Panacea Journal of Medical Sciences 2022;12(2):335–339 Content available at: https://www.ipinnovative.com/open-access-journals Panacea Journal of Medical Sciences Journal homepage: http://www.pjms.in/ Original Research Article A clinical study of primary open angle glaucoma (POAG) in myopia-An observational study Sumita Mohapatra1, Suresh Chandra Swain1,*, Debasmita Jena1 1Dept. of Ophthalmology, S.C.B. Medical College & Hospital, Cuttack, Odisha, India A R T I C L E I N F O Article history: Received 11-07-2021 Accepted 24-08-2021 Available online 17-08-2022 Keywords: Myopia Primary open-angle glaucoma spectral domain Optical Coherence Tomography A B S T R A C T Background: The Primary open-angle glaucoma is the most common type of glaucoma causing irreversible blindness. Myopia is one of the risk factor responsible for pathogenesis of glaucoma. The association between myopia and primary open angle glaucoma has been found in numerous case studies. The aim of the study to evaluate the relationship of myopia in primary open-angle glaucoma by classifying the eyes into low, moderate and high myopia. Materials and Methods: This prospective study was performed on 1414 axial myopic patients more > 18 years. Clinical examination included, slit-lamp biomicriscopy, Goldman applanation tonometry, refraction, dilated optic disc assessment, central corneal thickness, visual field analysis and optical coherence tonography. Results: Out of 1414 patients, 769(54.38%) were male and 645(45.62%) were female. Low myopia (<- 3D) cases are 938(66.32%), moderate myopia (-3D to -D) 309(21.88%), high myopia (>-6D), 107(11.8%). Maximum number of cases were in younger age group (20-30 years). Intraoccular Pressure > 21mmHg in 143 cases of low myopia, 78 cases in moderate myopia, 72 cases in high myopia. There were 138 cases with glaucomatous field changes. Out of 138 cases 86(62.32%) were high myopia, 35(25.36%) were moderate myopia and 17(10.8%) cases were low myopia. The CUP-DISC ratio <0.5 in 75.95% cases, 0.5-<0.9 in 20.37% cases, >0.9 in 3.68% cases. The average values of circumpapilary Nerve Fiber Layer thickness in micrometer of low myopia, moderate myopia, high myopia, with non-glaucomatous cases were 98.9, 97.3, 93.5 and with glaucomatous cases, 74.4, 73.7 and 73.3 respectively. The average values of Ganglion Cell Complex thickness in micrometer in low, moderate and high myopia without glaucoma were 94.9, 93.5, 92.7 and with glaucoma 77.3, 74.6, 70.2 respectively. Conclusion: This study shows there is strong relationship between myopia and primary open-angle glaucoma. Early detection of glaucoma in myopic patients is necessary in delaying blindness. This is an Open Access (OA) journal, and articles are distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. For reprints contact: reprint@ipinnovative.com 1. Background Myopia or short-sightedness is a refractive condition of the eye that makes distant objects to be blurry while close object appears normal. Among different etiological types myopia, axial myopia is commonest, in which their occurs axial elongation of eyeball. Axial elongation affect the * Corresponding author. E-mail address: suresh211167@gmail.com (S. C. Swain). eye’s intraocular structure (optic disc or macula), where glaucomatous damage can occur. Glaucoma, a progressive optic neuropathy causes irreversible blindness. 1 It is characterized by the loss of retinal nerve fiber tissues, recognized clinically as visual field defect and loss of the neuro retinal rim of the optic nerve head. The primary open-angle glaucoma (POAG) is the most common type of glaucoma. https://doi.org/10.18231/j.pjms.2022.063 2249-8176/© 2022 Innovative Publication, All rights reserved. 335 336 Mohapatra, Swain and Jena / Panacea Journal of Medical Sciences 2022;12(2):335–339 Elevated intraocular pressure (IOP) is a measure risk factor for POAG. 2 Other risk factors like age, gender, race, refractive errors, heredity and systemic factors may play a role in glaucoma pathogenesis. 