bank of iran: a complete translation from farsi mohammad ali javadi1,2, md; mozhgan rezaei kanavi3, md; sare safi4, phd 1ophthalmic research center, shahid beheshti university of medical sciences, tehran, iran 2central eye bank of iran, tehran, iran 3ocular tissue engineering research center, shahid beheshti university of medical sciences, tehran, iran 4ophthalmic epidemiology research center, shahid beheshti university of medical sciences, tehran, iran orcid: mohammad ali javadi: https://orcid.org/0000-0002-4886-7901 mozhgan rezaei kanavi: https://orcid.org/0000-0002-9725-2444 this article is based on a study first reported in farsi in the bina journal of ophthalmology, titled volume 24, issue 2 (winter 2019) 2019/05/28. original url: https://www.sid.ir/fa/journal/viewpaper.aspx?id=487896 abstract purpose: to report the 27-year statistical data from the central eye bank of iran (cebi) and its activity. methods: all cebi records regarding procured eyes, tissue utilizations, corneal transplants per capita, and indications for keratoplasty from 1991 to 2017 were analyzed. results: in total, 115,743 whole eyes were donated during the 27-year period. out of the 114,169 eyes donated between 1994 and 2017, 95,314 eyes were distributed for transplantation, and 95,057 corneas were actually transplanted. the mean annual rate of corneal transplants per capita was 55.10−6 ± 27.10−6. although penetrating keratoplasty (pkp, 70%) was the most common technique of corneal transplantation during the study period, it exhibited a decreasing trend between 2006 and 2017 (p = 0.048). it was in contrast to descemet stripping automated endothelial keratoplasty (dsaek) that demonstrated an increasing trend during the same period (p < 0.001). keratoconus (kcn, 39.70%) was the most leading indication for keratoplasty over the last three decades followed by bullous keratopathy (bk, 18.5%), corneal scar and opacities (15.7%), and graft failure (gf, 7.5%), with an increasing trend for bk, gf, and kcn. a majority of scleral tissues (83.7%) were utilized for orbital implant protection. conclusion: an increasing trend in the number of procured eyes was observed over the past 27 years in iran. the most leading indications for corneal transplantation were kcn and bk. while pkp was the most common keratoplasty technique, dsaek showed an increasing trend over the last 12 years. keywords: central eye bank of iran; corneal transplants per capita; descemet stripping automated endothelial keratoplasty; dsaek; penetrating keratoplasty j ophthalmic vis res 2020; 15 (2): 149–159 correspondence to: mozhgan rezaei kanavi, md. ocular tissue engineering research center, shahid beheshti university of medical sciences, tehran, iran. no 23, paidarfard st., boostan 9 st., pasdaran ave., tehran 16666, iran. e-mail: rezaeikanavi@sbmu.ac.ir received: 12-01-2019 accepted: 19-06-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i2.6731 introduction corneal blindness is the third leading cause of avoidable visual impairment worldwide after this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: javadi ma, kanavi mr, safi s. a 27-year report from the central eye bank of iran: a complete translation from farsi. j ophthalmic vis res 2020;15:149–159. © 2020 journal of ophthalmic and vision research | published by knowledge e 149 گزارش عملکرد سھ دھھ اي بانک چشم جمھوري اسالمي ایران http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i2.6731&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr central eye bank report; javadi et al cataract and glaucoma.[1] corneal transplantation via the restoration of visual function improves both the health status and the quality of life of patients undergoing keratoplasty.[2] leading indications for keratoplasty and implemented surgical techniques vary from one country to another depending on their geographic regions, socioeconomic conditions, and adaptation to recent surgical technological advancements.[3–11] for instance, in developed countries, bullous keratopathy (bk) and fuchs’ endothelial dystrophy (fed) are the leading indications for keratoplasty, and with the adaptation of endothelial keratoplasty (ek) techniques in these countries, descemet stripping automated endothelial keratoplasty (dsaek) and descemet membrane endothelial keratoplasty (dmek) are the procedures of choice to selectively replace the diseased corneal endothelium.[4–8, 11] however, the leading indications for keratoplasty in developing countries vary from keratoconus (kcn) in iran and zimbabwe[3, 12, 13] to infectious keratitis and corneal scarring in china and india.[14, 15] moreover, penetrating keratoplasty (pkp) is still the most common technique for corneal transplantation in these countries.[3, 12–15] the central eye bank of iran (cebi), the main eye bank in the center of the national corneal transplantation network over the last 27 years in iran, has been processing and distributing the tissues for corneal and scleral transplantations in accordance with the international medical standards.[16] herein, we report a 27-year statistical data and present a comprehensive picture of eye banking activity at the cebi. methods after obtaining full approval from the ethics committee of the ophthalmic research center, affiliated with shahid beheshti university of medical sciences in tehran, iran, a retrospective study was conducted to review and analyze all the compiled eye bank data between 1991 and 2017 at the cebi. the data compiled included annual and total rates of procured eyes (1991–2017), ocular tissue utilizations (2006–2017), corneal transplants per capita (2006–2017), indications for keratoplasty (1994– 2017), and post-transplantation adverse reactions (2006–2017). detailed data regarding postoperative adverse reaction reported to the cebi were not available before 2006. all the statistical analyses were performed using the statistical package for the social sciences (spss) software version 22 (spss, inc., chicago, il, usa). linear regression models were utilized to investigate any changing trend in the variables of interest. p-value < 0.05 was considered statistically significant. results eye procurement during the 27-year period, a total of 115,743 whole eyes from 58,804 donors were procured. the annual rates of corneal procurement are illustrated in figure 1, showing an increasing rate over the specified period excluding the last three years in which the corneal procurement rate showed a moderate reduction. considering that detailed data for 1,574 eyes (from 787 donors) procured between 1991 and 1993 were not available, the analysis of the majority of the variables was not possible for this certain time period. between 1994 and 2017, a total of 114,169 eyes from 58,017 donors were procured. donors’ age ranged from 1 month to 85 years, and 79.4% were male. the majority of donors were in the age range of 21–40 (43.1%) and 41–60 (37.7%) years. ocular tissue distribution and utilization among the 114,169 eyes procured between 1994 and 2017, 95,314 (83.5%) eyes were distributed for transplantation purposes, and 95,057 corneas were transplanted. small numbers of the procured eyes that were ineligible for transplantation were distributed and utilized for research purposes (933, 0.8%). the rate of keratoplasties per year is shown in figure 2, illustrating an increasing rate over the specified period. the distributed corneas were either in the form of excised corneoscleral discs (84.6%) maintained in cold storage media such as optisol gstm and eusol ctm or as whole globes (17.4%) preserved in cold moist chambers. moreover, 7.2% of the whole eyes had been frozen in –70°, and their corresponding defrosted corneas were transplanted. out of the distributed globes/corneas, 257 (0.3%) cases were returned non-transplanted to the cebi due to preor intraoperative technical errors at the time of surgery. pkp and similar procedures such as tectonic surgery and anterior lamellar keratoplasty 150 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 central eye bank report; javadi et al figure 1. the annual rates of corneal procurement in iran. note the increasing rate of corneal procurement between 1991 and 2017. accounted for all transplantation techniques used before 2006 with no exact data on each procedure. between 2006 and 2017, 71,796 corneas were utilized for keratoplasty. the rate of each transplantation technique and its corresponding relative trend over the last 12 years are illustrated in figure 3. over this period, pkp was the most common technique of corneal transplantation (70%), followed by anterior lamellar keratoplasty (alk, 14.24%), dsaek (12.41%), and tectonic surgery (3%). a significant decreasing trend was observed in the rates of pkp (p = 0.048), alk (p = 0.024), and tectonic surgery (p = 0.01), whereas dsaek demonstrated an increasing trend (p < 0.001) over the last 12 years [figure 4]. a small number of corneas were utilized for keratolimbal allografts (klals, 0.21%), glaucoma shunt coverage (gsc, 0.10%), and dmek procedure (0.04%) with an increasing trend since the introduction of the corresponding procedures (p < 0.001 for klal, p = 0.025 for gsc, and p = 0.023 for dmek) [figure 4]. almost all the klals performed during the study period utilized donor limbal tissues for recipients with primary or secondary limbal stem cell deficiency (lscd) of variable etiologies, among which chemical burn injuries and mustard gas keratopathies predominated. there were no specified data regarding the utilization of scleral tissues before 2006. from 2006 to 2017, out of the 83,149 procured donated eyes, 2,212 (2.7%) scleral tissues preserved in absolute alcohol were utilized to provide an additional protection in the orbital implants following enucleation (83.7%) and for glaucoma shunt patching (16.3%). corneal transplants per capita the calculated transplantation rate per million inhabitants in iran is shown in figure 5. the annual numbers of corneal transplants per capita over the last 24 years ranged from 16.10−6 to 95.10−6 (mean, 55.3.10−6 ± 27.10−6). this increasing rate of corneal transplants per capita paralleled the increase in the iranian population over the specified period. indications for corneal transplantation figures 6 and 7 illustrate the indications for keratoplasty and their corresponding trends between 1994 and 2017, respectively. the donors were predominantly male (61.2%) and aged from 6 months to 96 years. the majority of donors were between 21 and 40 years (38.2%), followed by those between 61 and 80 years (24.1%) and between 41 and 60 years (20.3%). kcn was the main leading indication for corneal transplantation (39.70%) followed journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 151 central eye bank report; javadi et al figure 2. the annual rate of keratoplasties in iran. note the increasing rate of corneal transplantation between 1994 and 2016. figure 3. the mean rate of transplantation procedures and their corresponding relative trends. (a) penetrating keratoplasty was the most common keratoplasty procedure (70%) over the last 12 years, followed by anterior lamellar keratoplasty (14.24%), descemet stripping automated endothelial keratoplasty (12.41%), tectonic (3%), keratolimbal allografts (0.21%), glaucoma shunt coverage (0.10%), and descemet membrane endothelial keratoplasty (0.04%). (b) the relative trends of corneal transplantation techniques between 2006 and 2017 were illustrated.alk, anterior lamellar keratoplasty; dmek, descemet membrane endothelial keratoplasty; dsaek, descemet stripping automated endothelial keratoplasty; klal, keratolimbal allografts; gsc, glaucoma shunt coverage; pkp, penetrating keratoplasty. by bk (18.5%), corneal scar and opacities (cso, 15.7%), graft failure (gf, 7.5%), corneal dystrophies (cd, 5.20%), and active keratitis (ak, 5.20%). the remaining indications (8.2%) which were considered “others” included chemical burn injuries, lscd, primary glaucoma tube shunt coverage, exposed glaucoma tube shunts, leaking filtering bleb, and cases with no specific diagnosis. a significant increasing trend for bk (p < 0.001), gf (p < 0.001), and kcn (p = 0.046) was observed; however, a decreasing trend for cso (p < 0.001) and cds (p = 0.002) over the last 24 years was observed. ak revealed no significant change in the trend during the specified period (p = 0.968). the four most leading cds were macular corneal dystrophy (mcd, 2.79%), fed (1.28%), congenital 152 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 central eye bank report; javadi et al figure 4. trends of keratoplasty techniques from 2006 to 2017 in iran. a significant decreasing trend for the rates of penetrating keratoplasty (p = 0.048), anterior lamellar keratoplasty (p = 0.024), and tectonic surgery (p = 0.01) is observed. a significant increasing trend of change for the rates of descemet stripping automated endothelial keratoplasty (p < 0.001), keratolimbal allografts (p < 0.001), glaucoma shunt coverage (p = 0.025), and descemet membrane endothelial keratoplasty (p = 0.023) since their introduction is observed. the regression r2 measures the goodness of fit of the regression line. dmek, descemet membrane endothelial keratoplasty; dsaek, descemet stripping automated endothelial keratoplasty; klal, keratolimbal allografts; gsc, glaucoma shunt coverage; pkp, penetrating keratoplasty. hereditary endothelial dystrophy (ched, 0.44%), and granular corneal dystrophy (0.41%). out of the 8,950 patients undergoing endothelial keratoplasty (8923, dsaek; 27, dmek), 78.7% had bk after cataract surgery, and 21.3% had either fed or ched. all the dmek surgeries utilized pre-stripped dmek tissues that were prepared at the cebi. ocular tissues used for glaucoma shunt patching between 2006 and 2017, sclera preserved in absolute alcohol was the most frequently used tissue for glaucoma shunt patching; however, in the last two years, frozen corneal tissues (in –70°c) that had unsuitable endothelial quality for keratoplasty were limitedly used as alternatives to scleral tissues for patching glaucoma shunts. adverse reactions based on the eye bank postoperative reports over the past 12 years, out of the 71,796 transplants performed in iran, adverse reactions were reported in 63 cases (0.088%). furthermore, 84.2% of all transplanted corneas were used for pkp/alk, and 12.5% were used for ek. the adverse reactions were reported in 26 (0.04%) and 37 (0.41%) cases after pkp/alk and ek, respectively. the most common adverse reactions after ek were related to the surgery (n = 22, 0.24%) followed by primary gf (n = 15, 0.17%). the most frequently reported adverse reactions after pkp/alk were primary gf (n = 13; 0.022%) followed by infectious keratitis (n = 7, 0.012%) and endophthalmitis (n = 6, 0.01%). the microbiologic pathogens in cases with transmission of infection were fungi (57%) and gram-negative organisms (43%). microbiologic pathogens were isolated in 83.3% of endophthalmitis cases, among which gram-positive organisms (60%) were the most common retrieved microorganisms. discussion increased number of corneal transplants in iran performed from 1991 to 2017 reflects an expanding journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 153 central eye bank report; javadi et al figure 5. the annual rates of corneal transplants per capita in iran. note an increasing rate of corneal transplants per capita from 1994 to 2017, ranging from 16.10−6 in 1995 to 95.10−6 in 2013. figure 6. mean rates (%) of indications for keratoplasty procedures utilizing corneas provided by the central eye bank of iran. keratoconus has been the most common indication for keratoplasty (39.70%) over the last 24 years, followed by bullous keratopathy (18.5%), corneal scar and opacities (15.7%), graft failure (7.5%), corneal dystrophies (5.20%), active keratitis (5.20%), and others (8.2%). ak, active keratitis; bk, bullous keratopathy; cd, corneal dystrophies; cso, corneal scar and opacities; gf, graft failure; kcn, keratoconus. activity of the cebi and associated cornea surgeons. the annual rate of corneal transplants per capita varied considerably over the last three decades in iran. the 27-year statistics of the cebi with a well-organized eye banking infrastructure shows a mean annual rate of 55.3.10−6 corneal transplants per capita, which is comparable with the annual rates of keratoplasty per capita in developed countries such as france (59.2.10−6), germany (54.0.10−6), and the uk (61.3.10−6).[18] this probably reflects the cebi’s ability to immediately supply corneal tissues according to the nation’s demands. moreover, it is worthy to know that iran is one of the self-sufficient countries among the 148 countries, with satisfactory access to donated corneas for transplant, without the need to import corneal tissues.[18] 154 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 central eye bank report; javadi et al figure 7. trends of the leading indications for keratoplasty in iran over the last 24 years. the trend of change for the rates of bullous keratopathy (p < 0.001), graft failure (p < 0.001), and keratoconus (p = 0.046) shows a significant increase. a significant decreasing trend is observed for the rates of corneal scar and opacities (p < 0.001) and corneal dystrophies (p = 0.002). no significant change of trend is noted for active keratitis (p = 0.968). the regression r2 measures the goodness of fit of the regression line. ak, active keratitis; bk, bullous keratopathy; cd, corneal dystrophies; cso, corneal scar and opacities; gf, graft failure; kcn, keratoconus. although pkp is the most common keratoplasty technique in our series, it showed a decreasing trend over the last decade. this is probably attributed to the increasing rate of dsaek performed for bk cases that showed a dramatic increase during the specified period. these results are consistent with those reported by the eye bank association of america (ebaa) in 2016[16] in which ek remained the top leading keratoplasty technique in the usa. similarly, the new zealand national eye bank reported decreasing trend of pkp and increasing trend of dsaek almost at the same time period.[19] although kcn, bk, cso, gf, cds, and ak are the main six indications for corneal graft in our series, the map of some indications has changed over the past three decades. consistent with our prior published report,[3, 12] indications for keratoplasty in iran are characterized by a larger proportion of kcn, but a lower frequency of ak and cds. moreover, bk, gf, and kcn showed a significantly increasing trend over the last 24 years. increasing trend of bk could be explained by the widespread application of phacoemulsification for cataract surgery in iran,[20] and the facts that the surgery was performed even in patients with low corneal endothelial cell counts [21–23] and by less experienced surgeons.[24] gf revealed an increasing trend over the past three decades, which was consistent with the increased number of patients undergoing corneal transplantation and concurrent with the widespread expansion in the rate of keratoplasties in iran. the increasing rate of gf can also be attributed to the increasing rate of ek techniques and the decreasing interest in performing alk techniques in iran. gf, defined as a loss of graft clarity or refractive quality, is mainly observed as a result of allogeneic immune rejections. however, nonimmune factors such as glaucoma, endothelial cell failure, aging, and viral and nonviral infections may cause gf.[25–27] although gf was reported as the most leading indication for keratoplasty in the uk three decades ago,[28] it did not remain on the top and declined to the third place in the later decade, which could be due to the significant increase in the number of alk operations performed.[29] journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 155 central eye bank report; javadi et al kcn in our series ranked the first place among the leading indications for keratoplasty in iran and showed an increasing trend up to 2012. however, as explained in our prior report,[3] a downward trend was observed after 2012, which could be due to the increasing rate of implementation of collagen corneal cross-linking and intracorneal rings in the moderate form of kcn. moreover, the overshadowing effect of the increasing trends of bk and gf over the last decade is considered another probable explanation. cso, in the current study, demonstrated a significant decreasing trend over the last 24 years. based on our prior reports,[3, 12] cso was replaced by bk and declined from the second to the third place, which can be partially overshadowed by the increasing trend of bk. however, in some developing countries, cso caused by infectious keratitis and trauma was considered as the most common indication for keratoplasty.[14, 30, 31] factors reducing the incidence of infectious keratitis, such as public awareness about the importance of early diagnosis and proper management of infectious keratitis and preventive measures,[30] may play significant roles in the decreasing trend of cso in iran. different from some western countries where fed is the most common indication for keratoplasty,[16, 32] cds along with ak ranked the fifth among the leading indications for keratoplasty in iran over the last three decades. moreover, consistent with prior studies,[3, 12] fed in our series was the second common indication for keratoplasty after mcd among the different types of cds. high prevalence of aging population in western countries and the increasing awareness regarding the benefits of the triple procedure employing ek techniques in cataractous cases with advanced fed may explain this difference.[8, 33] different from our prior published reports in which no significant change of trend in the number of procured eyes was shown, our present series showed a significant decreasing trend over the last three decades, which can be explained by the difference in the surveyed time periods. however, there is a possibility that the decreasing trend of cds might have been overshadowed by the increasing trend of bk and gf. regarding ak, our series did not show significant change of trend over the last three decades; this result is similar to that of our previous reports.[3, 12] different from iran and several developed countries where ak is not a common indication for corneal transplantation,[7, 16] ak is the most common indication for keratoplasty in the developing countries in asia. this difference may be explained by the presence of large agricultural communities with poor farm and work safety standards and limited medical services, leading to higher prevalence of ak in these developing countries.[9, 34, 35] despite it was anticipated that alk would replace pkp in corneal pathologies with normal endothelium,[6] our series revealed a significant decreasing trend for alk over the past 12 years; hence, alk decreased to its lowest rate in 2017. this can be explained by the decreasing rate of transplantation for kcn after 2012. another possible reason is that some surgeons may not have reported alk in their postoperative reports. to prevent some postoperative complications due to the transplantation of low-quality grafts (e.g., persistent epithelial defects, graft edema, and suture-related complications), some surgeons prefer to report they perform pkp when actually deep anterior lamellar keratoplasty is performed to receive a donor tissue with good quality. this issue needs a comprehensive strategic planning to address both the eye bank and the surgeons’ concerns. our series demonstrated a significant decreasing trend for tectonic graft for the past 12 years. tectonic graft, considered as a challenging and emergent corneal transplantation, is performed in corneal pathologies that threaten the globe integrity such as infectious or noninfectious keratitis. this reinforces the critical role cebi has in supplying donor corneas for tectonic purposes to retain corneal integrity and save the eye in such patients. the rate of tectonic graft in our series (3%) was significantly lower than the rate (11.4%) reported in a six-year analysis of the uk transplant registry.[36] this difference can be explained by the different time intervals in which the surveys were performed; the uk transplant registry analysis has been performed between 1999 and 2005[36] with no updated analysis on the data after 2005, whereas our survey analyzed the data on transplantation techniques after 2006. there has been an increasing trend for new transplantation techniques such as klal, gsc using corneal tissue, and dmek since their introduction in iran. therefore, cebi has been providing donated corneal tissues for these techniques of 156 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 central eye bank report; javadi et al transplantation since 2009. in our series, almost all the klals were performed in patients with lscd predominantly caused by chemical burns. although the management of chemical burninduced ocular surface disorders is significantly challenging, with the recent development in ocular surface reconstruction and the current use of translational medicine such as cultured autologous limbal epithelial transplantation for this purpose in iran,[39, 40] a decreasing rate of klal is anticipated over time. gsc using donor corneal tissue has been implemented for the last two years in iran, aiming to cover glaucoma shunt tubes primarily or manage the exposed tubes and leaking filtering blebs. it was well demonstrated that early surgical management of glaucoma tube-related complications reduces the risk of bleb-associated endophthalmitis.[41] the use of donor corneal tissues for gcs is not only a therapeutic option but also provides excellent cosmetic results.[42] although the number of gsc surgeries was small, it revealed a significant increasing trend over the last two years. dmek using cebiprepared pre-stripped tissues was implemented in a few tertiary eye centers in iran in 2016 and, despite having a small proportion, demonstrated an increasing trend since then. different from the usa in which dmek is more popular than dsaek,[18] dmek has still failed to gain popularity in iran. this can be explained by the easier handling of the dsaek lenticules as compared to delicate dmek tissues. moreover, the long learning curve for dmek might have limited the use of this surgical technique by cornea surgeons in iran. however, preparation of pre-stripped ready-to-use dmek tissues with healthy corneal endothelium and use of user-friendly dm delivery systems to simplify the dmek technique may encourage some cornea surgeons to substitute dsaek with dmek. over a 12-year period, the scleral tissues of 2.7% of the donated whole eyes were processed at the cebi and distributed for cosmetic or emergent eye conditions, predominantly for wrapping the orbital implants after enucleation. with the emergence of frozen corneas for covering the glaucoma tube shunts since 2016, some glaucoma surgeons use these tissues rather than scleral tissue to achieve optimum cosmetic results.[42] in our series, the overall rate of adverse reactions reported to the cebi (0.088%) was significantly low and even less than the reported rate in the usa (1.2%).[44] considering that we analyzed only the officially reported adverse reactions encountered during early postoperative period, one of our main drawbacks in this part is probably the insufficient evidence on the adverse reactions that were not reported to the cebi and the lack of a transplant registry report. in our analysis, the reported adverse reactions after ek, similar to the us report,[44] was more frequent than those after pkp/alk surgeries. this can be explained by long learning curves required for dsaek and dmek. similar to the report by the ebaa between 2007 and 2014,[45] primary gf predominated in our series over the last 12 years. different from the ebaa report in which candida species was the most frequent isolated pathogen in post-corneal graft endophthalmitis,[45] gram-positive microorganisms predominated in our series. regarding infectious keratitis, no significant difference was found between the rate of fungal keratitis and keratitis caused by gram-negative bacteria in our survey; this result is different from that of the ebaa report.[45] the present survey demonstrated a partial reduction in the rate of corneal procurement from the cebi after 2015, which was concurrent with launching a couple of minor eye banks in tehran and shiraz.[3] nevertheless, the activity of these minor eye banks in the national corneal transplantation network was not remarkable, and they had no roles in preparation of pre-cut dsaek lenticules and pre-stripped dmek tissues. in conclusion, the cebi has shown an expanding activity over the last 27 years, in a way that iran has become one of the self-sufficient countries in the world that does not need to import corneal tissues. the low rate of reported adverse reactions indicated a relatively high safety of the graft system from donor harvesting and preparation in the cebi to graft transplantation. with the emergence of ek techniques over the last decade in iran, there has been an increasing trend in the rates of these surgical procedures and a decreasing trend of pkp. despite this observation, pkp remained the most frequent transplantation procedure over the last 12 years. although kcn was the most leading indication for keratoplasty in iran, bk and gf showed an increasing trend over the last 24 years. eye bank preparation of pre-cut thin lenticules of high endothelial quality for dsaek was encouraging for the cornea surgeons to substitute pkp with dsaek journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 157 central eye bank report; javadi et al in cases with corneal endothelial diseases. it is anticipated that providing pre-stripped and preloaded dm tissues with healthy endothelial cells for dmek may motivate the surgeons to gradually substitute dmek for dsaek. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. world health organization. prevention of blindness and visual impairment: causes of blindness and visual impairment. available from: http://www.who.int/blindness/ causes/en/. 2. fasolo a, capuzzo c, fornea m, frigo ac, monterosso c, zampini a, et al. health status and patient satisfaction after corneal graft: results from the corneal transplant epidemiological study. j ophthalmol 2012;2012:230641. 3. rezaei kanavi m, javadi ma, motevasseli t, chamani t, rezaei kanavi m, kheiri b, et al. trends in indications and techniques of corneal transplantation in iran from 2006 to 2013; an 8-year review. j ophthalmic vis res 2016;11:146– 152. 4. cunningham wj, brookes nh, twohill hc, moffatt sl, pendergrast dg, stewart jm, et al. trends in the distribution of donor corneal tissue and indications for corneal transplantation: the new zealand national eye bank study 2000–2009. clin experiment ophthalmol 2012;40:141– 147. 5. dobbins kr, price fw jr, whitson we. trends in the indications for penetrating keratoplasty in the midwestern united states. cornea 2000;19:813–816. 6. ple−plakon pa, shtein rm. trends in corneal transplantation: indications and techniques. curr opin ophthalmol 2014;25:300–305. 7. frigo ac, fasolo a, capuzzo c, fornea m, bellucci r, busin m, et al. corneal transplantation activity over 7 years: changing trends for indications, patient demographics and surgical techniques from the corneal transplant epidemiological study (cortes). transplant proc 2015;47:528– 535. 8. tan jc, holland sp, dubord pj, moloney g, mccarthy m, yeung sn. evolving indications for and trends in keratoplasty in british columbia, canada, from 2002 to 2011: a 10−year review. cornea 2014;33:252–256. 9. wang jy, xie lx, song xs, zhao j. trends in the indications for penetrating keratoplasty in shandong, 2005−2010. int j ophthalmol 2011;4:492–497. 10. keenan td, jones mn, rushton s, carley fm, national health service blood and transplant ocular tissue advisory group and contributing ophthalmologists (ocular tissue advisory group audit study 8). trends in the indications for corneal graft surgery in the united kingdom: 1999 through 2009. arch ophthalmol 2012;130:621–628. 11. le r, yucel n, khattak s, yucel yh, prud’homme gj, gupta n. current indications and surgical approaches to corneal transplants at the university of toronto: a clinicalpathological study. can j ophthalmol 2017;52:74–79. 12. kanavi mr, javadi ma, sanagoo m. indications for penetrating keratoplasty in iran. cornea 2007;26:561–563. 13. mkanganwi n, nondo si, guramatunhu s. indications for corneal grafting in zimbabwe. cent afr j med 2000;46:300–302. 14. sony p, sharma n, sen s, vajpayee rb. indications of penetrating keratoplasty in northern india. cornea 2005;24:989–991. 15. xie l, song z, zhao j, shi w, wang f. indications for penetrating keratoplasty in north china. cornea 2007;26:1070– 1073. 16. van meter ws. 2016 eye banking statistical report. available from: http://restoresight.org/wp-content/ uploads/2017/04/2016_statistical_report-final-040717. pdf. 17. javadi ma, fayaz a, mirdehghan sa, ainollahi b. transmission of rabies by corneal graft. cornea 1996;15:431–433. 18. gain p, jullienne r, he z, aldossary m, acquart s, cognasse f, thuret g. global survey of corneal transplantation and eye banking. jama ophthalmol 2016;134:167–173. 19. kim bz, meyer jj, brookes nh, moffatt sl, twohill hc, pendergrast dg, et al. new zealand trends in corneal transplantation over the 25 years 1991–2015. br j ophthalmol 2017;101:834–838. 20. hashemi h, alipour f, mehravaran s, rezvan f, alaeddini f, fotouhi a. six year trend in cataract surgical techniques in iran. middle east afr j ophthalmol 2011;18:150–153. 21. thakur sk, dan a, singh m, banerjee a, ghosh a, bhaduri g. endothelial cell loss after small incision cataract surgery. nepal j ophthalmol 2011;3:177–180. 22. bourne rr, minassian dc, dart jk, rosen p, kaushal s, wingate n. effect of cataract surgery on the corneal endothelium: modern phacoemulsification compared with extracapsular cataract surgery. ophthalmology 2004;111:679–685. 23. bamdad s, bolkheir a, sedaghat mr, motamed m. changes in corneal thickness and corneal endothelial cell density after phacoemulsification cataract surgery: a double-blind randomized trial. electron physician 2018;10:6616–6623. 24. o’brien pd, fitzpatrick p, kilmartin dj, beatty s. risk factors for endothelial cell loss after phacoemulsification surgery by a junior resident. j cataract refract surg 2004;30:839–843. 25. qazi y, hamrah p. corneal allograft rejection: immunopathogenesis to therapeutics. j clin cell immunol 2013;2013. 26. williams ka, esterman aj, bartlett c, holland h, hornsby nb, coster dj. how effective is penetrating corneal transplantation? factors influencing long-term outcome in multivariate analysis. transplantation 2006;81:896–901. 27. williams ka, lowe m, bartlett c, kelly tl, coster dj. risk factors for human corneal graft failure within the australian corneal graft registry. transplantation 2008;86:1720– 1724. 158 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 http://www.who.int/blindness/causes/en/ http://www.who.int/blindness/causes/en/ http://restoresight.org/wp-content/uploads/2017/04/2016_statistical_report-final-040717.pdf http://restoresight.org/wp-content/uploads/2017/04/2016_statistical_report-final-040717.pdf http://restoresight.org/wp-content/uploads/2017/04/2016_statistical_report-final-040717.pdf central eye bank report; javadi et al 28. al-yousuf n, mavrikakis i, mavrikakis e, daya sm. penetrating keratoplasty: indications over a 10 year period. br j ophthalmol 2004;88:998–1001. 29. keenan td, jones mn, rushton s, carley fm, national health service blood and transplant ocular tissue advisory group and contributing ophthalmologists (ocular tissue advisory group audit study 8). trends in the indications for corneal graft surgery in the united kingdom: 1999 through 2009. arch ophthalmol 2012;130:621–628. 30. dasar l, pujar c, gill ks, patil m, salagar m. indications of penetrating keratoplasty in southern india. j clin diagn res 2013;7:2505–2507. 31. zhang c, xu j. indications for penetrating keratoplasty in east china, 1994–2003. graefes arch clin exp ophthalmol 2005;243:1005–1009. 32. röck t, bartz-schmidt ku, röck d. trends in corneal transplantation at the university eye hospital in tübingen, germany over the last 12 years: 2004–2015. plos one 2018;13:e0198793. 33. terry ma, shamie n, chen es, phillips pm, shah ak, hoar kl, et al. endothelial keratoplasty for fuchs’ dystrophy with cataract: complications and clinical results with the new triple procedure. ophthalmology 2009;116:631–639. 34. bajracharya l, gurung r, demarchis eh, oliva m, ruit s, tabin g. indications for keratoplasty in nepal: 2005–2010. nepal j ophthalmol 2013;5:207–214. 35. dong pn, han tn, aldave aj, chau ht. indications for and techniques of keratoplasty at vietnam national institute of ophthalmology. int j ophthalmol 2016;9:379–383. 36. hossain p, tourkmani ak, kazakos d, jones m, anderson d, nhs blood and transplant ocular tissue advisory group and contributing ophthalmologists. emergency corneal grafting in the uk: a 6-year analysis of the uk transplant registry. br j ophthalmol 2018;102:26–30. 37. shanbhag ss, saeed hn, paschalis ei, chodosh j. keratolimbal allograft for limbal stem cell deficiency after severe corneal chemical injury: a systematic review. br j ophthalmol 2018;102:1114–1121. 38. cheung ay, holland ej. keratolimbal allograft. curr opin ophthalmol 2017;28:377–381. 39. baradaran-rafii a, eslani m, djalillian ar. complications of keratolimbal allograft surgery. cornea 2013;32:561–566. 40. baradaran-rafii, ebrahimi m, kanavi mr, taghi-abadi e, aghdami n, eslani m, et al. midterm outcomes of autologous cultivated limbal stem cell transplantation with or without penetrating keratoplasty. cornea 2010;29:502– 509. 41. al-torbak aa, al-shahwan s, al-jadaan i, al-hommadi a, edward dp. endophthalmitis associated with the ahmed glaucoma valve implant. br j ophthalmol 2005;89:454– 458. 42. wigton e, c swanner j, joiner w, feldman a, mcgwin g jr, huisingh c, et al. outcomes of shunt tube coverage with glycerol preserved cornea versus pericardium. j glaucoma 2014;23:258–261. 43. boynton ge, woodward ma. eye-bank preparation of endothelial tissue. curr opin ophthalmol 2014;25:319– 324. 44. ple-plakon pa, shtein rm, musch dc, blachley t, saponara f, woodward ma. tissue characteristics and reported adverse events after corneal transplantation. cornea 2013;32:1339–1343. 45. edelstein sl, dematteo j, stoeger cg, macsai ms, wang ch. report of the eye bank association of america medical review subcommittee on adverse reactions reported from 2007 to 2014. cornea 2016;35:917–926. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 159 original article neutrophil-to-lymphocyte ratio and platelet-to-lymphocyte ratio in patients with retinal artery occlusion mahmut atum, md; gürsoy alagöz, md department of ophthalmology, sakarya university education and research hospital, adnan menderes caddesi saglik sokak, sakarya, turkey orcid: mahmut atum: https://orcid.org/0000-0001-8230-8137 abstract purpose: this study aimed to compare the neutrophil-to-lymphocyte (nlr) and plateletto-lymphocyte (plr) ratios in patients with retinal artery occlusion (rao) with those from a healthy control population and to identify the relationship between them. methods: forty-six patients with rao and fifty-one healthy control subjects were included in this retrospective case-control study. rao was diagnosed following an ophthalmic examination and fluorescein angiography (fa). blood neutrophil, lymphocyte, and platelet counts were recorded for each of the 97 subjects, from which nlr and plr values were calculated. results: there were 46 patients (28 male [m], 18 female [f]) in the rao group and 51 patients (27 m, 24 f) in the control group. no significant differences were found between patients with rao and the control subjects in terms of gender and age (p > 0.05). patients with rao had significantly increased nlr values (2.85 ± 1.70) than the control subjects (1.63 ± 0.59, p < 0.001). the mean plr in patients with rao was 123.69 ± 64.98, while that in control subjects was 103.08 ± 36.95; there was no significant difference between the two groups (p = 0.055). a logistic regression analysis revealed that nlrs were 3.8 times higher in patients with rao than in control subjects (odds ratio = 3.880; 95% confidence interval = 1.94 to 7.74; p < 0.001). conclusion: nlrs were significantly increased in patients with rao compared to the control subjects. keywords: hemogram; neutrophil-to-lymphocyte ratio; platelet-to-lymphocyte ratio; retinal artery occlusion; retinal vessels j ophthalmic vis res 2020; 15 (2): 195–200 correspondence to: mahmut atum, md. department of ophthalmology, sakarya university education and research hospital, adnan menderes caddesi saglik sokak, sakarya 54100, turkey. e-mail: mahmutatum@gmail.com received: 18-03-2019 accepted: 21-10-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i2.6737 introduction retinal artery occlusion (rao), generally seen in older adults,[1] is a serious condition requiring this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: atum m, alagöz g. neutrophil-to-lymphocyte ratio and platelet-to-lymphocyte ratio in patients with retinal artery occlusion. j ophthalmic vis res 2020;15:195–200. © 2020 journal of ophthalmic and vision research | published by knowledge e 195 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i2.6737&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr blood cell ratios in patients with rao; atum and alagöz emergency intervention. rao is characterized by sudden unilateral vision loss and/or visual field defect.[2] there are three types of rao: central retinal artery occlusion (crao), branch retinal artery occlusion (brao), and cilioretinal artery occlusion (clrao).[3] the distribution of the rao sub-types is as follows: crao, 57%; brao, 38%; and clrao 5%.[3] raos are usually caused by embolisms, which in turn are often caused by atherosclerotic plaques associated with carotid artery disease.[4] arruga et al showed that emboli causing rao are composed of cholesterol material (74%), calcific material (10.5%), and/or fibrin material (15.5%).[5] atherosclerosis is a chronic inflammatory condition,[6] and thrombosis and inflammation have been shown to be interconnected in a complex manner.[7] several previous studies have shown that a patient’s neutrophil-to-lymphocyte ratio (nlr) and platelet-to-lymphocyte ratio (plr) are indicative of systemic inflammation.[8–11] mean platelet volume (mpv) is also indicative of the status of platelets and is also associated with inflammation.[12] in their literature review, şahin et al found that only one study analyzed the relationship between mpv and rao showing that mpv values were significantly higher in patients with rao.[13] we could not find any publication that examined the association between nlr, plr, and rao. in this study, we compared the nlr and plr levels in patients with rao with those of healthy control subjects and examined the relationship between these values. methods this retrospective study was performed in the sakarya training and research hospital eye disease polyclinic. the records of patients diagnosed with crao, brao, and clrao between january 2016 and september 2018 were analyzed. the study included 46 patients with rao and 51 healthy control subjects. the rao patient group comprised of individuals who experienced sudden, painless loss of vision and were subsequently diagnosed with rao in an ophthalmology outpatient clinic. the control group consisted of subjects who presented with impaired vision and underwent cataract surgery. a routine blood analysis was performed before any cataract surgery in our clinic. age and sex were similar in the two groups, as was the number of patients with systemic hypertension. all subjects underwent a complete ophthalmic evaluation in both eyes, including a test of visual acuity using a snellen chart, inspection of the anterior and posterior segments with a slit-lamp biomicroscope, and applanation tonometry. fluorescein angiography (fa) was performed in all patients, and the diagnosis of rao was defined accordingly. the exclusion criteria for this study were as follows: cardiovascular diseases (such as congestive heart failure and heart valve disease treated with an anticoagulant), diabetes, history of stroke, history of smoking, blood disorders, anemia, renal failure, hepatic disorders, malignancies, and vasculitis. patients with a history of eye surgery, glaucoma, or eye trauma were also excluded. blood samples were taken from each rao patient within 2 h of diagnosis. the hemogram parameters of each subject were measured using a cell-dyn 3700 automated hematology analyzer (abbott diagnostics, abbott park, il, usa). the hemogram (neutrophil, lymphocyte, and platelet) results were entered in an excel (microsoft corp., redmond, wa, usa) spreadsheet to calculate their nlrs and plrs. this study was conducted according to the principles of the declaration of helsinki and the approval was obtained from the institutional ethics committee. ethical approval was obtained from the local ethics committee. statistical analysis data were analyzed using spss software version 18.0 (spss inc., chicago, il, usa). the results of numerical data analysis were given as mean and standard deviation. the independent groups were compared using a parametric student’s t-test. the cut-off point for nlr and plr between patients with rao and control subjects was determined using a receiver operating characteristic (roc) curve analysis. sensitivity and specificity were determined according to cut-off values. a univariate logistic regression analysis was used to determine the association between rao and nlr, plr, age, and sex data. the results were evaluated at a 95% confidence interval (ci) and p < 0.05 was considered significant. 196 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 blood cell ratios in patients with rao; atum and alagöz results this study consisted of 97 patients: 46 patients with rao and 51 healthy control subjects. the rao group consisted of 28 men and 18 women and the control group included 27 men and 24 women. the mean age of patients with rao was 63.02 ± 14.80 years and that of the control subjects was 61.33 ± 7.91 years. no significant difference was found between the rao and control subjects in terms of the gender (p = 0.437) or age (p = 0.479) (all data are summarized in table 1). the mean white blood cell count was 7.90 ± 2.16 109/l in the rao group and 7.48 ± 2.34 109/l in the control group; no significant difference was found between the two groups (p = 0.366). the mean neutrophil count of the rao group was 5.05 ± 1.88 109/l, which was significantly higher than that of the control group (4.00 ± 1.51 109/l) (p = 0.003). the mean lymphocyte count was 2.05 ± 0.75 109/l for the rao group and 2.64 ± 1.12 109/l for the control group, indicating a significantly lower value in patients with rao (p = 0.003). the mean platelet count was 222.96 ± 67.72 109/l in the rao group and 242.60 ± 52.91 109/l in the control group, showing no significant difference between the two groups (p = 0.113). the mean nlr of patients with rao was 2.85 ± 1.70, while that of the control subjects was 1.63 ± 0.59, revealing that nlr levels were significantly higher in the rao group (p < 0.001). the mean plr was 123.69 ± 64.98 in patients with rao and 103.08 ± 36.95 in control subjects, indicating that there was a borderline level of statistical significance between the two groups (p = 0.055) [table 1]. finally, the mean mpv values were 8.27 ± 1.04 fl for the rao group and 8.49 ± 1.88 fl for the control group; no significant difference was found between the two groups (p = 0.652). a roc curve is a graphical plot that illustrates the diagnostic ability. roc analysis was performed for the nlr values, and the area under the curve, cut-off value, sensitivity, and specificity were 0.780, 1.82, 72%, and 69%, respectively (95% ci: 0.690– 0.871). for the plr values, the area under the curve, cut-off value, sensitivity, and specificity were 0.582, 92.35, 67%, and 57%, respectively (95% ci: 0.468–0.696) [figure 1]. according to the logistic regression analysis we performed, nlr was in fact an indicator for rao (odds ratio (or) = 3.880; 95% ci = 1.94–7.74; p < 0.001). but plr was not an independent indicator of rao. (or = 1.036; 95% ci = 0.999-1.012; p = 0.126). discussion in this study, we found that nlr levels were significantly increased in patients with rao, demonstrating that it is in fact an independent indicator of rao. patients with high nlr levels are 3.8 times more likely to have rao than patients with low nlr levels. this study is the first to examine the association between nlr and rao. previous studies have shown that embolisms are the most common cause of rao, and that the main cause of embolisms is carotid artery disease caused by atherosclerosis.[4] atherosclerosis is associated with chronic inflammation,[6, 14] so it is possible that inflammatory biomarkers may play a significant role in predicting which patients may develop rao. nlr, which is calculated based on dividing a patient’s number of neutrophils by the lymphocyte count, is a simple and cheap indicator of systemic inflammation. systemic inflammation typically involves lymphopenia and neutrophilia.[15] in their retrospective study, gokhan et al reported that nlr was found to be an independent marker in cases of symptomatic carotid artery disease; it was also found to be higher in symptomatic than asymptomatic patients suffering from a stroke or a transient ischemic attack (p < 0.001).[16] in a different study, tokgoz et al showed that nlr is an important indicator of prognosis and mortality in stroke patients.[17] a meta-analysis showed that nlr may play a major role in the diagnosis and prognosis of peripheral vascular diseases.[18] in the current study, nlr was revealed to be significantly increased in patients with rao compared to control subjects, which may be further evidence that chronic inflammation may lead to the development of rao. logistic regression analysis indicated that nlr is an independent indicator of rao. dursun et al compared 40 patients with retinal vein occlusion with a control group and found that the nlr levels of patients with retinal vein occlusion were significantly higher than those in control patients.[19] the sensitivity and specificity of nlr reported by dursun et al were found to be 72% and 100%, respectively (cut-off value: 1.89), whereas in our study, these figures were 72% and 69%, respectively (cut-off value: 1.82).[19] journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 197 blood cell ratios in patients with rao; atum and alagöz table 1. demographic features and laboratory findings in the rao and control groups rao (n = 46) control (n = 51) p-value age (y) 63.02 ± 14.80 61.33 ± 7.91 0.479 sex (m/f) 28/18 27/24 0.437 wbc (109/l) 7.90 ± 2.16 7.48 ± 2.34 0.366 neutrophil (109/l) 5.05 ± 1.88 4.00 ± 1.51 0.003 lymphocyte (109/l) 2.05 ± 0.75 2.64 ± 1.12 0.003 platelet (109/l) 222.96 ± 67.72 242.60 ± 52.91 0.113 nlr 2.85 ± 1.70 1.63 ± 0.59 <0.001 plr 123.69 ± 64.98 103.08 ± 36.95 0.055 mpv (fl) 8.27 ± 1.04 8.49 ± 1.88 0.652 bold values are statistically significant measurements (independent samples t-test) f, female; m, male; mpv, mean platelet volume; nlr, neutrophil-to-lymphocyte ratio; plr, platelet-to-lymphocyte ratio; rao, retinal artery occlusion; wbc, white blood cell figure 1. roc curve analysis of nlr and plr in rao patients. nlr was determined to be more sensitive and had higher rate as a predictor of inflammation compared to plr. auc for nlr: 0.780, cut-off value: 1.82, sensitivity: 72%, specificity: 69%. (95% ci: 0.690–0.871). auc for plr: 0.582, cut-off value: 92.35, sensitivity: 67%, specificity: 57%. (95% ci: 0.468–0.696). auc, area under the roc curve; nlr: neutrophil-to-lymphocyte ratio; plr platelet-to-lymphocyte ratio; rao: retinal artery occlusion. plr, which is calculated via dividing a patient’s platelet count by the number of lymphocytes, is a cheap and easy test that reveals the condition of platelets and white blood cells. thrombocytes play a significant role in coronary artery disease and cardiovascular disorders.[20] research has also shown that platelets play a significant role in the development of atherosclerosis and embolisms.[21] azab et al identified a relationship between increased plr and long-term mortality in 198 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 blood cell ratios in patients with rao; atum and alagöz patients with myocardial infarction,[11] while ferroni et al reported a relationship between increased plr and the risk of venous thromboembolism.[22] in their review, balta et al demonstrated that a high plr level is associated with inflammation, atherosclerosis, and activated platelets.[23] our study showed that patients with rao had higher plrs than control subjects; however, logistic regression analysis showed that plr cannot be used as an indicator of rao. şahin et al reported that mpv values were significantly higher in patients with rao than in control subjects,[13] but we were unable to replicate this finding. we found no significant difference between the two groups in the current study. we believe that this discrepancy may be due to the difference in the number of patients in the respective studies. many cardiovascular disorders decrease the lymphocyte counts. bian et al reported that decreased lymphocyte levels can be used as a marker of acute coronary syndrome,[24] and several other studies have shown that a reduced percentage of lymphocytes in patients with acute heart failure is associated with morbidity and mortality.[25, 26] however, cooper et al reported that an increased neutrophil count could also be a marker of mortality in cases with left ventricular dysfunction.[27] similar to these studies, we found that blood neutrophil levels were significantly increased and lymphocyte counts were significantly decreased in patients with rao than in control subjects. this study had a few limitations. we examined a small number of patients using a retrospective design and did not assess body mass index and associated atherosclerosis. further studies including a larger number of patients are necessary to better investigate the role of serum nlr and plr in rao disease. in conclusion, we found that nlrs were significantly higher and lymphocyte counts were significantly lower in patients with rao than in control subjects. larger studies are needed to better understand the relationship between rao and nlr. references 1. pokhrel pk, loftus sa. ocular emergencies. am fam physician 2007;76:829–836. 2. kapoor kg, barkmeier aj, bakri sj. optical coherence tomography in retinal arterial occlusions: case series and review of the literature. semin ophthalmol 2015;30:74–79. 3. brown gc, magargal le, shields js, goldberg re, walsh pn. retinal arterial obstruction in children and young adults. ophthalmology 1981;88:18–25. 4. varma dd, cugati s, lee aw, chen cs. a review of central retinal artery occlusion: clinical presentation and management. eye 2013;27:688–697. 5. arruga j, sanders m. ophthalmologic findings in 70 patients with evidence of retinal embolism. ophthalmology 1982;89:1336–1347. 6. ross r. atherosclerosis: an inflammatory disease. n engl j med 1999;340:115–126. 7. wagner dd, burger pc. platelets in inflammation and thrombosis. arterioscler thromb vasc biol 2003;23:2131– 2137. 8. tamhane uu, aneja s, montgomery d, rogers ek, eagle ka, gurm hs. association between admission neutrophil to lymphocyte ratio and outcomes in patients with acute coronary syndrome. am j cardiol 2008;102:653–657. 9. akdag s, akyol a, asker m, duz r, gumrukcuoglu ha. platelet-to-lymphocyte ratio may predict the severity of calcific aortic stenosis. med sci monit 2015;21:3395–3400. 10. tsiara s, elisaf m, jagroop ia, mikhailidis dp. platelets as predictor of vascular risk, is there a practical index of platelet activity? clin appl thromb hemost 2003;9:177– 190. 11. azab b, shah n, akerman m, mcginn jr jt. value of platelet/lymphocyte ratio as a predictor of all-cause mortality after non-st elevation myocardial infarction. j thromb thrombolysis 2012;34:326–334. 12. ryu hj, lee mk, lee kh, seo mr, choi hj, baek hj. mean platelet volume is associated with behcet’s disease activity. ann rheum dis 2014;73:996–997. 13. şahin m, şahin a, yüksel h, türkcü fm, y𝚤ld𝚤r𝚤m a. mean platelet volume in patients with retinal artery occlusion. arq bras oftalmol 2016;79:12–14. 14. libby p, ridker pm, hansson gk, leducq transatlantic network on atherothrombosis. inflammation in atherosclerosis: from pathophysiology to practice. j am coll cardiol 2009;54:2129–2138. 15. zahorec r. ratio of neutrophil to lymphocyte counts rapid and simple parameter of systemic inflammation and stress in critically ill. bratisl lek listy 2001;102:5–14. 16. gokhan s, ozhasenekler a, mansur durgun h, akil e, ustündag m, orak m. neutrophil lymphocyte ratios in stroke subtypes and transient ischemic attack. eur rev med pharmacol sci 2013;17:653–657. 17. tokgoz s, kayrak m, akpinar z, seyithanoğlu a, güney f, yürüten b. neutrophil lymphocyte ratio as a predictor of stroke. j stroke cerebrovasc dis 2013;22:1169–1174. 18. bhat tm, afari me, garcia la. neutrophil lymphocyte ratio in peripheral vascular disease: a review. expert rev cardiovasc ther 2016;14:871–875. 19. dursun a, ozturk s, yucel h, ozec av, dursun fg, toker mi, et al. association of neutrophil/lymphocyte ratio and retinal vein occlusion. eur j ophthalmol 2015;25:343– 346. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 199 blood cell ratios in patients with rao; atum and alagöz 20. kurtul a, yarlioglues m, murat sn, ergun g, duran m, kasapkara ha, et al. usefulness of the platelet-tolymphocyte ratio in predicting angiographic reflow after primary percutaneous coronary intervention in patients with acute st segment elevation myocardial infarction. am j cardiol 2014;114:342–347. 21. kaplan zs, jackson sp. the role of platelets in atherothrombosis. hematology am soc hematol educ program 2011;2011:51–61. 22. ferroni p, riondino s, formica v, cereda v, tosetto l, la farina f, et al. venous thromboembolism risk prediction in ambulatory cancer patients: clinical significance of neutrophil/lymphocyte ratio and platelet/lymphocyte ratio. int j cancer 2015;136:1234–1240. 23. balta s, ozturk c. the platelet-lymphocyte ratio: a simple, inexpensive and rapid prognostic marker for cardiovascular events. platelets 2015;26:680–681. 24. bian c, wu y, shi y, xu g, wang j, xiang m, et al. predictive value of the relative lymphocyte count in coronary heart disease. heart vessels 2010;25:469–473. 25. nunez j, nunez e, minana g, sanchis j, bodí v, rumiz e, et al. effectiveness of the relative lymphocyte count to predict one-year mortality in patients with acute heart failure. am j cardiol 2011;107:1034–1039. 26. ali s, shahbaz au, nelson md, shirwany a, munir a, d’cruz ic, et al. reduced relative lymphocyte count in africanamericans with decompensated heart failure. am j med sci 2009;337:156–160. 27. cooper ha, exner dv, waclawiw ma, domanski mj. white blood cell count and mortality in patients with ischemic and nonischemic left ventricular systolic dysfunction (an analysis of the studies of left ventricular dysfunction [solvd]) am j cardiol 1999;84:252–257. 200 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 original article intravitreal injections and face masks: endophthalmitis risk before and during the covid-19 pandemic saeed karimi1, md; homayoun nikkhah1,2,3, md; amir mohammadzadeh1,2, md; alireza ramezani2,4, md; iman ansari1,2, md; hosein nouri1,5, md; seyed-hossein abtahi1,2,3, md 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2department of ophthalmology, torfeh medical center, shahid beheshti university of medical sciences, tehran, iran 3clinical research development unit of torfeh medical center, shahid beheshti university of medical sciences, tehran, iran 4ophthalmic epidemiology research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 5school of medicine, isfahan university of medical sciences, isfahan, iran orcid: saeed karimi: https://orcid.org/0000-0002-3231-8414 homayoun nikkhah: https://orcid.org/0000-0002-2414-4661 abstract purpose: to assess the added risk of acute endophthalmitis after intravitreal injections associated with the widespread use of face masks during the covid-19 pandemic. methods: in this retrospective, single-center study, records of patients with acute endophthalmitis following intravitreal bevacizumab (ivb) injections during the pre-covid era—that is, march 1st, 2013 to october 31st, 2019 —and the covid-19 era—that is, march 1st, 2020 to april 1st, 2021 —were reviewed and compared. results: a total of 28,085 ivb injections were performed during the pre-covid era; nine eyes of nine patients developed acute post-ivb endophthalmitis in this era, giving an overall incidence of 0.032% (3.2 in 10,000 injections). in the covid era, 10,717 ivb injections were performed; four eyes of four patients developed acute post-ivb endophthalmitis in this era, giving an overall incidence of 0.037% (3.7 in 10,000 injections). the incidences of post-ivb endophthalmitis during these two eras were not statistically significantly different (p = 0.779). conclusion: face masking protocols seem unlikely to impose any additional risk of post-ivb endophthalmitis. keywords: covid-19; endophthalmitis; face mask; intravitreal injection; infection j ophthalmic vis res 2023; 18 (3): 283–288 preprint: a preprint of this work has previously been posted at a preprint depository (research square; doi: 10.21203/rs.3.rs-1124994/v1). correspondence to: department of ophthalmology, torfeh medical center, shahid beheshti university of medical sciences, ibn sina st., baharestan sq., tehran 11498, iran. email: h.nikkhah52@gmail.com received: 05-02-2022 accepted: 16-11-2022 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i3.13776 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: karimi s, nikkhah h, mohammadzadeh a, ramezani a, nouri h, abtahi s-h. intravitreal injections and face masks: endophthalmitis risk before and during the covid19 pandemic. j ophthalmic vis res 2023;18:283–288. © 2023 karimi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 283 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i3.13776&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr face masking and post-ivb endophthalmitis; karimi et al introduction the importance of intravitreal injections, especially intravitreal anti-vascular endothelial growth factor (anti-vegf) injections, has increased in recent years due to their widespread use in managing retinal diseases such as diabetic macular edema (dme) and neovascular agerelated macular degeneration (namd).[1] along with its therapeutic benefits, the intravitreal delivery route carries the risk of some side effects and complications, including subconjunctival hemorrhage, uveitis, retinal tear or detachment, and endophthalmitis.[2, 3] endophthalmitis is a severe, sight-threatening complication of intravitreal injections; among its known risk factors are diabetes mellitus (dm), blebs, blepharitis, etc.[3, 4] adherence to standard injection protocol can significantly limit the incidence of post-intravitreal injection endophthalmitis.[3, 5] alterations in the former may give rise to changes in the latter. the probable impacts of health protocol amendments during the covid-19 pandemic, for example, mask-wearing mandates for patients and staff[5] and increasing application of hand disinfectant solutions in hospitals[6, 7] during the covid-19 pandemic[8, 9] on endophthalmitis incidence after intravitreal injection of anti-vegf drugs are under investigation; however, the findings have been inconsistent. while some have suggested an additional risk of endophthalmitis with patients wearing masks during the sessions— theoretically, through an upward direction of exhaled vapors toward the periocular area, increasing the risk of infectious complications,[10] others have found no increase in the overall risk of endophthalmitis, attributable to using face.[11] in the present study, we investigated the effect of these changes in health protocols during the covid pandemic on the incidence of post-intravitreal injections endophthalmitis and compared the endophthalmitis rate during the covid pandemic with the rate at which it occurred during the pre-covid era. intravitreal bevacizumab (ivb) was the most commonly used intravitreal anti-vegf in the center where the study was conducted; thus, the term “ivb” will be used instead of intravitreal anti-vegf injection throughout this paper. methods in this retrospective, single-center cohort study, the electronic medical records of the torfe eye hospital, affiliated with the shahid beheshti university of medical sciences, were accessed and queried for all cases of acute endophthalmitis following ivb injections, performed during two distinct periods—march 1st, 2013 to october 31st, 2019 and march 1st, 2020 to april 1st, 2021. the former period is from now on referred to as the “pre-covid era”, and the latter as the “covid era,” constituting approximately 80 and 12 months, respectively. the study protocol was approved by the local ethics committee and adhered to the tenets of the declaration of helsinki (ethics code: ir.sbmu.msp.rec.1396.737). the records of all patients who had undergone ivb injections during those periods were extracted from the hospital data archives using the respective current procedural terminology (cpt) code:67028. subsequently, among those records, all cases with acute post-ivb endophthalmitis were identified and extracted using the international classification of the disease-10 (icd-10) codes of endophthalmitis:h44.0-h44.1. the acquired information included demographic data, injection indications, treatments and outcomes, bacterial smear and culture results, best-corrected visual acuity scores (bcva) before the injection and after the onset of endophthalmitis symptoms, and three months after the treatment. post-ivb endophthalmitis cases were excluded if (i) their bevacizumab administration was part of another surgical procedure, (ii) they had any other intraocular procedures during the last six weeks before the ivb injection, and (iii) their acute endophthalmitis was secondary to other causes such as trauma or post-cataract surgery. acute endophthalmitis after ivb was defined as progressive inflammation in the vitreous cavity with or without inflammation of the anterior chamber, occurring within six weeks after the injection. the diagnosis was confirmed by a vitreoretinal surgeon. all injections at the torfe eye hospital were performed in the operating room under strict aseptic conditions. in the pre-covid era, no face masks were used by patients during the procedure; however, during the covid era patients had to wear face masks while being injected, holding them under their noses. before the procedure, 284 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 face masking and post-ivb endophthalmitis; karimi et al physicians scrubbed their hands and wore face masks and sterile gloves. topical tetracaine 0.5% drops were used to achieve local anesthesia. after cleaning the skin around the eye with a solution of povidone-iodine 10% and instilling a single drop of povidone-iodine 5% in the cul-de-sac, followed by setting an ophthalmic drape – without adhesive bands – a sterile lid speculum was placed. the rubber covering of the bevacizumab vial was wiped with cotton soaked in 5% betadine; 1.25 mg/0.05 ml avastin (genentech, ca, usa, 100 mg/4 ml vial; for injections before november 2018) or stivant (cinnagen, iran, 100 mg/4 ml vial; for injections in november 2018 and thereafter) was drawn into an insulin syringe for each injection— stivant, a biosimilar for avastin, became available to use in torfe medical center from november 2018. the needle was then changed, and a 30gauge needle was used for injection at 3–4 mm posterior to the limbus. topical antibiotic eye drops were prescribed for three days after injection.[12] except for the patients’ mask-wearing mandate, all mentioned measures were similar to the precovid era. in the case of post-ivb endophthalmitis, an immediate anterior chamber and vitreous tap was performed for all patients, followed by intravitreal injection of vancomycin (1 mg) and ceftazidime (2.25 mg). early standard threeport pars plana vitrectomy (ppv) was performed within 24 hr of diagnosis. fortified antibiotic eye drops (vancomycin and ceftazidime) and systemic intravenous vancomycin and ceftazidime were initiated for all patients—systemic intravenous antibiotic therapy preceded all other therapeutic measures and was initiated immediately after the patients’ admission. oral prednisolone 1 mg/kg was prescribed 24 hr after ppv and continued for 10 days. finally, to investigate the effect of the pandemicassociated adjustments in health protocols on the incidence of this complication, data from the two periods, that is, the pre-covid and the covid eras, were compared and analyzed. normal continuous variables were described as mean and standard deviation, and qualitative variables as frequency and percentage. chi-square test, wilcoxon signedrank test, and kruskal–wallis test were used to evaluate visual acuity changes in relation to other variables. the fisher’s exact test was applied when comparing variables from the pre-covid era with those from the covid era. a p-value of <0.05 was considered statistically significant. data was gathered and analyzed using ibm spss v.23.0. for windows. results data from the pre-covid era during the pre-covid era, 28,085 ivb injections were performed at the torfe eye hospital. nine eyes of nine patients developed acute post-ivb endophthalmitis, giving an overall incidence of 0.032% (3.2 in 10,000 injections)—no cluster pattern was observed in incident endophthalmitis episodes. the patients’ mean (±sd) age was 63.78 years (±13.8; range, 44–89). six patients (66.7%) were female. the indications for ivb injections were dme in four eyes (44.5%), vitreous hemorrhage due to proliferative diabetic retinopathy (pdr) in three eyes (33.3%), and neovascular amd (namd) in two eyes (22.2%). considering all ivb injections in the pre-covid era (28,085 injections), the incidences of post-ivb endophthalmitis were 0.014%, 0.010%, and 0.007% in pdr, namd, and dme patients, respectively (p > 0.05). in the pre-covid era, the mean (±sd) time between ivb injections and endophthalmitis presentation was 2.77 days (±1.25; range, 1–6). table 1 presents detailed information on the nine patients who developed post-ivb endophthalmitis in the pre-covid era. data from the covid era during the covid era, 10,717 ivb injections were performed at the torfe eye hospital. four eyes of four patients developed acute post-ivb endophthalmitis giving an overall incidence of 0.037% (3.7 in 10,000 injections), with no cluster pattern of incidence. the patients’ mean (±sd) age was 63.25 years (±6.5, range, 55–69). among the four, only one was male. the indication for ivb injections was dme in three eyes (75%) and namd in one eye (25%). the mean (±sd) time between ivb injections and the endophthalmitis presentation was 2.75 days (±1.71; range, 1–5). table 2 shows detailed information on patients with post-ivb endophthalmitis in the covid era. no significant difference was observed in the incidence of endophthalmitis in pre-covid and covid eras (0.032% vs 0.037%; p = 0.779). journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 285 face masking and post-ivb endophthalmitis; karimi et al table 1. demographic, clinical, and culture information of patients with post-ivb endophthalmitis during the pre-covid era. case no. sex age indication days to presentation pre-injection bcva presentation bcva final bcva culture snellen logmar snellen logmar snellen logmar 1 f 60 pdr 4 1/10 1 hm 2.6 cf1m 1.79 no growth 2 m 79 cnv 1 cf3m 1.31 lp 2.7 hm 2.6 no growth 3 f 86 pdr 6 2/10 0.7 nlp 3 nlp 3 staphyloccous epidermidis 4 m 65 dme 2 3/10 0.52 cf1m 1.79 2/10 0.7 no growth 5 f 44 dme 2 cf2m 1.48 hm 2.6 cf2.5m 1.39 no growth 6 f 58 cnv 2 2/10 0.7 hm 2.6 1/10 1 staphyloccous epidermidis 7 f 88 dme 2 cf3m 1.31 cf1m 1.79 cf2.5m 1.39 no growth 8 f 54 dme 4 1/10 1 lp 2.7 nlp 3 staphyloccous epidermidis 9 m 50 pdr 2 hm 2.6 lp 2.7 hm 2.6 no growth mean ± sd 63.78 ± 13.8 2.78 ± 1.56 1.18 ± 0.62 2.5 ± 0.42 1.94 ± 0.88 bcva, best-corrected visual acuity; cf, counting finger; cnv, choroidal neovascularization; dme, diabetic macular edema; f, female; hm, hand motion; logmar, logarithm of minimum angle of resolution; lp, light perception; m, male; nlp, no light perception; pdr, proliferative diabetic retinopathy; sd, standard deviation table 2. demographic, clinical, and culture information of patients with post-ivb endophthalmitis during the covid era. case no. sex age indication days to presentation pre-injection bcva presentation bcva final bcva culture snellen logmar snellen logmar snellen logmar 1 f 69 dme 1 4/10 0.4 1/10 1 4/10 0.4 no growth 2 f 55 dme 5 cf1m 1.79 hm 2.6 cf2m 1.48 no growth 3 f 61 dme 2 cf3m 1.31 hm 2.6 2/10 0.7 no growth 4 m 68 amd 3 2/10 0.7 hm 2.6 cf3m 1.31 no growth mean ± sd 63.25 (±6.5) 2.75 ± 1.71 1.05 ± 0.62 2.20 ± 0.80 0.97 ± 0.51 amd, age-related macular degeneration; bcva, best-corrected visual acuity; cf, counting finger; dme, diabetic macular edema; f, female; hm, hand motion; logmar, logarithm of minimum angle of resolution; m, male; sd, standard deviation culture results among the nine endophthalmitis cases documented during the pre-covid era, six (66.7%) showed negative culture results, while three (33.3%) showed staphylococcus epidermidis growth; one eye developed phthisis bulbi (11.1%). culture results were negative for all four endophthalmitis cases in the covid era. discussion the present study determined a post-ivb endophthalmitis rate of 0.032% (3.2 in 10,000 injections) in the pre-covid era and 0.037% (3.7 in 10,000 injections) in the covid era; our results are consistent with the ranges reported in previous studies.[13] post-ivb endophthalmitis is a serious complication. based on previous studies, factors affecting the development of endophthalmitis following intravitreal injections can be divided into clinical and technical categories. clinical factors that can increase the risk of endophthalmitis include dm, older age, and blepharitis. dm and older age have also been associated with immunosuppression and increased susceptibility to infection.[14,15] among technical factors is the type of surgical equipment used, as well as how 286 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 face masking and post-ivb endophthalmitis; karimi et al well health protocols are observed. it is worth mentioning that our university hospital is an evolving medical center with increasing referral rates over the past few years, which explains why the total number of cases referred for receiving ivb during the pre-covid era (∼ 6 years) was only 2.8 times than that during the covid-era (∼ 1 year). moreover, the change in the medication used (i.e., avastin until late 2018 vs stivant after that) is unlikely to have had any confounding effect on the results because endophthalmitis cases were not in clusters, and incidence was not changed between the two eras. furthermore, the small number of positive-culture cases precludes an accurate comparison and a meaningful, relevant discussion. overall, we found that altered health protocols during the covid pandemic had no statistically significant effect on the incidence of post-ivb endophthalmitis. a few studies have evaluated the effect of universal face mask-wearing and other pandemic health protocols on the rate of endophthalmitis after intravitreal injections.[11,16] a multicenter and retrospective study has reported that universal face mask use during intravitreal injections did not increase the risk of developing presumed endophthalmitis, but it was associated with a lower rate of culture-positive endophthalmitis.[16] in another study by patel et al, face mask use by physician did not influence the risk of post-injection endophthalmitis as compared to a no-talking policy.[11]. it was hypothesized that facial mask fitting by surgeons could effectively affect bacterial transmission and the risk of post-intravitreal injection endophthalmitis.[17] in a study by hadayer et al, it was emphasized that patients who wear face masks during intravitreal injections might be at a higher risk of endophthalmitis; hence, face masks with proper fitting, or taping the upper edges of the face masks with a medical adhesive tape, or using an adhesive surgical drape around the injected eye were recommended.[18] another study by simulation of intravitreal injections concluded that adding tape to the superior portion of the patient’s face mask reduces bacterial dispersion during intravitreal injections. also, bacterial dispersion was not different compared to wearing n95 masks.[19] another study suggested that securing the superior portion of the patient’s face mask with tape may reduce bacterial dispersion or air particles toward the eye.[20] however, it has been reported that this measure has no effect on endophthalmitis risk in patients undergoing ivb injections.[16] some limitations apply to the present study. given the retrospective nature of this study, potential errors in data registering in the hospital records could have been present; however, restrictive measures were taken to minimize such errors. in addition, with the ongoing pandemic, a decline in the number of patients—especially diabetic patients, many of whom suffer from other underlying comorbidities—referring to hospitals[21] is a limitation that applies to many hospital-based studies; this limitation is more prominent in cohort studies evaluating the incidence of an uncommon complication, such as ours. furthermore, results from this study may be inferred only to injection settings similar to that of this study; that is, office-based injections with variable degrees of adherence to standard injection protocols may present different complication incidences. in summary, the present study showed that the incidence of post-ivb endophthalmitis in the covid era was not significantly different from the pre-pandemic era. regardless of the pandemic-related alterations in health protocols adopted—mandatory face masking, in particular— endophthalmitis remains a rare complication after intravitreal injections. the time interval between the ivb injection and presentation of endophthalmitis is relatively short; prompt treatment with immediate intravitreal antibiotics and early ppv are vital in maximizing positive treatment outcomes. financial support and sponsorship none. conflicts of interest none. references 1. maloney mh, payne sr, herrin j, sangaralingham lr, shah nd, barkmeier aj. risk of systemic adverse events after intravitreal bevacizumab, ranibizumab, and aflibercept in routine clinical practice. ophthalmology 2021;128:417–424. 2. soliman mk, gini g, kuhn f, iros m, parolini b, ozdek s, et al. international practice patterns for the management journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 287 face masking and post-ivb endophthalmitis; karimi et al of acute postsurgical and postintravitreal injection endophthalmitis: european vitreo-retinal society endophthalmitis study report 1. ophthalmol retina 2019;3:461–467. 3. lyall da, tey a, foot b, roxburgh st, virdi m, robertson c, et al. post-intravitreal anti-vegf endophthalmitis in the united kingdom: incidence, features, risk factors, and outcomes. eye 2012;26:1517–1526. 4. fintak dr, shah gk, blinder kj, regillo cd, pollack j, heier js, et al. incidence of endophthalmitis related to intravitreal injection of bevacizumab and ranibizumab. retina 2008;28:1395–1399. 5. klompas m, morris ca, sinclair j, pearson m, shenoy es. universal masking in hospitals in the covid-19 era. n engl j med 2020;382:e63. 6. al-sayah mh. chemical disinfectants of covid-19: an overview. j water health 2020;18:843–848. 7. rabenau hf, kampf g, cinatl j, doerr hw. efficacy of various disinfectants against sars coronavirus. j hosp infect 2005;61:107–111. 8. advani sd, smith ba, lewis ss, anderson dj, sexton dj. universal masking in hospitals in the covid-19 era: is it time to consider shielding? infect control hosp epidemiol 2020;41:1066–1067. 9. wang x, ferro eg, zhou g, hashimoto d, bhatt dl. association between universal masking in a health care system and sars-cov-2 positivity among health care workers. jama 2020;324:703–704. 10. wen jc, mccannel ca, mochon ab, garner ob. bacterial dispersal associated with speech in the setting of intravitreous injections. arch ophthalmol 2011;129:1551– 1554. 11. patel sn, hsu j, sivalingam md, chiang a, kaiser rs, mehta s, et al. the impact of physician face mask use on endophthalmitis after intravitreal anti-vascular endothelial growth factor injections. am j ophthalmol 2021;222:194– 201. 12. storey p, dollin m, pitcher j, reddy s, vojtko j, vander j, et al. the role of topical antibiotic prophylaxis to prevent endophthalmitis after intravitreal injection. ophthalmology 2014;121:283–289. 13. xu k, chin ek, bennett sr, williams df, ryan eh, dev s, et al. endophthalmitis after intravitreal injection of vascular endothelial growth factor inhibitors: management and visual outcomes. ophthalmology 2018;125:1279–1286. 14. rayess n, rahimy e, storey p, shah cp, wolfe jd, chen e, et al. postinjection endophthalmitis rates and characteristics following intravitreal bevacizumab, ranibizumab, and aflibercept. am j ophthalmol 2016;165:88–93. 15. geerlings se, hoepelman ai. immune dysfunction in patients with diabetes mellitus (dm). fems immunol med microbiol 1999;26:259–265. 16. patel sn, tang ph, storey pp, wolfe jd, fein j, shah sp, et al. the influence of universal face mask use on endophthalmitis risk after intravitreal anti-vascular endothelial growth factor injections. ophthalmology 2021;128:1620–1626. 17. doshi rr, leng t, fung ae. reducing oral flora contamination of intravitreal injections with face mask or silence. retina 2012;32:473–476. 18. hadayer a, zahavi a, livny e, gal-or o, gershoni a, mimouni k, et al. patients wearing face masks during intravitreal injections may be at a higher risk of endophthalmitis. retina 2020;40:1651–1656. 19. patel sn, mahmoudzadeh r, salabati m, soares rr, hinkle j, hsu j, et al. bacterial dispersion associated with various patient face mask designs during simulated intravitreal injections. am j ophthalmol 2021;223:178–183. 20. schultheis wg, sharpe je, zhang q, patel sn, kuriyan ae, chiang a, et al. effect of taping face masks on quantitative particle counts near the eye: implications for intravitreal injections in the covid-19 era. am j ophthalmol 2021;225:166–171. 21. al-khersan h, kalavar ma, tanenbaum r, lazzarini ta, patel na, yannuzzi na, et al. emergent ophthalmic surgical care at a tertiary referral center during the covid-19 pandemic. am j ophthalmol 2021;222:368–372. 288 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 original article changes in pupil area during low-energy femtosecond laser-assisted cataract surgery alireza mirshahi1, md; katharina a. ponto2,3, md 1dardenne eye hospital, bonn, germany 2department of ophthalmology, university medical center mainz, germany 3center for thrombosis and hemostasis, university medical center mainz, germany orcid: alireza mirshahi: https://orcid.org/0000-0003-3899-8972 *the abstract of this study was presented at escrs annual meeting, lisbon, portugal, october 2017. abstract purpose: to study the potential changes in pupil area within low-energy femtosecond-laser assisted cataract surgery (flacs). methods: a retrospective assessment of the pupil size was performed in the eyes undergoing flacs using the ziemer ldv z8. we measured the pupil diameters as part of the images taken preoperatively and at the completion of laser pretreatment (after releasing the suction). we calculated the pupil area in 40 eyes of 40 patients (14 right and 26 left eyes). the mean ± standard deviation (sd) of age of the patients was 74 ± 7.4 years (range: 51-87). paired t-test was used for statistical analyses. subgroups were built with reference to age and preoperative pupil area (smaller than or equal to the median versus larger than the median). results: the mean ± sd axial length, anterior chamber depth, white-to-white distance and lens thickness were 24.01 ± 1.47, 3.23 ± 0.4, 11.97 ± 0.49, and 4.59 ± 0.41 mm, respectively. the mean ± sd pupil area was 39.33 ± 7.1 mm2 preoperatively and 39.3 ± 6.75 mm2 after laser pretreatment. the mean ± sd change in pupil area was -0.03 ± 2.12 mm2. there were no statistically significant changes between preoperative and post-laser pupil areas (p = 0.93, 95% ci: -0.71 to 0.65). comparisons within subgroups also did not detect pupil area reduction. conclusion: this study did not detect statistically significant changes in pupil area after laser pretreatment using low-energy flacs. this observation is in contrast to previous studies using other laser platforms. keywords: cataract surgery; femtosecond laser; pupil size; safety j ophthalmic vis res 2019; 14 (3): 251–256 correspondence to: alireza mirshahi, md, febo. dardenne eye hospital, friedrich-ebert-st., 23-25, bonn 53177, germany. e-mail: dr.mirshahi@gmail.com received: 18-11-2018 accepted: 24-04-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i3.4780 introduction femtosecond laser-assisted cataract surgery (flacs) has undergone considerable evolution since its introduction by nagy et al in 2009.[1–4] currently, flacs is thought to be safe and effective, as reported by several studies.[1, 5, 6] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: mirshahi a, ponto ka. changes in pupil area during low-energy femtosecond laser-assisted cataract surgery. j ophthalmic vis res 2019;14:251–256 @ 2019 j  o  v r | published by knowledge e 251 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i3.4780&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr pupil area in low-energy flacs; mirshahi and ponto nevertheless, several technology-specific complications and side effects have been reported with the use of flacs.[7, 8] intraoperative miosis has been repeatedly reported as a common problem in association with flacs. the narrowing of the pupil after laser pretreatment makes surgery more challenging to the surgeon, potentially resulting in a higher rate of capsule-related complications.[9] previous studies using early “high-energy” femtosecond lasers have shown a substantial increase in the number and severity of episodes of intraoperative miosis with a prevalence ranging between 9.5% and 32%.[7, 10–13] in a previous study, jun et al reported that the duration of laser pretreatment and patient age correlated with decreased pupil area measured by intraoperative surgical images.[13] researchers believe that increased levels of prostaglandin e2 (pge2), as measured immediately after laser pretreatment, are responsible for intraoperative narrowing of the pupil.[12–15] pge2 is released when ocular tissue is exposed to femtosecond laser cutting side effects.[16] conventional “high-energy” femtosecond lasers emit pulses with an energy in the 4 to 15 microjoule (𝜇j) range,[7, 10, 14] whereas the newer low-energy concept uses high-pulse repetition rates above 1 mhz and a low-pulse energy in the nanojoule range[16] this is achieved using a high numerical aperture in the laser focusing optics,[15] enabling small laser spot sizes. we hypothesized that the number and extent of episodes of intraoperative miosis would decrease in flacs using a low-energy femtosecond laser compared to previously published literature. therefore, we conducted this study to assess the change in pupil size in eyes undergoing cataract surgery using a low-energy femtosecond laser. methods this retrospective case series included eyes that had undergone flacs using a ziemer z8 femto ldv (ziemer ophthalmic system, port, switzerland) and an alcon infinity phacoemulsification system (alcon lab., fort worth, tx, usa) in dardenne eye hospital, bonn, germany. all surgeries were performed by one experienced surgeon (am) between september 2016 and april 2017. the following data were extracted from patient records: age, laterality of surgery, axial length, anterior chamber depth, lens thickness, white-towhite distance, and special notes in the surgery report. data on axial length, anterior chamber depth, lens thickness, and white-to-white were taken from laser biometry performed on the day of surgery (iolmaster 700, carl zeiss meditec, jena, germany). if data of both eyes of a patient were available, records of the first surgical eye were used. we used images taken from surgical videos at the following time points: (1) preoperatively, shortly before docking the laser and (2) immediately after vacuum suction released (end of femtosecond laser pretreatment). the ethics committee of the north rhine medical chamber ruled that approval was not required for this retrospective study. it was performed in accordance with the tenets of the declaration of helsinki. surgical technique one experienced surgeon (am) performed all femtosecond laser pretreatments and phacoemulsification procedures. all patients received the local standard-of-care preoperative pupil enlargement regimen consisting of tropicamide 5 mg/ml (mydriaticum stulln®ud, pharma stulln gmbh, stulln, germany) and phenylephrine 5% (neosynephrinpos®5%, ursapharm arzneimittel gmbh, saarbrücken, germany) eye drops, four times each. no patient received additional nonsteroidal antiinflammatory drugs (nsaids). all surgeries were performed under peribulbar anesthesia. with the surgeon sitting at the 12 o’clock position, the ziemer femto ldv z8 was positioned in an oblique angle. after disinfection and sterile draping, the femtosecond laser interface was positioned and vacuum suction was applied (approximately 420 mbar). standard laser parameters were 6-mm-diameter laser lens fragmentation in six pieces, at 105% laser energy followed by a 5.2-mm-capsulotomy diameter using 90% laser energy. suction was released after the completion of capsulotomy. no other surgical steps were done with the femtosecond laser system. the surgeon moved on with further surgical steps including posterior limbal main incision of 2.8 mm, two paracenteses of 1.1 mm each, introduction of a dispersive viscoelastic device 252 j  o  v r volume 14, issue 3, july–september 2019 pupil area in low-energy flacs; mirshahi and ponto into the anterior chamber, removal of capsulotomy by forceps, hydrodissection, hydrodelineation, high-vacuum phacoemulsification, bimanual removal of lens cortex, posterior capsule polishing, iol implantation, bimanual removal of viscoelastic device, and hydration of the paracentesis. pupil area measurement we used images taken from the surgical videos to measure the horizontal and vertical diameters of the pupil. fiji, an image processing package of imagej software version 2.0.0-rc-49/1.51a was used to measure the pupil diameters in pixels. the pixel measurements were then converted into millimeters, individually for each patient, using the constant limbus horizontal and vertical size as a reference. assuming the pupil has an ellipsoid shape, we calculated pupil area as vertical radius multiplied by horizontal radius multiplied by 𝜋. statistical analyses as there is no previous data on this topic, the present study was done as a pilot project. besides identification of potentially associated parameters, we aimed to establish baseline data to be used for a thorough sample size calculation in a future study. we calculated descriptive measurements for the pupil area at the time points mentioned earlier and the difference between preoperative and postlaser pupil areas. the main analysis examined possible differences in the pupil area of the individual measurements from the baseline preoperative measurement. to detect effects by larger or smaller preoperative pupil areas, a subgroup analysis was performed to evaluate the changes in pupil area in eyes with preoperative pupil areas smaller or larger than the median pupil size of all eyes included in the study. furthermore, we separately evaluated eyes of older and younger patients (age ≤ the median age versus age > the median age). we used paired t-tests for statistical analyses. p-values < 0.05 were considered statistically significant. all statistical analyses were performed using spss (statistical package for the social sciences, version 25, chicago, illinois). results we included 40 eyes of 40 patients in this retrospective study (mean age: 74 ± 7.4 years, range: 51-87) with complete data available within the study period. if data were available from both eyes, data from the first eye operated on were used. the study sample comprised 14 (35%) right and 26 (65%) left eyes. preoperatively, glaucoma and pseudoexfoliation were diagnosed in three eyes (7.5%). further descriptive data, including axial length, anterior chamber depth, lens thickness, and white-to-white distance are illustrated in table 1. preoperatively, the mean, standard deviation, median, minimum and maximum values were 7.01 ± 0.65, 7.12, 5.51, and 8.27 mm, respectively, for horizontal pupil diameter, 7.09 ± 0.65, 7.09, 5.75, and 8.46 mm, respectively, for vertical pupil diameters, and 39.33 ±7.1, 39.61, 26.87, and 54.64 mm2 , respectively, for the pupil area. the mean change between preoperative and post-laser pupil areas was -0.03 ± 2.12 mm2 (median: -0.35, minimum: -5.13, maximum: 4.16). figure 1 illustrates preoperative and post-laser pupil areas. a paired t-test revealed no statistically significant changes between preoperative and post-laser pupil areas (p = 0.93, 95% ci: -0.71 to 0.65). in the subgroup of eyes with larger preoperative pupils (pupil area before surgery above the median of 39.61 mm2), the mean change of the pupil area after flacs did not change significantly; in the group of eyes with a preoperative pupil area of 39.61 mm2 or smaller, it changed from 33.90 ± 4.41 mm2 preoperatively to 34.29 ± 5.00 mm2 after flacs (95% ci: -0.58 to 1.35; p = 0.412); and in the group of eyes with a preoperative pupil area larger than 39.61 mm2, it changed from 44.75 ± 4.68 mm2 preoperatively to 44.31 ± 4.02 mm2 after flacs (95% ci: -1.45 to 0.56; p = 0.367). in eyes of patients aged 75.5 years or younger, the mean change of pupil area after flacs was 0.08 ± 1.88 mm2 (95% ci: -0.80 to 0.96; p = 0.858), and in eyes of patients older than the median age of 75.5 years, it was -0.13 ± 2.38 mm2 (95% ci: -1.25 to 0.98; p = 0.803). discussion to the best of our knowledge, this retrospective study is the first to assess pupil sizes of eyes undergoing low-energy flacs. we could not detect any changes in the pupil area when comparing j  o  v r volume 14, issue 3, july–september 2019 253 pupil area in low-energy flacs; mirshahi and ponto table 1. preoperative values of the relevant morphologic parameters in 40 consecutive eyes undergoing low-energy femtosecond-laser assisted cataract surgery preoperative parameters mean ± standard deviation [mm] median [mm] minimum [mm] maximum [mm] axial length 24.01 ± 1.47 24.02 21.34 27.13 anterior chamber depth 3.23 ± 0.4 3.23 2.39 4.01 lens thickness 4.59 ± 0.41 4.62 3.69 5.32 white-to-white distance 11.97 ± 0.49 12.0 10.8 12.8 figure 1. preoperative and post-laser pupil areas in 40 consecutive and unselected eyes undergoing low-energy femtosecondlaser assisted cataract surgery (flacs). error bars showing the means ± standard deviations. preoperatively, the mean pupil area was 39.33 ± 7.1 mm2. immediately after the completion of laser pretreatment (after suction release), the mean pupil area was 39.3 ± 6.75 mm2. a paired t-test revealed no statistically significant changes between the preoperative and post-laser pupil areas (p = 0.93, 95% ci: -0.71 to 0.65). preoperative pupil status with post-laser size. this is in contrast to previous studies using other laser platforms that assessed pupil changes in highenergy flacs. diakonis et al compared the effect of three laser platforms (lensx; alcon laboratories, inc., fort worth, tx, catalys; abbott medical optics inc., santa ana, ca, and victus; and bausch & lomb, inc., rochester, ny) on pupil diameter[12] and found a mean pupillary miosis of 1.42 ± 1.26 mm for the lensx, of 0.66 ± 0.89 mm for the catalys, and of 0.14 ± 0.34 mm for the victus groups. almost one-quarter of eyes included in this study demonstrated a pupil diameter of 6 mm or less. jun et al report a 29.7% decrease in pupil area after femtosecond laser pretreatment in a study sample of 56 eyes.[13] the same study group reported, in a follow-up comparative study, that the preoperative topical ketorolac tromethamine 0.45% significantly reduced femtosecond laserassociated miosis and inhibited prostaglandin e2 elevation in the aqueous humor.[15] with those systems, a larger pupil diameter before flacs was associated with greater miosis. this is, again, in contrast to the present study, as we were not able to detect a flacs-induced miosis even in the subgroup of eyes with larger preoperative pupil areas. similarly, we did not observe any changes when subdividing data into various age groups. our results are of clinical relevance because small pupil size is generally considered a challenge, potentially leading to a higher incidence or severity of complications in cataract surgery.[9] thus, we believe that the absence of femtosecond laser-associated intraoperative miosis using a lowenergy platform may make surgery less challenging and less traumatizing. 254 j  o  v r volume 14, issue 3, july–september 2019 pupil area in low-energy flacs; mirshahi and ponto because pupils do not always have an exactly circular shape, measuring area changes are more accurate than considering only diameter in one dimension. thus, we believe the most appropriate—and probably most sensitive—value to be assessed in similar studies is the calculated pupil area, rather than diameters. when reporting pupil diameters, both horizontal and vertical diameters should be considered. the “low-energy” concept using a high numerical aperture in the femtosecond laser optics is thought to be a valuable evolutionary step forward toward smaller laser spots, thereby reducing collateral damage to the surrounding ocular tissue.[17] while ”high-energy” femtosecond lasers emit energy in the microjoule range, the modern low-energy concept combines high repetition rate above 1 mhz and pulse energies in the nanojoule range[17] in order to achieve precise tissue cuts with minimal mechanical side effects. one possible explanation for the observation made in our study is that a low-energy laser platform probably produces lower ”collateral damage” to the surrounding tissue, thus resulting in lower amounts of prostaglandins and, thereby, no (or negligible) intraoperative pupil narrowing. in fact, researchers could not detect meaningful increases in prostaglandin levels in the aqueous humor after low-energy flacs, as reported in a preliminary clinical study (personal oral communication with professor r. menapace, may 2018). this finding is in line with our observation of unchanged pupil area. furthermore, it supports the hypothesis that increased levels of prostaglandins are causative for intraoperative miosis in flacs.[16, 18] nevertheless, caution is warranted because those results have not yet been published in the peer-review literature. another possible explanation for our observation of unchanged pupil area could be the time lapse between the femtosecond laser pretreatment and other surgical parts: when using the ziemer z8 laser, the surgery can be continued immediately after the completion of laser pretreatment, while in other lasers, the patient must be transferred to another surgical table or theatre. the larger short time lapse between laser pretreatment and other surgical steps may be another explanation for much higher incidences of intraoperative miosis in previous studies.[13, 14, 18] flacs requires the application of a suction device to stabilize the laser head and focus the laser beam accurately. this may cause a significant escalation iop, which has been demonstrated for the femto ldv z8 in porcine eyes. ebner et al showed that during the vacuum application of the liquid patient interface values were higher in the anterior chamber compared with the intravitreal pressure measurements.[19] the higher predefined vacuum level (350 versus 420 mbar) resulted in significant higher intracameral iop. another porcine in vivo model showed that iop with the ziemer ldv femtosecond laser was lower using the liquid patient interface compared to the flat applanation system.[20] as the present study was retrospective in design, no interventions besides those done within the clinical routine were performed. therefore, we did not measure iop during laser application. there are no previous studies on iop in humans using the femto ldv z8. however, schultz et al reported a minor increase in the iop using the fluid-filled interface.[21] higher values have been reported in the literature with flat and curved applanating contact interfaces.[21] at the same time, miosis with the catalys has been reported.[22] therefore, we assume that it is not the iop alone that contributes to miosis and that other factors like energy used might be more relevant. the following limitations of our study merit consideration: (1) a relatively small sample size of 40 eyes; (2) the measurement of pupil sizes at only two time points; (3) the study sample was completely caucasian; (4) no intraoperative measurement of prostaglandins in aqueous humor; and (5) a very short time lapse between laser pretreatment and further surgical steps. future studies will need to shed light on these limitations. with this aim in mind, a thorough sample size estimation and power calculation are done on the basis of the present results and will be used for a future study that focuses mainly on the parameters found to be of potential interest in this baseline study. nevertheless, we believe our study results are valuable, as unchanged pupil dimensions will make a cataract surgery less challenging. financial support and sponsorship alireza mirshahi, md is a consultant to ziemer ophthamic, systems ag, port, switzerland; katharina ponto, md was funded by the federal ministry of education and research (bmbf 01eo1003). j  o  v r volume 14, issue 3, july–september 2019 255 pupil area in low-energy flacs; mirshahi and ponto conflicts of interest there are no conflicts of interest. references 1. dick hb, schultz t. a review of laser-assisted versus traditional phacoemulsification cataract surgery. ophthalmol ther 2017;6:7-18. 2. ewe sy, abell rg, vote bj. femtosecond laser-assisted versus phacoemulsification for cataract extraction and intraocular lens implantation: clinical outcomes review. curr opin ophthalmol 2018;29:54-60. 3. grewal ds, schultz t, basti s, dick hb. femtosecond laser-assisted cataract surgery–current status and future directions. surv ophthalmol 2016;61:103-131. 4. nagy z, takacs a, filkorn t, sarayba m. initial clinical evaluation of an intraocular femtosecond laser in cataract surgery. j refract surg 2009;25:1053-1060. 5. lundstrom m, dickman m, henry y, manning s, rosen p, tassignon mj, et al. femtosecond laser-assisted cataract surgeries reported to the european registry of quality outcomes for cataract and refractive surgery: baseline characteristics, surgical procedure, and outcomes. j cataract refract surg 2017;43:1549-1556. 6. nejat f, sarahati s, nobari sm, jadidi k, naderi m, nejat ma. preliminary results of femtosecond laser-assisted cataract surgery in a private clinic in iran. j ophthalmic vis res 2017;12:39-43. 7. nagy zz, takacs ai, filkorn t, kranitz k, gyenes a, juhasz e, et al. complications of femtosecond laser-assisted cataract surgery. j cataract refract surg 2014;40:20-28. 8. roberts tv, lawless m, bali sj, hodge c, sutton g. surgical outcomes and safety of femtosecond laser cataract surgery: a prospective study of 1500 consecutive cases. ophthalmology 2013;120:227-233. 9. hashemi h, seyedian ma, mohammadpour m. small pupil and cataract surgery. curr opin ophthalmol 2015;26:3-9. 10. bali sj, hodge c, lawless m, roberts tv, sutton g. early experience with the femtosecond laser for cataract surgery. ophthalmology 2012;119:891-899. 11. chang js, chen in, chan wm, ng jc, chan vk, law ak. initial evaluation of a femtosecond laser system in cataract surgery. j cataract refract surg 2014;40:29-36. 12. diakonis vf, kontadakis ga, anagnostopoulos ag, yesilirmak n, waren dp, cabot f, et al. effects of short-term preoperative topical ketorolac on pupil diameter in eyes undergoing femtosecond laser-assisted capsulotomy. j refract surg 2017;33:230-234. 13. jun jh, hwang ky, chang sd, joo ck. pupil-size alterations induced by photodisruption during femtosecond laser-assisted cataract surgery. j cataract refract surg 2015;41:278-285. 14. diakonis vf, yesilirmak n, sayed-ahmed io, warren dp, kounis ga, davis z, et al. effects of femtosecond laser-assisted cataract pretreatment on pupil diameter: a comparison between three laser platforms. j refract surg 2016;32:84-88. 15. jun jh, yoo ys, lim sa, joo ck. effects of topical ketorolac tromethamine 0.45% on intraoperative miosis and prostaglandin e2 release during femtosecond laser-assisted cataract surgery. j cataract refract surg 2017;43:492-497. 16. schultz t, joachim sc, stellbogen m, dick hb. prostaglandin release during femtosecond laser-assisted cataract surgery: main inducer. j refract surg 2015;31:7881. 17. mariacher s, ebner m, seuthe am, januschowski k, ivanescu c, opitz n, et al. femtosecond laser-assisted cataract surgery: first clinical results with special regard to central corneal thickness, endothelial cell count, and aqueous flare levels. j cataract refract surg. 2016;42:1151-1156. 18. schultz t, joachim sc, szuler m, stellbogen m, dick hb. nsaid pretreatment inhibits prostaglandin release in femtosecond laser-assisted cataract surgery. j refract surg 2015;31:791-794. 19. ebner m, mariacher s, januschowski k, boden k, seuthe am, szurman p, et al. comparison of intraocular pressure during the application of a liquid patient interface (femto ldv z8) for femtosecond laser-assisted cataract surgery using two different vacuum levels. brit j ophthalmol 2017;101:1138-1142. 20. williams gp, ang hp, george bl, liu yc, peh g, izquierdo l, et al. comparison of intra-ocular pressure changes with liquid or flat applanation interfaces in a femtosecond laser platform. sci rep 2015;5:14742. 21. schultz t, conrad-hengerer i, hengerer fh, dick hb. intraocular pressure variation during femtosecond laserassisted cataract surgery using a fluid-filled interface. j cataract refract surg 2013;39:22-27. 22. walter k, delwadia n, coben j. continuous intracameral phenylephrine-ketorolac irrigation for miosis prevention in femtosecond laser-assisted cataract surgery: reduction in surgical time and iris manipulation. j cataract refract surg 2019;45:465-469. 256 j  o  v r volume 14, issue 3, july–september 2019 photo essay simple congenital hamartoma of the retinal pigment epithelium austin s. nakatsuka1, md; touka banaee1,2, md; emma loucks1, md; jaafar el-annan1,3,4, md 1department of ophthalmology and visual sciences, university of texas medical branch, galveston, texas, usa 2department of ophthalmology, mashhad university of medical sciences, mashhad, iran 3university of texas at md anderson, houston, texas, usa 4blanton eye institute, houston methodist hospital, houston, texas, usa orcid: austin s. nakatsuka: https://orcid.org/0000-0002-4058-4763 jaafar el-annan: https://orcid.org/0000-0002-9783-7290 j ophthalmic vis res 2020; 15 (2): 261–263 presentation an asymptomatic 63-year-old woman presented for annual ophthalmic examination at university of texas medical branch eye clinic and was found to have a simple congenital hamartoma of the retinal pigment epithelium (rpe) in the left eye. the best corrected visual acuity was 20/20 and the visual field was within normal limits. on fundus examination, a circular hyperpigmented retinal lesion measuring less than the diameter of an optic disc was detected superonasal to the fovea. old records indicated that the lesion had been present since at least 12 years before, showing no significant morphological changes on serial fundus photographs [figures 1a and 1b]. the lesion showed hypoautofluorescence in autofluorescence imaging [figure 2a] and correspondence to: jaafar el annan, md. department of ophthalmology and visual sciences, university of texas medical branch. 301 university blvd, galveston, texas 77555, usa. e-mail: jaelanna@utmb.edu received: 04-03-2019 accepted: 26-05-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i2.6747 optical coherence tomography (oct) revealed high surface reflectivity with deep optical shadowing and full-thickness retinal involvement that had been stable over time [figures 2a and 2b]. bscan ultrasonography revealed a flat lesion showing medium to high internal reflectivity [figure 2c]. discussion simple congenital hamartoma of the rpe is a benign tumor composed of a hyperplastic rpe with variable vascularity and is often discovered incidentally in asymptomatic children and young adults.[1, 2] it is a rare tumor and presents as a pigmented mass protruding from the rpe into the retina and at times into the vitreous cavity, usually at the posterior pole.[1, 2] shields et al[2] reported the presence of a minimally dilated feeding retinal arteriole and a draining venule in five cases. we did not observe this finding in the present case. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: nakatsuka as, banaee t, loucks e, el-annan j. simple congenital hamartoma of the retinal pigment epithelium. j ophthalmic vis res 2020;15:261–263. © 2020 journal of ophthalmic and vision research | published by knowledge e 261 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i2.6747&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; nakatsuka et al figure 1. fundus photographs showing a simple congenital rpe hamartoma with no change from 2007 (a) to 2017 (b). figure 2. optical coherence tomography (oct) showing a retinal lesion with high surface reflectivity, deep optical shadowing, and full-thickness retinal involvement. image (a) was taken in 2009, and image (b) in 2017. the arrows on the left side autofluorescence (af) and infrared images show the level of b scans that although not registered pass through the same location based on fundus landmarks. the lesion shows hypoautofluorescence in af imaging. (c) b scan ultrasonography reveals a flat lesion with high internal reflectivity. according to previous studies, the retinal tissue surrounding the hamartoma may show minimal signs of traction,[3] which was not present in the current case. these lesions showed early hypofluorescence in fluorescein angiography with some variable hyperfluorescence seen in later frames due to either rpe atrophy or intrinsic tumor vasculature.[2] oct features of the lesion show a hyper-reflective surface and dense shadowing.[4] simple hamartomas of rpe are usually small and cannot be easily seen by ultrasonography. if visible, they have medium to high internal reflectivity on ultrasound.[2] differential diagnoses include combined hamartoma of the retina and rpe, adenoma or adenocarcinoma of the rpe, congenital hyperplasia of the rpe, choroidal nevus, choroidal melanoma, rpe hyperplasia, and intraocular foreign body.[2] the absence of a history of trauma, retinal traction, time-related growth features, and the typical funduscopic features of the lesion can help differentiate between these diagnoses. the present case is particularly interesting because the stability of lesion is documented by fundus photographs spanning a duration of 10 years and by oct images that are 8 years apart. financial support and sponsorship nil. 262 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 photo essay; nakatsuka et al conflicts of interest there are no conflicts of interest. references 1. kalman z, toth j. two cases of congenital simple hamartoma of the retinal pigment epithelium. retin cases brief rep 2009;3:283–285. 2. shields cl, shields ja, marr bp, sperber de, gass jd. congenital simple hamartoma of the retinal pigment epithelium: a study of five cases. ophthalmology 2003;110:1005– 1011. 3. shields ja, shields cl. tumors and related lesions of the pigmented epithelium. asia pac j ophthalmol 2017;6:215– 223. 4. shukla d, ambatkar s, jethani j, kim r. optical coherence tomography in presumed congenital simple hamartoma of retinal pigment epithelium. am j ophthalmol 2005;139:945–947. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 263 editorial world’s largest eye bank has served a nation for three decades mahmood farazdaghi, ms past president, international federation of eye banks, maryland, usa orcid: mahmood farazdaghi: https://orcid.org/0000-0001-7466-5126 j ophthalmic vis res 2020; 15 (2): 126–127 in this issue of jovr, javadi and co-authors have provided a comprehensive analysis and statistical report of the activities of the central eye bank of iran (cebi) over a period of 27 years.[1] cebi is globally the largest provider of transplantable cornea, recovering from one single city, tehran, the capital, with a population of approximately nine million. during the last 10 years alone, the eye bank has distributed 61,725 corneas suitable for transplant,[1] with a mean distribution of 6,172 surgical grade corneas per year. this number is by far more than the distribution of any eye bank of a major city. i have personally visited iran in multiple occasions since 1994, had the opportunity to visit cebi, review and provide input and guidance. i can confidently state that the quality of work in cebi is at par with any certified western eye bank. latest state-of-the-art equipment, clean rooms, stringent medical standard, highly trained and well-experienced technical personnel, and on-site availability of two co-medical directors specialized in ocular pathology for review and tissue release are a testament to the quality of work performed at this eye bank. all corneas are required to be evaluated, processed, released, and distributed to surgeons around the country within 48 h post procurement. forms and medical records are in english in this unique eye bank which is accommodating to international trainees as well as facilitating international review and inspection. the data presented by authors reveal a very large rate of transplantable corneas from procured whole globes or corneas. out of the 114,169 eyes procured over a 27-year period, 95,314 were suitable and distributed.[1] thus, providing a transplantable rate of 83.5%, which is again by far the highest amongst other eye banks. this uniqueness is attributed to (a) the knowledge and skills of technical staff in the screening of donors and (b) the eye bank policy, which in addition to contraindications requires a review of chart, medical history, and even preliminary cornea evaluation before the recovery of globe or cornea. in 2018, the eye bank association of america reported a transplant rate of 69.4 %.[2] probably the difference with cebi’s rate of 83.5% is due to the limited penlight evaluation which is mainly focused on foreign body or infiltrate in cornea, as well as screening, which is usually focused on absolute medical contraindications. the review of medical history and hospital chart is performed after procurement. in india, although the transplant rate for hospital retrieval is about 50%,[3] for home retrieval, it varies between 22 and 28%, as most voluntary donations are recovered to honor the wish of donor family and avoid discouragement and disappointment. the per capita procurement and transplant are of the most important for the analysis of eye bank activity and the status of corneal blindness in a given country. while per capita procurement provides insight on the status of public awareness, acceptance of donation or laws and traditions; per capita transplant reveals the status of dependency on importing cornea, scope of promotion of donation, efficiency of eye banking activities, and path to self-sufficiency and even equilibrium. while the population of iran has increased approximately by 33% from 1994 to 2017, the reported number of transplanted corneas has increased by 5.8-fold from 925 to 5,382, and the per capita transplants from 17 to 66. this volume and growth is unprecedented and cebi is to be commended for this milestone achievement. 126 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i2.6728&domain=pdf&date_stamp=2019-07-17 editorial; farazdaghi during 2018, us eye banks provided 85,441 transplantable corneas, out of which 51,294 were distributed domestically and 27,913 internationally.[2] with us population of 327.2 million per capita, the availability of transplant is 261 while per capita transplant is 156.8. given that us has no backlog and has enough corneas to provide for any domestic need at a given time, the per capita transplant rate of 156.8 per million population would be considered the equilibrium per capita rate of transplant for the us population. furthermore, this transplant rate of 156.8 per million population can be employed as a yardstick to determine the number of required corneas for a population of similar health status, and of course that needs to be adjusted for backlog. although many european countries are considered self-sufficient[4] and not dependent on importation of corneas, they still have not reached equilibrium. in 2018, to supplement local recovery, europe imported 1,778 corneas from the us, with the highest being 1,301 to germany.[2] cebi is to be congratulated for the extraordinary achievement of reaching a remarkable per capita transplant rate. with emerging new glimpse of eye banking in other cities as reported by authors, and with the guidance of cebi, we are confident that cebi’s success story will be duplicated many times over in new areas and populations, and the path to equilibrium will be much shorter. references 1. javadi ma, rezaei kanavi m, safi s. a 27 year eye banking statistical report for the central eye bank of iran. j ophthalmic vis res 2020; 15: 149–159. 2. van meter ws. 2018 eye banking statistical report. available from: https://restoresight.org/what-we-do/ publications/statistical-report/ 3. sharma n, arora t, singhal d, maharana pk, garg p, nagpal r, et al. procurement, storage and utilization trends of eye banks in india. indian j ophthalmol 2019;67:1056–1059. 4. gain p, jullienne r, he z, aldossary m, acquart s, cognasse f, et al. global survey of corneal transplantation and eye banking. jama ophthalmol 2016;134:167–173. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i2.6728 how to cite this article: farazdaghi m. world’s largest eye bank has served a nation for three decades. j ophthalmic vis res 2020;15:126–127. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 127 https://restoresight.org/what-we-do/publications/statistical-report/ https://restoresight.org/what-we-do/publications/statistical-report/ https://knepublishing.com/index.php/jovr review article von hippel-lindau disease and the eye saeed karimi1,2, md; amir arabi1,2, md, mph; toktam shahraki1,2, md; sare safi3, phd 1ophthalmic research center, shahid beheshti university of medical sciences, tehran, iran 2department of ophthalmology, torfeh medical center, shahid beheshti university of medical sciences, tehran, iran 3ophthalmic epidemiology research center, shahid beheshti university of medical sciences, tehran, iran orcid: saeed karimi: http://orcid.org/0000-0002-3231-8414 amir arabi: https://orcid.org/0000-0002-6523-7733 abstract retinal hemangioblastoma (also referred to as retinal capillary hemangioma) is a benign lesion originating from the endothelial and glial components of the neurosensory retina and optic nerve head. historically known as a manifestation of the von hippellindau (vhl) disease, it can be seen as an isolated finding or in association with some rare ocular conditions. in addition to characteristic ophthalmoscopic features, results of numerous ancillary tests including angiography, ultrasound, optical coherence tomography, and genetic tests may support the diagnosis and differentiate it from similar conditions. because of serious life-threatening complications of vhl disease, every ocular approach to retinal hemangioblastomas should be in relationship with additional multidisciplinary diagnostic and therapeutic efforts. in addition, any patient with actual or probable diagnosis of vhl disease should be screened for ocular involvement. unfavorable visual loss can occur early, and ocular complications of vhl range from exudative retinopathy to tractional retinal detachment, neovascular glaucoma, and phthisis bulbi. accordingly, various treatment methods have been tested with overall acceptable responses, including photocoagulation, cryotherapy, photodynamic therapy, plaque radiotherapy, vitrectomy, and more novel intravitreal injections of anti-vascular endothelial growth factors and propranolol. keywords: diagnosis; retinal capillary hemangioma; treatment; von hippel-lindau j ophthalmic vis res 2020; 15 (1): 78–94 correspondence to: amir arabi, md, mph. ophthalmic research center, shahid beheshti university of medical sciences, no. 23, paidarfdard st., boostan 9 st., pasdaran ave., tehran 16666, iran. e-mail: amir_arab_91@yahoo.com received: 31-05-2019 accepted: 22-08-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i1.5950 introduction retinal hemangioblastoma (rh), also known as retinal capillary hemangioblastoma, is a benign vascular neoplastic lesion originating in the neurosensory retina or optic disc. vigla described this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: karimi s, arabi a, shahraki t, safi s. von hippellindau disease and the eye. j ophthalmic vis res 2020;15:78–94. 78 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i1.5950&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr von hippel-lindau disease; karimi et al hemangioblastoma in a patient who died of central nervous system (cns) lesions for the first time in 1864.[1] hemangioblastoma presents as a highly vascular, and well-bordered, slowly growing neoplastic lesion that contains a mixture of stromal cells, endothelial cells, pericytes, and mast cells.[2] rhs are usually observed in von hippel–lindau (vhl) disease, which is an autosomal dominantly inherited condition, in which mutations in the vhl tumor suppressor gene is believed to cause the development of characteristic benign and malignant, mainly vascular, neoplasms or cysts in the cns and internal organs. rh is one of the earliest and most frequent manifestations of vhl disease.[3] sporadic rh can also occur in the absence of vhl disease. according to the webster et al’s report, the features of sporadic retinal hemangiomas including age of presentation, degree of visual morbidity, complications, morphology, and anatomic location of tumors are indistinguishable from those seen in the vhl disease.[4] the prevalence of vhl was reported as 30– 58% among patients with rhs.[5] in the study by niemelä et al including 36 patients with retinal hemangioblastomas, 11 cases had definite clinical diagnosis of vhl and ten cases were diagnosed with clinically suspected vhl.[5] in the same study, visual prognosis of affected individuals was more favorable in non-vhl patients than in vhl patients, which was in contrast with the finding of the study mentioned earlier.[4] some reports have disclosed that rhs exist in association with other retinal conditions, such as chorioretinal coloboma and marshall–stickler syndrome.[6, 7] given the life-threatening nature of some of the complications and manifestations of vhl, timely intervention needs appropriate surveillance, and proper diagnosis can be made based on clinical criteria and genetic evaluation for mutations in the vhl gene. method we searched pubmed and the web of knowledge databases to extract all published studies about vhl disease from inception to march 2019. “von hippel-lindau”, “retinal capillary hemangioma”, “diagnosis”, and “treatment” were used as the keywords. we also reviewed the reference lists of related studies. no language restriction was applied. two independent investigators screened the abstracts and titles of extracted articles to determine the eligible publications. they reviewed the full text of the pertinent articles. discrepancies were resolved through consensus. vhl disease vhl disease is an exceedingly penetrant, autosomal dominantly inherited, multisystem neoplasia disorder caused by mutations in the vhl gene. although vhl is hereditary in the majority of cases, new mutations are the cause in up to 20% of the cases.[8] cardinal manifestations include brain and spinal cord hemangioblastoma, renal cell carcinoma (rcc), rh, pheochromocytoma, epididymal and broad ligament cystadenomas, endolymphatic sac tumor, pancreatic neuroendocrine tumors, and renal and pancreatic cysts.[9] the approximate incidence of vhl disease is 1 in 36,000 live births, and the penetrance is over 90% by 65 years of age.[10] the most reported causes of mortality are metastasizing rcc and cns lesions,[11] and despite advances in clinical management, life expectancy for vhl patients remains low at 40–52 years.[8] however, improvements in early diagnosis, surveillance, and treatment have led to better prognoses, and an expert multispecialty team is necessary for the optimal management of this complex disease. history the first pieces of the vhl syndrome puzzle began to be recognized in the late 19th century.[12] these earliest findings of the disease have been summarized by melmon and rosen.[13] in 1904, von hippel published clinical data describing the features of a retinal disease in two patients and seven years later, he had been equipped to perform a histological examination on a subsequently enucleated eye of one of his patients; von hippel named the pathological findings “angiomatosis retinae.” in 1926, the swedish pathologist lindau revealed the relationship between retinal and cerebellar hemangioblastomas and their association with cysts in some viscera including the kidney, epididymis, and pancreas as components of a hereditary syndrome. accordingly, a cns hemangioblastoma was known as a “lindau tumor”, while the identical retinal lesion came to be known as a “von hippel tumor”. by the time melmon and rosen published their journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 79 von hippel-lindau disease; karimi et al review, the name of the familial syndrome was “lindau disease”. this term was changed to “vonhippel lindau (vhl)” disease in the 1970s. melmon and rosen published the initial clinical diagnostic criteria for vhl disease in a landmark paper in 1964.[13] seizinger and colleagues explained the linkage of the vhl gene to chromosome 3 in 1988,[14] and shortly thereafter, in 1993, latif and colleagues discovered the vhl tumor suppressor gene.[15] mechanism of cellular dysfunction vhl disease is caused by some mutations in a tumor suppressor gene, the vhl gene, present on chromosome 3 (3p25-26).[15] the product of the gene is the vhl protein (pvhl), which has been found to participate in cellular oxygen sensing. understanding of mechanisms related to the vhl gene has provided insight into cell signaling and function under normoxic and hypoxic conditions.[16] vhl gene contains three exons that produce two distinct spliced mrnas. the mrnas differ in the presence or absence of exon number 2, known as isoform i and ii, respectively. although it has been believed that the second isoform does not produce any endogenous tumor suppressor protein and the isoform i is the only form that results in functional protein, expression of the uncharacterized protein isoform pvhl172, which is translated from isomer ii, is shown to upregulate a subset of protumorigenic genes including tgfb1, mmp1, and mmp13.[17] following ubiquitous expression of vhl, isoform 1 encodes two isoforms of pvhl, which comprises 213 amino acids and 160 amino acids, respectively, and both of these isoforms have tumor suppressor activity.[18] pvhl, which is a part of the ubiquitin ligase complex and serves as the substrate-recognition subunit, assigns proteins for proteasomal degradation. hypoxia-inducible factor 1𝛼 (hif-1𝛼) and hypoxia-inducible factor-2𝛼 (hif-2𝛼) are among the targets of this ubiquitin ligase, which undergo prolyl-hydroxylation under normoxic conditions, authorizing for binding to pvhl and activation of ubiquitin peptides that result in proteasomal degradation of hifs.[19, 20] it is clear that in the absence of normal pvhl, hif-1𝛼 and hif-2𝛼 are not degraded, but form heterodimers with hypoxia-inducible factor 1𝛽 (hif1𝛽), and produce transcription factors for a wide array of over 800 genes.[16] upregulation of cell survival proteins by hif signaling, such as epidermal growth factor receptor and transforming growth factor alpha, in addition to angiogenesis factors, for instance vascular endothelial growth factor (vegf) and platelet-derived growth factor (pdgf), are hypothesized to play a key role in the development of neoplastic vascular lesions in vhl disease, including rh.[21–25] the significance of other actions of pvhl independent of hif signaling is unclear in vhl disease pathogenesis.[16] vhl disease is mostly received from a mutant copy of the vhl gene from an affected parent and a normal copy from the other parent. knudson’s two-hit model for tumorigenesis indicated that the somatic inactivation of the normal allele in one or more cells, in combination with a germline mutation in the other allele, causes the mutation to clinically manifest.[26] in a large study on 181 kindreds with vhl disease, 42 cases (23%) did not have any relevant family history, indicating a putative firstgeneration diagnosis.[27] in these cases, mosaicism may explain the underlying germline transmission from the unaffected parent. additionally, it can explain occasional cases in which vhl disease manifests clinically but initial genetic testing is negative for mutation.[28] stolle and colleagues published a report in 1998 on different genetic testing methods that helped in the identification of germline mutations in 100% of families with vhl disease, establishing the importance of vhl gene testing for the diagnosis of this condition.[29] mutations of vhl are highly varied, ranging from the base pair substitution in a single amino acid codon to the complete deletion of the gene.[30, 31] many of these mutations target pvhl regulation of hif signaling. however, the heterogeneous manifestations of vhl disease suggest that different mutations may affect pvhl-associated cellular mechanisms in different ways.[32] the relationship between the type of vhl mutation and the severity and prevalence of ocular complications has been investigated in several studies with contradictory results.[33] initial findings denied any association between the type of vhl mutation and visual function.[34] however, it is now believed that partial deletion, missense, and nonsense mutations are correlated with higher prevalence of rhs and worse visual prognosis, unlike complete deletion of the vhl gene.[35, 36] additionally, the location of a missense mutation in vhl correlates with the phenotype of ocular vhl disease, and mutations 80 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 von hippel-lindau disease; karimi et al in the alpha(a)-domain are associated with a higher rate of retinal and optic nerve hemangioblastomas than those in the beta(b)-domain.[37] different vhl gene mutations in four vhl families support the genotype–phenotype correlations.[33] diagnosis retinal and cns hemangioblastomas are two main clinical features of vhl disease and the other systemic abnormalities have less diagnostic significance. however, variability in systemic abnormalities is an important feature of this disease. only one systemic involvement manifests in some cases and not all abnormalities present together in many individuals. the diagnosis can be made when there are two hemangioblastomas, or one of them in combination with a visceral manifestation. it is notable that a positive family history is as valuable as a cns tumor in the diagnosis; one index tumor, such as hemangioblastoma, rcc, or pheochromocytoma, in association with a positive family history is sufficient to diagnose vhl disease.[38] genetic testing is useful in challenging cases for screening of at-risk family members of a patient with vhl disease with no family history or visceral lesions. screening and surveillance different guidelines have been published for screening of vhl disease. among these guidelines, the ones designed by choyke et al have suggested urinary catecholamine testing, ophthalmoscopy, brain magnetic resonance imaging, and abdominal computed tomography or ultrasound for early detection of the manifestations.[39] in the screening guideline, ophthalmoscopy is recommended to begin from infancy and to be repeated yearly. as vhl disease is complex, optimal management involves care by a multispecialty team with expertise in ophthalmology, otolaryngology, neurosurgery, endocrine surgical oncology, neuroradiology, urology, pathology, genetics, and rehabilitation medicine. ocular manifestation of vhl disease although rh is one of the most common clinical manifestations of vhl disease, the precise prevalence of ocular involvement is difficult to ascertain from case series. singh et al reported that retinal capillary hemangioma is the most frequent and the earliest manifestation of vhl disease. the frequency of occurrence has been reported to vary from 49% to 85%.[40] in another article, it is claimed that rhs are seen in as many as 60% of the patients, being the second most frequent manifestation after cns hemangioblastomas.[8] whether the most frequent or not, rhs are often the first manifestation. although retinal lesions are hamartomas in nature, they are usually not present at birth.[41] the mean and median age of onset is 25 and 21, respectively, which is the lowest among the other clinical features.[9, 42] rh often manifests as a solitary lesion. however, around one-third of patients may have multiple retinal hemangiomas and up to half of the patients may present with bilateral involvement.[40] it has been shown that there is no effect of gender on the laterality and severity of the ocular involvement.[43] in a large cross-sectional study in which participants were identified based on a diagnosis of vhl disease independent of ophthalmologic features, 335 of 890 patients from 220 unrelated pedigrees were found to have ocular involvement.[42] of those with ocular disease, 42% had unilateral involvement and 58% had bilateral involvement. affected patients were from 7 to 84 years old (mean – 36 years old), and 45% were male. in the study, rhs of vhl were found in all ages and racial groups, and in both sexes. results of the study confirmed the findings of one previous study about the lack of effect of sex on the ocular phenotype of vhl patients. among the main demographic features considered in the study, only age was found to have an effect on ocular phenotype, and only in some respects. however, the authors did not find a significant correlation between increasing age and either the laterality, number of rhs per eye, or the extent of peripheral retina angiomatosis. this suggests that the probability for the formation of new lesions in the eye may not remain constant over time. webster et al[43] also did not find an age correlation to number of tumors. dollfus et al[44] reported increases in rh number from the start to the end of their study, but a statistical relationship with age per se was not evaluated. the ophthalmoscopic findings of vhl disease are divided into two main groups: angiomatous versus non-angiomatous lesions. journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 81 von hippel-lindau disease; karimi et al angiomatous tumors or retinal capillary hemangiomas similar to other retinal lesions, retinal capillary hemangiomas are characterized by location, type, and size of the tumor. these tumors can be classified on the basis of morphology (endophytic, exophytic, and sessile), location within the retina (peripheral and juxtapapillary), and effects on the retina (exudative form and tractional form).[40] the retinal capillary hemangioma is usually a wellcircumscribed, round bulging with a red to orange color, with a variable appearance depending upon whether the tumor is endophytic, sessile, or exophytic. blood vessels, as draining and feeding vessels, appear as the tumor grows larger and begins to be increasingly enlarged and tortuous [figure 1(a)]. at this stage, extrapapillary rhs become exudative, with hard exudates and retinal edema near the tumor and/or in the macula. rhs at or near the optic disc have a distinct clinical appearance, making them difficult to discern with ophthalmoscopy when small in size or sessile in form. a localized fullness of the disc margin may be the primary finding, but with further growth, a bordered pink thickening becomes visible, with associated fine vessels in some cases. feeder and draining vessels are typically not visible in juxtapapillary lesions. although papillary hemangiomas sometimes show minimal growth over years, they usually lead to exudation eventually. in a study by wong et al it was reported that 85% of the affected eyes, manifested rhs exclusively in the peripheral retina (extrapapillary), 8% had rhs exclusively near the optic disc, and 7% had rhs in both the peripheral retina and juxtapapillary regions. among the 421 eyes with peripheral rhs, the mean tumor count was 2.5. a subtle red or grayish spot with a few hundred micrometers of diameter was the initial clinical appearance of an extrapapillary rh, with an ophthalmoscopic appearance mimicking a dilated capillary, microaneurysm, or small intraretinal hemorrhage. small tumors were sessile, but with growth, they often became more nodular. earlier, singh et al[41] reported 174 retinal capillary hemangiomas in 86 eyes of 68 patients with vhl disease, where 83% were extrapapillary and 17% were juxtapapillary; 58% of rhs were 1.5 mm or smaller in size. in addition to data from distribution of rhs, the authors reported that juxtapapillary hemangiomas are frequently located at the temporal border of the optic disc.[40, 41] the natural course of a single capillary hemangioma in the retina can be of progression, stability, or regression. a majority of rhs grow over time, but occasionally, untreated tumors may remain static for a long period, and rarely they may regress spontaneously.[45] secondary effects such as exudation of subretinal or intraretinal spaces are often limited to the territory of the hemangioma but can be far enough to produce a macular star exudate. retinal or vitreous hemorrhages are rarely observed, occurring in less than 3% of cases.[46] without treatment, large or multiple adjacent rhs may grow to displace the retinal structures and cause an exudative retinal detachment. fibrosis of the epiretinal space followed by posterior hyaloid contraction may accompany large rhs, causing macular epiretinal membrane with macular thickening, vitreomacular traction, or traction retinal detachment. as a rare complication, neovascularization of the iris can occur, which may lead to the development of neovascular glaucoma (nvg) and phthisis bulbi in eyes with multiple tumors. in a study involving a large cohort of patients, only 2% of eyes had neovascularization of the iris.[43] eventually, such eyes became phthisical or painful, requiring enucleation. visual function of patients with retinal capillary hemangiomas has been evaluated in some studies. chew, in her prospective case series,[35] reported that in 406 patients with vhl disease who had ocular involvement, visual acuity was 20/20 or better in 84.5% with hemangioblastomas, 3% were legally blind, and eventually, 8.2% had unilateral enucleations. in the cohort of the national eye institute, about 77% of eyes had a vision of 20/20 or better, and the prevalence of legal blindness, that is, vision less than 20/160 in the better-seeing eye, was 6%. however, to justify the burden of the disease, it was reported that approximately 20% of all patients with ocular vhl disease had at least some degree of unilateral visual impairment. a longitudinal analysis with the purpose of characterization of visual function and ocular vhl progression was conducted in 2012.[47] two hundred and forty-nine participants of the study were followed-up for more than two years. visual acuity, ocular manifestation of vhl disease, germline mutation in the vhl gene, demographic data, and patient characteristics were recorded in that study. the anatomic and functional ocular status was stable in most of the patients over a mean 82 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 von hippel-lindau disease; karimi et al figure 1. (a) color fundus photograph of an exudative extrapapillary rch. note enlarged and tortuous feeding vessels passing toward a peripheral rch, in addition to small rchs in macula. (b) wide field fundus angiogram. (c) montage modality of angiography for more peripheral lesions. follow-up period of 8.2 years. in addition, 88% of eyes with ocular vhl disease at baseline, did not demonstrate rhs in a new retinal location, 70% remained stable in terms of rh number, and 79% revealed no change regarding the extent of rh involvement. in all 498 studied eyes, visual acuity was decreased by 5.1 letters across followup, with 16.1% decreasing by more than 10 letters. in affected eyes, greater vision loss was related to the increase in rh number, the presence of juxtapapillary rhs, and formation of new rhs. there were correlations between younger age at onset of ocular vhl disease, bilateral ocular vhl disease, and missense or protein-truncating germline mutations and increase of anatomic involvement and functional worsening. various stages of retinal involvement in retinal hemangiomas have been determined by some authors. sigelman classified them into five stages. stage one represents small hemangioma without any feeder vessels. in stage two, they appear as a nodule with prominence of only the draining vein. in stage three, both feeding artery and draining vein are present with or without retinal exudates. partial and total exudative retinal detachment are observed in stages four and five, respectively.[48] similarly, vail’s classification[49] includes the following stages: stage i: angioma formation with feeding artery and draining vein stage ii: development of hemorrhages and exudation stage iii: massive exudation and retinal detachment stage iv: uveitis, absolute glaucoma, and loss of the eye the ophthalmoscopic findings of rhs are characteristic; thus, a good funduscopic examination is often sufficient to make an ocular vhl disease diagnosis. as mentioned earlier, small lesions may be difficult to be distinguished from microvascular abnormalities when other conditions are considered. on the other hand, some lesions may closely resemble larger rhs and may be difficult to be differentiated in some cases. vasoproliferative tumor of the ocular fundus is the main differential diagnosis of large rhs.[50] in addition, rhs in the presence of macular exudation can be misdiagnosed as retinal macroaneurysm or coats’ disease, and in some conditions such as vitreous hemorrhage which masks the tumor, dilated feeder vessels can be misdiagnosed as congenital retinal arteriovenous malformations and anastomoses between vessels of choroidal melanoma or retinoblastoma and retinal vessels. unilateral papilledema and papillitis, juxtapapillary choroiditis, choroidal hemangioma, choroidal neovascularization, and amelanotic choroidal melanoma can mimic juxtapapillary retinal capillary hemangioma.[51] non-angiomatous findings in ocular vhl disease some non-angiomatous retinal lesions associated with ocular vhl disease have been described. journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 83 von hippel-lindau disease; karimi et al these lesions include “twin vessels,” “vascular hamartomas,” and “vascularized glial veils.” schmidt, in 1995, found some unusual retinal lesions in his cases and called them vascular hamartomas.[52] the lesions were described as small, flat, moss fiber-like, vascular lesions without enlarged afferent and efferent vessels. they were located in the superficial retina. juxtapapillary fibrovascular membranes termed vascularized glial veils had been introduced by the same author seven years earlier. in the same year, de jong et al defined twin vessels as a paired retinal arteriole and venule that were separated by less than the diameter of one venule and that extended for a distance of more than one disc diameter.[53] in 2008, wai et al reported a form of vascular proliferation as fine superficial vessels in 16 eyes of 14 patients, often found in juxtapapillary locations.[54] these lesions most closely resembled vascularized glial veils. so that, the authors preferred the term “retinal vascular proliferation” to “vascularized glial veils” to include lesions that do not have a prominent fibrovascular component. although the lesion was stable in 7 of 13 eyes, in the remaining cases, the lesion was so progressed that it led to vision loss. ancillary tests fundus photography with wide-field modalities and montage methods seems to be an effective technique to monitor progression and growth of retinal hemangiomas, in addition to its use in detecting medium to large lesions [figures 1(b) and 1(c)]. ancillary testing becomes crucial in the evaluation of those patients with smaller lesions and those with peripheral exophytic hemangiomas to confirm the diagnosis. ancillary tests for retinal hemangiomas may include fluorescein angiography (fa), indocyanine green angiography (icg), optical coherence tomography (oct), and ultrasonography. vascular dye tests such as fa and icg angiography are advantageous diagnostic tools used in a range of ocular vascular growths such as retinal capillary hemangiomas, where fa is known as the most useful diagnostic tool because of the vascular nature of the tumor.[55] fa and icg angiography are critical in the assessment of any vascular lesion, helping in outlining the distinctive appearance, in addition to confirming any associated leakage.[56] fluorescein angiography primary hyperfluorescence of the feeder artery during the arterial phase associated with fine capillary filling of the retinal lump and cumulative hyperfluorescence within the entire tumor during later phases is the main finding of retinal angiography in rhs.[57] in more exophytic forms, fa may help clinicians to delineate the lesion, as well as the demarcation of the tortuous arterioles and venules. in circumstances that necessitate treatment, angiographic studies are also supportive in differentiating draining venules from feeding arterioles.[58] in juxtapapillary hemangioblastoma, fine vascular configuration can be revealed on angiograms. wide-angle angiography may be more beneficial, especially in finding peripheral lesions, which are more vulnerable to be missed because of their outlying position and subtle presentation. although it is helpful in diagnosis, handling, and assessing the therapy, it is not required to perform fa on all cases of characteristic capillary hemangioma. indocyanine green angiography icg may also be valuable in the assessment of rh, although, generally, it is used to assess choroidal vasculature. filling of the angiomas creates early, demarcated hyperfluorescence on icg that is in communication with retinal vasculature. absence of choroidal contribution on icg angiography supports the diagnosis of rh. icg is useful in distinguishing clinically similar situations, such as focalized choroidal hemangioma, which would be limited to the choroidal level.[40] associated retinal hemorrhages or retinal vascular leakage may be discovered by the blockage of adjacent vasculature on icg, as an adjunct to fa. indocyanine green-mediated photothrombosis has also been reported for the treatment of rhs.[59] ultrasonography ultrasound is a critical modality in assessing intraocular tumors. evaluating size, diameter, and internal echogenicity, b-scan remains an important test in approach to ocular tumors. in rhs, b-scan 84 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 von hippel-lindau disease; karimi et al shows a well-demarcated retinal lesion without choroidal properties. ultrasonography is predominantly helpful in the presence of opaque media.[60] moreover, an rh is characterized on a-scan by an opening spike with secondary high internal reflectivity.[40] other diagnostic tests sequence investigation of the vhl gene, can be important in the evaluation of rhs, as these assist in the diagnosis of vhl disease. oct may be used to discover macular edema and epiretinal membranes, as well as to evaluate features of a juxtapapillary rh. structural and molecular pathology findings rhs have two main components: glial proliferation and endothelial or vascular proliferation. the primary event is controversial. in fact, it is not determined whether the primary glial proliferation causes secondary vascular proliferation or glial proliferation follows endothelial proliferation. primary findings were of those studies conducted nearly half a century ago.[61, 62] it was shown that proliferation of glial cells surrounded the proliferated endothelial cells, which were arranged in well-formed vessels or small nests. the most prominent feature was a collection of large capillary-sized blood vessels that substituted the full thickness sensory retina. in addition, primary ultrastructural studies indicated that both endothelial and perithelial elements of the large capillary unit were morphologically regular. thus, capillary hemangioma was a more exact histopathologic description for the von hippel angioma than hemangioblastoma or hemangioendothelioma. this structure was reinforced in a study with the purpose of immunohistological evaluation of rh in two cases, where the authors reported that ultrastructural findings in both eyes contained endothelial/pericytelined vascular networks, shortened stromal cells, and fat and vacuolated stromal cells with ultrastructural features consistent with glial cells.[63] pathological findings of extrapapillary hemangiomas treated with xenon photocoagulation, argon laser therapy, and cryotherapy showed occlusion of the vascular channels, fibrous metaplasia of the retinal pigment epithelium, and secondary gliosis.[64] chan et al in 2007 tried to summarize discoveries in vhl pathology.[65] they concluded that loss of heterozygosity (loh) within the vhl gene is noticed in the stromal cells which originate from vascular/endothelial ancestry and form a unit with glial cells in retinal hemangiomas. parallel loh has been established in vhl disease-related cns hemangioblastomas, which are histopathologically analogous to rh. this finding is not compatible with the old belief about stromal cells, where they were supposed to be lipidized astrocytes or glial cells. chan et al have suggested that increase of hypoxia-inducible factor (hif), vegf, and ubiquitin are found in ocular hemangioblastomas. in their study, tumorlet cells were introduced as small, poorly differentiated cells with dense nuclei and minor cytoplasm, owning several stem cell and immunologic markers such as cd133 65. later in 2015, they found their pathological results to be consistent with previously described structure for rhs.[66] the mainstream of evidence supports the understanding that retinal hemangioma is a vascular growth arising as a malformed vascular unit containing an arteriole, capillaries, and venule with consequent growing of all its components. endothelial lineage of stromal cells and peripherally located glial cells indicates endothelial growth as the primary event. more discoveries about the molecular happenings in rh corpus may provide a therapeutic target for retinal hemangiomas. ocular vhl disease and pregnancy in 2009, hayden et al published a report of spinal hemangioma worsening in a pregnant vhl patient.[67] they believed that hormonal alterations during gestation hastened the growth of hemangioblastomas, leading to new symptoms. following the report, frantzen et al in their retrospective study involving 29 patients[68] claimed that pregnancy causes progression of cerebellar hemangioblastomas. however, in 2015, binderup et al criticized the two previous studies for their retrospective nature, short follow-up period, and limited samples.[69] their cohort study exclusively compared hemangioblastoma risk in pregnancy journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 85 von hippel-lindau disease; karimi et al with age-matched non-pregnant years in the same female group and evaluated the influence of pregnancy on both cns and rh progression. in contrast to the initial impression, they reported that gestation was associated with even lower rates of new tumor formation compared with the nonpregnancy period. it seems that pregnancy does not have any effect on the growth of preexisting rhs or development of new lesions.[69] treatment of ocular vhl disease early diagnosis, making decision for treatment versus observation monitoring for further growth after primary treatment, management of secondary retinal complications and treatment complications are some of the challenges in the field of ocular vhl disease management. the main goal of therapy is destruction of the lesion in order to reduce secondary damage to the retina. apparently, small tumors in the early phases of growth can be destroyed quite readily with minimal risk associated with the treatment. in contrast, as hemangioblastomas grow, it will be more difficult to ablate them, with higher risk of damage induced by the therapeutic procedures. accordingly, it seems that the principal issue in the management of ocular vhl disease is identification of rhs in the early stages of development, as well as timely therapy. however, even effectively managed, rhs can cause life-long visual loss in up to 25% of cases.[46] in order to achieve suitable management of rhs, an optimal approach should be initiated with adequate surveillance. indirect ophthalmoscopic and biomicroscopic examination of the retina, with occasional usage of ancillary tests are indicated every year for individuals with vhl disease, beginning in early childhood. documentation of any ocular lesions allows the clinician to select one of the treatment modalities, including observation,[70] laser photocoagulation,[71–74] cryotherapy,[75–78] plaque radiotherapy,[79] vitreoretinal surgery,[80, 81] external beam radiation, proton beam radiation, photodynamic therapy (pdt),[82, 83] trans-pupillary thermotherapy, intraocular injection of anti-vegf drugs or triamcinolone acetonide (ta). relative regression signs in a small rh may be detected with close surveillance. in a study by singh et al in 2002,[41] regarding management techniques in 68 patients who had been treated between 1974 and 1999, 82% of the 77 rhs that were primarily observed persisted stable for a median follow-up of 7 years. most of the rhs that were initially observed were 3.0 mm or smaller in size and almost the same percentage of juxtapapillary and extrapapillary rh were present. the authors reported that for the extrapapillary rh, efficiency of observation as a way of management was higher for hemangiomas that were 1.5 mm or less in size than for larger rh. in their opinion, cautious observation is indicated in a reliable case if the rh is very small (up to 500 𝜇m), is not associated with exudation, and is not vision threatening because of a nasal locality. ablative treatment of extrapapillary rhs ablative treatment includes various modalities such as thermal laser photocoagulation, cryotherapy, radiation (including brachytherapy, external beam radiation, and proton beam radiation), pdt, and trans-pupillary thermotherapy. laser photocoagulation laser photocoagulation may be applied in numerous sessions and is most effective in lesions that are 1.5 mm or smaller,[41] but it also has been used for rhs up to 4.5 mm with real regression.[72] although the modality is classically used for peripheral tumors, the effectiveness of laser photocoagulation for juxtapapillary rhs has been presented in some studies. permanent scotoma, poor visual outcome due to juxtaposition to optic nerve and posterior position are possible complications of laser photocoagulation for optic nerve hemangiomas.[70] various laser types, including argon, yellow dye, diode, green, and krypton, have all been used.[41] efficacy of all kinds of laser photocoagulation has been confirmed in several studies. for example, in singh’s study, argon/diode laser photocoagulation, applied over a mean of 1.2 sessions was 100% effective in treating retinal hemangiomas that were smaller than 1.5 mm. vascular lesions such as rhs can absorb yellow laser more than other laser wavelengths based on the absorption range of oxyhemoglobin;[84] therefore, green and yellow wavelengths are 86 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 von hippel-lindau disease; karimi et al usually used, with longer burn intervals (0.2– 0.4 seconds) than would be usual for panretinal photocoagulation or laser retinopexy, and with power adequate to generate whitening in the zone of the burn. no randomized trial for ablative laser type or technique has been performed. there are different types of photocoagulation techniques including direct photocoagulation of the rh,[64, 70, 71] treatment of the feeder vessel,[73] or combination of both the routes. because of the possibility of bleeding caused by laser treatment, in some studies, blood vessel photocoagulation has been recommended to diminish blood flow of the retinal lumps.[85] blodi’s study[73] revealed that both direct and feeder vessel photocoagulation procedures are effective, but laser photocoagulation of the feeder arterioles may cause the need for further laser sessions. in cases with small tumors, burns are generally restricted to an area appropriate to blanch the entire lesion surface; feeder vessels in these tumors are so small, if detectable at all. an effective laser photocoagulation yields a chorioretinal scar, which is occasionally associated with a wasted, pale pink remnant of the lesion, and other times with complete vanishing of the rh. a visible regressed lesion may be a sign of destruction sufficient to prevent further growth or exudation, but cured areas must be followed over time for any signal of a still viable rh. if required, retreatment technique will be the same. in larger tumors, it will be challenging to apply intense photocoagulation throughout the depth of the tumor. long duration burns (often more than 0.4 sec) with a lower power setting may be involved in the treatment of masses with a size between 1.5 and 4.0 mm in order to cause progressive whitening over the path of the burn. although the visibility of the feeder vessels is enhanced in large tumors, photocoagulation of the feeding arterioles has not considerably increased the probabilities of success or lowered the risks associated with the procedure. occasionally, indirect laser photocoagulation is applied for tumors that are present anterior to the equator, where slit lamp laser delivery may be difficult. in addition, reasonable accomplishment rates have been reported with the use of laser endophotocoagulation as an adjunct to vitreoretinal surgery[86]. following laser therapy of both small and large tumors, appearance of scarce intraretinal or preretinal hemorrhage on the treated tumor is common, but vitreous hemorrhage is rare. other reported complications of laser photocoagulation are subretinal fluid accumulation and exudative retinal detachment.[87] it is notable that for laser therapy, sessile masses are more suitable than very nodular ones, and exudation, preexisting hemorrhage, and epiretinal fibrosis may have a negative effect on proper laser treatment. in addition, practicability and usefulness of therapy depends on a number of issues such as tumor location, grade of exudation, presence of retinal detachment, associated chorioretinal scarring, location relative to the position of any previous scleral buckling, the number and appearance of other viable tumors, concomitant retinal vascular alterations or vascular proliferation, and reaction to prior treatment(s). mccabe et al reported a large series of patients that had been treated with laser photocoagulation with variable functional results. they concluded that due to the absence of standardization of laser photocoagulation, the functional consequences were not comparable.[88] huang et al reported the individual tumoral response in a total of 39 retinal capillary hemangiomas using a 532-nm laser system[87]. rhs < 1 optic disc diameter were directly photocoagulated. for rhs > 1 disc diameter, the nourishing vessel was photocoagulated first, followed by multiple tumor bulk photocoagulations until tumor atrophy occurred. of all tumor bodies treated with photocoagulation, 82.4% were controlled at the last visit. the percentage of tumors treated with photocoagulation was 76.5%, which was similar to the rate (74%) reported by singh et al.[41, 87] cryotherapy although there are few reports about the efficiency of laser photocoagulation for huge rhs, according to the experience of the authors of this review, a substantial number of rhs in this size range are not destroyed even following several sessions of laser photocoagulation. along with laser therapy, trans-scleral cryotherapy can be effective for the destruction of these masses, even in the presence of simultaneous exudation, hemorrhage, or journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 87 von hippel-lindau disease; karimi et al fibrosis. similarly, singh et al reported that accompanied with laser photocoagulation, cryotherapy is the backbone of treatment for rhs > 1.5 mm in diameter and are placed anteriorly with subretinal fluid.[41] for more anterior tumors, cryotherapy may be applied trans-conjunctivally in the office setting, while for posteriorly located tumors, a conjunctival incision may be needed to provide proper placement of the cryo probe. numerous studies have shown cryotherapy effectiveness, particularly when rhs < 3.75 mm.[64, 71, 76–78] as described by welch, cryotherapy should be applied till the ice ball completely encloses the rh.[72] double freeze–thaw technique is usually used for cryotherapy. use of cryotherapy seems to be associated with a more post-treatment exudative response than the use of laser photocoagulation. radiotherapy external beam radiotherapy, proton beam radiotherapy,[89] and plaque radiotherapy[79] are additional modalities for large tumors (> 4.0 mm in diameter), which demonstrate poor response to cryotherapy and laser photocoagulation. although commonly used in the management of choroidal hemangioma, brachytherapy was not used for the treatment of rh until 1998.[90] kreusel and colleagues reported the use of ruthenium106 brachytherapy for treatment of 25 eyes.[79] the mean width of treated hemangiomas was 3.8 mm, the mean apex dose was 126 ± 36 gy, and the mean scleral contact dose was 518 ± 85 gy. dose was transported over five to seven days. finally, the authors reported destruction of 23 out of 25 masses with a single radiotherapy session. nine eyes showed post-radiation complication including severe visual acuity reduction, a persisting exudative retinal detachment, or a recurrent traction detachment. risk factors for these complications included pre-treatment exudative retinal detachment and tumor size > 3.75 mm. it is recommended to restrict the use of brachytherapy to moderately sized rhs < 3.75 mm without exudative retinal detachment. in singh’s series, a total of four extrapapillary rhs with a mean size of 4.5 mm (3–6 mm) were treated with iodine 125 plaque, delivering an average apical dose of 34.8 gy.[41] for the first time, palmer and gragoudas successfully treated one patient with a juxtapapillary hemangioma with proton beam therapy.[89] sixteen years later, the report of seibel et al in 2014, described the treatment of a series of eight patients with symptomatic retinal papillary capillary hemangioma with proton beam therapy.[91] this series of progressive stages of papillary hemangioma demonstrated an acceptable anatomic outcome after proton beam therapy. however, poor early visual acuity attributable to central exudation and long persisting macular edema compromised the final visual outcome. the authors advise that even in those patients ineffectively treated with laser photocoagulation or pdt, exudation may entirely resolve when proton beam therapy is used as a secondary treatment. although proton beam therapy is a therapeutic option in the treatment of retinal papillary hemangioma, according to these findings, the treatment will remain challenging. not widely used, application of external beam radiation has been pronounced in advanced cases without favorable long-term consequence.[92] transpupillary thermotherapy transpupillary thermotherapy (ttt) has an uncertain role in the treatment of rhs. there are limited experiences in the treatment of vhl with this modality. parmar in 2000 and singh in 2002 reported treatment of juxtapapillary rhs with trans-pupillary thermotherapy in one and three patients, respectively.[93] in the first case, ttt caused an improvement in visual acuity from counting fingers to 6/24 and an obvious decline in exudates surrounding the hemangioma. however, in three patients in the second study, there was no apparent effect in two cases, although, in the third patient, it caused whole fibrosis of the juxtapapillary hemangioma associated with concomitant optic atrophy. photodynamic therapy (pdt) pdt is increasingly used for the treatment of rh, mainly for large tumors or juxtapapillary hemangiomas. studies using verteporfin pdt for both juxtapapillary and peripheral rh have revealed diverse anatomical and functional 88 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 von hippel-lindau disease; karimi et al conclusions.[94] schmidt-erfurth et al, in a prospective non-comparative case series, reported that pdt is effective in reducing tumor dimension and exudative activity of optic disc head hemangiomas.[82] a study reported the effect of pdt on four eyes with juxtapapillary rh. two eyes was treated by full pdf while two other eyes was treated by half pdt. tumor regression was observed in two eyes while no change was remarked in tumor size in other eyes.[94] the study showed that pdt can be effective in decreasing macular edema associated with rh, but this does not constantly correspond with an enhancement of visual acuity, particularly for juxtapapillary tumors. in a retrospective analysis of all patients with rh treated with pdt between 2003 and 2010,[95] it was concluded that the response of rhs to pdt is unpredictable; however, pdt may be used in juxtapapillary tumors where radiotherapy or cryotherapy is expected to result in simultaneous visual loss. recently, in huang’s study,[87] it was shown that good long-term vision outcomes were acquired in some peripheral rh cases after treatment; worsening of vision was detected in other cases even when the lesion regressed or was stable, and complications such as macular edema and exudates were resolved. in the latter study, it is suggested that pdt should be recommended for rh if available, but it is clear that therapies that are more effective are required for difficult rh cases, including juxtapapillary capillary hemangiomas and those with exudative retinal detachment or macular edema. in addition, the authors of this review have not found pdt to be effective enough to be used routinely. surgical excision of extrapapillary rhs as mentioned before, there are significant risks and low success rates of ablation in very large rhs. because of that, surgical excision of rhs during vitrectomy is sometimes employed. in addition, vitreoretinal intervention is frequently essential for larger rhs complicated by rhegmatogenous or tractional retinal detachment.[41] in a retrospective case series of three patients,[96] tumors 7 mm to 9 mm in diameter were removed via internal en bloc surgical resection using a bimanual technique. according to patients’ favorable outcomes, the authors suggested that surgical resection is a choice for those with large rhs. gaudric and colleagues reported a case series of 23 eyes that underwent vitreoretinal surgery for progressive ocular vhl disease, in which 14 eyes received cryotherapy or laser endophotocoagulation as adjunct to vitrectomy and the other 9 eyes had surgical removal of rhs.[86] for the nine eyes undergoing rh excision, a mean of two operations was needed, and eight out of nine eyes had an attached retina six months following the surgery. however, nvg and new tumor development occurred in four eyes between four and eight years after the rh excision, and visual acuity in remaining eyes was poor (20/320 or worse). the authors of the study claimed that vitreoretinal surgery is an effective treatment for severe vhl retinal hemangiomas, as in most cases, surgery enhanced or extended visual function. however, we believe that the combination of high rate of rh recurrence and post-surgery proliferative vitreoretinopathy restricts the accomplishment of this approach. new concepts in ocular vhl disease treatment anti-vegf therapy observation of the extremely vascularized nature of lesions in vhl disease led to a hypothesis that vegf, a hif-inducible protein and potent mediator of angiogenesis and vascular permeability, might be central in rhs progression, and there are numerous lines of evidence fingering vegf expression in the pathogenesis of vhl disease. vegf protein levels are raised in specimens from renal carcinomas demonstrating mutations of vhl.[97–99] anti-vegfs decrease the amount of intraretinal edema and bleed, thereby reducing the size of the lesion and the nourishing vessels. anti-vegfs have been displayed to accelerate the clearance of hemorrhages and exudation, which leads to the improvement of visual acuity along with diminished probabilities of re-bleeding.[100] in a retrospective interventional case series,[101] it was shown that intravitreal anti-vegf agents, unaided or in combination with other treatment modalities, may recover visual acuity, but additional trials assessing the dose, the quantity of injections, and the route of administration will be essential in evolving antiangiogenic therapies for rh. earlier, in one prospective study, dahr and coworkers assessed intravitreous pegaptanib sodium (3 mg) in five journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 89 von hippel-lindau disease; karimi et al patients manifesting juxtapapillary or extrapapillary rh.[102] pegaptanib sodium was administered every six weeks for at least six injections, and two of five patients finished the course and one year of follow-up. these two patients experienced a reduction in exudation, but no alteration in dimensions of the tumors. the other three patients demonstrated advancement of ocular disease and did not finish the course of treatment. in another interventional case series, wong et al evaluated the effect of intravitreal ranibizumab in five patients with retinal hemangiomas not responsive to standard treatments.[103] ranibizumab (0.5 mg) was administrated every one month for six months, with supplementary treatment through 12 months. participants received an average of 10 injections over a mean of 47 weeks. visual acuity declined by nine letters and there was no consistent reduction in rh tumor size or improvement in exudation. recently, agarwal et al[100] reported a case with rh located in the perifoveal region treated with two monthly intravitreal injections of bevacizumab followed by laser photocoagulation of feeder arterioles. this combination therapy resulted in a resolution of exudation, bleeding, and macular edema with improvement in visual acuity. intravitreal propranolol the therapeutic effect of intravitreal propranolol on retinal capillary hemangioma was reported in a patient with vhl. no short-term adverse effects except a mild transient inflammatory response were observed in this case report.[104] fluorescein leakage was decreased from the rhs located on the optic nerve head and in the inferonasal retinal periphery one month after the second intravitreal injection of propranolol. decrease of the hemangioma vascularity and augmentation of its fibrosis associated with the attenuation of the feeder vessel were observed. electroretinogram done one month after the first injection revealed no retinal toxicity. treatment of juxtapapillary rhs reduction of visual acuity, visual field loss, and development of central scotomas have limited the ablative therapies in managing juxtapapillary hemangiomas. according to findings of multiple studies mentioned earlier, reduced visual function has been associated with thermal laser photocoagulation.[105] on the other hand, pdt with verteporfin, which seems to have a safer profile than laser photocoagulation, has demonstrated incomplete success and fairly varied results.[82, 106] in a retrospective case series in 2000,[105] it was claimed that close follow-up and multiple treatments with argon laser are probably the best therapeutic approach, as if left untreated, papillary angiomatous lesions may evolve to exudative retinal detachment with severe visual acuity decreases. given these considerations, asymptomatic juxtapapillary rhs are usually observed with the hope that some lesions remain relatively static for long periods. it is believed that exudation may wax and wane and can remain compatible with good vision unless the central macula becomes chronically affected. in the absence of safe ablative choices, treatment is typically limited to alleviating the exudation affecting vision. pharmacotherapy using corticosteroids or vegf antagonists, proton beam therapy, and pdt may decrease exudation in some patients, but risks of therapy must be carefully evaluated, and success is often limited.[91, 102, 103] treatment of retinal vascular proliferation as mentioned earlier in the clinical manifestations section, a series of vhl patients have been described with an infrequent retinal proliferation varying in natural history, phenotype, and treatment.[54] they do not appear to carry the equal risk of vitreous hemorrhage or traction retinal detachment as neovascularization in other ischemic retinopathies, and they sometimes regress spontaneously. when they grow large to be more contractile due to fibrosis adjacent to the fovea, they can reduce visual acuity. it is essential to distinguish these lesions from rhs. retinal vascular proliferation does not typically cause exudation and does not regress easily in response to laser photocoagulation, in part due to its epiretinal situation. in cases of recognized progression, these lesions may be effectively addressed by excision with vitrectomy and membrane peeling.[54] summary rh is a benign vascular tumor of the neurosensory retina or optic disc that sometimes appears as a 90 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 von hippel-lindau disease; karimi et al sporadic lesion, but classically manifests as one or more tumors in the setting of vhl disease. referral of a patient with rh for clinical and genetic testing for vhl disease may be lifesaving, given the deadly nature of manifestations such as cns hemangioblastoma and rcc, and given the profits of surveillance and early treatment in affected individuals. other essential constituents of ophthalmologic management include suitable surveillance of patients with vhl disease for growth or development of rhs and retinal vascular proliferation. rhs developing in proximity to the optic disc exhibit a specific challenge, because they are normally not safe to abolish using traditional ablative procedures. improved knowledge of the molecular pathology of vhl disease presents possibility for development of non-ablative therapies to stop growth or accelerate the regression of rh in this condition. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. venkatesh p, takkar b. proposed classification system for retinal capillary angiomatosis. ophthal res 2019;61:115– 119. 2. resche f, moisan jp, mantoura j, de kersaint-gilly a, andre mj, perrin-resche i, et al. haemangioblastoma, haemangioblastomatosis, and von hippel-lindau disease. adv tech stand neurosurg 1993;20:197–304. 3. jesberg do, spencer wh, hoyt wf. incipient lesions of von hippel-lindau disease. arch ophthalmol 1968;80:632–640. 4. webster ar, maher er, bird ac, gregor zj, moore at. a clinical and molecular genetic analysis of solitary ocular angioma. ophthalmology 1999;106:623–629. 5. niemela m, lemeta s, sainio m, rauma s, pukkala e, kere j, et al. hemangioblastomas of the retina: impact of von hippel-lindau disease. invest ophthalmol vis sci 2000;41:1909–1915. 6. lasave af, deromedis p. solitary retinal capillary hemangioma in a patient with bilateral chorioretinal coloboma. retin cases brief rep 2017;13: 320–323. 7. shields ja, shields cl, deglin e. retinal capillary hemangioma in marshall-stickler syndrome. am j ophthalmol 1997;124:120–122. 8. varshney n, kebede aa, owusu-dapaah h, lather j, kaushik m, bhullar js. a review of von hippel-lindau syndrome. j kidney cancer vhl 2017;4:20–29. 9. lonser rr, glenn gm, walther m, chew ey, libutti sk, linehan wm, et al. von hippel-lindau disease. lancet 2003;361:2059–2067. 10. maher er, iselius l, yates jr, littler m, benjamin c, harris r, et al. von hippel-lindau disease: a genetic study. j med genet 1991;28:443–447. 11. binderup ml, jensen am, budtz-jorgensen e, bisgaard ml. survival and causes of death in patients with von hippel-lindau disease. j med genet 2017;54:11–18. 12. chou a, toon c, pickett j, gill aj. von hippel-lindau syndrome. front horm res 2013;41:30–49. 13. melmon kl, rosen sw. lindau’s disease. review of the literature and study of a large kindred. am j med 1964;36:595–617. 14. seizinger br, rouleau ga, ozelius lj, lane ah, farmer ge, lamiell jm, et al. von hippel-lindau disease maps to the region of chromosome 3 associated with renal cell carcinoma. nature 1988;332:268–269. 15. latif f, tory k, gnarra j, yao m, duh fm, orcutt ml, et al. identification of the von hippel-lindau disease tumor suppressor gene. science1993;260:1317–1320. 16. gossage l, eisen t, maher er. vhl, the story of a tumour suppressor gene. nat rev cancer 2015;15:55–64. 17. hascoet p, chesnel f, jouan f, le goff c, couturier a, darrigrand e, et al. the pvhl172 isoform is not a tumor suppressor and up-regulates a subset of protumorigenic genes including tgfb1 and mmp13. oncotarget 2017;8:75989–76002. 18. schoenfeld a, davidowitz ej, burk rd. a second major native von hippel-lindau gene product, initiated from an internal translation start site, functions as a tumor suppressor. proc natl acad sci usa 1998;95:8817–8822. 19. maxwell ph, wiesener ms, chang gw, clifford sc, vaux ec, cockman me, et al. the tumour suppressor protein vhl targets hypoxia-inducible factors for oxygendependent proteolysis. nature 1999;399:271–275. 20. min jh, yang h, ivan m, gertler f, kaelin wg, jr, pavletich np. structure of an hif-1alpha -pvhl complex: hydroxyproline recognition in signaling. science 2002;296:1886–1889. 21. semenza gl. regulation of mammalian o2 homeostasis by hypoxia-inducible factor 1. annu rev cell dev biol 1999;15:551–578. 22. bohling t, hatva e, kujala m, claesson-welsh l, alitalo k, haltia m. expression of growth factors and growth factor receptors in capillary hemangioblastoma. j neuropathol exp neurol. 1996;55:522–527. 23. reifenberger g, reifenberger j, bilzer t, wechsler w, collins vp. coexpression of transforming growth factoralpha and epidermal growth factor receptor in capillary hemangioblastomas of the central nervous system. am j pathol 1995;147:245–250. 24. carmeliet p, dor y, herbert jm, fukumura d, brusselmans k, dewerchin m, et al. role of hif-1alpha in hypoxiamediated apoptosis, cell proliferation and tumour angiogenesis. nature 1998;394:485–490. 25. kaelin wg, jr. molecular basis of the vhl hereditary cancer syndrome. nat rev cancer 2002;2:673–682. journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 91 von hippel-lindau disease; karimi et al 26. knudson ag, jr. mutation and cancer: statistical study of retinoblastoma. proc natl acad sci usa 1971;68:820–823. 27. sgambati mt, stolle c, choyke pl, walther mm, zbar b, linehan wm, et al. mosaicism in von hippel-lindau disease: lessons from kindreds with germline mutations identified in offspring with mosaic parents. am j hum genet 2000;66:84–91. 28. wu p, zhang n, wang x, li t, ning x, bu d, et al. mosaicism in von hippel-lindau disease with severe renal manifestations. clin genet 2013;84:581–584. 29. stolle c, glenn g, zbar b, humphrey js, choyke p, walther m, et al. improved detection of germline mutations in the von hippel-lindau disease tumor suppressor gene. hum mutation 1998;12:417–423. 30. zbar b, kishida t, chen f, schmidt l, maher er, richards fm, et al. germline mutations in the von hippel-lindau disease (vhl) gene in families from north america, europe, and japan. hum mutation 1996;8:348–357. 31. beroud c, joly d, gallou c, staroz f, orfanelli mt, junien c. software and database for the analysis of mutations in the vhl gene. nucleic acids res 1998;26:256–258. 32. czyzyk-krzeska mf, meller j. von hippel-lindau tumor suppressor: not only hif’s executioner. trends mol med 2004;10:146–149. 33. wittstrom e, nordling m, andreasson s. genotypephenotype correlations, and retinal function and structure in von hippel-lindau disease. ophthalmic genet 2014;35:91–106. 34. kurihara t, kubota y, ozawa y, takubo k, noda k, simon mc, et al. von hippel-lindau protein regulates transition from the fetal to the adult circulatory system in retina. development 2010;137:1563–1571. 35. chew ey. ocular manifestations of von hippel-lindau disease: clinical and genetic investigations. trans am ophthalmol soc 2005;103:495–511. 36. wong wt, agron e, coleman hr, reed gf, csaky k, peterson j, et al. genotype-phenotype correlation in von hippel-lindau disease with retinal angiomatosis. arch ophthalmol 2007;125:239–245. 37. mettu p, agron e, samtani s, chew ey, wong wt. genotype–phenotype correlation in ocular von hippel– lindau (vhl) disease: the effect of missense mutation position on ocular vhl phenotype. invest ophthalmol vis sci 2010;51:4464–4470. 38. schmid s, gillessen s, binet i, brandle m, engeler d, greiner j, et al. management of von hippel-lindau disease: an interdisciplinary review. oncol res treat 2014;37:761– 771. 39. choyke pl, glenn gm, walther mm, patronas nj, linehan wm, zbar b. von hippel-lindau disease: genetic, clinical, and imaging features. radiology 1995;194:629–642. 40. singh ad, shields cl, shields ja. von hippel-lindau disease. survey of ophthalmol 2001;46:117–142. 41. singh ad, nouri m, shields cl, shields ja, perez n. treatment of retinal capillary hemangioma. ophthalmology 2002;109:1799–1806. 42. wong wt, agron e, coleman hr, tran t, reed gf, csaky k, et al. clinical characterization of retinal capillary hemangioblastomas in a large population of patients with von hippel-lindau disease. ophthalmology 2008;115:181– 188. 43. webster ar, richards fm, macronald fe, moore at, maher er. an analysis of phenotypic variation in the familial cancer syndrome von hippel-lindau disease: evidence for modifier effects. am j hum genet 1998;63:1025–1035. 44. dollfus h, massin p, taupin p, nemeth c, amara s, giraud s, et al. retinal hemangioblastoma in von hippel-lindau disease: a clinical and molecular study. invest ophthalmol vis sci 2002;43:3067–3074. 45. whitson jt, welch rb, green wr. von hippel-lindau disease: case report of a patient with spontaneous regression of a retinal angioma. retina 1986;6:253–259. 46. webster ar, maher er, moore at. clinical characteristics of ocular angiomatosis in von hippel-lindau disease and correlation with germline mutation. arch ophthalmol 1999;117:371–378. 47. toy bc, agron e, nigam d, chew ey, wong wt. longitudinal analysis of retinal hemangioblastomatosis and visual function in ocular von hippel-lindau disease. ophthalmology 2012;119:2622–2630. 48. singh a, shields j, shields c. solitary retinal capillary hemangioma: hereditary (von hippel-lindau disease) or nonhereditary? arch ophthalmol 2001;119:232–234. 49. vail d. angiomatosis retinae, eleven years after diathermy coagulation. t am ophthalmol soc 1957;55:217–231; discussion 231–238. 50. shields cl, shields ja, barrett j, de potter p. vasoproliferative tumors of the ocular fundus. classification and clinical manifestations in 103 patients. arch ophthalmol 1995;113:615–623. 51. gass jd, braunstein r. sessile and exophytic capillary angiomas of the juxtapapillary retina and optic nerve head. arch ophthalmol 1980;98:1790–1797. 52. schmidt d, neumann hp. retinal vascular hamartoma in von hippel-lindau disease. arch ophthalmol 1995;113:1163–1167. 53. de jong pt, verkaart rj, van de vooren mj, majoorkrakauer df, wiegel ar. twin vessels in von hippellindau disease. am j ophthalmol 1988;105:165–169. 54. wong wt, yeh s, chan cc, kalina re, kinyoun jl, folk jc, et al. retinal vascular proliferation as an ocular manifestation of von hippel-lindau disease. arch ophthalmol 2008;126:637–643. 55. haining wm, zweifach ph. fluorescein angiography in von hippel-lindau disease. arch ophthalmol 1967;78:475– 479. 56. shechtman dl, gold as, mcintosh s, steen j, murray tg. atypical exophytic retinal capillary hemangioma and diagnostic modalities. optometry vision sci 2016;93:107– 112. 57. chin ek, trikha r, morse ls, zawadzki rj, werner js, park ss. optical coherence tomography findings of exophytic retinal capillary hemangiomas of the posterior pole. ophthal surg las im 2010:1–5. 58. turell me, singh ad. vascular tumors of the retina and choroid: diagnosis and treatment. mid east afr j ophthalmol 2010;17:191–200. 59. costa ra, meirelles rl, cardillo ja, abrantes ml, farah me. retinal capillary hemangioma treatment by indocyanine green-mediated photothrombosis. am j ophthalmol 2003;135:395–398. 92 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 von hippel-lindau disease; karimi et al 60. goes f, benozzi j. ultrasonography of haemangioma of the optic disc. bull soc belge ophtalmol 1980;190:87–97. 61. goldberg mf, duke jr. von hippel-lindau disease. histopathologic findings in a treated and an untreated eye. am j ophthalmol 1968;66:693–705. 62. nicholson dh, green wr, kenyon kr. light and electron microscopic study of early lesions in angiomatosis retinae. am j ophthalmol 1976;82:193–204. 63. grossniklaus he, thomas jw, vigneswaran n, jarrett wh, 3rd. retinal hemangioblastoma. a histologic, immunohistochemical, and ultrastructural evaluation. ophthalmology 1992;99:140–145. 64. annesley wh, jr, leonard bc, shields ja, tasman ws. fifteen year review of treated cases of retinal angiomatosis. trans sect ophthalmol am acad ophthalmol otolaryngol 1977;83:op446–op453. 65. chan cc, collins ab, chew ey. molecular pathology of eyes with von hippel-lindau (vhl) disease: a review. retina 2007;27:1–7. 66. chen s, chew ey, chan cc. pathology characteristics of ocular von hippel-lindau disease with neovascularization of the iris and cornea: a case report. j med case rep 2015;9:66. 67. hayden mg, gephart r, kalanithi p, chou d. von hippellindau disease in pregnancy: a brief review. j clin neurosc 2009;16:611–613. 68. frantzen c, kruizinga rc, van asselt sj, zonnenberg ba, lenders jw, de herder ww, et al. pregnancy-related hemangioblastoma progression and complications in von hippel-lindau disease. neurology 2012;79:793–796. 69. binderup ml, budtz-jorgensen e, bisgaard ml. new von hippel-lindau manifestations develop at the same or decreased rates in pregnancy. neurology 2015;85:1500– 1503. 70. schmidt d, natt e, neumann hp. long-term results of laser treatment for retinal angiomatosis in von hippel-lindau disease. eur j med res 2000;5:47–58. 71. bonnet m, garmier g. [treatment of retinal capillary angiomas of von hippel’s disease]. j fr d’ophtalmologie 1984;7:545–555. 72. lane cm, turner g, gregor zj, bird ac. laser treatment of retinal angiomatosis. eye 1989;3:33–38. 73. blodi cf, russell sr, pulido js, folk jc. direct and feeder vessel photocoagulation of retinal angiomas with dye yellow laser. ophthalmology 1990;97:791–795; discussion 6–7. 74. gorin mb. von hippel-lindau disease: clinical considerations and the use of fluorescein-potentiated argon laser therapy for treatment of retinal angiomas. semin ophthalmol 1992;7:182–191. 75. welch rb. von hippel-lindau disease: the recognition and treatment of early angiomatosis retinae and the use of cryosurgery as an adjunct to therapy. trans am ophthalmol soc 1970;68:367–424. 76. amoils sp, smith tr. cryotherapy of angiomatosis retinae. arch ophthalmol 1969;81:689–691. 77. shields ja. response of retinal capillary hemangioma to cryotherapy. arch ophthalmol 1993;111:551. 78. watzke rc. cryotherapy for retinal angiomatosis. a clinicopathologic report. arch ophthalmol 1974;92:399–401. 79. kreusel km, bornfeld n, lommatzsch a, wessing a, foerster mh. ruthenium-106 brachytherapy for peripheral retinal capillary hemangioma. ophthalmology 1998;105:1386–1392. 80. machemer r, williams jm, sr. pathogenesis and therapy of traction detachment in various retinal vascular diseases. am j ophthalmol 1988;105:170–181. 81. johnson mw, flynn hw, jr, gass jd. pars plana vitrectomy and direct diathermy for complications of multiple retinal angiomas. ophthal surg 1992;23:47–50. 82. schmidt-erfurth um, kusserow c, barbazetto ia, laqua h. benefits and complications of photodynamic therapy of papillary capillary hemangiomas. ophthalmology 2002;109:1256–1266. 83. aaberg tm, jr, aaberg tm, sr, martin df, gilman jp, myles r. three cases of large retinal capillary hemangiomas treated with verteporfin and photodynamic therapy. arch ophthalmol 2005;123:328–332. 84. mainster ma. wavelength selection in macular photocoagulation. tissue optics, thermal effects, and laser systems. ophthalmology 1986;93:952–958. 85. gass jd. treatment of retinal vascular anomalies. trans sect ophthalmol am acad ophthalmol otolaryngol 1977;83:op432–op42. 86. gaudric a, krivosic v, duguid g, massin p, giraud s, richard s. vitreoretinal surgery for severe retinal capillary hemangiomas in von hippel-lindau disease. ophthalmology 2011;118:142–149. 87. huang c, tian z, lai k, zhong x, zhou l, xu f, et al. longterm therapeutic outcomes of photodynamic therapybased or photocoagulation-based treatments on retinal capillary hemangioma. photomed laser surg 2018;36:10– 17. 88. mccabe cm, flynn hw, jr, shields cl, shields ja, regillo cd, mcdonald hr, et al. juxtapapillary capillary hemangiomas. clinical features and visual acuity outcomes. ophthalmology 2000;107:2240–2248. 89. palmer jd, gragoudas es. advances in treatment of retinal angiomas. int ophthalmol clin 1997;37:159–170. 90. sethi rv, macdonald sm, kim dy, mukai s. radiation therapy: retinal tumors. dev ophthalmol 2013;52:58–74. 91. seibel i, cordini d, hager a, riechardt ai, klein jp, heufelder j, et al. long-term results after proton beam therapy for retinal papillary capillary hemangioma. am j ophthalmol 2014;158:381–386. 92. cordes fc, schwartz a. angiomatosis retinae, von hippel’s disease, eleven years after irradiation. trans am ophthalmol soc 1952;50:227–239. 93. parmar dn, mireskandari k, mchugh d. transpupillary thermotherapy for retinal capillary hemangioma in von hippel-lindau disease. ophthal surg laser 2000;31:334– 336. 94. papastefanou vp, pilli s, stinghe a, lotery aj, cohen vm. photodynamic therapy for retinal capillary hemangioma. eye 2013;27:438–442. 95. hussain rn, jmor f, damato b, heimann h. verteporfin photodynamic therapy for the treatment of sporadic retinal capillary haemangioblastoma. photodiagnosis photodyn ther 2015;12:555–560. 96. schlesinger t, appukuttan b, hwang t, atchaneeyakasul lo, chan cc, zhuang z, et al. internal en bloc resection journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 93 von hippel-lindau disease; karimi et al and genetic analysis of retinal capillary hemangioblastoma. arch ophthalmol 2007;125:1189–1193. 97. na x, wu g, ryan ck, schoen sr, di’santagnese pa, messing em. overproduction of vascular endothelial growth factor related to von hippel-lindau tumor suppressor gene mutations and hypoxia-inducible factor-1 alpha expression in renal cell carcinomas. j urol 2003;170:588–592. 98. george dj, kaelin wg, jr. the von hippel-lindau protein, vascular endothelial growth factor, and kidney cancer. n engl j med 2003;349:419–421. 99. yang jc, haworth l, sherry rm, hwu p, schwartzentruber dj, topalian sl, et al. a randomized trial of bevacizumab, an anti-vascular endothelial growth factor antibody, for metastatic renal cancer. n engl j med 2003;349:427–434. 100. agarwal a, kumari n, singh r. intravitreal bevacizumab and feeder vessel laser treatment for a posteriorly located retinal capillary hemangioma. int ophthalmol 2016;36:747–750. 101. slim e, antoun j, kourie hr, schakkal a, cherfan g. intravitreal bevacizumab for retinal capillary hemangioblastoma: a case series and literature review. canadian j ophthalmol 2014;49:450–457. 102. dahr ss, cusick m, rodriguez-coleman h, srivastava sk, thompson dj, linehan wm, et al. intravitreal anti-vascular endothelial growth factor therapy with pegaptanib for advanced von hippel-lindau disease of the retina. retina 2007;27:150–158. 103. wong wt, liang kj, hammel k, coleman hr, chew ey. intravitreal ranibizumab therapy for retinal capillary hemangioblastoma related to von hippel-lindau disease. ophthalmology 2008;115:1957–1964. 104. karimi s, nikkhah h, ahmadieh h, safi s. intravitreal injection of propranolol for the treatment of retinal capillary hemangioma in a case of von hippel-lindau. retin cases brief rep 2018. 105. garcia-arumi j, sararols lh, cavero l, escalada f, corcostegui bf. therapeutic options for capillary papillary hemangiomas. ophthalmology 2000;107:48–54. 106. sachdeva r, dadgostar h, kaiser pk, sears je, singh ad. verteporfin photodynamic therapy of six eyes with retinal capillary haemangioma. acta ophthalmologica 2010;88:e334–e340. 94 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 letter to editor suicide and laser refractive surgery ali salimi, md, ms1; edsel ing, md, frcsc, mph, miad2; nicholas nianiaris, md, frcsc2 1department of ophthalmology, mcgill university, montreal, canada 2department of ophthalmology, university of toronto, toronto, canada orcid: ali salimi: https://orcid.org/0000-0003-0016-3478 edsel ing: https://orcid.org/0000-0003-0623-0934 j ophthalmic vis res 2020; 15 (3): 432–434 dear editor, laser refractive surgery (lrs) is one of the most frequently performed and successful operations in medicine with 96% postoperative patient satisfaction.[1] the possible sequelae of lrs include dry eye syndrome, blurred vision, glare, and night vision disturbance that are usually transient, but sometimes persist.[1] psychiatric complications such as psychosis, depression, suicidal ideation, attempted suicide or completed suicide (pds) following lrs are rare,[2] but generate marked media attention.[3, 4] given the tragedy of suicide after lrs, we reviewed the pubmed, embase, psycinfo, and google scholar databases from inception to october 2019 using keywords and mesh terms “laser refractive surgery” and “suicide”. we found the details of six patients, mainly young men, who completed suicide after lrs (table 1).[2, 4–7] the patient-support website lasikcomplications.com[8] lists approximately 34 patients with pds following lrs. from 2007 to 2018, approximately 8,230,000 lasik procedures correspondence to: edsel ing, md, frcsc, mph, miad. michael garron hospital, 650 sammon ave., k306, toronto, on. m4c 5m5, canada. e-mail: edinglidstrab@gmail.com received: 10-11-2019 accepted: 21-03-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7464 were performed in the united states.[9] given that, the incidence rate of completed suicide and pds in the us is estimated to be 7 per 100,000,000 individuals and 4 per 10,000,000 individuals undergoing lrs per annum, respectively. in the us, the age-adjusted suicide rate has increased by 33% over the last two decades, with 13.9 suicides per 100,000 individuals reported in 2018.[10] the proportion of patients with either completed suicide or pds after lrs is markedly lower than the proportion of suicide in the general population (p < 0.001). a thorough informed consent before lrs may help to exclude inappropriate surgical candidates. although it is impossible to list every possible outcome after lrs, and postoperative suicide is extremely rare, under a patient-centered standard of informed consent, the mandate to disclose the possibility of pds after lrs merits consideration. in addition, impaired vision and chronic pain were two of the five most common adverse outcomes resulting in legal disputes over duties to disclose treatment risks in a 2012 study from australia.[11] dry eye syndrome was associated with suicidal ideation at an odds ratio of 1.24 and lrs can exacerbate dry eye. psychologic and this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: salimi a, ing e, nianiaris n. suicide and laser refractive surgery. j ophthalmic vis res 2020;15:432–434. 432 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7464&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr suicide & lasik; salimi et al table 1. patients with completed suicide after lrs author, year age sex post-op eye pain blurred vision procedure latency between lrs and suicide clinical factors favaro, 2018[7] 54 m yes no prk 20 years reindl, 2018[4] 35 f yes yes smile 8 weeks fda, 2016 27 m yes yes prk enhancement 1 year veteran. post-traumatic stress disorder and depression van setten, 2015[2] 33 m no subjective lasik 8 weeks pre-existing psychologic instability. saw psychiatrist numerous times. lasikcomplications.com, 2011[8] 54 m yes yes lasik 1 year puglionesi, 2007[5] 28 m no yes lasik 6.5 years pre-operative dry eyes, mydriasis and depressive symptoms. m, male; f, female; lasik, laser-assisted in situ keratomileusis; lrs, laser refractive surgery; smile, small incision lenticule extraction; prk, photorefractive keratectomy; fda, u.s. food & drug administration. maude adverse event report: lasik 2016 https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfmaude/detail.cfm?mdrfoi__id=5434049 eye pain, postoperative dry eye pain. pharmacologic predispositions to post-lrs dissatisfaction include preoperative depression, the use of retinoic acid and antidepressants, antipsychotics or hypnotics with anticholinergic activity that may compound dry eye symptoms in patients with lrs.[12, 13] patients suffering from refractory pain after lasik can be referred to clinics specializing in dry eye syndrome, scleral contact lenses, or chronic pain. emergency psychiatric resources in addition to the hospital emergency room include psychiatry and suicide prevention hotlines. in conclusion, suicide following lrs is exceedingly rare. suicide is a complex mental health issue with a myriad of contributing factors, and to ascribe blame to lrs is a single cause fallacy. various publications have reported that: (i) patients with compensated pre-existing psychiatric disorders showed no increased incidence of pds postoperatively, (ii) mental health-related quality of life has been shown not to decrease after lrs, and (iii) lrs can improve psychological well-being.[14] acknowledgements none financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. keywords: depression; laser refractive surgery; lasik; suicide journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 433 https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfmaude/detail.cfm?mdrfoi__id=5434049 suicide & lasik; salimi et al references 1. eydelman m, hilmantel g, tarver m, hofmeister e, may j, hammel k, et al. symptoms and satisfaction of patients in the patient-reported outcomes with laser in situ keratomileusis (prowl) studies. jama ophthalmol 2017;135:13–22. 2. van setten g. suicide after excimer laser refractive surgery: on the importance of matching expectations. open j ophthalmol 2015;5:145–148. 3. w5. canadian ophthalmological society and canadian cornea, external disease and refactive surgery society statement to ctv news and w5. ctv news [internet]. 2019 april 5 [cited 2019 oct 14]. available from: https://www.ctvnews.ca/w5/canadian-ophthalmologicalsociety-and-canadian-cornea-external-disease-andrefactive-surgery-society-statement-to-ctv-news-andw5-1.4368071. 4. reindl j. detroit meteorologist jessica starr’s death by suicide puts focus on lasik safety. detroit free press [internet]. 2018 dec 18 [cited 2019 oct 13]. available from: https://www.usatoday.com/story/news/nation/2018/ 12/18/meteorologist-jessica-starr-death-suicide-lasikquestions/2346863002/. 5. puglionesi l. man commits suicide on haverford state grounds. delaware county times. 2007 july 6. 6. o’shea s, leffler b, willis-owen g. this week on 16:9 – may 28 – 20/20 hindsight. global news; 2011 august 5. 7. favaro a. painful side-effects from laser eye surgery linked to man’s suicide: family. ctv news [internet]. 2018 nov 28 [cited 2019 oct 13]. available from: https: //www.ctvnews.ca/health/painful-side-effects-from-lasereye-surgery-linked-to-man-s-suicide-family-1.4196890. 8. lasikcomplications.com. lasik complications. are you considering lasik, relex smile? [internet]. 2019 [cited 2019 oct 14]. available from: https://lasikcomplications. com/. 9. statista. number of lasik surgeries in the united states from 1996 to 2019 (in 1,000). [internet]. 2016 july 18 [cited 2019 oct 15]. available from: https://www.statista.com/ statistics/271478/number-of-lasik-surgeries-in-the-us/. 10. united health foundation. sucide in the united states, 2018 summary, america’s health rankings annual report. [internet]. 2018 [cited 2019 oct 14]. available from: https://www.americashealthrankings.org/explore/annual/ measure/suicide/state/all. 11. bismark m, gogos a, clark r, gruen r, gawande a, studdert d. legal disputes over duties to disclose treatment risks to patients: a review of negligence claims and complaints in australia. plos med 2012;9:e1001283. 12. cabral-macias j, garcia-de la rosa g, rodriguez-matilde d, vela-barrera i, ledesma-gil j, ramirez-miranda a, et al. pressure-induced stromal keratopathy after laser in situ keratomileusis: acute and late-onset presentations. j cataract refract surg 2018;44:1284–1290. 13. wong j, lan w, ong lm, tong l. non-hormonal systemic medications and dry eye. ocul surf 2011;9:212–226. 14. awwad s, alvarez-chedzoy n, bowman r, cavanagh h, mcculley j. quality of life changes after myopic wavefrontguided laser in situ keratomileusis. eye contact lens 2009;35:128–132. 434 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 https://www.ctvnews.ca/w5/canadian-ophthalmological-society-and-canadian-cornea-external-disease-and-refactive-surgery-society-statement-to-ctv-news-and-w5-1.4368071 https://www.ctvnews.ca/w5/canadian-ophthalmological-society-and-canadian-cornea-external-disease-and-refactive-surgery-society-statement-to-ctv-news-and-w5-1.4368071 https://www.ctvnews.ca/w5/canadian-ophthalmological-society-and-canadian-cornea-external-disease-and-refactive-surgery-society-statement-to-ctv-news-and-w5-1.4368071 https://www.ctvnews.ca/w5/canadian-ophthalmological-society-and-canadian-cornea-external-disease-and-refactive-surgery-society-statement-to-ctv-news-and-w5-1.4368071 https://www.usatoday.com/story/news/nation/2018/12/18/meteorologist-jessica-starr-death-suicide-lasik-questions/2346863002/ https://www.usatoday.com/story/news/nation/2018/12/18/meteorologist-jessica-starr-death-suicide-lasik-questions/2346863002/ https://www.usatoday.com/story/news/nation/2018/12/18/meteorologist-jessica-starr-death-suicide-lasik-questions/2346863002/ https://www.ctvnews.ca/health/painful-side-effects-from-laser-eye-surgery-linked-to-man-s-suicide-family-1.4196890 https://www.ctvnews.ca/health/painful-side-effects-from-laser-eye-surgery-linked-to-man-s-suicide-family-1.4196890 https://www.ctvnews.ca/health/painful-side-effects-from-laser-eye-surgery-linked-to-man-s-suicide-family-1.4196890 https://lasikcomplications.com/ https://lasikcomplications.com/ https://www.statista.com/statistics/271478/number-of-lasik-surgeries-in-the-us/ https://www.statista.com/statistics/271478/number-of-lasik-surgeries-in-the-us/ https://www.americashealthrankings.org/explore/annual/measure/suicide/state/all https://www.americashealthrankings.org/explore/annual/measure/suicide/state/all case report ciliary body seeding after pars plana transvitreal fine-needle aspiration biopsy of choroidal melanoma jideofor k. ndulue, md, msph; arman mashayekhi, md; carol l. shields, md wills eye hospital, ocular oncology service, philadelphia, pa, usa orcid: arman mashayekhi: https://orcid.org/0000-0002-1739-1322 abstract purpose: to report ciliary body seeding 20 years after pars plana transvitreal fine needle aspiration biopsy (fnab) of choroidal melanoma. case report: 67-year-old man with choroidal melanoma in left eye was previously managed with pars plana fnab using a 25-gauge needle followed by plaque radiotherapy. twenty years later, choroidal melanoma was regressed but there was a small flat focus of scleral pigment 3.0mm from the limbus at the fnab site. ultrasound biomicroscopy showed a contiguous ciliary body mass measuring 3.1mm in thickness. tumor seeding in the anterior chamber angle was noted inferiorly. these findings suggested melanoma recurrence along the needle tract. treatment was performed with iodine-125 radioactive plaque covering entire anterior segment and ciliary body recurrence. the tumor regressed to 2.2mm over one year. conclusion: pars plana transvitreal fnab of choroidal melanoma resulted in needle tract seeding in ciliary body and episcleral region 20 years later. keywords: choroid; ciliary body; extraocular extension; fine-needle aspiration biopsy; melanoma; seeding j ophthalmic vis res 2020; 15 (2): 252–255 introduction the diagnosis of uveal melanoma is usually based on ophthalmoscopic appearance and results of noninvasive tests, such as ultrasonography, transillumination, fluorescein angiography, and optical coherence tomography.[1, 2] fine-needle correspondence to: arman mashayekhi, md. ocular oncology service, 840 walnut st., suite 1440, philadelphia, pa 19107, usa. e-mail: arman_mash@yahoo.com received: 17-03-2019 accepted: 07-10-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i2.6744 aspiration biopsy (fnab) is occasionally performed to obtain a cytopathologic confirmatory diagnosis of suspected but atypical uveal melanoma.[1–3] moreover, over the past two decades, fnab has been used extensively for prognostication of uveal melanoma based on the results of cytogenetic testing and gene expression profiling. genetic testing has markedly increased the number of fnabs being performed in eyes with uveal melanoma.[1–3] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: ndulue jk, mashayekhi a, shields cl. ciliary body seeding after pars plana transvitreal fine-needle aspiration biopsy of choroidal melanoma. j ophthalmic vis res 2020;15:252–255. 252 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i2.6744&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr melanoma seeding after fna; ndulue et al fnab for choroidal melanoma, depending on the tumor location, can be performed safely with the direct transscleral approach into the tumor base or pars plana transvitreal approach into the tumor apex.[1–3] transient localized subretinal/preretinal or intravitreal hemorrhage at the tumor biopsy site is the most common complication of this procedure.[1–3] seeding along the needle tract is a rare complication.[4–7] here, we report a case of melanoma seeding along the needle tract in the ciliary body and extraocular tissue at the pars plana needle entrance site 20 years after pars plana transvitreal fnab of choroidal melanoma. case report a 67-year-old caucasian man was referred to the oncology service, wills eye hospital, for an evaluation of a peripheral iris elevation at the 9:00 o’clock position in the left eye (os). he had a history of choroidal melanoma os, confirmed using fnab and treated with iodine-125 plaque brachytherapy 20 years before referral. in the fnab, a 25-guage needle bent to an 85° angle was inserted via a 1.5mm partial-thickness scleral incision approximately 3.5 mm posterior to the limbus os along the 10:00 o’clock meridian. under indirect ophthalmoscopy, the needle was advanced through the vitreous cavity into the choroidal mass, and aspiration was performed. after aspiration, mild vitreous hemorrhage was noted, and hemostasis was achieved by applying direct pressure on the globe. a nylon suture was used to close the scleral incision site. cytological examination of the aspirate showed mixed spindle and epithelioid melanoma cells. on examination at our center, 20 years later, visual acuity was 20/20 in the right eye (od) and 20/25 os. intraocular pressure was 9 mmhg od and 11 mmhg os. the right eye was unremarkable. the os had a superonasal dilated episcleral blood vessel that perforated the sclera 3 mm from the limbus [figure 1(a)]. a flat, darkly pigmented episcleral mass, measuring 0.2 mm in the basal diameter was noted at the 10:00 o’clock meridian at the site of entry of the episcleral vessel [figure 1(a)]. the iris was elevated nasally along the 9:00 o’clock meridian. gonioscopy revealed confluent seeding in the inferior angle and multiple tiny seeds over the temporal and superior trabecular meshwork. funduscopy of the left eye revealed a flat retina with regressed choroidal melanoma measuring 8.0 × 6.0mm in basal dimensions and 1.9mm in thickness. the tumor was surrounded by an area of retinal pigment epithelium atrophy, and nasal retinal vessels had occlusion [figure 1(b)]. transillumination of the ciliary body revealed a superonasal dark shadow in the pars plana [figure 1(c)]. ultrasound biomicroscopy demonstrated a ciliary body mass of 3.1mm thickness at the site of the shadow, causing forward bulging of the peripheral iris [figure 1(d)]. based on these findings, a clinical diagnosis of ciliary body melanoma with anterior chamber invasion, angle seeding, and early extraocular extension was made. the patient was treated with a round 18mm custom-designed 125i radioactive plaque covering the entire anterior segment and delivering a dose of 7,000 cgy to the tumor apex at a depth of 4.0 mm. fnab of the ciliary body tumor for cytogenetic evaluation at the time of plaque placement showed a loss of 1p, disomy 3, gain of 6p, and disomy 8. at the one-year follow-up, choroidal melanoma had remained regressed at 1.9mm thickness, and ciliary body melanoma had regressed to 2.2mm thickness. the small extrascleral component remained stable with no evidence of orbital recurrence on clinical examination or orbital imaging. systemic evaluation showed no evidence of systemic metastasis. discussion fnab was initially used to obtain tissue for cytopathologic diagnosis of atypical tumors in the management of choroidal melanoma. recently, its use has expanded to cytogenetic prognostication of the metastatic risk.[1–3] therefore, the use of fnab for choroidal melanoma has increased at many centers. a recent study on reactions to and desire for prognostic testing for choroidal melanoma showed that even in the absence of prophylactic therapies to improve prognosis, 97% of respondents preferred knowing prognostic information.[8] a serious potential complication of fnab is extraocular tumor extension. nonetheless, several studies proved the safety of fnab for choroidal melanoma with the transscleral or pars plana transvitreal approach,[1–3] and cases of extraocular extension are rare.[4–7] schefler et al[4] reported extraocular extension in four patients journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 253 melanoma seeding after fna; ndulue et al figure 1. (a) dilated episcleral blood vessel superonasally perforates the sclera 3mm from the limbus with a pigmented spot of extrascleral extension (arrow). additional invasion of the peripheral iris is noted nasally. (b) fundus photograph of the same eye shows irradiated choroidal melanoma with surrounding retinal pigment epithelium atrophy. (c) transillumination demonstrates a dark shadow in the pars plana region (arrow). (d) ultrasound biomicroscopy shows a ciliary body mass measuring 3.1mm in thickness with bowing forward of the peripheral iris. with uveal melanoma, but three of them had undergone vitrectomy and/or open biopsy in addition to fnab. the interval between fnab and the detection of extraocular extension in their series ranged from five months to approximately nine years. caminal et al[5] reported epibulbar tumor seeding eight months after pars plana transvitreal fnab in one patient using a 25gauge needle and infusion. mashayekhi et al[6] reported one patient with extraocular extension of ciliochoroidal melanoma one and a half years after transscleral fnab using a 25-gaugeneedle without infusion. koch et al[7] reported pars plana seeding with localized extraocular extension 3.5 years after transretinal biopsy of choroidal melanoma using a 25-gauge vitrectomy probe followed by ruthenium-106 plaque radiotherapy. laboratory quantification of tumor seeding following fnab of the enucleated globes with uveal melanoma showed significantly fewer tumor cells in the needle tract of the pars plana transvitreal or translimbal approach compared to the transscleral approach.[9] other factors possibly associated with a higher risk of tumor seeding via the needle tract include a larger needle gauge, higher number of needles passing into the tumor, vitreous leakage through the scleral entrance site, manipulation of the needle within the tumor, and a higher number of viable malignant cells aspirated. additionally, fluid infusion into the vitreous cavity could theoretically increase the risk for tumor cell egress. immediate application of cryotherapy at the scleral entrance site as the needle is removed and application of radioactive plaque over the scleral entrance site could prevent tumor seeding.[4] the long interval of 20 years between fnab and the detection of ciliary body seeding in our case is an indication of the low-grade nature of the treated choroidal melanoma. in addition, the location of seeding in the ciliary body, a region hidden from 254 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 melanoma seeding after fna; ndulue et al direct view, contributed to the delay in detection of seeding. bosello et al reported delayed recurrence of uveal melanoma 45 years after treatment, possibly caused by the low malignant potential, tumor dormancy, and host immunity.[10] due to the lack of histopathology and molecular evidence, we cannot conclude that the ciliary body seed in our patient was similar to the original choroidal tumor. nevertheless, the possibility of a new ciliary body melanoma developing in the same eye as the choroidal melanoma exactly at the site of sclerotomy performed for fnab is low, supporting our belief that the tumor in the ciliary body was a seed from the original choroidal tumor. in summary, we report a rare case of fnabrelated needle tract seeding into the ciliary body with anterior chamber invasion and extraocular extension detected 20 years after pars plana transvitreal fnab of choroidal melanoma that was performed with a 25-gauge needle. long-term monitoring of all eyes with treated uveal melanoma is recommended, particularly at the scleral site of needle biopsy. financial support and sponsorship the study was supported the by eye tumor research foundation, philadelphia, pa (cls). the funders had no role in the design and conduct of the study, in the collection, analysis and interpretation of the data, and in the preparation, review, or approval of the manuscript. conflicts of interest there are no conflicts of interest. references 1. shields cl, mashayekhi a, shields ja. by sleight of hand, prognosis determined even for small choroidal melanoma. [commentary] jama ophthalmol 2018;136:488–489. 2. shields ja, shields cl, ehya h, eagle rc jr, de potter p. fine-needle aspiration biopsy of suspected intraocular tumors: the 1992 urwick lecture. ophthalmology 1993;100:1677–1684. 3. shields cl, say eat, hasanreisoglu m, saktanasate j, lawson bm, landy je, et al. personalized prognosis of uveal melanoma based on cytogenetic profile in 1059 patients over an 8-year period: the 2017 harry s. gradle lecture. ophthalmology 2017;124:1523–1531. 4. schefler ac, gologorsky d, marr bp, shields cl, zeolite i, dh abramson. extraocular extension of uveal melanoma after fine-needle aspiration, vitrectomy, and open biopsy. jama ophthalmol 2013;131:1220–1224. 5. caminal jm, sanz s, carreras m, isabel català, jorge arruga, guillermo roca. epibulbar seeding at the site of a transvitreal fine-needle aspiration biopsy. arch ophthalmol 2006;124:587–589. 6. mashayekhi a, lim rp, shields cl, eagle rc jr, shields ja. extraocular extension of ciliochoroidal melanoma after transscleral fine-needle aspiration biopsy. retin cases brief rep 2016;10:289–292. 7. koch kr, hishmi am, ortmann m, heindl lm. uveal melanoma cell seeding after transretinal tumor biopsy. ocul oncol pathol 2017;3:164–167. 8. beran tm, mccannel ta, stanton al, straatsma br, burgess bl. reactions to and desire for prognostic testing in choroidal melanoma patients. j genet couns 2009;18:265–274. 9. glasgow bj, brown hh, zargoza am, foos ry. quantitation of tumor seeding from fine needle aspiration of ocular melanomas. am j ophthalmol 1988;105:538–546. 10. bosello f, al-jamal rt, cohen vml. very late recurrence of iris melanoma: 45 years after treatment. melanoma res 2019. [epub ahead of print] journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 255 editorial the role of guidance and planning on safety of ophthalmic practice during the covid-19 pandemic saeid shahraz1, md, phd; seyed farzad mohammadi2, md, mph; sare safi3, phd 1institute for clinical research and health policy studies, tufts medical center, boston, massachusetts, usa 2translational ophthalmology research center, farabi eye hospital, tehran university of medical sciences, tehran, iran 3ophthalmic epidemiology research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran orcid: saeid shahraz:: https://orcid.org/0000-0003-4550-3843 j ophthalmic vis res 2020; 15 (3): 275–278 coronavirus disease 2019 (covid-19) caused by the severe acute respiratory syndrome coronavirus 2 (sars-cov-2) was reported for the first time in china in december 2019.[1] it has been spreading rapidly worldwide and has emerged as the most massive health crisis since world war ii.[2, 3] the world health organization (who) declared the sars-cov-2 outbreak as a pandemic on march 12, 2019.[4] the covid-19 pandemic is not only a health crisis but also has a significant impact on societies, economies, and progress rates toward the united nations’ sustainable development goals.[5] the eastern mediterranean region (emr) ranks third in the world in terms of the total number of confirmed cases among the six who regions.[6] iran, as one of the emr countries, has reported 217,724 confirmed cases and 10,239 deaths from february 19 to june 26, 2020 (figure 1).[2] a recently published meta-analysis reported that the risk of transmission is reduced by more than 75% through implementing three strategies by both healthcare workers and communities: at least a 1-m social distancing, use of a face masks (surgical or similar masks (12–16-layer cotton or gauze masks), n95 respirators or similar), and eye protection.[7] recently, the who has released interim guidance on the use of masks for avoiding transmission of covid19.[8] infected droplets can find their way into the ocular surfaces where the virus can replicate.[9] an overall pooled prevalence of ocular manifestations in patients with covid-19 was 5.5% in one report.[10] there is limited published evidence on the prevalence of ocular manifestations of covid-19 in iran.[11] in a case series including 43 patients in iran, reverse transcription-polymerase chain reaction (rt-pcr) on nasopharyngeal and tear samples indicated presence of viral material in 30% and 7% of cases, respectively. the nasopharyngeal rt-pcr results were indicative of the presence of the virus in all patients with positive tear rt-pcr results, which comprised a case with clinical conjunctivitis.[11] although the rate of ocular manifestations is low, protecting against viral transmission is vital in ophthalmology practice due to the proximity between the examiner and patients, the lengthy period of exposure during examinations, and direct contact with patient’s eye secretions.[12] many non-urgent ophthalmic services were ceased at the ophthalmology centers in iran, similar to other countries, during the early months of the pandemic to tackle the spread of covid19. government agencies, ophthalmology societies, and eye health centers have developed guidance and policy statements to reduce the risk of transmission on one hand and maintain continuity of eye care on the other.[13–19] these blueprints have included recommendations for modifying the clinical pathway and disinfecting protocols, initial screening, and necessary protective equipment for eye care providers, including ophthalmologists, optometrists, clinic/hospital managers, and staff. furthermore, triage for ophthalmic disorders and cessation of elective examinations, diagnostic procedures, and surgeries were addressed in the guidance.[13–18] in response to the covid-19 © 2020 journal of ophthalmic and vision research | published by knowledge e 275 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7445&domain=pdf&date_stamp=2019-07-17 editorial; shahraz figure 1. cumulative number of confirmed cases of covid-19 and death from february 2020 to june 2020 in iran. pandemic in iran, the knowledge management unit, ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, in collaboration with the iranian society of ophthalmology published a joint guidance in march 2020, which appears in this issue of the journal.[20] the ad hoc committee urged ophthalmologists to restrict non-emergent services and provide care for conditions such as retinal detachment, trauma, chemical burns, dangerously elevated intraocular pressure, and severe ocular infections. it recommended postponing elective surgeries and counsel patients using remote approaches. the use of face masks, goggles, gloves, and slit-lamp shields were emphasized for visiting urgent cases. infection control strategies, including handwashing, disinfecting ophthalmic examination equipment with 70% alcohol, and surfaces with bleach-based disinfectants were also recommended.[20] after leaving behind the first peak of the covid-19 infection, ophthalmology centers were reopened, and eye care services resumed to prevent sight-threatening eye disorders and to manage the backlog of postponed appointments.[21] new guidance was developed for the post-peak era, and existing recommendations were updated. naveed et al prepared guidance for modifying the ophthalmic workplace for the postpeak period.[22] the post-peak recommendation addressed different strategies, including engineering and administrative controls and protecting workers with personal protective equipment. the authors suggested tele-triage by a senior physician for urgent cases, minimizing face-to-face time in routine clinics, and limiting general anesthesia to absolutely necessary surgical cases.[22] the joint guidance was also updated to provide recommendations for protecting ophthalmic health workers and ophthalmology centers during the post-peak era. it now mandates physical distancing as well as requirements for protecting ophthalmologists and staff during surgeries. cataract surgery was considered as a semi-urgent operation that could be performed in cases prone to falls and subjects with significantly impaired vision.[20] eye health and prevention of blindness office of the center for non-communicable diseases control of the ministry of health and medical education issued an official point of view in late june. it offered detailed guidance for the public and health workers, in addition to eye health professionals during the covid-19 pandemic. it addresses ocular involvement by sars-cov-2 as well. 276 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 editorial; shahraz the who regional director for the emr notified a risk of an accelerated trend in the number of confirmed cases in emr countries as a consequence of easing restrictions.[23] estimations by the institute for health metrics and evaluation (ihme) also confirmed this trend.[24] therefore, to continue providing care for ophthalmic patients, it is crucial that ophthalmic care providers and staff follow the guidance strictly to reduce the risk of infection transmission from patients to medical care and vice versa. in summary, it seems that initial screening at the time of admission, mandating social distancing, washing hands, wearing face masks by healthcare providers and patients, use of slit lamp shields, and disinfecting the instruments are reasonable protective strategies recommended by various guidance. we have to consciously monitor the pandemic status, public health developments, and the evidence which emerges to tailor and update our control measures and eye care strategies. and we all know that the covid-19 pandemic, directly and indirectly, has affected medical care and will continue to transform it further in the coming decade. references 1. huang c, wang y, li x, ren l, zhao j, hu y, et al. clinical features of patients infected with 2019 novel coronavirus in wuhan, china. lancet 2020;395:497–506. 2. worldometer. covid-19 coronavirus pandemic. retrieved from: https://www.worldometers.info/coronavirus/. 3. undp. covid-19 pandemic humanity needs leadership and solidarity to defeat the coronavirus. retrieved from: https://www.undp.org/content/undp/en/home/ coronavirus.html. 4. who. who director-general’s opening remarks at the mission briefing on covid-19 march 12 2020covid. retrieved from: https://www.who.int/dg/speeches/detail/ who-director-general-s-opening-remarks-at-the-missionbriefing-on-covid-19---12-march-2020. 5. undp. covid-19 socio-economic impact. retrieved from: https://www.undp.org/content/undp/en/home/ coronavirus/socio-economic-impact-of-covid-19.html. 6. who. who coronavirus disease (covid-19) dashboard. retrieved from: https://covid19.who.int/. 7. chu dk, akl ea, duda s, solo k, yaacoub s, schünemann hj, et al. physical distancing, face masks, and eye protection to prevent person-to-person transmission of sars-cov-2 and covid-19: a systematic review and metaanalysis. lancet 2020;395:1973–1987. 8. who. advice on the use of masks in the context of covid19. retrieved from: https://www.who.int/publications/ i/item/advice-on-the-use-of-masks-the-communityduring-home-care-and-in-health-care-settings-in-thecontext-of-the-novel-coronavirus-(2019-ncov)-outbreak. 9. belser ja, rota pa, tumpey tm. ocular tropism of respiratory viruses. microbiol mol biol rev 2013;77:144– 156. 10. ulhaq zs, soraya gv. the prevalence of ophthalmic manifestations in covid-19 and the diagnostic value of ocular tissue/fluid. graefes arch clin exp ophthalmol 2020;258:1351–1352. 11. karimi s, arabi a, shahraki t, safi s. detection of severe acute respiratory syndrome coronavirus-2 in the tears of patients with coronavirus disease 2019. eye 2020;34:1220–1223. 12. euro times. update on covid-19 situation in belgium from dr. guy sallet. retrieved from: https://www.eurotimes.org/update-on-covid-19-situationin-belgium-from-dr-guy-sallet/. 13. the royal college of ophthalmologists. covid-19 clinical guidance for ophthalmologists. retrieved from: www.rcophth.ac.uk/2020/03/covid-19-update-andresources-for-ophthalmologists/. 14. american academy of ophthalmologists (aao). coronavirus and eye care. retrieved from: https://www. aao.org/headline/alert-important-coronavirus-context. 15. hu vh, watts e, burton m, kyari f, mathenge c, heidary f, et al. protecting yourself and your patients from covid-19 in eye care. comm eye health 2020;33:s1–s6. 16. international council of ophthalmology (ico). coronavirus information for ophthalmologists. retrieved from: www.icoph.org/news/news_detail/598/coronavirusinformation-for-ophthalmologists.html. 17. world council of optometry. statement regarding covid 19. retrieved from: https://worldcouncilofoptometry.info/ wco-statement-concerning-covid-19. 18. american academy of ophthalmologists (aao). list of urgent and emergent ophthalmic procedures. retrieved from: www.aao.org/headline/list-of-urgent-emergentophthalmic-procedures. 19. jacobson pd. transforming clinical practice guidelines into legislative mandates: proceed with abundant caution. jama 2008;299:208–210. 20. rajavi z, safi s, mohammadzadeh m. guidance for ophthalmologists and ophthalmology centers during the covid-19 pandemic. j ophthalmic vis res 2020;15:438– 441. 21. the international agency for the prevention of blindness (iapb). wha 73 – covid-19, eye health and iapb statement on behalf of the global eye care sector. retrieved from: https://www.iapb.org/news/wha-73covid-19-eye-health-and-iapb-statement-on-behalf-ofthe-global-eye-care-sector/. 22. naveed h, leung v, zarei-ghanavati m, leak c, liu c. ophthalmic workplace modifications for the post-covid era. j ophthalmic vis res 2020;15:400–407. 23. who. statement by who’s regional director dr ahmed al-mandhari on the covid-19 pandemic in the region. retrieved from: http://www.emro.who.int/media/news/ journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 277 https://www.worldometers.info/coronavirus/. https://www.undp.org/content/undp/en/home/coronavirus.html. https://www.undp.org/content/undp/en/home/coronavirus.html. https://www.who.int/dg/speeches/detail/who-director-general-s-opening-remarks-at-the-mission-briefing-on-covid-19---12-march-2020. https://www.who.int/dg/speeches/detail/who-director-general-s-opening-remarks-at-the-mission-briefing-on-covid-19---12-march-2020. https://www.who.int/dg/speeches/detail/who-director-general-s-opening-remarks-at-the-mission-briefing-on-covid-19---12-march-2020. https://www.undp.org/content/undp/en/home/coronavirus/socio-economic-impact-of-covid-19.html. https://www.undp.org/content/undp/en/home/coronavirus/socio-economic-impact-of-covid-19.html. https://www.who.int/publications/i/item/advice-on-the-use-of-masks-the-community-during-home-care-and-in-health-care-settings-in-the-context-of-the-novel-coronavirus-(2019-ncov)-outbreak https://www.who.int/publications/i/item/advice-on-the-use-of-masks-the-community-during-home-care-and-in-health-care-settings-in-the-context-of-the-novel-coronavirus-(2019-ncov)-outbreak https://www.who.int/publications/i/item/advice-on-the-use-of-masks-the-community-during-home-care-and-in-health-care-settings-in-the-context-of-the-novel-coronavirus-(2019-ncov)-outbreak https://www.who.int/publications/i/item/advice-on-the-use-of-masks-the-community-during-home-care-and-in-health-care-settings-in-the-context-of-the-novel-coronavirus-(2019-ncov)-outbreak https://www.eurotimes.org/update-on-covid-19-situation-in-belgium-from-dr-guy-sallet/. https://www.eurotimes.org/update-on-covid-19-situation-in-belgium-from-dr-guy-sallet/. www.rcophth.ac.uk/2020/03/covid-19-update-and-resources-for-ophthalmologists/. www.rcophth.ac.uk/2020/03/covid-19-update-and-resources-for-ophthalmologists/. https://www.aao.org/headline/alert-important-coronavirus-context. https://www.aao.org/headline/alert-important-coronavirus-context. www.icoph.org/news/news_detail/598/coronavirus-information-for-ophthalmologists.html. www.icoph.org/news/news_detail/598/coronavirus-information-for-ophthalmologists.html. https://worldcouncilofoptometry.info/wco-statement-concerning-covid-19 https://worldcouncilofoptometry.info/wco-statement-concerning-covid-19 www.aao.org/headline/list-of-urgent-emergent-ophthalmic-procedures. www.aao.org/headline/list-of-urgent-emergent-ophthalmic-procedures. https://www.iapb.org/news/wha-73-covid-19-eye-health-and-iapb-statement-on-behalf-of-the-global-eye-care-sector/. https://www.iapb.org/news/wha-73-covid-19-eye-health-and-iapb-statement-on-behalf-of-the-global-eye-care-sector/. https://www.iapb.org/news/wha-73-covid-19-eye-health-and-iapb-statement-on-behalf-of-the-global-eye-care-sector/. http://www.emro.who.int/media/news/statement-by-regional-director-dr-ahmed-al-mandhari-on-covid-19.html. http://www.emro.who.int/media/news/statement-by-regional-director-dr-ahmed-al-mandhari-on-covid-19.html. editorial; shahraz statement-by-regional-director-dr-ahmed-al-mandharion-covid-19.html. 24. ihme. covid-19 projections. retrieved from: https:// covid19.healthdata.org/iran-(islamic-republic-of). this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7445 how to cite this article: shahraz s, mohammadi sf, safi s. the role of guidance and planning on safety of ophthalmic practice during the covid19 pandemic. j ophthalmic vis res 2020;15:275–278. 278 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 http://www.emro.who.int/media/news/statement-by-regional-director-dr-ahmed-al-mandhari-on-covid-19.html. http://www.emro.who.int/media/news/statement-by-regional-director-dr-ahmed-al-mandhari-on-covid-19.html. http://www.emro.who.int/media/news/statement-by-regional-director-dr-ahmed-al-mandhari-on-covid-19.html. https://covid19.healthdata.org/iran-(islamic-republic-of) https://covid19.healthdata.org/iran-(islamic-republic-of) https://knepublishing.com/index.php/jovr case report ulcerative squamous eyelid papilloma: a rare presentation sharma reena1, md, dnb; krishna mani1, md; sharma brahma deo1, ms; khan asma2, mbbs 1department of ophthalmology, up university of medical sciences, saifai, etawah, uttar pradesh, india 2department of pathology, up university of medical sciences, saifai, etawah, uttar pradesh, india orcid: sharma reena: https://orcid.org/xxx abstract purpose: to highlight the importance of histopathological evaluation of a lid mass to prognosticate the disease. we report a case of ulcerative squamous cell papilloma with clinical features suggesting malignancy. case report: a 65-year-old man presented with a rapidly enlarging mass in the left upper eyelid, with clinical features suggesting a squamous cell carcinoma. however, a repeat histopathological examination showed no malignant cells. the patient was diagnosed with squamous cell papilloma. he was followed-up for 30 months and no recurrence was observed. no such case has previously been reported in the literature. conclusion: this report highlights the need for histopathological examination of all eyelid lesions to enable surgeons to prognosticate the disease. keywords: carcinoma; eyelid; histopathological; squamous papilloma j ophthalmic vis res 2019; 14 (4): 509–512 correspondence to: dr reena sharma, md, dnb, house-199, civil lines, etawah-206001, u.p., india. e-mail: drreenasharma98@gmail.com received: 06-12-2018 accepted: 01-06-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i4.5463 introduction eyelid papilloma is one of the most common eyelid tumors and typically occurs in middle-aged or elderly patients.[1, 2] these tumors are papillomatous and appear as a smooth, rounded, or pedunculated elevation of abnormal tissue. squamous papilloma may mimic other benign eyelid lesions with the same appearance, and malignant skin lesions, particularly squamous cell carcinoma. feeder vessels, hyperkeratosis, leukoplakic plaque, keratinization, scaling, and ulceration are considered as features suggestive of malignancy. nevertheless, atypical malignant behavior of a benign eyelid lesion is unusual. herein, we report the case of a lesion presenting with typical malignancy features that was histopathologically found to be benign. to the best of our knowledge and based on a review of the literature, ulcerative squamous papilloma of the eyelid has not been reported thus far. case report a 65-year-old man presented with a mass on the left upper eyelid that had been progressively this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: reena s, mani k, deo sb, asma k. ulcerative squamous eyelid papilloma. j ophthalmic vis res 2019;14:509–512. © 2019 journal of ophthalmic and vision research | published by knowledge e 509 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5463&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr ulcerative squamous eyelid papilloma; reena et al figure 1. (a) suspected squamous cell carcinoma in the left upper eyelid. (b) enlarged view of the same mass. figure 2. (a) patient after mass excision and first stage cutler–beard surgery. (b) patient after second stage cutler–beard surgery (two weeks). figure 3. histopathological section showing papillomatous features and total absence of atypia. 510 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 ulcerative squamous eyelid papilloma; reena et al enlarging for the past seven years. a pedunculated growth measuring 20 × 12 mm was observed involving the medial half of the eyelid. the mass was huge, with superficial ulceration and a red base with sharply defined indurated borders. it was pedunculated, such that the base of the mass was smaller than its superficial appearance. he was diagnosed with papilloulcerative squamous cell carcinoma [figure 1]. the mass was excised with a 4-mm free margin, creating a defect measuring 8 × 6 cm, which was reconstructed using a cutler– beard flap. the flap was prepared from the inferior eyelid below the tarsus to ensure compatibility with the superior eyelid defect by making a horizontal incision 4 mm below the lid margin. the bridge flap was advanced to the superior eyelid below the eyelash margin. the anterior and posterior lamellae were sutured separately to the levator muscle and the rest of the orbicularis muscle by placing the flap on the defect area [figure 2(a)]. second stage surgery was performed four weeks postoperatively to separate the superior and inferior eyelids and reconstruct the upper lid margin [figure 2(b)]. histopathological examination revealed no atypia; rather, the lesion was composed of papillae with vascularized connective tissue covered by acanthotic epithelium. hence, it was diagnosed as ulcerative squamous cell papilloma [figure 3]. a repeat examination with repeat tissue cuts and histopathology slide preparation performed by another pathologist did not change the diagnosis. the patient was followed-up for 30 months and no recurrence was observed. discussion ocular papillomas favor sites where the epithelium undergoes transition. they can occur at either the limbus or the eyelid margin. papillomas typically arise from the basal cells but, rarely, may form through the proliferation of squamous cells. squamous cell papilloma is the most common benign lesion of the eyelid, constituting 13–19.5% of benign eyelid tumors.[3, 4] for squamous cell papilloma, having surface ulceration and indurated margins is not unusual. in the present case, the clinical appearance suggested malignancy, but histopathology changed the diagnosis. kersten et al reported that the majority of the initially benign lesions were found to be malignant on repeat histopathology.[5] our case revealed an absence of atypia on repeat examination. furthermore, the patient was followed-up for two and a half years with no recurrence. although rare, case reports of surface pigmentation and hyperkeratosis in squamous papilloma exist.[6, 7] this also emphasizes the need for histopathological examination of all eyelid lesions to enable surgeons to prognosticate the disease and advise patients accordingly. the gold standard treatment for eyelid carcinomas is surgical resection with clear margins followed by reconstructive procedures. cutler– beard flap surgery is a successful procedure for superior eyelid tumors with wide tissue loss.[8, 9] the long-time closure of the eyelids, and the need for a second surgery are the major disadvantages of this procedure. the patient gave consent for reproduction of the photographs in the journal. declaration of patient consent the authors certify that they have obtained all appropriate patient consent forms. in the form the patient has given his consent for his images and other clinical information to be reported in the journal. the patient understand that his name and initial will not be published and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed. financial support and sponsorship nil. conflicts of interest there is no conflict of interest. references 1. deprez m, uffer s. clinicopathological features of eyelid skin tumors. a retrospective study of 5504 cases and review of literature. am j dermatopathol 2009;31:256– 262. 2. coroi mc, roşca e, muţiu g, coroi t, bonta m. eyelid tumors: histopathological and clinical study performed in county hospital of oradea between 2000-2007. rom j journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 511 ulcerative squamous eyelid papilloma; reena et al morphol embryol 2010;51:111–115. 3. bagheri a, tavakoli m, kanaani a, zavareh rb, esfandiari h, aletaha m, et al. eyelid masses: a 10-year survey from a tertiary eye hospital in tehran. middle east afr j ophthalmol 2013;20:187–192. 4. asproudis i, sotiropoulos g, gartzios c, raggos v, papoudou-bai a, ntountas l, et al. eyelid tumors at the university eye clinic of ioannina, greece: a 30year retrospective study. middle east afr j ophthalmol 2015;22:230–232. 5. kersten rc, ewing-chow d, kulwin dr, gallon m. accuracy of clinical diagnosis of cutaneous eyelid lesions. ophthalmology 1997;104:479–484. 6. d’hermies f, morel x, bourgade jm, meyer a, behar cohen f, dighiero p, et al. [hyperkeratosis papilloma of the eyelid. an anatomic clinical case]. j fr ophtalmol 2001;24:558–561. 7. mathur a, mehrotra ml, gupta a. pigmented squamous cell papilloma–a case report. indian j ophthalmol 1987;35:158–159. 8. rahmi d, mehmet b, ceyda b, sibel o. management of the large upper eyelid defects with cutler-beard flap. j ophthalmol 2014;2014:424567. 9. fischer t, noever g, langer m, kammer e. experience in upper eyelid reconstruction with the cutler-beard technique. ann plast surg 2001;47:338–342. 512 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 case report amniotic membrane patch graft in management of double chamber after deep anterior lamellar keratoplasty mehran zarei-ghanavati, md, fico; mahmood davoodabadi, md; ahad shahbazi, md translational ophthalmology research center, farabi eye hospital, tehran university of medical sciences, tehran, iran orcid: mehran zarei-ghanavati: https://orcid.org/0000-0002-0679-8055 abstract purpose: to describe a novel technique of amniotic membrane (am) patch graft in the management of double chamber treatment after big-bubble deep anterior lamellar keratoplasty (dalk). case report: a 35-year-old male patient with advanced keratoconus underwent bigbubble dalk. manual lamellar dissection was done due to failed big-bubble. first-day postoperative double chamber was detected. air bubbling and sf6 injection were tried without any success. double chamber resolved by fixation of am transplantation patch graft (1 × 1 mm) over the descemet’s membrane perforation with fibrin glue. conclusion: amniotic membrane patch graft can be used in the management of double chamber after dalk not responsive to intracameral gas injection. keywords: amniotic membrane; dalk; descemet perforation; double chamber j ophthalmic vis res 2020; 15 (4): 571–573 introduction deep anterior lamellar keratoplasty (dalk) is a preferred transplantation technique for advanced keratoconus. higher graft survival is the main advantage of dalk over penetrating keratoplasty.[1] big-bubble and melles technique are common methods for dalk. one of the major complication of these techniques is iatrogenic descemet’ membrane (dm) perforation.[1] this complication may occur during all stages of dalk correspondence to: ahad shahbazi, md. translational ophthalmology research center, farabi eye hospital, qazvin square, tehran, iran. e-mail: ahadshahbazi@yahoo.com received: 17-05-2019 accepted: 14-08-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7795 from trephination to graft suturing. the incidence of dm perforation during dalk was reported up to 39%.[2] dm perforation may cause double anterior chamber between donor stroma and recipient dm. although dm may be reattached spontaneously with a good visual outcome in some cases,[3, 4] surgical management of dm detachment is often necessary. it includes injection of air or gas into the anterior chamber, suturing dm to its position, or even repeating keratoplasty.[5–7] we report a novel technique of using amniotic membrane (am) as a patch for repairing the site of dm perforation refractory to anterior chamber gas injections. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: zarei-ghanavati m, davoodabadi m, shahbazi a. amniotic membrane patch graft in management of double chamber after deep anterior lamellar keratoplasty. j ophthalmic vis res 2020;15:571– 573. © 2020 journal of ophthalmic and vision research | published by knowledge e 571 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7795&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr amniotic membrane patch graft in management of double chamber after dalk; zarei-ghanavati et al figure 1. management of a dm perforation in a dalk case. (a) anterior segment-oct (as-oct) image showing a double anterior chamber and detached descemet membrane (double chamber was not resolved after two attempts of gas injection into the anterior chamber). (b) one week after the surgery: slit lamp photograph shows clear corneal graft with resolved double chamber. amniotic membrane patch graft is detectable between donor and recipient at the site of descemet perforation. case report a 35-year-old male patient diagnosed with advanced kcn was referred to us with. he had a complaint of gradually decreased vision in the left eye with the best-corrected visual acuity (bcva) of 2/10. rigid gas permeable lens could not be fitted for the patient. the left eye had the maximum keratometry of 75.4 diopters and minimum pachymetry of 397 microns. the patient underwent dalk with big-bubble technique. after partial trephination of 8 mm diameter, 27-gaugue needle attached to a 5 ml syringe of air was advanced from the superior rim of trephination toward paracentral zone of the cornea. during the air bubble expansion, dm was ruptured, and air penetrated to the anterior chamber (ac). a tear was detected in the inferior nasal periphery of dm in a diameter of nearly 0.3 mm. deep stromal dissection was achieved with melles’ spatula and 80% air was injected in the ac at the end of operation. double chamber was seen on the first day postoperatively. there was no change in size of double chamber after 4 days of medical treatment. therefore, injections of intracameral air and then sf6 were done without any success. we decided to patch dm perforation site with am graft. under general anesthesia, all donor graft sutures were removed and graft was put in normal saline container. air was injected in the ac and dm was dried with sponge. a patch (1 × 1 mm) of cryopreserved acellular am (sinacell, iran) was fixed over the perforation site with small amount of fibrin glue. the same graft was sutured to the receipt rim with 10-0 nylon separate sutures. on the first postoperative day, mild diffuse cornea stromal edema without noticeable double chamber was present. at one week after surgery, cornea was clear with the donor attached to dm without double chamber (figure 1). fifteen months after the surgery, bcva with –4.5–4.5 × 65 was 6/10. discussion this case showed that grafting of am patch is an effective procedure in post-dalk double chamber after failure of air bubbling. am has been used as a biological membrane for various indications including chemical burns, persistent epithelial defects, ulcers, and pterygium surgery. many studies have shown am’s clinical efficacy to stimulate wound healing, promoting epithelization, while suppressing inflammation, angiogenesis, and scarring. this tissue is used in two ways: (1) inlay technique that is applied as a permanent basement membrane substitute and (2) onlay technique that is temporarily placed on the ocular surface.[8, 9] in this case, we used am as a patch to seal the dm perforation site as a new indication for am. although, the literature suggests air injection for the management of double chamber, some studies have reported that the air or gas 572 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 amniotic membrane patch graft in management of double chamber after dalk; zarei-ghanavati et al bubble can cause pupillary block with a fixed dilated pupil (urrets–zavalia syndrome), anterior subcapsular lens opacities, and endothelial cell loss more than 20%.[10] furthermore, tamponade of inferior dm perforation with gas is a challenging issue. the use of fibrin glue application was successful in sealing the dm perforation.[11] another report described that stromal patch graft can be used in combination with fibrin glue after the failure of glue application alone.[12] in our case, we observed perforation of dm at inferonasal area during big-bubble technique. the aqueous then penetrated the space between dm and graft stroma. there was persistent double chamber even after air and sf6 injection. only after am patch graft, the perforation site was closed and double chamber resolved. am will not prevent from good apposition of dm and posterior surface of cornea because it is very thin and smooth in comparison to stromal patch. moreover, it will remain longer than fibrin glue alone to stop any leakage from the perforation site and increase the success rate. however, there are some limitations for the application of am patch in sealing of the dm perforation. some or all sutures should be removed to put am over the perforation site and glue it. we also observed interface haziness due to am remaining until the last follow-up (15 months). therefore, am patch cannot be used if the dm perforation site is located in the optical zone. in summary, it seems that the application of am patch to seal non-central perforations of dm is helpful to manage double chamber after dalk not responsive to air bubbling. references 1. borderie vm, sandali o, bullet j, gaujoux t, touzeau o, laroche l. long-term results of deep anterior lamellar versus penetrating keratoplasty. ophthalmology 2012;119:249–255. 2. sugita j, kondo j. deep lamellar keratoplasty with complete removal of pathological stroma for vision improvement. br j ophthalmol 1997;81:184–188. 3. passani a, sframeli at, loiudice p, nardi m. late spontaneous resolution of a double anterior chamber post deep anterior lamellar keratoplasty. saudi j ophthalmol 2017;31:58–60. 4. iradier mt, moreno e, aranguez c, cuevas j, garcía feijoo j, garcia sanchez j. late spontaneous resolution of a massive detachment of descemet’s membrane after phacoemulsification. j cataract refract surg 2002;28:1071–1073. 5. chow vw, agarwal t, vajpayee rb, jhanji v. update on diagnosis and management of descemet’s membrane detachment. curr opin ophthalmol 2013;24:356–361. 6. assia ei, levkovich-verbin h, blumenthal m. management of descemet’s membrane detachment. j cataract refract surg 1995;21:714–717. 7. kumar h, ali ms, mishra d. management of descemet’s membrane detachment by intra cameral air injection. ann int med den res 2016;2:ot01–ot04. 8. clare g, suleman h, bunce c, dua h. amniotic membrane transplantation for acute ocular burns. cochrane database syst rev 2012;9:cd009379. 9. rahman i, said dg, maharajan vs, dua hs. amniotic membrane in ophthalmology: indication and limitations. eye 2009;23:1954–1961. 10. maurino v, allan bd, stevens jd, tuft sj. fixed dilated pupil (urrets-zavalia syndrome) after air/gas injection after deep lamellar keratoplasty for keratoconus. am j ophthalmol 2002;133:266–268. 11. anwar hm, el-danasoury a, hashem an. the use of fibrin glue to seal descemet membrane microperforations occurring during deep anterior lamellar keratoplasty. cornea 2012;31:1193–1196. 12. ghaffari r, ghassemi h, latifi g, jabbarvand m, zamzam a, hashemi h. stromal patch with fibrin glue as a novel surgical technique to seal peripheral descemet’s membrane perforations in deep anterior lamellar keratoplasty. int ophthalmol 2019;39:2275–2282. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 573 original article seasonality of acute retinal necrosis alireza hedayatfar1, 2, md; maryam ashraf khorasani1, md; mehdi behnia2, md; ahad sedaghat1, md 1eye research center, rassoul akram hospital, iran university of medical sciences, tehran, iran 2noor ophthalmology research center, noor eye hospital, tehran, iran orcid: alireza hedayatfar: https://orcid.org/0000-0002-5667-5379 abstract purpose: to study the seasonal variability in the occurrence of acute retinal necrosis (arn) in a series of polymerase chain reaction (pcr)-positive patients. methods: consecutive patients clinically diagnosed with arn and a positive pcr result of aqueous humor during a seven-year period were studied retrospectively. patients’ demographics, causative viral agent(s), and the date of disease onset were extracted from medical records. results: twenty eyes of 20 patients were enrolled; the mean age at presentation was 39.6 ± 14.4 (range, 6–62) years. nine patients were female. the most common causative agent was varicella-zoster virus in 16 patients (80%), followed by herpes simplex virus in two patients (10%). the disease onset was in winter in 10 patients (50%), and the highest incidence was in february (five patients, 25%). the cumulative occurrence of arn was significantly higher in the first half of the year (winter and spring) compared to the second half of the year (summer and fall) (p = 0.030). in general, seasons with a high incidence of arn were preceded by cold seasons. conclusion: in our series, we observed seasonal variability in the incidence of arn, with the highest incidence during winter and spring. however, further epidemiologic studies in different geographical areas are required to elucidate the true seasonal nature of arn. keywords: acute retinal necrosis; herpetic viral retinitis; polymerase chain reaction; seasonal variation; varicella-zoster virus j ophthalmic vis res 2020; 15 (1): 53–58 correspondence to: alireza hedayatfar, md. ocular inflammation and uveitis clinic, noor eye hospital, no. 96 esfandiar blvd., vali’asr ave., tehran 19686, iran. e-mail:alireza.hedayatfar@gmail.com received: 03-12-2018 accepted: 17-07-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i1.5944 introduction acute retinal necrosis (arn) was first described in 1971 by urayama et al as a syndrome of acute panuveitis with retinal periarteritis progressing to diffuse necrotizing retinitis and retinal detachment (rd).[1] this uncommon but potentially blinding this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: hedayatfar a, ashraf khorasani m, behnia m, sedaghat a. seasonality of acute retinal necrosis. j ophthalmic vis res 2020;15:53–58. © 2020 journal of ophthalmic and vision research | published by knowledge e 53 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i1.5944&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr seasonality of arn; hedayatfar et al condition is usually noticed in immunocompetent hosts but occasionally among immunocompromised patients.[2, 3] in a nationwide survey in the uk, the estimated incidence of arn was one case per 2 million people per year, which had been stable over one decade.[4, 5] arn is caused by members of the herpesviridae family, most commonly varicella-zoster virus (vzv) and herpes simplex virus (hsv), and occasionally epstein–barr virus (ebv) and cytomegalovirus (cmv).[6–8] although arn is essentially a clinical diagnosis, ocular fluid polymerase chain reaction (pcr) testing has been widely used as an aid to the diagnosis and identification of the causative virus.[9–12] arn is a rapidly destructive disease. systemic antiviral therapy is the mainstay of treatment. corticosteroids are usually used along with antiviral agents to reduce the ocular inflammation. antivirals hasten the remission of retinitis in the affected eye and have a protective effect on the fellow eye.[13] moreover, early laser retinopexy can reduce the risk of rd,[14, 15] which is a complication that is considered a major cause of poor visual outcome in arn.[16, 17] therefore, early diagnosis and prompt management are important for reducing ocular morbidity, and can potentially save a significant number of eyes from severe vision loss. in this retrospective chart review, we observed a clustering tendency in the occurrence of arn in specific months of the year; this observation could highlight important aspects of the epidemiology of the disease. methods we retrospectively reviewed the medical records of patients diagnosed with arn at two referral centers in tehran from january 2011 to december 2017. only eyes with positive aqueous pcr were included. the study protocol was approved by the institutional review boards, and informed consent was obtained from the participants at the time of anterior chamber paracentesis. data on the demographics, causative viral agent(s), and date of the start of the ocular symptoms (considered as disease onset) were extracted. arn was clinically diagnosed based on the characteristic clinical features consisting of the presence of one or multiple peripheral foci of retinitis with rapid circumferential progression, occlusive retinal vasculitis (mainly arteritis), and prominent vitreous inflammation. wide-field fluorescein angiography was used to confirm the occlusive nature of vasculitis and extent of retinal ischemia. a tailored laboratory work-up was performed to assess the immune status of the patients and rule-out other causes of uveitis. the average temperatures in each month from january 2011 to december 2017 were extracted based on the data provided by the worldweatheronline.com in tehran, mehrabad airport. technique of anterior chamber paracentesis and pcr for aqueous sampling, anterior chamber paracentesis was performed using a 30-gauge needle attached to an insulin syringe, and 0.1– 0.2 cc of aqueous humor was aspirated. the procedure was generally performed in the clinic after the examination. for patients who received an intravitreal injection of ganciclovir, both sampling and injection were performed in the operating room. the samples were kept at 2–8∘c and delivered to the laboratory within 1 h and were stored at –20∘c. dna extraction was performed within one week using high pure viral nucleic acid kit (roche diagnostics gmbh, mannheim, germany) following the manufacturer’s instructions.[18] qualitative pcr was performed using the flash method by the dna technology kit (dna-technology, moscow, russia).[19] the results are expressed as mean ± standard error. due to the limited number of cases, fisher’s exact test was used to compare the cumulative occurrence of arn between the first and second halves of the year. a p-value < 0.05 was considered statistically significant. results twenty eyes of 20 patients were included in this study. the mean age at presentation was 39.6 ± 14.4 (range: 6–62) years. nine patients were female. none of the patients were hiv-positive. arn was unilateral in all patients except one [table 1]. the patient with bilateral arn did not consent for bilateral sampling, therefore, only the eye with more extensive involvement was sampled (positive 54 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 worldweatheronline.com seasonality of arn; hedayatfar et al table 1. demographics, causative viral agent(s), and date of disease onset in arn cases patient # pcr result gender age at onset (years) laterality arn onset (month) arn onset (year) 1 vzv m 41 od 6 2013 2 vzv m 30 os 5 2014 3 vzv f 56 od 1 2016 4 vzv f 28 os 4 2013 5 vzv m 58 od 10 2015 6 vzv m 53 os 2 2011 7 vzv m 45 od 5 2012 8 vzv f 44 ou 8 2013 9 vzv f 45 od 6 2017 10 vzv m 40 od 1 2015 11 vzv m 21 os 2 2017 12 vzv f 35 os 2 2016 13 vzv m 48 os 1 2017 14 vzv m 56 os 3 2015 15 vzv f 29 od 3 2015 16 vzv, ebv f 62 os 4 2016 17 hsv m 6 os 2 2017 18 hsv m 25 od 2 2014 19 ebv f 26 od 3 2017 20 cmv m 43 od 5 2014 arn, acute retinal necrosis; cmv, cytomegalovirus; ebv, epstein–barr virus; f, female; hsv, herpes simplex virus; m, male; od, right eye; os, left eye; ou, bilateral; pcr, polymerase chain reaction; vzv, varicella-zoster virus for vzv) while the other eye was excluded from the study. based on the pcr results, the most common causative agent was vzv detected in 16 patients (80%), followed by hsv in 2 patients (10%; hsv-1 and hsv-2 each in one patient). cmv was detected in one patient (5%) and ebv in one eye (5%). in one vzv-positive patient, a simultaneous co-infection by ebv was present [table 1]. in most patients (85%, 17 patients), the disease onset was in winter (ten patients, 50%) or spring (seven patients, 35%). summer (two patients, 10%) and autumn (one patient, 5%) were the seasons with the lowest incidence [figure 1(a)]. february was the month with the highest incidence of arn (five patients, 25%), and july, september, november, and december were the months with the lowest incidence (no cases) [figure 1(b)]. the cumulative occurrence of arn was significantly higher in the first half of the year (winter and spring) compared to the second half of the year (summer and fall) (p = 0.030). figure 2 shows the average temperature in each month during the study period. the coldest month in the study period was january (mean temperature, 5.1∘c), followed by february (mean temperature, 6.5∘c) and december (mean temperature, 7.0∘c). july (mean temperature, 34.0∘c), august (mean temperature, 32.9∘c), and june (mean temperature, 31.7∘c) were the warmest months. the coldest season that was winter (average temperature, 7.7∘c) had the highest incidence of arn (50%). autumn, which was the second coldest season (average temperature, 12.9∘c), had the lowest incidence of arn (5%). the high incidence rate of arn (35%) in spring suggests a time lag between the beginning of cold seasons and an increase in the incidence of arn. journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 55 seasonality of arn; hedayatfar et al figure 1. cumulative number of cases of acute retinal necrosis in each season (a) and month (b). discussion in this series, there was a tendency for the occurrence of arn during winter and spring. the seasons with a high incidence of arn were preceded by cold seasons. while the temperature began dropping mid-autumn, the peak of arn occurred during winter, and once the temperature started rising mid-spring, the incidence of arn declined in summer. previous studies have shown patterns of seasonal variability in the incidence of infections associated with the herpesviridae family. varicella shows pronounced seasonality in temperate climates and most tropical climates, with a peak incidence in the cooler, drier months during winter or spring.[20–23] in a study using the connecticut statewide hospital discharge database in the prevaccine era, 73.2% of the varicella hospitalizations occurred during winter and spring.[24] in contrast, zoster does not show any seasonal pattern in the uk, canada,[25] or western australia.[26] seasonal variations in the occurrence of herpetic keratitis were reported as well. in a study in japan, a negative correlation was observed between the incidence of dendritic keratitis recurrences 56 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 seasonality of arn; hedayatfar et al figure 2. average temperature in each month in the study period. and temperature and 42.2% of the recurrences occurred during winter.[27] gamus found the highest rate of herpetic eye attacks during january,[28] and others reported the highest incidence of herpetic keratitis in late autumn and winter.[29] seasonal cycles in infectious diseases are generally attributed to seasonal differences in weather conditions, seasonal rhythmicity in host susceptibility to infectious agents, and the virulence or prevalence of causal pathogens.[30, 31] the explanation of the seasonal variability in the incidence of arn in this series would be undoubtedly complex and multifactorial. tehran has a four-season climate. the weather is usually mild and rainy in spring, hot and dry in summer, mild to cold in autumn, but chilly and occasionally snowy in winters. records of the average monthly temperature also showed that winter and autumn were the coldest seasons. the higher incidence rate of arn in winter and spring suggests a temporal pattern in which the cold seasons preceded seasons with a high incidence of arn. however, this is an assumption and cannot be confirmed using statistical methods. administering the time series analysis, which is often used to extract possible correlations in similar situations, needs a large sample size far exceeding the number of cases included in the current study. to the best of our knowledge, this is the first report on the concept of seasonality in arn. we included a homogenous group of patients with pcr-proven arn and set tehran, a four-season city, as the reference to evaluate the probable climatological association. a limitation of the current study is the small sample size, which is due to the rarity of arn. the second limitation is that the temperature data were collected based on records provided from a single station in tehran (mehrabad airport). considering the area of the tehran metropolitan, a single station may not comprehensively reflect the whole climate of the source population. the knowledge of the seasonal variability in the incidence of arn could potentially be beneficial to ophthalmologists to expect new cases during specific months of the year and be prompt in diagnosis and treatment. however, further epidemiologic studies in different geographical areas are required to elucidate the true seasonal nature of arn. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 57 seasonality of arn; hedayatfar et al references 1. urayama a, yamada n, sasaki t. unilateral acute uveitis with periarteritis and detachment. j clin ophthalmol 1971;25:607–619. 2. freeman wr, lerner cw, mines ja, lash rs, nadel aj, starr mb, et al. a prospective study of the ophthalmologic findings in the acquired immune deficiency syndrome. am j ophthalmol 1984;97:133–142. 3. bonfioli aa, eller aw. acute retinal necrosis. semin ophthalmol 2005;20:155–160. 4. muthiah mn, michaelides m, child cs, mitchell sm. acute retinal necrosis: a national population-based study to assess the incidence, methods of diagnosis, treatment strategies and outcomes in the uk. br j ophthalmol 2007;91:1452–1455. 5. cochrane tf, silvestri g, mcdowell c, foot b, mcavoy ce. acute retinal necrosis in the united kingdom: results of a prospective surveillance study. eye 2012;26:370–377. 6. culbertson ww, blumenkranz ms, haines h, gass dm, mitchell kb, norton ew. the acute retinal necrosis syndrome. part 2: histopathology and etiology. ophthalmology 1982;89:1317–1325. 7. matsuo t, nakayama t, koyama t, matsuo n. cytological and immunological study of the aqueous humor in acute retinal necrosis syndrome. ophthalmologica 1987;195:38– 44. 8. ganatra jb, chandler d, santos c, kuppermann b, margolis tp. viral causes of the acute retinal necrosis syndrome. am j ophthalmol 2000;129:166–172. 9. nishi m, hanashiro r, mori s, masuda k, mochizuki m, hondo r. polymerase chain reaction for the detection of the varicella-zoster genome in ocular samples from patients with acute retinal necrosis. am j ophthalmol 1992;114:603–609. 10. de boer jh, verhagen c, bruinenberg m, rothova a, de jong pt, baarsma gs, et al. serologic and polymerase chain reaction analysis of intraocular fluids in the diagnosis of infectious uveitis. am j ophthalmol 1996;121:650–658. 11. gargiulo f, de francesco ma, nascimbeni g, turano r, perandin f, gandolfo e, et al. polymerase chain reaction as a rapid diagnostic tool for therapy of acute retinal necrosis syndrome. j med virol 2003;69:397–400. 12. tran th, rozenberg f, cassoux n, rao na, lehoang p, bodaghi b. polymerase chain reaction analysis of aqueous humour samples in necrotising retinitis. br j ophthalmol 2003;87:79–83. 13. palay da, sternberg p, jr, davis j, lewis h, holland gn, mieler wf, et al. decrease in the risk of bilateral acute retinal necrosis by acyclovir therapy. am j ophthalmol 1991;112:250–255. 14. han dp, lewis h, williams ga, mieler wf, abrams gw, aaberg tm. laser photocoagulation in the acute retinal necrosis syndrome. arch ophthalmol 1987;105:1051–1054. 15. lau ch, missotten t, salzmann j, lightman sl. acute retinal necrosis features, management, and outcomes. ophthalmology 2007;114:756–762. 16. sims jl, yeoh j, stawell rj. acute retinal necrosis: a case series with clinical features and treatment outcomes. clin exp ophthalmol 2009;37:473–477. 17. butler nj, moradi a, salek ss, burkholder bm, leung tg, dunn jp, et al. acute retinal necrosis: presenting characteristics and clinical outcomes in a cohort of polymerase chain reaction-positive patients. am j ophthalmol 2017;179:179–189. 18. roche diagnostics gmbh, germany. high pure viral nucleic acid kit. version: 19. 2015; august. cat. no. 11 858 874 001. available from: https://lifescience.roche.com 19. “dna-technology” multicorporate enterprise, russia. catalogue equipment. last version. available from: http:// www.dna-technology.ru 20. deguen s, chau np, flahault a. epidemiology of chickenpox in france (1991–1995). j epidemiol community health 1998;52:46s–49s. 21. lee bw. review of varicella zoster seroepidemiology in india and southeast asia. trop med int health 1998;3:886–890. 22. tobias m, reid s, lennon d, meech r, teele dw. chickenpox immunization in new zealand. n z med j 1998;111:274– 281. 23. bramley jc, jones ig. epidemiology of chickenpox in scotland: 1981 to 1998. commun dis public health 2000;3:282–287. 24. lin f, hadler jl. epidemiology of primary varicella and herpes zoster hospitalizations: the pre-varicella vaccine era. j infect dis 2000;181:1897–905. 25. brisson m, edmunds wj, law b, gay nj, walld r, brownell m, et al. epidemiology of varicella zoster virus infection in canada and the united kingdom. epidemiol infect 2001;127:305–314. 26. korostil ia, regan dg. varicella-zoster virus in perth, western australia: seasonality and reactivation. plos one 2016;10:11. 27. araki h, takamura e, shinozaki k, hori s. influence of seasonal variation and recurrence of herpes simplex virus keratitis. invest ophthalmol vis sci 2004;45:1648. 28. gamus d, romano a, sucher e, ashkenazi ie. herpetic eye attacks: variability of circannual rhythms. br j ophthalmol 1995;79:50–53. 29. bell dm, holman rc, pavan-langston d. herpes simplex keratitis: epidemiologic aspects. ann ophthalmol 1982;14:421–422, 424. 30. dowell, sf. seasonal variation in host-susceptibility and cycles of certain infectious diseases. emerg infect dis 2001;7:369–374. 31. shah ap, smolensky mh, burau kd, cech im, lai d. seasonality of primarily childhood and young adult infectious diseases in the united states. chronobiol int 2006;23:1065–1082. 58 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 https://lifescience.roche.com http://www.dna-technology.ru http://www.dna-technology.ru original article corneal refractive surgery in patients with history of optic neuritis majid moshirfar1,2, md; william d. wagner3, bs; steven h. linn1, od; tanner w. brown4, ba; jackson l. goldberg4, bs; aaron t. gomez5, bs; yasmyne c. ronquillo1, md, jd; phillip c. hoopes, jr.1, md 1john a. moran eye center, department of ophthalmology and visual sciences, university of utah school of medicine, salt lake city, ut, usa 2hdr research center, hoopes vision, draper, ut, usa 3virginia commonwealth university school of medicine, richmond, va, usa 4the university of texas health science center at houston school of medicine, houston, tx, usa 5the university of texas rio grande valley school of medicine, edinburg, tx, usa orcid: majid moshirfar: https://orcid.org/0000-0003-1024-6250 abstract purpose: the purpose of this study was to evaluate the risk of recurrence of optic neuritis after corneal refractive surgery in patients with a history of optic neuritis and to examine the safety and efficacy of the procedure in this population. methods: this was a retrospective chart review of patients with a history of optic neuritis who underwent laser-assisted in situ keratomileusis (lasik) or photorefractive keratectomy (prk) at a single tertiary center from june 1996 to december 2014. fifteen eyes of 14 patients were included in this study. visual acuity before and after the surgery was recorded. patients were followed-up for over five years postoperatively for the recurrence of optic neuritis. results: the average logmar best corrected visual acuity (bcva) preoperatively was 0.12 ± 0.19 (–0.10 to 0.60) and postoperatively was 0.06 ± 0.10 (–0.10 to 0.30). no eyes lost lines of bcva. the average logmar uncorrected distance visual acuity (udva) after surgery was 0.12 ± 0.13 (0.00 to 0.48). twenty-eight percent of patients reached a udva of 20/20 or better after refractive surgery. optic neuritis recurred in 3/15 (20%) eyes and 3/14 patients (21%). conclusion: while corneal refractive procedures appear safe in patients with a history of optic neuritis, our data suggest that their efficacy may be reduced. keywords: laser vision surgery; lasik; multiple sclerosis; optic neuritis; prk j ophthalmic vis res 2019; 14 (4): 436–441 correspondence to: majid moshirfar, md. hoopes vision, 11820 s. state street, suite 200, draper, ut, 84020, usa. e-mail: moshirfar@hoopesvision.com received: 25-07-2018 accepted: 29-04-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i4.5445 introduction there are various potential causes of optic neuritis, including multiple sclerosis (ms), systemic lupus erythematosus, antiphospholipid syndrome, sjogren’s syndrome, and multiple vasculitides.[1–4] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: moshirfar m, wagner wd, linn sh, brown tw, goldberg jl, gomez at, ronquillo yc, hoopes pc. refractive surgery in patients with optic neuritis. j ophthalmic vis res 2019;14:436–441. 436 © 2019 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5445&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr lasik and prk in optic neuritis; moshirfar et al optic neuritis is most commonly associated with ms, with approximately 50% of patients experiencing an episode during their lifetime.[5] the most common pathologic basis for optic neuritis is immune-mediated inflammatory demyelination of the optic nerve.[6] previous research has demonstrated disturbances during corneal wound healing in various growth factors, cytokines, and inflammatory cells commonly involved in the pathophysiology of optic neuritis.[7] while various studies have evaluated outcomes of refractive procedures in patients with other autoimmune diseases, there is limited data on patients with a previous history of optic neuritis.[8, 9] the aim of this study was to determine the risk of recurrence in patients with a previous history of optic neuritis after corneal refractive surgery. additionally, we evaluated the safety and efficacy of corneal refractive surgery in this population. methods this was a retrospective chart review of all patients with a history of optic neuritis, who underwent laser-assisted in situ keratomileusis (lasik) or photorefractive keratectomy (prk) at a single tertiary center from june 1996 to december 2013. a single surgeon performed all the procedures. at the time of surgery, the patients had experienced their most recent episode of optic neuritis at least two years previously. patients included in this study underwent complete refractive surgery workup to rule out herpes, keratoconus, posterior or anterior segment pathology, pars planitis, previous uveitis, or corneal ectasia. preoperative review of systems was negative for any ms-related symptoms, including bladder dysfunction, motor or sensory disturbances, or visual involvement. each patient received approval for lasik or prk through consultation with a neurologist and/or family physician who determined that there was no active disease at the time of surgery. all patients underwent standard preoperative refractive workup including uncorrected distance visual acuity (udva), best corrected distance visual acuity (cdva), manifest and cycloplegic refractions, applanation tonometry, slit lamp biomicroscopy, indirect ophthalmoscopy, pachymetry, and corneal topography. risks and benefits of the procedure were explained to the patients, and all patients provided written informed consent. twelve of the thirteen lasik procedures were performed using the visx excimer laser (santa clara, california, usa) with ablation zones of 6–8 mm and flap creation using the hansatome microkeratome (bausch & lomb, rochester, new york, usa). one procedure was performed using a 400 hz excimer laser (alcon, fort worth, texas, usa) with flap creation performed using alcon’s fs200 femtosecond laser. there were no intraoperative complications. patients were routinely examined one day, one week, and one, three, six, twelve, and twentyfour months after the surgery. postoperatively, patients received the standard pharmacological regimen, which included one week of topical prednisolone acetate 1% four times a day and a thirdor fourth-generation fluoroquinolone four times a day, as well as frequent doses of preservative-free topical lubricants for several months. the prk procedure consisted of scoring the corneal epithelium using an 8.0-mm trephine with alcohol-assisted epithelial debridement. laser ablation with a 6.0 mm optical zone and an 8mm blend was performed using a visx excimer laser. patients then received a bandage contact lens with fluoroquinolone and prednisolone acetate 1% drops, each four times a day. after the first week, the bandage contact lens and antibiotic drops were discontinued, and prednisolone acetate 1% was continued four times a day for three additional weeks. following this, the steroid was changed to fluorometholone 0.1%, whose dose was tapered over the course of additional eight weeks. postoperative follow-up was performed after one day, one week, and one, three, and six months. patients were followed over five years postoperatively and data collected included time from lasik or prk to the diagnosis of optic neuritis and visual acuity. the recurrence of optic neuritis was diagnosed clinically and confirmed by direct visualization of a pale optic nerve. in patients who developed recurrence postoperatively, the udva and cdva before and journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 437 lasik and prk in optic neuritis; moshirfar et al after the episode were recorded. visual acuity was converted to logmar as described by holladay.[10] results a total of 14 patients (15 eyes) underwent surgery. prk was performed on 4 eyes and lasik was performed on 11 eyes. of the 15 eyes, 6 were right and 9 were left. the ratio of female to male patients was 11:3. the age of the patients ranged from 23 to 55 years, with a mean age of 34 years. nine of the fourteen patients had been previously diagnosed with ms. the cause of optic neuritis was not known in the remaining five patients. all eyes demonstrated optic nerve pallor on preoperative funduscopic examination, except one patient in whom no optic nerve pallor was seen. refractive errors corrected included one hyperopic eye, two eyes with significant astigmatic error, and 12 myopic eyes ranging from –2.50 d to –10.00 d [table 1]. postoperative refraction revealed 10 patients (66.6%) with emmetropia and 4 (26.6%) with residual refractive error (+1.00 d to –2.13 d seq). visual acuity was measured in all patients within six months postoperatively. the average logmar udva after surgery was 0.12 ± 0.13 (0.00 to 0.48). twenty-eight percent of patients reached a udva of 20/20 or better after refractive surgery, excluding the eye that was targeted for monovision from the calculation [figure 1]). the udva in all patients was 20/40 or better, except in one patient with monovision and in another with residual refractive error. both the patients improved to 20/40 or better with correction. the average logmar bcva preoperatively was 0.12 ± 0.19 (—0.10 to 0.60) and postoperatively was 0.06 ± 0.10 (–0.10 to 0.30). no eye lost lines of cdva. ten patients had no change in cdva, two patients gained one line, and three patients gained two lines [figure 2]. three of the 15 eyes (20%) experienced recurrence of optic neuritis postoperatively. the recurrence occurred in one patient three years after prk and two patients after lasik at the fourth and fifth years, respectively. each of these three patients experienced persistent vision loss. cdva measured after resolution of acute optic neuritis was 20/40 in two patients and 20/60 in the third patient. discussion while various studies have examined the increased risk of developing optic neuropathy after intraocular surgery, there is limited literature on the risk of developing optic neuritis.[11, 12] our study examined patients with a history of optic neuritis in order to determine recurrence rates, visual outcomes, and safety of refractive surgery. it is well established that optic neuritis typically affects relatively young women. in this study, 11/14 patients (78.5%) were women, compared to 77.2% reported in the optic neuritis treatment trial (ontt).[5] in a retrospective chart review performed at the mayo clinic, the mean age of patients with optic neuritis was 31 years, which is marginally lower than the mean age of our sample population (34 years).[13] of note, only two patients were over 40 years of age. based on these demographics, our study population appears to serve as an appropriate sample of the general population of patients with optic neuritis. interestingly, one patient in our sample had a history of bilateral optic neuritis which is described as being less prevalent than unilateral optic neuritis.[14, 15] in the ontt, out of the patients who initially presented with unilateral optic neuritis, 9% subsequently developed bilateral symptoms. bilateral optic neuritis appears to have a good prognosis with recovery of vision if treated appropriately.[15] notably, our patient with bilateral optic neuritis did not have recurrence and improved to a cdva of 20/20 in both eyes after surgery. although, to the best of our knowledge, no studies have evaluated visual outcomes after refractive surgery in patients with a history of optic neuritis, hashemi et al investigated visual outcomes in 15 eyes of eight patients with ms after lasik.[16] our results are comparable with that reported in the aforementioned study, as average postoperative udva and cdva were approximately 20/25 when excluding the single eye that was targeted for monovision based on calculation of udva. while the percentage of patients in the general population with udva of 20/20 or better after lasik or prk has been reported as 42– 48%, only 28% of patients in our study reached this outcome.[17] thus, our study is consistent with previous reports and suggests the safety of refractive procedures in patients with a history of optic neuritis, but may indicate decreased efficacy. 438 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 lasik and prk in optic neuritis; moshirfar et al table 1. patients’ information. patient eye age sex nerve pallor ms preop bcva surgery postop udva postop bcva recurrence time to recurrence bcva post on recovery 1 od 34 female y y 20/20 lasik 20/20 20/20 os y y 20/20 lasik 20/20 20/20 2 od 27 female y n 20/30 lasik 20/30 20/25 3 od 41 female y y 20/25 prk 20/25 20/25 yes 3 years 20/40 4 os 34 male y n 20/50 lasik 20/30 20/30 5 od 39 male y y 20/30 lasik 20/30 20/30 yes 4 years 20/60 6 os 33 female y y 20/20 lasik 20/20 20/20 7 od 29 female y y 20/25 lasik 20/25 20/25 8 os 29 female y y 20/80 lasik 20/60 20/40 9 os 23 female y n 20/40 lasik 20/30 20/25 10 os 33 male y y 20/20 prk 20/20 20/20 11 os 55 female n n 20/15 prk 20/80 20/15 12 os 33 female y n 20/20 lasik 20/25 20/20 13 os 33 female y y 20/20 prk 20/25 20/20 14 od 35 female y y 20/25 lasik 20/25 20/20 yes 5 years 20/40 ms, multiple sclerosis; bcva, best corrected visual acuity; lasik, laser-assisted in situ keratomileusis; n, no; od, right eye; os, left eye; prk, photorefractive keratectomy; udva, uncorrected distance visual acuity; y, yes; postop, postoperative figure 1. postoperative uncorrected distance visual acuity (udva). cumulative udva at six months postoperatively. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 439 lasik and prk in optic neuritis; moshirfar et al figure 2. change in best corrected visual acuity (bcva). change in bcva preoperatively versus six months postoperatively. previous studies have reported an occurrence of optic neuritis shortly after refractive surgery; therefore, one of the aims of this study was to evaluate the risk of recurrence of optic neuritis after these procedures.[12] of note, the ontt offered long-term follow-up of patients after an episode of optic neuritis. after five years of follow-up, 30% of patients had experienced recurrence of optic neuritis, while our results showed recurrence after refractive surgery in 30% of eyes.[18] our data does not show an increased risk of recurrence of optic neuritis after refractive surgery compared to the general population; however, subsequent studies with larger sample sizes and inclusion of matched controls are needed to adequately address this comparison. while most patients in our study had a history of ms, five patients reported no history of conditions associated with optic neuritis. the ontt found that patients who met the clinical criteria for optic neuritis carried a 50% risk of developing ms over a 15year follow-up period.[19] it remains unclear whether optic neuritis in the five patients in our study was due to a demyelinating process or another underlying disease yet to be identified. further studies are needed to evaluate the outcomes of refractive surgery and the risk of recurrence in patients with non-demyelinating systemic conditions related to optic neuritis. in populations associated with increased risk of recurrence of optic neuritis, it is important to consider measures of vision other than standard visual acuity. contrast sensitivity can be used to detect deficits in vision that would otherwise be missed using a standard snellen chart.[20] optic neuritis is a known risk factor for loss of contrast sensitivity, with up to 78% of patients experiencing persistent impairment even after resolution of active disease, regardless of recovery of visual acuity.[18] additionally, refractive surgery has been shown to negatively impact contrast sensitivity.[21, 22] the presence of both risk factors and the possible compounding effects on visual outcomes warrants further investigation. absolute and relative contraindications to refractive surgery have been suggested to optimize patient outcomes and reduce postoperative complications. although active, uncontrolled autoimmune diseases are considered absolute contraindications, studies have shown that patients with a 440 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 lasik and prk in optic neuritis; moshirfar et al variety of well-controlled diseases can safely and effectively undergo surgery.[8] importantly, patients in this study were only included if they met specific criteria indicating control of disease. in order to achieve acceptable outcomes in patients with a history of optic neuritis who wish to undergo refractive surgery, clinicians must ensure appropriate preoperative evaluation of patients. all patients should receive surgical clearance by a neurologist or physician with experience in the diagnosis and management of optic neuritis. additionally, a comprehensive informed consent should include a discussion about the paucity of data available regarding the impact of optic neuritis on efficacy of surgery, recurrence of disease, and possible loss of contrast sensitivity. financial support and sponsorship none of the authors have financial interest in any products or methodology mentioned in this manuscript. this research has been supported by research to prevent blindness (new york, new york). conflicts of interest there are no conflicts of interest. references 1. hackett er, martinez rd, larson pf, paddison rm. optic neuritis in systemic lupus erythematosus. arch neurol 1974;31:9–11. 2. kadota y, tokumaru a, kamakura k, kohyama s, okizuka h, kaji t, et al. primary sjögren’s syndrome initially manifested by optic neuritis: mri findings. neuroradiology 2002;44:338–341. 3. cikes n, bosnic d, sentic m. non-ms autoimmune demyelination. clin neurol neurosurg 2008;110:905–912. 4. obenauf cd, shaw he, sydnor cf, klintworth gk. sarcoidosis and its ophthalmic manifestations. am j ophthalmol 1978;86:648–655. 5. the clinical profile of optic neuritis: experience of the optic neuritis treatment trial. arch ophthalmol 1991;109:1673– 1678. 6. lightman s, mcdonald wi, bird ac, francis da, hoskins a, batchelor jr, et al. retinal venous sheathing in optic neuritis. its significance for the pathogenesis of multiple sclerosis. brain 1987;110:405–414. 7. ljubimov av, saghizadeh m. progress in corneal wound healing. prog retin eye res 2015;49:17–45. 8. schallhorn jm, schallhorn sc, hettinger ka, venter ja, pelouskova m, teenan d, et al. outcomes and complications of excimer laser surgery in patients with collagen vascular and other immune-mediated inflammatory diseases. j cataract refract surg 2016;42:1742–1752. 9. moshirfar m, siddharthan ks, meyer jj, espandar l, wolsey dh, vitale at. risk for uveitis after laser in situ keratomileusis in patients positive for human leukocyte antigen-b27. j cataract refract surg 2008;34:1110–1113. 10. holladay jt. visual acuity measurements. j cataract refract surg 2004;30:287–290. 11. cameron bd, saffra na, strominger mb. laser in situ keratomileusis–induced optic neuropathy. ophthalmology 2001;108:660–665. 12. dotan s, beykin g, frucht-pery j. optic neuritis after refractive surgery: causal or coincidence? [cited july 10, 2018]. 13. rodriguez m, siva a, cross sa, o’brien pc, kurland lt. optic neuritis: a population-based study in olmsted county, minnesota. neurology 1995;45:244–250. 14. toosy at, mason df, miller dh. optic neuritis. lancet neurol 2014;13:83–99. 15. de la cruz j, kupersmith mj. clinical profile of simultaneous bilateral optic neuritis in adults. br j ophthalmol 2006;90:551–554. 16. hashemi h, tabrizi m, rezvan b. laser in situ keratomileusis for the treatment of refractive errors in patients with multiple sclerosis. iran j ophthalmol 2010;22:9–12. 17. yang x-j, yan h-t, nakahori y. evaluation of the effectiveness of laser in situ keratomileusis and photorefractive keratectomy for myopia: a meta-analysis. j med invest 2003;501:80–186. 18. beck rw, trobe jd, moke ps, gal rl, xing d, bhatti mt, et al. highand low-risk profiles for the development of multiple sclerosis within 10 years after optic neuritis: experience of the optic neuritis treatment trial. arch ophthalmol (chicago, ill 1960) 2003;121:944–949. 19. optic neuritis study group tons. multiple sclerosis risk after optic neuritis: final optic neuritis treatment trial followup. arch neurol 2008;65:727–732. 20. pelli dg, bex p. measuring contrast sensitivity. vision res 2013;90:10–14. 21. yamane n, miyata k, samejima t, hiraoka t, kiuchi t, okamoto f, et al. ocular higher-order aberrations and contrast sensitivity after conventional laser in situ keratomileusis. invest opthalmol vis sci 2004;45:3986. 22. katlun t, wiegand w. [change in twilight vision and glare sensitivity after prk]. ophthalmologe 1998;95:420–426. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 441 editorial how do we manage hla-b27-associated ocular inflammation refractory or intolerant to conventional immunomodulatory therapy? doan luong hien, md1,2; brandon huy pham, bs1; quan dong nguyen, md, ms1 1spencer center for vision research, byers eye institute, stanford university, palo alto, california, usa 2pham ngoc thach university of medicine, saigon, vietnam orcid: doan luong hien: https://orcid.org/0000-0003-0856-871x quan dong nguyen: https://orcid.org/0000-0002-6024-8441 j ophthalmic vis res 2020; 15 (4): 442–445 the hla-b27 gene is among the most studied genes in the history of medicine, and its relationship to ocular inflammation is well established. in particular, it has been known to be associated primarily with anterior chamber inflammation with clinical manifestations of nongranulomatous keratic precipitates, anterior chamber cells and flare, and in some cases, fibrin and/or hypopyon. with modern advanced imaging technologies, posterior segment involvement, including papillitis and retinal vasculitis can be detected in up to 31% of patients with hlab27-associated uveitis.[1] moreover, wide-angle imaging has allowed the diagnosis of peripheral retinal vasculitis that may be missed by standard imaging modalities.[2, 3] although the long-term visual prognosis of hla-b27-associated acute anterior uveitis (aau) is generally favorable,[4] patients with hla-b27associated aau are approximately five times more likely to have a visual acuity of 20/200 or worse as compared to patients without hlab27-positivity.[5] suboptimal visual outcomes may be complicated by steroid-induced side effects or delay in treatment of refractory cases; therefore, close monitoring with multimodality imaging and employing a stepladder approach in the management is necessary in every patient. unfortunately, since relatively few studies have examined hla-b27-associated aau, and even fewer have focused on refractory cases, hla-b27associated aau remains a significant therapeutic challenge for uveitis specialists. in their well-written manuscript and well-designed study published in the current issue of journal of ophthalmic and vision research (jovr), bajwa and colleagues[6] contribute to the literature by discussing the utility of infliximab in managing this particularly challenging disease. recent prospective randomized controlled trials have shown that intraocular inflammation can be controlled in 57.1–66.7% of cases with firstline immunomodulatory therapy (imt) agents, such as methotrexate and mycophenolate mofetil.[7] uveitis that involves the posterior segment may not always respond to first-line imt and at time requires adjustment to secondor thirdline agents, including biologics or other steroidsparing agents. infliximab and adalimumab are the two most commonly used biologic agents for noninfectious posterior uveitis (niu). unlike adalimumab, infliximab has not been approved by the fda for niu and is used off-label for ocular inflammation. data supporting the use of infliximab in niu stems largely from retrospective and small prospective trials.[8–17] infliximab can be used as first-line therapy for certain systemic diseases such as adamantiades-behçet disease[18] and in cases of sight-threatening disease in the setting of moderate to severe idiopathic retinal vasculitis and optic disc inflammation, or as a third-line therapy in uveitis refractory to corticosteroids and conventional imt. the efficacy of infliximab is fairly rapid-onset, with one study demonstrating 96% resolution of acute inflammation one day after infusion,[19] which is quite fast as compared to adalimumab, in which the typical time to effectiveness typically ranges from 2 to 16 weeks.[20] these findings are consistent with the study by bajwa et al,[6] which demonstrated 442 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7777&domain=pdf&date_stamp=2019-07-17 editorial; hien et al 81.25% responsiveness after three months and 87.5% responsiveness after six months. some imt agents, such as methotrexate and mycophenolate mofetil, may take 8–12 weeks before reaching maximum efficacy; adalimumab takes a median of six weeks.[20] therefore, three months of follow-up is inadequate to determine unresponsiveness. we typically follow our patient in the clinics for six months or more to fully assess drug efficacy and responsiveness. it is important to continue therapy during this time even if the disease is in stable condition in order to achieve long-term quiescence and remission. adalimumab was fda-approved for the treatment of niu after the completion of two successful phase-3 multicenter randomized controlled trials, visual i and ii, that investigated the use of adalimumab strictly for intermediate, posterior, or pan-uveitis.[21, 22] no specific data regarding the percentage and subtypes of hlab27-associated uveitis is available from the visual i and ii studies. it is quite interesting that many patients had refractory anterior uveitis in the bajwa study[6] prior to the study entry and 20.8% were considered to be unresponsive or intolerant to adalimumab therapy. it would be beneficial if bajwa and colleagues could provide information on prior immunosuppression treatment regimens including route, time, and dosage. moreover, no clear definition of “unresponsive inflammation” is provided. according to the study, 9.5–19% of patients experienced a flare up while on treatment with infliximab, and one patient developed vasculitis after 3 months of treatment which remained active until 24 months. we suspect that the authors may be more in favor of infliximab than other imt agents, having kept the patient on a similar treatment regimen. in addition, the authors discuss antibody formation against infliximab. it would be very helpful to know whether testing for this antibody was performed as well as how many patients were on concurrent imt (such as methotrexate or mycophenolate) to prevent or decrease the risk of antibody formation. in the bajwa study,[6] treatment was prematurely stopped in three patients, and one patient still had active disease at the end of 24 months. the authors can speculate or suggest what may be the next treatment option(s) for these patients. in summary, while infliximab is a robust treatment, roughly 10–20% of patients may not show an adequate response to therapy. these patients may need augmentation with additional therapeutic approaches. recent emerging and adopted therapies, including tocilizumab (stop study),[23] sarilumab (saturn study),[24] and sirolimus (save-2 and sakura studies),[25–28] have shown encouraging efficacy outcomes with a relatively favorable safety profile. other clinical trials evaluating the safety and efficacy of filgotinib,[29] tofacitinib,[30] and adrenocorticotropic hormone[31] in niu are currently in progress. amidst the current global covid-19 pandemic, one of the most common concerns we have received from patients on imt is whether their treatment might increase the risk of worsening a covid-19 infection if they were to contract severe acute respiratory syndrome coronavirus 2 (sarscov-2). currently, there is no clear evidence to suggest that imt for ocular diseases increases the risk for infection or complications from covid19. although further studies are needed, perhaps tocilizumab, which has recently been shown to reduce risk of death in patients with severe covid-19 disease,[32, 33] can be considered as an alternative treatment option for patients with niu who fail therapy with infliximab. financial support and sponsorship dlh and bhp have no relevant funding disclosures. qdn and his employer, stanford university, have received research funding from genentech, gilead, regeneron, and santen, among others. references 1. uludag g pj, onghangseng nl, halim ms, hassan m, doan hl, chea s, xiang j, akhavanrezayat a, do dv, sepah yj, nguyen qd: posterior segment manifestations in patients with hla-b27-associated uveitis. association for research in vision and ophthalmology (arvo) abstract a0503. 2. campbell jp, leder ha, sepah yj, gan t, dunn jp, hatef e, et al. wide-field retinal imaging in the management of noninfectious posterior uveitis. am j ophthalmol 2012;154:908–911.e2. 3. leder ha, campbell jp, sepah yj, gan t, dunn jp, hatef e, et al. ultra-wide-field retinal imaging in the management of non-infectious retinal vasculitis. j ophthalmic inflamm infect 2013;3:30. 4. braakenburg am, de valk hw, de boer j, rothova a. human leukocyte antigen-b27-associated uveitis: long-term follow-up and gender differences. am j ophthalmol 2008;145:472–479. 5. power wj, rodriguez a, pedroza-seres m, foster cs. outcomes in anterior uveitis associated journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 443 editorial; hien et al with the hla-b27 haplotype. ophthalmology 1998;105:1646–1651. 6. bajwa a, maleki a, payal ar, fandiño a, padrón mim, walsh m, foster cs. efficacy and safety of infliximab in hla-b27associated ocular inflammation refractory or intolerant to conventional immunomodulatory therapy. j ophthalmic vis res 2020;15:2–11. 7. rathinam sr, gonzales ja, thundikandy r, kanakath a, murugan sb, vedhanayaki r, et al. effect of corticosteroid-sparing treatment with mycophenolate mofetil vs methotrexate on inflammation in patients with uveitis: a randomized clinical trial. jama 2019;322:936–945. 8. markomichelakis n, delicha e, masselos s, fragiadaki k, kaklamanis p, sfikakis pp. a single infliximab infusion vs corticosteroids for acute panuveitis attacks in behcet’s disease: a comparative 4-week study. rheumatology 2011;50:593–597. 9. suhler eb, smith jr, giles tr, lauer ak, wertheim ms, kurz de, et al. infliximab therapy for refractory uveitis: 2-year results of a prospective trial. arch ophthalmol 2009;127:819–822. 10. markomichelakis n, delicha e, masselos s, sfikakis pp. intravitreal infliximab for sight-threatening relapsing uveitis in behcet disease: a pilot study in 15 patients. am j ophthalmol 2012;154:534–541.e1. 11. sfikakis pp, kaklamanis ph, elezoglou a, katsilambros n, theodossiadis pg, papaefthimiou s, et al. infliximab for recurrent, sight-threatening ocular inflammation in adamantiades-behcet disease. ann int med 2004;140:404–406. 12. miraldi utz v, bulas s, lopper s, fenchel m, sa t, mehta m, et al. effectiveness of long-term infliximab use and impact of treatment adherence on disease control in refractory, non-infectious pediatric uveitis. pediatr rheumatol 2019;17:79. 13. sfikakis pp, theodossiadis pg, katsiari cg, kaklamanis p, markomichelakis nn: effect of infliximab on sight-threatening panuveitis in behcet’s disease. lancet 2001;358:295–296. 14. ohno s, nakamura s, hori s, shimakawa m, kawashima h, mochizuki m, et al. efficacy, safety, and pharmacokinetics of multiple administration of infliximab in behcet’s disease with refractory uveoretinitis. j rheumatol 2004;31:1362–1368. 15. okada aa, goto h, ohno s, mochizuki m. multicenter study of infliximab for refractory uveoretinitis in behcet disease. arch ophthalmol 2012;130:592–598. 16. richards jc, tay-kearney ml, murray k, manners p. infliximab for juvenile idiopathic arthritis-associated uveitis. clin exp ophthalmol 2005;33:461–468. 17. rajaraman rt, kimura y, li s, haines k, chu ds. retrospective case review of pediatric patients with uveitis treated with infliximab. ophthalmology 2006;113:308–314. 18. hatemi g, christensen r, bang d, bodaghi b, celik af, fortune f, et al. 2018 update of the eular recommendations for the management of behcet’s syndrome. ann rheum dis 2018;77:808–818. 19. sfikakis pp, kaklamanis ph, elezoglou a, katsilambros n, theodossiadis pg, papaefthimiou s, et al. infliximab for recurrent, sight-threatening ocular inflammation in adamantiades-behçet disease. ann int med 2004;140:404–406. 20. biester s, deuter c, michels h, haefner r, kuemmerle-deschner j, doycheva d, et al. adalimumab in the therapy of uveitis in childhood. br j ophthalmol 2007;91:319–324. 21. jaffe gj, dick ad, brézin ap, nguyen qd, thorne je, kestelyn p, et al. adalimumab in patients with active noninfectious uveitis. n engl j med 2016;375:932– 943. 22. nguyen qd, merrill pt, jaffe gj, dick ad, kurup sk, sheppard j, et al. adalimumab for prevention of uveitic flare in patients with inactive non-infectious uveitis controlled by corticosteroids (visual ii): a multicentre, double-masked, randomised, placebocontrolled phase 3 trial. lancet 2016;388:1183–1192. 23. sepah yj, sadiq ma, chu ds, dacey m, gallemore r, dayani p, et al. primary (month-6) outcomes of the stop-uveitis study: evaluating the safety, tolerability, and efficacy of tocilizumab in patients with noninfectious uveitis. am j ophthalmol 2017;183:71–80. 24. heissigerova j, callanan d, de smet md, srivastava sk, karkanova m, garcia-garcia o, et al. efficacy and safety of sarilumab for the treatment of posterior segment noninfectious uveitis (sarilniu): the phase 2 saturn study. ophthalmology 2019;126:428–437. 25. ibrahim ma, sepah yj, watters a, bittencourt m, vigil em, do dv, et al. one-year outcomes of the save study: sirolimus as a therapeutic approach for uveitis. transl vis sci technol 2015;4:4. 26. nguyen qd, merrill pt, clark wl, banker as, fardeau c, franco p, et al. intravitreal sirolimus for noninfectious uveitis: a phase iii sirolimus study assessing double-masked uveitis treatment (sakura). ophthalmology 2016;123:2413–2423. 27. nguyen qd, merrill pt, sepah yj, ibrahim ma, banker a, leonardi a, et al. intravitreal sirolimus for the treatment of noninfectious uveitis: evolution through preclinical and clinical studies. ophthalmology 2018;125:1984–1993. 444 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 editorial; hien et al 28. merrill pt, clark wl, banker as, fardeau c, franco p, lehoang p, et al. efficacy and safety of intravitreal sirolimus for noninfectious uveitis of the posterior segment: results from the sirolimus study assessing double-masked uveitis treatment (sakura) program. ophthalmology 2020;27:p1405–p1415. 29. kenawy n, cleary g, mewar d, beare n, chandna a, pearce i. abatacept: a potential therapy in refractory cases of juvenile idiopathic arthritis-associated uveitis. graefes arch clin exp ophthalmol 2011;249:297–300. 30. marrani e, paganelli v, de libero c, cimaz r, simonini g. long-term efficacy of abatacept in pediatric patients with idiopathic uveitis: a case series. graefes arch clin exp ophthalmol 2015;253:1813–1816. 31. agarwal a, hassan m, sepah yj, do dv, nguyen qd. subcutaneous repository corticotropin gel for non-infectious panuveitis: reappraisal of an old pharmacologic agent. am j ophthalmol case rep 2016;4:78–82. 32. cortegiani a, ippolito m, greco m, granone v, protti a, gregoretti c, giarratano a, einav s, cecconi m: rationale and evidence on the use of tocilizumab in covid-19: a systematic review. pulmonology 2020; [epub ahead of print]. 33. toniati p, piva s, cattalini m, garrafa e, regola f, castelli f, et al. tocilizumab for the treatment of severe covid-19 pneumonia with hyperinflammatory syndrome and acute respiratory failure: a single center study of 100 patients in brescia, italy. autoimmun rev 2020;19:102568. correspondence to: quan dong nguyen, md, ms. spencer center for vision research, byers eye institute at stanford university 2452 watson court suite 200, palo alto, ca 94303, usa. e-mail: ndquan@stanford.edu access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7777 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: hien dl, pham bh, nguyen qd. how do we manage hla-b27-associated ocular inflammation refractory or intolerant to conventional immunomodulatory therapy?. j ophthalmic vis res 2020;15:442–445. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 445 https://knepublishing.com/index.php/jovr original article releasable suture versus autologous blood for pterygium surgery using conjunctival autografts gautam singh parmar, ms; bhushan ghodke, ms, dnb, fico; ashok kumar meena, ms department of cornea and refractive services, sadguru seva sang trust, chitrakoot, madhya pradesh, india orcid: bhushan ghodke: https://orcid.org/0000-0003-2769-9985 abstract purpose: to evaluate the efficacy of releasable single suture (rs) for conjunctival autograft (cag) and to compare it with sutureless gluefree (sg) technique in pterygium surgery. methods: we conducted a retrospective comparative study on patients with primary pterygium who underwent cag. in 150 patients, cag was additionally secured by a single 10-0 nylon releasable suture (rs) which was released on the first postoperative day. in 47 patients, no suture was applied, and cag was allowed to stick to the scleral bed by autologous fibrin only (sg group). the duration of surgery and size of cag (in mm2) was noted in both groups. all patients completed one year of follow-up. factors that were studied included graft stability, patient comfort, complications, and recurrence. results: the mean age of patients in rs and sg groups was 39.6 ± 11.8 and 47.3 ± 13.8 years, respectively. the mean duration of surgery was 4.84 ± 1.34 min in rs group and 4.90 ± 1.42 min in sg group (p = 0.001). the size of cag used in both groups was comparable with more stability in rs group postoperatively. graft retraction rate in rs group was 5.3% (1 mm retraction in cag more than 36 mm2) with no event of graft loss. the graft loss occurred in 6.3% of eyes in sg group. the recurrence rate in rs group was 4%, while in sg group it was 6.3% (p = 0.4). conclusion: rs, by augmenting the autologous blood mechanism, may offer an easy to learn option for pterygium surgery with good stability even in large sized cags. keywords: autologous blood; conjunctival autograft; pterygium; recurrence; releasable suture j ophthalmic vis res 2020; 15 (1): 32–37 correspondence to: bhushan ghodke, ms, dnb, fico. 3, new doctor’s building, sadguru seva sang trust, jankikund, chitrakoot, madhya pradesh 210204, india. e-mail: ghodke.bhushan@gmail.com received: 16-11-2018 accepted: 14-08-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i1.5938 introduction pterygium is a triangular “wing-like” growth consisting of conjunctival epithelium and hypertrophied subconjunctival connective tissue this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: parmar gs, ghodke b, meena ak. releasable suture versus autologous blood for pterygium surgery using conjunctival autografts. j ophthalmic vis res 2020;15:32–37. 32 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i1.5938&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr suture vs autologous blood for pterygium surgery; parmar et al that encroaches onto the cornea.[1] the surgical excision is the treatment of choice, but its propensity for recurrence is a major concern. switching from unacceptably high recurrence rate of bare sclera technique (60–80%)[2] to encouraging results of conjunctival autograft (cag) was popularized by kenyon et al.[3] to date, cag remains a time-tested and gold standard treatment with low recurrence and high stability.[3, 5] but, the debate over the best approach is focused on whether surgeons should use sutures or suture-less options like fibrin glue or autologous fibrin to secure the cag. fibrin glue has shorter duration of surgery, better patient comfort, and less chance of recurrences (14%) compared to other techniques for cag fixation.[4] important disadvantages are cost and accessibility. in fibrin-assisted surgery, complications such as dehiscence, graft retraction, and pyogenic granuloma were seen more frequently.[5, 6] suture assisted surgery ensures graft stability with acceptable recurrence rates of 5–15%.[7] the immediate postoperative patient discomfort with symptoms of pain, watering, foreign body sensation, and sub-conjunctival hematoma are its major disadvantages.[8, 9] thus, we proposed a newer suture assisted technique in which the cag was secured by a single 10-0 nylon suture with a releasable knot and was released on the first postoperative day. we compared its results with current accepted standard of autologous blood assisted pterygium surgery. methods we conducted a retrospective comparative observational study at our tertiary eye care center. medical records of 197 patients with primary pterygium were reviewed. all methods adhered to the tenets of the declaration of helsinki principles for research in human subjects. the treatment groups were assigned arbitrarily by one of the authors. in the rs group (n = 150), cag was secured by a single 10-0 nylon suture tied with a releasable knot. in the sg group (n = 47), patients’ own blood from the surgical area was used as a source of fibrin. we followed the slit-lamp grading system given by tan et al.[10] all patients were operated by a single surgeon. primary outcome measures were graft stability and recurrence. secondary outcome measures were patient comfort in terms of pain on visual analogue scale (vas) and best corrected visual acuity (bcva). descriptive and inferential statistical analysis was carried out in the present study. chisquare/fisher exact test was used to find the significance of study parameters on categorical scale between the two groups. the significance was assessed at 5% level of significance. the statistical software namely spss 15.0 was used for the analysis of the data and microsoft word and excel were used to generate graphs and tables. surgical technique the body of pterygium was firmly held at limbus by toothed forceps, and adhesion between the pterygium and sclera was sharply incised and separated using conjunctival scissors. the head of pterygium was avulsed from the underlying cornea. the fibrous tissue was scrapped off by bard-parker 15 number blade. only the fleshy subconjunctival hypertrophied tissue with tortuous vessels and adjacent thickened conjunctival tissue was excised. the size of the bare-scleral defect was measured in millimeter square (mm2) by castroviejo calipers. cag was taken from superior quadrant by ballooning the conjunctiva with 0.5 cc dexamethasone (4mg/ml) subconjunctival injection. a thin tenon-free cag was prepared. graft flip was done with an iris spatula and was transferred to bare sclera carefully to coincide the limbal to limbal area and keeping the epithelial side up. ironing of the graft was done with two iris spatulas. in rs group, though the cag was already stuck to the underlying bare sclera due to autologous fibrin, the center of cag was additionally stabilized (see figure 1, showing diagrammatic representation of a releasable suture (rs) in situ) by single 10-0 nylon suture tied in a releasable fashion keeping one end of suture longer than the other (see video, electronic supplementary material 1, showing the application of rs). in sg group, bleeding secondary to excision of vessel-rich tissue was used as a source of autologous fibrin. excessive bleeding was controlled by hemostasis with the help of sterile merocel sponge to avoid graft relift. graft was examined for apposition. end of surgery was noted after the removal of the eye speculum. journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 33 suture vs autologous blood for pterygium surgery; parmar et al after 24 h, on the first postoperative day, patient was examined using a slit-lamp (see figure 2, showing preoperative and postoperative slit-lamp photograph of patient 1). proparacaine 0.5% eye drop was used as topical anesthetic agent and the suture was released at slit-lamp by pulling the longer end of the 10-0 nylon suture in rs group; patient was re-examined for graft status, apposition, and retraction. the vas with grading from 1 to 10 was shown and explained to patients, asking them to report the severity of pain after the release of suture on the first postoperative day. postoperatively, all patients were given low potency steroid eye drops four times a day for the first week and tapered off over six weeks, while antibiotic drops were administered four times a day for two weeks. all patients were examined at week 2 and at months 3, 6, and 12. during each visit, patients were evaluated for visual acuity, graft apposition, pain on vas, complications, and pterygium recurrence. recurrence was defined as any fibrovascular regrowth extending beyond the surgical limbus involving the cornea. results both groups were comparable regarding the demographic profile [table 1]. the mean age of patients was 39.6 ± 11.8 years and 47.3 ± 13.8 years in rs and sg groups, respectively. the primary pterygium was present on the right side in the majority of patients. the predominant type of pterygium in our study was of tan’s grade 2 (60% in rs group and 68% in sg group); while 40% of patients were of tan’s grade 1 in rs group; and 29% of patients were of tan’s grade 3 in sg group. the mean duration of surgery in rs group was 4.84 ± 1.34 min with minimum of 3 min and maximum of 10 min. in sg group, the mean duration of surgery was 4.90 ± 1.42 min. in rs group, 36% of patients complained of pain of scale 2 following the release of suture on the first postoperative day, while in sg group, 44% of patients had a pain scale of grade 2. mean bcva before surgery was 0.27 ± 0.41 and 0.22 ± 0.33 logmar which improved to 0.16 ± 0.28 and 0.16 ± 0.22 logmar at 2 weeks after surgery and was maintained thereafter till the last followup visit in rs and sg groups, respectively. the maximum area of cag was 42mm2 in both rs and sg groups. in sg group, one patient suffered from the event of graft loss because of eye rubbing. a second procedure was done on the same day and a second cag was derived from the contralateral eye after obtaining an informed consent from the patient. while in rs group, eight (5.3%) patients in whom the cag was greater than 36mm2, the graft was retracted by 1 mm from the nasal margin during the release of the suture on the first postoperative day, which was successfully repositioned by graft ironing. in seven (4.6%) patients in the rs group, there was failed attempt in releasing the suture. in these patients, the suture was then cut with vanna’s scissor and removed. in six (4 %) patients in the rs group and three (6.3%) patients in the sg group, there was a recurrence of grade 1 (conjunctival), which did not involve the cornea at one year postoperatively. no patients were lost to followup. discussion from bare sclera technique to mini-simple limbal epithelial transplant,[11] surgical techniques for pterygium are constantly evolving. the majority of these techniques require sutures with postoperative suture related complications.[12, 13] this retrospective comparative study showed no significant difference in recurrence rate of pterygium after surgery in rs and sg groups. both techniques were equally effective in lowering the recurrence rate after pterygium surgery. however, with addition of a simple step of applying a single rs to the autologous fibrin technique, the surgeon can be assured of not losing the cag completely in cases with graft loss. this is important in patients coming from low socio-economic strata in developing countries, where the post operative period is complicated by a number of factors, especially eye rubbing. compared to sutures, sutureless options such as fibrin glue, introduced by koranyi et al,[4] and autologous blood[14, 15] are more popular adjuvants for cag. although considered safe, the theoretical potential risk of transmission of infections like parvovirus-b19, hepatitis b virus, human immunedeficiency virus, and anaphylaxis in susceptible individuals make fibrin glue, an “off-label” adjuvant by food and drug administration (fda) for the use in ophthalmology.[14, 16] on the other hand, the cost of fibrin glue is equal to five sutures making it less cost-effective.[16] improper adherence 34 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 suture vs autologous blood for pterygium surgery; parmar et al figure 1. diagrammatic representation of releasable single suture in situ. figure 2. preoperative and postoperative slit-lamp photograph of patient 1. of fibrin glue causing graft loss is a recognized complication.[17, 18] in last few years, several studies published results of autologous blood as a biological agent in pterygium surgery. commercially available fibrin glue consists of two components – sealer protein solution (human fibrinogen and a synthetic fibrinolysis inhibitor, aprotinin) and the thrombin solution (human thrombin). when mixed together, these two components combine and mimic the final stages of natural clotting cascade to form a cross-linked fibrin clot. whereas, the mechanism of action of autologous blood as a sealant is the natural clotting cascade resulting in fibrin polymerization. autologous fibrin is associated with disadvantages such as graft dehiscence and graft loss. in these patients with graft loss, a second surgery is generally required in which the cag is retrieved from the fellow eye being ultimately and reliably affixed by sutures.[19] in our study, there was one patient in sg group who suffered graft loss on the first postoperative day due to eye rubbing. the cag was then retrieved from the contralateral eye after proper counselling and written consent. in contrast, no event of graft loss occurred in the rs group. the most important step in patients operated with rs was releasing the suture on the first postoperative day. we experienced graft retraction of 1 mm in eight (5.3%) patients with large grafts (more than 36 mm2), after the suture was released. also, pulling the long end of the rs posed some difficulty in seven (4.6%) patients, which was then managed with vanna’s scissor. in rs group, the suture helped in proper and uniform adherence of autograft to the scleral bed during the immediate postoperative period especially first 24 h. the mean surgical time in the rs group was 4.84 ± 1.34 min, while a relatively longer mean operating time of 4.90 ± 1.42 min in the sg group was present which was statistically insignificant (p=0.86). studies in the past demonstrated the journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 35 suture vs autologous blood for pterygium surgery; parmar et al table 1. the details of demographic and other variables in respective groups variables categories rs group (n = 150) (rs-releasable suture) sg group (n = 47) (sg-sutureless gluefree) p-value age (in years) < 20 1(0.7%) 0(0%) 20–30 42(28%) 8(17%) 31–40 51(34%) 11(23.4%) 41–50 36(24%) 9(19.1%) 51–60 12(8%) 11(23.4%) > 60 8(5.3%) 8(17%) mean age (years) 39.65 ± 11.85 47.36 ± 13.84 gender male 62(41.3%) 25(53.2%) 0.15 female 88(58.7%) 22(46.8%) eye involved left 51(34%) 22(46.8%) 0.11 right 99(66%) 25(53.2%) pterygium grade 1 60(40%) 1(2.1%) 0.54(tan et al) 2 90(60%) 32(68.1%) 3 0 14(29.8%) duration of surgery 1-5 109(72.7%) 35(74.4%) 0.86 6-10 41(27.3%) 12(25.5%) mean duration (minutes) 4.84 ± 1.34 4.90 ± 1.42 recurrence 6 (4%) 3 (6.3%) 0.495 correlation of surgical time and success of pterygium surgery.[14] more intraoperative time leads to increased postoperative reaction and leads to infection.[20] the short time taken to apply a single rs means more pterygium surgeries in less time. the pain scale on vas was consistently less than 2 in all 197 patients on the first postoperative day. this result is comparable to studies in which fibrin glue[4] or autologous blood[14, 16] is used. complications like serious inflammatory reaction, infection, corneal ulceration, scleral melting or dellen were not noticed in any of the patients. mitra et al[20] mentioned that once the cag stays in place for the first 24–48 h, it is going to stick around. thus, the use of single suture for the first 24 h, as a simple additional step to the autologous fibrin technique, gives a psychological relief to the operating surgeon. hirst et al[21] reported that 97% of pterygium recurrences develop within the first 12 months of surgery. in our study, the conjunctival recurrence rate was 4% in the rs group and 6.3% in the sg group, which is comparable to the reports from other similar studies. there are several limitations in our study. firstly, the retrospective study design has its inherent limitation. secondly, a relatively small sample size of 197 patients. third, a follow-up period of one year may not be sufficient to comment on the efficacy of our technique with respect to the recurrence. further evaluation is required to study the recurrence rate and complications after rs, with larger sample size and randomized controlled trials. we recommend that the length of rs over the graft surface should be adequately long as governed by the area of cag. further studies are required to find the correlation of suture length and the area of cag and its impact on the graft stability. in conclusion, in pterygium surgery, rs did not significantly reduce postoperative pterygium recurrence. however, in cases with large-sized cags and in patients with increased frequency of eye rubbing, rs may offer an easy-to-learn and reliable method by augmenting the autologous fibrin mechanism. the postoperative patient comfort is comparable to the currently accepted standard of 36 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 suture vs autologous blood for pterygium surgery; parmar et al sutureless gluefree (sg) technique for pterygium surgery. references 1. duke-elder s. diseases of the outer eye. syst ophthalmol 1965;8:573–585. 2. hirst lw. the treatment of pterygium. surv ophthalmol 2003;48:145–180. 3. kenyon kr, wagoner md, hettinger me. conjunctival autograft transplantation for advanced and recurrent pterygium. ophthalmology 1985;92:1461–1470. 4. koranyi g, seregard s, kopp ed. the cut-and-paste method for primary pterygium surgery: long-term followup. acta ophthalmol 2005;83:298–301. 5. chen pp, ariyasu rg, kaza v, labree ld, mcdonnell pj. a randomized trial comparing mitomycin c and conjunctival autograft after excision of primary pterygium. am j ophthalmol 1995;120:151–160. 6. uy hs, reyes jm, flores jd, lim-bon-siong r. comparison of fibrin glue and sutures for attaching conjunctival autografts after pterygium excision. ophthalmology 2005;112:667–671. 7. ti se, chee sp, dear kb, tan dt. analysis of variation in success rates in conjunctival autografting for primary and recurrent pterygium. br j ophthalmol 2000;84:385–389. 8. fan xu, min li, yumei yan, lu k, cui l, chen q. a novel technique of sutureless and glueless conjunctival autografting in pterygium surgery by electrocautery pen. cornea 2013;32:290–295. 9. yasemin o, seda m, unsal h, ileri d, onal b, ilhan o, et al. a comparative study of tissue glue and vicryl suture for closing limbal conjunctival autografts and histologic evaluation after pterygium excision. cornea 2008;27:552–558. 10. tan dh, chee sp, dear kb, lim as. effect of pterygium morphology on pterygium recurrence in a controlled trial comparing conjunctival autografting with bare sclera excision. arch ophthalmol 1997;115:1235–1240. 11. hernándezbe, amescua g, navas a, garfias y, ramirezmiranda a, lichtinger a, et al. minor ipsilateral simple limbal epithelial transplantation (mini-slet) for pterygium treatment. br j ophthalmol 2015;99:1598–1600. 12. allan bd, short p, crawford gj, barrett gd, constable ij. pterygium excision with conjunctival autografting: an effective and safe technique. br j ophthalmol 1993;77:698–701. 13. tan d. conjunctival grafting for ocular surface disease. curr opin ophthalmol 1999;10:277–281. 14. kurian a, reghunadhan i, nair kgr. autologous blood versus fibrin glue for conjunctival autograft adherence in sutureless pterygium surgery: a randomised controlled trial. br j ophthalmol 2015;99:464–470. 15. d de wit, i athanasiadis, a sharma. sutureless and gluefree conjunctival autograft in pterygium surgery: a case series. eye 2010;24:1474–1477. 16. kaufman sc, jacobs ds, lee wb, deng sx, rosenblatt mi, shtein rm. options and adjuvants in surgery for pterygium. ophthalmology 2013;120:201–208. 17. jiang j, yang y, zhang m, fu x, bao x, yao k. comparison of fibrin sealant and sutures for conjunctival autograft fixation in pterygium surgery: one-year follow-up. ophthalmologica 2008;222:105–111. 18. karalezli a, kucukerdonmez c, akova ya, altan-yaycioglu r, borazan m. fibrin glue versus sutures for conjunctival autografting in pterygium surgery: a prospective comparative study. br j ophthalmol 2008;92:1206–1210. 19. foroutan a, beigzadeh f, ghaempanah mj, eshghi p, amirizadeh n, sianati h, et al. efficacy of autologous fibrin glue for primary pterygium surgery with conjunctival autograft. iran j ophthalmol 2011;23:39–47. 20. mitra s et al. autoblood as tissue adhesive for conjunctival autograft fixation in pterygium surgery. poster presented at the annual meeting of the american academy of ophthalmology. orlando, fl; 2011. 21. hirst lw, sebban a, chant d. pterygium recurrence time. ophthalmology 1994;101:755–758. supplemental video video showing technique of application of the releasable suture. journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 37 review article stem cell therapy in stargardt disease: a systematic review atousa moghadam fard1, md; reza mirshahi1, md; masood naseripour2, md; khalil ghasemi falavarjani2, md 1eye research center, the five senses health institute, rassoul akram hospital, iran university of medical sciences, tehran, iran 2stem cell and regenerative medicine research center, iran university of medical sciences, tehran, iran orcid: khalil ghasemi falavarjani: https://orcid.org/0000-0001-5221-1844 atousa moghadam fard: https://orcid.org/0000-0003-2763-1577 abstract this article aimed to review current literature on the safety and efficacy of stem cell therapy in stargardt disease. a comprehensive literature search was performed, and two animal and eleven human clinical trials were retrieved. these studies utilized different kinds of stem cells, including human or mouse embryonic stem cells, mesenchymal stem cells, bone marrow mononuclear fraction, and autologous bone marrow-derived stem cells. in addition, different injection techniques including subretinal, intravitreal, and suprachoroidal space injections have been evaluated. although stem cell therapy holds promise in improving visual function in patients with stargardt disease, further investigation is needed to determine the long-term benefits, safety, and efficacy in determining the best delivery method and selecting the most appropriate stem cell type. keywords: juvenile-onset macular degeneration; juvenile-onset macular dystrophy; stargardt disease; stem cell; stem cell therapy j ophthalmic vis res 2023; 18 (3): 318–327 introduction stargardt macular dystrophy, also known as stargardt disease, is the most common form of inherited autosomal recessive macular dystrophy in humans, with a prevalence of 1 in 10/000 people.[1–3] stargardt diseases causes juvenileonset bilateral progressive vision loss. the disease occurs due to macular retinal pigment epithelium (rpe) atrophy and photoreceptor loss, which starts from the foveal and para-foveal areas.[4] correspondence to: khalil ghasemi falavarjani, md. eye research center, rassoul akram hospital, sattarkhan niayesh st., tehran 14553, iran. email: drghasemi@yahoo.com received: 20-08-2022 accepted: 26-01-2023 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i3.13780 stargardt disease is caused by mutations in the atp-binding cassette subfamily a, member 4 (abca4) gene (also known as abcr), which is located in the short arm of chromosome 1 in the majority of cases.[5] although stargardt diseases is a monogenic disease, because of multiple mutations (different variants of abca4), there is heterogeneity in the age of onset of the disease and variations in clinical presentations.[6–8] currently, there is no fda-approved therapy for stargardt disease. several approaches, including stem cell therapy, gene therapy, complement this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: moghadam fard a, mirshahi r, naseripour m, falavarjani kg. stem cell therapy in stargardt disease: a systematic review. j ophthalmic vis res 2023;18:318–327. 318 © 2023 moghadam fard et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i3.13780&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr stem cell therapy in stargardt disease; moghadam fard et al inhibitors, and visual cycle modulators, have been proposed for the treatment of stargardt disease.[9, 10] several studies are in the preclinical or early clinical phases to determine the safety and efficacy of treatment modalities.[9, 11] stem cell therapy is one of the promising approaches on the horizon for the treatment of retinal dystrophies. stem cells are able to differentiate into various kinds of cell types to replace lost or damaged cells.[12] several studies have been conducted to determine the safety and efficacy of stem cell therapy for stargardt disease.[13–25] in addition, various stem cell types and delivery methods have been studied.[13–25] in this article, studies reporting stem cell therapy for the treatment of stargardt disease were reviewed. methods the present study was designed based on the guidelines of preferred reporting items for systematic review and meta-analysis (prisma).[26] a comprehensive literature search was performed on medline/pubmed and scopus databases on november 20, 2022, without a time limitation; with the following search strategy: (stargardt or stargardt’s or juvenile-onset macular degeneration or juvenile-onset macular dystrophy) and (stem cell or stem-cell). reviews and non-english articles were excluded. all original studies that evaluated stem cell therapy in stargardt disease were included in this systematic review. articles were reviewed to include studies on stargardt disease caused by abca4 mutations. all the mentioned processes of the search and screening were performed by two independent investigators (amf, rm). any disagreement was resolved by discussion. if an agreement could not be reached, the disagreement was resolved by a third investigator who was an expert in the study field (kgf). the quality of evidence for the studies which were finally included was assessed using the grading of recommendations, assessment, and evaluation (grade) approach developed by the cochrane collaboration. in this system, the randomized clinical trials (rcts) start the assessment process as high quality (four stars) and non-rcts start with a low-quality score (two stars). afterward, based on risk of bias, inconsistency, indirectness, imprecision, and publication bias, the study is downgraded. in rare instances, it is upgraded in case of large effect, dose response, or no plausible confounding.[27] results the initial literature search revealed 179 articles. finally, a total of 13 articles, including 2 animal and 11 human studies, met our inclusion criteria and were included in this review [figure 1]. in total, 95 eyes from 78 human participants were treated by stem cells [table 1]. among the 11 human studies, 7 reported the use of human embryonic stem cells (hesc),[13, 14, 16, 19, 21–23] 2 reported the use of autologous bone marrow-derived stem cells,[15, 20] 1 reported the use of adipose tissue-derived mesenchymal stem cells (mscs),[18] and 1 reported the use of bone marrow mononuclear fraction with cd34+ cells.[17] the delivery method in human studies was subretinal[13, 14, 16, 19–23] in eight articles, intravitreal[17] in one, suprachoroidal[18] in one, and a mix of methods including retrobulbar, subtenon, intravitreal, subretinal, and intravenous[15] in one study. complications among human studies included the occurrence of small subretinal hemorrhage at the injection site in two eyes, mild vitreous cavity hemorrhage in one eye, retinal detachment in two eyes, high postoperative intraocular presser in two eyes, acute vitreous culture-positive endophthalmitis (staphylococcus epidermidis) in one eye, and cataract in three eyes. furthermore, one eye experienced proliferative vitreoretinopathy. in addition, in one eye with a high dosage of stem cell injection, localized retinal thinning and decreased sensitivity in the hyperpigmentation area was reported. stem cell treatment led to significant improvement in visual acuity in 38 eyes as compared to the fellow untreated eyes. the quality of evidence was assessed as very low for all included studies as none of them were rcts. in addition, the low sample size number and lack of independent analysis were important factors in determining the final quality score. therefore, due to the bias induced by these factors, the final score was downgraded in all studies to the lowest possible quality score. journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 319 stem cell therapy in stargardt disease; moghadam fard et al discussion the results of this review show that stem cell therapy holds promise in improving visual function for stargardt disease. with stem cell therapy, the visual acuity improved significantly in 38 eyes out of 95 treated eyes. no tumor formation, teratoma formation, differentiation of stem cell into ectopic cells, or immune rejection of the transplanted tissue was found. the most reported adverse events following stem cell therapy in stargardt patients were hemorrhage (subretinal and vitreous cavity), retinal detachment, cataract, and high postoperative intraocular pressure. stargardt disease is a progressive, autosomal recessive disease which is caused by mutations in the abca4 gene, an atp-binding cassette transport gene superfamily member, which contains 50 exons and is on the short arm of chromosome number one (1p).[5, 19, 28, 29] the abca4 gene is localized to the rod and cone photoreceptors; the gene encodes the retinaspecific transmembrane protein that has a role in recycling the 11-cis-retinal. disruption of this cycle leads to lipofuscin accumulation, which is toxic to the rpe cells.[33–35] progressive bilateral atrophy of the rpe cells in stargardt disease occurs due to the accumulation of lipofuscin.[36] parmar et al[37] found that bis-retinoid n-retinyl-nretinylidene ethanolamine (a2e), which is a major component of lipofuscin, plays an important role in rpe death. in addition to what has been mentioned, in stargardt disease, lipofuscin-accumulated rpe cells display increased activity of c3 complement, and as there is a negative correlation between c3 and cd46 levels, the inhibition of the complement cascade decreases. this promotes the formation of membrane attack complex (mac) on the surface of rpe and leads to rpe death.[38] progressive reduction of visual function and photoreceptor death occur due to rpe atrophy, which occurs due to epoxides formation with blue light exposure in patients with stargardt disease.[15] exposure to light, especially ultraviolet (uv) light, and high doses of vitamin a accelerate the progression of stargardt disease.[39–42] a large amount of allelic heterogeneity has been reported in the abca4 gene; over 800 different mutations were mapped on the abca4 gene in stargardt disease, which causes various phenotypes and multiple severities of the disease.[43–45] the age of onset is a prognostic factor; patients with lower age of onset (early-onset) will experience more severe disease.[8] the typical presentation of stargardt disease is bilateral progressive central vision loss, including central scotoma and decreased visual acuity.[43] collison and fishman[46] evaluated the visual acuity of 221 stargardt patients aged >40 years; visual acuity decreased from the 20/200 to 20/400 or less, although none of the participants experienced profound visual loss. the typical clinical findings in stargardt disease are central macular atrophy and irregular yellowish–white fundus flecks in the posterior pole at the rpe level; the appearance of the fundus could vary.[39, 47–49] stem cells are a valuable resource of tissue transplantation due to their unlimited proliferation and their capacity to generate multiple cell lineages.[50] due to the low immunogenicity of stem cells, including embryonic or pluripotent stem cells (pscs), the chance of transplantation rejection is low.[51] different sources of stem cells including human embryonic stem cell (hesc), induced pluripotent stem cells (ipsc), mesenchymal stem cell (msc), and neural stem cells (nscs) are available.[18, 52] hescs and ipscs are pscs, which are derived from blastocysts and somatic cells, respectively.[53, 54] teratoma formation, cancer formation, immune rejection of the transplanted tissue, and differentiation of stem cells into unwanted ectopic cell types are the most critical safety concerns regarding hesc transplantation in humans.[21, 55] embryonic stem cells (escs) have immune rejection potential, and there are also ethical issues in using these cells; therefore, ipscs are preferred for clinical application.[56] due to the potential immune response or immune rejection of hescs, topical or systemic immune suppression is required in the transplantation of hescs.[57] mscs are stromal cells with multilineage differentiation ability that can be isolated from different sources, including bone marrow, adipose tissue, umbilical cord, endometrial polyp, and menses blood.[58] mscs have the ability to migrate and differentiate into the injured tissues, which is called homing ability. furthermore, mscs have immunomodulatory effects such as preventing the function and proliferation of t cells, b cells, and natural killer cells.[58, 59] the low immunogenicity of mscs is due to 320 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 stem cell therapy in stargardt disease; moghadam fard et al table 1. characteristics and outcomes of interventional studies that evaluated stem cell therapy for stargardt disease. author and publication year country study design human vs animal participants method stem cell type efficacy complications quality assessment score (grade) 2023 rodrigo a brant fernandes et al[13] brazil (phase 1 clinical trial) nonrandomized interventional clinical trial human study 12 eyes from 12 participants subretinal hesc no significant improvement in bcva was found no complications were found very low 2021 shi-yung li et al[14] china (phase 1 clinical trial) nonrandomized interventional clinical trial human study 7 eyes from 7 participants subretinal hesc no significant improvement was found except in one patient high postoperative intraocular pressure in two eyes very low 2021 jeffrey n weiss et al[15] usa open label, non-randomized interventional clinical trial human study 34 eyes from 17 participants retrobulbar, subtenons, intravitreal, subretinal and intravenous autologous bone marrowderived stem cell the visual acuity improved in 21 eyes with the mean improvement of +0.4095 logmar, or 4.29 lines of vision no complications were found very low 2021 youngje sung et al[16] republic of korea non-randomized interventional clinical trial human study 3 eyes subretinal hesc the visual acuity significantly improved in an eye with 19 etdrs letters bcva improvement retinal detachment in one eye very low 2020 carina costa cotrim et al[17] brazil open label, non-randomized interventional clinical trial human study 10 eyes intravitreal bone marrow mononuclear fraction with cd34+ cells the mean of visual acuity improved from 1.1 logmar to 0.96, 0.92, and 0.98 logmar at 1, 3, and 6 months after iv injection, respectively no complications were found very low 2018 ayse oner et al[18] turkey (phase 1/2 clinical trial) nonrandomized interventional clinical trial human study 4 eyes suprachoroidal adipose tissue-derived mesenchymal stem cell visual acuity and visual field improvement in all participants. the mean bcva improved from 1.52 logmar to 1.02 logmar no complications were found very low 2018 manjit s mehat et al[19] uk (phase 1/2 clinical trial) open-label, nonrandomized interventional clinical trial human study 12 eyes subretinal hesc no significant benefits were found at 12 months small subretinal hemorrhage in two eyes and mild vitreous cavity hemorrhage in one eye. very low 2016 ella h leung et al[20] usa case report human study 1 eye subretinal autologous bone marrowderived stem cell visual acuity improved from 1.3 logmar (20/400) to 1.2 logmar (20/300) temporary retinal detachment and proliferative vitreoretinopathy very low 2015 steven d schwaretz et al[21] usa (phase 1/2 clinical trial) nonrandomized interventional clinical trial human study 9 eyes subretinal hesc no significant improvement. visual acuity insignificantly improved in three eyes at twelve months acute vitreous endophthalmitis in one eye and three eyes developed cataracts very low 2015 won kyung song et al[22] republic of korea non-randomized interventional clinical trial human study 2 eyes subretinal hesc visual acuity improved with the mean of 15.5 etdrs. patient one from counting finger to 1.5 logmar, patient 2 from 1.5 to 1.1 logmar no complications were found very low 2012 steven d schwartz et al[23] usa (preliminary report) nonrandomized interventional clinical trial human study 1 eye subretinal hesc visual acuity improved from hand motion (0 etdrs) to 1.6 logmar (5 etdrs) no complications were found very low 2012 katherine j wert et al[24] usa animal interventional study animal study one postnatal day five mice subretinal mouse embryonic stem cell bcva was not determined presence of stem cells in 15 weeks mouse temporary retinal detachment very low 2009 bin lu et al[25] usa animal interventional study animal study the rcs rat, elov14 mouse, and the nih iii immunedeficient mouse model subretinal hesc treated eyes with stem cell injection had significantly better visual acuity than control eyes with sham injection. details of visual acuity were not determined no complications were found very low hesc, human embryonic stem cell; grade, grading of recommendations, assessment, and evaluation journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 321 stem cell therapy in stargardt disease; moghadam fard et al records identified by databases searching (n = 179) pubmed: 108 scopus: 71 records removed before screening: duplicate records removed (n = 43) identification of studies via databases id e n ti fi c a ti o n records screened (title/abstract) (n = 136) records excluded after screening of title/abstract (n = 78) full-texts assessed for eligibility (n = 58) reports excluded with reason: (n = 45) no assessment of stem cell therapy in stargardt disease, other types of macular degeneration (except stargardt), duplications, and reviews or non-clinical trial articles studies included in review (n = 13) human clinical trials: 11 animal clinical trials: 2 s c re e n in g in c lu d e d e li g ib il it y figure 1. prisma flow diagram of search steps and designs. low hla class і levels and the absence of hla class іі expression.[60] these features make mscs an appropriate candidate for stem cell transplantation. mscs include bone marrow mscs (bmmscs) and adipose tissue-derived mscs (admscs). there are advantages in using admscs as compared to bmmscs, such as higher immunomodulatory effects and easier harvest.[18] there are three main routes for stem cell delivery in retinal degeneration: subretinal, suprachoroidal, and intravitreal injections. most studies have chosen the subretinal injection method for stem cell transplantation.[15, 16, 19–25] subretinal space is an immune-privileged site; with a reduced chance of transplantation rejection.[61, 62] rpe suppresses t cell activation by secreting cytokines, such as transforming growth factor β, thrombospondin1, prostaglandin e2, cytotoxic t lymphocyteassociated antigen 2α, and retinoic acid.[61] in addition, rpe converts intraocular t cells into regulatory t cells by secretion of cytotoxic t lymphocyte-associated antigen 2 (ctla-2α).[63] in the subretinal approach, the injection is performed in the transition zone, which is between the atrophic and fairly healthy retina.[21, 64] due to the immune-privileged subretinal space, rejection occurs without obvious inflammatory infiltration, which is followed by cell loss and progressive function loss.[21, 65] retinal detachment and retinal perforation are the most reported adverse events related to the subretinal approach.[16, 20, 24, 66, 67] in the suprachoroidal method, no violation of the vitreous cavity is performed, which is an advantage 322 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 stem cell therapy in stargardt disease; moghadam fard et al of this method.[18] intravitreal transplantation of stem cells is the easiest route, and the safety of this method has been already shown in patients with atrophic age-related macular degeneration (amd).[68] animal studies have shown acceptable results of human rpe stem cell transplantation in retinal degenerative diseases.[69] lu and colleagues[25] showed the long-term safety of hesc-derived rpe cells in immune-deficient mice. furthermore, they showed the long-term function of hesc-derived rpe in the both elov14 mouse and royal college of surgeons (rcs) rats which are animal models of stargardt and amd, respectively. the hescderived rpe survived for more than eight months in rcs rats without any pathological findings, including teratoma or tumor formation in subretinal transplantation. elov14 mouse eyes that were treated with stem cell injection had significantly better visual acuity than control eyes treated with sham injection.[25] animal models, especially mouse models, have been investigated for several years to find the potential treatments for retinal degenerative diseases such as stargardt disease, amd, and retinitis pigmentosa.[70, 71] although wert et al[24] reported temporary retinal detachment as a possible adverse event of the subretinal delivery method, no teratoma formation or immune rejection of transplanted tissue was found in animal models with stargardt disease in stem cell therapy.[24, 25] considering the promising results of stem cell therapy in animal models, human studies were pursued. in 2012, the subretinal injection of hesc was performed in one eye from a patient with stargardt disease, and the patient was followed for four months; no signs of hyperproliferation, ectopic tissue formation, or immune-mediated transplant rejection was found during the followup period. transplanted hesc-rpe attached to bruch’s membrane and persisted during the followup period.[23] the patient’s vision improved from central hand motion (0 etdrs letter) to five etdrs letters, best-corrected visual acuity (bcva) of 20/800 at 1one, two, and three months. furthermore, improved color vision and contrast sensitivity and dark adaptation were reported subjectively by the patient.[23] in 2015, subretinal hesc transplantation was performed in two asian patients;[22] no complications were reported. no evidence of adverse proliferation, tumorigenicity, or ectopic tissue formation was found during the follow-up period, which confirmed the safety of hesc-derived rpe.[22] after a year of follow-up, the visual acuity in the treated eyes improved by 12 etdrs letters (from counting fingers at 2 feet to 20/640) in the first patient and 19 etdrs letters (from 20/640 to 20/250) in the second patient.[22] in 2015, a study by schwartz et al[21] evaluated subretinal transplantation of hesc-derived rpe in nine stargardt disease patients.[21] they did not find any complications related to the transplanted tissue, such as adverse proliferation, immune rejection, or any kinds of safety issues, which indicated the long-term safety and graft survival of pluripotent stem cell transplantation.[21] in their study, one eye developed inflammation in the vitreous cavity with acute vitreous culture-positive (staphylococcus epidermidis) endophthalmitis, however, they found no sign of infection in the subretinal space (hesc-rpe gram stain). furthermore, three operated eyes developed cataracts in the follow-up period. from nine treated eyes, seven had a 12-month assessment; among them, the visual acuity improved in three eyes.[21] although in five eyes ,which did not develop cataracts, the median of visual acuity was improved to 12 letters at the 12 month follow-up, the improvement was not significant between operated versus fellow eyes.[21] in 2016, leung et al[20] reported subretinal autologous bone marrow-derived stem cells transplantation in a patient with stargardt disease; the visual acuity improved from 20/400 to 20/300. they found macula-involving retinal detachment two months after subretinal stem cell injection and recurrent retinal detachment with proliferative vitreoretinopathy four months after subretinal stem cell injection, which could suggest potential complications of the subretinal method.[20] in 2018, mehat et al[19] reported subretinal transplantation of hesc in 12 patients with stargardt disease; no adverse proliferation or acute immune rejection was found. they reported a small subretinal hemorrhage at the injection site in two participants and mild vitreous cavity hemorrhage in one participant, furthermore in the hyperpigmentation area, localized retinal thinning and decreased sensitivity were reported.[19] borderline improvement of bcva was found in four participants, although the improvement journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 323 stem cell therapy in stargardt disease; moghadam fard et al was not sustained or matched to the control contralateral eye; no significant benefits were detected after 12 months of assessment.[19] oner et al[18] reported the suprachoroidal transplantation of ad-mscs in four participants with stargardt disease; after six months of the follow-up period, no ocular or systemic complication was found. improvement of bcva was experienced by all participants in this study. furthermore, all participants experienced visual field improvement on goldmann perimetry.[18] cotrim et al[17] reported intravitreal transplantation of bone marrow mononuclear fraction containing cd34+ cells in 10 patients with stargardt disease. during the six months of follow-up, no complications such as infection, retinal detachment, or tumor formation was found. in the eye with intravitreal injection, the mean of baseline visual acuity was 1.1 logmar at baseline which improved to 0.96, 0.92, and 0.98 logmar, at one, three, and six months after intravitreal injection, respectively. in the eye with the sham injection, the mean of visual acuity at baseline was 1.0 logmar which improved to 0.96, 0.94, and 0.96 at one, three, and six months, respectively. their results showed a significant difference in the treated eye at all of the follow-up times.[17] sung et al[16] published a study on subretinal transplantation of hescs in three stargardt disease patients. their findings suggested the long-term safety of subretinal transplantation of hesc-derived rpe cells; however, they noticed rhegmatogenous retinal detachment in one of the participants 19 weeks after the subretinal hesc transplantation.[16] after three years of follow-up, visual acuity improved 9, 19, and 6 etdrs letters in the first, second, and third patient, respectively; compared to the fellow eye, visual acuity improved in the second patient and remained stable in the other two patients.[16] four weeks after the transplantation, subretinal pigmentation was observed and increased until six weeks and then remained stable during three years’ follow-up.[16] weiss et al[15] evaluated the results of retrobulbar, subtenon, intravitreal, subretinal, and intravenous autologous bone marrow-derived stem cells transplantation in 34 eyes from 17 patients with stargardt disease. the visual acuity improved in 21 eyes (with the average visual acuity improvement of 33.3% or with the mean logmar improvement of +0.4095), remained stable in 8 eyes, and decreased in 5 eyes after one year, and no surgical complications were found.[15] they found no significant difference in the efficacy of multiple delivery methods.[15] li et al[14] reported the five-year follow-up of subretinal hesc-rpe transplantation in seven stargardt disease patients. high postoperative intraocular pressure (ranging from 26 to 32 mm hg) was observed in two participants 1– 2 months after the operation, although it was controlled by medications and silicone oil removal; none of the participants experienced retinal detachment, immune reaction, endophthalmitis, or tumor formation during the 5-year follow-up.[14] although the visual function of all participants remained stable or improved at four months after the operation, there was no significant difference between the operated and the fellow eye regarding visual acuity, pattern visual evoked potential (pvep), and full-field electroretinography (fferg) after five years of the follow-up period, except in one participant.[14] recently, brant fernandes et al[13] evaluated the subretinal transplantation of hesc-rpe in 12 eyes diagnosed with advanced stargardt disease. after a 12-month follow-up, their results showed no significant increase in bcva in the treated eyes, and they found no adverse events during the follow-up period such as ocular or systemic tumor development, cellular migration, corneal edema, ocular or systemic inflammation, endophthalmitis, ocular bleeding, retinal detachment, elevation of intraocular pressure, or transplantation rejection.[13] the subretinal approach has been assessed by most studies; retinal detachment and retinal perforation are reported as adverse complications of this approach. studies have isolated and characterized the rpe cells from different stem cell types. most studies evaluated hesc; however, there might be long-term safety issues including potential immune response or rejection, the ability of tumor formation, and adverse tissue formation or proliferation. on the other hand, some studies reported unsustained improvement in visual acuity which is one of the challenges of stem cell therapy in stargardt disease.[14, 19] currently, cell therapy is not fda-approved for stargardt disease; studies are ongoing to determine the best method of therapy for this disease. although the quality of evidence of studies included in this systematic review was assessed as very low, the research in this field is nascent and most investigations are 324 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 stem cell therapy in stargardt disease; moghadam fard et al pilot studies or phase 1/2 rcts. considering the promising results of these novel approaches, future studies with improved quality of evidence may determine the best stem cell type and the preferred delivery method. this study has some limitations. the sample size was small in retrieved studies and was not enough to evaluate the safety and efficacy of stem cell therapy in stargardt disease. also, the followup period varied in different studies. due to high heterogeneity among studies in various stem cell types and delivery methods, we were unable to perform a meta-analysis. adding other databases and involving other languages in the primary search may increase the number of studies. conclusion in conclusion, stem cell therapy has the potential to improve the visual function of patients with stargardt disease. although several studies have suggested benefits of stem cell therapy for stargardt disease, further rcts are needed to determine the long-term safety and efficacy of stem cell therapy in stargardt disease. further investigation is also needed to choose the best delivery method and stem cell type. financial support and sponsorship none. conflicts of interest none. references 1. ricca am, han ic, sohn eh. stargardt disease masquerades. curr opin ophthalmol 2021;32:214–224. 2. stone em, andorf jl, whitmore ss, deluca ap, giacalone jc, streb lm, et al. clinically focused molecular investigation of 1000 consecutive families with inherited retinal disease. ophthalmology 2017;124:1314–1331. 3. haddley k. stargardt disease: light at the end of the tunnel. drugs future 2011;36:527–533. 4. sears ae, bernstein ps, cideciyan av, hoyng c, charbel issa p, palczewski k, et al. towards treatment of stargardt disease: workshop organized and sponsored by the foundation fighting blindness. transl vis sci technol 2017;6:6. 5. haji abdollahi s, hirose t. stargardt-fundus flavimaculatus: recent advancements and treatment. semin ophthalmol 2013;28:372–376. 6. khan m, cremers fp. abca4-associated stargardt disease. klin monatsbl augenheilkd 2020;237:267–274. 7. jonsson f, westin im, österman l, sandgren o, burstedt m, holmberg m, et al. atp-binding cassette subfamily a, member 4 intronic variants c.4773+3a>g and c.546110t>c cause stargardt disease due to defective splicing. acta ophthalmol 2018;96:737–743. 8. tsang sh, sharma t. stargardt disease. adv exp med biol 2018;1085:139–51. 9. hussain rm, ciulla ta, berrocal am, gregori nz, flynn hw jr, lam bl. stargardt macular dystrophy and evolving therapies. expert opin biol ther 2018;18:1049–1059. 10. battu r, ratra d, gopal l. newer therapeutic options for inherited retinal diseases: gene and cell replacement therapy. indian j ophthalmol 2022;70:2316–2325. 11. strauss rw, ho a, muñoz b, cideciyan av, sahel ja, sunness js, et al. the natural history of the progression of atrophy secondary to stargardt disease (progstar) studies: design and baseline characteristics: progstar report no. 1. ophthalmology 2016;123:817–828. 12. jin zb, gao ml, deng wl, wu kc, sugita s, mandai m, et al. stemming retinal regeneration with pluripotent stem cells. prog retin eye res 2019;69:38–56. 13. brant fernandes ra, lojudice fh, zago ribeiro l, santos da cruz nf, polizelli mu, cristovam pc, et al. transplantation of subretinal stem cell-derived retinal pigment epithelium for stargardt disease: a phase i clinical trial. retina 2023;43:263–274. 14. li sy, liu y, wang l, wang f, zhao tt, li qy, et al. a phase i clinical trial of human embryonic stem cellderived retinal pigment epithelial cells for early-stage stargardt macular degeneration: 5-years’ follow-up. cell prolif 2021;54:e13100. 15. weiss jn, levy s. stem cell ophthalmology treatment study (scots): bone marrow-derived stem cells in the treatment of stargardt disease. medicines 2021;8:10. 16. sung y, lee mj, choi j, jung sy, chong sy, sung jh, et al. long-term safety and tolerability of subretinal transplantation of embryonic stem cell-derived retinal pigment epithelium in asian stargardt disease patients. br j ophthalmol 2021;105:829–837. 17. cotrim cc, vieira messias am, jorge r, siqueira rc. intravitreal use of a bone marrow mononuclear fraction (bmmf) containing cd34+ cells in patients with stargardt type macular dystrophy. stem cells int 2020;2020:8828256. 18. oner a, gonen zb, sevim dg, smim kahraman n, unlu m. suprachoroidal adipose tissue-derived mesenchymal stem cell implantation in patients with dry-type agerelated macular degeneration and stargardt’s macular dystrophy: 6-month follow-up results of a phase 2 study. cell reprogram 2018;20:329–336. 19. mehat ms, sundaram v, ripamonti c, robson ag, smith aj, borooah s, et al. transplantation of human embryonic stem cell-derived retinal pigment epithelial cells in macular degeneration. ophthalmology 2018;125:1765–1775. 20. leung eh, flynn hw jr, albini ta, medina ca. retinal detachment after subretinal stem cell transplantation. ophthalmic surg lasers imaging retina 2016;47:600–601. 21. schwartz sd, regillo cd, lam bl, eliott d, rosenfeld pj, gregori nz, et al. human embryonic stem cell-derived journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 325 stem cell therapy in stargardt disease; moghadam fard et al retinal pigment epithelium in patients with age-related macular degeneration and stargardt’s macular dystrophy: follow-up of two open-label phase 1/2 studies. lancet 2015;385:509–516. 22. song wk, park km, kim hj, lee jh, choi j, chong sy, et al. treatment of macular degeneration using embryonic stem cell-derived retinal pigment epithelium: preliminary results in asian patients. stem cell rep 2015;4:860–872. 23. schwartz sd, hubschman jp, heilwell g, francocardenas v, pan ck, ostrick rm, et al. embryonic stem cell trials for macular degeneration: a preliminary report. lancet 2012;379:713–720. 24. wert kj, skeie jm, davis rj, tsang sh, mahajan vb. subretinal injection of gene therapy vectors and stem cells in the perinatal mouse eye. j vis exp 2012;69:4286. 25. lu b, malcuit c, wang s, girman s, francis p, lemieux l, et al. long-term safety and function of rpe from human embryonic stem cells in preclinical models of macular degeneration. stem cells 2009;27:2126–2135. 26. page mj, mckenzie je, bossuyt pm, boutron i, hoffmann tc, mulrow cd, et al. the prisma 2020 statement: an updated guideline for reporting systematic reviews. bmj 2021;372:n71. 27. guyatt g, oxman ad, akl ea, kunz r, vist g, brozek j, et al. grade guidelines: 1. introduction-grade evidence profiles and summary of findings tables. j clin epidemiol 2011;64:383–394. 28. heath jeffery rc, chen fk. stargardt disease: multimodal imaging: a review. clin exp ophthalmol 2021;49:498–515. 29. walia s, fishman ga. natural history of phenotypic changes in stargardt macular dystrophy. ophthalmic genet 2009;30:63–68. 30. palejwala nv, gale mj, clark rf, schlechter c, weleber rg, pennesi me. insights into autosomal dominant stargardt-like macular dystrophy through multimodality diagnostic imaging. retina 2016;36:119–130. 31. donoso la, edwards ao, frost a, vrabec t, stone em, hageman gs, et al. autosomal dominant stargardt-like macular dystrophy. surv ophthalmol 2001;46:149–163. 32. vasireddy v, wong p, ayyagari r. genetics and molecular pathology of stargardt-like macular degeneration. prog retin eye res 2010;29:191–207. 33. schulz hl, grassmann f, kellner u, spital g, rüther k, jägle h, et al. mutation spectrum of the abca4 gene in 335 stargardt disease patients from a multicenter german cohort-impact of selected deep intronic variants and common snps. invest ophthalmol vis sci 2017;58:394– 403. 34. tsybovsky y, molday rs, palczewski k. the atp-binding cassette transporter abca4: structural and functional properties and role in retinal disease. adv exp med biol 2010;703:105–125. 35. lu lj, liu j, adelman ra. novel therapeutics for stargardt disease. graefes arch clin exp ophthalmol 2017;255:1057–1062. 36. sparrow jr, boulton m. rpe lipofuscin and its role in retinal pathobiology. exp eye res 2005;80:595–606. 37. parmar vm, parmar t, arai e, perusek l, maeda a. a2e-associated cell death and inflammation in retinal pigmented epithelial cells from human induced pluripotent stem cells. stem cell res 2018;27:95–104. 38. ng es, kady n, hu j, dave a, jiang z, pei j, et al. membrane attack complex mediates retinal pigment epithelium cell death in stargardt macular degeneration. cells 2022;11:3462. 39. tanna p, strauss rw, fujinami k, michaelides m. stargardt disease: clinical features, molecular genetics, animal models and therapeutic options. br j ophthalmol 2017;101:25–30. 40. chen y, okano k, maeda t, chauhan v, golczak m, maeda a, et al. mechanism of all-trans-retinal toxicity with implications for stargardt disease and age-related macular degeneration. j biol chem 2012;287:5059–5069. 41. radu ra, mata nl, bagla a, travis gh. light exposure stimulates formation of a2e oxiranes in a mouse model of stargardt’s macular degeneration. proc natl acad sci usa 2004;101:5928–5933. 42. teussink mm, lee md, smith rt, van huet ra, klaver cc, klevering bj, et al. the effect of light deprivation in patients with stargardt disease. am j ophthalmol 2015;159:964–972.e2. 43. fujinami k, strauss rw, chiang jp, audo is, bernstein ps, birch dg, et al. detailed genetic characteristics of an international large cohort of patients with stargardt disease: progstar study report 8. br j ophthalmol 2019;103:390–397. 44. lee w, xie y, zernant j, yuan b, bearelly s, tsang sh, et al. complex inheritance of abca4 disease: four mutations in a family with multiple macular phenotypes. hum genet 2016;135:9–19. 45. arrigo a, grazioli a, romano f, aragona e, bordato a, di nunzio c, et al. choroidal patterns in stargardt disease: correlations with visual acuity and disease progression. j clin med 2019;8:1388. 46. collison ft, fishman ga. visual acuity in patients with stargardt disease after age 40. retina 2018;38:2387– 2394. 47. fujinami k, zernant j, chana rk, wright ga, tsunoda k, ozawa y, et al. abca4 gene screening by next-generation sequencing in a british cohort. invest ophthalmol vis sci 2013;54:6662–6674. 48. lambertus s, van huet ra, bax nm, hoefsloot lh, cremers fp, boon cj, et al. early-onset stargardt disease: phenotypic and genotypic characteristics. ophthalmology 2015;122:335–344. 49. fujinami k, zernant j, chana rk, wright ga, tsunoda k, ozawa y, et al. clinical and molecular characteristics of childhood-onset stargardt disease. ophthalmology 2015;122:326–334. 50. ramsden cm, powner mb, carr aj, smart mj, da cruz l, coffey pj. stem cells in retinal regeneration: past, present and future. development 2013;140:2576–2585. 51. araki r, uda m, hoki y, sunayama m, nakamura m, ando s, et al. negligible immunogenicity of terminally differentiated cells derived from induced pluripotent or embryonic stem cells. nature 2013;494:100–104. 52. mead b, berry m, logan a, scott ra, leadbeater w, scheven ba. stem cell treatment of degenerative eye disease. stem cell res 2015;14:243–257. 53. klimanskaya i, hipp j, rezai ka, west m, atala a, lanza r. derivation and comparative assessment of retinal pigment epithelium from human embryonic stem cells 326 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 stem cell therapy in stargardt disease; moghadam fard et al using transcriptomics. cloning stem cells 2004;6:217– 245. 54. ahmed i, johnston rj jr, singh ms. pluripotent stem cell therapy for retinal diseases. ann transl med 2021;9:1279. 55. maeda a, mandai m, takahashi m. gene and induced pluripotent stem cell therapy for retinal diseases. annu rev genomics hum genet 2019;20:201–216. 56. han f, xu g. stem cell transplantation therapy for retinal degenerative diseases. adv exp med biol 2020;1266:127– 139. 57. sharma a, jaganathan bg. stem cell therapy for retinal degeneration: the evidence to date. biologics 2021;15:299–306. 58. ding dc, shyu wc, lin sz. mesenchymal stem cells. cell transplant 2011;20:5–14. 59. fu x, liu g, halim a, ju y, luo q, song ag. mesenchymal stem cell migration and tissue repair. cells 2019;8:784. 60. lin y, ren x, chen y, chen d. interaction between mesenchymal stem cells and retinal degenerative microenvironment. front neurosci 2021;14:617377. 61. xian b, huang b. the immune response of stem cells in subretinal transplantation. stem cell res ther 2015;6:161. 62. streilein jw, ma n, wenkel h, ng tf, zamiri p. immunobiology and privilege of neuronal retina and pigment epithelium transplants. vision res 2002;42:487– 495. 63. sugita s, horie s, nakamura o, maruyama k, takase h, usui y. acquisition of t regulatory function in cathepsin l-inhibited t cells by eye-derived ctla-2alpha during inflammatory conditions. j immunol 2009;183:5013–5022. 64. raimondi r, zollet p, de rosa fp, tsoutsanis p, stravalaci m, paulis m, et al. where are we with rpe replacement therapy? a translational review from the ophthalmologist perspective. int j mol sci 2022;23:682. 65. grisanti s, szurman p, jordan j, kociok n, bartzschmidt ku, heimann k. xenotransplantation of retinal pigment epithelial cells into rcs rats. jpn j ophthalmol 2002;46:36–44. 66. ho ac, chang ts, samuel m, williamson p, willenbucher rf, malone t. experience with a subretinal cell-based therapy in patients with geographic atrophy secondary to age-related macular degeneration. am j ophthalmol 2017;179:67–80. 67. hinkle jw, mahmoudzadeh r, kuriyan ae. cell-based therapies for retinal diseases: a review of clinical trials and direct to consumer “cell therapy” clinics. stem cell res ther 2021;12:538. 68. cotrim cc, toscano l, messias a, jorge r, siqueira rc. intravitreal use of bone marrow mononuclear fraction containing cd34+ stem cells in patients with atrophic age-related macular degeneration. clin ophthalmol 2017;11:931–938. 69. luo m, chen y. application of stem cell-derived retinal pigmented epithelium in retinal degenerative diseases: present and future. int j ophthalmol 2018;11:150–159. 70. chang b, hawes nl, hurd re, davisson mt, nusinowitz s, heckenlively jr. retinal degeneration mutants in the mouse. vision res 2002;42:517–525. 71. won j, shi ly, hicks w, wang j, hurd r, naggert jk, et al. mouse model resources for vision research. j ophthalmol 2011;2011:391384. journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 327 original article visual outcomes of adding erythropoietin to methylprednisolone for treatment of retrobulbar optic neuritis mostafa soltan sanjari1, md; farzad pakdel2, md; fatemeh moosavi1, md; niloofar pirmarzdashti2, md marzieh nojomi3, md; anoosheh haghighi4, md; masih hashemi1, md; mohsen bahmani kashkouli1, md 1ophthalmology department, eye research center, rassoul akram hospital, iran university of medical sciences, tehran, iran 2ophthalmology department, eye research center, farabi eye hospital, tehran university of medical sciences, tehran, iran 3department of community medicine, iran university of medical sciences, tehran, iran 4internal medicine department, rassoul akram hospital, iran university of medical sciences, tehran, iran orcid: mostafa soltan sanjari: https://orcid.org/0000-0003-1905-6138 farzad pakdel: https://orcid.org/0000-0001-7392-6056 abstract purpose: to compare the short-term visual function results and safety of erythropoietin as an add-on to the standard corticosteroid therapy in retrobulbar optic neuritis (ron). methods: in this prospective pilot study, adult patients with isolated ron with less than 10 days of onset were enrolled. patients were consecutively assigned to standard intravenous methylprednisolone treatment either in combination with intravenous erythropoietin (20,000 units/day for three days) (group-1) or intravenous methylprednisolone alone (group-2). primary outcome measure was best-corrected visual acuity (bcva), which was assessed up to 120 days from the day the treatment was begun. systemic evaluations were performed during and after treatment. results: sixty-two patients with ron (mean age = 26.6 ± 5.77 years; range = 18–40 years) were enrolled into the study (group-1, 𝑛 = 35; group-2, 𝑛 = 27). bcva three months after the treatment was 0.19 ± 0.55 logmar and 0.11 ± 0.32 logmar in group-1 and group-2, respectively (95% ci: −0.61 − 0.16; 𝑃 = 0.62). change in bcva after three months was 2.84 ± 3.49 logmar in group-1 and 2.46 ± 1.40 logmar in group-2 (95% ci: −0.93−1.91; 𝑃 = 0.57). pace of recovery was not significantly different between the groups. no complications were detected among patients. conclusion: intravenous erythropoietin as an add-on did not significantly improve the visual outcome in terms of visual acuity, visual field, and contrast sensitivity compared to traditional intravenous corticosteroid. this pilot study supports the safety profile of intravenous human recombinant erythropoietin, and it may help formulate future investigations with a larger sample size. keywords: contrast sensitivity; erythropoietin; optic neuritis; optic neuroprotection; optic nerve regeneration; visual acuity; visual function j ophthalmic vis res 2019; 14 (3): 299–305 correspondence to: farzad pakdel, md. ophthalmology department, eye research center, farabi eye hospital, tehran university of medical sciences, qazvin sq., tehran 13366, iran. e-mail: fapakdel@gmail.com received: 15-02-2018 accepted: 29-09-2018 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i3.4786 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: soltan sanjari m, pakdel f, moosavi f, pirmarzdashti n, nojomi m, haghighi a, et al. visual outcomes of adding erythropoietin to methylprednisolone for treatment of retrobulbar optic neuritis. j ophthalmic vis res 2019;14:299–305 @ 2019 j  o  v r | published by knowledge e 299 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i3.4786&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr erythropoietin for optic neuritis; soltan sanjari et al introduction acute optic neuritis is an inflammatory, demyelinating disorder. it is the most common optic neuropathy affecting young adults.[1] main pathologic features include microglial and t cell infiltration, edema, myelin breakdown, axonal and neuronal degeneration, and astrogliosis of the optic nerve.[2–4] following an episode of optic neuritis, the optic nerve undergoes atrophy.[5] although, in most patients, visual acuity recovers rapidly following an episode of acute optic neuritis, significant number of patients suffer from disturbances of visual functions such as best-corrected visual acuity (bcva), contrast sensitivity (cs), color vision, and visual field.[5–7] in an optic neuritis treatment trial (ontt) study, which involved longterm follow-up, 26% of the patients showed a visual acuity that was lower than 20/20 in the affected eye, and 33% showed abnormal cs and visual field.[7] methylprednisolone pulse therapy is the standard treatment for acute optic neuritis. although it accelerates visual recovery, it does not influence visual outcome, lesion length, or atrophy of the optic nerve.[4, 7, 8] furthermore, the safety of high dose corticosteroid treatment on retinal ganglion cell (rgc) survival is debated. an experimental study on an optic neuritis model showed that methylprednisolone increased rgc degeneration by inhibiting an endogenous neurotrophindependent pathway.[9] in addition to the treatment using antiinflammatory and immunomodulatory agents, neuroprotection and neuroregeneration are other intriguing treatment strategies. erythropoietin has shown neuroprotective and neuroregenerative properties. recent experimental and clinical studies support the efficacy of erythropoietin in various clinical optic nerve disorders including traumatic optic neuropathy,[10, 11] ischemic optic neuropathy,[12] toxic optic neuropathy,[13] and optic neuritis.[14, 15] in a recent study, patients treated with a combination of corticosteroid and erythropoietin were found to have higher retinal nerve fiber layer (rnfl) thickness and optic nerve diameter.[14] in the current study, we aimed to compare different optic nerve function parameters in patients with isolated retrobulbar optic neuritis (ron), who were subjected to high dose corticosteroid treatment either in combination with erythropoietin or alone. methods this was a prospective pilot study conducted in a tertiary university-based referral hospital. the ethics committee of eye research center affiliated to rassoul akram hospital, iran university of medical sciences approved this study. the purpose of the study and its possible outcomes and adverse events were explained to all participants, and written informed consents were obtained. the study was conducted according to the tenets of helsinki declaration. from november 2010 to march 2013, patients with acute visual loss and preliminary diagnosis of ron, who were referred from general and neuro-ophthalmology clinics, were evaluated. the eligibility criteria were mainly based on ontt [table 1]. all patients underwent a comprehensive ophthalmologic evaluation, which included assessment of detailed history, bcva (with a standard landolt c chart in a single room), relative afferent pupillary response, color vision (with ishihara plates), extra-ocular movements, and intra-ocular pressure (by application tonometry), in addition to dilated funduscopic examination (with 78 d lens) and anterior segment examination (with slit lamp). diagnosis of isolated ron was confirmed by an expert neuro-ophthalmologist. all patients were hospitalized. complete blood cell count, hematocrit, aspartate transaminase (ast), alanine transaminase (alt), alkaline phosphatase, blood urea nitrogen, blood creatinine, blood sugar, and c-reactive protein, in addition to serum sodium, calcium, phosphorus, and magnesium were evaluated. in the case of abnormal lab data, treatment was stopped and an internal medicine specialist was consulted. patients were subsequently assigned into one of the two treatment groups after obtaining informed consent; those receiving intravenous human recombinant erythropoietin and methylprednisolone for three successive days were assigned to group-1 and those receiving only intravenous methylprednisolone for three successive days were assigned to group-2. patients in both groups received oral prednisolone 1 mg/kg/day for additional 11 days after the intravenous treatment. all patients received 250 mg intravenous methylprednisolone every six hours. in addition, 20,000 international units of intravenous recombinant human erythropoietin (pdpoetin, 300 j  o  v r volume 14, issue 3, july–september 2019 erythropoietin for optic neuritis; soltan sanjari et al table 1. eligibility criteria inclusion criteria exclusion criteria acute visual symptoms pregnancy normal optic disc and fundoscopic exam with 78 d lens breastfeeding relative afferent pupillary defect clinically definite ms visual field defect in the affected eye hyperopia > 3 diopter, myopia > −5.0 diopter, irregular astigmatism age range of 18 years to 40 years elevated blood pressure (systolic > 140 mmhg, diastolic > 90 mmhg) no previous episodes of optic neuritis in the affected eye history of thrombi-embolic events no previous congenital or acquired ophthalmological morbidity hindering the visual functions malignancy no previous corticosteroid or erythropoietin treatment for optic neuritis seizures no systemic disease history of collagen vascular disease best-corrected visual acuity ≤ 20/40 sarcoidosis duration of symptoms less than 10 days graves’ disease heavy cigarette smoking history or clinical findings for severe ophthalmic diseases such as central retinal vein occlusion any hereditary or acquired macular disease history of any intraocular or keratorefractive surgery any abnormal findings in orbital or brain mri suggestive of decreased visual function mri, magnetic resonance imaging; ms, multiple sclerosis pooyesh darou pharmaceutical co., tehran, iran) was infused into 200 ml normal saline in group1. patients in group-2 received 200 ml normal saline per day as placebo. systolic and diastolic blood pressures were checked every 15 minutes during erythropoietin infusion. the patients were excluded from the study if they met the exclusion criteria. inclusion, group assignment, and management process were directed by an expert ophthalmologist (fp). follow-up examinations were performed using the same charts and instruments by a senior ophthalmology resident (fm). both neuroophthalmologist and examiner were blind to the treatment protocol. primary outcome measure was bcva. visual acuity was measured by standard landolt c acuity chart after best spectacle correction. color vision was checked with 15 ishihara plates if visual acuity was 20/160 (0.9 logmar) or better. contrast sensitivity (cs) was checked using a yang vision tester (sifi medtech group co., lavinaio, italy) at a distance of 3 m and spatial frequency of 6-cycle/degree (c/d) at 30–70 foot-lambert illumination. all visual functions were assessed before treatment and at days 1, 2, 3, 14, 30, 60, and 120 after treatment. visual field was evaluated with humphrey 750 using c-24-2 sita-standard strategy (target size = 3, white target) on days 0, 14, 30, 60, and 120 if bcva was 20/200 (logmar = 1.0) or better. hemoglobin, hematocrit, and platelet count were checked on days 0, 30, and 60 after treatment. a probability value of less than 0.05 was considered significant for all statistical tests. the independent sample t-test was used for the comparison of normal numeric parameters. kaplan–meier survival analysis was performed to estimate time to event; the cut-off point for bcva was logmar ≤ 0 and that for cs was ≥70.[15] statistical analyses were carried out with the statistical package for social j  o  v r volume 14, issue 3, july–september 2019 301 erythropoietin for optic neuritis; soltan sanjari et al sciences (spss package, version 22, ibm corporation, armonk, new york, usa). results we evaluated 102 patients with acute isolated ron. thirty-five patients received corticosteroid treatment in combination with erythropoietin (group1) and twenty-seven subjects received corticosteroid treatment alone (group-2). forty cases were excluded because they did not fulfill the inclusion criteria or because they met the exclusion criteria [table 1]. the mean age of the included patients was 26.6 ± 5.77 (range = 18–40) years. of 62 patients, 43 were female (69.35%). time delay in treatment (interval between the onset of symptoms and initiation of treatment) in both groups did not differ significantly. demographic data are shown in table 2. at baseline, there was no statistically significant difference in mean visual acuity (represented in logmar) between group-2 (2.35 ± 1.25) and group1 (2.15 ± 1.18) (p = 0.52). three months after treatment, bcva of 20/20 or better (logmar ≤ 0) was achieved in 48 (66.1%) patients, among which 29 (71.4%) patients belonged to group-1 and 19 (59.3%) to group-2. bcva at three months followup time-point was found to be 0.11 ± 0.32 logmar and 0.19 ± 0.55 logmar in group-2 and group-1 (p = 0.51), respectively [figure 1]. the pace of recovery was not different between the two groups. bcva of 20/20 or better (log mar ≤ 0) was achieved in 34.52 days after treatment in group-1 and in 41.12 days after treatment in group2 (p = 0.59). change in bcva after three months was 2.84 ± 3.49 logmar in group-1 and 2.46 ±1.40 in group-2 (p = 0.632), compared to pre-treatment baseline values. baseline cs (represented in 6 c/d) was 6.85 ± 9.1 in group-1 and 6.98 ± 7.36 in group-2. improvement of cs (cut-off point > 70) was achieved after three months in 25 (40.3%) patients with ron, among which 18 (51.4%) patients belonged to group-1 and 7 (25.9%) to group-2. cs was not significantly different between the two groups. cutoff point of cs (> 70) improved in 73.33 days (range = 58.13–88.53) in group-1 and in 85.71 days (range = 61.95–109.47) in group-2 [figure 2]. the change in cs after three months was observed to be 65.78 figure 1. best-corrected visual acuity (bcva) at different time intervals among patients with retrobulbar optic neuritis in the two treatment groups. iv mp, intravenous methylprednisolone; iv mp + epo, intravenous methylprednisolone in combination with intravenous erythropoietin. figure 2. comparison of contrast sensitivity in patients with retrobulbar optic neuritis in the two treatment groups. iv mp, intravenous methylprednisolone; iv mp + epo, intravenous methylprednisolone in combination with intravenous erythropoietin. ± 32.32 in group-1 and 51.09 ± 33.92 in group-2 (p = 0.078). analysis of mean deviation (md) showed insignificant differences among participants in group-1 and group-2 after three months. pattern standard deviation (psd) showed no significant differences between the two groups except on day 60 (p = 0.002) [figure 3]. mean baseline values of color vision test were 2.3 ± 2.06 and 3.37 ± 2.72 in group-1 and group2 (p = 0.377), respectively. four months after treatment, mean color vision values of patients in group-1 and group-2 were 11.96 ± 4.49 and 12.94 ± 2.68, respectively (p = 0.338). there was no significant difference in the platelet count change at days 30 and 60 after treatment in both groups. mean hematocrit change in the male and female patients of group-1 and group-2 after 30 and 60 days of treatment was statistically insignificant. we observed transient 302 j  o  v r volume 14, issue 3, july–september 2019 erythropoietin for optic neuritis; soltan sanjari et al table 2. demographics of patients with retrobulbar optic neuritis group-1 group-2 p value age (mean ± sd; years) 25.54 ± 5.943 27.70 ± 5.587 0.14 sex (f:m) 29 (70.7%): 12 (29.3) 25 (64.1%):14 (35.9%) 0.63 time interval ± sd (days)* 5.91 ± 2.66 5.29 ± 2.34 0.33 *time interval between onset of visual symptoms and starting protocol treatment group-1 = combined erythropoietin and methylprednisolone treatment group-2 = methylprednisolone treatment f, female; m, male; sd, standard deviation figure 3. mean deviation (md) in patients with retrobulbar optic neuritis in the two treatment groups. iv mp, intravenous methylprednisolone; iv mp + epo, intravenous methylprednisolone in combination with intravenous erythropoietin. increase in systolic blood pressure in a 35-yearold patient during intravenous infusion of erythropoietin. no further increase in blood pressure was recorded during follow-up. during treatment and follow-up period, no remarkable complications were detected among patients. discussion in this pilot study, we have compared short-term visual function results of intravenous methylprednisolone with and without erythropoietin as an addon in patients with acute ron. results of ontt showed that corticosteroids could accelerate visual recovery.[4] however, in about one-third of these patients, residual disturbances in various aspects of visual functions, including central visual acuity, cs, and visual field can persist.[7] optic neuritis is associated with rgc loss and rnfl thinning.[16] axonal loss in the rnfl has consistently been demonstrated following optic neuritis,[16] and after an episode of optic neuritis, 74% of the patients show thinning of rnfl, denoting axonal damage, and rgc loss in addition to their correlation to visual function deficit.[17] furthermore, high dose corticosteroid therapy possibly increases rgc apoptosis following optic neuritis; this is an issue of concern.[5] these findings signify permanent structural and functional deficits in the visual system after an episode of optic neuritis and, thus, justify the use of neuroprotective and regenerative treatment options. erythropoietin, which has long been known as a hematopoietic cytokine, can protect neurons from apoptosis[18–20] and show protective effects in experimental models of mechanical optic nerve trauma,[21] inflammation,[22, 23] cerebral and retinal ischemia,[23] and oxidative stress,[24] in addition to animal model of optic neuritis.[9, 25] clinical studies over the recent decade have also supported the use of erythropoietin as a neuroprotective and neuroregenerative agent in certain acquired optic neuropathies such as traumatic,[10,11] ischemic,[12] demyelinative, inflammatory,[14] and toxic[13] optic neuropathies. one study on experimental optic neuritis model suggested that both neuronal and axonal protection, in functional and structural aspects, are most effective when combined erythropoietin and methylprednisolone treatment regimen was commenced. isolated neuronal or axonal protection, without clinical benefit, was achieved under monotherapy with either erythropoietin or methylprednisolone.[25, 26] j  o  v r volume 14, issue 3, july–september 2019 303 erythropoietin for optic neuritis; soltan sanjari et al suhs et al demonstrated lower rnfl thinning and lower values of visual evoked potential parameters in patients with optic neuritis when they received 33,000 units/day of intravenous erythropoietin for three days as an addon therapy to methylprednisolone compared to those who received only methylprednisolone.[14] the aforementioned studies favored the structural and physiological effects of erythropoietin in treating optic neuritis. however, our study could not show a significant superior effect of the combined intravenous treatment (erythropoietin along with methylprednisolone) in terms of the extent and rapidity of recovery of cs, bcva, and visual field parameters. all our patients experienced partial or complete recovery of bcva after three months. recovery of cs, visual acuity, visual field, and color vision is characteristic after an episode of optic neuritis; the magnitude of the recovery of the aforementioned visual functions in the current study is comparable to other studies.[9] although we observed some trends that point toward the achievement of a better visual function in erythropoietin-treated patients, changes in functional parameters were not significantly different between the treatment groups. furthermore, suchs et al also did not observe any significant difference in visual acuity in patients who were administered erythropoietin as an add-on to methylprednisolone despite higher rnfl thickness in optical coherence tomography (oct) measurements.[14] such discrepancy may be explained at least in part by the fact that papillomacular bundle, rather than mean peripapillary nerve fiber layer thickness, subserves the fovea, which is responsible for the central visual acuity. cs is a more sensitive visual function than visual acuity. it remains impaired in 33% of the patients, years after acute optic neuritis.[7] we did assess cs, which has recently been reported to detect even subtle visual impairment.[15] during the final follow-up evaluation of patients, improved cs (> 70) was observed in 25 (40.3%) patients, of whom 18 (51.4%) belonged to group-1 and 7 (25.9%) to group-2. the major complications that were reported with erythropoietin include polycythemia, thromboembolic events,[27] hypertensive reactions,[27] and pure red cell aplasia.[28] we did not observe any significant change in hematocrit, platelet count, or any other clinical parameters that can be classified as adverse events. blood pressure of the participants in both groups remained stable during the treatment period and thereafter, it did not differ significantly between the treatment groups. however, there was an exception. one participant who had received combined erythropoietin and methylprednisolone treatment experienced a mild and transient elevation in systolic blood pressure, which returned to baseline level after the infusion was put on hold for 15 minutes; no further changes were observed after restarting the infusion. limitations of this pilot study included relatively small sample size and lack of randomization. authors cannot ignore one other possible reason for the absence of difference between the two groups, that is, the suppression of the neuroprotective effect of erythropoietin by concurrent corticosteroid therapy. in the future, randomized clinical trials with larger sample size may reveal statistically significant differences in the visual outcome after erythropoietin treatment. for future studies, our calculation shows that each group should have a sample size of 37 subjects to detect a difference of at least 0.2 logmar and to have 80% power. structural data such as that obtained through oct could provide useful complementary data, and it should be regarded in future studies. furthermore, follow-up time was short. longer follow-up periods are needed to justify any possible visual benefits in long-term scales in patients with optic neuritis. this may justify future studies with larger sample size and different erythropoietin doses. in conclusion, we found that adding intravenous human recombinant erythropoietin could not statistically improve short-term visual function results compared to systemic high dose methylprednisolone treatment. furthermore, this study supports the safety profile of intravenous human recombinant erythropoietin. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. 304 j  o  v r volume 14, issue 3, july–september 2019 erythropoietin for optic neuritis; soltan sanjari et al references 1. toosy at, mason df, miller dh. optic neuritis. lancet neurol 2014;13:83–99. 2. hickman sj, toosy at, jones sj, altmann dr, miszkiel ka, macmanus dg, et al. a serial mri study following optic nerve mean area in acute optic neuritis. brain 2004;127:2498–2505. 3. matsunaga y, kezuka t, an x, fujita k, matsuyama n, matsuda r, et al. visual functional and histopathological correlation in experimental autoimmune optic neuritis. invest ophthalmol vis sci 2012;53:6964–6971. 4. beck rw, cleary pa. optic neuritis treatment trial. oneyear follow-up results. arch ophthalmolo 1993;111:773– 775. 5. steinsapir kd, goldberg ra, sinha s, hovda da. methylprednisolone exacerbates axonal loss following optic nerve trauma in rats. restor neurol neurosci 2000;17:157– 163. 6. brück w, stadelmann c. inflammation and degeneration in multiple sclerosis. neurol sci 2003;24:s265–s267. 7. beck rw, gal rl, bhatti mt, brodsky mc, buckley eg, chrousos ga, et al. visual function more than 10 years after optic neuritis: experience of the optic neuritis treatment trial. am j ophthalmol 2004;137:77–83. 8. hickman sj, dalton cm, miller dh, plant gt. management of acute optic neuritis. lancet 2002;360:1953–1962. 9. diem r, hobom m, maier k, weissert r, storch mk, meyer r, et al. methylprednisolone increases neuronal apoptosis during autoimmune cns inflammation by inhibition of an endogenous neuroprotective pathway. j neurosci 2003;23:6993–7000. 10. kashkouli mb, pakdel f, sanjari ms, haghighi a, nojomi m, homaee mh, et al. erythropoietin: a novel treatment for traumatic optic neuropathy-a pilot study. graefes arch clin exp ophthalmol 2011;249:731–736. 11. kashkouli mb, yousefi s, nojomi m, sanjari ms, pakdel f, entezari m, et al. traumatic optic neuropathy treatment trial (tontt): open label, phase 3, multicenter, semiexperimental trial. graefes arch clin exp ophthalmol 2018;256:209–218. 12. pakdel f, sanjari ms, kashkouli mb, pirmarzdashti, n, haghighi a, moddareszade m. erythropoietin in recurrent anterior ischaemic optic neuropathy. neuroophthalmology 2012;36:249–252. 13. pakdel f, sanjari ms, naderi a, pirmarzdashti n, haghighi a, kashkouli mb. erythropoietin in treatment of methanol optic neuropathy. j neuroophthalmol 2018;38:167–171. 14. sühs kw,hein k, sättler mb, görlitz a, ciupka c, scholz k, et al. a randomized, double-blind, phase 2 study of erythropoietin in optic neuritis. ann neurol 2012;72:99– 210. 15. sun ts, wei sh. preliminary report of contrast sensitivity in idiopathic optic neuritis patients after recovery. zhonghua yan ke za zhi 2009;45:1068–1073. 16. quinn ta, dutt m, shindler ks. optic neuritis and retinal ganglion cell loss in a chronic murine model of multiple sclerosis. front neurol 2011;2:50. 17. costello f, coupland s, hodge w, lorello gr, koroluk j, pan yi, et al. quantifying axonal loss after optic neuritis with optical coherence tomography. ann neurol 2006;59:963–969. 18. weishaupt jh, rohde g, pölking e, siren al, ehrenreich h, bähr m. effect of erythropoietin axotomy-induced apoptosis in rat retinal ganglion cells. invest ophthalmol vis sci 2004;45:1514–1522. 19. juul s. erythropoietin in the central nervous system, and its use to prevent hypoxic-ischemic brain damage. acta paediatr suppl 2002;91:36–42. 20. jehle t, meschede w, dersch r, feltgen n, bach m, lagrèze wa. erythropoietin protects retinal ganglion cells and visual function after ocular ischemia and optic nerve compression. ophthalmologe 2010;107:347–353. 21. mammis a, mcintosh tk, maniker ah. erythropoietin as a neuroprotective agent in traumatic brain injury review. surg neurol 2009;71:527–531. 22. feng q. beyond erythropoiesis: the anti-inflammatory effects of erythropoietin. cardiovasc res 2006;71:615–617. 23. sun y, calvert jw, zhang jh. neonatal hypoxia/ischemia is associated with decreased inflammatory mediators after erythropoietin administration. stroke 2005;36:1672–1678. 24. katavetin p, tungsanga k, eiam-ong s, nangaku m. antioxidative effects of erythropoietin. kidney int suppl 2007;72:s10–s15. 25. sättler mb, merkler d, maier k. neuroprotective effects and intracellular signaling pathways of erythropoietin in a rat model of multiple sclerosis. cell death differ 2004;2:s181–s192. 26. abri aghdam k, soltan sanjari m, ghasemi falavarjani k. erythropoietin in ophthalmology: a literature review. j curr ophthalmol 2016;28:5–11. 27. fishbane s, besarab a. mechanism of increased mortality risk with erythropoietin treatment to higher hemoglobin targets.clin j am soc nephrol 2007;2:1274–1282. 28. zhu x, perazella ma. nonhematologic complications of erythropoietin therapy. semin dial 2006;19:279–284. j  o  v r volume 14, issue 3, july–september 2019 305 letter to editor does clear corneal cataract surgery influence conjunctivochalasis? tatsuya mimura1,2,3, md, phd; michiko iida2, md; hidetaka noma4, md, phd; yuko kamei2, md aki kondo2,3, md, phd; maiko yoshida2,3, md; manami oguri2, md; yuka tanaka2, md atsushi mizota1, md, phd 1department of ophthalmology, teikyo university school of medicine, tokyo, japan 2department of ophthalmology, tokyo women’s medical university medical center east, tokyo, japan 3department of ophthalmology, university of tokyo graduate school of medicine, tokyo, japan 4department of ophthalmology, hachioji medical center, tokyo medical university, tokyo, japan orcid: tatsuya mimura: https://orcid.org/0000-0001-5593-5338 j ophthalmic vis res 2020; 15 (2): 270–272 dear editor, conjunctivochalasis is a common ocular condition characterized by excess conjunctival folds and is associated with aging.[1–4] we previously demonstrated that the progression of conjunctivochalasis after sclerocorneal tunnel incisions was associated with the axial length of the eyeball and placement of conjunctival sutures.[4] conjunctival chemosis occurs more frequently in cases of sclerocorneal tunnel incisions than in cases of corneal incisions.[5] this suggests that a clear corneal incision may induce less postoperative conjunctival inflammation compared to a transconjunctival sclerocorneal incision. therefore, we evaluated the influence of clear corneal incision in cataract surgery on the severity of conjunctivochalasis based on a previously reported grading scale.[1] this study was conducted in accordance with the tenets of the declaration of helsinki and correspondence to: tatsuya mimura, md, phd. department of ophthalmology, teikyo university school of medicine, 2-11-1 kaga, itabashi-ku, tokyo 173-8605, japan. e-mail: mimurat-tky@umin.ac.jp received: 07-06-2019 accepted: 04-09-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i2.6749 was approved by the institutional review board. the inclusion criteria were: age > 40 years; nuclear cataract grades ii–iv based on the emery–little classification; and uncomplicated phacoemulsification surgery. a total of 83 patients (83 eyes) who underwent mini-incision (2.4 mm) phacoemulsification for corneal wound were enrolled, including 43 men and 40 women aged 72.3 ± 9.8 years (mean ± standard deviation), with an age range of 42–88 years. the severity of conjunctivochalasis was assessed using a modified grading system as previously described.[1, 2] cataract surgery was performed via a clear corneal incision created with a 2.4 mm knife at the superior or temporal position. we evaluated the severity of conjunctivochalasis after one week and one, three, and six months postoperatively. the total conjunctivochalasis score significantly increased after postoperative month 3 (p = 0.0017) but decreased after postoperative month 6 (p = 0.5806) [figure 1]. progression of conjunctivochalasis was defined as ≥ 2-point increase in the total conjunctivochalasis score. table 1 shows the results of the multivariate analysis using a stepwise this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: mimura t, iida m, noma h, kamei y, kondo a, yoshida m, oguri m, tanaka y, mizota a. . j ophthalmic vis res 2020;15:270–272. 270 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i2.6749&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr letter; mimura et al table 1. multivariate analysis of factors influencing progression of conjunctivochalasis (n = 83). variable or (95% ci) p-value age (years) 1.01 (1.00 – 1.02) 0.0660 gender (male) 1.21 (0.97 – 1.51) 0.0895 hypertension 1.11 (0.90 – 1.37) 0.3341 diabetes 1.00 (0.79 – 1.27) 0.9964 hyperlipidemia 0.94 (0.66 – 1.34) 0.7317 coronary heart disease 1.14 (0.87 – 1.50) 0.3435 refraction (diopters) 0.99 (0.96 – 1.02) 0.3293 anterior chamber depth 0.89 (0.68 – 1.17) 0.3972 lens thickness 1.00 (0.85 – 1.19) 0.9589 axial length (mm) 1.01 (0.93 – 1.10) 0.8196 corneal incision (superior / temporal) 1.06 (0.84 – 1.34) 0.6190 baseline total conjunctivochalasis score 0.90 (0.85 – 0.95) 0.0001 or, odds ratio; ci, confidence interval the total conjunctivochalasis score was calculated as the sum of the scores for the temporal, central, and nasal regions (0–9). figure 1. mean postoperative total conjunctivochalasis score at each time point. selection of factors associated with progression of conjunctivochalasis. the baseline total conjunctivochalasis score was significantly associated with the progression of conjunctivochalasis (odds ratio = 0.90, p = 0.0001). in this study, the postoperative total conjunctivochalasis score increased after postoperative week 1 but subsequently returned to the preoperative level. additionally, the preoperative severity of conjunctivochalasis was an independent determinant of the postoperative progression of conjunctivochalasis. these results suggest that a clear corneal incision did not change the severity of conjunctivochalasis. the severity of conjunctivochalasis showed a significant increase after the first postoperative week, which was probably due to postoperative conjunctival inflammation, as there was a subsequent return to baseline. we found that the axial length influences the severity of conjunctivochalasis.[3] our previous study had also demonstrated that the axial length was independently associated with the grade of conjunctivochalasis after adjustment for age.[3] in conclusion, our results showed no significant change in the severity of conjunctivochalasis after 24 postoperative weeks despite a transient early increase. this article complements our previous study on the progression of conjunctivochalasis after sclerocorneal tunnel incisions. financial support and sponsorship the ministry of education, culture, sports, science and technology of japan provided financial support in the form of a grant-in-aid for scientific research (16k11332). the sponsor had no role in the design or conduct of this research. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 271 letter; mimura et al conflicts of interest there are no conflicts of interest. references 1. meller d, tseng sc. conjunctivochalasis: literature review and possible pathophysiology. surv ophthalmol 1998;43:225–232. 2. mimura t, yamagami s, usui t, funatsu h, mimura y, noma h, et al. changes of conjunctivochalasis with age in a hospital-based study. am j ophthalmol 2009;147:171– 177. 3. mimura t, yamagami s, kamei y, goto m, matsubara m. influence of axial length on conjunctivochalasis. cornea 2013;32:1126–1130. 4. mimura t, iida m, oshima r, noma h, kamei y, goto m, et al. changes of conjunctivochalasis after cataract surgery via a superior transconjunctival sclerocorneal incision. int ophthalmol 2017;37:691–700. 5. sugai s, yoshitomi f, oshika t. transconjunctival singleplane sclerocorneal incisions versus clear corneal incisions in cataract surgery. j cataract refract surg 2010;36:1503–1507. 272 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 original article distribution of stromal cell subsets in cultures from distinct ocular surface compartments lei liu1, md, phd; ying yu2, md; qiuyue peng1, md; simone r porsborg1, phd; frederik m nielsen1, md annemette jørgensen3, md; anni grove4, md; chris bath5, md, phd; jesper hjortdal6, md, phd ole b christiansen3, md, phd; trine fink1, phd; vladimir zachar1, md, phd 1regenerative medicine group, department of health science and technology, aalborg university, aalborg, denmark 2department of neurosurgery, first hospital of jilin university, changchun, china 3department of gynecology and obstetrics, aalborg university hospital, denmark 4department of pathology, aalborg university hospital, denmark 5department of ophthalmology, aalborg university hospital, aalborg, denmark 6department of ophthalmology, aarhus university hospital, aarhus, denmark orcid: liu lei: https://orcid.org/0000-0002-0609-9932 zachar vladimir: https://orcid.org/0000-0002-5279-2690 abstract purpose: to reveal the phenotypic differences between human ocular surface stromal cells (hosscs) cultured from the corneal, limbal, and scleral compartments. methods: a comparative analysis of cultured hosscs derived from four unrelated donors was conducted by multichromatic flow cytometry for six distinct cd antigens, including the cd73, cd90, cd105, cd166, cd146, and cd34. results: the hosscs, as well as the reference cells, displayed phenotypical profiles that were similar in high expression of the hallmark mesenchymal stem cell markers cd73, cd90, and cd105, and also the cancer stem cell marker cd166. notably, there was considerable variation regarding the expression of cd34, where the highest levels were found in the corneal and scleral compartments. the multi-differentiation potential marker cd146 was also expressed highly variably, ranging from 9% to 89%, but the limbal stromal and endometrial mesenchymal stem cells significantly surpassed their counterparts within the ocular and reference groups, respectively. the use of six markers enabled investigation of 64 possible variants, however, just four variants accounted for almost 90% of all hosscs, with the co-expression of cd73, cd90, cd105, and cd166 and a combination of cd146 and cd34. the limbal compartment appeared unique in that it displayed greatest immunophenotype diversity and harbored the highest proportion of the cd146+cd34pericyte-like forms, but, interestingly, the pericyte-like cells were also found in the avascular cornea. conclusions: our findings confirm that the hosscs exhibit an immunophenotype consistent with that of mscs, further highlight the phenotypical heterogeneity in stroma from distinct ocular surface compartments, and finally underscore the uniqueness of the limbal region. keywords: cd146; cd34; flow cytometry; human ocular surface stromal cells; pericytes j ophthalmic vis res 2020; 15 (4): 493–501 © 2020 journal of ophthalmic and vision research | published by knowledge e 493 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7780&domain=pdf&date_stamp=2019-07-17 mesenchymal stem cells in ocular surface; liu et al introduction continuous maintenance of the cornea is imperative to preserve the normal vision. it has been shown that the transitional zone between cornea and sclera known as limbus plays an important role,[1, 2] and we have in our previous work highlighted some important aspects of the epithelial stem cells associated with this part of the ocular surface.[3–5] in addition to the limbal epithelial stem cells (lescs), the limbus harbors a group of stem cell-like stromal cells capable of multilineage differentiation.[6, 7] furthermore, it has been found that several subtypes of human ocular surface stromal cells (hosscs) display stem cell-like properties, with similar stem celllike features being attributed to stromal cells from avascular central cornea[8] and the sclera.[9] upon injury, the hosscs become mitotic, exhibit limited capacity for self-renewal and transit into myofibroblast phenotype.[10, 11] it has also been revealed that hosscs have a phenotype in common with mesenchymal stem cells (mscs), including the expression of cd29, cd54, cd71, cd90, cd105, cd106, and cd166.[8, 9, 12] the hosscs thus appear to represent a highly functional population, which likely plays an important role in the maintenance of cornea, and in the future may support a new generation of improved therapies for sight-threatening corneal diseases, such as limbal stem cell deficiency or corneal scarring. nevertheless, among the different ocular surface compartments, the co-expression of individual msc markers, and, importantly, the specific phenotypical variants, such as pericyteor adventitia-like cells, remains obscure. to this end, we embarked to isolate and culture the corneal (cscs), limbal (lscs), and scleral (sscs) stromal cells from each of the four individuals and carry out six-epitopes multicolor immunophenotyping correspondence to: vladimir zachar, md, phd. fredrik bajers vej 3b, 9280 aalborg, denmark. e-mail: vlaz@hst.aau.dk received: 03-01-2020 accepted: 26-06-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7780 using flow cytometry with reference to the wellestablished adipose-derived stem cells (ascs), endometrial mesenchymal stem cells (emscs), and human foreskin fibroblasts (hffs). we were especially meticulous to use consistent dissection and culture techniques so as to eliminate possible confounding factors from inter-donor variability[13] and culture conditions.[14–16] the results are expected to deepen our understanding of the hosscs phenotypical diversity and spur further research into biological significance of specific variants for corneal homeostasis. methods ocular surface tissue dissection and cell culture the tissue dissection and culture techniques were optimized based on our previous studies.[4] human ocular surface tissue without a corneal pathology but not suitable for transplantation was obtained from four donors free from ocular disease aged 22–86 years from the department of ophthalmology, aarhus university hospital (arhus, denmark) adhering to the danish legislation pertinent to tissue donation. after the removal of epithelial and endothelial cell layers by mechanical scraping, the ocular surface tissue was further separated into corneal, limbal, and scleral compartments under a stereo dissection microscope (nikon smz-2b; nikon, tokyo, japan). the compartments were next morcellated and placed in a mixture of collagenase type iv and dispase ii (both from life technologies, naerum, denmark) at 100 iu/ml and 2.4 iu/ml, respectively, in pbs at 37°c for 2 hours. the digested explants were cultured in 6-well culture plates in dmem supplied with 10% fcs and 1% pnc/streptomycin (all from life technologies). once the outgrowing cells reached the well edge, they were passaged from each well into a t75 flask (p1) together with this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: liu l, yu y, peng q, porsborg sr, nielsen fm, jørgensen a, grove a, bath c, hjortdal j, christiansen ob, fink t, zachar v. distribution of stromal cell subsets in cultures from distinct ocular surface compartments. j ophthalmic vis res 2020;15:493–501. 494 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 https://knepublishing.com/index.php/jovr mesenchymal stem cells in ocular surface; liu et al the tissue pieces, which would not attach and were discarded during the next media removal. the culture medium was changed every two– three days and the cells were passaged at 80% confluence at a 1:3 ratio until passage 3. ascs were obtained from in-house frozen stocks (p2–p4) of regenerative medicine group. aalborg university (aalborg, denmark) and cultured according to previous reports.[17, 18] hffs were cultured as previously described.[19] emscs were isolated from human endometrium tissue after hysterectomy was kindly donated by the department of gynecology and obstetrics, aalborg university hospital according to the danish legislature, following previously reported protocol.[20] flow cytometry co-expression of six epitopes, including the cd34, cd73, cd90, cd105, cd146, and cd166 was analyzed on trypsinized hosscs and reference cells using a batch of directly conjugated antibodies (all from bd bioscience, albertslund, denmark) using the cytoflex and the kaluza 1.3 software package (both from beckman coulter, copenhagen, denmark) as previously described.[21, 22] compensation values were established for each run to control for the bleed-through utilizing the bd compbeads set (bd bioscience) and the autocomp wizard in summit 6.1 (beckman coulter), and the kaluza 1.3 when analyzing the data. the gating protocol included a demarcation of each cell population from the cellular debris followed by the determination of the area of stable flow and selection of single cells. a cut-off value representing the top 2.5 percentile of the fluorescence minus one (fmo) control was then used to establish the positive population for each of the markers.[23, 24] statistical analysis the data are presented as a mean ± standard deviation (sd) derived from three independent experiments entailing three to four biological replicates of hosscs and three technical replicates of reference cell lines. statistical analysis was performed within hosscs and within the reference cells, respectively. routines from the spss 24.0 package (spss, chicago, il) included bartlett’s test for equality of variances, one-way analysis of variance (anova) together with post-hoc tukey’s honestly significant difference (hsd) test or nonparametric mann–whitney u test or kruskal–wallis test in case of multi-sample comparisons. p < 0.05 was considered as statistically significant. results cell morphology and single surface markers expression a representative corneal button as well as the isolated corneal, limbal, and scleral compartments and the explants thereof are shown in figure 1a. cell adhesion to the culture plates as outgrowth from the grafts was detected after 7–10 days. the outgrowing cells were morphologically typical of fibroblasts, assuming an elongated or spindle shape with a single nucleus and formed a monolayer by two weeks. the strategy to identify positivity boundaries for the studied markers in the flow cytometry is exemplified using the cd105 in figure 1b. it demonstrates the application of gates to remove the cellular debris, select the stable flow and single cells, and determine the cut-off value using the fmo control distribution. the expression of hossc surface markers with reference to the ascs, emscs, and hffs is presented in figure 2a. in general, all cell types expressed highly and uniformly the cd73, cd90, cd105, and cd166, with means ranging from 74.6% to 100%, but the expression of cd34 and cd146 was relatively lower and more variable. the means ranged from 2.7% to 32.5% for the cd34 and from 8.9% to 89.4% for the cd146. only the cd146 was expressed significantly higher by the lscs and emscs within the hossc and reference cell groups, respectively, and it is notable that it was the emscs that expressed this marker at the highest level (p < 0.01) when taking all the cell types into account. a donor-matched phenotypic analysis of the ocular compartments revealed marked inter-donor variability of the cd146 expression (figure 2b). across the donors, the expression of cd146 varied from 10.4% to 33.5% in cscs, 40.2% to 63.7% in lscs, and 11.3% to 61.4% in sscs. interestingly, with respect to the cd34, the limbal compartment exhibited significantly the least variability with 9.6% to 12.9% of positive cells, whereas, the journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 495 mesenchymal stem cells in ocular surface; liu et al figure 1. isolation of human ocular surface stromal cells and outline of gating strategy to determine single maker positive boundary. (a) donor corneal button with indicated (upper corner inset) and dissected (lower corner inset) corneal, limbal, and scleral compartments. the blue line demarcates cornea and limbus and the red line limbus and sclera (×20 original magnification). the representative images from explant cultures at days 0, 8, and 14 are shown. (b) steps to identify positive populations in the flow cytometric analysis are demonstrated in the example of the cd105. remaining two segments were more reminiscent of the cd146 pattern. the values namely ranged from 1.9% to 46.8% in cscs and 7.6% to 63.4% in sscs. distribution of phenotypical variants the combination of the studied six surface markers provided for 64 (2∧6) possible immunophenotypical variants. however, only a restricted number of specific combinations were detected within the ocular surface compartments. the most prevalent combinations were based on the simultaneous presence of cd73, cd90, cd105, and cd166, and alternating expression of cd146 and cd34, which in total represented 88.4% of all cells (figure 3). taking into account also the variants negative for the cd166, the proportion of major phenotypes reached on average 94.5%. the representation of the major variants differed between particular ocular surfaces, with cornea, limbus, and sclera averaging, 96.4%, 90.0%, and 97.1%, respectively. limbus clearly harbored, when compared to the other ocular compartments, the highest proportion of minor variants outside the hallmark triple combination of cd73+cd90+cd105+, and thus in terms of variant distribution appeared as the most heterogeneous segment. this conclusion could also be corroborated when looking at another, more qualitative, parameter, which was the frequency of the different minor variant types. regarding particular major variants, irrespective of the ocular location, the cd73+cd90+cd105+cd166+cd146–cd34– appeared to be the most prevalent and the cd73+cd90+cd105+cd166–cd146–cd34– the least prevalent phenotypes. with respect to the individual ocular compartments, it is of interest that limbus exhibited highest proportion of the pericyte-like cd146+cd34– phenotype. this phenotype was found mostly on the background of the cd73+cd90+cd105+cd166+ combination, but also with much less frequency in the context of the hallmark triple positivity for cd73, cd90, and cd105. co-expression of cd146 and cd34 since the cd146 and cd34 have previously been shown to delineate important stem cell variants related to pericytic, advential, and intermediate populations,[25] the hosscs were subsequently analyzed for their co-expression. no significant differences were observed among the three ocular compartment in the proportion of double-positive or -negative, or cd34 single-positive cells (figure 496 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 mesenchymal stem cells in ocular surface; liu et al figure 2. immunophenotypical profiles of human ocular surface stromal cells with reference to mesenchymal stem cells. (a) expression levels of single markers. (b) radar charts indicating inter-donor variability. the data are presented as means ± sd. the asterisks in panel a indicate a statistically significant (p < 0.05) difference between the means, and the asterisk in panel b denotes a significantly lower variability (p < 0.05) of the cd34 in the lsc group as compared to the cscs and sscs. n = 4 for cscs and sscs, and n = 3 for lscs, ascs, emscs, and hffs. cscs, corneal stromal cells; lscs, limbal stromal cells; sscs, scleral stromal cells; ascs, adipose-derived stem cells; emscs, endometrial mesenchymal stem cells; hffs, human foreskin fibroblasts. 4a). this could not be confirmed with the reference cells, probably as a consequence of remarkably high cd146 expression by emscs. interestingly, however, the hosscs were less uniform regarding the expression of the pericyte-like stromal cell phenotype featuring the cd146+cd34– profile. here, the limbal compartment surpassed the adjacent segments by more than two-fold, and similar pattern could be seen with the emscs within the reference cell group. the superior prevalence of pericytic phenotype in the limbus compartment is also clearly illustrated from the individual donor perspective (figure 4b). journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 497 mesenchymal stem cells in ocular surface; liu et al figure 3. distribution of phenotypical variants based on co-expression of six selected cd markers in stromal cells cultured from three distinct ocular surface compartments. the data are presented as means ± sd and asterisks indicate statistical significance at p < 0.05. n = 4 for cscs and sscs, and n = 3 for lscs. � the marker is expressed. � the marker is not expressed. cscs, corneal stromal cells; lscs, limbal stromal cells; sscs, scleral stromal cells. discussion our results demonstrated that the most prevalent pattern in the hossc cultures featured a canonical quadruple cd73, cd90, cd105, and cd166 coexpression, which is reminiscent of a general msc profile.[26] the frequent occurrence of variants with this signature may have a biological significance, since some of these markers were found to be involved in the corneal wound healing.[27] regarding the two minor antigens, the cd146 and cd34, they were not co-expressed consistently together with the canonical repertoire, and their levels were influenced by a substantial donorrelated variability. there was, however, an obvious trend toward low cd34 expression in the limbal cells, which was also well in accordance with the phenotype of the reference cells. although it is generally believed that cd34 expression is related to hematopoietic origin, more recent evidence demonstrates cd34 is also expressed by nonhematopoietic progenitor cells,[28] including neural crest-derived precursors from cornea.[29] therefore, the origin and function of cd34+ cells from different ocular surface stromal compartments is of interest and requires further exploration. as for the cd146, it has been reported to be expressed at a high level in emscs[30] and from the functional point of view, it has been proposed to be associated with high trilineage potency.[31] but in the context of the limbal niche, it is plausible that this phenotypical hallmark plays an important role in corneal homeostasis. this stems from previous findings that the irradiated fibroblasts isolated from the limbus supported better the growth of epithelial progenitors than the fibroblasts isolated from the central cornea or sclera[32] and that these cells typically featured the cd146.[33] another interesting result was provided by a comparative analysis of the three ocular surface compartments for the presence of distinctive msc subtypes, including the perivascular msc subpopulations, namely pericyte– (cd146+ cd34–)[31] and adventitial-like cells (cd146– cd34+),[34] as well as a group of cells at their intermediate stage (cd146+cd34+), which have 498 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 mesenchymal stem cells in ocular surface; liu et al figure 4. co-expression of the cd146 and cd34 in human ocular surface stromal cells with reference to mesenchymal stem cells and fibroblasts. (a) occurrence of pericytic (cd146+cd34–), adventitial (cd146–cd34+), and intermediate-like (cd146+cd34+) phenotypical variants. the data are presented as means + sd and asterisks indicate statistical significance at p < 0.05. n = 4 for cscs and sscs, and n = 3 for lscs, ascs, emscs, and hffs. (b) inter-donor variability of the cd146+cd34– pericyte-like phenotype. cscs, corneal stromal cells; lscs, limbal stromal cells; sscs, scleral stromal cells; ascs, adipose-derived stem cells; emscs, endometrial mesenchymal stem cells; hffs, human foreskin fibroblasts; n.a., not available. been suggested to possess a proliferative capacity.[25] strikingly, the pericytes were highly represented in the limbal compartment, irrespective of an inter-donor variability, which is known to impart a substantial confounding effect.[13] since the pericyte phenotype is cd34 negative, the implication is that this marker is in the limbal compartment encountered at invariably low levels, as noted above. the presence of pericyte-like cells in limbal stroma in this study is in line with previous reports,[35, 36] nevertheless, it is for the first time that we are showing that the limbal stromal cultures harbor a significantly higher proportion of pericyte-like cells than their donor-matched corneal or scleral counterparts. this finding thus indicates that an elaborate limbal msc niche entailing substantial cellular complexity and intricate cross-talk is essential for a normal self-renewal of the lescs. such networking is reminiscent of the role the msc niche plays in supporting the homeostasis of hematopoiesis.[37] journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 499 mesenchymal stem cells in ocular surface; liu et al it is also worthwhile to mention that this is the first time that the presence of perivascular mscs has been documented in avascular central corneal stroma. nonetheless, it is necessary to state that the association of these cell types with angiogenesis through examination of specific functional markers, such as ng2, smα, desmin, vimentin, and pdgfr-β, was not done in this study. thus, in light of our data, it appears that the classical paradigm associating specific phenotypes with perivascular microenvironment needs to be reconsidered, and it will be interesting to see in the future what biological role these cells play in the cornea. in conclusion, the hosscs represent a greatly heterogeneous population that seems to play an important role in the maintenance of ocular surface and most significantly, the cornea. better understanding of these cells undoubtedly holds promise for improvement of the in vitro protocols, which will ultimately spur the development of new generation of ocular surface stem cell-based products for sight-threatening corneal diseases such as limbal stem cell deficiency or corneal scarring. acknowledgements the authors are thankful to esben nielsen and henrik sejersen at the department of ophthalmology, aarhus university hospital, for their help with the collection of experimental material. conflicts of interest there are no conflicts of interest. references 1. dua hs, azuara-blanco a. limbal stem cells of the corneal epithelium. surv ophthalmol 2000;44:415–425. 2. pellegrini g, rama p, mavilio f, de luca m. epithelial stem cells in corneal regeneration and epidermal gene therapy. j pathol 2009;217:217–228. 3. bath c, muttuvelu d, emmersen j, vorum h, hjortdal j, zachar v. transcriptional dissection of human limbal niche compartments by massive parallel sequencing. plos one 2013;8:e64244. 4. bath c, yang s, muttuvelu d, fink t, emmersen j, vorum h, et al. hypoxia is a key regulator of limbal epithelial stem cell growth and differentiation. stem cell res 2013;10:349– 360. 5. liu l, nielsen fm, emmersen j, bath c, ostergaard hjortdal j, riis s, et al. pigmentation is associated with stemness hierarchy of progenitor cells within cultured limbal epithelial cells. stem cells 2018;36:1411–1420. 6. branch mj, hashmani k, dhillon p, jones dr, dua hs, hopkinson a. mesenchymal stem cells in the human corneal limbal stroma. invest ophthalmol vis sci 2012;53:5109–5116. 7. hashmani k, branch mj, sidney le, dhillon ps, verma m, mcintosh od, et al. characterization of corneal stromal stem cells with the potential for epithelial transdifferentiation. stem cell res ther 2013;4:75. 8. vereb z, poliska s, albert r, olstad ok, boratko a, csortos c, et al. role of human corneal stroma-derived mesenchymal-like stem cells in corneal immunity and wound healing. sci rep 2016;6:26227. 9. tsai cl, wu pc, fini me, shi s. identification of multipotent stem/progenitor cells in murine sclera. invest ophthalmol vis sci 2011;52:5481–5487. 10. carlson ec, wang ij, liu cy, brannan p, kao cw, kao ww. altered kspg expression by keratocytes following corneal injury. mol vis 2003;9:615–623. 11. jester jv, petroll wm, cavanagh hd. corneal stromal wound healing in refractive surgery: the role of myofibroblasts. prog retin eye res 1999;18:311–356. 12. polisetty n, fatima a, madhira sl, sangwan vs, vemuganti gk. mesenchymal cells from limbal stroma of human eye. mol vis 2008;14:431–442. 13. wegmeyer h, broske am, leddin m, kuentzer k, nisslbeck ak, hupfeld j, et al. mesenchymal stromal cell characteristics vary depending on their origin. stem cells dev 2013;22:2606–2618. 14. hagmann s, moradi b, frank s, dreher t, kammerer pw, richter w, et al. different culture media affect growth characteristics, surface marker distribution and chondrogenic differentiation of human bone marrowderived mesenchymal stromal cells. bmc musculoskelet disord 2013;14:223. 15. sidney le, hopkinson a. corneal keratocyte transition to mesenchymal stem cell phenotype and reversal using serum-free medium supplemented with fibroblast growth factor-2, transforming growth factor-beta3 and retinoic acid. j tissue eng regen med 2018;12:e203–e15. 16. sidney le, branch mj, dua hs, hopkinson a. effect of culture medium on propagation and phenotype of corneal stroma-derived stem cells. cytotherapy 2015;17:1706– 1722. 17. fink t, rasmussen jg, lund p, pilgaard l, soballe k, zachar v. isolation and expansion of adipose-derived stem cells for tissue engineering. front biosci 2011;3:256– 263. 18. zachar v, rasmussen jg, fink t. isolation and growth of adipose tissue-derived stem cells. methods mol biol 2011;698:37–49. 19. prasad sm, czepiel m, cetinkaya c, smigielska k, weli sc, lysdahl h, et al. continuous hypoxic culturing maintains activation of notch and allows long-term propagation of human embryonic stem cells without spontaneous differentiation. cell prolif 2009;42:63–74. 20. gargett ce, schwab ke, zillwood rm, nguyen hp, wu d. isolation and culture of epithelial progenitors and 500 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 mesenchymal stem cells in ocular surface; liu et al mesenchymal stem cells from human endometrium. biol reprod 2009;80:1136–1145. 21. nielsen fm, riis se, andersen ji, lesage r, fink t, pennisi cp, et al. discrete adipose-derived stem cell subpopulations may display differential functionality after in vitro expansion despite convergence to a common phenotype distribution. stem cell res ther 2016;7:177. 22. peng q, alipour h, porsborg s, fink t, zachar v. evolution of asc immunophenotypical subsets during expansion in vitro. int j mol sci 2020;21:1408. 23. roederer m. spectral compensation for flow cytometry: visualization artifacts, limitations, and caveats. cytometry 2001;45:194–205. 24. maecker ht, trotter j. flow cytometry controls, instrument setup, and the determination of positivity. cytometry a 2006;69:1037–1042. 25. zimmerlin l, donnenberg vs, rubin jp, donnenberg ad. mesenchymal markers on human adipose stem/progenitor cells. cytometry a 2013;83:134–140. 26. lv fj, tuan rs, cheung km, leung vy. concise review: the surface markers and identity of human mesenchymal stem cells. stem cells 2014;32:1408–1419. 27. west-mays ja, dwivedi dj. the keratocyte: corneal stromal cell with variable repair phenotypes. int j biochem cell biol 2006;38:1625–1631. 28. sidney le, branch mj, dunphy se, dua hs, hopkinson a. concise review: evidence for cd34 as a common marker for diverse progenitors. stem cells 2014;32:1380–1389. 29. yoshida s, shimmura s, nagoshi n, fukuda k, matsuzaki y, okano h, et al. isolation of multipotent neural crestderived stem cells from the adult mouse cornea. stem cells 2006;24:2714–2722. 30. fayazi m, salehnia m, ziaei s. differentiation of human cd146-positive endometrial stem cells to adipogenic-, osteogenic-, neural progenitor-, and glial-like cells. in vitro cell dev biol anim 2015;51:408–414. 31. crisan m, yap s, casteilla l, chen cw, corselli m, park ts, et al. a perivascular origin for mesenchymal stem cells in multiple human organs. cell stem cell 2008;3:301–313. 32. ainscough sl, linn ml, barnard z, schwab ir, harkin dg. effects of fibroblast origin and phenotype on the proliferative potential of limbal epithelial progenitor cells. exp eye res 2011;92:10–19. 33. bray lj, heazlewood cf, munster dj, hutmacher dw, atkinson k, harkin dg. immunosuppressive properties of mesenchymal stromal cell cultures derived from the limbus of human and rabbit corneas. cytotherapy 2014;16:64–73. 34. corselli m, chen cw, sun b, yap s, rubin jp, peault b. the tunica adventitia of human arteries and veins as a source of mesenchymal stem cells. stem cells dev 2012;21:1299– 1308. 35. fernandez-perez j, binner m, werner c, bray lj. limbal stromal cells derived from porcine tissue demonstrate mesenchymal characteristics in vitro. sci rep 2017;7:6377. 36. li gg, chen sy, xie ht, zhu yt, tseng sc. angiogenesis potential of human limbal stromal niche cells. invest ophthalmol vis sci 2012;53:3357–3367. 37. sa da bandeira d, casamitjana j, crisan m. pericytes, integral components of adult hematopoietic stem cell niches. pharmacol ther 2017;171:104–113. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 501 original article preferred learning styles among ophthalmology residents: an iranian sample samira hassanzadeh1, ms; hossein karimi moonaghi2,3, phd; akbar derakhshan4, md; seyed masoud hosseini5, phd; ali taghipour6, phd 1paramedical college, mashhad university of medical sciences, mashhad, iran 2evidencebased caring research center, department of medical surgical nursing, school of nursing and midwifery, mashhad university of medical sciences, mashhad, iran 3department of medical education, school of medicine, mashhad university of medical sciences, mashhad, iran 4eye research center, mashhad university of medical sciences, mashhad, iran 5school of nursing and midwifery, mashhad university of medical sciences, mashhad, iran 6social determinants of health research center, mashhad university of medical sciences, mashhad, iran orcid: samira hassanzadeh: https://orcid.org/0000-0003-0022-4410 hossein karimi moonaghi: https://orcid.org/0000-0003-0496-2306 abstract purpose: this study was performed to assess the learning styles of a sample of iranian residents through kolb’s and vark questionnaires. methods: in this descriptive-analytical study, 45 ophthalmology residents of mashhad university of medical sciences were enrolled. kolb’s and vark questionnaires were provided, and residents were oriented and guided on how to complete them. results: forty-three out of the forty-five ophthalmology residents completed the questionnaire (95.5% response rate). the preferred learning style among ophthalmology residents was assimilative (51.2%), followed by convergent (37.2%), accommodative (7.7%), and divergent (4.7%), based on kolb’s questionnaire. according to the results of the vark questionnaire, most ophthalmology residents were auditory learners (34.9%), followed by multimodal learners (30.2%). in addition, there was no significant relation between genders, stage of residency, and kolb’s and vark learning styles (p > 0.05 for all). conclusion: the most preferred learning styles of ophthalmology residents were assimilative and auditory. considering the dominant learning styles of learners and incorporating various teaching methods are recommended to enhance the learning among residents. keywords: learning style; resident; ophthalmology; vark inventory; kolb inventory; iran. j ophthalmic vis res 2019; 14 (4): 483–490 correspondence to: hossein karimi moonaghi, msn, mmeded, phd. department of medical education, school of medicine, mashhad university of medical sciences, azadi square, mashhad 9177948564, iran. e-mail: karimih@mums.ac.ir received: 26-12-2018 accepted: 26-06-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i4.5457 introduction learning is a complex process that can be affected by many factors, such as intelligence, motivation, this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: hassanzadeh s, karimi moonaghi h, derakhshan a, hosseini sm, taghipour a. learning styles among ophthalmology residents. j ophthalmic vis res 2019;14:483–490. © 2019 journal of ophthalmic and vision research | published by knowledge e 483 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5457&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr learning styles among ophthalmology residents; hassanzadeh et al environment, and learning style.[1] each student uses their unique learning style to learn and process information in different ways.[2] successful teaching in the field of medical sciences requires knowing a variety of students’ learning styles to meet the needs of learners.[3–7] to have a framework to systematically organize the learning style constructs, curry, in 1983, proposed the “onion ring model.” in this multilayer model, cognitive personality style is in the innermost layer, followed by information processing, social interaction, and instructional preferences in the outermost layer.[8] curry states that the outermost layer seems to be the less stable one and is likely to be influenced by external factors more than the other layers. kolb’s learning styles questionnaire is a well-known device to assess learning styles of learners,[9] which can then assess the information processing style of an individual. according to kolb’s theory, learning takes place in a cycle comprising four stages [figure 1]: (1) facing a topic or learning material (concrete experience); (2) observing and reflecting on it (reflective observation); (3) thinking and conceptualizing (abstract conceptualization); and (4) experiencing (active experimentation).[10] however, since learners have different preferences and interests, their function is not the same at each stage of the cycle. this is why different learners choose different careers or fields of study.[11] kolb divided learners into four learning style groups, based on their preferred action at different stages of kolb’s cycle: diverging, converging, accommodating, and assimilating learners.[12] students with a divergent learning style use objective experience to learn. they learn more through group discussions and brainstorming. converging learners use abstract thinking along with an active experience of information to decide how to solve a problem and find a solution. accommodating learners learn from the combination of objective experience and active experimentation and new experiences. for students with assimilative learning style, abstract thinking and observational evidence have a significant impact on their rational understanding.[1] mills and fleming, in 2004, introduced the vark learning styles questionnaire, which is an abbreviation of four learning styles: visual, auditory– aural, read–write, and kinesthetic. it tests the outer layer of curry’s onion ring model, which is “instructional preferences.”[8] a kinesthetic learner prefers to experience, move, touch, and do things. also, learners who use two or more of these learning preferences equally are called multimodal learners.[13] a good learner is one who uses all of these functions to learn efficiently, but most of the time, learners show a dominant learning style, which is detectable through this questionnaire. the vark questionnaire shows how people use their dominant learning style in an environment, while kolb’s questionnaire assesses how the students learn. previous studies have shown that most iranian medical students are converging learners.[14, 15] however, our knowledge about our residents’ learning styles in different fields is very low. studies show that knowing the learners’ dominant learning styles helps educational systems select teaching methods tailored to those styles.[10] hence, being familiar with the residents’ learning styles at different levels and in different fields of study and various educational settings is of great importance. in this study, we assessed the learning styles of a sample of iranian residents through kolb’s and vark questionnaires to evaluate these styles in different aspects and find a possible relation between the results of the two questionnaires. methods forty-five ophthalmology residents from the mashhad university of medical sciences were enrolled in this descriptive-analytical study in 2017–2018. the study was performed at the khatam alanbia eye hospital, mashhad, iran. informed consent was obtained from all participants, and ethical considerations, such as confidentiality of the participants’ personal information, were considered. we also secured an approval from our institutional ethics committee (code: 960226, ir.mums.fm.rec.1396.333). the residents first got acquainted with the questionnaires and then found out how to complete them. each participant was given the opportunity to familiarize themselves with the learning styles after the study, and the results of their analysis of responses were provided in case of interest. the validity and reliability of the persian version of kolb’s and vark questionnaires have been evaluated in several studies.[16–22] kolb’s questionnaire consists of 12 statements, each with four answers. participants must rank the answers from one to 484 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 learning styles among ophthalmology residents; hassanzadeh et al four according to their learning preferences. each statement indicates one element of kolb’s learning cycle. the sum of scores for each answer is plotted on a chart, and the participant’s tendency toward a specific learning style is determined. the vark questionnaire has 16 questions for which the participant must choose one or more of the four answers according to his/her performance in that situation. there is one point for each answer, and the sum of its score is compared with that of the others. since each question option indicates one vark learning style (visual, auditory, read and write, or kinesthetic), the highest score in each field reveals the participant’s dominant learning style. when the sum of scores in two or more answers is the same, the learner is considered a multimodal one. in this study, we tried to find a connection between the results of the two questionnaires. also, the relationship between gender, stage of residency, and preferred learning style of the participants was assessed. results forty-three out of the forty-five ophthalmology residents completed the questionnaires correctly (response rate 95.5%). the age of the participants in the study was 30.23 ± 3.40 years (range: 26–46 years), and 13 (30.2%) were female and 30 (69.8%) were male. the dominant kolb’s learning style among the participants was assimilative (51.2%), followed by convergent (37.2%), accommodative, (7.0%) and divergent (4.60%). the chi-square test showed no significant relation between learning style and gender (p = 0.636) [figure 2]. also, according to the χ2 test, there was no significant relation between learning styles and year of residency (p = 0.577) [table 1]. according to the vark questionnaire, most were auditory learners (34.9%), while the rest were multimodal (30.2%), visual (18.6%), read and write (9.0%), and kinesthetic ones (7.0%). among the multimodal learners, 61.5% were trimodal and 38.5% were bimodal. our results showed no significant relation between the preferred learning style obtained through the vark questionnaire and the gender of the residents (p = 0.562) [figure 3]. we did not also find any significant relation between vark learning styles and the stage of residency of participants (p = 0.728) [table 2]. discussion although several studies have been performed on learning styles of medical students in our country, the research on experiential learning styles of residents in different fields of medicine is scarce. according to our results, the preferred learning style among ophthalmology residents is assimilative. previous studies showed that the dominant kolb’s learning styles among iranian medical students were convergent[22–26] and assimilative.[1, 10, 21, 27, 28] studies on non-iranian residents in various specialties, especially in more practical residency fields such as surgical programs showed that most learners were converging ones.[14, 29–34] also, in those studies, more ophthalmology residents were converging learners.[35, 36] to our knowledge, the only study to assess the learning styles of iranian residents was conducted by ghajarzadeh and her colleagues at the tehran university of medical sciences in 2012,[1] in which 73 residents from seven specialties—pediatrics, general surgery, psychiatry, emergency medicine, internal medicine, radiology, and ophthalmology— were evaluated. according to their results, the dominant learning styles of all residents except for internists were assimilative and convergent. internal medicine residents’ preferred learning style was convergent. the preferred learning style among ophthalmology residents, according to kolb’s questionnaire, was assimilative, which is in concordance with our findings. according to kolb,[37] converging learners think and act more. convergent learning style tends to be the dominant one in careers like medicine and engineering. such learners are good at professions requiring technical, decision-making, and problemsolving skills. they prefer to experience ideas, practical learning, and simulations. on the other hand, assimilating learners think and watch more. they are oriented to mathematics and physical sciences, and good at planning and research, data gathering, and analysis. moreover, in learning situations, they prefer lectures and reading and thinking about analytical models.[37] kolb’s studies show that those majoring in applied areas such as medicine are mostly converging learners,[37] which contradicts the results of our study. however, some experts have criticized kolb’s theory for not paying enough attention to different conditions and cultures and the fact that journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 485 learning styles among ophthalmology residents; hassanzadeh et al figure 1. the experiential kolb’s learning cycle. figure 2. frequency distribution of kolb’s learning styles according to gender. table 1. distribution of kolb’s learning styles (in %) according to the year of residency assimilative convergent accommodative divergent 1st year 50.0 20.0 20.0 10.0 2nd year 61.5 38.5 0.0 0.0 3th year 50.0 50.0 0.0 0.0 4th year 41.7 41.7 8.3 8.3 486 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 learning styles among ophthalmology residents; hassanzadeh et al figure 3. distribution of vark’s learning styles according to gender. table 2. distribution of vark learning styles (in %) according to the year of residency auditory multimodal visual read & write kinesthetic 1st year 50.0 30.0 0.0 10.0 10.0 2nd year 23.0 38.5 15.4 15.4 7.7 3th year 37.5 12.5 37.5 0.0 12.5 4th year 33.3 33.3 25.0 8.4 0.0 the questionnaire has been examined in a few western societies.[12] a review study carried out by hashemi and his colleagues in 2014 showed a higher cataract surgery complication rate by iranian ophthalmology residents as compared to their counterparts from other countries.[38] phacoemulsification is one of the most common cataract procedures performed by ophthalmology residents. they found that while in some countries such as usa, the rate of vitreous loss had reached zero from 2001 to 2011, the same by iranian ophthalmology residents was 10.2%. they stated that as, nowadays, the approach is focused on active learning and problem solving, our educational residency program needs to be changed, with more emphasis on practicality, and orient more learners to be converging ones.[38] previous studies have shown that learning style can change during an educational course.[11] also, changes can be introduced to learning styles through practical learning.[39] however, the aim of the educational system is not changing teaching methods according to learners’ learning styles. instead, to achieve better learning outcomes, all students should be given the opportunity to apply all learning preferences according to kolb’s learning cycle during their educational program, and the key to reach this goal is knowing students’ educational needs. based on the results of the vark questionnaire, most ophthalmology residents are auditory learners. even among the multimodal learners, the aural–auditory mode is one of the preferences. most studies conducted on iranian medical students have revealed that auditory, followed by multimodal are the dominant learning preferences, which is in agreement with our results.[16, 18–20, 40–43] however, previous reports also showed that most non-iranian residents are multimodal learners.[44] an aural–auditory student learns best when they listen to lectures or presentations, discuss concepts, and watch tutorials, while a multimodal learner uses two or more ways of acquiring information to learn. according to the teacher-centered, journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 487 learning styles among ophthalmology residents; hassanzadeh et al lecture-based educational system in our country, it can be expected that the auditory learning style will be predominantly strengthened in our students. on the other hand, our ophthalmology residents are mostly assimilating learners. they learn best when they listen to lectures, watch things, and think about ideas; so, it seems logical if they dominantly prefer the auditory learning style. according to our findings, with both administered questionnaires, there is no significant relation between gender and the preferred learning style among ophthalmology residents. results of previous studies are controversial.[16, 20, 40–42] the reason can be the effect of cultural differences on learning styles.[45] kolb believes that in some cultures, where gender roles are less pervasive, men and women’s experiences are more homogenous.[37] considering kolb’s findings, the results of different studies carried out in different cultures can be different, so that, in some of them, there is a significant difference between men and women’s preferred learning styles. our results using kolb’s and vark questionnaires show no significant difference between residents in different years of residency and their dominant learning style. some reports state that there is a change in the learning style of medical students during the course of the undergraduate program[11] and then the residency program.[31] as our study was performed on residents in the same learning environment and same educational program, we can expect that they do not have significantly different preferred learning styles. although it is believed that learning styles can be flexible, based on curry’s theory, the inner layer of the onion ring model (information processing), which is assessed by kolb’s questionnaire, is likely to be more stable than the outermost layer (instructional preferences), which is evaluated using the vark questionnaire.[8] however, in concordance with the results of mitchell et al,[8] we did not find a significant change in learning styles of residents in different years of residency with both tools. it means that flexibility and changes in learning styles seem to be equal in both information processing and instructional preference modalities. our results show that most of our ophthalmology residents are assimilating learners for whom information processing is better done with abstract thinking and observational evidence. also, their preferred instructional modality is auditory or oral, which means they learn better when they listen to lectures or presentations, discuss concepts, and watch tutorials. finally, for researchers interested in similar works, we suggest recruiting residents from one surgical and one medical specialty, and comparing them to ophthalmology residents. performing more studies and comparing residents in different settings and specialties could be helpful in enhancing our knowledge about the variables that affect residents’ learning preferences. in summary, researchers believe that students adapt to the curriculum.[11] hence, we can change a teacher-centered, lecture-based model to a student-centered, problemand practical-based one. considering the predominant learning style of our residents—assimilative—and due to the practical nature of the field of ophthalmology, we should evaluate the curriculum and orient the learner’s learning style toward the goals and needs of the educational program. in addition, as we have different learners, various teaching methods should be incorporated to enhance learning outcomes of the residents. financial support and sponsorship this study has been supported by a research grant from the vice-chancellor for research at the mashhad university of medical sciences (no: 960226). conflicts of interest there are no conflicts of interest. acknowledgments this is an approved master thesis (code no: 960226) by the vice chancellor for research (vcr) at mashhad university of medical sciences who supported this study. the authors are thankful to the vcr and all of the ophthalmology residents who contributed to this research despite their lack of time. references 1. ghajarzadeh m, adili-aghdam f. learning styles of medical residents of different disciplines in tehran university of medical sciences. razi j med sci 2012;19:27–32. 488 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 learning styles among ophthalmology residents; hassanzadeh et al 2. alqahtani da, al-qahtani sm. assessing learning styles of saudi dental students using kolb’s learning style inventory. j dental educ 2014;78:927–933. 3. hossein km, fatemeh d, fatemeh os, katri vj, tahereh b. teaching style in clinical nursing education: a qualitative study of iranian nursing teacher experiences. nurse educ pract 2010;10:8–12. 4. karimi-moonaghi h, dabaghi f, oskouei f, vehviläinenjulkunen k, et al. learning style in theoretical courses: nursing students’perceptions and experiences. iran j med educ 2009;9:1–14. 5. kim rh, gilbert t. learning style preferences of surgical residency applicants. j surg res 2015;198:61–65. 6. kim rh, gilbert t, ristig k. the effect of surgical resident learning style preferences on american board of surgery in-training examination scores. j surg educ 2015;72:726– 731. 7. kolb d. experiential education: experience as the source of learning and development. englewood cliffs, nj: prentice hall; 1984. 8. mitchell ekl, james s, d’amore a. how learning styles and preferrences of firstyear nursing and midwifery students change. aust j educ 2015;59:158–168. 9. kolb da. individual learning styles and the learning process. cambridge, ma: mit; 1971. 10. hosseini sm, amery h, emadzadeh a, babazadeh s. dental students’ educational achievement in relation to their learning styles: a cross-sectional study in iran. global j health sci 2015;7:152–158. 11. bitran m, zuniga d, lafuente m, et al. influence of personality and learning styles in the choice of medical specialty. rev med chile 2005;133:1191–1199. 12. ashrafifard h, karimi moonaghi h, emadzadeh a. learning styles of faculty members. fmej, volume 9 issue 1 pages 9-17. doi: 10.22038/fmej.2019.35383.1229. 13. prithishkumar ij, michael s. understanding your student: using the vark model. j postgrad med 2014;60:183–186. 14. contessa j, ciardiello ka, perlman s. surgery resident learning styles and academic achievement. curr surg 2005;62:344–347. 15. fowler p. learning styles of radiographers. radiography 2002;8:3–11. 16. amini n, zamani be, abedini y. medical students’ learning styles. iran j med educ 2010;10:141–147. 17. karimi moonaghi h, dabbaghi, f, oskouie sf, vehvilainenjulkunen k, binaghi, t. teaching style in clinical nursing education: a qualitative study of iranian nursing teachers’ experiences. nurse education in practice 10 (2010) 8–12. 18. jannat alipour znn, jahanshahi m. evaluation of nursing students’ learning styles based on vark learning pattern in ramsar school of nursing & midwifery. biannual j med edu 2013;2:37–45. 19. javadinia a, sharifzade g, abedini m, khalesi m, erfaniyan m. learning styles of medical students in birjand university of medical sciences according to vark model. iran j med educ 2012;11:584–589. 20. mohammadi s, mobarhan mg, mohammadi m, ferns g. age and gender as determinants of learning style among medical students. british j med med res 2015;7:292–298. 21. sarchami r, hossaini s. relationship of learning styles with educational progress of nursing students in qazvin. j qazvin univ med sci 2004;30:64–67. 22. valizadeh l, zamanzadeh v. nursing and midwifery students’ learning styles in tabriz medical university. iran j med educ 2006;6:136–140. 23. allaa m, mirzadeh m, gharib m, reza baradaran h, khashayar p. assessing learning styles of the medical students and faculty in pre-clinical stage of medical education at tehran university of medical sciences. zanjan med educ j 2013;6:1–12. 24. ghazivakili z, norouzi nia r, panahi f, karimi m, gholsorkhi h, ahmadi z. the role of critical thinking skills and learning styles of university students in their academic performance. j adv med educ prof 2014;2:95–102. 25. kalbasi s, naseri m, sharifzadeh g, poursafar a. medical students’ learning styles in birjand university of medical sciences. strides dev med educ 2008;5:10–16. 26. meyari a, sabouri ka, gharib m, et al. comparison between the learning style of medical freshmen and fifthyear students and its relationship with their educational achievement. strides dev med educ 2009;6:110–118. 27. hosseinilorgani m, seif aa. to compare students’ learning styles according to gender, educational grade and major. q j re plan high educ 2001;7:93–114. 28. shafian h, azizzadeh fm, garrusi b, haghdoost a. predictors of learning styles in students of kerman university of medical sciences, iran. strides dev med educ 2014;11:90– 100. 29. baker jd, reines hd, wallace ct. learning style analysis in surgical training. am surg 1985;51:494–496. 30. caulley l, wadey v, freeman r. learning styles of firstyear orthopedic surgical residents at 1 accredited institution. j surg educ 2012;69:196–200. 31. engels pt, de gara c. learning styles of medical students, general surgery residents, and general surgeons: implications for surgical education. bmc med educ 2010;10:51– 56. 32. laeeq k, weatherly ra, carrott a, pandian v, cummings cw, bhatti ni. learning styles in two otolaryngology residency programs. laryngoscope 2009;119:2360–2365. 33. richard rd, deegan bf, klena jc. the learning styles of orthopedic residents, faculty, and applicants at an academic program. j surg educ 2014;71:110–118. 34. tuli sy, thompson la, saliba h, black ew, ryan ka, kelly mn, et al. pediatric residents’ learning styles and temperaments and their relationships to standardized test scores. j grad med educ 2011;3:566–570. 35. modi n, williams o, swampillai aj, waqar s, park j, kersey tl, et al. learning styles and the prospective ophthalmologist. med teach 2015;37:344–347. 36. stagg bc, jensen j, jorgensen a, olsen c, pettey j. learning styles among ophthalmology residents. invest ophthalmol vis sci 2015;56:144. 37. kolb a. the kolb learning style inventory 4.0: a comprehensive guide to the theory, psychometrics, research on validity and educational applications. philadelphia, pa: hay group; 2013. 38. hashemi h, babamahmoodi a, fotouhi a, asgari s. revisiting the cataract surgery curriculum for ophthalmology residents: a narrative review. iran j ophthalmol 2014;26: 178–182. 39. van den berg h. changes in learning styles induced by practical training. learn individ differ 2015;40:84–89. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 489 learning styles among ophthalmology residents; hassanzadeh et al 40. nasiri z, gharekhani s, ghasempour m. relationship between learning style and academic status of babol dental students. electron phys 2016;8:2340–2345. 41. salimi m, sadeghifar j, peyman h, shams l. visual, aural, read/write, and kinesthetic learning styles preferences in students of isfahan university of medical sciences, iran. health syst res 2012;8:1216–1224. 42. sarabi-asiabar a, jafari m, sadeghifar j, tofighi s, zaboli r, peyman h, et al. the relationship between learning style preferences and gender, educational major and status in first year medical students: a survey study from iran. iran red crescent med j 2015;17:e18250. 43. zamani n, kaboodi a. evaluation of the vark model learning styles selection in medical students. health res 2017;2:109–115. 44. shah k, ahmed j, shenoy n, srikant n. how different are students and their learning styles? int j res med sci 2017;1:212–215. 45. joy s, kolb d. are there cultural differences in learning style? int j intercult relat 2009;33:69–85. 490 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 original article topical umbilical cord serum for corneal epithelial defects after diabetic vitrectomy siamak moradian1,2, md; marzieh ebrahimi3, phd; azade kanaani1, md; amir faramarzi2, md; sare safi1, phd 1ophthalmic epidemiology research center, shahid beheshti university of medical sciences, tehran, iran 2ophthalmic research center, shahid beheshti university of medical sciences, tehran, iran 3department of stem cells, cell science research center, royan institute, tehran, iran orcid: siamak moradian: https://orcid.org/0000-0002-5328-7565 abstract purpose: to evaluate the role of topical umbilical cord serum (tucs) therapy in treating corneal epithelial defects (ceds) after diabetic vitrectomy. methods: in this double-masked, randomized clinical trial, we included 80 eyes of 80 patients who were candidates for vitrectomy due to proliferative diabetic retinopathy complications. in cases of corneal edema obscuring the fundus view during surgery, the corneal epithelium was removed using a 6-mm trephine and a blade no.15. the day after the surgery, patients were randomly divided into two groups: (1) the tucs group that received 20% tucs six times/day in addition to the conventional treatment of ced and (2) the control group, which was prescribed artificial tears as placebo in addition to the conventional treatment of ced. the rate of healing of ceds was measured via two maximum linear dimensions perpendicular to each other at the start of therapy and on postoperative days 1–5, 7, and 12. results: of 80 eyes, 40 were assigned to each treatment group. the mean times to complete ced healing were 2.4 ± 0.7 and 3.8 ± 2.1 days in the tucs and control groups, respectively (p < 0.001). persistent ced occurred in two eyes in the control group but in no eyes in the tucs group. conclusion: tucs therapy may be safe and effective in healing ceds after vitrectomy in patients with diabetes. keywords: corneal epithelial defect; diabetic vitrectomy; topical umbilical cord serum j ophthalmic vis res 2020; 15 (2): 160–165 correspondence to: siamak moradian, md. department of ophthalmology, labbafinejad medical center, shahid beheshti university of medical sciences, pasdaran ave., boostan 9 st., tehran 16666, iran. e-mail: moradian33195@yahoo.com received: 26-10-2018 accepted: 28-09-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i2.6732 introduction the removal of corneal epithelium may be necessary to improve a surgeon’s visualization of this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: moradian s, ebrahimi m, kanaani a, faramarzi a, safi s. topical umbilical cord serum for corneal epithelial defects after diabetic vitrectomy. j ophthalmic vis res 2020;15:160–165. 160 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i2.6732&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr umbilical cord serum for ced; moradian et al fundus during vitrectomy. in diabetic patients, abnormal postoperative healing of corneal epithelial defects (ceds) results in morbidity and prolongs the hospitalization period. generally, patients with diabetes are at a high risk of developing corneal disorders, a condition known as diabetic keratopathy due to insufficient epithelial adherence to the bowman’s membrane. significant recurrent corneal erosions can occur after intraocular surgery, particularly vitrectomy, in such patients.[1, 2] treatment options for diabetic keratopathy are limited. recent studies have reported the effectiveness of topical umbilical cord serum (tucs) in treating ocular surface disorders, such as neurotrophic keratitis, dry eye syndrome, and persistent ceds.[3–5] several growth factors, such as the epidermal growth factor (egf), acidic and basic fibroblast growth factors (fgfs), platelet-derived growth factor, hepatocyte growth factor, vitamin a, transforming growth factor-β (tgfβ), substance p, insulin-like growth factor-1 (igf-1), nerve growth factor (ngf), fibronectin, and α2-macroglobulin, are present in umbilical cord serum (ucs). furthermore, concentrations of egf, tgf-b, and ngf are several times higher in ucs than in peripheral blood.[4, 5] we performed this study to investigate whether tucs may have a beneficial role in healing ceds after diabetic vitrectomy. methods in this double-masked, prospective randomized controlled clinical trial (rct), we included all patients with type ii diabetes who underwent deep vitrectomy because of proliferative diabetic retinopathy (pdr) complications and had corneal epithelial edema during surgery that prompted removal of the corneal epithelium to improve the media clarity. a 6-mm trephine was used to equalize the basic ced size. the exclusion criteria were a history of herpetic, exposure, or neurotrophic keratitis, previous keratorefractive surgery, significant dry eye, trachomatous keratopathy, immune or nutritional deficiency, a history of autoimmune diseases, lid abnormality, use of glaucoma eye drops or any other eye drop after surgery (except for drops that were used during the study), and pregnancy. eyes with severe lid edema after surgery were also excluded. the study protocol was approved by the institutional review board of the ophthalmic research center of the shahid beheshti university of medical sciences. this study was conducted according to the declaration of helsinki and all participants gave written informed consent before entering the study. this rct was registered at www.clinicaltrial.gov (nct01168375). patients in the tucs group received 20% tucs eye drops (diluted with preservativefree artificial tears) six times/day in addition to the conventional treatment (chloramphenicol and betamethasone eye drops four times daily and cycloplegic eye drops three times daily). patients in the control group received the conventional treatment and a placebo (preservative-free artificial tears), without patching the eye between the drop administrations. patients were followed-up on postoperative days 1–5, 7, and 12. corneal photography was performed after administration of the fluorescein dye. the longest linear diameter and the longest vertical diameter of the ced area were measured and multiplied to obtain the area of the equivalent rectangle. the rate of healing of ceds was measured at each subsequent follow-up. the umbilical cord blood was obtained from healthy mothers with uncomplicated cesarean section delivery after screening for parenterally transmitted viral diseases, hepatitis b and c, human immunodeficiency virus, cytomegalovirus, and syphilis at the royan institute cord blood bank. briefly, samples that were negative for viruses and microbes were centrifuged at 1,500 rotations/min for 5 min, and the supernatant cells were discarded. no anticoagulants were used in the procedure. umbilical cord serum was stored at –20.0°c in 5 ml bottles. the maximum storage time was three months. to prepare eye drops, one bottle was opened, and ucs was diluted with preservative-free artificial tears to achieve the 20% concentration. samples were then stored at 4.0°c for three days. subsequently, a new bottle was opened, and the old bottle was discarded. randomization was performed using the random-block permutation method using a computer-generated randomized list. patients were then assigned to one of the two groups: case or control. a random allocation sequence was performed by a biostatistician. details of the series were unknown to the study investigators. all study personnel and participants were masked to the treatment throughout the study. tucs and placebo eye drops were prepared and labeled using codes journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 161 www.clinicaltrial.gov umbilical cord serum for ced; moradian et al by a non-study ward staff based on the randomization list provided. only the study biostatistician who had no contact with the study participants was unmasked to the treatment groups. sample size in the pilot study, the standard deviations of time to remission in the umbilical cord serum and placebo groups were 0.8 and 2.0, respectively. to achieve an 85% power in detecting one-day differences between the new intervention and conventional treatment groups with a type-i error of 5%, we needed 40 patients in each group. statistical analysis data are expressed as mean ± standard deviation, median, range, percent, and 95% confidence interval (ci). to evaluate differences between groups, we used the chi-square test, fisher’s exact test and t-test, whenever appropriate. relationships between age and duration of operation and time to remission were evaluated using spearman’s correlation coefficient. analyses were performed using spss (version 17.0, spss inc., chicago, il, usa). p < 0.05 was considered statistically significant. results in total, 80 eyes of 80 patients (42 women [52.5%] and 38 men [47.5%]), with a mean age of 58.5 ± 10.3 (median: 58; range: 34 to 80) years, were enrolled in this study. their mean basic ced size was 15.5 ± 6.5 (median: 14; range: 2 to 33) mm2 the day after the surgery [table 1]. as demonstrated in table 2 and figure 1, the rate of improvement of ceds was 1.3 days lesser in the case group than in the control group (95% ci: 0.6– 2.1, p < 0.001). there was no statistically significant difference between men and women in the rate of improvement (3.13 ± 1.74 in men vs 3.05 ± 1.73 in women, p = 0.833) in the case and control groups (p = 0.451 and p = 0.885, respectively). additionally, we found no significant correlation of the age or duration of operation with the overall rate of improvement in either group [table 3]. two cases of persistent ced occurred in the control group, but no eyes in the tucs group showed this complication. discussion diabetic vitrectomy typically necessitates pars plana vitrectomy to treat complications of pdr. corneal epithelial edema and late corneal decompensation can occur during vitreoretinal surgery.[6] intraoperative corneal epithelial edema causes media haziness; therefore, the surgeon may mechanically scrape the epithelium with a blade to improve the media clarity and visualization of the fundus. intraoperative removal of the corneal epithelium or accidental surgical trauma to the corneal epithelium results in postoperative ced, and healing of such lesions can be delayed, particularly in patients with diabetes.[2, 7] postoperative ced is a significant cause of morbidity in these patients. virata et al reported that 45% of such cases of ceds persisted for longer than one week and 28% lasted for four or more weeks. one reported case resulted in a bacterial corneal ulcer.[8] in one study, the overall rate of corneal epithelial debridement during vitrectomy averaged among 55 vitreoretinal surgeons was 17.4% ± 19.0% and ranged from 0% to 90%,[9] although other studies reported this rate to be approximately 14–34%.[10, 11] both structural (polymegathism and pleomorphism) and functional abnormalities (increased permeability and slower recovery from induced edema) are observed in the diabetic corneal epithelium and endothelium.[12] egf,[13–16] fgf, and interlukin-6[17] stimulate corneal epithelial migration and proliferation. fibronectin,[18] hyaluronan,[19] laminin,[20] and collagen type iv are the extracellular matrix components that can facilitate epithelial cell migration. neuronotrophic substances, such as substance p, igf-i, and ngf promote corneal epithelial migration; topical application promotes corneal wound healing.[21–25] egf, vitamin a, substance p, α2-macroglobulin, fibronectin, and acidic and basic fgfs are tear components that play major roles in proliferation, differentiation, and maturation of the corneal epithelial cells.[26, 27] autologous serum contains factors, such as glucose, proteins, calcium ion, vitamin a, egf, fibronectin, and glycoproteins, that facilitate corneal wound healing.[28–30] therefore, autologous serum eye drops are used to treat ocular surface disorders.[31] 162 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 umbilical cord serum for ced; moradian et al figure 1. rate of corneal epithelial defect improvement in the topical umbilical cord serum and control groups. ced, corneal epithelial defect; cum, cumulative table 1. baseline characteristics of participants variable statistics groups p-value umbilical cord serum (n = 40) placebo (n = 40) age (years) mean ± sd (range) 57.6 ± 9.6 (34 to 78) 59.5 ± 11.0 (37 to 80) 0.400† sex f/m (f%) 22/55 (55%) 20/20 (50%) 0.654* basic ced size mean ± sd (range) 15.3 ± 6.2 (2.3 to 30) 15.7 ± 6.8 (2 to 33) 0.801† operation duration (hours) mean ± sd (range) 1.65 ± 0.62 (1 to 4) 1.45 ± 0.50 (1 to 2) 0.118∗∗ †based on t-test; ∗based on chi-square test; ∗∗based on fisher’s exact test. ced, corneal epithelial defect; f, female; m, male; sd, standard deviation table 2. mean ± standard deviation (range) of the rate of improvement (days) operation groups umbilical cord serum (n = 40) placebo (n = 40) total diff (95% ci) p-value (between) vitrectomy 2.4 ± 0.7 (2 to 5) 3.8 ± 2.1 (2 to 12) –1.3 (–2.1 to –0.6) < 0.001† †based on t-test journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 163 umbilical cord serum for ced; moradian et al table 3. correlation of age and duration of operation in each group with the rate of improvement of corneal epithelial defects groups umbilical cord serum (n = 40) controls (n = 40) total correlation p-value correlation p-value correlation p-value age 0.205 0.211 –0.004 0.979 0.073 0.522 operation duration –0.202 0.219 –0.202 0.212 –0.218 0.054 based on spearman’s correlation coefficient autologous serum eye drops are effective in cases of keratoconjunctivitis sicca,[32] severe dry eye,[33, 34] superior limbal keratoconjunctivitis,[35] persistent ced, and neurotrophic keratopathies.[36] higher concentrations of egf, vitamin a, acidic and basic fgfs, fibronectin, ngf, substance p, and α2-macroglobulin, which are present in ucs, make it more effective than autologous serum in treating ocular surface disorders.[31] recently, vajpayee et al reported that tucs eye drops resulted in faster healing of persistent ced refractory to medical treatments compared to autologous serum drops.[37] yoon et al found that the application of tucs effectively treated dry eye and persistent ced due to neurotrophic keratitis.[3–5] autologous serum preparation requires collection of blood at regular intervals from patients and may induce discomfort. it is difficult to obtain blood samples from patients with a poor general condition or blood dyscrasia, but abundant serum can be drawn from the umbilical vein at once. many patients can benefit from this sampling approach, which minimizes discomfort.[5] in this study, we examined the effects of tucs therapy on improvement of ced after diabetic vitrectomy. our study showed that tucs hastened the healing of ceds after vitrectomy relative to the conventional therapy. persistent ced occurred in two cases in the control group but in no cases in the tucs group. the limitations of our study were the absence of dry eye tests before surgery and unavailability of precise measurement of ceds using image j or other digital measurement modalities. in conclusion, tucs may significantly accelerate the rate of improvement of ceds after diabetic vitrectomy and reduce the risk of persistent ced. further studies with larger sample size are needed. financial support and sponsorship none. conflicts of interest there are no conflicts of interest. references 1. bright bill fs, myers fl, bresnick g. post vitrectomy keratopathy. am j ophthalmol 1978;85:651–655. 2. foulds gn, thoft ra, perry hd, tolentino fi. factors related to corneal complications after closed vitrectomy in diabetics. arch ophthalmol 1979;97:1076–1077. 3. yoon kc, im sk, park yg, jung yd, yang sy, choi j. application of umbilical cord serum eye drops for the treatment of dry eye syndrome. cornea 2006;25:268– 272. 4. yoon kc, heo h, im sk, you ic, kim yh, park yg . comparison of autologous serum and umbilical cord serum eye drops for dry eye syndrome. am j ophthalmol 2007;144:86–29. 5. yoon kc, heo h, jeong iy, park yg. therapeutic effect of umbilical cord serum eye drops for persistent epithelial defect. korean j ophthalmol 2005;19:174–178. 6. bright bill fs, myers fl, bresnick gh. post vitrectomy keratopathy. am j ophthalmol 1978;85:651–655. 7. fribery tr, doran dl, lazenby fl. the effect of vitreous and retinal surgery on corneal endothelial cell density. ophthalmology 1984;91:1166–1169. 8. virata sr, kylstra ja, singh ht. corneal epithelial defects following vitrectomy surgery using hand–held, sew-on, and noncontact viewing lenses. retina 1999;19:287–290. 9. friberg tr, ohji m, scherer jj, tano y. frequency of epithelial debridement during diabetic vitrectomy. am j ophthalmol 2003;135:552–554. 10. oyakawa rt, schachat ap, michels rg, rice ta. complications of vitreous surgery for diabetic retinopathy: i. intraoperative complications. ophthalmology 1983;90:517–521. 11. chung h, tolentino fi, cagita vn, a losta j refojo mf. reevaluation of corneal complications after closed vitrectomy. arch ophthalmol 1988;106:916–919. 12. cisarik-fredenburg p. discoveries in research on diabetic keratopathy. optomery 2001;72:691–704. 164 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 umbilical cord serum for ced; moradian et al 13. brazzell rk, stern me, aquavella jv, beuerman rw, baird l. human recombinant epidermal growth factor in experimental corneal wound healing. invest ophthalmol vis sci 1991;32:339–340. 14. schultz gs, chegimini n, grant m, khaw p, mackay a. effect of growth factors on corneal wound healing. arch ophthalmol 1992:70:60–66. 15. maldorado ba, furcht lt. epidermal growth factor stimulates integrin-mediated cell migration of cultured human corneal epithelial cells on fibronectin and arginineglycerine-aspartic acid peptide. invest ophthalmol vis sci 1995;36:2120–2126. 16. david t, rieck p, renard g, hartmann c, courtois y, pouliquen y. corneal wound healing modulation using basic fibroblast growth factor after excimer laser photorefractive keratectomy. cornea 1995;14:227–234. 17. nishida t, nakamura m, mishiana h, otori t, hikida m. intreleukin 6 facilitates corneal epithelial wound closure in vivo. arch ophthalmol 1992;110:1292–1294. 18. ohji m, mandarinol, sundar raj n, thoft ra. corneal epithelial cell attachment with endogenous laminin and fibronectin. invest ophthalmol vis sci 1993;34:2487– 2492. 19. nakamura m, nishida i, hikida m, otori t. combined effects of hyalophane and fibronectin on corneal epithelial wound closure of rabbit in vivo. curr eye res 1994;13:385– 388. 20. maldonado ba, furcht lt. involvement of integrins with adhesion promoting, heparinbinding peptides of type iv collagen in cultured human corneal epithelial cells. invest ophthalmol vis sci 195;36:364–372. 21. nishida t, nakamura m, ofuji k, reid tw, manoes mj, murphy gj. synergistic effects of substance p with insulinlike growth factor-1 on epithelial migration of the cornea. j cell physiol 1990;169:159–166. 22. nokamura m, ofujik, chikama t, nishida. combined effects of substance p and insulinlike growth factor-1 on corneal epithelial would closure of rabbit in vivo. curr eye res 1997;16:275–278. 23. tan mh, bryars j .use of nerve growth to treat congenital neurotrophic corneal ulceration .cornea 2006;25:b352– b355. 24. bonni s, lambiase a, rama p, caprioglio g, aloe l. topical treatment with nerve growth factor for neurotrophic keratitis. ophthalmology 2000;107:1347–1351 . 25. lambiase a, rama p, bonni s, caprioglio g, aloe l. topical treatment with nerve growth factor for corneal neurotrophic ulcers. n eng j med 1998;338:1174–1180. 26. ohashi y, motokura m, kinoshita y, mano t, watanabe h, kinoshita s, et al. presence of epidermal growth factor in human tears. invest ophthalmol vis sci 1989;30:1879– 1887. 27. van setten g, teno t, tervo k, tarkkanen a. epidermal growth factor (egf) in ocular fluid: presence, origin and therapeutic consideration. acta ophthalmol 1992;202:54–59. 28. dua hs, gomes ja, singh a. corneal epithelial wound healing. br j ophthalmol 1994:78;401–408. 29. geerling g, maclennan s, hartwing d. autologous serum eye drops for ocular surface disorders. br j ophthalmol 2004;88:1467–1474. 30. tsubota k, goto e, shimmura s, shimazaki j. treatment of persistent corneal epithelial defect by autologous serum applications. ophthalmology 1999;106:1984–1987. 31. nobel ba, loh rsk, maclennan s, pesudovs k, reynolds a, bridges lr, et al. comparison of autologous serum eye drops with conventional therapy in a randomized controlled crossover trial for ocular surface disease. br j ophthalmol 2004:88:647–652. 32. fox ri, chan r, michelson j, belmont jb, michelson pe. beneficial effect of artificial tears made with autologous serum in patients with keratoconjunctivitis sica. arthritis rheum 1984;27:456–461. 33. poon ac, geerling g, dart jk, fraenkel ge, daniels jt. autologus serum eye drops for dry eyes and epithelial defects: clinical and in vitro toxi city studies. br j ophthalmol 2007;85:1188–1197. 34. tananuvat n, daniell m, sullivan lj, yi q, mckelvie p, mccarty dj. controlled study of the use of use of autologous serum in dry eye patients. cornea 2001;20:802– 806. 35. goto e, shimmura s, shimazski j, tsubota k. treatment of superior limbic kerato conjunctivitis by application of autologous serum. cornea 2001;20:807–810. 36. matsumoto y, dogru m, goto e, ohashi y, kojima t, ishida r, et al. autologous serum application in the treatment of neurotrophic keratopathy. ophthalmology 2004;111:1115– 1120. 37. vajpayee rb, mukerji n, tandon r, sharma n, pandey rm, biswas nr, et al. evaluation of umbilical cord serum therapy for persistent corneal epithelial defects. br j ophthalmol 2003;87:1312–1316. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 165 case report orbital cellulitis following uncomplicated glaucoma drainage device surgery: case report and review of literature cindy x. zheng, md; joshua h. uhr, md; jordan d. deaner, md; john anhalt, md; michael m. lin, md stephen j. moster, md; reza razeghinejad, md glaucoma research center, wills eye hospital, philadelphia, pa, usa orcid: cindy x. zheng: https://orcid.org/0000-0001-7313-9212 abstract purpose: orbital cellulitis (oc) is a rare postoperative complication of glaucoma drainage device (gdd) implantation. to date, there have only been 10 reported cases of oc following gdd implantation. case report: here, we report a case of oc in a 57-year-old man who developed pain, proptosis, and limited extraocular motility two days after uneventful ahmed fp7 implantation in the right eye. contrast-enhanced computed tomography of the orbits demonstrated fat stranding and a small fluid collection, consistent with oc. he had minimal improvement with intravenous antibiotics and ultimately underwent gdd explantation. a systematic review of the literature showed that the development of oc following gdd implantation can occur in the early or late postoperative period. immediate hospitalization with intravenous administration of broad-spectrum antibiotics is recommended. explantation of the infected gdd is often required for source control. conclusion: oc is a rare postoperative complication of gdd implantation. prompt evaluation and treatment are required, often combined with gdd explantation. keywords: ahmed tube shunt; orbital cellulitis; glaucoma drainage device j ophthalmic vis res 2020; 15 (3): 412–418 introduction glaucoma drainage devices (gdds) are surgical devices commonly implanted in eyes with correspondence to: cindy x. zheng, md. wills eye hospital glaucoma research center, 840 walnut st., suite 1140, philadelphia, pa 19107, usa. e-mail: cindyzheng9@gmail.com received: 29-05-2019 accepted: 31-08-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7460 refractory glaucoma. the development of orbital cellulitis (oc) following gdd implantation is rare, with only 10 reported cases in the literature.[1–9] here, we report a case of oc following the placement of an ahmed fp7 (new world medical, rancho cucamonga, ca) in a 57-year-old man who this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: zheng cx, uhr jh, deaner jd, anhalt j, lin mm, moster sj, razeghinejad r. orbital cellulitis following uncomplicated glaucoma drainage device surgery: case report and review of literature. j ophthalmic vis res 2020;15:412–418. 412 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7460&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr orbital cellulitis following uncomplicated gdd surgery; zheng et al figure 1. external photograph of the affected eye on the day of presentation, demonstrating periorbital edema, erythema, conjunctival injection, and chemosis. figure 2. contrast-enhanced computed tomography of the orbits showing findings consistent with orbital cellulitis, including proptosis of the right globe, thickening of the sclera and optic nerve insertion, small superior fluid collection, and mild anterior retrobulbar fat stranding (a). an ahmed tube shunt and baerveldt tube shunt are visualized in the right and left globes, respectively (b). showed minimal improvement with intravenous (iv) antibiotics and ultimately underwent gdd explantation. case report a 57-year-old incarcerated man with advanced primary open-angle glaucoma was referred to us because of poorly controlled intraocular pressure (iop). he had a surgical history of bilateral trabeculectomy and implantation of a baerveldt tube shunt implanted in the left eye approximately nine years ago. he had a medical history of gastroesophageal reflux disease and was not on any routine medications other than his glaucoma medications. on presentation, his visual acuity (va) was 20/200 in the right eye and light perception in the left eye. his iop was 13 mmhg in the right eye and 12 mmhg in the left eye on maximum topical therapy and oral acetazolamide. due to difficulty tolerating acetazolamide, he agreed to proceed with ahmed fp7 implantation in the right eye. gdd was implanted uneventfully with tutoplast processed sclera patch graft (katena products inc., denville, nj) in the superonasal quadrant because of conjunctival scarring from prior trabeculectomy. no intraoperative injections or mitomycin c were given. on postoperative day 1, he had a va of 20/200 and an iop of 10 mmhg, and the tube shunt was covered and well-positioned. the patient presented emergently on postoperative day 4 because of two days of right eye pain, swelling, and blurry vision. he reported that he did not receive his postoperative topical ofloxacin or prednisolone acetate drops from his facility. va was hand motion and iop was 20 mmhg. externally, the right orbit was tense with lid erythema and edema. his right globe was journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 413 orbital cellulitis following uncomplicated gdd surgery; zheng et al proptotic with limited extraocular motility (figure 1). there was a small opening in the conjunctiva over the patch graft, located 4 mm posterior to the limbus. a sample of purulent drainage from this opening was swabbed and sent for microbiologic testing. the anterior chamber was deep with rare cells. there was no vitritis. contrast-enhanced computed tomography (ct) demonstrated softtissue thickening, fatty infiltration, and a small fluid collection superiorly (figure 2). he was admitted for administration of iv vancomycin and piperacillin-tazobactam and topical fortified vancomycin and tobramycin. on hospitalization day 2, he received 8 mg of iv dexamethasone. improvement was minimal with the administration of iv antibiotics for 24 hours; therefore, surgical explantation of the gdd was performed. intraoperatively, there was an area of conjunctival melt over the tube with pockets of purulent material surrounding the valve. to prevent intraocular penetration of the infected material into the anterior chamber, a pursestring suture was passed around the tube entry site in the sclera and was tied-off while a surgical assistant withdrew the tube. the plate and tube were noted to be completely free, presumably because of the surrounding scleritis. the implant was removed, and the area was copiously irrigated with vancomycin and ceftazidime solution. after conjunctival closure with 8-0 vicryl sutures, subconjunctival injections of vancomycin and ceftazidime were administered. considering the patient’s monocular status with advanced glaucoma in the affected eye and a history of poorly controlled iop, concomitant micropulse transscleral cyclophotocoagulation (iridex corp., mountain view, ca) was performed for 140 sec to the inferior globe at a power of 2000mw and duty cycle of 31.3%. cultures showed light growth of methicillinsusceptible staphylococcus aureus and cutibacterium acnes (formerly propionibacterium acnes). he was discharged two days after the tube shunt explantation with oral moxifloxacin 400 mg and topical fortified vancomycin and gatifloxacin. six months after the surgery, va was hand motion and iop was 12 mmhg with three topical glaucoma medications. he had complete resolution of orbital signs. discussion a systematic literature review revealed a total of 11 cases of oc following gdd surgery, including the present case (table 1). most patients presented within two days of symptom onset.[1–8] on presentation, all patients had eyelid erythema and edema, and most patients had chemosis, proptosis or globe displacement, and limited extraocular motility. the most common gdd associated with post-implantation oc was the ahmed valve (n = 7),[2–7] although molteno,[1] krupin–denver,[2] and baerveldt[8, 9] implants have also been associated with post-implantation oc. in seven cases, symptoms of oc started in the immediate postoperative period (≤ 3 months after the surgery).[1, 2, 5–8] in the other four cases, oc developed after the postoperative month 3.[2–4, 9] in three of the four cases of delayed-onset oc,[2, 4, 9] the tube was exposed, presumably serving as a conduit for bacteria to travel from the ocular surface into the orbit. in one case of delayed-onset oc, the tube was not specifically exposed; however, the patient had concurrent endophthalmitis.[3] the authors theorized that organisms may have gained entry into the eye from the ocular surface and oc from drainage via the tube.[3] table 2 summarizes the management of oc. ct is the imaging modality of choice for oc and was the most common modality used.[10] all patients were hospitalized and administered iv antibiotics. although the choice of antibiotic varied, the consensus was to start with broad-spectrum coverage. in the present case, vancomycin was used owing to previous studies showing a high prevalence of methicillin-resistant staphylococcus aureus isolated from ocular infections.[11] the antibiotic coverage changed based on infectious disease consultation or culture sensitivities. topical antibiotics were commonly used.[1–5, 7, 8] although not routinely administered, iv steroids were used in two cases after the administration of iv antibiotics for 24 hours, including our case.[9] we administered steroids under the guidance of oculoplastic consultation to reduce orbital inflammation and to improve the ease of access during gdd explantation. previous studies have shown that steroids can help reduce the cytokine load and improve outcomes in bacterial oc.[12, 13] 414 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 orbital cellulitis following uncomplicated gdd surgery; zheng et al ta b le 1. d em og ra ph ic s, ba se lin e cl in ic al ch ar ac te ris tic s, an d in iti al pr es en ta tio n of or bi ta lc el lu lit is af te rg la uc om a dr ai na ge de vi ce im pl an ta tio n c a se n o . a u th o r a g e g e n d e r g la u co m a d ia g n o si s g d d t yp e lo ca ti o n b a se lin e v a p re se n ti n g v a in te rv a l∗ d u ra ti o n † c h e m o si s p ro p to si s e o m lim it a ti o n 1 ka rr [1] 1 m c on ge ni ta l m ol te no st n r n r 1m 1d ye s ye s ye s 2 c ha ud hr y[ 2] 11 f c on ge ni ta l kr up in – d en ve r st c f lp 9 d 1d ye s ye s ye s 3 c ha ud hr y 1 f c on ge ni ta l a hm ed m od el n r n r n r ff 8 m 2 d n o n o ye s 4 ka ss am [3 ] 3 m c on ge ni ta l a hm ed fp 7 n r n r n r 8 m 2 d ye s ye s n r 5 fa rid [4 ] 1 f c on ge ni ta l a hm ed m od el n r n r n r n r 10 m < 1d ye s n o ye s 6 es po rc at te [5 ] 1 m c on ge ni ta l a hm ed fp 7 n r n r n r 1m 2 d ye s ye s n r 7 m ar ce t[ 6 ] 44 m u ve iti c a hm ed m od el n r su pe rio r c f c f 1d < 1d ye s ye s ye s 8 g ol df ar b[ 7] 81 f po a g a hm ed m od el n r st 20 /2 0 0 c f 1d < 1d ye s ye s ye s 9 zh en g 57 m po a g a hm ed fp 7 sn 20 /2 0 0 h m 4 d 2 d ye s ye s ye s 10 b ec k[ 8] 53 m po a g b ae rv el dt 35 0 m m 2 n r 20 /3 2 20 /6 0 3 m 1d ye s ye s ye s 11 la vi na [9 ] 78 f c a c g b ae rv el dt 35 0 m m 2 n r 20 /4 0 0 n lp 15 m 3 d ye s n o ye s ∗ i nt er va lo ft im e be tw ee n g d d im pl an ta tio n an d pr es en ta tio n of o c † d ur at io n of sy m pt om s pr io rt o pr es en ta tio n g d d ,g la uc om a dr ai na ge de vi ce ;v a ,v is ua la cu ity ;e o m ,e xt ra oc ul ar m ov em en t; m ,m al e; f, fe m al e; st ,s up er ot em po ra l; sn ,s up er on as al ;n r ,n ot re po rt ed ;c f, co un t fin ge rs ;h m ,h an d m ot io n; lp ,l ig ht pe rc ep tio n; n lp ,n o lig ht pe rc ep tio n; ff ,fi xe s an d fo llo w s; d, da ys ;m ,m on th s journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 415 orbital cellulitis following uncomplicated gdd surgery; zheng et al ta b le 2 .m ed ic al an d su rg ic al m an ag em en to fo rb ita lc el lu lit is af te rg la uc om a dr ai na ge de vi ce im pl an ta tio n c a se n o . iv a n ti b io ti cs to p ic a l a n ti b io ti cs o ra l a n ti b io ti cs , d u ra ti o n tu b e e ro si o n tu b e e xp la n t t im e to e xp la n t in tr a o p e ra ti ve a n ti b io ti cs b lo o d cu lt u re e n d o p h th a lm it is in tr a vi tr e a l a n ti b io ti cs c u lt u re si te c u lt u re o rg a n is m 1 c ef ur ox im e to br am yc in y ,n r y y 1d irr ig at io n w ith ge nt am ic in n eg n n c ,d ,g d d g ro up a st re pt oc oc cu s, st ap hy lo co cc us ep id er m id is 2 g en ta m ic in , ce fa zo lin , sw itc he d to flu cl ox ac ill in , ce fo ta xi m e g en ta m ic in c ec lo rf or 10 d n n n a n a n a n n n a n a 3 c ef tr ia xo ne , ge nt am ic in v an co m yc in , ge nt am ic in c ec lo rf or 10 d y y 5 d ic an d sc va nc om yc in an d am ik ac in n a n n a c ,d n o gr ow th 4 v an co m yc in , ce fta zi di m e g at ifl ox ac in le vo flo xa ci n fo r2 1d n y 1d sc ge nt am ic in n eg y v an co m yc in , ce fta zi di m e c ,d ,v ,s st re pt oc oc cu s pn eu m on ia e 5 v an co m yc in , ce fta zi di m e, m et ro ni da zo le m ox ifl ox ac in n r y y 1d irr ig at io n w ith ge nt am ic in , po vi do ne ;s c va nc om yc in , ce fta zi di m e n eg y v an co m yc in , ce fta zi di m e g d d ,v n o gr ow th 6 v an co m yc in , ce fe pi m e g at ifl ox ac in a m ox ic ill in cl av ul an ic ac id fo r1 0 d n y sa m e da y su bte no n’ s va nc om yc in , ce fta zi di m e n eg y v an co m yc in , ce fta zi di m e g d d ,v st ap hy lo co cc us ep id er m id is 7 a m pi ci lli nsu lb ac ta m n r c ip ro flo xa ci n (d ur at io n n s) n n n a n a n a n n n a n a 8 v an co m yc in , ce ftr ia xo ne , sw itc he d to pi pe ra ci lli nta zo ba ct am m ox ifl ox ac in c ip ro flo xa ci n (d ur at io n n s) n y 2 d sc va nc om yc in , ce fta zi di m e n eg n n g d d ps eu do m on as ae ru gi no sa 416 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 orbital cellulitis following uncomplicated gdd surgery; zheng et al ta b le 2 .c on tin ue d. c a se n o . iv a n ti b io ti cs to p ic a l a n ti b io ti cs o ra l a n ti b io ti cs , d u ra ti o n tu b e e ro si o n tu b e e xp la n t t im e to e xp la n t in tr a o p e ra ti ve a n ti b io ti cs b lo o d cu lt u re e n d o p h th a lm it is in tr a vi tr e a l a n ti b io ti cs c u lt u re si te c u lt u re o rg a n is m 9 v an co m yc in , pi pe ra ci lli nta zo ba ct am v an co m yc in , to br am yc in m ox ifl ox ac in fo r7 d y y 2 d irr ig at io n w ith va nc om yc in , ce fta zi di m e; sc va nc om yc in , ce fta zi di m e n a n n c ,d st ap hy lo co cc us au re us , cu tib ac te riu m ac ne s 10 a m ox ic ill in cl av ul an ic ac id le vo flo xa ci n fl uc lo xa ci lli n an d am ox ic ill in cl av ul an ic ac id in 10 d n n n a n a n a n n c n o gr ow th 11 a m pi ci lli nsu lb ac ta m n r n r y y n a n a n a n n n a n o gr ow th n s, no ts pe ci fie d; n r ,n ot re po rt ed ;y ,y es ;n ,n o; d, da y; n eg ,n eg at iv e; g d d ,g la uc om a dr ai na ge de vi ce ;i c ,i nt ra ca m er al ;c ,c on ju nc tiv a; d ,d is ch ar ge ;a c ,a nt er io r ch am be r; v, vi tr eo us ;s ,s ut ur es ;n a no ta pp lic ab le ta b le 3 .o ut co m es an d ad di tio na ls ur gi ca li nt er ve nt io n af te rr es ol ut io n of or bi ta lc el lu lit is af te rg la uc om a dr ai na ge de vi ce im pl an ta tio n c a se n o . f o llo w -u p v is u a la cu it y in tr a o cu la r p re ss u re c o m p lic a ti o n a d d it io n a ls u rg ic a li n te rv e n ti o n 1 n r n r n r n on e n a 2 1y ea r h an d m ot io ns 7 n on e n a 3 7 ye ar s 20 /6 0 16 n on e n a 4 1m on th lo ca te ca nd y ba rs at 8 in ch es n r re tin al de ta ch m en t 2 re tin a su rg er ie s 5 1m on th fi xe s an d fo llo w s 19 el ev at ed in tr ao cu la rp re ss ur e c yc lo ph ot oc oa gu la tio n 6 n r ph th is is bu lb i n r ph th is is bu lb i n r 7 13 m on th s 20 /2 0 0 n r re -e xp os ur e of g d d re vi si on of g d d 8 4 m on th s 20 /10 0 n r n on e n a 9 6 m on th s h an d m ot io ns 12 n on e c yc lo ph ot oc oa gu la tio n at sa m e tim e as g d d ex pl an ta tio n 10 2 m on th s 20 /3 2 28 el ev at ed in tr ao cu la rp re ss ur e c yc lo ph ot oc oa gu la tio n 11 n r c ou nt fin ge rs n r n on e n a n r ,n ot re po rt ed ;n a ,n ot ap pl ic ab le ;g d d ,g la uc om a dr ai na ge de vi ce journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 417 orbital cellulitis following uncomplicated gdd surgery; zheng et al blood cultures were negative in all tested cases.[1, 3–5, 7] presumably, the infection remained localized to the orbit. since all cases presented within three days of symptom onset, the infection was rapidly managed with antibiotics, thus, bacteremia was less likely to occur. the gdd was surgically explanted in 8 of the 11 cases,[1–5, 7, 9] including all five cases of tube exposure[1, 2, 4, 9] and all three cases of concurrent endophthalmitis.[3–5] presumably, erosion allowed bacteria to seed the gdd, and the infection may be difficult to clear without explanting the infected gdd. explantation was performed in all children aged less than three years.[1–5] in this age group, it is difficult to perform an examination without the use of general anesthesia; therefore, it may be safer to perform explantation at the initial examination than to subject the patient to repeated episodes of anesthesia. in all cases of explantation, gdds were most frequently explanted within one to two days of presentation, suggesting that failure to respond to antibiotics can be quickly identified. during explantation, the area surrounding the tube was irrigated with antibiotics,[1, 4] or subconjunctival or sub-tenon’s injection of antibiotics were performed.[2–5, 7] in three cases, there was a sufficient improvement with iv antibiotics alone; consequently, no surgical interventions were undertaken.[2, 6, 8] when iv antibiotics were transitioned to oral antibiotics, fluoroquinolones were most commonly used,[4, 7–9] likely owing to their vitreous penetration and relatively broad coverage.[14] the duration was most commonly 10 days, as seen in four cases.[2, 5, 8] the duration of the therapy was likely associated with the severity of presentation and response to therapy. table 3 details the outcomes and additional procedures that were performed. in conclusion, oc is a rare postoperative complication of gdd implantation. immediate hospitalization with administration of broadspectrum iv antibiotics is recommended. explantation of the gdd is often required for source control. references 1. karr dj, weinberger e, mills rp. an unusual case of cellulitis associated with a molteno implant in a 1-year-old child. j pediatr ophthalmol strabismus 1990;27:107–10. 2. chaudhry ia, shamsi fa, morales j. orbital cellulitis following implantation of aqueous drainage devices. eur j ophthalmol 2007;17:136–140. 3. kassam f, lee be, damji kf. concurrent endophthalmitis and orbital cellulitis in a child with congenital glaucoma and a glaucoma drainage device. digit j ophthalmol 2011;17:58–61. 4. farid mf, awad ma, bella ea. consensual orbital cellulitis and endophthalmitis complicating pediatric glaucoma drainage implant. austin ophthalmol 2016;1:1004. 5. esporcatte bl, teixeira lf, rolim-de-moura c. panophthalmitis with orbital cellulitis following glaucoma drainage implant surgery in a pediatric patient. arq bras oftalmol 2016;79:123–125. 6. marcet mm, woog jj, bellows ar, mandeville jt, maltzman js, khan j. orbital complications after aqueous drainage device procedures. ophthalmic plast reconstr surg 2005;21:67–69. 7. goldfarb j, jivraj i, yan d, deangelis d. a case of pseudomonas orbital cellulitis following glaucoma device implantation. j glaucoma 2019;28:e14–16. 8. beck de, el-assal ks, doherty md, wride nk. orbital cellulitis following uncomplicated aqueous shunt surgery. j glaucoma 2017;26:e101–102. 9. laviña am, creasy jl, tsai jc. orbital cellulitis as a late complication of glaucoma shunt implantation. arch ophthalmol 2002;120:849–851. 10. tsirouki t, dastiridou ai, ibánez flores n, cerpa jc, moschos mm, brazitikos p, et al. orbital cellulitis. surv ophthalmol 2018;63:534–553. 11. asbell pa, sanfilippo cm, pillar cm, decory hh, sahm df, morris tw. antibiotic resistance among ocular pathogens in the united states: five-year results from the antibiotic resistance monitoring in ocular microorganisms (armor) surveillance study. jama ophthalmol 2015;133:1445– 1454. 12. fu sy, su gw, mckinley sh, yen mt. cytokine expression in pediatric subperiosteal orbital abscesses. can j ophthalmol 2007;42:865–869. 13. pushker n, tejwani lk, bajaj ms, khurana s, velpandian t, chandra m. role of oral corticosteroids in orbital cellulitis. am j ophthalmol 2013;156:178–183. 14. george jm, fiscella r, blair m, rodvold k, ulanski l, stokes j, et al. aqueous and vitreous penetration of linezolid and levofloxacin after oral administration. j ocul pharmacol ther 2010;26:579–586. 418 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 original article fourier analysis of keratometric data in epithelium removal versus epithelial disruption corneal cross-linking shahram bamdad1, md; seyed mohammad salar zaheryani1, md; sahar mohaghegh2, ms mohammad shirvani1, md 1poostchi ophthalmology research center, shiraz university of medical sciences, shiraz, iran 2school of rehabilitation, shahid beheshti university of medical science, tehran, iran orcid: seyed mohammad salar zaheryani: https://orcid.org/0000-0003-2812-8869 shahram bamdad: https://orcid.org/0000-0002-5609-016x abstract purpose: to compare epithelium-removal and epithelium-disruption corneal crosslinking (cxl) methods in fourier analysis of keratometric data and clinical outcomes. methods: in this double masked randomized clinical trial, each eye of 34 patients with bilateral keratoconus was randomly allocated to either the epithelium-removal or epithelium-disruption cxl treatment groups. ocular examination, refraction, uncorrected and best spectacle-corrected visual acuity (ucva and bscva, respectively) measurements, and pentacam imaging (keratometry, pachymetry, and fourier analysis) were performed at baseline and at six-month follow-up period. results: patients’ mean age was 23.3 ± 3.6 years. the preoperative thickness of the thinnest point was 459.20 ± 37.40 µm and 455.80 ± 32.70 µm in the epithelium-removal and epithelial-disruption cxl groups , respectively (p > 0.05). the corresponding figures were 433.50 ± 33.50 µm and 451.90 ± 39.70 µm, respectively, six months after the treatment (p = 0.0001). irregularity component of the fourier analysis was 0.030 ± 0.016 µm in the epithelium-removal group and 0.028 ± 0.011 µm in the epithelium-disruption group preoperatively (p > 0.05). this measurement was 0.031 ± 0.016 µm and 0.024 ± 0.009 µm, respectively at month 6 (p = 0.04). the epithelium-disruption cxl group had better results in terms of the thickness of the thinnest point and the irregularity component as compared to the epithelium-removal group. the two study groups were comparable in spherical equivalent, mean keratometry, ucva, bscva, or other fourier analysis components (spherical r min, spherical eccentricity, central, peripheral regular astigmatism, and maximum decentration) (p > 0.05). conclusion: this study shows that epithelium-disruption cxl is superior to epitheliumremoval cxl regarding the short-term changes in pachymetry and corneal irregularity. other evaluated parameters were comparable between the two techniques. keywords: corneal cross linking; epithelium disruption; epithelium removal; fourier analysis; keratoconus; randomized controlled trial; transepithelial j ophthalmic vis res 2020; 15 (1): 16–23 correspondence to: seyed mohammad salar zaheryani, md. poostchi ophthalmology research center, shiraz university of medical sciences, zand blv., shiraz 71936, iran e-mail: smszaheryany@gmail.com received: 01-10-2018 accepted: 18-07-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i1.5934 16 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i1.5934&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr epithelium removal vs epithelial disruption cxl; bamdad et al this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: bamdad s, zaheryani sms, mohaghegh s, shirvani m. fourier analysis of keratometric data in epithelium removal versus epithelial disruption corneal cross-linking. j ophthalmic vis res 2020;15:17–23. introduction keratoconus is a non-inflammatory bilateral progressive corneal ectasia characterized by corneal stromal thinning, protrusion, and irregular astigmatism that results in light scattering. it usually affects teenagers and young adults and causes decreased visual acuity.[1] keratoconus has a mental and economic burden on patients and drains the healthcare system budget.[2, 3] its prevalence was reported to be 1 in 2,000 patients globally and 0.02% in the tehran eye study.[1, 4] wollensak et al introduced corneal collagen cross-linking (cxl)[5] to halt the progression of keratoconus.[6, 7] since then, cxl treatment has been used widely in clinics across the world. its promising effects are also supported by a meta-analysis study.[6] in the conventional cxl method, the epithelium of the central cornea (7–9 mm) is removed, and riboflavin solution is applied. then, ultra-violet a is used to enhance crosslinking between adjacent corneal collagen fibers.[5] recently, some modifications were made to reduce the manipulation of the corneal epithelium, hence decreasing the initial pain, visual discomfort, and stromal haziness.[8] one suggested procedure is trans-epithelial cxl in which hypo-osmolar riboflavin is applied to the cornea through an intact epithelium. the efficacy of this modification, however, was reported to be less than that of the conventional method in some studies.[9, 10] therefore, partial epitheliumremoval cxl was developed, which uses vertical and horizontal strips of de-epithelization using a custom-designed surgical instrument (daya epithelium disruptor). the safety, efficacy, and better tolerability of this method have been reported in recent publications.[11–14] fourier analysis is a mathematical method that can convert periodic continuous data into unique expressions. fourier analysis transforms the extracted keratometric data using a pentacam scheimpflug camera into spherical r min, spherical eccentricity, maximum decentration, central and peripheral astigmatism, and irregularity components. fourier analysis can measure the 3-dimensional shape of the cornea, producing specific numbers that provides more comprehensive evaluation of cornea as compared to mean keratometric values. the repeatability and validity of fourier analysis based on data from a pentacam device were shown in a previous study by sideroudi et al.[15] this analysis provides a sensitive index for differentiating corneal ectasia and can be used for the prompt diagnosis of keratoconus.[16] it has been shown that fourier spherical and irregularity components change over a year in progressive keratoconus, but no significant changes occur in the other two components.[17] the aim of this randomized clinical trial (rct) study was to evaluate the whole shape of the cornea using fourier analysis of keratometric data obtained from a pentacam® hr (oculus, lynwood, wa, usa) and compare the results between epithelium-removal versus epithelium-disruption cxl techniques after six months of follow-up. methods study design this was a double-masked rct study that enrolled 34 bilateral keratoconus patients who had each eye examined and operated on at khalili hospital. stratified randomization was performed for the eyes and methods; for each patient, one eye underwent epithelium-removal cxl and the other eye underwent epithelium-disruption cxl in two consecutive sessions with at least two weeks’ interval. the study protocol was in accordance with the tenets of the declaration of helsinki and was approved by the local ethics committee of research at shiraz university of medical sciences. written informed consent was obtained from all participants. the rct was registered at iranian registry of clinical trials (number # irct2016112231028n1). patient enrollment and ocular examination the inclusion criteria were bilateral progressive keratoconus diagnosed according to the journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 17 epithelium removal vs epithelial disruption cxl; bamdad et al rabinowitz criteria for patients aged 18–25 years. the progression of the disease was defined by an increase of at least 1 diopter (d) in mean keratometry (k mean) or a reduction of at least one line in the best-corrected visual acuity, within the last 12 months. the exclusion criteria were corneal thickness < 400 µm and k max > 61 d. in addition, pregnant and lactating women, and patients with history of previous ocular surgery, ocular herpetic infection, concurrent keratitis, severe corneal opacity, or ocular surface diseases such as dry eye, or autoimmune disease were excluded. the demographic and clinical characteristics of all patients were collected using data forms. data including refraction, uncorrected and best spectacle-corrected visual acuity (ucva & bscva, respectively) expressed in the logarithm of minimum angle of resolution scale (logmar), and data obtained using a pentacam® hr device were compiled for all patients at baseline and six months after the cxl procedures. fourier analysis (corneal shape evaluation) fourier analysis transforms corneal keratometric data obtained from the pentacam device into spherical components (spherical r min, spherical eccentricity), regular astigmatism (central astigmatism, peripheral astigmatism), maximum decentration, and irregularity. the spherical and regular astigmatism components describe standard clinical parameters that can be compensated by spectacles. decentration is a tilt of the corneal apex with respect to the video-keratoscope axis, and irregularity refers to a range of optical imperfections that degrade retinal image quality. surgical technique in all cases, glaupin 2%® (pilocarpine 2%, sina darou, tehran, iran) eye drops were applied an hour before the surgery to assure miosis during the procedure and anestocaine 0.5%® (tetracaine 0.5%, sina darou, tehran, iran) eye drops were applied just before the surgery to provide topical anesthesia. in the epithelium-removal group, 8.5 mm of corneal epithelium was removed completely using a fukasaku hockey knife (millennium surgical corp, pennsylvania, usa). a standard preservative solution plus dextran-free riboflavin 0.1% (sina darou, tehran, iran) was applied at 3min intervals for 30 min. this step was followed by corneal irradiation with uv-a at a wavelength of 365 nm and power of 9 mw/cm2 at a short distance from the eye (about 5 cm) for 10 min using a ccl-365-vario (mlase ag, germering, germany). riboflavin was instilled every 3 min during corneal irradiation. finally, the eye was irrigated with 30 ml of balanced salt solution (bss) and a bandage contact lens (bcl) (ciba vision, duluth, ga, usa) was fitted over the cornea. in the other eye, the corneal epithelium was disrupted using a daya epithelium disruptor (duckworth & kent ltd, hertfordshire, uk); the rest of the procedure was performed the same way as that described earlier. ciprofloxacin 0.3% eye drop was instilled every 6 hours for a week and betamethasone 0.1% eye drop was instilled every 8 hours for a month in the operated eye, postoperatively. bcl was removed after corneal epithelial defects completely healed. after removing the bcl, patients were visited at weeks 1 and 3 to assess whether there were any complications. final follow-up examination was performed six months after the second procedure and included slit-lamp biomicroscopy, refraction, ucva, bscva, and pentacam® imaging. statistical analysis categorical variables are expressed as frequency (percentage) and continuous variables are expressed as the mean value ± standard deviation (sd). normality of the data was evaluated using the kolmogorov–smirnov test. a paired-samples t-test or wilcoxon test was used to compare preoperative and postoperative data . the study groups were compared using student’s t-test or the mann–whitney u-test. a p-value < 0.05 was considered statistically significant. results a total of 68 eyes of 34 patients (10 men and 24 women) with bilateral keratoconus were included in this rct. the mean age of the participants was 23.3 ± 3.6 years, ranging from 18 to 33 years. each eye of the patients was randomly assigned to either the epithelium-removal cxl group (n = 34) or epithelium-disruption cxl group 18 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 epithelium removal vs epithelial disruption cxl; bamdad et al (n = 34). except five patients who underwent cxl procedure unilaterally, the cxl was performed bilaterally in other subjects. finally, the epitheliumremoval and the epithelium-disruption cxl groups comprised 32 and 31 eyes, respectively. the baseline demographic and clinical characteristics and fourier transform components were matched between the two groups [table 1]. table 2 compares preoperative and postoperative parameters between the two groups. the mean number of days until bcl removal in the conventional and epitheliumdisruption cxl groups were 4.5 ± 1.3 and 3.1 ± 1.1 days, respectively (p < 0.0001). the two treatment groups differed significantly with respect to the postoperative thickness of the corneal thinnest point (p = 0.0001) and the postoperative irregularity component of the fourier analysis (p = 0.04). the epithelium-disruption cxl group had less reduction in the pachymetry of the corneal thinnest point and greater reduction in the fourier irregularity component in comparison to those in the conventional cxl group. there was no significant difference between the two treatment groups with respect to the other clinical outcomes, such as mean spherical equivalent, keratometry, ucva, bscva, and other components of the fourier analysis. discussion corneal crosslinking is a procedure that has changed the treatment pathway of keratoconus patients. before introducing this procedure, a fair prognosis for a young patient diagnosed with keratoconus was expected and the progressive nature of the disease in many cases led to corneal transplantation. however, despite the presence of many patients with advanced keratoconus requiring corneal transplantation, the future is promising for keratoconus treatment. the major cxl effect is to halt the progression of keratoconus and improve the visual acuity and keratometric data of many patients.