3 Most of the studies have suggested that moderate to high myopia is associated with increased risk of POAG. 4,5 Mechanical theory explains the association between myopia and primary open-angle glaucoma (POAG), which describes that damage to optic nerve head at Lamina Cribosa leads to Retinal Ganglion Cell atrophy and glaucomatous optic neuropathy, induced by increased IOP and a tensile sclera or by exacerbated shearing forces due to longer axial eye length. 2. Materials and Methods This is a prospective study, was conducted during the period of October 2018- September 2020 at Ophthalmology Department, S.C.B. Medical College, Cuttack, Odisha. Ethical Committee clearance was taken. Subjects with axial myopia >=-1D identified by a standardized subjective refraction and categorized into low myopia (<=-1D to >-3D), moderate (>-3D<-6D) or high myopia (>-6D) according to Sihota’s classification and taken for the study. Primary open-angle glaucoma diagnosed taking into account characteristic visual field loss combined with optic disc cupping and neuro retinal rim thinning with or without raised IOP. 2.1. Inclusion criteria All the myopic patients (>=-1D) of age >18 years who had given consent for study. 2.2. Exclusion criteria 1. Known case of any form of secondary glaucoma. 2. Angle closer glaucoma. 3. Lenticular opacity. 4. Keratoconus. 5. History of trauma. 6. History of surgery. A total of 1414 axial myopia patients included in this study. The examination included, medical history, best corrected of visual acuity, refraction by Auto refractometer and subjective refraction, Slit-lamp biomicroscopy, Goldmann applanation tonometry for Intra Ocular Pressure (IOP), Central Corneal Thickness (CCT) measurement by ultrasound Pachymeter, post dilation Optic Disc (OD) and retina evaluation with +90D fundus noncontact lens, visual field analysis by Humphrey Perimeter, Optical Coherence Tomography (OCT) for Optic Nerve Head (ONH), Ganglion Cell Complex (GCC) and circum papillary Retinal Nerve Fiber (cp RNFL) evaluation. 3. Results The above table shows 769 (54.38%) patients were male and 645 (45.62%) were female. Maximum number of myopic patients were younger age group, between 20-30 years. 438 cases were low myopics, 127 cases were moderate myopics and 68 cases were high myopics. Less number of patients were more than 40 years.Table 1 According to Sihota myopia is classified as low (<-3D), medium (-3D to -6D) and high (>-6D). Low myopia cases were 938 (66.34%), Moderate myopia and high myopia patients were 309 (21.85%), 167 (11.81%) respectively. BCVA of patients varied from 6/6 to <6/60. It could improve up to >6/60 in all the low myopics, 98.7% (305) of the moderate myopics, 97.01% (162) of high myopics and rest with BCVA <=6/60.Table 2 Normal intraocular pressure is taken to be between 11mmHg and 21mmHg with mean IOP as 16+-2.5mmHg. measurement of IOP was done by Goldmann applanation tonometer. 143 cases with low myopia, 78 cases with moderate myopia and 72 cases of high myopia had IOP>21mmHg. 1074 (75.95%) patients had C/D ratio <0.5, 288 (20.37%) patients had 0.5-<0.9 and 52 (3.68%) patients had C/D ratio >0.9.Table 3 Mean CCT in 938 cases low myopic group was 536.6, 309 cases of moderate myopic group was 531 and 167 cases that of high myopic group was 540.9 micrometer.Table 4 1405 patients with BCVA >6/60 were advised for 24- 2 visual field test done by Humphrey’s perimeter. Out of these 138 patients had glaucomatous field changes and 48 patients had non-glaucomatous changes. 1219 patients had no perimetry changes. Out of 138 patients with perimetric glaucoma 86 (62.32%) cases were high myopics, 38 (25.36%) cases were moderate myopics and 17 (12.32%) cases were low myopics.Table 5 The patients were subjected for SD-OCT scan. The average cp RNFL thickness was 98.9 micrometer in low myopic non-glaucomatous patients, 74.4 micrometer in glaucomatous cases. 97.3 micrometer in moderate myopic non-glaucomatous patients, 73.7 micrometer in glaucomatous cases. 93.5 micrometer in high myopic non- glaucomatous patients, 73.3 micrometer in glaucomatous cases. The superior and inferior cpRNFL thickness in micrometer were found to be less in glaucomatous group than non glaucomatous group like average cp RNFL thickness.Table 6 The average GCC parameters in micrometer measured by SDOCT scan was 94.9 micrometer in low myopic non- glaucomatous patients, 77.3 micrometer in glaucomatous patients. 93.5 micrometer in moderate myopic non- glaucomatous patients, 74.6 micrometer in glaucomatous cases. 92.7 micrometer in high myopic non-glaucomatous patients, 70.2 micrometer in glaucomatous cases. The superior and inferior GCC parameter were found to be less in glaucomatous group than non glaucomatous group like Mohapatra, Swain and Jena / Panacea Journal of Medical Sciences 2022;12(2):335–339 337 Table 1: A. Sex prevalence of myopia Category No. of patients Percentage Male 769 54.38 Female 645 45.62 Total 1414 100 B. Age group in years Age Group Low myopia Moderate High myopia <20 206 78 35 20-30 438 127 68 30-40 197 76 48 >40 97 28 16 Total 938 309 167 Table 2: A. Degree Of Myopia Degree of myopia Nunber % Low (< -3D) 938 66.34 Moderate (-3 to -6D) 309 21.85 High (> -6D) 167 11.81 Total 1414 100 B. Classification of patients on the basis of BCVA Degree of myopia BCVA >6/60 Percentage BCVA <=6/60 Percentage Low 938 100 0 Moderate 305 98.7 4 1.3 High 162 97.01 5 2.99 Table 3: A. IOP by Goldmann applanation tonometry in the patients Degree of myopia Iop range <10mmHg 10-21mmHg >21mmHg Total Low 233 562 143 938 Moderate 87 144 78 309 High 32 63 72 167 B. CUP-DISC ratio (C/D ratio) CUP-Disc Ratio Number of myopes % <0.5 1074 75.95 0.5-<0.9 288 20.37 >0.9 52 3.68 Table 4: CCT in micrometer in the patients Myopia groups Number Mean CCT Range 0 to -3D 938 536.6 305-684 >-3 to -6D 309 531 417-613 >-6D 167 540.9 417-614 Table 5: A. Perimetric changes No of patients done perimetry Perimetry suggestive of glaucomatous changes Perimetry suggestive of non-glaucomatous changes Perimetry having no changes 1405 138 48 1219 B.Grading of POAG on the basis of perimetric findings (Hodapp- Parrish- Anderson criteria) No of POAG patients with perimetric glaucoma No of patients with high myopia and perimetric glaucoma No of patients with moderate myopia & perimetric glaucoma No of patients with low myopia and perimetric glaucoma 138 86(62.32%) 35(25.36%) 17(12.32%) 338 Mohapatra, Swain and Jena / Panacea Journal of Medical Sciences 2022;12(2):335–339 Table 6: cp RNFL parameters in different grades of myopia (with and without glaucoma) cp RNFL thickness (µm) Low Myopia Moderate Myopia High NG Myopia NG G NG G G Average cpRNFL 98.9 74.4 97.3 73.7 93.5 73.3 Superior cpRNFL 99.5 76.5 96.8 75.6 92.9 74.3 Inferior cpRNFL 101.8 74.2 98.5 74.3 94.8 75.0 NG= no glaucoma G= glaucoma Table 7: GCC parameters in different grades of myopia (with or without glaucoma) GCC parameters (µm) Low myopia Moderate myopia High myopia NG G NG G NG G Average GCC 94.9 77.3 93.5 74.6 92.7 70.2 Superior GCC 96.9 80.3 95.4 77.3 94.8 74.1 Inferior GCC 95.1 71.4 94.6 70.6 94.4 68.1 average GCC thickness.Table 7 3.1. Statistical analysis The statistical analysis was formed using commercially available software (SPSS, version 15, SPSS Ink, Chicago, Illinois) including chi-square test. 4. Discussion Out of 1414 patients in our study, 769(54.38%) were male and 645(45.62%) were female (Table 1A). Male to female ratio 1.19:1. Maximum number of myopic patients were in younger age group. (Table 1B). Holden et al suggest variability in gender difference is owing to environmental influences, such as inequitable access to education, participation in physical activity and closed work. 6 In many of the study it is reported that gender prevalence exhibits a particular pattern with a greater prevalence of myopia in girls starting to appear at around the age of 9 years, continuing through teenage years and early adulthood and diminishing to no or minimal gender difference around the age of 50 to 60 years. Out of 1414 patients there were 938(66.34%) low myopia (<- 3D), 309(21.85%) moderate myopia (-3D to -6D) and 167(11.81%) of high myopia cases (>-6D) (Table 2A). Optic nerve head of myopic eyes are more susceptible to glaucomatous damage due to some structural changes. Increasing degree of myopia is a risk factor for glaucoma. Blue Mountains Eye Study, they found a strong relationship between glaucoma and myopia after adjusting for age, sex and other risk factors (odds ratio 2.3 for eyes with low myopia, 3.3 for moderate to high myopia). 