[6, 7] during the conventional cxl procedure, complete epithelium debridement is performed, which has adverse effects such as pain, increased risk of infection, long healing time, and some stromal haziness. patients with advanced keratoconus do not take advantage of conventional treatment methods for visual acuity[18] and pachymetry.[5] previous studies evaluating the characteristics influencing the outcomes of cxl for keratoconus revealed that patients with a corrected distance visual acuity (cdva) of 20/40 or worse or a maximum k of 55.0 d or more were most likely to have improvement after cxl.[18, 19] corneal cross-linking in patients with very mild keratoconus and visual acuity of 20/20 is accompanied by the risk of stromal haziness and reduced post-surgical visual acuity.[15] however, in severe cases with low pachymetry (< 400 µm), it might hurt the endothelium and intraocular structures.[5] epithelial-disruption cxl is a modified version of conventional cxl with reduced adverse effects. in this modified procedure, some controlled pores were induced on the epithelium surface using a daya custom-designed instrument to accelerate the diffusion of riboflavin molecules to the stromal layer. in other words, partial removal of the epithelium was implemented. this rct compared the six month results after epitheliumremoval cxl and epithelial-disruption cxl based on the clinical characteristics and fourier analysis findings. the results of the current study show that the epithelial-disruption cxl method induces a less reduction in corneal pachymetry in comparison to that induced by conventional cxl after six months. the difference between the mean pachymetry of the thinnest point at baseline and after six-months’ follow-up in the epithelial-disruption group was only 5 µm, while it was 25 µm in the epithelium removal cxl group. we suggest this difference is because of the different surgical methods. epithelial-disruption cxl is a less invasive method in comparison to the conventional cxl and little manipulation of the corneal epithelium is performed through this procedure. this results in a smaller reduction in the mean pachymetry measurement and a corneal thickness closer to the patients’ initial corneal thickness six months after the surgery in the epithelial-disruption cxl group. however, previous studies of epithelium removal cxl revealed that after one year of follow-up, postoperative pachymetry reaches its initial measured value.[20] the mean number of days until bandage removal following the epithelium-disruption cxl method was 3.1 days, while it was 4.5 days following the conventional cxl method. after the epithelium-disruption cxl procedure, the corneal ulcer was limited to the many perforations of the epithelial surface, journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 19 epithelium removal vs epithelial disruption cxl; bamdad et al table 1. baseline characteristics of the epithelium removal and epithelial-disruption cxl groups. variables epithelium-removal cxl (n=32) mean ± sd epithelial-disruption cxl (n=31) mean ± sd p-value sex (m/f) (31.3% / 68.7%) (29% / 71%) 0.84 age (years) 23.40 ± 3.80 23.20 ± 3.50 0.81 sph equivalent (d) –2.70 ± 2.70 –3.90 ± 3.20 0.20 bscva (logmar) 0.20 ± 0.20 0.19 ± 0.23 0.50 ucva (logmar) 0.55 ± 0.34 0.50 ± 0.37 0.69 mean keratometry (d) 47.60 ± 3.10 48.20 ± 3.20 0.46 thinnest point pachymetry (µm) 459.20 ± 37.40 455.80 ± 32.70 0.70 fourier analysis spherical r min 6.97 ± 0.56 6.8 ±0.64 0.56 spherical ecc 0.79 ± 0.24 0.87 ± 0.21 0.33 max decentration 0.78 ± 0.37 0.76 ± 0.35 0.95 central astigmatism 0.31 ± 0.19 0.27 ± 0.12 0.75 peripheral astigmatism 0.17 ± 0.11 0.18 ± 0.08 0.81 irregularity 0.03 ± 0.016 0.028 ± 0.011 0.74 cxl, corneal crosslinking; bscva, best spectacle-corrected visual acuity; cxl, crosslinking; d, diopter; f, female; logmar, log of the minimal angle of resolution; m, male; sph, spherical; ucva, uncorrected visual acuity; µm, micrometer while it was extended due to the completely removed epithelium after the conventional cxl method. therefore, the number of days before bcl removal was significantly reduced following the epithelium-disruption cxl method. the current results showed faster corneal stabilization following the epithelial-disruption method in comparison to the epithelium removal method. performing cxl in some advanced cases is risky and may be limited because of a thin cornea. epithelial-disruption cxl would be a preferable method in this scenario. there was no difference in the refractive components, ucva, bscva, or mean keratometry results between the two groups. our findings revealed that although epithelium removal cxl is more aggressive, it does not lead to better shortterm follow-up results. we made a comparison between our results and those of previous studies that had compared epithelium removal cxl with other cxl modifications [table 3]. hashemi et al compared epithelium removal cxl with partial trans-epithelial cxl (strips pattern deepithelization) after one year of follow-up.[13] they found better corneal flattening with epithelium removal cxl and less reduction in the central pachymetry results in the partial trans-epithelial cxl group. their findings of better corneal flattening was not consistent with our results, but their central pachymetry finding was similar to ours. our results from the fourier analysis showed a significant difference in corneal irregularity between the two groups, with better results achieved using the epithelial-disruption cxl method. in other words, patients in the epithelial-disruption group experienced a greater reduction in corneal irregularities than the epithelium removal cxl group after six months. this might be due to the reduced level of manipulation of the epithelium, which reveals the advantage of the epithelial-disruption cxl method over epithelium removal method. ziaei et al measured anterior corneal curvature variables immediately after epithelial debridement during the cxl procedure.[21] they found that the corneal epithelium plays a role in masking the irregularity of the underlying bowman’s layer in keratoconic eyes. their results revealed that the magnitude of anterior corneal keratometry, astigmatism, and prolateness significantly increased immediately after epithelial debridement during the cxl procedure, strengthening our results with respect to the preference of the epithelial-disruption 20 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 epithelium removal vs epithelial disruption cxl; bamdad et al table 2. clinical outcomes of epithelium removal cxl and epithelial-disruption cxl after a mean follow-up of six months variables epithelium-off cxl mean ± sd daya epithelial disruption cxl mean ± sd p-value spherical equivalent (d) before –2.70 ± 2.70 –3.90 ± 3.20 0.31 after –3.00 ± 2.60 –3.70 ± 2.70 bscva (logmar) before 0.20 ± 0.20 0.19 ± 0.23 0.23 after 0.22 ± 0.22 0.17 ± 0.19 ucva (logmar) before 0.55 ± 0.34 0.50 ± 0.37 0.79 after 0.47 ± 0.34 0.37 ± 0.31 mean keratometry (d) before 47.60 ± 3.10 48.20 ± 3.20 0.85 after 47.50 ± 3.30 48.20 ± 3.50 thinnest point pachymetry (µm) before 459.20 ± 37.4 455.80 ± 32.70 0.0001∗ after 433.50 ± 33.50 451.90 ± 39.70 fourier analysis spherical r min before 6.97 ± 0.56 6.80 ±0.64 0.99 after 6.90 ± 0.58 6.10 ± 0.66 spherical ecc before 0.79 ± 0.24 0.87 ± 0.21 0.29 after 0.84 ± 0.26 0.87 ± 0.21 max decentration before 0.78 ± 0.37 0.76 ± 0.35 0.92 after 0.77 ± 0.39 0.72 ± 0.36 central astigmatism before 0.31 ± 0.19 0.27 ± 0.12 0.85 after 0.30 ± 0.18 0.28 ± 0.12 peripheral astigmatism before 0.17 ± 0.11 0.18 ± 0.08 0.49 after 0.18 ± 0.09 0.18 ± 0.08 irregularity before 0.030 ± 0.016 0.028 ± 0.011 0.04∗ after 0.031 ± 0.016 0.024 ±0.009 bscva, best spectacle-corrected visual acuity; cxl, crosslinking; d, diopter; f, female; logmar, log of the minimal angle of resolution; m, male; ucva, uncorrected visual acuity; µm, micrometer. *indicates for statistically significant p-values, (p < 0.05) cxl method over the epithelium removal cxl method because the former induces less corneal irregularity after the cxl procedure. there was no significant difference in spherical r min, spherical eccentricity, maximum decentration, or central and peripheral astigmatism between the two groups. the results of the fourier components are compatible with the clinical characteristics findings. there was no difference in either spherical components or spherical equivalent, as well as central astigmatism or mean keratometry. the corneal irregularity component cannot be measured in routine clinical examination, although it is an indicator for distorted image quality after spectacle compensation for refractive error. to the best of our knowledge, no previous studies have compared different cxl methods using fourier analysis. a comparison between trans-epithelial cxl and epithelium removal cxl in an rct regarding higher order aberrations via zernike analysis was performed by godefrooij et al.[22] they hypothesized that more improvement in bscva following trans-epithelial cxl than following epithelium removal cxl was related to greater advancement in the higher order aberrations of the trans-epithelial group relative to the epithelium removal group. their results did not show any significant difference regarding higher order aberrations between the two groups. the irregularity component of the fourier analysis might serve as a better answer for that hypothesis. the study design was a point of strength. it was a double masked rct where both the patients and the optometrist who collected the clinical data were blinded to the surgical methods. consequently, a favorable setting to compare treatment effects without confounding factors was journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 21 epithelium removal vs epithelial disruption cxl; bamdad et al table 3. comparison of epithelium removal cxl with other cxl modifications reference number. variables study design mean k (d) bscva (logmar) ucva (logmar) ct (μm) f-u (m) number (li j study) epi-removal cxl vs control meta-analysis of rcts improvement in cxl δ = 1.65 p < 0.00001 improvement in cxl δ = 1.65 p < 0.00001 same p > 0.05 same p > 0.05 3–36 epi-removal = 175 control = 182 (li w study) epi-removal cxl vs trans-epi cxl meta-analysis of rcts more improvement in epi-off cxl δ = 1.05 p = 0.02 more improvement in trans-epi δ = 0.07 p = 0.007 same p > 0.05 same p > 0.05 12–24 epi-removal = 111 trans-epi = 133 (hashemi study) epi-removal cxl vs partial trans-epi cxl (strips pattern) retrospective more improvement in epi-off δ = 0.42 p = 0.015 more improvement in partial δ = 0.13 p = 0.001 same p > 0.05 less decrease in partial δ = 18 p < 0.001 12 epi-removal = 40 partial = 40 (current study) epi-removal cxl vs epidisruption rct same p > 0.05 same p > 0.05 same p > 0.05 less decrease in epidisruption δ = 20 p = 0.0001 6 epi-removal = 32 partial = 31 bscva, best spectacle-corrected visual acuity; ct, central corneal thickness; cxl, crosslinking; d, diopter; epi, epithelium; f-u, follow-up; logmar, log of the minimal angle of resolution; m, month; mean k, mean keratometry; rct, randomized clinical trial; ucva, uncorrected visual acuity; µm, micrometer; δ = difference in change between two groups provided. in addition, we selected our participants from a pool of patients with bilateral keratoconus and both treatment methods were performed in the same patient. as a result, we examined two groups with similar underlying healing factors. this study addressed the short-term results; consequently, other studies with more than one year of follow-up are recommended to compare the efficacy of these two methods in halting keratoconus progression in the long-term. in conclusion, the epithelial-disruption cxl method produced better results with respect to the thinnest point on pachymetry and corneal irregularity than the epithelium removal cxl method. there was no significant difference in the improvement in spherical equivalent, mean keratometry, ucva, bscva, or overall shape of the cornea according to fourier components (except irregularity) between the two cxl methods. references 1. rabinowitz ys. keratoconus. surv ophthalmol 1998;42:297–319. 2. rebenitsch rl, kymes sm, walline jj, gordon mo. the lifetime economic burden of keratoconus: a decision analysis using a markov model. am j ophthalmol 2011;151:768–773. 3. tatematsu-ogawa y, yamada m, kawashima m, yamazaki y, bryce t, tsubota k. the disease burden of keratoconus in patients’ lives: comparisons to a japanese normative sample. eye contact lens 2008;34:13–16. 4. hashemi h, khabazkhoob m, fotouhi a. topographic keratoconus is not rare in an iranian population: the tehran eye study. ophthalmic epidemiol 2013;20:385–391. 5. wollensak g, spoerl e, seiler t. riboflavin/ultravioleta-induced collagen crosslinking for the treatment of keratoconus. am j ophthalmol 2003;135:620–627. 6. li j, ji p, lin x. efficacy of corneal collagen cross-linking for treatment of keratoconus: a meta-analysis of randomized controlled trials. plos one 2015;10:e0127079. 7. sedaghat m, bagheri m, ghavami s, bamdad s. changes in corneal topography and biomechanical properties after collagen cross linking for keratoconus: 1-year results. middle east afr j ophthalmol 2015;22:212–219. 8. lesniak sp, hersh ps. transepithelial corneal collagen crosslinking for keratoconus: six-month results. j cataract refract surg 2014;40:1971–1979. 9. li w, wang b. efficacy and safety of transepithelial corneal collagen crosslinking surgery versus standard corneal collagen crosslinking surgery for keratoconus: a metaanalysis of randomized controlled trials. bmc ophthalmol 2017;17:262. 22 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 epithelium removal vs epithelial disruption cxl; bamdad et al 10. soeters n, wisse rp, godefrooij da, imhof sm, tahzib ng. transepithelial versus epithelium-off corneal crosslinking for the treatment of progressive keratoconus: a randomized controlled trial. am j ophthalmol 2015;159:821–828. 11. rechichi m, daya s, scorcia v, meduri a, scorcia g. epithelial-disruption collagen crosslinking for keratoconus: one-year results. j cataract refract surg 2013;39:1171– 1178. 12. hirji n, sykakis e, lam fc, petrarca r, hamada s, lake d. corneal collagen crosslinking for keratoconus or corneal ectasia without epithelial debridement. eye 2015;29:764– 768. 13. hashemi h, miraftab m, hafezi f, asgari s. matched comparison study of total and partial epithelium removal in corneal cross-linking. j refract surg 2015;31:110–115. 14. galvis v, tello a, carreño ni, ortiz ai, barrera r, rodriguez cj, et al. corneal cross-linking (with a partial deepithelization) in keratoconus with five years of followup. ophthalmol eye dis 2016; 8:17–21. 15. sideroudi h, labiris g, ditzel f, tsaragli e, georgatzoglou k, siganos h, et al. validation of fourier analysis of videokeratographic data. int ophthalmol 2018;38:1433– 1440. 16. sideroudi h, labiris g, georgatzoglou k, ditzel f, siganos c, kozobolis v. fourier analysis of videokeratography data: clinical usefulness in grade i and subclinical keratoconus. j cataract refract surg 2016;42:731–737. 17. oshika t, tanabe t, tomidokoro a, amano s. progression of keratoconus assessed by fourier analysis of videokeratography data. ophthalmology 2002;109:339– 342. 18. greenstein sa, hersh ps. characteristics influencing outcomes of corneal collagen crosslinking for keratoconus and ectasia: implications for patient selection. j cataract refract surg 2013;39:1133–1140. 19. sloot f, soeters n, van der valk r, tahzib ng. effective corneal collagen crosslinking in advanced cases of progressive keratoconus. j cataract refract surg 2013;39:1141–1145. 20. greenstein sa, shah vp, fry kl, hersh ps. corneal thickness changes after corneal collagen crosslinking for keratoconus and corneal ectasia: one-year results. j cataract refract surg 2011;37:691–700. 21. ziaei m, meyer j, gokul a, vellara h, mcghee cn. direct measurement of anterior corneal curvature changes attributable to epithelial removal in keratoconus. j cataract refract surg 2018;44:71–77. 22. godefrooij da, el kandoussi m, soeters n, wisse rp. higher order optical aberrations and visual acuity in a randomized controlled trial comparing transepithelial versus epithelium-off corneal crosslinking for progressive keratoconus. clin ophthalmol 2017;11:1931–1936. journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 23 letter to editor how much of hazardous blue light is transmitted by spectacle lenses? saeed rahmani1, phd; mohammadreza nazari1, ms; alireza akbarzadeh baghban2, phd mohammad ghassemi-broumand1, md 1department of optometry, school of rehabilitation, shahid beheshti university of medical sciences, tehran, iran 2proteomics research center, department of biostatistics, school of allied medical sciences, shahid beheshti university of medical sciences, tehran, iran orcid: saeed rahmani: https://orcid.org/0000-0001-6330-4405 j ophthalmic vis res 2020; 15 (3): 435–437 dear editor, the first region of the visible light spectrum is called blue light. blue light is beneficial to humans in color vision, night vision, and circadian rhythms.[1, 2] however, this type of light raises concerns as it carries high energy and can cause ocular damages, such as photic retinopathy. in addition to the sun, there are several artificial sources of blue light emission, such as lightemitting diodes (leds), light bulbs, and fluorescent light tubes. with the increasing use of digital bluerich led-backlight displays, such as in mobile devices and tablets, users’ eyes are more exposed to blue light.[2, 3] blue light can also induce eyestrain, however, the blue light-blocking lenses may reduce eye fatigue.[4, 5] currently, some lens manufactures claim that their products can alleviate eyestrain and ocular discomfort associated with the use of digital devices.[5] this raises important questions about the efficacy of blue light-control lenses. therefore, correspondence to: saeed rahmani, phd. department of optometry, school of rehabilitation sciences, shahid beheshti university of medical sciences, opposite to bou-ali hospital, damavand ave., tehran, iran. e-mail: medicalopto@yahoo.com received: accepted: access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7465 eight blank-white spectacle lenses (four with and four without blue light-blocking property) were collected from different optical companies. a spectrophotometer (cecil instrument, uk) was used to measure the blue light transmission. three ranges of blue light were evaluated: 400–450 nm, 455–500 nm, and 400–500 nm. for the statistical analysis, non-parametric mann–whitney test was employed. a p-value ≤ 0.05 was considered statistically significant. the mean transmission of blue light through lenses with and without blue light-blocking coating in the range of 400–455 nm were 58.76 ± 3.01% and 83.10 ± 1.71%, respectively. the differences were statistically significant (p = 0.02). the harmful portion of blue light is accumulated in this range as previous studies have shown that using filters capable of 50% reduction in 430 nm blue light transmission can prevent approximately 80% of photochemical damage to the retina. notably, there is currently no strict guideline for blue lightblocking coatings.[2] the mean transmission of blue light through lenses with and without blue light-blocking coating in the range of 455–500 nm were 95.58 ± 0.46% and 96.00 ± 0.57%, respectively. the differences were not statistically significant (p = 0.39). higher this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: rahmani s, nazari m, baghban aa, ghassemibroumand m. how much of hazardous blue light is transmitted by spectacle lenses?. j ophthalmic vis res 2020;15:435–437. © 2020 journal of ophthalmic and vision research | published by knowledge e 435 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7465&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr blue light filtering by spectacle lenses; rahmani et al figure 1. blue light transmission of lenses with and without blue light-blocking property in different wavelengths. figure 2. comparison between spectral transmittance of lenses with and without blue light-blocking property. wavelengths, that is, 455–500 nm, are considered useful light for color vision and circadian rhythm. the mean transmission of blue light through lenses with and without blue light-blocking coating in the range of 400–500 nm were 75.33 ± 1.51% and 88.40 ± 1.63%, respectively. the differences were statistically significant (p = 0.02). the lenses with blue light-blocking property could reduce the blue light transmission by approximately 25% in the wavelength range of 400–500 nm. thus, the filtering value was twice the amount in the lenses without blue light-blocking property (figures 1 and 2). finally, the spectacle lenses with blue lightblocking property could effectively attenuate hazardous lights. it is recommended to use the spectacle lenses that are equipped with blue light-blocking coating to reduce the risk of ocular diseases attributed to hazardous blue light. acknowledgments the authors thank the research affairs of the shahid beheshti university of medical sciences for their support. 436 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 blue light filtering by spectacle lenses; rahmani et al conflicts of interest there are no conflicts of interest. references 1. giannos sa, kraft er, lyons lj, gupta pk. spectral evaluation of eyeglass blocking efficiency of ultraviolet/high-energy visible blue light for ocular protection. optom vis sci 2019;96:513–522. 2. leung tw, li rw, kee cs. blue-light filtering spectacle lenses: optical and clinical performances. plos one 2017;12:e0169114. 3. smith bt, belani s, ho ac. ultraviolet and near-blue light effects on the eye. int ophthalmol clin 2005;45:107–115. 4. ide t, toda i, miki e, tsubota k. effect of blue lightreducing eye glasses on critical flicker frequency. asia pac j ophthalmol (phila) 2015;4:80–85. 5. downie le. blue-light filtering ophthalmic lenses: to prescribe, or not to prescribe? ophthalmic physiol opt 2017;37:640–643. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 437 original article influence of intraocular lens asphericity and blue light filtering on visual outcome, contrast sensitivity, and aberrometry after uneventful cataract extraction argyrios tzamalis1,2, md, phd, ma, febo; myron kynigopoulos2, md; grigoris pallas2, md ioannis tsinopoulos1, phd; nikolaos ziakas1, phd 12nd department of ophthalmology, aristotle university of thessaloniki, papageorgiou general hospital, thessaloniki, greece 2department of ophthalmology, clinic pallas, olten, switzerland orcid: argyrios tzamalis: https://orcid.org/0000-0002-3172-8542 abstract purpose: to evaluate the effect of asphericity and blue light filter (blf) of three different intraocular lenses (iols) on the visual performance, secondand third-order aberrations (defocus, coma, trefoil), and contrast sensitivity after uneventful cataract surgery. methods: one hundred and twenty eyes of 60 patients with clinically significant cataract were randomly assigned to receive one of the three iol types: bioline yellow accurate (aspheric, with blf, i-medical, germany), bioacryl 60125 (spherical, without blf, biotech, france), and h65c/n (aspheric, without blf, physiol, belgium). each iol was implanted in 40 eyes. complete ophthalmologic examination, functional acuity contrast testing and wavefront analysis were performed 60 days postoperatively. results: the mean postoperative best-corrected visual acuity (bcva) was 0.95 ± 0.08, not differing statistically among the iol groups (p = 0.83). mean defocus and coma values did not yield any statistically significant difference through the iol groups varying from –0.784 to –0.614 μm and 0.129 to 0.198 μm (p = 0.79 and 0.34, respectively). bioline yellow accurate iol presented less trefoil aberrations, 0.108 ± 0.05 μm, compared to the other two iol types (bioacryl [0.206 ± 0.19 μm] and physiol [0.193 ± 0.17 μm], p < 0.05). contrast sensitivity values did not differ among the groups under all lighting conditions. bioline yellow iol showed a statistically higher loss of contrast sensitivity (between mesopic and mesopic with glare conditions) compared to the bioacryl and physiol in 12 and 3 cpd spatial frequencies, respectively (p < 0.05). conclusion: bioline yellow iol indicated lower contrast sensitivity under mesopic conditions when glare was applied but resulted in less trefoil aberrations after uneventful cataract surgery. no further differences were noted in postoperative visual performance among three iol groups. keywords: aberrometry; asphericity; blue-light filtering; contrast sensitivity; intraocular lens j ophthalmic vis res 2020; 15 (3): 308–317 correspondence to: argyrios tzamalis, md, phd, ma, febo. 2nd department of ophthalmology, aristotle university of thessaloniki, papageorgiou general hospital, thessaloniki, greece. e-mail: argyriostzamalis@yahoo.com received: 19-01-2019 accepted: 31-12-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7449 introduction modern cataract surgery has recently evolved into a refractive procedure aimed at improving this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: tzamalis a, kynigopoulos m, pallas g, tsinopoulos i, ziakas n. influence of intraocular lens asphericity and blue light filtering on visual outcome, contrast sensitivity, and aberrometry after uneventful cataract extraction. j ophthalmic vis res 2020;15:308–317. 308 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7449&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr aspheric and blue light filtering iols; tzamalis et al visual quality in addition to increasing the visual acuity. therefore, it is routinely combined with the implantation of intraocular lenses (iols) of various materials and designs. since the initial introduction of iols, there has been great debate over the importance of light filtration.[1–5] ultraviolet (uv) light-filtering lenses have been the dominant iols used in the modern era since growing evidence indicated that uv light could result in photic retinopathy and other retinal pathologies.[6] there has recently though been support for increasing the range of light absorption by iols. the rationale was that uv light-filtering iols cannot offer protection to the retina from phototoxic damage induced by the high-energy, short-wavelength blue light (400–480 nm), which is considered to contribute to the pathogenesis of age-related macular degeneration (amd).[7, 8] in response to this potential damage, blue lightfiltering (blf) iols were introduced in 1996 and have been thereafter widely used, especially in cataract surgery candidates with signs of amd as a possible measure of preventing associated retinal pathology.[3, 9–12] the yellow tint of blf iols replicates the spectral transmission properties of the aged human crystalline lens in a much closer manner than the uv light-filtering iols do.[13] while the possible visual benefits of blf iols are still under debate, controversy has been raised whether a yellow-tinted iol could modify the visual performance of patients, specifically regarding the postoperative best-corrected visual acuity (bcva), contrast sensitivity, color vision, and glare. in addition to blf, another recently commercialized property of iols that has become increasingly popular is asphericity. spherical aberration has a strong influence on image quality.[14] it is well-established that conventionalspherical iols degrade image quality by increasing the spherical higher-order aberrations (hoas), and several authors have published studies indicating that aspheric iols may improve retinal image quality and mesopic contrast sensitivity at low spatial frequencies.[15–21] however, the combination of blf and asphericity in iols has not been clearly investigated regarding their effect on contrast sensitivity, aberrometry, and quality of vision. the purpose of this prospective randomized study was to evaluate the effect of blue light-filtering and aphericity of iol on visual quality by comparing the three different iol types: one aspherical iol with blf, one aspherical iol without blf, and one spherical iol without blf. methods this prospective, randomized clinical study comprised patients who underwent bilateral cataract surgery for visually significant cataract. sixty patients were randomly assigned to receive one of the three iol types. group a received bioline yellow accurate iol (aspheric with blf, i-medical, germany), group b had h65c/n iol (aspheric without blf, physiol, belgium), and group c had bioacryl60125 iol (spherical, without blf). each iol was implanted in 40 eyes of 20 randomly selected patients. all patients were recruited from the outpatient anterior segment unit of the clinic pallas ophthalmology department in olten, switzerland. the study was performed in adherence with the declaration of helsinki for research involving human subjects after approval was obtained from the institutional review boards of pallas clinic. patients with bilateral cataract with visual disturbance and no history of color vision deficiency were eligible for inclusion in the study. the exclusion criteria were ocular diseases such as corneal opacity or irregularity, astigmatism greater than 2.5 d, dry eye syndrome, inadequate visualization of the fundus, amblyopia, anisometropia, calculated iol power less than 10.0 diopters (d) or more than 30.0 d, surgical complications, iol tilt, previous or current use of medications known to cause color vision deficiencies, and incomplete follow-up. also, patients with a history of uveitis and current intraocular inflammation, uncontrollable glaucoma, proliferative diabetic retinopathy, or retinal detachment were excluded from the study. one experienced surgeon (gp) performed all surgeries with standard small incision phacoemulsification and iol implantation in the capsular bag. the time between first eye surgery and second eye surgery was six–eight days in all cases. all eyes were targeted for emmetropia. table 1 shows the characteristics of the iols implanted during the study period. all patients were given combined antibiotic–steroid eye drops for four weeks postoperatively. patients were examined before surgery and one, seven, and one to three months postoperatively. at all visits, the journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 309 aspheric and blue light filtering iols; tzamalis et al best corrected-distance visual acuity (bcdva) and uncorrected distance visual acuity (udva) were measured. contrast sensitivity assessment and aberrometry by means of wavefront analysis were evaluated at the baseline (preoperatively) and last follow-up visit which was performed one to three months postoperatively. visual acuity was measured using snellen chart under scotopic conditions (target luminance 1.5 candelas [cd]/m2). contrast sensitivity was assessed using functional acuity contrast testing (fact-optec6500, stereo optical inc., usa) with spectacle correction under photopic conditions (target luminance value 85 candelas [cd]/m2) and mesopic conditions (target luminance value 3 cd/m2) with and without glare. lighting conditions were controlled with a luxometer (gossen-starlite). the log base 10 contrast sensitivity values were used to construct a graph for each spatial frequency tested and then presented using the original test scale. a zywave hartmann-shack aberrometer (bausch & lomb, germany) was used for all aberrometry measurements. zywave was used to assess and compensate for the refractive errors, and, eye fogging system was acquired before each wavefront measurement to avoid patient accommodation. before use, the aberrometer was calibrated by an experienced bausch & lomb technician to ensure the accuracy. five measurements were performed by a single experienced technician to avoid interobserver variability in the results; of these, two measurements with higher deviations from the mean were excluded and the three best measurements were averaged and used for statistical analyses. patients were instructed to blink between measurements, and acquisition was obtained after a blink to ensure higher quality results by limiting tear film disruption. all results were exported as raw data so that individual zernike terms could be analyzed independently. the details of the zernike coefficients up to the third order were recorded and used for the statistical analysis. zywave measurements were obtained without any pharmacologic mydriasis and dark adaptation. nonetheless, all measurements were made in certain mesopic lighting conditions and it was confirmed that pupillary diameter was at least 6 mm in every case. total, corneal, and internal components for each of the high-order aberrations were obtained and used for the analysis. statistical analysis was performed using the spss (version 17.0 for windows, spss, inc. chicago, il) and medcalc statistical software (version 9.3.0.0, mariakerke, belgium). normality was checked using the kolmogorov–smirnov test. since data were not normally distributed in all cases, both parametric and nonparametric methods were used. for normally distributed data, pearson correlation was used to evaluate the association between two continuous variables and the one-way analysis of variance (anova) was applied to evaluate the influence of a qualitative factor on another continuous variable. the association of not normally distributed data was assessed using rank correlation calculating spearman’s coefficient rho. when parametric analysis was possible, the student’s t-test was used to compare the outcomes between two iol groups. categorical variables were compared using the fisher’s exact test. nonparametric kruskal–wallis and mann–whitney tests were also used to examine the associations between categorical variables and continuous or ordered outcomes. a p-value of < 0.05 was defined for all statistical tests as statistically significant. results a total number of 120 eyes of 60 patients (mean age, 72.4 ± 9.5 years) who underwent uneventful bilateral cataract surgery were found eligible and were finally enrolled in the statistical analysis. all eyes were divided into one of the three groups, based on the type of iol they received. the main demographic and clinical characteristics of each group are demonstrated in table 2. there were no statistically significant differences among the study groups in preoperative clinical and refractive values. preoperative total and internal components of aberrometry showed great deviations between cases, as patients with various degrees and types of cataracts were included. however, the preoperative corneal component of coma, defocus, and trefoil did not have any statistically significant difference among the three groups (p > 0.05). the mean snellen postoperative bcva was 0.95 ± 0.08 (0.023 logmar) with a mean postoperative spherical equivalent of –0.32 ± 0.13d; not differing statistically between the iol 310 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 aspheric and blue light filtering iols; tzamalis et al table 1. main characteristics and special features of the intraocular lenses used in the study bioline yellow h65c/n bioacryl optic material hydrophilic acrylic copolymer 26 % water hydrophilic acrylic copolymer hydrophilic acrylic optic design biconvex aspherical biconvex aspherical spherical optic diameter (mm) 6.0 6.5 6.0 length (mm) 12.0 12.5 12.5 design 360º square edge 360º reinforced edge design ”pco-barrier” 360º square edge haptic angulation (º) 0 5 5 ultraviolet filter with blf without blf without blf a-constant 118.8 118.9 118.0 refractive index 1.465 1.46 1.462 estimated anterior chamber depth (mm) 4.98 4.99 4.96 blf, blue light filtering table 2. main demographics and clinical characteristics of the study participants bioline yellow h65c/n bioacryl 60125 p-value† total gender 21f/19m 22/18m 19f/21m 0.79 62f/58m age (years) 70.3 ± 8.7 74.6 ± 8.3 72.5 ± 6.4 0.53 72.4 ± 9.5 axial length (mm) 24.1 ± 1.7 23.6 ± 2.2 23.7 ± 1.6 0.59 23.8 ± 2.1 preoperative se 0.19 ± 1.4 0.45 ± 1.5 0.39 ± 1.2 0.68 0.34 ± 1.5 postoperative se –0.32 ± 0.2 –0.34 ± 0.2 –0.31 ± 0.2 0.41 –0.32 ± 0.4 iol power 21.1 ± 2.9 22.5 ± 1.4 22.2 ± 2.6 0.15 21.8 ± 2.5 bcva preop, logmar (decimal) 0.38 (0.42 ± 0.16) 0.29 (0.53 ± 0.12) 0.32 (0.48 ± 0.18) 0.59 0.33 (0.47 ± 0.17) bcva postop, logmar (decimal) 0.018 (0.96 ± 0.07) 0.031 (0.93 ± 0.09) 0.022 (0.95 ± 0.08) 0.59 0.023 (0.948 ± 0.08) cr preop 7.65 ± 0.3 7.64 ± 0.3 7.66 ± 0.2 0.87 7.65 ± 0.3 cr postop 7.66 ± 0.3 7.66 ± 0.3 7.69 ± 0.2 0.93 7.67 ± 0.3 †p-value (significance level) was calculated by means of chi-square test, anova-test and kruskal–wallis test. se, spherical equivalent; bcva, best-corrected visual acuity; cr, corneal radius logmar, logarithm of the minimum angle of resolution groups (table 2; p > 0.05). the mean logmar uncorrected va (ucva) increased from 0.58 ± 0.25 (bioline yellow), 0.54 ± 0.23 (h65c/n), and 0.55 ± 0.26 at screening to 0.23 ± 0.12, 0.22 ± 0.11, and 0.24 ± 0.11, respectively, at postoperative followup. there was no statistically significant difference in the postoperative ucva among the iol groups. postoperative values were recorded at a mean time of 63.2 ±11.7 days after uneventful cataract surgery varying between 38 and 87 days, with no significant difference among the groups in the duration of follow-up (anova, p = 0.21). table 2 demonstrates the preoperative and postoperative refraction data in more details. mean defocus and coma values did not yield any statistically significant difference among iol groups varying from –0.784 to –0.614 and 0.129 to 0.198, respectively (table 3). bioline yellow accurate presented less trefoil aberrations, 0.108 ± 0.05 μm compared to the other two iol types (p < 0.05). table 3 illustrates the secondand thirdorder aberrations as well as their intergroup comparisons. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 311 aspheric and blue light filtering iols; tzamalis et al table 3. comparisons of secondand third-order aberrations among the three iol groups iol (group) defocus (z200) coma (z311, z310) trefoil (z331, z330) bioline yellow (group1) –0.7842 ± 0.9915 0.1288 ± 0.1075 0.1082 ± 0.049 physiol h65c/n (group2) –0.6557 ± 0.7235 0.1573 ± 0.1186 0.1929 ± 0.1736 bioacryl 60125 (group3) –0.6136 ± 0.6239 0.1984 ± 0.1599 0.2058 ± 0.1852 mean –0.69 ± 0.72 0.16 ± 0.13 0.16 ± 0.15 comparison between groups (p-value) group1–group2 0.52 0.11 0.03 group1–group3 0.59 0.43 0.042 group2–group3 0.8 0.36 0.82 table 4. mean loss of contrast sensitivity, expressed in logarithmic units, from photopic to mesopic lighting conditions (lc) and under glare conditions in mesopic lc. loss photopic to mesopic lc loss mesopic to mesopic with glare lc spatial frequency (cpd) 1.5 3 6 12 18 1.5 3 6 12 18 iol1 0.051 0.105 0.227 0.406 0.569 0.096 0.23 0.233 0.452 0.256 iol2 0.021 0.129 0.185 0.400 0.358 0.165 0.121 0.154 0.217 0.331 iol3 0.030 0.140 0.221 0.521 0.433 0.167 0.139 0.229 0.099 0.206 p(anova)† 0.69 0.62 0.69 0.69 0.27 0.17 0.04 0.75 0.02 0.64 p(t-test)1–2* 0.43 0.59 0.17 0.77 0.25 0.13 0.01 0.71 0.27 0.84 p(t-test)1–3* 0.53 0.31 0.60 0.34 0.41 0.20 0.05 0.84 0.04 0.81 p(t-test)2–3* 0.92 0.64 0.60 0.62 0.75 0.98 0.77 0.85 0.30 0.67 iol1, bioline yellow accurate; iol2, physiol h65c/n; iol3, bioacryl60125; cpd, cycles per degree †p-value comparing all three iol groups with one-way analysis of variance; *p-value comparing iol groups in couples with student’s t-test there was no statistically significant difference among the three iol groups in contrast sensitivity at any spatial frequency under all three lighting conditions. figure 1 (photopic 85 cd/m2), figure 2 (mesopic 3 cd/m2), and figure 3 (mesopic with glare) depict postoperative contrast sensitivity for all iol groups. in a separate analysis, bioline yellow was found to have a statistically lower contrast sensitivity under glare conditions compared to the bioacryl and physiol in 12 and 3 cpd spatial frequencies, respectively (p < 0.05). table 4 compares the postoperative contrast sensitivity among the iol groups. discussion modern cataract surgery with the implementation of specially designed iols has developed tremendously over the past decades, attempting to meet patients’ expectations for optimal visual outcomes.[11, 19, 21] contemporary diagnostic tools have extended our knowledge on the impact of hoas and contrast sensitivity on the quality of vision. therefore, in order to achieve the best outcome after phacoemulsification, the iol implantation should result in minimal aberrations and high-contrast sensitivity. iols with aspheric optics, designed to optimize postoperative spherical aberration and implants with blf as a possible measure of preventing associated retinal pathology have gained great popularity. however, there is still great controversy on their potential benefit and the effect of these features on the postoperative visual performance, specifically regarding the ultimate bcva, contrast sensitivity, color vision, and postoperative aberrations.[1–5, 9–12, 15–21] 312 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 aspheric and blue light filtering iols; tzamalis et al figure 1. postoperative contrast sensitivity (log) under photopic conditions (85 cd/m2) in various spatial frequencies for the iols included in the study [iol1 = bioline yellow accurate (i-medical, germany), iol2 = bioacryl 60125 (biotech, france), iol3 = h65c/n (physiol, belgium)]. the present prospective randomized study attempted to investigate the effect of blf and aspherical iol design on the final visual outcome. therefore, we compared the visual performance after the implantation of three different iols; one aspheric, with blf; one aspheric, without blf; and one spherical, without blf. our results showed that bcva did not differ statistically significantly among the iol groups. these results regarding the effect of blf in postoperative bcva are in concordance with a recent cochrane database systematic review which demonstrated, with moderate certainty, that the presence of blf in iols had no clinically meaningful effect on short-term bcva.[22] although no significant difference was found in our study among the different iol groups in the postoperative bcva, the group of patients implanted with an aspheric iol with blf indicated fewer trefoil aberrations when compared to the other iol groups included in the study. notably, the preoperative corneal component of hoas did not differ significantly among the three iol groups. therefore, the lower trefoil measurements shown in this group could be attributed to the internal components, mainly the iol itself. a postoperative iol tilt could also be a predisposing factor for increased aberrations. blue-light filtering is an add-on feature of iols, considered to offer an extra retinal protection against amd, although this has not been fully proven so far.[23] iols with blf are supposed to reduce longitudinal chromatic aberrations. theoretically, such a reduction should not affect spherical aberrations. however, in our study, the yellow-tinted iol achieved better results in postoperative trefoil when compared not only to the spherical iol but also to the aspheric one without blf. it should be noticed that the two aspheric iols used in this study had minimal differences in terms of optical design and material being produced by different manufacturers. this fact could also have some impact on the results reported. to the best of our knowledge, there are no journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 313 aspheric and blue light filtering iols; tzamalis et al figure 2. postoperative contrast sensitivity (log) under mesopic conditions (3 cd/m2) in various spatial frequencies for the iols included in the study [iol1 = bioline yellow accurate (i-medical, germany), iol2 = bioacryl 60125 (biotech, france), iol3 = h65c/n (physiol, belgium)]. published studies evaluating the effect of blf on spherical hoas by comparing the same iol types. as far as postoperative contrast sensitivity is concerned, no significant difference was found among iols in any spatial frequency under photopic, mesopic, and mesopic with glare-lighting conditions. however, the yellow-tinted aspheric iol was found to have a statistically higher loss of contrast sensitivity under glare conditions compared to the non-tinted iols at some spatial frequencies. in recent years, aspheric iols have gained increasing popularity among surgeons due to their theoretical advantage of being able to compensate for the spherical aberration of the human cornea, with the aim of restoring the optical performance of the eye.[14] most studies performed on this task have confirmed this theory reporting that aspheric iols implanted have significantly reduced the overall spherical aberrations, hence improving optical performance in certain cases.[15, 17–24] comparing the aspheric tecnis za9003 iol with the spherical acrysof sa60at iol (alcon, inc.), kim et al[25] reported a significant improvement in contrast sensitivity under mesopic and photopic conditions with the aspheric iol; the authors reported that the mean spherical aberration was significantly higher in eyes implanted with the spherical iol, although total higher order aberrations did not differ significantly between the results of two further prospective randomized studies performed by rocha et al and caporrosi et al, who concluded that eyes implanted with aspheric iols had less aberrations and performed better under mesopic condition compared to spherical iols.[18, 26] on the contrary, several researchers have reported no statistically significant differences in visual acuity and contrast sensitivity between spherical iols and aspheric iols.[27–29] we compared in our study the outcome of the three different iols, two aspheric and one spherical and found no statistically significant difference in the secondand third-order aberrations other 314 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 aspheric and blue light filtering iols; tzamalis et al figure 3. postoperative contrast sensitivity (log) under mesopic with glare conditions (3 cd/m2 with glare) in various spatial frequencies for the iols included in the study [iol1 = bioline yellow accurate (i-medical, germany), iol2 = bioacryl 60125 (biotech, france), iol3 = h65c/n (physiol, belgium)]. than trefoil aberrations that was lower in the eyes implanted with aspheric iol with a blf. surprisingly, no difference was noted between the two non-tinted iol groups, despite one of them having an aspherical design. one may hypothesize that blf added on yellow-tinted iols could reduce some spherical aberrations along with the longitudinal chromatic ones; however, this theory needs to be examined by further prospective randomized studies with larger population sizes to compare aberrations between iols of identical design and material. in the past decade, several manufacturers and distributors have promoted commercially available iols with blf properties. theoretically, blf iols may induce a reduction in mesopic and scotopic visual performance attributed to the purkinje shift, where differing peaks of spectral sensitivity for scotopic and photopic vision are identified.[1, 3] violet and blue lights are much more important for vision in dim-light environments than in brightlight environments, providing 45% of rod-mediated aphakic scotopic sensitivity but only 7% of photopic sensitivity for an iso-illuminance light source.[1, 2] however, the results reported in the literature are controversial regarding postoperative contrast sensitivity after the blf-iol implantation and do not indicate a significant decrease in the mesopic and scotopic visual function. kara-junior et al[30] investigated the long-term possible side effects after implantation of an iol with a blf. the authors found no significant differences in color perception, scotopic contrast sensitivity, or photopic contrast sensitivity between the blf iol and the iol with a uv-light filter only. in another study, greenstein et al[31] investigated contrast sensitivity in nine patients implanted with a blf iol (acrysof sn60at) in one eye and a uv-only filtering iol (acrysof sa60at) in the fellow eye. in addition, they compared the results with those obtained in nine young phakic patients and found no significant difference in hue discrimination or dark-adapted sensitivity between the two iols.[31] these results were comparable to the outcome of a study by muftuoglu et al[32] who compared photopic and scotopic cs in eyes journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 315 aspheric and blue light filtering iols; tzamalis et al with an acrysof sn60at iol (with blf) and eyes with a conventional acrysof sa60at iol (uv-only filtering) and reported no statistically significant differences between the two iol types. furthermore, hayashi et al[9] measured contrast visual acuity in 74 patients implanted bilaterally with either tinted iol (hoya ya60bb) or non-tinted iols (va60bb) and reported no significant difference between the iol groups. in concordance with these aforementioned studies, our results showed no statistically significant difference in contrast sensitivity between iols with and without blf. in an additional analysis, we evaluated the loss of contrast sensitivity after glare was applied in mesopic conditions and found that the tinted iol had a statistically greater loss of contrast sensitivity under glare compared to the non-tinted iols, but only in some spatial frequencies. although this may be an accidental finding, it is noteworthy as most previous studies did not include contrast sensitivity measurement in mesopic conditions under glare, a situation that is rather common in real life, such as night driving, and can substantially affect the patient’s quality of life after cataract surgery. a weakness worth mentioning of all studies reporting mesopic cs results after the implantation of iols with blf is the fact that all have utilized measures that are a function of only central vision, where macular pigment is also acting as a blf. moreover, one should consider that mesopic vision is mediated, at least in part, by cones, and therefore it is less likely to be adversely influenced by the transmittance properties of such blue-blocking iols. other limitations of our study include the relatively small sample size and the lack of a group with implantation of a spherical iol with blf; this type of iol was not commercially available at the time the study was conducted. in summary, the present study compared three iols varying in terms of asphericity and blf and showed only minimal differences in postoperative contrast sensitivity and aberrometry. all iols achieved comparable results in postoperative visual performance; an aspheric iol with blf, however, resulted in less trefoil aberrations and a greater loss of contrast sensitivity in mesopic conditions when glare was applied. further randomized patient-centered studies are needed to evaluate the long-term results of aspheric iol design and blf and to investigate whether these features are desirable for the patients’ quality of life. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. mainster ma. violet and blue light blocking intraocular lenses: photoprotection versus photoreception. br j ophthalmol 2006;90:784–792. 2. schwiegerling j. blue-light-absorbing lenses and their effect on scotopic vision. j cataract refract surg 2006;32:141–144. 3. yuan z, reinach p, yuan j. contrast sensitivity and color vision with a yellow intraocular lens. am j ophthalmol 2004;138:138–140. 4. cuthbertson f, peirson s, wulff k, foster rg, downes sm. blue light-filtering intraocular lenses: review of potential benefits and side effects. j cataract refract surg 2009;35:1281–1297. 5. henderson b, grimes k. blue-blocking iols: a complete review of the literature. surv ophthalmol 2010;55:284– 289. 6. ham wt jr, mueller ha, sliney dh. retinal sensitivity to damage from short wavelength light. nature 1976;260:153–155. 7. tomany sc, cruickshanks kj, klein r, klein bek, knudtson md. sunlight and the 10-year incidence of age-related maculopathy: the beaver dam eye study. arch ophthalmol 2004;122:750–757. 8. taylor hr, west s, munoz b, bressler sb, bressler nm. the long term effects of visible light on the eye. arch ophthalmol 1992;110:99–104. 9. hayashi k, hayashi h. visual function in patients with yellow tinted intraocular lenses compared with vision in patients with non-tinted intraocular lenses. br j ophthalmol 2006;90:1019–1023. 10. olson md, miller km. implanting a clear intraocular lens in one eye and a yellow lens in the other eye: a case series. am j ophthalmol 2006;141:957–958. 11. olson rj, werner l, mamalis n, cionni r. new intraocular lens technology. am j ophthalmol 2005;140:709–716. 12. cionni rj, tsai jh. color perception with acrysof natural and acrysof single-piece intraocular lenses under photopic and mesopic conditions. j cataract refract surg 2006;32:236–242. 13. brockmann c, schulz m, laube t. transmittance characteristics of ultraviolet and blue-light-filtering intraocular lenses. j cataract refract surg. 2008;34:1161– 1166. 14. applegate ra, sarver ej, khemsara v. are all aberrations equal? j refract surg 2002;18:556–562. 316 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 aspheric and blue light filtering iols; tzamalis et al 15. tzelikis pf, akaishi l, trindade fc, boteon je. spherical aberration and contrast sensitivity in eyes implanted with aspheric and spherical intraocular lenses: a comparative study. am j ophthalmol 2008;145:827–833. 16. pandita d, raj sm, vasavada va, vasavada va, kazi ns, vasavada ar. contrast sensitivity and glare disability after implantation of acrysof iq natural aspherical intraocular lens; prospective randomized masked clinical trial. j cataract refract surg 2007;33:603–610. 17. tzelikis pf, akaishi l, trindade fc, boteon je. ocular aberrations and contrast sensitivity after cataract surgery with acrysof iq intraocular lens implantation; clinical comparative study. j cataract refract surg 2007;33:1918– 1924. 18. rocha km, soriano es, chalita mr, yamada ac, bottós k, bottós j, et al. wavefront analysis and contrast sensitivity of aspheric and spherical intraocular lenses: a randomized prospective study. am j ophthalmol 2006;142:750–756. 19. kershner rm. retinal image contrast and functional visual performance with aspheric, silicone, and acrylic intraocular lenses; prospective evaluation. j cataract refract surg 2003;29:1684–1694. 20. denoyer a, le lez m-l, majzoub s, pisella p-j. quality of vision after cataract surgery after tecnis z9000 intraocular lens implantation; effect of contrast sensitivity and wavefront aberration improvements on the quality of daily vision. j cataract refract surg 2007;33:210–216. 21. belluccir, morselli s. optimizing higher-order aberrations with intraocular lens technology. curr opin ophthalmol 2007;18:67–73. 22. downie le, busija l, keller pr. blue-light filtering intraocular lenses (iols) for protecting macular health. cochrane database syst rev 2018;22:cd011977. 23. downes sm. ultraviolet or blue-filtering intraocular lenses: what is the evidence? eye 2016;30:215–221. 24. montés-micó r, alió jl, muñoz g, pérez-santonja jj, charman wn. postblink changes in total and corneal ocular aberrations. ophthalmology 2004;111:758–767. 25. kim sw, ahn h, kim ek, kim t-i. comparison of higher order aberrations in eyes with aspherical or spherical intraocular lenses. eye 2008;22:1493–1498. 26. caporossi a, martone g, casprini f, rapisarda l. prospective randomized study of clinical performance of 3 aspheric and 2 spherical intraocular lenses in 250 eyes. j refract surg 2007;23:639–648. 27. kurz s, krummenauer f, thieme h, dick hb. contrast sensitivity after implantation of a spherical versus an aspherical intraocular lens in biaxial microincision cataract surgery. j cataract refract surg 2007;33:393–400. 28. kasper t, buhren j, kohnen t. visual performance of aspherical and spherical intraocular lenses: intraindividual comparison of visual acuity, contrast sensitivity, and higher-order aberrations. j cataract refract surg 2006;32:2022–2029. 29. munoz g, albarran-diego c, montes-mico r, rodríguezgalietero a, alió jl. spherical aberration and contrast sensitivity after cataract surgery with the tecnis z9000 intraocular lens. j cataract refract surg 2006;32:1320– 1327. 30. kara-junior n, espindola rf, gomes ba, ventura b, smadja d, et al. effects of blue light-filtering intraocular lenses on the macula, contrast sensitivity, and color vision after a long-term follow-up. j cataract refract surg 2011;37:2115–2119. 31. greenstein vc, chiosi f, baker p, seiple w, holopigian k, et al. scotopic sensitivity and color vision with a bluelight-absorbing intraocular lens. j cataract refract surg 2007;33:667–672. 32. muftuoglu o, karel f, duman r. effect of a yellow intraocular lens on scotopic vision, glare disability, and blue color perception. j cataract refract surg 2007;33:658–666. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 317 original article ab externo imaging of human episcleral vessels using fiberoptic confocal laser endomicroscopy ken y. lin, md, phd; sameh mosaed, md gavin herbert eye institute, department of ophthalmology, university of california, irvine, usa orcid: ken y. lin: https://orcid.org/0000-0002-6467-7219 abstract purpose: there is a growing interest in targeting minimally invasive surgery devices to the aqueous outflow system to optimize treatment outcomes. however, methods to visualize functioning, large-caliber aqueous and episcleral veins in-vivo are lacking. this pilot study establishes an ex-vivo system to evaluate the use of a confocal laser microendoscope to noninvasively image episcleral vessels and quantify regional flow variation along the limbal circumference. methods: a fiber-optic confocal laser endomicroscopy (cle) system with lateral and axial resolution of 3.5 𝜇m and 15 𝜇m, respectively, was used on three porcine and four human eyes. diluted fluorescein (0.04%) was injected into eyes kept under constant infusion. the microprobe was applied to the sclera 1 mm behind the limbus to acquire real-time video. image acquisition was performed at 15-degree intervals along the limbal circumference to quantify regional flow variation in human eyes. results: vascular structures were visualized in whole human eyes without processing. schlemm’s canal was visualized only after a scleral flap was created. fluorescent signal intensity and vessel diameter variation were observed along the limbal circumference, with the inferior quadrant having a statistically higher fluorescein signal compared to the other quadrants in human eyes (𝑃 < 0.05). conclusion: this study demonstrates for the first time that the fiber-optic cle platform can visualize the episcleral vasculature with high resolution ex-vivo with minimal tissue manipulation. intravascular signal intensities and vessel diameters were acquired in real-time; such information can help select target areas for minimally invasive glaucoma surgery (migs) to achieve greater intraocular pressure reduction. keywords: aqueous outflow; laser imaging; minimally invasive glaucoma surgery j ophthalmic vis res 2019; 14 (3): 275–284 correspondence to: ken y. lin, md, phd. gavin herbert eye institute, department of ophthalmology, university of california, irvine. 850 health sciences road, irvine, ca 92697, usa. e-mail: linky@uci.edu received: 09-08-2018 accepted: 18-02-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i3.4783 introduction the last several years have witnessed a rapidly rising interest in both developing new and modifying current minimally invasive glaucoma surgery (migs) methods. this surge in momentum is spurred by the fact that the current standard glaucoma surgery methods, trabeculectomy, this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: lin ky, mosaed s. ab externo imaging of human episcleral vessels using fiberoptic confocal laser endomicroscopy. j ophthalmic vis res 2019;14:275–284 @ 2019 j  o  v r | published by knowledge e 275 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i3.4783&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr imaging of episcleral vessels in human eyes; lin and mosaed and tube shunt surgery, still have high complication rates, ranging from 27% in tube shunts to 74% in trabeculectomy.[1, 2] migs devices improve the outflow by bypassing or ablating the trabecular meshwork (tm) or creating new drainage routes into the suprachoroidal space.[3] clinical studies so far show that most migs procedures display improved safety profiles over traditional procedures. for instance, the most common complications are temporary hyphema and transient rise in intraocular pressure (iop) in the early postoperative period, occurring in 3–10% of trabectome[4] and 2% of istent patients.[5, 6] iop reduction in migs is generally not as dramatic as those in trabeculectomies and tube shunts. clinical studies show an average iop of 15.2 mmhg for phaco-trabectome at five years and 16.8 mmhg for the istent with phacoemulsification at five years.[4–6] since ablative type migs such as trabectome and kahook dual blade are capable of removing a large arc of tm, they can generally achieve lower iop endpoints compared to the bypass type, such as istent.[3] however, this comes at an expense of higher rates of transient postoperative iop rise and hyphema. furthermore, anatomic studies have implied that schlemm’s canal is highly segmented and discontinuous, and the location and number of collector channels may vary among individuals.[7, 8] bypassing an area of tm at great distance from the collector channels may thus not achieve the full potential of iop reduction. these lines of evidence all suggest that the real estate value of the tm is not the same across the entire 12 clock hours. in other words, knowing what segment of the tm to ablate or bypass may be crucial for achieving more targeted migs and potentially narrow the gap between the iop endpoints currently seen in migs and the theoretical limit of episcleral venous pressure.[9–11] one intuitive approach to target the highyield tm is to identify the collector channels via imaging.[9] several studies have successfully imaged outflow anatomy using 3d micro-computed tomography,[12] swept-source optical coherence tomography (ss-oct),[13] and endoscopic oct.[14] however, all these techniques require extensive tissue processing, which limits clinical applicability. here, we tested the hypothesis that a commercially available fiber-optic confocal laser microendoscope can visualize episcleral vessels and characterize their density and diameters after intracameral fluorescein injection in cadaveric human eyes with minimal tissue manipulation. the microendoscope is the world’s smallest microscope. it enables clinicians to perform real-time optical biopsy by visualizing the microvasculature in tissues as well as detecting abnormal cells. so far, it has been fda-approved for use in the detection of gastrointestinal, urological, and pulmonary pathologies, from barrett’s esophagus and colorectal lesions to lung nodules and urinary track lesions.[15–18] the first goal of the present study was to establish an ex-vivo system with cadaveric human eyes to determine if the microendoscope is capable of detecting episcleral vessels. the second goal was to determine if regional differences in episcleral vessel morphology can be detected and quantified across the 12 clock hours of the limbus. this pilot study aimed to pave the way for future studies to identify, preoperatively and noninvasively, areas of tm that migs procedures should access to yield the lowest postoperative iop possible. methods fiber-optic confocal laser microendoscope the imaging system, cellvizio (mauna kea technologies, paris, france), has been described previously.[15, 19] briefly, the system has three components [figure 1]: a fiber-optic microendoscope, a laser scanning unit, and a computer. a 488nm laser source is rastered by two mirrors on one end of a fiber bundle consisting of 30,000 optic fibers. the laser was sequentially directed into each fiber to reach the tissue. the fluorescent emission is collected in the same fiber that was used for excitation. the small core diameter of each fiber acts as a pinhole to give the probe optical sectioning capability. the microendoscope used in this study has a maximum depth of tissue penetration of 100 𝜇m. the microendoscope has a diameter of 1.5 mm and projects a field of view of 423 × 423 𝜇m. lateral and axial resolutions are 3.5 𝜇m and 15 𝜇m, respectively. this method had been previously compared to intravital fluorescent microscopy and histological staining in gastrointestinal tissues,[15] and all methods yielded statistically similar measurements of luminal diameters in the microvasculature. a postprocessing image frame or video is shown on a 276 j  o  v r volume 14, issue 3, july–september 2019 imaging of episcleral vessels in human eyes; lin and mosaed figure 1. the fiber-optic confocal laser microendoscope imaging system. the laser scanning unit emits light at 488 nm, which is fed into the flexible fiber-optic core. the fluorescent emission is collected in the same fiber that was used for illumination. the microendoscope has a diameter of 1.5 mm and projects a field of view of 423 × 423 𝜇m. lateral and axial resolutions are 3.5 𝜇m and 15 𝜇m, respectively. the operator maneuvers the tip of the fiber-optic microendoscope to image different areas. real-time image and video capture are activated via a foot pedal. monitor to allow surgeons to navigate along the limbus in real-time. fluorescent probe previous studies have injected fluorescein at 0.1– 0.15% into the anterior chamber for purposes of fluoroscopy.[20] much lower concentrations of fluorescein are likely sufficient to produce contrast when imaged with a confocal microendoscope. fluresstm contains 0.25% fluorescein and was diluted to 0.04% through serial 1:1 dilutions with balanced salt solution (bss). ex-vivo perfused porcine and human eye models three porcine eyes were used (alcon, irvine, california). the whole eye was first mounted onto a flat platform and secured with vacuum suction provided via a syringe [figure 2]. the iris plane was placed parallel to the ground and confirmed with axis assistant, an iphone-based application. a 360o limbal peritomy was performed using miniwestcott scissors, and the tenon’s membranes were bluntly dissected to expose the bare sclera. bss solution was placed at a 75 cmh2o position and delivered into the eye via a 26-gauge needle. a smaller-caliber 30-gauge needle was used to create a venting port at 90o away from the infusion port. we have found that the creation of a venting port helps maintain stable pressure throughout the infusion process, since supraphysiologic pressure may potentially cause schlemm’s canal to collapse. this bottle height and vent system were chosen as, together, they provide our ex-vivo perfused eye platform an iop of 25–30 mmhg. the iop was checked every three minutes by tonopen. a 26-gauge needle was inserted half-way between the infusion and venting ports to inject 0.2 cm3 of 0.04% fluorescein over five seconds once the tip of the needle reached a point 1 mm above the center of the anterior lens capsule with a bevel-up position to minimize the preferential delivery of fluorescein to a particular quadrant of the angle. four human eyes from two individuals were obtained from sightlife surgical (irvine, ca). the cadaveric human eyes were from a 78-year-old man and an 82-year old man, respectively, with no history of glaucoma or eye surgery. the eyes from the 82-year-old man were used for the initial study to determine the optimal image time window after fluorescein injection, while the eyes of the 78-yearold man were used for all subsequent studies. each j  o  v r volume 14, issue 3, july–september 2019 277 imaging of episcleral vessels in human eyes; lin and mosaed figure 2. eye perfusion system. balanced salt solution (bss) solution was delivered into the eye via a 26-gauge needle. intraocular pressure (iop) was maintained at between 25 and 30 mmhg. a smaller caliber 30-gauge needle was used to create a venting port at 90o away from the infusion port. a 26-gauge needle was inserted half-way between the infusion and venting ports to inject fluorescein. eye was mounted onto the perfusion platform as described earlier. the superior pole of the eye was identified based on the relative location of the optic nerve to the inferior oblique muscle insertion. both human eyes had only trace amounts of conjunctival and tenon’s tissues and no dissection or tissue manipulation was performed on the human eyes prior to mounting them. scleral flap construction to facilitate visualization of schlemm’s canal, which lies approximately 200 𝜇m underneath the sclera deep beyond the microendoscope’s 100 𝜇m penetration depth, a triangular limbal scleral flap was created. briefly, a no. 69 beaver blade was used to create a 3 × 3 mm triangular scleral flap with its base at the limbus. the blade was used to create two incisions at 50–75% of the scleral depth beginning at the posterior end of the surgical limbus extending toward the apex of the triangle. next, the no. 69 beaver blade was used in an almost horizontal manner across the apex of the triangle to lift the edge of the flap from the bottom of the grooves. non-toothed forceps were then used to lift the flap and create traction between the flap and scleral bed. the no. 69 blade was used in a horizontal position to cut across the scleral tissue. the dissection was carried anteriorly until the blue–gray zone of the limbus was visible. the microendoscope was then placed above the blue– gray zone to image schlemm’s canal. image acquisition was initiated immediately after fluorescein injection into the anterior chamber. determining optimal time for imaging after fluorescein injection the eye was mounted as previously described, and the microendoscope was gently pressed against the limbus at 180o away from the infusion port. video acquisition was initiated by the surgeon via a foot pedal after the completion of the fluorescein injection. the microendoscope was held stationary by the surgeon to maintain the same view and the increase in intraluminal fluorescence was observed in real-time on the monitor for eight minutes. the same protocol was used for both porcine and human eyes. image analysis was performed using imagecell (mauna kea technologies, paris, france). a circular region of interest (roi) was manually marked to match the field of view of the microendoscope. the total signal intensity within the roi at each frame was calculated and plotted against time. episcleral vessel segmentation to quantify vessel diameter and fluorescent signal along 360o of the limbus, we first marked the limbus with a surgical blue marker placed at 15o intervals [figure 2]. still images at each mark were acquired at five minutes for porcine eyes and seven minutes for human eyes. fluorescent intensity was expressed as fluorescent arbitrary units (au). a vessel segmentation algorithm was applied to each frame to outline the border of the lumen and compute the vessel diameter. this method had been previously described and validated.[21, 22] 278 j  o  v r volume 14, issue 3, july–september 2019 imaging of episcleral vessels in human eyes; lin and mosaed figure 3. rise in fluorescence after fluorescein injection into the anterior chamber in porcine and human eyes. the units are fluorescent arbitrary units (au). the plot shows that the optimal time to capture image is five minutes after injection in porcine eyes and seven minutes after injection in human eyes. roi, region of interest figure 4. visualization of episcleral vessels (a) and schlemm’s canal (b) with minimal tissue manipulation. episcleral vessels are seen emanating from deeper, larger-caliber vascular structures. the white bar represents a length of 50 𝜇m. visualization of schlemm’s canal (white arrow) is only possible after a scleral flap is introduced because the microendoscope is limited to a depth of 100 micron in scleral tissue. the white bar in (b) represents a length of 120 𝜇m. briefly, vessels were modeled as tubular structures with the intraluminal signal intensity displaying a gaussian distribution with the signal maxima denoting the luminal center, or “ridge.” given that vessel diameter can have local variations along the direction of the lumen, the ridges were detected at different scales, the medium response was computed, and the maxima of the responses through the scales were recorded. the scale at which a maximum ridge was detected led to an estimate of vessel radius. the segmentation algorithm thus generated several sets of connected points, with each set representing a vessel midline and each point within a set carrying associated diameter information. these points were denoted and overlaid onto the original image to provide a graphical representation of where the vessel borders were. a data table containing information on vessel diameters could then be exported to excel for statistical analysis. statistical analysis all values in this study are expressed as mean +/– standard error of the mean. no statistical analysis was performed on times of signal increase after fluorescein injection in three porcine and two human eyes as these were observational experiments aimed at determining the optimal timeframes for data collection in subsequent experiments. for j  o  v r volume 14, issue 3, july–september 2019 279 imaging of episcleral vessels in human eyes; lin and mosaed figure 5. distribution of fluorescence signal along the limbal perimeter. representative frames from individual quadrants were chosen to highlight the differences in fluorescence signals along the limbus (a). the differences can be quantified using a vessel segmentation algorithm, which automatically detects the vessel border and midline (b) and quantifies vessel diameter and signal intensity in the chosen region of interest. figure 6. episcleral vessel diameter distribution along the limbal perimeter in human eyes. larger-diameter episcleral vessels appear to group in clusters that span 40–50o. comparison of signal intensities between the inferior quadrants vs. all other quadrants, the signals from the inferior quadrants, defined as the areas from 225o to 315o from two human eyes were compared with signals from all other quadrants. a two-tailed t-test was used to determine statistical significance, where a p < 0.05 denotes significance. results optimal time for detection after fluorescein injection porcine eyes began to reach the plateau phase of fluorescent signal intensity five minutes after fluorescein injection. for human eyes, the peak 280 j  o  v r volume 14, issue 3, july–september 2019 imaging of episcleral vessels in human eyes; lin and mosaed figure 7. fluorescent signal intensity distribution along the limbal perimeter in human eyes. (a) signal intensity appears to concentrate more in the inferior quadrant in both human eyes. (b) the inferior quadrant has a statistically higher amount of fluorescence when compared to all other quadrants combined. fluorescence was measured in arbitrary units (au). roi, region of interest. time occurred at seven minutes after fluorescein injection [figure 3]. visualization of episcleral vessels and schlemm’s canal episcleral vessels with diameters ranging from 10–50 𝜇m were seen emanating into the scleral surface [figure 4(a)]. the images were obtained from human eyes without tissue processing. the microendoscope did not visualize schlemm’s canal ab externo because its tissue penetration is less than 100 𝜇m. construction of a scleral flap can assist in visualizing schlemm’s canal, which was confirmed by the dimensions of the tubular structure (75–100 𝜇m) and its peri-limbal location [figure 4(b)]. however, we were able to maintain the view to schlemm’s canal for only fewer than 10 seconds after fluorescein injection, likely because, as the eye was actively perfused, fluorescein was egressing the intrascleral vessels along the cut edges of the scleral flap. differences in vessel morphology along the limbus in human eyes regional variation in fluorescein intensity along the limbus could be qualitatively appreciated [figure 5(a)]. a vessel segmentation algorithm was applied to individual frames acquired at 15o intervals along the limbus. an example of a composite image is shown where the vessel border is outlined in blue and the vessel midline is marked in red [figure 5(b)]. the distribution of vessel diameters is nonuniform along the limbus in human eyes, with larger-diameter episcleral vessels seemingly grouped in clusters that span 40–50o [figure 6]. fluorescent signal intensity appears to concentrate more in the inferior quadrant in both human eyes [figure 7(a)]. in fact, when compared with the other quadrants combined, the inferior quadrant has a statistically higher amount of fluorescence (1742 +/– 271 au vs. 1300 +/– 316 au, p < 0.05) [figure 7(b)]. discussion the salient findings of this study are that: (1) a confocal laser microendoscope can visualize episcleral vessels in cadaveric human eyes with minimal tissue manipulation, (2) in our ex-vivo system involving a perfused eye, the optimal time to image episcleral vessels is seven minutes after fluorescein injection into the anterior chamber, and (3) episcleral vessel diameter and density can be acquired in real-time and show that the inferior quadrants of the two human eyes in this study have statistically greater amount of fluorescence compared to the other quadrants. this study showed that the microendoscope was able to image surface episcleral vessels. the flexibility of the microendoscope catheter also enables the operator to easily rotate the endoscope to image other areas of the limbus. as discussed later, j  o  v r volume 14, issue 3, july–september 2019 281 imaging of episcleral vessels in human eyes; lin and mosaed the ability to image episcleral vessels noninvasively may be of great diagnostic value. one factor that potentially limits the extent of iop reduction following migs is the lack of knowledge on which portion of the tm to ablate or bypass. the idea that location may play a crucial role in determining post-operative iop has spurred much interest in noninvasive imaging of the conventional outflow pathway.[9] one group has recently visualized the angle structure using swept source oct;[13] another group has visualized the intrascleral plexus using micro-ct. micro-ct has revealed, in great detail, the complexity of intraand episcleral vessels;[12] however, this imaging modality is limited to ex-vivo settings. while swept source oct has great clinical translatability, the authors admitted that image acquisition of the entire 360o may require up to several seconds and can be confounded by motion artifacts.[13] in addition, studies in mice[23] and humans[8] have shown that schlemm’s canal can partially collapse under increased iop. this can make consistent identification of the angle structures more challenging. lastly, oct provides ample anatomical data, but functional correlates to guide the choice of locations for migs are currently still lacking. a contrast-enhanced technique may be needed to help highlight the lumen of the outflow pathway. an intraoperative technique has recently been proposed to locate larger-caliber aqueous veins by observing episcleral venous fluid waves.[24] this technique is obviously limited to intraoperative use and is a largely qualitative and subjective method. however, it may be of value in cases where obvious sectoral differences in flow along the limbus exist. the confocal laser microendoscope in this study uses fluorescein to provide contrast. because the intracameral fluorescein would follow and thereby outline the functioning aqueous veins and episcleral vessels, the diameter and density of the episcleral vessels serve as a surrogate functional marker for flow associated with the limbal area imaged by the microendoscope. this pilot study shows that a vessel segmentation algorithm can quantify episcleral vessel morphology; furthermore, vessel diameter and the amount of flow both show regional variation, and that flow is more concentrated in the inferior quadrant in the two human eyes studied. finally, the flexibility of the microendoscope and the foot pedal also enhance the operator’s maneuverability. both of these features augment the clinical applicability of the microendoscope, as image acquisition can be performed in an ambulatory outpatient setting. there were two recent studies showing more collector channels in nasal and inferior quadrants.[25, 26] this is not necessarily in disagreement with our observations in this study. the study by li et al compares nasal vs. temporal quadrants, but does not compare other quadrants.[25] as such, their findings were not intrinsically incompatible with our findings. in addition, our observations were based on one pair of eyes from the same individual, and greater numbers are needed to determine if this is generalizable to a larger population. moreover, enhanced depth oct in the study by li et al nicely delineated the anatomy of the collector channel, but this may not imply that these open collector channels necessarily experience flow through them. there may be differences between contrast based imaging vs. anatomy based imaging, as the former visualizes actual flow and is thus more functional, while the latter reflects anatomy. the study by cha and colleagues did show that nasal and inferior quadrants contain the most collector channels. in summary, we do not believe that our results are inherently incompatible with these published results due to (1) the fact that our study lacked enough statistical power to support such a statement and that (2) functional vs. anatomic imaging may lead to different conclusions, as one looks for open and functioning collector channels while the other looks at open collector channels—this is mostly hypothetical at this point and would be an interesting topic for a future study. although fluorescein had been shown to be safe for intraocular use in human eyes,[20] future studies can potentially use indocyanine green to provide the source of contrast. a laser scanning unit that excites at the peak absorption of 600 nm of indocyanine is currently being developed to facilitate this goal. the current investigation is a feasibility study performed on a small number of cadaveric eyes. another limitation of the study is that fluorescein extravasation restricts the time window of image acquisition in eyes ex-vivo. additional studies are needed to establish if a greater amount of flow in the inferior quadrant, for instance, is specific to an individual or is generalizable to the population. future animal studies are also needed 282 j  o  v r volume 14, issue 3, july–september 2019 imaging of episcleral vessels in human eyes; lin and mosaed to determine if similar signal to noise ratios and resolutions still hold in live eyes. although not yet clinically applicable in its current form, contrastenhanced confocal laser microendoscopy may be one viable method to image intraand episcleral vessels and ultimately help surgeons target migs to areas of higher scleral flow. in other words, this is the first step toward the ultimate goal of clinical integration. additional optical modifications are already underway to refine the method presented in this pilot study and to ultimately make it more clinically applicable. financial support and sponsorship american society of cataract and refractive surgery (ascrs) foundation grants, 2014. conflicts of interest there are no conflicts of interest. references 1. quigley ha, broman at. the number of people with glaucoma worldwide in 2010 and 2020. br j ophthalmol 2006;90:262–267. 2. gedde sj, herndon lw, brandt jd, budenz dl, feuer wj, schiffman jc, et al. postoperative complications in the tube versus trabeculectomy (tvt) study during five years of follow-up. am j ophthalmol 2012;153:804–814. 3. kaplowitz k, schuman js, loewen na. techniques and outcomes of minimally invasive trabecular ablation and bypass surgery. br j ophthalmol 2014;98:579–585. 4. mosaed s, dustin l, minckler ds. comparative outcomes between newer and older surgeries for glaucoma. trans am ophthalmol soc 2009;107:127–133. 5. arriola-villalobos p, martínez-de-la-casa jm, díaz-valle d, fernández-pérez c, garcía-sánchez j, garcía-feijoó j. combined istent trabecular micro-bypass stent implantation and phacoemulsification for coexistent open-angle glaucoma and cataract: a long-term study. br j ophthalmol 2012;96:645–649. 6. voskanyan l, garcía-feijoó j, belda ji, fea a, jünemann a, baudouin c, et al. prospective, unmasked evaluation of the istent(r) inject system for open-angle glaucoma: synergy trial. adv ther 2014;31:189–201. 7. bentley md, hann cr, fautsch mp. anatomical variation of human collector channel orifices. invest ophthalmol vis sci 2016;57:1153–1159. 8. kagemann l, wollstein g, ishikawa h, nadler z, sigal ia, folio ls, et al. visualization of the conventional outflow pathway in the living human eye. ophthalmology 2012;119:1563–1568. 9. loewen na, schuman js. there has to be a better way: evolution of internal filtration glaucoma surgeries. br j ophthalmol 2013;97:1228–1229. 10. brubaker rf. determination of episcleral venous pressure in the eye. a comparison of three methods. arch ophthalmol 1967;77:110–114. 11. sit aj, mclaren jw. measurement of episcleral venous pressure. exp eye res 2011;93:291–298. 12. hann cr, bentley md, vercnocke a, ritman el, fautsch mp. imaging the aqueous humor outflow pathway in human eyes by three-dimensional micro-computed tomography (3d micro-ct). exp eye res 2011;92:104–111. 13. mckee h, ye c, yu m, liu s, lam ds, leung ck. anterior chamber angle imaging with swept-source optical coherence tomography: detecting the scleral spur, schwalbe’s line, and schlemm’s canal. j glaucoma 2013;22:468– 472. 14. ren j, gille hk, wu j, yang c. ex vivo optical coherence tomography imaging of collector channels with a scanning endoscopic probe. invest ophthalmol vis sci 2011;52:3921–3925. 15. lin ky, maricevich m, bardeesy n, weissleder r, mahmood u. in vivo quantitative microvasculature phenotype imaging of healthy and malignant tissues using a fiber-optic confocal laser microprobe. transl oncol 2008;1:84–94. 16. chang tc, liu jj, liao jc. probe-based confocal laser endomicroscopy of the urinary tract: the technique. j vis exp 2013;71:e4409. 17. kuiper t, van den broek fj, van eeden s, wallace mb, buchner am, meining a, et al. new classification for probe-based confocal laser endomicroscopy in the colon. endoscopy 2011;43:1076–1081. 18. sonn ga, mach ke, jensen k, hsiung pl, jones sn, contag ch, et al. fibered confocal microscopy of bladder tumors: an ex vivo study. j endourol 2009;23:197–201. 19. laemmel e, genet m, le goualher g, perchant a, le gargasson jf, vicaut e. fibered confocal fluorescence microscopy (cell-vizio) facilitates extended imaging in the field of microcirculation. a comparison with intravital microscopy. j vasc res 2004;41:400–411. 20. benedikt, o. [demonstration of aqueous outflow patterns of normal and glaucomatous human eyes through the injection of fluorescein solution in the anterior chamber (author’s transl)]. albrecht von graefes arch klin exp ophthalmol 1976;199:45–67. 21. smistad e, elster ac, lindseth f. gpu accelerated segmentation and centerline extraction of tubular structures from medical images. int j comput assist radiol surg 2014;9:561–575. 22. krissian k. model-based detection of tubular structures in 3d images. comput vis image underst 2000;80:130–171. 23. li g, farsiu s, chiu sj, gonzalez p, lütjen-drecoll e, overby dr, et al. pilocarpine-induced dilation of schlemm’s canal and prevention of lumen collapse at elevated intraocular pressures in living mice visualized by oct. invest ophthalmol vis sci 2014;55:3737–3746. 24. fellman rl, grover ds. episcleral venous fluid wave: intraoperative evidence for patency of the conventional outflow system. j glaucoma 2014;23:347–350. 25. li p, butt a, chien jl, ghassibi mp, furlanetto rl, netto cf, et al. characteristics and variations of in vivo j  o  v r volume 14, issue 3, july–september 2019 283 imaging of episcleral vessels in human eyes; lin and mosaed schlemm’s canal and collector channel microstructures in enhanced-depth imaging optical coherence tomography. br j ophthalmol 2017;101:808–813. 26. cha ed, xu j, gong l, gong h. variations in active outflow along the trabecular outflow pathway. exp eye res 2016;146:354–360. 284 j  o  v r volume 14, issue 3, july–september 2019 original article long-term outcomes of treat and extend regimen of anti-vascular endothelial growth factor in neovascular age-related macular degeneration andy lee, md; pooja g garg, md; alice t lyon, md; rukhsana mirza, md; manjot k gill, md department of ophthalmology, northwestern university feinberg school of medicine, chicago, il, usa orcid: andy lee: https://orcid.org/0000-0001-9965-6701 manjot k gill: https://orcid.org/0000-0002-6933-9331 abstract purpose: this study describes the long-term visual and anatomic outcomes of antivascular endothelial growth factor (vegf) treatment using a treat and extend dosing regimen. methods: this cross-sectional cohort study consisted of 224 treatment-naïve eyes with neovascular age-related macular degeneration (nv-amd) from 202 patients that were treated with anti-vegf agents bevacizumab, ranibizumab, and aflibercept using a treat and extend (tae) regimen by four physician investigators in a large urban referral center from 2008 to 2015. subjects were evaluated for visual acuity, injection frequency, and optical coherence tomography (oct). results: over a seven-year follow-up period (mean 3.4 years), an average 20.2 ± 14.7 injections were administered with 8.4 injections in the first year and 5.5 injections by the seventh year of remaining eyes undergoing treatment. visual acuity was 0.70 logmar (20/100 snellen) at the first visit and 0.67 logmar (20/93 snellen) at the final visit, with 74% of eyes maintaining or gaining more than 2 lines of vision. long-term, 45.1% of eyes achieved 20/50 or better, while 27.1% were 20/200 or worse. of the treated patients, 61.2% received monotherapy with no difference in visual acuity outcomes or number of injections between the agents used. oct analysis showed decreased fluid from initial to final follow-up visit: 70.1–15.6% with sub-retinal fluid (srf) and 47.3–18.8% with intraretinal fluid (irf) with no difference between the agents were used. conclusion: this study demonstrates that most patients (74%) improve or maintain visual acuity long-term using a tae model with a significant portion (45.1%) achieving 20/50 or better visual acuity with sustained treatment. keywords: age-related macular degeneration (amd); intraocular drugs; visual acuity j ophthalmic vis res 2020; 15 (3): 331–340 correspondence to: manjot k gill, md. department of ophthalmology, feinberg school of medicine, northwestern university, 645 north michigan ave., suite 440. chicago, il 60611, usa. email: mgill@nm.org received: 09-10-2019 accepted: 21-03-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7452 introduction neovascular age-related macular degeneration (nv-amd) is the leading cause of vision loss in this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: lee a, garg pg, lyon at, mirza r, gill mk. long-term outcomes of treat and extend regimen of anti-vascular endothelial growth factor in neovascular age-related macular degeneration. j ophthalmic vis res 2020;15:331–340. © 2020 journal of ophthalmic and vision research | published by knowledge e 331 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7452&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr treat and extend anti-vegf regimens; lee et al individuals aged 50 years or older. over the past decade, treatment has evolved to control subfoveal choroidal neovascularization (cnv) growth with intravitreal drug delivery directed toward inhibition of vascular endothelial growth factor (vegf). specifically, the marina and anchor studies were amongst the first to demonstrate the effects of targeting angiogenesis by blocking vegf-a with ranibizumab, a recombinant humanized monoclonal antibody fragment (fab). these studies clearly showed that monthly treatment was beneficial in preventing vision loss and allowing for visual gain compared to sham and photodynamic therapy (pdt), respectively, over a two-year period.[1–3] the view 1 and 2 trials demonstrated the efficacy of aflibercept, a soluble decoy receptor fusion protein with a higher affinity to vegf-a and vegf-b as well as placental growth factor (pigf) with decreased treatment burden allowing improvement or maintenance of vision over two years.[4, 5] however, monthly or bimonthly injections along with monthly follow-up is challenging for patients to maintain in clinical practice. due to treatment burden, pro re nata (prn) treatment was studied to examine the effects of monthly follow-up with an individualized retreatment regimen. catt and ivan trials demonstrated equivalent efficacy between ranibizumab versus bevacizumab; however, there was an overall less favorable outcome in the prn arms compared to monthly dosing with respect to final visual acuity.[6–8] in 2009, freund and colleagues were the first to describe the “treat-and-extend (tae)” regimen with treatment of type 3 cnv lesions in a small cohort over three years.[9] with use of ranibizumab and/or bevacizumab, they showed an overall improvement of vision from 20/80 to 20/40 with an average of 6–7 injections per year. since then, several other retrospective studies have proposed using a tae approach as an alternate to monthly or prn dosing to reduce treatment burden while maintaining or improving visual outcome.[10–12] despite the multitude of trials demonstrating the safety and efficacy of anti-vegf drug therapy, there have been limited studies describing the long-term follow-up of anti-vegf treatment. seven-up and catt were among the first studies to describe the long-term outcomes with either monthly or prn dosing.[13, 14] of the tae trials, the longest to date was by mrejen et al over a six-year period with 185 patients and a retention rate of 62.9%.[12] their study showed an improvement or maintenance in visual acuity with an average of 8.3 injections per year. they demonstrated that a greater number of injections was an independent predictor of better visual outcome. other studies have compared tae to prn revealing a worse visual outcome with a smaller number of injections with the prn group.[15, 16] specifically, calvo et al showed that over a three-year follow-up period, 42.4% in the tae dosing group versus 24.1% in the prn dosing group gained at least three lines of vision. over the study period, the tae group was treated with an average of 20.31 injections, while the prn group was treated with an average of 18.41.[15] tae is a practical option to reducing the number of injections and office visits as compared to a monthly and prn regimen. our current study reports a seven-year followup period of the long-term outcomes as measured by visual acuity and oct imaging of the treatmentnaïve nv-amd patients using a tae model. methods the institutional review board of northwestern university feinberg school of medicine approved this retrospective cohort study at a large urban tertiary medical center. study data was obtained through the northwestern medicine enterprise data warehouse (nmedw) and through direct chart review. our study population consisted of treatment-naïve patients of four retina specialists receiving intravitreal anti-vegf with the diagnosis of neovascular amd (icd-9 code 362.52) from march 2008 to october 2015. other inclusion criteria were: age more than 50 years, visual acuity of hand motion (hm) or better at baseline, and a follow-up duration of at least one year. all four physicians used a tae protocol consisting of initial intensive monthly anti-vegf injections until there was no evidence of exudation on oct followed by extension of treatment interval by two weeks up until 12 weeks. if there was a mild recurrence of subretinal fluid (srf), intraretinal fluid (irf), or a new macular hemorrhage, then the interval was reduced by one–two weeks until the macula was dry or hemorrhage stabilized. in the case of more severe recurrences, monthly treatment was reinitiated.[10] the interval was not increased 332 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 treat and extend anti-vegf regimens; lee et al in the presence of persistent but stable fluid, however, if a pigment epithelial detachment (ped) persisted in the absence of srf or irf, then the interval was extended. patient demographics, type of anti-vegf agent used (bevacizumab, ranibizumab, or aflibercept), number and frequency of injections, best-corrected visual acuities (bcva), and intraocular pressure (iop) were obtained at each office visit from the edw database. in this article, single-agent monotherapy is defined as treatment with only one type of anti-vegf agent over the entire treatment course, while multi-agent therapy is defined as treatment with multiple types of anti-vegf agents but not during the same office visit. oct images of the affected eye were obtained from direct chart review at baseline and at the last follow-up visit. oct images of each affected eye at baseline and the last follow-up visit were directly reviewed for the presence or absence of srf and irf. bcva and iop were extracted for each affected eye at the start of treatment and at time-points of six months, one year, and every year thereafter until the last office visit. measurements from the office visit whose date was closest to the specific time-point were selected but was required to be within three months of the specific timepoint to be included. visual acuity values were converted from snellen to logmar to allow the paired t-test comparisons. visual acuity values were also categorized as 20/50 or better, between 20/50 and 20/200, and 20/200 or worse for further interpretation. the number and types of injections were also tallied for each affected eye. subsequent numerical and statistical analyses were performed in microsoft excel 2016 (microsoft corporation, redmond, wa) and graphpad prism 7 (graphpad software, san diego, ca). the paired student t-test was performed to compare visual acuities and intraocular pressure at the first and last office visits. pearson’s correlation coefficient was calculated to test for the linearity of changes in visual acuity over time. statistical analysis was also performed for visual acuity categories using contingency tables with fisher’s exact test and the oct data was analyzed with mcnemar’s test. subgroup analysis was conducted on eyes treated with single-agent monotherapy to examine the visual acuity and oct outcomes for each drug. results in total, 224 treatment-naïve eyes of 202 patients were analyzed with an average follow-up period of 3.4 years (range, 1.0–7.6 years). the majority (80%) of patients in this study were between 70 and 89 years of age at initial presentation. of the 224 eyes, 137 (61.2%) were treated with only one type of anti-vegf agent: ranibizumab (71, 51.8%), aflibercept (47, 34.3%), or bevacizumab (19, 13.9%). visual acuity at baseline was 20/100 in snellen and did not differ significantly between the treatment groups (f = 1.33, p = 0.27). most eyes had either srf (70%) or irf (47%) present on oct imaging at baseline (table 1). the average visual acuity at baseline of 0.698 logmar (20/100 snellen equivalent) remained stable at the final follow-up visit at 0.666 logmar (20/93 snellen) (p = 0.30; figure 1a). a significant portion of eyes (40%) maintained their visual acuities within two snellen lines, while 34% of eyes gained more than two lines and 25% lost more than two lines. the percentage of eyes with visual acuities of 20/50 or better increased significantly from 34.8% at baseline to 45.1% by the last followup visit (fischer’s exact test, p = 0.037; figure 1b). there was no significant difference between baseline iop (14.8 ± 3.3) and iop at the last followup visit (15.2 ± 3.6) (p = 0.052). visual acuities of patients receiving ongoing injections recorded at six months, one year, and annually thereafter showed an overall steady gain that peaks near the end of the third year, with slight reductions thereafter (figure 2). the smaller sample size in these groups impedes any individual subgroup analysis of the treatment type. the baseline visual acuity at initial presentation was tested against the change in visual acuity along with demographic factors of sex and age as possible predictors of patient’s response to treatment. baseline visual acuities exhibited a weak linear correlation with the cumulative change in visual acuities at all time-points (pearson’s coefficient r averaged over timepoints = –0.45, p < 0.05). age was not found to be linearly correlated with the change in visual acuity at the last follow-up (pearson’s r = 0.13, p = 0.33). similarly, patients’ sex and also race (caucasian vs non-caucasian) were not correlated with the treatment response (t = – 1.13, p = 0.26 and t = –0.6, p = 0.55, respectively). journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 333 treat and extend anti-vegf regimens; lee et al table 1. patient baseline characteristics monotherapy (n = 137) multi-drug therapy (n = 87) total (n = 224) bevacizumab (n = 19) ranibizumab (n = 71) aflibercept (n = 47) eye – no (%) od 7(37) 33 (47) 21 (45) 48 (55) 109 (49) os 12(63) 38 (54) 26 (55) 39 (45) 115 (51) gender – no (%) f 16(84) 49 (69) 38 (81) 58 (67) 161 (72) m 3(16) 22 (31) 9 (19) 29 (33) 63 (28) race – no (%) caucasian 12(63) 52 (73) 40 (85) 72 (83) 176 (79) african american 2(11) 4 (6) 0 5 (6) 11 (5) hispanic 3(16) 1 (1) 0 2 (2) 6 (3) other/unknown 2(11) 14 (20) 7 (15) 8 (9) 31 (14) age mean 78.1 ± 12.6 82.1 ± 6.5 83.3 ± 6.4 78.2 ± 8.7 80.5 ± 8.3 50–69 -no. (%) 4 (21) 2 (3) 2 (4) 13 (15) 21 (9) 70–89 -no. (%) 12 (63) 62 (87) 40 (85) 66 (76) 180 (80) 90+ -no. (%) 3 (16) 7 (10) 5 (11) 8 (9) 23 (10) visual acuity (snellen) mean 20/94 20/124 20/91 20/89 20/100 20/50 or better no. (%) 7 (37) 19 (27) 20 (43) 32 (37) 78 (35) between 20/50 and 20/200 no. (%) 7 (37) 29 (41) 17 (36) 33 (38) 86 (38) worse than 20/200 no. (%) 5 (26) 23 (32) 10 (21) 22 (25) 60 (27) oct findings srf-no. (%) 14 (74) 42 (59) 30 (64) 73 (84) 159 (71) irf-no. (%) 8 (42) 43 (61) 27 (57) 28 (32) 106 (47) oct, optical coherence tomography; srf, subretinal fluid; irf, intraretinal fluid over the course of the study, 224 eyes received an average of 20.3 ± 14.7 injections (range, 2–95) during a mean of 3.4 years of follow-up (range, 1.0–7.6), for a total of 4,543 injections. of the 224 eyes, 137 (61.2%) were treated with a single agent for the duration of their treatment [71 (51.8%) with ranibizumab, 47 (34.3%) with aflibercept, and 19 (13.9%) with bevacizumab] while 87 (38.8%) eyes were treated with more than one agent type. for those patients receiving single-agent therapy, the number of total injections did not differ significantly based on the agent used (14.8 for bevacizumab vs 14.7 for ranibizumab vs 13.0 for aflibercept, p = 0.54) over the course of treatment, although the average duration of treatment in weeks varied significantly (35.5 for bevacizumab vs 28.6 for ranibizumab vs 21.7 for aflibercept, p = 0.014). the number of injections that patients received differed over time (figure 3). eyes in the first year of treatment received an average of 8.4 injections that decreased on average by 0.3 injections per year to 5.5 injections by the seventh year (r2 = 0.68). moreover, eyes that gained more than two lines received significantly more injections with an average number of 24.1 ± 15.3 injections, while eyes that maintained within two lines or lost more 334 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 treat and extend anti-vegf regimens; lee et al table 2. oct* characteristics of single-agent vs multi-agent anti-vegf therapy anti-vegf drug for single-agent monotherapy # srf + pre-treatment # srf + post-treatment p-value # irf + pre-treatment # irf + post-treatment p-value bevacizumab (n = 19) 14 2 p < 0.01 8 2 p = 0.077 ranibizumab (n = 71) 42 8 p < 0.001 43 16 p < 0.001 aflibercept (n = 47) 30 1 p < 0.001 27 10 p < 0.001 multi-agent therapy (n = 87) 73 24 p < 0.001 28 14 p < 0.001 total cohort (n = 224) 159 35 p < 0.001 106 42 p < 0.001 oct, optical coherence tomography; srf, subretinal fluid; irf, intraretinal fluid; vegf, vascular endothelial growth factor figure 1. comparison of mean visual acuity between baseline and last visit. figure 1a shows boxplot comparisons between baseline and final visual acuities. figure 1b shows the percentage of patients in each visual acuity category by the last follow-up visit compared to baseline. than two lines received 18.1 ± 13.3 injections and 18.6 ± 15.2 injections, respectively (p < 0.05). it was also found that eyes with visual acuities of 20/200 or better at last follow-up tended to receive treatment over a longer period (average 3.1 years vs 2.2 years, p < 0.01) and received a greater number of injections (average 23 vs 14, p < 0.001) compared to eyes with visual acuities of 20/200 or worse at last follow-up. in addition to visual acuity analysis, oct images were compared at baseline and at the last followup visit. out of the 224 eyes, 159 eyes had srf at baseline compared with 35 eyes by the date of last follow-up (p < 0.0001; figure 4). similarly, 106 eyes had irf at baseline compared with 42 eyes by the date of last follow-up (p < 0.0001). when aggregated, 208 eyes had some type of fluid at baseline, compared with 69 eyes by the date of last follow-up (p <0.0001). subset analysis of eyes receiving single-agent anti-vegf therapy did not reveal any differences in oct outcomes and mirrored the trends seen in the overall group. all treatment groups showed a statistically significant decrease in the presence of fluid over the course of the treatment except for the presence of irf in the bevacizumab group (table 2), although this may be attributed to the smaller sample size of this subgroup (n = 19). journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 335 treat and extend anti-vegf regimens; lee et al figure 2. cumulative gain in logmar over treatment course (mean ± se). visual acuities recorded during patients’ treatment visits were compared with the visual acuity at baseline. only those patients actively continuing to receive injections were included in this figure; patients who discontinued injections after a specific time were not included in subsequent time points in this graph. figure 3. number of injections over time. the figure shows the average annual number of injections administered over time. 336 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 treat and extend anti-vegf regimens; lee et al figure 4. comparison of oct finding between baseline and last visit. the figure shows the number of eyes with the presence of srf and irf preand post-treatment. discussion we report up to a seven-year (average, 3.4 years) follow-up period of treatment-naïve nvamd patients undergoing anti-vegf therapy using a tae model. all four investigators in our study used the consensus recommendations of the tae regimen following monthly injections until the macula was dry based on oct, then extending the interval between treatments by two weeks to a maximum of twelve weeks. if fluid recurred, then the interval would be shortened. using this approach, the patients’ treatment is individually tailored to its response. the tae regimen offers an alternate and preferred treatment practice due to reduced burden for office visits compared to monthly and oct-guided dosing regimens. prior to the development of tae regimen, longterm outcomes of monthly and prn anti-vegf treatments have been described in several other studies, most notably in the seven-up and 5-year catt study.[13, 14] the seven-up study reported on ranibizumab-treated patients after an average of 7.3 years from the time of first injection with patients receiving monthly injections in the first two years followed by prn treatment over the subsequent years. patients received an average of 6.8 total injections over a mean 3.4 year interval. the subgroup that received more frequent injections yielded a better result in visual acuity gains. in their study, 23% attained a visual acuity of 20/40 or better whereas 37% were 20/200 or worse. there was an overall mean decline of 8.2 letters over the course of follow-up.[14] in the five-year catt study, patients were followed an average of 5.5 years from the time of first injection. ranibizumabor bevacizumabtreated patients were stratified into monthly or prn arms in the first year with the monthly arm stratified again into monthly or prn treatment in the second year. in the subsequent three years, a variety of treatment drug combinations and regimens were used with patients receiving an average of 15.4 injections over three years. in their study, 49.6% attained visual acuity of 20/40 or better whereas 20% were 20/200 or worse. there was a mean overall decline of 3.3 letters.[13] journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 337 treat and extend anti-vegf regimens; lee et al since the initial description of the tae regimen, several studies have reproduced results favoring maintenance or improvement of bcva similar to monthly dosing while reducing injection frequency and treatment burden. our study is comparable to others that describe outcomes using a tae regimen.[18–23] similar to our study, bcva in these studies was either maintained or improved throughout treatment with 30–34% of patients on average improving by 2–3 lines and 94–97.5% patients losing less than 2–3 lines. the number of injections in the first year averaged a total of 7.6–8.6, which is comparable to our mean of 8.4. most of these studies, however, only reported on outcomes over a two-year follow-up while our study looks at outcomes over a longer treatment period. of note, in our study, the average number of injections decreased to 5.5 during the seventh year while maintaining bcva. a study by mrejen et al with a longer follow-up period of six years (average 3.5 years) compared to the aforementioned studies[18–23] demonstrated similar favorable results.[10–12] in their study, bcva peaked at 18 months with a steady decline afterward. on average, patients received 28.5 injections over the study period with 8.3 injections per year and a mean interval of 6.6 weeks between injections. the majority of their patients (64.3%) were treated with injection of a single agent of which 59% of them were ranibizumab alone, 4.3% were bevacizumab alone, and 1% was aflibercept alone. their multivariant analysis showed a greater number of injections as an independent predictor of better visual outcomes. on the other hand, older age of starting injections, hypertension, and anticoagulation were correlated with poorer visual outcomes. in the current study, we utilized a tae approach in which patients were followed for an average of 3.4 years (range, 1.0–7.6) receiving an injection regimen with an average of 20.3 ± 14.7 total injections with 8.4 injections in the first year and 5.5 injections by the seventh year of followup. the majority of patients (61.1%) were treated with a single anti-vegf agent for the duration of their treatment, of which 51.8% were ranibizumab alone, 34.3% were aflibercept alone, and 13.9% were bevacizumab alone. having more singleagent data analysis allows us to validate similarities of bcva outcomes regardless of the drug type. bcva peaked after three years of treatment with a slow decline thereafter. baseline visual acuity was weakly shown to be the only significant predictor of change in visual acuity. there were no significant differences between drug type and visual acuity effect, number of injections needed, or oct outcomes. eyes with a final visual acuity of 20/50 or better increased from 34.8% at the beginning of the study to 45.1% at the latest follow-up (p = 0.037), while eyes with 20/200 or worse remained stable at 26.8% at baseline compared to 27.7% at last follow-up (p = 0.92). in contrast, in the five-year catt study, eyes with 20/200 or worse increased significantly from 6% at baseline to 20% at the last follow-up[13] even though in our study there were more patients with baseline vision of 20/200 or worse. at the end of the seven-up study, 37% of patients were reported to have visual acuity of 20/200 or worse. overall, 74% of patients in our study maintained or gained at least two snellen lines of visual acuity, compared with the sevenup trial where only 55% of eyes maintained or improved their vision.[14] at the end of our study, eyes that improved by at least two lines received an average of 24 injections, while all other eyes received an average of 18 injections. similarly, in the seven-up study, eyes receiving a greater number of injections (11 vs 6.8) gained 3.9 letters overall and were more likely to show improvement in vision.[14] the better visual outcomes in our population compared to the five-year catt study may be explained by the oct analysis. at the last follow-up visit, 16% of eyes in our study had srf and 19% of eyes had irf. those without srf or irf had either a ped or were without any fluid. in comparison, at the end of five years in the catt study, 38% had srf and 61% had irf.[13] eyes with residual irf yield worse visual outcomes compared with eyes with residual srf or absence of fluid.[16] more frequent treatments may have an impact on the amount of fluid on oct to allow for maintenance or gain in visual acuity. however, other factors such as geographic atrophy also contribute to the final visual acuity. though not studied in our population, the catt study demonstrated that 24% of eyes with monthly dosing showed geographic atrophy compared to 15% in the prn group. similarly, in the ivan trial, 34% versus 26% showed progressive atrophy in the monthly versus prn groups, respectively.[8, 13, 17] 338 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 treat and extend anti-vegf regimens; lee et al our study demonstrates that a tae model allows for a frequent albeit lower treatment burden as compared to monthly dosing with reduction in fluid on oct. this may theoretically lower the rate of geographic atrophy while maintaining similar gains in visual potential compared with a monthly dosing regimen. there are several limitations in our study most notably its retrospective nature. with data being compiled via electronic database, records may be incomplete and there may be innate errors in how the data was recorded. patients began treatment at different times between 2008 and 2015 and there may be differences both in medical technology and in practice patterns amongst providers. there is no monthly regimen treatment arm to compare its efficacy with our tae model. due to the method of data collection, there were fewer patients with more than four to five years of treatment available for analysis thereby limiting sample size and comparisons across different anti-vegf agents. some patients have undergone cataract surgery during treatment period, which can confound bcva amongst patients. furthermore, more in-depth studies are needed to analyze the impact of residual fluid type on visual acuity. in conclusion, our retrospective uncontrolled review of a large urban cohort of nv-amd reveals favorable long-term visual and anatomic results of anti-vegf therapy using a tae regimen. our study demonstrates that visual acuity seems to improve with more frequent injections over a longer period of time. the majority of patients (74%) maintained or improved vision with 45% of patients achieving va of 20/50 or better at their last followup over a seven-year period. our study supports the use of a tae treatment paradigm to reduce both office visits and treatment burden while still achieving positive functional and anatomic results. financial support and sponsorship this study was supported in part by an unrestricted grant from research to prevent blindness and by the northwestern medicine enterprise data warehouse. the sponsor or funding organization had no role in the design or conduct of this research. conflicts of interest there are no conflicts of interest. references 1. rosenfeld pj, brown dm, heier js, boyer ds, kaiser pk, chung cy, et al. ranibizumab for neovascular age-related macular degeneration. new engl j med 2006;355:1419– 1431. 2. lalwani ga, rosenfeld pj, fung ae, dubovy sr, michels s, feuer w, et al. a variable-dosing regimen with intravitreal ranibizumab for neovascular age-related macular degeneration: year 2 of the pronto study. am j ophthalmol 2009;148:43–58e1. 3. brown dm, michels m, kaiser pk, heier js, sy jp, ianchulev t, et al. ranibizumab versus verteporfin photodynamic therapy for neovascular age-related macular degeneration: two-year results of the anchor study. ophthalmology 2009;116:57–65e5. 4. heier js, brown dm, chong v, korobelnik jf, kaiser pk, nguyen qd, et al. intravitreal aflibercept (vegf trap-eye) in wet age-related macular degeneration. ophthalmology 2012;119:2537–2548. 5. schmidt-erfurth u, kaiser pk, korobelnik jf, brown dm, chong v, nguyen qd, et al. intravitreal aflibercept injection for neovascular age-related macular degeneration: ninety-six-week results of the view studies. ophthalmology 2014;121:193–201. 6. investigators is, chakravarthy u, harding sp, rogers ca, downes sm, lotery aj, et al. ranibizumab versus bevacizumab to treat neovascular age-related macular degeneration: one-year findings from the ivan randomized trial. ophthalmology 2012;119:1399–1411. 7. comparison of age-related macular degeneration treatments trials research g, martin df, maguire mg, fine sl, ying gs, jaffe gj, et al. ranibizumab and bevacizumab for treatment of neovascular age-related macular degeneration: two-year results. ophthalmology 2012;119:1388–1398. 8. chakravarthy u, harding sp, rogers ca, downes sm, lotery aj, culliford la, et al. alternative treatments to inhibit vegf in age-related choroidal neovascularisation: 2-year findings of the ivan randomised controlled trial. lancet 2013;382:1258–1267. 9. engelbert m, zweifel sa, freund kb. ”treat and extend” dosing of intravitreal antivascular endothelial growth factor therapy for type 3 neovascularization/retinal angiomatous proliferation. retina 2009;29:1424–1431. 10. freund kb, korobelnik jf, devenyi r, framme c, galic j, herbert e, et al. treat-and-extend regiments with antivegf agents in retinal diseases: a literature review and consensus recommendations. retina 2015;35:1489–1506. 11. arnold jj, campain a, barthelmes d, simpson jm, guymer rh, hunyor ap, et al. two-year outcomes of ”treat and extend” intravitreal therapy for neovascular age-related macular degeneration. ophthalmology 2015;122:1212– 1219. 12. mrejen s, jung jj, chen c, patel sn, gallego-pinazo r, yannuzzi n, et al. long-term visual outcomes for a treat and journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 339 treat and extend anti-vegf regimens; lee et al extend anti-vascular endothelial growth factor regimen in eyes with neovascular age-related macular degeneration. j clin med 2015;4:1380–1402. 13. comparison of age-related macular degeneration treatments trials research g, maguire mg, martin df, ying gs, jaffe gj, daniel e, et al. five-year outcomes with anti-vascular endothelial growth factor treatment of neovascular age-related macular degeneration: the comparison of age-related macular degeneration treatments trials. ophthalmology 2016;123:1751–1761. 14. rofagha s, bhisitkul rb, boyer ds, sadda sr, zhang k, group s-us. seven-year outcomes in ranibizumabtreated patients in anchor, marina, and horizon: a multicenter cohort study (seven-up). ophthalmology 2013;120:2292–2299. 15. calvo p, wang y, ferreras a, lam wc, denevyl r, brent m. treat and extend versus treat and observe in wet age-related macular degeneration patients treated with ranibizumab: 3-year surveillance period. j clin exp ophthalmol 2014;5:1–5. 16. oubraham h, cohen sy, samimi s, marotte d, bouzaher i, bonicel p, et al. inject and extend dosing versus dosing as needed: a comparative retrospective study of ranibizumab in exudative age-related macular degeneration. retina 2011;1:26–30. 17. abedi f, wickremasinghe s, islam af, inglis km, guymer rh. anti-vegf treatment in neovascular age-related macular degeneration: a treat-and-extend protocol over 2 years. retina 2014;34:1531–1538. 18. gupta op, shienbaum g, patel ah, fecarotta c, kaiser rs, regillo cd. a treat and extend regimen using ranibizumab for neovascular age-related macular degeneration clinical and economic impact. ophthalmology 2010;117:2134– 2140. 19. rayess n, houston sk, 3rd, gupta op, ho ac, regillo cd. treatment outcomes after 3 years in neovascular agerelated macular degeneration using a treat-and-extend regimen. am j ophthalmol 2015;159:3–8e1. 20. shienbaum g, gupta op, fecarotta c, patel ah, kaiser rs, regillo cd. bevacizumab for neovascular agerelated macular degeneration using a treat-and-extend regimen: clinical and economic impact. am j ophthalmol 2012;153:468–473e1. 21. decroos fc, reed d, adam mk, salz d, gupta op, ho ac, et al. treat-and-extend therapy using aflibercept for neovascular age-related macular degeneration: a prospective clinical trial. am j ophthalmol 2017;180:142– 150. 22. wykoff cc, ou wc, brown dm, croft de, wang r, payne jf, et al. randomized trial of treat-and-extend versus monthly dosing for neovascular age-related macular degeneration. ophthalmol retina 2017;1:314–321. 23. jaffe gj, martin df, toth ca, daniel e, maguire mg, ying gs, et al. macular morphology and visual acuity in the comparison of age-related macular degeneration treatments trials. ophthalmology 2013;120:1860–1870. 24. holz fg, tuomi l, ding b, hopkins jj. development of atrophy in neovascular amd treated with ranibizumab in the harbor study. invest ophthalmol vis sci 2015;56. arvo e-abstract 890. 340 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 original article combining baerveldt implant with trabectome negates tube fenestration: a coarsened-matched comparison hamed esfandiari, md;1,2 kiana hassanpour, md, mph;2 peter knowlton, md;1 tarek shazly, md1 mehdi yaseri, phd;3 nils a. loewen, md, phd1,4 1department of ophthalmology, school of medicine, university of pittsburgh, pittsburgh, pennsylvania, united states 2ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 3department of epidemiology and biostatistics, school of public health, tehran university of medical sciences, tehran, iran 4department of ophthalmology, university of würzburg, würzburg, germany orcid: nils a. loewen: https://orcid.org/0000-0001-7167-1213 hamed esfandiari: https://orcid.org/0000-0001-7301-7047 abstract purpose: to assess the efficacy and survival rate of the trabectome-mediated ab interno trabeculectomy combined with non-fenestrated baerveldt glaucoma implant compared with the baerveldt glaucoma implant alone. method: in this retrospective comparative case series, 175 eyes undergoing primary glaucoma surgery (baerveldt–trabectome [bt] group: 60 eyes and baerveldt [b] group: 115 eyes) were included. participants were identified using the procedural terminology codes. groups were then matched by coarsened exact matching that resulted in the inclusion of 51 eyes in each group. the primary outcome measure was surgical success defined as 5 mmhg < intraocular pressure (iop) ≤ 21 mmhg, and iop reduction ≥ 20% from baseline, and no need to reoperation for glaucoma. secondary outcome measures were iop, number of glaucoma medications, and best-corrected visual acuity (bcva). results: the cumulative probability of success at one year was 61% in the bt group and 50% in the b group. iop decreased from 23.5 ± 2.4 mmhg at baseline to 14.1 ± 2.7 mmhg at the final follow-up in the bt group (p = 0.001). the corresponding values for the b group were 23.2 ± 2.0 mmhg and 13.9 ± 1.6 mmhg, respectively (p = 0.001). there was no significant difference between the groups in terms of iop at the final follow-up (p = 0.56). the number of medications at baseline was 2.3 ± 0.3 in both groups. however, the bt group needed fewer drops at all postoperative time intervals and used 1.1 ± 0.3 versus 2.0 ± 0.4 eye drops (group b) at the final follow-up visit (p = 0.004). eyes in b with phacoemulsification had a significantly higher iop on day 1 compared to b (23.2 ± 14.3 versus 17.9 ± 11.4, p = 0.041). during the oneyear follow-up, 7 (13.7%) patients in bt group and 18 (35.2%) in b group experienced hypotony (p = 0.04). no dangerous hypotony or hypertension occurred in bt group. the mean bcva at baseline was 0.64 ± 0.85 logmar and changed to 0.55 ± 0.75 logmar in bt and b groups, respectively (p = 0.663). the corresponding numbers for the final follow-up visit was 0.72 ± 1.07 and 0.63 ± 0.97 logmar, respectively (p = 0.668). conclusion: we observed similar rates of success and iop reduction using bt and b techniques. bt group needed fewer glaucoma medications. tube fenestration was unnecessary in bt group resulting in less postoperative ocular hypotony and hypertension. the results of our study indicate that additional trabectome procedure makes baerveldt glaucoma implant safer, easier to handle, and more predictable in the most vulnerable patients with advanced glaucoma. keywords: ab interno trabeculectomy; baerveldt glaucoma implantation; glaucoma drainage devices; trabectome surgery; tube ligation j ophthalmic vis res 2020; 15 (4): 509–516 © 2020 journal of ophthalmic and vision research | published by knowledge e 509 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7789&domain=pdf&date_stamp=2019-07-17 combining baerveldt implant with trabectome negates tube fenestration; esfandiari et al introduction trabeculectomy and large glaucoma drainage devices (gdds) are often chosen as primary surgical interventions for refractory glaucoma with a low target intraocular pressure (iop). both allow to bypass the impaired conventional outflow route and can achieve iops below that of the episcleral veins. trabeculectomy can be associated with a high rate of failure and sightthreatening complications.[1–4] recent studies show gdds have the same or a higher success rate than trabeculectomy in end-stage glaucoma but a better safety profile.[1, 2, 5] as a result, gdds are increasingly used for refractory glaucoma or as the primary procedure. one of the most frequently implanted gdds is the baerveldt implant (advanced medical optics, santa ana, california, usa). in contrast to the ahmed glaucoma implant (new world medical inc, rancho cucamonga, california, usa), another common device, the baerveldt implant does not have a flow restrictor and requires a ligature suture that ties off the lumen to prevent hypotony[6] until a capsule has formed around the implant after four to six weeks.[7] the clinical definition of hypotony is iop low enough to result in vision loss caused, for instance by corneal edema, astigmatism, cystoid macular edema, or maculopathy.[8] since gdds are often used in severe glaucoma with advanced optic neuropathy, a high postoperative iop can be detrimental. to prevent this, many surgeons use spatulated needles to create slitshaped fenestrations anterior to the ligature that permit limited flow.[9–11] however, titrating this is challenging and the effect can range from no flow to frank hypotony.[10] to address this problem and allow a complete tube ligature without fenestration, correspondence to: nils loewen, md, phd. josef-schneider-straße 11, 97080 würzburg, department of ophthalmology, university of würzburg, würzburg, germany. email: loewen.nils@gmail.com received: 2-07-2019 accepted: 13-04-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7789 we combined baerveldt device implantations with trabectome-mediated ab interno trabeculectomy (neomedix, tustin, ca, usa). we hypothesized that this would provide a moderate iop reduction until the ligature dissolves allowing safe flow into a fully integrated baerveldt implant. to achieve a balanced comparison of baerveldt implants to baerveldt implants with the same session trabectome surgery, we used coarsened exact matching (cem), a computation-intense, modern statistics method[12–15] that we applied to similar questions before.[16, 17] although a randomized controlled trial remains the most effective tool to reduce bias and patient selection, modern statistical matching strategies can deliver a highly balanced assessment of real-world patient data in a retrospective analysis. methods this study was approved by the institutional review board of the human subjects research committee at the university of pittsburgh. an informed consent was not required for this retrospective comparative case series. our research adhered to the tenets of the declaration of helsinki and the regulations of the health insurance portability and accountability act. we identified patients who underwent a primary baerveldt implantation (b) or primary baerveldt implantation with trabectome surgery (bt) between 2008 and 2015 using the current procedural terminology (cpt) codes. all procedures were performed by four glaucoma fellowship-trained surgeons. only patients older than 18 years with medically uncontrolled iop were included. the exclusion criteria were neovascular glaucoma, uveitic glaucoma, and history of prior ocular surgery (except uncomplicated phacoemulsification). we collected data including basic demographics, type of glaucoma, preoperative this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: esfandiari h, hassanpour k, knowlton p, shazly t, yaseri m, loewen na. combining baerveldt implant with trabectome negates tube fenestration: a coarsened-matched comparison. j ophthalmic vis res 2020;15:509–516. 510 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 https://knepublishing.com/index.php/jovr combining baerveldt implant with trabectome negates tube fenestration; esfandiari et al iop, number of glaucoma medications, bestcorrected visual acuity (bcva), and type of surgery and complications as well as the postoperative iop, number of medications, and bcva. the primary outcome measure was success defined as 5 mmhg < iop ≤ 21 mmhg and ≥ 20% reduction of iop from baseline at two consecutive visits, no need for further glaucoma surgery, and no loss of light perception. the secondary outcome measures were iop, bcva, and the number of medications. we defined hypotony as an iop low enough to cause vision loss from corneal edema, astigmatism, cystoid macular edema, or maculopathy.[8] we measured the iop with a goldmann applanation tonometer (gat; haag-streit, konig, switzerland) at the first day, 1 week, 4 ±1 weeks, 2–4 months, 5–7 months, 8–10 months, and 11–13 months. if more than one visit occurred during these intervals, the visit closest to the months 6, 9, or 12 was chosen. surgical technique in patients undergoing a baerveldt implantation associated with trabectome surgery, the trabectome surgery was performed first. briefly, the patient’s head was tilted 30° away from the surgeon and the microscope was tilted in the opposite direction. a temporal 1.6 mm clear corneal incision was created. the tip of the handpiece was advanced into the anterior chamber and engaged with the nasal trabecular meshwork (tm). ablation was initiated and advanced in anticlockwise direction for 90° followed by another clockwise 90° clockwise ablation at the original starting point. the handpiece was withdrawn from the anterior chamber, and the incision was hydrated to seal. at the beginning of the baerveldt implantation, a fornix-based conjunctival flap was fashioned, and the subtenon’s space was dissected until enough space was created for the implant. the wings of the 350 mm*mm baerveldt implant were inserted under the superior and lateral rectus muscles. the plate was sutured to the sclera 10 mm posterior to the limbus. the tube was cut with the bevel up to allow an intracameral length of 2 mm. the tube was ligated near the plate junction with a 7-0 polyglactin 910 suture (coated vicryl, ethicon, somerville, nj, united states) and tested with bss to confirm water tightness. the tube was then inserted into the anterior chamber through a tunnel created with 23gauge needle and secured to the sclera with a 7-0 polyglactin loop stitch. in group b, but not in group bt, the tube portion anterior to the ligature was fenestrated with a single pass of the spatulated 7-0 needle. the tube was covered with a scleral patch graft and the incision of conjunctiva and tenon’s layer was reapproximated. most of the procedures were performed by nal except a few eyes in b group that were operated by other surgeons. at the conclusion of the surgery, an antibiotic (moxifloxacin) and steroid (1% prednisolone acetate) drops were applied. the antibiotic was used four times per day for one week while the steroid eye drops were used four times per day for one month and then tapered by one drop application each week. statistical analysis demographical data were compared using the mann–whitney u test and chi-squared test for continuous and categorical variables, respectively. to avoid eliminating data with missing values, multiple imputation in r was used (core team r (2018) r: a language and environment for statistical computing. r foundation for statistical computing, vienna, austria). missing values of the incomplete dataset were imputed m > 1 times, thus creating m completed datasets. second, each of the m completed datasets were analyzed independently. finally, the results from each of the m analysis were pooled into a final result. missing data like age, gender, and race were imputed by generating five similar but nonidentical datasets. groups were then matched by coarsened exact matching in r,[18] based on the age, race, type of glaucoma, baseline iop, and number of preoperative glaucoma medications. univariate linear regression was used to examine iop reduction after surgery. variables statistically significant were included in the final multivariate regression model. a p-value < 0.05 was considered statistically significant. continuous variables were expressed as mean ± sd. all analyses were performed using r. to compute the survival of subjects in each group, kaplan–meier survival plots were determined and compared using the log-rank test. statistical significance was set at p < 0.05. success was defined as the 5 mmhg < iop ≤ 21 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 511 combining baerveldt implant with trabectome negates tube fenestration; esfandiari et al mmhg, and iop reduction ≥ 20% from baseline, and no need to reoperation for glaucoma. results a total of 175 eyes undergoing primary glaucoma surgery (60 eyes in the bt group and 115 eyes in the b group) were enrolled in this study. coarsened exact matching resulted in 51 eyes in the bt group matched to 51 eyes in the b group. all eyes had completed one year of follow-up visits. ina addition, there was no significant difference between the two groups regarding ethnicity, iop, the number of iop-lowering medications, glaucoma type, and the degree of vf loss (p > 0.05, table 1). the mean age of the study participants was 70.7 ± 11.1 years in the bt group and 67.2 ± 15.7 years in the b group (p = 0.116). thirty patients (59%) underwent phacoemulsification at the time of glaucoma surgery in each group (p =1.00). primary open-angle glaucoma was the most common diagnosis in both groups (65.0% and 56.5% in bt and b groups, respectively, p = 0.516). kaplan–meier survival curves (figure 1) showed a mean duration of survival of 261.9 ± 21.9 days in the bt group and 220.28 ± 17.5 in the b group with no statistically significant difference between the two groups (log rank = 2.53 p = 0.11). the cumulative probability of qualified success at 3, 6, and 12 months was 74%, 64%, and 61% respectively in the bt group, and 66%, 52%, and 50% in the b group. in the subgroup analysis (table 2), the mean survival duration was 285.5 ± 25.8 days in the bt group with phacoemulsification versus 225.8 ± 25.9 days in the b group with phacoemulsification (log rank = 2.17, p = 0.14). results for glaucoma surgery alone were 221 ± 37.2 days in the bt group and 215.5 ± 23.6 days in the b group (log-rank = 0.24, p = 0.624, figure 1). survival of bt with phacoemulsification was not significantly different from b with phacoemulsification (log-rank = 1.18, p = 0.18). similarly, there was no difference between the b with phacoemulsification and b alone (logrank = 0.45, p = 0.50). in cases with concurrent phacoemulsification, the success rate was 56% in the bt and 52% in the b (p = 0.65), while in the stand-alone glaucoma surgery, the success rate was 61% in the bt and 51% in the b group (p = 0.31). iop was significantly decreased from 23.5 ± 2.4 mmhg at baseline to 14.1 ± 2.7 mmhg at final follow-up in the bt group (p = 0.001, figure 2). the corresponding values for the b group were 23.2 ± 2.0 mmhg and 13.9 ± 1.6 mmhg, respectively (p = 0.001). iop varied more in the b group than in the bt group during the early postoperative phase with 6.3% of hypotony occurring in the bt versus 12.8% hypotony detecting in the b group. during the one-year follow-up, 7 (13.7%) patients in the bt group and 18 (35.2%) in the b group experienced hypotony (p =0.04). most of the hypotony episodes were within the first month before suture opening. there was no significant difference in iop at the final follow-up (p = 0.98). eyes in the bt group experienced a 9 ± 9.1 mmhg reduction in iop within one week after the surgery, compared to a 6 ± 12.3 mmhg iop reduction in the b group (p = 0.09). on day one, iop was comparable between bt with and bt without phacoemulsification (20.3 ± 11.1 mmhg versus 18.6 ± 12.7 mmhg, p = 0.56). the b group with phacoemulsification had a significantly higher iop on day 1 compared to the b group without phacoemulsification (23.2 ± 14.3 mmhg versus 17.9 ± 11.4 mmhg, p = 0.041). the baseline number of glaucoma medications was 2.3 ± 0.3 in both groups (figure 3). however, the bt group needed significantly fewer drops at all postoperative visits. at the final follow-up visit, the number of glaucoma medications was 1.1 ± 0.3 drops in the bt and 2.0 ± 0.4 drops in the b (p = 0.003, figure 3) groups. the mean bcva at the baseline was 0.64 ± 0.85 logmar in the bt and 0.55 ± 0.75 logmar in the b (p = 0.663) groups. corresponding numbers for the final follow-up visit were 0.72 ± 1.07 and 0.63 ± 0.97 logmar, respectively (p = 0.668). the most common observation after the surgery was hyphema in 30% of the eyes in the bt group and 10% in the b group. two eyes in the bt group and three eyes in the b group had shallow anterior chamber early after surgery which resolved spontaneously. there was one case of choroidal detachment in each group that responded to conservative management. discussion both bt and b techniques were effective in reducing iop. the iop reduction of 31% at the one-year follow-up was comparable to previous reports.[19–21] however, the success rate in our study was lower than the reported range in 512 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 combining baerveldt implant with trabectome negates tube fenestration; esfandiari et al figure 1. (a) kaplan–meier survival plots for the bt and b groups with success defined as a final iop of ≤ 21 mmhg and a 20% reduction from baseline. success rates of bt and b was similar in both groups. (b) survival plots of the bt and b for subgroup analysis separated by (b) glaucoma surgery alone and (c) same-session phacoemulsification (lower right). figure 2. iop in the b and bt groups. (a) iop in the bt group was similar to the b group and trended toward a lower average although tubes in the bt group were not fenestrated and trended toward a lower average iop. (b) b and bt techniques as standalone procedures. (c) b + phacoemulsification had a higher iop on day 1 compared to subsequent iops. no such peak was seen in the bt group. mean ± 95% confidence interval. the literature;[19–21] most likely the results of a lower baseline iop in our study as compared to others. although there was a trend toward greater iop reduction following bt technique compared to b technique, a statistical significance was not reached. however, the bt group required significantly fewer medications postoperatively. the number of glaucoma medications at onemonth postoperative visit was nearly three times as high in the b group as surgeons struggled journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 513 combining baerveldt implant with trabectome negates tube fenestration; esfandiari et al figure 3. preoperative and postoperative mean eyedrops for bt and b. mean preand postoperative glaucoma medications for subgroup analysis separated by glaucoma surgery only (b) and same session phacoemulsification (c). represented as mean ± 95% confidence intervals. to control the pressure in this phase of bleb maturation. early complications of gdds included hyphema, a shallow or flat anterior chamber, tube-corneal touch, corneal edema, and suprachoroidal effusion.[6, 22] these complications are induced by postoperative hypotony, more common in the non-valved devices when the flow is not restricted and when fenestration of the tube yields excessive flow.[23] complete ligation of the tube can prevent postoperative hypotony,[24–27] but high postoperative iops can be dangerous to eyes with advanced glaucoma damage. therefore, tube ligation is often carried out in conjunction with intraoperative longitudinally oriented, 2 mm fenestrations proximal to the ligation.[23] despite this, a postoperative hypertensive spike may develop secondary to obstruction of the fenestration, slit malfunction, or an insufficient number of fenestrations.[9, 28] it is hard to titrate the function of these fenestrations and they are hardly reproducible. intraoperative techniques such as irrigating the tube after fenestration, cautery of the bleeding episcleral vessels, and removing the debris from the field of surgery are proposed to improve the outcomes of fenestrations but it is still unpredictable. considering these limitations, we added the same session trabectome surgery to prevent postoperative iop spikes. this procedure enhances the outflow by plasmamediated ablation of the tm and has a long track record of efficacy and safety in various types of glaucoma.[29–33] although trabectome is a microsurgical glaucoma surgery and is often used in earlier glaucoma stages,[33] recent studies suggest it can be effective in more severe glaucoma.[34] while the success rate of trabectome after failed trabeculectomy and tube shunt procedure supports its role in the management of severe glaucoma,[35, 36] many eyes at that stage cannot afford a surgical failure, that can occur if the conventional drainage system downstream of the tm also has a reduced flow capacity. the effect of trabecular ablation is immediate and controls iop until absorbable ligation sutures dissolve, and the baerveldt implant begins to function. in contrast to the temporary effect of fenestrations, the iop lowering of trabectome persists after the ligature suture is absorbed and has the additive effect of reducing glaucoma medications. this is not a small feat as nearly half of all glaucoma patients experience local and systemic side effects of topical drops.[37] adverse medication effects are an important reason for non-adherence[38] and can also jeopardize the success of glaucoma surgery.[39, 40] conversely, reducing eye drops measurably improves the quality of life.[41] since cataract and glaucoma frequently coexist, many individuals in both groups underwent both surgeries. iop in bt group combined with phacoemulsification was not significantly different 514 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 combining baerveldt implant with trabectome negates tube fenestration; esfandiari et al from bt alone, reflecting our prior results that phacoemulsification does not add to the ioplowering effect when combined with trabectome surgery.[16, 17] although phacoemulsification has been advocated as providing a trabeculoplastylike, additional iop reduction,[42] glaucomatous tm is often unpredictable resulting in iop spikes at the time of stand-alone cataract surgery[43, 44] as we have observed here as well on day 1 in patients in group b with phacoemulsification. the results of our study showed that this potentially dangerous iop spike could be prevented by the same-session trabectome surgery. conversely, no severe hypotony was seen in the bt group which did not require tube fenestration. limitations of this study are inherent to the retrospective nature compared to randomized controlled trials. however, the cem strategy used here reduces imbalances without discarding valid data. although observational data is easy to collect compared to randomized experiments, how the treatments were assigned and other aspects of data generation are often ambiguous and difficult to control. cem is a newer form of automatic, nonparametric matching to control the confounding influence of pretreatment control variables by achieving an acceptable balance between treated and control groups.[18] additionally, this study was conducted at a single tertiary academic center, so the results cannot easily be generalized to other practice facilities. it should be noted that trabectome surgery is a new skill even for experienced surgeons and takes at least 30 eyes to maximize the outflow,[44] therefore, a complete 180° tm removal with trabectome may not always be achieved. in summary, we found that baerveldt implants with same-session trabectome surgery resulted in a significantly decreased number of glaucoma medications and avoided both severe hypertension and hypotension, thereby negating the need for tube fenestration. financial support and sponsorship the authors would like to acknowledge the support from the initiative to cure glaucoma, the eye and ear foundation of pittsburgh; nih core grant p30 ey08098 to the department of ophthalmology; an unrestricted grant from research to prevent blindness, new york, ny. conflicts of interest there are no conflicts of interest. funding references 1. gedde sj, schiffman jc, feuer wj, herndon lw, brandt jd, budenz dl, et al. treatment outcomes in the tube versus trabeculectomy (tvt) study after five years of follow-up. am j ophthalmol 2012;153:789–803.e2. 2. gedde sj, herndon lw, brandt jd, budenz dl, feuer wj, schiffman jc. postoperative complications in the tube versus trabeculectomy (tvt) study during five years of follow-up. am j ophthalmol 2012;153:804–814.e1. 3. esfandiari h, pakravan m, loewen na, yaseri m. predictive value of early postoperative iop and bleb morphology in mitomycin-c augmented trabeculectomy. f1000res 2017;6:1898. retrieved from: https://doi.org/10.12688/f1000research.12904.1 4. pakravan m, esfandiari h, yazdani s, douzandeh a, amouhashemi n, yaseri m, et al. mitomycin c-augmented trabeculectomy: subtenon injection versus soaked sponges: a randomised clinical trial. br j ophthalmol 2017;101:1275–1280. 5. tseng vl, coleman al, chang my, caprioli j. aqueous shunts for glaucoma. cochrane database syst rev 2017;7:cd004918. 6. patel s, pasquale lr. glaucoma drainage devices: a review of the past, present, and future. semin ophthalmol 2010;25:265–270. 7. minckler ds, francis ba, hodapp ea, jampel hd, lin sc, samples jr, et al. aqueous shunts in glaucoma: a report by the american academy of ophthalmology. ophthalmology 2008;115:1089–1098. 8. abbas a, agrawal p, king aj. exploring literaturebased definitions of hypotony following glaucoma filtration surgery and the impact on clinical outcomes. acta ophthalmol 2018;96:e285–e289. 9. kansal s, moster mr, kim d, schmidt cm jr, wilson rp, katz lj. effectiveness of nonocclusive ligature and fenestration used in baerveldt aqueous shunts for early postoperative intraocular pressure control. j glaucoma 2002;11:65–70. 10. ortiz arismendi ge, peña valderrama cdp, albis-donado o. results of a new technique for implantation of nonrestrictive glaucoma devices. j curr glaucoma pract 2013;7:130–135. 11. trible jr, brown db. occlusive ligature and standardized fenestration of a baerveldt tube with and without antimetabolites for early postoperative intraocular pressure control. ophthalmology 1998;105:2243–2250. 12. iacus sm, king g, porro g. cem: software for coarsened exact matching. j stat softw 2009;30:1–27. 13. iacus sm, king g, porro g. causal inference without balance checking: coarsened exact matching. polit anal 2012;20:1–24. 14. rubin db, thomas n. combining propensity score matching with additional adjustments for prognostic covariates. j am stat assoc 2000;95:573–585. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 515 https://doi.org/10.12688/f1000research.12904.1 combining baerveldt implant with trabectome negates tube fenestration; esfandiari et al 15. seeger jd, williams pl, walker am. an application of propensity score matching using claims data. pharmacoepidemiol drug saf 2005;14:465–476. 16. parikh ha, bussel ii, schuman js, brown en, loewen na. coarsened exact matching of phaco-trabectome to trabectome in phakic patients: lack of additional pressure reduction from phacoemulsification. plos one 2016;11:e0149384. 17. neiweem ae, bussel ii, schuman js, brown en, loewen na. glaucoma surgery calculator: limited additive effect of phacoemulsification on intraocular pressure in ab interno trabeculectomy. plos one 2016;11:e0153585. 18. iacus sm, king g, porro g. causal inference without balance checking: coarsened exact matching. polit anal 2012;20:1–24. 19. kostanyan t, shazly t, kaplowitz kb, wang sz, kola s, brown en, et al. longer-term baerveldt to trabectome glaucoma surgery comparison using propensity score matching. graefes arch clin exp ophthalmol 2017;255:2423–2428. retrieved from: https://doi.org/10.1007/s00417-017-3804-9. 20. christakis pg, zhang d, budenz dl, barton k, tsai jc, ahmed iik, et al. five-year pooled data analysis of the ahmed baerveldt comparison study and the ahmed versus baerveldt study. am j ophthalmol 2017;176:118– 126. 21. christakis pg, kalenak jw, tsai jc, zurakowski d, kammer ja, harasymowycz pj, et al. the ahmed versus baerveldt study: five-year treatment outcomes. ophthalmology 2016;123:2093–2102. 22. budenz dl, barton k, feuer wj, schiffman j, costa vp, godfrey dg, et al. treatment outcomes in the ahmed baerveldt comparison study after 1 year of follow-up. ophthalmology 2011;118:443–452. 23. aref aa, gedde sj, budenz dl. glaucoma drainage implant surgery. dev ophthalmol 2012;50:37–47. 24. molteno ac, van biljon g, ancker e. two-stage insertion of glaucoma drainage implants. trans ophthalmol soc n z 1979;31:17–26. 25. molteno ac, polkinghorne pj, bowbyes ja. the vicryl tie technique for inserting a draining implant in the treatment of secondary glaucoma. aust n z j ophthalmol 1986;14:343–354. 26. egbert pr, lieberman mf. internal suture occlusion of the molteno glaucoma implant for the prevention of postoperative hypotony. ophthalmic surg 1989;20:53– 56. 27. sherwood mb, smith mf. prevention of early hypotony associated with molteno implants by a new occluding stent technique. ophthalmology 1993;100:85–90. 28. campbell rj, buys ym, mcilraith ip, trope ge.) internal glaucoma drainage device tube fenestration for uncontrolled postoperative intraocular pressure. j glaucoma 2008;17:494–496. 29. kaplowitz k, bussel ii, honkanen r, schuman js, loewen na. review and meta-analysis of abinterno trabeculectomy outcomes. br j ophthalmol 2016;100:594–600. 30. ngai p, kim g, chak g, lin k, maeda m, mosaed s. outcome of primary trabeculotomy ab interno (trabectome) surgery in patients with steroid-induced glaucoma. medicine 2016;95:e5383. 31. ting jlm, damji kf, stiles mc, trabectome study group. ab interno trabeculectomy: outcomes in exfoliation versus primary open-angle glaucoma. j cataract refract surg 2012;38:315–323. 32. bussel ii, kaplowitz k, schuman js, loewen na, trabectome study group. outcomes of ab interno trabeculectomy with the trabectome by degree of angle opening. br j ophthalmol 2015;99:914–919. 33. minckler ds, baerveldt g, alfaro mr, francis ba. clinical results with the trabectome for treatment of open-angle glaucoma. ophthalmology 2005;112:962–967. 34. loewen rt, roy p, parikh ha, dang y, schuman js, loewen na. impact of a glaucoma severity index on results of trabectome surgery: larger pressure reduction in more severe glaucoma. plos one 2016;11:e0151926. 35. bussel ii, kaplowitz k, schuman js, loewen na, trabectome study group. outcomes of ab interno trabeculectomy with the trabectome after failed trabeculectomy. br j ophthalmol 2015;99:258–262 36. mosaed s, chak g, haider a, lin ky, minckler ds. results of trabectome surgery following failed glaucoma tube shunt implantation: cohort study. medicine 2015;94:e1045. 37. pisella pj, pouliquen p, baudouin c. prevalence of ocular symptoms and signs with preserved and preservative free glaucoma medication. br j ophthalmol 2002;86:418–423. 38. tsai jc, mcclure ca, ramos se, schlundt dg, pichert jw. compliance barriers in glaucoma: a systematic classification. j glaucoma 2003;12:393–398. 39. lavin mj, wormald rp, migdal cs, hitchings ra. the influence of prior therapy on the success of trabeculectomy. arch ophthalmol 1990;108:1543–1548. 40. broadway d, grierson i, hitchings r. adverse effects of topical antiglaucomatous medications on the conjunctiva. br j ophthalmol 1993;77:590–596. 41. loon sc, jin j, jin goh m. the relationship between quality of life and adherence to medication in glaucoma patients in singapore. j glaucoma 2015;24:e36–42. 42. poley bj, lindstrom rl, samuelson tw, schulze r jr () intraocular pressure reduction after phacoemulsification with intraocular lens implantation in glaucomatous and nonglaucomatous eyes: evaluation of a causal relationship between the natural lens and open-angle glaucoma. j cataract refract surg 2009; 35:1946–1955. 43. slabaugh ma, bojikian kd, moore db, chen pp. risk factors for acute postoperative intraocular pressure elevation after phacoemulsification in glaucoma patients. j cataract refract surg 2014;40:538–544. 44. weiner y, severson ml, weiner a. intraocular pressure 3 to 4 hours and 20 hours after cataract surgery with and without ab interno trabeculectomy. j cataract refract surg 2015;41:2081–2091. 45. dang y, waxman s, wang c, parikh ha, bussel ii, loewen rt, et al. rapid learning curve assessment in an ex vivo training system for microincisional glaucoma surgery. sci rep 2017;7:1605. 516 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 https://doi.org/10.1007/s00417-017-3804-9 original article myopia and regional variations in retinal thickness in healthy eyes feryal m. zereid1, phd; uchechukwu l. osuagwu2,3, ms, phd, od 1department of optometry & vision sciences, college of applied medical sciences, king saud university, riyadh, saudi arabia 2school of medicine, diabetes obesity and metabolism translational research unit (domtru), macarthur clinical school, parkside crescent, campbelltown, australia 3african vision research institute, university of kwazulu-natal, durban, south africa orcid: uchechukwu l. osuagwu: https://orcid.org/0000-0002-1727-6914 abstract purpose: to investigate the effects of refraction on retinal thickness measurements at different locations and layers in healthy eyes of saudi participants. methods: thirty-six randomly selected adults aged 27.0 ± 5.7 years who attended a riyadh hospital from 2016 to 2017 were categorized into three groups: non-myopic (spherical equivalent refraction [ser], +1.00 to –0.50 diopters [d]), low myopic (ser, – 0.75 to –3.00d), and moderate to high myopic (ser ≤ –3.25d). full, inner, and outer retinal thicknesses were measured at nine locations by spectral-domain stratus optical coherence tomography (optovue inc., fremont, ca, usa) and were compared according to refractive group and sex. results: the mean sers for the non-myopia, low myopia, and moderate to high myopia groups were 0.2 ± 0.6, –1.5 ± 0.5, and –7.5 ± 1.9 d, respectively. refractive error, but not sex, had significant effects on the retinal layer thickness measurements at different locations (p < 0.05). the parafoveal and outer retinal layers were significantly thicker than the perifoveal and inner retina layers in all groups (p < 0.05). the full foveal thickness was higher and the full parafoveal and perifoveal regions were thinner in moderate to high myopic eyes than in the non-myopic eyes (p < 0.05), but were similar to those in the low myopic eyes (p > 0.05). the foveal thicknesses measured in the inner and outer layers of the retina were higher but the thicknesses measured at the inner and outer layers of the parafoveal and perifoveal regions were lower in moderate to high myopic eyes. conclusion: there were regional differences in the retinal layer thicknesses of healthy saudi eyes, which was dependent on the central refractions. this is important when interpreting retinal nerve fiber layer thicknesses in myopia and disease management in saudi participants. keywords: fovea; myopia; refractive error; retinal thickness; saudi arabia; stratus optical coherence tomography j ophthalmic vis res 2020; 15 (2): 178–186 178 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i2.6735&domain=pdf&date_stamp=2019-07-17 retinal thickness in healthy myopic eyes; zereid and osuagwu correspondence to: uchechukwu l. osuagwu, ms, phd, od. school of medicine, diabetes obesity and metabolism translational research unit (domtru), macarthur clinical school, parkside crescent, campbelltown 2560 nsw, australia. e-mail: l.osuagwu@westernsydney.edu.au received: 10-12-2018 accepted: 12-11-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i2.6735 introduction the global prevalence of myopia is increasing rapidly. currently, 30% of the world population is myopic and almost 50% is projected to be so by 2050.[1] in asia, the prevalence of myopia is higher (approximately 80%) compared with that in other regions (approximately 25%).[2–4] uncorrected myopia is a major cause of visual impairment[5] and the majority of people with visual impairment reside in developing countries, including saudi arabia.[6] individuals with myopia are at an increased risk of developing significant ocular comorbidities which can lead to retinal atrophy and possible blindness.[7, 8] histological studies have shown significant reductions in scleral and retinal thicknesses as the degree of axial myopia increases,[9, 10] and these are responsible for the high incidence of retinal pathologies in high myopes.[7, 8, 11] the enlarged globe and the elongated axial length of the myopic eyes lead to an ocular dimension that is stretched beyond its normal limit, which may lead to retinal thinning.[12, 13] ocular conditions such as glaucoma, which are prevalent among individuals with highly myopic eyes, may also significantly affect the thickness of the inner retinal layers.[12, 13] optical coherence tomography (oct) offers a modern technique for in vivo measurements of retinal thickness and enables the assessment of the relationship between myopia and retinal thickness. this device can be used to correctly interpret and differentiate between an enlarged myopic optic disc[14–17] and optic disc changes often seen in glaucomatous eyes. however, the refractive error of patients affects the measurement of retinal thickness and can be a confounding factor when diagnosing eye pathologies. although studies have investigated the changes in retinal thickness in other populations,[17–28] they have considered only the central retinal region or recruited individuals with high or pathologic myopia,[17, 27] and the results have been inconclusive[17–28] due to the different methodologies used in the studies.[17–29] retinal thickness measurements by oct vary according to the population being studied;[30] thus, knowledge of such population-based differences in retinal thickness distribution is important in the evaluation, treatment, and follow-up of patients in a particular population and/or with various ocular pathologies.[17, 31] however, studies investigating the effects of refraction groups on retinal thickness measurements across different locations have shown different results.[23, 24, 28] the purpose of the present prospective hospital study was to investigate the changes in retinal thickness measured at different retinal regions (foveal, perifoveal, and parafoveal) and layers (full, inner, and outer retina) in non-myopic and myopic participants. the second aim of this study was to examine the effects of refraction on the retinal thickness measurements across retinal regions and layers of the macula. retinal thickness was assessed in myopic and non-myopic adults of similar ages by spectral-domain oct, and the measurements were compared between groups. we hypothesized that there would be significant differences in retinal thicknesses measured at different locations by oct between the myopic and nonmyopic eyes of saudi participants. histopathology studies have shown that in myopia, the retina thins and degenerates, especially at the posterior pole;[32] these changes in the retina of myopic eyes may reflect in retinal thickness measurements by oct. methods study population and setting from november 2016 to february 2017, 36 young adults (12 men [33.3%] and 24 women [66.7%]) this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: zereid fm, osuagwu ul. myopia and regional variations in retinal thickness in healthy eyes. j ophthalmic vis res 2020;15:178–186. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 179 https://knepublishing.com/index.php/jovr retinal thickness in healthy myopic eyes; zereid and osuagwu were recruited at random for the present study. in order to eliminate possible selection bias if the clinicians were to choose the participants themselves, an optometry student who was not part of the investigation team approached participants from among those attending a public hospital facility in saudi arabia. the examiner taking all oct measurements (fz) was blinded to the refractive group of the participants. the participants were categorized into three groups: non-myopic (spherical equivalent refraction [ser] range of +1.00 to – 0.50 diopters [d]), low myopic (ser, –0.75 to –3.00 d) and moderate to high myopic (ser ≤ –3.25d) groups. all participants had cylindrical refractions of < –1.00 d and underwent comprehensive eye examinations including distance visual acuity (va) assessment, autorefraction, intraocular pressure (iop) measurement using a non-contact tonometer, visual field testing, and dilated fundus examination. for all participants, only data from one eye, which was determined by random selection was used. the randomization process involved generating a series of random numbers from 1001 to 2001 through a microsoft excel spreadsheet. each number was printed, folded, and inserted into a black box by a member of the clinical staff. a student clinician in charge of the data to be analyzed but blinded to the initial process of number generation selected a paper from the black box each time a participant’s data was to be entered into the spreadsheet. a participant’s right eye data were included in the analysis if the number picked was even (e.g., 1008) and the left eye data were included if the number was odd. ethics approval for this study was obtained from the college of applied medical science, research ethics committee for human participants, and the study was conducted in accordance with the declaration of helsinki as revised in the year 2000. informed consent was obtained from all participants before their enrollment in this study [table 1]. inclusion and exclusion criteria participants were included in this study if the bestcorrected va was better than 6/9 in each eye and the difference in ser between eyes was < 1.00 d. the exclusion criteria were history of amblyopia, any ocular disease, surgery and/or medications, ocular trauma, in-cyclotorsion or ex-cyclotorsion of the eye, anisometropia (difference in ser between eyes ≥ 1.00 d), systemic diseases with ocular implications, the best-corrected va worse than 6/9, iop > 21 mmhg, a personal or family history of glaucoma or any neurologic condition with visual field effects or any other optic neuropathy. oct protocol retinal thickness was measured using the rtvue spectral domain oct (optovue inc., fremont, ca, usa). the instrument obtains retinal thickness information using the mm6 scan protocol [figure 1]. for all participants, both eyes were dilated by administering 1% tropicamide and 2.5% phenylephrine hydrochloride three times over a 10-min period before the oct procedure. only oct scans of sufficient quality (signal ≥ 50% of maximum strength, absence of imaging artifacts or distortions) were used. if the quality of the oct scans was insufficient, replicate measurements were taken. the instrument uses 12 radial lines, each 6 mm long, that are centered at the fovea to provide 1,024 a-scans, each of the full retinal thickness. using the rtvue-100 instrument software (version 4.0.5.39; optovue, inc., fremont, ca), the full retinal thickness was measured automatically at three concentric zones: a circle of 1 mm diameter centered at the fovea, a parafoveal region with an inner and an outer diameter of 1 mm and 3 mm, respectively, and a perifoveal region with an inner and an outer diameter of 3 mm and 6 mm, respectively. the nine zones of the retinal thickness shown in figure 2 were compared between the three refractive groups. the boundaries for segmentation by the software included: total retinal (tr) thickness, from the inner limiting membrane to the outer rpe; inner retinal thickness, from the inner limiting membrane to the outer boundary of inner plexiform layer; outer retinal thickness, from the outer boundary of inner plexiform layer to the outer rpe. statistical analysis data were analyzed using the ibm spss statistics for windows, version 22.0 (ibm corp., armonk, ny, usa). p < 0.05 was considered significant. all data were analyzed for normality using the shapiro– wilk test and the results were presented using 180 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 retinal thickness in healthy myopic eyes; zereid and osuagwu table 1. characteristics of study participants (n = 36 eyes) non-myopia low myopia moderate to high myopia p-values sex, n (males/females) 12 (4/8) 12 (4/8) 12 (4/8) 0.32 age, years 27.2 ± 5.3 27.3 ± 5.1 26.7 ± 6.9 0.59 ser, mean ± sd (range) (d) 0.18 ± 0.59 (+1.00 to –0.50) –1.54 ± 0.54 (–0.75 to –3.00) –7.50 ± 1.90 (–3.25 to –10.50) < 0.001* ser, spherical equivalent refraction; d, diopter; sd, standard deviation; n, number *statistical significance from analysis of variance (anova) values are expressed as mean (± standard deviations) table 2. mean retinal thickness measurements (µm) and comparisons between groups at nine locations in non-, low, and moderate to high myopic healthy saudi participants retinal thickness locations non-myopia low myopia moderate to high myopia p-values full retinal thickness at 1-mm zone 238.5 ± 8.4 253.4 ± 8.4 261.4 ± 8.1 < 0.0005𝑎,𝑏, 0.071𝑐 full retinal thickness at parafovea 317.4 ± 14.2 295.8 ± 3.5 288.2 ± 5.5 < 0.0005𝑎,𝑏, 0.143𝑐 full retinal thickness at perifovea 280.9 ± 11.3 274.0 ± 6.7 268.3 ± 5.3 0.138𝑎, 0.002𝑏, 0.296𝑐 inner retinal thickness at 1-mm zone 62.5 ± 3.8 65.9 ± 2.4 75.5 ± 4.0 0.065𝑎, < 0.0005𝑏,𝑐 inner retinal thickness at parafovea 128.1± 2.8 119.4 ± 3.3 112.3 ± 5.2 < 0.0005𝑎,𝑏,𝑐 inner retinal thickness at perifovea 107.8 ± 2.9 96.9 ± 3.7 91.4 ± 5.3 < 0.0005𝑎,𝑏, 0.007𝑐 outer retinal thickness at 1-mm zone 158.2 ± 3.9 164.6 ± 1.7 170.1 ± 4.0 < 0.0005𝑎,𝑏, 0.001𝑐 outer retinal thickness at parafovea 180.8 ± 3.1 177.4 ± 4.1 171.3 ± 2.5 0.048𝑎, < 0.0005𝑏,𝑐 outer retinal thickness at perifovea 175.3 ± 4.3 171.5 ± 2.6 167.3 ± 2.8 0.025𝑎, < 0.0005𝑏, 0.014𝑐 sd, standard deviation 𝑎the mean difference is significant at the 0.05 level for non-myopia versus low myopia 𝑏the mean difference is significant at the 0.05 level for non-myopia versus moderate-to-high myopia 𝑐the mean difference is significant at the 0.05 level for low myopia versus moderate-to-high myopia. results are post hoc analysis with bonferroni correction p-values are post hoc results of analysis of variance (anova) descriptive statistics. pearson correlation coefficients were used to determine the relationship between retinal thicknesses at different locations. independent t-test analysis, fisher’s exact test and chi-square analysis, and analysis of variance (anova) with “location” as a between-subject factor and “sex” as a within-subject factor were performed where appropriate. where significant differences were found, post hoc analysis was conducted after applying bonferroni correction for multiple comparisons. results a summary of the demographic data for the non-, low, and high myopic participants and the results of the comparative analysis are provided using descriptive statistics in table 1. the participants were matched for age (p = 0.50, unpaired t-test) and sex (p > 0.05, fisher’s test) but each group included more female than male participants (57% versus 43%). the mean ser for all participants ranged from +1.00 d to –10.50 d, and male participants were more myopic than female participants (mean ± sd, –6.18 ± 2.24 d versus –4.01 ± 1.75 d, p < 0.001) in this study. figure 3 shows the mean thicknesses across retinal locations for all participants. sex was not significantly correlated with the retinal thickness at each of the locations and did not affect the measured thicknesses at any of the nine locations (p > 0.05, for all results of independent t-test analysis). table 2 shows the full and regional retinal thickness values for each group and the differences between groups. significant differences journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 181 retinal thickness in healthy myopic eyes; zereid and osuagwu figure 1. full retinal layer scanning of a participant (right). rpe, retinal pigment epithelium; ipl, inner plexiform layer; ilm, inner limiting membrane; gcl, ganglion cell layer. figure 2. the nine zones of the optovue rtvue spectral-domain ocular coherence tomography (sd-oct) retinal map defined by standard the early treatment diabetic retinopathy study (etdrs) grid. were observed in the retinal thicknesses measured across the nine locations in each group (repeated measures anova, p < 0.001). the full retinal thickness at the parafoveal region was the highest among the refractive groups with averages of 317.4 µm, 295.8 µm, and 288.2 µm in the non-, low, and moderate to high myopic groups, respectively. in contrast, the inner retinal 1 mm zone had the lowest thickness, with an average of 62.5 µm, 65.9 µm, and 75.5 µm, in the non-, low, and moderate to high myopic groups, respectively. figure 4 shows the correlation coefficients (r) between retinal thickness and refractive error groups for the nine retinal locations representing each segment of the nine field early treatment diabetic retinopathy study (etdrs) grid. all correlations between refractive error group and retinal thicknesses at all locations were significant (p < 0.05). the refractive error group was strongly correlated with retinal thicknesses at all locations (r ≥ 0.70) except for the full retinal thickness at the perifoveal region, which showed moderate correlation (r = –0.55). significant differences were observed in mean retinal thicknesses between the refractive groups (p < 0.0001 for each location), and post hoc analysis showed no differences in the full retinal thickness measured at the 1 mm zone, the parafovea and peri-fovea regions, and between the low and the moderate to high myopic groups (p = 0.07, 0.14, 0.30, respectively), but there were significant differences in the full retinal thickness at the 1 mm and at parafovea zones (both, p < 0.001) but not in the perifovea zone (p = 0.14) when nonmyopic eyes were compared to low myopic eyes. we observed significant differences in mean retinal thickness values between the nonand moderate to high myopic groups (p < 0.05). at the 1 mm 182 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 retinal thickness in healthy myopic eyes; zereid and osuagwu figure 3. mean retinal thickness measurements (µm) at different locations in male and female saudi participants. figure 4. pearson correlation coefficients (r) between refractive errors and retinal thicknesses (µm) at nine retinal locations using the early treatment diabetic retinopathy study (etdrs) grid. zone, the retina was significantly thicker but was significantly thinner at every other location in the moderate to high myopic group than that in the non-myopic group [table 2]. overall, the mean retinal thickness was significantly lower in the paraand perifoveal regions and higher in the 1 mm zone in the moderate to high myopic group than in the other groups [table 2]. discussion this study measured retinal thickness in young, non-myopic saudi participants by spectral-domain oct and compared the measurements with those obtained in age-matched groups of participants with low and moderate to high myopia. we found that across the refractive groups, the parafoveal region was significantly thicker than the perifoveal retina and both were thicker than the fovea (1 mm zone). the full foveal thickness was significantly higher and the full parafoveal and perifoveal retinal thicknesses were significantly lower in the moderate to high myopic group than in the non-myopic and low-myopic groups. we observed a significant effect of refractive error on the measurements of retinal thickness across different regions and locations. the full retinal thickness measured at the perifoveal, parafoveal, and 1 mm central zone differed significantly between the moderate to high myopic group and the non-myopic group across all locations. the thicknesses measured at the perifoveal and parafoveal regions (including the inner and outer layers of the retina), and those measured at the 1 mm zone, were significantly higher and lower, respectively, in the non-myopic group than in the moderate to high myopic group [table 3]. the present study found that the degree of myopia was significantly related to the retinal thickness in the study cohort. the retinal thicknesses at the parafoveal and perifoveal regions rapidly decreased as the degree of myopia increased. similar findings have previously been reported.[18, 23, 24, 28, 33] the retinal thinning observed in myopic eyes has been linked to journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 183 retinal thickness in healthy myopic eyes; zereid and osuagwu mechanical stretching of the sclera due to the increased axial length of the enlarged myopic eyeball. the perifoveal region is also less resistant to traction and stretching forces and is devoid of large blood vessels,[34] which could partly explain these findings. a chinese study that recruited individuals with different refractions reported significant changes in macular thickness that varied with the degree of myopia. however, the patterns of change varied according to the different macular areas and layers.[28] in line with our findings, the authors also reported significant positive (slightly weaker than our study finding) correlations between ser and full parafoveal (r = 0.4, p < 0.001) and perifoveal thicknesses (r = 0.5, p < 0.001).[28] the fovea was thicker in the moderate to high myopic group than in the other refractive groups, similar to the findings of previous studies.[18, 23, 24] this observation has been attributed in part to genetic factors, particularly in myopic eyes, which cause increased thickness in the inner nuclear layer (inl), inner plexiform layer (ipl), and ganglion cell layer.[35] lam et al,[23] reported preservation of the retinal thickness in the most central foveal region in highly myopic eyes compared to low myopic eyes and attributed this difference to tangential traction resulting from the internal limiting membrane or posterior vitreous cortex.[22, 36] similar to another study,[36] we found that the perifoveal retinal region was thinner than the parafoveal retinal region across the refractive groups. the male participants in this study were generally more myopic than the female participants but sex did not significantly affect the refraction differences between the groups or the measured retinal thicknesses across the nine retinal locations (p > 0.05). contrary to our results, studies from china[37, 38] found significant differences between the sexes in absolute central retinal thickness, noting lower minimum foveal, average foveal (1 mm), and average inner ring macular thicknesses in women than those in men.[23] although these studies had larger sample sizes compared to our study, the population also differed, with other studies including mostly chinese participants. other studies, which recruited europeans in netherlands[39] and a mixture of europeans, africans, and african americans living in the us[40] also reported no effect of sex on retinal thickness as measured by oct,[39, 40] suggesting that the differences between the studies on the effects of sex may be due to the differences in the study populations. the limitations of this study include the small sample size. this was largely due to the strict selection criteria and the method of participant selection. due to the unavailability of ocular biometry measurements, we were unable to assess the effects of axial length on retinal thickness. therefore, it remains unclear whether the differences were due to axial or refractive myopia. however, the relationship between axial length and retinal thickness at various locations remains controversial: lam et al[23] reported a negative correlation between total macular thickness and axial length and a positive correlation between foveal thickness and axial length, while huynh et al[41] showed retinal thinning with increasing axial length in the outer and inner macular regions but not in the central macula. this study provided what we believe to be the first evidence of regional variations in retinal thicknesses within the saudi population and contributes to the growing body of evidence on the diagnostic use of oct in myopia. however, the study was limited by the narrow range of subjects’ ages and the exclusion of participants with diseases such as ocular hypertension, glaucoma, and diabetes, where precise measurement of central corneal thickness is also important. further studies including saudi participants with a wider age range and those diagnosed with ocular diseases are needed to confirm the findings of the present study. in conclusion, we observed regional variations in retinal thickness measurements, with greater thickness at the parafoveal region than in the perifoveal and central regions (1 mm) across refractive groups. the differences in retinal thickness measurements among the groups across locations were not dependent on the participant’s sex. nonmyopic eyes had significantly thicker retinas at the periand para-foveal regions but thinner retinas at the 1 mm foveal zone compared with the myopic eyes. in contrast, the fovea was significantly thicker at the 1 mm zone and thinner at other locations around the fovea of moderate to high myopes compared with non-myopes. evaluation of retinal thickness in disease conditions 184 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 retinal thickness in healthy myopic eyes; zereid and osuagwu such as glaucoma and macular degeneration should be interpreted in the light of the degree of refractive error and the region of measurement. acknowledgments the authors would like to acknowledge the deanship of scientific research, college of applied medical sciences research center at king saud university for their support. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. holden ba, fricke tr, wilson da, jong m, naidoo ks, sankaridurg p, et al. global prevalence of myopia and high myopia and temporal trends from 2000 through 2050. ophthalmology 2016;123:1036–1042. 2. goh ws, lam cs. changes in refractive trends and optical components of hong kong chinese aged 19–39 years. ophthalmic physiol opt 1994;14:378–382. 3. lin ll-k, shih y-f, tsai c-b, chen c-j, lee l-a, hung t, et al. epidemiologic study of ocular refraction among schoolchildren in taiwan in 1995. optom vis sci 1999;76:275–281. 4. vitale s, sperduto rd, ferris fl. increased prevalence of myopia in the united states between 1971–1972 and 1999– 2004. arch ophthalmol 2009;127:1632–1639. 5. xu l, wang y, li y, wang y, cui t, li j, et al. causes of blindness and visual impairment in urban and rural areas in beijing: the beijing eye study. ophthalmology 2006;113:1134.e1–1134.e11. 6. tabbara kf. blindness in the eastern mediterranean countries. br j ophthalmol 2001;85:771–775. 7. grossniklaus he, green wr. pathologic findings in pathologic myopia. retina 1992;12:127–133. 8. ikuno y. overview of the complications of high myopia. retina 2017;37:2347–2351. 9. wolter jr. clinicopathologic correlation of ocular disease. j pediatr ophthalmol strab 1979;16:141. 10. jonas j, xu l. histological changes of high axial myopia. eye 2014;28:113–117. 11. saw sm, gazzard g, shih-yen ec, chua wh. myopia and associated pathological complications. ophthalmol physiol opt 2005;25:381–391. 12. mitchell p, hourihan f, sandbach j, wang jj. the relationship between glaucoma and myopia: the blue mountains eye study. ophthalmology 1999;106:2010–2015. 13. grødum k, heijl a, bengtsson b. refractive error and glaucoma. acta ophthal 2001;79:560–566. 14. tay e, seah sk, chan s-p, lim at, chew s-j, foster pj, et al. optic disk ovality as an index of tilt and its relationship to myopia and perimetry. am j ophthalmol 2005;139:247– 252. 15. jonas jb, ohno-matsui k, panda-jonas s. optic nerve head histopathology in high axial myopia. j glaucoma 2017;26:187–193. 16. jonas jb, gusek gc, naumann go. optic disk morphometry in high myopia. graefe’s arch clin exp ophthalmol 1988;226:587–590. 17. wong y-l, ding y, sabanayagam c, wong c-w, verkicharla p, ohno-matsui k, et al. longitudinal changes in disc and retinal lesions among highly myopic adolescents in singapore over a 10-year period. eye contact lens 2018;44:286–291. 18. wakitani y, sasoh m, sugimoto m, ito y, ido m, uji y. macular thickness measurements in healthy subjects with different axial lengths using optical coherence tomography. retina 2003;23:177–182. 19. kelty pj, payne jf, trivedi rh, kelty j, bowie em, burger bm. macular thickness assessment in healthy eyes based on ethnicity using stratus oct optical coherence tomography. invest ophthalmol vis sci 2008;49:2668– 2672. 20. lim mc, hoh s-t, foster pj, lim t-h, chew s-j, seah sk, et al. use of optical coherence tomography to assess variations in macular retinal thickness in myopia. invest ophthalmol vis sci 2005;46:974–978. 21. wu p, chen y, chen c, chen y, shin s, yang h, et al. assessment of macular retinal thickness and volume in normal eyes and highly myopic eyes with third-generation optical coherence tomography. eye 2008;22:551–555. 22. luo h-d, gazzard g, fong a, aung t, hoh st, loon s-c, et al. myopia, axial length, and oct characteristics of the macula in singaporean children. invest ophthalmol vis sci 2006;47:2773–2781. 23. lam dsc, leung ks, mohamed s, chan w-m, palanivelu ms, cheung cyl, et al. regional variations in the relationship between macular thickness measurements and myopia. invest ophthalmol vis sci 2007;48:376–382. 24. sato a, fukui e, ohta k. retinal thickness of myopic eyes determined by spectralis optical coherence tomography. br j ophthalmol 2010;94:1624–1628. 25. cheng sc, lam cs, yap mk. retinal thickness in myopic and non-myopic eyes. ophthalmic physiol opt 2010;30:776–784. 26. giammaria d, ioni a, bartoli b, cofini v, pellegrini g, giannotti b. comparison of macular thickness measurements between time-domain and spectral-domain optical coherence tomographies in eyes with and without macular abnormalities. retina 2011;31:707–716. 27. teberik k, kaya m. retinal and choroidal thickness in patients with high myopia without maculopathy. pakistan j med sci 2017;33:1438–1443. 28. zhao z, zhou x, jiang c, sun x. effects of myopia on journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 185 retinal thickness in healthy myopic eyes; zereid and osuagwu different areas and layers of the macula: a fourier-domain optical coherence tomography study of a chinese cohort. bmc ophthalmol 2015;15:90. 29. tan cs, chan jc, cheong kx, ngo wk, sadda sr. comparison of retinal thicknesses measured using sweptsource and spectral-domain optical coherence tomography devices. ophthal surg las imag retina 2015;46:172– 179. 30. al-zamil wm, al-zwaidi fm, yassin sa. macular thickness in healthy saudi adults : a spectral-domain optical coherence tomography study. saudi med j 2017;38:63–69. 31. alonso-caneiro d, read sa, vincent sj, collins mj, wojtkowski m. tissue thickness calculation in ocular optical coherence tomography. biomed opt express 2016;7:629–645. 32. abbott cj, grünert u, pianta mj, mcbrien na. retinal thinning in tree shrews with induced high myopia: optical coherence tomography and histological assessment. vision res 2011;51:376–385. 33. kim ky, kwak hw, kim m, kim yg, yu s-y. new profiles of posterior pole retinal thickness map in healthy korean eyes measured by spectral-domain optical coherence tomography. retina 2013;33:2139–2148. 34. kobayashi k, ohno-matsui k, kojima a, shimada n, yasuzumi k, yoshida t, et al. fundus characteristics of high myopia in children. japanese j ophthalmol 2005;49:306–311. 35. park k-a, oh sy. analysis of spectral-domain optical coherence tomography measurements in amblyopia: a pilot study. british j ophthalmol 2011;95:1700–1706. 36. kitaya n, ishiko s, abiko t, mori f, kagokawa h, kojima m, et al. changes in blood–retinal barrier permeability in form deprivation myopia in tree shrews. vision res 2000;40:2369–2377. 37. massin p, erginay a, haouchine b, mehidi ab, paques m, gaudric a. retinal thickness in healthy and diabetic subjects measured using optical coherence tomography mapping software. eur j ophthalmol 2002;12:102–108. 38. wong a, chan c, hui s. relationship of gender, body mass index, and axial length with central retinal thickness using optical coherence tomography. eye 2005;19:292–297. 39. demirkaya n, van dijk hw, van schuppen sm, abràmoff md, garvin mk, sonka m, et al. effect of age on individual retinal layer thickness in normal eyes as measured with spectral-domain optical coherence tomography. invest ophth vis sci 2013;54:4934–4940. 40. wagner-schuman m, dubis am, nordgren rn, lei y, odell d, chiao h, et al. raceand sex-related differences in retinal thickness and foveal pit morphology. invest ophthalmol vis sci 2011;52:625–634. 41. huynh sc, wang xy, rochtchina e, mitchell p. distribution of macular thickness by optical coherence tomography: findings from a population-based study of 6-year-old children. invest ophthalmol vis sci 2006;47:2351–2357. 186 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 photo essay bilateral keratoconus in a patient with isolated foveal hypoplasia kiana hassanpour, md, mph; ramin nourinia, md; nazanin behnaz, md; mohsen azarmina, md setareh jalali, md; danial roshandel, md ophthalmic research center, shahid beheshti university of medical sciences, tehran, iran orcid: kiana hassanpour: https://orcid.org/0000-0002-1788-7352 danial roshandel: https://orcid.org/0000-0002-6716-6406 j ophthalmic vis res 2020; 15 (2): 256–258 presentation we present a 29-year-old woman complaining of low visual acuity since childhood being deteriorated in the past six months. ophthalmic examination revealed lowamplitude, jerky horizontal nystagmus in both eyes that worsened in end-gaze. the manifest refraction was –3.00 –9.5 × 20° and –2.5 –9.00 × 150° in her right and left eyes, respectively. the best spectacle-corrected visual acuity (bscva) was 20/70 in both eyes. in both eyes, bcva with rigid gas permeable lenses was 20/50. direct and consensual pupillary light reflexes were within normal limits and no relative afferent pupillary defect was detected. color vision tested by ishihara’s color plates revealed no deficits. slit lamp examination showed mild paracentral corneal thinning and bulging, fleischer’s ring, and vogt’s striae in both eyes. iris examination revealed no sign of transillumination. intraocular pressure measured by goldmann applanation tonometry was 15 mmhg in both eyes. dilated fundus correspondence to: danial roshandel, md. department of ophthalmology, labbafinejad medical center, paidarfard st., boostan 9 st., pasdaran, tehran 16666, iran. e-mail: danial.roshandel@gmail.com received: 26-07-2018 accepted: 17-03-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i2.6745 examination revealed generalized chorioretinal atrophy and no foveal reflex and no macular yellow hue. retinal capillaries at the macular area showed mild irregularity. both optic discs were pink and had sharp margins. placido disk-based topography showed asymmetric bow-tie pattern with skewed radial axes in both eyes [figure 1]. spectral domain optical coherence tomography (oct) scans showed the absence of the foveal depression and persistent inner retinal layers (similar to paramacular scans) within the fovea in both eyes [figure 2]. fluorescein angiography (fa) revealed a small capillary-free zone in both eyes with almost normal masked fluorescence in the macular area due to the presence of macular pigments [figure 3]. electroretinograms (both photopic and scotopic) and electrooculograms showed normal results in both eyes. discussion continuity of the inner retinal layers and absence or decrease of the foveal depression (also known as fovea plana) are typical oct findings in foveal hypoplasia (fh).[1] in our case, along with the this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: hassanpour k, nourinia r, behnaz n, azarmina m, jalali s, roshandel d. bilateral keratoconus in a patient with isolated foveal hypoplasia. j ophthalmic vis res 2020;15:256–258. 256 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i2.6745&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; hassanpour et al figure 1. placido disk-based topography showing asymmetric bow-tie patterns with skewed radial axes (srax) in both eyes. the steep and flat keratometry of the right eye was 65.00 d at 107º and 55.17 d at 17º, respectively. in the left eye, the steep and flat keratometry was 51.74 d at 55º and 43.03 d at 145º, respectively. figure 2. spectral-domain optical coherence tomographic section through the center of the macular area of the right (a) and left (b) eyes. a shallow foveal pit, continuity of the inner retinal layers, the presence of outer nuclear layer (onl) widening, and outer segment (os) lengthening in the macula of both eyes are noted. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 257 photo essay; hassanpour et al figure 3. fluorescein angiography of the right (a) and left (b) eyes showing a small capillary-free zone in each eye, with almost normal masked fluorescence in the macular area due to the presence of the macular pigments. presence of the typical clinical findings of fh, macular oct revealed a shallow foveal pit and abnormal persistence of the inner retinal layers in the foveal area. diagnosis of fh was further supported by demonstrating the abnormal extension of the retinal capillaries toward the foveal area in fa. many reports have linked chronic eye rubbing and keratoconus, especially in children.[2] our patient also had a history of habitual eye rubbing since her childhood, which may explain the development of keratoconus (kc). however, because of the consanguineous marriage of her parents, the inheritance of a recessive mutation should also be considered as a possible etiology for these findings. the visual system homeobox (vsx1) gene encodes vsx1, which is mainly present in human retinal cells. interestingly, mutations in this multifunctional gene have been described in kc and posterior polymorphous corneal dystrophy and may result in abnormal development of both the cornea and the retina.[3] although this rare and unique association may be an incidental finding, comprehensive genetic study is needed to confirm this hypothesis. financial support and sponsorship none. conflicts of interest there are no conflicts of interest. references 1. kwon jy, marmor m, kodsi sr. clinical characteristics of isolated foveal hypoplasia: a case series. j am assoc pediatr ophthalmol strabismus 2016;20:e36. 2. weed kh, macewen cj, giles t, low j, mcghee cn. the dundee university scottish keratoconus study: demographics, corneal signs, associated diseases, and eye rubbing. eye 2008;22:534. 3. vincent al, jordan c, sheck l, niederer r, patel dv, mcghee cn. screening the visual system homeobox 1 gene in keratoconus and posterior polymorphous dystrophy cohorts identifies a novel variant. mol vis 2013;19:852. 258 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 original article orthokeratology in moderate myopia: a study of predictability and safety kirti singh, md, dnb, frcs; mainak bhattacharyya, ms, dnb; abhishek goel, ms, dnb, fico ritu arora, md, dnb; nikhil gotmare, ms; himshikha aggarwal, mbbs guru nanak eye centre, maharaja ranjit singh marg, new delhi, india orcid: kirti singh: http://orcid.org/0000-0002-9181-5963 mainak bhattacharyya: http://orcid.org/0000-0002-0571-5764 abstract purpose: literature is relatively silent on safety profile and predictability of orthokeratology lenses in terms of myopia correction and prevention of further progression, especially in semi-tropical countries; this study was designed to fill this gap. methods: this prospective, intervention case series enrolled 30 eyes of 30 patients with myopia up to –5.5 diopters (d). patients were randomized into two groups of 15 each; the study group was prescribed overnight orthokeratology (ok) lenses, while the control group used daily wear conventional soft contact lenses. follow-up examinations were performed after 1 h and 6 h, and then at 1, 7, 15, 30 days, and 4 months post lens wear. uncorrected visual acuity (ucva), contrast sensitivity, keratometry, central corneal thickness (cct), and tear film break up time (tbut) were evaluated at each follow-up examination. results: all patients attained a visual acuity of 0.00 logarithm of the minimum angle of resolution (logmar) after one week of lens use, which was maintained throughout the study period. while patients allotted to the study group had a gain of 8.1 snellen lines (ucva), those in the control group gained 8.9 lines (bcva) at the end of follow-up period. in the ok group, cornea showed a flattening of 0.8 d (mean keratometry) after single overnight usage of ok lens and overall flattening of 1.2 d compared to baseline, at the end of four months. the change in contrast sensitivity, corneal endothelial specular count, axial length and tear film status was not significant in either group. conclusion: orthokeratology is an effective and safe modality to correct moderate myopia in motivated young adults. no side effects were encountered after a short-term follow-up in participants who resided in semi-tropical environments. keywords: contact lens; overnight wear; orthokeratology; moderate myopia; semi-tropical environments j ophthalmic vis res 2020; 15 (2): 210–217 correspondence to: mainak bhattacharyya, ms, dnb. 19/312, shivam khand, vasundhara, ghaziabad 201012, india. e-mail: drmainakb@gmail.com received: 28-03-2018 accepted: 16-04-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i2.6739 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: singh k, bhattacharyya m, goel a, arora r, gotmare n, aggarwal h. orthokeratology in moderate myopia: a study of predictability and safety. j ophthalmic vis res 2020;15:210–217. 210 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i2.6739&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr orthokeratology in moderate myopia; singh et al introduction orthokeratology (ok) is defined as “reduction, modification, or elimination of a refractive error by programmed application of contact lenses.”[1] its genesis arose following a serendipitous observation by wesley and jessen in the 1950s who found spectacle blur experienced by patients after wearing hard contact lenses. this perceived blurring was subsequently traced to lens-induced corneal reshaping, which was then utilized for therapeutic purposes.[2] the method was eventually discontinued due to problems of poor lens fitting, unpredictable results, and safety concerns.[3–6] this lost science of ok was revived in the late 1980s with the development of reverse-geometry contact lens designs by wlodyga and stoyan.[7] their design permitted more predictable results to be achieved over shorter periods. further refinement using very high oxygen-permeable materials ushered in an era of overnight lens wear. this overnight ok lens reduced daytime visual aid requirements and came to be known as “accelerated orthokeratology” because of the rapid onset of refractive and corneal topographic changes.[8] the ok lenses work by altering the corneal shape from prolate to oblate, resulting in a reduction in the central corneal curvature. this alteration of shape is a result of the flat lens design, causing a redistribution of corneal epithelium and anterior stromal tissue over the central treatment zone which is 5 to 6 mm in diameter.[9] the central treatment zone is dictated by pupil size, and treatment zone less than mesopic pupil dimensions can adversely affect vision in conditions of lowillumination and low-contrast. the reversibility of the procedure within two to four weeks of discontinuation of ok lens wear is a consequence of regression of corneal parameters.[10] common issues of concern with ok lens use include the unpredictability of visual gain due to issues of inadequate lens centration, poor contrast with persistent use, and increase in higherorder aberrations (hoa) and safety because of the inherent risk of microbial keratitis.[11] in semi-tropical environments, microbial growth is expected to be more florid, especially in the closed-eye conditions simulated by ok lens wear. these risks underscore the importance of safety profiling of ok lenses in semi-tropical environments. previous studies have also reported a high rate of keratitis associated with lens use in semi-tropical regions.[12, 13] stringent lens care regimens have made ok a safe overnight treatment modality, but evidence on safety and predictability of ok lens use in semitropical environments is relatively scarce; this study was designed to bridge this gap. methods this study was a prospective, interventional trial of ok lens wear in 30 eyes of 30 patients with myopia up to –5.5 diopters (d). this research followed the tenets of the declaration of helsinki. informed consent was obtained from all participants after explanation of the nature and possible consequences of the study. this research was approved by our local institutional ethical committee. inclusion criteria were: age 18–30 years; myopia up to –5.5 d, and with-the-rule astigmatism of up to –1.5 d or against-the-rule astigmatism up to –0.75 d with keratometry values between 40 and 45 d. patients with pathological myopia, corneal pathologies such as dry eyes, healed keratitis, ocular surgery, keratoconus and systemic comorbidities such as diabetes mellitus and thyrotoxicosis were excluded from the study. patients were randomized (using the closed envelope method) into two groups of 15 each: the study group (ok group) was prescribed ok lenses in one eye only and the control group was prescribed daily wear conventional soft contact lenses in both eyes. the evaluated parameters were cycloplegic refraction, uncorrected visual acuity (ucva), bestcorrected visual acuity (bcva) using a snellen chart, corneal topography and keratometry by orbscan iiz (bausch & lomb technolas topographer, usa), central corneal thickness (cct) (sonomed 300p pacscan; sonomed escalon, usa), tear film break up time (tbut), contrast sensitivity (using fact charts), corneal endothelial cell count (nidek cem 530, nidek co ltd, japan), and axial length. the study group was subjected to a trial of reverse geometry lenses, made of boston xo material with diffusion constant (dk) value 140 (orthok lucid korea lenses). these light blue colored lenses of 10.6 mm diameter were available in a power range of –0.50 d to –5.0 d with base curves ranging from 8.44 mm (40.00 d) to 7.42 mm (46.00 d). the flat k reading was used to calculate the base curve of the first trial lens. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 211 orthokeratology in moderate myopia; singh et al sequential flattening or steepening was performed in steps of 0.4–0.5 bc until an optimal fluorescein bull’s eye pattern was attained [figure 1]. a movement of 1 mm was the goal for dynamic fit, but a greater emphasis was placed on the static fit. patients were assessed after 1 h of wear to confirm adaptability and detect early improvements (if any) in visual acuity. the lens was then inserted in one eye, and the patient was admitted overnight to ensure initial comfort and adherence. ucva, contrast sensitivity, keratometry values, cct, and tbut were evaluated in the morning after the first night of ok wear. the patients were then discharged and asked to resume normal daily activities while using ok lenses during their 8– 9 h of night-time sleep. the duration of ok lens usage was determined based on the amount of myopia to be corrected. for mild myopia (–2.0 to –3.5 d), the ok lens was worn every night for three weeks followed by alternate nights. for moderate myopia (> –3.5d), the lens was worn every night. subjects were followed-up at days 7, 15, 30, and then monthly for four months. subjective assessments of the comfort and tolerability of lens wear were evaluated for each patient at the beginning and end of the study. the criteria used included quality of vision, comfort/difficulty of lens wear, ghosting of images, halos, flares, or difficulties in performing tasks in dim light. the cl group subjects were prescribed conventional daily wear soft contact lenses (silk lens) with a dk value of 50 and a thickness of 0.1 mm. these patients were not admitted for the first night, but instead were followed-up at 1 h and 6 h of lens wear on days 1, 7, 15, 30, and then monthly until four months. the lens usage was as per requirements, which ranged from 6–9 h per day. both eyes were prescribed soft lenses, but only one eye was included for the purpose of the study. statistical analysis continuous variables were expressed as means ± standard deviations, and categorical variables were expressed as frequencies and percentages. an independent t-test was used to compare the continuous variables between the ok and control groups, whereas a paired t-test was used to compare the change of measurement results for paired samples. a chi-squared test or fisher exact test was used to examine differences in categorical variables. statistically significant differences were defined as p < 0.05. statistical analyses were carried out using the statistical package for social sciences (spss) version 17.0 software. results the ok and control groups were age matched, with the average age being 22.3 ± 2.8 years in the ok group and 22.1 ± 6.8 years in the control group (p = 0.9). the sample consisted of 16 females and 14 males. the mean spherical refractive error in the ok group was –3.4 ± 1.3 d (–2.0 to –5.5 d), with a cylindrical error of –0.4 ± 0.5 d at 69 ± 32° (–0.25 to –1.5 d at 15–95°). the mean spherical refractive error in the control group was –3.4 ± 1.03 d (–1.8 to –5.3 d) with mean cylindrical error of –0.2 ± 0.3d at 95 ± 6° (–0.25 to –1.75d at 20–100°). no statistically significant intergroup differences were found in the distribution of refractive errors using the mann–whitney test (p = 0.351). visual acuity mean visual acuities in the ok and control groups at presentation were 1.07 ± 0.15 and 1.040 ± 0.11 log mar, respectively (p = 0.635). at all subsequent follow-ups, visual acuity measures were taken after the removal of the ok lens in the study group and with the soft lens in situ in the control group. post lens wear visual acuity at 1 h was 0.31 ± 0.3 logmar in the ok group versus 0.00 logmar in the control group. at day 7, the visual acuities were 0.05 ± 0.1 logmar versus 0.00 logmar in the ok and control groups, respectively. after that, both groups had a visual acuity of 0.00 logmar at all subsequent follow-ups. a statistically significant intergroup difference in visual acuity was seen only at 1 h and 6 h of lens wear (p < 0.001) [figure 2]. in the ok group, the gains in snellen lines of visual acuity were 4.98 at 1 h, 8.1 lines and the end of follow-up. in the control group, the gains were 8.9 lines at all follow-ups beginning at 1 h. this underscores the fact that ok lens wearers took time to attain good unaided visual acuity, whereas control wearers (the control group) had an instant gain of aided good vision. visual acuity of 0.0 logmar units (6/6 snellen) was achieved after one day of overnight wear in patients with mild myopia and by day 7 of overnight wear in patients with moderate myopia. the target 212 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 orthokeratology in moderate myopia; singh et al figure 1. sequential fitting from steep fit to ideal fit during trial fitting of an orthokeratology patient. figure 2. gain in number of snellen lines after lens wear. cl, contact lens; ok, orthokeratology of visual acuity of 0.0 logmar (snellen 6/6) was attained in all patients and was maintained for the entire four-month follow-up period. a drop of 1.2 lines in the evening time was documented in the ok group during the first week of the ok lens use. corneal alterations and effect on contrast sensitivity and tear film corneal alterations were assessed by evaluating changes in corneal topography, pachymetry, and endothelial cell counts. additional deleterious effects (if any) on contrast sensitivity and tear film dynamics were recorded [table 1]. corneal topography exhibited maximal changes in keratometry readings occurring within the first night of ok lens wear. these effects were particularly evident within the first hour of lens wear, reaching a significant level (p = 0.034). this change plateaued by 6 h of wear with no further significant change. over the longitudinal follow-up period, the maximal change in mean sim k (measured at central 3and 5mm central zones) occurred within the initial four weeks of ok lens wear [figures 3 and 4]. as depicted in table 1, this change was highly significant at the final follow-up at four months. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 213 orthokeratology in moderate myopia; singh et al figure 3. change in mean keratometry in both groups in 3-mm zone. cl, contact lens; k, keratometry; ortho k, orthokeratology. figure 4. change in mean keratometry in both groups in 5-mm zone. cl, contact lens; k, keratometry; ortho k, orthokeratology. table 1. change in corneal pachymetry, 3-mm and 5-mm zone keratometry, specular count tear film break-up time, axial length and contrast sensitivity in the study (ortho k) and control groups post lens wear ortho k group control group intergroup comparison pre lens wear post lens use (four months) pre lens wear post lens use (four months) corneal pachymetry 527 ± 28.4µm 525.8 ± 27.4 µm 532 ± 27.4 µm 530.80 ± 29.07 µm ns keratometry (3-mm zone) 44.37 ± 1.3 d 42.83 ± 1.1 d 1.54 (p = 0.000) 44.12 ± 0.9d 44.14 ± 0.9 d p = 0.002 significant keratometry (5-mm zone) 44.58 ± 1.2 d 43.38 ± 0.7 d 1.2 (p = 0.000) 43.72 ± 1.0 d 43.68 ± 0.9 d ns specular count 2901.40 ± 305.5 cells/mm3 2894 ± 294.6 cells/mm3 2772.87 ± 290.3 cells/mm3 2733.20 ± 249.6 cells/mm3 ns tear film break-up time (tbut) (in seconds) 11.9 ± 0.96 s 12.6 s 11.8 ± 1.1 s 12.1 ± 0.7 s ns axial length 24.13 ± 0.7 mm 24.01 ± 0.4 mm 23.47 ± 0.7 mm 23.13 ± 0.6 mm ns contrast sensitivity (by fact chart) 1.42 ± 0.12 1.423 ± 0.11 1.373 ± 0.09 1.37 ± 0.94 ns d, diopter; ns, not significant 214 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 orthokeratology in moderate myopia; singh et al corneal flattening by 1.5 d in mean k (3 mm zone) and 1.2 d (5 mm zone) was observed in ok group patients by the end of the study period. the 5mm zone keratometry documented the flattening earlier, beginning at 7 days compared to the 14 days for the 3-mm zone keratometry map. during the entire follow-up period, perceived lens tolerance and comfort were high, with no dropouts seen. there were no statistically significant changes in tbut between the baseline and four-month follow-up measurements in either group – 11.9 ± 0.96 s and 11.8 ±1.1 s, respectively, in the ok group (p = 0.112) and 12.3 ± 0.6 s and 12.1 ± 0.7 s, respectively, in the control group (p = 0.132). intergroup comparison revealed no statistically significant difference between the two groups in tbut values measured before intervention (p = 0.90) or after four months (p = 0.123). this implied that no significant tear film disruptions were observed at any of the follow-ups in either the study group or the control group. contrast sensitivity (cs) was measured using fact charts at 3 meters. there were no statistically significant differences in contrast sensitivity, as indicated by preto post lens prescription cs values, for either the ok (pre: 1.4 ± 0.1, post: 1.4 ± 0.1) (p = 0.189) or cl (pre: 1.37 ± 0.1, post: 1.37 ± 0.9) (p = 1.0) groups. the change in contrast sensitivity in the ok group (0.4 grid) was not significant as compared to no change in the cl group patients during the entire follow-up period of four months. subjective improvements in vision quality in the eyes treated with the ok lenses were adequate for the performance of daily activities with no additional vision aids. subjective score assessments improved in all patients at all follow-ups, with only a handful of patients complaining of ghosting of images, glare, or difficulties in dim light on day 1. these complaints resolved by the end of four months. no significant lens decentration, corneal abrasion, dry eye, or sight-threatening complications such as microbial keratitis was noted in any of the subjects over the entire follow-up. discussion orthokeratology utilizes contact lenses to “reduce, modify, or eliminate refractive errors.”[14] a resurgence of interest in this technology occurred after the advent of reverse-geometry lens designs and use of an extremely high dk material which makes these lenses easy to center and safer for the cornea. reverse-geometry ok lenses incorporate a secondary curve, steeper than the lens base curve, to aid centration and are fitted with a base curve flatter than the central corneal curvature. this applies pressure to the central treatment zone, altering the corneal shape from prolate to oblate after overnight wear.[15] ok is reportedly effective in slowing myopia progression over a 12year follow-up period with a clinically acceptable safety profile.[14] in our study, 60% of refractive correction was achieved after the first overnight ok wear, and almost 100% visual correction was achieved after one week of continuous overnight ok lens wear. this dramatic initial visual improvement is consistent with previous studies.[15, 16] the initial correction achieved in the morning after overnight okwear starts wearing off within hours due to the regression of the corneal shape, leading to visual blurring in the afternoon period.[13] this fact was confirmed by our results, with patients complaining of afternoon blur with a drop of 1.2 snellen lines in the evening during the first week. this effect is usually transient and resolves over a week.[17] stabilization of visual gain varies, with most studies reporting a gestation of four weeks and others— like ours—a period of 7–10 days.[15, 16, 18–20] a concern with ok lenses is loss of contrast; however, in this series contrast sensitivity (and visual acuity) did not deteriorate either in the ok group or the control group after lens wear.[22] a study by tang et al measuring contrast sensitivity under both photopic and mesopic conditions corroborated this finding.[23] corneal flattening by a mean of 1.2 d was observed by four months, with maximum flattening after initial overnight use. this correlated more with the 5-mm zone topography value, which also picked up the peripheral changes earlier. these discrepancies in the 3and 5-mm zones can be explained by the principle of ok where the lens hydraulically redistributes epithelial cells from the center toward the periphery and induces central corneal thinning and mid-peripheral thickening.[13] thus, 5-mm zone keratometry is a more sensitive indicator of ok-induced change and detects these changes earlier than the 3-mm zone map. the most common problem associated with ok lens use is inadequate lens centration with superior displacement due to bell’s phenomenon during journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 215 orthokeratology in moderate myopia; singh et al sleep, causing with-the-rule astigmatism.[11] sun et al have recently reported increased corneal irregularity and ocular hoa (spherical aberrations and comas) with ok lenses, despite improvements in refractive error.[24] no significant lens decentration was seen in our patients. in our series, no case of induced toxicity was noted, and no patient presented with any evidence of corneal damage or infiltration. this could be a result of the explicit lens care instructions that were given, and the vigilance of our motivated patients in carrying out lens hygiene measures. a review of literature on infectious keratitis associated with ok lens use reports that pseudomonas aeruginosa and acanthamoeba are the most commonly identified infectious agents with the majority of infections resulting in corneal scar formation, necessitating surgical intervention in 10% of eyes.[25] previous studies have emphasized the importance of proper lens care and maintenance of lens hygiene to ensure the safety of long-term ok lens wear.[26, 27] this study was designed as a pilot study evaluating efficacy and safety of ok, and longer follow-ups are necessary to establish the long-term effects of ok lenses. as the risk of keratitis is not high, substantial, long-term follow-up cohorts are necessary to evaluate the risk of keratitis associated with these contact lenses. no lens is considered completely safe for overnight wear. in addition, given that refractive surgeries such as lasik/smile are very popular, some may question the relevance of ok lenses.[28] however, ok lenses are noninvasive, reversible, and relatively safe to use (even in thin corneas) and hence stay relevant, especially in a developing country like ours. in conclusion, ok is an effective and safe method for correcting moderate myopia in motivated young adults. use of ok lenses was not associated with deleterious corneal complications, even in wearers residing in semi-tropical environments. acknowledgments the authors would like to thank dr. mamtamayi priyadarshani (prkamya visions) for her technical support and guidance. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. kerns rl research in orthokeratology. part i: introduction and background. j am optom assoc 1976;47:1047–1051. 2. wesley n, jessen g. advanced techniques in contact lens fitting. 2nd ed. chicago, il: contact lens publishing company; 1960:1–67. 3. jessen g. orthofocus techniques. conctacta 1962;6:200– 204. 4. kerns rl. research in orthokeratology. part viii. results, conclusions and discussion of techniques. j am optom assoc 1978;49:308–314. 5. coon lj. orthokeratology. part ii: evaluating the tabb method. j am optom assoc 1984;55:409–418. 6. polse ka, brand rj, schwalbe js, vastine dw, keener rj. the berkeley orthokeratology study, part ii: efficacy and duration. am j optom physiol optics 1983;60:187–198. 7. wlodyga rj, bryla c. corneal molding: the easy way. contact lens spectrum 1989;4:58–65. 8. grant sc, may ch. orthokeratology: a therapeutic approach contact lens procedures. contacto 1970;14:3. 9. swarbrick ha, wong g, o’leary dj. corneal response to orthokeratology. optom vis sci 1998;75(11): 791-9. 10. yoon ym, kim mk, lee jl. change of corneal parameters after removing reverse geometry lens in moderate degree myopia. j korean ophthalmol soc 2005;46:1478–1485. 11. kerns rl. research in orthokeratology. part iii: results and observations. j am optom assoc 1976;47:1505–1515. 12. cariello aj, passos rm, yu mc, hofling-lima al. microbial keratitis at a referral center in brazil. int ophthalmol 2011;31:197–204. 13. dos santos dl, kwitko s, marinho dr, araújo bs, locatelli ci, rott mb. acanthamoeba keratitis in porto alegre (southern brazil): 28 cases and risk factors. parasitol res 2018;117:747–750. 14. mountford j, pesudovs k. an analysis of the astigmatic changes induced by accelerated orthokeratology. clin exp optom 2000;85:284–293. 15. swarbrick ha. a possible aetiology for rgp lens binding (adherence). int contact/lens clinic 1998;15:13–19. 16. lee yc, wang jh, chiu cj. effect of orthokeratology on myopia progression: twelve-year results of a retrospective cohort study. bmc ophthalmol 2017;17:243. 17. cho p, cheung sw, edwards m. practice of orthokeratology by a group of contact lens practitioners in hong kong, part 2. clin exp optom 2002;86:42–46. 18. swarbrick ha, alharbi a. the effects of overnight orthokeratology lens wear on corneal thickness. invest ophthalmol vis sci 2003;44:2518–2523. 19. soni p, nguyen t. corneal parameter, anterior corneal curvature, posterior corneal curvature or corneal thickness, acute changes with reverse geometry orthokeratology lenses. j ocul pharmacol ther 2002;46:221–224. 20. luo m, ma s, liang n. clinical efficacy of toric orthokeratology in myopic adolescent with moderate to high astigmatism. eye sci 2014;29:209–213. 216 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 orthokeratology in moderate myopia; singh et al 21. lui wo, edwards mh. orthokeratology in low myopia. part 2: corneal topographic changes and safety over 100 days. cont lens anterior eye 2000;23:90–99. 22. santolaria-sanz e, cerviño a, gonzález-méijome jm. corneal aberrations, contrast sensitivity, and light distortion in orthokeratology patients: 1-year results. j ophthalmol 2016;2016:8453462. 23. tang w. the relationship between corneal topography and visual performance. j am optom assoc 1999;24:312–318. 24. sun y, wang l, gao j, yang m, zhao q. influence of overnight orthokeratology on corneal surface shape and optical quality. j ophthalmol 2017;2017:3279821. 25. kam kw, yung w, li gkh, chen lj, young al. infectious keratitis and orthokeratology lens use: a systematic review. infection 2017;45:727–735. 26. swarbrick h. overnight orthokeratology and the risk of microbial keratitis. eye contact lens 2005;31:201–208. 27. watt k, swarbrick h. trends in microbial keratitis associated with orthokeratology. eye contact lens 2007;33:373–377. 28. tian m, ma p, mu g. prospective cohort comparison of visual acuity and contrast sensitivity between femto laser in situ keratomileusis and orthokeratology for low-tomoderate myopia. eye contact lens 2018;44:s194–s198. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 217 case report unilateral duane retraction syndrome associated with unilateral congenital cataract majid farvardin, md; alireza bolkheir, md poostchi ophthalmology research center, shiraz university of medical sciences, shiraz, iran orcid: majid farvardin: https://orcid.org/0000-0001-9047-0329 alireza bolkheir: https://orcid.org/0000-0001-9528-615x abstract purpose: to report unilateral congenital cataract in a case of ipsilateral duane retraction syndrome. case report: in this case, we present a six year old girl who was referred with ocular deviation. she had a history of congenital cataract surgery in the left eye at the age of two years. the subject had no associated systemic disease, developmental delay, or positive family history. she was finally diagnosed as having duane retraction syndrome in the same eye. conclusion: duane retraction syndrome can be associated with congenital cataract due to the matching time of gestational development of the lens to that of ocular and nonocular anomalies associated with duane syndrome. as both of these disorders are rare, coincidence of both in the same person and the same eye by chance is a very remote possibility. keywords: congenital cataract; duane retraction syndrome j ophthalmic vis res 2020; 15 (1): 95–98 correspondence to: alireza bolkheir, md. strabismus and pediatric ophthalmology service, department of ophthalmology, khalili hospital, shiraz university of medical sciences, shiraz 71345, iran. e-mail: soroushbolkheir@ymail.com received: 27-06-2018 accepted: 06-02-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i1.5952 introduction duane retraction syndrome is a rare condition, for which mechanical, anatomical, and innervational disorders of the extraocular muscles are suggested as the etiologies.[1] as a teratogenic congenital cranial innervational disorder at 4th-8th weeks of gestation, duane retraction syndrome has a 12% chance of association with other congenital ocular anomalies.[2] in this article, we present a six year old girl who was referred with ocular deviation. she had a history of congenital cataract surgery in the left eye at the age of two years. she had no associated systemic disease or developmental delay and family history was unremarkable. she was finally diagnosed as having duane retraction syndrome in the left eye. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: farvardin m, bolkheir a. unilateral duane retraction syndrome associated with unilateral congenital cataract. j ophthalmic vis res 2020;15:95–98. © 2020 journal of ophthalmic and vision research | published by knowledge e 95 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i1.5952&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr unilateral duane syndrome with congenital cataract; farvardin and bolkheir case report a six year old girl was referred to the strabismus and pediatric ophthalmology service at the shahid mottahhari clinic (a referral eye clinic in the south of iran) due to outward deviation and decreased visual acuity in her left eye. she was the first child in her family, born by cesarean section because of her mother’s uncontrolled gestational diabetes mellitus. her birth weight was 3.2 kg. at the age of two years, she underwent lensectomy and posterior intraocular lens implantation due to a congenital cataract in the left eye. her family history was negative for congenital cataract and ocular deviations and she had no neurodevelopmental delay. the ophthalmologic examination revealed the best corrected visual acuity (bcva) as 20/25 in the right eye and 20/300 in the left eye. cycloplegic refraction was +0.25–0.25*125 in the right eye and +1.5–2.00*170 in the left eye. intraocular pressure, measured by air puff tonometry, was 17and 13mmhg in the right and left eyes, respectively. she had a left exotropia of 8 prism diopters in primary position. ocular motility examination showed limitation in adduction and abduction with narrowing of the palpebral fissure and downshoot and upshoot upon attempted adduction in the left eye which was consistent with a left duane retraction syndrome. vertical ductions were within normal limits in both eyes [figure 1]. an examination of the anterior segment revealed a posterior chamber intraocular lens in the capsular bag with a posterior capsular opacity in the left eye. the result of dilated fundus examination was unremarkable in both eyes. due to the small angle deviation and amblyopia in the left eye, we recommended right eye patching (4 hours per day) and follow up. discussion congenital cataract is the most common treatable reason for blindness in children, which occurs in 1– 15:10,000children.[3] only 20% of the patients have a positive family history and 3–15% have some types of infectious etiology.[3–5] it may be associated with other ocular or systemic abnormalities in half of the patients.[4] two-third of the patients have bilateral cataract, which includes more than 90% of the hereditary cases, but half of the sporadic cases are unilateral.[5] our patient had a congenital cataract only in the left eye and no family history of congenital cataract. her disease was diagnosed at the age of two years, but at the time of diagnosis, no concomitant ocular or systemic disorder was noticed. she underwent a cataract surgery in the left eye. the child described here had not been investigated for concomitant abnormalities until she was referred to us, when exotropia in the primary gaze, limitation in adduction and abduction, narrowing of the palpebral fissure, and downshoots and upshoots on attempted adduction (all in her left eye) led us to the diagnosis of duane retraction syndrome. duane retraction syndrome is expected to be diagnosed early, because the symptoms are usually quite evident. nevertheless, some cases have been reported with delayed diagnosis.[6] the mechanical etiology of duane retraction syndrome is suggested to be fibrosis of the extraocular muscles and abnormal insertions.[7] this syndrome has also been classified as a cranial dysinnervation due to the paradoxical innervation of the rectus muscles along with central nervous system anomalies.[1] duane retraction syndrome accounts for 1–4% of all strabismus patients and its incidence had been estimated as 0.04% in general population.[6, 8] according to derespinis and colleagues, the main ocular and non-ocular abnormalities associated with duane retraction syndrome occur during the 4th–8th gestational weeks, while the cranial nerves and nuclei (3, 4, and 6) develop during the 5th–8th and extraocular muscle innervation during the 4th–6th gestational weeks.[1] on the other hand, the lens forms during the invagination of the surface ectoderm overlying the optic vesicle at approximately the 4th week of gestation. the embryonic nucleus develops by the 6th week of gestation.[5] thus, the time of gestational development of the lens matches that of the ocular and non-ocular anomalies associated with duane retraction syndrome, and the same teratogenic factor may lead to both disorders. as both of these disorders are rare, coincidence of them by chance in the same person and the same eye is a very remote possibility. several non-ocular anomalies such as deafness, musculoskeletal disorders, cardiac defects, and other disorders have been associated with 96 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 unilateral duane syndrome with congenital cataract; farvardin and bolkheir figure 1. exotropic duane retraction syndrome, left eye. top row, upshoot upon adduction in the left eye. middle row, exotropia in primary position, limitation of abduction and adduction with retraction of the globe on adduction, all in the left eye. bottom row, downshoots upon attempted adduction in the left eye. duane retraction syndrome. the majority of cases are non-syndromic and sporadic, mainly occurring in female patients and in the left eyes.[1, 2, 9] although our patient had no developmental delay or systemic disorder, a number of cases may be associated with neurodevelopmental delay,[6] and some show inheritance and mutations.[10] mohan and colleagues reported 12% associated ocular abnormalities among 331 patients with duane retraction syndrome (291 unilateral and 40 bilateral cases). they reported the following findings in patients with unilateral duane retraction syndrome: congenital ptosis (8%), congenital nasolacrimal duct obstruction, conjunctival dermolipoma, and nystagmus (0.6% each), orbital dermoid cyst, congenital ptosis with marcus gunn phenomenon, distichiasis, multiple conjunctival nevi, bilateral congenital cataract, and situs inversus of the disc and nasal crescent (0.3% each). in the patients with bilateral duane retraction syndrome, they found congenital ptosis (5%), congenital ptosis with marcus gunn phenomenon, bilateral microcornea, choroidal coloboma, and nystagmus (2.5% each).[2] in their case series, they reported one patient with simultaneous unilateral duane syndrome and bilateral congenital cataract.[2] ahluwalia and colleagues reported another case of congenital cataract in their study of 20 patients with duane retraction syndrome.[8] derespinis et al described congenital cataract as a less frequent ocular finding in duane retraction syndrome.[1] an association of duane retraction syndrome and lenticonus has also been reported in two patients from canada, and china.[11, 12] several classifications have been suggested for duane retraction syndrome (types i, ii, iii) and the subtypes are suggested to stem from the same pathogenesis.[1] the most commonly used classification is categorizing patients as having esotropia, exotropia, or orthotropia.[1, 9] in our case, the patient experienced exotropic duane retraction syndrome. as the overall prevalence of duane retraction syndrome is low, it is important to know the main symptoms and signs of this syndrome and consider the differential diagnoses including the pseudo duane retraction syndrome. considering the gestational age of duane retraction syndrome development, ophthalmologists should be aware of any possible ocular or systemic anomalies that may occur at the same gestational age. familial inheritance is observed in 10% of cases with duane retraction syndrome;[1] therefore, ophthalmologists should examine the siblings and other family members for this disorder. report of new cases can improve the knowledge of ophthalmologists, ensure the timely treatment, and prevent further complications. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 97 unilateral duane syndrome with congenital cataract; farvardin and bolkheir references 1. derespinis pa, caputo ar, wagner rs, guo s. duane’s retraction syndrome. surv ophtalmol 1993;38:257– 288. 2. mohan k, sharma a, pandav ss. differences in epidemiological and clinical characteristics between various types of duane retraction syndrome in 331 patients. j aapos 2008;12:576–580. 3. yi j, yun j, li z-k, xu c-t, pan b-r. epidemiology and molecular genetics of congenital cataracts. int j ophtalmol 2011;4:422. 4. fakhoury o, aziz a, matonti f, benso c, belahda k, denis d. [epidemiologic and etiological characteristics of congenital cataract: study of 59 cases over 10 years]. j fran ophtalmol 2015;38:295–300. 5. wirth m, russell-eggitt i, craig j, elder j, mackey d. aetiology of congenital and paediatric cataract in an australian population. brit j ophtalmol 2002;86:782–786. 6. kansal s, miller m. bilateral duane syndrome with bilateral congenital glaucoma. j aapos 2001;5:325–326. 7. lueder gt. anomalous orbital structures resulting in unusual strabismus. surv ophtalmol 2002;47:27– 35. 8. ahluwalia bk, gupta nc, goel sr, khurana ak. study of duane’s retraction syndrome. acta ophthalmol (copenh) 1988;66:728–730. 9. akbari mr, manouchehri v, mirmohammadsadeghi a. surgical treatment of duane retraction syndrome. j curr ophtalmol 2017;29:248–257. 10. murillo-correa ce, kon-jara v, engle ec, zenteno jc. clinical features associated with an i126m alpha2chimaerin mutation in a family with autosomal-dominant duane retraction syndrome. j aapos 2009;13:245– 248. 11. ro a, gummeson b, orton rb, cadera w. duane’s retraction syndrome: southwestern ontario experience. can j ophthalmol 1989;24:200–203. 12. zhang f. clinical features of 201 cases with duane’s retraction syndrome. chin med j (engl) 1997;110:789– 791. 98 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 photo essay traumatic endothelial corneal rings hossein mohammad-rabei, md; amir a. azari, md; amir arabi, md, mph ophthalmic research center, shahid beheshti university of medical sciences, torfe medical center, tehran, iran orcid: hossein mohammad-rabei: https://orcid.org/0000-0003-3653-6272 amir arabi: https://orcid.org/0000-0002-6523-7733 j ophthalmic vis res 2020; 15 (4): 576–578 presentation a 49-year-old woman sustained corneal injury after explosion of a water heating system at home. on biomicroscopic examination, multiple foreign bodies were seen on the epithelial surface of the cornea without causing any damage to the stromal tissue. further examination revealed multiple annular ring-shaped opacities at the level of the corneal endothelium in both eyes. discussion traumatic corneal endothelial rings are a rare consequence of small high-velocity foreign body projectiles hitting the cornea most commonly from blast injuries.[1] in patients with endothelial corneal rings, the injury to the endothelial cells results from damage caused by mechanical stretching of the cornea. corneal stretching causes axial displacement of descemet’s membrane, producing radial tension transmitted further posteriorly damaging the delicate endothelial cells.[2] the ringshaped disruption of the endothelial cells likely forms as a result of a bell-shaped propagation of shock waves produced by trauma. as these waves travel through bowman’s membrane, corneal stroma, descemet’s membrane and correspondence to: amir arabi, md, mph. number 22, eastern alley 17, sarafha st., saadat-abad, tehran. email: amir_arab_91@yahoo.com received: 14-02-2019 accepted: 16-10-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7797 all the way to the endothelium, they impact the peripheral endothelial cells most severely while leaving the central endothelial cells relatively unaffected. maloney et al used specular microscopy in two patients with traumatic endothelial rings. based on their findings, they reported endothelial cell loss in all cases with traumatic endothelial rings.[3] endothelial rings appear soon after injury and tend to disappear in a just a few days. sung jin kim et al reported that the mean duration for the presence of rings was 4.6 days on average.[2] when the total number of endothelial cells lost is small, as evident when only a few corneal endothelial rings are present, one should expect an unremarkable clinical course; however, with more severe and extensive injuries, ophthalmologists should be wary of potential corneal decompensation if further endothelial cell loss is anticipated form future intraocular surgeries and procedures.[4] in our case, traumatic corneal endothelial rings were clinically visible immediately after the injury, and resolved completely within one week without any specific treatment. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: mohammad-rabei h, azari aa, arabi a. traumatic endothelial corneal rings. j ophthalmic vis res 2020;15:576–578. 576 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7797&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; mohammad-rabei et al figure 1. multiple small epithelial defects secondary to several high-velocity projectiles. note the central endothelial ring opacity. figure 2. at higher magnification, central healthy endothelial cells are surrounded by a well-defined ring shape opacity. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 577 photo essay; mohammad-rabei et al figure 3. a schematic view for propagation of the force from corneal epithelial surface to the endothelial layer. references 1. stulting rd, rodrigues mm, nay re. ultrastructure of traumatic corneal endothelial rings. am j ophthalmol 1986;101:156–159. 2. muqit mm, weir c, osborne s. occupational blast injury resulting in traumatic corneal endothelial rings. acta ophthalmol scand 2003;81:416–417. 3. maloney wf, colvard m, bourne wm, gardon r. specular microscopy of traumatic posterior annular keratopathy. arch ophthalmol 1979;97:1647–1650. 4. ng sk, rudkin ak, galanopoulos a. traumatic corneal endothelial rings from homemade explosives. int ophthalmol 2013;33:395–397. 578 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 letter to editor black diaphragm intraocular lens in patients with aniridia arjun srirampur, ms, frcs; pasyanthi balijepalli, ms anand eye institute, habsiguda, hyderabad, india j ophthalmic vis res 2020; 15 (4): 584–584 dear sir, we read with great interest the article by alrashidi sh on black diaphragm intraocular lens (iol) in patients with aniridia.[1] we would like to congratulate the author for the interesting and well-written paper, but we have some concerns regarding the article. first, the author should have mentioned the site and size of the corneal incision made for the implantation of the iol. as these iols are quite bulky, it would require at least a 9 mm incision to insert them into the anterior chamber. such a large incision has the potential to damage the limbal stem cell population which may subsequently accelerate epithelial healing problems in patients with aniridia. furthermore, these patients are prone to develop intraocular pressure elevation in the long term which may need a glaucoma filtering surgery, therefore it would be prudent to spare the superior limbus for possible future glaucoma procedures. second, most previous reports on the long-term results of aniridia iols mention a high risk of postoperative cystoid macular edema (cme) and iop elevation due to direct contact of the iol haptics with the trabecular meshwork.[2, 3] it would have been nice if this paper could have provided correspondence to: arjun srirampur, ms, frcs. consultant – cornea, cataract and refractive surgery, anand eye institute, habsiguda, hyderabad 500007, india. e-mail: sarjuneye@gmail.com received: 11-02-2019 accepted: 29-04-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7801 details of the postoperative status stating whether any patient developed cme. third, as mentioned earlier, glaucoma is the most commonly reported complication of black diaphragm iol implantation. most previous reports state risks as high as 40%.[4] but it is surprising to note that none of the patients in this study developed postoperative glaucoma in the followup period. on the contrary, all patients who were on anti-glaucoma medications preoperatively and did not require any medications in the postoperative period. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. al-rashidi. black diaphragm intraocular lens implantation in patients with aniridia. j ophthalmic vis res 2019;14:27– 31. 2. aslam sa, wong sc, ficker la, maclaren re. implantation of the black diaphragm intraocular lens in congenital and traumatic aniridia. ophthalmology 2008;115:1705–1712. 3. dong x, xu h, yu b, ying l, xie l. long-term outcome of black diaphragm intraocular lens implantation in traumatic aniridia. br j ophthalmol 2010;94:456–459. 4. reinhard t, engelhardt s, sundmacher r.black diaphragm aniridia intraocular lens for congenital aniridia: long-term follow-up. j cataract refract surg 2000;26:375–381. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: srirampur a, balijepalli p. black diaphragm intraocular lens in patients with aniridia. j ophthalmic vis res 2020;15:584–584. 584 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7801&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr original article slanted versus augmented recession for horizontal strabismus zhale rajavi1,2,3, md; mohadeseh feizi2,4, md; sayed aliasghar nabavi4, md; hamideh sabbaghi4,5, ms narges behradfar5, ms; mehdi yaseri6, phd; mohammad faghihi2, md; saeid abdi5, ms 1ophthalmic epidemiology research center, shahid beheshti university of medical sciences, tehran, iran 2department of ophthalmology, torfeh hospital, shahid beheshti university of medical sciences, tehran, iran 3negah specialty ophthalmic research center, shahid beheshti university of medical sciences, tehran, iran 4ophthalmic research center, shahid beheshti university of medical sciences, tehran, iran 5department of optometry, school of rehabilitation, shahid beheshti university of medical sciences, tehran, iran 6department of epidemiology and biostatistics, tehran university of medical sciences, tehran, iran orcid: zhale rajavi: https://orcid.org/0000-0002-4078-3017 hamideh sabbaghi: https://orcid.org/0000-0002-2627-7222 abstract purpose: to compare the surgical outcomes of slanted versus augmented recession in patients with horizontal strabismus. methods: in this randomized clinical trial, a total of 100 esotropic (et) and exotropic (xt) patients with a high ac/a ratio which was defined as a difference of ≥ 10 prism diopters (pd) between the distance and near deviations were included if the patients had a distance deviation ≥ 15 pd. patients were randomly assigned into the slanted (n = 26 in et and n = 24 in xt group) and augmented recession groups (n = 25 in et and n = 25 in xt group). in the slanted group, recession was performed on the superior and inferior poles of the muscle based on the distance and near deviations, respectively, while in the augmented recession group, the muscles were recessed 1.00 or 1.50 mm more than the standard amount according to the distance and near difference between 10 and 20 pd or > 20 pd, respectively. results: the mean age was 9.8 ± 9.6 years and 63% were female. there was a significant postoperative reduction of difference in convergence excess in et cases compared to patients who underwent the augmented recession procedure (12.65 ± 6.16 vs 8.64 ± 6.1 pd, p = 0.014). among our xt groups, there was no significant difference in postoperative reduction in the xt angle in the slanted group compared with the augmented group (p > 0.05). conclusion: slanted recession is recommended in convergence excess et patients. in xt patients, either slanted or augmented recession may be chosen according to the priority and experience of the surgeon. keywords: accommodative convergence to accommodation ratio; augmented recession; horizontal strabismus; slanted recession j ophthalmic vis res 2019; 14 (4): 465–473 correspondence to: hamideh sabbaghi, ms. ophthalmic research center, shahid beheshti university of medical sciences, 23 paidarfard, bostan 9, pasdaran ave., tehran, 16666, iran. e-mail: sabbaghi.opt@gmail.com received: 23-07-2018 accepted: 17-03-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i4.5453 introduction exotropic (xt) and esotropic (et) patients with abnormal accommodative convergence to this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: rajavi z, feizi m, nabavi sa, sabbaghi h, behradfar n, yaseri m, faghihi m, abdi s. slanted versus augmented recession. j ophthalmic vis res 2019;14:465–473. © 2019 journal of ophthalmic and vision research | published by knowledge e 465 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5453&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr slanted versus augmented recession; rajavi et al accommodation (ac/a) ratio present a difference between distance and near deviations which are manifested even after correction of refractive errors and achievement of the best corrected visual acuity (bcva).[1, 2] according to the literature, the main cause of this difference in et cases with a high ac/a ratio could be attributed to the excessive accommodative convergence with an insufficient fusional divergence at near distance of fixation.[3] in xt patients with a high ac/a ratio, near deviation is increased with bilateral +3.00 d lenses immediately after patching; otherwise, patients have true divergence excess (de). in both conditions, the possibility of esotropia at near may be present postoperatively. in addition, in xt patients with a low ac/a ratio, the weak fusional convergence and reduced accommodative amplitude have been reported as possible etiological factors of convergence insufficiency (ci).[1, 4] moreover, in xt patients with ci, surgery for distance deviation would show near under correction postoperatively. surgery is indicated in cases which do not respond to the non-surgical treatments including refractive error correction, orthoptic modalities, prism, and also in patients with distance deviation of ≥ 15 pd.[5, 6] slanted or augmented bilateral lateral rectus recession (lrrec) or bilateral medial rectus recession (mrrec) or new r & r (lrrec for distance and mrrec for near deviations) are suggested methods for these patients with a success rate of 69–92% in different studies.[1, 2, 7–10] et patients with less near deviation (low ac/a ratio) are rare, and there is not a consensus regarding the unique surgical procedure for these patients.[11] muscle slanted recession method seems more logical and is easier with fewer side effects compared to the other procedures such as posterior fixation suture and can be applied in both et and xt patients.[1, 2, 7–10] therefore, we aimed to compare the surgical outcomes of slanted and augmented recession methods on patients with horizontal strabismus having a different angle of deviation at distance and near positions with abnormal ac/a ratio either low or high. methods this randomized clinical trial was performed on 100 patients with horizontal deviation through sequential selection. all constant or intermittent et and xt patients with abnormal ac/a ratio (defined as a difference of ≤ 10 pd between distance and near deviations) were enrolled, if the patients had a distance deviation ≥ 15 pd. this study was approved by the ethics committee of the ophthalmic research center, shahid beheshti university of medical sciences, tehran, iran and was registered at https://clinicaltrials.gov (nct03555045). patients with simultaneous horizontal and vertical deviation, history of extraocular muscle surgery, extraocular muscle palsy, fixation instability (nystagmus, eccentric fixation), restrictive strabismus, orbital anomalies, mental retardation, general and ophthalmic disorders, simulated de, subjects less than five years old and those with poor cooperation were excluded from this study. after patients or their parents signed informed consent, questions regarding demographic characteristics such as the age at the time of operation, gender, parent consanguinity, family history of strabismus, and prematurity were asked and recorded in their files. ocular and visual examinations the comprehensive ophthalmic examination including cyclorefraction (45 min after instillation of tropicamide 1% and cyclopentolate 1%), assessment of bcva, and evaluation of extraocular muscle motility including version and duction were performed. next, ocular deviation was measured at both distant (6 m) and near (33 cm) using an alternate prism cover test. for accurate fixation, all patients were asked to fixate on an optotype of the snellen visual acuity chart sized one or two lines better than their bcva for distance deviation measurement and an accommodative target for near deviation measurement. aor v-pattern was also determined if the difference of deviation between 30° superior and inferior of primary position was 10 or 15 pd, respectively.[12, 13] stereopsis was measured using a titmus test at the near position. ocular anterior and posterior segments were examined using slit lamp and indirect ophthalmoscopy. 466 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 https://clinicaltrials.gov slanted versus augmented recession; rajavi et al definitions amblyopia was considered if the bcva was equal or worse than 0.30 logmar in one eye or two bcva lines of difference between the two eyes. stereopsis was classified into three groups of central (≤ 100 sec/arc), peripheral (100–3000 sec/arc), and suppression (≥ 3000 or not having any binocular depth perception). convergence excess (ce) was considered in et patients with more deviation (≥ 10 pd) at near compared to the distance after refractive error correction. simulated de was considered if tenacious proximal fusion (tpf) was broken in an xt patient with more deviation at near after patching of one eye for 60 min. high ac/a ratio in et patients was considered with more deviation (≥ 10 pd) at near compared to distance after refractive error correction (ce). high ac/a ratio was considered if near deviation was not increased with monocular patching in xt patients, but it was increased after wearing of +3.00d lenses. therefore, high ac/a ratio was detected; otherwise the diagnosis of de was considered.[14] ci was considered in cases that had higher exotropia at near compared with distance deviation (at least a difference of 10 pd) after refractive error correction. surgical procedure general points et and xt patients were studied in the two groups (slanted and augmented recession), and the procedures were performed on medial or lateral rectus muscles according to the deviation type. after limbal incision of conjunctiva and tendon, the selected rectus muscle was hooked, dissected, and sutured with 6-0 vicryl® (polyglactin 910, coated vicryl®, ethicon, blue ash, oh, usa), then the muscle was disinserted and resutured to the sclera posteriorly according to the park’s table.[15] slanted recession method in the slanted groups, the superior pole of the rectus muscles was recessed for distance deviation, and the inferior pole of the same rectus muscle was recessed for near deviation in both eyes. the amount of recession was considered based on the park’s table.[15] the amount of slant was defined as the absolute difference of superior and inferior recession of the medial or lateral rectus muscles. augmented recession method in the augmented recession group, the patients were operated bilaterally according to the distance measurement and based on the difference between distance and near deviations from 10 to 20 pd, 1 mm, and > 20 pd; 1.5 mm was added to or subtracted from the distance deviation as suggested by park’s table.[15] for instance, in patients with et = 20 and et’ = 35, bilateral lrrec was performed for et = 20 (4) + 1 = 5 mm. in patients with xt = 20 and xt’ = 35, bilateral lrrec was performed for xt = 20 (5) + 1 = 6 mm. in patients with xt = 30 and xt’ = 15 (either high ac/a ratio or true de), bilateral lrrec was performed for xt = 30 (7) – 1 = 6 mm. follow-up visits were performed on the first day, the first week, and the first, third, sixth, and twelfth months after the surgery. the results of patients who had at least three months of followup were analyzed. postoperative distance and near deviations were measured in the same way as the preoperative method. postoperative distance and near deviations < 10 pd were considered successful outcomes in each group. in addition, dose-response in both groups were calculated based on the following formula: dose response = |preoperative far and near difference – postoperative far and near difference| amount of slant or recession or |reduction| amount of slant or recession journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 467 slanted versus augmented recession; rajavi et al for instance, a patient with an xt = 30 at far and xt’ = 40 at near, a bilateral lrrec was performed 7 mm at the superior and 8 mm at the inferior poles of the muscle. regarding the calculation of dose-response, this value was used in the aforementioned formula, and two folds of slant were calculated for the analysis (2 × 1). sample size to have a power of 95% to detect a difference of 5 pd in transparency between the two groups, 25 samples in each group were required. in this calculation, the standard deviation of the transparency was assumed to be 5 in both groups, and the type i error was set at 0.05. randomization using a computer program, a biostatistician (my) generated the sequence of patients’ assignment with a permuted-block randomization method. the block length varied from two to six. the randomization sequence was concealed from the investigators. randomization was separately performed for et and xt groups. statistical analysis to present data, mean, standard deviation, median, and range were used. to evaluate the normal distribution of data, we used a kolmogorov–smirnov test and q-q plot. to compare the groups, a t-test and a mann–whitney u-test were used. additionally, we used a wilcoxon signed-rank test to assess changes within the groups. relationships of the different variables were assessed using spearman’s rank correlation coefficient. furthermore, the interaction analysis within the linear regression model was applied to evaluate the difference of esotropia and exotropia with regard to the inferiority of the slanted surgical technique. all statistical methods were performed with spss software (spss statistics for windows version 23.0, ibm corporation, armonk, ny, usa). all tests were two-sided, and p < 0.05 was considered statistically significant. results the present study was conducted on 100 patients with different horizontal deviation at distance and near ≥10 pd; 50 et and 50 xt patients randomly underwent surgery by the slanted or augmented recession technique, respectively. in this study, the mean surgical age was 9.83 ± 9.65 years old, and 63% of the study subjects were female. table 1 presents the baseline characteristics of our study population in both et and xt groups. although more study patients were female, the difference was not statistically significant between the slanted and augmented recession groups. in addition, there was no difference in these groups regarding other baseline characteristics, including age, prematurity, parental consanguinity, and family history of strabismus. all study subjects underwent follow-ups for at least three months with an average of 10 ± 9 months; 84% (n = 42) of et and 60% (n = 30) of xt patients had a minimum follow-up of six months. table 2 shows the clinical characteristics of slanted and augmented recession in both et and xt patients. amblyopia was detected in 13.4% (n = 13) of the study population, and it was found in 20% (n = 10) of et and 6% (n = 3) of xt patients. as seen, 27% of patients presented ≤ 100 sec/arc stereopsis after the surgery. preoperatively, in the et group, aand vpatterns as well as overaction of the inferior oblique muscle (iooa) were observed in 2%, 41%, and 45% of patients respectively, while more xt patients had a-pattern (12%) and fewer showed v-pattern (18%) and iooa (10%). postoperatively, 30.8 % of the slanted et cases had v-pattern, and no cases had a-pattern. in the slanted xt group, the percentages of aand v-pattern were equal (8%). in the present study, all et patients had ce esotropia with a high ac/a ratio. as table 3 shows, although there was not any significant difference in the distance and near disparity between the slanted and augmented recession groups preoperatively, statistically significant reduction was found in the slanted recession group compared with the augmented group postoperatively (12.65 vs 8.64, p = 0.014). the mean slant was 2.38 ± 1.33 mm (range, 1 to 5 mm) for et patients and 1.48 ± 0.79 mm 468 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 slanted versus augmented recession; rajavi et al (range, 0.5 to 3 mm) for xt patients, and the mean augmentation was 1.125 ± 0.25 mm for et and 1.02 ± 0.25 mm for xt patients. a 58% success rate was obtained in the slanted group and a 28% success rate was observed in the augmented recession group. as table 4 shows, 29 xt patients had ci and 20 patients had true de or exotropia with a high ac/a ratio. there was no significant difference between the slanted and augmented recession groups regarding distance and near disparity, preoperatively. the mean slant for the esotropia, exotropia, and augmented recession groups was 2.38 ± 1.33 mm, 1.48 ± 0.79 mm, and 1.00–1.50 mm, respectively. similar findings were also obtained in an analysis of each xt subgroup. in a comparison of the slanted technique between the et and xt patients, it was revealed that the difference of reduction was greater in et cases compared to the xt cases (12.65table 3 – 8.46table 4 = 4.2 pd, p = 0.04). there were no surgical complications such as postoperative diplopia, overcorrection, ocular torsion, and new cases of a–v patterns in our study groups. discussion esotropic patients there was a significant difference between slant and recession methods regarding the reduction of difference between far and near deviations, but less success rates of 58% and 28% was found in the slanted and augmented recession groups, respectively. bayramalar et al,[2] ahadzadegan et al,[16] and gharebaghi et al[17] reported a success rate of 87.6%, 69%, and 70% three and six months after surgery, respectively, in small case series with esotropia and high ac/a. khalifi et al conducted a study[10] on ce et patients by augmented and slanted recession as well as the pf method. they found no difference in reduction among them but, like previous studies, the small sample size was a limitation. ellis et al studied medical records of 131 ce et cases with a mean surgical age of nine years old.[9] the reduction was 14.23 pd in slanted recession (n = 27), 13 pd in pf (n = 22), 6.8 pd in augmented recession (n = 58), and 5.3 pd in standard mrrec (n = 73). they concluded that the slanted recession caused more reduction compared to other groups. they also observed greater reduction with longer follow-ups. according to the literature, the reported success rate of the slanted technique was between 69% and 87%, and for the augmented method, the corresponding values were 55% and 66%.[1, 2, 7–10] we had lower success for both our slanted and augmented methods. this discrepancy could be attributed to the differences in sample size, study design, duration of follow-up, and surgical value in both augmented and slanted groups in various studies. the amount of slanted recession is often decided based on distance and near disparity and shows a small difference in the literature.[2, 9] while greater discrepancy was found for augmented recession method resulting from different surgical options based on the surgeon’s priority such as: (1) 1.0 to 1.5 mm more recession, (2) recession for mean angle of distance and near deviations, and (3) 1.0 mm more recession for each 10 pd difference between distance and near deviations. in our study, the mean slanted recession was 2.38 ± 1.33 mm, while the augmented recession was 1.12 mm for et and 1.02 mm for xt patients. it could be possible to find a non-significant difference in the success rate of two groups if augmented recession was conducted 1.0 mm for each 10 pd difference between distance and near deviations. various hypotheses have been suggested to justify the mechanical effect of the slanted method such as separate innervation of the superior and inferior parts of the medial rectus muscle, and different muscle length in up and down gazes compared to the primary position.[21] although van der meulen-schot[18] and bietti[19] performed slanted recession of bimedial rectus muscles for a–v pattern in opposite directions and reduction of distance and near difference (and both achieved accepted results), kushner[20] concluded that correction of a–v pattern is achieved only by recession itself and not by slanting. kushner believed that the effect of slanted recession was neutralized after several weeks by remodeling of the muscular sarcomeres. however, an a–v pattern reduction, of 12 % and 14 % respectively, was observed in et and xt patients after the slant recession in our study. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 469 slanted versus augmented recession; rajavi et al table 1. baseline characteristics of slanted and augmented recession in both esoand exotropic patients factors total groups et xt slanted augmented p-value slanted augmented p-value n (%) 100 26 (26%) 24 (24%) 25 (25%) 25 (25%) age of operation (years) mean ± sd 9.83 ± 9.65 9.6 ± 9.84 7.64 ± 2.33 0.333† 11.21 ± 8.31 12.92 ± 13.48 0.449† sex m 37 (37.0%) 10 (38.5%) 10 (40.0%) > 0.999* 8 (33.3%) 9 (36.0%) 0.834* f 63 (63.0%) 16 (61.5%) 15 (60.0%) 16 (66.7%) 16 (64.0%) prematurity no 97 (97.0%) 26 (100.0%) 23 (92.0%) 0.054** 23 (95.8%) 25 (100.0%) 0.237** yes 3 (3.0%) 0 (0.0%) 2 (8.0%) 1 (4.2%) 0 (0.0%) parent consanguinity no 84 (84.0%) 19 (73.1%) 19 (76.0%) 0.822* 23 (95.8%) 23 (92.0%) 0.678** yes 16 (16.0%) 7 (26.9%) 6 (24.0%) 1 (4.2%) 2 (8.0%) family h/o strabismus no 88 (88.0%) 22 (84.6%) 21 (84.0%) > 0.999** 21 (87.5%) 24 (96.0%) 0.155** yes 12 (12.0%) 4 (15.4%) 4 (16.0%) 3 (12.5%) 1 (4.0%) et, esotropia; xt, exotropia; n, number; fu, follow-up; h/o, history of; m, male; f, female; p, probability †based on t-test *based on chi-square test **based on fisher exact test table 2. clinical characteristics of slanted and augmented recession in both esoand exotropic patients factors total groups et xt slanted augmented p-value slanted augmented p-value pre-op. se (d) mean ± sd 1.73 ± 2.51 1.29 ± 2.71 2.19 ± 2.23 0.070‡ 0.36 ± 1.69 0.30 ± 1.37 0.849‡ pre-op. bcva (logmar) mean ± sd 0.19 ± 0.21 0.14 ± 0.13 0.497‡ 0.10 ± 0.14 0.11 ± 0.11 0.310‡ post-op. bcva (logmar) mean ± sd 0.12 ± 0.16 0.17 ± 0.2 0.07 ± 0.09 0.002‡ 0.07 ± 0.12 0.09 ± 0.09 0.611‡ amblyopia (%) no 84 (86.6%) 18 (69.2%) 23 (92.0%) 0.075* 21 (91.3%) 22 (95.7%) > 0.99* yes 13 (13.4%) 8 (30.8%) 2 (8.0%) 2 (8.7%) 1 (4.3%) pre-op. stereopsis (%, sec/arc) central (≤ 100) 15 (15%) 1 (3.8%) 0 (0%) 0.477‡ 6 (25%) 8 (32%) 0.87‡ peripheral (100 to 3000) 15 (15.4%) 1 (3.8%) 3 (12%) 6 (25%) 5 (20%) suppression (≥ 3000) 70 (70%) 24 (92.3%) 22 (88%) 12 (50%) 12 (48%) post-op. stereopsis (%, sec/arc) central (≤ 100) 27 (27%) 2 (7.7%) 4 (16%) 0.516‡ 11 (45.8%) 10 (40%) 0.578‡ peripheral (100 to 3000) 31 (31%) 7 (26.9%) 8 (32%) 6 (25%) 10 (40%) suppression (≥ 3000) 42 (42%) 17 (65.4%) 13 (52%) 7 (29.2%) 5 (20%) et, esotropia; xt, exotropia; op, operation; se, spherical equivalent; d, diopter, bcva, best corrected visual acuity; logmar, logarithm of the minimum angle of resolution; sec/arc, second of arc; sd, standard deviation; p, probability *fisher exact test ‡based on mann–whitney test 470 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 slanted versus augmented recession; rajavi et al table 3. the mean difference of preand postoperative far and near deviations in convergence excess et cases and their controls factors et’ > et ≥10pd p-value‡ slanted augmented n 26 25 pre-op. difference mean ± sd 16.46 ± 5.97 13.56 ± 4.4 0.074 median (range) 15 (9 to 35) 10 (10 to 20) post-op. difference mean ± sd 3.81 ± 3.54 4.92 ± 4.04 0.275 median (range) 4 (0 to 12) 6 (0 to 13) reduction mean ± sd –12.65 ± 6.16 –8.64 ± 6.1 0.014 median (range) –12 (–35 to –5) –8 (–20 to 2) dose response mean ± sd –6.29 ± 3.38 –5.99 ± 3.49 median (range) –5.21 (–16 to –1.6) –7 (–10 to 2) success rate (%)** 58% 28% et, far esotropia; et’, near esotropia; pd, prism diopter; n, number; op, operation; sd, standard deviation; p, probability ‡based on mann–whitney test **success rate was defined as the postoperative far and near deviations less than 10 pd, which was stricter compared with the consideration of < 10 pd difference between the far and near deviations table 4. the mean difference of preand postoperative far and near deviations in both convergence insufficiency and divergence excess exotropic cases and their controls factors total xt’ > xt ≥ 10pd (ci) xt > xt’ ≥ 10pd (de) slanted augmented p‡ slanted augmented p‡ slanted augmented p‡ n 24 25 19 10 5 15 preop. difference mean ± sd 11.75 ± 3.29 11 ± 2.5 0.441 11.37 ± 2.79 11 ± 2.11 0.713 13.2 ± 4.87 11 ± 2.8 0.688 median (range) 10 (9 to 20) 10 (10 to 20) 10 (10 to 20) 10 (10 to 15) 10 (9 to 19) 10 (10 to 20) post-op. difference mean ± sd 3.29 ± 2.65 2.4 ± 2.94 0.163 3.42 ± 2.69 1.2 ± 1.69 0.026 2.8 ± 2.68 3.2 ± 3.36 0.928 median (range) 3 (0 to 8) 2 (0 to 10) 2 (0 to 8) 0 (0 to 4) 4 (0 to 6) 2 (0 to 10) reduction mean ± sd –8.46 ± 3.65 –8.6 ± 3.86 0.753 –7.95 ± 2.63 –9.8 ± 3.16 0.207 –10.4 ± 6.27 –7.8 ± 4.18 0.479 median (range) –8.5 (–19 to –2) –8 (–15 to 0) –8 (–12 to –2) –10 (–15 to –6) –10 (–19 to –4) –8 (–15 to 0) dose response mean ± sd –7.83 ± 5.54 –7.72 ± 2.85 –7.55 ± 5.18 –8.8 ± 1.69 –8.87 ± 7.34 –7 ± 3.27 median (range) –5.75 (–20 to –1) –8 (–10 to 0) –6 (–20 to –1) –10 (–10 to –6) –5 (–19 to –1.33) –8 (–10 to 0) success rate (%) 92% 92% 89% 100% 100% 87% xt, exotropia; ci, convergence insufficiency; de, divergence excess; pd, prism diopter; n, number; op., operation; sd, standard deviation; p, probability ‡based on mann–whitney test exotropic patients there was not a significant difference in reduction between bilateral lateral rectus in the slanted and augmented recession groups. in addition, the postoperative success rate of 92% was obtained for xt patients. our findings are in line with a study by chun et al[1] with a success rate of 84% in 31 ci xt children after six-months follow-up, and 1.0 mm slanted recession resulted in an 8.7 pd reduction. snir et al[22] studied 18 ci adult xt patients to compare slanted and standard recession of the lateral rectus muscle. the success rate was 92% in journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 471 slanted versus augmented recession; rajavi et al figure 1. preand postoperative difference between far and near deviation of both slanted and augmented groups in esotropic (a) and exotropic (b) patients. slanted cases and 100% for distance deviation of the standard group, while the near deviation was not reduced to less than 8 pd. the dose response was 4.6 pd for the slanted group. on the other hand, a study by yang et al[23] with 44 ci xt patients yielded a success rate of 60% in augmented recession (1.0 mm more recession) and 100% with the new r & r method, respectively (mrres for near and lrrec for distance deviation). their success was less in the augmented controls compared with the present study (92%). based on a literature review, there are limited numbers of studies about the surgical results of the slanted procedure on xt patients with ci, and we found no published article investigating the result of the slanted lrrec procedure on xt patients with true de or xt patients with high ac/a. all publications suggested to operate for distance deviation and correct near esotropia by prescription of bifocal glasses. the present study may be the first trial to investigate the slanted procedure on true de xt patients. appropriate sample size, consideration of the independent control group, and random sampling are the strong points of the present study. however, lack of comparison with other surgical techniques including pf is a limitation in the study of et patients. additionally, lack of equal distribution of patients in the slanted and augmented subgroups and lack of comparison with other surgical techniques including the new r & r method (mr res. for near and lr rec. for distance deviation) can be considered as the limitations in the study of xt patients. in conclusion, slanted recession is recommended for ce et patients. in xt patients, either slanted or augmented recession could be chosen according to the priority and experience of the surgeon. financial support and sponsorship nil. conflicts of interest there is no conflict of interest. references 1. chun by, kang km. early results of slanted recession of the lateral rectus muscle for intermittent exotropia with convergence insufficiency. j ophthalmol 2015;2015:380467. 2. bayramlar h, ünlü c, dag y. slanted medial rectus recession is effective in the treatment of convergence excess esotropia. j pediatr ophthalmol strabismus 2014;51:337– 340. 3. griffin jr, grisham jd. binocular anomalies: diagnosis and vision therapy. 4th edition. oxford, uk: usa, oep foundation, butterworth-heinemann; 2007:93. 4. kushner bj, morton gv. distance/near differences in intermittent exotropia. arch ophthalmol 1998;116:478–486. 5. hatt s, gnanaraj l. interventions for intermittent exotropia. cochrane database syst rev 2006:cd003737. 6. birnbaum mh, soden r, cohen ah. efficacy of vision therapy for convergence insufficiency in an adult male population. j am optom assoc 1999;70:225–232. 472 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 slanted versus augmented recession; rajavi et al 7. akbari mr, masoomian b, jafari ak, fard ma, ameri a, sadeghi am. slanted medial rectus recesection for treatment of exotropia with convergence insufficiency strabismus: a report of results in 15 cases. binocul vis strabolog q simms romano 2013;28:159–166. 8. raab el, parks mm. recession of the lateral recti effect of preoperative fusion and distance-near relationship. arch ophthalmol 1975;93:584–586. 9. ellis gs jr, pritchard ch, baham l, babiuch a. medial rectus surgery for convergence excess esotropia with an accommodative component: a comparison of augmented recession, slanted recession, and recession with posterior fixation. am orthopt j 2012;62:50–60. 10. khalifa ym. augmented medial rectus recession, medial rectus recession plus faden, and slanted medial rectus recession for convergence excess esotropia. eur j ophthalmol 2011;21:119–124. 11. west ce, repka mx. a comparison of surgical techniques for the treatment of acquired esotropia with increased accommodative convergence/accommodation ratio. j pediatr ophthalmol strabismus 1994;31:232–237. 12. yam jc, wu p, chong gs, wong us, chan cw, ko st. long-term ocular alignment after bilateral lateral rectus recession in children with infantile and intermittent exotropia. j aapos 2012;16:274–279. 13. rajavi z, lashgari a, sabbaghi h, behradfar n, yaseri m. the incidence of reoperation and related risk factors among patients with infantile exotropia. j pediatr ophthalmol strabismus 2017;54:22–30. 14. kushner bj. strabismus: practical pearls you won’t find in textbooks. springer international publishing; 2017:79. 15. parks mm. extraocular muscles. in: tasman w, jaeger ea, editors. duane’s clinical ophthalmology, revised edition, vol. 1. philadelphia: lippincott williams & wilkins, 1998;1–4. 16. ahadzadegan i. slanted recession of medial recti to treat convergence excess esotropia. iran j ophthalmol 2001;13:10–12. 17. gharabaghi d, zanjani lk. comparison of results of medial rectus muscle recession using augmentation, faden procedure, and slanted recession in the treatment of high accommodative convergence/accommodation ratio esotropia. j pediatr ophthalmol strabismus 2006;43:91–94. 18. van der meulen-schot hm, van der meulen sb, simonsz hj. caudal or cranial partial tenotomy of the horizontal rectus muscles in a and v pattern strabismus. br j ophthalmol 2008;92:245–251. 19. bietti gb. on a technical procedure (recession and fan-shaped oblique reinsertion of the horizontal rectusmuscles) for correction of v or a exotropias of slight degree in concomitant strabismus. boll ocul 1970;49:581–588. [article in italian] 20. kushner bj. insertion slanting strabismus surgical procedures. arch ophthalmol 2011;129:1620–1625. 21. da silva costa rm, kung j, poukens v, yoo l, tychsen l, demer jl. intramuscular innervation of primate extraocular muscles: unique compartmentalization in horizontal recti. invest ophthalmol vis sci 2011;52:2830–2836. 22. snir m, axer-siegel r, shalev b, sherf i, yassur y. slanted lateral rectus recession for exotropia with convergence weakness. ophthalmology 1999;106:992–996. 23. yang hk, hwang jm. surgical outcomes in convergence insufficiency-type exotropia. ophthalmology 2011;118:1512–1517. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 473 editorial systems biology approach for identification of essential growth factors in retinal regeneration zahra-soheila soheili, phd; hamid latifi-navid, ms department of molecular medicine, national institute of genetic engineering and biotechnology, tehran, iran orcid: zahra-soheila soheili: https://orcid.org/0000-0003-1292-465x j ophthalmic vis res 2021; 16 (1): 1–2 tissue engineering may be considered as a potential treatment modality for various types of retinal diseases. retinal regeneration depends on an optimal combination of scaffolds, cells, and growth factors. growth factors play a fundamental role in a variety of cellular processes such as proliferation, migration, differentiation, and multicellular morphogenesis.[1] growth factors expedite tissue growth/regeneration by providing the right signals to the cells.[2] systems biologyrelated approaches help us understand the mechanisms underlying retinal tissue engineering and investigate the effect of growth factors through protein–protein interaction network analyses. network centrality analysis using different criteria has the potential to reveal growth factors important for retinal regeneration. in the current issue of journal of ophthalmic and vision research, beheshtizadeh et al report an in-silico study which was aimed to determine the most important growth factors in retinal tissue engineering.[3] gene ontology (go) and degree centrality analysis were used to identify the most effective proteins for retinal regeneration. despite the remarkable results presented in the study, it should be stressed that the growth factors were determined only by degree centrality analysis. numerous studies have established that low connectivity growth factors may also be considered critical in biological processes and for network integrity.[4, 5] there are several types of centrality which include degree, closeness, between-ness, centroid value, bridging, eccentricity, and eigenvector centrality. degree centrality is used to evaluate the regulatory importance of immediate neighboring nodes. nodes with high degree centrality interact with different proteins and therefore usually play a key regulatory role in the network. the short average distance of a distinct node to the entire network of proteins is represented by the closeness index. proteins with high closeness index (compared to the network) impose a fundamental regulatory effect on other proteins and will be significantly affected by changes in the network. between-ness index represents the number of times that a specific node (via the shortest path) is used to hold communicating proteins together. the coherence and functionality of the network are likely maintained by the betweenness centrality index. to determine the functional ability of a distinct node to orchestrate discrete clusters of proteins, centroid value is used in the network. nodes with high centroid values coordinate the activity of other clusters to regulate a distinct cell function. bridging centrality index is employed to distinguish nodes that link clusters or densely connected regions. eccentricity index is used to distinguish nodes which are easily reachable by all other proteins. therefore, a protein with high eccentricity index affects, or gets more easily affected by, other proteins. to determine nodes with a central super-regulatory role or those that serve as key targets of a regulatory pathway, the eigenvector centrality index is used.[6] in summary, to comprehensively understand the importance of each node in any given network, different kinds of centrality analyses should be performed. moreover, integration of centrality analyses results helps one correct selection of the most important nodes in the network. it is highly recommended to use web servers such as david (database for annotation, visualization, and integrated discovery; https://david.ncifcrf.gov/) or enrichr (https://maayanlab.cloud/enrichr/) which have been specifically developed for gene ontology (go) and enrichment analyses.[7, 8] moreover, there exists a need for developing a © 2021 soheili et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 1 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8242&domain=pdf&date_stamp=2019-07-17 https://david.ncifcrf.gov/ https://maayanlab.cloud/enrichr/ editorial; soheili et al software which integrates servers that test for go category enrichment via recruiting the output and provide the resources for summarizing and visualizing data. references 1. ren x, zhao m, lash b, martino mm, julier z. growth factor engineering strategies for regenerative medicine applications. front bioeng biotechnol 2019;7:469. 2. vasita r, katti ds. growth factor-delivery systems for tissue engineering: a materials perspective. expert rev med devices 2006;3:29–47. 3. beheshtizadeh n, baradaran-rafii a, sistani ms, azami m. an in-silico study on the most effective growth factors in retinal regeneration using tissue engineering concepts. j ophthalmic vis res 2021;16:56-67. 4. tew kl, li xl, tan sh. functional centrality: detecting lethality of proteins in protein interaction networks. genome inform 2007;19:166–177. 5. mahadevan r, palsson bo. properties of metabolic networks: structure versus function. biophys j 2005;88:l07–l09. 6. jalili m, salehzadeh-yazdi a, gupta s, wolkenhauer o, yaghmaie m, resendis-antonio o, et al. evolution of centrality measurements for the detection of essential proteins in biological networks. front physiol 2016;7:375. 7. huang dw, sherman bt, tan q, collins jr, alvord wg, roayaei j, et al. the david gene functional classification tool: a novel biological module-centric algorithm to functionally analyze large gene lists. genome biol 2007;8:r183. 8. kuleshov mv, jones mr, rouillard ad, fernandez nf, duan q, wang z, et al. enrichr: a comprehensive gene set enrichment analysis web server 2016 update. nucleic acids res 2016;44:w90–w97. correspondence to: zahra-soheila soheili, phd. department of molecular medicine, national institute of genetic engineering and biotechnology, tehran, iran. email: zssoheili@gmail.com academic: soheili@nigeb.ac.ir received: 14-12-2020 accepted: 23-12-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8242 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: soheili z-s, latifi-navid h. systems biology approach for identification of essential growth factors in retinal regeneration. j ophthalmic vis res 2021;16:1–2. 2 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 https://knepublishing.com/index.php/jovr original article clinical characteristics and outcomes of endophthalmitis before and during the covid-19 pandemic blake h fortes1, md; prashant d tailor1, md; timothy t xu1, md; robert a churchill2, bs; matthew r starr2, md 1department of ophthalmology, mayo clinic college of medicine, rochester, mn, usa 2alix school of medicine, mayo clinic, rochester, mn, usa orcid: blake h fortes: http://orcid.org/0000-0002-3206-0062 matthew r starr: http://orcid.org/0000-0002-3021-5630 abstract purpose: to evaluate the clinical characteristics and visual acuity outcomes of patients who presented with endophthalmitis prior to and during the coronavirus disease 2019 (covid-19) pandemic. methods: this multicenter retrospective case series with historical controls included consecutive patients presenting with any form of endophthalmitis from march 1, 2019 to september 1, 2019 (pre-covid-19) and from march 1, 2020 to september 1, 2020 (covid-19) at mayo clinic rochester (mcr), health system (mchs), arizona (mca), and florida (mcf) sites. cases were divided into “pre-covid-19” versus “covid-19” groups depending on when they first presented with endophthalmitis. results: twenty-eight cases of endophthalmitis presented to all mayo clinic sites during the study period. of these, 10 patients presented during the first six months of the covid19 pandemic. during the same six-month period the year prior, 18 patients presented with endophthalmitis. endophthalmitis etiology (post-injection, post-cataract extraction, postglaucoma filtering surgery, post-pars plana vitrectomy, endogenous, and others) was similar between both groups (p = 0.34), as was post-injection endophthalmitis rate (p = 0.69), days to presentation (p = 0.07), initial management (p = 0.11), culture-positivity rate (p = 0.70), and need for subsequent pars plana vitrectomy (p = 1). visual acuity outcomes were similar between both groups at six months, however, the mean logmar visual acuity at presentation was worse in the covid-19 group compared to the pre-covid-19 group (2.44 vs 1.82; p = 0.026). conclusion: clinical characteristics and the post-injection endophthalmitis rate were similar during both periods, however, patients presented with worse vision during the pandemic suggesting that the pandemic may have contributed to delayed presentation, regardless, outcomes are still poor. keywords: covid-19; endophthalmitis; intravitreal injections j ophthalmic vis res 2023; 18 (3): 289–296 © 2023 fortes et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 289 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i3.13777&domain=pdf&date_stamp=2019-07-17 endophthalmitis during the covid pandemic; fortes et al introduction the coronavirus disease 2019 (covid-19) pandemic had profound impacts on the practice of medicine globally with numerous medical societies making recommendations to postpone all elective visits and surgeries, including the american academy of ophthalmology, the royal college of ophthalmologists, and the asia-pacific academy of ophthalmology, among others.[1–3] ophthalmology, which largely involves elective surgeries and outpatient appointments, is one of the medical specialties with the highest risk of covid-19 infection given the time spent in close proximity to the patient during the examination and possible conjunctival transmission.[4, 5] as a result, ophthalmology has experienced significant pandemic-related impact, with >90% decrease in medical and surgical volume during the beginning of the covid-19 pandemic.[6–9] fear of covid19 exposure and other factors also changed patients’ ability and willingness to attend their regularly scheduled follow-up appointments leading to high rates of cancellation and missed outpatient appointments.[10–18] in certain conditions requiring regular intravitreal injections for preservation of vision or other urgent/emergent conditions, these delays may potentially lead to irreversible loss of vision, as in neovascular age-related macular degeneration (namd) resulting in submacular hemorrhage, or more severe pathology necessitating more complex surgical intervention, as in rhegmatogenous retinal detachment (rrd).[19–23] endophthalmitis is another example of an emergent vision-threatening condition requiring prompt diagnosis and treatment to preserve vision. only one prior study by das et al has investigated the impact of the covid-19 pandemic on endophthalmitis presentation.[24] this was correspondence to: matthew r starr, md. mayo clinic, 200 1𝑠𝑡 st. sw, rochester, mn 55905, usa. email: starr.matthew2@mayo.edu received: 15-11-2022 accepted: 12-01-2023 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i3.13777 a cross-sectional study comparing the distribution of patients with endophthalmitis in india who presented during the covid-19 lockdown and unlock periods with patients who presented in the three years preceding the pandemic. this study found that there was a >50% decline in the number of patients who presented with endophthalmitis. additionally, there was an increase in the percentage of patients who presented with endogenous endophthalmitis and a decrease in post-traumatic endophthalmitis. however, this study did not investigate clinical characteristics, days to presentation, or visual acuity (va) outcomes of patients with endophthalmitis.[24] our study aims to evaluate the clinical characteristics and va outcomes of patients who presented with endophthalmitis of any etiology prior to and during the initial six-month period of the covid-19 pandemic. methods this multi-center, retrospective case series received approval from the mayo clinic institutional review board. the study conformed to the tenets of the declaration of helsinki and data were collected in accordance with the health insurance portability and accountability act of 1996 guidelines. study subjects who presented with endophthalmitis of any etiology were selected. patients were included if they presented with any form of endophthalmitis from march 1, 2019 to september 1, 2019 (pre-covid-19 cohort) and from march 1, 2020 to september 1, 2020 (covid-19 cohort) at mayo clinic rochester (mcr), mayo clinic arizona (mca), mayo clinic florida (mcf), or mayo clinic health system (mchs) sites during either time period. cases were divided into “pre-covid-19” cases versus “covid-19” cases depending on the initial date of endophthalmitis presentation. cases were excluded if they this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: fortes bh, tailor pd, xu tt, churchill ra, starr mr. clinical characteristics and outcomes of endophthalmitis before and during the covid-19 pandemic. j ophthalmic vis res 2023;18:289–296. 290 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 https://knepublishing.com/index.php/jovr endophthalmitis during the covid pandemic; fortes et al did not present during either time interval. patients were identified via endophthalmitis international classification of diseases-10 (icd-10) billing codes. these patients’ medical records were individually reviewed to confirm the endophthalmitis diagnosis. for patients confirmed to have developed endophthalmitis of any etiology during either time interval, we obtained the following variables: demographics, endophthalmitis etiology (postintravitreal injection, post-cataract extraction, post-glaucoma filtering surgery, post-pars plana vitrectomy (ppv), endogenous, or other causes such as post-traumatic or related to corneal ulceration), days to presentation, initial management (tap and inject, ppv, or medical management), subsequent ppv, signs and symptoms at presentation, snellen best corrected va at most recent visit prior to presentation, and va at presentation. if available, we recorded va at the following time points: at six months, at one-year, and final va. we also included the results of vitreous/aqueous gram stain and culture, and follow-up duration. for post-injection endophthalmitis cases, the intravitreal agent and injection indication were reviewed. endophthalmitis treatment protocol the diagnosis of endophthalmitis was based on a characteristic presentation of decreased vision, ocular pain, and intraocular inflammation. affected patients underwent initial treatment with one of the following: intravitreal antibiotic injection with vitreous/aqueous tap, ppv with vitreous tap and intravitreal injection of antibiotics, or medical treatment with cycloplegic and corticosteroid eye drops at the treating retinal specialist’s discretion. patients were usually treated with intravitreal ceftazidime (2.25 mg/0.1 ml) and vancomycin (1.0 mg/0.1 ml) at endophthalmitis presentation. patients with a penicillin allergy were treated with amikacin (0.4 mg/0.1 ml) instead of ceftazidime. topical medication regimen consisting of corticosteroid, cycloplegic, and antibiotic eye drops were variable and based on the preferences of the treating physician. all patients were closely followed. statistical analysis statistical analysis was performed utilizing rstudio: integrated development for r (rstudio, inc., rstudio team (2018), boston, massachusetts, https://www.rstudio.com). the primary outcomes were the fraction of endophthalmitis etiology, days to presentation, initial management, subsequent ppv, and va outcomes between the pre-covid19 and covid-19 groups. secondary outcomes included the microbial spectrum, and the rate of post-injection endophthalmitis between the precovid-19 versus the covid-19 cohorts. snellen va was converted to the logarithm of the minimum angle of resolution (logmar) va for statistical analysis. vision levels of count fingers, hand motion, light perception, and no light perception were assigned logmar values of 2.3, 2.6, 2.9, and 3.2, respectively, as established by prior studies.[25] fisher’s exact test was employed to compare categorical variables between the pre-covid-19 group and the covid-19 group. a wilcoxon rank sum test was performed to compare va outcomes, days to presentation, and follow-up duration. statistical significance was determined based on an alpha level of <0.05. results overall, this multicenter retrospective case series identified 28 patients who presented with endophthalmitis of any etiology throughout the study period. of these, 10 patients presented during the first six months of the covid-19 pandemic (covid-19 cohort). during the same sixmonth period the year prior, 18 patients presented with endophthalmitis (pre-covid-19 cohort). there were no differences in endophthalmitis etiology (p = 0.34), days to presentation (mean days to presentation: covid-19: 18 days vs precovid-19: 7 days; p = 0.07), initial management of endophthalmitis (p = 0.11), or subsequent ppv (p = 1.0) between the pre-covid-19 cohort and the covid-19 cohort [table 1]. women were more likely than men to present during the first six months of the covid-19 pandemic than the same time period the year prior (p = 0.016). of the cases sent for culture in the pre-covid19 group, 6 of 16 (38%) tested culture-positive (3 staphylococcus epidermidis, 1 streptococcus agalactiae, 1 cutibacterium acnes, and 1 fusarium falciformis) compared with 4 of 10 (40%) [1 s. aureus, 1 s. pneumoniae, 1 moraxella nonliquefaciens, and 1 candida albicans) in the covid-19 group (p = 0.70). in the pre-covid-19 group, f. falciformis was isolated in a patient with a corneal ulcer after a journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 291 endophthalmitis during the covid pandemic; fortes et al penetrating keratoplasty. the case of c. albicans in the covid-19 cohort occurred in a patient who had endogenous endophthalmitis related to a recent history of nephrolithiasis complicated by pyelonephritis. the mean va was similar between both groups at baseline prior to endophthalmitis presentation (pre-covid-19 logmar va: 0.68 [snellen va: 20/96] vs. covid-19 logmar va: 0.41 [snellen va: 20/51]; p = 0.59) [table 2]. likewise, va outcomes were similar between the pre-covid-19 group and the covid-19 group at six months (pre-covid19 logmar va: 0.92 [snellen va: 20/166] vs covid-19 logmar va: 0.92 [snellen va: 20/166]; p = 0.97), and at last follow-up (pre-covid-19 logmar va: 0.87 [snellen va: 20/148] vs covid19 logmar va: 1.25 [snellen va: 20/355]; p = 0.51). however, during the covid-19 pandemic, patients with endophthalmitis presented with worse va compared to patients during the pre-covid-19 era (pre-covid-19 logmar va: 1.82 [snellen va: 20/1321] vs covid-19 logmar va: 2.44 [count fingers]; p = 0.026). overall, there were 13,761 anti-vascular endothelial growth factor (anti-vegf) intravitreal injections performed during the pre-covid-19 era compared to 12,145 during the first six months of the covid-19 pandemic. there was no difference in the post-injection endophthalmitis rate between these two cohorts (covid-19: 1 in 3036 injections vs pre-covid-19: 1 in 1966 injections; p = 0.69) [table 1]. discussion this retrospective multi-center case series evaluated the clinical characteristics and va outcomes of patients who presented with endophthalmitis of any etiology during the initial six months of the covid-19 pandemic compared with patients who presented during the same six-month period the year prior. we found that patients who presented with endophthalmitis during the covid19 pandemic had worse va compared to those who presented prior to the pandemic. although the difference in days to presentation between both groups was not statistically significant (mean days to presentation: covid-19: 18 days vs pre-covid19: 7 days; p = 0.07), the sample size was quite limited suggesting that this study may have been underpowered. taken together, these findings support our hypothesis that the initial phase of the covid-19 pandemic led to delayed presentation of endophthalmitis with worse va at presentation compared to cases that presented prior to the pandemic. interestingly, delayed presentation during the pandemic did not translate to worse va outcomes either at six months or at final follow-up, as there were similar outcomes between both groups. this contrasts with other studies investigating the effect of delays in anti-vegf treatment for patients with neovascular amd, diabetic macular edema (dme), and central retinal vein occlusion (crvo), which have demonstrated that delays in care led to worse final va outcomes.[19, 26–29] in addition, this study did not identify a difference in the post-injection endophthalmitis rate during the pandemic compared to that of the previous year, corroborating a prior iris® registry (intelligent research in sight) study’s findings.[30] it is possible that no differences in va were found due to the poor outcomes that generally come from patients who develop endophthalmitis. even with delayed presentations, there appeared to be no difference in va. endophthalmitis etiology was similar between the pre-covid-19 and covid-19 groups both in terms of overall distribution of cases by etiology, but also by comparing rates of each etiology individually. it is important to note, however, that although intravitreal injection volume was similar between both groups, there was a remarkable reduction in surgical volume for elective surgeries, including cataract surgery, and glaucoma surgery, which likely impacted the number of patients who presented with endophthalmitis during the first six months of the covid-19 pandemic. similarly, there was only one patient who presented with endogenous endophthalmitis during the covid19 pandemic compared to the seven patients in the pre-covid-19 group. however, this was not a statistically significant difference. there was a similar rate of culture-positive results in both the pre-covid-19 cohort and the covid-19 cohort with a similar microbial spectrum in both groups. however, it was interesting to note a case of moraxella endophthalmitis, an atypical cause for endophthalmitis, in the covid-19 cohort as well as a case of endogenous candida infection.[31] it is now known that there appears to be a correlation of candidemia with covid-19 infection, with reports of endophthalmitis seen in these patients.[32–34] 292 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 endophthalmitis during the covid pandemic; fortes et al table 1. clinical characteristics of endophthalmitis cases that presented before the covid-19 pandemic compared to those during the covid-19 pandemic. pre-covid-19 n = 18 (%) covid-19 n = 10 (%) p-values total n = 28 (%) age at presentation (yr) mean (median, range) 72 (70, 53–89) 73 (73, 51–90) 0.72 72 (73, 51–90) sex male 11 (61) 1 (10) 12 (43) female 7 (39) 9 (90) 0.016 16 (57) affected eye right 10 (56) 7 (70) 17 (61) left 7 (39) 2 (20) 9 (32) both 1 (5) 1 (10) 0.48 2 (7) days to presentation mean (median, range) 7 (5, 1–34) 18 (7, 3–45) 0.07 11 (7, 1–45) endophthalmitis etiology 0.34 post-injection 7 (39) 4 (40) 1 11 (39) post-cataract extraction 1 (6) 1 (10) 1 2 (7) post-glaucoma filtering surgery 1 (6) 2 (20) 0.28 3 (11) post-pars plana vitrectomy 0 (0) 1 (10) 0.36 1 (4) endogenous 7 (39) 1 (10) 0.19 8 (29) others 2 (11) 1 (10) 1 3 (11) if post-injection, intravitreal injection agent bevacizumab 5 (71) 2 (50) 7 (64) ranibizumab 0 (0) 1 (25) 1 (9) aflibercept 2 (29) 1 (25) 0.81 3 (27) post-injection endophthalmitis 7 (0.0509%) 4 (0.0329%) 11 (0.0425%) 1 in 1966 injections 1 in 3036 injections 0.69 1 in 2355 injections positive vitreous or aqueous culture yes 6 (38) 4 (40) 10 (38) no 10 (63) 6 (60) 0.7 16 (62) initial management intravitreal tap and injection 18 (100) 8 (80%) 26 (93) pars plana vitrectomy 0 (0) 1 (10%) 1 (4) medical treatment 0 (0) 1 (10%) 0.11 1 (4) subsequent pars plana vitrectomy yes 3 (17) 2 (20%) 5 (18) no 15 (83) 8 (80%) 1 23 (82) follow-up duration (months) mean (median, range) 19.8 (26.7, 0.1–32.3) 13.7 (16.1, 1.6–21.5) 0.11 17.5 (18.5, 0.1–32.3) *bold values indicate significant p-value. journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 293 endophthalmitis during the covid pandemic; fortes et al table 2. visual acuity outcomes of endophthalmitis cases that presented before the covid-19 pandemic compared to those during the covid-19 pandemic. visual acuity pre-covid-19 covid-19 p-values n = 18 n = 10 mean baseline logmar va (snellen va) 0.68 (20/96) 0.41 (20/51) 0.59 mean logmar va at endophthalmitis presentation (snellen va) 1.82 (20/1321) 2.44 (cf) 0.026 mean logmar va at 6 months (snellen va) 0.92 (20/166) 0.92 (20/166) 0.97 mean logmar va at last follow-up (snellen va) 0.87 (20/148) 1.25 (20/355) 0.51 logmar, logarithm of the minimum angle of resolution; va, visual acuity ∗bold values indicate significant p-value. however, our patient was not infected with covid19 at the time of her infection. certainly, as the covid-19 pandemic continues, ophthalmologists should be cognizant of the risk of atypical infections with microbes normally confined to the oral mucosa, but potentially dispersed with poor-fitting or un-taped mask use with air reflux toward the ocular surface as well as fungal endogenous endophthalmitis in patients with superimposed covid-19 infections. this study is inherently limited by its retrospective design. additional limitations of this analysis include the fact that this study did not investigate endophthalmitis clinical characteristics during other periods of the covid-19 pandemic as policies became less stringent. inherently, there also is selection bias as patients who presented during the first six months of the covid-19 pandemic were more likely to have had severe disease compared to those who presented prior to the pandemic. comparing va of patients with endophthalmitis is also difficult to interpret as many patients present with different variations of count fingers, hand motion, or light perception vision. limited conclusions can be drawn from these levels of va. additionally, regarding the management of these cases, many patients were handled very differently during the height of the pandemic with limited operating room access making it difficult to interpret the findings on initial management strategies and final outcomes. many patients who would have undergone urgent ppv may have instead undergone a tap and inject due to limitations during the early phase of the pandemic, which possibly affected va. in summary, our study found that fewer patients presented with endophthalmitis of any etiology during the first six months of the covid-19 pandemic compared to the same six-month period the year prior. although clinical characteristics and the post-injection endophthalmitis rate were similar during both periods, patients presented with worse vision during the covid-19 pandemic suggesting that the pandemic may have contributed to delayed presentation. as the pandemic has drastically impacted the practice of ophthalmology, it is critical that ophthalmologists are prepared to diagnose and treat patients with more severe pathology who may have delayed presentation due to a variety of pandemic-related factors, including fear of exposure, which continues as the pandemic waves ebb and flow. ethical considerations the study protocol was reviewed and approved by the institutional review board at mayo clinic, rochester, mn, usa and under approval number 22-000845. financial support and sponsorship none. conflicts of interest dr. starr has served on advisory boards to genentech, alimera sciences, regenxbio, and gyroscope therapeutics. other authors report no conflicts of interest. references 1. the royal college of ophthalmologists. covid-19 resources: national government & health organisations 294 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 endophthalmitis during the covid pandemic; fortes et al updates [internet]. available from: https://www.rcophth. ac.uk/standards-and-guidance/covid-19-resources/ national-government-health-organisations-updates/ 2020;34:1189–1192. 2. american academy of ophthalmology: one network. recommendations for urgent and nonurgent patient care [internet]. 2020 march 18. available from: https://www.aao.org/headline/new-recommendationsurgent-nonurgent-patient-care 3. wong rlm, ting dsw, wan kh, lai khw, ko ch, ruamviboonsuk p, et al. covid-19: ocular manifestations and the apao prevention guidelines for ophthalmic practices. asia-pac j ophthalmol 2020;9:281–284. 4. rodríguez-ares t, lamas-francis d, treviño m, navarro d, cea m, lopez-valladares mj, et al. sars-cov-2 in conjunctiva and tears and ocular symptoms of patients with covid-19. vision 2021;5. 5. arora r, goel r, kumar s, chhabra m, saxena s, manchanda v, et al. evaluation of sars-cov-2 in tears of patients with moderate to severe covid-19. ophthalmology 2021;128:494–503. 6. azzolini c, donati s, premi e, baj a, siracusa c, genoni a, et al. sars-cov-2 on ocular surfaces in a cohort of patients with covid-19 from the lombardy region, italy. jama ophthalmol 2021;139:956–963. 7. romano mr, montericcio a, montalbano c, raimondi r, allegrini d, ricciardelli g, et al. facing covid-19 in ophthalmology department. curr eye res 2020;45:653– 658. 8. starr mr, israilevich r, zhitnitsky m, cheng qe, soares rr, patel lg, et al. practice patterns and responsiveness to simulated common ocular complaints among us ophthalmology centers during the covid-19 pandemic. jama ophthalmol 2020;138:981–988. 9. analysis: ophthalmology lost more patient volume due to covid-19 than any other specialty. eyewire [internet]. 2020 nov 5. available from: https://eyewire.news/articles/analysis-55-percent-feweramericans-sought-hospital-care-in-march-april-due-tocovid-19/?c4src=article:infinite-scroll 10. borrelli e, grosso d, vella g, sacconi r, querques l, zucchiatti i, et al. impact of covid-19 on outpatient visits and intravitreal treatments in a referral retina unit: let’s be ready for a plausible ”rebound effect”. graefes arch clin exp ophthalmol 2020;258:2655–2660. 11. dell’omo r, filippelli m, virgili g, bandello f, querques g, lanzetta p, et al. effect of covid-19-related lockdown on ophthalmic practice in italy: a report from 39 institutional centers. eur j ophthalmol 2022;32:695–703. 12. leng t, gallivan md, kras a, lum f, roe mt, li c, et al. ophthalmology and covid-19: the impact of the pandemic on patient care and outcomes: an iris® registry study. ophthalmology 2021;128:1782–1784. 13. pellegrini m, roda m, lupardi e, di geronimo n, giannaccare g, schiavi c. the impact of covid-19 pandemic on ophthalmological emergency department visits. acta ophthalmol 2020;98:e1058–e1059. 14. poyser a, deol ss, osman l, kuht hj, sivagnanasithiyar t, manrique r, et al. impact of covid-19 pandemic and lockdown on eye emergencies. eur j ophthalmol 2021;31:2894–2900. 15. savastano a, ripa m, savastano mc, kilian r, marchini g, rizzo s. impact of the covid-19 pandemic on ophthalmologic outpatient care: experience from an italian tertiary medical center. ann med 2021;53:1349–1357. 16. wickham l, hay g, hamilton r, wooding j, tossounis h, da cruz l, et al. the impact of covid policies on acute ophthalmology services-experiences from moorfields eye hospital nhs foundation trust. eye 2020;34:1189–1192. 17. yen cy, fang im, tang hf, lee hj, yang sh. covid-19 pandemic decreased the ophthalmic outpatient numbers and altered the diagnosis distribution in a community hospital in taiwan: an observational study. plos one 2022;17:e0264976. 18. agarwal r, sharma n, patil a, thakur h, saxena r, kumar a. impact of covid-19 pandemic, national lockdown, and unlocking on an apex tertiary care ophthalmic institute. indian j ophthalmol 2020;68:2391–2395. 19. romano f, monteduro d, airaldi m, zicarelli f, parrulli s, cozzi m, et al. increased number of submacular hemorrhages as a consequence of coronavirus disease 2019 lockdown. ophthalmol retina 2020;4:1209–1210. 20. li j, zhao m, she h, chandra a. the impact of the covid-19 pandemic lockdown on rhegmatogenous retinal detachment services-experiences from the tongren eye center in beijing. plos one 2021;16:e0254751. 21. patel lg, peck t, starr mr, ammar mj, khan a, yonekawa y, et al. clinical presentation of rhegmatogenous retinal detachment during the covid-19 pandemic: a historical cohort study. ophthalmology 2021;128:686–692. 22. jung jj, chang js, oellers pr, ali mh, do bk, tseng jj, et al. impact of coronavirus disease 2019 restrictions on retinal detachment: a multicenter experience. ophthalmol retina 2022;6:638–641. 23. schranz m, georgopoulos m, sacu s, reumueller a, reiter gs, mylonas g, et al. incidence and surgical care of retinal detachment during the first sars-cov-2 lockdown period at a tertiary referral center in austria. plos one 2021;16:e0248010. 24. das av, dave vp. effect of lockdown and unlock following covid-19 on the presentation of patients with endophthalmitis at a tertiary eye center over one year. cureus 2021;13:e19469. 25. gregori nz, feuer w, rosenfeld pj. novel method for analyzing snellen visual acuity measurements. retina 2010;30:1046–1050. 26. rush rb, rush sw. outcomes in patients resuming intravitreal anti-vascular endothelial growth factor therapy following treatment delay during the coronavirus-19 pandemic. retina 2021;41:2456–2461. 27. douglas vp, douglas kaa, vavvas dg, miller jw, miller jb. shortand long-term visual outcomes in patients receiving intravitreal injections: the impact of the coronavirus 2019 disease (covid-19)-related lockdown. j clin med 2022;11. 28. song w, singh rp, rachitskaya av. the effect of delay in care among patients requiring intravitreal injections. ophthalmol retina 2021;5:975–980. journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 295 https://www.rcophth.ac.uk/standards-and-guidance/covid-19-resources/national-government-health-organisations-updates/ https://www.rcophth.ac.uk/standards-and-guidance/covid-19-resources/national-government-health-organisations-updates/ https://www.rcophth.ac.uk/standards-and-guidance/covid-19-resources/national-government-health-organisations-updates/ endophthalmitis during the covid pandemic; fortes et al 29. stone lg, grinton me, talks js. delayed follow-up of medical retina patients due to covid-19: impact on disease activity and visual acuity. graefes arch clin exp ophthalmol 2021;259:1773–1780. 30. lum f, li s, liu l, li c, parke dw, williams ga. the pandemic is not associated with endophthalmitis decrease after anti-vascular endothelial growth factor injections. ophthalmology 2022;129:719–721. 31. lacroce sj, wilson mn, romanowski je, newman jd, jhanji v, shanks rmq, et al. moraxella nonliquefaciens and m. osloensis are important moraxella species that cause ocular infections. microorganisms 2019;7. 32. song g, liang g, liu w. fungal co-infections associated with global covid-19 pandemic: a clinical and diagnostic perspective from china. mycopathologia 2020;185:599– 606. 33. fossataro f, martines f, neri p, allegri p, pece a. management of presumed candida endophthalmitis during the covid-19 pandemic: case report and review of the literature. eur j ophthalmol 2022:11206721221092190. 34. agarwal m, sachdeva m, pal s, shah h, kumar rm, banker a. endogenous endophthalmitis: a complication of covid-19 pandemic: a case series. ocul immunol inflamm 2021;29:726–729. 296 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 original article efficacy and safety of infliximab in hla-b27-associated ocular inflammation refractory or intolerant to conventional immunomodulatory therapy asima bajwa, md*1,3, arash maleki, md*1,3, abhishek r payal, md1,3,4, adriana fandiño, md1,3 maría inés menéndez padrón, md1,3, marisa walsh, bs1,3, c stephen foster, md, facr, facs1,2,3 1massachusetts eye research and surgery institution, waltham, massachusetts 2harvard medical school, boston, massachusetts 3ocular immunology and uveitis foundation, waltham, massachusetts 5university of pennsylvania, scheie eye institute, philadelphia, pennsylvania orcid: asima bajwa: https://orcid.org/0000-0002-5823-3312 arash maleki: https://orcid.org/0000-0001-5533-9798 charles stephen foster: https://orcid.org/0000-0003-4760-8390 abstract purpose: to determine the efficacy and safety of infliximab therapy in patients with hla b-27-associated ocular inflammation resistant or intolerant to conventional immunomodulatory therapy. methods: this was a retrospective observational case series. all cases were uveitic patients with positive hla-b27, confirmed through hla testing, resistant or intolerant to conventional immunomodulatory therapy. the primary outcome of the study was to identify the efficacy of infliximab determined by the control of inflammation, duration of remission, and the ability to reduce conventional immunomodulatory therapy. the secondary outcome was an improvement of two or more lines of best-corrected visual acuity (bcva) on the snellen visual acuity chart. results: twenty-four patients (38 eyes) were included in the study. all patients were followed for 24 months. twenty-one (87.5%) patients completed 24 months of follow-up. sixteen (66.7%) patients had active uveitis at the beginning of therapy. one patient out of these active patients had active inflammation at the end of follow-up period. thirteen (87.5%) out of sixteen active patients were in steroid-free remission. the mean duration of treatment to induce remission was 16.5 months (range 6–24 months). corticosteroid was stopped in 19 (90.5%) patients by the end of the study. at the end of the study, in patients who achieved remission, 14 (58.3%) patients were in remission on infliximab therapy and 6 (25%) patients were in remission off infliximab therapy. of the 38 eyes, 8 (21.05%) showed improvement in bcva (three eyes had successful cataract extraction with intraocular lens implantation during infliximab therapy with no subsequent inflammation), while 26 eyes (68.4%) had stable bcva over the 24-month study period. the side effects included allergic reaction, fatigue, cellulitis, headache, restlessness, elevation of liver enzymes, and anemia. two patients (n = 24, 8.3%) experienced severe adverse effects and the treatment was stopped prematurely in these two patients. conclusion: infliximab might induce and maintain the steroid-free remission in hlab27-associated ocular inflammation in patients resistant or intolerant to conventional immunomodulatory therapy. keywords: hla-b27; immunomodulatory therapy; infliximab; tnf-α; uveitis; vasculitis j ophthalmic vis res 2020; 15 (4): 459–469 © 2020 journal of ophthalmic and vision research | published by knowledge e 459 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7786&domain=pdf&date_stamp=2019-07-17 infliximab for hla-b27 uveitis; bajwa and maleki et al introduction acute anterior uveitis (aau) is the most common form of intraocular inflammatory disease and can be associated with the human leukocyte antigen (hla)-b27 haplotype in approximately 55–71% of patients.[1, 2] it usually manifests at a young age as recurrent, acute, non-granulomatous uveitis, with a unilateral or alternating bilateral presentation. the disease may involve posterior segment in the form of optic disc edema, macular edema, choroidal folds and effusions, exudative retinal detachment, and anterior and posterior scleritis.[3] intense inflammation and protein coagulum in the aqueous may lead to temporary or permanent severe visual impairment. topical corticosteroids, the first line of therapy, are sometimes insufficient to control the intraocular inflammation. additional periocular and/or systemic corticosteroids and sometimes both are required to control the inflammation in more severe cases. corticosteroid treatment increases the risk of systemic and ocular complications such as glaucoma and cataract. therefore, corticosteroidsparing conventional immunomodulatory therapies such as methotrexate, azathioprine, and mycophenolate mofetil (mmf) have been employed in the treatment of these patients. biologic response modifier agents are the next step of the step ladder approach in the treatment of patients intolerant or resistant to conventional immunomodulatory therapy (imt).[4, 5] infliximab is a mouse–human chimeric immunoglobulin g1 (igg1) monoclonal antibody that binds both the soluble and the membrane-bound precursor of tumor necrosis factor-alpha (tnf-α) and acts as a tnf-α inhibitor. it has been employed off-label in the treatment of non-infectious ocular inflammatory diseases refractory to conventional imt with a high rate of inflammation control and few adverse effects.[6–14] correspondence to: charles stephen foster, md, facr, facs. 1440 main st., suite 201, waltham, ma 02451, usa. email: sfoster@mersi.com *co-first authorship received: 25-03-2020 accepted: 10-07-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7786 there are very few studies which have specifically focused on the hla b-27-associated ocular inflammation.[12, 13] even fewer studies have evaluated the efficacy and safety of infliximab therapy in patients with hla-b27-associated ocular inflammation resistant or intolerant to conventional imt.[13] in this study, the efficacy and safety of steroid-free infliximab therapy were assessed in an hla-b27 positive ocular inflammatory diseases in patients resistant or intolerant to conventional imt. methods this study was a single-center retrospective observational case series. approval for this study was obtained through the new england institutional review board, which issued a waiver of informed consent, as this was a retrospective chart review analysis. this study was performed in accordance with the declaration of helsinki and was hipaa compliant. electronic charts of patients with hla-b27associated ocular inflammation and infliximab (remicade; centocor, inc, malvern, pennsylvania) therapy between july 2005 and october 2012 were examined. those patients who received infliximab as the primary treatment were excluded. twenty-four patients (38 eyes) who had received at least one conventional imt and/or another biologic response modifier agent were included in the study. the baseline demographic data, clinical diagnosis, and previous treatments were extracted from the charts. the best-corrected visual acuity (bcva), slit lamp biomicroscopy, funduscopy positive findings, and intraocular pressure prior to and at 3, 6, 9, 12, 18, 24 months after starting the infliximab therapy were collected. flare-ups, dose, and frequency of infliximab infusions, duration of follow-up, and severe adverse effects of infliximab were noted. severe adverse effects were described as a severe side effect significant enough for the termination of infliximab therapy. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: bajwa a, maleki a, payal ar, fandiño a, padrón mim, walsh m, foster cs. efficacy and safety of infliximab in hla-b27associated ocular inflammation refractory or intolerant to conventional immunomodulatory therapy. j ophthalmic vis res 2020;15:459–469. 460 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 https://knepublishing.com/index.php/jovr infliximab for hla-b27 uveitis; bajwa and maleki et al standardization of uveitis nomenclature (sun) working group grading scheme was used for the assessment of anterior chamber cell and flare.[15] cases seen prior to the publication of sun guidelines were reclassified following the new anatomical classification system. inactive anterior uveitis was defined as less than one plus cells in anterior chamber and inactive vitreous inflammation was defined as less than one plus vitreous haze.[15, 16] inactive scleritis was defined based on sen et al’s study.[17] in this study, refractory ocular inflammation was described as unresponsive inflammation or intolerance to a three-month course of treatment with at least two different conventional immunomodulatory agents. patients without inflammation for the consecutive six months of infliximab therapy were categorized as ”remission on treatment” group. the ”remission off treatment” group was defined as inflammation-free for a period of six consecutive months without infliximab treatment. all patients had blood tests, which included a complete blood cell count (cbc), liver function tests (lfts), and renal function tests before each infusion. they also had purified protein derivative skin test or quantiferon blood test, and antinuclear antibody (ana) once at baseline and yearly afterward. all patients received a loading dose of 5 mg/kg at 0 and 2 weeks, then every 4 weeks for five more infusions. however, some patients received higher doses of infliximab such as 7.5 mg/kg then 10 mg/kg after the third infusion because of the presence of inflammation in the complete ocular examination and/or ancillary tests. after six months, the frequency of infusions was stretched gradually from 6 to 12 weeks based on the response to the treatment and the absence of the active inflammation. the treatment was stopped once the patient was stable at the 12-week infliximab infusion intervals for four consecutive infusions. in this study, the side effects were defined as adverse effects severe enough to justify the treatment termination. all patients responded to a questionnaire and the blood sample was collected to evaluate for possible medication toxicity in white blood cell (wbc), red blood cell (rbc), platelet (plt), alanine aminotransferase (alt), aspartate aminotransferase (ast), alkaline phosphatase (alkp), gamma glutamine transferase (ggt), blood urea nitrogen (bun), and creatinine (cr) before each infusion. the primary outcome of the study was to determine the efficacy of infliximab determined by the control of inflammation, duration of remission, and the ability to reduce conventional imt. the safety of the study was defined as the absence of severe side effects. the secondary outcome was an improvement of two or more lines of bcva on the snellen acuity chart. statistical analysis data were presented as descriptive statistics (mean, percentages, range). microsoft excel 2010 (microsoft, richmond, va) was used for statistical analysis. paired and unpaired two-tailed t-tests were used to compare the number of medications, intraocular pressure, and visual acuity changes before and after the treatment. the level of significance was set at p ≤ 0.05. results twenty-four patients (38 eyes) were included in the study. the average age of the patients was 44.7 ± 13.6 (12–67 years). of the 24 patients, 14 (58.3%) were women and 14 (58.3%) had bilateral involvement. the prevalence of one or more associated systemic illness including ankylosing spondylitis, reactive arthritis, inflammatory bowel disease, psoriatic arthritis, and juvenile rheumatoid arthritis was 70.8% (17 of 24) (table 1). sixteen patients (n = 24, 66.7%) at baseline had active ocular inflammation, which was reduced to only one patient (n = 21, 4.7%) at the 24-month followup visit (table 2). of the sixteen patients with active ocular inflammation at baseline, 6 patients (37.5%) and 10 eyes (38.5%) had chronic inflammation, while the other 10 patients (62.5%) and 16 eyes (61.5%) were diagnosed with an acute flare up. all patients were on at least one conventional imt and/or another biologic response modifier agent (table 3). the infliximab therapy was prematurely stopped in three patients (12.5%) between the threeand six months follow-up period due to one patient with a severe allergic reaction (itching, rash, and shortness of breath during the infusion), one patient with a significant rise in liver enzymes (alt and ast more than 10 times of the normal), and one journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 461 infliximab for hla-b27 uveitis; bajwa and maleki et al table 1. general characteristics and medication characteristics value age – yr mean ± sd 44.7 ± 13.6 range 12–67 female – no. (%) 14 (58.3) systemic diseases† – no. (%) 17 (70.8) as 9 (37.5) as and ra 2 (8.3) as and ibd 1 (4.1) pa 2 (8.3) nsa 2 (8.3) jia 1 (4.2) conventional therapy before infliximab patients (n = 24) (%) after infliximab patients (n = 24) (%) corticosteroids (by route) none 0 (0) 19 (79.1) topical 21 (87.5) 4 (16) periocular and/or intraocular¶ 8 (33.3) – oral and/or intravenous 13 (38.1) 3 (12.5) imt (by number of medications)‡ none 0 (0) 7 (29.1) 1 medication 7 (29.2) 14 (58.3) 2 medications 8 (33.3) 2 (8.3) ≥3 medications 9 (37.5) 1 (4.1) side effects after infliximab (n = 24) 12 (50) allergic reaction – 2 (8.3) fatigue – 3 (12.5) cellulitis – 2 (8.3) headache, restlessness – 1 (4.2) ast/alt elevation – 2 (8.3) anemia – 2 (8.3) †as, ankylosing spondylitis; ra, reactive arthritis; ibd, inflammatory bowel disease; pa, psoriatic arthritis; nsa, nonspecific arthritis; jia, juvenile inflammatory arthritis ¶ at least one month before infliximab therapy ‡imt, immunomodulatory therapy ast, aspartate aminotransferase; alt, alanine aminotransferase patient with insurance coverage problems (figure 1). of the eight inactive patients (33.3%) at baseline, six patients (25%) were started on infliximab treatment due to intolerance to previous conventional imt therapy. in the other two patients (8.3%), infliximab was started for an active systemic disease by their rheumatologist. the latter two developed an ocular inflammation during the first three months of follow-up. for the patients with active disease at baseline, the duration of the treatment required to induce remission varied from less than six months in four (n = 16, 25%) patients to more than one year in five (n = 16, 31.3%) patients. six patients (n =16, 37.5%) were in remission by the second 462 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 infliximab for hla-b27 uveitis; bajwa and maleki et al table 2. inflammation status before and after the infliximab therapy excluding inactive patients ocular inflammation before infliximab [patients (%)] (n =16) after infliximab [patients (%)] (n = 16) 3 months 6 months 12 months 18 months 24 months active 16 (100) 3 (16.6) 2 (12.5) 2 (12.5) 2 (12.5) 1 (6.25) anterior uveitis 11 (68.7) 1 (6.25) – – 1 (6.25) – scleritis 2 (12.5) – – – – – vitritis 1 (6.25) – – – – – retinal vasculitis – 1 (6.25) 1 (6.25) 1 (6.25) 1 (6.25) 1 (6.25) anterior uveitis with retinal vasculitis – – 1 (6.25) – – – vitritis with retinal vasculitis 1 (6.25) – – 1 (6.25) – – papillitis with retinal vasculitis – 1 (6.25) – – – – vitritis, papillitis, and retinal vasculitis 1 (6.25) – – – – – table 3. immunomulatory therapy before starting the infliximab therapy in patients with hla-b27 ocular inflammation immunomodulatory therapy number (%) methotrexate 10 (41.6%) mycophenolate mofetil 5 (20.8%) humira 5 (20.8%) cyclosporine 2 (8.33%) chlorambucil 1 (4.16%) daclizumab 1 (4.16%) etanercept 1 (4.16%) azathioprine 1 (4.16%) celecoxib 1 (4.16%) none 4 (16.6%) year of the follow-up period. at the end of the study, 14 (58.3%) patients were in remission on infliximab therapy and six (25%) were in remission off infliximab therapy (figure 2). the mean duration between starting the treatment and induction of remission was 16.5 months (range, 3–24 months). table 4 demonstrates how patients with flare up were treated during the study period. before employing infliximab therapy, all patients had received one or more routes of corticosteroid administration, including topical, periocular, systemic therapy based on the severity of the disease. twenty-one patients (87.5%) were receiving topical corticosteroids; six patients (37.5%), two patients (8.33%), and another two patients (8.33%) received transseptal, intravenous, and intravitreal corticosteroids, respectively. eleven patients (45.8%) were on oral prednisone; higher doses (30–60 mg) were employed in four patients (16.7%) with severe active inflammation. seven patients (29.1%) were on maintenance oral prednisone therapy with an average dose of 8.7 mg (range, 7–10). nineteen patients (90.5%) discontinued corticosteroids by the end of the study. at the 24-month follow-up, 13 patients (87.5%) out of the 16 active patients were in steroid-free remission. during the 24 months of follow-up, the number of conventional imt agents were reduced in 14 (58.3%) patients, the dosage of medications was halved in two patients (8.3%), and medications were discontinued in five (n = 21, 23.8%) patients (table 1). the average number of medications before starting treatment was 2.3 ± 1.14 and at the end of the follow-up period was journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 463 infliximab for hla-b27 uveitis; bajwa and maleki et al table 4. management of patients with ocular inflammation flare-up during the study period study period number of patients with flare-up of ocular inflammation treatment for flare-up 3-6 months 4 (17.4%, n = 23) 3 patients ( n = 23, 13%) – reducing the infliximab infusion interval 1 patient ( n = 23, 4.3%) – boosting infliximab dose 1 patient ( n = 23, 4.3%) with persistent vasculitis – mmf and csa were substituted for methotrexate and adalimumab 6–12 months 4 (19%, n = 21) 1 patient ( n = 21, 4.8%) with papillitis, vitritis, and retinal vasculitis – received additional intravenous pulse steroids and was switched to cyclophosphamide 2 patients ( n = 21, 9.5%) – received increased dose of infliximab 1 patient ( n = 21, 4.8%) with retinal vasculitis – received increased doses of infliximab along with mmf and csa 12–18 months 2 (9.5%, n = 21) 1 patient ( n = 21, 4.8%) with persistent retinal vasculitis – received increased dose of infliximab along with oral corticosteroids 1 patients ( n = 21, 4.8%) – relapsed with anterior uveitis and was restarted on infliximab 18–24 months 3 (14.3%, n = 21) 1 patient ( n = 21, 4.8%) – added methotrexate 1 patient ( n = 21, 4.8%) – reducing interval and boosting dose of infliximab 1 patient ( n = 21, 4.8%) – increasing the dose of infliximab with oral steroids mmf, mycophenolate mofetil; csa, cyclosporin-a figure 1. the number of patients in total, with active and inactive disease at each follow-up visits. 464 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 infliximab for hla-b27 uveitis; bajwa and maleki et al figure 2. the number of patients with active disease, remission on infliximab infliximab, remission off infliximab therapy before starting the treatment and at the end of the follow-up period. 0.08 ± 0.2. the difference in the average number of medications before starting the treatment and at the end of the study period was statistically significant (p < 0.0001). of the 38 eyes, 8 eyes (21.05%) showed improvement in bcva (three eyes had cataract extraction with intraocular lens implantation during infliximab therapy with no subsequent eye inflammation), while 26 eyes (68.4%) had stable bcva over the 24-month study period. the mean visual acuity before starting infliximab treatment was 20/30–20/40 (0.22 ± 0.43logmar) and was 20/25 (0.1 ± 0.24logmar) after the treatment. the mean difference of visual acuity before starting infliximab therapy and at the end of 24 months of follow-up was not statistically significant (p = 0.14). moreover, the changes in visual acuity in each eye before starting the treatment and at the last follow-up visit were not statistically significant (p = 0.06). the average intraocular pressure in all uveitic eyes of patients before starting infliximab therapy was 16.3 ± 4.56 mmhg (10–34). the averages of intraocular pressure in the worse and better eyes of patients were 18.2 ± 4.61 mmhg and 14.5 ± 3.44 mmhg, respectively. at the last followup visit, the average of intraocular pressure in all uveitic eyes of patients was 14.9 ± 2.00 mmhg (10–20). averages of intraocular pressure in the worse eyes and better eyes of patients were 14.9 ± 2.07 and 14.57 ± 2.2 mmhg, respectively. using the paired t-test, the difference between the intraocular pressure of the worse eye of each patient before starting the treatment and at the last follow-up was statistically significant (p = 0.004); however, this difference was not significant in the better involved eyes of each patient (p = 0.8). the primary dose of infliximab was 5 mg/kg body in 19 patients. in three patients (12.5%), infliximab was started at the highest dose of 10 mg/kg: one patient was monocular, one had severe scleritis, and one had extensive retinal vasculitis. the side effects included allergic reaction, fatigue, cellulitis, headache, restlessness, elevation of liver enzymes, and anemia. the treatment was discontinued in three (12.5%) patients; two due to the development of side effects and one due to insurance problems. these three patients were considered as treatment failures. discussion the association between hla-b27 positivity and aau with or without a spectrum of other inflammatory diseases was originally described in 1973 and is one of the strongest hla-disease associations.[18, 19] tnf-α gene controls the production of tnf-α, which is a cytokine journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 465 infliximab for hla-b27 uveitis; bajwa and maleki et al and inflammatory mediator in animal models of uveitis. tnf-α has been detected in the uvea and retina at the early stages of acute uveitis. in addition, tnf-α has been found in higher levels in the sera and aqueous humor of patients with uveitis.[5, 20] it may induce expression of chemokines, adhesion molecules, and other proinflammatory cytokines causing protracted inflammatory process.[21] its blockade is associated with decreased ocular inflammation in animal models.[22–24] sahrawi et al proposed that hla b27-positive individuals show a higher susceptibility toward development of intraocular inflammation in the presence of an a allele at nucleotide-238 and, to a lesser degree, at nucleotide-308 of the tnf-α gene promoter.[25] these findings formed the rationale for using the tnf-α inhibitor biologic agents in hla-b27-associated ocular inflammatory diseases. infliximab and adalimumab are the most common tnf-α inhibitor biologic response modifier agents employed in the field of ophthalmology. the successful use of infliximab and adalimumab for controlling ocular and systemic inflammatory conditions has been reported in different studies.[26–31] adalimumab is the only fda-approved biologic for the treatment of noninfectious uveitis.[29–31] the median age (44 years) of our study sample and the prevalence of associated systemic illness (70%) matched earlier studies.[27–31] infliximab was well-tolerated and bcva was improved or remained stable in the majority of our patients. previous studies reported the success of infliximab therapy in different ocular inflammatory diseases with various etiologies including hla-b27-associated uveitis.[29–32] in two studies by foeldvari et al and suhler et al, the success of infliximab in jia-associated uveitis and panuveitis, intermediate uveitis and posterior uveitis was 70% and 78%, respectively.[28, 31] kim et al and el-shabrawi et al found that infliximab (3–5 mg/kg body weight) was effective in 76.2% and 66.7% of patients with hla-b27 anterior uveitis.[33, 34] in our study, ocular inflammation was controlled in 83.3% of patients at the end of two years; higher than that reported in previous studies.[29, 32–34] this can be attributed to adjustment of infliximab dose up to 10 mg/kg based on the response to infliximab therapy.[28, 31–33] while previous studies used pulse or oral corticosteroid therapies to control acute inflammation, the aim of our study was to achieve steroid-free remission. thus, a significant number of our patients were not on steroids for their ocular inflammation at the 24month follow-up visit. this can be interpreted by the higher doses of infliximab and longer duration of treatment that we employed in our patients.[14, 35] the starting dose for infliximab therapy was 5 mg/kg in all patients except those with more severe involvement such as retinal vasculitis and scleritis. we followed the protocol of two loading doses and five infusions every four weeks before stretching the infusions. slow tapering of the infusions has been proved as an effective way to maintain remission in patients on antitnf-α inhibitor therapy.[34, 36–39] this was also demonstrated in our study. some of our patients needed to increase the dose of infliximab, which may be due to three possible hypotheses. the first hypothesis is the development of an antibody against the infliximab molecule due to its murine constituent. this may be prevented by adding a low-dose anti-metabolite to the regimen; however, we were unable to make this conclusion due to low sample size. a second possible reason to increase the dose of infliximab is tachyphylaxis to the medication itself. the third mechanism is the lower dose of medication per age in younger individuals due to their growth spurt and an increase in their weight. in this study, there were two patients with hlab27 associated active systemic inflammation and quiet eyes who were started on infliximab by the rheumatologists and their intraocular inflammation occurred early in the course of infliximab therapy. there are two explanations for this finding. first, it might be the natural course of the hla-b27associated anterior uveitis, which was not under control with the previous regimen and the time for infliximab to control the inflammation was not sufficient. second, in our experience, there are some patients with hla-b27-associated ocular inflammation who need higher doses of infliximab for controlling ocular inflammation. in these patients, ocular inflammation can recur despite their systemic symptoms being controlled with a standard dose of infliximab. that is why the dose adjustment for ocular inflammation control might be necessary after the third infliximab infusion. 466 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 infliximab for hla-b27 uveitis; bajwa and maleki et al our study had the inherent limitations of a retrospective study design with a small sample size. as a tertiary care clinic, a large proportion of our patients present with severe, long-standing, and often unresponsive disease. moreover, due to the nature of our referral center which has more severe and complicated cases, the trend is toward a more aggressive therapy such as infliximab rather than a less aggressive treatment such as adalimumab injection, and this can also be a source of selection bias. furthermore, similar to other retrospective studies, the inability to control for confounding factors such as changes in topical, local, and systemic corticosteroids and imts for eye and systemic conditions may allow for the development of uveitis early in the course of infliximab therapy. in summary, infliximab therapy might be an effective and safe method of treatment for inducing and sustaining the steroid-free remission in patients with hla-b27-associated ocular inflammation, which can be a serious and potentially blinding condition if left untreated or incompletely treated. however, to validate these findings, more potent studies are required. disclosure statement dr. c stephen foster declares the following: consultancies with aldeyra therapeutics (lexington, ma), allakos (redwood city, ca), bausch & lomb surgical, inc (rancho cucamonga, ca), eyegate pharma (waltham, ma), genentech (south san francisco, ca), novartis (cambridge, ma), psivida (watertown, ma). grants or grants pending with aciont (salt lake city, ut), alcon (aliso viejo, ca), aldeyra therapeutics (lexington, ma), bausch & lomb (rochester, ny), clearside biomedical (alpharetta, ga), dompé pharmaceutical (milan, italy), eyegate pharma (waltham, ma), mallinckrodt pharmaceuticals (staines-upon-thames, uk), novartis pharmaceuticals (cambridge, ma), psivida (watertown, ma), santen (osaka, japan). payment for lectures including service on speaking bureaus: alcon (aliso viejo, ca), allergan (dublin, ireland), mallinckrodt pharmaceuticals (staines-upon-thames, uk). stock or stock options: eyegate pharma (waltham, ma) other authors have nothing to declare. data availability statement the data that support the findings of this study are available from the corresponding author, [csf], upon reasonable request. acknowledgments asima bajva (ab) and arash maleki (am) share first co-authorship as they contributed equally to this manuscript. financial support and sponsorship none. conflicts of interest there are no conflicts of interest. references 1. chang jh, mccluskey pj, wakefield d. acute anterior uveitis and hla-b27. surv ophthalmol 2005;50:364–388. 2. ramsay a, lightman s. hypopyon uveitis. surv ophthalmol 2001;46:1–18. 3. anshu a, chee sp. posterior scleritis and its association with hla b27 haplotype. ophthalmologica 2007;221:275– 278. 4. loh ar, acharya nr. incidence rates and risk factors for ocular complications and vision loss in hla-b27associated uveitis. am j ophthalmol 2010;150:534– 542.e2. 5. de vos af, klaren vn, kijlstra a. expression of multiple cytokines and il-1ra in the uvea and retina during endotoxin-induced uveitis in the rat. invest ophthalmol vis sci 1994;35:3873–3883. 6. benitez-del-castillo jm, martinez-de-la-casa jm, patocour e, méndez-fernández r, lópez-abad c, matilla m, garcia-sanchez j. long-term treatment of refractory posterior uveitis with anti-tnfalpha (infliximab). eye (lond). 2005 aug;19(8):841-5. doi: 10.1038/sj.eye.6701689. 7. lopez-gonzalez r, loza e, jover ja, benitez del castillo jm, mendez r, hernandez-garcia c, et al. treatment of refractory posterior uveitis with infliximab: a 7-year followup study. scand j rheumatol. 2009 jan-feb;38(1):58-62. doi: 10.1080/03009740802366076. 8. joseph a, raj d, dua hs, powell pt, lanyon pc, powell rj. infliximab in the treatment of refractory posterior uveitis. ophthalmology 2003;110:1449–1453. 9. el-shabrawi y, mangge h, hermann j. anti-tumour necrosis factor alpha treatment in chronic recurrent inflammation of the anterior segment of the eye in patients resistant to standard immunomodulatory treatment. ann rheum dis 2003;62:1243–1244. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 467 infliximab for hla-b27 uveitis; bajwa and maleki et al 10. suhler eb, smith jr, giles tr, lauer ak, wertheim ms, kurz de, et al. infliximab therapy for refractory uveitis: 2year results of a prospective trial. arch ophthalmol. 2009 jun;127(6):819-22. doi: 10.1001/archophthalmol.2009.141. 11. sobrin l, kim ec, christen w, papadaki t, letko e, foster cs. infliximab therapy for the treatment of refractory ocular inflammatory disease. arch ophthalmol 2007;125:895– 900. 12. el-shabrawi y, hermann j. anti-tumor necrosis factoralpha therapy with infliximab as an alternative to corticosteroids in the treatment of human leukocyte antigen b27-associated acute anterior uveitis. ophthalmology 2002;109:2342–2346. 13. gueudry j, thorne je, bansie r, braun j, van hagen pm, bodaghi b. biologic therapy for hla-b27-associated ocular disorders. ocul immunol inflamm 2017;25:169–178. 14. kim m, won jy, choi sy, ju jh, park yh. anti-tnfα treatment for hla-b27-positive ankylosing spondylitisrelated uveitis. am j ophthalmol 2016;170:32–40. 15. jabs da, nussenblatt rb, rosenbaum jt. standardization of uveitis nomenclature for reporting clinical data. results of the first international workshop. am j ophthalmol 2005;140:509–516. 16. harper sl, chorich lj, foster cs. diagnosis of uveitis. in: foster cs, vitale at, editors. diagnosis and treatment of uveitis. philadelphia, pa: wb saunders co; 2002:79–103. 17. sen hn, sangave aa, goldstein da, suhler eb, cunningham d, vitale s, et al. a standardized grading system for scleritis. ophthalmology. 2011 apr;118(4):768-71. doi: 10.1016/j.ophtha.2010.08.027. epub 2010 nov 20. 18. brewerton da, hart fd, nicholls a, caffrey m, james dc, sturrock rd. ankylosing spondylitis and hl-a 27. lancet 1973;1:904–907. 19. schlosstein l, terasaki pi, bluestone r, pearson cm. high association of an hl-a antigen, w27, with ankylosing spondylitis. n engl j med 1973;288:704–706. 20. pérez-guijo v, santos-lacomba m, sánchez-hernández m, castro-villegas mdel c, gallardo-galera jm, collantes-estevez e. tumour necrosis factor-alpha levels in aqueous humour and serum from patients with uveitis: the involvement of hla-b27. curr med res opin 2004;20:155–157. 21. de vos af, klaren vn, kijlstra a. expression of multiple cytokines and il-1ra in the uvea and retina during endotoxin-induced uveitis in the rat. invest ophthalmol vis sci 1994;35:3873–3883. 22. koizumi k, poulaki v, doehmen s, welsandt g, radetzky s, lappas a, et al. contribution of tnf-alpha to leukocyte adhesion, vascular leakage, and apoptotic cell death in endotoxin-induced uveitis in vivo. invest ophthalmol vis sci. 2003 may;44(5):2184-91. doi: 10.1167/iovs.02-0589. erratum in: invest ophthalmol vis sci. 2016 feb;57(2):403. 23. sartani g, silver pb, rizzo lv, chan cc, wiggert b, mastorakos g, et al. anti-tumor necrosis factor alpha therapy suppresses the induction of experimental autoimmune uveoretinitis in mice by inhibiting antigen priming. invest ophthalmol vis sci 1996;37:2211–2218. 24. mo js, matsukawa a, ohkawara s, yoshinaga m. involvement of tnf alpha, il-1 beta and il-1 receptor antagonist in lps-induced rabbit uveitis. exp eye res 1998;66:547–557. 25. el-shabrawi y, wegscheider bj, weger m, renner w, posch u, ulrich s, et al. polymorphisms within the tumor necrosis factor-alpha promoter region in patients with hla-b27-associated uveitis: association with susceptibility and clinical manifestations. ophthalmology. 2006 apr;113(4):695-700. doi: 10.1016/j.ophtha.2006.01.004. 26. pasadhika s, suhler e, emmett jr c. use of biologic agents in the treatment of uveitis. rev ophthalmol retin insid 2010. available from: http://www.reviewofophthalmology. com/content/d/retinal_insider/i/1208/c/22770/ (accessed nov 5, 2013). 27. baughman rp, bradley da, lower ee. infliximab in chronic ocular inflammation. int j clin pharmacol ther 2005;43:7– 11. 28. matsuda j, kaburaki t, kobayashi s, numaga j. treatment of recurrent anterior uveitis with infliximab in patient with ankylosing spondylitis. jpn j ophthalmol 2013;57:104–107. 29. foeldvari i, nielsen s, kümmerle-deschner j, espada g, horneff g, bica b, et altumor necrosis factor-alpha blocker in treatment of juvenile idiopathic arthritis-associated uveitis refractory to second-line agents: results of a multinational survey. j rheumatol. 2007 may;34(5):114650. epub 2007 mar 1. 30. nguyen qd, merrill pt, jaffe gj, dick ad, kurup sk, sheppard j, et al. adalimumab for prevention of uveitic flare in patients with inactive non-infectious uveitis controlled by corticosteroids (visual ii): a multicentre, double-masked, randomised, placebo-controlled phase 3 trial. lancet. 2016 sep 17;388(10050):1183-92. doi: 10.1016/s0140-6736(16)31339-3. epub 2016 aug 16. erratum in: lancet. 2016 sep 17;388(10050):1160. 31. suhler eb, adán a, brézin ap, fortin e, goto h, jaffe gj, et al. safety and efficacy of adalimumab in patients with noninfectious uveitis in an ongoing open-label study: visual iii. ophthalmology. 2018 jul;125(7):1075-1087. doi: 10.1016/j.ophtha.2017.12.039. 32. suhler eb, smith jr, wertheim ms, lauer ak, kurz de, pickard td, et al. a prospective trial of infliximab therapy for refractory uveitis: preliminary safety and efficacy outcomes. arch ophthalmol 2005;123:903–912. 33. kim m, won jy, choi sy, ju jh, park yh. anti-tnfα treatment for hla-b27-postive ankylosing spondylitisrelated uveitis. am j ophthalmol 2016;170:32–40. 34. el-shabrawi w, hermann j. case series of selective antitumor necrosis factor alpha therapy using infliximab in patients with nonresponsive chronic hla-b27associated anterior uevitis: commnet on the articles by brandt et al. arthritis rheum 2002;46:2821–2822. 35. paccou j, baclé-boutry m-a, solau-gervais e, belephilippe p, flipo rm. dosage adjustment of anti-tumor necrosis factor-α inhibitor in ankylosing spondylitis is effective in maintaining remission in clinical practice. j rheumatol 2012;39:1418–1423. 36. richards jc, tay-kearney m-l, murray k, manners p. infliximab for juvenile idiopathic arthritis-associated uveitis. clin experiment ophthalmol 2005;33:461–468. 37. rajaraman rt, kimura y, li s, haines k, chu ds. retrospective case review of pediatric patients with uveitis treated with infliximab. ophthalmology 2006;113:308–314. 38. kahn p, weiss m, imundo lf, levy dm. favorable response to high-dose infliximab for refractory childhood uveitis. ophthalmology 2006;113:8604.e2. 468 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 http://www.reviewofophthalmology.com/content/d/retinal_insider/i/1208/c/22770/ http://www.reviewofophthalmology.com/content/d/retinal_insider/i/1208/c/22770/ infliximab for hla-b27 uveitis; bajwa and maleki et al 39. petropoulos ik, vaudaux jd, guex-crosier y. anti-tnfalpha therapy in patients with chronic non-infectious uveitis: the experience of jules gonin eye hospital. klin monbl augenheilkd 2008;225:457–461. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 469 photo essay diffuse pigment release in a patient undergoing tumor-infiltrating lymphocyte immunotherapy for acral malignant melanoma madison kerley1, md; niloofar piri2, md; aparna ramasubramanian3, md 1department of ophthalmology and visual sciences, university of louisville school of medicine, louisville, ky 2department of ophthalmology, saint louis university, st. louis, mo 3department of ophthalmology, phoenix children’s hospital, phoenix, az orcid: madison kerley: http://orcid.org/0000-0003-0086-6755 j ophthalmic vis res 2023; 18 (3): 339–341 presentation although acral malignant melanoma accounts for 2% of melanoma diagnoses, it has the lowest fiveand ten-year survival rates of melanoma subtypes.[1] its general presentation is a rapidly growing pigmented region on the soles of feet or the palms of hands.[1] treatment includes lesion excision, often with lymph node biopsy, molecularly targeted therapy, chemotherapy, and immunotherapy.[2] tumor-infiltrating lymphocyte immunotherapy (til) is an adoptive cell transfer variant where tumor-infiltrating lymphocytes extracted from a metastatic melanoma tumor are cultured with il2, which serves to activate t-cells. after extraction, the patient is given non-myeloablative lymphodepleting chemotherapy. chemotherapy allows for rapid growth of the il-2 cultured lymphocytes when they are re-introduced to the body.[3] the lymphocytes recognize tumor-related antigens, directly attacking cancer cells. correspondence to: madison kerley, md. 301 e muhammad ali blvd, louisville, ky 40202. email: madison.kerley@louisville.edu received: 30-06-2021 accepted: 26-01-2023 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i3.13783 although til has proven to be a powerful treatment for metastatic melanoma, it can lead to melanocyte-reactive t cells in other melanocyte containing regions.[3] herein, we present a unique case of acral metastatic melanoma, treated by adoptive cell transfer leading to asymptomatic intraocular pigmentary changes. a 51-year-old caucasian male with acral malignant melanoma initiated til for metastatic disease nine years following right toe amputation. three months after treatment initiation, anterior segment exam of both eyes revealed diffuse pigment dusting on the corneal endothelium, along with pigment deposits on the lens capsule and floating pigments in the anterior chamber [figure 1]. fundus photography of both eyes revealed partial depigmentation of the retinal pigment epithelium (rpe), similar to the sunset glow appearance in vogt-koyanagi-harada (vkh) disease [figure 2]. optical coherence tomography (oct) demonstrated normal integrity of outer retinal structures explaining preserved visual acuity. full field electroretinography (erg) this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: kerley m, piri n, ramasubramanian a. diffuse pigment release in a patient undergoing tumor-infiltrating lymphocyte immunotherapy for acral malignant melanoma. j ophthalmic vis res 2023;18:339–341. © 2023 kerley et al.. this is an open access article distributed under the creative commons attribution license | published by knowledge e 339 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i3.13783&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; kerley et al. figure 1. anterior segment image of the right eye demonstrating the pigment deposits on anterior lens capsule. the left eye demonstrated similar pigment deposition. figure 2. fundus imaging of the right eye revealing a sunset glow-like appearance due to partial depigmentation of retinal pigment epithelium. the left eye appeared similar. did not demonstrate rod or cone dysfunction at any voltage, supporting the fact that changes occurred only in rpe without visual sequelae. the patient was subsequently removed from the trial. twentytwo months later, the patient was asymptomatic. discussion this case report highlights ocular side effects associated with til use in the treatment of acral malignant melanoma. symptoms often parallel those of vkh disease, which demonstrates a heightened immune response to tyrosinase450−462 and gp10044−59, two melanocyte antigens found in the ears, skin, hair, meninges, and eyes.[4] our patient did not demonstrate dermatologic manifestations such as vitiligo and poliosis in contrast to yeh et al’s 2009 case.[4] he was asymptomatic with erg records within normal limits. the early ocular presentation of vkh is characterized by diffuse choroiditis, exudative 340 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 photo essay; kerley et al. retinal detachment, and hyperemia of the optic discs.[5] the late phase demonstrates clumping and migration of rpe with fundal depigmentation.[5] further studies on patients who receive til will help us better understand the disease entity, while allowing us to better understand the pathophysiology of similar autoimmune disorders such as vkh, potentially helping to find an immune target treatment. financial support and sponsorship this work was supported in part by an unrestricted institutional grant from research to prevent blindness, ny, ny. conflicts of interest none. references 1. bradford pt, goldstein am, mcmaster ml, tucker ma. acral lentiginous melanoma: incidence and survival patterns in the united states, 1986–2005. arch dermatol 2009;145:427–434. 2. nakamura y, fujisawa y. diagnosis and management of acral lentiginous melanoma. curr treat options oncol 2018;19:42. 3. dudley me, wunderlich jr, yang jc, sherry rm, topalian sl, restifo np, et al. adoptive cell transfer therapy following non-myeloablative but lymphodepleting chemotherapy for the treatment of patients with refractor metastatic melanoma. j clin oncol 2005;23:2346–2357. 4. yeh s, karne nk, kerkar sp, heller ck, palmer dc, johnson la, et al. ocular and systemic autoimmunity after successful tumor-infiltrating lymphocyte immunotherapy for recurrent, metastatic melanoma. ophthalmology 2009;116:98–989. 5. sakata vm, da silva ft, hirata ce, de carvalho jf, yamamoto jh. diagnosis and classification of vogtkoyanagi-harada disease. autoimmun rev 2014;13:550– 555. journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 341 editorial the development pathway for biosimilar biotherapeutics marco zarbin, md, phd institute of ophthalmology and visual science, new jersey medical school, rutgers university, newark, usa j ophthalmic vis res 2020; 15 (3): 273–274 many physicians have experience using generic drugs in their practice. generics tend to be small molecules with a relatively simple structure and are identical to licensed reference products. generic compounds typically are synthesized using organic medicinal chemistry. variations in the manufacturing process are unlikely to have a major impact on the final product, an outcome that is verified through analytical characterization of the generic. a biosimilar biotherapeutic is a protein. biosimilar products are quite different from generic drugs. a biosimilar has similar quality, safety, and efficacy to a licensed reference product, but it is not necessarily identical to the reference product with regard to these properties.[1] in contrast to generic drugs, biosimilars tend to have complex structures and may differ from the reference product in their primary amino acid sequence and other features such as glycosylation and pegylation that alter their tertiary structure (i.e., protein folding) as well as their immunogenicity.[2] these differences arise from the manufacturing process, which tends to be much more complex than that of generic drugs. typically, a biosimilar protein is synthesized by transfecting a target cell with a dna sequence that encodes the desired product. often, transfected mammalian cells are required to produce complex proteins, but these cells typically have lower yields than bacterial hosts. the initial product must be purified to remove undesired proteins. as one might expect, the use of different expression systems can be associated with different post-translational protein modifications. changes in the manufacturing process are thus critical (and essential to avoid patent infringement on proprietary biomanufacturing processes), as they may alter protein structure and function. analytical characterization of these compounds is not straightforward and, in any case, is not expected to reveal structure and properties identical to the reference product if different vectors, expression systems, purification steps, and excipients are used in the manufacturing process. analysis of the immunogenicity of a biosimilar, for example, is a critical aspect of evaluating the therapeutic modality, whereas a generic drug is expected to be identical to the reference product in this regard. the development process and quality control for biosimilars are challenging,[3, 4] which helps to explain why the manufacturing costs for biosimilars and generic drugs are quite different, averaging $100–200 million/molecule for the former and $3–5 million/molecule for the latter. accordingly, the price reduction for biosimilars versus generic drugs is less and might be on the order of 20–30%. clinical trials of biosimilars must demonstrate safety and efficacy comparable to the reference product regarding pharmacokinetic, pharmacodynamic, and immunogenic properties. if phase 3 studies are successful and a biosimilar is approved for one indication, it is approved for all other indications for which the reference product is approved, provided there is adequate scientific justification.[5, 6] in general, there is an expectation that a patient can switch from a biosimilar to the reference product and vice versa with no lapse in therapeutic efficacy or increased risk. switching studies demonstrating interchangeability of biosimilars and reference products have not been required for marketing approval by the european medicine agency,[6] whereas they are required by the us food and drug administration (us fda) (https://www.fda.gov/media/124907/download). in order to assist physicians in identifying biosimilars versus the reference product and avoid inadvertent © 2020 journal of ophthalmic and vision research | published by knowledge e 273 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7444&domain=pdf&date_stamp=2019-07-17 https://www.fda.gov/media/124907/download editorial; zarbin product substitution, the us fda determined that each biosimilar’s name should comprise a core name hyphenated with a four-letter suffix representing the developer.[7] studies such as the one reported by lashay and coworkers in this issue of the journal of ophthalmic and vision research constitute an essential step toward adopting use of stivant, a biosimilar to bevacizumab, for non-approved ophthalmic indications.[8] this work has been executed expertly and provides reassurance that stivant may well be an appropriate substitute for intravitreal bevacizumab, which is more expensive. the authors qualify their results with great care, but it may be worth emphasizing a few points. first, the rabbit retina is merangiotic and has no fovea. apart from the inability to identify drug effects on foveal function, these and other features of the rabbit eye may lead to differences in the intraocular and systemic pharmacokinetic profile of the drug associated with intravitreal injection in human patients. also, although the dose administered was much higher than that anticipated for human subjects, a dose response curve was not undertaken. while we may conclude that a dose of 1.25 mg in a normal size human eye is likely to be safe, we do not know the upper bound of a safe dose based on the data provided. naturally, these animals had healthy eyes. we do not know whether the safety profile observed in this work will be the same in eyes with damaged retina, retinal pigment epithelium, and/or choroid, as will be encountered in patients with diabetic retinopathy, retinal vein occlusion, and age-related macular degeneration. of course, these same limitations apply to studies using bevacizumab in rabbits, but biosimilars can differ in subtle ways from the licensed product they mimic. nonetheless, the data provided by lashay and coworkers are positive and justify additional studies that will enable stivant to be deployed for clinical use in patients with retinal vascular diseases. ultimately, efforts such as these will enable us to provide sightsaving therapy to many more patients through the cost savings realized by the use of biosimilars. i commend the authors for this excellent work and look forward to additional progress in this area. we and our patients will benefit enormously from their efforts. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. harvey rd. science of biosimilars. j oncol pract 2017;13:17s–23s. 2. tsuruta lr, lopes dos santos m, moro am. biosimilars advancements: moving on to the future. biotechnol prog 2015;31:1139–1149. 3. sharma a, kumar n, kuppermann bd, bandello f, loewenstein a. biotherapeutics and immunogenicity: ophthalmic perspective. eye 2019;33:1359–1361. 4. sharma a, kumar n, kuppermann bd, francesco b, lowenstein a. ophthalmic biosimilars: lessons from india. indian j ophthalmol 2019;67;1384–1385. 5. macdonald jc, hartman h, jacobs ia. regulatory considerations in oncologic biosimilar drug development. mabs 2015;7:653–661. 6. scavone c, rafaniello c, berrino l, rossi f, capuano a. strengths, weaknesses and future challenges of biosimilars’ development. an opinion on how to improve the knowledge and use of biosimilars in clinical practice. pharmacol res 2017;126:138–142. 7. cber/cder. nonproprietary naming of biological products: guidance for industry. rockville, md: us food and drug administration; 2017. 8. lashay a, faghihi h, mirshahi a, khojasteh h, khodabande a, riazi-esfahani h, et al. safety of intravitreal injection of stivant, a biosimilar to bevacizumab, in rabbit eyes. j ophthalmic vis res 2020;15:341–350. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7444 how to cite this article: zarbin m. the development pathway for biosimilar biotherapeutics. j ophthalmic vis res 2020;15:273–274. 274 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 https://knepublishing.com/index.php/jovr original article etiology and risk factors for infectious keratitis in south texas madeleine puig, md; menachem weiss, md; ricardo salinas, md; daniel a johnson, md; ahmad kheirkhah, md department of ophthalmology, long school of medicine, university of texas health at san antonio, san antonio, texas, usa orcid: ahmad kheirkhah: https://orcid.org/0000-0003-4217-3367 abstract purpose: to determine the causative organisms and associated risk factors for infectious keratitis in south texas. methods: this retrospective study was performed at a tertiary teaching hospital system in south texas. medical records of all patients who presented with infectious keratitis from 2012 to 2018 were reviewed. only patients with culture-proven bacterial, fungal, and acanthamoeba keratitis were included. results: in total, 182 eyes of 181 patients had culture-proven bacterial, fungal, or acanthamoeba keratitis. the age of patients ranged from 3 to 93 years, with a mean of 48.3 ± 20.8 years. the most common etiologic agent was bacteria, with 173 bacterial cultures (95.1%) recovered, followed by 13 fungal cultures (7.1%), and 3 acanthamoeba cultures (1.6%). of the 218 bacterial isolates, coagulase-negative staphylococcus was the most common (25.7%), followed by pseudomonas aeruginosa (23.4%), staphylococcus aureus (11.0%), and moraxella (7.8%). fusarium was the most common fungal isolate (46.2%). the most common risk factors for infectious keratitis included contact lens wear (32.4%), underlying corneal disease (17.6%), trauma (14.3%), and ocular surface disease (13.7%). conclusions: bacteria are the most common cause of infectious keratitis in this patient population, with coagulase-negative staphylococcus and pseudomonas as the most common isolates. the prevalence of culture-positive fungal keratitis is significantly lower than that of bacterial keratitis. contact lens wear is the most common risk factor associated with infectious keratitis in south texas. keywords: acanthamoeba; bacteria; corneal ulcer; fungus; keratitis j ophthalmic vis res 2020; 15 (2): 128–137 correspondence to: ahmad kheirkhah, md. medical arts and research center, 8300 floyd curl dr., san antonio, tx 78229, usa. e-mail: kheirkhah@uthscsa.edu received:15-06-2019 accepted: 24-11-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i2.6729 introduction infectious keratitis is a vision-threatening infection of the cornea caused by bacteria, fungi, parasites, this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: puig m, weiss m, salinas r, johnson da, kheirkhah a. etiology and risk factors for infectious keratitis in south texas. j ophthalmic vis res 2020;15:128–137. 128 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i2.6729&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr infectious keratitis in south texas; puig et al or viruses. infection usually begins with epithelial defects in the setting of a weakened ocular defense system and proceeds to stromal invasion, necrosis, and corneal ulceration.[1] ulcers can lead to visual impairment and may lead to corneal perforation and endophthalmitis. outcomes of these patients depend on timely diagnosis and treatment with close follow-up. in 2010 alone, keratitis accounted for over 700,000 doctor visits in the united states, 76.5% of which led to antimicrobial prescriptions. the combined cost of these visits is estimated to be $175 million in direct healthcare expenditure.[2] clinical management of infectious keratitis depends on the etiology of the infection, the extension of corneal involvement, practice location, risk factors, and response to previous therapy.[3–5] although the success of initial therapy relies on empiric broad spectrum antibiotics, identifying the organism responsible for the infection is valuable for a more specific treatment. stains of smears obtained from the ulcer may help determine the etiologic agent; however, cultures are ideal for diagnosing infectious keratitis, isolating the organism, and performing antibiotic sensitivity. antibiotic selection may be influenced by the availability of the drugs, cost of the treatment, and spectrum of pathogens in the community.[6, 7] therefore, efforts have been made to characterize geographic and temporal spectrums of responsible pathogens as well as antimicrobial resistance in different populations.[5, 8–12] bacterial infections predominate over other etiologies, with grampositive bacteria being more common than gramnegative ones.[12] fungal infections are responsible for a greater percentage of infectious keratitis in tropical climates, during summer months, and among agricultural workers.[12–16] acanthamoeba keratitis is rare but is typically associated with contact lens wear.[1] the purpose of this study was to characterize the etiologies of infectious keratitis presenting to a tertiary teaching hospital system in south texas to better guide future treatment. we aimed to identify the microbial spectrum in this population and compare these data to reports from other parts of the country as well as around the world. we hypothesized that the etiology and microbial spectrum of infectious corneal ulcers in south texas would be comparable to those in other locations with similar temperate climates, such as dallas (texas) and los angeles (california), and would vary from those in tropical climates, such as florida. methods this is a retrospective chart review study of patients visited at the university hospital system as well as the university of texas health at san antonio (san antonio, texas), both of which provide tertiary ophthalmic care to south texas. the study protocol was approved by the institutional review board at the university of texas health at san antonio, and the study complied with the health insurance portability and accountability act (hipaa). patients were identified by screening electronic medical records for encounters with infectious keratitis between 2012 and 2018. the screen included multiple international classification of diseases (icd)9 and icd10 codes to identify patients with keratitis and corneal ulcers. this search yielded 622 patient charts, which were each individually reviewed to confirm a diagnosis of bacterial, fungal, or acanthamoeba keratitis proven by a positive culture result. eyes with viral keratitis, negative cultures, or those which were not cultured were excluded. smears and cultures were obtained on a caseby-case basis but were typically collected in cases with infiltrates that were central, large, deep, chronic, refractory to antibiotic treatment, or atypical. corneal scrapings from the ulcer were directly obtained with a sterile cotton swab or sterile calcium alginate swab and immediately inoculated onto blood agar, chocolate agar, enriched thioglycolate broth, page’s saline, universal transport media, viral broth, and sabouraud dextrose agar. in addition, the scrapings were also placed on slides for gram staining and potassium hydroxide wet mounts. inoculated plates were immediately taken to the laboratory for microbiologic evaluation. from each chart, demographic and clinical data were collected including age, sex, culture isolate, and risk factors such as, but not limited to, contact lens wear, preceding trauma or inciting event, ocular disease, immunodeficiency, and steroid use. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 129 infectious keratitis in south texas; puig et al results of the 621 patients with presumptive infectious keratitis visited between 2012 and 2018, there were a total of 182 eyes of 181 patients with culture-proven bacterial, fungal, or acanthamoeba keratitis. a total of 440 eyes were excluded because cultures were not obtained (n = 279) or were negative (n = 157), or the corneal ulcers were proven by laboratory studies to be secondary to a viral infection (n = 4). therefore, of the eyes for which cultures were obtained, 53.6% had a positive culture. of the 181 patients, 92 were female and 89 were male. corneal ulcers were in the right eye in 106 and in the left eye in 74 patients, and were bilateral in one patient. the mean patients’ age was 48.3 ± 20.8 years (range, 3–93 years); 11 patients (6.1%) were younger than 18 years old, 53 (29.3%) were between 18 and 40 years old, and 117 patients (64.6%) were older than 40 years old; 103 (56.9%) patients were identified as hispanic, 61 (33.7%) as caucasian, 8 (4.4%) as african american, 3 (1.7%) as asian, and 6 (3.3%) as other ethnicities. of the total 182 eyes, cultures identified bacteria in 173 eyes (95.1%), fungi in 13 eyes (7.1%), and acanthamoeba in 3 eyes (1.6%); 146 eyes (80.2%) had monomicrobial infection and 36 eyes (19.7%) had polymicrobial infection. all three cases of acanthamoeba and four cases of fungal keratitis occurred in patients with concurrent bacterial ulcers. bacterial keratitis table 1 demonstrates all 218 bacterial organisms isolated during the study period. of the 36 eyes with polymicrobial infections, 27 eyes demonstrated growth of two organisms, and 9 eyes revealed three or more organisms. the most common bacterial isolate was coagulase-negative staphylococcus (cons) (n = 56, 25.7%), followed by pseudomonas aeruginosa (n = 51, 23.4%), and staphylococcus aureus (n = 24, 11.0%). in addition, 17 isolates (7.8%) of moraxella were identified. fungal keratitis the six fungal species cultured in south texas included fusarium (n = 6, 46.2%), paecilomyces lilacinus (n = 2, 15.4%), scedosporium (n = 2, 15.4%), pleosporales (n = 1, 7.7%), cladosporium (n = 1, 7.7%), and candida parapsilosis (n = 1, 7.7%). fungal elements were noted on smears or confocal microscopy of six other patients, but fungal cultures were negative. predisposing risk factors contact lens wear was encountered in 59 (32.4%) of the 182 eyes with positive bacterial, fungal, or acanthamoeba cultures. other predisposing factors, which included chemical burns, graft failure, corneal dystrophies, epithelial defects, bullous keratopathy, and rosacea-induced keratitis, were identified in 32 eyes (17.6%) with culture-proven keratitis; 26 eyes (14.3%) were noted to have preceding trauma to the affected eye, and 25 (13.7%) were found to have ocular surface diseases, including significant dry eye disease. thirtyseven patients were immunocompromised due to human immunodeficiency virus (hiv) infection, hepatitis, or the use of immunosuppressive drugs. table 2 exhibits the predisposing conditions in this cohort. no risk factors were identified in 18 patients. table 3 shows the prevalent bacterial organisms found in patients with more common risk factors. the most common bacterial organism associated with contact lens use was pseudomonas aeruginosa (n = 33, 57.9%), followed by cons (n = 16, 28.1%), and staphylococcus aureus (n = 4, 7.0%). in patients with ocular surface disease and underlying corneal disease, however, cons was the most common bacterial organism, which was found in 13 eyes each (52.0% and 44.8%, respectively) in these two groups. the observed risk factors in 13 patients with fungal keratitis included corneal diseases (n = 3, 23.0%), contact lens wear (n = 2, 15.4%), and preceding trauma (n = 2, 15.4%). two cases of acanthamoeba keratitis were associated with contact lens use (66.7%), whereas no predisposing factor was identified in the remaining acanthamoeba case. age distribution in different causative etiologies the average patient’s age in the groups with bacterial and fungal keratitis was 48.2 ± 21.0 years and 52.1 ± 18.9 years, respectively. the 130 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 infectious keratitis in south texas; puig et al table 1. spectrum of bacterial isolates observed in cases with bacterial keratitis in south texas bacteria number of cases percentage of bacterial isolates coagulase-negative staphylococcus 56 25.7% pseudomonas aeruginosa 51 23.4% staphylococcus aureus 24 11.0% moraxella species 17 7.8% propionibacterium acnes 9 4.1% streptococcus viridans 8 3.7% diphtheroids 8 3.7% bacillus species 6 2.8% streptococcus pneumoniae 6 2.8% serratia marcescens 5 2.3% methicillin-resistant staphylococcus aureus 4 1.8% actinobacter 3 1.4% achromobacter 2 0.9% enterobacter species 2 0.9% enterococcus species 2 0.9% streptococcus anginosus 2 0.9% rothia species 1 0.5% abiotrophia 1 0.5% actinomyces meyeri 1 0.5% atypical mycobacteria (mycobacterium chelonae-abscessus complex) 1 0.5% capnocytophaga species 1 0.5% corynebacterium species 1 0.5% granulicatella species 1 0.5% group b streptococcus 1 0.5% group g streptococcus 1 0.5% haemophilus parainfluenzae 1 0.5% morganella 1 0.5% neisseria species (not meningitidis or gonorrhea) 1 0.5% stenotrophomonas maltophilia 1 0.5% total 218 average patients’ age in the group with acanthamoeba keratitis was 32.0 ± 6.4 years which was lower than that in the other two groups. the majority of bacterial and fungal keratitis occurred in patients > 40 years old (63.4% and 76.9%, respectively), followed by patients aged from 18 to 40 years (30.2% and 23.1%, respectively) and patients < 18 years old (6.4% and 0%, respectively). a single case of acanthamoeba keratitis was identified in each age group. prevalence of risk factors according to age group the mean age of the subgroup with contact lensassociated keratitis was 35.8 ± 16.1 years, which was less than that of the subgroups with infectious keratitis caused by trauma (47.3 ± 16.1 years), ocular surface disease (57.5 ± 19.4 year), and underlying corneal diseases (63.8 ± 18.3 years). the majority of patients with contact lens-associated keratitis occurred in patients aged from 18 to 40 years journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 131 infectious keratitis in south texas; puig et al table 2. predisposing risk factors identified in patients with culture-proven keratitis based on etiology bacterial (n = 172) fungal (n = 13) acanthamoeba (n = 3) contact lens wear 57 2 2 underlying corneal disease 29 3 0 trauma 24 2 0 ocular surface disease 25 1 0 risk factors not addressed in documentation 16 3 1 immunocompromised only 10 0 0 topical steroid use 6 0 0 recent history of ophthalmic procedure 3 2 0 exposure to contaminated water 2 0 0 table 3. predisposing factors identified in patients with corneal ulcer caused by the most prevalent bacterial isolates cons p. aeruginosa s. aureus moraxella spp. p. acnes s. viridans diphtheroids s. pneumoniae bacillus spp. s. marcescens mrsa contact lens wear 16 33 4 2 2 1 0 1 0 4 0 trauma 5 6 4 5 3 2 0 1 2 0 1 ocular surface disease 13 3 2 1 1 1 3 0 1 1 0 underlying corneal disease 13 3 5 3 1 1 6 1 2 0 0 exposure to contaminated water 0 1 0 0 2 0 0 0 0 0 0 prior viral keratoconjunctivitis 1 0 0 1 0 0 0 0 0 0 0 recent history of ophthalmic procedure 0 0 2 1 0 0 0 0 0 0 0 topical steroid use 2 0 1 0 0 0 0 0 1 0 1 immunocompromised only 2 2 4 2 0 0 0 2 0 0 1 risk factors not documented 6 3 2 2 0 3 1 1 0 0 2 mrsa, methicillin-resistant staphylococcus aureus (54.2%), followed by patients>40 years old (33.9%) and those < 18 years old (11.9%). underlying corneal disease (93.8%), preceding trauma (73.1%), and ocular surface disease (33.9%) were significantly more common in patients > 40 years old as compared to the patients < 40 years old. table 4 summarizes the number of patients in each age subgroup with the four most common predisposing risk factors for corneal ulcer. seasonal variation the majority of cases with corneal ulcer (n = 104, 57.1%) presented between october and march, during which the average temperature is lowest in south texas, and the remaining cases presented between april and september (n = 78, 42.9%). the inclination toward lower temperatures was observed in the bacterial (n = 100, 58.1%) and acanthamoeba (n = 3, 100%) corneal ulcer. the occurrence of bacterial keratitis had a bimodal distribution, which included a peak in march and another in november–december [figure 1(a)]. the majority of cases with cons(58.9%) and moraxella (76.5%)-induced keratitis occurred in the colder months. no specific seasonal pattern was observed for the other bacterial cases. approximately two-thirds of the fungal corneal ulcers 132 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 infectious keratitis in south texas; puig et al table 4. distribution of the four most common predisposing risk factors in different age subgroups age group predisposing risk factor number of patients < 18 years old contact lens wear 7 trauma 1 ocular surface disease 2 underlying corneal disease – 18–40 years old contact lens wear 32 trauma 6 ocular surface disease 1 underlying corneal disease 2 > 40 years old contact lens wear 20 trauma 19 ocular surface disease 22 underlying corneal disease 30 table 5. rate of infectious keratitis in south texas compared with other locations % of culture-proven cases % of bacterial cases from total positive cultures % of fungal cases from total positive cultures % of acanthamoeba cases from total positive cultures south texas 53.6% 95.1% 6.9% 1.6% dei-la[17] 63% 89.8% 9.8% 0.4% lac + usc-la[17] 82% 89.4% 10.6% – dallas[18] 66% 85% 14.5% 0.5% miami[19–21] 40.1% 71.7% 20.8% – mexico city[22] 37.6% 87% 13% – bangladesh[23] 59% 21% 33% – south india[24] 70.6% 32.7% 34.4% 1% dei-la doheny eye institute – los angeles lac + usc-la los angeles county and university of southern california medical center – los angeles occurred during the warmer months [figure 1(b)]. all three cases of acanthamoeba keratitis occurred in november and december 2014. discussion in our study, of the 621 patients with a clinical diagnosis of keratitis, 181 patients had cultureproven keratitis, which was 53.6% of those for which cultures were obtained. the proportion of positive cultures acquired in this study was comparable with the reported ranges from studies in los angeles (california), dallas (north texas), miami (florida), mexico, bangladesh, and south india [table 5].[17–24] the sex distribution was virtually equal between females and males in our study, and the mean age of this patient population was similar to those reported in several other studies.[12, 17, 18, 22, 23, 25–27] in our study, bacterial keratitis was the most common type of infectious keratitis, followed by fungal and acanthamoeba keratitis. this is consistent with several other studies conducted in los angeles, dallas, florida, and mexico city, which have climate conditions comparable to south texas [table 5].[17–22] however, we found fewer cases of fungal keratitis compared with these studies. to identify the causative organisms, journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 133 infectious keratitis in south texas; puig et al table 6. percentage of bacterial isolates in south texas compared with other locations cons pseudomonas aeruginosa staphylococcus aureus moraxella streptococcus pneumoniae south texas 25.7% 23.4% 11% 7.8% 2.8% dei-la[17] 44.9% 13.1% 9.8% 1.9% lac+usc-la[17] 24.6% 7.6% 8.8% 1.8% 1.8% dallas[18] 19.2% 18.7% 9.6% 4.2% 6.9% miami[21] 1.3% 25.7% 19.4% 0.8% mexico city[22] 39.3% 13.4% 21.7% 1.5% 2.8% bangladesh[23] 32.9% 20% 26.2% 8.6% south india[24] 18.2% 19.9% 3.6% 0.8% 36% dei-la doheny eye institutelos angeles lac+ usc-la los angeles county and university of southern california medical center – los angeles table 7. percentage of fungal species retrieved from the total fungal-positive cultures in south texas compared with other locations fusarium aspergillus candida spp. south texas 46.2% – 7.7% dei-la[17] 9.1% 13.6% 50% lac + usc-la[17] 8.3% 12.5% 37.5% dallas[18] 28.1% 12.5% 15.6% miami[20] 54.1% 17.3% 26.2% mexico city[22] 50% 19.4% 1.4% bangladesh[23] 26.3 50.5% – south india[24] 41.9% 25% – dei-la doheny eye institute – los angeles lac + usc-la los angeles county and university of southern california medical center – los angeles we only used cultures because smears typically cannot be used to diagnose the type of organism, especially in bacterial and fungal infections. this might have contributed to fewer observed cases of fungal keratitis in our study, since cultures for the diagnosis of fungal keratitis are not as sensitive as other forms of diagnostic techniques.[28] in addition, although certain specialized stains, such as acridine orange, calcofluor white, and lactophenol-cotton blue, can be used to detect acanthamoeba in smears, such stains were not used in our study, and acanthamoeba keratitis was diagnosed only based on positive cultures. furthermore, although in vivo confocal microscopy can be used to detect acanthamoeba and fungi in the cornea,[29] we did not use this method as it is not available in many facilities. florida has a notably higher rate of fungal keratitis (20.8%) than south texas and several other locations in north america with similar latitudes [table 5]. this higher rate is likely due to the tropical climate in florida; this finding is further supported by the results of other studies that reported a high rate of fungal keratitis in tropical climate regions, such as bangladesh and south india.[19] in developing countries, however, this may be confounded by the large percentage of patients with fungal keratitis related to agricultural work.[19, 23, 24] the predominant bacterial isolate was cons, which is consistent with the findings from dallas, los angeles, mexico city, and bangladesh [table 6].[17–23] cons has consistently been shown to be a common cause of bacterial keratitis as it inhabits the skin and can invade a compromised 134 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 infectious keratitis in south texas; puig et al figure 1. seasonal distribution of occurrence of bacterial (a) and fungal (b) keratitis in south texas. cornea.[23] our study further supports this concept, as cons was the most common bacterial organism isolated in cases associated with underlying corneal and ocular surface diseases. interestingly, the proportion of pseudomonas keratitis, which was the second most common bacterial isolate, was higher in south texas and miami than the reported range of 7.6–20% found in other cities in the united states, bangladesh, and south india [table 6].[17–24] the prevalence of moraxella in south texas (7.8%) and dallas located in north texas (4.2%) was higher than most other locations across the world.[18] moraxella is known to commonly affect immunocompromised patients, which is consistent with our cohort as some of our moraxella-positive cases were immunocompromised individuals.[30] fusarium, a filamentous fungus, was found to be the predominant fungal isolate in our study, as well as in dallas, miami, mexico city, and south india [table 7].[18, 20, 22, 24] interestingly, aspergillus, which is typically associated with corneal trauma and tropical climates, was not isolated in south texas; however, it has been isolated in several other studies with similar patient characteristics and climates.[17, 18, 23, 31] filamentous fungi have been found to be more common than yeast fungi in areas with warmer climates, such as texas, florida, california, and mexico.[1] our findings are consistent with this finding as only a single yeast fungus, candida, was isolated in our study. several reports have found a positive association between filamentous fungal keratitis and contact lens use and ocular trauma,[32] which may account for the more substantial proportion of filamentous fungal keratitis observed in our study as contact lens wear was the leading predisposing risk factor for infectious keratitis. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 135 infectious keratitis in south texas; puig et al contact lens wear was the most frequent risk factor associated with infectious keratitis in our study, followed by underlying corneal diseases, preceding ocular trauma, and ocular surface diseases. it is well established that the majority of cases with infectious keratitis in developed countries are related to contact lens use, while most cases in developing countries are caused by ocular trauma.[14, 18, 23] in our study, contact lensassociated corneal ulcers were most prevalent in patients ≤ 40 years, whereas corneal ulcers associated with underlying corneal and ocular surface diseases were more frequently encountered in patients > 40 years old, which is similar to the results of previous studies.[25, 27, 33] furthermore, the occurrence of bacterial keratitis associated with contact lens use in our study is consistent with the range iterated by other studies in developed countries (31–53%).[26, 27, 34, 35] pseudomonas has been reported as the most common bacterial species associated with contact lens wear in south texas, dallas, and florida.[18, 21] in our study, approximately one-third of cases with fungal keratitis occurred in those with underlying corneal and ocular surface diseases. fungal keratitis has often been attributed to trauma and contact lens wear.[14, 23, 31] in a large multicenter study in the united states, 37% of fungal keratitis cases were associated with contact lens use, followed by ocular surface disease (29%) and ocular trauma (25%).[32] however, this rate varies in different locations; for example, contact lens use was found to be the most common risk factor associated with fungal keratitis (41%) in boston, but trauma was the most common risk for this type of infectious keratitis in florida (44%).[36, 37] despite many studies have reported an increase in infectious keratitis during the warmer months, the majority of our cases presented during the months with lower temperatures, showing a peak in march and november–december.[15, 27] cons and moraxella were the only bacterial isolates to have a significant seasonal distribution, with the majority of cases occurring during the cooler months. just over half of the cons cases associated with ocular surface disease were observed in the winter (53.8%). ocular surface disease exacerbated by low temperatures may have put these patients at an increased risk of keratitis.[38] as anticipated, the majority of cases with fungal keratitis occurred during the warmer months, which is consistent with the results of previous studies conducted in both developed and developing countries.[15, 39] in conclusion, bacteria were the most prevalent etiology of infectious corneal ulcers in south texas. coagulase-negative staphylococcus and pseudomonas were the most common bacterial isolates; this result is consistent with the results of other studies reporting the etiologies of bacterial keratitis in populations across the united states and the world. fusarium, a filamentous fungus, was the most frequent fungal isolate, but the overall prevalence of fungal keratitis was lower in south texas than in other cities of developed countries. as contact lens use is the most common risk factor associated with infectious keratitis in south texas and many other populations, contact lens wearers should always be reminded of this potential sightthreatening complication. financial support and sponsorship none. conflicts of interest there are no conflicts of interest. references 1. lakhundi s, siddiqui r, khan na. pathogenesis of microbial keratitis. microb pathog 2017;104:97–109. 2. collier sa, gronostaj mp, macgurn ak, cope jr, awsumb kl, yoder js, et al. estimated burden of keratitis–united states, 2010. mmwr morb mortal wkly rep 2014;63:1027– 1030. 3. mcleod sd, kolahdouz-isfahani a, rostamian k, flowers cw, lee pp, mcdonnell pj. the role of smears, cultures, and antibiotic sensitivity testing in the management of suspected infectious keratitis. ophthalmology 1996;103:23– 28. 4. rodman rc, spisak s, sugar a, meyer rf, soong hk, musch dc. the utility of culturing corneal ulcers in a tertiary referral center versus a general ophthalmology clinic. ophthalmology 1997;104:1897–1901. 5. forster rk. conrad berens lecture. the management of infectious keratitis as we approach the 21st century. clao j 1998;24:175–180. 6. baum jl. initial therapy of suspected microbial corneal ulcers: broad antibiotic therapy based on prevalence of organisms. surv ophthalmol 1979;24:97–105. 7. jin h, parker wt, law nw, clarke cl, gisseman jd, pflugfelder sc, et al. evolving risk factors and antibiotic sensitivity patterns for microbial keratitis at a large county hospital. br j ophthalmol 2017;101:1483–1487. 136 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 infectious keratitis in south texas; puig et al 8. erie jc, nevitt m, hodge do, ballard dj. incidence of ulcerative keratitis in a defined population from 1950 through 1988. arch ophthalmol 1993;111:1665–1671. 9. goldstein mh, kowalski rp, gordon yj. emerging fluoroquinolone resistance in bacterial keratitis: a 5-year review. ophthalmology 1999;106:1313–1318. 10. liesegang tj, forster rk. spectrum of microbial keratitis in south florida. am j ophthalmol 1980;90:38–47. 11. varaprasathan g, miller k, lietman t, whitcher jp, cevallos v, okumoto m, et al. trends in the etiology of infectious corneal ulcers at the f. i. proctor foundation. cornea 2004;23:360–364. 12. lichtinger a, yeung sn, kim p, amiran md, iovieno a, elbaz u, et al. shifting trends in bacterial keratitis in toronto: an 11-year review. ophthalmology 2012;119:1785–1790. 13. estopinal cb, ewald md. geographic disparities in the etiology of bacterial and fungal keratitis in the united states of america. semin ophthalmol 2016;31:345–352. 14. wong ty, ng tp, fong ks, tan dt. risk factors and clinical outcomes between fungal and bacterial keratitis: a comparative study. clao j 1997;23:275–281. 15. gorski m, yushvayev s, awwad a, awwad a, lazzaro dr. seasonal variation in the presentation of infectious keratitis. eye contact lens 2016;42:295–297. 16. leck ak, thomas pa, hagan m, kaliamurthy j, ackuaku e, john m, et al. aetiology of suppurative corneal ulcers in ghana and south india, and epidemiology of fungal keratitis. br j ophthalmol 2002;86:1211–1215. 17. sand d, she r, shulman ia, chen ds, schur m, hsu hy. microbial keratitis in los angeles: the doheny eye institute and the los angeles county hospital experience. ophthalmology 2015;122:918–924. 18. truong dt, bui mt, pauras m, cavanagh hd. microbial keratitis at an urban county hospital: a 10-year update. eye contact lens 2007;33:45–49. 19. estopinal cb, ewald md. geographic disparities in the etiology of bacterial and fungal keratitis in the united states of america. semin ophthalmol 2016;31:345–352. 20. alfonso ec, miller d, cantu-dibildox j, o’brien tp, schein od. fungal keratitis associated with non-therapeutic soft contact lenses. am j ophthalmol 2006;142:154–155. 21. alexandrakis g, alfonso ec, miller d. shifting trends in bacterial keratitis in south florida and emerging resistance to fluoroquinolones. ophthalmology 2000;107:1497–1502. 22. hernandez-camarena jc, graue-hernandez eo, ortizcasas m, ramirez-miranda a, navas a, pedro-aguilar l, et al. trends in microbiological and antibiotic sensitivity patterns in infectious keratitis: 10-year experience in mexico city. cornea 2015;34:778–785. 23. ahmed s, ghosh a, hassan sa, tarafder s, miah ra. predisposing factors and aetiologic diagnosis of infectious corneal ulcer. bangladesh j med microbiol 2010;4:28–31. 24. bharathi mj, ramakrishnan r, meenakshi r, padmavathy s, shivakumar c, srinivasan m. microbial keratitis in south india: influence of risk factors, climate, and geographical variation. ophthalmic epidemiol 2007;14:61–69. 25. jeng bh, gritz dc, kumar ab, holsclaw ds, porco tc, smith sd, et al. epidemiology of ulcerative keratitis in northern california. arch ophthalmol 2010;128:1022– 1028. 26. bourcier t, thomas f, borderie v, chaumeil c, laroche l. bacterial keratitis: predisposing factors, clinical and microbiological review of 300 cases. br j ophthalmol 2003;87:834–838. 27. lai th, jhanji v, young al. microbial keratitis profile at a university hospital in hong kong. int sch res notices 2014:689742. 28. ferrer c, alió jl. evaluation of molecular diagnosis in fungal keratitis. ten years of experience. j ophthalmic inflamm infect 2011;1:15–22. 29. labbé a, khammari c, dupas b, gabison e, brasnu e, labetoulle m, baudouin c. 30. contribution of in vivo confocal microscopy to the diagnosis and management of infectious keratitis. ocul surf 2009;7:41–52. 31. das s, constantinou m, daniell m, taylor hr. moraxella keratitis: predisposing factors and clinical review of 95 cases. br j ophthalmol 2006;90:1236–1238. 32. manikandan p, varga j, kocsubé s, anita r, revathi r, németh tm, et al. epidemiology of aspergillus keratitis at a tertiary care eye hospital in south india and antifungal susceptibilities of the causative agents. mycoses 2013;56:26– 33. 33. keay lj, gower ew, lovieno a, oechsler ra, alfonso ec, matoba a, et al. clinical and microbiological characteristics of fungal keratitis in the united states, 2001–2007: a multicenter study. ophthalmology 2011;118:920–926. 34. farrand k, fridman m, stillman iö, schaumberg da. prevalence of diagnosed dry eye disease in the united states among adults aged 18 years and older. am j ophthalmol 2017;182:90–98. 35. lin ty, yeh lk, ma dh, chen py, lin hc, sun cc, et al. risk factors and microbiological features of patients hospitalized for microbial keratitis: a 10-year study in a referral center in taiwan. medicine (baltimore) 2015;94:e1905. 36. ibrahim yw, boase dl, cree ia. epidemiological characteristics, predisposing factors and microbiological profiles of infectious corneal ulcers: the portsmouth corneal ulcer study. br j ophthalmol 2009;93:1319–1324. 37. jurkunas u, behlau i, colby k. fungal keratitis: changing pathogens and risk factors. cornea 2009;28:638–643. 38. rosa rh jr, miller d, alfonso ec. the changing spectrum of fungal keratitis in south florida, ophthalmology 1994;101:1005–1013. 39. song p, xia w, wang m, chang x, wang j, jin s, et al. variations of dry eye disease prevalence by age, sex and geographic characteristics in china: a systematic review and meta-analysis. j glob health 2018;8:020503. 40. lin cc, lalitha p, srinivasan m, prajna nv, mcleod sd, acharya nr, et al. seasonal trends of microbial keratitis in south india. cornea 2012;31:1123–1127. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 137 case report focal choroidal excavation in a case of choroidal osteoma associated with choroidal neovascularization mahdieh azimizadeh1; md; seyedeh maryam hosseini2, md; esmaeil babaei1,3, md 1eye research center, mashhad university of medical sciences, mashhad, iran 2retina research center, mashhad university of medical sciences, mashhad, iran 3eye research center, yazd university of medical sciences, yazd, iran orcid: mahdieh azimizadeh: https://orcid.org/0000-0001-9467-4249 esmaeil babaei: https://orcid.org/0000-0001-8490-3589 abstract purpose: to report a case of choroidal osteoma associated with reactivation of choroidal neovascularization (cnv) and development of focal choroidal excavation (fce). case report: a 34-year-old woman with choroidal osteoma complicated by cnv in the right eye for two years presented with deterioration of visual acuity in her right eye. a small retinal hemorrhage accompanied by subretinal fluid (srf) was seen in the macular area of the right eye. optical coherence tomography (oct) showed that the inner retina was intact, and the outer retinal layers had outward displacement. srf and a wedgeshaped choroidal depression were also seen. this choroidal excavation was not present on previous oct images. the integrity of the inner retinal layers was maintained, and an optically clear space was present between the neurosensory retina and the retinal pigment epithelium. conclusion: choroidal osteoma can be complicated by cnv and fce could occur as a consequence. again, fce can lead to cnv development. this cascade can deteriorate vision and sometime lead to permanent visual loss. keywords: bevacizumab; choroidal excavation; choroidal neovascularization; choroidal osteoma; multifocal j ophthalmic vis res 2020; 15 (3): 419–423 correspondence to: esmaeil babaei, md. retina research center, khatam al anbia eye hospital, mashhad, aboutaleb junction, gharanei blvd, mashahad university of medical sciences, mashhad 917789, iran. email: esmaeil.babaei@yahoo.com received: 10-12-2018 accepted: 29-02-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7461 introduction choroidal osteoma is a rare, ossifying, benign tumor of the choroid. it occurs predominantly in this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: azimizadeh m, hosseini sm, babaei e. focal choroidal excavation in a case of choroidal osteoma associated with choroidal neovascularization. j ophthalmic vis res 2020;15:419–423. © 2020 journal of ophthalmic and vision research | published by knowledge e 419 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7461&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr choroidal osteoma with excavation; azimizadeh et al figure 1. color fundus photograph of the right eye. young healthy women in the second and third decades of life and is unilateral in 80% of cases.[1] although it has been recognized as a benign tumor, it can grow in 51% of patients by 10 years and can be complicated by enlargement, decalcification, and choroidal neovascularization (cnv).[2] focal choroidal excavation (fce) refers to focal depression of the choroid that has been recently described thanks to the development of spectraldomain optical coherence tomography (sd-oct). it may be solitary or occur in association with other chorioretinal disorders such as central serous chorioretinopathy (csc), cnv, and polypoidal choroidal vasculopathy (pcv).[3] it has also been reported in eyes with choroidal osteoma associated with cnv.[4, 5] here, we report an interesting case involving a 34-year-old woman with bilateral choroidal osteoma complicated by cnv in the right eye, with development of fce following reactivation of the cnv. case report a 34-year-old healthy woman with bilateral choroidal osteoma complicated by cnv in the right eye for the two years presented with acute deterioration of visual acuity (va) in the right eye. the findings of multimodal imaging for this case were reported and published in 2015, and there was no fce in the right eye at that time.[6] best corrected visual acuity (bcva) of the right eye had decreased from 20/40 to 20/100, while that of the left eye was 20/20. fundus examination of both eyes showed a yellow–orange lesion with sharp borders at the level of the choroid (figure 1). a small retinal hemorrhage accompanied by subretinal fluid (srf) was seen in the macular area of the right eye. enhanced depth imaging oct (edi-oct) (spectralis hra + oct, heidelberg engineering, heidelberg, germany) showed that the inner retina was intact, although the outer retinal layers had outward displacement due to active cnv along with srf and a wedgeshaped choroidal depression in the right eye. the choroidal excavation involved the retinal pigment epithelium (rpe) and outer retinal layers up to the outer plexiform layer. the integrity of the inner retinal layers was maintained, and an optically clear space was present between the neurosensory retina and rpe. edi-oct showed thinning of the choriocapillaris and large choroidal vessels and a sponge-like choroidal lesion (figure 420 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 choroidal osteoma with excavation; azimizadeh et al figure 2. sdoct of the right eye: (a) spectral-domain oct (sd-oct) of the right eye performed in 2014 revealed subretinal fluid (srf) associated with choroidal osteoma complicated by choroidal neovascularization (cnv). (b) oct of the right eye (2016) clearly shows focal choroidal excavation and srf due to cnv development. (c) oct of the right eye clearly shows fce and complete resolution of srf after two consecutive intravitreal bevacizumab injections. 2). fluorescein angiography (fag) demonstrated mild hyperfluorescence in the choroidal osteoma due to window defect, as well as juxtafoveal hyperfluorescence corresponding to active cnv in the right eye (figure 3), which was better delineated on oct angiography (figure 4). thus, the diagnosis was reactivation of cnv associated with the development of fce in the right eye in a known case of choroidal osteoma. the patient received two consecutive intravitreal bevacizumab (avastin, genentech inc., san francisco, ca) injections, which resulted in improvement of bcva to 20/40. oct showed disappearance of srf and resolution of the disturbances in the outer retinal layers. fce was more clearly visible and associated with severe choroidal thinning after quiescence of the cnv (figure 2c). bcva was maintained in both eyes during a follow-up period of one year. discussion we report development of fce following reactivation of cnv after two years of inactivity in an eye with choroidal osteoma. initially, fce was defined as choroidal excavation in the submacular area without posterior staphyloma, any positive history of trauma, or any chorioretinal disease; however, some chorioretinal disorders such as csc, pcv, cnv, and choroidal osteoma have been reported in association with fce.[7] although the inner retina is commonly intact in eyes with fce, the outer retinal journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 421 choroidal osteoma with excavation; azimizadeh et al figure 3. fluorescein angiography (fag) showing choroidal neovascularization in the right eye. figure 4. octa images of the right eyes illustrate high-flow vessels above the rpe in the outer retina as well as in the choriocapillaris. layers, rpe, choriocapillaris, and choroid can be involved.[8] fce can be detected by sd-oct. however, in cases with bilateral involvement or multiple lesions in one eye, foveal sd-oct which is confined to the posterior pole may not detect all lesions. therefore, multiple imaging modalities such as fundus photography, fundus autofluorescence, indocyanine green angiography, and fag are considered helpful.[9] in the present case, fce developed adjacent to a previous cnv scar and the decalcified part of the tumor as seen on previous oct images, and it was detected two years after cnv occurrence. thus, we can conclude that fce was a consequence of the cnv scar and/or tumor decalcification that 422 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 choroidal osteoma with excavation; azimizadeh et al resulted in tissue loss, contraction of fibrosis, and outward displacement and excavation of the outer retina and choroid. on the other hand, fce may have been involved in reactivation of cnv,[4, 5] as choroidal excavation has been reported to be associated with the development or reactivation of cnv.[10] there are multiple options for treating cnv in eyes with choroidal osteoma,[11–14] although the best response has been achieved by intravitreal injection of anti-vascular endothelial growth factor agents such as bevacizumab.[15] this is a documented development of fce in an eye with cnv associated with choroidal osteoma. fce could occur as a consequence of cnv, tumor decalcification, or both. close followup and prompt treatment are necessary to achieve the best results. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. erol mk, coban dt, ceran bb, bulut m. enhanced depth imaging optical coherence tomography and fundus autofluorescence findings in bilateral choroidal osteoma: a case report. arq bras oftalmol 2013; 76:189-91. 2. shields cl, perez b, materin ma, mehta s, shields ja. optical coherence tomography of choroidal osteoma in 22 cases: evidence for photoreceptor atrophy over the decalcified portion of the tumor. ophthalmology 2007; 114:e53-8 3. cebeci z, bayraktar ş, oray m, k𝚤r n. focal choroidal excavation. turk j ophthalmol 2016; 46:296. 4. pierro l, marchese a, gagliardi m, introini u, parodi mb, casalino g, et al. choroidal excavation in choroidal osteoma complicated by choroidal neovascularization. eye (lond). 2017;31:1740-1743. 5. wakabayashi y, nishimura a, higashide t, ijiri s, sugiyama k. unilateral choroidal excavation in the macula detected by spectral-domain optical coherence tomography. acta ophthalmol 2010;88:e87-91. 6. mirnaghi m, nasser s, seyedehmaryam h, ali st. bilateral multifocal choroidal osteoma with choroidal neovascularization. case rep ophthalmol med 2015;2015:346415. 7. navarro vc, hernández jm, palop cn, fort pp, taulet ec. focal choroidal excavation: clinical findings and complications. arch soc esp oftalmol 2016;91:34-9. 8. liu gh, lin b, sun xq, he zf, li jr, zhou r, et al. focal choroidal excavation: a preliminary interpreta-tion based on clinic and review. int j ophthalmol 2015;8:513-21. 9. chung h, byeon sh, freund kb. focal choroidal excavation and its association with pachychoroid spectrum disorders. retina 2017;37:199-221. 10. xu h, zeng f, shi d, sun x, chen x, bai y. focal choroidal excavation complicated by choroidal neovascularization. ophthalmology 2014;121:246-250. 11. mansour am, arevalo jf, al kahtani e, zegarra h, abboud e, anand r, et al. role of intravitreal antivascular endothelial growth factor injections for choroidal neovascularization due to choroidal osteoma. j ophthalmol 2014;2014:210458. 12. shields cl, sun h, demirci h, shields ja. factors predictive of tumor growth, tumor decalcification, choroidal neovascularization, and visual outcome in 74 eyes with choroidal osteoma. arch ophthalmol 2005;123:1658-66. 13. browning d. j, choroidal osteoma: observations from a community setting, ophthalmology 2003;110:1327-34. 14. shields cl, perez b, materin ma, mehta s, shields ja. optical coherence tomography of choroidal osteoma in 22 cases: evidence for photoreceptor atrophy over the decalcified portion of the tumor. ophthalmology 2007;114:e53-8. 15. ahmadieh h, vafi n. dramatic response of choroidal neovascularization associated with choroidal osteoma to the intravitreal injection of bevacizumab (avastin). graefes arch clin exp ophthalmol 2007;245:1731-3. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 423 photo essay microsporidial keratoconjunctivitis r balamurugan, ms; parul chawla gupta, ms; surya prakash sharma, ms; neeti rana, mbbs jagat ram, ms, fams department of ophthalmology, post graduate institute of medical education and research, chandigarh, india orcid: r balamurugan: https://orcid.org/0000-0003-3363-1135 jagat ram: https://orcid.org/0000-0001-6251-2800 j ophthalmic vis res 2020; 15 (2): 259–260 presentation we report microsporidial keratoconjunctivitis in a young male exposed to muddy water while repairing a water distribution pipe successfully treated with topical voriconazole. discussion a 22-year-old healthy male who is a plumber by profession presented with chief complaints of sudden pain, redness, watering, and decreased vision in his left eye. these symptoms occurred two days after a water distribution pipe that he was repairing burst and the water came in contact with his eye. a slit-lamp examination of his left eye revealed multifocal, coarse, white corneal epithelial infiltrates [figure 1(a)]; he had a visual acuity of 20/200. in vivo confocal microscopy revealed epithelial rosettes and intraepithelial pinpoint hyper-reflective spores [figure 1(b)]. staining with potassium hydroxide–calcofluor white revealed oval bluish fluorescent bodies [figure 1(c)]. anterior segment optical coherence tomography demonstrated stuck-on-plaques correspondence to: jagat ram, ms, fams. department of ophthalmology, post graduate institute of medical education and research, sector-12, chandigarh 160012, india. e-mail: drjagatram@gmail.com received: 13-09-2019 accepted: 05-12-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i2.6746 on the surface of the cornea [figure 1(d)]. slitlamp biomicroscopy revealed a clear cornea after hourly treatment with voriconazole drops. after one week of treatment, the cornea was clear and visual acuity improved to 20/20 [figure 1(e)]. microsporidial keratoconjunctivitis occurs primarily in males and is usually unilateral. it has recently been observed to cause multifocal coarse punctate epithelial keratitis in immunocompromised individuals, in addition to the use of contact lenses, another risk factor for microsporidial keratoconjunctivitis that may be less recognized because of the lack of awareness among ophthalmologists is the exposure to muddy water[2, 3] predominantly observed during the rainy season[4] in developing countries. financial support and sponsorship none. conflicts of interest there are no conflicts of interest. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: balamurugan r, gupta pc, sharma sp, rana n, ram j. microsporidial keratoconjunctivitis. j ophthalmic vis res 2020;15:259– 260. © 2020 journal of ophthalmic and vision research | published by knowledge e 259 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i2.6746&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; balamurugan et al figure 1. (a) multifocal, coarse, white corneal epithelial infiltrates (b) in vivo confocal microscopy showing epithelial rosettes and intraepithelial pin–point hyperreflective spores (c) combined potassium hydroxide-calcofluor white staining showing oval bluish fluorescent bodies (d) anterior segment optical coherence tomography demonstrating stuck on plaques on the corneal surface (e) slit lamp biomicroscopy showing clear cornea after treatment. references 1. chan cm, theng jt, li l, tan dt. microsporidial keratoconjunctivitis in healthy individuals: a case series. ophthalmology 2003;110:1420–1425. 2. joseph j, sridhar ms, murthy s, sharma s. clinical and microbiological profile of microsporidial keratoconjunctivitis in southern india. ophthalmology 2006;113:531–537. 3. kwok akh, tong jmk, tang bsf, poon rws, li wwt, yuen ky. outbreak of microsporidial keratoconjunctivitis with rugby sport due to soil exposure. eye 2013;27:747– 754. 4. sharma s, das s, joseph j, vemuganti gk, murthy s. microsporidial keratitis: need for increased awareness. surv ophthalmol 2011;56:1–22. 260 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 review article minimally invasive surgery, implantable sensors, and personalized therapies kevin gillmann, md, mbbs, febophth, march1; kaweh mansouri, md, mph1,2 1glaucoma research center, montchoisi clinic, swiss visio, lausanne, switzerland 2department of ophthalmology, university of colorado school of medicine, denver, co, usa orcid: kevin gillmann: https://orcid.org/0000-0002-7856-6253 abstract glaucoma management has changed dramatically over the last decades, through clinical advances and technological revolutions. this review discusses the latest innovations and challenges faced in the field around three major axes: minimally-invasive glaucoma surgery (migs), implantable sensors and injectable therapeutics. indeed, the vast number of recently developed migs techniques has not only provided clinicians with a wide range of therapeutic options, but they have also enabled them to adjust their therapies more finely which may have contributed a more patient-centric decision-making process. yet, despite considerable advances in the field, the wide heterogeneity in clinical trial designs blurs the surgical outcomes, specificities and indications. thus, more high-quality data are required to make the choice of a specific migs procedure more than an educated guess. beyond the scope of migs, the potential of iop telemetry for self-assessment of iop-control through implantable sensors is developing into a real option for clinicians and an empowering opportunity for patients. indeed, providing patients with direct feedback enables them to take control and have a clearer representation of their care, in turn leading to a better control of the disease. however, there are potential issues with self-monitoring of iop, such as increased anxiety levels induced by measured iop fluctuations and peaks, leading to patients self-treating during iop spikes and additional office visits. furthermore, the advent of implantable therapeutics may soon provide yet another step towards personalized glaucoma treatment, by offering not only an efficient alternative to current treatments, but also a therapeutic option that may better adapt to patients’ lifestyle. after several decades of relative stagnation through the last century, glaucoma has now entered what many view as a golden age for the specialty. like every revolution, this one brings its fair share of uncertainty, clinical questioning and uneasy periods of adaptation to ever-changing expectations. yet, while it is impossible to guess what the landscape of glaucoma surgery will be like in ten or fifteen years, data suggest a bright outlook both for patients and clinicians. keywords: glaucoma; migs; quality of life; telemetry; eyemate; bimatoprost sr j ophthalmic vis res 2020; 15 (4): 531–546 © 2020 journal of ophthalmic and vision research | published by knowledge e 531 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7792&domain=pdf&date_stamp=2019-07-17 innovations in glaucoma surgery; gillmann et al introduction glaucoma is a leading cause of irreversible blindness, and it is estimated that by 2040, over 110 million people will suffer from glaucoma globally.[1] to face the increasing burden of glaucoma, its management has changed dramatically over the last decades, through clinical advances and technological revolutions. indeed, while the 1990s were the decade of glaucoma drainage devices (gdd) and novel topical therapeutic agents, the new millennium has witnessed an unprecedented growth in treatment options through the introduction and integration of minimally invasive glaucoma surgeries (migs), and the surgical applications of cross-disciplinary innovations. this review discusses the most remarkable innovations of the last decade and explores how they may affect the future of glaucoma surgery. methods multiple literature searches were conducted in preparation of this review. searches were conducted on pubmed and google scholar, using the following keywords. for section a on migs technologies: glaucoma surgery, migs, trabecular bypass, suprachoroidal drainage, subconjunctival filtration, trabectome, kahook dual blade, trabeculotomy, canaloplasty, hydrus microstent, istent, cypass, cyclophotocoagulation, preserflo, correspondence to: kaweh mansouri, md, mph. glaucoma research center, montchoisi clinic, swiss visio, lausanne, switzerland. e-mail: kwmansouri@gmail.com received: 01-05-2020 accepted: 08-07-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7792 xen gel stent, glaucoma physiology, aqueous outflow. for section b on intraocular sensors: iop variations, 24-hour iop, dynamic tonometry, telemetry, intraocular sensor, eyemate. for section c on implantable and injectable therapeutics: glaucoma pharmacology, prostaglandin, glaucoma treatment compliance, glaucoma drug delivery, intracameral implant, bimatoprost sr, durysta. furthermore, references from the reviewed articles and textbooks were considered for inclusion within this review, regardless of their publication date or language. results a. minimally invasive glaucoma surgery the first-line treatment for openangle glaucoma has long been topical pharmaceutical therapies or laser treatments. yet, until relatively recently, the only alternative when these failed was filtering surgery. with popularization of anti-metabolites in glaucoma surgery, from the start of the 1990s, filtering surgery evolved into highly effective procedures, with a reported intraocular pressure (iop) reduction as high as 50%.[2] however, this evolution was associated with an increase in severe adverse events such as chronic hypotony, bleb leak, or endophthalmitis, with a rate of late complications in excess of 30% in some reports.[3] migs were designed to bridge the gap between medical or laser therapies this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: gillmann k, mansouri k. minimally invasive surgery, implantable sensors, and personalized therapies. j ophthalmic vis res 2020;15:531–546. 532 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 https://knepublishing.com/index.php/jovr innovations in glaucoma surgery; gillmann et al and more invasive filtering surgeries in mild to moderate glaucoma. by essence, migs are meant to have an extremely favorable safety profile ensuring prompt postoperative recovery; however, the amount of iop reduction is not as high as traditional filtering surgery.[4] through the array of available techniques, migs have not only provided clinicians with a wider range of therapeutic options, but they have also enabled them to adjust their therapies more finely which may have contributed to a more patient-centric decision-making process. however, it can be a bit overwhelming to choose from such a large armamentarium, especially in the absence of evidence-based criteria. approaches migs are generally classified based on their anatomical sites of action. their mechanisms can focus on: (1) schlemm’s canal, (2) suprachoroidal space, (3) subconjunctival space, and (4) ciliary body. each class of migs has its own advantages and limitations, and several different devices or techniques coexist within most categories. most of these options differ in their dimensions, but in some instances, there may be some more fundamental technical variations. the main classes of migs are summarized in figure 1. schlemm’s canal: trabecular meshwork bypass and schlemm’s canal dilatation the trabecular or conventional pathway is the principal route for aqueous humor outflow in a physiological condition. aqueous percolates through the trabecular meshwork into schlemm’s canal, before entering a wide network of vessels through the collector channels. in primary open-angle glaucoma, however, trabecular meshwork outflow resistance increases, possibly in response to extracellular matrix changes, the etiology of which is still mostly unknown.[5, 6] furthermore, in the early 1960s, grant showed how ab interno 360° removal of the trabecular meshwork resulted in a 75% reduction of the total resistance in enucleated eyes at an iop of 25 mmhg.[7, 8] bypassing a site of increased outflow resistance (often considered the primary site of resistance) and enhancing the main physiological outflow pathway are two of the principles underlying the rationale of trabecular meshwork bypass or ablation. this class of migs aims to reduce outflow resistance and iop by facilitating aqueous drainage into schlemm’s canal either by bypassing the trabecular meshwork via some stent devices or by merely removing all or a portion of the trabecular meshwork. several variations of stent devices and trabecular meshwork ablation techniques exist. however, recent studies have suggested that contrary to the common belief that the main site of glaucoma resistance lies within the juxtacanalicular trabeculum, the iop elevation observed in primary open-angle glaucoma is more accurately caused by a combination of three equally determinant factors: (1) loss of permeability of the entire thickness of the trabecular meshwork, (2) collapse of schlemm’s canal, and (3) downstream resistance, notably with the closing of collector channel entrances.[11–13] this was further supported by the finding that schlemm’s canal dilatation was positively correlated with the magnitude of iop reduction.[9] it was, therefore, hypothesized that schlemm’s canal increased volume is associated with the stretching of its walls, which in turn causes the opening journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 533 innovations in glaucoma surgery; gillmann et al figure 1. illustration of the different classes of minimally invasive glaucoma surgery, their anatomical relationship with the ocular structures (top), and examples of implants and techniques available in each category. of pressure-dependent collector channels, leading to aqueous outflow.[10] based on these observations, another subcategory of migs specifically targets schlemm’s canal, with the aim of restoring a healthy schlemm’s canal function and opening closed collecting channels. two approaches were used to dilate schlemm’s canal: the mechanical dilatation using a temporary or resorbable medium and the use of a permanent implantable scaffold. despite theoretically different approaches, these two subcategories of migs are, in effect, physiologically related. indeed, 534 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 innovations in glaucoma surgery; gillmann et al figure 2. eyemate intraocular sensor (top) and a size comparison with a eurocent coin. while the latter group directly targets schlemm’s canal to cause its dilatation with aqueous humor and restore distal outflow capacity, studies have shown that the former group, while merely bypassing the trabecular meshwork, produces a similar effect. indeed, it has been reported that the magnitude of iop reduction following trabecular meshwork bypass implantation was directly correlated to the dilatation of schlemm’s canal.[11] furthermore, aqueous angiography techniques have shown that, beyond their effects on schlemm’s canal, trabecular bypass devices could increase collector channel outflow.[12] the limitation of both approaches is that they do not address any resistance that may be distal to the collector channels’ openings. therefore, there is a floor effect to iop reduction depending on distal outflow resistance. aqueous angiography: the road to personalized surgery the role of distal outflow resistance in iop reduction indicates the importance of targeting collector channels with migs. it was reported that trabeculotomies performed in the nasal hemisphere, where the concentration of collector channels is denser, increases the outflow more than trabeculotomies performed in the temporal hemisphere,[13] but more recent research suggests a more journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 535 innovations in glaucoma surgery; gillmann et al figure 3. intraoperative aqueous angiography showing the collector channels (arrows). s, superior; n, nasal nuanced reality. huang et al have designed a new imaging technique allowing collector channel visualization using intraoperative aqueous angiography. their first report suggested that targeting an area deprived of collector channel outflow could recruit new, previously closed, channels.[14] figure 2 shows collector channels identified with aqueous angiography. it could therefore be speculated that locating collector channels prior to migs or filtering surgery may result in a more targeted treatment. in the absence of dedicated comparative studies, however, the question remains controversial and most migs procedure continue to be performed supero-nasally, both for practical reasons and to target more collector channels. suprachoroidal space: suprachoroidal shunts the physiological proportion of aqueous humor draining through the suprachoroidal space is subject to debate due to the lack of techniques available to measure uveoscleral flow, but estimates range between 4% and 60%.[15, 16] it is, however, accepted that aging is responsible for a marked reduction in uveoscleral outflow.[17] this outflow pathway is created by a combination of relative ciliary body permeability, which is believed to be the site of main resistance in the uveoscleral pathway,[18] and the existence of a hydrostatic pressure gradient through the anterior chamber, the supraciliary space, and the suprachoroidal space.[19] such a negative gradient is believed to be produced by 536 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 innovations in glaucoma surgery; gillmann et al figure 4. bimatoprost sr injector (a) and the bimatoprost implant, compared with the size of a dime and a eurocent coin (b). the rapid absorption of aqueous from the suprachoroidal space into the large and dense choroidal vasculature.[20, 21] another characteristic of the uveoscleral pathway is that it is relatively pressure-independent and was shown to have a constant effect between 4 and 35 mmhg.[22] these last two characteristics suggest that exploiting uveoscleral pathway may theoretically make up for some of the conventional pathway limitations: the risk of distal resistance and the floor effect. however, devices targeting this pathway can be expected to have a whole different risk profile to trabecular bypass devices. indeed, the potentially greater outflow capacity of this approach could, in theory, be associated with higher risks of hypotony and choroidal detachment, especially in patients with a long history of prostaglandin therapy. while the cases are too rare to warrant for a prospective study, there have been anecdotal cases suggesting that patients who were chronically treated with prostaglandins may be at a higher risk of developing choroidal pathologies.[28–31] this may be related to the effect of prostaglandins, reducing collagens within the uveoscleral pathway.[23] furthermore, from a practical point of view, the suprachoroidal space may be less readily accessible and visualizable by a surgeon than the trabeculum. while there is no commercially available migs relying on suprachoroidal drainage, some new devices are under development and sound clinical data is available on a previously commercialized device. therefore, we will discuss the case of this device, some characteristics of which may be comparable to future devices of the same category. subconjunctival space: subconjunctival filtration contrary to the trabecular and the uveoscleral approaches, subconjunctival filtration does not seek to enhance or increase a physiological pathway. instead, it relies on the creation of an artificial canal between the anterior chamber and the subconjunctival space, typically through a stent. this process results in an iatrogenic filtration bleb from which aqueous humor diffuses into the surrounding subconjunctival tissue and is journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 537 innovations in glaucoma surgery; gillmann et al eventually reabsorbed into subconjunctival capillaries.[24] the idea of subconjunctival filtration is not new and stems from the anterior sclerectomy technique designed by de wecker in 1858.[25] while modern-day trabeculectomies and deep sclerectomies have considerably refined the technique, the use of the subconjunctival pathway has survived. like trabeculectomy, the success of subconjunctival migs procedure depends on the persistence of a healthy filtering bleb. therefore, these migs share many similarities with filtering surgeries, in terms of risks and advantages. one of the main advantages of subconjunctival filtration is precisely that it does not impact any of the physiological outflow pathways, and as such, preserves any remaining physiological filtration. another significant advantage of these techniques is that they do not rely on episcleral venous pressure or suprachoroidal pressure gradients to achieve filtration. instead, their filtration capacity is only dependent on the outflow resistances of the stent and the subconjunctival space. therefore, they can potentially achieve lower iops than physiological approaches. the outflow resistance of the subconjunctival space, however, is very much patient dependent and can be difficult to predict. a significant factor recognized to influence resistance is conjunctival scarring and fibrosis, which results in the failure of filtering surgery.[26] the pathophysiology of fibrosis is complex, but growth factors and cytokines expressed in inflammatory cells are clear culprits.[27] this is particularly problematic in glaucoma patients when inflammation is exacerbated through four mechanisms: (1) the predisposition of patients to conjunctival fibrosis through long-term use of topical prostaglandins or toxic preservative, both of which were associated with local inflammation,[28, 29] (2) the surgical procedure itself, (3) subconjunctival flow, by itself, constitutes a persistent mechanical stress to local tissue, which was shown to translate into pro-inflammatory biochemical signals,[39–41] and (4) the mere presence of aqueous humor in the subconjunctival space, where it is not naturally present, was shown to promote tissue fibrosis. some components, particularly tgf-b and vegf-a, present at increased levels in the aqueous humor of glaucoma patients are believed to be responsible for subconjunctival fibrosis.[30, 31] while both vegf antagonists and rho-kinase inhibitors were suspected to be beneficial in the context of bleb surgery, they have so far failed to demonstrate clear superiority or to translate into clinical practice,[32, 33] and, to date, the clinical recommendations with regards to inflammation mediation are the preoperative washout from pro-inflammatory topical medications and the prolonged postoperative use of topical steroids. this point, however, remains the major impediment to sustainable subconjunctival filtration. with this regard, migs may have a role to play in reducing the amount of inflammation caused by subconjunctival procedures. further risks common to all bleb-creating procedures include bleb dysesthesia, bleb leaks, blebitis, and bleb-related endophthalmitis. these complications can be common and some authors have reported rates of bleb interventions in excess of 50% following xen implantations.[34] hypotony is another inherent risk of bypassing physiologic outflow pathway, but this risk can theoretically be mediated by the adjustment of devices’ internal dimensions to create specific levels 538 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 innovations in glaucoma surgery; gillmann et al of outflow resistance.[35] finally, contrary to traditional filtration surgery, prospective studies and occasional case reports have highlighted a risk of stent displacement and occlusion, which are inherent to the placement of an artificial stent.[36, 37] ciliary body: reduction of aqueous humor production the ciliary body is site of aqueous production. reducing aqueous humor production is a logical alternative to enhancing aqueous outflow to lower iop. cyclophotocoagulation consists of using a laser to selectively deliver thermal energy to the pigmented tissues of the ciliary body and induce tissue coagulative necrosis.[38] historically, the technique that emerged in the 1930s as cyclodiathermy has long been exclusively indicated for refractory glaucoma and painful blind eyes. this was mostly due to the relatively high risk of intense and chronic postoperative inflammation, pain, hypotony, vision loss, and phthisis.[39, 40] however, recent innovations have allowed for more targeted treatments and less collateral tissue necrosis, leading to reduced complication rates and better safety profiles. this has led to cyclophotocoagulation’s gradual acceptance for the treatment of milder forms of glaucoma, and to some surgeons considering it a migs. the main theory underlying this change in practice is that the rates and severity of complications following cyclophotocoagulation are directly related to the total amount of energy used during the procedure.[41] however, despite a clear reduction in the rates of complications over the last decades, the risk of permanent visual loss to a sighted eye remains non-negligible,[42, 43] and a recent cochrane review concluded that there was still insufficient evidence to conclude positively on the effectiveness and safety of cyclophotocoagulation in non-refractory glaucoma.[44] furthermore, it has been speculated that the significant perilimbal conjunctival inflammation and scarring produced by transscleral cyclophotocoagulation could affect the outcome of subsequent filtering surgeries, casting further doubt over the indications of this type of treatment as an initial procedure. b. intraocular sensors with such an array of techniques designed specifically to lower iop, pressure control has become the key element of surgical outcomes and the cornerstone of glaucoma care as a whole. innovation, however, has been slower when it comes to iop measurement techniques, and the gold standard technique has essentially remained the same since 1950, when goldmann applanation tonometery (gat) was introduced.[45] gat relies on the imbert-fick principle to estimate iop based on the force that is required to flatten the 3.06 mm diameter area corresponding to the tip of the goldmann prism. yet, this technique is widely regarded as imperfect and studies have pointed out its flaws both in terms of design and concept. not only is gat relatively imprecise, its instant nature also fails to reflect the complexity of real-life iop variations.[58–60] indeed, over the last decades, there has been ample evidence that individuals’ iop are far from being static and fluctuate widely over the course of 24 hours and through the year, and even suggestions that iop variations may play a significant role in glaucoma progression regardless of their absolute values.[61–66] journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 539 innovations in glaucoma surgery; gillmann et al eyemate while several companies are actively working on iop-monitoring sensor prototypes, the german company implandata introduced the first implantable continuous monitoring device. it was ce-certified in 2017 for use in primary open-angle glaucoma patients, and is composed of three devices: the implantable sensor (or wireless intraocular transducer [wit]), the handheld reader unit, and the wireless module.[67–69] the sensor itself is implanted in the ciliary sulcus during routine cataract surgery and is designed to stay in the patient’s eye indefinitely. to offer options to patients regardless of their lens status or anterior chamber pathologies, another suprachoroidal approach was developed and is currently being assessed. figure 3 shows a picture of the eyemate sensor. technically, the wit consists of eight miniature pressure sensor cells, a temperature sensor, an identification encoder, an analogto-digital encoder, and a telemetry unit into a single microelectromechanical system (mems). the mems is attached to a gold circular antenna and the entire device is encapsulated in implantation-grade silicone. it weighs 0.1 g and comes in three sizes with a varying external diameter of 11.3 mm, 11.7 mm, or 12.1 mm, in order to accommodate varying sulcus diameter. it has an internal diameter of 7 mm and an overall thickness of 0.5 mm, while the thickness at the sensor area is 0.9 mm. each mems pressure sensor cell is made of two miniature parallel plates: a thin flexible plate that indents with changes in iop and a thicker rigid base plate integrated with an a/d converter for the digitalized pressure information. with changes in iop, the thin plate is mechanically defected. as the distance between the two plates varies, a corresponding analogue signal is generated and then converted to a digital signal that is transmitted externally by radiofrequency.[46] the handheld reader unit, that resembles a television remote control, receives the digital data and visually displays the iop values on its led display. the reader and the intraocular transponder unit must be within 5 cm of each other before a button is pressed on the reader to activate the electromagnetic coupling sequence and the two units can correspond with each other. this is all the cooperation required from the patient. the sensor does not require a battery. the handheld reader is battery powered and supplies the wit externally through electromagnetic inductive coupling at the time of communication. the sensor can conduct up to 10 iop measurements per second and there are a range of settings that allow for automatic monitoring at variable intervals. the base unit can store up to 3000 iop measurements, and additional memory modules can be added to the reader device. the wireless module can be installed to automatically download all measured data to a cloudbased server, allowing the clinical provider easy and instantaneous access to the data. the ophthalmologist receives the patient’s iop measurements and can easily create a tension profile, detect dips and peaks during diurnal and nocturnal iop fluctuations, and recognize situations that require adjustments of the therapy. in 2011, the argos-01 study investigated the safety of the eyemate and the accuracy of its iop measurements. six patients with poag underwent cataract surgery and ciliary sulcus placement of the sensor. the iop sensor was well tolerated by all the patients, despite four of them developing self-limited sterile anterior chamber inflammation. no difference 540 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 innovations in glaucoma surgery; gillmann et al in endothelial cell count and central corneal thickness was observed after 12 months in any of the patients. all patients were able to perform self-tonometry as instructed, and telemetric iop values correlated well with gat measurement, except for one patient who recorded negative values throughout the study.[47] since the original study, other reports illustrated how close self-monitoring could detect non-symptomatic iop variations that would otherwise go unnoticed. abnormal self-measurements can prompt the patients to obtain more iop measurements and search for repetitive patterns. in a published case report by rüfer et al, a patient even found a rare connection between the administration of his dorzolamide eyedrops and the subsequent iop rises before he received any medical input.[48] this suggests that placing the patient in charge and providing them with the means to easily and accurately self-monitor could improve glaucoma care by detecting iop aberrations earlier and eliciting causative factors with more ease. the increased frequency of iop measurement associated with the democratization of such sensors is likely to lead to an increased incidence of abnormal pressure readings. while this may represent crucial information on a patient’s individual iop control, more research will be needed to determine the clinical relevance of every fluctuation captured through continuous monitoring. c. implantable and injectable therapeutics despite all these innovations, the most common first-line treatment for open angle glaucoma remains pharmacological, and often consists of a topical prostaglandin analog (pga). numerous studies have confirmed their potential to achieve substantial iop reductions for up to 48 hours, providing both diurnal and nocturnal effect, contrary to topical beta-blockers that were proven to be somewhat inefficient at night. this class of medications act by primarily increasing uveoscleral outflow and, to some extent, enhancing trabecular outflow. while pga is a generally well-tolerated medication, a number of side effects are commonly reported, including cystoid macular edema, excessive eyelash growth, iris pigmentation, allergic reactions, and conjunctival hyperhemia and scarring. the latter of which was associated with increased risk of surgical failure in subsequent filtering procedures. beyond these adverse effects, topical pga suffer the same problems as all self-administered topical medications.[49] there is ample data, both self-reported and from pharmacies, indicating that adherence with topical anti-glaucoma treatments is generally poor. indeed, american studies have estimated that as many as 27% of all prescribed medications are simply not purchased by the patients, and nearly half of all glaucoma patients miss over 25% of their treatment doses.[74–76] unsurprisingly, poor compliance is associated with worse iop control and disease progression. in addition, even when topical medications are administered, patients’ instillation techniques can be poor and lead to a further decrease in treatment efficacy. to remedy these universal issues inherent to self-administered eye drops, several drug delivery approaches are being developed and will soon become available to the glaucoma specialists. they include options as varied as drug-eluting contact lenses or periocular rings, topical nebulizers releasing microdroplets of the active ingredient directly on the surface of the cornea, or subconjunctival injections. one journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 541 innovations in glaucoma surgery; gillmann et al of them, an intracameral bimatoprost-releasing implant, has already reached stage 3 clinical trials and is showing promising results.[50] it consists of a biodegradable matrix designed to be injected into the anterior chamber, where it gradually releases 15 μg of sustained-release bimatoprost over a period of up to six months. figure 4 shows the implant. in recent studies, the efficacy of the implant was comparable to that of daily instillation of the topical medication, with no observable side effects.[51] this mode of administration presents several clear advantages. firstly, with patients only having to attend a bi-annual appointment to receive their treatments, it would considerably reduce the potential for missed doses compared to topical therapies. secondly, the seemingly reduced contact and effect of bimatoprost on ocular surface may decrease the prevalence of long-term side effects and the negative impact of prolonged treatments on subsequent filtering surgeries. thirdly, and interestingly, contrary to topical instillation, no ceiling effect was identified for intracamerular instillation of bimatoprost. it has been speculated that it may be due to a direct lowering effect of intraocular bimatoprost on episcleral venous pressure. finally, after several intracameral injections, the ioplowering effect of the treatment appeared to persist considerably longer than the sixmonth lifespan of the implant, leading to prolonged periods of treatment free reduced iop.[52] the advent of implantable or injectable therapeutics may soon provide yet another step in the glaucoma treatment ladder. opinion the traditional landscape of glaucoma management has changed dramatically over the last decade, with the development of a large array of novel surgical techniques. while a surge in attention, investment and innovation and, eventually, treatment options foretells a bright future for the sub-specialty, at a clinical level, it raises the questions of patient-centered treatment choices and evidence-based decisions. indeed, one of the advantages of such a heterogenous range of surgical options is the chance to tailor therapy in an individualized manner. high quality data are required to make this choice more than an educated guess. to provide some objective criteria in the assessment of glaucoma surgery, and to guide innovation, the “10-10-10 goal” was set. according to these criteria, the ideal surgical technique would take less than 10 min to perform, be able to consistently achieve iops below 10 mmhg, and last >10 years without any significant complications. with procedures typically taking between 15 and 30 min to perform, migs have managed to significantly reduce surgical times. while this represents a 50% reduction from most traditional filtering procedure or glaucoma drainage device implantations, migs are yet to provide us with a simple enough procedure to be consistently carried out in <10 min by the average glaucoma surgeon. in terms of iop reduction potential, considering that the average candidate for migs surgery has a preoperative iop in the 20–25 mmhg range, it would require a 50–60% reduction to achieve postoperative pressures under the 10-mmhg threshold. in the literature, only rarely did some migs provide iop reduction of 50% or more. furthermore, the few incidences of iop reductions >50% could not be replicated, and the same surgical techniques showed more modest effects in alternative studies. it does, however, appear that the sub-conjunctival approach is more likely than other categories of migs to achieve iops in the low-teens. 542 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 innovations in glaucoma surgery; gillmann et al but in this context of intense innovation, new technologies will likely appear and reshuffle the cards in the years to come, including new devices offering variations on existing techniques, or all-new approaches such as drug-coated devices or ocular surface shunts. finally, it is, at present, difficult to assess the sustainability of migs efficiencies. since most migs have been commercially available for <5 years, there is a general lack of long-term data in the field, but knowledge is slowly accruing. this aim of longevity, however, should prompt us to design sound clinical trials early on, in order to obtain not only extensive, but also reliable long-term data. overall, reviews confirm the efficiency of most migs compared to standalone phacoemulsification, and the reported rates of complications also compare favorably with traditional filtering surgeries. but to be clinically advisable, a procedure needs not only be safe, but also to prove its non-inferiority to commonly accepted alternatives. however, there are only few studies comparing different migs techniques, especially considering the vast and growing number of procedures available nowadays, and even fewer assessing migs against topical medications. more comparative data, especially with gold standard therapies and common practice options could be extremely relevant for ophthalmologists and healthcare authorities, allowing to ascertain the best therapeutic option for the patients, and potentially reducing the medication burden and its associated costs. but considerably more evidence will be needed to achieve this level of certainty. indeed, current evidence, while non-negligible, is still mostly limited to non-randomized studies and uncontrolled retrospective comparisons with few quality randomized controlled trials. this leads to significant variability in studies’ results and a blurring of the outcomes, and further highlights the need for carefully designed randomized controlled trials. beyond the scope of migs, the potential of iop telemetry for self-assessment of iop control through implantable sensors is developing into a real option for clinicians and an empowering opportunity for patients. indeed, providing patients with direct feedback enables them to take control and have a clearer representation of their care, in turn leading to a better control of the disease.[68] building on the reports that patients’ adherence increases shortly before their medical appointments, continuous measurements may provide patients with an incentive for better adherence to treatment, and clinicians with a more accurate representation of out-of-clinic iops. it also might remove an element of self-deception where brief periods of adherence suffice to reassure both patients and treating clinicians.[53] this paves the way for personalized glaucoma care, in which the actual effect of lifestyle and treatments can be self-monitored by the patients and therapeutic decisions can be made accordingly in real time before there is further optic nerve injury. patients are increasingly demanding an equal role in clinical decision-making. many no longer accept the paternalistic model of medical care in which doctors decide and patients comply. however, there are potential issues with self-monitoring of iop, such as increased anxiety levels induced by measured iop fluctuations and peaks, leading to patients self-treating during iop spikes and additional office visits. the availability of continual iop monitoring will be a challenge to the current glaucoma management paradigm, journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 543 innovations in glaucoma surgery; gillmann et al which, however, has the important potential to improve patient health outcomes. after several decades of relative stagnation through the last century, glaucoma has now entered what many view as a golden age for the specialty. like every revolution, this one brings its fair share of uncertainty, clinical questioning, and uneasy periods of adaptation to ever-changing expectations. yet, while it is impossible to guess what the landscape of glaucoma surgery will be like in 10 or 15 years, data suggest a bright outlook both for patients and clinicians. financial support and sponsorship this review has been supported in part by the swiss glaucoma research foundation, lausanne, switzerland. conflicts of interest there are no conflicts of interest. references 1. tham yc, li x, wong ty, quigley ha, aung t, cheng c-yu. global prevalence of glaucoma and projections of glaucoma burden through 2040. a systematic review and meta-analysis. ophthalmology 2014;121:2081–2090. 2. chen cw. enhancing intraocular pressure controlling effectiveness of trabeculotomy by local application of mitomycin c. trans asia pac acad ophthalmol 1983;9:172–177. 3. gedde sj. the tube versus trabeculectomy study group. results from the tube versus trabeculectomy study. middle east afr j ophthalmol 2009;16:107–111. 4. saheb h, ahmed, ii. micro-invasive glaucoma surgery: current perspectives and future directions. curr opin ophthalmol 2012;23:96–104. 5. gottanka j, chan d, eichhorn m, lutjen-drecoll e, ethier cr. effects of tgf-beta2 in perfused human eyes. invest ophthalmol vis sci 2004;45:153–158. 6. fautsch mp, johnson dh. second arvo/pfizer research institute working group. aqueous humor outflow. what do we know? where will it lead us? invest ophthalmol vis sci 2006;47:4181–4187. 7. grant w. further studies on facility of flow through the trabecular meshwork. ama arch ophthalmol 1958;60:523e33. 8. rosenquist r, epstein d, melamed s, johnson m, grant wm. outflow resistance of enucleated human eyes at two different perfusion pressures and different extents of trabeculotomy. curr eye res 1989;8:1233e40. 9. andrew nh, akkach s, casson rj. a review of aqueous outflow resistance and its relevance to micro-invasive glaucoma surgery. surv ophthalmol 2020;65:18–31. 10. ellingsen ba, grant wm. trabeculotomy and sinusotomy in enucleated human eyes. invest ophthalmol 1972;11:21e8. 11. hann cr, vercnocke aj, bentley md, jorgensen sm, fautsch mp. anatomic changes in schlemm’s canal and collector channels in normal and primary open-angle glaucoma eyes using low and high perfusion pressures. invest ophthalmol vis sci 2014;55:5834e41. 12. zhao z, zhu x, he w, jiang c, lu y. schlemm’s canal expansion after uncomplicated phacoemulsification surgery: an optical coherence tomography study. invest ophthalmol vis sci 2016;57:6507–6512. 13. johnstone m. intraocular pressure control through linked trabecular meshwork and collector channel motion. in: knepper pa, samples jr, editors. glaucoma research and clinical advances 2016 to 2018. amsterdam, netherlands: kugler publications; 2016. 14. gillmann k, bravetti ge, mermoud a, mansouri k. a prospective analysis of istent inject microstent positioning: schlemm canal dilatation and intraocular pressure correlations. j glaucoma. 2019;28:613–621. 15. huang a, penteado r, papoyan v, voskanyan l, weinreb rn. aqueous angiographic outflow improvement after trabecular microbypass in glaucoma patients. ophthalmol glaucoma 2019;2:11–21. 16. ellingsen ba, grant wm. the relationship of pressure and aqueous outflow in enucleated human eyes. invest ophthalmol 1971;10:430e7. 17. huang as, saraswathy s, dastiridou a, begian a, mohindroo c, tan jch, et al. aqueous angiographymediated guidance of trabecular bypass improves angiographic outflow in human enucleated eyes. invest ophthalmol vis sci 2016;57:4558e65. 18. weinreb rn. uveoscleral outflow: the other outflow pathway. j glaucoma 2000;9:343–345. 19. weinreb rn, toris cb, gabelt bt, lindsey jd, kaufman pl. effects of prostaglandins on the aqueous humor outflow pathways. surv ophthalmol 2002;47:s53–s64. 20. toris cb, yablonski me, wang yl, camras cb. aqueous humor dynamics in the aging human eye. am j ophthalmol 1999;127:407–412. 21. figus m, posarelli c, passani a, albert tg, oddone f, sframeli at. the supraciliary space as a suitable pathway for glaucoma surgery: ho-hum or home run? surv ophthalmol 2017;62:828e37. 22. emi k, pederson je, toris cb. hydrostatic pressure of the suprachoroidal space. invest ophthalmol 1989;30:233e8. 23. kelly de, hageman gs, mcgregor ja. uveal compartmentalization in the hamster eye revealed by fine structural and tracer studies: implications for uveoscleral outflow. invest ophthalmol vis sci 1983;24:1288e304. 24. ring hg, fujino t. observations on the anatomy and pathology of the choroidal vasculature. arch ophthalmol 1967;78:431–444. 544 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 innovations in glaucoma surgery; gillmann et al 25. johnson m, mclaren jw, overby dr. unconventional aqueous humor outflow: a review. exp eye res 2017;158:94e111. 26. nakakura s, noguchi a, tabuchi h, kiuchi y. bimatoprostinduced late-onset choroidal detachment after trabeculectomy: a case report and review of the literature. medicine 2017;96:e5927. 27. hernández pardines f, molina martín jc, fernández montalvo l, balsalobre fa. bilateral choroidal effusion after selective laser trabeculoplasty. arch soc esp oftalmol 2017;92:295–298. 28. coban dt, erol mk, yucel o. hemorrhagic choroidal detachment after use of anti-glaucomatous eye drops: case report. arq bras oftalmol 2013;76:309–310. 29. krishnamurthy r, senthil s, garudadri cs. late postoperative choroidal detachment following an uneventful cataract surgery in a patient on topical latanoprost. bmj case rep 2015;2015;pii: bcr2015211408. 30. sagara t, gaton dd, lindsey jd, gabelt bt, kaufman pl, weinreb rn. topical prostaglandin f2alpha treatment reduces collagen types i, iii, and iv in the monkey uveoscleral outflow pathway. arch ophthalmol 1999;117:794–801. 31. gardiner bs, smith dw, coote m, crowston jg. computational modeling of fluid flow and intraocular pressure following glaucoma surgery. plos one 2010;5:1–11. 32. razeghinejad mr, spaeth gl. a history of the surgical management of glaucoma. optom vis sci 2011;88:e39– e47. 33. schlunck g, meyer-ter-vehn t, klink t, grehn f. conjunctival fibrosis following filtering glaucoma surgery. exp eye res 2016;142:76–82. 34. yamanaka o, kitano-izutani a, tomoyose k, reinach ps. pathobiology of wound healing after glaucoma filtration surgery. bmc ophthalmol 2015;15:157. 35. baudouin c, hamard p, liang h, creuzot-garcher c, bensoussan l, brignole f. conjunctival epithelial cell expression of interleukins and inflammatory markers in glaucoma patients treated over the long term. ophthalmology 2004;111:2186e2192. 36. stalmans i, sunaric megevand g, cordeiro mf, hommer a, rossetti l, goni f, et al. preservative-free treatment in glaucoma: who, when, and why. eur j ophthalmol 2013;23:518e525. 37. ingber de. cellular mechanotransduction: putting all the pieces together again. faseb j 2006;20:811e827. 38. pedersen ja, lichter s, swartz ma. cells in 3d matrices under interstitial flow: effects of extracellular matrix alignment on cell shear stress and drag forces. j biomech 2010;43:900e905. 39. guthoff r, klink t, schlunck g, grehn f. in vivo confocal microscopy of failing and functioning filtering blebs: results and clinical correlations. j glaucoma 2006;15:552e558. 40. lopilly park hy, kim jh, ahn md, park ck. level of vascular endothelial growth factor in tenon tissue and results of glaucoma surgery. arch ophthalmol 2012;130:685e689. 41. takai y, tanito m, ohira a. multiplex cytokine analysis of aqueous humor in eyes with primary open-angle glaucoma, exfoliation glaucoma, and cataract. invest ophthalmol vis sci 2012;53:241e247. 42. pro mj, freidl kb, neylan cj, sawchyn ak, wizov ss, moster mr. ranibizumab versus mitomycin c in primary trabeculectomy – a pilot study. curr eye res 2014;40:510– 515. 43. van de velde s, van bergen t, vandewalle e, kindt n, castermans k, moons l, et al. rho kinase inhibitor ama0526 improves surgical outcome in a rabbit model of glaucoma filtration surgery. prog brain res 2015;220:283–297. 44. tan sz, walkden a, au l. one-year result of xen45 implant for glaucoma: efficacy, safety, and postoperative management. eye 2018;32:324–332. 45. sheybani a, reitsamer h, ahmed ii. fluid dynamics of a novel micro-fistula implant for the surgical treatment of glaucoma. invest ophthalmol vis sci 2015;56:4789–4795. 46. gillmann k, bravetti ge, mermoud a, mansouri k. anterior chamber xen gel stent movements: the impact on corneal endothelial cell density. j glaucoma 2019;28:e93–e95. 47. gillmann k, mansouri k, bravetti ge, mermoud a. chronic intraocular inflammation as a risk factor for xen gel stent occlusion: a case of microscopic examination of a fibrinobstructed xen stent. j glaucoma 2018;27:739–741. 48. ndulue jk, rahmatnejad k, sanvicente c, wizov ss, moster mr. evolution of cyclophotocoagulation. j ophthalmic vis res 2018;13:55–61. 49. schuman js, bellows ar, shingleton bj, latina ma, allingham rr, belcher cd, et al. contact transscleral nd:yag laser cyclophotocoagulation. midterm results. ophthalmology 1992;99:1089–1094; discussion 1095. 50. ishida k. update on results and complications of cyclophotocoagulation. curr opin ophthalmol 2013;24:102–110. 51. sanchez fg, peirano-bonomi jc, grippo tm. micropulse transscleral cyclophotocoagulation: a hypothesis for the ideal parameters. med hypothesis discov innov ophthalmol 2018;7:94–100. 52. egbert pr, fladoyor s, budenz dl, dadzie p, byrd s. diode laser transscleral cyclophotocoagulation as a primary surgical treatment for primary open-angle glaucoma. arch ophthalmol 2001;119:345–350. 53. pokroy r, greenwald y, pollack a, bukelman a, zalish m. visual loss after diode laser cyclophotocoagulation for primary open-angle glaucoma and neovascular glaucoma. ophthalmic surg laser imag 2008;39:22–29. 54. michelessi m, bicket ak, lindsley k. cyclodestructive procedures for non-refractory glaucoma. cochrane database syst rev 2018;2018:cd009313. 55. gloor br, hans goldmann (1899–1991). eur j ophthalmol, 2010;20:1–11. 56. kouchaki b, hashemi h, yekta a, khabazkhoob m. comparison of current tonometry techniques in measurement of intraocular pressure. j curr ophthalmol 2017;29:92–97. 57. kawai m, kawai n, nakabayashi s, kinouchi r, yoshida a. comparison of intraocular pressure variability in glaucoma measured by multiple clinicians with those by one clinician. int ophthalmol 2017;37:95–101. 58. mccafferty s, lim g, duncan w, enikov et, schwiegerling j, levine j, et al. goldmann tonometer error correcting prism: clinical evaluation. clin ophthalmol 2017;11:835– 840. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 545 innovations in glaucoma surgery; gillmann et al 59. pearce jg, maddess t. the clinical interpretation of changes in intraocular pressure measurements using goldmann applanation tonometry: a review. j glaucoma 2019;28:302–306. 60. mansouri k, weinreb rn, medeiros fa. is 24-hour intraocular pressure monitoring necessary in glaucoma? semin ophthalmol 2013;28:157–164. 61. cheng j, xiao m, xu h, fang s, chen x, kong x, et al. seasonal changes of 24-hour intraocular pressure rhythm in healthy shanghai population. medicine 2016;95:e4453. 62. nuyen b, mansouri k. detecting iop fluctuations in glaucoma patients. open ophthalmol j 2016;10:44–55. 63. matlach j, bender s, könig j, binder h, pfeiffer n, hoffmann em. investigation of intraocular pressure fluctuation as a risk factor of glaucoma progression. clin ophthalmol 2019;13:9–16. 64. konstas ag, kahook my, araie m, katsanos a, quaranta l, rossetti l, et al. diurnal and 24-h intraocular pressures in glaucoma: monitoring strategies and impact on prognosis and treatment. adv ther 2018;35:1775–1804. 65. ittoop sm, soohoo jr, seibold lk, mansouri k, kahook my. systematic review of current devices for 24-h intraocular pressure monitoring. adv ther 2016;33:1679– 1690. 66. melki s, todani a, cherfan g. an implantable intraocular pressure transducer: initial safety outcomes. jama ophthalmol 2014;132:1221–1225. 67. dick hb, schultz t, gerste rd. miniaturization in glaucoma monitoring and treatment: a review of new technologies that require a minimal surgical approach. ophthalmol ther 2019;8:19–30. 68. gillmann k, bravetti ge, niegowski lj, mansouri k. using sensors to estimate intraocular pressure: a review of intraocular pressure telemetry in clinical practice. exp rev ophthalmol 2019;14:6, 263–276. 69. koutsonas a, walter p, roessler g, plange n. implantation of a novel telemetric intraocular pressure sensor in patients with glaucoma (argos study): 1-year results. invest ophthalmol vis sci 2015;56:1063–1069. 70. rüfer f, gillmann k, choritz l, thieme h, weinreb rn, mansouri k. the value of intraocular pressure telemetry in monitoring the therapeutic effect of glaucoma medications. j glaucoma 2020;29:e38–e40. 71. eyawo o, nachega j, lefebvre p, meyer d, rachlis b, lee cw, et al. efficacy and safety of prostaglandin analogues in patients with predominantly primary open-angle glaucoma or ocular hypertension: a meta-analysis. clin ophthalmol 2009;3:447–456. 72. mansouri k, iliev me, rohrer k, shaarawy t. compliance and knowledge about glaucoma in patients at tertiary glaucoma units. int ophthalmol 2011;31:369–376. 73. robin a, grover ds. compliance and adherence in glaucoma management. indian j ophthalmol 2011;59:s93–s96. 74. okeke co, quigley ha, jampel hd, ying gs, plyler rj, jiang y, et al. adherence with topical glaucoma medication monitored electronically the travatan dosing aid study. ophthalmology 2009;116:191–199. 75. wang bb, lin mm, nguyen t, turalba av. patient attitudes toward novel glaucoma drug delivery approaches. digit j ophthalmol 2018;24:16–23. 76. lewis ra, christie wc, day dg, craven er, walters t, bejanian m. bimatoprost sustained-release implants for glaucoma therapy: 6-month results from a phase i/ii clinical trial. am j ophthalmol 2017;175:137–147. 77. lee ss, almazan a, decker s, zhong y, ghebremeskel an, et al. intraocular pressure effects and mechanism of action of topical versus sustained-release bimatoprost. transl vis sci technol 2019;8:15. 78. welge-lüssen u, weise s, yu al. assessing the adherence behavior of glaucoma patients to topical eye drops. patient prefer adherence 2014;9:17–23. 546 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 photo essay profound presentation of retinopathy in a patient with sickle cell trait and diabetes mellitus gautam vangipuarm1, md; steven s. saraf1, md; qinqin zhang2, phd; ruikang wang1,2, phd; kasra a rezaei1, md 1department of ophthalmology, university of washington, seattle, wa, usa 2department of bioengineering, university of washington, seattle, wa, usa orcid: kasra a rezaei: https://orcid.org/0000-0003-4287-3187 j ophthalmic vis res 2020; 15 (1): 116–117 correspondence to: kasra a rezaei, md. university of washington, department of ophthalmology, seattle, wa, 908 jefferson st, seattle, wa 98104. e-mail: krezaei@uw.edu received: 01-01-2019 accepted: 01-05-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i1.5962 presentation a 43-year-old functionally monocular african american woman with longstanding type 2 diabetes mellitus presented for care of her better-seeing left eye. originally suspected of having proliferative diabetic retinopathy (pdr) as the cause of her bilateral visual impairment, fluorescein angiography and optical coherence tomography angiography revealed a marked peripheral nonperfusion which was out of proportion for a typical diabetic retinopathy (figure 1). a comprehensive uveitic and vasculopathic workup was therefore initiated. the workup was largely negative except for hemoglobin electrophoresis, which was consistent with the sickle cell trait (or hemoglobinopathy) (table 1). the patient was counseled on her diagnosis and continues to be treated with laser photocoagulation for her peripheral neovascularization. figure 1. color fundus photo, left eye (a) early (b) and late (c) fluorescein angiography of the left eye showing marked peripheral ischemia and posterior pole neovascularization. oct angiography (d) showing severely decreased vascular density. discussion this report strengthens the hypothesis that diabetic retinopathy and coexisting vasculopathic this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: vangipuarm g, saraf ss, zhang q, wang r, rezaei ka. profound presentation of retinopathy in a patient with sickle cell trait and diabetes mellitus. j ophthalmic vis res 2020;15:116–117. 116 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i1.5962&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; rezaei et al table 1. laboratory assessment of other etiologies for extensive peripheral non-perfusion including pro-thrombotic and vasculitic causes test ordered result (normal range) angiotensin converting enzyme (u/l) 26u/l (8–53 u/l) anti-nuclear antibody negative cryoglobulin negative erythrocyte sedimentation rate (mm/h) 60 mm/h high (0–20 mm/h) hiv ag and ab nonreactive anti-myeloperoxidase negative anti pr3 negative rheumatoid factor < 10 serologic syphilis panel negative anti-thrombin activity 123% (normal) c-reactive protein (mg/l) 24.9 mg/l high (0–10 mg/l) activated protein s (%) 113% (65–150%) activated protein c (%) 121% (55–150%) factor v leiden negative homocysteine negative prothrombin time (s) 14.1 s (10.7–15.6 s) inr (s) 1.1 s (0.8–1.3 s) cbc normal cmp glucose 353 mg/dl (62–125 mg/dl) herpes type 1&2 serology positive for hsv-1 and hsv-2 cmv (serum antibody) positive hemoglobin electrophoresis consistent with hbs trait quantiferon-tb gold negative cbc, complete blood count; cmp, comprehensive metabolic panel; cmv, antibodies to cytomegalovirus; hiv, human immunodeficiency virus; inr, international normalized ratio; mg/dl, milligrams per deciliter; mm/h, millimeter per hour u/l, units per liter diseases, even sickle cell trait, may have a synergistic effect on the overall disease burden. a broad differential must be maintained in patients with presumed diabetic retinopathy, especially those with uncharacteristic imaging findings.[1–5] financial support and sponsorship this study was supported by the department of ophthalmology, university of washington. conflicts of interest there are no conflicts of interest. references 1. tsaras g, owusu-anash a, boateng fo, amoatengadjepong y. complications associated with sct: a brief narrative review. am j med 2009;122:507–512. 2. downes s, hambleton i, chuang el, lois n, serjeant gr, bird ac, et al. incidence and natural history of proliferative sickle cell retinopathy. ophthalmology 2005;112:1869– 1875 3. jampol l, goldbaum m. peripheral proliferative retinopathies. surv ophthalmol 1980;25:1–14 4. jackson h, bentley cr, hingorani m, atkinson, p aclimandos wa, thompson gm. sickle retinopathy in patients with sickle trait. eye 1995;9:589–593. 5. nagpal kc, asdourian gk, patrianakos d, goldberg mf, rabb mf, goldbaum m. proliferative retinopathy in sct. report of seven cases. arch intern med 1977;137:325–328. journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 117 original article penetration of carbon nanotubes into the retinoblastoma tumor after intravitreal injection in lhbetabetabetatagagag transgenic mice reti-noblastoma model hakan demirci, md1; yichun wang, phd2,3; qiaochu li, phd4; cheng-mao lin, phd1 nicholas a kotov, phd2,3,5,6,7,8,9; anna beatriz diniz grisolia, md1; jay l. guo, phd4 1department of ophthalmology and visual sciences, kellogg eye center, university of michigan ann arbor, mi, usa 2biointerfaces institute, university of michigan ann arbor, mi, usa 3department of chemical engineering, university of michigan ann arbor, mi, usa 4electrical engineering and computer science, university of michigan ann arbor, mi, usa 5department of biomedical engineering, university of michigan ann arbor, mi, usa 6department of materials science and engineering, university of michigan ann arbor, mi, usa 7department of macromolecular science and engineering, university of michigan ann arbor, mi, usa 8michigan center for integrative research in critical care, university of michigan ann arbor, mi, usa 9michigan institute of translational nanotechnology, university of michigan ann arbor, mi, usa orcid: hakan demirci: https://orcid.org/0000-0003-1593-1476 abstract purpose: to evaluate the penetration of carbon nanotubes (cnts) throughout retinoblastoma in a transgenic mice model. methods: cnts functionalized with fluorescein isothiocyanate and targeting ligands biotin (ctn-fitc-bio, 0.5mg/ml), or folic acid (cnt-fitc-fa, 0.5mg/ml) were injected into the vitreous of one eye of lhbetatag transgenic mice. other eye did not receive any injection and was used as control. three mice were sacrificed at days 1, 2, and 3. eyes were enucleated and stained with 4,6-diamidino-2-phenylindole. the sections were imaged by fluorescent microscope. the images were transformed into grey-scale in matlab for intensity analysis. background intensity was normalized by marking squares outside the eyeball and using the mean intensity of these squares. fluorescent intensity (fi) for each image was measured by calculating the intensity of a same-sized square within retinoblastoma. results: nine eyes of nine mice were included in each cnt-fitc-bio and cnt-fitc-fa groups. the mean fi in cnt-fitcbio was 52.08 ± 6.33, 53.62 ± 9.00, and 65.54 ± 5.14 in days 1, 2, and 3, respectively. the mean fi in cnt-fitc-fa was 50.28 ± 7.37, 59.21 ± 6.43, and 58.38 ± 2.32 on days 1, 2, and 3, respectively. fi was significantly higher in eyes injected with cnt-fitc-bio and cnt-fitc-fa compared to the control eyes (p = 0.02). there was no difference in fi between eyes with cnt-fitc-bio and cnt-fitc-fa, and fi remained stable on days 1–3 in cnt-fitc-bio, cnt-fitc-fa, and control eyes (p > 0.05). conclusion: we observed higher fi in eyes with cnt-fitc-bio and cnt-fitc-fa compared to control eyes, showing penetration of cnts throughout retinoblastoma. cnts can be a carrier candidate for imaging or therapeutic purposes in retinoblastoma. keywords: carbon nanotubes; intravitreal injection; lhbetatag transgenic mice retinoblastoma model; nanoparticle; nanotubes; retinoblastoma j ophthalmic vis res 2020; 15 (4): 446–452 correspondence to: hakan demirci, md. department of ophthalmology and visual sciences, kellogg eye center, university of michigan, 1000 wall st., ann arbor, mi 48105, usa. e-mail: hdemirci@med.umich.edu received: 18-08-2019 accepted: 14-06-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7778 introduction retinoblastoma, a potentially deadly cancer, is the most common intraocular cancer of childhood.[1] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: demirci h, wang y, li q, lin c-m, kotov na, grisolia abd, guo jl. penetration of carbon nanotubes into the retinoblastoma tumor after intravitreal injection in lhbetatag transgenic mice reti-noblastoma model. j ophthalmic vis res 2020;15:446–452. 446 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7778&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr penetration of carbon nanotubes into retinoblastoma; demirci et al within the last decade, the use of intraarterial and intravitreal chemotherapies significantly changed the management of retinoblastoma. prior to intraarterial chemotherapy, systemic chemotherapy provided almost 100% globe salvage in group a, b, and c eyes when coupled with laser and cryotherapy and 48% in group d eyes.[2–4] the beneficial effect of intraarterial chemotherapy was more pronounced in group d eyes by improving the globe salvage rate up to 100%.[5–8] however, advanced group d eyes with vitreous seeds and group e eyes continued to be a challenging problem. the use of intravitreal injection especially improved the globe salvage rate in group d eyes with extensive vitreous seeds and group e eyes increasing the globe salvage rate from 27% to 73%.[9] the recurrence of main tumor rather than vitreous seeds was reported to be the reason of failure in globe salvage, suggesting the lack of penetration of chemotherapeutic agents in the main tumor.[10] carbon nanotubes (cnts) are unique tubular, hollow nanostructures that have been extensively utilized in biomedical applications including implantable devices.[11, 12] they can be singlewalled, double-walled, or multi-walled with diameters from < 1 nm up to 100 nm and lengths from 100 nm to microns. in vivo and in vitro studies showed that cnts have efficient drug-loading capacity with high length/diameter ratio and multifunctional surface chemistry.[11–14] in addition, they are biocompatible.[11, 13, 14] all these features make cnts an ideal candidate for consideration for drug delivery or tumor imaging. the most of current biodistribution data of cnts has been obtained based on the systemic administration in animal models.[15, 16] by using a three-dimensional (3d) hepatocellular carcinoma tissue culture, wang et al[17] showed that the surface of cnts can be engineered to enable deep and fast penetration into tissues. this is achieved by combining the classical 3d diffusion through the interstitial gaps with accelerated two-dimensional (2d) diffusion of the cnts over the cellular membranes. the combination of deep penetration into the tumor with the ability of cnts to carry anticancer drugs make them promising candidates for both the diagnostics and treatment of hard-to-reach intraocular tumors. retinoblastoma cells have a specialized high affinity carrier-mediated system for folic acid and biotin uptake.[18, 19] therefore, folic acid and biotin can be ideal targets to increase cnts uptake. in this study, we injected cnts functionalized with ligands fluorescein isothiocyanate (fitc) and folic acid (cnt-fitc-fa) or biotin (cnt-fitc-bio) into the vitreous of one eye with lhbetatag transgenic retinoblastoma model and compared the fluorescein intensity between the injected and uninjected control eyes to evaluate the ability of cnts to penetrate through the retinoblastoma tumor when injected intravitreally. methods animals all experiments are performed in accordance with the association for research in vision and ophthalmology (arvo) statement for the use of animals in ophthalmic and visual research. the protocol was approved by the university committee on use and care of animals of the university of michigan. all surgeries were performed under ketamine and xylazine anesthesia, and all efforts were made to minimize suffering. we used the lhbetatag transgenic mice as retinoblastoma animal mode at 8–10 weeks old. eye tumors in the lhbetatag transgenic mouse model showed the histological features of human retinoblastoma with endophytic and exophytic growth with invasion of the retina, choroid, and optic nerve.[20] this animal model has been extensively characterized and develops bilateral multifocal retinal tumors that are stable and grow at the predictable rate.[20] in this model, retinoblastoma develops when the mice is about six weeks old. when the mice reach the age of 8–10 weeks, about half of the globe is filled with the tumor, and at the age of 12–14 weeks, the entire mice globe is filed with retinoblastoma. examination of each mice was performed and it was confirmed that retinoblastoma tumor fills about 50% of the globe. preparation of targeted carbon nanotubes functionalized with fluorescein isothiocyanate and biotin (cnt-fitc-bio), and fluorescein isothiocyanate and folic acid (cnt-fitc-fa) cnts were targeted by covalent attachment of biotin and folic acid. receptors for biotin and folic acid are more highly overexpressed journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 447 penetration of carbon nanotubes into retinoblastoma; demirci et al on retinoblastoma cells than retinal pigment epithelium.[21] they were also attached with fitc to image them and to evaluate their penetration. in short, 0.5 mg cnts with an average diameter of 1.2 nm and a length of 1000 nm (0.5 mg/ml, p3swnt with 1.0–3.0 atomic % carboxylic acid, carbon solutions, inc.) were dispersed in phosphatebuffered saline (pbs) buffer followed by incubation with 8 mg of 1-ethyl-3-(3-(dimethylamino)propyl) carbodiimide (edac) for 1 min at room temperature, after which samples were immediately vortexed. next, biotin and fitc (life technologies, ca) (2 μg in 20 μl of dimethylformamide) were added together, and the resulting mixture was allowed to react for an additional 2 hours at 37°c in a rotator rocker. these samples were then washed by pbs and centrifuged at 1300 rpm for 20 min for three times to remove unbound antibodies and excess fitc in centricon ym-50 tubes (milliporesigma, ma), and the resulting cnt-fitcbio were suspended in 1 ml of serum-free eagle’s minimum essential medium (emem) and used immediately. similar procedure was applied to prepare cnts functionalized with folic acid to prepare the cnt-fitc-fa. surgical technique in this experiment, 1 µl of 0.5 mg/ml targeted cntfitc-bio, and cnt-fitc-fa were injected into the vitreous of one eye of lhbetatag transgenic mice. the other eye was not injected and was used as control. in each group of cnt-fitc-bio (nine eyes) and cnt-fitc-fa (nine eyes), nine eyes of nine mice were used. the control group comprised the uninjected eyes of nine mice. vitreous injections were performed by an experienced team member (cl) under direct visualization with the operating microscope, after dilating the pupil and confirming that injection was into the vitreous cavity, but not into the tumor. during the procedure, the tip of the needle was constantly monitored. three mice were sacrificed at each day 1, 2, and 3, and eyes were enucleated. histopathological preparation mice eyes were fixated with 10% formaldehyde in phosphate-buffered saline (pbs) for histology or with 4% paraformaldehyde in pbs followed by incubating with 30% sucrose in pbs. eyes were embedded in optimal cutting temperature (oct) compound and cryosectioned. they were stained with 4,6-diamidino-2-phenylindole (dapi, 1 mg/ml in pbs; sigma-aldrich) to visualize cell nuclei. image analysis each globe was sectioned in to 5 µm thick sections. five sections from each globe were evaluated and count of these five sections were averaged. the stained sections were imaged by olympus bx-51 fluorescent microscope under 10× magnification. the fluorescent cnts were excited by 480 nm light with the same laser power and the camera exposure was kept the same all the time (which is 102.6 ms). the images were transformed into grey-scale images in matlab for intensity analysis. in order to compare the intensity, all the images were normalized. for normalization, a blue square region (blue square marked in figure 1) outside the eyeball area was marked in each eye, and the mean intensity within these same-sized blue squares were calculated for each eye. it is understandable that the glass region should reflect same, fixed light intensity. therefore, all the images were normalized by setting the mean intensity of these blue squares to be the same. finally, the fluorescent intensity (fi) for each image was calculated by calculating the intensity of a same-sized red square region (red square marked in figure 1) within the eyeball area. we avoided the muscle cell area which could also show strong fluorescents. it is worth noting that the size of this square was determined by the largest possible area among the images. in order to compensate the false-positive results resulting from the photoconversion of dapi due to blue excitation and green emission as reported by jez et al,[22] we analyzed both control and injected eyes, and compared them with each other. statistical analysis the difference in the fluorescein intensity between eyes injected with cnt-fitc-bio and cnt-fitcfa, and the control eyes were compared by using the mann–whitney u test. similarly, the difference in the fluorescein intensity between eyes injected with cnt-fitc-fa and cnt-fitc-bio were also compared by using mann-whitney u test. the change in the fluorescein intensity in eyes injected 448 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 penetration of carbon nanotubes into retinoblastoma; demirci et al figure 1. (a) from left to right, eyes injected with cnt-fitc-bio on days 1, 2, and 3 and control eye (×10, dapi). (b) from left to right eyes injected with ctn-fitc-fa on days 1, 2, and 3 and control eye (×10, dapi). the blue squares in each image denotes the area in glass region, which is used for normalization. the red squares were used to calculate the averaged intensity within tumor. fitc-functionalized cnts appear as bright spots throughout the retinoblastoma tumor in colored images. figure 2. the change of average intensity of cnts functionalized with fluorescein isothiocyanate and biotin, and fluorescein isothiocyanate and folic acid over the time. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 449 penetration of carbon nanotubes into retinoblastoma; demirci et al with cnt-fitc-fa and cnt-fitc-bio and control eyes at different days were evaluated by using repeated measures anova test. results nine eyes of nine mice were included in each group of cnt-fitc-bio and cnt-fitc-fa. in all eyes of lhbetatag transgenic mice, retinoblastoma tumor occupied about 50% of mice eye. we found that the fluorescence intensity was higher in retinoblastoma tumor in eyes injected with cnt-fitc-fa and cntfitc-bio than the uninjected control eyes (table 1). the fi in the retinoblastoma tumor remained about the same on days 1 and 2, and mildly increased on day 3 for cnt-fitc-bio (figure 1a). the fi increased on day 2 and remained about the same on day 3 for cnt-fitc-fa (figure 2). we also observed that both cnt-fitc-bio and cntfitc-fa passed through the retinoblastoma and stained the retinal pigment epithelium, showing their penetration through the tumor (figure 1b). the mean fluorescein intensity was significantly higher in eyes injected with cnt-fitc-bio and cnt-fitcfa compared to the uninjected control eyes (p = 0.02). we did not observe any difference in the mean fluorescein intensity between cnt-fitc-bio and cnt-fitc-fa groups (p > 0.05). there was no significant change in the fluorescein intensity at different days in eyes injected with cnt-fitc-bio and cnt-fitc-fa and the uninjected control eyes (p > 0.05). beside the tumor, we did not observe staining in the lens, iris, or cornea. there was no doseor procedure-related complications (cataract or retinal detachment). discussion carbon nanotubes have gained tremendous attention as drug carriers or imaging tools due to their unique characteristics such as high surface area, enhanced cellular uptake, and the possibility to be easily conjugated with many therapeutic or diagnostic agents.[15–17] previous studies about cnts were usually based on animal studies or 3d tissue cultures.[15–17] in these studies, cnts were delivered systemically to the tumor through the blood vessels and penetrated through the vessel walls or added to the 3d tissue culture medium. in this study, intravitreal cnts penetrated and passed through the retinoblastoma tumor and reached the retinal pigment epithelium layer. this was the first study that showed that cnts can penetrate and diffuse through a solid tumor such as retinoblastoma when injected intravitreally. wang et al[17] investigated the diffusional transport of cnts in 3d tissue replica of hepatocellular carcinoma and found that diffusion coefficients of cnts were high and comparable to the diffusion rates of similarly charged molecules with molecular weights 10000x lower. the diffusivity of cnts in tissues was enhanced after functionalization with transforming growth factor β1. the high diffusion coefficient was attributed to the planar diffusion of cnts along cellular membranes reducing effective dimensionality of diffusional space and electrostatic repulsion between cnt and cellular membrane. although the penetration of cnts remained stable on the first and second days in the eyes injected with cnt-fitc-bio with mild increase on day 3, and the penetration increased on day 2 and remained stable on day 3 in eyes injected with cnt-fitc-fa, these changes were not found to be statistically significant. studies with larger number of animals and longer follow-up are needed to confirm these findings and if cnts will remain stable inside the retinoblastoma over time. with the introduction of well-tolerated intravitreal injection technique in retinoblastoma, intravitreal chemotherapy gained an attention by improving the control of vitreous seeds which were the main reason of treatment failures.[23–25] abramson et al[26] reviewed eyes treated with intravitreal chemotherapy for indications other than vitreous seeds including subretinal seeds and recurrent retinal tumors in 56 eyes of 52 patients and found the recurrence rate of retinal tumors in 19% of eyes and subretinal seeds in 11% of eyes. they concluded that intravitreal chemotherapy could be considered as adjuvant therapy in globesparing treatment. the penetration and diffusion of cnts in retinoblastoma in animal models suggest that they could be an ideal carrier for chemotherapeutic agents in retinoblastoma. this might provide treatment of vitreous or subretinal seeds or retinoblastoma. there are some limitations of our study. this was a pilot study that was performed in small numbers of animals and these eyes were evaluated on days 1, 2, and 3. we did not do any electron microscopy to show the distribution of cnts. however, higher fluorescein intensity throughout retinoblastoma 450 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 penetration of carbon nanotubes into retinoblastoma; demirci et al table 1. averaged intensities measured in eyes injected with cnt-fitc-bio and cnt-fitc-fa day1 day2 day3 control averaged intensity cnt-fitc-bio sample/a.u. 52.08 ± 6.33 (52,42.60–56.55) 53.62 ± 9.00 (53, 47.25–60) 65.54 ± 5.14 (62, 58.26–84.25) 34.47 ± 6.67 (34, 29.76–39.19) averaged intensity cnt-fitc-fa sample/a.u. 50.28 ± 7.37 (50, 45.07-55.49) 59.21 ± 6.43 (55, 50.11–73.19) 58.38 ± 2.32 (58, 56.74–60.01) 34.47 ± 6.67 (34, 29.76–39.19) *the fluorescein intensity was significantly higher in eyes injected with cnt-fitc-bio and cnt-fitc-fa compared to the control uninjected eyes (p = 0.02). **there was no difference in fluorescein intensity between cnt-fitc-bio and cnt-fitc-fa groups (p > 0.05). ***there was no significant change in fluorescein intensities at different days in the eyes with cnt-fitc-bio and cnt-fitc-fa and the uninjected control eyes (p > 0.05). tumors showed that cnts have significantly higher penetration throughout the retinoblastoma tumors. in this study, we did not evaluate the distribution of cnts on the other ocular structures in detail as well as their toxicities. future studies will be needed to address these issues. in conclusion, we showed that cnts can penetrate through the retinoblastoma tumor in a transgenic retinoblastoma model when administrated into the vitreous. there was no difference in tumor penetration between the cnt-fitc-bio and cnt-fitc-fa groups. the deep penetration into the tumor with the ability of cnts to carry chemotherapeutic agents make them promising carrier candidates for both diagnostics and treatment of these hard-to-reach intraocular tumors. financial support and sponsorship this study was supported by richard n and marilyn k witham professorship. conflicts of interest there are no conflicts of interest. references 1. young jl, smith ma, roffers sd, liff jm, bunin gr. retinoblastoma. in: ries la, smith ma, gurney jg, linet m, tamra t, young jl, et al., editors. cancer incidence and survival among children and adolescents: united states seer program 1975–1995. maryland: national cancer institute, seer program; 2012;73-79. 2. shields cl, depotter p, himelstein bp, shields ja, meadows at, maris jm. chemoreduction in the initial management of intraocular retinoblastoma. arch ophthalmol 1996;114:1330–1338. 3. murphree al, villablanca jg, deegan wf, sato jk, malogolowkin m, fisher a, et al. chemotherapy plus local treatment in the management of intraocular retinoblastoma. arch opthalmol 1996;114:1348–1356. 4. gallie bl, budning a, deboer gkoren g, verje, thiessen jj, e z, et al. chemotherapy with focal therapy can cure intraocular retinoblastoma without radiotherapy. arch ophthalmol 1996;114:1321–1328. 5. shields cl, jorge r, say ea, magrath g, alset a, caywood e, et al. unilateral retinoblastoma managed with intravenous chemotherapy versus intra-arterial chemotherapy. outcomes based on the international classification of retinoblastoma. asia pac j ophthalmol 2016;5:97–103. 6. manjandavida fp, stathopoulos c, zhang j, honavar sg, shields cl. intra-arterial chemotherapy in retinoblastoma a paradigm change. indian j ophthalmol 2019;67:740– 754. 7. munier fl, mosimann p, puccinelli f, gaillard mc, stathopoulos c, houghton s, et al. first-line intraarterial versus intravenous chemotherapy in unilateral sporadic group d retinoblastoma: evidence of better visual outcomes, ocular survival and shorter time to success with intra-arterial delivery from retrospective review of 20 years of treatment. br j ophthalmol 2017;101:1086–1093. 8. abramson dh, marr bp, dunkel ij, brodie s, zabor ec, driscoll sj, et al. intra-arterial chemotherapy for retinoblastoma in eyes with vitreous and/or subretinal seeding: 2-year results. intra-arterial chemotherapy for retinoblastoma in eyes with vitreous and/or subretinal seeding: 2-year result. br j ophthalmol 2012;96:499–502. 9. shields cl, alset ae, say ea, caywood e, jabbour p, shields ja. retinoblastoma control with primary intraarterial chemotherapy: outcomes before and during the intravitreal chemotherapy era. j pediatr ophthalmol strabismus 2016;53:275–284. 10. ghassemi f, amoli fa. pathological findings in enucleated eyes after intravitreal melphalan injection. int ophthalmol 2014;34:533–540. 11. ref tang z, wang y, podsiadlo p, kotov na. biomedical applications of layer-by-layer assembly: from biomimetics to tissue engineering. adv mater 2006;18:3203–3224. 12. gheith mk, pappas tc, liopo av, sinani v, shim bs, motamedi m, et al. stimulation of neural cells by lateral currents in conductive lbl films of single-walled carbon nanotubes. adv mater 2006;18:2975–2979. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 451 penetration of carbon nanotubes into retinoblastoma; demirci et al 13. mohajeri m, behnam b, sahebkar a. biomedical applications of carbon nanomaterials: drug and gene delivery potentials. j cell physiol 2018;234:298–319. 14. yang k, liu z. in vivo biodistribution, pharmacokinetics, and toxicology of carbon nanotubes. curr drug metabol 2012;13:1057–1067. 15. singh r, pantarotto d, lacerda l, patorin g, klumpp c, prato m, et al. tissue biodistribution and blood clearance rates of intravenously administered carbon nanotube radiotracers. proc natl acad sci usa 2006;103:3357– 3362. 16. sager tm, wolfarth mw, andrew m, hubbs a, friend s, chen th, et al. effect of multi-walled carbon nanotube surface modification on bioactivity in the c57bl/6 mouse model. nanotoxicology 2014;8:317–327. 17. wang y, bahng jh, che q, han j, kotov na. anomalously fast diffusion of targeted carbon nanotubes in cellular spheroids. acs nano 2015;9:8231–8238. 18. kansara v, paturi d, luo s, gaudana r, mitra ak. folic acid transport via high affinity carrier-mediated system in human retinoblastoma cells. int j pharm 2008;355:210– 219. 19. kansara v, luo s, balasubrahmanyam b, pal d, mitra ak. biotin uptake and cellular translocation in human derived retinoblastoma cell line (y-79): a role of hsmvt system. int j pharm 2006;312:43–52. 20. albert dm, griep ae, lambert pf, howes ka, windle jj, lasudry jg. transgenic models of retinoblastoma; what they tell us about its cause and treatment. trans am ophthalmol soc 1994;92:385–400. 21. jwala j, vadlapatla rk, vadlapudi ad, boddu sh, pal d, mitra ak. differential expression of folate receptoralpha, sodium-dependent multivitamin transporter, and amino acid transporter (b (0, +)) in human retinoblastoma (y-79) and retinal pigment epithelial (arpe-19) cell lines. j ocul pharmacol ther 2012;28:237–244. 22. jez m, bas t, veber m, košir a, dominko t, page r, et al. the hazards of dapi photoconversion: effects of dye, mounting media and fixative, and how to minimize the problem. histochem cell biol 2013;139:195–204. 23. francis jh, roosipu n, levin am, brodie se, dunkel ij, gobin yp, et al. current treatment of bilateral retinoblastoma: the impact of intraarterial and intravitreous chemotherapy. neoplasia 2018;20:757–763. 24. munier fl, gaillard mc, balmer a, soliman s, podilsky g, moulin ap, et al. intravitreal chemotherapy for vitreous disease in retinoblastoma revisited: from prohibition to conditional indications. br j ophthalmol 2012;96:1078– 1083. 25. shields cl, lally se, leahey am, jabbour pm, caywood eh, schwendeman r, et al. targeted retinoblastoma management: when to use intravenous, intra-arterial, periocular, and intravitreal chemotherapy. curr opin ophthalmol 2014;25:374–385. 26. abramson dh, ji x, francis jh, catalanotti f, brodie se, habib l. intravitreal chemotherapy in retinoblastoma: expended use beyond intravitreal seeds. br j ophthalmol 2018; june 6 [epub ahead of print]. 452 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 letter to editor guidance for ophthalmologists and ophthalmology centers during the covid-19 pandemic zhale rajavi1, md; sare safi1, phd; maryam mohammadzadeh2, md 1ophthalmic epidemiology research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran orcid: zhale rajavi: https://orcid.org/0000-0002-4094-1062 j ophthalmic vis res 2020; 15 (3): 438–441 dear editor, coronavirus disease (covid-19) caused by the sars-cov-2 virus usually manifests with respiratory symptoms including cough and dyspnea associated with fever and diarrhea, while it rarely presents with conjunctivitis. ophthalmologists are at high risk for being infected or transmitting the virus due to the following reasons: examining patients with conjunctivitis or asymptomatic carriers from a short distance (usually < 20 cm), the long duration of eye examinations/procedures (> 15 min), touching patients’ eyelids during slitlamp examination, and the possibility of viral shedding and transmission in contact with ocular secretions. during the pandemic peak of covid19 in march 2020, a guidance was prepared by the knowledge management unit at the ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, correspondence to: zhale rajavi, md. ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, 23 paidar fard, bostan 9, pasdaran ave., tehran 16666, iran. e-mail: zhalerajavi@gmail.com received: 28-05-2020 accepted: 22-06-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7466 iran for ophthalmologists and eye care centers.[1] we also discuss on necessary precautions for the post-peak period starting from may 2020 and during the partial recovery phase of the covid-19 pandemic. characteristics • person to person transmission is caused by respiratory droplets produced by cough and sneezes of the patient. furthermore, the virus can spread when someone touches infected surfaces and then touches their nose, mouth, and eyes.[1, 2] • symptoms can manifest early (in 2 days) or late (within 14 days) after exposure to the virus. since the incubation period is between 5 and 7 days, the quarantine period is considered to be at least 14 days. • even a carrier without any respiratory symptoms can transmit the infection. • the virus could survive for 24 hours on cardboard surfaces and credit cards, while it lasts for two–three days on plastic and metal surfaces. • no vaccines have been produced against the virus so far and research projects in this field are in process. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: rajavi z, safi s, mohammadzadeh m. guidance for ophthalmologists and ophthalmology centers during the covid-19 pandemic. j ophthalmic vis res 2020;15:438–441. 438 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7466&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr letter; rajavi et al • currently, there is no specific drug for prophylaxis and treatment of this virus. risk factors the risk of covid-19 infection is higher in persons with the following characteristics: • age > 55 years • history of respiratory disease • history of renal disease • diabetes (hba1c > 7.6%) • history of hypertension • history of cardiopulmonary disease • history of organ transplant and use of immunosuppressive drugs general precautions it is very important to follow routine health instructions against this virus such as washing hands frequently, disinfecting surfaces, and using personal protection equipment (ppe).[1–6] recommendations for ophthalmologists in the epidemic peak of march 2020 • cancel previously scheduled appointments and avoid scheduling new appointments for future months. • provide facilities for telemedicine communications with patients for further consultations, answering their questions, and dose adjustment of their medications.[3, 5, 6] • in case of unavoidable in-person appointments, ask the patient during a phone contact about symptoms such as cough, sneezing, fever, dyspnea, and traveling to high-risk regions. if their answer is yes, avoid visiting the patient at least for three weeks.[1–6] • the patients should be examined alone (without companions) and if needed only one person can accompany elderly patients and children.[6] • avoid crowding in the waiting room while maintaining at least 3 m distance between patients. if possible, encourage patients to wait for the appointment outside the facilities (i.e., in their cars) and notify them when they should return to the office.[3, 6] • it is recommended to screen patients and their companions for fever and respiratory symptoms and ask them to wear masks and wash their hands before entering the examination room. suspicious cases should be referred to relevant healthcare centers.[6] • limit ophthalmic examinations to urgent cases such as retinal detachment, trauma, chemical contact, and severe ocular infections. it is recommended to perform the examination faster and also avoid unnecessary ones.[5, 6] • it is recommended to postpone non-urgent examinations and elective surgeries. • it is necessary for the ophthalmologists to wear masks during the examination and it is also essential for doctors and health caregivers to wash their hands after contact with every patient.[1–6] • in order to prevent exposure to patients’ respiratory droplets, it is recommended to use slitlamp shield.[1, 5] • avoid talking with patients during the examination. • to prevent the patient to patient transmission, single-dose drops are preferred.[6] • use applicators to examine the eyelids. • if possible, use non-contact tonometer to measure the intraocular pressure.[3, 6] if not possible, disinfect the tip of goldmann applanation as follows. first of all, wash the tonometer with water and soap, then allow it to dry. afterward, put almost 2 mm of its tip in the bleach-based solution with 5% concentration. isopropyl alcohol and ethyl alcohol are also frequently used; however, they are not as effective as the aforementioned method. • it is recommended to disinfect the examination room, all equipment including slit-lamp and its accessories after every visit.[3, 6] • use disposable gloves when sanitizing surfaces and equipment. • use bleach-based disinfectants (with a concentration of one spoon in a gallon of water) for disinfecting surfaces and use alcohol 70% for instruments. • if possible, use telemedicine communication such as video or telephone consultations.[3, 5] • when examining confirmed or suspected cases, ophthalmologists should wear n95 face masks, goggles or face-protective shield, gloves, gown, and disposable overshoes. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 439 letter; rajavi et al • if any of the hospitalized patients need urgent diagnostic or therapeutic measures, in order to avoid patient transport, it is recommended to perform necessary procedures at the host hospital. if further examinations or urgent surgery is needed, refer the patient to an equipped ophthalmic center. recommendations for ophthalmic centres in the epidemic peak in march 2020 • it is recommended that managers assure their healthcare workers that all clients are going to be screened on arrival.[5] • managers should monitor cancelation of routine examinations and elective procedures. also, they should prevent companions from entering the center and keep the waiting rooms uncrowded. if necessary, each patient may only have one companion who should be screened in a similar manner as patients.[3, 6] • provide facilities for telemedicine consultations through phone calls, video conferences, and social networks.[3, 5] • healthcare personnel working hours should be scheduled to minimize work fatigue.[5] • educate personnel to distinguish and isolate high-risk patients. • educate and monitor the process of disinfection of ophthalmic instruments, surfaces, chairs, and elevator handles regularly.[3, 6] • give leave to non-essential personnel in each working shift. • provide enough disinfectants including soap, tissue paper, masks, disposable gloves, 70% alcohol, disinfectant gel, and thermometers for patients and healthcare workers.[1–6] • supply slit-lamp shields, goggles, and counter shields.[3, 5] • administrate social distancing while in selfservice dining rooms and handover foods in packages.[3, 6] recommendations for ophthalmologists and ophthalmic centres during the post-peak period all practitioners should follow these recommendations until food and drug administration (fda)-approved treatments and/or vaccines for covid-19 are available: • respect social distancing. • both patients and healthcare workers should utilize face masks. • maintain a lower in-office appointment numbers than that in the pre-covid-19 period. • lengthen the turnover time in the operating room. • consider cataract surgery as a semi-urgent surgery, not elective, when the patient cannot drive or work or has a risk of falling. • it is recommended to test ophthalmologists, health caregivers, and patients prior to elective visits and surgeries. the tests and their characteristics are: rt-pcr which is usually done on nasopharyngeal swab specimens can be positive even after 35 days since the onset of symptoms. the specificity of the sars-cov-2 antibody test is 99.8% and has no cross-reactivity to other coronaviruses. a positive serology test shows recent infection. however, the virus can shed for at least five weeks from the onset of the infection. the duration and degree of protection of the igg antibody response from reinfection are unknown. in regions where the prevalence of covid-19 is low, positive serologic tests, without prior covid19 (rt-pcr) positive test, is more probable to be an artifact or the testing error rather than true infections. a rapid antigen detection test is available but is more probable to report false-negative results and needs a fluorescent immunoassay analyzer to be acceptable. • in the case of in-office procedures that necessitate close interaction between the surgeon and patients, wearing surgical masks for both patients and surgeons is recommended. surgeons are also encouraged to wear eye protection and n95 masks. • during procedures needing general anesthesia (ga), caregivers without n95 mask should remain out of the operating room throughout intubation/extubation. furthermore, for procedures with monitored anesthesia/conscious sedation, the patient should wear a surgical mask. due to prolonged physical proximity between the ophthalmologist and the patient during surgery, it is recommended for the surgeon to wear an n95 mask. 440 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 letter; rajavi et al as time goes by, ophthalmologists will be required to perform routine in-office procedures and examine patients who have recovered or are recovering from covid-19. due to prolonged viral shedding (even reported for up to 37 days), it is recommended to repeat rt-pcr testing for patients who are being scheduled for operation < 6 weeks after their diagnosis (except for emergency cases). if the repeat test is positive, the patient should wear a surgical mask and the surgeon should wear an n-95 mask, gown, and eye protection. acknowledgements we appreciate the scientific committee of the iranian society of ophthalmology for their valuable comments and advice on this guidance. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. sallet g. update on covid-19 situation in belgium from dr. guy sallet [internet]. euro times; 2020 [accessed march 24, 2020]. available from: https: //www.eurotimes.org/update-on-covid-19-situation-inbelgium-from-dr-guy-sallet/. 2. the college of optometrists. coronavirus (covid-19) pandemic: guidance for optometrists [internet]. the college of optometrists; 2020 [accessed march 24, 2020]. available from: https://www.college-optometrists. org/the-college/media-hub/news-listing/coronaviruscovid-19-guidance-for-optometrists.html. 3. cdc, who. important coronavirus updates for ophthalmologists [internet]. american academy of ophthalmology; 2020 [accessed march 24, 2020]. available from: https://www.aao.org/headline/alertimportant-coronavirus-context. 4. cos prc. cos and acupo guidelines for ophthalmic care during covid-19 pandemic [internet]. cos prc; 2020 [accessed march 20, 2020]. available from: https://www.cosprc.ca/resource/guidelines-forophthalmic-care/. 5. coronavirus rcophth– summary of key actions [internet]; 2020 [accessed march 20, 2020]. available from: https://www.rcophth.ac.uk/wp-content/uploads/2020/03/ coronavirus-rcophth-key-points-march-19th.pdf. 6. nuijts rmma. escrs update on covid-19 [internet]. euro times; 2020 [accessed march 19, 2020]. available from: https://www.eurotimes.org/a-message-from-theescrs-president-on-covid-19/. accessed: march 19, 2020. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 441 https://www.eurotimes.org/update-on-covid-19-situation-in-belgium-from-dr-guy-sallet/ https://www.eurotimes.org/update-on-covid-19-situation-in-belgium-from-dr-guy-sallet/ https://www.eurotimes.org/update-on-covid-19-situation-in-belgium-from-dr-guy-sallet/ https://www.college-optometrists.org/the-college/media-hub/news-listing/coronavirus-covid-19-guidance-for-optometrists.html https://www.college-optometrists.org/the-college/media-hub/news-listing/coronavirus-covid-19-guidance-for-optometrists.html https://www.college-optometrists.org/the-college/media-hub/news-listing/coronavirus-covid-19-guidance-for-optometrists.html https://www.aao.org/headline/alert-important-coronavirus-context https://www.aao.org/headline/alert-important-coronavirus-context https://www.cosprc.ca/resource/guidelines-for-ophthalmic-care/ https://www.cosprc.ca/resource/guidelines-for-ophthalmic-care/ https://www.rcophth.ac.uk/wp-content/uploads/2020/03/coronavirus-rcophth-key-points-march-19th.pdf https://www.rcophth.ac.uk/wp-content/uploads/2020/03/coronavirus-rcophth-key-points-march-19th.pdf https://www.eurotimes.org/a-message-from-the-escrs-president-on-covid-19/. https://www.eurotimes.org/a-message-from-the-escrs-president-on-covid-19/. original article serum fibroblast growth factor 21 in patients with and without pterygia gholamhosein yaghoobi1, md; saeed shokoohi-rad2, md; hamid jafarzadeh2, md; elham abdollahi3, md 1ophthalmology department, birjand university of medical sciences, valiasr hospital, birjand, iran 2eye research center, mashhad university of medical sciences, mashhad, iran 3birjand university of medical sciences, birjand, iran orcid: saeed shokoohi-rad: http://orcid.org/0000-0001-5554-4230 gholamhosein yaghoobi: http://orcid.org/0000-0003-0510-1118 abstract purpose: pterygium is a common fibro-vascular-related eye disease. the fibroblast growth factor 21 (fgf21) helps reduce neovascularization. previous studies have shown that the serum level of fgf21 correlates with vascular eye diseases such as diabetic retinopathy and retinopathy of prematurity. in this study, the serum fgf21 is compared in patients with and without pterygium. methods: this descriptive-analytical cross-sectional study examines individuals with pterygium who visited the ophthalmology clinic of khatam-al-anbia hospital in mashhad, iran, during 2017–2018. control subjects were selected from healthy people without pterygium disease. patients with a history of acute illness, chronic liver and kidney disease, diabetes, cancer, malnutrition and drug use, women who were pregnant or breastfeeding, and subjects who were taking anticonvulsants or glucocorticoids were excluded as these may affect insulin and glycosuria levels. sixty people (30 in each group) were chosen using the convenient sampling method. intravenous blood samples were taken from all patients. after preparing the patients, the freeze was checked using the enzyme-linked immunosorbent assay (elisa) method after samples had been taken. data were analyzed by spss using an independent t-test, mann–whitney, chi-square, kruskal–wallis, and kolmogorov–smirnov tests (𝛼 = 0.05). results: the serum fgf21 levels were 319.09 ± 246.93 pg/ml and 608.88 ± 449.81 pg/ml (p = 0.005) in the pterygium group and control subjects, respectively. the average serum fgf21 was 281.55 ± 40.74 pg/ml in males and 361.375 ± 10.298 pg/ml in females in the pterygium group. the difference was not statistically significant (p = 0.19) conclusion: our study showed that fgf21 levels were lower in patients with pterygium than the control subjects to a statistically significant level. keywords: fibroblast; growth factor 21; pterygium; serum levels j ophthalmic vis res 2020; 15 (1): 38–44 correspondence to: saeed shokoohi-rad, md. eye research center, mashhad university of medical sciences, mashhad, iran. e-mail: shokoohirads@gmail.com received: 14-10-2018 accepted: 11-06-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i1.5940 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: yaghoobi g, shokoohi-rad s, jafarzadeh h, abdollahi e. serum fibroblast growth factor 21 in patients with and without pterygia. j ophthalmic vis res 2020;15:38–44. 38 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i1.5940&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr serum fgf 21 levels in patients with pterygia; yaghoobi et al introduction pterygium thickens on the bulbar conjunctiva as a prominent triangular mass and extends to the cornea. this condition involves degeneration of the elastoid collagen and invades the cornea with subepithelial fibrovascular tissue. this disease occurs in specific geographical zones with varying prevalence; with outdoor work increasing its incidence by 1.5 times. the reason for this is unknown. generally, pterygium is considered a trivial problem unless it adversely affects the visual axis, which is dependent on its location. however, it can be concerning for patients due to its unusual and inflammatory appearance.[1, 2] the decision to undergo surgery varies according to the growth speed of the mass and the degree of astigmatism. it is recommended to avoid surgery for only the cosmetic reasons.[3] despite numerous methods for treating pterygium, there is a 30–70% recurrence rate, which drives ocular surgeons to use adjunct medicines.[3] the fibroblast growth factor (fgf) group includes 22 members, each of which is divided into seven subfamilies based on homology and phylogeny. the subgroups of fgf19 including fgf15, fgf21, and fgf23 play a significant role in endocrine performance and metabolizing carbohydrates and lipids.[4] growth factors play an important role in many ocular diseases. in a study on mice, the administration of fgf21, which is a member of this family, reduced angiogenesis through adiponectin. in doing so, fgf21 increases adiponectin and as a result, decreases tnf𝛼.[5, 6] the serum level of fgf21 is reduced in diabetes type i but is increased in diabetes type ii. the unusual increase of fgf21 in diabetes type ii is a compensatory protective response[7] that induces hypoglycemia and improves sugar metabolism in the body.[8–10] recent studies have indicated that serum fgf21 is lower in patients with type i diabetes mellitus and in neonates with retinopathy of prematurity compared to a healthy control group.[8, 10, 11] moreover, some studies indicated that the administration of fgf21 reduced ldl, triglycerides, and cholesterol and increased hdl.[9] hence, fgf21 has a significant impact on improving obesityand diabetes-related complications.[8] considering the prevalence of pterygium, the fibrovascular nature of pterygium, the protective effects of fgf21 on angiogenesis, and the lack of published studies so far, the present researchers decided to compare the serum fgf21 in the blood samples of patients with and without pterygium. methods the study population included patients with clinical signs of pterygium who had presented to the ophthalmology clinic of khatam-al anbia hospital in mashhad, iran, during 2017–2018. all volunteered to participate in the study, were not under any drug regimen, and had no specific disease. the control group included patients without pterygium who presented to the aforementioned clinic and accepted to participate in the study. they also were not under any drug regimen, had no underlying disease, and were matched for age and gender with the case group [table 1]. patients who did not wish to participate or had a history of acute illness, chronic liver and kidney disease, diabetes, cancer, malnutrition, drug use, were pregnant, breastfeeding, or were taking anticonvulsants or glucocorticoids were excluded as these may affect insulin and glycosuria levels. participants were selected using the convenient sampling method. patients diagnosed with pterygium by an ophthalmologist were assigned to the case group. the same number of subjects who matched the case group in terms of age and gender were assigned to the control group. given the lack of any similar study, we used a sample volume of 30 patients per group as a pilot study. having selected the case and control subjects, 5 cc of venous blood was taken by a phlebotomist from the radial vein of each participant after fasting for 12 h. the blood samples were first centrifuged for 20 min at 3000 rpm, and the overlying serum was isolated. care was taken to have samples that were not severely hemolyzed, blurred, lipemic, or infected with microbes. the isolated sera were divided into small portions and kept at –20∘c until the testing began. the samples were examined using the enzyme-linked immunosorbent assay (elisa) method with special kits for human studies (china crystaldi co., purchased from pardisa tebazema co., mashhad, iran). then, the total serum rate of fgf21 was compared between the two groups. as there is a relationship between fgf21 and metabolic journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 39 serum fgf 21 levels in patients with pterygia; yaghoobi et al table 1. comparison of mean age and gender in pterygium and control groups group pterygium patients control patients independent t-test variable mean ± sd mean ± sd t = 1.8 age 42.21 ± 12.32 38.28 ± 10.83 p = 0.08 gender x2 = 0.27 male 17(56.7) 15(50.0) female 13(43.3) 15(50.0) total 30(100.0) 30(100.0) p = 0.6 sd, standard deviation table 2. comparison of mean serum fgf21 in patients with pterygium in terms of gender group male female mann–whitney test variable mean ± sd mean ± sd serum fgf21 281.55 ± 40.74 361.375 ± 10.298 z = 2.95 p = 0.198 fgf, fibroblast growth factor; sd, standard deviation factors like cholesterol and triglycerides, these factors were also measured and analyzed. the data were analyzed with spss using the chisquare and mann–whitney tests (𝛼 = 0.05). the two groups were matched for age and gender using the kruskal–wallis and mann–whitney tests, respectively. as the fgf21 data was not normally distributed, the nonparametric inconsistency test of mann–whitney was used. the required data were collected using a researchermade questionnaire developed based on our research goals. this checklist included items on their history with pterygium, age group, gender, and serum level of fgf21. the research proposal was approved by the research council of the school of medicine and the committee of ethics in human research at the birjand university of medical sciences. the research goals and procedures were thoroughly discussed with each patient and assured they would remain anonymous and that their information would be kept confidential. informed written consent was obtained from each patient. the participants could leave the study at any stage, with this not affecting their treatment. results this study consisted of 60 participants including 30 patients with pterygium and 30 healthy individuals forming the control group. no participants had any relevant medical history or were taking any medications that would impact our study’s outcomes. in the pterygium group, 96.7% of the patients had pterygium in the ocular nasal zone, 43.3% of patients had only one affected eye, while for the remaining 56.7%, both eyes were affected. patients with diabetes mellitus were excluded from the study. this was because it has been shown that the serum fgf21 level has a positive and negative correlation with type 2 and type 1 diabetes mellitus, respectively. regarding the comparison of serum fgf21 in patients with and without pterygium, the results of the mann–whitney test showed a statistically significant difference in the mean of the serum fgf21 between the pterygium (319.09 ± 246.93) and control (608.88 ± 449.81) groups (p = 0.005). moreover, regarding the comparison of serum fgf21 in pterygium patients in terms of gender, 40 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 serum fgf 21 levels in patients with pterygia; yaghoobi et al table 3. comparison of mean cholesterol, creatinine, urea, sgot, sgpt, hdl, and ldl between the pterygium and control groups group pterygium patients control patients independent t–test / mann–whitney test variable mean ± sd mean ± sd cholesterol 206.86 ± 50.77 155.53 ± 32.15 t = 4.67 p < 0.0001 triglyceride 138.66 ± 102.83 98.90 ± 50.52 z = 2.17 p = 0.03 ldl 101.71 ± 30.62 76.00 ± 22.26 t = 3.60 p = 0.001 hdl 48.17 ± 22.03 57.33 ± 33.7 z = 1.28 p = 0.2 creatinine 0.92 ± 0.18 0.95 ± 0.14 z = 1.28 p = 0.2 urea 28.07 ± 7.94 24.43 ± 6.86 t = 1.58 p = 0.07 sgot 26.58 ± 9.96 21.96 ± 6.90 z = 1.67 p = 0.09 sgpt 28.15 ± 17.14 23.21 ± 9.81 z = 0.77 p = 0.42 hdl, high-density lipoprotein; ldl, low-density lipoproteins; sd, standard deviation; sgot, serum glutamic-oxaloacetic transaminase the mann–whitney test indicated no significant difference between males (281.55 ± 40.74) and females (361.375 ± 10.298) (p = 0.198) [table 2]. a regular diet one week before the sampling session was enforced to more accurately evaluate the lipid serum levels after a 12-h fasting period. an independent t-test revealed a significant difference in the mean cholesterol levels between the cases (206.86 ± 50.77) and controls (155.53 ± 32.15), being significantly higher in patients with pterygium (p < 0.0001). the corresponding figures for ldl were 101.71 ± 30.62 and 76.00 ± 22.26 (p = 0.001). the results of the mann–whitney test further demonstrated a significant difference in triglyceride levels in patients with pterygium (138.66 ± 102.83) compared to the control group (98.90 ± 50.52; p = 0.03); however, there was no significant difference in terms of the hdl levels between the two groups (48.17 ± 22.0 and 57.33 ± 33.7, respectively; p = 0.2). liver and kidney functions were also assessed, as fgf21 secretes from and exerts through these two organs, respectively. the mann–whitney test suggested no significant difference in creatinine levels between the pterygium (0.92 ± 0.18) and control (0.95 ± 0.14) groups (p = 0.2). an independent t-test showed no significant difference in the urea level between the two groups (28.07 ± 7.94 and 24.43 ± 6.86, respectively; p = 0.07). the same test suggested no significant difference in the serum glutamic–oxaloacetic transaminase (sgot) and serum glutamic–pyruvic transaminase (sgpt) levels between the case and control groups (p = 0.09 and p = 0.42, respectively) [table 3]. discussion our findings showed a significant difference in serum fgf21 between the pterygium and control groups. the serum fgf21 was significantly lower in patients with pterygium compared to non-pterygium patients (p = 0.005). fibrovascular proliferation, along with several inflammatory factors, are important in pterygium pathogenesis. increased vascular endothelial growth factor journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 41 serum fgf 21 levels in patients with pterygia; yaghoobi et al (vegf) levels have been reported in immunohistological studies, with bevacizumab being used to improve the outcomes and reduce recurrences of pterygium.[12] however, fgf21 acts independently of vegf. our findings regarding the effects of fgf21 on inhibiting angiogenesis are consistent with the results of the study by fu et al in which they observed the inhibition of angiogenesis by systemically administering this factor to mice. this inhibitory effect was exerted through adiponectin and tnf𝛼 and was seen to be independent of vegf.[6] in humans, the administration of fgf21 increases adiponectin in a dose-dependent form.[13] low levels of adiponectin in human blood circulation may be associated with neovascularization-related diseases in the eyes.[14, 15] our results are consistent with the protective effects of this factor in neovascularization-related eye diseases, as described by previous studies. chavez et al compared the serum fgf21 in thin, fat, fasting blood sugar impaired and diabetic patients and found that people with type ii diabetes had higher serum fgf21 compared to other groups, linking this to the status of insulin resistance.[16] also, in a study by kralisch et al, the mean concentration of serum fgf21 in patients with type ii diabetes mellitus was 2.1 times higher compared to the healthy controls.[17] the level of this factor decreases in type i diabetes as it is synthesized in the liver and pancreas and people with type i diabetes have impaired pancreas function. the increased level of fgf21 in type ii diabetes is due to the compensatory effect induced by insulin resistance in these patients.[18] therefore, despite the beneficial effects of this factor on lipid metabolism[9] and reducing angiogenesis, it is asserted that tissue resistance to fgf21 in obesity[19], fatty liver, and related metabolic disorders[19, 20] are responsible for an increased serum level of fgf21. the same pathogenesis is suggested regarding insulin function in type 2 diabetes mellitus. this is similar to type 1 diabetes mellitus in which auto-immune degeneration of the pancreatic cells results in decreased insulin levels. in type 2 diabetes mellitus, the tissue resistance to insulin leads to hyperinsulinemia, and the physiologic level of insulin is not effective in controlling the serum glucose level.[20] given that the serum level of this factor is affected by various types of diabetes, people with diabetes were excluded from our study. our findings further showed a significant difference in the mean cholesterol level, mean triglyceride level, and mean ldl level between the pterygium and control patients. the means of these three indices were significantly higher in patients with pterygium compared to the control group. this study took into account the probability of such metabolic changes in pterygium patients. in line with our results, malekifar et al[21] showed that pterygium is significantly related to ischemic heart disease and obesity. accordingly, it can be suggested that pterygium is not an isolated disease and can present as a metabolic condition.[22] however, further studies are needed to confirm this idea. other observations in south korea revealed a relationship between obesity and pterygium. they showed that hyperlipidemia and obesity are more prevalent in patients with pterygium due to lower fgf21 serum levels.[23] moreover, consistent with our findings, a study by wente et al showed that fgf21 reduced lipid levels and improved lipid metabolism in rats.[24] in the study by zhang et al, the administration of fgf21 to type i diabetics diminished apoptosis, improved lipid metabolism, reduced fat accumulation in the organs, and decreased oxidative stress. overall, complications in these patients were reduced.[8] in the current study, the reduced level of fgf21 in patients with pterygium was associated with impaired lipid metabolism. if future studies confirm this finding, pterygium can be considered a cardiovascular risk factor. the serum fgf21 level was not significantly different between males and females in our study, while in zibar’s study, the serum fgf21 was higher in type i diabetic females compared to males. however, the serum fgf21 was not different between males and females in the healthy subjects, a finding that is consistent with our results.[25] we found no significant difference between the liver enzymes, urea, and creatinine between the two study groups. since fgf21 is produced by the liver and excreted by the kidney, the difference of this factor between the two groups does not appear to be related to liver and kidney function. in panchapak’s study conducted in australia on 3,564 patients aged 49 years or older, 7.3% 42 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 serum fgf 21 levels in patients with pterygia; yaghoobi et al of the patients had pterygium and 69.5% had pinguecula, with the prevalence being significantly higher among males than females.[26] the findings demonstrated that in more than 96% of the patients, the pterygium site was the ocular nasal zone. this is consistent with our study, in which pterygium was more likely to occur in the ocular nasal zone. most patients had unilateral pterygium. overall, 43.3% of patients were affected with pterygium in only one eye and 56.7% in both eyes. finding appropriate pharmacological therapy options for patients who do not wish to undergo surgery is a significant priority.[27] it is hoped that some non-surgical treatment methods and prophylactic procedures will soon be introduced. regarding the high prevalence of cardiovascular disorders and its resulting mortality and morbidity, there is growing attention toward new cardiovascular risk factors such as inflammatory cytokines and hair growth on the external ear, even in younger adults. the results of this study and its association with obesity and ischemic heart disease as seen in previous studies, suggest that pterygium should be considered a cardiovascular risk factor.[28] if pterygium was included in cardiovascular screening tests, cardiovascular complications might be reduced. in conclusion, our findings suggest that low serum fgf21 in patients with pterygium affects the condition and may be a protective factor. in addition, impaired lipid metabolism should be taken into account in these patients. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. kumar s, singh r. pterygium excision and conjunctival autograft: a comparative study of techniques. oman j ophthalmol 2018; 11: 124–128. 2. rosen r. amniotic membrane grafts to reduce pterygium recurrence. cornea 2018;37:189. 3. oduntan o, masige k. a review of the role of oxidative stress in the pathogenesis of eye diseases. afr vis eye health 2011;70:191–199. 4. fukumoto s. actions and mode of actions of fgf19 subfamily members. endocr j 2008;55:23–31. 5. yang x, hu l, kang y, xu j, wang x, lin h, et al. positive correlations between and prediction of fgf21, adiponectin, leptin and npy concentrations in the cerebrospinal fluid of chinese subjects using back propagating artificial neural networks. int j clin exp med 2016;9:2121– 2129. 6. fu z, gong y, liegl r, wang z, liu c-h, meng ss, et al. fgf21 administration suppresses retinal and choroidal neovascularization in mice. cell rep 2017;18:1606–1613. 7. chen c, cheung bm, tso aw, wang y, law ls, ong kl, et al. high plasma level of fibroblast growth factor 21 is an independent predictor of type 2 diabetes: a 5.4-year population-based prospective study in chinese subjects. diabetes care 2011;34:2113–2115. 8. zhang j, weng w, wang k, lu x, cai l, sun j. the role of fgf21 in type 1 diabetes and its complications. int j biol sci 2018; 14(9): 1000–1011. 9. kharitonenkov a, adams ac. inventing new medicines: the fgf21 story. mol metabol 2014;3:221–229. 10. lin y, xiao y-c, zhu h, xu q-y, qi l, wang y-b, et al. serum fibroblast growth factor 21 levels are correlated with the severity of diabetic retinopathy. j diabetes res 2014; 2014: 929756. 11. fu z, wang z, liu c-h, gong y, cakir b, liegl r, et al. fibroblast growth factor 21 protects photoreceptor function in type 1 diabetic mice. diabetes 2018;67:974–985. 12. nuzzi r, tridico f. efficacy of subconjunctival bevacizumab injections before and after surgical excision in preventing pterygium recurrence. j ophthalmol 2017;2017:6824670. 13. gaich g, chien jy, fu h, glass lc, deeg ma, holland wl, et al. the effects of ly2405319, an fgf21 analog, in obese human subjects with type 2 diabetes. cell metabol 2013;18:333–340. 14. fu z, gong y, löfqvist c, hellström a, smith le. adiponectin in retinopathy. biochimica et biophysica acta (bba)-molecular basis of disease 2016;1862:1392–1400. 15. fu z, lofqvist ca, shao z, sun y, joyal j-s, hurst cg, et al. dietary 𝜔-3 polyunsaturated fatty acids decrease retinal neovascularization by adipose–endoplasmic reticulum stress reduction to increase adiponectin. am j clin nutr 2015;101:879–888. 16. chavez ao, molina-carrion m, abdul-ghani ma, folli f, defronzo ra, tripathy d. circulating fibroblast growth factor-21 is elevated in impaired glucose tolerance and type 2 diabetes and correlates with muscle and hepatic insulin resistance. diabetes care 2009;32:1542–1546. 17. kralisch s, fasshauer m. fibroblast growth factor 21: effects on carbohydrate and lipid metabolism in health and disease. curr opin clin nutr metabol care 2011;14:354– 359. 18. johnson cl, weston jy, chadi sa, fazio en, huff mw, kharitonenkov a, et al. fibroblast growth factor 21 reduces the severity of cerulein-induced pancreatitis in mice. gastroenterology 2009;137:1795–1804. 19. chui pc, antonellis pj, bina ha, kharitonenkov a, flier js, maratos-flier e. obesity is a fibroblast growth factor 21 (fgf21)-resistant state. diabetes 2010;59:2781–2789. 20. rabinowitz d, zierler kl. forearm metabolism in obesity and its response to intra-arterial insulin. characterization journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 43 serum fgf 21 levels in patients with pterygia; yaghoobi et al of insulin resistance and evidence for adaptive hyperinsulinism. j clin invest 1962;41:2173–2181. 21. malekifar p, esfandiari h, behnaz n, javadi f, azish s, javadi ma, et al. risk factors for pterygium in ilam province, iran. j ophthal vis res 2017; 12: 270–274. 22. andrikopoulos gk, alexopoulos dk, gartaganis sp. pseudoexfoliation syndrome and cardiovascular diseases. world j cardiol 2014; 6: 847–854. 23. nam ge, kim s, paik j-s, kim h-s, na k-s. association between pterygium and obesity status in a south korean population. medicine (baltimore) 2016;95:e5664. 24. wente w, efanov am, brenner m, kharitonenkov a, köster a, sandusky ge, et al. fibroblast growth factor-21 improves pancreatic 𝛽-cell function and survival by activation of extracellular signal–regulated kinase 1/2 and akt signaling pathways. diabetes 2006;55:2470–2478. 25. zibar k, blaslov k, bulum t, ćuća jk, smirčić-duvnjak l. basal and postprandial change in serum fibroblast growth factor-21 concentration in type 1 diabetic mellitus and in healthy controls. endocrine 2015;48:848–855. 26. panchapakesan j, hourihan f, mitchell p. prevalence of ptrygium and pinguecula: the blue mountains eye study. aust nz j ophtalmol 1998;26:s2–s5. 27. reda am, shaaban ymm, el-din sas. histopathological parameters in pterygia and significant clinical correlations. j ophthal vis res 2018;13:110. 28. ali ra, asadollah m, hossien ra. the role of unknown risk factors in myocardial infarction. cardiol res 2010;1:15–19. 44 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 original article sensitivity, specificity, and accuracy of color doppler ultrasonography for diagnosis of retinal detachment mohammadreza akhlaghi1, md; masoomeh zarei1, md; majid ziaei2, md; mohsen pourazizi1,3, md 1department of ophthalmology, isfahan eye research center, isfahan university of medical sciences, isfahan, iran 2nafis private imaging center, isfahan, iran 3pediatric inherited diseases research center, research institute for primordial prevention of non-communicable disease, isfahan university of medical sciences, isfahan, iran orcid: mohammadreza akhlaghi: https://orcid.org/0000-0002-5395-1809 mohsen pourazizi: https://orcid.org/0000-0002-9714-8209 abstract purpose: this study evaluated the sensitivity, specificity, and diagnostic accuracy of color doppler ultrasonography (cdus) in patients with suspected retinal detachment (rd) who underwent surgery. methods: in this prospective, observational clinical study, 65 eyes of 65 consecutive patients with suspected rd with opaque media were included. following a standardized protocol, cdus of the retina of the affected eye was performed. the sensitivity, specificity, and diagnostic accuracy of cdus were determined and compared to the findings during surgery. results: the mean age of patients (18 men and 47 women) was 52.36 years (range: 8–77 years). the sensitivity, specificity, and overall accuracy of ocular cdus were 91.3%, 88.1%, and 89.2%, respectively. the false-negative rate (negative cdus images but presence of rd at operation) was 3.1% (2/65) and the false-positive rate (positive cdus images but absence of rd at operation) was 7.7% (5/65). conclusion: cdus of the retina could be considered as a promising tool in the diagnosis of rd in patients with opaque media. keywords: color doppler ultrasonography; retina; retinal detachment j ophthalmic vis res 2020; 15 (2): 166–171 correspondence to: mohsen pourazizi, md. department of ophthalmology, isfahan university of medical sciences, isfahan 81496, iran. e-mail: m.pourazizi@yahoo.com received: 26-08-2017 accepted: 23-09-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i2.6733 introduction retinal detachment (rd) is a serious eye disease with the potential risk of blindness. it requires this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: akhlaghi m, zarei m, ziaei m, pourazizi m. sensitivity, specificity, and accuracy of color doppler ultrasonography for diagnosis of retinal detachment. j ophthalmic vis res 2020;15:166–171. 166 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i2.6733&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr color doppler ultrasonography for rd; akhlaghi et al immediate management to prevent permanent vision loss.[1, 2] accurate diagnosis of rd may be difficult in some cases and is important as it affects the prognosis and treatment plan.[3] it is recommended that ophthalmologists rely on their clinical skills, including indirect ophthalmoscopy and biomicroscopic examination of the fundus with slit lamp, for the diagnosis of rd in suspected cases.[1] in the presence of dense media opacities (e.g., corneal edema, hyphema, cataract, vitreous hemorrhages) with clinical suspicion of rd, the diagnosis may not be accurate, and poor visual prognosis can be expected if the ophthalmologists wait for the media to clear.[4, 5] moreover, the decision to perform surgery in all clinically suspected cases poses additional costs on patients and the healthcare system. therefore, alternative diagnostic modalities, such as ocular ultrasound, are required in this clinical situation.[6] gray-scale ultrasound can identify rd in suspected cases with dense media opacities.[7] although gray-scale ultrasound can differentiate rd from other membranous structures in the presence of opaque media, it has some limitations that may lead to a diagnostic dilemma.[6, 8] differentiating individual retinal layers is not possible on grayscale ultrasound so it may be difficult to accurately differentiate retinoschisis from rd.[9] the posterior hyaloid membrane or central vitreous gel are not usually attached to the optic disc and are visualized as structures with weaker echogenicity and more variable thickness, with a greater mobility than rd. however, differentiating rd from those structures in the posterior segment is difficult in cases of shallow or localized rd.[10, 11] in such cases, color doppler ultrasound (cdus) can play an important role in the diagnosis of rd by demonstrating blood flow in the detached retina. cdus helps ophthalmologists examine the retinal blood flow, even in the presence of dense ocular opacities preventing a direct view of the posterior segment.[12] the detached retina is seen on cdus as a curvilinear structure in the vitreous cavity with blood flow.[8, 12] therefore, cdus can play an additional and more reliable role in the diagnosis through visualization of flow signals in the detached retina.[8] however, despite cdus having several potential benefits, a limitation of the application of cdus in the diagnosis of rd is that the evidence of its diagnostic accuracy is scattered and limited. the aim of this study was to evaluate the clinical utility and diagnostic value of cdus in the detection of rd in patients with dense ocular opacities. methods patients and study design this prospective, observational clinical study was approved by the ethics committee of isfahan university of medical sciences. the study protocol adhered to the tenets of the declaration of helsinki. signed informed consent was obtained from participants prior to the study. we enrolled 65 eyes of 65 patients with opaque media who were candidates for ocular surgery to clear the media and repair rd if present (pars plana vitrectomy +/– phacoemulsification, with or without corneal graft, etc.). patients who were inoperable because of any medical, surgical, or general condition and those with a past or current history of tumors in the vitreous cavity were excluded. doppler ultrasound imaging on the day of enrollment, cdus of the eye was performed for all individuals by an expert radiologist trained in ultrasound of the retina using a cdus unit and 13-mhz linear array transducer, medison v20 (medison co. ltd., seoul, korea). the evaluation techniques have been described previously.[8] patients were examined in the supine position to avoid any pressure on the eye. sterile coupling gel was applied to the closed eyelids, with the examiner’s hand resting on the orbital margin to minimize pressure on the globe, and color flow images were obtained.[8] rd was described as visualization of a flow signal (presence of vascularity) along the detached retina, while vitreous membranes were described as lack of vascularity.[10] reference standard fundus examination during surgery was considered as the gold standard for the diagnosis of rd. the final clinical diagnosis of rd was made by two expert ophthalmologists (first and second authors) during surgery. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 167 color doppler ultrasonography for rd; akhlaghi et al figure 1. (left) the funnel-shaped membrane has been marked on the gray-scale b scan. (right) the figure shows arterial flow and retinal detachment. figure 2. (left) the gray-scale image of the horizontally scanned eye demonstrates central partial retinal detachment. (right) color doppler ultrasound reveals thick linear and spotty color signals. statistical analysis statistical analyses were performed by a statistician using the spss software, version 16.0 (spss, chicago, il, usa). sensitivity and specificity were calculated for diagnostic cdus, with the final clinical diagnosis during the operation as the reference standard. sensitivity was calculated as the proportion of patients with actual rd who had an abnormal retina on cdus. specificity was calculated as the proportion of patients with no actual rd who had a normal retina on cdus. accuracy was calculated as the proportion of patients whose rd status was correctly predicted using ultrasound. results in this study, we performed cdus for 65 eyes of 65 patients, including 18 men and 47 women, suspected with rd. the mean age of patients was 52.36 years (range: 8–77 years). vitreous hemorrhage, cataract, total hyphema, and corneal opacity were detected in 44 (67.7%), 12 (18.58%), 6 (9.2%), and 3 eyes, respectively. 168 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 color doppler ultrasonography for rd; akhlaghi et al figure 3. color doppler ultrasonography shows no flow in the membrane seen in the left figure, ruling-out rd. the avascular membrane has been marked in the right figure. of the 65 patients, rd was diagnosed in 26 (40%) patients on cdus and in 23 (35.4%) patients during vitrectomy. as for the type of rd, all patients had rhegmatogenous rd. the sensitivity, specificity, and overall accuracy of ocular cdus were 91.3%, 88.1%, and 89.2%, respectively. the false-negative rate (negative with cdus but positive with operation) was 3.1% (2/65) and the false-positive rate (positive with cdus but negative with operation) was 7.7% (5/65). false-positive cases included four cases of severe neovascular membrane in proliferative diabetic retinopathy and one case of posterior vitreous detachment. discussion the current study demonstrated that cdus is sensitive and specific for the diagnosis of rd in patients with dense ocular opacities. in most cases, gray-scale b-mode ultrasonography allows differentiation of a total rd from a vitreous membrane; however, this differentiation may be challenging in some situations.[4, 13, 14] cases of partial rd and vitreous membrane can share similar ultrasonographic features.[4, 5, 14] in patients with atypical findings on gray-scale ultrasound of shallow rd, cdus can play an additional and more reliable role in the diagnosis by enabling detection of blood flow in the detached retina.[13, 15] advantages of performing cdus to diagnose rd are that cdus can be a quick, noninvasive, and safe method for detecting total and partial rds. cdus enables ophthalmologists to examine ocular blood flow, even in the presence of dense ocular opacities preventing a direct view to the posterior segment of the eye.[12] a previous study at isfahan eye research center by ghanbari et al indicated the diagnostic data of gray-scale sonography as follows: sensitivity, 87.5%; specificity, 64.5%; and accuracy, 72.4%.[16] in the current study performed at the same center, the sensitivity, specificity, and overall accuracy of ocular cdus compared to surgical findings were 91.3%, 88.1%, and 89.2%, respectively. these differences can be explained by limitations of gray-scale ultrasound in detection of rd as previously mentioned. there is no quick, noninvasive, and safe gold standard for the diagnosis of rd. although bscan has the aforementioned characteristics, there are some limitations.[8, 16] studies examining changes in ocular blood flow velocities in rd are limited.[10] ido et al found the usefulness of cdus in the diagnosis of rd in the presence of hazy media.[10] similar to ours, in their study, the absence or presence of rd was confirmed during surgery. their study on 33 consecutive patients demonstrated a sensitivity of 92.3%, a specificity of 100%, a positive predictive value of 100%, a negative predictive value of 93.3%, journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 169 color doppler ultrasonography for rd; akhlaghi et al and an accuracy of 96.3%. in their study, all patients with blood flow on cdus were confirmed to have rd during surgery.[10] in the study by han et al, cdus showed a color signal in approximately 60% of rd cases.[8] wong et al reported the sensitivity of cdus to be 100%.[17] the sensitivity and specificity of ocular cdus were both approximately 90% in our study. the difference between these results can be explained by certain factors, including the type of rd, duration of detachment, coexisting pathologies, etc. the ability of cdus to demonstrate flow in vascular structures and subsequently yield the diagnosis of rd in patients with dense ocular opacities depends on factors including flow velocity, vessel size, depth of the lesion, scanner sensitivity, and operator control.[8] therefore, the sensitivity, specificity, and accuracy can be affected.[8] most longstanding rds are peripheral, not involving the posterior pole. a reason for the difference in results of similar studies in this field is the presence of longstanding rd. cdus has a lower ability to detect blood flow in the retinal periphery. this may be a possible explanation for the false-negatives of cdus.[8] despite several potential benefits, the interobserver variability could be a possible explanation for cdus not being routinely used in ophthalmic practice.[18] to increase the detectability of doppler signals, several kinds of ultrasound contrast agents can be used. in the study by han et al, the sensitivity of cdus to detect flow in rd increased from approximately 60% to 90% after intravenous contrast administration.[8] although a highly accurate diagnosis is achieved using contrast-enhancing agents, the procedure would be invasive. in our study, two patients who were negative for rd on cdus were diagnosed with rd based on surgical data. we did not find any meaningful difference between the characteristics of these patients and others, for example, regarding the type of rd. negative results on cdus but positive results during operation may occur in the presence of any ischemic event in the retinal vessels, including arterial and venous occlusions. of the false-positive cases in the current study, four cases were of severe neovascular membrane in proliferative diabetic retinopathy and one case was of posterior vitreous detachment. there were no cases of traction rd. the overall accuracy of cdus was approximately 90%. in the study by wong et al,[17] all patients with rd were diagnosed using cdus, consistent with our results. there are some limitations in the current study, including the relatively small sample size. relative afferent pupillary defects were not recorded in this study, and their relationship with other findings was not evaluated. failure to use contrast-enhanced cdus is another shortcoming of the current study. the lower ability of cdus to detect blood flow in the retinal periphery is an inherent limitation of the technique. the prospective nature of this study on the accuracy of cdus in diagnosing rd in eyes with dense ocular opacities and suspected rd is a strength of the current study. in conclusion, cdus helps in distinguishing between rd and vitreous membrane in eyes with opaque media when the results of b-scan sonography are inconclusive. large, prospective studies are required to confirm the greater accuracy of cdus compared to other modalities in the diagnosis of rd in these patients. financial support and sponsorship none. conflicts of interest there are no conflicts of interest. references 1. hollands h, johnson d, brox ac, almeida d, simel dl, sharma s. acute-onset floaters and flashes: is this patient at risk for retinal detachment? jama 2009;302:2243– 2249. 2. jacobsen b, lahham s, patel a, spann s, fox jc. retrospective review of ocular point-of-care ultrasound for detection of retinal detachment. west j emerg med 2016;17:196–200. 3. hoogewoud f, chronopoulos a, varga z, souteyrand g, thumann g, schutz js. traumatic retinal detachment– the difficulty and importance of correct diagnosis. surv ophthalmol 2016;61:156–163. 4. dietrich um. oead, part 3: diagnostic ultrasonography. in: gelatt kn, editor. veterinary ophthalmology. 4th ed. volume 1. hoboken, nj: blackwell publishing; 2007:507– 519. 5. spaulding k. eye and orbit. in: penninck d, anjou ma, editors. atlas of small animal ultrasonography. hoboken, nj: blackwell publishing; 2008:49–90. 170 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 color doppler ultrasonography for rd; akhlaghi et al 6. kerman bm, coleman dj. b-scan ultrasonography of retinal detachments. ann ophthalmol 1978;10:903–911. 7. blaivas m, theodoro d, sierzenski pr. a study of bedside ocular ultrasonography in the emergency department. acad emerg med 2002;9:791–799. 8. han ss, chang sk, yoon jh, lee yj. the use of contrastenhanced color doppler ultrasound in the differentiation of retinal detachment from vitreous membrane. korean j radiol 2001;2:197–203. 9. agarwal a, fan s, invernizzi a, do dv, nguyen qd, harms nv, et al. characterization of retinal structure and diagnosis of peripheral acquired retinoschisis using high-resolution ultrasound b-scan. graefes arch clin exp ophthalmol 2016;254:69–75. 10. ido m, osawa s, fukukita m, sugimoto m, wakitani y, ito y, et al. the use of colour doppler imaging in the diagnosis of retinal detachment. eye 2007;21:1375–1378. 11. kaiser hj, schotzau a, flammer j. blood-flow velocities in the extraocular vessels in normal volunteers. am j ophthalmol 1996;122:364–370. 12. dimitrova g, kato s. color doppler imaging of retinal diseases. surv ophthalmol 2010;55:193–214. 13. santos l, capeans c, gonzalez f, lorenzo j, codesido j, salorio ms. ocular blood flow velocity reduction after buckling surgery. graefes arch clin exp ophthalmol 1994;232:666–669. 14. gonzalez em, rodriguez a, garcia i. review of ocular ultrasonography. vet radiol ultrasound 2001;42:485– 495. 15. stefanczyk l, orawiec b, gralek m, majka r, niwald a. [usefulness of color doppler ultrasonography in diagnosis of retinal detachment]. klin oczna 1996;98:287–290. 16. ghanbari h, dehghani a, akhlaghi m, naderi bani a, hoghooghi a. specifity and sensitivity of ocular sonography in the diagnosis of retinal detachment with vitreous hemorrhage. bina j ophthalmol 2008;13:432–436. 17. wong ad, cooperberg pl, ross wh, araki dn. differentiation of detached retina and vitreous membrane with color flow doppler. radiology 1991;178:429–431. 18. williamson th, baxter gm. central retinal vein occlusion, an investigation by color doppler imaging. blood velocity characteristics and prediction of iris neovascularization. ophthalmology 1994;101:1362–1372. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 171 original article intraocular injection of stivant® (a biosimilar to bevacizumab): a case series ahmad mirshahi, md; alireza lashay, md; hamid riazi-esfahani, md; nazanin ebrahimiadib, md hassan khojasteh, md; fariba ghassemi, md; fatemeh bazvand, md; alireza khodabande, md ramak roohipour, md; elias khalili pour, md; hooshang faghihi, md translational ophthalmology research center, farabi eye hospital, tehran university of medical sciences, tehran, iran orcid: ahmad mirshahi: https://orcid.org/0000-0002-4890-5023 elias khalili pour: https://orcid.org/0000-0001-8123-4375 hooshang faghihi: https://orcid.org/0000-0001-9371-4915 abstract purpose: to report the results of intravitreal injection of a bevacizumab biosimilar called stivant®. methods: this prospective interventional case series was conducted on eyes with neovascular age-related macular degeneration (namd), retinal vein occlusion (rvo), and diabetic macular edema (dme). stivant® was injected in three consecutive months and changes in best-corrected visual acuity (bcva) and central macular thickness (cmt) were measured at baseline and monthly up to one month after the third injection. results: three hundred and eighty-five eyes with dme (234 eyes, 61%), namd (87 eyes, 22%), and macular edema secondary to rvo (64 eyes, 17%) were enrolled. the mean ± standard deviation age of the patients was 61.7 ± 7.20 years. the mean bcva and cmt changed from 0.63 ± 0.3 to 0.51 ± 0.3 logmar (p = 0.12 ) and from 420.4 ± 47.3μm at baseline to 316.7 ± 50.6 μm (p < 0.001) in the dme group; from 0.79 ± 0.3 to 0.68 ± 0.3 logmar (p = 0.19) and from 376.1 ± 31.7 μm to 303 ± 31.3 μm (p = 0.019) in the namd group; and from 0.81 ± 0.4 to 0.63 ± 0.4 logmar (p = 0.05) and from 424.21 ± 18 μm to 303.4 ± 18.8 μm (p < 0.001) in the rvo group, respectively. conclusion: our limited experience showed that the intravitreal injection of stivant® was well tolerated. although the results of this case series showed relative improvement in cmt one month after the last injection of stivant®, bcva improvement was statistically significant only in the rvo group. this would be essential to design a randomized clinical trial to evaluate the non-inferiority of stivant® in comparison to bevacizumab. keywords: stivant®; bevacizumab; anti-vegfs; anti-vascular endothelial growth factors; diabetic macular edema; retinal vein occlusion; neovascular age-related macular degeneration j ophthalmic vis res 2021; 16 (1): 28–33 correspondence to: elias khalili pour, md; translational ophthalmology research center, farabi eye hospital, tehran university of medical sciences, tehran 13366, iran. e-mail: ekhalilipour@gmail.com hooshang faghihi, md. translational ophthalmology research center, farabi eye hospital, tehran university of medical sciences, tehran 13366, iran. email: faghihih@hotmail.com received: 01-09-2019 accepted: 06-11-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8248 introduction introduction of anti-vegfs has revolutionized the management of numerous retinal diseases over the past decade. they turned out to be this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: mirshahi a, lashay a, riazi-esfahani h, ebrahimiadib n, khojasteh h, ghassemi f, bazvand f, khodabande a, roohipour r, khalili pour e, faghihi h. intraocular injection of stivant® (a biosimilar to bevacizumab): a case series. j ophthalmic vis res 2021;16:28–33. 28© 2021 mirshahi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8248&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr a case series of stivant® intraocular injection; mirshahi et al the first-line treatment for diabetic macular edema (dme), neovascular age-related macular degeneration (namd), and retinal vein occlusion (rvo)-associated macular edema. among various anti-vegf drugs, the off-label intravitreal injection of bevacizumab [avastin; genentech/roche /basel, switzerland] as a less expensive and effective alternative is the preferred choice in many countries[1]. results of clinical trials such as catt (comparison of amd treatments trials), manta (multicentre anti-vegf trial in austria), ivan (the inhibition of vegf in age-related choroidal neovascularization), lucas (lucentis compared to avastin study), and gefal (groupe d’etude français avastin versus lucentis ) showed the noninferiority of bevacizumab in comparison to ranibizumab with the same safety profile[2–6]. besides, the 20 times lower cost of bevacizumab compared to ranibizumab and aflibercept makes this agent the most common anti-vegfs used for intravitreal injection[7]. the world health organization (who) defines biosimilar drugs as a biotherapeutic product that is similar in terms of quality, safety, and efficacy to an already licensed reference biotherapeutic product. biosimilars have the potential to reduce the healthcare costs relative to reference biologics, thereby increasing the treatment access [8–10]. stivant® (cinnagen co., iran) has been developed as a biosimilar to avastin®. both stivant® and the reference product are humanized monoclonal antibodies of the igg1 subclass. safety of this product has already been shown during an animal study conducted by our team on new zealand albino rabbits. intravitreal injection of 2.5 mg stivant® did not show any adverse effect on retinal function evaluated by electroretinography (erg). additionally, histologic examination of the enucleated globes did not reveal any visible histopathologic changes at the cellular level[8]. herein, we aimed to share our experience with visual and anatomical outcomes of intravitreal injection of stivant® in a case series. methods this prospective interventional case series was approved by the institutional review board of tehran university of medical sciences. written informed consent was obtained from participants before enrollment. patients with neovascular amd (namd), dme, and macular edema due to rvo were recruited from september 2018 to february 2019 at farabi eye hospital, tehran, iran. they were either treatment-naïve or had not receive the last intravitreal injection during the past six months. the exclusion criteria of the study included previous vitrectomy, signs of any ocular infection, history of cerebrovascular accident or myocardial infarction, pregnancy, or breastfeeding. all patients were scheduled for three monthly injections of stivant®. complete ocular examinations were performed by ophthalmologists and included measurement of best-corrected visual acuity (bcva) with the snellen chart being converted into logmar, applanation tonometry, slit-lamp biomicroscopy of the anterior and posterior segments, and indirect ophthalmoscopy at baseline and on days 1, 7, and 30 after each injection. spectral-domain optical coherence tomography (sd-oct) (rtvuexr; optovue, inc., fremont, ca, usa) imaging was obtained at baseline and 30 days after each injection for all patients. parameters for safety included severe inflammation or endophthalmitis and iop > 21 mm hg, retinal hemorrhages, retinal vasculitis, and retinal necrosis or detachment within three months post-injection. systemic evaluations at baseline and on days 1, 7, and 30 included a detailed medical history during which patients were asked about current medications and any systemic adverse events (aes), thromboembolic or neurological issues and measurement of arterial blood pressure. primary outcome measures were changes in cmt and bcva. secondary outcome measures comprised any ocular or systemic aes. intravitreal injection stivant® is manufactured in a vial with a concentration of 25 mg/ml identical to the reference product (avastin). intravitreal injections were performed in the operating room under the sterile situation. topical anesthetic drops were given first and then a lid speculum was inserted. after the application of povidone iodine 5% into the conjunctival sac for about 3 min, intravitreal injection of 1.25 mg/ 0.05 ml stivant® was performed with a 29-gauge needle (1 ml tuberculin syringes; dispovan) through the pars journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 29 a case series of stivant® intraocular injection; mirshahi et al plana 4 mm and 3.5 mm posterior to the limbus in phakic and pseudophakic eyes, respectively. the needle was carefully removed using a sterile cotton applicator to prevent reflux. pre-injection topical antibiotics were not ordered, but all patients received topical chloramphenicol 0.5% four times a day for five days after the injection. statistical analysis data were entered into a microsoft excel sheet and analyzed using the spss version 22 software (ibm). categorical data were represented in the form of frequencies and proportions. chi-square was used as the test of significance. continuous variables were summarized by count, mean, standard deviation, median, and minimum and maximum. bcva and cmt data were analyzed using two-tailed paired t-tests. p ≤ 0.05 was considered statistically significant. results three hundred and eighty-five eyes of 351 patients with dme (234 eyes, 61%), namd (87 eyes, 22%), and macular edema secondary to rvo (64 eyes, 17%) were enrolled. intravitreal injection of stivant® from separate glass vials was performed in both eyes of 34 patients with bilateral dme. the mean age of the patients was 61.7 ± 7.20 years. out of the 385 injections, 212 (55.1%) were performed in male patients. of the 385 eyes, 197 and 188 were phakic and pseudophakic, respectively. bcva findings the mean bcva improved from 0.67 ± 0.41 logmar at baseline to 0.57 ± 0.37 logmar one month after the last injection (p = 0. 10). the mean bcva improved from 0.63 ± 0.3 to 0.51 ± 0.3 logmar (p = 0.12) in the dme group; from 0.79 ± 0.3 to 0.68 ± 0.3 logmar (p = 0.19) in the namd group; and from 0.81 ± 0.4 to 0.63 ± 0.4 logmar (p = 0.05) in the rvo group [figure 1]. central macular thickness findings the mean cmt in all groups improved consistently from baseline through consequent injections. although there was a trend in decreasing cmt after the first injection, the amount of change was not statistically significant until the third injection. the mean cmt of 425 ± 54.9 μm at baseline decreased to 312.20 ± 40.81 μm one month after the last intravitreal injection (p < 0.001) in all groups. in the dme group, the mean thickness decreased from 420.4 ± 47.3 μm at baseline to 316.7 ± 50.6 μm (p < 0.001) one month after the last intravitreal injection and from 376.1 ± 31.7 μm to 303 ± 31.3 μm (p = 0.019) in the namd group and from 424.21 ± 18 μm to 303.4 ± 18.8 μm (p < 0.001) in the rvo group [figures 2 and 3]. adverse events (aes) there was no reported drug-related blurred vision and/or ocular pain at any of the follow-up visits. none of the eyes developed intraocular inflammation, endophthalmitis, corneal edema, cataract, vitritis, retinal detachment, or optic atrophy. vitreous hemorrhage was reported in a diabetic patient one day after injection, which resolved three weeks later. none of the patients experienced moderate or severe vision loss (>0.3 logmar). the mean iop at day 30 was 16.1 ± 3.0 mmhg. no systemic or serious aes were reported. discussion in the current case series, we showed the relative safety of intravitreal injection of a bevacizumab biosimilar (stivant®) in eyes with different indications for anti-vegf therapy. although the short-term results in the present study showed statistically significant improvement in terms of cmt reduction following intravitreal stivant® injection in all three groups, the mean bcva improvement reached statistical significance only in the rvo group. to demonstrate the substitutability of stivant® as a biosimilar of avastin, there is a need to design a randomized clinical trial (rct) with an appropriate sample size. we previously disclosed the safety of stivant® during an animal study. this biosimilar did not show histopathologic changes at the cellular level after being injected into the eyes of albino rabbits evaluated by clinical examinations, erg, and histopathological assessment.[8] biosimilars which are produced by modified cellular processes are identical to their reference biologic agents in terms of structure and active substance, although some minor variations are 30 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 a case series of stivant® intraocular injection; mirshahi et al figure 1. mean bcva (logmar) at baseline and one month after the third stivant® injection. (p-value = 0.12, 0.19, 0.05, and 0.10 in the dme, wet-type amd, rvo, and in all patients, respectively). figure 2. central macular thickness (cmt) changes. mean cmt ± se (μm) at baseline and one month after the first and third stivant® injection in the dme, amd, rvo, and in all patients. figure 3. response to stivant® injections; samples from each subgroup (dme, namd, rvo) under study (a–c). journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 31 a case series of stivant® intraocular injection; mirshahi et al inevitable. therefore, biosimilars are the end products similar to the original molecule with minor non-significant differences.[9–12] in february 2015, razumab® (intas pharmaceuticals, ahmedabad, india), the first biosimilar to ranibizumab, was approved by the drug controller general of india for the treatment of namd, dme, rvo-associated macular edema, and myopic choroidal neovascularization. in a prospective study, the safety and efficacy of razumab® was demonstrated in indian patients with retinal vascular diseases including rvo.[13, 14] afterward, warudkar et al showed the safety and efficacy of intravitreal injection of zybev (cadila healthcare, india) as a bevacizumab biosimilar for macular edema secondary to retinal vascular diseases.[15] as the patent of avastin has recently expired, it is speculated that its biosimilars will soon grow in number.[10, 11] biosimilar production is >25% cheaper than that of the reference drug.[10, 11] as a result, more patients, especially in developing countries, can adhere to their treatment protocols and sustain their vision. with the increasing production of biosimilar drugs in different countries and lower costs of these drugs compared to reference biologics, the widespread usage of these drugs requires special attention of healthcare systems to evaluate them from several aspects, including pharmacokinetics, pharmacodynamics, immunogenicity, safety, and efficacy in comparison to the reference drugs.[11] while the main focus of the reference drug producer is to display safety and efficacy in large clinical trials, biosimilar expansion mainly relies on thorough studies to approve that the product is indistinguishable from reference drug in terms of construction, synthesis, and in vitro activity. as a minimum, one clinical investigation is required to compare the pharmacokinetics between a reference and biosimilar drug and at least one adequately large randomized controlled trial to exhibit the clinical equality.[9–11] safety and efficacy equivalency of the biosimilar drugs to the reference drug concerning pharmacokinetic, pharmacodynamic, and immunogenic properties must be confirmed through well-designed clinical trials. if the results of these trials are satisfactory and a biosimilar drug is approved for one indication, all other indications, for which the reference product is approved, are accepted, provided there is appropriate scientific justification. in general, patients are expected to be able to shift from a biosimilar to a reference product and vice versa without a drug efficacy lapse or increased risk.[9, 10] recently, the us food and drug administration (fda) gave directions to address the extra administrative requirements that biosimilars need to be endorsed as compatible drugs, and has recommended patrons to conduct at least one switching investigation to exhibit that the biosimilar and the reference drug can be securely substituted without loss of efficacy. interestingly, in the european union (eu), the european medicines agency (ema) has not assigned biosimilars as interchangeable substitution of a reference medicine, leaving the choice to national authorities.[10] as mentioned previously, this study is just a case series of patients and our findings cannot replace a well-designed, controlled rct to show the equivalency of stivant® with the reference drug. the other limitations of our study are the short-term follow-up of four months and the lack of data on metabolic profiles such as hba1c and blood pressure of enrolled diabetic patients. in conclusion, our limited experience showed that the intravitreal injection of stivant® was well tolerated over four months. although the results of this case series showed relative improvement in cmt one month after the last injection of stivant®, the mean bcva improvement was statistically significant only in the rvo group. to evaluate the non-inferiority, safety, and efficacy of stivant® in comparison to the reference drug, it is essential to design a randomized clinical trial. acknowledgement the authors would like to thank leila buzh abadi and pouran fadakar for their kind contribution to this study. financial support and sponsorship the study received support from the eye research center, farabi eye hospital, tehran university of medical sciences, tums#40777. 32 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 a case series of stivant® intraocular injection; mirshahi et al conflicts of interest none of the authors have any proprietary interests or conflicts of interest related to this study. references 1. ferrara n, adamis ap. ten years of anti-vascular endothelial growth factor therapy. nat rev drug discov 2016;15:385. 2. berg k, pedersen tr, sandvik l, bragadóttir r. comparison of ranibizumab and bevacizumab for neovascular age-related macular degeneration according to lucas treat-and-extend protocol. ophthalmology 2015;122:146–152. 3. chakravarthy u, harding sp, rogers ca, downes sm, lotery aj, culliford la, et al. et al. alternative treatments to inhibit vegf in age-related choroidal neovascularisation: 2-year findings of the ivan randomised controlled trial. the lancet 2013;382:1258–1267. 4. ehlers jp. the manta 1-year results: the anti-vegf debate continues. bmj publishing group ltd; 2013. 5. group cr. ranibizumab and bevacizumab for neovascular age-related macular degeneration. n engl j med 2011;364:1897–1908. 6. kodjikian l, souied eh, mimoun g, decullier e, huot l, aulagner g. ranibizumab versus bevacizumab for neovascular age-related macular degeneration: results from the gefal noninferiority randomized trial. ophthalmology 2013;120:2300–2309. 7. parikh r, ross js, sangaralingham lr, adelman ra, shah nd, barkmeier aj. trends of anti-vascular endothelial growth factor use in ophthalmology among privately insured and medicare advantage patients. ophthalmology 2017;124:352–358. 8. lashay a, faghihi h, mirshahi a, khojasteh h, khodabande a, riazi-esfahani h, et al, et al. safety of intravitreal injection of stivant®, a biosimilar to bevacizumab, in rabbit eyes. j ophthalmic vis res 2020;15:341–350. 9. scavone c, rafaniello c, berrino l, rossi f, capuano a. strengths, weaknesses and future challenges of biosimilars’ development. an opinion on how to improve the knowledge and use of biosimilars in clinical practice. pharmacol res 2017;126:138–142. 10. sharma a, kumar n, kuppermann bd, bandello f, loewenstein a. understanding biosimilars and its regulatory aspects across the globe: an ophthalmology perspective. br j ophthalmol 2019;104:2–7. 11. sharma a, reddy p, kuppermann bd, bandello f, lowenstein a. biosimilars in ophthalmology: “is there a big change on the horizon?” clin ophthalmol 2018;12:2137. 12. zarbin m. the development pathway for biosimilar biotherapeutics. j ophthalmic vis res 2020;15:273–274. 13. sameera v, apoorva a, joshi s, guruprasad a. safety and efficacy of razumab–the new biosimilar in india: our experience. kerala j ophthalmol 2016;28:180. 14. sharma s, khan ma, chaturvedi a. real-life clinical effectiveness of razumab® (the world’s first biosimilar of ranibizumab) in retinal vein occlusion: a subgroup analysis of the pooled retrospective re-enact study. ophthalmologica 2019;241:24–31. 15. warudkar s. retrospective efficacy and safety analysis of zybev (biosimilar of bevacizumab) use at tertiary eye care centres in india: spectra trial. int j adv res 2018;6:406– 410. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 33 original article outbreak of multidrug-resistant pseudomonas aeruginosa endophthalmitis due to contaminated trypan blue solution pritam bawankar1, ms, dnb, fico; harsha bhattacharjee1, ms; manabjyoti barman1, dnb; ronel soibam1, ms hemalata deka1, ms; ganesh chandra kuri2, ms; jnanankar medhi3, ms 1department of vitreo-retina surgery, sri sankaradeva nethralaya, guwahati, assam, india 2department of oculoplastic, sri sankaradeva nethralaya, guwahati, assam, india 3department of cornea, sri sankaradeva nethralaya, guwahati, assam, india orcid: pritam bawankar: https://orcid.org/0000-0003-2277-5248 abstract purpose: to report the investigation of an outbreak of multidrug-resistant (mdr) pseudomonas aeruginosa endophthalmitis in 13 patients after cataract surgery and to emphasize on the importance of clinical profile, risk factors, and treatment outcomes. methods: this was a hospital-based, retrospective case study with 13 consecutive patients who had manual small-incision cataract surgery with intraocular lens (iol) implantation and developed acute postoperative pseudomonas aeruginosa endophthalmitis. the anterior chamber taps, vitreous aspirates, and environmental surveillance specimens were inoculated for culturing. antibiotic susceptibility testing was performed using the agar diffusion method. pulsed-field gel electrophoresis (pfge) was used to determine the relationship between bacterial isolates recovered from study patients and contaminated surveillance samples. results: pseudomonas aeruginosa was isolated from all 13 eyes with acute postoperative endophthalmitis and the trypan blue solutions used during surgery. sensitivity tests revealed that all isolates had an identical resistance to multiple drugs and were only susceptible to imipenem. genomic dna typing of pseudomonas aeruginosa isolates recovered from patients and trypan blue solutions showed an identical banding pattern on the pfge. despite the prompt use of intravitreal antibiotics and early vitrectomy with iol explantation in some patients, the outcome was poor in about 50% of patients. conclusion: positive microbiology and genomic dna typing results proved that the contaminated trypan blue solutions were the source of infection in this outbreak. postoperative endophthalmitis caused by pseudomonas aeruginosa is often associated with a poor visual prognosis despite prompt treatment with intravitreal antibiotics. keywords: multidrug resistance; pars plana vitrectomy; post-cataract surgery endophthalmitis; pseudomonas aeruginosa; small-incision cataract surgery j ophthalmic vis res 2019; 14 (3): 257–266 correspondence to: pritam bawankar, ms, dnb, fico. department of vitreoretina surgery services, sri sankaradeva nethralaya, assam 781028, india. e-mail: dr.pritambawankar@gmail.com received: 12-05-2018 accepted: 11-11-2018 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i3.4781 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: bawankar p, bhattacharjee h, barman m, soibam r, deka h, kuri gc, et al. outbreak of multidrug-resistant pseudomonas aeruginosa endophthalmitis due to contaminated trypan blue solution. j ophthalmic vis res 2019;14:257–266 @ 2019 j  o  v r | published by knowledge e 257 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i3.4781&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr outbreak of pseudomonas endophthalmitis; bawankar et al introduction approximately 12.5 million people are blind in india and cataract is the main contributor to this striking number accounting for 50–80% of cases.[1] manual small-incision cataract surgery (msics) is a faster, less expensive small-incision form of extracapsular cataract extraction (ecce) that is principally used in the developing world.[2] msics has the advantage of a self-sealing sutureless wound and is less dependent on expensive technology than phacoemulsification. with the improvement in preoperative prophylactic measures, sterilization protocols, surgical techniques, and good postoperative care, the infection rate after cataract surgery has decreased. however, there is still the possibility of infections, and the most devastating is endophthalmitis. postoperative endophthalmitis is a catastrophic complication of intraocular surgery mainly associated with cataract extraction and intraocular lens (iol) implantation, with an incidence of 0.08 to 1%.[3] the most common causative organisms are gram-positive coagulase negative bacteria; however, gram-negative organisms have been isolated from 6% to 29% of cases in larger reported series.[4] despite the low prevalence of gramnegative organisms, a more vigorous management approach including early vitrectomy is required, as these organisms are highly virulent. pseudomonas aeruginosa is a gram-negative bacillus, commonly found in soil and moist environments, which has emerged as an important opportunistic pathogen in hospitalized and immunocompromised patients affecting many anatomic sites, such as the skin, ears, lungs, heart, urinary tract, bone, and eyes.[5]the most common ocular infection caused by pseudomonas aeruginosa is contact lens-associated keratitis, but it may also cause post-surgical acute endophthalmitis.[6] outbreaks of acute postoperative pseudomonas aeruginosa endophthalmitis have been described in numerous case studies, most of which were caused by bacteria from air, iols, inadequately sterilized irrigation fluid, and surgical equipment.[7, 8] trypan blue is used for staining the anterior capsule during cataract surgery. eyes with mature cataracts and conditions resulting in a compromised red reflex such as corneal scarring and edema, asteroid hyalosis, vitreous hemorrhage, and retinal disease have poor visualization of the anterior capsule during cataract surgery, making capsulorrhexis extremely difficult.[9] therefore, capsular staining with trypan blue is helpful in enhancing visualization in such eyes. however, the risk of bacterial infection after instilling trypan blue into the eye remains real.[10] the purpose of this study was to investigate an outbreak of multidrug-resistant (mdr) pseudomonas aeruginosa endophthalmitis after cataract surgery in 13 patients and determine the importance of associated risk factors, clinical profile, microbiological analysis, early diagnosis, and therapy. methods this study is a hospital-based, retrospective case study, approved by the local institutional review board and conducted in accordance with the principles of the helsinki declaration. in march 2017, 13 patients (3 women and 10 men) who underwent standard msics with iol implantation developed acute postoperative endophthalmitis and were referred to our tertiary eye center for further management. all 13 patients were operated in the same operation theater by five different experienced surgeons over a period of five days at a district hospital in north-east india. the medical records of all 13 patients treated for multidrugresistant pseudomonas aeruginosa endophthalmitis after cataract surgery were reviewed. the following data were extracted from the patients’ medical records for this study: demographic information, eye affected, best corrected visual acuity (bcva) at the time of diagnosis of endophthalmitis, date and type of anesthesia and surgery, type of iol implanted, time between cataract surgery and diagnosis of endophthalmitis, presenting signs and symptoms, site of culture, antibiotic sensitivity testing, treatment, and outcomes. a 0.1 ml anterior chamber sample was collected from 10 patients using a 30-gauge needle and syringe before the administration of intravitreal antibiotics, while vitreous samples were collected from three patients at the time of pars plana vitrectomy and sent to the microbiology laboratory. cultures and smears for the detection of bacterial and fungal agents were carried out on the intraocular specimens within 30 minutes of their collection. the culture media used were blood 258 j  o  v r volume 14, issue 3, july–september 2019 outbreak of pseudomonas endophthalmitis; bawankar et al agar (5% sheep), chocolate agar (5% sheep blood), brain heart infusion broth, thioglycollate broth, and sabouraud dextrose agar (hi-media, mumbai). all the inoculated media were incubated at 37ºc except for sabouraud dextrose agar, which was incubated at 25ºc. chocolate agar was incubated in an atmosphere of 10% co2 (anaerobic system mark v jar, hi-media). gram and giemsa stains for cytology and potassium hydroxide (koh) preparation for detecting fungi were prepared from the anterior chamber tap and vitreous specimens. the criteria used to identify the isolated organism as the causative agent were: (i) growth on a single medium correlating with direct smear findings, (ii) growth of the same organism on two or more of the inoculated media, or (iii) confluent growth in any solid medium, or a combination of these criteria. antibiotic susceptibility to cephotaxime, cefuroxime, ceftriaxone, ceftazidime, chloramphenicol, vancomycin, amikacin, tobramycin, ciprofloxacin, moxifloxacin, cotrimoxazole, imipenem, and piperacillin-tazobactam was tested using the classic agar diffusion (kirby–bauer) method. furthermore, during the outbreak, microbiological analysis was also performed on the surveillance samples from the unopened bottles of povidone–iodine solution (apidine-5 appasamy associates, arumbakkam, chennai, india), trypan blue solution (sunblue, unison pharmaceuticals, ahmedabad, gujarat, india), hydroxypropyl methylcellulose ophthalmic solution (eyevisc, bio-tech ophthalmicus pvt. ltd., gandhinagar, gujrat, india), and the irrigation solutions [ringer’s lactate (rl, schwitz biotech, ahmedabad, gujarat, india)] from the same batch as used for the surgery. in addition, the polymethylmethacrylate (pmma, biovision, biotech vision care pvt. ltd. ahmedabad, gujarat, india) intraocular lenses, surgical instruments, dressings, air-conditioning system of the operating rooms, and autoclave efficacy were also tested. all the surveillance samples were obtained from the same operating theater during the endophthalmitis outbreak and were microbiologically analyzed using the protocol described by our laboratory in the hospital. subsequently, smear and cultures of the patients’ isolates, surveillance specimens, and bacterial isolates were genotyped to identify the similar isolates. to determine the relatedness of bacterial isolates, we analyzed the chromosomal restriction fragment patterns using pulsed-field gel electrophoresis (pfge) with standard techniques. all 13 patients were managed using the standard institutional protocol for the management of acute postoperative endophthalmitis. this essentially consisted of aqueous or vitreous sampling or both, microscopy, and culture sensitivity analysis of undiluted aqueous or vitreous samples, intravitreal antibiotics (vancomycin [1 mg/0.1 ml] plus ceftazidime [2.25 mg/0.1 ml]/n-formimidoylthienamycin (imipenem, 100 𝜇g/0.1ml]), and vitrectomy. intensive topical antibiotics (moxifloxacin 0.5% and tobramycin 0.3%) and a corticosteroid (prednisolone acetate 1%) were administered to all patients. initial treatment included intravitreal antibiotic injection in seven eyes, pars plana vitrectomy with iol explantation and injection of intravitreal antibiotics in four eyes, and evisceration in two eyes. intravitreal imipenem was administered to five patients following culture and sensitivity reports. additional procedures such as repeat intravitreal antibiotics or pars plana vitrectomy, corneal patch grafting, and tunnel wound repair were performed by the individual-treating physicians without a predefined study protocol. results thirteen patients (10 men and 3 women) underwent msics with posterior chamber iol implantation from march 7 to 11, 2017 at a district hospital in northeast india. all 13 patients developed acute pseudomonas aeruginosa endophthalmitis. the average age was 67 (range, 50–85) years. the right and left eyes were affected in seven and six patients, respectively. the mean interval between surgery and diagnosis of endophthalmitis was five (range, three–eight) days. the demographics, clinical settings, and culture sites are shown in table 1. all 13 patients developed varying degrees of ocular discomfort and decreased vision from postoperative day 1 to 3. bcva documented in 11 patients was perception of light and that of two patients was hand motion at the time of presentation. all patients had severe anterior chamber reaction and hypopyon at the time of presentation. six eyes had exposed scleral-corneal tunnels with infiltrate, whereas eleven had corneal edema with raised intraocular pressure, and one patient developed dense corneal infiltrate over the nasal cornea. all patients had clinically dense vitreous j  o  v r volume 14, issue 3, july–september 2019 259 outbreak of pseudomonas endophthalmitis; bawankar et al ta b le 1. d em og ra ph ic s, cl in ic al fin di ng s an d tr ea tm en to ut co m es in 13 pa tie nt s w ith m ul tid ru gre si st an tp se ud om on as ae ru gi no sa en do ph th al m iti s af te rc at ar ac ts ur ge ry p a ti e n t n o . a g e (y rs )/ g e n d e r e ye s ys te m ic d is e a se v is u a l a cu it y a t th e ti m e o f p re se n ta ti o n d a ys b e tw e e n s u rg e ry a n d e n d o p h th a lm iti s d ia g n o si s (d a ys ) c lin ic a ls ig n s c u lt u re s it e tr e a tm e n t* o u tc o m e 1 60 /f o s d m lp 3 ey el id ed em a, di sc ha rg e, co nj un ct iv al co ng es tio n, ch em os is , co rn ea le de m a, fib rin ou s ex ud at es co ve rin g pu pi l, 2m m hy po py on , tu nn el in fil tr at e, ex po se d tu nn el , ra gg ed w ou nd m ar gi n w ith iri s tis su e pr ol ap se d v itr eo us d ay 1– iv (v + c a ) d ay 2 – pp v + io l re m ov al + iv (v + c a )d ay 8 – iv (v + c a ) ph th is is bu lb ia fte r on e m on th 2 76 /m o d d m ,h tn lp 6 ey el id ed em a, di sc ha rg e, co nj un ct iv al co ng es tio n, ch em os is , co rn ea lh az e w ith de ns e in fil tr at e, fib rin ou s ex ud at es in a c ,3 -m m hy po py on ,t un ne li nfi ltr at e, ne cr os ed tu nn el ,w ou nd ga pi ng w ith iri s tis su e pr ol ap se d, io p m ar ke dl y ra is ed a qu eo us d ay 1– iv (v + c a ) n o im pr ov em en t, se ve re oc ul ar pa in , no lp ;e vi sc er at io n on da y 2 3 55 /m o s n il lp 3 ey el id ed em a, di sc ha rg e, co nj un ct iv al co ng es tio n, ch em os is , co rn ea le de m a, 1m m hy po py on v itr eo us , a qu eo us d ay 1– iv (v + c a ) d ay 2 – pp v + io l re m ov al + iv (v + c a ) b c v a 3/ 60 ,a c qu ie t, v c 3+ , se co nd or de rv es se l vi si bl e on fu nd os co py af te r on e m on th of pp v 4 75 /m o d n il lp 7 ey el id ed em a, di sc ha rg e, co nj un ct iv al co ng es tio n, ch em os is , co rn ea ld en se co rn ea li nfi ltr at e, fib rin ou s ex ud at es co ve rin g pu pi l, 3m m hy po py on ,t un ne li nfi ltr at e, ne cr os ed tu nn el ,w ou nd ga pi ng w ith iri s tis su e pr ol ap se d, io p m ar ke dl y ra is ed a qu eo us d ay 1– iv (im ) n o im pr ov em en t, se ve re oc ul ar pa in , no lp ;e vi sc er at io n on da y 3 260 j  o  v r volume 14, issue 3, july–september 2019 outbreak of pseudomonas endophthalmitis; bawankar et al ta b le 1. c on tin ue d. p a ti e n t n o . a g e (y rs )/ g e n d e r e ye s ys te m ic d is e a se v is u a l a cu it y a t th e ti m e o f p re se n ta ti o n d a ys b e tw e e n s u rg e ry a n d e n d o p h th a lm iti s d ia g n o si s (d a ys ) c lin ic a ls ig n s c u lt u re s it e tr e a tm e n t* o u tc o m e 5 50 /f o d n il lp 6 d is ch ar ge ,c on ju nc tiv al co ng es tio n, co rn ea le de m a, 2m m hy po py on , m em br an ou s ex ud at es on io l a qu eo us , v itr eo us d ay 1– iv (v + c a ) d ay 2 – pp v + io l re m ov al + fg e + so i+ iv (v + c a ) b c v a 6/ 60 ,a c qu ie t, si lic on fil le d ey e, re tin a he al th y on fu nd os co py af te r on e m on th of pp v 6 50 /f o d h tn lp 5 ey el id ed em a, di sc ha rg e, co nj un ct iv al co ng es tio n, ch em os is , co rn ea le de m a, se ve re fib rin ou s ex ud at es in a c ,2 -m m hy po py on v itr eo us d ay 1– pp v + io l re m ov al + fg e + lp fc + el + so i+ iv (v a + c a )1 8/ 04 /17 – so r + r r + m p + fg e + el + r e so i b c v a 2 /6 0, a c qu ie t, si lic on fil le d ey e, re tin a he al th y on fu nd os co py af te r th re e w ee ks of se co nd su rg er y 7 75 /m o d n il lp 5 ey el id ed em a, di sc ha rg e, co nj un ct iv al co ng es tio n, ch em os is , de ns e co rn ea li nfi ltr at e, co rn ea l ed em a w ith ra is ed io p, fu ll ch am be r ex ud at e, ne cr os ed tu nn el ,w ou nd ga pi ng w ith in ca rc er at ed an d ex po se d uv ea lt is su e a qu eo us se ve re oc ul ar pa in , no lp ;e vi sc er at io n on d ay 2 8 78 /m o s h tn lp 6 d is ch ar ge ,c on ju nc tiv al co ng es tio n, 1m m hy po py on ,fi br in ou s ex ud at es on io l a qu eo us , v itr eo us d ay 1– pp v + io l re m ov al + iv (v + c a ) b c v a 6/ 36 ,a c qu ie t, v c 2+ ,n or m al re tin al fin di ng s on fu nd os co py af te r on e m on th of pp v 9 58 /m o d n il lp 4 ey el id ed em a, co nj un ct iv al co ng es tio n, ch em os is ,c or ne al ed em a, ex ud at iv e m em br an e ov er pu pi l, 2m m hy po py on v itr eo us d ay 1– pp v + io l re m ov al + iv (v + c a )d ay 3 – iv (im ) d ay 5 – iv (im ) re tin al an d ch or oi da l de ta ch m en tw ith pr ol ife ra tiv e vi tr eo re tin op at hy af te rt hr ee w ee ks ; no fu rt he rf ol lo w -u p j  o  v r volume 14, issue 3, july–september 2019 261 outbreak of pseudomonas endophthalmitis; bawankar et al ta b le 1. c on tin ue d. p a ti e n t n o . a g e (y rs )/ g e n d e r e ye s ys te m ic d is e a se v is u a l a cu it y a t th e ti m e o f p re se n ta ti o n d a ys b e tw e e n s u rg e ry a n d e n d o p h th a lm iti s d ia g n o si s (d a ys ) c lin ic a ls ig n s c u lt u re s it e tr e a tm e n t* o u tc o m e 10 85 /m o s h tn , h em ip a r es is lp 6 ey el id ed em a, di sc ha rg e, co nj un ct iv al co ng es tio n, ch em os is , de ns e co rn ea li nfi ltr at e, se ve re fib rin ou s ex ud at es in a c ,3 -m m hy po py on ,t un ne li nfi ltr at e, ne cr os ed tu nn el w ith ra gg ed ed ge s, io p m ar ke dl y ra is ed a qu eo us d ay 1– iv (v + c a ) se ve re oc ul ar pa in ,n o lp , re st ric te d ey e m ov em en t, hi gh io p; ev is ce ra tio n on da y 2 11 75 /m o d tb ,r h d ,m v p, h tn , lp 8 ey el id ed em a, di sc ha rg e, co nj un ct iv al co ng es tio n, ch em os is , co rn ea li nfi ltr at e, co rn ea le de m a, fib rin ou s ex ud at es in a c ,3 -m m hy po py on ,t un ne li nfi ltr at e, ex po se d tu nn el a qu eo us , v itr eo us d ay 2 – pp v + io l re m ov al + iv (im ) n o im pr ov em en t, no lp ;p ht hi si s bu lb ia fte rs ix w ee ks 12 65 /m o s n il h m 6 ey el id ed em a, di sc ha rg e, co nj un ct iv al co ng es tio n, ch em os is , de ns e co rn ea li nfi ltr at e on na sa l si de of co rn ea ,fi br in ou s ex ud at es in a c co ve rin g pu pi l, 2m m hy po py on a qu eo us d ay 1– iv (v + c a ) d ay 3 – iv (im )d ay 5 – iv (im )d ay 7 – c or ne al pa tc h gr af t b c v a 4/ 60 ,g ra ft ha zy ,r es tc or ne a cl ea r, a c qu ie t, v c 3+ ,r et in a he al th y af te ro ne m on th . 13 70 /m o s n il h m 5 d is ch ar ge ,c on ju nc tiv al co ng es tio n, ch em os is ,c or ne al ed em a, ex ud at es in a c ,1 -m m hy po py on ,w ou nd ga pi ng a qu eo us d ay 1– iv (im )d ay 3 – iv (im )9 /4 /17 – iv (im )1 0/ 4/ 17 (g ap in g) w ou nd re pa ir + iv (im ) v a 6/ 60 ,c or ne a cl ea r, a c qu ie t, v c 2+ ,r et in a he al th y af te ro ne m on th *t re at m en t st ar te d fro m th e da y of pr es en ta tio n an d di ag no si s (e .g ., d ay 1 – tr ea tm en t re ce iv ed by th e pa tie nt on th e fir st da y of pr es en ta tio n an d di ag no si s of en do ph th al m iti s) a c ,a nt er io r ch am be r; b c v a ,b es tc or re ct ed vi su al ac ui ty ;c a ,c ef ta zi di m e; d m ,d ia be te s m el lit us ;e l, en do la se r; f, fe m al e; fg e, flu id ga s ex ch an ge ;h m ,h an d m ot io n; h tn ,h yp er te ns io n; im ,i m ip en em ;i o p, in tr ao cu la r pr es su re ;i v, in tr av itr ea l; lp ,l ig ht pe rc ep tio n; lp fc ,l iq ui d pe rfl ur oc ar ba n; m ,m al e; m p, m em br an e pe el in g; m v p, m itr al va lv e pr ol ap se ;o d ,o cu lu s de xt er ;o s, oc ul us si ni st er ;p pv ,p ar s pl an a vi tr ec to m y; r h d ,r he um at ic he ar td is ea se ;r r ,r et in al re tin ec to m y; r e so i, re -in je ct io n of si lic on e oi l; si o ,s ili co ne oi l; so r ,s ili co ne oi lr em ov al ;t b ,t ub er cu lo si s; v, va nc om yc in ;v c ,v itr eo us ce lls 262 j  o  v r volume 14, issue 3, july–september 2019 outbreak of pseudomonas endophthalmitis; bawankar et al haze and, thus, dark fundus reflex. despite the prompt use of intravitreal antibiotics and early vitrectomy with iol explantation, the outcome was poor in about 50% of the cases (evisceration and phthisis of four and two eyes, respectively, and retinal and choroidal detachment with extensive proliferative vitreoretinopathy in one eye). a moderate degree of improvement was observed in six eyes in the last control visit. seven eyes underwent vitrectomy and iol explantation with intravitreal antibiotics, including two cases that developed phthisis bulbi over a period of one month (cases 1 and 11), four cases that showed moderate improvement with a bcva ranging from 2/60 to 6/36 (cases 3, 5, 6, and 8), and a case that developed retinal detachment with gross proliferative vitreoretinopathy did not come for follow-up after three weeks (case 9). four eyes underwent evisceration. the remaining two eyes (cases 12 and 13) were treated with intravitreal n-formimidoyl-thienamycin (imipenem) injection, as the bcva at the time of presentation was hand motion with a less severe anterior chamber reaction, and they showed moderate vision improvement. with these two eyes, case 12 had corneal patch graft for dense nasal corneal infiltrate [figures 1(a) and (b)] and case 13 required suturing for exposed and gaped tunnel. in case 13, the resolution of hypopyon and good fundal reflex with a hazy view of disc was noted after two intravitreal injections of imipenem. after three weeks, the same patient (case 13) developed tunnel gaping, raised iop, recurrence of hypopyon, and a dark fundal reflex. the patient underwent wound repair and intravitreal injection of imipenem and showed significant improvement in visual acuity and clinical picture during the following weeks [figures 1(c) and (d)]. a summary of the clinical findings, treatment, and outcomes are presented in table 1. anterior chamber taps were performed in all patients; whereas adequate samples could not be collected from three patients because of thick fibrinous exudates in the anterior chamber. vitreous aspirate was collected from all patients who underwent vitrectomy and sent for culture. the anterior chamber and vitreous aspirates of all 13 patients yielded pseudomonas aeruginosa, which was also isolated from the surveillance samples from the unopened bottles of trypan blue solution from the same batch as used for the surgery. figure 1. anterior segment images showing nasal corneal abscess, hypopyon, and fibrinous exudates at the time of presentation (a) and corneal patch graft at the last visit (b) of case 12. anterior segment images of case 13 showing recurrence of hypopyon (c) and postoperative image at the last visit with no hypopyon (d). on the other hand, no microbial contamination was found in samples of povidone–iodine solution, hydroxypropyl methylcellulose ophthalmic solution, pmma iols, surgical instruments, dressings, air-conditioning system of the operating room, and the irrigation solution (ringer’s lactate). sensitivity tests revealed that all pseudomonas aeruginosa eye isolates had an identical multidrugresistance (mdr) susceptibility profile and were susceptible to imipenem but resistant to cephotaxime, cefuroxime, ceftriaxone, ceftazidime, chloramphenicol, vancomycin, amikacin, tobramycin, ciprofloxacin, moxifloxacin, co-trimoxazole, and piperacillin-tazobactam. genomic dna typing of pseudomonas aeruginosa isolates recovered from the study patients and trypan blue solutions showed an identical banding pattern on ethidium bromide-stained gels. no other strains of pseudomonas aeruginosa unrelated to the outbreak were typed on the pfge. discussion the current study describes an outbreak of cataract surgery-related mdr pseudomonas aeruginosa endophthalmitis caused by contaminated trypan blue ophthalmic solution. the outcome was evisceration or phthisis in six (46%) of the thirteen eyes, and a moderate degree j  o  v r volume 14, issue 3, july–september 2019 263 outbreak of pseudomonas endophthalmitis; bawankar et al of improvement in six eyes in the last control visit. one patient who did not follow-up after three weeks was diagnosed with retinal and choroidal detachment with extensive proliferative vitreoretinopathy. pseudomonas aeruginosa postoperative endophthalmitis is often associated with a poor visual prognosis even with early treatment with intravitreal antibiotics to which the isolates are susceptible. pinna et al[11] reported an outbreak of postcataract surgery endophthalmitis caused by pseudomonas aeruginosa in 20 patients, and although intravitreal antibiotics were promptly administered, 10 patients had evisceration or phthisis of the affected eye, 5 eyes showed a minimal degree of improvement, and 7 patients did not follow-up within one week after intravitreal antibiotic injection. zaluski et al[12] reported four cases of pseudomonas aeruginosa endophthalmitis caused by the contamination of the internal pathways of a phacoemulsifier; three of these four patients had evisceration or phthisis of the affected eye and one had visual acuity of 20/400. in a recent study by eifrig et al,[13] 18 of 28 eyes with pseudomonas aeruginosa endophthalmitis either developed phthisis bulbi or were eviscerated, and none of the remaining nine patients achieved a final visual acuity of 5/200 or better. pseudomonas aeruginosa is one of the most common gram-negative pathogens associated with hospital-acquired infections, and the clinical evidence indicates that multidrug resistance of this organism is growing and affecting the selection of proper treatment.[14] the increasing antibiotic resistance of pseudomonas aeruginosa involves several mechanisms including efflux pump over expression, decreased outer membrane permeability, production of metallo-beta-lactamases, and structural alterations of topoisomerases ii and iv, which are involved in quinolone resistance.[15] the current study confirmed that the detection of ocular pseudomonas aeruginosa isolate with multiple antibiotic resistance is common. in fact, multidrug resistance to cefazolin, chloramphenicol, tetracycline, aminoglycosides, piperacillintazobactam, and fluoroquinolones was observed with all isolates. this occurrence may, in part, explain the poor outcome in our patients, despite prompt treatment with intravitreal antibiotics. imipenem is a member of the beta-lactam class of antibiotics, which kills bacteria by binding to penicillin-binding proteins and inhibiting cell wall synthesis, exhibiting a broader spectrum of activity than that of cephalosporins and penicillins.[16] imipenem is regarded as an agent of choice in the treatment of severe nosocomial infections caused by sensitive strains of pseudomonas aeruginosa.[16] in the current study, pseudomonas aeruginosa strains isolated from patients showed multidrug resistance except against imipenem. in our study, despite the prompt use of intravitreal antibiotics, the outcome was poor in about 50% of patients [evisceration (cases 2, 4, 7, and 10) and phthisis (1 and 11)]. in all these cases, the sclerocorneal tunnel showed ragged wound margin, tunnel infiltrate, gaping with iris tissue prolapse, and severe fibrinous exudates in the anterior chamber with 2–3 mm hypopyon at the time of presentation. although the organisms isolated in all cases of endophthalmitis were the same, eyes with exposed and gaped tunnels presented with more fulminant manifestations and were ultimately blind. poorly constructed and distorted wounds could enhance the chances of postsurgical anterior chamber contamination and play pivotal roles in increased rates of endophthalmitis. although the poorly constructed wounds did not cause the development of endophthalmitis in the current series, we believe that they were associated with additional ocular complications after the development of endophthalmitis, worsening the outcome. several studies have reported increased rates of postsurgical endophthalmitis among male patients,[17, 18] those with low socioeconomic and immune-compromised status,[19] older age (mean age of 81 years),[20] diabetes mellitus,[20] and in patients with postoperative wound defects.[21, 22] all these factors were present in the six patients who exhibited very poor outcome: two were diabetic (cases 1 and 2), one had a history of stroke (patient 10), and one had a history of tuberculosis, rheumatic heart disease, and mitral valve prolapse (patient 11). we believe that these factors may not only have predisposed the patients to the development of endophthalmitis but could have also caused a more fulminant course, which might be a possible explanation for the fulminant course in these patients. pseudomonas aeruginosa is not a normal commensal on the periocular skin or conjunctiva, and most associated epidemics reported in the literature seem to have an exogenous 264 j  o  v r volume 14, issue 3, july–september 2019 outbreak of pseudomonas endophthalmitis; bawankar et al origin.[11] pseudomonas aeruginosa post cataract surgery endophthalmitis outbreaks have been reported in association with contaminated ophthalmic solutions used during the surgery (balanced salt solution, trypan blue, and hyaluronic acid),[8, 23–25] contaminated phacoprobe,[21] and contamination of internal fluid pathways of a phacoemulsifier.[12, 26–28] in our survey, the analysis of the surveillance samples showed pseudomonas aeruginosa contamination of trypan blue solution of the same batch used for the surgeries. on the other hand, no microbial contamination was found in other surveillance samples. furthermore, we confirmed that the pseudomonas aeruginosa isolated recovered from the study patients typed using pfge were similar to the strains recovered from the trypan blue solution. therefore, we believe that trypan blue solution is the culprit in causing the outbreak described. there are some limitations to this study. the case data provided by the district hospital had no records of intraoperative complications such as posterior capsular rupture with vitreous loss, subconjunctival and intracameral antibiotics at the end of surgery, and the use of topical povidone– iodine in all cases of cataract surgery. therefore, these factors could not be assessed in the current study. nonetheless, even with these limitations, the analysis provides clear evidence to support the notion that mdr pseudomonas aeruginosaassociated endophthalmitis is responsible for poor visual outcomes despite early and appropriate treatment. this occurrence of cluster endophthalmitis may be explained by the inoculation of a large bacterial burden and virulence of the organism. this case study provides additional information for primary care physicians, general ophthalmologists, and other eye care professionals regarding clinical profile, risk factors, early diagnosis, initiation of appropriate treatment and visual outcomes in cases of mdr postsurgical pseudomonas aeruginosa endophthalmitis. in conclusion, our case study confirmed that the outcome of cataract surgery-related endophthalmitis caused by mdr pseudomonas aeruginosa was poor, despite prompt treatment with intravitreal broad-spectrum antibiotics. susceptibility to imipenem suggests that this antibiotic may be a potential candidate for the treatment of ocular infections caused by multidrug-resistant pseudomonas aeruginosa. ophthalmologists should never assume that solutions or medications used intraoperatively are sterile and they should never be used for multiple operations. we also recommend the use of molecular biology techniques, such as pfge, to confirm the source of infection. financial support and sponsorship the authors would like to thank the sri kanchi sankara health and educational foundation for their support in completing the study. conflicts of interest there are no conflicts of interest. references 1. venkatesh r, das m, prashanth s, muralikrishnan r. manual small incision cataract surgery in eyes with white cataracts. indian j ophthalmol 2005;53:173–176. 2. kongsap p. visual outcome of manual small-incision cataract surgery: comparison of modified blumenthal and ruit techniques. int j ophthalmol 2011;4:62–65. 3. hanscom ta. postoperative endophthalmitis. clin infect dis 2004;38:542–546. 4. eifrig cw, scott iu, flynn hw, miller d. endophthalmitis caused by pseudomonas aeruginosa. ophthalmology 2003;110:1714 –1717. 5. ohl ca, pollack m. infections due to pseudomonas species and related organisms. in: kasper dl, braunwald e, fauci as, et al, editors. harrison’s principles of internal medicine. 16th ed. new york: mcgraw-hill; 2005:889–897. 6. o’brien tp, hazlett ld. pathogenesis of ocular infection. in: pepose js, holland gn, wilhelmus kr, editors. ocular infection and immunity. st. louis, mo: mosby; 1996:200– 205, 1314. 7. taban m, behrens a, newcomb rl, nobe my, saedi g, sweet pm, et al. acute endophthalmitis following cataract surgery: a systematic review of the literature. arch ophthalmol 2005;123:613–620. 8. swaddiwudhipong w, linlawan p, prasantong r, kiphati r, wongwatcharapaiboon p. a report of an outbreak of postoperative endophthalmitis. j med assoc thai 2000;83:902–907. 9. chang df. trypan blue versus indocyanine green: a clinical comparison of these dyes for capsular staining. cataract refract surg today 2005;5:34–37. 10. sunenshine r, schultz m, lawrence mg, shin s, jensen b, zubairi s, et al. an outbreak of postoperative gramnegative bacterial endophthalmitis associated with contaminated trypan blue ophthalmic solution. clin infect dis 2009;48:1580–1583. 11. pinna a, usai d, sechi la, zanetti s, jesudasan nc, thomas pa, et al. an outbreak of post-cataract surgery endophthalmitis caused by pseudomonas aeruginosa. ophthalmology 2009;116:23216. j  o  v r volume 14, issue 3, july–september 2019 265 outbreak of pseudomonas endophthalmitis; bawankar et al 12. zaluski s, clayman hm, karsenti g, bourzeix s, tournemire a, faliu b, et al. pseudomonas aeruginosa endophthalmitis caused by contamination of the internal fluid pathways of a phacoemulsifier. j cataract refract surg 1999;25:540 –545. 13. eifrig cw, scott iu, flynn hw, miller d. endophthalmitis caused by pseudomonas aeruginosa. ophthalmology 2003;110:1714 –1717. 14. obritsch md, fish dn, maclaren r, jung r. national surveillance of antimicrobial resistance in pseudomonas aeruginosa isolates obtained from intensive care unit patients from 1993 to 2002. antimicrob agents chemother 2004;48:4606–4610. 15. fusté e, lópez-jiménez l, segura c, gainza e, vinuesa t, viñas m. carbapenem-resistance mechanisms of multidrug-resistant pseudomonas aeruginosa. j med microbiol 2013;62:1317–1325. 16. rodloff ac, goldstein ejc, torres a. two decades of imipenem therapy. j antimicrob chemother 2006; 58:916–929. 17. freeman ee, roy-gagnon mh, fortin e, gauthier d, popescu m, boisjoly h. rate of endophthalmitis after cataract surgery in quebec, canada, 1996-2005. arch ophthalmol 2010;128:230–234. 18. endophthalmitis study group, european society of cataract and refractive surgeons. prophylaxis of postoperative endophthalmitis following cataract surgery: results of the escrs multicenter study and identification of risk factors. j cataract refract surg 2007;33:978–988. 19. du dt, wagoner a, barone sb, zinderman ce, kelman ja, macurdyte, et al. incidence of endophthalmitis after corneal transplant or cataract surgery in a medicare population. ophthalmology 2014;121:290–298. 20. jabbarvand m, hashemian h, khodaparast m, jouhari m, tabatabaei a, rezaei s. endophthalmitis occurring after cataract surgery: outcomes of more than 480 000 cataract surgeries, epidemiologic features, and risk factors. ophthalmology 2016;123:295–301. 21. aaberg tm, jr, flynn hw, jr, schiffman j, newton j. nosocomial acute-onset postoperative endophthalmitis survey. a 10-year review of incidence and outcomes. ophthalmology 1998;105:1004–1010. 22. montan pg, koranyi g, setterquist he, stridh a, philipson bt, wiklund k. endophthalmitis after cataract surgery: risk factors relating to technique and events of the operation and patient history: a retrospective case-control study. ophthalmology 1998;105:2171–2177. 23. boks t, van dissel jt, teterissa n, ross f, mahmut mh, utama ed, et al. an outbreak of endophthalmitis after extracapsular cataract surgery probably caused by endotoxin contaminated distilled water used to dissolve acetylcholine. br j ophthalmol 2006;90:1094–1097. 24. mateos i, valencia r, torres mj, cantos a, conde m, aznar j. nosocomial outbreak of pseudomonas aeruginosa endophthalmitis. infect control hosp epidemiol 2006;27:1249–1251. 25. arsan ak, adişen a, duman s, aslan b, koçak i. acute endophthalmitis outbreak after cataract surgery. j cataract refract surg 1996;22:1116–1120. 26. hoffmann kk, weber dj, gergen mf, rutala wa, hill c, tate g, et al. pseudomonas aeruginosa–related postoperative endophthalmitis linked to a contaminated phacoemulsifier. arch ophthalmol 2002;120:90–93. 27. kenchappa p, sangwan vs, ahmed n, rao kr, pathengay a, mathai a, et al. high-resolution genotyping of pseudomonas aeruginosa strains linked to acute post cataract surgery endophthalmitis outbreaks in india. ann clin microbiol antimicrob 2005;4:19. 28. cruciani m, malena m, amalfitano g, monti p, bonomi l. molecular epidemiology in a cluster of cases of postoperative pseudomonas aeruginosa endophthalmitis. clin infect dis 1998;26:330–333. 266 j  o  v r volume 14, issue 3, july–september 2019 original article choroidal thickness and hemoglobin a1c levels in patients with type 2 diabetes mellitus hamidreza torabi1, md; mohsen saberi isfeedvajani2, md; majid ramezani3, md seyed-hashem daryabari1, md 1health management research center, baqiyatallah university of medical sciences, tehran, iran 2medicine, quran and hadith research center and department of community medicine, faculty of medicine, baqiyatallah university of medical sciences, tehran, iran 3nephrology and urology research center, baqiyatallah university of medical sciences, tehran, iran orcid: hamidreza torabi: https://orcid.org/0000-0002-7127-3415 seyed-hashem daryabari: https://orcid.org/0000-0002-7264-8637 abstract purpose: the aim of this study was to assess the correlation of hemoglobin a1c (hba1c) levels with choroidal thickness in patients with type 2 diabetes mellitus (dm) using spectral domain optical coherence tomography (sd-oct). methods: in this prospective case series, 180 eyes from 90 patients with type 2 dm were classified into three study groups based on hba1c values: group 1 included patients with good glycemic control (hba1c ≤ 7%), group 2 included patients with moderate glycemic control (hba1c between 7% and 8%), and group 3 included patients with poor glycemic control (hba1c ≥ 8%). additionally, 50 eyes from 25 non-diabetic subjects were enrolled to group 4 as a control group. sub-foveal, nasal, and temporal choroidal thickness were measured and compared. results: mean central, nasal, and temporal choroidal thicknesses in diabetic patients (247.80, 238.63, and 239.30 𝜇m) were significantly less than non-diabetic healthy subjects (277.56, 262.92, and 266.32 𝜇m). additionally, mean central, nasal, and temporal choroidal thickness values in group 4 (277.56, 262.92, and 266.32 𝜇m) were significantly greater than the corresponding values in group 2 (248.34, 237.55, and 236.45 𝜇m) and group 3 (239.81, 234.62, and 233.94 𝜇m), but was not significantly different from corresponding values in group 1 (259.46, 246.12, and 251.00 𝜇m). conclusion: hba1c values have a significant correlation with choroidal thickness in diabetic patients, and better glycemic control with hba1c ≤ 7% may prevent choroidal thinning. keywords: choroidal thickness; diabetes mellitus; diabetic retinopathy; enhanced depth imaging optical coherence tomography; hba1c j ophthalmic vis res 2019; 14 (3): 285–290 correspondence to: seyed-hashem daryabari, md. health management research center, baqiyatallah university of medical science, mollasadra st., vanak square, tehran 19936, iran. e-mail: daryabari2020@yahoo.com received: 21-06-2018 accepted: 15-01-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i3.4784 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: torabi h, saberi isfeedvajani m, ramezani m, daryabari sh. choroidal thickness and hemoglobin a1c levels in patients with type 2 diabetes mellitus. j ophthalmic vis res 2019;14:285–290 @ 2019 j  o  v r | published by knowledge e 285 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i3.4784&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr choroidal thickness and hba1c levels; torabi et al introduction diabetic retinopathy (dr) is one of the major causes of visual impairment worldwide.[1] the clinical features and pathogenesis of dr are primarily related to retinal vascular changes; however, choroidal vascular damage may have an important role.[2] delayed filling of the choroidal vessels using indocyanine green angiography has been reported in eyes with dr.[3–5] moreover, reduction in the choroidal blood flow and choroidal volume has been demonstrated in eyes with both nonproliferative and proliferative dr using doppler flowmetry.[6] choroidal vascular changes, including choroidal aneurysms, choroidal vessel narrowing and tortuosity, choroidal neovascularization, and choroidal non-perfusion may occur in eyes with dr.[7, 8] optical coherence tomography (oct) is a noninvasive method that allows high resolution in vivo imaging of the posterior segment of the eye.[9] nowadays, improvement of the enhanced depth imaging (edi) software permits highly reliable measurement of the choroidal thickness.[10, 11] hemoglobin a1c (hba1c) is one of the standard tools for the assessment of glycemic control and its optimum value is 5.6–7% in patients with diabetes.[12] a previous study reported that at least 1% reduction in hba1c can lead to significant reduction of the serious complications of dm, including death, myocardial infarction, and microcellular damage. [13] the aim of this study was to evaluate the correlation of hba1c values with choroidal thickness in diabetic patients using edi-oct. methods patients with type 2 diabetes mellitus (dm) with no evidence of dr or with mild non-proliferative diabetic retinopathy (npdr) were enrolled in this cross-sectional study. the disease severity was determined based on the clinical findings and using the international clinical disease severity scale for dr.[14] in eyes with ”no diabetic retinopathy”, as the name implies, there were no diabetic changes in the fundus examination, and eyes with ”mild npdr” were characterized only by the presence of a few microaneurysms. all fundus examinations were performed by a single vitreoretinal specialist. the exclusion criteria were the presence of dr more than mild npdr, diabetic macular edema (dme), any other ocular disorders, history of ocular surgery, including laser photocoagulation or intraocular anti-vascular endothelial growth factor (anti-vegf) injection, myopia more than −3 diopters, hyperopia more than +3 diopters, and patients with a history of hypertension or any other systemic diseases besides dm. the current study was approved by the ethics committee of our institute and was performed in agreement with the ethical principles of the declaration of helsinki. informed consent was obtained from every enrolled subject. edi-oct using heidelberg spectral domain oct (sd-oct; spectralis, wavelength: heidelberg engineering co., heidelberg, germany) was performed without pupillary dilation on the same day as blood sampling. complete ophthalmic examinations were performed one or two days before edi-oct imaging. all oct scans were performed by the same experienced operator between 11 and 11:45 am to avoid potential choroidal thickness changes with circadian rhythm. central sub-foveal choroidal thickness was measured using the caliper that is present (spectralis software version 5.3; heidelberg engineering) from the hyper-reflective line corresponding to the bruch’s membrane under the retinal pigment epithelium (rpe) to the interface of the choroid and sclera, in the central horizontal b-scan passing directly through the foveal center. then, the nasal and temporal choroidal thickness were measured 500 𝜇m nasal and temporal to the central subfoveal point. choroidal thickness measurements were performed by a single vitreoretinal specialist who was masked to the identity of the patients and the study groups. twenty-five patients were selected randomly from different groups and their choroidal thickness was measured again. intraclass correlation coefficient for intra-observer reproducibility was 0.91. patients with inadequate image quality in whom the interface of the choroid and sclera was not recognizable were excluded. all subjects were enrolled into three study groups based on hba1c values: group 1 included patients with good glycemic control (hba1c ≤ 7%), group 2 included patients with moderate glycemic control (hba1c between 7% and 8%), and group 3 included patients with poor glycemic control (hba1c ≥ 8%). healthy 286 j  o  v r volume 14, issue 3, july–september 2019 choroidal thickness and hba1c levels; torabi et al non-diabetic subjects were enrolled to group 4 as a control group. sub-foveal, nasal, and temporal choroidal thickness were measured and compared in the eyes of all study groups. statistical analysis data were analyzed using spss version 24 (ibm corp, armonk, ny, usa). mean ± sd was reported for quantitative variables. percentage was reported for qualitative variables. the kolmogorov-smirnov test was used to evaluate normal distribution in quantitative variables. analysis of variance (anova) or an equivalent non-parametric test (kruskal-wallis h test) was used to compare quantitative variables between the four groups. post hoc test (tukey test) was used if the anova was significant. a correlation test (pearson coefficient when the variables had normal distribution or spearman coefficient when the distribution of variables was not normal) was used to evaluate the correlation of choroidal thickness and quantitative variables, such as fasting blood sugar (fbs), duration of diabetes, etc. an independent sample’s t-test or equivalent non-parametric test (mann-whitney u test) was used to compare between two groups, such as the diabetic and non-diabetic ones. the paired sample t-test was used to compare variables within each groups such as the comparison of central choroidal thickness between right and left eyes. 𝑃 -value < 0.05 was considered significant. results a total of 180 eyes from 90 diabetic patients and 50 eyes from 25 non-diabetic patients were enrolled in this study. group 1 included 48 eyes from 24 diabetic patients with good glycemic control (hba1c ≤ 7%), group 2 included 58 eyes from 29 diabetic patients with moderate glycemic control (hba1c between 7% and 8%), and group 3 included 74 eyes from 37 diabetic patients with poor glycemic control (hba1c ≥ 8%). additionally, group 4 included 50 eyes from 25 non-diabetic subjects as the control group. the mean age and duration of dm was similar among all study groups [table 1]. there was no significant difference between mean central choroidal thickness of the right (247.80 ± 39.74 𝜇m) and left eyes (248.12 ± 37.40 𝜇m) of diabetic patients in all study groups (𝑃 = 0.849). overall, the mean central, nasal, and temporal choroidal thickness in diabetic patients (180 eyes) were significantly lower than those in the nondiabetic healthy subjects (50 eyes) [table 2]; however, the mean central macular thickness in the diabetic eyes (251.51 ± 26.22 𝜇m) and non-diabetic eyes (246.24 ± 22.46 𝜇m) had no significant difference (𝑃 = 0.72). choroidal thickness in diabetic patients in group 1 had no significant difference with non-diabetic patients (𝑃 = 0.093, 𝑃 = 0.379, and 𝑃 = 0.450 for central, nasal, and temporal points, respectively) and diabetic patients in group 2 (𝑃 = 0.276, 𝑃 = 0.830, and 𝑃 = 0.465 for central, nasal, and temporal points, respectively) [table 3]. however, choroidal thickness in diabetic patients in group 1 was significantly greater than patients in group 3 (𝑃 = 0.016, 𝑃 = 0.042, and 𝑃 = 0.031 for central, nasal, and temporal points, respectively). choroidal thicknesses in diabetic patients in group 2 was significantly more than patients in group 3 (𝑃 = 0.003, 𝑃 = 0.026, and 𝑃 = 0.032 for central, nasal, and temporal points, respectively). choroidal thicknesses was significantly greater in non-diabetic eyes than diabetic eyes in group 2 (𝑃 = 0.043, 𝑃 = 0.025 and 𝑃 = 0.0.016 for central, nasal, and temporal points, respectively) and group 3 (𝑃 = 0.001, 𝑃 = 0.018 and 𝑃 = 0.004 for central, nasal, and temporal points, respectively). the mean central choroidal thickness in diabetic patients had no significant correlation with fbs (r = −0.063 and 𝑃 = 0.685), duration of diabetes (r = −0.092 and 𝑃 = 0.390), and age (𝑟 = 0.122 and 𝑃 = 0.253). since patients with dme were excluded from this study, the mean central macular thickness was not different among all study groups. discussion in this study, we found that the choroidal thickness in non-diabetic patients was significantly greater than in diabetic patients. moreover, this study showed that the choroidal thickness in nondiabetic patients was similar to that in diabetic patients with good glycemic control (hba1c ≤ 7%) and was significantly greater than that in diabetic patients with moderate or poor glycemic control (hba1c > 7%). lee and co-workers evaluated the choroidal thickness in diabetic patients using sd-oct.[11] j  o  v r volume 14, issue 3, july–september 2019 287 choroidal thickness and hba1c levels; torabi et al table 1. demographic data of subjects in all study groups group1 group2 group3 group4 p-value number of cases (patients/eyes) 24/48 29/58 37/74 25/50 age 56.20 ± 8.13 59.02 ± 6.43 57.45 ± 7.44 59.10 ± 6.43 0.723 sex (male/female) 13/11 16/13 17/20 13/12 0.682 duration of dm (years) 6.12 ± 4.51 6.81 ± 5.20 7.10 ± 4.26 0.249 mean hba1c 6.12 ± 0.53 7.55 ± 0.39 10.21 ± 1.16 <0.001 dm, diabetes mellitus; hba1c, hemoglobin a1c table 2. comparison of choroidal and central macular thickness between diabetic and non-diabetic subjects diabetic cases non-diabetic cases p-value central choroidal thickness 247.80 ± 39.74 277.56 ± 34.15 0.001 choroidal thickness at nasal point 238.63 ± 37.00 262.92 ± 34.44 0.004 choroidal thickness at temporal point 239.30 ± 37.32 266.32 ± 32.47 0.001 central macular thickness 251.51 ± 26.22 246.24 ± 22.46 0.72 they examined 203 eyes of 203 diabetic patients and 48 eyes of 48 non-diabetic controls and showed that the sub-foveal choroidal thickness was less in the eyes with npdr or pdr than that in the healthy non-diabetic eyes; however, there was no significant difference between the diabetic eyes with no dr and the normal control eyes. sudhalkar et al assessed choroidal thickness changes in different types of dr.[15] they showed that diabetic patients with or without dr had a significantly thinner choroid compared to non-diabetic control group. moreover, they found that patients with pdr had a thinner sub-foveal choroid than patients with npdr. the authors concluded that choroidal thinning continued with increasing stages of dr. in the current study, we showed that choroidal thickness in diabetic eyes is less than that in nondiabetic control eyes. this finding is in agreement with lee et al,[11] sudhalkar et al,[15] as well as some other previous studies reporting choroidal thinning in diabetic patients compared to nondiabetic patients.[16, 17] however, some other studies reported no significant difference in choroidal thickness between the diabetic and non-diabetic eyes.[18] a previous study showed that abnormalities in the choriocapillaris and reduction of choroidal blood flow occurred in the early stages of dr,[19] which may lead to choroidal hypoxia and ischemia and finally choroidal thinning. yazici and coworkers compared the choroidal thickness in diabetic patients with and without polyneuropathy and healthy control subjects.[20] they reported that the central choroid is thicker in diabetic patients compared to normal subjects and also showed that there was additional choroidal thickening in diabetic patients with polyneuropathy. they concluded that choroidal thickening may be related to autonomic dysregulation secondary to diabetic neuropathy. kocasarac et al compared the choroidal thickness between diabetic patients with nephropathy and diabetic patients without nephropathy and found that the choroid is thinner in patients with diabetic nephropathy.[21] additionally, faries et al reported that in diabetic patients with microalbuminuria, central choroidal thickness is less than diabetic patients without microalbuminuria.[22] microalbuminuria is an indicator of generalized vascular dysfunction;[21] therefore, choroidal thinning in these patients may be a sign of choroidal vascular damage and dysfunction. sahinoglu-keskek et al classified 122 eyes of 122 diabetic patients into three study groups including diabetic patients without dr, diabetic patients with dr and no macular edema, and diabetic patients with dr and macular edema.[23] they reported that the sub-foveal choroid in patients with no dr was significantly thicker than that in patients with dr and without macular edema. moreover, 288 j  o  v r volume 14, issue 3, july–september 2019 choroidal thickness and hba1c levels; torabi et al table 3. the mean choroidal and central macular thickness in all study groups central choroidal thickness choroidal thickness at nasal point choroidal thickness at temporal point central macular thickness group1 259.46 ± 39.73 246.12 ± 43.55 251.00 ± 42.91 258.29 ± 31.29 group2 248.34 ± 33.72 237.55 ± 31.67 236.45 ± 33.95 254.17 ± 17.84 group3 239.81 ± 43.08 234.62 ± 36.58 233.94 ± 35.27 245.03 ± 27.34 group4 277.56 ± 34.16 262.92 ± 34.45 266.32 ± 32.48 246.24 ± 8.46 they reported that no significant differences in hba1c levels were detected among the three study groups and concluded that there was no correlation between sub-foveal choroidal thickness and hba1c values. unlike sahinoghlu-keskek et al’s study, we classified diabetic patients with the same dr severity based on hba1c values and compared the choroidal thickness among them and found that the choroidal thickness in the healthy control group was nearly equal to that in patients with good glycemic control (hba1c ≤ 7%) and was significantly more than the choroidal thickness in diabetic patients with moderate or poor glycemic control (hba1c > 7%). permanent high blood sugar levels in diabetic patients with inadequate treatment may lead to choroidal vascular damage and cause choroidal thinning in patient with dr.[18] therefore, in patients with uncontrolled dm and high levels of hba1c, the choroid is expected to be thinner. unsal et al reported a weak to moderate negative correlation between the subfoveal choroidal thickness and hba1c values, which is compatible with our results.[24] poorly controlled hba1c is associated with more severe stages of dr;[25] this may be due to the lower choroidal blood flow and choroidal hypoxia in the higher concentrations of blood sugar that ultimately may lead to choroidal thinning. diabetic choroidopathy may play a major role in the pathogenesis of dr because the outer retinal layers are dependent on the choroid for nutrition and oxygenation.[7] in the current study, we found that there was no significant correlation between the duration of diabetes and choroidal thickness. this is compatible with the studies of sahinoghlu-keskek et al and shen et al.[23, 26] we are aware of some of the limitations of our study. first, we had no axial length data; however, the patients with high refractive errors were excluded. the possibility of measurement errors due to manual measurement and measurement by a single observer constitute other limitations. in conclusion, we showed that the choroidal thickness in normal control subjects was almost equal to diabetic patients with good glycemic control (hba1c ≤ 7%) and was significantly greater than choroidal thickness in diabetic patients with moderate or poor glycemic control (hba1c > 7%). therefore, better diabetic control with hba1c ≤ 7% may prevent choroidal vascular damage and choroidal thinning and finally prevent the development of dr. however, future studies with larger sample size are required to establish the correlation of choroidal thickness with hba1c and to determine the optimal cutoff value of hba1c that affects the choroidal vascular system. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. regatieri cv, branchini l, carmody j, fujimoto jg, duker js. choroidal thickness in patients with diabetic retinopathy analyzed by spectral-domain optical coherence tomography. retina 2012;32:563–568. 2. adhi m, brewer e, waheed nk, duker js. analysis of morphological features and vascular layers of choroid in diabetic retinopathy using spectral-domain optical coherence tomography. jama ophthalmol 2013;131:1267–1274. 3. shiragami c, shiraga f, matsuo t, tsuchida y, ohtsuki h. risk factors for diabetic choroidopathy in patients with diabetic retinopathy. graefes arch clin exp ophthalmol 2002;240:436–442. 4. fukushima i, mcleod ds, lutty ga. intrachoroidal microvascular abnormality: a previously unrecognized j  o  v r volume 14, issue 3, july–september 2019 289 choroidal thickness and hba1c levels; torabi et al form of choroidal neovascularization. am j ophthalmol 1997;124:473–487. 5. shiraki k, moriwaki m, kohno t, yanagihara n, miki t. age-related scattered hypofluorescent spots on latephase indocyanine green angiograms. int ophthalmol 1999;23:105–109. 6. schocket ls, brucker aj, niknam rm, grunwald je, dupont j, brucker aj. foveolar choroidal hemodynamics in proliferative diabetic retinopathy. int ophthalmol 2004;25:89–94. 7. hidayat aa, fine bs. diabetic choroidopathy: light and electronmicroscopic observations of seven cases. ophthalmology 1985;92:512–522. 8. fryczkowski aw, sato se, hodes bl. changes in the diabetic choroidal vasculature: scanning electronmicroscopy findings. ann ophthalmol 1988;20:299–305. 9. wojtkowski m, bajraszewski t, gorczyńska i, targowski p, kowalczyk a, wasilewski w, et al. ophthalmic imaging by spectral optical coherence tomography. am j ophthalmol 2004;138:412–419. 10. celik e, cakır b, turkoglu eb, doğan e, alagoz g. effect of cataract surgery on subfoveal choroidal and ganglion cell complex thicknesses measured by enhanced depth imaging optical coherence tomography. clin ophthalmol 2016;10:2171–2177. 11. lee hk, lim jw, shin mc. comparison of choroidal thickness in patients with diabetes by spectral-domain optical coherence tomography. korean j ophthalmol 2013;27:433–439. 12. tavakol moghadam s, najafi ss, yektatalab s. the effect of self-care education on emotional intelligence and hba1c level in patients with type 2 diabetes mellitus: a randomized controlled clinical trial. int j community based nurs midwifery 2018;6:39–46. 13. da costa d, dritsa m, ring a, fitzcharles ma. mental health status and leisure-time physical activity contribute to fatigue intensity in patients with spondylarthropathy. arthritis rheum 2004;51:1004–1008. 14. wilkinson cp, ferris fl, klein re, lee pp, agardh cd, davis m, et al. proposed international clinical diabetic retinopathy and diabetic macular edema disease severity scales. ophthalmology 2003;110:1677–1682. 15. sudhalkar a, chhablani jk, venkata a, raman r, rao ps, jonnadula gb. choroidal thickness in diabetic patients of indian ethnicity. indian j ophthalmol 2015;63:912–916. 16. esmaeelpour m, brunner s, ansari-shahrezaei s, nemetz s, povazay b, kajic v, et al. choroidal thinning in diabetes type 1 detected by 3-dimensional 1060 nm optical coherence tomography. invest ophthalmol vis sci 2012;53:6803–6809. 17. kim jt, lee dh, joe sg, kim jg, yoon yh. changes in choroidal thickness in relation to the severity of retinopathy and macular edema in type 2 diabetic patients. invest ophthalmol vis sci 2013;54:3378–3384. 18. kase s, endo h, yokoi m, kotani m, katsuta s, takahashi m, et al. choroidal thickness in diabetic retinopathy in relation to long-term systemic treatments for diabetes mellitus. eur j ophthalmol 2016;26:158–162. 19. nagaoka t, kitaya n, sugawara r, yokota h, mori f, hikichi t, et al. alteration of choroidal circulation in the foveal region in patients with type 2 diabetes. br j ophthalmol 2004;88:1060–1063. 20. yazici a, sogutlu sari e, koc r, sahin g, kurt h, ozdal pc, et al. alterations of choroidal thickness with diabetic neuropathy. invest ophthalmol vis sci 2016:57:1518–1522. 21. kocasarac c, yigit y, sengul e, sakalar yb. choroidal thickness alterations in diabetic nephropathy patients with early or no diabetic retinopathy. int ophthalmol 2017 apr. doi: 10.1007/s10792-017-0523-5. [epub ahead of print]. 22. farias lb, lavinsky d, schneider wm, guimaraẽs l, lavinsky j, canani lh. choroidal thickness in patients with diabetes and microalbuminuria. ophthalmology 2014:121:2071–2073. 23. sahinoglu-keskek n, altan-yaycioglu r, canan h, coban-karatas m. influence of glycosylated hemoglobin on the choroidal thickness. int ophthalmol 2017. doi: 10.1007/s10792-017-0668-2. [epub ahead of print]. 24. unsal e, eltutar k, zirtiloğlu s, dinçer n, ozdoğan erkul s, güngel h. choroidal thickness in patients with diabetic retinopathy. clin ophthalmol 2014:8:637–642. 25. long m, wang c, liu d. glycated hemoglobin a1c and vitamin d and their association with diabetic retinopathy severity. nutr diabetes 2017;7:e281. 26. shen zj, yang xf, xu j, she cy, wei ww, zhu wl, et al. association of choroidal thickness with early stages of diabetic retinopathy in type 2 diabetes. int j ophthalmol 2017;10:613–618. 290 j  o  v r volume 14, issue 3, july–september 2019 case report central serous chorioretinopathy in a case of regressed familial retinoblastoma saeed karimi1,2, md; amir arabi1,2, md, mph; toktam shahraki1,2, md; sare safi3, phd 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2department of ophthalmology, torfeh medical center, shahid beheshti university of medical sciences, tehran, iran 3ophthalmic epidemiology research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran orcid: saeed karimi: http://orcid.org/0000-0002-3231-8414 amir arabi: https://orcid.org/0000-0002-6523-7733 abstract purpose: to present a case of central serous chorioretinopathy (csc) in association with regressed familial retinoblastoma. case report: a 23-year-old man with regressed unilateral familial retinoblastoma in his left eye presented with decreased vision of the left eye since two months ago. the patient had undergone chemotherapy and cryotherapy for the treatment of retinoblastoma 20 years ago. in the left eye, funduscopy disclosed regressed mass of retinoblastoma, inferonasal to the optic disc, and focal subfoveal neurosensory detachment. optical coherence tomography (oct) and fluorescein angiography revealed csc. as there was no sign of recurrence of retinoblastoma and retinal findings did not show late-onset chemotherapy-related retinopathy, the patient was diagnosed with csc and followed up. after two months, visual acuity of the left eye improved, and repeated macular oct revealed absorption of the subretinal fluid. conclusion: subretinal fluid accumulation in a patient with regressed retinoblastoma is not always a sign of tumor recurrence or a treatment-related retinopathy. keywords: central serous chorioretinopathy; recurrence; retinoblastoma j ophthalmic vis res 2020; 15 (4): 559–564 introduction central serous chorioretinopathy (csc) is a retinal disease in which there is serous detachment correspondence to: amir arabi, md, mph. research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, no. 23, paidarfdard st., boostan 9 st., pasadaran ave., tehran 16666, iran. e-mail: amir_arab_91@yahoo.com received: 16-07-2019 accepted: 07-01-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7802 of the neurosensory retina, typically restricted to the macular area. the disease is believed to be a disorder with multiple etiologies that lead to a common pathway of choroidal vascular abnormality.[1] the pathogenesis is poorly known, and retrospective studies have recognized a number of risk factors. these include male sex,[2] psychological tension,[3] personality type a,[4] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: karimi s, arabi a, shahraki t, safi s. central serous chorioretinopathy in a case of regressed familial retinoblastoma. j ophthalmic vis res 2020;15:559–564. © 2020 journal of ophthalmic and vision research | published by knowledge e 559 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7802&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr cscr and rb association; karimi et al figure 1. (a) posterior fundus view of the left eye demonstrating the distance between the mass and fovea. (b) regressed retinoblastoma with intralesional cavitation, inferonasal to the optic disc. corticosteroid use,[5, 6] gestation,[7] and, infrequently, endocrine disorders (such as cushing’s syndrome)[8] or tumors with steroid products.[9] retinoblastoma is an inherited pediatric malignant neoplasia, assumed to be the most frequent intraocular malignancy in children.[10] concerns about patients with a history of retinoblastoma, especially those treated with external beam radiotherapy, are related to the risk of recurrence, secondary malignancies, and development of radiation retinopathy or retinal damage secondary to chemotherapy. all these conditions can develop even after a long period from the initial treatment.[11–13] here, we report a case of regressed retinoblastoma and coincidental csc in the same eye. the association between regressed retinoblastoma and csc has not been reported in the literature. case report a 23-year-old man presented to the ophthalmology clinic with a two-month history of blurred vision in the left eye. the patient had a history of 560 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 cscr and rb association; karimi et al figure 2. (a) sd-oct of the left eye; neurosensory detachment with echo-free subretinal fluid adjacent to a well-defined ped. (b) edi-oct of the same eye; note the increased thickness of the choroid and congested vasculature. unilateral familial retinoblastoma in the left eye, which had been treated with cryotherapy and systemic chemotherapy 20 years before. medical and drug histories were otherwise unremarkable. the patient had a positive family history of retinoblastoma, as his father and two siblings were diagnosed with bilateral familial retinoblastoma. ophthalmic examination showed a corrected distance visual acuity of 10/10 in the right eye and 5/10 in the left eye. intraocular pressure was normal, and relative afferent pupillary defect was negative. anterior segment examination showed normal findings. fundus examination of the left eye revealed a white elevated regressed retinoblastoma mass with intralesional cavitation and focal subfoveal neurosensory detachment (figure 1). the right eye was completely normal. spectral-domain optical coherence tomography (oct) revealed echo-free subfoveal fluid accumulation and a small pigment epithelial detachment. additionally, enhanced depth imaging oct of both eyes showed thick choroid and dilated choroidal vessels (figure 2). fluorescein angiography (fag) of the left eye revealed an expansile leaking dot near the fovea in the mid-to-late phase. indocyanine green angiography showed hyperpermeability of dilated choroidal vasculature (figure 3). based on clinical examination and paraclinical findings, a diagnosis of csc coincidental with regressed unilateral familial retinoblastoma was made. as there was no sign of retinoblastoma recurrence or secondary malignancy and the clinical findings did not reflect late-onset retinopathy related to prior treatment, a close follow-up was planned. during the follow-up period, oral propranolol was prescribed. at the two-month re-examination, the best corrected visual acuity of the affected eye improved to 7/10, journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 561 cscr and rb association; karimi et al figure 3. early and late phases of fluorescein angiography (left) and icg angiography (right) showing juxtafoveal subretinal leakage in addition to congestion of choroidal vessels. figure 4. macular sd-oct of the same eye two months later shows resolved subretinal fluid. 562 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 cscr and rb association; karimi et al the retinoblastoma mass was unchanged, and the new macular oct revealed absorption of the subretinal fluid (figure 4). discussion blurring of vision and new accumulation of subretinal fluid in a patient with history of retinoblastoma is usually suggestive of recurrent retinoblastoma, adverse effect of chemotherapy on the chorioretinal tissue, or late-onset radiation retinopathy. as there was no history of radiotherapy and intra-arterial chemotherapy in this case, ocular complications of these therapeutic interventions were not considered for the patient. posterior segment side effects of systemic chemotherapy have been studied for some drugs. secondary retinopathy with visual loss develops with cisplatin use;[14] however, retinal findings of cisplatin-induced retinopathy are different from those seen in our case. moreover, retinal ischemia and subsequent neovascularization have been reported in a patient receiving chemotherapy with bleomycin, etoposide, and cisplatin.[15] however, fag of this patient revealed no sign of retinal ischemia or neovascularization. subretinal fluid and choroidal changes have not been reported in ocular conditions associated with common agents used for systemic chemotherapy. the impact of intravenous chemotherapy on choroidal microvasculature was analyzed in a previous study, where the authors concluded that systemic chemotherapy cannot cause a significant change in choroidal thickness.[16] these findings support the impression of increased choroidal thickness in the current case as a primary event. recurrence of retinoblastoma may be manifested by a new retinal tumor, vitreous seeding, subretinal seeding, or extraocular findings.[17] following systemic chemoreduction, the recurrence rate of retinal tumors ranges from 24 to 44%.[18] the majority of new tumors will be detected within three years of initial retinoblastoma diagnosis. in a previous study, most retinal tumors recurred within five months of initiating chemoreduction, when the therapeutic period of chemotherapy had not ended.[19] although recurrence of retinoblastoma after 20 years is rare, complete retinal examination for any active retinal tumor was performed in our patient, and no sign of retinal recurrence was detected. in eyes presenting with exophytic tumors with subretinal seeding at presentation, recurrence of subretinal seeding is a particular concern.[17] shields et al suggested an average interval of two months for the recurrence of subretinal seeding after completion of chemotherapy. however, calculated recurrence rates of 53 to 62% at one and three years, respectively, suggested that subretinal recurrence may happen after several years.[18] the subretinal seeds may be free running or fixed to the external retinal surface.[20] retinal detachment, in addition to position-dependent ophthalmoscopic contours, is a characteristic finding in subretinal seeding of retinoblastoma.[20] features of subretinal fluid and its absorption on follow-up examinations ruled out the probability of recurrent subretinal seeding as the cause in our patient. csc is an ocular condition characterized by neurosensory detachment associated with pathological dilation of choroidal vessels. a number of systemic disorders, including autoimmune diseases, hypertension, allergic respiratory diseases,[2, 21] helicobacter pylori infection, obstructive sleep apnea,[22] and corticosteroid-releasing tumors have been reported to be related to the pathophysiology of csc. among these, no ocular malignancy has been shown to be associated with csc. although some conditions with choroidal origin such as radiation choroidopathy and choroidal neovascularization have been reported after treatment of retinoblastoma,[23] in case of subretinal exudation in an eye with regressed retinoblastoma, retinoblastoma recurrence or secondary malignant tumors are considered prior to choroidal conditions. this is the first report on the coincidence of csc and retinoblastoma in the same eye. although blurring of vision and accumulation of subretinal fluid in a case of retinoblastoma should be considered as indicators of recurrent retinoblastoma or treatment adverse effects, coincidence of csc and retinoblastoma could be detected in our patient. references 1. spaide rf, goldbaum m, wong dw, tang kc, iida t. serous detachment of the retina. retina 2003;23:820–846. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 563 cscr and rb association; karimi et al 2. haimovici r, koh s, gagnon dr, lehrfeld t, wellik s. risk factors for central serous chorioretinopathy: a case-control study. ophthalmology 2004;111:244–249. 3. islam qu, hanif mk, tareen s. frequency of systemic risk factors in central serous chorioretinopathy. j coll physicians surg pak 2016;26:692–695. 4. yannuzzi la. type a behavior and central serous chorioretinopathy. retina 2012;32:709. 5. wakakura m, ishikawa s. central serous chorioretinopathy complicating systemic corticosteroid treatment. br j ophthalmol 1984;68:329–331. 6. jain is, singh k. maculopathy a corticosteroid side-effect. j all india ophthalmol soc. 1966;14:250–252. 7. chumbley lc, frank rn. central serous retinopathy and pregnancy. am j ophthalmol 1974;77:158–160. 8. bouzas ea, scott mh, mastorakos g, chrousos gp, kaiser-kupfer mi. central serous chorioretinopathy in endogenous hypercortisolism. arch ophthalmol 1993;111:1229–1233. 9. thoelen am, bernasconi pp, schmid c, messmer ep. central serous chorioretinopathy associated with a carcinoma of the adrenal cortex. retina 2000;20:98–99. 10. krishna sm, yu gp, finger pt. the effect of race on the incidence of retinoblastoma. j pediatr ophthalmol strabismus 2009;46:288–293. 11. bellerive c, singh ad. radiation retinopathy 47 years following brachytherapy for retinoblastoma. ocul oncol pathol 2018;4:157–160. 12. kim sj, hubbard gb, 3rd. intravitreal bevacizumab (avastin) for radiation retinopathy 53 years after treatment of retinoblastoma. retin cases brief rep 2007;1:198–201. 13. shields cl, piccone mr, shields ja, eagle rc, jr., singer m. mushroom-shaped choroidal recurrence of retinoblastoma 25 years after therapy. arch ophthalmol 2002;120:844–846. 14. katz bj, ward jh, digre kb, creel dj, mamalis n. persistent severe visual and electroretinographic abnormalities after intravenous cisplatin therapy. j neuro-ophthalmol 2003;23:132–135. 15. kwan as, sahu a, palexes g. retinal ischemia with neovascularization in cisplatin related retinal toxicity. am j ophthalmol 2006;141:196–197. 16. sioufi k, say eat, ferenczy sc, leahey am, shields cl. optical coherence tomography angiography findings of deep capillary plexus microischemia after intravenous chemotherapy for retinoblastoma. retina 2019;39:371– 378. 17. berry jl, kogachi k, murphree al, jubran r, kim jw. a review of recurrent retinoblastoma: children’s hospital los angeles classification and treatment guidelines. int ophthalmol clin 2019;59:65–75. 18. shields cl, honavar sg, shields ja, demirci h, meadows at, naduvilath tj. factors predictive of recurrence of retinal tumors, vitreous seeds, and subretinal seeds following chemoreduction for retinoblastoma. arch ophthalmol 2002;120:460–464. 19. shields cl, shelil a, cater j, meadows at, shields ja. development of new retinoblastomas after 6 cycles of chemoreduction for retinoblastoma in 162 eyes of 106 consecutive patients. arch ophthalmol 2003;121:1571– 1576. 20. munier fl. classification and management of seeds in retinoblastoma. ellsworth lecture ghent august 24th 2013. ophthalmic genet 2014;35:193–207. 21. dada t. systemic findings associated with central serous chorioretinopathy. am j ophthalmol 2000;130:379. 22. kim jt, eichling ps, wang m. central serous chorioretinopathy associated with narcolepsy. retin cases brief rep 2011;5:302–305. 23. peiretti e, slakter js, wu s, iranmanesh r, yannuzzi la. late effect of external eye irradiation on choroidal circulation. eur j ophthalmol 2006;16:637–640. 564 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 original article in vivo corneal microstructural changes in herpetic stromal keratitis: a spectral domain optical coherence tomography analysis alejandro rodriguez-garcia, md; raul alfaro-rangel, md; andres bustamante-arias, md julio c. hernandez-camarena, md, phd tecnologico de monterrey, school of medicine and health sciences, institute of ophthalmology and visual sciences, cornea and external diseases service, monterrey, mexico orcid: alejandro rodriguez-garcia: https://orcid.org/0000-0002-1419-2109 abstract purpose: to describe and analyze the microstructural changes in herpetic stromal keratitis (hsk) observed in vivo by spectral-domain ocular coherence tomography (sd-oct) at different stages of the disease. methods: a prospective, cross-sectional, observational, and comparative sd-oct analysis of corneas with active and inactive keratitis was performed, and the pathologic differences between the necrotizing and non-necrotizing forms of the disease were analyzed. results: fifty-three corneas belonging to 43 (81.1%) women and 10 (18.8%) men with a mean age of 41.0 years were included for analysis. twenty-four (45.3%) eyes had active keratitis, and 29 (54.7%) had inactive keratitis; the majority (83.0%) had the non-necrotizing form. most corneas (79.1%) with active keratitis showed stromal edema and inflammatory infiltrates. almost half of the active lesions affected the visual axis, were found at mid-stromal depth, and had a medium density. by contrast, corneas with inactive keratitis were characterized by stromal scarring (89.6%), epithelial remodeling (72.4%), and stromal thinning (68.9%). in contrast to non-necrotizing corneas, those with necrotizing hsk showed severe stromal scarring, inflammatory infiltration, and thinning. additionally, most necrotizing lesions (77.7%) affected the visual axis and had a higher density (p = 0.01). conclusion: active hsk is characterized by significant epithelial and stromal thickening and the inactive disease manifests epithelial remodeling at sites of stromal thinning due to scarring. necrotizing keratitis is characterized by distorted corneal architecture, substantial stromal inflammatory infiltration, and thinning. in vivo sd-oct analysis permitted a better understanding of the inflammatory and repair mechanisms occurring in this blinding corneal disease. keywords: corneal infection; herpetic keratitis; hsv-1; sd-oct; stromal edema j ophthalmic vis res 2020; 15 (3): 279–288 correspondence to: alejandro rodriguez-garcia, md. centro medico zambrano hellion (piso 1, ote.) av., batallon de san patricio no. 112. col. real de san agustin. san pedro garza garcia, n.l. méxico. cp. 66278. e-mail: immuneye@gmail.com received: 14-06-2019 accepted: 05-02-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7446 introduction herpetic keratitis is the major cause of corneal blindness in many developed countries, with this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: rodriguez-garcia a, alfaro-rangel r, bustamantearias a, hernandez-camarena jc. in vivo corneal microstructural changes in herpetic stromal keratitis: a spectral domain optical coherence tomography analysis. j ophthalmic vis res 2020;15:279–288. © 2020 journal of ophthalmic and vision research | published by knowledge e 279 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7446&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr microstructural changes in herpetic stromal keratitis; rodriguez-garcia et al the stromal form representing almost one-third (29.5%) of all cases.[1, 2] herpetic stromal keratitis (hsk) accounts for up to 44% of recurrences, and the risk for recurrent infection increases after multiple attacks of keratitis.[3, 4] therefore, hsk represents a significant burden of ocular disease, being the most feared presentation of herpetic corneal infection due to its severe damage to the cornea.[5] most cases of hsk present as non-necrotizing.[6] non-necrotizing hsk or immune stromal keratitis is characterized by stromal inflammation leading to scarring, thinning, and vascularization of the cornea.[7, 8] the direct viral antigen stimulation of hsv-1-specific cd4𝛼𝛽 t-lymphocytes probably drives stromal inflammation. other likely pathogenic mechanisms are autoantigens unmasked and mimicked by hsv-1 corneal infection, bystander cytokine activation of cd4𝛼𝛽 t-cells, or a combination of all these mechanisms.[9–11] on the other hand, the necrotizing form is characterized by ulcerations, dense leukocytic stromal infiltration, and necrosis that may rapidly progress to corneal perforation.[9, 10] both viral antigens and replicating virions have been implicated in the pathogenesis of this form of keratitis.[12, 13] most of our knowledge of the pathologic alterations seen in hsk is based on direct slitlamp observations and histopathologic findings from fixed tissues.[14, 15] recently, in vivo confocal microscopy analysis of herpetic keratitis has shown that a significant and gradual decrease in superficial epithelial cell density is correlated with decreased corneal innervation.[16] the same imaging technique has also been used to monitor the inflammatory process of hsk.[17] spectral-domain optical coherence tomography (sd-oct) provides noncontact in vivo corneal cross-sectional, high-resolution images that allow a detailed delineation of the cornea.[18] the high speed of the technique permits the acquisition of high-definition frames with few motion artifacts.[19, 20] enlarged sections of averaged images permit the discrimination of all corneal layers.[21] sd-oct also enables more accurate measurements of the corneal thickness at a particular point, or in a 6 mm diameter pachymetry map even in the presence of corneal irregularity or opacity.[8, 22] the primary purpose of the present study was to describe and analyze the microstructural corneal alterations observed by sd-oct during the active and inactive stages of hsk and to compare those changes between non-necrotizing and necrotizing keratitis. this analysis adds to our understanding of the inflammatory and repair mechanisms of the cornea in this sight-threatening disease. methods this is a prospective, cross-sectional, descriptive, comparative, and observational study of patients diagnosed with hsk based on clinical findings. the inclusion criteria for the disease diagnosis were based on previous medical history, clinical manifestations, and therapeutic response to herpes-specific antiviral therapy. past medical histories of mucocutaneous herpetic vesicular eruption, oral herpetic stomatitis, and herpetic blepharoconjunctivitis were all considered for the diagnosis. previous or current clinical manifestations consisting of herpetic epithelial and/or stromal keratitis, characterized by dendritic or geographic ulceration, inflammatory stromal infiltration, stromal edema, and hypoesthesia were required for inclusion in the study. corneal examination parameters performed on all patients included a refractive power analysis (opdscan iii, nidek co., ltd. japan), a detailed comparative correlative slit lamp exam, including colored photographs and schematic drawings of the corneal lesions, as well as qualitative esthesiometry and fluorescein and lissamine green staining. therapeutic response to conventional antiviral therapy was also considered necessary for the diagnosis.[7–9] the exclusion criteria consisted of an unwillingness to participate in the study, any previous history of corneal pathology such as trauma, chemical burns, bacterial, fungal, adenoviral, or protozoan infection, and other forms of inflammatory or infectious external disease. corneas with disciform keratitis, endotheliitis, anterior uveitis, or neurotrophic keratitis were excluded from the analysis. additionally, cases with a doubtful diagnosis or with atypical hsk defined as corneas where dendritic or geographical ulcers, epithelial infiltration, and hypoesthesia were not evident were excluded from the analysis. before inclusion in the study, all patients read and signed an informed consent form previously approved by the research and ethics committees 280 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 microstructural changes in herpetic stromal keratitis; rodriguez-garcia et al of our institution according to the tenets of the declaration of helsinki. corneas included for analysis were divided according to the pathophysiologic classification into immunologic, or non-necrotizing, and infectious, or necrotizing, hsk. corneas were also categorized as inactive when corneal opacity and scarring due to herpetic keratitis was evident, and no signs or symptoms of inflammation or infection were present. active disease was considered when patients experienced related symptoms, including red eye, blurred vision, foreign body sensations, photophobia, tearing, and pain. additionally, signs of active inflammation, such as ciliary injection, corneal ulceration, active vascularization, inflammatory infiltration, stromal edema or melting, and keratic precipitates were observed under slit-lamp examination. sd-oct (rtvue-100®, optovue, inc., fremont, ca, usa) analysis was performed by the same technician (sis) to each eye using a corneal module adaptor (cam) l-lens (15 µm) and s-lens (10 µm), depending on whether the full extent or the details of corneal lesions, respectively, were analyzed as requested in a drawing scheme. while the wide-angle cam l-lens provides a scan width of up to 6 mm and a transverse resolution of 15 μm, the high magnification cam s-lens provides a scan width of up to 4 mm and a transverse resolution of 10 μm. additionally, the corneal adaptor module software (version 5.5) automatically processes five consecutive sets of eight high-definition meridional scans, of which the three most consistent sets are used to provide a 6 mm scan diameter pachymetry map and the minimum corneal thickness point.[20] specific measurements of corneal epithelial and stromal thicknesses were also performed manually at the site of the lesions. cursors were always placed perpendicular to the anterior corneal surface at the point of measurement. four thickness measurements were considered for analysis: the central corneal thickness (cct), minimal corneal thickness (mct), corneal thickness at the site of the lesion (ctl), and corneal epithelial thickness over the stromal lesion (cetl). multiple high-resolution meridional scans were performed for each corneal lesion related to hsk according to a drawing scheme prepared from direct observations under the slit lamp. representative scan images were selected for morphologic analysis by one of us (arg) based on representative slit-lamp observations and corneal color photographs registered just before sending the patients for sd-oct analysis. corneal lesions consisting of inflammatory infiltrates and stromal edema from eyes with active keratitis and scars or leukomas from eyes with inactive disease were studied. stromal edema assessed by sd-oct was defined as a hypodense area (grade i, < 33%) within the involved corneal stroma, accompanied by a ≥ 20% increase in thickness compared to the adjacent unaffected stroma. stromal thinning was defined as a ≥ 15% thickness reduction compared to an immediate adjacent healthy area. inflammatory infiltrate was described as a hyperdense lesion (grades ii, 34–66%, and iii, > 67%) within the involved corneal stroma, accompanied by a ≥ 10% increase in the thickness of an adjacent unaffected area. the following measurement parameters were analyzed: localization (central = 5 mm zone, or paracentral/peripheral = 5–12 mm zone); percentage of surface extension (small ≤ 25%, medium = 25–45%, and large ≥ 45%); depth (superficial ≤ 150 µm, medial = 150–350 µm, and deep ≥ 350 µm); and density, which was analyzed using the color scale provided by the sd-oct device. for this purpose, a classification system was created to quantify the density of each lesion by examining the warm tones (white, red, orange) that predominated in the image, which corresponded to the percentage of backscattering and reflective properties of the tissue analyzed (grade i, < 33%; grade ii, 34–66%; and grade iii, > 67%). statistical analysis was performed using the spss software version 23.0 (spss inc. chicago, il. usa). a shapiro-wilk test was performed to explore the normality of variable distribution; observing that the pachymetric measurements, density, and depth values of the corneal lesions were not distributed normally, nonparametric tests (mann–whitney u-test) were used to compare the difference in medians. a p-value < 0.05 was considered as statistically significant. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 281 microstructural changes in herpetic stromal keratitis; rodriguez-garcia et al ethical consideration ethics committee approval no. conbioetica19cei00820130520) research committee approval no. 13c119039138 cofepris authorization no. 13cei19039139 results sd-oct scanning was performed on 53 corneas of patients with unilateral hsk. these corneas belonged to 43 (81.1%) women and 10 (18.9%) men. the mean age at presentation was 41.0 years (range, 7 to 77 years). most eyes (83.1%) had immune or nonnecrotizing hsk, and only nine (16.9%) eyes had the infectious or necrotizing form. regarding the inflammatory status at the time of analysis, 24 (45.3%) eyes had active keratitis and 29 (54.7%) had inactive keratitis. in the group of patients with active keratitis, 17 (70.8%) corneas belonged to women and 7 (29.1%) to men with a mean age of 42.2 years (range, 9–77 years). the most frequent symptoms found in these patients were red eye, tearing, and photophobia, and the most frequent signs were red eye, stromal edema, and hypoesthesia. meanwhile, in the inactive keratitis group, 25 (86.2%) corneas belonged to women and only 4 (13.7%) to men with a younger mean age of 39.9 years (range, 7–70 years). apart from nonspecific symptoms of dry eye and discomfort, most of these patients were asymptomatic at the time of the analysis, and only those with corneal scarring along the visual axis or irregular astigmatism complained of blurred vision. sd-oct microstructural analysis for active keratitis table 1 shows the frequency of the sd-oct morphologic alterations from corneas with active keratitis. the most common findings were stromal edema and inflammatory infiltrates seen in 79.1% of eyes each, followed by epithelial thickening in 66.6% and stromal scarring in 62.5% of eyes. of the seven corneas with active necrotizing hsk, five (71.4%) showed epithelial ulceration over the stromal infiltration. half of the hsk lesions affected the visual axis, and the other 50% were located in the paracentral and peripheral cornea. additionally, nearly half of the active corneal lesions were found at mid-stromal depth, had a medium density, and covered an area between 25 and 45% of the corneas (table 2). the corneal shape was distorted within the affected zones, showing a hypodense and thickened stroma due to edema. there was also a higher reflectivity at the site of stromal inflammatory infiltrates compared to unaffected areas (figure 1). sd-oct microstructural analysis for inactive keratitis the most common sd-oct morphologic changes seen in corneas with inactive keratitis consisted of stromal scarring (89.6%), epithelial remodeling (72.4%), and stromal thinning (68.9%) (table 1). similar to the eyes with active hsk, nearly half of the lesions were located in the visual axis, and the other 48.3% were located in the paracentral and peripheral cornea. additionally, 44.8% of the lesions extended to the mid-stromal depth and had a medium density. finally, most of the inactive lesions (72.4%) covered an area between 25 and 45% of the ocular surface (table 2). in general, the sd-oct analysis of inactive hsk showed thinner corneas with stromal compaction due to fibrosis and scarring. the overlying epithelium was thicker in the affected areas, showing remodeling and thickness compensation. additionally, there was a higher reflectivity, particularly in areas of dense leukomas (figure 2). sd-oct microstructural differences between non-necrotizing and necrotizing hsk there was a clear difference in the morphologic appearance between non-necrotizing and necrotizing keratitis. all corneas with necrotizing hsk showed severe stromal scarring, and the vast majority also had significant stromal inflammatory infiltration and thinning (table 1). on the other hand, the non-necrotizing corneas showed significantly less inflammatory infiltration (p = 0.011). following the sd-oct cross-sectional analysis, the majority of necrotizing hsk lesions (77.7%) were located centrally, affecting the visual axis, and showed a higher density compared to non-necrotizing lesions (p = 0.01) (table 2). 282 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 microstructural changes in herpetic stromal keratitis; rodriguez-garcia et al a b c d figure 1. (a) slit-lamp photograph of a cornea with active necrotizing hsk showing stromal inflammatory infiltration and edema. (b) sd-oct pachymetry map showing a thickened cornea (max = 670 µm) corresponding to the area with stromal edema. (c) a cross-sectional view of the central lesion showing areas of epithelial thickening (max = 76 µm) over inflammatory infiltrates, corresponding to areas of hyperreflectivity, and hypodense areas, corresponding to stromal edema. (d) color scale of the same lesion showing the inflammatory infiltrates and scarring in warm (orange to yellow) tones. figure 2. (a) slit-lamp photograph of a cornea with inactive nonnecrotizing hsk, showing a diffuse leukoma with no stromal edema. (b) sd-oct pachymetry showing a thinner cornea (min = 423 µm) in the area of the lesion. (c) a cross-sectional view of the leukoma showing areas of epithelial remodeling and thickening compensation (max = 83 µm) under areas of scarring and stromal compaction (min = 470 µm). (d) color scale of the lesion showing higher density areas corresponding to fibrosis and scarring on the anterior and medial stroma, fading to yellow and green tones as the lesion becomes less dense. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 283 microstructural changes in herpetic stromal keratitis; rodriguez-garcia et al table 1. frequency of sd-oct morphologic changes of herpetic stromal keratitis according to inflammatory status and type of keratitis. corneal structure change (cross-sectional analysis) active hsk no. eyes (%) (n = 24) inactive hsk no. eyes (%) (n = 29) p-value non-necrotizing keratitis no. eyes (%) (n = 44) necrotizing keratitis no. eyes (%) (n = 9) p-value epithelial remodeling 1 (4.1) 21 (72.4) < 0.001* 19 (43.1) 3 (33.3) 0.02* epithelial thickening 16 (66.6) 1 (3.4) < 0.001* 13 (29.5) 4 (44.4) 0.387 epithelial damage (ulceration) 5 (20.8) 0 (0.0) < 0.001* 0 (0.0) 5 (55.5) < 0.001* stromal thinning (< 450 µm) 6 (25.0) 20 (68.9) 0.004* 20 (45.4) 7 (77.7) 0.080 stromal edema (> 570 µm) 19 (79.1) 1 (3.4) < 0.001* 15 (34.0) 4 (44.4) 0.652 stromal inflammatory infiltration 19 (79.1) 2 (6.8) < 0.001* 14 (31.8) 7 (77.7) 0.011* stromal scarring (> 35% surface) 15 (62.5) 26 (89.6) 0.042* 34 (77.2) 9 (100.0) 0.095 sd-oct, spectral-domain optical coherence tomography; hsk, herpetic stromal keratitis ∗p-value < 0.05 was considered as statistically significant (mann–whitney u-test for two independent samples). table 2. sd-oct cross-sectional analysis of most representative corneal lesions (scar, leukoma, or infiltrate) seen in eyes with herpetic stromal keratitis. lesion(s) parameter measured disease activity type of keratitis active hsk no. eyes (%) (n = 24) inactive hsk no. eyes (%) (n = 29) p-value non necrotizing keratitis no. eyes (%) (n = 44 ) necrotizing keratitis no. eyes (%) (n = 9 ) p-value localization: central (visual axis) 12 (50.0) 15 (51.7) 0.901 20 (45.4) 7 (77.7) 0.08 paracentral/peripheral 12 (50.0) 14 (48.3) 0.901 24 (54.6) 2 (22.3) 0.08 density: low (grade-i, < 33%) 7 (29.1) 10 (34.4) 0.464 17 (36.9) 0 (0.0) 0.040* medium (grade-ii, 34–66%) 11 (45.8) 13 (44.8) 0.942 21 (45.7) 3 (33.3) 0.956 high (grade-iii, > 67%) 6 (25.0) 6 (20.6) 0.777 8 (17.4) 6 (66.7) 0.010* depth: superficial (< 150 µm) 7 (29.2) 10 (34.5) 0.683 17 (38.6) 0 (0.0) 0.025* medial (150–350 µm) 11 (45.8) 13 (44.8) 0.942 21 (47.7) 3 (33.3) 0.434 deep (> 350 µm) 6 (25.0) 6 (20.7) 0.712 6 (13.6) 6 (66.7) 0.001* extension: small (< 25% surface) 4 (16.6) 6 (20.6) 0.712 10 (22.7) 0 (0.0) 0.116 medium (25–45% surface) 13 (54.1) 21 (72.4) 0.172 30 (68.1) 4 (44.4) 0.18 large (> 45% surface) 7 (29.1) 2 (6.8) 0.033* 4 (9.0) 5 (55.5) 0.001* sd-oct, spectral-domain optical coherence tomography; hsk, herpetic stromal keratitis ∗p-value < 0.05 was considered as statistically significant (mann–whitney u test for two independent samples). additionally, 66.7% of the lesions analyzed were located deep into the corneal stroma (p = 0.001), and many of them covered a significant area of the corneal surface (p = 0.001). by contrast, most non-necrotizing lesions were in the lowto medium-density range, extended between the superficial to medium stromal depths, and affected a smaller area of the cornea than in necrotizing keratitis (table 2). 284 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 microstructural changes in herpetic stromal keratitis; rodriguez-garcia et al table 3. mean pachymetry measurements by sd-oct of corneas with herpetic stromal keratitis according to inflammatory status and type of keratitis. disease activity type of keratitis measurement parameter (μm) eyes with active keratitis (n = 24) eyes with inactive keratitis (n = 29) p-value nonnecrotizing keratitis (n = 44) necrotizing keratitis (n = 9) p-value cct 561.7 482.3 < 0.001* 519.7 492.8 o.405 mct 483.5 436.4 0.007* 468.9 396.3 0.002* ctl 644.7 439.9 < 0.001* 528.2 473.5 0.711 cetl 68.7 78.4 0.048* 72.2 47.1 0.043* stromal thinning (irregular astigmastism†) no eyes (%) 5 (20.8%) 11 (37.9%)† 0.181 6 (13.6%) 5 (62.5%)† 0.001* sd-oct, spectral-domain optical coherence tomography; cct, central corneal thickness; mct, minimum corneal thickness; ctl, corneal thickness at lesion site; cetl, corneal epithelium thickness at lesion site; †confirmed by topography ∗p-value < 0.05 was considered as statistically significant (mann–whitney u test for two independent samples). figure 3. (a) a cross-sectional image of a cornea with inactive hsk showing epithelial remodeling (top arrow) over a zone of stromal fibrosis and compaction (bottom arrow) with the mct = 441 µm. (b) a cross-sectional image of a cornea with active hsk showing marked stromal edema (ctl = 641 µm) and an active inflammatory infiltrate (bottom arrow) underlying an area of epithelial edema. pachymetry comparative analysis the comparative analysis of corneal thickness between the active and inactive keratitis groups showed significant differences in the four measured parameters: cct, mct, ctl, and cetl (table 3). eyes with inactive hsk had significant stromal thinning compared to those with active disease (p ≤ 0.007). however, the corneal epithelial thickness at the site of the journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 285 microstructural changes in herpetic stromal keratitis; rodriguez-garcia et al lesion was significantly increased in the inactive cases (p = 0.048). on the other hand, the values of mct (p = 0.002) and cetl (p = 0.043) were significantly lower in corneas with necrotizing keratitis than in non-necrotizing keratitis. finally, almost one-third of the eyes showed irregular astigmatism and severe stromal thinning with a major predominance in the necrotizing group (p < 0.001). discussion clinically, the corneal pathologic characteristics seen in hsk depend on direct slitlamp observation of inflammatory stromal infiltration, edema, neovascularization, scarring, and thinning with a history of herpes infection and previously known herpetic epithelial ulceration and corneal hypoesthesia.[15, 23] sd-oct allows an in vivo, accurate, noncontact, and fast examination of the entire corneal microstructure in different inflammatory pathologies, including hsk.[24–26] to the best of our knowledge, no systematic microstructural analyses have been performed of the corneal pathologic changes seen in hsk using sdoct. in the present study, we described these changes in different stages of disease activity and severity. spectral-domain tomography permits a detailed analysis of the entire cornea in crosssections of variable orientations as well as en face fragmentation analysis.[24] most corneas analyzed in the inactive stage of the disease showed epithelial remodeling, consisting of thickening over the scarred stroma that was characterized by fibrosis, thinning, and compaction (figure 2). in contrast, more than two-thirds of the corneas from patients with active keratitis showed significant stromal edema characterized by increased cct and ctl (table 3), as well as a hypodense and thickened stromal appearance (figure 1). in general, patients with the inactive stage of hsk did not show corneal stromal edema; their cct measurements were in the low to normal range (356–537 µm), and the mean ctl was even lower (439.9 µm), corresponding to areas of stromal scarring and thinning. corneas from the active keratitis group showed a thicker epithelium than average at the site of the lesion (mean cetl = 68.7 µm) and a significantly increased corneal thickness (mean ctl = 644.7 µm), reflecting the presence of stromal inflammatory infiltration and edema. of note was the occurrence of severe corneal thinning in a total of 16 (30.1%) eyes with hsk, with a higher proportion in corneas with necrotizing disease (table 3). necrotizing hsk, the most severe form of herpetic keratitis, is characterized by significant leukocyte stromal infiltration and tissue necrosis with consequent thinning of the cornea, which explains the higher percentage of severe corneal thinning and irregular astigmatism seen in these corneas.[7, 27] sd-oct measures the intensity of a backscattered optical signal, which represents the reflectivity of the tissue.[28] since reflectivity varies among different tissues, we can differentiate them by measuring their reflectivities in transverse scans that can be displayed as false-color or grayscale cross-sectional images.[29, 30] the intensity of the backscattered optical signal is represented on a logarithmic scale with varying degrees of brightness. white corresponds to the highest reflection, while dark gray and black correspond to weaker back reflection.[30] sd-oct software allows toggling between grayand color scales for each image created. the color scale allows easier detection of subtle variations in the oct signal to define reflectivity levels. conversely, the grayscale allows the viewer to visualize contrast more easily.[31] we used the color scale to measure the density of inflammatory infiltrates in eyes with active keratitis and leukomas or scarring in eyes with inactive hsk. in both active and inactive disease, approximately two-thirds of the eyes showed medium to high density lesions; however, corneas with necrotizing stromal keratitis had a significantly higher percentage of high-density lesions (table 2). we found a particular limitation in differentiating between stromal edema and inflammatory infiltration in corneas with active keratitis, where both lesions coexisted within the same stromal area. however, differences in reflectivity, where stromal edema appears as a hypodense area of increased stromal thickness and low reflectivity 286 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 microstructural changes in herpetic stromal keratitis; rodriguez-garcia et al and stromal infiltrates as areas of increased stromal thickness but with higher reflectivity (yellow-toorange color), help to facilitate their differentiation. since there are no previous specific reports on sd-oct findings in this pathologic condition, we find the present study of value to improve our understanding of the in vivo pathologic changes occurring at different stages and severity of hsk. as in other corneal pathologies, we consistently found epithelial remodeling, consisting of zonal thickening at sites of fibrosis and scarring in inactive disease (figure 3a). epithelial remodeling has also been observed as a way of anterior curvature compensation in advanced keratoconus under areas of significant stromal thinning and ectasia.[32] in contrast, epithelial thickening was present in most eyes during active inflammation (figure 3b). in a clinical setting, corneal sd-oct could be useful to analyze scarring extension and leukoma depth, hence facilitating surgical decisions regarding partial or total corneal transplantation. additionally, it may be useful for the detection and grading of stromal edema during recurrent inflammation under challenging situations. during active hsk, leucocyte infiltration induces stromal edema characterized by diffuse haziness, giving a “ground glass” appearance in the area surrounding the inflammatory infiltrate. subtle stromal edema may hide in the infiltrate or under a dense leukoma. in such circumstances, corneal sd-oct represents a useful aid for its detection. the potential limitations of the present study include distortions that occur in the sd-oct scans as a result of the refractive indexes of the tissues. the acquisition of sd-oct scans was performed along meridional planes to minimize this effect, and all images were de-warped by the sd-oct system’s corneal adaptor module software.[31] in conclusion, in vivo sd-oct pathologic analysis of corneas with different disease activity and types of inflammation has permitted a better understanding of the pathologic mechanisms adopted by the affected corneas. additionally, it allowed the evaluation of the grade and extent of tissue damage and repair seen in hsk. future studies of hsk imaging analysis with sd-oct should be carried out to monitor disease progression or therapeutic response, including oct angiography of the cornea to analyze blood perfusion and neovascularization responses. additionally, the commercial development of ultra-high-definition octs for corneal and anterior segment imaging analysis surely would yield more detailed in vivo ultrastructure pathologic changes occurring in this sight-threatening disease. acknowledgements the authors are thankful to susana imperialsauceda for her technical support in performing all corneal sd-oct tests. financial support and sponsorship this study has been partially funded by the immuneye foundation. conflicts of interest there are no conflicts of interest. references 1. liesegang tj. herpes simplex virus epidemiology and ocular importance. cornea 2001;20:1–13. 2. labetoulle m, auquier p, conrad h, crochard a, daniloski m, bouée s, et al. incidence of herpes simplex virus keratitis in france. ophthalmology 2005;112:888–895. 3. wilhelmus k, beck rw, moke ps, dawson cr, barron ba, jones db, et al. acyclovir for the prevention of recurrent herpes simplex virus eye disease. n engl j med 1998; 339:300–306. 4. wilhelmus k, dawson c, barron b, bacchetti p, gee l, jones db, et al. risk factors for herpes simplex virus epithelial keratitis recurring during treatment of stromal keratitis or iridocyclitis. herpetic eye disease study group. br j ophthalmol 1996;80:969–972. 5. farooq av, shukla d. herpes simplex epithelial and stromal keratitis: an epidemiologic update. surv ophthalmol 2012;57:448–462. 6. barron ba, gee l, hauck ww, kurinij n, dawson cr, jones db, et al. herpetic eye disease study: a controlled trial of oral acyclovir for herpes simplex stromal keratitis. ophthalmology 1994;101:1871–1882. 7. holland ej, schwartz gs. classification of herpes simplex virus keratitis. cornea 1999;18:144–154. 8. wilhelmus kr. diagnosis and management of herpes simplex stromal keratitis. cornea 1987;6:286–291. 9. hendricks rl, tumpey tm. contribution of virus and immune factors to herpes simplex virus type iinduced corneal pathology. invest ophthalmol vis sci 1990;31:1929–1939. 10. streilein jw, dana mr, ksander br. immunity causing blindness: five different paths to herpes stromal keratitis. immunol today 1997;18:443–449. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 287 microstructural changes in herpetic stromal keratitis; rodriguez-garcia et al 11. remeijer l, osterhaus a, verjans g. human herpes simplex virus keratitis: the pathogenesis revisited. ocul immunol inflamm 2004;12:255–285. 12. brik d, dunkel e, pavan-langston d. herpetic keratitis: persistence of viral particles despite topical and systemic antiviral therapy. arch ophthalmol 1993;111:522–527. 13. holbach lm, font rl, baehr w, pittler sj. hsv antigens and hsv dna in avascular and vascularized lesions of human herpes simplex keratitis. curr eye res 2009;10:63– 68. 14. holbach lm, font rl, naumann go. herpes simplex stromal and endothelial keratitis: granulomatous cell reactions at the level of descemet´s membrane, the stroma, and bowman´s layer. ophthalmology 1990;97:722–728. 15. wilhelmus kr, mitchell bm, dawson cr, jones db, barron ba, kaufman he, et al. slit-lamp biomicroscopy and photographic image analysis of herpes simplex virus stromal keratitis. arch ophthalmol 2009;127:161–166. 16. hamrah p, sahin a, dastjerdi mh, shahatit bm, bayhan ha, dana r, et al. cellular changes of the corneal epithelium and stroma in herpes simplex keratitis. an in vivo confocal microscopy study. ophthalmology 2012;119:1791–1797. 17. hillenaar t, van cleynenbreugel h, verjans gm. monitoring the inflammatory process in herpetic stromal keratitis: the role of in vivo confocal microscopy. ophthalmology 2012;119:1102–1110. 18. khurana rn, li y, tang m, lai mm, huang d. high speed optical coherence tomography of corneal opacities. ophthalmology 2007;114:1278–1285. 19. de boer jf, cense b, park bh, pierce mc, tearney gj, bouma be. improved signal-to-noise ratio in spectraldomain compared with time-domain optical coherence tomography. opt lett 2003;28:2067–2069. 20. binder p, trokel s, salaroli c, li y, yiu s, ramos s, et al. corneal pathologies and surgeries. in: huan d, editor. rtvue fourier-domain optical coherence tomography primer series, vol. 2, 2nd edn. fremont, ca, usa: optovue inc.; 2009:46–53. 21. huang d, swanson ea, lin cp, schuman js, stinson wg, chang w, et al. optical coherence tomography. science 1991;254:1178–1181. 22. li y, shekhar r, huang d. corneal pachymetry mapping with high-speed optical coherence tomography. ophthalmology 2006;113:792–799. 23. pepose js, keadle tl, morrison la. ocular herpes simplex: changing epidemiology, emerging disease patterns, and the potential of vaccine prevention and therapy. am j ophthalmol 2006;141:547–557. 24. wirbelauer c. oct of corneal opacities. ophthalmology 2008;115:589–590. 25. sandali o, el sanharawi m, temstet c, hamiche t, galan a, ghouali w, et al. fourier-domain optical coherence tomography imaging in keratoconus: a corneal structural classification. ophthalmology 2013;120:2403–2412. 26. dhaini ar, fattah ma, el-oud sm, awwad st. automated detection and classification of corneal haze using optical coherence tomography in patients with keratoconus after cross-linking. cornea 2018;37:863–869. 27. heiligenhaus a, bauer d, meller d, steuhl kp, tseng sc. improvement of hsv-1 necrotizing keratitis with amniotic membrane transplantation. invest ophthalmol vis sci 2001;42:1969–1974. 28. mahdian, mina, ”tissue characterization using optical coherence tomography” (2015).master’s theses. 793. https://opencommons.uconn.edu/gs_theses/793 29. knuettel ar, bonev s, knaak w. new method for evaluation of in vivo scattering and refractive index properties obtained with optical coherence tomography. j biomed optometry 2004;9:265–273. 30. kholodnykh ai, petrova iy, larin kv, motamedi m, esenaliev ro. precision of measurement of tissue optical properties with optical coherence tomography. appl optomet 2003;42:3027–3037. 31. wojtkowski m, bajraszewski t, targowski p, kowalczyk a. real-time in vivo imaging by high-speed spectral optical coherence tomography. opt lett 2003;28:1745–1747. 32. sandali o, el sanharawi, temstet c, hamiche t, galan a, ghouali w, et al. fourier-domain optical coherence tomography imaging in keratoconus. a corneal structural classification. ophthalmology 2013;120:2403–2412. 288 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 https://opencommons.uconn.edu/gs_theses/793 original article choroidal thickness in acute non-arteritic anterior ischemic optic neuropathy homayoun nikkhah1,2, md; mohadeseh feizi1,2, md; naser abedi2, md; saeed karimi1,2, md mehdi yaseri3, phd; hamed esfandiari4, md 1ophthalmic research center, shahid beheshti university of medical sciences, tehran, iran 2department of ophthalmology, torfeh hospital, shahid beheshti university of medical sciences, tehran, iran 3department of epidemiology and biostatistics, school of public health, tehran university of medical sciences, tehran, iran 4department of ophthalmology, northwestern university feinberg school of medicine, chicago, usa orcid: homayoun nikkhah: https://orcid.org/0000-0002-2414-4661 mohadeseh feizi: https://orcid.org/0000-0002-7589-4550 abstract purpose: to compare the choroidal thickness in eyes with acute non-arteritic anterior ischemic optic neuropathy (naion) with healthy contralateral eye and normal controls. methods: thirty-eight eyes with naion, thirty-eight unaffected fellow eyes, and seventyfour eyes from 37 healthy, ageand sex-matched subjects were included in this prospective comparative case-control study. choroidal thickness was measured by enhanced depth imaging (edi) of spectral domain optical coherence tomography (sdoct). peripapillary choroidal thickness (pct) was measured at 1000 and 1500 𝜇m from bruch’s membrane opening (bmo). subfoveal choroidal thickness (sfct) was measured in central subfoveal area, and 500 microns apart in temporal and nasal sides. choroidal thickness among naion eyes, uninvolved fellow eyes, and control eyes were compared. results: the mean of pct at 1000 𝜇m was significantly thicker in naion and fellow eyes compared to control eyes (169.7 ± 47, 154.4 ± 42.1, and 127.7 ± 49.9 𝜇m, respectively, p < 0.001 and p = 0.42). the mean pct at 1500 𝜇m was also significantly thicker in naion and fellow eyes compared to control eyes (178.6 ± 52.8, 162.6 ± 46.1, and 135.1 ± 59 𝜇m, respectively, p = 0.007 and p = 0.048). the mean pct at 1000 and 1500 𝜇m was significantly greater in naion compared to fellow eyes (p = 0.027 and p = 0.035, respectively). the mean of sfct was significantly thicker in naion compared to control eyes (p = 0.032); however, there was no significant difference between uninvolved fellow and control eyes (p = 0.248). conclusion: thicker choroidal thickness in acute naion and uninvolved fellow eyes compared to normal eyes suggests a primary choroidal role in naion pathophysiology. keywords: choroidal thickness; non-arteritic ischemic optic neuropathy; optic nerve head; swept source optical coherence tomography j ophthalmic vis res 2020; 15 (1): 59–68 correspondence to: mohadeseh feizi, md. department of ophthalmology, torfeh hospital, shahid beheshti university of medical sciences, ibn sina st., tehran 11498, iran. e-mail: mohadeseh_feizi@yahoo.com received: 24-11-2018 accepted: 19-06-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i1.5946 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: nikkhah h, feizi m, abedi n, karimi s, yaseri m, esfandiari h. choroidal thickness in acute non-arteritic anterior ischemic optic neuropathy. j ophthalmic vis res 2020;15:59–68. © 2020 journal of ophthalmic and vision research | published by knowledge e 59 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i1.5946&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr choroidal thickness in acute naion; nikkhah et al introduction although the role of choroid in several sight-threatening ocular conditions such as polypoidal choroidal vasculopathy or choroidal neovascularization[1–4] is well-studied, it is only recently that the details of the choroid have been evaluated with enhanced depth imaging optical coherence tomography (edi-oct). edioct provides in vivo cross-sectional image of the choroidal layer.[5] since choroid is located adjacent to optic nerve and shares interconnected blood supply with optic disc, investigators have started to look at its possible role in two of the most common optic neuropathies, that is, non-arteritic anterior ischemic optic neuropathy (naion) and glaucoma.[6–9] naion is the most common acute optic neuropathy[10] and, as the name implies, it is presumed to be secondary to the vascular insufficiency within optic disc space, but the nature of the vasculopathy and its pathophysiologic mechanism is not definitely known yet.[11] evaluating choroidal thickness in acute naion may help identify choroidal role in naion and clarify if the choroidal thickness changes in naion is a predisposing factor for this condition or the consequence of acute optic neuropathy. the purpose of this case-control study was to evaluate the peripapillary choroidal thickness (pct) and subfoveal choroidal thickness (sfct) in eyes with acute naion and compare them with uninvolved fellow eyes and eyes of healthy controls. methods this prospective comparative case-control study was carried out at torfeh hospital as a universitybased tertiary eye center. the study protocol was approved by the ethics committee and review board of shahid beheshti university of medical sciences. all investigations were carried out in accordance with the declaration of helsinki. patients with acute naion and less than 14 days of clinical presentation were included from january 2014 to june 2015. the diagnosis of naion was based on the presence of a history of sudden painless visual loss associated with a relative afferent pupillary defect that was not attributed to any other ocular, neurologic, or systemic disease, optic disc swelling detected by biomicroscopic examination at the time of presentation and confirmed by peripapillary retinal nerve fiber layer thickness measurement using oct, visual field testing compatible with ischemic optic neuropathy, and resolution of disc swelling and appearance of optic atrophy within two months. the exclusion criteria were clinical symptoms of giant cell arteritis, high erythrocyte sedimentation rate (esr) or c-reactive protein (crp) level, any history or clinical evidence of retinal or neurologic disease, previous retinal procedure (e.g., laser photocoagulation), intraocular pressure (iop) > 21 mmhg, or usage of glaucoma medication, presence of glaucomatous optic nerve damage, any other optic nerve disease, and bilateral naion cases. healthy volunteers from the optometry clinic with a refractive error in the range of –4 to +4, and no history of intraocular surgery were recruited as the control group. for all cases and controls, comprehensive ophthalmic examination including best corrected visual acuity (bcva) assessment, slitlamp examination, goldmann applanation tonometry, gonioscopy, fundus examination, and perimetry (humphrey visual field analyzer; model 750; carl zeiss meditec, dublin, california, usa) were performed. axial length was measured using iol master (zeiss iolmaster, carl zeiss meditec ag, germany). oct imaging all oct measurements were performed using heidelberg spectral domain oct (spectralis; heidelberg engineering, heidelberg, germany) by the same experienced operator. for each eye, three oct images were acquired. pct was measured using horizontal and vertical raster edi-oct scans centered at optic nerve head (onh) [figure 1]. sfct was determined using horizontal raster edi-oct scans centered at the fovea. macular oct scan: 25 horizontal optical coherent tomographic sections were obtained in a 20𝜇× 20𝜇 rectangle centered around the fovea. three circular lines demonstrating 1, 3, and 6 mm of the central macula (early treatment diabetic retinopathy study (etdrs) macular grid) were obtained. the data of central 1 mm circle was defined as central macular thickness (cmt). in addition, ganglion cell-inner plexiform layer (gc-ipl) thickness in central 1 mm circle and inner macular 60 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 choroidal thickness in acute naion; nikkhah et al area (between the central and middle circles) were measured in four superior, inferior, temporal, and nasal quadrants, using instrument segmentation software. it has been shown that the spectralis software has an excellent reproducibility in the measurement of each individual retinal layer.[12] choroidal thickness was measured along the perpendicular distance from posterior border of retinal pigment epithelium to anterior scleral border (choroidal–scleral interface) using the oct manual measurement tool. for peripapillary choroid, we measured the choroidal thickness at 1000 (±10) and 1500 (±10) 𝜇m from bruch’s membrane opening (bmo) in superior, inferior, temporal, and nasal parts on vertical and horizontal raster scans (eight points). to compare the choroidal thickness at 1000 and 1500 𝜇m from bmo among the eyes with naion, uninvolved fellow eyes and control eyes, we calculated the mean of measurements at 1000 and 1500 𝜇m in superior, inferior, temporal, and nasal parts. in the subfoveal area, choroidal thickness was measured at the foveal center as well as 500 (±5) 𝜇m from the foveal center in both temporal and nasal sides [figure 2]. the mean of these three measurements was defined as the mean sfct. to better determine the choroidal– scleral interface, we changed the contrast and resolution scales of the oct device several times until we could find the exact borders. considering reports of diurnal variation in choroidal thickness, all oct images were carried out between 10 and 12 am. all choroidal measurements were done by the same surgeon (hn) and re-evaluated by two other co-authors (mf, he). statistical method to present data, we used mean, standard deviation, median, and range. to assess normal distribution of quantitative data, we used kolmogorov–smirnov test and q–q plot. to compare the results between groups at baseline, we used t-test, mann–whitney test, and chi-square test. considering the probability correlation of the measures, generalized estimating equation (gee) analysis was used to compare the groups. furthermore, adjusted results for hypertension and diabetes were obtained using another gee model. to consider the multiple comparisons, issue in pairwise comparisons, we used the bonferroni method. the correlation of variables was obtained by the pearson method. all statistical analyses were performed by spss software (ibm corp. released 2014. ibm spss statistics for windows, version 23.0. armonk, ny: ibm corp.). all tests were twosided and p < 0.05 was considered statistically significant. results among 46 enrolled eyes, 38 eyes with acute naion were included for final analysis. eight eyes were excluded because of poor-quality oct and inability to determine choroidal–scleral junction. thirty-eight uninvolved fellow eyes and seventyfour eyes of 37 healthy, ageand sex-matched subjects were included as the control group. the mean age of naion patients and control subjects were not significantly different (62 ± 11 and 61 ± 30 years, respectively, p = 0.95). the mean interval between the initiation of symptoms and oct acquisition was 6.7 ± 3.7 days (range, 1 to 14). there was no difference between naion, uninvolved contralateral, and control eyes regarding spherical equivalent (p = 0.64) and mean axial length (p = 0.87). affected cases were more likely to have diabetes mellitus (dm), but the prevalence of systemic hypertension was comparable in both affected and healthy individuals [table 1]. intraobserver and interobserver reproducibility of pct and sfct are shown in table 2. there was excellent reproducibility in the intraobserver and interobserver tests (ranging from 0.934 to 0.992 for the intraobserver and from 0.874 to 0.961 for the interobserver reproducibility). the mean pct at 1000 𝜇m from bmo (pct1000) was 169.7 ± 47, 154.4 ± 42.1, and 127.7 ± 49.9 𝜇m in naion eyes, uninvolved fellow eyes, and control eyes, respectively. pct1000 was significantly thicker in the involved eyes and uninvolved fellow eyes compared to the control eyes (p < 0.001 and p = 0.042, respectively). moreover, pct1000 was significantly thicker in involved eyes than uninvolved fellow eyes (p = 0.025) [table 3]. the mean pct at 1500 𝜇m from bmo (pct1500) was also significantly thicker in the naion and uninvolved fellow eyes than the control eyes (p = 0.007 and p = 0.048, respectively). in addition, pct1500 was significantly thicker in the eyes with naion than the uninvolved fellow eyes (p = 0.035) [table 3]. journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 61 choroidal thickness in acute naion; nikkhah et al figure 1. delineated sd-oct from affected eye: bruch’s membrane (dotted red line), anterior sclera (dotted yellow line), bmo, bruch’s membrane opening. figure 2. choroidal thickness at the center of the fovea and 500 𝜇m from the center at temporal and nasal side. the mean sfct was 275 ± 71.7, 258.3 ± 65, and 225.9 ± 91.2 𝜇m in eyes with naion, uninvolved fellow eyes, and control eyes, respectively. the mean sfct was thicker in the eyes with naion than the control eyes (p = 0.038), however, there was no statistically significant difference between the fellow and control eyes (p = 0.248) [table 4]. cmt was significantly higher in the naion than the uninvolved and control eyes (p < 0.001 and p < 0.001, respectively), but there was no significant difference between the fellow and control eyes (p = 1.000). central gc-ipl thickness was significantly thicker in the eyes with naion eyes than the uninvolved fellow and control eyes (p < 0.001 for both). central gc-ipl thickness in the eyes with naion was negatively correlated with the bcva (r = 0.31, p = 0.006). there was no statistically significant difference among the naion, uninvolved fellow, and control eyes regarding the gc-ipl thickness in the inner macular area [table 4]. the differences persisted once adjusted for dm and systemic hypertension [table 5]. discussion in the present study, we found significantly thicker choroid in both acute naion and unaffected fellow eyes compared to controls, both in peripapillary and subfoveal areas. all previous studies evaluated the pct in the chronic phase of naion.[8, 9] this study is the 62 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 choroidal thickness in acute naion; nikkhah et al table 1. demographic data of naion patients and healthy control subjects study groups p naion eyes uninvolved fellow eyes control eyes number (n) 38 38 74 (37) age (years) mean ± sd 62 ± 11 61 ± 30 0.959† median (range) 61 (30 to 87) 87 (62 to 10) sex m 20 (52.6%) 18 (48.6%) 0.525* f 18 (47.4%) 19 (51.4%) interval (days)1 mean ± sd 6.74 ± 3.82 median (range) 6.5 (1 to 14) dm no 21 (55.3%) 29 (78.4%) 0.010* yes 17 (44.7%) 8 (21.6%) htn no 21 (55.3%) 27 (73.0%) 0.077* yes 17 (44.7%) 10 (27.0%) se mean ± sd 0.39 ± 1.11 0.46 ± 1.16 0.27 ± 0.99 0.641† median (range) 0.38 (–2 to 3.75) 0.5 (–2 to 3.5) 0.25 (–3 to 3) axial length mean ± sd 22.74 ± 0.76 22.74 ± 0.78 22.83 ± 0.84 0.873† median (range) 22.98 ) 22.88 (21.05 to 23.85) 22.97 (21.09 to 24.31) 1: interval between initial symptom and ophthalmic evaluation dm, diabetes mellitus; htn, systemic hypertension; naion, nonarteritic anterior ischemic optic neuropathy; se, spherical equivalent †based on t-test ‡based on mann–whitney test *based on chi-square test table 2. intraclass correlation coefficients for pct and sfct in a random subset of 15 eyes intraobserver variability (95% confidence interval) interobserver variability (95% confidence interval) pct 1000 (temporal) 0.934 (0.841–0.973) 0.874 (0.710–0.948) pct 1000 (nasal) 0.971 (0.940–0.992) 0.963 (0.920–0.984) pct 1500 (temporal) 0.966 (0.914–0.986) 0.933 (0 .831–0.973) pct 1500 (nasal) 0.968 (0.922–0.985) 0.941 (0.853–0.974) sfct (temporal) 0.959 (0.910–0.981) 0.981 (0.960–0.992) sfct (nasal) 0.992 (0.951–0.996) 0.961 (0.912–0.983) pct, peri-papillary choroidal thickness; sfct, subfoveal choroidal thickness first one that measured pct in acute phase. by adjusting the contrast and resolution scale of the oct device, we were able to measure choroidal thickness despite edema and disc swelling. although the exact mechanism of naion is yet to be understood, ischemia and the so called “compartment syndrome” in optic disc space are the main determinants for the loss of visual function.[14, 15] whatever the mechanism of vascular insufficiency in naion, persistent hypoperfusion is required for the development of ischemic optic neuropathy. the paraoptic branches of the short posterior ciliary arteries are responsible for onh blood supply and the infarction in naion is journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 63 choroidal thickness in acute naion; nikkhah et al table 3. measurements of pct in different areas in naion, uninvolved and control eyes naion eyes(1) uninvolved eyes(2) control eyes(3) diff (1 vs 2) p1* diff (1 vs 3) p2* diff (2 vs 3) p3* mean ± sd mean ± sd mean ± sd pct s 1000 173.2 ± 59.4 164.9 ± 47.4 135.7 ± 57.3 8.2 1.000 37.4 0.007 29.2 0.065 pct i 1000 151.2 ± 62.4 131.5 ± 47.5 112.2 ± 51.7 19.7 0.076 39.0 0.012 19.3 0.112 pct t 1000 181.5 ± 69.9 167.9 ± 53.9 131.8 ± 58.7 13.7 0.429 49.7 0.001 36.1 0.043 pct n 1000 172.8 ± 61.9 153.5 ± 52.2 131.2 ± 54.9 19.3 0.027 41.6 0.005 22.3 0.221 mean pct 1000 169.7 ± 47 154.4 ± 42.1 127.7 ± 49.9 15.2 0.027 41.9 < 0.001 26.7 0.042 pct s 1500 175.3 ± 69.6 165.5 ± 51.3 141.2 ± 69.4 9.8 1.000 34.0 0.054 24.3 0.287 pct i 1500 155.5 ± 71.4 132.7 ± 47.4 113.8 ± 62.5 22.8 0.059 41.7 0.015 18.9 0.395 pct t 1500 208.7 ± 80.6 190.5 ± 67.7 144.9 ± 64.7 18.3 0.301 63.9 < 0.001 45.6 0.012 pct n 1500 172.7 ± 64.1 161.7 ± 55.6 140.5 ± 64 11.0 0.314 32.2 0.073 21.2 0.442 mean pct 1500 178.6 ± 52.8 162.6 ± 46.1 135.1 ± 59 16.0 0.035 43.5 0.007 27.5 0.048 pct, peri-papillary choroidal thickness; naion, non-arteritic anterior ischemic optic neuropathy; s, superior; i, inferior; t, temporal; n, nasal; 1000, at 1000micron from bruch’s membrane opening; 1500, at 1500micron from bruch’s membrane opening; sd, standard deviation; diff, difference * p-for pairwise comparison, based on post hoc analysis of gee, adjusted for the multiple comparison by bonferroni method table 4. measurements of gc-ipl, rfnl, sfct and cmt in different areas in study groups (naion, uninvolved, and control eyes) naion eyes uninvolved eyes control eyes diff (naion vs uninvolved eyes) p1* diff (naion vs control eyes) p2* diff (uninvolved vs control eyes) p3* mean ± sd mean ± sd mean ± sd gc-ipl c 20.1 ± 14.7 13.2 ± 5.3 13.1 ± 3.4 6.8 < 0.001 6.9 < 0.001 0.1 1.000 gc-ipl s 46.2 ± 14.1 45.8 ± 13 51.9 ± 5.4 0.4 1.000 –5.6 0.045 –6.0 0.019 gc-ipl i 45.8 ± 12.1 46.2 ± 12.8 51.4 ± 5.6 –0.3 1.000 –5.5 0.018 –5.2 0.033 gc-ipl t 41 ± 12.7 43.9 ± 13 45.7 ± 5.8 –2.9 0.687 –4.7 0.078 –1.8 1.000 gc-ipl n 45.7 ± 13.8 45.8 ± 12.5 49.6 ± 5.3 –0.1 1.000 –3.9 0.173 –3.8 0.167 sfct c 286.7 ± 72.7 271 ± 68.2 237.2 ± 89.1 15.7 0.352 49.4 0.034 33.7 0.234 sfct t 500 267.3 ± 72.9 250.8 ± 71 219.8 ± 99.6 16.6 0.701 47.5 0.032 30.9 0.323 sfct n 500 271 ± 76.3 253.1 ± 63.2 220.6 ± 94.1 17.8 0.345 50.3 0.035 32.5 0.245 mean sfct 275 ± 71.7 258.3 ± 65 225.9 ± 91.2 16.7 0.123 49.1 0.038 32.4 0.248 cmt 339.9 ± 131 274.8 ± 54.1 266 ± 25 65.1 < 0.001 73.9 < 0.001 8.8 1.000 gc-ipl, ganglion cell-inner plexiform layer; sfct, subfoveal choroidal thickness; cmt, central macular thickness; naion, non-arteritic anterior ischemic optic neuropathy; c, central; s, superior; i, inferior; t, temporal; n, nasal; t 500, 500micron temporal to fovea; n 500, 500micron nasal to fovea; sd, standard deviation; diff, difference. *p-for pairwise comparison, based on post hoc analysis of gee, adjusted for the multiple comparison by bonferroni method suggested to be predominantly located in the retrolaminar portion of the onh.[16] therefore, since the choroid mainly supplies – to a limited extent – more anterior optic nerve head regions, it is less likely that choroid has a substantial role in the pathogenesis of naion. however, several studies reported changes in choroidal thickness in naion,[7–9] which is consistent with the findings of the current study. fard et al evaluated the pct in chronic naion and reported increased thickness in both affected and unaffected fellow eyes compared to normal 64 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 choroidal thickness in acute naion; nikkhah et al table 5. pct, gc-ipl, and sfct values adjusted for hypertension and diabetes mellitus diff (naion vs control eyes) se p* diff (uninvolved vs control eyes) se p* pct s 1000 37.966* 11.5 0.007 31.075* 11.5 0.032 pct i 1000 44.470* 11.0 < 0.001 23.5 11.0 0.121 pct t 1000 50.309* 12.6 < 0.001 35.958* 12.6 0.019 pct n 1000 42.085* 11.6 0.001 22.6 11.6 0.167 mean 43.708* 9.7 < 0.001 28.282* 9.7 0.025 pct s 1500 38.097* 13.5 0.013 28.3 13.5 0.127 pct i 1500 45.619* 12.8 0.012 22.9 12.8 0.237 pct t 1500 63.130* 14.6 < 0.001 44.698* 14.6 0.013 pct n 1500 33.351* 12.9 0.044 23.4 12.9 0.321 mean 45.049* 11.3 < 0.001 29.826* 11.3 0.034 gc-ipl c 6.924* 1.7 < 0.001 0.0 1.7 1.000 gc-ipl s –5.411* 2.2 0.043 –5.708* 2.2 0.034 gc-ipl i –6.383* 2.0 0.005 –5.437* 2.0 0.025 gc-ipl t –5.0 2.1 0.057 –1.9 2.1 1.000 gc-ipl n –3.3 2.1 0.331 –2.9 2.1 0.612 mean gc-ipl –2.7 1.7 0.367 –3.2 1.7 0.201 sfct c 49.586* 18.2 0.025 33.9 18.2 0.201 sfct t 500 50.091* 17.4 0.012 34.4 17.4 0.172 sfct n 500 75.364* 15.5 < 0.001 8.8 15.5 1.000 mean sfct 49.838* 16.8 0.012 34.9 16.8 0.123 pct, peripapillary choroidal thickness; gc-ipl, ganglion cellinner plexiform layer; sfct, subfoveal choroidal thickness; diff, difference; se, standard error; naion, non-arteritic anterior ischemic optic neuropathy; c, central; s, superior; i, inferior; t, temporal; n, nasal; t 500, 500 𝜇m temporal to fovea; n 500, 500 𝜇m nasal to fovea; se, standard error; diff, difference *p-for pairwise comparison adjusted for the htn and diabetes, based on post hoc analysis of gee, multiple comparison considered by bonferroni method controls.[8] our finding also matches the finding of nagia et al that observed increased thickness of the pct, especially 1000 to 1500 𝜇m from bmo, in chronically affected naion and contralateral eyes compared to controls.[10] surprisingly, the mean pct in the affected eyes in our study was lower than the aforementioned studies with chronic naion. although one should be cautious to draw any conclusion from these cross-sectional studies, chronic cases were expected to have thinner choroid compared to the eyes at the acute stage if choroidal thickening was secondary to ischemic damage. however, longitudinal studies are needed to evaluate the changes of choroidal thickness following the ischemic damage. the lack of consistent choroidal filling defect in angiographic studies[17] further reinforces the primary role of choroid in the development of naion. crowded disc is known as a predisposing factor for naion, although the mechanism by which it contributes to ischemia is unclear.[11] increased pct may be a component of crowded disc morphology as suggested by fard et al.[8] they hypothesized that the thicker choroid may strain the optic nerve axon and its vessel within the narrow central cup and further restrict the crowded optic nerve space. thicker peripapillary choroid in naion eyes may be a structurally predisposing factor or may be a compensatory mechanism due to ischemia. thicker choroid, both in acute naion and uninvolved fellow eyes, rationally suggests the role of choroid as a predisposing factor rather than a compensatory mechanism. moreover, if increased journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 65 choroidal thickness in acute naion; nikkhah et al choroidal thickness was a compensatory factor, it must be decreased after the acute phase, but as mentioned earlier, the result of previous studies in the chronic phase also showed thicker choroid.[8, 9] the naion progresses through asymptomatic “incipient naion” to full blown ischemic neuropathy with characteristic clinical presentation in more than two-third of cases[18, 19]. by further contributing to “compartment syndrome” in already constricted scleral canal, increased choroidal thickness may have a role in the development of symptomatic axonal damage. in that sense, increased choroidal thickness acts as a “catalyzer” for the progression of ischemic optic neuropathy. moreover, beijing eye study showed no association between sfct and optic disc size in normal subjects, therefore choroidal thickness could affect the incidence and progression of naion independent of optic disc size.[20] thicker choroid may also be a sign of local auto-regulation dysfunction of the choroidal vessel.[21] in contrast to our study and others,[8, 9] garciabasterra et al[10] reported thinner pct in naion and unaffected fellow eyes compared to normal subjects. the differing results may be because they did not match the refractive state of control subjects and naion patients, and also they evaluated pct in chronic phase of aion. gonal et al[22] reported no difference between sub-macular choroidal thickness in acute and chronic naion eyes and control subjects, they included subjects with optic disc edema that had occurred in a time period of less than one month as an acute naion, but we included patients with initial symptoms occurring less than 14 days; they also measured choroidal thickness in farther points from the foveal center. interestingly, schuster et al reported thinner sfct in the affected and nonaffected fellow eyes of patients with naion.[7] although the authors considered the enrolled cases as acute naion, the duration of the disease that was considered acute is not reported in their paper, so we cannot confidently compare our findings with their results. besides, they used one horizontal line passing through fovea and ct was measured on 1 point on this line. we argue that measuring choroidal thickness at 1 selected point, which is performed manually, could be affected by irregularities of choroidal-scleral boundary.[23] in addition, not all factors affecting the choroidal thickness measurement were adjusted in that study. the thickening of central macular region in our study is in line with previous reports that have shown subretinal fluid accumulation in recent onset naion.[24–26] since macular oct is not routinely obtained in naion, the exact incidence of macular edema is unknown in these eyes but it is estimated to range from 10 to 50%.[23] there is no longitudinal study that has evaluated the course of macular edema after the naion and its effect on the final visual acuity. in the present study, we found that the gc-ip layer in the central 1 mm was significantly thicker in naion eyes compared to uninvolved fellow eyes and control eyes, while in all quadrants of 1 to 3 mm annulus, there was no significant difference among naion, uninvolved fellow, and control eyes in terms of gc-ip layer thickness. the thickening of gc-ipl in the central 1 mm may be due to intracellular edema due to greater ischemic stress on central fovea in the early phase of naion and contributes to vision deterioration. fard et al[27] reported that parafoveal gc-ipl thinning present in chronic naion eyes was associated with worse vision compared to glaucoma patients in which central vision is preserved and has no gc-ipl thinning in this area. parks et al reported the initial thinning of gc-ip layer in the macula occurring 46.1 ± 23.2 days after the onset of naion symptoms.[28] we measured gc-ipl thickness in the period of less than two weeks from initial symptoms, which showed thickening only in the affected eyes. the ischemia induced axoplasmic flow stasis results in axonal swelling[28] and is considered an early event in the “sequence of events” in naion.[29] in fact, this early axonal swelling is the stage where timely interventions such as anti-inflammatory and neuroprotective agents proved to be promising.[14, 31, 32] this study has several limitations. the sample size was relatively small but is comparable to previous studies on this subject and necessitates further longitudinal studies to clarify whether choroidal thickening precedes naion or it occurs following the ischemic incidence. although anterior scleral border was delineated manually, intraand interobserver reproducibility were excellent, which is in line with the high reproducibility reported in previous studies.[8, 9] furthermore, recent endeavors to quantify choroidal thickness with automated segmentation have shown 66 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 choroidal thickness in acute naion; nikkhah et al excellent consistency with manual labeling.[33] choroidal thickness has not been adjusted for iop in our study and it may have caused some random errors, although the induced bias may be far from significance. in summary, we showed that the boundaries of the choroid in acute naion could be delineated by excellent intraand interobserver reproducibility. moreover, our finding of increased choroidal thickness in both eyes of the affected patients compared to controls lends support to the theory of primary choroidal role in the development of naion. acknowledgements the authors would like to thank ms. marzieh mola mohammad rahimi and ms. masoumeh zarei (torfeh hospital, tehran, iran) for their technical support. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. yoshida t, ohno-matsui k, yasuzumi k, et al. myopic choroidal neovascularization: a 10-year follow-up. ophthalmology 2003;110:1297–1305. 2. imamura y, fujiwara t, margolis r, spaide rf. enhanced depth imaging optical coherence tomography of the choroid in central serous chorioretinopathy. retina 2009;29:1469–1473. 3. chung se, kang sw, lee jh, kim yt. choroidal thickness in polypoidal choroidal vasculopathy and exudative age-related macular degeneration. ophthalmology 2011;118:840–845. 4. spaide rf. choroidal neovascularization. in: pathologic myopia. new york, ny: springer; 2014:211–230. 5. spaide rf, koizumi h, pozzoni mc, pozonni mc. enhanced depth imaging spectral-domain optical coherence tomography. am j ophthalmol 2008;146:496–500. 6. park h-yl, lee n-y, shin h-y, park ck. analysis of macular and peripapillary choroidal thickness in glaucoma patients by enhanced depth imaging optical coherence tomography. j glaucoma 2014;23:225–231. 7. schuster ak, steinmetz p, forster tm, schlichtenbrede fc, harder bc, jonas jb. choroidal thickness in nonarteritic anterior ischemic optic neuropathy. am j ophthalmol 2014;158:1342–1347.e1. 8. fard ma, abdi p, kasaei a, soltani mogaddam r, afzali m, moghimi s. peripapillary choroidal thickness in nonarteritic anterior ischemic optic neuropathy. invest ophthalmol vis sci 2015;iovs-14-15661. 9. nagia l, huisingh c, johnstone j, kline lb, clark m, girard mj, et al. peripapillary pachychoroid in nonarteritic anterior ischemic optic neuropathy. invest ophthalmol vis sci 2016;57:4679–4685. 10. garcía-basterra i, lahrach i, morillo sánchez mj, kamalsalah r, ríus-díaz f, dawid milner ms, et al. analysis of peripapillary choroidal thickness in non-arteritic anterior ischaemic optic neuropathy. br j ophthalmol 2015;100:891–896. 11. miller nr, arnold ac. current concepts in the diagnosis, pathogenesis and management of nonarteritic anterior ischaemic optic neuropathy. eye 2015;29:65–79. 12. arnold ac. pathogenesis of nonarteritic anterior ischemic optic neuropathy. j neuroophthalmol 2003;23:157–163. 13. ctori i, huntjens b. repeatability of foveal measurements using spectralis optical coherence tomography segmentation software. plos one 2015;10:e0129005. 14. pakravan m, sanjari n, esfandiari h, pakravan p, yaseri m. the effect of high-dose steroids, and normobaric oxygen therapy, on recent onset non-arteritic anterior ischemic optic neuropathy: a randomized clinical trial. graefes arch clin exp ophthalmol 2016;254:2043–2048. 15. pakravan m, esfandiari h, hassanpour k, razavi s, pakravan p. the effect of combined systemic erythropoietin and steroid on non-arteritic anterior ischemic optic neuropathy: a prospective study. curr eye res 2017;42:1079–1084. 16. bernstein sl, johnson ma, miller nr. nonarteritic anterior ischemic optic neuropathy (naion) and its experimental models. prog retin eye res 2011;30:167–187. 17. oto s, yilmaz g, cakmakci s, aydin p. indocyanine green and fluorescein angiography in nonarteritic anterior ischemic optic neuropathy. retina 2002;22:187–191. 18. subramanian ps, gordon lk, bonelli l, arnold ac. progression of asymptomatic optic disc swelling to nonarteritic anterior ischaemic optic neuropathy. br j ophthalmol 2017;101:671–675. 19. hayreh ss, zimmerman mb. incipient nonarteritic anterior ischemic optic neuropathy. ophthalmology 2007;114:1763–1772. 20. wei wb, xu l, jonas jb, shao l, du kf, wang s, et al. subfoveal choroidal thickness: the beijing eye study. ophthalmology 2013;120:175–180. 21. dias-santos a, ferreira j, abegão pinto l, vicente a, anjos r, cabugueira a, et al. choroidal thickness in nonarteritic anterior ischaemic optic neuropathy: a study with optical coherence tomography. neuroophthalmology 2014;38:173–179. 22. gonul s, gedik s, koktekir be, yavuzer k, okudan s. evaluation of choroidal thickness in non-arteritic anterior ischaemic optic neuropathy at the acute and chronic stages. neuro-ophthalmology 2016;40:181–187. 23. gonul s, okudan s. choroidal thickness in nonarteritic anterior ischemic optic neuropathy. am j ophthalmol 2015;159:994–995. journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 67 choroidal thickness in acute naion; nikkhah et al 24. hedges tr 3rd, vuong ln, gonzalez-garcia ao, mendoza-santiesteban ce, amaro-quierza ml. subretinal fluid from anterior ischemic optic neuropathy demonstrated by optical coherence tomography. arch ophthalmol 2008;126:812–815. 25. tomsak rl, zakov zn. nonarteritic anterior ischemic optic neuropathy with macular edema: visual improvement and fluorescein angiographic characteristics. j neuroophthalmol 1998;18:166–168. 26. galvez-ruiz a. macular star formation in diabetic patients with non-arteritic anterior ischemic optic neuropathy (naaion). saudi j ophthalmol 2015;29:71–75. 27. fard ma, afzali m, abdi p, yasseri m, ebrahimi kb, moghimi s. comparison of the pattern of macular ganglion cell-inner plexiform layer defect between ischemic optic neuropathy and open-angle glaucoma. invest ophthalmol vis sci 2016;57:1011–1016. 28. park sw, ji ys, heo h. early macular ganglion cell–inner plexiform layer analysis in non-arteritic anterior ischemic optic neuropathy. graefes arch clin exp ophthalmol 2016;254:983–989. 29. hayreh ss. fluids in the anterior part of the optic nerve in health and disease. surv ophthalmol 1978;23:1–25. 30. hayreh ss. ischemic optic neuropathy. prog retin eye res 2009;28:34–62. 31. hayreh ss, zimmerman mb. non-arteritic anterior ischemic optic neuropathy: role of systemic corticosteroid therapy. graefes arch clin exp ophthalmol 2008;246:1029–1046. 32. sanjari n, pakravan m, nourinia r, esfandiari h, hafezimoghadam a, zandi s, et al. intravitreal injection of a rho-kinase inhibitor (fasudil) for recent-onset nonarteritic anterior ischemic optic neuropathy. j clin pharmacol 2016;56:749–753. 33. tian j, marziliano p, baskaran m, tun ta, aung t. automatic segmentation of the choroid in enhanced depth imaging optical coherence tomography images. biomed opt express 2013;4:397–411. 68 journal of ophthalmic and vision research volume 15, issue 1, january-march 2020 editorial erythropoietin for optic neuritis rod foroozan, md division of neuro-ophthalmology, baylor college of medicine, houston, tx, usa orcid: rod foroozan: https://orcid.org/0000-0002-7937-830x j ophthalmic vis res 2019; 14 (3): 240–242 inflammatory optic neuropathy remains the most common acute optic neuropathy in patients under the age of 50 years. the most common cause for inflammatory optic neuropathy is sterile inflammation from demyelination, with multiple sclerosis (ms) as the most common associated condition. this is the type of optic neuropathy most commonly referred to as “optic neuritis.” the inflammation more commonly occurs posteriorly, does not cause optic disc edema, and is termed retrobulbar optic neuritis. for the last 25 years or so, and primarily based on information from the optic neuritis treatment trial (ontt),[1] the standard treatment for acute inflammatory optic neuritis has been high dose corticosteroids, typically given intravenously for 3– 5 days, followed by oral steroids. the expectation is that corticosteroids will hasten visual improvement without altering the degree of recovery of visual function. there has been a relative paucity of adjunctive agents that have been used in conjunction with corticosteroids. given the persistent deficits that remain after a bout of optic neuritis, there remains an unmet need for neuroprotective therapy. erythropoietin, best recognized as a regulator of erythropoiesis, has shown potential neuroprotective properties in animal models of brain injury, including that from ischemia, trauma,[2, 3] epilepsy, and optic neuropathy.[4, 5] a rat model using immunization with myelin oligodendrocyte glycoprotein (mog) showed functional and histopathological improvement of retinal ganglion cells and optic nerves when erythropoietin treatment was combined with high dose methylprednisolone therapy.[6] the use of erythropoietin in humans with optic neuropathy has been reported in multiple studies from iran. the treated conditions included traumatic optic neuropathy,[7, 8] nonarteritic anterior ischemic optic neuropathy,[9, 10] multiple sclerosis,[11] and methanol optic neuropathy.[12–14] with some exceptions (particularly methanol optic neuropathy), the proof of benefit has been rather underwhelming thus far; however, the balance of evidence suggests that there has been no harm to visual function (although one patient was reported to develop cerebral venous sinus thrombosis[11]). one confounding issue with prior studies assessing the effect of erythropoietin on optic neuropathy is that the method of administration of the agent varied and included intravenous injection, intravitreal injection, and the use of microspheres. in addition, the dose of erythropoietin was inconsistent between the studies. in this issue, soltan sanjari and coworkers assessed the addition of intravenous recombinant human erythropoietin (ive) to intravenous methylprednisolone (ivmp) in patients with retrobulbar optic neuritis. thirty-five patients were treated with ivmp alone and twenty-seven with the combination of ivmp and ive (20,000 international units). both groups were treated with intravenous agents for 3 days and were then given 11 days of oral prednisolone at 1 mg/kg. the primary outcome measure was the change in best corrected visual acuity, which was assessed up to 120 days. other measures of visual function included contrast sensitivity (yang vision tester), color vision (ishihara pseudoisochromatic color plates), and automated perimetry (humphrey 24-2 sita standard).[15] while the cited inclusion criteria were described as those from the ontt, it was not clear what ancillary laboratory studies were performed, and specifically whether blood was sent for aquaporin4 and anti-mog antibodies.[15] by three months, there was no difference in the visual acuity between the two groups. in 240 @ 2019 j  o  v r | p  published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i3.4778&domain=pdf&date_stamp=2019-07-17 editorial; foroozan addition, there was no suggestion that the rate of visual recovery was different between the two groups. the mean deviation on automated perimetry showed no difference between the two groups at three months. there was also no difference in the contrast sensitivity and color vision between the two groups after treatment.[15] the authors should be commended for enrolling a relatively large number of patients with inflammatory optic neuropathy within a short (10 day) window of symptoms. it was slightly disappointing that there were no structural, objective measures such as optical coherence tomography (oct) of the retinal nerve fiber layer (rnfl), ganglion cell layer, or macula, particularly given the citation of work from another group which showed less rnfl thinning in patients with optic neuritis treated with ive (33,000 international units) and ivmp for three days.[16] while this was a negative study in terms of primary visual outcome, the authors point out that there was no evidence of clinically relevant side effects of ive treatment. this is consistent with the prior literature. regardless of the route of administration (including intravitreal injection), the use of erythropoietin appears to be safe, which is encouraging given the approval of a randomized, placebo-controlled trial [clinicaltrials.gov (nct01962571)] from a group of investigators in germany.[17] so far, ive for optic neuritis and demyelination[18] has not proven to be a game changer. if additional studies are performed, i would encourage the authors to include additional measures of structure and function of the visual pathways to ensure that the focus is not solely on central visual function. references 1. beck rw, cleary pa, anderson mm, jr., keltner jl, shults wt, kaufman di, et al. a randomized, controlled trial of corticosteroids in the treatment of acute optic neuritis. the optic neuritis study group. n engl j med 1992;326:581– 588. 2. king ce, rodger j, bartlett c, esmaili t, dunlop sa, beazley ld. erythropoietin is both neuroprotective and neuroregenerative following optic nerve transection. exp neurol 2007;205:48–55. 3. tan h, zhong y, shen x, cheng y, jiao q, deng l. erythropoietin promotes axonal regeneration after optic nerve crush in vivo by inhibition of rhoa/rock signaling pathway. neuropharmacology 2012;63:1182–1190. 4. weishaupt jh, rohde g, polking e, siren al, ehrenreich h, bahr m. effect of erythropoietin axotomy-induced apoptosis in rat retinal ganglion cells. invest ophthalmol vis sci 2004;45:1514–1522. 5. zhong l, bradley j, schubert w, ahmed e, adamis ap, shima dt, et al. erythropoietin promotes survival of retinal ganglion cells in dba/2j glaucoma mice. invest ophthalmol vis sci 2007;48:1212–1218. 6. diem r, sattler mb, merkler d, demmer i, maier k, stadelmann c, et al. combined therapy with methylprednisolone and erythropoietin in a model of multiple sclerosis. brain 2005;128:375–385. 7. kashkouli mb, pakdel f, sanjari ms, haghighi a, nojomi m, homaee mh, et al. erythropoietin: a novel treatment for traumatic optic neuropathy-a pilot study. graefes arch clin exp ophthalmol 2011;249:731–736. 8. entezari m, esmaeili m, yaseri m. a pilot study of the effect of intravenous erythropoetin on improvement of visual function in patients with recent indirect traumatic optic neuropathy. graefes arch clin exp ophthalmol 2014;252:1309–1313. 9. modarres m, falavarjani kg, nazari h, soltan sanjari m, aghamohammadi f, homaii m, et al. intravitreal erythropoietin injection for the treatment of non-arteritic anterior ischaemic optic neuropathy. br j ophthalmol 2011;95:992–995. 10. pakravan m, esfandiari h, hassanpour k, razavi s, pakravan p. the effect of combined systemic erythropoietin and steroid on non-arteritic anterior ischemic optic neuropathy: a prospective study. curr eye res 2017;42:1079–1084. 11. borhani-haghighi a, ghodsi m, razeghinejad mr, mardani s, mardani m, nikseresht ar, et al. erythropoietin for acute multiple sclerosis in patients with optic neuritis as a first demyelination event. neurosciences (riyadh) 2012;17:151– 155. 12. pakravan m, sanjari n. erythropoietin treatment for methanol optic neuropathy. j neuroophthalmol 2012;32: 325–328. 13. pakravan m, esfandiari h, sanjari n, ghahari e. erythropoietin as an adjunctive treatment for methanol-induced toxic optic neuropathy. am j drug alcohol abuse 2016;42:633– 639. 14. pakdel f, sanjari ms, naderi a, pirmarzdashti n, haghighi a, kashkouli mb. erythropoietin in treatment of methanol optic neuropathy. j neuroophthalmol 2018;38:167–171. 15. soltan sanjari m, pakdel f, moosavi f, pirmarzdashti n, nojomi m, haghighi a, et al. visual outcomes of adding erythropoietin to methylprednisolone for treatment of retrobulbar optic neuritis. j ophthalmic vis res 2019;299– 305. 16. suhs kw, hein k, sattler mb, gorlitz a, ciupka c, scholz k, et al. a randomized, double-blind, phase 2 study of erythropoietin in optic neuritis. ann neurol 2012;72:199– 210. 17. diem r, molnar f, beisse f, gross n, drüschler k, heinrich sp, et al. treatment of optic neuritis with erythropoietin (tone): a randomised, double-blind, placebo-controlled trial-study protocol. bmj open 2016;6:e010956. 18. suhs kw, papanagiotou p, hein k, pul r, scholz k, heesen c, et al. disease activity and conversion into multiple sclerosis after optic neuritis is treated with erythropoietin. int j mol sci 2016;17:1666. j  o  v r volume 14, issue 3, july–september 2019 241 editorial; foroozan this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i3.4778 how to cite this article: foroozan r. erythropoietin for optic neuritis. j ophthalmic vis res 2019;14:240–242. 242 j  o  v r volume 14, issue 3, july–september 2019 https://knepublishing.com/index.php/jovr original article intraocular pressure values using icare® rebound tonometer and correlation with postconceptional age in premature infants catarina monteiro, md; maria vivas, md; júlio almeida, md; mário ramalho, md, febo; mafalda mota, md susana teixeira, md; isabel prieto, md hospital professor doutor fernando da fonseca, amadora, portugal orcid: catarina mimoso monteiro: https://orcid.org/0000-0001-6057-3546 abstract purpose: this study aimed to determine a normative range of intraocular pressure (iop) values measured with icare rebound tonometer in premature infants and evaluate iop variation over time and its correlation with the progression of postconceptional age (pca). by doing so, we also evaluated advantages of this iop-measuring method in this population when compared to more traditional methods. methods: we conducted a single-center prospective study that included premature infants (gestational age ≤32 weeks) who were admitted to the neonatal intensive care unit (nicu) in hospital professor doutor fernando fonseca. the study took place between january and december 2021. iop was measured using icare tonometer on the occasion of the first retinopathy of prematurity (rop) screening requested by the nicu and again after a two-week interval if pca was still ≤37 weeks. iop measurements were stopped at 37 weeks or if the infant was discharged. the evaluated outcomes were mean iop values and their correlation with pca. results: thirty-four eyes of 17 preterm infants with a mean gestational age of 29.4 ± 2.3 weeks and a mean birth weight of 1222.9 ± 361.9 gr were evaluated. the mean iop registered was 16.1 ± 6.4 mmhg, with a median value of 15.3 mmhg. the top 90𝑡ℎ percentile was 22.1 mmhg and the bottom 10𝑡ℎ percentile was 9.0 mmhg. the average iop reduction was 4.8 ± 6.7 mmhg (p = 0.0019) within the two-week interval of pca. conclusion: the mean iop in premature infants was 16.1 ± 6.4 mmhg and this value significantly decreased by 4.8 ± 6.7 mmhg every two weeks of pca. keywords: intraocular pressure; postconceptional age; premature infants; rebound tonometry j ophthalmic vis res 2023; 18 (3): 267–271 correspondence to: catarina mimoso monteiro, md. ic19 276, 2720-276 amadora, portugal. email: catarinammonteiro@campus.ul.pt received: 09-07-2022 accepted: 04-01-2023 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i3.13774 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: monteiro c, vivas m, almeida j, ramalho m, mota m, teixeira s, prieto i. intraocular pressure values using icare® rebound tonometer and correlation with postconceptional age in premature infants. j ophthalmic vis res 2023;18:267–271. © 2023 monteiro et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 267 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i3.13774&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr iop values in premature infants; monteiro et al introduction in order to detect developmental abnormalities and congenital diseases in the eye, it is crucial to have a good understanding of normal intraocular pressure (iop) values and their changes over time in premature infants.[1] the characteristics of the anterior chamber angle in the premature infant differ from that in adults, and parameters such as anterior chamber depth, trabecular-iris angle and iris thickness seem to show a linear relation with postconceptional age (pca).[2] to this date and to the best of our knowledge, very few studies have reported iop in preterm infants, and with the advent of new handheld tonometers such as the icare, measuring iop could become part of the routine evaluation of these children. the purpose of this prospective longitudinal study is to determine average iop values for premature infants and to evaluate their progression over time. methods this single-center prospective study included preterm infants with either gestational ages between 24 and 32 weeks or a birth weight of <1500 gr, who were evaluated by the ophthalmology department as part of the routine retinopathy of prematurity (rop) screening program. children with chromosomal abnormalities and dysmorphic syndromes, congenital ocular abnormalities and children under invasive ventilation were excluded from the study. we included some eyes with early stages of rop (stages i and ii) but excluded all eyes with rop in more advanced stages and those eyes submitted to laser therapy or anti-vegf treatment. the study was conducted in the neonatal intensive care unit (nicu) of our hospital and all infants were examined while still hospitalized. pca was defined as the gestational age plus the number of weeks since birth. gestational age of the infants was determined based on obstetric history and first-trimester obstetric ultrasound. two experienced ophthalmologists specialized in pediatric ophthalmology performed the ocular examination in all studied infants. if the infant was irritable or crying, iop measurement was postponed until the child was calm to avoid a valsalva-like effect. no sedative drugs or muscle relaxants were given to the infants immediately before or during the examination, as these may have artificially lowered the iop values. the evaluation was only performed if the child was clinically stable. the infant was laid on his/her back in the incubator and iop was measured with an icare® ic200 rebound tonometer, without the use of topical anesthesia. the right eye was the first to be examined in all cases and measurements were obtained between 9 and 12 am. three iop measurements were taken for each eye and average iop was calculated. iop measurements were repeated every 2 weeks and stopped after 37 weeks of pca or if the infant was discharged. the study protocol was reviewed and approved by the ethics committee of the hospital professor doutor fernando da fonseca, amadora, portugal under approval number 39/2022. the protocol of the study complied with the guidelines for human studies and the world medical association declaration of helsinki. results this study included 34 eyes from 17 premature infants, 26 males and 8 females, with a mean gestational age of 29.4 ± 2.3 weeks (24.9–32.7 weeks) and a mean birth weight of 1222.9 ± 361.9 gr. as there was no statistically significant difference between right and left eyes (p = 0.8), the results were analyzed together. the mean pca was 33.9 ± 1.6 weeks with a range of 32 to 41 weeks. twelve patients underwent two evaluations and ten were only submitted to one observation. of the 34 included eyes, 6 had rop stage i or stage ii; none of these eyes were submitted to laser or anti-vegf therapy. at the end of the experiment, it was determined that the mean iop in both eyes for all measurements was 16.1 ± 6.4 mmhg. the mean iop in the right eye was 15.9 ± 5.7 mmhg (7.7 to 34.0 mmhg) and the mean iop in the left eye was 16.4 ± 7.1 mmhg (7 to 37.7 mmhg). the median was 15.3 mmhg. the top 90𝑡ℎ percentile (p90) for both eyes was 22.1 mmhg and the bottom 10𝑡ℎ percentile (p10) was 9.0 mmhg. as represented in the box and whisker plot [figure 1], the interquartile range (p25–p75) ranged between 12.0 and 19.6 mmhg. out of the 34 examined eyes, 24 had at least two iop measurements, separated by two weeks. in this subset, the mean iop showed an average 268 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 iop values in premature infants; monteiro et al figure 1. box and whisker plot of iop values. the box extends from the lower to the upper quartile values of the data (p25–p75) with a line at the median. the whiskers extend from the box to show the range of the data. beyond the whiskers, data is considered as outliers and is plotted as individual points. reduction of 4.8 ± 6.7 mmhg (p = 0.0019) every two weeks of increased pca, as represented in figure 2. discussion in 1999, ricci et al[3] evaluated the iop of 20 preterm infants and concluded that the mean iop following birth decreased progressively. as many other studies have shown since then, our study also reports that the iop of preterm infants decreases significantly with the increase of pca. normative values are not established as most studies use different tonometers and inclusion criteria. ng et al[4] reports that of all recent studies regarding iop in premature babies, the mean/median iop varies between 10.1 and 18.6 mmhg. in our sample, the average iop ranged between 12 and 19.6 mmhg (p25–p75) with a median value of 15.3 mmhg. these values are in agreement with mckibbin et al[5] and axer-siegel et al[6] whose analyses obtained mean iop values ranging between 15.5 and 16.3 mmhg. regarding iop decrease with pca, ng et al[4] reported an iop reduction of 0.11 mmhg (p < 0.001) for each week increase in the pca, however, it included evaluations of children with more than 40 weeks of age. lindenmeyer et al[7] reported a reduction of 0.29 mmhg (p = 0.047) per pca week. in the current study, iop reduction was significantly larger, 4.8 ± 6.7 mmhg (p = 0.0019) with every two weeks increase in pca. first of all, this may be explained by the fact that we included extremely preterm infants with very low gestational ages who were not included in other studies. secondly, the iop measuring method used was also different as tonopen ii was used. thirdly, artificial elevation of iop may occur in infants who are awake and react with vigorous resistance to the ophthalmic examination.[4] although the theory of iop decrease with increasing pca seems to have a relative consensus as shown in recent studies, the exact physiopathological mechanism behind this fact is still not well established. physiopathological mechanisms that may explain this consistent iop decrease with increasing pca include increasing size of ocular structures, anterior chamber angle maturation and progressive improvement of the aqueous drainage system and neuroendocrine changes. the exact mechanism is yet to be discovered. it is well known that infants with rop may have increased iop values due to several treatment options such as laser and anti-vegf therapy and changes in advanced rop stages that may lead to angle closure. there are other proposed physiopathological mechanisms that may cause increases in iop measurements which are not unique to rop but are related to prematurity in journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 269 iop values in premature infants; monteiro et al a a figure 2. (a) the figure shows a graphic representation of iop values variation with pca (in days) for each of the 24 preterm infants evaluated. (b) the graph shows an average iop decrease of 0.47 mmhg per day itself such as incomplete trabecular meshwork development, decreased anterior chamber depth, anteriorly displaced iris planes, and increased lens thickness.[9] in our study, we only included a small number of children with early stages of rop (stage i or ii). as none of them were submitted to laser or to anti-vegf therapy that could alter iop values, it is highly unlikely that early rop changes would lead to significant iop changes in these eyes and we chose to include them in the study. most studies regarding iop values in premature infants included the use of an eyelid speculum and anesthetic drops for the iop measurements which were obtained with the use of tonopen xl𝑇𝑀. we chose to use icare ic200 for measuring iop in preterm infants. this method has the advantage of not needing anesthetic drops or eyelid speculum placement. there have been studies that reported that the use of an eyelid speculum may raise iop by an average of 4 mmhg in children.[8] haus et al[10] compared the icare ic200 rebound tonometer (ict) with the tonopen xl (tp) measurements in premature infants and concluded that iop values evaluated by the ict were significantly lower than that of the tp. tonopen use requires anesthetic eye drop instillation and a large applanation area which implicates an increased width of the eyelid opening. this may cause discomfort to the child leading to falsely elevated iop values. therefore, the icare rebound tonometer might be a better option to measure iop in premature children. its main advantages include the extensive flexibility in positioning with the possibility of the patient being placed in a supine position, no need to anesthetic drops and little or no discomfort for the child. as far as we are aware, this is the first prospective longitudinal study using icare ic200 tonometer in preterm infants. this iop-measuring method is fast, accurate, and reliably repeatable, and thus it should be considered a first-line option for the iop evaluation in premature children. our study had certain inherent limitations. on one hand, eyelid edema after birth made some of the readings hard and probably less reliable as the infant had difficulty opening one or both eyes, and manual opening of the eyelid might have resulted in inadvertent pressure on the scleralcorneal interface that might have influenced iop measurements. on the other hand, the sample size of this study was relatively small, which may limit the statistical strength of the findings. we are also of the view that the study would have been strengthened if the measurement of corneal thickness and its correlation with iop values were considered. therefore, further studies with prospective, controlled design, and a larger number of included patients are needed to confirm our findings. financial support and sponsorship this research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. the authors also declare they have no relevant financial or non-financial interests to disclose. conflicts of interest there are no competing interests. references 1. tucker sm, enzenauer rw, levin av, morin jd, hellmann j. corneal diameter, axial length, and intraocular pressure in premature infants. ophthalmology 1992;99:1296–1300. 270 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 iop values in premature infants; monteiro et al 2. kobayashi h, kiryu j, kobayashi k, kondo, t. ultrasound biomicroscopic measurement of anterior chamber angle in premature infants. br j ophthalmol 1997;81:460–464. 3. ricci b. intraocular pressure in premature babies in the first month of life. j aapos 1999;3:125–127. 4. ng pc, tam bs, lee ch, wong sp, lam hs, kwok ak, et al. a longitudinal study to establish the normative value and to evaluate perinatal factors affecting intraocular pressure in preterm infants. invest ophthalmol vis sci 2008;49:87– 92. 5. mckibbin m, cassidy l, dabbs tr, verma d, mckibbin m. intraocular pressure, pulse amplitude and pulsatile ocular blood flow measurement in premature infants screened for retinopathy of prematurity. eye 1999;13:266–267. 6. axer-siegel r, bourla d, friling r, shalev b, sirota l, benjamini y, et al. intraocular pressure variations after diode laser photocoagulation for threshold retinopathy of prematurity. ophthalmology 2004;111:1734–1738. 7. lindenmeyer rl, farias l, mendonça t, fortes filho jb, procianoy rs, silveira rc. intraocular pressure in very low birth weight preterm infants and its association with postconceptional age. clinics 2012;67:1241–1245. 8. epley kd, tychsen l, lueder gt. the effect of an eyelid speculum on intraocular pressure measurement in children. am j ophthalmol 2002;134:926–927. 9. lenis tl, ledesma vicioso n, reddy v, kovacs kd, van tassel sh, orlin a. case report: glaucoma in an infant with retinopathy of prematurity. front pediatr 2021;9:786327. 10. haus ah, jonescu-cuypers c, seitz b, kaesmannkellner b. comparison between intraocular pressure measurements with icare rebound tonometry and tonopen xl tonometry in premature infants. invest ophthalmol vis sci 2008;49:712. journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 271 original article near points of convergence and accommodation in a population of university students in iran hassan hashemi1,2, md; mojgan pakbin1,3, ms; babak ali4, ms; abbasali yekta4, phd hadi ostadimoghaddam5, phd; amir asharlous1, phd; mohammadreza aghamirsalim6, md mehdi khabazkhoob7, phd 1noor research center for ophthalmic epidemiology, noor eye hospital, tehran, iran 2noor ophthalmology research center, noor eye hospital, tehran, iran 3research and technology deputy, tehran university of medical sciences, tehran, iran 4department of optometry, school of paramedical sciences, mashhad university of medical sciences, mashhad, iran 5refractive errors research center, mashhad university of medical sciences, mashhad, iran 6eye research center, tehran university of medical sciences, tehran, iran 7department of medical surgical nursing, school of nursing and midwifery, shahid beheshti university of medical sciences, tehran, iran orcid: hassan hashemi: https://orcid.org/0000-0002-2109-0856 abbasali yekta: https://orcid.org/0000-0003-4356-9064 abstract purpose: to determine the distribution of the near point of convergence (npc) and near point of accommodation (npa) in a young student population in iran. methods: the subjects were selected using a cluster sampling method. all students underwent optometry tests, including visual acuity measurement, refraction, and cover test, as well as ophthalmic examinations. the npc and npa were measured using an accommodative target (near snellen chart). results: of 1,595 students, the data of 1,357 were analyzed. the mean npc and npa in the total sample were 7.25 cm (95% confidence interval [ci], 7.02 to 7.48) and 9.99 cm (95% ci, 9.69 to 10.29), respectively. older age was associated with an increase in the npc, which increased from 6.98 cm in 18–20 years olds to 9.51 cm in those over 30 years. the npa was significantly associated with age and refractive errors in the multiple linear regression model, increasing from 9.92 cm in 18–20 years olds to 11.44 cm in those over 30 years (𝑃 = 0.003). hyperopic eyes had lower npa than myopic and emmetropic eyes (𝑃 = 0.001). in younger age groups, the mean accommodation amplitude was lower than the mean hofstetter value. moreover, with age, especially after 30 years, the mean values surpassed those determined using the hofstetter formula. conclusion: the npc values in this study were lower than those previously reported for identical age groups. the hofstetter formula is not always an accurate predictor of the accommodation amplitude in the iranian adult population. keywords: cross-sectional study; distribution; near point of accommodation; near point of convergence correspondence to: abbasali yekta, phd. department of optometry, school of paramedical sciences, mashhad university of medical sciences, no. 23, kolahdooz st., 1, ahmadabad blv., mashhad 91838, iran. e-mail: yektaa@mums.ac.ir received: 13-06-2018 accepted: 21-02-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i3.4787 j ophthalmic vis res 2019; 14 (3): 306–314 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: hashemi h, pakbin m, ali b, yekta a, ostadimoghaddam h, asharlous a, et al. near points of convergence and accommodation in a population of university students in iran. j ophthalmic vis res 2019;14:306–314 306 @ 2019 j  o  v r | p  published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i3.4787&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr npc and npa in university students; hashemi et al introduction non-strabismic vergence dysfunctions and accommodation anomalies are the main causes of symptoms such as occasional double vision, headaches, and blurred vision after prolonged near work.[1–3] students experience such symptoms more often than others do because of their higher demand for near vision, and this can affect their academic activities.[1] the high prevalence of accommodative and binocular dysfunctions, with estimates ranging between 13.5% and 42%, point to the importance of examining the binocular vision status during routine ophthalmic examinations.[4–7] however, this variation could also arise because of the variable definitions and diagnostic criteria used by different studies. convergence insufficiency (ci) is the most common vergence anomaly with a wide prevalence ranging from 0.8% to 13% in some studies.[4–10] the near point of convergence (npc) is an indicator for the diagnosis of ci and is a good measure for differentiating symptomatic from asymptomatic cases.[11] therefore, an analysis of the npc can be essential for people with high near task demand.[11] many studies have shown that the npc increases with age,[12–15] and some indicate that the npc is higher in men than in women,[15] but its relationship with sex remains unclear. some studies reported a relationship between heterophoria and refractive error,[16, 17] while another claimed that the npc was not related to refractive error.[15] accurate interpretation of npc measurements requires their comparison with normal values, which may vary from one population to another. accommodation insufficiency (ai), a situation in which the accommodation amplitude (aa) is lower than expected for a person’s age, is one of the most common accommodation dysfunctions leading to symptoms resulting from reading and near work.[18, 19] the measurement of the near point of accommodation (npa) provides an index for determining the aa. different opinions exist about the relationship between the aa and refractive error. while some studies reported better aas in myopes,[20–22] other studies found no association between refractive error and the aa.[23] moreover, studies on the npc and npa have reported different values. the variations in the values obtained from these studies can be attributed to differences in diagnostic methods, age, refractive errors, and race in the different studies.[9, 13, 24–27] in addition, they all examined small sample sizes, and their results cannot be generalized to other populations. therefore, the present study was designed to provide the npc and npa values in a large population of students in southern iran and to investigate their relationship with age, sex, and degree of refractive error. methods this cross-sectional study was conducted in 20162017 in kazerun, a city in fars province in southern iran. the target population of the study was all students enrolled at the four universities in kazerun at the time of the study. the ethics committee of mashhad university of medical sciences approved the study protocol, which adhered to the tenets of the declaration of helsinki. informed consent was obtained from all participants. the students were assured that the data were anonymous and confidential. sample selection involved a multistage stratified random cluster sampling approach, wherein each university was considered a stratum. after listing all the academic majors in each university, each major was considered a cluster, and 27 majors were randomly selected as the target clusters. thereafter, in each university, the roster of all students studying in each selected major was prepared, and a certain number of students, proportionate to the total size, was randomly selected from each major. finally, 1,462 students were invited to participate in the study. all examinations were conducted at each university site in a room under daylight condition. all students underwent complete vision tests performed by an expert optometrist and slit-lamp ophthalmic examinations performed by an experienced ophthalmologist. vision tests included the measurement of refraction with the topcon ar 8800 autorefractometer (topcon corporation, tokyo, japan), followed by uncorrected visual acuity measurement using a logmar chart and manifest refraction measurement by using retinoscopy. eventually, subjective refraction tests were performed using trial frames and ophthalmic lenses on the basis of the retinoscopy findings to determine the bestcorrected visual acuity. j  o  v r volume 14, issue 3, july–september 2019 307 npc and npa in university students; hashemi et al binocular vision tests included the cover test, measurement of the aa and npc, and depth perception. the aa and npc were measured using the push-up method and an astron accommodative rule (gulden ophthalmics, elkins park, pa).[28] the npa was measured using the best correction in place. while the participants focused monocularly on the “e” one line above their near visual acuity threshold, the near snellen e chart was gradually moved toward them until they reported that the letters were blurry, and they were no longer able to maintain a clear image. at this point of sustained blur, the distance between the target and the spectacle plane was measured in centimeters. the npa was measured three times, and the average of these measurements was recorded. the aa was calculated monocularly for each eye. the next step was npc measurement, which was performed with the best-corrected vision in place using an astron accommodative rule. this tool has a movable target and a rod marked in centimeters. a single column of letters equivalent to the 20/30 line was used at 40 cm as the target. the target was gradually moved towards the participants at a speed of 1 cm/s until they were no longer able to maintain a single image and reported double vision, or the examiner noted ocular divergence. the distance from the target to the spectacle plane was recorded as the npc distance in centimeters. to increase measurement accuracy, npc measurements were performed three times for each individual, and the average of the three measurements was recorded as the final npc. refractive errors in this study were measured on the basis of the spherical equivalent (se). an se refraction worse than 0.5 diopters was defined as hyperopia, and an se of less than −0.5 diopters was defined as myopia. individuals with a history of eye surgery and those with a diagnosis of tropia or amblyopia were excluded from the present study. statistical analysis in this study, the npc and aa in centimeters were summarized as means with 95% confidence intervals (cis). linear regression was used to explore the relationship of these indices with age and sex. analysis of variance was used to determine the differences between these indices by using refractive errors. finally, the relationship between each of these indices with age, sex, and refractive errors was examined in a multiple linear regression model. in this model, refractive errors were entered into the model by considering individuals with emmetropia as the reference group. the cluster effect was considered for more accurate estimation of the standard error. a significance level of 0.05 was considered in all the analyses. given the higher participation of female students, weighting for sex was applied. results of the 1,595 selected individuals, 1,462 participated in the study (91.66% participation rate). after applying the exclusion criteria (history of surgery, heterotropia, and amblyopia), a total of 1,357 individuals were analyzed in this study; of these, 1,008 (74.3%) were female. the age of the included students ranged from 18 to 39 years, and the mean age was 22.71 ± 3.0 years. the average se ± standard deviation was -0.73 ± 1.22 diopters (-10.0 to +2.50). figure 1 demonstrates the distribution of the npc and npa in this study using a boxplot. table 1 shows the mean npc by age and sex. the findings of the present study showed that the mean npc for all the students was 7.25 (95% ci, 7.02 to 7.48 cm). the mean npc was significantly higher in male students than in female students (𝑃 = 0.046). as shown in table 1, the npc increased from 6.98 cm in 18–20 years olds to 9.51 cm in those over 30 years. linear regression showed that a 1-year increase in age was associated with a 0.11 cm increase in the npc (𝑃 = 0.005). the mean npc in the emmetropic, myopic, and hyperopic groups was 7.29 (95% ci, 7.04 to 7.54), 7.21 (95% ci, 6.89 to 7.52), and 7.16 (95% ci, 5.6 to 8.73) cm, respectively, without any significant differences between the three groups in terms of the npc (𝑃 = 0.322). in the multiple linear regression model, after entering the variables of age, sex, and refractive error in the model, only age maintained a significant relationship with the npc. the npa was measured separately in each eye. owing to the correlation (pearson correlation = 0.983) of both eyes, the right eye was analyzed. the mean npa in the present population was 9.99 (95% ci, 9.69 to 10.29 cm). as shown in table 1, no significant difference in the npa was observed between male and female students (𝑃 = 0.637). the 308 j  o  v r volume 14, issue 3, july–september 2019 npc and npa in university students; hashemi et al table 1. the mean near point of convergence and near point of accommodation 𝑛 npc (95% ci) npa (95% ci) total 1357 7.25 (7.02–7.48) 9.99 (9.69–10.29) gender female 1008 7.12 (6.90–7.34) 9.95 (9.57–10.34) male 349 7.52 (7.14–7.89) 10.05 (9.73–10.38) age (years) 18–20 214 6.98 (6.69–7.27) 9.92 (9.59–10.25) 20–25 989 7.18 (6.90–7.46) 9.92 (9.56–10.29) 26–30 115 7.51 (7.09–7.92) 10.10 (9.55–10.65) > 30 39 9.51 (7.41–11.60) 11.44 (10.45–12.44) ci, confidence interval; n, number; npa, near point of accommodation; npc, near point of convergence (a) near point of convergence (cm) near point of accommodation (cm) (b) figure 1. (a) the distribution of the near point of convergence (b) and near point of accommodation in university students. npa increased from 9.92 cm in 18–20 years olds to 11.44 cm in those over 30 years (𝑃 = 0.003). as shown in figure 2, the npa was significantly different among the refractive error groups, with hyperopes having the lowest npa (𝑃 = 0.001). in the multiple linear regression model, older age was found to be associated with an increase in the npa (coefficient = 0.09). moreover, in this model, hyperopes had a lower npa than did the emmetropes (𝑃 < 0.001). discussion this study evaluated the aa and convergence in a young-to-middle-aged student population in a southern city. according to the findings of this study, the mean npc is approximately similar to the values reported by ostadimoghaddam et al[15] for the 20–29 years age range (7.59 cm). however, it is more proximal than the levels reported for the 19–30 years age group in other studies.[11, 13] conversely, some studies reported a mean npc lower than that reported in our study. ovenseriogbomo et al[2] and yekta et al[14] reached the values of 6 and 5.27 cm for the 15–28 years and 18–35 years age groups, respectively. table 2 summarizes the npc values reported in the different studies. these different results can be attributed to several factors, including the type of target used in the npc measurement, differences in the characteristics of the studied populations, and variations in the source and method of measurement. in the study by momeni-moghaddam et al,[11] the most important reason for the more distant npc (9.50 cm) than in the present study (7.25 cm) was the difference in the measurement method. in their study, the npc was defined as the distance between the break point and the j  o  v r volume 14, issue 3, july–september 2019 309 npc and npa in university students; hashemi et al hyperopia (se≥ +0.50d)myopia (se≤ -0.50d)emmetropia (se = -0.49 to +0.49) figure 2. the near point of accommodation in different refractive errors. se, spherical equivalent plane of the lateral canthus, while in our study, the measured distance was from the break point to the spectacle plane. considering a 12 to 15 mm vertex distance for the glasses, a 22 mm difference between the results is reasonable. the type of target is also an important factor in npc evaluation. it is suggested that accommodative targets result in a more proximal npc and underestimate the npc values. therefore, attention to clarity may interfere with convergence and may lead to a more proximal npc. siderov et al[29] measured the npc in 20–85 years old subjects using several types of targets and found that the npc results were influenced by the target type only in younger individuals but not in presbyopic individuals. thus, we can conclude that the npc is related to accommodation. this is not unexpected because in npc measurement, in fact, the absolute convergence is being evaluated, which is the combination of tonic, accommodative, proximal, and reflexive convergences. therefore, stimulating accommodation increases the total amount of absolute convergence by increasing accommodative convergence, and ultimately, the measured npc is underestimated; however, this does not occur with non-accommodative targets. regarding the measurement method, it has been suggested that targets that are mounted on a rule provide a higher estimated npc than targets that are moved manually and freely.[30] the findings of the present study indicate an increase in the npc values with age. larsson et al[24] and yekta et al[12] observed lower npc values in children (younger ages). studies have also shown that the npc recedes with aging.[25] this can be due to accommodation reduction with age, which results in reduced accommodative convergence and, consequently, a remote npc.[12, 14, 15] studies on the relationship between sex and the npc suggested a more distant npc in men[15] and boys,[12] even though the inter-sex difference in the npc in both studies was ≤ 0.1 cm, which was clinically insignificant. however, in our study, the mean npc in men was 0.37 cm further than that in women. we evaluated the npa in addition to the npc. given the students’ greater need for vision, especially near vision,[1] the aa is a key factor in the 310 j  o  v r volume 14, issue 3, july–september 2019 npc and npa in university students; hashemi et al table 2. the near point of convergence values reported by various studies author sample size age (year) mean npc (cm) target momeni-moghadam et al[11] 124 19–24 9.50 accommodative abraham et al[13] 150 accommodative 50 1–18 7.17 50 19–27 8.59 50 28–35 9.52 hashemi et al[9] 219 10–69 8.36 accommodative ostadimoghaddam et al[15] 2,433 10–86 8.59 accommodative present study 1,357 18–39 7.25 accommodative larsson et al[24] 217 10 6.2 non-accommodative ovenseri-ogbomo et al[2] 212 15–28 6 yekta et al[14] 382 18–35 5.27 accommodative yekta et al[12] 3,701 4–6 5.10 accommodative scheiman et al[27] 175 22–37 5 accommodative/penlight with red green glasses hussaindeen et al[25] 920 7–17 3 accommodative npc, near point of convergence rate of ocular symptoms resulting from prolonged near work. the aa is determined by measuring the npa, which provides an estimation of the aa. studies have shown that the aa decreases with age,[13, 14, 26] and our results concur with their findings. the present study showed that the npa increases with age, and thus, the aa decreases. table 3 summarizes the aas in different studies. most studies evaluated the aa in people under 18 years of age and reported higher values (more proximal npa) than in the present study.[24–26] this can be due to active accommodation in children and adolescents. the estimation of abraham et al[13] in 19–27-year-old indians was 1.0 diopter less than that measured in our study. rambo and sangal[31] posited the possible effect of geographic region on the aa and suggested that people residing in tropical climates tended to have a lower aa than the europeans. however, it must be noted that their population sample was presbyopic. a comparison of the aa in this study with the calculated values based on the hofstetter formula shows that the latter is not an accurate predictor for the adult iranian population. as demonstrated in figure 3, the mean aa in our younger age groups was lower than the mean estimated by hofstetter[32] and was significantly higher in the older age groups, especially after 30 years of age. this formula fits the studied population best at the age of 30 years; therefore, hofstetter’s formulas, which are widely used in the diagnosis of ai, may lead to false negative results in individuals under 30 years of age and false positive results in individuals over 30 years of age. results regarding the relationship between the aa and sex are inconsistent. in agreement with the study by castagno et al,[33] our study did not show a significant difference in the npa between women and men. however, hashemi et al[26] showed that the aa in 17-11-year-old girls was higher than that of boys in the same age group. they attributed the difference to factors such as education and nutrition. yekta et al, who studied presbyopic individuals, estimated a higher aa in women and suggested that hormonal factors might have a role, especially in post-menopausal women.[34] while some studies state that refractive errors do not correlate with the aa,[23] abraham et al[20] reported higher aas in myopes. this difference was observed in 35–44-year-old individuals, and no difference was observed between the types of refractive error after the age of 44 years. maheshwari et al reported similar results.[21] charman argued that myopic eyes have weaker sympathetic j  o  v r volume 14, issue 3, july–september 2019 311 npc and npa in university students; hashemi et al table 3. amplitude of accommodation reported by different studies author sample size age (year) aa (d) target larsson et al[24] 217 10 12 push-up/raf rule hashemi et al[26] 1,070 11–17 11.53 raf rule yekta et al[14] 382 18–35 11.14 push-up/accommodative target hussaindeen et al[25] 920 11–17 11 minus lens present study 1,357 18–39 9.99 push-up/accommodative target abraham et al[13] 50 10–18 10.02 minus lens 19–27 9.04 28–35 7.34 the amount of near point of accommodation was divided by 100 to convert it to the amplitude of accommodation in diopters. aa, amplitude of accommodation; d, diopter; raf, royal air force figure 3. the mean and minimum amplitudes of accommodation calculated by hofstetter’s formula according to age and mean amplitude of accommodation measured in the present study. innervation and stronger parasympathetic innervation than the hyperopic eyes, and therefore, when corrected with a negative lens, they have higher aas than the hyperopic eyes.[22] investigating the relationship between the npa and refractive errors in the present study showed a low level of npa in the hyperopic group. despite the greater accommodation demand with hyperopic spectacle correction than with myopic and emmetropic correction, we found a lower npa in hyperopic patients. there are several possible reasons for this finding. first, hyperopes may go without glasses, especially at younger ages. therefore, they use their accommodation for near work and even far vision more than emmetropic and myopic individuals do.[35] hence, the frequent use of accommodation may contribute to better development of accommodation and a stronger accommodation reflex. this is similar to orthoptic reinforcement exercises that increase the amplitude with repeated accommodation,[36, 37] which occurs naturally in hyperopic eyes. another reason may be the magnification effect of glasses.[38] the npa was measured with optical correction in place, and the refractive correction of hyperopia was achieved using convex lenses, which magnify the image. the blur caused by defocus is understood much later in the larger retinal images because the 312 j  o  v r volume 14, issue 3, july–september 2019 npc and npa in university students; hashemi et al details in a larger image are more recognizable than those in a smaller one. thus, the patients may report the blur much later.[39, 40] hyperopes may also report blur relatively later with the push-up method, and thus the npa may be underestimated. this study reports normative values in large university students using a valid method; however, it has some limitations. cycloplegic refraction was not performed. in addition, similar to other studies, refractive errors were measured based on se that may affect the interpretation of results in some cases such as mixed astigmatism. moreover, the age range of participants was relatively wide. in conclusion, this study estimated the npc and npa values in a large population of university students in southern iran. the npc values were lower than those reported in most other studies on this age group. clinicians should be aware of the impact of age and sex during the evaluation of ci symptoms and other binocular vision dysfunctions. the discord with the hofstetter formula also should be considered in the diagnosis of ai. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. grisham jd, sheppard mm, tran wu. visual symptoms and reading performance. optom vis sci 1993;70:384–391. 2. ovenseri-ogbomo go, eguegu op. vergence findings and horizontal vergence dysfunction among first year university students in benin city, nigeria. j optom 2016;9:258–263. 3. long j, cheung r, duong s, paynter r, asper l. viewing distance and eyestrain symptoms with prolonged viewing of smartphones. clin exp optom 2017;100:133–137. 4. hoseini-yazdi sh, yekta a, nouri h, heravian j, ostadimoghaddam h, khabazkhoob m. frequency of convergence and accommodative disorders in a clinical population of mashhad, iran. strabismus 2015;23:22–29. 5. lara f, cacho p, garcia a, megias r. general binocular disorders: prevalence in a clinic population. ophthalmic physiol opt 2001;21:70–74. 6. garcia-munoz a, carbonell-bonete s, canto-cerdan m, cacho-martinez p. accommodative and binocular dysfunctions: prevalence in a randomised sample of university students. clin exp optom 2016;99:313–321. 7. richman j, laudon r. a survey of the prevalence of binocular and accommodative dysfunctions in a sample of optometry students. j behav optom 2002;13:31–33. 8. hussaindeen jr, rakshit a, singh nk, george r, swaminathan m, kapur s, et al. prevalence of non-strabismic anomalies of binocular vision in tamil nadu: report 2 of band study. clin exp optom 2016;100:642–648. 9. hashemi h, nabovati p, khabazkhoob m, ostadimoghaddam h, doostdar a, shiralivand e, et al. the prevalence of convergence insufficiency in iran: a population-based study. clin exp optom 2017:100:704–709. 10. porcar e, martinez-palomera a. prevalence of general binocular dysfunctions in a population of university students. optom vis sci 1997;74:111–113. 11. hamed mm, david ag, marzieh e. the relationship between binocular vision symptoms and near point of convergence. indian j ophthalmol 2013;61:325–328. 12. yekta a, hashemi h, ostadimoghaddam h, haghighi b, shafiee h, mehravaran s, et al. strabismus and near point of convergence and amblyopia in 4-6 year-old children. strabismus 2016;24:113–119. 13. abraham ng, srinivasan k, thomas j. normative data for near point of convergence, accommodation, and phoria. oman j ophthalmol 2015;8:14–18. 14. yekta a, khabazkhoob m, hashemi h, ostadimoghaddam h, ghasemi-moghaddam s, heravian j, et al. binocular and accommodative characteristics in a normal population. strabismus 2017;25:5–11. 15. ostadimoghaddam h, hashemi h, nabovati p, yekta a, khabazkhoob m. the distribution of near point of convergence and its association with age, gender and refractive error: a population-based study. clin exp optom 2017;100:255–259. 16. ansons am, davis h. diagnosis and management of ocular motility disorders. hoboken, nj: john wiley & sons; 2008. 17. jorge j, de almeida jb, parafita ma. binocular vision changes in university students: a 3-year longitudinal study. optom vis sci 2008;85:e999–e1006. 18. scheiman m, wick b. clinical management of binocular vision: heterophoric, accommodative, and eye movement disorders. philadelphia, pa: lippincott williams & wilkins; 2008. 19. borsting e, rouse mw, deland pn, hovett s, kimura d, park m, et al. association of symptoms and convergence and accommodative insufficiency in school-age children. optometry 2003;74:25–34. 20. abraham lm, kuriakose t, sivanandam v, venkatesan n, thomas r, muliyil j. amplitude of accommodation and its relation to refractive errors. indian j ophthalmol 2005;53:105–108. 21. maheshwari r, sukul rr, gupta y, gupta m, phougat a, dey m, et al. accommodation: its relation to refractive errors, amblyopia and biometric parameters. nepal j ophthalmol 2011;3:146–150. 22. charman w. the accommodative resting point and refractive error. ophthalmic opt 1982;21:469. 23. iyamu e, iyamu je, oghovwerha l. anthropometry, amplitude of accommodation, and spherical equivalent refractive error in a nigerian population. isrn ophthalmol 2012;2012:295613. j  o  v r volume 14, issue 3, july–september 2019 313 npc and npa in university students; hashemi et al 24. larsson e, holmstrom g, rydberg a. ophthalmological findings in 10-year-old full-term children–a populationbased study. acta ophthalmol 2015;93:192–198. 25. hussaindeen jr, rakshit a, singh nk, swaminathan m, george r, kapur s, et al. binocular vision anomalies and normative data (band) in tamil nadu: report 1. clin exp optom 2017;100:278–284. 26. hashemi h, nabovati p, yekta aa, ostadimoghaddam h, forouzesh s, yazdani n, et al. amplitude of accommodation in an 11to 17-year-old iranian population. clin exp optom 2017;100:162–166. 27. scheiman m, gallaway m, frantz ka, peters rj, hatch s, cuff m, et al. nearpoint of convergence: test procedure, target selection, and normative data. optom vis sci 2003;80:214–225. 28. hayes gj, cohen be, rouse mw, de land pn. normative values for the nearpoint of convergence of elementary schoolchildren. optom vis sci 1998;75:506–512. 29. siderov j, chiu sc, waugh sj. differences in the nearpoint of convergence with target type. ophthalmic physiol opt 2001;21:356–360. 30. adler pm, cregg m, viollier aj, margaret woodhouse j. influence of target type and raf rule on the measurement of near point of convergence. ophthalmic physiol opt 2007;27:22–30. 31. rambo vc, sangal sp. a study of the accommodation of the people of india with further notes on the development of presbyopia at different ages in different peoples. am j ophthalmol 1960;49:993–1004. 32. hofstetter h. a useful age-amplitude formula. amer j opt arch am a 1947;24:202. 33. castagno vd, vilela ma, meucci rd, resende dp, schneid fh, getelina r, et al. amplitude of accommodation in school children. curr eye res 2017;42:604–610. 34. yekta a, hashemi h, ostadimoghaddam h, jafarzadehpur e, salehabadi s, sardari s, et al. amplitude of accommodation and add power in an adult population of tehran, iran. iran j ophthalmol 2013;25:182–189. 35. jones-jordan l, wang x, scherer rw, mutti do. spectacle correction versus no spectacles for prevention of strabismus in hyperopic children. cochrane database syst rev 2014:cd007738. 36. hussaindeen jr, shah p, ramani kk, ramanujan l. efficacy of vision therapy in children with learning disability and associated binocular vision anomalies. j optom 2017;11:40–48. 37. ma mm, scheiman m, su c, chen x. effect of vision therapy on accommodation in myopic chinese children. 2016;2016:1202469. 38. barbero s, portilla j. the relationship between dioptric power and magnification in progressive addition lenses. ophthalmic physiol opt 2016;36:421–427. 39. kragha ik. amplitude of accommodation: population and methodological differences. ophthalmic physiol opt 1986;6:75–80. 40. momeni-moghaddam h, kundart j, askarizadeh f. comparing measurement techniques of accommodative amplitudes. indian j ophthalmol 2014;62:683–687. 314 j  o  v r volume 14, issue 3, july–september 2019 original article intraocular pressure changes after water drinking test in surgically treated primary congenital glaucoma reza razeghinejad, md1, 2; zahra tajbakhsh, ms2; masoumeh beigom masoumpour, md2 m. hossein nowroozzadeh, md2 1glaucoma service, wills eye hospital, philadelphia, pa, usa 2poostchi ophthalmology research center, shiraz university of medical sciences, shiraz, iran orcid: m. hossein nowroozzadeh: https://orcid.org/0000-0002-7412-1900 reza razeghinejad: https://orcid.org/0000-0001-7961-8425 abstract purpose: to assess intraocular pressure (iop) changes after the water drinking test (wdt) in patients with primary congenital glaucoma (pcg). methods: in this prospective interventional study, 20 eyes of 20 patients with pcg were included. all patients had undergone trabeculotomy. six out of twenty eyes had received a glaucoma drainage device (gdd) implantation. iop was measured using an air-puff tonometer at baseline, and 15, 30, 45, and 60 min after wdt. the repeated-measures analysis of variance test was used to compare the mean iops at different time points. results: the mean (± standard deviation) of participants’ age was 9.9 ± 2.7 years (range, 6 to 16 years), and 8 (40%) participants were male. the mean iops at baseline and 15, 30, 45, and 60 minutes after the wdt were 15.8 ± 3.7, 18.6 ± 3.4, 19.0 ± 3.8, 17.9 ± 3.8, and 16.9 ± 3.5 mmhg, respectively (p < 0.001). pairwise comparisons revealed that the mean iops after 15 and 30 min were significantly greater than the baseline iop (p < 0.001 and p = 0.002, respectively); however, the difference in mean iops after 45 and 60 min were not statistically significant from the baseline iop. the averages of iop peak and iop fluctuation after the wdt were 20.0 ± 3.5 and 4.2 ± 2.9 mmhg, respectively. iop fluctuation in those who underwent trabeculotomy alone was twice that of those with gdds, but the difference was not statistically significant (5.0 vs 2.5 mmhg; p = 0.08). conclusions: in patients with pcg, wdt induced significant iop elevation 15 and 30 min after the test, which returned to pre-test values after 45 min. keywords: glaucoma drainage device; intraocular pressure; primary congenital glaucoma; trabeculotomy; water drinking test j ophthalmic vis res 2020; 15 (3): 318–325 correspondence to: m. hossein nowroozzadeh, md. poostchi ophthalmology research center, poostchi clinic, zand st., shiraz 713499, iran. email: nowroozzadeh@hotmail.com received: 14-04-2019 accepted: 03-04-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7450 introduction primary congenital glaucoma (pcg) is the most common hereditary type of glaucoma in this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: razeghinejad r, tajbakhsh z, masoumpour mb, nowroozzadeh mh. intraocular pressure changes after water drinking test in surgically treated primary congenital glaucoma. j ophthalmic vis res 2020;15:318–325. 318 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7450&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr water drinking test in congenital glaucoma; razeghinejad et al childhood.[1] several mechanisms have been suggested for the development of pcg, which result in angle dysgenesis and compromise outflow through the trabecular meshwork. goniotomy and trabeculotomy have been recommended as the initial procedures to improve outflow by removing the abnormal trabecular tissue and making a direct connection between the anterior chamber and the schlemm’s canal. trabeculectomy and glaucoma drainage device (gdd) implantation are employed if the intraocular pressure (iop) cannot be controlled with the aforementioned procedures or glaucoma medications.[2] the goal of glaucoma medical and surgical interventions is to keep the iop at a specific level in order to halt or slow down glaucoma progression.[3] iop is a dynamic parameter with an individual circadian rhythm. currently, management of glaucoma include iop measurements during clinic hours performed a few times a year. a diurnal curve may be used to evaluate glaucoma progression in a patient when the office iop is within an acceptable range. the most common methods for assessing the diurnal curve in glaucoma patients are iop readings at different time points during clinic hours and hospitalization in a sleep laboratory; both are cumbersome and costly. the water drinking test (wdt) has been suggested as a practical and easyto-perform test to estimate the diurnal iop profile in a more feasible and controlled fashion.[4, 5] iop changes after wdt have been evaluated in adult patients with various types of glaucoma,[6, 7] but not in children with pcg. previous studies also evaluated the wdt-iop profile of adult glaucoma patients who were taking glaucoma medications or had undergone trabeculectomy, deep sclerectomy, and gdd implantation.[8–11] however, there is no study in patients with pcg with prior trabeculotomy or gdd implantation. the main objective of the present study was to evaluate the iop changes after wdt in patients with pcg and to compare the iop changes in those with the history of trabeculotomy and those who underwent trabeculotomy followed by gdd surgery. methods this prospective interventional study was conducted in a tertiary eye care hospital after getting approval from the local ethics committee. the study followed the principles of the declaration of helsinki, and informed consent was obtained from the parents of all participants. all enrolled patients underwent a complete ophthalmological examination, which included checking visual acuity, iop measurement, and a dilated stereoscopic fundus examination to assess the amount of optic nerve head damage using disc damage likelihood scale.[12] subsequently, those who met the eligibility criteria were included. the average thickness of the peripapillary retinal nerve fiber layer (using optical coherent tomography) and the central corneal thickness were also recorded. at our center, all congenital glaucoma patients undergo trabeculotomy at the superonasal and inferotemporal sites in one session, and if the iop cannot be controlled using medications, ahmed glaucoma valve (fp7, new world medical, rancho cucamonga, la, usa) is implanted in the superotemporal quadrant. we do not perform trabeculectomy because of the high chance of failure. therefore, all patients in the current study had the history of trabeculotomy procedure as the first line treatment. the inclusion criterion was having a controlled pcg with office iop equal to or under 22 mmhg with or without medication. the exclusion criteria were the presence of ocular infection, corneal opacity, or scar preventing reliable iop measurements; active heart or renal diseases; and refusal of parents to enroll their children in the study. water drinking test subjects were instructed to refrain from food and fluid intake 3 hours preceding the wdt. after checking the baseline iop, patients drank 15 ml/kg of bottled water in five minutes. subsequently, iop was measured every 15 min for 1 hour. the iop was measured five times (baseline, 15, 30, 45, and 60 min after drinking water). one examiner measured the iop using a non-contact tonometer (ct80; topcon co., tokyo, japan). the average of three measurements was recorded and the measurements were repeated if the differences between the three measurements were greater than 3 mmhg. the following parameters were assessed: iop trough (lowest iop after drinking water), iop peak (highest iop after drinking water), iop mean (the mean of the four iops after drinking water), iop fluctuation (difference between peak iop and baseline), iop range (difference between peak iop and lowest iop reading after drinking water), and end-pressure difference (iop at 60 min versus baseline). journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 319 water drinking test in congenital glaucoma; razeghinejad et al statistical analysis the iop of both eyes was measured, but one eye was randomly selected (using a randomization chart generated by a randomization software) for inclusion in the study. all data were analyzed using ibm spss statistics software version 21 (spss inc., chicago, il) and medcalc version 12.2.1 (medcalc software, mariakerke, belgium). descriptive results were presented as the mean ± standard deviation (sd). a p-value < 0.05 was considered to be statistically significant. results patients’ baseline characteristics are presented in table 1. of the 20 studied patients, 17 (85%) had no associated systemic disease. cardiac disease (repaired ventricular septal defect), phenylketonuria, and glucose-6-phosphate dehydrogenase deficiency were each found in one patient. however, no subject was on systemic medications, and no patient was prohibited from undergoing the wdt by the pediatrician. the mean iops at baseline, and 15, 30, 45, and 60 min after wdt were 15.8 ± 3.7, 18.6 ± 3.4, 19.0 ± 3.8, 17.9 ± 3.8, and 16.9 ± 3.5 mm hg, respectively (p < 0.001, repeated-measures analysis of variance (anova); figure 1). pairwise comparisons using bonferroni correction revealed that the mean iops 15 and 30 min after wdt were significantly greater than the baseline iop (p < 0.001 and p = 0.002, respectively), however, the mean iops after 45 and 60 min were not (p = 0.062 and p = 1, respectively). the iop after 60 min was significantly lower than the iop after 30 min (p = 0.03). the values of different wdt-iop parameters were as following: iop trough, 16.2 ± 3.2 (range, 10.0 to 22.0) mm hg; iop peak, 20.0 ± 3.5 (13.0 to 25.0); iop mean, 18.1 ± 3.3 (12.0 to 23.3); iop fluctuation, 4.2 ± 2.9 (0.0 to 11.0); iop range, 3.8 ± 1.8 (1.0 to 7.0); and end-pressure difference, 1.1 ± 3.1 (–4.0 to 7.0). the first time-point to show an iop peak was 15 min in nine patients (45%), 30 min in six (30%) patients, 45 min in three (15%) patients, and 60 min in two (10%) patients. linear regression analysis revealed the iop baseline to be the only statistically significant determinant of the iop peak (r2 = 0.463; p = 0.001; figure 2a). the use of a higher number of topical medications was also associated with a trend toward higher iop peak values (r2 = 0.170; p = 0.071). iop fluctuation was significantly associated with the iop baseline (r2 = 0.216; p = 0.039; figure 2b); and it was lower in the gdd group compared with the trabeculotomy group (r2 = 0.158; p = 0.082). figure 2c and table 2 summarize the results of wdt in the gdd group and trabeculotomy alone group. the repeated measures analysis of covariance (assuming age, gender, body mass index (bmi), and number of topical medications as possible covariates) revealed no significant difference in wdt-iop changes between the two surgical groups (p = 0.46; figure 2c). similarly, with the exception of the iop fluctuation, which was marginally greater in the trabeculotomy alone group than in the gdd group (5.0 vs 2.5 mm hg; p = 0.08; table 2), the wdt-iop parameters were not significantly different. however, because of the small sample size of the groups, the possibility of a type 2 error should be considered while interpreting the insignificant p-values. figure 2d shows the wdt-iop changes in eyes that underwent trabeculotomy with and without adjunctive topical antiglaucoma medications. discussion previous studies evaluated the wdt response in medically treated glaucoma and in adults who underwent trabeculectomy or gdd implantation.[9, 11] in our study involving pcg patients, the mean iops 15 and 30 min, but not 45 and 60 min, after wdt were significantly greater than the baseline iop. the highest mean iop was observed after 30 min. in the study by martinez et al,[11] comparing the results of the wdt in 40 eyes of 34 primary open angle glaucoma (poag) patients who underwent trabeculectomy or gdd implantation, the highest mean iop in both groups was observed 30 min after wdt. similarly, 20 eyes from 20 poag or ocular hypertension patients had the highest mean iop after wdt 30 min following selective laser trabeculoplasty; however, before the laser procedure the highest mean iop was observed after 45 min.[13] in the study by mansouri et al[14] involving normal subjects, the highest mean iop was detected 15 min after the wdt. the ability of the outflow pathway to handle the load after wdt may have affected the time at which the highest mean iop was detected. in normal adults with normal outflow facility, the highest iop was observed after 15 min; however, in adult patients who underwent trabeculectomy or gdd implantation and in our patients, the highest iop was observed after 30 min.[11, 14] in our study the iop fluctuation in all patients (gdd plus trabeculectomy), and in each of the trabeculectomy, and gdd groups were 4.2, 5.0, 320 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 water drinking test in congenital glaucoma; razeghinejad et al table 1. baseline characteristics of patients with primary congenital glaucoma characteristic value age, year(s) 9.9 ± 2.7 (6 to 16)𝑎 gender, (male/female) 8/12 eye, (right/left) 12/8 weight, kg 30.3 ± 12.2 (14 to 53)𝑎 height, cm 134 ± 17 (104 to 169)𝑎 body mass index, kg/m2 16.1 ± 3.4 (12.9 to 23.0)𝑎 spherical equivalent refraction, diopter(s) –2.7 ± 4.7 (–17.5 to +1.3)𝑎 astigmatism, diopter(s) –1.1 ± 1.1 (–4.5 to 0.0)𝑎 central corneal thickness, μm 582 ± 47 (488 to 653)𝑎 cup-to-disc ratio, % 48 ± 24 (10 to 80)𝑎 average retinal nerve fiber layer thickness, μm 92 ± 23 (51 to 140)𝑎 number of topical medications 1.4 ± 1.1 (0 to 3)𝑎 lens status, n (%) phakic: 20 (100) operation, n (%) trabeculotomy only: 14 (70) gdd 6 (30) baseline intraocular pressure, mm hg 15.8 ± 3.7 (8.5 to 21.0)𝑎 𝑎scalar data are presented as mean ± standard deviation (range) table 2. comparison of wdt-iop parameters between the gdd (n = 6) and the trabeculotomy (n = 14) group parameter (mmhg) operation p-value𝑏 trabeculotomy𝑎 gdd𝑎 iop trough 16.0 ± 2.9 16.7 ± 4.1 0.66 iop peak 20.1 ± 3.4 19.6 ± 4.1 0.75 iop mean 18.0 ± 3.2 18.3 ± 3.9 0.86 iop fluctuation 5.0 ± 2.6 2.5 ± 3.1 0.08 iop range 4.2 ± 1.8 2.9 ± 1.6 0.14 end pressure difference 1.5 ± 3.1 0.3 ± 2.9 0.41 𝑎all data are presented as mean ± standard deviation; 𝑏calculated with independent samples t-test; all measurements passed the shapiro–wilk test of normality iop, intraocular pressure; gdd, glaucoma drainage device; wdt, water drinking test and 2.5 mmhg, respectively. the reported iop fluctuation in adult glaucoma patients managed medically ranged from 4.3 to 8.4 mmhg.[8–10, 15, 16] the reported iop fluctuations in eyes that underwent trabeculectomy ranged from 1.6 to 3.95 (table 3).[8, 10, 11] a study on gdds reported an iop fluctuation of 3.6 mmhg.[11] the iop fluctuation in our trabeculotomy group (4.2 mmhg) was greater than the values reported in trabeculectomy (3.95 mmhg) and gdd (3.6 mmhg) groups in previous studies. however, the iop fluctuation in our gdd group (2.5 mmhg) was lower than the value in poag patients with gdd (3.6 mmhg).[11] several studies have suggested that iop fluctuation is an important contributor to the risk of glaucoma progression.[8, 17] the early manifest glaucoma trial showed that even a 1 mmhg increase in iop was associated with an 11% increase in the hazard ratio for glaucoma progression.[18] the advanced glaucoma intervention study group suggested that iop peaks should be below 18 mmhg to prevent visualfield deterioration in patients with moderateor advanced-stage glaucoma.[19] as glaucoma progression is correlated with iop peaks and fluctuations,[20] accurate identification of at-risk patients has become imperative as the first step journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 321 water drinking test in congenital glaucoma; razeghinejad et al table 3. the results of the water drinking test in normal subjects, primary open angle glaucoma, ocular hypertension, and pseudoexfoliation syndrome authors diagnosis management of glaucoma average age of patients (years) iop baseline (mmhg) iop peak (mmhg) iop fluctuation (mmhg) ozyol et al[15] xfs (34) no treatment 16.3 18.1 1.8 xfg(30) medical therapy 65.6 19.7 26.9 7.2 de moraes et al[16] poag (22) medical therapy 54.3 12.4 20.00 7.6 danesh-meyers et al[29] poag trabeculectomy 70 10.4 11.7 1.3 medical therapy 68 11.4 17.3 5.9 mansouri et al[8] poag trabeculectomy 67.1 10.1 12.5 2.4 deep sclerectomy 72.5 13.8 17.6 3.8 latanoprost 71.2 15.9 21.1 5.2 mansouri et al[14] normal subjects (25) no treatment 35.6 14.9 16.8 1.9 guedes ra et al[10] normal subjects (20) no treatment 58.9 13.9 15.8 1.9 glaucoma subjects (21) no treatment 17.5 26 8.4 glaucoma subjects (21) dorzolamide-timolol 14.2 18.6 4.3 glaucoma subjects (15) deep sclerectomy 12.3 14.1 1.7 glaucoma subjects (21) trabeculectomy 10 11.6 1.6 kocabeyoglu et al[30] normal subjects (20) no treatment 64.4 14 15.5 1.5 xfs (20) no treatment 66.1 15 17.2 2.2 kerr et al[13] poag and ohtn before slt 73 16.9 21 4.1 after slt 14.2 16.5 2.3 martinez et al[11] poag trabeculectomy (20) 67.9 12.3 16.25 3.95 gdd (20) 66.2 12.5 16.15 3.6 xfs, pseudoexfoliation syndrome; xfg, pseudoexfoliative glaucoma; poag, primary open angle glaucoma; ohtn, ocular hypertension; slt, selective laser trabeculoplasty in preventing further irreversible glaucomatous damage.[21] it has been shown that, in two-thirds of glaucoma patients, the highest iop values occur outside regular clinic hours, frequently during the nocturnal/sleep period.[22] therefore, significant iop fluctuation may be missed if relying only on clinic iop measurements. twenty-four hour iop monitoring and provocative tests such as wdt were suggested as viable options for identifying a greater number of patients with poorly controlled glaucoma. a group of normal tension glaucoma patients underwent several clinical tests for predicting the progression of visual field loss, and the wdt was the most useful clinical predictor for visual field progression.[5] the iop peak occurred during home tonometry in approximately 30% of patients with progressive visual field loss while it occurred during home tonometry in 5% of patients with stable visual fields.[23] after drinking water, the ability of the outflow system to modulate the stress of an iop rise is the only mechanism that can control the iop. interventions that improve outflow facility can be expected to induce fewer changes in the iop after wdt. the smoother wdt-iop profile in our gdd group may have a protective effect on the damaged optic nerve. it is plausible that trabeculotomy increases aqueous outflow, but not as effective as gdd surgery, which bypasses the congenitally abnormal aqueous drainage pathway in pcg. the iop fluctuation in the trabeculotomy group was two times greater than that in the gdd group (5.0 vs 2.5 mmhg; p = 0.08). the iop profile in the trabeculotomy group on glaucoma medications was greater, though not statistically significant, compared to the trabeculotomy group who were not on medication 322 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 water drinking test in congenital glaucoma; razeghinejad et al figure 1. the average intraocular pressure at baseline and at each time-point after the water drinking test in patients with congenital glaucoma. (figure 2d). a trend toward a greater iop peak was observed as the number of topical medications increased (r2 = 0.170; p = 0.071). the use of glaucoma medications following the surgical procedure indicates insufficient iop control and suggests the existence of increased resistance to the outflow. in other words, the higher number of medications may be an indirect measure of the increased resistance in the outflow pathway. the baseline iop was the only significant determinant of the iop peak (r2 = 0.463; p = 0.001). this is in line with the findings of previous studies in adult patients demonstrating that a higher iop at baseline is associated with greater 24-hour iop changes when measured in the seated position.[24] the rate of aqueous production is steady and the outflow facility is the only determinant factor of iop. when the baseline iop is low, the possibility of iop fluctuation might be reduced because the outflow pathway can handle the load and vice versa. iop variation over time may be divided into diurnal, short-term, and long-term fluctuations. it is often difficult to get a true picture of a patient’s iop profile when it is measured only several times a year. the current method of iop measurements is simply a snapshot of the real iop over time and does not represent the actual iop profile. the wdt is utilized as a provocative test to evaluate outflow capacitance and the effect of medical or surgical glaucoma treatments on the iop peak and fluctuation.[19] studies have shown that the wdt-iop peak strongly correlates with the peak of shortened diurnal curves and the long-term iop profile.[6, 16] the exact mechanism that underlies iop elevation after water ingestion remains unclear. the proposed mechanisms include choroidal expansion, plasma hypo-osmolalityenhanced aqueous ultrafiltration, autonomic nervous system stimulation, and increased episcleral venous pressure.[7, 19] compared to the 24-hour iop curve measurement that requires the patient to stay in the hospital and involves the measurement of iops at night, the wdt could be an inexpensive and feasible alternative. this study has several limitations including the small number of patients, especially in the gdd group, and the fact that the iop was measured using an air-puff tonometer. in most studies that involved performing wdt in adult glaucoma patients, the number of participants was around 20–30 patients, and in some studies both journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 323 water drinking test in congenital glaucoma; razeghinejad et al figure 2. (a) the scatter diagram and regression line showing direct association between iop baseline and iop peak. (b) the scatter diagram and regression line showing reverse association between iop baseline and iop fluctuation. (c) the iop profile after the water drinking test in the trabeculotomy and glaucoma drainage device implantation groups. (d) the iop profile after the water drinking test in eyes that underwent trabeculotomy with and without adjunctive topical antiglaucoma medications. eyes were included (table 3). in this study, we included one eye from each patient. the global prevalence of glaucoma for the population aged 40–80 years is 3.54%, which is much greater than that for pcg (0.01–0.001%).[25, 26] the rarity of this disease makes recruiting pcg patients challenging. with respect to cooperation for iop measurement, non-goldmann tonometer are usually used for iop measurement in pediatric patients. it has been shown that, in pcg patients, iop values obtained using an air-puff tonometer are similar to those obtained using a goldmann tonometer.[27] additionally, in a recent metaanalysis that compared all available tonometers with the goldmann applanation tonometer, airpuff tonometers yielded the least amount of variability in iop values (mean difference of 0.2 mm hg).[28] in conclusion, the wdt induced significant iop elevation 15 and 30 min after the test in patients with pcg. this increased iop returned to pre-test values after 45 min. in eyes previously treated with trabeculotomy, the iop fluctuation was greater, though not statistically significant. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. taylor rh, ainsworth jr, evans ar, levin av. the epidemiology of pediatric glaucoma: the toronto experience. journal of aapos 1999;3:308–315. 2. ko f, papadopoulos m, khaw pt. primary congenital glaucoma. prog brain res 2015;221:177–189. 3. collaborative normal-tension glaucoma study group. the effectiveness of intraocular pressure reduction in the treatment of normal-tension glaucoma. am j ophthalmol 1998;126:498–505. 4. miller d. the relationship between diurnal tension variation and the water-drinking test. am j ophthalmol 1964;58:243–246. 5. yoshikawa k, inoue t, inoue y. normal tension glaucoma: the value of predictive tests. acta ophthalmologica 1993;71:463–470. 324 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 water drinking test in congenital glaucoma; razeghinejad et al 6. kumar rs, de guzman mh, ong py, goldberg i. does peak intraocular pressure measured by water drinking test reflect peak circadian levels? a pilot study. clin exp ophthalmol 2008;36:312–315. 7. susanna r, jr, clement c, goldberg i, hatanaka m. applications of the water drinking test in glaucoma management. clin exp ophthalmol 2017;45:625–631. 8. mansouri k, orguel s, mermoud a, haefliger i, flammer j, ravinet e, et al. quality of diurnal intraocular pressure control in primary open-angle patients treated with latanoprost compared with surgically treated glaucoma patients: a prospective trial. br j ophthalmol 2008;92:332–336. 9. danesh-meyer hv, papchenko t, tan yw, gamble gd. medically controlled glaucoma patients show greater increase in intraocular pressure than surgically controlled patients with the water drinking test. ophthalmology 2008;115:1566–1570. 10. guedes ra, guedes vm, chaoubah a. [use of water drinking test after non-penetrating deep sclerectomy]. j fr ophtalmol 2005;28:1076–1080. 11. martinez p, trubnik v, leiby be, hegarty se, razeghinejad r, savant s, et al. a comparative study of the water drinking test in eyes with open-angle glaucoma and prior trabeculectomy or tube shunt. j glaucoma 2017;26:119– 125. 12. spaeth gl, henderer j, liu c, kesen m, altangerel u, bayer a, et al. the disc damage likelihood scale: reproducibility of a new method of estimating the amount of optic nerve damage caused by glaucoma. trans am ophthalmol soc 2002;100:181–186. 13. kerr nm, lew hr, skalicky se. selective laser trabeculoplasty reduces intraocular pressure peak in response to the water drinking test. j glaucoma 2016;25:727–731. 14. mansouri k, medeiros fa, marchase n, tatham aj, auerbach d, weinreb rn. assessment of choroidal thickness and volume during the water drinking test by swept-source optical coherence tomography. ophthalmology 2013;120:2508–2516. 15. ozyol e, ozyol p, karalezli a. reproducibility of the waterdrinking test in patients with exfoliation syndrome and exfoliative glaucoma. acta ophthalmol 2016;94:e795– e798. 16. de moraes cg, furlanetto rl, reis as, vegini f, cavalcanti nf, susanna r, jr. agreement between stress intraocular pressure and long-term intraocular pressure measurements in primary open angle glaucoma. clin exp ophthalmol 2009;37:270–274. 17. asrani s, zeimer r, wilensky j, gieser d, vitale s, lindenmuth k. large diurnal fluctuations in intraocular pressure are an independent risk factor in patients with glaucoma. j glaucoma 2000;9:134–142. 18. bengtsson b, leske mc, hyman l, heijl a. fluctuation of intraocular pressure and glaucoma progression in the early manifest glaucoma trial. ophthalmology 2007;114:205–209. 19. chen ch, lu dw, chang cj, chiang ch, chou pi. the application of water drinking test on the evaluation of trabeculectomy patency. j ocul pharmacol ther 2000;16:37–42. 20. caprioli j, coleman al. intraocular pressure fluctuation a risk factor for visual field progression at low intraocular pressures in the advanced glaucoma intervention study. ophthalmology 2008;115:1123–1129.e1123. 21. nouri-mahdavi k, hoffman d, coleman al, liu g, li g, gaasterland d, et al. predictive factors for glaucomatous visual field progression in the advanced glaucoma intervention study. ophthalmology 2004;111:1627–1635. 22. barkana y, anis s, liebmann j, tello c, ritch r. clinical utility of intraocular pressure monitoring outside of normal office hours in patients with glaucoma. arch ophthalmol 2006;124:793–797. 23. zeimer rc, wilensky jt, gieser dk, viana ma. association between intraocular pressure peaks and progression of visual field loss. ophthalmology 1991;98:64–69. 24. sakata r, aihara m, murata h, saito h, iwase a, yasuda n, et al. intraocular pressure change over a habitual 24hour period after changing posture or drinking water and related factors in normal tension glaucoma. invest ophthalmol vis sci 2013;54:5313–5320. 25. tham yc, li x, wong ty, quigley ha, aung t, cheng cy. global prevalence of glaucoma and projections of glaucoma burden through 2040: a systematic review and meta-analysis. ophthalmology 2014;121:2081–2090. 26. abdolrahimzadeh s, fameli v, mollo r, contestabile mt, perdicchi a, recupero sm. rare diseases leading to childhood glaucoma: epidemiology, pathophysiogenesis, and management. biomed res int 2015;2015:781294. 27. zareei a, razeghinejad mr, nowroozzadeh mh, mehrabi y, aghazadeh-amiri m. intraocular pressure measurement by three different tonometers in primary congenital glaucoma. j ophthalmic vis res 2015;10:43–48. 28. cook ja, botello ap, elders a, fathi ali a, azuara-blanco a, fraser c, et al. systematic review of the agreement of tonometers with goldmann applanation tonometry. ophthalmology 2012;119:1552–1557. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 325 original article myoring implantation with and without corneal collagen crosslinking for the management of keratoconus mehrdad mohammadpour, md; ahmad masoumi, md; mahmoud dehghan, md mohammad nasser hashemian, md; shahab addin karami, md alireza mahmoudi, md translational ophthalmology research center, farabi eye hospital, tehran university of medical sciences, tehran, iran orcid: mehrdad mohammadpour: https://orcid.org/0000-0002-9383-6362 ahmad masoumi: https://orcid.org/0000-0002-9383-6362 abstract purpose: to evaluate the safety and efficacy of femtosecond laser-assisted myoring implantation with concurrent corneal collagen crosslinking (cxl) compared to myoring alone for the treatment of progressive keratoconus. methods: a total of 60 patients were enrolled in this randomized controlled trial. the patients were randomly allocated into two groups. in the first group, myoring was implanted, while in the second, it was inserted in the corneal stroma using the same technique, along with simultaneous cxl. visual, refractive, topographic, and abberometric outcomes were measured preoperatively and at every postoperative visit. results: data of 47 patients were available at the end of the study; 28 in the myoring group and 19 in the myoring + cxl group. the mean uncorrected distance visual acuity (udva) improved from 0.79 ± 0.39 logmar to 0.52 ± 0.31 logmar (p < 0.05) in the myoring + cxl group and from 0.65 ± 0.38 logmar to 0.62 ± 0.23 logmar (p = 0.70) in the myoring group. cdva changed from 0.33 ± 0.19 logmar to 0.25 ± 0.16 logmar (p = 0.10) in the myoring + cxl group and 0.32 ± 0.22 logmar to 0.33 ± 0.17 logmar (p > 0.50) in the myoring group. the mean keratometry (km) decreased from 47.5 ± 2.7 d to 43.8 ± 3.2 d (p < 0.001) in the myoring group and 49.3 ± 3.4 d to 45.1 ± 3.0 d (p < 0.001) in the myoring + cxl group. besides, horizontal coma was significantly lower in the myoring + cxl group (p = 0.022). conclusion: myoring insertion combined with cxl is a safe and effective method for the treatment of keratoconus. the visual and topographic outcomes were comparable to that for myoring insertion after 10 months; however, horizontal coma was significantly lower in the myoring + cxl group. keywords: corneal collagen crosslinking; keratoconus; myoring j ophthalmic vis res 2020; 15 (4): 486–492 correspondence to: ahmad masoumi, md. translational ophthalmology research center, farabi eye hospital, tehran university of medical sciences, qazvin sq, tehran 13366, iran. e-mail: ahmad.masoomi1990@gmail.com received: 21-05-2019 accepted: 25-06-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7790 introduction keratoconus is a non-inflammatory corneal ectasia resulting in progressive thinning and steepening this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: mohammadpour m, masoumi a, dehghan m, hashemian mn, karami sa, mahmoudi a. myoring implantation with and without corneal collagen crosslinking for the management of keratoconus. j ophthalmic vis res 2020;15:486–492. 486 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7790&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr myoring with and without cxl in keratoconus; mohammadpour et al of the cornea. patients usually present with decreased visual acuity, progressive myopia, irregular astigmatism, and central corneal scarring.[1] a wide range of options is available for the treatment of keratoconus. in early stages, patients can be treated with spectacles or contact lenses. however, in advanced stages with corneal scarring, corneal transplantation is the only available option to restore vision. for patients without corneal scarring intolerant to contact lenses, the new modality, intracorneal ring segment (icrs) or continuous intracorneal ring implantation in the corneal stroma may be used. the technique of insertion of a continuous intracorneal ring was developed in the late 20th century with the aim of correcting myopia. however, owing to technical difficulties and incision-related complications, continuous intracorneal rings were supplanted by icrs, which had been used to correct mild to moderate myopia,[2–4] but recently gained great popularity to treat keratoconus.[5–7] although icrs cannot completely avert corneal transplantation, it can delay the keratoconus progression.[8] icrss can flatten the corneal center and move the corneal apex to the center of cornea. it facilitates the fitting of the contact lens and optimizes the best corrected visual acuity. the introduction of femtosecond laser technology in the field of refractive surgery offered new hopes to treat human refractive errors and also provided a new surgical modality to create tunnels for precise icrs insertion. the femtosecond laser-assisted icrs implantation has several advantages over mechanical approaches including a more uniform dissection, less patient discomfort, quick recovery, and more predictable results.[9] corneal collagen crosslinking (cxl) uses ultraviolet a (uva) light and riboflavin to stiffen the corneal stroma. the irradiation of riboflavin results in formation of free radicals, inducing the formation of covalent bonds between the amino acid groups of collagen fibers.[10, 11] it halts the progression of keratoconus as shown by several studies.[10–13] icrs insertion can improve the corneal topography and correct myopia and astigmatism in keratoconic corneas; however, it has limited effect on the progression of keratoconus. in comparison, as stated earlier, cxl is a safe and effective method to stop the progression of ectatic corneal disorders. thus, hypothetically, the benefits of both methods can be obtained by combining the two procedures. several studies have been performed to test the safety and efficacy of the combined procedure.[14–17] however, only few studies have evaluated same-day icrs + cxl. this study was designed to assess and compare the long-term outcome of simultaneous insertion of myoring and cxl with myoring alone. methods this study was approved by the institutional review board of tehran university of medical sciences and was compliant with the tenets of the declaration of helsinki. informed consent was obtained from all patients prior to the study. a total of 60 patients aged between 18 and 35 years who were diagnosed with keratoconus based on the clinical and pentacam criteria were enrolled in this study. the inclusion criteria of the study were keratoconic eyes with central clear cornea, contact lens intolerance, and central corneal thickness > 380 µm. patients who had previously undergone any ophthalmic surgery, pregnant and lactating women, and those with a history of collagen vascular diseases were excluded from this study. patients were randomly allocated into two groups. in the first group, myoring was implanted at a depth of 300 µm using femtosecond laser. in the second group, myoring was implanted using the same technique with simultaneous cxl. preoperative and postoperative examinations included uncorrected distance visual acuity (udva), corrected distance visual acuity (cdva), dry and cycloplegic refraction, slit lamp biomicroscopy, dilated fundus examination, topographic and optical pachymetry using the pentacam system (oculus, wetzlar, germany), and corneal abbermotry (itrace, tracey technologies, houston, tx). patients were examined one day before the surgery and one day, one month, three months, and ten months postoperatively. the information for this trial is available to the public through the iranian national registry for clinical trials (http://www.irct.ir). surgical technique all surgeries were done by the same experienced surgeon (mm) at farabi eye hospital, tehran, journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 487 http://www.irct.ir myoring with and without cxl in keratoconus; mohammadpour et al iran. the procedure was performed under topical anesthesia using tetracaine 0.5% eye drops. the eyes were sterilized using povidone iodine, and an eyelid speculum was used to hold the eyes open. the cornea was marked in the pupillary center by a sinskey hook as a reference point for pocket creation. a 300 μm deep tunnel was created in the corneal stroma using the femtosecond laser (technolas 520f………). the laser creates dissection planes by focusing a 3 μm diameter laser beam with a frequency of 500 khz and a wavelength of 1054 nm at a predetermined stromal depth. a myoring with a diameter of 5 mm and a thickness of 240 µm was chosen for implantation. it was then inserted into the corneal pocket via a previously made temporal corneal incision. in the second group, after anesthetizing the eye and creating the pocket, riboflavin 0.1% was injected into the corneal pocket to completely fill it. after 5 min, diffusion of riboflavin was observed in the corneal stroma and anterior chamber. the myoring was then implanted using the mentioned technique. finally, the cornea was exposed to 370-nm uva light for 10 min with an irradiance of 9 mw/cm2. the myoring implantation and cxl procedure was uneventful without needing sutures. topical antibiotic and steroid drops, and artificial tears were used postoperatively. chloramphenicol 0.5% was used every 4 hours for the first 10 days. betamethasone eye drops were prescribed for every 2 hours after the procedure and gradually tapered in the following three months. statistical analysis statistical analysis was performed using the spss, version 21 (spss inc., chicago, il). a p-value < 0.05 was considered as significant. normality of data was tested suing the kolmogorov–smirnov test. the wilcoxon rank sum test was used to compare the postoperative and preoperative values. for comparison of outcomes between the two groups, the mann–whitney u test was performed. results data of 47 eyes of 47 patients were available at the end of the study; 28 patients in the myoring group and 19 in the myoring + cxl group. the two study groups were matched before treatment in terms of age, udva, cdva, pachymetry, keratometry (km), and higher order aberrations. table 1 shows the preoperative values. visual outcomes after 10 months, the mean udva improved from 0.79 ± 0.39 logmar to 0.52 ± 0.31 logmar (p < 0.05) in the myoring + cxl group. however, such an improvement was not observed in the myoring group. the improvement in cdva was statistically insignificant in both groups at the end of followup. the increase in udva was observed after six months in the myoring + cxl group. refractive outcomes statistical analysis revealed that the spherical equivalent (se) improved from –6.51 ± 3 to –1.80 ± 2 in the myoring group (p < 0.001) after 10 months. in the myoring + cxl group, the se improved from –6.63 ± 2.5 to –1.7 ± 2 (p < 0.001). there was a significant improvement in kmax in the myoring + cxl group (p < 0.05). the mean km improved significantly in both groups (p < 0.001). corneal aberrations the mean root mean square (rms) total decreased by 0.55 (p > 0.1) in the myoring + cxl group, while it increased by 0.95 µm in the myoring group (p > 0.05). the mean rms of higher order aberrations (rms hoa) increased by 0.01 in the myoring + cxl group (p > 0.1) and by 0.71 µm in the myoring group (p < 0.05). we also observed that the horizontal coma decreased by 0.37 µm in the myoring + cxl group (p < 0.05). tables 2 and 3 show the visual and topographic outcomes in the two groups after 10 months. comparison of myoring insertion and myoring insertion + cxl after 10 months, no significant difference was observed in the udva, cdva, and kmax in patients who underwent myoring insertion alone and those who underwent myoring + cxl. however, horizontal coma was significantly lower in the group that underwent myoring insertion associated with cxl. table 4 compares the refractive and visual outcomes in both groups after 10 months. 488 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 myoring with and without cxl in keratoconus; mohammadpour et al table 1. mean of the preoperative data myoring group myoring + cxl group p-value age 26.1 ± 4.6 24.9 ± 5.2 0.360 udva (logmar) 0.65 ± 0.38 0.79 ± 0.39 0.200 cdva (logmar) 0.32 ± 0.22 0.33 ± 0.19 0.878 spherical equivalent (d) –6.51 ± 3.01 –6.63 ± 2.51 0.745 km (d) 47.5 ± 2.7 49.3 ± 3.4 0.055 k max (d) 52.4 ± 5.19 54.2 ± 4.7 0.221 thinnest point (µm) 449 ± 41 441 ± 32 0.551 coma horizontal (µm) 0.70 ± 0.65 0.73 ± 0.46 0.735 coma vertical (µm) 1.39±1.07 1.19 ± 1.05 0.231 rms hoa (µm) 2.19±1.31 2.05 ± 0.74 0.734 udva, uncorrected distance visual acuity; cdva, corrected distance visual acuity; logmar, logarithm of minimum of angle of resolution; km, mean keratometry; rms hoa, root mean square value of total higher order aberrations in a simulated 6 mm pupil table 2. change in variables in the myoring group after 10 months of follow-up compared to baseline preoperative data postoperative 10month data p-value udva (logmar) 0.65 ± 0.38 0.62 ± 0.23 0.710 cdva (logmar) 0.32 ± 0.22 0.33 ± 0.17 0.906 spherical equivalent (d) –6.51 ± 3.07 –1.8 ± 2.11 0.001 k max (d) 52.4 ± 5.19 51.5 ± 4.1 0.312 thinnest point (µm) 449 ± 41 452 ± 40 0.423 coma horizontal (µm) 0.70 ± 0.65 0.99 ± 0.6 0.123 coma vertical (µm) 1.39 ± 1.08 2.01 ± 1.11 0.021 rms hoa (µm) 2.19 ± 1.31 2.91 ± 1.23 0.006 complications no complications such as migration of the myoring into the anterior chamber were observed during the surgery. as stated earlier, the procedure was uneventful in all of the eyes, and sutures were not needed. all eyes showed excellent tolerance to the implanted myorings, and no migration or extrusion was observed. moreover, none of the eyes developed corneal ulcers or stromal necrosis superficial to the segment. discussion this study compared the refractive and corneal aberrometric effect of myoring insertion alone and myoring with concurrent cxl. as shown in the results, combining cxl with myoring implantation is an efficient method for keratoconus treatment and can significantly decrease the km values. it can significantly increase the udva and decrease the se. when compared to the myoring group, horizontal coma was significantly lower in the myoring + cxl group; however, there was no significant difference in other topographic and refractive outcomes. the main indication of cxl is to halt the progression of ectatic corneal disorders such as keratoconus, pellucid marginal degeneration, and post-laser in-situ keratomileusis (lasik) corneal ectasia.[14, 18, 19] collagen fibrils are crucial for corneal stability. it has been demonstrated that the diagonal links between collagen fibrils are significantly reduced in keratoconic corneas.[20] this leads to corneal thinning in central and paracentral areas and causes myopia, irregular astigmatism, and decreased visual acuity. cxl stabilizes the diseased cornea by creating covalent journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 489 myoring with and without cxl in keratoconus; mohammadpour et al table 3. change in variables in the myoring + cxl group after 10 months of follow-up compared to baseline preoperative data postoperative 10month data p-value udva (logmar) 0.79 ± 0.39 0.52 ± 0.31 0.034 cdva (logmar) 0.33 ± 0.19 0.25 ± 0.16 0.118 spherical equivalent (d) –6.63 ± 2.51 –1.70 ± 2.41 0.001 k max (d) 54.2 ± 4.71 52.1 ± 3.75 0.032 thinnest point (µm) 442 ± 39 445 ± 51 0.623 coma horizontal (µm) 0.73 ± 0.46 0.37 ± 0.31 0.033 coma vertical (µm) 1.91 ± 1.14 1.62 ± 1.42 0.081 rms hoa (µm) 2.05 ± 0.74 2.06 ± 0.18 0.878 table 4. comparison of parameters in the myoring and myoring + cxl groups after 10 months myoring myoring + cxl p-value udva (logmar) 0.62 ± 0.23 0.52 ± 0.31 0.174 cdva (logmar) 0.33 ± 0.17 0.25 ± 0.16 0.105 spherical equivalent (d) –1.8 ± 2.11 –1.70 ± 2.41 0.920 km (d) 43.8 ± 3.2 45.1 ± 3.0 0.137 k max (d) 51.5 ± 4.1 52.1 ± 3.75 0.346 thinnest point (µm) 452 ± 40 445 ± 51 0.688 coma horizontal (µm) 0.99 ± 0.6 0.37 ± 0.31 0.022 coma vertical (µm) 2.01 ± 1.11 1.62 ± 1.42 0.661 rms hoa (µm) 2.91 ± 1.23 2.06 ± 0.18 0.896 bonds (cross links) between the collagen fibrils. it stops the progression of keratoconus without considerably changing the shape of the cornea. myoring implantation, on the other hand, can treat keratoconus by inducing a flattening effect, without affecting the underlying pathophysiology of ectasia. therefore, combining cxl with myoring implantation would hypothetically stabilize the progression of keratoconus and improve the visual acuity by flattening the cornea. there are limited studies evaluating the outcome of myoring implantation with simultaneous cxl. cxl, which has been used for treating keratoconus since 1990s, is believed to be the only treatment that can halt the progression of keratoconus. in this procedure, uva light is irradiated to the cornea after treatment with riboflavin solution, resulting in formation of free radicals and inducing covalent bonds between amino groups of the collagen molecule, thus increasing the biomechanical stability of the cornea.[21, 22] in this study, we used a rather new technique for cxl; riboflavin 0.1% solution was injected into the corneal pocket created by the femtosecond laser, followed by exposing the cornea to uva light for 10 min. the corneal epithelium is usually removed before the uv light is irradiated to the cornea to allow adequate penetration of riboflavin into the corneal stroma. simultaneous introduction of riboflavin 0.1% into the corneal pocket created by the femtosecond laser obviates the need for epithelial debridement and reduces pain and discomfort in the early postoperative period.[23, 24] however, the corneal stroma composed of tightly compacted collagen fibers is fairly resistant to molecular transport. the stromal barrier can be eliminated by injecting the riboflavin solution directly into the pocket, allowing more uniform distribution in the corneal stroma. dextran was not present in the solution as corneal toxicity might occur when it is directly injected into the corneal stroma. it has been demonstrated that a cross-linked cornea is less clear compared to a virgin cornea. therefore, femtosecond laser 490 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 myoring with and without cxl in keratoconus; mohammadpour et al penetration into the corneal stroma may be less effective in eyes that underwent cxl. el raggal found that channel creation by femtosecond laser is more challenging in eyes that had undergone cxl. they attributed this effect to the possible rigidity of collagen fibers in the deep corneal stroma in patients treated by cxl.[25] femtosecond laser energy can be increased to overcome this problem; however, this solution may lead to a persistent corneal reaction, postoperatively.[25] the keratoconic cornea is a highly aberrated cornea with significantly more coma and comalike aberrations compared to the normal eye. in this study, horizontal coma was significantly lower in eyes that underwent myoring implantation with simultaneous cxl. thus, combining cxl with myoring implantation might enhance the flattening effect of the segment without inducing considerable hoa. furthermore, a synergistic effect might also be present, when cxl is combined with icrs implantation, augmenting the therapeutic effect that is observed with either treatment.[15] hafez recently studied the outcomes of keraring and myoring implantation with simultaneous cxl.[15] patients who underwent myoring implantation plus cxl showed a significant reduction in kmean. however, there was little improvement in the astigmatic component of keratoconus with myoring implantation, and significant reduction of astigmatism was observed in patients treated by combination of keraring and cxl. in a retrospective study by bikbova et al, the efficacy of myoring implantation and myoring implantation + cxl after three years was reported. they found that myoring implantation with simultaneous cxl had slightly better outcomes, although the effect of myoring implantation alone was stable over time.[26] similarly, in this study, we found that the topographic and visual outcomes were comparable in the two groups after 10 months, although horizontal coma was significantly lower in patients who underwent myoring implantation with simultaneous cxl. el raggal evaluated the outcome of combined keraring insertion with cxl, performed in a single session or with a six-month interval. he observed that there was a significant improvement in udva, cdva, and keratometric values. however, patients treated using the same-day method had better topographic outcomes.[27] coskunseven and colleagues found that icrs implantation followed by cxl is more effective in improving cdva, se, and the mean km in keratoconus compared to cxl followed by icrs implantation. the mean interval between the treatments was seven months.[28] none of the patients during the study developed segment decentration and extrusion, partly due to application of femtosecond laser, which creates a more precise depth of incision. despite the limited number of cases, this study shows that the myoring + cxl procedure is a safe and effective method for treating keratoconus. it is comparable to myoring insertion alone for improvement in visual and topographic outcomes in the short term. moreover, a significant reduction in hoa is observed with the myoring + cxl procedure, which is of paramount importance in highly aberrant corneas with keratoconus. more studies with a longer follow-up are needed to better elucidate the efficacy and safety of this procedure. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. rabinowitz ys. keratoconus. surv ophthalmol 1998;42:297–319. 2. assil kk, barrett am, fouraker bd, schanzlin dj. one-year results of the intrastromal corneal ring in nonfunctional human eyes. arch ophthalmol 1995;113:159–167. 3. nosé w, neves ra, burris te, schanzlin dj, belfort r. intrastromal corneal ring: 12-month sighted myopic eyes. j refract surg 1996;12:20–28. 4. schanzlin dj, asbell pa, burris te, durrie ds. the intrastromal corneal ring segments: phase ii results for the correction of myopia. ophthalmology 1997;104:1067– 1078. 5. colin j, cochener b, savary g, malet f. correcting keratoconus with intracorneal rings. j cataract refract surg 2000;26:1117–1122. 6. colin j, cochener b, savary g, malet f, holmes-higgin d. intacs inserts for treating keratoconus: one-year results. ophthalmology 2001;108:1409–1414. 7. wachler bsb, chandra ns, chou b, korn ts, nepomuceno r, christie jp. intacs for keratoconus. ophthalmology 2003;110:1031–1040. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 491 myoring with and without cxl in keratoconus; mohammadpour et al 8. jabbarvand m, salamatrad a, hashemian h, mazloumi m, khodaparast m. continuous intracorneal ring implantation for keratoconus using a femtosecond laser. j cataract refract surg 2013;39:1081–1087. 9. ratkay-traub i, ferincz ie, juhasz t, kurtz rm, krueger rr. first clinical results with the femtosecond neodyniumglass laser in refractive surgery. j refract surg 2003;19:94–99. 10. raiskup f, spoerl e. corneal crosslinking with riboflavin and ultraviolet a. part ii. clinical indications and results. ocul surf 2013;11:93–108. 11. caporossi a, baiocchi s, mazzotta c, traversi c, caporossi t. parasurgical therapy for keratoconus by riboflavin– ultraviolet type a rays induced cross-linking of corneal collagen: preliminary refractive results in an italian study. j cataract refract surg 2006;32:837–845. 12. caporossi a, mazzotta c, baiocchi s, caporossi t. longterm results of riboflavin ultraviolet a corneal collagen cross-linking for keratoconus in italy: the siena eye cross study. am j ophthalmol 2010;149:585–593. 13. kymionis gd, grentzelos ma, liakopoulos da, paraskevopoulos ta, klados ne, tsoulnaras ki, et al. long-term follow-up of corneal collagen cross-linking for keratoconus—the cretan study. cornea 2014;33:1071– 1079. 14. hafezi f, kanellopoulos j, wiltfang r, seiler t. corneal collagen crosslinking with riboflavin and ultraviolet a to treat induced keratectasia after laser in situ keratomileusis. j cataract refract surg 2007;33:2035–2040. 15. hafez mi. combined cross-linking with femtosecond laser myoring implantation versus combined cross-linking with femtosecond laser keraring implantation for treatment of keratoconus. delta j ophthalmol 2016;17:1–8. 16. kazakbaeva g, bikbov m, usubov e. the evaluation of intrastromal myoring implantation with corneal collagen cross‐linking in keratoconus treatment. acta ophthalmologica 2016;94:s256. 17. wang sl, kanellopoulos aj. safety and efficacy of crosslinking following intacs implantation for the stabilization of keratoconus. invest ophthalmol vis sci 2011;52:5200. 18. wollensak g. crosslinking treatment of progressive keratoconus: new hope. curr opin ophthalmol 2006;17:356–360. 19. spadea l. corneal collagen cross-linking with riboflavin and uva irradiation in pellucid marginal degeneration. j refract surg 2010;26:375–377. 20. sherwin t, brookes nh. morphological changes in keratoconus: pathology or pathogenesis. clin experiment ophthalmol 2004;32:211–217. 21. gkika m, labiris g, kozobolis v. corneal collagen crosslinking using riboflavin and ultraviolet-a irradiation: a review of clinical and experimental studies. int ophthalmol 2011;31:309–319. 22. meiri z, keren s, rosenblatt a, sarig t, shenhav l, varssano d. efficacy of corneal collagen cross-linking for the treatment of keratoconus: a systematic review and meta-analysis. cornea 2016;35:417–428. 23. leccisotti a, islam t. transepithelial corneal collagen cross-linking in keratoconus. j refract surg 2010;26:942– 948. 24. kanellopoulos aj. collagen cross-linking in early keratoconus with riboflavin in a femtosecond lasercreated pocket: initial clinical results. j refract surg 2009;25:1034–1037. 25. el-raggal tm. effect of corneal collagen crosslinking on femtosecond laser channel creation for intrastromal corneal ring segment implantation in keratoconus. j cataract refract surg 2011;37:701–705. 26. bikbova g, kazakbaeva g, bikbov m, usubov e. complete corneal ring (myoring) implantation versus myoring implantation combined with corneal collagen crosslinking for keratoconus: 3-year follow-up. int ophthalmol 2018;38:1285–1293. 27. el-raggal tm. sequential versus concurrent kerarings insertion and corneal collagen cross-linking for keratoconus. br j ophthalmol 2011;95:37–41. 28. coskunseven e, jankov mr, hafezi f, atun s, arslan e, kymionis gd. effect of treatment sequence in combined intrastromal corneal rings and corneal collagen crosslinking for keratoconus. j cataract refract surg 2009;35:2084–2091. 492 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 original article multiplex pcr for detection of herpes simplex viruses type-1 and type-2, cytomegalovirus, varicella-zoster virus, and adenovirus in ocular viral infections ahmed nishat h1; mbbs, md; gita satpathy1; mbbs, md; rohan chawla2; mbbs, md radhika tandon2; mbbs, md 1ocular microbiology, dr. r p centre, all india institute of medical sciences, new delhi, india 2ophthalmology, dr. r p centre, all india institute of medical sciences, new delhi, india orcid: nishat ahmed: https://orcid.org/0000-0002-1683-4275 abstract purpose: most common viruses causing ocular infections are herpes simplex viruses (hsv) type 1 and type 2, cytomegalovirus (cmv), varicella-zoster virus (vzv), and few strains of adenovirus. diagnosis of these infections through clinical manifestations and using conventional methods has a number of limitations. the purpose of this study was to develop a multiplex polymerase chain reaction (pcr) for simultaneous detection of all pathogenic viruses from ocular infections. methods: ten uniplex pcrs were standardized, two each for hsv type 1 (hsv-1) and type 2 (hsv-2), cmv, vzv, and adenovirus. various multiplexing combinations of above pcrs were put to finalize targets and reaction conditions enabling diagnosis of all in a single reaction. the uniplex and multiplex pcrs were run for known positive and negative controls, and samples from clinically suspected patients and healthy controls. results: out of the 170 samples from suspected ocular infections, 24.7% were positive by uniplex pcr and 22.9% were correctly identified by multiplex pcr. none of the samples negative by uniplex pcrs was positive by the multiplex pcr. the sensitivity and specificity of multiplex pcr compared to the commonly used uniplex pcrs as gold standard was 92.86% and 100%, respectively. the prevalence of different viral pathogens was 13.5% for hsv-1, followed by 5.9% for adenovirus, 2.4% for vzv, 1.8% for hsv-2, and 1.2% for cmv. conclusion: the establishment of multiplex pcr has found immediate application in diagnosing ocular viral pathogens in a single reaction, thus saving time, manpower, and resources by fivefold. keywords: adenovirus; cytomegalovirus; herpes simplex virus; multiplex polymerase chain reaction; varicella-zoster virus j ophthalmic vis res 2021; 16 (1): 3–11 © 2021 nishat et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 3 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8243&domain=pdf&date_stamp=2019-07-17 multiplex pcr for ocular viral infections; nishat et al introduction it is estimated that by the year 2020, the blind population in india will grow to 15 million and ocular infections will account for 15% of the total burden.[1] viruses can cause a variety of ocular infections including conjunctivitis, keratitis, keratoconjunctivitis, uveitis, chorioretinitis, iridocyclitis, and acute retinal necrosis syndrome.[2–7] unattended/late treated ocular infections especially with members of herpesviridae family, including herpes simplex virus-1 (hsv-1), herpes simplex virus-2 (hsv-2), cytomegalovirus (cmv), varicella-zoster virus (vzv), and few serotypes (1–4, 7, 8, 11, 19, 37, 53, and 54) of adenovirus can lead to loss of vision.[8, 9] it is often challenging to determine the causative agent, as there could be significant overlap between the clinical features especially in the early stages of the disease leading to misdiagnosis. there is therefore a need to establish a prompt diagnostic testing that is both rapid and sensitive for an early detection and to determine the choice of treatment.[4] the conventional methods used for diagnosing ocular viral infections are either less sensitive and/or specific, require sophisticated equipment and infrastructure and/or explicit expertise, or have a long turnaround time. in recent decades, focus has been on molecular diagnostics for such infections, in which polymerase chain reaction (pcr) has proven to be a valuable technique. in this technique, the target gene of interest, called nucleic acid template, is amplified in a thermo-cycling reaction. from a single template, billions of copies are produced, which can then be identified by postamplification analysis. it overcomes the lower sensitivity of conventional laboratory techniques while maintaining specificity. in addition, it can also be performed on limited patient-derived ocular correspondence to: ahmed nishat h. mbbs, md. ocular microbiology section, dr. r p centre, all india institute of medical sciences, new delhi110029, india. e-mail: drnishathussain@gmail.com received: 07-02-2019 accepted: 22-05-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8243 specimen and is less time consuming, inexpensive, and rapid.[2] multiplex pcr is a variant in which all viruses in the differential can be diagnosed in a single pcr, thus saving time and cost. the technique works on the principle that different pairs of primers are unique to different infectious agents and their amplicon size varies in length so that the visual difference is observed when pcr reaction product is resolved on an agarose gel. it has an enormous clinical value as it allows simultaneous detection of multiple target organisms in a single reaction; thus, it is more informative and requires very less starting patient specimen. further, there are various technical advantages of using multiplex pcr including rapid diagnosis, less cumbersome procedure, cost effectiveness, and less time taken to obtain results than conventional diagnostic methods. it has increased accuracy of data normalization and is subject to fewer human pipetting errors.[10] standardization and establishment of multiplex pcr for the diagnosis of ocular viral infection has immense clinical and technical advantage. hence, this study was planned to standardize and establish a multiplex pcr targeting all common ocular viral pathogens for accurate and rapid laboratory confirmation, thereby aiding in the implementation of correct and timely treatment and to determine the prevalence of different viruses as ocular pathogens in our patient cohort. methods ethics approval of the institute ethics committee was taken, and the procedures were done in accordance with the helsinki declaration of 1975, as revised in 2000. written informed consent was obtained from all patients and controls. study design the current prospective case–control study was conducted over a duration of 21 months (july 2016 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: nishat ha, satpathy g, chawla r, tandon r. multiplex pcr for detection of herpes simplex viruses type-1 and type2, cytomegalovirus, varicella-zoster virus, and adenovirus in ocular viral infections. j ophthalmic vis res 2021;16:3–11. 4 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 https://knepublishing.com/index.php/jovr multiplex pcr for ocular viral infections; nishat et al to march 2018) in the ocular microbiology section of an apex healthcare institute of north india, which caters to the tertiary healthcare requirements of delhi and nearby six to seven states. selection and description of participants a total of 170 samples, clinically guided to undertake laboratory diagnostic tests for viral infections, were included as test samples. the patients had various clinical manifestations. vitreous and aqueous aspirates were collected in sterile eppendorf tubes; and samples like scrapings, tears, swabs, etc. were collected in sterile eppendorf tubes containing 1 ml of phosphate buffered saline (pbs, ph 7.2). maximum numbers of samples received were corneal scrapings (54), conjunctival swabs (45), and tears (33). fifty tear samples from individuals devoid of any clinical symptoms of ocular infections were included as controls. dna extraction dna extraction was done using the qiaamp dna extraction kit (qiagen, qiagen str. 1, 40724 hilden, germany), strictly following the manufacturer’s instructions. as the quantity of ocular specimens was very little, elution of dna was done in 60 µl of elution buffer. extracted dna samples were stored at 0–4°c until processed. standardization of multiplex pcr published primers unique and highly specific for hsv-1, hsv-2, cmv, vzv, and adenovirus were used for standardizing uniplex pcrs. a total of 10 uniplex pcrs were standardized, two each for hsv-1, hsv-2, cmv, vzv, and adenovirus.[11–13] results of uniplex pcrs were checked in control strains of all viruses, non-ocular stored clinical specimens positive for different study viruses, and also in extracted dna from cultures of staphylococcus, pseudomonas aeruginosa, acanthamoeba species, aspergillus flavus, and fusarium species. the uniplex pcrs were then run at different annealing temperatures and with some variations of cycle conditions to obtain the annealing temperature and cycle conditions suitable for all five study viruses. various multiplexing combinations of above pcrs were put to make it possible to diagnose all the above five viruses in a single reaction. the five targets, annealing temperature, and reaction conditions which were giving best results for all viruses in a single reaction were finalized. the multiplex reactions were run with control strains of all viruses, non-ocular clinical specimens positive for different study viruses, and dna extracted from the cultures of staphylococcus, p. aeruginosa, a. species, a. flavus, and f. species. all the results of uniplex and multiplex pcrs were finally verified in stored dna of ocular specimens with known results. subsequently, for all clinical samples and controls, five uniplex pcrs (one for each virus) and one multiplex was run. dna of atcc-vr-539d, hsv-1 strain mcintyre; atcc-vr-734d, hsv-2 strain g; oka vaccine strain of vzv; and pooled extracted dna positive for cmv and adenovirus from clinical samples were used as positive controls in each run. autoclaved milliq water controls were used as negative controls in each run. atcc strains were purchased through lgc promochem india private limited, bangalore, india. the details of primers for the five selected targets for the multiplex pcr are shown in table 1. both the uniplex and multiplex pcr amplification reactions were conducted in 25 µl volumes. the reaction mixture consisted of dntps (200 mm) – 0.5 µl, 10x buffer – 2 µl, mgcl2 – 1.2 µl, forward primer – 1 µl, reverse primer – 1 µl, taq dna polymerase 1u – 0.2 µl, test dna – 2 µl, and autoclaved milliq water – 12.1 µl made up to 25 µl. the amplification profile chosen was as follows: initial denaturation at 95°c for 5 min, followed by 40 cycles of denaturation at 95°c for 30 sec, annealing at 55°c for 35 sec, extension at 72°c for 40 sec, and final extension at 72°c for 10 min. electrophoresis and documentation following the pcr, the amplicons were resolved on a 1.5% agarose gel. visualization was done with the aid of ethidium bromide (0.5 µg/ml) under ultraviolet illumination using gel documentation system – biospectrum r 810 imaging system – uvp (2066 w. 11th st., upland, ca 91786, usa). figures 1a, 1b, and 1c show the gel images of positive controls and positive test samples by multiplex pcr. results of uniplex and multiplex pcrs were entered in microsoft excel sheets (microsoft𝑅 office journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 5 multiplex pcr for ocular viral infections; nishat et al table 1. details of primers for the five selected targets for the multiplex pcr name primers region sequence (5’-3’) size hsv 1 hsv 1-f rl-2 tgggacacatgccttcttgg 147 bp hsv 1-r rl-2 acccttagtcagactctgttacttaccc hsv 2 hsv 2-f gp-d gtcggtgtggtgttcggtcataagct 276 bp hsv 2-r gp-d ggctgaatctggtaaacacgcttc cmv cmv-f pol and gp-b cacggccgccaccaaggt 392 bp cmv-r pol and gp-b agtggttgggcaggataaa vzv vzv-f gp atcgcggcttgttgtttgtctaat 355 bp vzv-r gp gggcgaaatgtaggatataaagga adenovirus adenovirus-f hexon gccgcagtggtcttacatgcacatc 308 bp adenovirus-r hexon cagcacgccgcggatgtcaaagt rl, long repeat region; gp, glycoprotein region; pol, dna polymerase gene table 2. results of uniplex and multiplex pcrs in test samples pathogenic virus numbers identified by uniplex pcr numbers identified by multiplex pcr hsv-1 23 22 hsv-2 03 03 cmv 02 02 vzv 04 03 adenovirus 10 09 total positive 42 39 negative 128 131 excel𝑅 2007 [12.0.4518.1014] mso [12.0.4518.1014]). sensitivity, specificity, positive and negative predictive values, and accuracy of multiplex pcr was calculated with uniplex pcrs as gold standard. results controls both uniplex and multiplex pcrs were correctly able to identify the viruses from stored dna of positive ocular and non-ocular samples. none of the dna from non-viral ocular pathogens – staphylococcus, p. aeruginosa, a. species, a. flavus and f. species – was positive for any of the viruses by uniplex or multiplex pcr. none of the 50 control samples from healthy eyes were positive for any of the viruses by uniplex or multiplex pcr. clinical samples over the duration of 21 months, 170 specimens from clinically suspected ocular viral infections were received. uniplex and multiplex pcrs for hsv-1 and hsv-2, cmv, vzv, and adenovirus were performed for all patients’ specimens. table 2 shows the results of uniplex and multiplex pcrs in test samples. out of the 170 samples from cases of suspected ocular infections, 42 (24.7%) were positive for some of the five viruses tested by uniplex pcr. multiplex pcr was able to correctly detect 39 out of 42 positives of uniplex pcrs (22.9% of 170). none of the samples were positive for more than one virus. none of the samples negative by uniplex pcrs was positive by the multiplex pcr. thus, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the multiplex pcr was 92.86%, 100%, 100%, 97.71%, and 98.24%, respectively. 6 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 multiplex pcr for ocular viral infections; nishat et al table 3. results of uniplex and multiplex pcrs from patients with different clinical diagnosis clinical diagnosis number of specimens received positive by uniplex pcr positive by multiplex pcr conjunctivitis 41 17 16 keratitis 81 12 11 blepharitis 3 0 0 lid and periocular vesicles 5 4 3 uveitis 5 2 2 chorioretinitis 5 2 2 endophthalmitis 3 0 0 others 27 5 5 total 170 42 39 the prevalence of different viral pathogens causing ocular infections as determined by the pcr was found to be 13.5% for hsv-1 (23 out of 170 cases positive), followed by 5.9% (10 positive) for adenovirus, 2.4% (four positive) for vzv, 1.8% (three positive) for hsv-2, and 1.2% (two positive) for cmv (table 2). table 3 and figure 2 show the distribution of samples received from patients with different clinical diagnoses. maximum samples were from patients having keratitis, followed by conjunctivitis. viral infections could be diagnosed using multiplex pcr in 60% of patients having lid and periocular vesicles. viral etiology could also be clinched in 39% of conjunctivitis and 40% each of uveitis and chorioretinitis patients using the multiplex pcr. maximum positivity was observed in vesicle fluid and scrapings (60%), followed by lid scrapings (33.3%), conjunctival swabs (31.1%), and vitreous tap (30%). the positivity in tear samples was found to be 24.2% (figure 3). discussion ocular viral infections can range from simple selflimiting discomfort to possibly vision challenging manifestations. the clinical manifestations of such infections are not specific for a particular virus; frequently, the differential includes a number of viruses. there often is an overlap of signs and symptoms with non-viral infections and some noninfective conditions. this is more common in tertiary care centers where the patients often come after partial treatment performed outside, have some underlying immune-compromise, or have some complications of the infection. most common viruses causing ocular infections are hsv1, hsv-2, cmv, vzv, and adenovirus, which are difficult to differentiate by clinical findings alone; nevertheless, the differentiation is important as it determines the choice of treatment.[2] late or inappropriate treatment of such infections due to delayed diagnosis can compromise the vision of the patient. pcr is now a popular diagnostic test for viral infections; however, its application is limited in clinical situations where the differential diagnosis takes account of several pathogens. running a pcr for each pathogen in the differential is a timeand resource-consuming process; moreover, each extra reaction has its own share of errors; and sometimes it is not possible to do many reactions as the specimen size is minute in ocular infections. there is a dearth of an accurate, rapid, and cost-effective diagnostic test which can be undertaken on limited ophthalmic sample volume. a multiplex pcr was thus standardized targeting hsv-1, hsv-2, cmv, vzv, and adenovirus. this enabled the diagnosis of all five common ocular viral pathogens in a single reaction. the sensitivity and specificity of the multiplex pcr was found to be 92.5% and 100%, respectively. the multiplex pcr was made sensitive for diagnosing ocular viral infections by multiplexing the five most common pathogenic viruses. specificity was established by simultaneously using uniplex pcrs in all clinical specimens and controls; also, the multiplex pcr did not show any false positivity in dna from nonviral pathogens. the multiplex pcr was found to be useful in tear samples, which are the least invasive journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 7 multiplex pcr for ocular viral infections; nishat et al figure 1. gel images of positive controls and positive test samples by multiplex pcr. (a) multiplex pcr simultaneously detecting all five viruses, (b) ocular specimens positive for hsv-2 and vzv by multiplex pcr, and (c) ocular specimens positive for cmv, vzv, hsv-1, and adenovirus by multiplex pcr. of ocular specimens, showing viral detection in 24.2% of tear samples received. furthermore, the test was able to clinch diagnosis in 40% of uveitis and chorioretinitis cases, establishing the etiology of which is otherwise very difficult and timeconsuming. in the current study, we also looked for the prevalence of different viruses as ocular pathogens in our patient cohort, and for any asymptomatic carriage in control group. the overall positivity for viral pathogens in clinically suspected ocular viral infections as detected by uniplex pcr was 24.7% with hsv1 being the most common (14.4%), followed by adenovirus (5.9%). none of the healthy controls were positive for any of the viruses. 8 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 multiplex pcr for ocular viral infections; nishat et al figure 2. distribution of specimens received and results of uniplex and multiplex pcrs from patients with different clinical diagnosis. our results are comparable to similar studies done in india and abroad. a study from japan utilizing multiplex pcr for the detection of hsv-1, hsv-2, cmv, and vzv in different ocular infections has reported the multiplex pcr to be as good as uniplex pcrs for each of the viruses. they have reported a positivity of 57.6% in clinically suspected ocular viral infection cases. amongst the positives, hsv1 was the most common (68.4%), followed by vzv (31.6%).[13] sugitha et al from japan have recently described the results of utilization of a multiplex pcr for the detection of eight herpes viruses and the parasite toxoplasma gondii in cases with uveitis and endophthalmitis. they reported sensitivity and specificity of 91.3% and 98.8%, respectively. the positivity in their study group was 34%, with cmv and vzv being the most common viral pathogens.[14] elnifro et al in their study in united kingdom tested a multiplex pcr for detecting hsv, adenoviruses, and chlamydia in eye swabs. although they observed a 10-fold fall in the sensitivity of detection limit using multiplex pcr, there was no significant difference in the diagnostic sensitivity of multiplex pcr when compared to that of individual uniplex pcrs.[15] another similar study from india reported multiplex pcr for hsv, vzv, and cmv in ocular specimens. the authors have not compared their results with uniplex pcrs in all samples; however, they have established detection limits of multiplex pcr using several dilutions of standard strains. the sensitivity of uniplex pcr for hsv, vzv, and cmv was 4, 4, and 6 pfu/ml, respectively, while that of multiplex pcr was 4, 4, and 12 pfu/ml, respectively. the authors have also established specificity using diverse dna samples derived from non-viral infections and non-infectious conditions of the eyes. the most common viral infections found were hsv (83.6%), followed by vzv (2%) and cmv (1.4%).[12] the most recent study is from united states, in which bizpo et al have reported results of a qualitative multiplex real-time pcr for the journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 9 multiplex pcr for ocular viral infections; nishat et al figure 3. sample-wise distribution of results of uniplex and multiplex pcrs. identification of common pathogens causing uveitis. they have targeted viruses hsv-1, hsv-2, vzv, cmv and parasite t. gondii and have found the multiplex real-time pcr to be highly specific with a limit of detection of 20 genome copies for viral pathogens and 200 genome copies for t. gondii.[16] there are a few limitations of the study. we have not found the detection limit in terms of genome copy number of uniplex and multiplex pcr for each virus, which would be a better marker of sensitivity of the test. also, involvement of samples from other ophthalmic centers and inclusion of bioinformatics and in silico analysis would have added weight to the results of the present study. to conclude, the present study has shown that the multiplex pcr targeting five common viral infections can serve as a valuable diagnostic tool for ophthalmic viral infections. it reduces the turnaround time to diagnose specific viruses, and also the chances of errors associated with putting multiple reactions; at the same time saving on hands on work and cost of diagnosis. the study has also thrown light on current epidemiology of ocular viral infections. the understanding of current pattern of ocular viral infections and utilization of multiplex pcr for diagnosis can go a long way in improving the management of patients having viral infections of the eyes. acknowledgements the authors are thankful to the research section, all india institute of medical sciences, new delhi, for providing the institutional research grant for conducting this study. they are also grateful to mrs. shailamma joseph for her technical assistance. financial support and sponsorship the study was funded by the ’institutional research grant’ from all india institute of medical sciences, new delhi, india. 10 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 multiplex pcr for ocular viral infections; nishat et al conflicts of interest there are no conflicts of interest. references 1. thylefors b, négrel ad, pararajasegaram r, dadzie ky. global data on blindness. bull world health organ 1995;73:115–121. 2. sharma s. diagnosis of infectious diseases of the eye. eye 2012;26:177–184. 3. yamamoto s, pavan-langston d, kinoshita s, nishida k, shimomura y, tano y. detecting herpesvirus dna in uveitis using the polymerase chain reaction. br j ophthalmol 1996;80:465–468. 4. koizumi n, nishida k, adachi w, tei m, honma y, dota a, et al. detection of herpes simplex virus dna in atypical epithelial keratitis using polymerase chain reaction. br j ophthalmol 1999;83;957–960 . 5. cunningham et, short ga, irvine ar, duker js, margolis tp. acquired immunodeficiency syndrome–associated herpes simplex virus retinitis. clinical description and use of a polymerase chain reaction–based assay as a diagnostic tool. arch ophthalmol 1996;114:834–840. 6. alvarado ja, underwood jl, green wr, wu s, murphy cg, hwang dg, et al. detection of herpes simplex viral dna in the iridocorneal endothelial syndrome. arch ophthalmol 1994;112:1601–1609. 7. bialasiewicz a. adenoviral keratoconjunctivitis. sultan qaboos univ med j 2007;7:15–23. 8. klauss v, schaller uc, bialasiewicz aa. importance and epidemiology of infectious eye diseases. dev ophthalmol 2002;33:145–190. 9. krumpaszky hg, klauss v. epidemiology of blindness and eye disease. ophthalmol j int d’ophtalmologie int j ophthalmol z für augenheilkd 1996;210:1–84. 10. elnifro em, ashshi am, cooper rj, klapper pe. multiplex pcr: optimization and application in diagnostic virology. clin microbiol rev 2000;13:559–570. 11. echavarria m, forman m, ticehurst j, dumler s, charache p. pcr method for detection of adenovirus in urine of healthy and human immunodeficiency virus-infected individuals. j clin microbiol 1998;36:3323–3326. 12. chichili gr, athmanathan s, farhatullah s, gangopadhyay n, jalali s, pasricha g, et al. multiplex polymerase chain reaction for the detection of herpes simplex virus, varicella-zoster virus and cytomegalovirus in ocular specimens. curr eye res 2003;27:85–90. 13. zhang y, kimura t, fujiki k, sakuma h, murakami a, kanai a. multiplex polymerase chain reaction for detection of herpes simplex virus type 1, type 2, cytomegalovirus, and varicella-zoster virus in ocular viral infections. jpn j ophthalmol 2003;47:260–264. 14. sugita s, ogawa m, shimizu n, morio t, ohguro n, nakai k, et al. use of a comprehensive polymerase chain reaction system for diagnosis of ocular infectious diseases. ophthalmology 2013;120:1761–1768. 15. elnifro em, cooper rj, klapper pe, yeo ac, tullo ab. multiplex polymerase chain reaction for diagnosis of viral and chlamydial keratoconjunctivitis. invest ophthalmol vis sci 2000;41:1818–1822. 16. bispo pjm, davoudi s, sahm ml, ren a, miller j, romano j, et al. rapid detection and identification of uveitis pathogens by qualitative multiplex real-time pcr. invest ophthalmol vis sci 2018;59:582–589. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 11 photo essay cytomegalovirus retinitis in a patient on long-term mycophenolate mofetil treatment for myasthenia gravis shyam patel, md, alexander robin, bs department of ophthalmology, cook county hospital, chicago, il, usa orcid: shyam patel: 0000-0002-4858-3423 j ophthalmic vis res 2020; 15 (3): 428–431 presentation a 64-year-old man with myasthenia gravis (mg) presented with blurry vision in his left eye (os). his visual acuity was 20/20 in the right eye and 20/50 os. his intraocular pressures, pupils, and anterior segment were normal. he had 1+ vitritis and vaso-occlusive appearance of the retina with sclerotic vessels and hemorrhages in the inferonasal quadrant os (figure 1), consistent with features of cytomegalovirus (cmv) retinitis. he was immunocompromised secondary to mycophenolate mofetil (mmf) administered for mg, with 0.6% lymphocytes (normal: 26.0–46.0%), a lymphocyte count of 0.1×103 cells/μl, and a leukocyte count of 11.3×103 cells/μl. he was receiving 1000 mg of mmf bid. the human immunodeficiency virus (hiv) test result was negative, and no further workup for immunosuppression, including cancer, was conducted. the patient was administered with 0.05 ml ganciclovir (4 mg/0.1 ml) and 0.10 ml foscarnet (2.4 mg/0.1 ml) intravitreal injections on diagnosis. subsequently, his symptoms improved, and correspondence to: shyam patel, md. department of ophthalmology, cook county hospital, 1900 west polk st., ste. 617, chicago, 60612, il, usa. email: spatel0687@gmail.com received: 01-04-2018 accepted: 19-06-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7463 a 10-week course of oral valganciclovir (900 mg bid for 21 days followed by 900 mg qd for seven weeks) was administered. there was also a decrease in the dosage and eventual cessation of mmf with initiation of intravenous immunoglobulins. his lymphocytes improved to 9.8% (lymphocyte count, 0.7×103 cells/μl; leukocyte count, 6.9×103 cells/μl). on valganciclovir discontinuation in week 10, the patient had a visual acuity of 20/25 os with no inflammation and improvements in retinal hemorrhages and lesions. an epiretinal membrane was observed on macular optical coherence tomography (figure 2). the inferonasal retina showed inactive whitish atrophy (figure 3). discussion cmv retinitis is the most common ocular opportunistic infection associated with acquired immune deficiency syndrome.[1] the prevalence of cmv retinitis in hiv patients has decreased since the advent of highly active antiretroviral therapy (haart).[2] however, the rate of cmv retinitis in non-hiv patients is increasing, likely due to the use of aggressive immunosuppressive agents.[1] cmv is an infectious complication frequently associated with mmf.[3] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: patel s, robin a. cytomegalovirus retinitis in a patient on long-term mycophenolate mofetil treatment for myasthenia gravis. j ophthalmic vis res 2020;15:428–431. 428 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7463&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; patel et al figure 1. (a) a funduscopic photo of the left eye shows fluffy white lesions with intraretinal hemorrhage predominantly in the inferonasal quadrant. (b) a funduscopic photo of the left inferonasal quadrant five weeks after treatment initiation. figure 2. (a) oct of the macula of the left eye before treatment initiation showing vitreomacular adhesion and few vitreous cells. (b) oct of the macula of the left eye after 10 weeks from treatment initiation showing a fine epiretinal membrane. visual prognosis of cmv infection in nonhiv patients is similar to that in hiv patients with poor visual outcomes associated with retinal detachments and macular involvement.[1] cmv retinitis in patients with concomitant hiv infection lacks vitreous involvement.[2] in contrast, vitritis is more commonly associated with non-hiv-related cmv retinitis infections.[2] this is consistent with our patient’s presentation. cmv retinitis treatment in hiv patients involves haart and antiviral therapy.[1] in non-hiv patients, different etiologies of an immunocompromised state must be considered. commonly used treatment strategies include systemic ganciclovir, foscarnet, valganciclovir, and intravitreal ganciclovir. our patient received one initial intravitreal injection each of ganciclovir and foscarnet, as well as oral valganciclovir. intravitreal injections are important for the treatment of vision-threatening cmv infections and were used in our case.[4] nevertheless, the mainstay treatment of cmv retinitis remains systemic antivirals, and it is not always necessary to start with intravitreal injections. the combination of intravitreal ganciclovir journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 429 photo essay; patel et al figure 3. the inferonasal fundus photo of the left eye at 10 weeks showing preretinal fibrosis with a corresponding oct (over the white lesion, see arrow) showing an atrophic retina with resolved vitritis. a corresponding infrared image showing the line of scan of the oct. and foscarnet is effective in treating cmv retinitis.[5] in summary, we presented a patient with mg who developed cmv retinitis due to immunosuppression as a result of mmf treatment. he was treated successfully with intravitreal and systemic antivirals. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. 430 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 photo essay; patel et al references 1. kim d, jo j, joe s, kim j, yoon y, lee j. comparison of visual prognosis and clinical features of cytomegalovirus retinitis in hiv and non-hiv patients. retina 2017;37:376– 381. 2. iu l, fan m, lau j, chan t, kwong y, wong i. longterm follow-up of cytomegalovirus retinitis in non-hiv immunocompromised patients: clinical features and visual prognosis. am j ophthalmol 2016;165:145–153. 3. meier-kriesche hu, friedman g, jacobs m, mulgaonkar s, vaghela m, kaplan b. infectious complications in geriatric renal transplant patients: comparison of two immunosuppressive protocols. transplantation 1999;68:1496–1502. 4. pearce w, yeh s, fine h. management of cytomegalovirus retinitis in hiv and non-hiv patients. ophthalmic surg lasers imaging retina 2016;47:103–107. 5. velez g, roy ce, whitcup sm, robinson mr. high-dose intravitreal ganciclovir and foscarnet for cytomegalovirus retinitis. am j ophthalmol 2001;131:396–397. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 431 editorial glaucomatous optic neuropathy: the dark side of the moon shahin yazdani1,2, md 1ocular tissue engineering research center, shahid beheshti university of medical sciences, tehran, iran 2ophthalmic research center, research institute for ophthalmology and vision research, shahid beheshti university of medical sciences, tehran, iran orcid: shahin yazdani: http://orcid.org/0000-0002-9583-1434 j ophthalmic vis res 2021; 16 (2): 148–150 glaucoma is an enigmatic eye condition and serves as a perfect example for an ocular disease with complex pathophysiology, multifactorial nature, and close interplay with systemic factors. glaucomatous optic neuropathy (gon) is also probably the most important and prevalent eye condition linked to events within the central nervous system (cns). none of these is an overstatement when one recalls that the optic nerve head, the site where gon is diagnosed and monitored, is only one small sector of the second cranial nerve, otherwise known as the optic nerve. the major portion of the optic nerve courses in the cns and acquires physiologic features of neurons residing in the cns, for example myelination of fibers, just posterior to the lamina cribrosa (lc). another important fact is that the optic nerve is composed of bundled axons of retinal ganglion cells (rgcs) which have the privilege of “dual citizenship” resting partly in a peripheral organ and partly within the cns, the boundary being at the lc. the past decades have witnessed a surge of interest and a wealth of information on previously unknown and less explored aspects of glaucoma. these include the role of systemic factors such as vascular dysregulation, nocturnal systemic hypotension, positional intraocular pressure (iop) elevation, and episodes of hypoxia due to sleep apnea.[1–5] it has also become more evident that the damage associated with gon is not limited to the optic nerve and secondary/concomitant damage is present at higher centers within the cns including the lateral geniculate body and primary visual cortex.[6, 7] these observations are in favor of the notion that gon represents a neurodegenerative process beyond the eye. it has become increasingly known that compartments (and pressures within) adjacent to the optic nerve other than the intraocular compartment and iop have an important role in maintaining its homeostasis.[8] the retrolaminar portion of the optic nerve has attracted much attention and the most important compartment in this region seems to be the subarachnoid space bathed in cerebrospinal fluid (csf) which is connected to the subarachnoid space of the brain.[9, 10] one particular region of interest is the lc, where iop and csf pressure (csfp) meet, exerting pressure on either side of the lamina, thus creating a pressure gradient. the lc has long been considered as a major site of insult to rgcs triggering cell loss and apoptosis. various in vivo observations using enhanced depth imaging optical coherence tomography (edi-oct) and histological studies in animal and human eyes have demonstrated lc changes including displacement, compaction and bowing associated with gon.[11, 12] one simplified scheme used to conceptualize glaucomatous damage is to focus on mechanical factors at this region and ignore other physiologic alterations such as impaired nutrition and reduced clearance of neurotoxins. with this simplified mechanical scheme, one can consider iop and csfp as two opposing forces which not only affect lc position but also exert stress and strain on this important structure and the delicate retinal nerve fibers protected within the laminar pores. if the normal physiologic balance between these two pressure components is disturbed, the lamina becomes 148© 2021 yazdani et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9076&domain=pdf&date_stamp=2019-07-17 editorial; yazdani et al compressed and displaced either posteriorly, as in the case of gon, or anteriorly as in intracranial hypertension. having emphasized the importance of the pressure balance at the region of the lc, one cannot neglect the importance of intrinsic lc characteristics such as laminar area, thickness, rigidity/elasticity, compliance, deformability, and pore size. it has been shown that lc thickness may vary in different forms of glaucoma[13–15] and might arguably be associated with central corneal thickness, which may serve as a more accessible surrogate biomarker.[16] in this issue of jovr, cruz et al[17] report trans-lc pressure gradient (tlcpg) in addition to ocular perfusion pressure (opp) in a cohort of subjects with definite or suspicious open angle glaucoma stratified by optic disc size. although this group of investigators found no significant difference in opp, they reported significantly larger tlcpg in eyes with larger discs. this may reflect higher susceptibility of larger optic nerves to glaucomatous damage. this observation follows basic physical rules such as laplace’s law,[18] which explains that strain in a pressurized hollow structure is directly correlated with its diameter and inversely correlated with its thickness.[19] although there are limitations to applying purely physical rules to live tissue, the calculated tlcpg reported by the authors seems to be a fairly reasonable reflection of the actual physiologic reality. the authors are to be commended for their study, but at the same time we need to consider certain limitations of their methodology, partly addressed by the authors. first, csfp was not actually measured but rather derived mathematically using proxy parameters such as bmi, diastolic blood pressure, and age. however, one may argue that even with lumbar puncture and obtaining csfp values, the readings may not accurately reflect actual csfps at the lc. second, it is not clear whether major determinants of tlcpg, that is, iop and csfp, were comparable among the study groups and that it would be safe to conclude that the observed difference in tlcpg among the study groups was only due to different optic nerve size. last, it would have been interesting if lc thickness had also been evaluated by edi–oct and its measurements had been taken into account. the study by cruz et al[17] helps add to the literature much needed data which the ophthalmology community and glaucoma specialists in particular have been missing: the myriad of complex and less recognized factors intertwined in the pathophysiology of gon lurking in less accessible regions of the optic nerve, or “the dark side of the moon.” references 1. flammer j, orgül s, costa vp, orzalesi n, krieglstein gk, serra lm, renard jp, stefánsson e. the impact of ocular blood flow in glaucoma. prog retin eye res 2002;21:359– 393. 2. buchanan ra, williams td. intraocular pressure, ocular pulse pressure and body position. am j optom physiol opt 1985;62:59–62. 3. linder bj, trick gl, wolf ml. altering body position affects intraocular pressure and visual function. invest ophthalmol vis sci 1988;29:1492–1497. 4. mojon ds, hess cw, goldblum d, fleischhauer j, koerner f, bassetti c, et al. high prevalence of glaucoma in patients with sleep apnea syndrome. ophthalmology 1999;106:1009–1012. 5. marcus dm, costarides ap, gokhale p, papastergiou g, miller jj, johnson mh, chaudhary ba. sleep disorders: a risk factor for normal-tension glaucoma? j glaucoma 2001;10:177–183. 6. gupta n, yücel yh. brain changes in glaucoma. eur j ophthalmol 2003;13:s32–s35. 7. gupta n, ang lc, noël de tilly l, bidaisee l, yücel yh. human glaucoma and neural degeneration in intracranial optic nerve, lateral geniculate nucleus, and visual cortex. br j ophthalmol 2006;90:674–678. 8. killer he. compartment syndromes of the optic nerve and open-angle glaucoma. j glaucoma 2013;22:s19–s20. 9. jonas jb. role of cerebrospinal fluid pressure in the pathogenesis of glaucoma. acta ophthalmol 2011;89:505–514. 10. killer he, jaggi gp, flammer j, miller nr. is openangle glaucoma caused by impaired cerebrospinal fluid circulation around the optic nerve? clin exp ophthalmol 2008;36:308–311. 11. jonas jb, königsreuther ka, naumann goh. optic disc histomorphometry in normal eyes and eyes with secondary angle-closure glaucoma. ii. parapapillary region. graefe’s arch clin exp ophthalmol 1992;230:134– 139. 12. downs jc, girkin ca. lamina cribrosa in glaucoma. curr opin ophthalmol 2017;28:113–119. 13. park hy, jeon sh, park ck. enhanced depth imaging detects lamina cribrosa thickness differences in normal tension glaucoma and primary open-angle glaucoma. ophthalmology 2012;119:10–20. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 149 editorial; yazdani et al 14. kim m, bojikian kd, slabaugh ma, ding l, chen pp. lamina depth and thickness correlate with glaucoma severity. indian j ophthalmol 2016;64:358–363. 15. kim yw, jeoung jw, kim yk, park kh. clinical implications of in vivo lamina cribrosa imaging in glaucoma. j glaucoma 2017;26:753–761. 16. jonas jb, holbach l. central corneal thickness and thickness of the lamina cribrosa in human eyes. invest ophthalmol vis sci 2005;46:1275–1279. 17. cruz nfs, santos ks, matuoka ml, kasahara n. translaminar pressure difference and ocular perfusion pressure in glaucoma patients with different optic disc sizes. j ophthalmic vis res 2021;16:171-177. 18. szczudlowski k. glaucoma hypothesis: application of the law of laplace. med hypotheses 1979;5:481–486. 19. baneke aj, aubry j, viswanathan ac, plant gt. the role of intracranial pressure in glaucoma and therapeutic implications. eye 2020;34:178–191. correspondence to: shahin yazdani, md. ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, 23 paidar fard, bostan 9, pasdaran ave., tehran 16666, iran. email: shahinyazdani@yahoo.com received: 05-01-2021 accepted: 13-02-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9076 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: yazdani s. glaucomatous optic neuropathy: the dark side of the moon. j ophthalmic vis res 2021;16:148–150. 150 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 https://knepublishing.com/index.php/jovr photo essay an unusual presentation of vogt–koyanagi–harada sefik can ipek, md1; sadettin uslu, md2; gercek can, md2; ozlem ozbagcivan, md3; pinar cakar ozdal, md4 ali osman saatci, md1 1department of ophthalmology, dokuz eylul university, izmir, turkey 2department of rheumatology, dokuz eylul university, izmir, turkey 3department of dermatology, dokuz eylul university, izmir, turkey 4ulucanlar eye research and training hospital, university of health sciences, ankara, turkey orcid: ali osman saatci: https://orcid.org/0000-0001-6848-7239 sefik can ipek: https://orcid.org/0000-0002-4651-8177 j ophthalmic vis res 2021; 16 (1): 140–144 presentation in february 2018, a 21-year-old otherwise healthy female patient was diagnosed with a bilateral anterior uveitis by her local physician at a small rural hospital and was treated accordingly with topical prednisolone acetate drops. the patient also complained of a severe headache. however, no further investigation was carried out at that time. severe alopecia ensued in march and june 2018, the patient was examined by us due to the recurrence of bilateral anterior uveitis. her visual acuity was 20/25 ou. bilateral (++) anterior chamber cells, non-granulomatous in nature, and a few pigmented iris clumps were observed on the anterior lens capsules. according to the sun criteria, grade 0.5+ cells were noted in the vitreous bilaterally.[1] fundus examination revealed mildly blurred disc margins and numerous scattered yellowish-gray, round spot-like changes scattered 360° throughout the fundus ou (figures 1a and 1b). fluorescein angiography revealed correspondence to: ali osman saatci, md. mustafa kemal sahil bulvarı no: 73 a blok, daire 9 narlıdere, izmir, turkey. e-mail: osman.saatci@yahoo.com received: 08-01-2019 accepted: 17-10-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8263 lesions exhibiting early venous hyperfluorescence with late staining associated with mild bilateral disc leakage (figures 1c, 1d, 1e, and 1f). an indocyanine green angiogram (heidelberg spectralis, heidelberg engineering, heidelberg, germany) exhibited hypocyanesence of these lesions throughout the angiography sequences (figures 1g and 1h). most notably, no signs of serous retinal detachment were present (figures 1i and 1j). on the other hand, diffuse type of alopecia areata was evident (figure 2a) and the patient was referred to the dermatology and rheumatology departments. meticulous laboratory and imaging examinations were carried out. laboratory results showed that the erythrocyte sedimentation rate (esr) and cytoplasmic reactive protein (crp) were normal. anti-nuclear antibody (ana) was positive (homogeneous pattern; 1/100–1/320 with dilution). tests for hla b27, rheumatoid factor (rf), anticitrullinated peptide (anti-ccp), extractable nuclear antigen (ena) panel, anti-neutrophil cytoplasmic antibody, and anti-phospholipid antibody were negative. serum protein electrophoresis results this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: ipek sc, uslu s, can g, ozbagcivan o, ozdal pc, saatci ao. an unusual presentation of vogt–koyanagi–harada disease without an overt serous retinal detachment and with severe diffuse alopecia. j ophthalmic vis res 2021;16:140–144. 140 © 2021 ipek et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8263&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; ipek et al figure 1. composite of color fundus showing 360° scattered yellowish–gray spot like aggregates, (a) right eye, (b) left eye. early venous phase of composite fluorescein angiographic picture exhibiting staining of these spot-like lesions, (c) right eye, (d) left eye. late venous phase of composite fluorescein angiographic picture showing leakage from the optic disc, (e) (right eye), (f) left eye. mid-phase of composite indocyanine green picture demonstrating the hypocyanescent widespread spot-like opacities, (g) right eye, (h) left eye. normal foveal contour on optical coherence tomography, (i) right eye, (j) left eye. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 141 photo essay; ipek et al figure 2. (a) appearance of hair scalp from above depicting the diffuse alopecia. (b) colored picture of coexistent herpes labialis. and complement levels were normal. furthermore, cranial and orbital mri with contrast, chest x-ray imaging, and abdominal ultrasonography were all normal. no systemic treatment was administered as the patient had developed primary herpes labialis (figure 2b) at the systemic evaluation phase and topical steroid treatment seemed sufficient to control the anterior chamber inflammation. in october 2018, the patient experienced a bilateral non-granulomatous anterior uveitis attack without any further posterior segment changes. optical coherence tomography angiography and en-face oct (figures 3a, 3b, 3c, and 3d), as well as swept source-oct were performed (triton, topcon inc., oakland, new jersey, usa). this revealed that the subfoveal choroidal thickness was 512 and 498 μm in the right and left eyes, respectively (figures 3g and 3h). at this time, oral azathioprine 50 mg daily was prescribed together with topical prednisolone acetate eye drops. this case was diagnosed as incomplete vogt–koyanagi–harada (vkh) syndrome[2] without overt serous retinal detachment and a significant decrease in vision. the disease progressed to the convalescent stage of vkh syndrome (with alopecia, depigmentation of fundus, and peri-papillary atrophy) as no systemic treatment was given early in the course of the disease. discussion in the present case, we found that vkh syndrome can have some unusual clinical manifestations such as no initial visual loss and no overt serous retinal detachment together with the occurrence of relatively early-onset severe alopecia. as the correct diagnosis was not made by her local physician, high-dose systemic steroids and immunosuppressants were not prescribed early at the early stages of disease presentation. alopecia areata is a chronic, inflammatory disorder of the hair follicles that results in non-scarring, patchy hair loss of the scalp. histopathologically, alopecia areata associated with vkh disease is characterized with prominent pigment release, suggesting that the primary target is melanocytes and that keratinocytes might also be involved.[3] however, there was a very short time lapse of one month between the occurrence of bilateral uveitis and severe alopecia in the present case. in a recent study, alopecia was present in 38 of the 261 vkh patients (13.9%) in the early disease stages, whereas in 187 of the 373 vkh patients (49.6%) it occurred in the late stages.[4] the presence of serous retinal detachment can be considered as a hallmark of vkh disease. in the acute disease stages of vkh, serous retinal detachment has a positive predictive value of 100.[5] yang et al[4] reported that serous retinal detachment was present in 87.9% of their patients during the early stages of the disease. remarkably, serous retinal detachment was not detected in any visits during the disease course in our case and we believe that this is very unusual in vkh disease. systemic high-dose corticosteroid is the firstline treatment for vkh as posterior segment involvement is almost always severe at the initiation.[6] however, we examined the patient four months after the first episode of bilateral anterior uveitis. during the second anterior uveitis attack, the disease was in the convalescent stage. we decided to withhold systemic steroid and immunosuppressive therapy due to the presence of coexistent herpes labialis and the relative inactivity of the posterior segment lesions. 142 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 photo essay; ipek et al figure 3. (a&b) choriocapillaris slab of montage optical coherence tomography angiography and en-face oct image of the right. (c&d) left eyes revealing the patchy ischemia of choriocapillaris (arrows). color fundus pictures taken at the last visit showing slightly blurred disc margins with less apparent old scars with no new lesion. (e) right eye and (f) left eye. (g) swept source optical coherence tomographic subfoveal choroidal thickness was 512 μm in the right eye and (h) 498 μm in the left eye. systemic azathioprine was prescribed four months after our initial evaluation as soon as the patient experienced the third attack of bilateral anterior uveitis. in summary, this report presents an unusual case of vkh disease with early onset severe alopecia and the lack of overt bilateral serous retinal detachment during the early stages. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. jabs da, nussenblatt rb, rosenbaum jt. standardization of uveitis nomenclature for reporting clinical data. results of the first international workshop. am j ophthalmol 2005;140:509–516. 2. read rw, holland gn, rao na, tabbara kf, ohno s, arellanes-garcia l, et al. revised diagnostic criteria for vogt–koyanagi–harada disease: report of journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 143 photo essay; ipek et al an international committee on nomenclature. am j ophthalmol 2001;131:647–652. 3. dipreta ea, smith kj, williams j, skelton h. histopathologic findings in the alopecia associated with vogt-koyanagi-harada disease. j cutan med surg 2000;4:155–159. 4. yang p, zhong y, du l, chi w, chen l, zhang r, et al. development and evaluation of diagnostic criteria for vogt-koyanagi-harada disease. jama ophthalmol 2018;136:1025. 5. rao na, gupta a, dustin l, chee sp, okada aa, khairallah m, et al. frequency of distinguishing clinical features in vogt-koyanagi-harada disease. ophthalmology 2010;117:591–599, 599.e1. 6. o’keefe gad, rao na. vogt–koyanagi–harada disease. surv ophthalmol 2017;62:1–25. 144 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 case report optical coherence tomography findings in nodular anterior scleritis due to post-streptococcal syndrome kais benabderrahim, md department of ophthalmology, university hospital of médenine, faculty of medicine, sfax univer-sity, tunisia orcid: kais benabderrahim: https://orcid.org/0000-0002-0693-1979 abstract purpose: to report a case of nodular anterior scleritis due to poststreptococcal syndrome using optical coherence tomography imaging. case report: a 41-year-old woman with a history of acute rheumatic fever presented with a nodular anterior scleritis. common causes were excluded. optical coherence tomography of sclera showed enlarged vessels, inflammatory infiltrates, separated fibers, and a serous detachment. laboratory investigations showed an elevated erythrocyte sedimentation rate, raised anti-streptolysin o titer, and the presence of group a streptococcus in the throat. the scleritis rapidly improved with penicillin treatment. conclusions: poststreptococcal syndrome should be considered in the etiology of nonnecrotizing anterior scleritis. keywords: scleritis; optical coherence tomography; poststreptococcal syndrome j ophthalmic vis res 2021; 16 (1): 131–134 introduction poststreptococcal syndrome (pss) includes all nonsuppurative complications of infections with group a streptococci.[1, 2] it appears as an immunemediated reaction in any tissue of the body.[1] acute rheumatic fever and acute glomerulonephritis are the common entities of pss which most frequently involves young patients.[1, 2] ocular involvement of pss is uncommon and rare.[1, 2] more precisely, pss is not considered among the common causes of correspondence to: kais benabderrahim, md. university hospital of médenine, tataouine st., 4100, medenine, tunisia. e-mail: ben_abd_kais@yahoo.fr received: 07-05-2019 accepted: 15-06-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8260 scleritis.[3, 4] scleritis is an inflammatory condition characterized by ocular pain and redness of the sclera.[3] it can threaten vision in severe cases.[3] previous studies reported that optical coherence tomography (oct) showed different changes in the sclera within each grade of active scleritis.[5, 6] our aim is to describe a rare case of nodular anterior scleritis due to pss using oct imaging. case report a 41-year-old woman had a history of an acute rheumatic fever (arf) treated with penicillin in childhood. she presented with a two-day history this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: benabderrahim k. optical coherence tomography findings in nodular anterior scleritis due to poststreptococcal syndrome. j ophthalmic vis res 2021;16:131–134. © 2021 benabderrahim et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 131 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8260&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr anterior scleritis due to poststreptococcal syndrome; benabderrahim et al of redness and pain in her left eye. symptoms occurred few days after an acute pharyngitis. she reported a history of a similar episode in her right eye a year ago. best-corrected visual acuity was 20/20 in both eyes. slit lamp examination revealed a nodule in the superior sclera with hyperemia and chemosis around it [figure 1]. ocular examination and funduscopy excluded all forms of uveitis or suppurative infections. b-scan ultrasonography showed no abnormalities in the posterior segment of the left eye. spectral domain oct (3d oct-1maestero; topocon, japan) of the sclera showed enlarged vessels, inflammatory infiltrates (hyporeflective spaces), separated fibers, and a serous detachment between them [figure 1]. the scleral thickness at the level of visible layers was 659 µm on the nodular area and 555 µm around it. a surgical punch biopsy of conjunctiva and tenon’s tissue was performed at admission. histopathologic exam revealed mild and nonspecific inflammation and excluded bacterial or parasitological infections. investigations showed negative results for tuberculosis, syphilis, and rheumatoid arthritis (chest x-ray, throat culture, tuberculin skin testing, syphilis serology, antinuclear antibodies, rheumatoid factor). laboratory tests showed high erythrocyte sedimentation rate (35 mm in the first hour), raised anti-streptolysin o (aso) titer of 545 units/ml, the presence of group a streptococcus in the throat culture, c-reactive protein of 1 mg/l, a white blood count of 5600/mm3 (lymphocytes: 51%), and normal levels of blood electrolytes, glycemia, and azotemia. the patient received benzathine benzylpenicillin (extencilline: 1.2 million units intramuscularly twice monthly for three months). examination showed rapid improvement within six days and remarkable resolution of signs after two weeks [figure 1]. oct demonstrated accumulation of the liquid in the sub-tenon’s space after 6 days and improvement of the fibrous structure of the sclera after 15 days. recurrence of signs was observed in the right eye after 22 days [figure 1]. the patient declared that she had not received the second dose of extencilline. oct revealed hyporeflective areas due to an inflammatory fluid in the right sclera [figure 2] and normal findings in the left eye. extencilline treatment was administrated with the same doses in addition to oral corticosteroids. complete recovery of signs was noticed after one week [figure 2]. normal level of aso titers was reached after two months. discussion in this report, we described an uncommon case of nodular anterior scleritis induced by presumed pss. findings supporting the diagnosis of pss scleritis were the history of arf, pharyngitis, biopsy results, the high erythrocyte sedimentation rate, the raised aso antibody titer, the evidence of streptococcal infections, the rapid response to penicillin, the early recurrence when the patient stopped penicillin treatment, and the negative results for all main diseases responsible for scleritis.[1, 6–8] reported cases of an ocular involvement of pss include scleritis, in addition to uveitis, and rarely episcleritis, conjunctivitis, brown’s syndrome, optic disc edema, posterior scleritis, and glaucoma.[2, 7–12] however, previous studies reported pss as an uncommon cause of uveitis or scleral inflammation.[2] to our knowledge, pss was not figured among the possible causes of nodular anterior scleritis.[3, 4] anamnesis, clinical examination, and laboratory investigations were helpful to exclude causes of necrotizing forms of scleritis and to suggest pss. biopsy may be helpful in establishing the diagnosis in cases of scleritis, but cannot rule out special scleral diseases especially in cases of non-necrotizing scleritis.[6] according to the anatomo-clinical classification of scleritis, there are two forms of scleritis: anterior and posterior.[6] anterior scleritis is divided into nodular, diffuse, and necrotizing scleritis. the nodular scleritis has two forms: necrotizing and non-necrotizing forms. oct is useful to show the scleral changes and to classify the scleral inflammation. moreover, this tool is helpful in distinguishing all forms of anterior scleritis and monitoring them.[5, 6] the common scleral changes in anterior scleritis were separated fibers, dilated vessels, hyporeflective spaces and high thickness of sclera.[5, 6] although thickening of the episcleral layer was observed in both episcleritis and anterior scleritis, scleral layers were not affected in episcleritis.[13] oct imaging is useful for distinguishing between non-necrotizing and necrotizing anterior scleritis. in the cases of 132 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 anterior scleritis due to poststreptococcal syndrome; benabderrahim et al figure 1. (a) optical coherence tomography images of the left eye showed separated fibers (dashed arrow), enlarged vessels, inflammatory infiltrates (solid arrow), serous detachment between them (asterisk), and the site of conjunctival biopsy (arrow head). (b, c, d) evolution after penicillin treatment. figure 2. (a) optical coherence tomography showed separated fibers (dashed arrow) and inflammatory infiltrates (solid arrow) due to recurrence of anterior scleritis in the right eye. (b) resolution of signs in the final examination. non-necrotizing scleritis, the collagen fibers were simply separated and associated with an extracellular fluid without necrosis of tissue. in the second form, scleral oct showed destructive changes, in which any hyporeflectivity of the deep layers of the nodule corresponded to liquified tissues.[2, 5, 6, 10, 13] in addition, this tool is useful to grade anterior scleritis from mild to severe when the activity signs reach the deeper sclera and the suprachoroidal space.[5] in this case, oct findings strongly suggested non-necrotizing form of nodular scleritis as described in the previous reports.[1, 6–8, 13] sometimes, oct can suggest the etiology of anterior scleritis. common associated diseases were rarely found in the cases of non-necrotizing noninfectious scleritis.[6] however, oct was helpful in suggesting the etiology in some cases of necrotizing anterior scleritis. this tool showed destructive changes that involved the cornea, limbus, and the adjacent sclera in the case of a systemic vasculitis. however, the adjacent sclera was normal in the case of an idiopathic and rheumatoid-associated sclero-keratitis. the characteristic changes in rheumatoid arthritis are those of a venular journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 133 anterior scleritis due to poststreptococcal syndrome; benabderrahim et al occlusive scleritis affecting the vessels of the episcleral plexus.[5, 6, 10] in this patient, presumed pss scleritis rapidly improved with just penicillin. such a finding have been previously reported.[8] penicillin prophylaxis is needed to prevent pss complications and recurrence.[1, 7, 8, 12] presumed pss scleritis may be among refractory cases to standard corticosteroid treatment and may require penicillin for treatment.[7] the fluid space, that has been seen at admission (before the biopsy) and that has been increased at the follow-up examination of the left eye, seemed to be a new clinical event. in conclusion, pss should be considered in the etiology of nodular anterior scleritis. aso titer should be performed in any patient suffering from anterior scleritis and having a history of streptococcal infections. oct may be helpful in the diagnosis and follow-up of scleral lesions. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. ayoub em, ahmed s. update on complications of group a streptococcal infections. curr probl pediatr 1997;27:90– 101. 2. curragh ds, mcavoy ce, rooney m, mcloone e. poststreptococcal uveitis syndrome in a caucasian population: a case series. eye 2019;33:380–384. 3. wieringa wg, wieringa je, ten dam-van loon nh, los li. visual outcome, treatment results, and prognostic factors in patients with scleritis. ophthalmology 2013;120:379– 386. 4. akpek ek, thorne je, qazi fa, do dv, jabs da. evaluation of patients with scleritis for systemic disease. ophthalmology 2004;111:501–506. 5. levison al, lowder cy, baynes km, kaiser pk, srivastava sk. anterior segment spectral domain optical coherence tomography imaging of patients with anterior scleritis. int ophthalmol 2016;36:499–508. 6. watson p, romano a. the impact of new methods of investigation and treatment on the understanding of the pathology of scleral inflammation. eye 2014;28:915–930. 7. hilkert sm, koreishi af, pyatetsky d. poststreptococcal syndrome presenting as posterior scleritis in a child. j aapos 2017;21:163–165. 8. rospond-kubiak i, brązert a, kocięcki j, bręborowicz j. poststreptococcal syndrome mimicking conjunctival lymphoma. bmc infect dis 2013;13:149. 9. young n. poststreptococcal episcleritis. n z med j 2017;130:66–67. 10. shoughy ss, jaroudi mo, kozak i, tabbara kf. optical coherence tomography in the diagnosis of scleritis and episcleritis. am j ophthalmol 2015;159:1045–1049.e1. 11. faust ao, gillenwater jm, saulsbury ft. acquired brown’s syndrome in a child with poststreptococcal reactive arthritis. j rheumatol 2001;28:2748–2749. 12. ur rehman s, anand s, reddy a, backhouse oc, mohamed m, mahomed i, et al. poststreptococcal syndrome uveitis: a descriptive case series and literature review. ophthalmology 2006;113:701–706. 13. axmann s, ebneter a, zinkernagel ms. imaging of the sclera in patients with scleritis and episcleritis using anterior segment optical coherence tomography. ocul immunol inflamm 2016;24:29–34. 134 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 original article secondary piggyback intraocular lens for management of residual ametropia after cataract surgery zahra karjou, md; mohammad-reza jafarinasab, md; mohammad-hassan seifi, md kiana hassanpour, md, mph; bahareh kheiri, ms ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran orcid: mohammadreza jafarinasab: https://orcid.org/0000-0003-2429-8035 zahra karjou: https://orcid.org/0000-0002-2907-7955 abstract purpose: to investigate the indications, clinical outcomes, and complications of secondary piggyback intraocular lens (iol) implantation for correcting residual refractive error after cataract surgery. methods: in this prospective interventional case series, patients who had residual refractive error after cataract surgery and were candidates for secondary piggyback iol implantation between june 2015 and september 2018 were included. all eyes underwent secondary iol implantation with the piggyback technique in the ciliary sulcus. the types of iols included sulcoflex and three-piece foldable acrylic lenses. patients were followed-up for at least one year. results: eleven patients were included. seven patients had hyperopic ametropia, and four patients had residual myopia after cataract surgery. the preoperative mean of absolute residual refractive error was 7.20 ± 7.92, which reached 0.42 ± 1.26 postoperatively (p < 0.001). the postoperative spherical equivalent was within ±1 diopter of target refraction in all patients. the average preoperative uncorrected distance visual acuity was 1.13 ± 0.35 logmar, which significantly improved to 0.41 ± 0.24 logmar postoperatively (p = 0.008). there were no intraor postoperative complications during the 22.4 ± 9.5 months of follow-up. conclusion: secondary piggyback iol implantation is an effective and safe technique for the correction of residual ametropia following cataract surgery. three-piece iols can be safely placed as secondary piggyback iols in situations where specifically designed iols are not available. keywords: residual ametropia; intraocular lens implantation; piggyback iol implantation j ophthalmic vis res 2021; 16 (1): 12–20 correspondence to: mohammad reza jafarinasab, md. department of ophthalmology, labbafinejad medical center, boostan 9 st., pasdaran ave., tehran 16666, iran. email: dr_jafarinasab@yahoo.com received: 15-02-2020 accepted: 28-09-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8244 introduction cataract surgery currently plays a pivotal role in achieving the best possible postoperative this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: karjou z, jafarinasab mr, seifi mh, hassanpour k, kheiri b. secondary piggyback intraocular lens for management of residual ametropia after cataract surgery. j ophthalmic vis res 2021;16:12–20. 12 © 2021 karjou et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8244&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr piggyback iol in residual ametropia; karjou et al refraction, resulting in patients’ independence from spectacles. despite the advances in surgical techniques and intraocular lens (iol) power calculation, residual refractive error and refractive surprise occasionally occur and cause both patients’ and surgeons’ dissatisfaction.[1] inaccurate estimation of postoperative iol position, incorrect biometry measurements, and error in iol power selection are among the main causes of residual refractive error. additionally, patients with high ametropia are more prone to residual refractive error, mainly due to the limitations of iol calculation formula and imprecision of iol manufacturing in these extreme conditions.[2] there are multiple surgical techniques used to correct residual refractive error. various factors affect proper method selection, including the amount of residual refraction and experience of the surgeon, while laser refractive surgeries are considered for lower amounts of residual errors. iol exchange or piggyback lens implantation is required to correct higher amounts of residual errors.[3, 4] piggyback iol implantation was first introduced in 1993 by gayton and sanders[5] and involves the placement of another iol in the bag or more recently, in the sulcus.[6] higher safety profile, easier technique, and the potential for removing the second lens are the advantages of piggyback iol implantation over iol exchange.[4, 7] however, the increased risk of glaucoma, iris pigment release, and intralenticular opacification make this procedure controversial for many surgeons.[8–11] piggyback iol implantation is considered primary when the refractive error is higher than can be corrected with one iol and secondary when the residual refractive error is corrected. in secondary piggyback iol implantation, in which the second iol is placed in the ciliary sulcus, different iol designs and types are used, including monofocal, multifocal, and toric.[2] the present study aimed to investigate the clinical outcomes and complications of secondary piggyback iol implantation in a tertiary referral eye center. methods in this prospective interventional case series, all patients who underwent secondary piggyback iol implantation at labbafinejad medical center from june 2015 to september 2018 were included. the study protocol was approved by the ethics committee of the ophthalmic research center, which is the equivalent of the institutional review board at shahid beheshti university of medical sciences, and adheres to the tenets of the declaration of helsinki. patients who had hyperopic or myopic residual refractive errors following uneventful cataract surgery and had no compliance with spectacle correction were included in the study. the amount of refractive error required for surgery was individualized for each patient and did not have an exact cut-off. patients with ocular inflammation, iritis, glaucoma, significant guttate or corneal edema, and any complications in the previous surgery that precludes well-centered iol in the bag were excluded from the study. informed consent was obtained from all participants. preoperative assessment and piggyback iol power calculation an experienced optometrist measured the patients’ uncorrected distance visual acuity (udva) and best-corrected distance visual acuity (bcva) using the snellen chart. subjective refraction was measured and recorded for all patients. in patients with hyperopic residual refractive error, the power of the piggyback iol was calculated by multiplying the desired spherical equivalent by 1.5. in myopic patients, the power of the iol was similar to the desired spherical equivalent. this method was described by gayton et al.[12] the type of iol selection was individualized for each patient based on their refractive error, iol availability, and surgeon’s experience (table 1). surgical technique the minimum required interval between the first surgery and piggyback iol implantation was three months. all procedures were performed by one experienced cornea surgeon (m.j.). young and uncooperative patients underwent general anesthesia. in other patients, topical tetracaine 0.5% (anestocaine, sinadarou, tehran, iran) was instilled and coupled with intracameral journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 13 piggyback iol in residual ametropia; karjou et al lidocaine 2%. using a 2.8-mm keratome, a clear corneal incision was made on the steep meridian. after the formation of the anterior chamber and area behind the iris with the use of viscoelastic, the iol was inserted into the ciliary sulcus. ovd (ophthalmic viscosurgical devices) was thoroughly washed using an irrigation and aspiration probe. the incision was made watertight using stromal hydration or a nylon 10-0 suture. subconjunctival antibiotics were injected at the end of surgery. on postoperative day 1, topical 0.5% chloramphenicol (chlobiotic®, sina darou, tehran, iran) was started four times a day, and 0.1% betamethasone (betasonate, sinadarou, tehran, iran) was applied eight times a day. antibiotics were continued for one week, and betamethasone was tapered off for six weeks based on the postoperative degree of inflammation. the patients were closely monitored in terms of wound leakage, intraocular pressure (iop), and inflammation. postoperative assessment the patients were followed-up on days 1, 3, 7, and 21, and after three and six months postoperatively, and then yearly. complete ophthalmic examinations, including udva, bcva, slit-lamp biomicroscopy, and funduscopy were repeated at each visit. any complication was recorded during the patients’ follow-up. statistical analysis frequency (%), mean ± sd, median, and range were used to describe the data. to evaluate the difference between the two sets (before and after the surgery for spherical equivalent and udva), paired t-test was used. all statistical analyses were performed using spss (ibm corp. released 2017; ibm spss statistics for windows, version 25.0. armonk, ny: ibm corp.). results eleven eyes of 11 patients were enrolled in the present study. the mean age of the patients was 39.27 ± 29.28 (range, 0.5 to 71) years, and 72.7% of the patients were male (table 2). the absolute mean deviation from emmetropia in the entire cohort was 7.20 ± 7.92 diopters (d), with a median of 4.25 (–9.50 to +14.00 d). in seven patients who had hyperopic ametropia, the mean se before surgery was 6.85 ± 4.06 (+2 to +14) d. in myopic patients, the mean se was –7.81 ± 2.01 (–9.50 to –5.00) d. indications for surgery and type of iol seven patients with residual hyperopic ametropia and four patients with residual myopia underwent secondary piggyback iol implantation. in general, the inability to achieve accurate keratometric data was the most common cause of residual ametropia. the exact causes of inaccurate keratometric data are summarized in table 3. other causes include biometric error secondary to chorioretinal coloboma in one patient, biometric error secondary to silicone oil in another patient, and myopic shift following congenital cataract surgery in three patients (table 4). three-piece, 6mm optic, foldable acrylic iol (acrysof ma60ac, alcon laboratories, inc.) was placed in seven patients. the main reasons for choosing a threepiece iol in these patients did not include the availability and cost. in four patients, sulcoflex piggyback iol (sulcoflex; rayner intraocular lenses ltd, east sussex, uk) was placed in the ciliary sulcus. the properties of the two iols are summarized in table 1. refractive outcome and complications udva improved in all participants. the mean duration of follow-up was 22.4 ± 9.5 months. the average preoperative udva was 1.13 ± 0.35 logmar, which significantly improved to 0.41 ± 0.24 logmar postoperatively (p = 0.008) (table 2). postoperative se was within ± 1 diopter of target refraction in all patients (figure 1). there was no significant difference between preand postoperative iop (14.09 ± 2.5 mmhg vs 14.27 ± 1.67 mmhg, respectively, p = 0.54). there were no intraoperative complications, including primary iol and vitreoretinal complications, immediate pupillary block, hyphema, intraocular hemorrhage, and postoperative iop spike. similarly, no complications, such as pupillary block, glaucoma, pigment dispersion syndrome, postoperative uveitis, postoperative endophthalmitis, or 14 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 piggyback iol in residual ametropia; karjou et al table 1. comparison of two types of intraocular lenses variable acrysof sulcoflex generic name ma60ac sulcoflex aspheric country switzerland united kingdom company alcon rayner intraocular lenses pieces three-pieces one-piece overall diameter 13 mm 14 mm optic diameter 6 mm 6.5 mm other properties sharp optic edges aspheric, round edged optic lens material hydrophobic acrylic rayacryl hydrophilic acrylic haptic angle 10° 10° table 2. patients demographic mean ±±± sd median (range) age years 39.27 ± 29.28 47 (0.5,71) sex, n (%) male 8 (72.7%) female 3 (27.3%) eye, n (%) od 5 (45.5%) os 6 (54.5%) type of ametropia, n (%) hyperopia 7 (64%) myopia 4 (36%) od, right eye; os, left eye; sd, standard deviation; n, number table 3. postoperative clinical outcome of the study participants mean ±±± sd median (range) p-value preoperative arre (se) diopter 7.20 ± 7.92 4.25 (–9.5,14) <0.001 postoperative arre (se) diopter 0 ± 0.97 0.42 (–1,2) preoperative udva logmar 1.13 ± 0.35 1.31 (0.52,1.48) 0.008 postoperative udva 0.41 ± 0.24 0.3 (0.1,0.7) preoperative bdva logmar 0.41 ± 0.21 0.4 (0.1,0.7) preoperative se hyperopic 6.85 ± 4.06 6.5 (2, 14) <0.001 postoperative se 0.28 ± 0.8 0 (–0.5,2) preoperative se myopic –7.81 ± 2.01 –8.37 (–9.5,–5) <0.001 postoperative se 0.06 ± 2.43 –0.62 (–2 to 3) preoperative iop 14.09 ± 2.5 14 (11,17) 0.54 postoperative iop 14.27 ± 1.67 15 (11,16) complications none arre, absolute residual refractive error; udva, uncorrected distance visual acuity; bdva, best-corrected distance visual acuity; se, spherical error; iop, intraocular pressure journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 15 piggyback iol in residual ametropia; karjou et al table 4. indications, clinical outcome, and type of implanted iol in the study participants patient age/sex possible causes pre-op ucva pre-op bcva post-op ucva post-op bcva targeted se pre-op se postop se diff se (post-op & targeted) iol type/power 1 6 mo m incorrect keratometry – – – +3.00 +14.00 +2.00 +1.00 3-piece/ +21.00 2 4 y f known case of phpv pseudophakic myopic shift 20/800 3/10 2/10 3/10 0.00 -9.50 0.00 0.00 1-piece/ –10.00 3 41 y f biometric error due to chorioretinal coloboma 20/600 5/10 5/10 5/10 0.00 +10.0 0.00 0.00 3-piece/ +15.50 4 71 y m keratometric error due to corneal nebule 2/10 8/10 8/10 8/10 0.00 +5.00 0.00 0.00 3-piece/ +7.50 5 65 y f keratometric error due to kcn 1/10 7/10 7/10 7/10 0.00 +6.50 –0.50 0.00 3-piece/ +10.0 6 70 y m biometric error due to so 20/400 2/10 2/10 2/10 0.00 +7.00 +0.50 + 0.50 3-piece/ +10.00 7 47 y m (known case of rp) acceptable re 3/10 4/10 5/10 4/10 0.00 +2.00 0.00 0.00 3-piece/ +3.00 8 15 mo m known case of phpv myopic shift – – – – +4.00 –500 +3.50 –0.50 1-piece/ –9.00 9 57 y m wrong iol power, human error 20/400 4/10 5/10 4/10 0.00 +3.50 0.00 0.00 3-piece/ +5.00 10 11 y m hx of congenital cataract sx, myopic shift 20/800 2/10 2/10 2/10 0.00 –9.00 0.00 0.00 sulcuflex/ –10.00 11 64 y m keratometric error due to pmd 1/10 4/10 4/10 4/10 0.00 –7.75 –1.00 –1.00 sulcoflex/ –8.00 bcva, best-corrected visual acuity; ucva, uncorrected visual acuity; se, spherical error; phpv, persistent hyperplastic primary vitreous; rp, retinitis pigmentosa; so, silicon oil; re, refractive error; sx, surgery; kcn, keratoconus; pmd, pellucid marginal degeneration; iol, intraocular lens; op, operative; diff, difference; m, male; f, female; hx, history of; mo, month; y, year interlenticular opacification (ilo), were observed during the follow-up period. in follow-up examinations, all iols were well centered, and no cases of iol tilt or capture were observed. in the last follow-up, all patients were satisfied with their quality of vision, and none of them were dependent on spectacles for distance vision. patients undergoing either type of iol had comparable refractive outcomes and complications (table 4). postoperative complications such as endophthalmitis and cystoid macular edema did not occur. description of a presenting case a 41-year-old female patient with irido-choroidal coloboma in the left eye was referred to labbafinejad medical center with the complaint of poor vision. she had a history of uneventful cataract surgery and iol implantation at another 16 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 piggyback iol in residual ametropia; karjou et al figure 1. target refraction plotted against achieved refraction. triangles depict myopic patients and bullets represent hyperopic patients. all patients were within ± 1 diopters of target refraction. eye center three weeks before her presentation to us. her udva was 20/400 in the left eye with the snellen chart. her acuity increased to 20/40, with a refraction of +10.50 –1.50 × 150. slit-lamp biomicroscopy revealed iris and choroidal coloboma in both eyes; it was more severe in the left eye, in which the posterior pole was involved. the cornea was clear. the iop was within normal limits, and the iol was well centered in the capsular bag. a review of her previous surgery records revealed implantation of a three-piece acrylic iol (acrysof, sa60at, alcon, inc.) with 7.5 diopters calculated based on srk-t formula. axial length was measured using a lenstar ls 900 non-contact biometer (haag-streit ag, switzerland). an immersion a-scan ultrasound was used to repeat the biometry. a b-scan was also achieved simultaneously. using the srk/t formula, the power of iol was calculated to be 23 diopters, which had a large difference compared with the implanted iol (15.50 diopters). to calculate the power of the piggyback iol, the se was multiplied by 1.5, and the power was calculated to be 15.5 diopters, which was exactly the same as the difference value calculated by biometry. the patient underwent a piggyback iol implantation of a three-piece foldable iol of +15.50 d (ma60ac, acrysof, alcon, inc.) in the ciliary sulcus. postoperatively, her udva reached 20/50. the se of the residual refractive error was –0.25 d. discussion the present study reviewed the indications and clinical outcomes of secondary piggyback iol implantation at a tertiary referral center over a fiveyear period. the results revealed that patients with both myopic and hyperopic ametropia following cataract surgery achieved excellent refractive outcomes after the implantation of piggyback iol in the ciliary sulcus. various surgical modalities have been proposed to correct residual ametropia following cataract surgery.[13] laser refractive procedures, iol exchange, and secondary iol implantation are available strategies.[3] selection of the best journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 17 piggyback iol in residual ametropia; karjou et al one depends on many factors, including the magnitude of residual error and the surgeon’s preferences and experience. laser refractive surgery is an effective and safe method for residual refractive error correction; however, it can create potential complications that may be more common in older patients secondary to concomitant ocular morbidities, such as dry eye and deteriorated wound healing processes.[14] considering other alternatives, iol exchange with a new iol is a very difficult procedure, which requires a high level of expertise, and would impose excessive surgical risk to patients, even if it is performed by an experienced surgeon.[15] furthermore, this procedure achieves the best results when performed soon before the formation of capsular adhesions, which is not feasible in all patients.[4, 7, 10] recently, secondary piggyback iol implantation has received more attention due to its promising safety profile and easier surgical techniques.[6, 15–18] additionally, there are many studies reporting predictable refractive outcomes with the application of power calculation of the second iol, which is not very complicated.[19] another advantage of a secondary piggyback iol over iol exchange is that the implantation of a secondary iol is a reversible procedure, and if complications such as ilo, pupillary optic capture, pigment dispersion syndrome, or pigmentary glaucoma occur, the removal of piggyback iol can be considered.[13] the present findings are in line with other studies reporting piggyback iol implantation. gayton et al reported an excellent refractive outcome in patients who underwent piggyback iol implantation.[16] similarly, they chose a minuspower iol equal to the patient’s residual spherical error. this amount was multiplied by 1.5 in hyperopic patients, regardless of keratometry or axial length.[12] however, there are various methods to calculate secondary iol power with comparable or even superior results.[20, 21] our patients did not experience any intraor postoperative complications. complications of secondary piggyback iol implantation include ilo, pupillary optic capture, pigment dispersion syndrome, pigmentary glaucoma, and other adverse events that occur generally in ocular surgeries, such as retinal detachment, postoperative endophthalmitis, or uveitis.[8–11, 22] ilo is a unique complication in piggyback implantation, which occurs mainly due to retained regenerative cortical material similar to posterior capsular opacification.[8, 23] recently, the application of different iol materials and placement of secondary iol in the ciliary sulcus, which increases the distance between two iols, have reduced the incidence of ilo.[24] accordingly, no ilo was observed in our study series because all secondary iols were placed in the ciliary sulcus. a similar outcome was observed among patients with sulcoflex iol compared to patients who underwent three-piece iol implantation. secondary piggyback iols are available as monofocal, multifocal, toric, and multifocal models.[1, 15, 17, 18] there are three types of iols specifically designed for secondary implantation in the ciliary sulcus to correct pseudophakic ametropias or presbyopia: sulcoflex (sulcoflex; rayner intraocular lenses ltd., east sussex, uk),[19] add-on (human optics, add-on iols, germany),[1] and 1st add-on (1st gmblt, mannheim, germany).[25] in addition, implantable collamer lens and artiflex phakic iol are reported to be safely implanted as secondary iols.[18–20, 26] the sulcoflex, add-on, and 1st add-on iols were designed to reduce complication rates; no significant difference was observed in our series.[12] these specifically designed iols with different powers are not always available, especially in developing countries and countries with a transitional economy. their cost can also be a concern in these situations. threepiece iols are reported to be safely placed in the ciliary sulcus and capsular bag and are the preferred types of iol in situations where ciliary sulcus implantation is needed.[27],[28] to our knowledge, the use of three-piece iols as secondary piggyback implantation has not been previously reported. herein, we reported their safety and efficacy as secondary piggyback iol implantation during an approximately two-year follow-up. additionally, we described in more detail one of our patients with choroidal coloboma who had refractive surprise after an uneventful cataract surgery. this case highlights the rare possibility of postoperative refractive surprise due to incorrect measurements of the axial length by optical devices, or a-scan without accompanying b-scan, 18 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 piggyback iol in residual ametropia; karjou et al in eyes with posterior pole retinal coloboma or staphyloma. although all patients were satisfied with their visual outcomes, the small sample size, lack of matched control group, and relatively short followup duration are the important limitations of the current study. the present study reported the indications and clinical outcomes of a series of patients who underwent secondary piggyback iol implantation for residual ametropia correction following cataract surgery. this strategy is recommended as an effective and safe technique, especially in extreme ametropia, in the presence of corneal or systemic diseases that exclude laser refractive procedures, or when excimer laser platforms are not available. financial support and sponsorship nil. conflicts of interest the authors have no proprietary or commercial interest in any materials discussed in this article. references 1. basarir b, kaya v, altan c, karakus s, pinarci ey, demirok a. the use of a supplemental sulcus fixated iol (humanoptics add-on iol) to correct pseudophakic refractive errors. european journal of ophthalmology 2012; 22: 898-903. 2. alio jl, abdelghany aa and fernández-buenaga r. management of residual refractive error after cataract surgery. current opinion in ophthalmology 2014; 25: 291297. 3. jin sx and lee jk. refractive surgical corrective options after cataract surgery. annals of eye science 2019; 4. 4. el awady he and ghanem aa. secondary piggyback implantation versus iol exchange for symptomatic pseudophakic residual ametropia. graefe’s archive for clinical and experimental ophthalmology 2013; 251: 1861-1866. 5. gayton jl and sanders vn. implanting two posterior chamber intraocular lenses in a case of microphthalmos. journal of cataract & refractive surgery 1993; 19: 776-777. 6. masket s. piggyback intraocular lens implantation. journal of cataract & refractive surgery 1998; 24: 569-570. 7. fernández-buenaga r, alió jl, ardoy al, quesada al, pinilla-cortés l, barraquer ri. resolving refractive error after cataract surgery: iol exchange, piggyback lens, or lasik. journal of refractive surgery 2013; 29: 676-683. 8. gayton jl, apple dj, peng q, visessook n, sanders v, werner l, et al. interlenticular opacification: clinicopathological correlation of a complication of posterior chamber piggyback intraocular lenses. journal of cataract & refractive surgery 2000; 26: 330-336. 9. iwase t and tanaka n. elevated intraocular pressure in secondary piggyback intraocular lens implantation. journal of cataract & refractive surgery 2005; 31: 18211823. 10. mehta r and aref aa. intraocular lens implantation in the ciliary sulcus: challenges and risks. clinical ophthalmology 2019; 13: 2317-2323. 11. kim sk, lanciano jr rc and sulewski me. pupillary block glaucoma associated with a secondary piggyback intraocular lens. journal of cataract & refractive surgery 2007; 33: 1813-1814. 12. gayton j and raanan m. reducing refractive error in high hyperopes with double implants. maximizing results: strategies in refractive, corneal, cataract and glaucoma surgery thorofare, nj: slack 1996: 139-148. 13. sáles cs and manche ee. managing residual refractive error after cataract surgery. journal of cataract & refractive surgery 2015; 41: 1289-1299. 14. battat l, macri a, dursun d, pflugfelder sc. effects of laser in situ keratomileusis on tear production, clearance, and the ocular surface. ophthalmology 2001; 108: 1230-1235. 15. trindade fc. secondary piggyback with pmma iol for the correction of refractive surprise after phacoemulsification long-term results of 20 cases. revista brasileira de oftalmologia 2013; 72: 8-11. 16. gayton jl, sanders v, van der karr m, raanan mg. piggybacking intraocular implants to correct pseudophakic refractive error. ophthalmology 1999; 106: 56-59. 17. mcintyre js, werner l, fuller sr, kavoussi sc, hill m, mamalis n. assessment of a single-piece hydrophilic acrylic iol for piggyback sulcus fixation in pseudophakic cadaver eyes. journal of cataract & refractive surgery 2012; 38: 155-162. 18. sanders dr. matched population comparison of the visian implantable collamer lens and standard lasik for myopia of-3.00 to-7.88 diopters. journal of refractive surgery 2007; 23: 537-554. 19. falzon k and stewart og. correction of undesirable pseudophakic refractive error with the sulcoflex intraocular lens. journal of refractive surgery 2012; 28: 614-619. 20. habot-wilner z, sachs d, cahane m, alhalel a, desatnik h, schwalb e, et al. refractive results with secondary piggyback implantation to correct pseudophakic refractive errors. journal of cataract & refractive surgery 2005; 31: 2101-2103. 21. holladay jt, gills jp, leidlein j, cherchio m. achieving emmetropia in extremely short eyes with two piggyback posterior chamber intraocular lenses. ophthalmology 1996; 103: 1118-1123. 22. chang sh and lim g. secondary pigmentary glaucoma associated with piggyback intraocular lens implantation. journal of cataract & refractive surgery 2004; 30: 22192222. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 19 piggyback iol in residual ametropia; karjou et al 23. werner l, apple dj, pandey sk, solomon kd, snyder me, brint sf, et al. analysis of elements of interlenticular opacification. american journal of ophthalmology 2002; 133: 320-326. 24. gills jp and fenzl re. piggyback intraocular lens implantation. developments in ophthalmology 2002; 34: 209-216. 25. reiter n, werner l, guan j, li j, tsaousis kt, mamalis n, et al. assessment of a new hydrophilic acrylic supplementary iol for sulcus fixation in pseudophakic cadaver eyes. eye 2017; 31: 802. 26. akaishi l, tzelikis pf, gondim j, vaz r. primary piggyback implantation using the tecnis zm900 multifocal intraocular lens: case series. journal of cataract & refractive surgery 2007; 33: 2067-2071. 27. hayashi k and hayashi h. comparison of the stability of 1-piece and 3-piece acrylic intraocular lenses in the lens capsule. journal of cataract & refractive surgery 20 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 original article torpedo retinopathy ramesh venkatesh, ms; kushagra jain, ms; arpitha pereira, mrcsed, dnb; mb thirumalesh, md naresh kumar yadav, do, frcs department of retina and vitreous, narayana nethralaya, bangalore, india orcid: ramesh venkatesh: https://orcid.org/0000-0002-4479-9390 abstract purpose: torpedo lesions in the retina are rare. this study aimed to investigate torpedoshaped lesions in the retina in an adult population and to determine the spectrum and features of the disease. methods: the review of a database for clinical diagnosis identified nine patients who were diagnosed with torpedo-shaped lesions in the retina between june 2017 and february 2019. fundus photography and optical coherence tomography (oct) imaging were used to analyze the cases. multicolor imaging was also performed. results: nine patients with torpedo-shaped lesions in the fundus were identified. fundus images revealed that the lesion involved the macula in six eyes; in the remaining three eyes, the lesion was present outside the macula. oct identified six patients with type 1 torpedo lesions, one with type 2, and two with type 3. on multicolor imaging, the lesion was visualized as a region of increased reflectance in blue, green, and infrared light in all eyes, with notably increased infrared reflectance in eyes with focal choroidal excavation. choroidal neovascular membrane was evident in one patient on oct angiography. conclusion: torpedo lesions in the retina can occur away from the macula and exhibit features similar to those of torpedo maculopathy. as such, the authors propose a change in the nomenclature for torpedo lesions in the retina from “torpedo maculopathy” to “torpedo retinopathy.” keywords: imaging; maculopathy; retinopathy; torpedo j ophthalmic vis res 2020; 15 (2): 187–194 introduction congenital pathologies of the retinal pigment epithelium (rpe) include torpedo maculopathy correspondence to: ramesh venkatesh, ms. department of retina and vitreous, narayana nethralaya, #121/c, chord road, 1st r block rajaji nagar, bangalore 560010, india. e-mail: vramesh80@yahoo.com received: 15-03-2019 accepted: 24-11-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i2.6736 (tm), congenital hypertrophy of the rpe (chrpe), and rpe lesions apparent in gardner syndrome associated with familial adenomatosis polyposis and colon polyps. each of these pathologies has classical clinical descriptions, separating one from the other on the basis of the lesion characteristics.[1] in tm, as described by rossman and gass in 1992, the classical clinical description includes a non-progressive, this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: venkatesh r, jain k, pereira a, thirumalesh mb, yadav nk. torpedo retinopathy. j ophthalmic vis res 2020;15:187–194. © 2020 journal of ophthalmic and vision research | published by knowledge e 187 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i2.6736&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr torpedo retinopathy; venkatesh et al unilateral, horizontally oval, hypopigmented lesion(s) temporal to the fovea, with the tip pointing toward the central macula.[2, 3] chrpe is clinically described as an asymptomatic, flat, variably pigmented lesion at the level of the rpe and may have depigmented lacunae and/or a surrounding hypopigmented halo. the lesions are usually solitary; however, very rarely, they may occur in clusters sometimes referred to as congenital grouped pigmentation of the rpe or “bear tracks.”[4] chrpe has no systemic associations and rarely occurs in the macula (1%) but may enlarge over time. the rpe lesion in systemic conditions, such as gardner syndrome, are usually small (< 1 mm), multiple, and bilateral, and often located in the midperiphery.[5] however, in the clinic, there are a group of cases in which the lesions do not necessarily meet the diagnostic criteria of any of these three clinical entities. the aim of the present case series was to illustrate the spectrum of torpedo-shaped lesions in the retina, patient demographics, coinciding systemic conditions, and variable imaging appearances in patients in a tertiary eye hospital in south india and to explain the possible etiopathogenesis associated with these lesions. methods the analysis of medical records at a tertiary eye care hospital in south india identified nine patients with torpedo-shaped lesions in the retina between june 2017 and february 2019. torpedo lesions were characterized as oval, hypopigmented, or hyperpigmented lesions at the level of the rpe, with the tip of the lesion usually directed toward the macula. the medical records of these patients were reviewed and demographic information, clinical presentation, and medical history were recorded. all patients underwent fundus imaging using the topcon trc-50dx (topcon corporation, tokyo, japan) or optos (daytona, optos plc, united kingdom) devices. all patients underwent optical coherence tomography (oct), blue wavelength fundus autofluorescence (faf), and multicolor (mc) imaging using a confocal scanning laser ophthalmoscope and a heidelberg spectralis hra-oct (heidelberg engineering, dossenheim, germany). fluorescein angiography (fa) (spectralis, heidelberg engineering, heidelberg, germany) and oct angiography using the rtvue-xr avanti (optovue, fremont, ca, usa) device were performed in one patient while adaptive optics (ao) imaging using the rtx1 flood illumination-based fundus camera (imagine eyes, orsay, france) was performed in two patients. approval was obtained from the narayana nethralaya research and ethics committee. written informed consent was obtained from all patients to include anonymized data in the present research. results in the present series, nine eyes diagnosed with torpedo-shaped lesions were included. the average age of the patients (four males, five females) was 45.3 years (range, 20–67 years). all cases were unilateral, with five presenting lesions in the right eye and four with lesions in the left eye. all patients were asymptomatic on presentation. visual acuity in the affected eye ranged from 6/5 to 6/12 on the snellen visual acuity chart. the eye with 6/12 vision had significant cataract. none of the patients had any associated systemic conditions. on color fundus photography, all lesions were hypopigmented to varying degrees and were located in the temporal retina. they were oval and elongated in the horizontal axis. all lesions had a nasal pointed tip directed toward the posterior pole and a temporal rounded margin. there were varying degrees of associated hyperpigmented rpe changes surrounding the lesions. the exact location of the lesion was immediately adjacent to the fovea in four eyes, adjacent to the macula but away from the fovea in two eyes, immediately within the retinal arcade in one eye, and outside the retinal arcade in two eyes. oct was performed in all patients. the following features on oct through the torpedo lesion were searched for in each case: thinning of the inner retina; thinning of the outer nuclear layer; thinning of the inter-digitation and ellipsoid zones; presence of subretinal cleft or cavitation; and presence of hyper-reflectivity of choroid, choroidal thinning, focal choroidal excavation, and choroidal neovascular (cnv) membrane. on analysis, it was noted that the inner retina was normal in all eyes except one (patient 8). thinning of the outer nuclear layer, interdigitation zone, and ellipsoid zone was noted in all cases. subretinal cavitation/cleft was noted in two cases (patients 2 and 3). the choroid appeared normal on oct in two eyes (patients 1 and 7). 188 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 torpedo retinopathy; venkatesh et al figure 1. fundus and oct imaging of torpedo lesions (patients 1–9). the torpedo lesion in each panel is marked on the fundus image with white arrow. in panels, c, f, g and i, the torpedo lesion is located adjacent to the fovea. in panels b and e, the lesion is located adjacent to the macula but away from the fovea. in panel a, the lesion is just within the retinal arcade, and in panels d and h, the lesion is outside the retinal arcade. in every case, the oct scan passing through the torpedo lesion is depicted. thinning of the underlying choroid and increased hyper-reflectivity was noted in six cases (except patients 1, 2, and 7). focal excavation of the choroid was observed in two eyes (patients 2 and 6) [figure 1]. faf imaging using the short wavelength blue light identified the lesion as exhibiting hypoautofluorescence (af) with hyper-af boundaries in four eyes (patients 1, 2, 3, and 5), hyper af in three eyes (patients 4, 7, and 8), and a mixture of hyperand hypo-af in two eyes (patients 6 and 9). in three eyes with torpedo lesions, near infrared faf was also performed, which revealed the lesion to be hyper-af. fa in patient 3 revealed late hyper-fluorescence due to the window defect created by the torpedo lesion. oct angiography was performed in patient 6 with torpedo lesion and focal choroidal excavation, which revealed a decrease in the vessel density and flow areas in the region of the torpedo lesion, with the presence of a cnv membrane on the choriocapillaris slab [figure 2]. ao imaging in patients 3 and 9 revealed reduced cone density and increased cone spacing in the region of the lesion [figure 3]. mc imaging was performed in all eyes using the confocal scanning laser ophthalmoscopy (cslo) platform (heidelberg spectralis hra-oct, heidelberg engineering, dossenheim, germany) with a scanning field of 30° or 55° depending on the location of the lesion. the lesion was observed as a region of increased reflectance in blue, green, and infrared light in all eyes, with notably increased infrared reflectance in eyes with focal choroidal excavation. on mc images, the lesion was observed as an area of bright orange discoloration in all eyes. demographic information and imaging features are summarized in table 1. discussion in the current case series, there appeared to be similarities in terms of clinical and imaging features of torpedo lesions. all cases exhibited a hypopigmented lesion in the temporal retina, with some located immediately adjacent to the fovea and some lying outside the retinal arcade. in all cases, the lesion was oval, with a characteristic pointed tip aimed toward the macula. thus, our case series demonstrated two varieties of torpedo lesions: those involving the macula (routinely known as tm) and those lying outside the macula. the differentials for torpedo lesions lying outside the retinal arcade were chrpe and rpe lesions, observed in systemic disorders such as gardner syndrome and journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 189 torpedo retinopathy; venkatesh et al figure 2. oct angiography findings of patient 6 showing the torpedo lesion with focal choroidal excavation with presence of choroidal neovascular membrane. columns 1–5 show the automated segmentation scans through the superficial capillary plexus, deep capillary plexus, outer retina, choriocapillaris, and manual segmentation across the torpedo lesion with focal choroidal excavation, respectively. note the decreased flow areas and vessel density in the area of torpedo lesion. a choroidal neovascular membrane can be identified as well. figure 3. adaptive optics imaging of the right eye in patient 3 with torpedo lesion. raw images on adaptive optics imaging showing the exact site of cone density and spacing analysis (bold white arrow). adaptive optics imaging showing raw images, cone density, and cone spacing of right eye at 2° from the foveal center in all four quadrants. 190 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 torpedo retinopathy; venkatesh et al ta b le 1. d em og ra ph ic ,c lin ic al ,a nd im ag in g pr ofi le of pa tie nt s w ith to rp ed o le si on s in re tin a p a ti e n t a g e /s e x a ff e ct e d e ye v is u a l a cu it y c o lo r fu n d u s f u n d u s a f o c t f fa m u lt ic o lo r im a g in g a d a p ti ve o p ti cs im a g in g 1 43 /f r e 6ju n • ju st in si de su pe ro te m po ra la rc ad e h yp oa f w ith hy pe r bo rd er s • th in ni ng of th e ou te r nu cl ea rl ay er n ot do ne h yp er re fle ct an ce in b r ,g r ,i r n ot do ne • h yp op ig m en te d • th in ni ng of in te rd ig ita tio n zo ne • th in ni ng of el lip so id zo ne 2 54 /m r e 6ju n • te m po ra lt o m ac ul a h yp oa f w ith hy pe r bo rd er s • th in ni ng of th e ou te r nu cl ea rl ay er n ot do ne h yp er re fle ct an ce in ir n ot do ne • h yp op ig m en te d • th in ni ng of in te rd ig ita tio n zo ne • th in ni ng of el lip so id zo ne • pr es en ce of su br et in al cl ef t/c av ita tio n • fo ca lc ho ro id al ex ca va tio n 3 38 /m r e 6ju n • te m po ra lt o fo ve a h yp oa f w ith hy pe r bo rd er s • th in ni ng of th e ou te r nu cl ea rl ay er la te st ag e hy pe rflu or os ce nc e h yp er re fle ct an ce in b r ,g r ,i r d on e • h yp op ig m en te d • th in ni ng of in te rd ig ita tio n zo ne • th in ni ng of el lip so id zo ne • pr es en ce of su br et in al cl ef t/c av ita tio n • th in ni ng of in ne rc ho ro id 4 65 /f le 9ju n • o ut si de th e in fe ro te m po ra la rc ad e h yp er -a f • th in ni ng of th e ou te r nu cl ea rl ay er n ot do ne h yp er re fle ct an ce in b r ,g r ,i r n ot do ne • h yp op ig m en te d • th in ni ng of in te rd ig ita tio n zo ne • th in ni ng of el lip so id zo ne • th in ni ng of in ne rc ho ro id journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 191 torpedo retinopathy; venkatesh et al ta b le 1. c on tin ue d. p a ti e n t a g e /s e x a ff e ct e d e ye v is u a l a cu it y c o lo r fu n d u s f u n d u s a f o c t f fa m u lt ic o lo r im a g in g a d a p ti ve o p ti cs im a g in g 5 67 /m le 6ju n • in fe ro te m po ra lt o m ac ul a h yp oa f w ith hy pe r bo rd er s • th in ni ng of th e ou te r nu cl ea rl ay er n ot do ne h yp er re fle ct an ce in b r ,g r ,i r n ot do ne • h yp op ig m en te d • th in ni ng of in te rd ig ita tio n zo ne • th in ni ng of el lip so id zo ne • th in ni ng of in ne rc ho ro id 6 20 /f r e 6ju n • in fe ro te m po ra lt o fo ve a m ix tu re of hy po -a nd hy pe r-a f • th in ni ng of th e ou te r nu cl ea rl ay er n ot do ne h yp er re fle ct an ce in ir n ot do ne • m ix of hy po -a nd hy pe rp ig m en ta tio n • th in ni ng of in te rd ig ita tio n zo ne • th in ni ng of el lip so id zo ne • th in ni ng of in ne rc ho ro id , fo ca lc ho ro id al ex ca va tio n 7 33 /f le 6ju n • te m po ra lt o fo ve a h yp er -a f w ith fo ca l hy po -a f • th in ni ng of th e ou te r nu cl ea rl ay er n ot do ne h yp er re fle ct an ce in b r ,g r ,i r n ot do ne • h yp op ig m en te d • th in ni ng of in te rd ig ita tio n zo ne • th in ni ng of el lip so id zo ne 8 63 /f le 12 -j un • o ut si de th e in fe ro te m po ra la rc ad e h yp er -a f • th in ni ng of in ne rr et in a n ot do ne h yp er re fle ct an ce in b r ,g r ,i r n ot do ne • h yp op ig m en te d • th in ni ng of th e ou te r nu cl ea rl ay er • th in ni ng of in te rd ig ita tio n zo ne • th in ni ng of el lip so id zo ne • th in ni ng of in ne rc ho ro id 9 25 /m r e 6ju n • te m po ra lt o fo ve a m ix tu re of hy po -a nd hy pe r-a f • th in ni ng of th e ou te r nu cl ea rl ay er n ot do ne h yp er re fle ct an ce in b r ,g r ,i r d on e • h yp op ig m en te d • th in ni ng of in te rd ig ita tio n zo ne • th in ni ng of el lip so id zo ne • th in ni ng of in ne rc ho ro id m ,m al e; f, fe m al e; r e, rig ht ey e; le ,l ef te ye ;a f, au to flu or es ce nc e; o c t, op tic al co he re nc e to m og ra ph y; ff a ,f un du s flu or es ce in an gi og ra ph y; b r ,b lu e re fle ct an ce ;g r , gr ee n re fle ct an ce ;i r ,i nf ra re d re fle ct an ce 192 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 torpedo retinopathy; venkatesh et al familial adenomatous polyposis. chrpe is a flat congenital rpe lesion that appears pigmented or nonpigmented and characteristically has rounded or scalloped margins.[6] solitary chrpe is located most often in the equatorial or peripheral fundus, randomly in various quadrants, and rarely in the macula (1%).[1, 6] the rpe abnormalities associated with familial adenomatous polyposis and gardner syndrome are also similar to tm. however, individuals with familial adenomatous polyposis manifest a random distribution in the fundus and are often bilateral, significantly smaller, and more irregular in shape.[1, 7] the clinical description of torpedo lesion in our cases did not match with either chrpe or rpe lesions associated with systemic disorders. although a torpedo lesion is classically described as a solitary oval lesion with variable pigmentation, satellite lesions can also occur, as observed in patients 1 and 5 of our series. all satellite lesions reported to date have been located temporally and are usually small, round, and flat. oct imaging through the satellite lesions reveals changes similar to those in the main torpedo lesion. satellite lesions may add to our understanding of the morphology of these lesions because they appear to be an extension of the main lesion. the common features described on oct in eyes for scans passing through the tm lesion included thinning of the outer nuclear layer, interdigitation zone, ellipsoid zone, and inner choroid in all cases. additional features described by wong et al,[8] such as the presence of subretinal cavitation, have helped in classifying torpedo lesions into types 1 and 2. focal retinal and choroidal excavation in torpedo lesions were described as type 3 oct findings by tripathy et al.[9] similar oct features were noted for lesions lying outside the macula in the present series. no subretinal cavitation/cleft or focal excavation of the retina and/or choroid was noted in eyes in which the torpedo lesions were present outside the macula. mc imaging signatures of torpedo lesions in the series coincided with data previously published by our group.[10] the etiology of torpedo-shaped lesions in the retina remains speculative. due to the consistent location of torpedo lesions in previous reports of tm, the most commonly accepted hypothesis is a persistent defect in the development of rpe in the fetal temporal bulge.[11] in one patient who underwent ao imaging, we found fewer cone photoreceptors and increased cone spacing in the region of the torpedo lesion. however, the presence of lesions in regions other than the macula in our series explains the need to determine an alternative hypothesis for the development of torpedo lesions. the most probable explanation for the presence of these lesions could be abnormal choroidal vasculature, as observed on oct angiography as a loss of choriocapillaris in the area of the lesion.[12, 13] a similar finding was also noted in our case. however, in this series, oct angiography scans through the lesions located outside the macula could not confirm the probable choroidal vascular hypothesis. although, patients with torpedo lesions are asymptomatic and experience a benign and nonprogressive disease course, the cnv membrane in tm has been described.[14, 15] the presence of cnv can lead to disturbance in vision and deterioration in visual acuity. patient 6 in our series developed cnv. previous studies have suggested that patients exhibiting outer retinal damage and choroidal thinning have a higher risk for developing cnv. thus, we suggest that cnv development in torpedo lesions can occur in patients with type 2 or 3 findings on oct. to conclude, we present a series of cases in an adult population with torpedo-shaped lesions in the retina. contrary to previous reports in which torpedo lesions were classically described at the macula, in this series, we present cases located in the temporal half of the retina, away from the macula, outside the arcades, and exhibiting phenotypic and imaging features similar to those of tm. based on the findings from the current case series, we believe that torpedo lesions in the retina occur secondary to changes in the choroidal vasculature. furthermore, we propose a change in the nomenclature of torpedo lesions in the retina from “torpedo maculopathy” to “torpedo retinopathy.” financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 193 torpedo retinopathy; venkatesh et al references 1. villegas vm, schwartz sg, flynn hw jr, capó h, berrocal am, murray tg, et al. distinguishing torpedo maculopathy from similar lesions of the posterior segment. ophthalmic surg lasers imaging retina 2014;45:222–226. 2. roseman rl, gass jdm. solitary hypo-pigmented nevus of the retinal pigment epithelium in the macula. arch ophthalmol 1992;110:1358–1359. 3. golchet pr, jampol lm, mathura jr jr, daily mj. torpedo maculopathy. br j ophthalmol 2010;94:302–306. 4. traboulsi ei. pigmented and depigmented lesions of the ocular fundus. curr opin ophthalmol 2012;23:337–343. 5. traboulsi ei. ocular manifestations of familial adenomatous polyposis (gardner syndrome). ophthalmol clin north am 2005;18:163–166. 6. shields cl, mashayekhi a, ho t, cater j, shields ja. solitary congenital hypertrophy of the retinal pigment epithelium: clinical features and frequency of enlargement in 330 patients. ophthalmology 2003;110:1968–1976. 7. shields ja, shields cl. tumors and related lesions of the pigment epithelium. in: shields ja, shields cl, editors. intraocular tumors: an atlas and textbook. 2nd ed. philadelphia, pa: lippincott williams & wilkins; 2008:431–480. 8. wong en, fraser-bell s, hunyor ap, chen fk. novel optical coherence tomography classification of torpedo maculopathy. clin exp ophthalmol 2015;43:342–348. 9. tripathy k, sarma b, mazumdar s. commentary: inner retinal excavation in torpedo maculopathy and proposed type 3 lesions in optical coherence tomography. indian j ophthalmol 2018;66:1213–1214. 10. venkatesh r, bavaharan b, yadav nk. multicolor imaging findings in torpedo maculopathy. indian j ophthalmol 2019;67:295–297. 11. shields cl, guzman jm, shapiro mj, fogel le, shields ja. torpedo maculopathy at the site of the fetal ”bulge”. arch ophthalmol 2010;128:499–501. 12. hamm c, shechtman d, reynolds s. a deeper look at torpedo maculopathy. clin exp optom 2017;100:563–568. 13. chawla r, pujari a, rakheja v, kumar a. torpedo maculopathy: a primary choroidal capillary abnormality? indian j ophthalmol 2018;66:328–329. 14. parodi mb, romano f, montagna m, albertini gc, pierro l, arrigo a, et al. choroidal neovascularization in torpedo maculopathy assessed on optical coherence tomography angiography. ophthalmic surg lasers imaging retina 2018;49:e210–e213. 15. shirley k, o’neill m, gamble r, ramsey a, mcloone e. torpedo maculopathy: disease spectrum and associated choroidal neovascularisation in a paediatric population. eye 2018;32:1315–1320. 194 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 original article efficacy of intravitreal dexamethasone implant in different patterns of diabetic macular edema claudio furino, md, phd1; alfredo niro, md, phd2; michele reibaldi, md, phd3 francesco boscia, md4; giovanni alessio, md1 1department of medical science, neuroscience and sense organs, eye clinic, university of bari, bari, italy 2eye clinic, hospital “s. g. moscati”, asl ta, taranto, italy 3eye clinic, university of catania, catania, italy 4department of surgical, microsurgical and medical sciences, eye clinic, university of sassari, sassari, italy orcid: claudio furino: https://orcid.org/0000-0003-0254-7432 abstract purpose: different patterns of diabetic macular edema (dme) suggest different pathogenesis and drug response. we evaluated the outcomes after intravitreal dexamethasone (dex) implant for dme with or without serous retinal detachment (srd). methods: in this retrospective study, 22 naïve patients (23 eyes) with dme who underwent a single dex implant were evaluated. based on the optical coherence tomographic pattern of dme, 12 eyes had a cystoid macular edema pattern (group 1) and 11 eyes had an srd pattern (group 2). the best-corrected visual acuity (bcva), central retinal thickness (сrт), central retinal volume (crv), srd height (srdh), and intraocular pressure (iop) were recorded before and at two and four months after the treatment. results: there were no significant differences between the groups regarding demographic, clinical data and outcomes at baseline. in group 1, the crt and crv significantly decreased at two months (p = 0.002 and p = 0.01, respectively), while the bcva significantly improved at four months (p = 0.03). in group 2, the crt and crv significantly improved (p < 0.01 and p ≤ 0.01, respectively) during the follow-up period. at four months, both groups showed a recurrence of dme, group 1 in particular (two-month crt reduction, –149 ± 127 µm vs four-month crt reduction, –72 ± 174 µm; p = 0.04). the mean reduction in crv was significantly different at four months (group 1, –0.49 ± 1.7 mm3 vs group 2, –1.3 ± 1.3 mm3; p = 0.04). in group 2, the srdh significantly decreased at two (p = 0.01) and four months (p = 0.01). four cases with elevated iop were managed. conclusion: dex implants were found to be effective in different patterns of dme. the srd pattern may predict a longer-lasting morphologic efficacy. keywords: dexamethasone implant; diabetic macular edema; oct, ozurdex®; subretinal detachment j ophthalmic vis res 2020; 15 (4): 524–530 correspondence to: claudio furino, md, phd. department of medical science, neuroscience and sense organs, eye clinic, university of bari, piazza g. cesare, 1170124 bari, italy. email: claudiofurino@gmail.com received: 10-07-2019 accepted: 05-08-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7787 introduction diabetic macular edema (dme) is the main cause of visual loss in diabetic patients.[1] different patterns this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: furino c, niro a, reibaldi m, boscia f, alessio g. efficacy of intravitreal dexamethasone implant in different patterns of diabetic macular edema. j ophthalmic vis res 2020;15:524–530. 524 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7787&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr dexamethasone implant for diabetic macular edema; furino et al of nontractional macular edema have been revealed by optical coherence tomography (oct) including sponge-like swelling, cystoid macular edema (cme), and serous retinal detachment (srd).[2, 3] however, many eyes show more than one macular edema pattern in oct.[2–6] different patterns of cme and srd suggest different mechanisms of pathogenesis,[7–9] which lead us to speculate various possible mechanisms of drug action. at present, several pharmacologic approaches are effective for treating dme, including intravitreal anti-vascular endothelial growth factor (vegf) agents and intravitreal steroid implants. corticosteroids are effective owing to their anti-inflammatory, antiangiogenic, and blood retinal barrier (brb)stabilizing properties.[10] in dme, the sustainedrelease intravitreal dexamethasone (dex) implant was observed to be effective, requiring less frequent repeated injections as compared to anti-vegfs, with common complications such as intraocular pressure (iop) elevation and cataract formation/progression.[11] in an analysis of data from a phase ii randomized controlled study (nct00035906), dex implants were found to display a similar efficacy in different patterns of dme without reference to srd.[12] the purpose of this study was to analyze the safety and efficacy of a intravitreal dex implant in the treatment of diabetic cme with and without subretinal fluid. methods in this retrospective study, 23 eyes of 22 diabetic patients with clinically significant dme, as defined by the early treatment diabetic retinopathy study (etdrs),[13] were included. nontractional dme involving the central macula (1 mm central subfield thickness in the oct-modified etdrs grid) with a thickness ≥ 300 μm was considered. eyes with diffuse spongiform edema, advanced proliferative diabetic retinopathy, other retinal pathologies, or those who underwent previous laser photocoagulation within six months, ocular surgery, or intravitreal injection were excluded. patient data including age, sex, duration of diabetes, and baseline glycated hemoglobin (hba1c) levels were recorded. a complete ophthalmologic examination including bestcorrected visual acuity (bcva) measurement, slit-lamp examination, iop measurement, and fundus examination were performed before as well as two and four months after the treatment. bcva measured by etdrs chart was converted into a logmar notation for statistical analysis. at each visit, five hd-lines and macular cube (512 × 128) oct scans were performed using the cirrus sd-oct 4000 (carl zeiss meditec, inc., dublin, california, usa). the eligible eyes were categorized into two groups according to the oct pattern of macular edema: group 1 with cme consisting of intraretinal hyporeflective cystoid spaces and group 2 with intraretinal edema associated with srd. the central retinal thickness (crt, µm) at the foveal site and the central retinal volume (crv, mm3) for each group were recorded. in group 2, the maximum srd height (srdh, µm) at the fixation point was measured manually using calipers in the “high definition image analysis” mode (hd-oct software version 5, cirrus sd-oct 4000, carl zeiss meditec, inc, dublin, california, usa) and was defined as the average distance between the retinal pigment epithelium (rpe) and the outer neurosensory retinal surface on central vertical and horizontal scans. all oct scans and measurements were collected by the same observer. all patients received a single dose (700 µg) of dex as a sustained-release intravitreal implant (ozurdex®, allergan, inc., irvine, ca, usa). the mean bcva, crt, and crv changes were analyzed at all visits. the study was approved by the institutional review board (irb) of an eye clinic in italy and adhered to the tenets of the declaration of helsinki. an irb approved informed consent was obtained from all patients. quantitative data are presented as mean ± standard deviation. data from the same sample were analyzed using the wilcoxon test. the differences between the two samples before and after the implantation were assessed using fisher’s test for categorical variables and the mann– whitney test for quantitative variables. the sample size was determined considering a confidence level of 95% and a confidence interval of 20. a p-value < 0.05 was considered as statistically significant. statistical analysis was performed using graphpad prism, version 5. results twenty-three naïve eyes of 22 patients with type 2 diabetes mellitus were included. the patients journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 525 dexamethasone implant for diabetic macular edema; furino et al included 6 (27.3%) women and 16 (72.7%) men, with a mean age of 62 ± 7.7 years (range, 42–76 years). the mean overall diabetes duration was 6.4 ± 3.4 years, and the hba1c mean value was 7.5 ± 1% (table 1). all eyes were phakic with a mild-tomoderate grade cataract. of the 23 eyes, 12 (52%) had a cme pattern (group 1) and 11 (48%) had an srd pattern (group 2) on oct analysis. there was no statistically significant difference between the two groups in terms of age, sex, mean diabetes duration, or hba1c value (table 1). the mean overall bcva, crt, and crv improved significantly at two and four months after the dex implantation (table 2). in group 1, the mean bcva improved from 0.66 ± 0.34 logmar (snellen equivalent of 20/91) at baseline to 0.37 ± 0.17 logmar (snellen equivalent of 20/47) (p = 0.06) at two months and 0.32 ± 0.19 logmar (snellen equivalent of 20/42) at four months (p = 0.03). the mean crt decreased from 478 ± 147 µm at baseline to 329 ± 100 µm at two months (p = 0.002) and 405 ± 132 µm at four months (p = 0.15). the mean crv decreased from 12.8 ± 1.9 µm3 at baseline to 11.1 ± 1.5 mm3 at two months (p = 0.01) and 12.3 ± 1.7 mm3 at four months (p = 0.58; table 2). in group 2, the mean bcva improved from 0.65 ± 0.43 logmar (snellen equivalent of 20/89) at baseline to 0.42 ± 0.23 logmar (snellen equivalent of 20/53) at two months (p = 0.35) and 0.39 ± 0.24 logmar (snellen equivalent of 20/49) at four months (p = 0.39). the mean crt decreased from 542 ± 131µm at baseline to 347 ± 97 µm at two months (p = 0.006) and 393 ± 109 µm at four months (p = 0.003). the mean crv decreased from 13.7 ± 1.8 mm3 at baseline to 11.6 ± 1.5 mm3 at two months (p = 0.007) and 12.4 ± 1.0 mm3 at four months (p = 0.01; table 2). at baseline and over follow-up, no significant difference was observed in the functional and morphologic outcomes among the groups (p > 0.05) (table 2). the overall crt reduction over two months was significantly larger than the reduction observed over four months (p = 0.03). in the same way, the overall crv reduction over two months was significantly larger than the reduction observed over four months (p = 0.02). the difference between the mean change in bcva over the first two months and the overall four months was not statistically significant (p = 0.26). at the last follow-up, an improvement of three lines or more was reported in 12 (52%) patients; 7 (58%) in the cme group and five (45%) in the srd group (p = 0.6). the difference between bcva improvement over the first two and the overall four months within each group and among the groups was not statistically significant (p > 0.05). in each group, mainly in group 1, the mean crt and crv reduction after two months of follow-up were larger than those observed four months after the implantation. the mean reduction in crv was significantly different among the groups four months after the implantation (p = 0.04) (table 3). in group 2, the srdh significantly decreased at months 2 (p = 0.01) and 4 (p = 0.01) without a significant difference in the mean change at two time points (table 4). in group 2, a total resolution of srd was reported in three (27.3%) eyes and two (18.2%) eyes at two and four months, respectively. of the three eyes with a resolution of srd at two months, only one (9%) remained without any srd at four months. all eyes had a resolution of subretinal detachment without resolution of overlying neuroretinal edema. three eyes (13%) had a mild iop elevation (<25 mmhg), and only one case (3.8%) developed a high iop elevation (30 mmhg). all cases were medically managed. no other ocular adverse events were reported. discussion oct is the most useful tool for diagnosing and monitoring dme. based on the oct features of dme, we focused our study on the therapeutic efficacy of ozurdex® on two different patterns of nontractional dme, namely, the cystoid pattern and the retinal detachment pattern that occur in patients with diabetic retinopathy with a prevalence from 47–55%[2, 4] and from 15– 31%,[2, 5, 6] respectively. in our study, both systemic risk factors and morpho-functional data at baseline did not show significant differences among the two oct-pattern groups, allowing us to evaluate the effectiveness of the drug in two similar populations. moreover, vujosevic et al reported that systemic parameters, such as glycemic control and arterial hypertension, did not correlate with the presence of subretinal detachment, thus suggesting that ocular factors might be more important in the development of the features of dme.[14] intravitreal dex implants have demonstrated efficacy in the treatment of dme, causing both 526 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 dexamethasone implant for diabetic macular edema; furino et al table 1. characteristics of patients and their systemic risk factors. total group 1 group 2 p-value∗ female/male (no. of eyes) 6/16 23 4/8 12 2/8 11 0.43† mean age (yrs) ± sd 65 ± 10 67 ± 10 64 ± 9 0.35 mean diabetes duration (yrs) ± sd 6.4 ± 3.4 7.2±4.1 4.5 ± 1.6 0.06 hba1c (%) 7.5 ± 1 7.5 ± 0.9 7.4 ± 0.8 0.78 sd, standard deviation; hba1c, glycosylated hemoglobin; drt, diffuse retinal thickening; cme, cystoid macular edema; srd, serous retinal detachment ∗p-value (mann–whitney test); †p-value (fisher test) between groups 1 and 2; p-values < 0.05 were considered statistically significant table 2. the mean bcva, crt, and crv before and after the treatment at months 2 and 4 total group 1 group 2 p-value* baseline bcva (logmar ± sd) crt (μm ± sd) crv (mm3 ± sd) 0.66 ± 0.38 508 ± 141 13.2 ± 1.9 0.66 ± 0.34 478 ± 147 12.8 ± 1.9 0.65 ± 0.43 542 ± 131 13.7 ± 1.8 0.38 0.38 0.32 2𝑛𝑑 month bcva (logmar ± sd) p† crt (μm ± sd) p† crv (mm3 ± sd) p† 0.39 ± 0.19 0.03 337 ± 97 < 0.0001 11.4 ± 1.5 0.0002 0.37 ± 0.17 0.06 329 ± 100 0.002 11.1 ± 1.5 0.01 0.42 ± 0.23 0.26 347 ± 97 0.006 11.6 ± 1.5 0.007 0.58 0.77 0.29 4𝑡ℎ month bcva (logmar ± sd) p† crt (μm ± sd) p† crv (mm3 ± sd) p† 0.36 ± 0.21 0.02 398 ± 119 0.001 12.4 ± 1.4 0.001 0.32 ± 0.19 0.03 401 ± 133 0.15 12.3 ± 1.7 0.58 0.39 ± 0.24 0.19 393 ± 109 0.003 12.4 ± 1.0 0.01 0.44 0.97 0.64 bcva, best corrected visual acuity; logmar, logarithm of minimum angle of resolution; sd, standart deviation; crt, central retinal thickness; crv, central retinal volume; cme, cystoid macular edema; srd, serous retinal detachment ∗p-values (mann–whitney test), comparison between groups 1 and 2; †p-value (wilcoxon test), comparison between baseline and follow-up data (at two and four months) for all patients, and within single groups; p-value < 0.05 was considered statistically significant substantial improvement in bcva and significant reduction of crt.[11] in the current study, the mean overall bcva showed a statistically significant improvement with a larger increase at four months after the dex implant. an improvement of three lines or more was reported in 52% of patients without differences among the groups. these results are in line with those previously published.[11, 15–19] we observed that the mean bcva of the srd group remained lower than that of the group with a cystoid pattern over the follow-up period, and that the single-group analysis showed an equal trend of functional improvement without a significant difference in the mean functional recovery between the groups, as previously reported.[20] however, only the eyes with cme showed a significant improvement in visual acuity at four months. gaucher et al[21] suggested that the presence of subretinal fluid does not seem to be a negative prognostic factor, journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 527 dexamethasone implant for diabetic macular edema; furino et al table 3. the mean change of bcva, crt, and crv over four months. total group 1 (cme) group 2 (srd) p-value∗ bcva change (0–2 month) (logmar ± sd) crt change (0–2 month) (μm ± sd) crv change (0–2 month) (μm3 ± sd) –0.31 ± 0.51 –171 ± 135 –1.8 ± 1.76 –0.29 ± 0.46 –149 ± 127 –1.6 ± 1.7 –0.23 ± 0.64 –195 ± 146 –2.1 ± 1.9 0.71 0.34 0.56 mean bcva change (0–4 month) (logmar ± sd) p† mean crt change (0–4 month) (μm ± sd) p† mean crv change (0–4 month) (μm3 ± sd) p† –0.30 ± 0.54 0.26 –109 ± 150 0.03 –0.90 ± 1.56 0.02 –0.33 ± 0.46 0.21 –72 ± 174 0.04 –0.49 ± 1.7 0.10 –0.26 ± 0.64 0.56 –149 ± 123 0.37 –1.3 ± 1.3 0.10 0.64 0.06 0.04 bcva, best corrected visual acuity; logmar, logarithm of minimum angle of resolution; sd, standard deviation; crt, central retinal thickness; crv, central retinal volume; cme, cystoid macular edema; srd, serous retinal detachment ∗p-value (mann–whitney test), comparison between group 1 and group 2; †p-value (wilcoxon test), comparison within single groups; p-values < 0.05 were considered statistically significant table 4. serous retinal detachment height changes over follow-up group 2 (11 eyes) baseline 2𝑛𝑑 month 4𝑡ℎ month p-value∗ srdh (μm ± sd) p† srdh change (μm ± sd) 146 ± 82 72 ± 75 0.01 –74 ± 71 90 ± 61 0.01 –55 ± 59 0.38 srdh, serous retinal detachment height; sd, standard deviation ∗p-value (wilcoxon test), comparison between srdh changes at different follow-ups; †p-value (wilcoxon test), comparison with baseline; p-value < 0.05 was considered statistically significant while other authors have shown that the srd pattern had a worse prognosis on functional recovery after treatment as compared to the cme pattern[22–26] considering that subretinal fluid could induce photoreceptor degradation which would decrease its metabolism.[27] overall, the mean crt and crv showed a statistically significant reduction at all follow-up visits. the largest reduction in crt and crv was observed at two months when dex reached the highest concentration in the vitreous humor.[28] in both groups, we observed a reduction in the mean crt and crv at two months, followed by a moderate increase at four months. the group with a cystoid pattern showed less reduction and a significant recurrence of edema over follow-up, while the eyes with subretinal fluid showed a larger crt and crv reduction at two and four months, and a lower recurrence of edema than the eyes with cystoid edema. deepening the analysis, the srdh significantly decreased at all followup visits, showing the same trend of crt and crv. in the srd group, four patients showed a total resolution of subretinal detachment without resolution of overlying neuroretinal edema at different follow-up visits. the resolution of the subretinal fluid could appear despite persistence or worsening of the neuroretinal swelling and preceding or following its resolution.[21] horii et al[9] suggested several mechanisms causing different oct patterns of dme due to brb breakdown, including the movement of serum proteins, lipids, 528 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 dexamethasone implant for diabetic macular edema; furino et al blood constituents, and small molecules from or to the cystoid spaces. the inner brb dysfunction, at tight junctions and transendothelial vesicular transport in the capillary endothelial cells, leads to neuroretinal fluid accumulation causing edema.[7] in the cystoid pattern of dme, the occurrence of cysts from degenerating retinal mϋller cells remains a subject of debate, but their role in the formation of this pattern is certain.[29] an srd pattern has been postulated to be the result of the movement of fluid from the retina to the subretinal space.[8] the leakage of albumin into the subretinal space brings out fluid, but this does not explain the presence of retinal detachment when the subretinal osmotic pressure equilibrates with the vitreal space.[30, 31] other mechanisms can be involved in favoring subretinal fluid accumulation and might be targeted by steroid therapy. in this regard, external limiting membrane dysfunction can promote the diffusion of proteins into the subretinal space,[32–35] rpe pump failure found in diabetics and favored by a hypoxic state,[36, 37] and reduction of choroidal flow that would induce rpe dysfunction.[38] corticosteroids have a wide spectrum of antiinflammatory and anti-edema effects. in particular, these effects include the stabilization of the brb and increasing the integrity of tight junctions of the endothelial cells of blood vessels, leading to reduction of exudation and downregulation of inflammation.[39] therefore, our data suggest a greater and more lasting improvement in the morphologic outcomes of crt and crv in eyes with an srd pattern than eyes with cme features after a dex implant, probably due to a greater stabilization of the outer brb. regarding safety, few cases (4/23, 17.4%) had an iop elevation that could be managed pharmacologically without any surgical approach. this study has several limitations, including its retrospective, short-term, open-label, uncontrolled nature involving a relatively small number of eyes, which precluded any evaluation of longterm efficacy and need for ozurdex® reinjection. we selected only naïve patients with the aim of evaluating the therapeutic efficacy of dex implant as the first treatment, even though we are aware that these eyes are more responsive than eyes with dme refractory to anti-vegf.[40] a comparative analysis of the efficacy of dex on different oct patterns of dme between naïve and refractory eyes should be performed. in conclusion, the anatomical and functional improvements reported in our work could suggest a different therapeutic response of different patterns of dme to slow-release intravitreal dex implants. our findings are worthy of investigation in order to develop customized therapies for different tomographic patterns of dme. financial support and sponsorship none. conflicts of interest there are no conflicts of interest. references 1. yau jw, rogers sl, kawasaki r, lamoureux el, kowalski jw, bek t, et al. global prevalence and major risk factors of diabetic retinopathy. diabetes care 2012;35:556–564. 2. otani t, kishi s, maruyama y. patterns of diabetic macular edema with optical coherence tomography. am j ophthalmol 1999;127:688–693. 3. trichonas g, kaiser pk. optical coherence tomography imaging of macular oedema. br j ophthalmol 2014;98:24– 29. 4. kim by, smith sd, kaiser pk. optical coherence tomographic patterns of diabetic macular edema. am j ophthalmol 2006;142:405–412. 5. catier a, tadayoni r, paques m, erginay a, haouchine b, gaudric a, et al. characterization of macular edema from various etiologies by optical coherence tomography. am j ophthalmol 2005;140:200–206. 6. ozdemir h, karacorlu m, karacorlu s. serous macular detachment in diabetic cystoid macular oedema. acta ophthalmol scan 2005;83:63–66. 7. antonetti da, barber aj, khin s, lieth e, tarbell jm, gardner tw. vascular permeability in experimental diabetes is associated with reduced endothelial occludin content: vascular endothelial growth factor decreases occludin in retinal endothelial cells. penn state retina research group. diabetes 1998;47:1953–1959. 8. otani t, kishi s. tomographic assessment of vitreous surgery for diabetic macular edema. am j ophthalmol 2000;129:487–494. 9. horii t, murakami t, nishijima k, akagi t, uji a, arakawa n, et al. relationship between fluorescein pooling and optical coherence tomographic reflectivity of cystoid spaces in diabetic macular edema. ophthalmology 2012;119:1047– 1055. 10. ford ja, lois n, royle p, clar c, shyangdan d, waugh n. current treatments in diabetic macular oedema: systematic review and meta-analysis. bmj open 2013;1:3. 11. boyer ds, yoon yh, belfort r jr, bandello f, maturi rk, augustin aj, et al. ozurdex mead study group. threeyear, randomized, sham-controlled trial of dexamethasone intravitreal implant in patients with diabetic macular edema. ophthalmology 2014;121:1904–1914. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 529 dexamethasone implant for diabetic macular edema; furino et al 12. kuppermann bd, chou c, weinberg dv, whitcup sm, haller ja, blumenkranz ms, et al. intravitreous dexamethasone effects on different patterns of diabetic macular edema. arch ophthalmol 2010;128:642–643. 13. photocoagulation for diabetic macular edema. early treatment diabetic retinopathy study report number 1. early treatment diabetic retinopathy study research group. arch ophthalmol 1985;103:1796–1806. 14. vujosevic s, torresin t, berton m, bini s, convento e, midena e. diabetic macular edema with and without subfoveal neuroretinal detachment: two different morphological and functional entities. am j ophthalmol 2017;181:149–155. 15. guigou s, pommier s, meyer f, hajjar c, merite py, parrat e, et al. efficacy and safety of intravitreal dexamethasone implant in patients with diabetic macular edema. ophthalmologica 2015;233:169–75. 16. mastropasqua r, toto l, borrelli e, di antonio l, de nicola c, mastrocola a, et al. morphology and function over a one-year follow up period after intravitreal dexamethasone implant (ozurdex) in patients with diabetic macular edema. plos one 2015;10:e0145663. 17. matonti f, pommier s, meyer f, hajjar c, merite py, parrat e, et al. long-term efficacy and safety of intravitreal dexamethasone implant for the treatment of diabetic macular edema. eur j ophthalmol 2016;26:454–459. 18. aknin i, melki l. longitudinal study of sustained-release dexamethasone intravitreal implant in patients with diabetic macular edema. ophthalmologica 2016;235:187– 188. 19. pareja-ríos a, ruiz-de la fuente-rodríguez p, bonaquegonzález s, lópez-gálvez m, lozano-lópez v, romeroaroca p. intravitreal dexamethasone implants for diabetic macular edema. int j ophthalmol 2018;11:77–82. 20. castro-navarro v, cervera-taulet e, navarro-palop c, monferrer-adsuara c, hernández-bel l, monterohernández j. intravitreal dexamethasone implant ozurdex® in naïve and refractory patients with different subtypes of diabetic macular edema. bmc ophthalmol 2019;19:15. 21. gaucher d, sebah c, erginay a, haouchine b, tadayoni r, gaudric a, et al. optical coherence tomography features during the evolution of serous retinal detachment in patients with diabetic macular edema. am j ophthalmol 2008;145:289–296. 22. kim m, lee p, kim y, yu sy, kwak hw. effect of intravitreal bevacizumab based on optical coherence tomography patterns of diabetic macular edema. ophthalmologica 2011;226:138–144. 23. shimura m, yasuda k, yasuda m, nakazawa t. visual outcome after intravitreal bevacizumab depends on the optical coherence tomographic patterns of patients with diffuse diabetic macular edema. retina 2013;33:740–747. 24. wu pc, lai ch, chen cl, kuo cn. optical coherence tomographic patterns in diabetic macula edema can predict the effects of intravitreal bevacizumab injection as primary treatment. j ocul pharmacol ther 2012;28:59–64. 25. roh mi, kim jh, kwon ow. features of optical coherence tomography are predictive of visual outcomes after intravitreal bevacizumab injection for diabetic macular edema. ophthalmologica 2010;224:374–380. 26. shimura m, yasuda k, nakazawa t, hirano y, sakamoto t, ogura y, et al. visual outcome after intravitreal triamcinolone acetonide depends on optical coherence tomographic patterns in patients with diffuse diabetic macular edema. retina 2011;31:748–754. 27. murakami t, nishijima k, akagi t, uji a, horii t, ueda-arakawa n, et al. optical coherence tomographic reflectivity of photoreceptors beneath cystoid spaces in diabetic macular edema. invest ophthalmol vis sci 2012;53:1506–1511. 28. chang-lin je, attar m, acheampong aa, robinson mr, whitcup sm, kuppermann bd, et al. pharmacokinetics and pharmacodynamics of a sustained-release dexamethasone intravitreal implant. invest ophthalmol vis sci 2011;52:80–86. 29. daruich a, matet a, moulin a, kowalczuk l, nicolas m, sellam a, et al. mechanisms of macular edema: beyond the surface. prog retin eye res 2018;63:20–68. 30. takeuchi a, kricorian g, marmor mf. albumin movement out of the subretinal space after experimental retinal detachment. invest ophthalmol vis sci 1995;36:1298– 1305. 31. kang sw, park cy, ham di. the correlation between fluorescein angiographic and optical coherence tomographic features in clinically significant diabetic macular edema. am j ophthalmol 2004;137:313–322. 32. soliman w, sander b, jorgensen tm. enhanced optical coherence patterns of diabetic macular oedema and their correlation with the pathophysiology. acta ophthalmol scan 2007;85:613–617. 33. augustin a, loewenstein a, kuppermann bd. macular edema. general pathophysiology. dev ophthalmol 2010;47:10–26. 34. scholl s, augustin a, loewenstein a, rizzo s, kupperman b. general pathophysiology of macular edema. eur j ophthalmol 2011;21:10–19. 35. xu hz, le yz. significance of outer blood-retina barrier breakdown in diabetes and ischemia. invest ophthalmol vis sci 2011;52:2160–2164. 36. weinberger d, fink-cohen s, gaton dd, priel e, yassur y. non-retinovascular leakage in diabetic maculopathy. br j ophthalmol 1995;79:728–731. 37. spaide r, yannuzzi l. manifestations and pathophysiology of serous detachment of the retinal pigment epithelium and retina. in: marmor m, wolfensberger t, editors. the retinal pigment epithelium: function and disease. new york, new york: oxford university press, 1998:439–455. 38. nagaoka t, kitaya n, sugawara r, yokota h, mori f, hikichi t. alteration of choroidal circulation in the foveal region in patients with type 2 diabetes. br j ophthalmol 2004;88:1060–1063. 39. semeraro f, morescalchi f, cancarini a, russo a, rezzola s, costagliola c. diabetic retinopathy, a vascular and inflammatory disease: therapeutic implications. diabetes metab 2019;45:517–527. 40. iglicki m, busch c, zur d, okada m, mariussi m, chhablani jk, et al. dexamethasone implant for diabetic macular edema in naïve compared with refractory eyes: the international retina group real-life 24-month multicenter study. the irgrel-dex study. retina 2019;39:44–51. 530 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 original article memantine, simvastatin, and epicatechin inhibit 7-ketocholesterol-induced apoptosis in retinal pigment epithelial cells but not neurosensory retinal cells in vitro aneesh neekhra1, md; julia tran1, bs; parsa r. esfahani1, bs; kevin schneider1, phd; khoa pham1, md ashish sharma1, md; marilyn chwa1, ms; saurabh luthra1, md; ana l. gramajo1, md; saffar mansoor1, phd baruch d. kuppermann1, md, phd; m. cristina kenney1,2, md, phd 1gavin herbert eye institute, university of california, irvine, california 2department of pathology and laboratory medicine, university of california irvine, irvine, ca, usa orcid: aneesh neekhra: https://orcid.org/0000-0003-1638-9324 m. cristina kenney: https://orcid.org/0000-0003-1765-1750 abstract purpose: 7-ketocholesterol (7kch), a natural byproduct of oxidation in lipoprotein deposits is implicated in the pathogenesis of diabetic retinopathy and age-related macular degeneration (amd). this study was performed to investigate whether several clinical drugs can inhibit 7kch-induced caspase activation and mitigate its apoptotic effects on retinal cells in vitro. method: two populations of retinal cells, human retinal pigment epithelial cells (arpe-19) and rat neuroretinal cells (r28) were exposed to 7kch in the presence of the following inhibitors: z-vad-fmk (pan-caspase inhibitor), simvastatin, memantine, epicatechin, and z-ietd-fmk (caspase-8 inhibitor) or z-atad-fmk (caspase-12 inhibitor). caspase-3/7, -8, and -12 activity levels were measured by fluorochrome caspase assays to quantify cell death. incucyte live-cell microscopic images were obtained to quantify cell counts. results: exposure to 7kch for 24 hours significantly increased caspase activities for both arpe-19 and r28 cells (p < 0.05). in arpe cells, pretreatment with various drugs had significantly lower caspase-3/7, -8, and -12 activities, reported in % change in mean signal intensity (msi): z-vad-fmk (48% decrease, p < 0.01), memantine (decreased 47.8% at 1 µm, p = 0.0039 and 81.9% at 1 mm, p < 0.001), simvastatin (decreased 85.3% at 0.01 µm, p < 0.001 and 84.8% at 0.05 µm , p < 0.001) or epicatechin (83.6% decrease, p < 0.05), z-ietd-fmk (68.1% decrease, p < 0.01), and z-atad-fmk (47.7% decrease, p = 0.0017). in contrast, r28 cells exposed to 7kch continued to have elevated caspase3/7, -8, and -12 activities (between 25.7% decrease and 17.5% increase in msi, p > 0.05) regardless of the pretreatment. conclusion: several current drugs protect arpe-19 cells but not r28 cells from 7kchinduced apoptosis, suggesting that a multiple-drug approach is needed to protect both cells types in various retinal diseases. keywords: epicatechin; 7-ketocholesterol; memantine j ophthalmic vis res 2020; 15 (4): 470–480 470 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7781&domain=pdf&date_stamp=2019-07-17 inhibition of 7kch-induced caspase activation; neekhra et al introduction apoptosis is a highly regulated process of programmed cell death critical in various disease states and degenerations. these pathways are implicated in various neurodegenerative diseases (e.g., alzheimer’s disease, parkinson’s disease, amyotrophic lateral sclerosis), ocular diseases (e.g., glaucoma, diabetic retinopathy and age-related macular degeneration [amd]), and immunologic disorders.[1–6] while treatments for the wet form of amd rely on inhibiting choroidal neovascularization via anti-vascular endothelial growth factor (anti-vegf) injections,[7] there is currently no cure for the dry form of amd. a pro-apoptotic oxysterol implicated in amd is 7-ketocholesterol (7kch), a toxic metabolite generated from the oxidation of cholesterol-esters in low density lipoprotein (ldl), atheromatous plaques, and drusen.[6, 8–10] 7kch activates three distinct kinase signaling pathways via nfkb, mapk, and erk to upregulate proinflammatory cytokines: il-6, il-8, and vascular endothelial growth factor (vegf) which induce neovascularization in the choroid.[7, 8, 11–13] in previous studies, retinal pigment epithelial (rpe) cells and vascular endothelial cells had an 8to 10-fold increase in vegf levels,[14] and a 2-fold increase in endothelial smooth muscle cells after exposure to 7kch.[15] our previous studies showed that in both arpe-19 and rat neuroretinal r28 cell cultures, 7kch significantly increased the levels of pro-apoptotic caspase-3, -8, and -12 activities.[16–19] 7kch is also a chemoattractant that directs microglia to the outer retina to produce metalloproteinases that cause breaks in bruch’s membrane and produce pro-angiogenic substances.[11, 14, 20] a 2019 study showed that 7kch intravitreally injected into rat retinas induced apoptosis in photoreceptors and rpe cells correspondence to: m. cristina kenney, md, phd. department of ophthalmology, gavin herbert eye institute 843 health science road, room 2028, irvine, ca 92697, usa. e-mail: mkenney@hs.uci.edu received: 20-03-2020 accepted: 21-06-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7781 and caused microvilli detachment in the outer segment.[10] thus, the toxic accumulation of 7kch over decades may activate cellular processes that predispose patients to age-related ocular pathologies such as amd.[8] despite the strong evidence of 7kch’s role in age-related diseases, little is known about its detoxifying mechanisms. a 2019 study showed that compounds such as vitamin e, oleic acid, terpenoids, and polyphenols inhibit 7kch-induced apoptosis,[21] while resveratrol, an antioxidant and anti-inflammatory stilbenoid found in the skin of grapes and red wine inhibits 7kch-induced vegf expression.[22] successful inhibition by these natural compounds advances our knowledge related to functional food therapies.[21] thus, it is necessary to explore the potential drugs or inhibitors given the limited body of knowledge on 7kch detoxification. the present study investigates six different inhibitors (simvastatin [lipid lowering medication], memantine [used to treat alzheimer’s disease], epicatechin [flavonoid present in green tea], z-vad-fmk [pan-caspase inhibitor], z-ietd-fmk [caspase-8 inhibitor], and z-atad-fmk [caspase-12 inhibitor]) to identify drugs/agents that can block the 7kchinduced caspase activation. our results show that these drugs are effective in arpe-19 cells but not in r28 cells, implicating the need for a multidrug approach or novel therapies to inhibit 7kch in various cell types. methods cell culture r28 rat neurosensory cells have properties that resemble those of various human neurosensory cells. the r28 cells derived from retina of post-natal day 6 rats were cultured in dulbecco’s modified eagle’s media, this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: neekhra a, tran j, esfahani pr; pham k, schneider k, sharma a, chwa m, luthra s, gramajo al, mansoor s, kuppermann bd, kenney mc. memantine, simvastatin, and epicatechin inhibit 7-ketocholesterol-induced apoptosis in retinal pigment epithelial cells but not neurosensory retinal cells in vitro. j ophthalmic vis res 2020;15:470–480. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 471 https://knepublishing.com/index.php/jovr inhibition of 7kch-induced caspase activation; neekhra et al 10µg/ml gentamicin, 10mm non-essential amino acids, and high glucose (dmem high glucose; invitrogen-gibco, carlsbad, ca) with 10% fetal bovine serum. despite their clonal origin, r28 cells are characteristically heterogeneous, display both glial and neuronal cell markers, and have functional neuronal properties.[23] r28’s diversity of cell types, ability to respond to a variety of stimuli, and differentiation potential makes it an appropriate model for neuroretinal tissue.[24] a 1:1 mixture (vol/vol) of dulbecco’s modified eagle’s and ham’s nutrient mixture f-12 was used to grow arpe-19 cells (atcc, manassas, va); (invitrogen-gibco, carlsbad, ca), 0.37% sodium bicarbonate, 0.058% l-glutamine, 10% fetal bovine serum, antibiotics (100u/ml penicillin g, 0.1mg/ml streptomycin sulfate, 10µg/ml gentamicin), 10mm non-essential amino acids, and an anti-fungal agent (amphotericin-b 2.5µg/ml). arpe-19 cells are a homogeneous, retinal-derived cell line with functional and structural properties similar to human rpe cells.[25] all cells within the arpe19 culture express rpe-specific markers such as cralbp, best1, and rpe-65.[26] cell plating cells were plated on 24 well plates (becton dickinson labware, franklin lakes, nj) at 150,000 cells per well and incubated at 37°c in 5% co2 until confluent. cell incubation was performed in a serum-free media for 24 hours to prevent excessive proliferation. cells in the experimental group were then pretreated with various inhibitors while the cells in the control group were only exposed to dmso (the vehicle for 7kch). all experimental cells besides the control cells were then exposed to 30 µg/ml 7kch for 24 hours before caspase activity was assessed. caspase-3/7, -8, and -12 detection carboxyfluorescein flica caspase apoptosis detection kits (immunochemistry technologies llc, bloomington, mn) were used to quantify cells undergoing caspase-mediated apoptosis. the flica detection reagent contains a caspase inhibitor sequence linked to a fluorescent carboxyfluorescein probe with an optimal excitation range of 488–492 nm and an emission range of 515–535 nm. the probe only fluoresces when the flica reagent covalently binds to activated caspase-3/7 and -8 in vitro. the fluorescence intensity quantifies the number of whole, living cells undergoing caspase-mediated apoptosis since cells with premature, inactivated, or no caspase activity will not fluoresce. this was measured using the fluorescence image scanning unit (fmbio iii) instrument (hitachi, yokohama, japan). caspase-12 activity was detected using caspglow fluorescein caspase-12 staining kit (biovision). the assay utilizes the caspase12 inhibitor, z-atad-fmk (ala-thr-ala-aspfluoromethylketone), conjugated to fitc (fitcatad-fmk) as a marker. fitc-atad-fmk irreversibly binds to activated caspase-12 in cells undergoing apoptosis and is cell permeable and nontoxic. fresh culture media were used to rinse the wells at 24 hours. then, 300 µl/well of flica solution in culture media were placed in the wells for 1 hour. phosphate buffered saline (pbs) was used to wash the wells three times. the experimental groups were (1) r28 and arpe-19 cells with 30 µg/ml 7kch alone; (2) r28 and arpe-19 cells with inhibitor; and (3) r28 and arpe-19 cells with dmso. the different inhibitors used were 1 µm and 1 mm memantine (alexis biochemical, san diego), 0.01 µm and 0.05 µm simvastatin (merck and co., whitehouse station, nj), 5 µm epicatechin (sigma aldrich inc, st louis, mo), the pan-caspase inhibitor z-vad-fmk (val-ala-asp-fluoromethylketone, immunochemistry technologies llc, bloomington, mn), the caspase-8 inhibitor (z-ietd-fmk, iso-gluthr-asp-fluoromethylketone, calbiochem, la jolla, ca), and caspase-12 inhibitor (z-atad-fmk, alathr-ala-asp-fluoromethylketone, calbiochem, la jolla, ca). the inhibitors were added to the culture medium 1 hour before exposing cells to 7kch. in addition to the experimental groups, we also analyzed the following control groups: (1) untreated r28 cells and arpe-19 cells without flica or caspglow to exclude autofluorescence from cells; (2) untreated r28 and arpe-19 cells with flica or caspglow for comparison of caspase activity of treated cells; (3) tissue culture plate wells (without cells) with buffer alone to represent the background levels; (4) tissue culture plate wells without cells with culture media and dmso in order to exclude cross-reaction of culture media and/or dmso with the plastic material of the tissue culture 472 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 inhibition of 7kch-induced caspase activation; neekhra et al plate or cross-reaction of flica or caspglow; (5) r28 cells and arpe-19 cells with dmso and flica to account for any cross-fluorescence due to the cross-reaction of untreated cells with dmso; and (6) untreated r28 and arpe-19 cells with negative control z-fa-fmk and flica as a control for the pan caspase inhibitor. incucyte® live-cell imaging analysis was used to capture fluorescent images in real time. nuclight rapid red and caspase-3/7 green reagents were used to stain cells in 96-well plates at 5,000– 10,000 cells/well. the nuclight rapid red reagent quantifies the amount of cell proliferation in incucyte live-cell images by staining the nuclei of living cells. the caspase-3/7 green reagent contains an oligopeptide cleavage sequence (devd) conjugated to a dna-binding dye. the green reagent labels apoptotic cells at an emission maximum of 533 nm once the sequence is cleaved by caspase-3/7. images were captured per well every 3 hours for five days with brightfield, red, and green channels. apoptosis due to caspase-3/7 activity is discriminated from live and necrotic cells by overlapping the signal counts from nuclight red with the caspase-3/7 green. statistical analysis anova using graphpad prism 3.0 version statistics program (graphpad software inc., san diego, ca) was used for statistical analysis of the data. the data within each experiment were compared using the newman–keuls multiple comparison test. mean ± standard error of mean (sem) was used to present the data. experiments were performed in triplicate. p-values < 0.05 were considered statistically significant. results pan-caspase inhibitor z-vad-fmk reduces caspase-3/7 activity in only arpe-19 cells arpe-19 cells exposed to 7kch had increased caspase-3/7 activity (31,311 ± 766.7 msi, p < 0.0001) compared to the arpe-19 cells exposed only to dmso (6,086 ± 910 msi, figure 1a). caspase-3/7 activity in arpe-19 cells decreased significantly at 48.0% following pretreatment with z-vad-fmk (16,278 ± 323.1 msi, p < 0.0001, figure 1a). r28 cells exposed to 7kch had increased caspase-3/7 activity (34,014 ± 2,126 msi, p = 0.0001) compared to the r28 cells exposed only to dmso (1,975 ± 234.5 msi, figure 1b). caspase-3/7 activity in r28 cells did not decrease significantly at 12.3% following pretreatment with z-vad-fmk (29,805 ± 3,007 msi, p > 0.05, figure 1b). the pan-caspase inhibitor z-vad-fmk was not able to protect the r28 cells. 1 μm and 1 mm memantine reduce caspase3/7 activity in only arpe-19 cells arpe-19 cells exposed to 7kch had increased caspase-3/7 activity (32,972 ± 1,891 msi, p = 0.001) compared to arpe-19 cells exposed only to dmso (12,791 ± 1,501 msi, figure 2a). caspase-3/7 activity in arpe-19 cells decreased significantly at 47.8% following pretreatment with 1 µm memantine (17,218 ± 1,835 msi, p = 0.003, figure 2a) and even more so at 81.9% with 1 mm memantine (5,969 ± 1,596 msi, p < 0.001, figure 2a). r28 cells exposed to 7kch had increased caspase-3/7 activity (31,974 ± 2,599 msi, p < 0.001) compared to r28 cells exposed only to dmso (2,355 ± 254.4 msi, figure 2b). caspase-3/7 activity in r28 cells did not decrease significantly following pretreatment with 1 µm memantine (33,850 ± 1,894 msi, p > 0.05, figure 2b) nor with 1 mm memantine (33,422 ± 863.7 msi, p > 0.05, figure 2b). neither concentration of the nmda inhibitor memantine protected the r28 cells from apoptosis. 0.01 μm and 0.05 μm simvastatin reduce caspase-3/7 activity in only arpe-19 cells arpe-19 cells exposed to 7kch had increased caspase-3/7 activity (32,972 ± 1,891 msi, p = 0.001) compared to arpe-19 cells exposed only to dmso (12,791 ± 1,501 msi, figure 2c). caspase-3/7 activity in arpe-19 cells decreased significantly at 85.3% following pretreatment with 0.01 µm simvastatin (4,849 ± 500.2 msi, p < 0.001, figure 2c) and at 84.8% with 0.05 µm simvastatin (5,016 ± 968.5 msi, p < 0.001, figure 2c). r28 cells exposed to 7kch had increased caspase-3/7 activity (31,974 ± 2,599 msi, p < 0.001) compared to r28 cells exposed only to dmso (2,355 ± 254.4 msi, figure 2d). caspase-3/7 activity in r28 cells did not decrease significantly at 8.3% following pretreatment with journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 473 inhibition of 7kch-induced caspase activation; neekhra et al figure 1. caspase-3/7 activity in 7kch-treated arpe-19 and r28 cells in response to 7kch alone or pretreatment with z-vad-fmk. cells exposed to 7kch alone increased caspase-3/7 activity*** (a–b). arpe-19 cells pretreated with z-vad-fmk decreased caspase-3/7 activity*** (a). in contrast, r28 cells pretreated with z-vad-fmk did not have decreased caspase-3/7 activity (b). *p < 0.05, **p < 0.01, ***p < 0.001. the error bars represent the standard error of the mean (sem) of measurements for the three conditions in three separate runs (n = 9, a–b). 0.01 µm simvastatin (29,316 ± 897.9 msi, p > 0.05, figure 2d) nor with 0.05 µm simvastatin, which had a slight increase in activity at 17.5% (37,575 ± 1,629 msi, p > 0.05, figure 2d). neither concentration of simvastatin protected the r28 cells from apoptosis. 5 μm epicatechin reduces caspase-3/7 activity in only arpe-19 cells arpe-19 cells exposed to 7kch had increased caspase-3/7 activity (32,181 ± 4,839 msi, p = 0.005, figure 2e) compared to arpe-19 cells exposed only to dmso (5,936 ± 491.4 msi, figure 2e). caspase-3/7 activity in arpe-19 cells decreased significantly at 83.6% following pretreatment with 5 µm epicatechin (5,263 ± 4,344 msi, p < 0.05, figure 2e). r28 cells exposed to 7kch had increased caspase-3/7 activity (34,720 ± 3,197 msi, p < 0.001, figure 2f) compared to r28 cells exposed only to dmso (2,488 ± 116.3 msi, figure 2f). caspase-3/7 activity in r28 cells decreased at 25.7% following pretreatment with 5 µm epicatechin (25,806 ± 977.5 msi, p = 0.05, figure 2f), but the p-value was not significant. representative incucyte live-cell images of arpe-19 cells treated with dmso-control, 7kch, and 7kch with epicatechin, respectively, are shown in figure 2g. 7kch increased nuclight red signal, caspase-3/7 green signal, and overlap signal counts at 24 hours (figure 2g, second row) compared with dmso-control (figure 2g, first row) in arpe-19 cells. these counts are reduced when cultures are pretreated with inhibitors such as epicatechin before exposure to 7kch (figure 2g, third row). caspase-8 inhibitor z-ietd-fmk reduces caspase-8 activity in only arpe-19 cells arpe-19 cells exposed to 7kch had increased caspase-8 activity (28,037 ± 398 msi, p < 0.001, figure 3a) compared to arpe-19 cells exposed only to dmso (7,210 ± 478.8 msi, figure 3a). caspase-8 activity in 7kch exposed arpe-19 cells was significantly reduced at 68.1% following pretreatment with z-ietd-fmk (8,952 ± 283 msi, p < 0.01, figure 3a). r28 cells exposed to 7kch had increased caspase-8 activity (34,734 ± 944.5 msi, p = 0.001, figure 3b) compared to r28 cells exposed only to dmso (11,043 ± 55.5 msi, figure 3b). caspase-8 activity in 7kch-exposed r28 cells was not significantly reduced at 8.4% by pretreatment with z-ietd-fmk (31,825 ± 3,073, p > 0.05, figure 3b). caspase-12 inhibitor z-atad-fmk reduces caspase-12 activity in only arpe-19 cells arpe-19 cells exposed to 7kch had increased caspase-12 activity (38,585 ± 1,804 msi, p < 0.001, figure 3c) compared to arpe-19 cells exposed only to dmso (15,351 ± 636.5 msi, figure 3c). caspase-12 activity in 7kch-exposed arpe-19 cells was significantly reduced at 47.7% by pretreatment with z-atad-fmk (20,175 ± 719 msi, p = 0.001, figure 3c). r28 cells exposed to 7kch had an increased caspase-12 activity (31,234 ± 4,445 msi, p < 0.05, figure 3d) compared to r28 cells exposed only to dmso (10,043 ± 944.5 msi, figure 3d). caspase-12 activity in 7kch-exposed r28 cells was not significantly reduced at 9.1% by 474 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 inhibition of 7kch-induced caspase activation; neekhra et al figure 2. caspase-3/7 activity in 7kch-treated arpe-19 and r28 cells after pretreatment with memantine, simvastatin, or epicatechin. all cells exposed to 7kch alone increased caspase-3/7 activity (a–f). pretreatment of arpe-19 cells with 1 µm** and 1 mm*** memantine (a) 0.01 µm*** and 0.05 µm*** simvastatin (c), or 5 µm epicatechin* (e) showed decreased caspase-3/7 activity. in contrast, r28 cells pretreated with 1 µm and 1 mm memantine (b) 0.01 µm and 0.05 µm simvastatin (d), or 5 µm epicatechin (f) did not have significantly decreased caspase-3/7 activity. representative incucyte live-cell images of dmso-control, 7kch, and 7kch with epicatechin-treated arpe-19 cells at 24 hours (g). there are no major differences among treatments detected with brightfield microscopy (g, first column). arpe-19 cells stressed with 7kch demonstrate increased nuclear staining number, increased caspase-3/7 signal number, and an increased overlap signal number (g, second row). these counts decrease when arpe-19 cells are pretreated with epicatechin before 7kch (g, third row). *p < 0.05, **p < 0.01, ***p < 0.001. the error bars represent the standard error of the mean (sem) of measurements for the four conditions in three separate runs (n = 12, a–d) and three conditions in three separate runs (n = 9, e–f). scale bar = 400 μm (g). pretreatment with z-atad-fmk (28,379 ± 4518 msi, p > 0.05, figure 3d). discussion this study emphasized 7kch’s role in caspase activation and highlighted several clinical drugs that protected rpe cells but not r28 cells from 7kch-induced apoptosis. research in the past two decades has strongly supported 7kch’s role in amd pathogenesis. 7kch from ldl is esterified via two enzymes, cpla2α and soat1, to 7kchfatty acid esters (7kfaes), and effluxed by hdl to the liver for bile acid production.[27] cholesterol levels may therefore contribute to ocular disease as high serum levels of journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 475 inhibition of 7kch-induced caspase activation; neekhra et al figure 3. caspase-8 and -12 activity in 7kch-treated arpe-19 and r28 cells in response to 7kch alone or pretreatment with zietd-fmk or z-atad-fmk. all cells exposed to 7kch alone showed increased caspase-3/7 activity (a–f). arpe-19 cells pretreated with z-ietd-fmk** (a) or z-atad-fmk** (c) showed decreased caspase-8 and -12 activity, respectively. in contrast, r28 cells pretreated with z-ietd-fmk (b) or z-atad-fmk (d) did not show decreased caspase-8 nor -12 activities, respectively. *p < 0.05, **p < 0.01, ***p < 0.001. the error bars represent the standard error of the mean (sem) of measurements for the three conditions in three separate runs (n = 9, a–d). ldl or 7kfaes (which revert to 7kch), or low levels of hdl can result in increased 7kch levels.[27] 7kch may also accumulate over time from natural mechanisms such as the rhodopsin cycle and other photo-oxidative processes.[28] compared to controls, 7kch was found at 6to 50-fold higher levels in rpe and photoreceptor inner segments of photodamaged rat retinas,[9] and at 4-fold levels in bruch’s membrane and neuroretinal cells in photodamaged monkey retinas.[14, 28] excess 7kch can trigger caspase pathways, excess reactive oxygen species (ros) production, endothelial dysfunction, breaks in bruch’s membrane, induction of cytokines il-6 and il-8, and neovascularization in the choroid [16–20, 29–31], which are all consistent with amd. additional damage includes increased levels of dna fragmentation and increased chromatin condensation in both arpe-19 and r28 cells.[32] 7kch also damages mitochondria by inducing reactive oxygen/nitrogen species, reducing the mitochondrial membrane potential by 2.2-fold (p < 0.001), and decreasing levels of intact 16.2-kb mtdna.[16] the clinically available inhibitors used in this study all prevented 7kch induced caspase-3/7 activation in arpe-19 cells but not r28 cells: (1) memantine is a moderate-affinity, noncompetitive antagonist of the glutamatergic n-methyl-d-aspartate (nmda) receptors. it suppresses glutamate-excitotoxicity in animal models associated with neurological diseases such as alzheimer’s, vascular dementia, and retinal ganglion cell death after ischemic strokes.[33–37] by inhibiting downstream p53 and calpain-caspase-3, it reduces ca2+-dependent production of no and o2(–) and halts neuronal apoptosis in rats with middle cerebral artery occlusion.[36, 38, 39] a previous study showed that memantine reduces caspase-3/7 activity in staurosporine-treated neuronal cells.[40] the present study showed 1 μm and 1 mm of memantine reduced caspase-3/7 activity by 47.8% and 81.9% in arpe-19 cells, respectively, but only 5.9% and 4.5% in r28 cells (figures 2a–2b) despite evidence of immunoreactivity to nmda and gabaa receptors.[41] this may be because memantine can upregulate brainderived neurotrophic factor through the pi3-k/akt 476 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 inhibition of 7kch-induced caspase activation; neekhra et al pathway independent of nmda receptors.[42] furthermore, r28 cells derived from six-day old rat retina are not fully differentiated and may not have well-developed nmda receptors. r28 cultures are also heterogeneous and memantine may preferentially affect neural cells with nmda receptors over non-neural glial cells.[23] (2) simvastatin is a hydrophobic drug that inhibits 3-hydroxy-3-methyl-glytaryl coenzyme a (hmg-coa) reductase and is frequently utilized to reduce serum ldl in hyperlipidemic patients.[43] besides its lipid-lowering effects, it is also neuroprotective and upregulates bcl-2, a major cell survival protein,[44, 45] and induces hsp27, a heat shock protein that promotes retinal ganglion cell survival.[46] in rats with streptozotocininduced diabetes, therapeutic levels of simvastatin slowed progression of diabetic retinopathy by reducing vegf activation, vascular permeability, and endothelial-leukocyte adherence.[47] the effects of statins are notably biphasic: low concentrations of statins are pro-angiogenic, while high concentrations are angiostatic.[48–50] higher concentrations can also induce caspase3/7 apoptosis in human monocytes, pericytes, and tumor cells.[50–52] our results show that 0.01 μm and 0.05 μm of simvastatin reduced caspase-3/7 activity by 85.3% and 84.8%, respectively, in arpe19 cells (figure 2c), while 0.05 μm simvastatin increased caspase activity by 17.5% in r28 cells (figure 2d). the therapeutic dose in arpe-19 cells was toxic in r28 cells, suggesting underdeveloped drug import/export systems or excess hmg-coa reductase concentrations in r28 cells, but further studies are needed. (3) epicatechin is a powerful antioxidant flavanol found in many plant-based foods such as grapes, dark chocolate, and green tea. it is commonly used to reduce oxidative damage by inhibiting nicotinamide adenine dinucleotide phosphate (nadph) oxidase and maintaining nitric oxide (no) synthase, which prevents oxidized ldl endothelial dysfunction implicated in dementia.[53–55] it can also decrease levels ros in the hippocampus of rat models with hypertension and alzheimer’s.[56] other studies show that epigallocatechin gallate, a derivative with phenolic hydroxyl, injected into rat retinas attenuated sodium nitroprusside-induced oxidative stress in retinal ganglion cells.[57] our results show that epicatechin significantly reduced caspase-3/7 activity by 83.6% in arpe-19 cells, but only 25.7% in r28 cells (p = 0.05. figures 2e— 2f). unlike the first two inhibitors, epicatechin’s borderline p-value suggests it protects r28 cells by decreasing general oxidative burden. thus, targeting upstream ros production via nadph oxidase may protect multiple retinal cell types more effectively than targeting specific downstream enzymes or receptors. these results are consistent with those obtained by incucyte® live-cell imaging analysis which captures caspase-3/7-mediated apoptosis in real-time images (figure 2g). the overlapped signal (figure 2g, fourth column) shows increased caspase activity with 7kch (figure 2g, second row) that was reduced with epicatechin pretreatment (figure 2g, third row). figure 2g shows the representative images of arpe-19 cells treated with dmso-control (first row), 7kch (second row), and pretreated with epicatechin (third row). similar image results were obtained with arpe-19 cells pretreated with simvastatin or memantine. (4) z-vad-fmk is a direct pan-caspase inhibitor that irreversibly binds the catalytic site of various caspase proteases. it prevented cell shrinkage and dna fragmentation due to caspase-2, -3, -6, and -8 in flounder immune cells,[58] and prevented increases in p53, parp-1, and caspase-3 levels after 35 hours of glucose deprivation in retinal ganglion cells.[59] in arpe-19 cells, the z-vadfmk reduced 7-kch-induced caspase-3/7 activity by 48.0% but did not protect r28 (12.3%). (5) z-ietd-fmk is a direct caspase-8 inhibitor that disrupts the extrinsic caspase pathway. it reduced caspase-8 activity by 68.1% in arpe-19 cells but had no protective effects in neuroretinal cells (8.4%). (6) z-atad-fmk is a caspase-12 inhibitor that disrupts the endoplasmic reticulum stress-induced caspase pathway. in arpe-19 cells, it reduced caspase-12 activity by 47.7%. in contrast, there was no significant effect on r28 cells, with only 9.1% decrease in caspase activity. previous studies demonstrated that a component of cigarette smoke, benzo(e)pyrene [b(e)p], also induces caspase-3/7 activity in arpe19 cells and was inhibited by genistein, resveratrol, and memantine but not calpain, btic, simvastatin, or epicatechin.[60] when combined with the current study’s results, memantine could reverse both b(e)pand 7kch-induced caspase-3/7 activities in arpe-19 cells, but simvastatin and epicatechin only journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 477 inhibition of 7kch-induced caspase activation; neekhra et al reversed activity induced by 7kch not b(e)p. this indicates that the same cell type can have distinct pathways to activate and inhibit caspase-3/7, depending on the insult. likewise, the current study suggests that different cell types have distinct pathways to activate and inhibit apoptosis induced by 7kch. none of the drugs significantly reduced caspase activity in r28 cells, which strongly implies that tissue characteristics or processes maintain apoptosis in the presence of inhibitors. as mentioned previously, r28 cells are retinal precursor cells from six-day old rats that express genes and proteins specific to their developmental age, which may not include receptors that respond to the drugs.[41] furthermore, this heterogeneous population has cell types with distinct morphologies, biochemical characteristics, and neuronal-specific cell markers. a subset of r28 cells have receptors to neurotransmitters such as dopamine, serotonin, glycine, and acetylcholine; other cells have receptors that respond to nmda and gaba agonists; still others show immunoreactivity to glur1, glur2, and glur3.[24, 41] in contrast, arpe-19 cells are a homogeneous population of rpe cells that grow in a monolayer, express the same receptors and rpe-selective markers like cralbp, and have the same cobblestone morphology.[61] thus, receptoror enzyme-specific drugs such as the caspase inhibitors, memantine, or simvastatin will affect all arpe-19 cells equally and the global response is additive (–47.7% to –85.3% change in caspase activity, all p-values < 0.05). in contrast, only a fraction of r28 cells that express the target enzyme or receptor will be affected, and the global response is represented only by the subset (+17.5% to –25.7% change in caspase activity, all p-values > 0.05). in summary, the current study quantified caspase-3/7 activity as a marker of apoptosis between human arpe-19 cells and rat r28 cells after treatment with 7kch and various inhibitors. 7kch significantly induced caspase-3/7 for both cultures, yet pretreatment with anti-apoptotic drugs (memantine, simvastatin, epicatechin, z-vad-fmk, etc.) consistently reduced caspase activities only in the arpe-19 cells. this discrepancy in caspase deactivation between arpe-19 and r28 cells may be related to the differences in the heterogeneity of the cell population or the age and species of the original tissue. ultimately, the etiology of amd is multifactorial and future treatments may utilize combination therapy to inhibit common toxins, like 7kch and b(e)p, that affect multiple retinal cell targets. acknowledgments the authors are grateful to dr. gail m. seigel from the center for hearing and deafness, university at buffalo, the state university of new york, buffalo, new york and suny eye institute for all her contributions and particularly for providing the r28 cell cultures. financial support and sponsorship this work was supported by the discovery eye foundation, polly and michael smith, edith and roy carver, and nei r01 ey0127363 (mck and in part by an unrestricted departmental grant from research to prevent blindness. the authors are also thankful to the institute for clinical and translational science (icts) at university of california irvine. conflicts of interest there are no conflicts of interest. references 1. favaloro b, et al. role of apoptosis in disease. aging 2012;4:330–349. 2. hinton dr, he s, lopez pf. apoptosis in surgically excised choroidal neovascular membranes in age-related macular degeneration. arch ophthalmol 1998;116:203–209. 3. obulesu m, lakshmi mj. apoptosis in alzheimer’s disease: an understanding of the physiology, pathology and therapeutic avenues. neurochem res 2014;39:2301– 2312. 4. samadi a, et al. oxysterol species: reliable markers of oxidative stress in diabetes mellitus. j endocrinol invest 2019;42:7–17. 5. thomas cn, et al. caspases in retinal ganglion cell death and axon regeneration. cell death discov 2017;3:17032. 6. xu gz, li ww, tso mo. apoptosis in human retinal degenerations. trans am ophthalmol soc 1996;94:411– 430; discussion 430–431. 7. wei q, et al. combination of bevacizumab and photodynamic therapy vs. bevacizumab monotherapy for the treatment of wet age-related macular degeneration: a meta-analysis of randomized controlled trials. exp ther med 2018;16:1187–1194. 478 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 inhibition of 7kch-induced caspase activation; neekhra et al 8. pariente a, et al. inflammatory and cell death mechanisms induced by 7-ketocholesterol in the retina. implications for age-related macular degeneration. exp eye res 2019;187:107746. 9. rodriguez ir, larrayoz im. cholesterol oxidation in the retina: implications of 7kch formation in chronic inflammation and age-related macular degeneration. j lipid res 2010;51:2847–2862. 10. yang c, et al. 7-ketocholesterol disturbs rpe cells phagocytosis of the outer segment of photoreceptor and induces inflammation through erk signaling pathway. exp eye res 2019;189:107849. 11. indaram m, et al. 7-ketocholesterol increases retinal microglial migration, activation, and angiogenicity: a potential pathogenic mechanism underlying age-related macular degeneration. sci rep 2015;5:9144. 12. larrayoz im, et al. 7-ketocholesterol-induced inflammation: involvement of multiple kinase signaling pathways via nfkappab but independently of reactive oxygen species formation. invest ophthalmol vis sci 2010;51:4942–4955. 13. wang h, et al. thy-1 regulates vegf-mediated choroidal endothelial cell activation and migration: implications in neovascular age-related macular degeneration. invest ophthalmol vis sci 2016;57:5525–5534. 14. moreira ef, et al. 7-ketocholesterol is present in lipid deposits in the primate retina: potential implication in the induction of vegf and cnv formation. invest ophthalmol vis sci 2009;50:523–532. 15. dulak j, et al. vascular endothelial growth factor synthesis in vascular smooth muscle cells is enhanced by 7-ketocholesterol and lysophosphatidylcholine independently of their effect on nitric oxide generation. atherosclerosis 2001;159:325–332. 16. gramajo al, et al. mitochondrial dna damage induced by 7-ketocholesterol in human retinal pigment epithelial cells in vitro. invest ophthalmol vis sci 2010;51:1164–1170. 17. luthra s, et al. 7-ketocholesterol activates caspases-3/7, 8, and -12 in human microvascular endothelial cells in vitro. microvasc res 2008;75:343–350. 18. luthra s, et al. activation of caspase-8 and caspase-12 pathways by 7-ketocholesterol in human retinal pigment epithelial cells. invest ophthalmol vis sci 2006;47:5569– 5575. 19. neekhra a, et al. caspase-8, -12, and -3 activation by 7-ketocholesterol in retinal neurosensory cells. invest ophthalmol vis sci 2007;48:1362–1367. 20. javitt nb, javitt jc. the retinal oxysterol pathway: a unifying hypothesis for the cause of age-related macular degeneration. curr opin ophthalmol 2009;20:151–157. 21. brahmi f, et al. prevention of 7-ketocholesterol-induced side effects by natural compounds. crit rev food sci nutr 2018:1–20. 22. dugas b, et al. effects of oxysterols on cell viability, inflammatory cytokines, vegf, and reactive oxygen species production on human retinal cells: cytoprotective effects and prevention of vegf secretion by resveratrol. eur j nutr 2010;49:435–446. 23. sun w, seigel gm, salvi rj. retinal precursor cells express functional ionotropic glutamate and gaba receptors. neuroreport 2002;13:2421–2424. 24. seigel gm. review: r28 retinal precursor cells: the first 20 years. mol vis 2014;20:301–306. 25. dunn kc, et al. arpe-19, a human retinal pigment epithelial cell line with differentiated properties. exp eye res 1996;62:155–169. 26. moustafa mt, et al. protective effects of memantine on hydroquinone-treated human retinal pigment epithelium cells and human retinal muller cells. j ocul pharmacol ther 2017;33:610–619. 27. lee jw, huang jd, rodriguez ir. extra-hepatic metabolism of 7-ketocholesterol occurs by esterification to fatty acids via cpla2alpha and soat1 followed by selective efflux to hdl. biochim biophys acta 2015;1851:605–619. 28. rodriguez ir, et al. 7-ketocholesterol accumulates in ocular tissues as a consequence of aging and is present in high levels in drusen. exp eye res 2014;128:151–155. 29. jang er, lee cs. 7-ketocholesterol induces apoptosis in differentiated pc12 cells via reactive oxygen speciesdependent activation of nf-kappab and akt pathways. neurochem int 2011;58:52–59. 30. pedruzzi e, et al. nad(p)h oxidase nox-4 mediates 7-ketocholesterol-induced endoplasmic reticulum stress and apoptosis in human aortic smooth muscle cells. mol cell biol 2004;24:10703–10717. 31. shimozawa m, et al. 7-ketocholesterol enhances the expression of adhesion molecules on human aortic endothelial cells by increasing the production of reactive oxygen species. redox rep 2004;9:370–375. 32. ong jm, et al. oxysterol-induced toxicity in r28 and arpe19 cells. neurochem res 2003;28:883–891. 33. casson rj. possible role of excitotoxicity in the pathogenesis of glaucoma. clin exp ophthalmol 2006;34:54–63. 34. heinen-kammerer t, et al. added therapeutic value of memantine in the treatment of moderate to severe alzheimer’s disease. clin drug investig 2006;26:303–314. 35. kim tw, et al. neuroprotective effect of memantine in a rabbit model of optic nerve ischemia. korean j ophthalmol 2002;16:1–7. 36. lipton sa, rosenberg pa. excitatory amino acids as a final common pathway for neurologic disorders. n engl j med 1994;330:613–622. 37. woldemussie e, et al. neuroprotective effect of memantine in different retinal injury models in rats. j glaucoma 2002;11:474–480. 38. chen b, et al. memantine attenuates cell apoptosis by suppressing the calpain-caspase-3 pathway in an experimental model of ischemic stroke. exp cell res 2017;351:163–172. 39. ota h, et al. protective effects of nmda receptor antagonist, memantine, against senescence of pc12 cells: a possible role of nnos and combined effects with donepezil. exp gerontol 2015;72:109–116. 40. jantas-skotniczna d, kajta m, lason w. memantine attenuates staurosporine-induced activation of caspase3 and ldh release in mouse primary neuronal cultures. brain res 2006;1069:145–153. 41. seigel gm, et al. neuronal gene expression and function in the growth-stimulated r28 retinal precursor cell line. curr eye res 2004;28:257–269. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 479 inhibition of 7kch-induced caspase activation; neekhra et al 42. jantas d, et al. an involvement of bdnf and pi3-k/akt in the anti-apoptotic effect of memantine on staurosporineevoked cell death in primary cortical neurons. apoptosis 2009;14:900–912. 43. dias ihk, et al. simvastatin reduces circulating oxysterol levels in men with hypercholesterolaemia. redox biol 2018;16:139–145. 44. franke c, et al. bcl-2 upregulation and neuroprotection in guinea pig brain following chronic simvastatin treatment. neurobiol dis 2007;25:438–445. 45. johnson-anuna ln, et al. simvastatin protects neurons from cytotoxicity by up-regulating bcl-2 mrna and protein. j neurochem 2007;101:77–86. 46. kretz a, et al. simvastatin promotes heat shock protein 27 expression and akt activation in the rat retina and protects axotomized retinal ganglion cells in vivo. neurobiol dis 2006;21:421–430. 47. miyahara s, et al. simvastatin inhibits leukocyte accumulation and vascular permeability in the retinas of rats with streptozotocin-induced diabetes. am j pathol 2004;164:1697–1706. 48. muck ao, seeger h, wallwiener d. class-specific proapoptotic effect of statins on human vascular endothelial cells. z kardiol 2004;93:398–402. 49. urbich c, et al. double-edged role of statins in angiogenesis signaling. circ res 2002;90:737–744. 50. weis m, et al. statins have biphasic effects on angiogenesis. circulation 2002;105:739–745. 51. boucher k, et al. hmg-coa reductase inhibitors induce apoptosis in pericytes. microvasc res 2006;71:91–102. 52. fujino m, et al. counteracting effects of high density lipoprotein-cholesterol subfractions on statin-induced growth arrest. cardiovasc drugs ther 2005;19:113–118. 53. krikorian r, et al. concord grape juice supplementation improves memory function in older adults with mild cognitive impairment. br j nutr 2010;103:730–74. 54. steffen y, et al. protein modification elicited by oxidized low-density lipoprotein (ldl) in endothelial cells: protection by (-)-epicatechin. free radic biol med 2007;42:955–970. 55. steffen y, schewe t, sies h. epicatechin protects endothelial cells against oxidized ldl and maintains no synthase. biochem biophys res commun 2005;331:1277– 1283. 56. wang mh, et al. (-)-epigallocatechin-3-gallate decreases the impairment in learning and memory in spontaneous hypertension rats. behav pharmacol 2012;23:771–780. 57. zhang b, osborne nn. oxidative-induced retinal degeneration is attenuated by epigallocatechin gallate. brain res 2006;1124:176–187. 58. li s, et al. characterization of the responses of the caspase 2, 3, 6 and 8 genes to immune challenges and extracellular atp stimulation in the japanese flounder (paralichthys olivaceus). bmc vet res 2019;15:20. 59. li gy, fan b, su gf. acute energy reduction induces caspase-dependent apoptosis and activates p53 in retinal ganglion cells (rgc-5). exp eye res 2009;89:581–589. 60. mansoor s, et al. inhibition of apoptosis in human retinal pigment epithelial cells treated with benzo(e)pyrene, a toxic component of cigarette smoke. invest ophthalmol vis sci 2010;51:2601–2607. 61. kozlowski mr. the arpe-19 cell line: mortality status and utility in macular degeneration research. curr eye res 2015;40:501–509. 480 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 review article conjunctivitis: a systematic review amir a. azari, md1,2, amir arabi, md, mph1,2 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2department of ophthalmology, torfeh medical center, shahid beheshti university of medical sciences, tehran, iran orcid: amir a. azari: https://orcid.org/0000-0003-2013-3284 abstract conjunctivitis is a commonly encountered condition in ophthalmology clinics throughout the world. in the management of suspected cases of conjunctivitis, alarming signs for more serious intraocular conditions, such as severe pain, decreased vision, and painful pupillary reaction, must be considered. additionally, a thorough medical and ophthalmic history should be obtained and a thorough physical examination should be done in patients with atypical findings and chronic course. concurrent physical exam findings with relevant history may reveal the presence of a systemic condition with involvement of the conjunctiva. viral conjunctivitis remains to be the most common overall cause of conjunctivitis. bacterial conjunctivitis is encountered less frequently and it is the second most common cause of infectious conjunctivitis. allergic conjunctivitis is encountered in nearly half of the population and the findings include itching, mucoid discharge, chemosis, and eyelid edema. long-term usage of eye drops with preservatives in a patient with conjunctival irritation and discharge points to the toxic conjunctivitis as the underlying etiology. effective management of conjunctivitis includes timely diagnosis, appropriate differentiation of the various etiologies, and appropriate treatment. keywords: allergic; bacterial; conjunctivitis; covid-19; coronavirus; viral; toxic j ophthalmic vis res 2020; 15 (3): 372–395 introduction conjunctivitis is characterized by inflammation and swelling of the conjunctival tissue, accompanied correspondence to: amir a. azari, md. ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, no. 23, paidarfdard st., boostan 9 st., pasadaran ave., tehran 16666, iran. email: amirazarimd@gmail.com received: 18-02-2020 accepted: 25-04-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7456 by engorgement of the blood vessels, ocular discharge, and pain. many subjects are affected with conjunctivitis worldwide, and it is one of the most frequent reasons for office visits to general medical and ophthalmology clinics. more than 80% of all acute cases of conjunctivitis are reported to be diagnosed by non-ophthalmologists including internists, family medicine physicians, this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: azari aa, arabi a. conjunctivitis: a systematic review. j ophthalmic vis res 2020;15:372–395. 372 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7456&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr conjunctivitis; azari and arabi pediatricians, and nurse practitioners.[1] this imposes a great economic burden to the healthcare system and occupies a great proportion of the office visits in many medical specialties. it is estimated that the cost of treating bacterial conjunctivitis is $857 million annually in the united states alone.[2] it has been reported that nearly 60% of all patients with acute conjunctivitis receive antibiotic eye drops; and the vast majority receive their prescription from a non-ophthalmologist physician. for example, 68% of patients who visited a physician at an emergency room received antibiotic eye drops while this figure dropped to 36% for those who saw an ophthalmologist.[1] interestingly, patients from a higher socioeconomic status were more likely to receive and fill a prescription for their conjunctivitis.[1] there are several ways to categorize conjunctivitis; it may be classified based on etiology, chronicity, severity, and extend of involvement of the surrounding tissue. the etiology of conjunctivitis may be infectious or non-infectious. viral conjunctivitis followed by bacterial conjunctivitis is the most common cause of infectious conjunctivitis, while allergic and toxin-induced conjunctivitis are among the most common non-infectious etiologies. in terms of chronicity, conjunctivitis may be divided into acute with rapid onset and duration of four weeks or less, subacute, and chronic with duration longer than four weeks.[3] furthermore, conjunctivitis may be labeled as severe when the affected individuals are extremely symptomatic and there is an abundance of mucopurulent discharge. conjunctivitis may be associated with the involvement of the surrounding tissue such as the eyelid margins and cornea in blepharoconjunctivitis and viral keratoconjunctivitis, respectively. additionally, conjunctivitis may be associated with systemic conditions, including immunerelated diseases [e.g., reiter’s, stevens-johnson syndrome (sjs), and keratoconjunctivitis sicca in rheumatoid arthritis], nutritional deprivation (vitamin a deficiency), and congenital metabolic syndromes (richnerhanhart syndrome and porphyria)[4, 5] (table 1). it is extremely important to differentiate conjunctivitis from other causes of “red eye” associated with severe sightor life-threatening consequences such as acute angle closure glaucoma, uveitis, endophthalmitis, carotidcavernous fistula, cellulitis, and anterior segment tumors. methods the scientific literature published as of february 2020 was thoroughly reviewed by searching pubmed, the isi web of knowledge database, and the cochrane library using relevant keywords. the following keywords were used: ”bacterial conjunctivitis”, ”viral conjunctivitis,” ”allergic conjunctivitis”, ”treatment of bacterial conjunctivitis”, and ”treatment of viral conjunctivitis”. no language restriction was applied. articles published between march 2013 and february 2020 were screened and those that provided the best evidence-based information were included in this review. a total of 167 articles were finally included. the first study was published in 1964 and the last study was published in 2020. history and clinical examination how to diagnose conjunctivitis conjunctival injection or “red eye” is a shared presentation for many ophthalmic diseases, and it accounts for up to 1% of all primary care office visits.[6] the clinicians, whether ophthalmologist or not, must be aware that “red eye” may be the presenting sign for serious eye conditions such as uveitis, keratitis, or scleritis, or it may be secondary to more benign conditions that are limited just to the conjunctival tissue (e.g., conjunctivitis or subconjunctival hemorrhage). traditionally, it was believed that more harmful ophthalmic disorders are associated with disturbances in vision, disabling pain, and photophobia.[6] however, in a recent large metaanalysis,[6] anisocoria and mild photophobia were significantly associated with “serious eye conditions”; the presence of these two signs could discover 59% of cases of “serious eye conditions”, including anterior uveitis and keratitis. table 2 provides a summary of the journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 373 conjunctivitis; azari and arabi table 1. guideline to help differentiate the major etiologies in conjunctivitis clinical history and exam findings most probable etiologies alarming signs and symptoms decreased vision, severe pain, painful pupillary reaction, anisocoria, orbital signs uveitis, scleritis, keratitis, glaucoma, orbital, or parasellar pathology chronicity sudden onset, lasting less than four weeks infectious conjunctivitis, allergic conjunctivitis, acute systemic reactions (sjs/ten) insidious onset, chronic course conjunctivitis associated with systemic diseases, toxic conjunctivitis, allergic conjunctivitis recurrent course allergic conjunctivitis, conjunctivitis associated with systemic diseases associated symptoms skin lesions, arthropathy, genito-perineal involvement, oropharyngeal lesions conjunctivitis associated with systemic diseases, infectious diseases drug history long-term eye drop usage toxic conjunctivitis, allergic conjunctivitis recent initiation of a systemic medication acute systemic reactions (sjs/ten) sjs, stevens-johnson syndrome; ten, toxic epidermal necrolysis main etiologies of “red eye” and their clinical characteristics. how to distinguish infectious conjunctivitis from non-infectious conjunctivitis obtaining history from patients who present with conjunctivitis is crucial in order to arrive at the correct diagnosis. a focused ocular history should include the following: onset and duration of symptoms; laterality; impairment of vision; presence of itching; contact lens wear history; presence of fellow travelers such as recent upper respiratory infection, sinusitis, and lymphadenopathy; previous episodes of conjunctivitis; systemic allergies and medication; and history of exposure to chemical agents. the presence of constitutional signs such as fever, malaise, fatigue, and contact with individuals with conjunctivitis helps to further narrow down the differential diagnosis. physical examination, including checking for palpable lymph nodes, especially in the periauricular and submandibular areas, is of great importance. ophthalmic examination should be performed to determine the type of discharge. closer examination using a slit-lamp biomicroscope to evaluate the ocular surface structures including the palpebral conjunctiva for the presence of pseudomembranes, symblepharon, papilla or follicles, and the corneal tissue for the presence of opacities and infiltrates is absolutely essential. some of the clinical signs and symptoms that are used to help diagnose infectious conjunctivitis include the following: eye discharge, conjunctival injection, presence of red eye(s), eyelashes being stuck together in the morning, grittiness of the eye(s), eyelid or conjunctival edema, and history of contact with individuals with conjunctivitis.[7] allergic conjunctivitis may be underdiagnosed and undertreated.[8] it is presented with itching, chemosis, and redness in the absence of any significant corneal involvement.[9] the degree of conjunctival swelling is often out of proportion to conjunctival hyperemia. the main findings in vernal keratoconjunctivitis (vkc) are the presence of giant papillae in the superior tarsal conjunctiva accompanied by severe itching,[10] while the presence of conjunctival scar and anterior subcapsular cataract supports the diagnosis of atopic keratoconjunctivitis (akc).[11] another similar condition, chronic toxic conjunctivitis, may present with watery discharge, an initial papillary conjunctival reaction followed by a follicular reaction, punctate epithelial erosion of the cornea, and eyelid dermatitis.[12–14] 374 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 conjunctivitis; azari and arabi table 2. selected non-conjunctivitis etiologies of red eye differential diagnosis symptoms exam findings dry eyes burning and fb sensation. symptoms are usually transient, worse with reading or watching tv due to decreased blinking. symptoms are worse in dry, cold, and windy environments due to increased evaporation bilateral redness, superficial punctate keratopathy, meibomian glands dysfunction, decreased tear break-up time, small tear meniscus blepharitis similar to dry eyes redness greater at the margins of eyelids, inflammation, telangiectasia, and crust around eyelashes pterygium recurrent ocular redness visible conjunctival extension over the cornea hordeolum, chalazion eyelid pain and swelling palpable eyelid mass, may be tender or not anterior segment tumors variable variable corneal abrasion, keratitis, corneal foreign body fb sensation, relevant history including contact lens usage and occupational exposure corneal epithelial defects, corneal infiltration, corneal fb contact lens overwear relevant history corneal epithelial defect subconjunctival hemorrhage ocular redness blood under conjunctiva scleritis decreased vision, moderate to severe pain redness, bluish scleral hue iritis photophobia, pain, blurred vision. symptoms are usually bilateral decreased vision, poorly reacting pupils, constant eye pain radiating to temple and brow. redness, severe photophobia, presence of inflammatory cells in the anterior chamber angle closure glaucoma headaches, nausea, vomiting, ocular pain, decreased vision, light sensitivity, and seeing haloes around lights. symptoms are usually unilateral. firm eye upon palpation, ocular redness with limbal injection. appearance of a hazy/steamy cornea, moderately dilated pupils that are unreactive to light. carotid cavernous fistula chronic red eye, may have a history of head trauma dilated tortuous vessels (corkscrew vessels), bruits upon auscultation with a stethoscope endophthalmitis severe pain, photophobia, may have a history of eye surgery or ocular trauma redness, puss in the anterior chamber and photophobia cellulitis pain, double vision, and fullness redness and swelling of lids, may have restriction of the eye movements, may have a history of preceding sinusitis (usually ethmoiditis) fb, foreign body; tv, television how to distinguish bacterial conjunctivitis from viral conjunctivitis predicting the underlying etiology of conjunctivitis based on the presenting signs and symptoms may often result in an inaccurate diagnosis. in one study, centers with expertise in ocular surface disease had an accuracy rate of only 48% in making the correct diagnosis of adenoviral conjunctivitis.[15] several other studies demonstrated that bacterial pathogens are only isolated in 50% of cases of suspected bacterial conjunctivitis.[16] in addition, journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 375 conjunctivitis; azari and arabi one study reported that up to 52% of presumed cases of viral conjunctivitis were culture-positive for bacteria.[15] traditionally, the following associations between the clinical history and the etiology of conjunctivitis were believed to be true; these principles were presented in many textbooks and were used to select patients in many clinical trials.[17] for example, according to the major text books in ophthalmology (e.g., krachmer, duane, and kanski), involvement of one eye followed by the involvement of the second eye within 24–48 hours is indicative of bacterial infection, while if the second eye becomes infected after 48 hours with an accompanying enlarged periauricular lymph node, a viral etiology should be considered. according to the same textbooks, a papillary conjunctival reaction or pseudomembranous conjunctivitis strongly suggests a bacterial origin for conjunctivitis while follicular conjunctival reaction is more likely to indicate a viral etiology. there are many other associations between the etiology of conjunctivitis and symptoms that are thought to be true, but lack strong clinical evidence. for example, association between lack of itching and bacterial conjunctivitis have come under scrutiny in the recent years. other associations that once thought to be true but lack evidence include: recent upper respiratory tract infection and lymphadenopathy in favor of viral conjunctivitis; sinusitis, fever, malaise, and fatigue in association with bacterial conjunctivitis; and previous history of conjunctivitis with bilateral involvement of the eyes in favor of viral and allergic but not bacterial conjunctivitis. a meta-analysis in 2003 failed to find any clinical studies correlating the signs and symptoms of conjunctivitis with its underlying etiology.[17] following the above meta-analysis, a prospective study was conducted and found that combination of three signs, bilateral mattering of the eyelids, lack of itching, and no previous history of conjunctivitis were strong predictors of bacterial conjunctivitis.[18] having both eyes matter and their eyelashes adhere together in the morning was a stronger predictor for positive bacterial culture, and either itching or a previous episode of conjunctivitis made a positive bacterial culture less likely. in addition, types of the discharge (purulent, mucus, or watery) or other symptoms were not specific to any particular class of conjunctivitis. a more recent meta-analysis, which analyzed the clinical data of 622 patients from three clinical trials,[19] found that patients with purulent discharge or mild to moderate red eye were less likely to benefit from topical antibiotics; this finding reiterates lack of meaningful correlation between signs and symptoms and the underlying etiology in most cases of conjunctivitis. another recent study in 2013 found a strong likelihood of positive bacterial culture results in patients with the “gluing of the eyelids” upon waking up in the morning, and the age above 50 at presentation.[20] how do laboratory findings help us? clinicians may collect discharge samples from eyes with conjunctivitis and send them for microbiological evaluation. conjunctival cultures are generally reserved for cases of suspected infectious neonatal conjunctivitis, recurrent conjunctivitis, conjunctivitis recalcitrant to therapy, conjunctivitis presenting with severe purulent discharge, and cases suspicious for gonococcal or chlamydial infection.[21] swabs from the discharge are better to be taken before the initiation of antimicrobial therapy. the swabs are then plated in various growth mediums in the laboratory for obtaining cultures. sabouraud agar plates are used to identify fungus, and it should be utilized in patients with chronic blepharitis and those who are immunocompromised. anaerobic culture plates may also be helpful, especially in patients with a history of previous surgery or trauma.[22] if antimicrobial therapy has already been started, they should be stopped 48 hours prior to obtaining cultures. in a five-year review of 138 pediatric ocular surface infections, the most common organisms were coagulase-negative staphylococci, followed by pseudomonas aeruginosa and staphylococcus aureus.[23] nucleic acid amplification techniques, requiring special swabs, may be used in diagnosing viral infections, where a multitude of polymerase chain reaction (pcr) tests for detection of viruses are available. although primary studies from in-office rapid antigen testing for adenoviruses report 89% sensitivity and up to 94% specificity,[21] the results of more recent studies point toward a high specificity but only moderate sensitivity ranging from 39.5% to 50%.