7 Myopic subjects had a two three-fold increase risk of glaucoma compared with that of non myopic subjects. The Singapore Malays Eye Study showed Persons with moderate or high myopia had almost 3 times higher risk of POAG compared with those emmetropia. 8 143 cases with low myopia, 78 cases with moderate myopia and 72 cases of high myopia had IOP>21mmHg. Conversely 17(12.32%) patients of low with low myopia, 35(25.36%) patients with moderate myopia and 86(62.32%) with high myopia had perimetric glaucoma (Tables 3 and 5 ). There is increase in number patients with perimetric glaucoma as severity of myopia increases. Edgar and Rudnika found that low myopia was associated with doubling of the risk of glaucoma at any age and a three- fold increase with medium and high myopia compared to that emmetropia. 9 In our study the number of patients with cup-disc ratio 0.5-<0.9 were 288 (20.37%), and C/D ratio>0.9 were 52 (3.68%) patients. Study of ocular hypertention and glaucoma patients 10 found that the incidence of visual field defects increased markedly with CDR greater than 0.7. The mean CCT in low myopic group was 536.6 micrometer, moderate myopic group was 531 micrometer and high myopic group was 540.9 micrometer (Table 4). CCT difference is not statistically significant. cp RNFL and GCC parameters detected by SD-OCT is essential for glaucoma diagnosis and progression. All the average values were found to be less in glaucomatous group than the non glaucomatous group (Tables 6 and 7 ). Kim et al found similar results comparing glaucomatous group with non-glaucomatous group by SD-OCT measurements. 11 Assessment of GCC parameters is a useful technique complimentary to cpRNFL thickness assessment, for evaluating patients with glaucoma and high myopia by Shoji T et al. 12 5. Conclusion This study shows myopia is a risk factor for POAG as observed by many studies. But it is a proven fact that Mohapatra, Swain and Jena / Panacea Journal of Medical Sciences 2022;12(2):335–339 339 prevalence of POAG is more in moderate and high myopics. Myopia is relatively common in younger age group. So early detection of glaucoma in these patients will be helpful in delaying the blindness. Especially for Moderate and high myopia. 6. Conflict of Interest The authors declare that they have no conflict of interest. 7. Source of Funding None. References 1. Loyo-Berrios NI, Blustein JN. Primary-open glaucoma and myopia: a narrative review. WMJ. 2007;106(2):95–9. 2. Mcmonnies CW. Intraocular pressure spikes in keratectasia, axial myopia, and glaucoma. Optom Vis Sci. 2008;85(10):1018–26. doi:10.1097/OPX.0b013e3181890e91. 3. Ohana EB, Blumen MB, Bluwol E, Derri M, Chabolle F, Nordmann JP, et al. Primary open angle glaucoma and snoring: prevalence of OSAS. Eur Ann Otorhinolaryngol Head Neck Dis. 2010;127(5):159– 64. doi:10.1016/j.anorl.2010.07.003. 4. Knapp A. Glaucoma In myopic eyes. Trans Am Ophthalmol Soc. 1925;23:61–70. 5. Podos SM, Becker B, Morton WR. High myopia and primary open- angle glaucoma. Am J Ophthalmol. 1966;62(6):1038–43. 6. Holden BA, Fricke TR, Wilson DA. Global prevalence of myopia and high myopia and temporal trends from. 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Comparing the ganglion cell complex and retinal nerve fibre layer measurements by Fourier domain OCT to detect glaucoma in high myopia. Br J Ophthalmol. 2011;95(8):1115–21. 12. Shoji T, Nagaoka Y, Sato H, Chihara E. Impact of high myopia on the performance of SD-OCT parameters to detect glaucoma. Graefes Arch Chin Exp Ophthalmol. 2012;250(12):1843–9. Author biography Sumita Mohapatra, Professor Suresh Chandra Swain, Associate Professor Debasmita Jena, Senior Resident Cite this article: Mohapatra S, Swain SC, Jena D. A clinical study of primary open angle glaucoma (POAG) in myopia-An observational study. Panacea J Med Sci 2022;12(2):335-339. http://dx.doi.org/10.1097/OPX.0b013e3181890e91 http://dx.doi.org/10.1016/j.anorl.2010.07.003 http://dx.doi.org/10.1016/j.ophtha.2016.01.006 http://dx.doi.org/10.1016/s0161-6420(99)90416-5 http://dx.doi.org/10.1016/s0161-6420(99)90416-5 http://dx.doi.org/10.1001/archophthalmol.2010.125 http://dx.doi.org/10.1136/bjo.62.10.665