[24] accordingly, it may be suggested 376 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 conjunctivitis; azari and arabi that negative adeno-plus test results should be confirmed by real-time pcr owing to its suboptimal sensitivity. for those suspected of having allergic conjunctivitis, skin scratch test or intradermal injection of common allergens, and assays for detecting elevated in vitro levels of specific serum ige may be used; however, the diagnosis of allergic conjunctivitis remains a clinical one. viral conjunctivitis viral conjunctivitis is the most common overall cause of infectious conjunctivitis, and it is usually secondary to inoculation of the ocular surface with the adenoviruses.[25, 26] less frequently, other viruses may be the underlying etiology in viral conjunctivitis; amongst them, herpes simplex virus (hsv), varicella zoster virus (vzv), and enterovirus have been the subject of investigation.[27] adenoviral conjunctivitis as the leading cause of infectious conjunctivitis worldwide, up to 90% of viral conjunctivitis cases are caused by adenoviruses.[28] recent advances in genome sequencing of human adenoviruses (hadv) have identified over 72 unique hadv genotypes classified into seven different species (hadv-a through hadv-g), with hadv-d species having the most members and the strongest association with viral conjunctivitis.[29, 30] perhaps the most common form of infection by the adenoviruses in children is pharyngoconjunctival fever (pcf) caused by hadv types 3, 4, and 7.[31–33] this condition is usually characterized by the presence of fever, pharyngitis, periauricular lymphadenopathy, and acute follicular conjunctivitis. additional ocular surface findings include edema, hyperemia, and petechial hemorrhages of the conjunctiva as a result of interaction between pro-inflammatory cytokines and conjunctival vasculature.[32] this condition is self-limited, often resolving spontaneously in two–three weeks without any treatment. the most severe ocular manifestation of adenoviral infection is the epidemic keratoconjunctivitis (ekc); this condition affects both the conjunctiva and cornea, leaving behind long-lasting and permanent ocular surface changes and visual disturbances. ocular manifestations of ekc include conjunctival discharge, follicular conjunctivitis, corneal subepithelial infiltrates (sei), corneal scarring, development of conjunctival membranes and pseudomembranes, and symblepharon formation (figures 1 and 2). classically, serotypes 8, 19, 37, and less frequently serotype 4 were believed to be associated with ekc, but more recently, hadv-d53 and hadv-d54 have been identified in several outbreaks and are thought to be responsible for the majority of ekc cases.[30] pseudomembranes, which are sheets of fibrinrich exudates without blood or lymphatic vessels, may be encountered in the tarsal conjunctiva of the ekc patients.[35] depending on the intensity of inflammation, true conjunctival membranes may also form in ekc. true membranes, once form, can lead to the development of subepithelial fibrosis and symblepharon; additionally, they tend to bleed severely upon removal.[36] cornea is another tissue that may become adversely affected in ekc. replication of the virus in the corneal epithelium may cause superficial punctate keratopathy, followed by focal areas of epithelial opacities.[37] focal sei in the anterior stroma of the cornea appears approximately 7– 10 days following the initial involvement of the eyes with ekc[38] (figure 3). these opacities may persist for years, and they may be associated with visual disturbance, photophobia, and astigmatism. the incidence of sei formation in ekc has been reported to vary from 49.1 to 80%.[39] an immunologic reaction to the replicating adenoviruses in anterior stromal keratocytes is hypothesized to be the underlying mechanism for the formation of seis. the observation that these opacities recur following discontinuation of steroids supports the hypothesis.[40] adenovirus conjunctivitis is very contagious and it may be transmitted up to 50% of the time according to some reports.[41, 42] the virus may spread through contaminated fingers, medical devices, contaminated water at the swimming pools, or by sharing of personal items; as many as 46% of individuals with viral conjunctivitis had positive viral culture grown from their hands according to one study.[43] the adenovirus is a very hardy organism, and it is reported to be resistant to 70% isopropyl alcohol and 3% journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 377 conjunctivitis; azari and arabi figure 1. adenoviral conjunctivitis presenting as bilateral watery eyes. hydrogen peroxide.[44] the american academy of ophthalmology recommends using a 1:10 dilute bleach solution (sodium hypochlorite) to disinfect the office equipment and instruments against common infectious agents encountered in eye care clinics including the adenoviruses.[45] due to the highly contagious nature of viral conjunctivitis, frequent hand washing, meticulous disinfection of medical instruments, and isolation of conjunctivitis patients from the rest in the healthcare provider’s office has been recommended.[46] the incubation period for the adenovirus is approximately 5–12 days, while the infected individuals can transmit the disease for up to 14 days from the time they are infected.[41] there is no single effective treatment modality for viral conjunctivitis; however, use of frequent artificial tears, antihistamines containing eye drops, or cold-compresses seem to alleviate many of the clinical symptoms that are associated with this condition.[47, 48] topical and oral antiviral medications do not appear to be useful.[47, 48] in addition, antibiotic eye drops do not play a role in treating viral conjunctivitis and may even obscure the clinical picture by inducing ocular surface toxicity.[15, 16] other concerns with using antibiotic drops include increased bacterial resistance and the possibility of spreading the disease to the contralateral eye by cross-contamination through the infected bottles.[42] membranes or pseudomembranes may be peeled at the slit-lamp by using a pair of jeweler forceps or cotton swab after anesthetizing the ocular surface. this is done to alleviate patient discomfort and prevent future scar formation. monotherapy against viral conjunctivitis with povidone-iodine 2% have been investigated in a pilot study. the authors discovered that topical administration of povidone-iodine 2% four times a day for one week led to complete resolution of the disease in three-quarters of the eyes.[49] 378 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 conjunctivitis; azari and arabi figure 2. pseudomembrane formation in a patient with adenoviral conjunctivitis. the american academy of ophthalmology suggests that topical corticosteroids play an important role in the treatment of conjunctivitis, but they should be used judiciously and with caution in selected cases.[47] indications for steroid usage in viral conjunctivitis are membrane formation and sub-epithelial infiltration associated with severe photophobia and decreased vision. prolonging the duration of adenoviral conjunctivitis, exacerbation of hsv keratitis, and an increase in intraocular pressure are the main adverse effects of indiscriminate use of topical corticosteroids. prolongation of viral shedding following monotherapy with corticosteroids has been reported;[50] however, combination therapies with corticosteroids and anti-infective agents (i.e., antibiotics) have proven to be effective in treating viral and bacterial conjunctivitis.[51, 52] ophthalmic formulations of pvpi/dexamethasone are widely investigated. pvp-i 0.4%/dexamethasone 0.1% suspension, pvp-i 1.0%/dexamethasone 0.1%, and pvp-i 0.6%/dexamethasone 0.1% have been used, and the results suggest that the combination therapies reduce patient symptoms and eradicate the virus effectively.[50, 53–55] ongoing phase 3, randomized, doublemasked, controlled studies will further clarify the efficacy and safety of combined pvpi/dexamethasone in adenoviral conjunctivitis (clinicaltrials.gov identifiers: nct0299855441 and nct0299854142) and bacterial conjunctivitis (clinicaltrials.gov identifiers: nct03004924). use of 1 and 2% cyclosporine-a (csa) eye drops have been advocated for the treatment of seis, and it has been demonstrated to be effective in improving patient symptoms and reducing the amounts of infiltrates.[30, 56] however, jeng et al suggested that it might be difficult to wean patients completely off csa once they have started it; in their study, when csa was stopped, seis returned, necessitating reinstitution of the csa eye drops.[57] this finding is in contrast with the reinhard’s pilot study, where no recurrence was observed after discontinuation of the csa drops.[58] in a small study consisting of 39 patients, administration of 1% cyclosporine-a (four times a day) during the acute phase of viral conjunctivitis and continuing journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 379 conjunctivitis; azari and arabi figure 3. subepithelial infiltrations in a patient with adenoviral conjunctivitis. it thereafter for 21 days lowered the incidence of corneal opacities significantly.[59] a case-controlled double-blinded randomized clinical trial is needed to investigate the effectiveness of cyclosporine-a and to formulate an ideal tapering regiment for this medication. the use of topical tacrolimus eye drops has also been investigated for the treatment of seis secondary to adenoviral keratoconjunctivitis. when tacrolimus eye drops or ointments were used for an average of six months, a significant reduction in the size and numbers of seis was observed in 60% of the cases, while in 31.76% of the eyes, seis were eliminated after one year.[60] there was also a statistically significant improvement in the visual acuity of the patients with the use of topical tacrolimus. herpetic conjunctivitis it is estimated that 1.3–4.8% of all cases of acute conjunctivitis are caused by hsv infection.[61–63] hsv often causes a unilateral follicular conjunctivitis, which may be accompanied by a thin watery discharge and associated vesicular lesions on the skin of the eyelids. treatment consists of topical antiviral agents, including ganciclovir, idoxuridine, vidarabine, and trifluridine. the purpose of the treatment is to reduce virus shedding and the chance of the development of keratitis. ocular involvement with herpes zoster virus, especially when the first and second branches of the trigeminal nerve are involved, can lead to conjunctivitis in 41.1% of cases, eyelid lesions in 45.8%, uveitis in 38.2%, and corneal lesions such as seis, pseudodendrites, and nummular keratitis in another 19.1%.[64, 65] acute hemorrhagic conjunctivitis acute hemorrhagic conjunctivitis (ahc) is an extremely contagious form of viral conjunctivitis. it manifests by foreign body sensation, profuse tearing, eyelid edema, dilatation of conjunctival vessels, chemosis, and subconjunctival hemorrhage. in a small proportion of patients, fever, fatigue, and leg pain may ensue. two 380 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 conjunctivitis; azari and arabi picornaviruses, namely enterovirus 70 (ev70) and coxsackievirus a24 variant (ca24v), as well as certain subtypes of adenoviruses are believed to be the responsible pathogens.[66–68] like the other forms of conjunctivitis, ahc is also believed to be transmitted primarily by hand-toeye-to-hand contact and infected fomites.[69] the condition is self-limited and the symptoms diminish gradually during the first week of infection and completely resolves after 10–14 days.[69] medical intervention aims primarily at controlling the large outbreaks as well as instituting preventative measures to protect the vulnerable groups, such as children, elderly, pregnant women, and immunocompromised individuals, by encouraging frequent handwashing and reducing contact with the affected individuals.[68] miscellaneous viral conjunctivitis infection with molluscum contagiosum (mc) is characterized by multiple umblicated and papular skin lesions caused by pox-2 virus. skin-to-skin contact and sexual intercourse are the main routes of transmission. shedding of the viral proteins from the eyelid lesions into the tear film leads to chronic follicular conjunctival reaction, punctate keratopathy, and subepithelial pannus. rarely, primary mc lesions are found in the conjunctiva.[70] ebola hemorrhagic fever is a fatal disease caused by the species of ebolavirus. conjunctival injection, subconjunctival hemorrhage, and tearing have been reported in the affected individuals.[71] conjunctival injection, which is often bilateral and present in up to 58% of cases, has been identified in both the acute and late stages of this disease and may play an important role in the early diagnosis of this potentially deadly condition.[72] while humanto-human transmission through bodily fluids can spread the infection, the natural reservoir is thought to be the fruit bat.[73] coronaviruses include a broad family of viruses that normally affect animals, although some strains can spread from animals to humans.[74] the most recently isolated strain of coronavirus, “2019ncov” , has made the headlines since it was first recognized in december 2019 in china. covid-19 has been reported to cause fever, cough, shortness of breath, and even death.[75, 76] some reports have suggested that this virus can cause conjunctivitis and be transmitted via the conjunctival secretions of the infected individuals.[76] all healthcare professionals including the ophthalmologists should be vigilant in approaching patients with conjunctivitis and respiratory symptoms, especially if they report a recent history of travel to high risk regions.[76] bacterial conjunctivitis while in adults, bacterial conjunctivitis is less common than viral conjunctivitis, in children, it is encountered more frequently.[77] bacterial conjunctivitis can result from either a direct contact with infected individuals or from abnormal proliferation of the native conjunctival flora.[78] contaminated fingers,[41] oculogenital spread,[47] and contaminated fomites[79] are common routes of transmission. in addition, certain conditions such as compromised tear production, disruption of the natural epithelial barrier, abnormality of adnexal structures, trauma, and immunosuppressed status increase the likelihood of contracting bacterial conjunctivitis.[47] acute bacterial conjunctivitis is most often caused by staphylococcus species, haemophilus influenza, streptococcus species, moraxella catarrhalis, and gram-negative intestinal bacteria.[80] in younger children, minor epidemics may occur secondary to h. influenza or s. pneumonia. acute bacterial conjunctivitis manifests by foreign body sensation and increased ocular secretion in addition to moderate conjunctival hyperemia (figure 4). several studies on bacterial conjunctivitis[81, 82] demonstrate that sticky eyelids and itching may be present in approximately 90% of the affected individuals; these findings are followed by the less frequently encountered signs and symptoms such as purulent secretion and ocular burning. h. influenza conjunctivitis may be associated with acute otitis media and upper respiratory tract infection.[80] in more than 60% of cases, spontaneous cure occurs within one–two weeks,[83] and serious complications are extremely rare.[84] however, presence of a large population of bacteria on the conjunctiva exposes the patient to a higher risk of keratitis, particularly in conditions associated with corneal epithelial defects, such as dry eye.[80] although topical antibiotics reduce the duration of the disease, no difference in the outcome is seen journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 381 conjunctivitis; azari and arabi between the treatment and placebo groups. in a meta-analysis,[81], consisting of 3,673 patients from 11 randomized clinical trials, antibiotic treatment increased the rate of clinical improvement by 10% compared to placebo. both “2 to 5” and “6 to 10” day regiments were included in this analysis. although, highly virulent bacteria can potentially inflict serious damage to the ocular surface and the eye,[78], no sight-threatening complications were reported in any of the placebo groups in the aforementioned meta-analysis.[85] all broad-spectrum antibiotic eye drops seem to be effective in treating bacterial conjunctivitis and it is unlikely that there is a significant difference among various antibiotics in achieving clinical cure. factors that influence antibiotic choice are local availability, patient allergies, resistance patterns, and cost. from a large systematic review, it was concluded that topical antibiotics were more effective in achieving clinical and microbial cure when patients had positive bacterial cultures.[21] however, no significant difference has been reported in clinical cure rate when different frequencies of the antibiotics were administered.[86, 87] due to lengthening the course of the illness and potentiating the infection, topical steroids should be avoided[47] (table 3). methicillin-resistant s. aureus conjunctivitis the term methicillin-resistant s. aureus (mrsa) refers to staphylococcus aureus species that are resistant to methicillin antibiotic; however, nowadays the term is used to describe resistance to all β-lactam antimicrobials.[88] growing in prevalence, 3–64% of all ocular staphylococcus conjunctival infections are mrsa conjunctivitis.[89] suspected cases need to be treated with fortified vancomycin eye drops or ointments.[90] culturedirected administration of antimicrobials, effective dosing, considering the local resistance patterns, and appropriate antiseptic strategies should be applied to restrict the spread of mrsa conjunctivitis.[91] chlamydial conjunctivitis chlamydia trachomatis may cause a variety of ocular surface infections including trachoma, neonatal conjunctivitis, and inclusion conjunctivitis. serotype d-k are causative agents for neonatal conjunctivitis and adult inclusion conjunctivitis, while trachoma is caused by serotypes a, b, ba, and c.[92] inclusion conjunctivitis is reported to cause 1.8– 5.6% of all cases of acute conjunctivitis,[61, 62, 93] where the majority of cases are unilateral and have concurrent genital infection.[94] patients often present with mild mucopurulent discharge and follicular conjunctivitis persisting for weeks to months.[77] up to 54% of men and 74% of women are reported to have simultaneous genital infection.[95] the disease is frequently acquired via oculogenital spread.[47] treatment with systemic antibiotics such as oral azithromycin and doxycycline is efficacious, while addition of topical antibiotics is not beneficial. treatment of sexual partners and looking for the evidence of coinfection with gonorrhea must be instituted. as the leading cause of infectious blindness in the world, trachoma affects 40 million individuals worldwide; this infection is prevalent in areas with poor hygiene. although mucopurulent discharge is the initial presenting sign, in the later stages, scarring of the eyelids, conjunctiva, and cornea may lead to loss of vision. a single dose of oral azithromycin (20 mg/kg) in addition to oral tetracycline or erythromycin for three weeks is very effective. patients may also be treated with topical antibiotic ointments, such as tetracycline and erythromycin, for six weeks.[96, 97] in newborns, chlamydia can cause conjunctivitis following passage through an infected birth canal. the acute phase, which typically begins between days 5 and 14 following vaginal delivery, is characterized by purulent discharge, erythema and edema of the eyelids and conjunctiva.[98] more prevalent than gonococcal conjunctivitis (gc), neonatal conjunctivitis secondary to c. trachomatis is considered the most frequent infectious cause of neonatal conjunctivitis worldwide.[98–100] although the chlamydial conjunctivitis has a mild course, scarring of the cornea and/or conjunctiva have been reported in untreated cases.[101] it is important to note that up to 20% of the neonates who are exposed to chlamydia may develop pneumonia; in these, 50% demonstrate a previous history of conjunctivitis.[102] a recent meta-analysis supports the superiority of traditional treatment with systemic erythromycin at 50 mg/kg per day (given in four divided doses 382 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 conjunctivitis; azari and arabi table 3. ophthalmic drug therapies for acute bacterial conjunctivitis. antibiotic agents treatment aminoglycosides gentamicin ointment: 4 ×/d for 1 wk solution: 1-2 drops 4 ×/d for 1 wk tobramycin ointment: 3 ×/d for 1 wk fluoroquinolones besifloxacin 1 drop 3 ×/d for 1 wk ciprofloxacin ointment: 3 ×/d for 1 wk solution: 1-2 drops 4 ×/d for 1 wk gatifloxacin 3 ×/d for 1 week levofloxacin 1-2 drops 4 ×/d for 1 wk moxifloxacin 3 ×/d for 1 wk ofloxacin 1-2 drops 4 ×/d for 1 wk macrolides azithromycin 2 ×/d for 2 d; then 1 drop daily for 5 d erythromycin 4 ×/d for 1 wk sulfonamides sulfacetamide ointment: 4 ×/d and at bedtime for 1 wk solution: 1-2 drops every 2-3 h for 1 wk combination drops trimethoprim/polymyxin b 1 or 2 drops 4 ×/d for 1 wk figure 4. thick purulent discharge in a patient with acute bacterial conjunctivitis. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 383 conjunctivitis; azari and arabi figure 5. spectrum of allergic conjunctivitis. cs, corticosteroid figure 6. cobblestone appearance of large conjunctival papillae in a patient with vkc (left). limbal vkc with horner-trantas dots in another patient (right). for two weeks), in comparison to topical antibiotic therapy alone.[103] a recent study evaluating the efficacy of azithromycin in neonatal chlamydial conjunctivitis[104] demonstrated superiority of erythromycin over azithromycin; however, risk of pyloric stenosis related to the use of erythromycin may reduce its clinical use in neonates in the future.[103] additionally, lessfrequent dose of azithromycin may improve compliance.[105] gonococcal conjunctivitis (gc) typically viewed as a condition affecting the neonates, gc, however, affects other age groups as well.[106] neisseria gonorrhoeae is a common cause of hyperacute conjunctivitis in neonates and sexually active adults.[78] ocular infection with n. gonorrhea is associated with a high prevalence of corneal perforation.[80] gc should be considered as the causative agent in neonates who present with conjunctivitis in days 2 to 5 after delivery.[106] in both neonatal and non-neonatal populations, eye exam may reveal conjunctival injection and chemosis along with copious mucopurulent discharge; a tender globe with periauricular lymphadenopathy may also be associated with this type of conjunctivitis.[106] the suggested treatment for neonates include single dose of ceftriaxone (25 to 50 mg/kg), or cefotaxime (100 mg/kg iv or im), in addition to hourly saline irrigation of the ocular surface.[106–108] non-neonates can be treated with combination of 1 gm of im ceftriaxone given in a single dose and 1 gm of oral azithromycin (which is used to treat the frequently encountered chlamydial coinfection). irrigation of the ocular surface with saline solution is not necessary in adults.[106] allergic conjunctivitis ocular allergy can affect the entire ocular surface including conjunctiva, eyelids, and cornea. according to the immunological mechanism responsible for the final clinical picture, leonardi et al have classified ocular allergic conditions 384 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 conjunctivitis; azari and arabi figure 7. some systemic and dermatological conditions associated with conjunctivitis. figure 8. symblepharon formation in a patient with ocular cicatricial pemphigoid. into three main categories:[109] ige-mediated reactions, including seasonal allergic conjunctivitis (sac) and perennial allergic conjunctivitis (pac); combined ige and non-ige-mediated reactions, including vkc and akc; and non-ige-mediated reactions, including giant papillary conjunctivitis (gpc) and contact dermatoconjunctivitis (cdc) (figure 5). journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 385 conjunctivitis; azari and arabi seasonal allergic conjunctivitis (sac) and perennial allergic conjunctivitis (pac) sac and pac are considered as the most prevalent allergic ocular conditions, affecting 15–20% of the population.[110] the pathogenesis is predominantly an ige-mediated hypersensitivity reaction, and allergen-specific ige antibodies are found in almost all cases of sac and pac.[111] activation of mast cells contributes to increased levels of histamine, prostaglandins, and leukotrienes in the tear film. this phase, which is known as the early response phase, clinically lasts 20–30 min.[8] sac, also known as hay fever conjunctivitis, is seen in all age groups. the ocular manifestations occur predominantly during the spring and summer months when pollens from the trees and plants are released into the air. pac on the other hand can occur throughout the year with exposure to more common allergens such as animal hair, mites, and feathers.[112] clinical signs and symptoms are similar in sac and pac, and include itching and burning of the eyes, tearing, and rhinorrhea. corneal involvement is rarely seen.[9] vernal keratoconjunctivitis (vkc) vkc is known as the disease of young males who live in warmer climates.[113, 114] although vkc is frequently diagnosed in children, adults can also be affected with this condition.[115] a mixture of ige and non-ige reaction in response to nonspecific stimuli, such as wind, dust, and sunlight is often elucidated in this condition. accordingly, skin tests and serum ige antibody tests to well-known allergens are generally negative.[116] both clinical and histological findings support the concomitant role of t-helper 2 and ige in the pathogenesis of vkc.[8, 117] recently, il-17 has been reported to be linked to vkc, where its serum levels can serve as a marker for the severity of the disease.[118, 119] high percentage of antinuclear antibodies (ana) positivity and family history of autoimmune disorders in patients with vkc suggests a strong link between this condition and other autoimmune disorders including atopy.[120, 121] typical seasonal patterns as well as perennial forms have been reported in patients affected with vkc.[122] presence of papillary hyperplasia is essential for the diagnosis of vkc, and its presence allows for the differentiation of vkc from other related entities such as sac and pac.[123] conjunctival injection, profuse tearing, severe itching, and photophobia are the main clinical signs and symptoms that are associated with vkc. there are three clinical forms of vkc that include limbal, palpebral, and mixed type.[112] limbal type is characterized by limbal papillary reaction and gelatinous thickening of the limbus; when the disease is active, horner-trantas dots are usually present at the superior limbal margins.[112] the hallmark of the palpebral vkc is the presence of giant papillae, with consequent cobblestone appearance. the mixed type has the features of palpebral and limbal vkc simultaneously (figure 6). the corneal pathology that is seen in vkc is partly caused by the mechanical trauma from the tarsal conjunctival papillae and the inflammatory responses secondary to the release of cytokines. the inflammatory mediators are believed to be released by the eosinophils and mast cells that are infiltrated into the conjunctival tissue.[124, 125] in up to 6% of patients, corneal ulcers (i.e., shields ulcer) and plaques may develop, leading to the exacerbation of the clinical symptoms and worsening of the vision.[126, 127] these ulcers are usually found as oval lesions with elevated margins surrounding a chronic epithelial defect covered by eosinophilic and epithelial debris in the upper parts of the cornea.[128] keratoconus is another entity that is highly associated with vkc affecting nearly 15% of the patients with this condition.[129] atopic keratoconjunctivitis (akc) akc is characterized by chronic allergic disease of the eyelid, cornea, and conjunctiva. it is considered the ocular component of atopic dermatitis (ad), and roughly 95% of the patients with akc have concomitant ad;[8, 11] however, less than half of patients with ad have involvement of their ocular tissue.[130] many cytokines are released from the epithelial cells of the conjunctiva as well as the inflammatory cells that have infiltrated the conjunctival tissues in akc. this causes constant remodeling of the ocular surface connective tissue leading to mucus metaplasia, scar formation, and corneal neovascularization.[131] akc is typically diagnosed in the second and third decades of life, although scattered cases are seen in the early childhood as well as in the fifth 386 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 conjunctivitis; azari and arabi decade of life.[132] age of the onset, duration of the disease, and clinical presentations may help clinicians to distinguish this condition from vkc.[132] clinical manifestation of akc includes epiphora, itching, redness, and decreased vision. presentation is often bilateral; however, unilateral disease has been reported.[133] the eyelid skin may be edematous with a sandpaper-like texture. conjunctival injection and chemosis range from mild to severe, and conjunctival scarring is common.[11] trantas dots and giant papillae may or may not be present. in contrast to vkc, akc is associated with conjunctival fibrosis and corneal vascularization and opacities. an early cataract surgery is not uncommon in akc patients, as this condition is associated with formation of “atopic cataracts” at a relatively young age. shield-like cataracts, as well as nuclear, cortical and even posterior subcapsular cataracts may also occur. nearly 50% of akc patients test negative for common allergens.[8] giant papillary conjunctivitis (gpc) similar to vernal conjunctivitis, gpc is characterized by papillary hypertrophy of the superior tarsal conjunctiva.[134] although gpc is primarily considered as a complication of contact lens usage, this condition has also been reported in association with corneal foreign bodies, filtering blebs, ocular prostheses, exposed sutures, limbal dermoids, and tissue adhesives.[135–137] the classic signs of gpc consist of excessive mucous secretion associated with decreased contact lens tolerance.[137] mast cells and eosinophils may be found in the conjunctiva; however, there are no increases in the levels of ige or histamines in the tears of patients with gpc.[8] gpc can occur with both hydrogel and rigid contact lenses, and it has been reported with either hydroxyethyl methacrylate (hema), silicone polymers, or the new gas permeable polymers.[134] however, it is less frequent with rigid contact lenses. mechanical injuries due to contact lens wear and inflammatory reactions secondary to surface proteins of the lens can contribute to the chronic inflammatory damage of the ocular surface[110, 138] seen in this condition. contact allergy cdc is a classic example of type-iv delayed hypersensitivity reaction that occurs through interaction of antigens with t cells followed by release of cytokines.[139] low molecular weight allergens combine with host proteins to form the final allergens capable of exerting immune response. some of the known allergens for cdc include poison ivy, poison oak, neomycin, nickel, latex, atropine and its derivatives.[8] primary sensitization phase describes the process through which memory t cells derive from resident t cells of the ocular tissue, while the following elicitation phase includes the interaction between these memory cells and allergens.[8] il-17-producing th cells and regulatory t cells also play a role in the pathogenesis of cdc.[140] similar to akc, contact allergy involves the conjunctiva, cornea, and eyelids. the condition may be associated with itching, lid swelling, follicular reaction, and even cicatrization in later stages of the disease. the corneal involvement may be in the form of punctate keratitis, pseudodendritic keratitis, and grayish stromal infiltrates.[112, 141] treatment avoidance of the allergens is the main stay of treatment for many forms of allergies including allergic conjunctivitis. artificial tears provide a barrier function, dilute various allergens, and flush the ocular surface clean from many inflammatory mediators. the treatment options for allergic conjunctivitis include lubricating eye drops, anti-histamines, and mast cell stabilizers.[142, 143] many studies have demonstrated the superiority of topical antihistamines and mast cell stabilizers compared to placebo in alleviating the symptoms of allergic conjunctivitis; in addition, it has been demonstrated that antihistamines are more beneficial than mast cell stabilizers for providing short-term relief.[144] several eye drop preparations with dual action (antihistamine and mast cellstabilizing effects) including olopatadine, ketotifen, azelastine, and epinastine have been introduced to market in the recent years. these agents can provide simultaneous histamine receptor antagonist effects, stabilize mast-cell membranes, journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 387 conjunctivitis; azari and arabi and modify the action of eosinophils.[145] mast cell stabilizers require a loading period of several weeks, and therefore, they are better to be administered before the antigen exposure. oral antihistamines are commonly used for alleviating the ocular symptoms in patients with allergic conjunctivitis. second generation antihistamines are preferred due to their fewer adverse systemic side effects.[146] unfortunately, oral antihistamines induce ocular drying, which can significantly worsen the symptoms of allergic conjunctivitis.[147] steroids should be used judiciously and only in selected cases. topical and oral administration, in addition to supratarsal injections are often required if the condition is severe; unfortunately, any route of corticosteroid administration is associated with formation of cataracts and elevated intraocular pressure.[112] non-steroidal anti-inflammatory drugs such as ketorolac and diclofenac can also be added to the treatment regimen to provide additional benefits. moreover, other steroid-sparing agents such as cyclosporine-a and tacrolimus are effective in treating severe and chronic forms of ocular allergies. allergen-specific immunotherapy, which has gained popularity in the recent years, works by inducing clinical tolerance to a specific allergen. this appears to be an effective treatment options for those with allergic rhinoconjunctivitis who demonstrate specific ige antibodies.[148] traditionally, immunotherapy is performed via subcutaneous injections; however, sublingual immunotherapy (slit) has drawn the attention among allergists as an alternative. slit has been shown to effectively reduce the ocular and nasal signs and symptoms of allergic conjunctivitis, with a greater benefit toward improving the nasal symptoms.[112] conjunctivitis associated with systemic diseases conjunctivitis may be the initial presentation for many systemic diseases; therefore, a thorough history and systemic evaluation in selected cases may help in early diagnosis of many potentially disabling and even life-threatening conditions. a summary of systemic diseases associated with conjunctivitis is provided in figure 7. reactive arthritis conjunctivitis is one of the most common ocular manifestations of reactive arthritis; other associated ocular entities include uveitis, episcleritis, scleritis, and keratitis.[149] conjunctivitis in reactive arthritis entities manifests itself as conjunctival hyperemia with purulent discharge. occurring in nearly one third of the patients, conjunctivitis is an essential component of the “reiter’s triad”.[150] conjunctivitis usually happens early in the course of reactive arthritis and it may even precede it in some instances; given its mild initial clinical presentation, it is often missed. the signs and symptoms usually abate within one to four weeks; however, in some cases, progression to more severe ocular surface problems may ensue.[151] rosacea ocular surface may also be involved in the inflammatory course of ocular rosacea. the clinical findings include a follicular and papillary conjunctival reaction in association with interpalpebral conjunctival hyperemia. in addition, cicatrization of the conjunctival tissue, mimicking trachoma, may be seen in these patients. conjunctival scarring secondary to entropion and trichiasis has been reported to occur in approximately 10% of the cases. conjunctival granuloma, pinguecula, phlyctenule, and peripheral corneal infiltration and phlyctenule are amongst some of the other findings associated with ocular rosacea.[152] graft-versus-host disease conjunctival involvement is rarely seen in acute graft-versus-host disease (gvhd); however, its presence indicates more severe systemic involvement and a poor prognosis. conjunctival involvement in gvhd ranges from mild conjunctival injection to pseudomembranous and cicatrizing conjunctivitis.[153, 154] in acute gvhd, conjunctivitis is often ulcerative and manifests itself with numerous alternating episodes of conjunctival hemorrhage and 388 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 conjunctivitis; azari and arabi exudative discharge. sterile purulent discharge, pseudomembrane formation, and scarring are amongst the other findings in this condition.[153] in the chronic form of gvhd, one-fourth to three-fourth of the patients suffer from dry eyes, where its severity correlates with the severity of gvhd.[155] frequently, keratoconjunctivitis sicca persists after remission of gvhd.[156] four stages of conjunctival gvhd have been described in the literature. stage 1 is marked by simple conjunctival injection. stage 2 is characterized by an exudative response, which may lead to conjunctival chemosis. stage 3 is characterized by pseudomembrane formation; majority of the patients are diagnosed at this stage of the diseases. stage 4 is manifested by scarring and cicatrization of the conjunctival tissue.[153, 156] ocular cicatricial pemphigoid ocular cicatricial pemphigoid is a rare condition. patients are often in their fifth and sixth decades of life at presentation, and females are up to three times more frequently affected than males.[157] chronic inflammation, loss of conjunctival goblet cells along with an abnormal mucosal epithelial turn-over leads to desiccation of the ocular surface in this condition[158] (figure 8). disruption of conjunctival immune network increases the risk of ocular surface infection.[158] recurrent infectious conjunctivitis and trichiasis may lead to keratinization of the surface epithelium.[158] definitive diagnosis requires direct immunofluorescence, where deposits of immunoglobulins and/or complements produce areas of linear hyperfluorescence at the epithelial basement membrane. systemic immunosuppression along with frequent lubrication is often needed to adequately control this condition. stevens-johnson syndrome and toxic epidermal necrolysis ophthalmic manifestations of the acute stages of stevens-johnson syndrome (sjs) and toxic epidermal necrolysis (ten) range from conjunctival hyperemia to near-complete sloughing of palpebral conjunctiva and lid margins.[159] acute ocular involvement is reported to occur in up to 88% of the cases.[159] it remains unclear whether the severity of ocular involvement is any different between sjs and ten.[160] long-term adverse consequences following the acute stage of ocular surface disease include severe dry eyes, symblepharon formation, corneal limbal stem cell deficiency, and corneal scarring.[160] toxic conjunctivitis it has been recently realized that long-term use of topical eye medications may induce ocular surface changes including dry eyes, conjunctival inflammation, ocular surface fibrosis, and scarring.[161, 162] another area where the side effects of topical eye drops cause significant ocular morbidity is their use in glaucoma and in patients who have undergone glaucoma surgery. subclinical infiltration of the conjunctival epithelium and substantia propria by inflammatory cells has also been reported.[163, 164] the published literature during the past decade has pointed to the deleterious effects of benzalkonium chloride (bak), which is used as a preservative in eye drops, on the ocular surface.[165] allergic reactions are the most clinically noticeable side effect of the eye drops; however, they are far less frequent and harmful than their adverse toxic side effects.[166] the allergic reaction to eye drops includes simple conjunctival congestion, papillary conjunctivitis, and gpc.[165] the signs and symptoms usually manifest a few days after starting the offending eye drop and tend to resolve quickly when the medication is stopped.[166] observational studies have confirmed the high prevalence of dry eyes in glaucoma patients related to the number of eye drops being used. this ranges from 11% in those who use only one eye drop to 43% in those who use two or three different eye drops.[167] similarly, a cross-sectional study evaluating the ocular surface in 101 patients being treated for glaucoma reported that approximately 60% of them were symptomatic in at least one eye.[168] in a survey performed on 300 patients in the us between 2001 and 2004, adverse side effects were reported to be the second most common reason for switching eye drops.[169] journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 389 conjunctivitis; azari and arabi increase in fibroblast density in the conjunctiva, and development of subconjunctival fibrosis has been reported in patients who use antiglaucoma drops chronically.[165] in a series of 145 patients, thorne et al reported that exposure to antiglaucoma eye drops was the primary reason for development of pseudopemphigoid.[170] despite the indisputable data and the findings from multiple observational studies on the harmful side effects of bak, it is still used as the main preservative ingredient in most eye drop preparations due to lack of a better alternative.[165] limiting the exposure to preservatives may diminish the toxic side effects of eye drops; this will likely lead to higher patient compliance and result in a more favorable clinical outcome, especially in those who need to be on antiglaucoma medications. summary approximately 1% of all patient visits to their primary care physician is conjunctivitis related, and the estimated cost of infectious conjunctivitis to the healthcare is more than $800 million annually in the us alone.[2] the first step in approaching a patient with presumed conjunctivitis is to rule out serious ocular conditions that present with “red eye”, mimicking conjunctivitis. this must be done with obtaining a thorough history and performing a detailed ophthalmologic and physical examination. ancillary laboratory testing and imaging are also important components of evaluating these patients. various studies have demonstrated that obtaining a thorough history is essential to narrow down the differential diagnosis and discover the underlying etiology for the conjunctivitis, while relying solely on the presenting signs and symptoms can be misleading and often leads to an inaccurate diagnosis. viral conjunctivitis followed by bacterial conjunctivitis are the most common causes of infectious conjunctivitis.[15, 25, 81] the majority of viral conjunctivitis cases are due to adenoviruses,[28] and the use of rapid antigen test to diagnose adenoviral conjunctivitis may present an appropriate strategy to avoid overuse of antibiotics. bacterial pathogens are isolated in half of the cases of conjunctivitis,[61] and approximately 60% of culture-positive cases are known to be self-limited.[80] cultures should be obtained from the conjunctival swabs of patients that do not respond to therapy, and those suspected to have chlamydial infection and hyperacute conjunctivitis.[47] treatment with topical antibiotics is usually recommended for suspected cases of chlamydial and gonococcal conjunctivitis and contact lens wearers.[61, 80] the majority of cases of allergic conjunctivitis are due to seasonal allergies. antihistamines and mast cell stabilizers are widely used for treating allergic conjunctivitis. steroids must be used judiciously and only when indicated. for patients with chronic conjunctivitis, possibility of systemic diseases and adverse effects of eye drops with preservatives should be kept in mind. references 1. shekhawat ns, shtein rm, blachley ts, stein jd. antibiotic prescription fills for acute conjunctivitis among enrollees in a large united states managed care network. ophthalmology 2017;124:1099–1107. 2. smith af, waycaster c. estimate of the direct and indirect annual cost of bacterial conjunctivitis in the united states. bmc ophthalmol 2009;9:13. 3. ryder ec, benson s. conjunctivitis. in: statpearls. treasure island (fl): statpearls publishing llc; 2020. 4. de laet c, dionisi-vici c, leonard jv, mckiernan p, mitchell g, monti l, et al. recommendations for the management of tyrosinaemia type 1. orphanet j rare dis 2013;8:8–8. 5. sati a, sangwan vs, basu s. porphyria: varied ocular manifestations and management. bmj case rep 2013;2013:bcr2013009496. 6. narayana s, mcgee s. bedside diagnosis of the ’red eye’: a systematic review. am j med 2015;128:1220–1224.e1221. 7. everitt h, little p. how do gps diagnose and manage acute infective conjunctivitis? a gp survey. fam pract 2002;19:658–660. 8. la rosa m, lionetti e, reibaldi m, et al. allergic conjunctivitis: a comprehensive review of the literature. ital j pediatr 2013;39:18. 9. friedlaender mh. ocular allergy. curr opin allergy clin immunol 2011;11:477–482. 10. bielory l, frohman lp. allergic and immunologic disorders of the eye. j allergy clin immunol 1992;89:1–15. 11. bielory b, bielory l. atopic dermatitis and keratoconjunctivitis. immunol allergy clin north am 2010;30:323–336. 12. wilson-holt n, dart jk. thiomersal keratoconjunctivitis, frequency, clinical spectrum and diagnosis. eye 1989;3:581–587. 13. soparkar cn, wilhelmus kr, koch dd, wallace gw, jones db. acute and chronic conjunctivitis due to overthe-counter ophthalmic decongestants. arch ophthalmol 1997;115:34–38. 14. van ketel wg, melzer-van riemsdijk fa. conjunctivitis due to soft lens solutions. contact dermatitis 1980;6:321–324. 390 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 conjunctivitis; azari and arabi 15. woodland rm, darougar s, thaker u, cornell l, siddique m, wania j, et al. causes of conjunctivitis and keratoconjunctivitis in karachi, pakistan. trans royal soc trop med hygiene 1992;86:317–320. 16. bielory bp, o’brien tp, bielory l. management of seasonal allergic conjunctivitis: guide to therapy. acta ophthalmologica 2012;90:399–407. 17. rietveld rp, van weert hc, ter riet g, bindels pj. diagnostic impact of signs and symptoms in acute infectious conjunctivitis: systematic literature search. bmj 2003;327:789. 18. rietveld rp, ter riet g, bindels pj, sloos jh, van weert hc. predicting bacterial cause in infectious conjunctivitis: cohort study on informativeness of combinations of signs and symptoms. bmj 2004;329:206–210. 19. jefferis j, perera r, everitt h, van weert h, rietveld r, glasziou p, et al. acute infective conjunctivitis in primary care: who needs antibiotics? an individual patient data meta-analysis. br j gen pract 2011;61:e542–548. 20. van weert hc, tellegen e, ter riet g. a new diagnostic index for bacterial conjunctivitis in primary care. a rederivation study. eur j gen pract 2014;20:202–208. 21. azari aa, barney np. conjunctivitis: a systematic review of diagnosis and treatment. jama 2013;310:1721–1729. 22. drew rj, cole ts, newman w. how to use… eye swabs. arch dis child educ pract ed 2015;100:155–161. 23. wong vw, lai ty, chi sc, lam ds. pediatric ocular surface infections: a 5-year review of demographics, clinical features, risk factors, microbiological results, and treatment. cornea 2011;30:995–1002. 24. kam ky, ong hs, bunce c, ogunbowale l, verma s. sensitivity and specificity of the adenoplus point-of-care system in detecting adenovirus in conjunctivitis patients at an ophthalmic emergency department: a diagnostic accuracy study. br j ophthalmol 2015;99:1186–1189. 25. stenson s, newman r, fedukowicz h. laboratory studies in acute conjunctivitis. arch ophthalmology 1982;100:1275–1277. 26. fitch cp, rapoza pa, owens s, murillo-lopez f, johnson ra, quinn tc, et al. epidemiology and diagnosis of acute conjunctivitis at an inner-city hospital. ophthalmology 1989;96:1215–1220. 27. newman h, gooding c. viral ocular manifestations: a broad overview. rev med virol 2013;23:281–294. 28. o’brien tp, jeng bh, mcdonald m, raizman mb. acute conjunctivitis: truth and misconceptions. curr med res opin 2009;25:1953–1961. 29. singh g, zhou x, lee jy, yousuf ma, ramke m, ismail am, et al. recombination of the epsilon determinant and corneal tropism: human adenovirus species d types 15, 29, 56, and 69. virology 2015;485:452–459. 30. kuo ic. adenoviral keratoconjunctivitis: diagnosis, management, and prevention. curr ophthalmol rep 2019;7:118–127. 31. li j, lu x, sun y, lin c, li f, yang y, et al. a swimming pool-associated outbreak of pharyngoconjunctival fever caused by human adenovirus type 4 in beijing, china. int j infect dis 2018;75:89–91. 32. harley d, harrower b, lyon m, dick a. a primary school outbreak of pharyngoconjunctival fever caused by adenovirus type 3. comm dis intell 2001;25:9–12. 33. sinclair rg, jones el, gerba cp. viruses in recreational water-borne disease outbreaks: a review. j appl microbiol 2009;107:1769–1780. 34. darougar s, grey rh, thaker u, mcswiggan da. clinical and epidemiological features of adenovirus keratoconjunctivitis in london. br j ophthalmol 1983;67:1– 7. 35. jhanji v, chan tc, li ey, agarwal k, vajpayee rb. adenoviral keratoconjunctivitis. surv ophthalmol 2015;60:435–443. 36. chintakuntlawar av, chodosh j. cellular and tissue architecture of conjunctival membranes in epidemic keratoconjunctivitis. ocul immunol inflamm 2010;18:341– 345. 37. chigbu di, labib ba. pathogenesis and management of adenoviral keratoconjunctivitis. infect drug resist 2018;11:981–993. 38. richmond s, burman r, crosdale e, et al. a large outbreak of keratoconjunctivitis due to adenovirus type 8. the journal of hygiene 1984;93:285-291. 39. okumus s, coskun e, tatar mg, kaydu e, yayuspayi r, comez a, et al. cyclosporine a 0.05% eye drops for the treatment of subepithelial infiltrates after epidemic keratoconjunctivitis. bmc ophthalmol 2012;12:42. 40. ghanem rc, vargas jf, ghanem vc. tacrolimus for the treatment of subepithelial infiltrates resistant to topical steroids after adenoviral keratoconjunctivitis. cornea 2014;33:1210–1213. 41. gallenga pe, lobefalo l, colangelo l, della loggia g, orzalesi n, velati p, et al. topical lomefloxacin 0.3% twice daily versus tobramycin 0.3% in acute bacterial conjunctivitis: a multicenter double-blind phase iii study. ophthalmologica 1999;213:250–257. 42. udeh bl, schneider je, ohsfeldt rl. cost effectiveness of a point-of-care test for adenoviral conjunctivitis. am j med sci 2008;336:254–264. 43. jackson wb, low de, dattani d, whitsitt pf, leeder rg, macdougall r. treatment of acute bacterial conjunctivitis: 1% fusidic acid viscous drops vs. 0.3% tobramycin drops. can j ophthalmol 2002;37:228–237; discussion 237. 44. gordon yj, gordon ry, romanowski e, araullo-cruz tp. prolonged recovery of desiccated adenoviral serotypes 5, 8, and 19 from plastic and metal surfaces in vitro. ophthalmology 1993;100:1835–1839; discussion 1839– 1840. 45. junk ak, chen pp, lin sc, nouri-mahdavi k, radhakrishnan s, singh k, et al. disinfection of tonometers: a report by the american academy of ophthalmology. ophthalmology 2017;124:1867–1875. 46. bremond-gignac d, mariani-kurkdjian p, beresniak a, el fekih l, bhagat y, pouliquen p, et al. efficacy and safety of azithromycin 1.5% eye drops for purulent bacterial conjunctivitis in pediatric patients. pediatr infect dis j 2010;29:222–226. 47. varu dm, rhee mk, akpek ek, amescua g, farid m, garcia-ferrer fj, et al. conjunctivitis preferred practice pattern®. ophthalmology 2019;126:p94–p169. 48. leibowitz hm. antibacterial effectiveness of ciprofloxacin 0.3% ophthalmic solution in the treatment of bacterial conjunctivitis. am j ophthalmol 1991;112:29s–33s. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 391 conjunctivitis; azari and arabi 49. trinavarat a, atchaneeyasakul lo. treatment of epidemic keratoconjunctivitis with 2% povidone-iodine: a pilot study. j ocul pharmacol ther 2012;28:53–58. 50. kovalyuk n, kaiserman i, mimouni m, cohen o, levartovsky s, sherbany h, et al. treatment of adenoviral keratoconjunctivitis with a combination of povidone-iodine 1.0% and dexamethasone 0.1% drops: a clinical prospective controlled randomized study. acta ophthalmol 2017;95:e686–e692. 51. holland ej, bartlett jd, paterno mr, usner dw, comstock tl. effects of loteprednol/tobramycin versus dexamethasone/tobramycin on intraocular pressure in healthy volunteers. cornea 2008;27:50–55. 52. belfort r, jr., gabriel l, martins bispo pj, muccioli c, zacharias serapicos pc, clark l, et al. safety and efficacy of moxifloxacin-dexamethasone eyedrops as treatment for bacterial ocular infection associated with bacterial blepharitis. adv ther 2012;29:416–426. 53. clement c, capriotti ja, kumar m, et al. clinical and antiviral efficacy of an ophthalmic formulation of dexamethasone povidone-iodine in a rabbit model of adenoviral keratoconjunctivitis. investigative ophthalmology & visual science 2011;52:339-344. 54. pinto rd, lira rp, abe ry, fernandes felix jp, fernandes pereira av, leite arieta ce, et al. dexamethasone/povidone eye drops versus artificial tears for treatment of presumed viral conjunctivitis: a randomized clinical trial. curr eye res 2015;40:870–877. 55. pepose js, ahuja a, liu w, narvekar a, haque r. randomized, controlled, phase 2 trial of povidoneiodine/dexamethasone ophthalmic suspension for treatment of adenoviral conjunctivitis. am j ophthalmol 2019;205:197. 56. levinger e, slomovic a, sansanayudh w, bahar i, slomovic ar. topical treatment with 1% cyclosporine for subepithelial infiltrates secondary to adenoviral keratoconjunctivitis. cornea 2010;29:638–640. 57. jeng bh, holsclaw ds. cyclosporine a 1% eye drops for the treatment of subepithelial infiltrates after adenoviral keratoconjunctivitis. cornea 2011;30:958–961. 58. reinhard t, godehardt e, pfahl hg, sundmacher r. [local cyclosporin a in nummuli after keratoconjunctivitis epidemica. a pilot study]. ophthalmologe 2000;97:764– 768. 59. hillenkamp j, reinhard t, ross rs, böhringer d, cartsburg o, roggendorf m, et al. topical treatment of acute adenoviral keratoconjunctivitis with 0.2% cidofovir and 1% cyclosporine: a controlled clinical pilot study. arch ophthal 2001;119:1487–1491. 60. berisa prado s, riestra ayora ac, lisa fernandez c, chacon rodriguez m, merayo-lloves j, alfonso sanchez jf. topical tacrolimus for corneal subepithelial infiltrates secondary to adenoviral keratoconjunctivitis. cornea 2017;36:1102–1105. 61. cronau h, kankanala rr, mauger t. diagnosis and management of red eye in primary care. am fam phys 2010;81:137–144. 62. sheikh a, hurwitz b, van schayck cp, mclean s, nurmatov u. antibiotics versus placebo for acute bacterial conjunctivitis. cochrane database syst rev 2012;19:cd001211. 63. papa v, aragona p, scuderi ac, blanco ar, zola p, alessandro di b, et al. treatment of acute bacterial conjunctivitis with topical netilmicin. cornea 2002;21:43– 47. 64. puri lr, shrestha gb, shah dn, chaudhary m, thakur a. ocular manifestations in herpes zoster ophthalmicus. nepal j ophthalmol 2011;3:165–171. 65. sy a, mcleod sd, cohen ej, margolis tp, mannis mj, lietman tm, et al. practice patterns and opinions in the management of recurrent or chronic herpes zoster ophthalmicus. cornea 2012;31:786–790. 66. lim kh, yin-murphy m. epidemic conjunctivitis in singapore in 1970 and 1971. singapore med j 1973;14:86– 89. 67. kono r, sasagawa a, miyamura k, tajiri e. serologic characterization and sero-epidemiologic studies on acute hemorrhagic conjunctivitis (ahc) virus. am j epidemiol 1975;101:444–457. 68. zhang l, zhao n, huang x, jin x, geng x, chan tc, et al. molecular epidemiology of acute hemorrhagic conjunctivitis caused by coxsackie a type 24 variant in china, 2004-2014. sci rep 2017;7:45202. 69. langford mp, anders ea, burch ma. acute hemorrhagic conjunctivitis: anti-coxsackievirus a24 variant secretory immunoglobulin a in acute and convalescent tear. clin ophthalmol 2015;9:1665–1673. 70. serin s, bozkurt oflaz a, karabagli p, gedik s, bozkurt b. eyelid molluscum contagiosum lesions in two patients with unilateral chronic conjunctivitis. turk j ophthalmol 2017;47:226–230. 71. breman jg, heymann dl, lloyd g, mccormick jb, miatudila m, murphy fa, et al. discovery and description of ebola zaire virus in 1976 and relevance to the west african epidemic during 2013-2016. j infect dis 2016;214:s93– s101. 72. moshirfar m, fenzl cr, li z. what we know about ocular manifestations of ebola. clin ophthalmol 2014;8:2355– 2357. 73. bausch dg, schwarz l. outbreak of ebola virus disease in guinea: where ecology meets economy. plos negl trop dis 2014;8:e3056–e3056. 74. peiris js, lai st, poon ll, guan y, yam lyc, lim w, et al. coronavirus as a possible cause of severe acute respiratory syndrome. lancet 2003;361:1319-1325. 75. huang c, wang y, li x, ren l, zhao j, hu y, et al. clinical features of patients infected with 2019 novel coronavirus in wuhan, china. lancet 2020;395:p497–p506. 76. karimi s, arabi a, shahraki t, safi s. detection of severe acute respiratory syndrome coronavirus-2 in the tears of patients with coronavirus disease 2019. eye. retrieved from: https://doi.org/10.1038/s41433-020-0965-2. 77. epling j. bacterial conjunctivitis. bmj clin evid 2012;2012:0704. 78. shields t, sloane pd. a comparison of eye problems in primary care and ophthalmology practices. fam med 1991;23:544–546. 79. karpecki p, depaolis m, hunter ja, white em, rigel l, brunner ls, et al. besifloxacin ophthalmic suspension 0.6% in patients with bacterial conjunctivitis: a multicenter, prospective, randomized, double-masked, vehiclecontrolled, 5-day efficacy and safety study. clin ther 2009;31:514–526. 392 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 https://doi.org/10.1038/s41433-020-0965-2 conjunctivitis; azari and arabi 80. hovding g. acute bacterial conjunctivitis. acta ophthalmol 2008;86:5–17. 81. horven i. acute conjunctivitis. a comparison of fusidic acid viscous eye drops and chloramphenicol. acta ophthalmol 1993;71:165–168. 82. wall ar, sinclair n, adenis jp. comparison of fucithalmic (fusidic acid viscous eyedrops 1%) and noroxin (norfloxacin ophthalmic solution 0.3%) in the treatment of acute bacterial conjunctivitis. j drug assess 1998;1:549–558. 83. rose pw, harnden a, brueggemann ab, perera r, sheikh a, crook d, et al. chloramphenicol treatment for acute infective conjunctivitis in children in primary care: a randomised double-blind placebo-controlled trial. lancet 2005;366:37–43. 84. schiebel ne. evidence-based emergency medicine/systematic review abstract. use of antibiotics in patients with acute bacterial conjunctivitis. ann emer med 2003;41:407–409. 85. gong l, sun xh, qiu xd, zhang y-q, qu j, yuan zl, et al. [comparative research of the efficacy of the gatifloxacin and levofloxacin for bacterial conjunctivitis in human eyes]. [zhonghua yan ke za zhi] chinese j ophthalmol 2010;46:525–531. 86. tepedino me, heller wh, usner dw, brunner ls, morris tw, haas w, et al. phase iii efficacy and safety study of besifloxacin ophthalmic suspension 0.6% in the treatment of bacterial conjunctivitis. curr med res opin 2009;25:1159–1169. 87. hwang dg, schanzlin dj, rotberg mh, foulks g, raizman mb. a phase iii, placebo controlled clinical trial of 0.5% levofloxacin ophthalmic solution for the treatment of bacterial conjunctivitis. br j ophthalmol 2003;87:1004– 1009. 88. shanmuganathan va, armstrong m, buller a, tullo ab. external ocular infections due to methicillin-resistant staphylococcus aureus (mrsa). eye 2005;19:284–291. 89. zhang m, hu y, chen f. [clinical investigation of 0.3% levofloxacin eyedrops on the treatment of cases with acute bacterial conjunctivitis and bacterial keratitis]. yan ke xue bao [eye sci] 2000;16:146–148. 90. gross rd, lichtenstein s, schlech ba, gower la, potts sl. early clinical and microbiological responses in the treatment of bacterial conjunctivitis with moxifloxacin ophthalmic solution 0.5% (vigamox𝑇𝑀) using b.i.d. dosing. today ther trends 2003;21:227–237. 91. thareja t, kowalski r, jhanji v, kamyar r, dhaliwal d. mrsa keratitis and conjunctivitis: what does it mean practically? curr ophthalmol rep 2019;7:110–117. 92. burton mj. trachoma: an overview. br med bull 2007;84:99–116. 93. granet db, dorfman m, stroman d, cockrum p. a multicenter comparison of polymyxin b sulfate/trimethoprim ophthalmic solution and moxifloxacin in the speed of clinical efficacy for the treatment of bacterial conjunctivitis. j pediatr ophthalmol strabismus 2008;45:340–349. 94. leibowitz hm. the red eye. new engl j med 2000;343:345–351. 95. tabbara kf, el-sheikh hf, islam sm, hammouda e. treatment of acute bacterial conjunctivitis with topical lomefloxacin 0.3% compared to topical ofloxacin 0.3%. eur j ophthalmol 1999;9:269–275. 96. abelson mb, heller w, shapiro am, si e, hsu p, bowman lm. clinical cure of bacterial conjunctivitis with azithromycin 1%: vehicle-controlled, double-masked clinical trial. am j ophthalmol 2008;145:959–965. 97. cochereau i, meddeb-ouertani a, khairallah m, amraoui a, zaghloul k, pop m, et al. 3-day treatment with azithromycin 1.5% eye drops versus 7-day treatment with tobramycin 0.3% for purulent bacterial conjunctivitis: multicentre, randomised and controlled trial in adults and children. br j ophthalmol 2007;91:465–469. 98. darville t. chlamydia trachomatis infections in neonates and young children. semin pediatr infect dis 2005;16:235–244. 99. mallika p, asok t, faisal h, aziz s, tan a, intan g. neonatal conjunctivitis a review. malays fam phys 2008;3:77–81. 100. castro ochoa kj, mendez md. ophthalmia neonatorum. in: statpearls. treasure island (fl): statpearls publishing llc; 2020. 101. forster rk, dawson cr, schachter j. late follow-up of patients with neonatal inclusion conjunctivitis. am j ophthalmol 1970;69:467–472. 102. tipple ma, beem mo, saxon em. clinical characteristics of the afebrile pneumonia associated with chlamydia trachomatis infection in infants less than 6 months of age. pediatrics 1979;63:192–197. 103. zikic a, schunemann h, wi t, lincetto o, broutet n, santesso n. treatment of neonatal chlamydial conjunctivitis: a systematic review and meta-analysis. j pediatr infect dis soc 2018;7:e107–e115. 104. hammerschlag mr, gelling m, roblin pm, kutlin a, jule je. treatment of neonatal chlamydial conjunctivitis with azithromycin. pediatr infect dis j 1998;17:1049–1050. 105. srivastava k, arora a, kataria a, cappelleri jc, sadosky a, peterson am. impact of reducing dosing frequency on adherence to oral therapies: a literature review and metaanalysis. patient prefer adherence 2013;7:419–434. 106. costumbrado j, ng dk, ghassemzadeh s. gonococcal conjunctivitis. in: statpearls. treasure island (fl): statpearls publishing; 2020. 107. hammerschlag mr, smith-norowitz t, kohlhoff sa. keeping an eye on chlamydia and gonorrhea conjunctivitis in infants in the united states, 2010-2015. sex transm dis 2017;44:577. 108. pak ky, kim si, lee js. neonatal bacterial conjunctivitis in korea in the 21st century. cornea 2017;36:415–418. 109. leonardi a, de dominicis c, motterle l. immunopathogenesis of ocular allergy: a schematic approach to different clinical entities. curr opin allergy clin immunol 2007;7:429–435. 110. wong ah, barg ss, leung ak. seasonal and perennial allergic conjunctivitis. recent pat inflamm allergy drug discov 2014;8:139–153. 111. bonini s. atopic keratoconjunctivitis. allergy 2004;59:71– 73. 112. rathi vm, murthy si. allergic conjunctivitis. commun eye health 2017;30:s7–s10. 113. sofi ra, mufti a. vernal keratoconjunctivitis in kashmir: a temperate zone. int ophthalmol 2016;36:875–879. 114. katelaris ch. ocular allergy in the asia pacific region. asia pac allergy 2011;1:108–114. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 393 conjunctivitis; azari and arabi 115. de smedt s, wildner g, kestelyn p. vernal keratoconjunctivitis: an update. br j ophthalmol 2013;97:9–14. 116. jun j, bielory l, raizman mb. vernal conjunctivitis. immunol allergy clin north am 2008;28:59–82, vi. 117. zicari am, capata g, nebbioso m, de castro g, midulla f, leonardi l, et al. vernal keratoconjunctivitis: an update focused on clinical grading system. ital j pediatr 2019;45:64. 118. zicari am, nebbioso m, zicari a, mari e, celani c, occasi f, et al. serum levels of il-17 in patients with vernal keratoconjunctivitis: a preliminary report. eur rev med pharmacol sci 2013;17:1242–1244. 119. validad mh, khazaei ha, pishjoo m, safdari z. the study of interleukin-17 level in vernal keratoconjunctivitis disease and its relationship between symptom and sign severity. sem ophthalmol 2017;32:721–724. 120. occasi f, zicari am, petrarca l, nebbioso m, salvatori g, duse m. vernal keratoconjunctivitis and immunemediated diseases: one unique way to symptom control? pediatr allergy immunol 2015;26:289–291. 121. zicari am, nebbioso m, lollobrigida v, bardanzellu f, celani c, occasi f, et al. vernal keratoconjunctivitis: atopy and autoimmunity. eur rev med pharmacol sci 2013;17:1419–1423. 122. singhal d, sahay p, maharana pk, raj n, sharma n, titiyal js. vernal keratoconjunctivitis. surv ophthalmol 2019;64:289–311. 123. pucci n, novembre e, lombardi e, cianferoni a, bernardini r, massai c, et al. atopy and serum eosinophil cationic protein in 110 white children with vernal keratoconjunctivitis: differences between tarsal and limbal forms. clin exp allergy 2003;33:325–330. 124. kumagai n, fukuda k, fujitsu y, yamamoto k, nishida t. role of structural cells of the cornea and conjunctiva in the pathogenesis of vernal keratoconjunctivitis. prog retin eye res 2006;25:165–187. 125. leonardi a, bogacka e, fauquert jl, kowalski ml, groblewska a, jedrzejczak-czechowicz m, et al. ocular allergy: recognizing and diagnosing hypersensitivity disorders of the ocular surface. allergy 2012;67:1327– 1337. 126. solomon a. corneal complications of vernal keratoconjunctivitis. curr opin allergy clin immunol 2015;15:489–494. 127. cameron ja, mullaney pb. amblyopia resulting from shield ulcers and plaques of the cornea in vernal keratoconjunctivitis. j pediatr ophthalmol strabismus 1997;34:261–262. 128. cameron ja. shield ulcers and plaques of the cornea in vernal keratoconjunctivitis. ophthalmology 1995;102:985–993. 129. totan y, hepsen if, cekic o, gunduz a, aydin e. incidence of keratoconus in subjects with vernal keratoconjunctivitis: a videokeratographic study. ophthalmology 2001;108:824–827. 130. guglielmetti s, dart jk, calder v. atopic keratoconjunctivitis and atopic dermatitis. curr opin allergy clin immunol 2010;10:478–485. 131. offiah i, calder vl. immune mechanisms in allergic eye diseases: what is new? curr opin allergy clin immunol 2009;9:477–481. 132. chen jj, applebaum ds, sun gs, pflugfelder sc. atopic keratoconjunctivitis: a review. j am acad dermatol 2014;70:569–575. 133. li a, li s, ruan f, jie y. atopic keratoconjunctivitis: a diagnostic dilemma-a case report. medicine 2018;97:e0372. 134. elhers wh, donshik pc. giant papillary conjunctivitis. curr opin allergy clin immunol 2008;8:445–449. 135. forister jf, forister ef, yeung kk, ye p, chung my, tsui a, et al. prevalence of contact lens-related complications: ucla contact lens study. eye contact lens 2009;35:176– 180. 136. vengayil s, vanathi m, dada t, kai s, panda a. filtering bleb-induced giant papillary conjunctivitis. cont lens anterior eye 2008;31:41–43. 137. elhers w, donshik p. giant papillary conjunctivitis. curr opin allergy clin immunol 2008;8:445–449. 138. donshik pc, ehlers wh, ballow m. giant papillary conjunctivitis. immunol allergy clin north am 2008;28:83–103, vi. 139. niederkorn jy. immune regulatory mechanisms in allergic conjunctivitis: insights from mouse models. curr opin allergy clin immunol 2008;8:472–476. 140. oboki k, ohno t, saito h, nakae s. th17 and allergy. allergol int 2008;57:121–134. 141. dart j. corneal toxicity: the epithelium and stroma in iatrogenic and factitious disease. eye 2003;17:886–892. 142. schmid kl, schmid lm. ocular allergy: causes and therapeutic options. clin exp optom 2000;83:257–270. 143. gokhale ns. systematic approach to managing vernal keratoconjunctivitis in clinical practice: severity grading system and a treatment algorithm. indian j ophthalmol 2016;64:145–148. 144. owen cg, shah a, henshaw k, smeeth l, sheikh a. topical treatments for seasonal allergic conjunctivitis: systematic review and meta-analysis of efficacy and effectiveness. br j gen pract 2004;54:451–456. 145. mishra gp, tamboli v, jwala j, mitra ak. recent patents and emerging therapeutics in the treatment of allergic conjunctivitis. recent pat inflamm allergy drug discov 2011;5:26–36. 146. maziak w, behrens t, brasky tm, duhme h, rzehak p, weiland sk, et al. are asthma and allergies in children and adolescents increasing? results from isaac phase i and phase iii surveys in munster, germany. allergy 2003;58:572–579. 147. welch d, ousler gw, 3rd, nally la, abelson mb, wilcox ka. ocular drying associated with oral antihistamines (loratadine) in the normal population-an evaluation of exaggerated dose effect. adv exp med biol 2002;506:1051–1055. 148. broide dh. immunomodulation of allergic disease. ann rev med 2009;60:279–291. 149. szamocki s, martyn-hemphill c, green j. reactive arthritis: can’t see, can’t pee, can’t climb a tree…. trends urol men health 2016;7:17–20. 150. keat a. reiter’s syndrome and reactive arthritis in perspective. new engl j med 1983;309:1606–1615. 151. hamdulay ss, glynne sj, keat a. when is arthritis reactive? postgrad med j 2006;82:446–453. 394 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 conjunctivitis; azari and arabi 152. faraj hg, hoang-xuan t. chronic cicatrizing conjunctivitis. curr opin ophthalmol 2001;12:250–257. 153. jabs da, wingard j, green wr, farmer er, vogelsang g, saral r. the eye in bone marrow transplantation. iii. conjunctival graft-vs-host disease. arch ophthalmol 1989;107:1343–1348. 154. azari a, rezaei kanavi m, potter h, hematti p. autologous serum eye drop is safe and effective for treatment of dry eyes in graft-versus-host disease. invest ophthalmol vis sci 2013;54:4330–4330. 155. tabbara kf, al-ghamdi a, al-mohareb f, ayas m, chaudhri n, al-sharif f, et al. ocular findings after allogeneic hematopoietic stem cell transplantation. ophthalmology 2009;116:1624–1629. 156. nassar a, tabbara kf, aljurf m. ocular manifestations of graft-versus-host disease. saudi j ophthalmol 2013;27:215–222. 157. bedell aj. ocular pemphigus: a clinical presentation of kodachromes. trans am ophthalmol soc 1964;62:109– 122. 158. wang k, seitzman g, gonzales ja. ocular cicatricial pemphigoid. curr opin ophthalmol 2018;29:543–551. 159. kohanim s, palioura s, saeed hn, et al. acute and chronic ophthalmic involvement in stevens-johnson syndrome/toxic epidermal necrolysis a comprehensive review and guide to therapy. ii. ophthalmic disease. ocul surf 2016;14:168–188. 160. chow llw, shih kc, chan jcy, lai jsm, ng alk. comparison of the acute ocular manifestations of stevensjohnson syndrome and toxic epidermal necrolysis in chinese eyes: a 15-year retrospective study. bmc ophthalmol 2017;17:65. 161. broadway d, grierson i, hitchings r. adverse effects of topical antiglaucomatous medications on the conjunctiva. br j ophthalmol 1993;77:590–596. 162. schwab ir, linberg jv, gioia vm, benson wh, chao gm. foreshortening of the inferior conjunctival fornix associated with chronic glaucoma medications. ophthalmology 1992;99:197–202. 163. mietz h, niesen u, krieglstein gk. the effect of preservatives and antiglaucomatous medication on the histopathology of the conjunctiva. graefes arch clin exp ophthalmol 1994;232:561–565. 164. baudouin c, pisella pj, fillacier k, et al. ocular surface inflammatory changes induced by topical antiglaucoma drugs: human and animal studies. ophthalmology 1999;106:556–563. 165. baudouin c, labbe a, liang h, pauly a, brignolebaudouin f. preservatives in eyedrops: the good, the bad and the ugly. prog retin eye res 2010;29:312–334. 166. baudouin c. allergic reaction to topical eyedrops. curr opin allergy clin immunol 2005;5:459–463. 167. rossi gc, tinelli c, pasinetti gm, milano g, bianchi pe. dry eye syndrome-related quality of life in glaucoma patients. eur j ophthalmol 2009;19:572–579. 168. leung ew, medeiros fa, weinreb rn. prevalence of ocular surface disease in glaucoma patients. j glaucoma 2008;17:350–355. 169. zimmerman tj, hahn sr, gelb l, tan h, kim ee. the impact of ocular adverse effects in patients treated with topical prostaglandin analogs: changes in prescription patterns and patient persistence. j ocul pharmacol ther 2009;25:145–152. 170. thorne je, anhalt gj, jabs da. mucous membrane pemphigoid and pseudopemphigoid. ophthalmology 2004;111:45–52. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 395 original article choroidal thickness in different types of inherited retinal dystrophies hamideh sabbaghi1,2, phd; hamid ahmadieh3, md; jalil jalili4, phd; nazanin behnaz3, md maryam fakhri3, md; fatemeh suri3, phd; bahareh kheiri3, ms; mojtaba rajabpour2, bs morteza entezari3, md; narsis daftarian5, md 1ophthalmic epidemiology research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2department of optometry, school of rehabilitation, shahid beheshti university of medical sciences, tehran, iran 3ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 4medical physics and biomedical engineering department, school of medicine, tehran university of medical sciences, tehran, iran 5ocular tissue engineering research center, shahid beheshti university of medical sciences, tehran, iran orcid: hamideh sabbaghi: https://orcid.org/0000-0002-2627-7222 narsis daftarian: https://orcid.org/0000-0001-5846-8739 nazanin behnaz: https://orcid.org/0000-0001-6823-1348 abstract purpose: to compare the choroidal thickness among eyes with retinitis pigmentosa (rp), stargardt disease, usher syndrome, cone-rod dystrophy, and healthy eyes of sexand age-matched individuals. methods: in this comparative study, 503 eyes with rp (n = 264), cone-rod dystrophy (n = 109), stargardt disease (n = 76), and usher syndrome (n = 54) were included. to validate the data, 109 healthy eyes of 56 sexand age-matched individuals were studied as controls. choroidal imaging was performed using enhanced depth imaging-optical coherence tomography. choroidal thickness was measured manually using matlab software at 13 points in nasal and temporal directions from the foveal center with the interval of 500 µm and the choroidal area encompassing the measured points was calculated automatically. results: the mean age was 36.33 ± 13.07 years (range, 5 to 72 years). the mean choroidal thickness at 13 points of the control eyes was statistically significantly higher than that in eyes with rp (p < 0.001) and usher syndrome (p < 0.05), but not significantly different from that in eyes with stargardt disease and cone-rod dystrophy. among different inherited retinal dystrophies (irds), the choroidal thickness was the lowest in eyes with rp (p < 0.001). choroidal thickness in the subfoveal area correlated negatively with best-corrected visual acuity (r = −0.264, p < 0.001) and the duration of ocular symptoms (r = −0.341, p < 0.001) in all studied irds. no significant correlation was observed between the subfoveal choroidal thickness and central macular thickness (r = −0.24, p = 0.576). conclusion: choroidal thinning in four different types of irds does not follow a similar pattern and depends on the type of ird and the duration of ocular symptoms. a larger cohort is required to verify these findings. keywords: choroidal thickness; cone-rod dystrophy; enhanced depth optical coherence tomography; inherited retinal dystrophy; retinitis pigmentosa; stargardt disease; usher syndrome j ophthalmic vis res 2020; 15 (3): 351–361 © 2020 journal of ophthalmic and vision research | published by knowledge e 351 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7454&domain=pdf&date_stamp=2019-07-17 choroidal thickness in inherited retinal dystrophy; sabbaghi et al introduction photoreceptors and retinal pigment epithelial (rpe) cells as their protectors are the primary units for light photon translation into neural electric codes.[1] choroid is a complex vascular tissue that supplies oxygen and nutrients to these cells with a high metabolism rate. therefore, a healthy choroidal vasculature could provide optimum blood flow to rpe and photoreceptor cells.[2] inherited retinal dystrophies (irds) are ocular diseases that primarily involve progressive degeneration of rpe and/or photoreceptor cells.[3] retinitis pigmentosa (rp) is the most prevalent type of ird that has been estimated to affect approximately 1.5 million individuals worldwide.[4] stargardt disease is the most prevalent inherited macular dystrophy with an estimated prevalence of 1 per 10,000 individuals.[5] a recent study showed that mutations in more than 120 causative genes are responsible for different types of irds[6] and these mutations can be transmitted to the next generation by different mendelian patterns of inheritance.[7] generally, it appears that the outer retina and rpe cells are primarily involved, resulting in death of these cells.[8, 9] choriocapillaris may also be involved in the late stages of the disease, manifesting as chorioretinal atrophy in fundus examination.[9, 10] currently, there is no definite treatment for irds. however, recent advances have been reported in the field of gene therapy for rp, leber’s congenital amaurosis, and stargardt disease.[11] if gene therapy may be speculated to repair the correspondence to: narsis daftarian, md. ocular tissue engineering research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, no 23, paidarfard st., boostan 9 st., pasdaran ave., tehran 16666, iran. e-mail: nardaftarian@hotmail.com nazanin behnaz, md. ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, no 23, paidarfard st., boostan 9 st., pasdaran ave., tehran 16666, iran. e-mail: n.behnaz1990@gmail.com received: accepted: access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7454 defect in gene function, healthy choriocapillaries are necessary to provide enough blood flow to compensate for the normal metabolic needs of the outer retina. enhanced depth imaging (edi) by spectral domain optical coherence tomography (sd-oct), is a technique used to visualize the detailed structure of the choroidal tissue from the nasal region adjacent to the optic nerve to the subfoveal choroid and the temporal region of the choroid and can be used to measure the choroidal thickness.[12] measurement of the choroidal thickness can be informative in determining the pathophysiology and natural course of irds.[13–15] some studies have reported a significant reduction in the choroidal thickness in rp,[4, 15, 16] stargardt disease,[17] and cone dystrophy[18] when compared with healthy controls. however, no difference was observed in other studies.[5, 19] due to this discrepancy, the aim of the present study was to measure the choroidal thickness in a large iranian cohort with rp, stargardt disease, cone-rod dystrophy, and usher syndrome and to compare it with age-matched healthy subjects using edioptical coherence tomography (edi-oct). the study also aimed to evaluate the relationship of choroidal thickness with the best-corrected visual acuity (bcva), central macular thickness (cmt), and the duration of ocular symptoms. methods in this comparative study, 503 eyes of 253 patients diagnosed with irds including rp (264 eyes of 133 patients), stargardt disease (76 eyes of 38 patients), cone-rod dystrophy (109 of 55 patients), and usher syndrome (54 eyes of 27 patients) were included. for comparison, 109 normal eyes of 56 healthy subjects were included as controls. healthy controls were matched based on patients’ age and sex. data were extracted from the iranian national registry of irds (irdreg®). patients were recalled for additional examinations and imaging according to the standard protocol. this study was conducted this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: sabbaghi h, ahmadieh h, jalili j, behnaz n, fakhri m, suri f, kheiri b, rajabpour m, entezari m, daftarian n. choroidal thickness in different types of inherited retinal dystrophies. j ophthalmic vis res 2020;15:351–361. 352 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 https://knepublishing.com/index.php/jovr choroidal thickness in inherited retinal dystrophy; sabbaghi et al at labbafinejad medical center, tehran, iran, from january 2016 to august 2018. the ethics committee of the ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran approved this study and all procedures were in compliance with the tenets of the declaration of helsinki. written informed consent was obtained from all subjects for diagnostic procedures and choroidal imaging. visual and ocular examinations initially, all patients were interviewed to identify the age of disease manifestations and the common signs and symptoms including photophobia, color vision deficiency, nyctalopia, nystagmus, restricted visual field, and previous general and ocular conditions. all subjects underwent complete ophthalmic examination including bcva assessment, color vision testing using ishihara pseudoisochromatic plates, slit-lamp biomicroscopy, measurement of the intraocular pressure using the goldmann applanation tonometer, and dilated fundus examination using a +78d lens. in addition, visual field testing was performed with humphrey visual field (carl zeiss meditec inc., dublin, ca, usa) using 30-2 swedish interactive threshold algorithm standard method. additionally, sdoct scanning was performed and choroidal thickness was also measured using the edioct scan (spectralis, heidelberg engineering, heidelberg, germany). fundus photographs were obtained by a digital stereoscopic camera (visucam pro nm, carl zeiss meditec ag, germany). infrared imaging, fundus autofluorescence, and fluorescein angiography (heidelberg engineering gmbh, heidelberg, germany) were also performed. in addition, electrophysiological examinations including electroretinography (erg) and/or electrooculography (retiport 21 system, version 7/03, roland consult, osaka, japan) were conducted to confirm the clinical diagnosis. based on fundus examination, macular involvement was defined as the presence of any kind of macular abnormality from reduced foveal reflex to bull’s eye pattern or beaten bronze appearance. inclusion and exclusion criteria patients with syndromic rp, ird cases having optic atrophy due to other etiologies, visually significant cataract or other media opacities, high refractive errors (myopia ≥ 5.00 d, hyperopia ≥ 3.00 d, and astigmatism ≥ 3.00 d), nystagmus or wandering gaze, poor image quality, and any other associated retinal pathologies were excluded. patients with cystoid macular edema were also excluded from the analysis. we also excluded patients with systemic diseases affecting the choroidal thickness such as systemic hypertension, diabetes, and renal failure. the control group included sexand agematched healthy subjects with no ocular and systemic diseases and without high refractive errors. none of the controls had a positive family history of irds. final diagnosis the final diagnosis of retinal dystrophy was obtained based on clinical examinations, retinal multimodal imaging, and psychophysical tests such as erg, color vision, and visual fields. additionally, retinal dystrophy was confirmed by genetic findings in 98 patients (19.5%). cross-validation of patients’ response with clinical records was performed to increase the data validity. choroidal thickness measurement each patient underwent an edi-oct scan after dilation of the pupil by 1% tropicamide eye drop (figure 1, a1 to f2). edi-oct automatically sets the choroid closer to the zero-delay line and thus, theoretically provides better visualization of the choroidoscleral interface. one horizontal 9mm high-quality line scan through the fovea was obtained for each eye. the line scan was saved for analysis after averaging of 100 frames. choroidal measurements were performed using matlab 2016b program (mathworks, natick, ma, usa) at 13 points subfoveally and in nasal and temporal directions with the interval of 500 µm in a length of 6000 µm (figure 1, b1 and b2). all choroidal measurements were done by an ophthalmologist familiar with the matlab program. all measurements were performed from the outer portion of the hyper-reflective line corresponding to the rpe cells-bruch’s membrane journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 353 choroidal thickness in inherited retinal dystrophy; sabbaghi et al figure 1. representative enhanced depth imaging (edi) of four different inherited retinal dystrophies and of a healthy control. a1: right eye of a healthy control, a2: left eye of a healthy control b1, b2: examples of choroidal thickness measurement manually and automatically in the right and the left eyes, respectively, of a healthy subject c1, c2: edi of the right and the left eyes, respectively, of a patient with retinitis pigmentosa d1, d2: edi of the right and the left eyes, respectively, of a patient with usher syndrome e1, e2: edi of the right and the left eyes, respectively, of a patient with stargardt disease f1, f2: edi of the right and the left eyes, respectively, of a patient with cone-rod dystrophy figure 2. mean choroidal thickness in the subfoveal area and at six different spots along the nasal and the temporal directions in different types of inherited retinal dystrophies. rp, retinitis pigmentosa complex as the inner border to the hypo-reflective line corresponding to the sclerochoroidal interface as the outer border. subsequently, the program automatically measured choroidal thickness in the specified spots according to the spaces defined in the preceding step, measured the area of choroid in the specified region, and provided the information in an excel file. the aforementioned application was designed to work as follows. 354 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 choroidal thickness in inherited retinal dystrophy; sabbaghi et al figure 3. mean total choroidal thickness (at 13 spots of measurement) in different types of inherited retinal dystrophies. rp, retinitis pigmentosa *significant p-values between 0.01 and 0.05; ***significant p-values < 0.001 figure 4. mean choroidal area in different types of inherited retinal dystrophies rp, retinitis pigmentosa **significant p-values between 0.01 and 0.001 ***significant p-values < 0.001 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 355 choroidal thickness in inherited retinal dystrophy; sabbaghi et al 1. an edi-oct image was displayed in a window after loading the image into the application. the coordinates of all pixels and their intensities were shown in the image. 2. the program allowed the physicians to manually select the center of macula and the choroidal region on the edi-oct images. 3. based on the specified center and the area, six points with 500 μm intervals on each side of the center (13 points including the center) were automatically marked and the choroidal thickness was calculated at these points. 4. the program also provided charts related to changes in the choroidal thickness and other additional information including the area of the choroidal region. all edi-oct images from the patients and the controls were obtained from 2:00 to 6:00 pm to reduce the possible effect of diurnal variation on choroidal thickness. finally, two other board-certified retina specialists independently rechecked the measurements to avoid disagreements (cronbach’s 𝛼 = 0.794). in a few images with disagreement, the rpe-bruch’s membrane complex and the sclerochoroidal interface were rechecked and the measurements were repeated to be confirmed by the two retina specialists. statistical analysis data were presented as mean and standard deviation, median and range, and frequency and percentage. to compare the subject characteristics between the ird and the control groups, we used dunnet’s correction for multiple comparisons. to determine the possible correlation of the patients’ characteristics or the ird characteristics with the choroidal thickness and the choroidal area, generalized estimating equation analysis was used. all statistical analyses were performed using ibm spss statistics for windows, version 25.0. (ibm corp., armonk, ny, usa). all tests were two-sided and a pvalues < 0.05 were considered statistically significant. results in this comparative study, 503 eyes with a confirmed diagnosis of ird including three types of diffuse photoreceptor dystrophies (rp, usher syndrome, and cone-rod dystrophy) and one macular dystrophy (stargardt disease) were included. the age and gender distribution of the patients and controls are presented in table 1. we observed that for most of the cases, the duration since first recognition of the disease was 10 to 20 years (30.5%, p = 0.04). the distribution of the ird duration in 10-year periods was not significantly different among the types of irds. table 2 summarizes the clinical characteristics of the study subjects. comparison of central vision among different types of irds showed that the mean bcva of patients with conerod dystrophy was significantly lower than that of patients with stargardt disease (p = 0.009) and usher syndrome (p < 0.001). the mean cmt values of patients with stargardt disease and cone-rod dystrophy were significantly lower than those of patients from other groups (p < 0.001). figure 2 shows the linear comparison of mean choroidal thickness at each of the 13 different spots in different irds and the mean choroidal thickness in the control group. the mean subfoveal choroidal thickness in healthy controls (336.79 ± 82.75 µm) was greater than that in rp patients (p < 0.001), but did not differ significantly from mean subfoveal choroidal thickness in other irds including usher syndrome, cone-rod dystrophy, and stargardt disease. the mean total choroidal thickness (mean choroidal thickness at 13 points) in eyes with rp (p < 0.001) and usher syndrome (p = 0.042) was significantly lower than that in healthy eyes. there was no significant difference in mean total choroidal thickness between patients with stargardt disease and conerod dystrophy vs. healthy controls (p = ns). the mean choroidal thickness in rp patients was less than that in patients with stargardt disease (p < 0.001), cone-rod dystrophy (p < 0.001), and usher syndrome (p = 0.028) (figure 3). 356 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 choroidal thickness in inherited retinal dystrophy; sabbaghi et al ta b le 1. b as ic ch ar ac te ris tic s of th e st ud y su bj ec ts g ro u p s p a ra m e te rs le ve ls to ta l( n = 6 12 ) r p (n = 2 6 4 ) s ta rg a rd t (n = 7 6 ) c o n e r o d d ys tr o p h y (n = 10 9 ) u sh e r s yn d ro m e (n = 5 4 ) c o n tr o l (n = 10 9 ) p -v a lu e a ge (y ea rs ) m ea n ± sd 35 .7 5 ± 12 .8 1 40 .2 1± 13 .0 3 29 .4 7 ± 8. 82 32 .3 3 ± 13 .5 2 35 .0 4 ± 11 .0 1 32 .7 8 ± 11 .0 7 < 0. 07 5* m ed ia n (ra ng e) 34 (5 to 72 ) 39 (8 to 72 ) 30 (9 to 45 ) 32 (8 to 64 ) 36 (5 to 53 ) 31 (11 to 65 ) se x (% ) m al e 14 9 (4 8. 4% ) 69 (5 1.9 % ) 17 (4 4. 7% ) 30 (5 4. 5% ) 10 (3 7. 0 % ) 23 (4 1.8 % ) 0. 41 * fe m al e 15 9 (5 1.6 % ) 64 (4 8. 1% ) 21 (5 5 .3 % ) 25 (4 5 .5 % ) 17 (6 3. 0 % ) 32 (5 8. 2% ) in ci de nc e a ge (y ea rs ) m ea n ± sd 18 .8 7 ± 13 .0 9 20 .6 5 ± 14 .16 17 .0 5 ± 9. 46 17 .0 8 ± 12 .8 9 16 .3 8 ± 11 .8 5 __ __ 0. 17 1* m ed ia n (ra ng e) 17 (0 to 63 ) 18 (0 to 63 ) 15 (6 to 40 ) 16 (0 to 46 ) 14 (1 to 40 ) d ur at io n of d is ea se (y ea rs ) m ea n ± sd 18 .9 6 ± 13 .2 1 22 .2 2 ± 14 .5 7 12 .4 2 ± 8. 8 15 .8 3 ± 11 .3 4 18 .7 3 ± 10 .0 8 __ __ _ < 0. 0 0 1* m ed ia n (ra ng e) 16 .5 (0 to 61 ) 21 (0 to 61 ) 11 (1 to 35 ) 14 (0 to 45 ) 16 .5 (4 to 40 ) d ur at io n of d is ea se 0 – 10 69 (2 8. 0 % ) 29 (2 2 .7 % ) 17 (4 4. 7% ) 17 (3 2 .7 % ) 4 (15 .4 % ) __ __ _ 0. 04 † 10 – 20 75 (3 0. 5% ) 34 (2 6. 6% ) 12 (3 1.6 % ) 19 (3 6. 5% ) 10 (3 8. 5% ) 20 – 30 49 (19 .9 % ) 27 (2 1.1 % ) 7 (18 .4 % ) 8 (15 .4 % ) 7 (2 6. 9% ) 30 – 40 31 (12 .6 % ) 18 (14 .1% ) 2 (5 .3 % ) 7 (13 .5 % ) 4 (15 .4 % ) 40 – 50 17 (6 .9 % ) 15 (11 .7 % ) 0 (0 .0 % ) 1( 1.9 % ) 1( 3. 8% ) 50 – 60 5 (2 .0 % ) 5 (3 .9 % ) 0 (0 .0 % ) 0 (0 .0 % ) 0 (0 .0 % ) r p, re tin iti s pi gm en to sa ;s d ,s ta nd ar d de vi at io n; n, nu m be r *p -v al ue is ba se d on a n o v a (in al lt he ab ov e an al ys is ,m ul tip le co m pa ris on co rr ec tio n ha ve be en do ne w ith b on fe rr on im et ho d ) †b as ed on c hi -s qu ar e te st journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 357 choroidal thickness in inherited retinal dystrophy; sabbaghi et al ta b le 2 .c lin ic al ch ar ac te ris tic s of th e st ud y su bj ec ts g ro u p s p a ra m e te rs le ve l to ta l( n = 6 12 ) r p (n = 2 6 4 ) s ta rg a rd t (n = 7 6 ) c o n e r o d d ys tr o p h y (n = 10 9 ) u sh e r s yn d ro m e (n = 5 4 ) c o n tr o l( n = 10 9 ) p -v a lu e b c v a (l og m a r) m ea n ± sd 1.0 4 ± 0. 91 1.1 9 ± 0. 98 1.0 2 ± 0. 47 1.4 3 ± 0. 87 0. 84 ± 0. 69 0 ± 0 < 0. 0 0 1 m ed ia n (ra ng e) 0. 8 (0 to 2 .7 9) 0. 8 (0 to 2 .7 9) 0. 9 (0 .1 to 2 .3 1) 1.3 1( 0 to 2 .7 ) 0. 74 (0 .1 to 2 .7 ) 0 (0 to 0) se (d ) m ea n ± sd – 1.0 ± 1.7 8 –0 .8 8 ± 1.7 9 – 1.5 4 ± 1.3 3 –0 .8 8 ± 2 .0 7 – 1.6 7 ± 1.9 4 –0 .3 3 ± 0. 94 < 0. 0 0 1 m ed ia n (ra ng e) –0 .7 5 (– 6. 63 to 2 .7 5) –0 .5 (– 5 .7 5 to 2 .7 5) – 1.2 5 (– 5 .2 5 to 0. 75 ) –0 .3 1( –6 .6 3 to 2 .6 3) – 1.5 (– 5 .7 5 to 1.5 ) –0 .3 8 (– 2 to 2) c m t (µ m ) m ea n ± sd 21 5 .9 9 ± 72 .1 23 0. 66 ± 68 .8 1 16 5 .5 4 ± 65 .0 4 18 6. 0 3 ± 48 .5 9 24 4. 88 ± 99 .8 7 25 8. 72 ± 15 .7 1 < 0. 0 0 1 m ed ia n (ra ng e) 21 3 (8 0 to 69 0) 22 2 (9 5 to 67 4) 14 1( 80 to 37 8) 18 6. 5 (8 8 to 31 7) 22 9. 5 (9 0 to 69 0) 25 9. 5 (2 20 to 28 5) c ol or v is io n n or m al 16 4 (2 8. 1% ) 40 (16 .1% ) 6 (8 .3 % ) 2 (1. 9% ) 7 (14 .6 % ) 10 9 (10 0. 0 % ) < 0. 0 0 1 c v d 21 3 (3 6. 5% ) 71 (2 8. 6% ) 53 (7 3. 6% ) 62 (5 7. 9% ) 27 (5 6. 3% ) 0 (0 .0 % ) n /a 20 7 (3 5 .4 % ) 13 7 (5 5 .2 % ) 13 (18 .1% ) 43 (4 0. 2% ) 14 (2 9. 2% ) 0 (0 .0 % ) c at ar ac tt yp e (% ) n o 37 6 (6 2 .0 % ) 10 1( 38 .5 % ) 69 (9 5 .8 % ) 80 (7 3. 4% ) 17 (3 1.5 % ) 10 9 (10 0. 0 % ) c c 0 (0 .0 % ) 0 (0 .0 % ) 0 (0 .0 % ) 0 (0 .0 % ) 0 (0 .0 % ) 0 (0 .0 % ) < 0. 0 0 1 n s 44 (7 .3 % ) 29 (11 .1% ) 0 (0 .0 % ) 11 (10 .1% ) 4 (7 .4 % ) 0 (0 .0 % ) ps c 16 9 (2 7. 9% ) 12 0 (4 5 .8 % ) 3 (4 .2 % ) 16 (14 .7 % ) 30 (5 5 .6 % ) 0 (0 .0 % ) pc io l 14 (2 .3 % ) 12 (4 .6 % ) 0 (0 .0 % ) 2 (1. 8% ) 0 (0 .0 % ) 0 (0 .0 % ) po st er io rp ol ar 3 (0 .5 % ) 0 (0 .0 % ) 0 (0 .0 % ) 0 (0 .0 % ) 3 (5 .6 % ) 0 (0 .0 % ) o pt ic a tro ph y (% ) n o 46 (9 .1% ) 10 (3 .8 % ) 22 (2 8. 9% ) 14 (12 .8 % ) 0 (0 .0 % ) 0 (0 .0 % ) < 0. 0 0 1 ye s 45 7 (9 0. 9% ) 25 4 (9 6. 2% ) 54 (7 1.1 % ) 95 (8 7. 2% ) 54 (10 0. 0 % ) 0 (0 .0 % ) m ac ul ar in vo lv em en t( % ) n o 12 2 (19 .9 % ) 11 (4 .2 % ) 0 (0 .0 % ) 2 (1. 8% ) 0 (0 .0 % ) 10 9 (10 0. 0 % ) < 0. 0 0 1 ye s 49 0 (8 0. 1% ) 25 3 (9 5 .8 % ) 76 (10 0. 0 % ) 10 7 (9 8. 2% ) 54 (10 0. 0 % ) 0 (0 .0 % ) r p, re tin iti s pi gm en to sa ;b c v a ,b es tc or re ct ed vi su al ac ui ty ;l og m a r ,l og ar ith m m in im um an gl e of re so lu tio n; se ,s ph er ic al eq ui va le nt ;d ,d io pt er ;c m t, ce nt ra lm ac ul ar th ic kn es s; µm ,m ic ro m et er ;c v d ,c ol or vi si on de fe ct ;n /a ,n ot ap pl ic ab le ;c c ,c or tic al ca ta ra ct ;n s, nu cl ea rs cl er ot ic ;p sc ,p os te rio rs ub ca ps ul ar ;s d ,s ta nd ar d de vi at io n; n, nu m be r *t he se pa ra m et er s ar e pr es en te d ba se d on m on oc ul ar fin di ng s 358 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 choroidal thickness in inherited retinal dystrophy; sabbaghi et al the mean total choroidal area in different types of ird and in healthy controls is illustrated in figure 4. the mean total choroidal area in healthy subjects (1.9 ± 0.4 µm2) was significantly more than that in rp (1.4 ± 0.5 µm2, p < 0.001) and usher syndrome (1.6 ± 0.5 µm2, p = 0.006). among different irds, the mean total choroidal area was less in rp patients than in patients with stargardt disease (p < 0.001) and cone-rod dystrophy (p < 0.001). additionally, the subfoveal choroidal thickness was inversely correlated with bcva (r = −0.264, p < 0.001) and the duration of ocular symptoms (r = −0.341, p < 0.001) in all irds. however, no statistically significant correlation was observed between the subfoveal choroidal thickness and cmt (r = −0.24, p = 0.576) in all irds. discussion in the present comparative study, choroidal thickness was measured in a large group of patients with different types of irds including rp, stargardt disease, usher syndrome, and cone-rod dystrophy. we included ageand sex-matched controls for comparison. the mean choroidal thickness measured at 13 different spots in the nasal and in the temporal direction was significantly lower in patients with rp and usher syndrome when compared with healthy controls and patients with statgardt disease and cone-rod dystrophy. other studies have also reported similar findings.[4, 5, 13, 16] however, no significant reduction in choroidal thickness was reported in rp patients in the study by chhablani et al.[19] this discrepancy could be attributed to the different characteristics of the study population including better bcva (0.99 ± 0.94 logmar) and younger age (31.09 ± 13.40 years) than the bcva (1.19 ± 0.98 logmar) and age (40.21 ± 13.03 years) of patients in our study. high number of patients with rp (n = 264) was a strength of the present study. the number of rp patients was higher than those included in previous studies.[4, 13, 16, 19] sodi et al reported findings consistent with our results with no difference in mean choroidal thickness between healthy controls and patients with stargardt disease.[5] they described a statistically significant correlation between lower subfoveal choroidal thickness and longer duration of ocular symptoms; this finding was also observed in the current study.[5] to the best of our knowledge, this is the first study that compared the choroidal thickness among different types of irds. our investigation showed that the lowest choroidal thickness was observed in patients with rp. this finding could be explained by the possible trophic role of rpe cells, which support proper choroidal function through secretion of growth factors. conversely, the reduction in oxygen demand of the degenerating photoreceptors will subsequently result in reduced blood flow to the retina and the choroid, which is called primary vascular dysregulation in rp patients.[20, 21] additionally, rp has been associated with an imbalance in oxidant/antioxidant status and subclinical inflammatory processes that may stimulate the excessive production of endothelin-1 (et-1).[16, 19] therefore, retinal degeneration and choroidal thinning in patients with rp seem to interact with each other. the difference in the amount of choroidal thinning between rp and other irds can be explained by the pathogenesis of rp.[16] most of the mutations in rp are attributed to gene coding of proteins involved in the vision cycle at the level of photoreceptors and rpe cells. these mutations cause apoptosis and degeneration of photoreceptors and subsequent outer retinal thinning.[16, 22] photoreceptor atrophy results in reduced oxygen demand and blood flow. furthermore, trophic role of rpe cells through secretion of growth factors such as vascular endothelial growth factor[23] that support proper choroidal function is diminished. thus, choroidal thinning can be explained by reduced blood flow and rpe cell degeneration. yoshida et al observed cell, flare, and inflammatory cytokines in aqueous humor and vitreous fluid of patients with rp.[24] confirmation of reduced level of antioxidants in this group of patients by martinez et al is suggestive of the oxidative stress in rp.[25] subclinical ocular inflammatory process and hypoxic-oxidative stress elicit increased ocular and plasma levels of et-1.[16, 22] et-1 is the most powerful endogenous vasoconstrictor of small and large vessels. in the eye, its synthesis and secretion is performed by different tissues such as cornea, uveal tissue, retinal microvascular pericytes, rpe cells, and optic nerve. increased levels of et-1 and vasoconstriction effect result in vascular dysgenesis and impaired journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 359 choroidal thickness in inherited retinal dystrophy; sabbaghi et al ocular blood flow. this vicious cycle contributes to the amplification of the inflammatory response, altered intraocular perfusion, relative ischemia, and consequent degeneration of outer retinal layer and choroidal thinning.[22] in the present study, a negative correlation was observed between the subfoveal choroidal thickness and bcva and between subfoveal choroidal thickness and disease duration of the irds. however, no correlation was observed between cmt and choroidal thickness. some studies have reported a correlation between choroidal thickness and bcva and between choroidal thickness and the duration of ocular symptoms in irds including rp and stargardt disease.[4, 5, 19] however, other studies did not find such correlations.[10, 13, 16, 18] this difference may be due to a higher number of subjects and a longer duration of ocular symptoms in the present study. ayton et al[4] reported that choroid becomes thinner with increasing duration of rp symptoms, which is consistent with the findings of the present study. however, sodi et al[16] claimed that age might have more effect on choroidal thickness than the duration of rp itself. they suggested that this lack of association might be due to a very strict criterion for the definition of age at the onset of the disease. in the present study, additional ageadjusted analysis confirmed that age could not be a confounding variable and the findings may be directly related to the ird entity. previous studies have found a significant correlation between cmt and choroidal thickness in stargardt disease[5] and no relationship between them in rp patients.[13, 16, 19] in the present study with a larger sample size, no correlation was observed between cmt and subfoveal choroidal thickness in rp and in stargardt disease. as previously stated, patients with cystoid macular edema were not included in the statistical analysis. total choroidal area in the eyes of healthy subjects was significantly higher than that in eyes of patients with rp and usher syndrome. the choroid was generally thinner in rp patients when compared with patients having stargardt disease and cone-rod dystrophy. one of the strengths of the present study is the comparison of choroidal thickness among four relatively common types of irds including rp, stargardt disease, usher syndrome, and conerod dystrophy. additionally, a larger sample size compared to the sample size in previous studies is another merit of this study. the design of the novel software using matlab computer programming for automatic measurement of the choroidal parameters minimizes the chance of inter-operator and intra-operator errors. the measurement of the total choroidal area as well as the choroidal thickness at 13 different spots (including the center of the fovea) 6000 µm along the nasal and the temporal directions from the center of the fovea is another merit of the present study. the present study has some limitations including the lack of accessibility to the genetic data for all study subjects. another limitation of this study was relying on patients’ self-report for identification of the age of disease onset. of course, crossvalidation of patients’ response with clinical records was performed to increase the data validity. in conclusion, with the same duration of ocular symptoms, generalized choroidal thinning was observed in rp and usher syndrome, but not in stargardt disease and cone-rod dystrophy. therefore, different pathophysiologic and blood flow mechanisms may be implicated in each ird, which demands further cohort studies with special consideration of choroidal blood flow as a potential therapeutic target. financial support and sponsorship the study data were extracted from the iranian national registry of irds (irdreg®), which is financially supported by the deputy of research and technology of the iranian ministry of health and medical education, as well as shahid beheshti university of medical sciences, tehran, iran. conflicts of interest there are no conflicts of interest. references 1. srinivasan vj, dubra a. noninvasive imaging of the photoreceptor mosaic response to light stimulation. proc natl acad sci usa 2016;113:12902–12903. 2. rutkowski p, may ca. nutrition and vascular supply of retinal ganglion cells during human development. front neurol 2016;7:49. 3. hartong dt, berson el, dryja tp. retinitis pigmentosa. lancet 2006;368:1795–1809. 360 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 choroidal thickness in inherited retinal dystrophy; sabbaghi et al 4. ayton ln, guymer rh, luu cd. choroidal thickness profiles in retinitis pigmentosa. clin exp ophthalmol 2013;41:396–403. 5. sodi a, bacherini d, lenzetti c, caporossi o, murro v, mucciolo dp, et al. edi oct evaluation of choroidal thickness in stargardt disease. plos one 2018;13:e0190780. 6. öner a. recent advancements in gene therapy for hereditary retinal dystrophies. turk j ophthalmol 2017;47:338–343. 7. ecklund winters j. retinitis pigmentosa: distribution of inheritance patterns in a va blind rehabilitation center population. clin eye vis care 2000;12:107–112. 8. bertelsen m, jensen h, bregnhøj jf, rosenberg t. prevalence of generalized retinal dystrophy in denmark. ophthalmic epidemiol 2014;21:217–223. 9. oh kt, weleber rg, stone em, oh dm, rosenow j, billingslea am. electroretinographic findings in patients with stargardt disease and fundus flavimaculatus. retina 2004;24:920–928. 10. yeoh j, rahman w, chen f, hooper c, patel p, tufail a, et al. choroidal imaging in inherited retinal disease using the technique of enhanced depth imagingoptical coherence tomography. graefes arch clin exp ophthalmol 2010;248:1719–1728. 11. al-saikhan fi. the gene therapy revolution in ophthalmology. saudi j ophthalmol 2013;27:107–111. 12. mrejen s, spaide rf. optical coherence tomography: imaging of the choroid and beyond. surv ophthalmol 2013;58:387–429. 13. dhoot ds, huo s, yuan a, xu d, srivistava s, ehlers jp, et al. evaluation of choroidal thickness in retinitis pigmentosa using enhanced depth imaging optical coherence tomography. br j ophthalmol 2013;97:66–69. 14. heckenlively jr, yoser sl, friedman lh, oversier jj. clinical findings and common symptoms in retinitis pigmentosa. am j ophthalmol 1988;105:504–511. 15. laviers h, zambarakji h. enhanced depth imaging-oct of the choroid: a review of the current literature. graefes arch clin exp ophthalmol 2014;252:1871–1883. 16. sodi a, lenzetti c, murro v, caporossi o, mucciolo dp, bacherini d, et al. edi-oct evaluation of choroidal thickness in retinitis pigmentosa. eur j ophthalmol 2018;28:52–57. 17. adhi m, read sp, ferrara d, weber m, duker js, waheed nk. morphology and vascular layers of the choroid in stargardt disease analyzed using spectral-domain optical coherence tomography. am j ophthalmol 2015;160:1276– 1284.e1. 18. ayyildiz o, ozge g, kucukevcilioglu m, ozgonul c, mumcuoglu t, durukan ah, et al. is there a relationship between outer retinal destruction and choroidal changes in cone dystrophy? arq bras oftalmol 2016;79:315–318. 19. chhablani j, jonnadula gb, srinivasa rao p, venkata a, jalali s. choroidal thickness profile in retinitis pigmentosa correlation with outer retinal structures. saudi j ophthalmol 2016;30:9–13. 20. falsini b, anselmi gm, marangoni d, d’esposito f, fadda a, di renzo a, et al. subfoveal choroidal blood flow and central retinal function in retinitis pigmentosa. invest ophthalmol vis sci 2011;52:1064–1069. 21. konieczka k, flammer aj, todorova m, meyer p, flammer j. retinitis pigmentosa and ocular blood flow. epma j 2012;3:17. 22. sorrentino fs, bonifazzi c, perri p. the role of the endothelin system in the vascular dysregulation involved in retinitis pigmentosa. j ophthalmol 2015;2015:405234. 23. ford km, saint-geniez m, walshe t, zahr a, d’amore pa. expression and role of vegf in the adult retinal pigment epithelium. invest ophthalmol vis sci 2011;52:9478–9487. 24. yoshida n, ikeda y, notomi s, ishikawa k, murakami y, hisatomi t, et al. laboratory evidence of sustained chronic inflammatory reaction in retinitis pigmentosa. ophthalmology 2013;120:e5–e12. 25. martínez-fernández de la cámara c, salom d, sequedo md, hervás d, marín-lambíes c, et al. altered antioxidantoxidant status in the aqueous humor and peripheral blood of patients with retinitis pigmentosa. plos one 2013;8:e74223. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 361 case report photopigment bleaching phenomenon on fluorescein angiography in a patient with impending central retinal vein occlusion narges hassanpoor, md, mph1,2; ahmad mirshahi, md1; mohammad reza niyousha, md2 1retina & vitreous service, eye research center, farabi eye hospital, tehran university of medical sciences, tehran, iran 2retina & vitreous service, nikookari eye hospital, tabriz university of medical sciences, tabriz, iran orcid: narges hassanpoor: http://orcid.org/0000-0001-8296-0918 mohammad reza niyousha: http://orcid.org/0000-0002-1119-5902 abstract purpose: to present the second case of photopigment bleaching phenomenon in fluorescein angiography (fa) and the first case of this phenomenon due to impending central retinal vein occlusion (crvo). case report: a 32-year-old healthy female noticed blurred vision in her right eye one day before presentation. despite the 20/20 visual acuity at presentation, mild increased retinal vascular tortuosity and unilateral photopigment bleaching phenomenon in fa was observed in the right eye. three weeks later, she developed a complete crvo with visual acuity reduction to 20/40 that responded well to the intravitreal injection of aflibercept. conclusion: impending crvo can cause unilateral photopigment bleaching phenomenon in fa that may be due to retinal ischemia. keywords: autofluorescence; central retinal vein occlusion; fluorescein angiography; photopigment bleaching; scanning laser ophthalmoscopy j ophthalmic vis res 2021; 16 (2): 291–294 introduction rhodopsin is one of the visual pigments that are responsible for absorption of the excitation beam in fundus auto-fluorescence (faf) and fluorescein angiography (fa). after continued exposure to shortwavelength light, photoisomerization and saturation of the visual pigments correspondence to: mohammad reza niyousha, md. eye research center, nikookari eye hospital, tabriz 5154645395, iran. e-mail: mreza63neusha@gmail.com received: 31-06-2020 accepted: 23-12-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9093 can cause decrease in their absorptive capabilities and progressive increase in background autofluorescence. this phenomenon is called photopigment bleaching.[1, 2] similar increased background auto-fluorescence can be seen in patients with atrophic photoreceptors and retinal disorders involving the outer retina such as retinitis pigmentosa (rp), old central serous chorioretinopathy (cscr), reattached old retinal this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: hassanpoor n, mirshahi a, niyousha mr. photopigment bleaching phenomenon on fluorescein angiography in a patient with impending central retinal vein occlusion. j ophthalmic vis res 2021;16:291–294. © 2021 hassanpoor et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 291 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9093&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photopigment bleaching in impending crvo; hassanpoor et al figure 1. fundus photos of the right (a) and left (b) eyes at presentation. right eye funduscopy shows an increased vascular tortuosity and retinal dot and blot and flame shape hemorrhages that is compatible with an impending central retinal vein occlusion (crvo). the normal optical coherence tomography angiography (octa) at presentation (c). after three weeks of follow up, her fundus photo was compatible with crvo diagnosis with significantly increased vascular tortuosity and retinal hemorrhages (d). her octa showed obvious macular edema and sub-retinal fluid in fovea (e). detachment, and multiple evanescent white dot syndrome (mewds).[2–4] this phenomenon was previously described in faf.[3, 4] however, breazzano et al recently reported the first case of this phenomenon in a scanning laser ophthalmoscopy (slo)-based fa image.[2] here, we report the second case of photopigment bleaching in fa and the first case of the occurrence of this phenomenon in a case of impending central retinal vein occlusion (crvo). case report a 32-year-old healthy female was referred with a complaint of blurred vision in her right eye since one day before presentation. the bestcorrected visual acuity (bcva) was 20/20 in both eyes. there was a suspicious relative afferent pupil defect (rapd) in her right eye. results of anterior segment examination was unremarkable. the family history and her past medical history were negative. in funduscopy of the right eye, there were an increased vascular tortuosity and retinal dot and blot and flame shape hemorrhages [figure 1]. systemic work up was performed for hypertension, cardiac anomalies, diabetes, and hypercoagulability state that were all negative. fa was performed with confocal scanning laser ophthalmoscope system using the heidelberg retina angiograph (heidelberg engineering, carlsbad, ca). photopigment bleaching phenomenon was seen in the late-phase fa [figure 2d]. we reinvestigated the frame numbers taken from each eye and their time provided at the top of the print outs to rule out significant difference in number of frames taken or time of blue-light exposure in eyes. three weeks later, she came back with visual acuity reduction to 20/40 in her right eye. vascular tortuosity and retinal hemorrhages significantly increased in the right eye funduscopy [figure 1d]. octa (optovue, ca, usa) showed subretinal fluid and intraretinal cystic spaces and spongy edema in the foveal region [figure 1e]. after an intravitreal injection of 2 mg /0.05 ml aflibercept (eylea, bayer, germany), dramatic improvement in visual acuity was observed. discussion in fa, earlier phases images are sometimes acquired with 30or 55-degree lenses and later images are captured with 102-degree lenses. in this situation, when exposure to short wavelength is continued or decreased tolerance of photopigments is present (e.g., due to retinal ischemia in this case), the “photopigment bleaching phenomenon” may be observed. due to photo-isomerization and saturation of visual pigments in previously illuminated 55-degree 292 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 photopigment bleaching in impending crvo; hassanpoor et al figure 2. arterial (a), lamellar (b), and arterio–venous (c) phases of fluorescein angiography (fa) with 55-degree lens shows increased vascular tortuosity and blockage areas due to retinal hemorrhages. blue arrow: “photopigment bleaching phenomenon” (d). in previously illuminated 55-degree area, hyper-fluorescence area is seen that is surrounded with an unbleached hypofluorescent area in 102-degree image. the normal fellow eye 102-degree image at the same time as seen in (d) in which “photopigment bleaching phenomenon” is not visible (e). area, we have hyper-fluorescence in central 55 degree (in round or rectangular shape which is dependent on the lens type) that is surrounded with an unbleached hypo-fluorescent area in 102-degree images [figure 2d]. similar increased background auto-fluorescence can be seen in patients with atrophic photoreceptors and retinal disorders that involve the outer retina.[2–4] however, the term “photopigment bleaching phenomenon” should be used when there is not any atrophic photoreceptor layer and the increased autofluorescence is due to saturation of photopigments in the presence of structurally normal photoreceptors. in this case we did not observe any structural abnormality in macular oct. however, mild ischemia and stasis in vascular system due to impending crvo can cause earlier saturation of visual pigments and result in decrease of their absorptive capabilities. unilaterality of the phenomenon in this case can be a reason for the possible effect of ischemia in this phenomenon. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 293 photopigment bleaching in impending crvo; hassanpoor et al references 1. yung m, klufas ma, sarraf d. clinical applications of fundus autofluorescence in retinal disease. int j retin vitr 2016;2:12. 2. breazzano mp, fernandez-avellaneda p, kurup sk, freund kb. photopigment bleaching phenomenon with scanning laser ophthalmoscopy and fluorescein angiography. ophthalmic surg lasers imaging retina 2019;50:590–592. 3. choi ke, yun c, kim yh, kim sw, oh j, huh k. the effect of photopigment bleaching on fundus autofluorescence in acute central serous chorioretinopathy. retina 2017;37:568–577. 4. joseph a, rahimy e, freund kb, sorenson ja, sarraf d. fundus autofluorescence and photoreceptor bleaching in multiple evanescent white dot syndrome. ophthalmic surg lasers imaging retina 2013;44:588–592. 294 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 photo essay cavernous hemangioma of the conjunctiva noopur deokinandan nayak shinkre, md; ugam p.s. usgaonkar, md department of ophthalmology, goa medical college, goa, india orcid: noopur deokinandan nayak shinkre: http://orcid.org/0000-0001-5503-2710 j ophthalmic vis res 2021; 16 (2): 303–305 presentation a 23-year-old healthy male presented to our outpatient department with complaint of foreign body sensation and a painless, red mass on the nasal side of his right eye, which he had noticed approximately six months before. it had gradually increased to attain its present size. on examination, his visual acuity on snellen’s chart was 20/20 in both eyes. examination of his right eye revealed a bright red, vascular, smooth, lobulated mass on the nasal side of the bulbar conjunctiva, measuring approximately 5×5×4 mm, with tortuous and engorged conjunctival vessels at the base of the lesion [figure 1a]. the lesion was mobile and did not exhibit pulsations. other findings of his ocular examination were unremarkable. no similar lesions were detected elsewhere on his body. a clinical diagnosis of conjunctival hemangioma was made. the lesion was surgically excised under topical anesthesia. no extension was noted beyond the tenon’s capsule. histopathological examination of the lesion revealed a cavernous hemangioma of the bulbar conjunctiva [figure 1b]. postoperatively, the patient was treated with topical antibiotics and steroid eye drops [figure 2]. correspondence to: noopur deokinandan nayak shinkre, md. department of ophthalmology, goa medical college, goa, india. e-mail: noopur.shinkre@gmail.com received: 14-08-2019 accepted: 25-03-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9097 discussion cavernous hemangiomas are vascular malformations characterized pathologically by large, thin-walled, and cystically dilated blood vessels. they are rare vascular tumors of the ocular surface; unlike capillary hemangioma, lymphangioma, and pyogenic granuloma which are more common.[1, 2] occurrence of an isolated cavernous hemangioma of the conjunctiva has rarely been reported to date. in addition to the results of the surveys conducted by elsas et al[3] and shields et al,[2, 4] to the best of our knowledge, only nine cases have been reported in the english literature, and notably, most of them have occurred in young males. the reported lesions arose from either the caruncle or the temporal side of the bulbar conjunctiva. however, in our case, unlike the previously reported cases, the tumor was located on the nasal side of the bulbar conjunctiva, neither overlying nor involving the caruncle, thus making it, to the best of our knowledge, the first such case to be reported. in these cases, the primary concern is purely cosmesis. however, some cases may be associated with recurrent subconjunctival hemorrhage. excisional biopsy of the tumor is considered to be the treatment of choice.[5] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: noopur deokinandan nayak shinkre, ugam p.s. usgaonkar. cavernous hemangioma of the conjunctiva. j ophthalmic vis res 2021;16:303–305. © 2021 shinkre et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 303 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9097&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; shinkre et al figure 1. (a) image showing a bright red, smooth, lobulated mass on the nasal side of the bulbar conjunctiva with tortuous conjunctival vessels at its base. (b) histopathological evaluation of the lesion showing multiple, blood-filled cavernous spaces surrounded by a fibromyxoid stroma (hematoxylin and eosin, 10× magnification). figure 2. image acquired one day after excision of the lesion. the conjunctival defect is apposed with 10–0 nylon sutures. 304 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 photo essay; shinkre et al declaration of patient consent the authors certify that they have obtained all appropriate patient consent forms. in the form the patient has given his consent for his images and other clinical information to be reported in the journal. the patient understand that his name and initial will not be published and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. shields cl, shields ja. tumors of the conjunctiva and cornea. surv ophthalmol 2004;49:3–24. 2. shields ja, mashayekhi a, kligman be, kunz wb, criss j, eagle jr rc, et al. vascular tumors of the conjunctiva in 140 cases. ophthalmology 2011;118:1747–1753. 3. elsas fj, green wr. epibulbartumors in childhood. am j ophthalmol 1975;79:1001–1007. 4. shields cl, demirci h, karatza e, shields ja. clinical survey of 1643 melanocytic and nonmelanocytic conjunctival tumors. ophthalmology 2004;111:1747–1754. 5. honavar sg, manjandavida fp. tumors of the ocular surface: a review. indian j ophthalmol 2015;63:187–203. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 305 original article an in-silico study on the most effective growth factors in retinal regeneration utilizing tissue engineering concepts nima beheshtizadeh1,2, phd; alireza baradaran-rafii3, md; maryam sharifi sistani1, phd mahmoud azami1, phd 1department of tissue engineering and applied cell sciences, school of advanced technologies in medicine, tehran university of medical sciences, tehran, iran 2students’ scientific research center, tehran university of medical sciences, tehran, iran 3ocular tissue engineering research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran orcid: nima beheshtizadeh: https://orcid.org/0000-0002-2621-570x mahmoud azami: https://orcid.org/0000-0003-4209-0668 abstract purpose: considering the significance of retinal disorders and the growing need to employ tissue engineering in this field, in-silico studies can be used to establish a cost-effective method. this in-silico study was performed to find the most effective growth factors contributing to retinal tissue engineering. methods: in this study, a regeneration gene database was used. all 21 protein-coding genes participating in retinal regeneration were considered as a protein–protein interaction (ppi) network via the “string app” in “cytoscape 3.7.2” software. the resultant graph possessed 21 nodes as well as 37 edges. gene ontology (go) analysis, as well as the centrality analysis, revealed the most effective proteins in retinal regeneration. results: according to the biological processes and the role of each protein in different pathways, selecting the correct one is possible through the information that the network provides. eye development, detection of the visible light, visual perception, photoreceptor cell differentiation, camera-type eye development, eye morphogenesis, and angiogenesis are the major biological processes in retinal regeneration. based on the go analysis, shh, stat3, fgfr1, opn4, itgav, rax, and rpe65 are effective in retinal regeneration via the biological processes. in addition, based on the centrality analysis, four proteins have the greatest influence on retinal regeneration: shh, igf1, stat3, and ascl1. conclusion: with the intention of applying the most impressive growth factors in retinal engineering, it seems logical to pay attention to shh, stat3, and rpe65. utilizing these proteins can lead to fabricate high efficiency engineered retina via all aforementioned biological processes. keywords: effective growth factors; in-silico study; regenerative medicine; retinal tissue engineering; systems biology j ophthalmic vis res 2021; 16 (1): 56–67 correspondence to: mahmoud azami, phd. department of tissue engineering and applied cell sciences, school of advanced technologies in medicine, tehran university of medical sciences, tehran, iran. e-mail: m-azami@tums.ac.ir received: 15-08-2019 accepted: 21-03-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8251 introduction the aim of regenerative medicine as the primary process involved in cell growth and organ this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: beheshtizadeh n, baradaran-rafii a, sistani ms, azami m. an in-silico study on the most effective growth factors in retinal regeneration utilizing tissue engineering concepts. j ophthalmic vis res 2021;16:56–67. 56 © 2021 beheshtizadeh et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8251&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr growth factors in retinal regeneration; beheshtizadeh et al reconstruction is to return the main cell functions and recovery of the damaged tissue or organ via its replacing or regenerating.[1] in fact, there are three solutions for patients having organ impairment based on the severity of the destruction: graft implantation, substitution, and restoration. graft implantation has an extensive waiting list candidates all around the world; for example, the organ transplantation waiting list is updated every 15 min in the united states of america.[2] the ultimate prospect of tissue engineering is creating and providing tissues that are preferably autologous in organ substitutions through cells and biomaterials utilization simultaneously.[3, 4] besides, tissue engineering has been determined as an efficient method to assist in rescuing lives and improving the quality of life. considering the major components for tissue engineering, that is, scaffolds, cells, and growth factors and a variety of their available options would highlight the fact that selecting the most appropriate ones to fabricate an engineered tissue demands an optimization system. in fact, a wide range of biomaterials can be used as scaffolds; polymers and hydrogels are the most commonly used materials in this field.[5–7] selecting the appropriate material is in close relation with the destination tissue. poly-lactide-co-glycolide (plga), poly-caprolactone (pcl), poly-glycerol sebacate (pgs), and polymethyl methacrylate (pmma) are some of the high consumption polymers in retinal tissue engineering. in addition to scaffolds, growth factors play an essential role in tissue engineering.[8] growth factors are generally the regulators of substances, namely proteins or hormones that can stimulate cell proliferation and differentiation. growth factors play an important role in the healing and regeneration of the retina. retinal disorders directly affect vision; therefore, retinal tissue engineering is fundamental.[3, 9–11] to understand the effective mechanisms in this process, it is better to compare growth factors’ interaction with each other and then select the most appropriate one. looking at the literature, retinal regeneration and retinal tissue engineering have been studied by several researchers.[12–21] liu et al[22] studied the application of hyaluronic acid (ha) hydrogels in retinal progenitor cell transplantation. their reason for selecting ha was its role as a feeder layer in stem cell cultures. in addition, the relative ease with which various parameters could be controlled (e.g., hydrogel architecture, mechanics, and degradation) was effective in choosing the ha hydrogel. they concluded that ha hydrogels, with their developmentally relevant composition and malleable physical properties, provide a unique microenvironment for self-renewal and differentiation of the retinal progenitor cells (rpcs) for retinal repair. furthermore, fausett et al[23] showed that in the damaged zebrafish retina, the muller glia re-enter the cell cycle, increase α1tubulin (α1t) promoter activity, and generate new neurons and glia for retinal repair. they suggested that the achaete-scute family bhlh transcription factor 1a (ascl1a) is required to convert the quiescent muller glia into the actively dividing retinal progenitors, and that ascl1a is a key regulator in initiating the retinal regeneration. kador and goldberg[24] studied the delivery of cell transplants for retinal degeneration. focusing on the photoreceptor and progenitordirected approaches, the authors reviewed how advances in tissue engineering and cell scaffold design were enhancing cell therapies for retinal degeneration. furthermore, yao et al[25] reviewed the current literature on synthetic polymer scaffolds used for stem cell transplantation, especially rpcs. the advantages and disadvantages of different polymer scaffolds, the role of different surface modifications on cell attachment and differentiation, and the controlled drug delivery were discussed in their paper. tao and klassen[18] have also presented a wide range of practical biomaterials in retinal tissue engineering. they studied the role of stem cells in retinal repair, and then focused on the material side, followed by considering cells and materials in combination. they also examined the current status of retinal tissue engineering and looked ahead to the challenges that investigators are involved within this field. in addition, bainbridge et al[26] published their preliminary results of gene therapy for retinal degeneration. in their study, the patients were enrolled in trials of recombinant adeno-associated viral delivery of the retinoid isomerohydrolase (rpe65), which was administered as a subretinal injection during vitrectomy. the preliminary results from their investigations suggested that the procedure was safe in the short term, and their data were suggestive of efficacy. furthermore, nelson et al[27] found out that signal transducer and activator of transcription 3 (stat3) expression was observed in all muller journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 57 growth factors in retinal regeneration; beheshtizadeh et al glia, whereas ascl1a expression was restricted to only the mitotic ones. they suggested that while ascl1a and lin-28 homolog a (lin28a) are required for muller glia proliferation, stat3 is necessary for the maximal number of muller glia to proliferate during regeneration of the damaged zebrafish retina. in another study, spence et al[28] worked on the fibroblast growth factor (fgf)– hedgehog (shh) interdependence during retinal regeneration. their results support a model where the fgf and shh pathways work together to stimulate retinal regeneration. recently, singh et al[29] reviewed retinal tissue engineering from the pluripotent stem cells and summarized the progress in cell therapies of the retina, with a focus on the human pluripotent stem cell-derived retinal tissue, and critically evaluated the potential of retinal organoid approaches to solve a major unmet clinically needed retinal repair and vision restoration in conditions caused by retinal degeneration and traumatic ocular injuries. based on the published works, it can be concluded that there is no comprehensive study on the retinal growth factors that can draw up the existing relation among them. in addition, to the best of our knowledge, there is no insilico study of retinal tissue engineering. in fact, in retinal regeneration, several proteins are used therapeutically. if the interaction between them would be clear, and the biological function of each one is determined, they can be used as growth factors in retinal tissue engineering. in order to get the best results from the in-vitro and in-vivo tests, it is needed to select the best growth factors based on previous experiments and existing data. however, there are many reports about the effects of using each growth factor without any coherence and correlation among them. it seems that describing the interactions among growth factors is a critical fact that would lighten up the retinal tissue engineering path, that is, possible effects of increasing the amount of a growth factor on other growth factors’ functions. one of the least expensive methods for detecting this kind of facts is evaluating them with an in-silico study. in this work, retinal growth factors interactions have been studied via creating their interaction network. by creating this network, the influence of each growth factor on the biological processes can be determined. the higher degree in this network leads to higher interactions among them and causes much more effect. the main goal of this study is to find out which kind of retinal growth factor should be used to have the highest effect on the desired biological process. methods all in-vivo or in-vitro studies already performed on retinal tissue engineering were reviewed to know how cells were affected by their surrounding environmental factors. the final results of these studies were collected into databases to provide access to comprehensive and accurate information. in the current study, the regeneration gene database was used.[30] according to this database, 21 protein-coding genes participate in retinal regeneration. in order to reveal their interaction and realize how they affect each other, all of these proteins were gathered from this database. then a study on systems biology was performed. the mathematical modelling of complicated biological systems is called systems biology. for this purpose, the “string app” in “cytoscape 3.7.2 software” [1] was utilized. the string app is one of the cytoscape software apps related to the string database.[31] this database is utilized for investigating the protein–protein interaction (ppi). in this regard, the data source was adjusted on “string: protein query”, and all 21 proteins were included in this query. given that this study is on human proteins, the species section was set on homo sapiens, and the analysis results were matched for humans. selecting default options from multiple possible matches found for some proteins would lead to loading interactions from the string database. then, a primitive model of ppi graph was drawn, meanwhile having the ability to alter into other layouts, that is, grid, circular, and hierarchical. creating a ppi network, there are 21 nodes and 37 edges. in other words, a 21 node-included graph was drawn using the string app. then, gene ontology (go) analysis was performed. go analysis is a major bioinformatics initiative to unify the representation of gene and gene product attributes across all species.[32] the protein–coding genes which are involved in retinal regeneration are listed in table 1. in addition, a centrality analysis was performed based on the degree index. in network analysis, 58 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 growth factors in retinal regeneration; beheshtizadeh et al table 1. the list of protein-coding genes that are involved in retinal regeneration no name gene id degree 1 shh 6469 10 2 igf1 3479 8 3 stat3 6774 8 4 ascl1 429 7 5 cdh2 1000 7 6 wnt3a 89780 5 7 fgfr1 2260 5 8 vtn 7448 5 9 calb2 794 3 10 cntf 1270 3 11 mdk 4192 2 12 insm1 3642 2 13 opn4 94233 2 14 itgav 3685 2 15 c3 718 2 16 rax 30062 1 17 rpe65 6121 1 18 apobec2 10930 0 19 tuba1c 84790 0 20 hspa1l 3305 0 21 vps35 55737 0 based on graph theory, centrality indicators identify the most important nodes within a network. the results of this analysis lead to a degree based array of nodes in the network. in order to illustrate comprehensible figures, the circular layout was selected. also, to recognize the most effective proteins, degree sorted layouts were selected. results figure 1 shows the ppi network. in this figure, a ppi network and a go analysis of retinal regeneration effective growth factors presented by string app database are shown. this figure presents the relationship among all proteins participating in retinal regeneration. these proteins are also listed in table 1. based on figure 1, there are four proteins that act individually: heat shock protein family a member 1 (hspa1l), vps35 retromer complex component (vps35), apolipoprotein b mrna editing enzyme catalytic subunit 2 (apobec2), and tubulin alpha 1c (tuba1c). these proteins do not have any interactions with the other 17 effective proteins in the retina healing process. mentioned proteins can show activity individually or via activating other proteins. for instance, the vps35 impression is on the upregulation of the development process. as a matter of fact, there are 11 proteins involved in the upregulation of the development process, and vps35 is one of them. as mentioned previously, a centrality analysis based on the degree was performed. in order to get the best understanding, it is preferred to present the ppi network by the centrality analysis based on the degree. figure 2 illustrates this analysis. according to this centrality analysis, four proteins have the greatest influence on retinal regeneration: shh, insulin-like growth factor 1 (igf1), stat3, and achaete-scute family bhlh transcription factor 1 (ascl1). these proteins have the highest degree in the ppi network. the most impressive biological processes considered in this study, that is, eye development, journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 59 growth factors in retinal regeneration; beheshtizadeh et al figure 1. hierarchical layout of the ppi network performed by string app in cytoscape 3.7.2. this network presents go analysis of retina regeneration effective growth. each circle provides a schematic drawing of protein structure. the colors are set randomly, and the connection line’s thickness illustrates the relation of power. also, a thicker line presents much more evidence and documents to approve the connectivity. detection of visible lights, visual perception, photoreceptor cell differentiation, camera-type eye development, eye morphogenesis, and angiogenesis, lead to retinal regeneration. moreover, based on go analysis, the most effective protein-coding genes that act in the mentioned biological procedures are shh, stat3, fgfr1, opsin 4 (opn4), integrin subunit alpha v 60 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 growth factors in retinal regeneration; beheshtizadeh et al figure 2. the degree-sorted circular layout of the ppi network performed by string app in cytoscape 3.7.2. each circle provides a schematic drawing of protein structure. the colors are set randomly, and the connection line’s thickness illustrates the relation of power. also, a thicker line presents much more evidence and documents to approve the connectivity. (itgav), retina and anterior neural fold homeobox (rax), and rpe65. discussion in this study, two analyses were performed: go analysis and centrality analysis. based on the go analysis results, there were seven proteins participating in seven biological processes. in addition, the four most effective proteins in the retinal regeneration process were identified via degree index-based centrality analysis. to get the most appropriate growth factor for use in retinal tissue engineering, each protein’s role needs to be identified. considering the four isolated proteins in figure 1, it can be argued that these proteins are also involved in retinal regeneration; however, there should be some biological processes that these proteins could impress on. positive regulation of transport is a biological process in which vps35 and hspa1l participate. based on go analysis journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 61 growth factors in retinal regeneration; beheshtizadeh et al (go: 0051094), a process that causes and expands the rate of development is an “upregulation of developmental process”; it points to a biological procedure, which results in the development of an organism from the primary situation till the last condition; for example, from a zygote to an adult. in addition, “transport positive upregulation” is a process that grows the scope, rate, and frequency of substances movement such as ions, molecules in cells and between them by use of a factor, for example, a pore or a transporter (go: 0051050).[33] the four aforementioned proteins, which have the most influence on retinal regeneration based on centrality analysis, are shh, igf1, stat3, and ascl1. shh is a protein functional in embryo formation. interestingly, shh and fgf can induce stem/progenitor cells in the regeneration process, and these two have simultaneous interdependence on each other. for example, if shh is inhibited, fgf would also be inhibited and vice versa. therefore, fgf and hedgehog pathways work together to stimulate retinal regeneration. in fact, the complex relation between shh and fgf regulates this process.[18] shh has the highest degree in the network (figure 2). it could be noted that the hedgehog pathway plays an essential role as a modulator of retinal regeneration.[28] igf-1 has an impact on the activity of growth promotion. nerve injury causes phospho-akt inactivation; therefore, retinal ganglion cell (rgc) loss would occur. it is evident from the literature that supplementation of igf-1-induced phosphoakt expression upregulates and provides the cell survival of rgcs.[34] consequently, during primary levels of nerve damage, igf-1 would be a key molecule that possesses the apoptosis effect on rgcs.[34] igf-1 is at the second rank according to its special role in glial cell survival. moreover, stat3 is a transcription factor involved in retinal regeneration, supporting stem cell maintenance and tissue development. furthermore, muller glial cells are the kind of cells in the retina that support neurons like other glial cells. the role of stat3 in the regeneration process is providing maximum proliferation of muller glia cells in retinal damage. in fact, stat3 and ascl1 have an important place in retinal regeneration. considering and investing on them in tissue fabrication seems logical to get closer to the regeneration purpose. the study provides a mutual relation between the ascl1 factor and stat3 in the regeneration process. stat3 is expressed in all muller glial cells, while ascl1 is only expressed in proliferating muller glial cells. although the expression of the ascl1 is necessary for retinal regeneration, stat3 in cell proliferation has priority to ascl1. moreover, ascl1 takes part in stat3 expression. both factors are efficient in the regeneration of cell cycles. ascl1 is a critical regulatory factor in retinal regeneration. it helps and converts dormant muller glia to retinal progenitors that are able to divide. ascl1 is a protein expressed during retinal puncture and causes retinal regeneration by affecting the lin-28 factor.[23, 27] hence, according to centrality analysis, ascl1 is in relation with two important and high degree factors of the network, shh and stat3. as mentioned before, the relation of ascl1 and stat3 is direct and mutual, so it is important to consider the role of ascl1 in glial cell proliferation and survival, which stat3 is also involved in. the role of these four proteins is critical in retinal regeneration. furthermore, go analysis demonstrated that these proteins have incredible effects on some biological processes. seven most important biological processes were studied in this work. table 2 shows the biological processes and the relation with the mentioned protein-coding genes. based on go analysis, “eye development” (go: 0001654) is a process which its significant result is eye development over time along with the formation of the matured structures. in addition, “detection of visible lights” is a chain of incidents that a visible light stimulus is captured by a cell and turned into a molecular signal (go: 0009584). “eye morphogenesis” is a process in which the generation of anatomical structures of the eye happens and unifies (go: 0048592).[33] furthermore, “visual perception” is a chain of incidents, which are essential for an organism to capture a visual stimulus, turn it out into a molecular signal, and describe and identify the signal. signals are detected in the photon form and are converted to an image form (go: 0007601). the definition of “photoreceptor cell differentiation” in the go database is the specialization of formation of a photoreceptor, a cell that is responsive to electromagnetic ray, especially visible light (go: 0001754). drosophila 62 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 growth factors in retinal regeneration; beheshtizadeh et al table 2. proteins involved in retina biological processes biological process/ protein names shh stat3 fgfr1 opn4 itgav rax rpe65 eye development * * * * detection of visible lights * * visual perception * * * photoreceptor cell differentiation * * camera-type eye development * * * eye morphogenesis * * angiogenesis * * * melanogaster is an example of this procedure.[33] “camera-type eye development” (go: 0043010) is a biological process, which its specific outcome is the progression of the camera-type eye over time, from its formation to a mature structure. the camera-type eye is an organ of sight that receives light through an aperture and focuses it through a lens, projecting it on a photoreceptor field.[33] angiogenesis is another crucial process that can lead to prosperous tissue fabrication. in fact, blood vessel formation is called angiogenesis when new vessels emerge from the proliferation of the preexisting blood vessels. based on evaluations, three proteins are involved in this process: shh, fgfr1, and itgav. figure 3 shows these proteins involved in the ppi network. regarding the most impressive protein-coding genes, which participate in those seven biological procedures based on go analysis, that is, shh, stat3, fgfr1, opn4, itgav, rax, and rpe65, there are some interesting findings. shh is able to induce angiogenesis, characterized by distinct large-diameter vessels and also augmented bloodflow recovery. in-vitro, shh does not affect endothelial cell migration or proliferation; instead, it induces expression of two families of angiogenic cytokines, including all three vascular endothelial growth factor-1 (vegf1) isoforms and angiopoietins1 and -2 from the interstitial mesenchymal cells.[35] lack of fgf signaling in retinal pigment epithelium (rpe) during eye development strongly affects choroidal angiogenesis, including the absence of astrocytes, which are responsible for vegf production. fgf-induced angiogenesis also requires activation of the vegf system, while fgfs promote a strong angiogenic response.[36] the product of this gene belongs to the integrin alpha chain family. integrins are heterodimeric integral membrane proteins composed of an alpha subunit as well as a beta subunit that function in cell surface adhesion and signaling.[37] however, the protein encoded by rpe65 is a component of the vitamin a visual cycle of the retina, which supplies the 11-cis retinal chromophore of the photoreceptors’ opsin visual pigments. it performs the essential enzymatic isomerization step in the synthesis of the 11-cis retina. mutations in this gene are associated with early-onset severe blinding disorders, such as leber congenital amaurosis.[38] opsins are members of the guanine nucleotidebinding protein (g protein)-coupled receptor superfamily.[39] opn4 encodes a photoreceptive opsin protein that is expressed within the ganglion and amacrine cell layers of the retina. the protein functions as a sensory photopigment and may also have photoisomerase activity. furthermore, rax encodes a homeobox-containing transcription factor that functions in eye development.[40] rax is expressed early in the eye primordia and is required for retinal cell fate determination and regulates stem cell proliferation. mutations in this gene have been reported in patients with defects in ocular development, including microphthalmia, anophthalmia, and coloboma. therefore, based on the extracted data from table 2, shh is accounted for eye journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 63 growth factors in retinal regeneration; beheshtizadeh et al figure 3. angiogenesis involved proteins in retina regeneration, presented in a degree-sorted circular layout of the ppi network performed by string app in cytoscape 3.7.2. each circle provides a schematic drawing of protein structure. the colors are set randomly, and the connection line’s thickness illustrates the relation of power. also, a thicker line presents much more evidence and documents to approve the connectivity. development, camera-type eye development, and angiogenesis, whereas stat3 is dedicated to eye development, photoreceptor cell differentiation, and eye morphogenesis. fgfr1 and itgav are also only involved in angiogenesis. opn4 plays a great role in detecting visible lights and visual perception, while rax is active in eye development, visual perception, and camera-type eye development. finally, rpe65 is an impressive protein in all mentioned biological processes except angiogenesis. overall, explained biological processes and participated protein-coding genes must be considered in retina tissue fabrication. to fabricate artificial tissues or tissue regeneration, it is needed 64 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 growth factors in retinal regeneration; beheshtizadeh et al to understand the effective mechanisms to utilize them in an appropriate trend. applying these proteins as growth factors may help in retinal tissue engineering. the results of this study positively correlate with earlier published reports. in fact, a variety of proteins have been shown to play a role in the retina development and regeneration process. the salient examples of these proteins are small peptide growth factors, shh, taurine, epidermal growth factor (egf), and fgf.[41–43] rpe65, meanwhile, is considered as a strong marker for differentiation of bone marrow-derived stem cells (bmsc) into rpe.[44–46] furthermore, in the last decade, stat3 was introduced as a recently recognized regulator of rpe survival. in addition, proliferation and visual cycle maintenance are functional roles of stat3.[47] in summary, due to the importance of retinal disorders and the growing need for tissue engineering in this field, in-silico studies are very useful to predict the general condition. this would lighten up the path and lead us to the right answer in an inexpensive way. in order to find out the most effective growth factors in retinal tissue engineering, an in-silico study was performed. this study demonstrates the importance and preview of the 21 proteins that play different roles in retinal regeneration. according to each protein’s biological function and role in different paths, selecting the correct ones is possible through the information that the network provides. eye development, detection of visible lights, visual perception, photoreceptor cell differentiation, camera-type eye development, eye morphogenesis, and angiogenesis are the major biological processes in retinal regeneration. based on go analysis, each biological process has the most effective proteins in retinal regeneration, that is, shh, stat3, fgfr1, opn4, itgav, rax, and rpe65. in addition, based on degree index centrality analysis, the effectiveness of each protein on regeneration process was identified. in this regard, shh, igf1, stat3, and ascl1 are the proteins, which have the greatest influence on retinal regeneration. based on these perspectives and nodes with the highest degree in the network, as well as go analysis results, it is logical to focus on shh, stat3, and rpe65 in retinal tissue engineering. financial support and sponsorship this study has been funded and supported by tehran university of medical sciences (tums); grant no. 46271. conflicts of interest the authors declare that they have no conflict of interest. references 1. mason c, dunnill p. a brief definition of regenerative medicine. regen med 2008;3:1–5. 2. abouna gm. organ shortage crisis: problems and possible solutions. transplant proc 2008;40:34–38. 3. mao as, mooney dj. regenerative medicine: current therapies and future directions. proc natl acad sci usa 2015;112:14452–14459. 4. beheshtizadeh n, lotfibakhshaiesh n, pazhouhnia z, hoseinpour m, nafari m. a review of 3d bio-printing for bone and skin tissue engineering: a commercial approach. j mater sci 2020;55:3729–3749. 5. khan f, tanaka m. designing smart biomaterials for tissue engineering. int j mol sci 2017;19:17. 6. lee ej, kasper fk, mikos ag. biomaterials for tissue engineering. ann biomed eng 2014;42:323–337. 7. sudhakar ck, upadhyay n, verma a, jain a, narayana charyulu r, jain s. nanomedicine and tissue engineering. in: thomas s, grohens y, ninan n, editors. nanotechnology applications for tissue engineering. oxford: william andrew publishing; 2015:1–19. 8. vasita r, katti ds. growth factor-delivery systems for tissue engineering: a materials perspective. expert rev med devices 2006;3:29–47. 9. cervelló i, medrano jv, simón c. regenerative medicine and tissue engineering in reproductive medicine: future clinical applications in human infertility. in: laurence j, editor. translating regenerative medicine to the clinic. boston: academic press; 2016:139–151. 10. dzobo k, thomford ne, senthebane da, shipanga h, rowe a, dandara c, et al. advances in regenerative medicine and tissue engineering: innovation and transformation of medicine. stem cells int 2018;2018:24. 11. schwartz sd, pan ck, klimanskaya i, lanza r. retinal degeneration. in: lanza r, langer r, vacanti j, editors. principles of tissue engineering. 4th edition. boston: academic press; 2014:1427–1440. 12. abedin zadeh m, khoder m, al-kinani aa, younes hm, alany rg. retinal cell regeneration using tissue engineered polymeric scaffolds. drug discov today 2019;24:1669–1678. 13. goldman d. müller glial cell reprogramming and retina regeneration. nat rev neurosci 2014;15:431–442. 14. hamon a, roger je, yang x-j, perron m. müller glial celldependent regeneration of the neural retina: an overview across vertebrate model systems. dev dyn 2016;245:727– 738. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 65 growth factors in retinal regeneration; beheshtizadeh et al 15. kim hs, kim d, jeong yw, choi mj, lee gw, thangavelu m, et al. engineering retinal pigment epithelial cells regeneration for transplantation in regenerative medicine using peg/gellan gum hydrogels. int j biol macromol 2019;130:220–228. 16. lenkowski jr, raymond pa. müller glia: stem cells for generation and regeneration of retinal neurons in teleost fish. prog retin eye res 2014;40:94–123. 17. soleimannejad m, ebrahimi-barough s, nadri s, riaziesfahani m, soleimani m, tavangar sm, et al. retina tissue engineering by conjunctiva mesenchymal stem cells encapsulated in fibrin gel: hypotheses on novel approach to retinal diseases treatment. med hypotheses 2017;101:75–77. 18. tao sl, klassen h. 12 – biomaterials for retinal tissue engineering. in: chirila tv, harkin dg, editors. biomaterials and regenerative medicine in ophthalmology. 2nd ed. cambridge: woodhead publishing; 2016:291– 308. 19. wang p, li x, zhu w, zhong z, moran a, wang w, et al. 3d bioprinting of hydrogels for retina cell culturing. bioprinting 2018;12:e00029. 20. white dt, sengupta s, saxena mt, xu q, hanes j, ding d, et al. immunomodulation-accelerated neuronal regeneration following selective rod photoreceptor cell ablation in the zebrafish retina. proc natl acad sci usa 2017;11:e3719–e3728. 21. zhu j, luz-madrigal a, haynes t, zavada j, burke ak, del rio-tsonis k. β-catenin inactivation is a pre-requisite for chick retina regeneration. plos one 2014;9:e101748– e101748. 22. liu y, wang r, zarembinski ti, doty n, jiang c, regatieri c, et al. the application of hyaluronic acid hydrogels to retinal progenitor cell transplantation. tissue eng part a 2013;19:135–142. 23. fausett bv, gumerson jd, goldman d. the proneural basic helix-loop-helix gene ascl1a is required for retina regeneration. j neurosci 2008;28:1109–1117. 24. kador ke, goldberg jl. scaffolds and stem cells: delivery of cell transplants for retinal degenerations. expert rev ophthalmol 2012;7:459–470. 25. yao j, tao sl, young mj. synthetic polymer scaffolds for stem cell transplantation in retinal tissue engineering. polymers 2011;3:899. 26. bainbridge jw, smith aj, barker ss, robbie s, henderson r, balaggan k, et al. effect of gene therapy on visual function in leber’s congenital amaurosis. n engl j med 2008;358:2231–2239. 27. nelson cm, gorsuch ra, bailey tj, ackerman km, kassen sc, hyde dr. stat3 defines three populations of muller glia and is required for initiating maximal muller glia proliferation in the regenerating zebrafish retina. j comp neurol 2012;520:4294–4311. 28. spence jr, aycinena jc, del rio-tsonis k. fibroblast growth factor-hedgehog interdependence during retina regeneration. dev dyn 2007;236:1161–1174. 29. singh r, cuzzani o, binette f, sternberg h, west md, nasonkin io. pluripotent stem cells for retinal tissue engineering: current status and future prospects. stem cell rev 2018;14:463–483. 30. zhao m, rotgans b, wang t, cummins sf. regene: an online gene resource for animal regeneration with literature evidence. sci rep 2016;6:23167. 31. doncheva nt, morris jh, gorodkin j, jensen lj. cytoscape stringapp: network analysis and visualization of proteomics data. biorxiv 2018:438192. 32. consortium tgo. the gene ontology project in 2008. nucleic acids res 2007;36:d440–d444. 33. the gene ontology consortium. the gene ontology resource: 20 years and still going strong. nucleic acids res 2019;47:d330–d338. 34. homma k, koriyama y, mawatari k, higuchi y, kosaka j, kato s. early downregulation of igf-i decides the fate of rat retinal ganglion cells after optic nerve injury. neurochem int 2007;50:741–748. 35. pola r, ling le, silver m, corbley mj, kearney m, blake pepinsky r, et al. the morphogen sonic hedgehog is an indirect angiogenic agent upregulating two families of angiogenic growth factors. nat med 2001;7:706–711. 36. rousseau b, larrieu-lahargue f, bikfalvi a, javerzat s. involvement of fibroblast growth factors in choroidal angiogenesis and retinal vascularization. exp eye res 2003;77:147–156. 37. morandi em, verstappen r, zwierzina me, geley s, pierer g, ploner c. itgav and itga5 diversely regulate proliferation and adipogenic differentiation of human adipose derived stem cells. sci rep 2016;6:28889. 38. jauregui r, park ks, tsang sh. two-year progression analysis of rpe65 autosomal dominant retinitis pigmentosa. ophthalmic genet 2018;39:544–549. 39. nissila js, manttari sk, sarkioja tt, tuominen hj, takala te, kiviniemi vj, et al. the distribution of melanopsin (opn4) protein in the human brain. chronobiol int 2017;34:37–44. 40. voronina va, kozhemyakina ea, o’kernick cm, kahn nd, wenger sl, linberg jv, et al. mutations in the human rax homeobox gene in a patient with anophthalmia and sclerocornea. hum mol genet 2004;13:315–322. 41. hicks d, courtois y. fibroblast growth factor stimulates photoreceptor differentiation in vitro. j neurosci 1992;12:2022–2033. 42. osakada f, ikeda h, mandai m, wataya t, watanabe k, yoshimura n, et al. toward the generation of rod and cone photoreceptors from mouse, monkey and human embryonic stem cells. nat biotechnol 2008;26:215–224. 43. osakada f, ikeda h, sasai y, takahashi m. stepwise differentiation of pluripotent stem cells into retinal cells. nat protoc 2009;4:811–824. 44. enzmann v, yolcu e, kaplan hj, ildstad st. stem cells as tools in regenerative therapy for retinal degeneration. arch ophthalmol 2009;127:563–571. 45. akrami h, soheili zs, sadeghizadeh m, khalooghi k, ahmadieh h, kanavi mr, et al. evaluation of rpe65, cralbp, vegf, cd68, and tyrosinase gene expression in human retinal pigment epithelial cells cultured on amniotic membrane. biochem genet 2011;49:313–322. 46. regent f, morizur l, lesueur l, habeler w, plancheron a, ben m’barek k, et al. automation of human pluripotent stem cell differentiation toward retinal pigment epithelial cells for large-scale productions. sci rep 2019;9:10646. 66 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 growth factors in retinal regeneration; beheshtizadeh et al 47. patel ak, syeda s, hackam as. signal transducer and activator of transcription 3 (stat3) signaling in retinal pigment epithelium cells. jakstat 2013;2:e25434– e25434. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 67 original article the effect of contact lens–spectacle reversed galilean telescope on the visual field of patients with open-angle glaucoma mohammadreza moniritilaki, ms1*; maryam badakhsh, ms2*; asieh ehsaei, phd2,3; ramin daneshvar, md, ms4 1department of optometry and vision science, university of melbourne, victoria, australia 2refractive errors research center, mashhad university of medical sciences, mashhad, iran 3department of optometry, school of paramedical sciences, mashhad university of medical sciences, mashhad, iran 4eye research center, mashhad university of medical science, mashhad, iran orcid: mohammadreza moniritilaki: https://orcid.org/0000-0002-0941-9786 ramin daneshvar: https://orcid.org/0000-0002-0884-0907 abstract purpose: glaucoma causes irreversible visual field defects. this study aims to evaluate the effect of a reversed galilean telescope on the visual field of patients with open-angle glaucoma. methods: fifty-two glaucoma patients with a restricted visual field were recruited for this study. central 30° visual field measurements were performed using a humphrey visual field analyzer before and after applying the reversed galilean telescope. to be more cosmetically acceptable, a combination of contact lens–spectacle was used as the reversed galilean telescope. results: our data analysis showed that the reversed galilean telescope had a significant effect on all measured perimetric indices. visual field index (vfi) improved from a basic value of 44.38 ± 26.96 to 49.30 ± 29.83 percent by using the reversed telescope (p < 0.001). moreover, the mean deviation (md) was significantly improved from the initial value of –19.91 ± 7.19 db to a value of –18.69 ± 7.73 db (p < 0.001). however, our results showed a significant reduction in the pattern standard deviation (psd) comparing before (9.83 ± 2.82) and after (8.51 ± 3.30) values using the reversed galilean telescope (p < 0.001). conclusion: the contact lens–spectacle combination reversed galilean telescope significantly improved the central 30° visual field of glaucoma patients with the restricted visual field. keywords: glaucoma; reversed galilean telescope; visual field j ophthalmic vis res 2020; 15 (4): 502–508 *mohammadreza moniritilaki and maryam badakhsh contributed equally to this work and should be mentioned as co-first authors. correspondence to: ramin daneshvar, md. eye research center, khatam anbia eye hospital, gharani blvd., mashhad 91959, iran. e-mail: radaneshvar@gmail.com received: 07-04-2020 accepted: 13-08-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7779 introduction optical enhancement of restricted visual field in patients with visual field defects is a major concern this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: moniritilaki m, badakhsh m, ehsaei a, daneshvar r. the effect of contact lens–spectacle reversed galilean telescope on the visual field of patients with open-angle glaucoma. j ophthalmic vis res 2020;15:502–508. 502 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7779&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr effect of a reverse galilean telescope on visual fields; moniritilaki et al of practitioners.[1] reversed telescopic lenses have been widely used as field expanding devices to help patients with severely constricted visual filed in low vision clinics.[1–3] visual field defect is a known, disabling consequence of many diseases such as glaucoma and retinitis pigmentosa (rp).[1, 4] glaucoma is an irreversible, progressive optic neuropathy and its gradual visual field loss usually begins in the peripheral field. the peripheral visual field loss due to glaucoma causes decreased health-related quality of life.[5] epidemiological studies suggested that glaucoma causes bilateral blindness in nearly 6.7 million people worldwide. based on these studies, there are approximately 67 million glaucomatous patients in the world.[6] although patients with the restricted visual field have high demands and motivations to use visual field expanding instruments, few devices are available.[7] the reversed galilean telescope is an optical system which has been used as visual field expander to help patients with constricted visual field due to various underlying etiologies.[1, 8, 9] mehr and quillman[8] reported a 63-year-old man who suffered from peripheral visual field loss as a result of rp and demonstrated a noticeable visual field improvement from 5° central to 14° after using the reversed galilean telescope. their patient also reported that using the reversed galilean telescope was very useful in his daily tasks and had an unexpected social advantage for him. in a larger series, kennedy et al[1] assessed 10 participants with severe visual field loss due to rp. they evaluated visual acuity and visual field before and after using the reversed galilean telescope and reported subjective improvement in the visual field of six subjects. both of these studies have shown visual field improvement after using the reversed galilean telescope in participants who suffered peripheral visual field loss due to rp. in this study, we evaluated the hypothesis that using a reversed galilean telescope can improve the visual field of advanced glaucoma cases. we also used a modified version of the reversed galilean telescope which is cosmetically more acceptable. additionally, we evaluated the visual field with humphrey field analyzer which is more accurate than previously used tangent screen. methods participants fifty-two participants between the ages of 18 and 73 years (mean age 53.8 ± 13.0 years; 12 (24%) female) were recruited for this study. comprehensive eye examinations were performed to determine their eligibility. all included subjects had advanced primary open-angle glaucoma (based on the hodapp-anderson-parrish (hap) criteria), a best-corrected visual acuity of 20/200 or better, and at least three reliable visual fields on their records. an absolute spherical refractive error of fewer than 4.00 dioptres (d) with < 0.50 d of the cylinder was also an inclusion criterion. prior to the experiment, all participants provided a written informed consent. the study protocol was approved by the research ethics committee of mashhad university of medical sciences and adhered to the tenets of the declaration of helsinki. field expanding device technically, field expansion could be achieved by using a special optical system to minify the image size. the reversed galilean telescope is one of the most useful devices which has been used for over three decades in many studies to expand the visual field.[1–3] it consists of one converging lens serving as the eyepiece and a diverging lens as the objective. although many studies have shown improvement in the restricted visual field after using the reversed galilean telescope,[1, 8, 9] it is cosmetically not acceptable for most patients. in this study, we used an innovative, modified model of the reversed galilean telescope to be more user-friendly and practical. we used a contact lens as the eyepiece and a spectacle with a negative lens as the objective part of the telescope. to create a reversed galilean telescope, we used a spectacle with a constant power of –2.00 d for all participants. to calculate the power of the contact lens (bausch & lomb, rochester, new york, usa), we first measured the refraction for the far glasses and the dioptric addition they needed for near correction to do the perimetry. then, +2.00 d was added to the sum of far and near refractions. for example, in a patient with a far spectacle journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 503 effect of a reverse galilean telescope on visual fields; moniritilaki et al of +1.50 d and a near addition of +2.00 d, we put a +5.50 d contact lens over the cornea and a –2.00 d corrective lens in the lens holder of humphrey perimeter to create a reverse galilean telescope. visual field measurement visual field measurement was performed with a humphrey visual field analyzer (hfa-ii, carlzeiss meditec, dublin, ca, usa) using the swedish interactive threshold algorithm (sita)standard strategy and the central 30-2 program. we measured three global parameters of the hfa, namely the visual field index (vfi), mean deviation (md), and pattern standard deviation (psd), to assess the visual field changes after using the reversed galilean telescope.[10–14] visual field measurement was performed on the eligible eyes. if both eyes of a participant met the inclusion criteria, the eye with the worse visual field defect was included in the study. study protocol the following protocol was used for all participants. first, comprehensive ophthalmologic examinations were performed by a glaucoma fellowship-trained ophthalmologist to determine the eligibility of participants and the refractive status was evaluated by an experienced optometrist. before the main visual field evaluation in the experimental session, 5 min run was performed to ensure that the participants were familiar with the visual field test procedure. all included subjects had two successive visual field measurements with and without the introduction of the reversed galilean telescope and the order of the tests was randomized. there was a 1-hour rest period between the two tests. statistical analysis all statistical analyses were performed using the graphpad prism 6 software (www.graphpad.com, san diego, california, united states). paired t-tests were conducted to compare the global indices before and after applying the reversed galilean telescope. results the mean refractive error (spherical equivalent) of participants was +1.17 ± 1.68 d, and the mean best-corrected visual acuity was 0.21 ± 0.25 logmar. all measured perimetric indices were significantly different after using the reversed galilean telescope. interestingly, vfi increased significantly from 44.38 ± 26.96 percent to 49.30 ± 29.83 percent by using the reversed telescope (p < 0.001) (figure 1). similarly, md change was statistically significant from an initial value of – 19.91 ± 7.19 db to a post-intervention value of – 18.69 ± 7.73 db (p < 0.001) (figure 2). although the sensitivity of the retinal points had not been changed, the minified image transferred more test points from the damaged peripheral zone to the central, less damaged zone which resulted in a significant increase of md and vfi. figure 3 illustrates the psd changes before and after using the reversed galilean telescope in the central 30°. data analysis showed significant changes between the before (9.83±2.82) and after (8.51 ± 3.30) values using the reversed galilean telescope (p < 0.001). discussion in this study, we found that using the reversed galilean telescope leads to a visual field improvement in central 30° of glaucomatous participants. we used the standard automated perimetry to quantify visual field changes after the administration of this device. this method leads to significant increments in the vfi and md, denoting visual filed improvement. we also observed a significant decrement in the psd index after using the telescope indicating increased homogeneity in the visual field. as the results of the vfi and md suggest visual field improvement, the increase of homogeneity of the visual field has been interpreted as visual field enhancement. glaucoma patients usually have visual complaints more than what is estimated by a visual acuity eye chart.[15] moreover, glaucoma affects the ability to detect objects in low illumination and discriminating low-contrast objects which have been found important in daily activity.[16] visual field loss is a major disabling consequence of glaucoma and may 504 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 www.graphpad.com, effect of a reverse galilean telescope on visual fields; moniritilaki et al figure 1. vfi changes before and after using the reversed galilean telescope. data are presented as mean ± sem (n = 52 subjects). *denotes a significant difference. figure 2. md changes before and after using the reversed galilean telescope. data are presented as mean ± sem (n = 52 subjects). *denotes a significant difference. cause difficulties in daily life.[17] it has been demonstrated that even mild visual field defects can lead to a difficulty in outdoor navigation, which in turn results in anxiety and stress for the patients.[18] although, visual field defects are not reversible by current surgical and non-surgical treatments,[19] using optical methods and minified images can potentially improve the visual field. technically, these minifying optical systems bring images from journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 505 effect of a reverse galilean telescope on visual fields; moniritilaki et al figure 3. psd changes before and after using the reversed galilean telescope. data are presented as mean ± sem (n = 52 subjects). *denotes a significant difference. peripherally damaged visual field to the central less damaged field, which result in improved visual field.[20] this study showed that a reversed galilean telescope caused a significant improvement in the visual field. all measured perimetric indices were significantly affected by the implemented reversed galilean telescope. the use of this optical device resulted in a significant increment in md and vfi and also significant reduction in psd, expressing the visual field enhancement, which is consistent with the results of a study by campbell et al[9] who demonstrated a significant visual field enhancement from 4° central to 20– 40° by using the reversed galilean telescope. they reported that this optical system led to visual field improvement in a 25-year-old female who suffered from severe visual field constriction due to stroke. moreover, visual field improvement has been reported after using the reversed galilean telescope in patients with restricted visual field due to rp.[1, 8] kennedy and associates[1] used an optical device as a reversed galilean telescope consisting of three small lenses placed within a plastic tubular casing. the two front lenses which stick together formed the objective lens and the third one was the ocular lens. in another study, mehr and quillman[8] showed a significant visual field enhancement after using the reversed galilean telescope. they mounted a concave lens on the participant’s spectacle which had a convex lens to create 1.3× reversed galilean telescope. the reversed galilean telescopes used in each of these studies were not cosmetically acceptable for patients. however, in the current study, a modified contact lens–spectacle combination was used as a reversed galilean telescope which was more practical. the ocular piece of our device is a convex contact lens which is the result of adding +2.00 d to the summation of refraction and near addition. in addition, the objective lens in our optical system is a constant lens of –2.00 d which is placed in the lens holder of the humphrey perimeter. it is well-accepted that the retinal image size of a spectacle differs from a contact lens with the same power.[21] in our telescope, because of farther distance to the nodal point, the minifying effect of – 2.00 d spectacle is more than the magnifying effect of the +2.00 d contact lens. therefore, the optical system causes a minified retinal image, resulting in a wider visual field. in the standard automated perimeter, psd reveals the localized visual field defect. a high psd suggests more difference between the more and the less sensitive visual field points and a low 506 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 effect of a reverse galilean telescope on visual fields; moniritilaki et al psd means there is either a homogenous defect across the visual field or there is no defect.[14] therefore, regarding the results of the md and the vfi (showing improved visual field), decrement in psd suggests improved visual field homogeneity which is compatible with the results of md and vfi. various optical systems have been used over the decades to help patients with vision problems. implanted miniature telescope is an example of a magnifying optical system that has been used to help patients with age-related macular degeneration (armd).[22] this implantable optical system magnifies images, therefore bringing the image from the central visual field, which is damaged, to the peripheral visual field, leading to an increase in visual acuity and improved quality of life. hudson and coworkers[23] reported that the implantable miniature telescope in patients with end-stage armd causes three lines or more improvement in the best-corrected distance and near visual acuity and quality of life. on the other hand, the minifying optical system that has been used in this study displaces the image throughout the visual field. unlike the mentioned implantable miniature telescope, the reverse galilean telescope brings the image from the peripheral visual field to the central visual field which is less damaged; hence, resulting in the improved visual field. to the best of our knowledge, this is the first report on using a reversed galilean telescope to enhance the visual field of glaucoma patients; moreover, our particular contact lens–spectacle combination as a reversed galilean telescope has not been previously reported in clinical practice. this approach has its limitations, including but not limited to difficulties in using a contact lens in elderly glaucomatous patients. dry eye is a common co-morbidity in these patients and contact lens use may have more side effects. however, considering its proven efficacy, one can use this approach by proper case selection and patient education. in addition, a potential approach in treating the glaucomatous patient with cataract may make them somewhat myopic by implanting an over-powered intraocular lens. then, a reversed galilean telescope effect can be induced by using a corrective, minus spectacle to enhance the visual field. this is the subject of the authors’ ongoing research. financial support and sponsorship this study has received support from the vicechancellor of research, mashhad university of medical sciences, grant no. 910712. conflicts of interest there are no conflicts of interest. references 1. kennedy wl, rosten jg, young lm, ciuffreda kj, levin mi. a field expander for patients with retinitis pigmentosa: a clinical study. am j optomet physiol optics 1977;54:744– 755. 2. bailey i. field expanders. optom monthly 1978;69:813– 816. 3. ciuffreda k. a new field expander: a preliminary report. optom wkly 1977;63:126–130. 4. mcgwin g, xie a, mays a, joiner w, decarlo dk, hall ta, et al. visual field defects and the risk of motor vehicle collisions among patients with glaucoma. invest ophthalmol vis sc 2005;46:4437–4441. 5. gutierrez p, wilson mr, johnson c, gordon m, cioffi ga, ritch r, et al. influence of glaucomatous visual field loss on health-related quality of life. arch ophthalmol 1997;115:777–784. 6. quigley ha. number of people with glaucoma worldwide. br j ophthalmol 1996;80:389–393. 7. duke es, dobree jh. system of ophthalmology vol. x: disease of retina. henry kimpton: london; 1967:102. 8. mehr eb, quillman rd. field “expansion” by use of binocular full-field reversed 1.3 x telescopic spectacles: a case report. am j optomet physiol optics 1979;56:446– 450. 9. campbell m, ellison pj, strong jg, lovasik jv. unexpectedly large enhancement of a severely constricted field with reversed galilean telescopes. optomet vis sci 1989;66:239–242. 10. flammer j. the concept of visual field indices. graefes arch clin exp ophthalmol 1986;224:389–392. 11. heijl a, lindgren g, olsson j, asmanl p. on weighted visual field indices. graefes arch clin exp ophthalmol 1992;230:397–398. 12. artes ph, o’leary n, hutchison dm, heckler m, sharpe gp, nicolela mt, et al. properties of the statpac visual field index. invest ophthalmol vis sci 2011;52:4030–4038. 13. bengtsson b, heijl a. a visual field index for calculation of glaucoma rate of progression. am j ophthalmol 2008;145:343–353. 14. lachenmayr bj, vivell p, drance sm, blodi fc. principles of perimetry. perimetry and its clinical correlation. new york: thieme medical publishers inc; 1993:12–13. 15. szlyk jp, fishman ga, alexander kr, revelins bi, derlacki dj, anderson rj. relationship between difficulty in performing daily activities and clinical measures of visual function in patients with retinitis pigmentosa. arch ophthalmol 1997;115:53–59. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 507 effect of a reverse galilean telescope on visual fields; moniritilaki et al 16. szlyk jp, taglia dp, paliga j, edward dp, wilensky jt. driving performance in patients with mild to moderate glaucomatous clinical vision changes. j rehabil res dev 2002;39:467–482. 17. ramrattan rs, wolfs rcw, jonas sp, jonas jb, bakker d, pols ha. prevalence and causes of visual field loss in the elderly and associations with impairment in daily functioning: the rotterdam study. arch ophthalmol 2001;119:1788–1794. 18. ross je, bron aj, clarke dd. contrast sensitivity and visual disability in chronic simple glaucoma. br j ophthalmol 1984;68:821–827. 19. leske mc, heijel a, hussein m, bengtsson bo, hyman l, komaroff e. factors for glaucoma progression and the effect of treatment: the early manifest glaucoma trial. arch ophthalmol 2003;121:48–56. 20. holm oc. a simple method for widening restricted visual fields. arch ophthalmol 1970;84:611–612. 21. westheimer g. the visual world of the new contact lens wearer. j am optm assoc 1962;34:135–138. 22. lane ss, kuppermann bd. the implantable miniature telescope for macular degeneration. curr opin ophthalmol 2006;17:94–98. 23. hudson hl, lane ss, heier js, stulting rd, singerman l, lichter pr, et al. implantable miniature telescope for the treatment of visual acuity loss resulting from endstage age-related macular degeneration: 1-year results. ophthalmology 2006;113:1987–2001. 508 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 editorial corneal cross-linking for keratoconus: exploring the issues regarding accelerated protocols and thin corneas farhad hafezi, md, phd, farvo1,2,3,4,5 1ocular cell biology group, center for applied biotechnology and molecular medicine, university of zurich, switzerland 2elza institute ag, dietikon/zurich, switzerland 3department of ophthalmology, university of southern california, los angeles, ca, usa 4faculty of medicine, university of geneva, geneva, switzerland 5department of ophthalmology, wenzhou medical university, wenzhou, china orcid: farhad hafezi: https://orcid.org/0000-0001-8935-4558 j ophthalmic vis res 2021; 16 (3): 314–316 the current issue of journal of ophthalmic and vision research (jovr) observes the publication of two useful additions to the cross-linking literature: an in vitro confocal microscopy (ivcm) evaluation of structural changes that occur in thin keratoconic corneas following corneal cross-linking (cxl),[1] and an evaluation of accelerated versus standard dresden protocol cxl for treatment of progressive keratoconus in syria.[2] it is worth briefly reviewing the history of cxl. for over 20 years, cxl has been used for the treatment of corneal ectatic disorders such as keratoconus, and involves saturating the corneal stroma with riboflavin, followed by a period of ultraviolet (uv)-a irradiation to photoactivate the riboflavin and cause it to covalently cross-link molecules within the corneal stroma (principally collagen, but also other molecules such as glycoproteins) and strengthen the cornea with the intention of halting the progression of ectasia.[3] epithelial cells at the surface of the cornea are effective barriers against riboflavin penetration into the stroma, therefore these cells are typically debrided before riboflavin is applied (the “epi-off” approach). the original cxl protocol, developed 20 years ago, called the dresden protocol, is an epi-off protocol that involves irradiation of a riboflavin-saturated cornea with 30 min of uv-a light at an intensity of 3 mw/cm².[4] this delivers a total uv-a fluence (or “dose”) of 5.4 j/cm² and is still considered to be the gold standard for strengthening ectatic corneas. nevertheless, the dresden protocol has a number of drawbacks. for safety reasons and to protect corneal endothelial cells from potentially dangerous levels of uv-a exposure, only corneas 400 µm or thicker may be treated with the dresden protocol.[4] in addition, 30 min of uv-a irradiation is a long period and therefore accelerated protocols that increase the intensity of illumination with a proportionate reduction in irradiation time have been pursued. however, the discovery that oxygen is an essential component of the cross-linking phenomenon (and its diffusion into the stroma is a rate-limiting step) explains why increased intensityreduced time irradiation protocols result in less effective cross-linking.[5–8] the current consensus is that the most reasonable trade-off lies around 10 min of 9 mw/cm² irradiation which still provides most of the effect of the full 30 min irradiation protocol while cutting treatment time to one-third.[8] the article by salman et al[2] published in this issue of jovr reports a trial that compared an accelerated epi-off cxl irradiation protocol (10 mw/cm² for 9 min) with the standard dresden protocol (3 mw/cm² for 30 min). amongst the visual, corneal tomographic and topographic factors examined, the researchers noted that “this [was] the first study to compare the impact of different cxl protocols on posterior corneal astigmatism.” they found that accelerated cxl resulted in significantly greater anterior corneal flattening, a greater increase in posterior steepening, a larger decrease in posterior astigmatism, and a greater reduction in minimum thickness than the standard cxl protocol. they noted that both protocols showed improvement in postoperative visual acuity (va) and higher order aberrations, but the 314 © 2021 farhad hafezi. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i3.9425&domain=pdf&date_stamp=2019-07-17 cxl for kcn; farhad hafezi accelerated cxl protocol resulted in significantly better va than the standard protocol. although this study was performed on a relatively small sample (63 eyes, 40 patients), it adds to the body of evidence that accelerated cxl protocols might result in a greater flattening effect than standard cxl protocols, which is an encouraging finding indicating that accelerated cxl protocols might offer visual rehabilitation in subjects with ectatic corneas, as flattening is associated with a reduction in ectasia-associated myopia. corneal ectasias, however, can result in corneas that are thinner than 400 µm, and if these cases cannot be treated with cxl, they may ultimately require keratoplasty. a number of approaches have been taken to artificially thicken the cornea,[9] either through swelling the cornea to a thickness ≥400 µm using hypotonic riboflavin prior to and during uv-a irradiation[10] or through the placement of a riboflavin-soaked contact lens to artificially bulk the cornea.[11] both approaches have drawbacks, that is, less predictable or suboptimal strengthening outcomes,[5] but can still offer corneal strengthening and some level of protection against later ectasia progression. the ivcm paper by sufi et al[1] offers some insight on the use of hypertonic riboflavin to crosslink thin corneas. in this paper, 10 eyes from 10 patients with progressive keratoconus and corneal thickness ranging from 350 to 399 µm received cxl with hypotonic riboflavin and were examined by ivcm at postoperative months 1, 3, and 6. the authors observed evidence of edema at one month, which reduced gradually over the next five months; that the subepithelial nerve plexus was completely absent one month after cxl, but regenerated gradually over the next five months (albeit poorly in 2 out of 10 eyes); and stromal keratocyte apoptosis in the anterior stroma in all cases (which extended to the posterior stroma in four eyes) with gradual repopulation over the remainder of the study course. however, it was clear that thin cornea cxl significantly decreased the specular endothelial cell count by 8%, albeit without signs of endothelial trauma. the study by sufi et al[1] is a small report with its inherent limitations, but raises important questions about the uv dose applied to thin (<400 µm) corneas during cross-linking: there is less tissue in these thin corneas, the increased mass is simply 0.1% riboflavin solution. although riboflavin absorbs uv energy (and is consumed during the process), it may be the case that the tissue bulk in riboflavin-soaked corneas naturally thicker than 400 µm absorbs more uv energy and therefore shields the endothelial cells from uv-a energy better than the relatively sparse tissue in thin corneas artificially thickened by hypotonic riboflavin solution. fortunately, a newer approach is now available that adjusts the total fluence of uv-a based on immediate pre-irradiation corneal thickness; the so-called sub400 protocol[12] delivers a uv dose intended to avoid irradiating the 70 µm posterior stroma safety zone first defined in the dresden protocol without resorting to artificial thickening approaches. the sub400 protocol can even be used with the simplest first-generation cross-linking machines by only altering the duration of uv-a irradiation. references 1. sufi ars, gohil mn, keenan jd, prajna nv. structural changes in thin keratoconic corneas following crosslinking with hypotonic riboflavin: findings on in vivo confocal microscopy. j ophthalmic vis res 2021;16:325–337. 2. salman amdtr, haddad yh, shabaan rh, askar mz. accelerated versus standard corneal cross-linking for progressive keratoconus in syria. j ophthalmic vis res 2021;16:338–348. 3. randleman jb, khandelwal ss, hafezi f. corneal crosslinking. surv ophthalmol 2015;60:509–523. 4. wollensak g, sporl e, seiler t. [treatment of keratoconus by collagen cross linking]. ophthalmologe 2003;100:44– 49. 5. kling s, richoz o, hammer a, tabibian d, jacob s, agarwal a, et al. increased biomechanical efficacy of corneal crosslinking in thin corneas due to higher oxygen availability. j refract surg 2015;31:840–846. 6. richoz o, hammer a, tabibian d, gatzioufas z, hafezi f. the biomechanical effect of corneal collagen cross-linking (cxl) with riboflavin and uv-a is oxygen dependent. transl vis sci technol 2013;2:6. 7. torres-netto ea, kling s, hafezi n, vinciguerra p, randleman jb, hafezi f. oxygen diffusion may limit the biomechanical effectiveness of iontophoresis-assisted transepithelial corneal cross-linking. j refract surg 2018;34:768–774. 8. hammer a, richoz o, arba mosquera s, tabibian d, hoogewoud f, hafezi f. corneal biomechanical properties at different corneal cross-linking (cxl) irradiances. invest ophthalmol vis sci 2014;55:2881–2884. 9. deshmukh r, hafezi f, kymionis gd, kling s, shah r, padmanabhan p, et al. current concepts in crosslinking thin corneas. indian j ophthalmol 2019;67:8–15. 10. hafezi f, mrochen m, iseli hp, seiler t. collagen crosslinking with ultraviolet-a and hypoosmolar riboflavin solution in thin corneas. j cataract refract surg 2009;35:621–624. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 315 cxl for kcn; farhad hafezi 11. jacob s, kumar da, agarwal a, basu s, sinha p, agarwal a. contact lens-assisted collagen cross-linking (cacxl): a new technique for cross-linking thin corneas. j refract surg 2014;30:366–372. 12. hafezi f, kling s, gilardoni f, hafezi n, hillen m, abrishamchi r, et al. individualized corneal cross-linking with riboflavin and uv-a in ultrathin corneas: the sub400 protocol. am j ophthalmol 2021;224:133–142. correspondence to: farhad hafezi, md, phd, farvo. elza institute, webereistrasse 2, 8953 dietikon, switzerland. email: farhad@hafezi.ch received: 20-05-2021 accepted: 29-04-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i3.9425 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: hafezi f. corneal cross-linking for keratoconus: exploring the issues regarding accelerated protocols and thin corneas. j ophthalmic vis res 2021;16:314–316. 316 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 https://knepublishing.com/index.php/jovr original article the role of trace elements in pseudoexfoliation syndrome: a cross-sectional study mohammad reza talebnejad, md; ali azimi, md; mohammad reza khalili, md; aidin meshksar, md poostchi ophthalmology research center, department of ophthalmology, shiraz university of medical sciences, shiraz, iran orcid: mohammad reza talebnejad: https://orcid.org/0000-0001-8667-7490 ali azimi: https://orcid.org/0000-0001-7744-5858 abstract purpose: pseudoexfoliation syndrome (pxf) is an age-related condition, characterized by deposition of whitish flake-shaped materials in the anterior segment of the eye. although it occurs all over the world, a considerable racial variation exists. according to the high frequency of pxf in iran and the importance of prevention and early treatment, we evaluated the plasma level of iron, zinc, copper, and magnesium in patients with pxf. methods: in this study, 83 individuals were enrolled; 40 patients with cataract and pxf as the case group and 43 ageand sex-matched individuals with cataract but without pxf as the control group. the serum levels of the mentioned microelements were compared in two groups. results: in the case group, 25 (62.5%) male and 15 (37.5%) female subjects participated. in the control group, the corresponding figures were 22 (51.2%) and 21 (48.8%), respectively. the mean age of the case group was 66.07 ± 9.46 and that for the control group was 66.88 ± 8.04 years. regarding the case group, the serum levels of iron, zinc, copper, and magnesium were 60.58 ± 21.04, 84.7 ± 14.37, 120.23 ± 14.43, and 2.11 ± 0.23, respectively. these serum levels in the control group were 89.07 ± 26.06, 97.51 ± 17.42, 123.33 ± 19.01, and 2.14 ± 0.16. the serum levels of iron and zinc were significantly lower in the case group than the control group (p < 0.0001); however, such a difference was not observed in terms of copper and magnesium serum levels. conclusion: our study demonstrated that the serum iron and zinc levels were lower in pxf patients. nutritional deficiency may be a cause of zonular weakness in these patients. heme is a cofactor for the enzyme which contributes to the biosynthesis of fibrillin, the major protein in zonular fibers. therefore, iron can play a substantial role in the biosynthesis of the fibrils and also in the zonular stability. keywords: pseudoexfoliation; trace element; zonular stability j ophthalmic vis res 2021; 16 (2): 165–170 introduction pseudoexfoliation syndrome (pxf) is an agerelated condition which is clinically related with correspondence to: ali azimi, md. poostchi ophthalmology research center, department of ophthalmology, shiraz university of medical sciences, shiraz, iran. e-mail: ali.azimi1365@gmail.com received: 15-03-2019 accepted: 08-01-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9079 a variety of ocular disorders, including cataract, glaucoma, and increased risk of complications during intraocular surgery.[1] the syndrome is characterized by deposition of whitish flakeshaped fibrillar materials in the intraand extraocular tissues, more frequently on the anterior lens capsule and can also be detected on this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: talebnejad mr, azimi a, khalili mr, meshksar a. the role of trace elements in pseudoexfoliation syndrome: a cross-sectional study. j ophthalmic vis res 2021;16:165–170. © 2021 talebnejad et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 165 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9079&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr trace elements and pseudoexfoliation syndrome; talebnejad et al the lens zonules, iris surface, corneal endothelium, trabecular meshwork, anterior hyaloid surface and less frequently on the posterior lens capsule and even intraocular lens.[1, 2] due to the accumulation of pseudoexfoliative material in different visceral organs, pxf syndrome is known as a systemic disorder.[3] most cases can be diagnosed by a careful ophthalmic examination, especially after pupillary dilation.[2, 3] regarding the epidemiology, although pxf occurs all over the world, a considerable racial variation exists. the prevalence of pxf syndrome varies (0.69–23%) with the region and the study design.[1–4] the etiology of pxf syndrome is not exactly known, but a multifactorial complex model including genetic inheritance combined with environmental factors, such as geographic location, uv exposure, and decreased serum and aqueous levels of antioxidants have been suggested as the contributing factors.[5–10] according to the recent studies, oxidative stress plays a key role in the pathogenesis of pxf syndrome and decreased levels of different antioxidants has been investigated in the serum and aqueous samples of patients suffering from pxf syndrome.[2–4, 8–10] although in a few studies, the serum and aqueous levels of some microelements have been determined in these patients, the possible effect of microelements on the prevalence and/or severity of pxf syndrome has remained controversial.[11–13] based on the previous studies and considering the high frequency of pxf in iran, especially in rural areas and in malnourished subjects, the authors aimed to design the present study to determine the serum levels of iron, copper, zinc, and magnesium in patients with pseudoexfoliative cataract compared with the control group. methods patient selection in this cross-sectional study, using a simple random sampling method, 40 patients with visually significant senile nuclear cataract and pseudoexfoliation as the case group and 43 ageand sex-matched individuals with the same type of cataract but without pxf as the control group were enrolled. patients with secondary types of cataract such as traumatic or metabolic were excluded. all patients were referred to khalili hospital, affiliated to shiraz university of medical sciences, shiraz, iran for cataract surgery. all experiments were performed according to the declaration of helsinki and informed consent was obtained from all individuals. our local medical ethics committee approved the study. other exclusion criteria were history of ocular trauma, glaucoma, keratoconus, uveitis, any type of anemia, thyroid dysfunction, diabetes mellitus, wilson disease, collagen vascular and autoimmune diseases, and also those who received mineral supplements. patients were assessed for the presence or absence of pseudoexfoliative material on the border of pupil and on the anterior lens capsule and zonules after pupillary dilation. after at least 8 hr of night fasting, 10 ml blood sample was taken from each patient before cataract surgery. half of that was used to measure the level of hemoglobin using colorimetric technique and the remaining was centrifuged at 2400 rpm for 15 min to separate the serum. if the hemoglobin level was <14 mg/dl for males or 12 mg/dl for females, the individual was excluded. serum samples were kept in a freezer at –20°c until analysis. in this study, colorimetric technique was used for the measurement of cu, zn, and mg levels. the protocol for the measurement of cu was mixing 1000 lambda (λ) reagent with 50 λ serum. then, these two solutions were incubated for 10 min at 37°c. then, colorimetric method was carried out. the protocol for zn was the same as cu. for mg, the 10λ serum was mixed with 1000 λ reagents, and incubation time and temperature were the same as cu and zn. copper, zn, and mg levels were measured at 580, 560, and 546 nm wavelengths, respectively. for iron (fe), auto analyzer colorimeter (hitachi 912) was used. after mixing 300 λ reagents with 50 λ serum and 20 min incubation at 37°c, the auto analyzer was used. data were reported in μg/dl for cu and zn, and mg/dl for fe and mg. statistical analysis data were recorded and analyzed using spss statistics software, version 18 (spss inc., chicago, il). quantitative data were presented as mean ± standard deviation (sd). we used shapiro–wilk to check the normal distribution of data. it was 166 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 trace elements and pseudoexfoliation syndrome; talebnejad et al shown that fe and cu had normal distribution, but for mg and zn there was no normal distribution. independent t-test and mann–whitney u-test were used to compare the measurements obtained from quantitative variables and chi-square test were applied for qualitative variable parameter. p-value < 0.05 was considered as statistically significant. results forty patients were enrolled in the case group and 43 patients in the control group. there were no significant differences between the groups in terms of age and sex [table 1]. as table 1 shows, the plasma levels of iron and zinc were significantly lower in patients assigned to the case group compared with the control ones (pvalue < 0.001), however, there was no significant difference between the serum values of cu and mg between the two groups (p = 0.40, p = 0.55, respectively). discussion psuedoexfoliation syndrome (pxf) is a systemic disorder with ophthalmic manifestations.[14–18] the prevalence of pxf increases with age and is characterized by accumulation of fleck-like material in the anterior segment of the eye, especially around the pupillary border and on the surface of the lens. this material is primarily produced by the ciliary body epithelium, the pigmented epithelium of the iris, and also the pre-equatorial lens epithelium. the corneal endothelium, trabecular cells, vascular endothelia, and iris smooth muscle cells have also been suggested to play a role.[19–21] pxf material has a complex content which is mainly glycoprotein/proteoglycan composition and also elastic fibers epitopes.[22–24] a common gene variant in the lysyl oxidase homolog 1 (loxl1 ) enzyme, an enzyme critical for enhancing the tensile strength of collagen and elastin in extracellular matrices, has been found in approximately 90% of the pxf cases.[6, 25, 26] on the other hand, different environmental factors such as solar radiation, oxidant/antioxidant imbalance, and dietary factors such as high coffee consumption and low dietary folate intake are associated with increased risk of pxf.[7–10, 27] the role of trace elements in the hormonal imbalance has been investigated in previous studies. zhang et al showed that cu level increases and zn level decreases in polycystic ovarian syndrome which is related to hormonal imbalance.[28] our study showed a reduction in serum level of zn that can be due to the role of hormonal imbalance in the pathophysiology of pxf. the possible role of microelements on the prevalence or severity of pxf syndrome is a hot topic which has remained controversial based on different studies. yildirim et al reported that zinc level was decreased in the lens of cataract patients with pxf, and since zinc, copper and magnesium are essential for some metalloenzymes such as superoxide dismutase; there is a possibility of defective antioxidation mechanisms.[29] in another study, decreased level of selenium, which is an essential component of selenoproteins, in aqueous and conjunctiva of patients suffering from pxf, supported the possibility of oxidant/antioxidant impairment in the pathogenesis of pxf syndrome.[30] cumurcu et al showed that a significant increase in serum total oxidative stress status occurred in pxf.[31] as pxf is considered a systemic disorder, a simultaneous mechanism of local production of the material by anterior segment tissues and systemic accumulation of the material has been proposed. therefore, measurement of trace element levels in the serum may be helpful. our investigation showed decreased level of serum iron and zinc in patients with pxf. this results is in contrast with those of the study conducted by cumurcu et al which showed the elevated level of serum iron in pxf compared with the control group, but such a difference was not observed for zinc.[11] hohberger et al showed that the aqueous level of zn was decreased in pxf that is concordant to our results but there was an increase in iron level in pxf and primary open angle glaucoma.[12] another study performed by ceylan et al demonstrated that serum level of zn was not different in pxf and control groups; instead, some other trace elements such as manganese, molybdenum, and mercury were elevated in the serum of patients with pxf and pxf glaucoma.[13] one of the reasons for the difference in the results of our study and some of the mentioned researches might be the distribution of the serum level of iron in our population that is normally distributed, but in the aforementioned studies, this level was not normally distributed among the population. thus, trace elements may play different roles in different populations according to their distribution. this journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 167 trace elements and pseudoexfoliation syndrome; talebnejad et al table 1. comparison of the two groups in terms of demographic data and trace element values group frequency age𝑎,𝑑 sex𝑏,𝑒 serum fe(mg/dl)𝑎,𝑓 serum zn(μg/dl)𝑎,𝑔 serum cu(μg/dl)𝑐,ℎ serum mg(mg/dl)𝑐,𝑖 control 43 66.86 ± 8.046 f = 21 (48.8%) m = 22 (51.2%) 89.07 ± 26.063 97.51 ± 17.421 123.33 ± 19.011 2.144 ± 0.1637 case 40 66.03 ± 9.467 f = 15 (37.5 %) m = 25 (62.5 %) 60.58 ± 21.044 84.70 ± 14.376 120.23 ± 14.437 2.118 ± 0.0379 𝑎independent t-test was applied; 𝑏chi-square test was applied; 𝑐mann–whitney u-test was applied; 𝑑p-value = 0.66; 𝑒p-value = 0.30; 𝑓 p-value < 0.001; 𝑔p-value < 0.001; ℎp-value = 0.40; 𝑖p-value = 0.55 may support the effect of geographic location in the etiology of pxf syndrome. as microelements may play a role in the synthesis of exfoliative materials, it can also be supposed that the content of these materials might be different in patients affected by pxf syndrome according to the patients’ geographical area. on the other hand, our study has another message, which is the possible role of serum iron deficiency in the weakness of zonular fibers because iron is incorporated in the heme structure. there is a heme-containing cofactor in the biosynthesis of homocysteine that has a regulatory role and its absence leads to an increase in the homocysteine level.[32, 33] hubmacher et al showed that homocysteine can alter the structure and/or function of the microfibrils which contain fibrillin and cause zonular weakness and/or laxity.[34] previous studies showed that the homocysteine plasma level is increased in patients with pxf and the serum level of homocysteine is correlated with the severity of pxf.[35–38] homocysteine may be a correctable risk factor in the pathogenesis of pxf and elevated homocysteine level has been shown to be reversible by consumption of vitamins.[23] the results of our study can demonstrate the possible role of iron deficiency in the pathogenesis of zonular fiber weakness in pxf through the homocysteine pathway as iron is a part of the cofactor in the homocysteine metabolism. in conclusion, although the accumulation of exfoliative materials in the zonula is considered as the core mechanism of zonular weakness in pxf, our investigation also suggests a minor pathway. this is due to iron deficiency and occurs through the homocysteine pathway. therefore, further researches are needed to evaluate whether iron supplementation has any effect on the zonular stability. our study had some limitations. the first is that our sampling was from a single center; it may be helpful to have different groups of patients with pxf from different geographical locations for future researches. in addition, a larger sample size can be helpful for future studies. financial support and sponsorship no financial support was received for this submission. conflicts of interest the authors declare there are no conflict of interest. references 1. joshi rs, singanwad sv. frequency and surgical difficulties associated with pseudoexfoliation syndrome among indian rural population scheduled for cataract surgery: hospital-based data. indian j ophthalmol 2019;67:221. 2. aboobakar if, johnson wm, stamer wd, hauser ma, allingham rr. major review: exfoliation syndrome; advances in disease genetics, molecular biology, and epidemiology. exp eye res 2017;154:88–103. 3. tekin k, inanc m, elgin u. monitoring and management of the patient with pseudoexfoliation syndrome: current perspectives. clin ophthalmol 2019;13:453. 4. anastasopoulos e, founti p, topouzis f. update on pseudoexfoliation syndrome pathogenesis and associations with intraocular pressure, glaucoma and systemic diseases. curr opin ophthalmol 2015;26:82– 89. 5. schlötzer-schrehardt u, zenkel m. the role of lysyl oxidase-like 1 (loxl1) in exfoliation syndrome and glaucoma. exp eye res 2019;189:107818. 168 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 trace elements and pseudoexfoliation syndrome; talebnejad et al 6. zenkel m, schlötzer-schrehardt u. expression and regulation of loxl1 and elastin-related genes in eyes with exfoliation syndrome. j glaucoma 2014;23:s48–s50. 7. jiwani az, pasquale lr. exfoliation syndrome and solar exposure: new epidemiological insights into the pathophysiology of the disease. int ophthalmol clincs 2015;55:13. 8. oruc y, keser s, yusufoglu e, celik f, sahin i, yardim m, et al. decorin, tenascin c, total antioxidant, and total oxidant level changes in patients with pseudoexfoliation syndrome. j ophthalmol 2018;2018:7459496. 9. yaz ya, y𝚤ld𝚤r𝚤m n, yaz y, tekin n, i̇nal m, şahin fm. role of oxidative stress in pseudoexfoliation syndrome and pseudoexfoliation glaucoma. turk j ophthalmol 2019;49:61. 10. vulovic tss, pavlovic sm, jakovljevic vl, janicijevic kb, zdravkovic ns. nitric oxide and tumour necrosis factor alpha in the process of pseudoexfoliation glaucoma. int j ophthalmol 2016;9:1138. 11. cumurcu t, mendil d, etikan i. levels of zinc, iron, and copper in patients with pseudoexfoliative cataract. eur j ophthalmol 2006;16:548–553. 12. hohberger b, chaudhri ma, michalke b, lucio m, nowomiejska k, schlötzer-schrehardt u, et al. levels of aqueous humor trace elements in patients with openangle glaucoma. j trace elem med biol 2018;45:150–155. 13. ceylan om, demirdöğen bc, mumcuoğlu t, aykut o. evaluation of essential and toxic trace elements in pseudoexfoliation syndrome and pseudoexfoliation glaucoma. biol trace elem res 2013;153:28–34. 14. bettis di, allingham rr, wirostko bm. systemic diseases associated with exfoliation syndrome. int ophthalmol clin 2014;54:15–28. 15. vardhan a, haripriya a, ratukondla b, et al. association of pseudoexfoliation with systemic vascular diseases in a south indian population. jama ophthalmol 2017;135:348– 354. 16. špečkauskas m, tamošiūnas a, jašinskas v. association of ocular pseudoexfoliation syndrome with ischaemic heart disease, arterial hypertension and diabetes mellitus. acta ophthalmol 2012;90:e470–e475. 17. siordia ja, franco j, golden tr, dar b. ocular pseudoexfoliation syndrome linkage to cardiovascular disease. curr cardiol rep 2016;18:1–7. 18. wang w, he m, zhou m, zhang x. ocular pseudoexfoliation syndrome and vascular disease: a systematic review and meta-analysis. plos one 2014;9:e92767. 19. al-saleh sa, al-dabbagh nm, al-shamrani sm, khan n, arfin m, tariq m, et al. prevalence of ocular pseudoexfoliation syndrome and associated complications in riyadh, saudi arabia. saudi med j 2015;36:108. 20. arnarsson a, damji kf, sasaki h, sverrisson t, jonasson f. pseudoexfoliation in the reykjavik eye study: fiveyear incidence and changes in related ophthalmologic variables. am j ophthalmol 2009;148:291–297. 21. viso e, rodríguez-ares mt, gude f. prevalence of pseudoexfoliation syndrome among adult spanish in the salnés eye study. ophthalmic epidemiol 2010;17:118–124. 22. sharma s, chataway t, klebe s, griggs k, martin s, chegeni m, et al. novel protein constituents of pathological ocular pseudoexfoliation syndrome deposits identified with mass spectrometry. mol vis 2018;24:801. 23. ovodenko b, rostagno a, neubert ta, shetty v, thomas s, yang a, et al. proteomic analysis of exfoliation deposits. invest ophthalmol vis sci 2007;48:1447–1457. 24. schlötzer-schrehardt u. new pathogenetic insights into pseudoexfoliation syndrome/glaucoma. therapeutically relevant? ophthalmologe 2012;109:944–951. 25. zenkel m, krysta a, pasutto f, juenemann a, kruse fe, schlötzer-schrehardt u. regulation of lysyl oxidaselike 1 (loxl1) and elastin-related genes by pathogenic factors associated with pseudoexfoliation syndrome. invest ophthalmol vis sci 2011;52:8488–8495. 26. berner d, zenkel m, pasutto f, hoja u, liravi p, gusekschneider g, et al. posttranscriptional regulation of loxl1 expression via alternative splicing and nonsensemediated mrna decay as an adaptive stress response. invest ophthalmol vis sci 2017;58:5930–5940. 27. dewundara s, pasquale lr. exfoliation syndrome: a disease with an environmental component. curr opin ophthalmol 2015;26:78–81. 28. zheng g, wang l, guo z, sun l, wang l, wang ch, et al. association of serum heavy metals and trace element concentrations with reproductive hormone levels and polycystic ovary syndrome in a chinese population. biol trace elem res 2015;167:1–10. 29. yildirim z, uçgun ni, kilic n, gürsel e, sepici‐dinçel a. pseudoexfoliation syndrome and trace elements. ann ny acad sci 2007;1100:207–212. 30. yilmaz a, ayaz l, tamer l. selenium and pseudoexfoliation syndrome. am j ophthalmol 2011;151:272–276.e271. 31. cumurcu t, gunduz a, ozyurt h, nurcin h, at𝚤s o, egri m. increased oxidative stress in patients with pseudoexfoliation syndrome. ophthalmic res 2010;43:169–172. 32. majors ak, pyeritz re. a deficiency of cysteine impairs fibrillin-1 deposition: implications for the pathogenesis of cystathionine β-synthase deficiency. mol genet metab 2000;70:252–260. 33. zhao p, qian c, chen y-j, sheng y, ke y, qian z-m. cystathionine β-synthase (cbs) deficiency suppresses erythropoiesis by disrupting expression of heme biosynthetic enzymes and transporter. cell death dis 2019;10:1–11. 34. hubmacher d, cirulis jt, miao m, keeley fw, reinhardt dp. functional consequences of homocysteinylation of the elastic fiber proteins fibrillin-1 and tropoelastin. int j biol chem 2010;285:1188–1198. 35. tranchina l, centofanti m, oddone f, tang l, roberti g, liberatoscioli l, et al. levels of plasma homocysteine in pseudoexfoliation glaucoma. graefes arch clin exp ophthalmol 2011;249:443–448. 36. vessani rm, ritch r, liebmann jm, jofe m. plasma homocysteine is elevated in patients with exfoliation syndrome. am j ophthalmol 2003;136:41–46. 37. türkcü fm, köz ög, yarangümeli a, öner v, kural journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 169 trace elements and pseudoexfoliation syndrome; talebnejad et al g. plasma homocysteine, folic acid, and vitamin b12 levels in patients with pseudoexfoliation syndrome, pseudoexfoliation glaucoma, and normotensive glaucoma. medicina 2013;49:34. 38. yaghoubi g, heydari b, raza mm, zohre b. homocysteine levels in plasma of cataract patients with and without pseudoexfoliation syndrome. middle east afr j ophthalmol 2007;14:22. 170 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 original article eye care utilization among older subjects with visual impairment in northwest ethiopia aragaw kegne assaye1,2, ms; melkamu temeselew tegegn1, ms; gizachew tilahun belete1, ms 1department of optometry, school of medicine, college of medicine and health sciences, university of gondar, gondar, ethiopia 2optometry and vision science, school of medicine, university of new south wales, sydney, australia orcid: aragaw kegne assaye: https://orcid.org/0000-0002-4669-6985 abstract purpose: to find out the level of eye care service utilization and its determinants among the elderly visually impaired populations while visiting ophthalmic outreach locations in northwestern ethiopia, 2021. methods: an ophthalmic outreach-based cross-sectional study was conducted on 852 visually impaired older people. participants were selected by using a systematic random sampling method from january to july 2021. data were collected by using an interviewer-administered questionnaire and an ocular examination. the collected data were entered into the epi info 7, and analyzed using spss 20. a binary logistic regression was fitted. results: a total of 821 participants, with a response rate of 96.5%, were included in the study. the utilization of eye care services within the past two years prior to the study was 21.1% (95 % ci: 18.2–23.9). having systemic disease (aor = 3.2, 95% ci: 1.5–7.0), being a spectacle wearer (aor = 4.5, 95% ci: 2.0–9.4), having visual impairment at distance (aor = 2.9; 95% ci: 1.5–5.6), being blind (aor = 2.9; 95% ci: 1.5–5.6), duration of visual impairment ≤1 year (aor = 2.5; 95% ci: 1.3–4.9) were all significantly associated. conclusion: in this study, utilization of eye care services was low. being visually impaired at distance, being blind, recent onset of visual impairment, being a spectacle wearer, and having systemic disease were all related to the use of eye care services. the commonest barriers to utilization of eye care services were financial scarcity and long distances between eye care facilities. keywords: eye care services; ethiopia; visual impairments j ophthalmic vis res 2023; 18 (3): 306–317 correspondence to: aragaw kegne assaye, ms. department of optometry, school of medicine, college of medicine and health sciences, university of gondar, gondar, po box 196, ethiopia. email: a.assaye@unsw.edu.au; aragawkegne23@gmail.com received: 10-02-2022 accepted: 11-03-2023 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v18i3.13779 this is an open access article distributed under the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. how to cite this article: assaye ak, tegegn mt, belete gt. eye care utilization among older subjects with visual impairment in northwest ethiopia. j ophthalmic vis res 2023;18:306–317. 306 © 2023 assaye et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v18i3.13779&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr eye care among visually impaired; assaye et al introduction at least 2.2 billion people have a visual impairment globally; of these, around 1 billion people have a visual impairment that could have been prevented or is still unaddressed.[1] the calculated use of eye care services is uneven, and is determined by the availability, accessibility, affordability, and acceptability of services as well as the distribution of eye conditions and visual impairments.[2–5] about 43.3 million people are blind worldwide, of whom 89% of people with blindness or visual impairment are found in developing countries such as ethiopia.[1, 6–8] eye care service utilization by the population is the use of eye care services that has been provided in the society with the aim of preventing and treating ocular conditions, enhancing ocular wellbeing or gaining information about an individual’s eye health status and prognosis. eye care service utilization is a broadly investigated issue with important concerns and suggestions on the health condition of an individual and the community at large.[6, 9] the percentages of eye care service utilization by people in different areas across the world for the period ranging between one and five years prior to when the investigation was conducted include the following: a study in china, where 71.9% of the participants had never been to a hospital for examinations,[10]; in myanmar, among older individuals 87.4% sought eye care; in pakistan, 45.3% had an eye exam in the past year;[11] in south india, 35.5% had a history of eye examinations;[5] in usa, among visually impaired participants, 52% had not seen an eye care provider within the last year;[12]; in california (usa), 36% had an eye care visit in the past 12 months;[13] in south africa, 25.2% had an eye examination between two and five years;[3] in rural nigeria, 68% never had eye examinations before;[9, 14] and in ethiopia, 40 % of the participants’ failure to use an eye care service was due to indirect costs,[15] another recent study in ethiopia showed that the proportion of individuals who accessed eye care services within the last two years prior to the study was 23.8%.[6] researches suggested that people who lived in rural areas were characterized by: lower income, older ages, minor ethnicities, refugee populations, women, and inaccessible eye care service when needed.[2] being an urban resident, having a higher educational status, a higher family monthly income, a history of eye disease, being aware of regular eye checkups, wearing spectacles, and being visually impaired were all positively associated with seeking access to eye care services. however, being female and residing in rural communities were negatively associated with seeking access to eye care. the measured influence of age and having systemic diseases in seeking access to healthcare varied in different studies.[6–8, 16–18] researches revealed that the barriers to utilizing eye care services in different regions or countries included the following factors – cost, trust, communication, clinic accessibility, transportation, distance of the eye care service provider, perception that eye care is not needed due to old age, having good vision in the other eye, the need for escort and social engagement or cultural belief.[9, 14, 16, 17, 19–23] studying the utilization of eye care services and its associated factors at an ophthalmic outreach site is important in determining the major hindering factors toward considering utilization of eye care services. however, there was no such study at the ophthalmic outreach site in ethiopia. therefore, the main objective of this study was to determine the level of utilization of eye care services provided within a community and their associated factors among the visually impaired older population who attended ophthalmic outreach sites in northwest ethiopia in 2021. in addition, this study will give baseline information to healthcare planners and policy makers to take the required measures toward alleviating the barriers to utilizing eye care services. methods study design, period, and area an ophthalmic outreach-based cross-sectional study was conducted in two districts (chauhit and tekledingay) of the central gondar zone, northwest ethiopia among the visually impaired older population from january to july 2021. the university of gondar tertiary eye care and training center is the only tertiary center in the central gondar zone that provides comprehensive clinical and community eye health services. it also serves journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 307 eye care among visually impaired; assaye et al as a major referral center for 14 million people living in the amhara region, northwest ethiopia. the departments of optometry and ophthalmology at the university of gondar are providing continuous community eye care services through an outreach program in collaboration with the light for the world organization and other non-governmental organizations. according to the university of gondar tertiary eye care and training center report, about 293,927 people received eye care services in the outreach program between 2008 and 2019. these services included medical therapy, cataract surgery, trichiasis surgery, refraction with optical correction, and referral services. study population and eligibility criteria an older population group, aged ≥40 years, attending the ophthalmic outreach sites during the study period was selected for the study. however, those who were unable to answer the questionnaire due to mental health or communication problems were excluded from the study. sample size determination and sampling procedure a sample size was determined using a single population proportion formula with the assumption of the expected proportion of utilization of eye care service being 23.8%,[6] 95% confidence level, 3% desired precision, and 10% nonresponse rate. according to these parameters, the final calculated sample size was 852. the study participants were selected by applying a systematic random sampling technique from a registered logbook. operational definitions utilization of an eye care service if an individual reported that he/she had visited an eye care service provider center for an eye checkup or examination at least once in two years prior to the date of the research, it was considered as utilization of an eye care service. if no visits were made to an eye care service provider within this specified time period, the eye care service was considered as not being utilized.[6] distance visual impairment (vi) presenting distance visual acuity of worse than 6/12 to no light perception (nlp) in the worse eye. it was subcategorized as mild vi (presenting visual acuity [pva < 6/12 to ≤6/18], moderate vi [pva < 6/18 to ≤6/60], severe vi [pva< 6/60 to ≤3/60], and blindness [pva < 3/60 to nlp]).[24] ocular injury self-reported history of any previous injury to the eye.[24] near visual impairment binocular presenting near vision of ≤6/12 (n6) with the best-corrected distance visual acuity of ≥6/12.[25, 26] history of ocular surgery participants who had any eye surgery prior to data collection. awareness of causes and treatments for visual impairment this was determined by the responses of participants who answered “yes” to the following questions: “have you heard about the causes of visual impairment?” and “have you heard about the treatments for visual impairment?”, respectively.[27] data collection tool and procedure data were collected by conducting both faceto-face interviews using a pretested structured questionnaire and ocular examinations. the pretest was done in the kola diba district, gondar zone, which was outside of the study area. the questionnaire consisted of sociodemographic and economic data, behavioral factors, past ocular and medical history, and clinical characteristics of the study participants. the questions were adapted from previous literature[6, 13–15, 17, 19, 24, 28] distance visual acuity was assessed in each eye using a snellen acuity chart with tumbling e optotypes at 6 m in good illumination. similarly, binocular near visual acuity was tested by using 308 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 eye care among visually impaired; assaye et al a reduced snellen acuity chart at 40 cm. to assess the causes of visual impairment, an anterior segment examination was performed using a pen torch with a 2.5× magnified loupe, and a posterior segment examination was performed using a dilated direct ophthalmoscope. data processing and analysis after checking completeness and consistency of the data, it was coded and entered into the epi info version 7 (tm andrew, gd, usa), and then exported into the statistical package for social science (spss) version 20 (ibm corp., armonk, ny, usa) for analysis. descriptive statistics such as frequency distribution and measure of central tendency were used to summarize the descriptive part of the study. a binary logistic regression was fitted to identify factors associated with the utilization of eye care services, and the strength of this association was expressed using an adjusted odds ratio with a 95% of confidence interval. the significant variables were selected by using an enter variable selection technique, and fitness of the model was checked using the hosmer and lemeshow’s goodness of fit. variables with a p-value of <0.05 were considered statistically significant. results sociodemographic characteristics of the study participants the study population consisted of a total of 821 participants with a response rate of 96.5%, of whom 256 had history of eye examination before data collection. the median age of the participants with its interquartile range was 57 ± 23 (iqr) years. out of all participants, 486 (59.2%) were male, 508 (61.9%) were rural residents, and 458 (55.8%) were unable to read and write [table 1]. medical and ocular history of the study participants of the total study participants, 47 (5.7%), 110 (13.4%), and 46 (6.0%) had a history of systemic hypertension, ocular surgery and wearing of spectacles, respectively [table 2]. clinical characteristics of the study participants a total of 513 participants with distance visual impairment and 308 participants with near visual impairments were involved in the study. in the current study, only 33.6% of the participants with blindness and 27.1% participants with cataract utilized eye care services within the past two years [table 3] prior to the study. utilization of eye care services among visually impaired older population of the 821 study participants, 256 (31.2%) had previous history of eye examination before data collection, of which 175 (68.4%) had conducted an eye examination at an ophthalmic care hospital, whereas 81 (31.6%) had undergone an eye examination at an outreach ophthalmic site. this study revealed that the proportion of utilization of eye care services within the past two years was 21.1% (95% ci: 18.2–23.9). barriers to utilization of eye care services and need of eye care services the major barriers to utilizing eye care services reported by the participants included the following – a lack of money for eye examinations: 157 (27.8%), the distance of the eye care service provider: 156 (27.6%), and the ability to perform daily activities with the condition: 77(13.6%) [figure 1]. in the present study, the most required eye care service in both female and male participants was cataract surgery [table 4]. factors associated with the utilization of eye care service among visually impaired population a multivariable (binary) logistic regression analysis output showed that the presence of systemic disease, use of spectacles, history of ocular surgery, types of visual impairment, level of visual impairment at distance, and duration of visual impairment were significantly associated with the utilization of eye care services. participants who had systemic disease such as tuberculosis, hiv/ads, and arthritis were 3.2 times journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 309 eye care among visually impaired; assaye et al table 1. sociodemographic and economic characteristics of the study participants attending the ophthalmic outreach sites in the central gondar zone, northwest ethiopian, 2021 (number of participants = 821). variables time since the last eye examination p-value n no exam. ≤2 years (%) 3–5 years (%) >5 years (%) all 821 565 173 (21.1) 60 (7.3) 23 (2.8) age (yr) <0.001 40–49 254 (30.9) 205 (80.7) 33 (13.0) 10 (3.9) 6 (2.4) 50–59 185 (22.6) 133 (71.9) 36 (19.5) 13 (7.0) 3 (1.6) 60–69 162 (19.7) 103 (63.6) 39 (24.1) 14 (8.6) 6 (3.7) ≥70 220 (26.8) 124 (56.4) 65 (29.5) 23 (10.5) 8 (3.6) sex 0.25 male 486 (59.2) 325 (66.9) 109 (22.4) 40 (8.2) 12 (2.5) female 335 (40.8) 240 (71.6) 64 (19.1) 20 (6.0) 11 (3.3) residence 0.87 rural 508 (61.9) 352 (69.2) 108 (21.3) 37 (7.3) 11 (2.2) urban 313 (38.1) 213 (68.1) 65 (20.8) 23 (7.3) 12 (3.8) religion 0.32 christian 759 (92.6) 519 (68.4) 163 (21.5) 58 (7.6) 19 (2.5) muslim 62 (7.6) 46 (74.2) 10 (16.1) 2 (3.2) 4 (6.5) marital status (currently) 0.05 single 156 (19.0) 99 (63.5) 42 (26.9) 9 (5.8) 6 (3.8) married 665 (81.0) 466 (70.0) 131 (19.7) 51 (7.7) 17 (2.6) educational status 0.71 unable to read and write 458 (55.8) 323 (70.5) 98 (21.5) 29 (6.3) 8 (1.7) able to read and write 149 (18.1) 97 (65.1) 35 (23.5) 13 (8.7) 4 (2.7) primary and secondary school 112 (13.6) 83 (74.1) 20 (17.8) 4 (3.6) 5 (4.5) college and above 102 (12.4) 62 (60.8) 20 (19.6) 14 (13.7) 6 (5.9) occupational status 0.2 government employee 111 (13.5) 71 (63.9) 24 (21.6) 12 (10.8) 4 (3.6) merchant 54 (6.6) 39 (72.2) 7 (12.9) 3 (5.6) 5 (9.3) farmer 362 (44.1) 252 (69.6) 77 (21.3) 30 (8.3) 3 (0.8) housewife 245 (29.8) 175 (71.4) 49 (20.0) 12 (4.9) 9 (3.7) others* 49 (6.0) 28 (57.1) 16 (32.7) 3 (6.1) 2 (4.1) monthly income (ethiopia birrs‘) 0.67 ≤1000 402 (49.0) 265 (65.9) 92 (22.9) 32 (8.0) 13 (3.2) 1001–15000 169 (20.6) 126 (74.6) 33 (19.5) 8 (4.7) 2 (1.2) 1501–2000 78 (9.5) 57 (73.1) 15 (19.2) 5 (6.4) 1 (1.3) ≥2001 172 (20.9) 117 (68.0) 33 (19.2) 15 (8.7) 7 (4.1) health insurance 0.04 yes 288 (35.1) 190 (66.0) 72 (25.0) 19 (6.6) 7 (2.4) no 533 (64.9) 375 (70.4) 101 (18.9) 41 (7.7) 16 (3.0) had escort 0.4 yes 680 (82.8) 459 (67.5) 147 (21.6) 55 (8.1) 19 (2.8) no 141 (17.2) 106 (75.2) 26 (18.4) 5 (3.6) 4 (2.8) 310 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 eye care among visually impaired; assaye et al table 1. (continued). variables time since the last eye examination p-value n no exam. ≤2 years (%) 3–5 years (%) >5 years (%) living arrangement 0.09 living alone 85 (10.4) 57 (67.1) 24 (28.2) 1 (1.2) 3 (3.5) with family members 736 (89.6) 508 (69.0) 149 (20.3) 59 (8.0) 20 (2.7) family size 0.04 ≤5 700 (85.3) 491 (70.1) 139 (19.9) 50 (7.1) 20 (2.9) >5 121 (14.7) 74 (61.1) 34 (28.1) 10 (8.3) 3 (2.5) n, sample size; yr, years; others* included daily worker, retired, monk and unemployed the vertical sums in the second column (labeled n) are calculated out of the total sample size (821); the percentages of n = 821 are reflected in the brackets, and the horizontal sums (had examinations [labeled time since last examinations] plus no examinations) equals 100 as the percentage stated in the brackets the p-value is an output value of the binary logistic regression model figure 1. self-reported barriers to utilize eye care services among visually impaired older population attending the ophthalmic outreach sites in the central gondar zone, northwest ethiopia (n = 565). more likely to have utilized an eye care service than those who did not have systemic disease (aor = 3.2, 95% ci: 1.5–7.0). as compared to participants who did not use spectacles, participants who used spectacles were 4.5 times more likely to have utilized an eye care service (aor = 4.5, 95% ci: 2.0–9.4). similarly, participants who had a history of ocular surgery were 9.3 times more likely to utilize an eye care service than their counterparts (aor = 9.3; 95% ci: 5.6–15.4). participants who had distance visual impairment (either bilateral or unilateral) were 2.9 times more likely to utilize an eye care service as compared to those who presented with near visual impairment (aor = 2.9; 95% ci: 1.5–5.6). in addition, the odds of utilization of an eye care service were 2.0 times more likely for those participants with severe visual impairment (aor = 2.0; 95% ci: 1.03–3.8) 2.9 times more likely for those with blindness (aor = 2.9; 95% ci: 1.5–5.6) than the participants with normal vision at distance. participants who had a duration of visual impairment ≤1 year and 1–4 years were 2.5 times (aor = 2.5; 95% ci: 1.3–4.9) and 2.7 times (aor = 2.7; 95% ci: 1.5–5.0), respectively more likely to utilize an eye care service than participants who had a duration of visual impairment >4 years [table 5]. discussion in this study, the proportion of the society using eye care services among the visually impaired older population was 21.1% (95% ci: 18.2–23.9). journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 311 eye care among visually impaired; assaye et al table 2. medical and ocular history of study participants attending ophthalmic outreach sites in the central gondar zone, northwest ethiopia, 2021 (number of participants = 821). variables time since the last eye examination p-value n no exam. ≤2 years (%) 3–5 years (%) >5 years (%) all 821 565 173 (21.1) 60 (7.3) 23 (2.8) known diabetes mellitus 0.88 yes 27 (3.3) 15 (55.6) 6 (22.2) 5 (18.5) 1 (3.7) no 794 (96.7) 550 (69.3) 167 (21.0) 55 (6.9) 22 (2.9) known hypertension 0.74 yes 47 (5.7) 28 (59.6) 9 (19.1) 7 (14.9) 3 (6.4) no 774 (94.3) 537 (69.4) 164 (21.2) 53 (6.8) 20 (2.6) known other systemic diseases* 0.04 yes 38 (4.6) 21 (55.3) 13 (34.2) 1 (2.6) 3 (7.9) no 783 (95.4) 544 (69.5) 160 (20.4) 59 (7.5) 20 (2.6) history of ocular trauma 0.57 yes 40 (4.9) 27 (67.5) 7 (17.5) 3 (7.5) 3 (7.5) no 781 (95.1) 538 (68.8) 166 (21.3) 57 (7.3) 20 (2.6) history of ocular surgery <0.0001 yes 110 (13.4) 5 (4.5) 66 (60.0) 28 (25.5) 11 (10.0) no 711 (86.6) 560 (78.8) 107 (15.0) 32 (4.5) 12 (1.7) use of spectacle 0.02 yes 49 (6.0) 16 (32.6) 17 (34.7) 11 (22.5) 5 (10.2) no 772 (94.0) 549 (71.1) 156 (20.2) 49 (6.4) 18 (2.3) use of ocular self-medication 0.22 yes 46 (5.4) 28 (60.9) 13 (28.3) 3 (6.5) 2 (4.3) no 775 (94.6) 537 (69.3) 160 (20.6) 57 (7.4) 21 (2.7) use of traditional medication 0.98 yes 24 (2.9) 16 (66.7) 5 (20.8) 0 (0.0) 3 (12.5) no 797 (97.1) 549 (68.9) 168 (21.1) 60 (7.5) 20 (2.5) note: other systemic diseases* include tuberculosis, human immunodeficiency virus, arteritis, asthma, malaria the vertical sums in the second column are calculated out of the total sample size (821), and the horizontal sums (had examinations plus no examinations) equals 100 no exam means that the participants didn’t have eye examinations the p-value is an output value of the binary logistic regression model this finding was lower than the findings from studies conducted in hawassa city, ethiopia,[6] edo state, nigeria,[14] south africa,[3] rural south india,[29] pakistan,[11] myanmar (asia),[30] iran,[31] peru,[28] oregon (usa),[32] rural alabama (usa),[12] and california (usa).[13] the discrepancy might be due to the variations of the sociodemographic characteristics of the study participants. for 312 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 eye care among visually impaired; assaye et al table 3. clinical characteristics of study participants who attended ophthalmic outreach sites in central gondar zone, northwest ethiopia (number of participants = 821). variables time since the last eye examination p-value n no exam. ≤2 years (%) 3–5 years (%) >5 years (%) all 821 565 173 (21.1) 60 (7.3) 23 (2.8) types of visual impairment (vi) <0.0001 distance vi 513 (62.5) 319 (62.2) 135 (26.3) 46 (9.0) 13 (2.5) near vi 308 (37.5) 244 (79.2) 38 (12.4) 16 (5.2) 10 (3.2) level of distance vi in the worse eye (n = 513) <0.0001 mild 60 (7.3) 40 (66.7) 15 (25.0) 5 (8.3) 0 (0.0) moderate 167 (20.3) 110 (65.8) 36 (21.6) 16 (9.6) 5 (3.0) severe 149 (18.1) 93 (62.4) 38 (25.5) 15 (10.1) 3 (2.0) blind 137 (16.7) 76 (55.5) 46 (33.6) 10 (7.3) 5 (3.6) cause of visual impairment in the worse eye (n = 513) 0.02 cataract 291 (35.4) 181 (61.9) 79 (27.1) 25 (8.6) 7 (2.4) refractive error 84 (10.2) 60 (71.4) 16 (19.1) 7 (8.3) 1 (1.2) corneal opacity 45 (5.5) 25 (55.6) 11 (24.4) 7 (15.6) 2 (4.4) glaucoma 64 (7.8) 44 (68.8) 15 (23.4) 4 (6.2) 1 (1.6) other* 29 (3.5) 10 (34.5) 14 (48.3) 3 (10.3) 2 (6.9) duration of visual impairment (yr) 0.02 ≤1 229 (27.9) 172 (75.1) 48 (21.0) 6 (2.6) 3 (1.3) 2–4 443 (54.0) 293 (66.1) 106 (23.9) 37 (8.4) 7 (1.6) >4 149 (18.1) 100 (67.1) 19 (12.8) 17 (11.4) 13 (8.7) aware about the cause of vi <0.0001 yes 223 (27.2) 35 (15.7) 132 (59.2) 42 (18.8) 14 (6.3) no 598 (72.8) 530 (88.6) 41 (6.9) 18 (3.0) 9 (1.5) aware about treatment of vi <0.0001 yes 219 (26.7) 33 (15.1) 131 (59.8) 41 (18.7) 14 (6.4) no 602 (73.3) 532 (88.4) 42 (6.9) 19 (3.2) 9 (1.5) note: other*: diabetic retinopathy, age-related macular degeneration, advanced pterigyum vi, visual impairment; yr, years the vertical sums in the second column are calculated out of the total sample size (821), and the horizontal sums (had examinations plus no examinations) equals 100 no exam, means that the participants didn’t have eye examinations the p-value is an output value of the binary logistic regression model instance, the number of participants with a higher education level involved in the current study was small, and they were less educated than those in studies conducted in hawassa, ethiopia, and nigeria. however, the level of education in this study did not show or did not have any significance with eye care service utilizations. in addition, participants of the study done in south africa, usa, peru, iran, and pakistan were older, had higher educational status, had health insurance and systemic diseases. those conditions like being older in age could increase age-related eye journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 313 eye care among visually impaired; assaye et al table 4. need of eye care service among study participants, northwest ethiopia (n = 821). sex level of vi need of eye care service near correction (%) cataract surgery (%) trichiasis surgery (%) refractive error correction (%) glaucoma follow-up (%) low vision rehabilitation (%) others (%) male near (n = 182) 180 (98.9) 0 (0.0) 2 (1.1) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) mild (n = 32) 0 (0.0) 12 (37.5) 1 (3.1) 7 (21.9) 3 (9.4) 1 (3.1) 8 (25.0) moderate (n = 101) 0 (0.0) 50 (49.5) 3 (3.0) 27 (26.7) 12 (11.9) 3 (3.0) 9 (8.9) severe (n = 88) 0 (0.0) 57 (64.7) 1 (1.1) 5 (5.7) 13 (14.8) 6 (6.8) 6 (6.8) blind (n = 83) 0 (0.0) 48 (57.8) 0 (0.0) 3 (3.6) 17 (20.5) 8 (9.6) 4 (4.8) total (n = 486) 180 (37.0) 167 (34.4) 7 (1.4) 42 (8.6) 45 (9.3) 18 (3.7) 27 (5.6) female near (n = 126) 123 (97.6) 0 (0.0) 3 (2.3) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) mild (n = 28) 0 (0.0) 12 (42.8) 1 (3.6) 15 (53.6) 0 (0.0) 0 (0.0) 1 (3.6) moderate (n = 66) 0 (0.0) 37 (56.1) 1 (1.5) 17 (25.8) 8 (12.1) 1 (1.5) 1 (1.5) severe (n = 61) 0 (0.0) 41 (67.2) 0 (0.0) 6 (9.8) 7 (11.5) 2 (3.3) 4 (6.6) blind (n = 54) 0 (0.0) 34 (63.0) 3 (5.6) 4 (7.4) 4 (7.4) 6 (11.1) 4 (7.4) total (n = 335) 123 (36.7) 124 (37.0) 8 (2.4) 42 (12.5) 19 (5.7) 9 (2.7) 10 (3.0) vi, visual impairment mild vi (pva <6/12 – ≤6/18), moderate vi (pva <6/18 – ≤6/60), severe vi (pva< 6/60 – ≤3/60), and blindness (pva < 3/60 – nlp) disease, and having higher education level could also create awareness about the importance of accessing eye care services. however, this measurement of the proportion of the society utilizing eye care services was higher than a study conducted in ghana.[33] the possible reason could be the study in ghana was conducted at a food market where participants came to sell or to buy commodities. the increased number of rural participants who came for trade were more likely to be healthy because of their origin so their focus was on trade and not on seeking eye care services. participants who had systemic diseases such as tuberculosis, hiv/aids, and arthritis were 3.2 times more likely to have utilized an eye care service than those who did not have any systemic disease. this finding was in line with the studies conducted in kenya,[34] pakistan,[11] peru,[28] and oregon, usa.[32] these statistics justified that systemic diseases can aggravate the complications of vision-related disorders which leads to the prompting of seeking eye examinations. furthermore, people with other diseases may have become more familiar with the healthcare system and are able to use the facilities more than those who have never visited a healthcare facility. in this study, participants who had distance visual impairment were 2.9 times more likely to have utilized an eye care service as compared to participants who presented with near visual impairment; this revelation was supported by a study done in oregon (usa).[32] distance vision is required for a great variety of daily tasks especially for farmers who do activities like ploughing, sowing, herding, and other work responsibilities. the majority of the participants in this study were farmers, whose activities were specifically at distance, as mentioned earlier. so, those individuals are much more affected by impairments related to distance vision than near vision. in the present study, the likelihood of using an eye care service among the blind and severely visually impaired participants was 2.9 and 2.0 times, respectively, as compared to participants with normal vision at distance. this result was in agreement with the results from studies done in ethiopia,[15] south india,[20] tehran,[18] and china.[10] this study revealed that participants who used spectacles were 4. 5 times more likely to use eye care services than non-spectacle users. similarly, participants who had a history of ocular surgery were 9.3 times more likely to have utilized an eye care service than their counterparts. the possible explanation for this association is that individuals who used spectacles and underwent ocular surgery may be required to visit an eye care 314 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 eye care among visually impaired; assaye et al table 5. factors associated with utilization of eye care services within the past two years among the visually impaired population attending ophthalmic outreach sites in the central gondar zone, northwest ethiopia (n = 821). variables utilization of eye care service cor (95%ci) aor (95%ci) p-value yes no age (yr) 0.67 40–49 33 221 1.00 1.00 50–59 36 149 1.6 (1.0–2.7) 1.3 (0.7–2.2) 60–69 39 123 2.1 (1.3–3.5) 1.0 (0.5–1.8) ≥70 65 155 2.8 (1.8–4.5) 0.9 (0.5–1.6) current marital status 0.09 single 42 114 1.5 (1.01–2.2) 1.4 (0.9–2.4) married 131 534 1.00 1.00 health insurance 0.14 yes 72 216 1.4 (1.01–2.0) 1.3 (0.9–2.0) no 101 432 1.00 1.00 number of family 0.25 ≤5 139 561 1.00 1.00 >5 34 87 1.6 (1.02–2.4) 1.4 (0.8–2.3) known other systemic diseases 0.003 yes 13 25 2.0 (1.01–4.0) 3.2 (1.5–7.0) no 160 623 1.00 1.00 use of spectacle <0.0001 yes 17 32 2.1 (1.1–3.9) 4.5 (2.0–9.4) no 156 616 1.00 1.00 history of ocular surgery <0.001 yes 66 44 8.5 (5.5–13.1) 9.3 (5.6–15.4) no 107 604 1.00 1.00 types of visual impairment 0.002 distance vi 135 378 2.5 (1.7–3.8) 2.9 (1.5–5.6) near vi 38 270 1.00 1.00 level of visual impairment 0.03 normal vision 38 270 1.00 1.00 mild vi 15 45 2.4 (1.2–4.7) 2.1 (0.9–4.6) moderate vi 36 131 2.0 (1.2–3.2) 1.4 (0.8–2.7) severe vi 38 111 2.4 (1.5–4.0) 2.0 (1.03–3.8) blind 46 91 3.6 (2.2–5.9) 2.9 (1.5–5.6) duration of visual impairment (yr) 0.004 ≤1 48 181 1.8 (1.02–3.2) 2.5 (1.3–4.9) 1–4 106 337 2.2 (1.3–3.7) 2.7 (1.5–5.0) >4 19 130 1.00 1.00 the p-value is an output value of the binary logistic regression model vi, visual impairment; yr, years journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 315 eye care among visually impaired; assaye et al center on a more regular basis for prognosis and checkups than those who did not use spectacles or did not experience ocular surgery. in the present study, the duration of visual impairment was one of the significant factors associated with the utilization of an eye care service in which participants who had a duration of visual impairment of ≥4 years were 2.7 times more likely to have utilized an eye care service than those who had a duration of visual impairment of <4 years. the possible justification is that immediate onset of visual impairment can affect the performance of daily activities and cause stress wondering whether the vision would be recovered or not. these conditions would lead to a visit to an eye care service provider center. on the other hand, an individual who lived with visual impairment for a long duration will lose their hopes for visual recovery which reduces the desire for utilization of eye care services. in this study, the major barriers to utilizing eye care services reported by the participants included the following factors: lack of money and the distance of the eye care facility from the points of origin. this finding was in line with the studies done in the gurage zone, ethiopia,[15] edo state, nigeria,[14] india,[5, 29] china,[10] and florida, usa.[12] this finding justifies that poverty and inaccessibility of eye care services have their own effects on the utilization of eye care services. in order to encourage the utilization of eye care services, adequate provision of free eye care services at community level through the outreach program is required. in conclusion, in this study, the utilization of eye care services among the visually impaired population was low. history of ocular surgery, use of spectacles, level of visual impairment at distance, duration of visual impairment, and having systemic disease were significantly associated with the utilization of eye care services. the major barriers to utilizing eye care services reported by the participants were lack of money and the distance of the eye care facility. we recommend that eye health stakeholder organizations develop strategies for improving community utilization of the eye care services through eye health education and the provision of free eye care services to low-income populations. ethical considerations this study was conducted with respect to the principle of the declaration of helsinki. ethical approval was obtained from the university of gondar, college of medicine and health sciences, school of medicine, ethical review committee. after detailed explanation of the purpose of the study, written informed consent was obtained from all the participants. participants were informed about their right to withdraw from the study at any time during the interview and examination. the selected study participants were not receiving any incentive because of their participation in the study. the study participants’ confidentiality was maintained by removing personal identifiers from the data collection tools and locking the data with a password. acknowledgements the authors would like to thank the department of optometry, ophthalmology and the light for the world organization for preparing the community service that enabled them to do this research. financial support and sponsorship none. conflicts of interest none. references 1. bourne r, steinmetz jd, flaxman s, briant ps, taylor hr, resnikoff s, et al. trends in prevalence of blindness and distance and near vision impairment over 30 years: an analysis for the global burden of disease study. lancet glob health 2021;9:e130–e143. 2. who. who launches first world report on vision. 2019. 3. mashige k, martin c. utilization of eye care services by elderly persons in the northern ethekwini district of kwazulu-natal province, south africa. afr vision eye health 2011;70:175–181. 4. kumari r, singh kp, dubey g, awasthi aa, srivastava mr, garg p, et al. chronic impediment in utilization of eye-care services. j ophthalmol res 2020;3:45–56. 5. robin al, nirmalan pk, krishnadas r, ramakrishnan r, katz j, tielsch j, et al. the utilization of eye care services by persons with glaucoma in rural south india. trans am ophthalmol soc 2004;102:47–54. 316 journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 eye care among visually impaired; assaye et al 6. morka ed, yibekal bt, tegegne mm. eye care service utilization and associated factors among older adults in hawassa city, south ethiopia. plos one 2020;15:e0231616. 7. kimani k, karimurio j, gichuhi s, sheila m, nyaga g, wachira j, et al. barriers to utilization of eye care services in kibera and dagoreti divisions of nairobi. kenya; 2008. 8. adimassu nf, asefa nl, anibesei dh, belete g. poor eye care service utilization among adults in gondar city, northwest ethiopia. ec ophthal 2018;9:647–657. 9. arinze oc, eze bi, ude nn, onwubiko sn, ezisi cn, chuka-okosa cm. determinants of eye care utilization in rural south-eastern nigeria. j community health 2015;40:881–890. 10. li ls, ge zy, lohfeld l, zhou k, zhou wh, cui ll, et al. knowledge, attitudes and practices related to seeking medical eyecare services by adults with moderate-tosevere visual impairment in rural yueqing, wenzhou, china: a cross-sectional survey. int j ophthalmol 2020;13:1115–1123. 11. ahmad k, zwi ab, tarantola dj, azam si. eye care service use and its determinants in marginalized communities in pakistan: the karachi marine fishing communities eye and general health survey. ophthalmic epidemiol 2015;22:370–379. 12. elliott af, heskett m, spiker c, mcgwin g jr, owsley c. low rates of eye care utilization among visually impaired subsidized senior housing residents. aging ment health 2021;25:360–366. 13. morales ls, varma r, paz sh, lai my, mazhar k, andersen rm, et al. self-reported use of eye care among latinos: the los angeles latino eye study. ophthalmology 2010;117:207–215.e1. 14. ja e, go oo. barriers to utilization of eye care services in rural communities in edo state, nigeria. borno med j 2014;11:98–104. 15. melese m, alemayehu w, friedlander e, courtright p. indirect costs associated with accessing eye care services as a barrier to service use in ethiopia. trop med int health 2004;9:426–431. 16. vela c, samson e, zunzunegui mv, haddad s, aubin mj, freeman ee. eye care utilization by older adults in low, middle, and high income countries. bmc ophthalmol. 2012 apr;12:5. 17. aljied r, aubin mj, buhrmann r, sabeti s, freeman ee. eye care utilization and its determinants in canada. can j ophthalmol 2018;53:298–304. 18. fotouhi a, hashemi h, mohammad k. eye care utilization patterns in tehran population: a population based crosssectional study. bmc ophthalmol 2006;6:4. 19. chou cf, sherrod ce, zhang x, barker le, bullard km, crews je, et al. barriers to eye care among people aged 40 years and older with diagnosed diabetes, 2006–2010. diabetes care 2014;37:180–188. 20. kovai v, krishnaiah s, shamanna br, thomas r, rao gn. barriers to accessing eye care services among visually impaired populations in rural andhra pradesh, south india. indian j ophthalmol 2007;55:365–371. 21. ntsoane m, oduntan o. a review of factors influencing the utilization of eye care services. afr vision eye health 2010;69:182–192. 22. owsley c, mcgwin g, scilley k, girkin ca, phillips jm, searcey k. perceived barriers to care and attitudes about vision and eye care: focus groups with older african americans and eye care providers. invest ophthalmol vis sci 2006;47:2797–2802. 23. thompson ac, thompson m, sanislo sr, lin rc, sanislo sr, moshfeghi dm, et al. barriers to eye care service utilization and potential strategies to improve follow-up in patients with glaucoma, amd, and diabetic retinopathy. invest ophthalmol vis sci 2012;53:1432. 24. assefa nl, admas aw, adimasu nf. prevalence and associated factors of visual impairment among adults at debre berhan town, north shewa, ethiopia. bmc ophthalmol 2020;20:316. 25. cheng f, shan l, song w, fan p, yuan h. distanceand near-visual impairment in rural chinese adults in kailu, inner mongolia. acta ophthalmol 2016;94:407–413. 26. marmamula s, keeffe j, challa r, mohd j, khanna rc. near-vision impairment and effective near-vision spectacle coverage in two districts in telangana, india: a population-based cross-sectional study. bmj open 2021;11:e047131. 27. thapa ss, berg rv, khanal s, paudyal i, pandey p, maharjan n, et al. prevalence of visual impairment, cataract surgery and awareness of cataract and glaucoma in bhaktapur district of nepal: the bhaktapur glaucoma study. bmc ophthalmol 2011;11:2. 28. marmamula s, giridhar p, khanna rc. utilization of eye care services among those with unilateral visual impairment in rural south india: andhra pradesh eye disease study (apeds). int j ophthalmol 2017;10:473– 479. 29. kyaw k, nanthamonkolchai s, munsawaengsub c. eye care seeking behavior on prevention of blindness among elderly in urban area of magway township, myanmar [ijoes]. int j ophthalmol eye sci 2018;6:351–357. 30. katibeh m, sabbaghi h, kalantarion m, nikkhah h, mousavi b, beiranvand r, et al. eye care utilization in a community-oriented mobile screening programme for improving eye health in iran: a cluster randomized trial. ophthalmic epidemiol 2020;27:417–428. 31. barrenechea-pulache a, portocarrero-bonifaz a, hernández-vásquez a, portocarrero-ramos c, moscosocarrasco j. determinants of eye care service utilization among peruvian adults: evidence from a nationwide household survey. ophthalmic epidemiol 2021:1–10. 32. chheda k, wu r, zaback t, brinks mv. barriers to eye care among participants of a mobile eye clinic. cogent med 2019;6:1650693. 33. ilechie aa, otchere h, darko-takyi c, halladay ac. access to and utilization of eye care services in ghana. int j health res 2013;6 :7–14. 34. rono mmed hk, macleod d, bastawrous a, wanjala e, gichangi m, burton mj. utilization of secondary eye care services in western kenya. int j environ res public health 2019;16:3371. journal of ophthalmic and vision research volume 18, issue 3, july-sept 2023 317 original article clinical and multimodal imaging features of subretinal drusenoid deposits devesh kumawat md, dnb; srikanta k. padhy, md; vinod kumar, ms, dnb, frcs (glasg) dr rajendra prasad centre for ophthalmic sciences, all india institute of medical sciences, new delhi, india orcid: devesh kumawat: https://orcid.org/0000-0003-0204-7024 vinod kumar: https://orcid.org/0000-0002-3948-700x abstract purpose: to describe the multimodal imaging (mmi) features of subretinal drusenoid deposits (sdd) in indian population. methods: patients diagnosed to have sdd from january 2016 to december 2018 at our tertiary care center were recruited. the diagnosis of sdd was made on the basis of mmi consisting of a combination of color fundus photography (cfp), optical coherence tomography (oct), red-free (rf) imaging, blue autofluorescence (baf), and near-infra red reflectance (nir) imaging. the morphological type and distribution of sdd and the associated retinal lesions were reviewed. results: twenty-three patients with sdd were included. the mean age of the patients was 68.1 ± 12.2 years. sdd were noted in 77.8% of eyes clinically (n = 35/45) and could be detected in 100% of these eyes with oct. the morphology of sdd was nodular in 65.7% of eyes (n = 23/35), reticular in 5.7% (n = 2/35), and mixed pattern in the remaining cases. baf and nir showed hyporeflective nodular lesions often with a target configuration. the location was commonly in the perifoveal area, mostly involving the superotemporal quadrant (74.3%, n = 26/35). associated retinal lesions were type-3 neovascularization or retinal angiomatous proliferation in 17.1% (n = 6/35), disciform scar in 11.4% (n = 4/35), type-1 neovascularization in 8.5% (n = 3/35), and geographic atrophy in 5.7% (n = 2/35) of eyes. the mean subfoveal choroidal thickness was 186.2 ± 57.8 µm. conclusion: sdd commonly have a nodular morphology and their identification often requires confirmations with oct. advanced age-related macular degeneration features are frequently present in eyes with sdd and the fellow eyes. keywords: subretinal drusenoid deposits; pseudodrusen; multimodal imaging; optical coherence tomography; age-related macular degeneration j ophthalmic vis res 2021; 16 (2): 187–194 introduction drusen associated with pigmentary changes are risk factors for late age-related macular correspondence to: vinod kumar, md, dnb rpc, aiims. dr rajendra prasad centre for ophthalmic sciences, all india institute of medical sciences, ansari nagar, new delhi, india. e-mail: drvinod_agg@yahoo.com received: 08-03-2020 accepted: 16-01-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9082 degeneration (amd) and related ocular morbidity.[1–3] characteristically, drusen are extracellular deposits between the basal lamina of retinal pigment epithelium (rpe) and the inner collagenous layer of the bruch’s membrane. subretinal drusenoid deposits (sdd) also known this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: kumawat d, padhy sk, kumar v. clinical and multimodal imaging features of subretinal drusenoid deposits. j ophthalmic vis res 2021;16:187–194. © 2021 kumawat et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 187 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9082&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr subretinal drusenoid deposits; kumawat et al as reticular pseudodrusen (rpd) are a distinct entity.[4–6] these deposits occur in the subretinal space above the rpe and are seen predominantly in the perifoveal area. these may also be seen in the mid-periphery of the retina. initial description of sdds was using blue filters in fundus imaging; however, it was difficult to distinguish them clinically. with the arrival of modern high-resolution optical coherence tomography (oct), these can be picked up with high sensitivity and specificity.[7, 8] additional imaging investigations such as near infra-red reflectance (nir) imaging, red-free fundus (rf) imaging, and short-wave or blue autofluorescence (baf) may help increase the detection rates.[7] sdd have been found to be independent risk factors for late amd.[9, 10] a strong association has been noted between these and type-3 intraretinal neovascularization,[11, 12] outer retinal atrophy,[13, 14] and combined outer retinal and rpe atrophy or geographic atrophy.[9, 10, 15] although sdd have been studied in detail in the past few years, there are no studies describing sdd in the indian population. this study aims to describe the demography, clinical characteristics, and multimodal imaging (mmi) features of sdd in the indian population. methods this retrospective observational study was performed at a tertiary eye care center in north india. the study adheres to the tenets of the declarations of helsinki and to the institutional guidelines for research. informed consent was obtained from all the patients. the participants were the cases of sdd diagnosed at our center over a period of three years (2016 to 2018). the clinical database from the retina lab was reviewed to identify the patients. the diagnosis of sdd was made on the basis of mmi consisting of a combination of either color fundus photography (cfp), rf imaging, baf, nir imaging, and oct. the sdd appear as yellowishwhite deposits on cfp, present more superficial than the conventional drusen. the size is similar to that of the hard drusen. these are of three clinical types: nodular or dot type with dot-like uniformly arranged lesions [figure 1], reticular type with broad ribbon-like interlacing deposits [figure 2], and mixed type with a combination of these two [figure 3]. on oct, these deposits appear as hyperreflective conical or smooth mounds [figures 2 and 3], present in the subretinal space, and may erode into the ellipsoid zone as their stage progresses. later, these may undergo resolution with loss of the outer retinal bands and rpebruch’s complex. rf or blue-channel imaging highlights these lesions better as compared to cfp [figures 1 and 2]. on baf, these lesions are often hypoautofluorescent with a hyperautofluorescent core sometimes seen in nodular types with increasing stage. nir is also useful in picking up the nodular type of lesions and these appear as hyporeflective dots as well [figure 4]. they may often have a “target” configuration with a central hyper reflective core and surrounding hyporeflective annulus. the mmi imaging was performed using a swept-source platform (dri triton, topcon inc., oakland, new jersey, usa). in a subset of patients, the confocal scanning laser ophthalmoscope-based imaging system was used (spectralis hra, heidelberg, germany). fundus fluorescein angiography (ffa) and indocyanine green angiography (icga) were performed in a subset of patients to identify/document the coexisting intraretinal/subretinal/subrpe neovascular complex. the details such as demography, visual acuity, clinical fundus features, and mmi characteristics were noted for each case. the key parameters noted were the morphological type and distribution of sdd, and the associated retinal lesions. data were recorded on an excel spreadsheet and analyzed with stat 12.1 software. the parametric variables were represented with mean and sd, while the nonparametric variables were represented with median and range. the visual acuity was converted into the logmar scale with counting fingers (cf) vision at 1 feet distance corresponding to 2.3 units. results twenty-three patients with sdd were included. one eye of a patient had phthisis bulbi, therefore, a total of 45 eyes were finally studied. the mean age of the patients was 68.1 ± 12.2 years. of the 23 patients, 19 (78.3%) were >65 years old. the majority of patients were females (n = 16/23, 69.6%) with a male-to-female ratio of 0.43:1. 188 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 subretinal drusenoid deposits; kumawat et al figure 1. multimodal imaging of a case of sdd. (a) fundus photograph shows multiple dot-like regularly arranged array of whitish deposits predominantly in the perifoveal area. (b) the lesions are better delineated on blue channel or red-free photograph. (c) fundus photograph after a year shows presence of intraretinal hemorrhage and neovascular membrane suggesting the development of retinal angiomatous proliferation. the number of sdd has decreased. (d) the red-free photograph reveals only a few sdd in the nasal macula, suggesting the regression of sdd. sdd were clinically noted in 35 (77.8%) eyes. the sdd could be detected in all these eyes with oct. bilateral involvement was seen in 52.2% of the cases (n = 12/23). morphology of sdd was nodular in 23 eyes (65.7%), reticular in 2 eyes (5.7%), and mixed pattern in the remaining 10 eyes (28.6%). the spatial location was commonly in the perifoveal area, mostly involving the superotemporal quadrant (74.3%, n = 26/35) [table 1] followed by annular distribution (22.5%, n = 8/35). on studying the spatial location separately for different morphological types of sdd (see table 1), the superotemporal quadrant was involved in 19 of 23 eyes (82.6%) and 6 of 10 eyes (60%) with nodular and mixed types, respectively. the average logmar cdva in eyes with sdd was 0.53 ± 0.65 (median 0.3, range 0 to 2.3). cdva ≥ 20/40 was seen in 20 of 35 eyes (57.1%). soft drusen [figure 5] were present concurrently in 68.6% of eyes with sdd (n = 24/35), out of which three eyes had drusenoid ped as well. associated retinal lesions in eyes with sdd were as follows (see table 2): type-3 nv or retinal angiomatous proliferation (rap) [figure 1] in 17.1% (n = 6/35), disciform scar in 11.4% (n = 4/35), type-1 or sub-rpe cnv in 8.5% (n = 3/35), and geographic atrophy (ga) in 5.7% (n = 2/35) of the eyes. the mean subfoveal choroidal thickness (sfct) was 186.2 ± 57.8 µm [figure 6]. the sfct was <125 µm (cut-off for age-related choroidal atrophy) in 17.1% (n = 6/35) and >250 µm in 14.3% of eyes (n = 5/35). the fellow eyes without sdd (n = 10) had average logmar cdva of 1.8 ± 0.76 (median 2.3, range 0.6 to 2.3). soft drusen were noted in 20% of these eyes (n = 2/10). disciform scar, rap, and type-2 or subretinal cnv were noted in 70% (7/10), 20% (2/10), and 10% (1/10) of the fellow eyes without sdd, respectively. the mean sfct was 178.1 ± 50.4 µm in these eyes (obtained for nine eyes). discussion recognition of sdd/rpd in amd patients is important because it independently confers journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 189 subretinal drusenoid deposits; kumawat et al figure 2. multimodal imaging of a case of amd. (a) fundus photograph shows multiple soft drusen at the fovea with pigmentary changes suggestive of non-exudative amd. numerous confluent ribbon-like interlacing reticular drusen are seen predominantly in the perifoveal area in superotemporal quadrant (white arrows). (b) the reticular lesions (white arrows) are better delineated on redfree imaging. (c) the swept-source oct through the top white arrow in subfigure “a” shows broad mound-shaped deposits in the subretinal space (white arrows) deflecting the ellipsoid zone inward suggestive of reticular drusen. the black arrows point to the sub-rpe deposits suggestive of soft drusen. the subfoveal choroid seems markedly thin with obliteration of the choriocapillaris layer. figure 3. a case of mixed sdd. fundus photograph shows dot-like sdd (white arrowheads) near the fovea and reticular lesions (white arrows) in the temporal perifoveal and peri-papillary area. (b) ss-oct image through the white right arrow in subfigure “a” shows sharp peaked (white arrowheads) and broad mound-shaped deposits (white arrows) in the subretinal space suggestive of dot and reticular drusen, respectively. increased risk (above the usual risk associated with large soft drusen and pigmentary changes) of developing the late stage of amd.[9, 10] in this study, sdd were associated with late amd in 42.8% (15/35) of eyes. the risk of late amd also increases in the fellow eyes if sdd are present.[16] the rf or blue channel of cfp shows high specificity for sdd.[7] the rpe normally filters off the blue light and therefore the soft drusen, which are present external to rpe, appear yellow. sdd lie internal to rpe and are easily visualized in blue light. both the nodular and reticular types 190 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 subretinal drusenoid deposits; kumawat et al figure 4. near infra-red reflectance imaging of sdd. (a) numerous clearly visible perifoveal sdd appearing as hyporeflective dots. (b) numerous dot-like sdds with a “target” configuration. the central core appears hyperreflective with a hyporeflective annulus. figure 5. multimodal imaging of a case of amd. (a) fundus photograph shows multiple soft drusen at the fovea (white arrowheads). numerous dot-like sdd are seen predominantly in the perifoveal area (black arrowheads). (b) the sdd are better delineated than soft drusen on red-free imaging. (c) sd-oct image through the white arrow in subfigure “a” shows sharp peaked subretinal dot-like sdd (black arrowheads) disrupting the ellipsoid zone and smooth mounds sub-rpe suggestive of soft drusen (white arrowheads). journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 191 subretinal drusenoid deposits; kumawat et al figure 6. swept source-based choroidal imaging in eyes with sdd (a–d). while “a” and “d” show near-normal choroidal morphology, the choroid is severely thinned out in “b” and “c”. the subfoveal choroidal thickness was 166, 74, 115, and 244 in “a”, “b”, “c”, and “d”, respectively. table 1. spatial distribution of subretinal drusenoid deposits or pseudodrusen location of sdd∗ number of eyes (%) total (n = 35) nodular type (n = 23) reticular type (n = 2) mixed type (n = 10) superotemporal quadrant 26 (74.3) 19 (82.6) 1 (50) 6 (60) inferotemporal quadrant 7 (20) 5 (21.7) 0 2 (20) superonasal quadrant 6 (17.1) 5 (21.7) 1 (50) 0 inferonasal quadrant 2 (5.7) 2 (8.7) 0 0 annular 8 (22.8) 3 (13) 1 (50) 4 (40) ∗sdd, subretinal drusenoid deposits table 2. retinal features in eyes with subretinal drusenoid deposits parameters number of eyes (%) sdd∗ eyes fellow eyes (n = 10) total (n = 35) nodular type (n = 23) reticular type (n = 2) mixed type (n = 10) soft drusen 24 (68.6) 16 (69.6) 1 (50) 7 (70) 2 (20) drusenoid ped† 3 (8.6) 1 (4.3) – 2 (20) – type 1 nv‡ 3 (8.6) 1 (4.3) – 2 (20) – type 2 nv – – – – 1 (10) type 3 nv or rapx 6 ((17.1) 3 (13) 1 (50) 2 (20) 2 (20) geographic atrophy 2 (5.7) 2 (8.7) – – – disciform scar 4 (11.4) 4 (17.4) – – 7 (70) ∗sdd, subretinal drusenoid deposits; †ped, pigment epithelium detachment; ‡nv, neovascularisation; xrap, retinal angiomatous proliferation 192 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 subretinal drusenoid deposits; kumawat et al were visible better in blue channel cfp in the current study. the overlying sdd scatters the excitation light reaching the rpe and therefore sdd appear hypoautofluorescent on autofluorescence imaging.[7] the patients in our study were mostly elderly (65+ years) females. likewise, the populationbased studies have also shown that sdd/pd are associated with increasing age and female gender, the odds ratio reported by the rotterdam study being 1.2 and 2.1, respectively[17] and that reported by blue mountains eye study being 3.4 and 2.0, respectively.[18] in correlation with the existing literature,[19] the nodular or dot type was the most common type in our patients. the reticular or ribbon type uncommonly occurs in isolation and only two eyes in our series had this morphological type. the majority of the sdd were located in superotemporal quadrant in our study. sdd start developing in the superior quadrants and later spread to the inferior hemi-retina.[4] previous studies have also shown that sdd occur preferentially in the perifoveal area corresponding to an annular area with high rod photoreceptor density.[20] the impaired dark adaptation in eyes with sdd supports the hypothesis of origin of sdd from degenerating rod cells.[21] choroid is often severely thinned in eyes with sdd.[8, 22, 23] in a series of 58 eyes with sdd, zweifel et al reported severe choroidal thinning or choroidal atrophy (<125 µm) in 32 (55.2%) eyes.[8] although our study supports the observation of choroidal thinning in sdd, choroidal atrophy was noted in only 17.1% of eyes. binarization studies have shown decreased choroidal vascularity in eyes with sdd.[24, 25] since a few eyes with sdd also have normal or increased choroidal thickness (five eyes in this study), it is possible that the sdd are not directly responsible for the choroidal thinning. instead, rpe dysfunction may be responsible for both sdd formation and choroidal atrophy.[4] sdd are dynamic structures. with increasing stage, they reabsorb and fade out.[8, 14] the fellow eyes of 10 patients in our series did not have sdd but had advanced amd characteristics like disciform scar and rap lesions. perhaps, the sdd had regressed and were therefore not picked up in these eyes. many studies have shown that late amd commonly occurs in eyes with sdd.[9, 10, 13–15, 26] in a large series of 155 eyes with sdd, cohen et al reported features of amd including soft drusen in 65% (n = 101), cnv (active/ scarred) in 39.3% (n = 61), and ga in 17.4% (n = 27).[26] in our series also, the rates of soft drusen, cnv, and ga (68.6%, 37.1%, and 5.7%, respectively) were similar to those reported by cohen et al.[26] not only eyes with sdd had associated amd, the fellow eyes also had choroidal atrophy and cnv in our series. in addition to the macular neovascular disease and ga, spaide et al have also described outer retinal atrophy as a consequence of sdd.[13] there are few limitations of the present study including its retrospective nature. as sdd can be missed on routine examination, the rate of clinical sdd may be higher if specifically searched for. the sample size is relatively small and the study is based on a tertiary eye center, which could have led to selection bias. the prevalence and morphological type of sdd in amd cases was not noted, which might improve the understanding behind the association between sdd and amd. to conclude, the patients with sdd in indian settings are usually elderly females, with nodular type being the most common and mostly present in the perifoveal superior quadrants of the fundus. their identification often requires oct in addition to the cfp. these are frequently associated with advanced amd features in the same eye as well as in the fellow eye. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. bird ac, bressler nm, bressler sb, chisholm ih, coscas g, davis md, et al. an international classification and grading system for age-related maculopathy and age-related macular degeneration. the international arm epidemiological study group. surv ophthalmol 1995;39:367–374. 2. bressler sb, maguire mg, bressler nm, fine sl. relationship of drusen and abnormalities of the retinal pigment epithelium to the prognosis of neovascular macular degeneration. the macular photocoagulation study group. arch ophthalmol 1990;108:1442–1447. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 193 subretinal drusenoid deposits; kumawat et al 3. klein ml, ferris fl, armstrong j, hwang ts, chew ey, bressler sb, et al. retinal precursors and the development of geographic atrophy in age-related macular degeneration. ophthalmology 2008;115:1026– 1031. 4. spaide rf, ooto s, curcio ca. subretinal drusenoid deposits aka pseudodrusen. surv ophthalmol 2018;63:782–815. 5. sivaprasad s, bird a, nitiahpapand r, nicholson l, hykin p, chatziralli i, et al. perspectives on reticular pseudodrusen in age-related macular degeneration. surv ophthalmol 2016;61:521–537. 6. rabiolo a, sacconi r, cicinelli mv, et al. spotlight on reticular pseudodrusen. clin ophthalmol auckl nz 2017;11:1707–1718. 7. ueda-arakawa n, ooto s, tsujikawa a, querques l, bandello f, querques g. sensitivity and specificity of detecting reticular pseudodrusen in multimodal imaging in japanese patients. retina 2013;33:490–497. 8. zweifel sa, spaide rf, curcio ca, malek g, imamura y. reticular pseudodrusen are subretinal drusenoid deposits. ophthalmology 2010;117:303–312.e1. 9. schmitz-valckenberg s, alten f, steinberg js, et al. reticular drusen associated with geographic atrophy in age-related macular degeneration. invest ophthalmol vis sci 2011;52:5009–5015. 10. finger rp, wu z, luu cd, jaffe gj, fleckenstein m, mukesh bn, et al. reticular pseudodrusen: a risk factor for geographic atrophy in fellow eyes of individuals with unilateral choroidal neovascularization. ophthalmology 2014;121:1252–1256. 11. sawa m, ueno c, gomi f, nishida k. incidence and characteristics of neovascularization in fellow eyes of japanese patients with unilateral retinal angiomatous proliferation. retina 2014;34:761–767. 12. chang ys, kim jh, yoo sj, lew yj, kim j. felloweye neovascularization in unilateral retinal angiomatous proliferation in a korean population. acta ophthalmol 2016;94:e49–e53. 13. spaide rf. outer retinal atrophy after regression of subretinal drusenoid deposits as a newly recognized form of late age-related macular degeneration. retina 2013;33:1800–1808. 14. querques g, canouï-poitrine f, coscas f, massamba n, querques l, mimoun g, et al. analysis of progression of reticular pseudodrusen by spectral domain-optical coherence tomography. invest ophthalmol vis sci 2012;53:1264–1270. 15. xu l, blonska am, pumariega nm, ohrab ma, hageman gs, smith rt. reticular macular disease is associated with multilobular geographic atrophy in age-related macular degeneration. retina 2013;33:1850–1862. 16. marsiglia m, boddu s, chen cy, jung jj, mrejen s, gallego-pinazo r, et al. correlation between neovascular lesion type and clinical characteristics of nonneovascular fellow eyes in patients with unilateral, neovascular agerelated macular degeneration. retina 2015;35:966–974. 17. buitendijk ghs, hooghart aj, brussee c, de jong pt, hofman a, vingerling jr, et al. epidemiology of reticular pseudodrusen in age-related macular degeneration: the rotterdam study. invest ophthalmol vis sci 2016;57:5593–5601. 18. joachim n, mitchell p, rochtchina e, tan ag, wang jj. incidence and progression of reticular drusen in agerelated macular degeneration: findings from an older australian cohort. ophthalmology 2014;121:917–925. 19. suzuki m, sato t, spaide rf. pseudodrusen subtypes as delineated by multimodal imaging of the fundus. am j ophthalmol 2014;157:1005–1012. 20. curcio ca, sloan kr, kalina re, hendrickson ae. human photoreceptor topography. j comp neurol 1990;292:497– 523. 21. ooto s, ellabban aa, ueda-arakawa n, oishi a, tamura h, yamashiro k, et al. reduction of retinal sensitivity in eyes with reticular pseudodrusen. am j ophthalmol 2013;156:1184–1191.e2. 22. querques g, querques l, forte r, massamba n, coscas f, souied eh. choroidal changes associated with reticular pseudodrusen. invest ophthalmol vis sci 2012;53:1258– 1263. 23. garg a, oll m, yzer s, chang s, barile gr, merriam jc, et al. reticular pseudodrusen in early age-related macular degeneration are associated with choroidal thinning. invest ophthalmol vis sci 2013;54:7075–7081. 24. ueda-arakawa n, ooto s, ellabban aa, takahashi a, oishi a, tamura h, et al. macular choroidal thickness and volume of eyes with reticular pseudodrusen using sweptsource optical coherence tomography. am j ophthalmol 2014;157:994–1004. 25. corvi f, souied eh, capuano v, costanzo e, benatti l, querques l. choroidal structure in eyes with drusen and reticular pseudodrusen determined by binarisation of optical coherence tomographic images. br j ophthalmol 2017;101:348–352. 26. cohen sy, dubois l, tadayoni r, delahaye-mazza c, debibie c, quentel g. prevalence of reticular pseudodrusen in age-related macular degeneration with newly diagnosed choroidal neovascularisation. br j ophthalmol 2007;91:354–359. 194 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 review article ocular manifestations of covid-19: a systematic review and meta-analysis naser nasiri1, ms; hamid sharifi1, phd; azam bazrafshan2, ms; atefeh noori3, ms mohammad karamouzian1,4, ms; ali sharifi5, md 1hiv/sti surveillance research center, and who collaborating center for hiv surveillance, institute for futures studies in health, kerman university of medical sciences, kerman, iran 2neuroscience research center, institute of neuropharmacology, kerman university of medical sciences, kerman, iran 3department of health research methods, evidence, and impact, mcmaster university, hamilton, on, canada 4school of population and public health, faculty of medicine, university of british columbia, vancouver, bc, canada 5department of ophthalmology, shafa hospital, afzalipour school of medicine, kerman university of medical sciences, kerman, iran orcid: naser nasiri: https://orcid.org/0000-0002-1505-0866 ali sharifi: https://orcid.org/0000-0003-0713-088x abstract several studies have reported the characteristics of coronavirus disease 2019 (covid-19), yet there is a gap in our understanding of the ocular manifestations of covid-19. in this systematic review and meta-analysis, we investigated the prevalence of ocular manifestations in covid-19 patients. we searched pubmed, embase, scopus, web of science, and medrxiv from december 1, 2019 to august 11, 2020. two independent reviewers screened the articles, abstracted the data, and assessed the quality of included studies in duplicate. thirty-eight studies were eligible after screening of 895 unique articles, with a total of 8,219 covid-19 patients (55.3% female; n = 3,486 out of 6,308 patients). using data extracted from cross-sectional studies, we performed randomeffects meta-analyses to estimate the pooled prevalence of ocular symptoms along with 95% confidence interval (ci). the prevalence of ocular manifestations was estimated to be 11.03% (95% ci: 5.71–17.72). in the studies that reported the details of observed ocular symptoms, the most common ocular manifestations were dry eye or foreign body sensation (n = 138, 16%), redness (n = 114, 13.3%), tearing (n = 111, 12.8%), itching (n = 109, 12.6%), eye pain (n = 83, 9.6%) and discharge (n = 76, 8.8%). moreover, conjunctivitis had the highest rate among reported ocular diseases in covid-19 patients (79 out of 89, 88.8%). the results suggest that approximately one out of ten covid-19 patients show at least one ocular symptom. attention to ocular manifestations, especially conjunctivitis, can increase the sensitivity of covid-19 detection among patients. keywords: conjunctivitis; covid-19; meta-analysis; ocular manifestations; systematic review j ophthalmic vis res 2021; 16 (1): 103–112 correspondence to: ali sharifi, md. department of ophthalmology, shafa hospital, afzalipour school of medicine, kerman university of medical sciences, kerman, iran. e-mail: a_sharifi@kmu.ac.ir; sharifialim2@gmail.com received: 01-10-2020 accepted: 28-12-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8256 introduction severe acute respiratory syndrome coronavirus 2 (sars-cov-2) was initially detected in late this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: nasiri n, sharifi h, bazrafshan a, noori a, karamouzian m, sharifi a. ocular manifestations of covid-19: a systematic review and meta-analysis. j ophthalmic vis res 2021;16:103–112. © 2021 nasiri et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 103 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8256&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr ocular manifestations of covid-19; nasiri et al 2019 in wuhan, china,[1] and coronavirus disease 2019 (covid-19) swiftly spread across the globe, and was declared a pandemic on march 11, 2020.[2] by august 14, 2020, 21,092,096 people were infected with sars-cov-2, 757,727 of whom passed away due to covid-19 or its adverse health consequences.[3] covid-19 may pose challenges in clinical diagnosis because there is no pathognomonic symptom to detect the disease. several clinical symptoms have been frequently reported among covid-19 patients including but not limited to cough, fever, fatigue, sore throat, nasal obstruction, shortness of breath, headache, sputum production, and hemoptysis.[4] moreover, while some patients show a wider range of gastrointestinal symptoms such as diarrhea, abdominal pain, low appetite, and vomit,[5] others have shown renal and ocular symptoms.[6] most clinical research about sars-cov-2 have focused on respiratory manifestations; however, a growing body of evidence has raised concerns about the ocular complications caused by sarscov-2.[7] the reported ocular manifestations of the infection vary greatly and include dry eye, foreign body sensation, itching, blurring of vision, conjunctivitis, chemosis, and photophobia.[8] some studies have even reported conjunctivitis as an early sign for covid-19 diagnosis.[9] knowing the prevalence and type of ocular manifestations of covid-19 can help physicians diagnose the infection better and sooner in the course of the disease. therefore, we aimed to summarize the relevant published literature on the ocular manifestations of the covid-19 patients. methods we completed our systematic review in accordance with the preferred reporting items for systematic reviews and meta-analyses (prisma) guideline (see supplementary file s1 for prisma checklist).[10] for this systematic review and meta-analysis, we searched pubmed, embase, scopus, web of science, and medrxiv preprint server from december 1, 2019 to august 11, 2020 for studies published in english (see supplementary file s2 for a sample search strategy). we also searched the reference lists of related systematic reviews for potentially eligible studies. inclusion criteria and study selection we included empirical observational studies including cohort, case-control, cross-sectional, case-reports, or case-series that reported about ocular manifestations in covid-19 patients. we excluded editorials, commentaries, letters to editors, and reviews. two reviewers (nn and hsh) independently, and in duplicate, screened the titles and abstracts of identified citations, and assessed the full-text of potentially eligible studies for inclusion in the data synthesis. the reviewers resolved the disagreements on the process of study selection through feedback and discussion with the senior author (ash). data collection two authors (nn and ab) independently, and in duplicate, extracted data from each eligible study, including study characteristics (e.g., first author, publication date, study type, location, and total sample size) and patients’ information (e.g., age, sex, and ocular manifestations such as conjunctival hyperemia, clear secretions, conjunctivitis, follicles, petechia, and chemosis). quality assessment of the evidence two independent reviewers evaluated the quality of included studies duplicate using the joanna briggs institute critical appraisal tool.[11] the criteria suggested by joanna briggs to assess quality include eight items for case-report studies, nine items for cross-sectional studies, and ten items for case-series. reviewers resolved the disagreements by adjudication or feedback from the senior author. statistical analysis data were presented using descriptive statistics (i.e., mean, median, and standard deviation [sd] for continuous variables and frequency and percentage for categorical variables). to assess the proportion of patients with a particular manifestation, we calculated the sum of the patients with a particular manifestation in different papers and divided them to the number of included patients. to account for the different study designs included in the study, we only 104 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 ocular manifestations of covid-19; nasiri et al considered cross-sectional studies in our metaanalysis. using random-effects meta-analysis, we calculated the pooled estimated prevalence and 95% confidence interval (95% ci) of ocular manifestations, using metaprop command in stata version 14.2. we also assessed the heterogeneity among the included studies using i2 and the q-statistic. a value of ≥50% of i2 and a pvalue of <0.1 for the q-statistic was perceived as considerable heterogeneity. we then ran a meta-regression to assess the potential sources of heterogeneity. the following variables were included in the meta-regression: method of covid-19 diagnosis (polymerase chain reaction [pcr] or computed tomography scan [ct scan] vs clinical signs), the quality of studies (quality score < 4 vs quality score ≥ 4), the mean age of patients (age ≤ 45 years vs age > 45 years), the method of examination by ophthalmologist (standard ophthalmic exam vs non-standard ophthalmic exam), and the recruited sample size (sample size > 500 vs sample size ≤ 500). based on the reported information in the papers, we also aimed to assess whether the reported ocular manifestations preceded or followed the presence of systemic symptoms. to do so, we calculated the lag between ocular manifestation and systemic disease as well as the lag between systemic disease and ocular manifestation. all statistical analyses were performed in stata version 14.2 and all comparisons were two-tailed, with a threshold p-value of 0.05. results out of the 895 unique publications that were assessed, 38 studies[12–49] were included in this review (figure 1). overall, 13 studies were case reports,[37–49] six were case-series study,[13, 15, 18, 25, 28, 36] and the remaining 19 studies were cross-sectional.[12, 14, 16, 17, 19–24, 26, 27, 29–35] twenty-four studies reported aggregate-level[12–35] and fourteen[36–49]reported individual-level information about ocular manifestations. out of the 38 studies, 1 study[16] was conducted among healthcare providers (see supplementary file s3 for type of study, sex, mean age, and main ocular manifestations; supplementary file s4 for location, publication data, patient population, and chronic disease). moreover, out of the 38 included studies, 32 (3,719 out of 8,219 patients) were among inpatients, four among outpatients (2,353 out of 8,219 patients), and two included outpatient and inpatient individuals, simultaneously (2,147 out of 8,129 patients). demographic and clinical characteristics of covid-19 patients included in the reviewed studies are presented in table 1. a total of 8,219 patients with covid-19 were enrolled in the included studies. across all covid-19 studies, 6,308 reported sex distribution, 1,532 reported other comorbidities with covid-19, and 1,021 were at the individual level and reported ocular symptoms and signs. the number of enrolled patients in the included studies ranged from 1 to 1,452, most patients were female (n = 3,486 out of 6,308 patients, 55.3%), and the mean age of the participants ranged between 7 and 65.8 years. the diagnosis of sars-cov-2 was confirmed in 4,039 (49.1%) and 4,180 (50.9) patients using clinical signs and ct scans. the most detected comorbidities in patients were hypertension (593 out of 1,532), diabetes mellitus (294 out of 1,532), respiratory diseases (219 out of 1,532), and cardiovascular and cerebrovascular diseases (188 out of 1,532). quality assessment of included studies joanna briggs institute’s critical appraisal scores ranged from 2 to 6 for case reports (out of 8 possible points), and 0 to 5 for prevalence (crosssectional) studies (out of 9 possible points), and 3 to 7 (out of 10 possible points) for single case-series included in the review. quality assessment tools were different based on study design; therefore, scores could not be directly compared (see supplementary file s5). the pooled prevalence of ocular manifestations we included 19 cross-sectional studies corresponding to 7,300 individuals for metaanalysis of ocular manifestations among patients with covid-19. the pooled prevalence of all ocular manifestations among covid -19 patients was 11.03% (95% ci: 5.71 to 17.72) (figure 2), the most prevalent ocular manifestations were dry eye or foreign body sensation (n = 138, 16.0%), redness (n = 114, 13.3%), tearing (n = 111, 12.8%), itching (n = 109, 12.6%), eye pain (n = 83, 9.6%), and discharge (n = 76, 8.8%). the most prevalent ocular disease was conjunctivitis (n = 79, 88.8%). journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 105 ocular manifestations of covid-19; nasiri et al records identified through database search (n = 1,225) s c re e n in g in c lu d e d e li g ib il it y id e n ti fi c a ti o n records identified through other sources (n = 25) records after duplicates removed (n = 895) records screened (n = 895) records excluded (n = 815) full-text articles assessed for eligibility (n = 80) full-text articles excluded, with reasons (n = 11) reports were editorial, commentaries or reviews (n = 23) full text not found (n = 2) reported only tear pcr (n = 4) study did not report any information about ocular manifestation covid-19(n = 2) studies included in qualitative synthesis (n = 38) figure 1. flowchart of studies included in the systematic review of covid-19 ocular manifestation other rare conditions such as keratitis (n = 2, 2.2%), episcleritis (n = 2, 2.2%), keratoconjunctivitis (n = 2, 2.2%), hordeolum (n = 2, 2.2%), pingueculitis (n = 1, 1.1%), posterior ischemic optic neuropathy (n = 1, 1.1%) were also reported (table 2). no significant source of heterogeneity from the included variables in the meta-regression was detected (table 3). five studies reported the lag between ocular manifestation and systemic disease; however, nine studies reported the lag between systemic disease and ocular manifestation. weighted mean between onset ocular manifestations and systemic disease was 0.04 days (range, 1 to 3 days). however, weighted mean between systemic disease and ocular manifestation was 1.5 days (range, 2 to 21 days). discussion this systematic review and meta-analysis included 38 studies with a total of 8,219 covid-19 patients. 106 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 ocular manifestations of covid-19; nasiri et al figure 2. pooled prevalence of ocular manifestation among patients with covid-19 based on the existing evidence, we found the pooled prevalence of all ocular symptoms to be 11.03% (95% ci: 5.71 to 17.72) among covid19 patients. dry eye or foreign body sensation was the most common reported ocular symptoms (16.0%), followed by redness (13.3%) and tearing (12.8%). the most prevalent ocular disease was conjunctivitis (88.8%). this study showed that approximately one out of ten covid-19 patients included in this study showed at least one ocular manifestations. although these manifestations may not be frequent, they should not be overlooked by physicians and ophthalmologists.[50] these findings are comparable with the findings of previous studies on covid-19 or other coronaviruses. for example, vabret et al in a study in a french hospital, from november 2002 to april 2003, reported that ocular manifestations were 16.7% (3 out of 18) in patients diagnosed with human coronavirus nl63.[51] moreover, ulhaq et al in a systematic review study up to april 4, 2020 reported that ocular manifestations in covid-19 patients were 5.5%.[52] the reason for ocular manifestations among patients diagnosed with covid-19 and other coronaviruses could be related to the presence of ace2 receptor, the cell receptor for coronaviruses and sars-cov-2, in journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 107 ocular manifestations of covid-19; nasiri et al table 1. demographic and clinical characteristics of covid-19 infection included in the reviewed studies characteristics n (%) diagnostic approach (n = 8,219) only clinical signs and ct scan 4,180 (50.9) pcr laboratory confirmed 4,039 (49.1) sex (n = 6,308) male 2,822 (44.7) female 3,486 (55.3) comorbidity with covid-19 (n = 1, 532) hypertension 593 (38.7) diabetes 294 (19.2) respiratory system disease 219 (14.3) cardiovascular and cerebrovascular diseases 188 (12.3) cancer 60 (3.9) disease of immune system 59 (3.9) hepatitis 54 (3.5) liver disease 33 (2.1) kidney disease 32 (2.1) the eye cells.[8] transmission of sars-cov-2 by tear is not unlikely,[53] and the eye can be a way for entering the infection droplets to the body.[54] therefore, protecting eyes is essential for people, especially for healthcare providers to protect themselves against sars-cov-2. the most important ocular manifestations in covid-19 patients were dry eye or foreign body sensation, redness, tearing, itching, eye pain, and discharge. the mechanism of dry eye or foreign body sensation is unclear in covid19 patients and may not be directly associated with sars-cov-2. indeed, the occurrence of dry eye during the covid-19 epidemic could be due to wearing face masks and directing the expiratory air current toward eyes, especially when masks are loose against the face and nose. the stream of air against ocular surface causes accelerated evaporation of the tear and may create dry eye symptoms. in persons with preexisting dry eye or poor-quality tear film, the symptoms can be more common and prominent. limitation of access to lubricating agents in fear of contamination of hands and drug containers also deteriorates dry eye manifestations.[55, 56] furthermore, since the beginning of the pandemic, people spend more time looking at screens that may exacerbate dry eye sensation.[57, 58] while screen watching, the rate and intensity of blinks is significantly diminished, exacerbating the dry eye symptoms. loss of follow-up visits and reduced seeking care in patients with previous dry eye condition could be other factors that may have contributed to increased dry eye symptoms during the pandemic.[55, 56] conjunctivitis was the most common eye disease in patients. conjunctivitis could be developed by certain viruses (e.g., haemophilus influenzae and herpes simplex), bacteria (e.g., staphylococcal species, streptococcus pneumoniae, and neisseria gonorrhoeae), and allergies (e.g., pollen and animal dander).[59] conjunctivitis could also be developed by coronavirus and sars-cov-2.[60, 61] in a study in iran among 142 covid-19 patients, the most prevalent ocular finding was conjunctival hyperemia (44 persons; 31%); however, the most prevalent ocular manifestation among icu-admitted patients was chemosis (17 out of 28 admitted to icu; 60.7%), and 50.0% of the patients admitted to icu (14 of the 28) showed conjunctival hyperemia.[23] scalinci et al in a study among five italian covid-19 patients reported that conjunctivitis remained through the course of the disease among covid-19 patients.[38] hong et al in a study in china showed that some 108 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 ocular manifestations of covid-19; nasiri et al table 2. symptoms and diseases of ocular in covid-19 infection included in the reviewed studies (n = 1,021) characteristics n (%) symptom and sign (n = 932) dry eyes or foreign body sensation 138 (16.0) redness 114 (13.3) tearing 111 (12.8) itching 109 (12.6) eye pain 83 (9.6) discharge 76 (8.8) blurred vision or decreased vision 71 (8.2) photophobia 62 (7.2) chemosis 42 (4.9) irritation 21 (2.4) gritty feeling 14 (1.6) burning sensation 8 (0.9) lid edema 8 (0.9) subconjunctival hemorrhage 3 (0.3) pseudomembrane and hemorrhage 2 (0.2) pseudodendrite 1 (0.1) subepithelial infiltrates 1 (0.1) water secretion 1 (0.1) disease (n = 89) conjunctivitis 79 (88.8) keratitis 2 (2.2) episcleritis 2 (2.2) keratoconjunctivitis 2 (2.2) pingueculitis 1 (1.1) hordeolum 2 (2.2) posterior ischemic optic neuropathy 1 (1.1) table 3. meta-regression analysis of the effect of the factors on the ocular manifestations of the covid-19 patients variables multivariable meta-regression coefficient p-value [95% conf. interval] quality of the included papers (quality ≥4 vs quality < 4) 0.02 0.59 –0.07 – 0.11 the mean age of the patients (≤ 45 years vs > 45 years –0.11 0.29 –0.35 – 0.13 clinical examination (standard ophthalmic exam vs non-standard ophthalmic exam 0.12 0.33 –0.17 – 0.42 diagnostic method (pcr vs ct scan and clinical signs) –0.22 0.09 –0.50 – 0.05 the recruited sample size (sample size > 500 vs sample size ≤ 500) –0.22 0.13 –0.52 – 0.09 conf., confidence journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 109 ocular manifestations of covid-19; nasiri et al patients reported conjunctivitis after admission for treatment of covid-19.[19] chen et al in a crosssectional study in wuhan china reported that some patients had conjunctivitis as their first symptom and others reported conjunctivitis after the clinical symptom of covid-19 had begun.[21] in a study in canada, an association between conjunctivitis with corneal subepithelial infiltrations, corneal epithelial defects, development of tender preauricular lymphadenopathy, and conjunctival follicular reaction was observed among covid19 patients.[44] navel et al reported tarsal hemorrhage mucous filaments and tarsal pseudomembranous in one covid-19 patient. they observed the eyelids were irritated by numerous sticky secretions accumulating around the eyelashes, and described mucous filaments, tarsal pseudomembranous, and superficial punctuate keratitis.[39] assessing and observing the symptoms and ocular manifestations of covid-19 patients could improve clinicians’ diagnosis of the disease. during the ongoing pandemic, ophthalmologists should consider covid-19 as a potential diagnosis when observing ocular manifestations and conjunctivitis, especially with other manifestations of covid19-like respiratory signs or fever.[60] incidence of ocular symptoms may happen a few hours or days before the onset of covid-19 systemic signs such as fever and cough.[18, 19, 36] ophthalmologists are at a high risk for sarscov-2 given their close contact with patients. although the transmission of sars-cov-2 via tear is not unlikely[53] and the mechanism is uncertain,[8, 62] there exists a risk of transmission,[54] and ophthalmologists and other healthcare providers should adhere to recommendations about wearing eye protective gears in addition to face masks and other protective devises during clinical examinations.[63] this is particularly important when it comes to interactions with asymptomatic covid-19 patients.[1] we acknowledge the limitations of our study. first, ocular manifestations were measured by an ophthalmologist in some studies and through patient self-reports in others. second, given the significant variations between the studies, we could not merge the results of different study designs. third, most studies had a low sample size, and the quality of the included studies was low, and most were case reports and cross-sectional studies. lastly, most covid-19 patients are asymptomatic, but all patients enrolled in studies were symptomatic which could overestimate the infection’s manifestations. summary attention to ocular manifestations in combination with other covid-19 manifestations could help improve covid-19 diagnosis. the main ocular manifestations were dry eye, tearing, itching, redness, eye pain, and foreign body sensation. it is recommended that healthcare providers especially ophthalmologists who are in close contacts with patients wear eye protective goggles in addition to other recommended protective equipment. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. veritti d, sarao v, bandello f, lanzetta p. infection control measures in ophthalmology during the covid-19 outbreak: a narrative review from an early experience in italy. eur j ophthalmol 2020;30:621–628. 2. khalili m, karamouzian m, nasiri n, javadi s, mirzazadeh a, sharifi h. epidemiological characteristics of covid-19: a systematic review and meta-analysis. epidemiol infect 2020;148:e130. 3. worldometer. covid-19 coronavirus pandemic [internet]. worldometer; 2020. available from: https://www.worldometers.info/coronavirus/ 4. jin x, lian js, hu jh, gao j, zheng l, zhang ym, et al. epidemiological, clinical and virological characteristics of 74 cases of coronavirus-infected disease 2019 (covid-19) with gastrointestinal symptoms. gut 2020;69:1002–1009. 5. han c, duan c, zhang s, spiegel b, shi h, wang w, et al. digestive symptoms in covid-19 patients with mild disease severity: clinical presentation, stool viral rna testing, and outcomes. am j gastroenterol 2020;115:916– 923. 6. renu k, prasanna pl, valsala gopalakrishnan a. coronaviruses pathogenesis, comorbidities and multiorgan damage – a review. life sci 2020;255:117839. 7. seah i, agrawal r. can the coronavirus disease 2019 (covid-19) affect the eyes? a review of coronaviruses and ocular implications in humans and animals. ocul immunol inflamm 2020;28:391–395. 8. ho d, low r, tong l, gupta v, veeraraghavan a, agrawal r. covid-19 and the ocular surface: a review of transmission and manifestations. ocul immunol inflamm 2020;28:726–734. 110 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 https://www.worldometers.info/coronavirus/ ocular manifestations of covid-19; nasiri et al 9. mahayana it, angsana nc, kamila a, fatiha nn, sunjaya dz, andajana w, et al. literature review of conjunctivitis, conjunctival swab and chloroquine effect in the eyes: a current updates on covid-19 and ophthalmology. j med sci 2020;52:21–28. 10. moher d, liberati a, tetzlaff j, altman dg, group p. preferred reporting items for systematic reviews and meta-analyses: the prisma statement. plos med 2009;6:e1000097. 11. joanna briggs institute. the joanna briggs institute critical appraisal tools for use in jbi systematic reviews checklist for prevalence studies [internet]. joanna briggs institute; 2017. available from: http://joannabriggs.org/research/critical-appraisaltools.html 12. zhang x, chen x, chen l, deng c, zou x, liu w, et al. the evidence of sars-cov-2 infection on ocular surface. ocul surf 2020;18:360–362. 13. xia j, tong j, liu m, shen y, guo d. evaluation of coronavirus in tears and conjunctival secretions of patients with sars-cov-2 infection. j med virol 2020;92:589– 594. 14. wu p, duan f, luo c, liu q, qu x, liang l, et al. characteristics of ocular findings of patients with coronavirus disease 2019 (covid-19) in hubei province, china. jama ophthalmol 2020;138:575–578. 15. valente p, iarossi g, federici m, petroni s, palma p, cotugno n, et al. ocular manifestations and viral shedding in tears of pediatric patients with coronavirus disease 2019: a preliminary report. j aapos 2020:s1091– 8531(20)30115-4. 16. tostmann a, bradley j, bousema t, yiek wk, holwerda m, bleeker-rovers c, et al. strong associations and moderate predictive value of early symptoms for sars-cov-2 test positivity among healthcare workers, the netherlands, march 2020. euro surveill 2020;25:2000508. 17. kumar k, prakash aa, gangasagara sb, rathod sbl, ravi k, rangaiah a, et al. presence of viral rna of sars-cov2 in conjunctival swab specimens of covid-19 patients. indian j ophthalmol 2020;68:1015–1017. 18. karimi s, arabi a, shahraki t, safi s. detection of severe acute respiratory syndrome coronavirus-2 in the tears of patients with coronavirus disease 2019. eye 2020;34:1220–1223. 19. hong n, yu w, xia j, shen y, yap m, han w. evaluation of ocular symptoms and tropism of sars-cov2 in patients confirmed with covid-19. acta ophthalmol 2020;26:10.1111/aos.14445. 20. güemes-villahoz n, burgos-blasco b, arribi-vilela a, arriola-villalobos p, rico-luna cm, cuiña-sardiña r, et al. detecting sars-cov-2 rna in conjunctival secretions: is it a valuable diagnostic method of covid-19? j med virol 2020:10.1002/jmv.26219. 21. chen l, deng c, chen x, zhang x, chen b, yu h, et al. ocular manifestations and clinical characteristics of 535 cases of covid-19 in wuhan, china: a cross-sectional study. acta ophthalmol 2020;10.1111/aos.14472. 22. bostanci ceran b, ozates s. ocular manifestations of coronavirus disease 2019. graefes arch clin exp ophthalmol 2020:258:1959–1963. 23. abrishami m, tohidinezhad f, daneshvar r, omidtabrizi a, amini m, sedaghat a, et al. ocular manifestations of hospitalized patients with covid-19 in northeast of iran. ocul immunol inflamm 2020:28:739–744. 24. lapostolle f, schneider e, vianu i, dollet g, roche b, berdah j, et al. clinical features of 1487 covid-19 patients with outpatient management in the greater paris: the covid-call study. intern emerg med 2020:15:813–817. 25. ye y, song y, yan m, hu c, chen x, yu j, et al. novel coronavirus pneumonia combined with conjunctivitis: three cases report. zhonghua shiyan yanke zazhi/chinese j exp ophthalmol 2020;38:242– 244. 26. seah iyj, anderson de, kang aez, wang l, rao p, young be, et al. assessing viral shedding and infectivity of tears in coronavirus disease 2019 (covid-19) patients. ophthalmology 2020;127:977–979. 27. deng c, yang y, chen h, chen w, chen z, ma k, et al. ocular dectection of sars-cov-2 in 114 cases of covid-19 pneumonia in wuhan, china: an observational study [internet]. ssrn; 2020. available from: http://www. ssrn.com/abstract=3543587 28. xu l, zhang x, song w, sun b, mu j, wang b, et al. conjunctival polymerase chain reaction-tests of 2019 novel coronavirus in patients in shenyang, china [internet]. ssrn; 2020. available from: https://www.ssrn. com/abstract=3543592 29. guan w-j, ni z-y, hu y, liang w-h, ou c-q, he j-x, et al. clinical characteristics of coronavirus disease 2019 in china. n engl j med 2020;382:1708–1720. 30. zhou y, duan c, zeng y, tong y, nie y, yang y, et al. ocular findings and proportion with conjunctival sars-cov-2 in covid-19 patients. ophthalmology 2020;127:982–983. 31. lechien jr, chiesa-estomba cm, place s, van laethem y, cabaraux p, mat q, et al. clinical and epidemiological characteristics of 1420 european patients with mildto-moderate coronavirus disease 2019. j intern med 2020;288:335–344. 32. pardhan s, vaughan m, zhang j, smith l, chichger h. type and frequency of ocular and other known symptoms experienced by people who self diagnosed as suffering from covid-19 in the uk. medrxiv 2020. 33. liang l, wu p. there may be virus in conjunctival secretion of patients with covid-19. acta ophthalmol 2020;98:223. 34. sindhuja k, lomi n, asif mi, tandon r. clinical profile and prevalence of conjunctivitis in mild covid-19 patients in a tertiary care covid-19 hospital: a retrospective crosssectional study. indian j ophthalmol 2020;68:1546–1550. 35. wu f, zhou y, wang z, xie m, shi z, tang z, et al. clinical characteristics of covid-19 infection in chronic obstructive pulmonary disease: a multicenter, retrospective, observational study. j thorac dis 2020;12:1811–1823. 36. huang l, zhang x, zhang x, wei z, zhang l, xu j, et al. rapid asymptomatic transmission of covid-19 during the incubation period demonstrating strong infectivity in a cluster of youngsters aged 16-23 years outside wuhan and characteristics of young patients with covid-19: a prospective contact-tracing study. j infect 2020;80:e1– e13. 37. selvaraj v, sacchetti d, finn a, dapaah-afriyie k. acute vision loss in a patient with covid-19. r i med j 2020;103:37–38. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 111 https://www.ssrn.com/abstract=3543592 https://www.ssrn.com/abstract=3543592 ocular manifestations of covid-19; nasiri et al 38. scalinci sz, trovato battagliola e. conjunctivitis can be the only presenting sign and symptom of covid-19. idcases 2020;20:e00774. 39. navel v, chiambaretta f, dutheil f. haemorrhagic conjunctivitis with pseudomembranous related to sarscov-2. am j ophthalmol case rep 2020;19:100735. 40. li x, wang m, dai j, wang w, yang y, jin w. novel coronavirus disease with conjunctivitis and conjunctivitis as first symptom: two cases report. [zhonghua shiyan yanke zazhi] chinese j exp ophthalmol 2020;38:318– 321. 41. lan qq, zeng sm, liao x, xu f, qi h, li m. [screening for novel coronavirus related conjunctivitis among the patients with corona virus disease-19]. [zhonghua yan ke za zhi] chinese j ophthalmol 2020;56:e009. 42. daruich a, martin d, bremond-gignac d. ocular manifestation as first sign of coronavirus disease 2019 (covid-19): interest of telemedicine during the pandemic context. j fr ophtalmol 2020;43:389–391. 43. chen l, liu m, zhang z, qiao k, huang t, chen m, et al. ocular manifestations of a hospitalised patient with confirmed 2019 novel coronavirus disease. br j ophthalmol 2020;104:748–751. 44. cheema m, aghazadeh h, nazarali s, ting a, hodges j, mcfarlane a, et al. keratoconjunctivitis as the initial medical presentation of the novel coronavirus disease 2019 (covid-19). can j ophthalmol 2020;55:e125–e129. 45. chavis a, bakken h, ellenby m, hasan r. coronavirus disease-2019 and telehealth: prevention of exposure in a medically complex patient with a mild presentation. j adolesc health 2020;67:456–458. 46. ozturker zk. conjunctivitis as sole symptom of covid19: a case report and review of literature [published online ahead of print, 2020, jul 24]. eur j ophthalmol 2020;1120672120946287. 47. nayak b, poddar c, panigrahi mk, tripathy s, mishra b. late manifestation of follicular conjunctivitis in ventilated patient following covid-19 positive severe pneumonia. indian j ophthalmol 2020;68:1675–1677. 48. guo d, xia j, wang y, zhang x, shen y, tong jp. relapsing viral keratoconjunctivitis in covid-19: a case report. virol j 2020;17:97. 49. salducci m, la torre g. covid-19 emergency in the cruise’s ship: a case report of conjunctivitis. clin ter 2020;171:e189–e91. 50. lai c-c, ko w-c, lee p-i, jean s-s, hsueh p-r. extrarespiratory manifestations of covid-19. int j antimicrob agents 2020;56:106024. 51. vabret a, mourez t, dina j, van der hoek l, gouarin s, petitjean j, et al. human coronavirus nl63, france. emerg infect dis 2005;11:1225–1229. 52. ulhaq zs, soraya gv. the prevalence of ophthalmic manifestations in covid-19 and the diagnostic value of ocular tissue/fluid. graefes arch clin exp ophthalmol 2020;258:1351–1352. 53. abobaker a, raba aa, alzwi a. extrapulmonary and atypical clinical presentations of covid-19. j med virol 2020;10.1002/jmv.26157. 54. dockery dm, rowe sg, murphy ma, krzystolik mg. the ocular manifestations and transmission of covid19: recommendations for prevention. j emerg med 2020;59:137–140. 55. giannaccare g, vaccaro s, mancini a, scorcia v. dry eye in the covid-19 era: how the measures for controlling pandemic might harm ocular surface. graefes arch clin exp ophthalmol 2020;258:2567–2568. 56. patel s, henderson r, bradley l, galloway b, hunter l. effect of visual display unit use on blink rate and tear stability. optom vis sci 1991;68:888–892. 57. marinova e, dabov d, zdravkov y. ophthalmic complaints in face-mask wearing: prevalence, treatment, and prevention with a potential protective effect against sarscov-2. biotechnol biotechnol equip 2020;34:1323–1336. 58. moshirfar m, west wb, marx dp. face mask-associated ocular irritation and dryness. ophthalmol ther 2020;9:397–400. 59. azari aa, barney np. conjunctivitis: a systematic review of diagnosis and treatment. jama 2013;310:1721–1729. 60. amesty ma, alió del barrio jl, alió jl. covid-19 disease and ophthalmology: an update. ophthalmol ther 2020;9:1–12. 61. guo d, xia j, shen y, tong j. sars-cov-2 may be related to conjunctivitis but not necessarily spread through the conjunctiva sars-cov-2 and conjunctiva. j med virol 2020;10.1002/jmv.25856. 62. loon sc, teoh sc, oon ll, se-thoe sy, ling ae, leo ys, et al. the severe acute respiratory syndrome coronavirus in tears. br j ophthalmol 2004;88:861–863. 63. chen x, yu h, mei t, chen b, chen l, li s, et al. sarscov-2 on the ocular surface: is it truly a novel transmission route? br j ophthalmol 2020;bjophthalmol-2020-316263. 112 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 photo essay crystalline lens staining with intracameral phenylephrine during cataract surgery michael tsatsos, md, phd, frcophth1,2; ioannis athanasiadis, md, mrcsed(ophth)2; corrado gizzi, md, phd2 balal shafi, md2; marilita moschos, md, phd1; anant sharma, md, frcophth2 1aristotelian university of thessaloniki, thessaloniki, greece 2moorfields eye hospital, london, united kingdom orcid: michael tsatsos: https://orcid.org/0000-0003-1280-4113 ioannis athanasiadis: https://orcid.org/0000-0002-6236-7540 j ophthalmic vis res 2021; 16 (1): 135–136 presentation during intracameral use of low concentration phenylephrine in several consecutive routine phacoemulsification cases, we have consistently observed a “spikes” pattern of staining in the crystalline lens structures; however, it was not entirely clear whether this involved just the capsule, the cortex, or both (figure 1). although it appears that the staining occurs largely at the level of the anterior capsule, some very faint staining could possibly be seen on the anterior lenticular surface as well. the formulation of intracameral phenylephrine (minims® phenylephrine hydrochloride, bausch & lomb uk ltd.) that is routinely used in our practice consists of 0.5 ml of 10% phenylephrine preservative free minims mixed with 0.5 ml of 2% lidocaine and 1 ml of balanced salt solution with adrenaline. this mixture (0.2 ml) was injected in the anterior chamber. correspondence to: ioannis athanasiadis, md, mrcsed(ophth). moorfields eye hospital at bedford eye clinic, kempston road, bedford, mk42 9dj, united kingdom. e-mail: athana1972@yahoo.com received: 18-06-2018 accepted: 21-03-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8261 discussion phenylephrine is an 𝛼-adrenergic agonist regularly used as a dilating agent in the form of eye drops prior to intraocular surgery such as cataract surgery. it is also frequently used as an intracameral injection in conditions such as floppy iris syndrome to assist with pupillary dilation as well as to increase the iris tone.[1, 2] no evidence of capsular staining was observed in our patients at postoperative visits. there were no reported or observed cases of toxic anterior segment syndrome or other systemic or vision-threatening complications intraoperatively or during the postoperative period. although lockington et al reported the possibility of toxicity associated with the presence of free radicals in intracameral phenylephrine formulations, we report no relevant deviations from routine practice in our patients.[3] lens staining was consistent in all cases where the intracameral phenylephrine formulation was used. it began to appear in 20 sec, peaking at around 1 min after the intracameral injection (figure 2). we believe that the resulting appearance of the crystalline lens can facilitate capsulorrhexis in routine as well as in cases of borderline visibility this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: tsatsos m, athanasiadis i, gizzi c, shafi b, moschos m, sharma a. crystalline lens staining with intracameral phenylephrine during cataract surgery. j ophthalmic vis res 2021;16:135–135. © 2021 tsatsos et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 135 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8261&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; tsatsos et al figure 1. spike-like staining of the crystalline lens (arrows) following intracameral injection of phenylephrine hydrochloride. figure 2. early (left) and late (right) staining of the crystalline lens following intracameral use of phenylephrine hydrochloride in two different patients. where usually a staining agent such as trypan blue is considered by the surgeon. thus, no extra provisions need to be made resulting in reduced cost of surgery as well as less logistical burden on the operation theatre. furthering our understanding on the cause of crystalline lens staining related to intracameral phenylephrine and its implications will hopefully enable us to use this agent more effectively as a mydriatic and to facilitate capsulorrhexis in routine as well as complicated cases. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. lundberg b, behndig a. intracameral mydriatics in phacoemulsification cataract surgery. j cataract refract surg 2003;29:2366–2371. 2. lorente r, de rojas v, vázquez de parga p, moreno c, varela j, et al. intracameral phenylephrine 1.5% for prophylaxis against intraoperative floppy iris syndrome: prospective, randomized fellow eye study. ophthalmology 2012;119:2053–2058. 3. lockington d, macdonald ec, young d, stewart p, caslake m, ramaesh k. presence of free radicals in intracameral agents commonly used during cataract surgery. br j ophthalmol 2010;94:1674–1677. 136 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 letter to editor topical umbilical cord serum for corneal epithelial defects after diabetic vitrectomy arjun srirampur, ms, frcs anand eye institute, habsiguda, hyderabad, india orcid: arjun srirampur: https://orcid.org/0000000230168336 j ophthalmic vis res 2021; 16 (1): 145–146 dear editor, i have read with great interest the article by moradian et al on “topical umbilical cord serum for corneal epithelial defects after diabetic vitrectomy.”[1] they have performed the study to investigate whether topical umbilical cord serum (tucs) has any beneficial role in healing corneal epithelial defects (ced) after diabetic vitrectomy. however, i have a few concerns about the study. firstly, the postoperative intraocular pressures (iop) were not mentioned in both groups. elevated iop (which is common after a vitreoretinal surgery) is known to cause corneal edema and increase the risk of corneal complications such as epithelial defect and nonhealing epithelial defect.[2] it would be more informative if the authors had provided iop measurements in both groups, as it could influence the healing pattern of the epithelial defects. secondly, it is mentioned that all 80 eyes underwent deep vitrectomy but it is not mentioned what type of intraocular tamponade agent such as air, sulphur hexafluoride (sf6), perfluoropropane correspondence to: arjun srirampur, ms, frcs. consultant – cornea, cataract and refractive surgery, anand eye institute, habsiguda, hyderabad 500007, india. e-mail: sarjuneye@gmail.com received: 24-04-2019 accepted: 11-12-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8264 (c3f8), or silicone oil was used during the surgery. intraocular tamponade of long-acting expansile gases may induce corneal endothelial cell toxicity. the loss of corneal endothelial cells has also been reported to be significantly greater in eyes with c3f8 than in those with sf6.[3] this endothelial damage especially in a diabetic eye can lead to corneal edema and loose adhesions between the bowman’s layer and stroma which delays the epithelial healing mechanism. thirdly, even though the authors have admitted for the absence of dry eye testing in these eyes, they should have performed simple corneal sensations. it is well-known that diabetic eyes have corneal hypoesthesia due to peripheral neuropathy. the development of diabetic keratopathy has been suggested to be related to loss of nerve-derived trophic factors following a decrease in corneal sensation. this reduced corneal sensations can lead to neurotrophic keratopathy which can lead to disturbance in the healing of the epithelial defects. diabetic keratopathy may be associated with neuropathic keratitis in patients with a persistent corneal epithelial defect, and dry eyes may occur secondary to a reflex decrease of tear secretion due to corneal this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: arjun srirampur, ms, frcs. topical umbilical cord serum for corneal epithelial defects after diabetic vitrectomy. j ophthalmic vis res 2021;16:145–146. © 2021 arjun srirampur. this is an open access article distributed under the creative commons attribution license | published by knowledge e 145 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8264&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr letter to editor; arjun srirampur hypoesthesia and/or secondary to reduced tear and mucin secretion due to efferent nerve dysfunction.[4] also, the risk of allergies and possibilities of transmitting parenterally transmitted organisms must also be kept in mind when using tucs apart from the legal and ethical issues. a routine testing of the mothers and a rapid test on the sera for viral contaminants is required. when the event to the time between the testing of the mother for hiv and the preparation of cord serum from the placental blood is more than six months, hiv testing should be undertaken again at the time of serum delivery to account for the window period of the infection.[5] in consideration of the window period of hiv infection, additional hiv testing with a shortened window period, such as p24 antigen detection method, should be performed before the use of the tucs. references 1. moradian s, ebrahimi m, kanaani a, faramarzi a, safi s. topical umbilical cord serum for corneal epithelial defects after diabetic vitrectomy. j ophthalmic vis res 2020;15:160–165. 2. ytteborg j, dohlman ch. corneal edema and intraocular pressure ii. clinical results. arch ophthalmol 1965;74:477– 484. 3. mitamura y, yamamoto s, yamazaki s. corneal endothelial cell loss in eyes undergoing lensectomy with and without anterior lens capsule removal combined with pars plana vitrectomy and gas tamponade. retina 2000;20:59– 62. 4. toshida h, nguyen dh, beuerman rw, murakami a. evaluation of novel dry eye model: preganglionic parasympathetic denervation in rabbit. invest ophthalmol vis sci 2007;48:4468–4475. 5. vajpayee rb, mukerji n, tandon r, sharma n, pandey rm, biswas nr, et al. evaluation of umbilical cord serum therapy for persistent corneal epithelial defects. br j ophthalmol 2003;87:1312–1316. 146 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 photo essay anterior chamber migration of intravitreal dexamethasone implant in an eye with scleral-fixated intraocular lens neha goel, ms, dnb, mnams, frcs (glasg); aanchal mehta, dnb; jyoti batra, ms; reena choudhry, md, doms, dnb, frcs (glasg) department of ophthalmology, icare eye hospital and postgraduate institute, noida, uttar pradesh, india j ophthalmic vis res 2020; 15 (4): 581–583 presentation a 60-year-old woman with diabetes and hypertension presented with a decreased vision od to 6/18 n10 due to cystoid macular edema (cme) following vitrectomy for removal of the dislocated posterior chamber intraocular lens (pciol) and scleral-fixated intraocular lens (sfiol) implantation performed five months before. spectral domain optical coherence tomography (sd-oct) showed a central foveal thickness (cft) of 484 µm. intravitreal ranibizumab (lucentis®; genentech, inc) was administered; however, the cft increased to 533 µm after one month. she received intravitreal dexamethasone (dex) implant (ozurdex®, allergan inc.), which resulted in best corrected visual acuity (bcva) improvement to 6/12 n10 and cft reduction to 404 µm within a month. three months later, cft increased again to 677 µm and she received a second dex implant. seven weeks following the injection, she presented with pain, corneal haze, and intraocular pressure (iop) of 38 mmhg. a week later, iop decreased to 16 mmhg on brimonidine tartrate 0.2% and timolol maleate 0.5% bd; however, the dex implant was seen in the anterior chamber (figure 1a). complete pupillary dilatation in this correspondence to: neha goel, ms, dnb, mnams, frcs (glasg). d-91, anand niketan, new delhi 110021, india. e-mail: nehadoc@hotmail.com received: 24-10-2018 accepted: 29-07-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7798 vitrectomized eye allowed the implant to migrate forward through the gap between the iol edge and the pupil (figure 1b). there was no corneal edema and bcva was maintained at 6/12 n10. specular microscopy showed an endothelial count (ec) of 1144 cells/mm2 (figure 1c). sd-oct revealed a cft of 365 μm (figure 1d). a trial of wide pupillary dilatation with supine position failed to reposition the implant into the vitreous cavity. pros and cons of implant removal were discussed and patient opted for weekly follow-up. corneal clarity was maintained, ec was 1106, 1181, 1193, and 1205 cells/mm2 at each weekly visit, respectively, and iop remained <20 mmhg without treatment. within a month, the implant disappeared from the anterior chamber, although the cft increased again to 711 µm. due to the recent anterior migration of dex implant, three monthly doses of intravitreal ranibizumab were administered. suboptimal visual and anatomical results led us to inject dex implant again, with care taken not to dilate the pupil fully at any time. she underwent four intravitreal dex implants over the following year; bcva remained stable at 6/12 n8 with a clear cornea, iop < 20 mmhg in the absence of therapy, no recurrence of cme, and no anterior migration of the implant. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: goel n, mehta a, batra j, choudhry r. anterior chamber migration of intravitreal dexamethasone implant in an eye with scleral-fixated intraocular lens. j ophthalmic vis res 2020;15:581–583. © 2020 journal of ophthalmic and vision research | published by knowledge e 581 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7798&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; goel et al figure 1. (a) clinical photograph of the right eye showing a clear cornea, scleral-fixated posterior chamber intraocular lens (sfiol) in situ, and an intravitreally administered dexamethasone (dex) implant lying inferiorly in the anterior chamber. (b) a gap between the iol edge and pupil margin could be seen in upgaze (white arrow). (c) endothelial count of the right eye performed on the same day. (d) spectral domain optical coherence tomography (sd-oct) showing mild macular edema and hard exudates. discussion intravitreal dex implant is a safe and effective therapeutic option for post-surgical macular edema.[1] anterior chamber migration of the implant is a potential, though uncommon complication, in eyes with a compromised lens capsule, prior to vitrectomy and/or iris defects.[2, 3] very few cases of migration in eyes with an sfiol have been reported,[2, 4, 5] as has occurred in this case, reinforcing that the presence of an iol alone does not prevent the implant migration when the posterior capsule is not intact. as a precaution to minimize recurrent migration, the pupil size was kept reduced enough to cover the edge of the optic. corneal endothelial decompensation is the most serious complication resulting from the migration of implant into the anterior chamber.[1, 4] early migration (within three weeks of injection) could result in higher incidence of corneal edema as higher rigidity of the implant in the first weeks could cause greater mechanical endothelial trauma.[2] this would explain why our patient did not develop corneal edema and could avoid the additional procedure of immediate repositioning or removing the implant, which reduces the likelihood of permanent corneal edema.[2, 3] while vitrectomized eyes without an intact lens capsule are at risk for anterior migration of a dex implant, this subset of patients may also benefit most from having a dex implant administered for post-surgical macular edema. a regular postinjection follow-up can recognize and manage this rare, though potentially vision threatening, complication at the earliest. an individualized approach is recommended that takes into account the potential anterior segment complications as well as loss of drug effectiveness. a single episode of anterior chamber migration of the dex implant should not be considered as a contraindication for further injections if warranted. 582 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 photo essay; goel et al financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. bellocq d, pierre-kahn v, matonti f, burillon c, voirin n, dot c, et al. effectiveness and safety of dexamethasone implants for postsurgical macular oedema including irvinegass syndrome: the episodic-2 study. br j ophthalmol 2017;101:333–341. 2. khurana rn, appa sn, mccannel ca, elman mj, wittenberg se, parks dj, et al. dexamethasone implant anterior chamber migration: risk factors, complications, and management strategies. ophthalmology 2014;121:67– 71. 3. rahimy e, khurana rn. anterior segment migration of dexamethasone implant: risk factors, complications, and management. curr opin ophthalmol 2017;28:246–251. 4. marchese v, piscitello s, vaccaro c, giunchiglia g. management of intravitreal implant migration into the anterior chamber in a patient with a posterior chamber intraocular lens. jcrs online case rep 2014;2:e31–e34. 5. pacella f, agostinelli e, carlesimo sc, nebbioso m, secondi r, forastiere m, et al. management of anterior chamber dislocation of a dexamethasone intravitreal implant: a case report. j med case rep 2016;10:282. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 583 case report giant idiopathic angioid streaks brijesh takkar1,2, md; anubha rathi3, md; pradeep venkatesh4, md; atul kumar4, md 1department of ophthalmology, all india institute of medical sciences, bhopal, india 2smt kanuri santhamma centre for vitreoretinal diseases, lv prasad eye institute, hyderabad, india 3department of ophthalmology, dayanand medical college, ludhiana, india 4retina and uvea services, dr r p centre for ophthalmic sciences, all india institute of medical sciences, new delhi, india orcid: brijesh takkar: https://orcid.org/0000-0001-5779-7645 abstract purpose: to present a case of gigantic idiopathic angioid streaks. case report: a young male presented with macular choroidal neovascular membrane (cnvm) and peripheral retinal hemorrhages secondary to angioid streaks. swept source optical coherence tomography (ssoct) and ultrawide field imaging were performed. the latter revealed extension of the angioid streaks up to the equator in both eyes. ssoct showed breaks in the retinal pigment epithelium-bruch’s membrane complex in the area of peripheral retinal hemorrhages. the patient was extensively worked up for systemic associations, and the only significant finding was a long history of steroid abuse in the past. conclusion: advanced imaging techniques helped to diagnose angioid streaks in this patient. the possible role of steroid abuse in accentuating the presentation of angioid streaks may be explored further. keywords: angioid streak; choroidal neovascular membrane; pseudoxanthoma elasticum; swept source optical coherence tomography j ophthalmic vis res 2020; 15 (2): 240–245 introduction angioid streaks (as) are dehiscences in the bruch’s membrane, clinically seen to radiate from the peripapillary area and accompanied by atrophy of the overlying retinal pigment epithelium (rpe). correspondence to: brijesh takkar, md. smt kanuri santhamma centre for vitreoretinal diseases lv prasad eye institute, hyderabad 500034, india. e-mail: britak.aiims@gmail.com received: 08-03-2018 accepted: 01-02-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i2.6742 because of the blood vessel-like appearance, they were earlier believed to have a vascular origin but later proved to be cracks in the bruch’s membrane with secondary calcification. they may or may not have systemic association, the most common being pseudoxanthoma elasticum.[1, 2] the streaks are usually restricted to the posterior pole and very rarely involve the retinal periphery.[2] in this imaging report, we present ultrawide field (uwf) and swept source optical coherence tomography (ssoct) imaging features of a case of this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: takkar b, rathi a, venkatesh p, kumar a. giant idiopathic angioid streaks. j ophthalmic vis res 2020;15:240–245. 240 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i2.6742&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr giant idiopathic angioid streaks; takkar et al idiopathic as that extended from the optic disc to the pre-equatorial region. possible role of steroid abuse toward the unusual presentation in this patient is also discussed. case report all procedures performed in the present study was approved by the all india institute of medical sciences, new delhi research committee. a 35-year-old male presented with low vision in right eye for two months that was painless and gradual in onset. he had a history of being treated with two intravitreal injections of bevacizumab for subfoveal choroidal neovascular membrane (cnvm) in the left eye one year back. the best corrected visual acuity was 6/36 in the right eye and 6/60 in the left eye. anterior segment examination and intraocular pressure were within normal limits in both eyes. fundus examination revealed a spider web-like network of blackish–brown colored radially oriented interconnected streaks that emanated from the peripapillary region in both eyes. these streaks were seen to reach up to the pre-equatorial region of the inferior and temporal quadrants of both eyes on uwf imaging [figure 1] (optos, optos plc, dunfermline, uk). further, a subfoveal cnvm with subretinal bleed was seen in the right eye, while a disciform scar was noticed in the macular region of the left eye. extramacular retinal hemorrhages were visualized in temporal immediate periphery of both eyes [figure 1]. the patient was clinically diagnosed to have as in both eyes, with active cnvm in the right eye and macular scar in the left eye. uwf fluorescein angiography of the right eye revealed an actively leaking subfoveal cnvm with hypofluorescence corresponding to hemorrhages, while the left macula showed only staining [figure 2]. the as were visualized as curvilinear lines with alternating areas of hypo and hyperfluorescence in both eyes. additionally, the temporal as of the right eye that passed underneath the cnvm had minimal leakage in its peripheral, most extensions corresponding to the area of fresh retinal hemorrhages [figure 2]. ssoct imaging (topcon dri oct triton, topcon, tokyo, japan) of the as in this area showed multiple elevations corresponding to the as along with breaks in the rpe-bruch’s membrane complex [figure 3]. while the left eye had no subretinal fluid, ssoct angiography of the right eye revealed a type 2 cnvm in the macular region, while no such membrane was seen in the area corresponding to peripheral retinal hemorrhages [figure 4]. the patient was worked up for systemic associations of as, and pseudoxanthoma elasticum, paget’s disease and anemia were ruled out.[2, 3] the patient, however, gave the history of longterm over-the-counter steroid abuse in the past with the intention of weight gain and increase in muscle mass. he had consumed varying doses of oral methylprednisolone ranging from 10 to 40 mg daily for a period of three to five years up to the current presentation. he also had a history of long-term use of anabolic steroids. the patient was counseled against further self-medication and was offered intravitreal anti-vegf injection in the right eye. the patient however did not follow-up for the treatment despite adequate counseling. discussion angioid streaks are typically restricted to the posterior pole, and very rarely extend to the peripheral areas. they are typically described to be a few mm in length from the optic disc, and mostly much less than half a mm in width.[2] it is possible that the absence of uwf technology did not previously allow for clinical documentation of such large streaks. at the same time, it should be noted that studies have also been done on enucleated eyeballs with as,[2, 4] a fact that makes uwf findings of this case truly unusual. a study using uwf in 20 patients of pseudoxanthoma elasticum previously reported utility of this imaging technology in documenting other lesions associated with the disease in 72.5% of eyes, which were otherwise undetected with standard fundus photography.[1] these peripheral lesions included peaud’orange, coquille d’oeuf, cracked eggshell, comet lesions, peripheral retinal degenerations, parastreak atrophies, and peripheral hemorrhages. though the authors documented peripheral hemorrhages, they have not reported peripheral as in this highly vulnerable cohort.[1] it is said that as may grow in length, but such findings have not been documented with clinical studies.[2] spectral domain oct, enhanced depth imaging oct, ssoct, and enface oct (c-scans) have been previously used to document changes at the level of bruch’s membrane that corroborate journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 241 giant idiopathic angioid streaks; takkar et al figure 1. ultrawide field fundus images of the right and left eyes showing a peripapillary meshwork of angioid streaks at the posterior pole of both eyes along with peripheral extension up to the pre-equatorial region (arrow). a cnvm is noticeable in the right macula along with subretinal blood, while the left eye has a dense scar in the macular region. additionally, right eye has an area with peripheral retinal hemorrhages bounded by two peripheral streaks (encircled). figure 2. ultrawide field fluorescein angiogram of the patient showing (a) cnvm in the macular region of right eye and (b) scarring in the macula of left eye. encircled area shows minimal dye leakage corresponding to the peripheral angioid streaks that resulted in bleeding. figure 3. swept source optical coherence tomography through the temporal peripheral area of the right eye having hemorrhages. the scan has been acquired through an area of hemorrhage between two peripheral angioid streaks (inset). undulations can be seen in multiple areas at the level of the rpe (arrowheads). one of these areas also shows a break in the epithelium (arrow). 242 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 giant idiopathic angioid streaks; takkar et al figure 4. swept source optical coherence tomography angiography of the macula of the right eye scanned over an area of 4.5 mm × 4.5 mm. (a) the imaging slab has been at the level of the choriocapillaris. a well-defined meshwork of mature vessels of the cnvm can be seen along with the projection artifact of the retinal vessels. (b) in the figure showing the composite angiogram, cnvm is seen as blue colored vessels. figure 5. ultrawide field red free fundus photograph of the right eye showing the peripheral angioid streak as an extension of the central complex. with histopathological findings reported earlier.[5–8] reported features include hyper-reflection, undulations, and large dehiscence of the bruch’s membrane. a longitudinal study reports presence of undulations on oct as a sign of pressure points that would lead to future dehiscence of the bruch’s membrane and then possibly cnvm.[5] we used ssoct to scan the temporal area of the right eye harboring the peripheral as noted in uwf imaging and findings were similar to what has been reported earlier.[5–8] eyes with as are prone to retinal hemorrhages, even following insignificant journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 243 giant idiopathic angioid streaks; takkar et al ocular contusions.[1, 4] such bleeds may be seen in up to 5% of the cases and may cause vision loss.[1] dehiscence in the rpe–bruch’s membrane complex are a known feature of as.[5] as undulations represent a weak area and are prone to rupture,[1, 5] a peripheral dehiscence of the rpebruch’s membrane complex near an undulation [figure 3] explains the peripheral location of the retinal hemorrhages seen in this patient far away from the cnvm. this pathology may be very similar to retinal hemorrhages occurring in high myopia following the development of lacquer cracks.[9] uwf red free imaging clearly indicated that the peripheral as [figure 5] were extensions of the central anomaly and not a singular occurrence. these areas may also be a nidus for future peripheral cnvms, though no cnvm was detected with oct angiography or fluorescein angiography in that area. given the idiopathic nature of as in this patient, their peripheral extension is rather unusual. our initial workup for systemic associations did not reveal any finding to suggest a vulnerability for the as to assume a gigantic form. after leading questions and inter-departmental referrals, the only finding on clinical workup was the longterm steroid abuse for cosmetic reasons. steroids are known to alter serum calcium balance due to multiple mechanisms.[10] there are specific reports citing hypercalcemia following the use of anabolic steroids.[11, 12] it has also been theorized that high serum calcium levels may be responsible for as in patients with paget’s disease.[2] though current serum calcium levels were normal in this patient, they may have fluctuated earlier, resulting in the aggressive presentation and increased fragility of the otherwise elastic membrane. further, steroids can also affect wound healing of the damaged chorioretinal tissue and impair ocular response to undulations and breaks of the bruch’s membrane.[13] however this is an isolated case report, we conjecture that long-term abuse of systemic corticosteroids may have perpetuated the progression of streaks to assume the giant extensions seen in our patient. in future, it may be worthwhile to determine if there is any relationship between corticosteroid metabolism in the body and as. to conclude, as can rarely extend to the peripheral areas of the fundus and be a risk factor for not only central but peripheral vision threatening complications. role of steroids in aggravating disease progression needs to be further elucidated with larger series. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. marchese a, rabiolo a, corbelli e, carnevali a, cicinelli mv, giuffrè c, et al. ultra-widefield imaging in patients with angioid streaks secondary to pseudoxanthoma elasticum. ophthalmol retina 2017;1:137–144. 2. georgalas i, papaconstantinou d, koutsandrea c, kalantzis g, karagiannis d, georgopoulos g, et al. angioid streaks, clinical course, complications, and current therapeutic management. ther clin risk manag 2009;5:81. 3. mansour am. systemic associations of angioid streaks. int ophthalmol clin 1991;31:61–68. 4. clarkson jg, altman rd. angioid streaks. surv ophthalmol 1982;26:235–246. 5. marchese a, parravano m, rabiolo a, carnevali a, corbelli e, cicinelli mv, et al. optical coherence tomography analysis of evolution of bruch’s membrane features in angioid streaks. eye 2017;31:1600. 6. corbelli e, carnevali a, marchese a, cicinelli mv, querques l, sacconi r, et al. optical coherence tomography angiography features of angioid streaks. retina 2018;38:2128–2136. 7. hanhart j, greifner h, rozenman y. locating and characterizing angioid streaks with en face optical coherence tomography. retin cases brief rep 2017;11:203–206. 8. ellabban aa, tsujikawa a, matsumoto a, ogino k, hangai m, ooto s, et al. macular choroidal thickness and volume in eyes with angioid streaks measured by swept source optical coherence tomography. am j ophthalmol 2012;153:1133–1143. 9. mi l, zuo c, zhang x, liu b, peng y, wen f. fluorescein leakage within recent subretinal hemorrhage in pathologic myopia: suggestive of cnv? j ophthalmol 2018;2018. 10. hattersley at, meeran k, burrin j, hill p, shiner r, ibbertson hk. the effect of long-and short-term corticosteroids on plasma calcitonin and parathyroid hormone levels. calcif tissue int 1994;54:198–202. 11. samaha aa, nasser-eddine w, shatila e, haddad jj, wazne j, eid ah. multi-organ damage induced by anabolic steroid supplements: a case report and literature review. j med case rep 2008;2:340. 12. bento c, velho p, carvalho m. lots of steroids and vita244 journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 giant idiopathic angioid streaks; takkar et al mins, tons of complications. hypercalcemia and nephrocalcinosis as important complications of performanceenhancing drugs. nefrologia 2015;35:598–600. 13. wicke c, halliday b, allen d, roche ns, scheuenstuhl h, spencer mm, et al. effects of steroids and retinoids on wound healing. arch surg 2000;135:1265–1270. journal of ophthalmic and vision research volume 15, issue 2, april-june 2020 245 original article effects of oral vitamin d supplement therapy on clinical outcomes of intravitreal bevacizumab in diabetic macular edema saeed karimi1,2, md; vahid movafaghi1, md; amir arabi1,2, md; toktam shahraki1,2, md; sare safi3, phd 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2department of ophthalmology, torfeh medical center, shahid beheshti university of medicine sciences,tehran, iran 3ophthalmic epidemiology research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran orcid: saeed karimi: https://orcid.org/0000-0002-3231-8414 abstract purpose: to assess the effects of oral vitamin d supplement therapy on clinical outcomes of intravitreal bevacizumab (ivb) injections in patients with diabetic macular edema (dme). method: seventy-one patients with center-involving dme received ivb injections three times monthly. cases with serum 25-hydroxyvitamin d (25(oh)d) levels <30 ng/ml were divided into treatment and control groups. the treatment group received 50000 iu of oral vitamin d once a week for eight weeks. one month after the third ivb injection, changes in the best-corrected visual acuity (bcva) and central macular thickness (cmt) were analyzed for each group. results: thirty-seven patients had sufficient levels of 25 (oh) d, while 34 patients had insufficient levels. nineteen cases with deficient levels of 25(oh)d were treated with oral vitamin d, while 15 patients were assigned to the control group. the mean of serum 25(oh)d in patients was 27.9 ng/ml [mean 20.3 ± 5.4 and 17.3 ± 5.4 ng/ml in control and treatment groups, respectively (p = 0.231)]. after three ivb injections, bcva improved significantly in each group, but the difference between the study groups was not statistically significant. cmt decreased significantly in all the groups. the mean cmt reduction was more prominent in the vitamin d-treated group, but the difference between groups did not reach statistical significance (p = 0.29). conclusion: in dme patients with vitamin d deficiency, vitamin d supplement therapy had some beneficial effects on cmt reduction following three injections of ivb; nevertheless, these effects were not statistically significant. definite conclusion needs further prospective studies with a larger sample size. keywords: 25-hydroxyvitamin d; insufficiency; diabetic macular edema; intravitreal bevacizumab j ophthalmic vis res 2021; 16 (1): 34–41 correspondence to: saeed karimi, md. department of ophthalmology, torfeh medical center, shahid beheshti university of medical sciences, ibn sina st., baharestan sq., tehran 11498, iran. email: dr.saeedkarimi@gmail.com received: 09-01-2020 accepted: 14-06-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8249 introduction diabetic macular edema (dme) may develop in diabetic patients, independent of the severity this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: karimi s, movafaghi v, arabi a, shahraki t, safi s. effects of oral vitamin d supplement therapy on clinical outcomes of intravitreal bevacizumab in diabetic macular edema. j ophthalmic vis res 2021;16:34–41. 34 © 2021 karimi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8249&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr effects of vitamin d on the ivb injection outcomes; karimi et al of diabetic retinopathy (dr).[1] dme is the main cause of decreased vision in diabetic patients.[1] elevated levels of various inflammatory and angiogenic factors lead to serious damage of retinal vascular endothelial cells, and the consequent impairment of blood–retinal barrier (brb) causes fluid accumulation in the retinal tissue.[2] vitamin d is a well-known endocrine secosteroid which plays an essential role in many physiologic processes, including the control of cellular apoptosis and differentiation, as well as angiogenesis and metastasis potential of human cancer cells.[3–6] various cardiovascular, infectious, and autoimmune diseases have been revealed to be linked with vitamin d deficiency.[7] both the vitamin d activator enzyme (1-αhydroxylase ) and its receptor have been found in the retina,[8, 9] suggesting that 25(oh)d abnormal levels may participate in the development and progression of various retinal disorders, including dr. deficient serum 25(oh)d levels have been shown to be correlated with more advanced dr and its vision-threatening outcomes.[10, 11] in this study, we measured the serum vitamin d levels in patients scheduled to receive intravitreal bevacizumab (ivb) for dme. we investigated the influence of oral vitamin d supplement therapy on the outcomes of ivb injections in these patients. methods the current prospective comparative case series study was carried out between march 2017 and august 2018. the protocol was approved by the ethics committee of the ophthalmic research center at the shahid beheshti university of medical sciences and followed the declaration of helsinki. a written consent was obtained from all patients. one eye from each patient was enrolled in the study. a diagnosis of center-involving dme was made if the central macular thickness (cmt) (within central 1-mm of macula) was >300 μm on optical coherence tomography (oct) image (spectralis oct; heidelberg engineering, vista, ca). subjects were eligible for enrolment if bcva was between 20/40 and 20/320 according to the snellen chart in the eye enrolled in the study. the exclusion criteria were history of intravitreal anti-vegf injections in the last three months of enrolment, history of intraocular surgery other than uncomplicated cataract surgery, patients with proliferative dr, retinal vascular occlusions, glaucoma, a creatinine (cr) level > 3 mg/dl, thyroid and parathyroid diseases, liver disease or any other problem of vitamin d absorption, recent use of supplements containing vitamin d or 25(oh)d, use of medications with known effect on serum 25(oh)d levels such as anticonvulsants and corticosteroids, and serum 25(oh)d level ≤ 10 ng/ml. all patients were scheduled to receive ivb (avastin®, genentech/roche, ca, usa) three times monthly. all subjects underwent intravitreal injections at the torfeh eye hospital. ophthalmologists who performed the injections were masked to the groups. the study was performed during a single season to avoid variations in serum vitamin d levels due to seasonal exposures. before enrolment, all patients underwent complete ophthalmic examination. parameters including age, sex, bcva, and cmt were measured for each subject. on the day of first injection, venous blood specimen was analyzed for 25(oh)d, cr, and hba1c levels. patients with >30 ng/ml of 25-hydroxyvitamin d (25(oh)d) were considered as vitamin d-sufficient group. patients with <30 ng/ml were enrolled in the control group. the subjects were assigned to treatment groups on a random basis without considering the 25(oh)d levels. thus, we had three study groups: group 1 (vitamin d-sufficient group with serum vitamin d ≥ 30 ng/ml), group 2 (vitamin d-deficiency group treated with oral vitamin d supplement), and group 3 (vitamin d-deficiency control group). the treatment group received a pearl of vitamin d3 (d-vigel 50000 iu, daana pharmaceutical company, iran) once a week for eight consecutive weeks during the first two months of the ivb treatment period. fundus examination and oct imaging were repeated before any procedure. visual acuity measurements were obtained through snellen chart examination by a trained optometrist who was masked as to which group the patients were assigned to, and were converted to logmar values. severity of dr was determined by a single ophthalmologist using three field fundus photographs (optic disc centered, fovea centered, and centered on temporal edge of the macula), and was categorized according to the international dr severity scale.[12] ophthalmic evaluations were repeated one month after the journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 35 effects of vitamin d on the ivb injection outcomes; karimi et al third intravitreal injection. the mean changes in bcva and cmt from baseline to one month after the third injection were measured as primary and secondary outcomes, respectively. after the completion of the study protocol, patients of the control group were also treated with oral vitamin d supplement. to present data, mean and standard deviation were used. t-test was used for comparing serum vitamin d and hba1c between the groups, and the correlation between hba1c and vitamin d levels was evaluated by linear regression analysis. to evaluate the role of treatment on logmar and cmt changes, paired t-test analysis was used. the differences were considered as significant if pvalue was < 0.05 (figure 1). finally, to determine the adequacy of the sample size and the power of the study, a post-hoc analysis was performed. results eighty-three patients participated in the study. four patients were excluded due to urgent need for supplement therapy (vitamin d level < 10 ng/ml). eight patients (one patient from treatment group, five patients from control group, and two patients from sufficient group) did not complete the study. out of the 71 subjects analyzed at the end of study, 37 patients had sufficient levels of 25(oh)d, 19 had insufficient 25(oh)d and were treated with oral vitamin d supplement (treatment group), and 15 cases with insufficient 25(oh)d levels were enrolled as the control group. demographic characteristics and baseline parameters are summarized in table 1. the study groups were matched in terms of age, sex, and severity of dr (table 1). the average hba1c levels in the sufficient (n = 37) and the insufficient (n = 34) groups were 7.3% and 8.2%, respectively (p < 0.05, figure 1a). the difference of hba1c levels between the treatment and the control groups was not statistically significant (p > 0.05, 95% ci). the mean serum 25(oh)d level was 27.9 ng/ml and it did not show any statistical correlation with patients’ sex (p = 0.653). regression analysis showed that serum 25(oh)d levels had negative correlation with the hba1c levels (pearson’s correlation coefficient = –0.032) in all the patients. the p-value for the correlation was 0.007, showing a significant relationship (figure 2). the mean levels of serum 25(oh)d were 36.5 ± 6.7, 17.3 ± 5.4, and 20.3 ± 5.4 ng/ml in the sufficient group, the insufficient treatment group, and the insufficient control group, respectively (figure 1b). the mean 25(oh)d level was significantly higher in the sufficient group, while the difference between the control and the treatment groups was not statistically significant (p = 0.231, 95% ci) (table 1). the mean bcva values at the baseline were 0.51 ± 0.28, 0.48 ± 0.32, and 0.58 ± 0.25 logmar in the sufficient group, the insufficient treatment group, and the insufficient control group, respectively (p > 0.05, 95% ci). one month after the third ivb injection, bcva improved significantly in all the study groups. the mean changes in bcva were –0.13 ± 0.12, –0.15 ± 0.11, and –0.16 ± 0.17 logmar in the sufficient group, the insufficient treatment group, and the insufficient control group, respectively (p = 0.66). the mean changes in bcva were not significantly different between the study groups (table 2 and figure 3a). the mean cmt values were 517 ± 112 µm, 514 ± 105 µm, and 509 ±74 µm in the sufficient group, the insufficient treatment group, and the insufficient control group, respectively (p = 0.97, 95% ci). one month after the third ivb injection, the mean cmt decreased significantly in all the study groups. the mean cmt changes were –100 ± 97, –131 ± 67, and –91 ± 53 µm in the sufficient group, the insufficient treatment group, and the insufficient control group, respectively (p = 0.29). although the mean cmt decreased more in patients who received oral vitamin d supplement (–131 µm vs –100 µm and –91 µm), the difference was not statistically significant (p = 0.29, table 2 and figure 3b). post-hoc analysis showed that the sample size should be 41 in each group to find a significant difference (50 microns) in the changes of cmt to achieve the study power of 95%. however, the present study had a power of 60%. endophthalmitis or significant ocular or systemic complications were not observed. discussion we observed that vitamin d supplement therapy in the subset of diabetic patients with dme and insufficient levels of vitamin d could not improve the outcome of ivb therapy. according to our knowledge, this study was the first to investigate the effect of oral vitamin d supplement therapy on clinical outcomes of ivb injection in dme. 36 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 effects of vitamin d on the ivb injection outcomes; karimi et al figure 1. the mean hba1c (a) and vitamin d levels (b) in different study groups. figure 2. the correlation chart of vitamin d and hba1c levels. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 37 effects of vitamin d on the ivb injection outcomes; karimi et al figure 3. changes in visual acuity (a) and central retinal thickness (b) following ivb therapy. cmt, central macular thickness; logmar, logarithm of minimal angel resolution; ivb, intravitreal bevacizumab there is still a degree of uncertainty about the influence of serum vitamin d in occurrence, progression, and prognosis of dr. the controversy begins from the concept that serum vitamin d deficiency may not be correlated with a concurrent ocular deprivation. it is believed that the eye can produce vitamin d through exposure to ultraviolet light, and the brb can limit the transmission of vitamin d from blood to the eyes.[13, 14] accordingly, some authors have suggested that intraocular 25(oh)d levels may not depend on systemic 25(oh)d levels.[1] it has also been reported that the 1,25dihydroxycholecalciferol can upregulate the expression of the vegfs; it has been shown that the regulation of vegf promoter by vitamin d receptor increases the secretion of vegfs in vascular smooth muscles.[15, 16] a similar effect has not been established in retinal cells, however, this finding can hypothesize a correlation between high ocular vitamin d levels and high concentration of ocular vegfs.[1] previous studies have revealed paradoxical results about the relationship between the severity of dr and serum 25(oh)d levels. some authors have reported an inverse relationship,[10, 11, 17–19] while others have not shown such a correlation.[20, 21] a meta-analysis on the topic reported that those patients with dm type 2 and vitamin d deficiency have a higher risk of dr development compared to subjects with adequate levels of the vitamin.[22] on the other hand, a recent study performed by kim et al reported that patients with dme had a greater aqueous humor amounts of vitamin d than the patients without dme.[1] it should also be considered that studies on vitamin d levels encounter some challenges such as different cultural backgrounds as well as different 38 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 effects of vitamin d on the ivb injection outcomes; karimi et al table 1. demographic and clinical features factors levels total groups p-value sufficient insufficientcontrol insufficienttreatment insufficientcontrol and insufficienttreatment age mean ± sd 63 ± 8 65 ± 6 59 ± 8 64 ± 9 62 ± 9 0.076 median (range) 64 (40,84) 64 (52,84) 59 (45,74) 64 (40,84) 63 (40,84) sex male 37 (52.1%) 18 (48.6%) 7 (46.7%) 12 (63.2%) 19 (55.9%) 0.518 female 34 (47.9%) 19 (51.4%) 8 (53.3%) 7 (36.8%) 15 (44.1%) eye od 37 (52.1%) 22 (59.5%) 5 (33.3%) 10 (52.6%) 15 (44.1%) 0.252 os 34 (47.9%) 15 (40.5%) 10 (66.7%) 9 (47.4%) 19 (55.9%) dr npdr 32 (45.1%) 19 (51.4%) 5 (33.3%) 8 (42.1%) 13 (38.2%) 0.511 pdr 39 (54.9%) 18 (48.6%) 10 (66.7%) 11 (57.9%) 21 (61.8%) hba1c mean ± sd 7.7 ± 1.5 7.3 ± 1.6 7.9 ± 1.3 8.3 ± 1.1 8.2 ± 1.2 0.043 median (range) 7.6 (4.9,10.7) 6.7 (4.9,10.7) 8.2 (6.1,9.6) 8.1 (6.7,10.4) 8.1 (6.1,10.4) vitamin d (μg) mean ± sd 27.9 ± 10.8 36.5 ± 6.7 20.3 ± 5 17.3 ± 5.4 18.6 ± 5.4 <0.001 median (range) 31 (5,66.3) 34.2 (31,66.3) 22 (10,26.2) 18 (5,27) 19.5 (5,27) dr, diabetic retinopathy; npdr, nonproliferative diabetic retinopathy; od, right eye; os, left eye; pdr, proliferative diabetic retinopathy; hba1c, hemoglobin a1c; sd, standard deviation table 2. best-corrected visual acuity changes after three intravitreal bevacizumab injections bcva (logmar) total groups p-value sufficient insufficient-control insufficient-treatment baseline 0.51 ± 0.28 0.5 ± 0.28 0.58 ± 0.25 0.48 ± 0.32 0.587 final f/u 0.37 ± 0.24 0.38 ± 0.24 0.42 ± 0.24 0.33 ± 0.23 0.554 change –0.14 ± 0.13 –0.13 ± 0.12 –0.16 ± 0.17 –0.15 ± 0.11 0.659 p-value <0.001 0.002 <0.001 cmt (µm) baseline 514 ± 102 517 ± 112 509 ± 74 514 ± 105 0.97 final f/u 408 ± 96 417 ± 111 417 ± 61 383 ± 87 0.42 change –106± 83 –100± 97 –91± 53 –131± 68 0.29 p-value <0.001 <0.001 <0.001 bcva, best-corrected visual acuity; f/u, follow-up; cmt, central macular thickness clothing and diet styles. vitamin d in the body can be supplied both from dietary sources and from synthesis in the skin. accordingly, it is difficult to control the dietary, environmental, seasonal, and cultural factors, in addition to predict serum vitamin d levels through single measurement, which can cause inconclusive results. since the prior studies have not resulted in an exact conclusion about vitamin d and its role in dr, we investigated the treatment of dme with an anti-vegf agent, bevacizumab, in the presence of vitamin d deficiency. we also tested the role of concurrent vitamin d3 therapy in optimizing the ivb therapy for dme. we found that the concurrent vitamin d supplement therapy in this subset of patients did not significantly improve the outcomes of ivb in dme cases with vitamin d deficiency. although improvement in journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 39 effects of vitamin d on the ivb injection outcomes; karimi et al bcva and decrease in cmt was more prominent in the treatment group, the difference between the control and the treatment groups was not statistically significant. future studies on larger group of patients may reveal an association between vitamin d supplementation and improved outcomes of ivb injections in dme patients. we found a negative correlation between hba1c levels and serum 25(oh)d, implying that patients with 25(oh)d deficiency had a higher rate of uncontrolled hyperglycemia. this finding may be in accordance with prior reports regarding the correlation of vitamin d deficiency with poor glycemic control and dr severity.[22] it has been postulated that vitamin d may improve insulin secretion, stimulate insulin receptor, and improve glucose uptake in type 2 diabetes.[9, 23] according to these assumptions, vitamin d may improve insulin resistance. however, it should be proven in experimental studies. a small sample size in addition to the lack of a control for those habits and restrictions which may affect vitamin d storage in the body are the main limitations of the present study. although vitamin d deficiency was treated according to the standard protocol, effectiveness of vitamin d supplement therapy was not assessed at the end of the study. short-term follow-up could also be considered as another limitation of the present study; however, longer follow-up was not possible due to the ethical issues. in conclusion, we observed a negative correlation between hba1c and 25(oh)d levels. although vitamin d supplement therapy, added to ivb therapy, had some beneficial effects in terms of cmt reduction in dme patients with 25(oh)d deficiency, we could not find any statistically significant effect of the adjunctive therapy on the functional and anatomical outcomes of these patients. further studies are required to investigate the effect of d3 supplement therapy on optimizing the treatment of patients with dr. financial support and sponsorship none. conflicts of interest the authors have no conflicts of interest to declare. references 1. kim kl, moon sy, noh hm, park sp, kim yk. serum and aqueous humor vitamin d levels in patients with diabetic macular edema. graefes arch clin exp ophthalmol 2019;257:1191–1198. 2. romero-aroca p, baget-bernaldiz m, pareja-rios a, lopezgalvez m, navarro-gil r, verges r. diabetic macular edema pathophysiology: vasogenic versus inflammatory. j diabetes res 2016;2016:2156273. 3. diaz gd, paraskeva c, thomas mg, binderup l, hague a. apoptosis is induced by the active metabolite of vitamin d3 and its analogue eb1089 in colorectal adenoma and carcinoma cells: possible implications for prevention and therapy. cancer res 2000;60:2304–2312. 4. jeong y, swami s, krishnan av, williams jd, martin s, horst rl, et al. inhibition of mouse breast tumor-initiating cells by calcitriol and dietary vitamin d. mol cancer ther 2015;14:1951–1961. 5. scaglione-sewell ba, bissonnette m, skarosi s, abraham c, brasitus ta. a vitamin d3 analog induces a g1-phase arrest in caco-2 cells by inhibiting cdk2 and cdk6: roles of cyclin e, p21waf1, and p27kip1. endocrinology 2000;141:3931–3939. 6. iseki k, tatsuta m, uehara h, iishi h, yano h, sakai n, et al. inhibition of angiogenesis as a mechanism for inhibition by 1alpha-hydroxyvitamin d3 and 1,25-dihydroxyvitamin d3 of colon carcinogenesis induced by azoxymethane in wistar rats. int j cancer 1999;81:730–733. 7. holick mf. vitamin d: importance in the prevention of cancers, type 1 diabetes, heart disease, and osteoporosis. am j clin nutr 2004;79:362–371. 8. lin y, ubels jl, schotanus mp, yin z, pintea v, hammock bd, et al. enhancement of vitamin d metabolites in the eye following vitamin d3 supplementation and uv-b irradiation. curr eye res 2012;37:871–878. 9. albert dm, scheef ea, wang s, mehraein f, darjatmoko sr, sorenson cm, et al. calcitriol is a potent inhibitor of retinal neovascularization. invest ophthalmol vis sci 2007;48:2327–2334. 10. alcubierre n, valls j, rubinat e, cao g, esquerda a, traveset a, et al. vitamin d deficiency is associated with the presence and severity of diabetic retinopathy in type 2 diabetes mellitus. j diabetes res 2015;2015:374178. 11. he r, shen j, liu f, zeng h, li l, yu h, et al. vitamin d deficiency increases the risk of retinopathy in chinese patients with type 2 diabetes. diabet med 2014;31:1657– 1664. 12. wilkinson cp, ferris f, klein r, lee p, agardh c, davis m, et al. proposed international clinical diabetic retinopathy and diabetic macular edema disease severity scales. ophthalmology 2003;110:1677–1682. 13. jordan j, ruiz-moreno jm. advances in the understanding of retinal drug disposition and the role of blood-ocular barrier transporters. expert opin drug metab toxicol 2013;9:1181–1192. 14. yin z, pintea v, lin y, hammock bd, watsky ma. vitamin d enhances corneal epithelial barrier function. invest ophthalmol vis sci 2011;52:7359–7364. 40 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 effects of vitamin d on the ivb injection outcomes; karimi et al 15. cardus a, panizo s, encinas m, dolcet x, gallego c, aldea m, et al. 1,25-dihydroxyvitamin d3 regulates vegf production through a vitamin d response element in the vegf promoter. atherosclerosis 2009;204:85–89. 16. cardus a, parisi e, gallego c, aldea m, fernandez e, valdivielso jm. 1,25-dihydroxyvitamin d3 stimulates vascular smooth muscle cell proliferation through a vegfmediated pathway. kidney int 2006;69:1377–1384. 17. millen ae, sahli mw, nie j, lamonte mj, lutsey pl, klein be, et al. adequate vitamin d status is associated with the reduced odds of prevalent diabetic retinopathy in african americans and caucasians. cardiovasc diabetol 2016;15:128. 18. patrick pa, visintainer pf, shi q, weiss ia, brand da. vitamin d and retinopathy in adults with diabetes mellitus. arch ophthalmol 2012;130:756–760. 19. payne jf, ray r, watson dg, delille c, rimler e, cleveland j, et al. vitamin d insufficiency in diabetic retinopathy. endocr pract 2012;18:185–193. 20. alam u, amjad y, chan aw, asghar o, petropoulos in, malik ra. vitamin d deficiency is not associated with diabetic retinopathy or maculopathy. j diabetes res 2016;2016:6156217. 21. bonakdaran s, shoeibi n. is there any correlation between vitamin d insufficiency and diabetic retinopathy? int j ophthalmol 2015;8:326–331. 22. luo ba, gao f, qin ll. the association between vitamin d deficiency and diabetic retinopathy in type 2 diabetes: a meta-analysis of observational studies. nutrients 2017;9:307. 23. mitri j, muraru m, pittas ag. vitamin d and type 2 diabetes: a systematic review. eur j clin nutr 2011;65:1005–1015. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 41 original article water-drinking test and pharmacologic mydriasis as provocative tests in primary angle closure suspects reza razeghinejad1,2, md; m. hossein nowroozzadeh2, md 1glaucoma service, wills eye hospital, philadelphia, pa, usa 2poostchi ophthalmology research center, shiraz university of medical sciences, shiraz, iran orcid: reza razeghinejad: https://orcid.org/0000-0001-7961-8425 m. hossein nowroozzadeh: https://orcid.org/0000-0002-7412-1900 abstract purpose: to compare the water-drinking test (wdt) and pharmacologic mydriasis as provocative tests in patients with primary angle closure suspect (pacs). methods: this observational non-randomized comparative study evaluated changes in intraocular pressure (iop) in 21 patients with pacs who underwent pharmacologic mydriasis and compared it with iop changes in 26 patients given the wdt. ocular biometric and anterior chamber parameters were also assessed. tests were repeated on the same patient two weeks after performing laser peripheral iridotomy (lpi). results: the mean age ± standard deviation was 60 ± 7 and 57 ± 9 years in the mydriasis and wdt groups, respectively (p = 0.201). before lpi, both provocative tests were associated with a significant increase in iop (mydriasis: 15.1 ± 3.1 to 16.6 ± 3.5 mmhg, p = 0.025; wdt: 16.2 ± 2.8 to 18.5 ± 3.3 mmhg, p < 0.001). however, the iop changes were not statistically different between groups (p = 0.102). after lpi, only the wdt group showed a continued significant iop elevation after the test (mydriasis: 16.4 ± 3.3 to 16.7 ± 3.5 mmhg, p = 0.569; wdt: 14.9 ± 3.0 to 17.8 ± 4.1 mmhg, p < 0.001). the post-test iop change was significantly greater in the wdt than in the mydriasis group (3.0 versus 0.3 mmhg, respectively; p = 0.002). step-wise multiple regression analysis verified the type of provocative test as the only independent factor affecting the post-test iop change after lpi (regression coefficient: 2.664; p = 0.002). conclusion: pharmacologic mydriasis and the wdt had similar iop elevation before lpi, but after lpi, iop elevation was much greater in the wdt group. keywords: intraocular pressure; pharmacologic mydriasis; primary angle closure suspect; water-drinking test j ophthalmic vis res 2019; 14 (3): 267–274 correspondence to: m. hossein nowroozzadeh, md. poostchi ophthalmology research center, poostchi clinic, zand st., shiraz 71349, iran. e-mail: nowroozzadeh@hotmail.com received: 04-02-2018 accepted: 05-09-2018 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i3.4782 introduction primary angle closure glaucoma (pacg) is believed to be one of the leading causes of irreversible blindness with approximately 20 million people experiencing pacg worldwide.[1–3] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: razeghinejad r, nowroozzadeh mh. water-drinking test and pharmacologic mydriasis as provocative tests in primary angle closure suspects. j ophthalmic vis res 2019;14:267–274 @ 2019 j  o  v r | published by knowledge e 267 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i3.4782&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr water-drinking test and mydriasis in pacs; razeghinejad and nowroozzadeh the spectrum of angle closure disease includes a narrow angle with 180° or more of iridotrabecular apposition (primary angle closure suspect [pacs]), a narrow angle with increased intraocular pressure (iop) or peripheral anterior synechiae (primary angle closure, [pac]), and pac with optic neuropathy or pacg.[4] it has been reported that approximately 10% of pacs patients eventually develop glaucoma.[2] while there is some evidence that a prophylactic laser peripheral iridotomy (lpi) significantly reduces the risk of angle closure glaucoma in the contralateral eye of an individual with angle closure glaucoma, there is much confusion regarding the need for a prophylactic lpi for patients with asymptomatic narrow angles detected through gonioscopy. although lpi is an effective preventive therapy, we must consider the large number of candidates involved and the burden and cost of treating ten-folds for each eye that receives an actual benefit. therefore, identifying pacs eyes that would benefit from lpi through appropriate imaging or provocative tests is desirable. various provocative tests including the dark-room provocative test and pharmacologic mydriasis have been used to identify narrow angle eyes at risk of angle closure.[5] pharmacologic or dark-induced mydriasis leads to a relative pupillary block and increased iridotrabecular contact. the prone position in the dark room test may induce forward movement of the lens and enhance the effect of the relative pupillary block.[6] however, this provocative test has a low sensitivity and positive predictive value in detecting eyes susceptible to angle closure glaucoma.[7] therefore, we need to identify more appropriate provocative tests to determine pacs patients with the greatest risk of pacg and learn more about the mechanism of angle closure formation. the water-drinking test (wdt) is used as a provocative test for assessing the outflow facility of aqueous humor in patients with primary openangle glaucoma. choroidal expansion is a suggested mechanism of iop elevation in wdt.[8, 9] choroidal expansion has also been suggested as one of the mechanisms involved in pacg development.[10] the expansion of the choroid after wdt could push the iris-lens diaphragm forward and result in a decrease in anterior chamber volume.[8, 11] therefore, this test has the potential to be a provocative test in pacs. this study aimed to evaluate the changes in the iop, ocular biometric, and anterior chamber parameters in pacs patients who underwent wdt or pharmacologic mydriasis, before and after lpi. methods this observational non-randomized comparative study enrolled 47 consecutive patients with pacs who were referred to the glaucoma clinic of a tertiary eye care center. the first 21 referred patients received the pharmacologic mydriasis test and the next 26 patients underwent wdt. all procedures performed in this study were in accordance with the 1964 helsinki declaration and its later amendments. the study was approved by the local ethics committee and informed consent was obtained from all patients. the patients underwent a comprehensive ophthalmologic examination including slit lamp biomicroscopy, goldmann applanation tonometry (haag streit ag, bern, switzerland), indentation gonioscopy using a sussman 4-mirror gonio lens (volk optical inc., mentor, oh, usa), and stereoscopic assessment of the optic disc with a 90 diopter lens (volk optical inc., mentor, oh, usa). subjects were classified as pacs if they presented ≥ 180𝑜 of iridotrabecular contact, without peripheral anterior synechiae in indentation gonioscopy, glaucomatous optic neuropathy, or iop > 22 mmhg.[12] the exclusion criteria consisted of a history of ocular trauma, prior intraocular or refractive surgery, any intraocular disorder except cataract, secondary angle closure glaucoma, evidence of active keratitis or cornel pathology precluding gonioscopy and fundus examination, and the use of miotics or anticholinergics, pregnancy, hypertension, cardiac or kidney diseases, history of urinary retention, or inability to cooperate with any of the study measurements. water-drinking test (wdt) to perform the wdt, the patients refrained from food and fluid intake for three hours preceding the test. patients were instructed to drink one liter of bottled water within five minutes. all wdts were performed between 12 to 2 pm. the original wdt developed for primary open angle glaucoma detection and the majority of recent studies assessing the effect of wdt on iop fluctuation used one liter of water for this purpose.[13–16] therefore, we opted to use one liter instead of the 10–15 ml/kg 268 j  o  v r volume 14, issue 3, july–september 2019 water-drinking test and mydriasis in pacs; razeghinejad and nowroozzadeh reported by other studies. the measurements were obtained at baseline and at 30 minutes after drinking the water.[8] the patients then underwent lpi using a commercial ophthalmic nd: yag laser system (nidek yc-1800, nidek inc., japan) one week after the wdt. the laser parameters were as follows: one pulse with a power of 4–6 mj performed approximately 30 minutes after applying one drop of 2% pilocarpine eye drops.[17] two weeks after lpi, all measurements were repeated before and after 30 minutes of wdt. mydriasis test the measurements were obtained before and after the induction of pharmacologic mydriasis. in order to eliminate any possible effects of cycloplegic agents on the ciliary muscles and lens position, mydriasis was achieved with phenylephrine 5% drops applied every five minutes for a total of two applications. lpi was performed the week following the mydriasis test. all measurements were repeated before and after mydriasis, two weeks after lpi. measurements the main outcome measure was iop change after the tests. an increase in iop of ≥ 6 mmhg from baseline was considered a positive result on both provocative tests.[18] secondary outcomes were refraction ocular biometric parameters obtained using lenstar ls 900 (haag-streit ag, koeniz, switzerland) and pentacam hr (oculus, wetzlar, germany) optical biometers. the following parameters were collected from the lenstar biometer: mean keratometry (km), keratometric astigmatism (ka), central corneal thickness (cct), axial length (al), and lens thickness (lt). the pentacam hr was used to obtain km, central anterior chamber depth (acd; from the endothelium to the anterior lens surface), anterior chamber volume, and inferior anterior chamber angle. the following factors were calculated from the lenstar recordings: lens-axial length factor [laf = (lt/al) × 10]; lens position (lp = acd + 0.5 × lt); and relative lens position [rlp = (lp/al) × 10]. each instrument was calibrated at the beginning of the study, and at regular intervals afterward (as per manufacturer’s recommendations). all measurements were performed by the same experienced investigator using the criteria provided by the manufacturer of each device. statistical analysis ibm spss statistics software version 21 (spss inc., chicago, il) and medcalc version 12.2.1 (medcalc software, mariakerke, belgium) were used for statistical analyses. data from one eye of each patient, chosen at random, were included in the analysis. descriptive data were presented as mean (± standard deviation). the normality of data was assessed using the kolmogorov-smirnov test. the paired-samples t-test (or its nonparametric counterpart, the wilcoxon-signed rank test) was used to compare data before and after each test. the independent-sample t-test (or mann-whitney u test) was used to compare post-test changes between different groups. linear regression analysis was used to evaluate the effects of different parameters on the test results. a p-value of less than 0.05 was considered statistically significant. results data from 21 pacs patients in the pharmacologic mydriasis group were compared with 26 patients in the wdt group. table 1 summarizes the baseline characteristics of patients in each group. before lpi, both provocative tests were associated with a significant iop elevation (table 2). iop elevation in the wdt group was almost twice of the mydriasis group (2.4 versus 1.3); however, the difference was not statistically significant. following lpi, the wdt group had a significant increase in iop after the test, while the pharmacologic mydriasis group did not [table 2; figure 1]. the post-lpi wdt iop-change was significantly greater in the wdt than the mydriasis group (3.0 versus 0.3 mmhg, respectively; p = 0.002). before lpi, two (7.6%) patients in the wdt and one (4.7%) in the mydriasis group had positive test results (≥ 6 mmhg increase in iop), but after lpi, seven (26.9%) patients in the wdt group and none of the patients in the mydriasis group had positive test results (𝑃 = 0.01; chi-square test). there were no significant differences in biometric parameters for both tests before and after lpi (data not shown). because the two studied groups were not similar in terms of sex and refraction, we conducted a linear regression analysis to assess j  o  v r volume 14, issue 3, july–september 2019 269 water-drinking test and mydriasis in pacs; razeghinejad and nowroozzadeh table 1. baseline characteristics of patients suspected of primary angle closure that underwent provocative testing with either the pharmacologic mydriasis or water-drinking test provocative test pharmacologic mydriasis water-drinking test p-value number 21 26 age, years 60 ± 7 57 ± 9 0.201 sex, m/f 4/17 22/4 < 0.001 spherical equivalent of refraction, d 1.3 ± 1.2 0.6 ± 1.0 0.036 axial length, mm 22.5 ± 0.6 22.4 ± 0.8 0.731 anterior chamber depth, mm 2.20 ± 0.21 2.24 ± 0.24 0.579 anterior chamber volume, 𝜇m3 88.2 ± 13.7 94.3 ± 17.6 0.200 anterior chamber angle, degrees 25.6 ± 7.0 28.2 ± 5.5 0.167 central corneal thickness, 𝜇m 527 ± 35 535 ± 28 0.426 mean keratometry, d 44.6 ± 1.2 44.7 ± 1.7 0.736 d, diopter; f, female; m, male; mm, millimeter; 𝜇m, micrometer table 2. comparison of pharmacologic mydriasis and water-drinking tests as provocative tests in patients suspected of primary angle closure before and after laser peripheral iridotomy iop (mmhg) before laser peripheral iridotomy before test after test p-value changes* pharmacologic mydriasis 15.1 ± 3.1 16.6 ± 3.5 0.025 1.3 ± 2.2 water-drinking test 16.2 ± 2.8 18.5 ± 3.3 < 0.001 2.4 ± 2.1 p-value 0.102 iop (mmhg) after laser peripheral iridotomy pharmacologic mydriasis 16.4 ± 3.3 16.7 ± 3.5 0.569 0.3 ± 2.5 water-drinking test 14.9 ± 3.0 17.8 ± 4.1 < 0.001 3.0 ± 2.9 p-value 0.002 *defined as: post-test iop – pre-test iop iop, intraocular pressure the effects of different factors on the post-test iop changes after lpi (table 3). in simple regression analysis, sex, and the type of the provocative test appeared to be associated with the observed posttest iop changes after lpi (p < 0.1). figure 2 shows the effects of sex on iop changes after provocative tests were performed before and after lpi. sex had no significant association with iop changes either before or after lpi (mann-whitney u test). in line with this finding, step-wise multiple regression analysis showed that the sex had no independent effect, and the type of the provocative test was the only independent factor affecting the post-test iop changes after lpi (regression coefficient: 2.664; p = 0.002). discussion our results showed that the amount of iop elevation after pharmacologic mydriasis was less than wdt-iop elevation before and after lpi. there was no statistically significant difference between the pharmacologic mydriasis and wdt groups in terms of iop elevation before lpi, but after lpi, the increase in iop was statistically significantly greater in the wdt group. after lpi, the iop changes were lower in the mydriasis group compared with 270 j  o  v r volume 14, issue 3, july–september 2019 water-drinking test and mydriasis in pacs; razeghinejad and nowroozzadeh table 3. regression analysis of possible factors affecting iop change after provocative tests of water-drinking test and pharmacologic mydriasis in patients with primary angle closure suspect after laser peripheral iridotomy factors simple linear regression multiple regression p-value coefficient p-value age 0.332 sex 0.094* test (wdt vs. pharmacologic mydriasis) 0.002* 2.664 0.002 baseline iop 0.225 se refraction 0.359 anterior chamber depth 0.406 anterior chamber volume 0.301 anterior chamber angle 0.278 axial length 0.565 central corneal thickness 0.814 mean keratometry 0.118 *factors with p-value less than 0.1 were entered into a multiple stepwise regression model iop, intraocular pressure; se, spherical equivalent; wdt, water-drinking test figure 1. comparison of intraocular pressure (iop) changes after the water-drinking test (wdt) and pharmacologic mydriasis in primary angle closure suspect patients before and after laser peripheral iridotomy (lpi). before lpi measurements, while the iop changes were greater in the wdt group in measurements obtained after lpi than before lpi. after lpi, the iop changes in the mydriasis group were lower than before lpi (1.3 versus 0.3 mmhg), while the differences were greater in the wdt group (2.4 versus 3.00 mmhg). moreover, there was a greater number of patients with positive wdt test results after lpi compared to before lpi. the lower post-lpi iop change in the mydriasis group could be attributed to the resolution of the pupillary block component of iop elevation. a higher change in wdt-iop after lpi compared to before lpi has been reported previously in pacs patients.[19] the wdt-iop elevation mechanisms may not be dependent on the pupillary block, but it is directly associated with the outflow capability of aqueous humor. in a previous study, in 16 out of 18 eyes subjected to argon laser iridotomy, there was evidence of decreased trabecular outflow after lpi in tonography.[20] the decreased outflow may be explained by the possibility of damage from pigment release and inflammation after lpi to the already somehow impaired trabecular meshwork function due to the long-term apposition to the iris. the wdt is a stress test that was initially developed to screen for open-angle glaucoma; however, its diagnostic capabilities showed that the wdt lacked the sensitivity and specificity needed to be a reliable screening test. currently, the wdt is used to evaluate the aqueous outflow facility and the efficacy of surgical and medical glaucoma management, in addition to predicting the diurnal iop peak.[21, 22] sympathetic stimulation via yet-tobe-determined mechanisms has been suggested to be responsible for the wdt-iop elevation.[23] increased iris thickness, owing to sympathetic j  o  v r volume 14, issue 3, july–september 2019 271 water-drinking test and mydriasis in pacs; razeghinejad and nowroozzadeh figure 2. effect of sex on intraocular pressure (iop) changes after the water-drinking test (wdt) and pharmacologic mydriasis in primary angle closure suspect patients before and after laser peripheral iridotomy (lpi). stimulation of the iris dilator muscle and its resulting circumferential folding, may prompt angle closure in patients with narrow angle glaucoma. moreover, a significant increase in choroidal thickness and iop elevation and a decrease in anterior chamber depth after wdt have been observed in angle closure but not in open angle eyes.[8] the lack of any changes in the ocular biometric parameters in our patients of both groups is in line with other studies on the angle closure patients.[24–27] in a group of fellow eyes of 21 patients with acute primary angle closure and in 17 patients with pacg, the acd did not change following wdt.[26] the study by poon et al on pacg and primary openangle glaucoma revealed no association between wdt-iop changes and anterior chamber depth and axial length.[25] in a study on patients with pacs, pac, and pacg, the positive dark room and mydriasis tests were defined as an increase in iop of 6 mmhg. there was no difference in the anterior chamber depth between positive and negative testers (1.95 versus 1.89 mmhg, p = 0.3) with the dark room test, but it was shallower in the patients with a positive mydriasis test (1.77 versus 1.96 mmhg, p = 0.010). this difference could have resulted from the limited number of patients in each subgroup because the suggested mechanisms underlying both tests are similar.[27] in a study on pacs patients, no changes in ocular biometric or anterior chamber parameters including iridocorneal angle after peripheral iridotomy and/or pharmacologic mydriasis except for increments in anterior chamber volume were observed.[24] the mechanisms involved in wdt-iop elevation are still unknown and may be different in open and closed angle eyes. the resolution of the pupillary block after lpi and the lower iop elevation observed following pharmacologic mydriasis and the greater iop elevation with wdt may exclude the possibility of the pupillary block as the main mechanism of wdt-iop elevation in patients with closed angle eyes. long-term follow-up of patients for iop elevation may clarify the role of wdt in this group of patients. although it has been suggested that lpi be performed for narrow angles that fulfill the criteria of pacs, the decision of which subjects require prophylactic lpi remains highly subjective. it has been estimated that approximately one out of ten patients with anatomically narrow angles develop angle closure,[28] therefore, the option of treating all patients with narrow angles would result in a large majority undergoing unnecessary procedures and a waste of resources. there is a great demand to develop a test that could identify pacs likely to progress to pac. it has been suggested that angle closure may often be caused by other mechanisms, which would not be resolved by an iridotomy, such as peripheral iris crowding, a plateau iris or lens-related angle closure, and other unknown mechanisms.[29] interestingly, it has been reported that the extent of pas did not correlate with the rise in iop seen on provocative tests such as the dark room test, pharmacologic mydriasis, and the valsalva test in patients with pac.[18] parameters identifying eyes that continue to develop angle closure after an iridotomy would lead to better 272 j  o  v r volume 14, issue 3, july–september 2019 water-drinking test and mydriasis in pacs; razeghinejad and nowroozzadeh management of pac. although lpi is claimed to prevent pacs progression to pac or pacg, it is not guaranteed, as some patients progress despite successful lpi. iop elevation after wdt, but not after pharmacologic mydriasis, probably involves mechanisms other than pupillary block. limitations of our study include the relatively small sample size; thus our results require validation in future studies involving more patients. in addition, inherent variability of iop measurements because of diurnal changes and device repeatability issues might affect the results. we limited iop measurements to the same time frame on each day to minimize the confounding effects. another limitation is the lack of angle grading information. because the purpose of this study did not include the evaluation of angles before and after the lpi, we did not include the gonioscopy grading. however, patients in both groups had similar anterior chamber depth, anterior chamber angle width, anterior chamber volume, and axial length, which could indicate a lack of notable differences in angle configuration between the two groups. performing pharmacologic mydriasis before lpi may be regarded as an ethical limitation of the current study as it may induce an acute angle closure attack. none of the eyes in our study developed an acute attack during the tests and the iops prior to and following the lpi were very similar. diagnostic mydriasis appears to be relatively safe in patients with narrow angle. the risk of acute angle closure attack after pupillary dilation has been reported to be 0.03–0.3%.[30, 31] moreover, in a study in the uk, 81% of ophthalmologists doing provocative testing for pacs patients used pupillary dilation and only 15% used the dark room provocative test.[32] nevertheless, we explained the risks of the test to all patients. finally, there was a difference in the sex ratio between both groups, but in the multiple regression analysis, the only determinant factor affecting the iop changes of the provocative tests were the tests. another limitation could be the lack of long-term follow-up of the patients and the correlation of the final glaucoma status with the initial test results; however, conducting such a study would be difficult to execute. in conclusion, both pharmacologic mydriasis and wdt resulted in iop elevation before lpi, but after lpi the iop elevation was greater in the wdt group, which could be explained by the resolution of the pupillary block and consequently the lower iop elevation in the pharmacologic mydriasis group. the mechanism of iop elevation of wdt does not seem to be related to the biometric changes observed in pacs patients. pharmacologic mydriasis and wdt may involve different mechanisms for iop elevation, which may have the potential to advance our understanding about the mechanism of angle-closure glaucoma. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. quigley ha, broman at. the number of people with glaucoma worldwide in 2010 and 2020. br j ophthalmol 2006;90:262–267. 2. foster pj, oen ft, machin d, ng tp, devereux jg, johnson gj, et al. the prevalence of glaucoma in chinese residents of singapore: a cross-sectional population survey of the tanjong pagar district. arch ophthalmol 2000;118:1105–1111. 3. quigley ha. glaucoma. lancet 2011;377:1367–1377. 4. sihota r. classification of primary angle closure disease. curr opin ophthalmol 2011;22:87–95. 5. tornquist r. dark-room test on eyes with a shallow anterior chamber. acta ophthalmol (copenh) 1958;36:664–671. 6. kondo t, miyazawa d, unigame k, kurimoto y. ultrasound biomicroscopic findings in humans with shallow anterior chamber and increased intraocular pressure after the prone provocation test. am j ophthalmol 1997;124:632– 640. 7. wilensky jt, kaufman pl, frohlichstein d, gieser dk, kass ma, ritch r, et al. follow-up of angle-closure glaucoma suspects. am j ophthalmol 1993;115:338–346. 8. arora ks, jefferys jl, maul ea, quigley ha. choroidal thickness change after water drinking is greater in angle closure than in open angle eyes. invest ophthalmol vis sci 2012;53:6393–6402. 9. de moraes cg, reis as, cavalcante af, sano me, susanna r jr. choroidal expansion during the water drinking test. graefes arch clin exp ophthalmol 2009;247:385–389. 10. quigley ha. what’s the choroid got to do with angle closure? arch ophthalmol 2009;127:693–694. 11. quigley ha. angle-closure glaucoma-simpler answers to complex mechanisms: lxvi edward jackson memorial lecture. am j ophthalmol 2009;148:657–669. 12. razeghinejad mr, myers js. contemporary approach to the diagnosis and management of primary angle-closure disease. surv ophthalmol 2018;63:754–768. 13. leydhecker w. the water-drinking test. br j ophthalmol 1950;34:457–479. j  o  v r volume 14, issue 3, july–september 2019 273 water-drinking test and mydriasis in pacs; razeghinejad and nowroozzadeh 14. leighton da, phillips ci, gibbs ac. provocative outflow test. combining water drinking and homatropine. br j ophthalmol 1970;54:19–26. 15. kumar rs, de guzman mh, ong py, goldberg i. does peak intraocular pressure measured by water drinking test reflect peak circadian levels? a pilot study. clin exp ophthalmol 2008;36:312–315. 16. vasconcelos-moraes cg, susanna r jr. correlation between the water drinking test and modified diurnal tension curve in untreated glaucomatous eyes. clinics (sao paulo) 2008;63:433–436. 17. esmaeili a, barazandeh b, ahmadi s, haghi a, ahmadi hosseini sm, abolbashari f. assessment of the anterior chamber parameters after laser iridotomy in primary angle close suspect using pentacam and gonioscopy. int j ophthalmol 2013;6:680–684. 18. sihota r, rishi k, srinivasan g, gupta v, dada t, singh k. functional evaluation of an iridotomy in primary angle closure eyes. graefes arch clin exp ophthalmol 2016;254:1141–1149. 19. waisbourd m, savant sv, sun y, martinez p, myers js. water-drinking test in primary angle-closure suspect before and after laser peripheral iridotomy. clin exp ophthalmol 2016;44:89–94. 20. karmon g, vender t, savir h. evaluation of laser iridectomy in angle-closure glaucoma: provocative tests. br j ophthalmol 1982;66:471–473. 21. danesh-meyer hv, papchenko t, tan yw, gamble gd. medically controlled glaucoma patients show greater increase in intraocular pressure than surgically controlled patients with the water drinking test. ophthalmology 2008;115:1566–1570. 22. medeiros fa, pinheiro a, moura fc, leal bc, susanna r jr. intraocular pressure fluctuations in medical versus surgically treated glaucomatous patients. j ocul pharmacol ther 2002;18:489–498. 23. venugopal n. water drinking test and angle closure glaucoma. indian j ophthalmol 2015;63:172. 24. razeghinejad mr, lashkarizadeh h, nowroozzadeh mh, yazdanmehr m. changes in ocular biometry and anterior chamber parameters after pharmacologic mydriasis and peripheral iridotomy in primary angle closure suspects. j optom 2016;9:189–195. 25. poon yc, teng mc, lin pw, tsai jc, lai ic. intraocular pressure fluctuation after water drinking test in primary angle-closure glaucoma and primary open-angle glaucoma. indian j ophthalmol 2016;64:919–923. 26. nongpiur me, foo vh, de leon jm, baskaran m, tun ta, husain r, et al. evaluation of choroidal thickness, intraocular pressure, and serum osmolality after the water drinking test in eyes with primary angle closure. invest ophthalmol vis sci 2015;56:2135–2143. 27. yamada r, hirose f, matsuki t, kameda t, kurimoto y. comparison of mydriatic provocative and dark room prone provocative tests for anterior chamber angle configuration. j glaucoma 2016;25:482–486. 28. wang n, wu h, fan z. primary angle closure glaucoma in chinese and western populations. chin med j (engl) 2002;115:1706–1715. 29. yeung by, ng pw, chiu ty, tsang cw, li fc, chi cc, et al. prevalence and mechanism of appositional angle closure in acute primary angle closure after iridotomy. clin exp ophthalmol 2005;33:478–482. 30. wolfs rc, grobbee de, hofman a, de jong pt. risk of acute angle-closure glaucoma after diagnostic mydriasis in nonselected subjects: the rotterdam study. invest ophthalmol vis sci 1997;38:2683–2687. 31. patel kh, javitt jc, tielsch jm, street da, katz j, quigley ha, et al. incidence of acute angle-closure glaucoma after pharmacologic mydriasis. am j ophthalmol 1995;120:709–717. 32. sheth hg, goel r, jain s. uk national survey of prophylactic yag iridotomy. eye (lond) 2005;19:981–984. 274 j  o  v r volume 14, issue 3, july–september 2019 original article the long-term visual outcomes of primary congenital glaucoma hamed esfandiari1,2, md; alisa prager2, md, mph; kiana hassanpour3, md, mph; sudhi p. kurup1,2, md rebecca mets-halgrimson1,2, md; hawke yoon1,2, md; janice lasky zeid1,2, md; marilyn b. mets1,2, md bahram rahmani1,2, md, mph 1division of ophthalmology, ann & robert h. lurie children’s hospital of chicago, chicago, usa 2department of ophthalmology, northwestern university feinberg school of medicine, chicago, usa 3ophthalmic research center, institutue for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran orcid: hamed esfandiari: https://orcid.org/0000-0001-7301-7047 alisa prager: https://orcid.org/0000-0002-8474-9398 abstract purpose: to evaluate the long-term visual outcomes of ab externo trabeculotomy for primary congenital glaucoma (pcg) at a single pediatric ophthalmology center. methods: in this retrospective single-center case series, data from 63 eyes of 40 patients who underwent ab externo trabeculotomy between september 2006 and june 2018 were included. the data were analyzed for best corrected visual acuity (bcva), stereopsis, and surgical success. kaplan–meier analysis was performed using the surgical success criteria defined as intraocular pressure (iop) ≤ 21 mmhg and ≥ 20% below baseline without the need for additional glaucoma surgery. results: bcva at the time of diagnosis was 0.37 ± 0.48 logmar, which changed to 0.51 ± 0.56 logmar at the final follow-up (p = 0.08). twenty-five percent of patients had bcva equal to or better than 20/40 at the final visit. the mean refraction at baseline was –4.78 ± 5.87 diopters, which changed to less myopic refraction of –2.90 ± 3.83 diopters at the final visit. optical correction was prescribed in 66% of eyes at the final visit. the average final stereopsis was 395.33 sec of arc. the linear regression model showed a significant association between the surgery success rate and final bcva as well as stereoacuity (pvalues: 0.04 and 0.03, respectively). intraocular pressure (iop) decreased significantly from 29.79 ± 7.67 mmhg at baseline to 16.13 ± 3.41 mmhg at the final follow-up (p = 0.001). conclusion: patients with pcg can achieve an acceptable visual acuity and stereoacuity, particularly in cases of timely intervention and close follow-up. keywords: ab externo trabeculotomy; long-term outcomes; primary congenital glaucoma; stereopsis; visual function j ophthalmic vis res 2020; 15 (3): 326–330 correspondence to: alisa prager, md. department of ophthalmology, northwestern university feinberg school of medicine, 645 n michigan ave., chicago, illinois 60611, usa. email: alisa.prager@gmail.com received: 10-07-2019 accepted: 02-01-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7451 introduction primary congenital glaucoma (pcg) is the most common type of childhood glaucoma and a this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: esfandiari h, prager a, hassanpour k, kurup sp, mets-halgrimson r, yoon h, zeid jl, mets mb, rahmani b. the long-term visual outcomes of primary congenital glaucoma. j ophthalmic vis res 2020;15:326–330. 326 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7451&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr visual outcomes of congenital glaucoma; esfandiari et al major cause of blindness in children.[1, 2] pcg is secondary to angle dysgenesis and is primarily a surgical condition.[3] surgical options include angle surgeries, trabeculectomy, glaucoma drainage devices, and cyclodestructive procedures in advanced cases.[4] historically, the effect of angle surgeries on the intraocular pressure (iop) has been considered the main outcome measure in most studies on pcg. while surgical outcomes are thoroughly discussed in the literature, not much is known about the visual outcomes of glaucoma surgery in patients with pcg. studies have shown that unilateral disease, poor vision at the time of diagnosis, multiple surgeries, and ocular comorbidities are associated with poor visual outcomes.[5] even after a timely intervention, these patients need treatment and monitoring for amblyopia, which necessitate frequent visits or examination under anesthesia. the final visual outcome is strongly related to early diagnosis and management of amblyopia. frequent anesthesia or sedation, complexity of the disease, and the associated visual impairment could have significant impact on children’s psychological behavior and make the assessment of visual function more complicated.[6] thus, the ultimate goal of childhood glaucoma management is lifelong control of iop to maintain visual function.[7, 8] the purpose of this study was to report the long-term visual outcomes (including snellen visual acuity and stereopsis) of patients with pcg, treated with ab externo trabeculotomy at a single center. methods this study was approved by the institutional review board of the ann & robert h. lurie children’s hospital of chicago. we followed the tenets of the declaration of helsinki and regulations of the health insurance portability and accountability act. patients who underwent ab externo trabeculotomy for pcg at the lurie children’s pediatric ophthalmology center between september 2006 and june 2018 were identified using current procedural terminology (cpt) codes and included in the study. we collected data such as preoperative iop, baseline ocular biometric characteristics including axial length (al), central corneal thickness (cct), corneal diameter, presence of haab’s striae, number of preoperative glaucoma medications, type of surgery, and intraand postoperative complications. the severity of glaucoma was assessed using three parameters: iop, corneal diameter, and corneal clarity. each parameter was given a score of 1–3, and the total score decided the severity of pcg: mild (1–3), moderate (4–6), or severe (7–9) pcg.[9] at each postoperative visit, the best corrected visual acuity (bcva), stereopsis, iop, glaucoma medications, and complications were noted. surgical success criteria were defined as iop ≤ 21 mmhg and ≥ 20% below the baseline without the need for additional glaucoma surgery (except ab externo trabeculotomy). the exclusion criteria were as follows: history of intraocular surgery, combined surgical procedures, any forms of anterior segment dysgenesis, and a follow-up of less than six-months. stereopsis was quantitatively assessed with the titmus test (stereo optical inc., chicago, il) with fly and graded circles. during the examination, children wore their correction under the polaroid lenses, and the examiner used his index finger to guide fixation. patients were asked to grab the wings of the fly and point out to the circle that seemed to “jump” out of the book. in the case of a wrong answer, the immediately preceding target was repeated. the last correct target identified was used as the child’s stereopsis measurement. vision was measured with age-appropriate methods and converted to logmar for statistical analysis. all patients underwent complete ophthalmologic and orthoptic evaluation. cycloplegic refraction were performed by instilling two drops of 1% cyclopentolate hydrochloride in each eye at 5-min intervals. all surgeries were performed under general anesthesia. a fornix-based localized peritomy was created in the temporal or superior quadrant. triangular or rectangular 3mm limbal base superficial scleral flap was fashioned, followed by a radial incision to expose the schlemm canal under high magnification. scleral cutdown was initiated from the blue zone up to the white zone until aqueous was seen oozing out from the cut ends of the canal. the harms trabeculotome was then passed into each end of the schlemm canal to gently cut through the canal in the anterior chamber. the scleral journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 327 visual outcomes of congenital glaucoma; esfandiari et al flap and peritomy were sutured with vicryl sutures. all statistical analyses were performed using the spss software (spss statistics for windows, version 25, im corp., armonk, ny, usa). to compare the change in iop, we used an interaction analysis within a linear mixed model. to evaluate the baseline differences, we used the t-test, chisquare, and fisher’s exact tests. kaplan–meier survival plots were constructed to assess the longterm survival rates; these were compared using the log-rank test. linear regression analysis was used to evaluate the factors associated with surgical success. results sixty-three eyes of 40 patients were included in this study. the mean age at diagnosis was 6.8 ± 10.6 months and 62.5% of the patients were male. the mean follow-up time was 85.7 ± 32.9 months (table 1). the preoperative bcva was 0.37 ± 0.48, which changed to 0.51 ± 0.56 logmar at the final follow-up (p = 0.08). the baseline visual acuity was measured with fixation and following method in 27 eyes, teller acuity card in 30, lea symbols in 4, and hotv in 2. twenty-five percent of patients had bcva ≥ 20/40 at the final visit. the mean refraction of the patients was –4.78 ± 5.87 diopter at baseline, which changed to less myopic refraction of –2.90 ± 3.83 diopter at the final visit. sixty-six percent of eyes were prescribed optical correction at the final visit. the average final stereopsis was 395.33 sec of arc (range, 40–800). the linear regression model showed a significant association between surgical success and final bcva as well as stereoacuity (p-values: 0.04 and 0.03, respectively). the final stereoacuity corresponded to the final bcva of 0.61 logmar. the average baseline iop was 29.7 ± 7.6 mmhg, which decreased to 16.1 ± 3.4 mmhg at the final visit, corresponding to 44% reduction from the baseline. the kaplan–meier survival curves indicated a time to failure of 107.7 ± 9.04 months. among the baseline parameters, only age at diagnosis of less than three months was associated with a higher failure rate. of the 63 eyes, 21 met the criteria for mild, 29 for moderate, and 13 for severe pcg. while mild pcgs had significantly better visual acuity and stereopsis at the final follow-up (p < 0.05), there was no significant difference between the moderate and severe groups. thirty-five eyes (56%) underwent repeat trabeculotomy to treat a different area of the trabecular meshwork because of inadequately controlled iop after the first session. additional glaucoma surgery (glaucoma shunt procedure) was performed in seven patients. discussion the main goal of our study was to determine the long-term visual outcome of ab externo trabeculotomy for pcg. in our study, ab externo trabeculotomy resulted in 44% reduction in the iop with a long-term success rate of 65%. our success rate is consistent with those in previous reports, which ranged from 45% to 85%.[8, 9] the final visual acuity in our study was 0.51 logmar and 25% of the patients had corrected vision better than 20/40 at the final visit. the visual outcome in our study is comparable to that of other reports with similar demographic data.[10, 11] however, we found better final visual function than that reported previously in the aldarrab study in which 55% of the patients had bcva < 20/60.[6] poor visual outcomes in their study could be explained by more severe glaucoma population, high prevalence of cyp1b1 mutation, delayed diagnosis, and inadequate follow-up.[12] poor vision in children with pcg is multifactorial; high iop in early life causes structural changes in the eye such as globe enlargement, corneal edema and opacity, tears in the descemet’s membrane (haab’s striae), high refractive error, anisometropia, and glaucomatous optic neuropathy[13–15]. corneal edema was present in almost 55% of patients at the time of diagnosis, which resolved after surgery in all cases, but accompanying haab’s striae, with or without corneal edema, persisted in two-third of our patients. myopic refraction was the most frequent refractive error at baseline, which decreased with iop reduction. the correlation between myopia and glaucoma can be attributed to the increase in the axial diameter of the eye as a consequence of high iop.[14] sixty-six percent of our patients needed optical correction for myopia or myopic astigmatism at the final visit. astigmatism is usually related to asymmetric expansion of the anterior chamber, corneal scar, and haab’s striae. in most cases, only optical correction was prescribed, but in 7% of the eyes (5 eyes) optical devices were needed. telescopic systems (angular 328 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 visual outcomes of congenital glaucoma; esfandiari et al table 1. baseline characteristics of the patients. clinical characteristics (range) gender male 25 (62.5%) unilateral disease number (%) 17 (42.5%) age at the time of diagnosis mean ± sd (months) 6.89 ± 10.68 (0 – 63) follow-up mean ± sd (months) 85.74 ± 32.95 (3 – 156) iop mean ± sd (mmhg) 29.79 ± 7.67 (11 – 54) c/d ratio mean ± sd 0.55 ± 0.22 (0.2 – 0.95) corneal diameter mean ± sd (mm) 12.79 ± 1.26 (9.50 – 15.5) central corneal thickness mean ± sd (microns) 585.44 ± 76.57 (470 – 761) axial length mean ± sd (mm) 22.37 ± 2.50 (17.50 – 28.50) refraction mean ± sd (diopters) –4.78 ± 5.87 (–25.0 – +5.50) time of diagnosis by category ≤ 3 months 18 (31%) 3 < age ≤ 6 months 26 (48%) > 6 months 14 (24.1%) ocular signs presence of haab striae 45 (72.6%) buphthalmos 30 (83.3%) ocular symptoms tearing 30 (93.8%) photophobia 24 (82.8%) sd, standard deviation; iop, intraocular pressure; c/d ratio, cup to disc ratio magnification) were the most common aids used for improving vision. lower magnifications are beneficial in constricted visual field and low image illumination.[13] no patient needed optical aid for near vision, probably due to the large range of accommodation in children. optical devices can improve the visual function and promote daily activities; therefore, they should be employed as early as possible.[15] we did not find any association between the age at diagnosis and final visual acuity. this finding is in contrast to other studies that showed a close relationship between age at pcg diagnosis and visual function.[13] however, we found a positive association between iop control and final visual function. it is likely that timely intervention in our cohort and close follow-up reversed the detrimental effect of high iop on the function and structure of the eye. the average final stereopsis in our study was 395.33 sec of arc. the relationship between visual acuity of the amblyopic eye and stereoacuity is complex.[16] in general, worse visual acuity is associated with worse stereoacuity; however, it largely depends on the etiology of amblyopia; strabismic amblyopes have the worst stereoacuity, while anisometropic amblyopes retain some stereopsis.[17] furthermore, the presence of stereoacuity in patients with pcg can improve the outcomes of amblyopia treatment.[18, 19] the results of our study show that while stereoacuity is not normal, it is nevertheless functional in many patients. our study was limited by its retrospective nature, variable follow-up duration, and multiple examiners. additionally, this study was conducted at a single tertiary academic referral center, and the results may not be generalizable to other practice facilities. baseline visual acuity measurement was not optimal due to age, which made the comparison of preand post-surgery measurements less reliable. however, the aim of our study was to present the long-term outcomes of visual function of pcg. such data for visual acuity are scarce in the literature and there has been no study on stereopsis outcome in pcg. in summary, the result of our study showed that patients with pcg can achieve an acceptable visual acuity and stereoacuity with timely intervention and close follow-up. although our study was journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 329 visual outcomes of congenital glaucoma; esfandiari et al not designed to compare the visual function changes after ab externo trabeculotomy, we did not observe any improvement in visual acuity as this parameter could be reliably measured after the procedure. this lack of significant improvement should be discussed preoperatively to gauge the expectations. financial support and sponsorship none. conflicts of interest there are no conflicts of interest. references 1. stamper rl, lieberman mf, drake mv, becker b. beckershaffer’s diagnosis and therapy of the glaucomas. 8th ed. st. louis: mosby elsevier, 2009. 2. esfandiari h, taranum basith ss, kurup sp, metshalgrimson r, hassanpour k, yoon h, et al. long-term surgical outcomes of ab externo trabeculotomy in the management of primary congenital glaucoma. j aapos 2019;23:222.e1–222.e5. 3. yu chan jy, choy bn, ng al, shum jw. review on the management of primary congenital glaucoma. j curr glaucoma pract 2015;9:92–99. 4. morales j, al shahwan s, al odhayb s, al jadaan i, edward dp. current surgical options for the management of pediatric glaucoma. j ophthalmol 2013;2013:763735. 5. khitri mr, mills md, ying g-s, davidson sl, quinn ge. visual acuity outcomes in pediatric glaucomas. j aapos 2012;16:376–381. 6. aldarrab a, al qurashi m, al thiabi s, khandekar r, edward dp. functional visual ability and quality of life in children with glaucoma. am j ophthalmol 2019;200:95– 99. 7. jayaram h, scawn r, pooley f, chiang m, bunce c, strouthidis ng, et al. long-term outcomes of trabeculectomy augmented with mitomycin c undertaken within the first 2 years of life. ophthalmology 2015;122:2216–2222. 8. chang tc, cavuoto km. surgical management in primary congenital glaucoma: four debates. j ophthalmol 2013;612708. 9. al-hazmi a, awad a, zwaan j, al-mesfer sa, al-jadaan i, al-mohammed a. correlation between surgical success rate and severity of congenital glaucoma. br j ophthalmol 2005;89:449–453. 10. freedman bl, jones sk, lin a, stinnett ss, muir kw. vision-related quality of life in children with glaucoma. j aapos 2014;18:95–98. 11. dahlmann-noor a, tailor v, bunce c, abou-rayyah y, adams g, brookes j, et al. quality of life and functional vision in children with glaucoma. ophthalmology 2017;124:1048–1055. 12. moore db, tomkins o, ben-zion i. a review of primary congenital glaucoma in the developing world. surv ophthalmol 2013;58:278–285. 13. haddad mao, sampaio mw, oltrogge ew, kara-josé n, betinjane aj. visual impairment secondary to congenital glaucoma in children: visual responses, optical correction and use of low vision aids. clinics 2009;64:725–730. 14. yassin sa. long-term visual outcomes in children with primary congenital glaucoma. eur j ophthalmol 2017;27:705–710. 15. khanna a, ichhpujani p. low vision aids in glaucoma. j curr glaucoma pract 2012;6:20–24. 16. levi dm, pass af, manny re. binocular interactions in normal and anomalous binocular vision: effects of flicker. br j ophthalmol 1982;66:57–63. 17. mckee sp, taylor dg. the precision of binocular and monocular depth judgments in natural settings. j vis 2010;10:5. 18. levi dm, knill dc, bavelier d. stereopsis and amblyopia: a mini-review. vis res 2015;114:17–30. 19. birch ee. amblyopia and binocular vision. prog retin eye res 2013;33:67–84. 330 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 photo essay pigment epithelium macroadenoma mimicking iris or ciliary body melanoma sara sánchez-tabernero, md1; ciro garcía-alvarez, phd2; elena garcía-lagarto, md3; maria a saornil2, phd 1department of ophthalmology, anterior segment service, moorfields eye hospital, london, uk 2servicio de oftalmología, unidad de tumores intraoculares del adulto, hospital clínico universitario de valladolid, spain 3unidad de patología, hospial clínico universitario de valladolid, spain orcid: sara sánchez-tabernero: http://orcid.org/0000-0003-1745-2890 j ophthalmic vis res 2021; 16 (2): 306–307 presentation a 66-year-old man presented to the intraocular tumor unit at hospital clínico universitario of valladolid, spain, with a one-year history of gradual vision loss in the left eye. the patient had previously undergone cataract surgery. examination revealed a mass arising from the iris, invading the iridocorneal angle and ciliary body, and displacing the intraocular lens posteriorly. the dimensions were 11.51 × 11.39 × 7.53 mm, as measured under ultrasound biomicroscopy. the mass was hyperintense on t1and hypointense on t2-weighed magnetic resonance images. this is the most frequent pattern described in ciliary pigment epithelium adenomas, although hyperintensity on both t1and t2-weighted images has also been reported.[1] enucleation was performed because of suspected iris melanoma. histopathology demonstrated nests and cords of pigmented epithelial cells with an adenoid pattern, consistent with previous studies.[1, 2] atypia, mitotic figures, or infiltrative features were not observed. correspondence to: sara sánchez-tabernero, md. department of ophthalmology, anterior segment service, moorfields eye hospital, 51 north block, se1 7pj london, uk. email: s.t.sara.g@gmail.com received: 08-04-2020 accepted: 28-09-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9100 histopathology was diagnostic of macroadenoma of iris pigment epithelium, although a ciliary body origin could not be excluded. discussion histopathology demonstrated nests and cords of pigmented epithelial cells with an adenoid pattern, consistent with previous studies.[1, 2] atypia, mitotic figures, or infiltrative features were not observed. histopathology was diagnostic of macroadenoma of iris pigment epithelium, although a ciliary body origin could not be excluded. financial support and sponsorship nil. conflicts of interest the authors declare no interests. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: sánchez-tabernero s, garcía-alvarez c, garcíalagarto e, saornil ma. pigment epithelium macroadenoma mimicking iris or ciliary body melanoma. j ophthalmic vis res 2021;16:306–307. 306 © 2021 sánchez-tabernero et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9100&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; sánchez-tabernero et al a b c d e f figure 1. (a) slit-lamp biomicroscopy showing an iris mass. (b) ultrasound biomicroscopy. (c) mass on t1and t2-weighed magnetic resonance images. (d) enucleated eye. (e&f) hematoxylin and eosin stain, 4× and low-power magnification. references 1. chang y, wei wb, shi jt, xian jf, yang wl, xu xl, et al. clinical and histopathological features of adenomas of the ciliary pigment epithelium. acta ophthalmol 2016;94:e637–e643. 2. shields ja, shields cl, mercado g, gündüz k, eagle rc. adenoma of the iris pigment epithelium: a report of 20 cases. arch ophthalmol 1999;117:736–741. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 307 original article prevalence and risk factors of retinopathy of prematurity in iran mohammad zarei1, md; fatemeh bazvand1, md; nazanin ebrahimiadib1, md; ramak roohipoor1, md reza karkhaneh1, md; afsar farahani dastjani1, md; marjan imani fouladi1, md; mohammad riazi esfahani1,2, md; alireza khodabande1, md; samaneh davoudi3, md; hamed ghasemi1, md; bobeck s modjtahedi4, md 1eye research center, farabi eye hospital, tehran university of medical sciences, tehran, iran 2department of ophthalmology, gavin herbert eye institute, university of california, irvine, ca, usa 3department of ophthalmology, university of florida, gainesville, florida, usa 4eye monitoring center, kaiser permanente southern california, ca, usa orcid: mohammad zarei: https://orcid.org/0000-0002-8808-2244 ramak roohipoor: https://orcid.org/0000-0003-3168-1922 abstract purpose: the present study aimed to evaluate the frequency and risk factors of retinopathy of prematurity (rop) among iranian infants. methods: a retrospective cohort study was conducted on infants who had undergone screening for rop at farabi eye hospital, between march 2016 and march 2017. data were analyzed based on the presence of extreme prematurity (gestational age ≤ 28 weeks), extremely low-birth-weight (≤ 1000 g), and multiplegestation (mg) infants. results: the prevalence of rop was 27.28% (𝑛 = 543) among all screened infants, 74.4% for extremely preterm (ep) infants, 77.5% for extremely low birth weight (elbw) babies, and 27.25% for infants from mg pregnancies. on multivariate analysis, gestational age, birth weight, and history of transfusion (𝑃 < 0.0001, 𝑃 < 0.0001, and 𝑃 = 0.04, respectively) were found to be significantly associated with rop. more advanced stages of rop (𝑃 < 0.0001) were observed in ep and elbw infants. birth weight (𝑃 = 0.088), history of transfusion (𝑃 = 0.066), and intubation (𝑃 = 0.053) were not associated with increased risk of rop in ep infants, while gestational age (𝑃 = 0.037) and history of transfusion (𝑃 = 0.040) were significant risk factors for rop in elbw infants. gestational age (p < 0.001) and birth weight (𝑃 = 0.001) were significantly associated with rop in infants from mg pregnancies in multivariate analysis. conclusion: rop remains a commonly encountered disease, especially in elbw and ep infants. the history of transfusion may have a role in stratifying the risk for rop and guiding future screening guidelines. keywords: epidemiology; frequency; infants; pediatric; retinopathy of prematurity; risk factors j ophthalmic vis res 2019; 14 (3): 291–298 correspondence to: ramak roohipoor, md. eye research center, farabi eye hospital, tehran university of medical sciences, qazvin square, tehran 13366, iran. e-mail: ramakroohipour@yahoo.com received: 09-03-2018 accepted: 05-09-2018 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i3.4785 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: zarei m, bazvand f, ebrahimiadib n, roohipoor r, karkhaneh r, dastjani af, et al. prevalence and risk factors of retinopathy of prematurity in iran. j ophthalmic vis res 2019;14:291–298 @ 2019 j  o  v r | published by knowledge e 291 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i3.4785&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr review of 1,990 cases of rop; zarei et al introduction retinopathy of prematurity (rop) is the leading cause of visual impairment in premature infants and is characterized by abnormal peripheral retinal vascularization.[1] the incidence of rop is influenced by several factors including gestational age, birth weight, genetics, ethnicity, and level of neonatal care. gestational age is defined as the length of time of growth of the fetus in the uterus. screening programs should be regionally tailored to account for these differences. advances in prenatal and neonatal care have resulted in increasing rates of rop in the developing world.[2–4] gestational age and birth weight are the two most well-established risk factors for rop, with other factors such as oxygen therapy, history of transfusion, sepsis, and anemia being less significantly associated with rop.[5] rop is diagnosed only in a minority of premature infants, with a smaller subset requiring intervention. as a result, better understanding of risk factors of progression to rop, especially in those cases requiring treatment, would allow for more effective screening programs.[5, 6] the purpose of this study is to evaluate the prevalence of rop and associated risk factors in a tertiary eye center in tehran. additional subgroup analysis was done for patients in three high risk categories: extremely low birth weight (≤ 1,000 g, elbw), extremely preterm (≤ 28 weeks, ep), and multiple gestational (mg) infants. methods the current retrospective cohort study was performed at farabi eye hospital from march 2016 until march 2017 after obtaining approval from the institutional review board (irb) of tehran university of medical sciences. the tenets of the declaration of helsinki were followed. the medical records of all patients referred to the rop clinic were assessed. all infants with gestational age ≤ 37 weeks were included in this study. patients with incomplete medical records were excluded from the analysis. demographic data (gestational age, birth weight, and gender) and ophthalmic findings (rop stage, zone, and laterality) were collected and categorized for each patient. stages of rop were diagnosed based on the international classification of rop as follows: stage 0: immature retinal vasculature without pathologic changes stage 1: presence of a demarcation line between the vascularized and non-vascularized retina stage 2: presence of a demarcation line that has height, width, and volume (ridge); small, isolated tufts of neovascular tissue lying on the surface of the retina, commonly known as, “popcorn” may be present. stage 3: a ridge with extraretinal fibrovascular proliferation that may be mild, moderate, or severe, as judged by the amount of proliferative tissue present. stage 4: partial retinal detachment (a) extrafoveal retinal detachment; (b) retinal detachment involving the fovea stage 5: total retinal detachment with funnel configuration threshold is defined as retinal neovascularization with an extension of either a continuous five clock hour or eight cumulative clock hours in zone i or ii with plus disease. pre-threshold disease is characterized by all zone i and ii changes, except zone ii stage 1 and zone ii stage 2 without plus disease that do not include the criteria of threshold disease, and is divided into two types: type 1: zone i, any stage rop with plus disease, zone i, stage 3 rop without plus disease, or zone iii, stage 2 or 3 rop with plus disease type 2: zone i, stage 1 or 2 rop without plus disease and zone ii, stage 3 rop without plus disease for the purpose of analysis, the stage of rop in patients with bilateral disease was categorized based on the eye with the highest stage and lowest zone. additionally, the history of sepsis, transfusion, acute respiratory distress syndrome (ards), oxygen therapy, intubation, intraventricular hemorrhage (ivh), and phototherapy were analyzed as risk factors for rop. follow-up visits, indications for treatment, types of treatment, and final rop status at the last examination were also collected for each patient. data was analyzed using ibm spss version 19 (armonk, ny: ibm corp). mean ± standard deviation was used to report data. after confirmation 292 j  o  v r volume 14, issue 3, july–september 2019 review of 1,990 cases of rop; zarei et al of the normal distribution of data by shapirowilk test, the comparison between birth weight and gestational age of patients with and without rop was performed using student 𝑡-test. univariate logistic regression was performed to determine the significance of different potential predictive risk factors (gestational age, birth weight, transfusion, sepsis, ards, oxygen therapy, intubation, ivh, and phototherapy) in the development of rop (dependent variable). subsequently, the resultant significant risk factors were evaluated using multivariate logistic regression to discern the confounding factors. 𝑃-value < 0.05 in the 𝑡-test and logistic regression was considered statistically significant. results subjects a total of 1,990 patients met the inclusion criteria. mean gestational age was 32.29 ± 2.75 weeks (range: 24 ± 37 weeks) and mean birth weight was 1,757.99 ± 563.51 g. the cohort comprised of 51.5% (1024) male infants. retinopathy of prematurity the prevalence of rop was 27.28% (𝑛 = 543). four hundred and sixty-eight patients (23.52%) had bilateral disease and 75 (3.76%) cases had unilateral disease (23 right eyes and 52 left eyes). stage of rop is outlined in table 1. the mean number of examinations and the mean time to the first examination was 2.4 ± 2.6 (1–36) and 7.6 ± 9.1 weeks, respectively. cases of rop diagnosed at initial visit were as follows: pre-threshold 1 (57 patients, 2.9% of the total number of cases), threshold (77 patients, 3.9%), stage 4a (15 patients, 0.75%), stage 5 (26 patients, 1.3%), regressed rop with unfavorable outcome (3 patients, 0.15%), and other forms of rop (pre-threshold 2 and less severe) (365 patients, 18.3%). thirty-two patients were diagnosed with rop during follow-up visits. risk factors univariate and multivariate logistic regression analyses were performed to examine the relationship between the different risk factors and development of rop. gestational age, birth weight, transfusion, ards, oxygen therapy, sepsis, intubation, and ivh were significant risk factors on univariate analysis; however, only gestational age, birth weight, and transfusion remained significant on multivariate analysis. [tables 2 and 3]. gestational age (𝑃 = 0.010), birth weight (𝑃 < 0.0001), and ivh (𝑃 = 0.028) were significant risk factors for rop that required treatment. treatment one hundred and eighty patients underwent treatment, which included intravitreal injection of bevacizumab [ivb, (155 eyes, 86% of patients)], laser (98 eyes, 54%), scleral buckle (5 eyes, 0.05%), vitrectomy (7 eyes, 4%), combination of ivb and scleral buckle (2 eyes, 1%), and combination of ivb and vitrectomy (1 eye, 0.5%). twenty-nine patients (47 eyes) required retreatment, including 18 eyes with laser (previous treatment included ivb in 16 eyes and laser in 2 eyes), 17 eyes with ivb (previous treatment included ivb in all), 8 eyes with vitrectomy (previous treatment included laser in 4 eyes and ivb in 4 eyes), and 4 eyes with scleral buckle (previous treatment included laser in 2 eyes and ivb in 2 eyes). seven eyes required a third treatment: vitrectomy in five eyes (all were primarily treated with ivb, followed by laser), and sclera buckle in two eyes (both received ivb followed by vitrectomy). extremely preterm patients two hundred and twenty-three patients were born ep. mean gestational age and birth weight were 27.24 ± 0.96 weeks and 1,086.50 ± 268.41 g, respectively. multi-gestation births (56 patients, 25%), transfusion (142 patients, 63.7%), intubation (34 patients, 15.2%), sepsis (102 patients, 46%), ards (176 patients, 79%), oxygen therapy (159 patients, 71%, data of oxygen therapy in 34 patients with ards were not documented in the archived files), phototherapy (159 patients, 71%), and ivh (20 patients, 9%) were frequently encountered. one hundred and sixty-six (74.4%) ep patients developed rop: pre-threshold rop in 32 patients (14%), threshold rop in 45 patients (20%), stage 4a in 8 patients (3.6%), stage 5 in 12 patients (5.3%), other stages in 68 patients, and unfavorable structural outcome in 1 patient (0.4%). stage of rop was more advanced in ep infants than non-ep infants (chi-square test, 𝑃 < 0.001). j  o  v r volume 14, issue 3, july–september 2019 293 review of 1,990 cases of rop; zarei et al table 1. the rate and stage of rop in infants with gestational age equal or less than 37 weeks rop right eye left eye frequency (%) frequency (%) no rop 914 (45.9) 904 (45.4) immature retina (avascular area) 585 (29.4) 566 (28.4) prethreshold type 2 and less severe forms of rop 322 (16.2) 349 (17.5) pre-threshold rop type 1 60 (3) 56 (2.8) threshold rop 75 (3.8) 76 (3.8) stage 4a 11 (0.6) 14 (0.7) stage 5 21 (1.1) 22 (1.1) autoregressed rop with unfavorable outcome 2 (0.1) 3 (0.2) rop, retinopathy of prematurity table 2. data of univariate regression analysis of different risk factors in the development of retinopathy of prematurity with rop (n = 575) without rop (n = 1415) significance odds ratio 95% ci gestational age 29.98 ± 2.38 33.34 ± 2.50 < 0.001 0.594 0.565–0.620 birth weight 1,364.95 ± 417.21 1,936 ± 555.64 < 0.001 0.998 0.997–0.998 gender (female/male) 292/283 674/741 0.211 0.882 0.724–1.074 multiple gestations (mgs) 183 458 0.908 0.988 0.799–1.280 oxygen therapy 379 835 < 0.001 3.320 2.347–4.697 transfusion 229 190 < 0.001 4.269 3.347–5.444 intra ventricular hemorrhage 31 27 < 0.001 3.035 1.788–5.149 sepsis 223 422 0.005 1.358 1.097–1.680 ards 391 742 < 0.001 3.320 2.347–4.697 phototherapy 343 826 0.736 0.955 0.729–1.250 intubation 58 77 < 0.001 2.146 1.493–3.084 ards, acute respiratory distress syndrome; ci, confidence interval; rop, retinopathy of prematurity fifty-seven (25%) ep patients did not develop rop (no rop in 20 patients and immature retina in 37 patients). birth weight, transfusion, and intubation were not significant (although with a trend toward significance) risk factors for rop in ep infants on multivariate analysis (𝑃 = 0.088, 0.066, and 0.053, respectively). extremely low birth weight infants one hundred and sixty patients had elbw. transfusion (97 patients, 61%), intubation (25 patients, 15.6%), sepsis (66 patients, 41%), ards (123 patients, 77%), oxygen therapy (123 patients, 77%), phototherapy (99 patients, 62%), and ivh (14 patients, 8.7%) were commonly observed. one hundred and twenty-four (77.5%) patients were affected by rop: 24 (15%) patients with type 1 pre-threshold rop, 31 (19%) with threshold rop, 5 (3%) with stage 4a, 10 (6%) with stage 5, and 54 (33.8%) patients with other stages. thirty-six patients (22.5%) did not develop rop (no rop in 12 patients and immature retina in 24 patients). in multivariate analysis, gestational age (𝑃 = 0.037) and transfusion (𝑃 = 0.040) were found to be significantly associated with the development of rop. 294 j  o  v r volume 14, issue 3, july–september 2019 review of 1,990 cases of rop; zarei et al table 3. data of multivariate regression analysis of different risk factors in the development of retinopathy of prematurity wald significance odds ratio 95% ci gestational age 64.002 < 0.001 0.724 0.668–0.783 birth weight 19.313 < 0.001 0.999 0.999–0.999 gender 0.807 0.369 0.873 0.650–1.174 multiple gestations .011 0.915 1.017 0.747–1.385 oxygen therapy 0.463 0.496 1.253 0.655–2.397 transfusion 3.869 0.049 1.355 1.001–1.833 intra ventricular hemorrhage 2.094 0.148 1.728 0.824–3.624 sepsis 1.252 0.263 1.172 0.888–1.547 ards 1.686 0.194 1.401 0.842–2.333 phototherapy 0.125 0.724 0.937 0.652–1.345 intubation 1.480 0.224 1.349 0.833–2.184 ards, acute respiratory distress syndrome; ci, confidence interval multiple gestations six hundred and forty-two babies belonged to mg pregnancies including twins (511 cases, 79.6%), triplets (115 cases, 18%), quadruplets (9 cases, 1.4%), quintuplets (5 cases, 0.8%), and sextuplets (1 case, 0.15%). the mean gestational age was 32.36 ± 2.56 weeks and birth weight was 1,692.94 ± 457.12 g. transfusion (130 patients, 20%), intubation (39 patients, 6%), sepsis (216 patients, 33.7%), ards (369 patients, 57.4%), oxygen therapy (393 patients, 61.2%), phototherapy (399 patients, 62%), and ivh (16 patients, 2.5%) were encountered. one hundred and seventy-five patients (27.2%) developed rop: type 1 pre-threshold rop in 14 patients (2.2%), threshold rop in 29 patients (4.5%), stage 4a in 7 patients (1%), stage 5 in 5 patients (0.7%), and other stages in 120 patients (18.7%). four hundred and sixty-seven patients (72.7%) did not develop rop, of which 181 (28%) had immature retinas. on multivariate analysis, gestational age and birth weight were shown to be significant risk factors associated with rop (𝑃 < 0.001 and 0.001, respectively). fifty-eight babies (9%) were treated for rop. severity of rop and the rate of treated cases were similar between mg and single gestation babies. discussion in this series, the rate of rop was 27.28% on initial evaluation, with 1.6% developing rop on subsequent follow-up. the rate of rop reported in the literature ranges from 11.4 to 44% due to the differences in economic status, ethnicity, genetics, practice setting, screening programs, and level of perinatal care at the respective institutions.[6–14] a previous report from iran found an 8.5% prevalence of rop among premature infants.[15] the increased rate observed in the current study may be due to improved perinatal care, which has resulted in longer survival of high-risk infants. there is a considerable debate regarding the risk factors for rop. in the present cohort, low gestational age and birth weight, history of transfusion, ards, oxygen therapy, sepsis, intubation, and ivh were significant risk factors for rop on univariate analysis; however, on multivariate analysis only gestational age, birth weight, and history of transfusion were found to be statistically significant. gestational age, birth weight, and ivh were significantly associated with the treatment for rop among all infants on multivariate analysis (𝑃 = 0.010, < 0.001 and 0.028, respectively). table 4 provides a summary of the rates of rop and risk factors across several studies. multiple studies have identified lower gestational age and birth weight, higher number of days of oxygen therapy, mechanical ventilation, hyperglycemia, sepsis, transfusion, inadequate weight gain during the first two weeks, and ivh as risk factors for rop, with low gestational age and birth weight being the most consistently demonstrated risk factors.[6, 8, 11, 12, 16–18] khalesi et al.[19] observed gestational age, apnea score in the first minute, j  o  v r volume 14, issue 3, july–september 2019 295 review of 1,990 cases of rop; zarei et al table 4. the rate of development of rop and significant risk factors in some studies study sample size rate of rop risk factors liu et al[13] 1,846 12.8% birth weight, gestational age, days of oxygen supplementation, and myocardial injury after birth chen et al[12] 472 12.7% gestational age, birth weight, preeclampsia, and maternal oxygen supplement before or at the time of delivery port et al[6] 1,354 38.8% birth weight, gestational age, bronchopulmonary dysplasia, multiple gestation (mg), necrotizing enterocolitis, race and ethnicity mohamed et al[17] 582 29% univariate analysis: birth weight, gestational age, patent ductus arteriosus, sepsis, intraventricular hemorrhage (ivh), lung disease, days of hyperglycemia, and prescription of postnatal steroids multivariate analysis: gestational age, days of hyperglycemia, and days of mechanical ventilation bossi et al[9] 639 11.4% univariate analysis: extent of o2-exposure, elevated paco2, elevated pao2, paco2-fluctuations, transfusions, acidosis, and artificial ventilation multivariate analysis: acidosis, birth weight, artificial ventilation, multiple birth, and hours of fio2 greater than 0.4 mutlu et al[18] 318 37.1% gestational age ≤ 32 weeks, birth weight ≤ 1250 g, oxygen therapy, and sepsis kim et al[19] 211 42% poor weight gain during the first two weeks this study 1,990 28.9% univariate analysis: gestational age, birth weight, transfusion, ards, oxygen therapy, sepsis, intubation, and intraventricular hemorrhage (ivh) multivariate analysis: gestational age, birth weight, and history of transfusion ards, acute respiratory distress syndrome; rop, retinopathy of prematurity oxygen therapy, and phototherapy as significant risk factors, whereas dai et al.[5] suggested that maternal iron deficiency may be another significant risk factor in the development of rop. increased oxygen demand during sepsis as well as toxic effects of high oxygen production during transfusion might result in increased susceptibility to rop.[20] similarly, yau et al.[21] observed that the incidence of rop in patients with a mean gestational age of 26.4 weeks was 60.7%. lower birth weight, transfusion, and intubation approached statistical significance as risk factors for rop in the present cohort of ep patients (𝑃 = 0.088, 0.066 and 0.053, respectively). yau et al[21] retrospectively reviewed ep infants and reported that low gestational age, lighter birth weight, invasive ventilation were significant risk factors for the development of rop on univariate analysis. rop was common in patients with elbw (77.5%, 𝑛 = 124), which is consistent with the findings reported by celebi et al (75.5%).[25] a wide spectrum exists in studies examining the rate of occurrence of rop (32.8 ± 82.5%) and the rate of treatment for rop (12.7 ± 48.9%) in elbw infants.[4, 22–24] in multivariate analysis, we observed that lower gestational age (𝑃 = 0.037) and history of transfusion (𝑃 = 0.040) were significant risk factors for the development of rop in elbw infants. celebi et al reported that gestational age, birth weight, history of transfusion, and sepsis were significant factors associated with severe rop requiring treatment in all infants, while only gestational age was statistically significantly associated with rop requiring treatment in elbw infants.[25] among patients born of mg pregnancies, lower gestational age and birth weight were significant risk factors for rop (𝑃 < 0.001 and 0.001, respectively), and no significant difference existed in the severity of rop and rate of treatment between mg patients and those born of a single gestation. twin-twin transfusion syndrome has been found to increase the risk for rop compared to mg alone (𝑃 < 0.01).[26] yau et al[27] assessed the risk of 296 j  o  v r volume 14, issue 3, july–september 2019 review of 1,990 cases of rop; zarei et al development of type 1 rop in mg infants. mg was found to be a significant risk factor using univariate analysis but not in multivariate analysis. azad et al[28] observed an increased severity of rop in heavier mg babies and concluded that weight alone cannot be considered a predictive factor for the severity of rop. data from the current study support the view that mg is not a risk factor for the development or severity of rop. the current series presents a contemporary analysis of the rate of rop and risk factors from a large tertiary center in iran. the strengths of this study include the large sample size and diverse patient population; however, given the retrospective design, confounding and missing data were innate limitations in the analysis of risk factors for rop. rop remains a commonly encountered disease with approximately a quarter of preterm infants and three-quarters elbw or ep infants being affected. low birth weight and low gestational age are two essential risk factors for the development of rop. in both developed and developing countries, low gestational age and low birth weight are the commonly reported risk factors for rop; however, other factors appear to play a larger role in developing countries. on multivariate analysis, transfusion was a significant risk factor for rop in elbw infants and approached statistical significance in ep infants. with improvement in perinatal care in developing countries, the burden of rop is likely to increase. as a result, a better understanding of the patients at risk for rop, especially among higher risk sub-groups is critical. future studies should focus on creating models based on multiple risk factors to stratify the risk of rop and potentially creating more individualized screening guidelines. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. casteels i, cassiman c, van calster j, allegaert k. educational paper: retinopathy of prematurity. eur j pediatr 2012;171:887–893. 2. domanico r, davis dk, coleman f, davis bo. documenting the nicu design dilemma: comparative patient progress in openward and single family room units. j perinatol 2011;31:2818. 3. hellstrm a, smith le, dammann o. retinopathy of prematurity. lancet 2013;382:144557. 4. good wv, hardy rj, dobson v, palmer ea, phelps dl, quintos m, et al. the incidence and course of retinopathy of prematurity: findings from the early treatment for retinopathy of prematurity study. pediatrics 2005;116:15– 23. 5. dai ai, demiryürek s, aksoy sn, perk p, saygili o, güngör k. maternal iron deficiency anemia as a risk factor for the development of retinopathy of prematurity. pediatr neurol 2015;53:146–150. 6. port ad, paul chan rv, ostmo s, choi d, chiang mf. risk factors for retinopathy of prematurity: insights from outlier infants. graefes arch clin exp ophthalmol 2014;252:1669–1677. 7. palmer ea, flynn jt, hardy rj, phelps dl, phillips cl, schaffer db, et al. incidence and early course of retinopathy of prematurity. the cryotherapy for retinopathy of prematurity cooperative group. ophthalmology 1991;98:1628–1640. 8. bossi e, koerner f, flury b, zulauf m. retinopathy of prematurity: a risk factor analysis with univariate and multivariate statistics. helv paediatr acta 1984;39:307– 317. 9. yin h, li xx, li hl, zhang w. incidence and risk factor analysis of retinopathy of prematurity. zhonghua yan ke za zhi 2005;41:295–299. 10. chattopadhyay mp, pradhan a, singh r, datta s. incidence and risk factors for retinopathy of prematurity in neonates. indian pediatr 2015;52:157. 11. chen y, xun d, wang yc, wang b, geng sh, chen h, et al. incidence and risk factors of retinopathy of prematurity in two neonatal intensive care units in north and south china. chin med j 2015;128:914–918. 12. liu q, zin z, ke n, chen l, chen xk, fang j, et al. incidence of retinopathy of prematurity in southwestern china and analysis of risk factors. med sci monit 2014;20:1442–1451. 13. seiberth v, linderkamp o. risk factors in retinopathy of prematurity: a multivariate statistical analysis. ophthalmologica 2000;214:131–135. 14. larsson e, carle-petrelius b, cernerud g, ots l, wallin a, holmstrom g. incidence of rop in two consecutive swedish population based studies. br j ophthalmol 2002;86:1122–1126. 15. saeidi r, hashemzadeh a, ahmadi s, rahmani s. prevalence and predisposing factors of retinopathy of prematurity in very low-birth-weight infants discharged from nicu. iran j pediatr 2009;19:59–63. 16. mohamed s, murray jc, dagle jm, colaizy t. hyperglycemia as a risk factor for the development of retinopathy of prematurity. bmc pediatr 2013;13:78. 17. mutlu fm, altinsoy hi, mumcuoglu t, kerimoglu h, kilic s, kul m, et al. screening for retinopathy of prematurity in a tertiary care newborn unit in turkey: frequency, outcomes, and risk factor analysis. j pediatr ophthalmol strabismus 2008;45:291–298. j  o  v r volume 14, issue 3, july–september 2019 297 review of 1,990 cases of rop; zarei et al 18. kim j, jin jy, kim ss. postnatal weight gain in the first two weeks as a predicting factor of severe retinopathy of prematurity requiring treatment. korean j pediatr 2015;58:52–59. 19. khalesi n, shariat m, fallahi m, rostamian g. evaluation of risk factors for retinopathy in preterm infant: a case-control study in a referral hospital in iran. minerva pediatrica 2015;67:231–237. 20. weintraub z, carmi n, elouti h, rumelt s. the association between stage 3 or higher retinopathy of prematurity and other disorders of prematurity. can j ophthalmol 2011;46: 419. 21. yau gs, lee jw, tam vt, liu cc, wong iy. risk factors for retinopathy of prematurity in extremely preterm chinese infants. medicine (baltimore) 2014;93:e314. 22. fortes filho jb, eckert gu, procianoy l, barros ck, procianoy rs. incidence and risk factors for retinopathy of prematurity in very low and in extremely low birth weight infants in a unit-based approach in southern brazil. eye 2009;23:25–30. 23. kumar p, sankar mj, deorari a, azad r, chandra p, agarwal r, et al. risk factors for severe retinopathy of prematurity in preterm low birth weight neonates. indian j pediatr 2011;78:812–816. 24. fortes filho jb, borges fortes bg, tartarella mb, procianoy rs. incidence and main risk factors for severe retinopathy of prematurity in infants weighing less than 1000 grams in brazil. j trop pediatr 2013;59:502–506. 25. celebi arc, petricli is, hekimoglu e, demirel n, bas ay. the incidence and risk factors of severe retinopathy of prematurity in extremely low birth weight infants in turkey. med sci monit 2014;20:1647–1653. 26. gschlieer a, stifter e, neumayer t, moser e, papp a, dorner g, et al. twin-twin transfusion syndrome as a possible risk factor for the development of retinopathy of prematurity. graefes arch clin exp ophthalmol 2015;253:151–156. 27. yau gs, lee jw, tam vt, yip s, cheng e, liu cc, et al. differences in risk factors for retinopathy of prematurity development in paired twins: a chinese population study. sci world j 2014;2014:212183. 28. azad r, chandra p, patwardhan sd, gupta a. profile of asymmetrical retinopathy of prematurity in twins. indian j ophthalmol 2010;58:209–211. 298 j  o  v r volume 14, issue 3, july–september 2019 original article superficial and deep foveal avascular zone area measurement in healthy subjects using two different spectral domain optical coherence tomography angiography devices pasha anvari, md mph; amin najafi, md; reza mirshahi, md; mahsa sardarinia, md maryam ashrafkhorasani, md; pegah kazemi, bs; gholamhoseyn aghai, md; abbas habibi, md khalil ghasemi falavarjani, md eye research center, the five senses institute, rassoul akram hospital, iran university of medical sciences, tehran, iran orcid: pasha anvari: https://orcid.org/0000-0002-3765-4206 khalil ghasemi falavarjani: https://orcid.org/0000-0001-5221-1844 abstract purpose: to compare the area of the foveal avascular zone (faz) in the superficial and deep retinal layers using two different spectral-domain optical coherence tomography angiography (octa) devices. methods: a cross-sectional comparative study was conducted to obtain macular octa images from healthy subjects using optovue rtvue xr avanti (optovue, inc, fremont, ca) and spectralis hra+octa (heidelberg engineering, heidelberg, germany). two independent trained graders measured the faz area using automated slab segmentation. the faz area in the superficial and deep retinal layers were compared. results: twenty-three eyes of 23 subjects were included. the graders agreement was excellent (>0.86) for all measurements. the mean faz area was significantly larger at the superficial retinal layer as compared to the deep retinal layer on both devices (0.31 ± 0.08 mm2 vs 0.26 ± 0.08 mm2 in optovue and 0.55 ± 0.16 mm2 vs 0.36 ± 0.13 mm2 in spectralis, both p < 0.001). the mean faz area was significantly greater in the superficial and deep retinal layers using spectralis as compared to optovue measurements (p < 0.001 for both comparisons). conclusion: in contrast to previous reports, the faz area was larger in the superficial retina as compared to deep retinal layers using updated software versions. measurements from different devices cannot be used interchangeably. keywords: fovea avascular zone; optical coherence tomography angiography; optovue; spectraldomain; spectralis j ophthalmic vis res 2020; 15 (4): 517–523 correspondence to: khalil ghasemi falavarjani, md. eye research center, rassoul akram hospital, sattarkhan-niaiesh st., tehran, iran. email: drghasemi@yahoo.com ghasemifalavarjani.k@iums.ac.ir received: 25-02-2020 accepted: 20-07-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7791 introduction foveal avascular zone (faz) is the vessel-free central part of the macula surrounded by a this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: anvari p, najafi a, mirshahi r, sardarinia m, ashrafkhorasani m, kazemi p, aghai g, habibi a, falavarjani kg. superficial and deep foveal avascular zone area measurement in healthy subjects using two different spectral domain optical coherence tomography angiography devices. j ophthalmic vis res 2020;15:517–523. © 2020 journal of ophthalmic and vision research | published by knowledge e 517 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7791&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr fovea avascular zone in two octa devices; anvari et al continuous network of capillary plexus. faz integrity is vital for normal visual acuity. some retinal pathologies including retinal vascular occlusions and diabetic retinopathy alter faz shape; therefore, faz metrics can serve as prognostic biomarkers for visual acuity.[1–5] prior to the advent of optical coherence tomography angiography (octa), the most extensively used tools for evaluation of faz were fluorescein angiography (fa) and indocyanine green angiography (icga).[6–8] however, fa and icga are invasive procedures with side effects associated with intravenous administration of the dye.[9] in addition, dye leakage from incompetent vessels may fade faz border in retinal pathologies, complicating faz assessment. octa is a noninvasive modality to evaluate retinal and choroidal vasculature that generates flow maps of retinal vasculature through discrimination of blood motion signals.[10–13] multiple octa devices are commercially available with distinct built-in software, algorithms, and techniques for visualization of retinal and choroidal vasculature and layer segmentation. the reliability and reproducibility of images provided by each device and the inter-device correlations are of great importance in clinical decision-making and patients’ follow-up.[14] although several studies have reported the size of faz in octa images, automated segmentations of retinal slabs in older versions has remained a source of measurement error.[15, 16] the aim of this study was to measure and compare the faz area at the superficial and deep retinal layers using two different octa devices with the updated software versions. methods this cross-sectional comparative case-series was approved by the iran university ethics committee (no. ir.iums.rec 1396.32837). informed consent was obtained and the tenets of the declaration of helsinki were followed. in total 23 eyes of 23 healthy employees of rassoul akram hospital, without any medical conditions or ocular abnormalities, were enrolled between june 2018 and december 2018. all volunteers underwent a complete ophthalmic examination including best-corrected visual acuity (bcva), slit-lamp examination, and fundus examination. subjects with abnormal or suspicious findings during the examination were excluded. the right eye was considered as the target eye for octa imaging. all images were obtained on the same day, between 8 am and 11 am. octa images were obtained using the optovue rtvue xr avanti (3 × 3 mm centered on the fovea, software version 2017.1.0.15, optovue, inc., fremont, ca) and spectralis hra+octa (15° × 10° scan pattern, software version 6.9, 2017, heidelberg engineering, heidelberg, germany). the optovue device visualizes retinal vasculature using a split-spectrum amplitude decorrelation algorithm (ssada). the spectralis is based on a probability algorithm which determines the presence of motion in each pixel by full spectrum amplitude-decorrelation.[17] for optovue, images with a quality score of <5 were excluded, and imaging was repeated until acceptable quality was achieved. the superficial capillary plexus (scp) en face image was segmented automatically with an inner boundary set at the internal limiting membrane (ilm) and an outer boundary set 9 µm above the inner plexiform layer (ipl). the deep capillary plexus (dcp) en face image was segmented with an inner boundary 9 µm above the ipl and an outer boundary at 9 µm below the outer plexiform layer (opl). in the spectralis device, only images with q scores greater than 15 were included. the superficial vascular complex (svc) was segmented automatically from ilm to 17 µm above the bottom border of the ipl and the deep vascular complex (dvc) was bounded from 17 µm above the lower border of the ipl to the bottom of the outer plexiform layer. octa images were imported into imagej software (public domain software, national institutes of health, bethesda, maryland, usa). the measurement scale was calibrated using the known dimensions of the image (3 × 3 mm for optovue and 200 microns scale bar for spectralis) and the faz boundary was outlined manually using freehand selection tools by two independent trained graders (pa and ms) in the superficial, deep, and the full retinal slabs. statistical data analysis was performed using the spss (version 17.0; spss inc., chicago, il, usa). intra-class correlation coefficient (icc) between graders was calculated. the shapiro–wilk test was used to verify the normality of data. paired t-test was used to compare mean values between two 518 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 fovea avascular zone in two octa devices; anvari et al devices. the bland–altman plot was employed to assess the agreement between the two devices in measuring the faz area at different retinal layers. p-values < 0.05 were considered significant. results twenty-three eyes of 23 normal subjects including 14 females (60.9%) and 9 males (39.1%) with a mean age of 34.2 ± 8.7 (range 28–59) years were included. icc was 0.87, 0.88, and 0.86 for the measurements at superficial, deep, and full retina slabs with the optovue device and 0.92, 0.86, and 0.88 for the measurements with the spectralis device, respectively. in view of the excellent agreement between the graders, the mean values for the two graders were used for subsequent analysis. table 1 compares the faz measurements at the superficial and deep retinal layers with the two devices. the mean faz area in the superficial retinal layer was 0.55 ± 0.16 mm2 vs 0.31 ± 0.08 mm2 in the spectralis and optovue devices, respectively (figure 1, p < 0.001). similarly, the mean faz area in the deep retinal layer was significantly greater in the spectralis as compared to the optovue images (0.36 ± 0.13 mm2 vs 0.26 ± 0.08 mm2, p <0.001). the mean faz area of the full retina was also significantly larger with the spectralis as compared to the optovue device (0.36 ± 0.10 mm2 vs. 0.26 ± 0.07 mm2, p <0.001). with both devices, the mean faz area was significantly larger in the superficial retinal layer (both p-values < 0.001, figure 1). none of the eyes had smaller faz area in the superficial retina as compared to the deep retina. bland–altman plots (figure 2) demonstrated lack of agreement between the two devices measuring the faz area in superficial, deep, and full retinal slabs. discussion in this study, the faz measurements were significantly larger in the superficial retina as compared to deep retinal layers, and both measurements were significantly greater using the spectralis as compared to the optovue. the octa provides volumetric data for different retinal layers. each commercially available octa device uses a distinct built-in software for image processing and retinal layer segmentation. the details of segmentation algorithms are proprietary to manufacturers and are not publicly available. limited studies have reported the comparisons of measurements using different devices.[18] the methodology and results are conflicting between these studies. in the current study, the faz area was manually determined using the imagej in the images captured by two spectral domain devices, spectralis and optovue, after automated segmentation of superficial and deep retinal layers. an excellent agreement between the independent graders was observed for both devices. consequently, manual calculation of the faz area was a reliable and valid method. this is consistent with the results of previous studies reporting faz measurements in a single device.[12, 17, 19–25] in our study, the mean faz area measured with optovue was similar to previous studies (table 2).[12, 17, 19–25] however, spectralis octa measurements were larger than previously reported values, particularly in the svc. we believe that the discrepancy between our results and previous reports is a result of the recent software update and changes in segmentation reference lines. previous versions of spectralis segmented the scp from the ilm to the outer boundary of ipl, and the dcp from the outer boundary of the ipl to the outer boundary of the opl. in recent software upgrades, the slabs are segmented differently as mentioned in the methods section. similar to our study, mihailovic et al[24] showed that the faz area is larger in spectralis images as compared to the optovue device. the mean faz area measured by optovue was smaller than spectralis for all measured capillary plexuses. spaide et al[15] indicated that none of the automated segmentations by three different octa devices (cirrus 5000 [carl zeiss meditec], rtvue xr avanti [optovue], and triton dri oct [topcon medical systems]) correlated with histological sections. similarly, magrath et al[20] reported significant variability in faz measurements between optovue and zeiss cirrus hd-oct 5000 (carl zeiss meditec) devices, possibly due to different slab segmentation and dissimilarities in image spatial resolution. in contrast to previous reports, the mean faz area at the scp was significantly larger than journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 519 fovea avascular zone in two octa devices; anvari et al figure 1. foveal avascular zone area measurements of one eye using optovue and heidelberg spectralis devices at superficial, deep, and full retinal slabs. figure 2. the bland-altman plots showing lack of agreement between spectralis and optovue devices in measuring faz area at a) superficial, b) deep and c) full retinal slabs. sfaz, superficial foveal avascular zone; dfaz, deep foveal avascular zone; rfaz, foveal avascular zone in full retinal slab; loa, limit of agreement the dcp in the current study. octa instruments only approximately measure the scp and dcp in lieu of the four established capillary plexuses on histological examinations,[17] and current limitations of spatial resolution of different octa instruments may explain the observed discrepancies. rommel et al[16] revealed that the faz area may be different in manual segmentation of retinal layers as compared to those obtained with automated segmentations. they found that in canon device, the mean faz area was greater at the scp than dcp on manual slab segmentation simulating histologic sections.[16] we used the updated versions of the optovue and spectralis (figure 3), the new segmentation algorithms may be closer to histologic descriptions of retinal capillary plexuses, as described by spaides et al.[15] our study showed the importance of taking into account the instrument type as well as the software version in assessing quantitative metrics obtained from octa devices. this is particularly important when assessing the progression of a disease or response to an intervention using the faz area on octa images. we demonstrated the lack of agreement between spectralis and optovue in assessing 520 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 fovea avascular zone in two octa devices; anvari et al table 1. comparison of the mean foveal avascular zone area at different capillary plexuses between the spectralis and optovue devices slab optovue spectralis p-value* superficial capillary plexus (mm2) 0.31 ± 0.08 0.55 ± 0.16 p < 0.001 deep capillary plexus (mm2) 0.26 ± 0.08 0.36 ± 0.13 p < 0.001 full retina (mm2) 0.26 ± 0.07 0.36 ± 0.10 p < 0.001 ∗paired t-test table 2. foveal avascular zone area measured in previous studies using optovue or spectralis devices authors superficial (mm2) deep (mm2) subjects octa device shahlaee et al, 2015[12] 0.27 ± 0.101 0.34 ± 0.116 17 healthy subjects optovue, version 2014.2.0.93 samara et al, 2015[19] 0.266 ± 0.097 0.495 ± 0.227 70 eyes from 67 healthy subjects optovue, version 2014.2.0.13 magrath et al, 2016[20] 0.2855 0.3465 50 eyes in 25 healthy volunteers optovue, 2014.2.0.65 pilotto et al, 2018[21] 0.30 ± 0.08 0.35 ± 0.08 59 normal eyes spectralis unspecified version coscas et al, 2016[22] 0.28 ± 0.1 0.37 ± 0.12 135 eyes of 70 subjects optovue, version 2015.100.0.35 ghassemi et al, 2017[23] 0.27 0.35 224 eyes of 112 volunteers optovue, version 2016.1.0.23-beta corvi et al, 2017[17] spectralis: 0.2408 optovue: 0.2211 spectralis: 0.3178 optovue: 0.2619 36 eyes optovue, version 2016.1.0.2 spectralis, version sp 6.7a mihailovic et al, 2018[24] 0.329 0.335 24 normal eyes spectralis, unspecified version falavarjani et al, 2018[26] 0.32 ± 0.11 0.50 ± 0.13 70 eyes of 70 healthy subjects optovue, version 2016.1.0.26 faz area at different retinal layers. the average bias was larger when evaluating faz in the superficial retinal layers. similarly, mihailovic and colleagues[24] showed slight but significant differences among canon, heidelberg, and optovue in measuring the faz area. one of the limitations of this study was relatively small sample size. restricting the investigation to just two octa devices was another limitation. larger studies are required to establish the relationship between faz measurements using different octa devices. in addition, the segmentation algorithm was different in the two devices. further studies are warranted to demonstrate the repeatability of the measurements after manually changing segmentation boundaries to make them similar in different devices. in conclusion, octa measurements are reliable for evaluation of faz area in various retinal slabs, however, commercially available devices may yield different values depending on their segmentation algorithms. therefore, caution should be exercised in comparing measurements acquired by different octa devices. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 521 fovea avascular zone in two octa devices; anvari et al figure 3. comparison of foveal vascular zone area of one eye using two different software versions of the optovue device. scp, superficial capillary plexus; dcp, deep capillary plexus references 1. minnella am, savastano mc, federici m, falsini b, caporossi a. superficial and deep vascular structure of the retina in diabetic macular ischaemia: oct angiography. acta ophthalmol 2016;96:e647–e648. 2. balaratnasingam c, inoue m, ahn s, mccann j, dhramigavazi e, yannuzzi la, et al. visual acuity is correlated with the area of the foveal avascular zone in diabetic retinopathy and retinal vein occlusion. ophthalmology 2016;123:2352–2367. retrieved from: https://doi.org/10. 1016/j.ophtha.2016.07.008. 3. takase n, nozaki m, kato a, ozeki h, yoshida m, ogura y. enlargement of foveal avascular zone in diabetic eyes evaluated by en face optical coherence tomography angiography. retina 2015;35:2377–2383. retrieved from: https://doi.org/10.1097/iae.0000000000000849. 4. de salles mc, kvanta a, amrén u, epstein d. optical coherence tomography angiography in central retinal vein occlusion: correlation between the foveal avascular zone and visual acuity. investig ophthalmol vis sci 2016;57:oct242–oct246. retrieved from: https://doi. org/10.1167/iovs.15-18819. 5. khadamy j, abri aghdam k, falavarjani kg. an update on optical coherence tomography angiography in diabetic retinopathy. j ophthalmic vis res 2018;13:487–497. retrieved from: https://doi.org/10.4103/jovr.jovr_57_18. 6. kotsolis ai, killian fa, ladas id, yannuzzi la. fluorescein angiography and optical coherence tomography concordance for choroidal neovascularisation in multifocal choroidtis. br j ophthalmol 2010;94:1506–1508. retrieved from: https://doi.org/10.1136/bjo.2009.159913. 7. novotny hr, alvis dl. a method of photographing fluorescence in circulating blood in the human retina. circulation 1961;24:82–86. 8. stanga pe, lim ji, hamilton p. indocyanine green angiography in chorioretinal diseases: indications and interpretation: an evidence-based update. ophthalmology 2003;110:15–21. retrieved from: https://doi.org/10.1016/ s0161-6420(02)01563-4. 9. musa f, muen wj, hancock r, clark d. adverse effects of fluorescein angiography in hypertensive and elderly patients. acta ophthalmol scand 2006;84:740– 742. retrieved from: https://doi.org/10.1111/j.1600-0420. 2006.00728.x. 10. spaide rf, klancnik jm, cooney mj. retinal vascular layers imaged by fluorescein angiography and optical coherence tomography angiography. jama ophthalmol 2015;133:45. retrieved from: https://doi.org/10.1001/jamaophthalmol.2014.3616. 11. kashani ah, chen cl, gahm jk, zheng f, richter gm, rosenfeld pj, et al. optical coherence tomography angiography: a comprehensive review of current methods and clinical applications. prog retin eye res 2017;60:66– 100. retrieved from: https://doi.org/10.1016/j.preteyeres. 2017.07.002. 12. shahlaee a, pefkianaki m, hsu j, ho ac. measurement of foveal avascular zone dimensions and its reliability in healthy eyes using optical coherence tomography angiography. am j ophthalmol 2016;161:50–55e1. retrieved from: https://doi.org/10.1016/j.ajo.2015.09.026. 13. falavarjani kg. optical coherence tomography angiography of the retina and choroid; current applications and future directions. j curr ophthalmol 2017;29:1–4. 14. carpineto p, mastropasqua r, marchini g, toto l, di nicola m, di antonio l. reproducibility and repeatability of foveal avascular zone measurements in healthy subjects by optical coherence tomography angiography. br j ophthalmol 2016;100:671–676. retrieved from: https://doi. org/10.1136/bjophthalmol-2015-307330. 522 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 https://doi.org/10.1016/j.ophtha.2016.07.008 https://doi.org/10.1016/j.ophtha.2016.07.008 https://doi.org/10.1097/iae.0000000000000849 https://doi.org/10.1167/iovs.15-18819 https://doi.org/10.1167/iovs.15-18819 https://doi.org/10.4103/jovr.jovr_57_18 https://doi.org/10.1136/bjo.2009.159913 https://doi.org/10.1016/s0161-6420(02)01563-4 https://doi.org/10.1016/s0161-6420(02)01563-4 https://doi.org/10.1111/j.1600-0420.2006.00728.x https://doi.org/10.1111/j.1600-0420.2006.00728.x https://doi.org/10.1001/jamaophthalmol.2014.3616 https://doi.org/10.1016/j.preteyeres.2017.07.002 https://doi.org/10.1016/j.preteyeres.2017.07.002 https://doi.org/10.1016/j.ajo.2015.09.026 https://doi.org/10.1136/bjophthalmol-2015-307330 https://doi.org/10.1136/bjophthalmol-2015-307330 fovea avascular zone in two octa devices; anvari et al 15. spaide rf, curcio ca. evaluation of segmentation of the superficial and deep vascular layers of the retina by optical coherence tomography angiography instruments in normal eyes. jama ophthalmol 2017;135:259–262. retrieved from: https://doi.org/10.1001/jamaophthalmol.2016.5327. 16. rommel f, siegfried f, kurz m, brinkmann mp, rothe m, rudolf m, et al. impact of correct anatomical slab segmentation on foveal avascular zone measurements by optical coherence tomography angiography in healthy adults. j curr ophthalmol 2018;30:156–160. retrieved from: https://doi.org/10.1016/j.joco.2018.02.001. 17. corvi f, pellegrini m, erba s, cozzi m, staurenghi g, giani a. reproducibility of vessel density, fractal dimension, and foveal avascular zone using 7 different optical coherence tomography angiography devices. am j ophthalmol 2018;186:25–31. retrieved from: https://doi.org/10.1016/j. ajo.2017.11.011. 18. al-sheikh m, falavarjani kg, tepelus tc, sadda sr. quantitative comparison of swept-source and spectral-domain oct angiography in healthy eyes. ophthalmic surg lasers imag retin 2017;48:385–391. retrieved from: https://doi.org/10.3928/2325816020170428-04. 19. samara wa, say eat, khoo ctl, higgins tp, magrath g, ferenczy s, et al. correlation of foveal avascular zone size with foveal morphology in normal eyes using optical coherence tomography angiography. retina 2015;35:2188–2195. retrieved from: https://doi.org/10. 1097/iae.0000000000000847. 20. magrath gn, say eat, sioufi k, ferenczy s, samara wa, shields cl. variability in foveal avascular zone and capillary density using optical coherence tomography angiography machines in healthy eyes. retina 2017;37:2102–2111. 21. pilotto e, frizziero l, crepaldi a, della dora e, deganello d, longhin e, et al. repeatability and reproducibility of foveal avascular zone area measurement on normal eyes by different optical coherence tomography angiography instruments. ophthalmic res 2018;58:4847. retrieved from: https://doi.org/10.1159/000485463. 22. coscas f, sellam a, glacet-bernard a, jung c, goudot m, miere a, et al. normative data for vascular density in superficial and deep capillary plexuses of healthy adults assessed by optical coherence tomography angiography. investig ophthalmol vis sci 2016;57:oct211–223. retrieved from: https://doi.org/10.1167/iovs.15-18793. 23. ghassemi f, fadakar k, bazvand f, mirshahi r, mohebbi m, sabour s. the quantitative measurements of vascular density and flow areas of macula using optical coherence tomography angiography in normal volunteers. ophthalmic surg lasers imag retin 2017;48:478–486. 24. mihailovic n, brand c, lahme l, schubert f, bormann e, eter n, et al. repeatability, reproducibility and agreement of foveal avascular zone measurements using three different optical coherence tomography angiography devices. plos one 2018;13:e0206045. retrieved from: https://doi.org/10.1371/journal.pone.0206045. 25. falavarjani k, shenazandi h, naseri d, anvari p, kazemi p, aghamohammadi f, et al. foveal avascular zone and vessel density in healthy subjects: an optical coherence tomography angiography study. j ophthalmic vis res 2018;13:260. retrieved from: https://doi.org/10.4103/jovr. jovr_173_17. 26. falavarjani kg, shenazandi h, naseri d, anvari p, kazemi p, aghamohammadi f, et al. foveal avascular zone and vessel density in healthy subjects: an optical coherence tomography angiography study. j ophthalmic vis res 2018;13:260–265. retrieved from: https://doi.org/10.4103/ jovr.jovr_173_17. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 523 https://doi.org/10.1001/jamaophthalmol.2016.5327 https://doi.org/10.1016/j.joco.2018.02.001 https://doi.org/10.1016/j.ajo.2017.11.011 https://doi.org/10.1016/j.ajo.2017.11.011 https://doi.org/10.3928/23258160-20170428-04 https://doi.org/10.3928/23258160-20170428-04 https://doi.org/10.1097/iae.0000000000000847 https://doi.org/10.1097/iae.0000000000000847 https://doi.org/10.1159/000485463 https://doi.org/10.1167/iovs.15-18793 https://doi.org/10.1371/journal.pone.0206045 https://doi.org/10.4103/jovr.jovr_173_17 https://doi.org/10.4103/jovr.jovr_173_17 https://doi.org/10.4103/jovr.jovr_173_17 https://doi.org/10.4103/jovr.jovr_173_17 review article photodynamic therapy in ocular oncology mehdi mazloumi, md, mph1; lauren a dalvin, md2; seyed-hossein abtahi, md3; negin yavari, md4 antonio yaghy, md1; arman mashayekhi, md1; jerry a shields, md1; carol l shields, md1 1ocular oncology service, wills eye hospital, thomas jefferson university, philadelphia, usa 2department of ophthalmology, mayo clinic, rochester, usa 3isfahan eye research center, feiz hospital, isfahan university of medical sciences, isfahan, iran 4department of cardiovascular research, tehran heart center, tehran university of medical sciences, tehran, iran orcid: mehdi mazloumi: https://orcid.org/0000-0001-9481-9065 arman mashayekhi: https://orcid.org/0000-0002-1739-1322 abstract over the past two decades, we have witnessed the increasing use of photodynamic therapy (pdt) in the field of ocular oncology. based on a review of the literature and our own experience, we herein review the role of pdt for the management of intraocular tumors. the discussion includes two main topics. first, we discuss the application of pdt for benign tumors, including circumscribed choroidal hemangioma, choroidal osteoma, retinal astrocytoma, retinal capillary hemangioma (retinal hemangioblastoma), and retinal vasoproliferative tumor. second, we assess the role of pdt for malignant tumors, including choroidal melanoma and choroidal metastasis. keywords: choroid; eye; hemangioma; melanoma; metastasis; photodynamic therapy retina; tumor j ophthalmic vis res 2020; 15 (4): 547–558 introduction photodynamic therapy (pdt) is a form of laser therapy that targets abnormal capillaries and has been useful for the treatment of intraocular neovascularizations and neoplasms.[1, 2] the technique of pdt involves the intravenous administration of a photosensitizing chemical substance, currently verteporfin, followed by targeted application of a low power and long duration infrared laser beam. activation of verteporfin by the laser causes formation of correspondence to: arman mashayekhi, md. ocular oncology service, 840 walnut st., suite 1440, philadelphia, usa. e-mail: arman@shields.md received: 30-07-2020 accepted: 07-09-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7793 free radicals, which in turn leads to damage to the leaking blood vessels, resulting in the closure of the vessels and resorption of the related fluid. in the ophthalmic field, pdt was initially conceived as a therapy for macular choroidal neovascularization in eyes with age-related macular degeneration.[3] later, pdt was employed for polypoidal choroidal vasculopathy, central serous chorioretinopathy, and other retinal conditions.[4, 5] pdt has been also used as therapy for selected intraocular tumors. pdt acts through two mechanisms with regard to intraocular tumors: (1) direct tumor destruction via selective cytotoxic activity against tumor cells, and (2) through the promotion of intraluminal this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: mazloumi m, dalvin la, abtahi s-h, yavari n, yaghy a, mashayekhi a, shields ja, shields cl. photodynamic therapy in ocular oncology. j ophthalmic vis res 2020;15:547–558. © 2020 journal of ophthalmic and vision research | published by knowledge e 547 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7793&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photodynamic therapy in ocular oncology; mazloumi et al photothrombosis in the vessels supplying the tumor.[6] in this review, we present a summary on the role of pdt in the management of various benign and malignant intraocular neoplasms. methods a comprehensive literature search was performed using the pubmed and scopus databases for english-language publications using the keywords “photodynamic therapy”, “circumscribed choroidal hemangioma”, “choroidal osteoma”, “ retinal astrocytoma”, “retinal capillary hemangioma”, “retinal hemangioblastoma”, “ retinal vasoproliferative tumor”, “ choroidal melanoma”, “choroidal metastasis”, “intraocular tumors”, and “ocular oncology” for all papers published from january 2002, the time when pdt became available for use in the ophthalmic field, to may 2020. the relevant articles were reviewed, and key findings were extracted. pdt methods used in ocular oncology verteporfin (visudyne®; novartis international ag, basel, switzerland) with a total dose of 6 mg/m2 is injected intravenously slowly over 10 min and accumulates in the retinal, choroidal, and tumor vasculature. the following calculations can be performed to appropriately reconstitute verteporfin at the correct dosage for a patient based on body surface area (bsa): 1. bsa = √height (in) × weight (lbs) 3131 2. total drug dose = 6 mg/m2 × bsa 3. volume of reconstituted verteporfin = total drug dose ÷ 2.0 mg/ml 4. volume of dextrose 5% in water (d5w) = 30 ml – volume of reconstituted verteporfin the infrared laser beam (coherent opal photoactivator diode laser; coherent inc., santa clara, ca, usa) is then applied 5 min after the completion of infusion with the following properties (standard fluence): 1. wavelength: 689 nm 2. radiant exposure: 50 j/cm2 for 83 s (irradiance: 600 mw/cm2) in some cases, the half-fluence method is used to deliver 25 j/cm2 of energy and is usually utilized for more photosensitive tumors. while in some cases, double-dose method is used to deliver 100 j/cm2 by administering a total verteporfin dose of 12 mg/m2, in some cases, the method is used to deliver 100 j/cm2 by applying laser for 166 s.[1, 2] results indications for pdt in ocular oncology part a: benign tumors a.1: benign choroidal tumors i. circumscribed choroidal hemangioma circumscribed choroidal hemangioma (cch) is a benign vascular hamartoma, frequently diagnosed as a solitary, orange-red, dome-shaped mass in the posterior pole.[7] patients aged <20 years present with worse visual acuity and larger, more posterior tumors.[8] when the lesion is asymptomatic, usually as an extrafoveal mass detected in routine retinal examination, observation alone is appropriate. in cases with visual distortion or reduced visual acuity, due to a foveal or juxtafoveal tumor causing cystoid macular edema (cme) or subretinal fluid (srf), intervention can improve the long-term visual acuity outcomes.[9] due to the risk of retinal scarring and other ocular complications associated with radiation therapy, laser photocoagulation, and thermotherapy, these modalities are less favored as primary treatment.[10] pdt, in contrast, spares the overlying retina and has efficacy in both reducing cch thickness and causing resolution of associated serous srf, resulting in stability or improvement of visual acuity (figure 1).[11–15] shields et al, in a series of 458 cases, found that the management of cch in the pdt era has allowed for improved visual acuity outcomes compared with the pre-pdt era, with mean final visual acuity of 20/63 (pdt era) versus 20/400 (pre-pdt era).[16] ho et al reported that patients presenting before the age of 50 years with pretreatment best-corrected visual acuity (bcva) ≥ 20/200 and less foveal edema were most likely to benefit from pdt.[17] in a recent study by di nicola et al, investigating the predictive factors of visual outcome in 79 patients with cch treated with pdt, the authors found 548 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 photodynamic therapy in ocular oncology; mazloumi et al correlations between good final visual outcome (≥20/40) and good baseline visual acuity, smaller tumor size, lack of cme, and lack of treatment prior to pdt.[18] with regards to the treatment parameters, double-dose pdt (12 mg/m2) provided better tumor regression with similar resorption of srf compared with standard-dose pdt (6 mg/ m2). single-spot pdt was as effective and safe as overlapping-spot pdt (two to three spots).[19, 20] moreover, although bolus pdt (6 mg/m2 verteporfin infusion bolus in 1 min; treatment at 5 min; 100 j/cm2; 166 s) is capable of inducing tumor regression, the resulting retinal pigment epithelium (rpe) and retinal changes can lead to reduced visual acuity.[21] some clinicians have postulated that patients who require multiple treatment sessions might experience recurrent leakage at more frequent intervals.[22] ii. choroidal osteoma choroidal osteoma is a benign, ossifying tumor of unknown origin that often appears as a unilateral, orange–yellow choroidal mass with well-defined or scalloped borders located in the juxtapapillary or macular region of young women in their early twenties.[23, 24] in a series of 74 eyes with choroidal osteoma reported by shields et al, the authors found evidence of growth in 51% of eyes and decalcification in nearly 50% of eyes with poor visual acuity of 20/200 or worse in 56% of eyes by 10 years.[25] although benign, choroidal osteoma can result in significant visual acuity loss by profound outer retinal layer thinning and photoreceptor loss over the subfoveal portion of the tumor.[26] shields et al were the first to report the beneficial effect of pdt on extrafoveal choroidal osteoma. in their report, pdt was applied to the entire juxtapapillary choroidal osteoma with an overlying subretinal hemorrhage using a single 83-s laser spot at 689 nm (50 j/cm2). the hemorrhage resolved by one month and the complete regression of the osteoma was noted after nine months of follow-up (figure 2 ).[27] mazloumi et al recently evaluated the efficacy of pdt in nine eyes of nine patients with extrafoveolar choroidal osteoma and found complete (4/9, 44%) and partial (5/9, 56%) tumor regression with a mean of 73% regression in the pdt-treated areas after 49 months of follow-up, which was significantly greater than the spontaneous regression rate of 28% previously reported at a five-year follow-up. they concluded that pdt is a valuable modality for the management of extrafoveal choroidal osteoma, with the intent to decalcify and involute the tumor so that further tumor growth under the foveola would be prohibited and visual acuity would be preserved. they also cautioned that pdt should not be employed for subfoveal choroidal osteoma as this could lead to choroidal atrophy and secondary photoreceptor retraction in the central macular area with poor visual outcome.[28] a.2: benign retinal tumors iii. retinal astrocytoma benign retinal astrocytic tumors are comprised of three different entities: astrocytic hamartoma, acquired astrocytoma, and reactive retinal gliosis. astrocytic hamartoma, which is most frequently detected in children with tuberous sclerosis complex or neurofibromatosis, is typically a stable tumor.[29] however, acquired astrocytoma, which is most frequently found in young or middle-aged adults without tuberous sclerosis complex, is a sporadic tumor typically located in the macular or juxtapapillary region. acquired astrocytoma typically presents with abundant intrinsic vascularity, slow progressive growth, and exudation that can cause visual acuity loss and even lead to total exudative retinal detachment necessitating enucleation.[30–35] pdt, plaque radiotherapy, external beam radiotherapy, laser photocoagulation, endoresection, and enucleation have been used to control retinal astrocytoma with limited reports on their beneficial effects.[36–39] mennel et al reported a case of an exudative astrocytic hamartoma in a patient with tuberous sclerosis treated with pdt. tumor size reduction along with the resolution of srf and improvement in visual acuity were observed after treatment.[40] in 2008, shields et al successfully applied pdt in a patient with retinal astrocytoma and associated macular exudation, edema, srf, and decreased visual acuity to 20/70, which was unresponsive to laser photocoagulation.[31] after the treatment, the resolution of macular exudation, edema, and srf were noted, resulting in improved visual acuity initially of 20/50 (at one month) and ultimately 20/30 (at 4, 8, and 12 months).[31] house and journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 549 photodynamic therapy in ocular oncology; mazloumi et al figure 1. fundus photograph of the right eye of a patient with choroidal hemangioma located in the macula (a) before and (b) three months after photodynamic therapy (pdt). b-scan ultrasonography (c) before and (d) after pdt revealed a decrease in tumor thickness. figure 2. fundus photograph of the right eye of a patient with juxtapapillary choroidal osteoma associated with subretinal hemorrhage (a) before and (b) after pdt. pdt resulted in complete regression of the tumor and resolution of subretinal hemorrhage. figure 3. fundus photograph of the left eye of a patient with juxtapapillary retinal hemangioblastoma associated with macular edema and subretinal fluid and lipid exudation (a) before and (b) 20 months after pdt. pdt resulted in the regression of the tumor and the resolution of the macular edema confirmed by optical coherence tomography (oct) (c, d). 550 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 photodynamic therapy in ocular oncology; mazloumi et al figure 4. fundus photograph of the right eye of a patient with a vasoproliferative tumor located inferiorly (a) before and (b) 18 months after pdt. figure 5. fundus photograph of the right eye of a patient with amelanotic choroidal melanoma (a) before and (b) after pdt. pdt resulted in the regression of the tumor confirmed with b-scan ultrasonography (c, d). colleagues, in 2016, reported successful treatment of a juxtapapillary retinal astrocytoma with one session of pdt in a 50-year-old man with a visual acuity of 20/100. treatment resulted in complete resolution of surrounding srf and lipid exudation. at the 20 months follow-up, the visual acuity improved to 20/20 with complete tumor regression and normal foveal contour on optical coherence tomography.[41] eskelin et al reported two cases of aggressive retinal astrocytoma with secondary lipid exudation and exudative retinal detachment successfully treated with a single session of pdt.[34] the growing vascularized portion of both tumors regressed, and the exudative retinal detachment completely resolved. regression was associated with obliteration of the intrinsic vessels within the growing part of the tumors as well as closure of the dilated retinal capillaries over the tumors.[34] the authors proposed pdt as a first-line treatment for aggressive retinal astrocytoma. iv. retinal capillary hemangioma (retinal hemangioblastoma) genetically, retinal capillary hemangioma (rch) can be found either as an isolated lesion or as part of the von hippel–lindau (vhl) syndrome. in a recent study, the vhl syndrome was the underlying cause of rch in 84% of cases, more often than previously reported.[42] hence, genetic and clinical vhl screening should be performed in all patients with rch. phenotypically, rch can either be juxtapapillary or located elsewhere in the retina (extrapapillary). extrapapillary rch usually starts as a tiny red intraretinal lesion, journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 551 photodynamic therapy in ocular oncology; mazloumi et al figure 6. choroidal metastasis managed with pdt. fundus photograph of the left eye of a patient with choroidal metastasis located superior to the macula (a) and confirmed by b-scan ultrasonography (b). the tumor was associated with subfoveal fluid as seen on oct (c). following the pdt application, there was a complete tumor regression (d) confirmed by b-scan ultrasonography (e) and resolution of the subfoveal fluid as seen on oct (f). measuring less than a few hundred microns in diameter. with increasing size, rch might manifest more distinctive features, including increasing nodularity, feeding and draining blood vessels that become progressively dilated and tortuous, and exudative retinopathy.[43] fluorescein angiography (fa) is the best diagnostic modality for the detection and confirmation of rch because fa shows rapid filling of the feeding artery, then the tumor, followed by the rapid exit through the draining vein. more importantly, subclinical pinpoint tumors can be detected on fa before they become symptomatic.[44] disease progression can be devastating because exudation from the vascular tissue can affect the macula and cause glial proliferation and tractional retinal changes. the management of rch is debated and the feasibility and success of treatment depend on several factors, including size and location of the tumor, severity of exudation, associated retinal detachment, and epiretinal fibrosis or hemorrhage.[45–47] tumors associated with vhl syndrome tend to have more aggressive behavior. therefore, nearly all rchs must be considered for the treatment. if lesions are small (<2 mm) in size, laser photocoagulation or pdt can be applied; if medium (2–4.5 mm), pdt or cryotherapy can be used; and if large (>4.5 mm), cryotherapy, brachytherapy, or endoresection might be employed.[44] there may also be a beneficial role for injections of intravitreal anti-vascular endothelial growth factor (vegf) agents.[48] pdt has been used successfully for the management of rch.[49, 50] in a series of six eyes reported by sachdeva et al, pdt resulted in tumor regression or stabilization and improvement of srf and lipid exudation in all cases.[51] however, stabilization or improvement of visual acuity was noted in only 50% of the cases. the authors stated that the benefits of pdt might be limited by pre-existing macular changes and progression of epiretinal membrane.[51] in a series of five eyes with rch (four juxtapapillary and one extrapapillary tumors) by papastefanou et al, two different pdt treatment protocols were employed for eyes with juxtapapillary rch, that is, two eyes received double-duration, full-fluence pdt, while the other two eyes received single-duration, half-fluence pdt. this variable pdt protocol did not affect the treatment outcome as one eye in each group showed partial resolution of macular edema. despite the improvement in macular edema in 50% of the patients with juxtapapillary rch, this improvement did not result in an 552 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 photodynamic therapy in ocular oncology; mazloumi et al improvement in visual acuity after treatment.[52] however, the extrapapillary rch in this series showed regression of the tumor and macular edema with va improvement, suggesting a better anatomical and functional outcome following the pdt application for peripheral tumors.[52] the authors stated that although peripheral rch is presumed to be more amenable to the treatment due to its peripheral location, complications including epiretinal membrane formation and tractional rd can occur.[52] we believe that pdt should be considered as a nonablative modality for the treatment of rchs that <4.5 mm in diameter (figure 3). extrapapillary rch >4.5 mm in diameter pose a difficult challenge and pdt may be ineffective for these tumors.[45] v. retinal vasoproliferative tumors retinal vasoproliferative tumors (vpt) were first described in 12 patients in 1983 by shields et al,[53] and later, the same group provided clinical descriptions on 103 cases in 1995 [54] and 334 cases in 2013,[55] further improving our understanding of this uncommon retinal tumor. vpt is a reactionary glial cell proliferation with secondary vasoproliferation presenting as a vascular nodular tumor arising in the neurosensory retina with associated telangiectasia, lipid exudation, and srf.[56] while three-quarters are primary and isolated, roughly a quarter of such lesions are secondary to various preexisting inflammatory, infectious, congenital, iatrogenic, hereditary, or traumatic retinal conditions.[54, 57] vpt is less frequently observed in the posterior pole and has a predilection for the retinal periphery, especially the inferotemporal quadrant.[58] these lesions can be sightthreatening by causing lipid exudation with or without exudative retinal detachment, preretinal fibrosis, intraand subretinal hemorrhage, rpe proliferation, epiretinal membrane, and cme.[54] management options include observation, laser photocoagulation, cryotherapy, pdt, and plaque radiotherapy. asymptomatic and isolated small, peripheral vpts with minimal exudation posing no visual threat are best managed with cautious observation. treatment is necessary for tumors that threaten or affect visual acuity due to progressive exudation. smaller tumors can be managed with laser photocoagulation, pdt, or cryotherapy, while larger tumors (>2–3 mm) can be managed with plaque radiotherapy with reported tumor regression in >90% of cases.[59, 60] intravitreal anti-vegf medications have been recently used in few case reports with promising results. however, the effect seems to be short-lived and recurrence of exudation can occur following the cessation of treatment.[61, 62] application of pdt in the peripheral retina may be technically challenging, and there is much less experience on its successful use for the treatment of vpt.[63] pdt can be applied as single or multiple spots depending on the size of the lesion (figure 4). hussain et al in a series of 25 eyes with vpt treated with pdt found the resolution of exudation in 76% (19/25), regression of the tumor in 76% (19/25), and visual gain or stabilization in 92% (23/25).[64] the authors noted a decrease in the success rate in tumors with extensive exudation, as only one-half of the cases with exudative retinopathy achieved an adequate response.[64] blasi et al reported successful treatment of vpt with one session of pdt in three patients. they observed neither recurrence nor complications at a one-year followup.[65] in another study by barbazetto et al, a 47year old patient developed a secondary vpt and excessive exudation secondary to scleral buckling surgery. two different light doses (50 j/cm2 and 100 j/cm2) were applied in two consecutive pdt sessions, and the tumor became fibrotic and exhibited no sign of vascularity or leakage after the treatment.[56] part b: malignant tumors i. choroidal melanoma choroidal melanoma is the most common primary intraocular malignancy of adulthood, which appears as an amelanotic-to-solid brown, dome-shaped, or mushroom-shaped mass.[66, 67] choroidal melanoma usually occurs in caucasians with no sex predominance, and in contrast to cutaneous melanoma, ultraviolet radiation exposure plays no known role in its pathogenesis.[68] there is no strong familial inheritance pattern for this neoplasm in most patients, although some cases may be associated with the bap1 tumor predisposition syndrome.[69] shields et al in a large survey on 8,033 cases investigating clinical spectrum and prognosis journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 553 photodynamic therapy in ocular oncology; mazloumi et al of uveal melanoma found that there were 106 (1%) cases in young patients (≤20 years), 4,287 (53%) cases in mid adults (21–60 years), and 3,640 (45%) cases in older adults (>60 years).[70] the overall mortality rate of choroidal melanoma in their report was as high as 20% at 20 years, mainly due to metastasis to the liver.[70] prognosis of choroidal melanoma is dependent on several factors, including size and location of the tumor, extrascleral extension, and tumor cytogenetics.[71, 72] the management of choroidal melanoma involves careful evaluation of tumor size and location, with systemic workup for distant metastasis. for large tumors, enucleation may be required.[73] globe-sparing methods can be used for the treatment of small, medium, and some large choroidal melanomas, including radiotherapy (plaque, proton-beam, gamma knife, or stereotactic), transpupillary thermotherapy (ttt), and pdt.[74–76] plaque radiotherapy is currently the treatment of choice in most cases with local tumor control rates of as high as 97% and minimal damage to surrounding orbital tissues. however, damage to the retina, optic nerve, and anterior structures of the globe can occur in many cases despite adequate tumor control.[77] photocoagulation has been used in the past for the treatment of small choroidal melanomas but is associated with relatively high rates of local treatment failure and delayed local tumor recurrence.[78] non-coagulative laser therapy, referred to as ttt was commonly used for the treatment of small choroidal melanomas. mashayekhi et al in a study of small choroidal melanomas treated between 2001 and 2012 with ttt, found a kaplan–meier estimate for tumor recurrence of 11% at 5 years and 15% at 10 years.[76] the authors advised that, when possible, small choroidal melanomas with multiple risk factors should be treated with methods other than ttt. currently, ttt is typically reserved for small choroidal melanomas with one or two risk factors or as supplementary treatment following plaque radiotherapy or proton beam irradiation.[76, 79] pdt is a convenient, cost-effective, welltolerated option for outpatient settings and, in contrast to ttt, is painless at the time of application.[80] in a study on 12 amelanotic or lightly pigmented small choroidal melanomas managed with pdt, turkoglu et al found complete tumor regression after one (n = 3, 25%), two (n = 3, 25%), and three (n = 2, 17%) sessions of primary pdt, with a stable or improved visual acuity (figure 5).[74] campbell et al in another study on nine patients with posteriorly located amelanotic choroidal melanomas (one with a pigmented portion) found complete tumor regression in eight amelanotic cases. although the amelanotic portion of the mixed tumor flattened, the height of the pigmented part remained stable.[80] barbazetto et al conducted a study on four patients with choroidal melanoma who had local failure following plaque radiotherapy and ttt. after the secondary pdt application, two eyes were salvaged and two melanomas continued to grow, necessitating enucleation.[81] it is believed that for pdt to be effective, choroidal melanoma should be non-pigmented or minimally pigmented to allow penetration of the laser light to the intrinsic tumor vessels. however, fabian et al in a study on 15 patients with small pigmented posterior pole choroidal melanoma who were treated with three sessions of pdt found tumor control in 12 (80%) patients at 15 months follow-up. of note, all the three (20%) failed cases were 100% pigmented, de novo melanomas rather than transformed nevi, and showed a radial growth pattern rather than increased thickness.[82] it has been claimed that the presence of srf may be a harbinger of improved response to pdt due to the presence of underlying leaking vessels.[83, 84] although pdt of small choroidal melanomas is associated with a lower rate of tumor control (80– 89%) compared with radiotherapy (95–97%), the visual acuity can be maintained or improved after pdt compared with an increased possibility of vision loss following radiotherapy modalities.[83] some researchers have evaluated the efficacy of the combination of pdt with radiotherapy. blasi et al in a study on 26 patients have shown that pdt as neoadjuvant therapy before plaque radiotherapy reduced tumor thickness in 73% of cases, thereby decreasing the necessitated dose of radiation for subsequent radiotherapy without compromising disease control.[85] tuncer et al reported a patient with an amelanotic choroidal melanoma of 6.5 mm thickness who showed poor response to iodine plaque radiotherapy (80 gy apical dose) with no reduction in thickness at 16 months follow-up. the authors documented dramatic tumor regression over two months 554 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 photodynamic therapy in ocular oncology; mazloumi et al to a completely flat scar (1.3 mm thickness) following the application of pdt using three overlapping spots.[86] the authors hypothesized that primary radiotherapy might cause better ”recirculation and re-oxygenation” permitting improved concentration of photoactive dye in the tumor vasculature for subsequent pdt. ii. choroidal metastasis choroidal metastasis is the most common intraocular malignancy in adults, typically appearing as a solitary yellow mass with associated srf.[87, 88] in a large survey on 2,214 uveal metastasis by shields and colleagues, the primary tumor originated in the breast (37%), lung (26%), kidney (4%), gastrointestinal (gi) tract (4%), cutaneous melanoma (2%), lung carcinoid (2%), prostate (2%), thyroid (1%), pancreas (1%), other sites (3%), and unknown (16%). the worst survival was found in patients with pancreatic metastasis (mean 4.2 months) and the best survival with lung carcinoid (92% at 5 years).[89] choroidal involvement may occur at any stage of the primary malignancy, but those that tend to present in the late course of malignancy are associated with a worse prognosis.[88, 90] in the literature, several options have been proposed for the management of choroidal metastatic lesions based on the size, location, number of metastatic tumors, systemic status, and laterality.[88] observation, systemic chemotherapy, radiotherapy, ttt, and pdt are current treatment strategies. pdt is a safe, non-invasive procedure, and the highly vascular nature of choroidal metastatic tumors makes them amenable to pdt. several case reports and series have been published on the use of pdt in the management of choroidal metastasis, with acceptable results. in a recent retrospective interventional case series of 40 eyes with 58 choroidal metastatic tumors, pdt showed promising results, achieving tumor control with one (n = 32 tumors [71%]) or two (n = 3 tumors [7%]) sessions (figure 6). the study showed that the primary cancer site or ocular tumor features (size, location, color, shape, related srf) did not impact tumor control.[90] in a series by kaliki et al consisting of nine metastatic lesions in eight eyes, regression of the tumor was documented in seven tumors (78%) and stabilized or improved vision was noted in seven eyes (88%).[91] in another series by ghodasra et al, 17 of 21 tumors (81%) were flat at 12 months follow-up and 18 tumors (86%) showed complete resolution of srf.[92] discussion pdt is a well-tolerated outpatient modality for the treatment of selected benign or malignant intraocular tumors. over the past two decades, our knowledge of the potential role of pdt in the field of ocular oncology has increased substantially but further studies are needed to explore the full potential and limitations of this relatively novel therapeutic modality. financial support and sponsorship this review has been supported in part by the eye tumor research foundation, philadelphia, pa (jas, cls). the funders had no role in the design and conduct of the study, in the collection, analysis, and interpretation of the data, and in the preparation, review, or approval of the manuscript. conflicts of interest there are no conflicts of interest. references 1. kwiatkowski s, knap b, przystupski d, saczko j, kedzierska e, knap-czop k, et al. photodynamic therapy mechanisms, photosensitizers and combinations. biomed pharmacother 2018;106:1098–1107. 2. dolmans de, fukumura d, jain rk. photodynamic therapy for cancer. nat rev cancer 2003;3:380–387. 3. woodburn kw, engelman cj, blumenkranz ms. photodynamic therapy for choroidal neovascularization: a review. retina 2002;22:391–405. 4. hata m, tagawa m, oishi a, kawashima y, nakata i, akagikurashige y, et al. efficacy of photodynamic therapy for polypoidal choroidal vasculopathy associated with and without pachychoroid phenotypes. ophthalmol retina 2019;3:1016–1025. 5. erikitola oc, crosby-nwaobi r, lotery aj, sivaprasad s. photodynamic therapy for central serous chorioretinopathy. eye 2014;28:944–957. 6. blasi ma, pagliara mm, lanza a, sammarco mg, caputo cg, grimaldi g, et al. photodynamic therapy in ocular oncology. biomedicines 2018;6:17. 7. mashayekhi a, shields cl. circumscribed choroidal hemangioma. curr opin ophthalmol 2003;14:142–149. 8. dalvin la, lim ls, chang m, udyaver s, mazloumi m, vichitvejpaisal p, et al. circumscribed choroidal journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 555 photodynamic therapy in ocular oncology; mazloumi et al hemangioma: clinical features and outcomes by age category in 458 cases. saudi j ophthalmol 2019;33:219– 228. 9. shields cl, honavar sg, shields ja, cater j, demirci h. circumscribed choroidal hemangioma: clinical manifestations and factors predictive of visual outcome in 200 consecutive cases. ophthalmology 2001;108:2237– 2248. 10. shields ja, shields cl, materin ma, marr bp, demirci h, mashayekhi a. changing concepts in management of circumscribed choroidal hemangioma: the 2003 j. howard stokes lecture, part 1. ophthal surg laser imag 2004;35:383–394. 11. shields ja. photodynamic therapy for choroidal hemangioma. graefes arch clin exp ophthalmol 2006;244:1071–1072. 12. subira o, brosa h, lorenzo-parra d, arias-barquet l, catala-mora j, cobos e, et al. choroidal haemangioma and photodynamic therapy. anatomical and functional response of patients with choroidal hemangioma treated with photodynamic therapy. arch soc esp oftalmol 2017;92:257–264. 13. elizalde j, vasquez l, iyo f, abengoechea s. photodynamic therapy in the management of circumscribed choroidal hemangioma. can j ophthalmol 2012;47:16–20. 14. zhang y, liu w, fang y, qian j, xu g, wang w, et al. photodynamic therapy for symptomatic circumscribed macular choroidal hemangioma in chinese patients. am j ophthalmol 2010;150:710–5.e1. 15. blasi ma, tiberti ac, scupola a, balestrazzi a, colangelo e, valente p, et al. photodynamic therapy with verteporfin for symptomatic circumscribed choroidal hemangioma: fiveyear outcomes. ophthalmology 2010;117:1630–1637. 16. shields cl, dalvin la, lim ls, chang m, udyaver s, mazloumi m, et al. circumscribed choroidal hemangioma: visual outcome in the pre-photodynamic therapy era versus photodynamic therapy era in 458 cases. ophthalmol retina 2020;4:100–110. 17. ho yf, chao a, chen kj, chao an, wang nk, liu l, et al. clinical outcomes and predictors of response to photodynamic therapy in symptomatic circumscribed choroidal hemangioma: a retrospective case series. plos one 2018;13:e0197088. 18. di nicola m, williams bk jr, srinivasan a, al-dahmash s, mashayekhi a, shields ja, et al. photodynamic therapy (pdt) for circumscribed choroidal hemangioma in 79 consecutive patients: comparative analysis of factors predictive of visual outcome. ophthalmol retina 2020;s2468–6530:30171–30178. 19. lee jh, lee cs, lee sc. efficacy of double dose photodynamic therapy for circumscribed choroidal hemangioma. retina 2019;39:392–397. 20. su za, tang xj, zhang lx, su xh. comparison of outcomes between overlapping-spot and singlespot photodynamic therapy for circumscribed choroidal hemangioma. int j ophthalmol 2014;7:66–70. 21. pilotto e, urban f, parrozzani r, midena e. standard versus bolus photodynamic therapy in circumscribed choroidal hemangioma: functional outcomes. eur j ophthalmol 2011;21:452–458. 22. beardsley rm, mccannel ca, mccannel ta. recurrent leakage after visudyne photodynamic therapy for the treatment of circumscribed choroidal hemangioma. ophthalmic surg laser imag retina 2013;44:248–251. 23. alameddine rm, mansour am, kahtani e. review of choroidal osteomas. middle east afr j ophthalmol 2014;21:244. 24. shields cl, shields ja, augsburger jj. choroidal osteoma. surv ophthalmol 1988;33:17–27. 25. shields cl, sun h, demirci h, shields ja. factors predictive of tumor growth, tumor decalcification, choroidal neovascularization, and visual outcome in 74 eyes with choroidal osteoma. arch ophthalmol 2005;123:1658–1666. 26. shields cl, perez b, materin ma, mehta s, shields ja. optical coherence tomography of choroidal osteoma in 22 cases: evidence for photoreceptor atrophy over the decalcified portion of the tumor. ophthalmology 2007;114:e53–e58. 27. shields cl, materin ma, mehta s, foxman bt, shields ja. regression of extrafoveal choroidal osteoma following photodynamic therapy. arch ophthalmol 2008;126:135– 137. 28. mazloumi m, dalvin la, ancona-lezama d, mashayekhi a, shields cl. photodynamic therapy for extrafoveolar choroidal osteoma. retina 2020;40:966–971. 29. zimmer-galler ie, robertson dm. long-term observation of retinal lesions in tuberous sclerosis. am j ophthalmol 1995;119:318–324. 30. shields ja, eagle jr rc, shields cl, marr bp. aggressive retinal astrocytomas in four patients with tuberous sclerosis complex. trans am ophthalmol soc 2004;102:139. 31. shields cl, materin ma, marr bp, krepostman j, shields ja. resolution of exudative retinal detachment from retinal astrocytoma following photodynamic therapy. arch ophthalmol 2008;126:273–274. 32. house rj, mashayekhi a, shields ja, shields cl. total regression of acquired retinal astrocytoma using photodynamic therapy. retin cases brief rep 2016;10:41– 43. 33. mashayekhi a, shields cl, shields ja. transient increased exudation after photodynamic therapy of intraocular tumors. middle east afr j ophthalmol 2013;20:83. 34. eskelin s, tommila p, palosaari t, kivelä t. photodynamic therapy with verteporfin to induce regression of aggressive retinal astrocytomas. acta ophthalmol 2008;86:794–799. 35. shields cl, shields ja, eagle rc jr, cangemi f. progressive enlargement of acquired retinal astrocytoma in 2 cases. ophthalmology 2004;111:363–368. 36. vilaplana d, castilla m, poposki v, alameda f, shields cl. acquired retinal astrocytoma managed with endoresection. retina 2006;26:1081–1082. 37. tuncer s, cebeci z. dramatic regression of presumed acquired retinal astrocytoma with photodynamic therapy. middle east afr j ophthalmol 2014;21:283–286. 38. drummond sr, kemp eg. retinal astrocytoma managed by brachytherapy. ophthalmology 2009;116:597-e1. 39. bloom sm, mahl cf. photocoagulation for serous detachment of the macula secondary to retinal astrocytoma. retina 1991;11:416–422. 556 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 photodynamic therapy in ocular oncology; mazloumi et al 40. mennel s, hausmann n, meyer ch, peter s. photodynamic therapy for exudative hamartoma in tuberous sclerosis. arch ophthalmol 2006;124:597–599. 41. house rj, mashayekhi a, shields ja, shields cl. total regression of acquired retinal astrocytoma using photodynamic therapy. retin cases brief rep 2016;10:41– 43. 42. binderup mlm, stendell as, galanakis m, moller hu, kiilgaard jf, bisgaard ml. retinal hemangioblastoma: prevalence, incidence and frequency of underlying von hippel-lindau disease. br j ophthalmol 2018;102:942– 947. 43. singh ad, nouri m, shields cl, shields ja, smith af. retinal capillary hemangioma: a comparison of sporadic cases and cases associated with von hippel-lindau disease. ophthalmology 2001;108:1907–1911. 44. shields cl, douglass a, higgins t, samara wa, shields ja. retinal hemangiomas: understanding clinical features, imaging, and therapies. retina today [internet]. 2015:61– 67. available from: https://retinatoday.com/articles/2015july-aug/retinal-hemangiomas-understanding-clinicalfeatures-imaging-and-therapies. 45. wiley he, krivosic v, gaudric a, gorin mb, shields c, shields j, et al. management of retinal hemangioblastoma in von hippel-lindau disease. retina 2019;39:2254–2263. 46. singh ad, nouri m, shields cl, shields ja, perez n. treatment of retinal capillary hemangioma. ophthalmology 2002;109:1799–1806. 47. sturzeneker g, maia a, morales m, belfort r n. vitreoretinal surgery and panretinal photocoagulation in a patient with multiple large retinal capillary hemangiomas (von hippel-lindau disease): a novel approach. case rep ophthalmol 2019;10:327–333. 48. wong wt, liang kj, hammel k, coleman hr, chew ey. intravitreal ranibizumab therapy for retinal capillary hemangioblastoma related to von hippel-lindau disease. ophthalmology 2008;115:1957–1964. 49. caminal jm, maidana de, carnota p, cobos-martin e, arias l. retinal hemangioblastoma regression after single session of photodynamic therapy. jama ophthalmol 2014;132:559. 50. stattin m, kralinger m, haas g, zehetner c, bechrakis en. photodynamic therapy for retinal capillary hemangioblastoma. can j ophthalmol 2014;49:e32– e35. 51. sachdeva r, dadgostar h, kaiser pk, sears je, singh ad. verteporfin photodynamic therapy of six eyes with retinal capillary haemangioma. acta ophthalmol 2010;88:e334– e340. 52. papastefanou vp, pilli s, stinghe a, lotery aj, cohen vm. photodynamic therapy for retinal capillary hemangioma. eye 2013;27:438–442. 53. shields ja, decker wl, sanborn ge, augsburger jj, goldberg re. presumed acquired retinal hemangiomas. ophthalmology 1983;90:1292–1300. 54. shields cl, shields ja, barrett j, de potter p. vasoproliferative tumors of the ocular fundus: classification and clinical manifestations in 103 patients. arch ophthalmol 1995;113:615–623. 55. shields cl, kaliki s, al-dahmash s, rojanaporn d, shukla sy, reilly b, et al. retinal vasoproliferative tumors: comparative clinical features of primary vs secondary tumors in 334 cases. jama ophthalmol 2013;131:328– 334. 56. barbezetto ia, smith rt. vasoproliferative tumor of the retina treated with pdt. retina 2003;23:565–567. 57. gottlieb f, fammartino jj, stratford tp, brockhurst rj. retinal angiomatous mass. a complication of retinal detachment surgery. retina 1984;4:152–157. 58. honavar sg. retinal vasoproliferative tumor a proposal for classification. indian j ophthalmol 2018;66:185–186. 59. krivosic v, massin p, desjardins l, le hoang p, tadayoni r, gaudric a. management of idiopathic retinal vasoproliferative tumors by slit-lamp laser or endolaser photocoagulation. am j ophthalmol 2014;158:154–161.e1. 60. nickerson sj, al-dahmash sa, shields cl, shields ja. retinal vasoproliferative tumor with total retinal detachment managed with plaque radiotherapy. oman j ophthalmol 2012;5:53–54. 61. saito w, kase s, fujiya a, dong z, noda k, ishida s. expression of vascular endothelial growth factor and intravitreal anti-vegf therapy with bevacizumab in vasoproliferative retinal tumors. retina 2013;33:1959– 1967. 62. rogers c, damato b, kumar i, heimann h. intravitreal bevacizumab in the treatment of vasoproliferative retinal tumours. eye 2014;28:968–973. 63. osman sa, aylin y, gul a, celikel h. photodynamic treatment of a secondary vasoproliferative tumour associated with sector retinitis pigmentosa and usher syndrome type i. clin exp ophthalmol 2007;35:191–193. 64. hussain rn, jmor f, damato b, heimann h. verteporfin photodynamic therapy for the treatment of retinal vasoproliferative tumors. ophthalmology 2015;122:2361– 2363. 65. blasi ma, scupola a, tiberti ac, sasso p, balestrazzi e. photodynamic therapy for vasoproliferative retinal tumors. retina 2006;26:404–409. 66. egan km, seddon jm, glynn rj, gragoudas es, albert dm. epidemiologic aspects of uveal melanoma. surv ophthalmol 1988;32:239–251. 67. kaliki s, shields cl. uveal melanoma: relatively rare but deadly cancer. eye 2017;31:241–257. 68. jager mj, shields cl, cebulla cm, abdel-rahman mh, grossniklaus he, stern mh, et al. uveal melanoma. nat rev dis primers 2020;6:24. 69. masoomian b, shields ja, shields cl. overview of bap1 cancer predisposition syndrome and the relationship to uveal melanoma. j curr ophthalmol 2018;30:102–109. 70. shields cl, kaliki s, furuta m, mashayekhi a, shields ja. clinical spectrum and prognosis of uveal melanoma based on age at presentation in 8,033 cases. retina 2012;32:1363–1372. 71. vichitvejpaisal p, dalvin la, mazloumi m, ewens kg, ganguly a, shields cl. genetic analysis of uveal melanoma in 658 patients using the cancer genome atlas classification of uveal melanoma as a, b, c, and d. ophthalmology 2019;126:1445–1453. 72. mazloumi m, vichitvejpaisal p, dalvin la, yaghy a, ewens kg, ganguly a, et al. accuracy of the cancer genome atlas classification vs american joint committee on cancer classification for prediction of metastasis journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 557 https://retinatoday.com/articles/2015-july-aug/retinal-hemangiomas-understanding-clinical-features-imaging-and-therapies https://retinatoday.com/articles/2015-july-aug/retinal-hemangiomas-understanding-clinical-features-imaging-and-therapies https://retinatoday.com/articles/2015-july-aug/retinal-hemangiomas-understanding-clinical-features-imaging-and-therapies photodynamic therapy in ocular oncology; mazloumi et al in patients with uveal melanoma. jama ophthalmol 2020;138:260–267. 73. gamel j, mccurdy jb, mclean i. a comparison of prognostic covariates for uveal melanoma. invest ophthalmol vis sci 1992;33:1919–1922. 74. turkoglu eb, pointdujour-lim r, mashayekhi a, shields cl. photodynamic therapy as primary treatment for small choroidal melanoma. retina 2019;39:1319–1325. 75. shields cl, shields ja, perez n, singh ad, cater j. primary transpupillary thermotherapy for small choroidal melanoma in 256 consecutive cases: outcomes and limitations. ophthalmology 2002;109:225–234. 76. mashayekhi a, shields cl, rishi p, atalay ht, pellegrini m, mclaughlin jp, et al. primary transpupillary thermotherapy for choroidal melanoma in 391 cases: importance of risk factors in tumor control. ophthalmology 2015;122:600– 609. 77. lumbroso-le rouic l, chefchaouni mc, levy c, plancher c, dendale r, asselain b, et al. 125 i plaque brachytherapy for anterior uveal melanomas. eye 2004;18:911–916. 78. shields ja, glazer lc, mieler wf, shields cl, gottlieb ms. comparison of xenon arc and argon laser photocoagulation in the treatment of choroidal melanomas. am j ophthalmol 1990;109:647–655. 79. oosterhuis ja, journée-de korver hg, keunen je. transpupillary thermotherapy: results in 50 patients with choroidal melanoma. arch ophthalmol 1998;116:157–162. 80. campbell wg, pejnovic tm. treatment of amelanotic choroidal melanoma with photodynamic therapy. retina 2012;32:1356–1362. 81. barbazetto ia, lee tc, rollins is, chang s, abramson dh. treatment of choroidal melanoma using photodynamic therapy. am j ophthalmol 2003;135:898–899. 82. fabian id, stacey aw, papastefanou v, al harby l, arora ak, sagoo ms, et al. primary photodynamic therapy with verteporfin for small pigmented posterior pole choroidal melanoma. eye 2017;31:519–528. 83. rundle p. treatment of posterior uveal melanoma with multi-dose photodynamic therapy. br j ophthalmol 2014;98:494–497. 84. schmidt-erfurth u, hasan t, gragoudas e, michaud n, flotte tj, birngruber r. vascular targeting in photodynamic occlusion of subretinal vessels. ophthalmology 1994;101:1953–1961. 85. blasi ma, laguardia m, tagliaferri l, scupola a, villano a, caputo cg, et al. brachytherapy alone or with neoadjuvant photodynamic therapy for amelanotic choroidal melanoma: functional outcomes and local tumor control. retina 2016;36:2205–2212. 86. tuncer s, kir n, shields cl. dramatic regression of amelanotic choroidal melanoma with pdt following poor response to brachytherapy. ophthalmic surg laser imag 2012;43:e38–e40. 87. shields cl, shields ja, gross ne, schwartz gp, lally se. survey of 520 eyes with uveal metastases. ophthalmology 1997;104:1265–1276. 88. arepalli s, kaliki s, shields cl. choroidal metastases: origin, features, and therapy. indian j ophthalmol 2015;63:122. 89. shields cl, welch rj, malik k, acaba-berrocal la, selzer eb, newman jh, et al. uveal metastasis: clinical features and survival outcome of 2214 tumors in 1111 patients based on primary tumor origin. middle east afr j ophthalmol 2018;25:81–90. 90. shields cl, khoo ct, mazloumi m, mashayekhi a, shields ja. photodynamic therapy for choroidal metastasis: tumor control and visual outcome in 58 cases. the 2019 burnier international ocular pathology society (biopsy) lecture. ophthalmol retina 2019;4:310–319. 91. kaliki s, shields cl, al-dahmash sa, mashayekhi a, shields ja. photodynamic therapy for choroidal metastasis in 8 cases. ophthalmology 2012;119:1218– 1222. 92. ghodasra dh, demirci h. photodynamic therapy for choroidal metastasis. am j ophthalmol 2016;161:104– 9.e2. 558 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 review article intravitreal medications for retinal vein occlusion: systematic review and meta-analysis alireza lashay1, md; hamid riazi-esfahani1, md; masoud mirghorbani1, md, mph; mehdi yaseri1,2, phd 1translational ophthalmology research center, farabi eye hospital, tehran university of medical sciences, tehran, iran 2department of epidemiology and biostatistics, tehran university of medical sciences, tehran, iran orcid: alireza lashay: https://orcid.org/0000-0002-6409-4654 abstract purpose: to evaluate the outcomes of different intravitreal injections for the treatment of retinal vein occlusion including central retinal vein occlusion (crvo) and branch retinal vein occlusion (brvo). methods: pubmed, cochrane, the metaregister of controlledtrials, and clinicaltrials were searched for intravitreal anti-vascular endothelial growth factor (vegf) and steroids with relevant keywords and date limitation of 2009-2018. meta-analysis was performed on studies that met the defined inclusion criteria. main outcomes were visual acuity (va) and central macular thickness (cmt). results: out of 681 studies, 36 articles (including 21 reporting crvo and 15 dealing with brvo) were selected for systematic review. all five intravitreal drugs including triamcinolone, dexamethasone, ranibizumab, bevacizumab, and aflibercept showed improvement of cmt and va as compared to placebo or laser treatment. six randomized controlled trials were selected for meta-analysis in rvo patients. the pooled mean difference of visual improvement between sham and ranibizumab was 12.7 early treatment for diabetic retinopathy study (etdrs) letters (95%ci: 11.00 to 13.2), and the pooled mean difference in cmt reduction was 221𝜇m (95%ci: 153 to 284); both changes were significantly in favor of ranibizumab. the pooled mean difference of visual improvement between bevacizumab and triamcinolone was 5.3 etdrs letters in favor of bevacizumab (95%ci: 16 𝜇m to 17.5 𝜇m). triamcinolone led to 68.1 𝜇m greater cmt reduction than bevacizumab (95%ci: 58 𝜇m to 76 𝜇m). however, none of these differences were statistically significant. conclusion: treatment with anti-vegf agents in rvo is superior to observation. no significant difference was seen between the eyes treated with bevacizumab or triamcinolone based on these results. keywords: anti-vascular endothelial growth factor; dexamethasone; retinal vein occlusion; triamcinolone j ophthalmic vis res 2019; 14 (3): 336–365 correspondence to: alireza lashay, md. translational ophthalmology research center, farabi eye hospital, tehran university of medical sciences, qazvin square, tehran 13366, iran. e-mail: lashay3601@gmail.com received: 11-10-2018 accepted: 29-04-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i3.4791 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: lashay a, riazi-esfahani h, mirghorbani m, yaseri m. intravitreal medications for retinal vein occlusion: systematic review and meta-analysis. j ophthalmic vis res 2019;14:336–365 336 @ 2019 j  o  v r | p  published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i3.4791&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr intravitreal medications for rvo; lashay et al introduction retinal vein occlusion (rvo) is caused by thromosis in central, hemi-central, or branch retinal veins.[1] in central retinal vein occlusion (crvo), the obstruction usually occurs at the level of the lamina cribrosa, while in branch retinal vein occlusion (brvo), it involves a branch of the central retinal vein.[1–3] the clinical manifestations of rvo is largely related to the secondary elevation of vascular endothelial growth factor (vegf) levels in the vitreous and retina due to retinal ischemia.[1] the following conditions have been variably reported as associations of rvos: systemic hypertension, diabetes mellitus, hyperlipidemia, hyper-homocysteinemia, blood coagulation disorders, systemic inflammatory disorders, glaucoma, short axial length, and high body mass index.[2–6] two major consequences of rvo which lead to decreased visual acuity (va) are macular edema (me) and retinal ischemia. in eyes with nonischemic crvo, va improves significantly following resolution of me.[4, 6, 7] however, in the eyes with ischemic crvo, no significant association has been found between the presence or absence of me and improvement in va due to permanent damage to macular ganglion cells.[7] other factors may also affect the natural history of crvo. demographic factors such as age or male gender, systemic factors including vascular risk factors or high levels of blood hematocrit, and ocular factors such as macular pigmentary change, epiretinalmembrane formation following long-standing me, retinociliary collaterals, and glaucoma have been reported to be associated with poor functional outcomes.[8] the development of anterior segment neovascularization also has a detrimental effect on visual outcomes.[7, 8] based on the branch retinal vein occlusion study (bvos) study, the visual prognosis in brvo is better than crvo.[9] therefore, it is not surprising to observe relatively good outcomes in the control group of large randomized controlled trials (rcts) such as the study on the efficacy and safety of ranibizumab injection in patients with macular edema secondary to brvo (bravo). visual acuity improvement in eyes with macular brvo is usually more marked than eyes with major brvo.[10] ischemic insult to macular ganglion cells, pigmentary degeneration, and development of epiretinal membrane may adversely affect the visual outcome in brvo.[11] various treatments have been proposed for the management of rvo-related me and many rcts have been designed to compare these therapies and their long-term outcomes. the selection of the most efficacious therapy providing the best outcome in clinical practice necessitates ophthalmologists to be updated on the results of recent trials and adopt a comprehensive approach toward the patient. in the current study, we aim to provide an update on recent trials addressing the management of rvorelated me, compare the outcomes of these trials, and perform a meta-analysis on studies with similar arms according to the pre-defined inclusion and exclusion criteria. methods this systematic review and meta-analysis complies with the preferred reporting items for systematic reviews and meta-analyses (prisma) 2009 rules. search methods for identifying the studies two investigators (hr and mm) participated in the literature search via pubmed, cochrane, the metaregister of controlledtrials, and clinicaltrials in english language with date limitation of 2009-2018. in the search strategy which was last conducted on march 21, 2018, we used the mesh term “retinal vein occlusion” and the words “*rvo”, “*vitreal”, “*vegf*”, “bevacizumab”, “avastin”, “ranibizumab”, “lucentis”, “aflibercept”, “eylea”, “triamcinolone”, “implant”, and “ozurdex”. it should be noted that we only searched for the most popular agents in clinical practice and not the miscellaneous drugs presented in the case reports or case series. selection of studies for systematic review all titles and abstracts were independently screened by two co-authors (hr and mm) and the potential relevance was judged. any disagreement between the two authors was referred to the corresponding author (al) for final decision. the final list of included studies was re-evaluated to ensure proper study selection. only papers with full-texts or abstracts in english were selected. j  o  v r volume 14, issue 3, july–september 2019 337 intravitreal medications for rvo; lashay et al data collection data was collected separately by hr and mm from all included studies: • first and corresponding authors, journal, year, main criteria for inclusion in the study, any exclusion criteria, number of eyes, treatment arms, and length of the study. • means and standard deviations of changes in corrected va and central macular thickness (cmt) changes from baseline. each article was evaluated carefully and rated by the panel (hr, mm, and my) according to the level of evidence provided by the study. the level of evidence was assigned to each study according to the latest guidelines of the british centre for evidence-based medicine;[12] • level i: well-conducted and designed randomized clinical trials • level ii: lower-quality randomized, welldesigned case-control, and cohort studies • level iii: lower-quality cohort and casecontrol studies and case series outcome measurement the mean change of va from baseline was the primary outcome measure. the secondary outcomes included: (1) the proportion of patients gaining 15 early treatment for diabetic retinopathy study (etdrs) letters or more compared to baseline at different time points; (2) mean change of cmt on optical coherence tomography (oct) from baseline as the anatomical outcome measure. meta-analysis: inclusion and exclusion criteria studies were included in the meta-analysis if they met the following criteria: (1) randomized controlled clinical trials with level i of evidence, (2) mean follow-up of six months or more, (3) comparing anti-vegf or intravitreal corticosteroid with placebo or laser treatment for me due to crvo or brvo, (4) providing the proportion that gained 15 etdrs letters or more, (5) providing changes of va and cmt in the treatment and sham groups for calculating mean difference (md), odds ratio (or), and 95% confidence interval (95% ci). metaanalysis was performed on studies with level i evidence with comparable arms and methods. studies were excluded from meta-analysis if they were retrospective, non-controlled, non-randomized, or were not in english. we chose six months as the minimum time point for meta-analysis. the mean change in va and cmt was measured as a continuous variable and calculated as md with 95% ci. methodological quality/risk of bias assessment the methodological efficiency of studies was evaluated for the quality based on the modified jadad scoring system.[13, 14] through this assessment tool, we evaluated three main study characteristics including randomization, blinding, and participant dropout. studies with jadad score of three points or more were considered as high-quality studies. also, a risk of bias summary was provided by each data collector separately including selection bias, detection bias, and attrition bias in order to assess various potential sources of systemic-bias. heterogeneity assessment both clinical and methodological heterogeneities were assessed for meta-analysis. we considered i2 values more than 60% to indicate substantial statistical heterogeneity. the random-effects model was used for meta-analysis. statistical analysis all analyses were performed using the stata (statacorp. 2013. stata statistical software: release 13. college station,tx: statacorp lp). the mean post value of the studied outcomes was extracted from each study. using the forest plots, the 95% confidence interval of the difference of treatments in each study and the pooled effect of all studies were demonstrated. heterogeneity of studies was evaluated using cochran’s q-test and i-square index. an i-square more than 0.70 or a p-value < 0.05 was considered as the indication of heterogeneity. to compensate for the heterogeneity of the results of the studies, the random-effects model was applied. the funnel plot (qualitative method) and egger’s regression test (quantitative 338 j  o  v r volume 14, issue 3, july–september 2019 intravitreal medications for rvo; lashay et al method) were used for the evaluation of possible publication biases. whenever the bias was present, the pooled mean value was adjusted using the trimming method. results the combined searches yielded 681 studies which decreased to 410 articles after the duplicates were removed. the panel reviewed 131 articles in full text based on the inclusion criteria. of these, 36 articles (crvo: 21 and brvo: 15), 27 level ior ii-rated studies were selected for systematic review based on the compatibility with the inclusion criteria [tables 1 and 2]. studies with level i evidence and comparable arms and methods were chosen for meta-analysis. meta-analysis was done on studies that compared the effectiveness of bevacizumab versus triamcinolone acetonide and ranibizumab versus sham. due to the heterogeneity in the dosages of intravitreal steroid and follow-up periods, we were not able to perform a meta-analysis on all rcts; six rcts were selected for meta-analysis based on the inclusion and exclusion criteria [figure 1]. medical management in crvo description of the condition in crvo macular edema is one of the main causes of reduced va in crvo. it is presumed to be a result of the hypoxia-induced capillary permeability after vein occlusion and subsequent hemorrhage.[15] the most popular treatment in crvo is the intravitreal injection of an anti-vegf, such as bevacizumab, ranibizumab, and aflibercept. however, intravitreal steroid injection may also be considered especially in areas without access to anti-vegf agents. intravitreal dexamethasone implant is another therapeutic choice for crvo-induced me (crvo-me),[16] while other treatments such as fibrinolytic or anticoagulant agents, angiostatic agents, acetazolamide and isovolemic hemodilution, have not been approved.[17] some surgical options were also suggested including induced chorioretinal anastomosis, injection of a fibrinolytic agent by direct venous cannulation, and radial optic neurotomy; however, none of them has been proven effective in the treatment of crvo-me.[17] the summary of the interventional studies on the management of crvo-me with level i or ii of evidence are presented in table 1. intravitreal corticosteroids triamcinolone. intravitreal injection of steroids is effective in crvo-me by reducing the capillary permeability and inhibition of the vegf expression. in contrast to anti-vegf drugs with specific site of action, steroids suppress the expression of many cytokines. however, they may cause cataract and steroid-induced glaucoma. it should be noted that the effects of intravitreal triamcinolone may last up to nine months, depending on the dosage applied.[18–20] ip et al[18] reported the results of the standard care versus corticosteroid for retinal vein occlusion (score) study that compared 1 mg and 4 mg doses of preservative free intravitreal triamcinolone acetonide (ivt) with the observation for me-associated va loss in perfused crvo. at fourmonth follow-up, the median reduction in cmt was more in the 4 mg ivt group (p < 0.001). however, at 12-month follow-up, there was no difference in terms of cmt reduction and va improvement between the two triamcinolone groups. ivt led to a reduction in me with a moderate correlation with va. they reported that there was a significantly higher percentage of patients requiring iop-lowering medications and also higher rates of cataract development in the steroid groups, especially in the 4 mg ivt group. considering these efficacy and safety findings, 1 mg ivt was recommended in the treatment of crvo-me. in this study, the interval between the last triamcinolone application and the end of the follow-up period varied. hence, some eyes in the study groups might have been out of the effective phase of the triamcinolone injection at the evaluation time. ramezani et al[21] evaluated the effects of multiple intravitreal bevacizumab (ivb) injections versus ivt in the treatment of 86 eyes with me due to acute crvo. it was interesting that the differences were statistically significant in patients with ischemic crvo in favor of the ivb group. at all visits, mean iop rise was significantly higher in the ivt group in comparison with the ivb group. as a result, they recommended repeated ivb injections, specifically in ischemic cases. j  o  v r volume 14, issue 3, july–september 2019 339 intravitreal medications for rvo; lashay et al ta b le 1. st ud ie s on tr ea tm en to fc en tr al re tin al ve in oc cl us io n as so ci at ed w ith m ac ul ar ed em a tr e a tm e n t a u th o r, ye a r (s tu d y) le ve l n o .o f p a ti e n ts f /u (m ) in te rv e n ti o n ,r e g im e n v a fi n d in g s o c t fi n d in g s a d ve rs e e ff e ct s iv t ip et al , 20 0 9 (s c o r e) [1 8] i 27 1 12 iv t 1m g, 4 m g, an d sh am gr ou ps ; tre at ed at fo ur -m on th in te rv al s as ne ed ed (4 9% in 1m g iv t gr ou p an d 32 % in 4 m g iv t gr ou p re ce iv ed th re e do se s of tr ia m ci no lo ne in je ct io ns ) *1 5le tte rg ai n: 7% ,2 7% ,a nd 26 % in ob se rv at io n, 1m g an d 4 m g gr ou ps , re sp ec tiv el y *a t4 m on th s: m ed ia n de cr ea se in c m t w as gr ea te ri n th e 4 m g tr ia m ci no lo ne gr ou p (– 19 6 𝜇m ve rs us –7 7 𝜇m in th e iv t gr ou ps an d – 12 5 𝜇m in th e pl ac eb o gr ou p) *a t1 2 m on th s: no di ffe re nc e in c m t ch an ge s *h ig he st ra te of ca ta ra ct fo rm at io n, an d io p el ev at io n w as ob se rv ed in th e 4 m g gr ou p. r am ez an ie t al ,2 0 14 [2 1] ii 86 6 iv b 1.2 5 m g ve rs us iv t 2 m g; iv b gr ou p re ce iv ed th re e m on th ly in je ct io ns of 1.2 5 m g of iv b ,a nd iv t gr ou p re ce iv ed tw o in je ct io ns of 2 m g iv t tw o m on th s ap ar t *t he m ea n b c v a :i m pr ov ed fro m 0. 87 ± 0. 49 to 0. 41 ± 0. 35 lo gm a r in iv b gr ou p an d fro m 0. 81 ± 0. 45 to 0. 62 ± 0. 48 lo gm a r in iv t gr ou p *in te rgr ou p di ffe re nc es :r ea ch ed a si gn ifi ca nt le ve la tm on th s 4 an d 6 in fa vo ro ft he iv b gr ou p *a ts ix m on th s: hi gh er c m t re du ct io n in iv b gr ou p th an iv t gr ou p *t he m ea n io p ris e w as si gn ifi ca nt ly hi gh er in th e iv t gr ou p at al lv is its d in g et al , 20 11 [2 2] ii 32 9 iv b 1.2 5 m g ve rs us iv t 4 m g; a fte rb as el in e in je ct io n, pa tie nt s w er e gi ve n ad di tio na li nj ec tio ns if th ey ha d m e as de te rm in ed by op tic al co he re nc e to m og ra ph y th re e m on th s af te rt he fir st tr ea tm en to rv a lo ss of at le as tt w o lin es *a fte rt w o w ee ks :t he m ea n b c v a im pr ov em en tw as m or e in iv t co m pa re d w ith iv b (0 .2 9 ve rs us 0. 35 lo gm a r) *a fte rn in e m on th s: th e m ea n b c v a im pr ov em en tw as m ai nt ai ne d hi gh er in iv t gr ou p (0 .3 2 ve rs us 0. 38 lo gm a r) *t he m ea n c m t ch an ge s w er e no td iff er en t be tw ee n th e tw o tre at m en tg ro up s at an y tim e du rin g th e fo llo w -u p pe rio d *s ig ni fic an ti o p in cr ea se w as fo un d on ly in th e iv t gr ou p *p re -m ac ul ar m em br an es w er e de ve lo pe d in tw o pa tie nt s in th e iv t gr ou p 340 j  o  v r volume 14, issue 3, july–september 2019 intravitreal medications for rvo; lashay et al ta b le 1. c on tin ue d. tr e a tm e n t a u th o r, ye a r (s tu d y) le ve l n o .o f p a ti e n ts f /u (m ) in te rv e n ti o n ,r e g im e n v a fi n d in g s o c t fi n d in g s a d ve rs e e ff e ct s d ex a im pl an t h al le re ta l, 20 11 (g en ev a )[2 3− 24 ] i 1,2 67 (4 37 pa tie nt s w ith c rv o ) 12 in tr av itr ea ld ex im pl an t 0. 35 m g, 0. 7 m g, an d sh am gr ou ps in c rv o or b rv o ; a fte rb as el in e in je ct io n, in tr av itr ea ld ex im pl an t 0. 7 m g re in je ct io n in ea ch gr ou p at m on th 6 *1 5le tte rg ai n at on e m on th :7 % , 20 % ,a nd 21 % in ob se rv at io n, 0. 35 m g an d 0. 7 m g d ex gr ou ps , re sp ec tiv el y *1 5le tte rg ai n at tw o m on th s: 9% , 23 % ,a nd 29 % in ob se rv at io n, 0. 35 m g an d 0. 7 m g d ex gr ou ps , re sp ec tiv el y *1 5le tte rg ai n at si x m on th s: 12 % , 17 % ,a nd 18 % in ob se rv at io n, 0. 35 m g an d 0. 7 m g d ex gr ou ps , re sp ec tiv el y *1 5le tte rg ai n af te rr ei nj ec tio n (a t 12 m on th ): 32 % of ey es in d ex 0. 7 m g /0 .7 m g gr ou p o ve ra ll o c t ch an ge s (c rv o an d b rv o ): *a fte rt hr ee m on th s: si gn ifi ca nt m ea n de cr ea se of –2 0 8 𝜇m , – 17 7 𝜇m ,a nd –8 5 𝜇m in 0. 7 m g, 0. 35 m g, an d sh am ,r es pe ct iv el y *a fte rs ix m on th s: no di ffe re nc es be tw ee n tre at m en tg ro up s *a fte r1 2 m on th s: m ea n de cr ea se of –2 63 𝜇m in bo th 0. 35 m g /0 .7 m g an d 0. 7 m g /0 .7 m g gr ou ps ,w hi le m ea n de cr ea se of –2 67 𝜇m in sh am /0 .7 m g gr ou p *d ur in g th e in iti al 6 m on th s of tr ea tm en t, a si ng le in tr av itr ea l de xa m et ha so ne in je ct io n re su lte d in oc ul ar hy pe rt en si on in 3. 9% of tr ea te d ey es co m pa re d to 0. 7% in th e sh am gr ou p. *t he re w er e no si gn ifi ca nt di ffe re nc es in ca ta ra ct fo rm at io n at 6 m on th s *3 2 .8 % of st ud y ey es in 0. 7 m g /0 .7 m g d ex gr ou p ha d an io p in cr ea se of 10 m m h g at 60 da ys af te r re -in je ct io n, w hi ch no rm al iz ed at 18 0 da ys , so m et im es w ith io p m ed ic at io n. h oe ra uf et al , 20 16 (c o m r a d e) [2 6] ii 18 5 6 iv r 0. 5 m g ve rs us in tr av itr ea ld ex im pl an t 0. 7 m g; iv r gr ou p re ce iv ed th re e m on th ly iv r 0. 5 m g fo llo w ed by pr n iv r ,a nd th e ot he r gr ou p un de rw en td ex 0. 7 m g im pl an tf ol lo w ed by pr n sh am in je ct io n *a tm on th 2: no di ffe re nc e in b c v a be tw ee n iv r an d d ex im pl an t *f ro m m on th s 3 to 6: si gn ifi ca nt di ffe re nc e in b c v a ga in s in fa vo r of iv r *a tm on th 6: hi gh er m ea n b c v a ga in in iv r co m pa re d to d ex im pl an t( 12 .8 6 ve rs us 2 .9 6 le tte rs ) *t he re du ct io n in c m t w as ob se rv ed at m on th 2 an d m ai nt ai ne d un til th e en d of th e st ud y in th e iv r gr ou p, w hi le th e m ea n c m t in cr ea se d in th e d ex im pl an tg ro up st ar tin g at m on th 3 *a fte rs ix m on th s: m ea n ch an ge fro m ba se lin e w as –3 76 𝜇m in iv r an d – 16 8 𝜇m in d ex im pl an t *e le va te d io p w as re po rt ed in 7 pa tie nt s in th e iv r gr ou p (5 .6 % )a nd 38 pa tie nt s in th e d ex im pl an tg ro up (3 1.9 % ). *c at ar ac to cc ur re d in 1 pa tie nt in th e d ex im pl an t gr ou p (0 .8 % )a nd no pa tie nt s in th e iv r gr ou p. j  o  v r volume 14, issue 3, july–september 2019 341 intravitreal medications for rvo; lashay et al ta b le 1. c on tin ue d. tr e a tm e n t a u th o r, ye a r (s tu d y) le ve l n o .o f p a ti e n ts f /u (m ) in te rv e n ti o n ,r e g im e n v a fi n d in g s o c t fi n d in g s a d ve rs e e ff e ct s g ad o et al , 20 14 [2 7] ii 60 6 iv b 1.2 5 m g ve rs us in tr av itr ea ld ex im pl an t 0. 7 m g; iv b gr ou p re ce iv ed iv b at ba se lin e fo llo w ed by pr n re -in je ct io n an d th e ot he rg ro up un de rw en td ex 0. 7 m g im pl an t *a fte rs ix m on th s: no si gn ifi ca nt di ffe re nc e in b c v a im pr ov em en t be tw ee n th e tw o gr ou ps (0 .2 lo gm a r in ea ch gr ou p) *a fte ro ne m on th : st at is tic al ly si gn ifi ca nt th in ne rc m t in iv b gr ou p *f or th e re st of th e si x m on th s: no si gn ifi ca nt di ffe re nc e be tw ee n tw o gr ou ps *t he re w as a st at is tic al ly si gn ifi ca nt hi gh er io p in d ex im pl an tg ro up (c om pa re d w ith iv b )a t th re e– si x m on th s ki ng et al , 20 10 (r o c c st ud y) [2 8] i 32 6 iv r 0. 50 m g ve rs us sh am gr ou ps ; pa tie nt s re ce iv ed m on th ly iv r or sh am in je ct io ns fo rt hr ee co ns ec ut iv e m on th s an d th en pr n re -in je ct io n w ith th e sa m e dr ug *a tt hr ee m on th s: th e b c v a im pr ov ed by 16 le tte rs in th e iv r gr ou p, co m pa re d w ith a m ea n lo ss of 5 le tte rs in th e sh am gr ou p *a ts ix m on th s: th e b c v a im pr ov ed by 12 le tte rs in th e iv r gr ou p co m pa re d w ith a m ea n lo ss of 1 le tte ri n th e sh am gr ou p *a tt hr ee m on th s: th e m ea n ch an ge in c m t w as –4 11 𝜇m in th e iv r gr ou p an d 86 𝜇m in sh am *a ts ix m on th s: th e m ea n ch an ge in c m t w as 30 4 𝜇m in th e iv r an d 15 1𝜇 m in sh am *t w o pa tie nt s in th e iv r gr ou p ex pe rie nc ed a sm al lh em or rh ag e in th e vi tr eo us ca vi ty at tr ib ut ab le to vi tr eo us tr ac tio n, w hi ch re so lv ed w ith ou tf ur th er co m pl ic at io ns r an ib iz um ab b ro w n et al , 20 10 (c r u is e) [2 9] i 39 2 6 iv r 0. 3 m g, 0. 5 m g, an d sh am gr ou ps ; iv r gr ou p: re ce iv ed m on th ly in tr ao cu la r in je ct io ns of 0. 3 or 0. 5 m g of ra ni bi zu m ab sh am gr ou p: re ce iv ed sh am in je ct io n m on th ly *1 5le tte rg ai n: 17 % ,4 6% ,a nd 47 % in sh am ,0 .3 m g an d 0. 5 m g iv r gr ou ps ,r es pe ct iv el y *t he v a im pr ov em en ta fte rs ix m on th s: th e m ea n of 12 .7 an d 14 .9 le tte rs in pa tie nt s re ce iv in g 0. 3 m g an d 0. 5 m g iv r ,r es pe ct iv el y, co m pa re d w ith 0. 8 le tte rs in th e sh am gr ou p *a ts ix m on th s: th e m ea n de cr ea se of – 16 8 𝜇m ,– 43 4 𝜇m ,a nd –4 52 𝜇m in sh am ,0 .3 m g an d 0. 5 m g iv r gr ou ps ,r es pe ct iv el y *o ne no nf at al m yo ca rd ia li nf ar ct io n oc cu rr ed in ea ch tr ea tm en tg ro up s c am po ch ia ro et al ,2 0 11 (c r u is e) [3 0] i 39 2 12 iv r 0. 5 m g pr n re -in je ct io n af te rt he in iti al si xm on th st ud y in ea ch gr ou p *1 5le tte rg ai n: 50 .8 % in 0. 5 m g /0 .5 m g gr ou p ve rs us 33 .1% in sh am /0 .5 m g gr ou p *t he v a im pr ov em en ta fte r1 2 m on th s: th e m ea n of 13 .9 le tte rs in bo th iv r gr ou ps ve rs us 7. 3 le tte rs in sh am /0 .5 m g gr ou p *a t1 2 m on th s: th e m ea n de cr ea se of –4 72 𝜇m , –4 53 𝜇m ,a nd –4 61 𝜇m in sh am /0 .5 m g, 0. 3 m g /0 .5 m g, an d 0. 5 m g /0 .5 m g re sp ec tiv el y *in ci de nc e of ca ta ra ct : 3. 8% (0 .3 m g gr ou p, 12 -m o ra te ), 7. 0 % (0 .5 m g gr ou p, 12 -m o ra te ), 0 % (s ha m ; 6m o ra te ) 342 j  o  v r volume 14, issue 3, july–september 2019 intravitreal medications for rvo; lashay et al ta b le 1. c on tin ue d. tr e a tm e n t a u th o r, ye a r (s tu d y) le ve l n o .o f p a ti e n ts f /u (m ) in te rv e n ti o n , re g im e n v a fi n d in g s o c t fi n d in g s a d ve rs e e ff e ct s h ei er et al , 20 12 [3 1] (h or iz on ) ii 30 4 (o pe nla be l c r u is e ex te ns io n) 12 iv r 0. 5 m g at le as t ev er y th re e m on th s af te rt he in iti al 12 -m on th st ud y in c r u is e st ud y *t he v a im pr ov em en ta fte r2 4 m on th s fro m ba se lin e: th e m ea n of 9. 4, 14 .9 ,a nd 16 .2 le tte rs in th e sh am /0 .5 m g, 0. 3/ 0. 5 m g, an d 0. 5 /0 .5 m g gr ou ps ,r es pe ct iv el y. *t he b c v a w or se ne d ov er th e se co nd ye ar co m pa re d w ith th e v a on th e co m pl et io n of th e c r u is e st ud y *a t2 4 m on th s fro m c r u is e ba se lin e: th e m ea n re du ct io n w as –3 70 𝜇m an d –4 12 𝜇m in th e 0. 3/ 0. 5m g an d 0. 5m g tr ea tm en t gr ou ps an d –4 18 𝜇m in th e sh am /0 .5 -m g gr ou p *a t1 2 m on th s fro m h o r iz o n ba se lin e: th e m ea n c ft in cr ea se d by 79 𝜇m , 88 𝜇m ,a nd 68 𝜇m in th e sh am /0 .5 -m g, 0. 3/ 0. 5m g, an d 0. 5m g tr ea tm en t gr ou ps ,r es pe ct iv el y *n o se rio us oc ul ar an d no noc ul ar si de ef fe ct w as re po rt ed b ev ac iz um ab ep st ei n et al , 20 12 [3 6, 37 ] i 60 12 iv b 1.2 5 m g ve rs us sh am gr ou ps ; pa tie nt s re ce iv ed iv b ev er y si x w ee ks or sh am fo rs ix m on th s, an d th en al lp at ie nt s re ce iv ed iv b ev er y si x w ee ks fo rs ec on d si x m on th s *1 5le tte rg ai n af te rs ix m on th s: 60 % of iv b pa tie nt s ve rs us 20 % of sh am pa tie nt s *1 5le tte rg ai n af te r1 2 m on th s: 60 % of iv b /iv b pa tie nt s ve rs us 33 % of sh am /iv b pa tie nt s *a fte rs ix m on th s: th e m ea n de cr ea se of –4 26 𝜇m ve rs us – 10 2 𝜇m in iv b an d sh am gr ou ps *a fte r1 2 m on th s: th e m ea n de cr ea se of –4 35 𝜇m in iv b /iv b gr ou p ve rs us –4 04 𝜇m in sh am /iv b (n o di ffe re nc e) *n o se rio us oc ul ar an d no noc ul ar si de ef fe ct s w as re po rt ed r aj ag op al et al , 20 15 (c r a v e) [3 8] ii 98 6 iv b 1.2 5 m g ve rs us iv r 0. 5 m g gr ou ps ; pa tie nt s un de rw en t m on th ly in je ct io n in ea ch gr ou p *t he v a ga in w as 0. 33 an d 0. 34 lo gm a r in iv b an d iv r gr ou ps , re sp ec tiv el y *t he c m t re du ct io n w as –2 12 𝜇m an d –2 43 𝜇m in iv b an d iv r gr ou ps , re sp ec tiv el y a fli be rc ep t b oy er et al ,2 0 12 (c o pe r n ic u s) [4 3] i 18 9 6 ia i2 m g ve rs us sh am gr ou ps ; pa tie nt s un de rw en t m on th ly in je ct io n in ea ch gr ou p *1 5le tte rg ai n af te rs ix m on th s: 56 .1% of ia ip at ie nt s ve rs us 12 .3 % of th e sh am gr ou p *a fte rs ix m on th s: th e m ea n de cr ea se of –4 57 𝜇m ve rs us – 14 5 𝜇m in ia iv er su s sh am gr ou ps *o ne ca se of ar te ry oc cl us io n an d on e ca se of m ac ul op at hy w er e re po rt ed in th e afl ib er ce pt gr ou p j  o  v r volume 14, issue 3, july–september 2019 343 intravitreal medications for rvo; lashay et al ta b le 1. c on tin ue d. tr e a tm e n t a u th o r, ye a r (s tu d y) le ve l n o .o f p a ti e n ts f /u (m ) in te rv e n ti o n , re g im e n v a fi n d in g s o c t fi n d in g s a d ve rs e e ff e ct s b ro w n et al , 20 13 (c o pe r n ic u s) [4 4] i 18 9 12 ex te ns io n of b oy er et al st ud y; a fte rs ix m on th s, bo th ia ia nd sh am gr ou ps co nt in ue d to re ce iv e afl ib er ce pt fo rt he ne xt si x m on th s, pr n *1 5le tte rg ai n af te r1 2 m on th s: 55 .3 % of ia i/i a ig ro up ve rs us 30 .1% of sh am /ia ig ro up *a fte r1 2 m on th s: th e m ea n de cr ea se of –4 13 𝜇m an d –3 81 𝜇m in ia i/i a ia nd sh am /ia i gr ou ps ,r es pe ct iv el y *n o in tr ao cu la ro re xt ra oc ul ar co m pl ic at io n h ei er et al , 20 14 (c o pe r n ic u s) [4 5] i 18 8 24 ex te ns io n of b ro w n et al st ud y; a fte r1 2 m on th s, pa tie nt s w er e ev al ua te d at le as t qu ar te rly an d re ce iv ed ia ip r n *1 5le tte rg ai n af te r2 4 m on th s: 49 .1% in ia iq 4w ee ks /ia ip r n gr ou p ve rs us 23 .3 % in sh am /ia ip r n gr ou p *t he m ea n v a ga in af te r2 4 m on th s: 13 ve rs us 1.5 le tte rs in ea ch gr ou p, re sp ec tiv el y *a fte r2 4 m on th s: th e m ea n c m t w as re du ce d –3 90 𝜇m an d –3 43 𝜇m in ia iq 4w ee ks /ia ip r n gr ou p ve rs us sh am /ia ip r n gr ou p, re sp ec tiv el y *t he m os tf re qu en t oc ul ar se rio us ad ve rs e ev en tf ro m ba se lin e to th e m on th 24 w as vi tr eo us he m or rh ag e in bo th gr ou ps h ol z et al , 20 13 (g a li le o )[4 6] i 17 7 6 ia i2 m g ve rs us sh am gr ou ps ; pa tie nt s un de rw en t m on th ly in je ct io n in ea ch gr ou p *1 5le tte rg ai n af te rs ix m on th s: 60 % in ia ig ro up ve rs us 22 % in th e sh am gr ou p *t he m ea n ga in v a af te rs ix m on th s: a m ea n of 18 le tte rs in ia ic om pa re d to 3. 3 le tte rs in th e sh am gr ou p *a fte rs ix m on th s: th e m ea n de cr ea se of –4 49 𝜇m ve rs us – 16 9 𝜇m in ia ia nd sh am gr ou ps ,r es pe ct iv el y *n o in tr ao cu la ro re xt ra oc ul ar co m pl ic at io n ko ro be ln ik et al , 20 14 (g a li le o )[4 7] i 17 7 12 ex te ns io n of h ol z et al st ud y; fr om m on th 7 to 12 , th e ia ig ro up re ce iv ed afl ib er ce pt pr n an d th e sh am gr ou p co nt in ue d re ce iv in g sh am in je ct io ns *1 5le tte rg ai n af te r1 2 m on th s: 60 .2 % in th e ia ig ro up an d 32 .4 % in th e sh am gr ou p *t he m ea n ga in v a af te r1 2 m on th s: a m ea n of +1 6. 9 le tte rs ve rs us +3 .8 le tte rs in ia ia nd sh am gr ou ps , re sp ec tiv el y *a fte r1 2 m on th s: th e m ea n c m t re du ct io n fro m ba se lin e w as –4 32 𝜇m ve rs us –2 19 𝜇m in ia ia nd sh am gr ou ps ,r es pe ct iv el y *in cr ea se d in tr ao cu la r pr es su re w as re po rt ed in 17 .3 % of in je ct io ns th at re so lv ed sp on ta ne ou sl y o gu ra et al ,2 0 14 (g a li le o )[4 8] i 17 7 18 ex te ns io n of ko ro be ln ik et al st ud y; fr om m on th s 13 to 18 , pa tie nt s w er e m on ito re d ev er y ei gh t w ee ks ,a nd bo th gr ou ps re ce iv ed ia i2 m g pr n *1 5le tte rg ai n af te r1 8 m on th s: 57 .3 % in th e ia i/i a gr ou p an d 29 .4 % in th e sh am /ia ig ro up *t he m ea n ga in v a af te r1 8 m on th s: a m ea n of +1 3. 7 le tte rs ve rs us +6 .2 le tte rs in ia i/i a ia nd sh am /ia ig ro up s, re sp ec tiv el y *a fte r1 8 m on th s: th e m ea n c m t re du ct io n fro m ba se lin e w as –3 89 𝜇m ve rs us –3 0 6 𝜇m in ia i/i a ia nd sh am /ia i gr ou ps ,r es pe ct iv el y *n o in tr ao cu la ro re xt ra oc ul ar co m pl ic at io n 344 j  o  v r volume 14, issue 3, july–september 2019 intravitreal medications for rvo; lashay et al ta b le 1. c on tin ue d. tr e a tm e n t a u th o r, ye a r (s tu d y) le ve l n o .o f p a ti e n ts f /u (m ) in te rv e n ti o n ,r e g im e n v a fi n d in g s o c t fi n d in g s a d ve rs e e ff e ct s sa is hi n et al , 20 17 [4 9] ii 26 6 iv r 0. 5 m g ve rs us ia i2 m g gr ou ps ; b ot h gr ou ps re ce iv ed bi m on th ly in je ct io ns *t he b c v a im pr ov em en ta fte rs ix m on th s: 0. 31 lo gm a r ve rs us 0. 20 lo gm a r in iv r an d ia ig ro up s, re sp ec tiv el y (n ot si gn ifi ca nt ) *a fte rs ix m on th s: th e m ea n c m t re du ct io n fro m ba se lin e w as –3 74 𝜇m ve rs us –4 65 𝜇m in iv r an d ia ig ro up s, re sp ec tiv el y (th e di ffe re nc e w as no t st at is tic al ly si gn ifi ca nt ) *n o se rio us co m pl ic at io n w as re po rt ed sc ot te ta l, 20 17 (s c o r e2 )[5 0] i 36 2 6 ia i2 m g ve rs us iv b 1.2 5 m g gr ou ps ;n ew lin e b ot h gr ou ps re ce iv ed m on th ly in je ct io ns *t he b c v a im pr ov em en ta fte rs ix m on th s: 19 le tte rv er su s 18 .9 le tte ri n ia i an d iv b gr ou ps ,r es pe ct iv el y (n ot si gn ifi ca nt ) *1 5le tte rg ai n af te rs ix m on th s: 65 .1% in th e ia ig ro up co m pa re d w ith 61 .3 % in th e iv b gr ou p *a fte rs ix m on th s: th e m ea n c m t re du ct io n fro m ba se lin e w as –4 25 𝜇m ve rs us –3 87 𝜇m in ia i an d iv b gr ou ps , re sp ec tiv el y (th e di ffe re nc e w as no t st at is tic al ly si gn ifi ca nt ) *in th e ia ig ro up :f ou r pa rt ic ip an ts w ith io p m or e th an 10 m m h g gr ea te rt ha n ba se lin e; *in th e iv b gr ou p: ni ne pa rt ic ip an ts w ith io p m or e th an 10 m m h g gr ea te rt ha n ba se lin e an d tw o pa tie nt s w ith io p hi gh er th an 35 m m h g w er e re po rt ed c as se lh ol m d e sa lle s et al , 20 18 [5 1] ii 45 18 ia i2 m g ve rs us iv r 0. 5 m g gr ou ps ; a fte rt hr ee lo ad in g do se s, th e tr ea tm en t in te rv al s w er e ex te nd ed by 2 w ee ks to a m ax im um of 12 w ee ks .i nt er va ls w er e sh or te ne d by tw o w ee ks if ed em a re cu rr ed *t he b c v a im pr ov em en ta fte r1 8 m on th s: 22 .4 le tte rv er su s 20 le tte ri n ia i an d iv r gr ou ps ,r es pe ct iv el y (n ot si gn ifi ca nt ) *1 5le tte rg ai n af te r1 8 m on th s: 67 .4 % in th e w ho le co ho rt *a fte r1 8 m on th s: th e m ea n c m t re du ct io n fro m ba se lin e w as – 55 0. 4 𝜇m ve rs us – 55 1.8 𝜇m in ia ia nd iv r gr ou ps , re sp ec tiv el y (th e di ffe re nc e w as no t st at is tic al ly si gn ifi ca nt ) *n o in tr ao cu la r co m pl ic at io n w as re po rt ed c m t, ce nt ra lm ac ul ar th ic kn es s; d ex ,d ex am et ha so ne ;f /u ,f ol lo w up ;i a i, in tr av itr ea la fli be rc ep ti nj ec tio n; io p, in tr ao cu la r pr es su re ;i v b ,i nt ra vi tre al be va ci zu m ab ;i v r , in tr av itr ea lr an ib iz um ab ;i v t, in tr av itr ea lt ria m ci no lo ne ;m e, m ac ul ar ed em a; o c t, op tic al co he re nt to m og ra ph y; v a ,v is ua la cu ity j  o  v r volume 14, issue 3, july–september 2019 345 intravitreal medications for rvo; lashay et al ta b le 2 .s tu di es on th e tr ea tm en to fb ra nc h re tin al ve in oc cl us io n as so ci at ed w ith m ac ul ar ed em a tr e a tm e n t a u th o r, ye a r (s tu d y) le ve l n o .o f p a ti e n ts f /u (m ) in te rv e n ti o n ,r e g im e n v a fi n d in g s o c t fi n d in g s a d ve rs e e ff e ct s iv t sc ot te ta l, 20 0 9 (s c o r e) [1 8− 54 ] i 41 1 12 iv t 1m g, 4 m g, an d gr id la se rp ho to co ag ul at io n gr ou ps ; tr ea te d at fo ur -m on th in te rv al s as ne ed ed *1 5le tte rg ai n: 28 .9 % ,2 7. 2% ,a nd 25 .6 % in la se r, 1m g an d 4 m g gr ou ps , re sp ec tiv el y *a fte r1 2 m on th s: -iv ta 4 m g: .4 .0 le tte rs ga in , -iv ta 1m g: .5 .7 le tte rs ga in ; -l as er :4 .2 le tte rs ga in *a tf ou rm on th s: -iv ta 4 m g: – 14 2 𝜇m -iv ta 1m g: –7 7 𝜇m -l as er gr ou p: – 11 3 𝜇m *c m t in th e 4 m g tr ia m ci no lo ne gr ou p ha d de cr ea se d si gn ifi ca nt ly co m pa re d to th e ot he r gr ou ps *a t1 2 m on th s: -iv ta 4 m g: – 17 0 𝜇m -iv ta 1m g: – 14 9 𝜇m -l as er gr ou p: –2 24 𝜇m *a tt he 12 -m on th fo llo w -u p, al lg ro up s ha d ex pe rie nc ed a si m ila r m ea n re du ct io n in c m t *h ig he st ra te of ca ta ra ct fo rm at io n an d io p el ev at io n w as ob se rv ed in th e 4 m g gr ou p d ex a im pl an t h al le re ta l, 20 11 (g en ev a ) [2 3, 24 ] i 1,2 67 (8 30 pa tie nt s w ith b rv o ) 12 in tr av itr ea ld ex im pl an t 0. 35 m g, 0. 7 m g, an d sh am gr ou ps in c rv o or b rv o ; a fte rb as el in e in je ct io n, in tr av itr ea ld ex im pl an t 0. 7 m g re in je ct io n in ea ch gr ou p at m on th 6 *1 5le tte rg ai n at on e m on th :8 % ,1 7% , an d 21 % in ob se rv at io n, 0. 35 m g an d 0. 7 m g d ex gr ou ps ,r es pe ct iv el y *1 5le tte rg ai n at tw o m on th s: 15 % , 23 % ,a nd 24 % in ob se rv at io n, 0. 35 m g an d 0. 7 m g d ex gr ou ps ,r es pe ct iv el y *1 5le tte rg ai n at si x m on th s: 20 % ,2 1% , an d 23 % in ob se rv at io n, 0. 35 m g an d 0. 7 m g d ex gr ou ps ,r es pe ct iv el y *1 5le tte rg ai n af te rr ei nj ec tio n (a t1 2 m on th s) :3 2% of ey es in d ex 0. 7 m g /0 .7 m g gr ou p (c rv o + b rv o ) o ve ra ll o c t ch an ge s (c rv o an d b rv o ): *a fte rt hr ee m on th s: si gn ifi ca nt m ea n de cr ea se of –2 0 8 𝜇m , – 17 7 𝜇m ,a nd –8 5 𝜇m in 0. 7 m g, 0. 35 m g, an d sh am ,r es pe ct iv el y *a fte rs ix m on th s: no di ffe re nc es be tw ee n tre at m en tg ro up s *a fte r1 2 m on th s: m ea n de cr ea se of –2 63 𝜇m in bo th 0. 35 m g /0 .7 m g an d 0. 7 m g /0 .7 m g gr ou ps , w hi le m ea n de cr ea se of –2 67 𝜇m in sh am /0 .7 m g gr ou p *3 2 .8 % of st ud y ey es in 0. 7 m g /0 .7 m g d ex gr ou p ha d an io p in cr ea se of 10 m m h g at 60 da ys ,w hi ch no rm al iz ed at 18 0 da ys , so m et im es w ith io p m ed ic at io n (c rv o an d b rv o ) 346 j  o  v r volume 14, issue 3, july–september 2019 intravitreal medications for rvo; lashay et al ta b le 2 .c on tin ue d. tr e a tm e n t a u th o r, ye a r (s tu d y) le ve l n o .o f p a ti e n ts f /u (m ) in te rv e n ti o n , re g im e n v a fi n d in g s o c t fi n d in g s a d ve rs e e ff e ct s g ui gn ie re ta l, 20 13 [5 5] ii 19 6 iv b 1.2 5 m g ve rs us in tr av itr ea ld ex im pl an t0 .7 m g; iv b gr ou p re ce iv ed th re e m on th ly iv b 1.2 5 m g fo llo w ed by pr n iv b in je ct io n, an d th e ot he rg ro up un de rw en td ex 0. 7 m g im pl an t fo llo w ed by pr n d ex re -in je ct io n in th e fo ur th m on th *a tm on th 1: th e m ea n v a w as si gn ifi ca nt ly be tte ri n de xa m et ha so ne gr ou p *m on th s 2 to 6: th er e w as no lo ng er an y di ffe re nc e be tw ee n th e tw o gr ou ps *a lth ou gh th er e w as no di ffe re nc e in m ea n v a va lu es be tw ee n th e tw o gr ou ps at si x m on th s, th e pr op or tio n of ey es th at ga in ed 15 et d r s le tte rs or m or e w as hi gh er in iv b gr ou p th an in d ex im pl an tg ro up (3 0 % ve rs us 11 % ) *a tm on th 1: th e m ea n c m t w as si gn ifi ca nt ly lo w er in th e de xa m et ha so ne gr ou p *m on th s 2 to 6: th er e w as no lo ng er an y di ffe re nc e be tw ee n th e tw o gr ou ps *e le va te d io p w as re po rt ed in 9% of pa tie nt s in th e de xa m et ha so ne gr ou p w hi le th er e w as no ne in iv b gr ou p r an ib iz um ab c am po ch ia ro et al ,2 0 10 (b r a v o )[5 6] i 39 7 6 iv r 0. 3 m g, 0. 5 m g, an d sh am gr ou ps ; iv r gr ou p re ce iv ed m on th ly in tr ao cu la r in je ct io ns of 0. 3 or 0. 5 m g of ra ni bi zu m ab fo rs ix m on th s *1 5le tte rg ai n: 28 .8 % ,5 5 .2 % , an d 61 .1% in sh am ,0 .3 m g an d 0. 5 m g iv r gr ou ps ,r es pe ct iv el y. *t he v a im pr ov em en ta fte rs ix m on th s: th e m ea n of 16 .6 an d 18 .3 le tte rs in pa tie nt s re ce iv in g 0. 3 m g an d 0. 5 m g iv r re sp ec tiv el y, co m pa re d w ith 7. 3 le tte rs in th e sh am gr ou p *a ts ix m on th s: th e m ea n de cr ea se of – 15 7 𝜇m ,– 33 7 𝜇m ,a nd –3 45 𝜇m in sh am , 0. 3 m g, an d 0. 5 m g iv r gr ou ps ,r es pe ct iv el y *o ne ca se of en do ph th al m iti s in iv r 0. 5 m g gr ou p b ro w n et al , 20 11 (b r a v o )[5 7] i 39 7 12 iv r 0. 5 m g pr n in je ct io n af te rt he in iti al si xm on th st ud y in sh am gr ou p th e 0. 3 m g an d 0. 5 m g gr ou ps w er e co nt in ue d w ith th ei r or ig in al do se s *1 5le tte rg ai n: 56 % an d 60 .3 % in 0. 3 m g an d 0. 5 m g gr ou p ve rs us 43 .9 % in sh am /0 .5 m g gr ou p *t he v a im pr ov em en ta fte r1 2 m on th s: th e m ea n of 16 .4 an d 18 .3 le tte rs in 0. 3 m g an d 0. 5 m g gr ou ps ve rs us 12 .1 le tte rs in sh am /0 .5 m g gr ou p *a t1 2 m on th s: th e m ea n de cr ea se of –2 73 𝜇m ,– 31 3 𝜇m ,a nd –3 47 𝜇m in sh am /0 .5 m g, 0. 3 m g, an d 0. 5 m g, re sp ec tiv el y *t he m ea n im pr ov em en t fro m ba se lin e c m t at m on th 12 in th e sh am /0 .5 m g gr ou p w as si gn ifi ca nt ly le ss th an th at of th e ot he rt re at m en t gr ou ps *c at ar ac tr at e: 4. 5% [0 .3 m g] , 6. 2% [0 .5 m g] ,a nd 3. 1% [s ha m /0 .5 m g] *v itr eo us he m or rh ag e: 5 .2 % [0 .3 m g] , 1.5 % [0 .5 m g] ,a nd 4. 6% [s ha m /0 .5 m g] j  o  v r volume 14, issue 3, july–september 2019 347 intravitreal medications for rvo; lashay et al ta b le 2 .c on tin ue d. tr e a tm e n t a u th o r, ye a r (s tu d y) le ve l n o .o f p a ti e n ts f /u (m ) in te rv e n ti o n ,r e g im e n v a fi n d in g s o c t fi n d in g s a d ve rs e e ff e ct s h ei er et al , 20 12 (h or iz on )[3 1] ii 30 4 (o pe nla be l b r a v o ex te ns io n) 12 iv r 0. 5 m g at le as te ve ry th re e m on th s af te rt he in iti al 12 -m on th st ud y in b r a v o st ud y *t he v a im pr ov em en ta fte r2 4 m on th s fro m ba se lin e: th e m ea n of 15 .6 ,1 4. 9, an d 17 .5 le tte rs in th e sh am /0 .5 m g, 0. 3/ 0. 5 m g, an d 0. 5 /0 .5 m g gr ou ps ,r es pe ct iv el y *t he b c v a w or se ne d ov er th e se co nd ye ar co m pa re d w ith th e b c v a on th e co m pl et io n of th e b r a v o st ud y ex ce pt fo rt he sh am /0 .5 m g gr ou p. -iv r 0. 3 m g /0 .5 m g: –2 .3 -iv r 0. 5 m g /0 .5 m g: –0 .7 -s ha m /0 .5 m g: +0 .9 *a t2 4 m on th s fro m b r a v o ba se lin e: th e m ea n re du ct io n w as –3 07 𝜇m an d –3 60 𝜇m in th e 0. 3/ 0. 5m g an d 0. 5m g tr ea tm en t gr ou ps an d –2 98 𝜇m in th e sh am /0 .5 -m g gr ou p *a t1 2 m on th s fro m h o r iz o n ba se lin e: th e m ea n c m t in cr ea se d by +3 .7 𝜇m ,+ 6. 3 𝜇m , an d +3 5 .3 𝜇m in th e sh am /0 .5 -m g, 0. 3/ 0. 5m g, an d 0. 5m g tre at m en tg ro up s, re sp ec tiv el y *in cr ea se d io p in tw o pa tie nt s al lo ve rt he gr ou ps *n o no noc ul ar si de ef fe ct w as re po rt ed ta da yo ni et al , 20 16 (b r ig h te r) [5 8] i 45 5 6 iv r 0. 50 m g, iv r 0. 5 m g pl us la se r ph ot oc oa gu la tio n, an d la se rp ho to co ag ul at io n al on e; pa tie nt s tr ea te d w ith ra ni bi zu m ab w ith or w ith ou tl as er re ce iv ed a m in im um of th re e in iti al m on th ly ra ni bi zu m ab in je ctio ns un til v a st ab ili za tio n, an d th en v a -b as ed pr n do si ng *1 5le tte rg ai n af te rs ix m on th s w as 47 .2 % ,4 5% ,a nd 27 .8 % in iv r pl us la se r, iv r al on e, an d la se r al on e gr ou ps ,r es pe ct iv el y *a ts ix m on th s: th e b c v a im pr ov ed by 14 .8 le tte rs in th e iv r w ith an d w ith ou tl as er gr ou ps , co m pa re d w ith a m ea n ga in of si x le tte rs in th e la se rg ro up *a ts ix m on th s: th e m ea n ch an ge in c m t w as –2 40 𝜇m in th e iv r gr ou p, –2 23 𝜇m in iv b pl us la se rg ro up ,a nd –8 7 𝜇m in th e la se r gr ou p *c on ju nc tiv al he m or rh ag e an d ey e pa in w er e th e m os t co m m on ly re po rt ed oc ul ar ad ve rs e ev en ts in al lg ro up s ta n et al , 20 14 [5 9] ii 36 12 iv r 0. 50 m g ve rs us sh am ; iv r gr ou p re ce iv ed m on th ly in tr ao cu la ri nj ec tio ns of 0. 5 m g of ra ni bi zu m ab fo rs ix m on th s an d th en pr n sh am gr ou p re ce iv ed m on th ly sh am in je ct io ns g rid la se rw as ad m in is te re d at 13 an d 25 w ee ks in bo th gr ou ps if cr ite ria fo rl as er tre at m en tw er e m et *t he v a im pr ov em en ta fte r1 2 m on th s in iv r gr ou p: +1 2 .5 le tte r *t he v a w or se ne d in th e sh am gr ou p (– 1.6 le tte r) de sp ite re sc ue la se r *a t1 2 m on th s: th e m ea n ch an ge in c m t w as –3 61 𝜇m in th e iv r gr ou p an d – 17 5 𝜇m in th e sh am gr ou p *n o ne w oc ul ar or sy st em ic ad ve rs e ev en ts w er e ob se rv ed 348 j  o  v r volume 14, issue 3, july–september 2019 intravitreal medications for rvo; lashay et al ta b le 2 .c on tin ue d. tr e a tm e n t a u th o r, ye a r (s tu d y) le ve l n o .o f p a ti e n ts f /u (m ) in te rv e n ti o n ,r e g im e n v a fi n d in g s o c t fi n d in g s a d ve rs e e ff e ct s pi el en et al , 20 15 (r a b a m es )[6 0] ii 31 6 iv r 0. 50 m g, gr id la se r, or bo th ; pa tie nt s w ith a b c v a be tw ee n 20 /3 20 an d 20 /4 0 w er e ra nd om iz ed 1:1 :1 to re ce iv e gr id la se r or th re e m on th ly in je ct io ns of 0. 5 m g iv r or bo th fo llo w ed by th re e m on th s of ob se rv at io n *1 5le tte rg ai n af te rs ix m on th s w as 70 % in bo th iv r an d iv r + la se r gr ou p ve rs us 20 % in th e la se r gr ou p *m ea n ch an ge fro m ba se lin e b c v a at m on th 6 w as +2 ,+ 17 ,a nd +6 le tte rs in la se r, iv r ,a nd co m bi na tio n th er ap y, re sp ec tiv el y *a tm on th 6: th e m ea n de cr ea se in c m t w as – 12 8 𝜇m in th e la se r gr ou p, –2 37 𝜇m in th e ra ni bi zu m ab gr ou p, an d –9 7 𝜇m in th e co m bi na tio n gr ou p (p = 0. 10 fo ri v r ve rs us la se rg ro up an d p = 0. 0 8 fo ri v r ve rs us co m bi na tio n gr ou p) *n o se rio us oc ul ar ad ve rs e ev en t *o ne ca se of st ro ke af te r th e fir st in tr av itr ea l in je ct io n of ra ni bi zu m ab w hi ch re su lte d in st ud y di sc on tin ua tio n ac co rd in g to th e pa tie nt ’s de ci si on b ev ac iz um ab pa ro di et al , 20 15 [6 4] ii 35 12 iv b 1.2 5 m g ve rs us su bt hr es ho ld la se r gr ou ps ; iv b 1.2 5 m g w as gi ve n at ba se lin e an d th en on a pr n re gi m en ac co rd in g to m e pr es en ce on o c t. th e su bt hr es ho ld la se rw as ad m in is te re d on ce *1 5le tte rg ai n af te r1 2 m on th s: 58 % in th e be va ci zu m ab gr ou p ve rs us no ch an ge in b c v a in la se rg ro up *t he m ea n b c v a ch an ge d fro m 0. 92 ± 0. 3 (l og m a r) to 0. 99 ± 0. 2 in th e la se rg ro up ,w hi le in th e iv b gr ou p, th e m ea n b c v a sh ow ed a st at is tic al ly si gn ifi ca nt im pr ov em en tf ro m 0. 94 ± 0. 3 to 0. 72 ± 0. 2 *a fte r1 2 m on th s: c m t w as si gn ifi ca nt ly im pr ov ed in th e be va ci zu m ab gr ou p (– 21 3 𝜇m )a nd w as un ch an ge d in th e la se r gr ou p *n o se rio us oc ul ar an d th e no noc ul ar si de ef fe ct w as re po rt ed n ar ay an an et al , 20 15 (m a rv el )[6 5] ii 75 6 iv b 1.2 5 m g ve rs us iv r 0. 5 m g; ey es w er e tr ea te d w ith iv b or iv r in je ct io n at ba se lin e fo llo w ed by m on th ly pr n re -in je ct io ns *1 5le tte rg ai n af te rs ix m on th s: 59 .4 % an d 57 .8 % in iv r an d iv b gr ou ps ,r es pe ct iv el y *t he b c v a im pr ov em en tf ro m ba se lin e: 18 .1 ve rs us 15 .6 in iv r an d iv b gr ou ps ,r es pe ct iv el y *t he m ea n c m t de cr ea se d – 17 7 𝜇m ve rs us –2 0 1𝜇 m in iv r an d iv b gr ou ps , re sp ec tiv el y *n o se rio us oc ul ar an d no noc ul ar si de ef fe ct j  o  v r volume 14, issue 3, july–september 2019 349 intravitreal medications for rvo; lashay et al ta b le 2 .c on tin ue d. tr e a tm e n t a u th o r, ye a r (s tu d y) le ve l n o .o f p a ti e n ts f /u (m ) in te rv e n ti o n ,r e g im e n v a fi n d in g s o c t fi n d in g s a d ve rs e e ff e ct s c ek ic et al , 20 10 [6 6] ii 31 6 iv b 1.2 5 m g ve rs us iv ta 4 m g *t he b c v a im pr ov em en tf ro m ba se lin e: 7 le tte rs ve rs us 24 le tte rs in iv ta an d iv b gr ou ps ,r es pe ct iv el y *t he c m t re du ct io n w as – 19 0 𝜇m an d – 13 2 𝜇m in iv ta an d iv b gr ou ps , re sp ec tiv el y *c om pa re d to ba se lin e, av er ag e in tr ao cu la r pr es su re ch an ge fro m ba se lin e w as si gn ifi ca nt ly hi gh er in iv ta gr ou p at on e m on th af te ri nj ec tio n w hi le th os e of iv b gr ou p w er e no td iff er en t h ig as hy am a et al ,2 0 10 [6 7] i 43 12 iv b 1.2 5 m g ve rs us iv ta 4 m g; si ng le in je ct io n at ba se lin e w ith ad di tio na l tre at m en ts al lo w ed as ne ed ed af te rt hr ee m on th s *t he b c v a im pr ov em en tf ro m ba se lin e: 16 .5 le tte rs ve rs us 11 le tte rs in iv b an d iv ta gr ou ps ,r es pe ct iv el y *t he c m t re du ct io n w as –2 62 𝜇m an d –3 04 𝜇m in iv b an d iv ta gr ou ps , re sp ec tiv el y *e le va te d io p: -iv b :1 1% -iv ta :2 2% a fli be rc ep t c am po ch ia ro et al ,2 0 15 (v ib r a n t )[6 8] i 18 3 6 ia i2 m g ve rs us la se r; tr ea tin g m on th ly w ith ia i2 m g in ia ig ro up ; th e la se rw as do ne at ba se lin e an d th en re pe at ed at 12 w ee ks *1 5le tte rg ai n af te rs ix m on th s: 52 .7 % of ia ip at ie nt s ve rs us 26 .7 % of th e la se rg ro up *t he b c v a im pr ov em en tf ro m ba se lin e: 17 ve rs us 6. 9 le tte rs in ia i an d la se rg ro up s, re sp ec tiv el y *a fte rs ix m on th s: th e m ea n de cr ea se in c m t w as –2 80 𝜇m ve rs us – 12 8 𝜇m in ia iv er su s la se rg ro up s, re sp ec tiv el y *c om m on ad ve rs e ev en ts : -s ub co nj un ct iv al he m or rh ag e ia i: 19 .8 % la se r: 4. 3% -r et in al ne ov as cu la riz at io n ia i: 0 % la se r: 3% c la rk et al ,2 0 16 (v ib r a n t )[6 9] i 18 3 12 a fte rs ix m on th s, ia i gr ou p co nt in ue d to re ce iv e afl ib er ce pt ev er y ei gh tw ee ks (in st ea d of ev er y fo ur w ee ks )f or th e ne xt si x m on th s. th e la se ron ly gr ou p w as al lo w ed to re ce iv e ia ie ve ry ei gh t w ee ks *1 5le tte rg ai n af te r1 2 m on th s: 57 .1% of ia i/i a ig ro up ve rs us 41 .1% of la se r/i a ig ro up *t he b c v a im pr ov em en tf ro m ba se lin e: 17 .1 ve rs us 12 .2 le tte rs in ia i/i a ia nd la se r/i a ig ro up s, re sp ec tiv el y *a fte r1 2 m on th s: th e m ea n de cr ea se of –2 83 𝜇m an d –2 49 𝜇m in ia i/i a ia nd la se r/i a i gr ou ps ,r es pe ct iv el y *t ra um at ic ca ta ra ct in on e ey e (1. 1% )i n th e ia i gr ou p w as th e on ly se rio us oc ul ar ad ve rs e ev en t c m t, ce nt ra lm ac ul ar th ic kn es s; d ex ,d ex am et ha so ne ;f /u ,f ol lo w up ;i a i, in tr av itr ea la fli be rc ep ti nj ec tio n; io p, in tr ao cu la r pr es su re ;i v b ,i nt ra vi tre al be va ci zu m ab ;i v r , in tr av itr ea lr an ib iz um ab ;i v t, in tr av itr ea lt ria m ci no lo ne ;m e, m ac ul ar ed em a; o c t, op tic al co he re nt to m og ra ph y; pr n ,p ro re na ta ;v a ,v is ua la cu ity 350 j  o  v r volume 14, issue 3, july–september 2019 intravitreal medications for rvo; lashay et al records iden�fied through database searching (2010-2017) (n =681) s c re e n in g in c lu d e d e li g ib il it y id e n ti fi c a ti o n records after duplicates removed (n =271) records screened (n =410) records excluded (n =279) full-text ar�cles assessed for eligibility (n =131) full-text ar�cles excluded, with reasons (n =95) studies included in qualita�ve synthesis (n =36) studies included in quan�ta�ve synthesis (meta-analysis) (n =6) figure 1. prisma flowchart. source: moher d, liberati a, tetzlaff j, altman dg, the prisma group. preferred reporting items for systematic reviews and meta-analyses: the prisma statement. plos med 6(7): e1000097. for more information, visit www.prisma-statement.org. ding et al[22] compared the safety and efficacy of ivb and ivt in patients with crvo. no statistically significant difference was found during the nine-month follow-up between the two treatment groups. quicker visual recovery and improvement of cmt was observed in patients who underwent ivt injection compared with patients who received ivb. in addition, fewer injections were needed in the ivt group (1.31 ± 0.48) in comparison with the ivb group (2.38 ± 1.04). in this study, retreatment with ivb was performed three months after the first injection if persistent me was observed, instead of three consecutive monthly injections in the first three months. therefore, the ivb group might have been undertreated in this study. dexamethasone intravitreal implant (ozurdex). intravitreal dexamethasone implant is a slowrelease steroid in a biodegradable polymer form that lasts about three to four months.[23] the results of the global evaluation of implantable dexamethasone in retinal vein occlusion with macular edema (geneva) trial were reported by haller et al.[23] they evaluated the efficacy and safety of intravitreal dexamethasone implant in two dosages compared with placebo injection in eyes with rvome (either brvo or crvo). a total of 1,267 patients with va between 20/50 and 20/200 were enrolled. patients with dexamethasone implant (either 0.35 mg or 0.70 mg) improved significantly faster compared to the placebo regimen. from the first month to the third month of treatment, more eyes in the dexamethasone implant group achieved 15 etdrs letters compared to the placebo group (p < 0.001); the maximum response was observed at month 3. however, the proportion of eyes achieving 15 etdrs letter improvement after six months was not different between the three groups. the mean va improvement was more pronounced in the dexamethasone groups compared to the placebo group from month 1 to month 6 (p = 0.006); the greatest difference was observed at the end of the second month which was about seven etdrs letters. the mean decrease in cmt was also marked significantly more in eyes receiving each j  o  v r volume 14, issue 3, july–september 2019 351 intravitreal medications for rvo; lashay et al dose of dexamethasone implant compared with placebo at month 3; however, the difference was not sustained up to month 6. it seemed that these changes in cmt were parallel to changes in bcva. the observed clinical efficacy of dexamethasone implant had a limited duration, lasting between 90 to 120 days with a gradual decline thereafter. however, the peak response was observed after three months and was accompanied with the highest incidence of iop rise between days 60 to 90. this study embraced a large proportion of non-ischemic crvo patients that led to encouraging outcomes, but the use of dexamethasone in ischemic crvo remained questionable. visual acuity improvement was sustained after the extension of the geneva study to 12 months by repeated injections of dexamethasone implant. on the other hand, complications were observed more frequently with repeated doses of dexamethasone implant, but these side effects could be satisfactorily managed by either surgery or medications. after the second dexamethasone implant, a large number of patients were able to maintain the visual gain of more than 15 etdrs letters beyond six months although more steroid-related complications might occur.[24] in solo study (functional and anatomical results after a single intravitreal ozurdex injection in retinal vein occlusion), bezatis et al evaluated the efficacy period of ozurdex (dexamethasone implant) in both crvoand brvo-related me. like geneva study, this study showed that early reinjection of dexamethasone implant after 16 weeks instead of 24 weeks was required in most cases; 40.7% of the brvo group and 15% of the crvo group required reinjection after 17.5 and 17.6 weeks, respectively.[25] hoerauf et al in comrade c study (clinical efficacy and safety of ranibizumab versus dexamethasone for crvo) evaluated the efficacy of dexamethasone implant versus ranibizumab in eyes with crvo-me.[26] they showed that although both treatment groups had a similar outcome in the first two months, the efficacy of ranibizumab sustained throughout the study, while dexamethasone therapeutic effect decreased from month 3 onward. the limitation was that all eyes in the dexamethasone group were treated with only a single dosage during the six-month period of the study. based on the geneva and solo studies, the effect of treatment gradually decreases after three months and re-injection is needed. in other words, in clinical practice, dexamethasone re-implantation might be required earlier than six months. in a randomized clinical trial by gado et al, the efficacy of intravitreal dexamethasone implant versus repeated bevacizumab injections were evaluated in six months. they showed that both drugs provided the same effect on va gain and cmt reduction after the first six months of treatment although there was a significantly higher rate of iop rise in the dexamethasone implant group compared with the ivb group at three-six months.[27] anti-vegf agents ranibizumab. rocc study (a randomized study comparing ranibizumab to sham in patients with me secondary to crvo) was performed to compare ranibizumab with placebo regimen in patients with crvo-me. at each time point, bcva was improved in the ranibizumab group compared with the visual loss in the sham group (p = 0.001). eighty percent of cases (n = 12) in the ranibizumab group required more than three initial injections (4.3 ± 0.9) during the study. they concluded that monthly ranibizumab injection significantly improved me and bcva; maintaining the initial improvement would be possible with consecutive repeated injections.[28] ranibizumab for the treatment of macular edema after central retinal vein occlusion crvo (cruise) trial compared the efficacy of ranibizumab 0.3 mg or 0.5 mg with placebo in crvo-me.[29] after six months, the va of patients treated with either 0.3 mg or 0.5 mg ranibizumab improved significantly more than the placebo group. additionally, anatomical changes correlated well with the visual improvements. later, campochiaro et al[30] published the 12-month results of the cruise trial. in this extension of the study, patients were eligible to be treated with 0.5 mg ranibizumab on a pro re nata (prn) basis if bcva was less than 20/40 or cmt was more than 250 𝜇m. the superiority regarding the mean etdrs letter gain after one year was maintained in the ranibizumab treatment groups compared with the placebo group. after 12 months, the mean reduction of cmt was similar between the study groups. the number of needed injections was of interest as it determined the financial burden. the mean number of injections among all randomized patients was 3.3 to 3.8 at months 6 to 12 based on the prn approach. as a 352 j  o  v r volume 14, issue 3, july–september 2019 intravitreal medications for rvo; lashay et al result, ranibizumab was superior to sham based on the visual improvement at months 6 and 12, and the 0.5 mg ranibizumab was a more effective regimen in the treatment of crvo-me, based on this study. horizon trial (ranibizumab for macular edema due to retinal vein occlusions: long-term followup) provided data regarding ranibizumab use in 24 months and analyzed the long-term safety and efficacy of ranibizumab in rvo-related me (either brvo or crvo).[31] it was a multicenter singlearmed study with 304 patients from the bravo and 304 patients from the cruise studies being recruited. they were evaluated at three-month intervals and were candidates for 0.5 mg intravitreal ranibizumab if the recurrence of me or a drop in va was identified. indeed, horizon was an extension study of the bravo and cruise studies. in the second year, fewer ranibizumab injections in patients with crvo was associated with a more prominent worsening of visual outcomes compared to the brvo patients. a reasonable explanation is that retinal ischemia is more extensive in crvo, leading to a larger vegf drive that requires more frequent doses of ranibizumab injections. hence, fewer ranibizumab injections and reduced followup in the second year of treatment resulted in a decline in va of crvo patients. a post-hoc analysis study based on the data obtained by bravo and cruise trials evaluated the effects of ranibizumab on rvo-related me (789 patients: bravo, n = 397; cruise, n = 392). va improvement was observed just after seven days post-injection and was persistent up to 12 months by the prn regimen. the time to first gain of 15 etdrs letters of va in the crvo group was 4 months and in the brvo group was 5.2 months after repeated 0.5 mg monthly ranibizumab injections. overall, more than half of the patients who received monthly regimen achieved significant functional improvement after the first six months of the treatment.[32] bevacizumab. several retrospective and prospective studies reported the efficacy of intravitreal injection of bevacizumab in the improvement of va and reduction of cmt.[22, 33–35] in a prospective controlled clinical trial by epstein et al,[36] after six months, three times more patients in the study group had gained at least 15 letters than the sham group. the mean cmt reduction was significantly more pronounced in the bevacizumab group compared to the control group. the authors continued the study with a six-month extension period.[37] from 6 months to 12 months, all patients from both groups were candidates to be treated with prn bevacizumab every six weeks. cmt reduction was prominent in both sham/bevacizumab and bevacizumab/bevacizumab groups. however, vision improvement was more prominent in the bevacizumab/bevacizumab group versus the sham/bevacizumab group. although anatomic improvement occurred after crossing over of sham patients to bevacizumab, functional improvement was limited. therefore, earlier treatment might lead to better outcomes. rajacopare et al in crave study (bevacizumab versus ranibizumab in the treatment of macular edema due to retinal vein occlusion)[38] compared the efficacy of monthly ranibizumab or bevacizumab for rvo-me in a randomized clinical trial. after six months, changes in cmt and va were not different between the treatment groups. although the efficacy of bevacizumab and ranibizumab are reported to be quite similar in the treatment of crvo-me in many studies,[39–41] the use of bevacizumab in the management of rvo-me remains off-label. ding et al[22] evaluated the safety and efficacy of ivt versus ivb for crvo-me. after nine months, 5 of the 16 ivt eyes and 12 of the 16 ivb eyes needed re-treatment. the mean number of injections in the triamcinolone group (1.3) was less than in the bevacizumab group (2.4). bcva improvement occurred at all time points after the injections in both study groups, and no significant difference was observed between the two groups. some non-randomized studies reported more chance for vision gain in eyes treated with a combination of dexamethasone and ivb than eyes that received dexamethasone implant monotherapy[42]. aflibercept. the protein vegf trap-eye (aflibercept) comprises key domains of human vegf receptors 1 and 2, fused with human igg fc fragment. indeed, all isoforms of vegf-a and placental growth factor would be blocked by this protein. the main advantage of aflibercept is its longer duration of activity.[43] hence, it may reduce the dosing intervals of intravitreal injections in comparison with ranibizumab and bevacizumab. galileo (general assessment limiting infiltration of exudates in central retinal vein occlusion with vegf trap-eye) and copernicus (vascular j  o  v r volume 14, issue 3, july–september 2019 353 intravitreal medications for rvo; lashay et al endothelial growth factor [vegf] trap-eye: investigation of efficacy and safety in central retinal vein occlusion) are multicenter randomized clinical studies that evaluated the intravitreal aflibercept effects in patients with crvo-me.[43–48] in copernicus study,[43] va improvement and macular thickness reduction after six months were significantly more in the aflibercept treated eyes than the control group. they also reported that reduced ocular neovascularization was noted in the aflibercept group. later, brown et al[44] reported the 12-month results of copernicus study in which the previously established arms for the rct were eligible to be treated with prn doses of aflibercept 2 mg every four weeks from month 7 to month 12. after 12 months, the mean va improvement was 16.2 and 3.8 letters in the aflibercept + prn group and the sham + prn group, respectively. they concluded that fewer injections of aflibercept after the loading period could maintain the va gain; however, a delay in the treatment of me could lead to irreversible damage due to chronic edema and disintegrated retinal layers. heier et al[45] reported the 24-month results of the study. after the first year, based on the study protocol, patients were evaluated every three months and were treated with aflibercept if needed. the visual gain was significantly more in the aflibercept/prn group than the sham/prn group after two years (13 versus 1.5 letters in each group, respectively). the mean number of prn injections was less in the aflibercept + prn (2.7 ± 1.7) compared with the sham + prn (3.9 ± 2.0) during months 7 to 12, while during months 13 to 24 the number of prn injections were 3.3 ± 2.1 versus 2.9 ± 2.0 in the two groups, respectively. they also showed that the functional and anatomic improvements, after fixed dosing through six months, followed by prn regimen and monthly monitoring from months 7 to 12, were reduced after continued prn regimen and a reduced monitoring frequency from months 12 to 24 [table 1]. they suggested a beneficial effect of anti-vegf treatment in either group of patients with ischemic or nonischemic crvo; this effect was significantly lower if treatment was started with a delay in both subgroups. considering the time between diagnosis and treatment, they reported that the proportion of patients with 15 letter gain or more after six months was significantly more in patients who received the first intravitreal aflibercept injection during the first two months of diagnosis. they also showed that aflibercept is beneficial even in patients with poorpresenting va of less than 20/200. in a similar double masked rct named galileo, patients with crvo were randomized to intravitreal aflibercept 2 mg or placebo monthly for six months. based on galileo reports, the mean change in bcva and cmt were more marked in patients receiving aflibercept than the sham group at week 24 (p = 0.0001).[46] from months 7 to 12, patients were monitored monthly; the aflibercept group was treated with the intravitreal drug on a prn basis, and the placebo group continued to receive sham. from months 13 to 18, patients were monitored bimonthly, and both groups were treated with intravitreal aflibercept prn. this study showed that the functional and anatomic improvements after fixed monthly dosing in the first six months were largely sustained even with the extension of the treatment intervals. patients with a baseline bcva of 20/200 or worse had a greater visual improvement after 12 months compared to patients with a baseline bcva of better than 20/200. similar to copernicus study, this study revealed that, although delayed treatment with aflibercept led to anatomic improvement, the functional improvement was limited, and the effect could persist for two years. it showed that more improvement of vision might occur if treatment was started earlier.[47, 48] based on these studies, significant visual and anatomic improvements occurred in the first six months with fixed monthly aflibercept injections. these improvements were largely maintained by prn aflibercept injection with a mean of 2.5 to 2.7 injections in the next six months. therefore, a monthly loading dose for up to three months followed by bimonthly aflibercept may have similar efficacy to that of monthly ranibizumab.[47, 48] the efficacy of bimonthly intravitreal aflibercept and ranibizumab in crvo-me was evaluated by saishin et al. they concluded that although no significant difference was observed in visual improvement between the two groups, vegf may not be completely neutralized by bimonthly injections of ranibizumab in all patients with crvo, which may lead to the recurrence of me.[49] recently, in score ii study, the efficacy of monthly bevacizumab was compared with monthly aflibercept in patients with crvo-me. based on this study, monthly bevacizumab was not inferior to 354 j  o  v r volume 14, issue 3, july–september 2019 intravitreal medications for rvo; lashay et al aflibercept regarding visual improvement after six months. score ii extension studies probably will compare outcomes of these anti-vegf agents after six months, using regimens other than monthly dosing.[50] in a recent report of a randomized clinical trial, the injection frequency of aflibercept and ranibizumab in the treatment of crvo-me was investigated. patients were allocated to receive either intravitreal aflibercept (2mg) or ranibizumab (0.5mg) in a treat and extent regimen. after 18 months, the number of injections was significantly lower in the aflibercept group (10.9) compared to the ranibizumab group (14.4) (p = 0.001). the mean treatment interval was significantly longer in the aflibercept group compared with the ranibizumab group (10.0 versus 6.6 weeks) (p = 0.001). the mean changes in bcva and cmt were similar between the groups. the authors concluded that the application of treat and extent regimen with aflibercept in eyes with crvo might reduce the treatment burden and, to some extent, the need for close monitoring of patients.[51] medical management of brvo similar to crvo, me is the main reason for visual loss in brvo. based on the branch vein occlusion study (bvos), macular grid laser photocoagulation was an effective treatment in branch retinal vein occlusion-related macular edema (brvo-me).[9] pharmacologic intervention started with the use of corticosteroids: triamcinolone and dexamethasone. multiple formulations of ivt were used as an off-label drug in the treatment of brvo-me. the intravitreal dexamethasone sustained-release implant was approved in 2009 for the treatment of brvo-me by the u.s. food and drug administration (fda).[23, 24] in recent years, anti-vegf agents (ranibizumab, aflibercept, and bevacizumab) have become the most popular therapeutics for brvo-me. in addition, other modalities have been evaluated in the treatment of brvo including chorioretinal anastomosis with laser, separation of the common adventitia of the crossing artery and vein with removing the cortical vitreous following pars plana vitrectomy, and intra-vascular injection of t-pa through cannulation of the veins.[52, 53] interventional studies on the management of brvo-me with levels i or ii of evidence are summarized in table 2. intravitreal corticosteroids triamcinolone. in a study designed for the treatment of brvo-me, scott et al compared the effectiveness of standard care (grid laser photocoagulation) versus corticosteroid for retinal vein occlusion (score) study report 6.[54] this study was conducted to evaluate the efficacy of two doses of preservative-free intravitreal triamcinolone with grid photocoagulation in brvo-me patients with bcva between 20/40 and 20/400 and cmt of more than 250 𝜇m. at month 12, the va improvement was similar between the groups; however, more complications were observed with 4 mg triamcinolone (35% with cataract progression and 41% with the need for iop-lowering medications). during the first year, none of the treated eyes required glaucoma surgery. however, after 24 months, two eyes in the 4 mg ivt group required surgical interventions. score concluded that the therapeutic efficacy was quite similar in two groups although the 4 mg triamcinolone might lead to more adverse effects. dexamethasone intravitreal implant (ozurdex) in the geneva study, 830 patients from a total of 1,267 patients (66%) with rvo, who had a brvo for at least six weeks, were randomized to receive dexamethasone implant 0.7 mg, 0.35 mg, or placebo. eyes with a history of laser photocoagulation were not excluded in this study. visual improvement of 15 letters or more was achieved faster in both dexamethasone implant groups than the placebo group (p < 0.001). in addition, the percentage of eyes with sustained va improvement was higher in the dexamethasone implant groups compared to the sham group after the third month (p < 0.001). the therapeutic effect of these implants was not sustained after six months. however, from months 1 to 6, the overall mean increase in va from baseline was significantly higher in the dexamethasone implant groups compared with the placebo group. in eyes with brvo-me with a duration less than 90 days, even greater functional improvement might be achieved with dexamethasone implants comparing to eyes with me lasting more than three months based on the subgroup post-hoc analysis. the study did not mention cmt in each brvo subgroups, but overall (i.e., combined crvo j  o  v r volume 14, issue 3, july–september 2019 355 intravitreal medications for rvo; lashay et al and brvo) a significant reduction in cmt was seen in both implant groups compared with the sham group in the first three months. however, after six months, anatomical changes did not differ significantly between the groups.[24] two years later, guignier et al compared the dexamethasone implant with three monthly ivb injections in the treatment of brvo-me. the mean visual gain and cmt reduction was significantly more pronounced at the one-month visit in the intravitreal dexamethasone implant group which was compatible with a faster visual improvement. however, no difference was observed between the two groups at months 3,4, and 6. despite no difference in mean va between the study groups at month 6, a significantly higher proportion of eyes treated with bevacizumab gained 15 letters or more compared with the dexamethasone group. more reinjections at month 4 were needed with the dexamethasone implant compared with the ivb treatment.[55] anti-vegf agents ranibizumab. campochiaro et al[56] published the results of phase iii of bravo study that compared two ranibizumab doses of 0.3 mg and 0.5 mg with placebo in brvo-me. in cases of progressive refractory edema at month 3, rescue grid laser was done. after six months, the bcva improvement and cmt reduction were higher in both ranibizumab groups compared with the placebo (p < 0.0001).[57] after six months of initial monthly dosing, patients were switched to a prn injections; 0.5 mg of ranibizumab was injected in the placebo group, while the 0.3 mg and 0.5 mg groups were treated with their original doses. bcva improvement at six months was maintained in the ranibizumab groups after one year. after starting ranibizumab in the sham group, vision improved; however, this improvement was less than the visual gain in the ranibizumab groups (p < 0.01). the mean cmt change was higher in the 0.3 mg and 0.5 mg groups compared to the sham group (p < 0.05) at six months. horizon study[31] was a two-year extension trial of the bravo and cruise studies. in the brvo arm of the study, 304 patients were given evaluation at three-month intervals and were candidates for 0.5 mg ranibizumab if recurrence of me or a drop in va was identified. horizon study was not completed and led to the variable follow-up periods among the study patients; about 63% of patients (n = 205) from bravo trial completed the period of 12 months in the horizon study. the mean number of injections in each of the previous bravo groups ranged from 2.0 to 2.4 during 12 months of the trial. visual acuities were significantly increased compared with the bravo baseline bcva in each treatment group. however, considering the baseline values of the horizon study, no change or even slight decline in va was observed in the second year. the study suggested that maximal va improvement that can be achieved by monthly injections may decline slowly with decreased follow-up visits. comparison of 0.5 mg ranibizumab with or without adjunctive macular laser therapy, and laser therapy alone was done by tadayoni et al.[58] three monthly intravitreal ranibizumab injections were performed in the ranibizumab groups and subjects were subsequently re-treated prn according to the designed protocol. at six months, both ranibizumab groups showed significant visual improvement compared to the laser only group (p < 0.0001). there was no difference in the number of injections between the two ranibizumab groups. anatomically, the mean cmt reduction at six months was significantly more in the ranibizumab groups than the laser group (p < 0.0001). itan et al[59] compared intravitreal 0.5 mg ranibizumab with grid laser in brvo-me over one year. at the fourth and sixth months, more patients in the grid laser group (68.4% and 50.0%) received additional grid laser compared with the ranibizumab group (6.7% and 8.3%). they concluded that significant and sustained functional and anatomic improvements were provided by the intravitreal ranibizumab in eyes with brvo-me. in the ranibizumab for branch retinal vein occlusion associated macular edema study (rabames), patients with brvo-me were randomized to treatment with three monthly intravitreal 0.5 mg ranibizumab injections or grid laser or both 60. the mean bcva improvement after six months was significantly higher in the ranibizumab group compared to the other groups. the combination group required fewer laser retreatments at month 2 compared with the grid laser group (20% versus 70%). they concluded that ranibizumab might be more efficient in visual improvement compared to grid 356 j  o  v r volume 14, issue 3, july–september 2019 intravitreal medications for rvo; lashay et al laser photocoagulation. laser combined with ranibizumab neither augmented va gain and macular thickness reduction nor did it prevent recurrence of me. cmt increased gradually after stopping the injections in ranibizumab groups, while visual improvement was sustained, indicating that functional deterioration may occur after the structural disintegrities. reinjection of ranibizumab after the initial loading dosage, even with a proper response to treatment, may be necessary based on the visual and anatomical changes. bevacizumab. multiple studies[61–63] evaluated the efficacy of bevacizumab in brvo-me although most of them are retrospective or with small sample size. based on a prospective study by russo et al,[63] 30 eyes with brvo were randomized to treatment with monthly ivb or macular grid laser over 12 months. at all time-points of the study, more improvement in bcva and cmt was observed in the bevacizumab group than the laser group (p < 0.005). in a prospective randomized interventional study,[64] prn ivb and subthreshold grid laser were compared as second line therapy for me in brvo. this study showed better anatomic and functional results in the ivb group compared to the subthreshold grid laser group. in a prospective randomized clinical trial by marvel group, the efficacy of ivb and ranibizumab (ivr) in brvo-me was compared. the number of injections was not significantly different between the treatment groups (3.2 ± 1.5 versus 3.0 ± 1.4, respectively; p = 0.55). there was a significant improvement in va and cmt in eyes that underwent either bevacizumab or ranibizumab injection without any significant difference between the two drugs.[65] in one study, patients with brvo-me were randomly assigned to receive 4 mg ivt monotherapy (n = 17), 1.25 mg ivb monotherapy (n = 14), or a combination of 2 mg ivt and 1.25 mg ivb (n = 21). after one month, all groups showed significant improvement in va and cmt. at six months, the significant reduction in the cmt was sustained while only the bevacizumab monotherapy group demonstrated significant improvement in the bcva. based on these results, at six months, ivb might lead to better functional outcomes compared to the other regimens in this study. ocular side effects occurred more frequently in the 4 mg triamcinolone group compared to the other groups. a mean iop increase of 1.4, -0.1, and 0.5 mmhg occurred in three groups, respectively. also, cataract progression occurred 36%, 8%, and 10% in the three study arms, respectively.[66] in a study by higashyama,[67] eyes with brvome were randomly allocated to receive 4 mg ivt or 1.25 mg ivb with 12-month follow-up; additional injections were administered between 3 and 12 months if it was indicated based on the study criteria. after 12 months, the functional improvement from baseline was significantly higher in the ivb group, although no significant difference was seen in cmt reduction between the groups. therefore, intravitreal injection of bevacizumab may be a better treatment than that of triamcinolone acetonide for brvo-me. given the three-month delay in resuming the treatment after the initial injection, under-treatment of patients should be considered in the appraisal of the results of this study. aflibercept. vibrant study[68] (study to assess the clinical efficacy and safety of vegf trapeye in patients with brvo) was a double-masked randomized trial that evaluated the six-month outcomes of intravitreal aflibercept versus macular laser in brvo-me. after six months, monthly aflibercept injection was associated with more functional and structural improvements than macular grid laser in eyes with brvo-me. in the second phase of this study, after the first six months, aflibercept injection was allowed for patients primarily randomized to laser.[69] aflibercept was injected every eight weeks instead of every four weeks in the primary aflibercept group. it was interesting that even with the eightweek interval regimen, the functional and anatomical improvements gained with monthly injections during the initial six months of the study were maintained. in addition, the laser/aflibercept group had significant va improvement after initiating aflibercept; however, the improvement was still significantly less than in the eyes that received aflibercept from the beginning of the study (p = 0.02), indicating the importance of earlier initiation of treatment. at week 52, the mean cmt reduction from baseline was -283 and -249 𝜇m in the aflibercept and laser/aflibercept groups, respectively. in conclusion, anatomical outcome was not significantly changed even with deferral of the treatment, but maximum visual improvement which could be achieved with early aflibercept injection might not be attained in the deferral group. j  o  v r volume 14, issue 3, july–september 2019 357 intravitreal medications for rvo; lashay et al meta-analysis ranibizumab versus sham injections participants. a total of 555 patients with rvo-me were enrolled in three studies including rocc,[28] bravo,[56, 57] and cruise.[29, 30] the baseline characteristics of participants in these trials were not significantly different concerning age, gender, and systemic factors (e.g., ischemic heart disease, hypertension, and diabetes mellitus). mean change in bcva and cmt at six months. all three studies reported changes in bcva and cmt and reported measures of dispersion (sd or 95% ci). at month 6, the pooled mean change in bcva ranged from -2 to +7.3 letters and +11 to +18.3 letters in the sham and treatment groups, respectively. the highest gain in va was observed within two months of treatment with anti-vegfs, with no deterioration thereafter to six months in all studies. after six months, the pooled md between anti-vegf and sham was 12.7 letters (95% ci: 11.00 to 13.2). as the statistical heterogeneity was not considerable (i2 = 0%, p = 0.84), data was combined in the meta-analysis because the direction of effect was similar for all trials [figure 2a]. results showed superiority of ranibizumab compared to the sham. the pooled mean cmt improvement at six months ranged from -117 to -167 𝜇m and -304 to -452 𝜇m in the sham and treatment groups, respectively. meta-analysis of the data showed that patients who underwent ranibizumab injection had more reduction of pooled mean cmt compared with the sham group, (95% ci: -153 to -284 𝜇m). there was significant statistical heterogeneity (i2 = 80%, p < 0.01) [figure 2b]. hence, we used the random-effect model. this represents that, based on anatomical changes, anti-vegf treatment is associated with clinically significant benefits compared with sham at six months. bevacizumab versus intravitreal triamcinolone participants. a total of 149 patients, with me secondary to rvo, were enrolled in three studies (ramezani et al,[21] ding et al,[22] and cekic[66] et al). the baseline characteristics of participants in these trials were also similar. mean change in bcva and cmt at six months. all three studies reported changes in bcva, cmt, and measures of dispersion (sd or 95% ci) (ramezani et al, ding et al, and cekic et al). the pooled mean change in bcva letter score at six months ranged from +9 to +48 letters and +23.5 to +32 letters in the triamcinolone and bevacizumab groups, respectively. at six months, the pooled md between bevacizumab and triamcinolone was 5.3 letters in favor of bevacizumab (95% ci: -16 to 17.5). the statistical heterogeneity was not considerable (i2 = 50.3%, p = 0.13). since the direction of effect was the same for all of the studies, we combined data in the meta-analysis [figure 3a]. there was no significant difference in visual improvement between the two therapies. the pooled mean reduction in cmt at six months ranged from a -75 to -450 𝜇m and -132 to 408 𝜇m in the triamcinolone and bevacizumab groups, respectively. meta-analysis of the data suggests that the pooled mean cmt reduction was significantly more in the triamcinolone groups compared with the bevacizumab groups during the first month, with no significant differences in macular thickness after six-months follow-up. patients treated with triamcinolone had a pooled mean reduction in cmt of -68.1 𝜇m more than patients treated with bevacizumab, (95% ci: -58 to -76 𝜇m). there was a significant statistical heterogeneity (i2 = 72.1%, p = 0.02) [figure 3b]. therefore, randomeffect model was used. based on the anatomical changes, no clinically significant superiority of ivb over triamcinolone injections was observed at six months. discussion many pharmaceutical agents have been used for the treatment of rvo-me; however, three modalities including intravitreal ranibizumab, aflibercept, and dexamethasone implant are fda approved. the functional and anatomical results of randomized controlled trials of the five most common pharmaceutical agents used in the treatment of rvo-me are summarized in tables 1 and 2. almost all of them could improve the vision and reduce the macular thickness compared with sham injection or macular grid laser photocoagulation at months 6, 12, and 24. in addition, based on seven major rcts including bravo, cruise, horizon, epstein et al, copernicus, galileo, and vibrant, earlier treatment with these agents may lead to 358 j  o  v r volume 14, issue 3, july–september 2019 intravitreal medications for rvo; lashay et al figure 2. forest plot displaying pooled summary estimates with ranibizumab treatment versus sham injection at 24 weeks. (a) regarding va, there was no significant heterogeneity (i2 = 0%, p = 0.84). due to small number of included studies, either fixedeffect or random-effect analysis was applied or the overall 95%ci was meaningful (-0.35 to -0.01). (b) regarding cmt, there was significant heterogeneity (i2 = 80%, p < 0.01), hence, the random-effect model was used and the overall 95%ci was meaningful (-1.37 to -0.46). ci, confidence interval; cmt, central macular thickness; va, visual acuity better outcomes.[29–31, 36, 37, 43–48, 56, 57, 68, 69] significant ocular or systemic adverse effects of antivegf agents are rare. intraocular pressure rise and cataract progression mostly occurred following intravitreal corticosteroid injections. based on the score study,[18] the proportion of patients with crvo gaining 15 letters of etdrs after 12 months was 6.8%, 26.5%, and 25.6% in the observation, 1 mg ivt, and 4 mg ivt groups, respectively. at four months, the mean reduction in cmt was greater in the 4 mg ivt group. however, no difference was seen regarding cmt improvement among the treatment groups after 12 months. in the triamcinolone-treated patients, authors reported a reduction in me with a moderate correlation with va; however, there was a significantly higher percentage of patients requiring iop-lowering medications and a higher rate of cataract development in the 4 mg ivt group. hence, the authors suggested 1 mg ivt injection for me secondary to crvo. in eyes with brvo, the comparison was made between intravitreal triamcinolone and laser treatment. no significant difference was found although the 4 mg ivt group again was associated with the highest rate of adverse events.[18, 54] comparing intravitreal triamcinolone and anti-vegf agents, more functional improvement may occur with anti-vegf injection j  o  v r volume 14, issue 3, july–september 2019 359 intravitreal medications for rvo; lashay et al figure 3. forest plot displaying pooled summary estimates with bevacizumab treatment versus triamcinolone injection at 24 weeks. (a) regarding va, since there was no significant heterogeneity (i2 = 50%, p = 0.13), either fixed-effect or randomeffect analysis was applied or the overall 95%ci was not meaningful (-0.08 to 0.87). (b) regarding cmt, there was significant heterogeneity between included studies (i2 = 72%, p = 0.02) and thus, the random-effect model was used and the overall 95%ci was not meaningful (-0.80 to 0.48). ci, confidence interval; cmt, central macular thickness; va, visual acuity although triamcinolone may be accompanied with faster structural improvement.[21, 22, 66] dexamethasone implant was compared with the sham treatment in rvo eyes in the geneva study.[23, 24, 55] after three months, both structural and functional improvements were significantly higher in eyes treated with dexamethasone implant compared to sham injection, but this effect was not maintained after six months. the maximum therapeutic effect of intravitreal dexamethasone implant is about 12 weeks after injection. therefore, treatment repetition is necessary even with dexamethasone implantable agents. the peak response observed at three months is accompanied by the highest incidence of iop rise and cataract formation. the therapeutic effect (both structural and functional) was greater in eyes with crvo eyes than in eyes with brvo. patient selection in the geneva study was not randomized for retinal ischemia; a large proportion of non-ischemic rvo patients were enrolled. hence, the study didn’t address the use of ozurdex in ischemic crvo patients. a post-hoc analysis showed that dexamethasone implantation earlier than three months after the brvo occurrence 360 j  o  v r volume 14, issue 3, july–september 2019 intravitreal medications for rvo; lashay et al was associated with greater va improvement compared with the eyes with longer duration of me. according to the comrade study,[26] anti-vegf and dexamethasone implant treatment groups had a similar outcome in the first two months, however, dexamethasone’s efficacy decreased from month 3, while ranibizumab maintained its efficacy up to month 6. it showed that dexamethasone reimplantation might be required earlier than six months. the solo study also reported early reinjection of dexamethasone implants in most of the cases[25]. in the study by guignier et al, a higher percentage of eyes with brvo achieved 15 letters or more in the ivb group (30%) compared with the dexamethasone group (11%) after 6 months.[55] although faster functional and anatomical recovery during the first month was observed in eyes that received dexamethasone implant compared to the ivb-treated eyes, the reinjection rate at four months was also higher with dexamethasone. in cases undergoing treatment with antivegf injection, various protocols have been suggested. these protocols include loading doses of three to six monthly injections, followed by re-injections on a prn basis according to the functional and structural changes. it seems that aflibercept injection can be performed at longer intervals without a significant reduction in its efficacy. although the “treat-and-extend” regimen is frequently applied in anti-vegf treatment in age-related macular degeneration, this protocol has also been recently used in me due to rvos using aflibercept with good outomes.[51] all trials showed that repeated anti-vegf injection was associated with significant improvement in the functional outcomes at six months compared to the placebo. the functional improvement was also accompanied by favorable structural outcomes.[18, 23, 24, 29, 30, 36, 37, 43–48, 50, 54, 56, 57, 68, 69] the impact of treatment delay was evaluated in some studies including vibrant,[68, 69] copernicus,[43–45] epstein,[36, 37] and galileo.[47, 48, 64] these rcts suggested that a shorter interval between the diagnosis and the treatment of rvo-me was associated with the greatest benefit of anti-vegfs. the extension of main studies on anti-vegfs in which the control group received sham injections for six months and then were switched to prn regimen between months 7 and 12, further confirmed this evidence. postponing anti-veggf therapy for six months could still have a good structural outcome with no significant difference between the treatment groups at month 12. in contrast, while functional outcomes improved with switching to prn antivegf injections after six months in the sham group, these outcomes remained significantly lower at one year compared with the groups treated with anti-vegf agents from the outset (copernicus,[43–45] cruise,[29, 30] and epstein et al[36, 37]). in the horizon[31] study (the 24-month extension of cruise and bravo studies), visual outcomes, but not macular thickness, worsened in the second year of treatment especially in the crvo arm. this may be due to the reduced efficacy of anti-vegfs during the treatment course. the other reason may be lower treatment frequency from months 12 to 24, especially in patients with crvo. as we know, the non-perfusion area of retina is usually larger in crvo than in brvo, and this causes a higher concentration of vegf.[7] therefore, more intravitreal injections may be needed in the second year of treatment of eyes with crvome than those with brvo-me. regarding iris or retinal neovascularisation or neovascular glaucoma, anti-vegf therapy led to a significant reduction of neovascular complications compared to the sham treatment at six months (copernicus,[43–45] cruise,[29, 30] epstein et al,[36, 37] galileo,[46–48] rocc,[28] and vibrant[68, 69]). in eyes treated with aflibercept, the visual and anatomical improvements that occurred within the first 24 weeks of the study with monthly 2 mg dosing were maintained with bimonthly dosing. comparison of studies with different treatment modalities a direct comparison between cruise (ranibizumab) and copernicus/galileo (aflibercept), geneva (dexamethasone), score (triamcinolone)[18, 24, 29, 44, 47] is not appropriate due to several key differences in the study designs, protocols, and population. for instance, eyes with more severity of ischemia (e.g., the presence of an rapd) and more chronic disease were not enrolled in the bravo study but were allowed in score. hence, it is not surprising to see better results in bravo study. also, longer follow-up periods in the score might have led to under-treatment. likewise, in the geneva study, in the first six j  o  v r volume 14, issue 3, july–september 2019 361 intravitreal medications for rvo; lashay et al months of the study, only a single treatment with dexamethasone implant was allowed, probably resulting in the under-treatment as the implant’s peak effect is at two to three months. in the cruise[29, 30] trial, patients with sustained me of more than 12 months or an rapd were excluded, while prior treatment with anti-vegf therapy was not defined as an exclusion criteria. in contrast, in copernicus/galileo[43–48] trials, patients were specifically excluded if they had sustained me of more than nine-months duration or prior anti-vegf treatment, and the presence of an rapd was not mentioned in the exclusion criteria.[70, 71] it is also not possible to compare the results between cruise and score as cruise study might have included healthier eyes compared with score; in cruise trial (but not in score), patients were excluded if they had me for more than 12 months or an rapd (probably indicating extensive capillary dropout and ischemia); follow-up and retreatment in cruise was monthly, but it was implemented every four months in the score. therefore, direct comparison of these studies may lead to a misjudgment.[70] almost all trials reported that the greatest reduction in cmt occurred within a month of the first injection. also, the cmt improvement was sustained during the treatment period. however, this is in contrary to the observed course of cmt changes in the control groups, who demonstrated a smoother and linear reduction in cmt over the time. in this study, meta-analysis showed that treatment with ranibizumab was associated with more anatomical and functional improvement compared to the sham after six months, while there was no significant difference in anatomical and visual outcomes between bevacizumab and triamcinolone after six months. although inclusion criteria for meta-analysis was narrowed to permit including comparable studies with similar arms, it should be noted that some variables (i.e., the time needed to wait before starting the treatment) were not matched and could be a potential source of bias. summary this systematic review and the meta-analysis demonstrates that treatment with anti-vegfs provides significant structural and functional gains compared to the observation in eyes with rvo. there was no significant difference between eyes treated with bevacizumab and intravitreal corticosteroid based on this meta-analysis. however, it seems that repeated anti-vegf injections, especially for ischemic cases, may be accompanied with better visual outcomes and fewer side effects in the long term. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. green wr, chan cc, hutchins gm, terry jm. central retinal vein occlusion: a prospective histopathologic study of 29 eyes in 28 cases. retina 1981;1:27-55. 2. bertelsen m, linneberg a, christoffersen n, vorum h, gade e, larsen m. mortality in patients with central retinal vein occlusion. ophthalmology 2014;121:637-642. 3. elman mj, bhatt ak, quinlan pm, enger c. the risk for systemic vascular diseases and mortality in patients with central retinal vein occlusion. ophthalmology 1990;97:15431548. 4. dodson pm, galton dj, hamilton am, blach rk. retinal vein occlusion and the prevalence of lipoprotein abnormalities. br j ophthalmol 1982;66:161-164. 5. koizumi h, ferrara dc, brue c, spaide rf. central retinal vein occlusion case-control study. am j ophthalmol 2007;144:858-863. 6. wang yx, zhang js, you qs, xu l, jonas jb. ocular diseases and 10-year mortality: the beijing eye study 2001/2011. acta ophthalmol 2014;92:e424-e428. 7. hayreh ss. ocular vascular occlusive disorders: natural history of visual outcome. prog retin eye res 2014;41:1-25. 8. glacet-bernard a, coscas g, chabanel a, zourdani a, lelong f, samama mm. prognostic factors for retinal vein occlusion: prospective study of 175 cases. ophthalmology 1996;103:551-560. 9. argon laser photocoagulation for macular edema in branch vein occlusion. the branch vein occlusion study group. am j ophthalmol 1984;98:271-282. 10. varma r, bressler nm, suner i, lee p, dolan cm, ward j, et al. improved vision-related function after ranibizumab for macular edema after retinal vein occlusion: results from the bravo and cruise trials. ophthalmology 2012;119:21082118. 11. hayreh ss, podhajsky pa, zimmerman mb. branch retinal artery occlusion: natural history of visual outcome. ophthalmology 2009;116:1188-1194.e1-e4. 362 j  o  v r volume 14, issue 3, july–september 2019 intravitreal medications for rvo; lashay et al 12. oxford centre for evidence-based medicine. levels of evidence; 2009 [cited january 31, 2017.]. available from: http://www.cebm.net/index. aspx?o.1025. 13. crowther m, lim w, crowther ma. systematic review and meta-analysis methodology. blood 2010;116:3140-3146. 14. moher d, liberati a, tetzlaff j, altman dg, the pg. preferred reporting items for systematic reviews and meta-analyses: the prisma statement. plos med 2009;6:e1000097. 15. ip ms, gottlieb jl, kahana a, scott iu, altaweel mm, blodi ba, et al. intravitreal triamcinolone for the treatment of macular edema associated with central retinal vein occlusion. arch ophthalmol (chicago, ill : 1960) 2004;122:11311136. 16. braithwaite t, nanji aa, lindsley k, greenberg pb. antivascular endothelial growth factor for macular oedema secondary to central retinal vein occlusion. cochrane database syst rev 2014:cd007325. 17. mohamed q, mcintosh rl, saw sm, wong ty. interventions for central retinal vein occlusion: an evidence-based systematic review. ophthalmology 2007;114:507-519, 524. 18. ip ms, scott iu, vanveldhuisen pc, oden nl, blodi ba, fisher m, et al. a randomized trial comparing the efficacy and safety of intravitreal triamcinolone with observation to treat vision loss associated with macular edema secondary to central retinal vein occlusion: the standard care vs corticosteroid for retinal vein occlusion (score) study report 5. arch ophthalmol (chicago, ill : 1960) 2009;127:1101-1114. 19. jonas jb, degenring rf, kamppeter ba, kreissig i, akkoyun i. duration of the effect of intravitreal triamcinolone acetonide as treatment for diffuse diabetic macular edema. am j ophthalmol 2004;138:158-160. 20. jonas jb, jonas ra, neumaier m, findeisen p. cytokine concentration in aqueous humor of eyes with diabetic macular edema. retina 2012;32:2150-2157. 21. ramezani a, esfandiari h, entezari m, moradian s, soheilian m, dehsarvi b, et al. three intravitreal bevacizumab versus two intravitreal triamcinolone injections in recent onset central retinal vein occlusion. acta ophthalmol 2014;92:e530-e539. 22. ding x, li j, hu x, yu s, pan j, tang s. prospective study of intravitreal triamcinolone acetonide versus bevacizumab for macular edema secondary to central retinal vein occlusion. retina 2011;31:838-845. 23. haller ja, bandello f, belfort r, jr., blumenkranz ms, gillies m, heier j, et al. randomized, sham-controlled trial of dexamethasone intravitreal implant in patients with macular edema due to retinal vein occlusion. ophthalmology 2010;117:1134-1146.e3. 24. haller ja, bandello f, belfort r, jr., blumenkranz ms, gillies m, heier j, et al. dexamethasone intravitreal implant in patients with macular edema related to branch or central retinal vein occlusion twelve-month study results. ophthalmology 2011;118:2453-2460. 25. bezatis a, spital g, hohn f, maier m, clemens cr, wachtlin j, et al. functional and anatomical results after a single intravitreal ozurdex injection in retinal vein occlusion: a 6-month follow-up – the solo study. acta ophthalmol 2013;91:e340-e347. 26. hoerauf h, feltgen n, weiss c, paulus em, schmitzvalckenberg s, pielen a, et al. clinical efficacy and safety of ranibizumab versus dexamethasone for central retinal vein occlusion (comrade c): a european label study. am j ophthalmol 2016;169:258-267. 27. gado as, macky ta. dexamethasone intravitreous implant versus bevacizumab for central retinal vein occlusionrelated macular oedema: a prospective randomized comparison. clin exp ophthalmol 2014;42:650-655. 28. kinge b, stordahl pb, forsaa v, fossen k, haugstad m, helgesen oh, et al. efficacy of ranibizumab in patients with macular edema secondary to central retinal vein occlusion: results from the sham-controlled rocc study. am j ophthalmol 2010;150:310-314. 29. brown dm, campochiaro pa, singh rp, li z, gray s, saroj n, et al. ranibizumab for macular edema following central retinal vein occlusion: six-month primary end point results of a phase iii study. ophthalmology 2010;117:1124-1133.e1. 30. campochiaro pa, brown dm, awh cc, lee sy, gray s, saroj n, et al. sustained benefits from ranibizumab for macular edema following central retinal vein occlusion: twelve-month outcomes of a phase iii study. ophthalmology 2011;118:2041-2049. 31. heier js, campochiaro pa, yau l, li z, saroj n, rubio rg, et al. ranibizumab for macular edema due to retinal vein occlusions: long-term follow-up in the horizon trial. ophthalmology 2012;119:802-809. 32. thach ab, yau l, hoang c, tuomi l. time to clinically significant visual acuity gains after ranibizumab treatment for retinal vein occlusion: bravo and cruise trials. ophthalmology 2014;121:1059-1066. 33. kriechbaum k, michels s, prager f, georgopoulos m, funk m, geitzenauer w, et al. intravitreal avastin for macular oedema secondary to retinal vein occlusion: a prospective study. br j ophthalmol 2008;92:518. 34. prager f, michels s, kriechbaum k, georgopoulos m, funk m, geitzenauer w, et al. intravitreal bevacizumab (avastin) for macular oedema secondary to retinal vein occlusion: 12-month results of a prospective clinical trial. br j ophthalmol 2009;93:452-456. 35. zhang h, liu z-l, sun p, gu f. intravitreal bevacizumab for treatment of macular edema secondary to central retinal vein occlusion: eighteen-month results of a prospective trial. j ocul pharmacol ther 2011;27:615-621. 36. epstein dl, algvere pv, von wendt g, seregard s, kvanta a. bevacizumab for macular edema in central retinal vein occlusion: a prospective, randomized, double-masked clinical study. ophthalmology 2012;119:1184-1189. 37. epstein dl, algvere pv, von wendt g, seregard s, kvanta a. benefit from bevacizumab for macular edema in central retinal vein occlusion: twelve-month results of a prospective, randomized study. ophthalmology 2012;119:25872591. 38. rajagopal r, shah gk, blinder kj, altaweel m, eliott d, wee r, et al. bevacizumab versus ranibizumab in the treatment of macular edema due to retinal vein occlusion: 6-month results of the crave study. ophthalmic surg lasers imaging retina 2015;46:844-850. 39. costa ra, jorge r, calucci d, melo la, jr., cardillo ja, scott iu. intravitreal bevacizumab (avastin) for central and hemicentral retinal vein occlusions: ibevo study. retina 2007;27:141-149. j  o  v r volume 14, issue 3, july–september 2019 363 intravitreal medications for rvo; lashay et al 40. ferrara dc, koizumi h, spaide rf. early bevacizumab treatment of central retinal vein occlusion. am j ophthalmol 2007;144:864-871. 41. pai sa, shetty r, vijayan pb, venkatasubramaniam g, yadav nk, shetty bk, et al. clinical, anatomic, and electrophysiologic evaluation following intravitreal bevacizumab for macular edema in retinal vein occlusion. am j ophthalmol 2007;143:601-606. 42. mayer wj, remy m, wolf a, kook d, kampik a, ulbig m, et al. comparison of intravitreal bevacizumab upload followed by a dexamethasone implant versus dexamethasone implant monotherapy for retinal vein occlusion with macular edema. ophthalmologica 2012;228:110-116. 43. boyer d, heier j, brown dm, clark wl, vitti r, berliner aj, et al. vascular endothelial growth factor trap-eye for macular edema secondary to central retinal vein occlusion: six-month results of the phase 3 copernicus study. ophthalmology 2012;119:1024-1032. 44. brown dm, heier js, clark wl, boyer ds, vitti r, berliner aj, et al. intravitreal aflibercept injection for macular edema secondary to central retinal vein occlusion: 1year results from the phase 3 copernicus study. am j ophthalmol 2013;155:429-437.e7. 45. heier js, clark wl, boyer ds, brown dm, vitti r, berliner aj, et al. intravitreal aflibercept injection for macular edema due to central retinal vein occlusion: two-year results from the copernicus study. ophthalmology 2014;121:1414-1420.e1. 46. holz fg, roider j, ogura y, korobelnik jf, simader c, groetzbach g, et al. vegf trap-eye for macular oedema secondary to central retinal vein occlusion: 6-month results of the phase iii galileo study. br j ophthalmol 2013;97:278-284. 47. korobelnik jf, holz fg, roider j, ogura y, simader c, schmidt-erfurth u, et al. intravitreal aflibercept injection for macular edema resulting from central retinal vein occlusion: one-year results of the phase 3 galileo study. ophthalmology 2014;121:202-208. 48. ogura y, roider j, korobelnik jf, holz fg, simader c, schmidt-erfurth u, et al. intravitreal aflibercept for macular edema secondary to central retinal vein occlusion: 18month results of the phase 3 galileo study. am j ophthalmol 2014;158:1032-1038. 49. saishin y, ito y, fujikawa m, sawada t, ohji m. comparison between ranibizumab and aflibercept for macular edema associated with central retinal vein occlusion. jpn j ophthalmol 2017;61:67-73. 50. scott iu, vanveldhuisen pc, ip ms, blodi ba, oden nl, awh cc, et al. effect of bevacizumab vs aflibercept on visual acuity among patients with macular edema due to central retinal vein occlusion: the score2 randomized clinical trial. jama 2017;317:2072-2087. 51. casselholm de salles m, amren u, kvanta a, epstein dl. injection frequency of aflibercept versus ranibizumab in a treat-and-extend regimen for central retinal vein occlusion: a randomized clinical trial. retina 2019;39:1370-1376. 52. bavbek t, yenice o, toygar o. problems with attempted chorioretinal venous anastomosis by laser for nonischemic crvo and brvo. ophthalmologica 2005;219:267-271. 53. raszewska-steglinska m, gozdek p, cisiecki s, michalewska z, michalewski j, nawrocki j. pars plana vitrectomy with ilm peeling for macular edema secondary to retinal vein occlusion. eur j ophthalmol 2009;19:10551062. 54. scott iu, ip ms, vanveldhuisen pc, oden nl, blodi ba, fisher m, et al. a randomized trial comparing the efficacy and safety of intravitreal triamcinolone with standard care to treat vision loss associated with macular edema secondary to branch retinal vein occlusion: the standard care vs corticosteroid for retinal vein occlusion (score) study report 6. arch ophthalmol (chicago, ill : 1960) 2009;127:1115-1128. 55. guignier b, subilia-guignier a, fournier i, ballonzoli l, speeg-schatz c, gaucher d. prospective pilot study: efficacy of intravitreal dexamethasone and bevacizumab injections in the treatment of macular oedema associated with branch retinal vein occlusion. ophthalmologica 2013;230:43-9. 56. campochiaro pa, heier js, feiner l, gray s, saroj n, rundle ac, et al. ranibizumab for macular edema following branch retinal vein occlusion: six-month primary end point results of a phase iii study. ophthalmology 2010;117:11021112.e1. 57. brown dm, campochiaro pa, bhisitkul rb, ho ac, gray s, saroj n, et al. sustained benefits from ranibizumab for macular edema following branch retinal vein occlusion: 12-month outcomes of a phase iii study. ophthalmology 2011;118:1594-1602. 58. tadayoni r, waldstein sm, boscia f, gerding h, pearce i, priglinger s, et al. individualized stabilization criteriadriven ranibizumab versus laser in branch retinal vein occlusion: six-month results of brighter. ophthalmology 2016;123:1332-1344. 59. tan mh, mcallister il, gillies me, verma n, banerjee g, smithies la, et al. randomized controlled trial of intravitreal ranibizumab versus standard grid laser for macular edema following branch retinal vein occlusion. am j ophthalmol 2014;157:237-247.e1. 60. pielen a, mirshahi a, feltgen n, lorenz k, korb c, junker b, et al. ranibizumab for branch retinal vein occlusion associated macular edema study (rabames): six-month results of a prospective randomized clinical trial. acta ophthalmol 2015;93:e29-e37. 61. ehlers jp, decroos fc, fekrat s. intravitreal bevacizumab for macular edema secondary to branch retinal vein occlusion. retina 2011;31:1856-1862. 62. moradian s, faghihi h, sadeghi b, piri n, ahmadieh h, soheilian m, et al. intravitreal bevacizumab vs. sham treatment in acute branch retinal vein occlusion with macular edema: results at 3 months (report 1). graefe arch clin exp ophthalmol 2011;249:193-200. 63. russo v, barone a, conte e, prascina f, stella a, noci nd. bevacizumab compared with macular laser grid photocoagulation for cystoid macular edema in branch retinal vein occlusion. retina 2009;29:511-515. 64. parodi mb, iacono p, bandello f. subthreshold grid laser versus intravitreal bevacizumab as second-line therapy for macular edema in branch retinal vein occlusion recurring after conventional grid laser treatment. graefe arch clin exp ophthalmol 2015;253:1647-1651. 65. narayanan r, panchal b, das t, chhablani j, jalali s, ali mh. a randomised, double-masked, controlled study of the efficacy and safety of intravitreal bevacizumab versus ranibizumab in the treatment of macular oedema due to 364 j  o  v r volume 14, issue 3, july–september 2019 intravitreal medications for rvo; lashay et al branch retinal vein occlusion: marvel report no. 1. br j ophthalmol 2015;99:954-959. 66. cekic o, cakir m, yazici at, alagoz n, bozkurt e, faruk yilmaz o. a comparison of three different intravitreal treatment modalities of macular edema due to branch retinal vein occlusion. curr eye res 2010;35:925-929. 67. higashiyama t, sawada o, kakinoki m, sawada t, kawamura h, ohji m. prospective comparisons of intravitreal injections of triamcinolone acetonide and bevacizumab for macular oedema due to branch retinal vein occlusion. acta ophthalmol 2013;91:318-324. 68. campochiaro pa, clark wl, boyer ds, heier js, brown dm, vitti r, et al. intravitreal aflibercept for macular edema following branch retinal vein occlusion: the 24week results of the vibrant study. ophthalmology 2015;122:538-544. 69. clark wl, boyer ds, heier js, brown dm, haller ja, vitti r, et al. intravitreal aflibercept for macular edema following branch retinal vein occlusion: 52-week results of the vibrant study. ophthalmology 2016;123:330-336. 70. ehlers jp, kim sj, yeh s, thorne je, mruthyunjaya p, schoenberger sd, et al. therapies for macular edema associated with branch retinal vein occlusion: a report by the american academy of ophthalmology. ophthalmology 2017;124:1412-1423. 71. zacharias lc, lin t, migon r, ghosn c, orilla w, feldmann b, et al. assessment of the differences in pharmacokinetics and pharmacodynamics between four distinct formulations of triamcinolone acetonide. retina 2013;33:522-531. j  o  v r volume 14, issue 3, july–september 2019 365 review article pathogenic tau protein species: promising therapeutic targets for ocular neurodegenerative diseases mohammad amir mishan1, ms; mozhgan rezaei kanavi2, md; koorosh shahpasand3, phd; hamid ahmadieh4, md 1ocular tissue engineering research center, student research committee, shahid beheshti university of medical sciences, tehran, iran 2ocular tissue engineering research center, shahid beheshti university of medical sciences, tehran, iran 3department of brain and cognitive sciences, cell science research center, royan institute for stem cell biology and technology, acecr, tehran, iran 4ophthalmic research center, shahid beheshti university of medical sciences, tehran, iran orcid: mohammad amir mishan: https://orcid.org/0000-0001-8210-9322 mozhgan rezaei kanavi: https://orcid.org/0000-0002-1497-2260 abstract tau is a microtubule-associated protein, which is highly expressed in the central nervous system as well as ocular neurons and stabilizes microtubule structure. it is a phospho-protein being moderately phosphorylated under physiological conditions but its abnormal hyperphosphorylation or some postphosphorylation modifications would result in a pathogenic condition, microtubule dissociation, and aggregation. the aggregates can induce neuroinflammation and trigger some pathogenic cascades, leading to neurodegeneration. taking these together, targeting pathogenic tau employing tau immunotherapy may be a promising therapeutic strategy in fighting with cerebral and ocular neurodegenerative disorders. keywords: microtubule-associated protein; neurodegenerative disorders; tau; ocular neurons j ophthalmic vis res 2019; 14 (4): 491–505 correspondence to: mozhgan rezaei kanavi, md. ocular tissue engineering research center, shahid beheshti university of medical sciences, no. 23, paidarfard st., boostan 9 st., pasdaran ave., tehran 16666, iran. e-mail: mrezaie47@yahoo.com received: 07-12-2018 accepted: 11-06-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v14i4.5459 introduction tau is a microtubule (mt)-associated protein and the most common unfolded protein upon neurodegenerative disorders, which was described in 1975 by weingarten and colleagues.[1] this protein gene encoding (mapt), being located at chromosome 17q21,[2] is predominantly expressed in various regions of the human brain, mostly in neurons and to a lesser degree in astrocytes and oligodendrocytes.[3, 4]tau is an axonal protein, binds to mts by its mt-binding domain, stabilizing microtubule structure and the cytoskeleton.[5–7] other functions of tau are their roles in cargo conveyance and signaling pathways.[8, 9] tau aggregation is widely accepted as a pathological process in central nervous system (cns), leading to this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: mishan ma, kanavi mr, shahpasand k, ahmadieh h. pathogenic tau protein species. j ophthalmic vis res 2019;14:491–505. © 2019 journal of ophthalmic and vision research | published by knowledge e 491 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5459&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr tau protein and neurodegenerative diseases; mishan et al neurodegenerative disorders such as: alzheimer disease (ad) and post-traumatic brain injuries[10]. since ocular neurodegeneration is similar to cns neurodegenerative disorders, there are several evidences that pathogenic forms of tau are prone to aggregation and responsible for retinal degeneration in the subjects with ocular neurodegeneration, such as age-related macular degeneration (amd) and glaucoma.[11–13] with this in mind, we aimed to summarize scientific reports focusing on the role of tauopathy in the pathogenesis of neurodegenerative diseases, in particular in the eye, and to explain the role of targeted therapy as a promising therapeutic modality for pathogenic tau aggregations. tau gene the mapt gene include 16 exons, of which 11 are expressed in the human brain and 6 main isoforms of 37-46 kda tau mrna are produced by alternative splicing that results in production of six tau protein isoforms. difference between the isoforms is dependent on the n-terminal region where the number of copies of a repeated motif consisting of 29-amino acids (0n, 1n, or 2n), and the c-terminus including either three (3r tau) or four (4r tau) mt-binding repeats.[14–16] in human cns, the longest tau isoform with 441 amino acids, 2n4r, has 80 thr and ser residues that can be modified by numerous kinases[18] and a low proportion of hydrophobic amino acids, which renders tau a hydrophilic protein.[17] differential splicing that alters tau protein isoform expression occurs at every step of development and neuronal maturation.[10] in the adult brain, all six tau isoforms are expressed, in contrast to fetal brain where the shortest tau isoform (0n3r) is expressed.[16] in the cerebral cortex of healthy adults, approximately equal amounts of 3r and 4r tau isoforms are expressed.[16] additionally, it has been reported that there is 3r/4r ratio changes in the ad patient brains compared to the healthy subjects, demonstrating that the isoforms ratio is a determinant factor in tau pathogenicity and aggregation. regional splicing of tau mrna has also been observed in human brain. the expression rate of 0n3r tau isoform in the cerebellum is lower than other regions in human brain and 4r tau isoforms are highly expressed in the globus pallidus.[19, 20] tau protein structure tau protein has a flexible conformation with a low level of secondary structure[21, 22] and is subdivided into four domains with different biochemical properties. the n-terminal acidic domain with 1– 150 amino acids includes two n-terminal inserts. tau protein amino acids 151–243 are known as the proline-rich domain.[6] the mt-binding domain of tau consists of four repeated motifs that are separated from each other by flanking regions, which altogether provide a structure by which the tau can bind to and stabilize mts.[22, 23] amino acids 370–441 are known as the c-terminal region.[22] the n-terminal domain protrudes out of the mt surface, and although this domain does not bind directly to mts, it has a role in mt assembly regulation and affects the attachment or spacing between mts and other components in the cell.[24] the n-terminal inserts affect the distribution of tau molecules in the cell; it was demonstrated that each tau isoform (0n, 1n, and 2n) has different subcellular localizations in the mouse brain.[25] in addition, tau, via interacting with the membrane binding protein annexin a2, interacts with the plasma membrane by its n-terminal domain.[26, 27] the n-terminal domain can also bind to the cterminus of p150 in dynactin protein, which has an essential role in the connection between dynein and cargoes.[28] moreover, tau isoforms have distinct protein interaction patterns; for instance, apolipoprotein a1 can bind to 2n tau isoforms; however, synaptophysin and β-synuclein attach to 0n tau isoforms.[29] the proline-rich domain of tau has several recognition sites for attaching src homology-3 (sh3)-containing proteins such as the src family of protein kinases (lck, fgr, and fyn), the p85α regulatory subunit of phosphatidylinositol 3-kinase (pi3k), bridging integrator 1 (bin1), phospholipase c (plc), γ1, plcγ2, growth factor receptor bound protein 2, and peptidylprolyl cis/trans isomerases nima-interacting 1.[30] tau interactions with sh3containing proteins play an important role in modulating the signaling functions of tau. additionally, signaling pathways are associated with the activation of phosphatidylinositol and phosphatidylinositol bisphosphate, which collaborate with the tau proline-rich domain.[31, 32] furthermore, the tau proline-rich domain acts as a dna and rna recognition site.[33, 34] this domain also has an 492 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 tau protein and neurodegenerative diseases; mishan et al important role in the inter mt spacing and intracellular trafficking[35, 36] as well as actin binding,[37] highlighting an important role in neuronal cell signaling and neuronal plasticity. tau post-translational modifications although several post-translational modifications, in forms of phosphorylation, acetylation, glycation, cleavage or truncation, prolyl-isomerization, polyamination, nitration, ubiquitination, oxidation, and sumoylation have been identified to modulate tau protein,[38–40] the most well-known is phosphorylation in which the abnormal hyperphosphorylation is associated with tauopathy.[41] although phosphorylation is an essential tau modifier under physiological conditions,[1] abnormal phosphorylation or hyperphosphorylation are other modifiers by which tau gets prone to aggregation.[42, 43] for instance, hyperphosphorylated tau forms the oligomers and neurofibrillary tangles (nfts) that exert toxic effects on neuronal function and ad progression.[44] although 15–30 phosphorylation sites, that mostly corresponded to proline-directed sites in the proline-rich domain of tau were discovered in tau protein,[45] increased phosphorylation, especially at the mt-binding domains, has also been demonstrated in association with increased mt dynamicity and reduced levels of neuronal excitability in the early stages of ad.[46] threonine175 (thr175) is one of the important phosphorylation sites in tau protein that was first identified in ad[47] and then in amyotrophic lateral sclerosis (als) with cognitive impairment (alsci).[48–52] this modification site can be phosphorylated by multiple kinases related to tauopathy, including gsk3β, jnk, erk2, and p38,[53] that induce tau aggregation.[54] pthr175 tau induces gsk3β activation and can augment tau phosphorylation at thr231 and other residues. this results in dissociation of tau from mts, self-aggregation, and neuronal toxicity.[55] threonine231 (thr231) is another important phosphorylation site in tau protein that is phosphorylated or hyperphosphorylated in the cerebrospinal fluid of ad patients, and is correlated with memory loss and progression of ad from mild to severe cognitive impairments.[56] tau hyperphosphorylation may result from downregulation of phosphatases, especially protein phosphatase 2a by okadaic acid (oa).[57] it was shown that oa treatment induced phosphorylation of tau at ser202 and ser396 in cultivated neuroblastoma cells.[58] cystatin c (cysc) is a cysteine protease inhibitor of cathepsin family, lysosomal proteases, that is widely expressed in various cells and tissues.[59] cysc protein and its gene are upregulated in ad brains, posing a risk factor for late-onset ad.[60, 61] cysc does not affect production of cellular amyloid beta peptide (aβ); however, overexpression of cysc in neurons leads to inhibition of gsk3β turnover, augmentation of gsk3β levels in neurons that promotes gsk3βtau phosphorylation at ser396/404, mt instability, and neurodegeneration.[62, 63] gsk3β is one of the kinases having an important role in nft formation and dystrophic neurites by tau phosphorylation in the brain.[64–67] high activity of gsk3β can be detected in the frontal cortex[68] and hippocampus of ad patients.[65] it is notable that lithium, as a potent gsk3β inhibitor, is being widely prescribed for neurodegenerative disorders such as ad. cyclin-dependent kinase 5 (cdk5) is a prolinedirected ser/thre kinase, that can phosphorylate tau at several ser-pro and thre-pro motifs. phosphorylation at these residues affects mt stability via dissociation of tau from mts. cdk5 is highly expressed in axons and growth cones serving to induce neurite outgrowth and cell migration.[69] peptidyl-prolyl cis-trans isomerase nimainteracting 1 (pin1), a phospho-ser/thr isomerase with a regulatory role on tau function, is known to be a critical factor playing part in the ad development. pin1 converts cis to trans p-tau whereby preventing pathogenic cis p231-tau accumulation (cistauosis) and maintaining tau in a trans conformation.[70] tau aggregation insoluble tau deposits, resulting from tau misfolding and oligomerization, gradually accumulate in neurons, disrupt cell function, and initiate neurodegeneration.[71] two hexapeptide repeats, amino acids 306–311 (phf6, val-gln-ile-val-lystyr, vqivky) and 317–335 (phf6*, val-gln-ile-ilelys-tyr vqiink), in the c-terminal region of tau protein play a significant role in the formation of βsheets and fibrillary tangles.[6, 72, 73] phf6, located journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 493 tau protein and neurodegenerative diseases; mishan et al at the beginning of the third mt-binding repeat, is present in all tau isoforms, but phf6* is located at the beginning of the second mt-binding repeat. it was observed that phf6 and phf6* can attach to each other and form tau fibrillary tangles.[74] tau dimerization can occur by interaction between two phf6, two phf6*, or between one phf6 and one phf6* motif.[75] finally, tau oligomers elongate and form cross β-sheet structures, forming the aggregates.[76] although phf6 and phf6* are prone to self-assembly, native tau under physiological conditions is resistant to aggregation. factors enhancing the self-assembly of tau or neutralizing its charge can induce tau aggregation. due to the presence of phf6* encoded by exon 10, 4r tau isoforms are more prone to aggregation than 3r tau isoforms.[77, 78] mutations within the hexapeptide motifs, such as the p301l tau mutation, promote tau aggregation in patients with frontotemporal dementia and parkinsonism linked to chromosome 17 (ftdp-17).[79] in addition to the tendency of exon 10 for aggregation, the n-terminal insert encoded by exon 2 induces tau self-aggregation, whereas the expression of exon 3 has an inhibitory role on aggregation via a process modulated by the expression of exon 10.[80] also, deletion of the positively charged lys(k)280 residue can suppress tau self-assembly.[74, 80] it was demonstrated that anionic condensing agents can induce tau aggregation. for instance, heparin can bind to the second and third mt-binding repeats, the flanking region, and the n-terminal of tau protein, and induce tau aggregation.[81, 82] fatty acids, polyglutamic acid, and trna, can also induce tau aggregation.[83] it has been reported that preventing tau aggregation would rescue neurodegeneration. for example, curcumin, a tau aggregation inhibitor, efficiently suppresses neurodegeneration in tauopathy mouse models. pathogenic role of tau protein in neurodegenerative diseases in contrast to the normal physiological condition in which tau has a stable and unfolded monomeric conformation, in pathological conditions, tau is phosphorylated or hyperphosphorylated and self-aggregates, resulting in pathogenic conformations in neurodegenerative diseases, termed tauopathies.[7, 84] the roles of tau in physiological and pathological conditions in the cell are summarized in figure 1. phosphorylation of tau at multiple residues is characteristic of many neurodegenerative diseases, which reduces the affinity of tau to mts, increases tau self-assembly,[85, 86] and finally causes the formation of nfts.[87, 88] the presence of nfts in specific regions of the brain disrupts synaptic and neuronal communications, leads to progression of memory loss, and produces a rapid impairment of long-term potentiation with induction of toxic functions in the neurons.[43, 89] pathogenic forms of tau may spread in a prionlike manner upon tauopathies, whose molecular mechanisms remain uncertain.[8, 90] cell-to-cell transmission of the tau aggregates causes neuronal cell death and subsequent progression of disease.[91, 92] in ad, this process follows a distinct pattern along the neuronal connections from the entorhinal cortex to hippocampal areas and further on through the limbic system.[93] in other tauopathies, this process appears less hierarchical throughout the brain.[93] moreover, the localization of tau inclusions is widely different in various neurodegenerative diseases.[42, 94–96] in addition to ad,[7] tau aggregates were detected in a wide range of neurodegenerative diseases including progressive supranuclear palsy (psp), corticobasal dementia, argyrophilic grain disease, pick disease, huntington disease, ftdp-17, als, and parkinson’s disease with dementia.[97, 98] unlike ad that has aβ depositions in addition to tauopathy, psp is a relatively pure tauopathy in which only tau deposits are seen. psp was shown to have shared polygenic heritability with parkinson’s disease and als, and most of the corresponding genes were clustered around chromosome 17.[99, 100] interestingly, ad, primary age related tauopathy (part), and aging-related tau astrogliopathy (artag) are the predominant sporadic tauopathies, in which oligodendrocytes serve as targets for seeding and spreading pathologic tau proteins in the white matter.[101] given that the human retina lacks oligodendrocytes, these cells may not be a component in the pathogenesis of tauopathies in the eye. however, considering the presence of retinal microglial cells and their role in engulfing tau oligomers and induction of inflammation,[102] they may be involved in tau seeding in retinal neurodegenerations. 494 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 tau protein and neurodegenerative diseases; mishan et al figure 1. tau protein. (a) in physiological conditions, tau binds to microtubules by its microtubule binding domain in order to stabilize microtubules for several cellular functions in the cells, such as axonal transportation. (b) in pathological conditions, tau is phosphorylated or hyperphosphorylated (p-tau) by multiple kinases, leading to microtubule destabilization, pairing tau molecules to each other, formation of toxic oligomers, and finally nft formation. tau accumulation is also a result of traumatic brain injury (tbi) and chronic traumatic encephalopathy (cte), especially in sports that repeatedly expose athletes to mild traumatic brain injury (rmtbi) and in military personnel exposed to repeated traumas.[103–105] mitochondrial dysfunction and reactive oxygen species (ros) production can induce tau hyperphosphorylation.[106] it has been demonstrated that hyperphosphorylated tau reduces the release of cytochrome c from mitochondria as well as caspase-9 and caspase-3 activity, and protects cells from apoptosis.[107] moreover, tau via stabilizing β-catenin and increasing its nuclear translocation has the ability to antagonize apoptosis and promote cell survival.[107, 108] tau hyperphosphorylation confers cellular resistance to chemically induced apoptosis through upregulated glycogen synthase kinase-3β (gsk3β) and preserving βcatenin.[108] tau overexpression causes vascular changes in the cerebral cortex that are accompanied by cortical atrophy. this overexpression in the neurons can lead to dramatic cell-nonautonomous changes in cerebral endothelial cells, alter the integrity of the cerebral microvasculature, and induce neurodegeneration related to vascular abnormalities.[109] a similar situation occurs in amd, where dramatic neovascular changes accompany neurodegeneration.[110] additionally, tau overexpression would result in impaired axonal transport, leading to neurodegeneration. all six tau isoforms are expressed in both soluble and insoluble tau isolates in patients with cte and cte-als. the expression of oligomerized tau protein and activated gsk3β, pthr175 tau, and pthr231 tau were observed in hippocampal neurons and spinal motor neurons. phosphorylation of tau at thr175 and thr231 and activation of gsk3β are reported features of tauopathy in cte and cteals.[111] a direct association has been proposed between aβ toxicity and tau pathology.[112, 113] high levels of aβ in transgenic mice overexpressing amyloid precursor protein (app) accelerated tau phosphorylation. intracerebral injection of aβ into tau transgenic mice augmented pathogenic conditions.[114, 115] moreover, pathogenic tau augments the secretion of α-synuclein and induces its toxicity by promoting smaller α-synuclein inclusion formation in human neuroglioma cells.[116] journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 495 tau protein and neurodegenerative diseases; mishan et al it was also shown that α-synuclein can induce tau phosphorylation.[117, 118] cistauosis is a mechanism that occurs before insoluble tau deposition and within days after tbi. cis p-tau is a pathogenic form of tau protein that is prominently formed in human cte and uses a prion-like mechanism for its spreading in the brain. inhibition of cis p-tau by monoclonal antibodies was reported to decrease cellular neurotoxicity, histopathological changes, and behavioral deficits. cis p-tau is present in cortical axons and cerebrospinal fluid of human tbi and positively correlates with axonal injury. therefore, antibodies that target this pathogenic form of tau are potential novel treatments for neurodegenerative diseases.[70] tau isoform pathology 4r tau isoforms include a fourth mt-binding repeat encoded by exon 10, whereas the 3r tau isoform mrnas lacks exon 10. the majority of mutations occur in exon 10 or close by. approximately 40 pathogenic mutations in the mapt gene have been identified, most of them are associated with clinical signs of ftdp-17 with degeneration in the frontotemporal lobar regions.[119] tau mutations affecting splicing efficacy are located either in exon 10 or intron 10 and result in a change of the 4r/3r tau mrna ratio.[120, 121] all six tau isoforms and tau tangles in the brain of ad patients are formed from both 3r and 4r isoforms with equal ratio, similar to healthy adults;[122–124] however, a higher ratio of 4r/3r was observed in psp in comparison to ad patients and healthy adults.[124, 125] moreover, there have been several cases of psp and frontotemporal lobar degeneration (ftld) that had higher 4r tau/3r tau isoforms than ftdp-17 cases.[124] tau protein in inflammation pathogenic tau molecules, by attaching to each other, form large fibrillar molecules known as tangles. however, there is evidence to suggest that smaller soluble aggregates, named oligomers are the most toxic species and are formed prior to the tangles.[126, 127] tau oligomers may induce inflammatory signaling in the brain of patients with ftld, ad, and other neurodegenerative diseases. these toxic oligomers are associated with neuroinflammation markers suggesting their role in chronic neuroinflammation, physiological impairments, cellular dysfunction, and ultimately, neurodegeneration.[128–130] oligomers co-localize with astrocytes, microglia, pro-inflammatory cytokines, and high mobility group box-1 protein (hmgb1). moreover, astrocytes interact with tau oligomers but do not engulf them, while microglia[130] can engulf tau oligomers, secrete them by exosomes, facilitate their propagation, and induce inflammation.[102] therefore, tau oligomers augment inflammation and cause more damage to cells, which may increase oligomer formation.[130] in addition, in animal models of tauopathy, tau oligomers were detected to be associated with inflammatory cells in the retina, suggesting that the retina can be a valid and non-invasive biomarker for brain degenerative pathologies.[130] it is notable that tau aggregates would induce ros, resulting in inflammation in the cns of those tauopathy patients. pathogenic role of p-tau in ocular neurodegenerative diseases the retina is a part of the cns, containing various cell types, including photoreceptors, horizontal cells, amacrine cells, bipolar cells, and retinal ganglion cells (rgcs), and is easily accessible to noninvasive imaging techniques, such as scanning laser ophthalmoscopy (slo) and optical coherence tomography (oct). identifying retinal pathological changes with these techniques may be used as potential biomarkers for ad,[131] and therefore, ocular screening programs can be planned for identifying tauopathies such as ad.[132] although the sensitivity and specificity of non-retinal biomarkers has been determined in brain neurodegeneration,[133] there has been no report on the sensitivity and specificity of retinal biomarkers for ocular and brain neurodegenerative disorders. although there are reports demonstrating tau hyperphosphorylation and aggregation in ocular neurodegeneration, the actual tau pathogenicity upon the disease has not been extensively studied thus far.[131] and so, it seems difficult to clearly demonstrate the superiority of the pathologic form of tau as a marker in conventional behavioral tests and neuroimaging. some of the pathological changes in ad patients include reduced thickness of the retinal nerve 496 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 tau protein and neurodegenerative diseases; mishan et al fiber layer (nfl), attenuation in retinal blood flow and venous diameter, axonal degeneration in optic nerves, decreased number of rgcs, and astrocytosis.[134–137] moreover, reduction of macular thickness is inversely associated with the severity of ad.[138] there is a higher incidence of amd in patients with ad;[139] therefore, there is an strong correlation between amd and ad incidence and the retinal changes can be used as potential biomarkers for the diagnosis of cerebral neurodegenerative diseases.[136, 140] retinal degeneration in ad was triggered by a pathogenic form of tau via calpain-mediated tau hyperphosphorylation.[44] the presence of tau inclusions in human retinas was discovered for the first time in the corpora amylacea of the optic nerve and the retina.[141] pathogenic forms of tau in the form of oligomers or aggregations were detected in a variety of ocular disorders such as amd and glaucoma. tau was detected in various sublayers of the retina including the inner nuclear layer (inl), inner/outer plexiform layer, and nfl of the retinas from patients with amd.[142] amd, one of the leading causes of blindness worldwide,[143] is a complex age-related pathology that occurs as an interplay between oxidative stress, lowgrade inflammation, and aberrant accumulations of extracellular protein molecules.[144] induction of neuroinflammation[130] and aggregation of tau proteins within retinal layers of cases with agerelated retinal lesions[145] are two main methods by which tauopathy can act in the pathogenesis of amd. additionally, correlations between ad and glaucoma have been well documented.[146] p-tau plays a pathogenic role in the development of glaucomatous optic neuropathy and is upregulated in the retrolaminar region of the optic nerve head in glaucomatous eyes.[147] moreover, mislocalization of p-tau aggregates was detected in the somatodendritic compartments of rgcs that were subjected to high intraocular pressure.[147] importantly, tau knock-down using a targeted sirna protected rgc somas and axons from hypertension-induced damage.[148] tau oligomers were detected in the retina of an animal model of glaucoma and it was observed that tau inhibition could reduce retinal degeneration.[148] moreover, it was demonstrated that calpains, proteins belonging to a family of calcium-dependent and nonlysosomal cysteine proteases are activated after ocular hypertension, a condition in which increase of calcium in the retinas and increase of calpaindependent proteolysis of tau occurs that leads to neuronal cell death.[149, 150] it is noteworthy that augmentation of hyperphosphorylated tau has been identified in the vitreous samples of diabetic retinopathies that represent a form of ocular degeneration.[151] at8 tau with phosphorylation profile at ser202 and thr205 has been well characterized, and at8 antibody was used to stage human neuropathological diseases.[152] at8 hyperphosphorylated tau was detected in the outer border of the inl and specifically in the inner plexiform layer (ipl) of glaucomatous retinas. in addition, this form of tau colocalizes with parvalbumin in the retinal horizontal cells.[153] at8 tau protein was also detected with aβ depositions in various retinal layers including the rgc layer, ipl, inl, outer plexiform layer (opl), and outer nuclear layer (onl) in tg2576 mice.[154] photoreceptor cells have high energy demands and are significantly affected by ageing.[155, 156] tau aggregates were observed within the cytoplasm of rod and cone photoreceptors, and a positive correlation was observed between age and the number of inclusions in these cells.[145] conversely, p-tau is specifically accumulated in primate cones while reducing the cellular functions.[12] diffuse tau aggregates were found in the retinal inl of enucleated eyes that had abnormal retinal changes. they were also detected in the cytoplasm of several photoreceptor cells in patients older than 63 years, and a positive correlation was observed between the patients’ age and the numbers of rgcs with tau aggregates. in addition, aggregated tau was found within the cytoplasm of photoreceptor cells in the majority of patients above 63 years of age.[145] oa, one of the positive regulators of ptau accumulation, was shown to have a destructive role in the cytoskeleton network and growth-cone cells.[157] transgenic mice expressing p301s mutant human tau model tauopathy develop hyperphosphorylated tau aggregations in the cns. p301s mutant tau carries a substitution of ser instead of pro in exon 10 of the mapt gene.[158] in p301s retinas, hyperphosphorylated tau molecules are aggregated in the nerve fiber and rgc layers. also, rgc axonal outgrowth did not respond to neurotrophic stimuli in retinal explants cultured from p301s mice, suggesting that pathogenic tau can change neurotrophic signaling.[159] moreover, journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 497 tau protein and neurodegenerative diseases; mishan et al the mild tauopathy that developed in rgcs of p301s mice induced functional retinal changes and neuronal dysfunction by disrupting brainderived neurotrophic factor (bdnf) signaling, via the trkb receptor that is essential for neuronal survival and synaptic plasticity.[160] moreover, p301s tau aggregates in rgcs were associated with a reduction in anterograde and retrograde axonal transport in vivo, with a markedly increased effect of excitotoxic injury.[161] another tau gene mutation is p301l that expresses leu instead of pro at position 301 in both the shortest and longest four repeat tau isoforms, and forms nfts in the cns.[162] age-related neurodegenerative changes with significant reduced thickness of retinal inl were observed in p301l mice, and these changes were more pronounced at the peripheral areas and with increasing age. furthermore, an increase in the size of the rgcs obtained from tau p301l mice was observed with increasing age, in contrast to control mice in which rgc sizes decreased with increasing age.[163] the dynactin complex plays a pivotal role in the transportation network in many cell types by mediating the binding of mt motor complex dynein to its cargoes.[164] tau and dynactin have extensive interactions, and dynactin attachment to mts is facilitated by the binding of tau n-terminal domain to the c-terminus of the p150 subunit of dynactin.[28] mutation in the arginine residue in the n-terminal domain of tau was detected in patients with ftdp-17 that affects tau binding to dynactin, and tau was abnormally distributed in the rgc axons of tau p301s transgenic mice.[28] however, recombinant human tau promoted the attachment of the dynactin complex to axonal microtubules, which indicates a potential role of tau in axonal transportation.[28] transportation of organelles such as mitochondria and peroxisomes by kinesin molecules was inhibited in rat rgcs with abnormally aggregated tau, evidencing the essential role of tau in kinesinmediated transportation. thus, rat rgcs with accumulated tau suffered from loss of energy production and accumulation of ros due to perturbation of mitochondria and peroxisome function. moreover, the rate of anterograde transportation that include vesicles necessary for growth cones and synaptic function was slower.[165] oxidative damage was shown to be associated with death of cones in retinitis pigmentosa, and of both photoreceptor cell types, in amd.[166] thioredoxin 1 (trx1) in the retina plays a protective role against photooxidative damage.[167] rodderived cone viability factor (rdcvf) is a member of the thioredoxins family[168] and a trophic factor secreted by rods for maintaining cone viability and functionality.[169] in murine models, rdcvf is encoded by the nxnl1 gene that also encodes for a second polypeptide, rdcvfl, by alternative splicing. rdcvfl inhibits tau phosphorylation and protects tau from oxidative damage.[170] upregulation of tau phosphorylation has been well demonstrated in the retinas of nxnl1-/mice.[171, 172] therefore, therapeutic modalities augmenting the nxnl1 gene or the corresponding protein may be promising for the treatment of cerebral and ocular neurodegeneration. therapeutic strategies for targeting pathologic tau the pathogenic tau molecule is an excellent therapeutic target for neurodegenerative diseases using several strategies such as reducing levels, altering post-translational modifications, or blocking propagation of pathogenic tau. several tauopathy-based targeted therapies for neurodegenerative diseases have been introduced, such as suppressing tau misfolding,[173] targeting tau acetylation,[174] inhibiting tauinduced proteasome impairment,[175] and tau immunotherapy.[176–180] several therapeutic modalities for inhibiting tau aggregation have been reported,[19, 181] among which, the use of small molecules has recently gained much interest. several small molecules exhibit anti-tau aggregation properties;[182, 183] one of these is d-enantiomeric peptides that has modulating mechanisms on tau self-aggregation.[184] other small molecules that were shown to have antitau aggregation effects have an eight amino acid peptide named nap (davunetide).[185] clinically, nap (davunetide) exhibited its efficacy in prodromal ad patients that had equal 3r and 4r tau isoforms but not in the psp cases that had increased 4r tau.[186] cationic small molecules and cationic osmolyte urea also have inhibitory effects on tau accumulation.[187–189] moreover, the inhibitory effect of a cationic polymer polyethyleneimine and a cationic polypeptide arginine on the aggregation of vqivyk and 498 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 tau protein and neurodegenerative diseases; mishan et al gkvqiinkldl peptides in tau protein was also observed.[190] antisense oligonucleotides are other small molecules that selectively downregulate human tau at mrna and protein levels in adult mouse brain that express mutant p301s human tau.[191] moreover, the chaperone artemin was found to be an effective inhibitor of tau inclusions in both physiologic and supraphysiologic concentrations, in a dose-dependent manner and in a cell-free model system. this supports the idea that artemin can be a therapeutic option for people with ad.[192] although several specific small molecules for targeting pathogenic tau have been discovered, more studies are needed to illustrate the safety and efficacy of these molecules as novel drugs. more importantly, it is of crucial importance to clarify which epitope to target? we herein studied latest reports on tau pathology; especially in ocular neurodegeneration. although we may not clearly describe the pathogenic tau species playing part in ocular neurodegeneration, however, due to similarities between brain and eye neurodegeneration, the aforementioned treatment modalities for brain tauopathies sound like efficient therapeutic strategies in fighting with the ocular neurodegeneration. summary the current review, based on numerous studies on the role of pathogenic tau in neurodegeneration, attempts to highlight the connection between brain and eye diseases. pathogenic tau protein exerts destructive effects that are associated with cerebral degenerations such as ad, psp, and tbi, and ocular neurodegenerative disorders such as amd, glaucoma/ocular hypertension, and probably diabetic retinopathy. the destructive effects of the pathogenic form of tau can be exerted by several forms of tau such as soluble oligomers, insoluble aggregates, or even by cis p-tau which is an early driver of pathogenic tau. considering this evidence, targeted therapy based on pathogenic tau could be a promising therapeutic for patients with cns or ocular neurodegeneration, to not only prevent the more destructive effects of pathogenic tau, but also restore normal functioning to neural cells. moreover, with the identification of tauopathy-related retinal changes with noninvasive imaging techniques, screening programs for the early diagnosis of cns tauopathies such as ad can be planned. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. weingarten md, lockwood ah, hwo s-y, kirschner mw. a protein factor essential for microtubule assembly. proc natl acad sci 1975;72:1858–1862. 2. andreadis a. misregulation of tau alternative splicing in neurodegeneration and dementia. prog mol subcell biol 2006;44:89–107. 3. lopresti p, szuchet s, papasozomenos sc, zinkowski rp, binder li. functional implications for the microtubuleassociated protein tau: localization in oligodendrocytes. proc natl acad sci 1995;92:10369–10373. 4. dehmelt l, halpain s. the map2/tau family of microtubule-associated proteins. genome biol 2004;6:204. 5. feinstein sc, wilson l. inability of tau to properly regulate neuronal microtubule dynamics: a loss-of-function mechanism by which tau might mediate neuronal cell death. biochim biophys acta 2005;1739:268–279. 6. mandelkow e-m, mandelkow e. biochemistry and cell biology of tau protein in neurofibrillary degeneration. cold spring harb perspect med 2012;2:a006247. 7. khatoon s, grundke-iqbal i, iqbal k. levels of normal and abnormally phosphorylated tau in different cellular and regional compartments of alzheimer disease and control brains. febs lett 1994;351:80–84. 8. spires-jones tl, stoothoff wh, de calignon a, jones pb, hyman bt. tau pathophysiology in neurodegeneration: a tangled issue. trends neurosci 2009;32:150–159. 9. shahani n, brandt r. functions and malfunctions of the tau proteins. cell mol life sci 2002;59:1668–1680. 10. wang y, mandelkow e. tau in physiology and pathology. nat rev neurosci 2016;17:22. 11. mazzaro n, barini e, spillantini mg, goedert m, medini p, gasparini l. taudriven neuronal and neurotrophic dysfunction in a mouse model of early tauopathy. j neurosci 2016;36:2086–2100. 12. aboelnour a, van der spuy j, powner m, jeffery g. primate retinal cones express phosphorylated tau associated with neuronal degeneration yet survive in old age. exp eye res 2017;165:105–108. 13. gupta n, fong j, ang lc, yucel yh. retinal tau pathology in human glaucomas. can j ophthalmol 2008;43:53–60. 14. liu f, gong cx. tau exon 10 alternative splicing and tauopathies. mol neurodegener 2008;3:8. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 499 tau protein and neurodegenerative diseases; mishan et al 15. lee g, cowan n, kirschner m. the primary structure and heterogeneity of tau protein from mouse brain. science 1988;239:285–288. 16. goedert m, spillantini mg, jakes r, rutherford d, crowther ra. multiple isoforms of human microtubule-associated protein tau: sequences and localization in neurofibrillary tangles of alzheimer’s disease. neuron 1989;3:519–526. 17. avila j, jiménez js, sayas cl, bolós m, zabala jc, rivas g, et al. tau structures. front aging neurosci 2016;8:262. 18. martin l, latypova x, wilson cm, magnaudeix a, perrin m-l, yardin c, et al. tau protein kinases: involvement in alzheimer’s disease. ageing res rev 2013;12:289–309. 19. boutajangout a, wisniewski t. tau-based therapeutic approaches for alzheimer’s disease-a mini-review. gerontology 2014;60:381–385. 20. mcmillan p, korvatska e, poorkaj p, evstafjeva z, robinson l, greenup l, et al. tau isoform regulation is region-and cell-specific in mouse brain. j comp neurol 2008;511:788–803. 21. jeganathan s, von bergen m, mandelkow e-m, mandelkow e. the natively unfolded character of tau and its aggregation to alzheimer-like paired helical filaments. biochemistry 2008;47:10526–10539. 22. mukrasch md, bibow s, korukottu j, jeganathan s, biernat j, griesinger c, et al. structural polymorphism of 441-residue tau at single residue resolution. plos biol 2009;7:e34. 23. sillen a, barbier p, landrieu i, lefebvre s, wieruszeski j-m, leroy a, et al. nmr investigation of the interaction between the neuronal protein tau and the microtubules. biochemistry 2007;46:3055–3064. 24. chen j, kanai y, cowan n, hirokawa n. projection domains of map2 and tau determine spacings between microtubules in dendrites and axons. nature 1992;360:674. 25. liu c, götz j. profiling murine tau with 0n, 1n and 2n isoform-specific antibodies in brain and peripheral organs reveals distinct subcellular localization, with the 1n isoform being enriched in the nucleus. plos one 2013;8:e84849. 26. brandt r, léger j, lee g. interaction of tau with the neural plasma membrane mediated by tau’s amino-terminal projection domain. j cell biol 1995;131:1327–1340. 27. gauthier-kemper a, weissmann c, golovyashkina n, sebö-lemke z, drewes g, gerke v, et al. the frontotemporal dementia mutation r406w blocks tau’s interaction with the membrane in an annexin a2–dependent manner. j cell biol 2011;192:647–661. 28. magnani e, fan j, gasparini l, golding m, williams m, schiavo g, et al. interaction of tau protein with the dynactin complex. embo j 2007;26:4546–4554. 29. liu c, song x, nisbet r, götz j. co-immunoprecipitation with tau isoform-specific antibodies reveals distinct protein interactions, and highlights a putative role for 2n tau in disease. j biol chem 2016;291:8173–8188. 30. morris m, maeda s, vossel k, mucke l. the many faces of tau. neuron 2011;70:410–426. 31. flanagan la, cunningham cc, chen j, prestwich gd, kosik ks, janmey pa. the structure of divalent cationinduced aggregates of pip2 and their alteration by gelsolin and tau. biophys j 1997;73:1440–1447. 32. surridge cd, burns rg. the difference in the binding of phosphatidylinositol distinguishes map2 from map2c and tau. biochemistry 1994;33:8051–8057. 33. qi h, cantrelle fo-x, benhelli-mokrani h, smet-nocca c, buée l, lippens g, et al. nuclear magnetic resonance spectroscopy characterization of interaction of tau with dna and its regulation by phosphorylation. biochemistry 2015;54:1525–1533. 34. wang xs, wang dl, zhao j, qu mh, zhou xh, he hj, et al. the proline-rich domain and the microtubule binding domain of protein tau acting as rna binding domains. protein pept lett 2006;13:679–685. 35. eidenmüller j, thomas f, thorsten m, madeline p, sontag e, brandt r. phosphorylation-mimicking glutamate clusters in the proline-rich region are sufficient to simulate the functional deficiencies of hyperphosphorylated tau protein. biochem j 2001;357:759–767. 36. goode bl, denis pe, panda d, radeke mj, miller hp, wilson l, et al. functional interactions between the prolinerich and repeat regions of tau enhance microtubule binding and assembly. mol biol cell 1997;8:353–365. 37. he hj, wang xs, pan r, wang dl, liu mn, he rq. the proline-rich domain of tau plays a role in interactions with actin. bmc cell biol 2009;10:81. 38. gong c-x, liu f, grundke-iqbal i, iqbal k. post-translational modifications of tau protein in alzheimer’s disease. j neural transm 2005;112:813–838. 39. martin l, latypova x, terro f. post-translational modifications of tau protein: implications for alzheimer’s disease. neurochem int 2011;58:458–471. 40. min s-w, chen x, tracy te, li y, zhou y, wang c, et al. critical role of acetylation in tau-mediated neurodegeneration and cognitive deficits. nat med 2015;21:1154–1162. 41. xu l, zheng j, margittai m, nussinov r, ma b. how does hyperphopsphorylation promote tau aggregation and modulate filament structure and stability? acs chem neurosci 2016;7:565–575. 42. iqbal k, liu f, gong c-x. tau and neurodegenerative disease: the story so far. nat rev neurol 2016;12:15–27. 43. ballatore c, lee vm-y, trojanowski jq. tau-mediated neurodegeneration in alzheimer’s disease and related disorders. nat rev neurosci 2007;8:663–672. 44. zhao h, chang r, che h, wang j, yang l, fang w, et al. hyperphosphorylation of tau protein by calpain regulation in retina of alzheimer’s disease transgenic mouse. neurosci lett 2013;551:12–16. 45. morris m, knudsen gm, maeda s, trinidad jc, ioanoviciu a, burlingame al, et al. tau post-translational modifications in wild-type and human amyloid precursor protein transgenic mice. nat neurosci 2015;18:1183–1189. 46. rodríguez sm, gallardo as, pereyra pg, macías m, ordaz b, ortega fp, et al. phosphorylation of tau protein correlates with changes in hippocampal theta oscillations and reduces hippocampal excitability in alzheimer’s model. j biol chem 2018;293:8462–8472. 47. hanger dp, betts jc, loviny tl, blackstock wp, anderton bh. new phosphorylation sites identified in hyperphosphorylated tau (paired helical filament-tau) from alzheimer’s disease brain using nanoelectrospray mass spectrometry. j neurochem 1998;71:2465–2476. 500 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 tau protein and neurodegenerative diseases; mishan et al 48. strong m, yang w, strong w, leystra-lantz c, jaffe h, pant h. tau protein hyperphosphorylation in sporadic als with cognitive impairment. neurology 2006;66:1770–1771. 49. yang w, sopper mm, leystra-lantz c, strong mj. microtubule-associated tau protein positive neuronal and glial inclusions in als. neurology 2003;61:1766–1773. 50. yang w, leystra-lantz c, strong mj. upregulation of gsk3β expression in frontal and temporal cortex in als with cognitive impairment (alsci). brain res 2008;1196:131–139. 51. yang w, strong mj. widespread neuronal and glial hyperphosphorylated tau deposition in als with cognitive impairment. amyotroph lateral scler 2012;13:178–193. 52. behrouzi r, liu x, wu d, robinson ac, tanaguchiwatanabe s, rollinson s, et al. pathological tau deposition in motor neurone disease and frontotemporal lobar degeneration associated with tdp-43 proteinopathy. acta neuropathol commun 2016;4:33. 53. reynolds ch, betts jc, blackstock wp, nebreda ar, anderton bh. phosphorylation sites on tau identified by nanoelectrospray mass spectrometry. j neurochem 2000;74:1587–1595. 54. gohar m, yang w, strong w, volkening k, leystra-lantz c, strong mj. tau phosphorylation at threonine-175 leads to fibril formation and enhanced cell death: implications for amyotrophic lateral sclerosis with cognitive impairment. j neurochem 2009;108:634–643. 55. moszczynski aj, gohar m, volkening k, leystra-lantz c, strong w, strong mj. thr 175-phosphorylated tau induces pathologic fibril formation via gsk3β-mediated phosphorylation of thr 231 in vitro. neurobiol aging. 2015;36:1590–1599. 56. hampel h, blennow k, shaw lm, hoessler yc, zetterberg h, trojanowski jq. total and phosphorylated tau protein as biological markers of alzheimer’s disease. exp gerontol 2010;45:30–40. 57. gong c-x, lidsky t, wegiel j, zuck l, grundke-iqbal i, iqbal k. phosphorylation of microtubule-associated protein tau is regulated by protein phosphatase 2a in mammalian brain implications for neurofibrillary degeneration in alzheimer’s disease. j biol chem 2000;275:5535– 5544. 58. boban m, miskic t, leko mb, hof pr, simic g. human neuroblastoma sh-sy5y cells treated with okadaic acid express phosphorylated high molecular weight tau immunoreactive protein species. j neurosci methods 2018:284265. 59. abrahamson m, barrett aj, salvesen g, grubb a. isolation of six cysteine proteinase inhibitors from human urine. their physicochemical and enzyme kinetic properties and concentrations in biological fluids. j biol chem 1986;261:11282–11289. 60. deng a, irizarry mc, nitsch rm, growdon jh, rebeck gw. elevation of cystatin c in susceptible neurons in alzheimer’s disease. am j pathol 2001;159:1061–1068. 61. mathews pm, levy e. cystatin c in aging and in alzheimer’s disease. ageing res rev 2016;32:38–50. 62. duan j, marcellus ka, qin x, wang y, paudel hk. cystatin c promotes tau protein phosphorylation and causes microtubule instability by inhibiting intracellular turnover of gsk3β in neurons. mol cell neurosci 2018; 89:1–8. 63. bramblett gt, goedert m, jakes r, merrick se, trojanowski jq, lee vm. abnormal tau phosphorylation at ser 396 in alzheimer’s disease recapitulates development and contributes to reduced microtubule binding. neuron 1993;10:1089–1099. 64. pei j-j, braak e, braak h, grundke-iqbal i, iqbal k, winblad b, et al. distribution of active glycogen synthase kinase 3β (gsk-3β) in brains staged for alzheimer disease neurofibrillary changes. j neuropathol exp neurol 1999;58:1010– 1019. 65. pei j-j, tanaka t, tung y-c, braak e, iqbal k, grundkeiqbal i. distribution, levels, and activity of glycogen synthase kinase-3 in the alzheimer disease brain. j neuropathol exp neurol 1997;56:70–78. 66. yamaguchi h, ishiguro k, uchida t, takashima a, lemere ca, imahori k. preferential labeling of alzheimer neurofibrillary tangles with antisera for tau protein kinase (tpk) i/glycogen synthase kinase-3β and cyclin-dependent kinase 5, a component of tpk ii. acta neuropathol 1996;92:232–241. 67. hooper c, killick r, lovestone s. the gsk3 hypothesis of alzheimer’s disease. j neurochem 2008;104:1433–1439. 68. leroy k, yilmaz z, brion jp. increased level of active gsk3β in alzheimer’s disease and accumulation in argyrophilic grains and in neurones at different stages of neurofibrillary degeneration. neuropathol appl neurobiol 2007;33:43– 55. 69. nikolic m, dudek h, kwon yt, ramos yf, tsai lh. the cdk5/p35 kinase is essential for neurite outgrowth during neuronal differentiation. genes dev 1996;10:816–825. 70. kondo a, shahpasand k, mannix r, qiu j, moncaster j, chen c-h, et al. antibody against early driver of neurodegeneration cis p-tau blocks brain injury and tauopathy. nature 2015;523:431–436. 71. ward sm, himmelstein ds, lancia jk, binder li. tau oligomers and tau toxicity in neurodegenerative disease. biochem soc trans 2012; 40:667–671. 72. von bergen m, barghorn s, biernat j, mandelkow e-m, mandelkow e. tau aggregation is driven by a transition from random coil to beta sheet structure. biochim biophys acta 2005;1739:158–166. 73. ganguly p, do td, larini l, lapointe ne, sercel aj, shade mf, et al. tau assembly: the dominant role of phf6 (vqivyk) in microtubule binding region repeat r3. j phys chem b 2015;119:4582–4593. 74. von bergen m, barghorn s, li l, marx a, biernat j, mandelkow e-m, et al. mutations of tau protein in frontotemporal dementia promote aggregation of paired helical filaments by enhancing local β-structure. j biol chem 2001;276:48165–48174. 75. peterson dw, zhou h, dahlquist fw, lew j. a soluble oligomer of tau associated with fiber formation analyzed by nmr. biochemistry 2008;47:7393–7404. 76. meraz-ríos ma, lira-de león ki, campos-peña v, de anda-hernández ma, mena-lópez r. tau oligomers and aggregation in alzheimer’s disease. j neurochem 2010;112:1353–1367. 77. alonso ad, zaidi t, novak m, barra hs, grundke-iqbal i, iqbal k. interaction of tau isoforms with alzheimer’s disease abnormally hyperphosphorylated tau and in vitro phosphorylation into the disease-like protein. j biol chem 2001;276:37967–37973. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 501 tau protein and neurodegenerative diseases; mishan et al 78. hasegawa m, watanabe s, kondo h, akiyama h, mann dm, saito y, et al. 3r and 4r tau isoforms in paired helical filaments in alzheimer’s disease. acta neuropathol 2014;127:303–305. 79. lewis j, mcgowan e, rockwood j, melrose h, nacharaju p, van slegtenhorst m, et al. neurofibrillary tangles, amyotrophy and progressive motor disturbance in mice expressing mutant (p301l) tau protein. nat genet 2000;25:402–405. 80. zhong q, congdon ee, nagaraja hn, kuret j. tau isoform composition influences the rate and extent of filament formation. j biol chem 2012;287:20711–10719. 81. kuret j, chirita cn, congdon ee, kannanayakal t, li g, necula m, et al. pathways of tau fibrillization. biochim biophys acta 2005;1739:167–178. 82. sibille n, sillen a, leroy a, wieruszeski j-m, mulloy b, landrieu i, et al. structural impact of heparin binding to fulllength tau as studied by nmr spectroscopy. biochemistry 2006;45:12560–12572. 83. wilson dm, binder li. free fatty acids stimulate the polymerization of tau and amyloid beta peptides. in vitro evidence for a common effector of pathogenesis in alzheimer’s disease. am j pathol 1997;150:2181. 84. iqbal k, grundke-iqbal i. ubiquitination and abnormal phosphorylation of paired helical filaments in alzheimer’s disease. mol neurobiol 1991;5:399–410. 85. neddens j, temmel m, flunkert s, kerschbaumer b, hoeller c, loeffler t, et al. phosphorylation of different tau sites during progression of alzheimer’s disease. acta neuropathol commun 2018;6:52. 86. lin yt, cheng jt, liang lc, ko cy, lo yk, lu pj. the binding and phosphorylation of thr231 is critical for tau’s hyperphosphorylation and functional regulation by glycogen synthase kinase 3β. j neurochem 2007;103:802–813. 87. von bergen m, barghorn s, biernat j, mandelkow e-m, mandelkow e. tau aggregation is driven by a transition from random coil to beta sheet structure. biochim biophys acta 2005;1739:158–166. 88. kolarova m, garcía-sierra f, bartos a, ricny j, ripova d. structure and pathology of tau protein in alzheimer disease. int j alzheimers dis 2012;2012:731526. 89. de calignon a, polydoro m, suárez-calvet m, william c, adamowicz dh, kopeikina kj, et al. propagation of tau pathology in a model of early alzheimer’s disease. neuron 2012;73:685–697. 90. goedert m. alzheimer’s and parkinson’s diseases: the prion concept in relation to assembled aβ, tau, and αsynuclein. science 2015;349:1255555. 91. pooler am, polydoro m, wegmann s, nicholls sb, spiresjones tl, hyman bt. propagation of tau pathology in alzheimer’s disease: identification of novel therapeutic targets. alzheimers res ther 2013;5:49. 92. mohamed nv, herrou t, plouffe v, piperno n, leclerc n. spreading of tau pathology in alzheimer’s disease by cellto-cell transmission. eur j neurosci 2013;37:1939-1948. 93. wegmann s, bennett re, amaral as, hyman bt. studying tau protein propagation and pathology in the mouse brain using adeno-associated viruses. methods cell biol 2017;141:307–322. 94. bilkei-gorzo a. genetic mouse models of brain ageing and alzheimer’s disease. pharmacol ther 2014;142:244–257. 95. ojo jo, mouzon bc, crawford f. repetitive head trauma, chronic traumatic encephalopathy and tau: challenges in translating from mice to men. exp neurol 2016;275:389– 404. 96. kanaan nm, pigino gf, brady st, lazarov o, binder li, morfini ga. axonal degeneration in alzheimer’s disease: when signaling abnormalities meet the axonal transport system. exp neurol 2013;246:44–53. 97. hernandez f, avila j. tauopathies. cell mol life sci 2007;64:2219–2233. 98. lee vm, goedert m, trojanowski jq. neurodegenerative tauopathies. annu rev neurosci 2001;24:1121–1159. 99. leyns ce, holtzman dm. glial contributions to neurodegeneration in tauopathies. mol neurodegener 2017;12:50. 100. chen ja, chen z, won h, huang ay, lowe jk, wojta k, et al. joint genome-wide association study of progressive supranuclear palsy identifies novel susceptibility loci and genetic correlation to neurodegenerative diseases. mol neurodegener 2018;13:41. 101. ferrer i, garcía ma, carmona m, andrés-benito p, torrejón-escribano b, garcia-esparcia p, et al. involvement of oligodendrocytes in tau seeding and spreading in tauopathies. front aging neurosci 2019;11:112. 102. asai h, ikezu s, tsunoda s, medalla m, luebke j, haydar t, et al. depletion of microglia and inhibition of exosome synthesis halt tau propagation. nat neurosci 2015;18:1584. 103. johnson ve, stewart w, smith dh. widespread tau and amyloid-beta pathology many years after a single traumatic brain injury in humans. brain pathol 2012;22:142– 149. 104. mckee ac, stein td, kiernan pt, alvarez ve. the neuropathology of chronic traumatic encephalopathy. brain pathol 2015;25:350–364. 105. blennow k, hardy j, zetterberg h. the neuropathology and neurobiology of traumatic brain injury. neuron 2012;76:886–899. 106. kandimalla r, manczak m, fry d, suneetha y, sesaki h, reddy ph. reduced dynamin-related protein 1 protects against phosphorylated tau-induced mitochondrial dysfunction and synaptic damage in alzheimer’s disease. hum mol genet 2016;25:4881–4897. 107. wang h-h, li h-l, liu r, zhang y, liao k, wang q, et al. tau overexpression inhibits cell apoptosis with the mechanisms involving multiple viability-related factors. j alzheimers dis 2010;21:167–179. 108. li h-l, wang h-h, liu s-j, deng y-q, zhang y-j, tian q, et al. phosphorylation of tau antagonizes apoptosis by stabilizing β-catenin, a mechanism involved in alzheimer’s neurodegeneration. proc natl acad sci 2007;104:3591– 3596. 109. chung w-s, welsh ca, barres ba, stevens b. do glia drive synaptic and cognitive impairment in disease? nat neurosci 2015;18:1539. 110. rosenfeld pj, brown dm, heier js, boyer ds, kaiser pk, chung cy, et al. ranibizumab for neovascular age-related macular degeneration. n engl j med 2006;355:1419–1431. 111. moszczynski aj, strong w, xu k, mckee a, brown a, strong mj. pathologic thr175 tau phosphorylation in cte and cte with als. neurology 2018;90:e380–e387. 112. bloom gs. amyloid-β and tau: the trigger and bullet in alzheimer disease pathogenesis. jama neurol 2014;71:505–508. 502 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 tau protein and neurodegenerative diseases; mishan et al 113. lloret a, badia m-c, giraldo e, ermak g, alonso m-d, pallardó fv, et al. amyloid-β toxicity and tau hyperphosphorylation are linked via rcan1 in alzheimer’s disease. j alzheimers dis 2011;27:701–709. 114. götz j, chen fv, van dorpe j, nitsch r. formation of neurofibrillary tangles in p301l tau transgenic mice induced by aβ42 fibrils. science 2001;293:1491–1495. 115. lewis j, dickson dw, lin w-l, chisholm l, corral a, jones g, et al. enhanced neurofibrillary degeneration in transgenic mice expressing mutant tau and app. science 2001;293:1487–1491. 116. badiola n, de oliveira rm, herrera f, guardia-laguarta c, gonçalves sa, pera m, et al. tau enhances α-synuclein aggregation and toxicity in cellular models of synucleinopathy. plos one 2011;6:e26609. 117. marui w, iseki e, uéda k, kosaka k. occurrence of human α-synuclein immunoreactive neurons with neurofibrillary tangle formation in the limbic areas of patients with alzheimer’s disease. j neurol sci 2000;174:81–84. 118. qureshi hy, paudel hk. parkinsonian neurotoxin 1-methyl4-phenyl-1, 2, 3, 6-tetrahydropyridine (mptp) and αsynuclein mutations promote tau protein phosphorylation at ser262 and destabilize microtubule cytoskeleton in vitro. j biol chem 2011;286:5055–5068. 119. foster nl, wilhelmsen k, sima aa, jones mz, d’amato cj, gilman s, et al. frontotemporal dementia and parkinsonism linked to chromosome 17: a consensus conference. ann neurol 1997;41:706–715. 120. hutton m, lendon cl, rizzu p, baker m, froelich s, houlden h, et al. association of missense and 5′-splicesite mutations in tau with the inherited dementia ftdp-17. nature 1998;393:702. 121. varani l, hasegawa m, spillantini mg, smith mj, murrell jr, ghetti b, et al. structure of tau exon 10 splicing regulatory element rna and destabilization by mutations of frontotemporal dementia and parkinsonism linked to chromosome 17. proc natl acad sci 1999;96:8229–8234. 122. goedert m, spillantini m, jakes r, crowtherp r, vanmechelen e, probst a, et al. molecular dissection of the paired helical filament. neurobiol aging 1995;16:325–334. 123. ingelsson m, ramasamy k, cantuti-castelvetri i, skoglund l, matsui t, orne j, et al. no alteration in tau exon 10 alternative splicing in tangle-bearing neurons of the alzheimer’s disease brain. acta neuropathol 2006;112:439–449. 124. chambers cb, lee jm, troncoso jc, reich s, muma na. overexpression of four-repeat tau mrna isoforms in progressive supranuclear palsy but not in alzheimer’s disease. ann neurol 1999;46:325–332. 125. ingelsson m, ramasamy k, russ c, freeman sh, orne j, raju s, et al. increase in the relative expression of tau with four microtubule binding repeat regions in frontotemporal lobar degeneration and progressive supranuclear palsy brains. acta neuropathol 2007;114:471–479. 126. patterson kr, remmers c, fu y, brooker s, kanaan nm, vana l, et al. characterization of prefibrillar tau oligomers in vitro and in alzheimers disease. j biol chem 2011;286:23063–23076. 127. lasagna-reeves ca, l castillo-carranza d, r jackson g, kayed r. tau oligomers as potential targets for immunotherapy for alzheimer’s disease and tauopathies. curr alzheimer res 2011;8:659–665. 128. garwood cj, cooper jd, hanger dp, noble w. antiinflammatory impact of minocycline in a mouse model of tauopathy. front psychiatry. 2010;1:136. 129. jaworski t, lechat b, demedts d, gielis l, devijver h, borghgraef p, et al. dendritic degeneration, neurovascular defects, and inflammation precede neuronal loss in a mouse model for tau-mediated neurodegeneration. am j pathol 2011;179:2001–2015. 130. nilson an, english kc, gerson je, barton whittle t, nicolas crain c, xue j, et al. tau oligomers associate with inflammation in the brain and retina of tauopathy mice and in neurodegenerative diseases. j alzheimers dis 2017;55:1083–1099. 131. lu y, li z, zhang x, ming b, jia j, wang r, et al. retinal nerve fiber layer structure abnormalities in early alzheimer’s disease: evidence in optical coherence tomography. neurosci lett 2010;480:69–72. 132. ho w-l, leung y, tsang aw-t, so k-f, chiu k, chang rcc. tauopathy in the retina and optic nerve: does it shadow pathological changes in the brain? mol vis 2012;18:2700– 2710. 133. colligris p, perez de lara mj, colligris b, pintor j. ocular manifestations of alzheimer’s and other neurodegenerative diseases: the prospect of the eye as a tool for the early diagnosis of alzheimer’s disease. j ophthalmol 2018;2018:8538573. 134. berisha f, feke gt, trempe cl, mcmeel jw, schepens cl. retinal abnormalities in early alzheimer’s disease. invest ophthalmol vis sci 2007;48:2285–2289. 135. sadun aa, bassi cj. optic nerve damage in alzheimer’s disease. ophthalmology 1990;97:9–17. 136. guo l, duggan j, cordeiro mf. alzheimer’s disease and retinal neurodegeneration. curr alzheimer res 2010;7:3– 14. 137. danesh-meyer hv, birch h, ku jy, carroll s, gamble g. reduction of optic nerve fibers in patients with alzheimer disease identified by laser imaging. neurology 2006;67:1852–1854. 138. iseri pk, altinas o, tokay t, yuksel n. relationship between cognitive impairment and retinal morphological and visual functional abnormalities in alzheimer disease. j neuroophthalmol 2006;26:18–24. 139. frost s, guymer r, zaw aung k, lance macaulay s, sohrabi hr, bourgeat p, et al. alzheimer’s disease and the early signs of age-related macular degeneration. curr alzheimer res 2016;13:1259–1266. 140. koronyo-hamaoui m, koronyo y, ljubimov av, miller ca, ko mk, black kl, et al. identification of amyloid plaques in retinas from alzheimer’s patients and noninvasive in vivo optical imaging of retinal plaques in a mouse model. neuroimage 2011;54:s204–s217. 141. loeffler ku, edward dp, tso mo. tau-2 immunoreactivity of corpora amylacea in the human retina and optic nerve. invest ophthalmol vis sci 1993;34:2600–2603. 142. loffler ku, edward dp, tso mo. immunoreactivity against tau, amyloid precursor protein, and beta-amyloid in the human retina. invest ophthalmol vis sci 1995;36:24–31. 143. flaxman sr, bourne rr, resnikoff s, ackland p, braithwaite t, cicinelli mv, et al. global causes of blindness and distance vision impairment 1990–2020: a systematic review and meta-analysis. lancet glob health 2017;5:e1221–e1234. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 503 tau protein and neurodegenerative diseases; mishan et al 144. luthert pj. pathogenesis of age-related macular degeneration. diagn histopathol 2011;17:10–16. 145. leger f, fernagut po, canron mh, leoni s, vital c, tison f, et al. protein aggregation in the aging retina. j neuropathol exp neurol 2011;70:63–68. 146. wostyn p, audenaert k, de deyn pp. alzheimer’s disease and glaucoma: is there a causal relationship? br j ophthalmol 2009;93:1557–1559. 147. tseng h, kasmala l, proia a, mckinnon s. expression of protein markers of alzheimer’s disease in human glaucoma eyes. invest ophthalmol vis sci 2007;48:3269– 3269. 148. chiasseu m, cueva vargas jl, destroismaisons l, vande velde c, leclerc n, di polo a. tau accumulation, altered phosphorylation, and missorting promote neurodegeneration in glaucoma. j neurosci 2016;36:5785–5798. 149. oka t, tamada y, nakajima e, shearer tr, azuma m. presence of calpain-induced proteolysis in retinal degeneration and dysfunction in a rat model of acute ocular hypertension. j neurosci res 2006;83:1342–1351. 150. branca d. calpain-related diseases. biochem biophys res commun 2004;322:1098–1104. 151. yoneda s, hara h, hirata a, fukushima m, inomata y, tanihara h. vitreous fluid levels of β-amyloid (1–42) and tau in patients with retinal diseases. jpn j ophthalmol 2005;49:106–108. 152. goedert m, jakes r, vanmechelen e. monoclonal antibody at8 recognises tau protein phosphorylated at both serine 202 and threonine 205. neurosci lett 1995;189:167–169. 153. gupta n, fong j, ang lc, yucel yh. retinal tau pathology in human glaucomas. can j ophthalmol 2008;43:53–60. 154. liu b, rasool s, yang z, glabe cg, schreiber ss, ge j, et al. amyloid-peptide vaccinations reduce β-amyloid plaques but exacerbate vascular deposition and inflammation in the retina of alzheimer’s transgenic mice. am j pathol 2009;175:2099–2110. 155. linsenmeier ra, padnick–silver l. metabolic dependence of photoreceptors on the choroid in the normal and detached retina. invest ophthalmol vis sci 2000;41:3117– 3123. 156. calaza kc, kam jh, hogg c, jeffery g. mitochondrial decline precedes phenotype development in the complement factor h mouse model of retinal degeneration but can be corrected by near infrared light. neurobiol aging 2015;36:2869–2876. 157. nakayama t, goshima y, misu y, kato t. role of cdk5 and tau phosphorylation in heterotrimeric g protein–mediated retinal growth cone collapse. j neurobiol 1999;41:326– 339. 158. allen b, ingram e, takao m, smith mj, jakes r, virdee k, et al. abundant tau filaments and nonapoptotic neurodegeneration in transgenic mice expressing human p301s tau protein. j neurosci 2002;22:9340–9351. 159. gasparini l, crowther ra, martin kr, berg n, coleman m, goedert m, et al. tau inclusions in retinal ganglion cells of human p301s tau transgenic mice: effects on axonal viability. neurobiol aging 2011;32:419–433. 160. mazzaro n, barini e, spillantini mg, goedert m, medini p, gasparini l. tau-driven neuronal and neurotrophic dysfunction in a mouse model of early tauopathy. j neurosci 2016;36:2086–2100. 161. bull nd, guidi a, goedert m, martin kr, spillantini mg. reduced axonal transport and increased excitotoxic retinal ganglion cell degeneration in mice transgenic for human mutant p301s tau. plos one 2012;7:e34724. 162. spires tl, hyman bt. transgenic models of alzheimer’s disease: learning from animals. neurorx 2005;2:423–437. 163. ho wl, leung y, cheng ss, lok ck, ho ys, baum l, et al. investigating degeneration of the retina in young and aged tau p301l mice. life sci 2015;124:16–23. 164. schroer ta. dynactin. annu rev cell dev biol 2004;20:759–779. 165. stamer k, vogel r, thies e, mandelkow e, mandelkow em. tau blocks traffic of organelles, neurofilaments, and app vesicles in neurons and enhances oxidative stress. j cell biol 2002;156:1051–1063. 166. cingolani c, rogers b, lu l, kachi s, shen j, campochiaro pa. retinal degeneration from oxidative damage. free radic biol med 2006;40:660–669. 167. tanito m, masutani h, nakamura h, oka s-i, ohira a, yodoi j. attenuation of retinal photooxidative damage in thioredoxin transgenic mice. neurosci lett 2002;326:142– 146. 168. léveillard t, mohand-saïd s, lorentz o, hicks d, fintz ac, clérin e, et al. identification and characterization of rodderived cone viability factor. nat genet 2004;36:755. 169. sahel j-a. saving cone cells in hereditary rod diseases: a possible role for rod-derived cone viability factor (rdcvf) therapy. retina 2005;25:s38–s39. 170. leveillard t, sahel ja. rod-derived cone viability factor for treating blinding diseases: from clinic to redox signaling. sci transl med 2010;2:26ps16. 171. fridlich r, delalande f, jaillard c, lu j, poidevin l, cronin t, et al. the thioredoxin-like protein rod-derived cone viability factor (rdcvfl) interacts with tau and inhibits its phosphorylation in the retina. mol cell proteomics 2009;8:1206–1218. 172. byrne lc, dalkara d, luna g, fisher sk, clérin e, sahel ja, et al. viral-mediated rdcvf and rdcvfl expression protects cone and rod photoreceptors in retinal degeneration. j clin invest 2015;125:105–116. 173. hosokawa m, arai t, masuda-suzukake m, nonaka t, yamashita m, akiyama h, et al. methylene blue reduced abnormal tau accumulation in p301l tau transgenic mice. plos one 2012;7:e52389. 174. min s-w, chen x, tracy te, li y, zhou y, wang c, et al. critical role of acetylation in tau-mediated neurodegeneration and cognitive deficits. nat med 2015;21:1154–1162. 175. myeku n, clelland cl, emrani s, kukushkin nv, yu wh, goldberg al, et al. tau-driven 26s proteasome impairment and cognitive dysfunction can be prevented early in disease by activating camp-pka signaling. nat med 2016;22:46–53. 176. yanamandra k, kfoury n, jiang h, mahan te, ma s, maloney se, et al. anti-tau antibodies that block tau aggregate seeding in vitro markedly decrease pathology and improve cognition in vivo. neuron 2013;80:402–414. 177. castillo-carranza dl, sengupta u, guerrero-munoz mj, lasagna-reeves ca, gerson je, singh g, et al. passive immunization with tau oligomer monoclonal anti504 journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 tau protein and neurodegenerative diseases; mishan et al body reverses tauopathy phenotypes without affecting hyperphosphorylated neurofibrillary tangles. j neurosci 2014;34:4260–4272. 178. bi m, ittner a, ke yd, götz j, ittner lm. tau-targeted immunization impedes progression of neurofibrillary histopathology in aged p301l tau transgenic mice. plos one 2011;6:e26860. 179. boimel m, grigoriadis n, lourbopoulos a, haber e, abramsky o, rosenmann h. efficacy and safety of immunization with phosphorylated tau against neurofibrillary tangles in mice. exp neurol 2010;224:472–485. 180. ittner a, bertz j, suh ls, stevens ch, götz j, ittner lm. tau-targeting passive immunization modulates aspects of pathology in tau transgenic mice. j neurochem 2015;132:135–145. 181. brunden kr, ballatore c, crowe a, smith ab, lee vm-y, trojanowski jq. tau-directed drug discovery for alzheimer’s disease and related tauopathies: a focus on tau assembly inhibitors. exp neurol 2010;223:304–310. 182. mohamed t, hoang t, jelokhani-niaraki m, rao pp. tau-derived-hexapeptide 306vqivyk311 aggregation inhibitors: nitrocatechol moiety as a pharmacophore in drug design. acs chem neurosci 2013;4:1559–1570. 183. mohamed t, pn rao p. alzheimer’s disease: emerging trends in small molecule therapies. curr med chem 2011;18:4299–4320. 184. dammers c, yolcu d, kukuk l, willbold d, pickhardt m, mandelkow e, et al. selection and characterization of tau binding d-enantiomeric peptides with potential for therapy of alzheimer disease. plos one 2016;11:e0167432. 185. matsuoka y, jouroukhin y, gray aj, ma l, hirata-fukae c, li h-f, et al. a neuronal microtubule-interacting agent, napvsipq, reduces tau pathology and enhances cognitive function in a mouse model of alzheimer’s disease. j pharmacol exp ther 2008;325:146–153. 186. ivashko-pachima y, maor-nof m, gozes i. nap (davunetide) preferential interaction with dynamic 3-repeat tau explains differential protection in selected tauopathies. plos one 2019;14:e0213666. 187. eschmann na, do td, lapointe ne, shea j-e, feinstein sc, bowers mt, et al. tau aggregation propensity engrained in its solution state. j phys chem b 2015;119:14421–14432. 188. schafer kn, cisek k, huseby cj, chang e, kuret j. structural determinants of tau aggregation inhibitor potency. j biol chem 2013;288:32599–32611. 189. levine za, larini l, lapointe ne, feinstein sc, shea je. regulation and aggregation of intrinsically disordered peptides. proc natl acad sci 2015;112:2758–2763. 190. nadimidla k, ismail t, kanapathipillai m. tau peptides and tau mutant protein aggregation inhibition by cationic polyethyleneimine and polyarginine. biopolymers 2017;107:e23024. 191. devos sl, goncharoff dk, chen g, kebodeaux cs, yamada k, stewart fr, et al. antisense reduction of tau in adult mice protects against seizures. j neurosci 2013;33:12887–12897. 192. khosravi z, khalili man, moradi s, sajedi rh, zeinoddini m. the molecular chaperone artemin efficiently blocks fibrillization of tau protein in vitro. cell j 2018;19:569–577. journal of ophthalmic and vision research volume 14, issue 4, october-december 2019 505 original article association of timp-1 and col4a4 gene polymorphisms with keratoconus in an iranian population davood yari1, 2, 3, phd; zohreh ehsanbakhsh3, 4, bs; mohammad-hosein validad5, md farzaneh hasanian langroudi2, phd 1cellular and molecular research center, zahedan university of medical sciences, zahedan, iran 2department of clinical biochemistry, school of medicine, zahedan university of medical sciences, zahedan, iran 3mashhad university of medical sciences, mashhad, iran 4shariati hospital, mashhad university of medical sciences, mashhad, iran 5department of ophthalmology, alzahra eye hospital, zahedan university of medical sciences, zahedan, iran orcid: davood yari: https://orcid.org/0000-0001-6105-4326 abstract purpose: keratoconus (kc) is a bilateral and noninflammatory disease, characterized by progressive thinning and anterior protrusion of the cornea and may result in severe visual impairment due to irregular astigmatism. matrix metalloproteinases (mmp) are the main group of enzymes that degrade extracellular matrix proteins including collagens; type iv collagen is found in the corneal stroma. mmp enzymatic activity is inhibited by tissue inhibitor of metalloproteinase-1 (timp-1). a decrease in timp-1 level is associated with the development of kc. in the present study, we investigated the impact of col4a4 rs2228557 c/t and timp-1 rs4898 c/t (x-chromosome) variants on the odds of kc development in a sample of iranian population. methods: this case–control study was conducted on 140 patients with kc and 150 healthy control subjects. we used modified methods of nested-pcr and arms-pcr in combination (nestedarms-pcr) and confirmed their validity with rflp–pcr. results: significant differences were noticed between kc patients and healthy individuals regarding the genotype ty or t allele frequencies of rs4898 in the male subjects (or = 0.43, 95%ci: 0.20–0.92, p = 0.03), whereas no significant differences were identified in the female subjects (or = 1.07, 95%ci: 0.52–2.20, p = 0.85). the rs2228557, t allele was associated with kc (or = 0.69, 95% ci: 0.50–0.97, p = 0.035). conclusion: in the rs2228557 variant, t allele acts as a protective factor from the disease and decreases the risk of kc compared with the c allele. also, in our investigation about rs4898, we found that ty genotype or t allele decreased the risk of kc compared with the c allele in males and was a protective factor for kc in our population. keywords: collagen; col4a4; keratoconus; polymorphism; timp-1 j ophthalmic vis res 2020; 15 (3): 299–307 correspondence to: davood yari, phd. cellular and molecular research center, zahedan university of medical sciences, zahedan 98167, iran. email: davidyari.85@gmail.com received: 01-03-2019 accepted: 14-03-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7448 introduction keratoconus (kc) is defined as a bilateral, non-inflammatory, and progressive disease this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: yari d, ehsanbakhsh z, validad m-h, langroudi fh. association of timp-1 and col4a4 gene polymorphisms with keratoconus in an iranian population. j ophthalmic vis res 2020;15:299–307. © 2020 journal of ophthalmic and vision research | published by knowledge e 299 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7448&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr association of timp-1 and col4a4 gene polymorphisms with keratoconus; yari et al characterized by conical protrusion of the cornea. this disease may result in severe visual impairment due to irregular astigmatism and stromal scarring. kc eventually affects both eyes, although the involvement is usually asymmetric. the symptoms of kc-affected patients are different depending on the stage of the disease.[1–3] glasses or contact lenses can provide useful vision in the early stage of the disease; nonetheless, corneal transplantation is mandatory for visual rehabilitation in 20% of the patients who are in advanced stage. corneal thinning is considered as one of the identifying characteristics of kc. central corneal thickness (cct) is lower in kc patients by 75 µm as compared to normal controls.[4, 5] the incidence of kc is approximately 1 per 2,000, and its prevalence is 54.5 per 100,000. this disease occurs in both genders,[6] with different rates among different ethnic groups.[7] kc usually begins in teens, and its progression slows after the age of 30 years.[6] kc is a multi-factorial disorder; environmental factors cause kc in genetically susceptible individuals. the environmental factors that may play roles in the pathogenesis of kc include eye rubbing, allergy, connective tissue dysfunction, and contact lens wear. moreover, subjects with a family history of kc are more susceptible to this disorder.[8] using family-based linkage, several case–control studies have determined various genes that increase the odds of kc development.[9] the gene candidates for kc include lox,[10] vsx1,[11] gpx-1,[12] tgf-𝛽1,[13] col4a3 and col4a4[14] (polymorphism or mutation), and timp1,[15] mmp-2, mmp-9[16] (gene expression). kc is still an enigmatic disease in many aspects, including inheritance, basic pathophysiology, prevention, associated risk factors, disease development, as well as therapeutic approaches.[17] type iv collagen is only present in basement membranes and constitutes their main structural component. collagen type iv gene, alpha-4 (col4a4), is located in the region 2q35–q37 with a gene span composed of 113 kb and 48 exons.[18, 19] type iv collagen is not expressed in cornea in the normal condition and its presence indicates a corneal pathology; therefore, type iv collagen can be a potential candidate in the pathogenesis of kc. in support of this theory, alterations in the expression level of collagen type iv (α-4 chains) were observed in corneas inflicted by kc.[20, 21] matrix metalloproteinases (mmp) are the major expressed metalloproteases in the cornea. it has been demonstrated that the proteolytic activity of mmp increases in kc. this finding suggests that abnormal mmp activity plays a role in the pathogenesis of kc.[16, 22] four types of tissue inhibitor of metalloproteinase (timp1-4) have been detected; three of which, including timps-1, 3, and 4, are nested within an intron in the genes of synapsins. timp inhibits collagenases and proteoglycanase called matrix metalloproteinase. all four types of timps have various biological activities apart from their metalloproteinase inhibitory activity. these biological activities include the promotion of cell proliferation, cancer promotion, regulation of angiogenesis, as well as proand anti-apoptotic and synaptic flexibility activities, many of which are independent of metalloprotease inhibition. timp-1 is associated with synapsin 1 and its gene is located in x11p11.23–11.4 consisting of six exons. mature timp-1 is a 28.5 kda glycoprotein that consists of 184 amino acid residues. the natural precursor contains a signal peptide of 23 residues which are cleaved throughout the protein maturation.[23–27] timp-1 suppresses angiogenesis and controls the balance in the corneal tissue by inhibiting the action of matrix metalloproteinase to protect tissues from permanent damage.[28] furthermore, it has been demonstrated that increased mmp and decreased timp levels are associated with the development of kc.[29] col4a4 gene rs2228557 (f1644f) (hgvm1660028) is located in chromosome 2 exon 48, nm_000092.4 region. several studies examined the association between col4a4 and kc and revealed that this gene is associated with kc; however, some other studies failed to find the same relationship in different populations.[14, 22, 30, 31] timp-1 gene rs4898 (+372c/t) (hgvm6380940) is located within the intron of the synapsin gene, and single nucleotide polymorphism (snp) is located in exon 5, the region of nm_006950.3. some studies investigated the association of rs4898 gene polymorphism with disorders including intracerebral hemorrhage,[32] systemic sclerosis,[33] and severe sepsis.[34] the present study aimed to evaluate the possible association of timp-1 rs4898 c/t gene polymorphism and col4a4 rs2228557 c/t gene 300 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 association of timp-1 and col4a4 gene polymorphisms with keratoconus; yari et al polymorphism with the development of kc in a sample of iranian population. methods patients the current retrospective case–control study was conducted at the alzahra eye hospital, zahedan university of medical sciences, zahedan, iran and recruited 140 unrelated iranian patients with kc and 150 unrelated healthy controls. the patients were diagnosed with kc after a comprehensive ophthalmic examination using the following criteria: (1) clinical signs of kc (munson sign, protrusion, vogts striae, corneal thickness, scarring, fleischer ring) and abnormal findings in corneal topography (pentacam axl, oculus inc); (2) the three quantitative videokeratographic indices used for the screening of kc were central corneal power > 47.2 d, inferior–superior value > 1.4 d, sim-k astigmatism > 1.5 d, and skewed radial axes > 21°.[10, 35] patients with other ocular diseases were excluded from the study. controls were sexand age-matched healthy participants who were unrelated to the patients and were selected from a geographic area similar to that of kc subjects. the ethics committee of zahedan university of medical sciences, zahedan, iran approved the study protocol and informed consent was signed by all participants. this study complied with the tenets of the declaration of helsinki. analysis of the timp-1 (rs4898), col4a4 (rs2228557) polymorphisms blood samples were collected in edta-containing tubes and genomic dna was extracted from the peripheral blood leukocytes using salting out method as previously described.[36] all procedures were performed under a standardized setting to avoid variation in dna quality. snp rs2228557 col4a4 was evaluated by arms–pcr. for the detection of rs4898 timp-1, we used the combination of nested-polymerase chain reaction (nested-pcr)[37] and amplification refractory mutation system-pcr(arms-pcr)[38] (nestedarms-pcr). the verification of these methods was accomplished using restriction fragment length polymorphism (rflp-pcr).[39] the rs4898 location was very challengeable for arms-pcr; therefore, for the detection of the snp, we used nested or hemi-nested-pcr primers, as mentioned previously.[40] the advantages of this modification include elimination of non-specific products, protection of snp position for the next steps, low cost, and short duration of the process. pcr reactions were performed using pcr master mix (ampliqon taq 2x mastermix, denmark) according to the manufacturer’s instructions. for investigation of col4a4 (rs2228557), amplification reaction was provided in 20 μl volume including: 1 μl template dna (∼100 ng/μl), 1 μl of each primer (10 pmol/μl), 10 μl mastermix, and 7 μl dnase-free water. the pcr conditions were set as follow: 95°c for 5 min, 30 cycles of 95°c for 30 sec, 55°c for 35 sec, 72°c for 30 sec, and a final extension at 72°c for 5 min. pcr products were detected by electrophoresis on a 2% agarose gel staining by ethidium bromide (figure 1a). in the first stage of study for timp-1 rs4898, nested-pcr reaction was performed in 20 μl volume including: 1 μl template dna (∼100 ng/μl), 1 μl of each primer (10 pmol/μl), 10 μl mastermix, and 7 μl dnase-free water. the pcr conditions were set as follow: 95°c for 5 min, 30 cycles of 95°c for 30 sec, 64°c for 40 sec, 72°c for 30 sec, and a final extension at 72°c for 5 min. in the second phase, the pcr product obtained from the first stage (660 bp) was used as the template and diluted 1:50. primers for arms-pcr were designed to detect the snp (table 1). in this step, arms-pcr reaction was performed in 20 μl volume including: 1 μl template (1:50 dilution), 1 μl of each primer (10 pmol/μl), 10 μl mastermix, and 7 μl dnase-free water. the pcr conditions were set as follow: 95°c for 5 min, 17 cycles of 95°c for 30 sec, 56°c for 30 sec, 72°c for 30 sec, and a final extension at 72°c for 5 min. pcr products were detected by electrophoresis on a 2% agarose gel staining by ethidium bromide (202bp product). consequently, snp (rs4898) timp-1 was successfully detected with the combination of two methods (nested-pcr and arms-pcr) (figures b1 & b2). rflp-pcr was applied to validate the method and results of screening of rs4898 polymorphism in timp-1. as the original sequence of the region surrounding the polymorphism does not make a restriction enzyme site, a site-directed mutagenesis pcr primer (r*) was designed. this primer differs from the referent sequence in two journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 301 association of timp-1 and col4a4 gene polymorphisms with keratoconus; yari et al figure 1. electrophoresis pattern for the detection of snps in col4a4 rs2228557 and timp-1 rs4898. (a) arms-pcr products of col4a4 rs2228557, m: dna marker (100 bp). (b1) timp-1 rs4898, nested-pcr products, m: dna marker (100bp), product size (660 and 344bp), respectively. (b2) arms-pcr products, product size (202bp), (tt, tc, cc) demonstrate genotypes. (b3) rflp-pcr products, m: dna marker (50bp), product sizes were 344bp for tt, 344bp and 325bp for tc, 325bp for cc in female, 344bp for ty and 325bp for cy in male, (tt, tc, cc) demonstrate female and (tt = ty, cc = cy) demonstrate male genotypes, (y stands for the y-chromosome). table 1. the list of primers and methods used for detection of single nucleotide polymorphisms (snps) timp-1 rs4898 and col4a4 rs2228557 timp-1(rs4898) t/c primers(5’-3’) product size stage 1nested-pcr f tggggacaccagaagtcaac 660 bp r taagctcaggctgttccagg stage 2arms-pcr f common aggctctgatgagaatggtccca 202 bpr (c allele) cagattgttccagggagccaag r (t allele) cagattgttccagggagccaaa stage 3rflp-pcr f ccgccatggagagtgtctgc 344 bp r* aggctgttccagggagtcgc col4a4(rs2228557 ) c/t arms-pcr f common tgtctgagccctaattctct 183 bpr (c allele) gagccagaagctatacttatttgag r (t allele) gagccagaagctatacttatttgaa f, forward; r, reverse; r*, altered reverse 302 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 association of timp-1 and col4a4 gene polymorphisms with keratoconus; yari et al table 2. genotype and allelic frequencies of col4a4 rs2228557 and timp-1 rs4898 polymorphisms between keratoconus (kc) patients and healthy controls. variants kc patients n (%) controls n (%) *or (95% ci) p-value rs2228557,col4a4 cc 67 (47.8) 61 (40.7) ref. — ct 39 (27.9) 37 (24.7) 0.96 (0.54–1.69) 0.887 tt 34 (24.3) 52 (34.6) 0.59 (0.34–1.03) 0.067 allele c 173 (61.8) 159 (53) ref. — t 107 (38.2) 141 (47) 0.69 (0.50–0.97) 0.035 rs4898,timp-1 male male cy 46 (75.4) 37 (57) ref. — ty 15 (24.6) 28 (43) 0.43 (0.20–0.92) 0.038 female female cc 28 (47.5) 31 (52.5) ref. — ct 29 (49.2) 30 (50.8) 1.01 (0.46–2.19) 0.97 tt 22 (47.8) 24 (52.2) 1.07 (0.52–2.20) 0.854 allele c 85 (53.8) 92 (54.1) ref. — t 73 (46.2) 78 (45.9) 1.01 (0.66–1.56) 0.953 ref., reference; or, odds ratio; ci, confidence interval; n, number *adjusted for sex and age. (y states for the y-chromosome) table 3. correlation of clinical and keratometric parameters with col4a4 (rs2228557) and timp-1(rs4898) in keratoconus patients. parameters evaluated patients n (%) rs2228557 p-value rs4898 p-value male female kc ocular od 42 (30.0) 0.25 0.39 0.4os 36 (25.7) ou 62 (44.3) level of kc kk 1 33 (23.6) 0.81 0.014 0.97kk 2 45 (32.1) kk 3 62 (44.3) cxl od 39 (27.9) 0.58 0.71 0.37os 40 (28.6) ou 42 (30.0) candidate 19 (13.6) correlation of clinical and keratometric parameters with col4a4 (rs2228557) and timp-1 (rs4898) in keratoconus patients. kc, keratoconus; od, right eye; os, left eye; ou, both eyes; cxl, cross-linking surgery kk1, 2, 3 are phenotyping classification and show the level progress of keratoconus disease in patients journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 303 association of timp-1 and col4a4 gene polymorphisms with keratoconus; yari et al bases and lies close to the polymorphic spot to alter the sequence and provide a restriction enzyme site at product. thus, the original sequence of the region is tt(c) gtgg, while our pcr product was in fact tt(c) gcga. the c-variant is a palindrome which forms a site for the bsp68i (nrui) restriction enzyme (thermo scientific).[40] initially, we amplified pcr product (660bp) using the abovementioned conditions. for alteration in the restriction enzyme site, secondary primers were added to template 1:50 dilution of first stage using the following condition: 1 μl template (1:50 dilution), 1 μl of each primer (10 pmol/μl), 10 μl mastermix, and 7 μl dnase-free water. the pcr conditions were set as follow: 95°c for 5 min, 30 cycles of 95°c for 30 sec, 63°c for 30 sec, 72°c for 30 sec, and a final extension at 72°c for 5 min. pcr products were detected by electrophoresis on a 2% agarose gel with ethidium bromide (344bp product). for optimal results, pcr products were digested at 37°c for 5 h according to the manufacturer’s instruction. the restriction of the c-allele pcr product resulted in 325bp and 19bp digest products, whereas the t allele (wild type) products remained unrestricted (figure b3). statistical analysis statistical analyses were performed using the spss software version 19.0 (spss inc., chicago il, usa). frequencies were compared between the study groups using the chi-square test. association of gene polymorphisms with kc was investigated and compared between the groups using logistic regression analysis, estimation of odds ratio (or), and 95% confidence intervals (ci), respectively. a p-value < 0.05 was regarded as statistically significant. results a total of 140 patients (61 male and 79 female subjects), aged 28 ± 12.5 years, included the kc group. the control group consisted of 150 healthy controls (65 male and 85 female subjects), aged 29.8 ± 15.6 years. there was no significant difference between the two groups regarding the age and gender (p = 0.20). the col4a4 rs2228557 c/t variant, t allele was associated with a decrease in the risk of kc development (or = 0.69, 95% ci: 0.50–0.97, p = 0.035), as compared to c allele. our results indicated that tt was not associated with kc as compared to cc (or = 0.59, 95% ci = 0.34–1.03, p = 0.067) (table 2). table 2 demonstrates the genotype and allelic frequencies of timp-1 (rs4898) gene polymorphism in each study group. since timp-1 is an x-linked gene, the results were compared in male and female subjects separately. this analysis demonstrated that ty genotype or t allele decreased the risk of kc in male subjects as compared to the c allele (or = 0.43, 95% ci: 0.20–0.92, p = 0.03). however, no significant association was found between tt genotype (or = 1.07, 95% ci: 0.52–2.20, p = 0.854) or t allele (or = 1.01, 95%ci: 0.66–1.56, p = 0.95) and kc in female subjects. table 3 illustrates the associations of col4a4 (rs2228557) and timp-1 (rs4898) with kc severity. this polymorphism timp1 (rs4898 t/c) located at x chromosome exists in two alleles and their combination results in five possible genotypes. because men lack a second x-chromosome, the possible genotypes are cy and ty hemizygotes (y states for the y-chromosome). as for women, there are cc and tt homozygotes and ct heterozygotes (table 2). in fact, men just have allele and women have genotype and allele. for this reasons, calculation of timp1 (rs4898) distinctly separated in men and women was done. so, results in men and women can be different. discussion keratoconus is an eye disorder characterized by bilateral, asymmetrical, noninflammatory, and progressive thinning of the cornea. the shape of cornea progressively alters from the normal round shape to a cone shaped one. although the etiology of kc is not clear, defective cross-linking between adjacent collagen fibers may play an important role in its pathogenesis.[41] snps and gene variants suggest an intricate etiology or the convergence of multiple disease pathways.[42] biochemical investigations have suggested that the amount of collagen fibers decrease in kc. also, the weight of kc corneas was found to be reduced; 304 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 association of timp-1 and col4a4 gene polymorphisms with keratoconus; yari et al therefore, it can be assumed that collagenase enzymes might be involved.[43] in the current study, we investigated the impact of col4a4 and timp-1 variants on the risk of kc development in a sample of iranian population. our results showed that the t allele reduced the risk of disease development, as compared to the c allele. results in the distribution of genotypes (cc, ct, tt) in rs2228557 of the col4a4 gene between kc patients and controls in the stabuc-silih et al’s study were different from our results.[14] similar to our findings, kokolakis et al demonstrated that the tt genotype was significantly over-represented in healthy individuals and suggested a protective role for this genotype in the kc development.[31] the level of timp-1 significantly decreases in kc as compared to normal corneas. given the fact that kc is not associated with extensive scarring or inflammatory infiltrates, substantial degradation should occur in the extracellular matrix. a decreased level of timp-1 increases gelatinase and collagenase activities and apoptosis which are characteristic phenomena in kc. decreases in timp-1 might play a role in matrix degradation which is a characteristic feature of kc.[15, 44] furthermore, it has been recognized that increased mmp and decreased timp-1 levels are associated with the development of kc.[29] the timp-1 gene is located in xp11.3–p11.23 and has three types of polymorphism including timp1 (19 c/t) in the 5’-utr, timp-1 (261 c/t) in exon 4, and timp-1 (372 t/c) (rs4898) in exon 5. the timp-1 (rs4898) polymorphism is an important site which has been reported in other studies. this variation does not result in changes in the amino acid sequence (f124f). this polymorphism exists in two alleles and their combination results in five possible genotypes. because male subjects lack a second x-chromosome, the possible genotypes are cy and ty hemizygotes. in female subjects, however, there are cc and tt homozygotes and ct heterozygote genotypes.[40] our data suggest that c or t allele is associated with timp-1 (rs4898) polymorphism in patients or controls. the c allele of the 372t/c polymorphism was more frequently found in female than male controls.[45] however, in other studies, the c allele was detected more frequently in male patients with an abdominal aortic aneurysm.[46] meijer et al investigated the male subjects with inflammatory bowel disease carrying timp-1 (rs4898) t allele. they reported lower levels of timp-1 in surgically resected inflamed tissue, as compared to c allele carriers.[47] in addition, indelicato et al reported that timp-1 (rs4898) c allele frequency increased in males but not females with systemic sclerosis, as compared to healthy individuals.[48] along the same lines, wei et al revealed that c allele carriers of timp-1 (rs4898) run a greater risk of developing ankylosing spondylitis disease.[49] furthermore, it was found that among cirrhotic patients, males with timp-1 (372c/t) t allele developed cirrhosis at a younger age.[50] our findings indicated that timp-1 (rs4898) was associated with the clinical characteristics of kc only in our male sample population. nevertheless, the analysis of genotype and allele frequencies revealed no significant differences in female patients as compared to female controls. the t allele decreased the risk of kc, as compared to the c allele in males which can be attributed to the location of timp-1 gene at xp11.3–p11.23. males only have one x-chromosome, and the functional difference of genetic polymorphism of timp1 (rs4898) appears more obvious due to the lack of heterozygotes. we cannot compare our results with the literature because no previous study has evaluated the correlation between the timp-1 variants and the risk of kc development. in conclusion, our study showed that in the col4a4 rs2228557 c/t variant, the t allele acts as a protective factor against the disease and decreases the risk of kc. in addition, timp-1 rs4898 c/t the ty genotype or t allele in males can decrease the risk of kc in comparison with the c allele. further studies with a larger sample size and different ethnicities are required to confirm these findings. financial support and sponsorship this study was supported by a dissertation grant (m.sc. thesis of davood yari, no. 6077) from the deputy for research, zahedan university of medical sciences. conflicts of interests there are no conflicts of interest. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 305 association of timp-1 and col4a4 gene polymorphisms with keratoconus; yari et al references 1. burdon kp, vincent al. insights into keratoconus from a genetic perspective. clin exp optom 2013;96:146–154. 2. gajecka m, radhakrishna u, winters d, nath sk, rydzanicz m, ratnamala u, et al. localization of a gene for keratoconus to a 5.6-mb interval on 13q32. invest ophthalmol vis sci 2009;50:1531–1539. 3. lee lr, hirst lw, readshaw g. clinical detection of unilateral keratoconus. aust n z j ophthalmol 1995;23:129–133. 4. li x, bykhovskaya y, canedo al, haritunians t, siscovick d, aldave aj, et al. genetic association of col5a1 variants in keratoconus patients suggests a complex connection between corneal thinning and keratoconus. invest ophthalmol vis sci 2013;54:2696–2704. 5. grewal ds, brar gs, grewal sp. assessment of central corneal thickness in normal, keratoconus, and postlaser in situ keratomileusis eyes using scheimpflug imaging, spectral domain optical coherence tomography, and ultrasound pachymetry. j cataract refract surg 2010;36:954–964. 6. rabinowitz ys. keratoconus. surv ophthalmol 1998;42:297–319. 7. pearson ar, soneji b, sarvananthan n, sandford-smith jh. does ethnic origin influence the incidence or severity of keratoconus? eye 2000;14:625–628. 8. sahebjada s, schache m, richardson aj, snibson g, macgregor s, daniell m, et al. evaluating the association between keratoconus and the corneal thickness genes in an independent australian population. invest ophthalmol vis sci 2013;54:8224–8228. 9. bae ha, mills ra, lindsay rg, phillips t, coster dj, mitchell p, et al. replication and meta-analysis of candidate loci identified variation at rab3gap1 associated with keratoconus. invest ophthalmol vis sci 2013;54:5132– 5135. 10. hasanian-langroudi f, saravani r, validad mh, bahari g, yari d. association of lysyl oxidase (lox) polymorphisms with the risk of keratoconus in an iranian population. ophthalmic genet 2014;0:1–6. 11. heon e, greenberg a, kopp kk, rootman d, vincent al, billingsley g, et al. vsx1: a gene for posterior polymorphous dystrophy and keratoconus. hum mol genet 2002;11:1029–1036. 12. yari d, saravani r, saravani s, ebrahimian k, galavi hr. genetic polymorphisms of catalase and glutathione peroxidase-1 in keratoconus. iran j public health 2018;47:1567–1574. 13. guan t, liu c, ma z, ding s. the point mutation and polymorphism in keratoconus candidate gene tgfbi in chinese population. gene 2012;503:137–139. 14. stabuc-silih m, ravnik-glavac m, glavac d, hawlina m, strazisar m. polymorphisms in col4a3 and col4a4 genes associated with keratoconus. mol vis 2009;15:2848–2860. 15. lee je, oum bs, choi hy, lee su, lee js. evaluation of differentially expressed genes identified in keratoconus. mol vis 2009;15:2480–2487. 16. fullerton j, paprocki p, foote s, mackey da, williamson r, forrest s. identity-by-descent approach to gene localisation in eight individuals affected by keratoconus from north-west tasmania, australia. hum genet 2002;110:462–470. 17. patel d, mcghee c. understanding keratoconus: what have we learned from the new zealand perspective? clin exp optom 2013;96:183–187. 18. boye e, mollet g, forestier l, cohen-solal l, heidet l, cochat p, et al. determination of the genomic structure of the col4a4 gene and of novel mutations causing autosomal recessive alport syndrome. am j hum genet 1998;63:1329–1340. 19. mariyama m, zheng k, yang-feng tl, reeders st. colocalization of the genes for the alpha 3(iv) and alpha 4(iv) chains of type iv collagen to chromosome 2 bands q35-q37. genomics 1992;13:809–813. 20. stachs o, bochert a, gerber t, koczan d, thiessen hj, guthoff rf. [the extracellular matrix structure in keratoconus]. ophthalmologe 2004;101:384–389. 21. bochert a, berlau j, koczan d, seitz b, thiessen hj, guthoff r. [gene expression in keratoconus. initial results using dna microarrays]. ophthalmologe 2003;100:545– 549. 22. nielsen k, hjortdal j, pihlmann m, corydon tj. update on the keratoconus genetics. acta ophthalmol 2013;91:106– 113. 23. brew k, dinakarpandian d, nagase h. tissue inhibitors of metalloproteinases: evolution, structure and function. biochim biophys acta 2000;1477:267–283. 24. brew k, nagase h. the tissue inhibitors of metalloproteinases (timps): an ancient family with structural and functional diversity. biochim biophys acta 2010;1803:55–71. 25. guedez l, stetler-stevenson wg, wolff l, wang j, fukushima p, mansoor a, et al. in vitro suppression of programmed cell death of b cells by tissue inhibitor of metalloproteinases-1. j clin invest 1998;102:2002–2010. 26. usher pa, sieuwerts am, bartels a, lademann u, nielsen hj, holten-andersen l, et al. identification of alternatively spliced timp-1 mrna in cancer cell lines and colon cancer tissue. mol oncol 2007;1:205–215. 27. akahane t, akahane m, shah a, connor cm, thorgeirsson up. timp-1 inhibits microvascular endothelial cell migration by mmp-dependent and mmp-independent mechanisms. exp cell res 2004;301:158–167. 28. johnson md, kim hr, chesler l, tsao-wu g, bouck n, polverini pj. inhibition of angiogenesis by tissue inhibitor of metalloproteinase. j cell physiol 1994;160:194–202. 29. brown d, chwa mm, opbroek a, kenney mc. keratoconus corneas: increased gelatinolytic activity appears after modification of inhibitors. curr eye res 1993;12:571–581. 30. saravani r, hasanian-langroudi f, validad mh, yari d, bahari g, faramarzi m, et al. evaluation of possible relationship between col4a4 gene polymorphisms and risk of keratoconus. cornea 2015;34:318–322. 31. kokolakis ns, gazouli m, chatziralli ip, koutsandrea c, gatzioufas z, peponis vg, et al. polymorphism analysis of col4a3 and col4a4 genes in greek patients with keratoconus. ophthalmic genet 2014;35:226–228. 32. wang hx, yang qd, liu bq, zhang l, ma mm, hu zy, et al. timp-1 polymorphisms in a chinese han population with intracerebral hemorrhage. int j neurosci 2014;124:61–67. 306 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 association of timp-1 and col4a4 gene polymorphisms with keratoconus; yari et al 33. skarmoutsou e, d’amico f, marchini m, malaponte g, scorza r, mazzarino mc. association of timp-1 +372 snp with digital ulcer manifestation in female systemic sclerosis patients. hum immunol 2012;73:950–953. 34. lorente l, martin m, plasencia f, sole-violan j, blanquer j, labarta l, et al. the 372 t/c genetic polymorphism of timp-1 is associated with serum levels of timp-1 and survival in patients with severe sepsis. crit care 2013;17:r94. 35. mikami t, meguro a, teshigawara t, takeuchi m, uemoto r, kawagoe t, et al. interleukin 1 beta promoter polymorphism is associated with keratoconus in a japanese population. mol vis 2013;19:845–851. 36. hashemi m, amininia s, ebrahimi m, hashemi sm, yousefi j, eskandari-nasab e, et al. association between laptm4b gene polymorphism and breast cancer susceptibility in an iranian population. med oncol 2014;31:111. 37. haff la. improved quantitative pcr using nested primers. pcr methods appl 1994;3:332–337. 38. newton cr, graham a, heptinstall le, powell sj, summers c, kalsheker n, et al. analysis of any point mutation in dna. the amplification refractory mutation system (arms). nucleic acids res 1989;17:2503–2516. 39. dai s, long y. genotyping analysis using an rflp assay. methods mol biol 2015;1245:91–99. 40. naychov zd, hiyama e, uchida n, arihiro k, nagao m, takahashi s, et al. timp-1 c.t372c genetic polymorphism as a possible predictor for acute aortic dissection. hiroshima j med sci 2013;62:31–37. 41. ormonde s. refractive surgery for keratoconus. clin exp optom 2013;96:173–182. 42. crawford a, fassett rg, geraghty dp, kunde da, ball mj, robertson ik, et al. relationships between single nucleotide polymorphisms of antioxidant enzymes and disease. gene 2012;501:89–103. 43. collier sa. is the corneal degradation in keratoconus caused by matrix-metalloproteinases? clin experiment ophthalmol 2001;29:340–34. 44. kenney mc, chwa m, atilano sr, tran a, carballo m, saghizadeh m, et al. increased levels of catalase and cathepsin v/l2 but decreased timp-1 in keratoconus corneas: evidence that oxidative stress plays a role in this disorder. invest ophthalmol vis sci 2005;46:823–832. 45. krex d, rohl h, konig ir, ziegler a, schackert hk, schackert g. tissue inhibitor of metalloproteinases-1, 2, and -3 polymorphisms in a white population with intracranial aneurysms. stroke 2003;34:2817–2821. 46. hinterseher i, krex d, kuhlisch e, schmidt kg, pilarsky c, schneiders w, et al. tissue inhibitor of metalloproteinase1 (timp-1) polymorphisms in a caucasian population with abdominal aortic aneurysm. world j surg 2007;31:2248– 2254. 47. meijer mj, mieremet-ooms ma, van hogezand ra, lamers cb, hommes dw, verspaget hw. role of matrix metalloproteinase, tissue inhibitor of metalloproteinase and tumor necrosis factor-alpha single nucleotide gene polymorphisms in inflammatory bowel disease. world j gastroenterol 2007;13:2960–2966. 48. indelicato m, chiarenza v, libra m, malaponte g, bevelacqua v, marchini m, et al. analysis of timp-1 gene polymorphisms in italian sclerodermic patients. j clin lab anal 2006;20:173–176. 49. wei jc, lee hs, chen wc, shiu lj, yang sf, wong rh. genetic polymorphisms of the matrix metalloproteinase-3 (mmp-3) and tissue inhibitors of matrix metalloproteinases1 (timp-1) modulate the development of ankylosing spondylitis. ann rheum dis 2009;68:1781–1786. 50. ikebuchi y, ishida c, okamoto k, murawaki y. association of timp-1 and timp-2 gene polymorphisms with progression of liver fibrosis in patients with type c chronic liver disease. biochem genet 2013;51:564–574. 51. saravani r, yari d, saravani s, hasanian-langroudi f. correlation between the col4a3, mmp-9, and timp-1 polymorphisms and risk of keratoconus. jpn j ophthalmol 2017;61:218–222. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 307 case report when hiv immunodeficiency and heterochromia confuse the issue: recurrent zoster uveitis mistaken for fuchs’ uveitis ioannis papasavvas, md; bruno jeannin, cop; carle pierre herbort, md, pd retinal and inflammatory eye diseases, centre for ophthalmic specialized care (cos), clinic montchoisi teaching centre, lausanne, switzerland abstract purpose: we report a case with iris heterochromia misdiagnosed as fuchs’ uveitis which finally turned out to be a unilateral zoster uveitis in an hiv-positive patient. case report: a 45-year old patient was seen for a recurrent right anterior uveitis treated with prednisolone 1% drops bid. the iris of the right eye was hypochromic and atrophic and several small granulomatous keratic precipitates (kps) were present. after discontinuation of corticosteroid drops, severe uveitis developed with mutton-fat kps, and laser flare photometry (lfp) increased from 20 to 50.3 ph/ms. he had presented with right zoster ophthalmicus two years earlier and hiv-serology revealed to be positive. conclusion: iris heterochromia is not a good disease-defining criterion for fuch’s uveitis even when typical kps are present and can lead to misdiagnosis. more reliable criteria including stellate kps, low lfp values, absence of synechiae, vitreitis, and disc hyperfluorescence, all absent in this case, should be sought to confirm or exclude the diagnosis. keywords: herpes zoster uveitis; heterochromia; hiv j ophthalmic vis res 2021; 16 (2): 295–299 introduction fuchs’ uveitis (fu) is often underdiagnosed because too much importance is given to iris heterochromia at the expense of other more disease-defining clinical signs. the disease was described by ernst fuchs at the beginning of the last century in vienna, austria, inhabited by correspondence to: carl p. herbort jr, md, pd. centre for ophthalmic specialised care (cos), montchoisi teaching centre, rue charles-monnard 6, lausanne, switzerland. email: cph@herbortuveitis.ch received: 21-06-2020 accepted: 21-01-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9094 a caucasian population.[1, 2] iris heterochromia had a prominent part in the definition of the disease in his publications[1] and his textbook, which was translated into more than 10 languages including countries with all brown iris populations. in these countries such as japan[3] and many others, fu was underdiagnosed because clinicians were (1) looking in vain for heterochromia that does not exist in brown irises and (2) ignored the clinical sign of vitreitis present in close to 100% of cases.[4] therefore, strong and universal this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: papasavvas i, jeannin b, herbort cp. when hiv immunodeficiency and heterochromia confuse the issue: recurrent zoster uveitis mistaken for fuchs’ uveitis. j ophthalmic vis res 2021;16:295–299. © 2021 papasavvas et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 295 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9094&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr herpes zoster uveitis with heterochromia in an hiv patient; papasavvas et al disease-defining signs have to be used to confirm or exclude fu. these criteria, all present in >90% of non-operated cases, include vitritis,[4] small stellate keratic precipitates (kps), low aqueous flare values measured by laser flare photometry (lfp, ≤ 20 ph/ms),[5] absence of posterior synechiae, difference of texture of irises between the two eyes, absence of cystoid macular oedema, and hyperfluorescent disc on fluorescein angiography (fa).[6] here, we present a case where iris heterochromia led to falsely diagnosed fu in a case of recurrent zoster uveitis in an immunocompromised patient. case report a 45-year old teacher was referred to our uveitis clinic by his treating eye doctor for a recurrent right granulomatous uveitis. history revealed that he had gone through right herpes zoster ophthalmicus (hz.o) two years prior. at presentation, the patient was under the treatment of 1% prednisolone acetate eye drop, twice daily. uncorrected visual acuity ods was 1.0 on the snellen chart. on the right corneal endothelium, there were rare small randomly distributed stellate kps compatible with fu [figure 1]. the anterior chamber was uninflamed on slit-lamp examination but lfp measured a sub-clinical inflammation of 20.2 ph/ms (normal = 3–6 ph/ms). intraocular pressure was 12 mmhg od and 14 mmhg os. an iris heterochromia was noted with a lighter iris on the right and an altered hyalinized iris surface [figure 2]. there was no sectorial iris atrophy. there were rare cells in the anterior vitreous od. fundus examination as well as retinal and choroidal optical tomography (oct) were normal. we made the diagnosis of fu based on typical kps and heterochromia and stopped the corticosteroid drops. fa performed the following day did not show the disc hyperfluorescence usually seen in fu [figure 3] nor the limited peripheral vascular leakage often present in fu. ten days later, the patient returned with a severe granulomatous uveitis with numerous mutton-fat kps [figure 4] and increase of lfp values to 51.4 ph/ms associated with posterior synechiae [figure 4]. the diagnosis was revised to recurrent zoster uveitis and the patient was treated with valacyclovir 1000 mg tid and 1% prednisolone acetate drops 5× per day. the uveitis responded well to treatment with resolution of the mutton-fat kps and reduction of lfp values to 20.7 ph/ms. however, at each tapering attempt, the uveitis recurred. as we suspected an immune deficiency to varicellazoster virus or a more general immunodepression, we asked the patient to give us his consent to search for hiv infection. hiv serology was positive, and the cd4 lymphocyte count was reduced to 332 cells/mm3. after the two attempts to taper the treatment, we decided to leave the patient under combined systemic antiviral treatment and corticosteroid drops and to wait until the cd4 count would be back to normal after the initiation of antiretroviral therapy. discussion iris heterochromia is still too strongly associated with fu while better disease-defining criteria have been put forward.[6, 7] outside fu, viralrelated iris heterochromia has been described in association with cytomegalovirus[8] and with ebola virus.[9] in a large series of viral anterior uveitis cases with etiologic agents proven by aqueous pcr, iris heterochromia was never detected in varicella-zoster uveitis.[10] although a thorough literature search remained negative, it is not impossible “a priori” that zoster uveitis can produce heterochromia, which was the case in our patient. the differential diagnosis of fu and herpetic anterior uveitis can be easier when large, mutton fat-like kp’s are present, which can exclude fu. in the early stages of herpetic anterior uveitis, mutton-fat kp’s can very rarely be absent, confusing the ophthalmologist. they can also be absent after a period of local corticosteroid treatment, as it happened in our case, which can lead to misdiagnosis. discontinuing the corticosteroid drops and re-examining our patient after 10 days revealed abundant mutton-fat kps, increase of flare and posterior synechiae, features incompatible with fu. once fu was excluded and after two failed attempts to taper antiviral and corticosteroid treatment, we decided to search for an immune deficiency specifically to varicella-zoster virus (vzv) or a more global immunodeficiency. it is known that herpes zoster in patients under the age 296 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 herpes zoster uveitis with heterochromia in an hiv patient; papasavvas et al figure 1. sparse micro-granulomatous kps, seen in magnification (insert) at presentation under the treatment of 1% prednisolone drops bid. figure 2. heterochromia with a lighter-colored iris on the right (top). bottom two pictures show a right discolored iris with an altered hyalinized iris texture (left picture). journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 297 herpes zoster uveitis with heterochromia in an hiv patient; papasavvas et al figure 3. absence of disc hyperfluorescence in the right affected eye on fa in the presented case (top angiographic frames). in comparison, bottom two frames show the typical disc hyperfluorescence seen in fuchs’ uveitis. figure 4. massive mutton-fat kps deposition on the endothelium in the right eye (left picture) after discontinuation of corticosteroid drops and posterior ruptured synechiae (right picture), incompatible with fuchs’ uveitis. 298 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 herpes zoster uveitis with heterochromia in an hiv patient; papasavvas et al of 50 is associated with hiv infection. in patients with a cd4 count from 200 to 349 cells/mm3 which was the case for our patient, herpes zoster is listed as the third most frequent clinical condition (12%) of missed opportunity for earlier diagnosis of hiv infection.[11] another trial showed that herpes zoster was a clinical event in late presenters with hiv infection indicating missed opportunities for earlier diagnosis in 19.8% of the cases.[12] on the other hand, it was shown in a series of 89/581 (14.3%) hiv-positive uveitis patients that the first cause of anterior uveitis was due to vzv amounting to 43%.[13] vzv was shown to persist for much longer in tissues of hiv-positive patients and even that there was a rebound inflammation when anti-retroviral treatment was started.[14, 15] therefore, we left the patient under dual systemic antiviral and topical corticosteroid therapy after introduction of antiretroviral therapy and cd4 count recovery. the ophthalmologist, in presence of vzv pathology in patients under the age of 50, should function as a whistle blower in order not to miss an early diagnostic opportunity for hiv infection. financial support and sponsorship nil. conflicts of interest none. references 1. fuchs e. ueber komplikationen der heterochromie. z augenheilkd 1906;15:191–212. 2. herbort cp, khairallah m. editorial: fuchs uveitis: from imperial vienna to global appraisal. int ophthalmol 2010;30:449–452 3. higuchi m, ohno s, matsuda h. clinical characteristics of fuchs’ heterochromic iridocyclitis. rinsho ganka 1982;36:1275–1280. 4. bouchenaki n, herbort cp. fuchs’ uveitis: failure to associate vitritis and disc hyperfluorescence with the disease is the major factor for misdiagnosis and diagnostic delay. middle east afr j ophthalmol 2009;16:239– 244. 5. guex-crosier y, pittet n, herbort cp. evaluation of laser flare photometry in the appraisal and management of intraocular inflammation in uveitis. ophthalmology 1994;101:728–735. 6. bouchenaki n, herbort cp. fluorescein angiographic findings and clinical features in fuchs’ uveitis. int ophthalmol 2010;30:511–519. 7. tugal-tutkun i, güney-tefekli e, kamaci-duman f, corum i. a cross-sectional and longitudinal study of fuchs’ uveitis syndrome in turkish patients. am j ophthalmol 2009;148:510–515. 8. hedayatfar a, chee sp. posner schlossman syndrome associated with cytomegalovirus infection: a case series from a non-endemic area. int ophthalmol 2014;34:1123– 1129. 9. shantha jg, crozier i, varkey jd, et al. long-term management of panuveitis and iris heterochromia in an ebola survivor. ophthalmology 2016;123:2626–2628. 10. wensing b, relvas lm, caspers le, vidovic valentincic n, stunf s, groot-mijnes jdf, et al. comparison of rubella virus and herpes virus-associated anterior uveitis. ophthalmology 2011;118:1905–1910. 11. nanditha nga, st-jean m, tafessu h, guillemi sa, hull mw, lu m, et al. missed opportunities for earlier diagnosis of hiv in british columbia, canada: e retrospective cohort study. plos one 2019;14:e0214012. 12. van den bogaart l, ranzani a, oreni l, giacomelli a, corbellino m, rusconi s, et al. overlooked cases of hiv infection: an italian tale of missed diagnostic opportunities. eur j intern med 2020;73:30–35. 13. mwanza jc, kayembe dl. uveitis in hiv-infected patients. eur j opthalmol 2001;11:53–56. 14. biswas j, sudharshan s. anterior segment manifestations of human immunodeficiency virus/acquired immune deficiency syndrome. indian j ophthalmol 2008;56:363– 375. 15. martinez e, gatell j, moran y, aznar e, buira e, guelar a, et al. high incidence of herpes zoster in patients with aids soon after therapy with protease inhibitors. clin infect dis 1998;27:1510–1513. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 299 original article longitudinal growth differentiation factor 15 (gdf15) and long-term intraocular pressure fluctuation in glaucoma: a pilot study jonathan b. lin, md, phd1; arsham sheybani, md1; andrea santeford, ms1; rajendra s. apte, md, phd1,2,3 1departments of ophthalmology and vision science, washington university, usa 2departments of developmental biology, washington university, usa 3departments of medicine, washington university, usa abstract purpose: growth differentiation factor 15 (gdf15) was previously identified as a molecular marker of retinal ganglion cell stress in rodent models of glaucoma and was elevated in the aqueous humor (ah) of patients with primary open-angle glaucoma as a possible risk factor for glaucoma progression. the purpose of this study was to determine whether changes in the ah gdf15 levels were associated with intraocular pressure (iop) changes in eyes undergoing glaucoma surgery. methods: here, we performed a prospective, longitudinal pilot study in nine patients to determine whether changes in ah gdf15 levels from surgery to post-surgery follow-up were associated with iop fluctuation. an initial ah sample was taken from the peripheral corneal paracentesis during planned glaucoma surgery, and a second sample was taken during an outpatient follow-up visit, approximately six months later. results: there was a statistically significant correlation between gdf15 fold change and iop standard deviation (r = 0.87, p = 0.003), iop range (r = 0.87, p = 0.003), and maximum iop (r = 0.86, p = 0.003). there was no correlation between the gdf15 fold change and baseline iop (r = 0.50, p = 0.17), final iop (r = 0.038, p = 0.92), or mean iop (r = 0.40, p = 0.28). conclusion: our findings in this pilot study suggest that longitudinal changes in ah gdf15 may be associated with iop fluctuation during the postoperative period. further studies are necessary to corroborate these findings in a larger patient population and to explore the possibility that ah gdf15 may be used not only to improve treatment algorithms but also as a surrogate endpoint in clinical trials. keywords: gdf15; glaucoma; neurodegeneration; molecular markers j ophthalmic vis res 2021; 16 (1): 21–27 correspondence to: rajendra s. apte, md, phd. washington university, 660 south euclid ave., campus box 8096, st. louis, mo 63110, usa. e-mail: apte@wustl.edu received: 17-07-2020 accepted: 16-11-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8245 introduction glaucoma is a neurodegenerative disease characterized by progressive death of retinal this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: lin jb, sheybani a, santeford a, apte rs. longitudinal growth differentiation factor 15 (gdf15) and long-term intraocular pressure fluctuation in glaucoma: a pilot study. j ophthalmic vis res 2021;16:21–27. © 2021 lin et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 21 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8245&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr longitudinal gdf15 and iop fluctuation in glaucoma; lin et al ganglion cells (rgcs). although it is currently the second leading cause of blindness worldwide,[1] the molecular pathogenesis of rgc death remains elusive. therefore, interventions are currently centered on lowering intraocular pressure (iop), a risk factor for disease progression.[2] most clinical decision-making is based upon measuring iop and surrogates of glaucomatous neurodegeneration, such as humphrey visual field, cup-to-disc ratio, and nerve fiber layer thickness. unfortunately, these surrogate metrics are imprecise in their ability to quantify disease severity and, in some cases, are subjective and unreliable. therefore, there is a clinical need for molecular markers that measure rgc health and stress prior to cell death to guide optimal medical and surgical management of glaucoma patients. it was previously reported that growth differentiation factor 15 (gdf15), a member of the transforming growth factor beta (tgf-β) superfamily, is a molecular marker of rgc stress in rodent models of glaucoma.[3] validation studies in well-characterized human patients showed that gdf15 levels not only were elevated in the aqueous humor (ah) of primary open-angle glaucoma (poag) patients compared to control patients without glaucoma but also increased stepwise with increasing visual field loss by hodapp-parrish-anderson staging.[3] however, because of the cross-sectional study design, they were unable to determine whether changes in ah gdf15 levels were associated with iop changes, which have been reported as possible risk factors for progression. to explore this possibility, we performed a prospective, longitudinal pilot study to determine whether changes in ah gdf15 levels over a follow-up period of approximately six months are associated with iop changes in eyes undergoing glaucoma surgery. methods we recruited nine participants from one large academic institution. all patients gave written informed consent. this study was approved by the institutional review board (irb) of the human research protection office (hrpo) of the local ethics committee. all procedures adhered to the tenets of the declaration of helsinki. patients were included if they had any form of glaucoma, including poag or secondary glaucoma, and were determined to be candidates for molteno® glaucoma implant (molteno ophthalmic limited, dunedin, new zealand) or ahmed® glaucoma valve (new world medical, rancho cucamonga, ca) surgery. eyes were excluded if there was active inflammatory eye disease, any retinopathy, or any optic nerve degeneration from non-glaucomatous causes. to determine appropriate sample size, we performed a power analysis using g*power 3.1.9.2.[15] estimating an effect size of r = 0.75 based on previous data, we calculated a sample size of n = 9 to achieve 80% power at a two-tailed alpha of 0.05. two ah samples were obtained from each patient. the first ah sample was obtained in the operating room during planned glaucoma surgery. briefly, a blunt cannula attached to a tuberculin syringe was inserted into the initial peripheral corneal paracentesis and used to remove 50– 100 µl of ah. the second ah sample was obtained during a clinic visit, approximately six months after the initial surgery. briefly, using sterile technique, a needle on a syringe was used to enter the anterior chamber temporally, anterior to the limbus, to gently aspirate ah, with care taken to not deform the anterior chamber. in both cases, ah samples were immediately placed on dry ice and then stored at –80ºc until further analysis. we measured gdf15 levels of all ah samples at the same time using the commercially available human gdf15 quantikine enzyme-linked immunosorbent assay (elisa) kit (r&d systems), as described previously.[3] the individual performing gdf15 measurements (xxx) was masked to demographic and clinical information to minimize bias. demographic information, clinical information, and iop measurements were obtained by retrospective chart review. all iop values were measured by goldmann applanation tonometry, performed by ophthalmologists or optometrists who were masked to the study data. participants had iop measurements taken as a part of routine clinical care at postoperative day 1, postoperative week 1, postoperative month 1, and additional follow-up visits as clinically indicated. the primary variables of interest were measures of iop fluctuation that have been previously reported as risk factors for glaucoma progression, such as iop standard deviation, iop range, and maximum iop. we also analyzed baseline iop (measured at the clinic visit prior to glaucoma surgery), final iop (measured at the same clinic visit during which the 22 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 longitudinal gdf15 and iop fluctuation in glaucoma; lin et al second ah sample was collected), and mean iop over the follow-up period. we performed statistical analysis and data visualization with r version 3.6.2 and rstudio version 1.2.5003. to compare means between two groups, we used the mann–whitney u test due to small sample size. to compare preand post-surgery number of medications, we used the wilcoxon signed-rank test. to determine associations between continuous variables, we calculated pearson product-moment correlation coefficients. because of relatively small sample sizes, we also calculated kendall rank correlation coefficients to confirm our results. we considered p < 0.05 to be statistically significant. results demographic and clinical characteristics of the participants are shown in table 1. there were four male and five female participants. the mean age was 71.0 years (standard deviation: 9.6 years). eight patients had poag, while one patient had glaucoma secondary to presumed herpes simplex uveitis/trabeculitis, which had been inactive for greater than three months. three patients underwent placement of a molteno® glaucoma implant; six patients underwent placement of an ahmed® glaucoma valve. three patients underwent surgery in their left eye; six in the right eye. the mean follow-up duration was 183.4 days (standard deviation: 28.0 days, minimum: 131 days, maximum: 215 days). patients were on significantly fewer classes of medications after surgery compared to before surgery (p = 0.013). there was no significant correlation between baseline ah gdf15 and baseline iop, mean iop, or final iop (p > 0.05). similarly, there was no significant correlation between follow-up ah gdf15 and baseline iop, mean iop, or final iop (p > 0.05). of the nine participants, six had increased ah gdf15 levels over the follow-up interval, while three had decreased ah gdf15 levels at follow-up approximately six months later [figure 1]. all participants had between four to nine iop measurements during the follow-up period [figure 2]. when dichotomizing participants into those who had increased (“gdf15 up”; n = 6) versus decreased (“gdf15 down”; n = 3) ah gdf15 levels, there were no statistically significant differences in the baseline iop, final iop, mean iop, iop standard deviation, iop range, or maximum iop (p > 0.05 by mann–whitney u tests). gdf15 fold change from baseline to follow-up was not correlated with baseline iop, final iop, or mean iop [figures 3a– c]. in contrast, gdf15 fold change was strongly correlated with iop standard deviation, iop range, and maximum iop [figures 3d–f] with statistical significance achieved with both parametric and non-parametric tests. discussion in this prospective, observational pilot study, we analyzed whether changes in ah gdf15 levels from baseline to follow-up at approximately six months were associated with iop fluctuation. our findings suggest that ah gdf15 fold change is indeed associated with iop fluctuation. iop fluctuation that occurs over months to years has been reported as a risk factor for visual field progression in glaucoma in the advanced glaucoma intervention study (agis),[4, 5] the collaborative initial glaucoma treatment study (cigts),[6] and the japanese archive of multicentral databases in glaucoma (jamdig).[7] thus, our findings suggest that increases in ah gdf15 measurements may be associated with increased risk of glaucoma progression. although not all studies have corroborated iop fluctuation as a risk factor for glaucoma progression, kim and caprioli previously hypothesized that this discrepancy may be due to higher mean iop in some study populations that could potentially mask the effect of iop fluctuation.[8] given this possible role of iop fluctuation in glaucoma progression, especially for patients who show progression despite having iops near goal, the ability to use a molecular marker such as gdf15 as a marker of long-term iop fluctuation is highly desirable. routine iop measurements to assess for fluctuation is time-consuming given the need for repeated clinic visits and is rarely performed outside of clinical trials due to demands not only for the clinician but also for patients and their families. home tonometer devices such as the icare® home tonometer (icare usa, raleigh, nc) are available but have uncertain reliability. additionally, devices such as the triggerfish® contact lens sensor (sensimed, lausanne, switzerland) can measure changes in ocular dimensions thought to be related to iop but is typically used for only a 24-hr period and is still experimental, as studies investigating journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 23 longitudinal gdf15 and iop fluctuation in glaucoma; lin et al table 1. demographic and clinical characteristics of study participants characteristic value age, mean ± sd𝑎 71.0 ± 9.6 sex, n𝑏 (%) male 4 (44.4) female 5 (55.6) type of glaucoma, n (%) primary open-angle glaucoma 8 (88.9) glaucoma secondary to inflammation 1 (11.1) type of procedure, n (%) molteno® glaucoma implant 3 (33.3) ahmed® glaucoma valve 6 (66.7) study eye, n (%) os 3 (33.3) od 6 (66.7) pre-surgery medication classes, median (range) 4 (2 – 4) post-surgery medication classes, median (range) 2 (0 – 3)𝑐 𝑎sd: standard deviation; 𝑏n: number of participants; 𝑐there is a significant difference between preand post-surgery number of medication classes by the wilcoxon signed rank test: p = 0.013 � � � � � � � � � � � � � � � � � � 0 500 1000 1500 baseline follow−up a h g d f 1 5 ( p g /m l ) figure 1. of the nine participants, six had increased aqueous humor (ah) growth differentiation factor 15 (gdf15) from baseline to follow-up at approximately six months (shades of red), while three had decreased ah gdf15 (shades of blue). circles denote patients who received the ahmed® glaucoma valve; squares denote patients who received the molteno® glaucoma implant. 24 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 longitudinal gdf15 and iop fluctuation in glaucoma; lin et al � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �� � � � � � � � � � � � � � � � �� � � � � � � � � � � � � � � � � � gdf15 down gdf15 up 0 100 200 0 100 200 10 20 30 40 time (days) io p ( m m h g ) figure 2. serial intraocular pressure measurements by goldmann applanation tonometry for participants whose aqueous humor (ah) growth differentiation factor 15 (gdf15) increased (“gdf15 up”; n = 6; shades of red) and those whose ah gdf15 decreased (“gdf15 down”; n = 3; shades of blue). day 0 was set as the day of glaucoma surgery when the initial ah sample was collected. circles denote patients who received the ahmed® glaucoma valve; squares denote patients who received the molteno® glaucoma implant. their correlation with iop measurements obtained through other validated methods have yielded mixed results.[9] although glaucoma is one of the leading causes of blindness worldwide, identifying reliable molecular markers has been challenging.[10] this lack of molecular markers has led to reliance on surrogate markers of glaucomatous neurodegeneration for clinical decision-making, even though these surrogate markers are imprecise and sometimes unreliable. additionally, there is a great need for novel molecular markers of rgc health that can be used as reliable surrogate endpoints for clinical trials.[11] although further validation is necessary to demonstrate a direct link to glaucoma progression, we propose that ah gdf15 may be a molecular marker of long-term iop fluctuation that may be used in future therapeutic trials. one limitation of the present study is the relatively small sample size. although we achieved the necessary sample size for adequate statistical power, our small sample size does not permit us to control for possible covariates, such as age and gender. another limitation of the study is the heterogeneity of glaucoma subtype and the type of surgery that these patients underwent. we cannot rule out the possibility that differences in the underlying disease pathophysiology or underlying differences of the post-operative iop profiles of the ahmed® glaucoma valve versus the molteno® glaucoma implant may have influenced our findings. future longitudinal studies in larger populations are necessary to address these limitations and may also incorporate functional testing to directly measure glaucoma progression. one strength of our study is that we have a well-characterized patient population for whom we have longitudinal gdf15 measurements. this within-subjects design allowed us to account for inter-individual variability since gdf15 has shown to be elevated in other contexts, such as neurodegenerative and cardiovascular disease.[12, 13] although many groups have explored ah biomarkers for numerous ocular diseases,[14] many of these studies have analyzed samples journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 25 longitudinal gdf15 and iop fluctuation in glaucoma; lin et al � �gdf15 down gdf15 up � � � � � � � � � � � � � � � r=0.50, p=0.17 0 10 20 30 40 0 2 4 6 gdf15 fold change b a s e li n e i o p ( m m h g ) a � � � � � � � � �� � � � � � � � r=0.038, p=0.92 0 10 20 30 40 0 2 4 6 gdf15 fold change f in a l io p ( m m h g ) b � � �� � � � � � �� � � � � r=0.40, p=0.28 0 10 20 30 40 0 2 4 6 gdf15 fold change m e a n i o p ( m m h g ) c � � � � �� � � � � � �� � � � r=0.87, p=0.003 0 5 10 15 20 0 2 4 6 gdf15 fold change io p s tn d d e v ( m m h g ) d � � � � �� � � � � � �� � � � r=0.87, p=0.003 0 10 20 30 40 50 0 2 4 6 gdf15 fold change io p r a n g e ( m m h g ) e � � � � �� � �� � � �� � �� r=0.86, p=0.003 0 20 40 60 0 2 4 6 gdf15 fold change m a x i o p ( m m h g ) f figure 3. aqueous humor growth differentiation factor 15 (gdf15) fold change from baseline to six-month follow-up was not correlated with baseline intraocular pressure (iop; a), final iop (b), or mean iop (c). in contrast, there was a strong correlation between gdf15 fold change and iop standard deviation (stnd dev; d), iop range (e), and maximum (max) iop (f). r = pearson correlation coefficients. similar significance levels were found with non-parametric kendall rank correlation coefficients. shaded regions indicate 95% confidence interval bands. circles denote patients who received the ahmed® glaucoma valve; squares denote patients who received the molteno® glaucoma implant. obtained during cataract or glaucoma surgery. it is important to note that it is possible to collect ah in the outpatient setting. this procedure has minimal risks when performed by an experienced practitioner and was well tolerated by participants in this study. although it is somewhat invasive, we propose that the ability to quantitatively assess rgc health may outweigh any risks associated with such as a procedure. resource availability the data analyzed in this study are available from the corresponding author on reasonable request. financial support and sponsorship none. conflicts of interest there are no conflicts of interest. references 1. quigley ha, broman at. the number of people with glaucoma worldwide in 2010 and 2020. br j ophthalmol 2006;90:262–267. 2. ban n, siegfried cj, apte rs. monitoring neurodegeneration in glaucoma: therapeutic implications. trends mol med 2018;24:7–17. 3. ban n, siegfried cj, lin jb, shui y-b, sein j, pita-thomas w, et al. gdf15 is elevated in mice following retinal ganglion cell death and in glaucoma patients. jci insight 2017;2: e91455. 4. caprioli j, coleman al. intraocular pressure fluctuation a risk factor for visual field progression at low intraocular pressures in the advanced glaucoma intervention study. ophthalmology 2008;115:1123–1129.e3. 5. nouri-mahdavi k, et al. predictive factors for glaucomatous visual field progression in the advanced glaucoma intervention study. ophthalmology 2004;111:1627–1635. 26 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 longitudinal gdf15 and iop fluctuation in glaucoma; lin et al 6. musch dc, et al. intraocular pressure control and longterm visual field loss in the collaborative initial glaucoma treatment study. ophthalmology 2011;118:1766– 1773. 7. fujino y, et al. evaluation of glaucoma progression in large-scale clinical data: the japanese archive of multicentral databases in glaucoma (jamdig). invest ophthalmol vis sci 2016;57:2012–2020. 8. kim jh, caprioli j. intraocular pressure fluctuation: is it important? j ophthalmic vis res 2018;13:170–174. 9. dunbar ge, shen by, aref aa. the sensimed triggerfish contact lens sensor: efficacy, safety, and patient perspectives. clin ophthalmol 2017;11:875–882. 10. bhattacharya sk, lee rk, grus fh, group, the seventh arvo/pfizer ophthalmics research institute conference working group. molecular biomarkers in glaucoma. invest ophthalmol vis sci 2013;54:121. 11. medeiros fa. biomarkers and surrogate endpoints: lessons learned from glaucoma. invest ophthalmol vis sci 2017;58:bio20–bio26. 12. lindholm d, et al. association of multiple biomarkers with risk of all-cause and cause-specific mortality after acute coronary syndromes: a secondary analysis of the plato biomarker study. jama cardiol 2018;3:1160–1166. 13. maetzler w, et al. gdf15/mic1 and mmp9 cerebrospinal fluid levels in parkinson’s disease and lewy body dementia. plos one 2016;11:e0149349. 14. tamhane m, cabrera-ghayouri s, abelian g, viswanath v. review of biomarkers in ocular matrices: challenges and opportunities. pharm res 2019;36:40. 15. faul f, erdfelder e, buchner a, lang a-g. statistical power analyses using g*power 3.1: tests for correlation and regression analyses. behav res methods 2009;41:1149– 1160. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 27 perspective ocular gene therapy with adeno-associated virus vectors: current outlook for patients and researchers geoffrey a. casey1, bs (ee), bs (molbiol); kimberly m. papp2, bs; ian m. macdonald1,3, mdcm 1department of medical genetics, faculty of medicine and dentistry, university of alberta, canada 2faculty of science, university of alberta, canada 3department of ophthalmology, faculty of medicine and dentistry, university of alberta, canada orcid: geoffrey a. casey: https://orcid.org/0000-0001-5012-7147 ian m. macdonald: https://orcid.org/0000-0001-7472-8385 abstract in this “perspective”, we discuss ocular gene therapy – the patient’s perspective, the various strategies of gene replacement and gene editing, the place of adenoassociated virus vectors, routes of delivery to the eye and the remaining question “why does immunity continue to limit efficacy?” through the coordinated efforts of patients, researchers, granting agencies and industry, and after many years of pre-clinical studies, biochemical, cellular, and animal models, we are seeing clinical trials emerge for many previously untreatable heritable ocular disorders. the pathway to therapies has been led by the successful treatment of the rpe65 form of leber congenital amaurosis with luxturnatm. in some cases, immune reactions to the vectors continue to occur, limiting efficacy. the underlying mechanisms of inflammation require further study, and new vectors need to be designed that limit the triggers of immunity. researchers studying ocular gene therapies and clinicians enrolling patients in clinical trials must recognize the current limitations of these therapies to properly manage expectations and avoid disappointment, but we believe that gene therapies are well on their way to successful, widespread utilization to treat heritable ocular disorders. keywords: j ophthalmic vis res 2020; 15 (3): 396–399 introduction patients with hereditary retinal disorders are keenly interested in gene therapy. many recent media presentations feature patients who have experienced apparent benefit from gene therapy correspondence to: ian m. macdonald, mdcm, department of ophthalmology and visual sciences, university of alberta, 7-030 katz bldg. edmonton, alberta t6g2e1, canada. email: macdonal@ualberta.ca received: accepted: access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7457 treatments, increasing public awareness of gene therapy. it is true that gene therapy may conceptually be an ideal method to treat heritable eye diseases before irreparable damage has occurred to the eye, but it is crucially important to manage patient perspectives around their participation in clinical trials. the leading successful example of ocular gene therapy is luxturnatm (voretigene neparvovec-rzyl), an adeno-associated virus (aav) vector treatment this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: casey sa, papp km, macdonald im. ocular gene therapy with adeno-associated virus vectors: current outlook for patients and researchers. j ophthalmic vis res 2020;15:396–399. 396 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7457&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr ocular gene therapy; casey et al for leber congenital amaurosis. luxturnatm is now approved as a treatment in the usa and the european union. unfortunately, many patients believe that enrollment in a clinical trial means “early access” to a treatment or cure, when the trials have not yet reported fully their outcomes. as an example, some patients do not fully understand that luxturnatm is designed to treat a single genetic disorder caused by biallelic pathogenic variants in the rpe65 gene. patients with a progressive heritable eye disease are a distinctly vulnerable population. they may have incomplete knowledge of their condition and partially formed opinions on risks and benefits of experiments such as gene therapy. they carry with them the hope that a trial may lead to treatment but may also conflate the trial with finding a cure. after the patient passes the screening and consent process, they may face significant personal challenges of a rigorous and frequent follow-up schedule. they (or their families) may not be completely prepared for the possibility of harm or the systemic consequences of high-dose immunosuppression. according to the partner of one patient in the choroideremia clinical trial in alberta, “[the prednisone] was the hardest part for me. i was angry and upset and after my husband had to start a second round of it. i was kind of thinking, ‘was this the right thing to do?’[1] careful consideration of the patient’s experience throughout the clinical trial should be considered in the planning stages to avoid miscommunication and psychological harm. gene augmentation vs gene editing gene therapies typically employ a gene augmentation or gene editing strategy. in the case of gene editing, the entities introduced into patient cells (for example, a crispr/cas9 system) are designed to correct the mutation in the endogenous copy (or copies) of the gene. in augmentation gene therapy, the mutated/nonfunctional copies of the gene are ignored, and patient cells are supplemented with a functional copy of the gene.[2] this strategy depends upon sufficiently healthy residual cells being present that can be “rescued” by the therapy. if photoreceptors have already been lost, then alternate approaches must be utilized. in a gene therapy technique called “optogenetics”, non-photoreceptor cells are made photosensitive by expressing channel proteins. a clinical trial of the optogenetic approach is currently recruiting patients with retinitis pigmentosa regardless of the genetic etiology of their condition (clinicaltrials.gov nct03326336). clinical trials of ocular gene therapies to treat several monogenic disorders (choroideremia, xlinked retinoschisis, x-linked retinitis pigmentosa, achromatopsia, and leber hereditary optic neuropathy) are underway across north america. aav is a common choice as a vector for gene delivery. despite initial hope that aav vectors would be minimally immunogenic, preliminary results are available and adverse events have been reported in response to the vectors in some cases. routes of vector administration the route of administration for an ocular gene therapy vector depends on the target cells and the tropism of the vector itself, but will generally fall into one of two categories: intravitreal injection or subretinal injection.[3] wild-type aav vector capsids do not penetrate deeply into the retina when administered intravitreally, but the ability of novel aav capsids (produced via directed evolution) to transduce the posterior cells of the retina is under investigation.[4, 5] an additional barrier to successful transduction of any retinal cells via intravitreal injection is the humoral immune system; intravitreal injection of non-human primates with both the aav2 and aav8 serotypes was found to stimulate production of neutralizing antibodies in subjects with and without preexisting immunity to the serotype.[3, 6] conversely, subretinal injection directly exposes the posterior cells of the retina to the vector and evades humoral immune surveillance; however, the retinal detachment required to create space for vector administration triggers microglial activation and photoreceptor death.[7] the remaining question of immune response the natural triggers of immunity from the viral vectors remain problematic in experimental therapies.[8] in our center, in an investigatorsponsored (phase 1) trial of a subretinally injected aav gene therapy for choroideremia, journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 397 ocular gene therapy; casey et al one subject experienced a serious loss of vision.[9] unfortunately, the disease progressed without apparent benefit in all patients. we now question why this serious adverse event occurred? could it have been prevented by an alternative vector design? why was steroid (given perioperatively) not sufficient to manage inflammation? in our trial, all subjects were treated with high-dose oral steroid (prednisone 1 mg/kg/day 3 days prior to surgery, continuing for 21 days). the steroid was given as a prophylactic to suppress the potential risk to the eye of the subretinal injection. steroid has both local and systemic anti-inflammatory and immunosuppressive effects; briefly, prednisone inhibits neutrophil migration.[10] it decreases mononuclear phagocyte chemotaxis and the production of interleukins and tnf-α. it causes the redistribution of cd4+ and cd8+ t-lymphocytes, and inhibits t-lymphocyte activation, proliferation, and lymphokine production. at high doses, it inhibits immunoglobulin production by blymphocytes. while prophylactic steroids may aid in regulating players of adaptive immunity such as t-lymphocytes and b-lymphocytes, these cells would not occupy retinal tissue unless a severe breach had occurred in the blood– retinal barrier. for the purposes of retinal gene therapy, local innate immune factors are the primary influencers of an inflammatory response and are of therapeutic importance. to illustrate, our choroideremia gene therapy trial utilized a subretinal injection procedure to introduce an aav vector into the retina. retinal detachment induces local tnf-α secretion which in turn may promote autophagy of photoreceptors by resident microglia.[11] even without considering the immunological effects of the viral vector or the diseased microenvironment of the patients’ retinas, the gene therapy procedure itself calls for the incorporation of a local immune regulator to prevent such adverse events. both a diseased microenvironment and retinal detachment from the aav injection “prime” the local immune state to recognize and respond to viral vectors more effectively. aav viruses are dna-based and are thus recognized by toll-like receptor 9 (tlr9). tlr9 stimulation in retinal pigment epithelial cells (rpe) by cpg-dna induces secretion of the pro-inflammatory cytokine il-8, which represents the initiation of an inflammatory cascade.[12] preventing this tlr9-initiated inflammatory cascade is essential when designing an immunity regulator in aav-based retinal gene therapy. our team is investigating a modified aav vector that blocks the dimerization and immune signaling of tlr9. should this vector be effective in preventing rpe from releasing pro-inflammatory cytokines in response to aav treatment, we will move from cell culture models to animal models to confirm safety of the vector before attempting a second choroideremia gene therapy clinical trial. experimental vector gene therapies for hereditary ocular disorders will continue to improve, gain popular exposure, and march toward regulatory approval. a better understanding of the impacts of innate immunity in the retina will improve the safety profile of these therapies and improve the probability of positive outcomes for patients. financial support and sponsorship alberta innovates health solutions, canadian institutes of health research, fighting blindness canada. conflicts of interest there are no conflicts of interest. references 1. brooks s, benjaminy s, bubela t. participant perspectives on phase i/ii ocular gene therapy trial (nct02077361). ophthalmic genet 2019;40:276–281. 2. anguela x, high k. entering the modern era of gene therapy. ann rev med 2019;70:273–288. 3. li q, miller r, han p, pang j, dinculescu a, chiodo v, et al. intraocular route of aav2 vector administration defines humoral immune response and therapeutic potential. mol vis 2008;14:1760–1769. 4. woodard k, liang k, bennett w, samulski r. heparan sulfate binding promotes accumulation of intravitreally delivered adeno-associated viral vectors at the retina for enhanced transduction but weakly influences tropism. j virol 2016;90:9878–9888. 5. kay c, ryals r, aslanidi g, min s, ruan q, sun j, et al. targeting photoreceptors via intravitreal delivery using novel, capsid-mutated aav vectors. plos one 2013;8:e62097. 398 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 ocular gene therapy; casey et al 6. reichel f, peters t, wilhelm b, biel m, ueffing m, wissinger b, et al. humoral immune response after intravitreal but not after subretinal aav8 in primates and patients. invest ophthalmol vis sci 2018;59:1910–1915. 7. nakazawa t, hisatomi t, nakazawa c, kosuke n, marayuma k, she h, et al. monocyte chemoattractant protein 1 mediates retinal detachment-induced photoreceptor apoptosis. pnas 2007;104:2425–2430. 8. xiong w, wu dm, xue y, wang sk, chung mj, x ji, et al. aav cis-regulatory sequences are correlated with ocular toxicity. pnas 2019;116:5785–5794. 9. dimopoulos is, hoang sc, radziwon a, binczyk nm, seabra mc, maclaren re, et al. two-year results after aav2-mediated gene therapy for choroideremia: the alberta experience. am j ophthalmol 2018;193:130–142. 10. nussenblatt r, whitcup s. philosophy, goals, and approaches to medical therapy. in: uveitis. 4th edition. maryland heights, usa: mosby; 2010. 11. xie j, zhu r, peng y, gao w, du j, zhao l, et al. tumour necrosis factor-alpha regulates photoreceptor cell autophagy after retinal detachment. sci rep 2017;7:17108. 12. ebihara n, chen l, tokura t, ushio h, iwatsu m, murakami a. distinct functions between toll-like receptors 3 and 9 in retinal pigment epithelial cells. ophthalmic res 2006;39:155–163. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 399 letter authors’ reply siamak moradian1,2, md; marzieh ebrahimi3, phd; azade kanaani1, md; amir faramarzi2, md; sare safi1, phd 1ophthalmic epidemiology research center, shahid beheshti university of medical sciences, tehran, iran 2ophthalmic research center, shahid beheshti university of medical sciences, tehran, iran 3department of stem cells, cell science research center, royan institute, tehran, iran orcid: siamak moradian: https://orcid.org/0000-0002-5328-7565 j ophthalmic vis res 2021; 16 (1): 147–147 dear editor, we would like to thank dr arjun srirampur for his interest in our work. below please notice our replies: 1. all of our diabetic patients were operated upon due to proliferative diabetic retinopathy (pdr) complications such as non-clearing vitreous hemorrhage and traction retinal detachment but there was no case of rhegmatogenous retinal detachment; therefore no tamponade was used during surgery. 2. none of our patients had uncontrolled iop during the short follow-up period (two weeks) after surgery in both groups. the corneal epithelial defect (ced) was improved in all eyes except three; and in those three eyes, lateral tarsorrhaphy and application of a lubricant ointment resulted in healing of the ced less than one month after surgery. correspondence to: siamak moradian, md. department of ophthalmology, labbafinejad medical center, shahid beheshti university of medical sciences, pasdaran ave., boostan 9 st., tehran 16666, iran. e-mail: moradian33195@yahoo.com access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8265 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: moradian s, ebrahimi m, kanaani a, faramarzi a, safi s. authors’ reply. j ophthalmic vis res 2021;16:147–147. © 2021 moradian et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 147 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8265&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr original article evaluating the ectasia risk score system in cancelled laser in situ keratomileusis candidates mehrdad mohamadpour1, md; masoud khorrami-nejad1,2, ms; mohammad yaser kiarudi1, md keivan khosravi1, md 1translational ophthalmology research center, farabi eye hospital, tehran university of medical sciences, tehran, iran 2school of rehabilitation, shahid beheshti university of medical sciences, tehran, iran orcid: mehrdad mohamadpour: https://orcid.org/0000-0002-9383-6362 abstract purpose: to evaluate the ectasia risk score system in cancelled laser in situ keratomileusis (lasik) candidates at an academic hospital. methods: lasik candidates who had been cancelled by a surgeon considering the patient age, preoperative central corneal thickness, residual stromal bed thickness, or preoperative manifest refraction spherical equivalent were retrospectively reviewed, and their randleman ectasia risk score system score was calculated. results: the mean ectasia score of 194 eyes (97 patients) was 4.5 ± 2.67; 40 (20.6%), 46 (23.7%), and 108 (55.7%) eyes were classified as low-, moderate-, and high-risk eyes, respectively. the topography was abnormal in 69% of the patients. the mean manifest refraction spherical equivalent, central corneal thickness, and estimated residual stromal bed thickness were 4 (+0.50 to –15.50) diopters, 520 (439 to 608) µm, and 312.38 (61.5 to 424.12) µm, respectively. the main cause of cancellation in lowand moderate-risk patients (86 eyes) was the presence of unstable refractive error in the past year. conclusion: although promising, some other criteria, such as stable refraction, should be added to this scoring system to achieve greater practicality since a main cause of cancelling lasik candidates in this study was the presence of unstable refraction. keywords: j ophthalmic vis res 2020; 15 (4): 481–485 introduction ectasia, progressive steepening, and thinning of the cornea are uncommon but serious correspondence to: mehrdad mohammadpour, md. translational ophthalmology research center, farabi eye hospital, tehran university of medical sciences email: mahammadpour@yahoo.com received: 10-06-2019 accepted: 27-07-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7788 complications of excimer laser corneal refractive surgery that reduce uncorrected and often corrected distance visual acuity (cdva). they occur commonly after laser in situ keratomileusis (lasik) and infrequently after photorefractive keratectomy (prk).[1] because of the significant medical and legal consequences this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: mohamadpour m, khorrami-nejad m, kiarudi my, khosravi k. evaluating the ectasia risk score system in cancelled laser in situ keratomileusis candidates. j ophthalmic vis res 2020;15:481–485. © 2020 journal of ophthalmic and vision research | published by knowledge e 481 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7788&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr evaluating the ectasia risk score system; mohamadpour et al of this complication, studies have focused on this issue.[2–9] ectatic changes can occur as early as one week after lasik or be delayed for up to several years after the initial procedure.[10] histologic findings suggest that post-lasik keratectasia results in collagen fibril thinning and a decreased interfibrillar distance within the residual stromal bed (rsb).[11] clinical and topographical findings of ectasia are often indistinguishable from those of keratoconus.[12] to date, no method can definitively diagnose patients with ectasia. a practical task for clinicians is to improve the sensitivity of screening methods for identifying patients with mild keratoconus to prevent iatrogenic keratectasia. randleman et al[1] developed a scoring system to evaluate the risk of ectasia after lasik considering some parameters – such as preoperative topography, rsb thickness, age, preoperative corneal thickness, and degree of myopia – to better identify patients with a high risk for ectasia. they concluded that no single characteristic identifies all at-risk patients. instead, various factors should be considered in a weighted fashion. for all patients, special emphasis should be placed on the topographic pattern, and factors in addition to the inferior–superior value or computer-generated indices should be considered in the screening. for young patients, heightened scrutiny is warranted, and other aspects of their preoperative evaluation, particularly topographic patterns and refractive stability, should be within normal limits. the intraoperative corneal thickness should be measured if the variability of flap thickness is likely to put a patient at risk for ectasia. in the initial series, this scoring system showed a high sensitivity and specificity. subsequently, another study validated it and noted the ectasia risk score system (erss) to be a valid and effective method for detecting the eyes with ectasia after lasik.[13] this study was aimed at retrospectively evaluating the erss score in candidates for refractive surgery who were cancelled by a surgeon. we calculated the risk score of cancelled lasik candidates to evaluate the efficacy of erss for the preoperative screening. methods medical records of candidates for refractive surgery who had been cancelled by a surgeon (mm) at farabi eye hospital, tehran university of medical sciences, tehran, iran, between 2011 and 2015 were reviewed. causes of cancellation of these candidates were based on conventional and individual criteria, such as unstable refraction, defined as an increase in the spherical or cylindrical refractive error >0.5 diopters (d) in the past year, age <9 years, or suspected or abnormal topographical patterns, such as inferior steepening >1.4 d, central corneal thickness <480 µm, rsb <250 µm, or cdva <20/30. the exclusion criteria were a history of refractive or cataract surgery, keratoconus, collagen vascular disease, and diabetic retinopathy. data of all patients, including the age, sex, preoperative manifest refraction spherical equivalent, central corneal thickness, topographic pattern, and predicted rsb thickness were evaluated, and their randleman ectasia risk factor score was calculated. based on the randleman erss, as described previously,[1] a cumulative ectasia risk score was calculated for all patients. central corneal and rsb thicknesses were measured using a pentacam topographer (oculus, wentzler, germany). regarding the cumulative points, risk categories were as follows: 0–2 points, low risk; 3 points, moderate risk; and 4 points, high risk. results a total of 97 patients (194 eyes) were included in this study, with the mean age of 26.4 years (range: 18–50 years). sex distribution was approximately equal (48 women and 49 men). according to the randleman erss for preoperative refractive surgery, 40 (20.6%), 46 (23.7%), and 108 (55.7%) eyes had low-, moderate-, and high-risk scores, respectively. the mean score was 4.5 ± 2.67. the mean manifest refraction spherical equivalent, central corneal thickness, and estimated rsb thickness were 4 (+0.5 to –15.5) d, 520 (439 to 608) µm, and 312.38 (61.5 to 424.12) µm, respectively (table 1). refractive astigmatism ranged from 0.5 to 6.25 d. corneal astigmatism ranged from 0.04 to 4.90 d. internal astigmatism ranged from 0 to 2.25 d. unstable refraction was found in 86 (44.3%) eyes. table 2 shows the topographic characteristics of the patients. the symmetrical (normal) pattern, asymmetrical bow tie, inferior steepening 482 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 evaluating the ectasia risk score system; mohamadpour et al table 1. randleman ectasia risk score system for identifying eyes at high risk of developing ectasia after laser in situ keratomileusis parameter points 4 3 2 1 0 topography abnormal topography inf steep/sra abt normal/sbt rsb (µ) <240 240 to 259 260 to 279 280 to 299 ≥300 age (yrs) 18 to 21 22 to 25 26 to 29 ≥30 ct (µ) <450 451 to 480 481 to 510 ≥510 mrsd (d) >–14 >–12 to –14 >–10 to –12 >–8 to –10 >–8 or less low risk (0–2 points), moderate risk (3 points), high risk (≥4 points) abt, asymmetric bowtie; ct, corneal thickness; d, diopters; inf steep, inferior steepening pattern; mrse, manifest refraction spherical equivalent; rsb, residual stromal bed thickness; sbt, symmetric bowtie; sra, skewed radial axis; yrs, years table 2. characteristics of 97 patients (194 eyes) features mean (range) age (years) 26.44 (18 to 50) gender male female 49 (50.5%) 48 (49.5%) mrse (d) 4 (0.5 to 15.5) cct (µ) 520 (439 to 608) rsb (µ) 312.38 (61.5 to 424.12) cct, central corneal thickness; d, diopters; mrse, manifest refraction spherical equivalent; rsb, residual stromal bed thickness or skewed radial axis, and other abnormal topographic (pellucid) patterns were seen in 65 (33.51%), 87 (44.84%), 39 (20.1%), and 3 (1.54%) eyes, respectively. discussion in our study, a significant number of patients (86 eyes, 43.7%) who were not scheduled for lasik due to unstable refraction in the past year had a low or moderate erss score (1–3). therefore, this method, which is applied for categorizing and assessing the risk of ectasia, should be modified in consideration of unstable refractive errors. reports on erss are incongruent.[13–16] previously, randelman et al stated that this system, which was developed from case reports of ectasia, was more sensitive compared to traditional screening strategies. in a subsequent study, randelman et al validated their risk scoring system by applying it on 50 previously unpublished ectasia cases matched to 50 normal eyes. the sensitivity and specificity of their scoring system for the initial and comparison populations were 91% and 92%, respectively.[13] binder et al[15] retrospectively reviewed a surgeon’s lasik database to assess randleman ectasia risk scores in eyes with normal preoperative topography. risk scores of 5 or more, 4 or more, and 3 or more were found in 35 (2.1%), 92 (5.4%), and 208 (12.2%) eyes with a normal topography, respectively. none of these eyes developed ectasia. in their evaluation, three eyes of two patients in the entire database of 9,813 myopic eyes with variable follow-up periods developed ectasia. they noted that with this risk score system, 5.4% of eyes with 4 or more points would have been eliminated from lasik surgery, and an additional 6.8% of eyes with a score of 3 indicating a “moderate risk” would have required the surgeon to exercise caution. therefore, they concluded that in the eyes with normal preoperative topographies, this scoring system may not accurately predict an increased risk for developing postoperative lasik ectasia. this is consistent with our findings of a significant number of patients at a high risk whom the journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 483 evaluating the ectasia risk score system; mohamadpour et al table 3. topographic patterns of 194 eyes of 97 patients topographic pattern number (percentage) normal/symmetrical 65 (33.51) asymmetric bowtie 87 (44.84) inf steep/sra 39 (20.11) abnormal 3 (1.54) inf steep/sra, topographic pattern with inferior steepening and/or a skewed radial axis surgeon cancelled, while the risk score was low or moderate with erss. chan et al[14] retrospectively evaluated erss in 36 eyes with post-lasik ectasia. a low risk was seen in 25% of eyes. they reported the sensitivity of this method to be only 56% and concluded that erss can miss a significant proportion of patients at risk of ectasia. randleman et al[1] reported that unstable refractions may predict corneal ectasia after refractive surgery. this study suggests that other criteria, such as stable refraction, should be added to this scoring system for increased practicality since a main cause of cancelled lasik candidates in this study was unstable refraction. hodge et al[16] presented a case of unilateral keratectasia in a laser refractive surgery patient. lasik was performed in the first eye, but because of the difficulty in lifting the femtosecond-created cap in the fellow eye, prk was performed in that eye. in their report, the eyes had no risk factors for keratectasia and identical low randleman erss scores. according to them, the procedure of elevating the cap had a weakening effect. consistent with sorkin et al’s study,[17] a highly prevalent risk factor in our study was suspected and abnormal topographic patterns were found in approximately 64% of patients. this is consistent with former reports. nearly 50% of ectasia cases in randleman et al’s study and 69% in chan et al’s study had abnormal topographies. erss relies exclusively on placido-based images. recent topographic systems apply other corneal imaging, including orbscan ii and pentacam imaging. the limitations of erss include starting keratoconus from the posterior portion and the lack of assessment of posterior elevation. another factor not included in our study for erss was unstable refraction. randleman et al[1] considered refractive instability in borderline cases that could increase the risk of ectasia. we defined it as a spherical or cylindrical refractive error >0.5 d in the past year and found it in 86 (44.3%) eyes. this factor may be paramount for an effective refractive surgical screening. dawson et al evaluated the histopathology and ultrastructure of the corneas developing ectasia after lasik or prk and found no significant differences in any of the measurements in the lasik flap or interface wound; however, the ultrastructure of rsb significantly differed between the ectatic and non-ectatic regions. the primary effect of the biomechanical failure process involves the rsb (42% thickness reduction) compared to the lasik flap or hypocellular primitive stromal scar.[18] in this regard, preservation of at least a 250-μm thickness in the central stromal bed after ablation is important for the prevention of ectasia,[19]although the suggested range of minimum rsb varies from 200 to 318 μm.[20, 21] however, keratectasia can occur after lasik with an rsb thickness of >250 μm.[22] in our study, the mean rsb thickness of cancelled patients was 312 μm above the widely accepted 250 μm. moreover, in chan et al’s study, the average rsb was >250 μm.[14] therefore, it cannot be an isolated risk factor. we suggest considering refractive stability as a factor with a significant weight in a modified scoring system for the preoperative screening for ablative refractive surgery. validation of other possible values, such as the degree of astigmatism, between eye topographic asymmetry, and family history of keratoconus should be evaluated. moreover, studies should include a control group comprising the eyes that have undergone lasik at the same interval. in conclusion, randleman erss, although promising, is yet to be validated with a population of ectasia cases and controls. financial support and sponsorship none. 484 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 evaluating the ectasia risk score system; mohamadpour et al conflicts of interest there are no conflicts of interest. references 1. randleman jb, woodward m, lynn mj, stulting rd. risk assessment for ectasia after corneal refractive surgery. ophthalmology 2008;115:37–50. 2. giri p, azar dt. risk profiles of ectasia after keratorefractive surgery. curr opin ophthalmol 2017;28:337–342. 3. comaish if, lawless ma. progressive post-lasik keratectasia: biomechanical instability or chronic disease process? j cataract refract surg 2002;28:2206–2213. 4. kohnen t. iatrogenic keratectasia: current knowledge, current measurements. j cataract refract surg 2002;28:2065–2066. 5. binder ps. analysis of ectasia after laser in situ keratomileusis: risk factors. j cataract refract surg 2007;33:1530–1538. 6. saad a, binder ps, gatinel d. evaluation of the percentage tissue altered as a risk factor for developing post-laser in situ keratomileusis ectasia. j cataract refract surg 2017;43:946–951. 7. randleman jb. post-laser in-situ keratomileusis ectasia: current understanding and future directions. curr opin ophthalmol 2006;17:406–412. 8. belin mw, ambrósio r. analyzing tomographic corneal elevation for detecting ectasia. in: keratoconus. cham, switzerland: springer; 2017:65–75. 9. mohammadpour m. risk for ectasia with lasik. j cataract refract surg 2008;34:181–182. 10. rao sn, epstein rj. early onset keratectasia following laser in situ keratomileusis: case report and literature review. j refract surg 2002;18:177–184. 11. meghpara b, nakamura h, macsai m, sugar j, hidayat a, yue byjt, et al. keratectasia after laser in situ keratomileusis, a histopathologic and immunohistochemical study. arch ophthalmol 2008;126:1655–1663. 12. binder ps. ectasia after laser in situ keratomileusis. j cataract refract surg 2003;29: 2419–2429. 13. randleman jb, trattler wb, stulting rd. validation of the ectasia risk score system for preoperative laser in situ keratomileusis screening. am j ophthalmol 2008;145:813–818. 14. chan cc, hodge c, sutton g. external analysis of the randleman ectasia risk factor score system: a review of 36 cases of post lasik ectasia. clin experiment ophthalmol 2010;38:335–340. 15. binder ps, trattler wb. evaluation of a risk factor scoring system for corneal ectasia after lasik in eyes with normal topography. j refract surg 2010;26:241–250. 16. hodge c, lawless m, sutton g. keratectasia following lasik in a patient with uncomplicated prk in the fellow eye. j cataract refract surg 2011;37:603–607. 17. sorkin n, kaiserman i, domniz y, sela t, munzer g, varssano d. risk assessment for corneal ectasia following photorefractive keratectomy. j ophthalmol 2017;2017:2434830. doi: 10.1155/2017/2434830. 18. dawson dg, randleman jb, grossniklaus he, o’brien tp, dubovy sr, schmacket i, al. corneal ectasia after excimer laser keratorefractive surgery: histopathology, ultrastructure, and pathophysiology. ophthalmology 2008;15:2181–2191. 19. javadi ma, mohammadpour m, rabei hm. keratectasia after lasik but not after prk in one patient. j refract surg 2006;22:817–820. 20. wang z, chen j, yang b. posterior corneal surface topographic changes after laser in situ keratomileusis are related to residual corneal bed thickness. ophthalmology 1999;106:406–409. 21. esquenazi s. comparison of laser in situ keratomileusis and automated lamellar keratoplasty for the treatment of myopia. j refract surg 1997;13:637–643. 22. ou rj, shaw el, glasgow bj. keratectasia after laser in situ keratomileusis (lasik): evaluation of the calculated residual stromal bed thickness. am j ophthalmol 2002;134:771–773. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 485 original article topical interferon alpha 2b in the treatment of refractory diabetic macular edema arash maleki1,2,3, md; andrew phillips stephenson2,4, md; fedra hajizadeh3, md 1massachusetts eye research and surgery institution, waltham, ma, usa 2ocular immunology and uveitis foundation, waltham, ma, usa 3noor ophthalmology research center, noor eye hospital, tehran, iran 4university of cincinnati college of medicine, cincinnati, oh, usa orcid: arash maleki: https://orcid.org/0001-5533-9798 abstract purpose: to report the efficacy of topical interferon alpha 2b in the treatment of refractory diabetic macular edema. methods: in this retrospective interventional case series, five eyes of three individuals with diabetic macular edema resistant to multiple intravitreal injections of anti-vascular endothelial growth factor drugs and macular photocoagulation were included. results: all studied eyes had undergone multiple intravitreal injections including bevacizumab, combination of bevacizumab and triamcinolone and aflibercept, and macular laser photocoagulation before being included in this study. two intravitreal ranibizumab injections had also been performed in both eyes of one patient. two eyes had undergone pars plana vitrectomy, one for diabetic macular edema and the other for rhegmatogenous retinal detachment. after a discussion regarding the experimental topical interferon alpha 2b treatment, all patients agreed to start interferon alpha 2b drops four times a day. one month after the treatment, optical coherence tomography demonstrated a significant improvement in macular structure and thickness which was stable or improved at the three-month follow-up visit. visual acuity in all eyes was stable or improved throughout the three-month follow-up period. conjunctival injection and follicular conjunctivitis were the side effects of topical interferon alpha 2b and were treated with lubrication and steroids. conclusion: this case series demonstrated the potential efficacy of interferon alpha 2b in the treatment of refractory diabetic macular edema. it might be an option in patients with contraindications for intravitreal injections. keywords: diabetic macular edema; interferon α2b j ophthalmic vis res 2020; 15 (4): 453–458 correspondence to: arash maleki, md. massachusetts eye research and surgery institution 1440 main st. ste. 201, waltham, ma, usa. e-mail: arash.maleki01@gmail.com received: 16-11-2019 accepted: 20-07-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7785 introduction diabetic macular edema (dme) is one of the most common causes of visual loss in the working-age this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: maleki a, stephenson ap, hajizadeh f. topical interferon alpha 2b in the treatment of refractory diabetic macular edema. j ophthalmic vis res 2020;15:453–458. © 2020 journal of ophthalmic and vision research | published by knowledge e 453 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7785&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr interferon alpha 2b in dme; maleki et al population and can occur at any stage of diabetic retinopathy.[1] the prevalence of dme in patients with diabetic retinopathy is 2.7–11%, depending on the type and duration of diabetes.[2–6] the development of intraocular anti-vascular endothelial growth factor (anti-vegf) drugs has revolutionized the treatment of dme in recent years and has widely replaced macular laser photocoagulation (mpc); however, the response to anti-vegf therapy can be incomplete in some patients with dme despite multiple injections.[7] both animal and human clinical studies have demonstrated the importance of inflammatory processes in the pathogenesis of dme. various cytokines and chemokines, including il-6, il-8, tumor necrosis factor-alpha (tnf-α), nuclear factor kappa-light-chain-enhancer of activated b cells, protein kinase c, monocyte chemotactic protein, and nitric oxide synthase in addition to vegf are all key components to this pathogenesis.[8, 9] interferons, a large group of glycoproteins, act against vegf and other cytokines such as il-8, il-10, tissue growth factor beta (tgf-β), and tnf-α through inhibiting their production.[10] moreover, they enhance the barrier function of retinal microvasculature leading to a more unassailable retinal structure.[11] interferon alpha has an important role in the treatment of various types of vision-threatening uveitis.[12] recently, topical interferon alpha 2b (inf-α2b) has been successfully employed in the treatment of refractory pseudophakic macular edema.[13] moreover, sub-tenon injection of interferon alpha 2a (inf-α2a) has been effectively utilized in dme.[14] in this case series, topical inf-α2b was investigated for the treatment of refractory dme. methods this study was a retrospective interventional case series. all eyes were resistant to multiple intravitreal anti-vegf injections and mpc. the experimental topical inf-α2b treatment was discussed with the patients and a written informed consent was obtained. our compounding pharmacy prepared the topical drops by adding two milliliter of distilled water to one milliliter of inf-α2b in a three miu vials (3 miu/ml) (pdferon 3 miu, pooyesh pharmaceuticals, tehran, iran). treatment of topical inf-α2b began with the initial regimen of one drop four times per day for the first two or three months based on the investigators’ clinical judgment, including patient’s symptoms, subjective visual improvement, best-corrected visual acuity (bcva) improvement, ocular surface health, patient’s tolerability of the regimen and the improvement in retinal structure and contour compared to the baseline evaluation and optical coherence tomography (oct) findings at the one-month follow-up visit. the drops were then tapered by one drop every two or three months thereafter (table 1). results case 1. a 70-year-old male with a history of type 2 diabetes and hypertension for 16 years presented with severe non-proliferative diabetic retinopathy (npdr) and dme in november 2007. during his follow-up visits from 2007 to 2018, he received multiple intravitreal injections including bevacizumab, combination of bevacizumab and dexamethasone, combination of bevacizumab and triamcinolone, ranibizumab, and aflibercept in both of his eyes. additionally, mpc was employed in both eyes and pars plana vitrectomy was used to treat the dme in his left eye. all of these treatment modalities failed (figure 1a) and his vision decreased to 20/100 and 20/200 from 20/40 and 20/20 in his right and left eye, respectively. after discussing possible treatment options, he agreed to start a topical inf-α2b treatment. during the one-month follow-up visit, his vision improved by one line (to reach 20/80 and 20/100 in the right and left eye, respectively) and oct showed a significant improvement in macular thickness (figure 1b). during the three-month follow-up visit, both the visual acuity and the oct findings were stable (figure 1c). the patient developed follicular conjunctivitis one and a half months after the treatment initiation with the side effects responding to lubricants and low potency steroids. tapering of the study medication began at eight weeks. case 2. a 71-year-old male with a history of type 2 diabetes for 13 years, severe npdr, and dme in his both eyes was presented to us in february 2013. he had undergone cataract surgery in both eyes before presentation and visual acuity was measured at 20/40 in both eyes. for the treatment of dme, he received intravitreal bevacizumab, combination of bevacizumab and 454 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 interferon alpha 2b in dme; maleki et al figure 1. (a) shows the optical coherence tomography (oct) raster horizontal line passing through the center of the macula in right (upper left) and left eye (upper right) before starting topical interferon alpha 2b treatment . (b) and (c) are octs at oneand three-month follow-up visits, respectively, in the right (left picture) and left (right picture) eyes. in this case, tapering of the drop was started at eight weeks. figure 2. (a) demonstrates the optical coherence tomography (oct) before initiating the topical interferon alpha 2b treatment. the upper left and upper right are the horizontal raster of the right eye and vertical raster of the left eye, respectively, following the center of the fovea. (b) and (c) show the oct at oneand three-month follow-up visits. in this case, tapering of the drop was started at eight weeks. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 455 interferon alpha 2b in dme; maleki et al figure 3. (a) the optical coherence tomography (oct) depicts a significant diabetic macular edema before starting the topical interferon alpha 2b in the right eye. (b) the upper picture is the oct at one-month follow-up visit and indicates a significant improvement; however, this improvement is suboptimal. the lower oct picture shows the acceptable response one month later (two months after the treatment). the diagram shows the thickness changes between the oneand two-month follow-up visits. (c) shows the stability of the oct at three-month follow-up visit. in this case, tapering of the drop was started at 12 weeks. triamcinolone, and aflibercept injections in his both eyes. mpc was also utilized in both eyes. during his follow-up visits, he developed rhegmatogenous retinal detachment (rrd) in his left eye and underwent pars plana vitrectomy and silicone oil injection. the silicone oil was removed three months after the primary operation. this individual later developed proliferative diabetic retinopathy (pdr), and panretinal photocoagulation (prp) was implemented for the treatment of pdr in both eyes. as dme was unresponsive to the aforementioned treatment modalities and other options such as ranibizumab and brolucizumab were not available due to his financial concerns, he was started on topical inf-α2b after discussing the risks and benefits of the treatment. before treatment initiation, his visual acuity was 20/100 and 20/80 in the right and left eyes, respectively. figure 2a demonstrates the oct findings before starting the treatment. figures 2b and 2c show the changes in the oct during the oneand three-month followup visits, respectively. at the three-month visit, the visual acuity was 20/100 and 20/60 in the right and left eye, respectively. we started to taper the medication at eight weeks. case 3. a 64-year-old female with type 2 diabetes and hypertension for 18 years was presented to our clinic. at presentation, in june 2010, she was diagnosed with high-risk pdr and dme in both eyes. she was treated with prp. she 456 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 interferon alpha 2b in dme; maleki et al table 1. treatment protocol treatment protocol duration of the treatment four times a day eight to twelve weeks based on the clinical judgment and the optical coherence tomography findings at one-month follow-up visit. three times a day eight weeks two times a day eight weeks one time a day eight weeks one time every other day eight weeks also received multiple intravitreal bevacizumab, combination of bevacizumab and triamcinolone, and aflibercept injections. while the pdr regressed with prp, the dme in her right eye was resistant to all aforementioned injections. mpc was also performed and was unsuccessful in treating the dme in this eye (figure 3a). at this point, her vision was 20/100 in the right eye. she agreed to start topical inf-α2b after discussing all treatment options. during her one-month follow-up visit, impressive improvement was observed in the oct findings (figure 3b). the visual acuity in the right eye improved by one line. both visual acuity and oct findings were stable at the three-month follow-up visit (figure 3c). as the response to treatment was not complete at one month, the initial treatment was continued for three months when the medication was eventually tapered. discussion diabetic macular edema is a major complication of diabetic retinopathy and one of the leading causes of visual impairment in the working-age population.[1] inflammation has an important role in the pathogenesis of diabetic retinopathy and dme. systemic and local inflammatory biomarkers have been proven to have an important role in the development and progression of dme.[15] based on the importance of inflammatory processes in the pathogenesis of dme, systemic low-dose infliximab (tnf-α inhibitor) was employed in the treatment of the late-stage vision-threatening refractory dme with promising results.[16] inf-α might be effective in the treatment of dme due to its opposite effects on tnf-α.[12] this means that an increase in concentration of inf-α in a viable microenvironment can decrease the production and concentration of tnf-α and vice versa. moreover, inf-α has both anti-inflammatory and anti-proliferative properties. it inhibits the production of vegf in addition to il-8 and tnfα, two major local cytokines in the development of dme.[8–12, 14–16] the sub-tenon injection of inf-α2a was demonstrated to be effective in the treatment of refractory dme[14]; however, to the best of our knowledge, topical inf-α2b has not been previously employed in the treatment of dme. despite being a large molecule, its adequate penetration through the sclera and cornea has been demonstrated in previous studies.[13, 14, 17] the safety of topical use of inf-α2b has also been shown in previous studies and no major systemic or local side effects have been reported in the treatment of patients with ocular surface tumors with the same dose.[13] in the three patients in this series, all of the commonly used treatment modalities either failed due to ineffectiveness or were too expensive for the patients. these patients were finally started on topical inf-α2b four times a day with the anticipation that based on the importance of inflammatory processes in the development and progression of dme, this treatment would be effective. the treatment plan was continued for eight to twelve weeks based on the clinical judgment and oct findings. the treatment dose was tapered by one drop every eight weeks based upon established ocular inflammatory disease therapies and our successful experience of employing topical inf-α2b in the treatment of refractory cystoid macular edema (cme).[13] in these presented cases, topical inf-α2b was started when the effects of previous therapies such as intravitreal injections and mpc were proven futile and the patients needed further intervention. comparison of oct findings before and one-month after the treatment demonstrated an impressive improvement in macular structures and thickness in all cases. these findings were stable or improved journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 457 interferon alpha 2b in dme; maleki et al at the three-month follow-up visit. conjunctival injection and follicular conjunctivitis were the observed side effects and were treated with lubricants and low potency steroids. in conclusion, this case series demonstrates the effectiveness of topical interferon-α2b in the treatment of selected cases of refractory dme. this therapy might also be an option in selected patients who develop complications after intravitreal injections or in patients who have contraindications to intravitreal injections. however, more robust studies such as randomized clinical trials are required to support our findings. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. browning dj, stewart mw, lee c. diabetic macular edema: evidence-based management. indian j ophthalmol 2018;66:1736–1750. 2. xie xw, xu l, wang yx, jonas jb. prevalence and associated factors of diabetic retinopathy. the beijing eye study 2006. graefes arch clin exp ophthalmol 2008;246:1519–1526. 3. rubino a, rousculp md, davis k, wang j, girach a. diagnosed diabetic retinopathy in france, italy, spain, and the united kingdom. prim care diabetes 2007;1:75–80. 4. wong ty, klein r, islam fm, cotch mf, folsom ar, klein be, et al. diabetic retinopathy in a multi-ethnic cohort in the united states. am j ophthalmol 2006;141:446–455. 5. varma r, torres m, peña f, klein r, azen sp, los angeles latino eye study group. prevalence of diabetic retinopathy in adult latinos: the los angeles latino eye study. ophthalmology 2004;111:1298–1306. 6. yau jw, rogers sl, kawasaki r, lamoureux el, kowalski jw, bek t, et al. global prevalence and major risk factors of diabetic retinopathy. diabetes care 2012;35:556–564. 7. urias ea, urias ga, monickaraj f, mcguire p, das a. novel therapeutic targets in diabetic macular edema: beyond vegf. vision res 2017;139:221–227. 8. adamis ap, berman aj. immunological mechanisms in the pathogenesis of diabetic retinopathy. semin immunopathol 2008;30:65–84. 9. moisseiev e, loewenstein a. diabetic macular edema: emerging strategies and treatment algorithms. dev ophthalmol 2017;60:165–174. 10. george pm, badiger r, alazawi w, foster gr, mitchel ja. pharmacology and therapeutic potential of interferons. pharmacol ther 2012;135:44–53. 11. gillies mc, su t. interferon-alpha 2b enhances barrier function of bovine retinal microvascular endothelium in vitro. microvasc res 1995;49:277–288. 12. maleki a, meese h, sahawneh h, foster cs. prognosis in the understanding and utilization of biologic response modifiers in the treatment of uveitis. expert rev clin immunol 2016;12:775–786. 13. maleki a, aghaei h, lee s. topical interferon alpha 2b in the treatment of refractory pseudophakic cystoid macular edema. am j ophthalmol case rep 2018;10:203–205. 14. cellini m, balducci n, strobbe e, campos ec. subtenon injection of natural leukocyte interferon α-2a in diabetic macular edema: a case report. bmc ophthalmol 2013;13:63. 15. vujosevic s, simó r. local and systemic inflammatory biomarkers of diabetic retinopathy: an integrative approach. invest ophthalmol vis sci 2017;58:bio68– bio75. 16. sfikakis pp, grigoropoulos v, emfietzoglou i, theodossiadis g, tentolouris n, delicha e, et al. infliximab for diabetic macular edema refractory to laser photocoagulation: a randomized, double-blind, placebo-controlled, crossover, 32-week study. diabetes care 2010;33:1523–1528. 17. lincoff h, stanga p, movshovich a, palleroni a, madjarov b, rivera r, et al. choroidal concentration of interferon after retrobulber injection. invest ophthalmol vis sci 1996;37:2768–2771. 458 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 original article treatment of noninfectious retinal vasculitis using subcutaneous repository corticotropin injection stephen d. anesi, md1,2; peter y. chang, md1,2; arash maleki, md1,2; andrew stephenson, bs1,2 alyssa montieth, bs1,2; artur filipowicz, do1,2; sarah syeda, md1,2; soheila asgari, phd3 marisa walsh, bs1,2; jamie lynne metzinger, ms, mph1,2; c. stephen foster, md1,2,4 1massachusetts eye research and surgery institution, waltham, ma, united states 2the ocular immunology and uveitis foundation, waltham, ma, united states 3noor ophthalmology research center, noor eye hospital, tehran, iran 4harvard medical school, department of ophthalmology, boston, ma, united states orcid: stephen d. anesi: http://orcid.org/0000-0003-2141-0431 c. stephen foster: http://orcid.org/0000-0003-4760-8390 abstract purpose: to show whether subcutaneous repository corticotropin injection (rci, acthar® gel, a repository corticotropin injection, can be an effective potential therapeutic agent for noninfectious retinal vasculitis. methods: patients with active retinal vasculitis were followed with serial ultra-widefield fluorescein angiograms and treated with 80 units of subcutaneous repository corticotropin injection twice weekly. results: primary outcome of ≥50% improvement in response level (rl) for retinal vasculitis and percent improvement in retinal vasculitis severity scoring (rvss) by more than one quartile (≥25%) at week 12 was met in 15 and 16 of the 30 total eyes, respectively, including 1 eye with severe retinal vasculitis in each group. complete resolution of retinal vasculitis was seen in seven eyes with a mean time of 17.1 weeks. intraocular pressure elevation requiring therapy and cataract progression were noted in two and three eyes, respectively. one patient stopped medication due to side effects (injection site reaction). conclusion: repository corticotropin injection was well-tolerated overall. repository corticotropin injection may be an effective therapeutic agent in the treatment of noninfectious retinal vasculitis. keywords: acthar; corticotropin gel; fluorescein angiography; ocular inflammation; retinal vasculitis; uveitis j ophthalmic vis res 2021; 16 (2): 219–233 correspondence to: c. stephen foster, md. massachusetts eye research and surgery institution 1440 main st. ste. 201, waltham, ma, usa. e-mail: sfoster@mersi.com received: 15-03-2019 accepted: 01-02-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9086 introduction retinal vasculitis (rv) represents a group of sight-threatening and typically stubborn forms this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: anesi sd, chang py, maleki a, stephenson a, montieth a, filipowicz a, syeda s, asgari s, walsh m, metzinger jl, foster cs. treatment of noninfectious retinal vasculitis using subcutaneous repository corticotropin injection. j ophthalmic vis res 2021;16:219–233. © 2021 anesi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 219 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9086&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr treatment of retinal vasculitis with rci; anesi et al of ocular inflammation which may affect retinal arteries, veins, or capillaries. it can be potentially detrimental to vision by way of occlusive or nonocclusive mechanisms, leading to secondary unilateral or bilateral findings of retinal ischemia, macular edema, neovascular changes, retinal detachment, vitreous hemorrhage, and secondary glaucoma.[1, 2] noninfectious rv may present alone or as a manifestation of or an association with a wide variety of other ocular inflammatory diseases like idiopathic intermediate, posterior, and panuveitis or even potentially severe systemic conditions such as sarcoidosis and adamantiadesbehçet’s disease.[1, 3] the anatomy of the eye is such that examination allows for direct visualization of retinal vasculature, allowing one to observe and perform imaging of in vivo vascular structures during the course of active disease as well as response to employed therapeutic measures. findings suggesting rv include directly visible measures such as retinal sheathing, overlying inflammatory exudates, segmental vascular narrowing, as well as secondary signals of ischemia such as cotton wool spots and intraretinal hemorrhages. sometimes, however, this inflammation is not detectable via ophthalmoscopy alone. fluorescein angiography (fa) has long been the gold standard for imaging and evaluation of rv and other related entities. the availability of ultra-wide-field fluorescein angiography (uwfa) now allows greatly improved visibility and recognition of pathology involving the retina and retinal vasculature, particularly in the peripheral retina, and may also allow for imaging through a small pupillary aperture.[4, 5] recommended therapeutic options for sightthreatening noninfectious uveitis, as well as rv, generally include anti-inflammatory regimens involving corticosteroids in the short term followed by steroid-sparing therapy utilizing immunosuppressive medications, including chemotherapeutic (disease-modifying antirheumatic drugs or dmards) or biologic agents.[2, 6–8] novel means of addressing severe or recalcitrant ocular inflammation have been studied to give providers more options to choose from when trying to reduce or eradicate inflammation without relying on systemic corticosteroids. target molecules of more recently renewed interest include melanocortin peptides such as adrenocorticotropic hormone (acth), a key part of the signaling involved in the hypothalamic– pituitary–adrenal axis, and its cleavage product alpha-melanocyte stimulating hormone (α-msh). acth is thought to help suppress inflammation in part by a “steroid-dependent” mechanism by causing upregulation of the endogenous glucocorticoid in the adrenal cortices.[9, 10] other melanocortin, such as α-msh, bind to and activate separate melanocortin receptors (mcrs) from acth, and have also been shown to be instrumental in immune regulation in ocular inflammatory diseases via a separate “steroidindependent” mechanism.[11, 12] α-msh has long been known to contribute to ocular immune regulatory mechanisms and immune privilege.[13] in vitro studies have shown that α-msh may suppress both the innate and adaptive immune response, and can induce the conversion of effector t-lymphocytes into regulatory t-cells (tregs) which both suppress interferon-gamma (ifn-γ) production and produce transforming growth factor-beta (tgf-β).[14, 15] there are five known human mcrs, one of which (mcr2) exclusively binds acth and is responsible for cortisol production. the other mcrs (mcr1, mcr35) strongly bind α-msh (and to a lesser degree βand γ-msh) in various cells throughout the body including several located in ocular tissues, notably retina and retinal pigment epithelium, as well as various leukocytes involved in both innate and adaptive immunity.[16] repository corticotropin injection (rci, acthar® gel) is a naturally sourced complex mixture of adrenocorticotropic hormone analogs and other pituitary peptides. a major component in the formulated complex mixture is n-25 deamidated porcine acth (1-39). per the label, the major component is n-25 deamidated acth. if needed, you may further expand the description with the following: “the acthar gel manufacturing process converts the initial porcine pituitary extract with low acth content into a mixture having modified porcine acth and other related peptide analogs solubilized in gelatin. a major component in the formulated complex mixture is n-25 deamidated porcine acth (1-39). rci is known to bind to and activate all five mcrs in humans. it has an indication for and has been used to treat several systemic immune-mediated diseases including rheumatoid arthritis, systemic lupus erythematosus, sarcoidosis, and multiple sclerosis, and also has an fda indication for 220 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 treatment of retinal vasculitis with rci; anesi et al treating severe acute and chronic allergic and inflammatory processes involving the eye and its adnexa. because of its unique mechanism, rci represents a novel approach to treating ocular inflammatory disease, including disease that may be refractory to other forms of therapy. more recent data, unfortunately, on the use of rci in treating ocular inflammation is currently limited only to case reports. the purpose of this study is to further evaluate the possible effectiveness of rci in treating patients with retinal vasculitis who may either be treatment naïve or who have failed other forms of therapy. it is the hypothesis of the authors that use of rci in these patients may lead to improvement in markers of inflammatory activity on examination and imaging, and potentially to resolution of active inflammation altogether. methods study setting and patient population this was a prospective, nonrandomized, openlabel, proof-of-concept study conducted at a single, tertiary care uveitis center. patients with active retinal vasculitis as a manifestation of noninfectious ocular inflammatory disease were identified during routine follow-up care and invited to participate. the inclusion criteria for the study were: adult patients aged ≥18 years with active retinal vasculitis (involving arteries, capillaries, or veins) with a visible fundus via wide-field fa in the study eye and willingness to participate. the exclusion criteria included: patients who were currently pregnant; active infectious ocular, extraocular, and/or systemic disease; history of malignancy (with the exception of dermatologic entities of basal or squamous cell carcinoma which have been excised); systemic illness involving abnormalities of the hypothalamic– pituitary–adrenal axis; primary adrenocortical insufficiency or adrenocortical hyperfunction; known hypersensitivity to study drug and/or diagnostic tools; other severe disease that warrants critical attention and renders patients unable to participate in the study; retinal disease that may confound or obfuscate findings of retinal vasculitis (i.e., retinal vascular occlusion, significant diabetic retinopathy), and no visible fundus on dilated fundoscopy. patients were not enrolled if they had been treated with any oral, periocular, or intraocular suspension of corticosteroid within six weeks prior to the study; any intraocular dexamethasone corticosteroid implant within six months prior to the study; or any long-lasting fluocinolone corticosteroid implant within three years prior to the study. additionally, patients already prescribed and adherent to nonsteroidal immunosuppressive therapy continued their regimens throughout the study, but no modification of dose (increase or decrease) was permitted within six weeks of initiating the trial and throughout the duration of the treatment and follow-up periods. exceptions for changes in concomitant medications were only made for any patient that was deemed in need of rescue therapy by the investigator at any time during the study because of continued significant active disease despite study medication use, or if there was deemed poor tolerance of the medication and the patient required additional therapy to help control inflammation – these patients were then excluded from further analysis of clinical response of ocular inflammation to rci. safety data were extracted from all patients who had at least one follow-up visit after starting medication. the per protocol population (ppp) was defined by eyes of patients who were able to participate in the study without deviation from protocol for any portion of the study after the initial visit, and data extracted from the ppp was only utilized from visits for which strict adherence to the study protocol was maintained without deviation. deviations from study protocol included introduction of additional anti-inflammatory or immunomodulatory therapy, stoppage of the study medication, or any other reason for which the participant was no longer deemed appropriate by the investigator to include in the study prior to study completion. institutional review board approval was obtained prior to the initiation of the study. the study was conducted in accordance with the declaration of helsinki and adhered to good clinical practice guidelines. the clinical trial was registered and can be found at clinicaltrials.gov identifier: nct03066869. each subject signed an informed consent before participating in the study. definition of response level response level (rl) was defined at each visit as predefined percentage changes in retinal vasculitis journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 221 treatment of retinal vasculitis with rci; anesi et al activity versus baseline activity at the initial visit, with positive rl values indicating a reduced level of activity or a positive response while on therapy, and negative rl values indicating an increased level of activity or a negative response while on therapy. active retinal vasculitis status was defined as angiographic leakage on wide-field fa from retinal arteries, capillaries, or veins, as determined by one of the three investigators at the time of baseline and subsequent visits. rl scores used in data collection were determined after study completion by two of the investigators (sda and pyc) independently assessing imaging without referencing other clinical data from the visits. rls were graded in steps of either 0, 12.5 (1–12.5), 25 (13–25), 50 (26–50), 75 (51–75), or 100 (76–100) percent for improvement; if worsening occurred, the same was done with a negative score given. scores were later compared for possible discrepancy in grading, and if any were found, an acceptable score was then agreed upon by both investigators by utilizing the historical clinical impression of the investigator at the time of each visit. retinal vasculitis severity scoring to describe rv severity, retinal vasculitis severity scoring (rvss) was performed at the baseline, week-12, and week-24 visits. the scoring system was based on five sections, including an area 2.5 to 3 disc diameters surrounding the fovea incorporating the temporal arcades designated as the macula, and then diagonal separation of the superior, nasal, inferior, and temporal peripheral quadrants outside the arcades. each section received a score of 0 to 3 based on the severity of leakage in the late angiographic phase (venous phase). macular scoring was based on small vessel or capillary leakage in macular quadrants: 0 for no leakage, 1 for one quadrant, 2 for two to three quadrants, and 3 for all four quadrants. peripheral quadrant leakage was scored thusly: 0 for no leakage, 1 for staining of vessels with minimal leakage, 2 for more leakage with distinct vascular margins, and 3 for more leakage obscuring the vessel margins. total score initially of 1 to 15 was possible, and scoring was tabulated with retinal vasculitis severity score given as thus: mild for score 1 to 5, moderate for 5.5 to 10, and severe for 10.5 to 15. this scoring was applied by two investigators (sda and pyc) independently assessing imaging without referencing other clinical data from the visits separately from the assessment of rl. these values were then averaged for a final score at each time point. baseline-visit measurements were used in the initial description of retinal vasculitis severity. for comparison to the rl scoring previously described, the week 12 and week 24 rvss were individually divided by the baseline rvss, and these numbers were then subtracted from 1 and multiplied by 100 to give an rvss percent improvement (or worsening if negative) in each subject from baseline. of note, no worsening above a score of 15 was possible, limiting this method in this direction, however, this problem was not encountered. data collection patients were seen at baseline, as well as subsequent visits occurring at weeks 2, 4, 8, 12, and 24 after initiation of rci, with unscheduled visits permissible if necessary. study medication for all patients was started within two weeks following the baseline visit. data collected included best-corrected visual acuity (bcva), intraocular pressure, slit lamp biomicroscopy findings, dilated fundus examination, wide-field fa, weight, vital signs (blood pressure and heart rate), and laboratory assessments. macular imaging via spectral domain optical coherence tomography (oct) was obtained per investigator initiative. biomicroscopic findings included anterior chamber (ac) cell and flare as well as vitreous cell and haze as scored per sun criteria.[17] all assessments were repeated at each visit after baseline, apart from laboratory assessments, which were carried out at weeks 4, 12, and 24 only to assess for potential toxicity to medication. wfa was performed for the study eye. fundus photography, red-free photographs, and fundus autofluorescence were all completed prior to intravenous injection of fluorescein dye. photographs were taken immediately at dye injection, then every 10 s in the study eye followed by alternate eye, for up to 30 s. subsequently, photographs were captured every 30 s in the study eye, followed by the fellow eye for up to 2 min following the dye injection, then once per minute in the study eye, followed by the fellow eye for up to 7 min following the dye injection. 222 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 treatment of retinal vasculitis with rci; anesi et al oct was performed at initial assessment visit for most patients and then as needed; central macular thickness (cmt) was reported for patients if available. study outcome measures the primary outcome measure was the percentage of ppp eyes that improved during the study: (1) eyes that had ≥50% improvement by definition in rl by the week-12 visit or (2) eyes with rvss that improved by more than one quartile (>25%) by week 12. secondary outcomes included numeric rvss at baseline, week 12, and week 24. other secondary outcomes were vision, intraocular pressure, ac cell and flare, vitreous cell and haze, weight, blood pressure, and heart rate. cmt was collected via oct for most patients, and follow-up oct was obtained for patients with cystoid macular edema, which was defined as baseline cmt of 300 or more or demonstrable intraretinal fluid. safety assessments, including drug tolerability, adverse events, and all other ocular and/or systemic complications were also evaluated. side effects of rci and reasons for therapy discontinuation were gathered. treatment protocol rci was initiated at 80 units given subcutaneously twice weekly after the baseline visit. any changes made in the treatment regimen during the study resulted in the patient and eye(s) to no longer be included in the ppp at any subsequent visits. patients who did not show clinical or objective evidence on the assessment of improvement while taking therapy were rescued at 12 weeks; patients who showed worsening or concern for their condition prior to 12 weeks were also rescued with appropriate therapy at the discretion of the investigator. participants that were rescued were also followed through 24 weeks. statistical analysis categorical variables were described as counts and percentages. continuous variables were described as means, standard deviations, and ranges. statistical analysis was performed with r statistical package (version: 3.5.2). categorical variables were compared at each follow-up visit with the one before except the baseline and two weeks using chi-square and fisher’s exact test. qq plot was used to examine the normal distribution of quantitative variables. linear random mixed model was used to show the 24-week trends. in the analyses, the correlation between two eyes and the follow-up times (12and 24 week) were examined in an unstructured correlation matrix. the repeated measures analysis of variance was used to determine 24-week change of weight, hr, systolic and diastolic pressures. the eye was the unit of all calculations except for demographics and systemic side effects, where the patient was the unit of calculations. p-value ≤ 0.05 was considered significant. results twenty patients were originally recruited for the study. one patient did not return after the first visit and was thus excluded from any analysis. another patient (one eye) was excluded because of shallow peripheral retinal detachment. thirty-one eyes in 19 patients were followed until at least the second visit. table 1 lists a summary of patients’ demographic information. the mean length of time with known diagnosis of retinal vasculitis prior to screening was 5.8 ± 3.93 years (range, 0 to 13). then mean time since the onset of symptoms for current active inflammation was 2.0 ± 2.31 months (range, 0 to 7); 9 of 19 patients (47.4%) had idiopathic disease and 10 had an associated systemic disorder; 3 (15.8%) had hla-b27-associated uveitis, 2 (10.5%) had multiple sclerosis, and 5 (26.3%) had sarcoidosis [table 1]. at the time of screening, 8 of the 19 patients (42.1%) were already on some form of systemic anti-inflammatory or immunosuppressive therapy – these medications included mycophenolate mofetil, cyclosporine, interferon beta-1a, methotrexate, adalimumab, infliximab, sulfasalazine, and ibuprofen. table 2 demonstrates the comorbidities and/or complications of inflammation in 19 patients at the time of screening. table 2 presents the uveitis and characteristics of retinal vasculitis. examples of responses of rv in various ppp eyes at weeks 12 and 24 are shown in figure 1. furthermore, 30 eyes of 18 patients with active rv were included in the ppp. fourteen journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 223 treatment of retinal vasculitis with rci; anesi et al table 1. demographics – characteristics and baseline details patient demographics patients enrolled 20 patients with ≥1 follow-up (patients [eyes]) 19 [31] patients followed per protocol (patients [eyes]) 18 [30] mean age (yr) 43.0 sex, n (%) female 17 (89.5) male 2 (10.5) race, n (%) caucasian 16 (84.2) hispanic or latin 2 (10.5) south asian 1 (5.3) patients with uveitis, n (%) 18 (94.7) uveitis diagnosis, n (%) anterior 2 (10.5) intermediate 3 (15.8) posterior 1 (5.3) panuveitis 12 (63.2) mean time with uveitis prior to the study (yr) 5.8± 3.93 mean time with active symptoms prior to the study (months) 2.0± 2.31 patients with idiopathic disease, n (%) 9 (47.4) patients with systemic association, n (%) 10 (52.7) hla-b27 3 (15.8) multiple sclerosis 2 (10.5) sarcoidosis 5 (26.3) patients on systemic anti-inflammatory medication, n (%) 8 (42.1) table 2. comorbidities and complications of inflammation complications number (%) cataract 10 (52.6%) pseudophakia 3 (15.8%) glaucoma/ocular hypertension 6 (31.6%) cystoid macular edema 6 (31.6%) epiretinal membrane 2 (10.5%) peripheral retinal ischemia 1 (5.3%) papillitis 3 (15.8%) of the eighteen patients (23 of the 30 eyes [76.7%]) were able to continue rci in the ppp through 12 weeks. nine of the eighteen patients (14 of the 30 eyes [46.7%]) were then able to continue rci through the entirety of the 24 weeks of the study without change in protocol. nine eyes (30.0%) did not continue in the ppp past week 12 – three patients (five eyes) due to ineffectiveness, one (two eyes) due to noncompliance, and one (two eyes) due 224 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 treatment of retinal vasculitis with rci; anesi et al table 3. characteristics of retinal vasculitis and uveitis characteristics of retinal vasculitis eyes (n = 31) total vasculature involvement, n (%) veins 31 (100) capillaries 19 (63.2) arteries 1 (3.2) retinal vasculitis (rv), n (%) mild 15 (48.4) moderate 10 (32.3) severe 6 (19.4) quadrants involved, n (%) 1 4 (12.9) 2 6 (19.4) 3 8 (25.8) 4 13 (42.9) mean number of quadrants involved 2.97 types of uveitis total patients (n = 19) anterior uveitis 2 (10.5) intermediate uveitis 1 (5.3) posterior uveitis 2 (10.5) panuveitis 3 (15.8) rv, retinal vasculitis this was changed to retinal vasculitis (rv) table 4. changes in retinal vasculitis scoring system (rvss) and response level (rl) from baseline to week 12 and week 24. p-value was < 0.001 for the 24-week change of study indices by repeated measures analysis of variance without applying correlation between fellow eyes, as well as comparison of baseline and week 12, baseline and week 24, and weeks 12 and 24 with applying correlation between fellow eyes. baseline week 12 week 24 rvss1 6.92 ± 3.83 5.19 ± 4.67 3.81 ± 4.68 rl2 (os)3 (%) 0.00 ± 0.00 37.72 ± 31.50 61.06 ± 34.76 rl2 (ss)4 (%) 0.00 ± 0.00 59.82 ± 34.73 74.11 ± 34.13 1retinal vasculitis scoring system; 2response level; 3objective scoring; 4subjective scoring table 5. other ocular parameters screening 12 weeks 24 weeks p-value* bcva (logmar) 0.28 ± 0.22 0.22 ± 0.22 0.18 ± 0.22 <<<0.001 iop (mmhg) 14.36 ± 4.48 14.64 ± 4.09 13.64 ± 4.95 <<<0.001 ac cell 0.57 ± 0.92 0.00 ± 0.00 0.07 ± 0.18 0.264 ac flare 0.00 ± 0.00 0.36 ± 0.74 0.14 ± 0.36 nd vitreous cell 0.04 ± 0.13 0.14 ± 0.23 0.11 ± 0.21 <<<0.001 vitreous haze 0.25 ± 0.67 0.00 ± 0.00 0.29 ± 0.47 0.998 bcva, best-corrected visual acuity; iop, intraocular pressure; ac, anterior chamber; logmar, logarithm of the minimum angle of resolution journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 225 treatment of retinal vasculitis with rci; anesi et al figure 1. fluorescein angiography of per protocol study eyes (a–f) demonstrating changes in retinal vasculitis and generalized inflammation from week 0 (baseline) to week 12 to week 24. of note, varying levels of improvement were seen, from mild to moderate to complete resolution by week 24. to side effects as well as needing additional treatment. therapeutic response – retinal vasculitis the primary outcome of improvement in rl of at least 50% or more [figure 2], or improvement in rvss to at least the second quartile or more at week 12 [figure 3] was seen in 15 and 16 of 30 total eyes, respectively (50.0% and 53.3%), and of the 23 eyes that were followed on the study protocol without deviation to week 12, respectively (65.2% and 69.6%). changes in rvss, % improvement via rvss, and rl between baseline and week 12, between weeks 12 and 24, and between baseline and week 24 were statistically significant (p < 0.001) [table 4]. of the 15 who improved in rl to 50% by week 12, 7 were classified as having mild rv, 7 moderate, and 1 severe. of the 16 who improved in rvss to the second quartile or more by week 12, 8 were classified as having mild, 7 moderate, and 1 severe rv. of all 30 ppp eyes, the number of eyes followed in the study without deviation in protocol included 30 at week 2, 28 at week 4, 26 at week 8, 23 at week 12, and 14 at week 24. the mean rl and rvss along with percent improvement 226 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 treatment of retinal vasculitis with rci; anesi et al figure 2. comparison of response level (rl) between objective retinal vasculitis scoring system (a) and subjective retinal vasculitis scoring system (b). figure 3. mean rl for ppp eyes at each study visit after baseline. in rvss for ppp eyes at baseline, weeks 12 and 24 are shown in figure 4. time to any improvement and time to 50% improvement in rl in the total ppp eyes are demonstrated in figure 5. moreover, 7 of the 30 eyes (23.3%; ci 12.3 to 45.9%) experienced complete resolution of disease by rl at the end of rci use. the mean time to resolution was 17.1 weeks (range 12 to 24). therapeutic response – other ocular parameters changes in the mean bcva and intraocular pressure for all ppp eyes from screening to 12 weeks, and to 24 weeks were statistically significant (p < 0.001) [table 5]. percentages of ppp eyes for measures of anterior and posterior uveitis at each visit are shown in figure 6. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 227 treatment of retinal vasculitis with rci; anesi et al figure 4. percentage of ppp eyes with varying rl at each study visit after baseline. figure 5. slit lamp characteristics showing (a) anterior chamber (ac) cells, (b) ac flare, (c) vitreous cells, and (d) vitreous haze at each study visit. oct evaluation at screening occurred in 23 eyes of 14 patients. cme was found in eight eyes of six patients. improvement in cme was seen in five eyes (62.5%) of four patients during the ppp visits, with complete resolution occurring in three eyes (37.5%) of three patients during the ppp visits. 228 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 treatment of retinal vasculitis with rci; anesi et al safety measurements thirteen of the eighteen ppp (21 eyes) used rci throughout the entire 24-week course of the study. one patient stopped rci during the study due to an adverse reaction (injection site reaction), one due to compliance, and three due to poor efficacy of medication. nine of the thirteen patients to complete the course (14 eyes) had no change in therapy through the entire study, while the other four of the thirteen received additional systemic or local therapy to help control inflammation. other nonserious adverse events felt to be attributable to the addition of rci to therapy in this study group were insomnia (two patients), mood change (one patient), loss of appetite (one patient), and dizziness with mild nausea (one patient). no concerning changes in laboratory values were found in any patient during the study. the mean weight in ppp eyes at screening, week 12, and week 24 was 184.16 ± 48.83, 184.52 ± 49.90, and 189.31 ± 48.47 pounds, respectively (p < 0.001). the mean heart rate in the same group and time points was 79.78 ± 15.77, 78.33 ± 13.89, and 78.56 ± 14.43, respectively (p = 0.484). similarly, the systolic and diastolic blood pressure (bp) were 136.56 ± 15.56 over 90.56 ± 10.60, 130.22 ± 20.24 over 84.89 ± 8.62, and 133.11 ± 21.26 over 84.22 ± 9.32 beats per minute (bpm), respectively, (p < 0.001 for both measures). four eyes of two patients were started on either topical or oral iop-lowering medications at some point during the study. four eyes of another two patients had no changes made in therapy during the study. three of the thirty ppp eyes (10%) found in two patients had any recorded cataract progression during the study. one patient had cataract surgery in one eye between the week-12 and week-24 visits for worsening posterior subcapsular cataract which was noted after the patient was not using rci reliably – of note, surgery was performed when active uveitis was not seen on exam but only leakage on uwfa was seen. the other two eyes were in a single patient where one-step worsening cortical changes were noted in both eyes at the week-24 visit that were not present at the week-12 visit; the changes in this patient were not reported to be symptomatic. discussion the results of this study suggest that rci can be effective in the treatment of patients with retinal vasculitis of various etiologies. our primary outcome of improvement of 50% or more by week 12 was met in half the eyes studied and 65.2% of the eyes of patients by rl method who were able to continue the study medication without deviation until week 12, including an eye with severe vasculitis. in addition, our separate and more traditionally designed scoring method, or rvss, which was based on tabulation of defined features in various cross-sections of uwfa imaging, yielded percentages of eyes with the primary outcome for improvement in scoring that were similar at 53.3% and 69.6%, respectively at week 12. and while there is no standard accepted method to evaluate retinal vasculitis severity nor response to therapy, the consistency seen with these separately applied methods may demonstrate they both could be viewed as reasonable means of evaluating rv for the purposes of this study. there was also a statistically significant progressive increase in rl seen in eyes of patients who maintained the study protocol without deviation, despite the number of ppp patients decreasing through the trial period as would be expected in a proof of concept study [figures 2 and 3; table 4]. this is an important point to highlight, as it is the aim of the authors to show whether there is significant potential (>25%) for therapeutic benefit with use of this medication for a difficult-to-treat and variably presenting disease process such as retinal vasculitis. rapid onset of improvement (≤2.9 weeks) was also observed in this study. furthermore, 23 of the 30 (76.7%) eyes were able to make it to the week-12 visit without a deviation in study protocol for reason of adverse reaction or need for more therapy before this time point, which we argue is widely agreed upon as a sufficient amount of time to allow any therapeutic measure to show efficacy when evaluating whether response is acceptable to continue the current course or whether a change in therapy is required. it is also notable that almost one third of eyes experienced complete remission of disease by rl score by the end of rci use in this relatively short study time period of 24 weeks, occurring by a mean of only 17.1 weeks of rci use. the authors note that a statistically significant increase in vitreous cell was journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 229 treatment of retinal vasculitis with rci; anesi et al noted between baseline and week 12, however, the difference was minimal and fell below one standard deviation. removal of initial use of corticosteroid concomitant with rci employment also arguably provides the benefit of decreasing risk of potential adverse events with concomitant use of medications having similar side-effect profiles. and while there is no guarantee that patients in this study may have fared better or worse without the introduction of rci, it is arguable that a direct response to therapy could be a more reliable outcome measure than return in inflammation after corticosteroid therapy is withdrawn. rci appeared to be well tolerated, stopped in only one patient because of the side effect attributable to the medication itself, an injectionsite reaction. it is worth noting that this type of reaction may possibly be seen more frequently in patients who do not allow the medication to adjust to room temperature prior to withdrawal from the vial and injection (as is intended by the manufacturer). general side effects were minimally seen and tolerated by patients without causation alone for termination of study medication use. a significant increase in mean weight of almost 5 pounds was seen when comparing the ppp patients at week 24 to their screening visit, but no significant gain was seen in the larger amount of ppp patients at week 12 to their screening visit. this could suggest that weight gain, albeit modest in this case, is a potential side effect of rci and is more likely to manifest after use for more than three months, which then has implications for any potential long-term use of this medication. the effect of medication on systolic blood pressure, diastolic blood pressure, and heart rate was not significant; however, this is only relatable to shortterm employment of rci. a study by aggarwal and colleagues assessed the safety and efficacy of rci for treatment of 10 patients with polymyositis and dermatomyositis utilizing the same dose and schedule over 24 weeks, however, subjects were not only allowed to concomitantly utilize corticosteroid but also to increase by 10 mg as a rescue and remain in the study as needed.[18] nonserious adverse events were noted and more plentiful in this group than in our study (22 vs 5) with only half the participants, and serious adverse events were seen including avascular necrosis leading to hip arthroplasty and disseminated zoster with pneumonitis requiring hospitalization. the higher number of side effects including serious side effects such as avascular necrosis might be due to concomitant employment of oral corticosteroid with rci; however, this hypothesis should be examined with more potent and long-term studies. interestingly, they saw a similar gain in weight in their patients of approximately 5.72 pounds over 24 weeks, however, the change was not found to be significant. again, we suspect that higher rates of reactions or adverse events may be found in patients who concurrently use systemic corticosteroids and rci together, due to the partial mechanism of action in the latter and the similarly described potential side effect profile of each. no clinically significant increase in iop measurements was seen over the course of the study – although the mean iop did statistically increase by 0.28 between baseline and week 12, this was much less than 1 mmhg and fell well within one standard deviation. the mean iop then fell below the baseline level at week 24 but again this was less than 1-mmhg difference and much less than the standard deviation. despite the small sample size, these findings over 24 weeks seem to suggest significant or concerning elevation of iop is uncommon with rci use. retinal vasculitis is well known to be a severe type of ocular inflammation that is often refractory to conservative (or even some aggressive) therapeutic measures. several case reports and retrospective reviews have been published describing varying efforts to treat noninfectious retinal vasculitis, and any associated ocular inflammatory disease, that had previously been poorly responsive to other forms of therapy. vallet and colleagues showed anti-tumor necrosis factor (tnf) agents, specifically adalimumab and infliximab, to be effective in treating rv associated with behçet’s disease in 124 patients, with either >50% improvement in rv or some improvement along with significant reduction of systemic corticosteroid seen in 90 and 94.9%, respectively, after six months of therapy; they also noted that infliximab was more often used for patients with severe ocular disease, which included rv.[19] similarly, sharma and colleagues reported 88.23% of 60 patients with rv, associated with a large variety of ocular inflammatory conditions, who previously failed therapy with several conventional 230 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 treatment of retinal vasculitis with rci; anesi et al immunosuppressive medications and were later treated with infliximab after which they were able to attain clinical remission at six months after the initiation of therapy, with 100% achieving remission at 12 months.[20] a case of severe bilateral lupusassociated panuveitis and rv was seen to worsen despite pulse intravenous cyclophosphamide and methylprednisolone and later improve only when rituximab was added to these two medications.[21] there are only two previously published case reports of use of rci in a patient with intraocular inflammation – a patient with panuveitis and diffuse rv, who had previously failed systemic corticosteroid therapy and intravenous tocilizumab, showing sustained improvement in disease activity in this patient at the same dose used in this study,[22] as well as a series of three patients with bilateral, noninfectious anterior and intermediate uveitis who showed improvement in inflammation, stable vision, and ability to reduce mean systemic steroid without any reportable side effects over 14 months of therapy.[23] these examples highlight the importance of further investigation into newer and possibly more effective means of treating rv, such as rci, especially considering some patients may fail or have a contraindication or adverse reaction to other known typically effective medications. to the best of our knowledge, this is the first prospective study of patients with noninfectious retinal vasculitis being treated with rci. we adapted a simple 15-point scale to assess rv severity score and the clinical response via calculation of improvement (or worsening) of this score, which we feel is a feasible calculation that can easily be made even in a clinical setting. we also employed our own method to evaluate rv activity as well as response to therapy for the purpose of this study, as it is conceivably difficult (and often confusing) to objectively measure levels of a disease process that presents so variably, and there is no widely accepted standardized method in use for this form of ocular inflammation. clinically, retinal vasculitis is typically treated by observation of overall response to therapy, thus we believe subjective rl method to be easily translatable to practice for those with familiarity for interpreting fa. in finding a similar progression of score and response to therapy via two independent methods, we again feel this suggests that either of these methods could be a valid means of following rv severity and response to therapy. there are several limitations to this study, which include its open-label status, a limited study period of only 24 weeks, the lack of a control population, varied etiology and severity of disease, concomitant use of other immunomodulatory medications, as well as the use of patients either on or off these other forms of therapy. as stated above, the patient population represented a variable group of disease processes that had retinal vasculitis, as might be expected in a condition or population being studied where the number of patients is few. criticism could be made to this point of the validity of any conclusions brought forth in this manuscript, however, with the etiology of these processes being at least agreeably noninfectious in nature, the authors expect that these data contain merit in the way of an observed response of a noninfectious inflammatory process to a single given therapy. lastly, though this study was performed with funding provided by “mallinckrodt pharmaceuticals, bedminster, nj”, the authors were solely responsible for protocol development, initiation of patient recruitment, administration of study protocol, as well as manuscript production. in conclusion, given these findings, we therefore recommend that rci be considered as a potential agent in the treatment of patients with rv at a dose of 80u twice weekly, including patients who have not responded to other types of antiinflammatory therapy. we also contend that the use of prednisone need not be concurrent while still seeing rapid benefit in this population with tendency toward severe disease activity. these findings should be evaluated with more potent studies with larger sample sizes. financial support and sponsorship this trial was supported by an investigator-initiated research grant from mallinckrodt (staines-uponthames, united kingdom). mallinckrodt had no role in the design or conduct of this research nor production of this manuscript. conflicts of interest none of the authors have any conflict of interest with the content of this manuscript. clinicaltrials.gov identifier: nct03066869 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 231 treatment of retinal vasculitis with rci; anesi et al disclosures i. dr. c stephen foster declares the following: consultancies with aldeyra therapeutics (lexington, ma), allakos (redwood city, ca), bausch & lomb surgical, inc. (rancho cucamonga, ca), eyegate pharma (waltham, ma), genentech (south san francisco, ca), novartis (cambridge, ma), and psivida (watertown, ma). grants or grants pending with aciont (salt lake city, ut), alcon (aliso viejo, ca), aldeyra therapeutics (lexington, ma), bausch & lomb (rochester, ny), clearside biomedical (alpharetta, ga), dompé pharmaceutical (milan, italy), eyegate pharma (waltham, ma), mallinckrodt pharmaceuticals (staines-upon-thames, uk), novartis pharmaceuticals (cambridge, ma), psivida (watertown, ma), and santen (osaka, japan). payment for lectures including service on speaking bureaus: alcon (aliso viejo, ca), allergan (dublin, ireland), mallinckrodt pharmaceuticals (staines-upon-thames, uk). stock or stock options: eyegate pharma (waltham, ma). ii. dr. stephen d. anesi declares the following: consultancies with santen (osaka, japan), mallinckrodt (staines-upon-thames, uk), allakos (redwood city, ca), eyepoint (watertown, ma), and takeda (tokyo, japan). speakerships with abbvie (chicago, il), mallinckrodt (staines-upon-thames, uk), and eyepoint (watertown, ma). iii. dr. peter chang declares the following: consultancies with eyepoint (watertown, ma) and alimera (alpharetta, ga). speakerships with abbvie (chicago, il), mallinckrodt (staines-upon-thames, uk), and eyepoint (watertown, ma). all other authors have no proprietary or commercial interest in any materials discussed in this article or additional financial disclosures to declare. data availability statement the data that support the findings of this study are available from the corresponding author [csf] upon reasonable request. references 1. androudi s, dastiridou a, symeonidis c, kump l, praidou a, brazitikos p, et al. retinal vasculitis in rheumatic diseases: an unseen burden. clin rheumatol 2013;32:7– 13. 2. talat l, lightman s, tomkins-netzer o. ischemic retinal vasculitis and its management. j ophthalmol 2014;2014:197675. 3. ali a, ku jh, suhler eb, choi d, rosenbaum jt. the course of retinal vasculitis. br j ophthalmol 2014:98:785–789. 4. manivannan a, plskova j, farrow a, mckay s, sharp pf, forrester jv. ultra-wide field fluorescein angiography of the ocular fundus. am j ophthalmol 2005;140:525–527. 5. leder ha, campbell jp, sepah yj, gan t, dunn jp, hatef e, et al. ultra-wide-field retinal imaging in the management of non-infectious retinal vasculitis. j ophthalmic inflamm infect. 2013 feb 11; 3: 30. 6. hatemi g, silman a, bang d, et al. eular recommendations for the management of behcet disease. ann rheum dis 2008;67:1656–1662. 7. fabiani c, sota j, rigante d, vitale a, emmi g, lopalco g, et al. efficacy of adalimumab and infliximab in recalcitrant retinal vasculitis inadequately responseive to other immunomodulatory therapies. clin rheumatol 2018;37:2805–2809. 8. sharma pk, markov gt, bajwa a, foster cs. longterm efficacy of systemic infliximab in recalcitrant retinal vasculitis. retina 2015;35:2641–2646. 9. clemson cm, yost j, taylor aw. the role of alpha-msh as a modulator of ocular immunobiology exemplifies mechanistic differences beteween melanocrtins and steroids. ocul immunol inflamm 2017;25:179–189. 10. montero-melendez t. acth: the forgotten therapy. semin immunol 2015;27:216–226. 11. taylor aw, kitaichi n, biros d. melanocortin 5 receptor and ocular immunity. cell mol biol 2006;52:53–59. 12. lee dj, biros dj, taylor aw. injection of an alphamelanocyte stimulating hormone expression plasmid is effective in suppressing experimental autoimmune uveitis. int immunopharmacol 2009;9:1079–1086. 13. taylor aw, streilein jw, cousins sw. identification of alpha-melanocyte stimulating hormone as a potential immunosuppressive factor in aqueous humor. curr eye res 1992;11:1199–1206. 14. taylor a, namba k. in vitro induction of cd25+ cd4+ regulatory t cells by the neuropeptide alpha-melanocyte stimulating hormone (alpha-msh). immunol cell biol 2001;79:358–367. 15. 1taylor aw, lee dj. the alpha-melanocyte stimulating hormone induces conversion of effector t cells into treg cells. j transplant 2011;2011:246856. 16. lindqvist n, napankangas u, lindblom j, et al. proopiomelanocortin and melanocortin receptors in the adult rat retino-tectal system and their regulation after optic nerve transection. eur j pharmacol 2003;482:85– 94. 17. jabs da, nussenblatt rb, rosenbaum jt. standardization of uveitis nomenclature (sun) working group. standardization of uveitis nomenclature for reporting clinical data. results of the first international workshop. am j ophthalmol 2005;140:509–516. 232 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 treatment of retinal vasculitis with rci; anesi et al 18. aggarwal r, marder g, koontz dc, nandkumar p, qi z, oddis cv. efficacy and safety of adrenocorticotropin hormone gel in refractory dermatomyositis and polymyositis. annals rheum dis 2018;77:720–727. 19. vallet h, riviere s, sanna a, deroux a, moulis g, addimanda o, et al. efficacy of anti-tnf alpha in severe and/or refractory behcet’s disease: multicenter study of 124 patients. j autoimmun 2015;62:67–64. 20. sharma pk, markov gt, bajwa a, foster cs. longterm efficacy of systemic infliximab in recalcitrant retinal vasculitis. retina 2015;35:2641–2646. 21. hickman ra, denniston ak, yee cs, toescu v, murray pi, gordon c, et al. bilateral retinal vasculitis in a patient with systemic lupus erythematosus and its remission with rituximab therapy. lupus 2010;19:327–329. 22. agarwal a, hassan m, sepah yj, do dv, nguyen qd. subcutaneous repository corticotropin gel for noninfectious panuveitis: reappraisal of an old pharmacologic agent. am j ophthalmol case rep 2016;4:78–82. 23. sharon y, chu ds. adrenocorticotropin hormone gel for patients with non-infectious uveitis. am j ophthalmol case rep 2019;15:100502. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 233 editorial hypoxic-ischemic encephalopathy: impact on retinal neurovascular integrity and function ismail s. zaitoun1,2, phd; nader sheibani1,2,3,4, phd 1department of ophthalmology and visual sciences, university of wisconsin school of medicine and public health, madison, wi, usa 2mcpherson eye research institute, university of wisconsin school of medicine and public health, madison, wi, usa 3department of cell and regenerative biology, university of wisconsin school of medicine and public health, madison, wi, usa 4department of biomedical engineering, university of wisconsin school of medicine and public health, madison, wi, usa orcid: ismail zaitoun: https://orcid.org/0000-0001-7174-5403 nader sheibani: https://orcid.org/0000-0003-2723-9217 j ophthalmic vis res 2021; 16 (3): 317–319 hypoxic-ischemic encephalopathy (hie) along with its impact on vision has been recognized for some time. hie, one of the most common brain injuries, results from secondary oxygen deprivation and blood flow reduction to the brain. its incidence ranges from 1 to 8 per 1,000 live births in developed countries.[1] a considerable proportion of hie patients display visual impairment,[2, 3] which was considered to be solely due to lesions in the brain neural visual structures and processing.[4] although recent preclinical studies suggest a direct impact on the retinal visual function, the underlying mechanisms and the retinal cells targeted and affected in response to hie remain unknown. the preclinical rice-vannucci model is a frequently used acute hie model in mouse and rat pups.[5–9] this hypoxic-ischemic model is attained by constant occlusion of only one of the common carotid arteries (cca) followed by exposure of the animal to an air mixture with low oxygen. exposure to these conditions results in brain damage specific to the hemisphere on the side of the ligated cca.[10] the cca provides blood supply to the ophthalmic artery that renders the eye susceptible to hie insult. this model is frequently used to study the effect of hie on structural and functional integrity of the brain. in addition, this model has been used to demonstrate the damaging effect of the hie on the blood vessels[11] or the neurons[12, 13] of the rat retina. the development and homeostasis of both the neuronal and the vascular systems are interconnected.[14] to the best of our knowledge, we were first to report a detailed characterization of neurovascular damage in the neonatal mouse retina after exposure to rice-vannucci hie model.[15] we examined the effect of hi exposure of postnatal day 9 (p9) neonatal mice on retinal neurovascular integrity.[15] the mouse retina, like in the human, has three layers of blood vessels. our studies showed that blood vessels in different layers were either degenerated or failed to form. similarly, our studies demonstrated that exposure to hi conditions induce neuronal degeneration and glial activation. observed vascular and neuronal damages were irreversible and most noticeable in the periphery of the retina. ischemic stroke can also occur in juvenile humans and result in devastating and lasting disabilities including vision loss. we recently reported on the effect of hi exposure of juvenile mice (age 30 days) on the functional and structural integrity of the retinal blood vessels and neurons.[16] these studies revealed that blood vessels were damaged and that structural and functional integrity of the neurons of the injured retinas were affected as the b-wave and the inner retinal layers were compromised. of note, we found retinal damage after exposure to hi vary among individuals; some show mild to no damage, some show moderate injuries, and others show severe injuries. similar interindividual variabilities in the degree of damage after hie exposure were reported in mouse, rat, and human neonatal brains[7, 17–19] and retina.[13, 20–22] it is unknown why different individuals respond differently after exposure to the same hi conditions. maturation status of blood vessels © 2021 zaitoun and sheibani. this is an open access article distributed under the creative commons attribution license | published by knowledge e 317 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i3.9427&domain=pdf&date_stamp=2019-07-17 hypoxic-ischemic encephalopathy; zaitoun and sheibani and neurons could contribute to the severity of the damage after exposure to ischemic stroke. this is in line with the fact that we found the occurrence of severe retinal vascular damage to be much higher in neonates as compared with juvenile mice. also, the magnitude of the severe damage was far more apparent and devastating in the neonate mice. thus, age seems to play a significant role. it is also possible that variation in individual’s hemodynamic properties could contribute to the hi-caused damage,[23] since the vascular structure and hence hemodynamic properties varies among retinas. also, retinas of male and female animals may show different severity of injuries after exposure to the same hi conditions, as in the brain.[24, 25] recent clinical studies have also demonstrated that hie results in direct retinal damage in human neonates. at least 24.3% of eyes of newborns with a history of hie were found to have retinal hemorrhage.[22, 26] an independent study examined the retinal integrity of two infants diagnosed with hie using a handheld spectral domain optical coherence tomography (sd-oct) imaging system. one infant with a history of moderate hie was found to have severe retinal damage as manifested by thinning of all layers of the retina. the second infant with a history of severe hie had subretinal fluid but without other obvious retinal damage. these findings support the notion that the retina is a prime target of hi insult, and the severity of retinal damage is independent of the severity of brain damage. a more recent report found three out of eight (37.5%) examined infants with hie to have various types of retinal damage, such as macular cystoid spaces, thinning in the retinal ganglion cell layer, acute middle maculopathy, and abnormally thin fovea.[20] preclinical studies including ours and recent human reports demonstrate that both neurons and blood vessels of the retina in neonates and juveniles are vulnerable to hi exposure. these findings call for more clinical attention in assessing the structural and functional integrity of retina of neonates and juvenile humans after exposure to hypoxic-ischemic insults or ischemic stroke. in addition, it is important to start effort in developing interventional methods to prevent and treat hi-induced and ischemic stroke-induced retinal neurovascular damage. the underlying mechanisms that lead to damage of neurons and blood vessels in the retina after exposure to hi conditions remain unknown. the activation of cell death in brain begins within the first 3–24 hr after exposure to hi conditions.[27] it is likely that critical factors that are responsible for the neurovascular degeneration will be differentially expressed in the early stages of the response to the hi insult. single cell-rna sequencing (scrna-seq) method can be utilized to determine changes in the transcriptome profiles in the retina after the onset of the hi insult. identification of altered genes/pathways known to be important for cell death, angiogenesis, and/or neurogenesis could provide more details regarding the underlying mechanisms. these pathways can be targeted for development of new therapeutics to preserve neurovascular functions not only in the brain but also in the retina. financial support and sponsorship this work was supported in part by an unrestricted award from research to prevent blindness to the department of ophthalmology and visual sciences; the retina research foundation; nih grants p30 ey016665, p30 ca014520, s10 od018221, and ey026078. ns is a recipient of rpb stein innovation award. conflicts of interest there is no conflict of interest. references 1. douglas-escobar m, weiss md. hypoxic-ischemic encephalopathy: a review for the clinician. jama pediatr 2015;169:397–403. 2. cioni g, bertuccelli b, boldrini a, canapicchi r, fazzi b, guzzetta a, et al. correlation between visual function, neurodevelopmental outcome, and magnetic resonance imaging findings in infants with periventricular leucomalacia. arch dis child fetal neonatal ed 2000;82:f134–f140. 3. mcculloch dl, taylor mj, whyte he. visual evoked potentials and visual prognosis following perinatal asphyxia. arch ophthalmol 1991;109:229–233. 4. hoyt cs. brain injury and the eye. eye 2007;21:1285–1289. 5. sheldon ra, sedik c, ferriero dm. strain-related brain injury in neonatal mice subjected to hypoxia-ischemia. brain res 1998;810:114–122. 6. cikla u, chanana v, kintner db, udho e, eickhoff j, sun w, et al. eralpha signaling is required for trkb-mediated hippocampal neuroprotection in female neonatal mice after hypoxic ischemic encephalopathy(1,2,3). eneuro 2016;3. 7. rice je 3rd, vannucci rc, brierley jb. the influence of immaturity on hypoxic-ischemic brain damage in the rat. ann neurol 1981;9:131–141. 318 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 hypoxic-ischemic encephalopathy; zaitoun and sheibani 8. vannucci rc, vannucci sj. a model of perinatal hypoxicischemic brain damage. ann n y acad sci 1997;835:234– 249. 9. vannucci sj, seaman lb, vannucci rc. effects of hypoxiaischemia on glut1 and glut3 glucose transporters in immature rat brain. j cereb blood flow metab 1996;16:77– 81. 10. vannucci rc, vannucci sj. perinatal hypoxic-ischemic brain damage: evolution of an animal model. dev neurosci 2005;27:81–86. 11. steck j, blueml c, kampmann s, greene b, maier rf, arnhold s, et al. retinal vessel pathologies in a rat model of periventricular leukomalacia: a new model for retinopathy of prematurity? invest ophthalmol vis sci 2015;56:1830– 1841. 12. huang hm, huang cc, hung pl, chang yc. hypoxic– ischemic retinal injury in rat pups. pediatr res 2012;72:224–231. 13. jung s, polosa a, lachapelle p, wintermark p. visual impairments following term neonatal encephalopathy: do retinal impairments also play a role? invest ophthalmol vis sci 2015;56:5182–5193. 14. tam sj, watts rj. connecting vascular and nervous system development: angiogenesis and the blood-brain barrier. annu rev neurosci 2010;33:379–408. 15. zaitoun is, cikla u, zafer d, udho e, almomani r, suscha a, et al. attenuation of retinal vascular development in neonatal mice subjected to hypoxic–ischemic encephalopathy. sci rep 2018;8:9166. 16. zaitoun i, shahi p, suscha a, chan k, gj m, br p, et al. hypoxic-ischemic injury causes functional and structural neurovascular degeneration in the juvenile mouse retina. sci rep 2021; 11(1):12670. 17. nair j, kumar vhs. current and emerging therapies in the management of hypoxic ischemic encephalopathy in neonates. children 2018;5:99. 18. cengiz p, uluc k, kendigelen p, akture e, hutchinson e, song c, et al. chronic neurological deficits in mice after perinatal hypoxia and ischemia correlate with hemispheric tissue loss and white matter injury detected by mri. dev neurosci 2011;33:270–279. 19. ferriero dm, miller sp. imaging selective vulnerability in the developing nervous system. j anat 2010;217:429– 435. 20. mangalesh s, tran-viet d, pizoli c, tai v, el-dairi ma, chen x, et al. subclinical retinal versus brain findings in infants with hypoxic ischemic encephalopathy. graefes arch clin exp ophthalmol 2020;258:2039–2049. 21. tran-viet d, wong bm, mangalesh s, maldonado r, cotten cm, toth ca. handheld spectral domain optical coherence tomography imaging through the undilated pupil in infants born preterm or with hypoxic injury or hydrocephalus. retina 2018;38:1588–1594. 22. akin ma, sahin o, cansever m, sirakaya e, robertson nj. early retinal findings following cooling in neonatal encephalopathy. neuropediatrics 2019;50:15–21. 23. charriaut-marlangue c, bonnin p, leger pl, renolleau s. brief update on hemodynamic responses in animal models of neonatal stroke and hypoxia-ischemia. exp neurol 2013;248:316–320. 24. vannucci sj, hurn pd. gender differences in pediatric stroke: is elevated testosterone a risk factor for boys? ann neurol 2009;66:713–714. 25. hill ca, fitch rh. sex differences in mechanisms and outcome of neonatal hypoxia-ischemia in rodent models: implications for sex-specific neuroprotection in clinical neonatal practice. neurol res int 2012;2012:867531. 26. eris e, eris d, seymen z, karasu b, d𝚤racoglu a, perente i, et al. retinal haemorrhage rates and resolution time of retinal haemorrhage in newborns after hypothermic treatment for hypoxic-ischemic encephalopathy. arch pediatr 2020;27:29–32. 27. thornton c, leaw b, mallard c, nair s, jinnai m, hagberg h. cell death in the developing brain after hypoxiaischemia. front cell neurosci 2017;11:248. correspondence to: ismail zaitoun, phd. department of ophthalmology and visual sciences, university of wisconsin school of medicine and public health, 1111 highland ave., wimr 9418, madison, wi 53705, usa. e-mail: iszaitoun@wisc.edu received: 07-05-2021 accepted: 01-06-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i3.9427 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: zaitoun is, sheibani n. hypoxic-ischemic encephalopathy: impact on retinal neurovascular integrity and function. j ophthalmic vis res 2021;16:317–319. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 319 https://knepublishing.com/index.php/jovr original article long-term outcomes of collagen crosslinking for early keratoconus akbar derakhshan, md1,2; javad heravian, md3,4; milad abdolahian, ms4,5; shahram bamdad, md5 1cornea research center, mashhad university of medical sciences, mashhad, iran 2khatam-al-anbia hospital, mashhad university of medical sciences, mashhad, iran 3refractive errors research center, mashhad university of medical sciences, mashhad, iran 4department of optometry, school of paramedical science, mashhad university of medical sciences, mashhad, iran 5poostchi ophthalmology research center, shiraz university of medical sciences, shiraz, iran orcid: akbar derakhshan: http://orcid.org/0000-0002-0217-0156 shahram bamdad: http://orcid.org/0000-0002-5609-016x abstract purpose: to evaluate the long-term outcomes of collagen crosslinking in early keratoconus. methods: thirty eyes of twenty patients with early keratoconus were enrolled. uncorrected visual acuity (ucva), best spectacle corrected visual acuity (bscva), objective refraction, subjective refraction, corneal topography and pachymetry were assessed before and 3, 6, 12 months and 9 years after performing collagen crosslinking surgery. results: the patients’ mean age was 31.2 ± 5.59 years at nine-year follow-up (range, 25–44 years). the means of preoperative ucva and bscva were 0.57 ± 0.34 and 0.15 ± 0.12 logmar, respectively, and these values remained stable at the final follow-up (p = 0.990 and p = 0.227, respectively). the mean objective spherical equivalent decreased considerably from –6.00 ± 4.05 d preoperatively to –5.22 ± 3.71 d at the final follow-up (p < 0.05). the mean subjective spherical equivalent was –4.25 ± 2.87 d preoperatively and this value was stable at the last follow-up (p = 0.92). no considerable difference was found between the postand preoperative mean objective cylinder values (p = 0.34). the mean subjective cylinder value changed significantly from –4.05 ± 1.85 d preoperatively to –3.1 ± 1.42 d at the final follow-up (p < 0.05). the mean central corneal thickness was 496.97 ± 45.95 µm preoperatively and this value was stable at nine-year follow-up (p = 0.183). no significant difference was found between the preand postoperative mean maximum and mean minimum corneal curvature values (p = 0.429 and p = 0.248, respectively). there were no significant postoperative complications. conclusion: corneal crosslinking in early keratoconus seems to be a safe procedure that can effectively stabilize ucva, bscva, subjective se and cct, while improving objective spherical equivalent. keywords: cornea; collagen crosslinking; keratoconus j ophthalmic vis res 2021; 16 (2): 151–157 © 2021 derakhshan et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 151 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9077&domain=pdf&date_stamp=2019-07-17 longstanding outcomes of collagen crosslinking; derakhshan et al introduction keratoconus is a bilateral, progressive, asymmetric, noninflammatory corneal ectasia. the cornea presumes a conical form due to its biomechanical instability leading to irregular astigmatism and reduction in visual quality. treatment options available for increasing the visual acuity or/and halting the progression of keratoconus consist of spectacles, rigid gas permeable contact lenses,[1] collagen crosslinking,[2] intracorneal rings,[3] and keratoplasty.[4, 5] corneal collagen crosslinking (cxl) has been introduced as a promising method for keratoconus management. it was frequently reported that cxl could effectively stabilize the keratoconus progression, with a good safety profile.[6–8] in 2003, wollensak et al pioneered cxl treatment post-op progression of keratoconus. in cxl, the interaction between the riboflavin and ultraviolet-a (uva, 365 nm) results in crosslinking between the intracellular matrix and collagen of the stroma, overwhelmingly in the anterior 300 µm, leading to enhanced strength of the cornea.[8] studies have indicated that collagen crosslinking leads to an increase of collagen fiber diameter[10] and improves biomechanical stiffness[11] by inducing increased covalent bond formation within or between collagen fibers in the corneal stroma.[12] some studies have demonstrated improvement in visual acuity,[9, 13–15] apical curvature of the cornea,[9, 16–18] contrast sensitivity improvement,[19, 20] and a decrease in refractive error.[9, 16, 17, 21] however, most of the studies have short follow-up period; therefore, this study aimed to assess the long-standing outcomes of cxl for early keratoconus. methods our research was approved by khatam al anbia hospital affiliated to mashhad university of correspondence to: shahram bamdad, md. department of poostchi ophthalmology, zand st., shiraz, fars, iran e-mail: shahrambamdad@yahoo.com received: 12-03-2020 accepted: 01-01-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9077 medical sciences. all steps of this study were based on the principles of the declaration of helsinki, and an informed consent was obtained from each subject after explaining the goals of the study. in this hospital-based prospective study, 32 eyes of 22 patients with early keratoconus were initially enrolled but 2 of them missed the follow-ups; therefore, we removed their data from this study. the diagnosis was performed based on video keratographic findings and all patients demonstrated progression before the surgery by longitudinal evaluation using corneal topography. the indications of keratoconus progression included an increase of 1.00 d or more in the cylindrical component of the manifest refraction, an increase of 1.00 d or more in the maximum corneal curvature, an increase of 0.50 d or more in the spherical equivalent (se) manifest refraction in one year and a decrease of ≥5% in the central corneal thickness in three consecutive topographies in six months. preand postoperative evaluation after 3, 6, and 12 months and then 9 years of follow-up consisted of uncorrected visual acuity (ucva) and best spectacle corrected visual acuity (bscva) measurement, ultrasonic pachymetry (tomey, erlangen, germany), corneal computerized topography (technomed, baseweile, germany), and slit lamp and fundus examinations. corneal thickness <400 μm, herpetic keratitis history, and concurrent infectious or autoimmune disease were the exclusion criteria. all procedures were carried out by the same surgeon (ad) in our institute under sterile conditions. for performing the surgery, corneal epithelium was removed by mechanical debridement over 9.0 mm of the central region of the cornea following administration of the topical anesthesia. then, the photosensitizing solution (0.1% riboflavin within 20% dextran) was instilled every 3 min for 30 min, after epithelial debridement following topical anesthesia and inserting a wire lid speculum. riboflavin penetrated into the anterior chamber and corneal stroma completely and the penetration was checked by slit lamp examination. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: derakhshan a, heravian j, abdolahian m, bamdad s. long-term outcomes of collagen crosslinking for early keratoconus. j ophthalmic vis res 2021;16:151–157. 152 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 https://knepublishing.com/index.php/jovr longstanding outcomes of collagen crosslinking; derakhshan et al then, the uva was irradiated on the cornea for 30 min (radiance of 3 mw/cm2), utilizing a 370 nm uva double-diode light source. over irradiating, the riboflavin solution was dropped every 5 min, and balanced salt solution was frequently applied intraoperatively to prevent dehydration of the cornea. topical antibiotics were prescribed for five days along with tear substitutes for three to four weeks. data were analyzed using the spss.21 software (spss inc., chicago, illinois, usa). normality of the data was assessed using the kolmogorov–smirnov test. comparisons were made using paired sample t-test. in all tests, p-values < 0.05 were considered significant. results vision outcomes the mean age of patients was 31.2 ± 5.59 years at the nine-year follow-up period. the mean ucva was 0.57 ± 0.34 logmar preoperatively and it did not significantly change at the final follow-up examination (p = 0.990). no significant difference existed between the postand preoperative mean bscva (p = 0.227). at the last follow-up, bscva improved at least one snellen line in 11 eyes (36.66%) and remained stable in 9 eyes (30%); 10 eyes (33.33%) lost one line or more. the preand postoperative values are represented in table 1. figure 1 shows the ucva and bscva stability following corneal cxl. refractive results the mean objective se improved significantly from –6.00 ± 4.05 d preoperatively to –5.22 ± 3.71 d (p < 0.05) at the nine-year follow-up. no significant difference was found between the postand preoperative mean subjective se (p = 0.92) and mean objective cylinder value (p = 0.348). the mean subjective cylinder value significantly changed from –4.05 ± 1.85 d preoperatively to –3.1 ± 1.42 d at the nine-year follow-up (p = 0.002). figure 2 shows the changes in objective and subjective refraction. central corneal thickness no significant difference was found between the preoperative and postoperative mean central corneal thickness (p = 0.183). figure 3 shows the changes in the central corneal thickness. topographic outcomes no statistically significant difference was detected in the mean maximum (p = 0.429) and mean minimum corneal curvature (p = 0.248) at the nineyear follow-up. during the follow-ups, no macular and corneal abnormalities were observed. none of the cases underwent repeated cxl. discussion collagen crosslinking with riboflavin and uva is a surgical technique used in the treatment of keratoconus. cxl is a surgical method utilized to improve the corneal rigidity, stabilize the corneal ectasia, and inhibit the progression of the keratoconus.[5] previous studies reported that collagen crosslinking improved visual, refractive, topographic and aberrometric values.[15, 16, 21–25] however, some challenges are associated with the long-term outcomes of cxl.[18, 21, 23, 26–28] vinciguerra et al[26] reported that ucva and bscva significantly increased two years following cxl. raiskup-wolf et al[23] demonstrated stabilization and improvement of the cornea during long-term period following cxl. keratoconus stability in 44 eyes after a minimum follow-up of 48 months was reported by caporossi et al.[21] o’brart et al[27] also showed that cxl was a safe and effective method used to stabilize the progression of the keratoconus over a long-term period. hashemi et al[28] reported halting of keratoconus progression up to five years of follow-up, while wittig-silva et al[18] indicated improvements in maximum corneal curvature, ucva, and bscva over a three-year follow-up period. in our study, the stability of subjective se was demonstrated similar to the reports by wittig-silva et al[29] and grewal et al.[30] however, caporossi et al,[31] wollensak et al,[9] and vinciguerra et al[26] reported a decrease in subjective se. in this study, the subjective se and subjective astigmatism reduced significantly during the six-month followup and then gradually returned to the preoperative values. significant changes in the cylinder values were reported at the first-year follow-up in some studies.[32–34] given the visual outcomes of the subjects in this study, there was no significant journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 153 longstanding outcomes of collagen crosslinking; derakhshan et al figure 1. stability of logmar ucva and logmar bscva after corneal cxl. figure 2. changes in objective and subjective refraction (diopter). difference between preand postoperative values of ucva (p = 0.990) and bscva (p = 0.227). our results showed that 40% of patients had improved ucva and 40% had improved bscva, whereas only 43.33% lost lines of ucva and 23.33% lost bcva at the last follow-up. ucva and bscva increased significantly in the first six months due to reduction in refractive error and corneal steepening. caporossi et al[31] proposed that a decrease in the coma aberration following morphologic symmetry leads to an increase in bcva. in our study, ucva and bscva gradually returned to the preoperative values between the 6th and 12th postoperative months. at the final follow-up, the ucva and bscva did not change significantly compared with the preoperative values. caporossi et al[35] reported mean increases of +0.12 and +0.10 snellen lines in ucva and bcva 48 months after cxl, respectively. in our research, 30 of 32 cases were followed-up for nine years, while only 11 of 286 eyes included in their study had completed visits during four years. a 96% drop in the follow-up could lead to different results. similarly, a study by raiskup-wolf et al[23] revealed that only 5 out of 241 included eyes stayed in the study at six-year follow-up. one-year researches indicated that ucva tended to increase during the first year after cxl.[32, 33, 36] however, asri et al reported no statistically significant changes.[37] our results also showed that bscva did not change significantly at the last follow-up. some other researches demonstrated different results ranging from no change in bcva at one-year follow-up[37] to 1.26 snellen lines[9] and 0.1133 and 0.1832 logmar increase in bcva after cxl. in this study, there were no statistically significant changes in cct at any postoperative intervals. however, corneal thinning was reported in some studies.[28, 38] greenstein et al[38] showed corneal thinning and return to the standard values during the first three months and the first one year after treatment, respectively. an early reduction in cct was also reported by hashemi et al[28] at the first postoperative month after an increment and 154 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 longstanding outcomes of collagen crosslinking; derakhshan et al figure 3. changes in cct (µm). table 1. preoperative and postoperative patient data parameters preoperative 3-months postoperative 6-months postoperative 12-months postoperative 9-years postoperative logmar ucva p 0.57 ± 0.34 0.45 ± 0.34 p < 0.05 0.38 ±0.32 p < 0.05 0.38 ± 0.33 p< 0.001 0.57 ±0.37 p = 0.990 logmar bcva p 0.15 ± 0.12 0.11 ± 0.10 p < 0.05 0.05 ±0.06 p < 0.05 0.06 ± 0.07 p < 0.05 0.12 ±0.12 p = 0.227 obj se p −6.00 ± 4.0 −5.71±3.79 p = 0.09 –5.46 ± 3.44 p < 0.05 −5.40 ± 3.44 p < 0.05 –5.22 ± 3.71 p < 0.05 obj ast p −4.68±2.28 −4.75 ± 2.36 p = 0.37 –4.85 ± 2.03 p = 0.63 −4.64 ± 2.16 p = 0.42 –4.50 ± 2.06 p = 0.34 sub se p -4.25 ± 2.87 −3.72 ± 3.01 p = 0.055 –2.88 ± 2.23 p < 0.001 −3.75±2.83 p = 0.001 –3.8 ± 3.06 p = 0.09 sub ast p −4.05 ± 1.85 −3.04 ± 1.38 p < 0.05 –3.01 ± 1.48 p < 0.001 −3.52 ± 1.70 p < 0.05 –3.1 ± 1.42 p < 0.05 cct p 496.97 ± 45.95 496 ± 17.10 p = 0.21 508.88 ± 18.44 p = 0.52 504.20 ± 26.18 p = 0.07 491.43 ± 37.98 p = 0.18 k-max p 51.92 ± 5.47 54.71 ± 6.16 p = 0.23 48.06 ± 1.30 p = 0.45 50.95 ± 4.46 p = 0.23 51.40 ± 4.40 p = 0.42 k-min p 46.63 ± 4.36 43.55 ± 3.25 p = 0.477 44.91 ± 1.93 p = 0.18 45.71 ± 4.05 p = 0.85 46.34 ± 4.56 p = 0.24 ucva, uncorrected visual acuity; bcva, best corrected visual acuity; logmar, logarithm of the minimum angle of resolution; obj, objective; sub, subjective; se, spherical equivalent; ast, astigmatism; cct, central corneal thickness achieving a plateau in this period; no alteration was reported following one and over five postoperative years. caporossi et al[21] and o’brart et al[27] reported that ct did not change significantly after long-term follow-up. raiskup-wolf et al[23] showed an increase in cct in the second year after cxl. in our study, the steepest and flattest corneal curvatures following cxl did not change significantly at any interval after treatment. our topographic results showed a mean decrease of 2.42 d in 56.6% of patients and a mean increase of 1.93 d in 43.33% of patients in the steepest corneal curvature at the last follow-up. a mean decrease of 2.01 d was reported by wollensak et al in the maximum curvature values after four years.[9] a mean reduction of 2.10 d in minimum corneal curvature values after six months were reported by caporossi et al.[31] raiskup-wolf et al[23] reported 2.68 d, 2.21 d, and 4.84 d reduction of corneal curvature in the first, second, and third years after cxl, respectively. steepest corneal curvature was reported as a weak parameter for both efficacy of the cxl and the keratoconus progression.[40] the reason is that the steepest curvature characterizes the steepest curvature of the anterior corneal surface taken from a little region and it is not journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 155 longstanding outcomes of collagen crosslinking; derakhshan et al able to recognize the degree of ectasia; hence, keratoconus can progress without any change in the steepest corneal curvature.[41] in conclusion, we recommend the use of cxl for patients with early keratoconus. our findings indicate that the cxl procedure is an effective and a safe method for the treatment of keratoconus within a long-term postoperative follow-up duration. however, more studies with larger sample size are required to confirm the effectiveness of cxl. acknowledgements the authors thank prof. shokrpour for english editing of the paper. financial support and sponsorship nil. conflicts of interest none declared. references 1. mrazovac d, barišić kutija m, vidas s, kuzman t, petriček i, jandroković s, et al. contact lenses as the best conservative treatment of newly diagnosed keratoconus–epidemiological retrospective study. coll antropol 2014;38:1115–1118. 2. cannon d, foster c. collagen crosslinking in keratoconus. invest ophthalmol vis sci 1978;17:63–65. 3. hellstedt t, mäkelä j, uusitalo r, emre s, uusitalo r. treating keratoconus with intacs corneal ring segments. j refract surg 2005;21:236–246. 4. richard jm, paton d, gasset ar. a comparison of penetrating keratoplasty and lamellar keratoplasty in the surgical management of keratoconus. am j ophthalmol 1978;86:807–811. 5. wood to. lamellar transplants in keratoconus. am j ophthalmol 1977;83:543–545. 6. spoerl e, mrochen m, sliney d, trokel s, seiler t. safety of uvs-riboflavin cross-linking of the cornea. cornea 2007;26:385–389. 7. wollensak g, spoerl e, seiler t. stress-strain measurements of human and porcine corneas after riboflavin–ultraviolet-a-induced cross-linking. j cataract refract surg 2003;29:1780–1785. 8. greenstein sa, fry kl, hersh ps. in vivo biomechanical changes after corneal collagen cross-linking for keratoconus and corneal ectasia: 1-year analysis of a randomized, controlled, clinical trial. cornea 2012;31:21– 25. 9. wollensak g, spoerl e, seiler t. riboflavin/ultravioleta–induced collagen crosslinking for the treatment of keratoconus. am j ophthalmol 2003;135:620–627. 10. wollensak g, wilsch m, spoerl e, seiler t. collagen fiber diameter in the rabbit cornea after collagen crosslinking by riboflavin/uva. cornea 2004;23:503–507. 11. beshtawi im, o’donnell c, radhakrishnan h. biomechanical properties of corneal tissue after ultraviolet-a–riboflavin crosslinking. j cataract refract surg 2013;39:451–462. 12. mencucci r, marini m, paladini i, sarchielli e, sgambati e, menchini u, et al. effects of riboflavin/uvs corneal cross−linking on keratocytes and collagen fibres in human cornea. clin experiment ophthalmol 2010;38:49–56. 13. wollensak g, spörl e, mazzotta c, kalinski t, sel s. interlamellar cohesion after corneal crosslinking using riboflavin and ultraviolet a light. br j ophthalmol 2011;95:876–880. 14. jankov ii mr, jovanovic v, nikolic l, lake jc, kymionis g, coskunseven e. corneal collagen cross-linking. middle east afr j ophthalmol 2010;17:21. 15. vinciguerra p, albè e, trazza s, rosetta p, vinciguerra r, seiler t, et al. refractive, topographic, tomographic, and aberrometric analysis of keratoconic eyes undergoing corneal cross-linking. ophthalmology 2009;116:369–378. 16. hersh ps, greenstein sa, fry kl. corneal collagen crosslinking for keratoconus and corneal ectasia: one-year results. j cataract refract surg 2011;37:149–160. 17. padmanabhan p, radhakrishnan a, venkataraman ap, gupta n, srinivasan b. corneal changes following collagen cross linking and simultaneous topography guided photoablation with collagen cross linking for keratoconus. indian j ophthalmol 2014;62:229. 18. wittig-silva c, chan e, islam fm, wu t, whiting m, snibson gr. a randomized, controlled trial of corneal collagen cross-linking in progressive keratoconus: threeyear results. ophthalmology 2014;121:812–821. 19. lamy r, netto cf, reis rg, procopio b, porco tc, stewart jm, et al. effects of corneal cross-linking on contrast sensitivity, visual acuity, and corneal topography in patients with keratoconus. cornea 2013;32:591–596. 20. szczotka lb, barr jt, zadnik k. a summary of the findings from the collaborative longitudinal evaluation of keratoconus (clek) study. clek study group. optometry 2001;72:574–584. 21. caporossi a, mazzotta c, baiocchi s, caporossi t. longterm results of riboflavin ultraviolet a corneal collagen cross-linking for keratoconus in italy: the siena eye cross study. am j opthalmol 2010;149:585–593. 22. koller t, mrochen m, seiler t. complication and failure rates after corneal crosslinking. j cataract refract surg 2009;35:1358–1362. 23. raiskup-wolf f, hoyer a, spoerl e, pillunat le. collagen crosslinking with riboflavin and ultraviolet-a light in keratoconus: long-term results. j cataract refract surg 2008;34:796–801. 24. greenstein sa, fry kl, hersh mj, hersh ps. higherorder aberrations after corneal collagen crosslinking for keratoconus and corneal ectasia. j cataract refract surg 2012;38:292–302. 156 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 longstanding outcomes of collagen crosslinking; derakhshan et al 25. greenstein sa, fry kl, hersh ps. corneal topography indices after corneal collagen crosslinking for keratoconus and corneal ectasia: one-year results. j cataract refract surg 2011;37:1282–1290. 26. vinciguerra p, albè e, trazza s, epstein d. intraoperative and postoperative effects of corneal collagen crosslinking on progressive keratoconus. arch ophthalmol 2009;127:1258–1265. 27. o’brart dp, kwong tq, patel p, mcdonald rj, o’brart na. long-term followup of riboflavin/ultraviolet a (370 nm) corneal collagen cross-linking to halt the progression of keratoconus. br j ophthalmol 2013;97:433–437. 28. hashemi h, seyedian ma, miraftab m, fotouhi a, asgari s. corneal collagen cross-linking with riboflavin and ultraviolet a irradiation for keratoconus: long-term results. ophthalmology 2013;120:1515–1520. 29. wittig-silva c, whiting m, lamoureux e, sullivan lj, lindsay rg, snibson gr. a randomized controlled trial of corneal collagen crosslinking in progressive keratoconus: preliminary results. j refract surg 2008;24:s720–s725. 30. grewal ds, brar gs, jain r, sood v, singla m, grewal sp. corneal collagen crosslinking using riboflavin and ultraviolet-a light for keratoconus: one-year analysis using scheimpflug imaging. j cataract refract surg 2009;35:425–432. 31. caporossi a, baiocchi s, mazzotta c, traversi c, caporossi t. parasurgical therapy for keratoconus by riboflavin– ultraviolet type a rays induced cross-linking of corneal collagen: preliminary refractive results in an italian study. j cataract refract surg 2006;32:837–845. 32. arbelaez mc, sekito mb, vidal c, choudhury sr. collagen cross-linking with riboflavin and ultraviolet-a light in keratoconus: one-year results. oman j ophthalmol 2009;2:33. 33. henriquez ma, izquierdo jr l, bernilla c, zakrzewski pa, mannis m. riboflavin/ultraviolet a corneal collagen crosslinking for the treatment of keratoconus: visual outcomes and scheimpflug analysis. cornea 2011;30:281–286. 34. el-raggal tm. sequential versus concurrent kerarings insertion and corneal collagen cross-linking for keratoconus. br j ophthalmol 2011;95:37–41. 35. caporossi a, mazzotta c, baiocchi s, caporossi t, denaro r. age-related long-term functional results after riboflavin uva corneal cross-linking. j ophthalmol 2011;2011. 36. el-raggal tm. riboflavin-ultraviolet a corneal crosslinking for keratoconus. middle east afr j ophthalmol 2009;16:256. 37. asri d, touboul d, fournié p, malet f, garra c, gallois a, et al. corneal collagen crosslinking in progressive keratoconus: multicenter results from the french national reference center for keratoconus. j cataract refract surg 2011;37:2137–2143. 38. greenstein sa, shah vp, fry kl, hersh ps. corneal thickness changes after corneal collagen crosslinking for keratoconus and corneal ectasia: one-year results. j cataract refract surg 2011;37:691–700. 39. chan cc, sharma m, wachler bsb. effect of inferiorsegment intacs with and without c3-r on keratoconus. j cataract refract surg 2007;33:75–80. 40. belin mw, alizadeh r, torres-netto ea, hafezi f, ambrósio jr r, pajic b. keratoconus expert meeting, london, 2014. j kerat ect cor dis 2014;3:141–158. 41. mahmoud am, nuñez mx, blanco c, koch dd, wang l, weikert mp, et al. expanding the cone location and magnitude index to include corneal thickness and posterior surface information for the detection of keratoconus. am j ophthalmol 2013;156:1102–1111. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 157 photo essay oguchi disease associated with keratoconus ahmad mirshahi, md1; narges hassanpoor, md, mph1; hassan khojasteh, md1; mohammad reza baradaran, md2; hooshang faghihi, md1; alireza lashay, md1 1retina & vitreous service, farabi eye hospital, tehran university of medical sciences, tehran, iran 2vanak eye clinic, tehran, iran orcid: ahmad mirshahi: https://orcid.org/0000-0002-4890-5023 narges hassanpoor: https://orcid.org/0000-0001-8296-0918 j ophthalmic vis res 2021; 16 (1): 137–139 presentation a 22-year-old female came to a cornea specialist in our center to do refractive surgery. the bestcorrected visual acuity was 20/20 in both of her eyes with the following refraction: od: –4.5–0.75 x 180 and os: –4.75–2.00 x 110. scissors motion was obvious in her left eye during refraction. in funduscopic evaluation, an abnormal yellow to brown sheen was obvious in her both eyes (figure 1, right column). other ocular examinations were within normal limits and patient had no history of any other systemic or ocular disease. drug history and family history of ocular diseases were negative. due to scissors motion and abnormal pentacam (figure 2), she has been diagnosed with keratoconus, her refractive surgery has been held, and corneal cross linking (cxl) was suggested to her. both eyes optical coherence tomography (oct) were completely normal but due to abnormal yellow sheen in her both eyes funduscopy, she was referred for further evaluation to us before cxl. she denied any night blindness or decreased vision in her both eyes. oguchi disease diagnosis was made with presence of obvious mizuo-nakamura phenomenon (figure 1) and was confirmed with correspondence to: narges hassanpoor, md. eye research center, farabi eye hospital, qazvin sq., tehran 13366, iran. e-mail: nargeshassanpoor@gmail.com received: 19-01-2018 accepted: 23-12-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8262 genetic testing. her electroretinography (erg) was done based on the international society for clinical electrophysiology of vision (iscev) protocol (metrovision, pérenchies, france). due to rapid loss of dark adaptation by a short light exposure, dark adapted fundus photo and erg have been done in different visits but with same instruments. fundus photos have been captured by canon cr-2 af retinal camera. there was not any abnormality in her both eyes oct angiography (octa) by optovue octa (fremont, ca, usa). genetic testing has shown a homozygous mutation in sag (nm_000541.5) gene, variant c.874c>tp.r292 which is compatible with type one oguchi disease. discussion oguchi disease is a type of congenital stationary night blindness (csnb) with autosomal recessive inheritance. patients usually have normal visual acuity and do not complain from night blindness. the disease is very rare and around 50 cases have been reported up till now. most of the cases are from japan and pakistan.[1] patients have an abnormal fundus color that is described as having yellow to brown sheen or metallic appearance. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: mirshahi a, hassanpoor n, khojasteh h, baradaran mr, faghihi h, lashay a. oguchi disease associated with keratoconus. j ophthalmic vis res 2021;16:137–139. © 2021 mirshahi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 137 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8262&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; mirshahi et al figure 1. mizuo-nakamura phenomenon. fundus photo of right and left eyes before (left column) and after (right column) 6 hr of overnight dark adaptation. all photos have been taken in normal illumination. abnormal yellow sheen disappeared after dark adaptation. figure 2. pentacam of right (upper row) and left (lower row) eyes. right eye pentacam shows inferior steepening, high i-s value, posterior elevation, and inferior displacement of the thinnest point. pentacam of left eye shows significant inferior steepening, increased keratometries, anterior and posterior elevation, and inferior displacement of the thinnest point that is compatible with keratoconus diagnosis. 138 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 photo essay; mirshahi et al figure 3. erg before (a) and after (b) 6 hr of dark adaptation. her first erg (a) was performed after 30 min of dark adaptation which showed a severely reduced b-wave amplitude with a mild reduction of the a-wave that improved after 6 hr of overnight dark adaptation (b). prolonged dark adaptation can recover rhodopsin and re-normalize fundus color (mizuo-nakamura phenomenon).[2–4] oguchi disease has been reported in association with retinitis pigmentosa[4] and diabetic retinopathy,[1] but there is no report of its association with keratoconus or any other corneal abnormality up till now. however, there was a report of x-linked csnb associated with keratoconus in 2006 from uk by nguyen et al.[5] here, we report the first case of association of this disease with keratoconus in the world. to the best of our knowledge, this is the second case of oguchi reported from iran[1] but the first genetically proven oguchi disease type 1 of iran and middle east. the other case from iran has shown negative erg in photopic state with near flat erg in scotopic condition.[1] another case of oguchi disease was reported by francois et al with absent scotopic waves in 1956.[1] in conclusion, oguchi disease can be seen with keratoconus. although it could be accidental due to high prevalence of keratoconus in our population, further reports in future may suggest a pathogenic linkage between them. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. entezari m, ramezani a, ghamari h. a case of oguchi disease with diabetic retinopathy. iran j ophthal 2006;19:42–44. 2. curcio ca, johnson m. structure, function, and pathology of bruch’s membrane. in: retina wilkinson c, hinton d, sadda s, wiedemann p, ryan s, editors. anatomy and physiology. 5th ed. ca, usa: elsevier inc; 2012:465– 481. 3. fujinami k, tsunoda k, nakamura m, oguchi y, miyake y. oguchi disease with unusual findings associated with a heterozygous mutation in the sag gene. arch ophthalmol 2011; 129(10):1375-6. 4. maw ma, denton mj. oguchi disease, retinitis pigmentosa, and the phototransduction pathway. in: lavail mm, hollyfield jg, anderson re, editors. degenerative retinal diseases. boston, ma: springer; 1997:313–318. available from: https://doi.org/10.1007/9781-4615-5933-7_34 5. nguyen dq, hemmerdinger c, hagan rp, brown mc, quah sa, kaye sb. keratoconus associated with csnb1. br j ophthalmol 2007 jan; 91(1):116-7. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 139 https://doi.org/10.1007/978-1-4615-5933-7_34 https://doi.org/10.1007/978-1-4615-5933-7_34 review article alcohol and the eye saeed karimi1, 2, md; amir arabi1, 2, md, mph; toktam shahraki1, 2, md 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2department of ophthalmology, torfeh hospital, shahid beheshti university of medical sciences, tehran, iran orcid: saeed karimi: http://orcid.org/0000-0002-3231-8414 amir arabi: http://orcid.org/0000-0002-6523-7733 abstract in this article, we present a review of ocular conditions related to alcohol consumption. a search of the literature published from 1952 to march 2020 was performed. the titles and abstracts were screened and the eligible studies were selected. pubmed, isi web of knowledge database, scopus, embase, and the cochrane library were searched. we categorized the relationship between alcohol intake and ocular conditions by the type of ocular exposure to alcohol. accordingly, ocular findings following acute alcohol intoxication, optic neuropathy following methanol toxicity, congenital conditions related to maternal alcohol consumption, and ocular disease related to chronic alcoholism are discussed. the main feature of alcohol intoxication in the eye is abnormal eye movement. acute optic neuropathy secondary to methyl alcohol consumption is a serious ocular disease with permanent vision loss or scotoma. prenatal exposure to ethanol may end in fetal alcohol spectrum disease, where ocular findings are a constant component. the association between chronic alcohol consumption and increased risks of cataract, age-related macular degeneration, diabetic retinopathy, different types of optic neuropathy, impairment of visual quality, retinal vascular disease, and ocular surface disease has also been reported. along with detrimental medical and social effects, the role of alcohol consumption in different ocular conditions should be considered, as alcohol-induced visual disturbances may contribute to the heavy burden of alcohol abuse on the healthcare system and overall quality of life. keywords: alcohol; cornea; dry eye; ethanol; ethyl alcohol; eye; fetal alcohol; glaucoma; macular degeneration; methanol; optic neuropathy; retinopathy; teratogenicity j ophthalmic vis res 2021; 16 (2): 260–270 introduction as a potentially modifiable risk factor for many disorders, the importance of alcohol consumption correspondence to: amir arabi, md. ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, no. 23, boostan 9 st., paidarfard st., pasdaran ave., tehran 16666, iran. e-mail: amir_arab_91@yahoo.com received: 03-12-2019 accepted: 14-09-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9089 has already been documented in a variety of medical fields. the question is whether alcohol consumption should be considered as a contributing factor of ocular diseases. through a comprehensive review of the current literature, this article will discuss on some ocular conditions which have been reported to be associated with alcohol consumption. we have categorized the this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: karimi s, arabi a, shahraki t. alcohol and the eye. j ophthalmic vis res 2021;16:260–270. 260 © 2021 karimi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9089&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr alcohol and the eye; karimi et al topic as follows: i. alcohol intoxication and the eye ii. acute methyl alcohol optic neuropathy iii. alcohol and congenital ocular diseases iv. chronic alcoholism and the eye alcohol consumption refers to the intake of drinks containing ethyl alcohol. according to the definitions in the united states, approximately 14 g of pure alcohol in any type of drink is considered as a standard alcoholic drink.[1] the containing beverage can be regular beer, malt liquor, table wine, or distilled spirits. various studies have classified alcohol consumption differently. alcohol consumption may be called heavy or light drinking, based on the overall measurement of the history of alcohol consumption, or may be estimated based on the number of drinks consumed per day or week [table 1].[2, 3] the definition of heavy drinking varies in the literature. in this review, the concept of heavy drinking will be clarified through both quantitative and qualitative descriptions of daily alcohol consumption based on moderate or heavy alcohol abuse. method papers published from january 1952 to march 2020 was reviewed by searching isi web of knowledge database, pubmed, scopus, embase, and the cochrane library. the following keywords were used: “alcohol consumption”, “ethanol”, “ethyl alcohol”, “alcohol and the eye”, “alcohol and cataract”, “alcohol and glaucoma”, “alcohol and diabetic retinopathy”, “alcohol and retinal disease”, “alcohol and dry eye”, and “alcohol and age-related macular degeneration”. no language limitation was applied. articles and meta-analyses that published information about oral alcohol consumption and ocular disease were selected through review of abstracts, references, and titles. a total of 106 studies were included. the first study was published in 1952, and the last in 2019. alcohol intoxication intoxication means the effect of acute consumption of alcohol on different physiologic processes in the body. not only following binge drinking, it can even happen following acute intake of light or moderate levels of alcohol.[4] the main feature of alcohol intoxication refers to its effect on the central nervous system. however, change in visual functions have always been focused in ethanol intoxications. ocular findings may be related to reduction of gamma-aminobutyric acid (gaba) activity, which is a major inhibitory neurotransmitter in the brain.[5] gaba has been found in different parts of the visual pathway, from retinal ganglion and bipolar cells to the lateral geniculate nucleus, superior colliculus, and the visual cortex.[6] visual disturbance secondary to alcohol intoxication may manifest by impaired color perception,[4] decreased contrast sensitivity,[7] or abnormal eye movements.[8–10] impairment of cognitive processing in cns may cause subclinical alterations in the eye movements. these alterations may include a high latency for fixation, increased duration of fixations, and increased frequency of saccades.[11] in a study on alcohol intoxication and its ocular findings, volunteers of alcohol and placebo condition were evaluated by eye tracker to record eye movements during completion of visual maze test.[11] significant differences were reported in the first fixation latency, total task time, and number and duration of fixations and saccades. acute methyl alcohol intoxication methanol is a toxic alcohol found in industrial agents. methanol toxicity can occur via inhalation, ingestion, or transdermal absorption. it is absorbed via the gastrointestinal tract in less than 10 min.[12] methyl alcohol is metabolized to formic acid, which is known to be the main mediator of permanent neurologic damage following methanol intoxication.[13, 14] methanol can lead to ocular damage through two independent pathways: retinal damage and optic neuropathy. the former pathway refers to the damage to muller cells and photoreceptors.[15, 16] inner segment lesions of retinal photoreceptors have been reported to appear following methanol ingestion, where rods seems to be more sensitive to this insult, compared to cones.[17] however, methanol-induced acute optic neuropathy has been studied more widely, and is considered as the main ocular damage following methanol intoxication. ocular symptoms may occur in half of the intoxicated patients, and they often develop after 6 hr following methanol ingestion.[18] it is journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 261 alcohol and the eye; karimi et al table 1. types of alcohol consumptions according to “drinking patterns and their definitions alcohol research: current reviews”[1] type of alcohol consumption definition low-risk drinking and alcohol use disorder no more than 3–4 drinks on any single day and no more than 7–14 drinks per week moderate alcohol consumption up to 1–2 drinks per day binge drinking 4–5 drinks in a 2-hr time frame heavy drinking binge drinking on each of 5 or more days in the past 30 days manifested by blurry vision, visual hallucination, dense central scotoma, and decreased visual acuity. the main findings on examination include nystagmus, sluggish pupils, disc swelling, and optic disc hyperemia.[12, 17, 19] demyelination of the retrobulbar portion of the optic nerve is a histopathologic hallmark of the condition.[20] formic acid is believed to damage oxidative pathways through mitochondrial cytochrome c oxidase inhibition, which primarily affect susceptible zones of circulation including central nervous system and optic nerve watershed areas.[21, 22] in addition, interrupted axoplasmic conduction secondary to sodium–potassium adenosine triphosphatase inhibition causes axonal swelling in the optic nerve.[20] finally, increased production of reactive oxygen mediators results in neuronal lysis.[4, 14] methyl alcohol intoxication is a life-threatening condition, where its acute optic neuropathy is of secondary concern. however, presence of ocular signs and symptoms may help to make an early diagnosis, thus providing opportunity for more timely therapeutic measures. correction of metabolic acidosis, elimination of methanol from the blood using hemodialysis, and competitive inhibition of alcohol dehydrogenase by ethanol or fomepizole are the mainstays of treatment.[13] among the medications used for methanolinduced acute optic neuropathy, intravenous high-dose methylprednisolone may be beneficial in the visual recovery of these patients [table 2]. recently, intravenous erythropoietin (epo) added to high-dose intravenous steroids have been postulated to be an effective combination therapy.[23] in a study on the topic, 11 participants received intravenous epo (10,000 iu twice a day) for three days as an adjuvant to methylprednisolone, while other 11 participants received methylprednisolone only. both final bcva and thickness of retinal nerve fiber layer were reported to be significantly better in the epo group.[23] in a prospective, non-comparative case series on 32 eyes of 16 patients,[24] one or two courses of intravenous epo (20,000 units/day for three days) appeared to improve visual acuity in patients with methanol optic neuropathy. the erythropoietin in methanol associated optic neuropathy (epo-maon) trial (clinicaltrials.gov identifier: nct02376881) is designed as a randomized, controlled trial to assess the efficacy of 20,000 iu epo iv infusion for three successive days in improvement of visual outcome after three months following the treatment. fetal alcohol syndrome and the eye as markers of teratogenesis, presence of ocular findings are considered as a useful adjunct to the diagnosis of fetal alcohol syndrome (fas). it is believed that eye diseases occur in over 90% of children with the fas.[30] recently, it has been postulated that patients with fully developed fas present the highest rate of ocular findings.[31] alcohol has been shown to cause ocular defects by affecting expression of some transcription factors such as pax6 and otx2,[32–34] retinoic acid signaling,[35–37] and reactive agents of oxygen and nitrogen signaling.[38, 39] furthermore, hug et al reported abnormal retinal function according to abnormal electroretinograms in 10 fas patients.[40] short palpebral fissures, epicanthus, ocular hypertelorism, coloboma, strabismus, blepharoptosis, microphthalmia, and abnormalities of the fundus are ocular manifestations of fas.[41] also, some case reports of lens opacity associated with fas have been published.[42] the most frequent findings of the posterior segment are optic disc hypoplasia and tortuosity of the retinal vasculature.[43, 44] in the swedish cohort of children with fas, the prevalence of optic nerve hypoplasia and vascular tortuosity was reported to be 48% and 49%, respectively.[45] 262 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 alcohol and the eye; karimi et al table 2. a summary of studies performed on the efficacy of intravenous erythropoietin and high-dose corticosteroid as a medical treatment for methanol toxicity. study year type of study number of patients treatment protocol the main outcome pakdel et al[24] 2018 non-comparative case series 16 intravenous recombinant human epo consisted of 20,000 units/day for three successive days bcva significantly increased in the last follow-up examination pakravan et al[23] 2016 comparative case series 11 intravenous recombinant human epo consisted of 10,000 iu twice a day for three days as an adjuvant to methylprednisolone the final bcva was significantly better in the epo group yunard et al[25] 2016 case series 19 intravenous high-dose methylprednisolone with or without hemodialysis 73% of the cases showed va improvement sharma et al[26] 2012 case series 4 500 mg methylprednisolone twice a day for 3 days; followed by oral prednisolone 1 mg/kg/day for 11 days 100% of the cases showed va improvement abrishami et al[27] 2011 case series 6 250 mg intravenous methyl prednisolone every 6 hr for 4 days; followed by oral prednisolone 1 mg/kg/day for 10 days 100% of the cases showed va improvement triningrat et al[28] 2010 retrospective descriptive study 16 hemodialysis and intravenous methylprednisolone 1000 mg/day for three days, followed by oral prednisone 1 mg/kg/day for 11 days 100% of the cases showed va improvement shukla et al[29] 2006 case series 17 intravenous methylprednisolone 1000 mg/day for three days 82% of the cases showed va improvement bcva, best corrected visual acuity; epo, erythropoietin; va, visual acuity the high prevalence of ocular involvement in fas has led the researchers to present a diagnostic tool called “4-digit eye diagnostic code.” this tool uses four main ocular manifestation of fas, including visual acuity, refraction, strabismus, and structural abnormalities, to present a diagnostic help and guideline for follow-up examinations in fas patients.[31] not only for diagnosis, ocular examination permits appropriate management of ocular disease in fas, which prevents visual loss.[41] more recently, modulation of ion channel has been studied for their potential ability in reducing ocular defects in fas.[46] in animal models, blue light-mediated hyperpolarization of membranes through chr2d156a channels rescued ethanolinduced eye structural defects.[46] chronic alcoholism and the eye age-related macular degeneration (amd) amd is a frequent cause of blindness among the elderly in developed countries.[47, 48] numerous epidemiological studies have supported the probable link between alcohol consumption and amd,[2] however, the pathophysiological mechanisms remain unclear. alcohol is considered as a neurotoxin that causes brain damage via oxidative pathways. hence, the retina might be similarly affected.[49, 50] additionally, increased oxidant stress associated with excess alcohol consumption has caused tissue damage in different organs of animal journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 263 alcohol and the eye; karimi et al models.[51, 52] furthermore, due to poor nutrition in heavy drinkers, decreased intake levels of carotene and antioxidants are more likely to occur.[53, 54] some protective nutrients against amd, such as zinc and vitamin, are also lower in heavy drinkers compared to nondrinkers.[55, 56] finally, alcohol has been related to formation of new vessels and progression of choroidal neovascularization in animal studies.[57] a meta-analysis indicated that consumption of ≥30 g/day of alcohol was correlated to a higher risk of early amd by 47–67%.[58] additionally, some evidence showed that the type of alcohol may be relevant. in the beaver dam eye study (bdes), drinking of neither wine nor liquor was associated with early or late age-related maculopathy, while beer drinking was related to retinal drusen in men.[59, 60] in the melbourne collaborative cohort study, the largest and most recent prospective study on 20,963 participants since 2003 to 2007, consuming more than 20 g of alcohol per day increased the incidence of early amd by approximately 20% in both sexes.[61] this study also revealed that not only high levels but also social or moderate levels of alcohol consumption increase the risk of early amd.[61] diabetic retinopathy (dr) results of studies on the relationship between alcohol consumption and incidence of diabetic retinopathy (dr) have been contradictory. literature reports that the associations are limited and findings are confusing. among the initial studies in this field, a prospective study revealed that patients with diabetes who consumed more than 31 g of alcohol per day had a higher risk of developing dr compared to the nonto light drinkers.[62] in the following studies, no correlation between baseline alcohol intake and the progression of dr was evident over more than four years.[63, 64] in a recent meta-analysis of 15 observational studies, alcohol intake was not associated with an increased risk of dr.[65] in the subgroup analysis, no significant correlations were found between different stages of dr and various alcohol consumption groups. the main limitation of this meta-analysis was lower number of cohort studies included. retinal vein occlusion (rvo) hyperviscosity and severe dehydration resulting from a high alcohol intake has been linked to central retinal vein occlusion (rvo) in young patients.[66] in the eye disease case–control study, moderate alcohol consumption was reported to be protective, as it was linked to lower odds of rvo.[67] however, other studies, such as the bdes, revealed no such association between alcohol consumption and rvo.[68] other retinal conditions alcohol is a known risk factor for central serous chorioretinopathy (cscr).[69] it may contribute to nitric oxide-related abnormalities of autoregulation of the choroidal blood vessels.[70] altered regulation of the choroidal blood flow can increase the permeability of the vasculature as well as accumulation and leakage of the fluid. moreover, in a report of alcoholic liver disease and bilateral multifocal cscr, the authors postulated that endstage liver disease secondary to alcoholism could be the etiology of cscr.[71] in bdes, drinking more than four drinks/day of alcohol was associated with asteroid hyalosis.[72] adolescence is a period of important neurological development, and alcohol exposure in this period may cause some visual defects, particularly defects of color vision, which is more sensitive to neurotoxicants.[4] the visual scotopic performance also worsens with heavy alcohol consumption.[73] in a study on the topic, both the retinal image quality and visual performance under low-scotopic conditions were worsened after acute alcohol consumption. increased pupil size and tear film disturbances were presented as the etiological factors of decreased optical quality.[73] alcohol-related optic neuropathy toxic/nutritional optic neuropathy secondary to chronic alcohol consumption is characterized by central or cecocentral scotoma due to papillomacular bundle damage, associated with color vision defects.[74] a detailed history and ocular examination, color vision and visual field tests, and laboratory investigations for serum b12 and folate levels are required to obtain the 264 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 alcohol and the eye; karimi et al diagnosis.[18] the management includes reduction or cessation of alcohol intake, and vitamin b12 and folate supplementation.[75] glaucoma results of the framingham eye study were conflicting, as they suggested that high alcohol consumption might be associated with glaucoma.[76] in the long island glaucoma case– control study,[77] alcohol consumption was more frequent in patients with higher intraocular pressure (iop) compared to the controls. in a hospital-based study in japan, men with alcohol consumption showed a high risk of elevated iop.[78] in this study, 569 men and women participated, where alcohol consumption had a significantly positive association with the iop in men. interestingly, women did not show this association. a similar sex-related difference was reported in the barbados eye study: current alcohol consumption was positively related to iop in men. notably, the barbados study included black patients without glaucoma, and as a superiority over framingham study, the results were reported after controlling for obesity and hypertension.[79] similar results were reported in the studies of the chinese population: chinese men >65 years who were current alcohol consumers had higher iop compared to female consumers.[80] it is notable that in the latter study, non-contact tonometry was used to measure the iop. on the other hand, acute alcohol ingestion reportedly lowers iop in both healthy and glaucomatous eyes.[81, 82] both hyperosmotic effect and suppression of vasopressin by ethanol in the blood reduces blood flow and net water transport into the eye.[83] moreover, an inhibitory effect on the secretory cells in the ciliary process is reportedly related to alcohol intake.[84] although alcohol may decrease the blood flow of the anteriorly located ciliary body, posterior structures, such as the optic nerve, may receive more blood when alcohol is present in the circulation. this mechanism can be protective against the development of primary open-angle glaucoma (poag).[85] along with these basic evidences, a subset of case–control studies reported the protective effects of alcohol consumption against the incidence of poag and elevated iop.[86, 87] in a study on 100 ageand sex-matched ocular hypertensive patients and 100 ocular normotensive patients, absence of liquor consumption was significantly associated with the presence of ocular hypertension.[87] between these two extremes of converse results, various epidemiological studies reported no association between alcohol and iop elevation or glaucoma.[88] the only report on the longitudinal correlation of iop and alcohol consumption was delivered by the barbados eye study,[89] in which alcohol consumption at baseline was not associated with a higher four-year risk of elevated iop.[89] additionally, in a large prospective study on 856 participants including both sexes, chronic alcohol intake <30 g/day did not influence the risk of poag.[90] accordingly, the relationship between alcohol consumption and the risk of glaucoma requires a more prospective investigation with detailed assessments on alcohol use. alcohol and cataract a recent systematic review and meta-analysis revealed that heavy alcohol consumption significantly increased the risk of age-related cataract.[91] in this meta-analysis which was performed on 10 studies, the correlation of moderate alcohol consumption and senile cataract were marginally non-significant. heavy alcohol consumption could produce free radicals in the liver. transmission of the products to the lens may lead to aggregation of lens proteins, leading to cataract formation.[91, 92] acute alcohol exposure increases intracellular lens calcium levels through inhibition of the calcium pumps on lens fibers.[93] this disturbance in calcium homeostasis may lead to cataract formation. alcohol and ocular surface disease although topical administration of ethanol is a known cause of keratopathy and has been used for epithelial cell removal in different ocular surgeries,[94, 95] controversial opinions on the association between oral alcohol and ocular surface disease have been published. in a case– control study, 0.75g/kg of oral ethanol was administered to 10 volunteer men at 8 pm.[96] presence of ethanol in tears, tear osmolarity, schirmer test, and tear break-up time (tbut) were evaluated at midnight and the next morning. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 265 alcohol and the eye; karimi et al table 3. some ocular conditions related to alcohol consumption type of alcohol consumption ocular findings acute alcohol intoxication abnormal eye movements, altered color perception, decreased contrast sensitivity acute methanol optic neuropathy optic disc edema, retinal ganglion cell damages, permanent scotoma or vision loss alcohol teratogenicity short palpebral fissures, epicanthus, ocular hypertelorism, coloboma, strabismus, blepharoptosis, cataract, microphthalmia, hypoplasia of the optic nerve, tortuosity of the retinal vessels chronic alcoholism anterior segment cataract dry eye syndrome corneal epitheliopathy intraocular pressure primary open angle glaucoma optic nerve alcohol-induced optic neuropathy retina and choroid age-related macular degeneration diabetic retinopathy retinal vein occlusion central serous chorioretinopathy functional retinal disease asteroid hyalosis ethanol was detected in tears at midnight, while it was undetectable in the tear samples collected next morning. the authors reported that the presence of alcohol in tears was associated with increased tear osmolarity, decreased tbut, and staining of ocular surface with fluorescein. schirmer test and corneal sensitivity showed no change. in other publications, chia et al[97] argued the protective role of alcohol in the development of dry eye syndrome (des), while galor et al[98] showed that drinking increases the risk of des. the bdes reported a higher rate of des symptoms in individuals with a history of heavy alcohol consumption.[99] a comparative case–control study on men with alcohol consumption more than four drinks/day reported decreased schirmer test result and tbut, in addition to changed impression cytology of the conjunctiva.[100] some other researchers believed that des may have no association with alcohol consumption.[101–103] the results of a recent meta-analysis involving nine cross-sectional and one case–control studies indicated that alcohol consumption could increase the risk of des, irrespective of age and sex.[104] tear hyperosmolarity following alcohol consumption has been detected after heavy drinking.[73, 105] moreover, ethanol induces the expression of interleukin-1, interleukin-6, and interleukin-8 in the ocular surface cells.[106] as an additional mechanism, chronic alcoholism can induce vitamin a deficiency by reducing retinol in the liver. absence of vitamin a causes increased epidermal keratinization through loss of the goblet cells from the cornea and conjunctiva, which is a major pathogenesis of des.[107, 108] discussion many pathophysiological aspects of the deteriorating effects of alcohol consumption on ocular structures have been demonstrated, however, additional well-designed studies are required for a definite conclusion. according to the present medical literature, along with harmful effects on many other organs of the body, alcohol consumption may damage ocular tissues, from the cornea and conjunctiva to the retina and optic nerve. among them, alcohol teratogenicity and alcohol-related optic neuropathies are more definite and seem to be the most serious ocular conditions related to alcohol consumption [table 3]. 266 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 alcohol and the eye; karimi et al ophthalmologists should consider alcohol consumption as a modifiable risk factor for ocular disease. future direction on clinical aspects of the topic may be as follows: i. how to reduce the adverse effects of prenatal alcohol exposure in pregnant alcohol drinkers? ii. how to optimize the management of acute methanol toxicity and its optic neuropathy to preserve a higher level of vision and visual function? iii. how oral ethanol can expose heavy drinkers to ocular surface disease? references 1. alcohol research: current reviews editorial staff. drinking patterns and their definitions. alcohol res. 2018;39(1):17– 18. 2. wang s, wang jj, wong ty. alcohol and eye diseases. surv ophthalmol 2008;53:512–525. 3. weih lm, mukesh bn, mccarty ca, taylor hr. association of demographic, familial, medical, and ocular factors with intraocular pressure. arch ophthalmol 2001;119:875–880. 4. brasil a, castro aj, martins ic, lacerda em, souza gs, herculano a, et al. colour vision impairment in young alcohol consumers. plos one 2015;10:e0140169. 5. lobo ia, harris ra. gaba(a) receptors and alcohol. pharmacol biochem behav 2008;90:90–94. 6. xiao c, ye jh. ethanol dually modulates gabaergic synaptic transmission onto dopaminergic neurons in ventral tegmental area: role of mu-opioid receptors. neuroscience 2008;153:240–248. 7. galdino m, mendes, mendes-santos l, vieira j, de bustamante simas m, santos n. visual perception of radial sine-wave grating after the alcohol consumption. psicologia usp 2010;22:99–115. 8. marinkovic k, rickenbacher e, azma s, artsy e, lee akc. effects of acute alcohol intoxication on saccadic conflict and error processing. psychopharmacology 2013;230:487–497. 9. abroms b, gottlob l, fillmore m. alcohol effects on inhibitory control of attention: distinguishing between intentional and automatic mechanisms. psychopharmacology 2006;188:324–334. 10. schmitt ku, lanz c, muser mh, walz f, schwarz u. saccadic eye movements after low-dose oral alcohol exposure. j forensic leg med 2013;20:870–874. 11. silva jbs, cristino ed, almeida nl, medeiros pcb, santos nad. effects of acute alcohol ingestion on eye movements and cognition: a double-blind, placebo-controlled study. plos one 2017;12:e0186061–e0186061. 12. ashurst jv, nappe tm. methanol toxicity. in: statpearls. treasure island, fl: statpearls publishing llc.; 2019. 13. barceloux dg, bond gr, krenzelok ep, cooper h, vale ja. american academy of clinical toxicology practice guidelines on the treatment of methanol poisoning. j toxicol clin toxicol 2002;40:415–446. 14. givens m, kalbfleisch k, bryson s. comparison of methanol exposure routes reported to texas poison control centers. west j emerg med 2008;9:150–153. 15. martin-amat g, mcmartin ke, hayreh ss, hayreh ms, tephly tr. methanol poisoning: ocular toxicity produced by formate. toxicol appl pharmacol 1978;45:201–208. 16. kraut ja, kurtz i. toxic alcohol ingestions: clinical features, diagnosis, and management. clin j am soc nephrol 2008;3:208. 17. baumbach gl, cancilla pa, martin-amat g, tephly tr, mcmartin ke, makar ab, et al. methyl alcohol poisoning. iv. alterations of the morphological findings of the retina and optic nerve. arch ophthalmol 1977;95:1859–1865. 18. sharma p, sharma r. toxic optic neuropathy. indian j ophthalmol 2011;59:137–141. 19. al aseri z, altamimi s. keeping a high index of suspicion: lessons learned in the management of methanol ingestion. bmj case rep 2009;2009. 20. naeser p. optic nerve involvement in a case of methanol poisoning. br j ophthalmol 1988;72:778–781. 21. benton cd jr, calhoun fp jr. the ocular effects of methyl alcohol poisoning: report of a catastrophe involving three hundred and twenty persons. trans am acad ophthalmol otolaryngol 1952;56:875–885. 22. rotenstreich y, assia ei, kesler a. late treatment of methanol blindness. br j ophthalmol 1997;81:416–417. 23. pakravan m, esfandiari h, sanjari n, ghahari e. erythropoietin as an adjunctive treatment for methanolinduced toxic optic neuropathy. am j drug alcohol abus 2016;42:633–639. 24. pakdel f, sanjari ms, naderi a, pirmarzdashti n, haghighi a, kashkouli mb. erythropoietin in treatment of methanol optic neuropathy. j neuro-ophthalmol 2018;38:167–171. 25. yunard a, nusanti s, sidik m. methanol toxic optic neuropathy (characteristic and evaluation of therapy). ophthalmol india 2016;42:38–44. 26. sharma r, marasini s, sharma ak, shrestha jk, nepal bp. methanol poisoning: ocular and neurological manifestations. optom vis sci 2012;89:178–182. 27. abrishami m, khalifeh m, shoayb m, abrishami m. therapeutic effects of high-dose intravenous prednisolone in methanol-induced toxic optic neuropathy. j ocul pharmacol ther 2011;27:261–263. 28. triningrat aamp,rahayu nmk,manuabai bp. visual acuity of methanol intoxicated patients before and after hemodialysis, methyprednisolone and prednisone therapy. joi 2010;7:129–132. 29. shukla m, shikoh i, saleem a. intravenous methylprednisolone could salvage vision in methyl alcohol poisoning. indian j ophthalmol. 2006 mar;54(1):68–69. 30. brennan d, giles s. ocular involvement in fetal alcohol spectrum disorder: a review. current pharmaceutical design. 2014;20. 31. aring em, landgren m, svensson l, gronlund ma. an eye diagnostic code for evaluation of ophthalmological abnormalities in fetal alcohol syndrome disorders. invest ophthalmol vis sci 2015;56:1378–1378. 32. peng y, yang ph, ng ss, wong og, liu j, he ml, et al. a critical role of pax6 in alcohol-induced fetal microcephaly. neurobiol dis 2004;16:370–376. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 267 alcohol and the eye; karimi et al 33. yelin r, kot h, yelin d, fainsod a. early molecular effects of ethanol during vertebrate embryogenesis. differentiation 2007;75:393–403. 34. yelin r, schyr rb, kot h, zins s, frumkin a, pillemer g, et al. ethanol exposure affects gene expression in the embryonic organizer and reduces retinoic acid levels. dev biol 2005;279:193–204. 35. shukrun n, shabtai y, pillemer-amdur g, fainsod a. retinoic acid signaling reduction recapitulates the effects of alcohol on embryo size. genesis 2019;57:e23284. 36. shabtai y, fainsod a. competition between ethanol clearance and retinoic acid biosynthesis in the induction of fetal alcohol syndrome. biochem cell biol 2017;96(2):148160. 37. kot-leibovich h, fainsod a. ethanol induces embryonic malformations by competing for retinaldehyde dehydrogenase activity during vertebrate gastrulation. dis model mech 2009;2:295–305. 38. peng y, yang p-h, ng s, lum c, kung h-f, lin m. protection of xenopus laevis embryos against alcoholinduced delayed gut maturation and growth retardation by peroxiredoxin 5 and catalase. j mol biol 2004;340:819– 827. 39. peng y, yang ph, guo y, ng ss, liu j, fung pc, et al. catalase and peroxiredoxin 5 protect xenopus embryos against alcohol-induced ocular anomalies. invest ophthalmol vis sci 2004;45:23–29. 40. hug te, fitzgerald km, cibis gw. clinical and electroretinographic findings in fetal alcohol syndrome. j aapos 2000;4:200–204. 41. abdelrahman a, conn r. eye abnormalities in fetal alcohol syndrome. ulster med j 2009;78:164–165. 42. peragallo j, biousse v, newman nj. ocular manifestations of drug and alcohol abuse. curr opin ophthalmol 2013;24:566–573. 43. ribeiro im, vale pj, tenedorio pa, rodrigues pa, bilhoto ma, pereira hc. ocular manifestations in fetal alcohol syndrome. eur j ophthalmol 2007;17:104–109. 44. flanigan ey, aros s, bueno mf, conley m, troendle jf, cassorla f, mills jl, et al. eye malformations in children with heavy alcohol exposure in utero. j pediatr 2008;153:391–395. 45. strömland k. ocular involvement in the fetal alcohol syndrome. surv ophthalmol 1987;31:277–284. 46. pai v, adams d. preventing ethanol-induced brain and eye morphology defects using optogenetics. bioelectricity 2019;1:260-272. 47. klein r, klein be, linton kl. prevalence of age-related maculopathy. the beaver dam eye study. ophthalmology 1992;99:933–943. 48. friedman ds, o’colmain bj, muñoz b, tomany sc, mccarty c, de jong pt, et al. prevalence of agerelated macular degeneration in the united states. arch ophthalmol 2004;122:564–572. 49. agar e, demir s, amanvermez r, bosnak m, ayyildiz m, celik c. the effects of ethanol consumption on the lipid peroxidation and glutathione levels in the right and left brains of rats. int j neurosci 2003;113:1643–1652. 50. cederbaum ai. role of lipid peroxidation and oxidative stress in alcohol toxicity. free radic biol med 1989;7:537– 539. 51. rikans le, gonzalez lp. antioxidant protection systems of rat lung after chronic ethanol inhalation. alcohol clin exp res 1990;14:872–877. 52. rosenblum er, gavaler js, van thiel dh. lipid peroxidation: a mechanism for alcohol-induced testicular injury. free radic biol med 1989;7:569–577. 53. galan p, viteri fe, bertrais s, czernichow s, faure h, arnaud j, et al. serum concentrations of beta-carotene, vitamins c and e, zinc and selenium are influenced by sex, age, diet, smoking status, alcohol consumption and corpulence in a general french adult population. eur j clin nutr 2005;59:1181–1190. 54. stryker ws, kaplan la, stein ea, stampfer mj, sober a, willett wc. the relation of diet, cigarette smoking, and alcohol consumption to plasma beta-carotene and alphatocopherol levels. am j epidemiol 1988;127:283–296. 55. manari ap, preedy vr, peters tj. nutritional intake of hazardous drinkers and dependent alcoholics in the uk. addict biol 2003;8:201–210. 56. bergheim i, parlesak a, dierks c, bode jc, bode c. nutritional deficiencies in german middle-class male alcohol consumers: relation to dietary intake and severity of liver disease. eur j clin nutr 2003;57:431–438. 57. bora ps, kaliappan s, xu q, kumar s, wang y, kaplan hj, et al. alcohol linked to enhanced angiogenesis in rat model of choroidal neovascularization. febsj 2006;273:1403–1414. 58. chong ew, kreis aj, wong ty, simpson ja, guymer rh. alcohol consumption and the risk of age-related macular degeneration: a systematic review and meta-analysis. am j ophthalmol 2008;145:707–715. 59. ritter ll, klein r, klein be, mares-perlman ja, jensen sc. alcohol use and age-related maculopathy in the beaver dam eye study. am j ophthalmol 1995;120:190–196. 60. moss se, klein r, klein be, jensen sc, meuer sm. alcohol consumption and the 5-year incidence of age-related maculopathy: the beaver dam eye study. ophthalmology 1998;105:789–794. 61. adams mk, chong ew, williamson e, aung kz, makeyeva ga, giles gg, et al. 20/20–alcohol and age-related macular degeneration: the melbourne collaborative cohort study. am j epidemiol 2012;176:289–298. 62. young rj, mcculloch dk, prescott rj, clarke bf. alcohol: another risk factor for diabetic retinopathy? br med j 1984;288:1035–1037. 63. moss se, klein r, klein be. alcohol consumption and the prevalence of diabetic retinopathy. ophthalmology 1992;99:926–932. 64. moss se, klein r, klein be. the association of alcohol consumption with the incidence and progression of diabetic retinopathy. ophthalmology 1994;101:1962–1968. 65. zhu w, meng yf, wu y, xu m, lu j. association of alcohol intake with risk of diabetic retinopathy: a meta-analysis of observational studies. sci rep 2017;7:4. 66. francis pj, stanford mr, graham em. dehydration is a risk factor for central retinal vein occlusion in young patients. acta ophthalmol. scand 2003;81:415–416. 67. sperduto rd, hiller r, chew e, seigel d, blair n, burton tc, et al. risk factors for hemiretinal vein occlusion: comparison with risk factors for central and branch retinal vein occlusion: the eye disease case-control study. ophthalmology 1998;105:765–771. 268 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 alcohol and the eye; karimi et al 68. klein r, klein be, moss se, meuer sm. the epidemiology of retinal vein occlusion: the beaver dam eye study. trans am ophthalmol soc 2000;98:133–141; discussion 141–133. 69. liu b, deng t, zhang j. risk factors for central serous chorioretinopathy: a systematic review and meta-analysis. retina 2016;36:9–19. 70. tittl mk, spaide rf, wong d, pilotto e, yannuzzi la, fisher yl, et al. systemic findings associated with central serous chorioretinopathy. am j ophthalmol 1999;128:63–68. 71. gkotsi d, gupta m, lascaratos g, syrogiannis a, dhillon b. alcoholic liver disease and bilateral multifocal central serous retinopathy: a case report. j med case rep 2013;7:43. 72. moss se, klein r, klein be. asteroid hyalosis in a population: the beaver dam eye study. am j ophthalmol 2001;132:70–75. 73. castro jj, pozo am, rubino m, anera rg, jimenez del barco l. retinal-image quality and night-vision performance after alcohol consumption. j ophthalmol 2014;2014:704823. 74. kesler a, pianka p. toxic optic neuropathy. curr neurol neurosci 2003;3:410–414. 75. joseph s, al-ali s, tripathi a. tobacco-alcohol optic neuropathy. is complete recovery possible? oman j ophthalmol 2014;7:50. 76. kahn ha, milton rc. alternative definitions of open-angle glaucoma. effect on prevalence and associations in the framingham eye study. arch ophthalmol 1980;98:2172– 2177. 77. leske mc, warheit-roberts l, wu sy. open-angle glaucoma and ocular hypertension: the long island glaucoma case-control study. ophthalmic epidemiol 1996;3:85–96. 78. yoshida m, ishikawa m, kokaze a, et al. association of lifestyle with intraocular pressure in middle-aged and older japanese residents. jpn j ophthalmol 2003;47:191–198. 79. wu sy, leske mc. associations with intraocular pressure in the barbados eye study. arch ophthalmol 1997;115:1572–1576. 80. lin hy, hsu wm, chou p, liu cj, chou jc, tsai sy, et al. intraocular pressure measured with a noncontact tonometer in an elderly chinese population: the shihpai eye study. arch ophthalmol 2005;123:381–386. 81. giurlani bp, obie lg, petersen cg, presley dd. alcohol and open angle glaucoma–influence on detection, iop, bp/iop ratios. j am optom assoc 1978;49:409–416. 82. buckingham t, young r. the rise and fall of intra-ocular pressure: the influence of physiological factors. ophthal physl opt 1986;6:95–99. 83. houle re, grant wm. alcohol, vasopressin, and intraocular pressure. invest ophthalmol 1967;6:145–154. 84. leydhecker w, krieglstein gk, uhlich e. [experimental investigations on the mode of action of alcoholic liquor on the intra-ocular pressure (author’s transl)]. klin monatsbl augenh 1978;173:75–79. 85. kojima s, sugiyama t, kojima m, azuma ii, ito s. effect of the consumption of ethanol on the microcirculation of the human optic nerve head in the acute phase. jpn j ophthalmol 2000;44:318–319. 86. fan bj, leung yf, wang n, lam sc, liu y, tam os, et al. genetic and environmental risk factors for primary openangle glaucoma. chin med j 2004;117:706–710. 87. seddon jm, schwartz b, flowerdew g. case-control study of ocular hypertension. arch ophthalmol 1983;101:891– 894. 88. al owaifeer am, al taisan aa. the role of diet in glaucoma: a review of the current evidence. ophthalmol ther 2018;7:19–31. 89. nemesure b, wu sy, hennis a, leske mc. factors related to the 4-year risk of high intraocular pressure: the barbados eye studies. arch ophthalmol 2003;121:856– 862. 90. kang jh, willett wc, rosner ba, hankinson se, pasquale lr. prospective study of alcohol consumption and the risk of primary open-angle glaucoma. ophthalmic epidemiol 2007;14:141–147. 91. gong y, feng k, yan n, xu y, pan cw. different amounts of alcohol consumption and cataract: a meta-analysis. optom vis sci 2015;92:471–479. 92. beebe dc, holekamp nm, shui yb. oxidative damage and the prevention of age-related cataracts. ophthalmic res 2010;44:155–165. 93. zeng j, borchman d, paterson ca. acute effect of ethanol on lens cation homeostasis. alcohol 1998;16:189–193. 94. oh jy, yu jm, ko jh. analysis of ethanol effects on corneal epithelium. invest ophthalmol vis sci 2013;54:3852– 3856. 95. liu h-y, yeh p-t, kuo k-t, huang j-y, lin c-p, hou y-c. toxic keratopathy following the use of alcohol-containing antiseptics in nonocular surgery. jama ophthalmol 2016;134:449–452. 96. kim jh, kim jh, nam wh, yi k, choi dg, hyon jy, et al. oral alcohol administration disturbs tear film and ocular surface. ophthalmology 2012;119:965–971. 97. chia em, mitchell p, rochtchina e, lee aj, maroun r, wang jj. prevalence and associations of dry eye syndrome in an older population: the blue mountains eye study. clin exp ophthalmol 2003;31:229–232. 98. galor a, feuer w, lee dj, florez h, faler al, zann kl, et al. depression, post-traumatic stress disorder, and dry eye syndrome: a study utilizing the national united states veterans affairs administrative database. am j ophthalmol 2012;154:340–346.e342. 99. moss se, klein r, klein be. prevalence of and risk factors for dry eye syndrome. arch ophthalmol 2000;118:1264– 1268. 100. cumurcu t, gunduz a, cumurcu be, gül ig, akpolat n, karlidag r. the changes in tear film parameters and impression cytology in heavily drinking men. cornea 2013;32:237–241. 101. lu p, chen x, liu x, yu l, kang y, xie q, et al. dry eye syndrome in elderly tibetans at high altitude: a populationbased study in china. cornea 2008;27:545–551. 102. viso e, rodriguez-ares mt, gude f. prevalence of and associated factors for dry eye in a spanish adult population (the salnes eye study). ophthalmic epidemiol 2009;16:15– 21. 103. xu l, you qs, jonas jb. prevalence of alcohol consumption and risk of ocular diseases in a general population: the beijing eye study. ophthalmology 2009;116:1872–1879. 104. you ys, qu nb, yu xn. alcohol consumption and dry eye journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 269 alcohol and the eye; karimi et al syndrome: a meta-analysis. int j ophthalmol 2016;9:1487– 1492. 105. oh jy, yu jm, ko jh. analysis of ethanol effects on corneal epithelium. invest ophthalmol vis sci 2013;54:3852– 3856. 106. cumurcu t, gunduz a, cumurcu be, gul ig, akpolat n, karlidag r. the changes in tear film parameters and impression cytology in heavily drinking men. cornea 2013;32:237–241. 107. lieber cs. alcohol, liver, and nutrition. j am coll nutr 1991;10:602–632. 108. hatchell dl, sommer a. detection of ocular surface abnormalities in experimental vitamin a deficiency. arch ophthalmol 1984;102:1389–1393. 270 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 original article analyzing the carbon footprint of an intravitreal injection barry power, mb, bch, bao, mrcophth, ms; robert brady, mb, bch, bao, mrcophth; paul connell, mb, bch, bao, md, hdiphqm, frcsi (ophth), franzco vitreoretinal department, mater misericordiae university hospital, dublin, ireland orcid: barry power: http://orcid.org/0000-0002-7045-0264 abstract purpose: to estimate the carbon footprint of a single intravitreal injection in a hospitalbased intravitreal service. methods: greenhouse gas emissions attributable to the delivery of an intravitreal injection were calculated using a hybrid lifecycle analysis technique. data were collected regarding procurement of materials, patient travel, and building energy use. results: carbon emissions associated with a single intravitreal injection, excluding the anti-vegf agent, were 13.68 kg co2eq. this equates to 82,100 kg co2eq annually for our service. patient travel accounted for the majority of emissions at 77%, with procurement accounting 19% for and building energy usage for 4% of total emissions. the omission of items considered dispensable from injection packs would reduce carbon emissions by an estimated 0.56 kg per injection – an annual saving of 3,360 kg co2eq for our service. similar savings, if extrapolated to a country the size of the united kingdom, could yield annual carbon savings of 450,000 kg co2eq. for context, a single one-way economy transatlantic flight produces 480 kg co2eq per person. conclusion: wasteful practice in healthcare increases greenhouse gas production and drives climate change. the healthcare sector should be a leader in sustainable practice promotion and changes to high volume procedures have the largest impact on emissions. long-acting agents offer the greatest future potential for meaningful reductions. keywords: anti-vegf; climate change; medical retina; sustainability j ophthalmic vis res 2021; 16 (3): 367–376 introduction climate change is a serious global threat and the healthcare industry is a large net contributor. correspondence to: barry power, mb, bch, bao, ms. ophthalmology department, mater misericordiae university hospital, eccles street, dublin 3, ireland. e-mail: barry.power.1@ucdconnect.ie received: 18-11-2020 accepted: 03-02-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i3.9433 the climate of the earth has changed throughout history but the changes over the last 50 years are unprecedented for millennia. the national aeronautics and space administration (nasa) states that this change is highly likely (>95% probability) to be attributable to human activity and this is supported by multiple studies with the wider this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: power b, brady r, connell p. analyzing the carbon footprint of an intravitreal injection. j ophthalmic vis res 2021;16:367–376. © 2021 power et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 367 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i3.9433&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr carbon footprint of intravitreal injections; power et al scientific community in agreement.[1–4] this change is rapid with the current rate of warming 10 times faster than similar historical periods.[5] climate change will disproportionately affect developing countries.[6] greenhouse gases (ghgs) are those considered to be causative of global warming and carbon footprinting is the commonly accepted scientific methodology for quantifying the volume of ghgs a product or activity produces. carbon footprints typically break a process down into components, which are felt to contribute significantly to ghg production. the footprint puts particular emphasis on the emissions that are felt to drive climate change. four gases (carbon dioxide, methane, nitrous oxide, and sulphur hexafluoride) and two groups of gases (hydrofluorocarbons and perfluorocarbons) are described in the kyoto protocol as contributing to global warming. carbon dioxide (co2) is used as the reference gas with the total emissions expressed in units called carbon dioxide equivalents (co2eq). [7] in the united kingdom (uk) and the united states of america (usa), healthcare is responsible for 4% and 10% annual emissions respectively.[8, 9] amongst the public sector in the uk, healthcare is estimated to account for 25% of total emissions.[10] limited studies to date have described the carbon footprint of various healthcare processes.[11–13] in the ophthalmic literature, the carbon footprint of the cataract surgery pathway in a unit in the uk has been estimated to be 181 kg co2eq. [14] the uk national health service (nhs) aims to be a leader among global healthcare providers in facing up to its responsibilities concerning carbon emissions. the nhs carbon reduction strategy sets an ambition for the healthcare sector to drive the change toward a low carbon society.[15] taking 2007 levels as the baseline, the strategic goals are a 34% reduction in carbon production by 2020 and an 80% reduction by 2050. efforts to reduce healthcare-related carbon emissions are most effective when focused macroscopically on processes. high volume procedures, such as intravitreal injections, offer scope for meaningful net emission reductions with procedural changes. with an ageing population, the number of intravitreal injections performed continues to grow and an estimated 5.9 million intravitreal injections were performed in the usa in 2016.[16] in the uk, injection procedures increased by 215% between january 2010 and may 2014.[17] our aims for this paper are to: 1. estimate the overall carbon emission per injection; 2. understand where in the process the carbon is emitted; 3. identified hotspots within this process can then be targeted to achieve the most effective reductions. our target audience is those working in the healthcare sector including managers and clinicians. methods there are two main methods of carbon footprinting – lifecycle analysis (lca) and input–output-based analysis. a hybrid lca utilizes both methods in an attempt to address the inherent limitations of the two systems. we discuss our rationale for using this technique at the end of the section. the study was performed in the mater misericordiae university hospital dublin from june to august in 2018. this study adhered to the guidelines of the declaration of helsinki. all methods of carbon emission estimation must have a scope or boundary. for this study, we calculated emissions from three main components of the intravitreal injection process: (1) procurement of the materials utilized; (2) patient travel to and from the hospital; and (3) building energy use. greenhouse gas (ghg) emissions were converted to kilograms carbon dioxide equivalent (kg co2eq) which is the accepted common unit for measuring ghg production. this measure is the amount of carbon dioxide that would have the same global warming potential as the ghgs produced by the process measured. procurement procurement emissions are defined as the emissions associated with all of the elements of production, distribution, consumption, and disposal of an item. 368 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 carbon footprint of intravitreal injections; power et al production, distribution, and consumption of materials carbon emissions associated with production, distribution, and consumption were calculated using an input–output model. the input–output method is used when a lifecycle-based assessment is impractical due to difficulty in assigning boundaries to complex processes with many direct and indirect components. this form of carbon estimation uses the monetary cost of a product or process to estimate carbon emissions. different conversion factors exist for different industries; a conversion factor specific to the medical industry was used for the injection pack and a pharmaceutical conversion factor for comparison of the different agents. these carbon emission conversion factors were obtained from the 2011 uk department of environment and rural affairs (defra) emission modelling documents, using the 2018 price estimates.[19] the cost of the injection pack utilized was €10 (£9.10). the local costs of bevacizumab, ranibizumab, and aflibercept were €44, €820, and €1100, respectively – each purchased in prefilled syringes. these syringes are single dose units and come separately from the injection packs. waste disposal the carbon emissions associated with waste disposal were calculated using a lifecyclebased analysis. this type of analysis collects all of the materials utilized in a process and estimates emissions attributable to each item. the calculations were performed using the 2018 uk government ghg conversion publication.[20] the calculation is weight-based. each separate product used for delivering an intravitreal injection was weighed and its composition classified according to the document. conversion factors were used to convert this data into kg co2eq. the conversion factors consider the composition of the product disposed of and the method of disposal (clinical incineration or landfill). the conversion factor for incineration of clinical/hazardous waste (which is undertaken at higher heat and without energy extraction) was taken to be 1,833 in accordance with previous studies.[14] each healthcare provider performing injections in the service was surveyed (n = 6) and asked to document which waste disposal bin each item was placed in after use. the method of disposal was taken to be the majority result. the contents of the pack are summarized in table 3 in the results section. travel emission production attributable to patient travel to and from the hospital was calculated based on the distance travelled (hospital to home address) and the mode of transport. patients were consented for participation. google maps distance was used to calculate the distance travelled by the patient (www.googlemaps.ie). one hundred sequential patients were surveyed to document mode of travel and journeys were taken to be round-trips. the 2018 uk government ghg conversion publication was used to convert this data into kg co2eq per km travelled.[20] energy usage data pertaining to energy usage in the study hospital was not available so moorfield’s eye hospital was used as a representative substitute. the building energy use was estimated in a similar manner to previous studies.[14] energy use per m2 of floor space was estimated using the uk 2017 national estates return information collection database.[21] this data was then converted to kg co2 eq per kw using the carbon conversion factor. the 100m2 floor space utilized by the intravitreal injection service was defined as the check-in/waiting room and a two-bed laminar airflow injection suite. energy usage was taken to be that of standard clinical floor space. the waiting room is used for a variety of different purposes, so its contribution was adjusted accordingly. energy use per injection was calculated by estimating the proportional energy use of the floor space when utilized by the injection service and dividing it by the total number of injections performed per annum (6,000). the injection suite is not used for other purposes. this data is summarized in table 1. clinicians perform intravitreal injections with a surgical scrub to the elbow before an injection list. one facemask is used for a list. attire is typically office attire with one plastic apron per list. hands are sterilized between cases with a betadine scrub or alcohol hand gel. all clinicians use separate sterile gloves and an individual intraocular injection pack for each patient. the contents of the injection journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 369 www.googlemaps.ie carbon footprint of intravitreal injections; power et al table 1. emissions factors procurement emission factor (kg co2eq per £££) pharmaceutical 0.43 medical 0.28 waste disposal emission factor range (kg co2eq per ton) landfill 9-445 incineration 1833 travel method emission factor (kg co2eq per km) car 0.178 bus 0.101 train 0.044 walk/cycle 0 energy use emission factor (kg co2eq per kwh) electricity 0.59 kg co2eq, kilograms of carbon dioxide equivalents; km, kilometer; kwh, kilowatt hour table 2. patient travel emissions car bus train walk/cycle conversion factor 0.1778 0.11 0.044 0 average distance (km) 33 51 42 na patients 64 29 3 4 km, kilometers pack and their associated data are summarized in the results section in table 3. only items used for each separate injection were considered for analysis (facemask and apron used for the whole list, therefore not included). inclusions travel of patients to and from the hospital was included in the study. this maintains consistency with previous studies.[11–14] although it does not follow the pas 2050 guidelines, we believe that inclusion transport in this hybrid lca is appropriate. patient travel is essential to the procedure and represents a large component of the carbon production. due to the frequent and recurrent nature of intravitreal injections, travel is an important source of emissions. exclusions excluded components include but are not limited to: items deemed negligible to overall emissions score (e.g., ink, medical record documents), procurement of items used over the medium to long-term (computers, injection beds, diagnostic tools, e.g., oct, etc.), human inputs into the system, building/construction costs, food and drink, staff training, and research. methodology discussion we utilized a hybrid lca for the calculation of this carbon footprint. the main advantage of this methodology is that it provides a more comprehensive analysis than other techniques.[22, 23] it helps to reduce the impact of truncation error, which can be caused by the boundary placement required in pas 2050 adhering lcas. the disadvantage with this methodology is it can be less reproducible – particularly when the methodology is poorly defined. this can be problematic in formal industry assessments as it can make a direct comparison between processes more difficult. this study aimed 370 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 carbon footprint of intravitreal injections; power et al table 3. intravitreal injection pack contents and waste disposal emission data item weight (g) classification landfill incineration conversion fx kg co2eq nacl 14.68 plastic rigid 6 0 9 0.0001 paper towel 20.84 cloth 6 0 445 0.009 sterile gloves 31.58 plastic film 6 0 9 0.00003 drape 19.79 plastic film 0 0 9 0.0002 scleral marker 1.76 plastic rigid 2 4 1833 0.00004 speculum 2.8 metal 1 5 1833 0.00006 wooden cotton buds x 5 4.08 wood 2 4 1833 0.00009 2 ml syringe 2.72 plastic rigid 6 0 0 0.00002 syringe 3.71 plastic rigid 0 6 1833 0.00008 bevacizumab needle 0.59 metal 0 6 1833 0.00001 gauze square x 4 7.77 cloth 6 0 445 0.004 plastic forceps 9.64 plastic rigid 2 4 1833 0.0002 iodine minim 1.5 plastic rigid 6 0 9 0.00001 plastic container 30 ml 3.31 plastic rigid 6 0 9 0.00003 plastic container 30 ml 3.31 plastic rigid 6 0 9 0.00003 g proxymetacaine 1.59 plastic rigid 6 0 9 0.00001 g chloromycetin 1.59 plastic rigid 6 0 9 0.00001 plastic container outer 27.85 plastic rigid 6 0 9 0.00003 outer wrapping 37.5 plastic film 6 0 9 0.0003 fx, conversion factor; gs, weight in grams conversion; kg co2eq, kilograms of carbon dioxide equivalents to make an all-encompassing, accurate estimate of the component and total carbon production; for this, we felt the hybrid methodology was the most robust. regarding the use of input–output models to calculate carbon emissions, values are determined by the cost of materials. naturally, high cost materials will have large carbon estimates. these values can seemingly overestimate emissions. however, pharmaceutical agents, for example, require extensive research and development before coming to market. marketing of these agents, drug representative activities, and education of clinicians and patients are key components of the industry. all of these activities create emissions. thus, just as the monetary cost of these critical components of drug development are embedded in the cost of the product, it can be argued that the downstream carbon emissions are also embedded within the cost of the product. we produced estimates excluding and including the pharmaceutical agents due to their very large contribution to emission volumes. we did not consider potential/debatable differences in duration of action between agents to be a significant factor in emissions production. results one intravitreal injection, excluding the anti-vegf agent, was calculated to produce 13.68 kg co2 eq. the breakdown for the different contributions from the three main sources is outlined in figure 1. the single largest contributor to the carbon footprint was patient travel at 10.49 kg co2 eq (77%) per injection. the majority of patients travelled to and from their appointments by car. our service is situated in a tertiary referral center and our catchment area is the northern half of the province of leinster. the average one-way distance travelled was 38 km. table 2 outlines the travel emission conversion factors and the breakdown of the common modes of transport to the hospital. medical procurement (the injection pack) accounted for 2.54 kg co2 eq (19%). despite journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 371 carbon footprint of intravitreal injections; power et al figure 1. proportional carbon emissions. kg co2eq, kilograms of carbon dioxide equivalents figure 2. estimated carbon emissions associated with the injection pack, avastin, lucentis, and eylea. kg co2eq, kilograms of carbon dioxide equivalents a large amount of physical waste generated per intravitreal injection, the carbon emissions produced through waste disposal were negligible – just 0.05 kg co2 eq per injection or 0.04% of the total emissions. the contents of the injection packs, the method of waste disposal and the emissions data are summarized in table 3. materials deemed to be surplus to requirements (by >75% of clinicians) are highlighted in bold italics. when the different anti-vegf agents are included, emission estimates vary widely. using input–output analysis, bevacizumab, ranibizumab, and aflibercept procurement produce an estimated 20, 320, and 423 kg co2 eq, respectively, per injection. figure 2 compares the emissions estimates of the anti-vegf agents to those of the pack. opportunities for carbon reductions no immediate or realistic opportunity for carbon savings related to building energy use was identified. if the service facilities/logistics allow, patients can receive injections on the same day as clinic appointments, reducing overall hospital attendances and lowering emissions. the use of bilateral same-day injections is another potential mitigation strategy. bilateral same-day injections 372 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 carbon footprint of intravitreal injections; power et al are safe, however, patient safety and medico-legal concerns persist.[24, 25] we identified the procurement of the injection pack as an additional opportunity to reduce emissions. a survey of the clinicians performing the injections identified several items that were deemed to be safely dispensable from the intravitreal packs – these were: plastic tongs for betadine application, a 2 ml syringe, the hard outer plastic container, and the paper hand towel. betadine is generally applied to the patient’s skin using a cotton gauze held by hand, the 2 ml syringe was not used and the hand towel was not necessary because alcohol was used rather than hand washing to sterilize the hands between patients. removal of these items from our packs achieved a price reduction of €2.05 per pack, negotiated with our supplier. using the input–output model for production, distribution, and consumption and the lifecycle-based analysis for disposal, this equates to 0.56 kg co2 eq per injection (4%) or an overall reduction of 3,360 kg co2 eq per annum for our hospital-based intravitreal service (based on our annual provision of 6,000 injections). discussion discussion around the importance of sustainability in ophthalmology has increased over the past decade.[26, 27] to our knowledge, this is the first study to estimate the carbon emissions attributable to intravitreal injections. this intervention has rapidly become the most common invasive procedure performed in ophthalmology.[28] an intravitreal injection is a typical medical procedure. we hope that our breakdown of the sources of emissions, from the different components of the procedure, will help to identify the most suitable targets for carbon reduction strategies. current estimations of international rates of intravitreal injections differ. data from the usa estimates the 2013 rate at 130 injections per 100,000 population.[16] the usa estimates project a 10–20% per annum increase in numbers of injections performed. if we use an estimate of 15% and adjust the uk 2015 estimate of 714 per 100,000, the estimated rate for 2018 is 1,248 per 100,000. for the current uk population (66 million), this amounts to 824,000 injections. though pack contents will differ across units, similar changes to contents of injection packs used in the uk could yield a substantial reduction (approximately 460 ton co2 eq). to put the figures into context, a oneway, economy class transatlantic flight from london to new york city produces an estimated 480 kg co2eq per person. [29] in addition to the reductions possible in carbon emissions, the judicious omission of unnecessary single-use plastics from routine procedure packs has other environmental benefits. the european union (eu) has recently followed some countries in banning the use of several forms of single-use plastics.[30] plastic does not biodegrade and there are an estimated 269,000 tons of plastic floating in the ocean.[31] three of the four dispensable items in our packs are hard plastic. dialogue with manufacturing companies may be able to further reduce the plastic contents of the packs through omission of unnecessary items. the annual weight of the dispensable plastic in the packs used by our service is over 240 kg. in 2013, morris et al estimated the carbon emissions attributable to the cardiff cataract pathway to be 181 kg co2 eq, with an annual production of 63 mega ton kg co2 eq in england. [14] the proportional breakdown of the components of the cataract pathway differs slightly from that of an intravitreal injection. procurement was the largest proportional contributor in the cataract pathway at 53.8%. procurement would also be the highest proportional contributor in the intravitreal injection footprint should the anti-vegf agents use be included. proportional energy use was understandably greater for the cataract surgery pathway (36.1% vs 4%), as was the contribution of waste disposal (1.6% vs 0.05%). proportional travel estimates were less in the cataract surgery pathway (10.1% vs 76.6%) but gross travel emissions were greater (18.3 vs 10.49 kg co2 eq). the cataract pathway included two separate round-trip journeys per patient, potentially explaining the higher gross figure. our study has allowed us to identify some easily implemented changes, which would achieve a significant carbon reduction if extrapolated to a national level and is an example of a “bottom-up” change that is immediately realizable. the far larger contribution of the production, distribution, and consumption elements of procurement, compared with the waste disposal element, highlights the need to target emission generation at source. efforts to recycle (challenging in healthcare due journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 373 carbon footprint of intravitreal injections; power et al to infection control concerns) and improve waste management are likely to be small in comparison. the omission of unnecessary items eliminates all of the emissions embedded in the procurement process of an item. our study has some limitations. as demonstrated by the comparison of cataract surgery and intravitreal injection, carbon estimation is, by its nature, variable. it is impossible to measure every direct and indirect contribution to these complex processes. our boundaries exclude known and unknown sources of carbon emissions. methodologies for carbon estimation are not designed with specific industries in mind and interpretations of models can differ. patient travel estimates reflect the local geography and the boundaries of the studied catchment area; thus, variation is expected. calculations relating to the production of materials (or the “procurement” component of this footprinting analysis) may under and overestimate emissions as the estimates are based on price alone. these estimates are based on production in broadly defined industries, not directly on ophthalmology. we recognize the limitations of our estimates based on input–output data but feel that they are sufficiently accurate to satisfy our aims. other studies have estimated the ghg production associated with the production of pharmaceutical agents. parvatker et al recently performed a component lca of several inhaled anesthetic agents using a chemical-engineering scale-up technique.[32] this is a more accurate measure of the emissions associated with the simple production of a volume of a drug. it does not, however, consider the background emissions associated with research and development, marketing, etc. in addition, it is a technique, which is very complex to perform so it may be difficult for clinicians and non-specialists to replicate it. if sustainability is a goal of the wider ophthalmology community, intravitreal injections, due to their exponential increases in volume, should be a prime target for such efforts. despite some limitations, we feel our estimation is a good guide for the component breakdown of the carbon emission profile of an intravitreal injection. the calculation of a carbon footprint is clearly not necessary for every individual procedure. the results not always intuitive and analysis of a process can give us valuable insight into where to focus on reduction strategies. we echo morris et al in stressing the importance of focusing on procurement while again demonstrating the somewhat limited potential impact of waste recycling strategies.[14] in the future, the introduction of long-acting agents may reduce the number of injections performed.[33] this represents the greatest potential to achieve large scale emissions reductions associated with intravitreal injections as it would tackle both procurement and travel associated emissions. extensive carbon savings would be achievable, not to mention the obvious economic and service provision benefits. for many clinicians, the large quantity of ghg produced by our health sector may seem outside of their direct control or responsibility. nonetheless, clinicians should recognize that they can make simple changes that can have an immediate positive impact on carbon emissions. we must lead by example and address the harmful effects of mindless wastefulness in our daily practice. sensible alterations to pack contents can have economic benefits, as well as lowering ghg production. these reductions can have a large overall impact when extrapolated to a service or even a national level. in addition to lowering ghg production, the reduction in singleuse plastics has other environmental benefits beyond the scope of this study. pre-prepared packs are in widespread use for many minor procedures across healthcare, and our study may encourage other clinicians to make similar choices. we strongly advocate bottom-up interventions to drive an overall reduction in carbon emissions in ophthalmology and healthcare as a whole. acknowledgement the authors would like to thank prof. nick holden, university college dublin, school of biosystems and food engineering for his help in advising us on our carbon footprinting methodology. financial support and sponsorship none. conflicts of interest the authors declare no conflicts of interest. 374 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 carbon footprint of intravitreal injections; power et al references 1. santer bd, taylor ke, wigley tml, johns tc, jones pd, karoly dj, et al. a search for human influences on the thermal structure of the atmosphere. nature 1996;382:39– 46. 2. hegerl g, von storch h, hasselmann k. detecting greenhouse-gas-induced climate change with an optimal fingerprint method. j climate 1996;9:2281–2306. 3. ramaswamy v. anthropogenic and natural influences in the evolution of lower stratospheric cooling. science 2006;311:1138–1141. 4. santer b. contributions of anthropogenic and natural forcing to recent tropopause height changes. science 2003;301:479–483. 5. national research council. surface temperature reconstructions for the last 2,000 years. washington, dc: the national academies press; 2006. 6. ravindranath n, sathaye j. climate change and developing countries. dordrecht: springer netherlands; 2003. 7. united nations framework convention on climate change. kyoto protocol reference manual on accounting of emissions and assigned amount. unfccc; 2008 [cited 2020 february 10]. available from: https://unfccc.int/resource/docs/publications/ 08_unfccc_kp_ref_manual.pdf 8. sustainable development unit and uk national health service. carbon footprint update for the nhs in london, england. london: nhs; 2015 [cited 2020 february 10]. available from: https://www.sduhealth.org.uk/policystrategy/reporting/nhs-carbon-footprint.aspx 9. eckelman mj, sherman j. environmental impacts of the us healthcare system and effects on public health. plos one 2016;11:e0157014. 10. nhs england sustainable development commission. carbon emissions: carbon footprinting study, london. london: nhs; 2008 [cited 2020 february 10]. available from: https://www.sduhealth.org.uk/policy-strategy/ reporting/nhs-carbon-footprint.aspx 11. connor a, lillywhite r, cooke m. the carbon footprint of a renal service in the united kingdom. qjm 2010;103:965– 975. 12. connor a, lillywhite r, cooke m. the carbon footprints of home and in-center maintenance hemodialysis in the united kingdom. hemodialysis intl 2011;15:39–51. 13. zander a, niggebrugge a, pencheon d, lyratzopoulos g. changes in travel-related carbon emissions associated with modernization of services for patients with acute myocardial infarction: a case study. j public health 2010;33:272–279. 14. morris d, wright t, somner j, connor a. the carbon footprint of cataract surgery. eye 2013;27:495–501. 15. nhs england sustainable development unit. carbon reduction strategy 2009, london. london: nhs; 2009 [cited 2020 february 10]. available from: https: //www.sduhealth.org.uk/policy-strategy/engagementresources/nhs-carbon-reduction-strategy-2009.aspx 16. williams ga. ivt injections: health policy implications. rev ophthalmol 2014 [cited 2020 february 10]. available from: http://www.reviewofophthalmology.com/content/d/ retinal_insider/c/48732 17. hollingworth w, jones t, reeves b, peto t. a longitudinal study to assess the frequency and cost of antivascular endothelial therapy, and inequalities in access, in england between 2005 and 2015. bmj open 2017;7:e018289. 18. defra. specification for the assessment of the lifecycle greenhouse gas emissions of goods and services. london: british standards, carbon trust, pas2050; 2011 [cited 2020 february 10]. available from: http://shop.bsigroup. com/upload/shop/download/pas/pas2050.pdf 19. defra. guidelines to defra/ decc’s ghg conversion factors for company reporting: methodology paper for emission factors. london: defra; 2011 [cited 2020 february 10]. available from: https://assets.publishing. service.gov.uk/government/uploads/system/uploads/ attachment_data/file/69314/pb13625-emission-factormethodology-paper-110905.pdf 20. defra. greenhouse gas reporting: conversion factors 2018. london: defra; 2018 [cited 2020 february 10]. available from: https://www.gov.uk/government/ collections/government-conversion-factors-forcompany-reporting 21. nhs. estates return information collection, england, 2016– 17. england: nhs; 2017 [cited 2020 february 10].available from: https://digital.nhs.uk/data-and-information/ publications/statistical/estates-returns-informationcollection/estates-return-information-collection-2016-17 22. crawford rh, bontinck p-a, stephan a, wiedmann t, yu m. hybrid life cycle inventory methods – a review. j clean prod 2018;172:1273–1288. 23. suh s, lenzen m, treloar gj, hondo h, horvath a, huppes g, et al. system boundary selection in life-cycle inventories using hybrid approaches. environ sci technol 2004;38:657–664. 24. ruão m, andreu-fenoll m, dolz-marco r, gallego-pinazo r. safety of bilateral same-day intravitreal injections of anti-vascular endothelial growth factor agents. clin ophthalmol 2017;11:299–302. 25. juncal v, francisconi c, altomare f, chow dr, giavedoni lr, muni rh, et al. same-day bilateral intravitreal antivascular endothelial growth factor injections: experience of a large canadian retina center. ophthalmologica 2019;242:1–7. 26. somner j, connor a, benjamin l. eyes, economics and the environment: should green issues drive changes in ophthalmic care? –yes. eye 2010;24:1309–1311. 27. somner j, scott k, morris d, gaskell a, sheperd i. ophthalmology carbon footprint: something to be considered? j cataract refract surg 2009;35:202–203. 28. grzybowski a, told r, sacu s, bandello f, moisseiev e, loewenstein a, et al. 2018 update on intravitreal injections: euretina expert consensus recommendations. ophthalmologica 2018;239:181–193. 29. carbon footprint ltd. flight carbon footprint calculator [internet]. hampshire uk: carbon footprint ltd. available from: https://calculator.carbonfootprint.com/calculator. aspx?lang=en-gb&tab=3 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 375 https://unfccc.int/resource/docs/publications/08_unfccc_kp_ref_manual.pdf https://unfccc.int/resource/docs/publications/08_unfccc_kp_ref_manual.pdf https://www.sduhealth.org.uk/policy-strategy/reporting/nhs-carbon-footprint.aspx https://www.sduhealth.org.uk/policy-strategy/reporting/nhs-carbon-footprint.aspx https://www.sduhealth.org.uk/policy-strategy/reporting/nhs-carbon-footprint.aspx https://www.sduhealth.org.uk/policy-strategy/reporting/nhs-carbon-footprint.aspx https://www.sduhealth.org.uk/policy-strategy/engagement-resources/nhs-carbon-reduction-strategy-2009.aspx https://www.sduhealth.org.uk/policy-strategy/engagement-resources/nhs-carbon-reduction-strategy-2009.aspx https://www.sduhealth.org.uk/policy-strategy/engagement-resources/nhs-carbon-reduction-strategy-2009.aspx http://www.reviewofophthalmology.com/content/ d/retinal_insider/c/48732 http://www.reviewofophthalmology.com/content/ d/retinal_insider/c/48732 http://shop.bsigroup.com/upload/shop/download/pas/pas2050.pdf http://shop.bsigroup.com/upload/shop/download/pas/pas2050.pdf https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/69314/pb13625-emission-factor-methodology-paper-110905.pdf https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/69314/pb13625-emission-factor-methodology-paper-110905.pdf https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/69314/pb13625-emission-factor-methodology-paper-110905.pdf https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/69314/pb13625-emission-factor-methodology-paper-110905.pdf https://www.gov.uk/government/collections/government-conversion-factors-for-company-reporting https://www.gov.uk/government/collections/government-conversion-factors-for-company-reporting https://www.gov.uk/government/collections/government-conversion-factors-for-company-reporting https://digital.nhs.uk/data-and-information/publications/statistical/estates-returns-information-collection/estates-return-information-collection-2016-17 https://digital.nhs.uk/data-and-information/publications/statistical/estates-returns-information-collection/estates-return-information-collection-2016-17 https://digital.nhs.uk/data-and-information/publications/statistical/estates-returns-information-collection/estates-return-information-collection-2016-17 https://calculator.carbonfootprint.com/calculator.aspx?lang=en-gb&tab=3 https://calculator.carbonfootprint.com/calculator.aspx?lang=en-gb&tab=3 carbon footprint of intravitreal injections; power et al 30. european parliament. a european strategy for plastics in a circular economy. brussels: european commission; 2018 [cited 2020 february 10]. available from: https://eur-lex.europa.eu/legal-content/en/txt/?qid= 1516265440535&uri=com:2018:28:fin 31. xanthos d, walker t. international policies to reduce plastic marine pollution from single-use plastics (plastic bags and microbeads): a review. mar pollut bull 2017;118:17–20. 32. parvatker a, tunceroglu h, sherman j, coish p, anastas p, zimmerman jb, et al. cradle-to-gate greenhouse gas emissions for twenty anesthetic active pharmaceutical ingredients based on process scale-up and process design calculations. acs sust chem eng 2019;7:6580– 6591 33. ghosh j, nguyen a, bigelow c, et al. long-acting protein drugs for the treatment of ocular diseases. nat commun 2017;8:14837. 376 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 https://eur-lex.europa.eu/legal-content/en/txt/?qid=1516265440535&uri=com:2018:28:fin https://eur-lex.europa.eu/legal-content/en/txt/?qid=1516265440535&uri=com:2018:28:fin original article accelerated versus standard corneal cross-linking for progressive keratoconus in syria abdelrahman m salman1, md; taym r darwish1, md, phd; yusra h haddad2, md, phd rafea h shabaan3, md, phd; mohammad z askar2, md, ms 1department of ophthalmology, tishreen university, latakia, syria 2department of ophthalmology, damascus university, damascus, syria 3tartous university, faculty of medicine, tartous, syria orcid: abdelrahman m salman: https://orcid.org/0000-0002-1042-8153 abstract purpose: to compare the outcomes of accelerated versus standard corneal cross-linking for the treatment of progressive keratoconus. methods: in this retrospective comparative study, 63 eyes of 40 patients with progressive keratoconus were divided into two groups; 27 eyes in group one were treated with an accelerated protocol (10 mw/cm2, 9 min) and 36 eyes in group two were treated with the standard method (3 mw/cm2, 30 min). visual acuity, refraction, corneal topography, corneal tomography, and anterior and posterior corneal higher-order aberrations (hoas) were assessed preoperatively and 18–30 months postoperatively. results: the logmar uncorrected and corrected distance visual acuity values were improved in both groups postoperatively. however, the improvement was significantly higher in group one (p < 0.05, all). the flattening in the anterior keratometry readings, flat k, steep k, and average k were significantly higher in group two (p < 0.001, all). the maximum anterior keratometry (akf) values significantly decreased in both groups, whereas the maximum posterior keratometry (akb) values increased. the reduction in the minimum corneal thickness (thkmin) was significantly greater (36.49um) in group two, compared to 10.85um in group one. there was a significant increase in the posterior average keratometry, and a significant decrease in the posterior astigmatism, along 3 mm meridian in s-cxl (p = 0.03, p = 0.008, respectively), while the corresponding values showed no statistical significance in group one (p > 0.05). the anterior corneal trefoil was significantly reduced in group one (p = 0.002), whereas anterior total hoas and coma were significantly improved in group two (p < 0.0014, all). the posterior corneal spherical aberration decreased significantly in group one (p = 0.02), while group two revealed significant reduction in the posterior trefoil values (p = 0.011). the change in the anterior maximum keratometry was significantly and positively correlated to the preoperative maximum keratometry in group two (p = 0.53, p = 0.003). conclusion: an accelerated cross-linking protocol using 10 mw/cm2 for 9 min showed more visual improvement and less pachymetric reduction when compared to the standard protocol, however, anterior corneal flattening, posterior corneal steepening, and the change in the posterior astigmatism were significantly higher in the standard protocol; while corneal hoas were improved in both protocols. keywords: accelerated; corneal crosslinking; hoas; keratometry; posterior astigmatism; standard j ophthalmic vis res 2021; 16 (3): 338–348 338 © 2021 salman et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i3.9430&domain=pdf&date_stamp=2019-07-17 accelerated versus standard cxl; salman et al introduction corneal cross-linking was first introduced by wollensask et al in 2003.[1] zhang et al demonstrated that the term “collagen crosslinking” is misleading, as the actual cross-links, induced by interaction of ultraviolet a (uva) and riboflavin, occurs between the amino terminals of the collagen side chains and the proteoglycans of the extracellular matrix and not between and within the collagen fibers.[2] the standard corneal cross-linking (s-cxl) reported by wollensask et al depends on using 3 mw/cm2 fluence for 30 min to achieve a total irradiance of 5.4 j/cm2.[1] more recently, a variety of cxl protocols – in term of fluency, time, epithelial integrity, and different indications for cxl – have been introduced.[3–5] the accelerated corneal cross-linking (a-cxl) uses high energy (up to 30 mw/cm2) for shorter time (3–10 min). bunsen-rosoe law of reciprocity states that an increased intensity coupled with reduced exposure time theoretically delivers a total dose to the tissue equivalent to that applied in standard treatment.[6] evaluations of the difference of the outcomes between s-cxl and a-cxl and their impact on the anterior corneal flattening, hyperopic shift, astigmatism, and corneal thinning have gained a particular importance for the refractive surgeons in choosing the cxl protocol to combine with other refractive surgery procedure.[7–9] in this study, we aimed to compare the visual outcomes, topographic parameters, and corneal higher-order aberrations (hoas) values (anterior and posterior) of an a-cxl 10 mw/cm2, 9 min and the standard cxl protocol using 3 mw/cm2, 30 min. methods this study was approved by the research ethics committee of tishreen university in accordance correspondence to: abdelrahman m salman, md. honorary clinical lecturer at tishreen university, scientific director of tartous specialist eye center, tartous, syria p.o. box: 25. e-mail: abd.r.salman10@gmail.com received: 18-07-2020 accepted: 29-04-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i3.9430 with the tenets of the declaration of helsinki. informed consent, in arabic language, was obtained from all patients over 18 years or their guardians if under 18 at the time of cross-linking. a retrospective, comparative study was performed at the department of ophthalmology, tishreen university hospital, syria. all patients who underwent epithelium-off corneal cross-linking between january 2016 and february 2017 were recruited. sixty-three eyes of 40 patients were included in this analysis. patients in whom bilateral cross-linking was performed and underwent different types of procedure (a-cxl vs s-cxl) were included to avoid inter-eye correlation. subjects were divided into two groups: 27 eyes in group one were treated with a-cxl and 36 eyes of group two underwent s-cxl. diagnosis of keratoconus was made if (a) there was irregular cornea determined by distorted keratometry mires or distortion of the dilated retinoscopic reflex (or combination of these) in addition to (b) at least two of the following topographic/tomographic findings: abnormal posterior ectasia, abnormal thickness distribution, or symmetry index front (sif) > 1.17 d; or one of the following slit-lamp findings: vogt striae, 2-mm arc of fleisher ring, or corneal scaring consistent with keratoconus.[10] progression of keratoconus was defined as: at least 1 diopter increase in the anterior maximum keratometry (akf) or in the manifest refraction spherical equivalent (mrse), decrease of 5% in the minimum pachymetry, or loss of at least two lines of the corrected distance visual acuity (cdva) during the past 12 months. patients under 18 years were cross-linked without waiting for progression.[11] patients who had preoperative pachymetry < 400 µm, previous ocular surgery, corneal scar, pregnancy, lactation, herpetic keratitis, or dry eye were excluded. all patients had comprehensive ocular examination, including the measurement of uncorrected distance visual acuity (udva) and cdva, manifest refraction, slit lamp examination, and funduscopy. topographic and tomographic measurement, as well as corneal total hoas, this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: salman am, darwish tr, haddad yh, shabaan rh, askar mz. accelerated versus standard corneal cross-linking for progressive keratoconus in syria. j ophthalmic vis res 2021;16:338–348. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 339 https://knepublishing.com/index.php/jovr accelerated versus standard cxl; salman et al coma, trefoil, and spherical aberrations (anterior and posterior at 6 mm optical zone) were obtained by placido scheimpflug-tomographer, sirius (cso, italy). these investigations were carried out in all patients preoperatively and 18–30 months postoperatively. visual acuity was converted to logmar units. all patients were instructed to discontinue the use of hard or soft contact lenses, for at least three and one weeks, respectively, prior to their examination and cxl. surgical technique the “epi-off” cxl technique was used in both groups. topical proparacaine hydrochloride 0.5% (proparacaine rama, rama pharma, syria) anesthetic eye drops were administrated every 3 min starting 10–15 min before surgery. the central corneal epithelium (8–9 mm) was removed using blunt spatula and dry sponge, without alcohol assistance. riboflavin with dextran (0.1% riboflavin in 20% dextran, medicross, germany) solution was instilled every 3 min for 60 min, starting 30 min before irradiance and continuing for 30 min during the irradiance, in s-cxl group. in a-cxl group, riboflavin was instilled every 2 min for 29 min, starting 20 min before irradiance and continuing for 9 min during the uva irradiance. the irradiance was commenced after saturation of the anterior chamber with riboflavin. this was inspected by slit-lamp examination as fluorescence within the anterior chamber. in s-cxl group, eyes were treated with uv-x (peschke meditrade gmbh, hueneberg, switzerland) system; 3 mw/cm2 was applied for 30 min to achieve the total energy of 5.4 j/cm2. eyes of the a-cxl group were irradiated with the vega c.b.m-x linker (cso, italy) using the a-cxl 10 mw/cm2 for 9 min to reach the same total energy. after uva irradiance, the corneal surface was irrigated with balanced salt solution and soft contact lens was applied for 3–4 days. topical moxifloxacin 0.5% (megamox, rama pharma, syria) eye drop was prescribed four times daily for one week and topical fluorometholone 0.1% (methouflor 0.1%, diamond pharma, syria) eye drop was applied four times daily for two weeks, which was then tapered to twice daily for two weeks. statistical analysis statistical package for social sciences software version 20 (spss, inc, chicago, il, usa) was applied. data were expressed as mean ± standard deviation (sd). two samples independent t-test and paired t-test were applied for normally distributed variables, while non-parametric test was used if a paired t-test was applied to compare the postoperative with the baseline outcomes. pvalue < 0.05 was considered significant. results baseline characteristics sixty-three eyes of 40 patients were included in this study. of these, 27 eyes of 15 patients (9 females, 18 males, mean age; 23.13 ± 7.72 years) underwent a-cxl and 36 eyes of 25 patients (24 females, 12 males, mean age; 23.4 ± 7.37 years) underwent s-cxl. there was no significant difference between the two groups in terms of demographic, udva, cdva, mrse, topography, pachymetry, and corneal hoas except for anterior trefoil values, 0.94 ± 48 µm in a-cxl group versus 0.64 ± 0.41 µm in s-cxl (p = 0.011). females were significantly higher in a-cxl group (p = 0.009) [tables 1 and 4]. visual, refractive, and anterior keratometry outcomes the udva and cdva values were significantly improved postoperatively compared with baseline in a-cxl group (p < 0.05). in s-cxl, the udva and cdva values were improved but the improvement did not reach statistical significance (p > 0.05). in terms of mean mrse, there was a nonsignificant myopic shift in group one, and significant hyperopic shift in group two (a-cxl: 0.28 d, p = 0.65; s-cxl: –0.47 d, p = 0.05). both groups had slight reduction in the sim cylinder values postoperatively (a-cxl: –0.14 d, p = 0.39, s-cxl: –0.22 d, p = 0.08). k1, k2, and avg k did not show significant change in a-cxl group (0.19 d, –0.11 d, –0.04 d, respectively) (p ≥ 0.2, all), while the corresponding values were significantly decreased in s-cxl group (k1: 1.47 d, k2: 1.21 d, avg k: 1.34 d, p < 0.001, all). akf (maximum anterior keratometry) values were significantly reduced in both groups (a-cxl; 0.8 d, p = 0.03, s-cxl; 1.93 d, p = 0.001) [table 2]. the change in snellen cdva in both groups was as follows: in the a-cxl group, 39.13% and in the s-cxl group, 29.41% gained one 340 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 accelerated versus standard cxl; salman et al table 1. patient characteristics at baseline treatment type tech 9 min tech 30 min n (%) no. of subjects 15 (37.5) 25 (62.5) no. of eyes 27 (42.86) 36 (57.14) total p-value sex, n (%) m 18 (66.67) 12 (33.33) 30 (47.62) 0.009 f 9 (33.33) 24 (67.67) 33 (52.38) eye, n (%) od 16 (59.26) 19 (52.78) 35 (55.56) 0.608 os 11 (40.74) 17 (47.22) 28 (44.44) age, mean ± sd 23.13 ± 7.72 23.4 ± 7.37 23.3 ± 7.4 0.9138 p, paired test; values in bold are significant (p < 0.05) line postoperatively. the corresponding values were 4.35% and 14.71% regarding the gain of two or more lines, respectively. in the a-cxl group, 8.7% and in the s-cxl group, 5.88% lost one line. the corresponding figures were 0.0% and 17.65% in terms of the loss of two or more lines, respectively. totally, 47.83% of eyes in the a-cxl group and 32.35% in the s-cxl group displayed no change [figure 1]. pachymetry, posterior corneal keratometry, and astigmatism outcomes the minimum corneal thickness was reduced 10.85 µm in the a-cxl group and 36.49 µm in the s-cxl group (p = 0.029 and p = 0.002, respectively). the baseline values of akb (the steepest point of the posterior surface) increased from 77.08 d to 79.25 d in the a-cxl group, and from 78.08 d to 80.08 d in the s-cxl group. the average posterior keratometry avg k(bck) along 3and 5-mm back meridians were not significantly changed in the a-cxl group (p > 0.9, all), while they significantly increased (representing posterior steepening) in the s-cxl group (p < 0.05, all). the posterior corneal astigmatism (pca) did not significantly change along the corresponding meridians in the a-cxl group (p > 0.5, all). in the s-cxl group, pca values decreased (absolute values increased) significantly in the 3and 5-mm meridians (p < 0.009, all) [table 3]. anterior and posterior corneal higher-order aberrations outcomes in the a-cxl group, the anterior trefoil was significantly decreased (p = 0.0024), whereas total hoas, coma, and spherical aberrations showed no statistically significant difference (p > 0.05, all). the anterior total hoas and coma aberrations were significantly improved in the s-cxl group (p = 0.0008 and p = 0.001, respectively), while the trefoil and the spherical aberrations revealed nonsignificant change (p > 0.02, all). there was a significant reduction in the posterior spherical aberration values (p = 0.0027) in the a-cxl group; while the posterior total hoas, trefoil, and coma did not significantly change (p > 0.01, all). the total hoas, coma, and spherical aberrations were not significantly changed in the s-cxl group (p > 0.014, all), while the trefoil significantly decreased (p = 0.014) [table 4]. correlation analysis outcomes both groups revealed no significant correlation between the preoperative measurements (udva, cdva, and thkmin) and the change in akf values at the follow-up. however, the change in akf was significantly and positively correlated to the preoperative akf in group two (r = 0.53, p = 0.003) [table 5]. the mean difference for each parameter from baseline and final follow-up time were compared in both groups. the changes were not statistically significant between the two groups, except for journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 341 accelerated versus standard cxl; salman et al table 2. visual, refractive, and anterior keratometric outcomes tech 9 min (n = 27) tech 30 min (n = 36) mean std. dev. mean std. dev. p-value udva (logmar) preoperative 0.66 0.46 0.57 0.37 0.3433 postoperative 0.52 0.41 0.50 0.36 0.8176 mean change 0.14 0.20 0.07 0.26 0.2825 p* value 0.0029 0.11 cdva (logmar) preoperative 0.32 0.27 0.32 0.23 0.8333 postoperative 0.27 0.21 0.29 0.23 0.7371 mean change 0.06 0.11 0.03 0.20 0.5167 p* value 0.03 0.37 mrse (d) preoperative –2.49 2.89 –1.76 1.04 0.1623 postoperative –2.78 3.65 –1.29 1.71 0.042 mean change 0.28 2.99 –0.47 1.33 0.2004 p* value 0.65 0.05 topo cyl (d) preoperative –3.24 1.81 –2.83 1.39 0.2531 postoperative –3.10 1.39 –2.61 1.25 0.1716 mean change –0.14 0.77 –0.22 0.71 0.695 p* value 0.39 0.08 k1 (d) preoperative 44.91 0.34 45.50 3.08 0.3498 postoperative 44.73 0.35 44.03 2.57 0.2426 mean change 0.19 0.14 1.47 1.54 0.0001 p* value 0.20 <<<0.0001 k2 (d) preoperative 48.44 2.38 48.21 3.12 0.8272 postoperative 48.55 3.06 47.00 2.77 0.0431 mean change –0.11 1.39 1.21 1.20 0.0002 p* value 0.69 <<<0.0001 avg k (d) preoperative 46.83 2.08 46.80 3.01 0.9575 postoperative 46.86 2.61 45.46 2.55 0.0403 mean change –0.04 1.99 1.34 1.31 0.0019 p* value 0.9211 <<<0.0001 akf (d) preoperative 55.04 4.09 54.78 3.84 0.7238 postoperative 54.24 4.61 52.84 3.31 0.0531 mean change 0.80 1.39 1.93 2.73 0.1205 p* value 0.0312 0.0011 udva, uncorrected distance visual acuity; cdva, corrected distance visual acuity; mrse, manifest refraction spherical equivalent; cyl, sim cylinder value; k1, flat keratometry; k2, steep keratometry; avgk, anterior average keratometry; akf, apical keratoscopy front; d, diopter p, paired test; p*, student’s test; values in bold are significant (p < 0.05) thkmin, sim keratometry (k1, k2, kavg), kavg (bck, 5), anterior total hoas, trefoil and coma, and posterior total hoas and trefoil (p < 0.05, for all) [tables 2–4]. 342 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 accelerated versus standard cxl; salman et al table 3. pachymetry, posterior corneal keratometries, and astigmatism outcomes tech 9 min (n = 27) tech 30 min (n = 36) mean std. dev. mean std. dev. p-value thkmin (µm) preoperative 436.54 26.51 449.46 33.81 0.1062 postoperative 425.69 27.55 412.97 47.23 0.2252 mean change 10.85 22.05 36.49 51.07 0.0198 p* value 0.02 0.0002 akb (d) preoperative 77.08 7.69 78.69 8.74 0.9647 postoperative 79.25 8.33 81.08 9.56 0.6893 mean change –2.17 4.01 –2.39 9.73 0.93 p* value 0.0406 0.2315 avgk (bck, 3) (d) preoperative –7.22 0.70 –7.03 0.86 0.5818 postoperative –7.20 0.94 –6.66 1.29 0.0731 mean change –0.02 0.66 –0.36 0.97 0.1276 p* value 0.9131 0.0386 avgk (bck, 5) (d) preoperative –6.97 0.48 –6.88 0.74 0.787 postoperative –6.97 0.61 –6.59 0.93 0.0637 mean change 0.00 0.42 –0.29 0.60 0.0436 p* value 0.9609 0.011 cyl (back, 3) (d) preoperative –0.92 1.20 –1.09 0.53 0.3278 postoperative –1.36 0.74 –2.19 2.12 0.1088 mean change 0.44 1.25 1.10 2.18 0.186 p* value 0.1045 0.0086 cyl (back, 5) (d) preoperative –0.71 0.82 –0.88 0.55 0.7552 postoperative –1.21 1.22 –1.79 2.11 0.2665 mean change 0.50 1.32 0.91 1.85 0.3643 p* value 0.0819 0.0092 thikmin, minimum corneal thickness; akb, apical kertoscopy back; avgk (bck, 3), average keratometry along 3 mm back meridian; avgk (bck, 5), average keratometry along 5 mm back meridian; cyl (bck, 3), cylinder value along 3 mm back meridian; cyl (bck, 5), cylinder value along 5 mm back meridian; d, diopter p, paired test; p*, student’s test; values in bold are significant (p < 0.05) discussion several studies have revealed that both acxl and s-cxl are effective in halting the progression of keratoconus.[12, 13] tomita et al published the first article comparing the standard and accelerated protocols.[14] they reported no significant difference in the mean udva and cdva, keratometric readings, or the postoperative mrse values. in contrast, we found improvement in the logmar visual acuity in both groups. the udva and cdva significantly improved (0.14, p = 0.002 and 0.06, p = 0.03, respectively) in the a-cxl group, compared to 0.07, p = 0.11 and 0.03, p = 0.37, respectively, in the s-cxl group. there was no statistically significant difference between the two groups. however, 12 eyes of the a-cxl group lost two lines of the snellen dcva at three month postoperatively. the reduction in visual acuity at this stage was attributed to the increase in the corneal hoas and the decrease in the contrast sensitivity. ghanavati et al stated that increased corneal hoas and decreased contrast sensitivity were the factors responsible for deceased visual acuity at the early postoperative period after crosslinking.[15] fortunately, none of the eyes treated journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 343 accelerated versus standard cxl; salman et al table 4. anterior and posterior corneal hoas outcomes tech 9 min (n = 27) tech 30 min (n = 36) mean std. dev. mean std. dev. p-value anterior corneal hoas 6 mm anterior total hoas (rms, µm) preoperative 2.35 1.27 2.62 1.30 0.4248 postoperative 2.25 1.27 2.16 1.13 0.5737 mean change 0.10 0.33 0.46 0.73 0.0269 p* value 0.1329 0.0008 trefoil (rms, µm) preoperative 0.94 0.48 0.64 0.41 0.0115 postoperative 0.82 0.50 0.72 0.40 0.399 mean change 0.12 0.18 –0.08 0.42 0.0269 p* value 0.0024 0.2688 coma (rms, µm) preoperative 2.04 1.17 2.26 1.31 0.5091 postoperative 1.94 1.32 1.82 1.13 0.5074 mean change 0.10 0.41 0.44 0.74 0.0433 p* value 0.2323 0.0013 spherical aberration (rms, µm) preoperative 0.11 0.37 0.05 0.45 0.5833 postoperative 0.08 0.34 0.01 0.38 0.3639 mean change 0.04 0.15 0.04 0.31 0.9096 p* value 0.2567 0.4272 posterior corneal hoas 6 mm posterior total hoas (rms, µm) preoperative 0.86 0.49 1.19 1.00 0.0923 postoperative 0.93 0.50 0.90 0.57 0.8215 mean change –0.07 0.29 0.28 0.84 0.037 p* value 0.1912 0.0636 trefoil (rms, µm) preoperative 0.56 0.43 0.69 0.61 0.3604 postoperative 0.62 0.44 0.46 0.33 0.106 mean change –0.05 0.27 0.23 0.52 0.0115 p* value 0.2944 0.0146 coma (rms, µm) preoperative 0.38 0.21 0.54 0.45 0.052 postoperative 0.38 0.20 0.44 0.26 0.3425 mean change 0.00 0.12 0.10 0.40 0.2003 p* value 0.8433 0.1594 spherical aberration (rms, µm) preoperative –0.05 0.09 –0.14 0.27 0.209 postoperative –0.08 0.07 –0.14 0.22 0.106 mean change 0.03 0.07 0.00 0.24 0.519 p* value 0.027 0.9096 hoas, higher order aberrations; rms, root mean square p, paired test; p*, student’s test; values in bold are significant (p < 0.05) 344 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 accelerated versus standard cxl; salman et al table 5. correlation between akf change at follow-up and preoperative assessment variables akf change preop udva preop cdva preop thikmin preop akf tech 9 min r 0.3855 0.1228 –0.4321 –0.2302 p-value 0.1265 0.6387 0.0832 0.374 tech 30 min r –0.0207 0.0845 –0.0711 0.5365 p-value 0.9182 0.6751 0.7246 0.0039 udva, uncorrected distance visual acuity; cdva, corrected distance visual acuity; thikmin, minimum corneal thickness; akf, apical keratoscopy front p, student’s test; values in bold are significant (p < 0.05); r, correlation coefficient figure 1. corrected distance visual acuity changes after 9 and 30 min corneal cross-linking (snellen). with a-cxl lost two or more lines of snellen cdva at the final follow-up. however, this was not the case for the eyes treated with s-cxl, as six eyes lost two or more lines at the final examination. this could be explained by the significant persistent haze formation in four eyes and scar development in two eyes. our study showed a slight myopic shift of the mrse in the a-cxl group and significant hyperopic shift (o.47 d) in the s-cxl group, while sim cylinder values were nonsignificantly reduced in both groups. hashemi et al reported a significant reduction in keratometric readings in the s-cxl treated eyes but not in the a-cxl treated ones and concluded that the flattening effect was higher in the s-cxl group.[16] this is in agreement with our results. we found significant flattening in the mean flat, steep, and average keratometry values (1.47 d, 1.20 d, 1.99 d, respectively) with the s-cxl protocol, while the corresponding values did not show any statistically significantly deference in the a-cxl group. the anterior maximum keratometry or k max, which is considered as the most sensitive indicator for kc progression,[17, 18] was significantly reduced after treatment in both a-cxl and s-cxl groups (p < 0.05, all). the mean thkmin values decreased 10.85 µm in the a-cxl group compared to 36.49 µm in the s-cxl group. shetty et al observed that the minimum thickness reduction was higher in the s-cxl group.[19] greenstein et al suggested that the decrease in thickness was related to an increased compactness of the cross-linked cornea.[20] however, the marked reduction in corneal thickness after s-cxl in our study may represent a measurement artefact. dependence on scheimpfug-based pachymetric measurements was one of our study limitations. anterior segment optical coherence tomography (as-oct) showed higher repeatability compared with scheimpflug imaging devices in measuring the corneal thickness.[21] journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 345 accelerated versus standard cxl; salman et al patients with kc are more likely to develop cataract at a younger age than normal subjects[22] and many of them will eventually require cataract surgery and toric intraocular lens implantation. koch et al[23] reported that neglecting pca which is higher in kc patients compared to normal population[24] will lead to the overcorrection in eyes having with the rule astigmatism and the undercorrection in eyes with the against the rule astigmatism. safarzadeh et al found a nonsignificant difference in pca and a significant increase in the mean posterior maximum keratometry values after s-cxl treatment.[25] in contrast, we evaluated the changes of posterior astigmatism and posterior keratometry along the 3and 5-mm meridians between the baseline and the postoperative follow-up in both groups. the cyl (bck) values decreased (absolute values increased) nonsignificantly along with the studied meridians in the a-cxl group. while the decrease was significant in the s-cxl group. the difference in cyl (bck) values along the 3-mm meridian was 0.44 d in the a-cxl (p = 0.1) and 1.10 d in the s-cxl (p = 0.0086) groups. the mean posterior keratometry avgk (bck3) increased (absolute values decreased) nonsignificantly in the a-cxl group, while the increase was significant in the s-cxl group along the 3-mm meridian (0.02 d, p = 0.91; 0.36 d, p = 0.038, respectively). akb values (the steepest point of the posterior surface) increased postoperatively, 2.17 d in the a-cxl group and 2.39 d in the s-cxl group. we hypothesize the difference in pca outcomes between our study and the study by safarzadeh et al can be attributed to the difference in the type of the topographer used, as safarzadeh depended on pentacam measurement. although pentacam and sirius are both scheimpfug-based tomographers, sirius showed good to excellent repeatability[26–28] and was less affected than pentacam by the post-cxl haze.[29] the increase in both the posterior mean and maximum keratometries represent increased posterior corneal steepening. twa et al evaluated the corneal changes after 5,211 myopic lasik procedures. they suggested that the posterior steepening is a response to the anterior flattening induced by myopic lasik correction.[30] kirgiz et al considered posterior corneal steepening as important as anterior corneal flattening for stabilizing the keratometric values and enhancing the visual acuity.[31] recent studies have revealed increased spherical and coma aberrations in eyes with kc compared to normal population.[32] greenstein et al reported significant improvement in the anterior corneal hoas and coma after s-cxl treatment.[33] however, they found no statistically significant difference in the posterior corneal hoas. this is to some extent in agreement with our findings; anterior total hoas and coma were significantly reduced (p < 0.0014, all), while posterior corneal trefoil was significantly deceased in the s-cxl group. ozulken et al found significant difference in coma aberrations after 10 min at 9 mw/cm2 uva irradiance.[34] in our study, anterior trefoil and posterior spherical aberrations values were significantly improved in the a-cxl group (p = 0.002 and p = 0.02, respectively). ghanem et al concluded that the improvement in hoas in kc patients is attributed to the flattening of the corneal apex caused by the cxl effect.[35] to the best of our knowledge, this the first study to compare the impact of different cxl protocols on the pca. lack of demarcation line depth measurements, low number of patients, and the retrospective design of the study were limiting factors in this study. larger cohort studies to evaluate the effect of cxl on the orientation of the astigmatism and the correlation between the anterior and posterior astigmatism changes are needed. in summary, we found that s-cxl resulted in significantly higher anterior corneal flattening, more increase in posterior steepening, further decrease in posterior astigmatism, and more reduction in the minimum thickness than the accelerated-cxl. however, both protocols showed improvement in the postoperative visual acuity and the corneal hoas, but the improvement in the visual acuity was significantly higher in the a-cxl protocol. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. 346 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 accelerated versus standard cxl; salman et al references 1. wollensak g, spoerl e, seiler t. riboflavin/ultravioleta-induced collagen crosslinking for the treatment of keratoconus. am j ophthalmol 2003;135:620–627. 2. zhang y, conrad ah, conrad gw. effects of ultravioleta and riboflavin on the interaction of collagen and proteoglycans during corneal cross-linking. j biol chem 2011;286:13011–13022. 3. kirgiz a, eliacik m, yildirim y. different accelerated corneal collagen cross-linking treatment modalities in progressive keratoconus. eye vis 2019;6:16. 4. saleem mih, ibrahim elzembely ha, abozaid ma, elagouz m, saeed am, mohammed oa, et al. three-year outcomes of cross-linking plus (combined cross-linking with femtosecond laser intracorneal ring segments implantation) for management of keratoconus. j ophthalmol 2018;2018:6907573. 5. cifariello f, minicucci m, di renzo f, di taranto d, coclite g, zaccaria s, et al. epi-off versus epi-on corneal collagen cross-linking in keratoconus patients: a comparative study through 2-year follow-up. j ophthalmol 2018;2018:4947983. 6. bunsen rw, roscoe he. photochemical researches – part v. on the measurement of the chemical action of direct and diffuse sunlight. proc r soc lond 1863;12:306–312. 7. woo jh, iyer jv, lim l, hla mh, mehta js, chan cml, et al. conventional versus accelerated collagen cross-linking for keratoconus: a comparison of visual, refractive, topographic and biomechanical outcomes. open ophthalmol j 2017;11:262–272. 8. aldahlawi nh, hayes s, o’brart dp, meek km. standard versus accelerated riboflavin-ultraviolet corneal collagen crosslinking: resistance against enzymatic digestion. j cataract refract surg 2015;41:1989–1996. 9. zhu ay, jun as, soiberman us. combined protocols for corneal collagen cross-linking with photorefractive surgery for refractive management of keratoconus: update on techniques and review of literature. ophthalmol ther 2019;8:15–31. 10. arbelaez mc, versaci f, vestri g, barboni p, savini g. use of a support vector machine for keratoconus and subclinical keratoconus detection by topographic and tomographic data. ophthalmology 2012;119:2231–2238. 11. reeves sw, stinnett s, adelman ra, afshari na. risk factors for progression to penetrating keratoplasty in patients with keratoconus. am j ophthalmol 2005;140:607–611. 12. nicula c, pop r, rednik a, nicula d. 10-year results of standard cross-linking in patients with progressive keratoconus in romania. j ophthalmol 2019;2019:8285649. 13. bozkurt e, ozgurhan eb, akcay bi, kurt t, yildirim y, günaydin zk, et al. refractive, topographic, and aberrometric results at 2-year follow-up for accelerated corneal cross-link for progressive keratoconus. j ophthalmol 2017;2017:5714372. 14. tomita m, mita m, huseynova t. accelerated versus conventional corneal collagen crosslinking. j cataract refract surg 2014;40:1013–1020. 15. zarei-ghanavati s, khakshour h, vejdani m, ghooshkhanei h, vejdani a. evaluation of changes in visual acuity, contrast sensitivity and aberrations in patients with keratoconus after corneal collagen cross-linking. j ophthalmic vis res 2017;12:260–264. 16. hashemi h, fotouhi a, miraftab m, bahrmandy h, seyedian ma, amanzadeh k, et al. short-term comparison of accelerated and standard methods of corneal collagen crosslinking. j cataract refract surg 2015;41:533–540. 17. wittig-silva c, whiting m, lamoureux e, lindsay rg, sullivan lj, snibson gr. a randomized controlled trial of corneal collagen cross-linking in progressive keratoconus: preliminary results. j refract surg 2008;24:s720–s725. 18. sykakis e, karim r, evans jr, bunce c, amissah-arthur kn, patwary s, et al. corneal collagen cross-linking for treating keratoconus. cochrane database syst rev 2015;3:cd010621. 19. shetty r, pahuja nk, nuijts rm, ajani a, jayadev c, sharma c, et al. current protocols of corneal collagen crosslinking: visual, refractive, and tomographic outcomes. am j ophthalmol 2015;160:243–249. 20. greenstein sa, shah vp, fry kl, hersh ps. corneal thickness changes after corneal collagen crosslinking for keratoconus and corneal ectasia: one-year results. j cataract refract surg 2011;37:691–700. 21. wongchaisuwat n, metheetrairat a, chonpimai p, nujoi w, prabhasawat p. comparison of central corneal thickness measurements in corneal edema using ultrasound pachymetry, visante anterior-segment optical coherence tomography, cirrus optical coherence tomography, and pentacam scheimpflug camera tomography. clin ophthalmol 2018;12:1865–1873. 22. thebpatiphat n, hammersmith km, rapuano cj, ayres bd, cohen ej. cataract surgery in keratoconus. eye contact lens 2007;33:244–246. 23. koch dd, jenkins rb, weikert mp, yeu e, wang l. correcting astigmatism with toric intraocular lenses: effect of posterior corneal astigmatism. j cataract refract surg 2013;39:1803–1809. 24. aslani f, khorrami-nejad m, aghazadeh amiri m, hashemian h, askarizadeh f, khosravi b. characteristics of posterior corneal astigmatism in different stages of keratoconus. j ophthalmic vis res 2018;13:3–9. 25. safarzadeh m, nasiri n, doostdar a, kamali m. comparative study of changes of corneal curvatures and uncorrected distance visual acuity prior to and after corneal collagen crosslinking: 1-year results. taiwan j ophthalmol 2016;6:127–130. 26. finis d, ralla b, karbe m, borrelli m, schrader s, geerling g. comparison of two different scheimpflug devices in the detection of keratoconus, regular astigmatism, and healthy corneas. j ophthalmol 2015;2015:315281. 27. lanza m, paolillo e, gironi carnevale ua, lanza a, irregolare c, mele l, et al. central corneal thickness evaluation in healthy eyes with three different optical devices. cont lens anterior eye 2015;38:409–413. 28. kumar m, shetty r, jayadev c, rao hl, dutta d. repeatability and agreement of five imaging systems for measuring anterior segment parameters in healthy eyes. indian j ophthalmol 2017;65:288–294. 29. shetty r, agrawal a, deshmukh r, kaweri l, rao hl, nagaraja h, et al. effect of post crosslinking haze on the repeatability of scheimpflug-based and slit-scanning journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 347 accelerated versus standard cxl; salman et al imaging devices. indian j ophthalmol 2017;65:305–310. 30. twa md, roberts c, mahmoud am, chang js jr. response of the posterior corneal surface to laser in situ keratomileusis for myopia. j cataract refract surg 2005;31:61–71. 31. k𝚤rg𝚤z a, atalay k, çabuk kş, kald𝚤r𝚤m h, taşkap𝚤l𝚤 m. factors affecting visual acuity after accelerated crosslinking in patients with progressive keratoconus. arq bras oftalmol 2016;79:151–154. 32. alió jl, shabayek mh. corneal higher order aberrations: a method to grade keratoconus. j refract surg 2006;22:539–545. 33. greenstein sa, fry kl, hersh mj, hersh ps. higherorder aberrations after corneal collagen crosslinking for keratoconus and corneal ectasia. j cataract refract surg 2012;38:292–302. 34. özülken k, aksoy aydemir g, aydemir e, k𝚤z𝚤ltoprak h, yüksel e. comparison of two different accelerated corneal cross-linking procedure outcomes in patients with keratoconus. balkan med j 2020;37:131–137. 35. ghanem rc, santhiago mr, berti t, netto mv, ghanem vc. topographic, corneal wavefront, and refractive outcomes 2 years after collagen crosslinking for progressive keratoconus. cornea 2014;33:43–48. 348 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 editorial eye disorders in the post-covid era seyed-hossein abtahi1, md; hosein nouri1, md; siamak moradian2, md; shahin yazdani1, md hamid ahmadieh1, md 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2ophthalmic epidemiology research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran orcid: seyed-hossein abtahi: https://orcid.org/0000-0002-1459-6752 siamak moradian: https://orcid.org/0000-0002-5328-7565 j ophthalmic vis res 2021; 16 (4): 527–530 the covid-19 pandemic has substantially affected all aspects of healthcare, and these effects are still unfolding. covid-19 has caused ocular problems both directly and indirectly; further causes of concern are side effects of covid19 treatment and indirect consequences of lockdowns and shelter-in-place orders. despite the ongoing evolution of the coronavirus due to constant mutations,[1] the pandemic will eventually come to a relative end or at least slowdown, and we must prepare for what lies ahead. in this editorial, we will discuss the probable impacts of the pandemic on ophthalmic disorders and surgical indications over the coming years. various ocular manifestations have been reported in covid-19 cases, which involve different structures, including the eyelids, conjunctiva, cornea, episclera, retina, and cranial nerves. most retinal pathologies associated with covid19 have roots in vascular complications such as retinal vasculitis and retinal arteries and veins occlusions.[2] other causes of concern are potential adverse effects of covid19 medications such as anticoagulants.[3] furthermore, patients’ routine use of face masks may theoretically increase the risk of infections, as the exhalate is directed toward the periocular area during procedures such as intravitreal injections.[4, 5] covid-19 has also indirectly affected ophthalmology patients. the ophthalmology practice necessitates close, in-person visits and carries a high risk of viral transmission.[6] therefore, follow-up protocols and visit routines have been modified worldwide, particularly earlier in the pandemic, to reduce the risk of disease transmission.[7] the postponement of in-person follow-up visits and replacement with tele/virtual visits may predispose to delayed or wrong diagnoses and lead to insufficient treatment.[8] most hospitalized covid-19 patients receive systemic corticosteroids to alleviate systemic inflammation and prevent pulmonary fibrosis; dexamethasone is widely administered and has been shown to reduce mortality in patients receiving oxygen support or mechanical ventilation.[9] whatever their efficacy in the setting of covid-19, steroids have established causal links with several long-term ocular complications, including cataracts and glaucoma.[10] the associated risk tends to rise in a doseand duration-dependent fashion.[11] dexamethasone, in particular, is more potent than prednisolone and has a greater propensity to cause glaucoma and cataracts.[12] it is well-known that dexamethasone induces nuclear and posterior subcapsular cataracts.[13, 14] with the widespread use of steroids, we will probably witness a rise in cataract rates, especially early-onset cases, in the forthcoming decade leading to a decrease in the mean age of patients requiring cataract surgery. it is well documented that younger patients undergoing phacoemulsification are more prone to vitreoretinal problems;[15] the result may be an increase in the number of vitreoretinal surgeries. © 2021 abtahi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 527 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9740&domain=pdf&date_stamp=2019-07-17 editorial; abtahi et al glucocorticoids can affect the trabecular meshwork and reduce outflow facility leading to increased intraocular pressure.[16] genetic predisposition plays a pivotal role in this regard; while some individuals are more susceptible to steroid-induced complications, that is, steroid responders who constitute an estimated 37–39% of the general population, some are among steroid nonresponders.[17] previously diagnosed glaucoma patients are also at risk of exacerbation following steroids administration.[10] hence, the utilization of systemic steroids due to covid-19 may increase the number of glaucoma cases in need of treatment which, in turn, translates to a higher demand for antiglaucoma medications and glaucoma surgery. glucocorticoids also adversely affect glycemic control in patients with diabetes mellitus (dm). this correlation is well documented, and decreased insulin sensitivity is the primary mechanism.[18] high-dose dexamethasone has been documented to reduce insulin secretory capacity as well.[19] new-onset dm is also frequently observed with steroid use; the risk is more pronounced with higher doses and longer durations of treatment.[20] with the anticipated growth in the number of new dm cases and progression in established ones, a significant increase in the incidence of dm complications, such as cataracts and diabetic retinopathy may be expected in the years to come. this will ultimately increase the need for cataract surgery on the one hand and lasers, intravitreal injections, and vitreoretinal surgery for diabetic retinopathy on the other hand. diagnostic radiologic modalities emitting ionizing radiation have been extensively employed during the covid-19 pandemic; many hospitalized patients may undergo multiple imaging sessions during their stay.[21] the carcinogenic potential of cumulative low dose radiation (i.e., <100 mgy) remains controversial. however, a recent meta-analysis calculated an overall excessive relative risk of 0.03 (95% ci = 0.07 to 0.25) and 0.16 (95% ci = 0.37 to 5.32) for solid tumors and leukemia, respectively, associated with <100 mgy cumulative irradiation doses in adults.[22] of note, the thyroid is exposed to radiation during chest imaging sessions, which is a presumed risk factor for the development of graves’ ophthalmopathy.[23] with insufficient data on imaging protocols and cumulative exposure to ionizing radiation, any prediction regarding the incidence of malignancies with ophthalmic manifestations in the future remains speculative. multi-center surveys are warranted to determine if such risks are significant enough to be prospectively investigated among hospitalized covid-19 survivors. prolonged lockdowns, stay-home recommendations, and school closures have expectedly had substantial effects on the duration of interaction with digital screens and video games among school-age children.[24] some cultural and educational framework changes may probably be favored and adhered to even after the pandemic. altogether, with increased time spent on digital screens and near-work tasks, and restricted outdoor activities, especially among the pediatric population, an increased incidence of myopia and myopic progression may be encountered in the future.[25] in one or two decades, we may witness an increased demand for refractive surgery[26] and a greater need for vitreoretinal treatment for myopia complications. the majority of the issues discussed above point toward an exponential increase in the demand for ophthalmic surgery, especially vitreoretinal treatments. the additional expenses involved will impose a burden on healthcare systems and insurance companies.[27] all nations dealing with large numbers of covid cases, especially those with developing economies, will suffer. in summary, the huge morbidity and death toll imposed by the pandemic has led to the adoption of life-saving treatment protocols with the downside of complications. our concerns highlight the need for modification of unnecessary or overuse of corticosteroids. physicians should consider the inherent risks of high-dose corticosteroid use on the whole human body, including ocular side effects such as cataract formation. in individuals with a personal or familial background of dm or glaucoma, physicians should weigh the pros and cons of corticosteroid administration. the community should also be aware of the increased risk of childhood myopia due to stay-at-home orders and excessive near-vision tasks. acknowledgement in the loving memory of abbas ali nouri, hosein nouri’s late father who passed away 528 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 editorial; abtahi et al on september 1, 2021, because of a severe covid-19 infection, may his soul rest in eternal peace. financial support and sponsorship no funding was received for the preparation of this article. conflicts of interest the authors declare no financial or proprietary interests in any material discussed in this article. references 1. banoun h. evolution of sars-cov-2: review of mutations, role of the host immune system. nephron 2021;145:392–403. 2. roshanshad a, ali ashraf m, roshanshad r, kharmandar a, alireza zomorodian s, ashraf h. ocular manifestations of patients with coronavirus disease 2019: a comprehensive review. j ophthalmic vis res 2021;16:234–247. 3. dumitrascu om, volod o, bose s, wang y, biousse v, lyden pd. acute ophthalmic artery occlusion in a covid-19 patient on apixaban. j stroke cerebrovasc dis 2020;29:104982. 4. raevis jj, gjyzeli g, mititelu m, rogers j, lasarev m, chang js. face masks and bacterial dispersion toward the periocular area. ophthalmology 2021;128:1236–1238. 5. marin-nieto j, reino-perez c, santillana-cernuda g, díaz-bernal jm, luque-aranda r, garcía-basterra i. face mask contamination during covid-19 pandemic. study on patients receiving intravitreal injections. retina 2021; online ahead of print. 6. lawrenson jg, buckley rj. covid-19 and the eye. ophthalmic physiol opt 2020;40:383–388. 7. parke dw. ophthalmology after coronavirus disease 2019 (covid-19). jama ophthalmol 2020;138:599. 8. berkenstock mk, liberman p, mcdonnell pj, chaon bc. changes in patient visits and diagnoses in a large academic center during the covid-19 pandemic. bmc ophthalmol 2021;21:139. 9. dexamethasone in hospitalized patients with covid19. n engl j med 2021;384:693–704. 10. oray m, abu samra k, ebrahimiadib n, meese h, foster cs. long-term side effects of glucocorticoids. expert opin drug saf 2016;15:457–465. 11. james er. the etiology of steroid cataract. j ocul pharmacol ther 2007;23:403–420. 12. mohan r, muralidharan ar. steroid induced glaucoma and cataract. indian j ophthalmol 37:13–16. 13. huscher d, thiele k, gromnica-ihle e, hein g, demary w, dreher r, et al. dose-related patterns of glucocorticoid-induced side effects. ann rheum dis 2009;68:1119–1124. 14. richardson rb, ainsbury ea, prescott cr, lovicu fj. etiology of posterior subcapsular cataracts based on a review of risk factors including aging, diabetes, and ionizing radiation. int j radiat biol 2020;96:1339– 1361. 15. clark a, morlet n, ng jq, preen db, semmens jb. risk for retinal detachment after phacoemulsification. arch ophthalmol 2012;130:882. 16. razeghinejad mr, katz lj. steroid-induced iatrogenic glaucoma. ophthalmic res 2012;47:66– 80. 17. roberti g, oddone f, agnifili l, katsanos a, michelessi m, mastropasqua l, et al. steroidinduced glaucoma: epidemiology, pathophysiology, and clinical management. surv ophthalmol 2020;65:458–472. 18. clore jn, thurby-hay l. glucocorticoid-induced hyperglycemia. endocr pract 2009;15:469–474. 19. matsumoto k, yamasaki h, akazawa s, sakamaki h, ishibashi m, abiru n, et al. high-dose but not low-dose dexamethasone impairs glucose tolerance by inducing compensatory failure of pancreatic beta-cells in normal men. j clin endocrinol metab 1996;81:2621–2626. 20. hwang jl, weiss re. steroid-induced diabetes: a clinical and molecular approach to understanding and treatment. diabetes metab res rev 2014;30:96–102. 21. homayounieh f, holmberg o, umairi r al, aly s, basevičius a, costa pr, et al. variations in ct utilization, protocols, and radiation doses in covid19 pneumonia: results from 28 countries in the iaea study. radiology 2021;298:e141–e151. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 529 editorial; abtahi et al 22. hauptmann m, daniels rd, cardis e, cullings hm, kendall g, laurier d, et al. epidemiological studies of low-dose ionizing radiation and cancer: summary bias assessment and meta-analysis. jnci monogr 2020;2020:188–200. 23. jereczek-fossa ba, alterio d, jassem j, gibelli b, tradati n, orecchia r. radiotherapy-induced thyroid disorders. cancer treat rev 2004;30:369–384. 24. pandya a, lodha p. social connectedness, excessive screen time during covid-19 and mental health: a review of current evidence. front hum dyn 2021;3. 25. wong cw, tsai a, jonas jb, ohno-matsui k, chen j, ang m, et al. digital screen time during the covid19 pandemic: risk for a further myopia boom? am j ophthalmol 2021;223:333–337. 26. kamiya k, igarashi a, hayashi k, negishi k, sato m, bissen-miyajima h. a multicenter prospective cohort study on refractive surgery in 15011 eyes. am j ophthalmol 2017;175:159–168. 27. berkowitz st, sternberg p, patel s. cost analysis of routine vitrectomy surgery. ophthalmol retin 2021;5:496–502. correspondence to: siamak moradian, md. ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, paidar fard, boustan 9, pasdaran ave., tehran, iran. e-mail: moradian33195@yahoo.com access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9740 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: abtahi sh, nouri h, moradian s, yazdani s, ahmadieh h. eye disorders in the post-covid era. j ophthalmic vis res 2021;16:527–530. 530 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 https://knepublishing.com/index.php/jovr letter to editor the impact of the covid-19 pandemic on ophthalmology residency training naveed nilforushan1,2 md, navid abolfathzadeh2 md, mph 1eye research center, the five senses institute, rassoul akram hospital, iran university of medical sciences, tehran, iran 2department of ophthalmology, faculty of medicine, iran university of medical sciences, tehran, iran orcid: naveed nilforushan: http://orcid.org/0000-0001-7720-1757 j ophthalmic vis res 2021; 16 (2): 312–313 dear editor, the outbreak of coronavirus disease-2019 (covid-19) has impacted different aspects of life for people all around the world. students at different levels of education are among those who have been significantly affected by this pandemic. as a higher level of education, ophthalmology residency is a top specialty in different parts of the world including iran. ophthalmology residents are expected to learn highly technical surgeries and acquire knowledge throughout their training period. however, during the past year, residency programs have been negatively impacted by this crisis worldwide.[1–4] major reasons for this detrimental effect are restriction and suspension of clinical activities and elective surgeries, cancellation of conventional lecturing sessions and educational courses, periodic lockdown of cities, persistent psychological and emotional stress on both trainers and trainees as a consequence of close contact with patients, in addition to loss of colleagues, family members or friends. moreover, in order to reducing the chance of exposure correspondence to: naveed nilforushan, md. ophthalmology department, faculty of medicine, iran university of medical sciences, tehran 1445613131, iran. email: naveednil@yahoo.com received: 21-11-2020 accepted: 21-02-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9102 to infection, the patients themselves prefer to stay at home instead of seeking ophthalmic examinations at university-based centers and especially general hospitals, unless some urgent or emergent situations happen. overall, ophthalmology residents have had significant reduction in their clinical and surgical opportunities and are less motivated in their daily routine schedules.[1] cataract, strabismus, pterygium, lid, and nasolacrimal duct surgeries are among the mandatory group of surgeries in the training curriculum for ophthalmology which are mostly categorized as elective surgeries. on the other hand, urgent cases scheduled for surgery during the pandemic are usually sophisticated ones including vitreoretinal and glaucoma cases that need to be handled by experienced surgeons including fellows and/or attending physicians. even in the pre-covid-19 era, direct involvement in such cases was mostly limited and far from the general scope of the residency curriculum. therefore, the decision to involve residents in such difficult surgical cases in current practice raises multiple ethical dilemmas in the operating room. to involve residents in such cases, we usually prefer general anesthesia instead of routine topical and/or local anesthesia. this leads to prolongation of patient this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: nilforushan n, abolfathzadeh n. the impact of the covid-19 pandemic on ophthalmology residency training. j ophthalmic vis res 2021;16:312–313. 312 © 2021 nilforushan et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9102&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr letter to editor; nilforushan et al stay at the hospital and also higher workload for the anesthesiology team which can increase the risk of covid-19 infection for the patient and the medical staff. on the other hand, not including residents in the procedures can result in graduation of less experienced surgeons in future. therefore, each decision would be a great challenge for the mentors and the heads of ophthalmology departments. it is expected that the social and economic impacts of this crisis will persist for the next few years and that health systems may face other similar unpredictable crises in the future. therefore, health authorities should facilitate the incorporation of innovative ways of surgical training such as simulation-based or wet labbased training to fill this educational gap. we understand that it will take time and need more efforts to reprogram the educational curriculum for ophthalmology residency in the covid-19 pandemic. in addition, we know that moving toward such innovative ways will impose a significant economic burden on the health system especially in developing countries which are already under stress for funding sources related to the covid-19 pandemic; therefore, this approach may not be among the priorities of health policymakers. it is good to say that, besides the negative and tragic impacts of this pandemic, new opportunities have emerged in the field of education which will definitely change our practice in future. there are plenty of affordable e-learning facilities for improving residency education including offline surgical movie clips, online virtual grandrounds like web-based case presentations and journal clubs, webcasts and online national and international webinars. these positive changes have happened mostly after the covid-19 pandemic, in which online webinars are the most widespread ones. they let large numbers of ophthalmologists from all over the world to be involved, discuss, and learn simultaneously. such online gatherings will undoubtedly remain and continue even after the pandemic ceases. however, one should keep in mind that developing countries face obstacles in accessing online programs including internet connectivity and speed, in addition to the cost. these new circumstances have also changed our communication with patients and made telemedicine-based management more prominent. nowadays, patients can easily contact their physicians and send them information, images, and tests using smartphones. all of these may lead to safer and more cost-effective patient visits. telemedicine and its applications can be a part of the education during these hard times. last but not the least, it is important to perform and validate residency examination and evaluations in a standardized and uniform electronic format. attention should also be paid to necessary changes in the national curriculum of ophthalmology residency education, to prepare residents with non-surgical but fundamental skills such as crisis management and teamwork.[5] additionally, as a priority, we must ensure that our trainees are and will be safe and healthy during their education period, therefore all necessary protective equipment and measures should be provided to fulfill this goal. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. ferrara m, romano v, steel dh, gupta r, iovino c, et al. reshaping ophthalmology training after covid-19 pandemic. eye 2020;34: 2089–2097. 2. bakshi sk, ho ac, chodosh j, fung at, chan rvp, et al. training in the year of the eye: the impact of the covid19 pandemic on ophthalmic education. br j ophthalmol 2020;104:1181–1183. 3. alahmadi as, alhatlan hm, bin helayel h, khandekar r, al habash a, al-shahwan s. residents’ perceived impact of covid-19 on saudi ophthalmology training programs a survey. clin ophthalmol 2020;14:3755–3761. 4. mishra d, nair ag, gandhi ra, gogate pj, mathur s, bhushan p, et al. the impact of covid-19 related lockdown on ophthalmology training programs in india – outcomes of a survey. indian j ophthalmol 2020;68:999– 1004. 5. kumar a, agarwal d. commentary: restructuring residency training in ophthalmology during covid19 era: challenges and opportunities. indian j ophthalmol 2020;68:1005–1006. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 313 original article the adequate number of histopathology cross-sections of temporal artery biopsy in establishing the diagnosis of giant cell arteritis roshanak ali-akbar navahi, md; samira chaibakhsh, phd; sayyed amirpooya alemzadeh, md kaveh abri aghdam, md, phd eye research center, the five senses institute, rassoul akram hospital, iran university of medical sciences, tehran, iran orcid: roshanak ali-akbar navahi: https://orcid.org/0000-0002-8497-5053 kaveh abri aghdam: https://orcid.org/0000-0001-7568-6455 abstract purpose: to determine the appropriate number of histopathological cross-sections that are required for a conclusive diagnosis of giant cell arteritis (gca). methods: in this cross-sectional study, the number of sections per slide for paraffin-embedded blocks for 100 randomly selected cases where gca was suspected and those for negative temporal artery biopsies (tabs) were compared with the number of cross-sections per specimen for eight positive-tabs. all aforementioned examinations were conducted at our center from 2012 to 2016. then, negative-tabs were retrieved and re-evaluated using light microscopy considering the histopathological findings of gca. results: ninety-five paraffin blocks were retrieved. the original mean biopsy length was 15.39 ± 7.56 mm. comparison of the mean number of cross-sections per specimen for both the positiveand negative-tabs (9.25 ± 3.37 and 9.53 ± 2.46) showed that 9.87 ± 2.77 [95% confidence intervals (ci)] cross-sections per specimen were sufficient for a precise gca diagnosis. there was no statistically significant difference in the mean biopsy length (p = 0.142) among the eight positive-tabs. similarly, no significant difference was observed in the number of cross-sections per specimen (p = 0.990) for positive-tabs compared to those for the negative-tabs. after the retrieval of negative-tabs, the mean number of total preand post-retrieval cross-sections per specimen was 17.66 ± 4.43. among all retrieved specimens, only one case (0.01%) showed the histopathological features of healed arteritis. conclusion: positive-tabs did not reveal more histological cross-sections than the negative ones and increasing the number of cross-sections did not enhance the accuracy of tab. keywords: giant cell arteritis; histopathology cross-sections; temporal artery biopsy j ophthalmic vis res 2021; 16 (1): 77–83 correspondence to: kaveh abri aghdam, md, phd. department of ophthalmology, eye research center, the five senses institute, rassoul akram hospital, niayesh ave., sattarkhan st., tehran 14456, iran. e-mail: kaveh.abri@gmail.com received: 24-07-2019 accepted: 22-09-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8253 introduction giant cell arteritis (gca) is characterized by granulomatous vasculitis of large and mediumsized vessels, and its worldwide annual this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: navahi raa, chaibakhsh s, alemzadeh sa, abri aghdam k. the adequate number of histopathology cross-sections of temporal artery biopsy in establishing the diagnosis of giant cell arteritis. j ophthalmic vis res 2021;16:77–83. © 2021 navahi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 77 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8253&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr adequacy of tab histopathology cross-sections in giant cell arteritis; navahi et al incidence rate ranges from 1.28 to 29.1 per 100,000 among individuals aged over 50 years.[1–3] approximately 15–20% of gca patients may develop permanent loss of vision.[4] as per the guidelines of the american college of rheumatologists (acr), diagnosis of gca is primarily based on the presence of characteristic clinical features and laboratory findings of elevated levels of acute-phase reactants.[5–7] temporal artery biopsy (tab) is considered as the gold standard diagnostic test for gca.[8, 9] a positive-tab test is mainly defined as vasculitis with infiltration of mononuclear cells with or without the presence of multinucleated giant cells, disruption of the internal elastic lamina, and intimal hyperplasia.[10–12] however, sometimes tab may indicate intermediate findings that make it difficult to distinguish gca from other pathologies such as healed arteritis or even arteriosclerosis that occurs in elderly patients.[13, 14] thus, tab has low sensitivity and it may show negative results in 15– 40% of patients.[15–19] additionally, the number of biopsies, length of the artery sampled, sectioning techniques, and histopathological criteria for diagnosing arteritis, presence of skip lesions, and previous treatment with corticosteroids may contribute to false-negative results.[20, 21] this study was performed at a tertiary referral center to determine the appropriate number of cross-sections for a tab examination that are required for a conclusive gca diagnosis. methods in our center, tab cross-sections are routinely cut into 2–3 mm-long slices and each of them is embedded transversely in a paraffin block. next, hematoxylin and eosin-stained serial sections of 5μm thickness are prepared at three-step levels with 25-μm intervals. tab specimens are considered positive if a narrow lumen, irregular intimal thickening, and fragmentation of the internal elastic lamina with inflammation of the vessel wall (composed of lymphocytes and epithelioid histiocytes with or without multinucleated giant cells) are observed. in borderline cases including those wherein inflammation is limited to the adventitia, additional levels are requested. in this cross-sectional study, the histopathology reports of 205 archived temporal artery biopsies (tabs; performed between 2012 and 2016) were re-evaluated. the length of the biopsy and total number of cross-sections per specimen for eight positive-tab cases were compared with those for a 100 computer-assisted randomly selected negative-tabs, which were performed during the same period. then, paraffin-embedded blocks of these original negative-tabs were retrieved and >90% of each paraffin block was sectioned. a single ophthalmic pathologist (raan) re-evaluated all the newly retrieved sections, considering the previously mentioned histopathological findings that characterize gca. the methods and main outcomes of the study have been summarized in figure 1. in addition, the revised acr-2016 (racr) scores from the available medical records of patients with positiveand negative-tabs conducted in 2016 were evaluated. spss software version 22.0 (ibm corp., armonk, ny) was used for statistical analyses. results are reported as mean ± standard deviation. the mann–whitney u test was used to analyze quantitative variables. p-value < 0.05 was considered statistically significant. results of the total 205 tabs conducted during 2012– 2016, eight reports were positive for gca. from the remaining 197 negative biopsies, initially a 100 paraffin-embedded blocks were randomly selected for retrieval. since five paraffin blocks were not suitable for retrieval, finally the results of 95 specimens were evaluated. the mean age of the patients was 62.75 ± 12.83 years and 54% were female. two patients had nonsimultaneous bilateral biopsies. the mean biopsy length was 15.39 ± 7.56 mm. the number of slides per specimen, crosssections per slide, and the number of slides per mm of biopsy length before and after retrieval have been summarized in table 1. in the eight positive-tab specimens, the mean artery length was 16.70 ± 8.48 mm and the mean number of cross-sections per specimen was 9.25 ± 3.37. no statistically significant differences were found in the biopsy length (p = 0.142) and the number of cross-sections per specimen (p = 0.990) among the eight positive-tabs and when the positive tabs were compared to the pre-retrieval negative-tabs (table 1). comparison of the number of cross-sections per specimen for pre-retrieval 78 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 adequacy of tab histopathology cross-sections in giant cell arteritis; navahi et al figure 1. (a) healed arteritis: note the narrow lumen and minimal intramural lymphocytic infiltration, scarring, and fibrosis (asterisks) in areas with destroyed elastic lamina (short arrows) compared to the areas of intact elastic lamina (long arrows), (h&e staining ×40). (b) normal artery, negative for gca (h&e staining ×40). (c) active gca: note the obstruction of the lumen, arterial wall thickening, elastic lamina fragmentation, and intramural inflammation with multinucleated giant cells (arrow), (h&e staining ×100). gca, giant cell arteritis; h&e, hematoxylin and eosin mean cross-sec!ons/specimen: 9.25 ± 3.37 * 100 randomly selected paraffin blocks mean pre-retrieval cross-sec!ons/specimen: 9.53 ± 2.46 * mean post-retrieval cross-sec!ons/specimen: 8.12 ± 3.09 total preand post-retrieval cross-sec!ons/specimen: 17.66 ± 4.43 8 posi!ve tabs 197 nega!ve tabs 95 retrievable blocks total 205 tabs (2012–2016) 1 healed arteri!s 94 nega!ve tabs figure 2. summary of the methods and main outcomes of the study. *there was no significant difference in the mean number of cross-sections per specimen between the positiveand original negative-tabs (p = 0.990). based on the comparison of these two items, 9.87 ± 2.77 (95% confidence intervals) cross-sections per specimen were considered sufficient for precise results. in addition, retrieval of the original negative-tabs at multiple levels did not enhance the accuracy of tab for diagnosing gca. gca, giant cell arteritis; tab, temporal artery biopsy negative-tabs (9.53 ± 2.46) and those for the eight positive-tabs (9.25 ± 3.37) showed that 9.87 ± 2.77 [95% confidence intervals (ci): 9.16–10.59] crosssections per specimen were sufficient for precise diagnostic results. in the clinical evaluation of 95 negativetabs, we only found 50 cases with complete medical records that met the 2016 racr criteria,[7] and the mean overall racr score for these patients was 3.86 ± 1.12. in contrast, the mean overall racr score for the eight patients with positive tabs in our study was 5.87. histopathological evaluation of retrieved biopsies revealed only one case (0.01%) of healed arteritis with mild intramural lymphocytic infiltration, narrowing of the lumen, fragmentation, and destruction of the internal elastic lamina with scarring of the artery wall (figure 1). this patient had an racr score of 3, and had undergone bilateral tab, with original pathology reports showing negative results for gca. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 79 adequacy of tab histopathology cross-sections in giant cell arteritis; navahi et al table 1. comparison of positiveand negative-tabs (preand post-retrieval) parameter negative-tab (n = 95) positive-tab (n = 8) (original) p-value (between positive-tabs and pre-retrieval negative-tabs) pre-retrieval (original) post-retrieval mean biopsy length (mm) 15.39 ± 7.56 n/a 16.70 ± 8.48 p = 0.142 mean number of slides/specimen 3.24 ± 0.74 2.83 ± 0.96 3.25 ± 0.82 n/a mean number of cross-sections/slide 2.93 ± 0.26 2.84 ± 0.39 2.87 ± 0.36 n/a mean number of cross-sections/specimen 9.53 ± 2.46 8.12 ± 3.09 9.25 ± 3.37 p = 0.990* mean number of cross-sections/mm biopsy length 0.72 ± 0.29 n/a 0.55 ± 0.46 n/a mean number of total preand post-retrieval cross-sections/specimen 17.66 ± 4.43 n/a n/a *comparisons of positive-tabs and pre-retrieval negative-tabs n/a, not applicable; tab, temporal artery biopsy discussion currently, no specific guidelines have been formulated regarding the adequate number of cross-sections needed for accurate biopsy results of tab specimens. although tab is considered as the gold standard test for diagnosing gca, ambiguous findings may lead to inconclusive diagnosis or inaccurate results.[8, 9] the extent of sectioning, length of the artery, and presence of skip lesions as well as unilateral or bilateral biopsies are among the factors that may affect tab results. characteristic histopathological findings of active gca include pan-arteritis that is most pronounced in media, with or without multinucleated giant cells and fragmented internal elastic lamina. in contrast, healed arteritis is characterized by diffuse intimal thickening, intimal and medial fibrosis with variable degree of lymphocytic infiltration, loss of internal elastic lamina, and adventitial scarring which correlates with prior history of gca symptoms and a higherthan-normal erythrocyte sedimentation rate (esr). increased esr is part of the reparative process and not considered a marker for active arteritis.[22] however, occasionally, it may be difficult to distinguish the aforementioned pathology from changes resulting from aging and atherosclerosis.[23–25] according to the literature, routine evaluation of tabs at multiple levels does not enhance the diagnostic yield and is not cost-effective.[20, 26–29] in a study conducted by taylor et al[29] for determining the threshold specimen length for pathological examination and interpretation, there was no statistically significant difference between the number of total cross-sections per specimen used for positive-tabs (22.3) and those for the negative ones (21.6). in our study, there was no statistically significant difference in the mean biopsy length and mean number of cross-sections per specimen for the eight positive-tabs compared to those of the negative-tabs before retrieval. these results indicate that diagnosis in positivetab cases did not require a greater number of cross-sections than those required in negative ones. methods for the technical processing of a temporal artery differ across centers. some centers examine the artery in one longitudinal section and two transverse ones, which may be obtained from either end of the artery if the arterial length is sufficient.[20, 29, 30] tab processing at our center is performed using transverse sections 80 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 adequacy of tab histopathology cross-sections in giant cell arteritis; navahi et al according to a recommended protocol,[31] with some modifications that have been described in the methods section. in this study, we determined that 9.87 ± 2.77 cross-sections per specimen were sufficient to achieve precise results at our center. further, additional retrieval of the negative-tab specimens did not increase the chances of obtaining positive gca results. however, additional studies are required to determine the appropriate number of cross-sections for a tab evaluation. “skip lesions,” which are foci of discontinuous vasculitis, are found in 8–28% of gca-positive biopsies.[23, 26, 32] skip lesions are not common in temporal arteritis, and skipped areas are approximately 330 μm to 1 mm in length.[27] although the idea is controversial, it has been suggested that a length of 5–7 mm could be the threshold for diagnostic sensitivity of tab.[27, 33] this implies that even short tab specimens might be sufficient to visualize the histological features of arteritis.[27] our results indicate that there was only one case of healed arteritis among 95 negative-tab cases. these results are compatible with those of chakrabarty et al,[20] wherein only 1 out of 132 cases showed positive gca features after performing sections at multiple levels. however, the length of the artery in our positive case was 13 mm. the extent of the agreement between the first and second slide readings using the kappa coefficient before and after the retrieval of the negative-tab specimens could not be calculated due to high similarity between the results. however, regardless of statistical significance, there was approximately a 98% agreement between the two readings since 94 out of 95 negative-tab specimens were also negative in the second histopathological evaluation. in general, it is standard to perform a unilateral tab when gca is clinically suspected; the contralateral artery biopsy is done if the clinical suspicion is high and the first biopsy is negative.[34] otherwise, the chance of a positive second biopsy ranges from 5% to 9%,[35] and if the clinical suspicion is low, a unilateral biopsy is sufficient to rule out the diagnosis. the single biopsy after retrieval that was positive for healed arteritis was that of a left temporal artery from a 67-year-old female, which was taken seven days after a negative-gca result from the first biopsy of the right artery. she had been treated with intravenous methylprednisolone for three days followed by oral prednisolone at a dose of 1 mg/kg before performing tab. in general, for cases where gca is suspected, immediate treatment with high-dose steroids even before a biopsy is recommended. since the resolution of inflammatory infiltration is usually slow, the chance of detecting active inflammation is not affected by steroid therapy if the biopsy is performed within two weeks.[36] in our case of healed arteritis after retrieval, the specimen was taken seven days after starting steroid therapy. therefore, the findings could be due to a previous episode of gca rather than aging-related arterial changes. the diagnosis of gca does not always require a positive-tab, and approximately 15–40% of patients with gca are tab-negative.[15–19] this phenomenon where a high percentage of people who have negative biopsies are diagnosed with gca has resulted in disagreement among neuroophthalmologists and rheumatologists regarding the criteria for gca. it has been recommended that tab should be performed only for patients with racr scores of 3 and 4, since there is higher variability in tab results for other patients.[7] among the 95 suspected gca cases with negative tabs, we reviewed the medical records of 50 patients whose mean overall racr score was 3.86 ± 1.12. these results were similar to those of abri aghdam et al[37] (mean score of 3.88 ± 1.19 for negative biopsies). in addition, the mean overall racr score of the eight patients with positive-tabs in our study was 5.87. after retrieval of negative-tabs, we identified only one case of healed arteritis with an racr score of 3. positron emission tomography[38] and 3 tesla-magnetic resonance imaging[39] are new technologies that are now being regularly used in the diagnosis and monitoring of gca disease progression. although, the use of non-invasive color duplex ultrasonography reduces the chances of false-negative tabs due to skip lesions,[40] it is an operator-dependent technique. it is important to consider that the final diagnosis in tab-negative patients may indicate a spectrum of conditions mainly including other rheumatologic diseases, presence of non-temporal arteries with gca, infectious diseases, neoplastic diseases, and neuro-ophthalmic conditions.[7, 41] in conclusion, positive-tabs in our study did not require more cross-sections than the negative journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 81 adequacy of tab histopathology cross-sections in giant cell arteritis; navahi et al ones. further, tab examination at multiple levels did not increase the diagnostic yield of the test. in this study, 9.87 ± 2.77 cross-sections per specimen were sufficient for a precise diagnosis of gca. acknowledgements the authors would like to thank dr. fahimeh asadi amoli, professor of pathology at the farabi eye hospital for her technical support in providing histology sections. financial support and sponsorship this work was funded by the eye research center of iran university of medical sciences which did not have any role in the design, execution, and presentation of results. conflicts of interest there are no conflicts of interest. references 1. allsop c, gallagher p. temporal artery biopsy in giant cell arteritis: a reappraisal. am j surg pathol 1981;5:317–323. 2. mambo nc. temporal (granulomatous) arteritis: a histopathological study of 32 cases. histopathology 1979;3:209–221. 3. ramstead cl, patel ad. giant cell arteritis in a neuroophthalmology clinic in saskatoon, 1998-2003. can j ophthalmol 2007;42:295–298. 4. evans jm, hunder gg. polymyalgia rheumatica and giant cell arteritis. rheum dis clin north am 2000;26:493–515. 5. nesher g, breuer gs. giant cell arteritis and polymyalgia rheumatica: 2016 update. rambam maimonides med j 2016;7:e0035. 6. gajree s, borooah s, dhillon n, goudie c, smith c, aspinall p et al. temporal artery biopsies in south-east scotland: a five-year review. j r coll physicians 2017;47:124–128. 7. sait mr, lepore m, kwasnicki r, allington j, balasubramanian r, somasundaram sk, et al. the 2016 revised acr criteria for diagnosis of giant cell arteritis – our case series: can this avoid unnecessary temporal artery biopsies? int j surg open 2017;9:19–23. 8. hall s, persellin s, lie jt, o’brien pc, kurland lt, hunder gg., et al. the therapeutic impact of temporal artery biopsy. lancet 1983;2:1217–1220. 9. hall s, hunder gg. is temporal artery biopsy prudent? mayo clin proc 1984;59:793–796. 10. nesher g. the diagnosis and classification of giant cell arteritis. j autoimmun 2014;48–49:73–75. 11. hunder gg, bloch da, michel ba, stevens mb, arend wp, calabrese lh, et al. the american college of rheumatology 1990 criteria for the classification of giant cell arteritis. arthritis rheum 1990;33:1122–1128. 12. font rl, prabhakaran vc. histological parameters helpful in recognising steroid-treated temporal arteritis: an analysis of 35 cases. br j ophthalmol 2007;91:204–209. 13. zhou l, luneau k, weyand cm, biousse v, newman nj, grossniklaus he. clinicopathologic correlations in giant cell arteritis: a retrospective study of 107 cases. ophthalmology 2009;116:1574–1580. 14. stacy rc, rizzo jf, cestari dm. subtleties in the histopathology of giant cell arteritis. semin ophthalmol 2011;26:342–348. 15. burke a, virmani r. temporal artery biopsy of giant cell arteritis. pathol case rev 2001;6:265–273. 16. egge k, midtbo a, westby r. arteritis temporalis. acta ophthalmol 1966;14:49–56. 17. hauser wa, ferguson rh, holley ke, kurland lt. temporal arteritis in rochester minnesota, 1951 to 1967. mayo clin proc 1971;46:567–602. 18. roth am, milsow l, keltner jl. the ultimate diagnoses of patients undergoing temporal artery biopsies. arch ophthalmol 1984;102:901–903. 19. salvarani c, macchioni p, zizzi f, mantovani w, rossi f, castri c, et al. epidemiological and immunogenetic aspects of polymyalgia rheumatica and giant cell arteritis in northern italy. arthritis rheum 1991;34:351–356. 20. chakrabarty a, franks aj. temporal artery biopsy: is there any value in examining biopsies at multiple levels? j clin pathol 2000;53:131–136. 21. bhatti mt, tabandeh h. giant cell arteritis: diagnosis and management. curr opin ophthalmol 2001;12:393–399. 22. mcdonnell pj, moore gw, miller nr, hutchins gm, green wr. temporal arteritis. a clinicopathologic study. ophthalmology 1986;93:518–530. 23. lie jt. temporal artery biopsy diagnosis of giant cell arteritis: lessons from 1109 biopsies. anat pathol 1996;1:69–97. 24. bevan at, dunnill ms, harrison mj. clinical and biopsy findings in temporal arteritis. ann rheum dis 1968;2:271– 277. 25. ostberg g. temporal arteritis in a large necropsy series. ann rheum di 1971;30:224–235. 26. poller dn, van wyk q, jeffrey mj. the importance of skip lesions in temporal arteritis. j clin pathol 2000;53:137– 139. 27. mahr a, saba m, kambouchner m, polivka m, baudrimont m, brocheriou i, et al. temporal artery biopsy for diagnosing giant cell arteritis: the longer, the better? ann rheum dis 2006;65:826–828. 28. cohen dn, smith tr. skip areas in temporal arteritis: myth versus fact. trans am acad ophthalmol otolaryngol 1974;78:772–783. 29. taylor-gjevre r, vo m, shukla d, resch l. temporal artery biopsy for giant cell arteritis. j rheumatol 2005;32:1279– 1282. 30. sharma ns, gal a, benger r. longitudinal sectioning of temporal artery biopsy specimens. eye 2012;26:1593– 1595. 31. stone jr, basso c, baandrup ut, bruneval p, butany j, gallagher pj, et al. recommendations for processing cardiovascular surgical pathology specimens: a consensus statement from the standards and definitions 82 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 adequacy of tab histopathology cross-sections in giant cell arteritis; navahi et al committee of the society for cardiovascular pathology and the association for european cardiovascular pathology. cardiovasc pathol 2012;21:2–16. 32. klein rg, campbell rj, hunder gg, carney ja. skip lesions in temporal arteritis. mayo clin proc 1976;51:504– 510. 33. ypsilantis e, courtney ed, chopra n, karthikesalingam a, eltayab m, katsoulas n, et al. importance of specimen length during temporal artery biopsy. br j surg 2011;98:1556–1560. 34. miller nr. giant cell arteritis. j neuroophthalmol 2000;20:219–220. 35. hayreh ss, podhajsky pa, raman r, zimmerman b. giant cell arteritis: validity and reliability of various diagnostic criteria. am j ophthalmol 1997;12:285–296. 36. achkar aa, lie jt, hunder gg, o’fallon wm, gabriel se. how does previous corticosteroid treatment affect the biopsy findings in giant cell (temporal) arteritis? ann intern med 1994;120:987–992. 37. abri aghdam k, soltan sanjari m, manafi n, khorramdel s, alemzadeh sa, ali akbar navahi r. temporal artery biopsy in diagnosing giant cell arteritis: a ten-year review. j ophthalmic vis res 2020;15:201–209. 38. blockmans d, ceuninck l, vanderschueren s, knockaert d, mortelmans l, bobbaers h. repetitive 18f-fluorodeoxyglucose positron emission tomography in giant cell arteritis: a prospective study of 35 patients. arthritis rheum 2006;55:131–137. 39. bley ta, uhl m, venhoff n, thoden j, langer m, markl m. 3-t mri reveals cranial and thoracic inflammatory changes in giant cell arteritis. clin rheumatol 2007;26:448–450. 40. ball el, walsh sr, tang ty, gohil r, clarke jm. role of ultrasonography in the diagnosis of temporal arteritis. br j surg 2010;97:1765–1771. 41. breuer gs, nesher r, nesher g. negative temporal artery biopsies: eventual diagnoses and features of patients with biopsy-negative giant cell arteritis compared to patients without arteritis. clin exp rheumatol 2008;26:1103–1106. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 83 original article aggressive posterior retinopathy of prematurity (aprop): laser as the primary modality of treatment shilpi h narnaware1, ico, faico; prashant k bawankule2, fmrf, hon faico; dhananjay raje3, cstat, phd 1consultant vitreo-retina & rop specialist, sarakshi netralaya, rajiv nagar, wardha road, nagpur 440025, maharashtra, india 2vitreo-retinal surgeon, rajiv nagar, wardha road, nagpur 440025 maharashtra, india 3head, data analysis group, mds bio-analytics pvt. ltd., shankar nagar, nagpur 440010, maharashtra, india orcid: shilpi h. narnaware: https://orcid.org/0000-0003-3170-955x abstract purpose: to study the success rate of laser as a primary modality of treatment in aggressive posterior retinopathy of prematurity (aprop) cases. methods: this is a prospective case series of 56 eyes of 28 preterm babies (males = 21) with aprop who underwent laser therapy. babies were divided into groups on the basis of gestational age (ga), birth weight (bw), and postmenstrual age (pma) at which treatment was performed. ga (in weeks): <28 (n = 7), 28–30 (n = 11), >30 (n = 10). bw (in grams): <1000 (n = 8), 1000–1200 (n = 10), >1200 (n = 10). pma (in weeks): < 32 (n = 6), 32–34 (n = 18), >34 (n = 4). success was calculated as complete regression of disease without need for any other modality of treatment such as anti-vascular endothelial growth factor (anti-vegf) or pars plana vitrectomy. results: the overall success rate was 94.64% (53/56). two babies who needed additional modality of treatment were <28 weeks of ga (one eye) and 28–30 weeks (two eyes). one baby (one eye) was <1000 gm and the other (two eyes) was >1200 gm, while pma at which additional treatment was needed was 30 weeks in one baby (one eye) and 33 weeks in the other (two eyes). conclusion: in this era of anti-vegf treatment, even in cases of aprop, laser should still be considered as a primary modality of treatment, as it is a one-time treatment without the concern of systemic side effects and recurrent/persistent avascular zones. keywords: aggressive posterior retinopathy of prematurity; lasers; success rate j ophthalmic vis res 2021; 16 (3): 400–407 introduction aggressive posterior retinopathy of prematurity (aprop) is a distinct variant of retinopathy of correspondence to: shilpi h. narnaware, mbbs, d.o., fellowship in vitreoretina, ico (retina). sarakshi netralaya, plot no. 19, rajiv nagar, wardha road, nagpur 440025, maharashtra, india. e-mail: shilpi.narnaware@gmail.com received: 08-03-2020 accepted: 15-06-2019 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i3.9437 prematurity (rop) which does not respect various stages and can rapidly lead to blindness if untreated. according to various studies,[1–4] the overall incidence of rop varies from 38% to 51.9% in the indian subcontinent. nearly 26.4% of babies needed treatment for one of the stages of rop[4] almost half of them had aprop.[4] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: narnaware sh, bawankule pk, raje d. aggressive posterior retinopathy of prematurity (aprop): laser as the primary modality of treatment. j ophthalmic vis res 2021;16:400–407. 400 © 2021 narnaware et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i3.9437&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr rop in the anti-vegf era; narnaware et al many previous studies have shown more unfavorable outcomes in aprop (ranging from 15% to 29%) undergoing laser treatment compared with anti-vascular endothelial growth factor (antivegf) injection.[5–8] because of these unfavorable outcomes, alternatives in treatment of aprop were explored over the last few years. the first prospective, controlled, randomized trial was performed by mintz-hittner[9] showing significantly lower recurrence rate following intravitreal bevacizumab (ivb), compared to laser photocoagulation, especially in zone 1 rop. after that, several studies reported the success rate of around 85% in zone 1 and aprop with ivb monotherapy.[10, 11] however, none of these studies talked about the systemic side effects, recurrence rates, and need of laser treatment after ivb in their studies. in this study, we prospectively studied the structural success rate in cases of aprop after laser treatment and assessed various parameters like systemic side effects, complications, follow-up period and retreatment. methods a prospective case series including 56 eyes of 28 infants with aprop who were treated with laser photocoagulation between january 2015 and june 2018 and were followed-up for 12 months. various parameters including birth weight (bw), gestational age, postmenstrual age (pma), neonatal illness risk factors, and oxygenation were studied. diagnosis of aprop was made in accordance with the international classification of rop[12] and documented by retinal drawings and/or neoret images [figure 1a]. aprop was diagnosed according to the international classification,[12] which is described as follows: “the characteristic features of this type of rop are its posterior location, prominence of plus disease, and the ill-defined nature of the retinopathy.” all infants received confluent laser spots (less than half burn width apart) to cover the full avascular retina with green laser (532 nm) delivered through the indirect ophthalmoscopic system under topical anesthesia in the nicu setting. mean number of laser spots were 4200 +/– 600 per eye. completion of laser was confirmed by a second observer or neoret photography. pma at treatment, number of laser sittings, and outcome were noted. babies were followed-up for up to 12 months and the outcome was labeled as unfavorable if any of the following three situations/conditions were seen: (1) retinal detachment (stage 4a/4b/5), (2) falciform fold involving the macula, and (3) disc/macular dragging. follow-up and retreatment the follow-up examination after laser treatment with neoret photography [figure 1b] were performed weekly for one month, biweekly for two months, and then every three months for nine months. in cases where avascular non-covered areas were seen, fill-in laser was applied to the skipped areas usually one or two weeks after the initial laser session. mean number of laser spots during retreatment was 400 /+– 100 per eye. statistical methods the description for various risk factors such as gestational age, bw, pma, and regression week were obtained in terms of mean and standard deviation. the unfavorable event was treated as dependent variable and the effect of different risk factors was studied on outcome through univariate logistic regression. the odds ratio associated with each factor were obtained and interpreted. the number of babies with different complications were obtained and the association of outcome with the number of complications was represented through a stacked bar chart. further, the scatter plots showing association of bw with gestational age and pma were obtained highlighting the unfavorable events. all analyses were performed using spss version 20.0 (ibm corp, usa) and the graphical representations were obtained using microsoft excel. a p-value of less than 5% was considered as statistically significant. results fifty-six eyes of 28 preterm babies (21 male and 7 female) with aprop who underwent laser treatment were studied. the mean gestational age of mothers was 28.5 (sd: 2.01) weeks and the mean bw of babies was 1,128 (sd: 310) gr. the mean pma of mothers was 32.7 (sd: 1.63) weeks. the undesired event occurred in three eyes out journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 401 rop in the anti-vegf era; narnaware et al a b figure 1. fundus photos of eyes pre(a) and post-laser (b). a b c figure 2. column chart showing number of babies according to gestational age (a), birth weight (b), and pma (c). a b c figure 3. scatter plot showing success corresponding to birth weight and gestational age (a), birth weight and pma (b), and gestational age and pma (c). 402 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 rop in the anti-vegf era; narnaware et al figure 4. stacked bar chart showing number of babies according to number of risk factors. of 56 resulting in the overall success rate of 94.64%. the risk associated with various factors was studied though logistic regression and showed the following results. gestational age the odds associated with gestational age was 1.036 (95% ci: 0.577–1.858) indicating hardly any effect of gestational age on the success rate, and the effect was not statistically significant (p = 0.906). bw the odds associated with bw was 0.999 (95% ci: 0.995–1.003) indicating hardly any effect of bw on the success rate, and moreover the effect was statistically insignificant (p = 0.750) pma the odds associated with pma was 0.735 (95% ci: 0.339–1.591) indicating that the increase in pma reduced the risk of failure; however, the effect was not statistically significant (p = 0.434). regression week it was defined as the interval between application of laser to complete regression of the disease. the odds associated with regression week was 3.814 (95% ci: 0.446–32.641) indicating that any increase in the regression week increased the risk of failure, although the effect was found to be statistically insignificant (p = 0.222). figures 2a–2c show the distribution of babies according to gestational age, bw, and pma. with regard to gestational age, the majority, that is, 17 (60.7%) babies were born in 28–30 weeks of gestational age. there were 20 (71.42%) babies with bw >1000 gm; and there were 18 (64.29%) babies with mothers having pma between 32 and 34 weeks. figures 3a–3c, show the scatter plots demonstrating the structural success rates corresponding to the interplay between ga, pma, and bw. supplementary laser treatment was needed in 20 eyes, one to two weeks after the initial laser treatment. the mean regression period was 4.68 weeks (sd: 0.71) in babies with bw >1000 gm and 6.36 weeks (sd: 0.92) when the bw was <1000 gm. no relation was seen with ga or pma. out of the 56 eyes, 53 eyes had complete regression while of the other three eyes, two progressed to stage 5 and one progressed to stage 4a despite laser. one baby (two eyes), which progressed to stage 5 was 30 weeks of ga and >1200 gm bw, while the other baby (one eye) that progressed to stage 4a was <28 weeks and <1000 gm bw. table 1 illustrates the distribution of various risk factors/systemic illness in babies. supplemental unmonitored oxygen was the common factor among all the babies. in figure 4, the stacked bar chart representation reveals that as the number of risk factors increases, the likelihood of failure increases. failures were observed in cases with five or more complications. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 403 rop in the anti-vegf era; narnaware et al table 1. number of babies with different complications complication number % oxygen administration 28 100 neonatal jaundice 11 39.28 sepsis 10 35.71 rds 11 39.28 hypothermia 5 17.86 shock 3 10.71 blood transfusion 2 7.14 discussion in the present study, 53 out of 56 eyes had complete regression, while out of 3 eyes without complete regression, 2 progressed to stage 5 and 1 progressed to stage 4a. mean regression period was 4.68 weeks in babies with bw >1000 gm and 6.36 weeks when bw was <1000 gm. according to previous studies, mean ga and bw of infants with aprop were significantly lower than those with non-aprop.[13, 14] a study by tong et al[15] showed that older pma and low neutrophil count were associated as risk factors for retinal detachment in aprop. also, low bw was significantly associated with recurrence in aprop. many studies have shown the beneficial effect of ivb over laser in terms of structural outcome specially in cases of aprop. the studies by drenser et al[7] and pandya et al[8] reported that 8/44 eyes and 3/6 eyes, respectively, progressed to retinal detachment in spite of laser treatment. while 17% of eyes landed into retinal detachment in the study by sanghi et al,[6] in our study only 5.36% of babies progressed to stage 4/5 after laser treatment which is much less than the rates reported by previous studies. gunay et al from turkey reported 0/25 and 2/11 eyes progressing to retinal detachment in ivb group versus laser group[10] while nicoara et al reported the success rate of 94% in ivb group compared to 83% in laser group in the romanian population.[11] recently, many studies have reported reactivation of disease with ivb. in a study by lorenz et al,[16] only 25% of eyes with aprop showed regression with lower doses of bevacizumab, that is, 0.312 mg. in a recent study, mintz-hittner showed reactivation in 100% of eyes with aprop[17] while blair et al found 41% reactivation in aprop eyes in their study.[18] this difference in reactivation may be because of higher levels of vegfs in aprop eyes. because of late reactivation up to 69 weeks+ after anti-vegf treatment, longer-term follow-up is required.[19] the babies in our study were followed-up for up to one year of age to look for recurrence. the average number of visits in our study was 7–10 in a year. in study by simona et al,[20] babies receiving laser needed an average follow-up of up to 60 weeks with an average of 8–9 visits which is much less compared to a follow-up of up to 80 weeks and an average of 16–18 visits in the group receiving anti-vegf treatment. persistent avascular zones after ivb have been reported in up to 91.7% of cases by leopore et al,[21], while 100% of eyes needed additional treatment with laser because of persistent avascular zones which were confirmed on fluorescein angiography in a study by michael blair et al.[18] in the present study, 53 eyes after regression did not need any additional form of treatment in the form of anti-vegf injection or surgery. another concern is of the “crunch phenomenon” with ivb which causes fibrovascular contraction and tractional retinal detachment following intravitreal anti-vegf.[22] systemic safety is another concern. intravitreal injection causes breakdown of blood retinal barrier,[23] hence, anti-vegf is found in systemic circulation after intravitreal injection causing serum vegf levels to decrease.[23, 24] various studies demonstrated that serum vegf plasma levels may be lowered up to two to seven weeks after ivb.[25–27] these decreased vegf levels may cause adverse effects on vegf-dependent developments such as the development of brain, lungs, kidney, and normal neural retinal development.[28] few studies have 404 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 rop in the anti-vegf era; narnaware et al shown delay in growth and pulmonary dysplasia in bevacizumab-treated babies.[29] a study by morin et al reported that severe neurodevelopmental disabilities (bayley scores <70) was seen 3.1 times higher with bevacizumab compared to laser.[30] most recently, hypotension-related reports[31] and histopathologically proven new or reactivation of bronchopulmonary dysplasia have been noted after anti-vegf administration.[32] few studies were designed to study specific abnormalities related to anti-vegf treatment and detected no systemic complications.[29, 33, 34] these negative results may be due to the fact that infants with rop present more often with developmental disorders compared to other infants, causing difficulty in assessing systemic side effects of anti-vegf treatment.[35] none of the babies showed any signs of systemic complications in our case series. laser therapy in rop is associated with restricted visual field[36–39] and refractive error.[40, 41] it is postulated that increased laser ablation spots might induce more severe myopia and for every 100 laser spots myopia increases by –0.14 ± 0.05d.[42] prevalence of high myopia reported in literature varies from 8%[43] to 35%.[44] various studies have shown more chance of refractive anisometropia[43] and myopia[40, 41] in babies receiving laser therapy compared to ivb. however, the study by kua et al[42] and isaac et al[44] reported no statistically significant difference in refractive error between ivb and laser groups. because of conflicting results, one meta-analysis[45] has concluded the need to investigate the long-term effects of ivb therapy on refractive error development. although, myopia[40, 41] and field restriction[36–39] are the main adverse events associated with laser therapy, in our study, we only evaluated the structural success and the refractive status was not evaluated. this study had a few limitations; it was a noncomparative study with limited follow-up period of one year. due to being non-comparative, the refractive status was not evaluated and because of the small sample size, no significant association between bw, ga, pma, and risk factor could be detected. in summary, approximately 10% of rop cases in the indian subcontinent is aprop.[4] need for longterm follow-up and retreatment, concern about systemic complications and financial constraints still loom large in the indian subcontinent where compliance is a big challenge. laser therapy can be considered as primary modality of treatment specially in patients with expected poorer compliance and financial constraints. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. gopal l, sharma t, ramachandran s, shanmugasundaram r, asha v. retinopathy of prematurity: a study. ind j ophthal 1995;43:59–61. 2. charan r, dogra mr, gupta a, narang a. the incidence of retinopathy of prematurity in a neonatal care unit. ind j ophthalmol 1995;43:123–126. 3. varughese s, jain s, gupta n, singh s, tyagi v, puliyel jm. magnitude of the problem of retinopathy of prematurity. experience in a large maternity unit with a medium size level-3 nursery. ind j ophthalmol 2001;49:187–188. 4. hungi b, vinekar a, datti n, kariyappa p, braganza s, chinnaiah s, et al. retinopathy of prematurity in a rural neonatal intensive care unit in south india-a prospective study. ind j ped 2012;79:911–915. 5. nicoară sd, nascutzy c, cristian c, irimescu i, ștefănuț ac, zaharie g, et al. outcomes and prognostic factors of intravitreal bevacizumab monotherapy in zone i stage 3+ and aggressive posterior retinopathy of prematurity. j ophthalmol 2015;2015:102582. 6. sanghi g, dogra mr, katoch d, gupta a. aggressive posterior retinopathy of prematurity: risk factors for retinal detachment despite confluent laser photocoagulation. am j ophthalmol 2013;155:159–164.e2. 7. drenser ka, trese mt, capone a jr. aggressive posterior retinopathy of prematurity. retina 2010;30:s37–s40. 8. pandya hk, faia lj, robinson j, drenser ka. macular development in aggressive posterior retinopathy of prematurity. biomed res int 2015;2015:808639. 9. mintz-hittner ha, kennedy ka, chuang az, beat-rop cooperative group. efficacy of intravitreal bevacizumab for stage 3+ retinopathy of prematurity. n engl j med 2011;364:603–615. 10. gunay m, celik g, gunay bo, aktas a, karatekin g, ovali f, et al. evaluation of 2-year outcomes following intravitreal bevacizumab (ivb) for aggressive posterior retinopathy of prematurity. arq bras oftalmol 2015;78:300–304. 11. nicoară sd, ştefănuţ ac, nascutzy c, zaharie gc, toader le, drugan tc, et al. regression rates following the treatment of aggressive posterior retinopathy of prematurity with bevacizumab versus laser: 8-year retrospective analysis. med sci monit 2016;22:1192–1209. 12. international committee for the classification of retinopathy of prematurity. the international classification of retinopathy of prematurity revisited. arch ophthalmol 2005;123:991–999. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 405 rop in the anti-vegf era; narnaware et al 13. gunn dj, cartwright dw, gole ga. prevalence and outcomes of laser treatment of aggressive posterior retinopathy of prematurity. clin exp ophthalmol 2014;42:459–465. 14. ahn yj, hong ke, yum hr, lee jh, kim ks, youn ya, et al. characteristic clinical features associated with aggressive posterior retinopathy of prematurity. eye 2017;31:924–930. 15. tong q, yin h, zhao m, li x, yu w. outcomes and prognostic factors for aggressive posterior retinopathy of prematurity following initial treatment with intravitreal ranibizumab. bmc ophthalmol 2018;18:150. 16. lorenz b, stieger k, jäger m, mais c, stieger s, andrassidarida m, et al. retinal vascular development with 0.312 mg intravitreal bevacizumab to treat severe posterior retinopathy of prematurity: a longitudinal fluorescein angiographic study. retina 2017;37:97–111. 17. mintz-hittner ha, geloneck mm, chuang az. clinical management of recurrent retinopathy of prematurity after intravitreal bevacizumab monotherapy. ophthalmology 2016;123:1845–1855. 18. blair m, garcia gonzalez jm, snyder l, schechet s, greenwald m, shapiro m, et al. bevacizumab or laser for aggressive posterior retinopathy of prematurity. taiwan j ophthalmol 2018;8;243–248. 19. hu j, blair mp, shapiro mj, lichtenstein sj, galasso jm, kapur r. reactivation of retinopathy of prematurity after bevacizumab injection. arch ophthalmol 2012;130:1000– 1006. 20. nicoară sd, ştefănuţ ac, nascutzy fc, zaharie gc, toader le, drugan tc. regression rates following the treatment of aggressive posterior retinopathy of prematurity with bevacizumab versus laser: 8-year retrospective analysis. med sci monit 2016;22:1192–1209. 21. lepore d, quinn ge, molle f, baldascino a, orazi l, sammartino m, et al. intravitreal bevacizumab versus laser treatment in type 1 retinopathy of prematurity: report on fluorescein angiographic findings. ophthalmology 2014;121:2212–2219. 22. yonekawa y, wu w-c, nitulescu ce, paul chan rv, thanos a, thomas bj, et al. progressive retinal detachment in infants with retinopathy of prematurity treated with intravitreal bevacizumab or ranibizumab. retina 2018;38:1079–1083. 23. carneiro am, costa r, falcão ms, barthelmes d, mendonça ls, fonseca sl, et al. vascular endothelial growth factor plasma levels before and after treatment of neovascular age-related macular degeneration with bevacizumab or ranibizumab. acta ophthalmol 2012;90:e25–e30. 24. wang d, choi cs, lee sj. serum concentration of vascular endothelial growth factor after bilateral intravitreal injection of bevacizumab. korean j ophthalmol 2014;28:32–38. 25. sato t, wada k, arahori h, kuno n, imoto k, iwahashishima c, et al. serum concentrations of bevacizumab (avastin) and vascular endothelial growth factor in infants with retinopathy of prematurity. am j ophthalmol 2012;153:327–333. 26. wu w-c, lien r, liao p-j, wang n-k, chen y-p, a chao, et al. serum levels of vascular endothelial growth factor and related factors after intravitreous bevacizumab injection for retinopathy of prematurity. jama ophthalmol 2015;133;391–397. 27. hong yr, kim yh, kim sy, nam gy, cheon hj, lee sj. plasma concentrations of vascular endothelial growth factor in retinopathy of prematurity after intravitreal bevacizumab injection. retina 2015;35:1772–1777. 28. yang ch. anti-vascular endothelium growth factor therapy for retinopathy of prematurity: a continuing debate. taiwan j ophthalmol 2012;2:115–116. 29. martínez-castellanos ma, schwartz s, hernández-rojas ml, kon-jara va, garcía-aguirre g, guerrero-naranjo jl, et al. long-term effect of anti-angiogenic therapy for retinopathy of prematurity up to 5 years of follow up. retina 2013;33:329–338. 30. morin j, mai luu t, superstein r, ospina lh, lefebvre f, simard m-n, et al. neurodevelopmental outcomes following bevacizumab injections for retinopathy of prematurity. pediatrics 2016;137:4. 31. wu lh, yang yh, lin ch, lin yj, cheng cl. hypotension associated with intravitreal bevacizumab therapy for retinopathy of prematurity. pediatrics 2016;137:e20152005. 32. fernandez mp, berrocal am, goff tc, ghassibi mp, armitage harper c, chou e, et al. histopathologic characterization of the expression of vascular endothelial growth factor in a case of retinopathy of prematurity treated with ranibizumab. am j ophthalmol 2017;176:134– 140. 33. moran s, o’keefe m, hartnett c, lanigan b, murphy j, donoghue v. bevacizumab versus diode laser in stage 3 posterior retinopathy of prematurity. acta ophthalmol 2014;92:e496–e497. 34. araz-ersan b, kir n, tuncer s, aydinoglu-candan o, yildiz-inec d, akdogan b, et al. preliminary anatomical and neurodevelopmental outcomes of intravitreal bevacizumab as adjunctive treatment for retinopath of prematurity. curr eye res 2014;15:1–7. 35. hartnett me, penn js. mechanisms and management of retinopathy of prematurity. n engl j med 2012;367:2515– 2526. 36. quinn ge, dobson v, hardy rj, tung b, palmer ea, good wv, et al. visual field extent at 6 years of age in children who had high-risk prethreshold retinopathy of prematurity. arch ophthalmol 2011;129:127–132. 37. o’connor ar, wilson cm, fielder ar. ophthalmological problems associated with preterm birth. eye 2007;21:1254–1260. 38. larsson e, rydberg a, holmstrom g. contrast sensitivity in 10 year old preterm and full term children: a population based study. br j ophthalmol 2006;90:87–90. 39. dobson v, quinn ge, abramov i, hardy rj, tung b, siatkowski rm, et al. color vision measured with pseudoisochromatic plates at five-and-a-half years in eyes of children from the cryo-rop study. invest ophthalmol vis sci 1996;37:2467–2474. 40. hwang ck, hubbard gb, hutchinson ak, lambert sr. outcomes after intravitreal bevacizumab versus laser photocoagulation for retinopathy of prematurity: a 5-year retrospective analysis. ophthalmology 2015;122:1008– 1015. 41. geloneck mm, chuang az, clark wl, hunt mg, norman aa, packwood ea, et al. refractive outcomes following 406 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 rop in the anti-vegf era; narnaware et al bevacizumab monotherapy compared with conventional laser treatment: a randomized clinical trial. jama ophthalmol 2014;132:1327–1333. 42. kuo hk, sun it, chung my, chen yh. refractive error in patients with retinopathy of prematurity after laser photocoagulation or bevacizumab monotherapy. ophthalmologica 2015;234:211–217. 43. gunay m, celik g, gunay bo, aktas a, karatekin g, ovali f. evaluation of 2-year outcomes following intravitreal bevacizumab (ivb) for aggressive posterior retinopathy of prematurity. arq bras oftalmol 2015;78:300–304. 44. isaac m, mireskandari k, tehrani n. treatment of type 1 retinopathy of prematurity with bevacizumab versus laser. j aapos 2015;19:140–144. 45. tan q-q, christiansen sp, wang j. development of refractive error in children treated for retinopathy of prematurity with anti-vascular endothelial growth factor (anti-vegf) agents: a meta-analysis and systematic review. plos one 2019;14:12. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 407 original article translaminar pressure difference and ocular perfusion pressure in glaucomatous eyes with different optic disc sizes natasha f. s. cruz, md1; katia s. santos, md1; mateus l. matuoka, md1; niro kasahara, md1,2 1department of ophthalmology, irmandade da santa casa de misericordia de sao paulo, sao paulo, brazil 2santa casa de sao paulo school of medical sciences, sao paulo, brazil orcid: natasha f. s. cruz: https://orcid.org/0000-0002-5209-9204 niro kasahara: https://orcid.org/0000-0003-4101-0304 abstract purpose: intracranial pressure (icp) and ocular perfusion pressure (opp) are both involved with the pathogenesis of glaucoma. the orbital icp determines a retrolaminar counter pressure that is antagonistic to the intraocular pressure (iop). the purpose of this study is to evaluate whether the translaminar pressure difference (tlpd) and the opp varies in glaucoma patients with different optic disc sizes. methods: in this university hospital-based, observational, cross-sectional clinical study, all patients underwent an ophthalmic evaluation. blood pressure, height, weight, and the results of retinal nerve fiber layer examination with optical coherence tomography examination were recorded. tlpd and opp were calculated for each patient using proxy algorithms to attain indirect surrogate parameter values. patients’ eyes were stratified into three quantiles according to optic disc sizes and the differences compared. data from both eyes were used after using the appropriate correction for inter-eye dependency. results: the sample consisted of 140 eyes of 73 patients with primary open-angle glaucoma and suspects. patients with large disc size presented with higher tlpd as compared to those with average and small-sized discs (2.4 ± 4.5, 2.8 ± 3.8, and 3.7 ± 4.7 mmhg for first, second, and third tertile, respectively (p < 0.000). opp did not vary according to the optic disc size. conclusion: glaucoma patients with larger optic discs have higher tlpd. the pathological significance of this finding warrants further investigation. keywords: cerebrospinal fluid pressure; glaucoma; ocular perfusion pressure; optic disc; translaminar pressure j ophthalmic vis res 2021; 16 (2): 171–177 introduction primary open-angle glaucoma (poag) is a highly prevalent, sight-threatening, multifactorial correspondence to: niro kasahara, md. department of ophthalmology, irmandade da santa casa de misericordia de sao paulo, sao paulo, brazil. e-mail: niro.kasahara@fcmsantacasasp.edu.br received: 23-06-2019 accepted: 08-01-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9080 disease. its pathogenesis is associated with both mechanical and vascular factors. mechanical factors including increased intraocular pressure (iop) with posterior bulging of the cribriform blade, compression of the nerve fibers, and reduction of the retrograde and anterograde flow and this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: cruz nfs, santos ks, matuoka ml, kasahara n. translaminar pressure difference and ocular perfusion pressure in glaucomatous eyes with different optic disc sizes. j ophthalmic vis res 2021;16:171–177. © 2021 cruz et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 171 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9080&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr translaminar gradient and optic disc size; cruz et al vascular factors including decrease of perfusion pressure in the optic nerve head and deficiency in autoregulation leading to apoptosis of retinal ganglion cells and visual function loss may be involved.[1] recently, the intracranial pressure (icp) was thought to be involved in the pathogenesis of poag. some clinical and population studies reported that glaucoma patients have a lower icp compared to that of normal subjects.[2, 3] from an anatomical perspective, the icp at the orbit level and the optic nerve tissue pressure determine the retrolaminar counter pressure which is antagonistic to the iop. thus, it may be part of the critical translaminar gradient or simply a translaminar pressure difference (tlpd). presuming that there is a higher difference in the cribrosa translaminal pressure, a marked translaminar pressure gradient may damage the optic nerve, and therefore a low orbital icp may be associated with the pathogenesis of glaucoma. there has been a debate as to whether this is an epiphenomenon or that there is an actual causal relationship between icp and glaucoma.[4] several population-based and clinical studies support a strong association between ocular blood flow and the risk of poag prevalence and progression.[5, 6] the underlying pathologic mechanism is related to the reduction in blood perfusion caused by impaired vascular autoregulation. the ocular perfusion pressure (opp) is a physiologic function that delivers arterial blood to capillary bed for the eye tissues.[7] clinical variables such as tlpd and the opp are potential players in the glaucoma optic neuropathy. moreover, the optic disc size can vary substantially in the population.[8, 9] there is evidence suggesting that large optic discs may be more susceptible to glaucoma than small discs.[10] uncertainties regarding whether the tlpd and opp differ according to the optic disc size and its influence in the glaucoma optic neuropathy exist. this crosssectional, observational study aimed to assess whether tlpd and opp vary in glaucoma patients and suspects according to the size of the optic discs. methods this cross-sectional, observational clinical study was approved by the committee on human research of the institution. the participants were patients from the glaucoma service, santa casa de misericordia of sao paulo hospital. the study adhered to the tenets of the declaration of helsinki and its late amendments and the resolution 466/12, national council of health, brazilian ministry of health. after explaining the study procedures, all participants signed the informed consent. study population and inclusion criteria the sample included patients who were diagnosed with poag and met the following inclusion criteria: age > 40 years, any sex and ethnicity; no previous ocular lasers or incisional surgeries, except for cataract which occurred more than a year ago; optic disc with the presence of concentric increase or localized defect (notching) of the neural rim, disc hemorrhage, or a retinal nerve fiber layer (rnfl) defect; visual field defect characterized by at least three adjacent points on the pattern deviation map with p < 5% and one of the points with p < 1%, and/or pattern standard deviation (psd) decreased with p < 5%, and/or glaucoma hemifield test (ght) outside normal limits on a reliable exam. perimetric examination with up to 20% of fixation loss and <15% of false positives and false negatives were considered reliable. subjects with optic disc features of poag and normal visual fields were included as suspects. procedures after a brief medical interview, patients participated in the study procedures. demographic data including age, gender, ethnicity, and medical history (comorbidities and previous surgeries) were collected prior to the evaluations. height (cm) was measured with the patient’s back against the wall, without shoes, and feet together using a standard stadiometer. the body weight (kg) was measured on a calibrated manual platform scale with the patient wearing light clothing. the body mass index (bmi) of each participant was determined as the body mass divided by the square of the body height (kg/m2). brachial arterial blood pressure was measured with the aneroid sphygmomanometer (gurin products, llc, tustin, ca, usa) using the right arm with the patient in a sitting position. the participants received a complete ophthalmic examination which included measurement of visual 172 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 translaminar gradient and optic disc size; cruz et al acuity in the snellen table with optical correction, anterior segment biomicroscopy with a slit lamp, tonometry with the goldmann applanation tonometer (haag-streit ag, switzerland) after taking a drop of fluorescein and proparacaine, gonioscopy with goldmann goniolens (ocular instruments, bellevue, washington, usa), and optical disc evaluation with the 78d volk lens (volk optical inc., mentor, oh, usa) after pharmacological mydriasis with tropicamide eye drops 0.5% and visual field examination. computerized perimetry was performed with the hfv 750 (carl-zeiss humphrey, dublin, ca, usa), sita standard program 24-2, with appropriate optical correction by a technician. optical coherence tomography (oct) was performed with the oct angiography rtvue® avanti xr (version 2015.1.0.90; optovue inc., fremont, ca, usa). the oct images were obtained at a rate of 26,000 a-scan/s and with a frame rate between 256 and 4096 a-scan/frame. this provided a high tissue resolution (depth resolution of 5.0 μm and transverse resolution of 15 μm). the acquisition of images in all patients followed the same procedure and was carried out by one technician. the retinal ganglion cells in the macular region were assessed using the nerve fiber scan protocol after pharmacologic dilation of the pupils. images were excluded if the signal strength index (ssi) < 40; with overt decentration of the measurement circle location; or with overt misalignment of the surface detection algorithm on at least 10% of consecutive a-scans or 15% of cumulative a-scans, and a new image was taken again. the rnfl, cup-to-disc (c/d) ratio, and disc area were retrieved from the oct results. statistical analysis the opp was determined according to the following formula: opp = [2/3 mean ap] – iop; where, the mean ap (arterial pressure) is 1/3 [sap – dap] + dap. sap is the systolic arterial pressure and dap is the diastolic arterial pressure. the predictive icp was calculated according to the equation of xie et al:[11, 12] icp = (0.44 ××× bmi) + (0.16 ××× dbp) – (0.18 ××× age) – 1.91; where, icp is intracranial pressure (mmhg), bmi is body mass index (kg/m2), dbp is diastolic blood pressure (mmhg), and age input is in years. the tlpd was calculated as the arithmetic difference between the iop and icp (tlpd = iop – icp).[13] the sample was stratified into three quantiles according to the optic disc size, that is, the disc area (mm2) as measured by the oct. participants’ eyes with the same optic disc area were clustered together in the same quantile. the difference between the three groups was compared using the anova test. data from both eyes were used after applying the suitable correction for inter-eye dependency. statistical significance was set at p < 0.05. all analyses were performed by medcalc software, version 9.3.7.0 (medcalc software bvba, belgium). results the sample consisted of 73 patients who were either diagnosed with poag or suspected of having poag. the demographic features of all participants stratified by the optic disc area tertiles are displayed in table 1. most patients were white and female. the three groups did not differ in age, gender, or ethnic distribution. after applying the appropriate correction for inter-eye dependency, 140 eyes were included in the final analysis. the clinical features for each eye according to disc area tertile are depicted in table 2. the groups did not differ in either structural (rnfl thickness and c/d) or functional (md and psd) variables. the opp was lower in patients with smaller disc sizes and higher in patients with average discs. however, the difference did not reach statistical significance (p = 0.136). nevertheless, patients with larger optic disc area presented a higher tlpd as compared to patients with small or average discs (2.4 ± 4.5, 2.8 ± 3.8, and 3.7 ± 4.7 mmhg in the first, second, third tertile, respectively p < 0.001). discussion in this observational study, glaucoma patients with larger optic discs presented higher tlpd as compared to patients with smaller optic discs. to the best of our knowledge, this was the first study to evaluate the tlpd according to the optic disc size. differences in the size of the optic discs are associated with specific anatomical tissues variation of the rnfl and the optic nerve. these disc size-dependent variations may affect the risk journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 173 translaminar gradient and optic disc size; cruz et al table 1. demographic features of the study population according to optic disc size variable first tertile (n = 25) second tertile (n = 23) third tertile (n = 25) p-value age (yr) 69.2 ± 8.7 64.8 ± 9.8 67.4 ± 9.3 0.563 gender (m:f) 11:14 9:14 10:16 0.982 ethnicity 0.968 white 15 14 17 non-white 10 9 9 m, male; f, female table 2. clinical characteristics of 140 eyes stratified by optic disc size. variable 1st tertile (n = 46 eyes) 2nd tertile (n = 46 eyes) 3rd tertile (n = 48 eyes) p-value disc area (mm2) 1.8 ± 0.2 2.2 ± 0.1 2.8 ± 0.3 <.001 rnfl (μm) 74.5 ± 16.9 75.6 ± 15.8 79.4 ± 17.4 0.330 vertical c/d 0.78 0.84 0.85 0.08 md (db) -12.0 ± 8.7 -13.3 ± 9.4 -11.1 ± 7.5 0.961 psd (db) 6.9 ± 3.6 6.4 ± 3.3 7.1 ± 4.1 0.590 opp (mmhg) 50.9 ± 7.2 55.2 ± 13.6 51.6 ± 10.0 0.136 tlpd (mmhg) 2.8 ± 3.8 2.4 ± 4.5 3.7 ± 4.7 <.001 rnfl, average retinal nerve fiber layer thickness; c/d, median cup to disc ratio; md, mean deviation; psd, pattern standard deviation; opp, ocular perfusion pressure; tlpd, translaminar pressure difference and susceptibility to glaucoma.[10] some of the structural features observed in large optic discs include a proportionally larger number of nerve fibers, a larger neural rim area, a higher cup-to-disk ratio, and a larger and more numerous pores in the lamina cribrosa.[14–20] the optic nerve head is located in an area between the high-pressure intraocular space and low-pressure subarachnoid space. hence, the pressure imbalance between these two spaces can cause damage to the retinal ganglion cell axons that pass through the lamina cribrosa pores.[21–23] the pressure difference across the lamina cribrosa (iop minus icp) is the translaminar pressure gradient.[24] on physiological grounds, the mean iop is meagerly higher than the mean icp, which results in a small posteriorly directed translaminar pressure gradient difference of approximately 4 mmhg.[25] an iop within statistically normal limits in conjunction with a low icp produce the same pressure gradient across the lámina cribosa (lc) as a high iop in conjunction with a normal icp.[26] changes in the tlpd may cause pathological dysfunction and optic nerve damage attributable to alterations in axonal transportation, lc deformation, changes in blood flow or even all of them in combination.[2, 3, 21–23, 27, 28] a higher iop, lower icp, and larger tlpd correlates with enlargement in the c/d ratio and reduction in rnfl thickness.[2, 29] in our study, patients with a larger optic disc area presented with a higher tlpd. for these patients the ganglion cell axons could be more exposed to this pressure gradient. thus, patients with larger optic discs may be more vulnerable to iop insults, without simultaneous influence of opp which did not differ among the three groups. as such, patients with larger discs would be more likely to have glaucoma than patients with smaller optic discs. interestingly, in cases of progressive optic neuropathies, the optic nerve fiber counts and the anatomic reserve capability are higher in eyes with large optic heads than those with smaller optic discs.[14] moreover, discs >4.4 mm2 have an augmented number of cilioretinal arteries, which relates to the size of the optic disc area.[30] these characteristics may thwart against the tlpd insult and can work as a compensatory effect. recently, baneke et al have defined the strain in the lc as the function of tlpd times the 174 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 translaminar gradient and optic disc size; cruz et al square of its diameter divided by the square of its thickness [lc stress = (iop – icp) . lc radius2/lc thickness2].[31] in this model, the tlpd and disc size (radius) were considered as two independent variables of lc stress. if that is the case, larger discs would be vulnerable not only by its anatomic enlarged area but also to a larger tlpd. a possible association between glaucoma and decreased opp was demonstrated in several previous studies.[32–37] in contrast, the beijing eye study did not find a clear association between the opp and the prevalence of glaucoma.[38] in this study, the opp did not vary according to the optic disc size. thus, the vascular insult should be the same for all discs, regardless of the disc size, and the higher tlpd could be an isolated aggravating factor and independent of the opp. this study has one important limitation. the measurement of icp was not performed by the traditional method using lumbar puncture which is an invasive examination, with the risks of spinal cord injury. for ethical reasons, it was not performed for the study purposes without specific medical indications. the estimated icp was calculated using a mathematical formula based on the bmi and bp values developed in a population study of chinese individuals.[11] it is not certain how different the calculated icp is from the actual one measured by lumbar puncture. icp is not only influenced by circadian rhythm, but also by changes in posture, position, and pressure fluctuations in other compartments as in respiratory effort and blood pressure pulsations.[39] moreover, the production and resorption of cerebrospinal fluid rate are not linear, particularly at different icp levels.[39] hence, a linear prediction model for icp based on xie’s formula may be inaccurate, especially for pathologic conditions. in poag cases, hemodynamic disturbances are known comorbidities and icp regulation has been suggested to be abnormal. moreover, the cushing reflex or vasopressor response may be affected in these patients and the icp estimation on bp variation may be too simplistic. using such a surrogate measure could be misleading. this is a fundamental drawback to the study methodology which limits the generalizability of the finding. however, this same formula has been used in other large population studies.[12, 40] furthermore, the equation was validated in a cohort of 39 brazilian patients and showed that the estimated icp was very close to the measured icp (95% limits of agreement of –5 to +8 between lp measured and equation-estimated icp).[41] moreover, the measurement of icp by lumbar puncture may be different from the retrobulbar icp. in general, it is assumed that the lumbar icp represents the csf pressure in the optic nerve. however, given the extended length between the lumbar spine and the subarachnoid space of the optic nerve, it is debatable whether this statement is true, particularly in patients with optic nerve sheath diseases and compartmentalization.[42] in summary, this study revealed that the tlpd varies according to the optic disc size and that larger discs tend to have a higher tlpd. although additional studies are still needed to elucidate the possible role of icp and opp in the pathogenesis of glaucoma optic neuropathy, we believe that this study contributes to the acumen on how the optic disc size may be important in the pathogenesis of this disease. financial support and sponsorship nil. conflicts of interest the authors declare that they have no conflict of interest. references 1. weinreb rn, leung ck, crowston jg, medeiros fa, friedman ds, wiggs jl, et al. primary open-angle glaucoma. nat rev dis primers 2016;2:16067. 2. berdahl jp, allingham rr, johnson dh. cerebrospinal fluid pressure is decreased in primary open-angle glaucoma. ophthalmol 2008;115:763–768. 3. berdahl jp, fautsch mp, stinnett ss, allingham rr. intracranial pressure in primary open angle glaucoma, normal tension glaucoma, and ocular hypertension: a case-control study. invest ophthalmol vis sci 2008;49:5412–5418. 4. wang n, yang d, jonas jb. low cerebrospinal fluid pressure in the pathogenesis of primary open-angle glaucoma: epiphenomenon or causal relationship? the beijing intracranial and intraocular pressure (icop) study. j glaucoma 2013;22:s11–s12. 5. bonomi l, marchini g, marraffa m, bernardi p, morbio r, varotto, a. vascular risk factors for primary open angle glaucoma: the egna-neumarkt study. ophthalmol 2000;107:1287–1293. 6. sehi m, flanagan jg, zeng l, cook rj, trope ge. relative change in diurnal mean ocular perfusion pressure: a risk factor for the diagnosis of primary open-angle glaucoma. invest ophthalmol vis sci 2005;46:561–567. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 175 translaminar gradient and optic disc size; cruz et al 7. choi j, kim kw, jeong j, cho hs, lee ch, kook ms. circadian fluctuation of mean ocular perfusion pressure is a consistent risk factor for normal-tension glaucoma. invest ophthalmol vis sci 2007;48:104–111. 8. mansour am. racial variation of optic disc size. ophthalmic res 1991;23:67–72. 9. varma r, tielsch jm, quigley ha, hilton sc, katz j, spaeth gl, et al. race-, age-, gender-, and refractive error related differences in normal optic disc. arch ophthalmol 1994;112:1068–1076. 10. hoffmmann em, zangwill lm, crowston jg, weinreb rn. optic disk size and glaucoma. surv ophthalmol 2007;52:32–49. 11. xie x, zhang x, fu j, wang h, jonas jb, peng x, et al. noninvasive intracranial pressure estimation by orbital subarachnoid space measurement: the beijing intracranial and intraocular pressure (icop) study. crit care 2013;17:r162. 12. jonas jb, wang n, wang yx, you qs, xie x, yang d, et al. body height, estimated cerebrospinal fluid pressure and open-angle glaucoma. the beijing eye study 2011. plos one 2014;9:e86678. 13. marek b, harris a, kanakamedala p, lee e, amireskandari a, carichino l, et al. cerebrospinal fluid pressure and glaucoma: regulation of trans-lamina cribrosa pressure. br j ophthalmol 2014;98:721–725. 14. jonas jb, schmidt am, muller-bergh ja, schlötzerschrehardt u, naumann go. human optic nerve fiber count and optic disc size. invest ophthalmol vis sci 1992;33:2012–2018. 15. quigley ha, coleman al, dorman-pease me. larger optic nerve heads have more nerve fibers in normal monkey eyes. arch ophthalmol 1991;109:1441–1443. 16. jonas jb, mardin cy, schlötzer-schrehardt u, naumann go. morphometry of the human lamina cribrosa surface. invest ophthalmol vis sci 1991;32:401–405. 17. caprioli j, miller jm. optic disc rim area is related to disc size in normal subjects. arch ophthalmol 1987;105:1683– 1685. 18. jonas jb, budde wm, lang p. neuroretinal rim width ratios in morphological glaucoma diagnosis. br j ophthalmol 1998; 82:1366–1371. 19. garway-heath df, ruben st, viswanathan a, hitchings ra. vertical cup/disc ratio in relation to optic disc size: its value in the assessment of the glaucoma suspect. br j ophthalmol 1998;82:1118–1124. 20. crowston jg, hopley cr, healey pr, lee a, mitchell p. the effect of optic disc diameter on vertical cup to disc ratio percentiles in a population based cohort: the blue mountains eye study. br j ophthalmol 2004;88:766–770. 21. volkov vv. essential element of the glaucomatous process neglected in clinical practice. oftalmol zh 1976;31:500– 504. 22. morgan wh, chauhan bc, yu dy, cringle sj, alder va, house ph. optic disc movement with variations in intraocular and cerebrospinal fluid pressure. invest ophthalmol vis sci 2002;43:3236–3242. 23. burgoyne cf, downs jc, bellezza aj, suh jk, hart rt. the optic nerve head as a biomechanical structure: a new paradigm for understanding the role of iop-related stress and strain in the pathophysiology of glaucomatous optic nerve head damage. prog retin eye res 2005;24:39–73. 24. morgan wh, yu dy, alder va, cringle sj, cooper rl, house ph, constable ij. the correlation between cerebrospinal fluid pressure and retrolaminar tissue pressure. invest ophthalmol vis sci 1998;39:1419–1428. 25. gilland o. normal cerebrospinal-fluid. n engl j med 1969;280:904–905. 26. greenfield ds, wanichwecharungruang b, liebmann jm, ritch r. pseudotumor cerebri appearing with unilateral papilledema after trabeculectomy. arch ophthalmol 1997;115:423–426. 27. yang d, fu j, hou r, liu k, jonas jb, wang h, et al. optic neuropathy induced by experimentally reduced cerebrospinal fluid pressure in monkeys. invest ophthalmol vis sci 2014;55:3067–3073. 28. ren r, jonas jb, tian g, zhen y, ma k, li s, et al. cerebrospinal fluid pressure in glaucoma: a prospective study. ophthalmol 2010;117:259–266. 29. siaudvytyte l, januleviciene i, ragauskas a, bartusis l, meiliuniene i, siesky b, et al. the difference in translaminar pressure gradient and neuroretinal rim area in glaucoma and healthy subjects. j ophthalmol 2014;2014:937360. 30. jonas jb, gusek g, naumann go. macrodisks with physiologic macrocups (pseudo-glaucoma disks). papillometric characteristics in 17 eyes. klin monbl augenheilkd 1987;191:452–457. 31. baneke aj, aubry j, viswanathan ac, plant gt. the role of intracranial pressure in glaucoma and therapeutic implications. eye 2020;34:178–191. 32. hulsman ca, vingerling jr, hofman a, witteman jc, de jong pt. blood pressure, arterial stiffness, and openangle glaucoma: the rotterdam study. arch ophthalmol 2007;125:805–812. 33. leske mc, wu sy, hennis a, honkanen r, nemesure b, bess study group. risk factors for incident openangle glaucoma: the barbados eye studies. ophthalmol 2008;115:85–93. 34. topouzis f, wilson mr, harris a, founti p, yu f, anastasopoulos e, et al. association of open-angle glaucoma with perfusion pressure status in the thessaloniki eye study. am j ophthalmol 2013;155:843– 851. 35. cherecheanu ap, garhofer g, schmidl d, werkmeister r, schmetterer l. ocular perfusion pressure and ocular blood flow in glaucoma. curr opin pharmacol 2013;13:36–42. 36. harris a, werne a, cantor lb. vascular abnormalities in glaucoma: from population-based studies to the clinic? am j ophthalmol 2008;145:595–597. 37. werne a, harris a, moore d, benzion i, siesky b. the circadian variations in systemic blood pressure, ocular perfusion pressure, and ocular blood flow: risk factors for glaucoma? surv ophthalmol 2008;53:559–567. 38. xu l, wang yx, jonas jb. ocular perfusion pressure and glaucoma. eye 2009;23:734–736. 39. lyons mk, meyer fb. cerebrospinal fluid physiology and the management of increased intracranial pressure. mayo clin proc 1990;65:684–707. 40. jonas jb, wang n, nangia v. ocular perfusion pressure vs estimated trans-lamina cribrosa pressure difference in glaucoma: the central india eye and medical study (an 176 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 translaminar gradient and optic disc size; cruz et al american ophthalmological society thesis). trans am ophthalmol soc 2015;113:t6. 41. kasahara n, matuoka ml, santos ks, cruz nfs, martins ar, nigro s. validation of an equation model to predict intracranial pressure in clinical studies. innov clin neurosci 2018;15:27–29. 42. killer he. compartment syndromes of the optic nerve and open-angle glaucoma. j glaucoma 2013;22:s19–s20. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 177 letter cataract surgical coverage in kurdistan, iran seyed-farzad mohammadi1, md-fico; elham ashrafi1, phd; saman mohazzab-torabi1, md; hanieh delshad-aghdam1, ms; marzieh katibeh2,3, md 1translational ophthalmology research center, farabi eye hospital, tehran university of medical sciences, tehran, iran 2ophthalmic epidemiology research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 3centers for global health, department of public health, aarhus university, denmark orcid: seyed-farzad mohammadi: https://orcid.org/0000-0002-9209-3034 hanieh delshad-aghdam: https://orcid.org/0000-0002-3071-6021 j ophthalmic vis res 2021; 16 (4): 700–701 dear editor, this is an appendix of previously published paper: rapid assessment of avoidable blindness in kurdistan, iran.[1] despite a widely distributed access to cataract surgery in iran, we face populations in remote and marginal areas who have been left behind and/or are unaware of the need for surgery.[2–5] this report assesses surgical coverage and visual outcome of cataract surgery and the selfreported barriers of surgery among subjects aged 50 years or more in kurdistan province of iran. of the 3465 eligible persons who were invited to kurdistan rapid assessment of available blindness-diabetic retinopathy (raab-dr) study, 3203 participated (response rate: 92.4%). among the participants, 1,546 (44.6%) were males and 1,657 (55.4%) were females. the mean age of the participants was 62.7 ± 10.1 (range, 50– 99) years. of these, 12% (384 participants) had cataract surgery. cataract surgery coverage was 90% in males and 89% in females (p = 0.91). the corresponding coverage for rural versus urban correspondence to: hanieh delshad-aghdam, ms. qazvin square, tehran 1336616351, iran. e-mail: delshad.np.on@gmail.com received: 23-01-2021 accepted: 29-03-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9763 participants were 91% and 89% (p = 0.83). among the operated patients, 84.2% underwent cataract surgery in public hospitals, 14.5% in private hospitals, 0.8% in charity hospitals, and 0.5% in eye camps. cataract surgery was performed free or partially free of charge for 77% of participants. cataract surgical coverage (csc) for the presenting visual acuity (pva) of <3/60 was 95.0% (males 95.7%, females 94.1%), for the pva of <6/60 was 89.9% (males 91.7%, females 88.0%), and for the pva of <6/18 was 75.4% (males 75.5%, females 75.3%). the coverage difference between the two genders was not significant. information about barriers of surgery was obtained in 40 participants with bilateral visual acuity (va) < 6/60 (18 males and 23 females) and 111 participants with unilateral va < 6/60 due to cataract. “need not felt” was reported remarkably as the commonest barrier in 75% of bilateral and 83.5% unilateral blindness or severe visual impairment (pva < 6/60) due to cataract. it was followed by cost; 7.5% in bilateral and 8.7% in unilateral pva < 6/60 due to cataract. none of the patients complained about “treatment denied by the provider” and “cannot this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: mohammadi s-f, ashrafi e, mohazzab-torabi s, delshad-aghdam h, katibeh m. cataract surgical coverage in kurdistan, iran. j ophthalmic vis res 2021;16:700–701. 700 © 2021 mohammadi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9763&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr letter to editor; mohammadi et al access treatment”. “need not felt” was comparable in both genders (p = 0.8) and rural versus urban residence (p = 0.79). women were more likely to report “fear” as a barrier rather than men (p = 0.05). fear and cost were more significantly reported in rural areas than in urban population (p = 0.05 and p = 0.04, respectively). of those who underwent cataract surgery with an intraocular lens (iol) implantation, 71.5%, 17.3%, and 11.1% had good, borderline, and poor outcomes, respectively. poor outcomes in females and rural residents were 13.1% and 12.4%, respectively. there was no significant difference between the two genders and the place of residence in terms of rural versus urban areas in this regard. patient’s selection (75%) was the primary reason for the poor outcome and it resulted from the concurrent eye problems (e.g., glaucoma, optic atrophy). meanwhile, spectacles unmet need (49.2%) comprised most of the patients who had a borderline outcome. posterior capsule opacification in 1.4% and aphakia in 1.2% were other reasons of poor outcome. our csc at visual acuities <3/60, <6/60, and <6/18 were 94.9%, 89.9%, and 75.4%, respectively and this rate was remarkably high for all cut-off levels. in conclusion, the current raab survey in kurdistan demonstrated that csc at pva < 6/60 was 90% and was higher than similar studies. of note, we did not observe a significant gender gap with respect to cataract surgery service. different patterns of csc barriers were observed which were not similar to low-income countries where cost and unavailable resources are the main barriers. financial support and sponsorship the protocol of the current study was approved by the iran eye research network and tehran university of medical sciences (#27816). conflicts of interest none of the authors have any proprietary interests or conflicts of interest related to this submission. references 1. ashrafi e, mohammadi sf, katibeh m, ghaderi e, alinia c, nourmohammadi n, et al. rapid assessment of avoidable blindness in kurdistan, iran. j ophthalmic vis res 2019;14:179–184. 2. hashemi h, alipour f, mehravaran s, rezvan f, fotouhi a, alaedini f. five year cataract surgical rate in iran. optom vis sci 2009;86:890–894. 3. hashemi h, fotouhi a, rezvan f, etemad k, gilasi h, asgari s, et al. cataract surgical rate in iran: 2006 to 2010. optom vis sci 2014;91:1355–1359. 4. katibeh m, ziaei h, rajavi z, hosseini s, javadi ma. profile of cataract surgery in varamin iran: a population-based study. clin exp ophthalmol 2014;42:354–359. 5. rajavi z, katibeh m, ziaei h, fardesmaeilpour n, sehat m, ahmadieh h, et al. rapid assessment of avoidable blindness in iran. ophthalmology 2011;118:1812–1818. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 701 photo essay silicone oil opacification after prolonged intraocular retention parijat chandra1, md; vinod kumar1, ms; brijesh takkar2, md; devesh kumawat1, md 1dr. rajendra prasad centre for ophthalmic sciences, all india institute of medical sciences, new delhi, india 2department of ophthalmology, all india institute of medical sciences, bhopal, india orcid: parijat chandra: https://orcid.org/0000-0002-7516-1410 j ophthalmic vis res 2021; 16 (2): 300–302 presentation a 13-year-old boy had closed globe injury on the right eye with a cricket ball two years back and presented with loss of vision for the past one year. the right eye had perception of light, intraocular pressure of 32 mmhg, total cataractous lens, 210 degrees angle recession, and retinal detachment on b scan ultrasonography. the left eye was normal. the right eye underwent pars plana lensectomy and vitrectomy with 1000cs silicone oil tamponade. the neuroretinal rim was found to be pale with cup/disc ratio of 0.5. he was prescribed routine postoperative care. at one week, the bestcorrected visual acuity (bcva) was 20/400, media was clear, and retina was attached. the intraocular pressure was 20 mmhg with topical timolol maleate (0.5%) bid and brimonidine tartrate (0.15%) bid. he was scheduled to follow-up after three weeks but did not show up until one year later when he presented with gradual worsening of vision in the right eye. during this period, he did not use any medications. bcva of the right eye was perception of light with inaccurate projection. the intraocular pressure was 48 mmhg. the correspondence to: parijat chandra, md. room no. 373, third floor, dr. rajendra prasad centre for ophthalmic sciences, all india institute of medical sciences, new delhi 110029, india. e-mail: parijatchandra@gmail.com received: 26-02-2019 accepted: 24-01-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9096 silicone oil had been opacified with no evidence of emulsification. there was no fundal glow through the opaque silicone oil. however, the peripheral retina around the oil meniscus was clearly visible and attached. the child underwent uneventful silicone oil removal. the retina was well attached, but a total loss of the disc neural rim was noted. the aspirated silicone oil was opaque and white in color [figure 1], and heavier than normal silicone oil as it settled to the bottom under the infusion fluid [figure 2]. on first monthly follow-up, the bcva was perception of light with accurate projection, retina was attached, and intraocular pressure was 18 mmhg with topical medications. discussion silicone oil emulsification is a common complication, observed in cases where longstanding tamponade is performed following vitreoretinal surgery.[1] in a conference proceedings, spitzer et al reported opacification of 5000cs silicone oil without emulsification in 12 cases occurring a few weeks after surgery, traced to a single production lot, wherein the physicochemical analyses had revealed that the opaque oil was more heat-stable and was possibly deficient of a stabilizing agent against coloration.[2] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: chandra p, kumar v, takkar b, kumawat d. silicone oil opacification after prolonged intraocular retention. j ophthalmic vis res 2021;16:300–302. 300 © 2021 chandra et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9096&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr photo essay; chandra et al figure 1. opaque silicone oil intermixed with infusion fluid in extraction syringe intraoperatively. figure 2. left bottle: unused clear silicone oil. right bottle: opaque silicone oil with infusion fluid at top. white opaque oil is settled at the bottom (white arrow). ciardella et al previously reported that retained perfluorocarbon liquid bubbles in the silicone oil-filled vitreous cavity might lead to an opaque fluid consisting of both silicone oil and microdispersed perfluorocarbon liquid.[3] it is notable that no surgical adjuncts (intraocular steroids, perfluorocarbon liquids, or dyes) was used during the first surgery in the current case. it is unclear what complex physio–chemical changes occurred in the oil that may have led to the opacification. thus, long-term retained silicone oil can rarely lose its transparency in the absence of emulsification. however, the situation may be disturbing for the patient due to significant loss of visual acuity. this case highlights the need for timely silicone oil removal. financial support and sponsorship nil. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 301 photo essay; chandra et al conflicts of interest there are no conflicts of interest. references 1. miller jb, papakostas td, vavvas dg. complications of emulsified silicone oil after retinal detachment repair. semin ophthalmol 2014;29:312–318. 2. spitzer m, de vries jw, herrmann a, bartz-schmidt ku, dammeier s. clouding of intraocular silicone oil in the absence of emulsification. invest ophthalmol vis sci 2013;54:3316. 3. ciardella ap, langton k, chang s. intra-ocular dispersion of perfluorocarbon liquids in silicone oil. am j ophthalmol 2003;136:365–367. 302 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 case report complete traumatic luxation of the eyeball manpreet singh1, ms, dnb, faico; amandeep singh jassi2, md; manpreet kaur1, ms; pankaj gupta1, ms 1department of ophthalmology, advanced eye centre, post graduate institute of medical education and research, chandigarh, india 2department of radiodiagnosis, accuscan diagnostic centre, mohali, punjab, india orcid: manpreet singh: https://orcid.org/0000-0003-2846-0597 abstract purpose: to report the computed tomography features of a case with complete luxation of the globe after a road traffic accident. case report: a 35-year-old male presented with pain, loss of vision, and bleeding from the left eye 48 hr after a road traffic accident. the ophthalmic examination of the left upper and lower eyelids showed edema with subcutaneous hematoma, crepitus, and complete blepharoptosis. on retracting the eyelids, the left eyeball was not visible and the patient was not able to perceive light. the left temporal region appeared filled with a soft, palpable globular structure situated beneath the temporalis muscle. a noncontrast computed tomography (ncct) of the head and orbits showed a comminuted and displaced fracture of the floor, medial, and lateral orbital walls in addition to a displaced tripod fracture of the left zygomatic bone. the intact left eyeball was seen below the temporalis muscle without any optic nerve or extraocular muscle attachment. the virtual reality reconstruction highlighted a contributory supero-temporal defect in the bony orbit, which appeared large enough to accommodate the intact eyeball. conclusion: the computed tomography of the orbits provided a detailed location of the luxated eyeball and provided guidance in further management of the case. keywords: eyeball displacement; globe luxation; globe subluxation; ocular trauma; ophthalmic trauma j ophthalmic vis res 2021; 16 (4): 688–690 introduction a complete luxation of the eyeball is a rare and devastating ophthalmic trauma, which is correspondence to: manpreet singh, ms, dnb, faico. department of ophthalmology, advanced eye centre, post graduate institute of medical education and research, chandigarh 160012, india. email: drmanu83@gmail.com received: 16-07-2019 accepted: 12-04-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9760 occasionally accompanied by traumatic avulsion of the optic nerve and extraocular muscles.[1, 2] morris et al explained this mechanism in three categories: direct impact, wedge effect, and leverfulcrum action.[2] orbital computed tomography (ct) and magnetic resonance imaging revealed details of fractures, the location of the eyeball, optic nerve, and extraocular muscle attachments.[1, 2] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: singh m, jassi as, kaur m, gupta p. complete traumatic luxation of the eyeball. j ophthalmic vis res 2021;16:688–690. 688 © 2021 singh et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9760&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr traumatic globe luxation; singh et al figure 1. computed tomography images of the orbit, brain, and 3d face reconstruction. (a) axial scan illustrates left orbital fractures, pneumo-orbit, lost eyeball with transected medial rectus (yellow arrow), and optic nerve (black arrow). (b) the coronal section shows a luxated eyeball (yellow arrow) through the fracture space, pneumo-orbit, and left maxillary hemosinus. (c) the superior axial section shows the luxated eyeball beneath the anterior fibers of left temporalis muscle with air pockets and multiple small bone fragments. (d) the virtual reality image illustrates the left displaced tripod fracture of the zygomatic bone and a contributory wide bony space created (two black arrows). case report a 35-year-old male presented to ophthalmology emergency suffering with pain, loss of vision, and bleeding from his left eye for 48 hr after experiencing a road traffic accident whilst under the influence of alcohol. on presentation, the patient was calm, conscious, co-operative, and oriented to time, place, and person. his neurological examination was within normal limits. on ophthalmic examination, the right eye appeared normal with a visual acuity of 6/6. the left upper and lower eyelids were edematous with subcutaneous hematoma and complete blepharoptosis. crepitus was felt on the palpating eyelids. on retracting the eyelids with a desmarres retractor, the left eyeball was not visible, and the patient was not able to perceive light. the left temporal region appeared filled with a soft, palpable globular structure situated beneath the temporalis muscle. a non-contrast computed tomography (ncct) of the head and orbits was requested. the ncct axial images revealed a comminuted and displaced fracture of the medial and lateral orbital walls [figure 1a]. the coronal section also revealed a displaced tripod fracture of the left zygomatic bone and orbital floor [figure 1b]. the intact left eyeball was seen below the temporalis muscle without any optic nerve or extraocular journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 689 traumatic globe luxation; singh et al muscle attachment [figure 1c]. the virtual reality reconstruction highlighted a contributory superotemporal defect in the bony orbit, which appeared large enough to accommodate the intact eyeball [figure 1d]. after receiving informed consent, the removal of the eyeball from the sub-temporalis space was performed. intraoperatively, the eyeball was found to be hypotonus with a surrounding purulent foul-smelling discharge. the outer scleral surface was necrosed and the cornea was opaque. no optic nerve or muscle stump was identified. the specimen was sent for histopathological and microbiological examination. an open reduction internal fixation surgery using mini-plates was performed for the tripod fracture repair and reconstruction of the bony orbital rim. in order to achieve the best possible cosmetic rehabilitation, a second-stage orbital volume restoration using a dense porous polyethylene spherical implant was planned, to be followed by a customized ocular prosthesis. discussion a subluxated eyeball is routinely reposited back in the orbit, surgically or with tse’s maneuver (for spontaneous subluxation).[3] however, complete luxation of the eyeball accompanied with detachment of all recti and optic nerves justifies its removal, given its lost vitality and the presence of obvious future implications. the seven branches of muscular arteries, ciliary arteries (long – 2, short – 6 to 12) and the retinal artery, which contributes to the majority of the ocular blood supply, gets detached from the luxated eyeball. the loss of arterial blood supply initiates necrosis and enhances tissue infection. in our detailed published text entitled “subluxated globes”, we have comprehensively covered the etiopathogenesis, clinical features, and management of this disastrous condition.[4] we pointed out that orbital imaging provides vital information about the position of subluxated or luxated eyeballs, and the extent of surrounding tissue damage and orbital bone fractures.[4] the joint management of luxated eyeball cases by ophthalmologists, maxillo-facial surgeons, and neurosurgeons provides a holistic approach in achieving the best possible cosmetic and functional outcomes. in summary, the ct used to assess this particular case of luxation provided valuable information in determining the location of the eyeball, the detachment of arteries, the presence of orbital fractures and ocular related injuries. acknowledgment the authors are thankful to dr. kasturi bhattacharjee, head of orbit & ophthalmic plastic surgery, sri sankaradeva nethralaya, guwahati, assam, india for her support and guidance. financial support and sponsorship nil. conflicts of interest there is no conflict of interest. references 1. tucker b. two cases of dislocation of the eyeball through the palpebral fissure. j nerv ment dis 1907;34:391–397. 2. morris wr, osborn fd, fleming jc. traumatic evulsion of the globe. ophthal plast reconstr surg 2002;18:261–267. 3. tse dt. a simple maneuver to reposit a subluxed globe. arch ophthalmol 2000;118:410–411. 4. bhattacharjee k, bhattacharjee h, singh m, dey d. subluxated globes. in: mukherjee b, yuen h, editors. emergencies of the orbit and adnexa. new delhi: springer; 2017, pp. 19–25. 690 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 review article normal exophthalmometry values in iranian population: a meta-analysis: a complete translation from farsi abbas bagheri1,2, md; kourosh shahraki1, md; amir arabi1, md; mohsen bahmani kashkouli3, md 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2ophthalmic plastic and reconstructive surgery unit, labbafinejad eye hospital, shahid beheshti university of medical sciences, tehran, iran 3ophthalmic plastic and reconstructive surgery unit, rasoul-akram hospital, iran university of medical sciences, tehran, iran orcid: abbas bagheri: https://orcid.org/0000-0002-6736-7435 kourosh shahraki: https://orcid.org/0000-0001-6448-6351 this article is based on a study first reported in farsi in the bina journal of ophthalmology, titled volume 24, issue 2 (winter 2019) 2019/05/28. original url: https://binajournal.org/article-1-985-fa.pdf abstract there are limited studies on the normal values of eye protrusion in iran. systematic efforts to provide acceptable normal exophthalmometry values for iranian population are required for a proper approach to orbital diseases. english and farsi language publications in pubmed, the isi web of knowledge database, iranian sid, and iran medex were searched using the following keywords: “proptosis”, “eye protrusion”, “exophthalmous”, “hertel exophthalmometer” and “iran”. four articles from 1995 to 2010 were found and included in the meta-analysis. statistical analysis was performed using the metan command within stata 15.0 software. it included 3,696 subjects in whom the average eye protrusion was 16.5 mm (95% ci: 15.1–17.8) in men and 16.2 mm (95% ci: 14.6–17.7) in women (p = 0.5). mean left and right eye protrusion were 16.3 (95% ci: 14.7–18.1) and 16.4 mm (95% ci: 14.8–17.7), (p = 0.3), respectively. while iranian teenagers (13–19 years old) showed a mean value of 17.1 mm (95% ci: 15.0–19.1), older age group (≥20 years) showed a lower mean eye protrusion of 16.3 mm (95% ci: 14.8–17.7). considering the two standard deviations, the highest normal value of eye protrusion in iranian population is 20.1 mm. in conclusion, iranian normal eye protrusion values were higher than asians and lower than caucasians. keywords: exophthalmometry; hertel; iran; meta-analysis j ophthalmic vis res 2021; 16 (3): 470–478 introduction different types of exophthalmometers can evaluate eye protrusion. these instruments all correspondence to: kourosh shahraki, md. ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, boostan 9 st., pasdaran ave., tehran 16666, iran. e-mail: kourosh.shahyar@gmail.com received: 16-07-2020 accepted: 24-01-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i3.9441 use facial bones as static points to estimate the distance between the corneal apex and the base.[1] the reference points are the lateral orbital rims in the hertel exophthalmometer, inferior and superior orbital rims in the naugle exophthalmometer, and cheek and brow in the mutch exophthalmometer.[2, 3] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: bagheri a, shahraki k, arabi a, kashkouli mb. normal exophthalmometry values in iranian population: a meta-analysis: a complete translation from farsi. j ophthalmic vis res 2021;16:470–478. 470 © 2021 bagheri et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e بررسی مقادیر طبیعی اگزوفتالمومتري در جمعیت ایرانی: مطالعھ مرور نظامند و متاآنالیز http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i3.9441&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr normal exophthalmometric values; bagheri et al hertel exophthalmometer is the most commonly used exophthalmometer in clinical settings.[4] it measures the distance between the apex of the cornea to the zygomatic arch on the lateral edge of the orbit. although, previous studies have proved the reliability of the hertel exophthalmometer,[4, 5] some have shown limited reproducibility among the examiners.[6–8] such a limitation usually roots from irregularity of the lateral orbital rims, parallax errors, compression of adjacent soft tissues, and the absence of a uniform measuring procedure.[9] eye protrusion varies in different populations and factors such as age, sex, and refractive error may affect it. the exophthalmometry value could be relative (right–left difference) or absolute (comparing with normal values of each population).[10] relative value of >2 mm usually requires further investigations.[6] absolute exophthalmometry value is useful in the diagnosis of bilateral proptosis.[10–12] there are limited studies on normal values of eye protrusion in iran[13–16] which were analyzed (metaanalysis) in order to define both normal relative and absolute eye protrusion values for iranian teenagers and adults. methods the present meta-analysis was performed following the preferred reporting items for metaanalyses checklist (prisma).[17] search strategies the literature (prior to march 2019) was reviewed by searching pubmed, the isi web of knowledge database, iranian sid, and iran medex. the search strategy included the following keywords: “proptosis”, “eye protrusion”, “exophthalmos”, “hertel exophthalmometer”, and “iran”. crossreferences of any selected article were also used in the review. no language restriction was applied. studies providing evidence-based information about standard values of hertel exophthalmometry in iranian population were selected. of the 27 articles found through the search, 4 were included in this analysis. the first study was performed in 1995 and the last in 2010. we only included articles that had studied normal population in different cities of iran. data extraction two of the authors reviewed the extracted data independently using a purpose-designed form. the following information were collected: first author, year of publication, geographic location, mean age, sample size, gender, different age groups, mean eye protrusion in right eye, mean eye protrusion in left eye, average eye protrusion in both eyes, and normal upper limit of eye protrusion. data on eye protrusion were obtained using two-mirrored hertel exophthalmometry in all studies. eye protrusion is ethnic dependent; however, we did not study different iranian ethnic groups separately. statistical analysis summary estimates of the pooled differences and mean protrusion of iranian eyes for the normal value of hertel exophthalmometry and related upper normal limits were combined using the inverse variance method. statistical meta-analysis was performed using the metan command within stata 15.0 software (statacorp. 2017. stata statistical software: release 15. college station, tx: statacorp llc). between-study heterogeneity was assessed using cochran q and the inconsistency index (i2). it was considered statistically significant when p-value < 0.05 or i2 < 50%.[18] since a significant heterogeneity was found (i2 > 50%), a random effect model was used to assess mean estimation and difference (md), and 95% confidence intervals (95% ci). to explore possible foundations of heterogeneity, subgroup analyses were conducted for different age groups and genders, if applicable. to assess the influence of separate studies on the pooled measures, sensitivity analyses were directed by successively excluding studies. to further discover sources of heterogeneity, meta-regression analyses were performed. the potential publication bias was studied using the adjusted rank correlation test and the regression asymmetry test, respectively.[18, 19] in addition, we demonstrated the findings in each study as well as the pooled estimation in a forest plot. all statistical tests were twotailed and p < 0.05 was considered statistically significant. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 471 normal exophthalmometric values; bagheri et al results after a thorough text review, four articles published between 1995 and 2010 were included in the metaanalysis. bagheri et al’s study[13] included 926 randomly selected healthy individuals (481 men and 445 women) from kashan golabchi clinic whose age ranged from 15 to 60 years. those with ocular infections, history of orbital trauma, strabismus, endocrine system disease, significant myopia (>5 diopters [d]), children, and pregnant women were excluded from the study. one examiner using hertel exophthalmometer in the sitting position performed all measurements. each patient was examined once. selected age groups in the study were 15–24 (n = 250), 25–34 (n = 346), 35–44 (n = 211), 45–54 (n = 91), and 55–64 (n = 28) years. hadaegh et al[14] selected 404 normal subjects (15–75 years) by randomized stratified sampling from the east of tehran who participated in tehran lipid and glucose study (tlg). individuals with a history of ocular trauma, ocular surgery, thyroid disease, and those with >7d myopia were excluded. age groups were the same as the previous study and proptosis measurement was performed using hertel exophthalmometer. tohidi et al[15] recruited 1,303 healthy people from bushehr (661 men and 642 women) with similar age groups and technique of hertel exophthalmometery. those with orbital disease and myopia of >2d were excluded. kashkouli et al[16] used stratified random sampling and recruited 1,603 normal subjects at different age groups from the west of tehran.[16] three main age groups were determined according to the population poll statistics, including children (27.2%), teenagers (30%), and adolescents (42.8%). average of two measurements done by an oculofacial plastic surgeon was recorded for each person. exclusion criteria were similar to the previous studies. adding all the data of prior four studies resulted in 3,696 normal subjects (1,920 males and 1,776 females) of whom 2,774 were over the age of 20, 633 between 13 and 19, and 289 between 6 and 12 years [table 1]. subjects were from three cities in iran (tehran, kashan, bushehr). pooled estimates of the primary subgroup analyses showed that the mean eye protrusion of iranian adults (≥20 years of age) and teenagers (13–19 years) were 16.3 (95% ci: 14.85–17.79) and 17.1 mm (95% ci: 15.06–19.13), respectively [figures 1 and 2]. however, the mean eye protrusion difference between the two eyes was not significant (p = 0.2). the mean eye protrusion of the right and left eye were 16.3 (95% ci: 14.70–18.18) and 16.4 mm (95% ci: 14.86–17.79), respectively. the mean exophthalmometric value in iranian population was 16.3 mm (95% ci: 14.78–17.99) [figure 3]. it was 16.5 mm (95% ci: 15.11–17.89) in men and 16.2 mm (95% ci: 14.65–17.72) in women. gender differences are demonstrated in table 2. discussion iranian normal eye protrusion values were higher than that of asians and lower than that of caucasians [table 3]. results of this meta-analysis on 3,696 normal iranians showed that the mean eye protrusion was neither significantly different between men (16.5 mm) and women (16.2 mm) nor between the right (16.3) and the left (16.4 mm) eyes. the mean eye protrusion value decreased from 17.1 mm in teenagers (13–19 years) to 16.2 mm in adults (≥20 years). kashkouli et al[16] reported the normal eye protrusion in iranian children (6–12 years) as 14.1 ± 1.8 mm which was less than that found in the chinese population (14.4 mm), arabian (15.4 mm), american children aged 5–8 years old (14.4 mm), and american children aged 9–12 years (15.2 mm), but it was more than the indian (13 mm), italian (between 9.1 and 11.7 mm), and white european (14 mm) children. mean hertel exophthalmometry value increased in the second decade of life (13–19 years) in iranian population. in a study by erb and colleagues in asian normal subjects,[12] the mean eye protrusion calculated with hertel exophthalmometer was 14.4 ± 2.5 mm, which is about 2 mm less than the normal iranian population. contrary to our study, significant statistical differences were observed between men (15.5 ± 2.1) and women (13.5 ± 2.4 mm) in erb’s study. in the same study, there was no more than 1-mm difference between the two eyes in all the cases. in addition, the upper limit of normal exophthalmometric values in asian normal adults was 19.4 mm, which was slightly higher in men than in women (19.19 vs 18.3 mm). it is about 2 472 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 normal exophthalmometric values; bagheri et al table 1. normal eye protrusion values from the included studies* study/age groups (yr) bagheri et al[13] (2007) hadaegh et al[14] (2002) tohidi et al[15] (2013) kashan east tehran bushehr male female both genders both genders od os od os od os difference od os difference 15–24 17.18 ± 1.99 17.15 ± 2.01 16.52 ± 1.62 16.59 ± 1.66 16.50 ± 4.2 16.8 ± 4.4 0.31 ± 1.5 19.51 ± 0.88 19.75 ± 0.85 0.24 ± 0.28 25–34 17.03 ± 2.15 17.01 ± 2.18 16.52 ± 1.70 16.58 ± 1.68 16.2 ± 4 16.5 ± 4.4 0.22 ± 1.6 18.8 ± 1.36 18.97 ± 1.38 0.16 ± 0.27 35–44 17.13 ± 2.2 17.17 ± 2.19 15.60 ± 3.97 15.67 ± 1.96 16 ± 4 16.1 ± 4.2 0.13 ± 1.6 17.93 ± 1.03 18.09 ± 1.02 0.15 ± 0.3 45–54 16.22 ± 2.38 16.22 ± 2.38 15.37 ± 2.40 15.34 ± 1.98 15.8 ± 4.8 16 ± 4.9 0.18 ± 1.4 17.27 ± 1.21 17.47 ± 126 0.2 ± 0.3 55–64 16.35 ± 2.62 15.50 ± 2.47 15.92 ± 2.12 15.58 ± 2.41 15.2 ± 4.4 15.5 ± 4.6 0.28 ± 1.6 16.27 ± 1.11 16.31 ± 1.16 0.04 ± 0.4 65–75 – – – – 14.8 ± 2.5 15 ± 4.3 0.21 ± 1.8 15.98 ± 1.38 16.19 ± 1.61 0.2 ± 0.37 total 16.99 ± 2.18 16.99 ± 2.18 16.10 ± 1.86 16.25 ± 1.84 16 ± 4.4 16.2 ± 4.5 0.23 ± 1.5 17.91 ± 1.55 18.08 ± 1.59 0.16 ± 0.31 *the values of one of the studies “kashkouli et al[16]” was not provided in this table due to different age groups. table 2. eye protrusion values in different subgroups group mean exophthalmometric values lower and upper limit of normal exophthalmometric values male 16.5 12.55–20.45 female 16.26 12.7–19.82 age 13–19 yr 17.1 13.25–20.95 age >>>20 yr 16.32 12.62–20.02 od 16.33 12.59–20.07 os 16.44 12.64–20.24 total 16.38 12.61–20.15 figure 1. mean eye protrusion in adults >20 year old. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 473 normal exophthalmometric values; bagheri et al table 3. comparison of normal eye protrusion values in different ethnic groups study geographic area no. exophthalmometric value (mean ± sd) age difference (mm) sex difference (mm) laterality difference (mm) present study iran 3,696 16.38 13–19: 17.1 m: 16.5 od: 16.33 >20 : 16.32 f: 16.26 os: 16.44 erb et al[12] asians in usa 89 14.4 ± 2.5 m: 15.5 ± 2.1 f: 13.5 ± 2.4 chan et al[20] sri lanka 1,341 15.82 ± 2.73 m: 16.66 f: 15.27 sarinnapakorn[21] taiwan 277 m: 11.84 f: 11.44 wu et al[22] chinese han 2,010 8–14: 13.7 ± 1.6 od: 15 ± 1.5 15–19: 15.1 ± 1.6 os: 15 ± 2 20–69: 15.7 ± 1.8 70–87: 15.3 ± 2.2 bilen et al[23] turkish 480 m: 13.49 ± 2.6 f: 13.44 ± 2.6 dunsky et al[4] american black 309 m: 18.20 ± 2.97 f: 17.46 ± 2.64 migliori et al[1] american 681 in white: 16.5 white f: 14.4 in black: 18.5 black f: 17.8 od: 15.27 ± 2.5 ibraheem et al[24] nigeria 1,020 os: 15.31 ± 2.4 mourits et al[25] netherland 160 upper limit, m: 20 upper limit, f: 16 jarusaitiene et al[26] lithuania 397 14.91 ± 1.68 m: 15.18 ± 2.16 bolaños et al[27] mexico 301 f: 14.82 ± 1.98 *m, male; f, female; od, right eye; os, left eye mm less than the normal caucasian population. this value was 20.15 mm in iranian population.in a study by chan et al[20] including 1,341 adult cases from sri lankan population, the mean exophthalmometric value was 15.82 ± 2.73 mm, which was higher in men than in women. this difference was not significant between different sri lankan breeds (sinhalese, tamils, and moors) but it had a significant association with age, sex, height, weight, body mass index (bmi), and axial length. according to the findings of our study, the normal amount of eye protrusion is higher in males than in females, although these values are greater than the sri lankan race. in sarinnapakorn’s study in taiwan,[21] the normal protrusion of the eyes was 11.84 mm in men and 11.44 mm in women, which is about 5 mm less than the iranian population. in a study by wu et al in 2010 in han,[22] chinese native population in northeastern china had a mean of 15 ± 1.5 and 15 ± 2 mm protrusion in the left and right eyes, respectively, and the upper limit for the left and right eyes was 18.8 and 19 mm. gender had no effect on the protrusion of the eyes but age had a significant statistical relationship with it. these values are similar to those of other studies in east asia, and less than those of normal iranian population. in the study of bilen et al in northern turkey,[23] mean values of eye protrusion were 13.49 ± 2.6 and 13.44 ± 2.6 in men and women, respectively, which showed no significant difference between the two genders. the results of their study are similar to those of beden’s study in turkey. overall, turkish values are about 3 mm less than the iranian population. 474 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 normal exophthalmometric values; bagheri et al figure 2. mean eye protrusion in 13–19 years age group. in dunsky’s study performed on american normal black adults,[4] the mean eye protrusion was 18.2 mm in men and 18.46 mm in women and the upper limits in men and women were 24.44 and 22.74 mm, respectively, which are higher than those in iranian population with an average of 3.5 mm.migliori and gladstone studied 681 american adults (327 white and 354 black)[1] and reported a mean of 16.5 and 18.5 mm for normal eye protrusion in white and black men, respectively. the value was 14.4 for white women and 17.8 for black women, while abnormal values for white men, black men, white women and black women were 21.7, 24.7, 20.1, and 23 mm respectively. accordingly, a similarity was observed between american white population and iranian population. in ibraheem’s study,[24] 1,020 normal subjects in nigeria had an average values of 15.27 ± 2.5 and 15.31 ± 2.4 mm in the right and left eyes, respectively, which were lower than reported values from african americans, chinese, caucasian, and iranian population.in a study by mourits et al on normal population of netherlands,[25] the upper normal limit for exophthalmometry with hertel was reported as 16 mm in women and 20 mm in men. the values in our study were 19.8 mm for women and 20.4 mm for men, which show that in iranian population, unlike the dutch population, there is no significant difference in eye protrusion between men and women. jarusaitiene et al, in their study on normal population in lithuania,[26] reported a mean eye protrusion was 14.91 ± 1.68 mm. although eye protrusion was higher in women than in men, and in the right eye in comparison with the left eye, the difference was not statistically significant. in this study, there was a significant association between the range of protrusion and the age, weight, and height. in the iranian population, in contrast to the study of lithuania, the mean eye protrusion was higher in men than in women, and was greater in the left eye compared to the right; however, these values were not statistically significant. bolaños and colleagues reported mean eye protrusion in the normal population of mexico; 15.18 mm in men and 14.38 mm in women,[27] which are lower than those of normal iranian population. differences in baseline features between individuals were partially adjusted because of different study populations and formats. in conclusion, this meta-analysis provides the literature with cut-off values for normal eye protrusion in iranian population. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 475 normal exophthalmometric values; bagheri et al figure 3. mean eye protrusion in total population. summary there are limited studies on normalvalues of eye protrusion in iran, which were analyzed (metaanalysis) in order to define both normal relative and absolute eye protrusion values for iranian teenagers and adults. systematic efforts to provide acceptable normal exophthalmometry values for iranian population are required for a proper approach to orbital diseases. iranian normal eye protrusion values were higher than that of asians and lower than that of caucasians. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. migliori me, gladstone gj. determination of the normal range of exophthalmometric values for black and white adults. am j ophthalmol 1984;98:438–442. 2. cole hp 3rd, couvillion jt, fink aj, haik bg, kastl pr. exophthalmometry: a comparative study of the naugle and hertel instruments. ophthalmic plast reconstr surg 1997;13:189–194. 3. naugle tc jr, couvillion jt. a superior and inferior orbital rim-based exophthalmometer (orbitometer). ophthalmic surg 1992;23:836–837. 4. dunsky il. normative data for hertelexophthalmometry in a normal adult black population. optom vis sci 1992;69:562–564. 5. ameri h, fenton s. comparison of unilateral and simultaneous bilateral measurement of the globe position, using the hertelexophthalmometer. ophthalmic plast reconstr surg 2004;20:448–451. 6. kashkouli mb , beigi b, noorani mm, nojoomi m. hertelexophthalmometry: reliability and interobserver variation. orbit 2003;22:239–245. 7. lam ak , lam cf, leung wk, hung pk. intra-observer and inter-observer variation of hertelexophthalmometry. ophthalmic physiol opt 2009;29:472–476. 8. musch dc, frueh br, landis jr. the reliability of hertelexophthalmometry. observer variation between physician and lay readers. ophthalmology 1985;92:1177– 1180. 9. kim it , choi jb. normal range of exophthalmos values on orbit computerized tomography in koreans. ophthalmologica 2001;215:156–162. 10. lee bj. orbital evaluation. in: black eh, nesi fa, gladstone g, levine m, calvano cj, editors. smith and nesi’s ophthalmic plastic and reconstructive surgery. new york, ny: springer; 2012. 11. sisler hajf, trokel sl. ocular abnormalities and orbital changes of graves’ disease. in: duane td, tasman w, 476 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 normal exophthalmometric values; bagheri et al jaeger ea, editor. duane’s clinical ophthalmology. volume 2. philadelphia: jb lippincott; 1992. 12. erb mh, tran nh, mcculley tj, bose s. exophthalmometry measurements in asians. invest ophthalmol vis sci 2003;44:662. 13. bagheri a, behtash f. normal exophthalmometry range in kashan city. j gums 2007;16:101–106. 14. farzad h, fereydoun a, farzad p, maryam t. determination of the normal exophthalmometric values in tehran population/iran. ismj 2003;5: 161–166. 15. tohidi m, hormozi mk, nabipour i, vahdat k, assadi m, karimin f, et al. determination of normal values for eye protrusion in bushehr port population. ismj 2013;16:331– 337. 16. kashkouli mb, nojomi m, parvaresh mm, sanjari ms, modarres m, noorani mm. normal values of hertelexophthalmometry in children, teenagers, and adults from tehran, iran. optom vis sci 2008;85:1012– 1017. 17. moher d, shamseer l, clarke m, ghersi d, liberati a, petticrew m, et al. preferred reporting items for systematic review and meta-analysis protocols (prisma-p) 2015 statement. syst rev 2015;4:1. 18. li g, li y, chen x, sun h, hou x, shi j. circulating tocopherols and risk of coronary artery disease: a systematic review and meta-analysis. eur j prev cardiol 2016;23:748–757. 19. begg cb, mazumdar m. operating characteristics of a rank correlation test for publication bias. biometrics 1994;50:1088–1101. 20. chan w, madge sn, senaratne t, senanayake s, edussuriya k, selva d, et al. exophthalmometric values and their biometric correlates: the kandy eye study. clin exp ophthalmol 2009;37:496–502. 21. sarinnapakorn v, sridama v, sunthornthepvarakul t. proptosis in normal thai samples and thyroid patients. j med assoc thai 2007;90:679–683. 22. wu d, liu x, wu d, di x, guan h, shan z, et al. normal values of hertel exophthalmometry in a chinese han population from shenyang, northeast china. sci rep 2015;5:8526. 23. bilen h, gullulu g, akcay g. exophthalmometric values in a normal turkish population living in the northeastern part of turkey. thyroid 2007;17:525–528. 24. ibraheem wa, ibraheem ab, bekibele co. exophthalmometric value and palpebral fissure dimension in an african population. afr j med health sci 2014;13:90– 94. 25. mourits mp, lombardo sh, van der sluijs fa, fenton s. reliability of exophthalmos measurement and the exophthalmometry value distribution in a healthy dutch population and in graves’ patients. an exploratory study. orbit 2004;23:161–168. 26. jarusaitiene d, lisicova j, krucaite a, jankauskiene j. exophthalmometry value distribution in healthy lithuanian children and adolescents. saudi j ophthalmol 2016; 30:92–97. 27. bolaños gil de montes f, pérez resinas fm, rodríguez garcía m, gonzález ortiz m. exophthalmometry in mexican adults. rev invest clin 1999;51:341–343. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 477 original article evaluation and comparison of choroidal thickness in patients with behçet disease with versus without ocular involvement seyedeh maryam hosseini, md; negar morrovatdar, md; armin hemati, md; mozghan dolatkhah, md elham bakhtiari, md; zahra mirfeizi, md; mahdieh azimizadeh, md department of ophthalmology, mashhad university of medical sciences, mashhad, iran orcid: seyedeh maryam hosseini: https://orcid.org/0000-0002-4233-9243 mahdieh azimizadeh: https://orcid.org/0000-0001-9467-4249 abstract purpose: to assess the subfoveal choroidal thickness (sfct) in patients with behçet disease (bd) and compare the sfct in patients with and without ocular bd (obd) and between patients with active and quiescent phases of the behçet’s posterior uveitis. method: this prospective cross-sectional study was conducted on patients with bd (n = 51) between october 2016 and october 2018. complete ocular examinations including slit lamp biomicroscopy and fundus examination with dilated pupils were performed for all patients. the sfct values were compared between patients with and without obd. enhanced depth imaging optical coherence tomography (edi–oct) was done to measure the sfct, and wide field fundus fluorescein angiography (wf-fag) was performed to evaluate the ocular involvement and determine the active or quiescent phases of the behçet’s posterior uveitis. the correlation between the changes of sfct and the wf-fag scores was assessed. results: one hundred and two eyes of 51 patients with bd, aged 29 to 52 years were studied. of these, 23 patients were male. the mean age ± standard deviation in patients with obd and patients without ocular involvement was 38.71 ± 7.8 and 36.22 ± 10.59 years (p = 0.259) respectively. the mean sfct in patients with obd was significantly greater than in patients without obd (364.17 ± 93.34 vs 320.43 ± 56.70 µm; p = 0.008). the difference of mean sfct between the active compared to quiescent phase was not statistically significant when only wf-fag criteria were considered for activity (368.12 ± 104.591 vs 354.57 ± 58.701 µm, p = 0.579). however, when the disease activity was considered based on both wf-fag and ocular exam findings, sfct in the active group was higher than the inactive group (393.04 ± 94.88 vs 351.65 ± 58.63 µm, p = 0.060). this difference did not reach statistical significance, but it was clinically relevant. conclusion: choroidal thickness was significantly increased in bd patients with ocular involvement; therefore, edi-oct could be a noninvasive test for evaluation of ocular involvement in patients with bd. the increased sfct was not an indicative of activity in obd; however, it could predict possible ocular involvement throughout the disease course. keywords: behçet’s disease; behçet’s uveitis; choroidal thickness; enhanced depth imaging optical coherence tomography (edi-oct); ocular behçet; wide field fluorescein angiography j ophthalmic vis res 2021; 16 (2): 195–201 © 2021 hosseini et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 195 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9083&domain=pdf&date_stamp=2019-07-17 choroidal thickness in patients with behçet disease; hosseini et al introduction behçet disease (bd) is a chronic, recurrent, inflammatory, multisystem disease characterized by occlusive and necrotizing vasculitis.[1–3] the prevalence of bd is estimated to be 10.3 per 100,000 individuals and is higher in middle east, far east, and mediterranean countries.[4, 5] different classification criteria exist for bd, including the new “international criteria for bd.” ocular involvement is a common consequence of bd as 70–90% of the patients experience ocular impairments that are presented in different forms including posterior uveitis, retinal vasculitis, anterior uveitis, and optic neuropathy.[6] loss of vision has been correlated with the disease duration.[5] in 50–93% of the patients with ocular involvement, the posterior segment eye diseases are observed.[7] choroidal vessels can be involved in addition to retinal vessels as the primary focus or secondary to retinal inflammation.[8] recurrent inflammatory phases can severely impair the retinal structure and function and result in visual loss.[9–13] early detection of posterior segment involvement during the early phase of the disease is necessary for development of an effective treatment strategy.[9] fundus fluorescein angiography (ffa) is the standard method for monitoring and evaluating the progression of ocular behçet disease (obd).[10, 11, 13] this imaging modality has shown high sensitivity for detection of retinal vasculitis in bd cases.[10] indocyanine green angiography (icga) has been proposed as an alternative modality which evaluates choroidal circulation; however, it does not disclose the retinal circulation or evidence of retinal vasculitis as clear as ffa does.[14–16] several studies have investigated the choroidal thickness analysis with edi-oct in patients with obd.[6, 8, 14, 17, 18] their findings are controversial regarding the effects of obd disease on choroidal thickness. correspondence to: mahdieh azimizadeh, md. eye research center, khatam-al-anbia eye hospital, abutalib junction, kolahdouz blvd., mashhad, iran e-mail: azimi57@gmail.com received: 15-06-2019 accepted: 09-01-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9083 while some studies have reported that choroid thickness increases in obd patients,[6, 8, 17, 18] others have demonstrated that obd decreases the choroidal thickness.[14] these discrepancies in choroidal thickness could be attributed to the non-homogeneity in patients’ features in terms of activity, anatomical involvement, and obd duration.[8] in this study, we tried to investigate the subfoveal choroidal thickness (sfct) in behçet’s patients with and without ocular involvement using edi-oct modality. we also compared sfct between active and quiescent phases of obd and evaluated the correlations between the changes of sfct in edioct and the wf-fag scores. methods this prospective cross-sectional study was conducted on patients with bd (n = 51; eyes: 102) who had been referred to the uveitis clinic of khatam-al-anbia tertiary eye center, affiliated to mashhad university of medical sciences (mums) between october 2016 and october 2018. the study was approved by the local institutional review board and ethics committee of mums, mashhad, iran, and was in accordance with the ethical standards and regulations of the declaration of helsinki. the inclusion criteria of the study were patients older than 18 years with definite diagnosis of bd according to the diagnostic criteria of the international study group for bd with or without ocular involvement. patients who met the inclusion criteria were evaluated in three groups: (i) patients with ocular involvement and active uveitis (ii) patients with ocular involvement who were in remission (iii) patients without ocular involvement in examination or wf-fag behçet’s patients with posterior, intermediate, or pan-uveitis were included in the study. evidence this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: hosseini sm, morrovatdar n, hemati a, dolatkhah m, bakhtiari e, mirfeizi z, azimizadeh m. evaluation and comparison of choroidal thickness in patients with behçet disease with versus without ocular involvement. j ophthalmic vis res 2021;16:195–201. 196 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 https://knepublishing.com/index.php/jovr choroidal thickness in patients with behçet disease; hosseini et al of posterior uveitis was documented either on examination by the presence of inflammatory cells in the vitreous and/or retinitis, or retinal vasculitis manifesting as perivascular sheathing, or vascular leakage and/or occlusion on fluorescein angiograms. the exclusion criteria were age over 55 years, history of intraocular surgery, chronic systemic diseases such as diabetes mellitus, hypertension, vascular diseases and other rheumatologic involvement, any ocular diseases like agerelated macular degeneration (amd), central serous choroidopathy (csc), high refractive error (spherical equivalent >±3.00d), any media opacity precluding image acquisition, allergy to fluorescein and non-compliance with follow-up. patients with only anterior uveitis were excluded. demographic information of the patients and the ophthalmologic examinations data including best-corrected visual acuity (bcva), slit lamp biomicroscopy, tonometry, and dilated indirect ophthalmoscopy were collected for further analysis. bcva was measured by decimal snellen scale and then converted to the logarithm of the minimal angle of resolution (log mar) for statistical analysis. all patients underwent edi-oct and wf-fag imaging modalities. the sfct was measured using digital caliper provided by edi-oct (heidelberg engineering, heidelberg, germany). choroidal thickness was measured from the outer portion of the hyperreflective line corresponding to the retina pigment epithelium (rpe) to the inner surface of the sclera. to avoid diurnal variations, measurements of sfct with edi-oct were performed from 9 am to 1 pm. to reduce the bias, two expert ophthalmologists who were masked to the patient grouping measured the choroidal thickness independently in each eye. any case with 15% difference in the two measurements by the two experts was excluded from the study. all patients underwent wf-fag (heidelberg engineering, heidelberg, germany) procedure following intravenous (iv) administration of 2.5 ml sodium fluorescein 10% (fluorescite; alcon, inc, fort worth, tx). the angiographic scoring method described by tugal-tutkun et al[19] was used to score the fa. in this scoring method, they assigned scores to the fluorescein and icg angiographic signs that represented active inflammatory process in the posterior segment. a total maximum score of 40 was assigned to the fa signs, including optic disc hyperfluorescence, macular edema, retinal vascular staining and/or leakage, capillary leakage, retinal capillary nonperfusion, neovascularization of the optic disc, neovascularization elsewhere, pinpoint leaks, and retinal staining and/or subretinal pooling. a total maximum score of 20 was assigned to the icga signs, including early stromal vessel hyperfluorescence, choroidal vasculitis, dark dots or areas (excluding atrophy), and optic disc hyperfluorescence. results table 1 shows demographic information, age, gender, bcva, and sfct in the studied patients. there was no significant difference in terms of gender and age between the groups with and without ocular involvement. fifty-one patients (102 eyes) participated in this study (23 males and 28 females). twenty-eight eyes showed no ocular involvement. seventyfour eyes had ocular involvement in wf-fag or clinical examination; of these, twenty-eight eyes (37.8% ) demonstrated active ocular inflammation manifesting as posterior uveitis in ophthalmic examination, whereas the uveitis was quiescent in 46 eyes corresponding with 62.2% of patients with ocular involvement. however, in the wf-fag evaluation, 53 eyes (71.6% of patients with obd) had active uveitis (score >0) and 21 eyes (28.4%) showed inactive uveitis (score of 0) (wf-fag score range, 1–29). in evaluation of both ophthalmic examination and wf-fag in patients with ocular involvement, 26 eyes (36.5%) showed to be active and 20 eyes (27%) were inactive. the mean age of patients in the group without ocular involvement was 38.71 ± 7.8 years (29–52 years) and in the group with ocular involvement was 36.22 ± 10.59 (21–55 years) (p = 0.259). the mean duration of bd was 5.34 ± 4.6 years in all patients. the minimum duration of disease was in new cases and the maximum duration was 22 years. the mean bcva (log mar) in the bd patients with and without ocular involvement was 0.1403 ± 0.24 and 0.0035 ± 0.018 (p = 0.005), respectively. there was no eye with >15% variation in measurement of sfct between the ophthalmologists. the mean sfct in patients without ocular involvement measured on edioct was 320.43 ± 56.70 µm (222–452 µm) and in patients with ocular involvement on clinical journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 197 choroidal thickness in patients with behçet disease; hosseini et al table 1. demographic and clinical finding of patients without ocular involvement with ocular involvement p-value age 38.71 ± 7.8 (29–52 years) 36.22 ± 10.59 (21–55 years) 0.259 sex (m:f) 5:9 16:19 0.241 bcva 0.1403 ± 0.24 0.0035 ± 0.018 0.005 mean sfct (μm) 320.43 ± 567 364.17 ± 93.34 0.008 bcva, best-corrected visual acuity (logmar); sfct, sub-foveal choroidal thickness table 2. demographic and clinical finding of patients with ocular involvement only in wf-fag active uveitis inactive uveitis p-value age 35.60 ± 10.906 37.76 ± 9.833 0.433 sex (m:f) 33:20 3:18 0.001 bcva 0.2002 ± 0.28 0.0120 ± 0.038 0.003 duration of disease (yr) 5.018 ± 6.28 5.119 ± 3.65 0.945 5mean sfct (μm) 368.12 ± 104.591 354.57 ± 58.701 0.579 wf-fag, wide field fundus fluorescein angiography; bcva, best corrected visual acuity; sfct, subfoveal choroidal thickness examination or wf-fag was 364 ± 93.34 µm (88–519µm) (p = 0.008). the mann–whitney test showed significant correlations (p = 0.008) between sfct and ocular involvement (table 1). the sfct measured by edi-oct in the patients with active obd demonstrating only in wf-fag was 368.12 ± 16.64 µm (range: 88–519 µm), and in inactive eyes it was 354.57 ± 58.701 (range, 222– 452 µm) (p = 0.579) (table 2). the sfct values did not show significant correlation with wf-fag activity (p = 0.579). sfct values in the active group according to both wf-fag and clinical examination was higher than in the inactive group but it was not statistically significant regardless of the clinical relevance (393.04 ± 94.88 vs 351.65 ± 58.63) p = 0.060 (table 3). spearman correlation test showed significant negative correlation between sfct and bd duration (p = 0.013, r = –0.249) indicating inverse relationship between bd duration and sfct. the mean ± sd wf-fag score of active uveitis cases was 18 ± 7. there was an association between total wf-fag score and mean sfct in edi-oct so that higher total wf-fag scores resulted in higher mean sfct values, but the association was not statistically significant (p = 0.579). in addition, we evaluated the association between bcva and gender in the patients. the mean log mar bcva was 0.153 and 0.057 in males and females, respectively. bcva was significantly better in females and the mann–whitney test showed significant correlations between bcva and gender (p = 0.002). discussion in the current study, patients with obd had thicker choroid compared to patients without ocular involvement, and the subfoveal choroid was thicker in patients with active disease compared to those with quiescent disease. to the best of our knowledge, this is the first report of choroidal thickness measurement in bd with and without ocular involvement in iran. choroidal involvement in obd has been demonstrated in histopathology, ophthalmic ultrasonography, icga, and wf-fag.[20–22] edi–oct is a technique that provides noninvasive, in vivo, cross-sectional, histologic information of the choroid and retina with high resolution.[12, 16] wf-fag is the gold standard technique for evaluation of posterior involvement in obd. however, this technique is poorly sensitive for detailed evaluation of the choroidal circulation.[14] icga has been proposed for the assessment of 198 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 choroidal thickness in patients with behçet disease; hosseini et al table 3. demographic and clinical finding of patients with ocular involvement in both wf-fag and clinical exam active uveitis inactive uveitis p-value number (eyes) 26 20 age 36.56 ± 8.85 36.34 ± 9.573 0.385 sex (m:f) 12:14 8:12 0.259 bcva 0.2210 ± 0.14 0.0095 ± 0.056 0.03 mean sfct (μm) 393.04 ± 94.88 351.65 ± 58.63 0.060 bcva, best corrected visual acuity; sfct, subfoveal choroidal thickness choroidal circulation, but it shows low sensitivity for the evaluation of retinal circulation.[15, 16] we investigated mean sfct with edi–oct in 102 eyes of 51 patients with definite bd and found that choroid was thicker in patients with ocular involvement in both active and inactive uveitic phases compared to the choroidal thickness in patients without ocular involvement. sfct was also greater during an active uveitis in comparison to the cases in remission, but the difference was not statistically significant. this can be explained by either the possible subclinical involvement of the choroid in quiescent phase that results in an increase in the sfct or that attacks of uveitis may cause lasting changes in the choroidal structure and thickness. the mean age of patients with and without ocular involvement did not significantly differ and the age of patients in this study was similar to the age of patients in previously conducted studies that were in their third and fourth decades of life.[23] previous studies evaluated choroidal changes by edi–oct in bd. ishikawa et al[17] and kim et al[6, 9] reported that sfct in the active phase of obd was significantly greater than in remission phase. moreover, the choroidal thickness in both active and remission phases of obd was greater than the healthy subjects. this difference could be attributed to the subclinical inflammatory activity of the choroid during the quiescent phase, which could exacerbate, leading to an acute recurrent attack of uveitis.[6] their findings correlate with the findings of the current study. results of the study by atas et al also support our findings[18]. they reported that the sfct in the eyes in the remission phase of obd was greater than the healthy control eyes, but the difference was not statistically significant. in contrast, some studies contradicted our findings.[8] coskun et al[14] demonstrated that the choroid was significantly thinner in the eyes of behçet patients with active posterior uveitis compared to patients in remission and control healthy individuals after excluding patients with macular edema. they concluded that because of long duration of eye disease in the studied patients (4.1 years), prolonged inflammation resulted in choroidal fibrosis and shrinkage and decreased thickness.[14] onal et al analyzed the morphology of subfoveal choroid during an active obd phase.[8] they quantitatively segmented the choroid into choroidal stroma and choroidal vessel lumen in edi–oct images collected from patients with <4 year history of bd and acute posterior uveitis. patients with obd had a significantly higher choroidal stroma to choroidal vessel lumen compared to the healthy control group. choroidal stromal expansion in eyes with active obd was observed. however, choroidal stroma expansion was not associated with thickening of the choroid.[8] interestingly, kim et al reported no significant difference in sfct between the two eyes of bd patients with unilateral active uveitis because the choroid thickness was greater than the normal values in the uninvolved fellow eyes.[6] the discrepancies in choroidal thickness in these studies could be attributed to the nonhomogeneity in activity, anatomical involvement, and duration of obd.[8] we used the wide field angiographic scoring system to score wf-fag[19, 24–26] and observed an association between choroidal thickness and wffag activity score so that higher wf-fag activity results in greater sfct but the association was not statistically significant. the results of the current study contradicted the findings of kim et al[6] and onal et al[8] who reported significant correlations journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 199 choroidal thickness in patients with behçet disease; hosseini et al between sfct values and total wf-fag score, retinal vascular staining, and/or leakage. the other interesting finding of the present study was the negative correlation between choroidal thickness and duration of the disease; the plausible explanation for this finding may be replacement of choroidal stroma by fibrosis in the chronic phase of bd that results in thinning of choroid in cases with longer duration of obd in contrast to early involved patients.[14] in the current study, bcva was significantly better in females, which could be explained by the more severe course and more frequent involvement of the posterior segment in male patients with behcet ocular involvement.[5] in conclusion, our findings showed a significant change of sfct in bd. moreover, this study demonstrated that edi–oct modality is useful for evaluating the subclinical choroidal involvement even during the quiescent phase of the obd. this technique can be used to monitor the activity of disease in association with the angiographic findings.[6] this study has some limitations including small sample size and non-homogeneity of cases. although edi–oct is a good modality for assessment of ocular involvement in bd patients, the commercially available tools can not automatically calculate the sfct; manual measurements are tedious and time-consuming, and delineating the choroidal–scleral interface in subjects with a thick choroid is difficult. moreover, opaque ocular media due to significant vitreous haziness and/or cataract impedes smooth acquisition of the images. future developments in ss-oct may provide more effective assessment of the choroid in ocular behcet disease. financial support and sponsorship none. conflicts of interest the authors have no conflicts of interest to declare. references 1. france r, buchanan rn, wilson mw, sheldon mb jr. relapsing iritis with recurrent ulcers of the mouth and genitalia (behcet’s syndrome). review: with report of additional case. medicine 1951;30:335–355. 2. deuter cm, kötter i, wallace gr, murray pi, stübiger n, zierhut m. behçet’s disease: ocular effects and treatment. prog retin eye res 2008;27:111–136. 3. emre s, güven-y𝚤lmaz s, ulusoy mo, ateş h. optical coherence tomography angiography findings in behcet patients. int ophthalmol 2019;39:1–9. 4. tugal-tutkun i. imaging in the diagnosis and management of behçet disease. int ophthalmol clin 2012;52:183–190. 5. akkoç n. update on the epidemiology, risk factors and disease outcomes of behçet’s disease. best pract res clin rheumatol 2018;321–310. 6. kim m, kim h, kwon hj, kim ss, koh hj, lee sc. choroidal thickness in behcet’s uveitis: an enhanced depth imagingoptical coherence tomography and its association with angiographic changes. invest ophthalmol vis sci 2013;54:6033–6039. 7. khairallah m, abroug n, khochtali s, mahmoud a, jelliti b, coscas g, et al. optical coherence tomography angiography in patients with behcet uveitis. retina 2017;37:1678–1691. 8. onal s, uludag g, oray m, mengi e, herbort cp, akman m, et al. quantitative analysis of structural alterations in the choroid of patients with active behçet uveitis. retina 2018;38:828–840. 9. tugal-tutkun i, ozdal pc, oray m, onal s. review for diagnostics of the year: multimodal imaging in behçet uveitis. ocul immunol inflamm 2017;25:7–19. 10. tugal-tutkun i, onal s, altan-yaycioglu r, altunbas hh, urgancioglu m. uveitis in behçet disease: an analysis of 880 patients. am j ophthalmol 2004;138:373–380. 11. tugal-tutkun i. behçet’s uveitis. middle east afr j ophthalmol 2009;16:219–224. 12. atmaca ls. fundus changes associated with behçet’s disease. graefes arch clin exp ophthalmol 1989;227:340–344. 13. özdal p, ortac s, taşkintuna i, firat e. posterior segment involvement in ocular behçet’s disease. eur j ophthalmol 2002;12:424–431. 14. coskun e, gurler b, pehlivan y, kisacik b, okumus s, yayuspay𝚤 r, et al. enhanced depth imaging optical coherence tomography findings in behcet disease. ocul immunol inflamm 2013;21:440–445. 15. hassenstein a, meyer ch. clinical use and research applications of heidelberg retinal angiography and spectral−domain optical coherence tomography–a review. clin experiment ophthalmol 2009;37:130–143. 16. atmaca l, sonmez p. fluorescein and indocyanine green angiography findings in behçet’s disease. br j ophthalmol 2003;87:1466–1468. 17. ishikawa s, taguchi m, muraoka t, sakurai y, kanda t, takeuchi m. changes in subfoveal choroidal thickness associated with uveitis activity in patients with behcet’s disease. br j ophthalmol 2014;98:1508–1513. 18. ataş m, yuvac𝚤 i̇, demircan s, güler e, altunel o, pangal e, et al. evaluation of the macular, peripapillary nerve fiber layer and choroid thickness changes in behçet’s disease with spectral-domain oct. j ophthalmol 2014:865394. 19. tugal-tutkun i, herbort cp, khairallah m, group asfuw. scoring of dual fluorescein and icg inflammatory angiographic signs for the grading of posterior segment inflammation (dual fluorescein and icg angiographic 200 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 choroidal thickness in patients with behçet disease; hosseini et al scoring system for uveitis). int ophthalmol 2010;30:539– 552. 20. charteris d, barton k, mccartney a, lightman s. cd4+ lymphocyte involvement in ocular behclet’s disease. autoimmunity 1992;12:201–206. 21. george rk, chan c-c, whitcup sm, nussenblatt rb. ocular immunopathology of behçet’s disease. surv ophthalmol 1997;42:157–162. 22. mullaney j, collum lm. ocular vasculitis in behcet’s disease. a pathological and immunohistochemical study. int ophthalmol 1985;7:183–191. 23. branchini la, adhi m, regatieri cv, nandakumar n, liu jj, laver n, et al. analysis of choroidal morphologic features and vasculature in healthy eyes using spectraldomain optical coherence tomography. ophthalmology 2013;120:1901–1908. 24. invernizzi a, mapelli c, viola f, cigada m, cimino l, ratiglia r, et al. choroidal granulomas visualized by enhanced depth imaging optical coherence tomography. retina 2015;35:525–531. 25. kang hm, lee sc. long-term progression of retinal vasculitis in behçet patients using a fluorescein angiography scoring system. graefes arch clin exp ophthalmol 2014;252:1001–1008. 26. moon sw, kim bh, park uc, yu hg. inter-observer variability in scoring ultra-wide-field fluorescein angiography in patients with behçet retinal vasculitis. ocul immunol inflamm 2017;25:20–28. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 201 original article outcomes following pars plana vitrectomy for severe ocular trauma natalia k. bober1,2, mbbs; neruban kumaran1, phd, frcophth; tom h. williamson1,2, md, frcophth 1st thomas’ hospital, london, uk 2king’s college medical school, london, uk orcid: natalia k bober: https://orcid.org/0000-0002-2190-3992 tom h williamson: https://orcid.org/0000-0002-1879-449x abstract purpose: to investigate outcomes and presenting characteristics for subjects undergoing pars plana vitrectomy for ocular trauma. methods: retrospective study of 113 patients who underwent pars plana vitrectomy for severe ocular trauma at [name deleted to maintain the integrity of the review process] between 1999 and 2018. data were collected on age, gender, initial and final visual acuity (logmar), mode of injury, type of injury, number of surgeries performed, follow-up duration, type of tamponade, presence of phthisis, and retinal detachment. the birmingham eye trauma terminology system (betts) was employed. results: we identified assault and contusion injuries to be the most common mode and type of ocular injury in our cohort. furthermore, through follow-up we noted a varied number of operations required by patients presenting with ocular trauma and a statistically significant improvement in visual acuity from 1.73 (±0.86) logmar to 1.17 (±1.03; p <0.01) logmar. a statistically significant difference in final visual acuity was also noted between betts classified type of injury groups (p < 0.01). notably, only 7.3% and 8.2% of patients developed phthisis or a persisting retinal detachment, respectively, during follow-up. conclusion: our study demonstrates that ocular trauma requiring pars plana vitrectomy can require a varied number of operations with a guarded visual prognosis. however, a small percentage will proceed to develop phthisis following intervention. keywords: ocular trauma; visual outcome; vitrectomy j ophthalmic vis res 2021; 16 (3): 408–414 introduction ocular trauma can cause severe visual impairment with substantial impact on quality of life. correspondence to: tom h. williamson, md. department of ophthalmology, st thomas’ hospital, westminster bridge road, london, se1 7eh, uk. email: tom@retinasurgery.co.uk received: 05-05-2020 accepted: 29-03-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i3.9449 globally, ocular trauma accounts for blindness in approximately 1.6 million people with a further 2.3 million suffering from bilateral low vision and approximately 19 million with unilateral blindness or low vision.[1] furthermore, it is estimated that there can be around 120,000 of presentations to the accident and emergency department due to ocular injuries, annually in the united kingdom,[2] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: bober nk, kumaran n, williamson th. outcomes following pars plana vitrectomy for severe ocular trauma. j ophthalmic vis res 2021;16:408–414. 408 © 2021 bober et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i3.9449&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr vitreoretinal surgery for ocular trauma; bober et al with hospital admissions estimated to be 8.14 per 100,000 people.[3] surgical intervention following ocular trauma has two main objectives, firstly to protect ocular integrity and secondly to improve/stabilize vision. the majority of ocular injuries that causes substantial visual loss involve the posterior segment of the eye and as a result these patients often undergo posterior segment (vitreoretinal) surgery. pars plana vitrectomy (ppv) allows the reconstruction of the posterior segment of the eye, clear visually significant vitreous opacities, control inflammation, and where appropriate treat retinal detachment. it can also be used to manage posterior segment complications of closed-globe/contusion injuries including retinal detachment, macular hole, and vitreous hemorrhage.[4] ppv was found to have a good prognosis, contributing to significant improvements in visual outcomes following ocular trauma.[5, 6] when used as a primary procedure, it resulted in more eyes achieving the final vision of light perception (lp) or better, compared to those that did not undergo the surgery.[5] an important complication of open globe trauma and associated retinal detachment is proliferative vitreoretinopathy, an intraocular scarring process, which can lead to recurrent retinal detachment, associated with poor final visual outcomes.[7] many groups have investigated independent prognostic factors for ocular trauma. commonly reported poor prognostic factors include poor initial visual acuity, relative afferent pupillary defect, multiple surgeries, posterior ocular (zone iii, >5 mm posterior to the limbus) injury, vitreous hemorrhage, hyphema, lid laceration, and posterior wound location.[5, 6, 8–10] this was taken further by one group, who developed ocular trauma score (ots).[11] this score system uses the information of the initial visual acuity, presence of globe rupture, endophthalmitis, perforating injury, retinal detachment, and relative afferent pupillary to estimate the visual outcomes. furthermore, given a lack of standardization of classifications and definitions used in ocular trauma studies, the birmingham eye trauma terminology system (betts) was created, introducing a simple and consistent way of classifying ocular trauma, allowing easier and more objective comparison.[12] the epidemiology of eye injuries is known to vary depending on the population studied and is influenced by multiple factors including lifestyle, socioeconomic status, traffic state, and recreational activities.[13] a number of studies have investigated the epidemiology of ocular trauma. knowledge of specific risk factors associated with ocular injuries in a population can contribute to targeted campaigns that aim to reduce the incidence of ocular trauma in the community.[14] this in turn may involve specifically designed programs to increase the workplace safety and awareness of ocular injuries.[15] herein, we aim to investigate the frequency of both different modes and types (based on betts) of ocular trauma and surgical outcomes of ppv. methods a retrospective analysis of 113 patients who had undergone ppv at st thomas’ hospital, london, uk between july 23, 1999 and june 25, 2018 was conducted using the vitreor database (microsoft access, albuquerque, usa). the study was completed in adherence to the tenets of the declaration of helsinki and received appropriate local approvals. all patients underwent ppv for posterior segment complications requiring surgical intervention. data were collected on age, gender, visual acuity (logmar), mode of injury, type of injury, type of tamponade, number of surgeries performed, and time of follow-up. furthermore, outcomes of phthisis and retinal detachment were noted. mode of injury was classified into assault, domestic, industrial, road traffic accidents, and sport-related injury. similarly, the type of ocular injury was categorized as per the betts classification, that is, as follows: contusion (without a full-thickness wound to the eye), intraocular foreign body (iofb), penetrating (entrance wound alone), perforating (entrance and exit wound), and rupture (full thickness wound caused by a blunt trauma).[12] all patients included in the study, including those with ocular contusions, underwent ppv. all statistical analysis was performed using the spss statistics software package (ibm, new york, usa). the perforating injury group was excluded from analysis due to its comparatively low number. a chi-square test of independence was used to journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 409 vitreoretinal surgery for ocular trauma; bober et al investigate the difference in frequency of ocular trauma between men and women. the mean preoperative and postoperative visual acuities were compared using a paired t-test. a one-way analysis of variance (anova) and a subsequent tukey’s post-hoc test were used to investigate whether there was a difference in the age of presentation between each mode of injury and whether different betts classified types of injury were associated with the need for greater or fewer operations and a better or worse final visual acuity. multiple regression analysis was undertaken to investigate age, gender, initial visual acuity, and type of ocular injury (as defined by the betts classification) on final visual acuity. the study was completed in adherence to the tenets of the declaration of helsinki and received appropriate local approvals. results cohort demographics the study included 113 patients, of whom 99 were male and 14 female. age ranged from 6.2 years to 87.7 years with a mean age of 42.7 years (sd: ±18.8 years). longitudinal data were available for 110 patients with follow-up ranging from 1 day to 12.1 years with a mean follow-up of 1.8 years (±2.5). men were found to have a statistically significantly higher risk of ocular trauma, contributing to 87.6% of all analyzed cases (p < 0.01). in terms of mode of injury, assault (35 cases) and industrial (33 cases) were the most common modes of injury, followed by domestic (25 cases) and sport (14 cases). least common were road traffic accidents (6 cases). as per the betts classification, contusion was the most common type of injury recorded (47 cases), followed by iofb (25 cases). notably, all iofb injuries included posterior segment involvement. as demonstrated in figure 1, contusion injuries appeared to be most common in those suffering an assault (16 cases) while iofb were most common in industrial injuries (16 cases). furthermore, we identified a statistically significant difference in age of presentation between mode of injury groups (p < 0.01). post-hoc analysis revealed a higher mean age at presentation in domestic injuries (54.1 ± 25.0 years) when compared to the sports-related injuries (33.6 ± 19.4 years, p < 0.01) and industrial injuries (38.0 ± 12.3 years, p < 0.01). surgical outcomes the number of operations required varied from one to five with a mean number of 1.8 (±1.0) operations performed. we identified a statistically significant difference in the number of operations required between the betts classified types of injury (p = 0.02). the statistically significant difference was found when comparing the number of operations required for contusion injury, mean 1.51 (±0.91) with iofb injury, mean 2.28 (±1.24, p = 0.02), which are also the groups with respectively the smallest and biggest average numbers of surgeries performed per betts group. in our cohort, on follow-up, an improvement from presenting visual acuity was noted in 73 patients (66%); however, 25 patients (23%) were found to have a deterioration in visual acuity, while 12 patients (11%) were found to have no change. furthermore, the mean preoperative visual acuity in our cohort was 1.73 (±0.86) logmar which was noted to improve postoperatively to a mean of 1.17 (±1.03; p < 0.01) logmar. overall, all betts groups were noted to have improvement in final visual acuity, with the only exception of perforating group [table 2]. interestingly, as demonstrated in figure 2, a statistically significant difference in final visual acuity was noted between betts classified type of injury groups (p < 0.01). post-hoc analysis revealed that final visual acuity was statistically significantly better in the contusion group 0.92 (±0.91) logmar compared to the rupture group 1.68 (±1.08, p = 0.02) logmar. visual acuity was also found to be better in the iofb group 0.78 (±0.92) logmar when compared to the penetrating group 1.55 (±1.00, p = 0.05) logmar and rupture group (p = 0.01). patients who underwent ppv in our study required gas, oil, or no tamponade. gases used include sf6, c2f6, c3f8, and air. oil tamponade was found to be most commonly used in all betts groups 43.6% (n = 48) except contusion, followed by gas tamponade 30.9% (n = 34). ppv without tamponade was least commonly performed 25.5% (n = 28). best final visual acuity was found in a group with no tamponade 0.63 (±0.84) logmar, followed by gas tamponade 0.81 (±0.90) logmar. 410 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 vitreoretinal surgery for ocular trauma; bober et al figure 1. histograms showing betts classified type of injury in each mode of injury. this demonstrates increased frequency of contusion injuries in those suffering an assault and an increased incidence of intraocular foreign bodies in industrial injuries. figure 2. combined stacked scatterplots and box plots of final visual acuity outcomes in each betts classified type of injury. shown are stacked scatterplots and box plots for contusion injuries (45 eyes), intraocular foreign bodies (25 eyes), penetrating injuries (18 eyes), perforating injuries (3 eyes), and globe rupture (19 eyes). box plots with box spanning interquartile range with maximum and minimum values (excluding outliers) are provided. black and blue lines represent median and mean, respectively. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 411 vitreoretinal surgery for ocular trauma; bober et al table 1. demographics showing number of patients and age (mean and standard deviation) for each mode of injury mode of injury number of patients mean age standard deviation assault 35 41.3 15.0 domestic 25 54.1 25.0 industrial 33 38.0 12.3 road traffic accident 6 49.5 19.0 sport 14 33.6 19.4 total 113 42.7 18.8 table 2. initial pre-op and final post-op visual acuity with overall visual acuity change in different betts groups (mean and standard deviation)[logmar] cause of ppv pre-op va (mean ±±± sd) [logmar] post-op va (mean ±±± sd) [logmar] va change contusion 1.52 ± 0.85 0.92 ± 0.91 0.60 ± 0.19 iofb 1.40 ± 1.01 0.78 ± 0.92 0.62 ± 0.27 penetrating 1.95 ± 0.67 1.55 ± 1.00 0.40 ± 0.28 perforating 2.43 ± 0.29 2.70 ± 0.35 –0.27 ± 0.26 rupture 2.03 ± 0.59 1.68 ± 1.08 0.35 ± 0.28 ppv, pars plana vitrectomy; iofb, intraocular foreign body; va, visual acuity; logmar, logarithm minimum angle of resolution; sd, standard deviation as expected, oil tamponade was associated with the worst final visual acuity 1.70 (±0.97) logmar [table 3]. in our cohort, eight patients (7.3%) developed phthisis during their follow-up, with associated poor visual outcomes (with documented visual acuity ranging from hand movement to no lp). out of all eight patients, three noted no change and five had visual deterioration. furthermore, of the phthisis cases, four patients presented with ocular rupture – three with perforating injury and one in iofb injury, as per the betts classification system. retinal detachment persisted in nine patients (8.2%) with results of visual acuity improvement in one patient, no change in three patients, and deterioration in five patients. a multiple regression analysis was run to predict final va from age, gender, initial visual acuity, and type of ocular injury. presenting va (p < 0.01) and type of ocular injury (p = 0.046) were identified as statistically significant in predicting final va. discussion ocular trauma is known to be an important cause of visual loss with varying groups investigating ocular trauma in different countries in different settings.[5, 6, 16] in this study, we investigated both cross-sectional and longitudinal data in a large cohort of patients presenting with ocular trauma to a large tertiary referral center in london, uk. we identified men to have a statistically significantly increased risk of ocular trauma, in keeping with multiple other studies.[3, 5, 10, 16] furthermore, we identified a novel finding of assault as the commonest cause of ocular trauma in our cohort. assault has previously been described as a risk factor for poor visual outcomes.[17] while other groups have identified home[3] and workplace[6] as common locations, little has been known about the nature of ocular trauma outside of a conflict setting.[10] similarly, we also identified sports-related ocular injury to be more common in younger patients. this further emphasizes the importance of education on eye protection during sporting activities. through investigating outcomes using the betts classification,[12] we identified contusion injuries to be the most common, and furthermore required the least number of operations, achieving a statistically significantly better final visual acuity, when compared to the rupture group. contusion injuries by definition do not have a full-thickness 412 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 vitreoretinal surgery for ocular trauma; bober et al table 3. frequency of different types of tamponade use in betts groups with overall final visual acuity[logmar] cause of ppv percentage requiring gas tamponade percentage requiring oil tamponade percentage requiring no tamponade mean final visual acuity [logmar] contusion 37.8% (n = 17) 28.9% (n = 13) 33.3% (n = 15) 0.92 ± 0.91 iofb 28.0% (n = 7) 52.0% (n = 13) 20.0% (n = 5) 0.78 ± 0.92 penetrating 33.3% (n = 6) 50.0% (n = 9) 16.7% (n = 3) 1.55 ± 1.00 perforating 0% 100% (n = 3) 0% 2.70 ± 0.35 rupture 10.5% (n = 2) 63.2% (n = 12) 26.3% (n = 5) 1.68 ± 1.08 overall 30.9% (n = 32) 43.6% (n = 50) 25.5% (n = 28) mean final visual acuity 0.81 ± 0.90 1.70 ± 0.97 0.63 ± 0.84 iofb, intraocular foreign body; logmar, logarithm minimum angle of resolution ocular wound, and as such they would be expected to have a better prognosis. furthermore, we identified a guarded improvement in visual acuity following ppv for ocular trauma with improvement or stability of visual acuity noted in 66% of patients and an improvement from 1.73 (±0.86) logmar to 1.17 (±1.03; p < 0.01) logmar. the improvement was noted in all betts groups with the only exception of perforating group. while this does demonstrate a statistically significant improvement in visual acuity, it also highlights the guarded prognosis of final visual acuity for ppv following ocular trauma. notably, other groups have demonstrated similar improvements following ppv, albeit with different cohorts to ours. mansouri et al described an improvement from 2.36 (±0.72) logmar to 1.50 (±1.14) logmar following ppv in a smaller cohort (n = 90) in iran.[6] furthermore, guven et al described a statistically significant improvement in 337 out of their cohort of 633 patients who underwent ppv following ocular trauma.[10] however, it should also be noted that a large proportion (48.2%) of patients in this cohort had terror-related open globe injury, making it difficult to compare their findings with those of this study. interestingly, xia et al also describe an improvement in visual acuity from 2.20 (±0.63) logmar to 1.87 (±0.60) logmar in a longitudinal american cohort of 96 eyes, similar to ours.[16] overall, oil tamponade was the most commonly chosen agent and that group had worst final visual acuity 1.70 (±0.97) logmar; however, the reason for this was most likely the type and severity of ocular injury, with the need for a longer acting tamponade. therefore, in our study, type of tamponade cannot be used as a prognostic factor on its own. similarly, jiang et al concluded that use of silicone oil did not affect the visual acuity prognosis but the severity of presentation, in that case traumatic endophthalmitis, was the main factor determining the appropriate choice of treatment.[18] vaziri et al concluded that the type of tamponade used should be individualized according to the characteristics of the patient and medical presentation.[19] additionally, only 8 and 9 patients out of 110 patients followed-up developed phthisis and a persisting retinal detachment, respectively, at the final visit. furthermore, there was a wide variation of one to five surgeries required for patients with ocular trauma in our cohort, with a mean of 1.8 (±1.0) operations similar to other cohorts.[16] furthermore, we identified that presenting va (p < 0.01) and type of ocular injury (p = 0.05) as prognostic indicators for final va again suggesting that those with less severe injuries on presentation have a better prognosis. indeed, initial va was shown as an important prognostic factors in multiple previous studies.[5, 10, 20, 21] there are, however, limitations to our study. we were unable to investigate the presence of endophthalmitis, presence of afferent pupillary defect and zone of injury (as previously explored by the ots), and the impact of this on surgical outcome. secondly, our study does not involve information on the timing of the ppv. currently, there are no clear guidelines concerning the optimal timing of surgery. according to ryan et al and brinton et al, patients that underwent vitrectomy within first 14 days after presentation seemed to have better visual outcomes than those journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 413 vitreoretinal surgery for ocular trauma; bober et al who had to wait longer.[22, 23] however, others argue the timing of vitrectomy is not related to visual outcomes.[6, 24] for that reason it is difficult to estimate the effect that timing of the ppv may have. additionally, in the contusion group we were unable to investigate the specific indication for intervention, and in the iofb group while all iofbs involved the posterior segment, we were unable to investigate the location within the posterior pole. what is more, the retrospective nature of the study can introduce bias due to variability in reporting clinical findings. furthermore, as a single-center study, it is difficult to use our findings to inform practices in other countries. in summary, we present a study of prognostic factors and outcomes of vitreoretinal surgery in ocular trauma. we demonstrate a varied number of surgeries required following ocular trauma, visual acuity improvement following ppv but with a very guarded prognosis and, as expected, that patients without a full-thickness laceration have the best prognosis. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. négrel a, thylefors b. the global impact of eye injuries. ophthalmic epidemiol 1998;5:143–169. 2. rnib (royal national institute for the blind). future sight loss uk (1): the economic impact of partial sight and blindness in the uk adult population [internet]. london, uk: rnib; 2009 [cited 2019 october 27]. available from: https://www.rnib.org.uk/sites/default/files/ fsuk_report.pdf 3. desai p, macewen cj, baines p, minassian dc. incidence of cases of ocular trauma admitted to hospital and incidence of blinding outcome. br j ophthalmol 1996;80:592–596. 4. rejdak r, juenemann a, natarajan s. posterior segment ocular trauma: timing and indications for vitrectomy. j ophthalmol 2017;2017:1–2. 5. fujikawa a, mohamed y, kinoshita h, matsumoto m, uematsu m, tsuiki e, et al. visual outcomes and prognostic factors in open-globe injuries. bmc ophthalmol 2018;18:138. 6. mansouri mr, tabatabaei sa, soleimani m, kiarudi my, molaei s, rouzbahani m, et al. ocular trauma treated with pars plana vitrectomy: early outcome report. int j ophthalmol 2016;9:738–742. 7. banerjee p, cornelius v, phillips r, lo j, bunce c, kelly j, et al. adjunctive intraocular and peri-ocular steroid (triamcinolone acetonide) versus standard treatment in eyes undergoing vitreoretinal surgery for open globe trauma (ascot): study protocol for a phase iii, multicentre, double-masked randomised controlled trial. trials 2016;17:339. 8. schmidt g, broman a, hindman h, grant m. vision survival after open globe injury predicted by classification and regression tree analysis. ophthalmology 2008;115:202– 209. 9. rostomian k, thach a, isfahani a, pakkar a, pakkar r, borchert m. open globe injuries in children. j aapos 1998;2:234–238. 10. guven s, durukan ah, erdurman c, kucukevcilioglu m. prognostic factors for open-globe injuries: variables for poor visual outcome. eye 2019;33:392–397. 11. scott r. the ocular trauma score. community eye health 2015;28:44–45. 12. kuhn f, morris r, witherspoon c, heimann k, jeffers j, treister g. a standardized classification of ocular trauma. ophthalmology 1996;103:240–243. 13. aghadoost d. a brief overview of ocular trauma. arch trauma res 2014;3:e21639. 14. pandita a, merriman m. ocular trauma epidemiology: 10year retrospective study. n z med j 2012;125:61–69. 15. serinken m, turkcuer s, yilmaz a, cetin e, elicabuk h, karcioglu o. causes and characteristics of work-related eye injuries in western turkey. indian j ophthalmol 2013;61:497. 16. xia t, bauza a, soni ng, zarbin ma, langer pd, bhagat n. surgical management and outcome of open globe injuries with posterior segment complications: a 10-year review. semin opthamol 2018;33:351–356. 17. page r, gupta s, jenkins t, karcioglu z. risk factors for poor outcomes in patients with open-globe injuries. clin ophthalmol 2016;10:1461–1466. 18. jiang t, jiang j, wang r, lei j, zhou y. visual outcomes and prognostic factors after pars plana vitrectomy for traumatic endophthalmitis. biomed res int 2017;2017:1–4. 19. vaziri k, schwartz s, kishor k, flynn h. tamponade in the surgical management of retinal detachment. clin ophthalmol 2016;10:471–476. 20. agrawal r, wei h, teoh s. prognostic factors for open globe injuries and correlation of ocular trauma score at a tertiary referral eye care centre in singapore. indian j ophthalmol 2013;61:502. 21. han sb, yu hg. visual outcome after open globe injury and its predictive factors in korea. j trauma 2010;69:66– 72. 22. ryan s, allen a. pars plana vitrectomy in ocular trauma. am j ophthalmol 1979;88:483–491. 23. brinton g, aaberg t, reeser f, topping t, abrams g. surgical results in ocular trauma involving the posterior segment. am j ophthalmol 1982;93:271–278. 24. ahmadieh h, soheilian m, sajjadi h, azarmina m, abrishami m. vitrectomy in ocular trauma. retina 1993;13:107–113. 414 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 https://www.rnib.org.uk/sites/default/files/fsuk_report.pdf https://www.rnib.org.uk/sites/default/files/fsuk_report.pdf original article low-contrast pattern-reversal visual evoked potential in different spatial frequencies homa hassankarimi, ms1; ebrahim jafarzadehpur, phd2; alireza mohammadi, ms2 seyed mohammad reza noori, ms3 1department of medical physics, school of medicine, iran university of medical sciences, tehran, iran 2department of optometry, school of rehabilitation science, iran university of medical sciences, tehran, iran 3departments of medical physics and biomedical engineering, school of medicine, tehran university of medical sciences, tehran, iran orcid: homa hassankarimi: https://orcid.org/0000-0002-4451-800x ebrahim jafarzadehpur: https://orcid.org/0000-0002-4451-800x abstract purpose: to evaluate the pattern-reversal visual evoked potential (prvep) in lowcontrast, spatial frequencies in time, frequency, and time-frequency domains. methods: prvep was performed in 31 normal eyes, according to the international society of electrophysiology of vision (iscev) protocol. test stimuli had checkerboard of 5% contrast with spatial frequencies of 1, 2, and 4 cycles per degree (cpd). for each vep waveform, the time domain (td) analysis, fast fourier transform(fft), and discrete wavelet transform (dwt) were performed using matlab software. the vep component changes as a function of spatial frequency (sf) were compared among time, frequency, and time–frequency dimensions. results: as a consequence of increased sf, a significant attenuation of the p100 amplitude and prolongation of p100 latency were seen, while there was no significant difference in frequency components. in the wavelet domain, an increase in sf at a contrast level of 5% enhanced dwt coefficients. however, this increase had no meaningful effect on the 7p descriptor. conclusion: at a low contrast level of 5%, sf-dependent changes in prvep parameters can be better identified with the td and dwt approaches compared to the fourier approach. however, specific visual processing may be seen with the wavelet transform. keywords: discrete wavelet transform; fast fourier transform; spatial frequency; visual evoked potential j ophthalmic vis res 2020; 15 (3): 362–371 correspondence to: ebrahim jafarzadehpur, phd. department of optometry, rehabilitation faculty, iran university of medical sciences (iums), shahnazary st., mohseni sq., mirdamad blvd, tehran 15459, iran. e-mail: jafarzadehpour.e@iums.ac.ir received: 28-01-2019 accepted: 09-03-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7455 introduction contrast is the main issue in visual perception.[1, 2] as the first mechanism for visual detection, this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: hassankarimi h, jafarzadehpur e, mohammadi a, noori smr. low-contrast pattern-reversal visual evoked potential in different spatial frequencies. j ophthalmic vis res 2020;15:362–371. 362 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7455&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr low-contrast pattern-reversal vep; hassankarimi et al discrimination and perception may be affected by the contrast level of objects.[3, 4] high-contrast objects and symbols are used in the visual examination room as e or similar acuity charts.[5] however, objects in the real world do not show high contrast. therefore, in the real world, visual function is usually in a low to moderate contrast condition.[5, 6] evaluation of the visual system in a low-contrast situation may indicate its performance in the natural visual environment. visual evoked potential (vep) is a noninvasive and objective electrophysiological test for evaluating human visual function.[7] patternreversal visual evoked potential (prveps) directly mirrors neural activities or the extent of stimulated neural network in each eye using the afferent impulse toward the primary visual cortex (v1).[8] the most prominent and strongest peak in vep is p100, which has minimal variation and high repeatability. amplitude and latency of p100 depend on the stimulus conditions, such as the size, luminance, contrast, and spatial frequency (sf).[9] several studies examining the effects of sf changes on the time domain (td) parameters of vep have shown that sf has a significant impact on vep responses.[10–12] decomposition of the time function into its particular frequencies, amplitudes, and phases by means of the fourier transform is an objective and common method for the vep analysis.[13, 14] the fourier technique was successfully applied to determine features of steady-state vep (ssvep) and transient vep (tvep).[7, 15–21] the power of each frequency band in the frequency domain relates to signal amplitudes in the td, and phase spectrum provides precise estimation of latencies in td.[7] the fast fourier transform (fft) has been employed to measure the vep phase and amplitude spectrum of the even harmonic response to determine reliability of amplitude and for estimation latency, determine the neural mechanisms in frequency domain, and develop a fast and reliable tvep technique.[7, 21] zemon et al presented a set of frequency domain measurements that fully obtained the response content and demonstrated that their novel indices may be performed as a more powerful tool to evaluate the visual function. they offered that quantitative and objective measurements in the frequency domain provide a more precise and efficient method for the assessment of the visual system in healthy and diseased brains.[7] the wavelet transform (wt) is a valuable and efficient approach of biosignal processing. this method is widely applied in different studies to analyze, denoise, and extract new parameters of evoked potential signals (eps), ssvep, multifocal vep (mfvep), tvep, and prvep responses, all of which have totally emphasized on the effectiveness and usefulness of this method.[22–33] wt provides simultaneous estimation of time and frequency of vep signals, which yields noteworthy diagnostic information.[34] experiments on the ssvep analysis in time, frequency, and time–frequency domains have suggested that time–frequency and frequency analyses of these waveforms are more efficient than the td analysis.[35, 36] although several experiments have already evaluated how sf changes affect vep amplitudes and peak times in td and vep amplitude and phase spectrum in the frequency domain, to the best of our knowledge, this issue has not been investigated for the parameters of frequency or time–frequency domains, which are considered in this study. moreover, the efficiency of the three mentioned dimensions in representing changes of these parameters as a function of sf has not been compared. in the present study, we focused on the relationship between sf and extracted parameters for the prvep analysis in time, frequency, and time–frequency domains, and also compared the efficiency of these dimensions in revealing changes. methods thirty-one healthy individuals (19 men and 12 women; mean age, 25.6 ± 6.26 years) participated in this study. all subjects underwent ophthalmic tests and showed a normal visual acuity (minimum and maximum, 0.1 and 0.3 logmar, respectively). all procedures involving human participants were done in accordance with the ethical standards of the iran university of medical sciences and/or national research committee and with the 1964 declaration of helsinki and its later amendments or comparable ethical standards. written informed consent was obtained from all participants after informing them about the purpose of the study. considering the international society for clinical electrophysiology of vision (iscev) protocol, journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 363 low-contrast pattern-reversal vep; hassankarimi et al prveps were performed by metrovision monpack one (metrovision company, pérenchies, france) with gold-plated cupola electrodes, according to the 10–20 system. active and reference electrodes were placed on occiput (o𝑧 location) and frontal (f𝑧 location) zones, respectively. the ear lobe served as ground. the prvep signals were amplified 2,000 times, filtered in the range of 1–100 hz and sampled at 1,024 hz using 240 data points. a checkerboard pattern alternating at a rate of 2.5 times per second (temporal frequency of 2.5 hz) was utilized as a stimulus. test stimuli comprised of spatial frequencies of 1, 2, and 4 cycles per degree (cpd) (corresponding to check sizes of 30, 15, and 7 min of arc, respectively) and contrast level of 5% for each sf. the average sweep numbers per trial was 60. all vep waveforms were analyzed in time, frequency, and time–frequency domains using matlab software (matlab r2015b, the mathworks, inc., natick, massachusetts, usa). the p100 amplitudes and latencies were evaluated in td. following signal normalization, the fft and discrete wavelet transform (dwt) of p100 peak of all waveforms were carried out in matlab environment. matlab (matrix laboratory) is a highlevel language for high performance numerical computation and visualization. it is an extremely useful, powerful, and popular simulation tool with immense utility in biosignal processing.[37] the fft and power spectral density (psd) help determine the frequency components and distribution in fine detail. the mean frequency (fmean) was derived from fft, and the mode frequency (fmod) was extracted from welch psd of vep responses. fmean stands for the average frequency in terms of the sampling frequency. fmod stands for the most common frequency and refers to the frequency of maximum value in the power spectrum. hence, fmod demonstrates the dominant frequency in the psd. the wt is a convolution of frequency contents of the signal (scale) with the wavelet function, which describes a more useful signal information. discrete wavelet transform decomposes a signal into “detail” coefficients (high-pass filter components) and “approximation” coefficients (low-pass filter components). in dwt, the mother wavelet (ψ (t)) is decimated by a factor of two and is shifted. the discrete wavelet coefficients can be written as: 𝛾𝑗,𝑘 = ∫ +∞ −∞ 𝑥(𝑡)2−𝑗/2ψ(2−𝑗𝑡 − 𝑘)𝑑𝑡 (1) where integers j and k represent the scale and shift parameters, and x (t) denotes the original signal with the finite length n.[38, 39] the daubechies wavelets (db) are the most important and popular family of wavelets in dwt.[40] with respect to the high resemblance between daubechies wavelet order of 4 (db4) and prvep waveforms, db4 was considered as the proper mother wavelet function for discrete decomposition of prveps in this study. in all cases, the detail coefficients of levels less than 7 were discarded, as the frequency content of these bands was higher than the p100 frequencies. the approximation coefficients, detail coefficients, and 7p descriptor of all responses in level 7 were computed. the 7p descriptor is the energy percentage of a single wavelet coefficient to the total energy level at predetermined time intervals at level 7 and is extracted from the dwt scalogram. the approach of calculating and extracting the 7p descriptor from the dwt scalograms was previously explained by hassankarimi et al.[32] all data of td, fft, psd, and dwt were analyzed using the statistical package for the social sciences for windows, version 22.0 (inc., chicago, il, usa). after testing the normality of all data, the effect of sf changes on all mentioned parameters was evaluated through a one-way analysis of variance (anova) with the post-hoc fisher’s least significant difference (lsd) test. spatial frequencies of 1, 2, and 4 (cpd) were considered as groups 1, 2, and 3, respectively. results table 1 shows the results of one-way anova for comparisons of time, frequency, and wavelet domain parameters among three groups of spatial frequencies. for all spatial frequencies, increasing sf resulted in a decrease in the p100 amplitude (figure 1). the lsd test revealed that differences between 1 and 2 (cpd) groups (p = 0.001) and 1 and 4 (cpd) groups (p = 0.001) were significant. the latency component also showed a change with increasing spatial frequencies. however, this change was in favor of increasing delay 364 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 low-contrast pattern-reversal vep; hassankarimi et al table 1. results of one-way analysis of variance (anova) for three groups of spatial frequency component group mean ± sd** 𝑃 -value 1 6.09 ± 3.49 amplitude (µv) 2 3.45 ± 3.1 0.001* 3 2.529 ± 2.24 1 120.9 ± 10.31 latency (ms) 2 129.81 ± 15.01 0.021* 3 131.03 ± 19.35 1 8.15 ± 3.85 f𝑚𝑒𝑎𝑛 (hz) 2 7.50 ± 4.92 0.842 3 8.07 ± 5.30 1 2.06 ± 0.36 f𝑚𝑜𝑑 (hz) 2 2 ± 0.00 0.372 3 2 ± 0.00 1 –4.14 ± 7.27 approximation coefficient 2 0.516 ± 8.922 0.005* 3 2.969 ± 9.24 1 –0.914 ± 0.18 detail coefficient 2 –0.101 ± 0.205 0.008* 3 0.0411 ± 0.204 1 30.971 ± 16.41 descriptor 7p*** 2 30.618 ± 15.81 0.051 3 21.685 ± 17.84 *significant difference (p < 0.05); **standard deviation; ***descriptor of p100 amplitude time (figure 1). marked latency differences were observed between groups 1 and 2 (p = 0.025), and groups 1 and 3 (p = 0.011). comparing the results of the dwt coefficients revealed that the mean value of both approximation and detail coefficients considerably tended to increase with the increase of sf (table 1). according to the results of the lsd test, approximation coefficients differed significantly between groups 1 and 2 (p = 0.034), and groups 1 and 3 (p = 0.001). the increase in these coefficients was much greater by changing the frequency from 1 cpd to 2 cpd than from 2 cpd to 4 cpd. there was a meaningful influence of sf on detail coefficients between groups 3 and 1 (p = 0.010) and groups 3 and 2 (p = 0.006). the magnitude of the 7p energy descriptor, extracted from the dwt scalograms, showed no observable differences. the frequency domain components did not change significantly. at all spatial frequencies, the peak frequency (fmod) had almost a constant value of approximately 2 hz (figure 2). discussion in the present study, the relationship between sf increase and vep parameters of time, frequency, and wavelet domains at the contrast level of 5% were investigated. the 5% contrast was considered as the contrast threshold, given the decrease in vep amplitude due to reduction in contrast and the low signal to noise ratio and negligible vep responses at the contrast levels < 5%.[41] in agreement with previous studies, our results revealed dramatic changes in td parameters as a function of sf. an increase in sf resulted in p100 amplitude reduction and latency prolongation journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 365 low-contrast pattern-reversal vep; hassankarimi et al figure 1. pattern-reversal visual evoked potentials for one participant at 1, 2, and 4 cpd in the time domain. (figure 1).[11, 12, 42–44] it has been supposed that differences in the speed of information processing and conduction along the visual pathways, which are preferentially activated by specific spatial frequencies, lead to the sequential visual processing from low to high range of sfs.[11] several studies demonstrated that two or more parallel pathways from the retina to the primary visual cortex (v1) are involved in vep formation. at low contrasts, the magnocellular (mc) pathway dominantly contributes to the vep responses, whereas at high contrasts, mc, parvocellular (pc), and koniocellular (kc) pathways involve vep. the mc neurons preferentially detect the low sf and the high temporal frequency stimuli. they have a high contrast sensitivity, high temporal resolution, and short impulse conduction time, whereas pc neurons with a smaller receptive field are sensitive to low temporal and high spatial frequencies.[1, 8, 12, 35, 42, 45–49] therefore, mc signals (high sfs) are conveyed to v1 more rapidly than pc signals (low sfs). at high sfs, the optical properties of the eye noticeably reduce the retinal contrast, resulting in decreased amplitude and delayed latency.[8] it has been demonstrated that visual sensitivity progressively weakens with increase in sf or decrease in the size of the object.[1, 50] it can be caused by pre-neural factors, such as the optical quality of the eye or by contribution of higher levels of visual processing (beyond the lateral geniculate nucleus) for vep formation.[51] it is also suggested that quantal 366 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 low-contrast pattern-reversal vep; hassankarimi et al figure 2. fmod extracted from the power spectral density (psd) of pattern-reversal visual evoked potentials at 1, 2, and 4 cpd. fmod is the peak frequency in the psd (approximately 2 hz). fluctuations in light may give rise to sensitivity loss at high sfs.[52] to the best of our knowledge, fmean and fmod of prveps were not evaluated in previous studies. our results of the frequency domain analysis showed that changes in sf have no obvious effect on frequency parameters (table 1). frequency stability is a significant feature of normal vep signals. no significant change in fmean in all sfs can be explained by the fact that all recorded veps in this study were normal. the almost constant value of fmod recordings may indicate that, in all groups, vep responses were generated by the same subsystems and mechanisms. with respect to the stimulus conditions of this study (5% contrast), we conclude that the mc neuron activity dominantly contribute to eliciting the veps.[41] unlike frequency parameters, mean value approximation and detail coefficients represent marked increase as a function of sf (table 1). based on the capability of the wt in representing the signal frequency contents locally in time[53] and clear p100 latency prolongation with an increase in sf, considerable differences in time–frequency parameters as a function of sf were expected. the prveps induced by different sf stimuli originate from segregated neural activities in the visual system. in dwt, approximation coefficients consist of the low-frequency components and the identity of the signal, while the detail coefficients correspond to high-frequency components and fine details of the signal. statistically significant differences of approximation coefficients between sf groups reflect that the high frequency vep components at 4 cpd have different origins, generation mechanisms, and visual processing areas compared to other sfs. on the other hand, the low-frequency contents (detail coefficients) at sf of 1 cpd are elicited by different mechanisms compared to the spatial frequencies of 2 and 4 cpd. a possible explanation is that the processing of medium and high sf information occurs in the primary visual cortex (v1), while low spatial frequencies are mainly processed in the secondary visual area (v2).[1, 35] furthermore, sfs > 1.5 cpd generally elicit veps that are contrast specific in nature, whereas sfs < 1.5 cpd elicit veps that are mainly originated from local luminance changes.[51] moreover, since the stimulus conditions have a significant impact on the neural responses,[54] under our stimulus conditions, an increase in the dwt coefficients can result in simultaneous stimulation of similar neuronal circuits in the visual cortex and inner cortex interaction between neurons outside the receptive field. as mentioned journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 367 low-contrast pattern-reversal vep; hassankarimi et al earlier, mc and pc contribute to vep response formation. it has been proven that in the 4c layer in v1, the nerve endings projected by mc and pc axon terminals have significant overlapping. nonselective stimuli activate both magno and parvo systems and give rise to anatomical and functional overlapping.[51, 55] in the present experiment, although stimuli contrast was low, selective spatial frequencies had not been chosen specifically to activate the mc neurons. therefore, neuron activities were not exclusively recorded via vep responses. considering the results of the wavelet analysis, it seems that specific sf activates specific receptive field, and, in addition, other factors are also involved in the response formation mechanisms. in summary, the obtained results indicate that optical information processing is performed through parallel pathways in the visual system. in addition, the visual system can select a dedicated channel for processing of specific information according to different optical properties. this system has distinct spatial and contrast filters, and this filtration is associated with stimulus condition. in conclusion, the authors evaluated the sf effect on prvep features in time, frequency, and time–frequency domains and concluded that the td and dwt approaches are more efficient compared to the fft and psd approaches to detect the impact of sf on the vep parameters at a contrast level of 5%. furthermore, sources, mechanisms, and pathways involved in evoking and processing prvep responses are sf dependent. we suggest further research on more subjects with stimuli of different contrasts, using other wavelet functions. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. hess rf. early processing of spatial form. in: levin la, nilsson sfe, verhoeve j, wu sm, editors. adler’s physiology of the eye. 11th ed. philadelphia: elsevierhealth science division; 2011:613–626. 2. pelli dg, bex p. measuring contrast sensitivity. vis res 2013;90:10–14. 3. shapley r. the importance of contrast in the perception of brightness and form. trans am philos soc 1985;75:20–29. 4. shapley r. the importance of contrast for the activity of single neurons, the vep and perception. vis res 1986;26:45–61. 5. grosvenor t. primary care optometry. 5th ed. st louis: butterworth-heinemann; 2007. 6. elliot db. contrast sensitivity and glare testing. in: benjamin wj, editor. borish’s clinical refraction. 2nd ed. missouri: butterworth-heinemann; 2006:247–288. 7. zemon vm, gordon j. quantification and statistical analysis of the transient visual evoked potential to a contrast-reversing pattern: a frequency-domain approach. eur j nwurosci 2018;48:1765–1788. 8. fahle m, bach m. origin of the visual evoked potentials. in: heckenlively jr, arden gb, editors. principals and practice of clinical electrophysiology of vision. 2nd ed. cambridge: the mit press; 2006: 207–234. 9. odom jv, bach m, brigell m, holder ge, mcculloch dl, mizota a, et al. iscev standard for clinical evoked potentials: (2016 update). doc ophthalmol 2016;133:1–9. 10. mihayloya ms, hristov i, racheva k, totev t, mitov d. effect of extending gratings length and width on human visually evoked potentials. acta neurobiol exp 2015;75:293–304. 11. vassilev a, mihaylova m, bonnet c. on the delay in processing high spatial frequency visual information: reaction time and vep latency study of the effect of local intensity of stimulation. vis res 2002;42:851–864. 12. tobimatsu s, celesia gg. studies of human visual physiopathology with visual evoked potentials. clin neurophysiol 2006;117:1414–1433. 13. shapley r, lenni p. spatial frequency analysis in the visual system. ann rev neurosci 1985;8:547–583. 14. boon my, henry b, suttle cm, dain sj. the correlation dimension: a useful objective measure of the transient visual evoked potential? j vis 2008;8:6. 15. regan d. fourier analysis of evoked potentials: some methods based on fourier analysis. in: desmedt je, editor. visual evoked potentials in man: new developments. oxford: clarendon press; 1977:110–117. 16. norcia am, tyler cw. spatial frequency sweep vep: visual acuity during the first year of life. vis res 1985;25:1399– 1408. 17. tomoda h, celesia gg, toleikis sc. effect of spatial frequency on simultaneous recorded steady-state pattern electroretinograms and visual evoked potentials. electroencephalogr clin neurophysiol 1991;80:81–88. 18. victor jd, mast ja. new statistic for steady-state evoked potentials. electroencephalogr clin neurophysiol 1991;78:378–388. 19. mckeefry dj, russell mha, murray ij, kulikowski jj. amplitude and phase variations of harmonic components in human achromatic and chromatic visual evoked potentials. vis neurosci 1996;13:639–653. 20. boon my, suttle cm, henry b. estimating chromatic contrast thresholds from the transient visual evoked potential. vis res 2005;45:2367–2383. 368 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 low-contrast pattern-reversal vep; hassankarimi et al 21. tobimatsu s, kurita-tashima s, nakayama-hiromatsu m, kato m. effect of spatial frequency on transient and steadystate veps: stimulation with checkerboards, square-wave grating and sinusoidal grating patterns. j neurol sci 1993;118:17–24. 22. tzelepi a, bezerianos t, bodis-wollner i. functional properties of sub-bands of oscillatory brain waves to pattern visual stimulation in man. clin neurophysiol 2000;111:259–269. 23. drissi h, regragui f, antoine jp, bennouna m. wavelet transform analysis of visual evoked potentials: some preliminary results. itbm-rbm 2000;21:84–91. 24. borodina uv, aliev rr. wavelet spectra of visual evoked potentials: time course of delta, theta, alpha and beta bands. neurocomputing 2013;121:551–555. 25. thie j, sriram p, klistorner a, graham st. gaussian wavelet transform and classifier to reliably estimate latency of multifocal visual evoked potentials (mfvep). vis res 2012;52:79–87. 26. zhang jh, janschek k, bohme jf, zeng yj. multiresolution dyadic wavelet denoising approach for extraction of visual evoked potentials in the brain. ieee proc vis image sig proc 2004;151:180–186. 27. sivakumar r, hema b, karir p, nithyaklyani n. denoising of transient vep signals using wavelet transform. j eng appl sci 2006;1:242–247. 28. akbari m, azmi r. automatic classification of visual evoked potentials based on wavelet analysis and support vector machine. proceedings of the 6th international advanced technologies symposium (iats’11); 2011; elaz𝚤ğ, turkey, pp. 227–230. 29. hamzaoui e, regragui f. discrimination of visual evoked potentials using image processing of their time-scale representations. procedia technol 2014;17:359–367. 30. almurshedi a, khamim ismail a, skottun bc, skoyles jr. signal refinement: principal component analysis and wavelet transform of visual evoked response. res j app sci eng technol 2015;9:106–112. 31. quain quiroga r. obtaining single stimulus evoked potentials with wavelet denoising. physica d 2000;145:278–292. 32. hassankarimi h, jafarzadehpur e, mohamadi a, noori smr. advanced analysis of pattern reversal visual evoked potential (prvep) in anisometropic amblyopia. iran j med phys 2018;15:151–160. 33. quian quiroga r, sakowitz ow, basar e, schürmann m. wavelet transform in the analysis of the frequency composition of evoked potentials. brain res protoc 2001;8:16–24. 34. vivo al. quantitative evaluation of shape of visually evoked potentials [dissertation]. lithuania: lithuanian university of health sciences; 2017. 35. vialatte fb, maurice m, dauwels j, cichocki a. steadystate visually evoked potentials: focus on essential paradigms and future perspectives. prog neurobiol 2010;90:418–438. 36. schomer dl, lopes da silva fh. niedermeyer’s electroencephalography: basic principles, clinical applications, and related fields. 6th ed. philadelphia: wolters kluwer health/lippincott williams & wilkins; 2011. 37. ahmad dar j. core concepts in matlab programming; 2017. 1st ed. retrieved from: lulu.com. 38. mallat sg. a wavelet tour of signal processing the sparse way. 3rd ed. houston: academic press; 2009. 39. addison ps. the illustrated wavelet transform handbook: introductory theory and applications in science, engineering, medicine and finance. crc press; 2002;35– 95. 40. misiti m, misiti y, oppenheim g, poggi jm. wavelets and their applications. london: iste ltd.; 2007. 41. souza gs, gomes bd, saito ca, da silva filho m, silveira lcl. spatial luminance contrast sensitivity measured with transient vep: comparison with psychophysics and evidence of multiple mechanisms. invest ophthalmol vis sci 2007;48:3396–3404. 42. tyler cw, apkarian pa. effects of contrast, orientation and binocularity on the pattern evoked potential. vis res 1985;25:755–766. 43. bobak p, bodis-wollner i, guillory s. the effect of blur and contrast on vep latency: comparison between check and sinusoidal and grating patterns. electroencephalogr clin neurophysiol 1987;68:247–255. 44. tumas v, sakamoto c. comparison of the mechanisms of latency shift in pattern reversal visual evoked potential induced by blurring and contrast reduction. electroencephalogr clin neurophysiol 1997;104:96–100. 45. souza gs, gomes bd, lacerda emcb, saito ca, da silva filho m, silveira lcl. contrast sensitivity of pattern transient vep components: contribution from m and p pathways. psychol neurosci 2013;6:191–198. 46. rudvin i, valberg a, kilavik be. visual evoked potentials and magnocellular and parvocellular segregation. vis neurosci 2000;17:579–590. 47. derrington am, lennie p. spatial and temporal contrast sensitivities of neurons in lateral geniculate nucleus of macaque. j physiol 1984;357:219–240. 48. merigan wh, maunsell jhr. how parallel are the primate visual pathways? ann rev neurosci 1993;16:369–402. 49. lee bb. receptive field structure in the primate retina. vis res 1996;36:631–644. 50. schwartz sh. visual perception: a clinical orientation. 4th ed. new york: mcgraw-hill education; 2009. 51. mohammadi a, hashemi h, mirzajani a, yekta a, jafarzadehpur e, valadkhan m, et al. contrast and spatial frequency modulation for diagnosis of amblyopia: an electrophysiological approach. j curr ophthalmol 2018;31:72-79. 52. banks ms, geisler ws, bennett pj. the physical limits of grating visibility. vis res 1987;27:1915–1924. 53. addison p, walker j, guido r. time-frequency analysis of biosignals. ieee eng med biol mag 2009;28:14–29. 54. wu z, wu z. functional symmetry of the primary visual pathway evidenced by steady-state visual evoked potentials. brain res bull 2017;128:13–21. 55. murray ij, plainis s. contrast coding and magno/parvo segregation revealed in reaction time studies. vis res 2003;43:2707–2719. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 369 low-contrast pattern-reversal vep; hassankarimi et al appendix matlab codes code for normalizing the input %normalization range is [-2 2] function [normalized_output] = normalization(input) temp03 = .5 * (max(input) + min(input)); temp04 = .5 * (max(input) – min(input)); input = 2 * (input temp03) / temp04; t05 = isnan(input); input(t05) = 0; t06 = input > 2; input(t06) = 2; normalized_output = input; time domain analysis x = p; y = t; z = x; fs = 1024; % sampling frequency t = 1/fs; % sampling period l = 240; % length of signal t = (0:l-1)*t*1000; % time vector subplot(3,1,1);plot(t,x,’b’); subplot(3,1,2);plot(t,y,’b’); subplot(3,1,3);plot(t,z,’b’);xlabel(’time(ms)’);ylabel(’amplitude (µv)’); frequency domain analysis and power spectral density x = d; fs = 1024; % sampling frequency t = 1/fs; % sampling period l = 240; % length of signal tm = (0:l-1)*t*1000; % time vector subplot(2,2,1);plot(tm,x,’r’); y = fft(x); p2 = abs(y/l); p1 = p2(1:l/2+1); fr = fs*(0:(l/2))/l; subplot(2,2,2);plot(fr,p1); title(’single-sided amplitude spectrum of x(t)’) xlabel(’f (hz)’) ylabel(’|p1(f)|’); m = meanfreq(x,fs); pxx = pwelch(x); subplot(2,2,3);plot(pxx);xlabel(’f (hz)’); 370 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 low-contrast pattern-reversal vep; hassankarimi et al calculate approximation and detail coefficients of discrete wavelet transform data = normalization(b); wname = ’db4’; % wavelet mather functidn name nlevel = 7; % wavelxt decomposition level [c, l] = wavedec(data,nlevel,wname);% wavelet decomposition a7 = appcoef(c,l,wname,nlevel); % approximation coefficients d7 = detcoef(c,l,7); % detail coefficients of level 7 d6 = detcoef(c,l,6); % detail coefficients of level 6 d5 = detcoef(c,l,5); % detail coefficients of level 5 d4 = detcoef(c,l,4); % detail coefficients of level 4 d3 = detcoef(c,l,3); % detail coefficients of level 3 d2 = detcoef(c,l,2); % detail coefficients of level 2 d1 = detcoef(c,l,1); % detail coefficients of level 1 calculate d7 descriptor d7 = d7(1, 6)∧2; power_d7 = sum(d7.∧2); pd7 = d7/power_d7 *100; journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 371 perspective need for nurse practitioner fellowships in ophthalmology in the usa vishwani persaud-sharma, dnp, arnp-bc, msbme, mmsc; mary a. hooshmand, phd, msn, rn school of nursing and health studies, university of miami, miami, fl, usa orcid: vishwani persaud-sharma: https://orcid.org/0000-0002-6872-9004 abstract medical attention to vision impairment and associated eye care complications are a vital component of daily living and overall well-being. in the united states today, the physician to patient deficit places great strain on the availability of medical attention tenable to patients nationwide; in terms of specialty medicine, this deficit is even more widespread. the field of ophthalmology faced the same physician to patient deficit in 2020, a grim reality that has left many states void of ophthalmic care, rending millions of aging individuals without domestic eye care. the implementation of trained, ophthalmic nurse practitioners (nps) can fill the needs of this deficit; however, efficient, accredited, and board-approved american ophthalmic fellowships and residencies that secure proper ophthalmic np transitions from academia to clinical practice are nonexistent. though scant, evidence-based literature presents sound findings that support the efficacy and benefit for superior patient outcomes with care provided by ophthalmictrained nps, offering a viable, long-term solution to the need for ophthalmic medical providers across all states without mitigating patient care, emphasizing the great need for the implementation of ophthalmic np residencies and fellowships to ensure the continuity of impeccable ophthalmic care for all populations. keywords: fellowships; nurse practitioner; ophthalmology; post-graduate training; residency; united states j ophthalmic vis res 2021; 16 (1): 113–121 introduction to date, there exists a severe shortage of eye care providers that perpetuates unnecessary correspondence to: vishwani persaud-sharma, dnp, arnp-bc, msbme, mms. university of miami, school of nursing and health studies, 5030 brunson drive, coral gables 33146, fl, usa. e-mail: v.persaudsharma@miami.edu received: 17-08-2020 accepted: 13-12-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8257 vision impairment and blindness in developing and developed countries worldwide.[1] in the united states (us) and according to the association of american medical colleges (aamc), america will observe a physician shortage of approximately 122,000 by the year 2032.[2] the current physician shortage is pragmatic in primary care services, which is projected to rise due to the evergrowing population and increasing population this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: persaud-sharma v, hooshmand ma. need for nurse practitioner fellowships in ophthalmology in the usa. j ophthalmic vis res 2021;16:113–121. © 2021 persaud-sharma et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 113 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8257&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr nurse practitioner fellowships in ophthalmology; persaud-sharma et al age, estimated to account for 81% of the total population from 2010 to 2020.[3] specialty shortages also form a significant disparity in provider healthcare, where the projected medical specialist dearth rates are projected to fall between 1,900 and 12,100; the projected surgical specialist shortage is approximated to fall between 14,300 and 23,400, while other specialists like neurologist, pathologists, psychiatrists, and radiology specialists can anticipate a shortage of 20,600 to 39,100 by the fiscal year of 2032.[2] specifically, a total deficit of 45,400 primary care physicians and 46,100 medical specialists, a grand total of 91,500 medical doctors will be needed in the fiscal year of 2020 alone.[4] recent data acquired in 2020, post onset of the covid-19 pandemic, projects the physician shortage to dramatically worsen by 2033; in (i) primary care, the physician shortage will range from 21,400 to 55,200 physicians, (ii) in non-primary care specialties, the shortage will fall between 33,700 and 86,700 physicians, (iii) in surgical specialties, the shortage will be between 17,100 and 28,700 physicians, (iv) in medical specialties, the shortage will be between 9,300 and 17,800 physicians, and finally (v) in other specialties such as radiology, pathology, and psychiatry, there will be a 17,100 to 41,900 physician shortage.[5, 43] the cumulative need for physicians in the us emphasizes the roles of primary care nurse practitioner (np) and physician assistant (pa) workforces, which is anticipated to grow at a greater rate compared to physician supply; the supply of the primary care nps is expected to see a 30% increase, where primary care pas are expected to increase by 58% through 2020.[3] more recently, the 2019 role of the np has grown by over 270,000 in the us, as patients are now benefiting more than ever from comprehensive, high-quality, patient-centered healthcare services governed and provided exclusively by nps.[2] additionally, an aamc study analyzing the effective use of the np and pa workforce to compensate for the growing healthcare provider paucity projected a potential physician shortage decrease of 42,600 to 121,300 by 2030.[6] through the effective integration of advanced practice clinicians (apcs) in the medical field, the projected deficit of primary care physicians can decrease to 6,400.[3] studies conducted by spetz et al[7] and hoff et al[8] illustrate the positive patient perception and care provided by apcs in diverse patient populations including primary care and medical specialties. comparative studies conducted by jiao et al[9] detail the relative comparability of ambulatory prescribing among physicians and apcs alike. while hooker et al[10] delineates the different characteristics among apcs, nps have been specifically noted to fully utilize their apc skills, practice to the maximum capacity of their legal scope, are satisfied with their careers, and plan to stay in their jobs log-term, all while reporting greater practice autonomies.[7] in specialty fields, trends assessed by ray et al[11] acknowledge the lack of research addressing apc involvement in medical specialties. it was concluded that patient visits involving apcs in surgical and medical specialties increased from 3.3% between 2001 and 2003 to 6.9% between 2010 and 2013, lending credit to the effectiveness and increasing need of apc visits in specialty medicine.[11, 12] effective use of apc practice in specialties are further bolstered and defined by the implementation of apc fellowships and residencies, facilitating adequate transition into specialized medical care. additionally, education and training not only strengthen and develop the capabilities of global eye healthcare and the world health organization development goals in a sustainable way, but they also direct focus and bolster the skills and efficacy of ophthalmic providers in the us to ensure quality and precision care, while addressing the need for qualified and superiorly trained specialty eye care providers, a void that can be fulfilled by ophthalmic nps.[1] the purpose of this article is to draw attention to the need for nurse practitioner fellowships in the us with specific attention to np fellowships and residencies in specialty medicine like ophthalmology. the importance of np fellowships in the us the terms fellowship and residency are used synonymously in apc literature.[13] generally, medical and pharmacy fellowship and residency programs serve to provide adequate transition of the new healthcare practitioner from academia to clinical practice; the apc transition is no different, especially in specialty practices.[14] both pa and np accreditation bodies have established postgraduate training models governed by the (i) accreditation review commission on education for physician assistant (arc-pa) and 114 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 nurse practitioner fellowships in ophthalmology; persaud-sharma et al (ii) the american nurses credentialing center (ancc) and national nurse practitioner residency and fellowship training consortium, respectively.[15] as of 2007, 60 apc postgraduate training programs were functional in the us, with primary attention toward surgical specialties.[15] as of 2019, there existed 145,585 certified nps in the us; clinical areas of field certification include acute care, adult care, adult psychiatric-mental health, gerontology acute care, gerontology primary care, diabetes management, family medicine, pediatrics, psychiatric-mental health across lifespan, school nps, and emergency medicine.[16] while the np scope of practice is discussed at length by hudspeth and klein,[17] it is important to underscore the recent legislative changes that now enable more nps to practice autonomously in the majority of the states in the us. according to park et al,[18] greater np practice autonomy was attributed to full, independent prescriptive authority, whereas having independence governing medical diagnoses and treatment regimens only moderately affected prescriptive independence. such results indicate that expanded state np practice regulations correlated with an increase in np supply and greater access to care among rural and underserved populations deprived of a decrease in care quality.[19] recent literature directly affirms and correlates np autonomy and favorable relationships with leadership improves teamwork in the clinical provider workforce.[42] additionally, there is a clear correlation between interdisciplinary teams and better patient outcomes; interdisciplinary teams within clinical practice effectively facilitates teamwork, intercollegiality, and superior clinical provider and leadership relationships, which yield better care outcomes.[21–23] finally, a study conducted by poghosyan et al[20] also affirms and provides tangible evidence that np–physician teamwork directly affected clinician job satisfaction, intent to leave, and perceived quality of care within a given medical practice. though there are many facilitators and barriers that both aid and negate effective and confident np workforce transition, the implementation of np fellowships can serve as a platform to sustain effective shifts from the academic to clinical platform; facilitators like the establishment of mentorship, social support, meaningful work, and work–life balance as well as barriers to np workforce transition such as lack of support, role ambiguity, and workload exists have been founded to impede and bolster this process, a challenge that can be resolved by np fellowship implementation.[24] according to bryant and parker,[25] participation in a nurse practitioner fellowship instills greater confidence, job satisfaction, and increased job retention through the transition from novice to expert clinician; as a result, continued provision of np fellowships facilitate superior clinical practice leading to greater patient outcomes provided by nps. while nps are noted to deliver cost-effective, high-quality medical care that addresses the need for medical providers, graduate education often lacks specialized postgraduate fellowships, resulting in the acquisition of on-the-job training.[26] with emerging research highlighting the need for np fellowships across us specialty disciplines, kesten and el-banna[27] found that over 90% of program directors state an increase in np recruitment and retention following np fellowship implementation. additionally, the majority of decision-makers favor np fellowship implementation with few to no barriers and 84% of physician and administrative support and favor fellowship/residency acquisition.[27] np fellowships and residencies in specialties – what is known? as of 2016, more than 30 postgraduate fellowships are available for masters and doctorly prepared nps to enhance their teaching, clinical outcomes, advocacy, and research abilities.[13] a total of 68 active np fellowships and residencies were identified by martsolf et al[28] in the us, where 45.6% of programs were self-defined as residencies and 54.5% self-defined as fellowship programs. the average postgraduate np fellowships varied from 12 to 24 months in duration and offered predominantly full-time status with competitive salaries and benefits.[28] np fellowship salaries averaged $60,000 usd, with the highest noted at over $100,000 usd; some programs reported a salary of <$50,000 usd, whereas other fell within the $50,000 to $60,000 usd range.[28] in terms of admission requirements, 79.4% of the 68 np postgraduate programs required a state np license, 67.7% required a disciplinespecific certificate, 51.5% targeted new graduates, journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 115 nurse practitioner fellowships in ophthalmology; persaud-sharma et al 22.1% required additional certification specific to the program, 51.5% required an np specific degree such as pediatric or family np, and 17.7% required a drug enforcement agency number (dea).[28] performance and effect of increased ability, patient satisfaction, and quality of care are further evaluated in detail by hoff et al[8], kesten and el-banna,[27] sciacca and reville,[13] and spetz et al.[7] examples of recent specialty np fellowships successfully implemented within the last five years are depicted in table i, in the fields of oncology,[26] palliative care,[29] emergency medicine,[30] and neurology.[31] predominant np fellowship and residencies offered throughout the us to date are distributed disparately throughout each state, where some states do not offer any np fellowship programs whatsoever. np fellowships and residencies predominate in advanced practice, advanced practice nursing, acute adult care, cardiology, critical care, diabetes, dermatology, emergency medicine, family nurse practitioner, gastroenterology and hepatology, geriatric, neuroscience/neurology, oncology, orthopedic, palliative care, pediatrics, surgical, and wound reconstruction among other variations based on demographic and state need; however, there is no np ophthalmology fellowship or residency available to date.[32] defining the need for np fellowships in ophthalmology as a clear delineation circumscribes the countless benefits provided by np health services in the medical profession in terms of physician deficit burden, patient outcomes, and quality of care, clinical efficiency is bolstered through the implementation of np fellowships, especially in specialty medicine.[25, 27] to date, there is minute to no literature that supports the need to establish an np fellowship in the specialty field of ophthalmology. the value of advanced practice ophthalmology nursing while the physician to patient burden is prevalent in all medical disciplines, there is paralleled heightened urgency in the field of ophthalmology; by the year 2020 compared to 2000, the total population to ophthalmologist ratio has increased by 15% with a projected increase over time.[33] such a shift in demand can be largely attributed to the increase in the elderly population, who heavily rely on ophthalmic services, drawing attention to the need for additional ophthalmology health providers.[33] as illustrated by browning,[33] there are three predominant methods to address the need gap in ophthalmology care, namely (i) increase the number of ophthalmology providers, (ii) enable current and future ophthalmologists to work more hours, or (iii) institute and effectively utilize apcs in the field of ophthalmology. historically, an average of 52 pas were employed by ophthalmologists by 1990; that number has since increased to 70 as of the fiscal year 2015.[33] established duties known to ophthalmology pas include preoperative histories and physical exams for large cataract and refractive surgery; however, browning[33] states that pas can do more such as take call, conduct clinical work-in visits, perform intravitreal injections (ivts) for retinal specialties, and operate dry eye clinics. as effective as pa duties are in ophthalmology, the role of the np is even more so, making nps an invaluable addition to the field of ophthalmology. from a financial perspective, moore and barr[34] further define the potential resolution of bridging the ophthalmology physician deficit burden with the use of apcs, optometrists, faculty ophthalmologists, and resident ophthalmologists. though a detailed overview approximated the average salary and benefit wages to be $126,797, $117,021, $338,233, and $71,210, respectively, the study concludes that while the use of ophthalmology residents to address the ophthalmologist shortage is more cost-effective, they do not directly produce work relative value; therefore, long-term implementation of resident ophthalmologists to address the need is not a viable long-term solution.[34] advanced practice nps are educated to provide competent, independent, autonomous patient care; they have the ability to manage their own health clinics and provide adequate and efficient healthcare for their own governing patient populations.[35] advanced practice nps have the ability to adjust, expand, and integrate practical skills, and evidence-based research into patient care regimes to meet the demands and expectations of patients, governing bodies, and stakeholders.[35] in terms of ophthalmic medicine, 116 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 nurse practitioner fellowships in ophthalmology; persaud-sharma et al table 1. examples of us np fellowships across medical specialties in the past 5 years citation country program type model aim outcome alencar et al, 2018[26] usa arnp oncology fellowship arnp model define the need for arnp fellowship in oncology 1. structured arnp fellowships in oncology facilitate training, mentorship, and retention 2. implementing new np oncology fellowship lead to increased patient care, job and staff satisfaction dahlin et al, 2019[29] usa hospice & palliative care aprn fellowship hpna aprn fellowship guidelines detail aspects of six palliative aprn fellowships 1. aprn fellowship improved patient outcomes hardeman & hough, 2017[31] usa aprn and pa fellowship in neurology arnp and pa model define need for advanced practice practitioner fellowship in neurology 1. need for apc in neurology backed by statistics that reflects high patient burden 2. app neuro fellowship will train, retain, and ease neuro clinician shortage 3. app more costeffective, better patient outcomes gaudio & borensztein, 2018[30] usa arnp emergency medicine residency arnp model define the need for arnp residency in emergency medicine 1. increased enp self and job satisfaction 2. increased enp competency 3. stronger clinical foothold in em the benefits of ophthalmology np implementation is no different. ophthalmic np duties ophthalmology nps have the ability to evaluate, diagnose, treat, and discharge patients with ocular disorders.[35] they have the ability to manage care for referred patients from general and primary care providers, conduct baseline screenings, monitor disease development and outcomes, and treat chronic ocular conditions such as diabetic retinopathy, dry eyes, and glaucoma among other ocular disorders.[35] in terms of surgical care, ophthalmic nps can conduct initial, followup, and discharge assessments and education for ophthalmic surgery patients diagnosed with cataract among other ocular disorders; they can also manage care on a broad spectrum, from children to adults to the older adults.[35] additionally, ophthalmic nps can perform minor ophthalmic procedures autonomously without physician supervision, such as adnexal surgery and assisting in ophthalmic surgeries like yag laser capsulotomies.[35] tangible evidence of successful ophthalmology np implementation to date, there is currently one study that documents the successful implementation of a single pa into an ophthalmology consulting service in an academic setting; the purpose was to improve resident education with an outcome journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 117 nurse practitioner fellowships in ophthalmology; persaud-sharma et al of improved ophthalmic resident education facilitated by a pa overall.[36] the implementation of advanced practice nps into an ophthalmology clinic dates back to 2007, a case study that documents an ophthalmology np effectively providing np-led consultation services to a diabetic retinopathy patient in wales.[37] harty[37] clearly delineates the value of the ophthalmic nps in a patient’s most vulnerable state and reiterates the fact that if no ophthalmic np serves were provided, the patient would have suffered additional, unnecessary trauma and anguish potentially leading to blindness. a literature review complied by drury et al[38] of australia documents the effectiveness of advanced practice ophthalmology nps, indicating that while the majority of nurse-led ophthalmology clinics are supervised by ophthalmologists, there are many autonomous clinical skills performed by the ophthalmic np such as slit lamp examinations, fundus examinations via direct ophthalmoscope use, optic disc assessment, and anterior segment assessments.[38] additionally, drury et al[38] highlighted the variability in ophthalmic np training, stating that two documented studies delineated the training of ophthalmic np-led clinics who held a master’s degree with postgraduate training in pharmacology and extensive anterior segment training. such services are meant not to facilitate replacement of the ophthalmologist yet render adjunct ophthalmic services to shorten waiting lists and allow providers to spend more time caring for complex patient needs.[38] finally, in a scottish study by gallagher et al,[39] an advanced ophthalmic np delineated the effective and suitable implementation of ophthalmic nps in ivt clinics given their training and experience; demonstrating np expansion in the ophthalmic discipline in terms of ivt, macular assessment and follow-up, and effective patient care and outcomes for those diagnosed with age-related macular degeneration, macular edema-associated diabetic retinopathy, and retinal vein occlusion. findings of the study indicate that most of the polled ophthalmic population found the delivery of ivt provided by an ophthalmic np to be more educating, receptive to questions, and patient centered.[39] additionally, patients did not mind ivt delivery performance via a trained, ophthalmic np versus a physician, and of those who objected to ivt via an np over a physician cited concern for decreased training and experience to deal with consequential problems as the primary mode of concern.[39] summary: us ophthalmology np fellowships, it is needed. what now? to date, there are no established ophthalmology np fellowships recorded within the past 10 years in the us. given the increasing physician deficit to increased population burden that is echoed in the discipline of ophthalmology, the time for apc implementation in ophthalmology has arrived.[33] the importance of apc provider healthcare is boundless; with increased autonomy in the us for nps across various states; nps offer a costeffective, efficient, and patient-centered option to providing medical care across demographics and socioeconomically challenged populations. in an effort to standardize and direct the role of the np, the aprn consensus work group and national state boards of nursing formed the 2008 consensus model, mandating nps to obtain a proper education with a graduate degree or postgraduate certification from an accredited university among other requirements.[12] over time, np schooling requirements, clinical knowledge, and patient practicums have developed more rigorously to ensure efficacy of care provided. while the acquisition of postgraduate apc fellowships or residences are sparse, participation in accredited programs bolster the skillset, mental acuity, and evidence-based care provided to the given, served population. they function to bridge the gap in clinical practice among apcs.[15] it is here that the apc learns to transition their academic knowledge to the clinical setting in a safe, supervised, and directed platform. favorable outcomes of such programs have been noted to augment care, where patients feel reassurance in knowing that the apc underwent rigorous and accredited educational standards to ensure their privilege at the bedside as a medical care provider. as stated by cosme,[14] continued growth of residency and fellowship programs for apcs are needed in order to meet the growing demand of healthcare needs in terms of patient safety and decreased reimbursement; continued growth will safeguard increased selfreflection and drive research that will better both medicine and healthcare consumers as a whole. additionally, participating in a postgraduate np 118 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 nurse practitioner fellowships in ophthalmology; persaud-sharma et al training program, residency, or fellowship aids in the creation of valuable members of the healthcare team that can function during rapid changes in the american healthcare system.[13] moreover, participating in apc postgraduate residencies or fellowships aids to calm the anxiety associated with the transition from academia to clinical practice, all while obtaining supervised training and expert mentorship.[13] current ophthalmology statistics underscore the need and shortage of ophthalmologists, where 61% of americans had no ophthalmologist in 2011; a shift in population distribution toward an aging population surmises the need for ophthalmic services across the country.[33] while there are many solutions to bridging the need for ophthalmic physicians such as working longer hours and expanding medicare, the use of apcs can bridge the deficit.[33] although initial studies emphasized the efficacy of trained pas in ophthalmology, nps are equally if not more viable in terms of trainability, clinical experience, cost, and clinical background, making nps highly suitable for ophthalmic care following the successful completion of an accredited ophthalmology residency or fellowship. in terms of ophthalmology apcs, studies prove that successful postgraduate training for advanced practice nps in the field of ophthalmology enable efficient patient care in the various aspects of ophthalmic care.[37–39] as described by drury et al,[38] following np ophthalmic-specific training, nurse-led ophthalmic clinics successfully functioned to enable nps to complete common ophthalmic practice such as slit lamp exams, direct ophthalmoscope fundus examinations, optic disc assessments, and anterior segment assessments among other critical techniques and practices needed for independent ophthalmic assessment, care, and treatment. additionally, ophthalmology simulations offer cost-effective, heighted accessibility, objective ophthalmology training outcomes, and improved patient safety initiates to effectively train apcs with specific attention to nps in the specialty field of ophthalmology.[1] as current practices in the us do not facilitate ophthalmic fellowships or residencies, the purpose of this article was to delineate the need and benefit for immediate implementation. although the np workforce transition can be rigorous at times, there are many strategies that can facilitate the effective transition of the np into a proper clinician and leadership role; self-initiative, mentorship, experiential learning, professional socialization, and interprofessional training are effective and proven methods that facilitate operative, sustainable, and substantial clinician– patient relationships in an effort to provide superior patient care, methods that are absolutely critical and effective in molding impeccable ophthalmic nps.[40, 41] the primary objective of specialized postgraduate ophthalmic np fellowships would be to educate and train nps to be fast, logical thinkers under pressure and during emergent situations; decisions should compile assessment and utilization of prior studied information for accurate situation evaluation, all while rationalizing best patient outcomes, just as us physicians undergo in post-medical school residencies.[35] as martsolf et al[28] describes, the need to establish np ophthalmology fellowships coincides with the institute of medicine’s seminal report that urges the state boards of nursing, accrediting bodies, the federal government, and healthcare organizations to enact methods that support nurses’ completion of a transition-to-practice program, such as a residency or fellowship, after completing prelicensure, advanced practice degrees, or when transitioning into new clinical practice areas. the need for ophthalmology np fellowships in the us is clear; the time for establishment is now. acknowledgements the primary author would like to acknowledge the dnp clinical director for the college of nursing at the university of miami for their support throughout this process. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. flanagan jl, de souza n. simulation in ophthalmic training. asia pac j ophthalmol 2018;7:427–435. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 119 nurse practitioner fellowships in ophthalmology; persaud-sharma et al 2. aamc. new findings confirm predictions on physician shortage [internet]. aamc; 2019 [cited 2020 nov]. available from: https://www.aamc.org/news-insights/ press-releases/new-findings-confirm-predictionsphysician-shortage 3. hrsa health workforce. national and regional projections of supply and demand for primary care practitioners: 2013–2025 [internet]. health resources and services administration; november 2016. available from: https://bhw.hrsa.gov/sites/default/files/bureauhealth-workforce/data-research/primary-care-nationalprojections-2013-2025.pdf 4. kirch dg, henderson mk, dill mj. physician workforce projections in an era of health care reform. annu rev med 2012;63:435–445. 5. association of american medical colleges. new aamc report confirms growing physician shortage [internet]. aamc; 2020. available from: https: //www.aamc.org/news-insights/press-releases/newaamc-report-confirms-growing-physician-shortage 6. zhang x, lin d, pforsich h, lin vw. physician workforce in the united states of america: forecasting nationwide shortages. hum res health 2020;18:8. 7. spetz j, skillman sm, andrilla cha. nurse practitioner autonomy and satisfaction in rural settings. med care res rev 2017;74:227–235. 8. hoff t, carabetta s, collinson ge. satisfaction, burnout, and turnover among nurse practitioners and physician assistants: a review of the empirical literature. med care res rev 2019;76:3–31. 9. jiao s, murimi ib, stafford rs, mojtabai r, alexander gc. quality of prescribing by physicians, nurse practitioners, and physician assistants in the united states. pharmacotherapy 2018;38:417–427. 10. hooker rs, brock dm, cook ml. characteristics of nurse practitioners and physician assistants in the united states. j am assoc nurse pract 2016;28:39–46. 11. ray kn, martsolf gr, mehrotra a, barnett ml. trends in visits to specialist physicians involving nurse practitioners and physician assistants, 2001 to 2013. jama intern med 2017;177:1213. 12. niebruegge b, holbrook jm, vernon c, grotton c, maric a. the future of population medicine: investigating the role of advanced practice providers and simulation education in special patient populations. dis mon 2019;65:221–244. 13. sciacca k, reville b. evaluation of nurse practitioners enrolled in fellowship and residency programs: methods and trends. j nurse pract 2016;12:e275–e280. 14. cosme s. residency and fellowship programs for rns and advanced practice rns. j nurs adm 2015;45:416–417. 15. klimpl d, franco t, tackett s, cardin te, wolfe b, wright s, et al. the current state of advanced practice provider fellowships in hospital medicine: a survey of program directors. j hosp med 2019;14:401–406. 16. ancc. 2019 ancc certification data [internet]. nursingworld.org; 2019 [cited 2020, nov 20]. available from: https://www.nursingworld.org/~49a2df/ globalassets/docs/ancc/ancc-cert-data-website.pdf 17. hudspeth rs, klein ta. understanding nurse practitioner scope of practice: regulatory, practice, and employment perspectives now and for the future. j am assoc nurse pract 2019;31:468–473. 18. park j, athey e, pericak a, pulcini j, greene j. to what extent are state scope of practice laws related to nurse practitioners’ day-to-day practice autonomy? med care res rev 2018;75:66–87. 19. yang bk, johantgen me, trinkoff am, idzik sr, wince j, tomlinson c. state nurse practitioner practice regulations and us health care delivery outcomes: a systematic review. med care res rev 2020;1077558719901216. 20. poghosyan l, ghaffari a, liu j, friedberg mw. physiciannurse practitioner teamwork in primary care practices in new york: a cross-sectional survey. j gen intern med 2020;35:1021–1028. 21. bower p, campbell s, bojke c, sibbald b. team structure, team climate and the quality of care in primary care: an observational study. qual saf health care 2003;12:273– 279. 22. linzer m, manwell lb, williams es, bobula ja, brown rl, varkey ab, et al. working conditions in primary care: physician reactions and care quality. ann intern med 2009;151:28–36, w6–w9. 23. grumbach k, bodenheimer t. can health care teams improve primary care practice? jama 2004;291:1246– 1251. 24. faraz a. facilitators and barriers to the novice nurse practitioner workforce transition in primary care. j am assoc nurse pract 2019;31:364–370. 25. bryant s, parker k. participation in a nurse practitioner fellowship to instill greater confidence, job satisfaction, and increased job retention. j am assoc nurse pract 2020;32: 645–651. 26. alencar mc, butler e, macintyre j, wempe ep. nurse practitioner fellowship: developing a program to address gaps in practice. clin j oncol nurs 2018;22:142–145. 27. kesten ks, el-banna mm. facilitators, barriers, benefits, and funding to implement postgraduate nurse practitioner residency/fellowship programs. j am assoc nurse pract [preprint] 2020. 28. martsolf gr, nguyen p, freund d, poghosyan l. what we know about postgraduate nurse practitioner residency and fellowship programs. j nurse pract 2017;13:482–487. 29. dahlin c, wholihan d, johnstone-petty m. palliative aprn fellowship guidelines—a strategy for quality specialty practice: report of the hpna aprn fellowship council (th300). j pain symptom manage 2019;57:363. 30. gaudio fg, borensztein r. an emergency medicine residency for nurse practitioners: the new york presbyterian–weill cornell medicine experience. adv emerg nurs j 2018;40:119–126. 31. hardeman p, hough r. integration of advanced practice clinicians in neurology practices. jama neurol 2017;74:894–895. 32. graduatenursingedu.org. residency programs for nurse practitioners [internet]. graduatenursingedu.org; 2013 [cited 2020, nov 20]. available from: https: //www.graduatenursingedu.org/nurse-practitionerresidency-programs/ 33. browning dj. physician assistants and nurse practitioners in ophthalmology—has the time come? am j ophthalmol 2018;186:ix–xi. 34. barr w, moore d. the relative financial cost and benefit of an ophthalmology resident compared to an advanced 120 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 https://www.aamc.org/news-insights/press-releases/new-findings-confirm-predictions-physician-shortage https://www.aamc.org/news-insights/press-releases/new-findings-confirm-predictions-physician-shortage https://www.aamc.org/news-insights/press-releases/new-findings-confirm-predictions-physician-shortage https://bhw.hrsa.gov/sites/default/files/bureau-health-workforce/data-research/primary-care-national-projections-2013-2025.pdf https://bhw.hrsa.gov/sites/default/files/bureau-health-workforce/data-research/primary-care-national-projections-2013-2025.pdf https://bhw.hrsa.gov/sites/default/files/bureau-health-workforce/data-research/primary-care-national-projections-2013-2025.pdf https://www.aamc.org/news-insights/press-releases/new-aamc-report-confirms-growing-physician-shortage https://www.aamc.org/news-insights/press-releases/new-aamc-report-confirms-growing-physician-shortage https://www.aamc.org/news-insights/press-releases/new-aamc-report-confirms-growing-physician-shortage https://www.nursingworld.org/~49a2df/globalassets/docs/ancc/ancc-cert-data-website.pdf https://www.nursingworld.org/~49a2df/globalassets/docs/ancc/ancc-cert-data-website.pdf https://www.graduatenursingedu.org/nurse-practitioner-residency-programs/ https://www.graduatenursingedu.org/nurse-practitioner-residency-programs/ https://www.graduatenursingedu.org/nurse-practitioner-residency-programs/ nurse practitioner fellowships in ophthalmology; persaud-sharma et al practice provider, optometrist, or faculty ophthalmologist. j acad ophthalmol 2018;10:e185–e188. 35. moradi m. importance of ophthalmic nursing in primary healthcare systems. med hypothesis discov innov ophthalmol 2016;5:1–3. 36. lee b, d’souza m, singman el, wang j, woreta fa, boland mv, et al. integration of a physician assistant into an ophthalmology consult service in an academic setting. am j ophthalmol 2018;190:125–133. 37. hartry n. a reflective case for valuing nurse practitioners in ophthalmology clinics. br j nurs 2007;16:1234–1237. 38. drury v, aw at, lee ahs. an integrative literature review of the effectiveness of nurse-led clinics in ophthalmology. insight 2017;42:22–28. 39. gallagher m-j. introduction of a nurse-led intravitreal injection service in ophthalmology. br j nurs 2017;26:800–803. 40. speight c, firnhaber g, scott es, wei h. strategies to promote the professional transition of new graduate nurse practitioners: a systematic review. nurs forum 2019;54:557–564. 41. thomassen a. fellowship programs: reflections of an advanced practice nurse fellow. clin j oncol nurs 2018;22:383–385. 42. poghosyan l, liu j. nurse practitioner autonomy and relationships with leadership affect teamwork in primary care practices: a cross-sectional survey. j gen intern med 2016;31:771–777. 43. bureau of health workforce. projecting the supply and demand for primary care practitioners through 2020. bureau of health workforce; 2016. available from: https://bhw.hrsa.gov/health-workforce-analysis/primarycare-2020 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 121 https://bhw.hrsa.gov/health-workforce-analysis/primary-care-2020 https://bhw.hrsa.gov/health-workforce-analysis/primary-care-2020 original article amniotic membrane transplantation for persistent epithelial defects and ulceration due to pseudomonas keratitis in a rabbit model mohammad mehdi soltan dallal1,2, phd; farhad nikkhahi3, phd; seyed mostafa imeni4, phd saber molaei5, md; seyed kazem hosseini6, ms; zohreh kalafi2, ms; sara sharifi yazdi7, md hedroosha molla agha mirzaei8, ms 1division of microbiology, department of pathobiology, school of public health, tehran university of medical sciences (tums), tehran, iran 2food microbiology research center, tehran university of medical sciences, tehran, iran 3medical microbiology research center, qazvin university of medical science, qazvin, iran 4biodiversitat, ecología, technologia ambiental i alimentaria )beta tech center(, (tecnio network), u science tech, university of vic-central university of catalonia, carrer de la laura 13, 08500 vic, spain 5aja university of medical sciences, tehran, iran 6quality control manager of iranian tissue bank research & preparation center, director of stem cells preparation unit, tehran university of medical sciences, tehran, iran 7school of medicine, tehran university of medical sciences (tums), tehran, iran 8food microbiology research center, tehran university of medical sciences, tehran, iran orcid: mohammad mehdi soltan dallal: https://orcid.org/0000-0002-3421-3974 abstract purpose: the use of amniotic membrane has been suggested in the treatment of infectious keratitis for its intrinsic anti-infective properties probably mediated by its antiinflammatory effects. the aim of this study was to investigate the effect of amniotic membrane transplantation (amt) along with ciprofloxacin to cure the primary stages of pseudomonas keratitis. methods: in total, 28 rabbits were selected and divided in four groups as follows: group 1 as control, group 2 with amniotic membrane, group 3 with ciprofloxacin, and group 4 with amniotic membrane combined with ciprofloxacin. about 0.05 cc suspension of pseudomonas aeruginosa, 27853 atcc was injected into corneal stroma. results: the results showed groups of amt, amt + ciprofloxacin, and ciprofloxacin had 0% perforation while the control group had 85.6%. average infiltration of 5.5 mm was observed in ciprofloxacin group, 5 mm in amt + ciprofloxacin group, 24 mm in amt group, and finally 23.75 mm for control. amniotic membrane showed to be effective in prevention of cornea perforation as well as remission of pseudomonas keratitis. there was no significant difference between ciprofloxacin groups in comparison with ciprofloxacin + amt group. however, regarding the anti-inflammatory effect, the process of improvement of inflammation in ciprofloxacin + amt group was faster. conclusion: transplantation of amniotic membrane in the primary stages of pseudomonas keratitis treatment remarkably prevents the disease and it can be used to control its process. keywords: ciprofloxacin; human amniotic membrane; keratitis; pseudomonas aeruginosa; rabbit j ophthalmic vis res 2021; 16 (4): 552–557 552 © 2021 soltan dallal et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9744&domain=pdf&date_stamp=2019-07-17 amt for rabbit model of keratitis; soltan dallal et al introduction human amniotic membrane (am) forms the inner wall of the membranous sac that surrounds and protects the embryo during gestation. it consists of a single layer of ectodermally derived columnar epithelial cells attached to a basement membrane with an underlying layer of mesenchyme.[1] amniotic membrane transplantation (amt) is widely used in various ocular surface diseases such as neurotrophic keratitis and persistent epithelial defects,[2, 3] band keratopathy,[4] bullous keratopathy,[5, 6] after excimer laser photorefractive keratectomy,[7, 8] after the excision of a conjunctival mass,[9, 10] pterygium,[11, 12] ocular surface reconstruction in symblepharon,[13, 14] acute chemical injury,[15, 16] and a chronic limbal deficiency.[17, 18] when used as a graft (epithelial side up), am is expected to become incorporated in the recipient tissue. if it is used as a patch (epithelial side down), it works as a biological bandage affording a cover for a limited duration or a combination of these. the use of am has been also suggested in the treatment of infectious keratitis because of its intrinsic anti-infective properties probably mediated by its anti-inflammatory effects and because am may act as a long-term drug delivery system.[19–21] the antimicrobial effects of am have been demonstrated against several species such as escherichia coli, group a streptococci, pseudomonas aeruginosa, and staphylococcus aureus.[22, 23] am graft for epithelial reformation has been employed in order to eradicate the p. aeruginosa infection of keratitis and have exhibited desirable outcomes.[24] the aim of the current study was to investigate the effect of amt along with ciprofloxacin to cure the primary stages of pseudomonas keratitis. correspondence to: mohammad mehdi soltan dallal, phd. food microbiology research center (fmrc)/division of food microbiology, department of pathobiology, school of public health, tehran university of medical sciences (tums), tehran 6446-14155, iran. e-mail: soltanda@sina.tums.ac.ir/ msoltandallal@gmail.com received: 13-11-2020 accepted: 21-05-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9744 methods all experiments were carried out in accordance with the uk animals (scientific procedures) act, 1986 and associated guidelines, eu directive 2010/63/eu for animal experiments. in addition, this study is certified by accreditation research ethics national committee with issue code of ir.tums.rec.1394.2091. in total, 28 male rabbits with an average weight of 1.5–2 kg were selected. the am was prepared according to song and kim method.[25] human placenta was obtained after an elective caesarean section in a woman who was seronegative for human immunodeficiency virus, hepatitis b, c, and syphilis. under a lamellar flow hood, the placenta was first washed free of blood clots with sterile saline. the inner am was separated from the rest of the chorine by blunt dissection and flattened onto a nitrocellulose membrane.[26] the membrane with the filter was then washed three times with phosphate buffered saline (pbs) containing 50 μg/ml penicillin, 50 μg/ml streptomycin, and 2.5 μg/ml amphotericin b and put in m199 culture for 24 hr with antibiotic solution including streptomycin, cloxacillin, ceftriaxone, and amphotericin b, and finally packed in pieces of 1.5×1.5 in three of sterilized nylon and stored in –80ºc in freezer. twenty-eight rabbits were divided into four groups as follows: group 1 as control group [figure 1a], group 2 as am [figure 1-b], group 3 as ciprofloxacin [figure 1c], and group 4 as am combined with ciprofloxacin [figure 1d]. the rabbits were anesthetized with intramuscular injection of ketamine hydrochloride (30 mg/kg) and xylazine hydrochloride (5 mg/kg) and then a drop of tetracaine hcl 0.5% was applied to the rabbits’ right eye. about 0.05 cc suspension of p. aeruginosa 27853 atcc was injected into corneal stroma with a sterile 30 g needle connected to a micro-syringe, using an operating microscope. the experimental keratitis was allowed to proceed untreated for 20 hr. there this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: soltan dallal mm, nikkhahi f, imeni sm, molaei s, hosseini sk, kalafi z, yazdi ss, mirzaei hma. amniotic membrane transplantation for persistent epithelial defects and ulceration due to pseudomonas keratitis in a rabbit model. j ophthalmic vis res 2021;16:552–557. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 553 https://knepublishing.com/index.php/jovr amt for rabbit model of keratitis; soltan dallal et al was no interference in the control group. in groups 3 and 4, the am in pieces of 1.5×1.5 cm transplanted to the entire corneal surface by eight interrupted 10.0 nylon sutures. on the first day, ciprofloxacin drop was injected to groups 2 and 4 every 30 min. on the second day to seventh day every 2 hr, the results were registered in aspect of perforation in cornea and the amount of infiltration by the use of image j 1 software. results results were registered as clinical reports on the first, third, and seventh day [table 1]. during the first 20 hr, after injecting p. aeruginosa, a white opacity appeared in all rabbits. rabbits had corneal ulcers and on the second day, the conjunctiva was markedly hyperemic in four groups. at the end of the first week, hypopyon formation was noticed in five eyes in the amt group. corneal perforation was noticed in four cases in the control group but in no case in other groups. the results showed that the cornea had infiltration in which central part, an area with the size of 6 mm had descemeto cell and progress toward causing perforation in cornea control group (a: control group). on the other hand, amt group conjunctiva inflammation showed to be less than control group and in cornea examination the amount of infiltration showed to be 24 mm (b: amt group). for ciprofloxacin group, ciprofloxacin sediment was clearly visible (c: ciprofloxacin) and finally in the group with ciprofloxacin + amt as well as the ciprofloxacin group the decrease of opacity cornea was quite visible (d: amt + ciprofloxacin). the clinical results of four groups in examination of pseudomonas keratitis are also shown in table 2. these results showed that amt + ciprofloxacin group had 0% perforation and the control group had 85.7%. average infiltrations were 5 mm in amt + ciprofloxacin groups and 23.75 mm in control. the result showed that the amt, ciprofloxacin, and amt + ciprofloxacin were effective on perforation and infiltration on all groups compared to the control group. in addition, there was no significant difference between ciprofloxacin group and ciprofloxacin combination with am. in the same way, there was no significant difference between membrane amniotic group and ciprofloxacin compared with combined group of ciprofloxacin with membrane amniotic. discussion few studies have investigated the effect of amt in the surgical treatment of severe infectious keratitis with corneal ulceration or perforation.[19, 23, 27] the main advantages of amt in the treatment of bacterial keratitis that we observed are the epithelial bandage properties, which allowed early use of topical steroids; the anti-inflammatory and anti-scarring effects of the am, the promotion of epithelialization, and the possible benefits of a direct antimicrobial role of the am.[28] these studies found amt to be effective in treating neurotrophic ulcer, inflammatory corneal ulcer, bullous keratopathy, inflammatory or noninflammatory scleral ulcer and as an adjuvant treatment of pterygium excision. the basement membrane of an am promotes epithelial growth and differentiation, reinforces the adhesion of basal epithelial cells and prevents epithelial apoptosis. the stroma matrix suppresses tgfb signaling, proliferation, and myofibroblastic differentiation of normal human corneal and limbal fibroblasts and thus, inhibiting the unwanted production of extracellular matrix and scarring.[6] these properties have made the am an ideal reconstructive substrate for repairing persistent epithelial defects and corneal ulcers,[2] conjunctival defect,[9, 10] chemical or thermal injury,[15, 29] and limbal cell deficiency.[16, 17] the application of am in the treatment of corneal perforation and scleromalacia has been also reported.[30, 31] the human am possesses anti-inflammatory, antifibrotic, and antiangiogenic properties, and these attributes make it ideal for ocular surface reconstruction procedures.[32, 33] in addition, the am also has antimicrobial properties due partly to its anti-inflammatory effects, and also due to secretion of elfin and secretory leucocyte proteinase inhibitor, both of which have antimicrobial actions and act as components of the innate immune system.[34, 35] it also contains cystatin e, an analogue of cysteine proteinase inhibitors, which has complementary antiviral properties.[36] furthermore, am transplantation (amt) is reserved for cases of postinfectious ulcers after an appropriate period of anti-infective treatment when clinical signs are improving.[37] this is because the anti-infective properties of am are nonspecific and not considered to be potent enough to be effective in acute infective keratitis. this is the reason behind the concept 554 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 amt for rabbit model of keratitis; soltan dallal et al figure 1. cornea infiltration of the four groups of experiment. (a: control group; b: amt group; c: ciprofloxacin; d: amt + ciprofloxacin). table 1. clinical results of four groups on the first, third, and seventh day and in the first 20 hr* groups/days first day third day seventh day control average infiltration 2.25 mm with corneal opacity and without epithelial defect average infiltration 7.01 mm with corneal opacity, epithelial defect, and descemeto cell average infiltration 23.75 mm with corneal opacity and epithelial defect amt average infiltration 2.62 mm and without epithelial defect average infiltration 6.25 mm and without epithelial defect average infiltration 24 mm and without epithelial defect, melting, and scar ciprofloxacin average infiltration 2.35 mm and without epithelial defect average infiltration 4.51 mm and epithelial defect average infiltration 5.5 mm, epithelial defect, and scar with diameter 2.5×2.5 mm ciprofloxacin + amt average infiltration 2.6 mm and without epithelial defect average infiltration 4 mm and without epithelial defect average infiltration 5 mm and without epithelial defect and scar *findings in the first 20 hours only the first day for all groups **amt, amniotic membrane transplantation of fortifying am with antimicrobial drugs to make it a viable therapeutic modality in the setting of active infections of the cornea. antibioticimpregnated medical devices such as catheters, bone and cardiac implants have been in use for over a decade.[22, 38] various studies have shown the potential of such an approach, for example, in vascular surgery and arthroplasty, where they appear effective in reducing the risk of bloodstream infections or in limiting deep wound infections.[39, 40] am is effective in remission of pseudomonas keratitis and prevention of journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 555 amt for rabbit model of keratitis; soltan dallal et al table 2. clinical outcomes of perforation and infiltration in all four groups of pseudomonas keratitis results amt* amt + ciprofloxacin ciprofloxacin control perforation (0%) 0 (0%) 0 (0%) 0 (85.7%) 6 infiltration 24 mm 5 mm 5.5 mm 23.75 mm significant difference compared to control group (p-value) p < 0.5 p < 0.5 p < 0.5 – *amt, amniotic membrane transplantation cornea perforation and controlling as well as antipseudomonas effects. there was no difference between ciprofloxacin group in comparison with ciprofloxacin + amt group. however, regarding anti-inflammatory effects, the process of improvement of inflammation in ciprofloxacin + amt group was faster. during this research, we came to conclusion that transplantation of am in the primary stages of pseudomonas keratitis treatment remarkably prevents the disease and it can be used to control its process. acknowledgements this work was supported by a vice-chancellor for research grant (no. 10793) and approved by the committee for research ethics (no.ir.tums.res.1394.2091) of tehran university of medical sciences (tehran, iran). financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. marino t. ultrasound abnormalities of the amniotic fluid , membranes , umbilical cord , and placenta. obs gynecol clin north am 2004;31:177–200. 2. mastropasqua l, massaro-giordano g, nubile m, sacchetti m. understanding the pathogenesis of neurotrophic keratitis: the role of corneal nerves. cell physiol 2016;september:717–724. 3. remigio l, leonidas t. accelerated collagen cross-linking in the management of advanced acanthamoeba keratitis. j arq bras oftalmol 2019;8:103–106. 4. weng s, jan r, chang c, wang j, su s. risk of band keratopathy in patients with end-stage renal disease. sci rep 2016;6:28675. 5. stefan p, sanziana i, liliana v, costin l, vanessa p, ciuluvica r. pseudophakic bullous keratopathy. rom j ophthalmol 2017;61:90–94. 6. tonti e. different graft thicknesses after descemet stripping endothelial keratoplasty for bullous keratopathy in the two eyes of the same patient. int med case rep j 2019:55–59. 7. mifflin md, mortensen xm. intraoperative optical pachymetry in photorefractive keratectomy. j cart refract surg 2018;45:495–500. 8. ehlke gl, krueger rr. laser vision correction in treating myopia. asia-pacific j ophthalmol 2016;5:434–437. 9. palamar m, yaman b, akalin t, yagci a. amniotic membrane transplantation in surgical treatment of conjunctival melanoma: long-term results. turkish j ophthalmol 2018;48:15–18. 10. asoklis rs, damijonaityte a, butkiene l, makselis a, petroska d, pajaujis m, et al. ocular surface reconstruction using amniotic membrane following excision of conjunctival and limbal tumors. eur j ophthalmol 2011;21:552–558. 11. kaufman sc, jacobs ds, lee wb, deng sx, rosenblatt mi, shtein rm. options and adjuvants in surgery for pterygium. ophthalmology 2013;120:201–208. 12. mitomycin c. comparison of three methods for the treatment of pterygium: amniotic membrane graft, conjunctival autograft and conjunctival autograft plus. int j orbital disord oculoplastic lacrimal surg 2007;26:5–13. 13. gündüz k, uçakhan oo, kanpolat a, günalp i. nonpreserved human amniotic membrane transplantation for conjunctival reconstruction after excision of extensive ocular surface neoplasia. eye 2006;20:351–357. 14. grewal ds, mahmoud th. dehydrated allogenic human amniotic membrane graft for conjunctival surface reconstruction following removal of exposed scleral buckle. ophthalmic surg lasers imaging retina 2016;47:948–951. 15. tamhane a, vajpayee rb, biswas nr. evaluation of amniotic membrane transplantation as an adjunct to medical therapy as compared with medical therapy alone in acute ocular burns. ophthalmology 2005;112:1963– 1969. 16. pereira gomes ja, dos santos ms, cunha mc, mascaro vld, de nadai barros j, barbosa de sousa l. amniotic membrane transplantation for partial and total limbal stem cell deficiency secondary to chemical burn. ophthalmology 2003;110:466–473. 17. torabi t, abroun s. amniotic fluid, an effective factor for umbilical cord blood hematopoietic stem cells in cell 556 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 amt for rabbit model of keratitis; soltan dallal et al culture: an approach for bone marrow transplantation. transfus apher sci 2019;58:169–173. 18. tejwani s, kolari rs, sangwan vs, rao gn. role of amniotic membrane graft for ocular chemical and thermal injuries. cornea 2007;26:21–26. 19. nubile m, carpineto p, lanzini m, ciancaglini m, zuppardi e, mastropasqua l. multilayer amniotic membrane transplantation for bacterial keratitis with corneal perforation after hyperopic photorefractive keratectomy: case report and literature review. j cataract refract surg 2007;33:1636–1640. 20. gicquel j, bejjani ra, ellies p. amniotic membrane transplantation in severe bacterial keratitis. cornea 2007;26:27–33. 21. heidarzadeh s, ghasemian a, kalafi z, nikkhahi f, soltan mm. antimicrobial effects of amniotic membrane on some bacterial strains. immunopathol persa 2018;4:1–5. 22. mehdi m, soltan-dallal m, nikkhahi f, molaei s, hosseini k, kazem m, et al. effect of amniotic membrane combined with ciprofloxacin in curing the primary stages of pseudomonal keratit. j med bacteriol 2012;1:31–37. 23. kim hk, park hs. fibrin glue-assisted augmented amniotic membrane transplantation for the treatment of large noninfectious corneal perforations. cornea 2009;28:170– 176. 24. chen hc, tan hy, hsiao ch, huang scm, lin kk, ma dhk. amniotic membrane transplantation for persistent corneal ulcers and perforations in acute fungal keratitis. cornea 2006;25:564–572. 25. kim sj, song ch, sung hj, yoo yd, geum dh, park sh, et al. human placenta-derived feeders support prolonged undifferentiated propagation of a human embryonic stem cell line, snuhes3: comparison with human bone marrowderived feeders. stem cells dev 2007;16:421–428. 26. miller dd, simmons nl, stewart mw. recurrent corneal erosion: a comprehensive review. clin ophthalmol 2019;13:325–335. 27. bouchard cs, john t. amniotic membrane transplantation in the management of severe ocular surface disease: indications and outcomes. ocul surf 2004;2:201–211. 28. dua hs, gomes jap, king aj, maharajan vs. the amniotic membrane in ophthalmology. diagnostic surg tech 2004;49:51–77. 29. dogan c, sevki o, akif a, burak o. efficacy of fixation of the amniotic membrane on a symblepharon ring with continuous suturing in acute ocular chemical burn patients. int ophthalmol 2019;39:2103–2109. 30. hanada k, shimazaki j, shimmura s, tsubota k. multilayered amniotic membrane transplantation for severe ulceration of the cornea and sclera. am j ophthalmol 2001;131:324–331. 31. jeoung j, yoon y, lee j. the effect of amniotic membrane transplantation on the treatment of necrotizing scleritis after pterygium excision. j korean ophthalmol soc 2004;45:1981–1988. 32. azuara-blanco a, pillai ct, dua hs. amniotic membrane transplantation for ocular surface reconstruction. br j ophthalmol 1999;83:399–402. 33. sangwan vs, burman s, tejwani s, mahesh sp, murthy r. amniotic membrane transplantation: a review of current indications in the management of ophthalmic disorders. indian j ophthalmol 2007;55:251–260. 34. niknejad h, peirovi h, jorjani m, ahmadiani a, ghanavi j, seifalian m, et al. properties of the amniotic membrane for potential use in tissue engineering. eur cells mater 2008;15:88–99. 35. king ae, paltoo a, kelly rw, sallenave j, bocking ad, challis jrg. expression of natural antimicrobials by human placenta and fetal membranes. placenta 2007;28:161–169. 36. nguyen lunde n, haugland m, broe k, larsen b, damgaard i, pettersen sj, et al. glycosylation is important for legumain localization and processing to active forms but not for cystatin e/m inhibitory functions. biochimie 2017;139:27–37. 37. soltan-dallal mm, kalafi z, rastegar-lari a, hosseini sk, rahimi-foroushani a. the effect of reduced bacterial dilution on human amniotic membrane antibacterial activity, in vitro. zahedan j res med sci 2013;15:6–8. 38. quarello f, forneris g, borca m, pozzato m. do central venous catheters have advantages over arteriovenous fistulas or grafts? j nephrol 2006;19:265–279. 39. kowalewski m, pawliszak w, zaborowska k, navarese ep, szwed a. gentamicin-collagen sponge reduces the risk of sternal wound infections after heart surgery: meta-analysis. j thorac cardiovasc surg 2015;149:1631– 1640.e6. 40. harron k, mok q, hughes d, muller-pebody b, parslow r. generalisability and cost-impact of antibiotic-impregnated central venous catheters for reducing risk of bloodstream infection in paediatric intensive care units. plos one 2016;11:e0151348.5. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 557 original article variable expressivity of wolfram syndrome in a family with multiple affected subjects mehraban mirrahimi1*, ms; sare safi2*, phd; maryam mohammadzadeh3, md; azadeh doozandeh3, md fatemeh suri3, phd 1ocular tissue engineering research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2ophthalmic epidemiology research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 3ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran orcid: fatemeh suri: https://orcid.org/0000-0002-3170-2940 sare safi: https://orcid.org/0000-0002-5860-6908 mehraban mirrahimi: https://orcid.org/0000-0001-8220-7758 *first and second authors contributed equally to this work. abstract purpose: to study the genetic basis and clinical manifestations of wolfram syndrome in a multi-affected family. methods: complete clinical examinations including urological, ophthalmic, neurological, and endocrinologic assessment were performed for three affected family members. genomic dna was extracted from peripheral blood leukocytes with salting out method and all wfs1 exons and their flanking regions were sequenced. candidate variation was screened for segregation in the pedigree by sanger sequencing. results: a known pathogenic missense mutation in wfs1 gene (c.1885c>t which leads to p.arg629trp in the encoded protein) was identified in all affected individuals. both clinical and genetic investigations confirmed wolfram syndrome diagnosis with variable phenotypic features. conclusion: identical mutations in the wolfram syndrome causative gene can lead to variable manifestations of the syndrome even in the same family. although the medical findings and clinical examination are imperative for the diagnosis of wolfram syndrome, genetic testing is useful to confirm the diagnosis, especially in cases with possible reduced penetrance of the characteristic signs. keywords: variable clinical manifestations; wfs1 gene; wolfram syndrome j ophthalmic vis res 2021; 16 (4): 602–610 602 © 2021 mirrahimi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9750&domain=pdf&date_stamp=2019-07-17 variability of wolfram syndrome; mirrahimi et al introduction wolfram syndrome (wfs) also called didmoad (diabetes insipidus, diabetes mellitus, optic atrophy, deafness) is a progressive neurodegenerative disease affecting multiorgan systems.[1] wolfram and wagener first described this entity in four siblings in 1938.[2] it’s a kind of rare genetic disorder with a prevalence of approximately 1 per 770,000 in the united kingdom and 1 per 100,000 in north america.[1] wfs is inherited in an autosomal recessive pattern; therefore, it should be more prevalent in populations with high rates of consanguineous marriages. however, only limited cases have been reported from the eastern mediterranean countries where this kind of marriage is more common. there is no published data on the prevalence of the disease in iran.[3] the wfs manifestations are variable. however, juvenile-onset diabetes mellitus (dm) and optic atrophy (oa) are two characteristic features for clinical diagnosis of the syndrome that are typically exhibited at the mean age of 6 and 11 years, respectively. other common clinical manifestations include diabetes insipidus (di), sensorineural deafness, urinary tract involvement, and neuropsychiatric disorders.[1] wfs (wfs1; omim 222300) is caused by a deleterious mutation in the wfs1 gene (omim 606201) on chromosome 4p16, which encodes wolframin protein; a kind of endoplasmic reticulum (er) transmembrane glycoprotein highly expressed in pancreatic, beta insulinoma, and brain cells. the decline in wolframin protein leads to the er stress and malfunctioning of the cells.[4] not only more than 400 distinct mutations of the wfs1 correspondence to: fatemeh suri, phd. ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, no. 23, paidarfar st., boostan 9 st., pasdaran ave., tehran 16666, iran. e-mail: fatemehsuri@gmail.com. received: 31-01-2021 accepted: 25-04-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9750 gene have been reported till now (http://www. hgmd.cf.ac.uk/ac/gene.php?gene=wfs1), but the less frequent phenotypic and genotypic variant of wfs (wfs2; omim 604928) related to mutation in cisd2 gene (omim 6011507) encoding cdgsh iron sulfur domain 2 protein have also been recognized.[5] in this study, we analyzed the clinical characteristics and genetic findings of a multiaffected family with variable clinical manifestations of the syndrome. methods the research was approved by the ethics committee of the ophthalmic research center at shahid beheshti university of medical sciences, tehran, iran. all study procedures were explained to the subjects and were performed in accordance with the declaration of helsinki. the signed consent form was also obtained. subjects and clinical examination three affected siblings of persian ethnicity from four offspring of a consanguineous marriage diagnosed with wfs referred to torfeh medical center due to visual impairment were studied. diagnosis criteria for the wfs were dm and oa unexplained by any other causes. the clinical evaluations including urological, ophthalmic, neurological, and endocrinological examinations were performed for all affected individuals. the pedigree data was gathered [figure 1] and auditory evaluation was accomplished by pure tone audiometry, speech discrimination score, audiometric thresholds, and tympanometry. ophthalmic evaluations including slit lamp examination, tonometry, gonioscopy, indirect ophthalmoscopy, and fundus photography were also performed. in addition, the color vision and visual field were assessed but the results were unreliable due to patients’ severe visual loss. blood samples were taken from all participants this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: mirrahimi m, safi s, mohammadzadeh m, doozandeh a, suri f. variable expressivity of wolfram syndrome in a family with multiple affected subjects. j ophthalmic vis res 2021;16:602–610. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 603 https://knepublishing.com/index.php/jovr http://www.hgmd.cf.ac.uk/ac/gene.php?gene=wfs1 http://www.hgmd.cf.ac.uk/ac/gene.php?gene=wfs1 variability of wolfram syndrome; mirrahimi et al for genetic and biochemical evaluation. brain and spinal magnetic resonance imaging (mri) and total abdominopelvic sonography were conducted. genetic and molecular analysis genomic dna was extracted from peripheral blood leukocytes using the standard salting out protocol. primers were designed to amplify all exons and their flanking regions of the wfs1 gene using generunner version 3.05 software. to validate further, we checked them for the specificity to the target template with ncbi primer-blast (http://www.ncbi.nlm.nih.gov/tools/primer-blast/). polymerase chain reactions (pcr) were done and subsequently sequenced with the sanger protocol. all pcr products were sequenced using abi big dye terminator chemistry with an abi 3730xl genetic analyzer instrument (applied biosystems, foster city, ca, usa). sequences were analyzed using sequencher 5.0 software (gene codes corporation, ann arbor, mi, usa). the sequencing data was assembled to their reference sequence of wfs1 (ng_011700.1, nm_006005.3, and np_005996.2) to find the disease causative mutation. subsequently, the candidate causing variation was screened for segregation in all family members by sanger sequencing. results genetic results a homozygous missense mutation (c.1885c>t) on exon 8 of wfs1 gene that causes p.arg629trp in the encoded protein was detected in all three affected members of the family. the parents were heterozygous for the causative variant and the healthy sister was homozygous for the wildtype allele. figure 2 shows dna sequence chromatograms of c.1885 position in wfs1 in three different genotypic features in the members of this family. mutation c.1885c>t has been reported to be pathogenic in patients with wfs. clinical findings the clinical features of all participants have been represented in table 1. the parents are second cousins once removed, having four offspring; three of them manifesting signs and symptoms of wfs [figure 1]. case v.2 a 31-year-old male patient was referred to the ophthalmology clinic due to visual impairment. he was diagnosed with dm at the age of four and has been on insulin therapy since then. he has been suffering from visual impairment from the age of 6. he subsequently developed di and hearing loss at the age of 21. at the time of study, his serum hba1c level was 7.7%. the ophthalmic evaluation showed the best-corrected visual acuity of light perception bilaterally with no nystagmus. cataract was observed in both eyes and the intraocular pressure was 18 mmhg bilaterally. funduscopy revealed proliferative diabetic retinopathy (pdr) in the right eye and moderate nonproliferative diabetic retinopathy (npdr) in the left eye with no evidence of macular edema. oa with severe optic nerve head pallor was obvious in both eyes [figure 3a]. the history and ocular examinations approved the progressive oa in the context of wfs. abdominopelvic sonography revealed mild hydronephrosis in the right kidney with normal kidney size, normal parenchymal thickness, and echo pattern. also, mild bladder wall thickness with trabeculation was detected. these are consistent with neurogenic bladder. auditory tests with pure tone audiometry showed sensorineural hearing loss. brain and lumbar spine mris were normal. case v.3 a 24-year-old female patient was diagnosed with dm at the age of three who has been treated with insulin nph and regular. the presence of oa in both eyes was diagnosed at the age of 12. she developed urinary tract disorders and bladder dysfunction at the age of 12 for which she took nitrofurantoin twice daily for prophylaxis. the diagnosis of di was confirmed with clinical signs and symptoms, laboratory tests and water deprivation test abdominopelvic sonography revealed severe hydroureteronephrosis with cortical loss in both kidneys in addition to irregularity and increment in bladder wall thickness that is consistent with neurogenic bladder [figure 4]. her visual acuity was finger counting at 1–2 m. intraocular pressure was 19 mmhg in both eyes. fundus examination revealed bilateral severe oa and nerve fiber loss [figure 3b]. the audiometry showed sensorineural hearing loss in both ears which were moderate at 3000 hz 604 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 http://www.ncbi.nlm.nih.gov/tools/primer-blast/ variability of wolfram syndrome; mirrahimi et al figure 1. pedigree information of the wolfram syndrome family. black filled shapes represent affected patients. open shapes represent unaffected members. table 1. clinical features of patients with wolfram syndrome patient id current age (years) gender (m/f) clinical findings case v.2 31 m dm, di, oa, sensorineural hearing loss, neurogenic bladder, mild hydronephrosis case v.3 24 f dm, di, oa, sensorineural hearing loss, neurogenic bladder, severe hydroureteronephrosis case v.4 23 m dm, di, oa dm, diabetes mellitus; di, diabetes insipidus; oa, optic atrophy and severe at 6000 hz test tone [figure 5a]. tympanometry presented type a𝑛 in right and type a𝑠 in left ear which suggested the reduced tympanic membrane mobility in the left ear [figure 5b]. brain and lumbar spine mri revealed normal findings. case v.4 a 23-year-old man was diagnosed with insulindependent dm at the age of four which has been treated with insulin nph and regular since the diagnosis and subsequently was diagnosed with journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 605 variability of wolfram syndrome; mirrahimi et al figure 2. dna sequence chromatograms of the identified wfs1 variation in three different genotypic features in the family. figure 3. severe nerve fiber layer loss in cases v.2 and v.3. di. he subsequently developed visual impairment and oa at the age of 11. his serum hba1c level was 9.4% which represented uncontrolled dm. his bestcorrected visual acuity was finger counting at 20 cm in the right eye and hand motion in the left eye. he underwent phacoemulsification and intraocular lens implantation in both eyes. intraocular pressure was 18 mmhg bilaterally. on funduscopic examination, there was severe oa [figure 6]. his abdominopelvic sonography reported normal kidney sizes with normal parenchymal thickness and echo patterns. neither hydronephrosis 606 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 variability of wolfram syndrome; mirrahimi et al figure 4. abdominopelvic sonography in case v.3 showing severe hydronephrosis in both kidneys. figure 5. (a) tympanogram of both ears in case v.3. (b) audiograms of case v.3 showing sensorineural hearing loss in both ears. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 607 variability of wolfram syndrome; mirrahimi et al figure 6. severe optic atrophy with disc paleness in both eyes of case v.4. nor stone or occupying lesion was detected. additionally, bladder wall thickness and shape was normal without any evidence of trabeculation or neurogenic bladder. he occasionally reported urological symptoms which was proved by the normal results of his abdominopelvic sonography. he had no complaint of auditory loss and his auditory tests were normal. discussion wfs is a rare progressive neurodegenerative disorder characterized by oa and dm at childhood which is inherited in an autosomal recessive pattern.[6] patients affected by this syndrome can manifest different signs and symptoms of the disease, for example, di, sensorineural hearing loss, and neurological signs such as ataxia, and neurogenic bladder in combination with dm or oa.[6] according to clinical history and physical examination, the differential diagnosis could include other causes of progressive neurodegeneration like mitochondrial disorders, mutant wfs1 gene-induced deafness, autosomal dominant oa, friedreich ataxia, bardet–biedl syndrome, and alström syndrome.[7] among this wide spectrum of clinical manifestations, juvenile-onset dm and oa are both initial and fundamental features of wfs.[8] in this study, we reported the clinical and genetic characteristics of three patients with wfs from a consanguineous marriage. so far, a wide range of wfs1 gene variants has been recognized as cause of the disease.[4] most of these mutations result in loss of function protein expression which is responsible for wolframin protein inactivation and consequent disease manifestations; however, the exact genotype–phenotype correlation in wfs-affected patients is not well understood.[9, 10] in this study, we detected a known homozygous pathogenic mutation (c.1885c>t) in exon 8 of wfs1 gene in all the three affected patients that has been reported in other studies as cause of the disease.[11–13] furthermore, we discovered that both parents were heterozygous for the causative variant who were healthy and the youngest sister of the family was homozygous for the wild-type allele. therefore, not only the clinical diagnostic criteria but also the genetic analysis in all three cases was consistent with wfs. dm usually occurs during the first decade of patients’ lives.[11] in our study, all of our cases suffered from juvenile-onset dm with the average age at onset of 3.8 years (ranging from 3.5 to 4 years). while diabetes ketoacidosis (dka) may occur as the presenting features of the syndrome,[14] none of our cases have experienced any episodes of dka or severe hypoglycemia yet. as previously mentioned, wolframin protein is found in the er of langerhans β-cells and loss of function mutations of the wfs1 gene can lead to wolframin protein dysfunction which consequently leads to er stress.[15] this phenomenon can lead to non-autoimmune-mediated/induced destruction of β-cells and subsequently, dm occurs. this pathophysiology is consistent with the early onset dm in wfs-affected patients in comparison with autoimmune-mediated destruction of β-cells in type 1 dm which is triggered later during life.[16] patients with wfs will progressively develop ophthalmic complications in consequence of dm, that is, diabetic retinopathy and cataract.[8] we discovered diabetic retinopathy and cataract in both eyes in one of the cases (case v.2) which is justified by longer duration of disease (27 years) 608 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 variability of wolfram syndrome; mirrahimi et al in comparison with other participants. in addition to dm, oa is another characteristic feature of the syndrome which usually develops after dm at the mean age of 11 years.[1, 11] according to oa pathogenesis, wfs1 gene mutation reduces the retinal ganglion cells survival which leads to retinal axon layer atrophy and optic nerve shrinkage. the latter will also result in progressive oa.[8] all of our cases had symptoms and signs of oa after the diagnosis of dm. the mean age at the onset of oa in our cases was 9.6 years. other studies have reported hearing impairment in 60% of wfs cases at the mean age of 16 years.[17] auditory features of this hearing impairment were compatible with sensorineural hearing loss in mid to high frequencies. the pathophysiology of this kind of hearing loss could be the result of dysfunction in cochlear neurons, vestibular nerve fibers of cranial nerve viii, and the central nervous system (including brain stem and inferior colliculus).[18] in our study, we detected a sensorineural hearing loss in high frequencies confirmed by an audiometry in two of our cases (cases v.2 and v.3). urinary tract involvement is one of the signs of the wfs. this manifestation mainly has a primary feature rather than being secondary to dm, di, or wfs-induced myelopathy and could be present independent of other features.[19] in our study, we have found evidence of neurogenic bladder, that is, hydronephrosis and bladder wall trabeculation in two cases (cases v.2 and v.3) which was mild in the former and severe in the latter. these findings could be a result of diabetic-induced peripheral neuropathy,[20] however, since neither of our cases presented any signs and symptoms of autonomic or peripheral neuropathy, this finding will not be probable. in our study, we found no signs and symptoms of neurological complications neither in physical examination nor in mri images of the brain and spine. in conclusion, our study showed that an identical mutation in wfs1 gene can represent variable severity of clinical features of the disease even in the same family. more studies on ageand sexmatched cases may shed light on reasons behind this variable clinical presentation and the role of genetic background and environmental factors. additionally, further studies exploring different wfs1 mutations will improve our knowledge about genotype–phenotype correlations of this syndrome. acknowledgement the authors would like to thank dr. mahboobeh karimi and dr. alireza abrishami for their valuable contribution to this study. financial support and sponsorship none. conflicts of interest there are no conflicts of interest. references 1. pallotta mt, tascini g, crispoldi r, orabona c, mondanelli g, grohmann u, et al. wolfram syndrome, a rare neurodegenerative disease: from pathogenesis to future treatment perspectives. j transl med 2019;17:238. 2. wolfram d, wagener hp, editor. diabetes mellitus and simple optic atrophy among siblings. mayo clin proc 1938;13:715–718. 3. naderian g, ashtari f, nouri-mahdavi k, sajjadi v. a case of wolfram syndrome. j ophthalmic vis res 2010;5:53. 4. rigoli l, lombardo f, di bella c. wolfram syndrome and wfs1 gene. clin genet 2011;79:103–117. 5. amr s, heisey c, zhang m, xia xj, shows kh, ajlouni k, et al. a homozygous mutation in a novel zinc-finger protein, eris, is responsible for wolfram syndrome 2. am j hum genet 2007;81:673–683. 6. eller p, föger b, gander r, sauper t, lechleitner m, finkenstedt g, et al. wolfram syndrome: a clinical and molecular genetic analysis. j med genet 2001;38:e37. 7. urano f. wolfram syndrome: diagnosis, management, and treatment. curr diab rep 2016;16:6. 8. ari ş, keklíkçí u, çaça i̇, ünlü k, kayabaşi h. wolfram syndrome: case report and review of the literature. compr ther 2007;33:18–20. 9. bodoor k, batiha o, abu-awad a, al-sarihin k, ziad h, jarun y, et al. identification of a novel wfs1 homozygous nonsense mutation in jordanian children with wolfram syndrome. meta gene 2016;9:219–224. 10. cano a, rouzier c, monnot s, chabrol b, conrath j, lecomte p, et al. identification of novel mutations in wfs1 and genotype–phenotype correlation in wolfram syndrome. am j med genet a 2007;143:1605–1612. 11. aloi c, salina a, pasquali l, lugani f, perri k, russo c, et al. wolfram syndrome: new mutations, different phenotype. plos one 2012;7:e29150. 12. marshall ba, permutt ma, paciorkowski ar, hoekel j, karzon r, wasson j, et al. phenotypic characteristics of early wolfram syndrome. orphanet j rare dis 2013;8:64. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 609 variability of wolfram syndrome; mirrahimi et al 13. sobhani m, tabatabaiefar ma, rajab a, kajbafzadeh am, noori-daloii mr. significant expressivity of wolfram syndrome: phenotypic assessment of two known and one novel mutation in the wfs1 gene in three iranian families. mol biol rep 2014;41:7499–7505. 14. kinsley bt, swift m, dumont rh, swift rg. morbidity and mortality in the wolfram syndrome. diabetes care 1995;18:1566–1570. 15. inoue h, tanizawa y, wasson j, behn p, kalidas k, bernalmizrachi e, et al. a gene encoding a transmembrane protein is mutated in patients with diabetes mellitus and optic atrophy (wolfram syndrome). nat genet 1998;20:143. 16. rohayem j, ehlers c, wiedemann b, holl r, oexle k, kordonouri o, et al. diabetes and neurodegeneration in wolfram syndrome: a multicenter study of phenotype and genotype. diabetes care 2011;34:1503–1510. 17. megighian d, savastano m. wolfram syndrome. int j pediatr otorhinolaryngol 2004;68:243–247. 18. genis d, davalos a, molins a, ferrer i. wolfram syndrome: a neuropathological study. acta neuropathologica 1997;93:426–429. 19. tekgul s, oge o, simsek e, yordam n, kendi s. urological manifestations of the wolfram syndrome: observations in 14 patients. j urol 1999;161:616–617. 20. aboseif s, gasparini m, schmidt r, tanagho e. wolfram’s (didmoad) syndrome and its urological manifestation. br j urol 1993;72:106–111. 610 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 original article carrier status for p.gly61glu and p.arg368his cyp1b1 mutations causing primary congenital glaucoma in iran ali heshmati1a, ms; peyman taghizadeh1a, ms; hamid ahmadieh2, md; mehdi yaseri3, phd fatemeh suri2, phd; mahsa alizadeh4, marjan dadashzadeh5, hajar khatami6, msc monireh moradkhah navi7, parisa zamanparvar8, hassan behboudi9*, md; elahe elahi1*, phd 1school of biology, university college of science, university of tehran, tehran, iran 2ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 3department of epidemiology and biostatistics, school of public health, tehran university of medical sciences, tehran, iran 4astaneh health center, astaneh, guilan, iran 5rasht health center, rasht, guilan, iran 6anzali health center, anzali, guilan, iran 7talesh medical center, talesh, guilan, iran 8lahijan medical center, lahijan, guilan, iran 9department of ophthalmology, guilan university of medical sciences, rasht, iran athese two authors contributed equally orcid: elahe elahi: http://orcid.org/0000-0002-6897-2223 abstract purpose: to estimate carrier frequencies of cyp1b1 mutations p.gly61glu and p.arg368his, respectively, in talesh and the east of guilan province in iran with a maximum error of 2%. previously, it was shown that these cyp1b1 mutations may be relatively prevalent in these regions. methods: population-based screenings were performed. dna was extracted from saliva samples of 1036 individuals from talesh and 3029 individuals from the east of guilan. p.gly61glu and p.arg368his screenings were performed, respectively, by rflp and arms-based pcr protocols. for confirmation, the dna of individuals with mutations was sequenced using the sanger protocol. results: nine individuals from talesh (0.86%; 95%ci: 0.45–1.64%) carried the p.gly61glu mutation, and 73 from the east of guilan (2.41%; 95%ci: 1.91–3.04%) carried p.arg368his. there was no significant difference in frequencies between urban and rural regions of the various cities, nor among four cities within the east of guilan. conclusion: the frequencies of p.gly61glu carriers in talesh and of p.arg368his carriers in the east of guilan were within the 95% confidence interval of a previous study based on screenings of fewer individuals. the reliability of the recent estimates is higher, as the confidence interval for p.gly61glu decreased from 6.5% to 1.19% and the interval for p.arg368his decreased from 4% to 1.13%. based on the new findings, the maximum expected frequency of p.gly61glu carriers in talesh is 1.64%, and of p.arg368his carriers in the east of guilan is 3%. the need for performing premarital screenings in the respective cities can be evaluated. keywords: cyp1b1; guilan; iran; p.arg368his; p.gly61glu; primary congenital glaucoma j ophthalmic vis res 2021; 16 (4): 574–581 574 © 2021 heshmati et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9747&domain=pdf&date_stamp=2019-07-17 carrier status of cyp1b1 mutations; heshmati et al introduction glaucoma is a major cause of irreversible blindness worldwide.[1] on the basis of the anatomy of the anterior chamber drainage angle and age of onset, primary glaucoma is classified as primary congenital glaucoma (pcg; omim 231300), primary open angle glaucoma (poag), and primary angle closure glaucoma (pacg). pcg which is the subject of this report is the most severe form of glaucoma.[2] it is characterized by an anatomical defect (trabeculodysgenesis) in the trabecular meshwork and the age of onset in the neonatal period or before the age of three years.[3] pcg occurs in both sporadic and familial patterns. in familial cases, inheritance is usually autosomal recessive.[3, 4] while less common than the adult onset forms, pcg is an important cause of childhood blindness.[5, 6] the incidence of pcg is geographically and ethnically variable, and highest in populations with high rates of consanguineous marriages such as saudi arabia (1:2500).[7, 8] genetic analysis of recessive pcg-affected families have identified four associated loci, glc3a – d.[9, 10] the causative gene in two of the loci have been identified: cyp1b1 in glc3a and ltpbp2 in glc3d that encode, respectively, cytochrome p450 family 1 subfamily b polypeptide 1 and latent transforming growth factor-β binding protein 2. more recently, mutations in tek that encodes tunica interna endothelial cell kinase have been reported in both sporadic and autosomal dominant familial pcg patients.[4, 11] mutations in cyp1b1 are by far the most commonly known cause of pcg. nevertheless, the proportion of pcg patients whose disease is attributable to cyp1b1 is different among populations, ranging from 20% in japan to 90% in saudi arabia and 100% in *correspondence to: hassan behboudi, md. department of ophthalmology, guilan university of medical sciences, rasht, iran. e-mail: behboudi_dr@yahoo.com elahe elahi, phd. school of biology, college of science, university of tehran, tehran, iran. e-mail: elaheelahi@ut.ac.ir received: 02-02-2021 accepted: 24-05-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9747 slovakia roma.[7, 12–14] more than 130 putative pcg-causing mutations distributed in the coding regions of cyp1b1 have been documented (human genome mutation database; http://www.hgmd.cf. ac.uk/ac/index.php). the degree of heterogeneity of cyp1b1 mutations in different populations is quite variable.[15] a study in which cyp1b1 was screened in 104 iranian pcg patients identified a mutation in approximately 70% of the patients.[16] this suggested that mutations in cyp1b1 significantly contributes to pcg burden in iran. although 19 different disease-associated mutations were identified, four of these constituted 77.3% of the identified mutated alleles. the four common mutations caused p.gly61glu, p.arg368his, p.arg390his, and p.arg469trp. another important finding of the same study was that pcg incidence is not evenly distributed in iran, and that incidence is relatively high in the west and northwest of iran. guilan, which is located in the northwest of iran, was one of the provinces with a high incidence of pcg. the findings of the early study summarized above suggested that the frequency of pcgunaffected individuals in iran who harbor one allele of the four aforementioned cyp1b1 mutations may be considerable, particularly in regions with high incidence of the disease. it was considered that a correspondingly relatively high frequency of marriages may occur between carriers of these mutations. the likelihood of giving birth to a pcg-affected offspring would increase in such marriages. in this light, a pilot study was performed in which the four common cyp1b1 mutations were screened in 700 individuals from the province of guilan.[17] the individuals screened were from a cross-sectional population-based survey in guilan that included clusters in urban and rural areas.[18] only carriers of the p.gly61glu and p.arg368his–causing mutations were identified in the more recent survey, which suggested this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: heshmati a, taghizadeh p, ahmadieh h, yaseri m, suri f, alizadeh m, dadashzadeh m, khatami h, navi mm, zamanparvar p, behboudi h, elahi e. carrier status for p.gly61glu and p.arg368his cyp1b1 mutations causing primary congenital glaucoma in iran. j ophthalmic vis res 2021;16:574–581. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 575 https://knepublishing.com/index.php/jovr http://www.hgmd.cf.ac.uk/ac/index.php http://www.hgmd.cf.ac.uk/ac/index.php carrier status of cyp1b1 mutations; heshmati et al that regional frequencies of cyp1b1 mutations do not necessarily mirror national frequencies. furthermore, the p.gly61glu and p.arg368hiscausing mutations were not geographically randomly distributed in guilan; most of the individuals with the p.gly61glu mutation were from talesh, and most of the individuals with the p.arg368his mutation were from the east of guilan. the study whose results are reported here was performed to gain a more accurate assessment of the frequency of the c.182g>a mutation that causes p.gly61glu in the population of talesh and of the c.1103g>a mutation that causes p.arg368his in the population of cities in the east of guilan. these objectives were achieved by screening larger numbers of individuals. methods this research was performed in accordance with the declaration of helsinki and with the approval of the ethics board of the university of tehran and the ophthalmic research center of shahid beheshti university of medical sciences. population sampling we aimed to perform population-based mutation screenings to achieve estimates of the frequency of p.gly61glu cyp1b1 mutation carriers in the population of talesh and of p.arg368his carriers in the population of the east of guilan with a maximum error of 2%. the frequency of p.gly61glu carriers in talesh based on screening of 173 individuals in an earlier study was 2.9% (95% confidence interval: 0.8–7.3%).[17] to achieve a maximum error of 2%, it was calculated that 1000 individuals would need to be screened in the new survey. we chose to recruit 1400 individuals (485 males, 915 females) as a safety net to assure successful screening in at least 1000 individuals. the frequency of p.arg368his carriers in the east of guilan based on the screening of 268 individuals was 2.2% (95% confidence interval: 0.8–4.8%.[17] to achieve a maximum error of 2%, it was calculated that 3012 individuals would need to be screened in the new survey.[19] we choose to recruit 3400 individuals (1088 males, 2312 females). the east of guilan is constituted by the urban and rural regions of the cities rasht, lahijan, bandar anzali, and astaneh ashrafieh. the size of the population of the cities studied and their urban/rural distribution were obtained from the statistical center of iran (amar.org.ir). the number of individuals studied from each of the cities and the urban/rural distribution of each of these are shown in tables 1 and 2. the urban/rural distribution of individuals recruited was always proportional to the urban/rural distribution of the population of each of the cities in these two regions. the distribution of the 3400 individuals recruited from east guilan was proportional to the population size of the four cities that constitute east of guilan. individuals from each rural or urban region were recruited according to a cluster sampling protocol.[20] for this purpose, homes in residential areas were randomly selected based on postal codes obtained from iran post which is the national postal service of iran. sample collection was done at selected residences. only one individual from any single home was recruited. cyp1b1 mutation screening each participating individual after having thoroughly rinsed her/his mouth with water provided 1–2 ml saliva. the 15 ml tubes containing the saliva samples were retained at room temperature at a medical center in guilan until delivery to the university of tehran. the samples were transported in batches of 40 over a period of approximately two months. for dna extraction, 1.5 cc saliva was added to a 15 ml tube that contained 1.5 cc lysis buffer (13 mm edta, 11 mm sodium citrate, 10 mm tris-hcl ph 8, 1% sds). the protocol for dna extraction was immediately pursued, or the samples were stored in the lysis buffer at 4°c for up to one week or at –20°c for up to 10 months. for samples delivered to the university of tehran within a week of donation, the tubes containing the samples and lysis buffer were vortexed at high speed for approximately 1 min to promote cell and nucleus lysis. for samples with a longer lapse between donation and delivery, the contents of the tubes were mixed but vortexing was not necessary. subsequently, 400 μl of each tube was transferred to an eppendorf tube, and 150 μl 6 m nacl and 600 μl chloroform were added. the tubes were inverted 10 times, retained at room temperature for 5 min, and then centrifuged in a microfuge for 15 min at 14000 rpm. the clear supernatant was transferred to a new tube and an equal volume of cold (–20°c) isopropanol was 576 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 carrier status of cyp1b1 mutations; heshmati et al added. after several times of inversion, clots of precipitated dna were often visible. the tubes were placed at –20°c for 30 min to overnight, and subsequently centrifuged for 10 min at 12000 rpm at 4°c. after centrifugation, the supernatant was discarded, and the precipitated dna was washed with 70% cold ethanol, dried, and dissolved in 30 μl h2o. the concentration of dna in the samples was quite variable. appropriate dilutions were made, and 20 ng dna was used as template in subsequent pcr reactions. the p.gly61glu causative mutation was screened in the dna of the individuals from talesh by a restriction fragment length polymorphism (rflp) protocol, and the p.arg368his causative mutation in the dna of the individuals from the cities of the east of guilan was screened by an amplification-refractory mutation system (arms) protocol as previously described.[17] briefly, an 830 bp exon 2 fragment that includes c.182g>a that causes p.gly61glu, and an 872 bp exon 3 fragment that includes c. 1103g>a that causes p.arg368his were pcr amplified. the restriction enzymes taqi was used in the rflp reactions for detection of c.182g>a. the unmutated exon 2 amplicon contains two taqi recognition sites. the c.182g>a mutation creates a novel recognition site, and digestion by taqi results in a changed pattern upon electrophoresis of digested products [figure 1a]. for the arms reaction pertaining to c.1103g>a that causes p.arg368his, wild type-specific and mutation-specific pcr primers were designed such that amplification of wild type alleles would proceed only in the presence of the primer specific for the unmutated sequence, and amplification of mutated alleles would proceed only in the presence of the primer specific for the mutated sequence. primers for amplification of a control irrelevant dna fragment were included in all arms reactions. the sequences of all primers used have been published.[17] for confirmation of putative mutant alleles identified, these alleles were sequenced using the sanger dideoxynucleotide termination protocol. statistical analysis to present the prevalence of the mutations, the 95% confidence interval was derived using exact binomial method. the cluster effect was considered by incorporating the design effect into the calculations. all statistical analyses were performed using stata 14.0 (stata corp., texas, usa). results successful genotyping results were achieved for the dna of 1036 of the 1400 individuals (74.0%) recruited from talesh. based on electrophoretic patterns, nine individuals (four male, five female) were carriers of the p.gly61glu mutation, corresponding to a carrier frequency of 0.86% (95% confidence interval: 0.45–1.64%) [figure 1b; table 1]. sanger sequencing confirmed the electrophoresis results in all the nine individuals [figure 1c]. the carrier frequencies of the talesh urban (0.85%) and rural regions (0.88%) were not significantly different. successful genotyping results were achieved for the dna of 3029 of the 3400 individuals (89.1%) recruited from the cities of the east of guilan. based on electrophoretic patterns, 73 individuals (12 male, 61 female) were carriers of the p.arg368his mutation, corresponding to a carrier frequency of 2.41% (95% confidence interval: 1.91–3.04%) [figure 2a; table 2]. sanger sequencing confirmed the electrophoresis results in 20 randomly chosen putative mutation carriers [figure 2b]. the carrier frequencies of the four cities of the east of guilan were not significantly different. similarly, the carrier frequencies of the urban and rural regions in each of the cities were not significantly different [table 2]. discussion whereas earlier genetic screenings pertaining to glaucoma were performed using dna extracted from the peripheral blood, dna extracted from cells in the saliva was used in the present study.[15, 17] clearly, obtaining saliva samples for populationbased studies and for studies with a relatively large number of participants is more feasible than getting blood samples. whereas the quality of blood-derived dna is almost invariably suitable for genetic and molecular studies, this is not necessarily the case for saliva-derived dna. in our hands, approximately 75% of the dnas of the talesh samples and 90% of the dnas of the samples from the cities of east guilan functioned as template in pcr reactions. we believe that lack of success in genotyping for some samples journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 577 carrier status of cyp1b1 mutations; heshmati et al figure 1. p.gly61glu mutation in cyp1b1 caused by the c.182g>a mutation in exon 2 of the encoding gene. (a) schematic diagram of 830 bp pcr amplicon that includes part of exon 2 of cyp1b1. taq1 restriction enzyme recognition sites in the amplicon containing normal and mutated exon 2 sequences, respectively, are shown by arrows above and below the amplicon. the size of dna digestion products predicted for the two types of alleles are indicated. the circle shows position of the start of exon 2 within the pcr amplicon. (b) pcr products relevant to screening of p.gly61glu. pp, the exon 2 containing pcr amplicon without restriction enzyme treatment; nn, digestion pattern of the amplicon of an individual known to be homozygous for normal sequence; mn, electrophoresis patterns of digestion products of seven of the nine individuals from talesh who were carriers of the p.gly61glu mutation. (c) dna sequence chromatograms of a wild type cyp1b1 genotype (top) and the heterozygous genotype for the two c.182g>a mutation carriers that causes p.gly61glu (bottom). was primarily due to presence of debris in the samples that could have been eliminated by better washing of the mouth prior to saliva donation. issues of delay in transport contributed to a lesser extent. our study design allowed comparison of the frequency of mutation carriers in urban and rural regions of each of the cities studied. as pcg inheritance is usually autosomal recessive, it was considered that pcg frequencies and 578 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 carrier status of cyp1b1 mutations; heshmati et al figure 2. p.arg368his mutation in cyp1b1 caused by the c.1103g>a mutation in exon 3 of the encoding gene. (a) electrophoresis patterns of pcr products relevant to screening of p.arg368his by arms protocol. two patterns are presented for each individual, one that represents products obtained with primer specific for normal allele (pn) and another that represents products obtained with primer specific for mutated allele (pm). the 474 bp fragment is the control fragment. the 207 bp fragment is from cyp1b1. nn, electrophoresis pattern of pcr products of individual known to be homozygous for the normal allele; mn, electrophoresis patterns of seven of representative individuals from east of guilan who were carriers of the p.arg368his mutation. (b) dna sequence chromatograms of a wild type cyp1b1 genotype (top) and two heterozygous genotypes for the c.1103g>a mutation that causes p.arg368his (bottom). correspondingly mutation carrier frequencies may be higher in rural regions because of presumed higher rates of consanguineous marriages. in fact, statistically significant differences between frequencies of mutation carriers in urban and rural regions of the various cities was journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 579 carrier status of cyp1b1 mutations; heshmati et al not observed. the apparent relatively high frequency of carriers in the rural region of bandar anzali (5.66%) may be due to sample size issues. the most important findings of the present study are estimates of p.gly61glu and p.arg368his mutation carrier frequencies, respectively, in talesh and the cities of the east of guilan. the estimated frequency of p.gly61glu carriers in talesh based on screening of 1036 individuals was 0.86% which is notably less than the earlier estimate of 2.9% based on screening of 173 individual. the frequency estimated in the present study is at the lower edge of the earlier 95% confidence interval frequency range (0.8–7.3%). as expected, the range of the 95% confidence interval (1.64–0.45% = 1.19%) is approximately five times less than the range of the 95% confidence interval (0.8–7.3% = 6.5%) of the earlier screening. this clearly suggests that the recent finding is more informative, and that the maximum expected frequency of p.gly61glu carriers in talesh is 1.64% rather than 7.3%. the estimated frequency of p.arg368his carriers in the east of guilan based on screening of 3029 individuals was 2.41% which is close to the earlier estimate of 2.2% based on screening of 268 individual. the range of the 95% confidence interval (3.04–1.91% = 1.13%) is approximately four times less than the range of the 95% confidence interval (4.8–0.8% = 4%) of the earlier screening. again, the recent finding is more reliable, and suggests that the minimum estimated frequency of p.arg368his carriers in the east of guilan is 1.91% rather than the previous estimate of 0.8%. the carrier frequency may be as high as 3%. the new and more reliable estimates of carrier frequencies as compared to the estimates of the earlier study are encouraging in the sense that the maximum frequency of p.gly61glu mutation carriers in talesh has decreased from 7.3% to 1.64%, and the maximum frequency of p.arg368his carriers in the east of guilan has decreased from 4.8% to 3.04%. the possibility that the frequency of p.arg368his may be higher in some localities within the east of guilan such as astaneh ashrafieh can be assessed by larger screenings within these localities [table 2]. the need for screening of the p.gly61glu and p.arg368his mutations before marriage in the respective regions should be considered. the appropriateness of implementation of measures to encourage screening of specific genes or specific mutations before marriage depends on various factors including cost and feasibility of screening and cost and size of disease burden. based on the 95% confidence level (0.45–1.64%) for frequency of p.gly61glu carriers in talesh, and assuming random mating, it is expected that between 0.002% (0.45% × 0.45%) and 0.003% (1.64% × 1.64%) of marriages in talesh will be carriers of this mutation. one fourth of the offspring of such marriages are expected to be affected with pcg. therefore, assuming equal numerical contribution of all marriages to the population of the following generation, it is expected that among one million children born in talesh, 5–7.5 ([0.25 × 0.002%] – [0.25 × 0.003%]) will be affected with pcg as a consequence of marriages between p.gly61glu mutation carriers. the figures for the p.arg368his mutation in the east of guilan are somewhat more disturbing. assuming random mating, between 0.036% (1.91% × 1.91%) and 0.103% (3.04% × 3.04%) of marriages in this region of guilan will be between carriers of the p.arg368his mutation. it can be expected that among 100,000 children born in the eastern region of guilan, 9–25.8 ([0.25 × 0.036%] – [0.25 × 0.103]) will be affected with pcg as a consequence of marriages between p. arg368his mutation carriers. it is to be noted that the arms protocols developed for screening of the p.arg368his-causing mutation is relatively inexpensive and easy to implement in clinical laboratories. it is also to be noted that premarital mutation screening programs in iran and elsewhere for thalassemia and cystic fibrosis have resulted in reduced disease incidence.[21, 23, 24] with respect to pcg, to the best of our knowledge, premarital screenings is not routinely performed in any country. this protocol is perhaps best advisable and feasible in a country such as saudi arabia where the frequency of the disease is relatively high and where a single cyp1b1 mutation makes a very significant contribution to disease incidence.[7, 8] acknowledgement the authors acknowledge the assistance of employees of the statistical center of iran and iran post for providing the information needed for the plan of the study. 580 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 carrier status of cyp1b1 mutations; heshmati et al financial support and sponsorship the research was funded and sponsored by the vice chancellor for research and technology of guilan university of medical science, the ophthalmic research center of shahid beheshti university of medical sciences, and the research division of the university of tehran. conflicts of interest there are no conflicts of interest. references 1. foster pj, buhrmann r, quigley ha, johnson gj. the definition and classification of glaucoma in prevalence surveys. br j ophthalmol 2002;86:238–243. 2. lewis cj, hedberg-buenz a, deluca ap, stone em, alward wlm, fingert jh. primary congenital and developmental glaucomas. hum mol genet 2017;26:r28–r36. 3. sarfarazi m, stoilov i, schenkman jb. genetics and biochemistry of primary congenital glaucoma. ophthalmol clin north am 2003;16:543–554. 4. souma t, tompson sw, thomson br, siggs om, kizhatil k, yamaguchi s, et al. angiopoietin receptor tek mutations underlie primary congenital glaucoma with variable expressivity. j clin invest 2016;126:2575–2587. 5. gilbert ce, canovas r, de canovas rk, foster a. causes of blindness and severe visual impairment in children in chile. dev med child neurol 1994;36:326–333. 6. tabbara kf, badr ia. changing pattern of childhood blindness in saudi arabia. br j ophthalmol 1985;69:312– 315. 7. bejjani ba, stockton dw, lewis ra, tomey kf, dueker dk, jabak m, et al. multiple cyp1b1 mutations and incomplete penetrance in an inbred population segregating primary congenital glaucoma suggest frequent de novo events and a dominant modifier locus. hum mol genet 2000;9:367–374. 8. hewitt a, mackinnon j, elder j, giubilato a, craig j, mackey a. familial transmission patterns of infantile glaucoma in australia. invest ophthalmol vis sci 2005;46:3207. 9. narooie-nejad m, paylakhi sh, shojaee s, fazlali z, rezaei kanavi m, nilforushan n, et al. loss of function mutations in the gene encoding latent transforming growth factor beta binding protein 2, ltbp2, cause primary congenital glaucoma. hum mol genet 2009;18:3969–3977. 10. firasat s, riazuddin sa, hejtmancik jf, riazuddin s. primary congenital glaucoma localizes to chromosome 14q24.21-24.3 in two consanguineous pakistani families. mol vis 2008;14:1659–1665. 11. young tl, whisenhunt kn, jin j, lamartina sm, martin sm, souma t, et al. svep1 as a genetic modifier of tek-related primary congenital glaucoma. invest ophthalmol vis sci 2020;61:6. 12. zhou x, fan n, liu x. advances in molecular genetics of glaucoma. zhonghua shiyan yanke zazhi/chinese j exp ophthalmol 2015;33:263–269. 13. plášilová m, stoilov i, sarfarazi m, kádasi l, feráková e, ferák v. identification of a single ancestral cyp1b1 mutation in slovak gypsies (roms) affected with primary congenital glaucoma. j med genet 1999;36:290–294. 14. mashima y, suzuki y, sergeev y, ohtake y, tanino t, kimura i, et al. novel cytochrome p4501b1 (cyp1b1) gene mutations in japanese patients with primary congenital glaucoma. invest ophthalmol vis sci 2001;42:2211–2216. 15. chakrabarti s, kaur k, kaur i, mandal ak, parikh rs, thomas r, et al. globally, cyp1b1 mutations in primary congenital glaucoma are strongly structured by geographic and haplotype backgrounds. invest ophthalmol vis sci 2006;47:43–47. 16. chitsazian f, tusi bk, elahi e, saroei ha, sanati mh, yazdani s, et al. cyp1b1 mutation profile of iranian primary congenital glaucoma patients and associated haplotypes. j mol diagnostics 2007;9:382–393. 17. qashqai m, suri f, yaseri m, elahi e. p.gly61glu and p.arg368his mutations in cyp1b1 that cause congenital glaucoma may be relatively frequent in certain regions of gilan province, iran. j ophthalmic vis res 2018;13:403– 410. 18. katibeh m, behboudi h, moradian s, alizadeh y, beiranvand r, sabbaghi h, et al. rapid assessment of avoidable blindness and diabetic retinopathy in gilan province, iran. ophthalmic epidemiol 2017;24:381–387. 19. armitage p, beery. g. statistical methods medical scientific. wiley; 1987. 20. ahmed s. methods in survey sampling survey errors [dissertation on the internet]. the johns hopkins university; 2009. available from: http://ocw.jhsph.edu/ courses/statmethodsforsamplesurveys/pdfs/lecture4.pdf 21. hadipour dehshal m, ahmadvand a, yousefi darestani s, manshadi m, abolghasemi h. secular trends in the national and provincial births of new thalassemia cases in iran from 2001 to 2006. hemoglobin 2013;37:124–137. 22. madan n, sharma s, sood s, colah r, bhatia h. frequency of β-thalassemia trait and other hemoglobinopathies in northern and western india. indian j hum genet 2010;16:16–25. 23. ratbi i, génin e, legendre m, le floch a, costa c, cherkaoui-deqqaqi s, et al. cystic fibrosis carrier frequency and estimated prevalence of the disease in morocco. j cyst fibros 2008;7:440–443. 24. chitsazian f. assessment of frequency of mutation in exon 3 of cyp1b1 in 60 iranian pcg patients. master’s degree thesis, university of tehran, 2007. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 581 http://ocw.jhsph.edu/courses/statmethodsforsamplesurveys/pdfs/lecture4.pdf http://ocw.jhsph.edu/courses/statmethodsforsamplesurveys/pdfs/lecture4.pdf case report metastatic intraocular tumor due to colorectal adenocarcinoma: case report and literature review deivy cruzado-sanchez1, md; luis a. saavedra-mejia2, md; walter a. tellez2, md grissnery maquera-torres3, md; solon serpa-frias1, md 1ophthalmic oncology service, instituto nacional de enfermedades neoplásicas, lima, peru 2sociedad científica de estudiantes de medicina villarrealinos, universidad nacional federico villarreal, lima, peru 3pathology service, instituto nacional de enfermedades neoplásicas, lima, peru orcid: deivy cruzado-sanchez: https://orcid.org/0000-0003-0826-8928 abstract purpose: to describe the clinical and histopathological findings of a case of intraocular metastasis due to colorectal adenocarcinoma and to carry out a literature review. case report: a 64-year-old man with a history of tumor resection due to infiltrating colorectal adenocarcinoma three years previously sought ophthalmological care because of severe ocular pain without response to medical treatment and progressive vision loss in the left eye. on ultrasonographic examination, there was a heterogeneous intraocular choroidal tumor, which occupied approximately 40% of the vitreous cavity, as well as peritumoral serous retinal detachment. the patient underwent left eyeball enucleation. the histopathological diagnosis was metastatic tubular adenocarcinoma involving the retina and choroid that partially infiltrated the sclera and the proximal optic nerve. conclusion: the present case highlights a rare pathological entity associated with variable therapeutic schemes and survival times and poor prognosis in patients with metastatic intraocular tumors due to colorectal adenocarcinoma. keywords: colorectal neoplasms; eye neoplasms; neoplasm metastasis j ophthalmic vis res 2020; 15 (4): 565–570 introduction colon cancer is the second cause of death associated with cancer in developed countries, correspondence to: deivy cruzado-sanchez, md. 2520 angamos avenue, ophthalmic oncology service, instituto nacional de enfermedades neoplásicas, 15038 lima, peru. e-mail: dcruzados@gmail.com received: 24-02-2019 accepted: 13-01-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i4.7794 representing 9% of all cancer estimated deaths;[1] while in developing countries like peru, it is the fifth cause of death, accounting for 6 deaths per 100,000 inhabitants.[2] the most frequent sites of metastasis are liver (77%), peritoneum (25%), and lungs (22%), while intraocular involvement is infrequent and rarely reported.[3–5] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: cruzado-sánchez d, saavedra-mejía la, tellez wa, maquera-torres g, serpa-frias s. metastatic intraocular tumor due to colorectal adenocarcinoma: case report and literature review. j ophthalmic vis res 2020;15:565–570. © 2020 journal of ophthalmic and vision research | published by knowledge e 565 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i4.7794&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr ocular metastasis from colorectal adenocarcinoma; cruzado-sánchez et al the aim of this report is to describe the clinical and histopathological findings of a case of intraocular metastasis from colorectal adenocarcinoma and to carry out a literature review. case report the patient was a 64-year-old man with six months of severe and progressive vision loss in the left eye associated with severe ocular pain. he had a history of resection of a moderately differentiated colorectal adenocarcinoma with muscle layer involvement, invasive borders, and involvement in 3 of the 25 regional lymph nodes (t3n1m0) three years ago. he refused complementary treatment with chemotherapy at that time (figures 1a1 and 1a2). the ophthalmological examination showed a visual acuity (va) of 20/20 in the right eye and no light perception in the left eye. intraocular pressure was 16 mmhg in the right eye and 50 mmhg in the left eye. biomicroscopic examination showed moderate conjunctival hyperemia, mydriatic and unreactive pupil, moderate corneal edema, and moderate crystalline opacity in the left eye and unremarkable findings in the right eye. funduscopy revealed extensive whitish tumor mass with multiple hemorrhagic foci on its surface, moderate vitreous opacity and retinal detachment in the left eye. on ultrasonographic examination, there was a heterogeneous intraocular choroidal tumor, which occupied approximately 40% of the vitreous cavity, as well as peritumoral serous retinal detachment (figure 2). computed tomography preformed for metastasis work-up demonstrated tumoral lesions in the lungs. he was diagnosed as a secondary noncontrolled glaucoma due to probable metastatic choroidal tumor. he received maximum antihypertensive ocular treatment in the left eye with poor response and persistence of pain. due to the evidence of a blind, painful eye with a large intraocular tumor, left eyeball enucleation was performed with patient’s informed consent. the histopathological diagnosis was metastatic tubular adenocarcinoma involving the retina and choroid, partially infiltrating the sclera and the proximal optic nerve. immunohistochemical study was positive to cdx2; some tumor cells expressed ck20 focally, and the tumor was negative for ck7. all these findings were consistent with a primary colorectal adenocarcinoma as the source of metastasis (figures 1b1–1b5). medical oncology team assessed the patient. treatment with chemotherapy and palliative radiotherapy was indicated, but he refused it and just accepted palliative pain therapy. he died six months after the enucleation. discussion metastasis of colorectal carcinoma to the eye is infrequent,[3] and it is associated with advanced stages of the disease with an unfavorable prognosis and poor survival.[6] we performed a literature review through a systematic search in pubmed and google scholar using an appropriate search strategy for each database (supplementary material 1) and reviewed the references of the reports included in the systematic search to increase the chances of identifying all reported cases of intraocular metastasis due to colorectal adenocarcinoma. we included 23 case reports and 1 case series (table 1), accounting for 25 cases, for which 19 patients presented with metastasis only to the choroid,[4–23] three with metastasis only to the retina,[24–26] one with metastasis to the retina and choroid,[27] one with metastasis to the sclera, retina, and optic nerve,[28] and one with metastasis to the choroid and optic nerve.[29] the average age was 55.2 years (ranging from 30 to 80 years), and 15 patients were men. regarding the source of the primary neoplasia, 12 were derived from the colon, 12 from the rectum, and 1 was colorectal. however, most of the papers did not report the tnm staging. the average time of detection of intraocular metastasis after the diagnosis of the primary colorectal neoplasm was 24.7 months (ranging from immediately up to 96 months); only in five cases was the diagnosis of intraocular metastasis made at the same time as the primary colorectal neoplasm diagnosis.[8, 10, 13, 18, 24] in addition to intraocular metastasis, an involvement of other organs have also been found, such as liver, lung, skin, bone, brain, and cerebellum (table 1). in the current case, intraocular metastasis was detected 36 months after the diagnosis of the primary tumor. in the cases reported in the literature (table 1), the most frequent reason for ophthalmological consultation was some type of vision dysfunction 566 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 ocular metastasis from colorectal adenocarcinoma; cruzado-sánchez et al figure 1. primary neoplasms from a1 to a3. (a1) colonic macroscopy of a single tumor above the junction of the rectum and sigmoid. (a2) tubular adenocarcinoma moderately differentiated in the submucosal layer of colon pt3n1b. intraocular metastasis from b1 to b5. (b1) eyeball with exophytic tumor. h&e staining. (b2) metastasis of tubular adenocarcinoma in the retina. (b3) metastasis of tubular adenocarcinoma in the optic nerve. (b4) positive nuclear staining for cdx2. (b5) positive focal expression of ck20. figure 2. (a) ocular ultrasound demonstrating a heterogeneous intraocular choroidal tumor associated with retinal detachment. (b) enucleated surgical tissue from the eye with a whitish tumor mass with signs of hemorrhage. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 567 ocular metastasis from colorectal adenocarcinoma; cruzado-sánchez et al table 1. characteristics of previous intraocular metastasis cases due to colorectal adenocarcinoma reported in the literature author year of publication sex age colorectal cancer intraocular metastasis other sites of metastasis survival time (months) primary lesion tnm or stage intraocular site time to diagnosis (months) symptom treatment kennedy[24] 1958 m 51 rectosigmoid ns retina s blurred vision enucleation none 9 howard[27]∗ 1968 m 63 colon ns retina, choroid 36 visual disturbance enucleation orbit 16 cole[7]∗ 1985 f 48 rectum t4a choroid 23 blurred vision rt, ct lung 4 tano[8]∗ 1989 m 30 rectum ns choroid s blurred vision enucleation bone, skin 4 endo[9]∗ 1997 f 49 rectum ns choroid 84 flashes enucleation liver, lung 3 ward[10] 2000 f 52 colon ns choroid s vision loss none intraabdominal 1 nakamura[11] 2002 m 79 colon iiib choroid 18 blurred vision ct lung ns fujiwara[12]∗ 2004 m 53 rectum ns choroid 30 vision loss rt, ct liver, lung, bone 1 linares[13] 2004 m 47 rectum ns choroid s blurred vision rt, ct liver, lung 9 apte[25] 2005 m 39 colon ns retina 3 visual disturbance rt, ct liver, lung 7 hisham[28] 2006 f 32 rectum ns sclera, retina, optic nerve 10 ocular pain rt spine, breast, orbit 0.5 kuo[14] 2008 f 65 colon ns choroid 20 vision loss intravitreous bev brain 5 sashiyama[15] 2010 m 49 rectum ns choroid 15 vision loss ct lung, bone 11 lin[16] 2010 m 43 colon ns choroid 96 vision loss ct, intravitreous bev bone 4 neale[17] 2010 m 43 rectum t2n0m0 choroid 18 blurred vision ns lung, pelvis, brain ns miyake[18]∗ 2012 m 74 rectum ns choroid s vision loss ct liver, lung 8 tei[19] 2014 m 60 rectum t1 choroid 30 floaters rt lung 27 maudgil[20] 2015 f 57 colon ns choroid 18 vision loss intravitreous bev ns ns 2015 m 80 colon ns choroid 6 vision loss intravitreous bev liver ns kawhaja[4] 2015 f 60 rectum t3n1m0 choroid 42 flashes rt, ct, systemic bev lung 31 huo[21] 2015 f 51 colon t3n1m0 choroid 27 ocular redness, foreign body sensation rt lung, bone 2.5 nookala[26] 2016 m 56 colon t3n0mx retina 25 vision loss and ocular pression sensation rt liver, lung ns boss[22] 2016 f 68 rectum t3n0mx choroid 96 floaters and flashes intravitreous bev lung, cerebellum ns ha[23] 2016 f 78 colon t3n0m0 choroid 6 visual disturbance ct lung, skin 8 walker[29] 2017 m 54 colon t1n0m0 choroid, optic nerve 16 vision loss rt, systemic bev, ct, photodynamic therapy lung 24 present case 2018 m 64 rectosigmoid t3n1m0 choroid , retina, optic nerve, sclera 36 ocular pain and vision loss enucleation lung 6 *the data from these articles were extracted secondarily from other articles that cited them because it was not possible to access to the full-text article. m, male; f, female; ns, not specified; rt, radiotherapy; ct, chemotherapy; bev, bevacizumab; s, simultaneous 568 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 ocular metastasis from colorectal adenocarcinoma; cruzado-sánchez et al supplementary material 1. literature review through a systematic search of pubmed and google scholar date results pubmed (”neoplasm metastasis”[mesh terms] or ”metastasis”[title/abstract] or ”metastases”[title/abstract] or ”ocular metastasis”[title/abstract] or ”intraocular metastasis”[title/abstract]) and (”choroid”[mesh terms] or ”choroid”[title/abstract] or ”retina”[mesh terms] or ”retina”[title/abstract]) and (”case reports”[publication type] or ”case study”[title/abstract] or ”case report”[title/abstract]) october 2018 593 google scholar (”neoplasm metastasis” or ”metastasis” or ”metastases” or ”ocular metastasis” or ”intraocular metastasis”) and (”choroid” or ”retina”) and (“colorectal cancer” or “colon cancer” or “colonic neoplasm” or “colonic cancer”) october 2018 17200 (decreased va, blurred vision, floaters or flashes), whereas in the present case, the patient had severe ocular pain related to uncontrolled secondary glaucoma in addition to vision loss, similar to a case reported in malaysia.[28] four cases of eyeball enucleation have been reported in the literature.[8, 9, 24, 27] currently, enucleation is considered a reserved therapeutic option for intraocular malignant tumors in advanced stages with extensive ocular involvement and severe pain due to secondary glaucoma.[30, 31] in the present case, enucleation was performed because of the extensive ocular involvement, absent visual function, secondary uncontrollable glaucoma, and the refusal of the patient to submit to other therapeutic proposals. the survival time ranged from 14 days to 31 months after the diagnosis of intraocular metastasis in previously published reports (table 1). in the present case, the patient’s survival time was six months. in previous cases treated with enucleation,[8, 9, 24, 27] the survival time ranged from 3 to 16 months, while longer survival times were reported in patients treated with radiotherapy, chemotherapy, and systemic bevacizumab treatment (24 and 31 months). in the present case, the immunohistochemical assessment of the intraocular tumor was positive for cdx2, focally positive for ck20, and negative for ck7. these results showed an immunohistochemical profile with high sensitivity and specificity for colorectal adenocarcinoma (cdx2+, ck7-/ck20+).[32] the focal positivity of the ck20 marker is consistent with the pattern of expression in colorectal adenocarcinoma, with greater expression in rectal carcinomas than in nonrectal carcinomas,[32] so the focal expression in this case may be due to the greater expression of this marker in tumor cells derived from the rectum than in those derived from the sigmoid colon. in conclusion, the present case highlights a rare pathological entity that has been increasingly reported in recent years and has been observed in relation to variable therapeutic schemes and survival times, and simultaneous metastasis to other organs has also been observed. therefore, clinicians should consider the possibility of intraocular metastasis when managing patients with colorectal cancer in advanced stages. references 1. siegel r, miller k, jemal a. cancer statistics, 2017. ca cancer j clin 2017;67:7–30. 2. dirección general de epidemiología. análisis de la situación del cáncer en el perú 2013. ministerio de salud [internet]. lima: ashka; 2013 [cited august 28, 2017]. available from: http://www.dge.gob.pe/portal/docs/ asis_cancer.pdf 3. hess kr, varadhachary gr, taylor sh, wei w, raber mn, lenzi r, et al. metastatic patterns in adenocarcinoma. cancer 2006;106:1624–1633. 4. khawaja m, minturn j, spittler a, chiorean e. ocular metastasis of colorectal cancer: an uncommon presentation of a common malignancy. hematol oncol stem cell ther 2015;8:176–180. 5. shields cl, shields ja, gross ne, schwartz gp, lally se. survey of 520 eyes with uveal metastases. ophthalmology 1997;104:1265–1276. 6. konstantinidis l, damato b. intraocular metastases – a review. asia pac j ophthalmol 2017;6:208–214. 7. cole md, farah nb. the choroid – an unusual site for metastasis in patients with adenocarcinoma of the rectum – a case report. eur j surg oncol 1985;11:275–278. 8. tano s, hayashi h, momoeda s. metastasis of rectal carcinoma to the choroid: a case report. nihon ganka kiyo 1989;40:1284–1288. 9. endo h, tajika t, takebayashi h, shiota h, yoshida m, kudo e. a case report of choroidal metastasis from rectal cancer. ganka rinsho iho 1997;91:1141. journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 569 http://www.dge.gob.pe/portal/docs/asis_cancer.pdf http://www.dge.gob.pe/portal/docs/asis_cancer.pdf ocular metastasis from colorectal adenocarcinoma; cruzado-sánchez et al 10. ward sd, byrne bj, kincaid mc, mann es. ultrasonographic evidence of a mushroom-shaped choroidal metastasis. am j ophthalmol 2000;130:681– 682. 11. nakamura h, harada a, sakakibara t, ishikawa t, yaguchi t, murakami y. metastatic choroidal tumor from cancer of the ascending colon a case report. j jpn surg assoc 2002;63:1031–1035. 12. fujiwara t, machida s, murai k, tazawa y, baba y, shimooki o. a case of choroidal tumor metastasized from rectal cancer. ganka 2004;46:1099–1103. 13. linares p, castanon c, vivas s, diz p, garcia-palomo a, llano c, et al. bilateral choroidal metastasis as the initial manifestation of a rectal cancer. j gastroenterol hepatol 2004;19:726–727. 14. kuo ic, haller ja, maffrand r, sambuelli rh, reviglio ve. regression of a subfoveal choroidal metastasis of colorectal carcinoma after intravitreous bevacizumab treatment. arch ophthalmol 2008;126:1311–1313. 15. sashiyama h, abe y, sasagawa s, hanada h, hatori y, kubota m, et al. a case of choroidal metastasis from rectal cancer manifesting visual loss as the initial recurrence symptom. jpn j gastroenterol surg 2010;43:746–751. 16. lin cj, li kh, hwang jf, chen sn. the effect of intravitreal bevacizumab treatment on choroidal metastasis of colon adenocarcinoma – case report. eye 2010;24:1102–1103. 17. neale ja, valsdottir e, zeger e, shields c, marks j. cerebral and choroidal metastases with retinal detachment, secondary to rectal cancer: a case report. world j colorectal surg 2010;2:1–9. 18. miyake e, moriwaki m, sunada t, takemura j. regression of choroidal metastasis from rectal cancer following chemotherapy. atarashii ganka 2012;29:701–704. 19. tei m, wakasugi m, akamatsu h. choroidal metastasis from early rectal cancer: case report and literature review. int j surg case rep 2014;5:1278–1281. 20. maudgil a, sears ks, rundle pa, rennie ig, salvi sm. failure of intravitreal bevacizumab in the treatment of choroidal metastasis. eye 2015;29:707–711. 21. huo sm, an hj, lee je, eum s, kim my, jang yn, et al. choroidal metastasis from colon cancer treated with palliative radiotherapy. korean j med 2015;89:723–727. 22. boss jd, lieu p, tewari a. effect of treatment of rectal cancer metastasis with intravitreal bevacizumab (avastin) in a patient with subretinal fluid and macular oedema: short-term follow-up. bmj case rep 2016;2016. doi: 10.1136/bcr-2016-216273 23. ha jy, oh eh, jung mk, park se, kim jt, hwang ig. choroidal and skin metastases from colorectal cancer. world j gastroenterol 2016;22:9650–9653. 24. kennedy rj, rummel wd, mccarthy jl, hazard jb. metastatic carcinoma of the retina; report of a case and the pathologic findings. ama arch ophthalmol 1958;60:12–18. 25. apte rs, dibernardo c, pearlman jr, patel s, schachat ap, green wr, et al. retinal metastasis presenting as a retinal hemorrhage in a patient with adenocarcinoma of the cecum. arch ophthalmol 2005;123:850–853. 26. nookala r, batchu vv, lee hm, loghmani a, chhabra gs. difficult diagnosis of colon adenocarcinoma metastasis to retina: a case report and literature review. int j hematol oncol stem cell res 2016;10:186–190. 27. howard gm. retinal hole in an eye with choroidal metastasis. trans am acad ophthalmol otolaryngol 1968;72:186–190. 28. hisham rb, thuaibah h, gul ya. mucinous adenocarcinoma of the rectum with breast and ocular metastases. asian j surg 2006;29:95–97. 29. walker cr, reichstein da. bilateral metastases of colorectal cancer to the choroid and optic disc. int j ophthalmol vis sci 2017;2:65–68. 30. koylu mt, gokce g, uysal y, ceylan ml, ak𝚤nc𝚤oglu d, gunal a. indications for eye removal surgeries. a 15-year experience at a tertiary military hospital. saudi med j 2015;36:2015–2019. 31. kanthan gl, jayamohan j, yip d, conway rm. management of metastatic carcinoma of the uveal tract: an evidence-based analysis. clin exp ophthalmol 2007;35:553–565. 32. bayrak r, haltas h, yenidunya s. the value of cdx2 and cytokeratins 7 and 20 expression in differentiating colorectal adenocarcinomas from extraintestinal gastrointestinal adenocarcinomas: cytokeratin 7-/20+ phenotype is more specific than cdx2 antibody. diagn pathol 2012;7:9. 570 journal of ophthalmic and vision research volume 15, issue 4, october-december 2020 original article anterior chamber characteristics, endothelial parameters, and corneal densitometry after descemet stripping automated endothelial keratoplasty in patients with fuchs dystrophy remzi karadag, md1; kristin m. hammersmith, md2; parveen k. nagra, md2; christopher j. rapuano, md2 1veni vidi eye center, istanbul, turkey 2cornea service, wills eye hospital, sidney kimmel medical college at thomas jefferson university, philadelphia, usa orcid: remzi karadag: https://orcid.org/0000-0002-7745-0726 abstract purpose: to compare anterior segment parameters in patients with fuchs endothelial dystrophy (fed) who underwent descemet stripping automated endothelial keratoplasty (dsaek) in one eye and no corneal surgery in the fellow eye. methods: this prospective study was conducted on 28 eyes of 14 patients with fed who underwent dsaek in one eye at least one year prior (dsaek group) and no corneal surgery in the fellow eye (control group). each eye was analyzed with the anterior segment optical coherence tomography, specular microscopy, and scheimpflug imaging systems. data were compared between the two groups. results: the mean age of the patients was 76.9 ± 7.0 years. there were no statistically significant differences in the mean central corneal thickness (cct), central anterior chamber depth, anterior chamber angle parameters, cylinder and keratometry values between two groups (all p-values > 0.05). the paracentral corneal thickness, corneal volume, endothelial cell density, and hexagonal cell ratio measurements were statistically significantly higher in the dsaek group than the control (all p-values < 0.05), and anterior chamber volume in the dsaek group was significantly less than the control (p = 0.046). while posterior and total corneal densitometry values in the dsaek group were statistically significantly lower than the control (p < 0.001 and p = 0.011, respectively), there were no statistically significant differences in the anterior or middle corneal densities (p = 0.108 and p = 0.134, respectively). conclusion: we found that total corneal densitometry value decreased in dsaek group. although dsaek surgery did not affect the anterior chamber angle parameters, it reduced the anterior chamber volume and increased the corneal volume and paracentral corneal thickness due to the addition of the dsaek graft. keywords: anterior chamber parameters; corneal densitometry; corneal thickness; descemet stripping automated endothelial keratoplasty; dsaek; endothelial cell; fuchs dystrophy j ophthalmic vis res 2021; 16 (2): 158–164 158 © 2021 karadag et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9078&domain=pdf&date_stamp=2019-07-17 anterior chamber parameters after dsaek in fuchs; karadag et al introduction fuchs endothelial dystrophy (fed) is a fairly common corneal disorder that can result in visual impairment and require corneal transplantation.[1] because the pathology is primarily localized to the posterior corneal layers including descemet membrane and endothelium, posterior lamellar keratoplasty is the treatment of choice for patients with fed. descemet stripping automated endothelial keratoplasty (dsaek) is one of the most commonly performed posterior lamellar surgeries for fed. this method involves the replacement of the posterior diseased part of the cornea with donor endothelium, descemet membrane, and a small amount of stroma.[2] this technique has a number of advantages over penetrating keratoplasty (pk), including less induced astigmatism, fewer suture-related complications, fewer high-order aberrations, faster visual rehabilitation, and a stronger wound.[2, 3] in the literature, a few studies have investigated biomechanical properties and keratometry of cornea, and some anterior segment (as) parameters after the dsaek surgery in patients with fed.[4, 4–7] some studies have shown that dsaek leads to a small hyperopic shift,[4, 5] residual corneal aberrations, glare and reduced contrast sensitivity compared to normal.[6, 7] to the best of our knowledge, no studies have characterized the anterior chamber and corneal parameters using three different devices after dsaek surgery in one eye in patients with fed. the aim of this study was to compare anterior chamber and corneal parameters after dsaek in one eye and no corneal surgery in the other eye in patients with fed. methods this intra-subject comparative study was performed at the wills eye hospital cornea correspondence to: remzi karadag, md. veni vidi eye center, istanbul, turkey. e-mail: drrkaradag@yahoo.com received: 31-03-2020 accepted: 06-11-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9078 service, philadelphia, pa. ethics committee approval was obtained from the wills eye hospital institutional review board. a written informed consent was obtained from all participants before entering the study. this study was conducted on 28 eyes of 14 patients with the diagnosis of fed who underwent dsaek in one eye at least one year prior (dsaek group) and no corneal surgery in the fellow eye of the same patient (control group). patients with other ocular comorbidities besides fed and a history of cataract surgery were not included. we only accepted bilateral pseudophakic patients with posterior chamber intraocular lenses in order to standardize the two groups. in addition to routine ophthalmic testing, additional measurements were obtained by one examiner (rk) using the following three imaging systems. each subject had both eyes imagined with the visante td-oct (carl zeiss meditec, inc., dublin, california, usa), the pentacam hr scheimpflug imaging system (pentacam hr, oculus, wetzlar, germany), and specular microscopy (konan non-contact specular microscope, noncon robo-ca, konan medical inc, hyogo, japan). the measurements obtained with as-oct included paracentral corneal thickness (3 mm from the corneal center), anterior chamber depth, dsaek graft diameters, scleral spur (ss) angle, angle opening distance (aod), and trabeculariris-space area (tisa) in eight different angles meridians (0, 45, 90, 135, 180, 225, 270, and 315 degree angles). ss-based measurements at all angles were measured with the internal calculation tool of the visante device [figure 1a]. the aod500 and aod750 were calculated as the distance between the trabecular meshwork and the iris 500 and 750 μm anterior from the ss, respectively. tisa 500 and tisa750 space area are defined as the area between the inner cornea-scleral wall and iris surface, which measured 500 and 750 μm anterior from ss, respectively. the calculation of aod and tisa values using the internal visante this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: karadag r, hammersmith km, nagra pk, rapuano cj. anterior chamber characteristics, endothelial parameters, and corneal densitometry after descemet stripping automated endothelial keratoplasty in patients with fuchs dystrophy. j ophthalmic vis res 2021;16:158–164. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 159 https://knepublishing.com/index.php/jovr anterior chamber parameters after dsaek in fuchs; karadag et al tool is demonstrated in figure 1. because all measurements were obtained only at 0 and 180 degrees in all patients, 0 and 180 degree values were used for statistical analysis for ss angle, aod, and tisa values. four measurements were taken for central corneal thickness (cct), central donor graft thickness, and anterior chamber depth, and the mean of the four measurements were used for statistical analysis [figure 1b]. corneal lamellar thickness measurements for dsaek graft and recipient cornea were obtained using the measurement caliper provided by the software in all eight meridians and centrally. the corneal side of graft diameter and the anterior chamber side of graft diameter were measured, defined as the straight-line distance between the anterior edges and the posterior edges of the graft, respectively [figure 1b]. specular microscopy was used to measure endothelial cell density (ecd) and hexagonal cell ratio [figures 2a and 2b]. keratometry, cylinder, anterior chamber volume, corneal volume (cv), and corneal clearance were measured using the pentacam scheimpflug imaging system. pentacam software module enables a standardized corneal densitometry analysis to be performed. we used anterior, central, posterior, and total corneal layers densitometry measurements in the central 4 mm zone of the cornea for the statistical analysis. statistical analysis was performed with analysis software (statistical package for social science, version 16; spss inc., chicago, il). comparison of measurements between two groups was analyzed by student t-test. p < 0.05 was considered statistically significant. results we included six female and eight male patients. the mean age was 76.9 ± 7.0 years. dsaek surgery was performed in nine right and five left eyes. the mean time after dsaek was 28.1 ± 9.2 months. the mean corneal side of graft diameter was 8.16 ± 0.26 mm and the mean anterior chamber side of graft diameter was 7.80 ± 0.27 mm [table 1]. patients’ demographics are shown in table 1. as-oct results are shown in tables 2 and 3. there were no statistically significant differences in mean cct value between the two groups (p = 0.253). mean paracentral corneal thickness measurements were found statistically significantly higher in the dsaek group than the control group in all eight meridians (p-values < 0.05) [table 2]. although mean anterior chamber depth values were lower in the dseak group than the controls, there was no statistically significant difference between groups (p = 0.32). there were also no statistically significant differences between groups according to aod500, aod750, tisa500, tisa 750, and ss angle measurements in 0and 180degree meridians (p-values > 0.05) [table 3]. ecd and hexagonal cell ratio values measured by specular microscopy were found statistically significantly higher in the dsaek group than the controls (p < 0.001 and p = 0.001, respectively) [table 1]. there were no statistically significant differences in the cylinder and keratometry values measured by pentacam scheimpflug imaging (p-values > 0.05). the mean cv in the dsaek group was statistically significantly higher than the control group (p < 0.001) and the anterior chamber volume in the dsaek group was statistically significantly lower than the control group (p = 0.046). when the groups were compared in terms of corneal densitometry measurements, the posterior and total corneal densitometry values in the dsaek group were statistically significantly lower than the control (p < 0.001 and p = 0.011, respectively). although there were lower values in the anterior or middle corneal densitometry in dsaek group, the differences were not statistically significant (p = 0.108 and p = 0.134, respectively) [table 1]. discussion fuchs endothelial dystrophy is a common indication for keratoplasty in developed countries. pathologic findings of fed are localized to descemet’s membrane and endothelial cells. therefore, replacement of only the endothelial cells and descemet’s membrane should improve the symptoms and findings of the disease.[2, 8] dsaek is one of the posterior lamellar surgeries. although, it has several advantages over pk, it suffers some drawbacks. one of the disadvantages of dsaek is a high surgically induced loss of endothelial cells. current long-term endothelial cell studies have shown a slowing of the endothelial cell loss as compared with pk after the first year.[9–12] in the current study, when we compared 160 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 anterior chamber parameters after dsaek in fuchs; karadag et al figure 1. (a) anterior chamber angle parameters were measured by as-oct. (b) anterior chamber depth, corneal thickness, and graft thickness. ecd between the eye with dsaek and the fellow eye with no corneal surgery, we found that the ecd was significantly higher in eyes with dsaek than the fellow eye with fed. corneal transparency has been evaluated using the pentacam scheimpflug system, which has the capability to measure light scattering and corneal haze by densitometry.[5, 13] the corneal epithelial cell layer and the corneal endothelium are the major origins of light scattering while the corneal stroma retains low scattering property.[14] deterioration of the collagen matrix due to edema in fed and subsequent corneal scarring can cause an increase in the light scattering and result in glare. arnalich-montiel et al demonstrated that densitometry values after dsaek were significantly higher than in normal subjects for full thickness, posterior and anterior parts of the paracentral cornea, and for the anterior part of the central cornea.[15] they reported that their results could depend on the optical effect of the dsaek interface. similarly, baratz and journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 161 anterior chamber parameters after dsaek in fuchs; karadag et al figure 2. (a) endothelial cells parameters in eye with fed. (b) endothelial cells parameters in dsaek. colleagues suggested that glare might be caused by scarring at the lamellar graft–host interface or by abnormalities in the residual anterior host cornea in dsaek.[16] in the present study, when the groups were compared in terms of corneal densitometry measurements, we found the posterior and total corneal densitometry values in the dsaek group were statistically significantly lower than the control eye with fed. although there were lower corneal densitometry values in the anterior or middle layers in the dsaek group, the differences were not statistically significant. it was demonstrated that dsaek surgery was associated with improved corneal densitometry when compared with the fellow eye with fed, most likely due to the lack of corneal edema. bahar et al[17] showed that anterior corneal astigmatism, anterior chamber angle, anterior chamber depth, and anterior chamber volume values measured by pentacam did not change significantly following dsaek surgery, although cct value was significantly decreased and cv value and posterior corneal astigmatism were significantly increased. they did not give any information regarding the graft thickness they used in their study.[17] in the present study, we noticed that mean cv value was significantly higher in eyes with dsaek than the fellow eyes with fed. we also found that the mean central graft thickness was 145 μm. we believe that the increase in cv probably represents the replacement of the recipient’s descemet membrane and endothelium by the donor’s lenticule which contains some donor stroma; this was greater than the decrease in corneal edema in eyes with dsaek. additionally, we measured dsaek graft diameters (corneal and anterior chamber side) in this study. we did not find any correlation among graft diameters and the others anterior chamber parameters. terry et al reported that preoperative dsaek graft thickness might have a small effect on visual outcomes in the extremes of thickness, but not in the common range of 100–200 𝜇m.[18] there is only one study in the literature evaluating angle parameters after dsaek surgery in patients with fuchs.[17] the pentacam scheimpflug device was used in that study. bahar et al[17] only measured the anterior 162 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 anterior chamber parameters after dsaek in fuchs; karadag et al chamber angle as the anterior chamber angle parameter. they found that dseak did not significantly change the anterior chamber angle. in our study, we investigated multiple anterior chamber angle parameters (angle degree, aod500, aod750, tisa 500, and tisa 750). unlike the bahar et al study,[17] we used an as-oct device instead of pentacam scheimpflug imaging for these measurements. in our study, there were no statistically significant differences between groups according to aod500, aod750, tisa500, tisa 750, and ss angle measurements. in dsaek, only the posterior lamella is changed as compared to full-thickness pkp that gives it the benefit of faster visual improvement. suture-related problems especially astigmatism is also reduced. dsaek is associated with a hyperopic shift of the order of approximately 0.8–1.5 d, depending on the lenticule thickness being transplanted. hence, the intraocular lens power needs to be refined according to this phenomenon while doing dseak combined with cataract surgery. unexpected refractive errors may sometimes occur in some patients who have undergone dsaek and cataract surgery.[19] piggy-back intraocular lenses may be needed for the treatment of these patients. as seen in this study, it should be kept in mind that the anterior chamber depth and volume may be affected by dseak surgery in such patients and measurements should be made accordingly. in conclusion, we found that total corneal densitometry value decreased in the dsaek group. although dsaek surgery does not affect the anterior chamber angle parameters, it decreases the anterior chamber volume and increases the cv and paracentral corneal thickness due to the dsaek graft thickness. we believe that due to the reduced anterior chamber volume, the anterior chamber lenses should be used with caution in these patients. financial support and sponsorship nil. conflicts of interest there is no conflict of interest. references 1. elhalis h, azizi b, jurkunas uv. fuchs endothelial corneal dystrophy. ocul surf 2010;8:173–184. 2. hjortdal j, ehlers n. descemet’s stripping automated endothelial keratoplasty and penetrating keratoplasty for fuchs’ endothelial dystrophy. acta ophthalmol 2009;87:310–314. 3. price mo, gorovoy m, benetz ba, price fw jr, menegay hj, debanne sm, et al. descemet’s stripping automated endothelial keratoplasty outcomes compared with penetrating keratoplasty from the cornea donor study. ophthalmology 2010;117:438–444. 4. jun b, kuo an, afshari na, carlson an, kim t. refractive change after descemet stripping automated endothelial keratoplasty surgery and its correlation with graft thickness and diameter. cornea 2009;28:19–23. 5. scorcia v, matteoni s, scorcia gb, scorcia g, busin m. pentacam assessment of posterior lamellar grafts to explain hyperopization after descemet’s stripping automated endothelial keratoplasty. ophthalmology 2009;116:1651–1655. 6. hindman hb, huxlin kr, pantanelli sm, callan cl, sabesan r, ching ss, et al. post-dsaek optical changes: a comprehensive prospective analysis on the role of ocular wavefront aberrations, haze, and corneal thickness. cornea 2013;32:1567–1577. 7. terry ma, shamie n, chen es, phillips pm, hoar kl, friend dj. precut tissue for descemet’s stripping automated endothelial keratoplasty: vision, astigmatism, and endothelial survival. ophthalmology 2009;116:248– 256. 8. nielsen e, ivarsen a, kristensen s, hjortdal j. fuchs’ endothelial corneal dystrophy: a controlled prospective study on visual recovery after endothelial keratoplasty. acta ophthalmol 2016;94:780–787. 9. chen es, phillips pm, terry ma, shamie n, friend dj. endothelial cell damage in descemet stripping automated endothelial keratoplasty with the underfold technique: 6and 12-month results. cornea 2010;29:1022–1024 10. price mo, bidros m, gorovoy m, price fw jr, benetz ba, menegay hj, et al. effect on incision width on graft survival and endothelial cell loss after descemet stripping automated endothelial keratoplasty. cornea 2010;29:523–527. 11. price mo, gorovoy m, price fw jr, benetz ba, menegay hj, lass jh. descemet’s stripping automated endothelial keratoplasty: three-year graft and endothelial cell survival compared with penetrating keratoplasty. ophthalmology 2013;120:246–251. 12. ang m, mehta js, lim f, bose s, htoon hm, tan d. endothelial cell loss and graft survival after descemet’s stripping automated endothelial keratoplasty and penetrating keratoplasty. ophthalmology 2012;119:2239– 2244. 13. alnawaiseh m, rosentreter a, prokosch v, eveslage m, eter n, zumhagen l. changes in corneal densitometry in patients with fuchs endothelial dystrophy after endothelial keratoplasty. curr eye res 2017;42:163–167. 14. otri am, fares u, al-aqaba ma, dua hs. corneal densitometry as an indicator of corneal health. ophthalmology 2012;119:501–508. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 163 anterior chamber parameters after dsaek in fuchs; karadag et al 15. arnalich-montiel f, hernández-verdejo jl, oblanca n, muñoznegrete fj, de miguel mp. comparison of corneal haze and visual outcome in primary dsaek versus dsaek following failed dmek. graefes arch clin exp ophthalmol 2013;251:2575– 2584. 16. baratz kh, mclaren jw, maguire lj, patel sv. corneal haze determined by confocal microscopy 2 years after descemet stripping with endothelial keratoplasty for fuchs corneal dystrophy. arch ophthalmol 2012;130:868– 874. 17. bahar i, kaiserman i, livny e, slomovic a, slomovic a. changes in corneal curvatures and anterior segment parameters after descemet stripping automated endothelial keratoplasty. curr eye res 2010;35:961– 966. 18. terry ma, straiko md, goshe jm, li jy, davis-boozer d. descemet’s stripping automated endothelial keratoplasty: the tenuous relationship between donor thickness and postoperative vision. ophthalmology 2012;119:1988– 1996. 19. singh r, gupta n, vanathi m, tandon r. corneal transplantation in the modern era. indian j med res 2019;150:7–22. 164 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 review article side effects of brolucizumab tahmineh motevasseli1,2,3, md; saeed mohammadi4,5, md; fatemeh abdi6, md; william r. freeman2,3, md 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2department of ophthalmology, shiley eye institute, university of california san diego, la jolla, ca, usa 3jacobs retina center, university of california san diego, la jolla, ca, usa 4farabi eye hospital, tehran university of medical sciences, tehran, iran 5department of ophthalmology, abadan university of medical sciences, abadan, iran 6eye research center, the five senses institute, rassoul akram hospital, iran university of medical sciences, tehran, iran orcid: tahmineh motevasseli: https://orcid.org/0000-0001-7969-0187 william r. freeman: https://orcid.org/0000-0001-9979-2500 abstract age-related macular degeneration and its complication, subretinal neovascularization, are common causes of progressive, irreversible impairment of central vision. antivascular endothelial growth factor (anti-vegf) therapy has improved the visual outcome and provided an evolution in the treatment of retinal disease. the current four antivegf drugs – pegaptanib, ranibizumab, aflibercept, and bevacizumab – have been administered for many years. a new anti-vegf agent, brolucizumab, was approved by the u.s. food and drug administration (fda) in late 2019 for the treatment of wet agerelated macular degeneration. brolucizumab is a novel single-chain fragment variable antibody that inhibits all isoforms of vegf-a and has been suggested to have more tissue penetration. despite all the benefits, there are some reports of serious side effects that need to be understood in managing patients. brolucizumab has been reported to cause occlusive retinal vasculitis in the setting of intraocular inflammation, which has not been seen in other anti-vegf medications. a pubmed and scopus search was performed and all article types were included. in the present article, we have reviewed the reported side effects of brolucizumab. keywords: anti-vascular endothelial growth factor; brolucizumab; wet age-related macular degeneration j ophthalmic vis res 2021; 16 (4): 670–675 introduction age-related macular degeneration (amd) is the leading cause of blindness in the developed correspondence to: william r. freeman, md. shiley eye institute, 9415 campus point drive, #0946, la jolla, ca 92093, usa. e-mail: wrfreeman@health.ucsd.edu received: 23-04-2021 accepted: 19-08-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9757 countries and is forecasted to affect 288 million individuals by 2040.[1] pharmacologic treatment of neovascular amd (namd) was first introduced using pegaptanib as an anti-vegf drug but was then revolutionized by introduction of this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: motevasseli t, mohammadi s, abdi f, freeman wr. side effects of brolucizumab. j ophthalmic vis res 2021;16:670–675. 670 © 2021 motevasseli et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9757&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr side effects of brolucizumab; motevasseli et al newer anti-vascular endothelial growth factors (anti-vegf) such as bevacizumab (avastin; genentech, south san francisco, california), ranibizumab (lucentis; genentech, south san francisco, california), and aflibercept (eylea; regeneron, tarrytown, new york).[2–4] however, despite significant advancements, long-term results are less promising, since about 30% of involved eyes will experience significant vision loss due to geographic atrophy in the course of the treatment.[5, 6] considering the burden of repeated injections and consequent lower patient’s compliance, the need for newer and more efficient treatments is clear.[7] brolucizumab (beovu, novartis pharma ag, basel, switzerland) is a novel single-chain fragment variable (scfv) antibody that inhibits all isoforms of vegf-a and prevents binding of this ligand to vegfr-1 and vegfr-2.[8] in comparison to a full antibody (bevacizumab) or a fab fragment (ranibizumab), this 26 kda humanized antibody is half the size of ranibizumab and may have[9] a relatively easier manufacturing process,[10] and has been suggested to have more tissue penetration with 2.2 and 1.7 times higher exposure in neurosensory retina and retinal pigment epithelium (rpe), respectively[11] due to its smaller size. it likely also has a more rapid elimination half-life which may partially offset the improved penetration. in theory, the small size also results in more rapid renal clearance and theoretically fewer systemic side effects[12, 13] due to smaller size. according to hawk and harrier studies, this novel drug has superior anatomic results with greater fluid resolution in wet macular degeneration. it was demonstrated that brolucizumab could achieve a similar bestcorrected visual acuity (bcva) compared to aflibercept with the advantage of the possibility of extension of the regimen to 12-week intervals.[14] despite all the hopes of starting a new area in the treatment of namd, reports of serious side effects have endangered this idea. in this article, we have reviewed the reported side effects of brolucizumab. methods a pubmed and scopus search was performed in february 2021 using each of the following keywords: “brolucizumab”, “side effects”, “eye”, “ocular”, “hawk”, and “harrier” in different combinations. all article types including original articles, reviews, and case reports that described the side effects of brolucizumab were identified. no limitation for the time of publication was applied. abstracts only and non-english articles were excluded. all selected articles were reviewed thoroughly by the authors and relevant articles describing the side effects of brolucizumab were discussed. results intraocular inflammation/retinal vasculitis since february 2020 which was when the initial cases of serious ocular side effects were reported, more have come into light. eleven and twenty-one cases of occlusive vasculitis were reported in february 23rd and march 30th of 2020, respectively, by the american society of retina specialists (asrs).[15] on march 31, 2020, huag and colleagues[16] reported an 88 year-old patient who developed painless decrease of vision in association with photosensitivity in both eyes four weeks after bilateral intravitreal brolucizumab due to namd. examination revealed anterior chamber reaction in both eyes with retinal arterial occlusion, vasculitis, and optic nerve inflammation in fluorescein angiography (fa). intravitreal dexamethasone was implanted in left eye which resulted in improvement of the inflammation. they hypothesized that type iv hypersensitivity reaction is responsible for intraocular inflammation (ioi). jain and coworkers[17] reported a 92-year-old patient who developed decreased vision in left eye after third intravitreal brolucizumab injection for namd. funduscopy revealed mild vitritis in association with flame-shaped hemorrhage at the superior optic disc margin, retinal whitening surrounding the proximal portion of the superotemporal branch of the central retinal artery, and intra-arteriolar greyish material in the left eye. fa showed delayed filling of several arterioles in early and late phases without perivasculature or optic disc leakage in the left eye. the patient was closely observed as there was no active inflammation. baumal and colleagues[18] evaluated 15 eyes of 12 patients with retinal vasculitis and ioi due to intravitreal injection of brolucizumab from 10 centers in united states to identify features and outcomes of this condition. they reported that retinal vasculitis and ioi is journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 671 side effects of brolucizumab; motevasseli et al mostly diagnosed 30 days after the most recent injection of brolucizumab. they showed that the affected eyes develop focal or elongated segmental sheathing, vascular nonperfusion, sclerotic vessels, cotton-wool spots, irregularity and dilation of veins, perivenular hemorrhages, and foci of phlebitis. fa showed delayed arterial filling, vascular nonperfusion, and dye leakage from the optic nerve and vessels. steroids were effective in improvement of inflammation and fa findings; however, an improvement in visual acuity was related to the location and severity of retinal occlusive vasculitis. although, two patients underwent pars plana vitrectomy, no improvement was seen. witkin et al.[19] evaluated 26 eyes of 25 patients with retinal vasculitis among postapproval cases (the number of postapproval cases is unknown) following the initial study containing 37,000 patients who received over 70,000 injections of beovu for treatment of namd and were reported to the american society of retina specialists (asrs) until april 1, 2020. postapproval cases of retinal vasculitis voluntarily reported to the asrs as of april 1, 2020. first symptoms of intraocular inflammation primarily happened 25 days following the intravitreal injection of brolucizumab. patients developed decreased vision, floaters, pain, and redness; however, two of them were asymptomatic and were diagnosed of the follow-up examinations. about one third of the patients only had anterior ioi, a third only had posterior ioi, and another third had both anterior and posterior segments inflammation; however, two eyes had no ioi other than retinal vasculitis. retinal arteries, veins, and choroidal vessels were involved. optic nerve leakage and choroidal ischemia was also noted on fa. although, there was no established treatment method, most of the patients received topical corticosteroids, nearly half of the patients received systemic corticosteroids, about fourth of them received intravitreal corticosteroids, and 15% of the patients underwent pars plana vitrectomy. ioi and retinal vasculitis resulted in permanent decrease in vision following resolution of the inflammation. the fda has reported a 4% chance of ioi and a 1% chance of retinal artery occlusion.[20] post-hoc analysis reports from two-year, double-masked, multicenter, active-controlled randomized phaseiii clinical trials (hawk and harrier) among 1817 brolucizumab-treated eyes revealed 50 patients with definite/probable drug-related side effects within the spectrum of ioi, retinal vasculitis, and/or vascular occlusion. the incidence of ioi was 4.6%, retinal vasculitis associated with ioi was 3.6%, and retinal vascular occlusion occurred in 2.1% of the patients.[21, 22] sharma et al. evaluated 42 patients who were previously treated with anti-vegf drugs in brew study. they followed their patients for a mean period of 7.2 ± 3.6 weeks, assessed the occurrence of ocular or systemic adverse events, and reported no case of inflammation, vasculitis, or any other ocular or systemic adverse effects.[23] narayanan et al.[24] reported a 62-year-old female who previously received 30 intravitreal injections of aflibercept, ziv-aflibercept, ozurdex, and ranibizumab. the patient also underwent reduced fluence pdt in the course of the treatment. the vision deteriorated due to significant subretinal scar, atrophy of outer retinal layers, and cataract. cataract surgery was performed, and the patient received intravitreal injection of brolucizumab due to persistent intraretinal fluid one month after the previous intervention. one day after the injection, the patient had minimal conjunctival injection, 1 mm hypopyon, without lid edema, and no view of the fundus due to intense vitritis. the patient underwent pars plana vitrectomy and intravitreal injection of ceftazidime and vancomycin. vitreous sample showed no growth on culture neither any organism on the smear. polymerase chain reaction for eubacteria was also negative. prednisolon acetate 1% was started frequently in association with topical moxifloxacin and homatropine eye drops which resulted in significant improvement of the vision on the fifth day. they hypothesized that along with delayed hypersensitivity reaction which causes retinal vasculitis, immediate hypersensitivity reaction similar to toxic anterior segment syndrome (tass) could also happen due to intravitreal injection of brolucizumab. iyer et al.[25] reported a 76-year-old woman with namd who had persistent subretinal fluid and a large pigment epithelial detachment in the right eye despite receiving multiple intravitreal anti-vegf treatment. the patient received three monthly injection of brolucizumab in the right eye and developed decreased vision, anterior chamber reaction, vitritis, and peripheral vascular sheathing one week after the third injection. this condition was improved by using topical prednisolone acetate 1%. the patient was switched to ranibizumab, one month after the previous brolucizumab injection. she developed decreased 672 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 side effects of brolucizumab; motevasseli et al vision due to significant occlusive retinitis which was unresponsive to corticosteroid treatment. she underwent pars plana vitrectomy in order to remove the inflammatory mediators in association with intravitreal triamcinolone injection which resulted in mild improvement of vision and signs of retinitis. they suggested that delayed onset inflammatory mechanisms (especially type iii) are responsible for ioi due to intravitreal injection of brolucizumab. kondapalli[26] reported a 77year-old women who developed retinal vasculitis after second intravitreal injection of brolucizumab. the patient had been previously treated with anti-vegf drugs. numerous keratic precipitates, vitreous cells, and retinal vasculitis was revealed in ophthalmic examination and fa showed retinal ischemia with capillary nonperfusion and disc leakage which were consistent with the diagnosis of occlusive retinal vasculitis. the patient was unresponsive to corticosteroids. phase-ii clinical trial for evaluation of the efficacy and safety of intravitreal brolucizumab showed that the most common adverse effects of brolucizumab is subconjunctival hemorrhage, vitreous floaters, reduced visual acuity, and vitreous detachment. although upper respiratory tract infection and urinary tract infection were the most commonly reported non-ocular adverse effects, the systemic adverse events were similar in the brolucizumab and aflibercept groups without a significant difference. the incidence of eye inflammation and keratitis was reported to be 2.3% among 44 participants in the study. the other reported adverse events were cataract and macular fibrosis which were seen in both groups and were probably related to the age and progression of amd.[27] the 48-week report of the hawk and harrier (phase-iii clinical trial for the evaluation of the efficacy and safety of intravitreal brolucizumab) studies reported that the most common adverse effects are conjunctival hemorrhage and reduced visual acuity. incidence of uveitis and iritis were reported to be 2.2% with brolucizumab; 90% of these cases were mild to moderate and treated with a short course of topical corticosteroids without any sequels. retinal artery occlusion was reported to happen in 0.6% and 0.3% of the participants after 48 weeks in hawk and harrier studies, respectively. other reported side effects were lenticular opacities, punctate keratitis, corneal abrasion, posterior capsule opacification, cataract, increased intraocular pressure, blepharitis, conjunctivitis, and iritis.[14] the 96-week report of hawk and harrier study showed that the most common adverse effects are conjunctival hemorrhage and reduced visual acuity. iritis and uveitis were the most frequent inflammatory adverse effects. in hawk study, iritis occurred in 0.8% and 2.5% of the patients and uveitis occurred in 1.7% and 2.2% of the patients in 3 mg and 6 mg study group, respectively; however, harrier study revealed <1% incidence of iritis and uveitis for 6 mg group. these studies showed that about 50% of ioi events happen in the first 12 weeks after injection. arterial thromboembolic events occurred in 1.1% and 1.4% of the patients in 3 mg and 6 mg study group of hawk study, respectively; and in 1.6% of the brolucizumab receiving patients in harrier study. among them, four patients in the 3 mg group and six patients in the 6 mg group had retinal artery occlusion and all of them had cardiovascular comorbidities such as hypertension or cardiac arrhythmias. the other mentioned adverse effects in the study were retinal hemorrhage, cataract, dry eye, eye pain, posterior capsule opacification, increased intraocular pressure, blepharitis, retinal pigment epithelial tear, punctate keratitis, corneal abrasion, conjunctivitis, and macular fibrosis. discussion brolucizumab, a recently approved single-chain fragment variable (scfv) is targeted to vegf for treatment of namd. its approval was thought to produce better patient care as it has better fluid control with less frequent injection schedule in eyes with namd. it was also beneficial for eyes that were nonresponsive to available anti-vegf drugs. however, the relatively high incidence of ioi particularly retinal vascular inflammation and occlusion has raised safety concerns, since about 30% of the eyes will develop visual loss due to retinal arterial events. unlike the hawk and harrier studies which reported the incidence of retinal vasculitis with retinal vascular occlusion 2.1%, it was recently reported to be 4.6 per 10,000 injections in the post-marketing surveillance.[28] this difference might be due to difference in recruited population who were treatment naïve in the phase-iii clinical trial, since patients who were previously treated with anti-vegf drugs were more susceptible to ioi. few points should be noted regarding the clinical presentation of ioi; journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 673 side effects of brolucizumab; motevasseli et al first is the predilection of ioi to affect arteries more than veins. the other issue is gender predominance; ioi mainly happens in women who had been previously treated with anti-vegf drugs. ioi has also been reported with other anti-vegf drugs such as bevacizumab,[29] ranibizumab,[30] and aflibercept.[31] single-chain fragment variable is the smallest functional part of an antibody and results in a higher molar concentration and higher antigenic load of the drug which may be responsible for the longer duration of action. antidrug antibodies (ada) existed in about 35–50% of the treatment naive eyes in the hawk and harrier trials which could be the reason for antigen-antibody immune complex deposition and subsequent type-iii hypersensitivity reaction which is postulated to be reason for ioi and retinal vasculitis.[32] summary the clinical usefulness of this novel fda-approved drug for the treatment of namd is now being questioned because of the incidence of adverse effects; however, it should be carefully evaluated in order not to lose this treatment option. references 1. wong wl, su x, li x, cheung cm, klein r, cheng cy, et al. global prevalence of age-related macular degeneration and disease burden projection for 2020 and 2040: a systematic review and meta-analysis. lancet glob health 2014;2:e106–e116. 2. gragoudas es, adamis ap, cunningham et, jr, feinsod m, guyer dr, group visionct. pegaptanib for neovascular age-related macular degeneration. n engl j med 2004;351:2805–2816. 3. comparison of age-related macular degeneration treatments trials research g, writing c, martin df, maguire mg, fine sl, ying gs, et al. ranibizumab and bevacizumab for treatment of neovascular age-related macular degeneration: two-year results. ophthalmology 2020;127:s135–s145. 4. heier js, brown dm, chong v, korobelnik jf, kaiser pk, nguyen qd, et al. intravitreal aflibercept (vegf trap-eye) in wet age-related macular degeneration. ophthalmology 2012;119:2537–2548. 5. rofagha s, bhisitkul rb, boyer ds, sadda sr, zhang k, group s-us. seven-year outcomes in ranibizumabtreated patients in anchor, marina, and horizon: a multicenter cohort study (seven-up). ophthalmology 2013;120:2292–2299. 6. maguire mg, martin df, ying gs, jaffe gj, daniel e, grunwald je, et al. five-year outcomes with anti-vascular endothelial growth factor treatment of neovascular age-related macular degeneration: the comparison of age-related macular degeneration treatments trials. ophthalmology 2016;123:1751–1761. 7. holz fg, tadayoni r, beatty s, berger a, cereda mg, cortez r, et al. multi-country real-life experience of anti-vascular endothelial growth factor therapy for wet age-related macular degeneration. br j ophthalmol 2015;99:220–226. 8. sharma a, parachuri n, kumar n, sharma r, bandello f, kuppermann bd, et al. brolucizumab-another anti-vegf or beyond. eye 2020;34:1499–1500. 9. gaudreault j, gunde t, floyd hs, ellis j, tietz j, binggeli d, et al. preclinical pharmacology and safety of esba1008, a single-chain antibody fragment, investigated as potential treatment for age-related macular degeneration. invest ophthalmol vis sci 2012;53:3025. 10. sharma a, kumar n, kuppermann bd, bandello f. brolucizimab-leading an era of structural revolution for long-term vegf suppression. eye 2020;34:611–613. 11. mohammadi ss, hosseinzadeh f, nejatollahi f. production of specific anti-egfr single chain antibodies: a promising strategy in the immunotherapy of egfr expressing tumor tissues. int j cancer manag 2017;10:e6666. 12. hosseinzadeh f, mohammadi s, nejatollahi f. production and evaluation of specific single-chain antibodies against ctla-4 for cancer-targeted therapy. rep biochem mol biol 2017;6:8–14. 13. kholodenko rv, kalinovsky dv, doronin ii, ponomarev ed, kholodenko iv. antibody fragments as potential biopharmaceuticals for cancer therapy: success and limitations. curr med chem 2019;26:396–426. 14. dugel pu, koh a, ogura y, jaffe gj, schmidt-erfurth u, brown dm, et al. hawk and harrier: phase 3, multicenter, randomized, double-masked trials of brolucizumab for neovascular age-related macular degeneration. ophthalmology 2020;127:72–84. 15. american society of retina specialists (asrs). beovu update for asrs members [internet]. chicago, il: asrs; 2020. available from: https://www.asrs.org/clinical/ clinical-updates 16. haug sj, hien dl, uludag g, ngoc ttt, lajevardi s, halim ms, et al. retinal arterial occlusive vasculitis following intravitreal brolucizumab administration. am j ophthalmol case rep 2020;18:100680. 17. jain a, chea s, matsumiya w, halim ms, yasar c, kuang g, et al. severe vision loss secondary to retinal arteriolar occlusions after multiple intravitreal brolucizumab administrations. am j ophthalmol case rep 2020;18:100687. 18. baumal cr, spaide rf, vajzovic l, freund kb, walter sd, john v, et al. retinal vasculitis and intraocular inflammation after intravitreal injection of brolucizumab. ophthalmology 2020;127:1345–1359. 19. witkin aj, hahn p, murray tg, arevalo jf, blinder kj, choudhry n, et al. occlusive retinal vasculitis following intravitreal brolucizumab. j vitreoretin dis 2020;4:269– 279. 20. novartis. us fda approves updated novartis beovu label, to include additional safety information [internet]. novartis; 2020 [cited 2021 mar 1]. available from: https://www.novartis.com/news/novartis-providesupdate-use-and-safety-beovu-patients-wet-amd 674 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 https://www.asrs.org/clinical/clinical-updates https://www.asrs.org/clinical/clinical-updates https://www.novartis.com/news/novartis-provides-update-use-and-safety-beovu-patients-wet-amd https://www.novartis.com/news/novartis-provides-update-use-and-safety-beovu-patients-wet-amd side effects of brolucizumab; motevasseli et al 21. rajan k. safety review committee releases report on inflammation events due to brolucizumab [internet]. american academy of ophthalmology; 2020 [cited 2021 mar 1]. available from: https://www.aao.org/headline/ safety-review-committee-releases-report-on-inflamm 22. mones j, srivastava sk, jaffe gj, tadayoni r, albini ta, kaiser pk, et al. risk of inflammation, retinal vasculitis, and retinal occlusion-related events with brolucizumab: post hoc review of hawk and harrier. ophthalmology 2020;128:1050–1059. 23. sharma a, kumar n, parachuri n, sadda sr, corradetti g, heier j, et al. brolucizumab-early real-world experience: brew study. eye 2020;35:1045–1047. 24. narayanan r, tyagi m, gupta sr, nayaka a, jayadev c. immediate onset of sterile endophthalmitis with hypopyon after intravitreal brolucizumab in a case of polypoidal choroidal vasculopathy. indian j ophthalmol 2021;69:469–470. 25. iyer pg, peden mc, suner ij, patel n, dubovy sr, albini ta. brolucizumab-related retinal vasculitis with exacerbation following ranibizumab retreatment: a clinicopathologic case study. am j ophthalmol case rep 2020;20:100989. 26. kondapalli ssa. retinal vasculitis after administration of brolucizumab resulting in severe loss of visual acuity. jama ophthalmol 2020;138:1103–1104. 27. dugel pu, jaffe gj, sallstig p, warburton j, weichselberger a, wieland m, et al. brolucizumab versus aflibercept in participants with neovascular age-related macular degeneration: a randomized trial. ophthalmology 2017;124:1296–1304. 28. beovu® (brolucizumab). dafety of beovu® (brolucizumab) [internet]. novartis; n.d. [cited 2021 mar 19]. available from: https://www.brolucizumab.info/ 29. gonzalez s, rosenfeld pj, stewart mw, brown j, murphy sp. avastin doesn’t blind people, people blind people. am j ophthalmol 2012;153:196–203.e1. 30. cox jt, eliott d, sobrin l. inflammatory complications of intravitreal anti-vegf injections. j clin med 2021;10:981. 31. greenberg jp, belin p, butler j, feiler d, mueller c, tye a, et al. aflibercept-related sterile intraocular inflammation outcomes. ophthalmol retina 2019;3:753–759. 32. sharma a, kumar n, parachuri n, singh s, bandello f, kuppermann bd, et al. brolucizumab-related retinal vasculitis: emerging disconnect between clinical trials and real world. eye 2020;35:1292–1294. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 675 https://www.aao.org/headline/safety-review-committee-releases-report-on-inflamm https://www.aao.org/headline/safety-review-committee-releases-report-on-inflamm https://www.brolucizumab.info/ letter to editor bilateral optic disc edema in a patient with lead poisoning paolo pigatto1,2, md; gianpaolo guzzi3, dds 1clinical dermatology, irccs istituto ortopedico galeazzi, milano mi, italy 2department of biomedical, surgical and dental sciences, university of milan, milan, italy 3italian association for metals and biocompatibility research – airmeb, milan, italy j ophthalmic vis res 2021; 16 (3): 524–525 dear editor, in their important contribution as a “case report”, abri aghdam et al[1] described a man with bilateral optic disc edema due to lead (pb) poisoning and complicated by opium addiction.[1] this is an excellent description of papilledema induced by pb overexposure,[1] which is a rare but serious optic nerve damage attributed to systemic pb toxicity.[2, 3] however, we would like to emphasize the role of whole-blood in diagnosing the pb poisoning. the patient’s serum contained very high levels of pb, which was 164 µg/dl.[1] in humans, the normal blood pb level is zero.[4, 5] we wonder whether whole-blood pb concentrations were determined. in our view, the serum is not the primary and proper indicator medium as a biomarker of pb exposure. in fact, serum alone (with no red blood cells) does not adequately reflect the 2% of the total body burden of the pb, which is found in the circulating wholeblood.[4, 5] correspondence to: gianpaolo guzzi, dds. italian association for metals and biocompatibility research – airmeb (not-for-profit organization), via a. banfi, 4, 20122 milan, italy. e-mail: gianpaolo_guzzi@fastwebnet.it received: 13-02-2021 accepted: 13-04-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i3.9450 in toxicology, the whole-blood pb concentrations have been used in conjunction with urinary pb levels as a primary measure of pb exposure in humans.[6] toxicological studies suggest that exposure to pb during developmental periods may lead to longterm visual deficits both in in vitro and in animal models.[7] toxic optic neuropathy may be the unique clinically significant alteration in patients with pb poisoning.[2, 3] fortunately, pb poisoning is a rare circumstance not commonly encountered by ophthalmologists.[8–11] consistent with this notion, pb and other toxic metals (i.e., organic mercury, thallium) are to be considered “neurotoxicants”, primarily due to toxic effects on the optic nerve.[12–14] with regard to the issue of toxic optic neuropathy, over the past two decades, we have noticed only one case in which papilledema was associated with overexposure to nickel salts. their interesting case report[1] reminds us that pb poisoning is a topic of growing interest among ophthalmologists[15] and conveys the fact that the eyes can be injured due to pb intoxication. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: pigatto p, guzzi g. bilateral optic disc edema in a patient with lead poisoning. j ophthalmic vis res 2021;16:524–525. 524 © 2021 pigatto and guzzi. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i3.9450&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr lead poisoning and papilledema; pigatto and guzzi financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. abri aghdam k, zand a, soltan sanjari m. bilateral optic disc edema in a patient with lead poisoning. j ophthalmic vis res 2019;14:513–517. 2. boudouresques j, guillot p. [papilledema, solitary manifestation of lead poisoning]. mars med 1957;94:693– 695. 3. viaud m, greau h, colas j, baron a, lhermitte r. [lead poisoning encephalopathy with papilledema; value of treatment with chelating agents; report of a case]. rev otoneuroophtalmol 1958;30:191–198. 4. guzzi g, spadari f, bombeccari gp, pigatto pd. maxillofacial gunshot wounds and diagnostic tests for lead in the blood. br j oral maxillofac surg 2017;55:105. 5. pigatto pd, ronchi a, guzzi g. iron overload, g6pd deficiency, and lead levels on blood smears. int j hematol 2016;103:724. 6. casarett lj, doull j, klaassen cd. casarett and doull’s toxicology: the basic science of poisons. 6th ed. new york: mcgraw-hill medical pub. division; 2001. p. xix, 1236. 7. fox da, kala sv, hamilton wr, johnson je, o’callaghan jp. low-level human equivalent gestational lead exposure produces supernormal scotopic electroretinograms, increased retinal neurogenesis, and decreased retinal dopamine utilization in rats. environ health perspect 2008;116:618–625. 8. citirik m, acaroglu g, mutluay ah, zilelioglu o. lead poisoning: report of a case. ann ophthalmol 2004;36:32– 36. 9. gilhotra js, von lany h, sharp dm. retinal lead toxicity. indian j ophthalmol 2007;55:152–154. 10. nagpal ag, brodie se. supranormal electroretinogram in a 10-year-old girl with lead toxicity. doc ophthalmol 2009;118:163–166. 11. sharma p, sharma r. toxic optic neuropathy. indian j ophthalmol 2011;59:137–141. 12. grzybowski a, zulsdorff m, wilhelm h, tonagel f. toxic optic neuropathies: an updated review. acta ophthalmol 2015;93:402–410. 13. saldana m, collins ce, gale r, backhouse o. diet-related mercury poisoning resulting in visual loss. br j ophthalmol 2006;90:1432–1434. 14. pamphlett r, kum jew s, cherepanoff s. mercury in the retina and optic nerve following prenatal exposure to mercury vapor. plos one 2019;14:e0220859. 15. phelps j. headliners: lead exposure and vision. environ health perspect 2005;113:a163. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 525 original article diode green laser in the lid trichiasis treatment raquel galvão bezerra1, md; roberta lílian fernandes de sousa meneghim1, md; carlos roberto padovani2, phd; silvana artioli schellini1, md 1department of ophthalmology, são paulo state university (unesp), faculty of medicine of botucatu, 18618687, botucatu, são paulo, brazil 2department of biostatistics, são paulo state university (unesp), institute of biosciences of botucatu, 18618687, botucatu, são paulo, brazil orcid: raquel galvão bezerra: https://orcid.org/0000-0002-1935-7451 silvana artioli schellini: https://orcid.org/0000-0002-6938-1230 abstract purpose: to validate the standard values and evaluate the success rate in the treatment of minor and major trichiasis using thermoablation with a diode green laser. methods: in this interventional prospective study, individuals with minor or major trichiasis who were treated with thermoablation using diode green laser were included. the patients’ mean age was 72.1 years; the majority were females (54.1%) and caucasian (98%). the parameters of the diode laser were wavelength of 532 nm, application time of 200 ms, target size of 50 μm, interval between the shots 150 to 200 ms, and power of 600 to 750 mw. the number of shots was defined by the depth of ablation sufficient to reach the pilus hair bulb. the patients were evaluated by slit-lamp every 3 to 4 months, for up to 15 months. the treatment success rate and the association between variables were analyzed. results: the study sample was comprised of 98 patients with 135 affected lids and 337 lashes with trichiasis. minor trichiasis (91.8%), unilateral trichiasis (67.3%), trichiasis affecting the lower eyelid (85.9%), and trichiasis resulting from blepharitis (64.3%) were the most common presentation profiles. the overall cure rate at the end of the study was 85%, with 69% being cured with a single session and 82.8% with two treatment sessions. conclusion: thermoablation using a diode green laser applying the specified parameters to treat minor and major trichiasis is effective and results in high cure rate. keywords: ablation techniques; diode lasers; success rate; trichiasis j ophthalmic vis res 2021; 16 (3): 320–324 introduction laser thermoablation is a simple procedure, capable of permanently treating overlapping correspondence to: silvana artioli schellini. medical school, são paulo state university, unesp, botucatu, são paulo state 18618-000, brazil. e-mail: sschellini@gmail.com received: 09-01-2020 accepted: 21-01-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i3.9428 trichiatic lashes, with minimal damage to the lid tissues and with a low risk of complications.[1–3] laser thermoablation has already proved to be a good modality of treatment for trichiasis.[1–3] argon laser, ruby laser, and diode laser are all suggested for the treatment of trichiasis;[4–6] however, the majority of studies have reported on argon laser treatment for trichiasis.[1, 4, 7–16] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: bezerra rg, de sousa meneghim rlf, padovani cr, schellini sa. diode green laser in the lid trichiasis treatment. j ophthalmic vis res 2021;16:320–324. 320 © 2021 bezerra et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i3.9428&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr laser treatment of trichiasis; bezerra et al although the diode laser is less popular, three previous studies report good results.[6, 17, 18] however, standard laser treatment parameters have not been established and success rates vary, which impedes popularity of the procedure. this study aimed to validate the standard values and success rate with the application of diode green laser for the treatment of minor and major trichiasis in order to reinforce the good results with this technique. methods the ethics research committee of the faculty of medicine of botucatu (fmb), são paulo, brazil approved this study. all patients signed a consent form prior to treatment. this longitudinal, prospective, interventional study enrolled patients from july 2016 to april 2017 with minor (less than five lashes touching the ocular surface) or major (five or more lashes touching the ocular surface) trichiasis, who underwent thermoablation of the lashes using a diode green laser at clinical hospital of fmb, brazil. individuals were excluded from the study if they had more than 10 trichiatic lashes, had distichiasis, an inability to position themselves in the slit-lamp to receive treatment, less than six months follow-up, and those who refused to participate in the study. prior to laser delivery, a combination of proxymetacaine hydrochloride 5mg/ml (anestalcon®, novartis biociências, são paulo, sp) and lidocaine ointment 25mg/g + prilocaine 25mg/g (medicaína® 5%, cristália, itapira, sp) were applied to the region of treatment. the patient was positioned to receive the laser through a slit-lamp adapted to a diode laser with green light emission (visulas 532s green laser system; zeiss, jena, germany), with fixation of the chin and forehead, eye aligned to the center of the equipment, palpebral margin everted with cotton tip to better expose the lashes to be treated and oriented to look in the direction opposite to the region planned for laser application. the diode green laser parameters were standardized and defined from a previous study of the argon laser,[16] with modifications based on empirical observations as follows: application time of 200 ms, target of 50 μm, range of 150 to 200 ms, power of 600 to 750 mw. the laser light beam was applied by around 10 different doctors who received training in the procedures before starting the study. lashes were treated one by one and no more than 10 lashes were destroyed in each session. the laser beam was focused parallel to the base of the abnormal hair follicle to be treated. the initial application vaporized the lash and applications were done until a crater was created in the lid margin. the number of shots was defined by the depth of the crater sufficient to reach the hair bulb, considering ablation of 2.5 mm for lashes in the upper eyelid and 1.5 mm for those located in the lower lid. the depth of 2.5 mm was considered based on the bevel length of an insulin needle.[16] after application, the treated area received neomycin sulfate, polymyxin b sulfate, and dexamethasone ointment (maxitrol®, alcon, são paulo, sp) twice daily for seven days. the patients were re-evaluated by a slit-lamp three to four months after the laser session. in case of relapse or recurrence, new applications were performed using the same parameters, with reassessments following the same periodicity until the end of the study. the established criterion for successful treatment was the absence of trichiatic cilia in at least two consecutive evaluations. the success rate of the treatment was calculated from the number of laser sessions the patient received to obtain the cure. the association of success to other variables was analyzed. ophthalmologic and lid examination data were collected in an excel spreadsheet (microsoft corp., redmond, wa, usa). data were collected on the location of the misdirected lashes, etiology of trichiasis and number of treated lashes, mean number of shots needed for ablation of the trichiatic lashes, and the outcomes (recurrence/relapse, or cure). data were analyzed with the goodman homogeneity test, involving contrasts between multinomial populations, considering p < 0.05 and the mann–whitney test and kruskal wallis test complemented with dunn’s multiple comparisons for non-parametric variables, given the possibility of nonadherence of the variable to the normal distribution of probabilities. results the study comprised of 98 patients (130 eyes, 135 affected lids and 337 lashes with trichiasis). sixtysix (67.3%) patients had unilateral involvement, the journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 321 laser treatment of trichiasis; bezerra et al right side was affected in seventy-one (54.6%), and the lower lid was affected in one-hundred-sixteen (85.9%) patients. the treatment was applied to treat minor trichiasis in 124 (91.8%) lids and major trichiasis in 11 (8.2%) lids. the mean age of the individuals was 72.1 ± 12.3 years; the majority were female (53/54.1%) and caucasian (96/98%). the most commonly associated etiology was blepharitis (63/64.3%), idiopathic trichiasis (15/15.3%) followed by the association of blepharitis with ectropion (9/9.2%) or other causes [table 1]. there was no statistical significance comparing the variables age, sex, race, etiology, or systemic diagnosis with the presence or quantity of the number of lashes with trichiatic cilia (p > 0.05). the average diode green laser shots needed to crater reach the depth of 2.5 mm in the upper eyelid or 1.5 mm in the lower was 60.7/cilia. the number of shots was statistically proportional to the number of misdirected lashes (p < 0.001), however, there was no significance compared to the number of shots with the sessions. follow-up time ranged from 6 to 15 months, with participants having a minimum of one and a maximum of four sessions. eighty-seven patients completed follow-up and eleven (11.2%) patients did not. hence, 87 patients comprised the study sample available for analysis. success was observed in 74 (85%), with 60 (69%) cases achieving success in a single session, 12 (13.8%) with two sessions, 1 (1.1%) with three or four sessions. treatment was unsuccessful in 13 (15%) patients who had relapses or recurrence at the last follow-up [table 2]. there was a reduction from 3.0 to 0.9 trichiatic lashes per patient and from 2.5 to 0.7 eyelid lashes (p < 0.001) with only one treatment session. there was no statistical significance (p > 0.05) for the comparison of successful treatment to the number of misdirected lashes. according to the etiology of trichiasis, the cure rate in the idiopathic etiology was higher (91.7%) than the others, while chronic inflammation of the lid margin was the cause with a lower cure rate (80.7%) (p < 0.05). discussion although laser thermoablation is considered the effective treatment for trichiasis, there is still no standardized application pattern. hence, we performed this study using the diode green laser (532 nm), time of application of 200 ms, target of 50 μm, interval of 150 to 200 ms, power of 600 to 750 mw, resulting in an 85% success rate. elderly individuals with a mean age of 72.1 years, females, and caucasian comprised the majority of our sample, similar to previous studies.[5, 13] although males and fair skin were the most affected, those parameters were not relevant to success.[6] the vast majority of our cases had minor trichiasis like other studies,[8, 10, 13] with unilateral involvement in 67.3% of the patients and 85.9% of our patients had the lower eyelid affected, presumably because of greater exposure of the lower lid.[4–6, 10, 16] chronic blepharitis, scarring of the palpebral margin, and idiopathic etiology had the greatest association to trichiasis. although trachoma is considered the main cause of trichiasis[4, 17] and bilateral and the upper eyelid pathology occur in patients with trichiasis associated to trachoma,[6, 19] it was detected in only 4.1% of our study group. we included 98 patients treated with diode green laser with a follow-up period ranging from 6 to 18 months. these patients required between one to four treatment sessions for a successful outcome. however, 11.2% of the patients were non-compliant with the follow-up schedule. the majority of the sample was composed of elderly patients with limiting comorbidities, which may be a barrier to the adherence. additionally, reduced patient compliance can occur due to pain or discomfort during application of the laser, despite instillation of topical anesthesia. minimal or absent discomfort has been reported without anesthesia,[10] with topical anesthesia,[9, 16, 20] with injectable anesthesia,[13, 15] or with a combination of both.[4, 8] if patients are given the choice, they would prefer the injectable anesthesia.[4] different types of laser equipment and parameters can result in a variable rate of success for the treatment of trichiasis. additionally, according to the manufacturer, the devices require calibration of the energy measurement at least yearly or earlier for optimal performance.[21] different parameters may lead to decreased laser light absorption by the melanin of the lash,[22] which may explain diverse results. only three other studies have been performed using the diode laser for treatment of trichiasis. one study used the same wavelength laser as the present study (532 nm) but with a higher power (up to 1,000 mw) and reported 322 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 laser treatment of trichiasis; bezerra et al table 1. etiology of trichiasis in patients treated with diode green laser etiology total blepharitis 63 (64.3%) idiopathic 15 (15.3%) blepharitis + ectropion 9 (9.2%) ectropion 4 (4.1%) trachoma 4 (4.1%) blepharitis + entropion∗ 2 (2.0%) entropion 1 (1.0%) ∗some of these entropion may have elapsed from cicatricial trachoma a lower success rate than ours (67.9% with two sessions).[17] the diode green laser was used in previous studies with a longer wavelength of 806[18] or 810 nm.[16] however, the sample from one of the studies was small (22 patients) and thermoablation was used for patients with trachomatous trichiasis, with lower success rates,[17] probably due to the chronic character of lid inflammation.[15] additionally, much lower energy of 20 j/cm² was used[18] compared to our study since we used energies ranging from 600 to 750 mw, equivalent to 48 to 60 j/cm². treatment success was achieved in 69% of our cases with only one laser green diode application and the rate increased to 82.8% with two laser sessions, concurring with previous literature.[6] with subsequent sessions, the success rate did not increase significantly. the success rates using argon laser to treat trichiasis was similar to ours, reaching 80% with three sessions using 2,000 mw and 0.05 to 0.1 exposure time;[9] or 85.2% with three sessions using 500mw and exposure time of 0.3 s;[8] or 62.6% success with just one session of 1,000 or 1,200 mw and a target of 100 um.[15] success rates can be improved using four or five argon laser sessions, increasing success rates from 67.9% to 100%[10] or 37.7% to 98.7%.[16] using ruby laser, complete success in trichiasis treatment occurred in 60% of cases,[5] a much lower rate compared to 85% that we obtained with the diode green laser. however, few patients were included and only three shots per lash was applied,[5] with a possibility to reduce success because the laser hardly reached the hair bulb. the number of shots applied during the sessions in our study was directly proportional to the number of misdirected lashes, having more shots a direct association with the number of lashes altered per lid.[15] our results point to the good outcomes with diode green laser application enhanced by a reduction of number of trichiatic lashes/patient (3.0 to 0.9 trichiatic lashes per patient) and number of misdirected lashes per session (2.5 to 0.7 lashes/lid with only one session) (p < 0.001). a study of 44 patients reported slightly better results using higher energy density (between 57 and 70 j/cm²), observing reduction from 3.58 to 0.73 cilia/lid, equivalent to a 78.6% reduction with one session[6] but the follow-up period was just three months. we observed the highest success rate in idiopathic trichiasis (91.7%), similar to previous reports.[8, 15] despite a few trachomatous trichiasis cases, the success rates may be significantly lower due to the fact that these individuals may present anatomical changes in the eyelid, making it difficult to reach the hair bulb,[15] in addition to the chronic and persistent inflammation. the present study had limitations including nonadherence of 11.2% of the participants and the fact that several ophthalmologists had applied the treatment, even though they were all trained and standardized prior to the study. the criteria for successful treatment and the success rate in our study were based on the relapse/recurrence of the trichiasis during follow-up. although the definitions of recurrence and relapse differ, it was not possible to differentiate them because there was no photographic documentation in this study. the strengths of our study were the prospective nature of the study, the high number of participants, journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 323 laser treatment of trichiasis; bezerra et al the application of standardized parameters, the long follow-up period and the statistical analysis of the data that allowed a higher chance of success with the application of diode green laser for the treatment of trichiasis. the major advantages of diode green laser therapy are precision and selectivity of application. diode laser application is an easy procedure, no need for infiltrative anesthesia resulting in mild inflammation and no scarring. in conclusion, thermoablation using the diode green laser with a wavelength of 532 nm, application time of 200 ms, target of 50 μm, interval of 150 to 200 ms, power of 600 to 750 mw was effective for treating minor and major trichiasis, with success achieved in 85% of the patients. it took up to two sessions for successful treatment in most patients, with an insignificant increase in success with more sessions. financial support and sponsorship nil. conflicts of interest the authors do not have any conflicts of interest. references 1. hanumanthu s, webb la, lee wr, williamson j. histological and morphometric analysis of the effects of argon laser epilation. br j ophthalmol 2003;87;984– 987. 2. ferreira is, bernardes tf, bonfioli aa . trichiasis. semin ophthalmol 2010;25:66–71. 3. rajak sn, collin jro, burton mj. trachomatous trichiasis and its management in endemic countries. surv ophthalmol 2012;57:105–135. 4. fonseca jr nl, lucci lmd, paulino lv, rehder jrcli. argon laser in the treatment of trichiasis. arq bras oftalmol 2004;67;277–281. 5. moore j, de silva sr, o’hare k, humphry rc. ruby laser for the treatment of trichiasis. lasers med sci 2009;24;137–139. 6. pham rth, biesman bs, silkiss rz. treatment of trichiasis using an 810-nm diode laser: an efficacy study. ophthal plast reconstr surg 2006;22;445–447. 7. sahni j, clark d. argon laser and trichiasis: a helpful tip. br j ophthalmol 2001;85:762. 8. al-bdour md, al-till mi. argon laser: a modality of treatment for trichiasis. int j biomed sci 2007;3:56–59. 9. campbell dc. thermoablation treatment for trichiasis using the argon laser. aust n z j ophthalmol 1990;8:427– 430. 10. sharif kw, arafat afa, wykes wc. the treatment of recurrent trichiasis with argon laser photocoagulation. eye 1991;5:591–595. 11. huneke jw. argon laser treatment for trichiasis. ophthal plast reconstr surg 1992;8:50–55. 12. gossman md, yung r, berlin aj, brightwell jr. prospective evaluation of the argon laser in the treatment of trichiasis. ophthalmic surg 1992;23:183–187. 13. bartley gb, lowry jc. argon laser treatment of trichiasis. am j ophthalmol 1992;113:71–74. 14. yung cw, massicotte sj, kuwabara t. argon laser treatment of trichiasis: a clinical and histopathologic evaluation. ophthal plast reconstr surg 1994;10:130–136. 15. yeung ym. argon laser treatment of trichiasis in hong kong. br j ophthalmol 1995;79:506–507. 16. hata mm, schellini sa, aragon ff, monteiro ecl, padovani cr. [argon laser in trichiasis and distichiasis treatment]. arq bras oftalmol 1999;62:285–295. 17. oguz h, aras c, ozdamar a. thermoablation treatment for trichiasis in trachoma using the semiconductor diode pumped laser. eur j ophthalmol 1999;9:85–88. 18. strempel i, strempel h, lange p. treatment of trichiasis with a diode laser. ophthalmologe 2000;97:633–634. 19. wanzeler acv, do nascimento mf, sousa rlf, padovani cr, schellini sa, wanzeler acv, et al eyelid disorders: frequency of occurrence and profile of carriers in a brazilian population sample. rev bras oftalmol 2015;74:231–234. 20. başar e, ozdemir h, ozkan s, cicik e, mirzataş c. treatment of trichiasis with argon laser. eur j ophthalmol 2000;10:273–275. 21. rodrigues er, zotter r. manual do usuário visulas 532s instructions to use [internet]. [cited 2018 jun 2]. available from: http://www.eyesolution.com.br/pdf/visulas532.pdf 22. drummond am de c, monteiro ec, gouvea pmp de (2007). confiabilidade metrológica de equipamentos eletromédicos a laser e a luz intensa pulsada. pontifical catholic university of rio de janeiro; 2007. available from: https://www.maxwell.vrac.puc-rio.br/busca_etds. php?strsecao=resultado&nrseq=10706@1 324 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 http://www.eyesolution.com.br/pdf/visulas 532.pdf https://www.maxwell.vrac.puc-rio.br/busca_etds.php?strsecao=resultado&nrseq=10706@1 https://www.maxwell.vrac.puc-rio.br/busca_etds.php?strsecao=resultado&nrseq=10706@1 perspective ophthalmic workplace modifications for the post-covid era hasan naveed1,2, mbbs, bs (hons); victor leung3, msc, cih, roh, crsp mehran zarei-ghanavati4, md, fico; christopher leak5, bs, ba, bmbs, mcoptom, msc, mphil, frcophth christopher liu1,2,5 obe, frcophth, frcsed, frcp, certlrs 1sussex eye hospital, brighton and sussex university hospitals nhs trust, uk 2brighton and sussex medical school, uk 3core extension health & safety, canada 4eye research center, farabi eye hospital, tehran university of medical sciences, tehran, iran 5moorfields eye hospital, croydon, uk 6tongdean eye clinic, uk orcid: hasan naveed: https://orcid.org/0000-0001-7668-3168 christopher liu: https://orcid.org/0000-0002-1045-196x abstract the covid-19 pandemic necessitates implementation of exposure control measures in all facets of the healthcare sector. healthcare professionals who work in busy ophthalmology clinics and theaters are amidst the highest at-risk of contracting covid19. the authors review the up-to-date scientific evidence of sars-cov-2 transmission to demystify and explain the exposure control options available for ophthalmic workplace and offer insights from an industrial hygiene standpoint. as the we enter the post-covid world, these measures will be critical to enhance workplace safety, and thus protect patients and staff alike. keywords: covid-19; ophthalmic workplace; protecting healthcare workers; sars-cov-2; personal protective equipment j ophthalmic vis res 2020; 15 (3): 400–407 introduction covid-19, caused by novel severe acute respiratory syndrome coronavirus 2 (sarscov2), was declared a pandemic by the world health organization (who) on march 12, 2020.[1] it has since displayed its destructive potential by correspondence to: christopher liu, obe, frcophth, frcsed, frcp, certlrs. sussex eye hospital, eastern road, brighton, united kingdom bn2 5bf. e-mail: cscliu@aol.com received: 10-06-2020 accepted: 25-06-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v15i3.7458 overwhelming the hospital systems of some of the most well-resourced countries and claiming over 360,000 fatalities in its wake.[2] furthermore, the cessation of nonurgent elective work in order to increase capacity to manage the predicted surge of cases, whilst necessary, has had significant impact on the care of patients with other comorbidities by restricting access and delaying treatments. measures including national lockdowns, enforcing social distancing measures, contact tracing, universal masking, shielding of the this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: naveed h, leung v, zarei-ghanavati m, leak c, liu c. ophthalmic workplace modifications for the post-covid era. j ophthalmic vis res 2020;15:400–407. 400 © 2020 journal of ophthalmic and vision research | published by published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v15i3.7458&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr workplace adjustments post-covid; naveed et al vulnerable, and quarantining the infected may have slowed the spread of the disease and reduced impact. in fact, most countries have now passed the peak of their covid-19 cases. however, without a vaccine there is little evidence to suggest that the complete eradication of covid-19 will be achieved and experts predict recurrent postpandemic outbreaks. we have to accept that the virus will be a part of our lives for the foreseeable future.[3] the challenge for healthcare professionals now is to safely resume the necessary healthcare services. the onus is to ensure that this time is used as a valuable opportunity and collective expertise is utilized to innovate genuine improvements for the ultimate benefit of patients. sars-cov-2 description sars-cov2 is a positive-sense singlestranded rna virus which infects cells in the lower respiratory tract, gaining entry via the ace2 receptors, similar to sars-cov.[4] infected individuals can remain asymptomatic or develop symptoms that are predominantly on the respiratory pathological spectrum.[5, 6] most common symptoms experienced are mild in nature and include anosmia, sore throat, cough, fever, and myalgia; however 15% get affected by severe pneumonia leading to acute respiratory distress syndrome requiring intensive care.[6, 7] the virus has a propensity to affect the elderly, the comorbid, and the immunocompromised more severely; however, this is not exclusive as an increased viral dose and inoculation can also lead to severe disease phenotype.[4, 8] early analysis by liu et al (2020) has shown that viral shedding and viral load found in the nasopharyngeal mucosa are directly proportional to the severity of symptoms experienced.[9] it has also been shown that asymptomatic individuals are capable of spreading the virus as well.[10] sars-cov2 is highly efficient in its transmission from person to person for a low infective dose, and primarily spreads via respiratory droplets, aerosols, and contact.[4] the total number of particles and ratio of respiratory aerosols (< 5µm) to droplets (> 5µm) is directly proportional to the airway effort and disruption involved in breathing, speaking, coughing, or sneezing.[11–13] this is important because larger droplets of respiratory origin do not usually travel more than 2 m, but smaller aerosolized particles can travel further and remain in the air for longer durations.[11, 14] for example, particles with aerodynamic diameters of 0.5 and 10 µm will settle 5 feet in 41 h and 8.2 min, respectively.[14] these aforementioned facts make it scientifically plausible that infected individuals constantly spread the virus in their environment, where it lasts in air attached to the aerosols, and also on inanimate surfaces such as plastics for up to 72 h.[15] enhancing safety in ophthalmology settings many eye units around the globe had come to a halt during the pandemic. for example, in the uk, the royal college of ophthalmologists had recommended the suspension of all nonurgent elective eye operations and postponement of low-risk non-urgent outpatient clinics which lasted approximately 12 weeks.[16] these measures, whilst essential, had a significant impact on the organization and delivery of ophthalmic services. ophthalmic units now face the challenge of resuming services with a tremendous increase in workload through the added backlog which cannot be ignored. ophthalmology is already one of the busiest outpatient specialties in healthcare. each patient’s journey includes several healthcare personnel interacting to undertake routine objective assessments which is often followed by specialized imaging. the clinical consultation can take an average of 8 min and includes a close proximity slit-lamp examination to systematically inspect the eye and its adnexa. during the wuhan outbreak of covid-19, nosocomial transmission was reported to be highest in ent and ophthalmology.[17] the standard high-volume practice observed in ophthalmic units is therefore very high-risk and cannot be underestimated in subjecting staff and patients to contracting sars-cov2. thus, the resumption of effective ophthalmic services mandates several key modifications to safely diagnose and treat patients. exposure mitigation measures in the ophthalmology need to be specifically tailored including infection control, engineering control, administrative journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 401 workplace adjustments post-covid; naveed et al control, and provision of appropriate protective equipment. infection control • regular handwashing with soap and running water for 20 sec should be followed by staff. patients should also gel hands on entry to the unit and before leaving. upon arrival at home, they should again wash hands • clinical interactive surfaces should be cleaned with alcohol-based or bleach-based disinfectants. this is also true for slit-lamp and imaging devices. • all personnel in the eye department should be instructed never to touch face. this is to ensure that there is protection of all mucous membranes; eyes, nose, and mouth. • there should be strict non-touch of all surfaces unless unavoidable. • there should be no handshakes between staff and patients. administrative control emergency clinics • emergency eye services should continue to run as a priority to provide timely care to those absolute emergencies where there is a risk of loss of sight. • all emergency cases should undergo telephone triage by a senior clinician to ascertain the urgency of review and/or provide reassurance. an effective alternative is to utilize video consultations, such as the nhs’s attend anywhere, which has reduced ophthalmic a&e attendances by 30%. the success of the video consultations has pushed for its development in other ophthalmic specialties. • it is also recommended that clinicians use a standardized questionnaire during appointment bookings and selection to flag out high-risk patients based on reported symptoms and contact history. routine clinics • restarting clinical work will require case selection so as to reduce any excessive and avoidable exposure to staff and patients, many of whom are elderly and at an increased risk of becoming infected leading to severe illness with a high mortality rate. • stratification systems to prioritize patients will need to be developed on the basis of potential harm and urgency due to delay. patients who have been postponed and now require urgent treatment will need to have virtual reviews with their notes to classify and prioritize their reviews/treatment. • face-to-face time and slots in clinics still need to be minimized. virtual clinics and telephone triage should be done in specially designated clinics with the patients’ notes available. this can be used to identify patients that necessitate further checks, examination, or procedures in person. such patients can then be booked into designated face-to-face clinics. • there should be a dedicated patientaccessible eye hospital website detailing information about common ophthalmic conditions and procedures vetted by the ophthalmologists of that institution. there can be supportive video content exploring expectations of different procedures to educate the patient. • hospitals must invest in it infrastructure for safe remote prescribing by liaising with local and regional pharmacies. this will aid repeat prescriptions and allow clinicians to review any continuing treatments, such as for glaucoma patients. surgical theatres • general anesthetic in all cases should be considered only when absolutely necessary due to intubation being considered as an aerosolgenerating procedure (agp). local anesthetic, if possible, should be explained to patients and considered. • careful consideration needs to be given to cases requiring surgical methods involving exploration of the orbit with high-speed drills should be avoided as it generates aerosols. • only operating on absolute emergencies where there is a risk of loss of sight during the pandemic and any further waves of infection. • patients undergoing elective procedures should self-isolate for two weeks before the surgery and undergo covid testing (antigen pcr) 48 h before the surgery. 402 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 workplace adjustments post-covid; naveed et al clinical pathways • patient pathways and flow through the department needs to be carefully considered so that least number of stations are visited for the different tests and required examinations. the pathways should also consider being seen by the least number of professionals possible. • face-to-face clinics should operate on specific time slots with well-staggered time intervals. patients should come alone, or with one relative/carer. • patients should be encouraged to arrive at a specific time and wait in car until called in for their appointment. upon entry, the patients must be screened again for covid-19 symptoms. • self-check in computerized stations should be placed at the entrances where patient can register for their appointment and staff can remotely inquire about covid-19 symptoms. there can also be remote temperature-checking equipment for the patient to self-check for fever. this can also be used to take a history from the patient. • following the check-in, patient should be allowed to enter the department. all patients should cover their mouth and nose with medical masks, cloth masks, or simply with a piece of cloth (unless contraindicated). upon entry, they should be directed to the clinic room as quickly as possible without any undue delay and waiting. • clinic room face-to-face meeting should be primarily examination-based. all examinations must be focused. • all explanation and consultations after examinations should be done remotely to reduce face-to-face time and discussion in clinics. • conversations should also be kept to a minimum and all patients should be instructed to speak little. there should be no talk during the slitlamp examination. • departmental patient numbers should not accrue more than an upper limit, which is defined on the basis of physical space available and ventilation. staff • staff should not accrue in rooms and maintain a distance of at least 1 m at all times. • there should not be any face-to-face meetings, and where possible telephone and e-meetings should be organized instead. • universal masking throughout the premises should be mandated for all staff (unless contraindicated). environmental control patient separation • there should be a red pathway for covid positive, symptomatic, and suspect patients who necessitate examination, with a separate entrance and exit and designated room for examination. red-labelled operating rooms should also be separated. • for all patients who are covid-negative or asymptomatic, there should be a green stream involving a separate entrance and exit. there should also be designated rooms for examination and operating. outpatients • there should be a designated separate entrance and exit for all attending patients. • two separate doorways should be individually designated and labelled as exit and entrance for clarity of staff and patients alike. • there should be flow markings on the floor, and directions on the walls (similar to supermarkets). • consider setting up a physical barrier (such as a plexiglass wall) between reception and patient area and adjust ventilation system to have the reception area a positive pressure zone. this way, any direct droplet and airborne particle spread can be blocked from the patient areas. • waiting room must have a seating arrangement with a gap of at least 1 m between seats. clinics and equipment • ophthalmic clinics must be conducted in a designated well-ventilated room. ventilation systems should be fitted with high efficiency particulate air (hepa) filters to purify air in the clinical areas. if this is not possible, windows can be opened to maintain airflow in spacious rooms. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 403 workplace adjustments post-covid; naveed et al • all slit lamps should be modified to incorporate a clear thick plastic or perspex shield breath guards with sufficient dimensions to provide cover for the examining ophthalmologist and patient. • in imaging clinics, the machinery can be encompassed by a specialized perspex box-type enclosure with glove entrances. these enclosures can be linked to the exhaust fan with high efficiency particulate air (hepa) filter to create negative pressure system for your operation. operating theatres • operating theatres should be properly ventilated to meet the designed air change requirement or with ambient air recycled with hepa systems to reduce risk of aerosol spread and deposition in the environment. ashrae recommends 20 air changes per hour for operating rooms.[18] • there should be a designated separate entrance and exit to the theatre. personal protective equipment personal protective equipment (ppe) provisions are paramount in reducing transmission of sarscov-2 to the healthcare workers. staff must also be trained in the proper donning and doffing procedures. eye protection eye protection encompasses several different types of safety devices including safety goggles, visors, and face shields. ideally, eye protection should be offered in the form of visors or goggles that fit snugly by forming a seal around the eyes. there have been case reports suggesting that coronavirus is transmissible through conjunctival tissue as well.[19] gloves and gown gloves and gowns are recommended when dealing with high-risk cases, particularly when in an aerosol-generating environment. high-risk areas are cohorted in most hospitals, so the staff should refrain from deploy donning and doffing repeatedly in these areas. ppe donning should only be done in a designated clean area while a separate designated area should be used for ppe removal. this is because doffing can shed virus that may become airborne and contaminate bits of gear, face, or hands. every surface including used ppe should be considered contaminated. gloves use should be mandatory to prevent crosscontamination between hand-surface material cross-contamination and when examining ocular and adnexal tissues. masks and respirators formal use of surgical masks has been recommended at least since the early 1900s to avoid droplet contamination during surgical procedures.[20] respiratory personal protection is paramount as it protects the mucosa of nose and mouth. nowadays, there are various types of surgical masks and respirators available to the healthcare workforce (table 1).[21, 22] surgical masks comprise of three layers: an inner soft absorbent layer, a middle polypropylene barrier, and an outer hydrophobic fabric which mold to the user’s nasal bridge to cover nose, mouth, and chin. they act as a barrier to infectious droplets. they also assist in the maintenance of a sterile field by reducing the spread of droplets from the wearer’s nose and mouth.[13, 23, 24] filtering facepiece respirators (ffps), on the other hand, provide additional benefit to surgical masks by providing an air-tight seal and containing a mechanical filter, which can remove airborne contaminants through interception. health and safety executive and british safety industry federation recommend fit testing to ensure the respirator is suited to the user’s facial structure and therefore performs optimally. there are three categories of ffp in europe: ffp1, ffp2 (equivalent to n95), and ffp3. class three (ffp3) provides the highest quality of protection and is the only one approved for uk healthcare settings, especially in agps, such as intubation and non-invasive ventilation. they must meet industry-standard regulations including strict industry tests with biological aerosols and cannot exceed 2% leakage. ffp3 masks provide 99% efficiency in filtering particles 404 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 workplace adjustments post-covid; naveed et al sized above 100 nm, including small airborne droplets.[22, 24] based on the scientific rationale provided in this article and established practice in the fareastern countries, masks or facial coverings must be worn by all patients and staff at all times.[25] this reduces the spread of respiratory droplets in the environment and deposition on fomites and therefore protects from inhalation of virus-laden aerosols. close contact with symptomatic patients who have more respiratory aerosol production necessitates the use of respirators. conserving and procuring personal protective equipment it is envisioned that by streamlining the service during the covid-19 pandemic to exclusively treat emergencies and operating on the life-, limb-, or organ-threatening conditions, we would conserve the limited supply of specialized protective equipment necessary to provide safe care. however, if this pandemic lasts for a longer duration, with more and more people being infected, then we may be threatening to fast deplete our supply of resources and ppe kit with the current model of single use or single session use. the issue of ensuring a steady supply of ppe equipment will require commissioning production of these items nationally. in the uk, industrial plants that have machinery to produce face shields or masks have already started to offer a helping hand to the government by developing and supplying ppe to hospitals. similarly, there are also in-house 3d printing technology centers that can be used to make face shields, visors, and goggles. countries in short supply need to explore the possibility of further importing from china, where they now have spare capacity. as large variation in quality in masks have been reported, ppe procurement should obtain small batch samples to verify ppe effectiveness prior to mass ordering. given the finite resources, it is also paramount that mask reusability and extended wear is explored as a priority. taiwan was able to successfully limit its public to purchase a maximum of two masks per week, which allowed appropriate distribution to all and enforced reuse.[26] masks have been shown to be reusable in studies using energetic methods such as germicidal ultraviolet light and microwaved steam.[27–29] us food and drug administration has given an emergency go-ahead to a novel battelle critical care decontamination systemtm which uses vaporized hydrogen peroxide to sterilize and does not degrade filter performance of respirators.[30] there are also unlicensed recommendations to utilize autoclaves or ovens to sterilize masks and perhaps that will be effective for a limited number of cycles before the mask efficiency degrades to substandard levels. in these desperate times, we have no choice but to be resourceful and adapt during this pandemic by using the existing scientific knowledge of decontamination with our understanding of sarscov-2 virus.[29] conserving medical, nursing, and allied healthcare workforce healthcare workers are at the most risk of repetitive exposure to this pathogen that increases their viral load predisposing them to contracting severe pneumonia and end up hospitalized. there have several fatalities of frontline staff around the world; in italy, ∼8% of the total cases affected were healthcare workers.[31] this risk is highest to healthcare workers participating in agps and to ent and ophthalmology staff who see an increased outpatient load at close quarters.[17] risk assessment of bame, co-morbid, and older members of staff should be prioritized to ensure safe working standards and appropriate job roles are allocated. we also have to ensure that staff are tested regularly to maintain a strong battlefront against this pandemic. it should also be compulsory for staff to self-monitor twice daily temperatures and development of infective symptoms, as was done in national university hospital, singapore.[32] depending on the availability of tests, regular sars-cov-2 testing should also be mandated for all working and returning staff to prevent asymptomatic spread in the healthcare workplace.[33] summary veni, vidi, vici. i came, i saw, i conquered. covid19 came and unleashed untold harm to society journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 405 workplace adjustments post-covid; naveed et al table 1. comparison of different commonly used face mask/respirator in the market[21,22] mask type standards filtration effectiveness surgical mask china yy 0469 3.0 microns ≥ 95% 0.1 microns ≥ 30% usa astm f2100 level 1 level 2 level 3 3.0 microns ≥ 95% 3.0 microns ≥ 98% 3.0 microns ≥ 98% 0.1 microns ≥ 95% 0.1 microns ≥ 98% 0.1 microns ≥ 98% europe en 14683 type i type ii type iii 3.0 microns ≥ 95% 0.3 microns ≥ 98% 0.3 microns ≥ 98% 0.1 microns x 0.1 microns x 0.1 microns x respirator mask usa niosh (42 cfr 84) n95/kn95 n99/kn99 n100/kn100 china gb2626 0.3 microns ≥ 95% 0.3 microns ≥ 99% 0.3 microns ≥ 99.97% europe en149 :2001 ffp1 ffp2 ffp3 0.3 microns ≥ 80% 0.3 microns ≥ 94% 0.3 microns ≥ 99% 3.0 microns: bacteria filtration standard (bfe) 0.1 microns: particle filtration efficiency standard (pfe) 0.3 microns: used to represent the most penetrating particle size x: no requirements and will linger on with possibility of further waves unless it self-attenuates, or safe effective vaccines arrive. in the light of current knowledge of covid19, we have put together important considerations for protecting patients and staff. primum non nocere – we need to be certain that we are protecting patients from contracting the coronavirus. at the same time, we also have a duty of care to staff. there is not only a contractual duty but a moral duty to protect medical, nursing, and other healthcare staff. conserving highly trained healthcare staff is of course a national interest. the prevention of spread is done through education, guidelines, rules, and the law. it behooves governments and healthcare regulators to put these in place. in a century’s time, we want future ophthalmologists to be able to look back and say their forebears had done well in the year 2020 protecting ophthalmology patients and staff and laid foundations for new pathways and new ways of delivering safe ophthalmic care, thus transforming ophthalmology despite the challenge of high volume and high risk. financial support and sponsorship none. conflicts of interest there are no conflicts of interest. references 1. who. who announces covid-19 outbreak a pandemic [internet]. who; 2020. available from: http://www.euro.who.int/en/health-topics/healthemergencies/coronavirus-covid-19/news/news/2020/ 3/who-announces-covid-19-outbreak-a-pandemic. 2. johns hopkins, school of medicine. coronavirus resource center statistics [internet]. johns hopkins university; 2020 [cited june 6, 2020]. available from: https://coronavirus. jhu.edu/map.html. 3. kissler sm, tedijanto c, goldstein e, grad yh, lipsitch m. projecting the transmission dynamics of sarscov-2 through the postpandemic period. science 2020;368:860–868. 4. guo yr, cao qd, hong zs, tan yy, chen sd, jin hj, et al. the origin, transmission and clinical therapies on coronavirus disease 2019 (covid-19) outbreak an update on the status. mil med res 2020;7:11. 5. nishiura h, kobayashi t, suzuki a, jung s-mok, hayashi k, kinoshita r, yang y, et al. estimation of the asymptomatic ratio of novel coronavirus infections (covid-19). int j infect dis 2020;94:154–155. 6. guan wj, ni zy, hu y, liang wh, ou cq, he jx, liu l, et al. china medical treatment expert group for covid19. clinical characteristics of coronavirus disease 2019 in china. n engl j med 2020;382:1708–1720. 7. hopkins c, kumar n. loss of smell as a marker for covid-19 infection [document]. ent uk; 2020. available 406 journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 http://www.euro.who.int/en/health-topics/health-emergencies/coronavirus-covid-19/news/news/2020/3/who-announces-covid-19-outbreak-a-pandemic http://www.euro.who.int/en/health-topics/health-emergencies/coronavirus-covid-19/news/news/2020/3/who-announces-covid-19-outbreak-a-pandemic http://www.euro.who.int/en/health-topics/health-emergencies/coronavirus-covid-19/news/news/2020/3/who-announces-covid-19-outbreak-a-pandemic https://coronavirus.jhu.edu/map.html https://coronavirus.jhu.edu/map.html workplace adjustments post-covid; naveed et al from: https://www.entuk.org/sites/default/files/files/loss% 20of%20sense%20of%20smell%20as%20marker% 20of%20covid.pdf. 8. heneghan c, brassey j, jefferson t. oxford covid19 evidence service team. sars-cov-2 viral load and the severity of covid-19 [internet]. centre for evidence-based medicine; 2020. available from: https://www.cebm.net/covid-19/sars-cov-2-viral-loadand-the-severity-of-covid-19/. 9. liu y, yan l, wan l, xiang t, le a, liu j, et al. viral dynamics in mild and severe cases of covid 19. lancet infect dis 2020;20:656–657. 10. lai cc, liu yh, wang cy, wang yh, hsueh sc, yen my, et al. asymptomatic carrier state, acute respiratory disease, and pneumonia due to severe acute respiratory syndrome coronavirus 2 (sars-cov-2): facts and myths. j microbiol immunol infect 2020:s1684–1182:30040– 30042. 11. annex c. respiratory droplets. in: atkinson k, chartier y, pesso-silva cl, jensen p, li y, seto w, editors. natural ventilation for infection control in healthcare settings. geneva: who; 2009. 12. zayas g, chiang mc, wong e, macdonald f, lange cf, senthilselvan a, et al. cough aerosol in healthy participants: fundamental knowledge to optimize dropletspread infectious respiratory disease management. bmc pulm med 2012;12:11. 13. leung nhl, chu dkw, shiu eyc, chan k, mcdevitt jj, hau bjp, et al. respiratory virus shedding in exhaled breath and efficacy of face masks. nat med 2020;26:676–680. 14. ashrae. position paper on infectious aerosols [internet]. atlanta, georgia: ashrae; 2020 available from: https://www.ashrae.org/file{%}20library/about/ position{%}20documents/pd_infectiousaerosols_2020. pdf 15. van doremalen n, bushmaker t, morris dh, holbrook mg, gamble a, williamson bn, et al. aerosol and surface stability of sars-cov-2 as compared with sars-cov-1. n engl j med 2020;382:1564–1567. 16. royal college of ophthalmologists. management of ophthalmology services during the covid pandemic. uk: rcophth; 2020. available from: https://www.rcophth.ac.uk/wp-content/uploads/2020/ 03/rcophth-management-of-ophthalmology-servicesduring-the-covid-pandemic-280320.pdf 17. china.org.cn. state council information office briefing on the science-based treatment of severe covid-19 cases [internet]. wuhan, china: march 2020 [cited march 26, 2020]. available from: http://www.china.org.cn/china/ 2020-03/20/content_75839939.htm. 18. ansi/ashrae/ashe. standard 170 ventilation of health care facilities. atlanta, ga: ashrae; 2008. available from: http://sspc170.ashraepcs.org/pdf/170_2008_final.pdf 19. li jo, lam dsc, chen y, ting dsw. novel coronavirus disease 2019 (covid-19): the importance of recognising possible early ocular manifestation and using protective eyewear. br j ophthalmol 2020;104:297–298. available from: https://bjo.bmj.com/content/104/3/297. 20. spooner jl. history of surgical masks. aorn j 1967;5:76– 80. 21. robertson p. comparison of masks standards, ratings and filtration effectiveness [internet]. smart air; 2020. available from: https://smartairfilters.com/en/blog/comparisonmask-standards-rating-effectiveness/. 22. lee sa, hwang dc, li hy, tsai cf, chen cw, chen jk. particle size-selective assessment of protection of european standard ffp respirators and surgical masks against particles-tested with human subjects. j healthc eng 2016;1–12. doi: 10.1155/2016/8572493. 23. patel rb, skaria sd, mansour mm, smaldone gc. respiratory source control using a surgical mask: an in vitro study. j occup environ hyg 2016:13;569–576. 24. gawn j, clayton m, makeison c, crook b. evaluating the protection afforded by surgical masks against influenza bioaerosols: gross protection of surgical masks compared to filtering facepiece respirators. buxton: health and safety executive; 2008; 33. 25. chan wm, liu dt, chan pk, chong kk, yuen ks, chiu ty, et al. precautions in ophthalmic practice in a hospital with a major acute sars outbreak: an experience from hong kong. eye 2006:21;304–305. 26. hsieh vc. putting resiliency of a health system to the test: covid-19 in taiwan. j formos med assoc 2020:119;884– 885. 27. heimbuch bk, wallace wh, kinney k, lumley ae, wu cy, woo mh, et al. a pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with h1n1 aerosols and droplets. am j infect control 2011:39:e1–e9. 28. lore mb, heimbuch bk, brown tl, wander jd, hinrichs sh. effectiveness of three decontamination treatments against influenza virus applied to filtering facepiece respirators. ann occup hyg 2012:56;92–101. 29. lin m. how to fight coronavirus sars-cov-2 and its disease, covid-19 [internet]. linlab briefing; 2020. available from: https://radiology.ucsf.edu/sites/radiology. ucsf.edu/files/wysiwyg/patientcare/patient-safety/covid19/lin_lab_covid_presentation_2020-03-16.pdf 30. batelle systemtm. instructions for healthcare facilities: preparation and collection of compatible n95 respirators for decontamination by the battelle memorial institute using the battelle decontamination system [internet]. available from: https://www.battelle.org/docs/defaultsource/commercial-offerings/industry-solutions/ instructions-for-healthcare-facilities---03-29-2020--615pm-revision.pdf? 31. oke j, heneghan c. oxford covid-19 evidence service team. global covid-19 case fatality rates [internet]. cebm; 2020. available at: https://www.cebm.net/covid-19/globalcovid-19-case-fatality-rates/. 32. jun isy, hui kko, songbo pz. perspectives on coronavirus disease 2019 control: measures for ophthalmology clinics based on a singapore center experience. jama ophthalmol 2020;138:435–436. available from: https://jamanetwork.com/journals/ jamaophthalmology/fullarticle/2764085. 33. rivett l, sridhar s, sparkes d, routledge m, jones nk, forrest s, et al. screening of healthcare workers for sarscov-2 highlights the role of asymptomatic carriage in covid-19 transmission [published online ahead of print, 2020 may 11]. elife 2020;9:e58728. journal of ophthalmic and vision research volume 15, issue 3, july-september 2020 407 https://www.entuk.org/sites/default/files/files/loss%20of%20sense%20of%20smell%20as%20marker%20of%20covid.pdf https://www.entuk.org/sites/default/files/files/loss%20of%20sense%20of%20smell%20as%20marker%20of%20covid.pdf https://www.entuk.org/sites/default/files/files/loss%20of%20sense%20of%20smell%20as%20marker%20of%20covid.pdf https://www.cebm.net/covid-19/sars-cov-2-viral-load-and-the-severity-of-covid-19/ https://www.cebm.net/covid-19/sars-cov-2-viral-load-and-the-severity-of-covid-19/ https://www.ashrae.org/file{%}20library/about/position{%}20documents/pd_infectiousaerosols_2020.pdf https://www.ashrae.org/file{%}20library/about/position{%}20documents/pd_infectiousaerosols_2020.pdf https://www.ashrae.org/file{%}20library/about/position{%}20documents/pd_infectiousaerosols_2020.pdf https://www.rcophth.ac.uk/wp-content/uploads/2020/03/rcophth-management-of-ophthalmology-services-during-the-covid-pandemic-280320.pdf https://www.rcophth.ac.uk/wp-content/uploads/2020/03/rcophth-management-of-ophthalmology-services-during-the-covid-pandemic-280320.pdf https://www.rcophth.ac.uk/wp-content/uploads/2020/03/rcophth-management-of-ophthalmology-services-during-the-covid-pandemic-280320.pdf http://www.china.org.cn/china/2020-03/20/content_75839939.htm http://www.china.org.cn/china/2020-03/20/content_75839939.htm http://sspc170.ashraepcs.org/pdf/170_2008_final.pdf https://bjo.bmj.com/content/104/3/297 https://smartairfilters.com/en/blog/comparison-mask-standards-rating-effectiveness/ https://smartairfilters.com/en/blog/comparison-mask-standards-rating-effectiveness/ https://radiology.ucsf.edu/sites/radiology.ucsf.edu/files/wysiwyg/patientcare/patient-safety/covid-19/lin_lab_covid_presentation_2020-03-16.pdf https://radiology.ucsf.edu/sites/radiology.ucsf.edu/files/wysiwyg/patientcare/patient-safety/covid-19/lin_lab_covid_presentation_2020-03-16.pdf https://radiology.ucsf.edu/sites/radiology.ucsf.edu/files/wysiwyg/patientcare/patient-safety/covid-19/lin_lab_covid_presentation_2020-03-16.pdf https://www.battelle.org/docs/default-source/commercial-offerings/industry-solutions/instructions-for-healthcare-facilities---03-29-2020---615pm-revision.pdf? https://www.battelle.org/docs/default-source/commercial-offerings/industry-solutions/instructions-for-healthcare-facilities---03-29-2020---615pm-revision.pdf? https://www.battelle.org/docs/default-source/commercial-offerings/industry-solutions/instructions-for-healthcare-facilities---03-29-2020---615pm-revision.pdf? https://www.battelle.org/docs/default-source/commercial-offerings/industry-solutions/instructions-for-healthcare-facilities---03-29-2020---615pm-revision.pdf? https://www.cebm.net/covid-19/global-covid-19-case-fatality-rates/ https://www.cebm.net/covid-19/global-covid-19-case-fatality-rates/ https://jamanetwork.com/journals/jamaophthalmology/fullarticle/2764085 https://jamanetwork.com/journals/jamaophthalmology/fullarticle/2764085 original article prognostic factors associated with ocriplasmin efficacy for the treatment of symptomatic vitreomacular adhesion and full-thickness macular hole: analysis from four studies brian c. joondeph, md, mps1; paul willems, md2; thomas raber, phd2; luc duchateau, phd3 joseph markoff, phd, md4,5 1colorado retina associates, denver, colorado, usa 2oxurion, leuven, belgium 3biometrics research group, ghent university, gent, belgium 4wills eye hospital, philadelphia, pennsylvania, usa 5thomas jefferson medical college, philadelphia, pennsylvania, usa orcid: brian c. joondeph: https://orcid.org/0000-0001-8781-4370 abstract purpose: to assess the effect of patient baseline characteristics on the efficacy of ocriplasmin treatment for symptomatic vitreomacular adhesion (vma) with full-thickness macular hole (ftmh) from phase 3/4 studies. methods: patients with symptomatic vma and ftmh at baseline and receiving ocriplasmin treatment 125 𝜇g were pooled from the mivi-trust, oasis, and orbit studies. multivariable logistic regression analysis was used to evaluate whether patient baseline characteristics were predictors of having vma resolution by day 28 and ftmh closure by month 6. results: two hundred and seventy-four patients receiving ocriplasmin treatment were assessed. overall, 22.6% (62/274) of the patients experienced both vma resolution by day 28 and non-surgical ftmh closure by month 6. patients with ftmh ≤250 µm at baseline had a significantly higher success rate compared to those with ftmh >400 µm (29.9% [41/137] vs 2.2% [1/48]; p = 0.009). in patients with vma resolution by day 28, both small ftmh size (p = 0.001) and ftmh width at rpe (p = 0.012) were significantly associated with a higher ftmh closure rate. patients with vma resolution had higher rates of ftmh closure. previously identified baseline predictive factors, including age, lens status, or presence of epiretinal membrane (erm) were not found to be predictive of both vma release and ftmh closure. conclusion: the analysis revealed that fmth ≤250 µm was the only factor predictive for achieving both pharmacological vma resolution by day 28 and nonsurgical ftmh closure by month 6; neither lens status or presence of erm, previously identified baseline characteristics favoring vma resolution, showed statistically significant predictive power for both outcomes. keywords: ocriplasmin; full-thickness macular hole; vitreomacular adhesion; symptomatic vitreomacular adhesion; vitreomacular traction; vitreoretinal interface j ophthalmic vis res 2021; 16 (1): 42–55 42 © 2021 joondeph et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8250&domain=pdf&date_stamp=2019-07-17 patient baseline characteristics and ocriplasmin efficacy; joondeph et al introduction aging of the eye often leads to separation between the posterior vitreous cortex and the internal limiting membrane, known as posterior vitreous detachment (pvd).[1, 2] this process may be affected by vitreomacular adhesion (vma), or adherence of the vitreous cortex to the macula after partial detachment.[3–5] symptomatic vma (also referred to as vitreomacular traction) can occur if mechanical forces are large enough to cause anatomical changes to the macula.[6, 7] effects resulting from symptomatic vma may also lead to the development of a full-thickness macular hole (ftmh).[4] the occurrence of vma and ftmh can lead to visual disturbances such as decreased visual acuity, photopsia, metamorphopsia, scotomas, and may result in irreversible vision loss if left untreated.[3, 4, 8–12] treatment options for symptomatic vma include watchful waiting, vitrectomy, pneumatic vitreolysis, and pharmacological vitreolysis with ocriplasmin. ocriplasmin was approved in the us in 2012 and the eu in 2013 based on the results of two pivotal phase 3 clinical trials (mivi-trust) that established its efficacy and safety in patients with symptomatic vma with or without an associated ftmh ≤400 𝜇m.[13] an earlier post hoc analysis of the pivotal trials suggested that the efficacy of ocriplasmin may be increased by patient baseline characteristics, including younger age, phakic lens status, focal vma, absence of epiretinal membrane (erm), and presence of ftmh.[14] subsequently, both prospective and retrospective studies ranging from 5 to 74 eyes were undertaken that assessed the effect of these baseline factors with respect to vma release.[13, 15–32] vma release rates in these studies ranged from 0% to 71%, with 14 of 18 studies showing higher efficacy than the pivotal phase 3 trial rate of 26.5% vma release at day 28.[13] a meta-analysis of these studies, which also included correspondence to: brian c. joondeph, md, mps. 8101 e. lowry blvd, suite 210 denver, colorado 80230 (303) 261-1600, usa. e-mail: bjoondeph@retinacolorado.com received: 02-06-2020 accepted: 23-10-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8250 the phase 3 pivotal trials, confirmed that focal vma, absence of erm, phakic lens status, and younger age were all positive predictive factors for vma release.[33] the rate of ftmh closure for ocriplasmin-treated eyes was 40.6% in the pivotal clinical trials and 30.0% in the oasis study.[13, 34] although analysis of baseline predictive factors has resulted in realworld rates of vma release higher than those in the pivotal phase 3 trials, multiple real-world studies have reported ftmh closure rates lower than those observed in these studies, suggesting that the predictive factors for ftmh closure may not be the same as those for vma release and are not as well understood.[24, 28, 35] for instance, the absence of erm did not have a clear association with ftmh closure in the mivi-trust trials.[36] in addition, the predictive value of successful vma release on ftmh closure remains unclear; there was no clear association between vma release and ftmh closure in the mivi-trust trials,[36] although a recent study showed a strong association between vma release and ftmh closure.[37] although the baseline factors associated with vma resolution and ftmh closure have been investigated individually, to our knowledge no study has assessed factors that may predict both vma resolution and ftmh closure following ocriplasmin treatment. the current study aimed at assessing the baseline factors that may be predictive of both vma release together with ftmh closure in patients treated with ocriplasmin in the completed phase 3/4 studies. methods study population patients diagnosed with both symptomatic vma and ftmh at baseline and receiving treatment of ocriplasmin 125 𝜇g were pooled from the mivitrust, oasis, and orbit studies. mivi-trust this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: joondeph bc, willems p, raber t, duchateau l, markoff j. prognostic factors associated with ocriplasmin efficacy for the treatment of symptomatic vitreomacular adhesion and full-thickness macular hole: analysis from four studies. j ophthalmic vis res 2021;16:42– 55. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 43 https://knepublishing.com/index.php/jovr patient baseline characteristics and ocriplasmin efficacy; joondeph et al (nct00781859 and nct00798317) consisted of two phase 3, prospective, randomized, multicenter, double-blind, placebo-controlled clinical trials (tg-mv-006 and tg-mv-007) in which patients were randomized to receive a single intravitreal ocriplasmin (125 𝜇g) or placebo injection.[13] oasis (nct01429441) was a phase 3b, randomized, multicenter, double-masked, sham-controlled clinical trial in which patients were randomized to receive a single intravitreal ocriplasmin 125 𝜇g injection or sham treatment.[34] orbit (nct02079883) was a phase 4, prospective, multicenter, observational study to assess a single intravitreal ocriplasmin injection of 125 𝜇g.[38] full details of individual study designs, treatment plans, and adherence to ethics practices have been published elsewhere.[13, 34, 38] baseline demographics and patient characteristics the following baseline demographic and ocular characteristics were evaluated in the study population based on availability across datasets: age (<65 years, ≥65 years), lens status (phakic, pseudophakic), erm status (present, absent), ellipsoid zone (ez) status (normal, abnormal), subretinal fluid (srf) status (present, absent), bcva (<65, 65–75, >75 etdrs letters), diameter of vma (≤1500 𝜇m, >1500 𝜇m), width of ftmh (≤250, >250–400, >400 𝜇m), and width of ftmh at the retinal pigment epithelium (rpe) (≤600 𝜇m, >600 𝜇m) (supporting information table s1). for the mivi-trust trials, the presence and size of vma and ftmh status at baseline were assessed by a central reading center (crc), using mandatory time-domain optical coherence tomography (td-oct) as required per protocol; additional spectral-domain (sd)-oct readings if available were only used as supportive information for evaluation of individual cases.[13] ftmh was defined as a macular hole with bare/exposed rpe, with the largest of the minimum hole width measurements considered as the hole width based on macular thickness map (mtm) or fast macular thickness map (fmtm) scans. in the more recent oasis study, the presence and size of vma and ftmh status at baseline were assessed by a crc using sd-oct.[34] ftmh diameter was defined as the largest of the minimum hole width measurement. although patients were enrolled in the oasis trial based on favorable baseline characteristics,[14] determination of ocular characteristics differed between investigator and crc assessment, resulting in inclusion of some patients despite their crc assessment meeting exclusion criteria in retrospect (ftmh > 400 𝜇m, presence or erm).[34] in the orbit study, the presence of vma and ftmh was determined by sd-oct according to the treating physician before enrollment and reviewed independently by a crc in retrospect. ftmh diameter was defined as the greatest width of the minimum distance between sides of the ftmh measured within the middle two thirds of the retina (not at surface and not at rpe) in any line of the 49-line volume scan. the review of the presence of vma and ftmh by the crc was performed post-treatment in all studies and was not used for treatment decisions. ez status was evaluated in the central macular region in all studies. srf assessments were defined in each of the studies. in the mivi-trust trials, srf was a measure of the fluid beneath retina to other material perpendicular to bruch’s membrane at the foveal center from the retina to the rpe, not including fluid within the retinal layer (cysts) or fluid below the rpe. in the oasis study, three foveal center point measurements were taken, including srf, rpe elevation and/or subretinal hyper-reflective material (shrm) such as choroidal neovascularization, and total retinal thickness. the total retinal thickness measurement included the rpe layer, rpe elevation, any shrm, any srf, and the retina at the foveal center. when a value was not reported for srf or rpe elevation and/or shrm, it was considered not present or ungradable. in the orbit study, srf was considered present if it was identified in any line scan in the absence of ftmh. statistical analysis the integrated database included all patients who presented with symptomatic vma and ftmh at baseline, were treated with ocriplasmin 125 𝜇g, and had both a baseline assessment and at least one follow-up visit. three different variables (i.e., treatment response) were considered: pharmacological resolution of vma by day 28 (vmares), nonsurgical ftmh closure by month 6 (mhclos), and combined success when experiencing both events (vmares + mhclos). first, 44 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 patient baseline characteristics and ocriplasmin efficacy; joondeph et al table 1. patient demographics and ocular baseline characteristics in the four studies and the integrated dataset characteristic mivi-trust*(n = 106) oasis (n = 50) orbit(n = 118) integrated(n = 274) age (years) mean (sd) 68.7 (7.4) 66.5 (6.3) 66.7 (7.3) 67.5 (7.2) median 69.0 65.5 66.0 67.0 min, max 48, 85 49, 79 45, 88 45, 88 age group (years), n (%) <65 years 31 (29.2) 20 (40.0) 42 (35.6) 93 (33.9) ≥65 years 75 (70.8) 30 (60.0) 76 (64.4) 181 (66.1) sex, n (%) male 22 (20.8) 10 (20.0) 28 (23.7) 60 (21.9) female 84 (79.2) 40 (80.0) 90 (76.3) 214 (78.1) race, n (%) white 99 (93.4) 46 (92.0) 105 (89.0) 250 (91.3) black or african american 3 (2.8) 4 (8.0) 9 (7.6) 16 (5.8) asian 2 (1.9) 0 (0) 3 (2.5) 5 (1.8) other 2 (1.9) 0 (0) 1 (0.9) 3 (1.1) lens status, n (%) phakic 81 (76.4) 43 (86.0) 93 (78.8) 217 (79.2) pseudophakic 25 (23.6) 7 (14.0) 24 (20.3) 56 (20.4) aphakic 0 (0) 0 (0) 1 (0.9) 1 (0.4) erm status, n (%) present 18 (17.0) 6 (12.0) 14 (11.9) 38 (13.9) absent 82 (77.3) 44 (88.0) 104 (88.1) 230 (83.9) missing 6 (5.7) 0 (0) 0 (0) 6 (2.2) ez status, n (%) abnormal 0 (0) 49 (98.0) 116 (98.3) 165 (60.2) normal 0 (0) 1 (2.0) 2 (1.7) 3 (1.1) missing 106 (100) 0 (0) 0 (0) 106 (38.7) srf status, n (%) present 77 (72.7) 49 (98.0) 0 (0) 126 (46.0) absent 26 (24.5) 1 (2.0) 118 (100) 145 (52.9) missing 3 (2.8) 0 (0) 0 (0) 3 (1.1) bcva (etdrs letters), n (%) <65 89 (84.0) 37 (74.0) 96 (81.4) 222 (81.0) 65–75 16 (15.1) 12 (24.0) 19 (16.1) 47 (17.2) >75 1 (0.9) 1 (2.0) 3 (2.5) 5 (1.8) ftmh size, n (%) ≤250 𝜇m 48 (45.3) 23 (46.0) 66 (55.9) 137 (50.0) >250–400 𝜇m 38 (35.9) 17 (34.0) 33 (28.0) 88 (32.1) >400 𝜇m 19 (17.9) 10 (20.0) 19 (16.1) 48 (17.5) missing 1 (0.9) 0 (0) 0 (0) 1 (0.4) vma diameter, n (%) ≤1500 𝜇m 90 (84.9) 43 (86.0) 110 (93.2) 243 (88.7) >1500 𝜇m 3 (2.8) 2 (4.0) 1 (0.9) 6 (2.2) missing 13 (12.3) 5 (10.0) 7 (5.9) 25 (9.1) ftmh width at rpe (𝜇m) n 104 50 0 154 mean (sd) 647.1 (283.8) 634.2 (320.8) – 642.9 (295.4) median 611.0 596.0 – 611.0 min, max 113, 1572 164, 2120 – 113, 2120 ftmh width at rpe, n (%) ≤600 𝜇m 49 (46.2) 25 (50.0) 0 (0) 74 (27.0) >600 𝜇m 55 (51.9) 25 (50.0) 0 (0) 80 (29.2) missing 2 (1.9) 0 (0) 118 (100) 120 (43.8) ∗mivi-trust consisted of two phase 3 clinical trials (nct00781859 and nct00798317) bcva, best-corrected visual acuity; erm, epiretinal membrane; etdrs, early treatment diabetic retinopathy study; ez, ellipsoid zone; ftmh, full-thickness macular hole; rpe, retinal pigment epithelium; sd, standard deviation; srf, subretinal fluid; vma, vitreomacular traction journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 45 patient baseline characteristics and ocriplasmin efficacy; joondeph et al table 2. rates of vma resolution and ftmh closure in the four studies and the integrated dataset mivi-trust* n (%) oasis n (%) orbit n (%) integrated n (%) number of patients 106 50 118 274 vma resolution 53 (50.0) 27 (54.0) 74 (62.7) 154 (56.2) ftmh closure 43 (40.6) 15 (30.0) 38 (32.2) 96 (35.0) vma resolution: yes ftmh closure: yes 24 (22.6) 8 (16.0) 30 (32.2) 62 (22.6) vma resolution: yes ftmh closure: no 29 (27.4) 19 (38.0) 44 (37.3) 92 (33.6) vma resolution: no ftmh closure: yes 19 (17.9) 7 (14.3) 8 (6.8) 34 (12.4) vma resolution: no ftmh closure: no 24 (22.6) 8 (16.0) 30 (25.4) 86 (31.4) *mivi-trust consisted of two phase 3 clinical trials (nct00781859 and nct00798317) ftmh, full-thickness macular hole; vma, vitreomacular adhesion table 3. univariable logistic regression analysis for the effect of patient demographics and ocular baseline characteristics on vma resolution by day 28 and ftmh closure by month 6 in the integrated dataset vma resolution ftmh closure vma resolution + ftmh closure characteristic status success (%) p-value success (%) p-value success (%) p-value age <65 years 65/93 (69.9) 0.0015 32/93 (34.4) 0.9783 22/93 (23.7) 0.735 ≥65 years 89/181 (49.2) 64/181 (35.4) 40/181 (22.1) lens status phakic 130/217 (59.9) 0.0129 71/217 (32.7) 0.1888 47/217 (21.7) 0.647 pseudophakic 23/56 (41.1) 24/56 (42.9) 14/56 (25.0) erm status present 12/38 (31.6) 0.0028 13/38 (34.2) 0.7999 4/38 (10.5) 0.067 absent 137/230 (59.6) 81/230 (35.2) 56/230 (24.3) ez status normal 1/3 (33.3) 0.3667 3/3 (100) 0.9852 1/3 (33.3) 0.645 abnormal 100/165 (60.6) 50/165 (30.3) 37/165 (22.4) srf status present 67/126 (53.2) 0.2874 48/126 (38.1) 0.2327 28/126 (22.2) 0.124 absent 85/145 (58.6) 46/145 (31.7) 33/145 (22.8) bcva (etdrs letters) <65 127/222 (57.2) 0.6215 71/222 (32.0) 0.0606 49/222 (22.1) 0.645 65–75 25/47 (53.2) 22/47 (46.8) 13/47 (27.7) >75 2/5 (40.0) 3/5 (60) 0/5 (0) vma diameter ≤1500 µm 144/243 (59.3) 0.7324 87/243 (35.8) 0.8514 56/243 (23.0) 0.489 >1500 µm 3/6 (50) 2/6 (33.3) 2/6 (33.3) ftmh size ≤250 µm 75/137 (54.7) 0.3412 67/137 (48.9) <0.0001 41/137 (29.9) 0.009>250–400 µm 54/88 (61.4) 26/88 (29.6) 19/88 (21.6) >400 µm 24/48 (50) 2/48 (4.2) 1/48 (2.2) ftmh width at rpe ≤600 µm 40/74 (54.1) 0.5185 38/74 (51.4) 0.0004 21/74 (28.4) 0.015 >600 µm 39/80 (48.8) 19/80 (23.8) 10/80 (12.5) bcva, best-corrected visual acuity; erm, epiretinal membrane; etdrs, early treatment diabetic retinopathy study; ez, ellipsoid zone; ftmh, full-thickness macular hole; rpe, retinal pigment epithelium; srf, subretinal fluid; vma, vitreomacular adhesion 46 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 patient baseline characteristics and ocriplasmin efficacy; joondeph et al table 4. univariable logistic regression analysis for the effect of patient demographics and ocular baseline characteristics on ftmh closure by month 6 for patients with vma resolution by day 28 in the integrated dataset patient characteristic status success (%) p-value age <65 years 22/65 (33.8) 0.177 ≥65 years 49/89 (55.1) lens status phakic 47/130 (36.2) 0.027 pseudophakic 14/23 (60.9) erm status present 4/12 (33.3) 0.619 absent 56/137 (40.9) ez status normal 1/1 (100.0) 0.986 abnormal 37/100 (37.0) srf status present 28/67 (41.8) 0.231 absent 33/85 (38.8) bcva (etdrs letters) <65 49/127 (38.6) 0.43465–75 13/25 (52.0) >75 2/2 (100.0) vma diameter ≤1500 µm 56/144 (38.9) 0.311 >1500 µm 2/3 (66.7) ftmh size ≤250 µm 41/75 (54.7) 0.001>250–400 µm 19/54 (35.2) >400 µm 1/24 (4.2) ftmh width at rpe ≤600 µm 21/40 (52.5) 0.012 >600 µm 10/39 (25.6) bcva, best-corrected visual acuity; erm, epiretinal membrane; etdrs, early treatment diabetic retinopathy study; ez, ellipsoid zone; ftmh, full-thickness macular hole; rpe, retinal pigment epithelium; srf, subretinal fluid; vma, vitreomacular adhesion the effect of each patient baseline characteristic on success was evaluated separately in a univariable logistic regression model that also included study as a fixed-effects factor to accommodate for the clustering in the data due to combining data from different studies. next, all patient baseline characteristics that were significant at the 5% significance level were included in a multivariable regression analysis to identify independent patient baseline characteristics that were significantly associated with treatment success. additionally, the same analysis was performed for mhclos for those patients that experienced vmares. results demographics and baseline characteristics a total of 274 patients were pooled from the mivitrust, oasis, and orbit studies on the basis of having both symptomatic vma and ftmh at baseline and having received a single intravitreal injection of ocriplasmin 125 𝜇g. demographics and ocular characteristics are shown in table 1. overall, the demographics and ocular characteristics were generally comparable in patients across the three datasets. the mean age of the patients was 67.5 years, with an age range of 45–88 years. seventy-nine percent of the patients had phakic lens status. a majority (60.2%) of patients had ez status categorized as abnormal, and 46.0% of patients had srf present (table 1). vma resolution an average of 56.2% (154/274) of eligible patients experienced vma resolution by day 28 (table 2). the proportion of patients experiencing vma resolution by day 28 in this patient subpopulation journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 47 patient baseline characteristics and ocriplasmin efficacy; joondeph et al supplemental table 1. availability of baseline characteristics and outcome measures in the ocriplasmin studies mivi-trust oasis orbit outcome measures pharmacological vma resolution at day 28, post-resolution vitrectomy considered as a failure yes yes no pharmacological vma resolution at day 28, post-resolution vitrectomy not considered as a failure yes yes yes non-surgical ftmh closure by end of study (post-closure vitrectomy not considered as a failure) eos (up to m6) m6 eos (up to m24) m6 m12 baseline characteristics age (years) available available available lens status phakic pseudophakic phakic pseudophakic phakic pseudophakic aphakic erm present absent present minimal present significant absent present* absent* ez not available definitely fully intact likely site(s) of incomplete ez definite site(s) of incomplete ez unable to grade normal* abnormal* srf present absent present absent present* absent* bcva (etdrs) available available available after transformation ftmh size (𝜇m) available available available vma diameter available available available ftmh width at rpe available available not available *assessed by sd-oct bcva, best-corrected visual acuity; elm, external limiting membrane; eos, end of study; erm, epiretinal membrane; etdrs, early treatment diabetic retinopathy study; ez, ellipsoid zone; ftmh, full-thickness macular hole; m, month; rpe, retinal pigment epithelium; sd-oct, spectral-domain optical coherence tomography; srf, subretinal fluid; vma, vitreomacular adhesion with ftmh at baseline was consistently higher than or equal to 50% for all studies (table 2). vma resolution by day 28 was achieved significantly more frequently in younger patients, in the absence of erm at baseline and for eyes with phakic lens status at baseline (table 3). in the multivariable model including these three variables, age (p = 0.006) and erm status at baseline (p = 0.010) remained significant, but not lens status at baseline (p = 0.179). ftmh closure the average rate of ftmh closure by month 6 in the integrated dataset was 35.0% (96/274) (table 2). closure rates varied from 30.0% for the oasis database and 32.2% for the orbit study 48 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 patient baseline characteristics and ocriplasmin efficacy; joondeph et al to 40.6% for the mivi-trust trials (table 2). ftmh closure by month 6 occurred significantly more often with smaller ftmh size and smaller ftmh width at rpe (table 3). we did not construct the multivariable model as these two variables are highly interrelated: the percentage of patients with ftmh width at rpe ≤600 µm decreases from 64.8% (46/71) to 45.5% (25/55) and 10.7% (3/28) for the ≤250 µm, >250–400 µm, and >400 µm ftmh size categories, respectively. vma resolution by day 28 was a positive predictor for ftmh closure by month 6. patients with vma resolution by day 28 had a higher percentage of mh closure of 40.3% (62/154) compared to patients without vma release equal to 28.3% (34/120) (p = 0.028). within the group of patients who had vma resolution by day 28, mh closure by month 6 occurred significantly more for eyes with pseudophakic lens status at baseline, with smaller ftmh size and smaller ftmh width at rpe (table 4). in the multivariable models including lens status with one of the two ftmh measurements at a time, lens status was no longer significant (p = 0.244 with ftmh size and p = 0.173 with ftmh width at rpe), nor was the ftmh size (p = 0.057), but the ftmh width at rpe remained significant (p < 0.001). vma resolution and ftmh closure overall, 22.6% (62/274) of patients in this analysis experienced both vma resolution by day 28 and ftmh closure by month 6 (table 2). in contrast, 12.4% (34/274) experienced ftmh closure by month 6 without vma resolution by day 28; 33.6% (92/274) experienced vma resolution by day 28 without ftmh closure by month 6; and 31.4% (86/274) showed neither vma resolution by day 28 nor non-surgical ftmh closure by month 6 (table 2). univariable logistic regression analysis revealed a statistically significant effect for ftmh size at baseline on treatment success (p = 0.009; table 3), with success increasing from 2.2% for patients with ftmh size at baseline >400 µm to 21.6% for patients with ftmh size at baseline between 250 and 400 µm, and further to 29.9% for patients with ftmh size at baseline <250 µm. similarly, ftmh width at rpe at baseline had a significant effect on treatment success in the univariable logistic regression analysis (p = 0.015; table 3), with treatment success increasing from 12.5% for patients with ftmh width at baseline >600 µm to 28.4% for patients with ftmh width at baseline <600 µm. none of the other patient characteristics previously shown to be predictive for vma resolution, including younger age, phakic lens status, or absence of erm,[14, 33] showed a statistically significant association with treatment success (table 3). as the two significant patient baseline characteristics are necessarily highly correlated, and additionally ftmh width at rpe at baseline was unavailable for the oasis dataset, they were not used jointly in a multivariable logistic regression analysis. case studies two patients are herein presented as case studies to exemplify real-world clinical findings with ocriplasmin use in patients with symptomatic vma and ftmh. case 1 a 71-year-old white woman had initial presentation of blurred central vision for four–six weeks and ghosting of letters while reading in the left eye. medical and ocular history were noncontributory. visual acuity was 20/60 at initial visit. sd-oct revealed vma with tractional macular hole of 300 𝜇m, with no presence of erm (figure 1a). the left eye had phakic lens status. the patient opted for ocriplasmin treatment and received the intravitreal injection 18 days after initial visit. visual acuity was 20/60 pre-injection. one week following the ocriplasmin injection, vma resolved and the macular hole closed (figure 1b). however, there was increased presence of srf (figure 1b). visual acuity remained at 20/50. at seven weeks post-treatment, macular hole remained closed with no evidence of srf (figure 1c). visual acuity improved to 20/40. case 2 a 63-year-old white woman initially presented with symptoms of blurred central vision for two–three months in the left eye. medical history included essential hypertension. visual acuity was 20/150 at initial visit. patient had phakic lens status in the left eye. upon examination, sd-oct showed journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 49 patient baseline characteristics and ocriplasmin efficacy; joondeph et al figure 1. case 1. spectral domain optical coherence tomography of a 71-year-old female with vma and a tractional macular hole in the left eye. (a) baseline visit. no presence of erm; bcva 20/60. (b) one week post ocriplasmin injection. vma resolved and macular hole closed, but increased presence of srf; bcva 20/50. (c). seven weeks post treatment. macular hole remains closed, no evidence of srf; bcva 20/40. bcva, best-corrected visual acuity; erm, epiretinal membrane; inj, injection; m, month; srf, subretinal fluid; w, week ftmh with vma, with no erm or presence of srf (figure 2a). the size of the tractional macular hole size at baseline was 145 𝜇m, minimum linear diameter (mld). the patient opted for ocriplasmin treatment and received the intravitreal injection 14 days after the initial visit. pre-injection visual acuity was 20/150. one month following the treatment with ocriplasmin, the vma released, but the macular hole remained open, enlarging to a size of 428 𝜇m, mld (figure 2b). visual acuity decreased to 20/200. the patient underwent standard macular hole repair via vitrectomy, internal limiting membrane peeling, and gas injection. the hole did not close and subsequent surgery including an internal limiting membrane patch and silicone oil was performed with macular hole closure. at the last examination, visual acuity was count fingers (cf) at 4 ft with a dense cataract and macular hole closure by oct. discussion this study is the first to examine the baseline predictors of success for both vma resolution and ftmh closure following ocriplasmin treatment. our results show that ftmh ≤ 250 𝜇m at baseline is significantly associated with vma release by day 28 and ftmh closure by month 6 (p = 0.009), and may be the only positive baseline predictor for both pharmacological vma release and nonsurgical ftmh closure, including previously identified predictors such as age, lens status, and absence of erm. baseline factors associated with successful vma release following ocriplasmin treatment have been 50 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 patient baseline characteristics and ocriplasmin efficacy; joondeph et al figure 2. case 2. spectral domain optical coherence tomography of a 63-year-old female showing vma with ftmh. (a) baseline visit. no erm or presence of srf; bcva 20/150. (b) one month post treatment. vma released, but macular hole remained open, with the base enlarging to 1323 𝜇m. bcva decreased to 20/200. bcva, best-corrected visual acuity; erm, epiretinal membrane; inj, injection; m, month; srf, subretinal fluid widely studied following approval in 2012.[14–32] a post hoc analysis of the phase 3 mivi-trust trials revealed that baseline characteristics such as younger age, focal adhesions (vma ≤ 1500 𝜇m), phakic lens status, and absence of erm promoted vma resolution,[14] and these characteristics have since been confirmed in multiple studies.[15–32] these predictive characteristics were also shown to statistically favor vma release (odds ratios 2.37– 7.85) in a meta-analysis of 19 studies published in 2016.[33] however, in our current analysis, most of these validated baseline factors were not shown to be predictive when analyzed for both vma release and ftmh closure. the baseline factors of younger age, absence of erm, and lens status did not reach statistical significance, with only ftmh size of ≤ 250 𝜇m at baseline emerging as the only statistically significant factor favoring both vma release and ftmh closure. the fact that lens status was no longer significant in the multivariable model is due to the correlation between variables. the lens status of younger patients was more frequently phakic compared to older patients (93.6% vs 71.8%), and similarly, the lens status of patients without erm at baseline was more frequently phakic compared to patients with erm at baseline (83.0% vs 57.9%). for ftmh, the percentage of phakic lens status increases with increasing ftmh size, with 80.0% (60/75), 85.2% (46/54), and 100.0% (24/24) for the ≤250 µm, >250–400 µm, and >400 µm ftmh size categories, respectively, and with increasing ftmh width, with 85.0% (34/40) and 89.7% (35/39) for the ≤600 µm and >600 µm ftmh width at rpe categories, respectively. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 51 patient baseline characteristics and ocriplasmin efficacy; joondeph et al historically, whether ftmh at baseline serves as a predictive factor for successful vma release has remained unclear. the presence of ftmh was initially identified as a predictive characteristic in the post hoc analysis of the mivi-trust trials.[14] subsequently, chatziralli et al performed a meta-analysis and did not conclude that the presence of ftmh was a predictive factor for vma release.[33] however, only 8 of the 19 analyzed studies assessed mh size as a predictive factor.[13, 15, 17, 23, 24, 28, 30, 32] kuppermann (2015)[39] reported the results of 10 retrospective studies which assessed the presence of ftmh on vma resolution, including 4 studies not included in chatziralli et al.[40–43] eight of these 10 studies[19, 23, 31, 32, 40–43] showed that the subgroup of patients with a ftmh had higher vma resolution rates than those without.[39] these results were also consistent with the prospective oasis trial.[34] however, other studies have not shown greater rates of vma resolution in patients with ftmh at baseline.[28, 29] therefore, the value of ftmh as a predictive factor for vma resolution needs to be further elucidated. in our current analysis, the majority of patients failing to achieve both vma resolution and ftmh closure were due to lack of macular hole closure. whereas vma resolution rates were 50% or higher from all studies in this patient population (i.e., those with symptomatic vma and ftmh at baseline treated with ocriplasmin with at least one follow-up visit), ftmh closure rates for oasis and orbit studies were lower than that of the original phase 3 mivi-trust trials, albeit higher than the closure rates experienced in the control groups (15.4% and 10.6%, respectively). these results suggest that the known baseline factors predictive of vma resolution, which were used as key inclusion criteria for the oasis study, may be necessary but not sufficient to predict ftmh closure. nevertheless, consistent with our findings, previous studies investigating ftmh closure rates following ocriplasmin treatment have repeatedly shown ftmh size at baseline to be the most consistent predictive factor, with a greater proportion of patients experiencing hole closure with an ftmh ≤ 250 𝜇m compared to those with an ftmh > 250–400 𝜇m.[14, 36, 37, 44] in contrast, the natural history of untreated ftmh has revealed that spontaneous closure rates are low, ranging from 3–11%.[45–49] although smaller holes have a comparatively better chance of spontaneous closure compared to larger ones, previous studies have shown that the majority of stage 2 macular holes (<400 𝜇m) progress to stage 3 and beyond if left untreated.[50–53] whether vma resolution is correlated with ftmh closure has also remained unclear. recently, feng et al demonstrated that successful vma resolution was a statistically significant positive predictor for ftmh closure following ocriplasmin treatment (p = 0.042).[37] this is consistent with our findings, which showed that patients with vma resolution by day 28 had a significantly higher rate of ftmh closure compared to those without vma resolution. however, other analyses have not shown an association between vma resolution and ftmh closure. in one study, 40% of patients required surgical closure for macular holes despite successful vma resolution,[54] suggesting that additional factors may impact ftmh closure. although our finding that vma resolution showed a positive correlation with ftmh closure is notable, beyond initial hole size, baseline characteristics predictive of macular hole closure prior to treatment have remained elusive. for instance, our findings are consistent with previous analyses showing that, unlike for vma resolution, absence of erm did not significantly impact ftmh closure rates.[35, 36] additional studies have suggested that other factors, such as macular hole architecture, may affect closure.[55, 56] recently, steel et al found that macular hole “width factor,” defined as the base diameter (bd) minus the mld, was the most predictive factor of macular hole closure; holes having a bd close in size to the mld were shown to have higher probability of closure compared to those with a wider base.[56] a similar outcome is shown in case 2, where despite vma resolution, the macular hole widens at the base with the edge elevated by a cuff of srf. this is consistent with previous cases showing failure of ftmh closure due to base enlargement following ocriplasmin treatment and subsequent vma resolution.[37, 57] srf did not have a statistically significant predictive value in our analysis; however, the number of patients showing successful vma resolution and ftmh closure with srf were strikingly different between the mivi-trust and oasis vs orbit studies (srf present: 87% [20/23], 100% [8/8], and 0% [0/30], respectively), perhaps owing in part to differences in srf measurement protocols at study enrollment 52 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 patient baseline characteristics and ocriplasmin efficacy; joondeph et al and therefore limiting interpretation. in case 1, presence of srf did not impact vma resolution or ftmh closure, although visual acuity improved following srf resolution. when selecting a treatment option for patients with vma and ftmh, the risks and benefits of ocriplasmin versus vitrectomy should be carefully considered. for these patients, vitrectomy is considered the standard of care, with macular hole closure rates reported for 87.5% of patients in a meta-analysis.[33, 58, 59] however, persistence of a macular hole after vitrectomy remains one of the major complications of this type of surgery, with approximately one in eight macular holes failing to close.[58] a persistent macular hole typically increases in diameter, with an accompanying loss of visual acuity, and studies have shown lower treatment success for subsequent surgery.[55, 58] additional complications of vitrectomy include cataract formation, retinal detachment, and hemorrhage.[33, 59–64] in addition, based on the oasis trial, patients who underwent vitrectomy experienced retinal tear and retinal detachment more often than patients receiving ocriplasmin. most adverse events in the ocriplasmin group were transient in nature, had a short onset time, and were mild to moderate in severity.[34] strengths of the current analysis include a robust and homogeneous patient sample pooled from multiple clinical trials, utilizing the same ocriplasmin treatment regimen. limitations include the post hoc nature of the analysis, which was not prespecified in the clinical trials, as well as the lack of availability of certain baseline ocular characteristics in all trials. since the pivotal clinical trials, continued study and analysis has been undertaken to more fully understand the efficacy and safety of ocriplasmin, including the baseline characteristics predictive of vma resolution and ftmh closure. these results suggest that patients presenting with symptomatic vma and ftmh ≤ 250 𝜇m may be ideal candidates for ocriplasmin treatment. acknowledgements the authors are thankful to all personnel involved in this study and michael howell, phd, for editorial assistance in the preparation of this manuscript that was supported by oxurion. financial support and sponsorship this study was funded by oxurion. all authors, including those affiliated with the study sponsor, were involved in the design of the study, interpretation of the data, writing of the manuscript, and the decision to submit the manuscript for publication. conflicts of interest the authors declare the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: bj: consultant for oxurion; pw: consultant for oxurion; tr: employee of oxurion; ld: consultant for oxurion; jm: consultant for oxurion. research involving human participants and informed consent this manuscript represents a retrospective analysis of four prospective phase 3/4 clinical trials. full details of adherence to ethics practices have been previously published [13, 34, 38]. author contribution all authors contributed to the conception or design of the work, analysis and interpretation of the data, critical revision of the manuscript, and approval of the final version to be published. references 1. johnson mw. perifoveal vitreous detachment and its macular complications. trans am ophthalmol soc 2005;103:537–567. 2. sebag j. vitreous: the resplendent enigma. br j ophthalmol 2009;93:989–991. 3. garcia-layana a, garcia-arumi j, ruiz-moreno jm, ariasbarquet l, cabrera-lopez f, figueroa ms. a review of current management of vitreomacular traction and macular hole. j ophthalmol 2015;2015:809640. 4. stalmans p, duker js, kaiser pk, heier js, dugel pu, gandorfer a, et al. oct-based interpretation of the vitreomacular interface and indications for pharmacologic vitreolysis. retina 2013;33:2003–2011. 5. steel dh, lotery aj. idiopathic vitreomacular traction and macular hole: a comprehensive review of pathophysiology, diagnosis, and treatment. eye 2013;27:s1–s21. 6. chang lk, fine hf, spaide rf, koizumi h, grossniklaus he. ultrastructural correlation of spectral-domain optical coherence tomographic findings in vitreomacular traction syndrome. am j ophthalmol 2008;146:121–127. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 53 patient baseline characteristics and ocriplasmin efficacy; joondeph et al 7. witkin aj, ko th, fujimoto jg, schuman js, reichel e, duker js. vitreofoveal attachment causing metamorphopsia: an ultrahigh-resolution optical coherence tomography finding. retina 2006;26:1085– 1087. 8. john vj, flynn hw jr, smiddy we, carver a, leonard r, tabandeh h, et al. clinical course of vitreomacular adhesion managed by initial observation. retina 2014;34:442–446. 9. shao l, wei w. vitreomacular traction syndrome. chin med j 2014;127:1566–1571. 10. wittich w, overbury o, kapusta ma, watanabe dh, faubert j. macular hole: perceptual filling-in across central scotomas. vis res 2006;46:4064–4070. 11. hong-kee n, azhany y, lieh-bin o. full thickness macular hole: early intervention is an important factor in visual prognosis. malays fam physician 2014;9:42–48. 12. de giacinto c, pastore mr, cirigliano g, tognetto d. macular hole in myopic eyes: a narrative review of the current surgical techniques. j ophthalmol 2019;2019:3230695. 13. stalmans p, benz ms, gandorfer a, kampik a, girach a, pakola s, et al. enzymatic vitreolysis with ocriplasmin for vitreomacular traction and macular holes. n engl j med 2012;367:606–615. 14. haller ja, stalmans p, benz ms, gandorfer a, pakola sj, girach a, et al. efficacy of intravitreal ocriplasmin for treatment of vitreomacular adhesion: subgroup analyses from two randomized trials. ophthalmology 2015;122:117– 122. 15. chatziralli i, theodossiadis g, parikakis e, datseris i, theodossiadis p. real-life experience after intravitreal ocriplasmin for vitreomacular traction and macular hole: a spectral-domain optical coherence tomography prospective study. graefes arch clin exp ophthalmol 2016;254:223–233. 16. chin ek, almeida dr, sohn eh, boldt hc, mahajan vb, gehrs km, et al. incomplete vitreomacular traction release using intravitreal ocriplasmin. case rep ophthalmol 2014;5:455–462. 17. hager a, seibel i, riechardt a, rehak m, joussen am. does ocriplasmin affect the rpe-photoreceptor adhesion in macular holes? br j ophthalmol 2015;99:635–638. 18. itoh y, kaiser pk, singh rp, srivastava sk, ehlers jp. assessment of retinal alterations after intravitreal ocriplasmin with spectral-domain optical coherence tomography. ophthalmology 2014;121:2506– 2507.e2502. 19. kim bt, schwartz sg, smiddy we, doshi rr, kovach jl, berrocal am, et al. initial outcomes following intravitreal ocriplasmin for treatment of symptomatic vitreomacular adhesion. ophthalmic surg lasers imaging retina 2013;44:334–343. 20. knudsen vm, kozak i. a retrospective study of a single practice use of ocriplasmin in the treatment of vitreomacular traction. saudi j ophthalmol 2014;28:139– 144. 21. lommatzsch ap, gutfleisch m, dietzel m, heimes b, spital g, bohme m, et al. [initial clinical experience in the treatment of vitreomacular traction and macular holes with ocriplasmin]. klin monbl augenheilkd 2014;231:909–914. 22. maier m, abraham s, frank c, feucht n, lohmann cp. [ocriplasmin as a treatment option for symptomatic vitreomacular traction with and without macular hole. first clinical experiences]. ophthalmologe 2015;112:990–994. 23. meyer jc, shah gk, blinder kj, waheed nk, reichel e, stalmans p, et al. early evolution of the vitreomacular interface and clinical efficacy after ocriplasmin injection for symptomatic vitreomacular adhesion. ophthalmic surg lasers imaging retina 2015;46:209–216. 24. miller jb, kim la, wu dm, vavvas dg, eliott d, husain d. ocriplasmin for treatment of stage 2 macular holes: early clinical results. ophthalmic surg lasers imaging retina 2014;45:293–297. 25. novack rl, staurenghi g, girach a, narendran n, tolentino m. safety of intravitreal ocriplasmin for focal vitreomacular adhesion in patients with exudative age-related macular degeneration. ophthalmology 2015;122:796–802. 26. quezada-ruiz c, pieramici dj, nasir m, rabena m, steinle n, castellarin aa, et al. outer retina reflectivity changes on sd-oct after intravitreal ocriplasmin for vitreomacular traction and macular hole. retina 2015;35:1144–1150. 27. reiss b, smithen l, mansour s. transient vision loss after ocriplasmin injection. retina 2015;35:1107–1110. 28. sharma p, juhn a, houston sk, fineman m, chiang a, ho a, et al. efficacy of intravitreal ocriplasmin on vitreomacular traction and full-thickness macular holes. am j ophthalmol 2015;159:861–867.e862. 29. singh rp, li a, bedi r, srivastava s, sears je, ehlers jp, et al. anatomical and visual outcomes following ocriplasmin treatment for symptomatic vitreomacular traction syndrome. br j ophthalmol 2014;98:356–360. 30. steel dh, sandinha mt, white k. the plane of vitreoretinal separation and results of vitrectomy surgery in patients given ocriplasmin for idiopathic macular hole. invest ophthalmol vis sci 2015;56:4038–4044. 31. warrow dj, lai mm, patel a, raevis j, berinstein dm. treatment outcomes and spectral-domain optical coherence tomography findings of eyes with symptomatic vitreomacular adhesion treated with intravitreal ocriplasmin. am j ophthalmol 2015;159:20–30.e21. 32. willekens k, abegao pinto l, vandewalle e, stalmans i, stalmans p. improved efficacy of ocriplasmin for vitreomacular traction release and transient changes in optic disk morphology. retina 2015;35:1135–1143. 33. chatziralli i, theodossiadis g, xanthopoulou p, miligkos m, sivaprasad s, theodossiadis p. ocriplasmin use for vitreomacular traction and macular hole: a meta-analysis and comprehensive review on predictive factors for vitreous release and potential complications. graefes arch clin exp ophthalmol 2016;254:1247–1256. 34. dugel pu, tolentino m, feiner l, kozma p, leroy a. results of the 2-year ocriplasmin for treatment for symptomatic vitreomacular adhesion including macular hole (oasis) randomized trial. ophthalmology 2016;123:2232–2247. 35. khan ma, haller ja. ocriplasmin for treatment of vitreomacular traction: an update. ophthalmol ther 2016;5:147–159. 36. dugel pu, regillo c, eliott d. characterization of anatomic and visual function outcomes in patients with fullthickness macular hole in ocriplasmin phase 3 trials. am j ophthalmol 2015;160:94–99.e91. 54 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 patient baseline characteristics and ocriplasmin efficacy; joondeph et al 37. feng hl, roth db, hasan a, fine hf, wheatley hm, prenner jl, et al. intravitreal ocriplasmin in clinical practice: predictors of success, visual outcomes, and complications. retina 2018;38:128–136. 38. khanani am, duker js, heier js, kaiser pk, joondeph bc, kozma p, et al. ocriplasmin treatment leads to symptomatic vitreomacular adhesion/vitreomacular traction resolution in the real-world setting: the phase iv orbit study. ophthalmol retina 2018;3:32–41. 39. kuppermann bd. ocriplasmin efficacy – an analysis of real-world results from 2013 to 2015. eur ophthal rev 2015;9:141–146. 40. coskey a, brown dm, hooten c, kao lk, wykoff cc, major jc, et al. ocriplasmin for vitreomacular adhesion (vma) in the clinical setting: rates of vma release, development of macular hole, and visual outcomes. the association for research in vision and ophthalmology (arvo) annual meeting. orlando, fl. 41. diaz-rohena r, flores-sanchez b. ocriplasmin in clinical practice. pan-american retina and vitreous society (sprv) meeting. san juan, puerto rico. 42. nudleman e, franklin ms, ruby aj, wolfe jd. ocriplasmin for vitreomacular adhesion: aftermarket experience and findings. american society of retina specialists (asrs) annual meeting. san diego, ca. 43. o’neill bp, shah ap, coney jm. resolution of vitreomacular traction using ocriplasmin (jetrea) and its potential role in diabetic macular edema. the association for research in vision and ophthalmology (arvo) annual meeting. orlando, fl. 44. haynes rj, yorston d, laidlaw da, keller j, steel dh. real world outcomes of ocriplasmin use by members of the british and eire association of vitreoretinal surgeons. eye 2017;31:107–112. 45. hikichi t, akiba j, trempe cl. effect of the vitreous on the prognosis of full-thickness idiopathic macular hole. am j ophthalmol 1993;116:273–278. 46. chew ey, sperduto rd, hiller r, nowroozi l, seigel d, yanuzzi la, et al. clinical course of macular holes: the eye disease case-control study. arch ophthalmol 1999;117:242–246. 47. guyer dr, de bustros s, diener-west m, fine sl. observations on patients with idiopathic macular holes and cysts. arch ophthalmol 1992;110:1264–1268. 48. ezra e, gregor zj, morfields macular hole study group report no 1. surgery for idiopathic full-thickness macular hole: two-year results of a randomized clinical trial comparing natural history, vitrectomy, and vitrectomy plus autologous serum: morfields macular hole study group raeport no. 1. arch ophthalmol 2004;122:224–236. 49. freeman wr, azen sp, kim jw, el-haig w, mishell dr 3rd, bailey i. vitrectomy for the treatment of full-thickness stage 3 or 4 macular holes. results of a multicentered randomized clinical trial. the vitrectomy for treatment of macular hole study group. arch ophthalmol 1997;115:11– 21. 50. hikichi t, yoshida a, akiba j, trempe cl. natural outcomes of stage 1, 2, 3, and 4 idiopathic macular holes. br j ophthalmol 1995;79:517–520. 51. hikichi t, yoshida a, akiba j, konno s, trempe cl. prognosis of stage 2 macular holes. am j ophthalmol 1995;119:571–575. 52. kim jw, freeman wr, el-haig w, maguire am, arevalo jf, azen sp. baseline characteristics, natural history, and risk factors to progression in eyes with stage 2 macular holes. results from a prospective randomized clinical trial. vitrectomy for macular hole study group. ophthalmology 1995;102:1818–1828; discussion 1828–1819. 53. kim jw, freeman wr, azen sp, el-haig w, klein dj, bailey il. prospective randomized trial of vitrectomy or observation for stage 2 macular holes. vitrectomy for macular hole study group. am j ophthalmol 1996;121:605–614. 54. roth db, feng hl, modi kk, fine hf, wheatley hm. predictors of success with intravitreal ocriplasmin in the treatment of symptomatic vitreomacular adhesion. invest ophthalmol vis sci 2014;55:298. 55. hillenkamp j, kraus j, framme c, jackson tl, roider j, gabel vp, et al. retreatment of full-thickness macular hole: predictive value of optical coherence tomography. br j ophthalmol 2007;91:1445–1449. 56. steel dh, parkes c, papastavrou vt, avery pj, el-ghrably ia, habib ms, et al. predicting macular hole closure with ocriplasmin based on spectral domain optical coherence tomography. eye 2016;30:740–745. 57. benarous a, le mer y. long-term results of vitrectomy for macular holes after failure of vitreolysis. ophthalmologica 2018;240:14–22. 58. hoerauf h. predictive values in macular hole repair. br j ophthalmol 2007;91:1415–1416. 59. mester v, kuhn f. internal limiting membrane removal in the management of full-thickness macular holes. am j ophthalmol 2000;129:769–777. 60. cheng l, azen sp, el-bradey mh, scholz bm, chaidhawangul s, toyoguchi m, et al. duration of vitrectomy and postoperative cataract in the vitrectomy for macular hole study. am j ophthalmol 2001;132:881– 887. 61. cherfan gm, michels rg, de bustros s, enger c, glaser bm. nuclear sclerotic cataract after vitrectomy for idiopathic epiretinal membranes causing macular pucker. am j ophthalmol 1991;111:434–438. 62. melberg ns, thomas ma. nuclear sclerotic cataract after vitrectomy in patients younger than 50 years of age. ophthalmology 1995;102:1466–1471. 63. thompson jt, glaser bm, sjaarda rn, murphy rp. progression of nuclear sclerosis and long-term visual results of vitrectomy with transforming growth factor beta2 for macular holes. am j ophthalmol 1995;119:48–54. 64. van effenterre g, ameline b, campinchi f, quesnot s, le mer y, haut j. [is vitrectomy cataractogenic? study of changes of the crystalline lens after surgery of retinal detachment]. j fr ophtalmol 1992;15:449–454. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 55 case report heads-up digitally assisted surgical viewing with intraoperative optical coherence tomography for myopic schisis repair renato menezes palácios, md1,2; kim vieira kayat, md1,2; michel eid farah, md, phd1; françois devin, md2 1department of ophthalmology-retina, federal university of são paulo, são paulo, brazil 2department of ophthalmology-retina, centre monticelli paradis d’ophtalmologie, marseille, france orcid: renato menezes palácios: https://orcid.org/0000-0003-2682-9899 abstract purpose: to describe the surgical approach with a screen-based heads-up, threedimensional (3-d) digital viewing with intraoperative optical coherence tomography (ioct) for the successful repair of a myopic macular schisis (mms) case. case report: a 62-year-old woman with vision loss in the left eye was scheduled for pars plana vitrectomy (ppv) and mms repair. surgery was performed using the ngenuity® system for surgical viewing, and foveal-sparing internal limiting membrane (fs-ilm) peeling was performed without gas tamponade, after confirming the absence of iatrogenic macular hole with i-oct. there were no intraoperative or postoperative complications. visual acuity improved to 20/40 and the subfoveal macular thickness improved from 706 µm (preoperative) to 221 µm after seven months of follow-up. conclusion: heads-up digitally assisted viewing technology with i-oct may be useful or preferred for patients requiring vitreoretinal surgery in the setting of mms. keywords: heads-up surgery; 3-d; intraoperative optical coherence tomography; myopic macular schisis; foveal-sparing internal limiting membrane peeling j ophthalmic vis res 2021; 16 (1): 127–130 introduction myopic macular schisis (mms) is a pathology that is typically seen in high myopic patients, which is distinguished by progressive secession of the neurosensory retinal layers. many articles have shown that pars plana vitrectomy (ppv), with or correspondence to: renato menezes palácios, md. av. serzedelo correa, 681, apto 1401, belém/pa 66033-265, brazil. e-mail: renatompalacios@hotmail.com received: 10-04-2019 accepted: 22-05-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8259 without internal limiting membrane (ilm) peeling and gas tamponade, is a successful treatment for this condition.[1–4] here, we describe an mms case treated with ppv and foveal-sparing internal limiting membrane (fs-ilm) peeling [figure 1], without gas tamponade, using intraoperative optical coherence tomography (i-oct) and digitally-assisted vitreoretinal threedimensional (3-d) viewing. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: palácios rm, kayat kv, farah me, devin f. headsup digitally assisted surgical viewing with intraoperative optical coherence tomography for myopic schisis repair. j ophthalmic vis res 2021;16:127– 130. © 2021 palácios et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 127 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8259&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr heads-up 3-d viewing with i-oct for myopic macular schisis repair; palácios et al figure 1. intraoperative snapshot showing fs-ilm peeling using 3-d surgical viewing. figure 2. intraoperative snapshot showing fs-ilm peeling using 3-d surgical viewing and i-oct. the i-oct shows no evidence of any iatrogenic complication. figure 3. (a) preoperative appearance, (b) partial resolution of the macular schisis one month postoperatively, and complete resolution of the schisis (c) four and (d) seven months after the surgery. visual acuity improved from 20/200 to 20/40 and subfoveal macular thickness improved from 706 to 221 µm after seven months of follow-up. 128 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 heads-up 3-d viewing with i-oct for myopic macular schisis repair; palácios et al case report a 62-year-old woman with mms in the left eye of few month duration underwent a complete ophthalmologic examination that included best-corrected visual acuity (bcva), slit-lamp biomicroscopy, fundus examination, and applanation tonometry. spectral domain optic coherence tomography (sd-oct) images were obtained with cirrus hd-oct (carl zeiss ag, oberkochen, germany) at baseline and at all follow-up visits (one, four, and seven months). subfoveal macular thickness was 706 micrometers (µm), vision was 20/200, and ppv was scheduled. the patient had a history of phacoemulsification in the left eye. the anesthetists performed sedation and a retrobulbar block. the ngenuity® digitally assisted vitreoretinal surgery system (alcon, inc., fort worth, tx) was connected to replace the oculars of the microscope. the 3-d high definition real-time video was displayed on the ngenuity®4k 3-d flat-panel placed at 1.3 m from the surgeon. to be able to see in 3-d, the surgeon wore polarized glasses. traditional vitreoretinal techniques, with the constellation vision system (alcon, inc, fort worth, tx), were performed without obstacles, including core vitrectomy, posterior hyaloid detachment, and peripheral vitrectomy. brilliant blue g (dorc, zuidland, the netherlands) was used to stain the ilm and the surgeon performed fs-ilm peeling using disposable 25-gauge end-grasping forceps under i-oct [figure 2]. the i-oct also proved that there were no iatrogenic lesions [video 1], so it was decided not to perform gas tamponade. the subfoveal macular thickness improved from 706 µm (preoperative), 540 µm (after one month), 214 µm (after four months) to 221 µm (after seven months) [figure 3] and the visual acuity improved to 20/40 after seven months of follow-up. discussion in the current case, a 62-year-old woman was scheduled for ppv and mms repair in the left eye, using the 3-d system. foveal sparing ilm peeling was performed, without gas tamponade, after confirming the absence of iatrogenic macular hole with i-oct. mms has already been described by many authors, showing a wide variety of therapeutic interventions. in most reported cases in which ppv was performed, ilm peeling was advised to completely remove residual traction on the retina, enabling the inner surface to adjust to the mold of the posterior staphyloma.[2] it is still a surgical challenge to measure accurately the dimensions of ilm sparing intraoperatively. with the development of 3-d system[5] with i-oct, real-time visualization of vitreoretinal interface, definition of the various plans of epiretinal membranes (erm) and macular holes (mh), and visualization of ilm undulation after successful peeling can help in unequalled exactitude in an otherwise assumptive surgery.[6] visualization of resolution of traction following vitrectomy and erm removal can also help determine the surgical termination. addition of such an advance would further improve management of mms to very small precision.[3] in the current case, similar to kumar et al,[3] fsilm peeling was performed under direct i-oct visualization of the requisite area of sparing to prevent intraoperative deroofing of the cysts and mh formation. gas tamponade has been used in the treatment of mms, provoking retinal repositioning by pushing the retina back. however, it remains unknown whether gas tamponade is necessary and its efficacy has not been established. kim et al[4] showed resolution of mms in six of the eight eyes (75.0%) after ppv and ilm peeling without gas tamponade. on the other hand, figueroa et al[2] achieved resolution of mms in 93% of 30 patients after ppv with ilm peeling and gas tamponade. our case demonstrates that heads-up digitally assisted viewing with i-oct was suitable and effective to manage these challenging retinal disorders. financial support and sponsorship none. conflicts of interest there are no conflicts of interest. references 1. gohil r, sivaprasad s, han lt, mathew r, kiousis g, yang y. myopic foveoschisis: a clinical review. eye 2015;29:593– 601. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 129 https://knepublishing.com/index.php/jovr/article/view/8259/14339 heads-up 3-d viewing with i-oct for myopic macular schisis repair; palácios et al 2. figueroa ms, ruiz-moreno jm, gonzalez del valle f, govetto a, de la vega c, plascencia rn. long-term outcomes of 23-gauge pars plana vitrectomy with internal limiting membrane peeling and gas tamponade for myopic traction maculopathy: a prospective study. retina 2015;35:1836–1843. 3. kumar a, ravani r, mehta a, simakurthy s, dhull c. outcomes of microscope-integrated intraoperative optical coherence tomography-guided center-sparing internal limiting membrane peeling for myopic traction maculopathy: a novel technique. int ophthalmol 2018;38:1689–1696. 4. kim ks, lee sb, lee wk. vitrectomy and internal limiting membrane peeling with and without gas tamponade for myopic foveoschisis. am j ophthalmol 2012;153:320– 326. 5. eckardt c, paulo eb. heads-up surgery for vitreoretinal procedures: an experimental and clinical study. retina 2016;36:137–147. 6. ehlers jp, kaiser pk, srivastava sk. intraoperative optical coherence tomography utilizing the rescan 700: preliminary results from the discover study. br j ophthalmol 2014;98:1329–1332. 130 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 original article effect of contact lenses on contrast sensitivity under various lighting conditions monireh mahjoob1, phd; samira heydarian2, phd 1health promotion research center, zahedan university of medical sciences, zahedan, iran 2department of rehabilitation sciences, school of allied medical sciences, mazandaran university of medical sciences, sari, iran orcid: monireh mahjoob: http://orcid.org/0000-0001-9455-0721 samira heydarian: http://orcid.org/0000-0002-4383-8255 abstract purpose: to assess contrast sensitivity in clear and colored soft contact lenses under different lighting conditions. methods: this study was performed on 34 medical students. visual acuity was measured using a tumbling e chart at a distance of 6 m, and contrast sensitivity was determined by pelli robson chart at a distance of 1 m. these tests were repeated in mesopic (3 lux) and glare (2000 lux) conditions. then, a clear contact lens was applied to one eye and a colored contact lens was applied to the other. after 2 hr, visual acuity and contrast sensitivity were measured for each individual. the results were compared with and without contact lenses under normal, mesopic, and glare conditions. results: the mean refractive error was 0.44 ± 0.20 diopters. repeated measures anova showed a decline in contrast sensitivity with colored and clear contact lenses as compared to no-lens condition (p < 0.001). additionally, lighting conditions had a significant impact on contrast sensitivity (p < 0.001); contrast sensitivity was lower in mesopic and glare conditions than under normal lighting condition. conclusion: in addition to the drop in contrast sensitivity under unusual lighting conditions (e.g., glare and mesopic), wearing soft contact lenses can further reduce contrast sensitivity in different lighting conditions. therefore, people who wear contact lenses should be aware of this reduction in visual performance in conditions like driving at night or in the fog. keywords: contact lens; contrast sensitivity; glare; visual acuity j ophthalmic vis res 2021; 16 (4): 538–543 introduction contact lenses are gaining increasing popularity nowadays. approximately 125 million people use correspondence to: samira heydarian, phd. department of rehabilitation sciences, school of allied medical sciences, mazandaran university of medical sciences, sari 4747193711, iran. e-mail: opt_heydarian@yahoo.com received: 29-04-2020 accepted: 04-12-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9742 contact lenses worldwide.[1] alongside its cosmetic aspect, the most important indication for using a contact lens is to correct refractive errors. due to changing the color of the eyes, colored contact lenses are mainly used for cosmetic purposes, especially by women and young people.[2] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: mahjoob m, heydarian s. effect of contact lenses on contrast sensitivity under various lighting conditions. j ophthalmic vis res 2021;16:538–543. 538 © 2021 mahjoob et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9742&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr contact lenses and contrast sensitivity; mahjoob et al among the various types of contact lenses, rigid gas permeable lenses (rgps) are the least common and are fitted by about 2% due to the preference of practitioners and patients for soft contact lenses and the main reasons for this include the initial discomfort with rigid lenses and easier fitting of soft contact lenses.[3] silicone hydrogel contact lenses were initially developed for extended wear to eliminate hypoxia during overnight wear and they comprise 41% of all soft contact lenses fitted.[4, 5] despite extensive studies on adverse symptoms with hydrogel and silicone hydrogel contact lenses, there is no evidence that silicone hydrogel contact lenses have significantly improved comfort compared to hydrogel contact lenses for daily wear.[5, 6] in addition, the incidence of microbial adverse events of the two types of soft contact lenses were found to be similar.[5, 7] one of the most significant issues in refractive correction is the quality of vision under different lighting conditions. research findings suggest that contrast sensitivity (cs) tests show a more accurate assessment of quality of vision than visual acuity tests.[8] people are also exposed to different lighting conditions in their daily lives, such as driving in foggy conditions or at night, which can affect their quality of vision.[9, 10] according to existing evidence, information obtained from cs tests under normal lighting conditions is not adequate.[9, 10] therefore, measuring cs under different lighting conditions can determine people’s vision quality more accurately. contrast of the retinal image can be reduced due to light scattering. lens and cornea are two important sources of light scattering in the eye which are highly dependent on the age and opacity of the ocular media.[11] applying contact lenses, as an optical surface, can affect the rate of light scattering in the eye.[12] multifocal contact lenses can trigger visual problems like visual haloes, decreased cs, and fluctuating vision due to pupil size variations.[13, 14] previous studies have reported different results for cs changes in single focal contact lenses.[2, 15, 16] wachler et al observed a drop in cs only at high spatial frequencies for clear contact lenses.[17] however, some other studies have noted changes in cs occurring only in colored contact lenses.[2, 16, 18] considering the inconsistencies in the findings of previous studies and the importance of evaluating visual quality with contact lenses in various light conditions (especially in young individuals who are the main users of contact lenses), this study was designed to investigate the changes in cs resulting from wearing clear and colored hydrogel contact lenses, as the most common types of contact lens fitted, under different light conditions. methods in this cross-sectional study, 34 medical students were recruited from zahedan university of medical sciences. at the outset, a questionnaire was used to screen the general health of the participants and complete ocular examinations were performed. individuals with systemic diseases, eye diseases such as dry eye, glaucoma, opacity in the ocular media, any obvious ocular abnormality, and a history of trauma and eye surgery were excluded from the study. refractive errors were determined using auto refractometer (ar 8800, topcon, japan). individuals with an uncorrected visual acuity of 6/6 were enrolled in the study. the mean refractive error of the subjects was 0.20 ± 0.46 d (–0.5 to +1.25). moreover, the subjects had an astigmatism below 0.5 d. visual acuity was measured using a tumbling e chart at a distance of 6 m, and the pelli robson chart was positioned at a distance of 1 m to assess cs. this chart consists of eight rows and each one comprises two separate three-letter columns, with the highest contrast represented in the highest left row and the lowest contrast shown in the lowest row, while the right side of the chart has a log contrast equal to 2.25. the criterion for recording the log cs was reading at least two letters from each threeletter segment.[19] these tests were also recorded in mesopic (3 lux) and glare (2000 lux) conditions, where illumination was measured with tes 1337 b photometer (es electrical electronic corp. taiwan). a 60 w tungsten lamp was placed at a distance of 18 cm from the patient’s eye and 2 cm above the patient’s head (an angle of 10º to the line of sight) in order to create glare. it should be noted that patients were exposed to each lighting condition for at least 20 min in order to make the eyes adapt to light. then, visual acuity and cs were measured. in each lighting condition, pupil size was measured using a hemispherical scale ruler. the sequence of lighting conditions was chosen randomly. while the most fitted contact lenses are hydrogel contact lenses, in this study a clear hydrogel contact lens [bausch & lomb (soflens), overall diameter of 14.0, bace curve radius (bcr) of 8.7, journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 539 contact lenses and contrast sensitivity; mahjoob et al water content of 38.6%] was applied to one eye, and a colored contact lens (clearcolor, overall diameter of 14.5, bcr of 8.6, water content of 42%, and pigment-free optical zone of 6 ml) to the other eye. in order to reduce the effect of eye laterality on cs, the patient’s eyes were randomly selected to fit colored and clear lenses. after 30 min, the fit, movements, cornea coverage, and centration of the contact lenses were evaluated. in case of appropriate fitting, visual acuity and cs tests were measured after 2 hr for each eye under different lighting conditions. data analysis repeated measures anova was employed to analyze the effect of contact lenses on cs under different lighting conditions. the results of pairwise comparison with bonferroni correction were expressed as the mean and 95% confidence interval of differences. p < 0.05 were considered statistically significant. ethical considerations all procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the helsinki declaration and its later amendments. approval was obtained from the ethics committee of zahedan university of medical sciences (ethics approval number: ir.zaums.rec.1399.003). informed consent was obtained from all participants. results thirty-four students (14 females and 20 males) aged 19 to 23 years (mean, 21.29 ± 1.08 years) participated in this research. the pupil size in right and left eyes was similar in all participants. the mean and standard deviation of pupil diameters were 3.03 ± 1.09 in normal light condition, 5.28 ± 0.94 in mesopic condition, and 1.56 ± 0.59 in glare condition, indicating significant variations in the three lighting conditions (p < 0.001). the visual acuity of all subjects was 20/20 which did not change under different light conditions with and without contact lenses. the mean scores of cs in different light conditions with and without contact lenses are given in table 1. repeated measures anova displayed the significant impact of contact lenses on cs (p < 0.001). furthermore, pairwise comparison showed a decrease in cs when contact lenses were applied compared to the situation where no contact lens was used (mean difference of cs; without cl and with clear cl: 0.031, 95% ci: 0.008–0.053; p = 0.005, without cl and with colored cl: 0.029, 95% ci: 0.007–0.052; p = 0.007). meanwhile, the change in cs was not significantly different in the two types of contact lenses [clear and colored (p > 0.99)]. in addition, the effect of lighting conditions on cs was significant (p < 0.001) with cs under mesopic and glare conditions lower than that under normal lighting condition; more specifically, cs was lower under mesopic condition than that under glare condition (mean difference of cs; between normal light condition and mesopic condition: 0.325, 95% ci: 0.290–0.360; p <0.001, between normal and glare condition: 0.108, 95% ci: 0.058–0.159; p < 0.001, between glare and mesopic condition: 0.217, 95% ci: 0.168–0.266; p < 0.001). moreover, no significant interaction was found between contact lenses and various lighting conditions (p = 0.227). hence, it could be inferred that the effect of contact lenses on reducing cs is similar under different lighting conditions. to further explore the impact of contact lenses in various lighting condition, we studied the change in cs due to contact lenses (cs without contact lenses minus cs with contact lenses) under three different lighting conditions for each participant [figure 1]. the results of anova test exhibited no significant disparity in cs difference under three lighting conditions (p = 0.829). discussion since cs tests provide a better assessment of the quality of vision, the present study investigated cs under different lighting conditions in clear and colored contact lenses. the results proposed that these contact lenses reduce cs but do not affect visual acuity. this cs reduction was similar in both clear and colored contact lenses. consistent with our results, briggs reported a decline in cs as a result of wearing colored and clear contact lenses and similarly found no difference in cs between the two types of contact 540 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 contact lenses and contrast sensitivity; mahjoob et al table 1. mean and standard deviation of log contrast sensitivity under different lighting conditions in clear and colored contact lenses normal light condition glare condition mesopic light condition without cl 1.81 ± 0.11 1.69 ± 0.09 1.51 ± 0.10 clear cl 1.74 ± 0.10 1.65 ± 0.12 1.46 ± 0.07 tinted cl 1.74 ± 0.12 1.64 ± 011 1.46 ± 0.12 cl, contact lens figure 1. change in contrast sensitivity (contrast sensitivity without contact lenses minus contrast sensitivity with clear/colored contact lenses) under three lighting conditions. lenses.[20] another research showed that clear contact lenses, as opposed to colored contact lenses, did not reduce cs.[16] the greater corneal edema in colored contact lenses compared to clear lenses was not a possible cause in their study and it was stated that the main reason for this difference was the lower optical quality of colored lenses compared to clear ones.[16] other studies suggested that the diameter of pigmentfree optical zone in colored contact lenses plays a substantial role in aberrations, visual acuity, and cs; aberrations and cs in colored contact lenses with an optical diameter of 6 mm do not differ from those of clear contact lenses. however, cs decline at spatial frequency of 12 cycles per degree under photopic condition has been more intense in colored contact lenses with an optical diameter of 4–5 mm than in clear contact lenses.[18] previous studies have attributed the drop in cs in soft contact lenses to the lack of astigmatism correction, lens deposition, and corneal edema secondary to reduced oxygen supply caused by the contact lens.[20, 21] in the present study, the patients had 6/6 visual acuity without optical correction and the power of contact lenses used were plano; therefore the lack of astigmatism correction or spherical aberration cannot explain the decrease in cs. besides, since the contact lenses were disposable, deposition had no role in diminishing cs. we assessed cs 2 hr after contact lenses were worn. previous studies have indicated that corneal edema occurs even 1 hr after wearing contact lenses.[22] hence, the most likely explanation for the decrease in cs in our study may be corneal edema resulting from contact lens application. however, one of the limitations of our study was that we did not measure corneal thickness before and after 2 hr of lens wearing. it would have been better to measure the thickness of cornea in order to understand corneal edema more accurately. in addition, similarity in cs reduction in the two types of clear and colored contact lenses in this study journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 541 contact lenses and contrast sensitivity; mahjoob et al could be due to the large diameter of the pigmentfree optical zone in the colored contact lens (6 mm), which is in keeping with the study by jung et al.[18] this finding supports the ineffectiveness of optical parameters of clear and colored plano contact lenses and, on the other hand, reinforces the active role of corneal edema in cs reduction. the present study revealed that visual acuity does not change under different lighting conditions with and without contact lenses. our results showed that both glare and mesopic conditions led to a cs lower than that obtained by normal lighting conditions. moreover, cs was lower under mesopic condition than under glare condition. additionally, both types of contact lenses caused approximately equal amount of reduction in cs under different lighting conditions. speraul observed that soft contact lenses diminish visual performance in both glare and mesopic conditions.[23] another study concluded that contact lens could heighten glare sensitivity if it causes corneal epithelial edema; alternatively, no change in glare sensitivity would occur if this edema does not emerge.[24] this unchanged glare sensitivity has been noted in colored contact lenses as well.[25] another study showed that while soft contact lenses do not affect glare disability, they can induce glare effects.[26] since placing an additional optical surface such as a contact lens can augment the amount of light scattering and absorption, it is plausible to observe a decline in cs under different lighting conditions when contact lenses are worn. moreover, the reason for the sharper drop in cs under mesopic conditions can be explained by the development of mydriasis. this dilation of the pupil, in addition to increasing aberrations, can cause flare and further reduce cs when contact lenses are applied. this is due to the fact that pupil diameter exceeds the diameter of the optical zone of the lens. our results revealed no significant difference in cs reduction under three lighting conditions using two types of clear and colored contact lenses. this could be related to the type of test used to measure cs. in fact, pelli robson only evaluates cs at low spatial frequencies (one cycle per degree), and it fails to assess visual performance at mid and high spatial frequencies. it should be reminded that previous studies have observed the decline in cs only at high spatial frequencies with contact lenses.[17, 18] it is recommended that future researchers explore cs by other tests which cover a wider range of spatial frequencies. furthermore, it is better to compare the cs reduction in various types of contact lenses in the future studies. in summary, this study indicated that clear and colored contact lenses reduce cs. since glare and mesopic lighting conditions can also reduce cs, the effect of contact lenses on critical visual functions should be considered in real-world tasks such as driving at night or in the fog. acknowledgments the authors of this article appreciate farkhondeh khosravi baghdad, mehdi modabber, and the assistance and facilities provided by the vice chancellor of research and technology of zahedan university of medical sciences (ethic code: ir.zaums.rec.1399.003). financial support and sponsorship this study was funded by zahedan university of medical sciences (grant number: ir.zaums.rec.1399.003). conflicts of interest the authors declare that they have no conflict of interest. references 1. barr j. annual report: contact lens spectrum’s annual report of major corporate and product developments and events in the contact lens industry in 2004, as well as predictions for 2005. contact lens spectrum 2005;january. 2. morgan pb, efron n. patterns of fitting cosmetically tinted contact lenses. cont lens anterior eye 2009;32:207–208. 3. efron n. obituary-rigid contact lenses. cont lens anterior eye 2010;33:245–252. 4. orsborn g, dumbleton k. eye care professionals’ perceptions of the benefits of daily disposable silicone hydrogel contact lenses. cont lens anterior eye 2019;42:373–379. 5. guillon m. are silicone hydrogel contact lenses more comfortable than hydrogel contact lenses? eye contact lens 2013;39:86–92. 6. santodomingo-rubido j, barrado-nacascues e, rubidocrespo m-j. ocular surface comfort during the day assessed y instant reporting in different types of contact and non-contact lens wearers. eye contact lens 2010;36:96–100. 7. stapleton f, keay l, edwards k, holden b. the epidemiology of microbial keratitis with silicone hydrogel contact lenses. eye contact lens 2013;39:79–85. 542 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 contact lenses and contrast sensitivity; mahjoob et al 8. mahjoob m, anderson aj. contrast discrimination under task-induced mental load. vision res 2019;165:84–89. 9. mahjoob m, heydarian s, koochi s. effect of yellow filter on visual acuity and contrast sensitivity under glare condition among different age groups. int ophthalmol 2016;36:509–514. 10. maniglia m, thurman sm, seitz ar, davey pg. effect of varying levels of glare on contrast sensitivity measurements of young healthy individuals under photopic and mesopic vision. front psychol 2018;9:899. 11. de waard p, ijspeert j, van den berg t, de jong p. intraocular light scattering in age-related cataracts. invest ophthalmol vis sci 1992;33:618–625. 12. cervino a, gonzalez-meijome jm, linhares jm, hosking sl, montes-mico r. effect of sport-tinted contact lenses for contrast enhancement on retinal straylight measurements. ophthalmic physiol opt 2008;28:151–156. 13. garcía-lázaro s, ferrer-blasco t, madrid-costa d, albarrán-diego c, montés-micó r. visual performance of four simultaneous-image multifocal contact lenses under dim and glare conditions. eye contact lens 2015;41:19–24. 14. llorente-guillemot a, garcía-lazaro s, ferrer-blasco t, perez-cambrodi rj, cerviño a. visual performance with simultaneous vision multifocal contact lenses. clin exp optom 2012;95:54–59. 15. grey c. changes in contrast sensitivity when wearing low, medium and high water content soft lenses. journal of the british contact lens association 1986;9:21–25. 16. özkagnici a, zengin n, kamis ü, gündüz k. do daily wear opaquely tinted hydrogel soft contact lenses affect contrast sensitivity function at one meter? eye contact lens 2003;29:48-49. 17. wachler b, phillips cl, schanzlin dj, krueger rr. comparison of contrast sensitivity in different soft contact lenses and spectacles. clao j 1999;25:48–51. 18. jung jw, kim sm, han sh, kim ek, seo ky. effect of the pigment-free optical zone diameter of decorative tinted soft contact lenses on visual function. br j ophthalmol 2016;100:633–637. 19. arditi a. improving the design of the letter contrast sensitivity test. invest ophthalmol vis sci 2005;46:2225– 2229. 20. briggs st. contrast sensitivity assessment of soft contact lens wearers. int contact lens clin 1998;25:99–102. 21. bernstein ih, brodrick j. contrast sensitivities through spectacles and soft contact lenses. am j optom physiol optic 1981;58:309–313. 22. grey c. changes in contrast sensitivity during the first hour of soft lens wear. am j optom physiol optic 1986;63:702– 707. 23. spraul cw, roth h, gäckle h, lang ge, lang gk. influence of special-effect contact lenses (crazy lenses) on visual function. clao j 1998;24:29–32. 24. miller d, wolf e, geer s, vassallo v. glare sensitivity related to use of contact lenses. arch ophthalmol 1967;78:448– 450. 25. lutzi f, chou b, egan d. tinted hydrogel lenses: an assessment of glare sensitivity reduction. am j optom physiol optic 1985;62:478–481. 26. applegate ra, jones dh. disability glare and hydrogel lens wear–revisited. optom vis sci 1989;66:756–759. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 543 original article scleral buckling for primary retinal detachment: outcomes of scleral tunnels versus scleral sutures matthew r. starr, md1; edwin h. ryan, md2; anthony obeid, md1; claire ryan, ba2; xinxiao gao, md2 malika l. madhava, bs2; sean m. maloney, md2; adam z. adika, md3; krishi v. peddada, md4 kareem sioufi, md2; luv g. patel, md1; michael j. ammar, md1; nora j. forbes, ms2; antonio capone jr., md5 geoffrey g. emerson, md, phd6; daniel p. joseph, md, phd7; dean eliott, md8; carl d. regillo, md1 jason hsu, md1; omesh p. gupta, md, mba1; yoshihiro yonekawa, md1 for the primary retinal detachment outcomes (pro) study group 1wills eye hospital, mid atlantic retina, thomas jefferson university, philadelphia, pa, usa 2vitreoretinal surgery, minneapolis, mn, usa 3lewis katz school of medicine at temple university, philadelphia, pa, usa 4department of ophthalmology, drexel university college of medicine, philadelphia, usa 5associated retinal consultants, oakland university william beaumont school of medicine, royal oak, mi, usa 6the retina center, minneapolis, mn, usa 7the retina institute, st. louis, mo, usa 8massachusetts eye and ear, harvard medical school, boston, ma, usa orcid: matthew r. starr: http://orcid.org/0000-0002-3021-5630 yoshihiro yonekawa: http://orcid.org/0000-0002-6847-7169 abstract purpose: there are primarily two techniques for affixing the scleral buckle (sb) to the sclera in the repair of rhegmatogenous retinal detachment (rrd): scleral tunnels or scleral sutures. methods: this retrospective study examined all patients with primary rrd who were treated with primary sb or sb combined with vitrectomy from january 1, 2015 through december 31, 2015 across six sites. two cohorts were examined: sb affixed using scleral sutures versus scleral tunnels. preand postoperative variables were evaluated including visual acuity, anatomic success, and postoperative strabismus. results: the mean preoperative logmar va for the belt loop cohort was 1.05 ± 1.06 (snellen 20/224) and for the scleral suture cohort was 1.03 ± 1.04 (snellen 20/214, p = 0.846). the respective mean postoperative logmar vas were 0.45 ± 0.55 (snellen 20/56) and 0.46 ± 0.59 (snellen 20/58, p = 0.574). the single surgery success rate for the tunnel cohort was 87.3% versus 88.6% for the suture cohort (p = 0.601). three patients (1.0%) in the scleral tunnel cohort developed postoperative strabismus, but only one patient (0.1%) in the suture cohort (p = 0.04, multivariate p = 0.76). all cases of strabismus occurred in eyes that underwent sb combined with ppv (p = 0.02). there were no differences in vision, anatomic success, or strabismus between scleral tunnels versus scleral sutures in eyes that underwent primary sb. conclusion: scleral tunnels and scleral sutures had similar postoperative outcomes. combined ppv/sb in eyes with scleral tunnels might be a risk for strabismus post retinal detachment surgery. keywords: rhegmatogenous retinal detachment; scleral buckle; scleral suture; scleral tunnels; strabismus j ophthalmic vis res 2021; 16 (3): 377–383 © 2021 starr et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 377 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i3.9434&domain=pdf&date_stamp=2019-07-17 scleral tunnels vs sutures for sb; starr et al introduction the use of scleral buckles (sbs) to repair rhegmatogenous retinal detachments (rrds) was pioneered by custodis in 1949, with the first reported scleral buckling procedure performed in the united states in 1951 by schepens.[1] schepens’ initial technique describes a lamellar dissection of the sclera and placement of an element with external diathermy for retinopexy.[1, 2] an initial report had a success rate of 65%,[2] but over the years, scleral buckling has evolved and lamellar dissection is rarely performed. currently, the most commonly performed is the use of scleral suturing to secure the sb directly on the surface of the sclera, but the use of scleral tunnels to affix the encircling buckle to the sclera is a popular technique as well.[3] the selection largely depends on surgeon’s preference, and little data is available regarding comparative efficacy and outcomes.[3] diplopia from strabismus following sb surgery is often temporary, but chronic or permanent strabismus may also occur and is a well-known complication, with a reported incidence between 5% and 25%.[4] the management of postoperative strabismus usually begins with prism therapy which may resolve the strabismus in the majority of patients, while other patients may require strabismus surgery or buckle removal.[4, 5] similar to the lack of reports examining anatomic outcomes following the use of scleral tunnels or scleral sutures, there have been no reports assessing the development of strabismus comparing these two techniques for buckle fixation. the purpose of this paper is to present the anatomic outcomes following scleral buckling surgery comparing scleral tunnels to scleral fixated sutures, but additionally, to assess the development of postoperative strabismus between these two modalities. correspondence to: yoshihiro yonekawa, md. mid atlantic retina, retina service of wills eye hospital 840 walnut st. suite 1020, philadelphia, pa, 19107, usa. e-mail: yyonekawa@midatlanticretina.com received: 21-05-2021 accepted: 02-03-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i3.9434 methods the primary retinal detachment outcome (pro) study is a multicenter, interventional, retrospective cohort study of patients who underwent repair of noncomplex primary rrd from january 1, 2015 through december 31, 2015 from vitreoretinal surgery in minneapolis, the retina center in minneapolis, the retina institute in st. louis, associated retinal consultants/william beaumont hospital in detroit, mass. eye & ear in boston, and mid atlantic retina/wills eye hospital in philadelphia.[6] institutional review board approval was obtained at each participating institution, and the study complied with the health insurance portability and accountability act of 1996 and adhered to the tenets of the declaration of helsinki. this report is a subgroup analysis of the pro study. we examined the outcomes of patients who received sbs (either primary scleral buckling or in combination with vitrectomy), and compared visual and anatomic outcomes, as well as the rates of postoperative strabismus, as defined as ocular misalignment. complex retinal detachments including retinal detachments that had previously undergone repair, tractional retinal detachments, and retinal detachments due to inflammation or endophthalmitis were excluded. eyes with fewer than three months postoperative follow-up were excluded, as were eyes where the scleral suture or scleral tunnel metric was not recorded. additionally, eyes that underwent vitrectomy without sb, non-encircling sb surgery, pneumatic retinopexy, or laser barricade were excluded. eyes that underwent scleral buckling procedures after the initial procedures, namely reoperations for recurrent retinal detachment, were excluded as well. detailed demographic, preoperative, intraoperative, and postoperative follow-up variables were collected from each site using the secure online redcap database. the primary this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: starr mr, ryan eh, obeid a, ryan c, gao x, madhava ml, maloney sm, adika az, peddada kv, sioufi k, patel lv, ammar m, forbes nj, capone a, emerson gg, joseph dp, eliott d, regillo cd, hsu j, gupta o, yonekawa y. scleral buckling for primary retinal detachment: outcomes of scleral tunnels versus scleral sutures. j ophthalmic vis res 2021;16:377–383. 378 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 https://knepublishing.com/index.php/jovr scleral tunnels vs sutures for sb; starr et al outcomes considered were single surgery anatomic success, postoperative visual acuity, and the development of postoperative strabismus that was noted at the final postoperative visit, which must have taken place more than three months following the surgery. single surgery anatomic success was defined as posterior retinal attachment with no tamponade present, and no presence of subretinal fluid which could spread at three months postoperatively. stable, localized subretinal fluid following primary sb was not considered a failure. sub-analyses included outcomes of sb band type and eyes with only primary sb surgery without pars plana vitrectomy (ppv). for statistical analysis, we used jmp software version 15.0 (sas institute, cary, nc). for withingroup comparisons between baseline and final metrics, a paired t-test was used, and for comparisons between groups, the wilcoxon ranksum test was performed. group comparisons of the categorical data were performed using the fisher’s exact test. a repeated-measures mixed model regression analysis was performed for multivariate analysis comparing sb sutures versus scleral tunnels controlling for surgeon, type of surgery (ppv with sb versus primary sb), buckle type, postoperative epiretinal membrane, and cataract status was performed. a p-value < 0.05 was considered to be statistically significant. results there were 1,148 eyes that met the inclusion criteria and underwent sb or combined ppv and sb for primary, noncomplex rrd, with 289 eyes (25.2%) undergoing sb and 859 eyes (74.8%) undergoing combined ppv with sb. the mean age of the patients was 56.4 ± 14.1 years with 38.4% being female. the mean follow-up after surgery was 365 ± 186 days. the mean preoperative logmar va for all eyes was 1.04 ± 1.05 (snellen va 20/219) and the mean postoperative logmar va was 0.46 ± 0.58 (snellen 20/58, p-value < 0.0001). the single surgery success rate for all eyes was 88.2%. of these 1,148 eyes, 302 had the encircling sb affixed to the sclera with scleral tunnels, while 846 eyes had scleral sutures placed. demographic data for these cohorts are detailed in table 1. briefly, the mean preoperative logmar va for the belt loop cohort was 1.05 ± 1.06 (snellen 20/224) and for the scleral suture cohort was 1.03 ± 1.04 (snellen 20/214, p = 0.846). the mean postoperative logmar va for the belt loop cohort was 0.45 ± 0.55 (snellen 20/56) and for the scleral suture cohort was 0.46 ± 0.59 (snellen 20/58, p = 0.574). the single surgery success rate for the belt loop cohort was 87.3% versus 88.6% for the suture cohort (p = 0.601). three eyes (1.0%) in the belt loop cohort developed postoperative strabismus while only one eye (0.1%) developed postoperative strabismus in the suture cohort (p = 0.04, table 1). on logistic regression analysis accounting for surgeon identification (univariate analysis, p = 0.38), type of surgery (ppv with sb versus sb, p = 0.12), preoperative macular detachment status (p = 0.49), postoperative epiretinal membrane formation (p = 0.33), and postoperative cataract formation (p = 0.51), there was no longer any significant difference in the development of postoperative strabismus with a p-value of 0.76. when accounting for the type of anesthesia (retrobulbar, sub-tenon, or general anesthesia), there was also no difference in the postoperative strabismus (p = 0.17). the distribution of buckle types is presented in table 2, with the most common buckle used in each cohort being a 41 band. as one may expect, the belt loop cohort received smaller bands (more 240 and 41) compared with sutured bands (42) (p < 0.0001). when analyzing only those eyes that had sbs placed (without vitrectomy), there were 287 cases. of these, there were 61 (21.3%) with scleral tunnels and 226 (78.3%) with scleral sutures. there was no difference in single surgery success rate, postoperative visual acuity, or postoperative strabismus in this cohort (table 3). there were no cases of strabismus following scleral buckling without vitrectomy (p = 0.02). during the follow-up period, there were three cases of sb removal, one for infection and two for symptomatic diplopia. the buckles removed for symptomatic diplopia belonged to both the belt loop and scleral suture cohorts. the belt loop patient had the buckle removed seven months following the surgery while the scleral suture patient had it removed five months following the surgery. both patients received a 41 band and underwent combination ppv + sb. the patient with the infected buckle received a 4050 band, was also in the ppv + sb cohort, had the buckle affixed with scleral sutures, and the patient had the buckle journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 379 scleral tunnels vs sutures for sb; starr et al table 1. demographics and visual and anatomic outcomes comparing scleral tunnels versus scleral sutures in fixation of scleral buckle during retinal detachment surgery for both scleral buckle surgery and pars plana vitrectomy combined with scleral buckle scleral tunnels (n = 302) suture (n = 846) p-value age 57.7 ± 13.6 55.9 ± 14.3 0.04∗ sex (female) 117 (38.8%) 314 (37.1%) 0.63 preoperative logmar (snellen) 1.05 ± 1.06 (20/224) 1.03 ± 1.04 (20/214) 0.85 postoperative logmar (snellen) 0.45 ± 0.55 (20/56) 0.46 ± 0.59 (20/58) 0.57 p-value <0.0001∗ <0.0001∗ single surgery success rate 87.3% 88.6% 0.60 postoperative strabismus 3 (1.0%) 1 (0.1%) 0.02∗ eyes with encircling band only 278 (92.1%) 816 (96.5%) 0.01∗+ eyes with 41 band 246 (81.4%) 525 (62.0%) <0.0001∗+ follow-up (days) 368 ± 185 363 ± 187% 0.99 logmar, logarithm of the minimum angle of resolution ∗statistically significant value +fischer’s exact test table 2. analysis of buckle type between the belt loop and scleral suture cohort buckle element scleral tunnels (n = 302) suture (n = 846) 240 53 (17.6%) 57 (6.7%) 40 2 (0.7%) 36 (4.3%) 41 246 (81.4%) 524( 62.0%) 42 1 (0.3%) 183 (21.6%) other 0 (0%) 46 (5.4%) removed eight months following the surgery. there were no cases of buckle extrusion or intraoperative perforation in either cohort reported. discussion the routine method of sb fixation is typically dependent on the surgeon’s preference. scleral sutures can be used to anchor the buckle element to the scleral surface, either to secure an encircling band in place or to imbricate a segmental element into the eye wall. the vast majority of eyes received encircling bands in this study. encircling bands can also be secured to the scleral via scleral tunnels, which are fashioned by creating partial thickness scleral tunnels in all four quadrants. the band is then passed through the scleral tunnels. scleromalacia may bias a surgeon toward scleral sutures, but for routine placement, surgeon preference likely plays the biggest role in the decision to secure the buckle via sutures or scleral tunnels. there is very limited comparative data on the two techniques, and the present study represents the first large-scale study to examine the question. a recent small study of 35 eyes examined the outcomes following combined ppv with sb surgery and compared scleral tunnels versus scleral sutures and found no difference in anatomic outcomes with no cases of buckle extrusion or infection.[7] similarly, the visual and anatomic outcomes were comparable in our significantly larger cohort. the single surgery success rate for all eyes in our series was 88.2% and when analyzed by fixation of the encircling band, there was no difference in the anatomic outcomes or visual acuity. the use of scleral tunnels to secure an sb, though, appeared to be associated with a higher rate of postoperative strabismus in our study. 380 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 scleral tunnels vs sutures for sb; starr et al table 3. demographics and visual and anatomic outcomes comparing scleral tunnels versus scleral sutures in fixation of a scleral buckle during retinal detachment surgery in only eyes undergoing scleral buckling only scleral tunnels (n = 61) suture (n = 226) p-value mean age (yr) 44.7 ± 16.8 47.1 ± 16.1 0.21 sex (female) 20 (32.8%) 112(49.6%) 0.02∗ preoperative logmar (snellen) 0.34 ± 0.57 (20/44) 0.55 ± 0.74 (20/71) 0.003∗ postoperative logmar (snellen) 0.27 ± 0.41 (20/37) 0.27 ± 0.37 (20/37) 0.812 single surgery success rate 85.2% 89.8% 0.32 postoperative strabismus rate 0 (0%) 0 (0%) 1.00 follow-up (days) 373 ± 210 352 ± 173 0.58 logmar, logarithm of the minimum angle of resolution ∗statistically significant value however, when accounting for other metrics that may account for postoperative strabismus on multivariate analysis such as surgical approach or buckle type, there was no difference in postoperative strabismus. interestingly, all cases of strabismus occurred in eyes that underwent combined scleral buckling and vitrectomy. this combination approach might have led to increased orbital inflammation and scarring of the periorbital tissue leading to strabismus. there were no cases of strabismus in eyes that received a primary buckle. perhaps this cohort is better suited to identify any differences in outcomes in vision, anatomic success, or strabismus by excluding ppv. there were no differences in any metrics between scleral tunnels and scleral sutures. certainly, this finding may support the conclusion that combination surgery is the inciting factor for strabismus. there was a difference in the buckle element chosen between the two cohorts. sutures theoretically have more flexibility in the size of buckle that can be placed with ease. for example, larger elements would require large scleral tunnels, which may be technically challenging and at higher risk for flap amputation or dissections going too deep. it would be technically easier to place sutures to accommodate larger elements. this trend was seen in our study as well, where the 42 band (4 mm wide, 1.25 mm thick) was sutured more frequently, while the 240 (2.5 mm wide, 0.6 mm thick) and 41 (3.5 mm wide, 0.75 mm thick) bands were used for scleral tunnels more often. it would be more plausible that the wider buckle, the 42 band, would be associated with a higher incidence of postoperative strabismus, but these were hardly used in the belt loop cohort and much more common in the scleral suture cohort (see table 2), which had lower risk of postoperative strabismus. the mechanism of this counter intuitive finding is difficult to explain. in our series, both scleral tunnels and scleral sutures were successful in repairing retinal detachment. in the previous smaller study of 35 eyes by landa and colleagues, they also reported no buckle complications and additionally there were no cases of postoperative strabismus in either of their cohorts.[3] previous studies have found an incidence of postoperative strabismus following retinal detachment surgery to range from 5% to 25%.[4, 8, 9] this is much higher than seen in our series, in which <1% of patients developed postoperative strabismus. perhaps, our study did not capture patients with minor strabismic deviations and only captured those patients with symptomatic strabismus with significant prismatic deviations. there are several hypotheses regarding the etiology of postoperative strabismus following retinal detachment surgery, the majority of which are felt to be mechanical.[4, 10] direct interference of the muscle due to the sb is certainly plausible (and of course if the rectus muscle is split), but some have also proposed direct muscle injury or disinsertion of the muscle as well as scarring of the orbit may also lead to postoperative strabismus.[4, 5, 11–13] conceivably, sb positioning may play a minor role compared to postoperative orbital inflammation and scarring as no patients in the primary sb cohort developed strabismus and it was only seen in those eyes that had combined journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 381 scleral tunnels vs sutures for sb; starr et al ppv and sb. previous studies, though, have shown a similar incidence between sb and ppv, with sb patients having slightly larger prismatic deviations.[14] additionally, the type of anesthesia may play a role in postoperative strabismus with direct inoculation of the rectus muscle with anesthesia, however, we did not see an effect on postoperative strabismus in our series between the types of anesthesia (retrobulbar versus sub-tenon’s versus general anesthesia, p = 0.15). this study is limited inherently by its design as a retrospective analysis. this study was also a sub-analysis of a larger dataset not specifically designed to address the development of strabismus and perhaps lead to such low reported rates of strabismus. additionally, as with any surgical outcomes study with several surgeons, a number of intraoperative factors cannot be accounted for that certainly could bias the results, such as suture or scleral tunnel length and depth, and how the buckle is manipulated around the extraocular muscles, including the amount of tenon’s capsule dissection. however, we controlled for surgeon id, which theoretically would account for differences in surgical techniques. another consideration when evaluating the data is that the vast majority of eyes in this cohort received encircling bands, as opposed to segmental elements. the dimensions of commonly used segmental buckles are relatively larger (usually tires or sponges), though they are usually not placed 360º around the eye if used in isolation. therefore, the data in the present study may or may not be generalizable to segmental buckles that are imbricated in limited areas of the sclera. that being said, segmental elements are most often sutured in place, because imbrication is required to optimize the buckling effect, rather than encircling bands that provide elevation by tightening the band circumference. it is also certainly possible that combination ppv/sb is the inciting factor, rather than the method of affixing the sb to the sclera, as strabismus was only noted in this cohort. the numbers in this cohort were significantly smaller and thus the decision to include ppv in the entire cohort was made. the most prominent limitation of the current study is the lack of descriptive and quantitative characteristics of the strabismus and techniques with which it was evaluated and corrected. perhaps most of the strabismus was a specific alignment and thus more information could have been gleaned and the etiology better understood. the mean follow-up of the eyes was roughly one year, so certainly some of the patients with strabismus may have resolved without intervention if followed long enough, albeit less likely by a year. additionally, the incidence of preoperative strabismus was not recorded, but only patients with new strabismus following sb surgery were recorded as having postoperative strabismus. certainly, knowing the preoperative status may strengthen the study, but would not have changed the rate of new postoperative strabismus following the surgery. in summary, regardless of the method of securing encircling sbs during retinal detachment repair, there were no differences in the rate of anatomic success. the use of either tunnel or suture is entirely surgeon dependent, both of which provide similar visual and anatomical outcomes. the use of scleral tunnels was associated with a higher risk of postoperative strabismus, but not when accounting for multiple variables, in eyes treated with a combination of vitrectomy and scleral buckling. the etiology is unclear, but perhaps scleral tunnels may be associated with a higher rate of postoperative strabismus. further studies to elucidate this potential association are warranted. financial support and sponsorship this study was supported by the phillips eye institute foundation and the vitreoretinal surgery foundation. conflicts of interest consultant for alcon (de, og, yy), grant support from alcon (ac), royalties from alcon (ehr), stockholder in aldeyra therapeutics (de), consultant for dutch ophthalmic (de), scientific advisory board for pykus therapeutics (de), stockholder in valiant and glaukos (gge). references 1. rezaei ka, abrams gw. the history of retinal detachment surgery. in: kreissig i, editor. primary retinal detachment [internet]. berlin/heidelberg: springer-verlag; 2005 [cited 2019 oct 13]. p. 1–24. available from: http://link.springer. com/10.1007/3-540-26801-4_1 2. new york society for clinical ophthalmology; april 7, 1952. am j ophthalmol 1953;36:520–524. 3. michels rg. scleral buckling methods for rhegmatogenous retinal detachment. retina 1986;6:1–49. 382 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 http://link.springer.com/10.1007/3-540-26801-4_1 http://link.springer.com/10.1007/3-540-26801-4_1 scleral tunnels vs sutures for sb; starr et al 4. farr ak, guyton dl. strabismus after retinal detachment surgery. curr opin ophthalmol 2000;11:207–210. 5. sauer a, bouyon m, bourcier t, speeg-schatz c. [diplopia complicating scleral buckling surgery for retinal detachment]. j fr ophtalmol 2007;30:785–789. 6. ryan e, joseph d, ryan c, forbes n, yonekawa y, mittra r, et al. primary retinal detachment outcomes study (pro study): methodology and overall outcomes—pro study report #1. ophthalmol retina; in press. 7. landa g, benevento j, rosen r. sutureless belt loops versus sutured buckle technique in combination with vitrectomy for retinal detachment repair: a comparative analysis. ophthalmologica 2018;239:225–230. 8. ganekal s, nagarajappa a. strabismus following scleral buckling surgery. strabismus 2016;24:16–20. 9. akbari mr, mirmohammadsadeghi a, makateb a, ghassemi f, norooznezhad ah, khodabande a, et al. ocular movement disorders following scleral buckling surgery: a case series study. j curr ophthalmol 2019;31:195–200. 10. wu t-ej, rosenbaum al, demer jl. severe strabismus after scleral buckling: multiple mechanisms revealed by high-resolution magnetic resonance imaging. ophthalmology 2005;112:327–336. 11. fison pn, chignell ah. diplopia after retinal detachment surgery. br j ophthalmol 1987;71:521–525. 12. rabinowitz r, velez fg, pineles sl. risk factors influencing the outcome of strabismus surgery following retinal detachment surgery with scleral buckle. j aapos 2013;17:594–597. 13. goezinne f, berendschot ttjm, van daal ewm, janssen lch, liem ata, lundqvist ij, et al. diplopia was not predictable and not associated with buckle position after scleral buckling surgery for retinal detachment. retina 2012;32:1514–1524. 14. kasbekar sa, wong v, young j, stappler t, durnian jm. strabismus following retinal detachment repair: a comparison between scleral buckling and vitrectomy procedures. eye 2011;25:1202–1206. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 383 review article atopobiosis and dysbiosis in ocular diseases: is fecal microbiota transplant and probiotics a promising solution? triana hardianti gunardi1, md; diannisa paramita susantono1, md; andi arus victor2, md ratna sitompul2, md 1faculty of medicine, universitas indonesia, jakarta, indonesia 2department of ophthalmology, dr. cipto mangunkusumo national general hospital – faculty of medicine, universitas indonesia, jakarta, indonesia orcid: ratna sitompul: http://orcid.org/0000-0002-7434-0118 triana hardianti gunardi: http://orcid.org/0000-0003-3388-9304 abstract purpose: to highlight the role of atopobiosis and dysbiosis in the pathomechanism of autoimmune uveitis, therefore supporting fecal microbiota transplant (fmt) and probiotics as potential targeted-treatment for uveitis. methods: this review synthesized literatures upon the relation between gut microbiota, autoimmune uveitis, fmt, and probiotics, published from january 2001 to march 2021 and indexed in pubmed, google scholar, crossref. results: the basis of the gut–eye axis revolves around occurrences of molecular mimicry, increase in pro-inflammatory cytokines, gut epithelial barrier disruption, and translocation of microbes to distant sites. in patients with autoimmune uveitis, an increase of gut fusobacterium and enterobacterium were found. with current knowledge of aforementioned mechanisms, studies modifying the gut microbiome and restoring the physiologic gut barrier has been the main focus for pathomechanism-based therapy. in mice models, fmt and probiotics targeting repopulation of gut microbiota has shown significant improvement in clinical manifestations of uveitis. consequently, a better understanding in the homeostasis of gut microbiome along with their role in the gut–eye axis is needed to develop practical targeted treatment. conclusion: current preliminary studies are promising in establishing a causative gut–eye axis relationship and the possibility of conducting fmt and probiotics as targeted treatment to mitigate autoimmune uveitis, to shorten disease duration, and to prevent further complications. keywords: atopobiosis; autoimmune; dysbiosis; gut–eye axis; uveitis j ophthalmic vis res 2021; 16 (4): 631–643 © 2021 gunardi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 631 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9754&domain=pdf&date_stamp=2019-07-17 atopobiosis and dysbiosis in ocular diseases; gunardi et al introduction humans require commensal microorganisms to carry out vital bodily functions.[1] these microorganisms (in groups: microbiome) live most abundantly within the human gut; and are heavily influenced by internal (age, race, ethnicity, gender, genetics) as well as external factors (diet, consumption of antibiotics, sanitation, geographic domicile).[1, 2] the perspective of viewing the human body as a vast interchangeable ecosystem, alters how medicine works in practice.[1] instead of treating microbiome as a harmful target, we recognize the efficacy of nurturing and repopulating it to its homeostatic state within human body.[2] many studies have reported on how its altered composition may induce systemic immune response, hematogenic spread, and even translocation of microbes to distant sites.[1] focusing on preventing these mechanisms, is expected to provide an alternative solution to autoimmune diseases. among the autoimmune diseases with ocular involvement, uveitis is one of the most complex and is accountable for 25% blindness in the world.[3] it may manifest as a localized or part of a systemic disease. autoimmune diseases in relation to the eyes can be divided into: (a) systemic diseases with ocular manifestations, such as sarcoidosis, behcet’s disease, multiple sclerosis, systemic lupus erythematosus (sle), rheumatoid arthritis, ocular cicatrical pemphigoid, sjögren syndrome; (b) localized autoimmune ocular diseases, such as sympathetic ophthalmia, birdshot retinochoroidopathy, and mooren’s ulcerative keratitis.[4] current treatments for uveitis include topical and systemic anti-inflammatory drugs (nonsteroidal anti-inflammatory drugs and correspondence to: prof. ratna sitompul, md. jl. kimia no.8-10, pegangsaan, kec. menteng, jakarta pusat, dki jakarta 10320, indonesia. e-mail: ratna_sitompul@yahoo.com received: 09-09-2020 accepted: 31-06-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9754 corticosteroids), and immunomodulation-based therapies in severe cases.[5] effective targeted therapies are yet to be discovered. available data on gut microbiota in association with uveitis or ocular diseases in humans are still very limited. this review summarized the current knowledge on the role of gut microbiota in uveitis through atopobiosis and dysbiosis mechanisms, followed by a proposed alternative concept for potential uveitis-targeted treatment. methods literature search strategy we performed a systematic literature search using electronic database: pubmed, google scholar, crossref; using the following keywords, “atopobiosis” or “dysbiosis” or “gut microbiota” or “gut microbiome” and “ocular diseases” or “autoimmune diseases” or “immune-related diseases” or “uveitis” or “autoimmune uveitis” and “fecal microbiota transplant” or “probiotics” or “treatment” or “therapy”. we focused on two main purposes: (1) summarizing the current knowledge on the role of gut microbiota in uveitis through atopobiosis and dysbiosis mechanism; (2) proposing an alternative concept for potential uveitis-targeted treatment. articles discussing dysbiosis and/or atopobiosis in other ocular diseases were included as supporting evidence of the gut–eye axis. eligibility criteria all accessible full articles, published from january 2001 to august 2020 were included. duplicates were omitted. we retrieved 115 articles from selected database, followed by exclusion of doubles and non-accessible full papers, yielding 56 articles which have undergone thorough review to be summarized. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: gunardi th, susantono dp, victor aa, sitompul r. atopobiosis and dysbiosis in ocular diseases: is fecal microbiota transplant and probiotics a promising solution?. j ophthalmic vis res 2021;16:631–643. 632 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 https://knepublishing.com/index.php/jovr atopobiosis and dysbiosis in ocular diseases; gunardi et al results the gut microbiome, atopobiosis, and dysbiosis the microbiome is spread throughout the human body. they work in a bidirectional relationship with the host’s immune system, creating balance between pro-inflammatory (e.g., th1, th17) and anti-inflammatory (e.g., treg) mechanisms. as demonstrated in mice models, segmented filamentous bacteria promote pro-inflammatory th1 and th17 cells in the lamina propria, while treg cells facilitate anti-inflammatory response through short-chain-fatty-acid production.[6, 7] bacteroides fragilis and faecalibacterium prausnitzii promote the accumulation of treg cells.[8, 9] in human adults, bacteroides spp. (gram-negative bacteria) and firmicutes (gram-positive bacteria) usually predominate >93% of the gut microbial population. the rest is occupied by minor constituents.[10, 11] both major and minor constituents exert significant impact on the microbiome homeostasis. table 1 illustrates the taxonomic gut microbiota.[10] the 16s rrna assays and shotgun metagenomics have been utilized in characterizing gut microbiome composition, up to genus and species, respectively, and also its alteration by controlled interventions.[12] these assays allow identification of microbes that cannot be cultured, due to exiguous numbers or peculiar conditions.[13–15] for example, there is an increase of sulphate-reducing bacteria has been found in the feces of ankylosing spondylitis patients compared to healthy controls of identical age and gender. meanwhile, there is an increase of bacterodales, decrease of firmicutes/bacteroidetes ratio, and a reduction of lachnospiraceae and ruminococcaceae within the fecal microbiome profile of sle patients compared to the healthy control group.[16, 17] although no standard or “normal” microbiome ratio has ever been established, evidence suggests shifts in the microbiome has a significant impact on host immune system. dysbiosis is the shifting of microbiome composition into a pathogenic state, while atopobiosis is the translocation of microbes to places other than their normal location.[18] the two conditions have been recognized in the pathogenesis of multiple immune-mediated inflammatory diseases, such as rheumatoid arthritis, inflammatory bowel disease, and multiple sclerosis.[13] gut dysbiosis is particularly established to play a role in altering treg– th17 balance by causing a th17 expansion, thus signaling the release of pro-inflammatory cytokines (il-6, il-17, il-21, il-23, ifn-𝛾) in the gut lamina propria.[14] this pro-inflammatory state suppresses tight junction proteins (occludin and claudin), causing increased permeability of the lamina propria allowing antigen exposure from the gut microbiome. these contents from the gut microbiome may be presented as antigens to the antigen presenting cell (apc)s; or in the case of atopobiosis, the microbes may translocate to other sites.[14, 18] whichever pathway they were taken into, the process continues as cytokines and other inflammatory-mediators activate t-cells, b-cells, and dendritic-cells from the gut, which then travel through the lymphatic drainage to the mesenteric lymph nodes. antigen presentation and cell differentiation proceeds, leading to the production of activated b-cells, th17-cells, and plasma cells. within this cascade, gut microbes are suspected to play role as mimicry antigens leading to the stimulation of autoreactive t-cells and b-cells.[6, 14] in many autoimmune diseases, presence of these autoreactive immune cells and/or translocation of the pathogen to target organs leads to inflammatory reaction, thus it has become the basis of multiple gut-organ axis hypotheses (e.g., gut–brain axis, gut–joint axis).[18] autoimmune uveitis is hypothesized to be an inflammatory reaction following the aforementioned cascade.[13, 14, 18–20] the relationship between autoimmune uveitis with gut dysbiosis has been demonstrated in multiple studies, whereas its association with atopobiosis is less established. a recent study by deng et al has revealed that the widely accepted to be sterile−aqueous humor has shown microbial presence. these findings were found in patients with amd and glaucoma, in which disease-specific microbial signatures were found.[21] gómez et al also reported microbiome translocation from periodontal infection to placenta. porphyromonas gingivalis from pregnant mothers could translocate to the placenta, thus activating inflammatory response of the decidual tissue. it created a switch of the th-1 profile balance toward an inflammatory state, mediated by monocyte chemoattractant protein-1 (mcp-1) and macrophages.[22] these mechanisms manifested clinically as adverse journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 633 atopobiosis and dysbiosis in ocular diseases; gunardi et al figure 1. flowchart for study selection process. pregnancy outcomes (apos). the apos observed included low birth weight, preterm premature rupture of membranes, preterm birth, and other clinical signs related to chorioamnionitis.[22] these findings suggest microbiome translocation and possibly a hematogenic spread via the blood brain barrier and/or placental circulation. further studies are imperative to investigate the intraocular microbiome profile in uveitis and the corresponding gut microbiome. early evidence of the gut–eye axis: a look into microbiome shift in autoimmune uveitis microbiome alterations have been found in ocular diseases including dry eyes, uveitis, diabetic retinopathy, age-related macular degeneration (amd), etc. [table 2].[1, 2, 19, 23] among the evidence supporting the gut–eye axis, its correlation with autoimmune uveitis is one of the most heavily studied. uveitis is a complex inflammation of the eye, a manifestation of >30 different etiologies, including infectious and autoimmune origins.[24] characterization of the gut microbiota in patients with uveitis has been done in both animal models and humans. lin et al studied transgenic mice carrying the hla-b27 gene, a major risk factor for acute anterior uveitis. they found increased numbers of paraprevotella and bacteroides vulgatus, and decrease of rikenellaceae in hla-b27 mice compared to wild-type mice.[25] characterization of gut microbiota in humans with behçet’s disease revealed an altered gut microbiota composition with reduced butylate production and increased fecal secretory iga.[26, 27] ye et al revealed an increased level of bilophila spp., parabacteroides spp., paraprevotella spp., and decreased level of clostridium spp., methanocelleus spp., methanomethylophilus spp. in the gut of behçet’s disease patients. kalyana chakravarthy et al studied the gut composition of patients with vogt-koyanagi-harada and 634 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 atopobiosis and dysbiosis in ocular diseases; gunardi et al figure 2. illustrated pathogenesis of atopobiosis and dysbiosis in relation to uveitis. (1) microbe recognition. (2) bypass via tight junction. (3) transcytosis via m-cells. (4) phagocytosis by dcs and apcs. (5a) microbes or bacteria enter the mesenteric lymph node. (6a) bacteria enter the systemic circulation. (7a) translocation of bacteria to ocular endothelial site. (5b) dcs, t cells, b cells enter the mesenteric lymph nodes. (6b) these cells may undergo cascades and enter the systemic circulation. (7b) activated retina specific t-cells surpass the blood–retinal barrier causing inflammation. tlr, toll-like receptor; dc, dendritic cell; apc, antigen presenting cell; th17, t helper journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 635 atopobiosis and dysbiosis in ocular diseases; gunardi et al table 1. taxonomic terminology of the human gut microbiota phylum class genus species actinobacteria actinomycetales corynebacterium bifidobacteriales bifidobacterium bifidobacterium longum bifidobacterium bifidum coriobacteriia atopobium firmicutes clostridia faecalibacterium faecalibacterium prausnitzii clostridium clostridium spp. roseburia roseburia intestinalis ruminococcus ruminococcus faecis negativicutes dialister dialister invisus bacilli lactobacillus lactobacillus reuteri enterococcus enterococcus faecium staphylococcus staphylococcus leei bacteroidetes sphingobacteriia sphingobacterium bacteroidia bacteroides bacteroides fragilis bacteroides vulgatus bacteroides uniformis tannerella parabacteroides parabacteroides distasonis alistipes alistipes finegoldii prevotella prevotella spp. verrucomicrobia verrucomicrobia akkermansia akkermansia muciniphila fusobacteria fusobacteriia fusobacterium fusobacterium nucleatum proteobacteria gamma proteobacteria escherichia eschericia coli shigella shieflla flexneri delta proteobacteria desulfovibrio desulfovibrio intestinales bilophila bilophila wadsworthia epsilon proteobacteria helicobacter helicobacter pylori the firmicutes and bacteroidetes predominant the gut microbiome in human[11] idiopathic uveitis. they found decreased level of faecalibacterium, bacteroides, lachnospira, ruminococcus, and enrichment of prevotella and streptococcus. meanwhile the gut fungal microbiome profile showed increased numbers of pathogenic fungi including malassezia restricta, candida albicans, candida glabrata, aspergillus gracilis, compared to healthy controls.[28] there were no significant differences were seen in the microbiome profile of autoimmune uveitis compared to idiopathic uveitis, suggesting both were influenced by dysbiosis.[3] further association of the gut microbiota’s role in manifestation of uveitis was demonstrated using the b10.riii mice model which develop uveitis when injected with interphotoreceptor retinoid binding protein (irbp) antigens.[29] nakamura et al intervened with the gut composition of this mice model using oral broad-spectrum antibiotics (ampicillin, metronidazole, neomycin, vancomycin) one week before inducing uveitis. they compared them to b10.riii mice that had not received antibiotics. the antibiotic-treated mice showed reduced severity of uveitis.[29] singular antibiotic administration in this model revealed significant signs of uveitis only when given metronidazole or vancomycin, meanwhile administration of ampicillin or neomycin did not.[29] these conditions 636 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 atopobiosis and dysbiosis in ocular diseases; gunardi et al table 2. gut microbiota proportions in ocular diseases disease findings dry eye in sjögren’s mice: increased numbers of enterobacter, escherichia/shigella, pseudomonas, and decreased numbers of clostridium.[52] human: increased numbers of bacteroides*, parabacteroides*, actinobacteria, pseudobutyrivibrio, escherichia/shigella, blautia, streptococcus, and decreased numbers of firmicutes, faecalibacterium, prevotella, viellonella.[52, 53] uveitis mice: decreased numbers of rikenellaceae and increased numbers of paraprevotella.[25] human: increased numbers of fusobacterium and enterobacteriaceace.[51] diabetic retinopathy mice: increased numbers of firmicutes and decreased bacteroidetes.[54] human: decreased numbers of bacteroides and lactobacillus.[55, 56] age-related macular degeneration mice: increased numbers of firmicutes and clostridia, and decreased numbers of bacteroidetes and erysipelotrichi.[30] human: increased numbers of ruminococcaceae, prevotella, anaerotruncus, oscillibacter, ruminiococcus torques, and eubacterium ventriosum.[51, 57] bacterial keratitis human: increased numbers of proteobacteria and firmicutes.[58] *there were discrepancies between studies provide a clue on the particular groups of microbes playing a role in this pathway. the mouse model when treated with oral broad-spectrum antibiotics showed an increase in foxp3+ regulatory t-cells (tregs) in the cervical and mesenteric lymph nodes, receiving lymph drainage from the eye and the gut, respectively.[29] this finding suggests there was influence on the immune response in the eye and in the gut. several studies also provide evidence of the gut microbiota’s role in other ocular diseases, thus supporting the presence of gut–eye axis. zaheer et al[21] studied the cd25ko murine model that exhibit spontaneous features of severe sjögren syndrome (i.e., dacryoadenitis, sialadenitis, and keratoconjunctivitis). this study revealed that cd25ko mice raised in germfree (gf) environment have greater corneal barrier disruption, lower conjunctival goblet cell density, and greater lacrimal gland lymphocytic infiltration that progresses to complete gland atrophy compared to conventional cd25ko.[23] meanwhile, rowan et al[30] demonstrated the gut–eye axis in mice model with amd. mice fed with high-glycemia diet developed amd features, such as rpe hypopigmentation, rpe atrophy, and photoreceptor degeneration. higher proportion of firmicutes and clostridia as well as lower proportion of bacteroidetes and erysipelotrichi were also found in mice with greater retinal damage.[30] the role of gut microbiome in autoimmune uveitis furthermore, the specific role of gut microbiome in autoimmune uveitis has been linked with the presence of peculiar memory responses toward retinal arrestin and irbp. both (retinal arrestin and irbp) are proteins expressed in a niche location behind a tight blood–retina barrier. the blood retina barrier may only be crossed by activated lymphocytes, this is done by initiating a transient breakdown in the blood–retina barrier via cell rolling, extravasation through venules, and reduced claudin and occludin. although the mechanism is not quite clear, similar observations have been seen in the cns.[20] however, in order to activate the specific t-cells, it is necessary to be exposed to the retinal arrestin and/or irbp. thus, suggesting presence of mimicry antigens outside the eye leading to retina-specific t-cell activation independent of endogenous retinal antigen.[19] horai et al proposed that gut microbiota provides signals directly to the retina-specific t-cell receptor thus causing these autoreactive t-cells to trigger uveitis. the study proposed the possibility of (a) gut microbiota mimicking journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 637 atopobiosis and dysbiosis in ocular diseases; gunardi et al retinal antigens or (b) microbiota as an adjuvant providing innate signals, in which both (a) and (b) mechanisms amplify host immune response in activating autoreactive lymphocytes specific for neuroretina.[19, 31] they studied r161h mice, which are designed to develop spontaneous uveitis via the expression of r161 t-cell receptor specific for 161-80 of irbp.[19] in these mice, activated uveitis-relevant t-cells were apparent in the lamina propria of small and large intestines even before the onset of clinical uveitis, suggesting activation of t-cells in the periphery. this activation step in the periphery is crucial because only then will the retina-specific lymphocytes be able to breach the blood–retinal barrier. depletion of commensal microbiota in r161h mice, via antibiotic treatment or gf conditions, resulted in significant attenuation of spontaneous uveitis and reduced populations of th17 cells in the gut lamina propria. spontaneous uveitis development was associated with increased populations of th17 cells in the intestinal lamina propria.[32] this supports the findings in depleted r161h and gf r161h where clinical manifestation and th17 cells of the lamina propria is reduced.[19, 32] in an earlier study by horai et al, it is recognized that t-cell activation in the intestine is independent of endogenous irbp expression.[32] they crossed r161h mice to rbp3– /– mice, which lack irbp expression. the r161h– rbp3–/– mice did not developed uveitis, due to lack of target antigen in their eyes. however, irbpspecific t-cells were still found within the mice and were functionally responsive to irbp. when these activated irbp-specific t-cells were transferred to native white mice, it successfully induced severe uveitis.[32] these findings suggest endogenous irbp is not mandatory in activation of irbp-specific t-cells in r161h mice.[19, 31, 32] as the role of dysbiosis in ocular autoimmune diseases is further studied, the role of microbe translocation is still less known. microbial translocation in other diseases have been observed, including rheumatoid arthritis, sle, etc.[14, 18] microbe translocation to the eye contradicts with the widely accepted concept of a sterile intraocular environment due to the blood–retina barrier. however, a study from deng et al recently revealed preliminary evidence of disease-specific microbial presence in human aqueous humor, which is previously known to be sterile, in patients with amd and glaucoma.[21] they also found propionibacterium acnes in most eyes from patients who underwent cataract surgery. this species of bacterium was one of the most common bacteria detected in chronically inflamed eyes after cataract procedure.[21] these early findings favor microbiome’s role in the ocular inflammatory states. fecal microbiota transplantation (fmt) fmt is performed by the administration of donor fecal solution into the recipient intestinal tract, which can be done via oral route or direct implantation using colonoscopy. the key mechanism by which fmt may influence disease progression is through repopulating and returning gut microbe colonization into its homeostatic state as well as improving the intestinal tight junction. in murine models following fmt intervention, bacteroidetes (proinflammatory) phylum was found to be decreased, while the firmicutes and lactobacillus (probiotic) phylum were increased.[33, 34] these conditions enhance gut barrier integrity, limit microbiota and byproduct from entering systemic circulation, hence preventing the activation of inflammatory cascade.[13, 34] desirable outcome of fmt has been reported in numerous studies mentioning various organs, from infection to autoimmune origin, for example, clostridium dificille infection,[35, 36] irritable bowel disease,[37] chronic fatigue syndrome,[38] nonalcoholic fatty liver disease, idiopathic thrombocytopenic purpura,[39] and multiple sclerosis.[40] in ocular diseases, fmt has demonstrated apparent gut–eye relationship in mice model. ye et al observed a significantly exacerbated experimental autoimmune uveitis (eau) manifestation after administering fmt from humans with behcet’s disease to b10riii mice. this was further supported with investigation using rt-pcr, in which they found increased production of inflammatory cytokines including il-17 and ifn-𝛾 in the spleen.[28] zaheer et al developed a murine model, cd25 knock out (cd25ko), mice lacking of il-2 receptor alpha chain (cd25) – which exhibit no il-2 signaling, lack of treg cells, and hindered apoptosis of their autoreactive t-cells. this mice model undergoes spontaneous development of severe sjögren syndrome features such as dacryoadenitis, 638 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 atopobiosis and dysbiosis in ocular diseases; gunardi et al sialadenitis, and keratoconjunctivitis. they compared clinical manifestations, quantified the expression of t-cell and inflammatory cytokines between the cd25ko raised in gf environment versus the conventional cd25ko. gf cd25ko showed greater corneal barrier disruption, lower conjunctival goblet cell density, and greater lacrimal gland lymphocytic infiltration that progresses to complete gland atrophy, compared to the conventional cd25ko. however, after transplanting fecal slurry contained intestinal microbiota from the conventional c57bl mice to gf cd25ko via oral gavage, the gf cd25ko showed decreased generation of pathogenic cd4+ifn-𝛾+ cells, resulting in improved lacrimal gland pathology and greater goblet cell density, thus shortening the disease duration. the corneal barrier function showed significant improvement, with similar esophagogastroduodenoscopy staining level compared to the oregon-green dextran (ogd) dye conventional cd25ko, thus preventing further physiological state disruption.[23] receiving heavy recognitions from multiorgan system, the study of fmt in relation to ocular diseases in humans is still unavailable, therefore we propose a new insight upon this. a standard criteria for feces donor is not yet defined, however, amsterdam protocol has been the main reference for this field.[42] fecal material is gained from healthy donors who meet specific requirements (e.g., the absence of antibiotics consumption in certain duration, no history of intravenous drug use, high-risk behavior, or any infectious, neoplastic, metabolic, autoimmune, or allergic disease).[42] in its frozen state, stool for fmt can be stored for six months without loss of clinical efficacy or bacteria viability.[43] fmt can be delivered through oral consumption, esophagogastroduodenoscopy, nasojejunal tube, nasogastric tube, colonoscopy, or retention enema.[49] studies upon fmt safety and efficacy are growing and appear to be safe. a review from smits et al reported from >3000 fmt at the centre for digestive diseases in australia and >200 at the academic medical center in amsterdam, with no serious adverse events observed for a six-months to two-years follow-up.[42] currently, there are 114 studies registered at www.clinicaltrials.gov for fmt as therapeutic treatment, and are still recruiting. these findings indicate the feasibility of fmt as a targeted and practical therapeutic agent. probiotics probiotics are live strains of selected microorganisms which when administered in adequate amounts, confer health benefit to the host by improving the gut flora, preventing growth of unwanted pathogens, and improving immunity. probiotics are resistant to gastric acid, bile, and trypsin, and are still viable to colonize, thus proliferate inside the gut afterward.[44] probiotics play a role in the immune system through several mechanisms: (1) enhancing the gut chemical and biological barriers via the spaceoccupying effect, (2) increasing the tight junction protein synthesis between epithelial cells via promotion of mucous glycoprotein secretion, and (3) regulating innate and adaptive immunity via gut-associated lymphoid tissues (galt). probiotic and its metabolites possess antigens that are phagocytized by m-cells to form endosomes. the antigen in m-cells are then released and received by dendritic cells, thus presenting them to naive tand b-cells of the lymph nodes, creating immune responses mediated by tlr, nod-, nlr, th1/2, treg, tgf-beta. as the tand b-cells turn into different effector subpopulations, they correspond to different immune functions.[44–46] probiotics are commonly used in multiple diseases. however, its usage in ocular autoimmune diseases are still scarce. a study in mice model with eau by kim et al showed decreased manifestation of uveitis when given irt-5 probiotics-mix (a mixture of lactobacillus casei, l. acidophilus, l. reuteri, bifidobacterium bifidum, and streptococcus thermophilus). they found decreased numbers of tregs in the cervical lymph nodes and decrease of cd8+ t-cells in the given irt-5 probiotics-mix mice.[45] in human studies, topical ocular probiotics have been used in patients with vernal keratoconjunctivitis by iovien et al.[47] meanwhile oral probiotics have been used in a study by miraglia del giudice et al, in which bifidobacterium mixture (b. longum bb536, b. infantis m-63, b. breve m-16v) improved symptoms in children with seasonal rhinoconjunctivitis and intermittent asthma.[48] iovien et al demonstrated the use of lactobacillus acidophilus diluted as eye drops to vernal keratoconjunctivitis, resulting in improved clinical outcomes within two to four weeks. lactobacillus acidophilus is suspected to have journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 639 www.clinicaltrials.gov atopobiosis and dysbiosis in ocular diseases; gunardi et al anti-inflammatory properties via il-10 and tgfbeta.[47] probiotics modulate immune responses via stimulation of the th1 pathway and restoration of t regs leading to improved allergic responses.[48] zmora et al administered 11 species of common probiotic bacteria (lactobacilli, bifidobacteria, lactococcus lactic, streptococcus thermophiles) to healthy participants for 28 days. they detected the probiotic bacteria in several participants’ feces sample, suggesting that transient engraftment was depended on the initial host’s microbiome composition.[49, 50] further longitudinal studies are needed to evaluate their efficacy. discussion recent studies supporting the gut–eye axis have revealed more information on the possible pathomechanism of autoimmune uveitis.[1, 3, 4, 13, 15, 20, 29, 30] to date, studies targeting the microbiome for therapy of uveitis are still very limited. among the available treatments for autoimmune uveitis, effective targeted therapy is yet to be uncovered. from this point, the concept of atopobiosis and dysbiosis are elaborated as the etiology or exacerbating factor of autoimmune uveitis.[19, 32] hence, we believe halting these pathomechanisms as a targeted treatment might be a promising solution. atopobiosis/dysbiosis–uveitis relationship our hypothesized pathogenesis of gut atopobiosis and dysbiosis in relation to uveitis has been synthesized and demonstrated in figure 1. microbes, especially bacteria in the gut lumen communicate with the enterocyte through four possible distinct pathways: (1) recognition of microbe-associated molecular pattern by toll-like receptors (tlr); (2) bypassing the tight junction following an inflammatory state which increases the intestinal permeability; (3) transcytosis via microfold cells; (4) phagocytosis of microbes and antigen presentation by dendritic cells (dc) or apc. in the case of atopobiosis, microbes enter the mesenteric lymph node and gain access to the systemic circulation. the translocated microbe may or may not cause systemic manifestation depending on its dormancy and numbers. the microbe may travel further to ocular endothelial sites and may be able to surpass the blood–retina barrier if it were not intact [figure 1.5a–1.7a). although the intraocular environment was long established as a sterile environment, recent preliminary studies reveal microbial intraocular presence. thus, suggesting the possibility of microbial gut translocation to the eye, warranting the need for ocular microbiome identification to further shed light on a possible causative relationship.[21] in contrast, dysbiosis occurs by dcs, t-cells, and b-cells entering mesenteric lymph node. some may undergo the cascade of antigen presentation from dc to t-cells and differentiation of b-cells to plasma cells. these cells may also further be present in the lamina propria, in which the retina-specific t-cells may encounter mimicry antigens (such as proposed microbes), leading to activation of retinal-specific t-cells. as these retinal-specific t-cells are capable of passing the blood retina barrier, they may cause local inflammation in the eye [figure 1.5b–1.7b]. although much more limited compared to dysbiosis,[3, 13, 15, 17, 25, 29, 30, 51] evidence for atopobiosis is found for other organ diseases.[18, 21, 22] a recent study by gómez et al[22] has revealed the association of atopobiosis of p. gingivalis from dental infection to the placenta, resulting in outcomes adverse pregnancy outcomes (apos) including low birth weight, preterm birth, preterm premature rupture of membranes, as well as other conditions related to chorioamnionitis. using 16s rrna assay, they found the periodontal infection microbes (p. gingivalis) in the placenta of women presented with apos, and not in women with healthy pregnancy. it was hypothesized that the microbe translocates via systemic and placental route, thus activating inflammatory response of the decidual tissue. it then shifted the th-1 profile balance toward an inflammatory state, mediated by mcp-1 and macrophages. microbes were found in the placenta; and placental cytokine patterns showing reduced il-10, il-17f, and a th-1 profile which induced macrophage activation by increased mcp-1, were found in these women who clinically presented with apos.[22] the possibility of a similar occurrence in the eyes was seen by deng et al.[21] the blood–retina barrier which protects the sterile intraocular environment would typically prevent the passage of hematogenic pathogens. however, staggering recent evidence from deng et al shows findings of intraocular microbial presence. in their study, a disease-specific microbial signature was 640 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 atopobiosis and dysbiosis in ocular diseases; gunardi et al found in aqueous humor of patients with amd and glaucoma.[21] as the aqueous humor has no direct access to the external environment, the possibility of a hematogenic spread via the blood–retina barrier comes into question. factors affecting the intact barrier such as trauma or local immune responses in particular diseases, such as amd, may factor in the penetration of the blood–retina barrier. thus, with current findings of atopobiosis in multiple target organs and presence of intraocular microbes, further investigation is mandated to determine a causative relationship. as numerous studies[1, 3–6, 11–13, 15, 18–26, 33–38, 48, 52–56] mentioned in this review contribute toward the hypothesis of gut dysbiosis in relation to ocular autoimmune uveitis, it is only wise that we explore further the possibility of targeting gut microbiome as a mean to alter clinical manifestation. as current therapy for autoimmune uveitis mainly rely on to suppress symptoms, it is appealing to find alternative targeted therapy with less adverse effects. challenges for future studies up to this date, there is still no established cut-off of the “normal gut microbiome”, as it is highly affected by numerous internal and external factors, for example, genetics, age, ethnicity, diet, geographical region of domicile; making it individually distinct. a metagenomic characterization in 2018 revealed that every anatomical region of mammalian gastrointestinal tract demonstrates distinct oxygenation level, ph, host-derived antimicrobial and transit time.[12, 28] in 2019, the recent shotgun metagenomic characterization of gut microbiome successfully demonstrated bacteria to the speciesand strain-level classification, also fungal residents’ characterization.[12] those aspects together influence the local microbiome assemblage, adding another question in the characterization of the “normal gut microbiome”: which section should we refer to when defining normal gut flora?[28] the two main methods used for microbiome characterization are the 16s rrna assays and the shotgun metagenomic, which enables microbiome identification to the genus-level and speciesand strain-level, respectively. however, the shotgun metagenomic requires extravagant cost and advanced bioinformatics.[12, 30] both approaches mainly identify bacteria and recently fungi. these suggest potential diagnostic tools for further studies. further techniques capable of evaluating the functional status of microbes and other non-prokaryotic constituents of the gut are also needed. further studies on the mechanism of atopobbiosis in the gut–eye axis should involve a series intraocular microbiome profiling. the intraocular microbiome profiling should include ocular diseases such uveitis and amd, followed by profiling of the corresponding gut microbiome within the same test subjects. moreover, microbiome profiling of the aqueous humor and gut in test subjects receiving active interventions to the gut microbiome such as fmt and probiotics is suggested for future studies. thus, elucidating the complex relationship of the gut–eye axis. current studies targeting the microbiome for therapy of uveitis are still very limited. studies utilizing fmts in uveitis patients have only progressed to the use of mice treated with fmts from human samples, which has been done by ye et al with 11 mice subjects.[28] present studies characterizing the gut microbiome of uveitis patients are not only small in sample size, but also mainly focuses on patients with behcet disease and vogt-koyanagi-harada syndrome, which are only a fraction of uveitis patients. once we can agree on a consensus defining the “normal microbiome”, how to detect it, and characterize the gut microbiome of heterogenic uveitis subjects, only then we can gain robust evidence to proceed to clinical trials for fmt and probiotics in humans. future longitudinal studies with microbiome sequencing involving greater number of autoimmune patients are expected to elucidate how atopobiosis and dysbiosis influence the microbiome profile. clinical trials for fmt and probiotics are expected, particularly seeing this might come as a promising solution to mitigate autoimmune uveitis, to shorten disease duration, also to prevent further physiological state disruption. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 641 atopobiosis and dysbiosis in ocular diseases; gunardi et al references 1. cavuoto km, banerjee s, galor a. relationship between the microbiome and ocular health. the ocular surface 2019;17:384–392. 2. thursby e, juge n. introduction to the human gut microbiota. biochem j 2017;474:1823–1836. 3. kalyana chakravarthy s, jayasudha r, sai prashanthi g, ali mh, sharma s, tyagi m, et al. dysbiosis in the gut bacterial microbiome of patients with uveitis, an inflammatory disease of the eye. indian j microbiol 2018;58:457–469. 4. stern me, schaumburg cs, dana r, calonge m, niederkorn jy, pflugfelder sc. autoimmunity at the ocular surface: pathogenesis and regulation. mucosal immunol 2010;3:425–442. 5. moura-coelho n, proença rp, palestine a, o’keefe gd, duta-medeiros m. treatment of uveitis [internet]. american academy of ophthalmology (aao); 2019. available from: https://eyewiki.aao.org/treatment_of_uveitis 6. gaboriau-routhiau v, rakotobe s, lécuyer e, mulder i, lan a, bridonneau c, et al. the key role of segmented filamentous bacteria in the coordinated maturation of gut helper t cell responses. immunity 2009;31:677–689. 7. arpaia n, campbell c, fan x, dikiy s, van der veeken j, deroos p, et al. metabolites produced by commensal bacteria promote peripheral regulatory t-cell generation. nature 2013;504:451–455. 8. round jl, mazmanian sk. inducible foxp3+ regulatory t-cell development by a commensal bacterium of the intestinal microbiota. proc natl acad sci usa 2010;107:12204–12209. 9. qiu x, zhang m, yang x, hong n, yu c. faecalibacterium prausnitzii upregulates regulatory t cells and antiinflammatory cytokines in treating tnbs-induced colitis. j crohn’s colitis 2013;7:e558–e568. 10. rinninella e, raoul p, cintoni m, franceschi f, miggiano g, gasbarrini a, et al. what is the healthy gut microbiota composition? a changing ecosystem across age, environment, diet, and diseases. microorganisms 2019;7:14. 11. ottman n, smidt h, de vos wm, belzer c. the function of our microbiota: who is out there and what do they do [internet]? front cell inf microbio 2012 [cited 2020 jul 3];2:104. available from: http://journal.frontiersin.org/ article/10.3389/fcimb.2012.00104/abstract 12. rausch p, rühlemann m, hermes bm, doms s, dagan t, dierking k, et al. comparative analysis of amplicon and metagenomic sequencing methods reveals key features in the evolution of animal metaorganisms. microbiome 2019;7:133. 13. forbes jd, van domselaar g, bernstein cn. the gut microbiota in immune-mediated inflammatory diseases [internet]. front microbiol 2016 [cited 2019 sep 8];7:1081. available from: http://journal.frontiersin.org/article/10. 3389/fmicb.2016.01081/abstract 14. van der meulen t, harmsen h, bootsma h, spijkervet f, kroese f, vissink a. the microbiome-systemic diseases connection. oral dis 2016;22:719–734. 15. baim ad, movahedan a, farooq av, skondra d. the microbiome and ophthalmic disease. exp biol med 2019;244:419–429. 16. stebbings s. comparison of the faecal microflora of patients with ankylosing spondylitis and controls using molecular methods of analysis. rheumatology 2002;41:1395–1401. 17. hevia a, milani c, lópez p, cuervo a, arboleya s, duranti s, et al. intestinal dysbiosis associated with systemic lupus erythematosus. mbio 2014;5:e01548-14. 18. potgieter m, bester j, kell db, pretorius e. the dormant blood microbiome in chronic, inflammatory diseases. fems microbiol rev 2015;39:567–591. 19. horai r, caspi rr. microbiome and autoimmune uveitis. front immunol 2019;10:232. 20. crane ij, liversidge j. mechanisms of leukocyte migration across the blood–retina barrier. semin immunopathol 2008;30:165–77. 21. deng y, ge x, li y, zou b, wen x, chen w, et al. identification of an intraocular microbiota. cell discov 2021;7:13. 22. gómez la, de avila j, castillo dm, montenegro da, trujillo tg, suárez lj, et al. porphyromonas gingivalis placental atopobiosis and inflammatory responses in women with adverse pregnancy outcomes. front microbiol 2020;11:591626. 23. zaheer m, wang c, bian f, yu z, hernandez h, de souza rg, et al. protective role of commensal bacteria in sjögren syndrome. j autoimmun 2018;93:45–56. 24. jabs da. immunosuppression for the uveitides. ophthalmology 2018;125:193–202. 25. lin p, bach m, asquith m, lee ay, akileswaran l, stauffer p, et al. hla-b27 and human b2-microglobulin affect the gut microbiota of transgenic rats. plos one 2014;9:9. 26. shimizu j, kubota t, takada e, takai k, fujiwara n, arimitsu n, et al. bifidobacteria abundance-featured gut microbiota compositional change in patients with behcet’s disease. plos one;11:e0153746. 27. consolandi c, turroni s, emmi g, severgnini m, fiori j, peano c, et al. behçet’s syndrome patients exhibit specific microbiome signature. autoimmun rev 2015;14:269–276. 28. jayasudha r, kalyana chakravarthy s, sai prashanthi g, sharma s, tyagi m, shivaji s. implicating dysbiosis of the gut fungal microbiome in uveitis, an inflammatory disease of the eye. invest ophthalmol vis sci 2019;60:1384. 29. nakamura yk, metea c, karstens l, asquith m, gruner h, moscibrocki c, et al. gut microbial alterations associated with protection from autoimmune uveitis. invest ophthalmol vis sci 2016;57:3747. 30. rowan s, jiang s, korem t, szymanski j, chang ml, szelog j, et al. involvement of a gut–retina axis in protection against dietary glycemia-induced agerelated macular degeneration. proc natl acad sci usa 2017;114:e4472–e4481. 31. horai r, sen hn, caspi rr. commensal microbiota as a potential trigger of autoimmune uveitis. expert rev clin immunol 2017;13:291–293. 32. horai r, zárate-bladés cr, dillenburg-pilla p, chen j, kielczewski jl, silver pb, et al. microbiota-dependent activation of an autoreactive t cell receptor provokes autoimmunity in an immunologically privileged site. immunity 2015;43:343–353. 642 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 https://eyewiki.aao.org/treatment_of_uveitis http://journal.frontiersin.org/article/10.3389/fcimb.2012.00104/abstract http://journal.frontiersin.org/article/10.3389/fcimb.2012.00104/abstract http://journal.frontiersin.org/article/10.3389/fmicb.2016.01081/abstract http://journal.frontiersin.org/article/10.3389/fmicb.2016.01081/abstract atopobiosis and dysbiosis in ocular diseases; gunardi et al 33. zhou d, pan q, shen f, cao h, ding w, chen y, et al. total fecal microbiota transplantation alleviates high-fat dietinduced steatohepatitis in mice via beneficial regulation of gut microbiota. sci rep 2017;7:1529. 34. blackwood bp, yuan cy, wood dr, nicolas jd, grothaus js, hunter cj. probiotic lactobacillus species strengthen intestinal barrier function and tight junction integrity in experimental necrotizing enterocolitis. j prob health [internet] 2017 [cited 2019 sep 8];05:159. available from: https://www.omicsonline.org/open-access/probioticlactobacillus-species-strengthen-intestinal-barrierfunction-andtight-junction-integrity-in-experimentalnecrotizing-ent-2329-8901-1000159.php?aid=85246 35. khoruts a, dicksved j, jansson jk, sadowsky mj. changes in the composition of the human fecal microbiome after bacteriotherapy for recurrent clostridium difficile-associated diarrhea. j clin gastroenterol 2010;44:354–360. 36. van nood e, vrieze a, nieuwdorp m, fuentes s, zoetendal eg, de vos wm, et al. duodenal infusion of donor feces for recurrent clostridium difficile. n engl j med 2013;368:407–415. 37. hamilton-miller j. probiotics in the management of irritable bowel syndrome: a review of clinical trials. microb ecol health dis 2001;13:212–216. 38. borody t, nowak a, torres m. bacteriotherapy in chronic fatigue syndrome: a retrospective review. am j gastroenterol suppl 2012;107:s591–s592. 39. borody t, campbell j, torres m, nowak a, leis s. reversal of idiopathic thrombocytopenic purpura [itp] with fecal micro-biota transplantation [fmt]. am j gastroenterol suppl 2011;106:s352. 40. borody t, leis sm, campbell j. fecal microbiota trans-plantation (fmt) in multiple sclerosis (ms). am j gastroenterol 2011;106:s352. 41. ye z, zhang n, wu c, zhang x, wang q, huang x, et al. a metagenomic study of the gut microbiome in behcet’s disease. microbiome 2018;6:135. 42. smits lp, bouter kec, de vos wm, borody tj, nieuwdorp m. therapeutic potential of fecal microbiota transplantation. gastroenterology 2013;145:946–953. 43. costello sp, conlon ma, vuaran ms, roberts-thomson ic, andrews jm. faecal microbiota transplant for recurrent clostridium difficile infection using long-term frozen stool is effective: clinical efficacy and bacterial viability data. aliment pharmacol ther 2015;42:1011–1018. 44. zeng w, shen j, bo t, peng l, xu h, nasser mi, et al. cutting edge: probiotics and fecal microbiota transplantation in immunomodulation. j immunol res 2019;2019:1–17. 45. kim j, choi s, kim y, jeong h, ryu j, lee h, et al. clinical effect of irt-5 probiotics on immune modulation of autoimmunity or alloimmunity in the eye. nutrients 2017;9:1166. 46. liu y, alookaran j, rhoads j. probiotics in autoimmune and inflammatory disorders. nutrients 2018;10:1537. 47. iovieno a, lambiase a, sacchetti m, stampachiacchiere b, micera a, bonini s. preliminary evidence of the efficacy of probiotic eye-drop treatment in patients with vernal keratoconjunctivitis. graefes arch clin exp ophthalmol 2008;246:435–441. 48. miraglia del giudice m, indolfi c, capasso m, maiello n, decimo f, ciprandi g. bifidobacterium mixture (b longum bb536, b infantis m-63, b breve m-16v) treatment in children with seasonal allergic rhinitis and intermittent asthma. ital j pediatr 2017;43:25. 49. zmora n, zilberman-schapira g, suez j, mor u, doribachash m, bashiardes s, et al. personalized gut mucosal colonization resistance to empiric probiotics is associated with unique host and microbiome features. cell 2018;174:1388–1405.e21. 50. khoruts a. targeting the microbiome: from probiotics to fecal microbiota transplantation. genome med 2018;10:80. 51. lin p. the role of the intestinal microbiome in ocular inflammatory disease. curr opin ophthalmol 2018;29:261–266. 52. de paiva cs, jones db, stern me, bian f, moore ql, corbiere s, et al. altered mucosal microbiome diversity and disease severity in sjögren syndrome. sci rep 2016;6:23561. 53. mendez r, watane a, farhangi m, cavuoto km, leith t, budree s, et al. gut microbial dysbiosis in individuals with sjögren’s syndrome. microb cell fact 2020;19:90. 54. beli e, yan y, moldovan l, vieira cp, gao r, duan y, et al. restructuring of the gut microbiome by intermittent fasting prevents retinopathy and prolongs survival in db/db mice. diabetes 2018;67:1867–1879. 55. delzenne nm, cani pd, everard a, neyrinck am, bindels lb. gut microorganisms as promising targets for the management of type 2 diabetes. diabetologia 2015;58:2206–2217. 56. kasselman lj, vernice na, deleon j, reiss ab. the gut microbiome and elevated cardiovascular risk in obesity and autoimmunity. atherosclerosis 2018;271:203–213. 57. zinkernagel ms, zysset-burri dc, keller i, berger le, leichtle ab, largiadèr cr, et al. association of the intestinal microbiome with the development of neovascular age-related macular degeneration. sci rep 2017;7:40826. 58. kalyana chakravarthy s, jayasudha r, ranjith k, dutta a, pinna nk, mande ss, et al. alterations in the gut bacterial microbiome in fungal keratitis patients. plos one 2018;13:e0199640. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 643 https://www.omicsonline.org/open-access/probiotic-lactobacillus-species-strengthen-intestinal-barrier-function-andtight-junction-integrity-in-experimental-necrotizing-ent-2329-8901-1000159.php?aid=85246 https://www.omicsonline.org/open-access/probiotic-lactobacillus-species-strengthen-intestinal-barrier-function-andtight-junction-integrity-in-experimental-necrotizing-ent-2329-8901-1000159.php?aid=85246 https://www.omicsonline.org/open-access/probiotic-lactobacillus-species-strengthen-intestinal-barrier-function-andtight-junction-integrity-in-experimental-necrotizing-ent-2329-8901-1000159.php?aid=85246 https://www.omicsonline.org/open-access/probiotic-lactobacillus-species-strengthen-intestinal-barrier-function-andtight-junction-integrity-in-experimental-necrotizing-ent-2329-8901-1000159.php?aid=85246 original article potential effect of human platelet lysate on in vitro expansion of human corneal endothelial cells compared with y-27632 rock inhibitor mohammad amir mishan1, ms; sahar balagholi2, phd; tahereh chamani3, ms; sepehr feizi4, md zahra-soheila soheili5, phd; mozhgan rezaei kanavi1, md 1ocular tissue engineering research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2blood transfusion research center, high institute for research and education in transfusion medicine, tehran, iran 3central eye bank of iran, tehran, iran 4ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 5national institute of genetic engineering and biotechnology, tehran, iran orcid: mohammad amir mishan: https://orcid.org/0000-0001-8210-9322 mozhgan rezaei kanavi: https://orcid.org/0000-0002-1497-2260 abstract purpose: corneal endothelial cell (cec) therapy can be used as a promising therapeutic option for patients with various corneal endothelial dysfunctions. in this study, we compared the proliferative effect of human platelet lysate (hpl), as a xeno-free medium supplement, with y-27632 rho/rho-associated protein kinase (rock) inhibitor, as a wellknown proliferative and adhesive agent for cecs, and fetal bovine serum (fbs) as the control, in the culture medium of human corneal endothelial cells (hcecs). methods: we isolated hcecs from human donors and treated the cells as three different treatment groups including 20% hpl only, 10 μm y-27632 rock inhibitor, combination of 20% hpl and 10 μm y-27632 rock inhibitor, and 20% fbs as the control group. elisa cell proliferation assay and cell counting was performed on the treated cells. finally, hcecs were characterized by morphology and immunocytochemistry (icc). results: there was no significant proliferative effect of hpl on cell proliferation compared with the cells treated with y-27632 rock inhibitor or the combination of hpl and y-27632 rock inhibitor, but all the respected treatments had significant inducible effect on cell proliferation as compared with fbs-treated cells. the cells grown in all three treatment groups exhibited cec morphology. also, there was a higher expression of na+/k+-atpase and zo-1, as cec characteristic markers, in the culture of hcecs treated with hpl as compared with fbs. conclusion: hpl offers a xeno−free and affordable medium supplement for cec expansion that can be used in clinical applications. keywords: cell proliferation; corneal endothelial cells; human platelet lysate; rock inhibitor j ophthalmic vis res 2021; 16 (3): 349–356 © 2021 mishan et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 349 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i3.9431&domain=pdf&date_stamp=2019-07-17 in vitro expansion of endothelial cells; mishan et al introduction corneal endothelium plays a pivotal role in the corneal transparency by regulating the flow of water from the aqueous humor into cornea.[1] corneal endothelial cell (cec) density is above 2000 cells/mm2 in healthy people; however, corneal endothelial dysfunction and abnormal corneal hydration can occur following a decrease in cec density to fewer than 400 cells/mm2. [2] loss of cecs also occurs as the result of fuchs’s endothelial corneal dystrophy (fecd) or following any form of corneal endothelial insult.[1] current treatments for these situations include penetrating keratoplasty (pkp) and endothelial keratoplasty techniques for replacing the damaged endothelial layer.[3, 4] these surgical procedures are invasive and have several side effects. more importantly, there is a need for an alternative solution based on cell therapy and/or tissue engineering to overcome the global shortage of donor corneas.[5, 6] therefore, cell therapy based on cultivated human corneal endothelial cells (hcecs) from cadaveric donor corneas has been suggested in several studies.[7, 8] rho gtpases family plays a pivotal role at many aspects of cell cycle progression.[9] it was shown that inhibition of rho/rho-associated protein kinase (rock) signaling by selective y-27632 rock inhibitor could promote the proliferation of several primary adult cells[10–12] and also the cecs.[13] moreover, rock inhibitors have been introduced for several diseases such as pulmonary disease, cardiovascular disease, and cancer.[14] among several techniques introduced for expansion and adhesion of cecs for clinical purposes,[15, 16] the use of rock inhibitors has become popular.[17, 18] on the other hand, the platelet-rich plasma (prp) as an autologous correspondence to: mozhgan rezaei kanavi, md. ocular tissue engineering research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran. no. 23, paidarfard st., boostan 9 st., pasdaran ave., tehran 1666673111, iran. e-mail: rezaeikanavi@gmail.com received: 30-01-2021 accepted: 07-04-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i3.9431 blood product contains several growth factors and signaling molecules needed for tissue regeneration, and it has attracted researchers’ attention in this field.[19–21] the use of platelet lysate obtained from prp, as a xeno−free and accessible medium supplement, has also gained popularity and can be used based on good manufacturing practice (gmp) standards.[22–24] in this study, we aimed to investigate the effect of human platelet lysate (hpl) as a valuable source of growth factors on the proliferation behavior of hcecs as compared with y-27632 rock inhibitor. methods to conduct the study, full ethical approval was obtained from the institutional review board of the central eye bank of iran and the ethics committee of the ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran. tissue preparation twelve human pre-stripped descemet’s membrane (dm) with cec density of >2500 cells/mm2 and preserved in optisol-gs (chiron vision, irvine, ca, usa) at 4°c were provided from the central eye bank of iran (tehran, iran). the corresponding donors were aged 26–50 years and the death to preservation time was <30 hr. the preparation of pre-stripped dm endothelial keratoplasty tissue at the central eye bank of iran has previously been described.[25] briefly, after making a circumferential incision to the trabecular meshwork, without the use of dye or trephine, the edge of the dm from one side was gently grasped and peeled toward the opposite side and then transferred to optisolgs at 4°c. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: mishan ma, balagholi s, chamani t, feizi s, soheili zs, kanavi mr. potential effect of human platelet lysate on in vitro expansion of human corneal endothelial cells compared with y-27632 rock inhibitor. j ophthalmic vis res 2021;16:349–356. 350 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 https://knepublishing.com/index.php/jovr in vitro expansion of endothelial cells; mishan et al human platelet lysate (hpl) preparation prps were provided from iranian blood transfusion organization (tehran, iran). the samples were pooled from three different healthy donors with a platelet count of 2.4 × 105/μl. hpl was obtained according to the repeated freeze-thaw method.[26] accordingly, the pooled prps were kept at −80°c for 24 hr, then thawed at 37°c in a water bath for 1 hr, and this action was repeated three times. after that, the solution was centrifuged at 2000 g for 10 min to remove the debris. finally, the supernatant containing hpl was filtered using a 0.2 μm sterile filter. isolation and culture of hcecs our experiment on cultivated hcecs was composed of two main parts (elisa in part one and cell counting, morphology, and immunocytochemistry [icc] in the second part). each part was performed in triplicate. for each run, the dms from six different cornea donors were pooled and incubated in 3.5 mg/ml collagenase a (roche, usa) at 37°c for 50 min and then centrifuged at 300 g for 5 min. finally, the pooled cells were cultured in dmem: f12 supplemented with 20% fetal bovine serum (fbs; gibco), 120 mg/ml penicillin (sigma, germany), and 220 mg/ml streptomycin (sigma, germany) on a 24-well plate coated with 20 mg/ml of fibronectin (sigma, usa) at 37°c and 5% co2. all experiments were performed when the cells were in p1. for this purpose, after two weeks of cell isolation and culture, the cells were passaged by trypsin/edta and seeded on a 24-well plate at a seeding density of 1 × 104 cells per well with dmem: f12 culture medium supplemented with three different treatment groups including 20% hpl, 10 μm y27632 rock inhibitor (stemcell technologies, usa), combination of 20% hpl and 10 μm y-27632 rock inhibitor, and 20% fbs as the control group. the concentration of y-27632 rock inhibitor was designated based on the previous studies.[18, 27, 28] elisa cell proliferation assay hcecs were seeded on 96-well plates at 5000 cells/well in 200 μl culture medium. the culture medium in each well was first changed with 100 ml of dmem: f12 1:1 and then supplemented with 20% hpl, 10 μm y-27632 rock inhibitor, combination of 20% of hpl and 10 μm y-27632 rock inhibitor, and 20% fbs (control group). to determine whether the hpl and/or y-27632 rock inhibitor altered cell proliferation, bromodeoxyuridine (brdu) was added after 24 hr of treatment and the proliferation assay was performed according to the manufacturer’s instructions (roche diagnostic, mannheim, germany). an elisa reader (elx 808 absorbance reader, biotek instruments, winooski, vt) was implemented to read the absorption of the investigated samples at specified wavelengths. cell counting to assess hcecs proliferation after treatments, phase contrast micrographs at ×100 magnification of three random photos were recorded and the number of cells were counted using imagej software (national institutes of health) and then averaged.[29] hcecs characterization the characteristics of the cultured hcecs were verified based on the morphology and the expression of molecular markers. polygonal/hexagonal appearance as the characteristic of cecs, was used to differentiate these cells from human corneal stromal fibroblasts with spindle-shaped appearance (olympus ix71, tokyo, japan). also, the expression of the molecular markers was detected using icc. immunocytochemistry (icc) two groups of treatments, the cultured hcecs with 20% hpl and 20% fbs, in a 24-well plate were fixed by incubating in –10°c methanol for 10 min. then, the cells were permeabilized using triton x-100 (0.25%) and blocked in 1% bovine serum albumin (bsa) in pbs for 1 hr at room temperature. the expressions of na+/k+atpase, zonula occludens-1 (zo-1) and vimentin were detected at protein levels by 1:500 of primary rabbit anti-human na+/k+-atpase (santa cruz biotechnology inc., dallas, usa, sc-28800) and 1:400 of primary rabbit anti-human zo-1 (santa cruz biotechnology inc., dallas, usa, sc-10804) for 90 min each, and 1:800 of primary rabbit antihuman vimentin (santa cruz biotechnology inc., journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 351 in vitro expansion of endothelial cells; mishan et al dallas, usa, sc-5565) for 60 min. thereafter, the slides were incubated with 1:200 of goat anti-rabbit igg-fluorescein isothiocyanate (fitc) conjugated antibody (santa cruz biotechnology inc., dallas, usa, sc-2012) for 45 min in darkness and at room temperature. after washing with pbs, the slides were counterstained with 1.5 mg/ml of 4,6diamidino-2-phenyindole dihydrochloride (dapi, santa cruz, usa) for 10 min. the images were then captured using a fluorescence microscope (olympus ix71, tokyo, japan) equipped with a digital camera (olympus u-tv0.63xc; tokyo, japan) and an excitation wavelength of 450– 520 nm. imagej software (imagej 1.48; national institute of health; http://rsb.info.nih.gov/ij/) was used to quantify the corrected total cellular fluorescence (ctcf) per image and the mean values were compared between the hpl-treated and fbs, as the control cells. statistical analysis data were quantitatively compared between the treated groups using one-way anova and tukey’s multiple comparison test for elisa cell proliferation assay and cell counting, and t-test for ctcf analysis by the graph pad prism (version 6.0). results were expressed as the means ± standard deviation (sd) obtained from three independent experiments. results cell proliferation assay hpl at 20% concentration significantly increased the cell proliferation rate compared with the control cultures in 20% fbs-containing medium. however, the proliferation of cultured hcecs after 24 hr treatment with hpl was similar to those treated with y-27632 rock inhibitor and also with combination of hpl and y-27632 rock inhibitor. besides, y-27632 rock in a concentration of 10 μm significantly increased hcecs as compared to 20% fbs control [figure 1]. cell counting after one and five days, the number of cells was recorded from respected photos using imagej software and results showed that the cell numbers were significantly higher in all three treatment groups compared with fbs as the control group, at both time points as shown in figure 2. morphology the morphologies of cultured hcecs in dmem/f12 medium supplemented with all three treatment groups and fbs as the control are shown in figure 3. polygonal/hexagonal shape, characteristics of cecs, were observed in the cultures, as it was confirmed with immunostaining for na+/k+-atpase [figure 4d] and zo-1 [figure 4e] markers. the cells reached over 80% confluency after five days of culture. immunocytochemistry (icc) the icc results revealed that the cultivated cells were immune reactive for na+/k+-atpase [figure 4d] and zo-1 [figure 4e] markers, confirming the identity of the cultured cells as cecs. na+/k+atpase expression was detected in approximately 100% of the hcecs, and >94% and >98% of the hcecs expressed zo-1 and vimentin, respectively. ctcf results showed higher expressions of the hcecs for na+/k+-atpase [figure 4g] and zo-1 [figure 4h] proteins in 20% hpl-treated hcecs as compared to the fbstreated (control) group. also, means of ctcf for vimentin expression were not significantly different between the two groups [figure 4i]. taken together, these results indicate that the cells expressed the original characteristics of cecs. the negative controls without primary antibody did not show any fitc reactivity (data were not shown). discussion the results of this study indicate that hcecs gained a potential proliferation after treatment with 20% hpl in comparison with fbs as the control group although this proliferation effect was comparable to that in the y-27632 rock inhibitortreated group. to the best of our knowledge, there is no published investigation comparing the effects of hpl with y-27632 rock inhibitor on hcecs culture. given that hpl can be of gmp grade and is a cost-benefit supplement for cell culture, it can be a superior proliferative agent for in vitro expansion of hcecs for therapeutic goals. 352 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 http://rsb.info.nih.gov/ij/ in vitro expansion of endothelial cells; mishan et al figure 1. cell proliferation assay. results show a higher proliferative effect of all treatment groups as compared to the control group (*p < 0.05 and **p < 0.01). figure 2. the numbers of hcecs after (a) one and (b) five days of treatments. as illustrated, the numbers of hcecs treated with hpl, combination of hpl and y-27632 rock inhibitor, and y-27632 rock inhibitor alone was significantly higher than fbs (control)-treated group (**p < 0.01 and ***p < 0.001). more importantly, hpl was provided using a freeze/thaw method in the current study. it was previously demonstrated that this method ensures maximum release of growth factors and cytokines from the platelet compartment, providing enrichment of growth factors such as platelet-derived growth factor (pdgf)-ab/bb, platelet factor-4, epidermal growth factor (egf), transforming growth factor (tgf)-β1, and fibroblast growth factor (fgf)-2.[30] the proliferative potential of hpl, as an alternative to fbs, has been demonstrated for various primary cells to avoid risk of zoonosis for cell banking and clinical purposes.[31, 32] in addition, it was demonstrated that bovine cecs expanded in platelet releasate had good intercellular adhesion together with hexagonal morphologies.[33] in another study, it was observed that all three different hpls prepared via different ways induced proliferation of the bce c/d-1b cells as a bovine cec line, without noticeable differences compared to 10% fbs.[34] therefore, hpl has been introduced as a xeno−free supplement for culturing cecs[16] and according to the results of our study, hpl journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 353 in vitro expansion of endothelial cells; mishan et al figure 3. representative photomicrographs of cultivated hcecs in treated and control groups (a–d) one and (e–h) five days after treatments. the morphology of hcecs after five days of cultures in (e) 20% fbs, (f) 10 μm y-27632 rock inhibitor, (g) combination of 20% hpl and 10 μm y-27632 rock inhibitor, and (h) 20% hpl. figure 4. expression of na+/k+-atpase, zo-1 and vimentin proteins in the hcecs cultured in 20% hpl and 20% fbs, as the control group, after five days of treatments. (a) a merged fitc-na+/k-atpase antibody and dapi image in the cells treated with 20% fbs. (b) a merged fitc-zo-1 antibody and dapi image in the cells treated with 20% fbs. (c) a merged fitcvimentin antibody and dapi image in the cells treated with 20% fbs. (d) a merged fitc-na+/k-atpase antibody and dapi image in the cells treated with 20% hpl. (e) a merged fitc-zo-1 antibody and dapi image in the cells treated with 20% hpl. (f) a merged fitc-vimentin antibody and dapi image in the cells treated with 20% hpl. mean ctcf values of (g) na+/k+-atpase and (h) zo-1 protein expressions show a significant increase in the hpl-treated hcecs as compared to the control group (***p < 0.001 and ****p < 0.0001, respectively). (i) means of ctcf for vimentin expression were not significantly different between the two groups. induces a higher proliferative effect on the expansion of hcecs than fbs. rock signaling pathway is involved in the regulation of important cellular functions including cytoskeleton organization, cell proliferation and migration,[35, 36] and initiation of apoptotic signaling pathways in stressful conditions.[37, 38] also, this signaling pathway negatively regulates cell adhesion through actin depolymerization inhibition; however, it was demonstrated that inhibition of rock by y-27632 agent promotes actin reorganization and results in cec adhesion 354 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 in vitro expansion of endothelial cells; mishan et al induction.[8, 13] more studies have suggested that y-27632 rock inhibitor is a safe and effective additive agent for expansion of cecs.[7, 13, 28, 39] interestingly, it was observed that y-27632 improved the attachment and proliferation of hcecs isolated from young donors; however, these effects were not observed in hcecs isolated from older donors aged 60 and above.[18] this may be due to the increase of cyclin kinase inhibitors p16ink4a and p21waf1/cip1 that results in an age-dependent increase in negative regulation of cell cycle.[40] in the current study, although y-27632 rock inhibitor exerted an elevated proliferation of hcecs in culture as compared with the control group, its effect was not superior to that of 20% hpl. surprisingly, the combination of hpl and y-27632 rock inhibitor had a similar effect on cell proliferation compared with y-27632 rock or hpl alone. further investigation will be required to verify the proposed statement. in addition to the superior effects of the hpl over fbs on the cell proliferation, this natural prp-derived supplement has also other advantages. it can be prepared simply as an autologous blood product from the recipients of hcecs allografts, which may be of great importance in reducing the risk of rejection and the need for immune suppression strategies.[41, 42] moreover, given that prp is an ideal source of autologous growth factors,[41] it can be a proper agent for corneal endothelial tissue engineering and cell-based therapies in near future. in conclusion, hcecs culture data showed a higher proliferation rate in the cells treated with 20% hpl in comparison to those treated with fbs. on the other hand, the effects of hpl on the proliferation of the hcecs were comparable with y-27632 rock inhibitor alone and with the combination of hpl and y-27632 rock inhibitor. therefore, hpl can be used as a cost-benefit and xeno-free supplement in the culture of hcecs rather than y-27632 rock inhibitor or fbs. other advantages of hpl are its autologous and gmp grade characteristics that can ensure its safety in future clinical cellbased therapies. however, further investigations based on animal models and clinical trials are needed to elucidate the efficacy of hpl in comparison with y-27632 rock inhibitor in vivo. acknowledgements the authors express their gratitude to the central eye bank of iran for providing the donor eyes. financial support and sponsorship the manuscript was funded by shahid beheshti university of medical sciences (grant number: 15739-5). conflicts of interest all authors declare that they have no conflicts of interests. references 1. dawson dg, ubels jl, edelhauser hf. cornea and sclera. in: levin la, nilsson sfe, ver hoeve j, wu sm, editors. adler’s physiology of the eye. elsevier; 2011. 2. bourne wm. clinical estimation of corneal endothelial pump function. trans am ophthalmol soc 1998;96:229– 242. 3. tan dt, dart jk, holland ej, kinoshita s. corneal transplantation. lancet 2012;379:1749–1761. 4. gain p, jullienne r, he z, aldossary m, acquart s, cognasse f, et al. global survey of corneal transplantation and eye banking. jama ophthalmol 2016;134:167–173. 5. parekh m, ahmad s, ruzza a, ferrari s. human corneal endothelial cell cultivation from old donor corneas with forced attachment. sci rep 2017;7:142. 6. nuzzi r, marolo p, tridico f. from dmek to corneal endothelial cell therapy: technical and biological aspects. j ophthalmol 2018;2018: 6482095. 7. kinoshita s, koizumi n, ueno m, okumura n, imai k, tanaka h, et al. injection of cultured cells with a rock inhibitor for bullous keratopathy. n engl j med 2018;378:995–1003. 8. okumura n, koizumi n, ueno m, sakamoto y, takahashi h, tsuchiya h, et al. rock inhibitor converts corneal endothelial cells into a phenotype capable of regenerating in vivo endothelial tissue. am j pathol 2012;181:268–277. 9. coleman ml, marshall cj, olson mf. ras and rho gtpases in g1-phase cell-cycle regulation. nat rev mol cell biol 2004;5:355–366. 10. sun cc, chiu ht, lin yf, lee ky, pang jhs. y-27632, a rock inhibitor, promoted limbal epithelial cell proliferation and corneal wound healing. plos one 2015;10:e0144571. 11. chapman s, mcdermott dh, shen k, jang mk, mcbride aa. the effect of rho kinase inhibition on long-term keratinocyte proliferation is rapid and conditional. stem cell res ther 2014;5:60. 12. wang t, kang w, du l, ge s. rho-kinase inhibitor y-27632 facilitates the proliferation, migration and pluripotency of human periodontal ligament stem cells. j cell mol med 2017;21:3100–3112. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 355 in vitro expansion of endothelial cells; mishan et al 13. okumura n, ueno m, koizumi n, sakamoto y, hirata k, hamuro j, et al. enhancement on primate corneal endothelial cell survival in vitro by a rock inhibitor. invest ophthalmol vis sci 2009;50:3680–3687. 14. liao jk, seto m, noma k. rho kinase (rock) inhibitors. j cardiovasc pharmacol 2007;50:17–24. 15. feizi s, soheili zs, bagheri a, balagholi s, mohammadian a, rezaei-kanavi m, et al. effect of amniotic fluid on the in vitro culture of human corneal endothelial cells. exp eye res 2014;122:132–140. 16. thieme d, reuland l, lindl t, kruse f, fuchsluger t. optimized human platelet lysate as novel basis for a serum-, xeno-, and additive-free corneal endothelial cell and tissue culture. j tissue eng regen med 2018;12:557– 564. 17. okumura n, sakamoto y, fujii k, kitano j, nakano s, tsujimoto y, et al. rho kinase inhibitor enables cellbased therapy for corneal endothelial dysfunction. sci rep 2016;6:26113. 18. peh gs, adnan k, george bl, ang hp, seah xy, tan dt, et al. the effects of rho-associated kinase inhibitor y-27632 on primary human corneal endothelial cells propagated using a dual media approach. sci rep 2015;5:9167. 19. sample sj, racette ma, hans ec, volstad nj, schaefer sl, bleedorn ja, et al. use of a platelet-rich plasmacollagen scaffold as a bioenhanced repair treatment for management of partial cruciate ligament rupture in dogs. plos one 2018;13:e0197204. 20. spanò r, muraglia a, todeschi mr, nardini m, strada p, cancedda r, et al. platelet-rich plasma-based bioactive membrane as a new advanced wound care tool. j tissue eng regen med 2018;12:e82–e96. 21. fernandes g, yang s. application of platelet-rich plasma with stem cells in bone and periodontal tissue engineering. bone res 2016;4:16036. 22. naskou mc, sumner sm, chocallo a, kemelmakher h, thoresen m, copland i, et al. platelet lysate as a novel serum-free media supplement for the culture of equine bone marrow-derived mesenchymal stem cells. stem cell res ther 2018;9:75. 23. švajger u. human platelet lysate is a successful alternative serum supplement for propagation of monocyte-derived dendritic cells. cytotherapy 2017;19:486–499. 24. saury c, lardenois a, schleder c, leroux i, lieubeau b, david l, et al. human serum and platelet lysate are appropriate xeno-free alternatives for clinical-grade production of human mustem cell batches. stem cell res ther 2018;9:128. 25. chamani t, javadi ma, kanavi mr. trephine-and dyefree technique for eye bank preparation of pre-stripped descemet membrane endothelial keratoplasty tissue. cell tissue bank 2019;20:321–326. 26. şeker ş, elçin ae, elçin ym. autologous protein-based scaffold composed of platelet lysate and aminated hyaluronic acid. j mater sci mater med 2019;30:127. 27. su cc, chen cw, ho wt, hu fr, lee sh, wang ij. phenotypes of trypsin-and collagenase-prepared bovine corneal endothelial cells in the presence of a selective rho kinase inhibitor, y-27632. mol vis 2015;21:633–643. 28. pipparelli a, arsenijevic y, thuret g, gain p, nicolas m, majo f. rock inhibitor enhances adhesion and wound healing of human corneal endothelial cells. plos one 2013;8:e62095. 29. rasband ws. imagej. bethesda, maryland, usa: national institutes of health; 1997–2016. 30. strandberg g, sellberg f, sommar p, ronaghi m, lubenow n, knutson f, et al, standardizing the freezethaw preparation of growth factors from platelet lysate. transfusion 2017;57:1058–1065. 31. carducci a, scafetta g, siciliano c, carnevale r, rosa p, coccia a, et al. gmp-grade platelet lysate enhances proliferation and migration of tenon fibroblasts. front biosci 2016;8:84–99. 32. burnouf t, strunk d, koh mb, schallmoser k. human platelet lysate: replacing fetal bovine serum as a gold standard for human cell propagation? biomaterials 2016;76:371–387. 33. chou ml, burnouf t, wang tj. ex vivo expansion of bovine corneal endothelial cells in xeno-free medium supplemented with platelet releasate. plos one 2014;9:e99145. 34. wang tj, chen ms, chou ml, lin hc, seghatchian j, burnouf t. comparison of three human platelet lysates used as supplements for in vitro expansion of corneal endothelium cells. transfus apher sci 2017;56:769–773. 35. olson mf, ashworth a, hall a. an essential role for rho, rac, and cdc42 gtpases in cell cycle progression through g1. science 1995;269:1270–1272. 36. coleman ml, olson mf. rho gtpase signalling pathways in the morphological changes associated with apoptosis. cell death differ 2002;9:493–504. 37. riento k, ridley aj. rocks: multifunctional kinases in cell behaviour. nat rev mol cell biol 2003;4:446–456. 38. amano m, fukata y, kaibuchi k. regulation and functions of rho-associated kinase. exp cell res 2000;261:44–51. 39. okumura n, koizumi n, ueno m, sakamoto y, takahashi h, hamuro j, et al. the new therapeutic concept of using a rho kinase inhibitor for the treatment of corneal endothelial dysfunction. cornea 2011;30:s54–s59. 40. enomoto k, mimura t, harris dl, joyce nc. age differences in cyclin-dependent kinase inhibitor expression and rb hyperphosphorylation in human corneal endothelial cells. invest ophthalmol vis sci 2006;47:4330–4340. 41. sánchez m, anitua e, delgado d, sanchez p, prado r, orive g, et al., platelet-rich plasma, a source of autologous growth factors and biomimetic scaffold for peripheral nerve regeneration. expert opin biol ther 2017;17:197– 212. 42. vis pw, bouten cv, sluijter jp, pasterkamp g, van herwerden la, kluin j. platelet-lysate as an autologous alternative for fetal bovine serum in cardiovascular tissue engineering. tissue eng part a 2010;16:1317–1327. 356 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 letter authors’ reply kaveh abri aghdam, md, phd; amin zand, md; mostafa soltan sanjari, md eye research center, the five senses institute, rassoul akram hospital, iran university of medical sciences, tehran, iran j ophthalmic vis res 2021; 16 (3): 526–526 dear editor, we sincerely thank dr guzzi for the interest in our case report[1] and would like to take this opportunity to make some clarifications as follows: the main concern raised by dr guzzi was that serum lead level alone does not adequately reflect the total body burden of the lead and the whole-blood lead level in conjugation with its urinary levels is a primary measure of lead exposure in humans.[2–4] we fully agree with dr guzzi based on the available literature on this subject. however, one month before the referral, our patient had been diagnosed with lead poisoning just based on serum lead level and had undergone chelation therapy in another tertiary center by a neurologist. shortly after the completion of treatment, he came to our neuro–ophthalmology clinic for the evaluation of persistent blurred vision in both eyes. therefore, we could only rely on his previous clinical and paraclinical documents. in the letter written by dr guzzi, the term “papilledema” was used for the description of correspondence to: amin zand, md. eye research center, rassoul akram hospital, sattarkhan-niaiesh st., tehran 1445613131, iran. e-mail: sandpost3@gmail.com received: 01-04-2021 accepted: 01-05-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i3.9451 our patient’s ocular condition. however, as we mentioned in our article, papilledema is defined as optic disc edema due to increased intracranial pressure (icp) and should be differentiated from papillitis. the lumbar puncture in this patient showed that icp was within normal limits, which ruled out papilledema. therefore, we considered the condition of the patient as bilateral hemorrhagic optic disc swelling.[1] references 1. abri aghdam k, zand a, soltan sanjari m. bilateral optic disc edema in a patient with lead poisoning. j ophthalmic vis res 2019;14:513–517. 2. guzzi g, spadari f, bombeccari gp, pigatto pd. maxillofacial gunshot wounds and diagnostic tests for lead in the blood. br j oral maxillofac surg 2017;55:105. 3. pigatto pd, ronchi a, guzzi g. iron overload, g6pd deficiency, and lead levels on blood smears. int j hematol 2016;103:724. 4. casarett lj, doull j, klaassen cd. casarett and doull’s toxicology: the basic science of poisons. 6th ed. new york: mcgraw-hill medical pub. division; 2001. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: aghdam ka, zand a, sanjari ms. authors’ reply. j ophthalmic vis res 2021;16:526–526. 526 © 2021 aghdam et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i3.9451&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr surgical technique femtosecond laser-assisted allogenic additive stromal keratoplasty with or without excimer laser donor keratomileusis for management of keratoconus mohammad-reza jafarinasab1, md; yasaman hadi2, md; goldis espandar1, md 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2eye research center, rassoul akram hospital, iran university of medical sciences, tehran, iran orcid: mohammadreza jafarinasab: https://orcid.org/0000-0001-7558-0351 yasaman hadi: https://orcid.org/0000-0001-8332-2950 abstract we describe a modified allogenic intrastromal lenticule implantation technique for management of keratoconus (kcn). patients with advanced kcn already scheduled for corneal transplantation were enrolled. an allogenic corneal lenticule was implanted inside a stromal pocket created by femtosecond laser. in three cases, the estimated refractive error of the recipient eyes was corrected on the donor lenticules using an excimer laser. all operated eyes underwent corneal crosslinking at the time of surgery. this method was named “femtosecond laser-assisted allogenic stromal keratoplasty without and with excimer laser-assisted donor keratomileusis”; briefly called fask and fask plus edk, respectively. two out of five patients were satisfied with the results. there was a decrease in the average simulated keratometric values as well as myopia when fask plus edk was performed. increased corneal thickness was achieved in all cases. graft edema gradually decreased over weeks but interface wrinkling and lenticule folds in the visual axis remained as a problem during follow-up period. no other complications were encountered. keywords: allogenic; ectasia; keratoconus j ophthalmic vis res 2021; 16 (4): 691–697 introduction keratoconus (kcn) is the most common primary corneal ectasia characterized by non-inflammatory, correspondence to: yasaman hadi, md. eye research center, rassoul akram hospital, iran university of medical sciences, tehran 1445613131, iran. e-mail: hadi.yasaman@gmail.com received: 16-10-2020 accepted: 26-06-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9761 slowly progressive thinning and steepening of the central or paracentral part of the cornea of unknown etiology, resulting in irregular astigmatism and progressive decrease in quality of vision.[1, 2] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: jafarinasab mr, hadi y, espandar g. femtosecond laser-assisted allogenic additive stromal keratoplasty with or without excimer laser donor keratomileusis for management of keratoconus. j ophthalmic vis res 2021;16:691–697. © 2021 jafarinasab et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 691 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9761&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr fask for corneal ectasia; jafarinasab et al depending on the diagnostic criteria and different diagnostic tools employed, estimation of the incidence and prevalence of kcn in any given population is different.[3–5] management of kcn in the early stages includes use of spectacles, rigid gas permeable contact lenses, and intracorneal ring segments (icrs) implantation.[6–9] in cases with severe irregular astigmatism where spectacles or contact lenses are not tolerated, lamellar or penetrating keratoplasty is usually considered.[6] corneal collagen cross-linking (cxl) has been shown to be effective in slowing down or arresting the progression of kcn.[10] since corneal transplantation is costly and an invasive procedure entailing possible complications, treatments that may replace or postpone corneal transplantation are a desirable solution and an ongoing subject of research. in recent years, synthetic intrastromal corneal ring segments (icrs) have proven effective treatment for ectatic corneal disorders. [9] despite favorable topographic and visual outcomes, there are risks associated with implanting a synthetic substance within the cornea. complication rates up to 30% have been reported in some series [9] including misalignment, migration, extrusion, corneal perforation, infection, and tissue reactions. [9, 11–13] from the point of biocompatibility, use of biological inlays, derived from allogenic donor corneas may offer advantages over synthetic icrss and inlays.[12, 13] in recent years application of stromal tissue addition for potential management of corneal ectasia with or without cxl has been a hot topic in some studies.[14, 15] the aim of the current pilot study was to introduce a modified allogeneic inlay for management of kcn and report the feasibility, refractive outcomes, and possible complications. patient selection from october 2015 to january 2016, five consecutive patients with advanced kcn at the cornea and refractive surgery service of labbafinejad medical center already scheduled for lamellar or penetrating keratoplasty were enrolled. patients with history of corneal surgery or any corneal pathology other than kcn and patients with central corneal thickness <400 microns or opacities were excluded. the study was approved by the ethics committee of the ocular tissue engineering research center at shahid beheshti university of medical sciences. after explaining the procedure and possible complications, informed consent was obtained from all patients. surgical method pocket creation under topical anesthesia, in the usual sterile manner, a stromal pocket was created using the lamellar keratoplasty mode of the technolas® femtosecond workstation (technolas perfect vision, bausch and lomb, munich, germany). the energy setting and spot distance were 1600 nj and 4.1/4.1 µm, respectively. the depth of the pocket was set at 75% depth of the thinnest point (300– 400 μ) and the pocket diameter was selected 2.50 mm smaller than the vertical corneal diameter. two pocket entries 4 and 5 mm in size were created on the steepest corneal topographic axis 180° away using the astigmatism keratotomy mode. donor preparation prepared corneal allograft tissues from the iranian eye bank, (eye bank of the i.r. iran) eligible for dalk (type i) or dsaek (type ii) were employed. the epithelium and descemet’s membrane (dm) of donors prepared for dalk (type i) were removed. in cases where precut tissue suitable for dsaek was used (type ii), the posterior lamella had already been used for dsaek and we made sure that the anterior free cap was completely deepithelialized. both type i and type ii corneal tissues were punched using the hessberg’s punch at a diameter 20% smaller than that of the pocket. correction of refractive errors for patients #2 and 5, no refractive correction was performed on the lenticule while in the other three subjects we decided to correct the refractive error as much as possible on the donor lenticule before insertion. first, we registered the patient’s eye for the planned correction and manually marked reference points at 3, 6, and 9 clock hour positions. the donor lenticule was placed over the cornea and marked exactly at the same 692 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 fask for corneal ectasia; jafarinasab et al locations as the patient’s cornea. the lenticule was then removed and a soft contact lens (14 mm diameter) was fitted to protect the recipient cornea from unwanted ablation. the lenticule was put back on the contact lens and its position was adjusted aligning the preset marks. laser ablation was subsequently performed on the lenticule using the allegretto ex500 excimer laser machine (wavelight allegretto wave eye-q laser devices; alcon laboratories, usa). preparation for cxl both the donor lenticule and the recipient cornea underwent epithelium on, cxl, after soaking the lenticule in riboflavin 0.1% riboflavin in 20% dextran t500 and injection of the same material into the recipient corneal pocket for 30 min. insertion of the lenticule into the pocket the femtosecond laser-created arcuate incisions and intrastromal pockets were gently dissected using a blunt dissector. the riboflavin soaked lenticule was inserted into the pocket and its meridian of orientation was matched with meridian of the recipient cornea using the preset marks. the incisions were secured using 10-0 nylon sutures. completion of cxl cxl was completed using uv fluence of 9mw/cm2 for 10 min to obtain a total energy of 5.4 j/cm2. post operation medications and follow-up postoperatively, patients were prescribed betamethasone 0.1% eye drops (sina darou, tehran, iran) four times a day, non-preserved levofloxacin 0.5% eye drops (sina darou, tehran, iran) four times a day, and non-preserved artificial tears artelac (baush and lomb, rochester, ny usa) four to six times a day. levofloxacin drops were discontinued in seven days and betamethasone drops tapered off over six weeks. sutures were removed no later than four weeks after surgery. patients were visited regularly on the first day, first week, and first month after surgery and then every three months. at each visit, they underwent complete ophthalmic examinations, including refraction, corrected distance visual acuity (cdva) and uncorrected distance visual acuity (udva) measurements, intraocular pressure monitoring, and thorough slit lamp examination. results five eyes of five patients with advanced kcn were operated. mean age of patients was 29 (range, 20 to 46) years. mean follow-up was 28.4 (range 8 to 55) months. patients’ demographics and follow-up periods are presented in table 1. table 2 contains preand postoperative visual acuity, refractive and keratometric data for each individual. patients number 2, 3, and 4 were not happy with the final visual outcome and underwent dalk after 8, 12, and 18 months, respectively. patient number 1 and 5 were satisfied with the results and were willing to wait and try topography-guided photorefractive keratectomy. in terms of safety, only one patient (number 3) lost more than one line of cdva. no intraoperative or postoperative complications such as stromal allogenic rejection, infection, or progressive corneal haze were observed except for early graft edema which decreased gradually in addition to wrinkling and folds in the lenticule and recipient cornea [figure 1]. there was a decrease in the average simulated keratometric values in cases 1, 3, and 4 in contrast to cases 2 and 5. corneal thickness was increased in all patients. the main cause for persistent visual dissatisfaction leading to corneal transplantation were wrinkles or folds in the lenticule and recipient cornea [figure 2]. representative case a 20-year old lady with advanced kcn in her right eye had severe distortion of the retinoscopy reflex and high levels of irregular astigmatism ucva was 20/1000 which was not correctable. she had abandoned hard contact lenses because of dissatisfaction since last year. ucva of the left eye was 20/200 which was improved to 20/80 with spectacle correction of –8.0 –7.25@160 and to 20/30 with rgp contact lenses. all the surgical options for the right eye including icrss and dalk were thoroughly discussed with the patient and she decided to try our new treatment option. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 693 fask for corneal ectasia; jafarinasab et al table 1. demographics and follow up time case number age sex eye f/u(m) final plan 1 21 f od 55 t-cat 2 46 f od 8 dalk 3 29 m os 12 dalk 4 20 m os 16 dalk 5 31 m os 51 t-cat t-cat, topography-guided custom laser ablation; dalk, deep anterior lamellar keratoplasty table 2. preand postoperative visual, refractive, and keratometric values ucdva cdva refraction(d) simks(d) simkf(d) simk/avg(d) type of surgery 1 pre 20/800 ni irregular 55.49@105 46.60@15 51.05 fask-plus post 20/120 20/50 –4.25–1.00@65 50.74@104 47.98@14 49.36 diff +5 lines +7 lines _ –4.75 d +1.38 d –1.64 d 2 pre 20/400 20/200 –9.25–4.4@50 49.99@144 46.94@54 48.7 fask post 20/400 ni irregular 56.50@73 54.5@163 55.5 diff 0 –1 line +6.51 d +7.56 d +6.8 d 3 pre 20/400 20/80 –6.25–1.75@175 48.75@75 46.5@165 47.12 fask-plus post 20/200 20/160 –0.25–1.75@105 49.5@165 45.00@75 45.25 diff +1 line –2 line +6.00 d +0.75 d –1.5 d –1.87 d 4 pre 20/400 ni irregular 48.00@95 45.75@5 46.88 fask-plus post 20/300 20/200 –2.5–2.5@175 47.25@60 45.00@150 45.25 diff +1 line _ –0.8 d –0.75 d –1.63 d 5 pre 20/80 ni irregular 54.90@45 50.50@135 52.7 fask post 20/200 20/40 –7.25–3.25@153 55.50@77 51.50@167 53.5 diff –3 lines +3 lines +0.6 d +1.00 d +0.8 d ucdva, uncorrected distance visual acuity; cdva, corrected distance visual acuity; diff, difference; ni, no improvement; simk, simulated keratometry; d, diopter; avg, average; fask, femtosecond laser-assisted allogenic stromal keratoplasty preoperative simulated keratometry (simk) in the right eye was 55.49@105/46.65@15 and topographic astigmatism was 8.84105. a stromal pocket 9.0 mm in diameter and at 360 µ depth was created as described in the methods section. a full thickness corneal lenticule with a diameter of 7.5 mm was punched from a donor cornea (type i). after preparing the lenticule, based on topographic simk, we corrected the refractive error including corneal astigmatism and myopia on the donor lenticule. we planned to achieve an average simk of about 44.0 d postoperatively and correct six diopters of astigmatism. calculated refractive error correction for this target was –5.50–6.00 @15 with se of about –8.50 d. after lenticule insertion into the stromal pocket and cxl as described above, a silicone-hydrogel bandage contact lens (bausch & lomb incorporated, rochester, ny, usa) was placed on the cornea. on the first day after the operation, the lenticule was edematous and ucva was about 20/400. lenticule edema decreased over the next few weeks and ucva was improved to 20/200 after one month. refractive error 6 and 18 months after surgery was –2.50 –1.0@62 and –3.37 –2.0@30, respectively. cdva improved to 20/60 18 months after surgery. refraction and cdva, 55 months after surgery were stable. preand postoperative cct were 487 and 727 microns, respectively. preoperative topography together 694 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 fask for corneal ectasia; jafarinasab et al figure 1. slit photo of case number 5, 51 months after fask shows mild haziness and wrinkling of interface. figure 2. anterior segment oct of case number 2. wrinkling of anterior and posterior interface can be seen. with postoperative slit photo and anterior oct of the patient are represented in figure 3. discussion the concept of tissue addition for correction of refractive errors was first introduced by jose barraquer in 1949.[16] with the development of laser vision correction and synthetic intrastromal inlays, the barraquer technique of epikeratophakia and keratomileusis were substituted by newer techniques, however, concerns were raised regarding diffusion of nutrients across the synthetic inlay.[13] recently, lenticules extracted from eyes undergoing smile have been used as autograft or allografts for correction of hyperopia based on barraquer‘s law of thickness.[17–20] the lenticule harvested from a myopic-smile procedure is convex-shaped and can be used to steepen the central cornea of a hyperopic eye. by implanting a concave lenticule, inside a stromal pocket, the anterior corneal curvature can theoretically be reshaped to be less steep or less hyper-prolate, hence improving visual function. even though autologous lenticule implantation can be considered in exceptional cases of significant antimetropia, in the vast majority of cases such lenticules should be synthetic or allogenic in nature. improving corneal irregularity in addition to correction of refractive errors and stromal thinning in advanced kcn using tissue addition remains a challenge. the method we have devised increases corneal thickness with the addition of allogenic stroma and also allows the refractive error to be addressed by reshaping the donor lenticule applying customized excimer laser ablation before implantation along with cxl, alternatively refractive error correction may be postponed after stabilization and be later performed on a thickened and cross-linked cornea. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 695 fask for corneal ectasia; jafarinasab et al figure 3. preoperative topography, postoperative slit photo, and anterior oct of patient number one. faint haziness of visual axis without any interface wrinkling is seen 55 months after surgery. we performed excimer laser ablation on the donor lenticule in an attempt to correct the refractive error in cases number 1, 3, and 4. in these three cases, postoperative average keratometry and consequently myopia were decreased whereas average keratometry increased in cases number 2 and 5 for whom laser refractive correction was not performed. clinically, we noted no significant difference in terms of patient satisfaction regarding corrected visual acuity between subjects who received refractive corrected lenticules and those who received a non-modified lenticule [table 2]. biological inlays, proposed in the current pilot study, theoretically offer superior permeability and biocompatibility as compared to synthetic inlays. lenticule implantation is essentially a selective lamellar keratoplasty procedure; hence it still carries the risk of rejection if the lenticule is not autogenic. however, the risk of rejection is expected to be low, as compared to full-thickness or lamellar corneal transplantation, because the antigenic load of purely stromal lenticule should be less than pkp or dalk due to absence of the more antigenic epithelium and endothelium.[18] in addition, the intrastromal implanted lenticule may be better protected from immune reactions inside the recipient corneal pocket due to lack of exposure to tears and aqueous humor, and farther distance from the limbus. predictability of refractive results following lenticule implantation for kcn warrants investigation; however, our results show that correction of recipient refractive error on the donor lenticule could significantly reduce central corneal steepness which contrasts with lenticules with no refractive ablation. thickness of implanted lenticule as well as the depth of implantation and corneal wound healing response probably determines the final corneal refractive power. our principal purpose in current study was to increase and stabilize corneal thickness, and to prepare it for correction of total refractive error including lower and higher order aberrations by customized or t-cat prk. in three patients we had to perform dalk after three to six months due to patient dissatisfaction. the main cause of visual deterioration seems to be graft folds and wrinkling 696 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 fask for corneal ectasia; jafarinasab et al in the visual axis. another reason could be a thick layer of donor tissue in the central 3 mm zone. two patients agreed to wait longer for a second procedure. corneal thickness and power were stabilized after one year and remained stable until 55 and 51 months after implantation. the lenticule folds and wrinkling were significantly decreased on the last visit and their clarity was the same as the recipient stromal cornea. in summary, the current report demonstrated the feasibility of femtosecnd laser-assisted allogenic stromal keratoplasty without and with excimer laser-assisted donor keratomileusis, briefly “fask” and “fask plus edk” in the management of kcn; with superior refractive and keratometric outcomes in the “fask plus edk” group. nevertheless, visual outcomes were not satisfactory in three of five patients several months after surgery which indicates the long time for visual recovery and stabilization by both of these methods. it means that patients need to wait more than one or two years for visual recovery which is not acceptable for most of them. considering limitations of the current series including small sample size due to strict ethical issues, this new surgical modality could open a new path to treatment of primary corneal ectasia, reducing the need for conventional keratoplasties. although using a thick center lenticule (what we used) did not work well, our results provide encouraging preliminary information for the design of future studies on allogenic intrastromal rings, paracentral segments or lenticules with a thinner center. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. romero-jiménez m, santodomingo-rubido j, wolffsohn js. keratoconus: a review. cont lens anterior eye 2010;33:157–166. 2. vellara hr, patel dv. biomechanical properties of the keratoconic cornea: a review. clin exp optom 2015;98:31– 38. 3. rabinowitz ys, yang h, rasheed k, li x. longitudinal analysis of the fellow eyes in unilateral keratoconus. invest ophthalmol vis sci 2003;44:1311–1315. 4. nielsen k, hjortdal j, aagaard nohr e, ehlers n. incidence and prevalence of keratoconus in denmark. acta ophthalmol scand 2007;85:890–892. 5. ziaei h, jafarinasab mr, javadi ma, karimian f, poorsalman h, mahdavi m, et al. epidemiology of keratoconus in an iranian population. cornea 2012;31:1044–1047. 6. andreanos kd, hashemi k, petrelli m, droutsas k, georgalas i, kymionis gd. keratoconus treatment algorithm. ophthalmol ther 2017;6:245–262. 7. bromley jg, randleman jb. treatment strategies for corneal ectasia. curr opin ophthalmol 2010;21:255–258. 8. barnett m, mannis mj. contact lenses in the management of keratoconus. cornea 2011;30:1510–1516. 9. rabinowitz ys. intacs for keratoconus. curr opin ophthalmol 2007;18:279–283. 10. lang pz, hafezi nl, khandelwal ss, torres-netto ea, hafezi f, randleman jb. comparative functional outcomes after corneal crosslinking using standard, accelerated, and accelerated with higher total fluence protocols. cornea 2019;38:433–441. 11. vega-estrada a, alió jl, plaza-puche ab. keratoconus progression after intrastromal corneal ring segment implantation in young patients: five-year follow-up. j cataract refract surg 2015;41:1145–1152. 12. liu yc, teo epw, ang hp, seah xy, lwin nc, yam ghf, et al. biological corneal inlay for presbyopia derived from small incision lenticule extraction (smile). sci rep 2018;8:1831. 13. coskunseven e, kymionis gd, tsiklis ns, atun s, arslan e, siganos cs, et al. complications of intrastromal corneal ring segment implantation using a femtosecond laser for channel creation: a survey of 850 eyes with keratoconus. acta ophthalmol 2011;89:54–57. 14. almodin em, ferrara p, camin fma, colallilo jma. femtosecond laser-assisted intrastromal corneal lenticule implantation for treatment of advanced keratoconus in a child’s eye. jcro 2018;6: 25–29. 15. ganesh s, brar s. femtosecond intrastromal lenticular implantation combined with accelerated collagen crosslinking for the treatment of keratoconus—initial clinical result in 6 eyes. cornea 2015;34:1331–1339. 16. ratner bd, hoffman as, schoen fj, lemons je. biomaterials science: an introduction to materials in medicine. 3rd ed. academic press; 2012:931. 17. jing z, yang s, mi t, sun l, zhao y, zhang x, et al. corneal lenticule allotransplantation after femtosecond laser small incision lenticule extraction in rabbits. cornea 2017;36:222–228. 18. damgaard ib, riau ak, liu yc, tey ml, yam gh, mehta js. reshaping and customization of smile-derived biological lenticules for intrastromal implantation. invest ophthalmol vis sci 2018;59:2555–2563. 19. liu yc, teo ep, ang hp, seah xy, lwin nc, yam gh, et al. biological corneal inlay for presbyopia derived from small incision lenticule extraction (smile). sci rep 2018;8:1–0. 20. jacob s, kumar da, agarwal a, agarwal a, aravind r, saijimol ai. preliminary evidence of successful near vision enhancement with a new technique: presbyopic allogenic refractive lenticule (pearl) corneal inlay using a smile lenticule. j refract surg 2017;33:224–229. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 697 original article comparing two inferior oblique weakening procedures: disinsertion versus myectomy kaveh abri aghdam, md, phd; reza asadi, md; mostafa soltan sanjari, md; ali sadeghi, md meshkat razavi, md eye research center, the five senses institute, rassoul akram hospital, iran university of medical sciences, tehran, iran orcid: kaveh abri aghdam: https://orcid.org/0000-0001-7568-6455 ali sadeghi: https://orcid.org/0000-0001-5009-5771 abstract purpose: to compare two methods for treating inferior oblique overaction (iooa): disinsertion versus myectomy of the muscle. methods: in this prospective interventional case series, patients were randomly assigned to undergo either io myectomy or disinsertion. the changes in vertical and horizontal deviations following these two surgical procedures were evaluated. the postoperative io function of grade 0 or +1 and the fundus extorsion of grade 0 or +1 was considered as the successful outcome. results: thirty-six patients (50 eyes) with a mean age of 12.67 ± 4.05 years were included. in the myectomy group, the mean preoperative hyperdeviation in adduction was 29.5 ± 9.32 prism diopter (pd), which decreased to 9.15 ± 7.86 pd after surgery (p = 0.001). in the disinsertion group, these measurements were 32.73 ± 12.42 and 12.65 ± 9.34 pd before and after the surgery, respectively (p = 0.001). the success rate of surgery based on the iooa grading was 87.4% and 92.3% in the myectomy and disinsertion groups, respectively (p = 0.780). the successful correction rate of abnormal fundus torsion was 91.6% in the myectomy and 88.4% in the disinsertion group (p = 0.821). in comparison, 48% of the cases in the myectomy group and 50% in the disinsertion group were within the normal range of torsional position postoperatively (p = 0.786). there was no statistically significant difference in terms of changes in the horizontal or vertical deviations, v-pattern, and dissociated vertical deviation between the two groups. conclusion: both surgical techniques seem to be effective for treatment of inferior oblique muscle overaction. keywords: disinsertion of inferior oblique muscle; inferior oblique muscle overaction; strabismus j ophthalmic vis res 2021; 16 (2): 212–218 correspondence to: ali sadeghi, md. department of ophthalmology, eye research center, the five senses institute, rassoul akram hospital, sattarkhan-niayesh st., tehran 1445613131, iran. e-mail: alisadeghi40@yahoo.com received: 16-08-2019 accepted: 23-10-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9085 introduction of the esotropic and the exotropic patients, 70% and 30% have inferior oblique overaction this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: abri aghdam k, asadi r, sanjari ms, sadeghi a, razavi m. comparing two inferior oblique weakening procedures: disinsertion versus myectomy. j ophthalmic vis res 2021;16:212–218. 212 © 2021 abri aghdam et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9085&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr io disinsertion versus myectomy; abri aghdam et al (iooa) respectively. oblique muscle dysfunction is the primary cause of pattern strabismus. the most common type of pattern strabismus is v pattern esotropia with iooa.[1] inferior oblique (io) weakening procedures are self-adjusting; different amounts of deviation can be corrected surgically with the same method.[2] surgical procedures, including myectomy, myotomy, recession, total extirpation, disinsertion, denervation, and io muscle fixation, can successfully weaken the io muscle. seemingly, none of them is superior to the other methods. surgeon’s preference and skill are the main factors in decision-making about the type of procedure. io disinsertion is a safe and straightforward procedure without a need for suturing. however, the io recession is preferred to disinsertion, myectomy, and myotomy by many surgeons because of the ability to achieve a graded response[3] and the lower risk of unpredictable reattachment of io muscle to the sclera.[4] some studies have supported io disinsertion because of its simplicity, decreased risk of hemorrhage, and a similar success rate to other methods.[5–8] in contrast, some authors believe that io myectomy is more effective, despite the increased risk of bleeding using this surgical technique. [9] considering the controversial opinions on the effectiveness of these surgical procedures, we conducted this study to evaluate the outcomes of io disinsertion versus myectomy. methods this prospective interventional case series was conducted on 50 eyes of 36 patients from august 2016 to september 2017 at rassoul akram hospital, tehran, iran. the ethics committee of iran university of medical sciences approved the study design, and the study was conducted in compliance with the declaration of helsinki; written informed consent was obtained from all patients or their parents before the start of the protocol. for grading of iooa, if the abducting eye was the fixing eye and was fixating straight in abduction, minimal upshoot of the adducting eye was considered as grade +1 of iooa. the adducting eye’s obvious upshoot when the abducting eye looks straight across at the lateral canthus was rated as grade +2 of iooa. the severe upshoot of the adducting eye was recognized as +3 of iooa. a very severe upshoot of the adducting eye was considered as +4 of iooa.[10] figure 1 shows the iooa grading schematically. all patients with iooa ≥ +2 requiring io muscleweakening operation were included in this study. all participants underwent a comprehensive ophthalmologic examination, and those with prior strabismus surgery, restrictive strabismus, a history of neurologic, genetic, or craniofacial disorders, and simultaneous dissociated vertical deviation (dvd) were excluded. fundus photography and indirect ophthalmoscopy were used for the assessment of ocular torsion before and after the surgery. the amount of abnormal torsion was determined using a grading system from “trace” to “+4,” as described by guyton.[10] normally, the fovea is within the upper third of the optic disc in the indirect ophthalmoscope view. for each one-eighth of the disc diameter that fovea lies upper than this border, +1 fundus extorsion is estimated.[11] the prism and alternate cover test were used to measure the vertical and horizontal deviations before the surgery compared to final values. the deviation in the primary position at both near and far fixation and lateral gaze at distance fixation was recorded. v pattern existed when the difference between the horizontal deviation at the upper 30 degrees and lower 30 degrees was ≥15 prism diopters (pds). iooa in a patient with a positive head tilt test was classified as secondary iooa. each patient was randomly assigned to the myectomy or disinsertion groups. in bilateral cases, both eyes underwent the same surgical procedure, and the operations were performed by one surgeon (mss). the successful outcome was defined as the final io function of grade +1 or 0 and the fundus extorsion of grade 0 or +1. surgical technique all operations were performed under general anesthesia. in both groups, a small fornix-based incision was developed inferotemporally, and tenon’s capsule incision was made to reach the bare sclera. the lateral rectus muscle was secured on a muscle hook. io muscle was dissected, isolated from surrounding tissues, and then the hook holding the lateral rectus was removed. in the disinsertion group, the muscle was disinserted and released to retract into the tenon’s sleeve. in the journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 213 io disinsertion versus myectomy; abri aghdam et al figure 1. schematic picture for classification of inferior oblique overaction (iooa): (a) grade +1: minimal upshoot of the adducting eye. (b) grade +2: obvious upshoot of the adducting eye when the abducting eye looks straight across at the lateral canthus. (c) grade +3: severe upshoot of the adducting eye is seen with the abducting eye in straight abduction. (d) grade 4: very severe upshoot is considered as grade +4 of iooa. myectomy group, two muscle clamps 5-mm apart from each other were used to hold the muscle, and the muscle located between two clamps was excised and removed. then the cut ends were cauterized. the muscle was released, and the proximal portion was allowed to be pulled back into the tenon’s sleeve. to ensure that no residual fiber remained, guyton’s exaggerated forced duction test was performed in both groups.[12] horizontal eye muscle surgery was performed based on the type of horizontal deviation after io weakening. patients were evaluated one day, one week, one month, and six months following the surgery to determine the grade of iooa, fundus torsion, horizontal or vertical deviation, v pattern, and dvd. an experienced orthoptist who was unaware of the type of surgery performed the measurements in all patients. statistical analysis statistical data analysis was performed with the spss 16.0 statistical software package (spss inc., chicago, il, usa). each eye was considered a single case to compare the io muscles’ function following myectomy and disinsertion. for evaluating the horizontal and vertical deviations, v pattern, or dvd, each patient was considered as one case for statistical evaluation. for describing data, mean ± standard deviation, frequency, and percentage were used. for evaluation of the difference between groups, the mann–whitney u-test, the wilcoxon signed-rank test, chi-square, and fisher exact tests were conducted. p-values < 0.05 were considered statistically significant. results overall, 36 patients (50 eyes) were enrolled in this study. the patients’ mean age was 12.67 ± 4.05 years (range, 6 to 22 years), and 52% of them were male. the mean follow-up time was 6.45 ± 4.3 and 7.03 ± 4.8 months in the myectomy and disinsertion groups, respectively (p = 0.359). fourteen patients had bilateral iooa (six patients in the myectomy and eight patients in the disinsertion groups); the same technique was used in bilateral cases. secondary iooa (ipsilateral superior oblique underaction) was found in 16 eyes, including 29.1% of the eyes in the myectomy group and 34.6% in the disinsertion group. table 1 represents the baseline demographic and clinical characteristics of the patients. they were matched in terms of age, sex, amount of vertical deviation, and the differences between groups were not statistically significant. 214 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 io disinsertion versus myectomy; abri aghdam et al table 1. baseline demographic and clinical characteristics of the patients. variable myectomy group disinsertion group p-value patient number (18 patients, 24 eyes) (18 patients, 26 eyes) age (yr) 13.47 ± 4.62 11.96 ± 3.39 0.938 sex (male/female) 10 (55.5%)/8 (44.4%) 9 (50%)/9 (50%) 0.605 mean follow-up (month) 6.45 ± 4.3 7.03 ± 4.8 0.359 unilateral/bilateral 12 (66.6%)/6 (33.38%) 10 (55.5%)/8 (44.4%) 0.781 bcva (logmar) 0.22 ± 0.14 0.23 ± 0.17 0.838 spherical equivalent +2.6 ± 3.01 +3 ± 3.24 0.515 primary/secondary iooa 17 (70.8%)/7 (29.2%) 17 (65.3%)/9 (34.7%) 0.573 bcva, best-corrected visual acuity; logmar, logarithm of the minimum angle of resolution; iooa, inferior oblique muscle overaction table 2. distribution of eyes with various grades of iooa and fundus torsion in each group preand postoperatively preoperative postoperative myectomy (24 eyes) disinsertion (26 eyes) myectomy (24 eyes) disinsertion (26 eyes) grade of iooa +4 5 (20.8%) 6 (21.13%) 0 0 +3 10 (41.6%) 13 (50%) 0 0 +2 9 (37.5%) 7 (26.9%) 3 (12.5%) 2 (7.6%) +1 0 0 10 (41.6%) 5 (19.2%) 0 or trace 0 0 11 (45.8%) 19 (73%) grade of fundus torsion +4 7 (29.1%) 6 (23.07%) 0 0 +3 11 (45.8%) 10 (38.4%) 0 0 +2 6 (25%) 10 (38.4%) 2 3 (11.5%) +1 0 0 11 (45.8%) 10 (38.4%) 0 or trace 0 0 11 (45.8) 13 (50%) iooa, inferior oblique overaction twenty-seven patients had concurrent horizontal deviations in the primary position (esotropia in 15 patients and exotropia in 12 cases) and received simultaneous surgery on the horizontal muscles during io weakening surgery. nine patients underwent io weakening alone. no v pattern was observed postoperatively. table 2 demonstrates the grades of iooa and fundus torsion in both groups before and after the surgery. the distribution of iooa was similar between the groups preoperatively (p = 0.867). at baseline, 62.5% of the eyes in the myectomy group and 73.1% in the disinsertion group had +3 or +4 iooa. the successful outcome was defined as the final io function of grade +1 or 0 and the fundus extorsion of grade 0 or +1. the success rate of surgery based on iooa grading was 87.4% and 92.3% in the myectomy and disinsertion groups, respectively (p = 0.780). the successful correction rate of abnormal fundus torsion was 91.6% in the myectomy group and 88.4% in the disinsertion group (p = 0.821). the median preoperative grade of iooa was +3 (with an interquartile range of +1) in both groups (p = 0.084). the median postoperative grade of iooa was +1 (with an interquartile range of +1) in both groups (p = 0.097). the median preoperative grade of fundus torsion was +3 (with an interquartile range of +2) in the myectomy group and +3 (with an interquartile range of +1) in the disinsertion group (p = 0.642). the median journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 215 io disinsertion versus myectomy; abri aghdam et al table 3. amount of hypertropia in the primary position and adduction before and after the surgery in the unilateral cases myectomy disinsertion before after p-value before after p-value ht in pp (pd) 12.7 ± 3.9 3.8 ± 2.6 0.001 13.42 ± 2.8 4.06 ± 2.7 0.001 ht in add (pd) 29.5 ± 9.32 9.15 ± 7.86 0.001 32.73 ± 12.42 12.65 ± 9.34 0.001 add, adduction; ht, hypertropia; pd, prism diopters; pp, primary position table 4. comparison of myectomy and disinsertion in the subgroups of primary and secondary iooa myectomy disinsertion p-value primary iooa 17 17 0.999 secondary iooa 7 9 0.742 mean reduction in ht in add (primary iooa) (pd) 20.86 ± 11.45 21.46 ± 12.76 0.864 mean reduction in ht in add (secondary iooa) (pd) 21.43 ± 11.38 22.42 ± 12.19 0.832 success rate based on iooa grading (primary iooa) 88.2% 88.2% 0.999 success rate based on grading of fundus torsion (primary iooa) 85.7% 100% 0.853 success rate based on the iooa grading (secondary iooa) 88.2% 88.2% 0.999 success rate based on the grading of fundus torsion (secondary iooa) 100% 85.7% 0.853 add, adduction; ht, hypertropia; iooa, inferior oblique overaction; pd, prism diopters; pp, primary position postoperative grade of fundus torsion was +1 (with an interquartile range of +1) in both groups (p = 0.960). table 3 shows the amount of hypertropia in the primary position and adduction before and after the surgery in both groups. the amount of hypertropia in the primary position and adduction significantly decreased in both groups (p = 0.001). there was no statistically significant difference between the two groups in terms of the mean reduction in hypertropia in the primary position (p = 0.086) and adduction (p = 0.187). table 4 demonstrates the comparison between the myectomy and disinsertion within two subgroups of primary and secondary iooa. no significant difference was found between the two subgroups regarding the mean reduction in hypertropia in the primary position, adduction, success rate based on iooa, and fundus torsion (all p-values > 0.05). postoperative io underaction was observed only in one case in the myectomy group. in one single case in the disinsertion group, iooa developed in the opposite eye. no new dvd was developed postoperatively. significant complications such as scleral perforation, retrobulbar hemorrhage, or fat adherence syndrome did not occur during the study period. discussion according to our results, both myectomy and io disinsertion techniques can improve iooa and achieve gratifying results. disinsertion of io muscle is a safe and effective treatment for most cases with iooa. jones et al performed io disinsertion on 337 patients and found a successful result in 88% of primary io disinsertion.[5] for secondary iooa, a successful result was reported in 72% of patients. similarly, duranglu[2] reported a success rate of 73.6% in the disinsertion group of patients with infantile esotropia and primary iooa.[13] our findings are also in line with previous findings of sanjari et al, who compared three surgical procedures for the treatment of iooa, including disinsertion, myectomy, and anterior transposition.[14] they concluded that all these procedures were useful for treating primary and secondary iooa with minimal side effects. one of the most common phenomena following unilateral io weakening procedures is the occurrence of iooa in the contralateral eye. the reported average time from the first disinsertion to the contralateral second disinsertion was about 23 months.[5] in our study, iooa in the opposite eye occurred only in only one eye in the disinsertion 216 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 io disinsertion versus myectomy; abri aghdam et al group. however, the length of follow-up is not enough to conclude. de angelis et al have observed multiple insertions and duplications of io muscles during surgery in 17% and 8% of cases, respectively.[12] they concluded that the recurrence of iooa following the weakening surgery might be due to incomplete muscle capture in the surgical procedure; however, we performed guyton’s exaggerated forced duction test for the io muscles at the end of surgery for all patients.[15] parks compared io muscle recession with disinsertion and myectomy.[16] he found a recession to be superior due to the occurrence of an adherence syndrome following some cases of disinsertion and myectomy. however, recession and myectomy are more complicated than disinsertion, and there is no logical reason for the development of adherent syndrome. we observed fat adherence syndrome neither in the myectomy nor in the disinsertion groups. in our study, the amount of preoperative hypertropia in the primary position and adduction was similar in both groups; therefore, the similar corrective effect of both surgical methods could be due to the same effect on the function of the inferior rectus muscle. wertz et al[2] studied the muscle length shortening following io myectomy and disinsertion surgery in rhesus monkeys. they observed a wide variation in the io reattachment site. therefore, the same weakening procedure for different amounts of iooa could result in similar outcomes, which might be related to the selfadjusting nature of io myectomy and disinsertion. they also found that the average muscle length was equal in both procedures after 6 to 20 weeks. io muscle shortened to two-thirds of its normal length. this similar effect on muscle length could also be the reason for a similar effect on muscle function and comparable postoperative outcomes. awadein and gawdat reported that symmetric io myectomy might have a symmetrizing effect in cases of asymmetric iooa.[17] they measured the degree of iooa and the degree of fundus torsion by guyton’s method and reported that the degree of fundus torsion in their cases did not always correlate with the degree of iooa; this finding may also relate to the self-adjusting nature of io muscle, which allows muscle retraction to find a proximal site of insertion. the degree of io tightness partially determines the new insertion site. the tightness of io muscle on the side with more overaction would cause more retraction and gain more proximal new insertion. akbari et al showed that io disinsertion effectively corrected primary position vertical deviation of unilateral congenital superior oblique palsy patients as io myectomy when preoperative vertical deviation was ≤15d.[18] however, when preoperative hypertropia was >15d, io myectomy had a more prominent effect in reducing primary position vertical deviation. however, the nonrandomized design of their study may confound these results. finally, chang et al reviewed four different io muscle-weakening surgeries for vertical strabismus in superior oblique palsy: myectomy, recession, anterior transposition, and disinsertion.[19] they could not find highquality evidence to support recommendations for surgical treatment choice in patients with vertical strabismus due to superior oblique palsy. nevertheless, this study showed that both io myectomy and io disinsertion are effective and safe treatments for iooa, and both techniques have similar successful results. disinsertion is a safe procedure eliminating clinically significant v pattern and high-grade extorsion, and it is not associated with any clinically significant under or overaction according to our results. disinsertion is also technically easier than myectomy with less bleeding, and io muscle is preserved for potential future surgeries if needed. the present study has several limitations, including a small sample size in each group, short follow-up time, and subjective measurement of fundus torsion. a randomized controlled trial with a large sample size and longer follow-up could lead to more accurate results. in conclusion, both disinsertion and myectomy can effectively reduce the degree of iooa, and the success rate is comparable in the two surgical methods. financial support and sponsorship nil. conflicts of interest the authors do not have any conflicts of interest. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 217 io disinsertion versus myectomy; abri aghdam et al references 1. caldeira j. v-pattern esotropia: a review; and a study of the outcome after bilateral recession of the inferior oblique muscle: a retrospective study of 78 consecutive patients. binocul vis strabismus q 2003;18:35–48; discussion 49– 50. 2. wertz rd, romano pe, wright p. inferior oblique myectomy, disinsertion, and recession in rhesus monkeys. arch ophthalmol 1977;95:857–860. 3. kushner bj. multiple mechanisms of extraocular muscle ”overaction”. arch ophthalmol 2006;124:680–688. 4. jaeger ea, tasman w. duane’s ophthalmology. philadelphia, pa: lippincott williams & wilkins; 2009. 5. jones tw, lee da, dyer ja. inferior oblique surgery: experience at the mayo clinic from 1960 to 1981. arch ophthalmol 1984;102:714–716. 6. dyer ja. tenotomy of the inferior oblique muscle at its scleral insertion: an easy and effective procedure. arch ophthalmol 1962;68:176–181. 7. mulvihill a, murphy m, lee jp. disinsertion of the inferior oblique muscle for treatment of superior oblique paresis. j pediatr ophthalmol strabismus 2000;37:279. 8. yanyali a, elibol o, talu h, karabas l, alp b, caglar y. a comparative study of the effectiveness of disinsertion and anterior transposition of the inferior oblique in the treatment of unilateral superior oblique palsy. strabismus 2001;9:83–90. 9. rajavi z, molazadeh a, ramezani a, yaseri m. a randomized clinical trial comparing myectomy and recession in the management of inferior oblique muscle overaction. j pediatr ophthalmol strabismus 2011;48:375–380. 10. guyton dl. ocular torsion reveals the mechanisms of cyclovertical strabismus the weisenfeld lecture. invest ophthalmol vis sci 2008;49:847–857. 11. guyton dl. clinical assessment of ocular torsion. am orthopt j 1983;33:7–15. 12. de angelis d, makar i, kraft sp. anatomic variations of the inferior oblique muscle: a potential cause of failed inferior oblique weakening surgery. am j ophthalmol 1999;128:485–488. 13. duranoglu y, yücel í, kivrakdal s. comparison of the inferior oblique weakening by disinsertion or disinsertionresection and tucking in the patient with infantile esotropia. ann ophthalmol 2006;38:29–33. 14. sanjari ms, shahraki k, nekoozadeh s, tabatabaee s-m, shahraki k, aghdam ka. surgical treatments in inferior oblique muscle overaction. j ophthalmic vis res 2014;9:291. 15. guyton dl. exaggerated traction test for the oblique muscles. ophthalmology 1981;88:1035–1040. 16. parks mm. the weakening surgical procedures for eliminating overaction of the inferior oblique muscle. am j ophthalmol 1972;73:107–122. 17. awadein a, gawdat g. bilateral inferior oblique myectomy for asymmetric primary inferior oblique overaction. j aapos 2008;12:560–564. 18. akbari mr, sadeghi am, ghadimi h, nikdel m. outcome of inferior oblique disinsertion versus myectomy in the surgical treatment of unilateral congenital superior oblique palsy. j aapos 2019;23:77.e1–77.e6. 19. chang my, coleman al, tseng vl, demer jl. surgical interventions for vertical strabismus in superior oblique palsy. cochrane database syst rev. 2017;11:cd012447– cd. 218 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 review article ocular manifestations of patients with coronavirus disease 2019: a comprehensive review amirhossein roshanshad1,2, md; mohammad ali ashraf1,2, md; romina roshanshad1,2, md ali kharmandar3,4, md; seyed alireza zomorodian1, md; hossein ashraf2, md 1student research committee, shiraz university of medical sciences, shiraz, iran 2poostchi ophthalmology research center, shiraz university of medical sciences, shiraz, iran 3non-communicable disease research center, fasa university of medical sciences, fasa, iran 4health policy research center, institute of health, shiraz university of medical sciences, shiraz, iran orcid: amirhossein roshanshad: https://orcid.org/0000-0001-6725-0045 hossein ashraf: https://orcid.org/0000-0003-4429-1658 abstract apart from conjunctival involvement which is the most well-known ocular manifestation of coronavirus infectious disease 2019 (covid-19), there are multiple reports of the involvement of other ocular structures by severe acute respiratory syndrome coronavirus 2 (sars-cov-2). we comprehensively reviewed pubmed, scopus, embase, and google scholar for available evidence regarding covid-19 various ocular manifestations, with special focus on less known and unusual ocular findings. we then categorized the findings based on the parts of the eye which was involved. in anterior sections of the eye, the involvement of the eyelid (tarsadenitis), conjunctiva and cornea (follicular conjunctivitis, pseudomembranous conjunctivitis, and keratoconjunctivitis), episclera (nodular episcleritis), uvea (anterior uveitis) were reported. also, third, fourth, and sixth nerve palsy, retinal vasculitis, retinal optical coherence tomography (oct) changes (hyper-reflective lesions and increased retinal nerve fiber layer thickness [rnflt]), optic neuritis, papillophlebitis, miller fisher syndrome, posterior reversible leukoencephalopathy (pres), ophthalmic artery and central retinal artery occlusion, and polyneuritis cranialis were reported in different studies. postmortem evaluation of covid-19 patients detected no viral rna in different anterior and posterior segments of the eyes. however, another study revealed a 21.4% positivity of the retinal biopsies of dead patients. the results of this study can help ophthalmologists to be vigilant when they see these findings in a suspected case of covid-19. in addition, wearing face masks and protective goggles or eye shields are recommended, especially in high risk contacts. keywords: coronavirus; covid-19; manifestations; ocular; ophthalmologic j ophthalmic vis res 2021; 16 (2): 234–247 234 © 2021 roshanshad et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9087&domain=pdf&date_stamp=2019-07-17 ocular manifestations of covid-19; roshanshad et al introduction since december 2019, coronavirus has caused more than 990,000 deaths and contamination of more than 32.7 million people globally till september 27, 2020.[1] coronavirus disease 2019 (covid-19) can be transmitted directly through person to person contacts via droplets released during sneezing or coughing. indirect transmission of severe acute respiratory syndrome coronavirus 2 (sars-cov-2) through surface contamination can be regarded as the second way of getting infected.[2–4] in addition, sars-cov-2 has been detected in tears and conjunctival secretions of infected people.[5] therefore, adhering to personal hygiene principles is a fundamental part of covid19 prevention, especially for healthcare workers. ophthalmologists are at high risk of contracting covid-19 due to their close contact with the patients during routine ophthalmologic exams such as slit lamp examinations and direct ophthalmoscopy.[6] also, the patients’ prolonged stay at ophthalmology clinics for multiple ophthalmology examinations imposes ophthalmologists and other patients at increased risk of covid-19.[7] a recent study revealed a high probability of contamination of environmental surfaces of ophthalmology clinics.[8] ocular presentations of covid-19 usually occur about two weeks after the first symptoms. however, it can be the presenting finding of newly diagnosed covid-19 patients, especially when the virus enters from the eye mucosa.[9] consequently, knowing the latest presentations of covid-19 is crucial for every ophthalmologist. it helps ophthalmologists to consider covid-19 as a possible causative agent when they see these findings. like sars-cov, angiotensin-converting enzyme 2 (ace 2) receptor is the mediator of sarscov-2 for entering the host cells.[10–12] ace 2 receptor is expressed in different human tissue, correspondence to: hossein ashraf, md. poostchi ophthalmology research center, zand blvd, poostchi st, shiraz, iran. e-mail: hosseinashraf@yahoo.com received: 03-10-2020 accepted: 10-01-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9087 including the pulmonary system, proximal tubule of kidney and bladder urothelium, myocardial cells, esophagus, and ileum.[13] in the eye, ace 2 receptor expression is reported in the conjunctiva, limbus, cornea, retina, and aqueous humor.[14–17] it was thought earlier that covid-19 only involves conjunctiva, cornea, and tear. however, recent studies have revealed the involvement of the other eye structures, such as eyelid, episcleral, and retina. therefore, we gathered available data about ocular manifestations of covid-19, focusing on recently reported manifestations. methods we systematically searched four databases, including medline (pubmed), scopus, embase, and google scholar for articles about ocular manifestations of covid-19. we used the following keywords for searching the databases : (“coronavirus” or “covid-19” or “2019-ncov” or “sars-cov-2”) and (“ocular” or “eye” or “cornea” or “conjunctivitis” or “conjunctiva” or “conjunctival” or “congestion” or “uvea” or “uveitis” or “retina” or “retinal” or “retinitis” or “optic” or “lens” or “chemosis” or “blepharitis” or “ophthalmic” or “ophthalmologic” or “ophthalmoplegia” or “ophthalmoparesis” or “nerve palsy”). we also searched the references of the included studies for more relevant articles. the primary search was done on june 19, 2020 and was updated on august 27, 2020. the inclusion criteria were original articles about the ocular manifestations of covid-19 patients. case reports and case series, letters, and editorials were also included. studies without any information about ocular manifestations of covid-19 were excluded. also, some of the studies reporting duplicate and repeated well-known ocular manifestations of covid-19 were excluded, and the main focus was put on the less reported ophthalmologic presentations. included studies were categorized in this study and divided based on the involved part of the eye. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: roshanshad a, ashraf ma, roshanshad r, kharmandar a, zomorodian sa, ashraf h. ocular manifestations of patients with coronavirus disease 2019: a comprehensive review. j ophthalmic vis res 2021;16:234–247. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 235 https://knepublishing.com/index.php/jovr ocular manifestations of covid-19; roshanshad et al we used joanna briggs institute (jbi)’s critical appraisal tool[18] to assess the risk of bias of the included studies. the scores were calculated as percentages and studies with scores of >60% and <30% of total scores were regarded as lowand high risk of bias, respectively. title and abstract screening, data extraction and risk of bias assessment were done by two authors (ar and ma) independently and disagreements were checked by another author (rr). as shown in figure 1, a total of 5,288 studies were initially found after searching the databases according to the aforementioned search strategy. after title and abstract screening, 85 studies were chosen for full-text evaluation. finally, 40 studies were matched with our inclusion criteria to enter the study. conjunctival involvement and conjunctival and tear covid-19 pcr positivity have been reported before. furthermore, there are several reports of some rare ocular manifestations of covid-19, which are unfamiliar to many ophthalmologists and physicians. therefore, we summarized the conjunctival findings part in our study and focused more on the less reported and less known ocular manifestations. the findings of each part of the eye are discussed separately. ocular manifestations eyelid a woman from wuhan, china, who presented with lower eyelid swelling, pain, and tenderness in the lateral canthus of the right eye was diagnosed as acute tarsadenitis. the patient had visited her parents who had tested positive for covid-19 one day before the onset of these manifestations. along with the resolution of tarsadenitis, the patient developed subconjunctival hemorrhage. radiologic and pcr test results were in favor of covid-19 infection.[19]another study reported multiple cases of chalazion in three icu nurses and ten additional cases in a hospital in paris.[20] pcr results of the icu nurses were negative. because of the role of bacterial infection in eyelid disorders such as blepharitis and meibomian gland diseases,[21, 22] it is far from the mind that sars-cov-2 itself could be responsible for the observed tarsadenitis and chalazion. however, it is thought that the cluster of chalazion was mainly due to the occupational conditions while managing covid-19 patients. firstly, prolonged use of eye goggles and the following reduced eye blinking can facilitate the evaporation of the tear film and hardening of the meibomian gland secretions. secondly, the use of some disinfectants for cleaning eye shields can be irritating for the eyes.[20] thirdly, due to the role of blood supply on fat synthesis, we hypothesize that impaired blood flow due to the hypercoagulable state in covid-19 patients[23] can change the composition of meibomian gland secretions and predispose the eyes to bacterial infection and following meibomian gland infection and tarsadenitis.[24] summary of the findings of eyelid, ocular surface, uvea, episclera, and ocular motor nerves are presented in table 1. ocular surface: conjunctiva and cornea hyperemia, epiphora, increased secretion, chemosis, and follicular conjunctivitis are the main symptoms of conjunctival involvement with sars-cov-2.[25] based on the “report of the who−china joint mission on coronavirus disease 2019 (covid−19),” conjunctival congestion occurs in about 0.8% of covid-19 patients.[26] however, other studies showed higher rates. in chen et al study, about 5% of covid-19 patients had conjunctival congestions, 15% of whom as the initial presentations. another study showed that 3.1% of covid-19 patients presented with conjunctivitis, 0.7% of whom as the first symptom of the disease.[27] a high prevalence of conjunctivitis was reported to be 32% in wu et al’s study.[9] a meta-analysis stated that the overall prevalence of conjunctivitis among covid-19 patients is about 1.1%. it also showed that this prevalence was 0.7% in non-severe cases and 3% in severe ones.[28] common ocular symptoms of conjunctival congestion are increased conjunctival secretion, ocular pain, photophobia, dry eye, and tearing. it was also shown that conjunctival congestion is higher in patients with more hand– eye contact.[29] in another study, a patient presented with conjunctival hyperemia, secretion, follicles, petechiae, tarsal hemorrhages, and chemosis with easily removed yellowish membrane on the tarsal conjunctiva of the lower lids. he was diagnosed as pseudomembranous conjunctivitis and punctate keratitis.[30] 236 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 ocular manifestations of covid-19; roshanshad et al records iden!fied through database searching pubmed 1195 embase 1173 scopus 2723 google scholar 157 (n = 5248) s c re e n in g in c lu d e d e li g ib il it y id e n ! fi c a ! o n addi!onal records iden!fied through other sources (n = 40) records a#er duplicates removed (n = 3450 ) records screened (n = 3450 ) records excluded (n = 3365 ) full-text ar!cles assessed for eligibility (n = 85 ) full-text ar!cles excluded, with reasons (n = 45 ) studies included in qualita!ve synthesis (n = 40 ) figure 1. prisma flow chart of the screened and assessed articles. positive sars-cov-2 detection in conjunctival samples or ocular secretions has been reported in several studies.[31, 32] a systematic review showed that conjunctival/tear pcr samples were positive in about 2% of covid-19 patients.[27] different studies revealed variation in positive pcr rate from 3 to 16%, with an average of 5.8%.[33] these variations may be due to the technical problems during collecting, keeping, and handling of the specimen, low viral load in the conjunctival secretion of some participants, and also the difference between the severity of the disease in different studies.[34, 35] journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 237 ocular manifestations of covid-19; roshanshad et al reminding the experience with sars-cov1 increased transmission during unprotected eye contacts,[36] and possible transmission of sars-cov-2 through the conjunctiva, wearing protective goggles should become routine among healthcare workers with high risk contacts.[37] it should be kept in mind that keratoconjunctivitis can be the initial manifestation of patients with covid-19 infection.[38] therefore, first-line healthcare providers should ask questions regarding other manifestations of covid-19 like fever and cough and a history of suspicious contact in patients presenting with a red eye. it is also revealed that conjunctival/tear pcr samples may be positive in some patients despite not having any ocular manifestations.[27] it prompts the need for adherence to protective measures and wearing personal protective equipment even if no clinical symptoms are observed. episcleral involvement a case of episcleritis was reported in spain. a woman came with cough, myalgia, anosmia, and ageusia and had a positive pcr result for covid-19. after these symptoms were resolved, she came to the ophthalmologic clinic with red eye, foreign-body sensation, epiphora, and photophobia, and nodular episcleritis was diagnosed. besides, a study from turkey revealed a 2.2% prevalence of episcleritis in covid-19 patients. it was also shown that episcleritis was associated with a higher d-dimer level.[25] the relationship between episcleritis and other viruses such as ebola, hbv, hcv, and herpes zoster and immune-vascular factors and thrombotic complications of covid-19 have risen the suspicion of the role of covid-19 in developing episcleritis.[39] glaucoma and uveitis a case of bilateral anterior uveitis following multisystem inflammatory syndrome in a covid19 patient has been reported so far.[40] in addition, the involvement of uvea in other animals has been reported by other coronaviruses.[41, 42] to the best of our knowledge, no study has reported glaucoma as a presentation of covid-19 yet. however, herpes virus detection in the trabecular meshwork and the following trabeculitis can result in intraocular pressure (iop) elevation.[43] cytomegalovirus (cmv)-related anterior uveitis and the following rise of iop in immunocompetent patients have been reported before, which is accompanied by the detection of cmv-dna in aqueous humor.[44–47] hypertensive anterior uveitis can present with acute, recurrent, or chronic symptoms. by knowing the expression of ace 2 receptor in aqueous humor[16] and the role of cmv, herpes simplex virus, and ebola virus in developing uveitic glaucoma, we can hypothesize the possible role of sars-cov2 in developing, exacerbation, or recurrence of glaucoma.[43, 44, 48] therefore, it is not far from the mind that there will be more reports of uvea involvement or glaucoma progression in the future. if so, ophthalmologists should consider covid-19 infection in patients with suspicious symptoms of sars-cov-2 and recurrent rise of iop. ophthalmoparesis and nerve palsy dinkin et al reported two cases with ophthalmoparesis after their covid-19 pcr became positive. in the first case, the patient developed areflexia, third nerve palsy of the left eye, and sixth nerve palsy of the right eye, resulting from immune response to the virus or direct invasion of the virus and the following demyelination process.[49] the second case presented with diplopia, abduction deficit, and optic nerve sheath enhancement of the right eye, suggesting optic nerve involvement. however, whether optic nerve involvement resulted from cns invasion of the virus or it was only a coincidence is not clear.[50, 51] in spite of the intact abducens nerve in mri, sixth nerve palsy could not be ruled out in this case. in falcone et al’s study, a patient developed diplopia and abduction deficit three days after the onset of the respiratory symptoms. mri findings showed lateral rectus atrophy and denervation, all of which favored complete abducens nerve palsy.[52] another study revealed bilateral trochlear nerve palsy in a covid-19 patient with evidence of cerebral vasculitis in brain mri.[53] overall, all of the aforementioned cranial nerve involvements can be the spectrum of neurological manifestations of covid-19, caused by either direct involvement of 238 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 ocular manifestations of covid-19; roshanshad et al table 1. characteristics and main findings of the included studies (eyelid, ocular surface, episcleral, uveal, and ocular motor nerve findings) first author∗ date of publication number of cases risk of bias ocular manifestations or findings additional findings/remarks diagnosis eyelid xu[19] april 2020 1 medium pain in the lateral canthus and lower eyelid swelling the same as symptoms tarsadenitis megarbane†[20] may 2020 3 high red eye, painless eyelid swelling, and tearing in three cases single non-tender inflammatory nodules in the middle of the lower eyelid, conjunctival redness without altered visual acuity or corneal abrasion chalazion conjunctiva and cornea bostanci ceran[25] june 2020 93 low 21% of the patients had ocular problems. photophobia (16.1%), itchiness (15.7%), burning sensation (8.4%), gritty feeling (6%), blurred vision (4.8%) hyperemia (21.5%), epiphora (9.7%), increased secretion (6.5%) chemosis (3.2%), follicular conjunctivitis (8.6) who[26] february 2020 55,924 n/a 0.8% of the patients had conjunctival congestion loffredo[28] april 2020 1,167 medium overall rate of conjunctivitis was 1.1%; 0.7% in non-severe cases and 3% in severe cases chen[29] may 2020 535 high increased conjunctival secretion (9.7%), ocular pain (4.3%), photophobia (3%), dry eye (21%) and tearing (10.3%) 5% had conjunctival congestion, 15% of whom as the initial finding. other findings were: conjunctivitis (6.2%), xerophthalmia (4.5%), and keratitis (2.6%) navel[30] may 2020 1 low follicles, petechias, tarsal hemorrhages, and chemosis mucous filaments and tarsal pseudomembranous pseudomembranous conjunctivitis cheema[38] april 2020 1 low red eye, watery discharge, photophobia conjunctival injection, follicles, pseudodendrite in the cornea, and subepithelial infiltrates with overlying epithelial defects at the limbus keratoconjunctivitis wu[9] 38 high 31.6% had ocular manifestations consistent with conjunctivitis including hyperemia (7.9%), chemosis (21%), epiphora (18.4%), or increased secretions (18.4%) journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 239 ocular manifestations of covid-19; roshanshad et al table 1. continued) first author∗ date of publication number of cases risk of bias ocular manifestations or findings additional findings/remarks diagnosis sarma[27] april 2020 854 low 3.2% had conjunctivitis/red eye, 0.7% reported conjunctivitis as the first symptom of the disease. 2% positive conjunctival/tear pcr samples chen[31] april 2020 1 low positivity of conjunctival swab specimens till 19 days after the disease onset conjunctivitis colavita[32] august 2020 1 medium higher viral load in late ocular samples than nasal swabs positivity of ocular samples till 21 days after the disease onset conjunctivitis aiello[33] may 2020 252 medium 12/204 (5.8%) had positive pcr of conjunctival swab episclera mendez mangana[39] june 2020 1 low red eye, foreign-body sensation, epiphora, and photophobia elevated epibulbar area with hyperemia at the inferotemporal sector without fluorescein defect nodular episcleritis bostanci ceran[25] june 2020 93 low 2.2% of the patients had episcleritis episcleritis uvea and glaucoma bettach[40] june 2020 1 low bilateral blurry vision conjunctival hyperemia, central corneal edema with descemet’s membrane folds, multiple keratic precipitates, and +1 anterior chamber cells and flare anterior uveitis ocular motor nerve dinkin[49] may 2020 2 high case 1: ptosis, diplopia case 2: diplopia, abduction deficit case 1: mydriasis, ptosis and limited depression, adduction, and abduction case 2: enhancement of the optic nerve sheaths and posterior tenon capsules case 1: third and sixth nerve palsy case 2: optic nerve involvement falcone[52] june 2020 1 medium binocular diplopia esotropia and limitation of abduction of the left eye. atrophic left lateral rectus muscle in mri sixth nerve palsy de oliveira[53] june 2020 1 low binocular diplopia and occipital headache mri showed vertebrobasilar system vasculitis, inflammation in the periaqueductal region and trochlear nuclei topography fourth nerve palsy *the studies are categorized based on the section of the eye involved in a study †in this study, participants were three nurses working in a covid-19 icu but had negative pcr test results n/a, not available 240 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 ocular manifestations of covid-19; roshanshad et al table 2. characteristics and main findings of the included studies (retina, neuro–ophthalmology, thromboembolic, and postmortem findings) first author∗ date of publication number of cases risk of bias ocular manifestations or findings additional findings/remarks diagnosis retina casagrande[55] may 2020 14 medium positivity of retinal biopsy samples in 3 of 14 (21.4%) covid-19 patients marinho[56] may 2020 12 high hyper-reflective lesions in ganglion cell and inner plexiform layers more obvious at the papillomacular bundle, normal oct-angiography and ganglion cells complex analysis in all patients, cotton wool spots and microhemorrhages in four (33.3%) patients quintanacastanedo[59] july 2020 1 high visually asymptomatic retinal vasculitis on the equator of the left eye, one perivascular infiltrate, and extended retinal exudates retinal vasculitis burgosblasco[60] july 2020 5 medium visually asymptomatic seven out of eight (87.5%) eyes showed an increase in rnflt insaustigarcía[61] july 2020 1 low reduced sensitivity of the visual field in left eye tortuous and dilated retinal vessels, retinal hemorrhages, and disc edema papillo-phlebitis raony[62] june 2020 0 n/a cytokine storm can aggravate retinal lesions in infected patients with dm. cd-147 may also facilitate retinal invasion of sars-cov-2 neuro-ophthalmology gutiérrezortiz[70] april 2020 2 medium case 1: right ino and fascicular oculomotor palsy case 2: bilateral abducens palsy case 1: albuminocytologic dissociation, positive gd1b-igg antibodies case 2: albuminocytologic dissociation case 1:mfs case 2: polyneuritis cranialis lantos[71] may 2020 1 low left eye drooping, blurry vision, reduced sensation in both legs, ataxia third cranial nerve enhancement and enlargement in mri consistent with third nerve palsy, bilateral sixth nerve palsy decreased sensation below the knees to all modalities mfs kaya[73] april 2020 1 medium acute confusional state, vision loss mri showed vasogenic edema similar to posterior reversible leukoencephalopathy (pres) pres doo†[74] july 2020 2 high visually asymptomatic bilateral posterior cerebral vasogenic edema in one case pres journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 241 ocular manifestations of covid-19; roshanshad et al table 2. continued) first author∗ date of publication number of cases risk of bias ocular manifestations or findings additional findings/remarks diagnosis agarwal†[75] august 2020 115 high 30% of covid-19 patients with brain mri had leukoencephalopathy and/or cerebral microbleeds cariddi[76] june 2020 1 high blurred vision, altered mental status decreased nasolabial fold, tone and strength of the legs, and all deep tendon reflexes pres parauda†[77] july 2020 4 high visually asymptomatic imaging showed cerebral vasogenic edema in four cases pres zhou[78] june 2020 1 medium bilateral subacute vision loss of both eyes. pain with eye movements bilateral disc edema and venous congestion. retinal perivenous hemorrhages in the right eye. positive mog-igg. both optic nerve enhancement optic neuritis associated with mog-igg thromboembolic events dumitrascu[79] may 2020 1 medium sudden onset vision loss, no light perception retinal and optic disc edema, retinal exudates, attenuated retinal vessels, and absent macular cherry-red spot ophthalmic artery occlusion acharya[80] june 2020 1 high sudden onset vision loss indistinct optic nerve margins, cherry red spot, significant retinal whitening central retinal artery occlusion postmortem findings casagrande[55] may 2020 14 medium mentioned in the retinal findings part löffler[86] june 2020 3 high case 1: optic atrophy case 2: epiretinal gliosis, retinal paving-stone and spot bleeding, and drusen case 3: amd, macular atrophy, photoreceptor loss of outer retina, choroid thinning, and pinguecula case 1: ms case 2: diabetic and hypertensive case 3: parkinsonism bayyoud[87] june 2020 5 medium no viral rna in samples of corneal stroma, endothelium and epithelium, conjunctival fluid swabs, bulbar-limbal conjunctiva, anterior chamber fluid bayyoud[88] june 2020 1 low no viral rna in conjunctival fluid swabs, bulbar conjunctiva, corneal epithelium, stroma, and endothelium, anterior chamber fluid, lens, iris, vitreous, retina, uvea, sclera, and optic nerve fuest[89] july 2020 23 medium no viral rna in conjunctival swabs *the studies are categorized based on the section of the eye involved in a study †in these studies, the patients did not have any ophthalmologic findings or symptoms; however, due to the presence of ocular manifestations in some patients with pres and leukoencephalopathy, the studies were included ino, internuclear ophthalmoplegia; gd1b-igg antibody, antibody against ganglioside complex gd1b; mog, myelin oligodendrocyte glycoprotein; pres, posterior reversible leukoencephalopathy; mfs, miller fisher syndrome; n/a, not available 242 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 ocular manifestations of covid-19; roshanshad et al the cns, excessive cytokine release, or endothelial dysfunction.[54] retinal findings a study on retinal biopsies of 14 deceased patients with covid-19 showed positivity of sars-cov-2 in three (21%) of them.[55] it is in line with the expression of ace 2 receptor in the human retina.[15] another study evaluated retinal findings in covid-19 patients. it revealed hyperreflective lesions at the level of ganglion cell and inner plexiform layers. besides, four patients had microhemorrhages and cotton wool spots. other ophthalmologic investigations, including oct angiography and ganglion cells complex analysis, visual acuity, and pupillary reflexes, were normal.[56] due to the previous reports of retinitis in animals and these two reports,[57, 58] the involvement of retina by sars-cov-2 is expectable. interestingly, a patient was diagnosed with retinal vasculitis without any ophthalmologic symptoms.[59] however, because of the absence of a control group and low sample size in this study, it is hard to differentiate whether sars-cov-2 or incidental findings cause these findings. another study compared oct findings of optic nerve before and after covid-19 infection in eight eyes of five patients. this study revealed an overall increase in rnflt in seven of eight eyes, which can result from optic nerve inflammation.[60] aggravation of retinal lesions in diabetic retinopathy and papillophlebitis were also attributed to sars-cov-2-induced cytokine storm and inflammatory process in two studies.[61, 62] in addition to the direct involvement of the retina by sars-cov-2, covid-19 can alter the pattern of some retinal diseases. studies showed that covid-19 lockdown was associated with less or delayed presentation and diagnosis of retinal detachment[63] and a higher prevalence of proliferative vitreoretinopathy, accompanied by a lower response to surgery.[64, 65] summaries of the retinal, neuro-ophthalmologic, thromboembolic, and postmortem findings are presented in table 2. neuro-ophthalmologic manifestations like sars-cov, cns involvement is seen in covid-19 infection due to the expression of ace2 receptor in nervous tissue and high affinity of sars-cov and sars-cov-2 with this receptor.[66, 67] guillain-barré syndrome in covid-19 patients has been reported in several studies.[51, 68, 69] also, miller fisher syndrome, a variant of guillain-barré syndrome presenting with ophthalmoplegia has been observed in covid-19 infection.[70, 71] in gutiérrez-ortiz et al’s study, the first patient presented with fascicular oculomotor palsy and internuclear ophthalmoparesis of the right eye, and the second patient had bilateral abducens nerve palsy. both of them had albuminocytologic dissociation, areflexia, and positive oropharyngeal pcr swab test, and covid-19 was confirmed. while the first patient was a miller fisher syndrome case, the second was diagnosed as polyneuritis cranialis.[70] in another study, a case with a previous history of strabismus of the left eye presented with left oculomotor nerve palsy, and after workup, miller fisher syndrome was diagnosed. the nasopharyngeal pcr test was positive for covid-19. mri showed significant enlargement and enhancement of the third cranial nerve. later, the patient manifested with bilateral abducens nerve palsy.[71] in another study conducted by kaya et al, a 38-year-old man was admitted due to covid-19 developing with sudden onset vision loss. brain mri findings showed vasogenic edema similar to what is observed in pres. the exact association between sars-cov-2 and pres and the etiology of pres is not clear in this study. however, due to the neurotropism of sars-cov-2,[72] it is thought that pres can be the result of direct invasion of the virus and the inflammatory process in the setting of covid-19 infection.[73] it should be mentioned that several other studies reported pres as a rare presentation of covid-19, especially in severely ill patients.[74–77] the severity of vision loss varies significantly in these studies, ranging from blurred vision to severe vision loss detecting only hand motions. we also found a report of optic neuritis associated with the myelin oligodendrocyte glycoprotein (mog) antibody and covid-19 infection, which can be another aspect of the neuro–ophthalmologic manifestations of covid19.[78] thromboembolic event dumitrascu et al presented the first ocular vascular complication of covid-19. a 48-year-old journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 243 ocular manifestations of covid-19; roshanshad et al obese man with severe covid-19 infection and following upper and lower extremities dvts was discharged from the hospital. firstly, enoxaparin was administered for him, but later, it was changed to apixaban. one day after the apixaban start, he developed sudden onset vision loss of right eye without light perception and obvious relative afferent pupillary defect. based on this history and a funduscopic examination, incomplete ophthalmic artery occlusion (oao) was diagnosed.[79] a case of central retinal artery occlusion was also reported in a patient with confirmed covid-19 infection. interestingly, contrary to the former case, no previous history of thrombotic events and anticoagulant consumption were reported for this patient.[80] due to the hypercoagulability state caused by covid-19 infection,[81–83] ophthalmologists should consider sars-cov-2 as a possible cause of oao in patients with acute vision loss, especially in ones with underlying hypercoagulability state or thrombophilia. also, more studies are needed to determine the optimal anticoagulant in covid-19 patients to prevent such complications, especially in those with a hypercoagulable state.[84, 85] post-mortem findings in löffler et al’s study, three patients were evaluated for postmortem ocular findings. the findings were mainly due to their underlying diseases and conditions. for example, optic atrophy was found in a multiple sclerosis patient, and epiretinal gliosis, retinal paving-stone and spot bleeding, and drusen were observed in a diabetic hypertensive case. the third case, a 95year-old patient with parkinsonism, presented with age-related macular degeneration (amd), macular atrophy, photoreceptor loss of the outer retina, choroid thinning, and pinguecula; in addition, autolytic changes were seen in microscopic evaluation of three cases. in another study, three of 14 retinal samples were positive for sars-cov-2 rdrp-gene, e-gene, and orf ncov-gene-specific sequences, which is consistent with the existence of ace 2 receptors in human retinal cells.[15, 55, 86] however, due to the absence of data on examining these patients before covid-19 infection, we cannot ensure that coronavirus did not have any role in the occurrence or aggravation of these presentations. additionally, three other studies evaluated the sars-cov-2 positivity in different ocular tissues of 29 deceased patients, all of which were negative.[87–89] overall, it seems that there is a low risk of ocular tissue involvement by sars-cov-2. however, studies with more sample sizes are needed to confirm this assumption. these findings should be considered when designing ophthalmology practice guidelines and criteria for corneal donors in the covid-19 era. other coronaviruses have been reported to cause pyogranulomatous anterior uveitis, optic neuritis, choroiditis with retinal detachment, and retinal vasculitis in animals.[41, 42] due to the presence of ace 2 receptors in the ciliary body, vitreous body, and muller cells,[90, 91] there may be further reports of the involvement of ocular structures by sars-cov-2 not reported yet. it also prompts ophthalmologists to remain vigilant about ocular manifestations of covid-19. furthermore, adhering to eye hygiene principles not only reduces the risk of sars-cov-2 transmission through the eye, but also reduces the risk of dry eye, bacterial infections, and the following ocular disorders. acknowledgment the authors would like to thank the research consultation center (rcc) of shiraz university of medical science for their assistance in revising the manuscript. financial support and sponsorship this project was not funded or sponsored by any agency or organization. conflicts of interest the authors have no competing interests to declare. references 1. chou r, dana t, buckley di, selph s, fu r, totten am. epidemiology of and risk factors for coronavirus infection in health care workers. ann intern med 2020;173:120–136. 2. douglas kaa, douglas vp, moschos mm. ocular manifestations of covid-19 (sars-cov-2): a critical review of current literature. in vivo 2020;34:1619–1628. 3. rothan ha, byrareddy sn. the epidemiology and pathogenesis of coronavirus disease (covid-19) outbreak. j autoimmun 2020:102433. 244 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 ocular manifestations of covid-19; roshanshad et al 4. santarpia jl, rivera dn, herrera vl, morwitzer mj, creager hm, santarpia gw, et al. aerosol and surface contamination of sars-cov-2 observed in quarantine and isolation care. sci rep 2020;10:12732. 5. xia j, tong j, liu m, shen y, guo d. evaluation of coronavirus in tears and conjunctival secretions of patients with sars-cov-2 infection. j medical virology 2020;92(??):589-594. 6. lai tht, tang ewh, chau sky, fung ksc, li kkw. stepping up infection control measures in ophthalmology during the novel coronavirus outbreak: an experience from hong kong. graefes arch clin exp ophthalmol 2020;258:1049–1055. 7. cadet j. harmless effects of sterilizing 222-nm far-uv radiation on mouse skin and eye tissues. photochem photobiol 2020;96:949–950. 8. aytoğan h, ayintap e, y�lmaz nö. detection of coronavirus disease 2019 viral material on environmental surfaces of an ophthalmology examination room. jama ophthalmol 2020;138:990–993. 9. wu p, duan f, luo c, liu q, qu x, liang l, et al. characteristics of ocular findings of patients with coronavirus disease 2019 (covid-19) in hubei province, china. jama ophthalmol 2020;138:575. 10. wan y, shang j, graham r, baric rs, li f. receptor recognition by the novel coronavirus from wuhan: an analysis based on decade-long structural studies of sars coronavirus. j virol 2020;94:e00127–e00200. 11. li w, moore mj, vasilieva n, sui j, wong sk, berne ma, et al. angiotensin-converting enzyme 2 is a functional receptor for the sars coronavirus. nature 2003;426:450– 454. 12. letko m, marzi a, munster v. functional assessment of cell entry and receptor usage for sars-cov-2 and other lineage b betacoronaviruses. nat microbiol 2020;5:562– 569. 13. zou x, chen k, zou j, han p, hao j, han z. single-cell rnaseq data analysis on the receptor ace2 expression reveals the potential risk of different human organs vulnerable to 2019-ncov infection. front med 2020;14:185–192. 14. zhou l, xu z, castiglione gm, soiberman us, eberhart cg, duh ej. ace2 and tmprss2 are expressed on the human ocular surface, suggesting susceptibility to sars-cov-2 infection. ocul surf 2020;18:537–544. 15. senanayake pd, drazba j, shadrach k, milsted a, runggerbrandle e, nishiyama k, et al. angiotensin ii and its receptor subtypes in the human retina. invest ophthalmol vis sci 2007;48:3301–3311. 16. holappa m, valjakka j, vaajanen a. angiotensin (17) and ace2,“the hot spots” of renin-angiotensin system, detected in the human aqueous humor. open j ophthalmol 2015;9:28. 17. collin j, queen r, zerti d, dorgau b, georgiou m, djidrovski i, et al. co-expression of sars-cov-2 entry genes in the superficial adult human conjunctival, limbal and corneal epithelium suggests an additional route of entry via the ocular surface. ocul surf 2020;19:190–200. 18. critical appraisal tools | joanna briggs institute [internet]. joannabriggs.org; 2020 [cited 2020 december 4]. available from: https://joannabriggs.org/critical-appraisaltools 19. xu m, zhang h, niu x. covid-19 patient firstly visiting eye doctor due to tarsadenitis and subconjunctival hemorrhage: a case report. zhonghua shiyan yanke zazhi/chinese journal of experimental ophthalmology 2020;38:374–376. 20. megarbane b, tadayoni r. cluster of chalazia in nurses using eye protection while caring for critically ill patients with covid-19 in intensive care. occup environ med 2020;77:584–585. 21. mcculley jp, dougherty jm, deneau dg. classification of chronic blepharitis. ophthalmology 1982;89:1173–1180. 22. mcculley jp, dougherty j. bacterial aspects of chronic blepharitis. trans ophthalmol soc uk 1986;105:314–318. 23. terpos e, ntanasis-stathopoulos i, elalamy i, kastritis e, sergentanis tn, politou m, et al. hematological findings and complications of covid-19. am j hematol 2020;95:834–847. 24. knop e, knop n, millar t, obata h, sullivan da. the international workshop on meibomian gland dysfunction: report of the subcommittee on anatomy, physiology, and pathophysiology of the meibomian gland. invest ophthalmol vis sci 2011;52:1938–1978. 25. bostanci ceran b, ozates s. ocular manifestations of coronavirus disease 2019. graefes arch clin exp ophthalmol 2020;258:1959–1963. 26. who. report of the who–china joint mission on coronavirus disease 2019 (covid-19). who; 2020. 27. sarma p, kaur h, kaur h, bhattacharyya j, prajapat m, shekhar n, et al. ocular manifestations and tear or conjunctival swab pcr positivity for 2019-ncov in patients with covid-19: a systematic review and meta-analysis. ssrn 2020. available from: https://ssrn.com/abstract= 3566161 28. loffredo l, pacella f, pacella e, tiscione g, oliva a, violi f. conjunctivitis and covid-19: a meta-analysis. j med virol 2020;92:1413–1414. 29. chen l, deng c, chen x, zhang x, chen b, yu h, et al. ocular manifestations and clinical characteristics of 535 cases of covid-19 in wuhan, china: a cross-sectional study. acta ophthalmol 2020;98:e951–e959. 30. navel v, chiambaretta f, dutheil f. haemorrhagic conjunctivitis with pseudomembranous related to sarscov-2. am j ophthalmol case rep 2020:100735. 31. chen l, liu m, zhang z, qiao k, huang t, chen m, et al. ocular manifestations of a hospitalised patient with confirmed 2019 novel coronavirus disease. br j ophthalmol 2020;104:748–751. 32. colavita f, lapa d, carletti f, lalle e, bordi l, marsella p, et al. sars-cov-2 isolation from ocular secretions of a patient with covid-19 in italy with prolonged viral rna detection. ann int med 2020;173:242–243. 33. aiello f, afflitto gg, mancino r, li j-po, cesareo m, giannini c, et al. coronavirus disease 2019 (sars-cov2) and colonization of ocular tissues and secretions: a systematic review. eye 2020;34:1206–1211. 34. corman vm, landt o, kaiser m, molenkamp r, meijer a, chu dk, et al. detection of 2019 novel coronavirus (2019-ncov) by real-time rt-pcr. eurosurveillance 2020;25:2000045. 35. lin c, ye r, xia y. a meta-analysis to evaluate the effectiveness of real-time pcr for diagnosing novel journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 245 https://joannabriggs.org/critical-appraisal-tools https://joannabriggs.org/critical-appraisal-tools https://ssrn.com/abstract=3566161 https://ssrn.com/abstract=3566161 ocular manifestations of covid-19; roshanshad et al coronavirus infections. genet mol res 2015;14:15634– 15641. 36. raboud j, shigayeva a, mcgeer a, bontovics e, chapman m, gravel d, et al. risk factors for sars transmission from patients requiring intubation: a multicentre investigation in toronto, canada. plos one 2010;5:e10717. 37. qing h, li z, yang z, shi m, huang z, song j, et al. the possibility of covid-19 transmission from eye to nose. acta ophthalmol 2020;98:e388. 38. cheema m, aghazadeh h, nazarali s, ting a, hodges j, mcfarlane a, et al. keratoconjunctivitis as the initial medical presentation of the novel coronavirus disease 2019 (covid-19). can j ophthalmol 2020;55:e125–e129. 39. mendez mangana c, barraquer kargacin a, barraquer ri. episcleritis as an ocular manifestation in a patient with covid-19. acta ophthalmol 2020;98:e1056–e1057. 40. bettach e, zadok d, weill y, brosh k, hanhart j. bilateral anterior uveitis as a part of a multisystem inflammatory syndrome secondary to covid-19 infection. j med virol 2020;93:139–140. 41. doherty m. ocular manifestations of feline infectious peritonitis. amer vet med ass j 1971;159:417–424. 42. seah i, agrawal r. can the coronavirus disease 2019 (covid-19) affect the eyes? a review of coronaviruses and ocular implications in humans and animals. ocul immunol inflamm 2020;28:391–395. 43. amano s, oshika t, kaji y, numaga j, matsubara m, araie m. herpes simplex virus in the trabeculum of an eye with corneal endotheliitis. am j ophthalmol 1999;127:721–722. 44. carmichael a. cytomegalovirus and the eye. eye 2012;26:237–240. 45. choi ja, kim ks, jung y, park hyl, park ck. cytomegalovirus as a cause of hypertensive anterior uveitis in immunocompetent patients. j ophthalmic inflamm infect 2016;6:32. 46. chee s, jap a. cytomegalovirus anterior uveitis: outcome of treatment. br j ophthalmol 2010;94:1648–1652. 47. accorinti m, gilardi m, pirraglia m, amorelli g, nardella c, abicca i, et al. cytomegalovirus anterior uveitis: long-term follow-up of immunocompetent patients. graefes arch clin exp ophthalmol 2014;252:1817–1824. 48. varkey jb, shantha jg, crozier i, kraft cs, lyon gm, mehta ak, et al. persistence of ebola virus in ocular fluid during convalescence. n engl j med 2015;372:2423–2427. 49. dinkin m, gao v, kahan j, bobker s, simonetto m, wechsler p, et al. covid-19 presenting with ophthalmoparesis from cranial nerve palsy. neurology 2020;95:221–223. 50. gala f. magnetic resonance imaging of optic nerve. indian j radiol imaging 2015;25:421. 51. zhao h, shen d, zhou h, liu j, chen s. guillain-barré syndrome associated with sars-cov-2 infection: causality or coincidence? lancet oncol 2020;19:383–384. 52. falcone mm, rong aj, salazar h, redick dw, falcone s, cavuoto km. acute abducens nerve palsy in a patient with the novel coronavirus disease (covid-19). j aapos 2020;24:216–217. 53. de oliveira rdmc, santos dh, olivetti bc, takahashi jt. bilateral trochlear nerve palsy due to cerebral vasculitis related to covid-19 infection. arquivos de neuropsiquiatria 2020;78:385–386. 54. chwalisz bk, dinkin mj. disease of the year: covid-19 and its neuro-ophthalmic complications. j neuroophthalmol 2020;40:283–284. 55. casagrande m, fitzek a, puschel k, aleshcheva g, schultheiss hp, berneking l, et al. detection of sarscov-2 in human retinal biopsies of deceased covid-19 patients. ocul immunol inflamm 2020;28:721–725. 56. marinho pm, marcos aaa, romano ac, nascimento h, belfort r jr. retinal findings in patients with covid-19. lancet 2020;395:1610. 57. seah i, agrawal r. can the coronavirus disease 2019 (covid-19) affect the eyes? a review of coronaviruses and ocular implications in humans and animals. ocul immunol inflamm 2020;28:391–395. 58. wang y, detrick b, yu z-x, zhang j, chesky l, hooks jj. the role of apoptosis within the retina of coronavirusinfected mice. invest ophthalmol vis sci 2000;41:3011– 3018. 59. quintana-castanedo l, feito-rodríguez m, fernándezalcalde c, granados-fernández m, montero-vega d, mayor-ibarguren a, et al. concurrent chilblains and retinal vasculitis in a child with covid-19. j eur acad dermatol venereol 2020;34:e764–e766. 60. burgos-blasco b, güemes-villahoz n, donate-lopez j, vidal-villegas b, garcía-feijóo j. optic nerve analysis in covid-19 patients. j med virol 2020;93:190–191. 61. insausti-garcía a, reche-sainz ja, ruiz-arranz c, lópez vázquez á, ferro-osuna m. papillophlebitis in a covid19 patient: inflammation and hypercoagulable state. eur j ophthalmol 2020:1120672120947591. 62. raony í, saggioro de figueiredo c. retinal outcomes of covid-19: possible role of cd147 and cytokine storm in infected patients with diabetes mellitus. diabetes res clin pract 2020;165:108280. 63. rohl a, kalhorn a, singh j, mandava n. decreased retinal detachments during a covid-19 lockdown period in colorado. acta ophthalmol 2020. available from: https: //doi.org/10.1111/aos.14570 64. awad m, poostchi a, orr g, kumudhan d, zaman a, wilde c. delayed presentation and increased prevalence of proliferative vitreoretinopathy for primary rhegmatogenous retinal detachments presenting during the covid-19 pandemic lockdown. eye 2020:1–2. 65. poyser a, deol ss, osman l, sivagnanasithiyar t, kuht hj, manrique r, et al. impact of covid-19 pandemic and lockdown on retinal detachments. eye 2020:1–2. 66. netland j, meyerholz dk, moore s, cassell m, perlman s. severe acute respiratory syndrome coronavirus infection causes neuronal death in the absence of encephalitis in mice transgenic for human ace2. j virol 2008;82:7264– 7275. 67. wrapp d, wang n, corbett ks, goldsmith ja, hsieh c-l, abiona o, et al. cryo-em structure of the 2019-ncov spike in the prefusion conformation. science 2020;367:1260– 1263. 68. toscano g, palmerini f, ravaglia s, ruiz l, invernizzi p, cuzzoni mg, et al. guillain–barré syndrome associated with sars-cov-2. n engl j med 2020;382:2574–2576. 69. nordvig as, rimmer kt, willey jz, thakur kt, boehme ak, vargas ws, et al. potential neurological manifestations of covid-19. neurol clin pract 2020. available from: https: //doi.org/10.1212/cpj.0000000000000897 246 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 https://doi.org/10.1111/aos.14570 https://doi.org/10.1111/aos.14570 https://doi.org/10.1212/cpj.0000000000000897 https://doi.org/10.1212/cpj.0000000000000897 ocular manifestations of covid-19; roshanshad et al 70. gutiérrez-ortiz c, méndez a, rodrigo-rey s, san pedromurillo e, bermejo-guerrero l, gordo-mañas r, et al. miller fisher syndrome and polyneuritis cranialis in covid-19. neurology 2020;95:e601–e605. 71. lantos je, strauss sb, lin e. covid-19-associated miller fisher syndrome: mri findings. ajnr 2020;41:1184–1186. 72. conde g, pájaro ldq, marzola idq, villegas yr, salazar lrm. neurotropism of sars-cov 2: mechanisms and manifestations. j neurol sci 2020;412:116824. 73. kaya y, kara s, akinci c, kocaman as. transient cortical blindness in covid-19 pneumonia; a pres-like syndrome: case report. j neurol sci 2020;413:116858. 74. doo fx, kassim g, lefton dr, patterson s, pham h, belani p. rare presentations of covid-19: preslike leukoencephalopathy and carotid thrombosis. clin imaging 2020. 75. agarwal s, jain r, dogra s, krieger p, lewis a, nguyen v, et al. cerebral microbleeds and leukoencephalopathy in critically ill patients with covid-19. stroke 2020;51:2649– 2655. 76. cariddi lp, damavandi pt, carimati f, banfi p, clemenzi a, marelli m, et al. reversible encephalopathy syndrome (pres) in a covid-19 patient. j neurol 2020;267:3157– 3160. 77. parauda sc, gao v, gewirtz an, parikh ns, merkler ae, lantos j, et al. posterior reversible encephalopathy syndrome in patients with covid-19. j neurol sci 2020;416:117019. 78. zhou s, jones-lopez ec, soneji dj, azevedo cj, patel vr. myelin oligodendrocyte glycoprotein antibody-associated optic neuritis and myelitis in covid-19. j neuroophthalmol 2020;40:398–402. 79. dumitrascu om, volod o, bose s, wang y, biousse v, lyden pd. acute ophthalmic artery occlusion in a covid-19 patient on apixaban. j stroke cerebrovasc dis 2020;29:104982. 80. acharya s, diamond m, anwar s, glaser a, tyagi p. unique case of central retinal artery occlusion secondary to covid-19 disease. id cases 2020;21:e00867. 81. giannis d, ziogas ia, gianni p. coagulation disorders in coronavirus infected patients: covid-19, sars-cov1, mers-cov and lessons from the past. j clin virol 2020;127:104362. 82. tang n, bai h, chen x, gong j, li d, sun z. anticoagulant treatment is associated with decreased mortality in severe coronavirus disease 2019 patients with coagulopathy. j thromb haemost 2020;18:1094–1099. 83. han h, yang l, liu r, liu f, wu k-l, li j, et al. prominent changes in blood coagulation of patients with sars-cov2 infection. clin chem lab med 2020;1(ahead-of-print). 84. barnes gd, burnett a, allen a, blumenstein m, clark np, cuker a, et al. thromboembolism and anticoagulant therapy during the covid-19 pandemic: interim clinical guidance from the anticoagulation forum. j thromb thrombolysis 2020;50:72–81. 85. barrett cd, moore hb, yaffe mb, moore ee. isth interim guidance on recognition and management of coagulopathy in covid-19: a comment. j thromb haemost 2020;18:2060–2063. 86. löffler ku, reinhold a, herwig-carl mc, tzankov a, holz fg, scholl hpn, et al. ocular post-mortem findings in patients having died from covid-19. ophthalmologe 2020;117:648–651. 87. bayyoud t, iftner a, iftner t, bartz-schmidt ku, rohrbach jm, ueffing m, et al. absence of severe acute respiratory syndrome-coronavirus-2 rna in human corneal tissues. cornea 2020;40:342–347. 88. bayyoud t, iftner a, iftner t, bartz-schmidt ku, ueffing m, schindler m, et al. absence of severe acute respiratory syndrome-coronavirus-2 rna in ocular tissues. am j ophthalmol case rep 2020;19:100805. 89. fuest m, boor p, knuechel r, walter p, salla s. postmortem conjunctival and nasopharyngeal swabs in sars-cov-2 infected and uninfected patients. acta ophthalmol 2020. 90. luhtala s, vaajanen a, oksala o, valjakka j, vapaatalo h. activities of angiotensin-converting enzymes ace1 and ace2 and inhibition by bioactive peptides in porcine ocular tissues. j ocul pharmacol ther 2009;25:23–28. 91. tikellis c, johnston c, forbes jm, burns wc, thomas mc, lew ra, et al. identification of angiotensin converting enzyme 2 in the rodent retina. curr eye res 2004;29:419– 427. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 247 original article association of il4 rs2070874, foxp3 rs3761548 polymorphisms with keratoconus in algeria wafaa meteoukki1,2, ms; mostefa fodil2,3, phd; nawel adda negaz2,4, md; nesrine rahmoun1, phd sarah lardjam hetraf1, phd; hadjira ouhaibi djellouli1, phd; ahlem djelti messal1, phd; meriem abdi1, phd meriem samia aberkane1, phd; abdelillah chiali4, md; amine derdour5, md; aicha idder2,5, md faouzia zemani-fodil1,2, phd 1laboratoire de génétique moléculaire et cellulaire (lgmc), université des sciences et de la technologie d’oran mohamed boudiafusto-mb, bp 1505, el m’naouer, 31000 oran, algérie 2agence thématique de recherche en sciences de la santé (atrss)– oran, algérie 3ecole supérieure des sciences biologiques d’oran (essbo) 4clinique chiali, oran, algérie 5laboratoire de génétique médicale appliquée à l’ophtalmologie, clinique hammou boutlélis oran, algérie orcid: wafaa meteoukki: https://orcid.org/0000-0001-9821-5808 abstract purpose: the aim of this case–control study was to determine the impact of environmental factors on the predisposition to develop keratoconus in a sample of western algerian population. subsequently, we were interested in the implication of two single nucleotide polymorphisms (snps) il4 rs2070874 and foxp3 rs3761548, previously described as contributing to the occurrence of allergy, in the development of keratoconus. methods: the study included 70 unrelated kc cases and 70 controls originating from western algeria. dna genotyping was done using predesigned probe-based allelic discrimination taqman® assays. allele and genotype frequencies were compared between the cases and controls by chi-square test and odds ratios with 95% confidence intervals. results: a significant association between risk factors such as family history, atopy, eye rubbing, and the development of keratoconus was found in our sample. smoking would provide a protective effect against the pathology. no statistically significant differences were found in the allele and genotype frequencies between cases and controls neither for il4 rs2070874 nor for foxp3 rs3761548. conclusion: our study provides, for the first time, a clear demonstration of the absence of association of the allergy-associated il4 and foxp3 polymorphisms with kc in a sample from western algerian population. keywords: case–control study; foxp3 gene; il4 gene; keratoconus; polymorphisms; western algeria j ophthalmic vis res 2021; 16 (4): 558–565 558 © 2021 meteoukki et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9745&domain=pdf&date_stamp=2019-07-17 keratoconus associated genes in algeria; meteoukki et al introduction keratoconus (kc) is a degenerative bilateral corneal dystrophy characterized by gradual thinning of the cornea leading to a loss of visual acuity. kc is classified as a noninflammatory disease;[1] however, several studies rejected this theory after the discovery of the expression of inflammatory mediators such as cytokines in the tears of patients suffering from kc.[2, 3] kc is a multifactorial disease resulting from the interaction of environmental and genetic factors. although the etiology of kc is not clearly established, genetic and environmental factors such as allergy or eye rubbing seem necessary for disease expression,[4] despite the positive associations found between atopy (allergy, asthma, eczema) and kc.[5–7] no study has focused on the association between kc and polymorphisms in inflammatory mediators genes of these immune disorders. interleukin 4 is a pleiotropic cytokine produced by activated t-lymphocyte and mast cells.[8] this cytokine plays a major role in type 2 immune responses characterized by the production of immunoglobulin e (ige) and immunoglobulin g1 (igg1).[9] ige is strongly implicated in atopic and allergic diseases.[10] several genetic variants in the il4 gene and its receptor il4-r have been found associated with allergic rhinitis (ar).[11] the il4 rs2070874 has been reported as associated with asthma and atopy in several studies.[12, 13] haijun yang performed a meta-analysis and found that this polymorphism is correlated with increased asthmatic risk.[14] the forkhead box transcription factor (foxp3) has an important role in the development and function of regulatory t cells (tregs), and also in peripheral tolerance.[15] many severe lymphoproliferative diseases occur due to treg correspondence to: wafaa meteoukki, ms. laboratoire de génétique moléculaire et cellulaire, université des sciences et de la technologie d’oran mohamed boudiafusto-mb, bp 1505, el m’naouer, 31000 oran, algérie. email: wafaa.meteoukki@univ-usto.dz received: 23-11-2020 accepted: 15-04-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9745 deficiencies resulting from foxp3 mutation. thus, tregs mediate dominant tolerance to self and have also been shown to be equally important in the control of autoimmune diseases, allergy, fetal–maternal tolerance, allograft tolerance, and immunopathology.[16] the rs3761548 polymorphism of foxp3 gene was identified as being associated with ar in heterozygous form in han chinese patients,[17] and in hungarian ar patients.[18] to the best of our knowledge, this is the first study dedicated to the study of kc in algeria and africa in order to find a possible association between the inflammatory gene polymorphisms (rs2070874 and rs3761548) and the disease pathology. methods subjects in total, 70 kc cases and 70 healthy controls originating from western algeria were included in this study. patients were recruited from the specialized hospital, institute of ophthalmology ehs (établissemnt hospitalier specialisé) hammou boutelilis in oran algeria as well as from a private ophthalmology clinic. the control group included voluntary donors from the blood transfusion center of oran hospital “chuo” (centre hospitalouniversitaire d’oran), as well as student volunteers [table 1]. the present study was conducted according to the principles set out in the declaration of helsinki,[19] and was approved by the ethics committee at the national evaluation and planning committee of the algerian university research. an informed written consent was obtained from all participants. detection of kc was performed by an experienced ophthalmologist based on visual acuity assessment, findings of slit lamp as: corneal this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: meteoukki w, fodil m, negaz na, rahmoun n, hetraf sl, djellouli ho, messal ad, abdi m, aberkane ms, chiali a, derdour a, idder a, zemani-fodil f. association of il4 rs2070874, foxp3 rs3761548 polymorphisms with keratoconus in algeria. j ophthalmic vis res 2021;16:558–565. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 559 https://knepublishing.com/index.php/jovr keratoconus associated genes in algeria; meteoukki et al table 1. study population’s characteristics characteristics kc cases (%) healthy controls (%) p-value number of subjects 70 70 – men 21 (30%) 40 (57%) 0.001 women 49 (70%) 30 (43%) age (mean ± se), years 30.40 ± 11.33 30.14 ± 9.29 0.396 family history of kc 15 (21%) 2 (3%) 0.0007 consanguinity 21 (30%) 15 (21%) 0.24 atopy 48 (69%) 11 (16%) 1×10−6 eye rubbing 56 (80%) 1 (1%) 1×10−6 uv exposure 40 (57%) 50 (71%) 0.077 exposure to cigarette smoke 27 (39%) 59 (84%) 1×10−6 kc, keratoconus; p, significance the values are presented as the mean ± standard error; the p-value for each comparison is calculated and is timed significant if it is superior than 0.05. table 2. details of the snp used in the study gene db snp id assay id location gene/function il4 rs2070874 c__16176215_10 chr.5: 132674018 5 prime untranslated variant foxp3 rs3761548 c__27476877_10 chr.x: 49261784 intron variant snp, single nucleotide polymorphism; db snp, single nucleotide polymorphism database; chr, chromosome table 3. genotypes and alleles distribution of il4 rs2070874 and foxp3 rs3761548 variants between keratoconus patients and control group gene/snp genotype/allele kc patients n = 70 (%) controls n = 70 (%) x² p-value or [ci] il4 rs2070874 tt cc tc 6 (9) 43 (61) 21 (30) 3 (4) 49 (70) 18 (26) 1.62 0.44 _ t c 33 (24) 107 (76) 24 (17) 116 (83) 1.78 0.18 0.67 [0.37–1.21] tt+tc cc 27 (39) 43 (61) 21 (30) 49 (70) 1.14 0.28 1.45 [0.72–2.91] gene/snp genotype/allele kc patients n = 70 (%) controls n = 70 (%) x² p-value or [ci] foxp3 rs3761548 tt gg gt 12 (17) 32 (46) 26 (37) 12 (17) 33 (47) 25 (36) 0.03 0.98 _ t g 50 (36) 90 (64) 49 (35) 91 (65) 0.02 0.900 1.03 [0.63–1.68] tt + gt gg 38 (54) 32 (46) 37 (53) 33 (47) 0.03 0.86 1.06 [0.55–2.05] kc, keratoconus; p, significance; or, odds ratio; ci, 95% confidence interval 560 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 keratoconus associated genes in algeria; meteoukki et al thinning, vogt’s striae,[20] and fleischer’s ring and topographic data. patients previously grafted for one or both eyes were considered as cases. all kc patients with ar reported having common classical symptoms mentioned in allergic rhinitis and its impact on asthma (aria) guidelines-2016 revision,[21] as nasal itching, sneezing, rhinorrhea, and nasal congestion, and other kc patients stated that they already suffered from ocular symptoms as allergic rhinoconjunctivitis associated with itching and redness of the eyes and tearing. the 70 control subjects had no ocular disease or previous eye surgeries and no family ocular history; all controls wearing glasses or suffering from myopia were excluded. dna extraction eight ml peripheral blood was collected from patients and healthy controls using edta containing tubes and stored at –20°c until analyses. genomic dna was extracted using the salting out method.[22] genotyping of il4 rs2070874 and foxp3 rs3761548 polymorphisms molecular genotyping of snps was performed using taqman® snp genotyping assay (applied biosystems foster city, ca, usa) [table 2] on qtower³ real-time polymerase chain reaction (pcr) machine (analytik jena, germany). a 20 µl pcr reaction contained 1x taqman® genotyping master mix (applied biosystems foster city, ca, usa), 1x snp genotyping assay mix, and 20 ng dna. pcr cycling parameters included predenaturation at 60°c for 30 sec, denaturation at 95°c for 10 sec, followed by 50 cycles of denaturation at 95°c for 15 sec each, and finally annealing/extension at 60°c for 90 sec. the pcr products were measured at 60°c for 30 sec, which are proportional to the level of the fluorescence vic® and fam®. statistical analysis the hardy–weinberg equilibrium (hwe) in the control group was calculated using chi-square test. the comparison of quantitative variants between kc patients and control group, the frequencies of the allele and genotype were analyzed using the pearson’s chi-square (χ2) test. p-values < 0.05 were considered significant. risk was assessed by the odds ratios (ors) and 95% confidence intervals (cis) were also estimated. the genotype relative risk (grr) method (a single genotype versus the others) was calculated to compare the genotype distribution in patients and controls. all the analyses were done using 2×2 contingency tables. results the demographic and other characteristics of all subjects are shown in table 1. we first looked at the sex ratio; the gender distribution between patients and controls was found to be significantly different (p = 1×10−3). the mean age of kc patients was 30.40 ± 11.33 (range 6–70 years), while the mean age of the healthy group was 30.14 ± 9.29 (range, 19–62 years), there was no statically significant difference in the mean age between the two groups. then, we were interested in the most discriminating risk factors; we observed a clear significant difference between cases and controls concerning atopy, eye rubbing with a high number of cases than controls also exposure to cigarette smoke as risk factor but with a large number of controls than cases (p = 1×10−6). kc patients had more family history of the pathology than healthy controls (21% vs 3%, p = 7×10−4). we also noted that there was no statistically significant difference between the case and control groups regarding the consanguinity and ultraviolet radiation (uv) exposure (p = 0.24 and 0.077, respectively). the distribution of allele frequencies for the two snps in control group did not deviate significantly from hwe (p > 0.05). the details of gentotypic and allelic frequencies are summarized in table 3. the frequency distributions of il4 rs2070874 genotypes between cases and controls revealed no statistical significance (p = 0.44). the allelic distribution of the polymorphism in the control population revealed that the allele c of il4 rs2070874 represents the major allele (0.83) and the allele t represents the allele minor (0.17), there were no significant differences in the frequency’s distribution of the il4 rs2070874 c/t alleles (p = 0.18) even in the presence of at least one copy of the allele t of il4 rs2070874 among the genotypes (p = 0.28). the distributions of genotype’s frequencies of foxp3 rs3761548 in kc cases were: gg, 46%; gt, journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 561 keratoconus associated genes in algeria; meteoukki et al 37%; and tt, 17%; and the distribution in control group were: gg, 47%; gt, 36%; and tt, 17%. no significant association was observed between kc patients and healthy controls concerning foxp3 rs3761548 genotypes (p = 0.98), the allele frequency distribution was also nonsignificant (p = 0.9; or = 1.03; 95%ci [0.63–1.68]), with minor t allele frequency 0.35 and major g allele frequency 0.65. the presence of at least one copy of the allele t of foxp3 rs3761548 showed nonsignificant association between cases and controls (p = 0.86; or = 1.06; 95%ci [0.55–2.05]). discussion we investigated the impacts of the most discriminating risk factors and il4 rs2070874 and foxp3 rs3761548 polymorphisms on a group of kc patients and controls from western algeria. to the best of our knowledge, this is the first study on the impact of il4 and foxp3 polymorphisms in a population originating from algeria. our results showed a higher female prevalence in our study population (p = 0.001). this female predominance of kc found in our sample is the opposite of what is found in the literature. some studies have shown a male predominance among patients from the united states,[23] while others have shown no significant difference.[24] these results remain to be confirmed on a larger number of patients in order to be able to explain this female predominance in our population [table 1]. the mean age in our sample of patients is equivalent to that found in several studies that demonstrate that kc usually affects adolescents at puberty as well as young adults until the fourth decade of life.[25] the mean age of kc cases in our study was 30.40 ± 11.33 years [table 1], which fits perfectly with the study of cozma et al[26] concerning the white patient group in his work about the influence of ethnic origin on the incidence of kc. in our sample, there was a significant difference between cases and controls groups concerning family history with kc (p = 7×10−4) [table 1]. indeed, the familial link with kc represents a serious risk factor,[27] since gordon-shaag et al showed that the risk of developing kc was 15 to 67 times higher compared to the general population.[28] in addition, they reported that 5 to 27.9% of patients with kc had a positive family history.[28] consanguinity has also been proposed as a risk factor of kc in israeli arabs and palestinian arabs,[28–30] as studies have shown that the high number of consanguineous marriages among muslims is a cause of the increased incidence of kc.[31] however, we did not find any significant difference between cases and controls in our population for this factor (p = 0.24) [table 1]; this could be caused by the small number of kc patients group. for more than 50 years, atopy has been identified as a risk factor.[32] in addition, several studies have shown that asthma and allergy are associated with kc with statistical significance (p = 0.0008 for asthma and 0.04 for allergy).[7] our results correlate with this work since in our sample, atopy was reported in 69% of cases compared to 16% in controls with a statistically significant difference (p = 1×10−6) [table 1], knowing that all patients are from western algeria – a coastal region known for its humid and marine climate and neighboring industrial areas. a study in the region of eastern algeria confirmed that climatology would increase the risk of developing allergic diseases, and atopy based on family criteria was very common in this population.[33] another risk factor is related to patients’ habits, the eye rubbing. the rubbing of the eyes is currently the most important risk factor that is clearly identified. this risk factor triggers the onset and progression of the disease through several effects, including the stimulation of inflammation. most authors report that approximately half of the kc patients rub their eyes, although this varies with the usual duration of rubbing and that the rubbing of the eyes is mild or vigorous.[28, 34] the results of our study are in perfect correlation with the literature. we have shown that 80% of patients with kc rubbed their eyes regularly compared to 1% in controls. thus, in our sample, eye rubbing seems to be associated with the appearance of the kc (p = 1×10−6) [table 1]. indeed, several studies have attempted to explain the involvement of this risk factor in the development of kc. in fact, the micro-trauma caused to the epithelium by the eye rubbing generates high levels of matrix metalloproteases (mmp-1 and mmp-13) secreted by the epithelial and stromal cells, in addition, the release of inflammatory mediators (il-6 and tnfα) is one of the processes leading to kc and its progression.[35] 562 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 keratoconus associated genes in algeria; meteoukki et al in our sample, we found that there was no statistically significant difference between the case and control groups concerning sun exposure risk factor (p = 0.07) [table 1]. studies have shown that the prevalence of kc is higher in sunny countries than in europe or north america, high sun exposure in these countries would explain the high prevalence of kc.[27] in addition to the genetic component, uv light has an additive effect by causing oxidative damage which would be among the causes of the acceleration of the pathological process of kc.[28] however, it should be noted that uv could provide, at a controlled dose, a beneficial effect by inducing the reticulation of corneal collagen, thus attenuating the development or progression of the disease.[36] in 2008, a study was able to demonstrate for the first time that cigarette smoking appeared to have a protective effect against kc.[37] our results seem to support this hypothesis, since in our sample, we observed a greater frequency of smoking in controls (84%) compared to kc patients (39%). moreover, this difference is statistically significant (p = 1×10−6) [table i], and exposure to cigarette smoke appears to have a protective effect (or = 0.1 [0.055–0.269]). other studies concluded that there was no significant association between smoking and kc.[30] the hypothesis of testing the effect of the il4 rs2070874 and foxp3 rs3761548 polymorphisms in the predisposition to kc development is based on the fact that these polymorphisms known to be associated with allergies could be either directly associated with the development of kc or indirectly, via inflammation induced by microtrauma due to eye rubbing.[34] indeed, our results [table 1] showed that atopy and eye rubbing in patients with kc were significantly associated with the pathology in our study sample (p = 1×10−6) [table 1]. according to our results, the t allele of il4 rs2070874 represents the minor allele (0.17) [table 3]. this allelic distribution is close to the findings of a study performed in 2018 on a sample of 58 subjects in the western algeria (0.10).[38] the same observation was reported in other populations such as italians (0.12),[39] swedish, australian, finnish, and english populations (0.16).[40] this frequency is lower than that reported in the africanamericans (0.43)[41] and indians (0.39).[42] however, the t allele of foxp3 rs3761548 represents the minor allele with a frequency of 0.35 [table 3]. this minor allele frequency (maf) is in line with the egyptian study (0.34),[43] but different from those reported in turkish and indian populations, 0.61 and 0.56, respectively.[44, 45] this variability in the results of the studies may be due to ethnic factors and the size of the sample studied [table 3]. our case–control study suggests no association between (il4 rs2070874, foxp3 rs3761548) polymorphisms and susceptibility to kc, even in the presence of at least one copy of the allele t of il4 rs2070874 or t allele of foxp3 rs3761548 [table 3]. according to bawazeer et al,[34] allergy is indirectly associated with the development of kc and its effect is probably due to inflammation caused by rubbing eye movements. these results, once confirmed in a larger cohort, would be further evidence.[34] indeed, most authors report that about half of the patients with kc rub their eyes regularly, although the percentage varies among studies.[28] it is interesting to note that in cases of asymmetric kc, the most affected eye has been rubbed the most vigorously.[46] coyle et al reported the case of an 11-year-old boy who at the age of 5, discovered that he could stop his tachycardia by vigorously massaging his left eye (up to 20 min/day).[47] at age 7, he hadn’t developed anything in his eyes. at the age of 11, the child developed unilateral kc in only his left eye which was massaged vigorously. another case of kc has been reported in a patient with a history of vigorous daily massage of the left eye which led to unilateral kc in that eye only.[48] a series of cases confirms the asymmetrical expression of the disease in patients who usually rub the most affected eye.[46, 49, 50] thus, eye rubbing would cause micro-trauma leading to the secretion of high levels of mmp.[35] these factors can lead to progression of kc associated with apoptosis of keratocytes,[51] and atopic episodes can contribute and interact with other inflammatory processes related to kc.[52] this is the first demonstration of the implication of susceptibility genes to allergy in the development of kc, and this is the first time that the il4 and foxp3 genes association was analyzed with kc risk in an algerian population. our results showed that there would be a significant association in our study sample between risk factors such as family history with disease, atopy and eye rubbing, and kc development. in addition, our results confirmed journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 563 keratoconus associated genes in algeria; meteoukki et al that smoking would provide a protective effect against the pathology. however, it has been shown that there is no association between the il4 rs2070874 and foxp3 rs3761548 polymorphisms and the occurrence of kc in the population of western algeria. however, because of the moderate size of the sample, the statistical power of the present study was relatively low, being 50% and 59% for the il4 rs2070874 and foxp3 rs3761548 polymorphisms, respectively. in summary, our results provide precise and upto-date information on the association of the two polymorphisms studied with kc in the population of western algeria. the small size of our study requires a replication of the results in a larger sample of the population in order to confirm or affirm the association. nevertheless, the present study does not exclude the effect of il4 and foxp3 gene polymorphisms in the pathophysiological process of the kc disease. for this reason, the present study may be considered as a pilot study. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. krachmer jh, feder rs, belin mw. keratoconus and related noninflammatory corneal thinning disorders. surv ophthalmol 1984;28:293–322. 2. lema i, sobrino t, durán ja, brea d, díez-feijoo e. subclinical keratoconus and inflammatory molecules from tears. br j ophthalmol 2009;93:820–824. 3. jun as, cope l, speck c, feng x, lee s, meng h, et al. subnormal cytokine profile in the tear fluid of keratoconus patients. plos one 2011;6:e16437. 4. davidson ae, hayes s, hardcastle aj, tuft sj. the pathogenesis of keratoconus. eye lond engl 2014;28:189– 195. 5. harrison rj, klouda pt, easty dl, manku m, charles j, stewart cm. association between keratoconus and atopy. br j ophthalmol 1989;73:816–822. 6. mcmonnies cw, boneham gc. keratoconus, allergy, itch, eye-rubbing and hand-dominance. clin exp optom 2003;86:376–384. 7. nemet ay, vinker s, bahar i, kaiserman i. the association of keratoconus with immune disorders. cornea 2010;29:1261–1264. 8. bijlsma fj, van kuik j, van hoffen e, de jonge n, tilanus mgj, gmelig-meyling fhj, et al. acute cardiac transplant rejection is associated with low frequencies of interleukin-4 producing helper t-lymphocytes rather than with interleukin-4 promoter or splice variants. hum immunol 2002;63:317–323. 9. vijayanand p, seumois g, simpson lj, abdul-wajid s, baumjohann d, panduro m, et al. interleukin-4 production by follicular helper t cells requires the conserved il4 enhancer hypersensitivity site v. immunity 2012;36:175– 187. 10. harada y, tanaka s, motomura y, harada y, ohno s, ohno s, et al. the 3′ enhancer cns2 is a critical regulator of interleukin-4-mediated humoral immunity in follicular helper t cells. immunity 2012;36:188–200. 11. movahedi m, amirzargar aa, nasiri r, hirbod-mobarakeh a, farhadi e, tavakol m, et al. gene polymorphisms of interleukin-4 in allergic rhinitis and its association with clinical phenotypes. am j otolaryngol 2013;34:676–681. 12. gervaziev yv, kaznacheev va, gervazieva vb. allelic polymorphisms in the interleukin-4 promoter regions and their association with bronchial asthma among the russian population. int arch allergy immunol 2006;141:257–264. 13. suzuki i, hidaka n, yamaguchi e, kawakami y. association between a c+33t polymorphism in the il-4 promoter region and total serum ige levels. clin htmlent glyphamp asciiamp exp allergy 2000;30:1746–1749. 14. yang h-j. association between the interleukin-4 gene c589t and c+33t polymorphisms and asthma risk: a metaanalysis. arch med res 2013;44:127–135. 15. denyer mp, pinheiro dy, garden oa, shepherd aj. missed, not missing: phylogenomic evidence for the existence of avian foxp3. pappalardo f, éditeur. plos one 2016;11:e0150988. 16. maruyama t, konkel je, zamarron bf, chen w. the molecular mechanisms of foxp3 gene regulation. semin immunol 2011;23:418–423. 17. zhang l, zhang y, desrosiers m, wang c, zhao y, han d. genetic association study of foxp3 polymorphisms in allergic rhinitis in a chinese population. hum immunol 2009;70:930–934. 18. fodor e, garaczi e, polyánka h, koreck a, kemény l, széll m. the rs3761548 polymorphism of foxp3 is a protective genetic factor against allergic rhinitis in the hungarian female population. hum immunol 2011;72:926–929. 19. world medical association. world medical association declaration of helsinki: ethical principles for medical research involving human subjects. jama 2013;310:2191–2194. 20. hollingsworth jg, efron n. observations of banding patterns (vogt striae) in keratoconus: a confocal microscopy study. cornea 2005;24:162–166. 21. brożek jl, bousquet j, agache i, agarwal a, bachert c, bosnic-anticevich s, et al. allergic rhinitis and its impact on asthma (aria) guidelines – 2016 revision. j allergy clin immunol 2017;140:950–958. 22. miller sa, dykes dd, polesky hf. a simple salting out procedure for extracting dna from human nucleated cells. nucleic acids res 1988;16:1215. 23. kennedy rh, bourne wm, dyer ja. a 48-year clinical and epidemiologic study of keratoconus. am j ophthalmol 1986;101:267–273. 564 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 keratoconus associated genes in algeria; meteoukki et al 24. li x, rabinowitz ys, rasheed k, yang h. longitudinal study of the normal eyes in unilateral keratoconus patients. ophthalmology 2004;111:440–446. 25. rabinowitz ys. keratoconus. surv ophthalmol 1998;42:297–319. 26. cozma i, atherley c, james nj. influence of ethnic origin on the incidence of keratoconus and associated atopic disease in asian and white patients. eye 2005;19:924– 925. 27. moussa s, grabner g, ruckhofer j, dietrich m, reitsamer h. genetics in keratoconus – what is new? open ophthalmol j 2017;11:201–210. 28. gordon-shaag a, millodot m, shneor e, liu y. the genetic and environmental factors for keratoconus. biomed res int 2015;2015:795738. 29. barbara r, gordon-shaag a, millodot m, shneor e, essa m, anton m. prevalence of keratoconus among young arab students in israel. int j keratoconus ectatic corneal dis 2014;3:9–14. 30. gordon-shaag a, millodot m, essa m, garth j, ghara m, shneor e. is consanguinity a risk factor for keratoconus? optom vis sci 2013;90:448–454. 31. georgiou t, funnell cl, cassels-brown a, o’conor r. influence of ethnic origin on the incidence of keratoconus and associated atopic disease in asians and white patients. eye 2004;18:379–383. 32. galvis v, sherwin t, tello a, merayo j, barrera r, acera a. keratoconus: an inflammatory disorder? eye 2015;29:843–859. 33. boumendjel a, tridon a, ughetto s, messarah m, salah boulakoud m. environnement allergénique d’une population d’enfants asthmatiques à annaba (algérie). ann biol clin (paris) 2010;68:317–324. 34. bawazeer am, hodge wg, lorimer b. atopy and keratoconus: a multivariate analysis. br j ophthalmol 2000;84:834–836. 35. balasubramanian sa, pye dc, willcox md. effects of eye rubbing on the levels of protease, protease activity and cytokines in tears: relevance in keratoconus: eye rubbing in keratoconus. clin exp optom 2013;96:214–218. 36. chan e, snibson gr. current status of corneal collagen cross-linking for keratoconus: a review: cross-linking and keratoconus. clin exp optom 2013;96:155–164. 37. spoerl e, raiskup-wolf f, kuhlisch e, pillunat le. cigarette smoking is negatively associated with keratoconus. j refract surg 2008;24:s737–s740. 38. rahmoun n, el mecherfi ke, bouchetara a, lardjem hetraf s, dahmani amira c, adda neggaz l, et al. association of rel polymorphism with cow’s milk proteins allergy in pediatric algerian population. fetal pediatr pathol 2018;37:74–83. 39. vargiolu m, silvestri t, bonora e, dolzani p, pulsatelli l, addimanda o, et al. interleukin-4/interleukin-4 receptor gene polymorphisms in hand osteoarthritis. osteoarthr cartil 2010;18:810–816. 40. fitzgerald lm, zhao s, leonardson a, geybels ms, kolb s, lin dw, et al. germline variants in il4, mgmt and akt1 are associated with prostate cancer-specific mortality: an analysis of 12,082 prostate cancer cases. prostate cancer prostatic dis 2018;21:228–237. 41. battle nc, choudhry s, tsai h-j, eng c, kumar g, beckman kb, et al. ethnicity-specific gene–gene interaction between il-13 and il-4rα among african americans with asthma. am j respir crit care med 2007;175:881–887. 42. majumder p, panda sk, ghosh s, dey sk. interleukin gene polymorphisms in chronic periodontitis: a case– control study in the indian population. arch oral biol 2019;101:156–164. 43. elsohafy m, elghzaly a, abdelsalam h, gaballah m. assessment of the possible role of foxp3 gene (rs3761548) polymorphism in psoriasis vulgaris susceptibility and pathogenesis: egyptian study. indian dermatol online j2019;10:401. 44. cekin n, pinarbasi e, bildirici ae, donmez g, oztemur z, bulut o, et al. foxp3 rs3761548 polymorphism is associated with knee osteoarthritis in a turkish population. int j rheum dis 2018;21:1779–1786. 45. jahan p, ramachander vrv, maruthi g, nalini s, latha kp, murthy tsr. foxp3 promoter polymorphism (rs3761548) in breast cancer progression: a study from india. tumor biol 2014;35:3785–3791. 46. zadnik k, steger-may k, fink ba, joslin ce, nichols jj, rosenstiel ce, et al. between-eye asymmetry in keratoconus. cornea 2002;21:671–679. 47. terrence coyle j. keratoconus and eye rubbing. am j ophthalmol 1984;97:527–528. 48. gritz dc, mcdonnell pj. keratoconus and ocular massage. am j ophthalmol 1988;106:757–758. 49. jafri b, lichter h, stulting rd. asymmetric keratoconus attributed to eye rubbing. cornea 2004;23:560–564. 50. koenig sb. bilateral recurrent self-induced keratoconus. eye contact lens sci clin pract 2008;34:343–344. 51. rehany u, lahav m, shoshan s. collagenolytic activity in keratoconus. ann ophthalmol 1982;14:751–754. 52. mcmonnies cw. inflammation and keratoconus. optom vis sci off publ am acad optom 2015;92:e35–e41. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 565 original article 3d printed models for teaching orbital anatomy, anomalies and fractures roya vatankhah1, ms; ali emadzadeh1, phd; sirous nekooei2, md; bahar tafaghodi yousefi3, md majid khadem rezaiyan4, md; hossein karimi moonaghi5, phd; mohammad etezad razavi6, md 1department of medical education, school of medicine, mashhad university of medical sciences, mashhad, iran 2department of radiology, mashhad university of medical sciences, mashhad, iran 3oculoplastic & strabismus, khatam eye hospital, mashhad university of medical sciences, mashhad, iran 4department of community and public health, mashhad university of medical sciences, mashhad, iran 5nursing and midwifery care research center, department of medical surgical nursing, school of nursing and midwifery, and department of medical education, school of medicine, mashhad university of medical sciences, mashhad, iran 6eye research center, mashhad university of medical sciences, mashhad, iran orcid: roya vatankhah: https://orcid.org/0000-0002-8219-6371 mohammad etezad razavi: https://orcid.org/0000-0001-9148-4300 abstract purpose: the aim of this study was to determine the efficacy of using 3d printing models in the learning process of orbital anatomy and pathology by ophthalmology residents. methods: a quasi-experimental study was performed with 24 residents of ophthalmology at mashhad university of medical sciences. each stratum was randomized into two groups. the educational booklets were distributed, and various forms of orbital 3d models were printed from orbital computed tomography (ct) scans. knowledge enhancement on the topics was measured by comparing pretest and posttest scores. results: thirteen residents who were trained using traditional methods were deemed the control group; while 11 residents who were trained using the 3d printed models were classed as the intervention group. the control group was younger than the intervention group (p = 0.047). the results showed that there was a statistically significant difference in the total posttest scores between the two groups. based on the repeated measures of the analysis of variance (anova), score variables were significant between the two groups (p = 0.008). interestingly, the use of the 3d educational model was more effective and statistically significant with the year one residents as compared to the year two residents (p = 0.002). conclusion: this study is the first one in iran quantifying the effects of learning using 3d printed models in medical education. in fact, 3d modeling training is seemingly effective in teaching ophthalmic residents. as residents have never encountered such technology before, their experience using 3d models proved to be satisfactory and had a surprising positive effect on the learning process through visual training. keywords: 3d printed models; learning; ophthalmology residents; orbit j ophthalmic vis res 2021; 16 (4): 611–619 © 2021 vatankhah et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 611 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9751&domain=pdf&date_stamp=2019-07-17 orbital 3d printed models; vatankhah et al introduction in the era of communication, innovative changes in the science and technology industry have facilitated greater access to valuable information. as a consequence, the educational system should focus on student-centered structural learning as it pertains to technology, to ensure continued synergy. a place for the teaching-learning process has begun under the idea of technology. the rapid advancement of science is influenced by computer technologies that are used in the education process and will remove the limitations of traditional education.[1] the advent of 3d printing has created new ways to complement the health practice. these exciting new technologies allow for the uniqueness and customized visualization in the production of various imaging process of medical tools and also assist in devising complex and customized objects.[2] when used for specific medical purposes, 3d printing technology is recognized as one of the newest devices in expanding the use of health-related innovations.[2] loke et al examined the effect of the use of a three-dimensional model on the learning process. the results showed that as a result of the use of the 3d models in training, the pediatric cardiopulmonary residents were motivated to acquire more information about congenital heart disease.[3] the purpose of our study was to determine the impact of learning on ophthalmology residents using 3d printing of models from orbital ct for training purposes. the effectiveness of applying 3d models for teaching and learning in various subjects indicates the useful application of these models. 3d modeling is effective in improving students’ visual-spatial skills in the teaching–learning process.[4] one distinguishing feature of 3d models is that it provides immediate feedback to student, interacting and providing enhanced correspondence to: mohammad etezad razavi, md. mashhad eye research centre, khatam eye hospital, abotaleb cross road, mashhad university of medical sciences, mashhad 9195965919, iran e-mail: etezadm@mums.ac.ir received: 01-12-2020 accepted: 21-05-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9751 realistic learning experiences in a clinical setting.[5] orbit surgery can be challenging due to the compact anatomy of the orbit.[6] interestingly, 3d models may also be developed for tissue repair in orbital surgery to assist in the prevention of tissue hernias inside the sinuses; in addition, actual 3d models may be used in repairing orbit fractures to cover bone defects.[7] according to the studies, a 3d printing model can be used in ophthalmology as a tool in assisting the restoration of facial bones, especially orbital wall fractures.[8] although it mentioned that 3d models can help to facilitate the understanding of anatomy and anomalies in conjunction with the use of the 2d images.[9] understanding particular body parts that have certain complexities such as orbital and other complex mid face bones from using 2d images is indeed complicated. in fact, it is not entirely possible to ascertain with 2d or even 3d images. however, by providing models that are fully compliant with the ct scan, normalsized dimensions of patients’ affected regions would assist in visualizing a better environment from different angles and enabling touch from multiple anatomical areas, thus making it easier for residents to understand the inherent pathologies and anatomies. instructional teaching materials should be made available in a manner that is uncomplicated and affordable due to the importance of empowering students to learn concepts effectively through visual aids and touch training, which provides better understanding, as sensory aids may improve memory and the learning process.[10] methods this quasi-experimental study evaluated the effect of using 3d models on educational outcomes. the residents were categorized based on their educational stage (namely, first or second year enrollment), and then stratified randomization this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: vatankhah r, emadzadeh a, nekooei s, tafaghodi yousefi b, khadem-rezaiyan m, karimi moonaghi h, etezad razavi m. 3d printed models for teaching orbital anatomy, anomalies and fractures. j ophthalmic vis res 2021;16:611–619. 612 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 https://knepublishing.com/index.php/jovr orbital 3d printed models; vatankhah et al was performed. however, randomization is more effective when the sample size is higher than 100 in each group, which was not the case in the present study. this issue was considered in the interpretation of results, where it was highlighted in the main text. the study was performed on the selected ophthalmology residents of mashhad university of medical sciences in two phases. firstly, a standardized educational booklet was prepared based on the reference source of the ophthalmology (american academy of ophthalmology 2017–2018) and secondly, an educational model was designed based on 3d printing obtained from radiological images, including normal orbital ct scans, various types of fractures, and some congenital abnormalities. how to produce 3d models has been discussed in detail in another study.[11] after the randomization was performed based on the residents’ academic id, the subjects from each academic year were divided into two groups defined as the intervention and control group, respectively. the inclusion criteria consisted of the selected ophthalmology residents in the first and second academic years (2019 and 2020). those who were unwilling to participate in the research were excluded from the study. the standard training booklet about knowing orbital anatomy and pathology was prepared with the cooperation of specialists in medical education and ophthalmology. the training booklet was given to both the intervention and the control groups to revise the topics related to anatomy, anomalies, and orbital fractures. the level of information retained was measured using various methods of training. the 3d model technique was taught to the intervention group during a 2-hr session. an ophthalmologist provided detailed explanations, and answered questions. all residents, in both the control and the intervention groups were tested twice at different intervals, firstly, three days after the initial training, residents were tested on their short-term ability to retain information (memorization) and secondly at fourteen days after training to determine their retention of information. the pretest and posttest included 12 multiple choice questions with onepoint for correct choices and zero points for wrong choices or unanswered ones. pretest and posttest questions were different because we assumed that using identical questions would reduce the responsiveness, and increase recall bias. to ensure that the two tests were analyzed with the same parameters, the discrimination and difficulty index of the test were calculated and reported. the data analyzer was unaware of which of the groups were assigned to the analysis. data were described using spss software version 16 where a per-protocol design was considered. the quantitative data were displayed in terms of average and standard deviation, while the qualitative data were described in terms of frequency and percentage. pretest scores followed normal distribution in both the control and the intervention groups, but posttest scores did not follow a normal distribution. the comparison between quantitative variables recorded in the two groups was performed using student t-test for the pretest and mann–whitney for the posttest at threeand fourteen-day intervals. qualitative variables in the two groups were evaluated using chi-square. the trend of the score variables within the two groups was calculated using the repeated measures of anova. the relationship between the use of the studying booklet and the posttest scores was evaluated using the pearson’s correlation test. all tests were two-tailed, and the significance level was less than 0.05. results among the 24 first and second year residents of ophthalmology, 12 were men (50%); the overall average age was 29.66. table 1 shows the frequency and number of groups studied by grade, age, and gender. the control group was three years younger than the intervention group (p = 0.047) [table 1]. thirteen residents were trained traditionally using medical definitions and 1d images for anatomy, fractures, and orbital diseases, while eleven residents were trained using the printed 3d model technique. the difficulty index of the pretest was 0.76, its discrimination index was 0.34, the difficulty index of the posttest was 0.76, and its discrimination index was 0.60. the results showed a statistical difference between the total posttest scores in the control and intervention groups [table 2]. figure 1 illustrates the variables in scores in the two study groups along with error bars (1 se). journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 613 orbital 3d printed models; vatankhah et al table 1. basic characteristics of the studied groups control group (n = 13) intervention group (n = 11) significance level gender male 8 (61.5) 4 (27.3) 0.0931 female 5 (38.4) 7 (63.6) age 28 ± 1.5 31.2 ± 3.9 0.0472 academic year first year 6 (46.1) 6 (54.5) 0.0881 second year 7 (53.8) 5 (45.4) 1probability value test chi2 2mann–whitney test data reported as mean ± standard deviation or frequency (%) table 2. the total scores of the groups studied in the pretest and posttest control group intervention group significance level pretest scores 7.46 ± 1.89 7.90 ± 2.02 0.058* posttest scores three days 2.25 ± 7.69 10.63 ± 2.15 0.003** fourteen days 8.15 ± 2.19 10.27 ± 2.10 >0.001** *t-test **mann–whitney test the trend of score variables based on the repeated measures of anova was significant between the two groups (p = 0.008). the study of the linear relationship between the score variables at the baseline, then at three days and fourteen days posttest was performed using the pearson’s correlation test. the changes in scores from baseline to three days was positively correlated with the number of pages studied (r = 0.416, p = 0.043). in addition, the change in score at three days and fourteen days positively correlated with the number of pages studied (r = 0.487, p = 0.016). the amount of the pages of the educational booklet studied three times did not differ significantly between the two groups. in the subgroup analysis based on the residents’ academic year in the whole study, the 3d training intervention had significantly better results in oneyear residents. interestingly, in this study the 3d educational model was found to be more effective and statistically significant in junior (year one) residents rather than their senior counterparts [table 3]. discussion the purpose of this study was to determine the impact on learning of ophthalmology residents using 3d printing models from orbital ct scans. it was observed that the intervention of 3d training through models was influential in motivating residents to learn. based on the total scores, the findings of the present study showed that the educational model was more applicable and effective in the intervention group, which was statistically more significant than the control group. figure 1 shows the changes in the scores, which can be generalized throughout the community. this figure suggests perpetual learning from the control group, but the intervention group, which possessed the same baseline as the control baseline, increased their scores and then decreased significantly during the time interval between three days after the posttest and fourteen posttest were justified. the use of 3d models for training process has many positive effects on learning. loke et al (2017) found that the learning intervention group of cardiac assistants as compared to the control group were effectively taught the 3d model technique of fallot tetralogy disease.[3] montgomery (2019) asserted that 3d modeling of complex fractures in orthopedic assistants’ training programs could be a valuable training tool, especially for first-year assistants.[12] in the same regard, the weinmann 2014 study also found that 3d technology had a 614 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 orbital 3d printed models; vatankhah et al table 3. subgroup analysis based on the academic year studied groups academic year year one year two pretest scores control group 7.33 ± 1.86 7.57 ± 2.07 intervention group 9.16 ± 1.16 6.40 ± 1.81 p-value 0.068* 0.334* posttest three days control group 7.83 ± 2.13 7.57 ± 2.50 intervention group 12 ± 0.0 9.00 ± 2.34 p-value 0.002** 0.285** posttest fourteen days control group 8.66 ± 1.96 7.71 ± 2.42 intervention group 10.66 ± 1.50 9.80 ± 2.77 p-value 0.049** 0.071** *t-test **mann–whitney data reported as mean ± standard deviation or frequency (%) figure 1. changes in scores in the two study groups along with error bars (1 se) meaningful impact on facilitating and developing influential learning environments, which was effective in creating positive learning experiences and motivation in students. in addition, 3d printers were essential tools in the development of people’s visual spatial intelligence.[13] canessa referred to 3d printers as essential tools in increasing interest in the classroom, also in developing efficient learning activities for teaching conceptual information or complex situations.[14] lütolf also stated that students’ motivation in contributing to the development phase of the 3d project was on the rise, as they are fully interested in the project.[15] blikstein proposed journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 615 orbital 3d printed models; vatankhah et al that their 3d printers were effective in teaching and increasing motivation, performance, and knowledge retention in students.[16] slavkovsky also found 3d printers to be successful in teaching social studies courses.[17] also, krassenstein noted that the production of abstract or rigid educational materials, especially in the social sciences (e.g., geography, history, geology), has important implications for further understanding of compelling learning experiences.[18] the findings of the present study showed that there was a statistically significant difference between the two groups after 14 days of follow-up. the difference between the mean score of the control and intervention groups indicated that the intervention group scores were higher than the control scores. thus, learning with physical models inherently influences and potentially enhances the knowledge of assistants, consistent with the 2015 study by yammine et al.[19] the sisson 2012 study also showed a 3d interactive learning technique to facilitate learning and long-term knowledge with ancillary teaching materials.[20] the lim et al 2018 study revealed three-dimensional models were considered by orthopedic assistants to be a desirable training method which indicated increase in accurate diagnoses of tabular fractures.[21] in summary, the use of 3d teaching materials can positively affect in the learning of 3d understanding of orbital and midfacial anatomy and anomalies. these educational models were considered to be able to sense for better understanding and visualization. the varied benefits of 3d touch training models include abstract reinforcement of points and content, stimulation of the imagination, enhancement of perception, increased student retention, expanded memory capacity, and increased attention and focus in the classroom.[22] according to the literature reviewed, this is the first study in iran to determine the effect on learning through the use of 3d printed models in medical education as it relates to specialized ophthalmology residency. residents who experienced multiple levels of training were all given access to the same materials and assessments. it was determined that 3d printing makes it possible to convert medical images, computed tomography (ct), into tangible models thereby providing solutions to address particular issues such as dealing with orbital bone, fissures, and the complex anatomy of the orbit. as residents had never encountered such technology before this study and have had no such experience before, it has been proven that the investigation of the use of 3d models in training of complex anatomical and pathological body structures was successful. this method of teaching may have surprising positive effect on the trainee’s visual and perceptive competencies as well as the whole learning process. acknowledgements this article was a part of an msc dissertation in educational technology in medical sciences conducted at mashhad university of medical sciences. the authors would like to thank all the colleagues who participated in different stages of this project especially dr. tahereh sadeghi. financial support and sponsorship the authors thank the research and educational chancellor of mashhad university of medical sciences for the material-spiritual support, in particular edc. conflicts of interest none declared. 616 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 orbital 3d printed models; vatankhah et al appendix the project implementation of the 3d printing-based model is shown as follows;[11] (a written consent was taken from the residents to publish theirs photo.) journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 617 orbital 3d printed models; vatankhah et al references 1. simsek i. the effect of 3d virtual learning environment on secondary school third grade students’ attitudes toward mathematics. turkish online journal of educational technology-tojet 2016;15:162–168. 2. lupton d. fabricated data bodies: reflections on 3d printed digital body objects in medical and health domains. social theory & health 2015;13:99–115. 3. loke yh, harahsheh as, krieger a, olivieri lj. usage of 3d models of tetralogy of fallot for medical education: impact on learning congenital heart disease. bmc medical education 2017;17:54. 4. ayala alvarez fj, blazque parra eb, montes t. assessment of 3d models used in contours studies. universal journal of educational research 2015;3:877–890. 5. loke y-h, harahsheh as, krieger a, olivieri lj. usage of 3d models of tetralogy of fallot for medical education: impact on learning congenital heart disease. bmc medical education 2017;17:54. 6. meyer er, james am, cui d. hips don’t lie: expert opinions guide the validation of a virtual 3d pelvis model for use in anatomy education and medical training. haps educator 2018;22:105–118. 7. weadock wj, heisel cj, kahana a, kim j. molds for shaping implants for surgical repair of orbital fractures. academic radiology 2019;27:536–542. 8. kang s, kwon j, ahn cj, esmaeli b, kim gb, kim n, et al. generation of customized orbital implant templates using 3-dimensional printing for orbital wall reconstruction. the royal college of ophtalmologists 2018;32:1864–1870. 9. elrod r. tinkering with teachers: the case for 3d printing in the education library. education libraries 2016;39:1–13. 10. chen h, kelly m, hayes c, van reyk d, herok g. the use of simulation as a novel experiential learning module in undergraduate science pathophysiology education. advances in physiology education 2016;40:11. 618 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 orbital 3d printed models; vatankhah et al 11. vatankhah r, etezad-razavi m, nekoei s, khademrezaiyan m, tafaghodi-yousefi b, karimi-monaghi h, et al. three-dimensional (3d) visualization educational modeling for ophthalmology residents’ training. mjiri. in press. 12. montgomery sj, kooner ss, ludwig te, schneider ps. impact of 3d printed calcaneal models on fracture understanding and confidence in orthopedic surgery residents. journal of surgical education 2019:77:472–478. 13. weinmann j. makerspaces in the university community [dissertation on the internet]. germany: technische universität münchen; 2014. [cited 2014 august 21] available from: https://fabfoundation.org/resource-folder/ pdfs/weinmann_masters_thesis.pdf 14. canessa e, fonda c, zennaro m, deadline n. lowcost 3d printing for science, education and sustainable development. low-cost dd printing 2013;22:11. 15. lütolf g. using 3d printers at school: the experience of 3drucken.ch. in: canessa e, fonda c, zennaro m, editors. low-cost 3d printing for science, education and sustainable development. trieste, italy: the abdus salam international centre for theoretical physics (ictp); 2013. p. 149–158. 16. blikstein p. digital fabrication and ‘making’ in education: the democratization of invention. in: walter-herrmann j, büching c, editors. fablabs: of machines, makers and inventors. bielefeld: transcript publishers; 2013. 17. slavkovsky ea. feasibility study for teaching geometry and other topics using three-dimensional printers. harvard university; 2012. 18. krassenstein e. why 3d printing needs to take off in schools around the world [internet]. 3dprint.com; 2014 [cited 2014 december 21]. available from: https://3dprint. com/27743/3d-printing-benefits-schools/ 19. yammine k, violato c. the effectiveness of physical models in teaching anatomy: a meta-analysis of comparative studies. advances in health sciences education 2016;21:883–895. 20. sisson sd, rastegar da, ughes mt, bertram ak, yeh h. learner feedback and educational outcomes with an internet-based ambulatory curriculum: a qualitative and quantitative analysis. bmc medical education 2012;12:55. 21. lim pk, stephenson gs, keown tw, byrne c, lin cc, marecek gs, et al. use of 3d printed models in resident education for the classification of acetabulum fractures. journal of surgical education 2018;75:6. 22. wonjin j, jang hi, harianto ra, so jh, lee h, lee hj, et al. introduction of 3d printing technology in the classroom for visually impaired students. journal of visual impairment & blindness 2016;110:115–121. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 619 https://fabfoundation.org/resource-folder/pdfs/weinmann_masters_thesis.pdf https://fabfoundation.org/resource-folder/pdfs/weinmann_masters_thesis.pdf https://3dprint.com/27743/3d-printing-benefits-schools/ https://3dprint.com/27743/3d-printing-benefits-schools/ review article pattern of uveitis in iran: a systematic review masood bagheri, md1,2; mohammad-hosein ahoor, md2; ahad jafari, md2; hesam sadat hashemi, md2 mehdi mohammadkhani, md2 1department of ophthalmology, imam khomeini eye center, kermanshah university of medical sciences, kermanshah, iran 2department of ophthalmology, nikookari eye center, tabriz university of medical sciences, tabriz, iran orcid: masood bagheri: https://orcid.org/0000-0002-9288-7475 abstract purpose: uveitis is the third leading cause of blindness worldwide. this study aimed to summarize the pattern of uveitis in iran through a systematic review. methods: this review was conducted according to the guidelines for systematic reviews in the following four steps: literature search, study selection and assessment, inclusion and exclusion criteria, and statistical analysis. results: one hundred and fifteen articles were identified by an encyclopedic literature search, and three independent investigators examined them according to the defined inclusion and exclusion criteria. eventually, 109 manuscripts were retrieved and six crosssectional studies covering 3,567 patients were included and reviewed. according to the results, the mean age of patients was 40 years, and sex was not a statistically significant predisposing factor. the most common anatomical pattern of involvement was anterior uveitis, and the prevalence of the other three types of uveitis, including middle, posterior, and pan-uveitis, were almost equal. overall, the most common etiologies of uveitis in the iranian population were idiopathic uveitis, toxoplasmosis, behcet’s syndrome, and fuchs heterochromic iridocyclitis. conclusion: this study depicted the pattern of uveitis in the iranian society; this can help physicians in the diagnostic approach, management, and treatment of patients. keywords: epidemiology; iran; systematic review; uveitis j ophthalmic vis res 2021; 16 (1): 93–102 introduction uveitis is an umbrella term that includes a wide spectrum of intraocular inflammatory conditions in which the various parts of the eye may be attacked by the immune system.[1] correspondence to: masood bagheri, md. department of ophthalmology, imam khomeini eye center, kermanshah university of medical sciences, kermanshah, iran. e-mail: bagheri.m1368@gmail.com received: 03-01-2020 accepted: 23-10-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i1.8255 uveitis refers to inflammation of the uveal tract (iris, ciliary body, and choroid); however, retina, vitreous body, optic nerve, and sclera may also be involved.[2] the etiology of the disease is categorized into traumatic, infectious, and noninfectious-immunologic causes and masquerade syndromes.[3, 4] this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: bagheri m, ahoor m-h, jafari a, hashemi hs, mohammadkhani m. pattern of uveitis in iran: a systematic review. j ophthalmic vis res 2021;16:93–102. © 2021 bagheri et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 93 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i1.8255&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr pattern of uveitis in iran; bagheri et al noninfectious-immunologic uveitis comprises vision-threatening diseases that can be associated with systemic or ocular autoimmune disease, with specific or unknown etiology.[5] more than two million patients worldwide have uveitis,[1] and it has an estimated incidence of 17–52/100,000 person-years. approximately 35% of these individuals experience severe visual loss and legal blindness[2] and it is the third leading cause of blindness (approximately 5– 10% worldwide).[1, 6, 7] intermediate, posterior, and pan-uveitis are responsible for visual disabilities in most of these patients. the most common sight-threatening complications are macular edema, retinal detachment, retinal vasculitis, and optic neuropathy. other causes include phthisis bulbi, hypotony,[8] band keratopathy, and glaucoma.[1] the prevalence, phenotypic features, and distribution of different types of uveitis depend on genetic and epidemiologic factors such as age, sex, race, geographic and environmental influence, and social habits.[6, 9] uveitis may occur in any age group, from infancy to adulthood, but individuals aged 20–60 years old are more susceptible (the incidence in adults is approximately fivefold of that in children).[2] global studies have found anterior uveitis to be the most common type of involvement seen in both adults and children, but the underlying etiologies differ; for example, juvenile idiopathic arthritis (jia)-associated uveitis is more common in children and hlab27-associated uveitis predominantly affects young adults.[9] in most studies, male and female patients were equally affected.[3, 10] however, some causes are more prevalent in a particular gender; for example, hla-b27-associated anterior uveitis is more common among male patients,[2] and jiaassociated uveitis and multiple sclerosis (ms)associated intermediate uveitis are more common in young girls.[11–13] the epidemiology of non-infectious uveitis is more dependent on racial rather than regional features.[14] the prevalence of infectious uveitis (estimated at 30–50% of all uveitis cases) and some non-infectious posterior uveitis, such as behcet’s and vogt-koyanagi-harada (vkh) syndrome, is higher in developing countries.[4, 15, 16] common infectious causes include toxoplasmosis,[15, 17] tuberculosis (tb), onchocerciasis, cysticercosis, leprosy, and leptospirosis.[2] the prevalence of some causes of non-infectious uveitis depends on the regional area: for instance, sarcoidosis in japan.[18] behcet’s disease in countries along the ancient silk road (iran, turkey, china, japan, saudi arabia, and greece),[9, 19] and vkh syndrome in asian or eurasian countries.[18] generally, the prevalence of infectious uveitis is lower in developed countries; common causes are herpes virus and toxoplasmosis, while other infections, such as tb and syphilis, are rare.[4] ocular inflammation embraces a broad range of pathologies, both with respect to its etiology and the anatomical location within the eye. for proper listing of the differential diagnosis, practitioners should survey all important information, such as the anatomical location of involvement, pathology (granulomatous vs non-granulomatous), laterality (unilateral vs bilateral), and chronicity (acute, recurrent, or chronic) of the inflammation.[4] the classification of uveitis helps physicians in the diagnostic approach, management, and treatment of patients. to date, several classification systems have been proposed that vary according to the anatomical location of involvement (primary site of the inflammation), clinical course, etiology, and histopathology.[20, 21] based on the standardization of uveitis nomenclature working group,[21] the anatomical location of involvement is classified into four types as follows: anterior, intermediate, posterior, and pan-uveitis (table 1). this classification is widely accepted today and is now the standard required for the publication of uveitis studies in peer-reviewed literature. the etiologic distribution of uveitis varies from region to region and parallels that of many studies that have investigated the pattern of uveitis in different parts of the world. most of the data in this field are from the us and europe, and reports from developing countries are limited.[4, 14, 22] today, an acceptable number of reports that focus on the epidemiology of uveitis in iran are available; however, all these studies have been conducted in university-based ophthalmology centers. in this study, we review all the available articles on the epidemiology of uveitis in iran to discuss novel and interesting data regarding the pattern of the disease. 94 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 pattern of uveitis in iran; bagheri et al table 1. anatomical location of involvement in uveitis based on the standardization of uveitis nomenclature (sun) working group type primary site of inflammation includes anterior uveitis anterior chamber iritis iridocyclitis anterior cyclitis intermediate uveitis vitreous pars planitis posterior cyclitis hyalitis posterior uveitis retina or choroid focal, multifocal, or diffuse choroiditis chorioretinitis retinochoroiditis retinitis neuroretinitis panuveitis anterior chamber, vitreous, and retina or choroid methods this review was conducted according to the guidelines for systematic reviews in healthcare[23] in four steps as described below (methodology described in figure 1): literature search an encyclopedic literature search for articles published up to july 2019 was conducted on medline, embase, and the cochrane library. no language limitations were applied. all studies that reported the epidemiology of uveitis in iranian patients were detected based on the medical subject heading (mesh) terms for the following search strategy: “{[(“uveitis” or “panuveitis” or “ophthalmia, sympathetic” or “uveitis, anterior” or “uveitis, posterior” or “uveitis, intermediate” or “pars planitis” or “uveitis, suppurative” or “panophthalmitis”).af.] and (ocular inflammation) and (iran.mp. [mp=ti, ot, ab, tx, ct, sh, kw, ps, sj, do, dv, po, go, rs, nm, hw, an, ui])}.” in addition, a broad literature search was conducted using persian databases such as iranmedex (www.iranmedex.com), scientific information database (www.sid.ir), and magiran (www.magiran.com). a manual search was performed in the following journals: journal of ophthalmic and vision research (http: //www.jovr.org), journal of current ophthalmology (https://www.journals.elsevier.com/journal-ofcurrent-ophthalmology), and bina journal of ophthalmology (binajournal.org). finally, the cited references in the obtained studies were manually reviewed for relevant articles. a total of 15 articles were found in this step. study selection & assessment articles that were most relevant to our topic were selected, and among them, the reported prevalence, incidence, or epidemiologic pattern of uveitis were thoroughly studied. inclusion & exclusion criteria two researchers, m.b. (md, ophthalmologist, vitreoretinal surgeon) and a.j. (md, general ophthalmologist), independently assessed the titles and abstracts identified in the previous step for potential eligibility, and the fulltext articles were retrieved for studies on the epidemiological pattern of uveitis in the iranian population. fifty-nine studies were found and all their full-text versions were obtained. to avoid potential bias or errors, three independent individuals, m.b., a.j., and h.s.h. (md, statisticians) examined the quality of the papers separately according to the checklist journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 95 www.iranmedex.com www.sid.ir www.magiran.com http://www.jovr.org http://www.jovr.org https://www.journals.elsevier.com/journal-of-current-ophthalmology https://www.journals.elsevier.com/journal-of-current-ophthalmology pattern of uveitis in iran; bagheri et al ta b le 2 .t he ch ar ac te ris tic s of th e in cl ud ed st ud ie s fo rm et aan al ys is an d su m m ar iz ed uv ei tis pa tte rn in th e st ud ie s ca rr ie d ou ta tt er tia ry op ht ha lm ol og y re fe rr al ce nt er s in ira n s tu d y f ir st a u th o r c it y (u n iv e rs it y) p u b lic a ti o n d a te (d u ra ti o n o f st u d y) s a m p le si ze m e a n a g e (r a n g e ) m a le / fe m a le u n ila te ra l/ b ila te ra l a n t. u ve it is n (% ) in t. u ve it is n (% ) p o st . u ve it is n (% ) p a n u ve it is n (% ) in fe ct io u s/ n o n in fe ct io u s g ra n u lo m a to u s/ n o n g ra n u lo m a to u s pa tte rn s of u ve iti s at a te rt ia ry re fe rr al c en te ri n n or th ea st er n ira n [ 2 5] h os se in is m ey e re se ar ch c en te r, m as hh ad u ni ve rs ity of m ed ic al sc ie nc es , m as hh ad ,i ra n. 20 18 (f eb 20 13 to m ar 20 14 ) 23 5 35 .7 5 ± 16 .3 4 (3 –8 2) 94 /14 1 85 /15 0 87 (3 7) 28 (11 .9 ) 10 (4 .2 5) 11 0 (4 6. 8) 46 /18 9 32 /17 9 (2 4 un de fin ed ) c lin ic al c ou rs e of u ve iti s in c hi ld re n in a te rt ia ry o ph th al m ol og y c en te ri n n or th w es t ira n[ 26 ] a liz ad eh g ha vi de ll d ep ar tm en to f o ph th al m ol og y, n ik oo ka ri ey e c en te r, ta br iz u ni ve rs ity of m ed ic al sc ie nc es ,t ab riz ,i ra n. 20 17 (2 0 0 3 to 20 15 ) 24 3 12 .3 ± 4. 53 (1– 18 ) 11 3/ 13 0 10 5 /13 8 73 (3 0) 14 6 (6 0. 1) 12 (4 .9 ) 12 (4 .9 ) 28 /2 15 40 /2 0 3 d em og ra ph ic an d c lin ic al fe at ur es of pe di at ric u ve iti s at a te rt ia ry re fe rr al c en te ri n ira n[ 27 ] r ah im im d ep ar tm en to f o ph th al m ol og y, po us tc hi ey e re se ar ch c en te r, sh ira z u ni ve rs ity of m ed ic al sc ie nc es ,s hi ra z, ira n. 20 16 (j an 20 07 to d ec 20 13 ) 54 12 .5 ± 5 (2 – 18 ) 24 /3 0 31 /2 3 22 (4 0. 7) 18 (3 3. 3) 10 (18 .5 ) 4 (7 .5 ) 10 /4 4 — c lin ic al pa tte rn s of u ve iti s in an ira ni an te rt ia ry ey eca re c en te r[ 2 8] ki an er si f is fa ha n ey e re se ar ch c en te r, fe iz ey e h os pi ta l, is fa ha n u ni ve rs ity of m ed ic al sc ie nc es ,i sf ah an , ira n. 20 15 (19 99 to 20 12 ) 20 16 33 .7 6 ± 10 .5 6 (2 .5 –9 8) 91 5 /11 0 1 12 32 /7 84 86 5 (4 2 .9 ) 39 0 (19 .3 ) 43 2 (2 1.4 2) 32 9 (16 .3 ) 47 4/ 15 42 17 6/ 18 40 pa tte rn s of u ve iti s at a te rt ia ry re fe rr al c en te ri n so ut he rn ira n[ 29 ] r ah im im po us tc hi ey e re se ar ch c en te ra nd o ph th al m ol og y d ep ar tm en t, sh ira z u ni ve rs ity of m ed ic al sc ie nc es ,s hi ra z, ira n. 20 14 (j un 20 0 5 to ju ly 20 11 ) 47 5 30 .5 ± 15 .4 (5 – 56 ) 21 6/ 25 9 29 2 /18 3 19 0 (4 0) 53 (11 .1) 13 3 (2 8) 99 (2 0. 8) 11 0/ 36 5 52 /4 23 pa tte rn s of uv ei tis in a te rt ia ry ey e ca re ce nt er in ira n[ 30 ] so he ili an m o cu la ri nfl am m at or y an d u ve iti s se rv ic e, o ph th al m ol og y d ep ar tm en ta nd o ph th al m ic re se ar ch c en te r, la bb afi ne ja d m ed ic al c en te r, sh ah ee d b eh es ht iu ni ve rs ity of m ed ic al sc ie nc es ,t eh ra n, ira n. n eg ah ey e c en te r, te hr an ,i ra n. 20 04 (19 97 to 20 0 0) 54 4 32 .3 ± 15 .2 (— ) 23 8/ 30 6 27 5 /2 69 20 9 (3 8. 41 ) 96 (17 .6 ) 10 1( 18 .6 ) 13 8 (2 5 .4 ) 90 /4 54 79 /4 65 a nt .u ve iti s: an te rio ru ve iti s; in t. uv ei tis :i nt er m ed ia te uv ei tis ;p os t. uv ei tis :p os te rio ru ve iti s 96 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 pattern of uveitis in iran; bagheri et al table 3. common etiologies of uveitis in different types in studies carried out at tertiary ophthalmology referral centers in iran study (first author) ant. uveitis (%) int. uveitis post. uveitis pan-uveitis (%) total (%) hosseini sm, et al (2018)[25] idiopathic (27.5) > fhi (17.24) > herpetic uveitis (13.7) = seronegative spondyloarthropathy (13.7) > jia (4.6) idiopathic (60.7) > behcet’s syndrome (10.7) = seronegative spondyloarthropathy (10.7) > sarcoidosis (7.1) toxoplasmosis (30) > serpiginous choroidopathy (20) > idiopathic (10) = herpetic uveitis (10) = sarcoidosis (10) = presumed tuberculosis (10) idiopathic (22.72) = behcet’s syndrome(22.72) = vkh(22.72) = herpetic uveitis (6.3) = presumed tuberculosis (6.3) idiopathic (28.5) > behcet’s syndrome (16.6 > vkh (10.6) > herpetic uveitis (21) > seronegative spondyloarthropathy (6.8) > fu (6.4) rahimi m, et al (2016)[27] idiopathic (59) > jia (22.7) > posner-schlossman (9) > herpetic uveitis (4.5) = all-l2 (4.5) idiopathic (94.4) > sarcoidosis (5.6) toxoplasmosis (40) = toxocariasis (40) > idiopathic (20) idiopathic (50) > vkh (25) > sympathetic ophthalmia (25) idiopathic (62.9) > jia (9.2) > toxoplasmosis (7.4) = toxocariasis (7.4) > herpetic uveitis (1.8) kianersi f, et al (2016)[28] idiopathic (50.5) > fhi (32.8) > herpetic uveitis (7.6) > behcet’s syndrome (2.6) > jia (1.3) idiopathic (81.6) > behcet’s syndrome (6.1) >multiple sclerosis (4.1) toxoplasmosis (90.7) > idiopathic (4.7) > behcet’s syndrome (1.4) behcet’s syndrome (48) > idiopathic (32) > vkh (2.7) > arn (2.4) = sarcoidosis (2.4) idiopathic (43.9) > toxoplasmosis (19.3) > fhi (14.1) > behcet’s syndrome (10.5) > herpetic uveitis (3.2) rahimi m, et al (2014)[29] idiopathic (44.2) > fhi (17.8) > seronegative spondyloarthropathy (10) > herpetic uveitis (7.8) = jia (7.8) idiopathic (92.4) toxoplasmosis (42.1) > behcet’s syndrome (15.7) > arn (8.2) > vkh (6) > toxocariasis (4.7) behcet’s syndrome (34.3) > vkh (17.1) > endogenous endophthalmitis (11.4) > sympathetic ophthalmia (3) idiopathic (37.9) > behcet’s syndrome (12.4) > toxoplasmosis (11.8) > fhi (7.1) > vkh (5.2) soheilian m, et al (2004)[30] idiopathic (52.1) > fhi (17.2) > seronegative spondyloarthropathy (10) > jia (4.8) > herpetic uveitis (3.8) idiopathic (86.5) > sarcoidosis (7.3) > multiple sclerosis (4.2) toxoplasmosis (54.5) > eales disease (11.9) > toxocariasis (10.9) > arn (8.9) > serpiginous choroidopathy (4) = apmppe (4) behcet’s syndrome (34.1) > idiopathic (22.5) > vkh (15.2) > multifocal choroiditis and panuveitis (10.1) > sarcoidosis (5.1) = sympathetic ophthalmia (5.1) idiopathic (45.5) > toxoplasmosis (10.1) > behcet’s syndrome (8.6) > fhi (6.6) > vkh (3.9) ant. uveitis: anterior uveitis; int. uveitis: intermediate uveitis; post. uveitis: posterior uveitis literature search • medline, pubmed, mbase and cochrane ( n= 91) • sid, iran medex, magiran and hand search in journals ( n= 17) 115 studies obtained • relevant cited study ( n= 7) selection study & assessment • irrelevant study excluded ( n= 52 ) • reviews excluded ( n= 3) 56 studies excluded • comments and letters excluded ( n= 1) inclusion & exclusion criteria • study extracted by independent investigators ( n= 51) • 53 studies excluded • doplication study excluded ( n= 2) included study • study included ( n= 6) statistical analysis • data collected • illustration funnel plot and forest plot • overall effect size and fixed-effects model figure 1. the methodology of the study step by step. during an encyclopedic literature search and survey of relevant cited studies, 115 studies were found, where 56 were excluded in the second step (irrelevant studies, reviews, comments and letters). after reviewing the inclusion and exclusion criteria, 53 more studies were excluded, and finally, 6 studies were included for statistical analysis. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 97 pattern of uveitis in iran; bagheri et al study name (first author) subgroup within study event rate lower limit upper limit event rate and 95% ci ant. uveitis hosseini sm, et al (2018) [25] 0.370 0.311 0.434 alizadeh l, et al (2017) [26] 0.300 0.246 0.361 rahimi m, et al (2016) [27] 0.407 0.285 0.542 kianersi f, et al (2016) [28] 0.429 0.408 0.451 rahimi m, et al (2014) [29] 0.400 0.357 0.445 soheilian m, et al (2004) [30] 0.384 0.406 0.344 0.390 0.426 0.422 int. uveitis hosseini sm, et al (2018) [25] 0.119 0.084 0.167 alizadeh l, et al (2017) [26] 0.601 0.538 0.661 rahimi m, et al (2016) [27] 0.333 0.221 0.468 kianersi f, et al (2016) [28] 0.193 0.177 0.211 rahimi m, et al (2014) [29] 0.112 0.086 0.143 soheilian m, et al (2004) [30] 0.176 0.212 0.147 0.198 0.211 0.227 post. uveitis hosseini sm, et al (2018) [25] 0.043 0.023 0.077 alizadeh l, et al (2017) [26] 0.049 0.028 0.085 rahimi m, et al (2016) [27] 0.185 0.103 0.311 kianersi f, et al (2016) [28] 0.214 0.197 0.233 rahimi m, et al (2014) [29] 0.280 0.241 0.322 soheilian m, et al (2004) [30] 0.186 0.209 0.155 0.195 0.221 0.223 pan-uveitis -1.00 -0.50 0.00 0.50 1.00 hosseini sm, et al (2018) [25] alizadeh l, et al (2017) [26] rahimi m, et al (2016) [27] kianersi f, et al (2016) [28] rahimi m, et al (2014) [29] soheilian m, et al (2004) [30] 0.468 0.049 0.074 0.163 0.208 0.254 0.206 0.405 0.028 0.028 0.148 0.174 0.219 0.192 0.532 0.085 0.181 0.180 0.247 0.292 0.220 figure 2. pattern of uveitis based on anatomical location of involvement explained in this figure according to the studies separately. ant. uveitis: anterior uveitis; int. uveitis: intermediate uveitis; post. uveitis: posterior uveitis for critical appraisal and data extraction for systematic reviews of prediction modelling studies (charms).[24] then, the data were extracted. discrepancies were resolved by a consensus or discussion with the fourth reviewer, m.h.a. (md, ophthalmologist, vitreoretinal surgeon), if necessary. eventually, six cross-sectional studies covering 3,567 patients and data extracted by the investigators were included, and the final data were matched. statistical analysis the following data were collected from each study: the name of the first author, publication date, city or academic center, duration of the study, number of patients, demographic characteristics, anatomical pattern of involvement, etc. (table 2). data were analyzed using the comprehensive meta-analysis.2 (cma.2) software. the heterogeneity index was assessed using the 98 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 pattern of uveitis in iran; bagheri et al i2 test. a random-effects model was employed if the test revealed substantial heterogeneity (i2 > 50%). if non-significant (i2 ≤ 50%), a fixed-effects model was used.[31] the level of significance for both heterogeneity and the pooled effect was adjusted at p < 0.05. results of the nine studies that examined the epidemiology of uveitis in the iranian society, three were excluded because two were duplicates[32, 33] and one was conducted only in patients with posterior uveitis.[34] finally, data from six studies were analyzed; two involved cases of pediatric uveitis and four involved adults. except for two studies that examined pediatric uveitis (patients enrolled in the age range <18 years),[26, 27] the mean age of the patients included in the studies was 40 years.[25, 28–30]. in all reports, the disease was more common in women than in men, except in the study by hosseini et al, where this ratio was statistically significant (female to male ratio was 1.5).[25] statistical analysis showed that the most common anatomical pattern of involvement in the tertiary referral ophthalmology centers was anterior uveitis (event rate: 40.6% among all uveitis patients), but the prevalence of the other three types including middle, posterior, and pan-uveitis was almost equal (because of the non-significant i2, the fixed-effects model was used to estimate the overall effect size; data not shown). in the majority of studies, the most common anatomical site of involvement was anterior uveitis[27–30] except in the reports by hosseini et al[25] (pan-uveitis was prevalent in 110 out of 235 involved; 46.8%) and alizadeh-ghavidel et al[26] (intermediate uveitis was prevalent with 146 out of 243 involved; 60.1%). the rarest anatomical site of involvement in three studies was pan-uveitis;[26–28] however, this was not the case in the reports by hosseini et al[25] (posterior uveitis was the rarest with 10 out of 235 cases involved; 4.25%), rahimi et al,[29] and soheilian et al[30] (intermediate uveitis was the rarest with 53 out of 475 cases [11.1%] and 96 out of 544 cases [17.6%], respectively). the study-wise pattern of uveitis based on the anatomical location of involvement has been shown in figure 2. in most studies, binocular involvement was more common, but in the studies by hosseini et al and alizadeh-ghavidel et al, monocular involvement was more prevalent.[25, 26] in all studies conducted in ophthalmology referral centers, the most common type of pathological involvement in patients was non-granulomatosis uveitis (compared to the granulomatous type). the prevalence of non-infectious uveitis in all studies was higher than that of infectious uveitis, although in the pattern of posterior uveitis, the infectious type was more common than the non-infectious type due to toxoplasma retinochoroiditis. table 2 summarizes the uveitis pattern in the studies carried out at tertiary ophthalmology referral centers in iran. in the study by hosseini et al, which was conducted at an ophthalmology referral center in north eastern iran, idiopathic uveitis was more common overall (67 cases of 235; 28.5%) and in different uveitis types, except posterior uveitis in which toxoplasma retinochoroiditis was prevalent (3 cases, 10; 10%). after idiopathic uveitis, behcet’s syndrome (39 patients; 16.6%), vkh (25 patients, 10.6%), herpetic uveitis (21 patients, 8.9%), and seronegative spondyloarthropathy (16 patients, 6.8%)[25] were the other common etiologies in different uveitis types. in the study by alizadeh-ghavidel et al, which was conducted at an ophthalmology referral center in the northwest of iran, idiopathic uveitis was more common overall (117 cases of 243; 48.1%), followed by toxoplasma retinochoroiditis (5.3%).[26] in the study by kianersi et al, conducted at an ophthalmology referral center in iran, idiopathic uveitis was more common overall (882 cases of 2016; 43.9%), followed by toxoplasma retinochoroiditis (19.3%), fuchs heterochromic iridocyclitis (fhi) (14.1%), behcet’s syndrome (10.5%), and herpetic uveitis (3.2%).[28] in the study by rahimi et al, which was conducted at an ophthalmology referral center in southern iran, idiopathic uveitis was more common overall (180 cases of 475; 37.9%). the most common etiologies of idiopathic uveitis were behcet’s syndrome (12.4%), toxoplasma retinochoroiditis (11.8%), fhi (7.1%), and vkh (5.2%).[29] the first study on the epidemiology of uveitis in the iranian population was reported by soheilian et al in 2004 at a tertiary referral center in tehran. similar to other studies, idiopathic uveitis was the most common type of involvement (231 patients out of 544; 45.5%). other prevalent etiologies journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 99 pattern of uveitis in iran; bagheri et al in different uveitis types were toxoplasma retinochoroiditis (10.1%), behcet’s syndrome (8.6%), fhi (6.6%), and vkh (3.9%).[30] table 3 shows the common etiologies of uveitis in different types of studies carried out at tertiary ophthalmology referral centers in iran. discussion uveitis as a potentially sight-threatening ocular disease poses diagnostic and therapeutic challenges for general ophthalmologists as well as uveitis specialists. epidemiological studies of the pattern and etiologies of uveitis can help clinicians diagnose, manage, and treat the disease. however, epidemiological studies on the disease at a national level can aid in assessing the burden of the disease on the country’s health community, making it possible to plan for the future. in contrast, studies on the incidence and prevalence of uveitis in our society are limited, especially in the general population. based on the extensive literature review, to the best of our knowledge, no study has reported the epidemiological pattern of uveitis in the general iranian population, and no study has been conducted in the field of general ophthalmology (all reports were from referral tertiary ophthalmology centers). the clinical pattern of uveitis may change over time for several reasons such as emerging diseases, new surgical procedures that can lead to uveitis as a complication, and new laboratory equipment that may help to better understand or further diagnose the disease. certainly, the limitations of laboratory equipment can make it difficult to detect some etiologies and cause some specific diagnosis to fall into the category of idiopathic uveitis. thus, the pattern of uveitis in one community may be different from that in other societies and may also change over time. this justifies the need for national and regional studies and repeated epidemiological studies over time. comparison of these studies could help identify the predisposing factors in different regions, provide new insights into the pathogenesis of the disease, and clarify the path for future studies. in the present study, the mean age of the patients included in the articles reviewed was 40 years, and gender was not a statistically significant predisposing factor. the most common anatomical pattern of involvement was anterior uveitis. however, the prevalence of the other three types including middle, posterior, and panuveitis was almost equal. the most common clinical features of the disease were binocular uveitis (compared to the monocular), non-granulomatosis uveitis (compared to the type of granulomatosis), and non-infectious (compared to the infectious) involvement. overall, the prevalent etiologies were idiopathic uveitis, toxoplasmosis, behcet’s syndrome, and fhi. in the subgroup analysis, the most common etiologies for anterior uveitis were idiopathic uveitis, fhi, and herpetic uveitis; for intermediate uveitis, behcet’s syndrome and ms were common; and for posterior uveitis toxoplasmosis, idiopathic uveitis and behcet’s syndrome were common. in pan-uveitis, behcet’s syndrome, idiopathic uveitis, and vkh syndrome were most prevalent. all published studies have examined the epidemiology of uveitis in university referral ophthalmology centers. therefore, the results of this study cannot be generalized to the public because there are significant differences between the pattern of disease in these studies compared to general ophthalmology practice or the community. similar to the present study, most worldwide reports have shown that anterior uveitis is the most common type of involvement, followed by panuveitis, posterior, and intermediate uveitis.[1, 9, 35, 36] however, most of these studies have been carried out in university referral centers, and their results cannot be applied to the general public. in these settings, a higher proportion of patients with posterior and pan-uveitis and a lower proportion of those with anterior uveitis are expected to be comparable.[4, 37] the pattern of uveitis can be influenced by several epidemiologic factors; therefore, any comparison should consider these differences. the regional-based epidemiological studies can be useful for both diagnostic and therapeutic guidance. this may be more important in developing countries such as iran because of its resource constraints and a higher prevalence of the disease in some uveitic entities (compared to developed countries), and its complications, especially blindness.[4, 22, 38–40] this study has some limitations. first, this study was limited by the inclusion and exclusion criteria of the studies reviewed; for example, all studies considered traumatic uveitis as exclusion criteria, 100 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 pattern of uveitis in iran; bagheri et al while das et al reported a prevalence of 5%.[35] second, reports on the epidemiology of uveitis in iran have covered different time periods that may be difficult to compare. even in a single community, the pattern of uveitis can change over time for several reasons such as emerging diseases, advances in laboratory equipment, and changes in diagnostic criteria. however, when comparing studies from different cities, some factors such as the socioeconomic level of the region, can change the face of the disease. in under-resourced areas, an underrepresentation of mild or moderate cases of uveitis is expected because of limited access to medical facilities.[4, 22, 38–40] third, this study was limited by the inclusion of all types of uveitis and different age ranges; considering the heterogeneity in the selected studies and the nonrepresentative population, aggregate estimates for the prevalence of uveitis could not be made in the current review. however, according to the survey in the iranian population, the heterogeneity of patients in terms of racial factors compared to other global studies was minimal. finally, the survey of the referral centers may have been influenced by referral bias; therefore, they do not reflect an appropriate view of the disease pattern in society or in general practice. therefore, subsequent analysis focusing on homogeneous age groups can provide more accurate results regarding the pattern of uveitis. in addition, future epidemiologic studies are recommended in the general population and in the field of general ophthalmology. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. anesi sd, vitale at, chu d, metzinger jl, cerón o. the ocular immunology and uveitis foundation (oiuf) preferred practice patterns of uveitis management; 2015. 2. de smet md, taylor sr, bodaghi b, miserocchi e, murray pi, pleyer u, et al. understanding uveitis: the impact of research on visual outcomes. prog retin eye res 2011;30:452–470. 3. mccannel ca, holland gn, helm cj, cornell pj, winston jv, rimmer tg, et al. causes of uveitis in the general practice of ophthalmology. am j ophthalmol 1996;121:35– 46. 4. london nj, rathinam sr, cunningham et. the epidemiology of uveitis in developing countries. int ophthalmol clin 2010;50:1–17. 5. vallet h, seve p, biard l, baptiste fraison j, bielefeld p, perard l, et al. infliximab versus adalimumab in the treatment of refractory inflammatory uveitis: a multicenter study from the french uveitis network. arthritis rheumatol 2016;68:1522–1530. 6. tsirouki t, dastiridou a, symeonidis c, tounakaki o, brazitikou i, kalogeropoulos c, et al. a focus on the epidemiology of uveitis. ocul immunol inflamm 2018;26:2–16. 7. jaffe gj, dick ad, brézin ap, nguyen qd, thorne je, kestelyn p, et al. adalimumab in patients with active noninfectious uveitis. new engl j med 2016;375:932–943. 8. daniel e, pistilli m, pujari ss, kaçmaz ro, nussenblatt rb, rosenbaum jt, et al. risk of hypotony in noninfectious uveitis. ophthalmology 2012;119:2377–2385. 9. chang jh-m, wakefield d. uveitis: a global perspective. ocul immunol inflamm 2002;10:263–279. 10. oruc s, kaplan ad, galen m, kaplan hj. uveitis referral pattern in a midwest university eye center. ocul immunol inflamm 2003;11:287–298. 11. cunningham et, suhler eb. childhood uveitis—young patients, old problems, new perspectives. j aapos 2008;12:537–538. 12. laroni a, calabrese m, perini p, albergoni mp, ranzato f, tiberio m, et al. multiple sclerosis and autoimmune diseases. j neurol 2006;253:636–639. 13. zein g, berta a, foster s. multiple sclerosis-associated uveitis. ocul immunol inflamm 2004;12:137–142. 14. yang p, zhang z, zhou h, li b, huang x, gao y, et al. clinical patterns and characteristics of uveitis in a tertiary center for uveitis in china. curr eye res 2005;30:943– 948. 15. khairallah m, yahia sb, ladjimi a, messaoud r, zaouali s, attia s, et al. pattern of uveitis in a referral centre in tunisia, north africa. eye 2007;21:33. 16. hamade ih, elkum n, tabbara kf. causes of uveitis at a referral center in saudi arabia. ocul immunol inflamm 2009;17:11–16. 17. de-la-torre a, lópez-castillo ca, rueda jc, mantilla rd, gómez-marín je, anaya jm. clinical patterns of uveitis in two ophthalmology centres in bogota, colombia. clin eexp ophthalmol 2009;37:458–466. 18. wakabayashi t, morimura y, miyamoto y, okada aa. changing patterns of intraocular inflammatory disease in japan. ocul immunol inflamm 2003;11:277–286. 19. tugal-tutkun i. behçet disease in the developing world. int ophthalmol clin 2010;50:87–98. 20. bloch-michel e, nussenblatt rb. international uveitis study group recommendations for the evaluation of intraocular inflammatory disease. am j ophthalmol 1987;103:234–235. 21. group sounw. standardization of uveitis nomenclature for reporting clinical data. results of the first international workshop. am j ophthalmol 2005;140:509–516. 22. rathinam s, namperumalsamy p. global variation and pattern changes in epidemiology of uveitis. indian j ophthalmol 2007;55:173. journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 101 pattern of uveitis in iran; bagheri et al 23. egger m, dickersin k, smith gd. problems and limitations in conducting systematic reviews. in: systematic reviews in health care: meta-analysis in context; 2001:43–68. 24. moons kg, de groot ja, bouwmeester w, vergouwe y, mallett s, altman dg, et al. critical appraisal and data extraction for systematic reviews of prediction modelling studies: the charms checklist. plos med 2014;11:e1001744. 25. hosseini sm, shoeibi n, ebrahimi r, ghasemi m. patterns of uveitis at a tertiary referral center in northeastern iran. j ophthalmic vis res 2018;13:138–143. 26. ghavidel la, mousavi f, bagheri m, asghari s. clinical course of uveitis in children in a tertiary ophthalmology center in northwest iran. crescent j medical biol sci 2017;4:200–204. 27. rahimi m, oustad m, ashrafi a. demographic and clinical features of pediatric uveitis at a tertiary referral center in iran. middle east afr j ophthalmol 2016;23:237–240. 28. kianersi f, mohammadi z, ghanbari h, ghoreyshi sm, karimzadeh h, soheilian m. clinical patterns of uveitis in an iranian tertiary eye-care center. ocul immunol inflamm 2015;23:278–282. 29. rahimi m, mirmansouri g. patterns of uveitis at a tertiary referral center in southern iran. j ophthal vis res 2014;9:54. 30. soheilian m, heidari k, yazdani s, shahsavari m, ahmadieh h, dehghan m. patterns of uveitis in a tertiary eye care center in iran. ocul immunol inflamm 2004;12:297–310. 31. borenstein m, hedges lv, higgins jp, rothstein hr. a basic introduction to fixed-effect and random-effects models for meta-analysis. res synth methods 2010;1:97– 111. 32. soheylian m, heydari k, khosravi-jafari m. epidemiology and referral pattern of uveitis in a tertiary eye care center in tehran; 2002. 33. kianersi f. clinical patterns of uveitis in an iranian tertiary eye care center. bina j ophthalmol 2005;10:147–154. 34. ghavidel la, arshadi m, mousavi f. clinical patterns and causes of posterior uveitis in a tertiary referral eye center in northwest of iran. crescent j medical biol sci 2018;5:345– 349. 35. das d, bhattacharjee h, bhattacharyya pk, jain l, panicker m, das k, et al. pattern of uveitis in north east india: a tertiary eye care center study. indian j ophthalmol 2009;57:144. 36. pathanapitoon k, kunavisarut p, ausayakhun s, sirirungsi w, rothova a. uveitis in a tertiary ophthalmology centre in thailand. br j ophthalmol 2008;92:474–478. 37. henderly de, genstler aj, smith re, rao na. changing patterns of uveitis. am j ophthalmol 1987;103:131–136. 38. chams h, rostami m, mohammadi s, ohno s. epidemiology and prevalence of uveitis: review of literature. iran j ophthalmol 2009;21:4–16. 39. khairallah m, gargouri s. epidemiology of uveitis in the middle east and north africa. acta ophthalmologica 2010;88. 40. nashtaei em, soheilian m, herbort cp, yaseri m. patterns of uveitis in the middle east and europe. j ophthal vis res 2011;6:233. 102 journal of ophthalmic and vision research volume 16, issue 1, january-march 2021 perspective macular optical coherence tomography imaging in glaucoma alireza kamalipour, md; sasan moghimi, md hamilton glaucoma center, shiley eye institute, viterbi family department of ophthalmology, university of california, san diego, la jolla, ca, united states orcid: alireza kamalipour: https://orcid.org/0000-0003-2916-9187 sasan moghimi: https://orcid.org/0000-0002-9375-4711 abstract the advent of spectral-domain optical coherence tomography has played a transformative role in posterior segment imaging of the eye. traditionally, images of the optic nerve head and the peripapillary area have been used to evaluate the structural changes associated with glaucoma. recently, there is growing evidence in the literature supporting the use of macular spectral-domain optical coherence tomography as a complementary tool for clinical evaluation and research purposes in glaucoma. containing more than 50% of retinal ganglion cells in a multilayered pattern, macula is shown to be affected even at the earliest stages of glaucomatous structural damage. risk assessment for glaucoma progression, earlier detection of glaucomatous structural damage, monitoring of glaucoma especially in advanced cases, and glaucoma evaluation in certain ocular conditions including eyes with high myopia, positive history of disc hemorrhage, and certain optic disc phenotypes are specific domains where macular imaging yields complementary information compared to optic nerve head and peripapillary evaluation using optical coherence tomography. moreover, the development of artificial intelligence models in data analysis has enabled a tremendous opportunity to create an integrated representation of structural and functional alterations observed in glaucoma. in this study, we aimed at providing a brief review of the main clinical applications and future potential utility of macular spectral-domain optical coherence tomography in glaucoma. keywords: artificial intelligence; glaucoma; imaging; macula; optical coherence tomography j ophthalmic vis res 2021; 16 (3): 478–489 introduction glaucoma, characterized by progressive loss of retinal ganglion cells (rgcs) and their axons accompanied by concomitant characteristic visual field (vf) damage, is globally a leading cause correspondence to: sasan moghimi, md. shiley eye institute, university of california, san diego, 9500 campus point drive, la jolla, ca, 92093-0946, usa. e-mail: sasanimii@yahoo.com received: 15-01-2021 accepted: 22-04-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i3.9442 of irreversible blindness.[1–5] earlier diagnosis and monitoring of disease progression are two fundamental tasks for clinicians managing glaucoma.[2, 6, 7] developments in imaging modalities in the last three decades have led to recent advances in glaucoma diagnosis and management.[8–15] optical coherence tomography (oct) is now the imaging modality of choice for this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: kamalipour a, moghimi s. macular optical coherence tomography imaging in glaucoma. j ophthalmic vis res 2021;16:478–489. 478 © 2021 kamalipour and moghimi. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i3.9442&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr macular oct in glaucoma; kamalipour and moghimi objective assessment of glaucomatous structural alterations due to fast and highly reproducible scan acquisition.[16–18] in clinical practice, most attentions on oct imaging in glaucoma has been paid to the evaluation of the optic disc that together with vf assessment using 6° apart test points (e.g., the 24–2 or 30–2 test pattern) constitute the common clinical paradigm.[19, 20] however, evidence shows that sole reliance on common clinical paradigm might be insufficient in certain clinical aspects. importantly, glaucomatous damage to the macular area may happen early in the disease course and such damage can be underestimated or even missed using common clinical paradigm.[19] also, evaluating glaucoma progression especially at the advanced stage where optic nerve head (onh) and circumpapillary retinal nerve fiber layer (cprnfl) measurements have reached to an apparent floor is limited by the current common clinical paradigm. another challenge happens in the evaluation of glaucoma patients with high myopia where the oct segmentation algorithms are more prone to errors at the onh area as a result of anatomical alterations such as peripapillary atrophy, onh tilt, and stretching of the cprnfl. macular oct imaging with high resolution scans of different layers can be a useful adjunct to common clinical paradigm in these scenarios. moreover, the application of artificial intelligence (ai) techniques to analyze the big data obtained from these high-resolution images shows promise to improve the currently available diagnostic modalities and structure–function relationships in glaucoma. glaucomatous damage to the macular area that contains around 50% of retinal rgcs in a multilayered fashion has been reported for a long time using histological studies.[18] potential damage to this area leads to impairments in the central vf which is associated with a dramatic decline on the functional status in glaucoma patients. moreover, macular evaluation in glaucoma has recently regained a specific focus of interest based on the possibility of early involvement in the disease process.[21] new sd-oct post acquisitional algorithms provide automated segmentation of different layers of macular area that focuses on interest in glaucoma evaluation and monitoring including macular retinal nerve fiber layer (mrnfl), ganglion cell layer (gcl), ganglion cell/inner plexiform layer (gc/ipl), and ganglion cell complex (gcc). consequently, the utility of these sd-oct-derived macular parameters for glaucoma detection and monitoring of disease progression have been shown in many previous studies. in this perspective, we aim at providing more insight on the potential utility of sd-oct macular imaging in glaucoma practice. different macular oct imaging instruments cirrus high-definition oct (hd-oct) cirrus hd-oct (carl zeiss meditec, dublin, ca) is one of the instruments that provides high macular images using sd-oct technology [figure 1a]. the cirrus hd-oct performs volumetric scan (200 × 200 or 512 × 128 a-scans) of the macula over an area of 6 × 6 × 2-mm3 in an emmetropic eye that is centered on the fovea. in the ganglion cell analysis (gca) printout, it provides the gcipl parameter that includes the combined thickness measurements of gcl and ipl. gca printout displays global average gcipl, minimum gcipl, and sectoral gcipl measurements that are presented over six wedgeshaped regions bound by a horizontally oval area (4.8 × 4.0 mm2) after the removal of a central perifoveal ellipse (1.2 × 1.0 mm2). in addition to the mentioned parameters, gca provides a colorcoded deviation map of gcipl measurements over the aforementioned elliptical area that compares localized thickness measurements to age-adjusted normative database of the built-in software.[18] rtvue sd-oct the rtvue (optovue inc., fremont, ca) is another sd-oct imaging modality that is capable of performing a 3-d volumetric scan of the macula over a 7mm square that is centered 0.75 mm temporally to the fovea. in the printout, it displays average, superior, and inferior gcc (including the combination of mrnfl, gcl, and ipl) measurements [figure 1b]. moreover, two colorcoded maps are provided in the software output that display the absolute gcc measurements and gcc deviation patterns based on the ageadjusted normalized database of the software. cross-sectional high-resolution b-scans are also shown for further structural evaluation and detection of possible image artifacts.[18] journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 479 macular oct in glaucoma; kamalipour and moghimi figure 1. (a) cirrus hd-oct ganglion cell ou analysis of a patient with glaucoma. thickness map, deviation, sector map, and average/minimum gcipl can be provided by cirrus oct. various types of optic neuropathy, including compressive optic neuropathy and ischemic optic neuropathy, can affect the macula and ganglion cell inner plexiform layer (gcipl). however, in glaucoma, the inferotemporal region is frequently affected first. the temporal raphe sign is an important sign for distinguishing glaucoma from other neuropathies. the temporal raphe sign is positive if there is a horizontal straight line longer than onehalf of the inner-to-outer-annulus length on the macular gcipl thickness map. (b) optovue onh/gcc ou report of a glaucoma patient. ganglion cell complex (gcc) significant map shows thinning of inner macula layers in the inferior regions. tabular data also provides the average gcc, as well as focal loss volume (flv) and general loss volume (glv). (c) heidelberg posterior pole asymmetry analysis report: thickness of whole retina as well as individual layers will be shown on an 8 × 8 grid and hemisphere asymmetry map. thinning of inferotemporal macula is evident in both maps. (d) topcon wide glaucoma report provides gcipl data (gcl+) or gcc data (gcl++, not shown) in the macula and optic nerve and can be combined with vf results (hood glaucoma report). 480 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 macular oct in glaucoma; kamalipour and moghimi figure 2. (a) myopic eye without glaucoma. myopic eye shows “red disease” with abnormal sectors in the inferotemporal, supratemporal, and temporal sectors which is probably due to temporal displacement of rnfl peaks and not glaucomatous damage. this is confirmed by normal macula thickness in the posterior pole map. (b) myopic eye with glaucoma. the oct image shows thinning of the inferior and superior quadrants. this “red disease” might be due to the temporal displacement of rnfl peak. however, gcipl report shows typical raphe sign (yellow arrow) and inferotemporal macula inner layer thinning suggesting glaucomatous damage. detailed examination of rnfl profile also depicts a decrease in thickness of superior peak (red arrow). spectralis sd-oct spectralis oct (heidelberg engineering gmbh) instrument uses posterior pole analysis (ppa, or posterior pole asymmetry analysis) algorithm to capture macular images composed of 61 distinct horizontal b-scans (x768 a-scans) that are aligned in parallel to bruch’s membrane opening (bmo)-fovea axis. each horizontal bscan is repeated 9–11 times and averaged to decrease speckle noise. the latest software (glaucoma module premium edition) provides journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 481 macular oct in glaucoma; kamalipour and moghimi figure 3. an early glaucoma case with normal vf (a) in which spectralis rnfl single report shows normal mean rnfl thickness values and normal sectoral value (b). posterior pole thickness map and hemisphere asymmetry map shows area of thinning in the macular area corresponded to the location of narrow rnfl defect in optic disc photo. automated segmentation of the layers of interest. the output displays an 8 × 8 thickness grid (64 superpixels, 3° wide) for each layer of interest and enables direct comparison between the superpixels of the fellow eyes as well as the corresponding superior and inferior superpixels of the same eye. currently, no comparison to the normative data is available on the ppa[18] [figure 1c]. topcon 3d-oct there are multiple topcon 3d-oct (topcon, inc., paramus, nj) instruments of different generations including 3d-oct 1000, 3d-oct 2000, and a newer swept-source oct (dri oct-1) device. topcon 3d-oct measures a 6 × 6 mm2 area with a protocol of 128 × 512 a-scans/image. dr oct-1 performs faster measurements and is capable of acquiring wide-field scans over a 12 × 9 mm2 area with 256 × 512 a-scans/image protocol. in the wide-field report, measurements of mrnfl, gcipl, and gcc are presented[18] [figure 1d]. utility in the detection of early glaucoma it is well-known that disease severity affects the diagnostic performance of oct parameters in glaucoma[22–25] which is mostly represented using the area under the receiver operating characteristic curve (auroc). hence, attempts have been made to evaluate the diagnostic accuracy of macular oct parameters and compare their performance to those of onh and cprnfl thickness at earlier (pre-perimetric and mild perimetric) stages of glaucoma. their findings reveal excellent and comparable diagnostic performance of macular and cprnfl parameters in early glaucoma.[26–34] in one of these studies, kim et al found inferotemporal gcipl as the macular parameter with the highest diagnostic performance (auroc = 0.82) comparable to those of best parameters of rnfl (7 o’clock sector, auroc = 0.76) and onh (rim area, auroc = 0.77).[32] other studies have reported comparable diagnostic performances of macular gcipl and cprnfl deviation maps in the detection of preperimetric glaucoma and good performance of macular gca maps in the detection of early glaucoma (vf mean deviation [md] > –6db) with the detection rate of up to 87.8% (in the deviation map).[28, 33] importantly, it is shown that glaucomatous damage to the macular region can happen early in the disease course and sole reliance on a combination of 24-2 vf tests and optic disc oct can underestimate or even miss the damage.[19] with this respect, kim and 482 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 macular oct in glaucoma; kamalipour and moghimi colleagues studied a group of 186 glaucoma patients using cirrus hd-oct instrument and found that in a subgroup of patients, defects are evident on macular gcipl but not on cprnfl deviation maps. however, all cases with a defect on cprnfl deviation map had a corresponding defect on macular gcipl deviation map. based on these findings, they suggested that macular oct is capable of identifying early glaucomatous damages that may not be apparent on oct scans of the disc area.[35] another useful sign for the diagnosis of early glaucoma in macular oct is the presence of temporal horizontal raphe on gcipl deviation maps [figure 1a]. it is defined based on the intuition that early glaucomatous damage preferentially affects one hemifield more than the other. kim et al developed gcipl hemifield test which is an automated program for the detection of glaucoma based on this finding. they showed that this test has a very high diagnostic performance for the detection of pre-perimetric glaucoma (auroc = 0.97) and early perimetric glaucoma (auroc = 0.96).[36] moreover, in a separate study it was shown that the presence of this sign can be a useful indicator to discriminate glaucomatous from other non-glaucomatous causes of optic neuropathy in eyes with gcipl thinning.[37] however, these findings from separate groups of asian glaucoma patients with a presumable high prevalence of normal tension glaucoma may not be generalizable to glaucoma patients of other ethnicities. the association between distinct glaucomatous optic disc appearance and the presence of central vf defects has been a recent focus of interest. ekici and collaborators demonstrated that early macular damage in glaucoma patients tends to happen more in optic discs with focal ischemic and myopic phenotypes compared to those with generalized cup enlargement phenotype.[38] likewise, eyes with optic disc hemorrhage have been associated with more degree of central macular involvement and parafoveal scotoma. in a study by liu et al, gcipl showed higher proportional rates of thinning and greater association with functional progression compared to cprnfl.[39] accordingly, macular structural evaluation using oct can be tailored to the individual patients based on the optic disc appearance and this has the potential to enhance the diagnosis and management of early glaucoma. monitoring of advanced glaucoma monitoring of advanced glaucoma is another challenging task in clinical practice where vf tests show increased variability. evaluating structural change alongside functional performance can be a useful adjunct if the measurements are reproducible, demonstrate acceptable global and regional structure–function relationship, and fall within the dynamic range of variability. the concept of measurement floor points to another limitation in the evaluation of advanced glaucoma. it is ascribed to a level beyond which the structural measurements no longer show a decremental pattern with worsening of the disease and is believed to represent the thickness of the remining non-neural tissues. despite that the dynamic range for cprnfl extends to –8 to –10 db md, macular oct reaches measurement floor at more advanced glaucomatous damage.[18, 40] bowd and collaborators defined a region of interest approach to estimate the measurement floors of optic disc and macular parameters in a longitudinal cohort of moderate to advanced glaucoma patients (md ≤ –8 db). they found that the baseline region of interest percentage above the measurement floor for advanced glaucoma cases (md ≤ – 12 db) was highest for gcipl thickness (36%), followed by minimum rim width (19%) and cprnfl thickness (14%). as a conclusion, they suggested that macular gcipl thickness might be a better candidate for monitoring progression in advanced glaucoma compared to optic disc parameters.[41] in another study, belghith and colleagues found that only gcipl thickness (compared to cprnfl) had a significantly faster rate of progression in highly advanced glaucoma patients (md < –21 db) compared to healthy subjects.[42] similarly, lavinsky et al based on an average of four years of follow-up including eyes with a median md of –10.2 db reported an average –0.57 µm/year decline in gcipl thickness compared to a nonsignificant rate of change for cprnfl (0.009 µm/year).[43] in addition, macular oct measurements have shown high reproducibility in advanced disease, good correlation with vf sensitivity measures, and preserved dynamic range at a stage when the reliability of vf tests decline. a small number of studies have shown that the variability of macular measurements does not significantly increase as the disease gets worse.[44, 45] this recommends macular measurements like gcc and gcipl journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 483 macular oct in glaucoma; kamalipour and moghimi thickness as possible biomarkers for the evaluation of advanced glaucoma; however, it must be kept in mind that accurate segmentation of different macular layers becomes more challenging with worsening of the disease.[18] utility in the detection of glaucoma in myopic eyes evaluation of glaucoma in myopic eyes is another area where macular images may yield additional benefit compared to onh images. evaluation and diagnosis of glaucoma in highly myopic eyes is challenging. it has been shown that onh parameters have a worse performance in the detection of glaucoma in highly myopic eyes compared to non-highly myopic eyes while gcc’s performance remains the same.[46] we know that myopia affects the patterns of rnfl distribution measured by the sd-oct instruments resulting in temporal displacement of rnfl peaks on thickness plots with possible influence on the diagnostic performance of oct measurements.[47] therefore, the so-called “red disease” is not uncommon when clinicians evaluate onh repots in these patients [figure 2a]. this false positive in cprnfl color code is especially common in inferior quadrants.[48] in addition, the morphology of the onh might be altered in highly myopic patients as a result of onh tilt and the presence of peripapillary atrophy. these anatomical changes may lead to oct artifacts[49] and potentially affect the performance of segmentation algorithms especially in the onh due to a more complex anatomy compared to the macula.[50, 51] in the same line, investigators have shown the superiority of macular over onh parameters for the diagnosis of glaucoma in highly myopic eyes;[52–56] although, there are some reports showing a comparable performance between the measurements of these two areas.[29, 57–60] inferotemporal gcipl thickness is the best macular parameter to detect glaucomatous damage in highly myopic eyes especially at the pre-perimetric stage [57] [figure 2b]. kim and colleagues studied asian high myopic patients and demonstrated an excellent diagnostic accuracy for gcipl hemifield test to detect glaucomatous damage (auroc = 0.94).[59] hence, the presence of temporal horizontal raphe on gcipl thickness map in high myopic eyes may serve as a useful diagnostic clue to detect glaucoma. risk assessment as glaucomatous vf damage is generally irreversible, early intervention is required to prevent further functional deterioration and potential blindness.[61, 62] this highlights the role of earlier disease detection and risk stratification of patients according to the future rates of glaucoma progression. clinical parameters that are associated with prognostic utility in terms of future glaucoma progression are age, the level and fluctuation of intraocular pressure, central corneal thickness, disc hemorrhage, and the diagnosis of pseudoexfoliative glaucoma.[63–71] certain high risk groups may not only benefit from earlier intervention, but also require closer follow-up appointments and diagnostic tests for the evaluation of disease progression. macular oct imaging can be a useful modality in some of these patients. recently, shukla and colleagues[72] showed that the presence of disc hemorrhage is associated with more severe damage on 10-2 vf test and faster rate of central vf progression. hence, this subgroup of patients may benefit from regular macular oct monitoring for earlier detection of glaucoma progression. another study showed that the presence of temporal raphe sign on baseline macular gcipl deviation maps of elderly patients with enlarged vertical cup-todisc ratio is associated with faster progression to normal tension glaucoma.[73] in addition to the aforementioned clinical settings, it has been shown that evaluating macular structure using oct can further enhance the performance of prognostic models and consequently improve our understanding of glaucoma progression. anraku and associates evaluated the performance of different baseline structural (macular and cprnfl oct) and functional parameters in a cohort of early glaucoma eyes for the detection of future vf progression. the cohort was classified into two groups of slow (md rate > –0.4 db/year) and fast (md rate < –0.4 db/year) progressors. only thinner macular gcc at baseline was a significant predictor of future fast progression.[74] moreover, in two separate studies, zhang and colleagues demonstrated that among baseline sd-oct measurements, gcc focal loss volume (flv) is the best single predictor for subsequent glaucoma conversion in pre-perimetric glaucoma patients[75] and for vf progression in patients with established glaucoma.[76] in the first study, 484 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 macular oct in glaucoma; kamalipour and moghimi they found that eyes with abnormal or borderline gcc–flv have a four-fold increase in the risk of future glaucoma conversion over a six-year period. in the second study, they reported that abnormal gcc–flv at baseline leads to a triple increase in the risk of future vf progression based on an average 3.7 years follow-up of 277 eyes with established glaucoma and average baseline vf md of –4.8 db. hou et al evaluated the temporal relationship between progressive gcipl thinning, cprnfl thinning, and vf progression in a cohort of patients with primary open-angle glaucoma with a follow-up duration of more than five years. they found that progressive gcipl and cprnfl thinning are mutually predictive and both are indicative of vf progression.[77] they suggested that integrating macular and cprnfl parameters may probably lead to earlier detection of disease progression in glaucoma patients. applications of artificial intelligence (ai) in the recent years, the applications of ai in general (and deep learning networks in particular) into medicine has led to the introduction of numerous automated diagnostic modalities. ai techniques have many implications in machine vision tasks including image classification with the performance sometimes higher than that of humans[78] and unsupervised identification of different patterns that exist in large datasets of images. a widespread use of different imaging modalities in ophthalmology research and clinical practice makes this medical subspecialty a major area for the implementation of these novel algorithms to assist in diagnosis and improve the currently used image analysis techniques.[79] a great proportion of publications on ai methods in glaucoma have focused on the detection of the disease using different inputs like fundus and oct images. asaoka and colleagues developed and validated a deep learning model to accurately (auroc = 93.7%) detect early open-angle glaucoma (md > –5 db) using macular oct information.[80] another recent study developed a 3d deep learning system to detect patients that need to be referred to a glaucoma specialist based on the volumetric macular oct information. the overall accuracy of their proposed surveillance system was high (auroc = 0.88) with a relatively well preserved performance among eyes with different degrees of myopia.[81] development of deep learning models to evaluate the details of structure–function relationship has been another focus of ai investigations in glaucoma. these models have shown a high accuracy to extract and use the relevant information obtained from macular volumetric oct scans and provide a corresponding simulation of central vf in glaucoma patients.[82–84] moreover, nouri-mahdavi et al in a recent study showed that vf progression in moderate to advance glaucoma can be partly predicted using combined oct measurements of peripapillary and macular areas. of note, they developed and compared separate models using macular or peripapillary measurements and showed that macular models performed better than peripapillary models to detect vf progression. this finding highlights the potential of macular oct in monitoring patients with moderate to advanced glaucoma.[85] hopefully, by further refining these ai approaches, automated precise systems for the detection and monitoring of disease progression in glaucoma will become available in the future. what we should do as clinicians while it is common clinical practice to obtain an oct scan of the disc, many clinicians do not routinely obtain a scan of the macular region for patients with glaucoma or suspected glaucoma. as previously discussed, macula sd-oct has been helpful for the earlier detection of glaucoma – particularly in eyes with certain onh phenotypes, eyes with dh, and myopic eyes. for example, figure 3 shows a case in which the cprnfl report appears normal, while the macula scan shows apparent gcipl thinning. macula scans may also serve as a clue for clinicians for the presence of parafoveal scotoma, which should receive attention and be further evaluated with a 10-2 vf test. in addition, macula scans play an important role in monitoring eyes with advanced disease, as they may help clinicians identify disease progression and decide to escalate treatment. consequently, one may ask, “when do you perform an oct scan of the macula?” although macula scans can be selectively ordered for those patients who may be most likely to benefit from it (as discussed earlier), obtaining oct scans is so efficient today that many experts recommend routinely performing both disc and macula scans for all patients with glaucoma and suspected glaucoma, thus have journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 485 macular oct in glaucoma; kamalipour and moghimi a comprehensive glaucoma assessment of the patients. limitations like every other imaging modality, there are some limitations in the use macular oct for glaucoma practice and research that clinicians need to consider. first, gcipl analysis with the sdoct may be complicated by coexisting macular pathology and scan artifacts. most currently available data on macular oct in glaucoma are obtained from studies that have excluded eyes with other macular pathologies and also poor quality images like those with artifacts and lower signal strength. thus, one needs to expect higher variability of macular measurements in real world scenarios. the presence of age-related macular pathologies and drusen may disrupt the correct segmentation of the macular layers that are important in the diagnosis and monitoring of glaucoma patients especially in the elderly. recent studies using gcipl analysis have excluded up to 6% of scans due to machine segmentation or acquisition error.[86] moreover, any retinal diseases involving macular areas such as the epiretinal membrane, age-related macular degeneration, or macular edema can affect macular gcipl thickness and reducing performance of the macula scans for detection of glaucoma. similarly, macula scans are not helpful for detection of glaucoma in eyes with myopic myopathy. even in eyes without maculopathy, abnormal diagnostic classifications on gcipl map can be seen in up to 40% of myopic eyes with diffuse, circular pattern being the predominant form.[87] in addition, macular measurements obtained by different oct devices are not interchangeable despite showing a fair degree of correlation.[88] finally, it has to be mentioned that glaucomatous damage with a high angular distance from the bmo–fovea axis may fall out of the measurement territory of macular oct images depending on the oct instrument and software and consequently not be identifiable on the deviation maps. clinicians need to be aware of this issue and take it into consideration.[28, 32] conclusion macular oct is a useful imaging modality in glaucoma management and research. it provides complementary information to the conventionally used modalities by glaucoma specialists especially in the evaluation of patients with early macular damage and/or high myopia and monitoring of the advanced disease. with the development and widespread use of ai techniques in medicine, macular oct information can be integrated with the information obtained from optic disc oct and vf assessment to provide a more comprehensive picture of the true nature of glaucomatous damage and progression. this will definitely enhance the quality of medical care and research in the future. financial support and sponsorship this study was supported by the uc tobacco related disease research program grant t31ip1511. conflicts of interest there are no conflicts of interest. references 1. weinreb rn, leung ck, crowston jg, medeiros fa, friedman ds, wiggs jl, et al. primary open-angle glaucoma. nat rev dis primers 2016;2:1–19. 2. weinreb rn, aung t, medeiros fajj. the pathophysiology and treatment of glaucoma: a review. jama 2014;311:1901– 1911. 3. quigley ha, broman at. the number of people with glaucoma worldwide in 2010 and 2020. br j ophthalmol 2006;90:262–267. 4. quigley ha, dunkelberger gr, green wr. retinal ganglion cell atrophy correlated with automated perimetry in human eyes with glaucoma. am j ophthalmol 1989;107:453–464. 5. quigley ha, nickells rw, kerrigan la, et al. retinal ganglion cell death in experimental glaucoma and after axotomy occurs by apoptosis. invest ophthalmol vis sci 1995;36:774–786. 6. coleman al. glaucoma. the lancet 1999;354:1803–1810. 7. weinreb rn, friedman ds, fechtner rd, cioffi ga, coleman al, girkin ca, et al. risk assessment in the management of patients with ocular hypertension. am j ophthalmol 2004;138:458–467. 8. alencar lm, zangwill lm, weinreb rn, bowd c, vizzeri g, sample pa, et al. agreement for detecting glaucoma progression with the gdx guided progression analysis, automated perimetry, and optic disc photography. opthalmology 2010;117:462–470. 9. alexandrescu c, dascalu a, panca a, sescioreanu a, mitulescu c, ciuluvica r, et al. confocal scanning laser ophthalmoscopy in glaucoma diagnosis and management. j med life 2010;3:229. 486 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 macular oct in glaucoma; kamalipour and moghimi 10. andreou pa, wickremasinghe ss, asaria rh, tay e, franks wa. a comparison of hrt ii and gdx imaging for glaucoma detection in a primary care eye clinic setting. eye 2007;21:1050–1055. 11. belghith a, balasubramanian m, bowd c, weinreb rn, zangwill lm. a unified framework for glaucoma progression detection using heidelberg retina tomograph images. comput med imaging graph 2014;38:411–420. 12. haleem ms, han l, van hemert j, fleming a, pasquale lr, silva ps, et al. regional image features model for automatic classification between normal and glaucoma in fundus and scanning laser ophthalmoscopy (slo) images. j med syst 2016;40:132. 13. lin sc, singh k, jampel hd, hodapp ea, smith sd, francis ba, et al. optic nerve head and retinal nerve fiber layer analysis: a report by the american academy of ophthalmology. ophthalmology 2007;114:1937–1949. 14. sharma p, sample pa, zangwill lm, schuman js. diagnostic tools for glaucoma detection and management. surv ophthalmol 2008;53:s17–s32. 15. stein jd, talwar n, laverne am, nan b, lichter pr. trends in use of ancillary glaucoma tests for patients with open-angle glaucoma from 2001 to 2009. ophthalmology 2012;119:748–758. 16. drexler w, fujimoto jg. state-of-the-art retinal optical coherence tomography. prog retin eye res 2008;27:45– 88. 17. schuman js, hee mr, arya av, pedut-kloizman t, puliafito ca, fujimoto jg, et al. optical coherence tomography: a new tool for glaucoma diagnosis. curr opin ophthalmol 1995;6:89–95. 18. mohammadzadeh v, fatehi n, yarmohammadi a, woong lee j, sharifipour f, daneshvar r, et al. macular imaging with optical coherence tomography in glaucoma. surv ophthalmol 2020;65:597–638. 19. hood dc, de moraes cg. challenges to the common clinical paradigm for diagnosis of glaucomatous damage with oct and visual fields. invest ophthalmol vis sci 2018;59:788–791. 20. hood dc, de moraes cg. four questions for every clinician diagnosing and monitoring glaucoma. j glaucoma 2018;27:657. 21. hood dc, raza as, de moraes cgv, liebmann jm, ritch rjpir. glaucomatous damage of the macula. prog retin eye res 2013;32:1–21. 22. zangwill lm, jain s, racette l, ernstrom kb, bowd c, medeiros fa, et al. the effect of disc size and severity of disease on the diagnostic accuracy of the heidelberg retina tomograph glaucoma probability score. invest ophthalmol vis sci 2007;48:2653–2660. 23. rao hl, leite mt, weinreb rn, zangwill lm, alencar lm, sample pa, et al. effect of disease severity and optic disc size on diagnostic accuracy of rtvue spectral domain optical coherence tomograph in glaucoma. invest ophthalmol vis sci 2011;52:1290–1296. 24. medeiros fa, zangwill lm, bowd c, sample pa, weinreb rn. influence of disease severity and optic disc size on the diagnostic performance of imaging instruments in glaucoma. invest ophthalmol vis sci 2006;47:1008–1015. 25. leite mt, zangwill lm, weinreb rn, rao hl, alencar lm, sample pa, et al. effect of disease severity on the performance of cirrus spectral-domain oct for glaucoma diagnosis. invest ophthalmol vis sci 2010;51:4104–4109. 26. nouri-mahdavi k, nowroozizadeh s, nassiri n, cirineo n, knipping s, giaconi j, et al. macular ganglion cell/inner plexiform layer measurements by spectral domain optical coherence tomography for detection of early glaucoma and comparison to retinal nerve fiber layer measurements. am j ophthalmol 2013;156:1297–1307.e2. 27. shin h-y, park h-yl, jung y, choi j-a, park ckjo. glaucoma diagnostic accuracy of optical coherence tomography parameters in early glaucoma with different types of optic disc damage. ophthalmology 2014;121:1990–1997. 28. hwang yh, jeong yc, kim hk, sohn yhjo. macular ganglion cell analysis for early detection of glaucoma. ophthalmology 2014;121:1508–1515. 29. jeoung jw, choi yj, park kh, kim dm. macular ganglion cell imaging study: glaucoma diagnostic accuracy of spectral-domain optical coherence tomography. invest ophthalmol vis sci 2013;54:4422–4429. 30. mwanza j-c, durbin mk, budenz dl, sayyad fe, chang rt, neelakantan a, et al. glaucoma diagnostic accuracy of ganglion cell–inner plexiform layer thickness: comparison with nerve fiber layer and optic nerve head. ophthalmology 2012;119:1151–1158. 31. shin h-y, park h-yl, jung k-i, choi j-a, park ck. glaucoma diagnostic ability of ganglion cell–inner plexiform layer thickness differs according to the location of visual field loss. ophthalmology 2014;121:93–99. 32. kim mj, jeoung jw, park kh, choi yj, kim dm. topographic profiles of retinal nerve fiber layer defects affect the diagnostic performance of macular scans in preperimetric glaucoma. invest ophthalmol vis sci 2014;55:2079–2087. 33. kim mj, park kh, yoo bw, jeoung jw, kim hc, kim dm. comparison of macular gcipl and peripapillary rnfl deviation maps for detection of glaucomatous eye with localized rnfl defect. acta ophthalmol 2015;93:e22– e28. 34. sung m-s, yoon j-h, park s-w. diagnostic validity of macular ganglion cell-inner plexiform layer thickness deviation map algorithm using cirrus hd-oct in preperimetric and early glaucoma. j glaucoma 2014;23:e144–e151. 35. kim yk, jeoung jw, park kh. inferior macular damage in glaucoma: its relationship to retinal nerve fiber layer defect in macular vulnerability zone. j glaucoma 2017;26:126– 132. 36. kim yk, yoo bw, kim hc, park kh. automated detection of hemifield difference across horizontal raphe on ganglion cell–inner plexiform layer thickness map. ophthalmology 2015;122:2252–2260. 37. lee j, kim yk, ha a, kim yw, baek su, kim j-s, et al. temporal raphe sign for discrimination of glaucoma from optic neuropathy in eyes with macular ganglion cell–inner plexiform layer thinning. ophthalmology 2019;126:1131– 1139. 38. ekici e, moghimi s, hou h, proudfoot j, zangwill lm, do jl, et al. central visual field defects in patients with distinct glaucomatous optic disc phenotypes. am j ophthalmol 2021;223:229–240. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 487 macular oct in glaucoma; kamalipour and moghimi 39. liu x, lau a, hou h, moghimi s, proudfoot ja, chan e, et al. progressive thinning of retinal nerve fiber layer and ganglion cell–inner plexiform layer in glaucoma eyes with disc hemorrhage. ophthalmol glaucoma 2021:s2589– s4196(21)00031-4. 40. miraftabi a, amini n, morales e, henry s, yu f, afifi a, et al. macular sd-oct outcome measures: comparison of local structure-function relationships and dynamic range. invest ophthalmol vis sci 2016;57:4815–4823. 41. bowd c, zangwill lm, weinreb rn, medeiros fa, belghith a. estimating optical coherence tomography structural measurement floors to improve detection of progression in advanced glaucoma. am j ophthalmol 2017;175:37–44. 42. belghith a, medeiros fa, bowd c, liebmann jm, girkin ca, weinreb rn, et al. structural change can be detected in advanced-glaucoma eyes. invest ophthalmol vis sci 2016;57:oct511–oct518. 43. lavinsky f, wu m, schuman js, lucy ka, liu m, song y, et al. can macula and optic nerve head parameters detect glaucoma progression in eyes with advanced circumpapillary retinal nerve fiber layer damage? ophthalmology 2018;125:1907–1912. 44. miraftabi a, amini n, gornbein j, henry s, romero p, coleman al, et al. local variability of macular thickness measurements with sd-oct and influencing factors. transl vis sci technol 2016;5:5–5. 45. pearce jg, maddess t. inter-visit test-retest variability of oct in glaucoma. optom vis sci 2017;94:404–410. 46. akashi a, kanamori a, ueda k, inoue y, yamada y, nakamura m. the ability of sd-oct to differentiate early glaucoma with high myopia from highly myopic controls and nonhighly myopic controls. invest ophthalmol vis sci 2015;56:6573–6580. 47. kang sh, hong sw, im sk, lee sh, ahn md. effect of myopia on the thickness of the retinal nerve fiber layer measured by cirrus hd optical coherence tomography. invest ophthalmol vis sci 2010;51:4075–4083. 48. kim nr, lim h, kim jh, rho ss, seong gj, kim cy. factors associated with false positives in retinal nerve fiber layer color codes from spectral-domain optical coherence tomography. ophthalmology 2011;118:1774–1781. 49. akman a, bayer a, nouri-mahdavi k. optical coherence tomography in glaucoma: a practical guide. springer, 2018. 50. kim ke, park kh. macular imaging by optical coherence tomography in the diagnosis and management of glaucoma. br j ophthalmol 2018;102:718–724. 51. lee m-w, park k-s, lim h-b, jo y-j, kim j-y. long-term reproducibility of gc-ipl thickness measurements using spectral domain optical coherence tomography in eyes with high myopia. sci rep 2018;8:1–8. 52. nakano n, hangai m, noma h, nukada m, mori s, morooka s, et al. macular imaging in highly myopic eyes with and without glaucoma. am j ophthalmol 2013;156:511–523.e6. 53. shoji t, nagaoka y, sato h, chihara e. impact of high myopia on the performance of sd-oct parameters to detect glaucoma. graefes arch clin exp ophthalmol 2012;250:1843–1849. 54. shoji t, sato h, ishida m, takeuchi m, chihara e. assessment of glaucomatous changes in subjects with high myopia using spectral domain optical coherence tomography. invest ophthalmol vis sci 2011;52:1098– 1102. 55. wang w-w, wang h-z, liu j-r, zhang x-f, li m, huo y-j, et al. diagnostic ability of ganglion cell complex thickness to detect glaucoma in high myopia eyes by fourier domain optical coherence tomography. int j ophthalmol 2018;11:791. 56. zhang y, wen w, sun x. comparison of several parameters in two optical coherence tomography systems for detecting glaucomatous defects in high myopia. invest ophthalmol vis sci 2016;57:4910–4915. 57. seol br, jeoung jw, park kh. glaucoma detection ability of macular ganglion cell-inner plexiform layer thickness in myopic preperimetric glaucoma. invest ophthalmol vis sci 2015;56:8306–8313. 58. choi yj, jeoung jw, park kh, kim dm. glaucoma detection ability of ganglion cell-inner plexiform layer thickness by spectral-domain optical coherence tomography in high myopia. invest ophthalmol vis sci 2013;54:2296–2304. 59. kim yk, yoo bw, jeoung jw, kim hc, kim hj, park kh. glaucoma-diagnostic ability of ganglion cell-inner plexiform layer thickness difference across temporal raphe in highly myopic eyes. invest ophthalmol vis sci 2016;57:5856–5863. 60. akashi a, kanamori a, ueda k, inoue y, yamada y, nakamura m. the ability of sd-oct to differentiate early glaucoma with high myopia from highly myopic controls and nonhighly myopic controls. invest ophthalmol vis sci 2015;56:6573–6580. 61. caprioli j. the importance of rates in glaucoma. am j ophthalmol 2008;145:191–192. 62. hernández r, burr j, vale l, azuara-blanco a, cook ja, banister k. monitoring ocular hypertension, how much and how often? a cost-effectiveness perspective. br j ophthalmol 2016;100:1263–1268. 63. caprioli j, coleman al. intraocular pressure fluctuation: a risk factor for visual field progression at low intraocular pressures in the advanced glaucoma intervention study. ophthalmology 2008;115:1123–1129.e3. 64. gardiner sk, johnson ca, demirel s. factors predicting the rate of functional progression in early and suspected glaucoma. invest ophthalmol vis sci 2012;53:3598–3604. 65. jiang x, varma r, wu s, torres m, azen sp, francis ba, et al. baseline risk factors that predict the development of open-angle glaucoma in a population: the los angeles latino eye study. ophthalmology 2012;119:2245–2253. 66. leske mc, heijl a, hussein m, bengtsson b, hyman l, komaroff e, et al. factors for glaucoma progression and the effect of treatment: the early manifest glaucoma trial. arch ophthalmol 2003;121:48–56. 67. leske mc, heijl a, hyman l, bengtsson b, dong l, yang z. predictors of long-term progression in the early manifest glaucoma trial. ophthalmology 2007;114:1965–1972. 68. malihi m, moura filho er, hodge do, sit aj. long-term trends in glaucoma-related blindness in olmsted county, minnesota. ophthalmology 2014;121:134–141. 69. medeiros fa, sample pa, weinreb rn. corneal thickness measurements and frequency doubling technology perimetry abnormalities in ocular hypertensive eyes. ophthalmology 2003;110:1903–1908. 70. nouri-mahdavi k, hoffman d, coleman al, liu g, li g, gaasterland d, et al. predictive factors for glaucomatous 488 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 macular oct in glaucoma; kamalipour and moghimi visual field progression in the advanced glaucoma intervention study. ophthalmology 2004;111:1627–1635. 71. sung kr, cho jw, lee s, yun s-c, choi j, na jh, et al. characteristics of visual field progression in medically treated normal-tension glaucoma patients with unstable ocular perfusion pressure. invest ophthalmol vis sci 2011;52:737–743. 72. shukla ag, sirinek pe, de moraes cg, blumberg dm, cioffi ga, skaat a, et al. disc hemorrhages are associated with the presence and progression of glaucomatous central visual field defects. j glaucoma 2020;29:429–434. 73. ha a, kim yk, kim j-s, jeoung jw, park kh. temporal raphe sign in elderly patients with large optic disc cupping: its evaluation as a predictive factor for glaucoma conversion. am j opthalmol 2020;219:205–214. 74. anraku a, enomoto n, takeyama a, ito h, tomita g. baseline thickness of macular ganglion cell complex predicts progression of visual field loss. graefes arch clin exp ophthalmol 2014;252:109–115. 75. zhang x, loewen n, tan o, greenfield ds, schuman js, varma r, et al. predicting development of glaucomatous visual field conversion using baseline fourier-domain optical coherence tomography. am j opthalmol 2016;163:29–37. 76. zhang x, dastiridou a, francis ba, tan o, varma r, greenfield ds, et al. baseline fourier-domain optical coherence tomography structural risk factors for visual field progression in the advanced imaging for glaucoma study. am j opthalmol 2016;172:94–103. 77. hou hw, lin c, leung ck-s. integrating macular ganglion cell inner plexiform layer and parapapillary retinal nerve fiber layer measurements to detect glaucoma progression. ophthalmology 2018;125:822–831. 78. he k, zhang x, ren s, sun j. delving deep into rectifiers: surpassing human-level performance on imagenet classification. proc ieee int conf comput vis, 2015:1026– 1034. 79. medeiros fa. deep learning in glaucoma: progress, but still lots to do. the lancet digital health 2019;1:e151–e152. 80. asaoka r, murata h, hirasawa k, fujino y, matsuura m, miki a, et al. using deep learning and transfer learning to accurately diagnose early-onset glaucoma from macular optical coherence tomography images. am j ophthalmol 2019;198:136–145. 81. russakoff db, mannil ss, oakley jd, ran ran a, cheung cy, dasari s, et al. a 3d deep learning system for detecting referable glaucoma using full oct macular cube scans. transl vis sci technol 2020;9:12. 82. hashimoto y, asaoka r, kiwaki t, sugiura h, asano s, murata h, et al. deep learning model to predict visual field in central 10° from optical coherence tomography measurement in glaucoma. br j ophthalmol 2020;4:507– 513. 83. xu l, asaoka r, kiwaki t, murata h, fujino y, matsuura m, et al. predicting the glaucomatous central 10-degree visual field from optical coherence tomography using deep learning and tensor regression. am j ophthalmol 2020;218:304–313. 84. asano s, asaoka r, murata h, hashimoto y, miki a, mori k, et al. predicting the central 10 degrees visual field in glaucoma by applying a deep learning algorithm to optical coherence tomography images. sci rep 2021;11:1–10. 85. nouri-mahdavi k, mohammadzadeh v, rabiolo a, edalati k, caprioli j, yousefi s. prediction of visual field progression from oct structural measures in moderate to advanced glaucoma. am j ophthalmol 2021;226:172–181. 86. awadalla ms, fitzgerald j, andrew nh, zhou t, marshall h, qassim a, et al. prevalence and type of artefact with spectral domain optical coherence tomography macular ganglion cell imaging in glaucoma surveillance. plos one 2018;13:e0206684. 87. kim ke, jeoung jw, park kh, kim dm, kim sh. diagnostic classification of macular ganglion cell and retinal nerve fiber layer analysis: differentiation of false-positives from glaucoma. ophthalmology 2015;122:502–510. 88. mahmoudinezhad g, mohammadzadeh v, amini n, toriz v, pourhomayoun m, heydarzadeh s, et al. local macular thickness relationships between 2 oct devices. 2021;4:209–215. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 489 perspective oct angiography-based evaluation of the choriocapillaris in neovascular age-related macular degeneration varsha pramil1,2, ms; eric m. moult3, bs; james g. fujimoto3, phd; nadia k. waheed1, md, mph 1new england eye center, tufts medical center, boston, massachusetts, usa 2tufts university school of medicine, boston, massachusetts, usa 3department of electrical engineering and computer science and research laboratory of electronics, massachusetts institute of technology, cambridge, massachusetts, usa orcid: varsha pramil: http://orcid.org/0000-0002-1448-4961 nadia k. waheed: http://orcid.org/0000-0002-8229-7519 abstract neovascular age-related macular degeneration (amd) can lead to rapid, irreversible vision loss in untreated eyes. while the pathogenesis of neovascular amd remains incompletely understood, the choriocapillaris has been hypothesized as the initial site of injury. due to limitations of dye-based angiography, in vivo imaging of the choriocapillaris has been a longstanding challenge. however, the clinical introduction of optical coherence tomography angiography (octa) has enabled researchers and clinicians to noninvasively image the choriocapillaris vasculature, allowing the evaluation of the choriocapillaris in eyes with a variety of pathologies. in this perspective, we review important octa-based findings regarding choriocapillaris impairment in neovascular amd and discuss limitations and future directions of octa technologies in the context of this disease. keywords: choriocapillaris; neovascular amd; octa; wet amd j ophthalmic vis res 2021; 16 (4): 676–681 introduction age-related macular degeneration (amd) is a leading cause of visual impairment and is projected to affect 288 million individuals by 2040.[1] over time, amd can progress from correspondence to: nadia k. waheed, md, mph. new england eye center 260 tremont st., boston, ma 02116, usa. e-mail: nadiakwaheed@gmail.com received: 14-06-2021 accepted: 18-07-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9758 earlier stages of dry amd, characterized by drusen and pigmentary changes, to late-stage amd, defined by neovascularization and/or complete retinal pigment epithelium (rpe) and outer retinal atrophy (crora).[2, 3] neovascular amd—also known as wet amd—is characterized by choroidal neovascularization (cnv), which can present as abnormal blood vessel formation in this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: pramil v, moult em, fujimoto jg, waheed nk. oct angiography-based evaluation of the choriocapillaris in neovascular agerelated macular degeneration. j ophthalmic vis res 2021;16:676–681. 676 © 2021 pramil et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9758&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr octa evaluation of choriocapillaris in armd; pramil et al the sub-rpe space (type i), subretinal space (type ii), and/or neurosensory retina (type iii), or even a combination of these subtypes.[4, 5] neovascularization can additionally be classified as exudative, with leakage from blood vessels, or non-exudative, without leakage.[6] while the pathophysiology of neovascular amd is insufficiently understood, evidence of choriocapillaris dysfunction has been found in affected eyes, and it has been hypothesized that the choriocapillaris is the initial site of injury.[7–10] the choriocapillaris is the dense, monolayer capillary network of the choroid below bruch’s membrane and the rpe which is responsible for nutrient supply and waste removal to and from the rpe and outer retina.[11] due to its important role in supporting the rpe, researchers have suggested that choriocapillaris flow impairment leads to increased ischemia and vascular endothelial growth factor (vegf) expression by the rpe, which, in turn, promotes neovascularization.[5, 7] imaging and evaluating the choriocapillaris in eyes with neovascular amd is therefore of great research and clinical interest. longitudinal changes in the choriocapillaris have been, until recently, difficult to assess because traditional dye-based angiography is not well suited for choriocapillaris imaging. for example, fluorescein angiography (fa) obscures fine choriocapillaris vasculature due to leakage from neovascularization; and, while indocyanine green angiography (icga) does not suffer from leakage, lack of depth resolution results in the choriocapillaris being obscured by larger choroidal vasculature. moreover, dye-based methods are invasive, can cause discomfort, and, more rarely, allergic reactions.[12] however, the recent clinical introduction of optical coherence tomography angiography (octa),[13–15] a functional extension of oct, has provided clinicians and researchers with a noninvasive, depth-resolved tool that is well suited for choriocapillaris imaging. since its introduction, octa has been extensively used to qualitatively and quantitatively analyze the choriocapillaris in eyes with neovascular amd. in this perspective, we overview some of these octa-based findings, note current technological limitations, and discuss promising future directions. octa imaging of the choriocapillaris in neovascular amd although fa has been historically considered the gold-standard imaging technique for identifying neovascular amd, octa is able to detect cnv with similar sensitivity and specificity and is now more commonly used to detect neovascular amd and assess the choriocapillaris vasculature of patients with neovascular amd.[16, 17] octa studies have consistently reported choriocapillaris impairment in the area below and surrounding cnv lesions secondary to neovascular amd. additionally, choriocapillaris flow impairment have also been reported to be larger throughout the macula in patients with neovascular amd compared to agematched controls.[18, 19] more recently, researchers have used octa to quantitatively analyze the spatial distribution of choriocapillaris impairment surrounding cnv lesions. for example, studies have shown that in eyes with cnv secondary to amd, choriocapillaris flow impairment is most severe in the region immediately surrounding the lesion.[19–22] these findings agree with histological studies, which have reported similar spatial trends in choriocapillaris impairment,[23, 24] and seem consistent with the hypothesis that choriocapillaris impairment precedes cnv development. octa studies have also examined differences in choriocapillaris impairment amongst eyes with varying types of cnv secondary to amd. in one study, greater choriocapillaris flow deficits were reported in the peripheral macula in eyes with type 3 cnv than in eyes with type 1 and/or type 2 cnv.[25] increased choriocapillaris flow impairment in fellow eyes of patients with unilateral type 3 cnv compared to fellow eyes of patients with unilateral type 1 or type 2 cnv has also been observed.[26] additionally, statistically significant increases in choriocapillaris flow impairment have been shown in patients with exudative, neovascular cnv compared to their fellow eye with non-exudative, cnv.[27] because all types of cnv has been shown to be present in areas with choriocapillaris impairment and cnv has also been shown to be associated with reduced growth of ga, cnv development may be an adaptive mechanism to overcome decreased choriocapillaris flow and ischemia.[21, 27–29] these findings suggest that changes in the choriocapillaris vasculature may play an important role in the development and progression of neovascular amd. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 677 octa evaluation of choriocapillaris in armd; pramil et al currently, the standard treatment for neovascular amd consists of intravitreal injections of vegf inhibitors. before the availability of antivegf treatments, patients with neovascular amd experienced rapid and severe vision loss due to leakage of blood and fluid from abnormal vessels. anti-vegf treatment has been shown to be effective in resolution of fluid and hemorrhage and improvement of visual acuity.[30–32] although many patients benefit from this treatment, others continue to experience progressive vision loss or show improvement for only a short period of time. factors such as baseline visual acuity and age have been shown to predict anti-vegf treatment response in neovascular amd.[33, 34] however, the pathophysiology leading to insufficient response to anti-vegf treatment is unknown. increased complexity and size of cnv lesion has been found to be associated with increased number of anti-vegf injections required for adequate response.[35] using octa, more complex and larger cnvs have also been shown to be associated with choriocapillaris flow deficits.[36] thus, it is possible that increased choriocapillaris flow deficits may predict poor response to anti-vegf treatment. additionally, in one study, reduced choriocapillaris vessel density was found in patients with neovascular amd receiving continuous and long-term antivegf treatment.[37] this could be due to initially decreased choriocapillaris blood flow in these patients leading to the increased necessity for continuing treatment. this finding was further corroborated in a study showing decreased baseline choriocapillaris vessel density in neovascular amd patients with decreased response to anti-vegf treatment.[38] further evaluation of the choriocapillaris using octa may help determine additional qualitative and quantitative metrics for prediction of anti-vegf response. limitations of octa imaging of the choriocapillaris in neovascular amd although octa imaging has proved to be a valuable tool for in vivo choriocapillaris imaging, it has limitations that clinicians and researchers should consider. perhaps most important in the context of choriocapillaris evaluation is the difference in performance between the two types of currently available commercial octa devices: spectral-domain octa (sd-octa) and swept-source octa (ss-octa). the shorter, ∼840 nm wavelength light used in commercially available spectral domain octa (sd-octa) instruments is more strongly attenuated by the rpe compared to the longer, ∼1050 nm wavelength light used in commercially available swept source octa (ss-octa) instruments. these attenuation differences are exacerbated by certain pathological features present in eyes with neovascular amd, including drusen and exudation.[39–41] therefore, when available, we recommend ss-octa for choriocapillaris imaging in neovascular amd, and urge caution when interpreting sd-octa choriocapillaris data. artifacts in octa choriocapillaris imaging can also arise through processing and analysis steps. for example, neovascular amd often results in substantial distortion of normal retinal anatomy, which can cause errors in automated retina layer segmentation, lead to incorrect choriocapillaris slab boundaries, and, therefore, to erroneous choriocapillaris en face images. octa images are obtained from structural oct data and octa cannot be reliably performed in regions with lower oct signal additionally, some octa algorithms are not normalized by the oct signal level, which results in a strong interdependence between the octa signal level and oct signal intensity. thus, without correction, areas of low oct signal can appear to have low octa signal, irrespective of blood flow.[42] conversely, normalized octa algorithms require removal or masking of low oct signal regions which have invalid octa data. this can result in the opposite effect, blood flow can be present, but not visualized in octa.[43] therefore, it is important to understand processing and analysis steps when interpreting choriocapillaris octa data. for more details, we refer readers to recently published reviews on octa and choriocapillaris imaging.[14, 44] future directions of octa imaging of the choriocapillaris in neovascular amd the enthusiasm for octa imaging in the clinical, commercial, and research communities has resulted in continuing innovation and improvement in octa technology, which will have a positive impact on octa imaging of the choriocapillaris in the future. one direction of investigation, which 678 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 octa evaluation of choriocapillaris in armd; pramil et al has been pursued by our group and others, is octa imaging using variable interscan times. specifically, as noted in the early development of octa, the ability of octa to detect blood flow is closely related to the interscan time—the time between repeated b-scans.[45–49] by varying the interscan time, different blood flow speeds can be detected and resolved, and relative blood flow speeds can be inferred.[48, 49] we expect that octa utilizing multiple interscan times will be better able to detect subtle choriocapillaris blood flow impairments. for example, using the variable interscan time analysis (vista) procedure, our group has demonstrated that some choriocapillaris flow deficits surrounding cnv lesions are apparent at shorter (1.5 ms)—but not longer (3.0 ms)—interscan times, suggesting different levels of blood flow impairment as opposed to full choriocapillaris vasculature loss.[22] we are also enthusiastic about instrument and processing advances that will improve the resolvability of the choriocapillaris vasculature. currently, commercial octa instruments cannot resolve structural details of the tightly packed choriocapillaris vasculature, particularly in the fovea where it is most dense, due to a combination of limited transverse oct resolution, a-scan density, and speckle noise. however, research groups have demonstrated wellresolved foveal choriocapillaris vasculature using adaptive optics[50] as well as mhz a-scan rate systems.[50–53] volumetric averaging has also shown the ability to improve the resolvability of choriocapillaris vasculature.[54, 55] we believe that these approaches may enable researchers to study morphological features of the choriocapillaris vasculature in addition to areas of flow impairment. summary octa imaging enables noninvasive imaging of the choriocapillaris, including in eyes with neovascular amd. octa studies have shown choriocapillaris alterations around and beneath cnv lesions, with impairment most pronounced in regions closest to the lesion. despite its advantages, the complexity of octa processing and analysis introduces potential artifacts, particularly for choriocapillaris imaging, where the oct beam is attenuated by the rpe, precise segmentation is required. nevertheless, due to the importance of choriocapillaris evaluation in neovascular amd and other retinal pathologies, innovations from clinicians, researchers, and companies are poised to make substantial advances in choriocapillaris imaging for the next generation octa instruments. financial support and sponsorship this study was supported by a grant from research to prevent blindness. conflicts of interest nkw: allegro (c), regeneron (c), apellis (c), optovue (r), heidelberg (r), nidek (r, c), topcon (c), zeiss (r), stealth (c), genentech (c), astellas (c), gyroscope (employee), ocudyne (shareholder), boehringer ingelheim (c); jgf: optovue (i, p), topcon (f), vista-octa (p); vp: none; em: vistaocta (p), gyroscope (c). references 1. wong wl, su x, li x, cheung cm, klein r, cheng cy, et al. global prevalence of age-related macular degeneration and disease burden projection for 2020 and 2040: a systematic review and meta-analysis. lancet glob health 2014;2:e106–e116. 2. mitchell p, liew g, gopinath b, wong ty. age-related macular degeneration. lancet 2018;392:1147–1159. 3. sadda sr, guymer r, holz fg, schmitz-valckenberg s, curcio ca, bird ac, et al. consensus definition for atrophy associated with age-related macular degeneration on oct: classification of atrophy report 3. ophthalmology 2018;125:537–548. 4. grossniklaus he, green wr. choroidal neovascularization. am j ophthalmol 2004;137:496– 503. 5. freund kb, ho iv, barbazetto ia, koizumi h, laud k, ferrara d, et al. type 3 neovascularization: the expanded spectrum of retinal angiomatous proliferation. retina 2008;28:201–211. 6. bailey st, thaware o, wang j, hagag am, zhang x, flaxel cj, et al. detection of nonexudative choroidal neovascularization and progression to exudative choroidal neovascularization using oct angiography. ophthalmol retina 2019;3:629–636. 7. mcleod ds, taomoto m, otsuji t, green wr, sunness js, lutty ga. quantifying changes in rpe and choroidal vasculature in eyes with age-related macular degeneration. invest ophthalmol vis sci 2002;43:1986– 1993. 8. mcleod ds, grebe r, bhutto i, merges c, baba t, lutty ga. relationship between rpe and choriocapillaris in agerelated macular degeneration. invest ophthalmol vis sci 2009;50:4982–4991. 9. moreira-neto ca, moult em, fujimoto jg, waheed nk, ferrara d. choriocapillaris loss in advanced age-related macular degeneration. j ophthalmol 2018;2018:8125267. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 679 octa evaluation of choriocapillaris in armd; pramil et al 10. biesemeier a, taubitz t, julien s, yoeruek e, schraermeyer u. choriocapillaris breakdown precedes retinal degeneration in age-related macular degeneration. neurobiol aging 2014;35:2562–2573. 11. ferrara d, waheed nk, duker js. investigating the choriocapillaris and choroidal vasculature with new optical coherence tomography technologies. prog retin eye res 2016;52:130–155. 12. uji a, balasubramanian s, lei j, baghdasaryan e, al-sheikh m, sadda sr. choriocapillaris imaging using multiple en face optical coherence tomography angiography image averaging. jama ophthalmol 2017;135:1197–1204. 13. de carlo te, romano a, waheed nk, duker js. a review of optical coherence tomography angiography (octa). int j retina vitreous 2015;1:5. 14. spaide rf, fujimoto jg, waheed nk, sadda sr, staurenghi g. optical coherence tomography angiography. prog retin eye res 2018;64:1–55. 15. kashani ah, chen cl, gahm jk, zheng f, richter gm, rosenfeld pj, et al. optical coherence tomography angiography: a comprehensive review of current methods and clinical applications. prog retin eye res 2017;60:66– 100. 16. faridi a, jia y, gao ss, huang d, bhavsar kv, wilson dj, et al. sensitivity and specificity of oct angiography to detect choroidal neovascularization. ophthalmol retina 2017;1:294–303. 17. giocanti-auregan a, dubois l, dourmad p, cohen sy. impact of optical coherence tomography angiography on the non-invasive diagnosis of neovascular age-related macular degeneration. graefes arch clin exp ophthalmol 2020;258:537–541. 18. moult e, choi w, waheed nk, adhi m, lee b, lu cd, et al. ultrahigh-speed swept-source oct angiography in exudative amd. ophthalmic surg lasers imaging retina 2014;45:496–505. 19. keiner cm, zhou h, zhang q, wang rk, rinella nt, oldenburg ce, et al. quantifying choriocapillaris hypoperfusion in patients with choroidal neovascularization using swept-source oct angiography. clin ophthalmol 2019;13:1613–1620. 20. alagorie ar, verma a, nassisi m, nittala m, velaga s, tiosano l, et al. quantitative assessment of choriocapillaris flow deficits surrounding choroidal neovascular membranes. retina 2020;40:2106–2112. 21. scharf jm, corradetti g, alagorie ar, grondin c, hilely a, wang d, et al. choriocapillaris flow deficits and treatment-naïve macular neovascularization secondary to age-related macular degeneration. invest ophthalmol vis sci 2020;61:11. 22. moult em, alibhai ay, rebhun c, lee b, ploner s, schottenhamml j, et al. spatial distribution of choriocapillaris impairment in eyes with choroidal neovascularization secondary to age-related macular degeneration: a quantitative oct angiography study. retina 2020;40:428–445. 23. moreira-neto ca, moult em, fujimoto jg, waheed nk, ferrara d. choriocapillaris loss in advanced age-related macular degeneration. j ophthalmol 2018;2018:8125267. 24. seddon jm, mcleod ds, bhutto ia, villalonga mb, silver re, wenick as, et al. histopathological insights into choroidal vascular loss in clinically documented cases of age-related macular degeneration. jama ophthalmol 2016;134:1272–1280. 25. corvi f, cozzi m, corradetti g, staurenghi g, sarraf d, sadda sr. quantitative assessment of choriocapillaris flow deficits in eyes with macular neovascularization. graefes arch clin exp ophthalmol 2021;259:1811–1819. 26. borrelli e, souied eh, freund kb, querques g, miere a, gal-or o, et al. reduced choriocapillaris flow in eyes with type 3 neovascularization and age-related macular degeneration. retina 2018;38:1968–1976. 27. treister ad, nesper pl, fayed ae, gill mk, mirza rg, fawzi aa. prevalence of subclinical cnv and choriocapillaris nonperfusion in fellow eyes of unilateral exudative amd on oct angiography. transl vis sci technol 2018;7:19. 28. pfau m, möller pt, künzel sh, von der emde l, lindner m, thiele s, et al. type 1 choroidal neovascularization is associated with reduced localized progression of atrophy in age-related macular degeneration. ophthalmol retina 2020;4:238–248. 29. hwang ck, agrón e, domalpally a, cukras ca, wong wt, chew ey, et al. progression of geographic atrophy with subsequent exudative neovascular disease in age-related macular degeneration: areds2 report 24. ophthalmol retina 2021;5:108–117. 30. ricci f, bandello f, navarra p, staurenghi g, stumpp m, zarbin m. neovascular age-related macular degeneration: therapeutic management and new-upcoming approaches. int j mol sci 2020;21:8242. 31. wong ty, chakravarthy u, klein r, mitchell p, zlateva g, buggage r, et al. the natural history and prognosis of neovascular age-related macular degeneration: a systematic review of the literature and meta-analysis. ophthalmology 2008;115:116–126. 32. jaffe gj, martin df, toth ca, daniel e, maguire mg, ying gs, et al. comparison of age-related macular degeneration treatments trials research group: macular morphology and visual acuity in the comparison of age-related macular degeneration treatments trials. ophthalmology 2013;120:1860–1870. 33. finger rp, wickremasinghe ss, baird pn, guymer rh. predictors of anti-vegf treatment response in neovascular age-related macular degeneration. surv ophthalmol 2014;59:1–18. 34. amoaku wm, chakravarthy u, gale r, gavin m, ghanchi f, gibson j, et al. defining response to anti-vegf therapies in neovascular amd. eye 2015;29:721–731. 35. nesper pl, soetikno bt, treister ad, fawzi aa. volumerendered projection-resolved oct angiography: 3d lesion complexity is associated with therapy response in wet agerelated macular degeneration. invest ophthalmol vis sci 2018;59:1944–1952. 36. nesper pl, ong jx, fawzi aa. exploring the relationship between multilayered choroidal neovascularization and choriocapillaris flow deficits in amd. invest ophthalmol vis sci 2021;62:12. 37. hikichi t, agarie m. reduced vessel density of the choriocapillaris during anti-vascular endothelial growth factor therapy for neovascular age-related macular degeneration. invest ophthalmol vis sci 2019;60:1088– 1095. 680 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 octa evaluation of choriocapillaris in armd; pramil et al 38. lee b, yoo g, yun c, oh j. short-term effects of antivascular endothelial growth factor on peripapillary choroid and choriocapillaris in eyes with neovascular age-related macular degeneration. graefes arch clin exp ophthalmol 2019;257:2163–2172. 39. novais ea, adhi m, moult em, louzada rn, cole ed, husvogt l, et al. choroidal neovascularization analyzed on ultrahigh-speed swept-source optical coherence tomography angiography compared to spectral-domain optical coherence tomography angiography. am j ophthalmol 2016;164:80–88. 40. miller ar, roisman l, zhang q, zheng f, rafael de oliveira dias j, yehoshua z, et al. comparison between spectraldomain and swept-source optical coherence tomography angiographic imaging of choroidal neovascularization. invest ophthalmol vis sci 2017;58:1499–1505. erratum in: invest ophthalmol vis sci 2017;58:2166. 41. lane m, moult em, novais ea, louzada rn, cole ed, lee b, et al. visualizing the choriocapillaris under drusen: comparing 1050-nm swept-source versus 840-nm spectral-domain optical coherence tomography angiography. invest ophthalmol vis sci 2016;57:oct585–590. 42. zhang q, zheng f, motulsky eh, gregori g, chu z, chen c-l, et al. a novel strategy for quantifying choriocapillaris flow voids using swept-source oct angiography. invest ophthalmol vis sci 2018;59:203-211. 43. cole ed, moult em, dang s, choi w, ploner sb, lee b, et al. the definition, rationale, and effects of thresholding in oct angiography. ophthalmol retina 2017;1:435–447. 44. chu z, zhang q, gregori g, rosenfeld pj, wang rk. guidelines for imaging the choriocapillaris using oct angiography. am j ophthalmol 2021;222:92–101. 45. jaillon f, makita s, yasuno y. variable velocity range imaging of the choroid with dual-beam optical coherence angiography. opt express 2012;20:385–396. 46. tokayer j, jia y, dhalla a-h, huang d. blood flow velocity quantification using split-spectrum amplitudedecorrelation angiography with optical coherence tomography. biomedical optics express 2013;4:1909– 1924. 47. braaf b, vermeer ka, vienola kv, de boer jf. angiography of the retina and the choroid with phase-resolved oct using interval-optimized backstitched b-scans. opt express 2012;20:20516–20534. 48. choi w, moult em, waheed nk, adhi m, lee b, lu cd, et al. ultrahigh-speed, swept-source optical coherence tomography angiography in nonexudative agerelated macular degeneration with geographic atrophy. ophthalmology 2015;122:2532–2544. 49. ploner sb, moult em, choi w, waheed nk, lee b, novais ea, et al. toward quantitative optical coherence tomography angiography: visualizing blood flow speeds in ocular pathology using variable interscan time analysis. retina 2016;36:s118–s126. 50. kurokawa k, liu z, miller dt. adaptive optics optical coherence tomography angiography for morphometric analysis of choriocapillaris [invited]. biomed opt express 2017;8:1803–1822. 51. migacz jv, gorczynska i, azimipour m, jonnal r, zawadzki rj, werner js. megahertz-rate optical coherence tomography angiography improves the contrast of the choriocapillaris and choroid in human retinal imaging. biomed opt express 2018;10:50–65. 52. marsh-armstrong b, migacz j, jonnal r, werner js. automated quantification of choriocapillaris anatomical features in ultrahigh-speed optical coherence tomography angiograms. biomed opt express 2019;10:5337–5350. 53. poddar r, migacz jv, schwartz dm, werner js, gorczynska i. challenges and advantages in widefield optical coherence tomography angiography imaging of the human retinal and choroidal vasculature at 1.7-mhz a-scan rate. j biomed opt 2017;22:1–14. 54. chu z, zhou h, cheng y, zhang q, wang rk. improving visualization and quantitative assessment of choriocapillaris with swept source octa through registration and averaging applicable to clinical systems. sci rep 2018;8:16826. 55. uji a, balasubramanian s, lei j, baghdasaryan e, al-sheikh m, sadda sr. choriocapillaris imaging using multiple en face optical coherence tomography angiography image averaging. jama ophthalmol 2017;135:1197–1204. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 681 review article artifacts in optical coherence tomography angiography pasha anvari, md, mph1; maryam ashrafkhorasani, md1; abbas habibi, md1; khalil ghasemi falavarjani, md1,2 1eye research center, the five senses institute, rassoul akram hospital, iran university of medical sciences, tehran, iran 2stem cell and regenerative medicine research center, iran university of medical sciences, tehran, iran orcid: pasha anvari: http://orcid.org/0000-0002-3765-4206 khalil ghasemi falavarjani: http://orcid.org/0000-0001-5221-1844 abstract we performed a comprehensive search of the published literature in pubmed and google scholar to identify types, prevalence, etiology, clinical impact, and current methods for correction of various artifacts in optical coherence tomography angiography (octa) images. we found that the prevalence of octa image artifacts is fairly high. artifacts associated with eye motion, misidentification of retinal layers, projections, and low optical coherence tomography signal are the most prevalent types. artifacts in octa images are the major limitations of this diagnostic modality in clinical practice and identification of these artifacts and measures to mitigate them are essential for correct diagnosis and follow-up of patients. keywords: artifact; artefact; capillary plexus; image quality; optical coherence tomography angiography; projection; segmentation; vessel density j ophthalmic vis res 2021; 16 (2): 271–286 introduction optical coherence tomography angiography (octa) is an imaging method that provides threedimensional images from the microcirculation of the retina, choroid, and optic nerve head. considering its noninvasive nature and fast acquisition time, octa has gained priority over fluorescein angiography (fa), the traditional correspondence to: khalil ghasemi falavarjani md, eye research center, rassoul akram hospital, sattarkhan-niaiesh st, tehran, iran. email: drghasemi@yahoo.com and ghasemifalavarjani.k@iums.ac.ir received: 25-11-2020 accepted: 05-01-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9091 standard technique for evaluating retinal vasculature, for several retinal and choroidal disorders.[1–6] in addition, depth-resolved octa images have improved our understanding of the pathogenesis, classification, and management of posterior segment diseases.[7, 8] despite prominent advantages of octa, different types of artifacts may limit the interpretation and clinical application of this imaging modality.[9] previous studies have reported several types of artifacts impacting octa-derived metrics.[9–14] overall, the prevalence of artifacts ranges from 72 to 100%.[13–17] although various artifacts in octa images (e.g., segmentation this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: anvari p, ashrafkhorasani m, habibi a, falavarjani kg. artifacts in optical coherence tomography angiography. j ophthalmic vis res 2021;16:271–286. © 2021 anvari et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 271 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9091&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr artifacts in octa; anvari et al artifact, shadow artifact, etc.) are similar to those reported in oct images, several types of the artifacts are unique to octa. recognition and minimizing or controlling such artifacts is crucial to avoid clinical misinterpretation[18]. this study aimed to review the literature describing octa artifacts. methods a comprehensive literature search was performed on august 9, 2020, in pubmed and google scholar using the key words “oct angiography” or “optical coherence tomography angiography” or “octa” and “artifact” or “artifacts” or “artefact” or “artefacts” to extract english-language original and review articles. two researchers evaluated the abstracts and included relevant articles. case reports were excluded. results of the 9,220 and 206 studies found in google scholar and pubmed, respectively, 59 studies were found eligible and included for this review. prevalence the prevalence of artifacts varied based on the octa device, setting, type of artifacts studied, and underlying disease [table 1]. ghasemi falavarjani et al[13] assessed octa images of 57 eyes including healthy subjects, individuals with agerelated macular degeneration (amd), and cystoid macular edema secondary to diabetic retinopathy (dr) or retinal vein occlusion (rvo). in 89.4% of images, at least one artifact was found. the most prevalent error was banding artifact (89.4%) followed by segmentation (61.4%), motion (49.1%), unmasking (15.8%), blink (8.8%), vessel doubling (1.7%), masking (1.7%), and out-of-window artifacts (1.7%). in diseased eyes, banding, motion, and segmentation artifacts were more prevalent. chen and colleagues[19] reviewed 60 octa images for motion artifacts as horizontal dark lines or bands not visible on oct reflectivity maps. these lines were evident in 100% of the octa images from the outer retina, 90% of images from sattler’s layer, and 70% of the images from haller’s layer. holmen et al[15] reported at least one artifact in 97.3% of images. severe artifacts were recognized in 53.5% of scans and the three most common artifacts were shadow (26.9%), defocus (20.9%), and movement (16%). artifact prevalence did not differ among imaging systems or scan protocols. in a more recent study,[17] 88.34% of octa images of the superficial vascular plexus of 343 eyes of 183 subjects including 100 glaucoma patients and 83 healthy participants showed at least one type of artifact. the most common artifact was projection (100%) followed by motion artifact (75.22%). stepien et al[14] reported that vessel density (vd) in 74% of eyes with retinal disease and 54.7% of normal subjects was unreliable due to artifacts. in 72% of images with unreliable vd, more than one artifact was found. say et al[20] reported a higher frequency of artifacts in eyes with underlying pathology or low vision and described loss of focus followed by broad blink lines (55 and 37%, respectively) as the most common artifacts in eyes with unilateral choroidal melanoma. in another study, projection artifacts, segmentation errors, and motion artifacts were reported in 100%, 55%, and 49% of eyes of 6 healthy eyes and 69 eyes with underlying retinal disorders (including amd, dr, rvo, and retinal artery occlusion), respectively.[21] iftikhar et al[16] reported that some degree of artifact was noticed in 97.1% of images from healthy subjects and patients with multiple sclerosis. the most frequent artifact was motion artifact (96.3%). the probability of motion artifacts in these patients was higher in those with longer disease duration or history of optic neuritis. ghasemi falavarjani et al[22] reported that 33% of healthy eyes and 100% of diabetic eyes showed segmentation errors. all studies reported a higher prevalence of artifact(s) in eyes with underlying pathologies. in addition, low image quality has been reported to be associated with a higher prevalence of artifacts.[15, 23] different octa devices utilize various propriety algorithms to detect, process, and visualize decorrelation signals. relatively rapid advances in software updates to reduce the artifacts impede practical comparison of these devices. in a study by li and colleagues[24] evaluating the clinical performance of five octa devices (angiovue, angioplex, spectralis, angioscan, and octa ss oct angiotm), the authors found that angiovue had the least motion artifacts. theoretically, swept source (ss) octa instruments employing longer wavelength light 272 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 artifacts in octa; anvari et al table 1. the prevalence of optical coherence tomography angiography artifacts authors design studied group artifacts reported device type and software version chen et al, 2016[19] prospective observational study normal retinal diseases glaucoma motion (100%) fringe washout (100%) projection (100%) masking and unmasking (100%) stromal decorrelation signal (100%) retinal vessels duplication (5%) rtvue xr avanti system (optovue inc., ca, us) ghasemi falavarjani et al, 2016[13] retrospective observational study age-related macular degeneration diabetic retinopathy retinal vascular occlusions band (89.4%) segmentation (61.4%) motion (49.1%) unmasking (15.8%) blink (8.8%) doubling of the retinal vessels (1.7%) out of window (1.7%) masking (1.7%) projection (0.0%) stretch artifacts (0.0%) crisscross (0.0%) topcon oct instrument (dri oct triton plus, topcon, tokyo, japan). al-sheikh et al, 2017[23] prospective comparative study healthy subjects band (17.64–70.58%) segmentation (5.8–11.6%) motion (5.8%) projection (0–47.05%) dri oct triton, topcon inc., tokyo, japan say et al, 2017[20] observational study treated unilateral posterior uveal melanoma and fellow eye loss of focus (55%) broad blink lines (37%) motion (26%) specular dot (25%) edge duplication (8%) the optovue rtvue xr avanti, version 2014.2.0.13 holmen et al, 2019[15] cross-sectional study diabetic retinopathy eye movement (93.1%) defocus (74.9%) shadow (62.3%) tilt (50.5%) z offset (43.8%) refraction shift (31.8%) segmentation (24.6%) decentration (21.4%) projection (6.7%) blink (1%>) stretch artifact (1%>) edge duplication (1%>) loss of signal (1%>) cirrus hd-oct 5000, with the angioplex module, version 10.0.0.13424 or the optovue avanti rtvue xr, version 2018.0.0.5). enders et al, 2019[21] prospective observational study healthy subjects neovascular age-related macular degeneration diabetic retinopathy retinal vascular occlusions projection (100%) segmentation (55%) motion (49%) masking (45%) band (43%) blink (28%) window artifact (8%) vessel doubling (0.0%) stretch artifacts (0.0%) spectral domain oct cirrus 5000 equipped with the angioplex module) iftikhar et al, 2019[16] prospective cross-sectional study multiple sclerosis healthy subjects motion (96.3%) blink (51.9%) loss of focus (25.1%) spectralis® oct-a prototype, oct2 (heidelberg, germany) journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 273 artifacts in octa; anvari et al table 1. continued. authors design studied group artifacts reported device type and software version eastline et al, 2019[68] prospective observational study healthy eyes displacement artefact (96.34%) shadowing (92.27%) white line artefacts (63.41%) vessel doubling (35.37%). plex elite 9000 scanner (carl zeiss meditec, inc., dublin, ca). central 3 * 3 and 12 * 12 mm scans of the four quadrants (wide field) weijing et al, 2020[17] retrospective observational study glaucomatous eyes healthy eyes projection (100%) motion (75.22%) blink (2.62%) stretching (0.87%) blurred images (24.78%) decentration (21.28%) vignetting (2.04%) unmasking (0.87%) segmentation (1.17%) out of window (0.29%) vessel doubling (0.58%) n/a bontzos et al, 2020[69] prospective observational study eyes with idiopathic epiretinal membranes healthy eyes segmentation (0% in healthy eyes, 64.1% in erm patients) motion (7.5 % in healthy eyes, 53.8 % in erm patients) angiovue, rtvue xr avanti sd-oct, optovue software version: 2016.2.0.35 are less affected by mask artifacts as compared to spectral domain octas. reich et al showed that ss-octa can mitigate shadow artifacts imposed by subretinal fluid on the choriocapillaris in the subjects with acute central serous chorioretinopathy and retinal detachment.[25] studies investigating artifacts in disc octa are scarce. the frequency of various artifacts and predisposing factors in disc octa have yet to be determined. in a study by moghimi and colleagues,[26] 20% of disc octa scans were graded as poor quality images. similarly, rao and colleagues[27] found that 17% of disc octa scans had poor quality precluding useful interpretation. types of artifacts table 2 provides an overview of artifacts. artifacts can be categorized as patient-related (e.g., motion), software-related (e.g., motion, stretch, etc.), and operator-related (e.g., defocus). some artifacts can be related to more than one subset of these categories (e.g., motion artifact).[15] artifacts associated with eye movement any eye movement can lead to image artifacts. the cardiac cycle, breathing, tremors, and microsaccades cause pulsations. the consequence of these pulsations is motion of the choroid and retina.[9, 19] several types of artifacts associated with eye movement including motion artifacts, doubling of retinal vessels, blink artifacts, stretch artifacts, and crisscross artifacts have been reported.[9] lauermann et al[28, 29] categorized motion artifacts under two groups: those caused by eye movement (blink lines and displacement) and artifacts due to software correction of eye movement (stretch artifacts, quilting, and vessel doubling). blink lines are caused by eye closure during image acquisition and result in loss of information. lost adjacent b-scans cause end-to-end black 274 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 artifacts in octa; anvari et al table 2. different types of artifacts in optical coherence tomography angiography images. type of artifact definition motion blink end-to-end black band displacement waviness or discontinuity of the retinal vessels doubling duplication of vessels stretch stretched vessels or presence of linear bands at the edge of octa image (edge duplication) quilting (crisscross) rectangular or checker-board pattern band bands with various brightness segmentation retinal boundaries misidentification projection presence of false flow in the avascular area projection removal traces left in the deeper layer after the removal of projected superficial vessels masking light blockage unmasking light hyper-transmission shadow ghost image of the superficial retinal vessels on the deeper layer z offset (out of window) vertical misaligned b-scans on the screen tilt more than 50% of b scans are not focused clearly refraction shift differing reflectivity of adjacent b-scans (probably the same as banding artifact) decentration not well-centered on the macula defocus whole b cans are not focused well suspended scattering particles in motion (sspim) extra-vascular octa signals corresponding to hyperreflective intraretinal fluid fringe washout dark appearance of choroidal vessels bands with a width dependent on the duration of eye closure.[13, 29] displacement of multiple adjacent b-scans leads to linear distortion of an image seen as waviness or discontinuity of retinal vessels.[13, 30] doubling artifacts are defined as duplication of vessels or appearance of two or more similar non-overlapping images caused by software correction of eye motion.[13, 29, 30] stretch artifact is the result of motion artifact correction by the machine software. intermittent changes in signals causes edge duplication which presents as a linear streak at the edge of an en-face image.[16, 29] furthermore, stretched vessels appear to be flattened.[13] quilting (crisscross or checkerboard defect) is a result of failure of the software to correct multiple saccades. quilting appears as a rectangular pattern of artifacts [figure 1].[29] while lauermann et al considered quilting artifact as banding or checkerboard,[29] ghasemi falavarjani et al[13] provided different definitions for banding artifact, in which multiple adjacent bscans form bands of different brightness compared to neighboring areas on en-face oct or octa images. banding artifact [figure 2] is thought to be caused by a temporary change in corneal refractive power during blinking which causes a part of the image to be out of focus (also known as refractive shift).[15] introduction of software with fast and accurate tracking has significantly reduced the rate of motion-related artifacts.[13] misidentification of retinal layers (segmentation artifact) octa en-face images show the microvascular network in different slabs. slabs are tissue layers limited by two retinal layer boundaries and are commonly divided into the superficial plexus, the deep plexus, the outer avascular retina, and the choriocapillaris.[28] any error journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 275 artifacts in octa; anvari et al figure 1. crisscross artifact as well as stretching artifact (yellow arrow), white line artifact (green arrow) and displacement of the course of the retinal vessel (blue arrow). figure 2. banding artifact. note a band with different brightness. 276 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 artifacts in octa; anvari et al figure 3. segmentation error artifact. (a) en face optical coherence tomography angiography (octa) at segmented outer retinal slab with segmentation error in delineation of retinal pigment epithelium, showing large choroidal vessels masquerading as neovascularization. (b) en face octa at outer retinal slab after segmentation correction. note that large choroidal vessels are now eliminated. in detecting the correct position of retinal boundaries leads to segmentation artifacts [figures 3–5].[13] a recent study defined segmentation error as a deviation exceeding 50% of the thickness of the pertinent plexus.[15] segmentation errors are more prevalent in low-quality images and in eyes with retinal pathologies.[21] projection artifact octa imaging is based on detection of a significant change in light characteristics (intensity, phase, or a combination), reflected from the same location at short intervals. these changes are then attributed to moving blood cells within the vessels. however, the transmitted light through a vessel may be erroneously perceived as flow when it is reflected from underlying reflecting surfaces (e.g. rpe).[9] therefore, projection or tailing artifacts are the presence of false flow in deeper slabs [figure 6].[31] projection artifact should be considered if vessels in the deep capillary plexus (dcp) appear to have the same pattern as the superficial vessels.[10] in addition, projection of superficial retinal vessels on deeper layers[9] should be considered in the evaluation of choroidal neovascularization, because projected images from either the superficial retinal vessels or intraretinal migrant pigments may be misinterpreted as cnv.[9] this is particularly important in cases with retinal pigment epithelium detachment (rped), because in these cases, the highly reflective nature of the rpe induces a projection artifact that appears as a bright ring at the edge of a ped.[32] chen et al demonstrated that rpe hyperplasia overlying ped may cause false flow signal in deeper layers.[33] projection artifact can be used to examine the anatomy of the choroidal vessels. by moving and placing the segmentation line behind the choroid, the vascular pattern of choroidal vessels can be projected onto the sclera.[34] although recently updated software programs can efficiently remove projection artifacts, another artifact may be introduced by eliminating the projection artifact. this “projection removal” artifact is defined as obscuration of vessels in deeper layers due to removal of projected superficial vessels by the device software.[10] the details of projection artifact removal (par) journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 277 artifacts in octa; anvari et al c e f a b d figure 4. enface octa, structural oct and vessel density map of deep capillary plexus in a subject with diabetic macular edema, before (a–c) and after (d–f) segmentation correction at inner plexiform layer (green line) and outer plexiform layer (red line). note a significant change in enface octa and vessel density map following segmentation correction. algorithms is beyond the scope of this review. the main idea is taking account of the oct and octa parameters of a given point in relation to its neighboring and anterior structures to differentiate true flow from the projections.[35] despite advances in par algorithms, fayed and fawzi[35] demonstrated that commercial par-octa might not be able to completely eliminate false flow associated with hard exudates and pigment migrations in retinal angiomatous proliferation. low-oct-signal artifacts numerous factors may contribute to low oct signals including vignetting, ocular 278 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 artifacts in octa; anvari et al figure 5. misidentification of bruch‘s membrane (black line) in a subject with macular neovascularization (a), following manual correction of bruch‘s membrane (b). note better delineation of neovascular network after segmentation correction. figure 6. projection artifact. (a) en face optical coherence tomography angiography (octa) at superficial capillary plexus. (b) en face octa at outer retinal slab. note prominent projection of superficial vessels, making detection of type 2 macular neovascularization challenging. (c) en face octa of outer retina after projection artifact removal using angiovue software. note the outline of neovascular tuft is now clearly visible and projection of the superficial capillary plexus removed. figure 7. masking (shadow) artifact in enface optical coherence tomography angiography and optical coherence tomography b scan in a subject with vitreous opacity. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 279 artifacts in octa; anvari et al figure 8. decentration artifact. (a) decentration of fovea in en face optical coherence tomography angiography (octa) at the level of superficial capillary plexus. (b) decentration of the grid over en face octa vessel density map. aberrations, system aberrations, angle-dependent backscattering, retina moving out of focus, signal roll-off, any media opacity, intraor sub-retinal fluid and hemorrhage, vascular shadowing, and rpe clumping. vignetting is one of the main causes of low-oct-signal artifacts and is exacerbated with increased field size and smaller pupil diameter. vignetting may occur as a result of partial or complete blockage of the incident beam by the iris.[36] low oct signals may result in segmentation error, as described above. de pretto et al proposed three strategies to detect low oct signal on octa images.[36] in the simplest and most reliable approach, namely, cross-sectional approach, careful b-scan-by-b-scan analysis, or b scan fly-through is performed to detect areas of low signal or segmentation errors. in the en face approach, oct and octa en face images are compared alongside. low-octsignal leading to segmentation error creates an abrupt signal alteration on en face oct images. the en face approach provides a general view of data and facilitates the recognition of artifacts around the lesion of interest. in orthoplane approach, which is a combination of the two former strategies, an en face approach is used to recognize areas of low oct signal and then a cross-sectional analysis is employed to assess these areas.[36] octa thresholding is the procedure for removal of areas with low or noisy oct signals. if octa thresholding does not take place, low oct signal areas form regions with low octa signal, independent of presence or absence of blood flow. this is named thresholding artifact.[36, 37] light blockage as a result of more anterior lesions including vitreous opacities, pigment clumps, etc. does not permit the beam to reach deeper layers. this causes masking or shadow artifacts [figure 7].[13] on the contrary, the excess transmission of light due to rpe or retinal atrophy gives rise to increased oct reflectivity which is labeled as unmasking or hyper-transmission.[10, 13] although octa has been shown to be superior to conventional dye-based angiography in detecting macular neovascularization in the context of macular atrophy,[38] special emphasis should be laid on the interpretation of findings. anterior displacement of larger choroidal vessels along with unmasking artifact in areas of geographic atrophy may falsely create the impression of macular neovascularization.[39] “ghost images” are shadows of large superficial retinal vessels on deeper layers that impede extraction of vascular information from the areas beneath these vessels.[8] in other words, masking artifacts from large retinal vessels are considered as shadow artifacts.[19] shadow artifacts occasionally refer to the attenuated signals caused by an opacity or an obstruction due to retinal bleeding, subretinal fluid, or drusen.[25] 280 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 artifacts in octa; anvari et al wide-field octa wide-field octa provides a wider field of view compared to the traditional 3x3 and 6x6 images. there are several factors that may contribute to increased prevalence of image artifacts in wide-field octa. longer image acquisition time may lead to poor patient cooperation and increased motion artifacts. peripheral regions might get out of focus due to retinal curvature. the longer wavelength of ss-octa has lower axial resolution which may result in lower contrast between retinal layers and consequently higher rates of segmentation errors. a wider field of view is more sensitive to oct beam–pupil misalignment and lowsignal artifacts.[36, 40] in addition, there are some artifacts specific to wide-field imaging. alignment error is unique to montage octa images and is understood to be caused by projection removal in processing of depthcoded images. in this artifact, the superior and inferior half of the image appears to origin from different depths.[40] eyelash artifact has recently been described on widefield images as a new subset of shadow artifact.[41] other artifacts some artifacts are less frequent. z-offset (or out of window) artifact results from vertical displacement of b-scans on the screen.[13, 15] tilt artifact occurs in the presence of severe angle of incidence, head placement, and/or high myopia which result in half of the b scans being defocused.[15] a refraction shift artifact can occur with an alteration in reflective intensity between adjacent scans due to blinking or an alteration of corneal surface refractive index. refraction shift artifact is ostensibly a subtype of banding artifact as described before.[15] decentration artifact arises when a scan is not centered on the macula [figure 8].[15] in addition, the etdrs grid that is overlaid on the vd map, may fail to detect the center of the fovea, previously described as grid decentration artifact on structural oct images.[42] defocus artifact is defined as reduced definition of retinal microvasculature on en face octa images and decreased reflectivity of inner retinal layers compared to normal standard oct images and is caused by a defocused image.[15] suspended scattering particles in motion (sspim) are responsible for nonvascular decorrelation signals in hyperreflective fluid associated with various exudative maculopathies including dr, rvo,[43] and coats disease.[10] brownian movements of lipoproteinacious particles in intraretinal cysts, similar to moving red blood cells (rbc) in vessels, are detected by octa instruments. these signals are not representative of rbcs within vessels and may be considered as artifacts. maltsev et al[44] demonstrated that the presence of sspim in eyes with diabetic macular edema may artefactually increase vessel densities in the dcp when a 3-mm scan protocol is employed. hyperreflective crystalline deposits in amd can produce multiple hyper-intense vertical lines passing through these lesions, extending anterior and posteriorly in cross-sectional b-scans.[45] fringe washout artifact occurs in en face choroidal slabs. in contrast to retinal vasculature, choroidal vessels appear as cord-like dark vessels. this poor backscattered signal is in contrast to the surrounding hyper-reflective choroidal stroma and allows visualization of the vessel outline. fringe washout artifact occurs in sattler’s and haller’s layers.[19, 46] to point out the nature of the hyperreflective area around dark choroidal vessels, maruko et al[47] proposed that the surrounding whitish area is due to projection artifact from the overlying choriocapillaris layer. while an hourglass signal pattern is present in large retinal vessels, choroidal vessel lumen seems dark. if rpe atrophy happens, an hourglass pattern in choroidal vessels appears. therefore, it seems that the “masking” effect of rpe is the main cause for choroidal vessels appearing as dark regions.[48] movements in the vessels and consequently, flow signal can be detected even if the laser beam is not centered on the vessel.[9] therefore, vessel diameter may be erroneously displayed. ghasemi falavarjani et al showed that in octa images, vessel diameter measurements were significantly larger than those obtained on color fundus photographs, particularly for smaller vessels.[49] artifacts grading system some articles suggest a scoring system for artifact grading. however, the proposed systems are not journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 281 artifacts in octa; anvari et al widely employed. a simple grading protocol was introduced by munk et al[50] to compare four octa devices. they graded artifacts as motion artifacts (1 = no artifacts, 0 = some artifacts, –1 = severe motion artifacts) and image artifacts (1 = no artifacts, 0 = some artifacts, –1 = severe image artifacts). the image artifact category included segmentation and projection artifacts. for grading motion artifacts, a motion artifact score (mas; scores i–iv) has been proposed.[28, 29] the grading ranges from mas 1 (no or slight quilting, absence of other motion artifacts) to mas 4 (artifacts in more than two quadrants, with either moderate or significant quilting, displacement, vessel doubling, stretch artifact). for evaluation of segmentation accuracy, lauermann et al[28] introduced the segmentation accuracy score (sas; score i–iib) that can be used in all retinal diseases. more than 50 μm deviation of segmentation from the correct reference plane was defined as inaccurate. presence of inaccurate segmentation in <5% of all single b scans; in each boundary (ilm, ipl, or cc) is graded as sas i. if this happens in >5% of scans, it is defined as sas ii. the involvement of only one reference plane is categorized as sas iia, while the presence of errors in more than one plane is defined as sas iib.[28] later a more general grading system was introduced by holmen et al.[15] they described a severity scale of 0 to 3 for each artifact, in which 0 is no artifact and 3 is the appearance of artifacts in >10% of oct b-scans within the inner or central subfield. discussion the ability of octa to capture microvascular network images in different retinal layers and its high resolution and high speed characteristics renders it as a promising and invaluable imaging modality for the diagnosis and management of posterior segment diseases.[51] however, the impact of artifacts on the interpretation and precision of octa-derived metrics should be cautiously monitored.[15] artifacts are frequently observed on octa images and may occur during image acquisition, processing, and analysis.[52] low image quality and underlying posterior segment pathology are associated with a higher prevalence of artifacts. the frequency and types of artifacts may differ according to the underlying disease. furthermore, a lesion may cause more than one type of artifact. the frequency and severity of artifacts may be influenced by the type of octa device. some artifacts such as segmentation artifacts and duplication of vessels have been reported to be more dependent on the type of octa device; however, motion artifacts, either in scp or dcp images, are less dependent on the type of octa machine [24]. the frequency of different types of artifacts varies among layers. while motion and banding artifacts are common in superficial and deep retinal layers, segmentation and projection artifacts are more prevalent in deep retinal layers. masking artifacts occur more frequently in the choroidal layer.[21] with growing popularity of wide-field imaging in clinical practice, artifacts in wide-field octa images warrant special attention. failure to recognize and address artifacts on wide-field images can lead to incorrect diagnosis of peripheral non-perfusion or inability to visualize retinal neovascularization. this issue is especially important in evaluation of non-perfusion areas (npa) in dr because low signal artifacts can masquerade as npa.[36, 41] in a study by pichi et al, manual segmentations was necessary in the majority of eyes to enhance the characterization of neovascularization.[53] some general practical measures may be employed to minimize artifacts in octa imaging. proper attention should be paid to identify the subjects more prone to artifacts. these include systemic conditions such as parkinsonism or ocular pathologies including retinochoroidal diseases or ocular surface disorders. ocular surface conditions should be optimized in eyes with dry eye disease by instilling artificial tears. dilating eye drops should be used for widefield imaging. instructions should be provided for patients regarding the procedure. stable and comfortable position and regular breaks during image acquisition are crucial. proper transverse and axial alignment of the oct beam may be judged by checking the retinal b scans.[36] strategies to reduce motion artifacts can be applied during or after image acquisition. eye-tracking systems and scanning protocols can help curtail artifacts during image 282 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 artifacts in octa; anvari et al acquisition, and different algorithms can be utilized to reduce motion artifacts after taking the images.[54, 55] although post-processing motion correction techniques may not tolerate gross saccadic motion and induce additional artifacts, a combination of post-processing algorithms along with modified scanning protocols and eye-tracking systems are promising.[54, 55] automated segmentation algorithms may cause incorrect recognition of layers,[22] especially in the peripapillary area.[56] this misalignment can be corrected by the “edit band/propagation” tool on the optovue device software. by using this tool, users can fix one or few b-scans and propagate the correction to the rest of the adjacent scans.[22, 56, 57] ghasemi falavarjani et al[58] demonstrated that by implementing stepwise correction of segmentation lines, it is possible to reach complete correction by addressing this error on a relatively few number of b-scans in eyes with diabetic macular edema. notably, correction of central foveal b-scan had the most significant impact on vd measurements. recently, hanna and colleagues[56] showed that automated peripapillary retinal segmentation using the spectralis device may lead to underestimation of vessel densities at nerve fiber layer vascular plexus in normal and glaucomatous eyes. the process of manual segmentation, however, was time-consuming (5 hr per eye) and thus not practical in clinical settings. correcting segmentation error artifacts is more important when comparing octa metrics in longitudinal studies.[59] in the short term, manual correction of segmentation lines appears to be the best practical method to tackle segmentation errors. however, recent advances in deep learning/machine learning might be superior using to fixed models for retinal segmentations. various techniques of machine learning including support vector machines[60] and neural networks[61, 62] have been employed and appear to be promising. different strategies have been implemented to address projection artifacts. these include simple superficial vessel subtraction and different projection resolved (pr) algorithms.[35, 63, 64] it has been shown that par software can alter scp and dcp vd measurements and may interfere with vd assessment. this should be considered when comparing studies reporting vd using different software updates.[12, 65] evaluation of choriocapillaris blood flow in dry amd demonstrated changes in vascular density of the choriocapillaris.[66] confounding factors including projection and shadow artifacts can affect estimation of non-perfusion areas in the choriocapillaris. shadows on the choriocapillaris may originate either from large retinal vessels or overlying drusen. in case of any suspicion about flow impairment in the choriocapillaris in patients with macular lesions, flow images should be interpreted alongside structural en face images and oct b scans.[67] srf can affect the choriocapillaris octa signal. swept-source oct technology utilizes a longer wavelength and higher scan speed, therefore shadow artifacts are reduced with this generation of machines.[25] in summary, image artifact is a major concern in the interpretation and quantification of octa images. despite recent advances in octa technology, there is an emerging need for eliminating image artifacts. retinal specialists and octa technicians should be familiar with different types of artifacts and strive to eliminate or minimize them. the most important aspect is allocating enough time and attention for detecting possible artifacts on octa images. adding structural oct image data and 3d evaluation of the images are crucial. there is an emerging need for developing a grading system for artifacts. however, given their qualitative nature, consensus on a universally accepted grading system poses certain challenges. remote octa-viewing software may help clinicians to look for the artifacts in a systematic approach. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. liew g, wang jj, mitchell p, wong ty. retinal vascular imaging: a new tool in microvascular disease research. circ cardiovasc imag [internet] 2008;1:156–161. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 283 artifacts in octa; anvari et al 2. spaide rf, klancnik jm, cooney mj. retinal vascular layers imaged by fluorescein angiography and optical coherence tomography angiography. jama ophthalmol [internet] 2015;133:45. 3. pellegrini m, cozzi m, staurenghi g, corvi f. comparison of wide field optical coherence tomography angiography with extended field imaging and fluorescein angiography in retinal vascular disorders. plos one [internet] 2019;14:e0214892. 4. fang pp, lindner m, steinberg js, müller pl, gliem m, charbel issa p, et al. [clinical applications of oct angiography]. ophthalmologe [internet] 2016;113:14–22. 5. naseripour m, ghasemi falavarjani k, mirshahi r, sedaghat a. optical coherence tomography angiography (octa) applications in ocular oncology. eye [internet] 2020;34:1535–1545. 6. akil h, falavarjani kg, sadda sr, sadun aa. optical coherence tomography angiography of the optic disc; an overview. j ophthalmic vis res [internet] 107;12:98–105. 7. tan acs, tan gs, denniston ak, keane pa, ang m, milea d, et al. an overview of the clinical applications of optical coherence tomography angiography. eye [internet] 2018;32:262–286. 8. de carlo te, romano a, waheed nk, duker js. a review of optical coherence tomography angiography (octa). int j retin vitr [internet] 2015;1:5. 9. spaide rf, fujimoto jg, waheed nk. image artifacts in optical coherence tomography angiography. retina [internet] 2015 [cited 2017 jul 13];35:2163–2180. 10. hsu st, vajzovic l. handbook of pediatric retinal oct and the eye–brain connection. elsevier; 2020. chapter 8, identifying artifacts in oct angiography; 45–54. 11. tomlinson a, hasan b, lujan bj. importance of focus in oct angiography. ophthalmol retin [internet] 2018;2:748–749. 12. govindaswamy n, gadde sg, chidambara l, bhanushali d, anegondi n, sinha roy a. quantitative evaluation of optical coherence tomography angiography images of diabetic retinopathy eyes before and after removal of projection artifacts. j biophotonics [internet] 2018;11:e201800003. 13. ghasemi falavarjani k, al-sheikh m, akil h, sadda sr. image artefacts in swept-source optical coherence tomography angiography. br j ophthalmol [internet] 2017 [cited 2017 jul 13];101:564–568. 14. stepien ke, konda sm, etheridge t, holmen i, kopplin l, pak jw, et al. impact of artifacts in optical coherence tomography angiography image analysis. invest ophthalmol vis sci 2020;61:4818. 15. holmen ic, konda sm, pak jw, mcdaniel kw, blodi b, stepien ke, et al. prevalence and severity of artifacts in optical coherence tomographic angiograms. jama ophthalmol 2020;138:119–126. 16. iftikhar m, zafar s, gonzalez n, murphy o, ohemaa kwakyi ms, sydney feldman bs, et al. image artifacts in optical coherence tomography angiography among patients with multiple sclerosis. curr eye res 2019;44:558–563. 17. weijing c, zhang x, wang w. artifacts associated with swept-source oct-angiography measurements in glaucoma. invest ophthalmol vis sci 2020;61:4117. 18. chen jj, kardon rh. avoiding clinical misinterpretation and artifacts of optical coherence tomography analysis of the optic nerve, retinal nerve fiber layer, and ganglion cell layer. j neuroophthalmol 2016;36:417. 19. chen fk, viljoen rd, bukowska dm. classification of image artefacts in optical coherence tomography angiography of the choroid in macular diseases. clin experiment ophthalmol 2016;44:388–399. 20. say eat, ferenczy s, magrath gn, samara wa, khoo ctl, shields cl. image quality and artifacts on optical coherence tomography angiography: comparison of pathologic and paired fellow eyes in 65 patients with unilateral choroidal melanoma treated with plaque radiotherapy. retina [internet] 2017;37:1660–1673. 21. enders c, lang gkge, dreyhaupt j, loidl m, lang gkge, werner ju. quantity and quality of image artifacts in optical coherence tomography angiography. plos one 2019;14:e0210505. 22. ghasemi falavarjani k, habibi a, anvari p, ghasemizadeh s, ashraf khorasani m, shenazandi h, et al. effect of segmentation error correction on optical coherence tomography angiography measurements in healthy subjects and diabetic macular oedema. br j ophthalmol [internet] 2020;104:162–166. 23. al-sheikh m, ghasemi falavarjani k, akil h, sadda sr. impact of image quality on oct angiography based quantitative measurements. int j retin vitr [internet] 2017;3:13. 24. li x-x, wu w, zhou h, deng j-j, zhao m-y, qian t-w, et al. a quantitative comparison of five optical coherence tomography angiography systems in clinical performance. int j ophthalmol [internet] 2018;11:1784–1795. 25. reich m, boehringer d, rothaus k, cakir b, bucher f, daniel m, et al. swept-source optical coherence tomography angiography alleviates shadowing artifacts caused by subretinal fluid. int ophthalmol [internet]. 2020;40:2007–2016. 26. moghimi s, zangwill lm, penteado rc, hasenstab k, ghahari e, hou h, et al. macular and optic nerve head vessel density and progressive retinal nerve fiber layer loss in glaucoma. ophthalmology [internet] 2018;125:1720–1728. 27. rao hl, pradhan zs, weinreb rn, riyazuddin m, dasari s, venugopal jp, et al. vessel density and structural measurements of optical coherence tomography in primary angle closure and primary angle closure glaucoma. am j ophthalmol [internet] 2017;177:106–115. 28. lauermann jl, woetzel ak, treder m, alnawaiseh m, clemens cr, eter n, et al. prevalences of segmentation errors and motion artifacts in oct-angiography differ among retinal diseases. graefe’s arch clin exp ophthalmol 2018;256:1807–1816. 29. lauermann jl, treder m, heiduschka p, clemens cr, eter n, alten f. impact of eye-tracking technology on oct-angiography imaging quality in age-related macular degeneration. graefe’s arch clin exp ophthalmol 2017;255:1535–1542. 30. ho j, dans k, you q, nudleman ed, freeman wr. comparison of 3 mm × 3 mm versus 6 mm × 6 mm optical coherence tomography angiography scan sizes in the evaluation of non-proliferative diabetic retinopathy. retina [internet] 2019;39:259–264. 284 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 artifacts in octa; anvari et al 31. zhang a, zhang q, wang rk. minimizing projection artifacts for accurate presentation of choroidal neovascularization in oct micro-angiography. biomed opt express [internet] 2015;6:4130–4143. 32. louzada rn, de carlo te, adhi m, novais ea, durbin mk, cole e, et al. optical coherence tomography angiography artifacts in retinal pigment epithelial detachment. can j ophthalmol [internet] 2017;52:419–424. 33. chen l, zhang x, gan y, liu b, zhang y, wen f. retinal pigment epithelium hyperplasia overlying pigment epithelial detachment in age-related macular degeneration can masquerade as neovascularization on optical coherence tomography angiography. graefe’s arch clin exp ophthalmol 2018;256:2283–2291. 34. maruko i, spaide rf, koizumi h, sawaguchi s, izumi t, hasegawa t, et al. choroidal blood flow visualization in high myopia using a projection artifact method in optical coherence tomography angiography. retina [internet] 2017;37:460–465. 35. zhang m, hwang ts, campbell jp, bailey st, wilson dj, huang d, et al. projection-resolved optical coherence tomographic angiography. biomed opt express [internet] 2016;7:816–828. 36. de pretto lr, moult em, alibhai ay, carrasco-zevallos om, chen s, lee b, et al. controlling for artifacts in widefield optical coherence tomography angiography measurements of non-perfusion area. sci rep [internet] 2019;9:9096. 37. spaide rf, fujimoto jg, waheed nk, sadda sr, staurenghi g. optical coherence tomography angiography. prog retin eye res [internet] 2018;64:1–55. 38. corvi f, cozzi m, invernizzi a, pace l, sadda sr, staurenghi g. optical coherence tomography angiography for detection of macular neovascularization associated with atrophy in age-related macular degeneration. graefe’s arch clin exp ophthalmol [internet] 2020;259:291–299. 39. nesper pl, lutty ga, fawzi aa. residual choroidal vessels in atrophy can masquerade as choroidal neovascularization on optical coherence tomography angiography: introducing a clinical and software approach. retina [internet] 2018;38:1289–1300. 40. cui y, zhu y, wang jc, lu y, zeng r, katz r, et al. imaging artifacts and segmentation errors with wide-field swept-source optical coherence tomography angiography in diabetic retinopathy. transl vis sci technol [internet] 2019;8:18. 41. borrelli e, viggiano p, evangelista f, toto l, mastropasqua r. eyelashes artifact in ultra-widefield optical coherence tomography angiography. ophthalmic surg lasers imaging retin 2019;50:740–743. 42. falavarjani kg, khadamy j, safi h, karimi n, amirkourjani f. effect of grid decentration on macular thickness measurements in normal subjects and patients with diabetic macular edema. eur j ophthalmol [internet] 25:218–221. 43. kashani ah, green km, kwon j, chu z, zhang q, wang rk, et al. suspended scattering particles in motion: a novel feature of oct angiography in exudative maculopathies. ophthalmol retin 2018;2:694–702. 44. maltsev ds, kulikov an, kazak aa, freund kb. suspended scattering particles in motion may influence optical coherence tomography angiography vessel density metrics in eyes with diabetic macular edema. retina 2020; online ahead of print. 45. fragiotta s, fernández-avellaneda p, breazzano mp, yannuzzi la, curcio ca, freund kb. linear and planar reflection artifacts on swept-source and spectral-domain optical coherence tomography due to hyperreflective crystalline deposits. graefe’s arch clin exp ophthalmol [internet]. 2020;258:491–501. 46. hua r, wang h. dark signals in the choroidal vasculature on optical coherence tomography angiography: an artefact or not? j ophthalmol 2017;2017:5498125. 47. maruko i, kawano t, arakawa h, hasegawa t, iida t. visualizing large choroidal blood flow by subtraction of the choriocapillaris projection artifacts in swept source optical coherence tomography angiography in normal eyes. sci rep 2018;8:1–8. 48. bernucci mt, merkle cw, srinivasan vj. investigation of artifacts in retinal and choroidal oct angiography with a contrast agent. biomed opt express [internet] 2018;9:1020. 49. ghasemi falavarjani k, al-sheikh m, darvizeh f, sadun aa, sadda sr. retinal vessel calibre measurements by optical coherence tomography angiography. br j ophthalmol 2017;101:989–992. 50. munk mr, giannakaki-zimmermann h, berger l, huf w, ebneter a, wolf s, et al. oct-angiography: a qualitative and quantitative comparison of 4 oct-a devices. plos one 2017;12:e0177059. 51. ang m, tan acs, cheung cmg, keane pa, dolz-marco r, sng cca, et al. optical coherence tomography angiography: a review of current and future clinical applications. graefe’s arch clin exp ophthalmol 2018;256:237–245. 52. bazvand f, ghassemi f. artifacts in macular optical coherence tomography. j curr ophthalmol 2020;32:123. 53. pichi f, smith sd, abboud eb, neri p, woodstock e, hay s, et al. wide-field optical coherence tomography angiography for the detection of proliferative diabetic retinopathy. graefes arch clin exp ophthalmol 2020;258:1901–1909. 54. camino a, zhang m, gao ss, hwang ts, sharma u, wilson dj, et al. evaluation of artifact reduction in optical coherence tomography angiography with real-time tracking and motion correction technology. biomed opt express 2016;7:3905–3915. 55. sharma u, everett mj. data acquisition methods for reduced motion artifacts and applications in oct angiography. google patents [internet] 2014. 56. hanna v, sharpe gp, west me, hutchison dm, shuba lm, rafuse pe, et al. peripapillary retinal segmentation in oct angiography. ophthalmology [internet] 2020;127:1770– 1772. 57. optovue, inc. new angiovue® software streamlines octa interpretation. in: zhou q, editor. optical coherence tomography angiography (octa) quantification through angioanalyticstm. fremont, ca: optovue, inc.; 2017. 58. ghasemi falavarjani k, mirshahi r, ghasemizadeh s, sardarinia m. stepwise segmentation error correction in optical coherence tomography angiography images of patients with diabetic macular edema. ther adv ophthalmol [internet] 2020;12:251584142094793. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 285 artifacts in octa; anvari et al 59. mirshahi r, falavarjani kg, molaei s, habibi a, anvari p, khorasani ma, et al. macular microvascular changes after intravitreal bevacizumab injection in diabetic macular edema. can j ophthalmol [internet] 2020;56:57–65. 60. srinivasan pp, kim la, mettu ps, cousins sw, comer gm, izatt ja, et al. fully automated detection of diabetic macular edema and dry age-related macular degeneration from optical coherence tomography images. biomed opt express 2014;5:3568–3577. 61. venhuizen fg, van ginneken b, liefers b, van grinsven mjjp, fauser s, hoyng c, et al. robust total retina thickness segmentation in optical coherence tomography images using convolutional neural networks. biomed opt express 2017;8:3292–3316. 62. roy ag, conjeti s, karri spk, sheet d, katouzian a, wachinger c, et al. relaynet: retinal layer and fluid segmentation of macular optical coherence tomography using fully convolutional networks. biomed opt express 2017;8:3627–3642. 63. wang j, zhang m, hwang ts, bailey st, huang d, wilson dj, et al. reflectance-based projection-resolved optical coherence tomography angiography [invited]. biomed opt express [internet] 2017;8:1536–1548. 64. liu y, carass a, filippatou a, he y, solomon sd, saidha s, et al. projection artifact suppression for inner retina in oct angiography. in: 2019 ieee 16th international symposium on biomedical imaging (isbi 2019). ieee; 2019. p. 592–596. 65. ashraf m, sampani k, abu-qamar o, cavallerano j, silva ps, aiello lp, et al. optical coherence tomography angiography projection artifact removal: impact on capillary density and interaction with diabetic retinopathy severity. transl vis sci technol 2020;9:10. 66. nesper pl, soetikno bt, fawzi aa. choriocapillaris nonperfusion is associated with poor visual acuity in eyes with reticular pseudodrusen. am j ophthalmol 2017;174:42–55. 67. kayat kv, roisman l, zett c, novais ea, farah me. choriocapillaris hypoperfusion artifact in oct angiography. ophthalmic surg lasers imaging retina 2018;49:603–610. 68. eastline m, munk mr, wolf s, schaal kb, ebneter a, tian m, et al. repeatability of wide-field optical coherence tomography angiography in normal retina. transl vis sci technol 2019;8:6. 69. bontzos g, kabanarou sa, garnavou-xirou c, gkizis i, kontou e, triantafyllou d, et al. segmentation errors and motion artifacts in oct-a associated with epiretinal membranes. can j ophthalmol 2020;55:293–300. 286 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 letter to editor transforming ophthalmology training via mobile learning during the covid-19 pandemic mohammad-mehdi sadoughi1, md; soleiman ahmady2, md, phd; masomeh kalantarion1,2, ms nasrin khajeali3, phd 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2department of medical education, virtual school of medical education and management, shahid beheshti university of medical sciences, tehran, iran 3department of medical education, ahvaz jundishapur university of medical sciences, ahvaz, iran orcid: mohammad-mehdi sadoughi: https://orcid.org/0000-0003-2611-0526 masomeh kalantarion: https://orcid.org/0000-0003-4778-3973 j ophthalmic vis res 2021; 16 (4): 698–699 dear editor, the coronavirus disease 2019 (covid-19) pandemic was reported as a public health crisis. the quick spread of covid-19 has had a huge effect on many aspects of our life, including social development and education.[1] it has forced measures of social distancing and challenges in the delivery of “in-person” education. medical universities, involved in training ophthalmologists, are using innovative strategies to continue their standard of education.[2, 3] in this letter, we discuss a new strategy that was utilized to maintain ophthalmic education during this time of the covid-19 pandemic. one of the pioneering strategies that played a vital role during this pandemic is mobile learning. mobile learning is a learning strategy that supports the mobility of students as it facilitates learning at any time and place via the use of mobile devices.[4] the advantages and disadvantages of mobile learning has been widely discussed by many researchers.[5, 6] mobile learning is helping to promote knowledge and learning beyond the walls of the classroom and also facilitate continued student–teacher relations. other inherent advantages of mobile learning are that it is ubiquitous, portable, hybrid, interactive, and coordinative. on the other hand, some of the inescapable disadvantages of mobile learning include the use of small screens, the loss of security, the low knowledge of mobiquette, and the experience of virtual fatigue. however, advances in technology have provided alternatives to the use of small screens and have also enhanced the security of using these devices. it was also discovered that interactive webinar mobile applications (apps) might decrease the experience of virtual fatigue.[4] mobile learning has afforded us the opportunity to not only improve our knowledge but also improve our skills through simulation, which is very useful in ophthalmology education. during their period of training, residents should execute qualifying technical ophthalmic surgeries. as a result of social distancing, patients prefer to stay at home instead of being referred to educational hospitals for ophthalmic visits. consequently, ophthalmology residents have had a significant reduction in their surgical activities. to respond to this challenge, certain educational mobile platforms were recommended. one such recommendation was “touch surgery”, which is a surgical simulation app that includes ophthalmology and 11 other surgical specialties. these surgical simulation apps increase procedural proficiency and lessen intraoperative errors.[5] in this crisis, social media has also played a vital role in ophthalmic education. one such social media platform is twitter, which provides a forum for connecting peer students with ophthalmology educators who can address the educational needs of their students. mobile learning has also facilitated the use of innovative and interactive smartphone apps that are suitable learning resources for 698 © 2021 sadoughi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9762&domain=pdf&date_stamp=2019-07-17 letter to editor; sadoughi et al ophthalmologists. these applications that have been developed such as american academy of ophthalmology ophthalmic education app, ophthalmology guide app, ophthalmic instruments app, eye handbook app,[7] can be utilized for a range of topics, from teaching the anatomy via virtual reality or augmented reality to learning clinical information, self-assessment, and procedural skills. in summary, we have discovered that through mobile learning, the utilization of these innovative applications may expand opportunities for accessing standard ophthalmic education while also facilitating student-to-student and student-toteacher interactions. during the covid-19 period, mobile learning can be a valid solution to the ophthalmology-training gap experienced because of the social restrictions. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. yusoff ms, hadie sn, mohamad i, draman n, al-aarifin im, rahman wf, et al. sustainable medical teaching and learning during the covid-19 pandemic: surviving the new normal. malays j med sci 2020;27:137–142. 2. ferrara m, romano v, steel dh, gupta r, iovino c, van dijk ehc, et al reshaping ophthalmology training after covid19 pandemic. eye 2020;34:2089–2097. 3. mishra d, nair ag, gandhi ra, gogate pj, mathur s, bhushan p, et al the impact of covid-19 related lockdown on ophthalmology training programs in india – outcomes of a survey. indian j ophthalmol 2020;68:999–1004. 4. mckechnie t, levin m, zhou k, freedman b, palter vn, grantcharov tp. virtual surgical training during covid19: operating room simulation platforms accessible from home. ann surg 2020;272:e153–e154. 5. al-emran m. mobile learning during the era of covid-19. rev virtual univ catol norte 2020;61:1–2. 6. masters k, ellaway rh, topps d, archibald d, hogue rj. mobile technologies in medical education: amee guide no. 105. med teach 2016;38:537–549. 7. yang m, lo acy, lam wc. smart phone apps every ophthalmologist should know about. int j ophthalmol 2020;13:1329–1333. correspondence to: masomeh kalantarion, ms. department of medical education, virtual school of medical education and management, shahid beheshti university of medical sciences, tehran, 1966645643, iran. email: kalantarion65@gmail.com received: 23-04-2021 accepted: 08-05-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9762 this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: sadoughi mm, ahmady s, kalantarion m, khajeali n. transforming ophthalmology training via mobile learning during the covid-19 pandemic. j ophthalmic vis res 2021;16:698–699. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 699 https://knepublishing.com/index.php/jovr original article prn treatment of neovascular amd with cycles of three monthly injections touka banaee, md1; shadan alwan, bs1; clint kellogg, md1; ilyse kornblau, md1; jaafar el-annan, md1,2,3 1university of texas medical branch in galveston, texas, usa 2university of texas at md anderson, houston, texas, usa 3blanton eye institute, houston methodist hospital, houston, texas, usa orcid: touka banaee: http://orcid.org/0000-0003-0312-487x jaafar el-annan: http://orcid.org/0000-0002-9783-7290 abstract purpose: to report the one and two year outcome of cycles of three, monthly anti-vegf injections given upon reactivation of the disease in eyes with neovascular age-related macular degeneration (namd). methods: retrospective study of naïve namd cases with more than one year of followup, treated with a protocol of cycles of three monthly injections of anti-vegf drugs upon reactivation. visual acuity (va) and central macular thickness (cmt) are the main outcome measures. results: twenty-six patients with a mean age of 78.15 ± 9.29 years (57.7% female) were included. the mean follow-up was 30.89 ± 6.95 months. treatment started with bevacizumab in all patients but in six patients was switched to aflibercept due to inadequate response to intravitreal bevacizumab injection. the mean va at baseline and at 12 and 24 months was 53.87 ± 21.84, 60.54 ± 21.13, and 53.68 ± 27.16 etdrs letters, respectively. patients gained a mean of 6.67± 13.7 (p = 0.013, 95% ci= 0.60 to 12.65) and 0.77±15.21 (p = 0.4, 95% ci: –5.65 to 7.2) letters at 12 and 24 months. cmt at baseline, 12, and 24 months was 403.55 ± 147.59, 323.95 ± 79.58, and 298.59 ± 77.161 µm, respectively. the number of injections in the first and second years were 7.65 ± 2.64 and 5.52 ± 3.01, respectively. three eyes (12.5%) lost >15 letters at 24 months. conclusion: this protocol can stabilize or improve vision in 87.5% of namd patients and can reduce the number of visits. keywords: age-related macular degeneration; anti-vegf; naïve; neovascular; real world j ophthalmic vis res 2021; 16 (2): 178–186 introduction intravitreal injection of anti-vegf drugs is currently the standard treatment of the neovascular form correspondence to: jaafar el-annan, md. university of texas medical branch at galveston, 300 university blvd., galveston, texas 77555, usa. e-mail: jaelanna@utmb.edu received: 19-03-2020 accepted: 16-01-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9081 of age-related macular degeneration (namd). the randomized clinical trials that proved efficacy of different anti-vegf drugs administered monthly or bimonthly intravitreal injections of these medications.[1–3] however, fixed monthly injections protocol seems to be a great burden in this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: banaee t, alwan s, kellogg c, kornblau i, elannan j. prn treatment of neovascular amd with cycles of three monthly injections. j ophthalmic vis res 2021;16:178–186. 178 © 2021 banaee et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9081&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr prn treatment of neovascular amd with cycles of three injections; banaee et al a real-world setting. less than monthly protocols have been examined; quarterly injections of ranibizumab did not meet the non-inferiority criteria compared to the monthly injections in pier and excite studies.[4, 5] pro-re-nata (prn) dosing based on pre-specified criteria of activity showed more promising results.[6, 7] treat and extend (t&e) was another protocol first suggested by spaide to lessen the burden of injections and visits.[8] prn and t&e are among the most popular ones.[9] in major randomized clinical trials of anti-vegf agents in namd, a loading dose of three monthly injections has usually been applied followed by fixed interval dosing protocol of injections.[1–3] as a loading dose seems to be an accepted logic for the initial suppression of choroidal neovascular membrane (cnv) activity, it may also be more effective than just one injection in reactivations of cnv. based on this logic, instead of giving just one injection, we gave a cycle of three successive monthly injections of anti-vegf drugs with every reactivation of the disease (prn protocol). this report is the visual and anatomic results at 12 and 24 months of using this protocol in the treatment of naïve namd eyes. methods this is a retrospective study of naïve eyes with namd treated with injection of anti-vegf drugs in cycles of three injections upon reactivation of the disease. data of patients who presented to one of the three retina clinics of university of texas medical branch at galveston (utmb) from october 2014 to december 2016 and treated by a single surgeon (je) were retrieved from the emr of the utmb. the study was approved by the irb and followed the tenets of the declaration of helsinki. patients who were followed for more than one year were included in this study. one eye per patient was included and in case of bilateral amd the first involved eye was studied. there was no threshold for the level of vision for inclusion in the study. patients had complete ophthalmic examination including determination of best-corrected visual acuity (bcva) with the snellen chart, tonometry, slit lamp examination, and dilated fundoscopy at presentation and at each followup visit. fluorescein angiography (fa) (hra2, heidelberg engineering, germany) was performed at presentation for all patients. repeat fa was at the discretion of the treating physician. optical coherence tomography (oct) (spectralis, heidelberg engineering, germany) was performed at the initial and each follow-up visit. visual acuity (va) was measured with snellen chart, and converted to etdrs letters based on the protocol previously described[10] with the formula: approximate etdrs letters = 85 + 50x log (snellen fraction). logmar va was calculated and used for comparison of the baseline and 12 and 24 months data. va of counting fingers was considered equal to 1/200 or three letters of etdrs chart.[11] anti-vegf drugs used were aflibercept (eylea; regeneron, inc., eastview, ny), bevacizumab (avastin; genentech, inc., south san francisco, ca), and ranibizumab (lucentis; genentech, inc., south san francisco, ca). all patients were started with bevacizumab and in case of inadequate response were switched to one of the other two medications. the criteria for switching were: <100 μm reduction in central macular thickness (cmt), worsening, or no significant changes in the amount of subretinal/intraretinal fluid after three monthly injections of bevacizumab, or persistence of subretinal/intraretinal fluid after six monthly injections of bevacizumab. injection sessions were separate from visit sessions due to the process needed for provision of the medicine. protocol at the commencement of treatment and upon discovery of disease activity at any visit, patients were treated with three monthly doses of antivegf drugs. follow-up examinations after each series of injections were scheduled monthly for the first two months; extended to bimonthly and after two bimonthly visits to every three months and continued as such if there was no activity of the disease. patients were also instructed to check their central vision at home and return promptly in case of any new metamorphopsia, scotoma, or change in vision. disease activity was judged based on the presence or absence of intraretinal or subretinal fluid in oct scans, or the presence of intraretinal or subretinal blood on fundoscopy. statistical analysis descriptive statistics are provided as mean ±sd, median (25–75 quartiles) or percentage. va and journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 179 prn treatment of neovascular amd with cycles of three injections; banaee et al central foveal thickness data were analyzed with the shapiro–wilk test and their distribution was found not to be normal, so a comparison of vision or central foveal thickness results were made by wilcoxon signed rank test. p-value < 0.05 was considered significant. statistical analysis was performed by statistical package for social studies (spss) version 25 (ibm inc., armonk, ny). results twenty six patients with a mean age of 78.15 ± 9.29 years (57.7% female) were included. the mean follow-up was 30.89 ± 6.95 months. all patients were started with bevacizumab injections (off label use), six were subsequently switched after a mean of nine injections to aflibercept. second time switching to ranibizumab was performed in one patient. twenty three (88.46%) patients completed two years of follow-up. one patient did not have complete follow-up of two years. one patient was lost to follow-up in the second year. patients missed their appointments (either injection or non-injection visits) for more than one month in two cases during the first year (1.5 and 2 months of delay) and in four cases during the second year (2 ± 1 months). va at baseline was from 3 to 80 etdrs letters with a mean of 53.87 ± 21.84 letters (0.65 ± 0.51 logmar). six (23.08%) patients had a vision of >20/40 (70 etdrs letters) and eight (30.77%) ≤20/200 (35 etdrs letters) at presentation. the range of va at 12 months was 3 to 85 with a mean of 60.54 ± 21.13 etdrs letters (0.51 ± 0.51 logmar) significantly different from the baseline vision (p = 0.013). twelve eyes (46.15%) had a vision of >20/40 and four (15.38%) ≤20/200 at 12 months. the range of va at 24 months was 0 to 85 with a mean of 53.68 ± 27.16 etdrs letters (0.68 ± 0.67 logmar), which was not different from baseline (p = 0.4). eleven (45.83%) patients had a vision of >20/40 and six (25%) ≤20/200 at 24 months. patients gained a mean of 6.67± 13.7 (95% ci = 0.60 to 12.65) letters at 12 months, which equals to a mean logmar change of –0.14 ± 0.36. at 24 months, patients gained a mean of 0.77 ±15.21 (95% ci: –5.65 to 7.2) letters compared to baseline which equals to a mean change in logmar of –0.01 ± 0.38. the number of patients with gain and loss of vision are provided in table 1. changes in logmar va and cmt are presented in figure 1. of the six patients with baseline va of 20/40 or more (70 etdrs letters), all had a vision of 20/40 or more at 12 months. only one eye had a vision of <20/40 at 24 months. there were a total of 10 eyes (38.46%) at 12 months and 9 eyes (37.5%) at 24 months with a vision of 20/40 or more. of the eight patients with baseline va of 20/200 or less (35 etdrs letters), four in the first year and five in the second retained the vision of <20/200. there were a total of four (15.38%) eyes at 12 months and six (25%) eyes at 24 months with a vision of 20/200 or less. of the six cases with a vision of 20/200 or less at 24 months, only one case had a better vision at baseline. the mean cmt at baseline, 12, and 24 months was 403.55 ± 147.59, 323.95 ± 79.58, and 298.59 ± 77.161 µm, respectively [figure 1]. there was a reduction of cmt relative to baseline of – 88.24 ± 148.41 µm in the first year (p = 0.013, 95% ci = –164.81 to –14.77) and –103.16 ± 108.61 (p < 0.001, 95% ci = –155.50 to –50.81) µm in the second year. oct was fluid free at 12and 24-months encounters in 52% and 72.7% of eyes, respectively. seven and eight eyes had intraretinal and subretinal fluid at the 12 months’ visit, respectively. these numbers were 6 and 1 for the 24 months’ and 6 and 3 for the last visits, respectively. patients received a mean of 7.65 ± 2.64 injections in the first year and 5.52 ± 3.01 injections in second. the mean total number of injections over 24 months was 15 ± 6.9 given in a mean of 4.85 ± 2.18 cycles. the total number of non-injection visits was 4.92 ± 1.55 during the first year and 5.04 ± 1.46 during the second. seven patients (27%) achieved long-term periods of inactivity of >12 months (mean, 16.93, range, 14.5–22 months) which started in year 1 and extended into year 2. the longest injection-free period for the remaining patients was 2.95 ± 2.8 (0 to 8.00) months in the first year and 3.65 ± 2.35 (0-8.00) months in the second. all patients were first treated with bevacizumab and six of them were switched to aflibercept after a mean of nine injections; one was further switched to ranibizumab, so we can consider them to be practically treated with bevacizumab during the first year. of the total of seven switching episodes in six eyes, vision improved in three eyes (13.25 ± 7.68 letters), remained stable in three, and worsened in one after one cycle of treatment with the new medication, and fluid in oct improved in 180 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 prn treatment of neovascular amd with cycles of three injections; banaee et al figure 1. changes in logmar visual acuity and central macular thickness at baseline and 12 and 24 months. five cases, and remained stable in two after one cycle of treatment. injections were discontinued in three eyes in the second year due to the development of central geographic atrophy or futility of treatment. discussion intravitreal injections of anti-vegf drugs in cycles of three injections on a prn basis in naïve neovascular amd cases resulted in a visual gain of 6.67 letters at 12 months and a gain of 0.77 letters at 24 months. the visual results at one year are better than most real-world studies and the 24 months’ results are comparable.[12–14] although clinical trials that proved efficacy of intravitreal injection of anti-vegf drugs reported vision gains of 6.5–11.3 letters in the first and second years,[1–3] real-world studies have not corroborated those results.[12–14] in routine clinical practice as opposed to clinical trials, injections are usually given based on a variable dosing schedule rather than monthly,[9] treatment is offered to all presenting with the disease and patients are not selected to fulfill certain va, lesion size, or composition criteria. another important difference is complying with the follow-up visits which are not as accurately followed by the patients and physicians as in a predesigned clinical trial. many studies have explored the cause for inferior results in the real-world setting. while some have found no or weak correlations between the number of injections and visual results,[7, 14] others believe that there is a correlation between the number of injections and visual gain, especially when the number of injections falls <5–6 per year, the visual results get worse.[13, 15–18] use of variable dosing regimens instead of monthly injections is another area of debate. although major clinical trials such as catt and ivan have provided proof to the similarity of results between monthly and prn dosing in the first year, visual results differ in favor of monthly treatment after two years (–2.4 letters difference, 95% ci, –4.8 to –0.1; p = 0.046, catt trial).[19–21] contribution of all the aforementioned factors results in real-world treatment to be mostly preventive of further visual deterioration instead of increasing vision as expected by results journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 181 prn treatment of neovascular amd with cycles of three injections; banaee et al table 1. the number of patients with gain or loss of vision at 12 and 24 months 12 months 24 months gain of >15 letters 12 (46.15%) 8 (33.33%) gain of >5 letters 13 (50%) 11 (45.83%) <5 letters change 9 (34.61%) 7 (29.16%) loss of >5 letters 4 (15.38%) 6 (25%) loss of >15 letters 1 (4%) 3 (12.5%) of clinical trials.[12–14] physicians have devised newer strategies to improve the results in routine clinical practice, such as the “observe and plan” protocol.[22, 23] reports of observe and plan protocol seem very promising, however, results are still not available in a real-world setting, besides the protocol seems too complicated to be followed thoroughly in a routine clinical practice. in nearly all major rcts of anti-vegf agents and also in clinical practice, treatment is started with a loading dose of three monthly injections,[3, 6, 24] which has been shown to result in better visual outcomes compared to prn dosing from the outset.[25] we speculate that for an active cnv, there is a need for continuous suppression of vegf for at least three months until the cnv becomes quiescent and we generalized this concept to every reactivation, so we treated every reactivation of the disease with another three monthly series of injections with the hope that adoption of this strategy within an as-needed protocol may improve the results by replacing some of the noninjection visits with injection visits. this is similar to the protocol used in the ivan study.[20, 21] the difference between our and ivan’s protocols is in the follow-up visits, which were kept monthly in the ivan study but were extended upon inactivity in two successive visits in the current study, that is, incorporation of a t&e philosophy within the prn protocol. another major difference of the current study with ivan is that ivan was a prospective randomized controlled clinical trial, whereas this study is a retrospective realworld description of the results of the protocol. in spite of being a real-world study, the results of this study compare to those of ivan [table 2]. prn treatment of amd with anti-vegf drugs was first examined in the pronto study, which was not a controlled study, and reported visual results comparable to the results of marina and anchor trials. in this prospective study, patients with namd were treated based on visual, angiographic, and oct objective criteria of reactivation. the study followed a strict monthly follow-up of patients and treatment was started with three monthly injections followed by an as-needed treatment. there was a +9.3 (11 median) letter improvement in the first year and 11.1 ± 12.2 letter improvement in the second. the authors of pronto study conclude that their results are similar to the pivotal phase iii trials with lower number of injections.[6, 7] prn treatment was compared with monthly regimens in some prominent rcts. for example, in catt study, monthly and prn treatment of ranibizumab had a comparable visual results at 12 months. analysis was inconclusive for bevacizumab monthly versus as needed in that trial. worse visual results were reported at 24 months for eyes receiving prn treatment of either ranibizumab or bevacizumab (–2.4 letters difference, 95% ci, –4.8 to –0.1; p = 0.046).[19, 26] ivan study similarly showed that the difference in visual gain at 12 and 24 months was neither non-inferior nor inferior in prn treatment when compared to monthly treatment.[20, 21] the results of t&e protocol are even more promising.[27, 28] in a long-term study of the t&e protocol, berg et al[29] reported a visual gain of 6.1 letters in the first year and >7.4 letters up to four years after the initiation of the treatment in a real-world setting. in a meta-analysis of realworld studies, t&e protocol had a better visual results than prn treatment with +8.5 versus +3.5 letters improvement in the first year and +6.7 versus +1.3 letters in the second, respectively.[30] systematic reviews have also shown better results with t&e protocol compared to prn dosing.[27, 28] comparison of the prn and t&e protocols in realworld studies have provided similar results.[31–33] 182 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 prn treatment of neovascular amd with cycles of three injections; banaee et al ta b le 2 .a na to m ic an d vi su al re su lts of se le ct ed re al -w or ld st ud ie s an d cl in ic al tr ia ls at 12 an d 24 m on th s* s tu d y n o o f p a ti e n ts m e d ic a ti o n u se d b a se lin e 12 m o n th s 2 4 m o n th s n o te s v is io n et d r s (l o g m a r ) c m t c ha ng e in vi si on :e td r s (l o g m a r ) > 3 lin e ga in in vi si on (% ) > 3 lin e lo ss in vi si on (% ) c ha ng e in c m t m ea n nu m be r of in je ct io ns c ha ng e in vi si on :e td r s (l o g m a r )* > 3 lin e im pr ov em en t in vi si on (% )† > 3 lin e w or se ni ng in vi si on (% )† c ha ng e in c m t* m ea n nu m be r of in je ct io ns in tw o ye ar s c ur re nt 26 b ev /a fl/ r an 53 .8 7 ± 21 .8 4 (0 .6 5 ±± ± 0 .5 1) 40 3. 55 ± 14 7. 59 6. 67 ± 13 .7 ( 0 .1 4 ±± ± 0 .3 6 ) (p = 0. 0 13 ) 46 .15 4 –8 8. 24 ± 14 8. 41 p = 0. 0 13 7. 65 ± 2 .6 4 0. 77 ± 15 .2 1 (0 .0 1 ±± ± 0 .3 8 ) (p = 0. 4) 33 .3 3 12 .5 – 10 3. 16 ± 10 8. 61 ,p < 0. 0 0 1 15 ± 6. 9 re tro sp ec tiv e st ud y r ao p et al [14 ] 67 23 b ev (0 .6 1 ±± ± 0 .5 7 ) n a (– 0 .0 4 8 ±± ± 0 .4 4 ) 22 .7 14 .3 n a 5 .9 ± 2 .4 n a n a n a n a n a a re al -w or ld re tro sp ec tiv e st ud y of an tiv eg f m on ot he ra py fro m th e a a o ir is re gi st ry c iu lla et al [13 ] 19 21 b ev (7 0 % ), a fl (13 % ), r an (17 % ) 47 .5 – +3 .1 (p < 0. 0 1) 12 .1 a re al -w or ld re tro sp ec tiv e st ud y of an tiv eg f m on ot he ra py fro m th e v es tr um h ea lth re tin a d at ab as e 19 5 b ev (7 1% ), a fl (12 % ), r an (17 % ) 43 .1 – –0 .7 (p = 0. 34 ) 7. 3 lo te ry a et al [12 ] 33 50 (r an ) 43 0 0 (a fl) 57 .5 ± 21 .2 (r an )5 8. 5 ± 20 .7 (a fl) − 0. 30 ± 14 .8 /(r an )− 0. 19 ± 14 .7 (a fl) 10 .8 (r an )1 1 (a fl) 10 .6 (r an )1 0. 4 (a fl) 6. 70 ± 2 .5 4 (r an )7 .0 0 ± 2 .4 0 (a fl) re al -w or ld st ud y –u s iv a n st ud y[ 20 ,2 1] 25 8 d is co nt in uo us gr ou p: b ev , r an 62 .9 ± 15 4. 99 ± 11 .1 m ed ia n: 7 iq r : 6, 9 3· 5 ± 13 ·1 13 (8 to 17 ) m ed ia n (iq r) c at t[ 19 ,2 6] 51 5 a sne ed ed gr ou ps of b ev , r an 60 .4 ± 13 .4 (b ev )6 1.5 ± 13 .2 (r an ) 46 1± 17 5 (b ev ) 45 8 ± 19 3 (r an ) +5 .9 ± 1.0 (b ev )+ 6. 8 ± 0. 8 (r an ) 28 (b ev )2 5 (r an ) 8 (b ev )5 (r an ) − 15 2 ± 11 (b ev ) − 16 8 ± 11 (r an ) 7. 7 ± 3. 5 (b ev ) 6. 9 ± 3. 0 (r an ) 5· 87 ± 16 ·3 28 .3 (b ev )3 0. 7 (r an ) 11 .6 (b ev )7 .2 (r an ) – 15 3 ± 18 9 (b ev )– 16 6 ± 19 0 (r an ) 14 .1 ± 7. 0 (b ev ) 12 .6 ± 6. 6 (r an ) pr o n to [6 ,7 ] 40 pr n ,r an 56 .2 m ed ia n: 57 39 3. 9 m ed ia n: 38 4. 5 +9 .3 m ed ia n: +1 1.0 35 5 – 17 7. 8 m ed ia n: -1 85 .5 5 .6 ± 2 .3 11 .1 ± 12 .2 43 2 .5 –2 12 9. 9 ± 5 .3 n o co rr el at io ns be tw ee n ba se lin e vi si on or le si on si ze an d th e nu m be ro f in je ct io ns .n o co rr el at io ns be tw ee n vi su al ou tc om es an d th e nu m be ro f in je ct io ns o bs er ve an d pl an [2 2] 10 2 (11 2 ey es ) a fl 61 .8 ± 15 .4 43 8 ± 14 8 8. 0 ± 12 .0 26 % 1% – 15 4 8. 7 ± 3. 0 6. 2 ± 14 .6 20 % 8% – 15 0 15 .3 ± 5 .2 pr os pe ct iv e o bs er ve an d pl an [3 6] 10 4 (11 5 ey es ) r an 58 .3 ± 18 34 2 ± 85 9. 7 30 3 –9 9 7. 8 ± 3. 1 9. 2 33 4 –9 6 13 .6 ± 0. 1 pr os pe ct iv e *a ll nu m be rs ar e in th e fo rm of m ea n ± sd un le ss st at ed ot he rw is e; † c ha ng es co m pa re d to ba se lin e. a a o ,a m er ic an a ca de m y of o ph th al m ol og y; a fl, afl ib er ce pt ;b ev ,b ev ac iz um ab ;c at t, co m pa ris on of a m d tr ea tm en tt ria l; c m t, ce nt ra lm ac ul ar th ic kn es s; iq r ,i nt er qu ar til e ra ng e; ir is re gi st ry ,i nt el lig en tr es ea rc h in si gh tr eg is tr y; iv a n ,i nh ib it v eg f in ag ere la te d ch or oi da l ne ov as cu la riz at io n tr ia l; pr o n to ,p ro sp ec tiv e o c t im ag in g of pa tie nt s w ith ne ov as cu la ra m d tr ea te d w ith in tr ao cu la rr an ib iz um ab ;r an ,r an ib iz um ab journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 183 prn treatment of neovascular amd with cycles of three injections; banaee et al in the routine clinical practice, physicians mostly use the prn or t&e protocols for the treatment of namd,[9] so the real-world studies reported based on electronic databases usually include patients treated by these two protocols in practice. in spite of the promising results of clinical trials, and aforementioned studies, visual results of real-world studies are not very impressive. rao et al[14] in a real-world study of intravitreal injection of antivegf drugs for the treatment of amd in the us, based on data from the intelligent research in sight (iris) registry, compared the one-year outcomes of the injections of bevacizumab, ranibizumab, and aflibercept. patients gained –0.04 to –0.053 logmar in the first 12 months with a mean of 5.9–6.4 injections of bevacizumab, ranibizumab, or aflibercept. similarly, ciulla et al[13] reporting results from vestrum health retina database from the us stated that there was no change of vision (– 0.7 etdrs letters, p = 0.43) at 12 months with 7.3 injections of the three drugs. lotery et al[12] found a change of −0.30 ± 14.8 and −0.19 ± 14.7 letters with 6.7–7 injections of ranibizumab and aflibercept, respectively, at 12 months in cases retrieved form a standard emr in the us. although different studies cannot be directly compared with each other, with a mean gain of 6.67 ± 13.7 etdrs letters at 12 months and 0.77 ± 15.21 at 24 months, results of the current study seem to be better than the results of most real-world studies in the us and compares to the results of the ivan trial, which was a prospective study [table 2]. having similar results at 12 and 24 months to a prospective study is promising. as irregular follow-ups can be a cause of poor visual outcomes in the real-world studies, having few missed appointments in this study may discuss the similarity of results with a prospective study. however, in the current study, the follow-ups were extended to three months, mostly in the second year, while in the ivan study, monthly follow-ups were pursued through the second year. undertreatment has been stated as an important factor causing lower visual results in real-world settings.[13] the number of injections in the first and second years in the current study was 7.65 ± 2.64 and 5.52 ± 3.01, respectively, for a cumulative number of 15 ± 6.9 during the two years. this number compares with both the real-world studies and the prn groups of ivan, catt, and pronto studies [table 2]. the number of non-injection visits in the first and second years was 4.92 ± 1.55 and 5.04 ± 1.46, respectively. the current study was performed where bevacizumab would usually be injected in a separate visit because of logistics in preparation of the medication. if same-day injection was possible, the number of non-injection visits would certainly be lower than the current results. we also believe that with the aforementioned situation, this protocol of prn cycles of injections has saved patients many unnecessary visits. also, the prn nature of decision-making has spared patients from many injections. indeed, 27% of patients in this study achieved inactivity of the disease for 14–22 months without injections. in the current study, oct was fluid-free in 52% and 72.7% at 12 and 24 months, respectively. the corresponding rates in the ivan study were 31 and 37% in the discontinuous treatment group.[20, 21] in catt study, 19 and 13.9% of eyes in the prn bevacizumab group and 23.9 and 22.3% of eyes in the prn ranibizumab group were without any fluid in oct at 12 and 24 months, respectively.[19, 26] the monthly treatment groups of both ivan and catt had higher rates of absence of fluid in oct at 12 and 24 months: 44 and 54% for the continuous treatment group – ivan study; 26 and 30.2% in the bevacizumab monthly – catt study; and 43.7 and 45.5% for ranibizumab monthly – catt study. in a study by hatz et al,[32] which was a prospective study comparing the t&e and prn protocols, the rate of absence of any fluid in oct at 12 months was 67% in the t&e and 47% in the prn group. the results of our study seem to be comparable to the results of this study, sitting somewhere between the prn and t&e groups. there is a worse visual outcome in the second year in spite of less activity of the disease in oct [figure 1]. as we did not restrict inclusion of patients based on va levels, lesion size, or components, it is possible that the development of atrophy or scar in eyes with more advanced lesions during the second year of the study have skewed the results toward lower vision range. this study is a retrospective study and limitations of retrospective studies apply to it. one of the major limitations is that va is not measured by the etdrs chart and is reported as approximate etdrs letters which is a calculated number. some real-world studies have provided that patients who are lost to follow-up have worse vision at their 184 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 prn treatment of neovascular amd with cycles of three injections; banaee et al last visit compared to those who are followedup.[13, 17, 34, 35] thus, by not including patients lost to follow-up before one year, we may have introduced a selection bias toward patients with better visual results. the small number of patients is another limitation of the current study. as previously stated, because of the unavailability of same-day injections, the number of non-injection visits may have been overestimated. in conclusion, the visual results of the current study in the first year are very promising. the protocol is easy to implement and the compliance rate is very high. in the second year of the study, there is a decrease in the gained letters of va in spite of a higher rate of inactivity of the lesions in oct. continuing monthly follow-ups may reduce the vision loss in the second year. references 1. rosenfeld pj, brown dm, heier js, boyer ds, kaiser pk, chung cy, et al. ranibizumab for neovascular age-related macular degeneration. n engl j med 2006;355:1419–1431. 2. brown dm, kaiser pk, michels m, soubrane g, heier js, kim ry, et al. ranibizumab versus verteporfin for neovascular age-related macular degeneration. n engl j med 2006;355:1432–1444. 3. heier js, brown dm, chong v, korobelnik jf, kaiser pk, nguyen qd, et al. intravitreal aflibercept (vegf trap-eye) in wet age-related macular degeneration. ophthalmology 2012;119:2537–2548. 4. regillo cd, brown dm, abraham p, yue h, ianchulev t, schneider s, et al. randomized, double-masked, shamcontrolled trial of ranibizumab for neovascular age-related macular degeneration: pier study year 1. am j ophthalmol 2008;145:239–248. 5. schmidt-erfurth u, eldem b, guymer r, korobelnik jf, schlingemann r, axer-siegel r, et al. efficacy and safety of monthly versus quarterly ranibizumab treatment in neovascular age-related macular degeneration: the excite study. ophthalmology 2011;118:831–839. 6. fung ae, lalwani ga, rosenfeld pj, dubovy sr, michels s, feuer wj, et al. an optical coherence tomographyguided, variable dosing regimen with intravitreal ranibizumab (lucentis) for neovascular age-related macular degeneration. am j ophthalmol 2007;143:566– 583. 7. lalwani ga, rosenfeld pj, fung ae, dubovy sr, michels s, feuer w, et al. a variable-dosing regimen with intravitreal ranibizumab for neovascular age-related macular degeneration: year 2 of the pronto study. am j ophthalmol 2009;148:43–58.e1. 8. spaide r. ranibizumab according to need: a treatment for age-related macular degeneration. am j ophthalmol 2007;143:679–680. 9. rezaei ka, stone tw. 2015 global trends in retina survey. chicago, il.: american society of retinal specialists; 2015. 10. gregori nz, feuer w, rosenfeld pj. novel method for analyzing snellen visual acuity measurements. retina 2010;30:1046–1050. 11. mehta h, tufail a, daien v, lee ay, nguyen v, ozturk m, et al. real-world outcomes in patients with neovascular age-related macular degeneration treated with intravitreal vascular endothelial growth factor inhibitors. prog retin eye res 2018;65:127–146. 12. lotery a, griner r, ferreira a, milnes f, dugel p. realworld visual acuity outcomes between ranibizumab and aflibercept in treatment of neovascular amd in a large us data set. eye 2017;31:1697–1706. 13. ciulla ta, huang f, westby k, williams df, zaveri s, patel sc. real-world outcomes of anti–vascular endothelial growth factor therapy in neovascular age-related macular degeneration in the united states. ophthalmology retina 2018;2:645–653. 14. rao p, lum f, wood k, salman c, burugapalli b, hall b, et al. real-world vision in age-related macular degeneration patients treated with single anti-vegf drug type for 1 year in the iris registry. ophthalmology 2018;125:522–58. 15. cohen sy, mimoun g, oubraham h, zourdani a, malbrel c, queré s, et al. changes in visual acuity in patients with wet age-related macular degeneration treated with intravitreal ranibizumab in daily clinical practice: the lumiere study. retina 2013;33:474–481. 16. holz fg, tadayoni r, beatty s, berger a, cereda mg, cortez r, et al. multi-country real-life experience of anti-vascular endothelial growth factor therapy for wet age-related macular degeneration. br j ophthalmol 2015;99:220–226. 17. gillies mc, campain a, barthelmes d, simpson jm, arnold jj, guymer rh, et al. long-term outcomes of treatment of neovascular age-related macular degeneration: data from an observational study. ophthalmology 2015;122:1837– 1845. 18. souied eh, oubraham h, mimoun g, cohen sy, quere s, derveloy a, et al. changes in visual acuity in patients with wet age-related macular degeneration treated with intravitreal ranibizumab in daily clinical practice: the twin study. retina 2015;35:1743–1749. 19. martin df, maguire mg, ying gs, grunwald je, fine sl, jaffe gj. ranibizumab and bevacizumab for neovascular age-related macular degeneration. n engl j med 2011;364:1897–1908. 20. chakravarthy u, harding sp, rogers ca, downes sm, lotery aj, wordsworth s, et al. ranibizumab versus bevacizumab to treat neovascular age-related macular degeneration: one-year findings from the ivan randomized trial. ophthalmology 2012;119:1399–1411. 21. chakravarthy u, harding sp, rogers ca, downes sm, lotery aj, culliford la, et al. alternative treatments to inhibit vegf in age-related choroidal neovascularisation: 2-year findings of the ivan randomised controlled trial. lancet 2013;382:1258–1267. 22. parvin p, zola m, dirani a, ambresin a, mantel i. two-year outcome of an observe-and-plan regimen for neovascular age-related macular degeneration treated with aflibercept. graefes arch clin exp ophthalmol 2017;255:2127–2134. 23. mantel i, niderprim sa, gianniou c, deli a, ambresin a. reducing the clinical burden of ranibizumab treatment journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 185 prn treatment of neovascular amd with cycles of three injections; banaee et al for neovascular age-related macular degeneration using an individually planned regimen. br j ophthalmol 2014;98:1192–1196. 24. chakravarthy u, harding sp, rogers ca, downes s, lotery aj, dakin ha, et al. a randomised controlled trial to assess the clinical effectiveness and costeffectiveness of alternative treatments to inhibit vegf in age-related choroidal neovascularisation (ivan). health technol assess 2015;19:1–298. 25. gupta b, adewoyin t, patel sk, sivaprasad s. comparison of two intravitreal ranibizumab treatment schedules for neovascular age-related macular degeneration. br j ophthalmol 2011;95:386–390. 26. martin df, maguire mg, fine sl, ying gs, jaffe gj, grunwald je, et al. ranibizumab and bevacizumab for treatment of neovascular age-related macular degeneration: two-year results. ophthalmology 2012;119:1388–1398. 27. rufai sr, almuhtaseb h, paul rm, stuart bl, kendrick t, lee h, et al. a systematic review to assess the ’treat-and-extend’ dosing regimen for neovascular agerelated macular degeneration using ranibizumab. eye 2017;31:1337–1344. 28. chin-yee d, eck t, fowler s, hardi a, apte rs. a systematic review of as needed versus treat and extend ranibizumab or bevacizumab treatment regimens for neovascular age-related macular degeneration. br j ophthalmol 2016;100:914–917. 29. berg k, roald ab, navaratnam j, bragadóttir r. an 8year follow-up of anti-vascular endothelial growth factor treatment with a treat-and-extend modality for neovascular age-related macular degeneration. acta ophthalmol 2017;95:796–802. 30. kim ln, mehta h, barthelmes d, nguyen v, gillies mc. metaanalysis of real-world outcomes of intravitreal ranibizumab for the treatment of neovascular age-related macular degeneration. retina 2016;36:1418–1431. 31. johnston rl, carius hj, skelly a, ferreira a, milnes f, mitchell p. a retrospective study of ranibizumab treatment regimens for neovascular age-related macular degeneration (namd) in australia and the united kingdom. adv ther 2017;34:703–712. 32. hatz k, prünte c. treat and extend versus pro re nata regimens of ranibizumab in neovascular age-related macular degeneration: a comparative 12 month study. acta ophthalmol 2017;95:e67–e72. 33. lee ay, lee cs, egan ca, bailey c, johnston rl, natha s, et al. uk amd/dr emr report ix: comparative effectiveness of predominantly as needed (prn) ranibizumab versus continuous aflibercept in uk clinical practice. br j ophthalmol 2017;101:1683–1688. 34. krüger falk m, kemp h, sørensen tl. four-year treatment results of neovascular age-related macular degeneration with ranibizumab and causes for discontinuation of treatment. am j ophthalmol 2013;155:89–95.e3. 35. rasmussen a, bloch sb, fuchs j, hansen lh, larsen m, lacour m, et al. a 4-year longitudinal study of 555 patients treated with ranibizumab for neovascular age-related macular degeneration. ophthalmology 2013;120:2630– 2636. 36. gianniou c, dirani a, ferrini w, marchionno l, decugis d, deli a, et al. two-year outcome of an observeand-plan regimen for neovascular age-related macular degeneration: how to alleviate the clinical burden with maintained functional results. eye 2015;29:342–349. 186 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 original article acquired vitelliform macular degeneration: characteristics and challenges of managing subretinal fluid joseph juliano, md; sagar patel, md; hossein ameri, md, phd, frcsi, mrcophth usc roski eye institute, keck medicine of university of southern california, los angeles, ca, usa orcid: joseph juliano: http://orcid.org/0000-0003-2527-0667 hossein ameri: http://orcid.org/0000-0002-5270-2800 abstract purpose: to highlight diagnostic challenges in patients with acquired vitelliform macular degeneration (avmd) with subretinal fluid (srf) and to examine the characteristics of image findings in patients with avmd. methods: in this retrospective review, the electronic medical record of 22 eyes of 16 patients with avmd was studied. the rates of srf, drusen, pigment epithelial detachment (ped), and patient clinical information such as age, length of follow-up, and best-corrected visual acuity (bcva) were assessed. results: the mean age at diagnosis with avmd was 72 years with a mean follow-up time of 29 months. median bcva 20/33 at presentation and 20/33 at final follow-up. drusen was found in 13 of 22 eyes (59.1%), peds in 4 of 22 eyes (18.2%), and srf in 10 of 22 eyes (45.5%) at some point during their follow-up. of the 10 eyes with srf, 70% were center involving, and recurrence occurred in 40%, all in the same location as the initial presentation of srf. three eyes received an anti-vascular endothelial growth factor injection for srf. in 66% of cases receiving an injection, the fluid later relapsed and remitted without further injections during the course of follow-up. conclusion: avmd occurs in the same demographic as age-related macular degeneration (amd) and has many common features. srf in avmd tends to be center involving and recurs usually in the same location as its origin. the use of anti-vegf injections did not seem to improve srf in contrast to the srf seen in wet amd. proper differentiation of avmd may prevent unnecessary long-term treatment with intravitreal anti-vegf injections. keywords: age-related macular degeneration; vitelliform macular degeneration; vitelliform maculopathy j ophthalmic vis res 2021; 16 (4): 582–591 introduction vitelliform lesions encompass a wide clinical spectrum of macular pathology. in addition correspondence to: hossein ameri, md, phd, frcsi, mrcophth. usc roski eye institute, 1450 san pablo st, los angeles, ca 90033, usa. e-mail: ameri@med.usc.edu received: 31-08-2021 accepted: 22-03-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9748 to juvenile best disease and adult onset foveomacular vitelliform dystrophy, which are associated with hereditary inheritance, there are acquired vitelliform lesions often present in the elderly. these degenerative lesions are not this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: juliano j, patel s, ameri h. acquired vitelliform macular degeneration: characteristics and challenges of managing subretinal fluid. j ophthalmic vis res 2021;16:582–591. 582 © 2021 juliano et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9748&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr acquired vitelliform macular degeneration; juliano et al well characterized, and sometimes have been grouped with adult onset foveomacular vitelliform dystrophy.[1–3] in this study, we focus on acquired vitelliform lesions and use the term acquired vitelliform macular degeneration (avmd) to focus on the spectrum of cases without a family history of the disease. pseudovitelliform and vitelliform are terms used interchangeably to describe lesions seen in avmd.[4] while not a classic vitelliform lesion like in best disease, in this study we will use the term vitelliform lesion to refer to the characteristic lesion appearance on fundus exam in avmd, which is a yellow, elevated lesion usually associated with pigmentary features.[5] lesions in avmd appear in the same demographic as dry age-related macular degeneration (amd)[6] and are often associated with drusen;[7] while in avmd the lipofuscin accumulation is within the subretinal space,[5] in amd it accumulates below the retinal pigment epithelium (rpe) and still these two entities can still be easily confused. furthermore, subretinal fluid (srf) can be present in avmd[8, 9] which, when in the context of drusen, might be concerning for conversion of dry to wet amd; or, interestingly some cases of dry amd can have srf without evidence of choroidal neovascularization (cnv).[10] thus, in these difficult circumstances, clinicians are presented with the question: has dry amd converted to wet amd, or is this srf in the context of a vitelliform lesion? in best disease, an abnormal electrooculogram (eog) has been used as a reliable diagnostic tool,[11] however, eog is typically normal in avmd.[12] practical considerations make it challenging to employ such diagnostic modalities in a busy clinic, and while imaging modalities have been employed to aid in the diagnosis such as the use of fluorescein angiogram (fa), fundus autofluorescence (faf), or optical coherence tomography angiography (octa), they cannot always definitively distinguish avmd from wet amd. information regarding the prevalence, natural course of avmd associated with srf and its management in the literature is limited. here, we review a set of cases of patients with avmd with particular focus on patients that develop concurrent srf in the context of avmd. in this study, we describe the characteristics of srf in avmd, the response of srf with intravitreal injections, and suggest a general diagnostic algorithm that can be used in the clinic in order to distinguish avmd with srf from wet amd. methods study population this study is an irb-approved retrospective study of patients diagnosed with avmd at a single institution over a period from 2015 to 2020. informed consent was not required for this study. this study was conducted in accordance with the declaration of helsinki. the collection and evaluation of all protected patient health information was performed in a health insurance portability and accountability act (hipaa)-compliant manner. the study was approved by the institutional review board of the university of southern california health sciences. clinical assessment patients were diagnosed with avmd after meeting characteristic clinical features by combination of optical coherence tomography (oct) and fundus exam findings. fundus exam features included the presence of focal yellowish macular lesions and rpe changes in absence of dense pigment clumps. characteristic oct changes included nonhomogenous hyper reflectivity at the level of rpe that could not be classified as pigment epithelial detachment (ped) or drusen. none of the patients had a family history of the disease. all clinic visit notes were reviewed for each patient and data were obtained on age, gender, eye laterality, previous medical and ocular history, date of diagnosis, visual acuity, and type of intravitreal injection. imaging features consisted of collecting information from clinical fundoscopic exam, fundus photos, oct, octa, and faf and fa if present. visual acuity data were converted to logmar and all numerical data were reported as median or mean with standard deviation. results clinical characteristics the study included a total of 22 eyes of 16 patients with avmd. the median logmar bcva at presentation was 0.22 (20/33), and at the last final journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 583 acquired vitelliform macular degeneration; juliano et al follow-up 0.22 (20/33). five patients had diagnoses of avmd in both eyes, eight had avmd in the right eye, and four had avmd in the left eye. the mean age at diagnosis was 71.6 ± 10.1 years (mean ± sd, range: 45.8–90.4 years). there were seven female and nine male patients in the study. across all patients, the mean follow-up time was 28.5 ± 17.6 months (mean ± sd, range: 0–51.3 months). three patients had a history of diabetes mellitus type 2 (dm2), but only one eye had evidence of diabetic retinopathy and was diagnosed as mild non-proliferative diabetic retinopathy without macular edema. three patients had central serous chorioretinopathy (cscr) on the differential, and 17 eyes had a prior history of dry amd of which 1 eye had a history of wet amd in the non-avmd eye. nine (9/14, 64%) patients were symptomatic with either blurry vision or metamorphopsia at diagnosis. three patients received an injection prior to diagnostic confirmation of avmd. among these individuals, the mean follow-up time was 44.5 ± 4.3 months. the bvca of these patients at presentation was 0.13 ± 0.23 logmar (20/26) and at the final follow-up 0.19 ± 0.25 logmar (20/30). at one month prior to injection, the bcva was 0.19 ± 0.2 logmar (20/30) and by one month post-injection the bcva was 0.22 ± 0.16 logmar (20/33). imaging characteristics of the 22 eyes, 10 (45%) had a diagnosis of avmd with concurrent srf. one eye had srf without a diagnosis of avmd but had a diagnosis of wet amd in that eye (see patient 7 clinical course). there were four eyes with peds at diagnoses. no eyes with avmd had the presence of irf with srf. drusen was found in 13 eyes (59.1%) clinically, and in 15 eyes (68.2%) on oct. drusen was found bilaterally in nine patients on oct. in 10 eyes with srf, all but one eye had drusen, and three of these eyes were considered to be possibly consistent with cscr but the diagnosis was not supported by fa. among the patients with srf, the total followup time was 35.2 ± 13.3 months. the average va at presentation was 0.16 ± 0.13 logmar (20/28) and 0.19 ± 0.15 logmar (20/30) at final follow-up. in six eyes (6/10, 60%), the srf was present on the first visit. srf was bilateral in one patient. the average time to occurrence of the first srf was 3.6 ± 5.6 (0–16) months and the average time it took for the disappearance of the first occurrence of srf was 7.6 ± 5.6 months (0.9–14.2) months. in two eyes, the srf did not disappear. of these two eyes, in one eye the srf was approximately the same size during the course of their follow-up over the period of one year, and in the other eye, it decreased in size but never fully resolved. while 9 of the 10 eyes showed decrease in the srf over the course of their follow-up, 4 of these eyes had recurrence of the srf, and the recurrence occurred in the same location as the initial location of srf in all cases. also, in three of the four eyes with ped, the presence of srf was noted. the most common location for srf was sub-foveal at the vitelliform lesion in 70% of eyes. three eyes were given an intravitreal injection for the presence of srf. none had a history of diabetes. in one eye, the srf resolved after one month without further recurrence over the course of follow-up over three years. in one eye, the srf resolved within one month, but then later appeared in the same location a year later and resolved one month later without injection due to patient preference. in the third case, the srf exhibited no response to the injection and resolved on its own over the course of one year to later relapse and remit an additional year later without further injection. here we describe some avmd cases in further detail to highlight the diagnostic and therapeutic challenges associated with this condition. case 1: patient no. 7 a 76-year-old female presented to clinic for blurry vision in the left eye. she had a prior history of wet amd with disciform scar in the right eye. her vision on presentation was 20/300 in the right eye, and 20/50 in the left eye. she reported metamorphopsia and an abnormal amsler grid in the right eye. the anterior segment exam was notable for 2+ nuclear sclerosis in both eyes. funduscopic examination demonstrated a macular disciform scar, and a peripheral choroidal nevus in the right eye. the left eye was notable for drusen in the macula. on oct, the right eye demonstrated chronic changes from wet amd notable for subretinal hyperreflective material, srf, intraretinal fluid, and distorted foveal contour [figure 1a]. in the left eye, there was a small pocket of srf, with adjacent hyperreflective materials at the level of rpe, drusen, and erm [figure 584 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 acquired vitelliform macular degeneration; juliano et al 1b]. given the clinical picture and history of wet amd in the right eye, the patient was treated with an intravitreal injection of ranibizumab with a presumptive diagnosis of wet amd in the left eye. one week later, bcva was unchanged at 20/60 and oct showed little to no change suggesting the diagnosis of avmd consistent with oct findings [figure 1c]. soon after, she received cataract extraction with intraocular lens implantation and her vision improved to 20/30. over the course of follow-up, the vitelliform lesion stayed largely stable with relapsing and remitting srf without further injection. four years later, during one follow-up visit there was new srf in the left eye which was more srf than seen at presentation [figure 1d]. fa was performed which showed stippled staining and leakage [figure 1e]. given a suspicion of wet amd, the patient was offered a repeat trial of anti-vegf injection, but she elected to be observed. by the next follow-up in one month, the srf had resolved on its own [figure 1f]. at the time of last follow-up, five years after presentation, the patient continued to have no evidence of srf on oct and the hyperreflective materials and foveal drusen resolved in the left eye [figure 1g]. her visual acuity at final follow-up was 20/500 in the right eye and 20/30 in the left eye. throughout the course of her follow-up, despite the relapsing and remitting srf in the left eye, she was asymptomatic and without abnormalities in her amsler grid at each follow-up in the left eye. case 2: patient no. 12 a 67-year-old female presented for establishing care. she had a history of dry amd in the right eye and a presumed recent diagnosis of wet amd in the left eye for which she had received a total of three monthly bevacizumab injections. her last injection was three months prior to presentation [figure 2a]. at presentation, the patient had a va of 20/30 and 20/25 with normal intraocular pressure. she was asymptomatic in the left eye with a normal amsler grid. an evaluation of past medical records and prior oct and octa images did not show features of cnv, therefore the prior diagnosis of wet amd was put in question. the patient was followed with serial octs without change until eight months later when the oct showed appearance of small pocket of srf with an adjacent shallow ped in the left eye [figure 2b]. the oct changes did not support presence of wet amd; however, given her presumed history of wet amd, the patient was offered a trial injection of anti-vegf or observation. the patient opted to observe and the srf resolved spontaneously a month later [figure 2c]. two years after presentation, the patient had a recurrence of srf and appearance of hyperreflective materials [figure 2d]. after this recurrence of srf, the srf was somewhat persistent but was significantly reduced in size as the hyperreflective material began to coalesce and condense at last follow-up three years after presentation [figure 2e]. at the time of last followup, the vision was 20/25 in both eyes. throughout the course of her follow-up, she denied complaints of metamorphopsia and had a normal amsler grid. case 3: patient no. 11 a 79-year-old female presented to retina clinic for evaluation of amd in both eyes. va at the time of diagnosis was 20/40 in the right eye and 20/50 in the left eye. she had symptomatic complaints of “mild fuzzy vision” in both eyes over the past year with some subjective complaints of wavy lines in both eyes. the amsler grid was abnormal focally at one spot temporally on each eye. iop and the anterior exam was unremarkable. her fundus exam showed dry amd in both eyes, a choroidal nevus in the left eye and a vitelliform lesion in the right eye just nasal to the fovea [figure 3a]. over the course of two-year follow-up, the patient developed significant progression of the vitelliform lesion in the right eye and trace srf within the lesion [figure 3b]. based on the characteristic appearance of avmd in this patient, she was observed without injection. at the day of last followup, three years after her first presentation, she had a stable small srf and a vitelliform lesion [figure 3c] that was observed without injection. her vision on final follow-up was 20/50 in the right eye and 20/40 in the left eye. over the course of her follow-up, she reported occasional metamorphopsia in the right eye with a consistently abnormal amsler grid; while in the left eye it appeared to be normal for the course of her followup after her first abnormal amsler grid on initial presentation. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 585 acquired vitelliform macular degeneration; juliano et al table 1. clinical and imaging characteristics at diagnosis and last visit patient number – eye involved age at dx/sex va at dx last va concurrent retinal pathology fut (mo) srf d srf l ped drusen fundus drusen oct 1 – od 1 – os 79/m 20/40 20/60 20/40 20/60 dry amd dry amd 46 – – – – + – + + + + 2 – od 45/f 20/20 20/20 – 3 – – – – – 3 – os 57/f 20/30 20/30 asteroid hyalosis 51 + – + – – 4 – od 4 – os 76/f 20/40 20/100 20/40 20/100 dry amd dry amd 0 – – – – – – + – – – 5 – od 66/m 20/30 20/30 – 0 – – – – – 6 – od 6 – os 68/f 20/25 20/30 20/25 20/30 dry amd dry amd 41 + – – – – – – + + + 7 – os 76/f 20/60 20/30 dry amd 47 + – – + + 8 – od 76/f 20/30 20/30 dry amd, erm 32 + – – – + 9 – od 63/f 20/20 20/20 dry amd 40 + – + + + 10 – od 67/m 20/40 20/70 dry amd 34 + – – + + 11 – od 11 – os 80/f 20/40 20/50 20/50 20/40 dry amd choroidal nevus os, dry amd 33 + – + – – – + + + + 12 – os 65/f 20/25 20/25 dry amd 47 – – + + + 13 – od 90/m 20/40 20/30 dry amd 20 – + – + + 14 – od 14 – os 62/m 20/20 20/20 20/20 20/20 htn retinopathy 38 – – – – – – – – – – 15 – od 83/f 20/25 20/25 dry amd, mild npdr, no dme 24 – – – – + 16 – od 16 – os 73/m 20/40 20/20 20/40 20/20 dry amd, cscr dry amd, cscr 8 – – – + – – + + + + dx, diagnosis; m, male; f, female; va, visual acuity; fut, follow-up time; mo, months; srf, subretinal fluid; d, diagnosis; l, last visit; ped, pigment epithelial detachment; oct, optical coherence tomography; od, oculus dexter; os, oculus sinister; amd, age-related macular dystrophy; hx, history; poag, primary open angle glaucoma; erm, epiretinal membrane case 4: patient no. 3 a 57-year-old male presented for retinal evaluation and establishing care. one and a half years prior to presentation, he had received an unknown injection in the left eye by a different provider. presenting visual acuity was 20/20 in the right eye and 20/30 in the left eye. iop and anterior exam was unremarkable. the patient complained of symptomatic distortion in the left eye and had an abnormal amsler grid. on funduscopic examination, the patient had rpe mottling in the right eye and a vitelliform lesion in the left eye [figure 4a]. while the patient appeared to have srf in the left eye that could be consistent with csr or vitelliform, by fa it appeared the pattern was less characteristic for csr or cnv [figure 4b]. on oct, the right eye was unremarkable but the left eye demonstrated avmd with the presence of srf [figure 4c]. given the characteristic appearance for vitelliform lesion, the lesion was observed without injection. over a period of two years without injection, the vitelliform lesion coalesced, and the srf resolved spontaneously [figure 4d]. by followup at five years from the initial presentation, the vitelliform lesion had collapsed [figure 4e]. throughout the course of the follow-up, the patient reported improvement of vision in the left eye with a final visual acuity of 20/30 (and 20/30 in the right eye) but continued complaints of metamorphopsia and abnormal amsler grid in the left eye. discussion there is a considerable diagnostic challenge with avmd. given the older average age, presence 586 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 acquired vitelliform macular degeneration; juliano et al figure 1. patient number 7 clinical course. (a) oct of the right eye demonstrating end-stage wet amd with cnv, subretinal hyperreflective material notable for fibrosis, fluid and distorted retinal contour. (b) oct of the left eye at presentation was notable for a vitelliform lesion with associated subretinal fluid. (c) one week after treatment with ranibizumab demonstrating persistent subretinal fluid and vitelliform lesion. (d) four years later, new srf appeared in the left eye adjacent to the persistent vitelliform lesion, but at that time there was no evidence of cnv by fa (e). (f) one month later, the srf disappeared without any injections. (g) one year later, the vitelliform lesion regressed completely. of drusen in a large percentage of patients with avmd, distinction from dry amd is challenging. while modern multimodal imaging remains helpful, there is not a single diagnostic test or imaging modality that can provide a definitive diagnosis. worse yet, at times subretinal fluid (srf) accompanies avmd lesions which presents a diagnostic dilemma to the clinician: does this represent progression from dry to wet amd, or simply srf associated with avmd? in this study we focused on acquired vitelliform lesions that presented diagnostic challenges as a result of the association of srf with these vitelliform lesions. the characteristic lesion appearance of avmd on ophthalmic exam is a yellow, elevated lesion approximately 1/3 to 1 disc diameter in size[13] with the presence of nonhomogenous hyperreflectivity that accumulates within the subretinal space, in contrast to the appearance of ped or drusen which accumulate below the level of the rpe. these lesions appear similar to the vitelliform lesions found in best disease but unlike hereditary vitelliform diseases, acquired diseases appear in a much older demographic, typically around 70 years of life.[7] the yellow appearance is a result of a particular amount of accumulated loose lipofuscin and photoreceptor debris.[5] srf in this entity is considered to be a result of mechanical displacement between the outer retinal layers and the rpe[10] inhibiting the rpe from pumping out the liquified lipofuscin debris. alternatively, it may represent incompetent rpe unable to move fluid into the choriocapillaris. visual acuity tends to typically remain good at presentation despite the vitelliform lesion at the fovea. in one study of 17 eyes, among eight patients with avmd, the median va acuity was 20/40 at presentation, and by final follow-up 71% retained vision within one to two lines of their initial visual acuity.[7] these characteristic features were similar to our study. the mean age of our patient population on diagnosis was 72 years and the median journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 587 acquired vitelliform macular degeneration; juliano et al figure 2. patient number 12 clinical course. (a) oct on presentation, three months after a previous injection of bevacizumab for presumed diagnosis of wet amd by an outside provider. (b) eight months after no treatment for the srf, patient presents with new-onset srf adjacent to a small ped. the patient was offered an injection but elected to observe; one month later, the srf spontaneously resolved (c). (d) new-onset srf which continued to relapse and remit over the course of her follow-up, but three years after her initial presentation (e) the vitelliform lesion condensed as well as the srf. figure 3. clinical course for patient number 11. (a) vitelliform lesion on presentation in the right eye. (b) two years later, progression and enlargement of the vitelliform lesion with the presence of trace subretinal fluid. (c) observed without injection over the course of three years and demonstrates stability of the vitelliform lesion and srf. visual acuity in our study at both diagnosis and final follow-up was approximately 20/29 over an average follow-up interval of approximately 2.4 years. although we suspect that the average visual acuity was similar to presentation because during the course of their follow-up patients underwent cataract extraction. the appearance of these lesions, particularly in the context of dry amd, can be concerning for progression to cnv, and ancillary imaging such as oct and fa can be particularly useful. other studies have noticed a presence of drusen anywhere between 33 and 60% of patients concurrently diagnosed with avmd.[2, 14, 15] our patients similarly had concurrent macular degeneration which made the diagnosis challenging. of the 22 eyes, 17 (77%) had concurrent diagnosis of dry amd in addition to a diagnosis of avmd. additionally, 68.2% had drusen notable on oct. the vitelliform lesion itself may have pigment which can be helpful in differentiating from cnv. in vitelliform lesions, the pigment is located centrally and surrounded by a hypopigmented halo. the vitelliform lesions tend to be less vascular and demonstrate decreased density of blood vessels at the superficial, deep capillary plexus and choriocapillaris[16] thought to be a result of accumulation of the vitelliform material that physically displaces the capillary network. in our study, we used octa in some 588 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 acquired vitelliform macular degeneration; juliano et al figure 4. clinical course of patient 3. (a) vitelliform lesion in the left eye. (b) fa showing staining and leakage of the vitelliform lesion without evidence of cnv. (c) vitelliform lesion in the left eye with associated srf. given the appearance of vm, the patient was observed without injection. two years later (d), the vitelliform lesion coalesced and the srf resolved spontaneously. (e) five years after from presentation, the vitelliform lesion spontaneously collapsed. cases with srf but failed to detect any cnv. additionally, no eyes with avmd were found to have concurrent srf and irf which further decreased the likelihood of fluid caused by cnv. we relied predominately on funduscopic exam and oct to assess and diagnose avmd. characteristically, the lesion is located in the subretinal space between the rpe and neurosensory retina[17] which is where our lesions were predominately located as seen in the patient images throughout this study. we found the existence of ped in four eyes in our study (18%), and srf in 10 of 22 eyes (46%) which was a bit higher than other studies identifying peds in approximately 7–8% of eyes;[8, 9] and another study demonstrating 21.1% of eyes had evidence of srf associated with the acquired vitelliform lesions.[8] in this study, the majority of eyes with srf also had drusen. notably, among all eyes but one (a patient with wet amd), there was no srf in the fellow eye unless a vitelliform lesion was present which suggests that the srf was likely due to vitelliform material accretion and was unlikely to have developed due to other conditions such as diabetes or undiagnosed inflammatory/infectious diseases. we showed that the srf tended to be located sub-foveally adjacent to the area of the vitelliform lesion, and when the fluid recurred as found in 40% of patients journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 589 acquired vitelliform macular degeneration; juliano et al with srf, it was located in the same location as on presentation. the impact of anti-vegf in these lesions remain unclear and current literature offers no consensus on their benefit in this disease entity. in one case report, only one injection of bevacizumab was done and over time, the srf decreased,[18] while in another case report, there was little improvement with these lesions.[19] as a result of the diagnostic confusion regarding avmd, patients often receive many anti-vegf agents prior to finally being diagnosed with avmd. in one study, six patients were initially diagnosed to have occult cnv from amd and were not diagnosed with avmd until after finishing a series of three injections of ranibizumab with little response on oct.[20] in our series, we report the results of three patients who were given anti-vegf injections (two with bevacizumab, one with ranibizumab) because avmd could not be differentiated from wet amd. in this study, we predominately used the response of antivegf to gauge whether the srf accumulation was a result of progression to wet amd or the coexistence of srf with avmd. there was no clear response to anti-vegf injections, and most often the srf resolved spontaneously without the use of injections. among those that did have an injection, in one eye the srf resolved, but in the other two it either exhibited no response, or relapsed and remitted even without further use of injections as illustrated by cases 1 and 2. we suggest that while the use of anti-vegf may not be useful to treat these patients, a treatment trial can be useful in difficult situations where there is a suspicion of avmd in the setting of new onset srf. current diagnostic modalities such as genetic testing are often impractical for the patient presenting in clinic with srf. fa and octa can be useful to characterize the presence of cnv, however, they may still have difficulty detecting occult cnv. in our study, there was leakage on fa even in the absence of cnv. in these uncertain diagnostic situations, a clear discussion with the patient can help delineate appropriate management options. there are two options that can be presented: one is to monitor closely and start treatment when the srf continues to increase and the patient becomes symptomatic. the other option is to give the patient an anti-vegf injection and bring the patient back in one to two weeks to determine the response. if the srf has either been unchanged or only minimally changed, the patient can be presumptively diagnosed with avmd and monitored closely. if the fluid does resolve after the first injection, it is possible that this patient has cnv. as illustrated by case 2, however, srf may spontaneously resolve on its own without injection, so if an injection is given and the fluid resolves, it may be a result of the natural history of relapsing and remitting srf in avmd rather than the effect of the injection itself. thus, periods of anti-vegf holidays may be helpful to distinguish between avmd and amd. recurrence or worsening of fluid would be suggestive of amd, whereas resolution or stability of fluid would be suggestive of avmd. in summary, the diagnosis of avmd can be challenging given its heterogenous appearance. when srf develops, these cases provide a diagnostic dilemma to the clinician who may suspect possible progression to wet amd. we suggest close observation or a trial of anti-vegf for the srf and re-evaluation in one to two weeks. if there is no response to an injection, then consider observing the srf rather than providing repeated monthly treatments. further work is needed to properly differentiate the heterogenous appearance of these disease processes and the response to anti-vegf agents in order to avoid unnecessary treatment. financial support and sponsorship the authors received no financial support for the research, authorship, and/or publication of this article. conflicts of interest the authors declare no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. references 1. chowers i, tiosano l, audo i, grunin m, boon cjf. adult-onset foveomacular vitelliform dystrophy: a fresh perspective. prog retin eye res 2015;47:64–85. 2. greaves ah, sarks jp, sarks sh. adult vitelliform macular degeneration: a clinical spectrum. aust n z j ophthalmol 1990;18:171–178. 590 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 acquired vitelliform macular degeneration; juliano et al 3. jun i, lee js, lee jh, lee cs, choi s, gee hy, et al. adult-onset vitelliform macular dystrophy caused by best1 p.ile38ser mutation is a mild form of best vitelliform macular dystrophy. sci rep 2017;7:1–11. 4. sabates r, pruett r, hirose t. pseudovitelliform macular degeneration. retina 1982;2:197–205. 5. arnold jj, sarks jp, killingsworth mc, kettle ek, sarks sh. adult vitelliform macular degeneration: a clinicopathological study. eye 2003;17:717–726. 6. freund kb, laud k, lima lh, spaide rf, zweifel s, yannuzzi la. acquired vitelliform lesions. retina 2011;31:13–25. 7. lima lh, laud k, freund kb, yannuzzi la, spaide rf. acquired vitelliform lesion associated with large drusen. retina 2012;32:647–651. 8. freund kb, laud k, lima lh, spaide rf, zweifel s, yannuzzi la. acquired vitelliform lesions: correlation of clinical findings and multiple imaging analyses. retina 2011;31:13–25. 9. saito m, iida t, freund kb, kano m, yannuzzi la. clinical findings of acquired vitelliform lesions associated with retinal pigment epithelial detachments. am j ophthalmol 2014;157:355–365. 10. sikorski bl, bukowska d, kaluzny jj, szkulmowski m, kowalczyk a, wojtkowski m. drusen with accompanying fluid underneath the sensory retina. ophthalmology 2011;118:82–92. 11. deutman af. electro-oculography in families with vitelliform dystrophy of the fovea: detection of the carrier state. arch ophthalmol 1969;81:305–316. 12. krämer f, white k, pauleikhoff d, gehrig a, passmore l, rivera a, et al. mutations in the vmd2 gene are associated with juvenile-onset vitelliform macular dystrophy (best disease) and adult vitelliform macular dystrophy but not age-related macular degeneration. eur j hum genet 2000;8:286–292. 13. hanif am, yan j, jain n. pattern dystrophy: an imprecise diagnosis in the age of precision medicine. int ophthalmol clin 2019;59:173–194. 14. burgess db, olk rj, uniat lm. macular disease resembling adult foveomacular vitelliform dystrophy in older adults. ophthalmology 1987;94:362–366. 15. gass j. a clinicopathologic study of a peculiar foveomacular dystrophy. trans am ophthalmol soc 1974;72:139–156. 16. querques g, zambrowski o, corvi f, miere a, semoun o, srour m, et al. optical coherence tomography angiography in adult-onset foveomacular vitelliform dystrophy. br j ophthalmol 2016;100:1724–1730. 17. benhamou n, messas-kaplan a, cohen y, gaudric a, souied eh, soubrane g, et al. adult-onset foveomacular vitelliform dystrophy with oct 3. am j ophthalmol 2004;138:294–296. 18. montero ja, ruiz-moreno jm, de la vega c. intravitreal bevacizumab for adult-onset vitelliform dystrophy: a case report. eur j ophthalmol 2007;17:983–986. 19. kandula s, zweifel s, freund kb. adult-onset vitelliform detachment unresponsive to monthly intravitreal ranibizumab. ophthalmic surg lasers imaging 2010;41:s81–s84. 20. gallego-pinazo r, dolz-marco r, pardo-lópez d, arevalo jf, díaz-llopis m. primary intravitreal ranibizumab for adult-onset foveomacular vitelliform dystrophy. graefe’s arch clin exp ophthalmol 2011;249:455–458. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 591 original article change in the foveal avascular zone and macular capillary network density after hyperbaric oxygen therapy in healthy retina sadık görkem çevik1, md; bekir selim bağlı2, md 1department of ophthalmology, yuksek ihtisas education and training hospital, bursa, turkey 2department of underwater and hyperbaric medicine, yuksek ihtisas education and training hospital, bursa, turkey orcid: sadık görkem çevik: https://orcid.org/0000-0002-5653-5800 bekir selim bağlı: https://orcid.org/0000-0002-0942-2619 abstract purpose: this study aimed to evaluate responses in retinal tissue by swept source oct angiography (oct-a) to hyperoxia after hyperbaric oxygen (hbo2) therapy. methods: the study was conducted in volunteers who received hbo2 treatment but did not have any eye disease. patients underwent detailed eye examinations including dilated fundus examination, visual acuity, and refraction before being admitted for hbo2 therapy. measurements were made before and immediately after hbo2 therapy. enface images of the retinal vasculature were obtained from the superficial and deep retinal plexus (sp/dp). quantitative analysis of the vessel density (vd) and foveal avascular zone (faz) area was performed. results: in total, 31 patients (15 female) with healthy retina were included in the study. the mean age was 42.8 years. the mean sp vascular density measurements before hbo2 therapy for the right and left eyes were 15.18 ± 1.2 mm−1 and 15.01 ± 1.3 mm−1, respectively; the measurements after hbo2 therapy for the right and left eyes were 14.34 ± 1.4 mm−1 and 14.48 ± 1.19 mm−1. the mean dp vascular density measurements before hbo2 therapy for the right and left eyes were 16.03 ± 1.69 mm−1 and 16.1 ± 1.45 mm−1, respectively; the measurements after hbo2 therapy for the right and left eyes were 15.02 ± 1.65 mm−1 and 15.12 ± 2.16 mm−1, respectively. reduction of mean vd in superficial and deep plexus after hbo2 was statistically significant (p = 0.001 and p = 0.000, respectively). changes in mean faz area before and after hbo2 therapy were not statistically significant (p = 0.719). conclusion: the healthy retina responds to oxygen supersaturation with hbo2 therapy by eventually decreasing vascular density in all layers. these findings may be important for further studies especially related to retina and choroidal oxygenation. keywords: hyperbaric oxygen; oct-a; retinal ischemic disease j ophthalmic vis res 2021; 16 (3): 393–399 © 2021 çevik et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 393 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i3.9436&domain=pdf&date_stamp=2019-07-17 macular changes after hyperbaric o2; çevik et al introduction hyperbaric oxygen (hbo2) therapy is a medical treatment method that aims to increase the level of dissolved oxygen in tissues. patients intermittently breathe near 100% oxygen while inside a hyperbaric chamber that is pressurized to greater than sea level pressure (1 atmosphere absolute [ata]) and high tissue oxygen level remains high for up to 4 hr after the therapy.[1] retina blood flow is provided by two primary sources: the retinal artery and the choroid. the retina has an internal autoregulatory system that preserves blood flow and stable oxygenation by altering it in response to unexpected conditions.[2] this regulatory system changes blood flow and vascular density for unexpected conditions and may not work correctly under some conditions, such as diabetic retinopathy or age-related macular degeneration.[3–9] macular microvasculature is a complex system consisting of three capillary plexuses for the blood supply of the inner retina: the superficial retinal plexus (sp) located in the retinal nerve fiber layer and the two-plexus located at the inner and outer border of the inner nuclear layer (inl), which constitute the deep retinal plexus (dp).[10] noninvasive retinal blood-flow imaging techniques, such as scanning laser doppler and doppler oct, have previously been described.[11–14] oct angiography (oct-a) is a novel, noninvasive technique for retinal vasculature imaging that allows segmentation and quantification of the retinal microvasculature.[15] the present study aimed to evaluate changes in foveal avascular zone (faz) area and perifoveal capillary network density in sp and dp, with the aid of swept source oct-a in patients undergoing hbo2 therapy. correspondence to: sadık görkem çevik, md. yüksek i̇htisas education and training hospital, bursa 16310, turkey. e-mail: gorkemcevik@hotmail.com received: 27-11-2020 accepted: 17-02-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i3.9436 methods this prospective, interventional study was handled between april 2017 and october 2017 after the ethics committee of hospital approved the protocol. the study adhered to the declaration of helsinki, and patients were informed about the treatment options and possible complications. the preprocedural written informed consent was obtained from patients. the study was carried on in volunteers who did not have any known eye disease and who received hbo2 treatment for other reasons. volunteer patients underwent detailed eye examinations that included dilated fundus examination and visual acuity and refraction before they were admitted for hbo2 therapy. exclusion criteria were: age <18 years; any ocular diseases; inability to maintain stable fixation for scanning; visual acuity worse than 20/40; refractive errors >−4.00 or +2.00 diopters; media opacity; history of ocular surgery; and systemic diseases that may affect microc0irculation (e.g., diabetes mellitus, hypertension). measurements were made using the dri oct triton (topcon cotokyo-japan) system before and immediately (approximately 1 min) after the fifth session of hbo2 therapy (every day one session). faz, superficial vascular plexus (sp) [figure 1] and deep vascular [figure 3] plexus (dp) density measurements were made. the dri oct triton system uses a swept-source laser with a center wavelength of 1050 nm and a scan speed of 100,000 a-scans per second. oct-a is based on the topcon oct angiography ratio analysis (octara) algorithm. this system distinguishes mobile blood flow from tissue using motion contrast measure. an active eye tracker was used to decrease motion artifacts during octa imaging. each 3 × 3 mm volume scan contained 320 × 320 pixels. in the present study, we applied automated layer segmentation to sp (from 2.6 μm below the internal limiting membrane to 15.6 μm below the junction between the inner plexiform and inner nuclear layers [ipl/inl]) and dp (from this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: çevik sg, bağlı bs. change in the foveal avascular zone and macular capillary network density after hyperbaric oxygen therapy in healthy retina. j ophthalmic vis res 2021;16:393–399. 394 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 https://knepublishing.com/index.php/jovr macular changes after hyperbaric o2; çevik et al figure 1. swept source oct-a image before (left) and after (right) hbo2 treatment (superficial plexus). figure 2. skeletonized vessel maps of the superficial plexus image before (left) and after (right) hbo2 treatment. 15.6 μm below of ipl/inl to 70.2 μm below the ipl/inl). all measurements were obtained between 9:00 am and 12:00 am to avoid the effects of diurnal variations and blood pressure and pulse were recorded. poor-quality oct-a due to blinking or fixation loss were excluded from the study. the qualitative examination of the oct-a of the sp and dp were then independently performed by two masked examiners (dr akdogan and dr tok). quantitative analysis of 3 × 3 mm oct angiograms, including faz area and capillary vessel density (cvd; i.e., sp–dp) measurement, was performed using imagej software (developed by wayne rasband, national institutes of health, bethesda, md; available at http://rsb.info.nih.gov/ij/index.html). the original octa images of the sp and the dp were binarized to convert them from grayscale into black and white images using the imagej software, and the faz area was manually marked and measured in original images of sp. to measure the cvd, the binarized octa images were skeletonized, showing the blood vessels as a 1-pixel-wide line, and imagej was used to count the number of black pixels and total pixels [figures 2 and 4]. cvd was then calculated as ([pixels of vessels,3/256])/(area in squared millimeter) in mm−1 and this method was described by khairallah et al previously.[27] cases with projection artifact were excluded from the analysis of vessel density. hbo2 therapy was administered in multiple chambers at 2.4 ata. each session of hbo2 therapy lasted about 120 min composed of three 25-min oxygen periods during which patients breathed 100% oxygen at 2.4 ata, separated by 5-min air brakes, with compression and decompression during the remaining time. data analysis was performed using spss statistics for windows, version 22.0 (spss inc., chicago, il, united states). all differences associated with a chance probability of 0.05 or less were considered statistically significant. statistical journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 395 http://rsb.info.nih.gov/ij/index.html macular changes after hyperbaric o2; çevik et al figure 3. swept source oct-a image before (left) and after (right) hbo2 treatment (deep plexus). figure 4. skeletonized vessel maps of the deep plexus image before (left) and after (right) hbo2 treatment. significance between before and after hbo2 therapy was tested with dependent samples t-test. results this study included 31 patients (15 female, 48%) with healthy retinas. the mean age was 42.8 ± 15.3 (19–73) years. indications of hbo2 therapy were femur bone avascular necrosis (15 patients, 48%), chronic osteomyelitis (8 patients, 25%), idiopathic sudden sensorineural hearing loss (6 patients, 19%), malign otitis externa (1 patient, 3%), crush injury (1 patient, 3%), as summarized in table 1. the mean sp vascular density measurements before hbo2 therapy for the right and left eyes were 15.18 ± 1.2 mm−1 (min 13.1 mm−1 – max 17.1 mm−1) and 15.01 ± 1.3 mm−1 (min 13.3 mm−1 – max 17.2 mm−1) respectively; the measurements after hbo2 therapy for the right and left eyes were 14.34 ± 1.4 mm−1 (min 12.1 mm−1 – max 16.2 mm−1) and 14.48 ± 1.19 mm−1, (min 12.3 mm−1 – max 16.2 mm−1) respectively. these changes were statistically significant (p = 0.001 and p = 0.001, respectively). the mean dp vascular density measurements before hbo2 therapy for the right and left eyes were 16.03 ± 1.69 mm−1 (min 13.82 mm−1 – max 18.12 mm−1) and 16.1 ± 1.45 mm−1 (min 13.82 mm−1 – max 18.03 mm−1), respectively; the measurements after hbo2 therapy for the right and left eyes were 15.02 ± 1.65 mm−1 (min 13.23 mm−1 – max 17.05 mm−1 ) and 15.12 ± 2.16 mm−1 (min 12.10 mm−1 – max 18.23 mm−1) , respectively. these changes were statistically significant (p < 0.000 and p < 0.000, respectively). (measurement data before and after hbo2 therapy are shown in table 2.) the mean faz area for the right eye was 0.363 ± 0.15 (0.20–0.62) mm2 before hbo2 therapy and 0.372 ± 0.34 (0.21–0.49) mm2 after the therapy. the mean faz area for the left eye was 0.354 ± 0.32 (0.28–0.47) mm2 before hbo2 therapy and 0.357 396 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 macular changes after hyperbaric o2; çevik et al table 1. indications of hbo2 therapy for patients indications number of patients femur bone avascular necrosis 15 (48 %) chronic osteomyelitis 8 (25 %) idiopathic sudden sensorineural hearing loss 6 (19 %) severe otitis externa 1 (3 %) crush injury 1 (3 %) total 31 table 2. measurement data before and after hbo2 therapy before hbo2 therapy after hbo2 therapy p-value mean right eye superficial capillary density (mm−1) 15.18 ± 1.2 14.34 ± 1.4 0.001 mean right eye deep capillary density (mm−1) 16.03 ± 1.69 15.02 ± 1.65 0.000 mean left eye superficial capillary density (mm−1) 15.01 ± 1.3 14.48 ± 1.19 0.001 mean left eye deep capillary density (mm−1) 16.1 ± 1.45 15.12 ± 2.16 0.000 mean right eye faz (mm2) 0.363 0.372 0.374 mean left eye faz (mm2) 0.354 0.357 0.719 mm2 ± 0.22 (0.23–0.46) after the therapy. these changes were not statistically significant (p = 0.374, p = 0.719). discussion in the present study, we aimed to investigate the effect of five sessions hbo2 therapy on the retina. we found significant decreases in sp and dp capillary network density in the macular region. however, there was no effect on faz measurements. the retina has unique dual circulation and complicated autoregulatory systems. the outer retina and faz are nourished with diffusion from the choroidal circulation (cc).[20, 26] responses to hypoxia in retinal artery circulation (rc) and cc are different.[18] yi et al reported that cc responds poorly in hypoxia conditions.[19] linsenmeier and braun found that the inner retina was well-preserved under hypoxic condition by the help of increased rc during hypoxia, while blood flow in cc remained unchanged in cats’ retina.[20] retinal response to hyperoxia is different between mammalian species. the rat, rabbit, and guinea pig that are commonly demanded mammalian in ophthalmic research and they have different responses to systemic hyperoxia.[3] hyperoxia changes total human retinal blood flow, as measured by other measurement methods before.[13–16] the autoregulatory response protects retinal tissue from the adverse effects of hypoxia and hyperoxia. hagag et al found that hyperoxia caused a significant decrease in the flow index (11%) and the vd of the deep capillary plexus (dp) of the retina (7.8%). however, decreases in the vessel densities of the superficial and intermediate plexuses were not statistically significant. in hagag et al’s study, oxygen was supplied with a face mask for individuals; the mask flow rate was 15 l/min.[17] hagag et al hypothesized that the response of dp in different oxygen concentrations could be significant and essential because cc did not respond like dp and the blood flow of the sp also decreased in over-oxygenation but supplying oxygen with a face mask may not be enough to produce a statistically significant decrease. contrary to hagag et al’s study, reduction in both sp and dp vd was statistically significant in our study. we think that this may be the result of a high amount of dissolved oxygen in the plasma that was supplied by hbo2. hbo2 therapy increased dissolved oxygen levels in all retinal layers, including the superficial retinal layers. during hbo2, the oxygen concentration in the avascular outer retina increases due to higher journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 397 macular changes after hyperbaric o2; çevik et al supply from the cc, which maintains constant flow at high o2 level. to preserve steady oxygen flux in the outer retina, the dp must compensate with greater vasoconstriction.[25, 28–30] in the present study, the changes in faz before and after hbo2 therapy were not statistically significant. faz area changes can be seen in retinal disease and five hbo2 sessions may be short to describe certain effect of hbo2 on faz.[21–24] the limitations of our study are: small sample size, limited number of hbo2 sessions, measurement of vascular plexus density by an external software, and assessment of only 3 × 3 mm macular area. in summary, swept source oct-a evaluate retinal vascular plexus and faz and we reported a significant decrease of foveal capillary network density in sp and dp with hbo2 therapy. this finding gives us new evidence regarding the interaction between choroidal and retinal circulation and offers us new perspective about retinal oxygenation with hbo2 treatment. acknowledgement the authors are thankful to dr mediha tok and dr muberra akdogan for evaluating images. financial support and sponsorship nil. conflicts of interest there is no conflict of interest. references 1. weaver lk. hyperbaric oxygen therapy indications. 13th ed. durham, nc: best publishing, 2014. p. 1–8, 247. 2. rassam sm, patel v, chen hc, kohner em. regional retinal blood flow and vascular autoregulation. eye 1996;10:331– 337. 3. cringle sj, yu dy. regulation of oxygen tension in the mammalian retina during systemic hyperoxia is species dependent. adv exp med biol 2018;1072:241–244. 4. friedman e. a hemodynamic model of the pathogenesis of age-related macular degeneration. am j ophthalmol 1997;124:677–682. 5. schmetterer l, wolzt m. ocular blood flow and associated functional deviations in diabetic retinopathy. diabetologia 1999;42:387–405. 6. kohner em, patel v, rassam sm. role of blood flow and impaired autoregulation in the pathogenesis of diabetic retinopathy. diabetes 1995;44:603–607. 7. pemp b, schmetterer l. ocular blood flow in diabetes and age-related macular degeneration. can j ophthalmol 2008;43:295–301. 8. gilmore ed, hudson c, nrusimhadevara rk, harvey pt, mandelcorn m, lam wc, et al. retinal arteriolar diameter, blood velocity, and blood flow response to an isocapnic hyperoxic provocation in early sight-threatening diabetic retinopathy. invest ophthalmol vis sci 2007;48:1744– 1750. 9. remsch h, spraul cw, lang gk, lang ge. changes of retinal capillary blood flow in age-related maculopathy. graefes arch clin exp ophthalmol 2000;238:960–964. 10. strenn k, menapace r, rainer g, findl o, woltz m. reproducibility and sensitivity of scanning laser doppler flowmetry during graded changes in po2. br j ophthalmol 1997;81:360–364. 11. riva ce, grunwald je, sinclair sh. laser doppler velocimetry study of the effect of pure oxygen breathing on retinal blood flow. invest ophthalmol vis sci 1983;24:47–51. 12. bower ba, zhao m, zawadzki rj, izatt ja. real-time spectral domain doppler optical coherence tomography and investigation of human retinal vessel autoregulation. j biomed opt 2007;12:041214. 13. pechauer ad, huang d, jia y. detecting blood flow response to stimulation of the human eye. biomed res intl 2015;2015:121973. 14. pechauer ad, tan o, liu l, jia y, hou v, hills w, et al. retinal blood flow response to hyperoxia measured with en face doppler optical coherence tomography. invest ophthalmol vis sci 2016;57:oct141–oct145. 15. jia y, tan o, tokayer j, potsaid b, wang y, liu jj, et al. split-spectrum amplitude decorrelation angiography with optical coherence tomography. opt express 2012;20:4710–4725. 16. tam j, dhamdhere kp, tiruveedhula p, manzanera s, barez s, bearse ma jr, et al. disruption of the retinal parafoveal capillary network in type 2 diabetes before the onset of diabetic retinopathy. invest ophthalmol vis sci 2011;52:9257–9266. 17. hagag, am, pechauer ad, liu l, wang j, zhang m, jia m, et al. oct angiography changes in the 3 parafoveal retinal plexuses in response to hyperoxia. ophthalmol retina 2018;2:329–336. 18. lange ca, bainbridge jw. oxygen sensing in retinal health and disease. ophthalmologica 2012;227:115–131. 19. yi j, liu w, chen s, backman s, shebani n, sorenson cm, et al. visible light optical coherence tomography measures retinal oxygen metabolic response to systemic oxygenation. light sci appl 2015;4:e334. 20. linsenmeier ra, braun rd. oxygen distribution and consumption in the cat retina during normoxia and hypoxemia. j gen physiol 1992;99:177–197. 21. nelson da, burgansky-eliash z, barash h, loewenstein a, barak a, bartov e, et al. high-resolution wide-field imaging of perfused capillaries without the use of contrast agent. clin ophthalmol 2011;5:1095–1106. 398 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 macular changes after hyperbaric o2; çevik et al 22. kim dy, fingler j, zawadzki rj, park ss, morse ls, schwardz dm, et al. noninvasive imaging of the foveal avascular zone with high-speed, phase-variance optical coherence tomography. invest ophthalmol vis sci 2012;53:85–92. 23. tam j, dhamdhere kp, tiruveedhula p, lujan bj, johnson rn, bearse ma jr, et al. subclinical capillary changes in nonproliferative diabetic retinopathy. optom vis sci 2012;89:e692–e703. 24. miyamoto k, khosrof s, bursell se, rohan r, murata t, clermont ac, et al. prevention of leukostasis and vascular leakage in streptozotocin-induced diabetic retinopathy via intercellular adhesion molecule-1 inhibition. proc natl acadsci usa 1999;96:10836–10841. 25. wangsa-wirawan nd, linsenmeier ra. retinal oxygen: fundamental and clinical aspects. arch ophthalmol 2003;121:547–557. 26. snodderly dm, weinhaus rs. retinal vasculature of the fovea of the squirrel monkey saimiri sciureus: three-dimensional architecture, visual screening, and relationships to the neuronal layers. j comp neurol 1990;297:145–163. 27. khairallah m, abroug n, khochtali s, mahmoud a, jelliti b, coscas g, et al. optical coherence tomography angiography in patients with behçet uveitis. retina 2017;37:1678–1691. 28. delaey c, van de voorde j. regulatory mechanisms in the retinal and choroidal circulation. ophthalmic res 2000;32:249–256. 29. geiser mh, riva ce, dorner gt, diermann u, luksch a, schmetterer l. response of choroidal blood flow in the foveal region to hyperoxia and hyperoxia-hypercapnia. curr eye res 2000;21:669–676. 30. cringle sj, yu dy. a multi-layer model of retinal oxygen supply and consumption helps explain the muted rise in inner retinal po(2) during systemic hyperoxia. comp biochem physiol a mol integr physiol 2002;132:61–66. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 399 original article a simple inner-stopper guarded trephine for creation of uniform keratectomy wounds in rodents peter b. le1,2,#, bs; fang chen1,2,#, phd; david myung1,2,3, md, phd 1department of ophthalmology, stanford university school of medicine, ca, usa 2va palo alto health care system, palo alto, ca, usa 3department of chemical engineering, stanford university, ca, usa orcid: peter le: https://orcid.org/0000-0002-1932-9995 fang chen: https://orcid.org/0000-0002-6675-5508 david myung: https://orcid.org/0000-0002-7980-3070 abstract purpose: creating controllable, reproducible keratectomy wounds in rodent corneas can be a challenge due to their small size, thickness, and the lack of usual tools available for human eyes such as a vacuum trephine. the purpose of this work is to provide a consistent, reproducible corneal stromal defect in rats using a simple, economical, and customized innerstopper guarded trephine. methods: the inner-stopper guarded trephine is used to induce a circular wound in rat corneas. after trephination, the corneal flap can be removed by manual dissection using a blunt spatula. we used optical coherence topography (oct) to measure the defect wound depth induced in ex vivo rat eyes. results: despite a minor learning curve, this simple device enables depth control, reduces variability of manual keratectomy wound depth in rats, and decreases the risk for corneal perforation during keratectomy. corneal defect creation was highly reproducible across different researchers and was independent of their surgical training. conclusion: this inner-stopper guarded trephine can be utilized and applied to pre-clinical testing of a wide range of corneal wound healing therapies, including but not limited to biotherapeutics, corneal prosthetics, and regenerative technologies. keywords: anterior lamellar keratoplasty (alk); corneal defect model; inner-stopper guarded trephine; keratectomy; rat corneal wound model; trephine design j ophthalmic vis res 2021; 16 (4): 544–551 introduction the cornea is the transparent, outermost part of the eye that is responsible for protecting intraocular correspondence to: david myung, md, phd. 1651 page mill rd. palo alto, ca 94304, usa. e-mail: djmyung@stanford.edu #these authors contributed equally. received: 29-05-2020 accepted: 01-07-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9743 eye structures and focusing light onto the retina.[1] it is susceptible to exposure-related injuries such as burns involving chemical, thermal, and radiation sources, as well as physical trauma.[2] diseases and injuries to the cornea result in impaired vision due to scarring, clouding, thinning, among this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: le pb,# chen f,# myung d. a simple inner-stopper guarded trephine for creation of uniform keratectomy wounds in rodents. j ophthalmic vis res 2021;16:544–551. 544 © 2021 le et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9743&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr new trephine for rodent studies; le et al others, and in advanced cases, blindness.[3] many ongoing therapeutic efforts in corneal research include the use of pre-clinical animal models on rodents such as rats.[4, 5] this disease model can be used to investigate potential corneal wound healing treatments, such as cell transplantation, amniotic membranes, fibrin gel, as well as polymers and biopolymers.[6] larger animal models with similar ocular anatomy to humans have been widely used to study wound healing in the cornea. we recently developed a 3d printable modified trephine that can create consistent anterior lamellar keratectomy wounds in rabbits.[7] this trephine was used to create defects to study the ocular wound-healing effects of novel in situ forming hydrogels in rabbits.[8–10] the development of a similar trephine for rats is equally important because one of the many advantages of using rodents is the availability of visual function tests available for rodents, but not larger animals.[11, 12] also, the cost for rat studies are much lower than that of larger animals. therefore, rats serve as an important model for the study of wound healing in the cornea. the size of their cornea is large enough to allow for the study of wounds and subsequent tissue collection and analyses.[13] however, rats have smaller eyes and their average central corneal thickness (cct) is 159 μm,[14] so studying cornea wound healing in rats involves producing defects with precision and reproducibility. thus, there is a need to develop a reliable system to create consistent and controlled corneal defects in rats in a way that minimizes the risk of corneal perforation. here, we report an inner-stopper guarded trephine to create consistent anterior lamellar keratectomy in rats. there are many variables to consider when deciding on a wound model for studying the cornea. some studies require only debridement of the epithelium, thereby preserving the basement membrane, while others require wounds that penetrate the basement membrane and extend into the stroma.[15–17] the proposed method will focus on the latter because it allows the researcher to consistently remove corneal stromal tissue for studies involving wounds that penetrate the stroma. currently, there are several techniques available to produce anterior wounds to the corneal stroma. manual keratectomy (mk) involves applying and rotating a sharp trephine or circular biopsy punch to the surface of the cornea, gradually increasing pressure to produce a wound and subsequently excising the corneal flap. another method, photorefractive keratectomy (prk), uses an excimer laser to ablate corneal tissue. compared to mk, laser excimer ablation is more precise and reduces the variability in the depth of the injury.[18] however, laser ablation requires extensive training by the surgeon and has high equipment costs.[19–21] alternatively, microkeratomes are another tool that can be potentially utilized to create a corneal stromal defect.[22] however, there are no microkeratomes that currently exist for rats. therefore, a method for creating corneal wounds using manual, mechanical tools would be an important advance for preclinical research on small animals. of the reported studies involving the need to model corneal injuries in rats, there is no systematic model to produce consistent manual corneal defects. achieving similar corneal cut depths across eyes is difficult to achieve manually. to reliably assay the effects of therapeutics on corneal wound healing, confounding variables such as the degree of corneal deformation during trephination must be taken into consideration. perforation of the cornea results in leakage of anterior chamber fluid, in which case the globe and consequently the animal may have to be euthanized unless the eye is still usable for study after globe repair with sutures.[23] accordingly, a corneal defect that is too superficial and does not cut deeply enough will likely be repaired by the animal’s innate wound healing mechanisms rather than the treatment itself.[24] therefore, the purpose of this method is to design a disease model for a consistently deep but non-perforating stromal defect in rat corneas. we developed a handheld trephine with an inner stopper that allows for reproducible corneal stromal defects in rat eyes. after the trephination, we performed keratectomies on ex vivo rat corneas with a blunt spatula and imaged them using optical coherence topography (oct). we quantified the depth of the excised rat cornea using oct stromal thickness measurements and demonstrated that the device and protocol can be used to produce defects of consistent depth in rats between different users. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 545 new trephine for rodent studies; le et al methods no live rats were operated on for the data collection that supports the use of this method. however, if the techniques described in this paper are to be used in vivo, then researchers should abide with the arvo statement for the use of animals in ophthalmic and vision research. rat eyeballs were purchased from vision tech (sunnyvale, texas, usa) and pel-freeze biologicals (rogers, ar, usa). 2 mm biopsy punches (rbp-20) were purchased from robbins instruments, inc. (sunnyvale, ca, usa). ring forceps (11106-09), micro spatula (10089-11), and fine-point surgical forceps (11445-12) were purchased from fine science tools (foster city, ca, usa). teflon polytetrafluoroethylene (ptfe) sheets, 0.127 mm (8569k16) and 2.38 mm (8545k14), were purchased from mcmaster-carr (elmhurst, il, usa) creating the inner-stopper guarded trephine use a 2 mm biopsy punch to punch a piece of 2.38 mm thick teflon sheet. this piece of teflon sheet is used as the inner stopper. use the same 2 mm biopsy punch in the previous step to punch a piece of teflon sheet that is 127 µm thick. this thinner piece of teflon sheet is used as the trephination depth calibrator. note that this second piece of teflon can be adjusted to a thickness equal to the desired depth of the corneal defect. transfer and insert the two teflon sheets into a new 2 mm biopsy with the inner stopper sheet further away from the blade and the calibrator sheet closer to the blade. refrain from denting the new 2 mm biopsy punch to keep the blade sharp. using a blunt needle, push the teflon sheets from the posterior end of the trephine until two sheets are contacting closely and the calibrator sheet is flush with the edge of the blade. apply a few drops of cyanoacrylate to the posterior end of the trephine to keep the stopper sheet in place. remove the calibrator sheet from the anterior of trephine. performing the keratectomy using the inner-stopper guarded trephine, begin by preparing the ex vivo rat eyeball or animal for aseptic surgery. place the inner-stopper guarded trephine on the center of the rat cornea. press the trephine blade toward the cornea. a dent will form on the cornea without cutting into the corneal stromal tissue. rotate the trephine in one direction (either clockwise or counter-clockwise) for at least 90°, and then rotate again in the other direction for 90°. repeating the rotation multiple times will allow the blade cut into corneal stroma. discontinue rotation when the trephine blade does not go into the stroma any deeper. gently pull out the trephine from the eye. removing the stromal tissue to remove the layer of anterior stroma after trephination, lift the flap of the incised cornea at one end using fine-point surgical forceps under a bright-field microscope. use an angled blunt spatula to dissect the stromal tissue along a lamellar plane on the posterior edge of the trephination. continue the dissection process with careful, fine sweeping motions along the plane until the flap is completely detached from the cornea. remove and discard the excised cornea. data analysis after the keratectomies were performed, anterior segment oct was used to image the eyes. the oct images of the cornea were then analyzed by image j to measure the depth of the cut. the depth of the cut was analyzed by measuring the thickness of the wounded cornea and the adjacent intact cornea. the percentage of excised cornea was calculated based on these two measurements by the following: (thickness of intact cornea – thickness of wounded cornea) / thickness of intact cornea × 100. statistical analysis means, standard deviations, and p-values were calculated in microsoft excel 2016. significance was determined using a two-tailed student’s ttest, and p-values < 0.05 were considered to be significant. pearson’s coefficient was calculated using the pearson function in microsoft excel 2016. results figure 1 illustrates the sagittal cross-section of the inner-stopper guarded trephine. the 2.38 mm 546 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 new trephine for rodent studies; le et al measurement refers to the inner stopper. the 0.13 mm measurement represents the trephination depth calibrator that is removed during the assembly of the trephine. oct images in figure 2 show the range of defect depths possible by this method, from shallow (approximately 20%) to deep (approximately 80%). panel a shows an intermediate defect, whereas panel b shows a deeper defect and nearperforation of the cornea. panel c shows a more superficial defect and panel d shows a photo of the ex vivo rat eyeball after introducing the defect. the degree of defect, represented by the percentage of excised cornea, were graphed alongside the diameter and weight of the rat eyeballs. figure 3 shows the linear relationship between these measurements and the defects produced by the inner-stopper guarded trephine. the weight (pearson’s r = 0.0665) and diameter (pearson’s r = 0.1206) of the rat eyes had a weak positive correlation with the percentage of excised cornea. figure 4 shows the consistency of the corneal defect depth between two different users. user two had about one month of keratectomy experience, compared to user one who had six months of keratectomy experience. on average, user one used the inner-stopper trephine to cut approximately 56.5% of the cornea with a standard deviation of 12.4%. out of twenty-six eyes, two were perforated and discarded (7.7% perforation). the relative standard deviation for the percentage of corneal stromal tissue excised was 21.9%. the minimum percentage was found to be 33.8% and the maximum was 81.7%. user two cut approximately 57.4% of the cornea with a standard deviation of 15.2%. the relative standard deviation for the percentage of cornea cut was 26.4%. the minimum defect was 20.9% and the maximum was 80.5%. out of the 24 eyes, user two perforated 5 eyes. there was no significant difference between the values for weight (p = 0.7218), diameter (p = 0.6842), and percentage of cornea excised (p = 0.8569) between the two users, indicating that the procedure is consistent between the two users. the perpendicularity of the stromal defects were also objectively measured. on average, user one created defects that had an angle of 135.7°, with a standard deviation of 32.7. user two created defects that had an angle of 136.7°, with a standard deviation of 22.9. while this is less than ideal for the use of corneal transplantation and donor-recipient matching, this method nonetheless creates substantial stromal defects that can be filled with in situ forming hydrogels similar to what can be done in rabbits.[8–10] figure 5 shows an oct image of the application of an in situ forming hydrogel to a corneal defect introduced by the described method. discussion in many cases, keratectomies performed in rat models are irregular and vary significantly between different cornea samples. the protocol in this study describes a simple modification of a trephine that produces a relatively consistent corneal keratectomy wounds in rats. when using the trephine, it is critical to ensure that the circular blade of the trephine is positioned over the center of the eye. if not centered, the size of the defect will be less accurate due to the changing corneal thickness that is dependent on the location where the trephine is placed on the cornea.[11] because rat corneas are considerably thinner than those of other larger animal models, there is a much decreased margin for error and greater risk of perforation. another vital aspect of performing the keratectomy is to take advantage of the shear stress of the trephine blade by using extensive rotation and avoiding excess perpendicular pressure to the cornea, which can also result in perforation. in the beginning stages of using this method, there may be difficulty in producing incisions in the cornea. one major complication is that the blade may glide along the surface of the cornea when one is trying to make an incision. to avoid this, the surgeon could attempt to gently pat the surface of the cornea with a tissue or sterile cotton swab. when performing the keratectomy, the eye should be immobilized. any movement of the eyeball will reduce the amount of force imposed on the circular defect and potentially cause the trephine to glide along the surface of the cornea and scrape the surrounding layer of epithelial cells. for animal surgery, globe movement can be restricted by using ring forceps. this simple trephine modification allows for the creation of uniform corneal defects between animals to study corneal wound healing in a very journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 547 new trephine for rodent studies; le et al figure 1. schematic representation and illustration of the inner stopper guarded trephine. cost-effective way. once the defects are created, researchers can attempt to treat the wound using various methods and analyze wound healing clinically and histopathologically without worrying about wound uniformity between surgeries and between surgeons. in rat eyes, the trephine seems to create oblique defects rather than perpendicular defects. we propose that this is due to the biomechanics, small size, and high curvature of the rat cornea. after the trephine is inserted to cut the stroma and removed, the elasticity of the now substantially thinned cornea may have caused some of the tissue to move back toward the center of the defect. additionally, the high curvature of the rat cornea makes it more difficult for the trephine to cut a perpendicular angle in the stroma. despite this difficulty to create perpendicular defects, this method is still useful to study therapies that can conform to the shape of the defect, such as hydrogels. we found in our prior published work that wound perpendicularity could be achieved reliably in rabbits, which have substantially thicker corneas with different biomechanical properties and lower curvature compared to those of rats.[7] compared to other methods such as mechanical keratectomy, excimer laser ablation, and microkeratomes, using an innerstopper guarded trephine is more economical and simpler to use. for studies involving larger animal models, the protocol to create the inner-stopper trephine can be modified and replicated by using a larger biopsy punch to create a circular incision with a larger diameter. in summary, we reported a simply designed inner-stopper guarded trephine-based protocol for producing consistent stromal defects in rat corneas, which is critical to study the effects of various therapeutics on corneal wound healing in a rat model. the inner stopper is essential for controlling the trephination depth. financial support and sponsorship the authors would like to acknowledge the support from the national institutes of health (national eye institute k08ey028176 and a departmental p30-ey026877 core grant), the stanford spark translational research grant and maternal & child health research institute (mchri) (d.m.), the core grant and career development award from research to prevent blindness (rpb), the matilda ziegler foundation, the va rehabilitation research and development small projects in rehabilitation effectiveness (spire) program (i21 rx003179), and the byers eye institute at stanford. acknowledgements the authors thank david buickians for providing the illustration of the inner-stopper guarded trephine. 548 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 new trephine for rodent studies; le et al figure 2. optical coherence tomography (oct) of the rat corneas after alk. (a) intermediate defect of the cornea. (b) deep defect of the cornea. (c) superficial defect of the cornea. (d) rat eyeball after alk with the inner-stopper guarded trephine. figure 3. correlations between the diameter (a) and weight (b) of the eyes and the percentage of cornea excised by the innerstopper guarded trephine. the linear dependence was considered weak when the pearson’s r value is below 0.2. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 549 new trephine for rodent studies; le et al figure 4. comparison of corneal defects created by the inner-stopper guarded trephine by two users with different keratectomy experiences. user one had six months of experience in performing keratectomies and user two had one month of experience. there was no significant difference in the percentage of cornea excised between the two users. figure 5. oct image of a rat corneal defect filled in with a novel in situ forming therapeutic hydrogel. conflicts of interest none. references 1. sridhar ms. anatomy of cornea and ocular surface. indian j ophthalmol 2018;66:190–194. 2. delmonte dw, kim t. anatomy and physiology of the cornea. j cataract refract surg 2011;37:588–598. 3. wilson sl, el haj aj, yang y. control of scar tissue formation in the cornea: strategies in clinical and corneal tissue engineering. j funct biomater 2012;3:642–687. 4. yamamoto t, otake h, hiramatsu n, yamamoto n, taga a, nagai n. a proteomic approach for understanding the mechanisms of delayed corneal wound healing in diabetic keratopathy using diabetic model rat. int j mol sci 2018;19:3635. 5. nagai n, fukuoka y, ishii m, otake h, yamamoto t, taga a, et al. instillation of sericin enhances corneal wound healing through the erk pathway in rat debrided corneal epithelium. int j mol sci 2018;19:1123. 6. bukowiecki a, hos d, cursiefen c, eming sa. woundhealing studies in cornea and skin: parallels, differences and opportunities. int j mol sci 2017;18:1257. 7. chen f, buickians d, le p, xia x, montague-alamin sq, blanco varela i, et al. 3d printable, modified trephine designs for consistent anterior lamellar keratectomy wounds in rabbits. curr eye res 2021;46:1105–1114. 8. fernandes-cunha gm, chen km, chen f, le p, hee han j, mahajan la, et al. in situ-forming collagen hydrogel crosslinked via multi-functional peg as a matrix therapy for corneal defects. sci rep 2020;10:16671. 9. chen f, le p, lai k, fernandes-cunha gm, myung d. simultaneous interpenetrating polymer network of collagen and hyaluronic acid as an in situ-forming corneal defect filler. chem mater 2020;32:5208–5216. 10. chen f, le p, fernandes-cunha gm, heilshorn sc, myung dj. bio-orthogonally crosslinked hyaluronatecollagen hydrogel for suture-free corneal defect repair. biomaterials 2020;255:120176. 11. kretschmer f, tariq m, chatila w, wu b, badea tc. comparison of optomotor and optokinetic reflexes in mice. j neurophysiol 2017;118:300–316. 12. thomas bb, samant dm, seiler mj, aramant rb, sheikholeslami s, zhang k, et al. behavioral evaluation of visual function of rats using a visual discrimination apparatus. j neurosci methods 2007;162:84–90. 13. blanco-mezquita jt, hutcheon aek, stepp ma, zieske jd. αvβ6 integrin promotes corneal wound healing. invest ophthalmol vis sci 2011;52:8505–8513. 550 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 new trephine for rodent studies; le et al 14. schulz d, iliev me, frueh be, goldblum d. in vivo pachymetry in normal eyes of rats, mice and rabbits with the optical low coherence reflectometer. vis res 2003;43:723–728. 15. iglesia dd, stepp ma. disruption of the basement membrane after corneal debridgement. invest ophthalmol vis sci 2000;41:1045–1053. 16. hirata h, mizerska k, dallcasagrande v, guaiquil vh, rosenblatt mi. acute corneal epithelial debridement unmasks the corneal stromal nerve responses to ocular stimulation in rats: implications for abnormal sensations of the eye. j neurophysiol 2017;117:1935–1947. 17. hutcheon ae, sippel kc, zieske jd. examination of the restoration of epithelial barrier function following superficial keratectomy. exp eye res 2007;84:32–38. 18. stepp ma, zieske jd, trinkaus-randall v, kyne bm, palghosh s, tadvalkar g, et al. wounding the cornea to learn how it heals. exp eye res 2014;121:178–193. 19. mohan rr, stapleton wm, sinha s, netto mv, wilson se. a novel method for generating corneal haze in anterior stroma of the mouse eye with the excimer laser. exp eye res 2008;86:2. 20. khakshoor h, mehran zg, ladan s. mechanical superficial keratectomy for corneal haze after photorefractive keratectomy with mitomycin c and extended wear contact lens. cornea 2011;30:117–120. 21. puliafito ca, steinert rf, deutsch tf, hillenkamp f, dehm ej, adler cm. excimer laser ablation of the cornea and lens: experimental studies. ophthalmology 1985;6:741– 748. 22. xia lk, yu j, chai gr, wang d, yang l. comparison of the femtosecond laser and mechanical microkeratome for flap cutting in lasik. int j ophthalmol 2015;8:784–790. 23. castro n, gillespie sr, bernstein am. ex vivo corneal organ culture model for wound healing studies. j vis exp 2019;144:e58562. 24. mobaraki m, abbasi r, vandchali so, ghaffari m, moztarzadeh f, mozafari m. corneal repair and regeneration: current concepts and future directions. front bioeng biotechnol 2019;7:135. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 551 review article ocular manifestations of the sturge–weber syndrome kiana hassanpour1,2, md, mph; ramin nourinia1, md; ebrahim gerami1, md; ghavam mahmoudi1, md hamed esfandiari3, md 1ophthalmic research center, research institute for ophthalmology and vision science, shahid beheshti university of medical sciences, tehran, iran 2department of ophthalmology, labbafinejad medical center, shahid beheshti university of medical sciences, tehran, iran 3department of ophthalmology, northwestern university feinberg school of medicine, chicago, il, usa orcid: kiana hassanpour: http://orcid.org/0000-0002-1788-7352 ramin nourinia: http://orcid.org/0000-0002-2630-1069 abstract sturge–weber syndrome (sws) or encephalotrigeminal angiomatosis is a non-inherited congenital disorder characterized by neurologic, skin, and ocular abnormalities. a somatic activating mutation (r183q) in the gnaq gene during early embryogenesis has been recently recognized as the etiology of vascular abnormalities in sws. approximately, half of the patients with sws manifest ocular involvement including glaucoma as the most common ocular abnormality followed by choroidal hemangioma (ch). the underlying pathophysiology of glaucoma in sws has not been completely understood yet. early onset glaucoma comprising 60% of sws glaucoma have lower success rates after medical and surgical treatments compared with primary congenital glaucoma. primary angle surgery is associated with modest success in the early onset sws glaucoma while the success rate significantly decreases in late onset glaucoma. filtration surgery is associated with a higher risk of intraoperative and postoperative choroidal effusion and suprachoroidal hemorrhage. ch is reported in 40–50% of sws patients. the goal of treatment in patients with ch is to induce involution of the hemangioma, with reduction of subretinal and intraretinal fluid and minimal damage to the neurosensory retina. the decision for treating diffuse chs highly depends on the patient’s visual acuity, the need for glaucoma surgery, the presence of subretinal fluid (srf), its chronicity, and the potential for visual recovery. keywords: choroidal hemangioma; glaucoma; ocular manifestations; sturge-weber syndrome j ophthalmic vis res 2021; 16 (3): 415–431 introduction sturge–weber syndrome (sws) or encephalotrigeminal angiomatosis is a rare correspondence to: ramin nourinia, md. labbafinejad medical center, department of ophthalmology, paidarfard st., boostan 9 st., pasdaran, tehran 16666, iran. email: ramin.retin@gmail.com received: 05-07-2020 accepted: 08-04-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i3.9438 congenital disorder that mainly affects the brain, skin, and eyes. the complete spectrum of sws is characterized by leptomeningeal hemangioma, facial angiomatosis or port-wine stain (pws), and ocular abnormalities.[1] roach et al classified sws into three types: type 1 (the most common) includes leptomeningeal and this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: hassanpour k, nourinia r, gerami e, mahmoudi g, esfandiari h. ocular manifestations of the sturge–weber syndrome. j ophthalmic vis res 2021;16:415–431. © 2021 hassanpour et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 415 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i3.9438&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr sturge-weber syndrome; hassanpour et al facial angioma with or without glaucoma; type 2 presents with facial angioma as the most prominent manifestation with or without glaucoma, but no brain involvement; leptomeningeal angioma is the only manifestation of type 3, the rarest type, that is frequently diagnosed by brain scans.[2] sws occurs sporadically with an incidence ranging from 1 in 20,000 to 50,000 live births. no race or gender predilection has been identified. despite a few familial clusters, sws is considered non-hereditary.[3] children with sws usually present with pws or nevous flammeus as a congenital birthmark. pws occurs in 3 per 1,000 births as a red or pink macula on the forehead, frequently unilateral. however, only 5–15% of children with pws show other features of sws.[4, 5] v1 or v2 distribution of pws, the original description of pws, has been recently challenged by waelchli et al.[6] they proposed that facial involvement follows embryological vasculature rather than trigeminal nerve distribution.[6] neurologic signs and symptoms including seizure, headache, stroke-like episodes, hemiparesis, visual field deficits, and cognitive impairment variably present throughout life. seizure is often the initial neurologic presentation in 80% of sws patients, starting in the first year of life.[7] mental retardation is also a common neurologic feature.[8, 9] the eye is found to be affected in approximately half of the patients with sws. in the present review, we aim to further discuss the ocular manifestations of sws with emphasis on glaucoma and diffuse choroidal hemangioma (ch) as the two most common ocular complications. methods we searched medline using pubmed and google scholar, reviewing articles published between 1970 and 2020. our keywords included multiple combinations of “sturge-weber syndrome”, “glaucoma”, “pathophysiology”, and “pathogenesis”. the following medical subject headings (mesh) were also used. • sturge-weber syndrome/complications* • sturge-weber syndrome/physiopathology* • sturge-weber syndrome/surgery* • sturge-weber syndrome/therapy* • disease management* • glaucoma*/diagnosis • glaucoma*/etiology • glaucoma*/therapy • humans • intraocular pressure/physiology* • sturge weber syndrome • syndrome, sturge-weber the articles were reviewed and only articles published in english language with available fulltexts were included in the present study. pathophysiology of sws most sws manifestations result from vascular abnormalities. there are mainly two hypotheses proposed primarily to explain vascular malformations in sws. the first hypothesis assumes a genetic mutation affecting vascular regulation during early embryogenesis, while the second hypothesis emphasizes on the role of a focal vascular dysplasia in the brain and subsequent involvement of the overlying eye and skin. shirly et al[10] found a somatic activating mutation (r183q) in the gnaq gene which produces a protein (g alpha subunit q) regulating the signaling process that results in cell proliferation and inhibition of apoptosis. the mutation is also reported in the pws blood vessels, either in isolation or associated with sws.[11–13] the sporadic inheritance of the disease supports the occurrence of a somatic mutation that does not affect the germline. the primitive vascular plexus enters the brain, skin, and eye in the first trimester.[14] therefore, somatic mutation within this interval correlates well with the clinical signs of sws. parsa et al proposed a local primary venous dysplasia in the brain as the primary insult. consequently, collateral venous vessels transmit venous hypertension to the overlying eye and skin causing choroidal vascular anomalies and pws, respectively.[15] parsa’s hypothesis does not contradict the occurrence of a somatic mutation like gnaq, however, it is unable to completely explain the bilateral pws and absence of brain involvement in some patients with sws.[14] ocular manifestations a significant portion of the patients with sws present with ocular involvement, especially 416 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 sturge-weber syndrome; hassanpour et al figure 1. left image shows conjunctival and episcleral abnormal tortuous vessels in a patient with sturge-weber syndrome. presence of blood in the schlemm’s canal in gonioscopy of the same patient. figure 2. left image shows diffuse choroidal hemangioma as diffuse dark and saturated red areas making “tomato-ketchup appearance” in the fundus of a patient with sturge-weber syndrome. severe exudative retinal detachment is evident in optical coherence tomography images of the same patient. glaucoma. table 1 summarizes the ocular manifestations of sws [table 1].[16] glaucoma glaucoma remains the most common ocular complication of sws, which occurs in 30–70% of the patients. glaucoma in sws has a bimodal presentation: early onset glaucoma in 60% of the cases and late onset glaucoma in 40% of patients. the mechanism of early onset glaucoma is not determined yet but is attributed to abnormal angle development. while the appearance of the angle shares common abnormalities with primary congenital glaucoma including the anterior iris insertion to the trabecular meshwork (tm), direct attachment of the ciliary muscles to the tm rather than to the scleral spur, and increased opacification of tissues of the angle,[17] the exact site of pathology is not identified. some distinct characteristics of angle in sws include flat iris insertion in some parts of the angle,[18] prominent vascular loops at the iris root, and the presence of blood in schlemm’s canal [figure 1].[17, 19] in a histopathologic study, rosenbaum et al did not find any tm abnormality with light and electron microscopic examination but abnormal vessels were present in all of their four cases.[20] the link between early onset glaucoma and sws could be explained with the fact that sws is primarily a vascular abnormality and there is a strong body of evidence that suggests sc and collector channels are developed from a venous plexus in early weeks of gestation.[21] therefore, it is plausible to think that the resistance to outflow in early onset glaucoma is located in the distal outflow pathway. the less than favorable response to angle surgery in these cases also supports more distal pathology rather than tm. there is not enough evidence regarding the role of elevated episcleral venous pressure (evp) in early onset glaucoma; engorged vessels that are seen in adult onset glaucoma have not been reported in early onset glaucoma. since the collagen fibers are more elastic in early years of life, these children often develop secondary structural changes such as globe journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 417 sturge-weber syndrome; hassanpour et al table 1. summary of ocular findings in sturge-weber syndrome[16] orbital general proptosis lids ptosis port-wine birthmarks of eyelid extraocular sclera nevoid marks or vascular dilation of the episclera large, anomalous vessels in the episclera dilation and tortuosity of episcleral vessels episcleral hemangiomas conjunctiva conjunctival telangiectasia conjunctival hemangiomas dilation and tortuosity of conjunctival vessels large, anomalous vessels in the conjunctiva intraocular anterior segment increased corneal diameter iris discoloration telangiectasia of the iris with heterochromia dilation and tortuosity of the iris vessels sluggish pupils anisocoria or other disturbances in pupil reactions deep anterior chamber angle glaucoma ectopia lentis choroid choroidal hemangioma angioid streaks retina dilation and tortuosity of retinal vessels retinal arteriovenous aneurysm varicosity of retinal veins glioma retinal detachment central retinal vein occlusion optic nerve arteriovenous angioma papilledema optic atrophy optic nerve cupping optic nerve drusen other strabismus nystagmus loss of vision cortical blindness abnormal visual field due to the lesions in visual pathway anisometropia 418 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 sturge-weber syndrome; hassanpour et al table 2. summary of important studies investigating different surgeries in the treatment of glaucoma associated with sturgeweber syndrome author, year surgery no. of eyes no. of patients age at surgery (mean ±±± sd, and/or range) outcome length of follow-up (mean ±±± sd, and/or range) wagner et al[40] 1988 trabeculotomy combined with cyclotherapy 6 5 three weeks to nine years all achieved controlled iop two patients needed additional surgery average 4.5 years from three to eight years iwach et al[38] goniotomy[49] trabeculotomy[9] trabeculectomy[21] 20 eyes early onset 16 eyes late onset 30 patients not separately reported median stable time for goniotomy and medical therapy 101 months. for trabeculotomy 21 months for trabeculectomy 23 months mean 10 years range: 2–21 years olsen et al[39] 1998 goniotomy trabeculotomy 12 4 14 mean 10 ± 4 months zero days to four years iop ≤ 22 mm hg in 66.7% of the eyes after one or more goniotomy or trabeculotomy 5.4 years range: 1.4–15 years wu et al[44] 2017 trabeculotomy ab externo 34 32 median (iqr) = 3 months (1.25, 6.75) cumulative proportion of overall success: 94.1%, 90.5%, 86.6%, 86.6%, and 86.6% at three months, six months, one year, two years, and three years, respectively median (iqr) = 15.5 months (9.50, 25.50) irkec et al[37] 1999 trabeculotomy and guarded filtration surgery 6 5 between 23 days and 9 years lowered iop in five eyes; two eyes needed additional medical therapy 6.3 range: 2–11 years sood et al[46] 2017 combined trabeculotomy and trabeculectomy 22 20 mean 18.64 ± 29.74 months 0.7–96 months 41.7% (10/24) of eyes qualified and modified qualified success no complete success mean sd 134.73 ± 67.77 months 61–288 months board and shields[48] (1981) combined trabeculotomy and trabeculectomy 5 5 two months to fifteen years despite postoperative iop control, it increased in three patients who had longer follow-ups no additional surgeries were needed median 11 months 6–36 months journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 419 sturge-weber syndrome; hassanpour et al table 2. continued. author, year surgery no. of eyes no. of patients age at surgery (mean ±±± sd, and/or range) outcome length of follow-up (mean ±±± sd, and/or range) agarwal et al[47] 1993 combined trabeculotomy and trabeculectomy 18 16 mean 17.8 months range: birth–7 years (≤22 mm hg) in 11 eyes (61.1%) 42 months range: 1–8 years mandal et al[45] 1999 combined trabeculotomy and trabeculectomy 10 9 1.5 ± 3.0 years range: 1 month–9 years all eyes maintained a postoperative iop < 16 mmhg without medication 27.6 ± 16.4 months range: 12–64 months ali et al[49] 1990 trabeculectomy 7 6 mean 22.42 years range: 7–38 years two eyes w/o meds four eyes with meds one eye needed repeat trabeculectomy nine months to nine years mohamed et al[54] 2018 trabeculectomy with mmc with ologen 10 10 8 8 3–5 years complete and qualified success in 80% and 20% in mmc, 70% and 20% in ologen 12 months hamush et al[56] 1999 ahmed glaucoma valve implantation 10 9 10 days–25.5 years only three >10 years cumulative probability of success of 79%, 59%, and 30% at 24, 42, and 60 months, respectively mean 910.5 days (sd 6 574.1 days) kaushik et al[57] 2019 ahmed glaucoma valve implantation 24 18 7.91 ± 5.02 range: 1–15 cumulative probability of success rate was 75% 2.12 ± 0.87 years budenz et al[58] 2000 baerveldt glaucoma implantation 10 9 six weeks and thirteen years all eyes had adequate iop control (≤21 mmhg) without the need for additional glaucoma surgery 35 months range: 10–50 amini et al[59] 2007 molteno drainage device 9 7 9.6 +/– 3.7 years range: 5–17 years the cumulative probability of success was 97.2% at 12 months, 78.02% at 24 months, and 43.34% at the final follow-up 32 +/– 4.7 months range: 20–36 months 420 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 sturge-weber syndrome; hassanpour et al table 2. continued. author, year surgery no. of eyes no. of patients age at surgery (mean ±±± sd, and/or range) outcome length of follow-up (mean ±±± sd, and/or range) audren et al[55] 2006 non-penetrating deep sclerectomy 9 9 eleven days to twenty-four years success rates (including no need for anti-glaucoma medications) were 56%, 28%, and 0% at 6, 13, and 26 months post surgery 26.3 months range: 6–48 months table 3. summary of important studies investigating different treatment strategies in diffuse choroidal hemangioma associated with sws. only studies with more than three cases were included author, year treatment modality no. of eyes age at surgery (mean ±±± sd, and/or range) outcome randon et al[76] 2018 external beam radiotherapy (20 gy in 10 fractions) 26 eyes of 25 patients five years (4–41) years reduced tumor thickness (4.5 mm, 2.7 mm at the last visit) resolved retinal detachment in all except two schilling et al[77] 1999 external beam radiotherapy (20 gy) 15 eyes of 12 patients with diffuse ch 18.3 years exudative rd resolution shrinkage of the tumor was seen in five eyes arepalli et al[82] 2013 plaque brachytherapy (iodine-125 plaque) 5 eyes 13 years median 11 range: 11–27 years complete regression of srf in all cases zografos et al[81] 1998 proton beam radiotherapy 6 eyes with diffuse ch not reported resolution of exudative rd tumor regression enlargement, tears in descemet’s membrane, and corneal edema. elevated evp secondary to episcleral and choroidal vascular abnormalities contribute to lateonset glaucoma. evp normally ranges between 8 and 10 mmhg. the exact relationship between chronic evp rise and iop is yet to be determined; however, chronically untreated elevated evp can increase the iop and remains the primary mechanism of glaucoma in etiologies like carotidcavernous fistula, thyroid ophthalmopathy, and late-onset glaucoma in sws. in support of this pathophysiology, phelps et al[18] investigated evp in 12 patients with sws. the mean evp (±sd) was 18.1 ± 6.4 mm that was significantly higher than an average of 9.1 ± 1.6 mm hg in the normal fellow eyes. subsequently, shiau et al[22] confirmed their findings in 22 eyes with sws. the possible role of sc and collector channels dysfunction which could potentially exacerbate the effect of high evp in adult glaucoma has not been evaluated. accelerated aging of the angle structures has been reported in pathological investigations of late-onset glaucoma. first proposed by cibis et al, a similar mechanism like primary open-angle glaucoma is also considered as the underlying mechanism.[17] it is not clear if these changes are primary or develop in response to long-term high iop. angle closure glaucoma has also been reported in sws, although significantly less common than open-angle mechanism. murayama et al[23] reported a 14-year-old boy with unilateral acute angle closure glaucoma secondary to posterior journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 421 sturge-weber syndrome; hassanpour et al scleritis in sws. they postulated swelling of the ciliary body, choroidal effusion, anterior rotation of the ciliary processes, and swelling of the lens to be the underlying mechanism of angle closure. ectopia lentis[24] and angle neovascularization secondary to retinal pathologies[25] have been reported to contribute to angle-closure glaucoma in sws. diagnosis all infants born with pws should undergo thorough and frequent ophthalmic examinations. repeat ophthalmic examinations every few months during the first years of life are recommended. iop measurement in all sessions is mandatory even if the angle structure appears normal. if no sign of glaucoma is detected, an annual ophthalmic checkup is recommended.[26] the risk of glaucoma is associated with the pattern of pws and is estimated to be 25% with a large unilateral pws and 35% with bilateral involvement.[27, 28] it is notable that nearly 40% of sws patients have bilateral pws.[29] glaucoma treatment glaucoma management in sws is challenging and depends on the onset of the disease and the underlying pathophysiology. while medical therapy is usually tried as first-line therapy for early onset glaucoma, surgery is ultimately needed for the majority of the patients. medical management remains the first choice in the late-onset glaucoma in sws. medical treatment aqueous suppressants (beta-blockers and carbonic anhydrase inhibitors) and the outflow facilitators such as prostaglandin analogs have been successfully used. agents lowering evp are the potential future drugs that are not currently available.[22] awad et al[30] reviewed 22 eyes with mostly early onset glaucoma (20 eyes) and found that antiglaucoma medications successfully controlled the iop in only seven eyes of five patients within 62 months of follow-up. van emelen et al[31] retrospectively reviewed the records of 19 sws patients with the mean age of 8.2 years. eight patients developed glaucoma (eight eyes with early onset glaucoma vs one eye with lateonset glaucoma). seven out of eight patients (87.5%) treated by beta-blockers and carbonic anhydrase inhibitors needed glaucoma surgery to lower the iop. latanoprost is the most frequently investigated hypotensive agent.[32–34] yang et al[34] used latanoprost in six sws glaucoma with the age ranging from 4 to 19 years. only two eyes that had juvenile onset glaucoma responded to latanoprost with a mean iop reduction of 8.8 mm hg. similarly, altuna et al[32] investigated latanoprost in 18 sws patients with the mean age of 19.7 ± 12.4 years and reported a success rate of 16.7% (3 of 18 patients) at the six-months follow-up. the causes for failure in this study were glaucoma surgery (seven patients), additional medical therapy (three patients), and intolerable conjunctival hyperemia (one patient). in another study by ong et al, 17 eyes with sws glaucoma who started on latanoprost were retrospectively evaluated. the mean age of the patients at the onset of glaucoma diagnosis and the latanoprost start was 2.59 and 6.8 years, respectively. fifty percent of the patients achieved successful outcomes after one year. however, treatment failure was reported as early as one month after the start of latanoprost in five (29.4%) patients.[33] wagnanski et al[35] investigated the effect of oral propranolol (2 mg/kg) on iop in four sws infants with age ranging from 8 to 44 weeks. despite iop reduction at one week after the initiation of the treatment, iop increased to an average of 20.7 (range 14–30) mmhg after one month. subsequently, kaushik et al[36] used oral propranolol (2 mg/kg divided into two doses) one week before glaucoma surgery in sws patients. these studies indicate that while oral propranolol temporarily lowers the iop and can potentially be useful perioperatively, it is not suitable for long term in sws glaucoma. surgical treatment in glaucoma unresponsive to medical treatment, the choice of surgery needs to be decided on a case by case basis. some surgeons prefer angle surgery as the primary operation in early onset glaucoma.[39, 40] while the exact pathology of early onset glaucoma in sws is not determined, several studies reported favorable outcomes with goniotomy or trabeculotomy.[37–40] angle surgery 422 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 sturge-weber syndrome; hassanpour et al removes the resistance at the level of tm and enhances the outflow through the physiologic pathways. studies investigating goniotomy or trabeculotomy as the initial surgical procedure report modest efficacy. iwach et al[38] reviewed angle surgery in 20 eyes with early onset and 16 eyes with late-onset sws glaucoma. they reported the median stable time after a single goniotomy to be eight months in early onset glaucoma. however, it increased to nearly nine years after multiple goniotomies and adjunctive medical therapy. they found significantly shorter stable period in patients older than four years after goniotomy. furthermore, trabeculectomy was performed in 21 eyes and achieved a stable duration interval with a median of 26 months. additionally, 40% in the early onset and 17% in the late-onset group experienced choroidal effusion. considering the higher rates of complications after trabeculectomy, the authors recommended goniotomy as the initial surgical choice in early onset sws glaucoma. in another study by olsen et al,[39] 16 eyes of 14 patients with sws glaucoma were studied. all patients were under four years of age. twelve eyes underwent goniotomy while four eyes received trabeculotomy. two-third of patients in the goniotomy group and half of the patients in the trabeculotomy group required a second procedure. one or more angle procedures resulted in iop control in 66.7% of the patients after a median follow-up of 5.4 years. wu et al[41] retrospectively reviewed the clinical outcomes of trabeculutomy ab externo in 34 eyes with sws glaucoma. the median age of patients at the time of surgery was three months. complete (without any need for further glaucoma medications) and qualified (with the use of topical medications) success was achieved in 86.6% and 66%, respectively, with a median follow-up of 15.5 months. the authors concluded early diagnosis of glaucoma in sws patients might lead to higher surgical success after trabeculotomy ab externo. nevertheless, angle surgeries in sws glaucoma achieve lower success rates compared with primary congenital glaucoma.[42] most individuals will need further surgeries or adjunctive medications to achieve the target iop.[43] lower success rate of angle surgery in sws indicates resistance in more distal outflow pathway. wu et al[44] showed that individuals with multiple episcleral vascular abnormal networks responded poorly to trabeculotomy compared to individuals with a simple episcleral vascular abnormal network. their study supports a role for vessel-related factors in early onset glaucoma. gonioscopy before any angle surgery is recommended in sws to look for the landmarks of the angle as well as the presence of blood in the sc. the risk of intraoperative or postoperative hyphema varies between 25% and 88.2% after trabeculotomy in different studies.[37–39, 41] combined trabeculotomy/trabeculectomy as the initial operation has been suggested in early onset glaucoma to address more distal resistance.[45–48] recently, sood et al[46] reported combined trabeculotomy/trabeculectomy in 24 eyes of 20 patients with sws glaucoma with the overall success rate of 41.7% within 134.7 ± 67.7 months follow-up. board and shields investigated combined trabeculotomy/trabeculectomy in five sws patients with the age ranging from 2 months to 15 years. median length of follow-up was 11 months. three patients with a longer duration of follow-up experienced iop increase, however, none of the patients underwent additional surgeries. in another study, the records of combined trabeculotomy/trabeculectomy was reviewed in 10 eyes of which 9 had early onset sws glaucoma with the mean age of 1.5 ± 3 years. postoperative iop remained <16 mmhg in all patients within the mean follow-up period of 27.6 ± 16.4 months.[45] similarly, agarwal et al[47] investigated combined trabeculotomy/trabeculectomy in 18 eyes with sws glaucoma. eleven eyes (61.1%) had iop ≤22 mm hg after a mean follow-up of 42 months. three patients underwent repeat surgeries. trabeculectomy remains an important surgical option in late-onset glaucoma associated with sws. ali et al[49] reported favorable outcomes with trabeculectomy in six patients with late-onset glaucoma (mean age of 22.4 years) in nine months to nine years of follow-up. nevertheless, four patients needed additional medical treatment and one patient underwent repeat trabeculectomy. in sws patients, there is a serious risk of choroidal effusion or expulsive hemorrhages after trabeculectomy. iwach et al[38] reported intraoperative choroidal effusions in 24% of cases undergoing trabeculectomy including 40% of five cases in the early onset group and 17% of 12 cases of the late-onset group. direct communication between the arteriolar system and choroidal vasculature, without any intervening vascular journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 423 sturge-weber syndrome; hassanpour et al bed, results in a high choroidal vascular pressure. this high pressure is opposed by an increased iop associated with increased evp. when the iop is reduced during the filtration surgery, the unopposed high choroidal vascular pressure causes choroidal effusion.[38] the mechanism underlying choroidal effusion is similar to effusion formation observed with significant iop reduction after glaucoma surgery, which results in rapid transudation of fluid from the intravascular spaces into the extravascular space.[50] however, faster formation, more massive effusions, and higher prevalence are observed after filtration surgeries in patients with sws.[48, 51] accordingly, the presence of ch poses the eyes at a greater risk of both intraoperative or postoperative choroidal effusions. pandey et al[52] reported that 83.3% of the eyes that developed choroidal effusion had ch. regardless of ch, higher choroidal vascular pressure and also vascular abnormalities such as abnormal vascular innervation[7] and significant fragility[51] make these patients more susceptible to choroidal effusion or hemorrhage. to reduce the risk of choroidal effusion or expulsive hemorrhage, various modifications during surgery have been reported. prophylactic posterior sclerotomy has been traditionally used by many surgeons.[43] however, eibschitztimoshi et al questioned the need for sclerotomy after investigating 17 eyes undergoing trabeculectomy.[53] the authors reported no significant suprachoroidal hemorrhage and effusion in surgeries with modern techniques. measurements such as generous use of viscoelastic devices for ac formation, maximum preoperative iop control, prophylactic radiotherapy or laser photocoagulation of the ch are recommended to prevent the suprachoroidal hemorrhage.[43] in a randomized clinical trial, mohamed et al compared the outcomes of mitomycin-c (mmc) augmented trabeculectomy and collagen matrix implant (ologen) in the management of glaucoma in sws.[54] twenty eyes of 16 sws glaucoma patients with the age ranging from three to five years were divided into two groups. complete and qualified success accounted for 80% and 20%, respectively, of patients in the mmc group after one year, while the corresponding values in the ologen group were 70% and 20%, respectively. complications in the mmc group included polycystic bleb in six patients, blebitis in one patient, and shallow anterior chamber in two eyes. despite failure in 10%, the complication rate was minimal in the ologen group. while physical spacers could improve the long-term outcomes of bleb function, these biodegradable implants could simultaneously act as physical resistance against overfiltration in the early postoperative days which is beneficial in offsetting suprachoroidal hemorrhage in sws patients. non-penetrating surgeries like deep sclerectomy serve as alternatives to trabeculectomy. these modalities hypothetically lower the risk of choroidal effusion because of lower fluctuation of iop during the procedures. audren et al[55] investigated non-penetrating deep sclerectomy in a series of nine eyes. the success rates without additional need for medical treatment were 56%, 28%, and 0% at 6, 13, and 26 months after surgery, respectively. however, two eyes developed choroidal effusion after npds. glaucoma drainage devices have been effectively used in sws glaucoma. hamush et al implanted ahmad glaucoma valve (agv) in 11 sws glaucoma patients.[56] the cumulative probability of success was 79%, 59%, and 30% at 24, 42, and 60 months, respectively. similarly, kaushik et al reported the results of agv implantation in 24 eyes of 20 patients.[57] the cumulative probability of success was 75% with a mean follow-up of 2.12 ± 0.87 years. reported complications included intraoperative hyphema in four (16.67%) eyes, hypotony in three (12.5 %) eyes, and choroidal detachment in three eyes. budenz et al studied two-staged baerveldt glaucoma implantation in 10 eyes of nine patients and reported adequate iop control in all operated eyes (≤21 mmhg) without the need for additional glaucoma surgery.[58] amini et al investigated molteno implantation in nine eyes of seven patients.[59] the cumulative probability of relative success was 97.2% at 12 months, 78.02% at 24 months, and 43.34% at the final follow-up. postoperatively, massive choroidal effusion occurred in three patients which needed surgical drainage. two eyes experienced bleb encapsulation and underwent needling bleb revision with 5-fluorouracil. visually significant cataract and corneal endothelial touch prompting tube repositioning occurred in two patients, respectively. cyclodestructive procedures are usually limited to the eyes with low visual potential or eyes at 424 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 sturge-weber syndrome; hassanpour et al higher risk of intraoperative complications.[40] however, van emelen et al used it as the primary surgical option in seven eyes with sws glaucoma.[31] the authors found that cyclodestructive procedures reduced the iop to <22 mm hg in six of the seven eyes with a mean duration of 4.5 years. the presence of episcleral hemangioma over the ciliary body makes the procedure more challenging.[42] table 2 summarizes various surgical treatments in the glaucoma associated with sws. regardless of surgery types, patients need frequent and close follow-up examinations. complications such as choroidal effusion and hypotony should be treated accordingly because chronically untreated choroidal effusions often lead to bleb failure or reduced visual acuity. laser treatment of facial pws raised the concern of increasing iop through the reduction of vascular channels serving to balance the venous pressure gradient.[15] sharan et al retrospectively compared 28 cases that underwent facial laser treatment and patients without laser treatment and did not find any difference between groups in terms of newly developed or exacerbating glaucoma.[60] choroidal hemangioma (ch) ch, arising from choroidal vasculature, is a benign vascular tumor classified into two types of circumscribed and diffuse. diffuse ch invariably correlates with sws; patients with sws often develop a diffuse type of ch. however, circumscribed ch has been occasionally reported in sws.[61, 62] the prevalence of diffuse ch is 40–50% and is usually ipsilateral to the pws.[63] diffuse ch is often detected during funduscopy as dark and saturated red area with the “tomato ketchup” appearance. symptomatic patients present with reduced visual acuity, scotoma or flashing, refractive error, serous or exudative retinal detachment, macular edema, and retinal pigment epithelium (rpe) alterations with macular involvement. histopathologic investigations of diffuse chs show some differences with circumscribed chs and reveal containing considerable numbers of the enlarged pre-existing vessel and vascular channels lined with endothelium and complete lack of cellular proliferation of vessel walls. areas of clustered vascular abnormalities mimicking circumscribed types have also been reported in diffuse hemangiomas.[64] diagnosis indirect ophthalmoscopy reveals the characteristic pattern of the fundus, so-called tomato ketchup appearance [figure 2].[65] ultrasound, both b-scan and a-scan mode, is routinely used to confirm the hemangioma diagnosis in sws patients. diffuse thickening of the choroid in b-scan combined with high internal reflectivity of a-scan spikes confirms diffuse ch diagnosis.[66] fluorescein angiography, though difficult in children, shows rapid and speckled hyperfluorescent areas in the early phases due to the choroidal and vascular nature of the tumor. similar to the circumscribed hemangiomas, though more widespread, staining with or without late leakage appears in the late phases.[67] however, fa is more helpful in adults and patients with circumscribed ch. indocyanine green (icg) angiography shows the extension, vascularity, and arteriovenous shunts of choroidal changes; but this is an invasive diagnostic modality and may not be used in all cases especially in children.[68] recently, enhanced depth optical coherence tomography (edi-oct) has been employed in the diagnosis of chs and following their response to treatment as well.[69] diffuse choroidal thickening in the involved eye and the fellow eye as well are observed by edi-oct.[70] surve et al investigated the role of swept-source optical coherence tomography (ss-oct) in a large series of 34 eyes of 17 sws patients.[71] ss-oct findings included loss of choroidal vascular pattern, increased choroidal thickness, and invisible sclerochoroidal interface. the authors reported a detection rate of 86.36% for ss-oct compared with 50% clinically, 52.94% with fa, and 82.35% with icg angiography. in addition, it has been shown that the outer retinal layers may be thinner in sws patients with ch.[72] a recent study reported small white dot-shaped “micro-drusen-like” changes of the retina in patients with diffuse ch.[73] furthermore, griffith et al showed ocular enhancement in magnetic resonance imaging of sws patients consistent with diffuse chs.[74] it has been shown that the ch on mri images looks like sickle-shaped enhanced regions, thickest over the posterior portion of the globe and thinner toward the ciliary body. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 425 sturge-weber syndrome; hassanpour et al the authors proposed mri may play a substantial role in the diagnosis of diffuse ch. the advantage of mri is that the children with sws require neuroimaging irrespective of ocular findings that can be combined with ophthalmic sequences.[75] management the goal of treatment in patients with chs is to induce involution of the hemangioma, with reduction of subretinal and intraretinal fluid and minimal damage of neurosensory retina. the decision for treating diffuse chs highly depends on the patients’ visual acuity, the need for glaucoma surgeries, the presence of srf and its chronicity and the visual recovery potential. treatment of chs may be difficult and therapeutic modalities may be limited because both juxtapapillary and foveal regions are often involved. the main risk of surgery in these cases is the increased risk of hemorrhage secondary to abnormal dilated episcleral and choroidal vasculature. various treatment modalities have been investigated including laser photocoagulation, plaque brachytherapy, external beam, proton beam, and stereotactic radiotherapy, photodynamic therapy (pdt), and anti-vegf injections. the primary goal of treatment remains the resolution of srf, however, treatment can also lead to the shrinkage of the ch mass. radiation-based modalities including external beam, plaque brachytherapy, proton beam, and stereotactic are rapidly expanding techniques. randon et al investigated external beam radiotherapy (20 gy in 10 fractions) in a large series (26 eyes of 25 patients) with diffuse ch.[76] the treatment resulted in tumor regression; the mean thickness reached from 4.5 mm at baseline to 2.8 mm in the first year, and 2.7 mm at the last visit. the retinal detachment was resolved in all except two patients. similarly, schilling et al reported the result of low-dose radiation therapy in ch.[77] their study included 15 eyes of 12 patients with diffuse ch associated with sws. the resolution of retinal detachment (in all patients) besides the shrinkage of the tumor (in five patients) was observed. many other small case series reported the promising result of ebrt.[78–80] other techniques of radiation have been investigated in diffuse ch treatments. proton beam radiation delivers an exact dose of radiation to a specific tissue. zografos et al used the proton beam to treat six eyes with diffuse ch. they reported full resolution of the srf in all of the treated eyes.[81] arepalli et al investigated plaque brachytherapy in five cases with diffuse ch associated with sws.[82] complete regression of srf was observed in all patients. the main drawback of these technologies remains the high cost and unavailability in many hospitals. furthermore, srf generally resorbs slower after radiation (over several months) compared with pdt. normal ocular tissues are also exposed to radiation doses with subsequent radiation-induced cataract, retinopathy, and optic neuropathy. however, the latter disadvantage occurs generally after ebrt and is reduced with other radiation-based treatments. pdt allows for selective occlusion of vascular structures by photochemical destruction of vascular endothelial cells. pdt with verteporfin showed promising results for circumscribed ch. correspondingly, multispot treatment has been applied in diffuse ch which causes the atrophy of the hemangioma vessels and reduces the leakage. various isolated case reports used pdt and consistently reported complete resolution of srf besides tumor involution.[83–87] the main advantage of pdt includes the selective nature of the treatment preserving the overlying retinal vasculature and rpe. currently, no significant complication has been reported with pdt. however, the studies investigating pdt in diffuse ch are usually small case series (to date <15 cases) that make concluding difficult. some studies showed reduction of srf after intravitreal injection of anti-vegf agents.[88] however, the continuous production of vegf leads to unsuccessful long-term results with anti-vegf therapy.[89] oral propranolol therapy was investigated in a few reports and revealed moderate effects in the resolution of exudative retinal detachment.[90] the mechanisms which have been proposed for propranolol as a treatment modality for hemangioma can be classified into short-, mid, and long-term effects. the most probable cause of the short-term effect is vasoconstriction. 426 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 sturge-weber syndrome; hassanpour et al blocking the release of proangiogenic factors such as vegf, bfgf, mmp-2, and mmp-9 may lead to mid-term effects. the long-term effects may be related to the induction of apoptosis in endothelial cells and subsequent tumor regression.[91, 92] serious side effects such as bradycardia and hypotension have been reported in cases using high-dose systemic propranolol. it has been shown that the intravitreal injection of propranolol leads to higher concentration of propranolol at the retinal level and lack of systemic side effects in comparison to the systemic usage of propranolol.[93, 94] the safe dose of intravitreal propranolol was determined in animal models and an experimental study showed that the intravitreal injection of propranolol was safe.[95] intravitreal propranolol has also been reported to be effective for the treatment of retinal angiomatosis.[96] in addition, nourinia et al successfully treated two cases of sws with exudative retinal detachment secondary to diffuse ch with an intravitreal injection of propranolol (unpublished data). other ocular abnormalities pws presents in the face of most patients with sws. vascular lesions on the eyelid, abnormal vascular lesions of the conjunctiva, episcleral hemangiomas, and dilated vessels of the retina are variably present in sws patients and all are often ipsilateral to the pws. abnormal conjunctival vessels may be diffuse or localized. the diffuse type usually makes a pink or red hue in the affected eye. iris heterochromia may also be present and is interestingly associated with a higher risk (45%) of ipsilateral glaucoma development.[16, 97] ocular melanocytosis and iris mammillations have also been reported in sws.[61, 98] combined cilioretinal artery occlusion and hemiretinal vein occlusion was reported in a nine-year old boy diagnosed with sws.[99] visual acuity results of 25 studies and visual field results of 12 studies were systematically reviewed to analyze the visual outcome of patients with sws. the authors reported that va was significantly reduced in 28% of eyes with glaucoma and 67% of eyes with diffuse ch. however, 70% of total sws patients have normal visual acuity. homonymous hemianopia was the most commonly reported visual field defect and was present in approximately 40% of the patients.[100] summary as the sws mainly affects the brain, skin, and the eyes, a multidisciplinary approach including the neurologic, ophthalmic, and dermatologic evaluations are essential in the management of the disease. all involved specialists may face challenges in diagnosis, treatment, and determining the prognosis in patients with sws. considering the rare nature of the disease, most studies focusing on sws are small case series. currently, most patients with glaucoma associated with sws need surgical management. since the lower success rates are achieved in these patients, the adjunctive medical therapy and the need for repeat surgeries should also be considered. the elucidation of the exact mechanism of glaucoma as the most common ocular complication can help better control of the disease. elevated evp as a possible mechanism in the early onset glaucoma needs more clinical and experimental investigations. if the role of elevated evp is further recognized, combined trabeculotomy and trabeculectomy can serve as the initial surgical procedure in the early onset glaucoma. moreover, medical interventions targeting the evp may have promising results. the effect of sws on the quality of life has been investigated with emphasis on neurological signs and symptoms[101] but the possible effect of ocular complications on the quality of life of these patients has not been evaluated. furthermore, the discovery of genetic mutations can be helpful in diagnosis and management of sws.[102] further recognition of mutations, the possible molecular and cellular interactions and their downstream proteins can be targeted as promising treatments.[103] biomarker development to detect the association between clinical symptoms and disease prognosis is another area of research. ocular involvement mostly diagnosed by optical coherence tomography will be a part of the future biomarkers.[104] financial support and sponsorship nil. conflicts of interest the authors do not have any conflicts of interest. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 427 sturge-weber syndrome; hassanpour et al references 1. thomas-sohl ka, vaslow df, maria bl. sturge-weber syndrome: a review. pediatr neurol 2004;30:303–310. 2. comi am, roach es, bodensteiner j. sturge-weber 5 syndrome. 2015. handbook of clinical neurology, elsevier; volume 132; pages 157-168 3. behrman re, vaughan vc. nelson textbook of pediatrics. j dev behav pediatr 1988;9:239–243. 4. ch’ng s, tan st. facial port-wine stains – clinical stratification and risks of neuro-ocular involvement. j plast reconstr aesthet surg 2008;61:889–893. 5. nguyen c, yohn j, huff c, weston w, morelli j. facial port wine stains in childhood: prediction of the rate of improvement as a function of the age of the patient, size and location of the port wine stain and the number of treatments with the pulsed dye (585 nm) laser. br j dermatol 1998;138:821–825. 6. waelchli r, aylett se, robinson k, chong wk, martinez ae, kinsler va. new vascular classification of port-wine stains: improving prediction of sturge-weber risk. br j dermatol 2014;171:861–867. 7. comi am. topical review: pathophysiology of sturgeweber syndrome. j child neurol 2003;18:509–516. 8. pascual-castroviejo i, díaz-gonzalez c, garcía-melian rm, gonzalez-casado i, muñoz-hiraldo e. sturgeweber syndrome: study of 40 patients. pediatr neurol 1993;9:283–288. 9. pascual-castroviejo i, pascual-pascual s-i, velazquezfragua r, viaño j. sturge-weber syndrome. study of 55 patients. can j neurol sci 2008;35:301–307. 10. shirley md, tang h, gallione cj, baugher jd, frelin lp, cohen b, et al. sturge–weber syndrome and port-wine stains caused by somatic mutation in gnaq. n engl j med 2013;368:1971–1979. 11. nakashima m, miyajima m, sugano h, iimura y, kato m, tsurusaki y, et al. the somatic gnaq mutation c.548g>a (p.r183q) is consistently found in sturge-weber syndrome. j hum genet 2014;59:691–693. 12. tan w, nadora dm, gao l, wang g, mihm jr mc, nelson js. the somatic gnaq mutation (r183q) is located within the blood vessels of port wine stains. j am acad dermatol 2016;74:380. 13. uchiyama y, nakashima m, watanabe s, miyajima m, taguri m, miyatake s, et al. ultra–sensitive droplet digital pcr for detecting a low–prevalence somatic gnaq mutation in sturge–weber syndrome. sci rep 2016;6:22985. 14. comi am. sturge–weber syndrome. in: islam mp, roach es, editors. handbook of clinical neurology. volume 132. elsevier; 2015. p. 157–168. 15. parsa cf. focal venous hypertension as a pathophysiologic mechanism for tissue hypertrophy, port-wine stains, the sturge–weber syndrome, and related disorders: proof of concept with novel hypothesis for underlying etiological cause (an american ophthalmological society thesis). trans am ophthalmol soc 2013;111:180–215. 16. levin av, enzenauer rw. the eye in pediatric systemic disease. springer; 2017. 17. cibis gw, tripathi rc, tripathi bj. glaucoma in sturgeweber syndrome. ophthalmology 1984;91:1061–1071. 18. phelps cd. the pathogenesis of glaucoma in sturgeweber syndrome. ophthalmology 1978;85:276–286. 19. mwinula jh, sagawa t, tawara a, inomata h. anterior chamber angle vascularization in sturge-weber syndrome. report of a case. graefes arch clin exp ophthalmol 1994;232:387–391. 20. rosenbaum lj. glaucoma in sturge-weber syndrome. birth defects orig artic ser 1982;18:645–649. 21. ramírez jm, ramírez ai, salazar jj, rojas b, de hoz r, triviño a. schlemm’s canal and the collector channels at different developmental stages in the human eye. cells tissues organs 2004;178:180–185. 22. shiau t, armogan n, yan db, thomson hg, levin av. the role of episcleral venous pressure in glaucoma associated with sturge–weber syndrome. j aapos 2012;16:61–64. 23. maruyama i, ohguro h, nakazawa m. a case of acute angle-closure glaucoma secondary to posterior scleritis in patient with sturge–weber syndrome. jpn j ophthalmol 2002;46:74–77. 24. su ww. acute primary angle-closure in sturge-weber syndrome. am j ophthalmol case rep 2018;10:101–104. 25. lee dh, shin j, seo jh, byon is, jung jh, lee je. mobile lens-induced angle closure glaucoma and rubeosis iridis in sturge weber syndrome. int j ophthalmol 2015;8:1080– 1082. 26. comi am. an overview of current and future treatment options for sturge–weber syndrome. expert opin orphan drugs 2014;2:1015–1025. 27. hennedige aa, quaba aa, al-nakib k. sturge-weber syndrome and dermatomal facial port-wine stains: incidence, association with glaucoma, and pulsed tunable dye laser treatment effectiveness. plast reconstr surg 2008;121:1173–1180. 28. piram m, lorette g, sirinelli d, herbreteau d, giraudeau b, maruani a. sturge–weber syndrome in patients with facial port-wine stain. pediatr dermatol 2012;29:32–37. 29. uram m, zubillaga c. the cutaneous manifestations of sturge-weber syndrome. j clin neuroophthalmol 1982;2:245–248. 30. awad ah, mullaney pb, al-mesfer s, zwaan jt. glaucoma in sturge-weber syndrome. j aapos 1999;3:40–45. 31. van emelen c, goethals m, dralands l, casteels i. treatment of glaucoma in children with sturge-weber syndrome. j pediatr ophthalmol strabismus 2000;37:29– 34. 32. altuna jc, greenfield ds, wand m, liebmann jm, taglia dp, kaufman pl, et al. latanoprost in glaucoma associated with sturge-weber syndrome: benefits and side-effects. j glaucoma 1999;8:199–203. 33. ong t, chia a, nischal k. latanoprost in port wine stain related paediatric glaucoma. br j ophthalmol 2003;87:1091–1093. 34. yang cb, freedman sf, myers js, buckley eg, herndon lw, allingham rr. use of latanoprost in the treatment of glaucoma associated with sturge-weber syndrome. am j ophthalmol 1998;126:600–602. 35. wygnanski-jaffe t, spierer a, melamed s, ben-zion i. the effect of oral propranolol on intraocular pressure in infants with sturge–weber syndrome glaucoma. eur j ophthalmol 2015;25:134–136. 428 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 sturge-weber syndrome; hassanpour et al 36. kaushik s, kataria p, joshi g, singh r, handa s, pandav ss, et al. perioperative propranolol: a useful adjunct for glaucoma surgery in sturge-weber syndrome. ophthalmol glaucoma 2019;2:267–274. 37. irkeç m, kiratli h, bilgiç s. results of trabeculotomy and guarded filtration procedure for glaucoma associated with sturge-weber syndrome. eur j ophthalmol 1999;9:99– 102. 38. iwach ag, hoskins jr hd, hetherington jr j, shaffer rn. analysis of surgical and medical management of glaucoma in sturge-weber syndrome. ophthalmology 1990;97:904– 909. 39. olsen ke, huang as, wright mm. the efficacy of goniotomy/trabeculotomy in early-onset glaucoma associated with the sturge-weber syndrome. j aapos 1998;2:365–368. 40. wagner r, caputo a, del rn, neigel j. trabeculectomy with cyclocryotherapy for infantile glaucoma in the sturgeweber syndrome. ann ophthalmol 1988;20:289–291, 295. 41. wu y, yu r, chen d, xu l, zhu l, li m, et al. early trabeculotomy ab externo in treatment of sturge-weber syndrome. am j ophthalmol 2017;182:141–146. 42. patrianakos td, nagao k, walton ds. surgical management of glaucoma with the sturge weber syndrome. int ophthalmol clin 2008;48:63–78. 43. javaid u, ali mh, jamal s, butt nh. pathophysiology, diagnosis, and management of glaucoma associated with sturge-weber syndrome. int ophthalmol 2018;38:409– 416. 44. wu y, peng c, ding x, zeng c, cui c, xu l, et al. episcleral hemangioma distribution patterns could be an indicator of trabeculotomy prognosis in young sws patients. acta ophthalmol 2020;98:e685–e690. 45. mandal ak. primary combined trabeculotomytrabeculectomy for the management of glaucoma associated with sturge–weber syndrome. ophthalmology 1999;106:1621–1627. 46. sood d, rathore a, sood i, kumar d, sood nn. longterm intraocular pressure after combined trabeculotomytrabeculectomy in glaucoma associated with sturgeweber syndrome. eur j ophthalmol 2018;28:210–215. 47. agarwal h, sandramouli s, sood n. sturge-weber syndrome: management of glaucoma with combined trabeculotomy-trabeculectomy. ophthalmic surg lasers imaging retina 1993;24:399. 48. board rj, shields mb. combined trabeculotomytrabeculectomy for the management of glaucoma associated with sturge-weber syndrome. ophthalmic surg lasers imaging retina 1981;12:813–817. 49. ali ma, fahmy ia, spaeth gl. trabeculectomy for glaucoma associated with sturge-weber syndrome. ophthalmic surg lasers imaging retina 1990;21:352– 355. 50. bellows ar, chylack jr lt, hutchinson bt. choroidal detachment: clinical manifestation, therapy and mechanism of formation. ophthalmology 1981;88:1107– 1115. 51. bellows ar, chylack lt, epstein dl, hutchinson bt. choroidal effusion during glaucoma surgery in patients with prominent episcleral vessels. arch ophthalmol 1979;97:493–497. 52. pandey a, balekudaru s, george r, lingam v, panday m. surgical management of glaucoma in sturge–weber syndrome. glauc open access 2015;1:1. 53. eibschitz-tsimhoni m, lichter pr, del monte ma, archer sm, musch dc, schertzer rm, et al. assessing the need for posterior sclerotomy at the time of filtering surgery in patients with sturge-weber syndrome. ophthalmology 2003;110:1361–1363. 54. mohamed th, salman ag, elshinawy rf. trabeculectomy with ologen implant versus mitomycin c in congenital glaucoma secondary to sturge weber syndrome. int j ophthalmol 2018;11:251. 55. audren f, abitbol o, dureau p, hakiki s, orssaud c, bourgeois m, et al. non-penetrating deep sclerectomy for glaucoma associated with sturge–weber syndrome. acta ophthalmol scand 2006;84:656–660. 56. hamush ng, coleman al, wilson mr. ahmed glaucoma valve implant for management of glaucoma in sturgeweber syndrome. am j ophthalmol 1999;128:758–760. 57. kaushik j, parihar jks, jain vk, mathur v. ahmed valve implantation in childhood glaucoma associated with sturge–weber syndrome: our experience. eye 2019;33:464–468. 58. budenz dl, sakamoto d, eliezer r, varma r, heuer dk. two-staged baerveldt glaucoma implant for childhood glaucoma associated with sturge-weber syndrome. ophthalmology 2000;107:2105–2110. 59. amini h, razeghinejad mr, esfandiarpour b. primary single-plate molteno tube implantation for management of glaucoma i children with sturge–weber syndrome. int ophthalmol 2007;27:345–350. 60. sharan s, swamy b, taranath da. port-wine vascular malformations and glaucoma risk in sturge–weber syndrome. j aapos 2009;13:374–378. 61. abdolrahimzadeh s, scavella v, felli l, cruciani f, contestabile mt, recupero sm. ophthalmic alterations in the sturge–weber syndrome, klippel-trenaunay syndrome, and the phakomatosis pigmentovascularis: an independent group of conditions. bio med res int 2015;2015:786519. 62. formisano m, abdolrahimzadeh b, mollo r, bruni p, malagola r, abdolrahimzadeh s. bilateral diffuse choroidal hemangioma in sturge weber syndrome: a case report highlighting the role of multimodal imaging and a brief review of the literature. j curr ophthalmol 2019;31:242– 249. 63. ferry a, combs j. other phakomatoses. retina 2001;1:596–600. 64. witschel h, font rl. hemangioma of the choroid. a clinicopathologic study of 71 cases and a review of the literature. surv ophthalmol 1976;20:415–431. 65. shanmugam pm, ramanjulu r. vascular tumors of the choroid and retina. indian j ophthalmol 2015;63:133. 66. scott iu, alexandrakis g, cordahi gj, murray tg. diffuse and circumscribed choroidal hemangiomas in a patient with sturge-weber syndrome. arch ophthalmol 1999;117:406–407. 67. horgan n, o’keefe m, mcloone e, lanigan b. fundus fluorescein angiographic characterization of diffuse choroidal hemangiomas. j pediatr ophthalmol strabismus 2008;45:26–30. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 429 sturge-weber syndrome; hassanpour et al 68. giovannini a, scassellati-sforzolini b, d’altobrando e, mariotti c, rutili t, tittarelli r. choroidal findings in the course of idiopathic serous pigment epithelium detachment detected by indocyanine green videoangiography. retina 1997;17:286–293. 69. shields cl, manalac j, das c, saktanasate j, shields ja. review of spectral domain enhanced depth imaging optical coherence tomography of tumors of the choroid. indian j ophthalmol 2015;63:117. 70. arora ks, quigley ha, comi am, miller rb, jampel hd. increased choroidal thickness in patients with sturgeweber syndrome. jama ophthalmol 2013;131:1216–1219. 71. surve a, azad s, venkatesh p, kumar v, chawla r, gupta v, et al. choroidal vascular pattern in cases of sturge-weber syndrome. ophthalmol retina 2019;3:1091–1097. 72. abdolrahimzadeh s, felli l, plateroti am, perdicchi a, contestabile mt, recupero sm. spectral domain optical coherence tomography evidence of retinal nerve fiber layer and ganglion cell loss in adult patients with neurofibromatosis type 1. retina 2016;36:75–81. 73. abdolrahimzadeh s, parisi f, mantelli f, perdicchi a, scuderi g. retinal pigment epithelium–photoreceptor layer alterations in a patient with sturge–weber syndrome with diffuse choroidal hemangioma. ophthalmic genet 2017;38:567–569. 74. griffiths pd, boodram mb, blaser s, altomare f, buncic jr, levin av, et al. abnormal ocular enhancement in sturge-weber syndrome: correlation of ocular mr and ct findings with clinical and intracranial imaging findings. am j neuroradiol 1996;17:749–754. 75. griffiths p. sturge-weber syndrome revisited: the role of neuroradiology. neuropediatrics 1996;27:284–294. 76. randon m, lévy-gabriel c, abbas r, dendale r, lumbroso l, desjardins l, et al. results of external beam radiotherapy for diffuse choroidal hemangiomas in sturge–weber syndrome. eye 2018;32:1067–1073. 77. schilling h, sauerwein w, lommatzsch a, friedrichs w, brylak s, bornfeld n, et al. long term results after low dose ocular irradiation for choroidal haemangiomas. br j ophthalmol 1997;81:267–273. 78. ritland j, eide n, tausjø j. external beam irradiation therapy for choroidal haemangiomas. visual and anatomical results after a dose of 20 to 25 gy. acta ophthalmol scand 2001;79:184–186. 79. grant lw, anderson c, macklis rm, singh ad. low dose irradiation for diffuse choroidal hemangioma. ophthalmic genet 2008;29:186–188. 80. gottlieb jl, murray tg, gass jdm. low-dose external beam irradiation for bilateral diffuse choroidal hemangioma. arch ophthalmol 1998;116:815–817. 81. zografos l, egger e, bercher l, chamot l, munkel g. proton beam irradiation of choroidal hemangiomas. am j ophthalmol 1998;126:261–268. 82. arepalli s, shields cl, kaliki s, emrich j, komarnicky l, shields ja. diffuse choroidal hemangioma management with plaque radiotherapy in 5 cases. ophthalmology 2013;120:2358–2359.e2. 83. anand r. photodynamic therapy for diffuse choroidal hemangioma associated with sturge weber syndrome. am j ophthalmol 2003;136:758–760. 84. bains hs, cirino ac, ticho bh, jampol lm. photodynamic therapy using verteporfin for a diffuse choroidal hemangioma in sturge–weber syndrome. retina 2004;24:152–155. 85. hussain rn, jmor f, damato b, heimann h. verteporfin photodynamic therapy for the treatment of choroidal haemangioma associated with sturge-weber syndrome. photodiagnosis photodyn ther 2016;15:143–146. 86. singh a, rundle p, vardy s, rennie i. photodynamic therapy of choroidal haemangioma associated with sturge–weber syndrome. eye 2005;19:365–367. 87. tsipursky ms, golchet pr, jampol lm. photodynamic therapy of choroidal hemangioma in sturge-weber syndrome, with a review of treatments for diffuse and circumscribed choroidal hemangiomas. surv ophthalmol 2011;56:68–85. 88. shoeibi n, ahmadieh h, abrishami m, poorzand h. rapid and sustained resolution of serous retinal detachment in sturge-weber syndrome after single injection of intravitreal bevacizumab. ocul immunol inflamm 2011;19:358–360. 89. wong wt, liang kj, hammel k, coleman hr, chew ey. intravitreal ranibizumab therapy for retinal capillary hemangioblastoma related to von hippel-lindau disease. ophthalmology 2008;115:1957–1964.e3. 90. thapa r, shields cl. oral propranolol therapy for management of exudative retinal detachment from diffuse choroidal hemangioma in sturge-weber syndrome. eur j ophthalmol 2013;23:917–919. 91. lamy s, lachambre m-p, lord-dufour s, béliveau r. propranolol suppresses angiogenesis in vitro: inhibition of proliferation, migration, and differentiation of endothelial cells. vasc pharmacol 2010;53:200–208. 92. ristori c, filippi l, dal monte m, martini d, cammalleri m, fortunato p, et al. role of the adrenergic system in a mouse model of oxygen-induced retinopathy: antiangiogenic effects of β-adrenoreceptor blockade. invest ophthalmol vis sci 2011;52:155–170. 93. martini d, monte md, ristori c, cupisti e, mei s, fiorini p, et al. antiangiogenic effects of β2−adrenergic receptor blockade in a mouse model of oxygen−induced retinopathy. j neurochem 2011;119:1317–1329. 94. mains j, tan le, wilson c, urquhart a. a pharmacokinetic study of a combination of beta adrenoreceptor antagonists–in the isolated perfused ovine eye. eur j pharma biopharma 2012;80:393–401. 95. nourinia r, kanavi mr, kaharkaboudi a, taghavi si, aldavood sj, darjatmoko sr, et al. ocular safety of intravitreal propranolol and its efficacy in attenuation of choroidal neovascularization. invest ophthalmol vis sci 2015;56:8228–8235. 96. karimi s, nikkhah h, ahmadieh h, safi s. intravitreal injection of propranolol for the treatment of retinal capillary hemangioma in a case of von hippel-lindau. retin cases brief rep 2020;14:305–309. 97. aggarwal nk, gandham sb, weinstein r, saltzmann r, walton ds. heterochromia iridis and pertinent clinical findings in patients with glaucoma associated with sturge– weber syndrome. j pediatr ophthalmol strabismus 2010;47:361–365. 98. plateroti am, plateroti r, mollo r, librando a, contestabile mt, fenicia v. sturge-weber syndrome associated with 430 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 sturge-weber syndrome; hassanpour et al monolateral ocular melanocytosis, iris mammillations, and diffuse choroidal haemangioma. case rep opthalmol 2017;8:375–384. 99. bakri ss, jomar d, alsulaiman sm, abouammoh ma. combined cilioretinal artery and hemi-retinal vein occlusion in sturge weber syndrome: expanding the clinical spectrum. saudi j ophthalmol 2018;32:234–237. 100. koenraads y, van egmond−ebbeling mb, de boer jh, imhof sm, braun kp, porro gl, et al. visual outcome in sturge–weber syndrome: a systematic review and dutch multicentre cohort. acta ophthalmol 2016;94:638–645. 101. lo w, marchuk da, ball kl, juhász c, jordan lc, ewen jb, et al. updates and future horizons on the understanding, diagnosis, and treatment of sturge–weber syndrome brain involvement. dev med child neurol 2012;54:214– 223. 102. alejandro j, luat af, juhász c, ho ml, argersinger dp, cavuoto km, et al. a multidisciplinary consensus for clinical care and research needs for sturge-weber syndrome. pediatr neurol 2018;84:11–20. 103. nguyen v, hochman m, mihm mc, nelson js, tan w. the pathogenesis of port wine stain and sturge weber syndrome: complex interactions between genetic alterations and aberrant mapk and pi3k activation. int j mol sci 2019;20:2243. 104. comi am, sahin m, hammill a, kaplan eh, juhász c, north p, et al. leveraging a sturge-weber gene discovery: an agenda for future research. pediatr neurol 2016;58:12–24. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 431 original article ideal illumination for smartphone-based trabeculectomy bleb photography gagan kalra1, mbbs; parul ichhpujani1, ms; sahil thakur2, ms; urvashi sharma1, b optom 1department of ophthalmology, government medical college and hospital, sector-32, chandigarh, india 2department of ocular epidemiology, singapore eye research institute, singapore orcid: gagan kalra: https://orcid.org/0000-0002-3367-3047 parul ichhpujani: https://orcid.org/0000-0001-6256-4002 abstract purpose: ophthalmology has seen numerous novel uses for smartphones over the years including fundus photography, telemedicine, and operative videography. however, anterior segment photography for assessing and documenting trabeculectomy bleb morphology using a smartphone has not been explored in detail. with the current study, we aim to characterize ideal illumination for the anterior segment smartphone photography in trabeculectomy patients. methods: thirty status post-trabeculectomy patients were enrolled in this study. native camera application and filmic pro camera application were used on iphone x to compare bleb images using yellow and white pen-torches as illumination source. measured bleb area was compared using imagej software from the two apps in different illumination settings by charting boxplots and using one-way anova test using r software to establish consistency. bland-altman interoperability for repeatability of blebarea measurements was analyzed by plotting bland-altman plots. signal-to-noise ratio was calculated using imagej for native camera images using slit-lamp camera images as reference. subjective rating of these images was then performed by two experienced ophthalmologists and kappa coefficient was calculated for inter-operator repeatability. statistical analysis was performed. results: the measured bleb area from images taken from both apps showed no significant difference, thereby establishing consistency, and bland-altman analysis indicated good repeatability and reproducibility. it was noted that snr was lower for images shot in close illumination as compared to the ones shot in intermediate and distant illumination. cohen’s kappa coefficient was 0.7 for images with distant illumination using white light and 0.65 for images clicked with illumination at an intermediate distance using yellow light, suggesting substantial agreement between the observers. conclusion: smartphone photography is a reliable tool for morphological assessment trabeculectomy blebs. optimal illumination helps achieve results free from digital noise and better delineation of specific morphological features. intermediate illumination and distant illumination provides much better results in terms of high snr while avoiding overexposure and clipping of highlight information in the images. keywords: bleb; smartphone photography; teleophthalmology; trabeculectomy j ophthalmic vis res 2021; 16 (3): 357–366 © 2021 kalra et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 357 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i3.9432&domain=pdf&date_stamp=2019-07-17 smartphone bleb photography; kalra et al introduction recent technology and advances in optics of smartphones has persuaded ophthalmologists to use smartphones for numerous novel purposes including fundus photography, telemedicine, operative videography, ophthalmological teaching, training, ophthalmic screening in an emergency setting, etc.[1–4] the novelty of using smartphones in ophthalmic practice lies in the widespread availability, affordability, and network accessibility that they bring to the table.[5, 6] these applications have the ability to decentralize expert care from a tertiary care center and make it accessible to primary care peripheral centers by the means of tele-ophthalmology.[7] there are multiple studies that demonstrate the effectiveness and safety of smartphones for ophthalmological applications.[5, 6, 8] however, anterior segment photography for assessing and documenting trabeculectomy bleb morphology using a smartphone has not been explored in much detail. currently, there are no objective guidelines directing appropriate illumination parameters for the ocular surface for better smartphone-based trabeculectomy bleb morphology assessment. in the current study, we attempt to characterize the same. methods this pilot observational study compared the impact of alteration in illumination in terms of distance from ocular surface and color of light source on iphone x-assisted trabeculectomy bleb photography. thirty patients who had undergone trabeculectomy for refractory primary open or angle closure glaucoma and registered in glaucoma clinic of department of ophthalmology, government medical college and hospital, chandigarh, india were enrolled in the study after obtaining written, informed consent in their correspondence to: parul ichhpujani, ms. department of ophthalmology, government medical college and hospital, sector-32, chandigarh 160030, india. e-mail: parul77@rediffmail.com received: 02-08-2020 accepted: 10-05-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i3.9432 vernacular language. this study conforms to the tenets of declaration of helsinki. equipment the native ios camera app with automatic focusing exposure control was used and the results were compared with those with a third-party camera app – filmic pro (cinegenix llc, seattle, wa, usa; http://filmicpro.com/) that allowed precise manual control for parameters like focus assist, iso, and shutter speed. we chose filmic pro app as it has been previously validated for use in ocular photography.[1, 6, 9] a 5-watt yellow led pen-torch and a white led pen-torch (with single fresh aaa battery) were used. by increasing the distance between the light source and the ocular surface, illumination was changed from close (4 cm) to intermediate (7 cm) to distant illumination (12 cm), in order to evaluate the impact of light source distance on image quality. our null hypothesis was that there would be no significant difference in the bleb area measured on smartphone imaging with variation in light color and illumination distance. lux light meter pro app (elena polyanskaya) for iphone was used to quantify the changes in the light intensity (in foot-candles [fc]) at the ocular surface for each scenario. a 15-cm surgical ruler (viscot medical, llc) held by an assistant was used to measure all distances from the outer canthus of the patient’s eye as a landmark to standardize the distances in this study. smartphone photography each patient underwent smartphone photography (same photographer, gk) in the same examination room with a fluorescent tube-light (luminous flux: 2500 lm; power 36w; lamp current: 0.44a; 103v) facing patient’s back. the details of the session were discussed with the patient in order to avoid any menace reflex. the room had no windows to avoid any optical interference. as examiner retracted the upper eyelid, the patient was asked to this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: kalra g, ichhpujani p, thakur s, sharma u. ideal illumination for smartphone-based trabeculectomy bleb photography. j ophthalmic vis res 2021;16:357–366. 358 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 https://knepublishing.com/index.php/jovr http://filmicpro.com/ smartphone bleb photography; kalra et al fix gaze in downward direction in order to minimize discomfort from the light source. initially, three illumination readings were taken at the superior bulbar conjunctiva without any additional light source using the lux light meter pro app by keeping the iphone steady at a fixed distance (focusing distance) in front of the eye, and the mean of three readings was calculated to account for the ambient light in the examination room and that came out to be 21.5 lux. an assistant (us) then held a pen torch with yellow light against the measuring scale placed at the outer canthus of the eye [figure 1] at close, intermediate, and distant illumination sequentially, and sets of three illumination readings (in fc) were obtained from the ocular surface using the lux light meter pro app. images were then obtained from iphone x in the three lighting scenarios using no attachment and keeping the iphone steady at the minimum focusing distance from the ocular surface. subsequently, the exercise was repeated using a pen torch with white light. image processing the images obtained from the native app were shot with the iphone x (1×) optical lens at 12.0 mp (4000×3000 pixels) resolution with focusing and exposure locked by pressing and holding on the area of interest and then dragging down to adjust exposure. images were obtained as high-quality screen captures from the 4k (3840×2160 pixels) 60 fps video recordings from the filmic pro app on the iphone x. for the filmic pro video recording, grades analyzed both the unedited video and the still frames. audio was removed from the video recording to eliminate bias. mean of the three fc readings obtained by the exercise was corrected for ambient lighting by subtracting the mean lux readings of the ambient light from the mean lux readings obtained from the exercise. the corrected readings [table 1] for each lighting scenario were used to quantify and standardize the illumination from the chosen light sources. the images from the two apps were set to scale in the imagej software using the ruler captured in all images [figure 2]. subsequently, bleb area was annotated on the scaled images inside of imagej using the “free form selection” tool, twice by the senior ophthalmologist (pi). the annotation of the images was carried out on microsoft surface pro 4 (microsoft inc.) device using the new surface pen which has 4,000 levels of pressure sensitivity and 0.2 ms latency. data analysis data of bleb area from the images was compiled and indexed for different lighting scenarios in a microsoft excel data sheet. differences in bleb area in white light and yellow light for the three distances between filmic–filmic images, native– native images, and native–filmic pro images were analyzed for all 30 patients with an objective of ensuring repeatability and reproducibility. one-way anova was used to compare mean differences between the different scenarios, namely wl f–yl f, wl n–yl n, wl n–yl f at three different distances. this gives 8º of freedom and 261 residuals for 30 observations each. anova test was run on the dataset for differences in measured bleb areas in different lighting scenarios of all 30 patients using r software and p-values for all scenarios elucidated in table 2. bland–altman agreement test was used to assess agreement on bleb area measurement in different lighting scenarios between two graders and plots were compiled (supplementary data). accounting for low light and image noise signal-to-noise ratio (snr) was chosen as the parameter of choice as an objective measure of image quality in terms of image noise due to low light.[10] a reference image was chosen from images collected from a slit-lamp camera as this allowed comparison with the gold standard. as highlighted earlier, the images from the two different apps had slightly different resolutions and to prevent this from affecting results, the native app images were all cropped to match the resolution of images obtained from the slitlamp camera. snr was then calculated for all the images in the native camera app sample using the imagej software with the snr plugin (written by daniel sage at the biomedical image group, epfl, switzerland) wherein low snr means higher noise than reference image and vice-versa. accounting for overexposure and glaring manual evaluation of all patients’ images in the three illumination settings were done by two journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 359 smartphone bleb photography; kalra et al figure 1. bleb image being captured using smartphone. table 1. corrected illumination readings from the ocular surface using the lux light meter pro app for iphone obtained by holding iphone x at the focusing distance from the ocular surface foot-candle (fc) readings using the lux light meter pro app for iphone illumination light source close intermediate distant yellow light 301.392 lux (28 fc) 129.162 lux (12 fc) 43.056 lux (4 fc) white light 290.628 lux (27 fc) 118.404 lux (11 fc) 32.292 lux (3 fc) table 2. significance level (p-values) difference in bleb areas using anova test in different lighting scenarios hhhhhhhhhhhhhhhhhhscenarios distance from the ocular surface close (4 cm) p-value intermediate (7 cm) p-value distant (12 cm) p-value wl f–yl f 0.5691 0.6623 0.0460 wl n–yl n 0.7390 0.3525 0.4393 wl n–yl f 0.9911 0.9639 0.0559 wl f, white light filmic; yl f, yellow light filmic; wl n, white light native; yl n, yellow light native; wl f, white light filmic; yl n, yellow light native 360 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 smartphone bleb photography; kalra et al figure 2. native camera app images: (a) close, (b) intermediate, (c) distant with yellow pen torch; (d) close, (e) intermediate, (f) distant with white pen torch; filmic pro app images: (g) close, (h) intermediate, (i) distant with yellow pen torch; (j) close, (k) intermediate, (l) distant with white pen torch. table 3. exif data for the images obtained at the focusing distance from the native camera app on iphone x hhhhhhhhhhhhhhhhhcamera parameters illumination setting close illumination (4 cm) intermediate illumination (7 cm) distant illumination (12 cm) iso (absolute value) 16–20 20–30 30–50 shutter-speed (in seconds) 1/250–1/331 1/120–1/200 1/80–1/100 table 4. snr analysis summary for different lighting scenarios, namely close, intermediate, and distant parameter close intermediate distant mean 1.261726 2.210459762 2.812866 standard error 0.089813 0.123797842 0.138773 median 1.187366 2.09632066 2.914794 standard deviation 0.701462 0.958933961 1.065938 sample variance 0.492049 0.919554341 1.136225 difference in mean snr close-intermediate intermediate-distant close-distant p-value 3.83e-13 5.93651e-06 4.37e-15 difference 0.9 0.6 1.5 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 361 smartphone bleb photography; kalra et al figure 3. box-plots for differences in measured bleb area in six different lighting scenarios for native camera application: (a) whitelight close filmic vs yellow-light close filmic; (b) white-light close native vs yellow-light close native; (c) white-light close filmic vs yellow-light close native; (d) white-light intermediate filmic vs yellow-light intermediate filmic; (e) white-light intermediate native vs yellow-light intermediate native; (f) white-light intermediate filmic vs yellow-light intermediate native; (g) white-light distant filmic vs yellow-light distant filmic; (h) white-light distant native vs yellow-light distant native; and (i) white-light distant filmic vs yellow-light distant native. experienced ophthalmologists (pi and st) twice (in the second round the order of presentation of images was changed) and images were rated from ex1 to ex5. ex1 represented gross overexposure where bleb morphology was completely obliterated; ex2 represented mild overexposure wherein bleb morphology was somewhat retained; ex3 represented the ideal exposure wherein all morphological features of the bleb were best assessed; ex4 represented mild underexposure wherein bleb features were dark but visible; and ex5 represented underexposure wherein bleb features were too dark to assess. results the exif data from the images obtained using the native camera app varied over ranges [table 3] instead of a specific value as the imaging parameters cannot be prefixed using the native camera app. even though this was the case, the overall trend does reflect the changes in illumination as with decreasing illumination the iso ranges increase and the shutter speed ranges decrease.[11] the parameters on the filmic pro app were manually set for closest focusing distance, lowest possible iso value of 22, and a fast shutter speed of 1/144 s. the minimum iso setting possible on iphone x was chosen as it ensured minimal noise in the image. a fast shutter speed was chosen as it allowed the images to be shot without motion blur in the three illumination settings. the results of bleb area analysis reflect that there was no significant difference in measuring bleb area from the images obtained in the three illumination settings using both the apps. one-way anova results indicate that there is no significant difference in bleb area measurement amongst groups as p-value > 0.05 and there is failure to reject null hypothesis. class-wise significance was also calculated and is summarized in table 1. bland-altman analysis for bleb area measurement 362 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 smartphone bleb photography; kalra et al figure 4. supplementary data: bland-altman plots for bleb area measurement between two graders for all eyes included in this study under different lighting scenarios. between two graders (pi and gk) indicated that all measurements fell between +0.08 and –0.06 mm2 of the mean bleb area. the plots are shown in supplementary data. cohen’s kappa coefficient for subjective rating was 0.7 for images with distant illumination using white light and 0.65 for images clicked with illumination at an intermediate distance using yellow light, suggesting significant agreement between the observers in these scenarios. results from the snr analysis snr for images at various distances is summarized in table 4. images taken at close distance had significantly lower snr compared to intermediate (snr difference = 0.9, p < 0.001) and distant (snr difference = 1.5, p < 0.001) illumination. there was no significant difference between intermediate and distant illumination (snr difference = 0.6, p < 0.001). discussion with advances in smartphone technology, the application of smartphones in ophthalmology has increased manifold all around the world, especially in the developing countries due to limited access to more sophisticated equipment such as slitlamp camera, anterior segment oct, or other complex imaging methods.[7, 12–14] applications in telemedicine, tele-teaching, and archiving have become much more accessible as a result of upcoming smartphone-based photography techniques that enable a reliable examination of different parts of the eye.[7, 12–14] the native camera app on iphone has automatic exposure metering wherein it self-adjusts the image parameters such as shutter-speed, iso etc., to compensate for decreasing illumination. we know that the digital camera sensors are able to achieve the best image quality at their native iso level (lowest iso setting).[11] same holds true for the 1.22 um 12 mp pdaf sensor on iphone x with ois (optical image journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 363 smartphone bleb photography; kalra et al stabilization). automatic exposure metering on the native app increases iso levels and decreases the shutter speed for decrease in scenic illumination. this results in loss in image quality, substantial increase in image noise, and introduction of motion blur. the image quality on iphone x, with its newer optics and a11 bionic processor, showed high level of compensation for changing illumination especially when using the tap to focus and exposure box. however, as per the newton’s inverse square law, intensity of electromagnetic waves, emitted from a point source, is inversely proportional to the squared distance from the point source.[15] light intensity at a given point ∝ 1/𝑅2, where r is the distance of the given point from the point source. bleb area measurement did not show statistically significant difference between different lighting scenarios. this establishes good consistency of smartphone-based bleb photography using illumination settings presented in this study. blandaltman analysis indicated good inter-operator reliability thereby establishing reproducibility of the results. this is particularly relevant for bleb morphology assessment as these images may be reliably used for partial ibags classification or wuerzburg classification of bleb morphology.[16–18] snr measures of native app images in different illumination settings clearly reflect the decreasing illumination as introduction of image noise is evident when illumination distance increases. also, the qualitative rating scale of the filmic pro app images demonstrates that image characteristics needed for bleb assessment do vary with changing illumination. our general observation was that the best results (high snr and ex: 2–4) were obtained from intermediate illumination settings (12 fc) as there was adequate illumination to prevent highiso levels while not exceeding the threshold to have caused glaring and overexposure. glare noted in 100/360 (28%) images under close illumination and underexposure seen in 30/360 (8%) images under distant illumination can be explained by the exponential increase in light intensity at the ocular surface by reducing the distance and vice-versa, respectively, in accordance to the inverse square law. therefore, we suggest that using the high shutter-speed setting can help expose correctly the overexposed area but it is harder to achieve uniform exposure of the entire field of interest as the area closer to the light source is heavily overexposed and the area slightly away is in shadow. this was noted in the close illumination native app images as automatic exposure metering results in higher shutter-speeds and gross underexposure of the shadow areas of the globe. the restricted dynamic range of smartphone cameras is an understandable reason for this limitation.[19] there are built-in tools like hdr mode (high dynamic range mode) that use advanced software processing to try to preserve details in highlights and shadows to overcome this limitation in exposure metering. however, there is also a considerable fall in snr with this due to exposure bracketing and therefore for our study we left this mode off. using high iso, as the native app does automatically and filmic pro does manually, may help achieve adequate exposure even in low light but this introduces digital noise in the image and thereby impedes complete assessment of the morphological features of the area of interest. small sensor size and processing within smartphones is an understandable reason for this limitation.[19] on the filmic pro app, we were able to demonstrate marked differences in illumination with our image sets as we had fixed all camera parameters to predecided values (iso: 22 and shutter-speed: 1/144) allowing for no automatic exposure compensation. the use of a thirdparty app that allows manual control of all camera parameters on iphone helped us overcome automatic exposure metering encountered on the native camera app, therefore allowing us to illustrate radical differences in image exposure with change in the intensity of incident ocular light. the more precise control of focus point, a very high shutter-speed, and a fixed low iso setting achieved using this third-party app enabled the highestquality images without motion blur with only variables being the illumination setting. the best results obtained were dramatically demonstrated with illumination at intermediate illumination range than from close or distant illumination where we observed overexposure or underexposure of the area of interest, respectively. snr is meaningless unless put in context using reference images. this application of snr as a quality metric has been implemented in the past for both imageand video-quality assessment.[20–22] the snr analysis in this study involved use 364 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 smartphone bleb photography; kalra et al of reference images from slit-lamp camera for comparison. this enabled comparison between image quality varying distance in different lighting scenarios. snr for the close illumination setting was significantly lower than other settings. this can be explained by the small zone of illumination in this setting that results in a large part of image receiving little to no light. more distanced illumination setting makes a more diffuse zone of illumination thereby resulting in more uniformly illuminated image hence the better snr. there were limitations to the current study. images obtained from the filmic pro app and the native iphone camera app had different native resolutions. this poses challenges that need processing like image resizing, binning, and scaling to enable comparisons. snr calculated for native app images in this study used images from a slit-lamp camera as reference. this enabled comparison of images obtained with iphone amongst themselves but posed challenges for comparing iphone images to slit-lamp images. snr was not calculated for filmic pro images as those were captured stills from 4k video images. a thirdparty app that captures images at native resolution would perhaps be better suited for comparison. in summary, anterior segment photography using the newer iphones has been successfully implemented for assessing trabeculectomy bleb morphology. using a third-party camera application provides added control over the image parameters and helps restrict the image noise although bleb area measurement did not have any statistically significant difference from the native camera application. ideal lighting is essential for ensuring optimal image quality and we found that distance illumination had the best snr. our subjective rating analysis indicated that distance illumination with white light is the ideal illumination for classification of bleb images. high snr was highly associated with better subjective rating from our graders. future research is warranted to expand upon utility of this imaging technique for illustrating a variety of bleb morphologies for a larger group of patients. smartphones have provided telemedicine opportunities that were not available in the past. with newer advances in camera technology in these mobile devices, high-resolution ocular imaging can be achieved. further research to develop better-quality metrics for standardization of testing is needed for these images. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. panwar n, huang p, lee j, keane pa, chuan ts, richhariya a, et al. fundus photography in the 21st century—a review of recent technological advances and their implications for worldwide healthcare. telemed j e health 2016;22:198– 208. 2. stanzel b, meyer c. smartphones in ophthalmology: relief or toys for physicians? ophthalmologe 2012;109:8–20. 3. chhablani j, kaja s, shah va. smartphones in ophthalmology. indian j ophthalmol 2012;60:127. 4. lord rk, shah va, san filippo an, krishna r. novel uses of smartphones in ophthalmology. ophthalmology 2010;117:1274.e3. 5. kumar s, wang e-h, pokabla mj, noecker rj. teleophthalmology assessment of diabetic retinopathy fundus images: smartphone versus standard office computer workstation. telemed j e health 2012;18:158– 162. 6. haddock lj, kim dy, mukai s. simple, inexpensive technique for high-quality smartphone fundus photography in human and animal eyes. j ophthalmol 2013;2013:518479. 7. mohammadpour m, heidari z, mirghorbani m, hashemi h. smartphones, tele-ophthalmology, and vision 2020. int j ophthalmol 2017;10:1909–1918. 8. kim dy, delori f, mukai s. smartphone photography safety. ophthalmology 2012;119:2200–2201. 9. myung d, jais a, he l, blumenkranz ms, chang rt. 3d printed smartphone indirect lens adapter for rapid, high quality retinal imaging. j mob technol med 2014;3:9–15. 10. hasinoff sw, durand f, freeman wt. noise-optimal capture for high dynamic range photography. in: 2010 ieee computer society conference on computer vision and pattern recognition; 2010; p. 553–560. 11. petschnigg g, szeliski r, agrawala m, cohen m, hoppe h, toyama k. digital photography with flash and no-flash image pairs. acm trans graph 2004;23:664–672. 12. collon s, chang d, tabin g, hong k, myung d, thapa s. utility and feasibility of teleophthalmology using a smartphone-based ophthalmic camera in screening camps in nepal. asia pac j ophthalmol 2020;9:54. 13. ludwig ca, newsom mr, jais a, myung dj, murthy si, chang rt. training time and quality of smartphone-based anterior segment screening in rural india. clin ophthalmol 2017;11:1301. 14. prasanna p, jain s, bhagat n, madabhushi a. decision support system for detection of diabetic retinopathy using smartphones. in: 2013 7th international conference on pervasive computing technologies for healthcare and workshops; 2013; p. 176–179. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 365 smartphone bleb photography; kalra et al 15. goats gc. appropriate use of the inverse square law. physiotherapy 1988;74:8. 16. kalra g, ichhpujani p, thakur s, singh rb, sharma u, kumar s. a pilot study for smartphone photography to assess bleb morphology and vasculature posttrabeculectomy. int ophthalmol 2021;41:483–490. 17. cantor lb, mantravadi a, wudunn d, swamynathan k, cortes a. morphologic classification of filtering blebs after glaucoma filtration surgery: the indiana bleb appearance grading scale. j glaucoma 2003;12:266–271. 18. furrer s, menke mn, funk j, töteberg-harms m. evaluation of filtering blebs using the ‘wuerzburg bleb classification score’compared to clinical findings. bmc ophthalmol 2012;12:24. 19. hasinoff sw, sharlet d, geiss r, adams a, barron jt, kainz f, et al. burst photography for high dynamic range and low-light imaging on mobile cameras. acm trans graph 2016;35:192. 20. behrendt ff, schmidt b, plumhans c, keil s, woodruff sg, ackermann d, et al. image fusion in dual energy computed tomography: effect on contrast enhancement, signal-tonoise ratio and image quality in computed tomography angiography. invest radiol 2009;44:1–6. 21. sijbers j, scheunders p, bonnet n, van dyck d, raman e. quantification and improvement of the signal-tonoise ratio in a magnetic resonance image acquisition procedure. magn reson imaging 1996;14:1157–1163. 22. wang zj, yamamura j, keller s. signal-to-noise ratio assessment of muscle diffusion tensor imaging using single image set and validation by the difference image method. br j radiol 2019;92:20190133. 366 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 surgical technique the use of tutoplast as an adjunct in scleral buckle procedure in patients with extremely thin sclera matthew r. starr, md; sophie j. bakri, md department of ophthalmology, mayo clinic, rochester, mn, usa orcid: matthew r. starr: https://orcid.org/0000-0002-3021-5630 abstract extremely thin sclera often necessitates abortion of scleral buckle procedures. in patients in whom a scleral buckle is desired, previous techniques have included the use of cyanoacrylate glue and continuing with surgery or placing donor tissue over the areas of thin sclera, but this can delay surgery. this was a retrospective review of three patients with thin sclera encountered during scleral buckling procedures. all patients had tutoplast pericardial graft placed over the areas of thin sclera which allowed the scleral buckle to be sutured onto the tutoplast rather than the thin sclera. tutoplast pericardial graft is a useful adjunct in scleral buckle procedures with extremely thin sclera, and a scleral buckle can be safely placed over it and lead to successful retinal reattachment. keywords: retinal detachment; scleral buckle; scleral thinning; scleromalacia j ophthalmic vis res 2021; 16 (3): 521–523 introduction encountering thin sclera during retinal detachment surgery can pose a significant problem, particularly when a scleral buckle is to be performed. sternberg and colleagues pioneered the use of sutureless scleral buckling in 1988 with the use of cyanoacrylate glue.[1] previous reports had glued the buckle directly onto the sclera which did not allow the surgeons to adjust the buckle. sternberg et al described fixing a series of plates with belt loops to the sclera using cyanoacrylate glue with which the buckle could be threaded through and then further adjusted. other reports correspondence to: matthew r. starr, md. department of ophthalmology, mayo clinic, 200 first st., southwest rochester, mn 55905. e-mail: mstarr1724@gmail.com received: 14-02-2021 accepted: 11-04-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i3.9448 have discussed the use of donor scleral tissue to repair thin sclera, but delaying retinal detachment surgery.[2] we present three patients who during retinal detachment surgery were noted to have extremely thin sclera. rather than avoiding a scleral buckle, tutoplast pericardial graft (katena products inc., denville, nj) was used to reinforce the sclera and continue with the scleral buckle procedure. tutoplast is a dehydrated, processed pericardium from human donor tissue that is converted into a multidirectional, collagen tissue matrix with a thickness of 400 microns.[3] it is meant to use for the repair, replacement, reconstruction, or augmentation of soft tissue. this research complied with hipaa and the declarations of this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: starr mr, bakri sj. the use of tutoplast as an adjunct in scleral buckle procedure in patients with extremely thin sclera. j ophthalmic vis res 2021;16:521–523. © 2021 mathew and bakri. this is an open access article distributed under the creative commons attribution license | published by knowledge e 521 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i3.9448&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr tutoplast for sb; mathew and bakri figure 1. intraoperative external photograph of an 80-year-old female during placement of a scleral buckle showing extensive scleral thinning in the superotemporal quadrant (a). additional scleral thinning was noted inferotemporally as well (b). figure 2. intraoperative external photograph of the same patient in figure 1 showing tutoplast covering the extensive scleral thinning superotemporally with 7-0 vicryl sutures tacking the tutoplast to thicker sclera at each corner (a). a horizontal mattress suture using 5-0 nylon is then placed within the tutoplast and not in the sclera itself (b). the suture is then tied around the scleral buckle (a–c) and the knot is rotated inferiorly (c). helsinki. consent to publish these findings and images were gathered from the patients. surgical method for all three patients, a conjunctival peritomy was performed 360º at the limbus and bluntly dissected down to bare sclera. the tenon was then bluntly dissected in all four quadrants. the four rectus muscles were then looped and isolated using 2-0 silk suture. the scleral quadrants were inspected, and there was found to be extensive scleral thinning in one or more quadrants in all three eyes [figures 1a and 1b]. in all patients, tutoplast pericardial graft was placed over the areas of thin sclera in order to facilitate the placement of the scleral buckle. the size of the tutoplast was adjusted in order to be large enough to avoid passing a suture through the thin sclera. the tutoplast was sutured onto the sclera with one 7-0 vicryl suture in each of the corners with the sutures placed where the sclera was noticeably thicker [figure 2a]. a 287 scleral buckle with a 240 band was then looped underneath the four rectus muscles and over the tutoplast. subsequently, a 5-0 nylon suture was placed in a mattress fashion within the tutoplast with the sutures 9 mm apart [figures 2a–2c]. the nylon sutures were tied and the knot was rotated posteriorly. the remainder of the case was completed as normal and the tenon and conjunctival layers were closed over the tutoplast at the limbus without difficulty in all three patients. 522 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 tutoplast for sb; mathew and bakri results all three patients had concomitant vitrectomies at the time of the scleral buckle surgery with the use of endolaser with no cryotherapy performed. one patient detached one month following the scleral buckle, due to the development of proliferative vitreoretinopathy but then was successfully reattached with silicone oil (six years of follow-up) while the other two remained attached at the time of the last follow-up visit (three years of follow-up for both patients). discussion tutoplast is a viable alternative to donor tissue or glue when thin sclera is encountered during scleral buckling surgery. tutoplast can be readily stored in operating rooms and has a five year shelf life.[3] certainly, other procedures for retinal detachment repair such as a primary pars plana vitrectomy should be considered when thin sclera is encountered, but if a buckle is felt to be absolutely needed, tutoplast can be applied over the areas of thin sclera and offer support for the scleral buckle. as outlined by sternberg and colleagues, the use of cyanoacrylate adhesive is an additional means for affixing a scleral buckle to the sclera without the use of sutures or scleral tunnels.[1] certainly, this method may provide immediate adhesion, but long-term buckle placement may be a potential downfall. with the use of tutoplast, the patch graft is anchored to the sclera with sutures and then the buckle sutures are placed into the tutoplast itself, offering longterm viability. other sutureless buckling methods such as scleral tunnels are also not possible in patients with advanced scleromalacia due to the persistent perforation risk. finally, if only a single quadrant of sclera is thin, the use of sutures or tunnels in a triangular pattern for three-point fixation, rather than four-point, is possible, and can provide appropriate buckle support. in our series, one patient had already failed primary vitrectomy and thus was felt to require scleral buckle placement, while the other two had inferior pathology which was felt to be best supported with buckle placement in addition to pars plana vitrectomy and thus the decision was made to proceed with tutoplast-assisted scleral buckling. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. ethics approval: irb approval waived. consent to participate: consent to publish these findings and images were gathered from the patients. references 1. sternberg p jr, tiedeman j, prensky jg. sutureless scleral buckle for retinal detachment with thin sclera. retina 1988;8:247–249. 2. stunf s, lumi x, drnovsek-olup b. preserved scleral patch graft for unexpected extreme scleral thinning found at the scleral buckling procedure: a case report. indian j ophthalmol 2011;59:235–238. 3. katena products. tutoplast®pericardium � 4 x 5 cm [internet]. katena [cited 2019 july 1]. available from: https: //www.katena.com/tutoplastrpericardium-68252 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 523 https://www.katena.com/tutoplastrpericardium-68252 https://www.katena.com/tutoplastrpericardium-68252 perspective from the hypotheses to clinical evidence in retinal therapy bradley beatson, bs; j. fernando arevalo, md, phd wilmer eye institute, johns hopkins university school of medicine, baltimore, md orcid: bradley beatson: https://orcid.org/0000-0002-9290-1062 j. fernando arevalo: https://orcid.org/0000-0001-6104-5737 abstract the off-label, therapeutic use of intravitreal bevacizumab (ivb) in vascular retinal diseases such as diabetic macular edema and proliferative diabetic retinopathy (pdr) has increased significantly due to its ability to reduce retinal neovascularization and slow progression of disease. here, we will review the literature and investigative developments on the use of ivb as a preoperative adjuvant to vitrectomy in severe pdr, specifically focusing on its ability to reduce intraand postoperative complications and its risk for progression or development of traction retinal detachment. in particular, this review will highlight the natural progression of evidence from case series and observations to prospective, randomized clinical trials. keywords: diabetic macular edema; diabetic retinopathy; intravitreal bevacizumab; tractional retinal detachment; vascular endothelial growth factor; vitrectomy j ophthalmic vis res 2021; 16 (2): 287–290 introduction proliferative diabetic retinopathy (pdr) is an advanced form of diabetic retinopathy and is a leading cause of new onset blindness in adults.[1] it is a common complication of diabetes mellitus (dm) with an estimated global prevalence of 7% amongst the diabetic population.[2, 3] diabetic retinopathy is characterized by increased retinal capillary permeability with leakage and occlusion, while pdr is the result of subsequent chronic correspondence to: j. fernando arevalo, md, phd. retina division, wilmer eye institute, johns hopkins university school of medicine, 600 n wolfe st., maumenee 713, baltimore, md 21287, usa. email: arevalojf@jhmi.edu received: 13-02-2020 accepted: 21-11-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9092 retinal ischemia and refers to the development of neovascularization in the retina or optic disc. pdr can lead to complications such as neovascular glaucoma, vitreous hemorrhage, and tractional retinal detachment (trd). elevated levels of vascular endothelial growth factor (vegf) in the vitreous fluid have been associated with pdr and are a driving factor in the development of retinal neovascularization.[4–6] the introduction of intravitreal anti-vegf therapies such as bevacizumab (avastin; genentech inc, san francisco, ca), have thus offered a promising, lessinvasive alternative to panretinal photocoagulation (prp), the historical gold standard treatment for uncomplicated pdr. in clinical trials, the this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: beatson b, arevalo jf. from the hypotheses to clinical evidence in retinal therapy. j ophthalmic vis res 2021;16:287–290. © 2021 beatson et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 287 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9092&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr hypotheses to clinical evidence in retinal therapy; beatson et al use of intravitreal anti-vegf treatment has been shown to be non-inferior to prp and effective in reducing retinal neovascularization in pdr.[7–9] the use of anti-vegf agents has also proven useful as adjuvant agents to vitrectomy, which is performed in cases of severe pdr or pdr associated with complications such as trd.[10, 11] when used as adjuvants to vitrectomy, these agents are reported to improve clinical outcomes by reducing intraoperative bleeding, iatrogenic retinal breaks, and the incidence of recurrent vitreous hemorrhage.[12] however, their utilization as adjuvants has also been associated with the progression or development of trd in up to 5% of patients, which has resulted in a lack of consensus regarding the appropriateness of their use.[13, 14] this review discusses current literature on the use of anti-vegf therapeutics, particularly intravitreal bevacizumab (ivb), as adjuvants to vitrectomy. in particular, this review will highlight the natural progression of evidence from case series and observations to prospective, randomized clinical trials. trd following ivb for pdr in 2006, chen and park[10] and avery et al[11] suggested that adjuvant ivb can help facilitate vitrectomy in severe pdr cases. a meta-analysis was later published and identified that ivb preoperative before vitrectomy resulted in significantly less intraoperative bleeding and frequency of endodiathermy (p < 0.01), less surgical time (p = 0.003), and improved final best-corrected visual acuity (bcva) (p = 0.003) relative to vitrectomy alone. however, in 2008, we published a retrospective, multicenter case series of 211 eyes that received preoperative ivb before vitrectomy, with 11 of these eyes (5.2%) experiencing subsequent progression or development of trd following ivb.[13] records were obtained from seven sites in the united states, brazil, argentina, puerto rico, costa rica, and venezuela, and all patients had pdr refractory to prp treatment that was performed at least two months prior to ivb. the mean time from ivb injection to trd was 13 days (range, 3–31 days), which would be supportive of a cause– effect relationship. in this case series, most of the patients that developed trd had poorly controlled dm with a mean hba1𝑐 of 10.6%, and all used insulin for glycemic control. nine out of eleven (81.8%) developed trd at least five days after the ibv injection, further suggesting that increased time from ivb to vitrectomy may lead to a higher incidence of trd. however, a weakness of this retrospective case series was that the presence of trd as a natural progression of severe pdr could not be ruled out, due to the absence of a control group. in 2011, we published a follow-up to our initial data with a larger sample size, where we examined the incidence and risk factors associated with development of trd in 698 eyes that had adjuvant ivb before vitrectomy for refractory pdr.[15] in this study population, 25 (3.5%) eyes developed or had progression of a trd following adjuvant ivb. the statistically significant risk factors for trd identified in this study were a higher dose (2.5 mg vs 1.5 mg) of ivb (p = 0.022), more than 13 days from ivb to vitrectomy (p < 0.001), and a history of dm for more than 15 years at the time of ivb (p = 0.009). these findings were noteworthy, given that avery et al[11] had previously reported that diabetic eyes may be uniquely sensitive to ivb. these results also suggested that timely surgery should be prioritized following ivb administration, especially in eyes at risk of vision-threatening trd progression into the central macular region. furthermore, the use of low-dose ivb in eyes with pre-existing retinal traction would be recommended, given the increased frisk at higher doses. however, the findings of this study were similarly limited by its retrospective, nonrandomized, and uncontrolled nature. prospective analysis – preoperative ivb vs sham these retrospective analyses were valuable in understanding the risk of developing trd following preoperative ivb for vitrectomy and the risk factors associated with its occurrence, yet a controlled, prospective analysis was still needed to determine whether the effectiveness of ivb outweighed the risk of this complication. consequentially, in 2019, we released the results of our prospective, randomized, and doublemasked clinical trial investigating adjuvant ivb with vitrectomy for trd in the setting of pdr in 224 eyes.[16] this study was a multicenter study conducted by the pan-american collaborative 288 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 hypotheses to clinical evidence in retinal therapy; beatson et al retina study (pacores) group, taking place at 13 clinical sites in nine countries within latin america, the united states, saudi arabia, and spain. enrolled patients were randomized in a 1:1 ratio to either vitrectomy plus ivb or vitrectomy plus sham (control arm). ivb administration occurred three to five days before surgery. patients’ baseline characteristics were similar with no statistical difference in age, gender, manner of glycemic control, or lens status. the results showed that ivb had a significant positive effect on reducing intraoperative bleeding and reducing associated complications and iatrogenic retinal breaks. specifically, it was found that 67.6% of eyes in the study group experienced intraoperative bleeding of any degree, while 89.2% of eyes in the control group experienced intraoperative bleeding (p < 0.001). additionally, 31.3% of study eyes had grade-2 intraoperative bleeding versus 51.7% of control eyes (p = 0.004). the required use of endodiathermy occurred more frequently in the control group relative to the study group (66.9% vs 27.4%; p < 0.001), and the presence of at least one iatrogenic retinal break was also found more frequently in the control group (58.9% vs 34.3%; p = 0.001). relative to baseline, there was a statistically significant improvement in bcva in both the study and control groups, although there was not a statistically significant difference between the two groups. at 12 months of follow-up, 73% of the study group achieved an improvement in two or more lines (10 letters) of etdrs vision compared to 67.8% of the control group (p = 0.555). when the control and study groups were divided into subgroups according to the presence or absence of vitreous hemorrhage before surgery, there were significant increases in bcva by final follow-up relative to baseline, but there were still no statistically significant differences between ivb and sham. furthermore, the majority of eyes had retinas reattached with one procedure at the time of final follow-up at 12 months, with reattachment rates of 94.12% in the ivb group and 87.5% in the control group. this difference was not statistically significant (p = 0.097). trd progression following injection was only seen in the ivb group, and occurred in three eyes (2.94%). however, despite the trd progression, bcva improved following vitrectomy in those three cases. discussion the use of ivb in the treatment of retinal diseases, including as an adjuvant to vitrectom, has long been controversial. since first reports of its off-label use began in 2005, it has grown in popularity due to the much higher price of ranibizumab and aflibercept, the two vegf inhibitors approved for ophthalmic disease.[17–19] with the results of our prospective study, we believe that it is possible to save more eyes using preoperative ivb before vitrectomy in cases of severe pdr. the anti-neovascular effects of ivb have shown to reduce intraand postoperative bleeding relative to a control arm and thus abate the incidence of iatrogenic retinal breaks and facilitate intraoperative fibroproliferative membrane dissection. while progression or development of trd is a possibility in these cases, the risk can be managed using lower dose of ivb (1.5 mg), performing vitrectomy within four days of ivb administration, and considering judicious use in patients with a notably long history of dm. summary both retrospective and prospective studies have shown the use of ivb to be effective in reducing intraand postoperative complications when used as a preoperative adjuvant in vitrectomy for severe pdr, especially in repair of trd. while there is a small risk (2.5–5%) of trd progression or development following ivb administration, this risk can be managed by using low-dose ivb (1.5 mg) and performing surgery shortly following the administration of ivb. financial support and sponsorship unrestricted grant from research to prevent blindness (wilmer eye institute), dr. arevalo is the edmund and virginia ball professor. conflicts of interest there are no conflicts of interest. references 1. solomon sd, chew e, duh ej, et al. diabetic retinopathy: a position statement by the american diabetes association. dia care 2017;40:412–418. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 289 hypotheses to clinical evidence in retinal therapy; beatson et al 2. zhang x, saaddine jb, chou c-f, et al. prevalence of diabetic retinopathy in the united states, 2005–2008. jama 2010;304:649. 3. yau jwy, rogers sl, kawasaki r, et al. global prevalence and major risk factors of diabetic retinopathy. diabetes care 2012;35:556–564. 4. adamis ap, miller jw, bernal m-t, et al. increased vascular endothelial growth factor levels in the vitreous of eyes with proliferative diabetic retinopathy. am j ophthalmol 1994;118:445–450. 5. aiello lp, avery rl, arrigg pg, et al. vascular endothelial growth factor in ocular fluid of patients with diabetic retinopathy and other retinal disorders. n engl j med 1994;331:1480–1487. 6. nicoletti v, nicoletti r, ferrara n, meli g, reibaldi m, reibaldi a. diabetic patients and retinal proliferation: an evaluation of the role of vascular endothelial growth factor (vegf). exp clin endocrinol diabetes 2003;111:209–214. 7. writing committee for the diabetic retinopathy clinical research network, gross jg, glassman ar, et al. panretinal photocoagulation vs intravitreous ranibizumab for proliferative diabetic retinopathy: a randomized clinical trial. jama 2015;314:2137. 8. sivaprasad s, prevost at, vasconcelos jc, et al. clinical efficacy of intravitreal aflibercept versus panretinal photocoagulation for best corrected visual acuity in patients with proliferative diabetic retinopathy at 52 weeks (clarity): a multicentre, single-blinded, randomised, controlled, phase 2b, non-inferiority trial. lancet 2017;389:2193–2203. 9. sun jk, glassman ar, beaulieu wt, et al. rationale and application of the protocol s anti–vascular endothelial growth factor algorithm for proliferative diabetic retinopathy. ophthalmology 2019;126:87–95. 10. chen e, park ch. use of intravitreal bevacizumab as a preoperative adjunct for tractional retinal detachment repair in severe proliferative diabetic retinopathy. retina 2006;26:699–700. 11. avery rl, pearlman j, pieramici dj, et al. intravitreal bevacizumab (avastin) in the treatment of proliferative diabetic retinopathy. ophthalmology 2006;113:1695– 1705.e6. 12. zhao l-q, zhu h, zhao p-q, hu y-q. a systematic review and meta-analysis of clinical outcomes of vitrectomy with or without intravitreal bevacizumab pretreatment for severe diabetic retinopathy. br j ophthalmol 2011;95:1216–1222. 13. arevalo jf, maia m, flynn hw, et al. tractional retinal detachment following intravitreal bevacizumab (avastin) in patients with severe proliferative diabetic retinopathy. br j ophthalmol 2008;92:213–216. 14. jonas jb, schmidbauer m, rensch f. progression of tractional retinal detachment following intravitreal bevacizumab. acta ophthalmol 2009;87:571–572. 15. arevalo jf, sanchez jg, saldarriaga l, et al. retinal detachment after bevacizumab. ophthalmology 2011;118:2304.e3–2304.e7. 16. arevalo jf, lasave af, kozak i, et al. preoperative bevacizumab for tractional retinal detachment in proliferative diabetic retinopathy: a prospective randomized clinical trial. am j ophthalmol 2019;207:279– 287. 17. hutton d, newman-casey pa, tavag m, zacks d, stein j. switching to less expensive blindness drug could save medicare part b $18 billion over a ten-year period. health aff 2014;33:931–939. 18. anothaisintawee t, leelahavarong p, ratanapakorn t, teerawattananon. the use of comparative effectiveness research to inform policy decisions on the inclusion of bevacizumab for the treatment of macular diseases in thailand’s pharmaceutical benefit package. ceor 2012:361. 19. grisanti s, ziemssen f. bevacizumab: off-label use in ophthalmology. indian j ophthalmol 2007;55:417. 290 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 case report isolated intraconal meningioma mohammad taher rajabi1, md; kasra cheraqpour1, md, mph; s. saeed mohammadi1,6, md mohammad veshagh2, md; seyedeh zahra poursayed lazarjani1,3, md; farideh hosseinzadeh4, md fahimeh asadi amoli5, md; simindokht hosseini1, md 1eye research center, farabi eye hospital, tehran university of medical sciences, tehran, iran 2ophthalmic research center, research institute for ophthalmology and vision science, labbafinejad medical center, shahid beheshti university of medical sciences, tehran, iran 3department of ophthalmology, guilan university of medical sciences, rasht, iran 4ent and head & neck research center, the five senses health institute, iran university of medical sciences, tehran, iran 5pathology department, farabi eye hospital, tehran university of medical sciences, tehran, iran 6department of ophthalmology, abadan university of medical sciences, abadan, iran orcid: mohammad taher rajabi: https://orcid.org/0000-0001-7379-6861 seyedeh zahra poursayed lazarjani: https://orcid.org/0000-0003-4560-9787 abstract purpose: to report a rare case of isolated intraconal meningioma. case report: a 24-year-old woman presented with painless proptosis in her left eye which started and progressed during her pregnancy about 10 months ago. hertel exophthalomometry revealed anterior displacement of the globe with 4 mm of proptosis which was remarkable. magnetic resonance imaging (mri) demonstrated an intraconal circumscribed oval-shaped mass with hypointense signals on t1-weighted images and hyperintense signals on t2-weighted images, mimicking cavernous hemangioma. this mass, however, was free of any connections to optic nerve or bones. due to the imaging characteristics, more prevalent diagnoses like cavernous hemangioma were placed on the top of the differential diagnoses list. however, during the surgical excision, the tumor’s consistency and gross features were not compatible with cavernous hemangioma. the pathologic findings instead determined meningotheliomatous meningioma, a very rare condition, which was far from our expectations prior to the surgery. conclusion: ectopic orbital meningiomas are rare tumors that are not easily diagnosed without postoperative histopathology. despite its low prevalence, they should be considered in the differential diagnosis list of intraconal masses with hypointense signals on t1-weighted images and hyperintense signals on t2-weighted images. keywords: ectopic meningioma; intraconal meningioma; orbital meningioma; primary meningioma j ophthalmic vis res 2021; 16 (4): 682–687 682 © 2021 rajabi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9759&domain=pdf&date_stamp=2019-07-17 intraconal meningioma; rajabi et al introduction orbital meningiomas account for 0.4–2% of all meningiomatous tumors.[1] these lesions are further subdivided into three classifications. the first classification is primary optic nerve sheath meningiomas (onsm) originating from the arachnoid layer of the optic nerve (<30% of cases). the second classification is secondary onsm arising from the sphenoid wing (e.g., intracranial meningiomas accounting for <70% of orbital meningiomas). the last rare group is ectopic meningiomas which are free from any connections to the optic nerve or intracranial meninges (<1%).[2–9] ectopic orbital meningioma is usually located on the medial part of the orbit.[10] this uncommon entity of meningiomas usually reveals as a well-circumscribed mass but an ill-defined border does not rule out this type of tumor.[10] herein, we report a rare case of ectopic (isolated) intraconal meningioma. case report a 24-year-old woman presented with painless proptosis in her left eye, which started and progressed during her pregnancy about 10 months ago. her uncorrectedand best-corrected visual acuity (ucva and bcva) were 20/25 and 20/20, respectively. in addition, the relative afferent pupillary defect (rapd) in the left eye was negative. while the hertel exophthalmometry revealed an anterior displacement of the globe with 4 mm of proptosis, the fundoscopy showed a left optic disc edema. other slit-lamp examinations were normal. magnetic resonance imaging (mri) demonstrated an intraconal circumscribed oval-shaped mass with hypointense signals on t1-weighted images and hyperintense signals on t2-weighted images [figure 1] mimicking cavernous hemangioma. correspondence to: seyedeh zahra poursayed lazarjani, md. eye research center, department of eye, amiralmomenin hospital, school of medicine, guilan university of medical sciences, rasht 416584346, iran. e-mail: s.poursayed@gmail.com received: 04-03-2020 accepted: 23-12-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9759 as a consequence, the patient underwent uncomplicated superomedial orbitotomy which resulted in the removal of a 3×1×0.5 cm necrotic white mass without any bleeding and which was also free of connections to the optic nerve sheath. a histopathological examination showed tumoral cells with syncytial and whirling arrangement, indistinct cell membranes, eosinophilic cytoplasma, and rather uniform nuclei. some intranuclear pseudoinclusions were also present. mitotic figures were rare. immunohistochemistry revealed positive staining for epithelial membrane antigen (ema) a progesterone receptor (pr) [figure 2] and negative staining for s100, cd34, and bcl2. ki67 showed proliferative activity in about 1–2% of tumor cells. as a result, a meningotheliomatous meningioma (who grade 1) diagnosis was made. postoperative radiotherapy was performed on the orbital tumor bed. after a one-year follow-up, no complications or changes in the patient’s perimetry, visual acuity, and rapd were detected. discussion when assessing an intraconal mass with hypointense signals on t1-weighted images and hyperintense signals on t2-weighted images, several differential diagnoses should be considered, such as cavernous hemangioma, schwannoma, lymphoma, and neurofibroma. in our case, the orbital mass was intraconal without connections to the optic nerve or bones. due to the imaging features of the lesion, a more prevalent diagnosis, such as cavernous hemangioma was expected. however, during the surgical excision of the lesion, the tumor’s consistency and gross features were different from that of a cavernous hemangioma and the pathological evaluation of the mass determined meningotheliomatous meningioma. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: rajabi mt, cheraqpour k, mohammadi ss, veshagh m, lazarjani szp, hosseinzadeh f, amoli fa, hosseini s. isolated intraconal meningioma. j ophthalmic vis res 2021;16:682–687. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 683 https://knepublishing.com/index.php/jovr intraconal meningioma; rajabi et al figure 1. orbital magnetic resonance imaging (mri). (a) coronal image illustrating a superonasal intraconal mass on t1-weighted images which is separated from optic nerve. (b & c) axial image illustrates a hypointense oval-shaped intraconal mass on t1weighted images and hyperintense on t2-weighted images. figure 2. histopathology. (a) hematoxylin and eosin (h&e) staining illustrating meningioma, tumoral cells with syncytial and whirling arrangement. (b) h&e staining showing intranuclear pseudo-inclusions. (c & d) immunohistochemistry illustrating positive staining for epithelial membrane antigen (ema) (cytoplasmic), progesterone receptor (pr) (nuclear), respectively. as a result, our patient underwent an orbitotomy with a partial tumor resection due to its fragile nature. systemic work up was normal and the patient was referred for adjunctive radiotherapy. although recurrence is rare in cases of complete excision, it should be mentioned that incisional biopsy has been known to accelerate spreading and recurrence of the tumor.[11] it should be mentioned that other possible diagnoses such as sclerosis or hyperplasia of the superior orbital rim or asymmetry of the sinuses[7] were ruled out in our case. orbital meningiomas most commonly arise from the base of skull or optic nerve sheath while ectopic orbital meningiomas are extremely rare accounting for <1% of cases. many previous studies have reported ectopic orbital meningiomas being located along the medial wall and superonasal rim.[10] origin of ectopic meningiomas has always been debated. these 684 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 intraconal meningioma; rajabi et al table 1. brief review on recent reports no. [ref] patient history & examination va imaging treatment outcome gündüz et al[10] 56/f *3 months of slowly progressive proptosis and eyelid swelling *5 mm of proptosis (od) 20/20 *mri: ill-defined mass in the right superior orbit with isointense signals and respect to the orbital fat and cerebral gray matter on t1wi, hypointense signals on t2wi, and moderate contrast enhancement *ct scan: superiorly located mass producing thinning of the overlying bone subtotal resection through superonasal orbitotomy + conventional external beam radiotherapy *74 months f/u without recurrence *va of cf at 2 meters due to radiation retinopathy 27/m *slowly progressive proptosis over 6 months *12 mm of proptosis *limitation on elevation and abduction *conjunctival edema and injection over the lr muscle insertion (os) 20/20 *mri: well-defined tumor laterally in the orbit with hypointense signals on t1wi, hyperintense signals on t2wi, and moderate contrast enhancement *ct scan: no connection to the bony orbit anterior orbitotomy via a superolateral approach resulted in resection of 70% of the tumor + intensity modulated radiotherapy *at 24 months f/u, va was 20/20, and there was 2 mm of residual proptosis decock et al[3] 66/m *4 years of growing orbital mass protruding upper eyelid *a firm mass not adherent to bone or skin (os) 20/20 *ct scan: extensively calcified mass located at the anterior edge of the lacrimal fossa without hyperostosis or involvement of the adjacent orbital bone translid surgical approach 15 months of f/u without recurrence huang et al[13] 7/m *5 months of proptosis, upper eyelid edema, and diplopia 1.2 *coronal t1wi showed a superonasal mass. axial t2wi showed an ill-defined and heterogeneous mass and adjacent mr. (misdiagnosed as capillary hemangioma) complete surgical resection in all cases no recurrence or diminution of vision in none of cases 18/f *24 months of proptosis, ptosis, upper eyelid edema, and diplopia 1.2 *axial t1 showed an ill-defined and heterogeneous superonasal mass and adjacent mr (misdiagnosed as capillary hemangioma) 31/m *12 months of proptosis, upper eyelid edema, and diplopia lp *t1wi mri was hypointense and t2wi mri was hyperintense * axial ct scan showed a well-defined intraconal mass adjacent to the anterior optic nerve (misdiagnosed as cavernous hemangioma) 35/m *72 months of proptosis, ptosis, upper eyelid edema, and diplopia 1.0 *coronal t1 w1 showed the superonasal mass and no adjacent mr. axial t1 w1 showed the ill-defined and heterogeneous superonasal mass (misdiagnosed as eosinophilic granuloma) journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 685 intraconal meningioma; rajabi et al table 1. continued no. [ref] patient history & examination va imaging treatment outcome 56/m *3 months of proptosis, ptosis, upper eyelid edema, and diplopia 1.0 *t1wi mri was hypointense and t2wi mri was hyperintense *axial ct scan showed a well-defined intraconal lesion with a calcified mass. optic nerve was compressed and dislocated but integrated into the structure (undiagnosed) 52/f *6 months of proptosis, ptosis, upper eyelid edema, and diplopia 0.5 *t1wi mri was hypointense and t2wi mri was hyperintense (in all 6 cases) (misdiagnosed as neurofibromatosis) pushker et al[7] 30/f *18-month of proptosis *3 mm proptosis and limitation in elevation (os) 20/20 *ct scan: ill-defined, heterogenous enhancing soft tissue mass involving the left superior extraconal space + associated expansion and sclerosis of the left half of the frontal bone and roof of the left orbit with few ill-defined lytic lesions excision through the anterior orbitotomy via a sub-brow incision *recurrence after 8 months resulted in re-surgery *no diminution of vision and further recurrence over an 18-month period 40/m *2-year history of painless, progressive proptosis *6 mm of proptosis and limitation in elevation (os) 20/20 *ct scan: homogeneous well-defined, intensely enhancing soft tissue mass in the left superomedial orbit rupturing of mass during excision resulted in piecemeal removal *recurrence of the mass after 11 months resulted in re-surgery *no further recurrence or diminished vision over 2 years f/u 9/m *2.5-year history of progressive proptosis *5 mm of proptosis with (os) 20/20 *ct scan: diffuse, mildly enhancing and associated with hyperplasia of the adjacent bone piecemeal removal no diminished vision over 3 months tendler et al[11] 9/f *gradual painless swelling of the medial upper eyelid *2 mm of proptosis and a firm mobile palpable mass in the superior nasal orbit of the (os) 20/25 *mri: extraconal enhancing mass in the left medial orbit with notable ethmoid sinus asymmetry excision + proton beam therapy and surgical debulking after recurrence not reported va, visual acuity; f, female; m, male; od, right eye; os, left eye; mri, magnetic resonance imaging (mri); ct scan, computed tomography scan; t1w1, t1-weighted image; t2w1, t2-weighted image; f/u, follow-up; cf, counting fingers; lp, light perception; lr, lateral rectus; mr, medial rectus tumors may originate from congenitally dislocated nests of meningothelial cells, regressed orbital meningoceles located within the orbit, or curiously associated with dislocated meningeal tissues into the orbit secondary to penetrating injury or trauma.[10] interestingly, several reports exist regarding extracranial or extradural meningiomas found in unusual sites such as the neck, skin, finger, lung, mediastinum, and adrenal gland.[11] 686 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 intraconal meningioma; rajabi et al lee teak tan et al reported a case of presumed ectopic orbital meningioma which was decidedly diagnosed as olfactory groove meningioma. as a consequence, he hypothesized that a number of the previously reported cases have had similar scenarios of misdiagnosis. having said that, other distinguished researchers continue to consider ectopic meningioma as a distinct entity where the origin and existence of ectopic orbital meningioma is still being debated.[12] to date, there have been few reports of intraconal ectopic meningioma cases. a brief review of some of the recent reports of ectopic meningioma cases and other related issues such as demographic data, history, imaging findings, treatment, and final outcomes are summarized in table 1. the unique aspect of this case which has not been reported in prior studies is the development of an ectopic meningioma during pregnancy. this coincidental discovery on the possible association between pregnancy and the development and enlargement of meningiomatous tumors currently has no precedence and hence no available supporting data. however, it is recommended that treatment of these tumors be executed to ensure prevention of focal aggression.[11] as a consequence, future case would need to be monitored to ensure all avenues are investigated. in summary, as ectopic orbital meningiomas are characteristically very rare tumors and are not easily diagnosed with orbital imaging because of similar resemblance to other intraorbital tumors, serious consideration should be made in ensuring execution of postoperative histopathology to determine the existence or absence of these low prevalent tumors. the possible occurrence of these meningiomas should also be considered in the differential diagnosis of intraconal masses with hypointense signals on t1-weighted images and hyperintense signals on t2-weighted images. this approach would ensure the accurate diagnosis of conditions and would encourage the appropriate course of treatment. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. bondy m, ligon bl. epidemiology and etiology of intracranial meningiomas: a review. j neurooncol 1996;29:197–205. 2. lang ff, macdonald ok, fuller gn, demonte f. primary extradural meningiomas: a report on nine cases and review of the ct-era literature. j neurosurg 2000;93:940– 950. 3. decock ce, kataria s, breusegem cm, van den broecke cm, claerhout ij. ectopic meningioma anterior to the lacrimal gland fossa. ophthalmic plast reconstr surg 2009;25:57–59. 4. arai ks, t. matsumoto, h. free-lying ectopic meningioma within the orbit. br j neurosurg 1997;11:560–563. 5. farah se, konrad h, huang dt, geist ce. ectopic orbital meningioma: a case report and review. ophthalmic plast reconstr surg 1999;15:463–466. 6. johnson te, weatherhead rg, nasr am, siqueira eb. ectopic (extradural) meningioma of the orbit: a report of two cases in children. j pediatr ophthalmol strabismus 1993;30:43–47. 7. pushker n, shrey d, kashyap s, sen s, khurana s, sharma s. ectopic meningioma of the orbit. int ophthalmol 2013;33:707–710. 8. tan k, lim a. primary extradural intra-orbital meningioma in a chinese girl. br j ophthalmol 1965;49:377. 9. yokoyama t, nishizawa s, sugiyama k, yokota n, ohta s, uemura k, et al. primary intraorbital ectopic meningioma. skull base surg 1999;9:47–50. 10. gündüz k, kurt ra, erden e. ectopic orbital meningioma: report of two cases and literature review. surv ophthalmol 2014;59:643–648. 11. tendler i, belinsky i, abramson dh, marr bp. primary extradural ectopic orbital meningioma. ophthalmic plast reconstr surg 2017;33:s99–s101. 12. tan lt, stewart cm, sheerin f, macdonald b, silva p, norris jh. ectopic orbital meningioma: fact or fiction? orbit 2017;36:144–146. 13. huang x, tang d, wu t, jian t, sun f. ectopic orbital meningioma: a retrospective case series. bmc ophthalmol 2018;18:296. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 687 original article outcomes of phaco-viscocanalostomy in primary open angle glaucoma versus pseudoexfoliation glaucoma ebrahim azaripour1, md; yaser khakpour1, md; reza soltani-moghadam1, md; zahra moravvej1, md abdolreza medghalchi1, md; hassan behboudi1, md; yousef alizadeh1, md; soheil soltanipour2, md shila kianmehr1, ms 1eye research center, department of ophthalmology, amiralmomenin hospital, school of medicine, guilan university of medical sciences, rasht, iran 2gi cancer screening and prevention research center, department of community medicine, school of medicine, guilan university of medical sciences, rasht, iran orcid: ebrahim azaripour: https://orcid.org/0000-0001-7309-1503 reza soltani-moghadam: https://orcid.org/0000-0001-9661-3036 abstract purpose: viscocanalostomy represents an alternative to standard penetrating glaucoma surgery. the aim of this study is to compare the outcomes of combined phacoemulsification and viscocanalostomy in eyes with primary open-angle glaucoma (poag) versus eyes with pseudoexfoliation glaucoma (pexg). methods: in this prospective non-randomized comparative study, eyes with cataract and poag or pexg were enrolled. preand postoperative data including best corrected visual acuity (bcva), intraocular pressure (iop), and the number of antiglaucoma medications administered were recorded at each visit. all patients underwent phacoviscocanalostomy. complete success was defined as the iop of 21 mmhg or less without the administration of medication while a qualified success reported the same iop parameters either with or without the administration of medication. results: fifty-four eyes with poag and fifty-four with pexg underwent phacoviscocanalostomy. the mean follow-up time was 23.36 ± 8.8 months (range, 6–40 months). the mean postoperative iop reduced significantly in both groups, although the mean iop reduction was significantly greater in pexg eyes (14.7 ± 8.9 vs 10.1 ± 7.7 mmhg) (p = 0.05). at the final follow-up visit, the mean postoperative iop was 14.1 ± 2.1 and 16.6 ± 3.5 mmhg in the pexg and poag eyes, respectively (p = 0.001). a complete success rate of 88.9% and 75.9% was achieved in pexg and poag eyes, respectively (p = 0.07). the qualified success rate was 100% in the pexg and 85.2% in poag groups (p = 0.03). conclusion: phacoviscocanalostomy achieved significant iop reduction and visual improvement in both poag and pexg patients. our results indicated that in terms of iop reduction, this procedure was more effective in treating pexg. keywords: primary open-angle glaucoma intraocular pressure; phacoviscocanalostomy; pseudoexfoliation j ophthalmic vis res 2021; 16 (4): 566–573 566 © 2021 azaripour et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9746&domain=pdf&date_stamp=2019-07-17 phaco-viscocanalostomy in poag vs pxfg; azaripour et al introduction primary open-angle glaucoma (poag) and pseudoexfoliation glaucoma (pexg) are chronic and progressive processes causing optic neuropathy. pseudoexfoliation syndrome is featured by the deposition of specific fibrillar material in the anterior segment of the eye.[1, 2] this sedimentation of material on the trabecular meshwork (tm) may cause glaucoma and subsequent optic neuropathy.[3] various surgical procedures exist for managing glaucoma; these include penetrating and nonpenetrating filtering procedures and tube shunt surgery.[4, 5] nonpenetrating procedures, such as deep sclerectomy and viscocanalostomy (vcs) have been designed to alleviate the complications of penetrating surgery[6]. vcs, as defined by stegmann et al, involves the injection of high-viscosity sodium hyaluronate into the schlemm’s canal until aqueous outflow drainage is improved.[7] it has been suggested that physiologic aqueous humor drainage may be attained without bleb formation. although trabeculectomy has proven to be more effective than nonpenetrating procedures in terms of iop reduction, it is more prone to complications.[9] vcs releases less inflammatory mediators causing lower rates of bleb failure. phacoviscocanalostomy represents an alternative to standard phacotrabeculectomy with antimetabolites.[8] recent reports show good midterm results of phacoviscocanalostomy in eyes with medically uncontrolled glaucoma.[10–12] in this study, we aim to compare the clinical outcomes of phacoviscocanalostomy with intraocular lens implantation in pexg and poag eyes. correspondence to: reza soltani-moghadam, md. eye research center, eye department, amiralmomenin hospital, school of medicine, guilan university of medical sciences, rasht 4139637459, iran e-mail: reza_sm76@yahoo.com received: 02-12-2020 accepted: 24-05-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9746 methods this prospective comparative study was conducted on 108 of 108 eyes with pexg (54 eyes) and poag (54 eyes). the criteria used in choosing the participants for the study included eyes with medically uncontrolled poag and pexg (iop > 21 mmhg with maximum medical therapy and glaucomatous visual field defects) and visually significant cataract (visual acuity that significantly affects the patient’s daily activities). patients with other ocular pathologies and history of any ocular surgery or laser procedures were excluded from the study. demographic and preoperative data which included best corrected visual acuity (bcva) in logmar, iop (goldmann tonometry), gonioscopic (four-mirror glass goniolens), and funduscopic findings were recorded. standard automated perimetry (humphrey field analyzer, program 242) and glaucoma severity staging done according to hodapp-parrish-anderson criteria was also obtained from all patients. postoperative followups were conducted initially on day seven and subsequently at 1, 3, 6, 12, 24, 30, and 40-month intervals. complete slit-lamp examinations were performed in each follow-up visit along with bcva and iop measurements. the study was conducted in accordance with the principles of the declaration of helsinki and was approved by the local ethics committee. patients were informed about the aim of the study and written informed consent was obtained from all participants before the surgery. at the ophthalmology clinic, all eyes underwent surgery and follow-up examinations, both of which were performed by a single surgeon (ea). statistical analysis was calculated using the spss v19.1 application. preoperative and postoperative data were compared using paired sample t-test and wilcoxon sign test (for nonparametric data). comparison between the two this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: azaripour e, khakpour y, soltani-moghadam r, moravvej z, medghalchi a, behboudi h, alizadeh y, soltanipour s, kianmehr s. outcomes of phaco-viscocanalostomy in primary open angle glaucoma versus pseudoexfoliation glaucoma. j ophthalmic vis res 2021;16:566– 573. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 567 https://knepublishing.com/index.php/jovr phaco-viscocanalostomy in poag vs pxfg; azaripour et al groups was performed using student’s t-test and the mann–whitney u test (for nonparametric data). comparisons of the outcome of the glaucoma at different stages were done using the kruskal– wallis test. the frequency of intraoperative and postoperative complications was assessed in both groups. p-value < 0.05 was considered to be statistically significant. according to international consensus statements, complete success was characterized as an iop ≤21 mmhg without antiglaucoma medication while qualified success was determined as achieving the same iop values but either with or without antiglaucoma medication. failure was described as an iop >21 mmhg with the administration of medication, or when an eye required further glaucoma drainage surgery.[13] surgical technique surgical procedures were performed either utilizing peribulbar or general anesthesia depending on the patient’s medical history. prior to performing vcs, patients underwent standard phacoemulsification with intraocular lens implantation. phacoemulsification was performed through a temporal 2.8 mm clear cornea incision. after executing continuous circular capsulorhexis (ccc), the nucleus was emulsified using “stop and chop” or “divide and conquer” techniques. after complete nuclear and cortical material removal, a foldable intraocular lens was inserted into the capsular bag. in order to perform vcs, a fornixbased conjunctival peritomy was made and a square-shaped superficial scleral flap (5.0 х 5.0 mm) was created by a crescent blade. a second deeper scleral flap (4.0 х 4.0 mm) was dissected and continued anteriorly to the scleral spur to expose the trabeculo-descemet membrane (tdm). the deep scleral flap and the roof of schlemm’s canal were cut to facilitate aqueous humor drainage. sodium hyaluronate 1.4% (healon gv) was then injected into the schlemm’s canal. the superficial scleral flap was closed tightly with two interrupted 10-0 nylon sutures, and the conjunctival wound was sutured with 10-0 nylon. results a total of 108 eyes of 108 patients with pexg (54 eyes) and poag (54 eyes) were included in the study. the mean age of the participants was 70.3 ± 8.03 years and 61 (56.5%) of them were male. all patients completed postoperative follow-up for at least 12 months. the mean follow-up time after surgery was 23.36 ± 8.8 months (range 12–40 months). the demographic and baseline data of the two groups is shown in table 1. there was no significant difference between the pexg and the poag groups in terms of glaucoma severity (p = 0.585). the gonioscopy results revealed slightly narrower angles in the pexg group as compared to the poag group, although this difference was not statistically significant (79.6% in pexg vs 100% in poag were classified as open-angle, p = 0.057). all patients had a significant improvement in bcva, postoperatively (p = 0.001). there was no statistically significant difference in terms of postoperative bcva between the poag and the pexg groups (p = 0.88). the mean iop decreased significantly one week after surgery in both groups (p = 0.001) and remained significantly lower than its preoperative value at all follow-up visits [figure 1]. the mean iop was significantly lower in the pexg group as compared to the poag group at the 12and 24month follow-up visits. this trend continued until the last follow-up visit although not statistically significant [table 2]. at the final follow-up, the mean postoperative iop reduction in the pexg group was significantly greater than the poag group (14.7 ± 8.9 vs 10.1 ± 7.7 mmhg, p = 0.01). overall, the number of antiglaucoma medications required reduced significantly after surgery (1.2 ± 1.2 to 0.12 ± 0.46, p = 0.001), although not statistically different between the two study groups [table 1]. the most common intraoperative and postoperative complication of phacoviscocanalostomy was microperforation of the tdm and fibrin formation, respectively [table 3]. at the final follow-up, complete success was noted in 88.9% (48 eyes) and 75.9% (41 eyes) of the pexg and poag patients, respectively (p = 0.07). qualified success was achieved in all eyes (100%) of the pexg group and 85.2% of the poag group (p = 0.03). in both the pexg and poag groups, complete success rates were not significantly different among the varying stages of glaucoma (p = 0.587 for stages of pexg and p = 0.252 for stages of poag). the cumulative probability estimated using the kaplan–meier survival curve of complete success 568 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 phaco-viscocanalostomy in poag vs pxfg; azaripour et al table 1. demographic data, baseline, and postoperative data at final follow-up visit in the study groups pexg (n=54) poag (n=54) p-value age (yr) 72.0 ± 7.8 68.5 ± 7.9 0.02 gender (male/female) 33/21 28/26 0.33 preoperative bcva (logmar) 0.97 ± 0.4 0.91 ± 0.4 0.32* postoperative bcva (logmar) 0.38 ± 0.35 0.39 ± 0.35 0.88* preoperative iop (mmhg) 28.5 ± 9.0 24.0 ± 8.7 0.004* preoperative antiglaucoma medication (n) 1.06 ± 1.02 1.5 ± 1.32 0.07 postoperative antiglaucoma medication (n) 0.11 ± 0.31 0.28 ± 0.57 0.06 follow-up time (months) 23.7 ± 8.2 22.9 ± 9.4 0.67 cup-to-disc ratio 0.84 ± 0.1 0.85 ± 0.1 0.85 severity, n (%) 0.585† mild 4 (7.4) 6 (11.1) moderate 15 (27.8) 11 (20.4) severe 35 (64.8) 37 (68.5) data is expressed as mean ± sd poag, primary open-angle glaucoma; pexg, pseudoexfoliation glaucoma; bcva, best-corrected visual acuity; iop, intraocular pressure; sd, standard deviation ∗mann–whitney u test; †chi-square test table 2. mean iop (mmhg) over 40 months (ms) follow-up in the two study groups 1 week n =108 1 m n =108 3 ms n =108 6 ms n =108 12 ms n =108 24 ms n =92 30 ms n =84 40 ms n =76 pexg 10.5 ± 3.9 13.0 ± 4.3 13.7 ± 2.7 16.4 ± 2.3 14.1 ± 2.3 14.5 ± 2.1 15.2 ± 2.1 13.5 ± 1.9 poag 9.9 ± 3.1 12.9 ± 3.0 13.2 ± 2.5 15.4 ± 4.6 15.5 ± 3.0 16.8 ± 3.7 16.3 ± 2.8 15.8 ± 1.3 p-value* 0.35 0.33 0.45 0.62 0.009 0.001 0.17 0.08 data is expressed as mean ± sd poag, primary open-angle glaucoma; pexg, pseudoexfoliation glaucoma *students t-test (iop < 21 mmhg without medication) in the study groups is illustrated in figure 2. a moderately stable level of surgical success was achieved as was noted during the follow-up periods. no patients required additional glaucoma surgery. discussion viscocanalostomy in comparison to trabeculectomy, is a nonpenetrating technique known to decrease intraand postoperative complications of glaucoma surgery.[14–16] owing to its pathophysiology, pexg eyes are more prone to trabeculectomy-related complications.[17, 18] the blood–ocular barrier dysfunction and iris stromal vasculopathy may contribute to postoperative inflammation, fibrin formation, and iop elevation.[19] stegmann et al in 1999 reported the first study of vcs on 214 eyes with open-angle glaucoma (oag) with a mean follow-up of 35 months.[7] they achieved a complete success rate (iop ≤ 22mmhg without medication) and a qualified success rate (iop ≤ 22 mmhg with medication) of 82.7% and 89%, respectively. another study in 2004 reported a complete success rate of 35.3% and a qualified success rate of 73.9% after three years, following the vcs in poag eyes.[20] performing vcs without phacoemulsification, in addition to the reported higher preoperative iop (36.0 ± 8.0 mmhg) as compared to our study (24.0 ± 8.7 mmhg) may journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 569 phaco-viscocanalostomy in poag vs pxfg; azaripour et al table 3. intraoperative and postoperative complications complications pexg n (%) poag n (%) descemet membrane microperforation 3 (5.6) 2 (3.7) fibrin reaction 5 (9.2) 3 (5.6) zonular dehiscence 3 (5.6) 0 poag, primary open-angle glaucoma; pexg, pseudoexfoliation glaucoma figure 1. mean intraocular pressure (iop) over time in two groups. pexg, pseudoexfoliation glaucoma; poag, primary open angle glaucoma. be reasons for the lower success rates achieved in their study. the combined procedures of phacoemulsification and nonpenetrating glaucoma surgery is being used frequently as it has produced good evidence of visual improvements and longterm iop control.[16, 21] a 12-year follow-up study by gunenc et al showed superior success rates in eyes undergoing phacoviscocanalostomy as compared with performing vcs on its own.[22] in our present study, we noted significant reduction in the mean iop levels after performing phacoviscocanalostomy in both poag and pexg eyes. however, significantly lower iop levels were achieved in pexg eyes at the 12and 24-month follow-up visits. this finding may be partly due to significantly higher preoperative iop in the pexg patients. at all postoperative follow-ups, a similar comparative study reported significantly lower mean iop in the pexg group after performing phacoviscocanalostomy.[23] in a retrospective one-year study, moghimi et al reported a 37% complete success rate (defined as iop ≤ 21 mmhg without medication) in 46 oag eyes (including pexg) having undergone phacoviscocanalostomy.[24] in another study, eyes with advanced glaucoma having undergone phacoviscocanalostomy achieved complete and qualified success rates of 30.6% and 80%, respectively.[25] stangos et al performed phacoviscocanalostomy on 50 eyes with medically uncontrolled oag and clinically significant agerelated cataract. the results reported an overall success rate (iop ≤ 20 mmhg with or without medication) of 82% and a complete success rate (iop ≤ 20 mm hg without medication) of 67% at the 36-month follow-up visit.[26] in comparison to the aforementioned studies,[24–26] we experienced higher rates of complete and qualified success. our study also indicated higher rates of complete success in the pexg as compared to that of the poag eyes (88.9 vs 75.9%). all pexg eyes in 570 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 phaco-viscocanalostomy in poag vs pxfg; azaripour et al figure 2. kaplan–meier survival curve of complete success (iop < 21 mmhg without medication) in pseudoexfoliation glaucoma (pexg) and primary open-angle glaucoma (poag). our study and 85.2% of the poag eyes achieved qualified success. likewise, awadalla et al reported complete surgical success of 93.3% in pexg eyes and of 83.3% in poag eyes.[23] their study resulted in qualified success of all patients in both groups. wishart et al also achieved higher complete success rates (defined as iop ≤ 18 mmhg without medication) in pexg as compared to poag eyes after a mean follow-up of six years (95% and 76%, respectively), they also experienced 100% qualified success in pexg and 90.2% in poag eyes.[27] according to our current study and the studies mentioned above, phacoviscocanalostomy success rates were higher in pexg as compared to poag patients.[13, 14, 23] the type of glaucoma may also influence iop reduction after cataract surgery. numerous studies over the past few decades have shown that cataract surgery leads to a sustained decrease in iop in poag and pseudoexfoliation patients.[28] masis et al performed a systematic review and meta-analysis of the clinical data to estimate the net effect of cataract surgery on iop. a total of 37 treatment arms from 32 different studies from january 1997 to january 2017 were included. for angle-closure glaucoma, results showed an iop decrease of −6.4 mmhg (95% ci: −9.4 to −3.4) at final follow-up (12 months and longer). for the oag group, there was an overall iop change of −2.7 mmhg (95% ci: −3.7 to −1.7) from the baseline and for pexg there was an overall iop change of −4.8 mmhg (95% ci: −7.5 to −2.0).[29] in most studies, patients with pexg have a significantly greater drop in iop after phacoemulsification than patients with poag. reduction of iop has been previously reported in patients with pexg after phacoemulsification was performed. it is suggested that phacoemulsification may remove the fibrillar material source in pex eyes and facilitate aqueous humor drainage in the trabecular meshwork.[25] moreover, wider angles resulting from phacoemulsification and cataract removal increases the aqueous outflow from the tm and schlemm canal.[30] therefore, in patients with significant cataract and uncontrolled glaucoma, performing phacoviscocanalostomy can result in better outcomes than performing vcs alone. comparable to previous reports, microperforation of the tdm was the most common journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 571 phaco-viscocanalostomy in poag vs pxfg; azaripour et al intraoperative complication while fibrin formation was the most common postoperative complication of phacoviscocanalostomy.[14, 23] as compared to prior studies, the main advantage of our study in comparing phacoviscocanalostomy in pexg and poag was the use of a relatively higher number of cases with longer follow-up periods. according to literature, longer follow-up periods for patients tends to show a decrease in the success rate.[12, 22] we, however, demonstrated rather stable success rates after the 12 month follow-up session until the last follow-up visit at 40 months post operation. our study had several limitations. firstly, iop monitoring and grouping were done by an examiner who was not masked to the groups which might contribute to possible bias in the results. considering the average follow-up time of this study, we recommend longer-term followup sessions for glaucoma patients undergoing phacoviscocanalostomy. it is also recommended that for better comparison of vcs in pexg and poag, the procedure should be performed in patients who have not had cataract removal. multiple factors may affect the reported success rate of phacoviscocanalostomy, including: preoperative iop levels, different levels of the surgeons’ experience, the surgical techniques chosen, the follow-up time, the various criteria used to determine the success rate and the patients’ medical history. longer follow-up durations could affect the success rate, mainly due to the time taken for the deposition of fibrillar material in the angle of pseudoexfoliative eyes and the scarring ostia of the schlemm’s canal. various definitions of the success rate, study designs, and the execution of multiple followup times are contributory factors toward making comparison between studies challenging. for future studies, it is recommended that authors continue to utilize the international criteria for intraocular pressure (iop) levels, to ensure that the comparison between studies remain practical. in summary, phacoviscocanalostomy is a safe and effective procedure in achieving iop reduction for both pexg and poag eyes, as it increases bcva and decreases trabeculectomyrelated complications. therefore, this technique is recommended for eyes with therapeutically uncontrolled pexg and poag with cataract. financial support and sponsorship none. conflicts of interest all authors declare that they have no conflicts of interests. references 1. naumann go, schlötzer-schrehardt u, küchle m. pseudoexfoliation syndrome for the comprehensive ophthalmologist: intraocular and systemic manifestations. ophthalmology 1998;105:951–968. 2. rao kn, ritch r, dorairaj sk, kaur i, liebmann jm, thomas r, et al. exfoliation syndrome and exfoliation glaucomaassociated loxl1 variations are not involved in pigment dispersion syndrome and pigmentary glaucoma. mol vis 2008;14:1254. 3. leske mc, heijl a, hussein m, bengtsson b, hyman l, komaroff e. factors for glaucoma progression and the effect of treatment: the early manifest glaucoma trial. arch ophthalmol 2003;121:48–56. 4. caretti l, buratto l. non-penetrating glaucoma surgery (npgs): viscocanalostomy, deep sclerectomy and canaloplasty. glaucoma surgery: springer; 2018. p. 23–40. 5. chiselita d. non-penetrating deep sclerectomy versus trabeculectomy in primary open-angle glaucoma surgery. eye 2001;15:197–201. 6. sayed ms, lee rk. recent advances in the surgical management of glaucoma in exfoliation syndrome. j glaucoma 2018;27:s95. 7. stegmann r, pienaar a, miller d. viscocanalostomy for open-angle glaucoma in black african patients. j cataract refract surg 1999;25:316–322. 8. o’brart d, shiew m, edmunds b. a randomised, prospective study comparing trabeculectomy with viscocanalostomy with adjunctive antimetabolite usage for the management of open angle glaucoma uncontrolled by medical therapy. br j ophthalmol 2004;88:1012–1017. 9. gabai a, cimarosti r, battistella c, isola m, lanzetta p. efficacy and safety of trabeculectomy versus nonpenetrating surgeries in open-angle glaucoma: a meta-analysis. j glaucoma 2019;28:823–833. 10. ho dk-h, garrick a, aazem s, mathews d. effect of primary phacoviscocanalostomy/viscocanalostomy on intraocular pressure of normal tension glaucoma patients: 3-year results. bmc ophthalmol 2017;17:1–6. 11. mandić z, sarić d, bojić l. visco and phacoviscocanalostomy in managing glaucoma patients. coll antropol 2002;26:165–169. 12. shoji t, tanito m, takahashi h, park m, hayashi k, sakurai y, et al. phacoviscocanalostomy versus cataract surgery only in patients with coexisting normal-tension glaucoma: midterm outcomes. j cataract refract surg 2007;33:1209–1216. 572 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 phaco-viscocanalostomy in poag vs pxfg; azaripour et al 13. hassan k, awadalla m. results of combined phacoemulsification and viscocanalostomy in patients with cataract and pseudoexfoliative glaucoma. eur j ophthalmol 2008;18:212–219. 14. park m, hayashi k, takahashi h, tanito m, chihara e. phaco-viscocanalostomy versus phaco-trabeculotomy: a middle-term study. j glaucoma 2006;15:456–461. 15. tanito m, park m, nishikawa m, ohira a, chihara e. comparison of surgical outcomes of combined viscocanalostomy and cataract surgery with combined trabeculotomy and cataract surgery. am j ophthalmol 2002;134:513–520. 16. mendrinos e, mermoud a, shaarawy t. nonpenetrating glaucoma surgery. surv ophthalmol 2008;53:592–630. 17. ritch r, schlötzer-schrehardt u. exfoliation syndrome. surv ophthalmol 2001;45:265–315. 18. conway rm, schlötzer−schrehardt u, küchle m, naumann go. pseudoexfoliation syndrome: pathological manifestations of relevance to intraocular surgery. clin experiment ophthalmol 2004;32:199–210. 19. cursiefen c, hammer t, küchle m, naumann go, schlötzer−schrehardt u. pseudoexfoliation syndrome in eyes with ischemic central retinal vein occlusion: a histopathologic and electron microscopic study. acta ophthalmol scand 2001;79:476–478. 20. yalvac is, sahin m, eksioglu u, midillioglu ik, aslan bs, duman s. primary viscocanalostomy versus trabeculectomy for primary open-angle glaucoma: threeyear prospective randomized clinical trial. j cataract refract surg 2004;30:2050–2057. 21. want a, ho dk-h, karri b, mathews d. the efficacy of viscocanalostomies and combined phacoemulsification with viscocanalostomies in the treatment of patients with glaucoma: a non-randomised observational study. bmc ophthalmol 2018;18:1–8. 22. gunenc u, ozturk t, arikan g, kocak n. long-term results of viscocanalostomy and phacoviscocanalostomy: a twelve-year follow-up study. int j ophthalmol 2015;8:1162. 23. awadalla ma, hassan km. phacoviscocanalostomy in pseudoexfoliation glaucoma versus primary open-angle glaucoma. can j ophthalmol 2011;46:77–82. 24. moghimi s, hamzeh n, mohammadi m, khatibi n, bowd c, weinreb rn. combined glaucoma and cataract surgery: comparison of viscocanalostomy, endocyclophotocoagulation, and ab interno trabeculectomy. j cataract refract surg 2018;44:557– 565. 25. tsagkataki m, bampouras t, choudhary a. outcomes of viscocanalostomy and phaco-viscocanalostomy in patients with advanced glaucoma. graefes arch clin exp ophthalmol 2018;256:1481–1487. 26. stangos an, mavropoulos a, sunaric-megevand g. phacoviscocanalostomy for open-angle glaucoma with concomitant age-related cataract. clin ophthalmol 2007;1:497. 27. wishart pk, wishart ms, choudhary a, grierson i. long−term results of viscocanalostomy in pseudoexfoliative and primary open angle glaucoma. clin experiment ophthalmol 2008;36:148–155. 28. friedman ds, jampel hd, lubomski lh, kempen jh, quigley h, congdon n, et al. surgical strategies for coexisting glaucoma and cataract: an evidence-based update. ophthalmology 2002;109:1902–1913. 29. masis m, mineault pj, phan e, lin sc. the role of phacoemulsification in glaucoma therapy: a systematic review and meta-analysis. survey of ophthalmology 2018;63:700–710. 30. park m, tanito m, nishikawa m, chihara e. ultrasound biomicroscopy of intrascleral lake after viscocanalostomy and cataract surgery. j glaucoma 2004;13:472–478. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 573 review article prevalence rates and risk factors for primary open angle glaucoma in the middle east rana torabi1, md; alon harris2, ms, phd, farvo; brent siesky2, phd; ryan zukerman2,3, ba; francesco oddone4, md, phd; sunu mathew1, mbbs, dnb; ingrida januleviciene5, md, phd; alice c. verticchio vercellin2, md, phd 1eugene and marilyn glick eye institute, department of ophthalmology, indiana, university school of medicine, indianapolis, in, usa 2icahn school of medicine at mount sinai, new york, ny, usa 3university of miami miller school of medicine, miami, fl, usa 4irccs fondazione bietti, rome, italy 5eye clinic of medical academy of lithuanian university of health sciences, kaunas, lithuania orcid: rana torabi: https://orcid.org/0000-0001-6356-9243 alon harris: https://orcid.org/0000-0001-8770-3726 abstract glaucoma is a multifactorial disease and a leading cause of irreversible blindness worldwide. current data has demonstrated the approximate distribution of primary openangle glaucoma (poag) in patients of european, african, hispanic, and eastern asian descent. however, a significant gap in the literature exists regarding the prevalence of poag in middle eastern (me) populations. current studies estimate me poag prevalence based on a european model. herein we screened 65 total publications on me prevalence of poag and specific risk factors using keywords: “glaucoma”, “prevalence”, “incidence”, “risk factor”, “middle east”, “mideast”, “persian”, “far east”, as well as searching by individual me countries through pubmed, embase, ovid, scopus, and trip searches with additional reference list searches from relevant articles published up to and including march 1, 2021. fifty qualifying records were included after 15 studies identified with low statistical power, confounding co-morbid ophthalmic diseases, and funding bias were excluded. studies of me glaucoma risk factors that identify chromosomes, familial trend, age/gender, socioeconomic status, lifestyle, intraocular pressure, vascular influences, optic disc hemorrhage, cup-to-disc ratio, blood pressure, obstructive sleep apnea, and diabetes mellitus were included in this systematic review. we conclude that the prevalence of poag in the me is likely higher than the prevalence rate that european models suggest, with me specific risk factors likely playing a role. however, these findings are severely limited by the paucity of population-level data in the me. well-designed, longitudinal population-based studies with rigorous inclusion and exclusion criteria are ultimately needed to accurately assess the epidemiology and specific mechanistic risk factors of glaucoma in me populations. keywords: epidemiology; glaucoma; middle east; prevalence; risk factors j ophthalmic vis res 2021; 16 (4): 644–656 644 © 2021 torabi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9755&domain=pdf&date_stamp=2019-07-17 poag in the middle east; torabi et al introduction glaucoma is a leading cause of irreversible blindness (defined as 6/120 visual acuity) and is responsible for up to 12% of all cases worldwide according to a 2014 meta-analysis by tham et al.[1, 2] glaucoma is a chronic, progressive optic neuropathy with a characteristic acquired optic nerve atrophy from retinal ganglion cell loss. there are two major subtypes of glaucoma: primary open-angle (poag) and closed-angle glaucoma, both being based on the anterior chamber angle as demonstrated by gonioscopy.[3] poag is a multifactorial disease and a leading cause of irreversible blindness worldwide. different populations present with different risk factors (rf) for and occurrence profiles for poag. in recent years, glaucoma has been shown to disproportionately affect people of asian and african descent (ad) compared to those of european descent (ed) (table 1a).[4] however, there have been few studies that focus specifically on the prevalence rates of glaucoma in the middle eastern (me) population. in 2017, alshawa et al identified the lack of extensive research into characterizing poag in the me.[5] this is concerning given the extrapolation that by 2040 over 110 million people worldwide will be affected by some form of glaucoma, with a disproportionate impact on asian and african patients.[2] the prevalence of poag and its rf have been well documented in patients from african, european, hispanic, and eastern asian countries.[1, 2, 6] this review seeks to determine the true prevalence rate of poag in me population. to the best of our knowledge, only two published studies specifically address me patients in their poag analysis – using a european model to create estimates for them.[1, 7] correspondence to: alon harris, ms, phd, farvo. icahn school of medicine at mount sinai 1468 madison avenue, annenberg 22-86 new york 10029, ny, usa. e-mail: palonharris@gmail.com received: 30-04-2021 accepted: 09-09-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9755 however, we postulate that poag prevalence in me patients is more similar to asian countries given the geographical, lifestyle, and epidemiological similarities they share. poag prevalence rates in asia are considerably higher than european model estimates (2.82%; 95% confidence interval, ci, 1.67-3.06% versus 1.47%; 95%ci 1.06-2.06%; table 1a), and reported clinical data from me countries shows a higher prevalence of poag than european estimates (table 1b). due to the multi-factorial nature of poag, a more specific understanding of me geographicspecific rf is also important for improving longterm poag management. rf for poag have been studied at length; however, there is a gap in the literature with regards to the rf of glaucoma in me patients. these rf may possibly include demographics such as age, gender, lifestyle, or genetics; as well as other ocular parameters such as intraocular pressure (iop), vascular influences, optic disc hemorrhage (dh), cup-to-disc ratio (c/d); and systemic comorbidities such as blood pressure (bp) and anti-hypertensive medications, obstructive sleep apnea (osa), and diabetes mellitus (dm) . overall, the goal of this review is to discuss current knowledge of poag in me countries, and to explore rf that may increase risk, or conversely be protective, for the development and progression of glaucoma in me populations. methods pubmed, embase, ovid, scopus, and trip searches were conducted from all available published articles through march 1, 2021 using mesh searches involving the terms “glaucoma”, “prevalence”, “incidence”, “risk factor”, “age”, “gender”, “lifestyle”, “genetics”, “iop”, “dh”, “c/d”, “bp”, “osa”, “dm”, “middle east”, “mideast”, “persian”, “far east”, as well as searching by individual me countries (i.e., saudi arabia, bahrain, kuwait, iraq, syria, oman, united arab emirates, jordan, qatar, lebanon, egypt, iran, this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: torabi r, harris a, siesky b, zukerman r, oddone f, mathew s, januleviciene i, verticchio vercellin a.c. prevalence rates and risk factors for primary open angle glaucoma in the middle east. j ophthalmic vis res 2021;16:644–656. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 645 https://knepublishing.com/index.php/jovr poag in the middle east; torabi et al yemen, palestine, and israel) to evaluate all pertinent articles, abstracts, and ongoing research projects. example of mesh search from pubmed: {(glaucoma [mesh terms]) and (prevalence [mesh terms])} and (iran [mesh terms]). reference lists from all relevant articles were reviewed to crossmatch and capture all pertinent articles. sixty-five records were screened and fifty were included in the qualitative synthesis [figure 1]. all studies were published in english. gray literature was not included. due to the paucity of available articles, a wide variety of studies were included (i.e., cross-sectional, population based, review, prospective cohort, and random quota sampling.) in order to maximize the quality of this review, only journal articles with clinically significant differences in chromosomal factors, familial trends, ocular factors, and systemic comorbidities of interest were included in this systematic review by various members of our team. articles that did not meet those standards or had low sample size (n < 500), confounding variables (e.g., co-morbid ophthalmic diseases), or funding bias were excluded. results epidemiology the average prevalence rate of poag in me countries was based off clinical studies conducted in the region of interest. we specifically included iran, israel, qatar, oman, and saudi arabia (sa) in our calculations due to data availability. a summary of the major me articles relating to poag prevalence have also been listed [table 2]. average prevalence of high-tension glaucoma (htg), normal-tension glaucoma (ntg), acute angle closure glaucoma (acg), and other forms were calculated by dividing the number of affected individuals by the number of individuals in the studied population at that particular time [table 3].[6, 8–17, 19] while worldwide rates of blindness secondary to glaucoma are predicted to decrease from 8.49 (95% ci 2.99–15.66) in 2015 to 8.43 (95% ci 2.75– 15.96) in 2020, the prevalence in the me are expected to keep rising from 6.89 (95% ci 2.20– 13.16) to 6.94 (95% ci 2.04–13.57).[20] we compared five me countries to approximate the prevalence of glaucoma and we estimate true me poag rates to be lower than patients of african or latino descent but greater than caucasian and east asian (ea) patients [figure 2]. immigrants from the me make up a considerable amount of the united states immigrant population with a 36% increase witnessed from 2010–2016 to over 1.1 million lawful permanent residents.[21] given the geographic diversity of the me, some of the rf for developing poag specific in subset regions like north africa or west asia (structural ocular differences, iop, myopia) could also be applied to patients of me descent.[4, 22, 23] genetic characteristics chromosomal influences in 2014, takamoto et al identified several genomewide candidate genes that may be involved, including the s1 rna binding-domain region on chromosome 2p21 and the caveolin regions on 7q31, to name a few.[24] similarly, in 2015, nakano et al identified three genetic loci through a genomewide association study (gwas) associated with poag in a japanese population.[25] follow-up of these alleles, and several others, in an me population, however, has led to largely negative associations with poag.[26–31] more recently, kondkar et al identified several polymorphisms of the endothelial nitric oxide synthase (nos3) gene that may modify the risk of poag in the sa population, possibly supporting the oxidative stress hypothesis for the pathogenesis of poag.[32] additionally, polymorphism of the six1/six6 gene locus has been identified in sa (genotype distribution, p = 0.012).[33] meanwhile in iran, a cohort study of 65 unrelated patients had a statistically significant increased occurrence of poag and the p53 pro72 allele (p < 0.05),[34] and a more recent iranian study demonstrated that polymorphisms of the il-10 gene promoter are significantly associated with susceptibility to poag similar to findings demonstrating il-10 polymorphisms to be predictive of poag pathogenesis in china.[35, 36] finally, a 2019 gwas connecting the apbb2 gene with poag risk in patients with african ancestry included individuals from sa (as individuals with african ancestry admixture), indicating that the apbb2 gene polymorphisms associated with poag may have further association with the greater me population.[37] 646 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 poag in the middle east; torabi et al table 1. current worldwide estimates of primary open-angle glaucoma including: (a) middle eastern (me) prevalence which is based on the european model. (b) revised me and worldwide prevalence which is based on the clinical studies presented in this study[3] world region ratio glaucoma to population >>>40 (a) me prevalence based on european model (b) me prevalence based on published clinical data in the literature middle east 1.47% 3.07% europe 2.23% southeast asia 2.38% india 2.55% china 2.66% latin america 3.35% japan 3.70% africa 4.32% world 2.65% 3.03% records iden�fied through database searching (n = 63) addi�onal records iden�fied through other sources (n = 2) records screened (n = 65) records excluded (n = 15) studies included in qualita�ve synthesis (n = 50) figure 1. flow chart showing method of literature search and results of literature review. familial trends glaucoma is associated with familial trends. the baltimore eye study conducted a populationbased survey and demonstrated higher rates of glaucoma in siblings (odds ratio, or = 3.69) than parents (or = 2.17) or children (or = 1.12).[38] no recent publications from the me have evaluated familial trends of glaucoma except for a single cross-sectional observational study of acg in iranian siblings which showed increased risk of acg among siblings (57.9%; 95% ci 52.6–73.7).[39] demographic risk factors age and gender in 2013, a review of glaucoma rates in central iran showed a ratio of 37:50 between men and women in poag occurrence.[14] this matches a survey of the united states that showed women to have higher self-reported visual impairment from glaucoma than men (or = 1.20; 95% ci 0.99– 1.45) and, generally, worldwide data on glaucoma incidence.[40, 41] journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 647 poag in the middle east; torabi et al table 2. summary of articles relating to primary open-angle glaucoma prevalence in middle eastern countries. study authors year of publication sample size age of patients prevalence of poag prevalence of glaucoma types and legal blindness from glaucoma in the western region of saudi arabia: a hospital-based study eid tm, el-hawary i, el-menawy w.[7] 2009 2,354 ≥20 years 30.5% prevalence and determinants of glaucoma in citizens of qatar aged 40 years or older: a community-based survey al-mansouri fa, kanaan a, gamra h, et al.[8] 2011 3,149 ≥40 years 1.71% oman eye study 2005: prevalence and determinants of glaucoma khandekar r, jaffer ma, al raisi a, et al.[9] 2008 3,324 ≥30 years 4.75% the prevalence and causes of blindness in the sultanate of oman: the oman eye study (oes) khandekar r, mohammed aj, negrel ad, et al.[10] 2002 11,417 0 to +60 years 1.02% glaucoma in oman: a review khandekar r, zutshi r.[11] 2006 estimate based on population of 1,869,580 ≥40 years 1.14/1000 the maccabi glaucoma study: treatment patterns and persistence with glaucoma therapy in a large health organization in israel goldshtein i, levkovitch-verbin h, shalev v, et al.[12] and levkovitch-verbin h, goldshtein i, chodick g, et al.[13] 2013 5,934 ≥45 years 1.61% a population-based survey of the prevalence and types of glaucoma in central iran: the yazd eye study pakravan m, yazdani s, javadi m-a, et al.[14] 2013 2,098 40-80 years 4.4% prevalence and risk factors of glaucoma in an adult population from shahroud, iran hashemi h, mohammadi m, zandvakil n, et al.[15] 2018 6,311 40-67 years 1.92% prevalence and causes of visual impairment among saudi adults attending primary health care centers in northern saudi arabia al-shaaln ff, bakrman ma, ibrahim am, et al.[17] 2011 617 ≥18 years 5.8% the prevalence and determinants of glaucoma among 40 years and older saudi residents in the riyadh governorate (except the capital) – a community based survey khandekar r, chauhan d, yasir zh, et al.[18] 2019 940 ≥40 years 5.6% socioeconomic status prevalence of poag in central iran are stratified by socioeconomic status and education, with 4% prevalence in urban and 7.7% prevalence in rural communities and more than 80% of the glaucoma population at <6th grade education.[14] a similar study in sa demonstrated 48.9% of the poag population to be illiterate, and 42.3% unemployed.[17] this overall trend 648 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 poag in the middle east; torabi et al table 3. prevalence of the different types of glaucoma in the middle east[5, 7–16, 18] iran israel oman saudi arabia qatar poag ntg 3.20% 1.70% 1.61% 1.55% 1.93% 2.92% 0.78% htg 1.50% 0.06% angle closure suspect 0.11% 0.11% 1.80% 2.71% 0.16% other glaucoma 0.40% 0.17% 1.02% 0.17% 0.27% total glaucoma 4.40% 2.20% 4.75% 5.80% 1.71% htg, high tension glaucoma; ntg, normal tension glaucoma; poag, primary open angle glaucoma table 4. average cup-to-disc ratios in patients of african, european, and asian descent[46–48] cup-to-disc ratio (c/d) african descent 0.35 european descent 0.24 korea 0.34 +/– 0.12 china 0.44 +/– 0.17 singapore 0.40 +/– 0.15 matches a 2015 uk study which correlated individuals reporting glaucoma with more adverse socioeconomic characteristics, based on the townsend deprivation index.[42] lifestyle in 2013, a multivariate model distinguished certain lifestyle characteristics that may be associated with higher rates of poag in the general population. certain factors, such as alcohol usage (not associated with poag; p < 0.05), matched existing literature.[43] interestingly, heavy tobacco usage (≥40 pack-years) showed an association with increased poag rates (or 3.93; 95% ci 1.12–13.80; p = 0.03).[43] currently no studies have investigated tobacco usage in me poag patients. ocular risk factors intraocular pressure (iop) many patients with glaucomatous visual impairment experience disease progression despite physiologic or medically lowered iop. specifically, asian epidemiologic studies have evaluated 52–92% of poag cases to have ntg.[23] the rates of ntg, however, varies widely among different patient population groups (57.1% in ad vs 20–28.9% in ed) despite similar rates of poag (2.02+/–1.21%). interestingly, even mean iop varies among asian countries; mean iop values assessed in japan were 13.1 mmhg (standard deviation, sd = 3.0) and 16.1 mmhg in korea (sd = 3.2).[23] in the me, a comprehensive study of iop in healthy (non-glaucomatous) iranian patients found a mean iop of 14.5 mmhg (sd = 2.5).[44] no studies comparing ntg or htg were found. vascular influences reductions in the retinal capillary and retrobulbar blood flow (bf) have been shown to strongly correlate with changes in optic nerve head (onh) and macular thickness in poag patients of ad.[4] this data suggests that ocular vascular health may be a pathophysiologic explanation for the higher rates of poag seen in patients of ad versus ed.[4] studies of bf and bulk perfusion have not been published in me population. optic disc hemorrhages (dh) dh flame-shaped bleeds typically occur around the temporal portion of the optic disc. in 2003, gazzard et al analyzed a cohort of 167 south east asian patients with poag and found only 5 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 649 poag in the middle east; torabi et al table 5. summary of possible risk factors of primary open angle glaucoma in middle eastern countries versus non-middle eastern countries risk factors non-middle eastern countries middle eastern countries chromosomes o o[32–36] familial trends o ? age and gender o o[14, 17] socioeconomic status o o[14, 17] lifestyle o ? intraocular pressure o o[44] vascular o ? optic disc hemorrhage o ? cup-to-disc ratio o ? blood pressure o ? obstructive sleep apnea o ? diabetes mellitus x x[59] key: x, no association; o, association; ?, unclear/unknown association figure 2. graphical representation of worldwide primary open-angle glaucoma and angle closure glaucoma prevalence rates. cases of dh, with 80% associated with poag.[45] overall, they reported a level of dh prevalence as 2.99%, which is comparable to rates in caucasian patients at 2.44%. interestingly, dh were not seen as frequently in ntg patients in their study.[45] whether or not these values can be replicated in a larger study and also be applied to me populations has yet to be determined. cup-to-disc ratio (c/d) increased c/d is a known rf for the progression of glaucoma (0.3 healthy, 0.7 glaucomatous). as early as 1985, beck et al recorded an average c/d of 0.35 in ad patients and 0.24 in caucasian patients (p < 0.0001) showcasing higher vertical c/d ratios for ad patients.[46] currently such studies have not been performed in me patients. 650 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 poag in the middle east; torabi et al systemic comorbidities blood pressure (bp) and anti-hypertensive medications while bp control is an essential part of care for many patients, hypertensive medications may be associated with glaucoma progression.[47] in 2017, a study of patients from several me countries reported a prevalence of ht at 31%.[48] at the time, 47% of this group was receiving antihypertensive treatment – with only 19% successfully reaching physiologic bp. specifically, older women had a higher frequency of systemic arterial hypertension (ht) treatment than men and younger patients (p < 0.0001) suggesting a correlation between prevalence of glaucoma and overtreatment of ht in female patients.[48] the link between lowered bp and glaucoma progression is supported by the thessaloniki eye study, which used tomography to measure the optic disc while recording systolic bp (sbp) and diastolic bp (dbp). stratification for bp and antihypertensive drug classes showed that dbp < 90 mmhg led to increased c/d.[49] similarly, a meta-analysis from the usa suggests physiological dips in nocturnal bp may lead to glaucoma progression over a two-year span (or 3.32 [1.84–6.00] dbp; or 2.09 [1.20–3.64] sbp).[50] obstructive sleep apnea (osa) a 2019 study by fan et al demonstrated a significantly increased risk of rnfl thinning progression (hazard ratio, hr, 8.448, 95% ci 1.464–48.752, p = 0.017) in taiwanese patients with severe osa, indicative of a higher risk of glaucomatous structural deterioration.[51] recent prevalence studies and meta-analyses have also demonstrated a correlation between severe osa and glaucoma; in 2015, wu et al demonstrated a significantly increased risk of glaucoma in patients with osa/hypopnea syndrome (osahs) (or = 1.65, 95% ci 1.44–1.88; i2 = 43%).[52–54] as for poag specifically, in 2018 friedlander et al demonstrated a significant association between poag and osa, noting a prevalence rate of 20.49% in patients with osa when compared to the general population (2.5%) among a study sample of 225 patients (p < 0.00001).[55] additionally, a subgroup analysis of a 2015 meta-analysis from wu et al demonstrated increased poag risk among osa patients (or = 1.87, 95% ci 1.54–2.33, i2 = 0%).[52] there is only one 2019 study from sa, which demonstrates the prevalence of glaucoma in sa osa patients was higher than in similar studies conducted in europe and asia, but less than the united states, suggesting a possible geographic contribution.[56] diabetes mellitus (dm) over 343 million people worldwide are affected by type ii dm, and the me has the second highest rate of increase in dm.[57] poag and dm are both diseases with vascular components, and dm may portend to the progression of poag by predisposing patients to vascular autoregulatory dysfunction and impaired release of endothelial factors in retinal, choroidal, and retrobulbar circulation.[58] in the me, however, a small study in yemen evaluating glaucomatous visual impairment in diabetic patients found only 4.4% of patients to have concurrent glaucoma and dm; other ocular diseases occurred more frequently in the dm me population.[59] similarly, a european gwas demonstrated no correlation between dmand glaucoma-related traits.[60] discussion glaucoma is a leading cause of irreversible blindness that with careful monitoring can be managed. however, current studies in the literature have not specifically studied the me population. based on current data we suggest the me has a higher poag prevalence than previously documented in the literature, which is based on european model instead of rigorous, clinical studies. we also explore factors that may increase risk, or conversely be protective, for the development and progression of glaucoma in me populations. table 5 summarizes current knowledge about known rf in me versus nonme countries. based on the aforementioned studies, due to lack of published studies the rf of familial trends, lifestyle, odh, vascular, c/d, bp, and osa are termed as having an unclear association between poag and the me population. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 651 poag in the middle east; torabi et al genetic characteristics many genes have been implicated in the development of poag and given the rate of consanguinity/endogamy in the me, warrant significant consideration in this population. as previously mentioned by nakano et al, several gwas of the japanese population have identified specific alleles with a strong association with glaucoma.[24] at this time, however, there are only isolated studies looking at specific chromosomal factors and their relationship to glaucoma prevalence or its pathogenesis. current studies performed on me patients do not readily point to an all-encompassing genetic correlation of poag rates between me, european, or asian patients. such studies are important and could be the next step in developing stricter screening guidelines for at-risk families, especially those who are not aware of their medical family history. there are certain demographic characteristics that may also lead to higher rates of glaucoma in the middle east. poag is already commonly known to be associated with an aging population, but features like gender, lifestyle, and socioeconomic status may also play a role in prevalence and progression rates. there are few studies reporting age/gender rf for me patients. however, preliminary data seems to suggest a gender bias for aging women to have higher rates of reported visual impairment.[12] this may simply be due to reporting bias, gender inequality for accessing healthcare, or possible loss of protective factors such as estrogen as women age. another factor is socioeconomic status. individuals with less education or those in a more rural home environment portend to have a higher prevalence of poag.[12, 15, 41] the data suggests a possible correlation to a lack of adequate preventive healthcare, leading to more diagnoses of poag. lastly, lifestyle characteristics may be a significant rf. alcohol was not associated with increased prevalence of poag; however, according to our literature search tobacco has been studied and is correlated with higher poag prevalence.[42] this is particularly concerning for the me, as arab nations are experiencing a tobacco epidemic with approximately half of all men reporting daily smoking habits, and half of this population smoking >20 cigarettes/day.[61] ocular risk factors there are certain physiological parameters of the eye itself that predispose to the occurrence of glaucoma including, but not limited to, iop, dh, and c/d ratios. iop remains the only approved modifiable treatment target in poag. it is well-known that asian populations have a higher incidence of ntg.[22] since we are estimating that me patients have a closer glaucoma prevalence to asian population, it would be interesting to study whether or not there is a higher prevalence of htg or ntg in the me population. per our literature search, this type of study has not been conducted yet. decreased capillary bf may also correlate with poag. vascular health, however, is complicated and multifactorial. bulk perfusion, or ocular perfusion pressure (opp), is related to mean arterial pressure (map) and iop through the formula opp = map – iop. as such, vascular insult can occur during iop and bp fluctuations, both of which are mediated by vascular autoregulation and can affect glaucoma prevalence.[3] ultimately, this interplay between opp and bp may explain the pathophysiology of poag patients even with medication controlled iop, especially those found in ea and me countries.[62, 63] in regard to dh, these may be an rf for glaucoma progression due to structural and functional damage from the bleed, specifically poag versus ntg. lastly, postulations have been made between glaucoma and its connection with increased disc cupping. similar results of increased c/d can be seen when comparing the prevalence of c/d between various asian nations with comparable vertical cupping of approximately 0.39 in korean, chinese, and singaporean populations [table 4].[64–66] using a multiple regression analysis, positive associations for increased c/d (p < 0.001) were observed with factors such as increasing age, increasing iop, and decreased diastolic bp, while body mass index had a negative association.[65, 66] overall, the prevalence of increased disc cupping in asians was comparable to patients of ad despite their lower rates of glaucoma.[65, 66] despite its high association with glaucoma progression in ad patients, the same increase of c/d was not noted to have a similar rise in poag in asian patients when normalizing for other confounding variables. such correlations question whether or not c/d is a 652 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 poag in the middle east; torabi et al significant determinant of glaucoma risk in patients of asian or me descent. systemic comorbidities certain systemic illnesses have also been postulated to affect the incidence and progression of glaucoma including systemic arterial ht, osa, and dm. ht and aggressive bp control can lead to glaucoma progression as shown in the thessaloniki eye study and the bowe et al group.[54, 55] this data warrants evaluation in asian and me patients with physiologic iop as it suggests low bp as a pathogenetic factor for glaucoma. in regard to osa in the me, data is generally lacking about osa, but available data suggests a dramatic increase in the prevalence of osa, likely due to an uncontrolled obesity epidemic. epidemiologically, it is estimated that 33.3% of sa patients, 16.8% of jordanian patients, 27.3% of iranian patients, and 20.9% of patients in dubai should be considered high-risk for osa.[67–71] still, there is limited data describing the interplay of osa and glaucoma in the me. there is currently a high rate of dm in the me, which has been shown to influence and likely dysregulate vascular endothelial factors affecting bf. previous data showed that changes in retinal capillary bf correlated more strongly with changes in onh morphology in patients with dm, suggesting that changes in retinal bf may play a larger role in glaucomatous disease progression in patients with poag with diabetes. however, current studies reviewing the prevalence of poag have not shown a significant association between glaucoma and dm, suggesting that the high prevalence of dm in the me may not be a large rf for glaucoma.[19, 72–74] given the limited nature of me studies, however, it is possible for either hypothesis to be true. limitations in reviewing the prevalence of glaucoma and potential role of rf in the me population, there are significant challenges and limitations to acknowledge. first, there is the relative ambiguity of the definition of the me, which generally includes west asia and north africa, but sometimes includes turkey, the south caucuses, afghanistan, and pakistan.[75] notably, prevalence data was not available from all me countries – including jordan and kuwait (though glaucoma has become the leading cause of registered blindness in the kuwaiti population over 60).[76] for similar reasons, north africa was excluded from review. importantly, the definition of glaucoma also varies among studies – generally following world health organization (who) definitions or using more arbitrary iop values to define disease. similarly, population sizes and characteristics (e.g., age range) varied between studies. given the paucity of robust, uniform randomizedcontrolled clinical studies in me populations, a limitation of this review includes not being able to present data as a meta-analysis. lastly, selection bias may also affect studies with data collected from local/state hospitals and may be less representative of an entire country’s population. summary despite growing prevalence of glaucoma globally, studies investigating glaucoma in me populations are underrepresented. of the available data, many studies have methodological limitations affecting the consensus of published studies. european modeling to estimate me prevalence rates likely underestimate true values. accurate poag rates in me populations are likely higher than in ed and ea countries, and lower than ad or lad populations. similarly, rf presented in this review may influence me rates of poag, but data is lacking to confirm their role in disease pathogenesis. early associations have been found between the factors of chromosomes, age/gender, socioeconomic status, iop, and vascular influences in me population. no known associations have been found linking dm. rf including familial trends, lifestyle, od hemorrhages, cdr, bp, and osa have unclear associations such that an association can be proved or disproved at this time for me population. therefore, we encourage well-designed, longitudinal population-based me studies with carefully considered inclusion and exclusion criteria to accurately assess the epidemiology of glaucoma and specific mechanistic rf in me populations for better outcomes and improvement in quality of life. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 653 poag in the middle east; torabi et al financial support and sponsorship alon harris was supported by nih grant (r01ey030851), nsf dms (1853222/2021192), and in part by a challenge grant award from research to prevent blindness, ny. conflicts of interest the authors declare no competing interests. dr. alon harris would like to disclose that he received remuneration from adom, qlaris, luseed, and cipla for serving as a consultant, and he serves on the board of adom, qlaris, and phileas pharma. alon harris holds an ownership interest in adom, luseed, oxymap, qlaris, phileas pharma, and qulent. all relationships listed above are pursuant to icahn school of medicine’s policy on outside activities. the contribution of the author dr. francesco oddone was supported by fondazione roma and by the italian ministry of health. none of the other authors listed have any financial disclosures. references 1. quigley ha, broman at. the number of people with glaucoma worldwide in 2010 and 2020. br j ophthalmol 2006;90:262–267. 2. tham y-c, li x, wong ty, quigley ha, aung t, cheng c-y. global prevalence of glaucoma and projections of glaucoma burden through 2040: a systematic review and meta-analysis. ophthalmology 2014;121:2081–2090. 3. prum be, rosenberg lf, gedde sj, mansberger sl, stein jd, moroi se, et al. primary open-angle glaucoma preferred practice pattern guidelines. ophthalmology 2016;123:41–111. 4. huck a, harris a, siesky b, kim n, muchnik m, kanakamedala p, et al. vascular considerations in glaucoma patients of african and european descent. acta ophthalmol 2014;92:e336–e340. 5. alshawa l, harris a, gross j, snyder a, rao a, siesky b. primary open-angle glaucoma in patients of middle eastern descent. saudi j ophthalmol 2017;31:209–210. 6. cheng j-w, zong y, zeng y-y, wei r-l. the prevalence of primary angle closure glaucoma in adult asians: a systematic review and meta-analysis. plos one 2014;9:e103222. 7. eid tm, el-hawary i, el-menawy w. prevalence of glaucoma types and legal blindness from glaucoma in the western region of saudi arabia: a hospital-based study. int ophthalmol 2009;29:477–483. 8. al-mansouri fa, kanaan a, gamra h, khandekar r, hashim sp, al qahtani o, et al. prevalence and determinants of glaucoma in citizens of qatar aged 40 years or older: a community-based survey. middle east afr j ophthalmol 2011;18:141–149. 9. khandekar r, jaffer ma, al raisi a, zutshi r, mahabaleshwar m, shah r, et al. oman eye study 2005: prevalence and determinants of glaucoma. east mediterr health j 2008;14:1349–1359. 10. khandekar r, mohammed aj, negrel ad, al riyami a. the prevalence and causes of blindness in the sultanate of oman: the oman eye study (oes). br j ophthalmol 2002;86:957–962. 11. khandekarl r, zutshi r. glaucoma in oman: a review. j glaucoma 2006;15:271–273. 12. goldshtein i, levkovitch-verbin h, shalev v, zigman n, chodick g. phs78 persistence with glaucoma therapy in a lrage health organization in israel. value health 2013;16:a199. 13. levkovitch-verbin h, goldshtein i, chodick g, zigman n, shalev v. the maccabi glaucoma study: prevalence and incidence of glaucoma in a large israeli health maintenance organization. am j ophthalmol 2014;158:402–408.e401. 14. pakravan m, yazdani s, javadi m-a, amini h, behroozi z, ziaei h, et al. a population-based survey of the prevalence and types of glaucoma in central iran: the yazd eye study. ophthalmology 2013;120:1977–1984. 15. hashemi h, mohammadi m, zandvakil n, khabazkhoob m, hassan emamiane m, shariati m, et al. prevalence and risk factors of glaucoma in an adult population from shahroud, iran. j curr ophthalmol 2018;31:366–372. 16. al-bahlal a, khandekar r, al rubaie k, alzahim t, edward dp, kozak i. changing epidemiology of neovascular glaucoma from 2002 to 2012 at king khaled eye specialist hospital, saudi arabia. indian j ophthalmol 2017;65:969– 973. 17. al-shaaln ff, bakrman ma, ibrahim am, aljoudi as. prevalence and causes of visual impairment among saudi adults attending primary health care centers in northern saudi arabia. ann saudi med 2011;31:473–480. 18. khandekar r, chauhan d, yasir zh, al-zobidi m, judaibi r, edward dp. the prevalence and determinants of glaucoma among 40 years and older saudi residents in the riyadh governorate (except the capital) – a community based survey. saudi j ophthalmol 2019;33:332–337. 19. khandekar r, mohammed aj. visual disabilities among diabetics in oman. saudi med j 2005;26:836–841. 20. kahloun r, khairallah m, resnikoff s, cicinelli mv, flaxman sr, das a, et al. prevalence and causes of vision loss in north africa and middle east in 2015: magnitude, temporal trends and projections. br j opthalmol 2018. 21. cumoletti m, batalova, j. middle eastern and north african immigrants in the united states [internet]. online j mpi. 2018 [cited 2020 september 15]. available from: https://www.migrationpolicy.org/article/middle-easternand-north-african-immigrants-united-states-2016. 22. sit aj. intraocular pressure variations: causes and clinical significance. can j ophthalmol 2014;49:484–488. 23. cho hk, kee c. population-based glaucoma prevalence studies in asians. surv ophthalmol 2014;59:434–447. 24. takamoto m, araie m. genetics of primary open angle glaucoma. jpn j ophthalmol 2014;58:1–15. 25. nakano m, ikeda y, taniguchi t, yagi t, fuwa m, omi n, et al. three susceptible loci associated with primary openangle glaucoma identified by genome-wide association 654 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 https://www.migrationpolicy.org/article/middle-eastern-and-north-african-immigrants-united-states-2016 https://www.migrationpolicy.org/article/middle-eastern-and-north-african-immigrants-united-states-2016 poag in the middle east; torabi et al study in a japanese population. proc natl acad sci 2009;106:12838–12842. 26. kondkar aa, azad ta, almobarak fa, abu-amero kk, alobeidan sa. polymorphism rs7961953 in tmtc2 gene is not associated with primary open-angle glaucoma in a saudi cohort. ophthalmic genet 2019;40:74–76. 27. kondkar aa, azad ta, almobarak fa, kalantan h, sultan t, al-obeidan sa, et al. polymorphism rs11656696 in gas7 is not associated with primary open angle glaucoma in a saudi cohort. genet test mol biomark 2017;21:754–758. 28. kondkar aa, sultan t, almobarak fa, kalantan h, abuamero kk, al-obeidan sa. plexin domain containing 2 (plxdc2) gene polymorphism rs7081455 may not influence poag risk in a saudi cohort. bmc res notes 2018;11:733. 29. kondkar aa, edward nb, kalantan h, al-kharashi as, altuwaijri s, mohamed g, et al. lack of association between polymorphism rs540782 and primary open angle glaucoma in saudi patients. j negat results biomed 2017;16:3. 30. abu-amero kk, kondkar aa, mousa a, almobarak fa, alawad a, altuwaijri s, et al. analysis of cyclin-dependent kinase inhibitor-2b rs1063192 polymorphism in saudi patients with primary open-angle glaucoma. genet test mol biomark 2016;20:637–641. 31. narooie-nejad m, rasouli a, mousavi m, rohani mr. study of myoc gene mutation in poag patients in zahedan, iran. clin lab 2017;63:1283–1291. 32. kondkar aa, azad ta, sultan t, osman ea, almobarak fa, al-obeidan sa. association of endothelial nitric oxide synthase (nos3) gene polymorphisms with primary open-angle glaucoma in a saudi cohort. plos one 2020;15:e0227417–e0227417. 33. kondkar aa, azad ta, almobarak fa, kalantan h, sultan t, alsabaani na, et al. polymorphism rs10483727 in the six1/six6 gene locus is a risk factor for primary open angle glaucoma in a saudi cohort. genet test mol biomark 2018;22:74–78. 34. neamatzadeh h, soleimanizad r, atefi a, zare-shehneh m, gharibi s, shekari a, et al. association between p53 codon 72 (arg72pro) polymorphism and primary open-angle glaucoma in iranian patients. iran biomed j 2015;19:51–56. 35. fakhraie g, parvini f, ghanavi j, saif s, farnia p. association of il-10 gene promoter polymorphisms with susceptibility to pseudoexfoliation syndrome, pseudoexfoliative and primary open-angle glaucoma. bmc med genet 2020;21:32. 36. zhang yh, xing yq, chen z, ma xc, lu q. association between interleukin-10 genetic polymorphisms and risk of primary open angle glaucoma in a chinese han population: a case-control study. int j ophthalmol 2019;12:1605–1611. 37. the genetics of glaucoma in people of african descent (gglad) consortium. association of genetic variants with primary open-angle glaucoma among individuals with african ancestry. jama 2019;322:1682–1691. 38. tielsch jm, katz j, sommer a, quigley ha, javitt jc. family history and risk of primary open angle glaucoma. the baltimore eye survey. arch ophthalmol 1994;112:69– 73. 39. yazdani s, akbarian s, pakravan m, afrouzifar m. prevalence of angle closure in siblings of patients with primary angle-closure glaucoma. j glaucoma 2015;24:149–153. 40. vajaranant ts, nayak s, wilensky jt, joslin ce. gender and glaucoma: what we know and what we need to know. curr opin ophthalmol 2010;21:91–99. 41. ryskulova a, turczyn k, makuc dm, cotch mf, klein rj, janiszewski r. self-reported age-related eye diseases and visual impairment in the united states: results of the 2002 national health interview survey. am j pub health 2008;98:454–461. 42. shweikh y, ko f, chan mpy, patel pj, muthy z, khaw pt, et al. measures of socioeconomic status and self-reported glaucoma in the uk biobank cohort. eye 2015;29:1360– 1367. 43. renard jp, rouland jf, bron a, sellem e, nordmann j-p, baudouin c, et al. nutritional, lifestyle and environmental factors in ocular hypertension and primary open-angle glaucoma: an exploratory case-control study. acta ophthalmol 2013;91:505–513. 44. hashemi h, kashi ah, fotouhi a, mohammad k. distribution of intraocular pressure in healthy iranian individuals: the tehran eye study. br j ophthalmol 2005;89:652–657. 45. gazzard g, morgan w, devereux j, foster p, oen f, seah s, et al. optic disc hemorrhage in asian glaucoma patients. j glaucoma 2003;12:226–231. 46. beck rw, messner dk, musch dc, martonyi cl, lichter pr. is there a racial difference in physiologic cup size? ophthalmology 1985;92:873–876. 47. deb ak, kaliaperumal s, rao va, sengupta s. relationship between systemic hypertension, perfusion pressure and glaucoma: a comparative study in an adult indian population. indian j ophthalmol 2014;62:917–922. 48. yusufali am, khatib r, islam s, alhabib kf, bahonar a, swidan hm, et al. prevalence, awareness, treatment and control of hypertension in four middle east countries. j hypertens 2017;35:1457–1464. 49. topouzis f, coleman al, harris a, jonescu-cuypers c, yu f, mavroudis l, et al. association of blood pressure status with the optic disk structure in non-glaucoma subjects: the thessaloniki eye study. am j ophthalmol 2006;142:60– 67. 50. bowe a, grunig m, schubert j, demir m, hoffmann v, kütting f, et al. circadian variation in arterial blood pressure and glaucomatous optic neuropathy– a systematic review and meta-analysis. am j hypertens 2015;28:1077–1082. 51. fan yy, su ww, liu ch, chen hs-l, wu s-c, chang shl, et al. correlation between structural progression in glaucoma and obstructive sleep apnea. eye 2019;33:1459–1465. 52. wu x, liu h. obstructive sleep apnea/hypopnea syndrome increases glaucoma risk: evidence from a meta-analysis. int j clin exp med 2015;8:297–303. 53. shi y, liu p, guan j, lu y, su k. association between glaucoma and obstructive sleep apnea syndrome: a meta-analysis and systematic review. plos one 2015;10:e0115625. 54. chaitanya a, pai vh, mohapatra ak, ve rs. glaucoma and its association with obstructive sleep apnea: a narrative review. oman j ophthalmol 2016;9:125–134. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 655 poag in the middle east; torabi et al 55. friedlander ah, graves ll, chang ti, kawakami kk, lee uk, grabich sc, et al. prevalence of primary open-angle glaucoma among patients with obstructive sleep apnea. oral surg oral med oral pathol oral radiol 2018;126:226– 230. 56. bagabas n, ghazali w, mukhtar m, alqassas i, merdad r, maniyar a, et al. prevalence of glaucoma in patients with obstructive sleep apnea. j epidemiol glob health 2019;9:198–203. 57. abuyassin b, laher i. diabetes epidemic sweeping the arab world. world j diabetes 2016;7:165–174. 58. gerber al, harris a, siesky b, lee e, schaab tj, huck a, et al. vascular dysfunction in diabetes and glaucoma: a complex relationship reviewed. j glaucoma 2015;24:474– 479. 59. al-akily sa, bamashmus ma, gunaid aa. causes of visual impairment and blindness among yemenis with diabetes: a hospital-based study. east mediterr health j 2011;17:831– 837. 60. laville v, kang jh, cousins cc, iglesias ai, nagy r, cooke bailey jn. genetic correlations between diabetes and glaucoma: an analysis of continuous and dichotomous phenotypes. am j ophthalmol 2019;206:10. 61. global tobacco surveillance system collaborating group. global tobacco surveillance system (gtss): purpose, production, and potential. j sch health 2005;75:15–24. 62. cherecheanu ap, garhofer g, schmidl d, werkmeister r, schmetterer l. ocular perfusion pressure and ocular blood flow in glaucoma. curr opin pharmacol 2013;13:36–42. 63. choi j, kook ms. systemic and ocular hemodynamic risk factors in glaucoma. biomed res int 2015;2015:141905. 64. kim yj, kim jm, shim sh, bae jh, park kh, the epidemiologic survey committee of the korean ophthalmological s. associations between optic cupto-disc ratio and systemic factors in the healthy korean population. korean j ophthalmol 2015;29:336–343. 65. amerasinghe n, wong ty, wong wl, mitchell p, shen sy, loon s-c, et al. determinants of the optic cup to disc ratio in an asian population: the singapore malay eye study (simes). arch ophthalmol 2008;126:1101–1108. 66. kuang tm, liu cj, ko yc, lee sm, cheng cy, chou p. distribution and associated factors of optic disc diameter and cup-to-disc ratio in an elderly chinese population. j chin med assoc 2014;77:203–208. 67. mahboub b, safarainni b, alhariri h, vats m. sleep breathing disorders in female population of dubai, uae. health 2013;05:2091–2096. 68. bahammam as, alrajeh ms, al-jahdali hh, binsaeed aa. prevalence of symptoms and risk of sleep apnea in middle-aged saudi males in primary care. saudi med j 2008;29:423–426. 69. bahammam as, al-rajeh ms, al-ibrahim fs, arafah ma, sharif mm. prevalence of symptoms and risk of sleep apnea in middle-aged saudi women in primary care. saudi med j 2009;30:1572–1576. 70. khassawneh b, ghazzawi m, khader y, alomari m, amarin z, shahrour b, et al. symptoms and risk of obstructive sleep apnea in primary care patients in jordan. sleep breath 2008;13:227–232. 71. khazaie h, maroufi a. obstructive sleep apnea syndrome; a neglected cause of traffic collision among iranian public transport drivers. j inj violence res 2014;6:99–99. 72. al-nozha mm, al-maatouq ma, al-mazrou yy, al-harthi ss, arafah mr, khalil mz, et al. diabetes mellitus in saudi arabia. saudi med j 2004;25:1603–1610. 73. al-till mi, al-bdour md, ajlouni km. prevalence of blindness and visual impairment among jordanian diabetics. eur j ophthalmol 2005;15:62–68. 74. herman wh, aubert re, engelgau mm, thompson tj, ali ma, sous es, et al. diabetes mellitus in egypt: glycaemic control and microvascular and neuropathic complications. diabet med 2004;15:1045–1051. 75. scharnweber g. introduction: what and where is the middle east. in: teachmideast, editor. teaching the middle east: a resource guide for american educators. teachmideast.org: middle east policy council. p. 6. 76. pandova mg, al-merjan ji, sadeq na. registered blindness in kuwait–15 years of dynamic changes. ophthalmic epidemiol 2019;26:75–83. 656 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 review article phosphodiesterase type 5 inhibitors and visual side effects: a narrative review francisco barroso1, md; joão crispim ribeiro2, md; eduardo p. miranda1, md 1federal university of ceara, fortaleza, ceara, brazil 2christus university center, fortaleza, ceara, brazil orcid: francisco barroso: https://orcid.org/0000-0003-3152-8839 abstract phosphodiesterase type 5 inhibitors such as sildenafil citrate and tadalafil are well known for the treatment of erectile dysfunction. however, their use in the presence of pulmonary hypertension can cause ophthalmologic side effects, including non-arteritic optic ischemic neuropathy, chorioretinopathy, glaucoma, and optic atrophy. the present review aimed to identify these visual side effects and provide recommendations. we identified articles published from january 2000 to march 2019 on diseases arising from the management of sexual dysfunction in urology or pulmonary hypertension in pneumonia that could cause pathologic alterations in eye structure based on a literature search of the medline electronic database using keywords for the most common adverse effects and different kinds of phosphodiesterase 5 inhibitors. after applying the exclusion criteria, we selected 36 of the 77 articles initially identified to write the narrative review and added 20 additional articles to completely describe the pathological entities. phosphodiesterase type 5 inhibitors can cause side effects in the eye including ocular surface abnormalities, increased intraocular pressure and glaucoma, uveitis, non-arteritic ischemic neuropathy, chorioretinopathy, retinal occlusion, and visual field changes. there is an increased need for well-performed studies to better understand these side effects, which are common due to the wide use of sildenafil. keywords: adverse effects; eye manifestations; physiological; review; sexual dysfunction; sildenafil citrate j ophthalmic vis res 2021; 16 (2): 248–259 introduction erectile dysfunction (ed) is defined as a persistent inability to achieve and/or maintain an erection correspondence to: francisco barroso, md. manuel jacare st. 150. fortaleza, ceara 60175-110, brazil. e-mail: fvictorcbarroso@gmail.com received: 03-11-2019 accepted: 10-11-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i2.9088 to allow satisfactory sexual relations. it is a prevalent condition, with over 18 million men affected worldwide. ed affects an estimated 9.1% of men aged 40–49 years, 15.2% of men aged 50–59 years, 29.4% of men aged 60–69 years, and 54.9% of men older than 70 years.[1] the first line of treatment for ed is phosphodiesterase this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: barroso f, ribeiro jc, miranda ep. phosphodiesterase type 5 inhibitors and visual side effects: a narrative review. j ophthalmic vis res 2021;16:248–259. 248 © 2021 barroso et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i2.9088&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr pde5i and ocular side effects; barroso et al type 5 inhibitors (pde5i). this drug was first developed to treat pulmonary hypertension and muscle spasms; however, its most notable side effect, prolonged erection, soon became the focus of its use in clinical practice. in 1998, the food and drug administration (fda) approved its use as a clinically effective and safe treatment for ed.[2] there are 11 types of pdes, all of which function to degrade cyclic adenosine monophosphate (ampc) to adenosine monophosphate (amp) and gmpc to guanosine monophosphate (gmp).[3] sildenafil citrate (sc), a selective inhibitor of pde5i present in the cavernous bodies in the penis, is responsible for smooth muscle relaxation and, consequently, inducing an erection.[1] pde5i can cross the blood– brain and blood–retinal barriers and may partially inhibit the pde 6 enzyme present in the retina, with significant dose-dependent changes in photoreceptors and the optical nerve.[4–6] the main contraindication for the use of pde5i is its concomitant use with nitrates, which can lead to hypotension and ischemic events.[4] the main reported side effects of pde5i are headaches, dizziness, blushing, nasal congestion, dyspepsia, and visual changes. the most common visual side effects are photophobia, cyanopsia, and haze. most of the visual effects can be reversed weeks after stopping use of the medication.[3] other ophthalmologic disturbances described in the literature include keratitis, ocular surface abnormalities, chorioretinopathy, vessel occlusion, retinal detachment, and optic neuropathy.[1, 4, 5, 7] considering the wide use of pde5i, clinicians should know its side effects profile. this study reviewed the most common ocular effects related to the use of pde5i. methods a literature search was conducted through the medline online electronic database for articles written in english published from january 2000 to march 2019. the reason to delimitate the research to this period was to evaluate recent developments regarding pde5i and their side effects. thus, this review aimed to perform a current, but thorough, analysis of published articles. we used the following descriptors in sequence, all of which had to be present in the title of the article: (1) keratitis or (2) surface abnormalities or (3) chorioretinopathy or (4) ocular or (5) intraocular pressure or (6) glaucoma or (7) nonarteritic anterior ischemic optic neuropathy or (8) retinal occlusion or (9) optic atrophy or (10) visual changes or (11) electroretinography or (12) uveitis or (13) retinal and (14) sildenafil and (15) phosphodiesterase 5 inhibitors and (16) tadalafil and (17) viagra and (18) vardenafil and (19) avanafil and (20) udenafil and (21) mirodenafil and (22) lodenafil and 2000/01/01: 2019/03/31. the keywords from 1 to 13 were searched again with and 14 added; the same process was performed to add keywords 15 to 22. results we selected 36 of the 77 articles initially identified for the literature review, including both clinical and experimental studies. we also included 20 additional articles to completely describe the pathological entities [figure 1]. we analyzed the articles for the inclusion and exclusion criteria. the inclusion criteria were articles that had in their titles at least one combination of the descriptors in the search strategy, publications written in the english language, and relevant content in the article regarding the research topic. the exclusion criteria were articles that had in the title or abstract nonophthalmic pde adverse effects related to pde5i use; reviews and book chapters; non-original studies including editorials, exam alteration studies, preface and brief communication; duplicate articles, articles written in a language other than english; and unavailable study abstract or full text. we added two studies related to non-arteritic anterior ischemic optic neuropathy (naion) since our search method identified few studies. furthermore, we also included 13 letters to editors that described important side effects. we did not find optic atrophy studies related to our topic; similarly, no studies on mirodenafil, udenafil, or lodenafil were identified. each retrieved article was carefully read and checked for relevance before being included in the review [figure 1]. we divided the visual side effects into the following categories: keratitis, other surface abnormalities, chorioretinopathy, intraocular journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 249 pde5i and ocular side effects; barroso et al figure 1. inclusion and exclusion criteria. 250 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 pde5i and ocular side effects; barroso et al table 1. the best studies for each category finding authors concise methods brief outcomes strength of evidence chart 1: studies related to intraocular pressure alterations increased intraocular pressure nazari et al. 2017[20] -110 patients -weekly sildenafil of 50mg average dose after 3 months -significantly differences between intraocular pressure values -p=0,003 -grade b wirostko et al. 2012[15] -277 adults changes in intraocular pressure mean showed in 95% confidence interval (ci) -grade b ermis et al. 2004[25] -28 male volunteers -no significantly changes in intraocular pressure -p=0.37 -grade b dündar et al. 2001[26] -14 healthy male volunteers no significantly changes in intraocular pressure grade b no increased intraocular pressure yajima et al. 2000[24] -study 1with 16 subjects and study 2with 48 subjects -no major changes grade b chart 2: other surface abnormalities finding authors concise methods brief outcomes strength of evidence surface abnormalities matieli et al 2016[8] -case control with eyes in case group and 13 eyes in control group -28 eyes (70%) using sildenafil, while only 13 eyes (35%) in the group control grade b chart 3: keratitis finding authors concise methods brief outcomes strength of evidence -keratitis matieli et al 2016[8] -case control with 20 patients -one-third of individuals grade b chart 4: chorioretinopathy finding authors concise methods brief outcomes strength of evidence central serous chorioretinopathy turkuc et al 2013[11] -43 patients treated -sildenafil citrate did not lead to central serous chorioretinopathy -grade b chart 5: uveitis finding authors concise methods brief outcomes strength of evidence uveitis french et al[12] -case report 6 episodes of uveitis grade c journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 251 pde5i and ocular side effects; barroso et al table 1. continued. chart 6: non-arteritic ischemic optic neuropathy finding authors concise methods brief outcomes strength of evidence pomeranz et al[34] -literature review 40 case report studies reported grade c galvez-ruiz et al[36] -case series 10 patients who after regular intake of sildenafil presented in 1 eye grade c naion gedik et al[37] -case report 36-year-old male who presented blurry vision in his left eye after 100 mg sildenafil intake grade c hafidi et al[38] case report 40-year old man with vision loss after 100 mg sildenafil for two consecutive days grade c pomeranz et al[39] case series 5 patients presented after ingestion of 50 to 100 mg of sildenafil grade c pomeranz et al[40] -case series 6 of 7 patients who took sildenafil presented vision loss within 24 hours grade c chart 7: retinal vessel occlusion finding authors concise methods brief outcomes strength of evidence supratemporal retinal artery branch occlusion tripathi et al[33] -case report 69-year-old male who presented with sudden painless vision loss after two days of sildenafil 100 mg intake -grade c cilioretinal artery occlusion hafidi et al[38] -case report -40-year-old male who presented with acute vision loss after 2 days of sildenafil 100 mg intake -grade c murthy et al[47] -case report -bilateral concurrent cilioretinal artery occlusion in a 37-year-old female patient after once daily for four weeks -grade c cilioretinal vessel occlusion pinto et al[49] -case report -36-year-old male presented with cilioretinal vessel occlusion -grade c chart 8: visual change finding authors concise methods brief outcomes strength of evidence -color discrimination alterations cordell et al[56] -clinical trial any significant evidence after compared sildenafil intake for 6 months daily -grade a 252 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 pde5i and ocular side effects; barroso et al pressure and glaucoma, uveitis, naion, and retinal occlusion. we described each category in different sections; namely, epidemiology and pathophysiology, clinical presentation, literature review, and final statement recommendation. discussion keratitis epidemiology and pathophysiology in less developed countries, infectious keratitis affects about 10% of the population. eye injury during agricultural work may predispose infectious agents to cause keratitis. in developed countries, the main cause of this condition is the use of contact lenses. clinical presentation keratitis presents intense itching accompanied by redness, pain, photophobia, red eye, and a “gritty” sensation.[4] literature review we did not find any association between pde5i use for ed and keratitis. however, a case–control study that evaluated ocular toxicity in patients with pulmonary arterial hypertension (pah) reported a higher incidence of keratitis following chronic sc use. twenty patients in each group were administered sc from 1 to 60 months at daily doses of 60 mg, except for two patients treated with 120 mg per day. one-third of pah individuals using sc had severe noninfectious bilateral keratitis. such patients were not contact lens users. a multivariate analysis using a linear regression model showed that dry eye keratitis was significantly associated with sc use. the patients had no other risk factors for dry eye, suggesting that sc use was possibly the main cause of keratitis in these patients.[8] final statement recommendation patients who will start chronic pde5i use and have complaints of dry eye or who use contact lenses should be counseled about an increased risk of keratitis. referral for routine ophthalmic assessment and use of preservative-free tear substitutes should be considered.[8] other surface abnormalities epidemiology and pathophysiology dry eye disease (ded) is the most common disorder related to surface abnormalities and has been associated with a wide range of traits, including systemic and metabolic conditions. clinical presentation dryness, burning, itching, watering, stickiness, and crustiness.[9] literature review only one article was identified related to this topic. in the same case–control study that evaluated ocular toxicity in pah patients using sc, all participants presented ocular motility, contrast sensitivity, color vision, schirmer test, intraocular pressure (iop), and optical coherence tomography (oct) within the normal ranges. at least one of these other abnormalities of the ocular surface (tarsal gland dysfunction, conjunctival hyperemia, cornea verticillata, and decreased rupture time) were present in 28 eyes (70%) using sc, compared to only 13 eyes (35%) in the control group. considering the presence of at least one abnormality in biomicroscopy, sc users (40 eyes of 20 patients) had a statistically higher occurrence of anterior superficial anomalies (fisher’s test p = 0.012).[8] final statement recommendation patients with pah chronically treated with sc should undergo routine ophthalmologic evaluations to identify ocular surface abnormalities.[8] chorioretinopathy epidemiology and pathophysiology central serous chorioretinopathy (csc) typically affects men and women between their third and sixth decades of life.[11] the major risk factors are the state of refraction, systemic hypertension, male sex, older age, black ethnicity, and use of corticosteroids.[10] journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 253 pde5i and ocular side effects; barroso et al clinical presentation csc presents as a painless dark, blurred, distorted, dimmed area in the central vision.[11] literature review two articles on this topic found no association between sc use and csc. in a prospective study, 43 patients with a mean age of 49.1 years (range 28–67) were treated for ed with sc (50 mg two to three times per week for one month). the patients were evaluated in the first week and at the end of treatment. macular thickness and volume assessments with oct did not differ significantly in the central and parafoveal areas (p > 0.05). the study concluded that sc in therapeutic doses did not lead to csc and visual abnormality.[11] french et al[12] studied 577 men aged 59 years and younger with newly diagnosed csc. to avoid confounding factors, this study did not include individuals with age-related macular degeneration and history of corticosteroid use. the authors found that 111 patients (19.2%) were prescribed pde5i before csc onset, and most (>99%) were administered sc doses of 100 mg or more [odds ratio: 1.05, 95% confidence interval (ci): 0.74–1.22].[12] in contrast, gordon-bennett et al[13] reported an inkblot appearance near the fovea in a 51-year-old male patient 24 hr following the ingestion of more than 20 mg tadalafil. final statement recommendation patients who are about to start ed treatment with pde5i should be advised to consult an ophthalmologist in case they experience vision problems.[11] intraocular pressure and glaucoma epidemiology and pathophysiology the global prevalence of glaucoma was over 57 million individuals in 2015 and is expected to increase to over 65 and 111 million individuals by 2020 and 2040, respectively. angle closure and reduction of ocular blood flow are additional mechanisms for the development of glaucoma, which can be triggered by the systemic use of vasodilators, including some pde5i.[14–17] clinical presentation in primary open-angle glaucoma, which is the most common type of glaucoma, the patient is usually oligosymptomatic and visual changes are present only in advanced stages. in acute-angle glaucoma, sudden visual pain followed by nausea and vomiting is usually the initial presentation.[18] literature review nine articles discussed this topic. some authors reported increased iop after sc use.[19] nazari et al[20] reported increased mean iop after three months in 110 patients aged 42–60 years with weekly sc doses of 25–100 mg (p = 0.002).[20] furthermore, chen et al[21] evaluated the prevalence of self-reported glaucoma in a telephone-based interview in men aged over 40 years. they found that 482 of 7,081 participants reported a diagnosis of glaucoma and the use of sc in the previous year. however, the dose and frequency of pde5i intake were not investigated.[21] gerometta et al[22] studied nine healthy male and female volunteers aged 18–74 years, in which the iop increased 60 min after sc administration (p < 0.005) and returned to the control values within 2 hr.[22] gerometta et al[23] also demonstrated increased iop in 21 normal sheep after ingestion of both sc (50 and 100 mg) and tadalafil. other research has shown no association between sc use and iop increase. yajima et al[24] did not detect any major changes in iop 24 hr after the oral administration of 10–150 mg sc i. furthermore, wirostko et al[15] reported no changes in iop among 277 adults with idiopathic pah in a doubleblind study using oral sc (20, 40 or 80 mg) or placebo (1:1:1:1) three times daily for 12 weeks.[15] ermis et al[25] failed to show any significant effects of sc use on iop in 28 healthy volunteers with a mean age of 51 years receiving sc (50 and 100 mg).[25] moreover, in a double-blind, randomized, placebo-controlled, crossover study, grunwald et al[16] reported no significant acute changes on iop after a single oral dose of sc l 100 mg in 15 subjects aged 63 ± 14 years with bilateral chronic open-angle glaucoma.[16] dündar et al[26] also showed no change in iop after the administration of a single oral dose of 50 mg sc to 14 healthy male volunteers tested immediately before and 1 hr after sc administration.[26] 254 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 pde5i and ocular side effects; barroso et al final statement recommendation there is a lack of prospective randomized trials to determine whether there is a true causal association between pde5i use and elevation of iop leading to glaucoma development or deterioration. however, it is advisable to monitor iop periodically in high-risk patients[20] [table 1]. uveitis epidemiology and pathophysiology the prevalence of idiopathic uveitis is similar in studies from different countries. although the understanding of the pathogenesis of uveitis is evolving, approximately 24–55% of patients with uveitis have idiopathic or undifferentiated uveitis.[27] clinical presentation uveitis is an intraocular inflammation due to an inflammation of the uvea presenting as redness and swelling of the uvea.[28] literature review only one article discussed this topic. the association of pde5i and the onset of uveitis is limited to one case report, which described a 38-year-old man diagnosed with behçet’s disease 15 years prior and without any occurrence of uveitis for the past 12 years. after starting sc for ed, he developed recurrent posterior uveitis in his left eye. the uveitis episode started after the second or third dose of sc, with a total of six episodes.[29] final statement recommendation patients with ed who plan to start pde5i should be informed of the risk for ocular side effects. if a recurrence of ocular symptoms is observed concomitant to pde5i intake, patients should be informed to stop treatment.[29] naion epidemiology and pathophysiology the annual incidence of naion is 1 in 10,000 cases and affects men and women equally. it is more common in caucasians than in african, american, and hispanic descendants. naion is a multifactorial disorder[30] and is believed to be related to vascular insufficiency in the optic nerve head. the condition is also associated with short posterior ciliary artery dysfunction. however, the mechanisms related to the vasculopathy and ischemia remain unclear and there is no consensus regarding the possible associations between naion and pde5i.[31, 32] clinical presentation the primary presentation includes acute, painless, unilateral visual loss, which confers an increased risk of contralateral vision loss. the condition may worsen over hours or days, with optic disc edema and an afferent pupillary defect. altitudinal defects are a more common presentation in the visual field.[16, 33] literature review in their literature review, pomeranz et al[34] described 40 case reports of naion. posterior ischemic optic neuropathy was also related to sc use in some letters to the editor.[30, 35] galvezruiz et al[36] reported a series of 10 patients who presented with naion with routine exposure to sc (>2–3 times per week) during the weeks and months before the ocular ischemia. naion was diagnosed based on clinical presentations, fundus features consistent with naion, and exclusion of other possible etiologies. half of the patients in the study had a primary episode of unilateral ischemic optic neuropathy. despite the initial adverse event (first episode of naion), all patients continued to use the medication and developed a second episode of naion in the contralateral eye. only 1 of the 10 patients presented with bilateral simultaneous naion.[36] another report described a 36-year-old male patient presenting with blurred vision in his left eye and afferent pupillary defect after the ingestion of 100 mg of sc. funduscopy revealed hyperemia and edema in the lower portion of the left optic disc.[37] hafidi et al[38] reported an acute unilateral visual loss in a previously healthy 40-year-old man after ingestion of 100 mg sc for two consecutive days before the onset of this visual symptom. in this particular case, journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 255 pde5i and ocular side effects; barroso et al sc was associated with naion and cilioretinal and central retinal vein occlusion (crvo).[38] pomeranz et al[39] (2002) reported on five patients ranging in age from 42 to 69 years after sc ingestion. they demonstrated the characteristic findings of naion, including altitudinal visual field loss and associated optic disc and/or peripapillary hemorrhages. pomeranz et al[39] later reported on seven patients aged 50–69 years who had typical symptoms of naion within 36 hr after the ingestion of sc for ed.[37, 40] however, in a cohort of 8,893 patients prescribed sc by their primary care physicians in england between april and june 1999, naion was reported only in a 61-year-old patient who had other risk factors for naion; thus, it was not possible to confirm any association between sc and naion.[40, 41] however, peter et al[42] reported an naion case in a patient with no known vasculopathy risk factors. final statement recommendation a history of naion should be an absolute contraindication to pde5i therapy[43] and patients who are at higher risk for naion (such as small cupto-disc ratio and systemic arterial hypertension) should be counseled and undergo ophthalmologic assessments.[35, 38, 44] retinal vessel occlusion epidemiology and pathophysiology central retinal artery occlusion (crao) occurs in an estimated 1 in 100,000 individuals in the general population and accounts for 1 in 10,000 ophthalmological outpatient visits.[45] an embolism is the most common cause of crao.[46] clinical presentation crao appears as a sudden, catastrophic visual loss.[46] literature review tripathi et al[33] reported a case of a 69-year-old man presenting with a sudden painless loss of vision in the left eye two days previously. fundus examination of the right eye was normal whereas the left eye showed a supratemporal branch retinal artery occlusion. as the patient did not have any of the risk factors for arterial occlusion, a more detailed history was sought. the patient indicated that he had taken sc (100 mg) a few hours before he experienced the loss of vision in his left eye.[33] murthy et al[47] reported a case of bilateral concurrent crao in a 37-year-old female african– american patient with sickle cell disease and pah. she had been treated with tadalafil (40 mg) once daily for four weeks. fluorescein angiography (fa) revealed delayed transit time with areas of blocked fluorescence due to retinal edema,[48] and spectraldomain oct revealed inner retinal edema in the macula.[47] hafidi et al[38] reported a case of crao and crvo observed by oct and fa. the 40year-old male patient was previously healthy and presented with acute visual loss of the left eye after two days of 100 mg sc use.[47] pinto et al[49] reported a case of a 36-year-old man with chronic renal failure who was diagnosed with crvo by fa after ingesting 100 mg sc. final statement recommendation acute and severe complaints should alert clinicians to crao. patients with increased risks for thromboembolic events should be counseled about crao. despite the anecdotal cases, it is not possible to establish a link between pde5i use and crao.[47, 50] visual changes epidemiology and pathophysiology most cases of visual changes after pde5i are believed to be dose dependent and lead to mild alterations in the visual system. these alterations lead to complaints of blue-tinged vision and increased brightness perception.[51] sc also inhibits phosphodiesterase type 6 (pde6),[52] an essential enzyme involved in the activation and modulation of the phototransduction cascade, impairing the ability of pde6 to shorten the time of integration between the visual system and light level.[53] the sensitivity of sc for pde6 isoenzymes is thought to be the basis for the reduced electrophysiological response on electroretinograms (erg) in patients prescribed 50 mg sc, as well as the transient color vision abnormalities more likely to be observed with higher doses of sc.[54] 256 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 pde5i and ocular side effects; barroso et al clinical presentation patients report changes related to color perception.[55] literature review in a comparative case series study, matieli et al[8] analyzed the visual effects of sc use for pah by assessing symptoms such as bluish vision, photophobia, and green or blue or yellow patterns on farnsworth d15-color test saturated panels. sc was used from 1 to 60 months. the sc user and control groups included 17 women each. onethird of the treated group showed severe bilateral keratitis. in contrast, cordell et al[56] randomized 244 subjects to receive tadalafil (5 mg, 85 patients), sc (50 mg, 77 patients), or placebo (82 patients) daily for six months. no significant differences in the visual function of color discrimination by the farnsworth–munsell 100-hue color vision test were observed between the treatment and placebo groups.[56] final statement recommendation despite its low occurrence, patients should be counseled about transient color changes associated with pde5i use for ed or pah.[8] summary pde5i are one of the most prescribed drugs worldwide, with a very good safety profile. however, naion, chorioretinopathy, and color changes are important issues reported in the literature. although these visual side effects have been reported in patients using pde5i, there is not enough evidence to prove a causal association. given the low incidence of such side effects, these should not preclude the usual indications for pde5i. however, patients with histories of ophthalmologic conditions or optic nerve issues or those at high risk for any eye disease require specific clearance before the commencement of therapy. acknowledgement the authors would like to thank federal university of ceara and christus university center for collaboration and editage (www.editage.com) for english language editing. financial support and sponsorship nil. conflicts of interest there is no conflict of interest. references 1. selvin e, burnett al, platz ea. prevalence and risk factors for erectile dysfunction in the us. am j med 2007;120:151– 157. 2. kehat r, bonsall dj, north r, connors b. ocular findings of oral sildenafil use in term and near-term neonates. j aapos 2010;14:159–162. 3. sowka jw, neiberg mn, vollmer la. optic atrophy after sildenafil use. optometry 2007;78:122–128. 4. hom mm, nguyen al, bielory l. allergic conjunctivitis and dry eye syndrome. ann allergy asthma immunol 2012;108:163–166. 5. keay l, stapleton f, schein o. epidemiology of contact lens-related inflammation and microbial keratitis: a 20year perspective. eye contact lens 2007;33:346–353, discussion 62–63. 6. gupta n, tandon r, gupta sk, sreenivas v, vashist p. burden of corneal blindness in india. indian j community med 2013;38:198–206. 7. nirmalan pk, katz j, tielsch jm, robin al, thulasiraj rd, krishnadas r, et al. ocular trauma in a rural south indian population: the aravind comprehensive eye survey. ophthalmology 2004;111:1778–1181. 8. matieli l, berezovsky a, salomao sr, allemann n, martins en, hirai fe, et al. ocular toxicity assessment of chronic sildenafil therapy for pulmonary arterial hypertension. graefes arch clin exp ophthalmol 2016;254:1167–1174. 9. the definition and classification of dry eye disease: report of the definition and classification subcommittee of the international dry eye workshop (2007). ocul surf 2007;5:75–92. 10. damar e, toklu y, tuncel a, balci m, aslan y, simsek s, et al. does therapeutic dose of sildenafil citrate treatment lead to central serous chorioretinopathy in patients with erectile dysfunction? am j mens health 2013;7:439–443. 11. turkcu fm, yuksel h, sahin a, murat m, bozkurt y, caca i. central serous chorioretinopathy due to tadalafil use. int ophthalmol 2013;33:177–180. 12. french dd, margo ce. central serous chorioretinopathy and phosphodiesterase-5 inhibitors: a case-control postmarketing surveillance study. retina 2010;30:271– 274. 13. gordon-bennett p, rimmer t. central serous chorioretinopathy following oral tadalafil. eye 2012;26:168–169. 14. kapetanakis vv, chan mp, foster pj, cook dg, owen cg, rudnicka ar. global variations and time trends in the prevalence of primary open angle glaucoma (poag): a systematic review and meta-analysis. br j ophthalmol 2016;100:86–93. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 257 www.editage.com pde5i and ocular side effects; barroso et al 15. wirostko bm, tressler c, hwang lj, burgess g, laties am. ocular safety of sildenafil citrate when administered chronically for pulmonary arterial hypertension: results from phase iii, randomised, double masked, placebo controlled trial and open label extension. bmj 2012;344:e554. 16. grunwald je, jacob ss, siu k, piltz j, dupont j. acute effects of sildenafil citrate (viagra) on intraocular pressure in open-angle glaucoma. am j ophthalmol 2001;132:872– 874. 17. lee wj, seong m. sildenafil citrate and choroidal thickness. retina 2011;31:1742; author reply -3. 18. garg a, gazzard g. selective laser trabeculoplasty: past, present, and future. eye 2018;32:863–876. 19. ramasamy b, rowe f, nayak h, peckar c, noonan c. acute angle-closure glaucoma following sildenafil citrate-aided sexual intercourse. acta ophthalmol scand 2007;85:229–230. 20. nazari a, tabrizi yt, mokhtaree m. effect of periodic sildenafil dosage on intraocular pressure in patients with erectile dysfunction. electron physician 2017;9:5229– 5232. 21. chen sp, singh k, lin sc. use of phosphodiesterase inhibitors and prevalence of self-reported glaucoma in the united states. plos one 2017;12:e0183388. 22. gerometta r, alvarez lj, candia oa. effect of sildenafil citrate on intraocular pressure and blood pressure in human volunteers. exp eye res 2011;93:103–107. 23. gerometta r, alvarez lj, candia oa. effects of sildenafil and tadalafil on intraocular pressure in sheep: implications for aqueous humor dynamics. invest ophthalmol vis sci 2010;51:3139–3144. 24. yajima t, yajima y, koppiker n, grunwald je, laties am. no clinically important effects on intraocular pressure after short-term administration of sildenafil citrate (viagra). am j ophthalmol 2000;129:675–676. 25. ermis ss, inan uu, samli m, ozturk f. acute effects of sildenafil on humphrey visual field and intraocular pressure. int ophthalmol 2004;25:69–72. 26. dundar so, dundar m, kocak i, dayanir y, ozkan sb. effect of sildenafil on ocular haemodynamics. eye 2001;15:507– 510. 27. han ys, rivera-grana e, salek s, rosenbaum jt. distinguishing uveitis secondary to sarcoidosis from idiopathic disease: cardiac implications. jama ophthalmol 2018;136:109–115. 28. krishna u, ajanaku d, denniston ak, gkika t. uveitis: a sight-threatening disease which can impact all systems. postgrad med j 2017;93:766–773. 29. isik m, kilic l, dogan i. recurrent uveitis due to sildenafil usage in a patient with bechet’s disease. rheumatol int 2013;33:803. 30. su dh, ang ps, tow sl. bilateral posterior ischemic optic neuropathy associated with use of sildenafil. j neuroophthalmol 2008;28:75. 31. li a, li l, li m, shi x. a new characterization for nonarteritic anterior ischemic optic neuropathy. int j clin exp med 2015;8:18681–18688. 32. boshier a, pambakian n, shakir sa. a case of nonarteritic ischemic optic neuropathy (naion) in a male patient taking sildenafil. int j clin pharmacol ther 2002;40:422– 423. 33. tripathi a, o’donnell np. branch retinal artery occlusion; another complication of sildenafil. br j ophthalmol 2000;84:934–935. 34. pomeranz hd. erectile dysfunction agents and nonarteritic anterior ischemic optic neuropathy. neurol clin 2017;35:17–27. 35. coca mn, morgan ml, gupta p, elkeeb a, lee ag. bilateral posterior ischemic optic neuropathy associated with the use of sildenafil for pulmonary hypertension. can j ophthalmol 2016;51:e96–e99. 36. galvez-ruiz a, arishi n. sequential, non-arteritic anterior ischemic optic neuropathy in patients taking sildenafil: a report of ten cases. saudi j ophthalmol 2013;27:241–246. 37. gedik s, yilmaz g, akova ya. sildenafil-associated consecutive nonarteritic anterior ischaemic optic neuropathy, cilioretinal artery occlusion, and central retinal vein occlusion in a haemodialysis patient. eye 2007;21:129–130. 38. hafidi z, handor h, laghmari m, daoudi r. cilioretinal artery and central retinal vein occlusion after sildenafil use. emerg med j 2014;31:535. 39. pomeranz hd, smith kh, hart wm jr, egan ra. sildenafilassociated nonarteritic anterior ischemic optic neuropathy. ophthalmology 2002;109:584–587. 40. pomeranz hd, bhavsar ar. nonarteritic ischemic optic neuropathy developing soon after use of sildenafil (viagra): a report of seven new cases. j neuroophthalmol 2005;25:9–13. 41. oguz h. sildenafil-associated vascular casualties. eye 2007;21:676–677; author reply 7–8. 42. peter nm, singh mv, fox pd. tadalafil-associated anterior ischaemic optic neuropathy. eye 2005;19:715–717. 43. pepin s, pitha-rowe i. stepwise decline in visual field after serial sildenafil use. j neuroophthalmol 2008;28:76–77. 44. fraunfelder fw, fraunfelder ft. central serous chorioretinopathy associated with sildenafil. retina 2008;28:606–609. 45. varma d, lee aw, chen cs. reply: ’a review of central retinal artery occlusion: clinical presentation and management’. eye 2014;28:1270. 46. rudkin ak, lee aw, chen cs. vascular risk factors for central retinal artery occlusion. eye 2010;24:678–681. 47. murthy rk, perez l, priluck jc, grover s, chalam kv. acute, bilateral, concurrent central retinal artery occlusion in sickle cell disease after use of tadalafil (cialis). jama ophthalmol 2013;131:1471–1473. 48. bertolucci a, latkany ra, gentile rc, rosen rb. hemiretinal artery occlusion associated with sexual activity and sildenafil citrate (viagra). acta ophthalmol scand 2003;81:198–200. 49. pinto lm, morekar s, mahashur aa. central retinal vein occlusion in a patient after being commenced on sildenafil citrate for pulmonary arterial hypertension. indian j chest dis allied sci 2009;51:249–251. 50. li as, pomeranz hd. food and drug administration adverse event reports of retinal vascular occlusions associated with phosphodiesterase type 5 inhibitor use. j neuroophthalmol 2016;36:480–481. 51. kinoshita j, iwata n, shimoda h, kimotsuki t, yasuda m. 258 journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 pde5i and ocular side effects; barroso et al sildenafil-induced reversible impairment of rod and cone phototransduction in monkeys. invest ophthalmol vis sci 2015;56:664–673. 52. laties am, fraunfelder ft. ocular safety of viagra, (sildenafil citrate). trans am ophthalmol soc 1999;97:115– 125; discussion 25–28. 53. stockman a, sharpe lt, tufail a, kell pd, ripamonti c, jeffery g. the effect of sildenafil citrate (viagra) on visual sensitivity. j vis 2007;7:4. 54. farooq mu, naravetla b, moore pw, majid a, gupta r, kassab my. role of sildenafil in neurological disorders. clin neuropharmacol 2008;31:353–362. 55. sinha s, pathak-ray v, ahluwalia h, morgan je. viagra or what? eye 2004;18:446–448. 56. cordell wh, maturi rk, costigan tm, marmor mf, weleber rg, coupland sg, et al. retinal effects of 6 months of daily use of tadalafil or sildenafil. arch ophthalmol 2009;127:367–373. journal of ophthalmic and vision research volume 16, issue 2, april-june 2021 259 original article near vision tasks and optical quality of the eye jessica rafaela moreira gomes, ms; sandra maria de braga franco, phd centre of physics, university of minho, campus de gualtar, braga, portugal orcid: jessica rafaela moreira gomes: https://orcid.org/0000-0002-1033-3584 sandra maria de braga franco: https://orcid.0000-0002-2296-3073 abstract purpose: to study the effect of near-vision reading task on optical quality of the eye when performed on a computer monitor and on printed paper, and to identify which of the two results in greater changes. methods: two groups of subjects performed a 30-min reading task in two different conditions: on a computer monitor and on printed paper. ocular, corneal, and internal wavefront aberrations (zernike coefficients up to 6th order), root-mean-square of lowand high-order aberrations, spherical equivalent, vectoral components of ocular astigmatism (j45 and j0), and the compensation factor between internal and corneal aberrations were measured before and after the tasks. their changes were analyzed in each group and between groups. results: statistically significant changes in wavefront aberrations and in root mean square of lowand high-order aberrations were observed in both groups which was significantly greater when the task was performed on printed paper. partial loss of compensation mechanism and variation in spherical equivalent in a negative direction occurred after both reading tasks; however, it was statistically significant only with printed paper reading task. the vectoral components of ocular astigmatism did not show statistically significant changes in either groups. conclusion: near-vision reading tasks can change the optical quality of the eye, especially when the task is performed on printed paper. keywords: computer; near-vision task; optical quality; paper; wavefront aberrations j ophthalmic vis res 2021; 16 (4): 620–630 introduction the use of near vision to perform different tasks is currently increasing, both at work and during correspondence to: sandra maria de braga franco, phd. centre of physics, university of minho, campus de gualtar, braga 4710057, portugal. email: sfranco@fisica.uminho.pt received: 10-02-2021 accepted: 28-10-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9753 entertainment. the use of digital devices such as computers, tablets, and smartphones to perform these tasks is also rising exponentially. due to the excessive use of these devices, many studies have been conducted to address issues related to health and safety of the users. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: gomes jrm, franco smb. near vision tasks and optical quality of the eye. j ophthalmic vis res 2021;16:620–630. 620 © 2021 gomes et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9753&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr near vision tasks and optical quality; gomes et al many ocular symptoms including eye strain, headache, ocular discomfort, double vision, and blurred vision at near and far distance are linked to the use of these devices.[1, 2] these symptoms are more common in subjects who spend over 4 hr on electronic devices and increase significantly in individuals who use electronic devices for more than 7 hr a day.[2] some studies were designed to explain the cause for these symptoms that affect around 90% of the electronic device users.[1, 3] some studies[1–7] reported the effect of computer screen use on visual system, and others[7, 10] about the same parameters but on the paper. in the study by chu et al,[8] the subjects performed two reading tasks on paper and on computer display at 50 cm distance for 20 min. the subjects then classified the intensity of the symptoms between 0 and 10. all symptoms were more intense during the reading task on computer except for blurred vision at far, which was worse for the task performed on paper. therefore, it is important to understand if these symptoms are specific to the use of digital devices or they are manifestation of the increased use of near vision. the accommodative response also changes with near vision tasks. there are studies about the changes in accommodative response after a near reading task on a digital device and on printed paper; however, the results are inconclusive. penisten et al[9] and ferreira et al[10] noted a higher accommodative response on computer reading task compared to paper. on the other hand, wick and morse[4] measured the accommodative response in five emmetropic subjects reading a text on a computer screen and on hard copy. the accommodative lag showed more increase with the reading task on computer. hue et al also found a higher increase in accommodative lag with computer use compared to printed copy.[7] however, collier and rosenfield claimed that there were no changes in ocular accommodation of their 20 subjects after performing a reading task on computer for 30 min.[5] moulakaki et al concluded that the accommodative response appears to be independent of the type of electronic device used.[11] they analyzed the accommodative response in 18 subjects for different accommodative demands (0, 1, 2, 3, and 4 d) after a 10-min reading task on two different electronic devices (tablet and smartphone) and did not find any statistically significant differences. on the other hand, phamonvaechavan et al found a decrease in accommodation amplitude in 40 subjects after a 20-min continuous reading task which was more significant when the subjects used a tablet compared to when they used a computer screen.[12] however, the focus of these studies was only on changes in ocular accommodation and the symptoms present in its use, and the results are still inconclusive. several studies found a transient myopia caused by near vision work, between –0.12 d and – 1.30 d.[13–15] resolution of symptoms occurs 30/60 min after completing the task in symptomatic subjects.[16, 17] it has been suggested that the eyelid forces, during near vision tasks, causes significant changes in eye aberrations.[18] buehren et al noted that there was an increase in ocular high-order aberrations (hoa) following a 2-hr reading task which was more significant in myopic subjects and in eyes with large pupil diameters (4 and 5 mm).[19] the changes in ocular aberrations depend also on the requirements of the tasks. the recent study of jimánez et al found a higher increase in rms astigmatism when subjects performed a task with higher-cognitive demands which persisted 10 min after completing the task.[20] previous studies showed that ocular aberrations change significantly with accommodation and the rms of ocular low-order aberrations (loa) and hoa increases.[21–27] the most significant change is in the fourth-order spherical aberration, which is positive in the relaxed state and becomes negative with accommodation.[24] the direction of the changes in coma and astigmatism is not clear.[22, 25] these changes in optical aberrations with accommodation can be explained by alterations in the shape and position of the lens during accommodation.[21, 28] since most current daily tasks require ocular accommodation which in particular results in changes in eye aberrations, it is important to understand the effect of near-vision tasks on ocular, corneal, and internal optics. it is already known that there is a partial compensation between cornea and internal optics.[29–33] artal et al found a compensation of the corneal coma and spherical aberration by the lens, leading to a better optical quality.[29] a significant compensation of horizontal and vertical astigmatism, coma, and spherical aberration between cornea and lens were also journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 621 near vision tasks and optical quality; gomes et al observed in other studies.[31, 32] some natural (such as age[34, 35]) and artificial (such as ocular surgeries[36–38]) factors can alter this compensation effect and decrease the optical quality of the eye. as ocular accommodation during near-vision tasks changes the optical properties of the lens, the compensation mechanism might also be altered.[21] there is evidence that near-vision tasks cause adverse symptoms and can lead to changes in spherical equivalent and accommodative response, and consequently might result in changes in wavefront aberrations and their balance between corneal and internal surfaces. however, it is not clear whether these changes are greater when the task is performed on paper or on digital devices. studying the changes in optical quality of the eye with near-vision tasks can provide a better understanding of their effect on visual system. it can also help to understand which condition, paper or digital device, is more harmful. in addition, the origin of symptoms, which appears to be different on paper and electronic device reading tasks, can be explained by differences in optical quality. the purpose of this study was to assess the effect of a near-vision task in different conditions (computer screen and paper) on ocular, corneal, and internal aberrations and on compensation mechanism. it was also intended to observe which condition affects these parameters more. methods subjects the subjects were recruited from the students of the university of minho. in a preliminary session, each one received a comprehensive optometric evaluation to ensure suitability for inclusion in the study. the examination included the assessment of visual acuity, objective and subjective refractive error, binocular vision, accommodation, and ocular health condition. two groups of subjects participated in the study; a group with 19 subjects (mean age 22.7 years; range, 19–25 years) who performed a reading task on a computer screen and another group with 34 subjects (mean age 20 years; range, 18–27 years) who performed the same task on printed paper. the sampling method was simple random. all subjects in both groups were emmetropic with monocular uncorrected distance visual acuity of 20/20 or better. the emmetropic error was defined as a mean spherical equivalent ranging from –0.50 d to +0.50 d, and an astigmatism ≤0.50 d. the mean spherical equivalent of the subjects was +0.02 ± 0.27 d and +0.11 ± 0.25 d, and astigmatism –0.31 ± 0.15 d and 0.16 ± 0.18 d for computer and paper groups, respectively. moreover, subjects had no binocular and/or accommodative dysfunctions, history of ocular pathology or surgery, systemic disease, and they were not on any medication affecting vision. normal binocular vision was defined according to sheard criteria in cases with exophoria, and percival criteria in subjects with esophoria.[39] an informed consent was obtained from each subject after providing a verbal explanation of the nature and possible consequences of the study. the study was approved by the ethics subcommittee for the life sciences and health of university of minho. experimental procedure the data collection encompassed two sessions: pre-task and post-task. for each subject, three measures of ocular and corneal wavefront aberrations of right eye were taken in each session and the mean was determined. after the first measurement, the subjects were seated comfortably and instructed to read a text at 50 cm distance (2.00 d of accommodative demand) in an illuminated room (photopic conditions) for 30 min. the text was a prose fiction in black letters and 12 font size, on a white background. in the computer group, the eye level was at the top of the computer screen, whereas in the paper group the printed text was placed on a table and therefore the subjects had downward gaze. all subjects were supervised to maintain the same position throughout the procedure. immediately after performing the reading task, the wavefront ocular aberrations were remeasured. the acquisition was implemented under mesopic lighting conditions (150 lux) and natural pupil size (without mydriatic medication), ensuring a pupil diameter close to 5.0 mm during far and near distance measurements. for all procedures, ocular and corneal aberrations were then exported for a 5 mm pupil in the form of zernike coefficients up to the sixth order. 622 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 near vision tasks and optical quality; gomes et al the ocular and corneal aberrations were obtained before and after the task with visionix vx 120 (visionix luneau, chartes, france) analyzer, a closed view aberrometer. the repeatability of the measures intra-sections using this equipment was reported by a previous study[40] and showed high levels for this parameter. the results of this study showed that all within-subject standard deviation (s𝑤) for corneal power measurements were <0.26 d, with intraclass correlation coefficient (icc) >0.982. the s𝑤 for corneal astigmatism at different areas (3, 5, and 7 mm) was <0.21 d, with icc >0.913. regarding the axis of astigmatism, its s𝑤 was <11.27º, with icc >0.975. the s𝑤 and icc for corneal eccentricity were 0.067 and 0.957, respectively. the s𝑤 and icc for hoa root mean square (rms) were <0.048 µm and >0.901, respectively. thirdand fourth-order aberrations, all s𝑤 were <0.037 µm and all icc were >0.84, except for quadrafoil rms (icc = 0.689). moreover, according to irene sanchez et al, vx 120 device showed good reproducibility results, suggesting that this equipment is suitable for patients’ followup, due to small differences between sessions.[41] data analysis the values were exported in the form of zernike coefficients up to sixth order, for 5 mm pupil diameter. the values were analyzed for this pupil diameter because it was the most approximate value of the natural pupil in our subjects. the first three zernike terms were excluded from the analysis since they do not affect the image quality. as the refraction based on wavefront aberration maps can accurately determine the spherocylindrical refraction,[42] the spherical equivalent (m) was calculated using the paraxial curvature matching (i.e., the second-order paraxial focus, the fourth-order sa, and the sixth-order sa zernike coefficients), using equation (1):[42] 𝑀 = (−4×√3×𝑍02 +12×√5×𝑍 0 4 −24× √7×𝑍 0 6)/𝑟 2, (1) where r is the radius of the pupil. the two components of astigmatism, j45 and j0, were estimated by the least-squares fitting method, using equations (2) and (3),[42] respectively. 𝐽45 = (−2 × √6 × 𝑍−22 )/𝑟 2, (2) 𝐽0 = (−2 × √6 × 𝑍22)/𝑟 2. (3) the rms of high-order ocular aberrations (hoa) were also calculated. the contribution of the internal wavefront aberrations to the overall eye aberrations was investigated by subtracting corneal aberrations from the ocular aberrations. moreover, the compensation factor (cf) was calculated as:[32] 𝐶𝐹 = (𝑅𝑀𝑆𝑐𝑜𝑟𝑛𝑒𝑎 − 𝑅𝑀𝑆𝑜𝑐𝑢𝑙𝑎𝑟)/𝑅𝑀𝑆𝑐𝑜𝑟𝑛𝑒𝑎. (4) a positive cf indicates a compensation; values around zero, a lack of compensation; and negative values, addition of aberrations by the lens. data were analyzed using the ibm spss statistics, version 24.0. (ibm corp, armonk, ny; usa). the normality of the data was tested using the shapiro–wilk test. to compare the mean values between pre and post tasks in each study group, paired t-test was applied when the data followed a normal distribution; otherwise, wilcoxon test was used. to evaluate the differences between groups, t-test and mann–whitney u-test were used for normal and non-normal distribution data, respectively. p-values ≤ 0.05 was considered statistically significant. results the ocular, corneal, and internal aberrations up to sixth order were measured before and after the reading tasks in both groups and their differences were analyzed and compared between the groups. the changes with the task for all zernike coefficients from third to sixth order in both groups are shown in table 1, and the statistically significant differences between the changes in both groups are marked. in the computer group, no statistically significant differences were found in the ocular zernike coefficients; however, corneal z (5,–5) (p = 0.016), z (5,–3) (p = 0.027), and z (6,2) (p = 0.016) terms changed significantly. the same zernike coefficients also showed statistically significant differences in the internal optics (p = 0.016, p = 0.031, and p = 0.012, respectively), as well as the term z (6,4) (p = 0.049). journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 623 near vision tasks and optical quality; gomes et al t a b le 1. o cu la r, co rn ea l, an d in te rn al ze rn ik e co ef fic ie nt m ea n ch an ge s [a nd st an da rd de vi at io ns (s d )] of th ird ,f ou rt h, fif th ,a nd si xt h or de rs w ith th e ta sk ,i n th e co m pu te r an d pa pe rg ro up s, an d th e di ffe re nc e be tw ee n th ei rc ha ng es (c om pu te rc ha ng e m in us pa pe rc ha ng e) m e a n ch a n g e s w it h th e ta sk (s d ) (μ m ) d iff e re n ce b e tw e e n th e ch a n g e s o f th e co m p u te r a n d p a p e r g ro u p s (μ m ) c om pu te r pa pe r o cu la r c or ne al in te rn al o cu la r c or ne al in te rn al o cu la r c or ne al in te rn al z (3 ,– 3 ) 0. 0 0 6 (0 .0 24 ) –0 .0 0 6 (0 .0 68 ) 0. 0 12 (0 .0 63 ) *0 .0 2 6 (0 .0 6 1) –0 .0 67 (0 .2 29 ) 0. 0 51 (0 .2 40 ) –0 .0 20 0. 0 61 –0 .0 39 z (3 ,– 1) –0 .0 17 (0 .0 53 ) 0. 0 0 5 (0 .0 0 5) –0 .0 21 (0 .12 7) *– 0 .0 2 1 (0 .0 5 7 ) *0 .0 8 1 (0 .2 2 7 ) *– 0 .0 7 3 (0 .2 2 6 ) 0. 0 04 –0 .0 77 0. 0 51 z (3 ,1 ) –0 .0 14 (0 .0 43 ) 0. 0 11 (0 .0 85 ) –0 .0 25 (0 .0 87 ) –0 .0 07 (0 .0 32 ) –0 .0 02 (0 .0 53 ) *– 0 .0 8 0 (0 .1 0 2 ) –0 .0 10 0. 0 14 *0 .0 5 5 z (3 ,3 ) –0 .0 02 (0 .0 26 ) –0 .0 44 (0 .19 1) 0. 04 2 (0 .17 9) –0 .0 10 (0 .0 39 ) 0. 0 18 (0 .12 5) –0 .0 25 (0 .14 9) 0. 0 07 –0 .0 62 0. 0 67 z (4 ,– 4 ) –0 .0 0 3 (0 .0 19 ) –0 .0 34 (0 .18 5) 0. 0 31 (0 .17 6) –0 .0 0 6 (0 .0 29 ) 0. 0 0 8 (0 .10 5) –0 .0 12 (0 .11 1) 0. 0 0 3 –0 .0 41 0. 04 2 z (4 ,– 2 ) 0. 0 0 15 (0 .0 15 ) 0. 0 19 (0 .0 86 ) –0 .0 17 (0 .0 86 ) 0. 0 02 (0 .0 19 7) 0. 0 0 1( 0. 0 52 ) 0. 0 0 1( 0. 0 52 ) –0 .0 0 1 0. 0 18 –0 .0 18 z (4 ,0 ) –0 .0 0 1( 0. 02 6) –0 .0 12 (0 .0 40 ) 0. 0 11 (0 .0 49 ) *– 0 .0 14 (0 .0 3 0 ) 0. 02 2 (0 .10 1) 0. 04 8 (0 .10 0) 0. 0 13 –0 .0 34 *– 0 .0 3 8 z (4 ,2 ) –0 .0 0 5 (0 .0 22 ) 0. 0 0 1( 0. 0 36 ) –0 .0 12 (0 .0 37 ) *0 .0 10 (0 .0 4 1) –0 .0 32 (0 .12 8) *0 .0 3 7 (0 .1 2 7 ) *– 0 .0 14 0. 0 39 –0 .0 49 z (4 ,4 ) 0. 0 0 1( 0. 02 1) 0. 0 0 3 (0 .0 48 ) –0 .0 0 3 (0 .0 60 ) *– 0 .0 16 (0 .0 3 7 ) *0 .0 3 7 (0 .1 2 7 ) –0 .0 63 (0 .12 0) *0 .0 16 –0 .0 34 *0 .0 6 0 z (5 ,– 5 ) –0 .0 04 (0 .0 13 ) *0 .0 4 0 (0 .0 7 7 ) *– 0 .0 4 3 (0 .0 7 9 ) –0 .0 0 1( 0. 02 4) –0 .0 0 6 (0 .0 88 ) 0. 0 07 (0 .0 83 ) –0 .0 0 3 0. 04 6 –0 .0 50 z (5 ,– 3 ) 0. 0 02 (0 .0 12 ) *– 0 .0 17 (0 .0 3 0 ) *0 .0 19 (0 .0 3 5 ) 0. 0 0 3 (0 .0 26 ) –0 .0 07 (0 .0 72 ) 0. 0 0 9 (0 .0 74 ) –0 .0 0 1 –0 .0 10 0. 0 10 z (5 ,– 1) –0 .0 0 6 (0 .0 17 ) 0. 0 0 0 (0 .0 25 ) –0 .0 0 6 (0 .0 28 ) –0 .0 0 8 (0 .0 23 ) 0. 0 11 (0 .0 79 ) –0 .0 16 (0 .0 77 ) 0. 0 02 –0 .0 10 0. 0 10 z (5 ,1 ) 0. 0 0 1( 0. 0 13 ) 0. 0 07 (0 .0 25 ) –0 .0 0 6 (0 .0 27 ) *0 .0 0 1 (0 .0 13 ) 0. 0 0 1( 0. 0 14 ) –0 .0 0 3 (0 .0 22 ) 0. 0 0 0 0. 0 0 6 –0 .0 0 3 z (5 ,3 ) –0 .0 0 1( 0. 0 11 ) –0 .0 11 (0 .0 72 ) 0. 0 10 (0 .0 72 ) 0. 0 0 5 (0 .0 16 ) –0 .0 12 (0 .0 42 ) *0 .0 16 (0 .0 4 8 ) *– 0 .0 0 6 0. 0 0 1 –0 .0 0 6 z (5 ,5 ) 0. 0 0 3 (0 .0 11 ) 0. 0 0 8 (0 .11 0) –0 .0 0 5 (0 .11 0) –0 .0 02 (0 .0 23 ) 0. 0 0 8 (0 .0 86 ) –0 .0 13 (0 .0 80 ) 0. 0 0 5 0. 0 0 0 0. 0 0 8 z (6 ,– 6 ) –0 .0 0 1( 0. 0 0 5) 0. 0 0 6 (0 .0 61 ) –0 .0 07 (0 .0 64 ) –0 .0 0 3 (0 .0 12 ) 0. 0 04 (0 .0 55 ) –0 .0 0 3 (0 .0 57 ) 0. 0 02 0. 0 02 –0 .0 0 3 z (6 ,– 4 ) 0. 0 0 1( 0 0 0 6) –0 .0 0 8 (0 .0 40 ) 0. 0 0 9 (0 .0 40 ) 0. 0 02 (0 .0 12 ) –0 .0 04 (0 .0 29 ) 0. 0 02 (0 .0 34 ) 0. 0 0 0 –0 .0 04 0. 0 07 z (6 ,– 2 ) –0 .0 02 (0 .0 0 5) 0. 0 04 (0 .0 27 ) –0 .0 04 (0 .0 29 ) –0 .0 0 0 (0 .0 07 ) 0. 0 0 1( 0. 0 19 ) –0 .0 0 1( 0. 0 17 ) 0. 0 0 0 0. 0 0 3 –0 .0 0 3 z (6 ,0 ) –0 .0 0 1( 0. 0 0 6) 0. 0 02 (0 .0 0 8) –0 .0 0 3 (0 .0 0 9) 0. 0 0 3 (0 .0 14 ) –0 .0 0 1( 0. 0 32 ) 0. 0 02 (0 .0 32 ) –0 .0 04 0. 0 0 3 –0 .0 0 5 z (6 ,2 ) 0. 0 02 (0 .0 0 6) *– 0 .0 0 7 (0 .0 11 ) *0 .0 0 7 (0 .0 11 ) –0 .0 0 1( 0. 0 15 ) 0. 0 0 1( 0. 04 4) –0 .0 0 1( 0. 0 39 ) 0. 0 0 1 *– 0 .0 0 8 *0 .0 0 9 z (6 ,4 ) –0 .0 02 (0 .0 07 ) 0. 0 15 (0 .0 41 ) *– 0 .0 16 (0 .0 3 7 ) 0. 0 0 3 (0 .0 13 ) –0 .0 04 (0 .0 39 ) 0. 0 11 (0 .0 39 ) –0 .0 04 0. 0 19 *– 0 .0 2 7 z (6 ,6 ) 0. 0 0 0 (0 .0 07 ) –0 .0 18 (0 .0 69 ) 0. 0 18 (0 .0 68 ) –0 .0 0 1( 0. 0 12 ) 0. 0 02 (0 .0 62 ) –0 .0 10 (0 .0 51 ) 0. 0 0 1 –0 .0 20 0. 02 8 *s ta tis tic al ly si gn ifi ca nt di ffe re nc e 624 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 near vision tasks and optical quality; gomes et al on the other hand, the paper group had statistically significant differences in ocular, corneal, and internal aberrations. cornea suffered significant differences in z (3,–1) (p = 0.013) and z (4,4) (p = 0.028) terms, internal optics in z (3,–1) (p = 0.035), z (3,1) (p < 0.001), z (4,2) (p = 0.049), and z (5,3) (p = 0.049) terms and ocular in z (3,–3) (p = 0.019), z (3,–1) (p = 0.027), z (4,0) (p = 0.013), z (4,2) (p = 0.018), z (4,4) (p = 0.023) and z (5,–1) (p = 0.046) terms. the alterations caused by the task were compared between paper and computer groups [table 1]. the changes observed after the task were greater in the paper group in several areas [ocular z (4,2) (p = 0.004), z (4,4) (p = 0.01), and z (5,3) (p = 0.024); internal z (3,1) (p = 0.025), z (4,0) (p = 0.007), z (4,4) (p = 0.033)], when compared to the changes in the computer group. on the other hand, corneal z (6,2) (p = 0.014) and internal z (6,2) (p = 0.006) and z (6,4) (p = 0.001) showed greater changes in the computer group than in the paper group. another zernike terms showed no statistically significant differences between the changes observed with the task in the paper and computer groups. it was also interesting to note that all corneal and internal zernike coefficients of both groups, except z (3,1) for the computer group and z (3,1), z (4,0), and z (4,–2) for the paper group, changed in opposite directions. in other words, when the corneal aberration became more negative, the internal aberration became more positive, and vice versa. these opposite changes led to less alterations in ocular aberrations, despite some significant ocular and internal changes. the changes of ocular, corneal, and internal rms of loa, hoa, and third, fourth, fifth, and sixth orders were calculated in both groups and compared with each other [figure 1]. in the computer group, the corneal and internal rms of loa and hoa, and the third, fourth, fifth, and sixth orders increased after the task; however, no statistically significant differences were observed. on the other hand, in the paper group, ocular rms of loa (p = 0.001), fourth (p = 0.01), fifth (p < 0.001), and sixth (p < 0.001) orders had a statistically significant increase after the task. moreover, corneal rms of fifth (p = 0.01) and sixth (p = 0.025) order and all internal orders (p < 0.001 in all orders) changed significantly in this group. the changes in rms of ocular fifth (p = 0.001) and sixth (p = 0.007) orders, corneal third (p < 0.001) and fourth (p < 0.001) orders, and internal loa (p < 0.001), hoa (p = 0.002), and third (p = 0.002), fourth (p = 0.006), fifth (p = 0.027), and sixth (p = 0.007) orders were significantly greater in the paper group than the changes found in the computer group. the values of the differences between the changes of these two groups are shown in table 2, and the statistically significant differences are identified. the cf was calculated to evaluate the compensation or addition of corneal aberrations by the internal optics before and after the task and to identify which task condition, computer or paper, cause more changes in this parameter. their changes for loa, hoa, and third, fourth, fifth, and sixth-order aberrations in both groups are represented in figure 2. this parameter decreased in all orders after the task, except for the fifth order in the computer group, which has remained almost unchanged. however, the changes were only statistically significant in the loa (p = 0.048) and fourth (p = 0.043) and sixth (p = 0.043) orders in the paper group. although the paper group showed more significant differences than the computer group, the differences between the two groups were not statistically significant, that is, none of the groups had variations in the cf significantly higher than the other. the changes with the task of two vectoral components of ocular astigmatism (j45 and j0) were not statistically significant in either group [figure 3]. furthermore, none of the groups showed significantly greater differences than the other. the spherical equivalent (m) was also calculated in pre and post task conditions and the mean differences were obtained in both groups [figure 3]. the spherical equivalent became more negative after the task. although, the changes were only statistically significant (p < 0.001) in the paper group, there were no statistically significant differences between the changes observed with the task in the paper and computer groups. discussion the focus of this study was to investigate the changes in eye optical quality after a near reading task in two different conditions, on a computer screen and on printed paper, and to compare them to each other. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 625 near vision tasks and optical quality; gomes et al figure 1. changes in ocular, corneal, and internal rms of third, fourth, fifth, and sixth-order aberrations and hoa between pre and post task conditions in both computer and paper groups, with 95%-confidence-interval error bars. there is a statistically significant increase of ocular, corneal, and internal rms in several orders in the paper group and no statistically significant changes in the computer group. the changes in the paper group were significantly greater than the changes in the computer group. table 2. differences between the changes of the computer and paper groups in ocular, corneal, and internal low, third, fourth, fifth, and sixth, and high order root mean square difference between the changes of the computer and paper groups (μm) rms loa rms third order rms fourth order rms fifth order rms sixth order rms hoa ocular –0.054 0.000 –0.016 *–0.020 *–0.010 –0.015 corneal 0.054 *0.132 *0.153 –0.009 –0.0048 –0.066 internal *–0.272 *–0.126 *–0.066 *–0.046 *–0.033 *–0.165 *statistically significant difference for this purpose, the subjects in both groups read the same text for 30 min, and the ocular and corneal wavefront aberrations were measured before and after the task. through zernike coefficients, spherical equivalent, two vectoral components of astigmatism (j45 and j0), and rms of hoa were calculated. furthermore, the effect of near-vision tasks on compensation mechanism between corneal and internal optics was also investigated. changes in some corneal and internal zernike coefficients were observed in the computer group [table 1]. however, depending on how the corneal and internal aberrations changed in opposite directions, the increase of ocular aberrations was attenuated. corneal and internal aberrations changed more significantly in the paper group, and caused variations in ocular aberrations, despite the reverse changes that had also occurred in this group. the corneal wavefront variations found in this study are supported by the variations noted in previous studies,[16, 17] which showed changes in the corneal topography after reading, caused by the eyelid forces. however, as the position of the eyelids is different during the reading tasks on 626 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 near vision tasks and optical quality; gomes et al figure 2. compensation factor mean changes of loa, hoa, and third, fourth, fifth, and sixth-order aberrations with the reading task in the computer and paper groups and the differences between their changes, with 95%confidence-interval error bars. cf decreased with the task, and statistically significant changes were found in the paper group. there were no statistically significant differences between the changes found in the paper and computer groups with the task. figure 3. changes of vector components of ocular astigmatism j45 and j0 and spherical equivalent of computer and paper group and the differences between their changes, with 95%-confidence-interval error bars. there were no statistically significant changes of astigmatism j45 and j0. spherical equivalent became more negative with statistically significant change in the paper group. the changes found in both groups were not statistically significantly different. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 627 near vision tasks and optical quality; gomes et al paper and on a computer screen, the differences of wavefront aberrations might be in different zernike polynomials, depending on the position of the eyes during the task. furthermore, according to ghosh et al the changes in ocular aberrations are greater when the subjects perform a task in downward gaze, (reading a paper) than when they perform a task in primary gaze (using a computer screen) which is in accordance with the results of this study.[43] on the other hand, the variations in internal aberrations are attributed to the alterations resulted by ocular accommodation during nearvision task, which seems to maintain residual changes following the task. the compensatory effect of wavefront aberrations between cornea and lens, already known in relaxed state,[44] was also observed in this study; however, some changes were noticed following the task. the cf indicates that the task caused a general loss of compensation between corneal and internal aberrations which was statistically significant in the paper group [figure 2]. changes in the optical quality of eye components and loss of compensation can cause adverse symptoms in subject after performing a near-vision task. a previous study found more adverse symptoms with a task performed on a computer monitor compared to paper; however, blurred distance vision was more intensified with the task performed on printer paper.[8] this finding is in accordance with the results of the present study that found more optical quality loss after the near-vision task on paper. a future study can also be conducted to evaluate and correlate the symptomatology during different vision tasks with the changes in optical quality. furthermore, the decrease in pupil diameter induced by the luminance of the screen during the computer task (according to a previous study,[45] there is a reduction of up to 20% in pupil size with tasks performed on electronic devices compared to printed paper) helps reduce high-order rms and decrease blurred vision; contrary to the tasks performed on paper, during which the pupil diameter is larger, therefore resulting in a greater decrease in optical quality. moreover, the reduction in pupil size caused by the luminance of the computer screen increases focus depth and thus decreases the accommodative effort necessary to maintain the text unblurred. therefore, the changes in internal optics (caused by accommodation) are minor when the task is performed on a screen which does not occur on printed paper. the results of this study also support the above as the changes in internal optics were greater with paper compared to the computer. the aberrations of the eye can be affected by several factors, such as accommodation[46, 47] and pupil diameter.[48] according to artal et al,[49] this dynamic of ocular optics may compromise the efficiency of a refractive surgery that is only customized for static eye. this study also showed that near-vision tasks can change the corneal and internal optics of the eye and may affect the outcomes expected by refractive surgery. changes in compensation between corneal and internal aberrations were also reported by qingzhong et al, who investigated this parameter during orthokeratology.[50] in addition, they observed changes in internal and corneal aberrations in opposite direction for some zernike polynomials [z (3,–1), z (3,1), z (4,0), and z (6,0)]. the changes in corneal wavefront aberrations caused by refractive surgery or orthokeratology may affect the compensation effect, not only in relaxed states, but also with near-vision tasks. thus, these variations should be considered for the aberrometry performed to evaluate optical aberrations before and after the refractive surgery and orthokeratology.[49] furthermore, the compensatory effect between corneal and internal optics should be taken into account to improve vision quality after refractive surgery or orthokeratology. the spherical equivalent became more negative after the reading task in this study, although this alteration was only statistically significant in the paper group [figure 3]. these findings are consistent with previous studies[13, 14] and suggest that the transient myopia can occur when the task is performed on paper or on computer. ghosh et al found changes in spherical equivalent in the negative direction during a task performed in downward gaze, even when there is no accommodation.[43] as the paper task is performed in downward gaze, their finding is in agreement with the greater change in this group observed in our study. several studies argue that this effect is involved in the development of myopia.[15, 19, 51, 52] there were no statistically significant differences in the vector components of astigmatism j45 and 628 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 near vision tasks and optical quality; gomes et al j0 in either group. however, analyzing the small changes that occurred, j0 became more negative with the task on computer (primary gaze) and more positive when the task was performed on paper (downward gaze). on the other hand, j45 became more positive in the computer group and more negative in the paper group. these findings were supported by the results of ghosh et al’s study[43] that observed a similar trend even when the task was performed with no accommodation. therefore, the eyelid forces, depending on their position during visual tasks, appear to be responsible for the changes in ocular astigmatism. as previously mentioned, a study found highest increase in ocular astigmatism after tasks with higher cognitive demands.[20] future studies are required to analyze the changes in wavefront aberrations with more exigent tasks, to maintain a higher concentration of the subjects in the task, and the changes may be more significant. moreover, it is important to understand the duration that these changes remain effective after the task is completed, and the impact on the eye of continuous. in summary, near-vision tasks can affect ocular, corneal, and internal aberrations and ocular compensation. consequently, these changes can cause adverse symptoms that are reported in this study. the changes are more significant when the subjects perform the task on a printed paper than when the task is performed on a computer screen. acknowledgement the authors would like to thank luneau technology portugal for lending the visionix vx120. financial support and sponsorship this work was supported by the portuguese foundation for science and technology (fct) in the framework of the strategic funding uid/fis/04650/2019 and by the project ptdc/fisoti/31486/2017. conflicts of interest the authors have no conflicts of interest to declare. references 1. hayes jr, sheedy je, stelmack ja, heaney ca . computer use, symptoms, and quality of life. optom vis sci 2007;84:738–755. 2. rossignol am, morse ep, summers vm, pagnotto ld. video display terminal use and reported health symptoms among massachusetts clerical workers. j occup med off publ ind med assoc 1987;29:112–118. 3. daum km, clore ka, simms ss, vesely jw, wilczek dd, spittle bm, good gw. productivity associated with visual status of computer users. optometry 2004;75:33–47. 4. wick b, morse s. accommodative accuracy to video display monitors: poster# 28. optom vis sci 2002;79:218. 5. collier jd, rosenfield m. accommodation and convergence during sustained computer work. optometry 2011;82:434–440. 6. rosenfield m, gurevich r, wickware e, lay m. computer vision syndrome: accommodative and vergence facility. invest ophthalmol vis sci 2009; 50:5332. 7. hue je, rosenfield m, saá g. reading from electronic devices versus hardcopy text. work 2014;47:303–307. 8. chu c, rosenfield m, portello jk, benzoni ja, collier jd. a comparison of symptoms after viewing text on a computer screen and hardcopy. ophthalmic physiol opt 2011;31:29– 32. 9. penisten dk, goss da, philpott g, pham a, west rw. comparisons of dynamic retinoscopy measurements with a print card, a video display terminal, and a prio system tester as test targets. optom am optom assoc 2004;75:231–240. 10. ferreira a, lira m, franco s. accommodative and convergence response to computer screen and printed text. int soc opt photonics 2011;8001:800139. 11. moulakaki ai, recchioni a, águila-carrasco ajd, esteve-taboada jj, montés-micó r. assessing the accommodation response after near visual tasks using different handheld electronic devices. arq bras oftalmol 2017;80:9–13. 12. phamonvaechavan p, nitiapinyasagul r. a comparison between effect of viewing text on computer screen and ipad ® on visual symptoms and functions. smj 2017;69:185–189. 13. ehrlich dl. near vision stress: vergence adaptation and accommodative fatigue. ophthalmic physiol opt 1987;7:353–357. 14. ong e, ciuffreda kj. nearwork-induced transient myopia. doc ophthalmol 1995;91:57–85. 15. ciuffreda kj, wallis dm. myopes show increased susceptibility to nearwork aftereffects. investig ophthalmol vis sci 1998;39:1797–1803. 16. golnik kc, eggenberger e. symptomatic corneal topographic change induced by reading in downgaze. j neuro-ophthalmology 2001;21:199–204. 17. knoll ha. bilateral monocular diplopia after near work. optom vis sci 1975;52:139–140. 18. buehren t, collins mj, carney l. corneal aberrations and reading. optom vis sci 2003;80:159–166. 19. buehren t, collins mj, carney lg. near work induced wavefront aberrations in myopia. vision res 2005;45:1297–1312. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 629 near vision tasks and optical quality; gomes et al 20. jimánez r, cardenas d, gonzález-anera r, jiménez jr, vera j. measuring mental workload: ocular astigmatism aberration as a novel objective index. ergonomics 2018;61:506–516. 21. wang y, shao y, yuan y. simultaneously measuring ocular aberration and anterior segment biometry during accommodation. j innov opt health sci 2015;8:1–6. 22. cheng h, barnett jk, vilupuru as, marsack jd, kasthurirangan s, applegate ra, roorda a. a population study on changes in wave aberrations with accommodation. j vis 2004:272–280. 23. press ain. wavefront aberrations in the accommodated human eye based on individual eye model. optik 2007;118:271–277. 24. he jc, burns sa, marcos s. monochromatic aberrations in the accommodated human eye. vision res 2000;40:41– 48. 25. ninomiya s, fujikado t, kuroda t. changes of ocular aberration with accommodation. eye contact lens 2002:924–926. 26. lópez-gil n, fernández-sánchez v, legras r, montésmicó r, lara f, nguyen-khoa jl. accommodationrelated changes in monochromatic aberrations of the human eye as a function of age. invest ophthalmol vis sci. 2008;49:1736–1743 27. zhou x, wang l, zhou x, yu z-q. wavefront aberration changes caused by a gradient of increasing accommodation stimuli. eye 2015;29:115–121. 28. shi g, wang y, yuan y, wei l, lv f, zhang y. measurement of ocular anterior segment dimension and wavefront aberration simultaneously during accommodation. j biomed opt 2012;17:120501. 29. artal p, guirao a. contributions of the cornea and the lens to the aberrations of the human eye. opt lett 1998;23:1713–1715. 30. artal p, guirao a, berrio e, williams dr. compensation of corneal aberrations by the internal optics in the human eye. j vis 2001;1:1. 31. kelly je, mihashi t, howland hc. compensation of corneal horizontal/vertical astigmatism, lateral coma, and spherical aberration by internal optics of the eye. j vis 2004;4:2. 32. artal p, benito a, tabernero j. the human eye is an example of robust optical design. j vis 2006;6:1. 33. lu f, wu j, shen y, qu j, wang q, xu c, et al. on the compensation of horizontal coma aberrations in young human eyes. ophthalmic physiol opt 2008;28:277–282. 34. guirao a, gonzalez c, redondo m, geraghty e, norrby s, artal p. average optical performance of the human eye as a function of age in a normal population. invest ophthalmol vis sci 1999;40:203–213. 35. artal p, ferro m, miranda i, navarro r. effects of aging in retinal image quality. josa a 1993;10:1656–1662. 36. benito a, redondo m, artal p. laser in situ keratomileusis disrupts the aberration compensation mechanism of the human eye. am j ophthalmol 2009;147:424–431. 37. guirao a, redondo m, geraghty e, piers p, norrby s, artal p. corneal optical aberrations and retinal image quality in patients in whom monofocal intraocular lenses were implanted. arch ophthalmol 2002;120:1143–1151. 38. li x, wang y, dou r. aberration compensation between anterior and posterior corneal surfaces after small incision lenticule extraction and femtosecond laserassisted laser in-situ keratomileusis. ophthalmic physiol opt 2015;35:540–551. 39. benjamin wj. borish’s clinical refraction [internet]. 2nd ed. oxford, uk: butterworth-heinemann; 2006. 40. piñero dp, lópez-navarro a, cabezos i, fez d, caballero mt, camps vj. corneal topographic and aberrometric measurments obtained with a multidiagnostic device in healthy eyes: intrasession repeatability. j ophthalmol 2017;2017:2149145 41. sanchez i, ortiz-toquero s, martin r. intrasession repeatability and intersession reproducibility measurments using vx120 multidiagnostic unit. eye contact lens 2018;44:s266–s272 42. thibos ln, hong x, bradley a, applegate ra. accuracy and precision of objective refraction from wavefront aberrations. j vis 2004;4:329–351. 43. ghosh a, collins mj, read sa, davis ba, iskander dr. the influence of downward gaze and accommodation on ocular aberrations over time. j vis 2011;11:17. 44. tabernero j, benito a, alcón e, artal p. mechanism of compensation of aberrations in the human eye. j opt soc am a 2007;24:3274–3283. 45. nunes-pereira e, miranda am, nunes-pereira ej, baskaran k, macedo a. eye movements, convergence distance and pupil-size when reading from smartphone, computer, print and tablet. sjovs 2018;11:1 46. iida y, shimizu k, ito msm. influence of age on ocular wavefront aberration changes with accommodation. j refract surg 2008;24:696–701. 47. franco s, gomes j. real-time measurement of ocular wavefront aberrations in symptomatic subjects. biomed res int 2018;2018. 48. liang j, williams dr. aberrations and retinal image quality of the normal human eye. j opt soc am a 1997;14:2873– 2883. 49. artal p, fernandez ejms. are optical aberrations during accommodation a significant problem for refractive surgery? j refract surg 2002;18:s563–s566. 50. chen q, li m, yuan y, et al. interaction between corneal and internal ocular aberrations induced by orthokeratology and its influential factors. biomed res int 2017;3703854. 51. vera-díaz fa, strang nc, winn b. nearwork induced transient myopia during myopia progression. curr eye res 2002;24:289–295. 52. ebenholtz sm. accommodative hysteresis: a precursor for induced myopia? investig ophthalmol vis sci 1983;24:513–515. 630 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 original article optic nerve head optical coherence tomography angiography findings after coronavirus disease mojtaba abrishami1, md, ms; ramin daneshvar1, md, ms; zahra emamverdian1, msc; nasser shoeibi1, md, ms shima sedighi2, md; talieh saeidi rezvani3, phd; neda saeedian4, md; saeid eslami5, 6, 7, pharmd, phd 1eye research center, mashhad university of medical sciences, mashhad, iran 2department of emergency medicine, university of florida college of medicine, jacksonville, jacksonville, fl, usa 3department of education and psychology, ferdowsi university of mashhad, mashhad, iran 4department of internal medicine, faculty of medicine, mashhad university of medical sciences, mashhad, iran 5department of medical informatics, faculty of medicine, mashhad university of medical sciences, mashhad, iran 6department of medical informatics, amsterdam public health, amsterdam umc, university of amsterdam, amsterdam, the netherlands 7pharmaceutical research center, school of pharmacy, mashhad university of medical sciences, mashhad, iran orcid: mojtaba abrishami: http://orcid.org/0000-0003-2001-7929 ramin daneshvar: http://orcid.org/0000-0002-0884-0907 zahra emamverdian: http://orcid.org/0000-0002-1659-1488 nasser shoeibi: http://orcid.org/0000-0003-3544-0105 talieh saeidi rezvani: http://orcid.org/0000-0003-0460-8454 neda saeedian: http://orcid.org/0000-0003-2128-0315 saeid eslami: http://orcid.org/0000-0003-3755-1212 this study has been presented at the 8th international congress on oct and oct angiography (icoor 2020 virtual) as an oral presentation. abstract purpose: to quantify the microvasculature density of the optic nerve head (onh) using optical coherence tomography angiography (octa) analysis in patients recovered from coronavirus disease 2019 (covid-19). methods: in a comparative cross-sectional, observational study, patients recovered from covid19 whose initial diagnosis was confirmed by a rrt-pcr of a nasopharyngeal sample were included in this study. octa of onh was performed in included patients and normal controls. vascular density (vd) of the all vessels (av) and small vessels (sv) inside the disc and radial peripapillary capillary (rpc) network density were measured in covid-19 recovered patients and compared with similar parameters in an age-matched group of normal controls. results: twenty-five covid-19 patients and twenty-two age-matched normal controls were enrolled in the study and one eye per participant was evaluated. the mean whole image sv vd in the covid-19 group (49.31 ± 1.93) was not statistically significantly different from that in the control group (49.94 ±. 2.22; p = 0.308). a decrease in rpc vd was found in all av and sv vd measured, which became statistically significant in whole peripapillary sv vd, peripapillary inferior nasal sv vd, peripapillary inferior temporal sv vd, peripapillary superior nasal sv vd, and grid-based av vd inferior sector (p < 0.05). inside disc sv vd in the covid-19 group (49.43 ± 4.96) was higher than in the control group (45.46 ± 6.22) which was statistically significant (p = 0.021). conclusion: unremarkable decrease was found in onh microvasculature in patients who had recovered from covid-19. these patients may be at risk of onh vascular complications. increase in inner disc sv vd may be an indicator of onh hyperemia and edema. keywords: coronavirus disease 2019 (covid-19); optic nerve head; optical coherence tomography angiography (octa); radial peripapillary capillary network; severe acute respiratory syndrome corona virus 2 (sars-cov-2) j ophthalmic vis res 2021; 16 (4): 592–601 592 © 2021 abrishami et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9749&domain=pdf&date_stamp=2019-07-17 disc octa findings in covid-19; abrishami et al introduction severe acute respiratory syndrome coronavirus 2 (sars-cov-2) is a new member of the coronaviridae family of viruses, which can cause serious life-threatening respiratory illness, severe pneumonia,[1] and even multiorgan failure.[2, 3] various clinical presentations and fatal consequences of the associated disease, coronavirus disease 2019 (covid-19), have been reported, but scarce reports regarding ocular manifestations are available.[4, 5] angiotensin-converting enzyme (ace)-2 is considered as the main receptor for sars-cov-2 infection.[6] ace2 as a member of the reninangiotensin-aldosterone system (raas) is present in different cell types including type ii alveolar cells in the lung, arterial and venous endothelial cells, enterocytes of the small intestine, and smooth muscle cells of arterial vasculature of most organs.[7] its homologous enzyme is ace, which is the main effector in the raas and ace2 counterbalances and regulates its activity by reducing the amount of angiotensin-ii and increasing ang (1-7).[8] ace and ace2 have been presented in the choroid and different cell types of the retina including retinal vascular endothelial cell, photoreceptor cells, müller cells, and ganglion cells.[9] moreover, their expression in neurons and glial cells in the central nervous system (cns) have been reported.[10] hence, it seems reasonable to expect ocular, and specifically optic nerve head (onh) and cns manifestations of the sars-cov-2 infection. the majority of reports on the ocular involvement in covid-19 describe ocular surface manifestations including conjunctival congestion, chemosis, and conjunctivitis.[11] reports of the retinal findings are numerable. marinho and colleagues described various retinal correspondence to: mojtaba abrishami, md. eye research center, khatam-al-anbia eye hospital, qarani blvd, mashhad 9195965919, iran. e-mail: mojtaba_abrishami@yahoo.com received: 18-02-2021 accepted: 23-07-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9749 manifestations of covid-19 like cotton wool spots and hemorrhages.[12] in our previous report, we found decrease in macular vessel density in superficial and deep capillary peluxuses of the retina, using optical coherence tomography angiography (octa) in otherwise healthy relatively young patients.[13] however, no similar report on onh microvascular findings was avaiable in patients infected with sars-cov-2. as the choroid, retina and nervous tissues could be targets of infection, because of binding of the virus to ace2 receptor, and previous reports on ocular posterior segment lesions in covid-19 individuals include nonspecific findings, like retinal hemorrhages or cotton wool spots, we aimed to evaluate the onh microvasculature in relatively young and otherwise healthy patients recovered from covid-19 and compare it with a normal group. methods study participants a cross-sectional study was conducted at the imam reza general hospital, mashhad, iran. nurses and physicians working at mashhad university of medical sciences (mums) with a definite diagnosis of covid-19, confirmed by a positive test result of a nasopharyngeal swab sample real-time, reverse transcription-polymerase chain reaction, who recovered from the systemic symptoms at least two weeks prior to the enrolment, were included. detailed ocular and systemic histories were obtained from each participant and those with a history of autoimmune disease, migraine, diabetes mellitus, current pregnancy and breastfeeding, or any history of intraocular surgery were excluded. additional exclusion criteria included absolute spherical refractive error >5 diopters and cylindrical refractive error >2 diopters, bestcorrected visual acuity <20/20, and evidence of glaucoma or clinically apparent retinal disease. this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: abrishami m, daneshvar r, emamverdian z, shoeibi n, sedighi s, rezvani ts, saeedian n, eslami s. optic nerve head optical coherence tomography angiography findings after coronavirus disease. j ophthalmic vis res 2021;16:592–601. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 593 https://knepublishing.com/index.php/jovr disc octa findings in covid-19; abrishami et al those with ocular media opacity, like cataract or corneal haziness, preventing high-quality imaging or reduced octa scan quality (i.e., quality scan index <7/10) were also excluded from the analysis. the age-matched control groups were healthy nurses and physicians employed by the mums who were imaged on the same octa machine at the imam reza hospital in 2019; this group was recruited as part of an ongoing, longitudinal cohort study, persian organizational cohort study in mums. complete medical systemic history regarding the patients’ covid-19 symptoms, hospitalization, and disease course were recorded. oxygen saturation at the time of examination was measured by a portable pulse oximeter. image acquisition and analysis octa scans were performed with the angiovue (rtvue xr avanti, optovue, fremont, ca, usa; software version 2018.0.0.14), an octa machine with a-scan-rate of 70,000 scans/sec. each b scan line is repeated to evaluate the image decorrelation. optic disc cubes, angiodisc 4.5 × 4.5 mm hd scan (400 lines × 400 a-scans) protocols, were scanned in the horizontal and vertical orthogonal directions. all measurements were primarily acquired using the automated default segmentation with the preset settings for the radial peripapillary capillary (rpc) network. the 3d projection artifact removal by oct 3d volume set were utilized. all images were centered on the optic disc and displayed a scan quality index of at least 7/10. images with undesirable quality or image artifact were discarded and reacquired. all images in the study, mostly segmentation accuracy, were carefully reviewed by two authors (ma, rd) to ensure sufficient quality and resolution and any images with artifact significant enough to interfere with vessel density analysis were also excluded. for all subjects, cases or controls, only the data of the eye with better image quality was used for analysis. to evaluate the rpc layer, a slab between the outer limit of the retinal nerve fiber layer (rnfl) and the internal limiting membrane were used. all images were checked for segmentation errors and manually adjusted before testing the vessel density. all vessels (av), including both large and small vessels (sv), and sv vascular density (vd) were evaluated separately in the rpc layer. the whole image, inside disc area, in peripapillary whole, peripapillary superior and inferior hemifields, and eight segments sv rpc vd were reported. for the evaluation of av vd, including both large vessels and sv, the whole image was divided into nine (three by three) grid-based sections, and av vd in all sections was reported separately. moreover, the whole image, inside the disc area, in peripapillary whole, peripapillary superior and inferior hemifields av were reported. statistical analysis the normal distribution of variables was examined using the shapiro–wilk test and normality plots and homogeneity of variances were ascertained by levene’s test. based on data distribution and type, either the independent-samples t-test, paired t-tests, or mann–whitney u test were used for comparisons. chi-square test and fisher’s exact test were used for categorical variables. the level of statistical significance was set at 0.05. all statistical analyses were performed using the spss program for windows, version 20 (ibm spss statistics, ibm corporation, chicago, il, usa). ethical considerations the study protocol adhered to the tenets of the declaration of helsinki. all participants provided written informed consent before enrollment and the ethical aspects of the study were approved by the regional committee on medical ethics at mashhad university of medical sciences, mashhad, iran (ir.mums.rec.1399.104). results twenty-five recovered covid-19 patients (10 females, 40%) with a mean age of 41.5 ± 10.5 years and 22 healthy normal controls (10 females, 45.4%) with a mean age of 36.7 ± 7.3 years were enrolled in the study. age (p = 0.086) and gender (p = 0.706) were not significantly different between the two groups. onh parameters like cup–disc ratio and rim area were not different between the groups [table 1]. none of the patients or controls had other systemic comorbidity except recent covid-19 in last six months. 594 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 disc octa findings in covid-19; abrishami et al table 1. comparison of optic nerve head parameters and age of covid-19 patients eyes versus normal eyes normal eyes (n = 22) mean ±±± sd (range) covid-19 patients eyes (n = 25) mean ±±± sd (range) p-value (compare to normal) age (yr) 41.5 ± 10.5 (24.00–53.00) 36.7 ± 7.3 (25.00–61.00) 0.086 cup/disc area ratio 0.14 ± 0.09 (0.00–0.33) 0.12 ± 0.10 (0.00–0.35) 0.415 cup/disc vertical ratio 0.37 ± 0.18 (0.00–0.60) 0.30 ± 0.21 (0.00–0.61) 0.283 cup/disc horizontal ratio 0.32 ± 0.16 (0.00–0.55) 0.27 ± 0.19 (0.00–0.59) 0.356 rim area 1.67 ± 0.27 (1.18–2.29) 1.58 ± 0.32 (1.09–2.40) 0.313 disc area 1.97 ± 0.31 (1.47–2.74) 1.81 ± 0.30 (1.22–2.40) 0.076 cup volume 0.09 ± 0.18 (0.00–0.87) 0.06 ± 0.08 (0.00–0.34) 0.469 peripapillary rnfl 108 ± 10.77 (101.00–129.00) 112.04 ± 7.69 (83.00–133.00) 0.151 rnfl, retinal nerve fiber layer; covid-19, coronavirus disease 2019; sd, standard deviation table 2. comparison of small vessels (sv) vessel density (vd) of covid-19 patients eyes versus normal eyes covid-19 patients eyes mean ±±± sd (range) normal eyes mean ±±± sd (range) p-value whole image – sv vd 49.31 ± 1.93 (44.90–53.40) 49.94 ± 2.22 (44.50–53.20) 0.308 inside disc – sv vd s (37.70–56.40) 45.46 ± 6.22 (24.80–53.00) 0.021 whole peripapillary – sv vd 51.76 ± 1.92 (47.00–55.20) 53.14 ± 2.31 (46.00–56.70) 0.032 peripapillary superior hemi – sv vd 52.01 ± 2.16 (46.90–55.70) 53.12 ± 2.90 (44.40–57.10) 0.148 peripapillary inferior hemi – sv vd 51.79 ± 3.31 (44.90–62.00) 53.16 ± 2.13 (47.70–57.90) 0.095 peripapillary nasal superior – sv vd 49.37 ± 2.96 (42.40–53.70) 49.99 ± 3.84 ( 37.90–56.10) 0.547 peripapillary nasal inferior – sv vd 48.20 ± 4.63 (39.00–57.90) 49.52 ± 4.71 (38.00–64.50) 0.337 peripapillary inferior nasal – sv vd 48.54 ± 2.94 (42.30–52.90) 53.21 ± 4.12 (45.40–59.50) <0.001 peripapillary inferior temporal – sv vd 56.93 ± 3.14 (46.60–61.50) 59.78 ± 3.25 (53.60–65.20) 0.004 peripapillary temporal inferior – sv vd 52.15 ± 3.57 (47.30–60.40) 53.69 ± 3 (45.40–58.20) 0.632 peripapillary temporal superior – sv vd 55.86 ± 4.02 (44.20–61.30) 55.96 ± 4.50 (44.50–63.80) 0.889 peripapillary superior temporal – sv vd 55.24 ± 2.76 (50.50–60.20) 57.0 ± 3.92 (49.50–63.30) 0.087 peripapillary superior nasal – sv vd 49.03 ± 3.39 43.60–55.50) 51.14 ± 3.72 (41.20–58.70) 0.049 sv, small vessels; vd, vessel density; sd, standard deviation; covid-19, coronavirus disease 2019 all patients were symptom-free for at least two weeks, and the mean recovery time interval between becoming symptom free and octa image acquisition was 20.3 ± 2.9 days (median: 18 days; authors range: 13–29 days). past medical history was otherwise unremarkable for almost all of the patients and controls. none of the included subjects, covid-19 cases or controls, endorsed a history of diabetes mellitus. two covid-19 patients had a history of grade 1 hypertension which was well controlled with medications or diet. nine patients (36%) had a history of hospitalization for covid-19. o2 saturation was in the normal range (94–99%) in these patients and was not different from non-hospitalized patients (p = 0.513). the mean scan quality was 8.28 ± 0.73 in the covid cases and 8.50 ± 0.67 in the normal controls (p = 0.293). right eye octa was analyzed for 11 patients and left eye for 14 patients. the 4.5 × 4.5 mm mean whole image sv vd in the covid-19 group (49.31 ± 1.93) was not statistically different from that in the normal control group (49.94 ± 2.22) (p = 0.308) although it seems to be lower in the covid-19 recovered patients journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 595 disc octa findings in covid-19; abrishami et al table 3. comparison of all vessels (av), including both small and large vessels, vessel density (vd) of covid-19 patients eyes versus normal eyes covid-19 patients eyes mean ±±± sd (range) normal eyes mean ±±± sd (range) p-value whole image – av vd 56.08 ± 1.89 (52.50–60.20) 56.44 ± 2.29 (51.40–59.10) 0.566 inside disc – av vd 56.05 ± 4.14 (49.50–63.90) 57.25 ± 5.46 (40.40–63.80) 0.057 whole peripapillary – av vd 58.31 ± 1.65 (55.00–61.80) 59.33 ± 2.34 (52.90–62.60) 0.110 peripapillary superior half – av vd 58.75 ± 1.64 (56.10–61.50) 59.50 ± 2.63 (52.00–63.70) 0.257 peripapillary inferior half – av vd 57.90 ± 2.08 (53.20–62.60) 59.11 ± 2.30 (53.90–63.60) 0.066 grid based av vd supero temporal 57.63 ± 4.21 (43.30–63.10) 59.14 ± 3.02 (52.60–64.00) 0.161 grid based av vd temporal 56.46 ± 3.08 (46.60–62.00) 57.01 ± 3.37 (50.40–61.50) 0.565 grid based av vd infero temporal 58.49 ± 4.47 (42.60–64.40) 58.67 ± 3.43 (49.20–64.10) 0.879 grid based av vd superior 56.85 ± 2.77 (52.50–62.10) 58.68 ± 3.36 (50.80–63.40) 0.051 grid based av vd central 58.10 ± 4.56 (50.00–64.60) 60.35 ± 3.23 (49.00–64.40) 0.061 grid based av vd inferior 60.68 ± 2.14 (55.30–64.50) 62.56 ± 3.15 (54.10–66.90) 0.023 grid based av vd supero nasal 51.71 ± 4.19 (43.90–58.20) 52.09 ± 3.36 (43.60–59.90) 0.739 grid based av vd nasal 52.30 ± 5.48 (43.80–67.90) 52.52 ± 3.50 (44.60–62.40) 0.869 grid based av vd inferonasal 50.29 ± 3.91 (44.40–59.80) 50.35 ± 3.84 (41.60–58.10) 0.903 av, all vessels; vd, vessel density; sd, standard deviation; covid-19, coronavirus disease 2019 table 4. comparison of small vessels (sv) vessel density (vd) of hospitalized versus non-hospitalized/outpatients treated covid-19 patients outpatients (n = 16) mean ±±± sd (range) hospitalized (n = 9) mean ±±± sd (range) p-value whole image – sv vd 46.77 ± 4.74 (29.70–53.60) 46.45 ± 4.08 (40.30–54.00) 0.860 inside disc – sv vd 47.64 ± 4.89 (31.70–55.20) 47.05 ± 4.86 (38.50–55.60) 0.764 whole peripapillary – sv vd 48.76 ± 4.26 (34.70–56.10) 47.10 ± 4.48 (41.70–53.20) 0.344 peripapillary superior hemi – sv vd 49 ± 4.45 (34.30–55.70) 47.48 ± 4.79 (41.50–54.20) 0.412 peripapillary inferior hemi – sv vd 47.96 ± 4.90 (33.20–56.90) 46.38 ± 4.49 (41.00–54.10) 0.415 peripapillary nasal superior – sv vd 48.90 ± 4.64 (34.40–55.90) 47.64 ± 5.11 (42.60–55.90) 0.512 peripapillary nasal inferior – sv vd 49.70 ± 3.60 (43.40–55.30) 49.85 ± 3.03 (45.70–55.70) 0.910 peripapillary inferior nasal – sv vd 49.59 ± 3.65 (42.80–54.90) 49.71 ± 2.86 (46.20–54.90) 0.930 peripapillary inferior temporal – sv vd 49.79 ± 3.69 (43.90–55.60) 50 ± 3.30 (45.20–56.40) 0.884 peripapillary temporal inferior – sv vd 32.07 ± 5.11 (18.10–40.20) 34 ± 9.32 (14.10–45.40) 0.463 peripapillary temporal superior – sv vd 52.16 ± 3.61 (45.80–58.50) 52.02 ± 3.54 (46.60–58.00) 0.919 peripapillary superior temporal – sv vd 52.16 ± 3.64 (46.30–58.20) 51.82 ± 3.38 (46.70–57.50) 0.809 peripapillary superior nasal – sv vd 52.18 ± 3.74 (45.20–58.80) 52.21 ± 3.75 (46.50–58.50) 0.987 sv, small vessels; vd, vessel density; sd, standard deviation; covid-19, coronavirus disease 2019 [table 2]. the 4.5 × 4.5 mm mean whole image av vd in the covid-19 cohort (56.08 ± 1.89) was also not statistically significantly different with that in the controls (56.44 ± 2.29) (p = 0.566); however, there was a tendency for lower values in the former group [table 3; figure 1]. of note, whole peripapillary sv vd (51.76 ± 1.92 vs 53.14 ± 2.31; p = 0.032), peripapillary inferior nasal sv vd (48.54 ± 2.94 vs 53.21 ± 4.12; p < 596 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 disc octa findings in covid-19; abrishami et al table 5. comparison of all vessels (av), including both small and large vessels, vessel density (vd) of hospitalized versus nonhospitalized/outpatients treated covid-19 patients non-hospitalized (n = 16) mean ±±± sd (range) hospitalized (n = 9) mean ±±± sd (range) p-value whole image – av vd 48.58 ± 4.83 (33.40–56.30) 47.92 ± 4.28 (41.90–55.30) 0.725 inside disc – av vd 49.54 ± 4.86 (31.90–56.40) 48.12 ± 3.95 (41.80–54.90) 0.444 whole peripapillary – av vd 48.51 ± 4.24 (35.10–56.50) 46.68 ± 4.35 (41.60–53.00) 0.292 peripapillary superior half – av vd 45.28 ± 4.34 (30.80–53.40) 43.71 ± 4.04 (38.60–49.70) 0.362 peripapillary inferior half – av vd 52.93 ± 4.21 (40.40–59.20) 50.60 ± 4.93 (43.90–57.60) 0.197 grid based av vd superotemporal 52.41 ± 3.54 (45.30–57.80) 52.68 ± 3.02 (48.80–56.80) 0.843 grid based av vd temporal 51.53 ±4.19 (43.90–58.20) 51.16 ± 4.06 (45.30–58.60) 0.824 grid based av vd inferotemporal 52.93 ± 3.81 (46.50–59.80) 52.22 ± 3.08 (46.70–57.40) 0.622 grid based av vd superior 51.79 ± 3.91 (44.40–58.30) 51.97 ± 4.43 (45.60–59.20) 0.911 grid based av vd central 49.87 ± 6.10 (39.50–62.90) 49.52 ± 3.44 (43.00–54.00) 0.874 grid based av vd inferior 49.88 ± 6.07 (40.30–63.50) 49.07 ± 3.21 (43.90–53.70) 0.712 grid based av vd superonasal 49.77 ± 6.24 (38.60–62.20) 49.95 ± 3.81 (42.00–54.30) 0.937 grid based av vd nasal 53.35 ± 5.56 (42.10–63.60) 53.38 ± 3.78 (46.50–58.00) 0.986 grid based av vd inferonasal 48.56 ± 6.64 (39.30–62.90) 48.66 ± 3.73 (43.30–55.10) 0.967 av, all vessels; vd, vessel density; sd, standard deviation; covid-19, coronavirus disease 2019 figure 1. en-face optical coherence tomography angiograms (octa) segmented at the level of the radial peripapillary capillary (rpc) network from four recovered covid-19 patients (a–d) versus four age-matched normal controls (e–h). note the remarkable flow deficits present in the en-face angiograms from the covid cases. 0.001), peripapillary inferior temporal sv vd (56.93 ± 3.14 vs 59.78 ± 3.25; p = 0.004), and gridbased av vd in inferior sector (60.68 ± 2.14 vs 62.56 ± 3.15; p = 0.023) were significantly lower in covid-19 patients, compared with normal controls. in addition, in all other parameters, except inside disc sv vd, covid-19 patients had lower vd in av and sv vd, but the differences were not statistically significant. inside disc sv vd in covid-19 patients (49.43 ± 4.96) was higher than the inside disc sv vd in the normal control group (45.46 ± 6.22), which was statistically significant (p = 0.021). journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 597 disc octa findings in covid-19; abrishami et al moreover, subgroup analysis between hospitalized and outpatient treated patients revealed no statistically significant difference between two groups although unremarkable lower values were observed in hospitalized patients versus outpatients [tables 4 and 5]. discussion in the present study, we used octa to determine the vd in the onh and the rpc layer of optic disc in a relatively young, mild involvement, without other comorbidity and minority hospitalized, cohort of recovered covid-19 patients and compare it with an age-matched normal control group. except inside disc sv vd which was higher in the covid19 patients, in all rpc measured sv and av vd recovered covid-19 patients showed lower values, which became statistically significant in whole peripapillary sv vd, peripapillary inferior nasal sv vd, peripapillary inferior temporal sv vd, and grid-based av vd inferior sector. in other segments of peripapillary sv vd and grid-based sectors of av vd, vessel densities tend to be lower in the covid group but this did not reach statistical significance. in a subgroup analysis, in hospitalized patients we found in all rpc measured sv and av vd unremarkable lower values versus outpatient treated covid-19 patients which were not statistically significant. in an autopsy study, casagrande and associates detected sars-cov-2 viral particles in the retina of patients who had deceased due to covid19.[14] presence of ace2 receptors in cns and various layers of the retina and choroid have been reported;[9, 10] hence, pathologic changes in the ocular tissues, and especially in onh and retina, may be expected. in a recent case series using zeiss cirrus 5000 hd oct angioplex, rpc plexus perfusion density was lower in 80 covid-19 recovered patients compared to 30 controls. moreover, patients treated with lopinavir, ritonavir, or antiplatelet therapy during admission had lower rpc flow index and rpc perfusion density.[15] it indicates probable onh involvement in covid-19. moreover, guillainbarré syndrome and miller–fisher-like syndrome have also been reported in association with sars-cov-2 infection.[16, 17] in recent studies, sars-cov-2 potential for neuroinvasion has been suggested.[18] it seems that in-line with the previous reports of retinitis and optic neuritis induced by coronaviruses in animal models,[19] and the proposed neuroinvasion hypothesis, sars-cov-2 can cause neuro-inflammation and neuro-infection in humans too. besides the neurologic involvements, as retinal ganglion cells, müller cells, and blood vessels are potential targets of the virus, the onh and retinal findings in covid-19 are well anticipated. vascular changes can be either primary or secondary to alternations in the hemodynamic demands of the inflamed and damaged tissues. macular octa analysis also found similar results. in another study by our group, using optovue angiovue imaging system, macular vd was decreased in covid-19 patients compared with normal controls.[13] in another similar study in turkey with a same machine, parafoveal vd in the superior and nasal quadrants of the superficial capillary plexus and in all quadrants of the deep capillary plexus were significantly lower in covid-19 patients.[20] moreover, in a case–control study in patients stratified to mild, moderate, and severe covid-19 disease activity, and normal controls, patients with moderate and severe disease had decreased macular vd as compared with control subjects or even those who were asymptomatic or paucisymptomatic.[21] it has been proposed that sars-cov-2 infection, as a systemic multi-organ infection, may affect retinal vasculature beside other organs and marks retinal microvasculature.[22] octa analysis is an invaluable tool in the evaluation of vascular changes in the retina and onh for diagnosis, staging, and monitoring in glaucoma.[23, 24] in addition, in several neurologic conditions, including preclinical alzheimer’s disease, octa was found to be helpful.[25] in other neurodegenerative diseases and even mild cognitive disorders, octa has been proposed as an additional biomarker for the early diagnosis and disease activity monitoring.[26, 27] in this study, we found that onh microvasculature was somewhat decreased compared to the age-matched controls. in all segments, vd was numerically decreased in these comparative analyses, although the differences were statistically significant in some segments. an intriguing finding in our study was the higher sv inside disc vd, which was statistically higher than normal controls. previously, it has been reported that onh, nerve fiber layer thickness, is 598 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 disc octa findings in covid-19; abrishami et al increased in covid 19 recovered patients.[28, 29] in a case report, acute bilateral optic neuritis has been reported in a 44-year-old hispanic male patient with no past medical history. multimodal ocular, orbit, and cns imaging and paraclinic evaluations were performed to determine the possibility of demyelinating or other autoimmune disease and these evaluations were negative as well as other laboratory assessment. therefore, it has been concluded that his infection with covid-19 virus has triggered his immune system to present onh findings.[30] besides our findings, increase in sv vd inside the disc area, which is in contrary to rpc vd findings, may be associated with onh edema and hyperemia, indicating potential optic nerve involvement in covid-19 patients, in line with our previous findings of nerve fiber layer thickening in covid19 patients. essentially, the retina and optic nerve are considered to be intraorbital extensions of the cns, so evaluation of the retinal, and more specifically onh changes, may help us to identify the cns disease as well. indeed, onh and prnfl changes have been already reported in patients with cns pathologies like alzheimer, multiple sclerosis, and diabetic polyneuropathy.[31–33] in a recent review, neuro– ophthalmic manifestations of covid-19 was divided to afferent and efferent manifestations.[34] the examples of the afferent complications include papilledema, optic neuritis, papillophlebitis, and even vision loss due to stroke, while the efferent complications include ocular myasthenia gravis, cranial neuropathies, miller fisher syndrome, and adie’s pupils.[34] these presentations magnifies the importance of onh evaluations in covid19 patients, as these presentations beyond ophthalmic importance which may affect visual function of patients, should be considered as cns involvement which may be more disabling or even fatal. our control group was recruited from healthy personnel of mums, as part of a longitudinal cohort study, persian organizational cohort study in mums.[35] the controls were evaluated and octa images were acquired to build a local normal octa normative database and cohort analysis. the individuals in the control group were examined when no covid-19 cases were formally reported in iran in 2019. therefore, there is no chance for presence of any symptom-free patient among our control group. this study has several limitations. first, octa images were acquired during the recovery of the disease and not during the acute phase when the systemic condition was active. second, longitudinal analysis of the patients was not performed. third, we had a limited sample size, which can explain the lack of statistical significance in some comparisons. a largerscale study with octa performed during the symptomatic phase of the disease, followed by repeat imaging at fixed intervals, would provide valuable information regarding both the short and long-term effects of covid-19 on the onh vascular system. to the best of our knowledge, it’s the first report of onh octa findings in patients with a history of covid-19. the clinical relevance of our finding is unclear, as the patients were all asymptomatic with 20/20 vision at the time of this analysis. this can indicate the acute inflammatory phase of the ocular involvement and the associated vasodilation. it is noteworthy that the systemic and ocular disease phases can be unparalleled and occur at different times. nevertheless, our findings in a relatively young group of covid-19 confirmed patients who had no other comorbidity, and the comparison with an age-matched normal control group, similarly imaged, is novel and may highlight the importance of continued vigilance for the detection of nervous tissue and ocular complications associated to covid-19 as the pandemic evolves. in conclusion, our study demonstrated onh vd alterations in patients with a history of covid19 and without other comorbidities, including a decrease in av and sv rpc vd. these findings beside previous microvascular retinal findings in these patients indicate potential retinal and onh ischemic changes, which may be a manifestation of cns potential vascular involvement. moreover, increase in inside disc sv vd may be an indicator of onh hyperemia and edema. acknowledgement the authors would like to thank abbas saberi and hojjat salmani at mashhad persian cohort center, for their kind assistance with this research project. it is a pleasure for them to also acknowledge the kind support of capt. mehdi madadi. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 599 disc octa findings in covid-19; abrishami et al financial support and sponsorship the authors would like to acknowledge the financial support of the vice-chancellor of research of mashhad university of medical sciences for this research project (code: 990069). the funding organization had no role in the design or conduct of this study. conflicts of interest the authors declare no potential conflicts of interest for the research, authorship, and/or publication of this article. references 1. ahn dg, shin hj, kim mh, lee s, kim h-s, myoung j, et al. current status of epidemiology, diagnosis, therapeutics, and vaccines for novel coronavirus disease 2019 (covid19). j microbiol biotechnol 2020;30:313–324. 2. gheblawi m, wang k, viveiros a, nguyen q, zhong j-c, turner aj, et al. angiotensin-converting enzyme 2: sarscov-2 receptor and regulator of the renin-angiotensin system: celebrating the 20th anniversary of the discovery of ace2. circ res 2020;126:1456–1474. 3. huang c, wang y, li x, ren l, zhao j, hu y, et al. clinical features of patients infected with 2019 novel coronavirus in wuhan, china. lancet 2020;395:497–506. 4. li jo, lam dsc, chen y, ting dsw. novel coronavirus disease 2019 (covid-19): the importance of recognising possible early ocular manifestation and using protective eyewear. br j ophthalmol 2020;104:297–298. 5. mungmungpuntipantip r, wiwanitkit v. ocular manifestation, eye protection, and covid-19. graefes arch clin exp ophthalmol 2020;258:1339. 6. wan y, shang j, graham r, baric rs, li f. receptor recognition by the novel coronavirus from wuhan: an analysis based on decade-long structural studies of sars coronavirus. j virol 2020;94:e00127–e00120. 7. hamming i, timens w, bulthuis ml, lely at, navis g, van goor h. tissue distribution of ace2 protein, the functional receptor for sars coronavirus. a first step in understanding sars pathogenesis. j pathol 2004;203:631–637. 8. chamsi-pasha ma, shao z, tang wh. angiotensinconverting enzyme 2 as a therapeutic target for heart failure. curr heart fail rep 2014;11:58–63. 9. choudhary r, kapoor ms, singh a, bodakhe sh. therapeutic targets of renin-angiotensin system in ocular disorders. j curr ophthalmol 2017;29:7–16. 10. zhou z, kang h, li s, zhao x. understanding the neurotropic characteristics of sars-cov-2: from neurological manifestations of covid-19 to potential neurotropic mechanisms. j neurol 2020;267:2179–2184. 11. abrishami m, tohidinezhad f, daneshvar r, omidtabrizi a, amini m, sedaghat a, et al. ocular manifestations of hospitalized patients with covid-19 in northeast of iran. ocul immunol inflamm 2020;28:739–744. 12. marinho pm, marcos aaa, romano ac, nascimento h, belfort r jr. retinal findings in patients with covid-19. lancet 2020;395:1610. 13. abrishami m, emamverdian z, shoeibi n, omidtabrizi a, daneshvar r, rezvani ts, et al. optical coherence tomography angiography analysis of the retina in patients recovered from covid-19: a case-control study. can j ophthalmol 2021;56:24–30. 14. casagrande m, fitzek a, puschel k, aleshcheva g, schultheiss h-p, berneking l, et al. detection of sarscov-2 in human retinal biopsies of deceased covid-19 patients. ocul immunol inflamm 2020;28:721–725. 15. savastano a, crincoli e, savastano mc, younis s, gambini g, de vico u, et al. peripapillary retinal vascular involvement in early post-covid-19 patients. j clin med 2020;9:2895. 16. su xw, palka sv, rao rr, chen fs, brackney cr, cambi f. sars-cov-2-associated guillain-barre syndrome with dysautonomia. muscle nerve 2020;62:e48–e49. 17. fernandez-dominguez j, ameijide-sanluis e, garciacabo c, garcia-rodriguez r, mateos v. miller–fisher-like syndrome related to sars-cov-2 infection (covid 19). j neurol 2020;267:2495–2496. 18. dossantos mf, devalle s, aran v, capra d, roque nr, de mattos coelho-aguiar j, et al. neuromechanisms of sarscov-2: a review. front neuroanat 2020;14:37. 19. seah i, agrawal r. can the coronavirus disease 2019 (covid-19) affect the eyes? a review of coronaviruses and ocular implications in humans and animals. ocul immunol inflamm 2020;28:391–395. 20. turker ic, dogan cu, guven d, kutucu ok, gul c. optical coherence tomography angiography findings in patients with covid-19. can j ophthalmol 2021;56:83–87. 21. zapata má, banderas garcía s, sánchez-moltalvá a, et al. retinal microvascular abnormalities in patients after covid-19 depending on disease severity [published online ahead of print, 2020 dec 16]. br j ophthalmol 2020;bjophthalmol-2020-317953. 22. sim ss, cheung cmg. does covid-19 infection leave a mark on the retinal vasculature? can j ophthalmol 2021;56:4–5. 23. ma zw, qiu wh, zhou dn, yang wh, pan xf, chen h. changes in vessel density of the patients with narrow antenior chamber after an acute intraocular pressure elevation observed by oct angiography. bmc ophthalmol 2019;19:132. 24. lommatzsch c, rothaus k, koch jm, heinz c, grisanti s. vessel density in oct angiography permits differentiation between normal and glaucomatous optic nerve heads. int j ophthalmol 2018;11:835–843. 25. van de kreeke ja, nguyen ht, konijnenberg e, tomassen j, den braber a, kate mt, et al. optical coherence tomography angiography in preclinical alzheimer’s disease. br j ophthalmol 2020;104:157–161. 26. pellegrini m, vagge a, ferro desideri lf, bernabei f, triolo g, mastropasqua r, et al. optical coherence tomography angiography in neurodegenerative disorders. j clin med 2020;9:1706. 27. criscuolo c, cennamo g, montorio d, carotenuto a, strianese a, salvatore e, et al. assessment of retinal vascular network in amnestic mild cognitive impairment 600 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 disc octa findings in covid-19; abrishami et al by optical coherence tomography angiography. plos one 2020;15:e0233975. 28. abrishami m, daneshvar r, emamverdian z, tohidinezhad f, eslami s. optic nerve head parameters and peripapillary retinal nerve fiber layer thickness in patients with coronavirus disease 2019. ocul immunol inflamm 2021 feb:1–4. 29. burgos-blasco b, guemes-villahoz n, donate-lopez j, vidal-villegas b, garcia-feijoo j. optic nerve analysis in covid-19 patients. j med virol 2020;93:190–191. 30. sawalha k, adeodokun s, kamoga gr. covid-19-induced acute bilateral optic neuritis. j investig med high impact case rep 2020;8:2324709620976018. 31. cabrera debuc d, gaca-wysocka m, grzybowski a, kanclerz p. identification of retinal biomarkers in alzheimer’s disease using optical coherence tomography: recent insights, challenges, and opportunities. j clin med 2019;8:996. 32. pietroboni am, carandini t, dell’arti l, bovis f, colombi a, de riz ma, et al. evidence of retinal anterograde neurodegeneration in the very early stages of multiple sclerosis: a longitudinal oct study. neurol sci 2020;41:3175–3183. 33. salvi l, plateroti p, balducci s, bollanti l, conti fg, vitale m, et al. abnormalities of retinal ganglion cell complex at optical coherence tomography in patients with type 2 diabetes: a sign of diabetic polyneuropathy, not retinopathy. j diabetes complications 2016;30:469–476. 34. tisdale ak, dinkin m, chwalisz bk. afferent and efferent neuro-ophthalmic complications of coronavirus disease 19. j neuroophthalmol 2021;41:154–165. 35. tohidinezhad f, khorsand a, zakavi sr, rezvani r, zarei-ghanavati s, abrishami m, et al. the burden and predisposing factors of non-communicable diseases in mashhad university of medical sciences personnel: a prospective 15-year organizational cohort study protocol and baseline assessment. bmc public health 2020;20:1637. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 601 review article ankylosing spondylitis nazanin ebrahimiadib1,2, md; sahar berijani2, md; mohammadreza ghahari2, md fatemeh golsoorat pahlaviani2, md 1retina service, ocular immunology and uveitis foundation, farabi eye hospital, tehran university of medical sciences, tehran, iran 2retina service, farabi eye hospital, tehran university of medical sciences, tehran, iran orcid: nazanin ebrahimiadib: https://orcid.org/0000-0002-2058-9225 fatemeh golsoorat pahlaviani: https://orcid.org/0000-0002-5792-295x abstract the seronegative spondyloarthropathies are a group of autoimmune inflammatory diseases lacking rheumatoid factor or antinuclear antibody in their serum. they include ankylosing spondylitis (as), reactive arthritis, psoriatic arthritis, spondylitis associated with crohn’s disease and ulcerative colitis, and undifferentiated spondyloarthropathies. inflammation mostly affects the axial joints, entheses, and extra-articular structures such as uveal tract, gastrointestinal tract, mucocutaneous tissue, and heart. uveitis is the most common extra-articular manifestation. spondyloarthropathies, especially as, have a strong association with the presence of human leukocyte antigen (hla)-b27 gene. as happens earlier in hla-b27 patients and men are more prone to the disease. uveitis, typically unilateral nongranulomatous acute anterior uveitis, occurs in up to 50% of the patients with as. hla-b27 positivity correlates with more frequent flare-ups. conjunctivitis and scleritis are rare ocular manifestations of as. to establish the diagnosis of as, at least one clinical and one radiologic parameter are required for definitive diagnosis. magnetic resonance imaging (mri) or bone scan can help early detection of the axial skeleton inflammation. the course of eye and joint involvement are not correlated. short-term treatment with topical corticosteroids and cycloplegic agents control the uveitis attack. in resistant cases, local or systemic therapy with corticosteroids are recommended. nsaids, disease-modifying anti-rheumatic drugs (dmards), methotrexate, azathioprine, anti-il-17a monoclonal antibodies, and tnfα antagonists are effective treatments for ocular and systemic manifestations of as. if not treated adequately, uveitis may become recalcitrant and extend posteriorly. functional impairment due to joint destruction can also occur as a result of undertreatment. keywords: ankylosing spondylitis; spondyloarthritis; uveitis j ophthalmic vis res 2021; 16 (3): 462–469 462 © 2021 ebrahimiadib et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i3.9440&domain=pdf&date_stamp=2019-07-17 ankylosing spondylitis; ebrahimiadib et al introduction origin/history the seronegative spondyloarthropathies include the following: • ankylosing spondylitis (as) • reactive arthritis (also referred to as reiter’s syndrome) • psoriatic arthropathy • spondylitis associated with nonspecific inflammatory bowel diseases (ibd) such as crohn’s disease and ulcerative colitis • undifferentiated spondyloarthropathies.[1, 2] in 1970, physicians described the shared clinical symptoms of the seronegative spondyloarthropathies as a distinct category of diseases distinct from rheumatoid arthritis.[3] when referring to patients with as (bechterew disease, marie-strumpell disease), they are considered “seronegative” because they typically have a negative rheumatoid factor and antinuclear antibody. spondyloarthropathy is an umbrella term for a group of rheumatologic diseases that have common clinical features: (1) inflammation of joints (primarily axial spine and sacroiliac, though peripheral joints may also be affected), (2) enthesitis, which is defined by inflammation of where tendons, ligaments, and joint capsules are attached to the bone, (3) extra-articular involvement such as uveitis, gastrointestinal (gi) disease, mucocutaneous lesions and cardiac abnormalities, and (4) the presence of human leukocyte antigen (hla)-b27 gene.[2] ocular involvement, especially in the form of anterior uveitis, is the most common correspondence to: fatemeh golsoorat pahlaviani, md. retina service, farabi eye hospital, tehran university of medical sciences, tehran, iran. unit 9, no. 38, 14th east alley, north allameh tabatabaee st., sa’adat abad st., tehran 1997863811, iran e-mail: arezoupahlaviani@gmail.com received: 23-05-2020 accepted: 21-11-2020 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i3.9440 extra-articular manifestation of the seronegative spondyloarthropathies.[4] among the seronegative spondyloarthropathies, as is known to have the highest association with anterior uveitis.[1] this section will focus on the ocular manifestations of as. methodology: we used pubmed and google scholar databases to review the literature. the keywords used were “spondyloarthritis” and “ankylosing spondylitis” and “uveitis”. out of the 212 results obtained from the search, we selected the articles based on the relevancy to our topic and validity of the studies. epidemiology as is the most common form of seronegative spondyloarthropathies with the prevalence of 0.03–1.8%, which varies according to the frequency of hla-b27 in the population.[3] in the caucasian population, it ranges between 0.15% and 1.8%. the incidence has been estimated between 0.49 (japan) and 10 (norway) per 100,000.[3] correlation between hla-b27 and acute anterior uveitis is weakest in african–americans, intermediate in asians, and strongest in whites.[4] uveitis affects up to 50% of patients with as while it occurs in approximately 2–5% of patients with inflammatory bowel disease and in about 7% of patients with psoriatic arthritis.[5] among the seronegative spondyloarthropathies, as has the strongest association with hla-b27. up to 90% of patients with as have the hlab27 haplotype, while this number in the general population is <10%. nevertheless, only 1–5% of all hla-b27-positive individuals will develop the disease, indicating that other genes may play a role in the pathogenesis.[6, 7] the association of hlab27 and as disease is, however, less dramatic in non-caucasians. for example, in a study of a moroccan population with as, the hla-b27 had a frequency of 64%.[8] in terms of clinical presentation, the typical patient with as is a young man who presents this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: ebrahimiadib n, berijani s, ghahari mr, pahlaviani fg. ankylosing spondylitis. j ophthalmic vis res 2021;16:462–469. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 463 https://knepublishing.com/index.php/jovr ankylosing spondylitis; ebrahimiadib et al with insidious onset of low back pain and morning stiffness. the disease onset is earlier in hla-b27 patients. it usually occurs in the second decade of life and rarely occurs after the age of 45. men are more prone to the disease and they more frequently develop anterior uveitis.[1] pathophysiology/etiology the pathogenesis of as is unknown. however, the trigger of the inflammation may be an immune reaction to an environmental or bacterial antigen in a person with a predisposed genetic background.[2] this may prompt the overexpression of interleukin-12 (il-12), il-17, and tumor necrosis factor alpha (tnf-α).[9, 10] high levels of tnf-α have been detected in the aqueous and sera of patients with different underlying causes of anterior uveitis including as.[2] the genetic component, hla-b27, has been identified as the major predisposing factor for the disease. like many other hla class one molecules, it has a high degree of genetic polymorphism. to date, up to 105 subtypes, encoded by 132 alleles, have been identified. the correlation of these subtypes with susceptibility to as varies. dominant subtypes that are most commonly associated with the disease are hla-b*27:05 (caucasians), hlab*27:02 (mediterranean populations), and hlab*27:04 (chinese).[11] hla-drb1 alleles have been also identified as another genetic risk factor for as. hla-drb1*08 positivity is associated with higher levels of tnf-α in the aqueous humor of patients with active uveitis.[11] definition and criteria for diagnosis the modified new york criteria described in 1984 outlines the diagnostic criteria for as. it is based on clinical manifestations and evidence of sacroiliitis on x-ray. at least one clinical and one radiologic parameter are required for definitive diagnosis of as.[1] the clinical manifestations/parameters include: (1) history of inflammatory pain and morning stiffness in the lumbar spine for at least three months that improves with exercise and is not relieved by rest, (2) limitation of lumbar spine motion in both frontal and sagittal planes, and (3) limitation of chest expansion compared to normal values for age and gender. the radiographic parameters include x-ray evidence of grade two to four sacroiliitis bilaterally or grade three or four sacroiliitis unilaterally.[12] sclerosis and obliteration of the joint space, ligamentous calcification, squaring of the vertebrae, and in end stage disease, the characteristic ankylosed “bamboo” spine can be seen on plain radiography. it is noteworthy that seropositivity is neither necessary nor sufficient for establishing the diagnosis of as.[13] establishing the diagnosis of as relies on a thorough history and physical examination besides radiologic confirmation. the disease should not be ruled out if the aforementioned criteria are not met.[2] radiologic evidence of lumbar spine involvement may not appear in the first year of disease onset, so probable diagnosis of as in the presence of typical clinical manifestation must continue to be a consideration. other risk factors that may help to establish an earlier diagnosis are: absence of rheumatoid factor, hlab27 seropositivity, family history, male gender, disease onset prior to the age of 40 years, and frequent gastroenteritis.[2, 14] during the annual scientific meeting of the american college of rheumatology in 2009, new criteria for the diagnosis of as were discussed and magnetic resonance imaging (mri) was included to aid with the diagnosis of axial skeleton inflammation.[2] this imaging modality has been proven to be more sensitive in detecting joint inflammation many years earlier than conventional radiography. with earlier diagnosis and treatment, permanent cartilage damage and bony erosions causing spinal deformity can be prevented.[15, 16] therefore, it is of utmost importance to suspect as in patients with a history of inflammatory spinal pain or recurrent attacks of anterior uveitis. if plain radiography is negative in situations of high clinical suspicion, mri and hla-b27 testing should be requested. if mri is contraindicated, bone scan can also be helpful in diagnosis of as if plain films are normal.[15, 16] laboratory findings in patients with as may serve as markers of chronic disease but are not specific or diagnostic. these include normochromic and normocytic anemia, mild leukocytosis, increased erythrocyte sedimentation rate (esr), increased c-reactive protein (crp), and elevations in alkaline phosphatase and iga.[2] 464 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 ankylosing spondylitis; ebrahimiadib et al symptoms and signs systemic inflammation systemic inflammation primarily affects the sacroiliac joint, the spine, and the entheses. the patient may feel a unilateral or intermittent pain in the gluteal region or the lumbosacral area that within a few months becomes persistent and bilateral. in advanced disease, chronic and progressive inflammation leads to fusion of the sacroiliac joint and spine with progressive loss of spinal movement, loss of lumbar lordosis and kyphosis, and restricted respiratory excursion. “bamboo spine” is a radiologic sign for an advanced disease. in addition, enthesopathy, such as achilles tendonitis, plantar fasciitis, intercostal muscle tendonitis, and dactylitis can occur early in the disease and are painful and recurrent, resulting in structural damage. other peripheral joints such as knee, hip, and shoulder can also be involved, typically as an asymmetric oligoarthritis that predominantly affects the lower limbs.[2] rare extra-articular manifestations of the disease include upper lobe pulmonary fibrosis, cardiac involvements, aortic regurgitation, chronic prostatitis, cauda equina syndrome, occult bowel lesions, and amyloid deposition. these manifestations may present years after active disease.[2] patients may also present with constitutional symptoms including low grade fever, anorexia, fatigue, and weight loss.[2] ocular manifestations acute anterior uveitis is the most common nonarticular manifestation of as and presents in up to 30% of patients during the course of the disease and may increase to 50% with longer follow-up.[4] uveitis is most often characterized by recurrent, asymmetric and bilateral iridocyclitis, involving only one eye at a time and is not related to the severity and course of joint involvement.[17] it may be the first manifestation of as, preceding the other articular symptoms. underlying as is diagnosed in about 24.3% of patients presenting with idiopathic acute anterior uveitis.[18] as a result, ophthalmologists play an important role in early diagnosis and treatment of the disease, which can lead to a more favorable prognosis.[19] hla-b27 positivity correlates with more frequent relapses and worse prognosis of uveitis. the interval between attacks is highly variable and can range from one month to 35 years, although most commonly they occur between 14 and 25 months.[4] common forms of anterior uveitis in as are iritis (with inflammatory cells in the anterior chamber and no involvement of the anterior vitreous), iridocyclitis (primary inflammation of the iris and secondary inflammation of the ciliary body; inflammatory cells present in both the anterior chamber and anterior vitreous), and cyclitis (inflammation of mainly the ciliary body).[2] patients typically present with sudden ocular pain, redness, photophobia, and decreased vision.[20] the main findings on examination are limbal injection, fine whitish–gray keratic precipitates, moderate to severe amounts of cells which may sometimes cause hypopyon and fibrinous exudate in the anterior chamber.[5] inflammatory cells in the anterior chamber of patients with as are more static in nature. thus, hypopyon seen in patients with as can be distinguished from hypopyon that shifts easily in patients with bechet’s disease.[21] although, non-granulomatous anterior uveitis is the typical manifestation, patients may present with posterior uveitis (choroiditis or retinochoroiditis), intermediate uveitis (vitritis, peripheral retinitis, and pars planitis), or panuveitis.[1, 4] initial therapies include topical corticosteroids and mydriatic drugs to avoid posterior synechia.[2] if not treated properly, inflammation can extend to the posterior segment of the eye and vitritis, papillitis, retinal vasculitis, cystoid macular edema, epiretinal membrane, and pars plana exudate can occur.[22] conjunctivitis and scleritis are other less common ocular manifestations of as. conjunctivitis is often bilateral, non-purulent, and self-limited. scleritis may occur early or years after the disease activation.[2] disease monitoring there is no individual blood marker to measure disease activity. monitoring of the disease is subjective and is based on the clinical assessment. functional deterioration can help monitor disease activity.[23] ophthalmologists can schedule the frequency of follow-up visits based on the number and severity of uveitis episodes per year. radiographic imaging such as contrast enhanced mri of the sacroiliac joint helps journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 465 ankylosing spondylitis; ebrahimiadib et al in evaluating joint damage and gives further information about ongoing inflammation. this information in addition to measuring serologic acute phase reactants, such as crp and esr, may be useful in monitoring disease activity and the potential for further damage to the sacroiliac joint.[23] risk factors acquired acquired risk factors that have been proposed include previous urogenital or gi infections. previously implicated bacteria include chlamydia trachomatis, gram-negative enterobacteria including klebsiella, salmonella, yersinia, shigella, and campylobacter jejuni.[2] patients with spondyloarthropathy, especially male gender, have increased colonization of these bacteria and subsequently higher titers of related antibodies. colonization of klebsiella in the bowel has been shown to be associated with higher number of anterior uveitis episodes in these patients.[14] genetic the most important factor is the presence of hlab27 on the short arm of chromosome six. however, other genes that are believed to have a role in this disease are hla-b60, hla-b61, hla-dr8, hladrb1, and mica (mhc class i chain-related gene a).[2, 6, 7, 9, 11] treatment acute episodes of anterior uveitis associated with as respond well to frequent topical corticosteroids and cycloplegic agents for a short period of time. most patients recover full vision within two months of resolution of a flare.[4] delayed or insufficient treatment makes uveitis more recalcitrant to therapy. approximately 13–19% of patients are resistant to topical therapies, and often the disease in these patients becomes chronic.[2] if topical therapies alone are not effective, periocular injection of triamcinolone (40 mg/ml), intraocular injection of corticosteroids, or a short course of systemic corticosteroid therapy may be necessary, particularly in cases complicated by cystoid macular edema.[1] non-steroidal anti-inflammatory drugs (nsaids) or coxibs alleviate symptoms of inflammatory back pain and may have positive effects on uveitis attacks and provide the opportunity for steroidfree remission.[24] coxibs carry less risk of gi sideeffects than nsaids and can be used in patients who are intolerant to nsaid therapy.[24] disease-modifying anti-rheumatic drugs (dmards) are a group of medications that are effective in inducing remission in as. sulfasalazine works by inhibiting the synthesis of prostaglandins. it has been used in recurrent acute anterior uveitis in as, especially in patients with peripheral arthritis.[2] it has been shown to reduce the number and severity of uveitis relapses.[20] uveitis that is refractory to sulfasalazine may benefit from steroid-sparing immunosuppression which can decrease the number of flares. methotrexate (7.5–25 mg), dosed weekly, and azathioprine (1–2 mg/kg), dosed daily, are two examples of immunosuppressive therapy that may be used for the uveitis associated with as.[25] methotrexate is considered an anti-metabolite and works by competitively inhibiting dihydrofolate reductase (dhfr), ultimately interfering with dna synthesis. the role of methotrexate on the natural course of uveitis is conflicting in the literature. some studies report that it can reduce the number of uveitis relapses, while others refute its ability to modify the disease or reduce the uveitis crisis.[2, 25, 26] patients taking methotrexate or azathioprine must be monitored with questions about side effects and frequent blood tests.[25] in cases refractory or intolerable to nsaids, sulfasalazine and immunosuppressant drugs or in severe disease with extension of inflammation into the posterior segment, anti-tnf-α therapy is indicated.[27] some authors even suggest that after failure of two trials of nsaids for more than three months or intolerable side-effects, therapy with tnf-α inhibitors should be initiated.[27] biologic agents, including tnf-α inhibitors, have revolutionized the treatment of spondyloarthropathies as they have been shown to modify the course of the disease and significantly reduce the rate of uveitis recurrences.[4] tnf-α inhibitors consist of four monoclonal antibodies (adalimumab, certolizumab, golimumab, and infliximab) and one tnf-receptor fusion protein (etanercept). by binding to tnf-α, they prevent it from binding to lymphocyte fc receptors. 466 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 ankylosing spondylitis; ebrahimiadib et al therefore, cellular immunity is suppressed. in addition to their rapid onset of action and promising results in modifying the inflammatory course of the disease, this class of medications has substantially contributed to improved joint mobility and visual recovery,[28, 29] and can be used as monotherapy.[2] all four tnf-α antagonists have been proven to be equally effective in controlling the spinal manifestations of as and uveitis; however, infliximab and adalimumab have been shown to be slightly more effective for the treatment of extra-spinal features of the disease including acute uveitis. these two agents, especially infliximab, significantly reduce the number of uveitis flareups.[30] however, their high cost and potential complications prevent them from being used as the first-line therapy in uveitis. etanercept, although in the same overall class of medications, is not efficacious in the treatment of ocular inflammation and has been reported to paradoxically cause uveitis.[10] some potential side-effects of tnf-α antagonists include infection (particularly tuberculosis and histoplasmosis), exacerbation of demyelinating diseases, bilateral anterior optic neuropathy, and sudden death in patients with congestive heart failure.[2] anti-il-17 monoclonal antibodies have been approved for the treatment of as; however, they are mostly effective for the joint manifestations rather than ocular inflammation.[32] functional impairment and pain are the two major areas that should also be addressed in the treatment of arthritis in as. depending on the joint involved, patients with as need to undergo physical therapy to improve function and mobility. patient education is critical. posturing exercises, local heat, and job modification can help patients to maintain muscle strength and flexibility even with progression of ossification and ankyloses.[33] similar to other types of uveitis, patients may develop complications such as glaucoma and cataract which require surgical management.[34] trabeculectomy and ahmed valve procedure are the most common surgeries performed for glaucoma, although valve surgery is usually preferred due to the propensity of these patients to scar.[35] cataract extraction is often complex. patients often have small pupils secondary to posterior synechia requiring lysis and pupil-dilating devices at the time of surgery. before proceeding with cataract surgery, the patient must be free of inflammation for at least three months and the surgeon should counsel the patient about the need for frequent corticosteroid drops and/or oral corticosteroids as well as topical nsaids before and after surgery.[36] in rare cases of extension of inflammation to the vitreous cavity or vitreomacular traction, vitrectomy may be required.[37] prognosis long-term treatment with anti-inflammatory drugs is usually required in patients with as. the goal of treatment is preserving the high quality of life with maximum function. some risk factors for poor prognosis are as follows: involvement of peripheral joints, disease onset during youth, endless steroid therapy, and poor response to nsaids.[2] the prognosis of uveitis in as is usually good except for refractory cases with involvement of the posterior segment. most patients regain full vision in two months.[4] unfortunately, delayed and ineffective therapy of patients is very common. hla-b27 positivity is associated with higher frequency of uveitis recurrence and therefore with worse visual prognosis.[4] early stages of sacroiliitis can be detected in about 63% of patients with acute anterior uveitis using sophisticated techniques of imaging such as bone scan.[30] this may allow a prompt diagnosis and earlier effective care. the prognosis of joint involvement is also good; however, intermittent flare-ups between bouts of clinical remission can cause complete spinal ankylosis. vertebral fusion, which includes the cervical region, results in severe kyphosis and limited mobility. this makes patients vulnerable to fracture even with trivial trauma. hip and shoulder involvement require total joint replacement.[2] these are important signs that the ophthalmologist should pay attention to in the evaluation of their patients. some patients remain in the “non-radiographic” phase for years. the major predictor of progression of disease from non-radiographic to radiographic stage is the amount of inflammation. therefore, in patients with an elevated crp and evidence of active inflammation in the sacroiliac joint detected by mri, structural damage of the sacroiliac joint is more likely to occur.[19, 31] journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 467 ankylosing spondylitis; ebrahimiadib et al complications complications can occur secondary to chronic and recurrent episodes of uveitis or delayed and insufficient treatment. posterior synechia is the most common anterior segment complication (13–91%) followed by cataract (7–28%). this complication can make cataract surgery more complicated. glaucoma, diffuse vitritis (the most common form of posterior segment involvement), as well as cystoid macular edema (the most common cause of visual impairment) are often observed.[18] cervical spinal subluxation, aortic regurgitation, respiratory failure, and amyloidosis are rare potentially fatal systemic complications of the disease.[2] future directions nsaids and tnf-α antagonists are two mainstays of therapy in as. tnf-α antagonists are the most effective agent in controlling inflammation, however, about 20–30% of patients are unresponsive to this class of drugs. other new biologic response modifiers that target il-23 or il-17, especially il-17, are being considered as an alternative to anti-tnf-α antagonists in treatment of seronegative spondyloarthropathies. secukinumab is an example of anti-il-17a monoclonal antibody that has shown promising results in these patients.[32] new therapies that may provide functional relief to patients are on the horizon. further studies are expected to include ocular manifestations of the disease, as these can cause significant morbidity in patients with ankylosing spondyloarthropathies. financial support and sponsorship nil. conflicts of interest there are no conflicts of interest. references 1. gouveia eb, elmann d, morales ms. ankylosing spondylitis and uveitis: overview. rev bras rheimatol 2012;52:742– 756. 2. khan ma. spondyloarthropathies. rheum dis clin north am 1992;18:1–276. 3. zochling j, smith eu. seronegative spondyloarthritis. best pract res clin rheumatol 2010;24:747–756. 4. chang jh. acute anterior uveitis and hla-b27. surv ophthalmol 2005;50:364–388. 5. rosenbaum jt. uveitis in spondyloarthritis including psoriatic arthritis, ankylosing spondylitis, and inflammatory bowel disease. clin rheumatol 2015;34:999–1002. 6. brown ma, wordsworth bp, reveille jd. genetics of ankylosing spondylitis. clin exp rheumatol 2002;26:s43– s49. 7. reveille jd. genetics of spondyloarthritis – beyond the mhc. nat rev rheumatol 2012;8:296–304. 8. el mouraghi i, quarour a, ghozlani i, collantes e, solana r, el maghraoui a. polymorphisms of hla-a, -b, -cw and drb1 antigens in moroccan patients with ankylosing spondylitis and a comparison of clinical features with frequencies of hla-b*27. tissue antigens 2015;85:108– 116. 9. reveille jd, ball ej, khan ma. hla-b27 and genetic predisposing factors in spondyloarthropathies. curr opin rheumatol 2001;13:265–272. 10. raffeiner b, ometto f, bemardi l, botsios c, punzi l. inefficacy or paradoxical effect? uveitis in ankylosing spondylitis treated with etanercept. case rep med 2014;2014:471319. 11. zhang z1, dai d, yu k, yuan f, jin j, ding l, et al. association of hla-b27 and erap1 with ankylosing spondylitis susceptibility in beijing han chinese. tissue antigen 2014;83:324–329. 12. van der linden s, valkenburg ha, cats a. evaluation of diagnostic criteria for ankylosing spondylitis. a proposal for modification of the new york criteria. arthritis rheum 1984;27:361–368. 13. khan ma, khan mk. diagnostic value of hla-b27 testing ankylosing spondylitis and reiter’s syndrome. ann intern med 1982;96:70–76. 14. rosenbaum jt, davey mp. time for a gut check: evidence for the hypothesis that hla-b27 predisposes to ankylosing spondylitis by altering the microbiome. arthritis rhuem 2011;63:3195–3198. 15. haroon m, o’rourke m, ramasamy p, murphy cc, fitzgerald o. a novel evidence-based detection of undiagnosed spondyloarthritis in patients presenting with acute anterior uveitis: the duet (dublin uveitis evaluation tool). ann rheum dis 2015;74:1990–1995. 16. bennett an, mcgonagle d, o’connor p, hensor em, sivera f, coates lc, et al. severity of baseline magnetic resonance imaging-evident sacroiliitis and hla-b27 status in early inflammatory back pain predict radiographically evident ankylosing spondylitis at eight years. arthritis rheum 2008;58:3413–3418. 17. rosenbaum jt. characterization of uveitis associated with spondyloarthritis. j rheumatol 1998;16:792–796. 18. beckingsale ab, davies j, gibson jm, rosenthal ar. acute anterior uveitis, ankylosing spondylitis, back pain, and hla-b27. br j ophthalmol 1984;68:741–745. 19. reveille jd. biomarkers for diagnosis, monitoring of progression, and treatment responses in ankylosing spondylitis and axial spondyloarthritis. clin rheumatol 2015;34:1009–1018. 468 journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 ankylosing spondylitis; ebrahimiadib et al 20. sampaio-barros pd, conde ra, bonfiglioli r, bertolo mb, samara am. characterization and outcome of uveitis in 350 patients with spondyloarthropathies. rheumatol int 2006;26:1143–1146. 21. foster cs, vitale at. diagnosis and treatment of uveitis. 2nd ed. jp medical ltd.: india; 2013. p. 795. 22. rodriguez a, akova ya, pedroza-seres m, foster cs. posterior segment ocular manifestations in patients with hla-b27-associated uveitis. ophthalmology 1994;101:1267–1274. 23. braun j, kiltz u, sarholz m, heldmann f, regel a, baraliakos x. monitoring ankylosing spondylitis: clinically useful markers and prediction of clinical outcomes. expert rev clin immunol 2015;5:1–12. 24. fiorelli vm, bhat p, foster cs. nonsteroidal antiinflammatory therapy and recurrent acute anterior uveitis. ocul immunol inflamm 2010;18:116–120. 25. altan l, bingol u, karakoc y, aydiner s, yurtkuran m, yurtkuran m. clinical investigation of methotrexate in the treatment of ankylosing spondylitis. scand j rheumatol 2001;30:255–259. 26. chen j, liu c. methotrexate for ankylosing spondylitis. cochrane database syst rev 2004;3:cd004524. 27. greiner k, murphy cc, willermain f, duncan l, plskova j, hale g, et al. anti-tnf-alpha therapy modulates the phenotype of peripheral blood cd4+ t cells in patients with posterior segment intraocular inflammation. invest ophthalmol vis sci 2004;45:170–176. 28. neri p, zucchi m, allegri p, lettieri m, mariotti c, giovannini a. adalimumab (humiratm): a promising monoclonal anti-tumor necrosis factor alpha in ophthalmology. int ophthalmol 2011;31:165–173. 29. rudwaleit m, rodevand e, holck p, vanhoof j, kron m, kary s, et al. adalimumab effectively reduces the rate of anterior uveitis flares in patients with active ankylosing spondylitis: results of a prospective open-label study. ann rheum dis 2009;68:696–701. 30. braun j, baraliakos x, listing j, sieper j. decreased incidence of anterior uveitis in patients with ankylosing spondylitis treated with the anti-tumor necrosis factor agents infliximab and etanercept. arthritis rheum 2005;52:2447–2451. 31. poddubnyy d, rudwaleit m, haibel h, listing j, märkerhermann e, zeidler h, et al. rates and predictors of radiographic sacroiliitis progression over 2 years in patients with axial spondyloarthritis. ann rheum dis 2011;70:1369–1374. 32. mcgonagle dg, mcinnes ib, kirkham bw, sherlock j, moots r. the role of il-17a in axial spondyloarthritis and psoriatic arthritis: recent advances and controversies. ann rheum dis 2019;78:1167–1178. 33. bostan ee, borman p, bodur h, barça n. functional disability and quality of life in patients with ankylosing spondylitis. rheumatol int 2003;23:121–126. 34. ji sx, yin xl, yuan rd, zheng z, huo y, zou h. clinical features of ankylosing spondylitis associated with acute anterior uveitis in chinese patients. int j ophthalmol 2012;5:164–166. 35. ozdal pc, vianna rn, deschênes j. ahmed valve implantation in glaucoma secondary to chronic uveitis. eye 2006;20:178–183. 36. baheti u, siddique ss, foster cs. cataract surgery in patients with history of uveitis. saudi j ophthalmol 2012;26:55–60. 37. gupta p, gupta a, gupta v, singh r. successful outcome of pars plana vitreous surgery in chronic hypotony due to uveitis. retina 2009;29:638–643. journal of ophthalmic and vision research volume 16, issue 3, july-september 2021 469 review article intravitreal methotrexate fatemeh abdi1, md; s. saeed mohammadi2, md; khalil ghasemi falavarjani1,3, md 1eye research center, the five senses institute, rassoul akram hospital, iran university of medical sciences, tehran, iran 2farabi eye hospital, tehran university of medical sciences, tehran, iran 3stem cell and regenerative medicine research center, iran university of medical sciences, tehran, iran orcid: khalil ghasemi falavarjani https://orcid.org/0000-0001-5221-1844 fatemeh abdi https://orcid.org/0000-0002-0280-2969 abstract intravitreal methotrexate (mtx) has been proven to be an effective treatment for various intraocular diseases. in this article, a comprehensive review was performed on intravitreal applications of methotrexate. different aspects of the administration of intravitreal mtx for various clinical conditions such as intraocular tumors, proliferative vitreoretinopathy, diabetic retinopathy, age-related macular degeneration, and uveitis were reviewed and the adverse effects of intravitreal injection of mtx were discussed. the most common indications are intraocular lymphoma and uveitis. other applications remain challenging and more studies are needed to establish the role of intravitreal mtx in the management of ocular diseases. keywords: inflammation; intraocular tumor; intravitreal injection; methotrexate; proliferative vitreretinopathy; uveitis j ophthalmic vis res 2021; 16 (4): 657–669 introduction methotrexate (mtx), a food and drug administration (fda)-approved folic acid antagonist, inhibits dna synthesis, repair, and subsequently cellular proliferation. mtx (formerly known as amethopterin) and its analog aminopterin were developed in 1947.[1, 2] structural similarities of these drugs to folic acid and their ability correspondence to: khalil ghasemi falavarjani, md. eye research center, rassoul akram hospital, sattarkhan-niayesh st., tehran, iran. e-mail: drghasemi@yahoo.com postal code: 1445613131 received: 04-02-2021 accepted: 17-08-2021 access this article online website: https://knepublishing.com/index.php/jovr doi: 10.18502/jovr.v16i4.9756 to inhibit folate-dependent enzymes made them good choices for the treatment of cancers.[3–5] mtx reduces the synthesis of polyamines by inhibition of dihydrofolate reductase (dhfr), an enzyme that catalyzes the reduction of dihydrofolate which results in decreased production of ammonia and hydrogen peroxide and lessens subsequent injury. mtx also increases the release of adenine nucleotides into the extracellular space which are converted to adenosine by cell-surface enzymes and exerts its inhibitory effects on nearly all inflammatory cells.[5] inhibiting the reduction of dihydrobiopterin to tetrahydrobiopterin by mtx results in the this is an open access journal, and articles are distributed under the terms of the creative commons attribution-noncommercial-sharealike 4.0 license, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. how to cite this article: abdi f, mohammadi ss, falavarjani kg. intravitreal methotrexate. j ophthalmic vis res 2021;16:657–669. © 2021 abdi et al. this is an open access article distributed under the creative commons attribution license | published by knowledge e 657 http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v16i4.9756&domain=pdf&date_stamp=2019-07-17 https://knepublishing.com/index.php/jovr intravitreal methotrexate; abdi et al production of reactive oxygen species. increased reactive oxygen species activate jun n-terminal kinase which leads to activation of apoptosis and induction of cell cycle arrest.[6] mtx modulates expression of lincrna-p21, a long non-coding rna, that regulates the p53-mediated apoptotic response without affecting the regulation of the cell cycle.[4, 7] activation of signal transducer and activator of transcription proteins by receptorassociated janus kinases (jak-stat signaling pathway) is also inhibited by mtx which leads to decrease in the production of inflammatory signals.[8] mtx also has modulatory effects on the t-cells, monocytes, and fibroblast-like synoviocytes functions.[9–11] mtx is one of the best choices in the treatment of systemic immune-mediated diseases such as rheumatoid arthritis (ra), psoriasis, juvenile idiopathic arthritis (jia), multiple sclerosis (ms), systemic lupus erythematosus (sle), and inflammatory bowel diseases (ibd). it is also useful for the prevention of graft rejection and treatment of malignant disorders due to its anti-inflammatory and immunomodulatory activities.[2, 12] recently, promising results have been shown for the application of mtx in ophthalmic diseases. the effect of systemic mtx in the treatment of anterior, intermediate, posterior, and pan-uveitis, ocular mucous membrane pemphigoid, and scleritis has already been shown.[13] however, intravitreal injection of mtx has been recently investigated widely as an approach to increase the drug availability to intraocular tissues and to decrease the systemic adverse effects. in this article, we reviewed the current evidence on the application of intravitreal mtx. methods a pubmed and scopus search was performed in october 2020 using each of the following keywords: “methotrexate”, “mtx”, “eye”, “ocular”, “intravitreal mtx”, “intraocular mtx”, “intravitreal methotrexate”, “intraocular methotrexate” in different combinations. all article types including original articles, reviews, and case reports that described the ocular applications of mtx were identified. no limitation for the time of publication was applied. abstracts only and non-english articles were excluded. all selected articles were reviewed thoroughly by the authors and relevant articles describing the application of intravitreal mtx were discussed. results overall, 1066 articles were identified. from these, 146 articles described the use of intravitreal mtx. intravitreal mtx was injected for intraocular tumors, uveitis, complex retinal detachment, diabetic retinopathy, age-related macular degeneration (amd), and other indications. preclinical studies ericson et al[14] investigated the safety profile of intravitreal mtx in rabbits. they injected 0.3 ml of 2.5–30 mg/ml concentration of mtx into the vitreous cavity of rabbits and showed that these concentrations would result in a flare in the anterior chamber, precipitation in the vitreous, and clouding of the lens. however, these concentrations are highly above routine intravitreal dose of mtx and side effects are much more likely with these concentrations. ozkan et al[15] evaluated the ultrastructural changes of retina induced by intravitreal mtx. early changes were retinal edema, vacuolization, and disintegration of mitochondria of the retinal cells and long-term changes were edema in the photoreceptors and inner nuclear and ganglionic cell layers, three days and one month after four weekly injections of 800 µg intravitreal mtx. they showed that high dose intravitreal mtx results in significant ultrastructural changes in the rabbit retina in varying severities. in another study, aly and ebrahim[16] assessed the effect of mtx toxicity on electroretinogram (erg) and retinal caspase-3 activity which has an executive role in apoptosis of pigment epithelial cell, outer nuclear layer cell, and ganglion cells[17] after injection of a single dose of 800 µg mtx. they showed that intravitreal injection of mtx leads to a significant reduction in aand b-waves with an increase in caspase3 activity. hara and colleagues[18] evaluated the effect of intravitreal mtx on embryonic stem cell differentiation and teratogenicity. they integrated embryonic stem cells into the retinas of adult mice and showed that injection of a single dose of intravitreal mtx four weeks after transplantation could increase neuronal differentiation, decrease expression of teratogenic markers, and reduce 658 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 intravitreal methotrexate; abdi et al the proliferative activity of transplanted cells compared with non-treated retina. palakurthi and colleagues[19] evaluated the safety of mtx-loadedbiodegradable microneedle implants which were made using solving cast method. implants were inserted into deep lamellar scleral pockets of both eyes of three rabbits. animals were sacrificed and enucleated four weeks after implantation. enucleated eyes were studied histopathologically for any evidence of inflammation or toxicity related to implant or embedded drug. no evidence of drug toxicity or inflammation and infection was seen around the implantation site and they showed that mtx-containing sustained release implant could be nontoxic and well tolerated by rabbit eyes. sunalp et al[20] investigated the effect of intravitreal mtx on the experimental model of proliferative vitreoretinopathy (pvr). they showed that intravitreal injection of 250,000 homologous dermal fibroblasts into the rabbit vitreous with 10 nmol and 1 µmol concentration of mtx resulted in 71% and 83% retinal detachment, respectively, which was not lower than control cases. they proposed that as mtx inhibits dhfr, it is only effective on the fraction of cells that are at the s phase of the cell cycle and therefore active proliferation.[21] this might explain the ineffectiveness of intravitreal injection of mtx in the reduction of pvr and subsequent retinal detachment. deng et al[22] investigated the antimicrobial property of intravitreal mtx. they established a rabbit model of endophthalmitis induced by staphylococcus epidermidis and assessed the effect of intravitreal injection of dexamethasone and mtx by grading the degree of vitreous haze and pathologic evaluation of ocular structures. the dexamethasone group had the most and the mtx group had the least intraocular inflammation and vitritis. live bacteria were only isolated from the dexamethasone group and not in the mtx group. pathologic evaluation revealed severe ocular destruction in the dexamethasone group and intact structures in the mtx group. they suggested that intravitreal mtx can reduce the risk of the development of bacterial endophthalmitis and associated ocular destruction compared with intravitreal dexamethasone. abbaszadeh hasiri and colleagues[23] evaluated the effect of intravitreal administration of mtx with two different doses for the treatment of endotoxininduced uveitis (eiu) in the rabbit. they showed that mean histopathological inflammation intensity scores in both groups of intravitreal mtx (400 µg vs 800 µg) were significantly higher than the control group and intravitreal mtx did not have significant anti-inflammatory effects on eiu in rabbits. clinical studies mtx has been used to treat various ocular conditions. this part summarizes the clinical studies in which the intravitreal injection of mtx have been performed. intraocular tumors (i) retinoblastoma retinoblastoma is the most common intraocular tumor in children.[24] it was nearly 100% fatal about a century ago; however, therapeutic advances have led to a >90% survival rate.[25] primarily enucleation was the method of choice for the treatment of retinoblastoma. nowadays, this method is only reserved for unsalvageable eyes.[26] the most prevalent drugs used for chemoreduction are vincristine, etoposide, and carboplatin followed by transpupillary thermotherapy, cryotherapy, and brachytherapy which cures >90% of group a–c and about 50% of group d and e eyes with retinoblastoma.[27] kivela et al reported intravitreal mtx monotherapy for the management of intraocular relapse of retinoblastoma after chemoreduction in six eyes.[28] they used an established protocol that was developed for primary intraocular lymphoma.[29] induction phase consisted of weekly intravitreal injections of 400 µg mtx for two months; consolidation and maintenance injections followed every two and four weeks for two and eight months, respectively.[28] objective response to intravitreal mtx alone occurred in five of six eyes.[28] their results are consistent with previous in vitro studies which showed that about one-third of retinoblastomas are sensitive to mtx.[28, 30] (ii) intraocular lymphoma primary cns lymphomas (pcnsl), characterized by an aggressive clinical course and poor outcome, are extranodal lymphomas arising exclusively inside the central nervous system and about 25% of these patients will develop vitreoretinal involvement.[31] in the past three decades, the mean survival rate of pcnsl patients was journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 659 intravitreal methotrexate; abdi et al significantly improved from 19.1% to 30.1% due to developments in chemotherapeutic agents.[32] however, treatment protocols for intraocular lymphoma have not been fully validated and the need for low toxicity regimens that maintain high efficacy is undeniable. intraocular lymphomas are divided into four major groups, vitreoretinal lymphomas which are mostly high-grade b-cell lymphoma, primary choroidal lymphomas which are mainly lowgrade b-cell lymphomas, secondary uveal lymphomas, and primary iridial lymphomas.[33] primary vitreoretinal lymphoma (pvrl), a great masquerader, is the most common and aggressive form of intraocular lymphoma and is usually associated with pcnsl. the characteristic feature of intraocular involvement of pcnsl is the presence of vitreous cells, especially in clumps which could be a masquerader of chronic nonresponsive uveitis.[34] several methods have been proposed for the treatment of intraocular involvement of pcnsl. orbital radiation in combination with systemic chemotherapy with mtx was used and showed effectiveness; however, several studies reported ocular side effects such as cataract formation, dry eye and persistent corneal epithelial defects, radiation retinopathy, and optic neuropathy after orbital irradiation.[35–37] in recent years, intravitreal mtx has been used more widely for the treatment of vitreoretinal involvement of pcnsl and has been found to be effective in induction of remission with acceptable morbidity.[38–40] fishburne and colleagues[38] developed a protocol for the treatment of intraocular lymphoma by the intravitreal injection of 400 µg mtx. intravitreal injection of 400 µg of mtx was performed twice weekly until the vitreous was clinically cleared of malignant cells, then weekly for one month, followed by monthly injections for one year. seven eyes were treated based on this protocol which resulted in remission without any serious ocular adverse effects. frenkel et al[29] described their 10-year experience in treating vitreoretinal involvement of pcnsl by intravitreal injections of mtx. their treatment protocol included injection of 400 µg mtx intravitreally twice weekly for four weeks, once weekly for eight weeks, and then once monthly for nine months. they reported their experience with 44 eyes of 26 patients. sixteen patients were previously diagnosed with cns or systemic lymphoma, and six were primarily diagnosed as chronic nonresponsive uveitis. seventeen eyes completed the treatment protocol and 95% of the eyes were cleared from malignant cells and retinal infiltrates with a maximum of 13 injections (mean injections of 6.4). those eyes which had poor initial visual acuity showed little improvement; however, those who had higher visual acuity showed more improvement in vision. corneal epitheliopathy was the most common side effect that occurred in all patients. it appeared after the third injection and resolved when intervals between injections increased. since there was no intraocular recurrence and no significant side effect, they proposed their protocol as a good firstline treatment option for intraocular lymphoma. ma et al[41] evaluated the outcomes of 19 patients with intraocular lymphoma who were treated with a combined intravenous high-dose mtx (6–8 g/m2) and intravitreal mtx (400 µg). they reported that the patients with concurrent cns involvement had worse therapeutic outcomes compared to those with isolated primary intraocular lymphoma who remained disease-free after salvage treatment. in another study, smith and colleagues[39] evaluated the effect of intravitreal mtx in the management of pcnsl involving the eye. all 26 eyes of 16 patients were cleared of malignant cells after a maximum of 12 mtx injections. three patients experienced recurrence who were treated with another course of intravitreal mtx. the most common side effect in the study was the progression of preexisting cataracts, followed by corneal epitheliopathy, maculopathy, and vitreous hemorrhage. (iii) systemic lymphoma lymphoid proliferations can affect the intraocular structures in various ways. involvement of ocular tissues by systemic lymphoma is rare and could masquerade benign ocular lesions.[42] lee ong et al presented a patient with systemic chronic lymphocytic lymphoma and secondary anterior uveitis and hypopyon which was confirmed by anterior chamber tap and vitreous biopsy. as intravitreal triamcinolone in association with intrathecal mtx failed to improve the patient’s vision, intravitreal mtx (400 µg) was injected weekly. following the first injection, the patient’s vision improved and the second injection resulted in the resolution of the hypopyon.[43] iris and ciliary body involvement are extremely rare in acute lymphoblastic leukemia (all). mello and colleagues reported a patient with unilateral infiltration of iris and ciliary body by all which 660 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 intravitreal methotrexate; abdi et al resulted in decreased vision and pseudohypopyon and iris irregularity. anterior chamber reaction, iris, and ciliary body involvement was resolved after eight intravitreal mtx injections and the patient’s visual acuity improved. although the patient developed mtx-associated keratopathy, it was treated with frequent lubrication.[44] intraocular involvement of mycosis fungoides (cutaneous t-cell lymphoma) is an uncommon phenomenon. reddy et al presented a case of mycosis fungoides with anterior chamber involvement, mutton fat keratic precipitate (kps), and exudative retinal detachment which resulted in decreased vision. it was confirmed by vitreous biopsy and intravitreal mtx (400 µg) was administered weekly for one month and then every two weeks. this regimen resulted in the resolution of exudative retinal detachment and infiltrations. to prevent recurrence, the patient continued to receive monthly injection of intravitreal mtx.[45] ryan and coworkers reported a patient with systemic large b-cell lymphoma which presented with decreased vision and retinal pigment epithelial changes, as well as a yellow–white infiltrative macular lesion with adjacent retinal whitening and hemorrhage in the right and left eyes, respectively. diagnostic vitrectomy confirmed the presence of large lymphoma cells with associated reactive lymphocytes. although, pet scan, lumbar puncture, and bone marrow biopsy showed no evidence of malignancy, the patient received one treatment of intrathecal mtx (12 mg) at the time of the lumbar puncture in association with two treatment sessions of combination of intravitreal mtx (400 µg) and rituximab (1 mg) in her left eye at monthly intervals. twenty-six months following initiation of the treatment, the patient showed no evidence of recurrence.[46] mantle cell lymphoma has poor long-term survival and is almost considered incurable.[47] this aggressive nonhodgkin lymphoma rarely involves the eye. singer and colleagues reported a patient with mantle cell lymphoma who presented with decreased vision and bilateral optic disc swelling in the course of the disease. resolution of optic disc swelling initiated in the temporal disk margin after intravitreal mtx injections with regression of the infiltrative process.[48] in another study, zhang et al reported a patient with metastatic large b-cell lymphoma which presented as recurrent iridocyclitis with mutton-fat kps, hypopyon, and decreased vision in both eyes. aqueous humor tap confirmed the diagnosis and the patient was planned to receive 25 intravitreal injections of 400 µg mtx which was administrated twice a week for four weeks; once a week for eight weeks; and then monthly for a total of nine months. in the course of treatment, patient received systemic high dose of mtx due to cutaneous relapse of lymphoma. hypopyon was completely disappeared and only few cells were visible in the anterior vitreous cavity after the sixth injection. however, the patient experienced severe corneal toxicity; therefore, subsequent injections were cancelled. epitheliopathy was treated with carboxymethyl cellulose sodium drops and patient’s vision improved.[49] wickremasinghe and colleagues also reported two patients with systemic t-cell lymphoma which presented with fibrinous exudate in the anterior chamber and thickened and nodular iris. the first patient received one dose of intravitreal injection of mtx (400 µg) and responded well to therapy; five days after injection, the patient’s vision improved, and uveitis and fibrinous exudate were resolved. the other case received three doses of intravitreal injection of mtx every six weeks and showed rapid improvement.[50] uveitis uveitis, intra-ocular inflammation of various causes, leads to irreversible visual loss if not treated properly.[51] treatments of infectious uveitis are mainly aimed at the pathogens; however, in noninfectious uveitis, corticosteroids are the main regimen to decrease inflammation.[52] local injections might be preferable in specific conditions, such as those patients without a concomitant systemic disease, those who are unable to take systemic therapy, or those who have very asymmetric ocular disease. also, uveitic cme is one of the indications of local therapy. local therapy leads to a high concentration of the drug at the site of disease activity and decreases the risk of systemic toxicity.[53] hardwig and colleagues[54] evaluated the safety of intravitreal mtx for improvement of ocular diseases such as uveitis and advanced proliferative diabetic retinopathy (pdr), epithelial downgrowth, and idiopathic fibrovascular proliferation. patients were treated with a single dose of 400 µg intravitreal mtx. seven of nine uveitis eyes showed improvement in visual acuity, one remained stable, and one patient had decreased visual acuity which seemed journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 661 intravitreal methotrexate; abdi et al to be due to the advanced preexisting pathology and natural history of the disease rather than the treatment intervention. in another retrospective case series, taylor and colleagues[55] showed that a single injection of 400 µg intravitreal mtx in patients with unilateral noninfectious intermediate, posterior, or panuveitis and/or cme could lead to improvement of ocular inflammation, visual acuity, cme, and reduction of systemic immunosuppressive therapy. five of the fifteen patients experienced uveitic flare after a median of four months. four patients who achieved a partial improvement of cme after injection of intravitreal mtx showed no further improvement following ivta injection. in a larger multicenter interventional case series, taylor et al[56] confirmed the result of the previous study. they showed that intravitreal injection of 400 µg mtx could effectively improve visual acuity and/or reduce cme in 30 of 38 eyes. in some patients, it also reduced the need for systemic immunosuppressive drugs. in another study, khalil and coworkers,[57] evaluated the efficacy of intravitreal mtx in controlling posterior segment involvement of behcet’s disease (bd) in comparison to retrobulbar triamcinolone acetonide (ta). they showed that improvement of anterior chamber reaction and vitreous inflammation was similar between the two groups; however, relapses were noted less in patients who received intravitreal injection of 400 µg mtx. they suggested that intravitreal mtx has a promising result and may ensure better control of the inflammatory reaction and longer remission in comparison to retrobulbar ta in bd patients. in a similar study by bae et al,[58] the effect of intravitreal mtx in the treatment of refractory retinal vasculitis due to bd was evaluated. intravitreal injection of 400 µg mtx was given monthly until visual acuity and intraocular inflammation were stable. patients experienced significant improvement in visual acuity, decrease in fluorescein leakage, and levels of aqueous humor’s interleukin (il)-6 and il-8, four weeks after intravitreal mtx without any significant change in iop. as the increase in levels of il-6 and il-8 is associated with refractory retinal vasculitis in bd, intravitreal mtx could be effective in these patients. serpiginous choroiditis is defined as chronic, progressive, and recurrent inflammation of the choroid that leads to loss of choriocapillaris and atrophy of rpe and photoreceptors.[59] in some patients, there is an association with underlying mycobacterium tuberculosis infection and hypersensitivity to its components.[60] this condition usually responds well to antitubercular therapy and systemic corticosteroids; however, inflammatory damage may limit visual outcomes and continuation of antibiotics with the addition of immunomodulatory drugs such as mtx may result in disease quiescence.[61] tsui et al[62] reported a patient with serpiginous-like choroiditis (sc), from a tb-endemic area and positive quantiferon assay which was refractory to anti-tuberculosis regimen and systemic corticosteroids. within six weeks of starting anti-tb medication, the patient started receiving azathioprine 150 mg daily. despite receiving antibiotics, prednisolone, and azathioprine, steady sc extension was seen. therefore, intravitreal mtx was injected and subcutaneous mtx was prescribed. following the second intravitreal injection of mtx, the progression of the lesion stopped and borders of the lesion started to contract. the lesion remained quiescent 24 months after treatment. in another study, sahin et al[63] investigated the antiproliferative and anti-inflammatory effect of intravitreal mtx on suppressing intraocular inflammation in two patients with presumed tuberculosis-related uveitis. both patients received 400 mg of intravitreal mtx at the eighth week of anti-tuberculous therapy and showed improvement of visual acuity, suppression of intraocular inflammation, and resolution of cme. no recurrence was observed eight months after cessation of the anti-tuberculous regimen. chin et al[64] reported a patient who had latent extrapulmonary tuberculosis with choroidal granulomas (tuberculomas) that had been treated with antitubercular therapy one year earlier. systemic prednisolone provided visual improvement; however, avascular necrosis of the hip complicated the therapy. as cessation of systemic corticosteroid led to worsening of visual symptoms in this patient, diagnostic pars plana vitrectomy (ppv) in addition to intravitreal injection of mtx (400 µg) was performed. visual acuity improved after surgery and an intravitreal dexamethasone implant was inserted one week later which resulted in sustained resolution of choroidal infiltration. viral retinitis is a rare ocular infection that usually results in high rates of visual impairment. while acute retinal necrosis (arn) occurs in immunocompetent patients, progressive outer 662 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 intravitreal methotrexate; abdi et al retinal necrosis (porn) and cytomegalovirus (cmv) retinitis usually happen in immunocompromised patients.[65] the human herpesvirus family includes herpes simplex virus, varicella-zoster virus (vzv), epstein-barr virus (ebv), and cmv. cmv infection is the leading viral cause of visual impairment in immunocompromised patients, especially those who had undergone organ transplants. huang et al[66] reported a patient who had acute myeloid leukemia (aml) and developed bilateral cmv retinitis with bilateral cme, and optic disc swelling in the right eye six months following bone marrow transplantation. four weekly injections of intravitreal mtx (400 µg) were performed in the right eye which was more severely affected in combination with oral valganciclovir. visual acuity improved, optic disc swelling was resolved, and macular edema was subsided in the mtx-injected eye one month after injection. however, the non-injected eye showed no sign of resolution of macular edema. no recurrence of macular edema was observed in the right eye during the next eight months of follow-up. mashima and colleagues[67] presented a patient with interstitial pneumonia and chronic pyelonephritis who had been on methylprednisolone for 20 years. the patient developed vitreous opacity and extensive necrotizing retinitis with retinal hemorrhage sparing the posterior pole. polymerase chain reaction (pcr) of the vitreous sample was positive for ebv but negative for hsv, vzv, and cmv. the patient was unresponsive to intravenous ganciclovir and intravenous acyclovir, therefore, intravitreal mtx (400 µg) was tried for the patient. three days after intravitreal injection of mtx, the white–yellowish lesion in the ocular fundus was regressed. in line with regression of the lesion, copy numbers of ebv-dna in aqueous humor were also decreased. proliferative vitreoretinopathy (pvr) pvr is defined as the growth of fibroglial tissue on both sides of the detached retina and posterior hyaloid face.[68] it may be presented as low as the presence of cellular debris in the vitreous cavity to the presence of full-thickness retinal folds.[69] pvr occurs in 5–10% of cases of rhegmatogenous retinal detachments (rrd) and is the main cause of surgical failure after the repair of rrd.[70] several studies have shown the role of inflammation in the pathogenesis of pvr and reported the effectiveness of corticosteroids on inhibiting the development of pvr.[71, 72] denstedt and colleagues,[73] reported a case of a needle penetrating injury of the globe which resulted in retinal detachment and progressive post-traumatic pvr. the patient underwent multiple vitrectomies in association with multiple intravitreal injections of 200 μg mtx every two to three weeks. the patient’s best-corrected visual acuity (bcva) was 20/40 and the retinal periphery was flat with stable fibrosis in the last follow-up, 15 months after the initial treatment. benner et al[74] treated five eyes with severe pvr and recurrent retinal detachment using relaxing retinectomy, extended perfluorocarbon liquid tamponade for four weeks, and a series of intravitreal mtx injections (100– 200 μg) every two weeks. injections started within one week after re-detachment surgery. patients were followed for 11–27 months and interestingly, all patients remained attached and four eyes recovered to ambulatory vision (>20/200) with normal intraocular pressure (iop). this study showed that multiple intravitreal mtx injections could be beneficial for treating complex retinal detachment associated with pvr. ghasemi falavarjani et al[75] evaluated the role of intrasilicone oil (so) injection of mtx at the end of vitrectomy surgery for rrd with associated pvr. they injected 250 µg mtx into the silicone oil at the end of the surgery in 22 eyes of 22 patients with rrd associated with grade c pvr and compared the rate of retinal detachment with 22 eyes of 22 control patients. they showed that the rate of re-detachment was lower among the mtx group, although the difference was not statistically significant. nourinia and coworkers[76] evaluated the effect of repeated intra-silicone oil injections of mtx on the outcomes of surgery for rrd associated with grade c pvr. at the end of the vitrectomy and intraocular injection of so, and at the 3rd and 6th week after the surgery, the patient received 250 μg of intravitreal mtx. eleven eyes were treated and followed for about nine months; the retina of all treated eyes remained attached and bcva was significantly improved at the last follow-up visit. they stated that repeated intra-silicone injection of mtx could be a promising adjunctive procedure for the treatment of rrds complicated by pvr. sadaka et al[77] evaluated the effect of intravitreal mtx infusion during ppv for retinal detachment in patients with high risk for journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 663 intravitreal methotrexate; abdi et al the development of pvr (severe recurrent pvr with tractional retinal detachment [trd] and/or a history of severe ocular inflammation). a mixture of 500 ml balanced saline solution with added 40 mg of mtx was used as an infusion bottle during the surgery of 29 eligible patients. they believed that this solution yields intraocular mtx levels equivalent to that used in intraocular lymphoma (400 μg intravitreal injection).[54, 78] six months after the treatment, 83% of the patients had stable or improved bcva and 90% of the retinas remained attached. therefore, they suggested that intravitreal infusion of mtx during the surgery could be beneficial for those eyes which are at high risk for pvr development due to a history of prior pvr or intraocular inflammation. there is also an ongoing phase 3 clinical trial regarding the effectiveness of intravitreal mtx on the rate of re-detachment due to pvr that requires surgery. during gain understanding against retinal detachment (guard) trial, patients with recurrent retinal detachment due to pvr with star folds in at least three cumulative clock hours documented on retinal imaging, or for retinal detachment associated with open globe injury are enrolled. at the end of the vitrectomy or on first postoperative day, and then weekly for eight weeks, followed by every-other-week treatment through the 16th postoperative week, patients receive adx-2191 (intravitreal mtx 0.8%, aldeyra therapeutics) injections.[79] proliferative diabetic retinopathy ghasemi falavarjani et al[80] evaluated the effect of intra-silicone oil injection of mtx at the end of vitrectomy for advanced pdr and assessed the rate of retinal re-detachment associated with fibrovascular proliferation or pvr. they injected 250 µg mtx intravitreally into 19 eyes with severe diabetic tractional macular detachment or combined tractional or rhegmatogenous retinal detachment and compared the outcomes with 19 eyes of a control group. retinal re-detachment with fibrovascular proliferation or pvr occurred in seven eyes (36.8%) in the mtx group and eight eyes in the control group which was not statistically significant. therefore, they showed that intra-silicone injection of mtx at the end of vitrectomy for retinal detachment associated with severe pdr did not reduce the risk of postoperative retinal detachment due to fibrous or fibrovascular proliferation. in another study, hardwig et al[54] reported five patients with pdr associated with trd or cme. three patients received 200 µg and two were treated with a total of 400 µg of intravitreal mtx. two patients with pdr and trd experienced decreased vision, two patients with pdr and trd/dme showed increase in vision, and one patient with pdr and trd experienced no change in visual acuity. diabetic macular edema (dme) inflammation plays an important role in the pathogenesis of dme. intraocular inflammatory mediators increase in the course of the disease.[81] several studies have shown that intravitreal injection of corticosteroids results in improvement of dme mainly through suppressing the inflammatory mediators.[81–83] however, glaucoma and cataract formation are major drawbacks in intravitreal corticosteroid injections.[83] intravitreal mtx has been investigated as an anti-inflammatory agent in the treatment of persistent dme. in a prospective interventional case series, intravitreal mtx (400 µg) was injected in 18 eyes of 16 patients with persistent center-involving dme unresponsive to at least three consecutive intravitreal bevacizumab (ivb) injections or two consecutive bevacizumab injections plus macular photocoagulation. intravitreal injection of mtx resulted in statistically significant anatomical and visual improvement.[84] in another study, the efficacy of ivb combined with intravitreal mtx (ivm) in the treatment of dme was investigated. thirty-six eyes of 18 patients were randomly allocated into the two groups to receive three monthly injections of ivb (1.25 mg) plus ivm (400 µg) or ivb alone. in contrast to the previous study, no significant therapeutic effects for ivb combined with ivm compared to ivb alone were seen over a three-month follow-up.[85] age-related macular degeneration although vascular endothelial growth factor (vegf) is the main mediator in neovascular amd, other inflammatory mediators play a significant role in its pathogenesis. an increase in reactive oxygen species which can cause cellular damage, caspase activation inducing cell death, complement activation, breakdown of bruch’s membrane 664 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 intravitreal methotrexate; abdi et al and retinal pigment epithelium (rpe) by matrix metalloproteinases, and production of cytokines are the major inflammatory reasons for neovascular activity in amd.[86] therefore, interrupting the angiogenesis cascade by inhibiting inflammatory agents may prove effective in the treatment of neovascular amd. kurup et al[87] treated two patients who were refractive to conventional antivegf therapy. they injected 400 µg intravitreal mtx and at the two-week follow-up visit, visual acuity improved, and perifoveal subretinal fluid and leakage were decreased. as safety indices are unknown, they proposed that this treatment should be used for selected patients who are refractory to traditional treatments. soheilian and coworkers[88] assessed the effect of combined intravitreal mtx and bevacizumab on choroidal neovascularization in amd. they injected 400 µg of mtx combined with 1.25 mg of bevacizumab. the mean visual acuity improved and the mean central macular thickness (cmt) decreased. they suggested that the addition of intravitreal mtx to bevacizumab is safe and may enhance the therapeutic effect of bevacizumab for regression of neovascular complex. they proposed that mtx may also decrease the development of fibrous component and scar formation based on oct and fundus images. epithelial downgrowth epithelial downgrowth, characterized by intraocular migration of epithelial cells, can lead to endothelial decompensation, angle-closure glaucoma, intractable pain, and trd.[89] several methods such as membrane peeling, argon laser, excision of affected intraocular structures, and fluorouracil injection have been reported for treatment of this condition;[90] however, more than half of these patients are unresponsive to treatment.[89] lambert et al[91] reported the use of multiple intravitreal injection of mtx for treatment of a patient with recurrent epithelial downgrowth. the patient was followed for 14 months after his last injection and neither recurrence nor any side effect was seen. in another study, a patient who was suffering from epithelial downgrowth due to previous radial keratotomy and trabeculectomy was treated successfully with the injection of 400 µg intravitreal mtx every two weeks for six doses. epithelial downgrowth was successfully resolved and no remnant of the epithelial downgrowth was visible.[92] hardwig reported a patient with idiopathic fibrovascular proliferation for whom intravitreal injection of 200 µg mtx was done. the patient experienced four lines increase in visual acuity three months after the treatment.[54] mtx toxicity corneal epitheliopathy as the most common adverse effect of intravitreal injection of mtx is believed to be due to the local spillage of mtx into the subconjunctival space resulting in damage to the limbal stem cells which causes a transient limbal stem cell deficiency, and therefore corneal haze and epithelial breakdown.[93] in some studies, all patients develop some form of keratopathy, ranging from diffuse punctate keratopathy to severe epitheliopathy, which usually appears after the third injection. these patients usually respond well to short courses of topical lubricants, topical steroids, and increasing the interval between injections. topical folinic acid 0.003% and systemic folic acid 1 mg once daily could be effective in those who were unresponsive to lubrication.[29, 39, 93] zhou et al attempted to reduce the incidence of keratopathy caused by intravitreal mtx. they divided patients into two groups. group a received intravitreal mtx at a dosage of 400 μg twice a week for the first four weeks, weekly for the following eight weeks, and then monthly for the last nine months. patients in group b were started on the treatment protocol described above and switched directly to monthly injection for nine months when ocular remission was achieved. they showed that with a reduced injection frequency, the incidence of keratopathy could be lowered by about 60% without ocular recurrence during follow-up.[94] in another study, sahay et al reported a patient with diffuse large b-cell lymphoma and ocular involvement which was treated with weekly injections of intravitreal mtx in both eyes. the patient developed severe photophobia, tearing, and a decrease in vision due to severe limbitis with annular corneal epitheliopathy and corneal haze. further injections were discontinued and the patient received topical lubricants, cyclosporine, loteprednol, folinic acid, and systemic folic acid which resulted in complete resolution at twoweek follow-up.[95] ghasemi falavarjani and colleagues evaluated the effect of intravitreal mtx injection (400 µg) on corneal endothelial journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 665 intravitreal methotrexate; abdi et al cells in eyes with persistent dme. they assessed corneal endothelial cell features using specular microscopy. after six months of follow-up, they showed that intravitreal injection of 400 µg mtx had no significant effect on corneal endothelial cell measurements.[96] they did not observe clinically significant keratopathy in their series. progression of preexisting cataract is also noted as a side effect of intravitreal mtx injection, however, the majority of evaluated patients were vitrectomized that predisposed the eyes to the progression of cataract.[39] band keratopathy and iris and anterior chamber angle neovascularization with subsequent neovascular glaucoma were also reported as a rare complications of intravitreal injection of mtx.[29] choudhury et al reported two patients, one having idiopathic retinal vasculitis and the other having pars planitis in association with cme who received intravitreal injection of mtx. following intravitreal injections, both patients experienced pain and a decrease in vision within 24 hr of receiving intravitreal mtx injection. vitreous samples and cultures of used and unused vials of mtx from the same batch grew ralstonia pickettii. patients received intravitreal injection of vancomycin, amikacin, and dexamethasone with the diagnosis of acute endophthalmitis which resulted in visual recovery. this outbreak was caused by drug contamination at the compounding pharmacy.[97] hardwig and colleagues showed that intravitreal mtx is safe for non-pcnsl indications, as there was only one case among 16 treated patients who developed corticosteroid-responsive sterile endophthalmitis.[54] in another study, hardwig et al evaluated the visual results of intra-silicone injection of mtx at the time of or after the surgery for retinal detachment. they suggested that cumulative dosages of mtx ranging from 200 µg to 1200 µg is safe as there were no adverse effects observed following single injection or serial injections.[98] maculopathy, vitreous hemorrhage, and optic atrophy were also reported as rare complications of intravitreal mtx.[39] discussion intravitreal mtx has been used in several ophthalmic conditions such as intraocular tumors, dme, amd, pvr, uveitis, and epithelial downgrowth, showing promising results in many of these conditions. while the treatment is highly effective in intraocular lymphoma and uveitis, the efficacy in other diseases remains to be confirmed. mtx, a steroid-sparing agent, is becoming more popular and even the first-choice drug in some conditions that require long-term immunosuppression.[99] mtx exerts its antiinflammatory and immunomodulatory effects through several mechanisms such as inhibition of dhfr, increasing level of intracellular and extracellular adenosine, inhibiting the reduction of dihydrobiopterin to tetrahydrobiopterin, modulation of expression of lincrnap21, inhibition of jak-stat signaling pathway, and modulation of functions of t-cells and monocytes.[2] the mechanism of action of the intravitreal mtx is believed to be similar to its administration for other systemic diseases.[2, 100] intravitreal mtx is considered safe with the current doses. the most common side effect is corneal epitheliopathy after repetitive injections which is easily treated with frequent lubrication and increasing the interval between injections. few other side effects such as progression of preexisting cataracts, neovascular glaucoma, maculopathy, vitreous hemorrhage, and corneal endotheliopathy are very rare and the causal associations are unclear. intravitreal mtx is generally well tolerated and avoids the side effects of systemic administration of mtx or alternative drugs. although current routine clinical applications are limited to some forms of intraocular tumors and uveitis, the use of intravitreal mtx needs further investigations for other clinical applications. different studies have shown some promise for intravitreal mtx in diabetic retinopathy, amd, and after retinal detachment surgery; however, larger, randomized, multi-center clinical trials with long-term follow-ups are required to clarify the benefits of intravitreal mtx in different vitreoretinal diseases. financial support and sponsorship nil. conflicts of interest the authors do not have any conflicts of interest. references 1. mukherjee s. the emperor of all maladies: a biography of cancer. scribner, 2011. 666 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 intravitreal methotrexate; abdi et al 2. cronstein bn, aune tm. methotrexate and its mechanisms of action in inflammatory arthritis. nat rev rheumatol 2020;16:145–154. 3. green jm. glucarpidase to combat toxic levels of methotrexate in patients. ther clin risk manag 2012;8:403–413. 4. weinblatt me. methotrexate in rheumatoid arthritis: a quarter century of development. trans am clin climatol assoc 2013;124:16–25. 5. cronstein bn, sitkovsky m. adenosine and adenosine receptors in the pathogenesis and treatment of rheumatic diseases. nat rev rheumatol 2017;13:41–51. 6. crabtree mj, tatham al, hale ab, alp nj, channon km. critical role for tetrahydrobiopterin recycling by dihydrofolate reductase in regulation of endothelial nitricoxide synthase coupling: relative importance of the de novo biopterin synthesis versus salvage pathways. j biol chem 2009;284:28128–28136. 7. huarte m, guttman m, feldser d, garber m, koziol mj, kenzelmann-broz d, et al. a large intergenic noncoding rna induced by p53 mediates global gene repression in the p53 response. cell 2010;142:409–419. 8. malemud cj. the role of the jak/stat signal pathway in rheumatoid arthritis. ther adv musculoskelet dis 2018;10:117–127. 9. spurlock cf, 3rd, gass hmt, bryant cj, wells bc, olsen nj, aune tm. methotrexate-mediated inhibition of nuclear factor kappab activation by distinct pathways in t cells and fibroblast-like synoviocytes. rheumatology 2015;54:178– 187. 10. olsen nj, spurlock cf, 3rd, aune tm. methotrexate induces production of il-1 and il-6 in the monocytic cell line u937. arthritis res ther 2014;16:r17. 11. brown pm, pratt ag, isaacs jd. mechanism of action of methotrexate in rheumatoid arthritis, and the search for biomarkers. nat rev rheumatol 2016;12:731–742. 12. chan es, cronstein bn. mechanisms of action of methotrexate. bull hosp jt dis 2013;71: s5–s8. 13. gangaputra s, newcomb cw, liesegang tl, kaçmaz ro, jabs da, levy-clarke ga, et al. methotrexate for ocular inflammatory diseases. ophthalmology 2009;116:2188– 2198 e2181. 14. ericson l, karlberg b, rosengren bh. trials of intravitreal injections of chemotherapeutic agents in rabbits. acta ophthalmol 1964;42:721–726. 15. ozkan eb, ozcan aa, sekeroglu ht, kuyucu y, ozgun h, polat s. intravitreal injection of methotrexate in an experimental rabbit model: determination of ultrastructural changes. indian j ophthalmol 2013;61:329–333. 16. aly e, ebrahim a. apoptosis and electroretinogram after intravitreal injection of methotrexate in an experimental rabbit model. gen physiol biophys 2016;35:231–236. 17. tian xm, zhu y. apoptosis of rabbit retinal cell after eyeball rupture. asian pac j trop med 2013;6:273–279. 18. hara a, niwa m, kumada m, aokie h, kunisadae t, oyamaa t, et al. intraocular injection of folate antagonist methotrexate induces neuronal differentiation of embryonic stem cells transplanted in the adult mouse retina. brain res 2006;1085:33–42. 19. palakurthi nk, correa zm, augsburger jj, banerjee rk. toxicity of a biodegradable microneedle implant loaded with methotrexate as a sustained release device in normal rabbit eye: a pilot study. j ocul pharmacol ther 2011;27:151–156. 20. sunalp m, wiedemann p, sorgente n, ryan sj. effects of cytotoxic drugs on proliferative vitreoretinopathy in the rabbit cell injection model. curr eye res 1984;3:619–623. 21. dorr rt, fritz wl. cancer chemotherapy handbook. elsevier; 1980. 22. deng sx, penland s, gupta s, fiscella r, edward dp, tessler hh, et al. methotrexate reduces the complications of endophthalmitis resulting from intravitreal injection compared with dexamethasone in a rabbit model. invest ophthalmol vis sci 2006;47:1516–1521. 23. abbaszadeh hasiri m, baghaei moghaddam e, khalili mr, amini ah, eghtedari m, azizzadeh m, et al. intra-vitreal injection of methotrexate in experimental endotoxininduced uveitis in rabbit. vet res forum 2018;9:315–321. 24. abramson dh, schefler ac. update on retinoblastoma. retina 2004;24:828-848. 25. hurwitz rl, chevez-barrios p, boniuk m, chintagumpala m, hurwitz my. retinoblastoma: from bench to bedside. expert rev mol med 2003;5:1–14. 26. shields cl, shields ja. diagnosis and management of retinoblastoma. cancer control 2004;11:317–327. 27. shields cl, mashayekhi a, au ak, czyz c, leahey a, meadows at, et al. the international classification of retinoblastoma predicts chemoreduction success. ophthalmology 2006;113:2276–2280. 28. kivela t, eskelin s, paloheimo m. intravitreal methotrexate for retinoblastoma. ophthalmology 2011;118:1689, 1689 e1681–1686. 29. frenkel s, hendler k, siegal t, shalom e, pe’er j. intravitreal methotrexate for treating vitreoretinal lymphoma: 10 years of experience. br j ophthalmol 2008;92:383–388. 30. gorlick rg, abramson dh, sowers r, mazza ba, dunkel ij. impairments in antifolate transport are common in retinoblastoma tumor samples. pediatr blood cancer 2008;50:573–576. 31. chihara d, dunleavy k. primary central nervous system lymphoma: evolving biologic insights and recent therapeutic advances. clin lymphoma myeloma leuk 2020;21:73–79. 32. shiels ms, pfeiffer rm, besson c, clarke ca, morton lm, nogueira l, et al. trends in primary central nervous system lymphoma incidence and survival in the u.s. br j haematol 2016;174:417–424. 33. coupland se, damato b. understanding intraocular lymphomas. clin exp ophthalmol 2008;36:564–578. 34. coupland se, heimann h, bechrakis ne. primary intraocular lymphoma: a review of the clinical, histopathological and molecular biological features. graefes arch clin exp ophthalmol 2004;242:901–913. 35. hoffman pm, mckelvie p, hall aj, stawell rj, santamaria jd. intraocular lymphoma: a series of 14 patients with clinicopathological features and treatment outcomes. eye 2003;17:513–521. 36. isobe k, ejima y, tokumaru s, shikama n, suzuki g, takemoto m, et al. treatment of primary intraocular lymphoma with radiation therapy: a multi-institutional survey in japan. leuk lymphoma 2006;47:1800–1805. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 667 intravitreal methotrexate; abdi et al 37. teckie s, yahalom j. primary intraocular lymphoma: treatment outcomes with ocular radiation therapy alone. leuk lymphoma 2014;55:795–801. 38. fishburne bc, wilson dj, rosenbaum jt, neuwelt ea. intravitreal methotrexate as an adjunctive treatment of intraocular lymphoma. arch ophthalmol 1997;115:1152– 1156. 39. smith jr, rosenbaum jt, wilson dj, doolittle nd, siegal t, neuwelt ea, et al. role of intravitreal methotrexate in the management of primary central nervous system lymphoma with ocular involvement. ophthalmology 2002;109:1709–1716. 40. goldberg s, frenkel s, blumenthal ez, solomon a, pe’er j. intraocular lymphoma. ophthalmology 2007;114:1236– 1237. 41. kaur m, sahu s, sharma n, titiyal js. femtosecond laserassisted cataract surgery in phakic intraocular lens with cataract. j refract surg 2016;32:131–134. 42. omoti ae, omoti ce. ophthalmic manifestations of lymphoma. ann afr med 2007;6:89–93. 43. ong yl, white s. intra-vitreal methotrexate leads to resolution of intraocular chronic lymphocytic leukaemia. br j haematol 2010;148:181. 44. mello lgm, de paula effgen p, kiefer k. intravitreal methotrexate for iris and ciliary body relapse in acute lymphoblastic leukemia. j pediatr ophthalmol strabismus 2018;55:e16–e19. 45. reddy r, kim sj. intraocular t-cell lymphoma due to mycosis fungoides and response to intravitreal methotrexate. ocul immunol inflamm 2011;19:234–236. 46. ryan me, shantha jg, grossniklaus he, yeh s. secondary vitreoretinal lymphoma masquerading as acute retinal necrosis. ophthalmic surg lasers imaging retina 2015;46:1048–1050. 47. schieber m, gordon li, karmali r. current overview and treatment of mantle cell lymphoma. f1000res 2018;7: f1000 faculty rev-1136. 48. singer jr, nigalye ak, champion mt, welch mj. intravitreal methotrexate for mantle cell lymphoma infiltration of the optic nerves: a case report. retin cases brief rep 2018;12:5–9. 49. zhang p, tian j, gao l. intraocular lymphoma masquerading as recurrent iridocyclitis: findings based on in vivo confocal microscopy. ocul immunol inflamm 2018;26:362–364. 50. wickremasinghe ss, ojaimi e, lim l, stawell r, mckelvie p, zamir e. intravitreal methotrexate as adjunctive, palliative therapy in intraocular t-cell lymphoma. ocul immunol inflamm 2010;18:184–186. 51. rothova a, suttorp-van schulten ms, frits treffers w, kijlstra a. causes and frequency of blindness in patients with intraocular inflammatory disease. br j ophthalmol 1996;80:332–336. 52. chen sc, sheu sj. recent advances in managing and understanding uveitis. f1000res 2017;6:280. 53. shah kk, majumder pd, biswas j. intravitreal therapeutic agents in noninfectious uveitic macular edema. indian j ophthalmol 2018;66:1060–1073. 54. hardwig pw, pulido js, erie jc, baratz kh, buettner h. intraocular methotrexate in ocular diseases other than primary central nervous system lymphoma. am j ophthalmol 2006;142:883–885. 55. taylor sr, habot-wilner z, pacheco p, lightman sl. intraocular methotrexate in the treatment of uveitis and uveitic cystoid macular edema. ophthalmology 2009;116:797–801. 56. taylor sr, banker a, schlaen a, couto c, matthe e, joshi l, et al. intraocular methotrexate can induce extended remission in some patients in noninfectious uveitis. retina 2013;33:2149–2154. 57. khalil he, el gendy ha, youssef ha, haroun he, gheita ta, bakir hm. the effectiveness of intraocular methotrexate in the treatment of posterior uveitis in behcet’s disease patients compared to retrobulbar steroids injection. j ophthalmol 2016;2016:1678495. 58. bae jh, lee sc. effect of intravitreal methotrexate and aqueous humor cytokine levels in refractory retinal vasculitis in behcet disease. retina 2012;32:1395–1402. 59. dutta majumder p, biswas j, gupta a. enigma of serpiginous choroiditis. indian j ophthalmol 2019;67:325–333. 60. vasconcelos-santos dv, rao pk, davies jb, sohn eh, rao na. clinical features of tuberculous serpiginouslike choroiditis in contrast to classic serpiginous choroiditis. arch ophthalmol 2010;128:853–858. 61. gupta v, bansal r, gupta a. continuous progression of tubercular serpiginous-like choroiditis after initiating antituberculosis treatment. am j ophthalmol 2011;152:857–863 e852. 62. tsui e, fern cm, goldberg nr. treatment of refractory tubercular serpiginous-like choroiditis with intravitreal methotrexate. retin cases brief rep 2021;15:169–173. 63. sahin o, ziaei a. the role of methotrexate in resolving ocular inflammation after specific therapy for presumed latent syphilitic uveitis and presumed tuberculosis-related uveitis. retina 2014;34:1451–1459. 64. chin ek, almeida dr, mahajan vb. management of choroidal granulomas involving the macula in corticosteroid-intolerant patients. jama ophthalmol 2015;133:1351–1352. 65. wu xn, lightman s, tomkins-netzer o. viral retinitis: diagnosis and management in the era of biologic immunosuppression: a review. clin exp ophthalmol 2019;47:381–395. 66. huang ej, wang cp, lai ch, chen c-c, kuo c-n. rapid regression of cystoid macular edema associated with cytomegalovirus retinitis in adult acute myeloid leukemia by intravitreal methotrexate combined with oral valganciclovir: a case report with comparison of binocular outcome. taiwan j ophthalmol 2016;6:145–149. 67. mashima a, usui y, umazume k, muramatsu d, goto h. successful treatment of necrotizing retinitis with epsteinbarr virus-positive ocular fluid by intravitreal methotrexate injection. ocul immunol inflamm 2020;28:552–555. 68. machemer r, aaberg tm, freeman hm, irvine ar, lean js, michels rm. an updated classification of retinal detachment with proliferative vitreoretinopathy. am j ophthalmol 1991;112:159–165. 69. leiderman yi, miller jw. proliferative vitreoretinopathy: pathobiology and therapeutic targets. semin ophthalmol 2009;24:62–69. 70. pastor jc, de la rua er, martin f. proliferative vitreoretinopathy: risk factors and pathobiology. prog retin eye res 2002;21:127–144. 668 journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 intravitreal methotrexate; abdi et al 71. rubsamen pe, cousins sw. therapeutic effect of periocular corticosteroids in experimental proliferative vitreoretinopathy. retina 1997;17:44–50. 72. gagliano c, toro md, avitabile t, stella s, uva mg. intravitreal steroids for the prevention of pvr after surgery for retinal detachment. curr pharm des 2015;21:4698– 4702. 73. denstedt j, schulz dc, diaconita v, sheidow t. acupuncture resulting in eye penetration and proliferative vitreoretinopathy – surgical and medical management with intraocular methotrexate. am j ophthalmol case rep 2020;18:100605. 74. benner jd, dao d, butler jw, hamill ki. intravitreal methotrexate for the treatment of proliferative vitreoretinopathy. bmj open ophthalmol 2019;4:e000293. 75. falavarjani kg, hadavandkhani a, parvaresh mm, modarres m, naseripour m, alemzadeh sa. intra-silicone oil injection of methotrexate in retinal reattachment surgery for proliferative vitreoretinopathy. ocul immunol inflamm 2020;28:513–516. 76. nourinia r, borna f, rahimi a, bonyadi mhj, amizadeh y, daneshtalab a, et al. repeated injection of methotrexate into silicone oil-filled eyes for grade c proliferative vitreoretinopathy: a pilot study. ophthalmologica 2019;242:113–117. 77. sadaka a, sisk ra, osher jm, toygar o, duncan mk, riemann cd. intravitreal methotrexate infusion for proliferative vitreoretinopathy. clin ophthalmol 2016;10:1811–1817. 78. chan es, cronstein bn. methotrexate–how does it really work? nat rev rheumatol 2010;6:175–178. 79. nih. the guard trial part 1: a phase 3 clinical trial for prevention of proliferative vitreoretinopathy [internet]. nih; 2019. available from: https://clinicaltrials.gov/show/nct04136366. 80. ghasemi falavarjani k, modarres m, hadavandkhani a, moghaddam ak. intra-silicone oil injection of methotrexate at the end of vitrectomy for advanced proliferative diabetic retinopathy. eye 2015;29:1199–1203. 81. das a, mcguire pg, rangasamy s. diabetic macular edema: pathophysiology and novel therapeutic targets. ophthalmology 2015;122:1375–1394. 82. rangasamy s, mcguire pg, das a. diabetic retinopathy and inflammation: novel therapeutic targets. middle east afr j ophthalmol 2012;19:52–59. 83. diabetic retinopathy clinical research n, beck rw, edwards ar, aiello lp, bressler nm, ferris f, et al. threeyear follow-up of a randomized trial comparing focal/grid photocoagulation and intravitreal triamcinolone for diabetic macular edema. arch ophthalmol 2009;127:245– 251. 84. falavarjani kg, golabi s, modarres m. intravitreal injection of methotrexate in persistent diabetic macular edema: a 6month follow-up study. graefes arch clin exp ophthalmol 2016;254:2159–2164. 85. fazel f, oliya b, mirmohammadkhani m, fazel m, yadegarfar g, pourazizi m. intravitreal injections of bevacizumab plus methotrexate versus bevacizumab alone for the treatment of diabetic macular edema: a randomized, sham-controlled trial. j curr ophthalmol 2020;32:164–169. 86. bandyopadhyay m, rohrer b. matrix metalloproteinase activity creates pro-angiogenic environment in primary human retinal pigment epithelial cells exposed to complement. invest ophthalmol vis sci 2012;53:1953– 1961. 87. kurup sk, gee c, greven cm. intravitreal methotrexate in therapeutically resistant exudative age-related macular degeneration. acta ophthalmol 2010;88:e145–e146. 88. soheilian m, movaseghi m, ramezani a, peyman ga. pilot study of safety and effect of combined intravitreal bevacizumab and methotrexate for neovascular agerelated macular degeneration. eur j ophthalmol 2011;21:77–82. 89. weiner mj, trentacoste j, pon dm, albert dm. epithelial downgrowth: a 30-year clinicopathological review. br j ophthalmol 1989;73:6–11. 90. wong rk, greene dp, shield dr, eberhart cg, huang jj, shayegani a. 5-fluorouracil for epithelial downgrowth after descemet stripping automated endothelial keratoplasty. cornea 2013;32:1610–1612. 91. lambert ng, wilson dj, albert dm, chamberlain wd. intravitreal methotrexate for recurrent epithelial downgrowth. jama ophthalmol 2019;137:1082–1083. 92. lee md, wu f, schallhorn jm. successful treatment of epithelial ingrowth with intravitreal methotrexate. ophthalmology 2019;126:48. 93. gorovoy i, prechanond t, abia m, afshar ar, stewart jm. toxic corneal epitheliopathy after intravitreal methotrexate and its treatment with oral folic acid. cornea 2013;32:1171– 1173. 94. zhou x, zhou x, shi h, lai j, wang q, li y, et al. reduced frequency of intravitreal methotrexate injection lowers the risk of keratopathy in vitreoretinal lymphoma patients. bmc ophthalmol 2020;20:189. 95. sahay p, maharana pk, temkar s, chawla r. corneal epithelial toxicity with intravitreal methotrexate in a case of b-cell lymphoma with ocular involvement. bmj case rep 2018;2018: bcr2018226005. 96. ghasemi falavarjani k, golabi s, hadavandkhani a. effect of intravitreal injection of methotrexate on human corneal endothelial cells. cornea 2016;35:217–219. 97. choudhury h, jindal a, pathengay a, flynn hw, jr. an outbreak of ralstonia pickettii endophthalmitis following intravitreal methotrexate injection. clin ophthalmol 2015;9:1117–1120. 98. hardwig pw, pulido js, bakri sj. the safety of intraocular methotrexate in silicone-filled eyes. retina 2008;28:1082– 1086. 99. sipkova z, insull ea, david j, turner he, keren s, norris jh. early use of steroid-sparing agents in the inactivation of moderate-to-severe active thyroid eye disease: a stepdown approach. clin endocrinol 2018;89:834–839. 100. mateo-montoya a, baglivo e, de smet md. intravitreal methotrexate for the treatment of choroidal neovascularization in multifocal choroiditis. eye 2013;27:277–278. journal of ophthalmic and vision research volume 16, issue 4, october-december 2021 669